THE UNIVERSITY OF SHEFFIELD
DEPARTMENT OF ENGINEERING MATERIALS

RESEARCH PROJECT LIST FOR 2012/2013

(A) ADVANCED CHARACTERISATION

1 NANOTOMOGRAPHY AND 3D NANOMETROLOGY
Supervisor: G Möbus

Nanomaterials are intrinsically 3-dimensional materials, as their properties depend on surface-proximity and confinement, also referred to as low-dimensional matter. Imaging of surfaces or simple planar cross-sections is therefore no longer sufficient. In this project we develop new experimental acquisition sequences for applying the established method of computed axial tomography (CAT) to nanomaterials, where objects are rotated under irradiation around an axis, with special emphasis on 3D chemical and structural mapping. For students with skills and interest in computer software also the development of improved data reconstruction procedures will feature. State-of-the-art aberration corrected electron microscopy is available for projection imaging. Applications will comprise, depending on the interest of the student, e.g. nanoparticles, nanoparticle arrays, nanocomposites, functional nanotips and porous materials. This topic is an example of many more characterisation-based possible PhD topics, see www.moebus.staff.shef.ac.uk/phdtopics.pdf.

2 MATERIALS CHARACTERISATION BY ENERGY SELECTIVE SCANNING ELECTRON MICROSCOPY
Supervisor: Dr C Rodenburg

Scanning Electron Microscopes (SEMs) have been the workhorse for material science since the 1960s, mostly to visualise topography or material differences. In recent years much emphasis has been placed on the development of scanning microscopes that provide smaller probes size with the aim of achieving better resolution. Less attention is given to the detection of secondary electrons (SEs) in spite the fact that imaging using SEs of a certain energy range are expected to give better results in a number of applications such imaging magnetic materials, doping in semiconductors, mapping of electrical potential distributions. We have one of only a few SEMs worldwide that enables us to easily carry out energy selective with high lateral resolution. You will be expected to test the theoretical models experimentally and identify potential new applications for energy selective SEM. By doing so you could be instrumental in opening up a new era for SEM.

3 SITE SPECIFIC SAMPLE PREPRATATION TECHNIQUES FOR RAPID QUANTITATIVE DOPANT PROFILING IN THE SCANNING ELECTRON MICROSCOPE (SEM)
Supervisor: Dr C Rodenburg

Doping is the heart of all semiconductor devices because the dopants determine the electric properties of devices. The semiconductor industry has identified the need to measure dopant distribution in three dimensions with high spatial resolution and accuracy as one of the ten crucial requirements for the future of the industry. We have demonstrated such a two dimensional dopant mapping technique which relies on SEM images of cleaved semiconductors. However to be useful to the semiconductor industry we need to be able to use the technique at specific well defined sites of a device structure which can hardly be achieved by cleaving. A very well established technique for site specific sample preparation is the use of a focused ion beam (available at the Department Electronic and Electrical Engineering) but routine usage of such an instrument does not produce suitable specimens for dopant profiling in the SEM. You will be expected to develop a site specific sample preparation technique for semiconductor device structures that prove suitable for quantitative three dimensional dopant mapping using SEM.

(B) ADVANCED METALLIC MATERIALS

4 PROCESSING AND PROPERTIES OF HIGH MELTING POINT METAL FOAMS
Supervisor: Dr R Goodall

Metal foams produced from higher melting point metals (such as copper, nickel, titanium, superalloys and shape memory alloys) would be of interest in a wide range of applications, including biomedical implants and the absorption of sound in aero engines. The replication process, where metal is cast into the spaces in an assembly of grains of a refractory but water soluble material, which is then dissolved away to leave a sponge-like structure of metal, has been shown to provide good control of the foam pore size, shape and structure, but has only been extensively explored for aluminium.

Work in this area includes the development of processing techniques to give controlled foam structures, and the characterisation of the materials produced in order to understand the links between foam structure and metal microstructure and the material properties, such as mechanical behaviour or thermal and electrical conductivity. Once these links have been made they can be used to design optimum foam structures for applications.

5 PROPERTIES OF POROUS STRUCTURES WITH INTERMEDIATE LEVELS OF ORDER
Supervisor: Dr R Goodall

are either stochastic (i.e. random) metal foams or sponges, or highly ordered lattice structures with regular unit cells. The former are often produced by the injection of gas or removable solid phase into a melt or powder mixture, and as such the properties are frequently close to being isotropic, while the latter may be created by layer manufacturing techniques, which can be time consuming for large production runs of identical components.

In this project, processing techniques to create structures combining elements of both of these classes will be investigated, and the mechanical, electrical and thermal properties of the resulting materials will be investigated. This will include methods for combining regions of random pores with lattice structured regions, to obtain anisotropic properties or specific behaviour such as negative Poisson’s ratio (auxetic) materials. Structural modelling will be used to suggest which structural combinations could show promise for certain applications, and these predictions will be validated experimentally.

6 EFFECT OF HIGH STRAIN RATE DEFORMATION PROCESSES ON THE DAMAGE TOLERANCE AND SERVICE PERFORMANCE OF AEROSPACE TITANIUM ALLOYS
Supervisors: Dr M Jackson

The majority of aerospace titanium alloy components will be either high-speed machined, peened using laser shock or mild steel shot and/or burnished. Such techniques impart a high degree of surface deformation at very high strain rates. Peening, for example, is an established technique designed to impart compressive residual stresses that provide enhanced damage tolerance. However, recent work at Sheffield has shown it to be deleterious to the surface microstructure of the component, providing enhanced oxygen diffusion kinetics and leading to a loss of creep strength. The aim of this project is to determine the effect of important high deformation processes, such as shot peening, laser shock peening and high speed machining on the surface microstructure and subsequent damage tolerance for a range of titanium alloys. The deformation mechanism with regard to alpha-beta morphology and texture will investigated using both scanning and transmission electron microscopy, including electron backscatter diffraction. The effect of thermal cycling during service will also be investigated to determine the alpha case formation and oxygen diffusion kinetics measured using secondary ion mass spectrometry. The subsequent change in mechanical properties will be measured via standard tensile and fatigue testing.

7 DEVELOPMENT OF SOLID STATE DOWNSTREAM PROCESSING ROUTES FOR THE PRODUCTION OF LOW COST TITANIUM ALLOYS FOR NON-AEROSPACE MARKETS
Supervisors: Dr M Jackson

Over the last decade, a number of low cost titanium reduction technologies have received a lot of attention and sponsorship. These processes have the potential to compete with the Kroll process, providing an alternative source of material, particularly for the non-aerospace market sectors. An alternative, cheaper source of titanium powder and significant developments in processing cost reduction are essential if target markets such as the automotive industry are to be penetrated to any extent at all. Although many of the emerging extraction processes produce a powder/granular final product, there has been little emphasis on downstream processing of such feedstock into a useable form. If there is to be a step change in the cost of titanium (similar to that achieved in aluminium in the late nineteenth century) then disruptive technologies that consolidate the titanium particulate through affordable non-melt routes directly into non-aerospace grade useable forms is essential. The proposed programme of work aims to develop cheap non-melt consolidation methods for titanium alloy powder feedstock, with a view to providing downstream processing routes for powder from emerging reduction technologies. A major outcome of the work will determine whether it is economically and commercially viable for the production of titanium alloy bar/rod and sheet via such non-melt routes.

8 PREDICTION OF MICRO-TEXTURAL AND PROPERTY EVOLUTION OF TITANIUM ALLOYS USED FOR HIGH STRENGTH AIRFRAME AND LANDING GEAR FORGINGS
Supervisors: Dr M Jackson and Dr B Wynne

Isothermal forging (IF) is essential for the fabrication of titanium aerospace components, such as high strength landing gear forgings. To reduce the high processing costs it is essential for the industry to accurately predict microstructural and microtextural evolution and thus, property evolution with respect to IF variables. A testing methodology for evaluating and predicting the microstructural evolution of titanium alloys during subtransus IF has been developed at Sheffield. The project will exploit the unique World leading thermomechanical compression facility within the department to forge high strength beta titanium alloys at near beta transus temperatures to obtain microstructural and textural information for a range of strains within a single specimen. The rheological behaviour of beta titanium alloys, which generally exhibits flow softening, will be fitted using a recently developed constitutive approach that incorporates an internal microstructural variable. The aim will be to use a finite element modelling package to produce strain and lambda profiles, which correspond to the equivalent microtextural profiles of the test specimens, providing a database of texture and subsequent mechanical properties for defined IF conditions.

9 EFFECT OF FRICTION AND LUBRICATION ON MULTIPASS HOT DEFORMATION
Supervisor: Dr E J Palmiere

In the conventional production of iron and aluminium alloys, a large variety of rolling conditions occur by which a complex forming history is imposed on the material. The effects of the multipass deformation on the final material properties may be manifold and furthermore, the interdependence of process parameters can significantly affect the eventual microstructure and subsequently its properties according to the type of rolling schedule and equipment. The issue is further complicated with the incorporation of the imminent effects of friction and lubrication of the slab. Past researches on Plane Strain Compression (PSC) testing and Finite Element (FE) modelling have shown that strains within the PSC testing samples are not uniform and thus eventually the variation in microstructure. This research was setup to study the effects of lubrication and friction on the tests; incorporating with it developing a practice guide in the positional sampling of microstructures in PSC test pieces. The research would include the use of the new Servotest machine in the department and the JEOL 6400 SEM particularly the EBSD technique. Quantification of the microstructure would be performed by quantitative metallurgy methods developed.

10 THERMOMECHANICAL PROCESSING OF PLATE STEELS UNDER NON-EQUILIBRIUM CONDITIONS
Supervisor: Dr E J Palmiere

Plate steels represent an important class of steels to the construction, energy and shipbuilding industries This project will focus on the influence of processing history (e.g., under conditions of dynamic changes in deformation temperature, strain, strain rate, cooling rate) in both single phase austenite and ferrite+austenite regions, together with alloy chemistry on the mechanical properties. As such, this project will involve the use of physical deformation simulations of flat rolling processes coupled with quantitative microscopy (optical and electron microscopy, including EBSD) and mechanical testing.

11 THERMOMECHANICAL PROCESSING FOR ULTRA-FIN FERRITE GRAINS IN DUAL PHASE STEELS
Dr E J Palmiere

Dual phase steels represent an important class of steels to the automotive industry. This project will focus on the influence of processing history (e.g., deformation temperature, strain, strain rate, cooling rate) and alloy chemistry on the final sheet formability. The overall aim will be to determine processing windows which result in ultra-fine ferrite grains, and the impact that such a microstructure will have on mechanical properties. As such, this project will involve the use of physical deformation simulations of flat rolling processes coupled with quantitative microscopy (optical and electron microscopy, including EBSD).

12 INTENSE WATER-COOLING DURING OR AFTER HOT ROLLING TO IMPROVE STEEL PRODUCTION
Supervisors: Dr E J Palmiere and Visiting Professor A A Howe, in association with Tata Steel

Intense water-cooling after the final hot rolling pass is a well-established technology to improve product properties, but has certain limitations, e.g. grain refinement and property improvement through thicker products, or maintenance of the required shape and flatness. Various adjustments can be made to the rolling schedule, e.g. rolling overall at lower temperatures, or particularly with a period of intense cooling during a hold in the rolling schedule, that could reduce the need for accelerated cooling after rolling, and/or allow further improved properties than can be accomplished by established approaches. This project will investigate these approaches and will make extensive use of the department’s thermomechanical simulation equipment and modelling expertise, and liaison with steel industry personnel.

13 DEVELOPMENT OF CoCrMo ALLOYS FOR HIP JOINT PROSTHETIC APPLICATIONS
Supervisor: Prof WM Rainforth

In recent years, metal-on-metal (MoM) hip replacements based on CoCrMo alloys have increasingly become the preferred choice for younger and/or more active patients due to their superior wear resistance, longer service duration and reduced inflammatory osteolysis resulting from such devices. CoCrMo is generally regarded as a corrosion resistant alloy, due to the tenacious oxide film (1–4nm thick) formed on the metallic surface containing mainly Cr2O3. Nevertheless, CoCrMo is reported to be susceptible to corrosion when implanted into the human body, especially within a tribological contact such as a knee or hip. Implant components fabricated from CoCr based alloys have been reported to produce elevated Co, Cr (and Ni) ion concentrations in body fluids. It is important, therefore, to understand the mechanisms, such as wear, that lead to the liberation of the metal ions. There have been a number of investigations into the wear mechanisms that occur in the artificial hip joints. Abrasive wear has been seen on some of the retrieved CoCrMo hip joints and is one of the possible wear mechanisms on such joints. Interestingly, there has also been much interest in the role of a so-called nanocrystalline layer that forms on the surface of CoCrMo alloys, with some suggestions that it enhances wear resistance, but other evidence suggest it enhances the rate of corrosion. In all cases, the surface degradation mechanisms are related to the composition and microstructure of the alloy, although there remains significant controversy on which is the optimum microstructure. This project will seek to manufacture a range of CoCrMo alloys with varying composition and microstructure. Detailed analysis of the wear resistance will be undertaken in simulated body fluids. Detailed electron microscopy will be used to understand the deformation mechanisms that occur at the worn surfaces. Based on this information, further alloy development will be undertaken.

14 DEVELOPMENT OF NEW SHAPE MEMORY ALLOYS
Supervisors: Prof WM Rainforth, Prof I Todd

Shape memory alloys (SMAs) are well established commercial materials that have stimulated huge academic interest, the most common by some margin being Nitinol (50.8%Ni 49.2%Ti). The shape memory effect is associated with a phase transformation from the equilibrium crystal structure to a metastable martensite under the influence of applied stress or a temperature change. The transformation is reversible, simply by heating. The behaviour of SMAs clearly depends strongly on the martensite start (Ms) and finish (Mf) temperatures. A wide range of temperatures can be obtained through a wide range of alloy compositions, from the binary (Ti-V, Ti-Mo, and Ti-Nb) through the ternary (Ti-Mo-Ge, Ti-Mo-Sn, Ti-Nb-Sn, Ti-Nb-Al etc) and quaternary (Ti-25Pd-24Ni-1W). Recently, it has been realised that SMAs have interesting wear properties since substantial elastic deflections at contacting asperities can significantly reduce the local contact stress and dissipate the contact stresses through a larger volume of material. An additional issue with the use of Nitinol in biomedical applications is the potential for biotoxicity from the presence of nickel. Therefore, there is extensive international research aimed at developing Ti based shape memory alloys that do not contain nickel, using elements that are known to be bioinert. This project will manufacture and test some of these promising binary and ternary shape memory alloys (such as the Ti–30Ta–1Al and Ti–30Ta–1Sn noted above). The microstructure will be investigated in detail. The wear properties will also be explored.

15 PROCESSING AND STRUCTURE OF HIGH STRENGTH STEELS
Supervisors: Professor W M Rainforth and Dr E J Palmiere

Many key value added alloys require intercritical processing to give the required properties: high strength steels for the automotive sector for high strength:weight ratio (short term target of 1000MPa strength and 25% ductility); high strength plate steels for large diameter trans-continental gas pipelines. Regardless of whether intercritical processing involves deformation or heat treatment, product properties depend on the extent to which chemical partitioning between phases approaches equilibrium and therefore on the properties of the individual phases. In recent years there have been significant strength gains by using dual phase (DP), transformation induced plasticity (TRIP) and multiphase steels but it is anticipated that further gains will require process and composition changes. We have developed laboratory simulations which accurately replicate the whole commercial process route from hot rolling through complex intercritical anneal (including the rapid heating and cooling cycles) right the way through to the bake hardening cycle. We are therefore in a unique position to study the effect of changes to the chemical composition, particularly in microalloying, and to determine the microstructural evolution throughout the process. In high strength plate steels the sections are substantially thicker, resulting in significant microstructural gradients through the material, while the additional thermal mass of the material makes microstructural refinement more difficult. This project will make use of our world leading thermomechanical simulation equipment to develop the microstructure/property relationships as a function of process route for the latest high strength steels.

122 NEW CASTING TECHNOLOGIES
Supervisor : Dr RP Thackray

The development of technologies such as thin slab casting, direct strip casting and twin roll casting have resulted in a number of engineering challenges such as the design of materials suitable for metal delivery, design of mould and SEN systems, understanding of heat transfer and solidification, microstructural and property characterisation and the influence of roll properties on product quality. With the increasing use of new steel grades, (HSLA, TRIP, TWIP, DP) there may be a need for an understanding of the behaviour of these steels or assessment of the feasibility of these steels for use in these casting processes. This can be achieved by understanding of the heat transfer and microstructure development during strip casting use and implementation of PROCAST and CALCOSOFT continuous casting programmes to give us the capability of modelling traditional continuous casting processes but also twin roll and strip casting. Previous work has found that twin roll or direct cast material suffers from consistency issues (particularly low C steel), so additional work could concentrate on investigation of alloy chemistry on properties of strip cast material and development of thermal treatments for strip cast materials.

16 TUNDISH MODELLING AND VALIDATION
Supervisor : Dr R P Thackray (with Sheffield Forgemasters)

In the continuous casting of steel a tundish is a vessel situated between the ladle and the mould, and is primarily designed to ensure the smooth transfer of steel into the mould. But the tundish also plays a very important role in the production of reproducibly high quality steel. Rather than being seen as simply a distribution vessel or holding tank, various operations such as inclusion removal and modification, alloy addition, and temperature and compositional homogenisation, can be carried out in the tundish, and so the tundish is a key factor in the production of, for example clean steel.

Many studies have been carried out in recent years to investigate fluid flow phenomena in tundish systems, using combinations of physical and mathematical modeling techniques such as CFD, particle image velocimetry (PIV), water modeling, and pulse tracer addition to simulate the complex flow in tundishes with arrangements of dams and weirs, and to provide estimates of parameters such as residence time distribution (RTD).

However, there have been comparatively few studies which have taken a through process approach to look at the effect of tundish design on the quality of the final product. This proposal aims to do that using a combination of modeling and experimentation to study the critical issues in steelmaking and thermomechanical processing in the production of turbine rotors.

17 EFFECT OF ZrO2 ADDITIONS ON MOULD FLUX PERFORMANCE
Supervisors: Dr R P Thackray

One of the most common and damaging accidents occurring during continuous casting is the so called sticker breakout, where the solid outer shell of steel collapses, and the molten core pours through, causing operations to be shut down for long periods of time. Causes of these accidents are thought to be poor lubrication, and examination of material from a sticker breakout reveals a build up of ZrO2 at the affected site.
This project will examine the effect of ZrO2 on the properties of selected mould fluxes to ascertain whether;

i) ZrO2 affects the break temperature
ii) ZrO2 acts as a nucleation site
iii) ZrO2 significantly affects the flux viscosity
iv) ZrO2 affects the mould flux crystallinity, and therefore the heat transfer characteristics
v) A variety of techniques including viscosity measurements, hot stage microscopy, and numerical modelling will be used.

18 PERFORMANCE ON DEMAND: CONTROL AND PREDICTION OF AEROSPACE ALLOY MICROSTRUCTURES
Supervisor: Professor I Todd

Additive manufacturing technologies, such as Direct and Shaped Metal Deposition (DMD/SMD), as well as finding use in the rapid prototyping of engineering components are looking increasingly promising as rapid manufacturing methods. Until now the development of the technology has focussed on producing the required component form on-demand and for the production of one-off or non-structural components this has proved highly effective: this could be referred to as Form On-Demand (FOD). Moving this technology on from one associated with rapid prototyping to one which can be used to form structurally critical components will also require that we can produce components which have both the desired form and suitable metal microstructures: we can term this combination Performance on Demand (POD). There has been significant research effort in the field of FOD and much of the published work in the open literature on direct metal deposition technologies deals with this aspect. In contrast, there are very few widely published papers dealing with the control of solidification microstructures – the majority of the published work being concerned with Ti alloys and functionally graded materials.

Building an understanding of the solidification microstructure selection process and a predictive modelling capacity would clearly be advantageous when designing a deposition strategy, from the point of view of obtaining a component microstructure that is fit for purpose. Knowing the local solidification conditions and being able to influence control over them is also advantageous from the perspective of controlling the size and morphology of carbides, nitrides and intermetallic phases in Nickel based superalloys.

19 HIGH ENTROPY ALLOYS – A GATEWAY TO NOVEL METALLIC MATERIALS?
Supervisor: Professor I Todd

High entropy alloys are equiatomic multicomponent (usually greater than 5 elements) alloys which have been recently reported as possessing remarkable strengths (>2GPa) and deformation to failure (>20%). This combination of properties is clearly of interest but there is no clear understanding of whether a particular collection of metallic elements will lead to the formation of a suitable microstructure. These alloys – in spite of their being multicomponent – usually consist of only 2 phases bcc and fcc and the behaviour of the alloys seems to be strongly dependent on the spatial distribution and volume fractions of the two phases. This project will take an approach based on recent work related to the development of novel Ti alloys and bulk metallic glasses as a departure point and will seek to clarify the underlying mechanisms behind the formation and properties of this new class of alloys.

20 DEFORMATION MECHANISMS IN NANOSTRUCTURED HEXAGONAL CLOSE PACKED METALS
Supervisors: Professor I Todd, Dr B Wynne and Professor M Rainforth

Research in ultrafine grained (ufg) and nanocrystalline (nc) metals has concentrated, generally speaking, on fcc materials where huge increases in yield strength have been observed in pure metals and structures combining these high strengths with improved ductility have also been reported. There is less work on cph metals and the aim of this research would be to develop a deeper understanding of the mechanisms in cph metals when the grain size falls below 100nm. The influence of texture and other microstructural features such as twin density on mechanical behaviour will also form an intrinsic part of the research.

21 DEVELOPMENT OF Ti BASE ALLOYS FOR BIOMEDICAL APPLICATIONS
Supervisor: Professor P Tsakiropoulos

Titanium alloys offer several benefits for biomedical applications, including lower elastic modulus, excellent corrosion resistance and enhanced biocompatibility. Commercial purity and alpha-beta Ti alloys are the primary Ti alloys currently used for biomedical application; metastable beta Ti alloys also offer great opportunities for biomedical applications. The potential to have low modulus of elasticity is particularly important for hard tissue replacement where stress shielding, a phenomenon where re-absorption of natural bone and implant loosening arises because of the difference in elastic modulus between natural bone and hard tissue implant, is one of the primary causes requiring revision surgery. This project will investigate the design and development of Ti base alloys suitable for biomedical applications with reduced elastic modulus and close to that of the bone.

22 DESIGN AND DEVELOPMENT OF OXIDATION RESISTANT COATINGS FOR REFRACTORY METAL ALLOYS
Supervisor: Professor P Tsakiropoulos

The temperatures experienced by turbine engine airfoils with TBC coatings can approach 1150 °C. This is essentially the limit for nickel-based superalloys. In order to achieve service temperatures higher than those of nickel-base superalloys materials with significantly higher melting points are required. Currently, Nb and Mo silicide base alloys are considered as likely candidates. However, even the most oxidation resistant of these alloys would require oxidation protection with coatings. Furthermore, both Mo and Nb suffer from pest oxidation at T<800 °C. In this project single or multiphase oxidation resistant coatings/bond coats will be designed to provide oxidation protection in both the pest oxidation (<800C) and high temperature (>1100 °C) regimes. The project is suitable for PhD candidates that are interested in alloy design, phase equilibria, and microstructural characterisation using x ray diffraction and electron probe microanalysis.

23 PHASE TRANSFORMATION IN Nb SILICIDE BASE ALLOYS
Supervisor: Professor P Tsakiropoulos

The temperatures experienced by modern gas turbine engine airfoils with TBC coatings can approach 1150 °C. This is essentially the limit for nickel-based superalloys because most advanced superalloys melt at 1350 °C, chemical segregation in the superalloy can lead to incipient melting at 1270 °C and the interaction zone between the bond coat of the TBC and the airfoil can melt at temperatures less than 1250 °C. For the high-temperature applications required for the next generation of jet engines, refractory metal alloys, in particular Nb- and Mo-silicide base alloys with melting temperatures exceeding 1750 °C are considered to be the most likely candidates. In this project solid state phase transformations in selected Nb silicide base alloys that are currently under development in the Department will be studied. The project is suitable for PhD candidates that are interested in alloy design, phase equilibria, physical metallurgy and microstructural characterisation using x ray diffraction and electron microscopy and microanalysis.

24 THERMOMECHANICAL PROCESSING AND MICROSTRUCTURE ANALYSIS OF HIGH TEMPERATURE AEROSPACE ALLOYS
Supervisor: Dr B P Wynne

Aluminium and magnesium alloys are popular choice materials for introducing high strength to weight ratios in applications such as automobiles. However, in most industrial hot working operations the deforming material experiences a large range of varying deformation conditions. One such variation is the strain path which the material experiences which can vary significantly in both space and time. Therefore, knowledge of such effects on flow behaviour and microstructure evolution is important for developing accurate models of the industrial process. This project intends to investigate this by using a state of the art strain path test machine which has seamless control on strain path at strain rates close to those experienced by the material in the industrial process. The test material can be decided at the start of the project but it must be deformed at hot working temperatures. Data such as flow stress, recrystallised grain size and crystallographic texture will then be used to quantify the effects of a non-linear strain path history.

25 ELECTRON BACKSCATTERED DIFFRACTION ANALYSIS (EBSD) ANALYSIS OF THERMOMECHANICALLY PROCESSING METALS AND ALLOYS
Supervisor: Dr B P Wynne

This project will use a recently acquired field emission gun (FEG) SEM equipped with EBSD analysis equipment. Recent advances in the EBSD technique, that have significantly improved angular resolution, in conjunction with a FEGSEM have made it a feasible alternative to the TEM as a tool for quantifying deformation microstructure. Parameters such as sub-grain orientation and size, misorientation distribution, misorientation gradients, and orientations and growth rates of recrystallising grains can now be routinely quantified over a statistically significant sample size. Such variables form the basis of the newly developing physically-based equations that describe microstructure evolution in hot-worked metals. Therefore this project will examine the applicability of the EBSD technique for a wide range of thermomechanical processed alloys including aluminium, IF steel and Ti-based alloys.

(C) BIOMATERIALS AND TISSUE ENGINEERING

NON-INVASIVE IMAGING OF 3D TISSUE ENGINEERED MODELS USING A NOVEL GROUP OF FLUOROPHORES
Supervisors: Prof John Haycock, Department of Materials Science & Engineering, Kroto Research Institute, Sheffield University - Dr Nicola Green, Kroto Research Institute, Sheffield University - Dr James Thomas, Department of Chemistry, Sheffield University

Background:
We have expertise in growing 3D in vitro tissue engineered models of a number of different human tissues, including skin [1] and oesophagus [2]. In these systems cells derived from human tissue are cultured on 3D scaffolds, providing more realistic models of normal human tissue (reviewed in [3]) and also a route towards the reduction, refinement and replacement of animal use in scientific experiments (the 3Rs). By including human cancer cells within these constructs, models for the study of the impact of the tumour environment, cell-cell and cell-stromal interactions upon tumour cell proliferation and invasion have also been developed [4].

In parallel, studies have developed several novel ruthenium (II) complexes capable of binding to DNA without prior membrane permeabilisation. These molecules display quenched luminescence in aqueous media but fluoresce following interaction with DNA [5,6]. Studies on cells growing in traditional 2D cultures demonstrate these probes specifically image canonical and non-canonical DNA structures through luminescence. However, the behaviour of these probes in 3D cultures is much less well characterised.

This is an interdisciplinary project covering chemistry, biomaterials and biology. It will provide the prospective PhD student with experience in chemical synthesis, confocal microscopy techniques and tissue engineering.

Aims, objectives and rationale:
This project aims to investigate the use of this novel group of fluorescent nuclear probes to non-invasively study the growth and behaviour of cells in 3D constructs. The response of different cell types within the tissue engineered constructs will also be studied, with particular attention put upon the potential to employ these probes for cancer imaging and therapy.

The specific objectives are

1. Produce 3D tissue engineered models of human skin and oesophagus.
2. Characterise the behaviour of various ruthenium (II) complexes in 3D tissue engineered constructs – including assessing the impact of cell cycle, DNA structure and cell viability.
3. Incorporate cancer cells into the model.
4. Investigate the possibility of differential uptake and binding to the different cell types.
5. Investigate the potential for cancer imaging and therapy using the 3D tissue engineered models.

26 MAGNETIC POSITIONING OF BIOLOGICAL CELLS
Supervisors: Dr D A Allwood and Prof J W Haycock

This project will use the magnetic field from magnetic structures to position magnetically-labelled biological cells. This will be used to investigate nerve tissue generation from Schwann cells positioned with a magnetic ‘template’. Schwann cells initiate nerve growth but do not respond to chemical cues. The magnetic template will allow a physical cue of cell proximity to be introduced and for the effect of inter-cell separation to be studied. A background either in the physical or biological science/engineering is required.

27 DEVELOPMENT OF HYBRID NANOMATERIALS FOR CANCER CELL IMAGING AND THERAPY
Supervisors: Dr B Chen and Professor S MacNeil

Cancer is one of the leading causes of death in the world. Current treatments of cancer mainly involve surgery, chemotherapy and/or radiotherapy, which are highly invasive. This project proposes to develop novel hybrid nanomaterials for a minimally invasive cancer treatment approach and for cancer cell imaging, thus providing simultaneous cancer imaging and treatment for different types of cancer in particular for cutaneous melanoma. This is an interdisciplinary project covering nanomaterials, biomaterials and biology. It will involve synthesis and characterisation of hybrid nanomaterials, and assessment of the materials as potential agents for cancer cell imaging and killing behaviour by using in vitro cell cultures of cancer and normal cells and subsequently 3D melanoma model. Apart from development of the new technology, a sound scientific understanding of the materials and their performance is also expected from the project.

28 MULTIFUNCTIONAL NANOCOMPOSITE HYDROGELS FOR TARGETED DRUG DELIVERY
Supervisors: Dr B Chen and Professor J Haycock

Targeted therapy represents an attractive approach to treatment of diseases because of its potential to improve bioavailability of costly drugs and reduce side effects of toxic drugs. This is relevant for the delivery of agents to tissues in the body e.g. nerve and skin. This project aims to develop novel hydrogels containing stimulus-responsive nanoparticles and organic compounds for targeted drug delivery. A range of experimental techniques will be employed in the project, ranging from materials synthesis, characterisation to evaluation of cytocompatibility and drug delivery behaviour. The project will start by investigating the biological behaviour using in vitro cell cultures of neural, glial, epithelial and mesenchymal cells, which depending on progress will move towards a 3D in vitro tissue model. This research will potentially advance the knowledge and technology of drug delivery as well as the understanding of stimulus-responsive hydrogels as ‘smart’ drug delivery systems.

29 THE EFFECT OF PATCHING ON THE WALL AND FLOW PROPERTIES OF CAROTID ARTERY
Supervisor: Dr C K Chong

Carotid artery endarterectomy (CAE) is one of the most common vascular surgical procedures and it has remained the standard management strategy for significant carotid stenosis. However, there is still uncertainty if patching should be performed. It is unclear if selective patching is preferable to routine patching, how narrow an artery should be before it must be patched, what materials (biological or synthetic) should be used and what should be the width of the patch. These uncertainties, perhaps, are compounded by recurrent stenosis of up to 30% while the true mechanism remains unknown. There is evidence from studies on the pathogenesis of vascular diseases and on bypasses at the coronary and below-knee regions that the vessel geometry and material properties have a strong influence on thrombogenesis, intimal hyperplasia, atherogenesis, the key processes which lead to stenosis in arteries and restenosis in vascular surgery. This project aims to investigate if and how patching alters the vessel wall and flow characteristics, and how these physical parameters could influence the long-term outcome of CAE. This project involves developing a computational fluid-structure interaction model based on physiological data to address and analyse systematically medical problems. The ultimate goal is to develop a guideline for CAE on material selection and the construction of the carotid patch. The project is highly multidisciplinary and would suit an applicant with a strong fluid and solid mechanics background and an outstanding analytical and computational skills/experience with CFD/FEM modeling. Some knowledge of human anatomy/cell biology would be advantageous.

30 DEVELOPMENT AND ASSESSMENT OF SMART MECHANICALLY-RESPONSIVE AND PHARMACOLOGICALLY-ACTIVE STENTS
Supervisor: Dr C K Chong

Restenosis due to thrombosis and neointimal tissue formation are widely believed to be the consequence of vascular injury induced by balloon inflation and stent expansion associated with endovascular stent treatment. To mitigate restenosis, drug-eluting stent (DES) is now commonly-used. To achieve its purpose, this stent must be able to deliver the coated/embedded drugs and deposit strategically and effectively in targeted tissues to suppress inflammation, thrombosis, and neointimal tissue formation while encouraging endothelialisation and healing of the vascular tissues. Such delivery and deposition of drugs, however, could be influenced by interactions between the physical variables e.g. the mass transport process, the structural and morphological features of the stent and vascular wall, as well as the properties of the drugs. This project aims to develop a smart DES with functionalized polymer which could respond to the dynamic environment subjected by the blood flow to meet the therapeutic demand of the vascular tissue. An important feature of the DES would be the ability to provide sustained controlled-release of drugs/pharmacologically-active agents to induce repair of the lesion. The ultimate aim is to develop a “programmable” stent for more effective therapeutic action customised for specific vascular geometry and location. This project would suit an applicant offering strong chemistry/polymer/biomaterials background with outstanding laboratory experience/skills. Some knowledge of fluid/solid mechanics and computational modeling skills/experience would be advantageous.

31 TISSUE-ENGINEERING PRE-SHAPED VASCULAR GRAFT FOR SUSTAINED SURGICAL INTERVENTIONS
Supervisor: Dr C K Chong

Surgical intervention using bypass graft is routinely performed to treat vascular disease. However, the lack of suitable small diameter (< 5mm) vessels that could provide a sustained patency lasting the patient’s lifetime is an outstanding issue. The poor patency is a result of restenosis associated with intimal hyperplasia developing at the distal site where the graft is sutured to the diseased native vessel. While improved surgical techniques could potentially improve its patency, some studies have shown that the material properties of the graft could play an important role, while our studies have also suggested that the performance of these grafts could benefit from a properly defined anastomotic configuration at the distal sites. This project aims to develop tissue-engineered pre-shaped vascular grafts with appropriate biomechanical properties that will provide sustained surgical intervention. The overall challenge will be to develop patient-specific pre-shaped vascular graft based on specific mechanical loadings that can be used to condition tissues that would be fit for implantation at the coronary/peripheral arteries. The project involves designing a modular test-section based on our in-house developed flow-bioreactor system (FBS) for developing pre-shaped vascular grafts, developing/seeding with cells a pre-shaped scaffold and maintaining it in the FBS, characterising structural and biomechanical properties of pre-seeded and post-cultured scaffold. How the structural and mechanical properties of the scaffold and the dynamic loading conditions (e.g. flow waveforms and flowrates) affect the graft development in vitro is of interest. This project is highly multidisciplinary but would suit a student with a solid background in biomedical/mechanical/chemical/materials engineering with some experience in biomechanics/tissue engineering.

32 EFFECTS OF SCAFFOLD STRUCTURES AND MASS TRANSPORT ON REGENERATIVE PROCESSES
Supervisor: Dr C K Chong and Dr F Claeyssens

Scaffold plays an important role in tissue regenerative process which may take place either in vivo (with or without cell seeding) or in vitro (with cell seeding). This regenerative process involves cell attachment, proliferation, migration and extracellular matrix (ECM) deposition. To ensure that these events are taking place effectively, it is important that the cells are in their metabolically-active state and this requires efficient mass transfer. Studies have suggested that cellular events could be influenced by the structural properties of scaffold. However, their exact correlation and the mechanism involved are yet to be established. The proposed project aims to gain more insights on the effects of scaffold structure and mass transport on regenerative process and how tissue regeneration could be optimized. It involves (i) the design, development, and characterisation of scaffold perfusion/construct culture system, (ii) selection, fabrication and characterization (e.g. pore size, porosity, interconnectivity) of stabilized porous scaffolds, (iii) measurement/computation of mass transfer parameters (e.g. diffusivity, flow rate, shear stress distribution), (iv) culture of cell-seeded scaffold and assessment of cellular events (histological studies, metabolic activities and ECM deposition), (v) correlation analysis, and (vi) the formulation of a mathematical model to describe the correlation. This project is highly multidisciplinary allowing student to work at the interface between engineering and life sciences.

33 QUANTITATIVE ANALYSIS OF HAEMODYNAMIC FORCES ON CELLULAR RESPONSE IN CO-CULTURE
Supervisor: Dr C K Chong

Haemodynamic (or biomechanical) forces have been suggested to play important roles in arteriosclerosis, intimal thickening (IT), and restenosis related to stented arteries or surgical anastomosis. Certain flow features e.g. low mean shear stress, oscillating shear stress, abnormal temporal and spatial shear stress gradients, and high particle residence times, are found in the locations where early IT is greatest, suggesting a possible correlation between blood flow features and cellular responses, and failure of the endovascular device or surgical bypasses. This project aims to better understand this correlation quantitatively by deriving biological outputs from physical inputs extracted from well-defined/controlled experimental and computational studies. The scope of the project involves developing and characterising an in vitro EC-SMC co-culture model based on our in-housed developed flow-bioreactor system capable of reproducing highly accurate physiological flow and pressure parameters, and performing parametric studies. The mechanism/pathway involved or how certain key genes are being switched on/off or proteins being expressed/up regulated/down regulated by the biomechanical forces derived from blood flow are of interest. The project is highly multidisciplinary and would suit an applicant with a strong fluid and solid mechanics background and an outstanding computational skills/experience with CFD/FEM modeling. Some background/experience on cell culture/fluorescence microscopy/image processing would be advantageous. Biologists with a strong interest on biomedical engineering and mechanotransduction could also be considered.

34 DIRECT LASER WRITING OF VASCULATURE
Supervisor: Dr F Claeyssens

One of the most important issues problems that need to be solved for successfully tissue engineering of large and complex organs is the inclusion of vasculature in the scaffold to provide oxygen and nutrients to the growing tissue and carry away waste products.
In this project we will investigate building a synthetic analogue to these natural vascular networks via Direct Laser Write (DLW). With this revolutionary production technique, in which we use a short pulse-length (sub-nanosecond) Nd-YAG laser to produce 3D objects via two-photon polymerisation. This technique allows for the formation of tailor-made structures directly from a 3D computer model, via localised photopolymerization of materials. With this technique it is possible to construct micrometer-sized 3D features making this an ideal technique for integrating materials with biology.

We will direct write a proto-vasculature in biodegradable biocompatible polymers and use these tubes to seed a vascular network within a scaffold. This network will incorporate the appropriate growth factors to enhance vascularisation. The tissue engineering scaffold with proto-vascular network will be integrated in a bioreactor which will provide perfusion of the scaffold. The perfusion medium will be seeded with endothelial cells to build up a capillary network. We will specifically concentrate on vascularisation for skin tissue engineering in collaboration with Prof. S. MacNeil.

This interdisciplinary research project will provide the prospective PhD student with experience in polymer/biomaterials synthesis, laser-based production techniques, materials analysis techniques and cell culture.

35 CONTROLLED 3D BIOMATERIALS MANUFACTURE
Supervisor: Dr F Claeyssens

This project has a two-fold aim, (i) production of three-dimensional (3D) objects in biocompatible materials (i.e. materials that do not have toxic or harmful effects to biological systems) and (ii) application of these structures in biology.

The building of biocompatible 3D structures will be achieved via microstereolithography (SL), a laser based direct-write technique. This technique allows for the formation of tailor-made structures directly from a 3D computer model, via localised photopolymerization of materials. With this technique it is possible to construct micrometer-sized 3D features making this an ideal technique for integrating materials with biology.

Applications of this technology in tissue engineering will be investigated during this project, specifically for tissue engineering. The production of a living 3D tissue of its constituent cells starts with providing a 3D scaffold for cells to attach to and to grow in and this project will investigate the production of these ‘tissue scaffolds’. These scaffolds will be built from a biocompatible material and will give the initial rigidity to the engineered tissue, so that the cells can build up their own connective tissue or Extra Cellular Matrix (ECM). Once the ECM is built the engineered scaffold becomes redundant, so this project will concentrate on biodegradable polymers as scaffold material. We are particular interesting in producing scaffolds for neural tissue engineering.

This interdisciplinary research project will provide the prospective PhD student with experience in polymer/biomaterials synthesis, laser-based production techniques, materials analysis techniques and cell culture.

36 LASER BIOPRINTING
Supervisor: Dr F Claeyssens

This project aims to build up a laser-based printing technique for biology. This printing technique utilises the Laser Induced Forward Transfer (LIFT) process to print biological molecules onto surfaces. This versatile technique is able to print solids, viscous liquid materials and powders. Furthermore, previous work has shown that biomolecules (proteins, DNA) and even entire cells can be printed without significant degradation or denaturation. This technique enables to print complex 2D micrometer patterns of biomolecules and cells, and the project will investigate biomolecule printing on biocompatible and biodegradable materials.

This technique will produce in a first iteration 2D patterned tissue sheets, and these will be at a later stage combined to attempt the layer-by-layer build up of 3D tissues. The sheets will be constructed from biodegradable materials, so these sheets will provide an initial structure for cells to grow in, while they build up their own extracellular matrix (ECM).

This interdisciplinary research project will provide the prospective PhD student with experience in polymer/biomaterials synthesis, laser-based production techniques, materials analysis techniques and cell culture.

37 SENSING VIA RESPONSIVE HYDROGELS
Supervisors: Dr F Claeyssens, Dr J Dean and Dr D Allwood

In this project we will study the synthesis of responsive hydrogels. Hydrogels are water swollen cross-linked polymer networks, and these materials can be rendered responsive to given chemical cues via inclusion of different chemical groups in the hydrogels structure. For example via inclusion of acidic or basic groups within the hydrogel these networks become pH responsive, i.e. they change from a swollen to collapsed state with varying pH. The speed of response of these hydrogels to the chemical environment will be critically dependent on the microstructure of the hydrogels. Porous or structured hydrogels will have a fast response to the chemical. In this project we will tune the porosity of the hydrogel to optimise the response time. Additionally we will look at mechanisms to either steer or sense the chemical response.

38 SIMULATING THE CONTROL OF MINERAL GROWTH BY SOFT MATTER
Supervisor: Professor J Harding

Minerals in biological systems (such as shells, teeth and bones) grow into complex shapes, often nothing like the shapes expected from conventional crystal chemistry. Somehow, organic molecules (whether individually or in arrays) are controlling this in the environment where the mineral grows. It is likely that the mineral begins as a soft, hydrated, amorphous material and only later becomes a hard, crystalline materials. This project will use a range of simulation techniques to investigate how biomolecules and arrays of organic molecules can control the growth of minerals such as carbonates and phosphates. This project is linked to collaborations with experimental groups both in the UK and elsewhere. Most of the codes required to do this have already been written, but there will be possibilities for people to develop programming skills if they so wish.

39 TISSUE ENGINEERING OF PERIPHERAL NERVE
Supervisor: Professor JW Haycock

Peripheral nerve tissue has the potential to repair and re-grow following trauma or injury, in contrast to the spinal cord. In practice, repair is frequently not achieved because of a lack of physical and chemical guidance at an injury site. For small gap injuries (typically less than 2cm), the use of nerve guidance conduits have a basic but limited ability for redirecting growth, with early clinical trials showing some promise. Longer gap injuries are always treated by autografting, and this has the major disadvantage of patients losing donor nerve function. This project aims to advance on the design of basic nerve conduit devices by creating unaxial micro-fibres from synthetic biodegradable polymers. Fibres will contain neuronal cells and Schwann cells that are needed for the optimal provision of growth factors for aiding axon growth and myelin production. This project is multidisciplinary with training in 3D cell culture, bioreactor design, biochemical detection, confocal microscopy imaging and biomaterials science.

40 DRUG DELIVERY BY BIOACTIVE SURFACE ADHESION
Supervisor: Professor JW Haycock

This project is based on the use of potent synthetic calixarene-peptide compounds that can be used to treat biomaterial surfaces (or tissue engineered scaffolds) where inflammation is a major problem. An integrated one-stage method for reducing local tissue inflammation is expected to benefit patient health care and have socio-economic benefits. It will involve the design and use of novel analytical techniques in biochemistry / cell and molecular biology for the evaluation, design and synthesis of bioactive materials. Achieving this will therefore require an interdisciplinary approach spanning cell biology and synthetic chemistry / biomaterial science. An understanding on the use of calixarene-peptide chemistry will be expected to have commercial potential, as the proposed generic approach will be applicable to designing other biologically active peptides for many medical device / tissue engineering applications. This project will therefore be suitable for graduates with backgrounds in pharmacy, materials science, biology/biochemistry or chemistry.

41 A 3D IN VITRO MODEL FOR DRUG AND COSMETIC SCREENING
Supervisor: Prof JW Haycock and Prof S MacNeil

Existing approaches that test compounds for irritation, toxicity or inflammation consist largely of very simple cellular tests or inappropriate animal models. There is therefore an increasing need to develop more relevant and accurate reporter systems of cellular stress for developing 3D tissue engineered models for toxicity testing. A European Council Directive (76/768/EEC) will enforce developing alternative tests for irritants and prohibit the use of animals for toxicological testing from 2009. This highlights that alternative methods must replace animals traditionally used for irritation, corrosivity and phototoxicity tests. Such alternative approaches include the use of reconstructed skin equivalents that match the properties of human skin as closely as possible. Using our engineered model of this tissue we will use genetically transfected reported constructs to detect the response of toxic agents in 3D. This will be an interdisciplinary project encompassing biomaterials, cell culture, molecular biology, biochemistry and confocal microscopy.

42 DEVELOPMENT OF A 3D TISSUE ENGINEERING PERIPHERAL NERVE MODEL
Supervisor: Prof JW Haycock

Three-dimensional in vitro cell culture models are seeing a rapid rate of development, principally driven by the need for conducting studies in a more relevant environment compared to the culture of cells in two dimensions, against a background of the 3Rs (replacement refinement, reduction) in regards to animal usage and scientific experimentation. While an increasing number of mammalian tissues have been reconstructed using three dimensional techniques, often by combining scaffolds and the co-culture of cells (e.g. skin), little work has been conducted on peripheral nerve. The development of such models holds considerable value for a breadth of studies, from a basic understanding of neuronal-glial development through to the design of improved scaffolds for nerve tissue reconstruction following injury. We have recently described a controlled process for producing aligned synthetic microfibers with discrete diameters (between 1 µm to and 8 µm) and correlated the response of neuronal cells and Schwann cells separately as single cultures and as glial-neuronal co-cultures. This has also extended to using dorsal root ganglion cultures for forming aligned 3D neuronal-glial co-cultures. Thus the aim for the next stage of research is to develop the organised peripheral nerve structures which are formed and apply the model to the study of disease, in partilcuar de-myelinating condition of the nervous system. This project will be interdisciplinary and encompass biomaterials, cell neuronal culture, molecular biology, biochemistry and confocal microscopy.

43 DELIVERING AND TRACKING LIMBAL EPITHELIAL CELLS TO THE CORNEA FOR TREATING CORNEAL DISEASES
Prof S MacNeil, Dr F Claeyssens, Dr S J Matcher

Over the last 15 years the technology of culturing limbal epithelial stem cells ( LEC) from thecornea to replace damaged corneal tissue has been developed and has reached a reasonable stage of maturity. The culture of the cells does not pose a particular problem but their survival on often damaged and inflamed and aggressive wound beds is a different matter. This project relates to an ongoing Wellcome funded project between the University of Sheffield and LV Prasad Institute of Ophthalmology in Hyderabad, India where around 600 patients have received cultured LEC . The challenge now is to develop ways to improve the survival and long term clinical outcome of these cells.

This project has two distinct objectives towards this aim:

1. To improve the delivery and survival of LEC transplanted to the cornea.
2. To develop methods to track the fate of transplanted LEC on the cornea.

The approaches to delivering cultured cells to the cornea which we wish to undertake are based on producing microfabricated biodegradable scaffolds with in-built limbal stem cell niches. This is technology established in the group of Dr Claeyssens, working with Professor MacNeil. We have developed electrospun scaffolds which degrade over a matter of a few weeks but they are being designed to have a slower degrading outer ring with microfabricated pockets within them to act as artificial stem cell niches. One of the challenges of this project will be to explore different architectures of microfabricated niches and to explore material with different rates of degradation from a permanent non-degradable material through to a material that can degrade rapidly.

Assessment of delivery of LEC from the scaffold with limbal stem cell niches will be by looking at the survival and phenotype of cells within these scaffolds over periods of up to four weeks in culture. Cells will also be assessed for their ability to leave the scaffold and form a new epithelium on an ex-vivo rabbit cornea model which has been deliberately denuded of epithelium for this purpose. With respect to cell tracking, the challenge here is to explore cell tracking agents that can be used for experimental purposes (of which there are many, such as fluorescent dyes) and iron containing nanoparticles through to materials that can hopefully be translated into clinical use. Here we have two possibilities under examination – naturally occurring melanin and some recently described polypyrroles being developed as contrast agents for OCT imaging. Imaging of cells in the limbal stem cell niches and on the cornea will use confocal microscopy and optical coherence tomography.

This is a strongly multidisciplinary based project. It relates to an area of strong clinical need and will give the PhD student a strong background in tissue engineering, electrospinning, microfabrication, confocal microscopy and OCT imaging.

44 USE OF 3D HUMAN TISSUE ENGINEERED SKIN MODEL TO INVESTIGATE THE ROLE OF CALCIUM IN WOUND REPAIR, SKIN CONTRACTION AND THE DEVELOPMENT OF PSORIASIS
Supervisor: Professor S MacNeil

The MacNeil laboratory has developed 3D tissue engineered skin which has gone into clinical use and is also being used to explore many aspects of normal and abnormal skin biology (MacNeil 2007). This 3D skin model will allow us to investigate the role of calcium in normal wound healing, skin graft contraction and a very common skin pathology, psoriasis. The motivation behind undertaking these studies is that a better understanding of calcium signalling in normal and abnormal skin will lend itself to the development of pharmacological approaches to accelerate wound healing, reduce skin graft contraction and ameliorate the symptoms of psoriasis.

Hypotheses to be investigated:

1. That a temporary reduction in intracellular calcium will accelerate wound repair.
2. That temporary reduction in intracellular calcium will reduce skin contraction.
3. That the psoriatic phenotype which we can induce in this model will be associated with a low intracellular calcium and that known agents which elevate calcium (such as vitamin D) will reduce the symptoms of this disease.

This PhD project will suite a candidate with a cell biology, physiology or biochemistry background. The student will acquire a good knowledge of 3D tissue engineering , of calcium signalling and pharmacology and of skin biology and skin pathologies including psoriasis. The project will involve developing a methodology for measuring changes in intracellular calcium in the 3D skin model using multiphoton confocal microscopy. Additionally it is anticipated that the biological data generated in this model will be used to inform a computational model of calcium signalling in human skin to be undertaken in collaboration with the Institute of Bioengineering, University of Auckland.

45 IMMUNE SURVEILLANCE AND TISSUE ENGINEERING HUMAN SKIN
Supervisors: Professor S MacNeil and Prof J Haycock

Background
In normal skin biology immune cells regularly survey the skin and on detecting allergens or inflammation or any cell abnormalities will travel to the lymph node, eventually leading to the activation of T lymphocytes. These will travel back to the skin to for example, kill cancer cells. While 3D tissue engineered skin has been successfully produced and taken to the clinic ( see MacNeil 2007) attempts to introduce immune components into skin are in their infancy. In this project two types of cells will be introduced into the skin model – normal dendritic cells which are capable of responding to antigens, and also selected activated human T lymphocytes (obtained through a collaboration with Professor Rod Dunbar, Department of Biology, University of Auckland, New Zealand). The overall aim is to undertake a feasibility study of introducing immune surveillance into tissue engineered skin to make this a much more physiologically relevant model for studying skin biology and also reducing animal experimentation.

Hypotheses to be investigated:

1. That challenging keratinocytes with common allergens will lead to dendritic cell activation.
2. That reducing intracellular calcium or adding putrescine (see Harrison et al) in this model will induce a psoriatic phenotype in the keratinocytes which will lead to the activation of dendritic cells and possibly T cells when these are added to skin.
3. That introducing activated T cells will induce a psoriatic phenotype in the tissue engineered skin.

This PhD project will suit a candidate with a cell biology, physiology or biochemistry background. This project will involve a good grounding in tissue engineering and in skin immunology and will involve imaging fluorescence labelled cells within 3D skin using multipihoton confocal microscopy and also developing the use of flow bioreactors in which to study immune cell-skin cell interactions. Two conditions will be studied – that of contact dermatitis where allergans such as detergents and chromium will be used as examples of common skin sensitisers and induction of the psoriatic phenotype (using putrescine) will be used to induce a common skin condition, psoriasis, where immune cells are known to be activated.

46 USE OF HUMAN FAT DERIVED ADULT STEM CELLS FOR DEVELOPING MATERIALS FOR REPAIR OF HUMAN FEMAL PELVIC FLOOR
Supervisors: Professor S MacNeil and Prof C Chapple

Stress incontinence and pelvic organ prolapse are depressingly common in woman from middle age onwards. This is due to a weakening of the pelvic floor associated with age and childbirth. The patient’s tissues become stretched and weakened and this leads to prolapse of the uterus and/or vagina and urinary incontinence particularly under any conditions of mild stress. Over the years there have been an impressive array of surgical procedures to tackle pelvic floor weakness and stress incontinence (which often co-exist). Buttressing repair with non autologous biological substitutes is problematic as these are eventually resorbed leaving little trace and can fail quite abruptly, often from 6 months onwards. Synthetic meshes initially provide excellent mechanical strength but as they do not contain any cells they can result in erosion and we don’t have adequate long term follow up data and there is the concern that they will result in morbidity many years later. Certainly, with the reasonable expectation that we are all living longer then a condition such as stress incontinence in the early 40s requires approaches to treatment which will reliably last decades rather than a few years.

To get sustained repair it is clear that there must be cells present. The MacNeil group working with Professor Chapple have recently started to tackle this problem by undertakng a simple approach to making a new tissue engineered tissue by combining the patient’s oral fibroblasts with natural or synthetic scaffolds. This project explores an alternative source of cells for this tissue repair derived from human fat.

Hypothesis:
That cells isolated from human fat will, with relatively simple magnetic bead separation techniques, be able to take on the phenotype of either stromal connective tissue cells or of pre-angiogenic cells to then be combined and introduced into scaffold materials for repair of the weakened tissues of the human female pelvis.

This PhD project will suite a candidate with a cell biology or biomaterials background. This project will involve a good grounding in tissue engineering and adult stem cell biology and will involve imaging fluorescence labelled cells within 3D constructs using multiphoton confocal microscopy as well as electrospinning of biodegradable scaffolds. Recent work from studies of fat derived cells suggest that one can select a population of CD34 cells (as an indicator of stem cell potential) and then further divide these into those cells that express CD31 (as a marker of angiogenesis) and those cells that do not express CD31,indicative of mesenchymal stromal cells respectively. Initial experiments will work with cells selected using magnetic beads to which CD34 and CD31 antibodies are coupled, subsequently characterising the behaviour of these cells and their ability to behave as fibrous tissue producing cells and to behave as cells capable of producing blood vessels. The challenge will then be to combine these cells in appropriate ratios to produce a cell populated tissue (based on electrospun scaffolds) which can be developed for repair of weakened female pelvic tissues.

47 MICROFABRICATION AND EVALUATION OF CORNEAL STEM CELL NICHES
Supervisors: Professor S MacNeil, Dr F Claeyssens and Dr M Evans (CSIRO Melbourne)

In vivo corneal limbal stem cells live within pockets or stem cell niches known as the Palisades of Vogt of approximately 150 x 30 μm. These provide a recessed pocket in which limbal stem cells are thought to proliferate and survive. There is recent evidence (Shortt et al 2007) that these niches become shallower and less well defined in eyes from elderly patients consistent with increased corneal problems with age. One popular theory that has been proposed is that these pockets provide physical protection for the maintenance of a population of slowly dividing corneal stem cells under conditions of physical stress. However there is also conflicting evidence on the role played by stem cell niches in protection of corneal stem cells and it is difficult to study this in vivo. The aim of this project is to get a better understanding of the role, and therefore therapeutic application of, such stem cell niches by using microfabricated pockets to explore the behaviour of corneal limbal stem cells within these pockets.

Hypotheses to be explored:

1. That cells will populate microfabricated pockets made in biocompatible materials and will make an extracellular matrix to assist their attachment and growth within these pockets.
2. That pockets will provide physical protection to cells from the shear forces induced by flowing media over the cells in a flow bioreactor.
3. That pockets will lead to the generation of cells with a stem cell phenotype which can be cultured for longer than normal without undergoing terminal differentiation.

This interdisciplinary PhD project will suite a candidate with a Biomaterials or a Cell biology background. The student will acquire a good knowledge of microfabrication and of corneal cell biology and of tissue engineering for corneal defects. Microfabrication will be by micro-SL,as described with poly-caprolactone-based polymers by Claeyssens et al. 2009 .The project will also involve developing a methodology for imaging cells in polymeric microfabricated constructs using multiphoton confocal fluorescent imaging and developing a flow bioreactor for studying cells under perfused conditions. Two materials will be used to make microfabricated pockets-polycaprolactone and a patented perfluoropolymer currently used in an implanted contact lens and which will be available for research through a collaboration with Dr Meg Evans CSIRO Melbourne. The perfluoropolymer will be manufactured into a tubed ring for LEC implantation (work to be conducted at CSIRO in Melbourne). Rabbit corneal epithelial cells will be used as a model system looking at how the presence of a microfabricated pocket affects stem cell turnover, response to mechanical trauma (induced by placing cells in a flow bioreactor) and lifespan.

48 OPTICAL MEASUREMENT OF THE MECHANICAL PROPERTIES OF THE STATUM CORNEUM AND CORRELATION WITH THE CLINICAL EFFECTS OF TOPICAL
Supervisors: Dr S J Matcher and Prof M Cork (Medical School).

Optical coherence tomography (OCT) is a biomedical imaging technique related to ultrasound imaging that is widely used in clinical ophthalmology and its use in dermatology is increasing steadily also, because its combination of depth resolution and imaging depth are ideally suited to studying the epidermis and dermis. Atopic eczema is a disease which affects up to 25% of children and arises as a result of breakdown of the skin barrier allowing allergens to gain access to the immune system. Topical treatments for atopic eczema must repair this defective skin barrier in order to control the disease. Many skin medications have a greater effect on the structure of skin that one might realise. The surface stratum corneum in particular can be damaged through a breakdown of corneodesmosomes and lipid lamellae leading to a fall in the cohesive force between corneocytes which form the skin barrier. This can then lead to an exacerbation of the defective skin barrier in atopic eczema and related diseases. Currently the best way of detecting such breakdown is a procedure called tape-strip trans epidermal water loss (tape-strip TEWL). This involves stripping off the surface layers of skin cells using adhesive tape and then measuring how ‘leaky’ the skin is via the rate of evaporation of water. The need to strip of skin cells however makes this procedure unsuitable for use in widespread clinical trials of drugs and so a better alternative is needed. One possibility is to exploit the fact that a fall in cohesive forces between cells in the stratum corneum should cause a fall in its mechanical properties such as the Young’s modulus. A way of determining this number for the stratum corneum in-vivo is thus needed.

Surface elastic waves are a potential solution to this challenge. If the skin surface is subjected to a short mechanical stimulus then viscoelastic shear waves propagate away from the stimulus site at speeds of a few metres per second. The time delay for the surface waves to reach a certain distance can be measured using OCT and this speed is determined by the Young’s modulus of the skin. Theory and measurements suggest that whilst the mechanical properties of the dermis dominate for high-frequency waves (> a few hundred Hz), lower frequency waves have a speed which predominantly reflects the properties of the stratum corneum. If true for very thin layers of stratum corneum (< 40 microns) this could potentially be the ideal tool to non-invasively study the effects of drugs that damage the corneal desmosomes and could provide a surrogate marker for tape-strip TEWL that would be more suited to large-scale clinical trials. The project will combine experiment (dynamic OCT elastography), theory (finite element modelling of elastic waves) and clinical studies in order to deliver the required results.

49 OPTICAL MONITORING OF BONE REGENERATION
Supervisors: Dr S J Matcher and Dr G Reilly

The ability to regenerate bone tissue is a major goal of tissue engineering. Bone tissue is a complex biomaterial consisting of a collagen scaffold on which calcium phosphate crystals are deposited via the process of biomineralization. Current approaches to artificially recreating this material involve seeding polymer scaffolds with mesenchymal stem cells and then stimulating these cells to generate collagen matrix and deposit mineral. This process occurs in a specialised environmental chamber: the 'bioreactor'. Great interest currently surrounds the use of mechanical stimulation to promote collagen and hydroxyapatite formation and there is a recognised need for a tool that can monitor the biomineralization process in real-time and in a bioreactor. In previous work we have demonstrated that the degree to which bone tissue scatters light correlates with bone mineralization. We have also demonstrated that a novel technique, optical coherence tomography (OCT) can measure the light scattering of bone samples in a bioreactor and have related the OCT measurements to a "gold-standard" technique, quantitative x-ray computed tomography (qCT). Interestingly, we have found preliminary evidence that the changes in light scattering measured by OCT might be a more sensitive measurement of the mechanical strength of the bone than the qCT measurements. This raises the important questions a) how do the light scattering properties of bone relate to its microstructure and b) how does the microstructure influence the mechanical strength? This project will investigate the relationship between optical scattering, qCT densitometry, mechanical strength and tissue microstructure in a systematic way. Techniques to be employed include OCT, qCT, SEM and confocal Raman spectroscopy.

50 OPTICAL COHERENCE TOMOGRAPHY MEASUREMENT OF THE COLLAGEN STRUCTURE OF ARTICULAR CARTILAGE AND ITS DEGRADATION IN OSTEOARTHRITIS
Supervisors: Dr S J Matcher and Prof J M Wilkinson (Medical School)

Optical coherence tomography (OCT) is a biomedical imaging technique related to ultrasound imaging that is widely used in clinical ophthalmology and its use in other areas of medicine is increasing steadily also, because of its unique combination of spatial resolution, imaging depth and speed. An area of untapped potential is in orthopaedics and specifically the management of osteoarthritis. Osteoarthritis affects millions of people every year and is a major cause of pain and disability, especially in the old. It arises because of degradation of the articular cartilage that forms the sliding surfaces in articular joints such as the hip, knee and wrist. Articular cartilage is chiefly composed of type-II collagen, water and proteoglycans. It lacks blood vessels and thus when damaged it has a limited ability to repair itself because of a poor supply of blood-borne nutrients and growth factors. The most popular treatments include autologous chondrocyte implantation (which aims to fill small voids and defects in the collagen with a form of scar tissue) and total joint replacement (when the cartilage is so extensively damaged as to be unrepairable).

There is an urgent need to develop improved way to assess the physical condition of articular cartilage. Currently articular joints can be imaged non-invasively using x-ray or magnetic resonance imaging however the resolution is not high enough to reveal the structure of the cartilage itself. Minimally invasive video imaging (arthroscopy) is currently the best available tool to gauge cartilage degradation however it is limited to visually studying the surface of cartilage.

This project will involve developing a new experimental method called polarization-sensitive optical coherence tomography (PS-OCT) to look in detail at the 3-D collagen structure of cartilage in a rapid, non-destructive and minimally invasive way. This technique has the potential to greatly enhance the capability of arthroscopy to detect early structural changes in cartilage. It may also be of value for evaluating tissue-engineered approaches to cartilage repair, as it is a prerequisite of a tissue-engineered construct that it possess a collagen structure that is a close match to that of the native tissue it is replacing.

The project will involve experimental work using a PS-OCT system to characterise normal healthy cartilage as well as cartilage from patient donors undergoing total joint replacement treatments for severe osteoarthritis. Mathematical modelling to extract structural information from the PS-OCT data may also be involved. The goal will be to establish PS-OCT as a new tool to allow orthopaedic surgeons to assess the extent of damage to cartilage before an operation, in order to plan the extent of the joint replacement that is performed.

51 OPTICAL MEASUREMENT OF CELLULAR RESPIRATION IN BIOENGINEERED TISSUES
Supervisors: Dr S Matcher and Professor S MacNeil

Tissue engineering currently lacks reliable, non-destructive and non-invasive tools to monitor the growth and viability of artificial tissues. Optical imaging and spectroscopy offer one technology that is ideally suited to fulfilling this requirement. This project will aim to use optical spectroscopy to monitor the viability of cells cultured in an artificial matrix via bioenergetic signals from respiratory chain enzymes. At the cellular level, fluorescence spectroscopy will be used to determine mitochrondrial redox potential from the nadh/fad fluorescencne ratio. On larger tissue volumes, optical reflectance spectroscopy will be used to determine the redox state of cytochrome-oxidase. The utility of these measurements in improving the quality of artificial skin, oral mucosa, cornea etc will be fully investigated using established tissue models.

52 SPECTROSCOPIC INVESTIGATION OF THE EFFECT OF THERAPEUTIC DRUGS ON METASTATIC MELANOMA CANCER CELLS
Supervisors: Dr. IU. Rehman, Prof. S. MacNeil

This project aims to investigate melanoma cancer cell lines by Raman spectroscopy to demonstrate the biochemical differences between cell types which are resistant or sensitive to chemotherapeutic treatments.

The incidence of melanoma has increased dramatically this century, which is attributed to changed patterns of behaviour of peoples in the sun. Artificial ultraviolet light (UV) exposure allows individuals in colder climates to expose their skin to UV doses hitherto unprecedented, which has potentially grave effects on the incidence of melanoma in these populations.

One of the great challenges is not only the early detection of melanoma, but to treat with the appropriate drug. Metastatic melanoma remains a particularly difficult tumour to treat and the treatment of melanoma is still essentially surgical but there remains considerable controversy about the optimal margins of excision of the primary tumour.

Resistance to chemotherapy is one of the main problems happening during the treatment of cancer, which can lead to relapse of the condition. It is believed that a proper approach in choosing the chemotherapeutic agents can lead to better treatment results. In this study, melanoma cancer cell lines will be analyzed by Raman spectroscopy to demonstrate the biochemical differences between cell types which are resistant or sensitive to chemotherapeutic treatments.

Spectral analysis of the samples provide distinct spectra which can be used to distinguish between the cell types. The main differences will be observed in the area related to cellular proteins and nucleic acids. In addition, simple classifier technique (using specific spectral bands as classification tools) will be employed in distinguishing between resistant and sensitive cell lines.

The project is multidisciplinary in nature – it involves investigating the behaviour of well characterised melanoma cell lines and using these to evaluate how these differ with respect to changes in their proteins, lipids and carbohydrates correlating these to resistant and sensitive cell lines.

53 AN ALTERNATIVE TO ANIMAL TESTING OF BONE GROWTH AROUND IMPLANTS USING TISSUE ENGINEERING
Supervisors: Dr. IU. Rehman, Dr. G. Reilly

The proposed project aims to develop 3D in vitro tissue engineered bone to act as a pre-screening environment for testing implant materials for orthopaedic research. Currently implant materials are evaluated in crude 2D cell culture studies or in small animal models to establish whether they might enable good bone attachment. Our tissue engineered bone would be a bridge between these tests, providing a 3D bone-like matrix containing a co-culture of human cells from bone marrow, in a dynamic environment. We intent to establish whether implant materials with different bone attachment properties can be distinguished in our in vitro system.

Better methods need to be devised to test orthopaedic implant materials in a more representative environment than a 2D model, and alternative methods to animal testing need to be devised to address the limitations of current animal models and future restrictions on the use of animals in scientific research. Therefore, we intend to test the hypothesis that:

Tissue engineered bone grown in a 3D scaffold can be used as an in vitro test system to examine bone matrix growth around orthopaedic implant materials.

54 SYNTHESIS AND CHARACTERISATION OF A NOVEL BIODEGRADABLE MEMBRANE TO BE USED FOR PERIODONTAL TISSUE HEALING
Supervisor: Dr IU. Rehman

There are around more than 500 species of micro-organisms that can harbour the oral cavity, which are initiating factor for a long list of periodontal problems. According to latest survey conducted, the gum diseases or periodontal diseases are now on a hike and becoming more common than problems like fever or flu throughout the world. There prevalence is more than cancer, heart diseases, AIDS, obesity, arthritis and many other diseases in the public eye. Researchers are looking at all aspects to decrease the treatment time and enhance the healing of not just the bone but also the ligaments attached in the tooth socket.

In this project, the aim is to combine the bone regenerative and tissue regenerative agents together in a membrane to enhance healing time and efficacy. The fabrication will be through elecrtospinning, and its chemical, physical, biological and mechanical properties will be evaluated.

This project will focus on the inkjet printing of discrete layers, each of which contains a chemotherapeutic drug mainly 5-Fluorouracil on the surface of polymeric stents, which can be used for the treatment of oesophageal cancer.

55 DESIGN AND DEVELOPMENT OF A NOVEL DRUG ELUTED POLYMERIC BIODEGRADABLE OESOPHAGEAL STENT-GRAFT FOR THE PALLIATIVE TREATMENT OF SQUAMOUS CELL CARCINOMA OF THE PROXIMAL AND MID OESOPHAGUS
Supervisor: Dr IU Rehman

Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor. There is a major clinical need to improve palliative treatment for patients with advanced oesophageal cancer (squamous cell carcinoma) of the proximal and mid-oesophagus. The oesophageal stent acts mechanically by pushing aside the tumour mass, thereby reinstituting a limited oral diet, hence obviating the need for hospitalisation making it an attractive palliative option.

In the past, rigid plastic oesophageal tubes were in use two decades ago and have been replaced by metallic oesophageal stents, as there a number of disadvantages with the metallic stents requiring a dedicated expensive delivery device. In addition, due to the poor radial strength and being compressed within a delivery system, several episodes of post-deployment balloon dilatation is also needed, and still early and late complication rates involved in oesophageal stenting remain high.

Research work would focus on the development of polymeric biodegradable drug-eluted Auxetic stent-graft as serious long-term complications in oesophageal stenting can be avoided by the degradable nature of the stent. Various chemotherapeutic, immunosuppressive, and anti-neoplastic agents will be selected and coated on the Auxetic stent-graft for the programmable retarded drug release. Different techniques, such as, inkjet printing will be used for coatings.

56 POROUS TITANIUM FOR IMPROVED ORTHOPAEDIC IMPLANT DESIGN
Supervisors: Dr G Reilly and Dr R Goodall

Over 100,000 people received total joint replacements under the NHS in 2008. These implants frequently fail and require revision surgery partly due to lack of bone in-growth onto the smooth metal surface and because metals have a higher stiffness than bone. The goal of this project is to produce and validate a novel titanium orthopaedic implant structure using graded porosity. Prototype implants will be designed with a dense core that becomes progressively more porous towards the surface using sintering and rapid prototyping techniques. The core will provide mechanical stability while the graded porous architecture will be optimal for in-growth of bone cells and matrix The project will address have three key goals: 1) To compare processing methods for creating a graded interconnected porous architecture in medical grade titanium. 2) To optimise the biofunctionality of prototype implant structures. 3) To elucidate the potential for bone in-growth using a novel 3D culture method. This is a highly interdisciplinary project in which the student will learn materials processing and biological analysis and cell culture techniques.

57 USING TISSUE ENGINEERED BONE TO EXAMINE COLLAGEN AND MINERAL GROWTH AROUND METAL IMPLANTS
Supervisor: Dr G Reilly

There has recently been much interest in the use of tissue engineered structures to test procedures in vitro (outside the body) that are currently tested in vivo. For instance, tissue engineered bone, grown in scaffolds in a bioreactor environment, could be used to test how bone grows around an implant before using this type of implant clinically. This project will use cubes of tissue engineered bone, made by growing cells in 3D polymer scaffolds as a test site for implanting implants made from metals and other clinically utilised materials. The bone/implant construct will be mechanically loaded to simulate the in vivo environment. Bone growth around the implants will be imaged by microCT, confocal microscopy and histology. The results from the project will be compared with finite element simulations being performed at the University of Hull with our collaborator Michael Fagan. This project would best suit someone with a materials/ biomaterials/ engineering background but a student with a good biology background and an interest in bioengineering could also undertake this project.

58 MECHANISMS BY WHICH BONE CELLS RESPOND TO MECHANICAL FORCES
Supervisor: Dr G Reilly

Bone cells respond to mechanical forces such as those induced by exercise, therefore the cell must have a 'mechanotransduction mechanism' - a way of detecting force and transmitting it to a biochemical signal. Previous work in our laboratory has shown a small solitary cilia that sticks out of the cell called the primary cilia may be one of the ways in which force is detected. Another candidate is the coat of the cell or glycocalyx. We have shown that if we remove the primary cilia or the glycocalyx bone cells can not respond to loading so well and less bone matrix is produced. In this project we will investigate how signals from these membrane components of the cells are transmitted within the cell biochemically and how this information can be used to improve bone matrix structure for instance in elderly people suffering form diseases of low bone mass such as osteoporosis. This project will involve cell biology and biochemical techniques, microscopy and the use of fluid flow and compression bioreactors for cell stimulation.

(D) MULTIFUNCTIONAL MATERIALS AND DEVICES

(i) Ceramics

59 SIMULATING DIFFUSION IN CERAMICS AND MINERALS
Supervisor: Professor J Harding

How fast atoms move and where they end up is a major issue in understanding (and so controlling the properties of ceramics). The first is the problem of diffusion; the second the problem of segregation. This project will investigate the mechanisms of diffusion for a range of ceramics from perovskites to pyrochlores and garnets. It will also consider the segregation of atoms and ions to surfaces and grain boundaries and what difference this makes to the properties of these structures. Of static and dynamic simulation methods will be used including ab initio methods. Depending on the materials chosen, the project could link to a range of experimental work in the Department: from batteries and ferroelectric materials to nuclear waste disposal. The codes to do the calculations already exist, but there will be opportunities for writing scripts and codes if people are interested.

60 SIMULATING NANOSTRUCTURES: A MULTISCALE PROBLEM
Supervisor: Professor J Harding

Nanostructures such as quantum dots, carbon nanotubes, nanowires, nanoparticles and ultra-thin films are sometimes small enough that one can hope to simulate the entire system. Moreover, these systems have unique structures and properties because of the high surface/volume ratio. The problem is that the timescale of the processes you are interested is too long for any simulation to manage. Dynamical simulations last of the order of hundreds of nanoseconds. Processes like diffusion, film growth, self-assembly can take place on timescales of seconds to years. There is no possibility of a direct simulation unless special methods are used. A range of these have been and are being developed. This project would work in collaboration Prof Mark Rodger (Warwick) who are currently developing long timescale codes for the new HECTOR machine in Edinburgh. Depending on your interests, this project could either focus on the development of codes, or their applications to nanostructures, or both.

61 SIMULATING THE CONTROL OF MINERAL GROWTH BY SOFT MATTER
Supervisor: Professor J Harding

Minerals in biological systems (such as shells, teeth and bones) grow into complex shapes, often nothing like the shapes expected from conventional crystal chemistry. Somehow, organic molecules (whether individually or in arrays) are controlling this in the environment where the mineral grows. It is likely that the mineral begins as a soft, hydrated, amorphous materials and only later becomes a hard, crystalline materials. This project will use a range of simulation techniques to investigate how biomolecules and arrays of organic molecules can control the growth of minerals such as carbonates and phosphates. This project is linked to collaborations with experimental groups both in the UK and elsewhere. Most of the codes required to do this have already been written, but there will be possibilities for people to develop programming skills if they so wish.

62 IRRADIATION INDUCED SYNTHESIS OF NANOPARTICLES
Supervisors: Dr G Möbus

Selected compound materials can serve as precursors for the electron beam induced reduction into pure metals. Using carefully chosen irradiation conditions the reduction process can be used for the fabrication of metallic nanoparticles via a diffusion, nucleation and growth process. Of particular interest is the local fabrication of Al, Ag, and Bi nanostructures, as well as of ferromagnetic metals, e.g. Ni and Co. The study will examine: (i) Synthesis of individual particles and nanorods by live observation via in-situ TEM, (ii) Mass fabrication of nanoparticles on a support film, (iii) Metal grain crystallisation in nanocomposites and fabrication of agglomerated architectures of nanoparticles, (iv) Fabrication of metal nanobeads and study of planar defects in fcc-nanostructures. The fabrication will be accompanied by high-resolution imaging and spectroscopy, especially concerning the plasmon resonance of the freshly fabricated particles, with respect to prospective applications in nanooptics. This topic is an example of many more nanomaterials-based possible PhD topics, see
www.moebus.staff.shef.ac.uk/phdtopics.pdf.

63 ATOMIC RESOLUTION DETAILS OF CERIUM OXIDE SURFACES AND SUBSURFACE REGIONS
Supervisors: Dr G Möbus

Latest progress in imaging technology with electron microscopes allows to image ceramic particles in the thinnest areas of the object, such as corners, edges, projected surfaces, etc… The importance of these capabilities is in visualising surface reconstructions, local changes of lattice constants, and possible elemental depletion of layers.

A first emphasis is on the stability of facets against irradiation induced atomic displacements, which would be indicative of surface activity, while the second emphasis is on surface and sub-surface redox-chemistry changes, both aspects being essential for the functional applications of cerium oxide e.g. catalysts. The project is available in various flavours, depending on skills and interest of the student, including synthesis of ceria nanostructures, atomic resolution imaging and spectroscopy, and computer simulation of the image formation process of wedge-shaped model crystals.

64 HIGH RESOLUTION CHARACTERISATION OF HETEROGENEITIES IN FUNCTIONAL CERAMICS
Supervisors: Professor W M Rainforth, Professor A R West, Professor D C Sinclair and Professor I M Reaney

The performance of virtually all ceramics is controlled by interfaces, which are a source of both intentional and unintentional heterogeneity. Not surprisingly, there have been a number of extensive studies of the interface structure using techniques such as HREM, ELNES, XPS etc. Many of the successful studies have been undertaken on model systems (e.g. bicrystals of SrTiO3). Consequently, good interface structural models have been developed, but these only apply to the specific interface structure studied. Of course, real ceramics comprise a wide range of boundary types that rarely conform to the model system. The ability to characterise materials at high spatial resolution, in terms of chemical, physical and electrical structure, is currently going through a revolution. We are in a unique position to take advantage of integrating different techniques to bring a completely new insight to the microstructure/property relationships in real ceramic materials, including existing important materials such as BaTiO3, emerging materials (e.g. CaCu3Ti4O12), thin films, devices and new materials developed within the CCL. Techniques that will be used include: a) Scanned probe microscopy (e.g. Kelvin Probe Microscopy) to characterise local electrical structure: b) Focused ion beam microscopy (FIB) to extract specific boundaries that have been characterised by SPM for characterisation in the TEM. C) High resolution TEM to determine local chemical composition and bonding structure information at the interface of interest. The information from these techniques will be correlated with the processing and electrical characterisation of the ceramic.

65 SUPERSTRUCTURE/PROPERTY RELATIONS IN OXIDES AT THE MESO AND NANOSCALE
Professor I M Reaney and Prof D C Sinclair

The functional properties of oxides often arise from structural transitions which multiply the unit cell. The occurrence of superstructure reflections modes in diffraction and spectroscopic data therefore can be used to interpret the functional behaviour of oxides used in device technology. The project will focus specifically on the combination of advanced transmission electron microscopy and Raman spectroscopy and will emphasise the meso and nano scale superstructure, difficult to resolve with X-ray and neutron diffraction, but intrinsic to material properties.

66 TUNABLE DIELECTRICALLY LOADED ANTENNAS
Professor I M Reaney and Professor D C Sinclair and O Leisten (Sarantel Ltd)

The holy grail of mobile technology is to develop antennas with high efficiency and sufficient bandwidth to cover several frequencies of operation. The current generation of smart phones use antennas with a broad bandwidth but low efficiencies (~5%). Dielectrically loaded antennas offer a very high efficiency (~50%) but a very narrow bandwidth. One approach to solve this problem is to utilise dielectrically loaded antennas which are tunable under electric field. This project pursues this target application using a combination of passive low loss coupled to a tunable dielectric layer. In this manner small changes in permittivity (and thus frequency) may be obtained under the application of an electric field. The project is in collaboration with Sarantel Ltd.

67 LOW SINTERING TEMPERATURE MW DIELECTRIC CERAMICS FOR SUSTAINABLE MANUFACTURING
Professor I M Reaney and Professor D C Sinclair

Recently, several authors have published a number of MW ceramic compositions with ultra low sintering temperatures (<700 oC). The ideal target device for such materials is not clear at the present time but it is evident that such low sintering temperature (low energy cost) materials represent a major step forward towards sustainable manufacturing. This project explores ways in which low sintering temperature ceramics may be utilised in multilayer and bulk geometries to create low energy cost devices. The project will study a range materials varying from in-house composition such as Bi4B2O9 to the recently published Li2WO4.

68 ADVANCED CHARACTERISATION OF FERROELECTRIC THIN FILMS USING TRANSMISSION ELECTRON MICROSCOPY
Professor I M Reaney and Susan Mckinstry (Pennsylvania State University)

The control of the defect- and microstructure of thin films is difficult even using modern advanced deposition equipment. Often defects are present such as vacancies and low angle boundaries which affect the properties by interacting with ferroelectric domain walls and impeding their motion. It is imperative that interaction of defects with domain wall is understood to improve the performance of ferroelectric film. This project is focussed on the characterisation of films fabricated in the group of Susan Mckinstry at Pensylvania State University. The student will use advanced transmission electron microscopy to study defect domain interactions as well as the general microstructure of the films. The student will be expected to spend time in Susan Mckinstry’s group working alongside film depositors.

69 ENERGY MATERIALS: NOVEL THERMOELECTRIC OXIDES
Supervisor: Professor D C Sinclair

We are currently exploring the thermoelectric properties of solid oxides for a variety of energy-related applications. Thermoelectrics are materials that can convert heat into electricity ( in a ‘clean’ fashion) and are proving to be very useful in a raft of ‘portable’ (near room temperature) applications, eg conversion of body heat into electricity and may prove to be extremely useful for converting waste heat from high temperatures (eg > 600 oC). Current materials are based on non-oxides (eg Bi2Te3), are far from optimised and are restricted to operating near room temperature. Recently we have discovered several transition-metal containing oxides that are stable at high temperatures that have promising Thermoelectric properties and we wish to explore these compounds and their properties in more detail. The project would involve synthesis and characterisation of transition metal containing oxides and would involve crystallography (X-ray and Neutron Diffraction) for structure determination, thermal analysis (H2-reduction thermogravimetry, dilatometry, Differential Scanning Calorimetry, Thermal Conductivity), to establish the oxygen-content, the presence of phase transitions and the thermal properties (eg expansion coefficient, conductivity), electron microscopy (ceramic microstructure of ceramics) and electrical characterisation (Impedance Spectroscopy and Seebeck coefficient measurements) to establish the electrical conductivity, carrier-type and Thermo-electric power properties.

70 EXPLORING PEROVSKITE SCIENCE
Prof D C Sinclair, Prof N C Hyatt, Prof J Harding and Prof I M Reaney

Perovskite-based materials (general formula ABO3) exhibit a wide range of useful electrical and/or magnetic properties, such as ferro-/ piezo-electricity, ionic/mixed conduction, metal-insulator transitions, superconductivity and giant magneto-resistance. The key to discovering and understanding these materials and the need to modify/optimise the desired property requires knowledge about the interrelationship between chemical composition, crystal structure, defect chemistry and the desired property. At Sheffield, we study the structure-composition-property relationships of a wide variety of perovskite-based materials with useful functional properties, eg BaTiO3, Ba3LaNb3O12, BaCo1/3Nb2/3O3,CaCu3Ti4O12_ -and wish to expand our knowledge of such materials. All projects will involve some or all of the following; chemical synthesis (compositional control), crystallography (crystal structure determination), atomistic simulations (defect chemistry) and electrical/magnetic property measurements. Perovskites of general interest include; B-site deficient hexagonal perovskites (AnBn-1O3n), oxygen-deficient perovskites (ABO3-) and A or B-site ordered perovskites (A1/4A’3/4BO3, AB1/3B’2/3O3). Technologically important perovskites of interest include; (Na,K)NbO3 and (Na1/2Bi1/2)TiO3 as Pb-free piezoelectrics and doped-BaTiO3 for capacitor applications. Contact Prof Sinclair for further details.

71 DIELECTRIC MATERIALS FOR THE 21ST CENTURY
Supervisors: Professor D C Sinclair and Professor I M Reaney

Dielectric materials (ferro-, pyro-, piezo-electrics and high permittivity, low dielectric loss solids) continue to play an important role in our every day lives, eg computer technology, smart sensors and actuators and in telecommunication devices such as mobile phones and global position systems. Despite the vast array of applications there is a constant need to improve the properties of existing dielectric materials (eg. higher permittivity, piezoelectric coefficients, ferroelectric Curie Temperature and lower dielectric loss) and to find new materials with superior properties or additional functionality (eg multi-ferroics which exhibit both ferro-electricity and ferro-magnetism). For some applications, homogeneous materials are required, whereas for others it is important to engineer chemical heterogeneity (usually by chemical doping and/or close control of oxygen partial pressure), either to create core-shell regions within grains or to produce grain boundaries and/or surface layers with different composition to the grains. In these projects, samples are prepared in the form of ceramics or films and characterised by a wide variety of techniques including; X-ray, Neutron and Electron Diffraction; Scanning, Analytical and Transmission Electron Microscopy; Impedance Spectroscopy (mHz- MHz) and/or Microwave dielectric measurements (GHz) over a wide temperature range (5- 1000K). The overall aim is establish the structure-composition-property relationships in this important class of electroceramics. Please contact Prof Sinclair for more details.

72 ENERGY MATERIALS: SOLID ELECTROLYTES FOR ELECTROLYSIS CELLS
Supervisor: Professor D C Sinclair

There is current interest in using electrolysis cells based on oxide-ion conductors to covert H2O and CO2 into fuel (syn gas H2/CO). One of the limitations is the resistivity of the oxide-ion conducting electrolyte (usually Yttria-stabilised ZrO2(YSZ)). A recent advance to overcome this problem has been to make bilayers consisting of YSZ with a mixed (oxide-ion/electronic)conductor such as Gd-doped CeO2 (GDC). In this project we will use tape-casting to make ceramic bilayers of YSZ with a variety of novel mixed conductors (perovskites and/or Bi-based fluorites) and characterise their microstructure/interfaces by electron microscopy and their electrical microstructure by Impedance Spectroscopy. This should allow us to develop electrolysis cells based on bilayer electrolytes that are capable of working at lower temperatures and/or with higher efficiency. This project involves ceramic processing (eg, powder preparation, tape casting, sintering), and materials characterisation (eg X-ray Diffraction, Electron Microscopy, Impedance Spectroscopy). We will collaborate with a group in Chemical and Biological Engineering (Dr Rachael Elder) to perform testing of the electrolysis cells.

73 NEW AND IMPROVED ELECTRODE MATERIALS FOR RECHARGEABLE LITHIUM BATTERIES
Supervisor: Professor A R West

Rechargeable lithium batteries currently use intercalation cathodes based on LiCoO2 and, more recently, LiMn2O4, which give reversible charge-discharge cycling at ~3.8 V and capacities of ~ 120 mAh/g. Because of the cost and environmental toxicity of Co, and the poor long-term performance of LiMn2O4, there is much interest in finding improved cathode materials. We are currently interested in layered rock salt structured materials, such as Li(Mn,Ni,Fe)O2, which have high capacities and stable long-term cycling performance; new anion materials based on the rutile structure: new oxynitride materials for potential electrode and electrolyte applications. Projects involve a combination of solid state synthesis procedures, crystal structure determination using X-ray and neutron powder diffraction, thermal analysis to assess high temperature stability, electrical property measurements to determine the intrinsic levels of both electronic conductivity and lithium ion conductivity, electrochemical testing by constructing test cells using the new materials. We have a very well-equipped laboratory for such studies, which forms part of the EPSRC-funded Ceramics and Composites Laboratory. This is a fundamental scientific project, with outcomes of direct relevance to the lithium battery industry.

74 IONICALLY-CONDUCTING CERAMIC ELECTROLYTES
Supervisor: Professor A R West

Ceramic materials that exhibit high levels of ionic conductivity have a range of applications, depending on the conducting species, in fuel cells, battery systems and sensors. There is much interest in the discovery of new lithium-ion conducting ceramics, which, if available, could lead to the fabrication of all solid-state, thin-film lithium batteries, without containment problems associated with liquid electrolytes. Several groups of crystalline and glassy materials are of current interest, including materials with the garnet structure and other 3D framework structures. The approach to be used in this project is based on crystal engineering in which synthetic strategies are used to modify a parent crystal structure so as to open up conduction pathways by the introduction of either mobile interstitial ions or the creation of ion vacancies. The project involves a combination of synthesis by solid state reaction methods, diffraction studies to solve the structures of new phases and electrical conductivity measurements. New lithium-ion conducting solids will be tested as potential electrolytes in solid-state lithium test cells.

75 ELECTRONIC CERAMICS
Supervisor: Professor A R West

Many electroceramic materials are heterogeneous electrically and may be regarded as composites on the nanoscale, with grains and grain boundaries that have very different electrical characteristics. This category of materials has increasing applications as ceramic sensors, voltage and current overload protection devices and charge storage materials such as barrier-layer capacitors. We are investigating several groups of such materials with different structure types, including: BaTi2O5 with a complex 3D framework structure, tetragonal tungsten bronze structured phases in materials such as BaO-Nd2O3-TiO2-Ta2O5 and the classic ferroelectric, BaTiO3, doped with an amphoteric ion such as Ho3+. We are also investigating enrirely new materials including the new ferroelectrics, Ag2Nb4O11 and Na2Nb4O11. Projects are available in each of these areas; all involve sample synthesis, ceramic fabrication, microstructural characterisation by electron microscopy, crystallographic studies by X-ray and neutron diffraction and electrical property measurements, using a range of techniques. This project is part of the EPSRC-funded Ceramics and Composites Laboratory and may involve several members of staff in the Department for collaborative studies on, for instance, thin-film fabrication, electron microscopy and electrical property measurements.

76 NANOSCALE PHENOMENA IN OXIDE MATERIALS
Supervisor: Professor A R West

Many phenomena and applications, including catalysis, sensors, redox electrodes and most-recently, memristors, are controlled by nanoscale phenomena at interfaces and contacts, for instance, metal-oxide, oxide-oxide and oxide-air interfaces. In particular, absorption/desorption of oxygen molecules on/from sample surfaces frequently leads to changes in electronic structure at and below the surface of the materials. Memristor action involves charge transfer, both ionic and electronic, across interfaces. Suitable electrodes for use in solid oxide fuel cells must also exhibit interfactial charge transfer phenomena. This project will investigate recently-discovered non-ohmic phenomena in oxide ceramics through a combination of surface characterisation, electrical property measurements and advanced electron microscopy techniques.

(ii) Magnetics

77 CONTROLLED MAGNETIC BEHAVIOUR AT THE EXTREME NANOSCALE
Supervisors: Dr D A Allwood and Dr T J Hayward

The behaviour of ‘soft’ magnetic materials such as Ni80Fe20 can be controlled using the sample shape and scale. Improvements in nanofabrication techniques have led to huge developments in demonstrations of magnetic devices with a characteristic length-scale of hundreds of nanometres. This PhD will use the latest generation of nanofabrication tools to investigate magnetic behaviour in structures with a characteristic length-scale approaching 10 nm. This will make use of a new electron beam lithography system to create well-controlled structures in order to study fundamental magnetism and develop novel devices, such as memory chips. The project will give experience of thin film deposition and patterning, nanomagnetism, computational modelling and a host of structural and analytical techniques relevant to nanoscale magnetism (e.g. magneto-optical magnetometry, scanning probe microscopy, X-ray microscopy).

78 RAPID MANUFACTURE OF MAGNETIC MATERIALS FOR ENERGY APPLICATIONS
Supervisors: Prof M R J Gibbs and Dr D A Allwood

Magnetic materials are at the heart of electrical energy technologies such as transformers, motors and turbines, making them vital to an energy-efficient society. For example, just a 1 % improvement in the performance of ‘soft’ magnetic materials could lead to a 20 M tonne reduction in CO2 emissions worldwide. This PhD project will investigate new alloy compositions and processing routes to achieving improvements in the performance of hard and soft magnetic materials. Sub-micrometre thick films will be deposited by sputter deposition, while novel rapid manufacturing techniques such as inkjet printing and aerosol spray deposition will be used to create thicker samples from solution or nanoparticle precursors. This PhD project will give experience of materials fabrication techniques, energy materials and magnetic materials.

79 HIGHLY RESOLVED OPTICAL MICROSCOPY OF MAGNETIC STRUCTURE
Supervisors: Dr D A Allwood and Prof M R J Gibbs

This PhD project will seek to build and understand better analytical tools for observing nanoscale magnetic structure in bulk, thin film and nanostructured magnetic samples. Optical techniques have the potential to offer high throughput, simple sample preparation requirements, dynamic sensitivity and resolution of a few hundred nanometres but this full potential has not yet been explored. The project will also involve using the improved optical techniques to study nanomagnetic systems in new detail, e.g. domain walls in magnetic nanowires. The project will give experience of optics, thin film and nanoscale magnetism, and computational techniques for performing calculations and experiment control.

80 MAGNETIC NANOSTRUCTURES FOR TRAPPING AND POSITIONING ULTRACOLD ATOMS
Supervisors: Dr D A Allwood and Dr T J Hayward

Certain magnetic nanostructures and magnetic configurations can be used as nanoscale sources of magnetic field. These fields can be strong close to the magnetic surface and have extremely large field gradients, making them good candidates for controlling a secondary system. This project builds on our existing collaboration with atomic physicists at the University of Durham to use the stray field from magnetic nanostructures to trap ultra-cold (sub-milliKelvin) atoms. The magnetic structures will either be made from low magnetocrystalline anisotropy materials, such as Ni80Fe20, with in-plane magnetisation or high anisotropy materials, such as CoPt, with out-of-plane magnetisation. The project will involve developing suitable nanostructures for atom trapping/transporting and understanding better the magnet-atom interaction. This will be achieved using experimental and computational techniques. The long-term goal of this project is to develop magnetic atom chip architectures to perform quantum computation algorithms.

81 MULTIFERROICS
Supervisors: Professor M R J Gibbs, Professor I M Reaney, Dr D A Allwood

As functional materials have to become “smart” in new ways to meet the demands of a growing range of sensor and actuator applications, so multiferroic materials have come under the spotlight. A multiferroic material usually demonstrates both ferroelectric and ferroelastic properties. Whilst the search goes on for monolithic materials showing high multiferroic coefficients above room temperature, this project will study the alternative route of composites of two or more materials with components showing either ferroelasticity of ferroelectric response. In making the composites careful consideration has to be given to interfaces and their effect on overall response. Composites will be made using deposition techniques and/or traditional bonding strategies and performance will be assessed. The project will involve careful materials preparation and a range of characterisation techniques including detaild electron microscopy of the interfaces. A number of applications, including switchable data storage, will be investigated. Micromagnetic and mechanical modelling will support the studies.

82 MAGNETOSTRICTION IN THIN FILMS
Supervisors: Professor M R J Gibbs and Dr J S Dean

A number of ferromagnetic alloys (FeCo. FeGa, a-FeSiB) exhibit large saturation magnetostriction constants; that is an applied field can cause significant dimensional change, or applied strain can change the state of magnetisation. In the form of thin films magnetostriction can be a source of unwanted anisotropies (e.g. NiFe in data storage read heads) or a route to increased device functionality (e.g. in microelectromechani9cal systems (MEMS)). This project will look at routes to the control of magnetostriction in thin films, and its optimisation in such applications as magnetic MEMS. Various thin film deposition (sputtering, thermal evaporation) and characterisation techniques will be used, and modelling of both the micromagnetics and overall systems will be used. There are already a number of known applications in the MEMS area.

83 SIMULATING MAGNETIC NANOPARTICLES
Supervisor: Professor J Harding with Dr C L Freeman

There are increasing numbers of exciting and dynamic uses for magnetic iron-oxide nanoparticles; for example in magnetic resonance imaging and high density media storage. New methods are needed to produce regularly-sized and shaped particles. Current methods are not simple or cheap and required the use of organic solvents or very high temperatures. However, nature has been producing ordered magnetic particles for two billion years. This project will investigate the methods used by magnetotactic bacteria to control the growth of iron oxide particles using computational modelling in collaboration with experimental groups at Leeds. Computational methods will be used to build up models of the magnetite-water interface which will explain the stability of the observed crystal morphologies. The effect of proteins on this interface can then be simulated. How do these molecules bind to the iron oxide surfaces? Do they stabilise particular crystal surfaces? Understanding and control of growth is an ambitious and exiting project which will improve scientific methods and offer benerfits to healthcare and technological systems.

84 UNDERSTANDING AND CONTROLLING STOCHASTIC BEHAVIOUR IN NANOMAGNETIC DEVICES
Supervisor: Dr T J Hayward

Nanomagnetic and spintronic technology is of great importance in many key applications, not least through its now ubiquitous usage in both the read-sensors and storage media of contemporary hard-disk drives. Many other promising nanomagnetic technologies are also under development including magnetic memory devices, devices for medical diagnostics, magnetic logic technologies and microwave resonators. In all of these devices “stochastic” thermal effects introduce randomness into the magnetic behaviour, limiting a device’s effectiveness and inhibiting development of lab-based prototypes into fully fledged technologies. This project will attempt to use a combined experimental and modelling approach to understand, predict and mitigate the effects of stochastic behaviour, thus overcoming an inhibitive problem in the development of new technology.

85 CONTROLLING MAGNETIC DOMAIN WALL BEHAVIOUR IN-PLANE/OUT OF PLANE NANOWIRE SYSTEMS
Supervisor: Dr T J Hayward

The properties of domain walls confined within planar ferromagnetic nanowires are currently of great interest due to their particle-like properties that allow them to be propagated controllably around nanowire circuits in a manner analogous to the movement of electrical charge in standard microelectronics. This has led to designs for memory, sensor and logic devices that use DWs to separate binary data, represented by uniformly magnetised domains. In the past most device designs have been based around “soft ferromagnetic materials” where the materials magnetisation lies in the sample plane and device geometry plays a dominant role in determining magnetic behaviour. More recent studies have favoured the use of “perpendicular anisotropy” materials, where the device’s magnetisation is perpendicular to the sample plane. However, in these systems magnetic behavior is much less sensitive to device geometry making it harder to control. In this project we will attempt to combine the useful properties of perpendicular anisotropy materials with the shape dependent properties of soft ferromagnetic materials by creating hybrid systems that contain nanowires fabricated from both kinds of material.

86 CRYSTALLINE AND AMORPHOUS Fe-Ga-Si-B FILMS
Dr N A Morley and Professor M R J Gibbs

The recently discovered Fe-Ga is a novel magnetostrictive alloy, which has great potential for practical applications. This project involves the fabrication of Fe-Ga-Si-B films using dc sputtering and evaporation, in an unique deposition chamber. The additions of Si should produce amorphous films, which in principle could have higher magnetostriction constants compared to the crystalline films. The project will investigate how the magnetic and structural properties of the films vary with composition, with the aim to achieve films with large (>60ppm) magnetostriction constants. The magnetic and structural properties of these films will be characterised using a range of techniques, including magnetometry, XRD, AFM/MFM and electron microscopy.

87 MAGNETIC SHAPE MEMORY ALLOYS
Supervisors: Dr N Morley and Prof I Todd

Magnetic shape memory alloys have giant magnetic-induced strains due to the reorientation of the martensitic variant. This project investigates the magnetic and structural properties of Ni-Fe-Ga as a function of composition in both bulk and thin films. Its aim is to develop a phase diagram which gives the composition at which the largest induced-strain occurs as a function of thickness. The films will be fabricated using a co-sputtering-evaporation technique, while the bulk samples will be fabricated using arc-melting. The structure and magnetic properties will be characterised using a range of techniques including XRD, electron microscopy, magnetometry and strain measurements.

88 DESIGN AND DEVELOPMENT OF A MEMS ENERGY HARVESTER
Dr N A Morley, Dr D A Allwood and Professor M R J Gibbs

Energy harvesters are devices which convert mechanically motions such as vibrations into electrical energy. Energy harvesters can be used for applications where a long-lasting portable power source is required. One application where energy harvesters could be beneficial is in micro-electrical mechanical systems (MEMS), where they could be used rather than batteries to power the devices. This project uses the computer simulation programme COMSOL to design a MEMS energy harvester using magnetostrictive materials. Once the optimum overall design and materials have been determined, the MEMS device will then be fabricated and tested, using the equipment available in the SCAMMD group.

(iii) Polymers

DEVELOPING IMPACT RESISTANT POLYMERS AND COMPOSITES
Supervisor: Dr J Foreman

Fracture toughness measures the ability of a cracked material to resist fracture but it is notoriously difficult to measure accurately and consistently. Recently, we have developed a model based on Griffith fracture mechanics which can predict the fracture toughness for amorphous polymers. The technique takes advantage of the power and speed of Group Interaction Modelling to accurately predict the properties of polymers. The project will involve developing the model to predict fracture toughness across a range of amorphous polymeric resins (e.g. epoxy, phenolic), temperatures and strain rates. Alongside this, an experimental programme will be implemented to provide validation data for the model. Ultimately the model will be used to help develop more impact resistant polymers and composites.

RAPID MULTI-SCALE MODELLING OF POLYMER COMPOSITE STRENGTH
Supervisor: Dr J Foreman

The strength of a polymer composite system is difficult to predict with accuracy due to the huge number of variables associated with a multiphase system. These include complexity associated with linear elastic reinforcements embedded in a thermosetting polymer matrix which displays strain rate dependent viscoelastic properties. Recently, we have developed a multi-scale model which predicts the strength of a polymer composite as a function of temperature and strain rate based on Group Interaction Modelling of polymer properties. The material properties are used to populate a FE/statistical model which predicts composite strength via the transfer of strain between adjacent fibres. This project will involve developing the multi-scale model and comparing it to a range of experimental validation measurements. The overall aim of the project will be to use the model to develop stronger composites by fine-tuning the properties of the constituent materials.

HOW IS THE SERVICE LIFE OF POLYMER COMPOSITES AFFECTED BY ENVIRONMENTAL DEGRADATION?
Supervisor: Dr J Foreman

Over an extended period of time, water and other diluents play a significant role in degrading the properties of polymers and polymer composites. The effects can be rapidly and accurately predicted using a newly-developed modelling technique called Group Interaction Modelling. The main innovation in this project will be to design an extension to the existing model that will predict the amount of diluent each polymer can absorb over time based on the underlying chemistry. This will also involve empirical measurement of water uptake to provide validation and parameterisation. The model will be used to predict how subtle changes to the polymer chemistry or any additives present can be used to enhance the service life of polymer and composite parts.

POLYMER DISCOVERY: SCREENING THOUSANDS OF POLYMERS USING HIGH-THROUGHPUT MODELLING
Supervisor: Dr J Foreman

Drug Discovery is an established technique used in the pharmaceutical industry to screen many thousands of potential candidates for efficacy before expensive and time-consuming experimental synthesis begins. The same principles can be applied to the development of polymers due to recent developments in Group Interaction Modelling. Importantly, the technique allows the rapid prediction of polymers properties and will therefore be developed into a new tool called ‘Polymer Discovery’. This project will develop such a high-throughput model and apply it to arrays containing several hundred polymers or more, many of which will be ‘new’. Samples of the best candidates will then be manufactured and tested to assess how well the model works. The eventual aim of the project is to use the tool to provide new materials and directions for polymer science.

89 SURFACE ADSORPTION AND CHARACTERISATION OF FUNCTIONALISED GRAPHENE NANOSHEETS
Supervisors: Dr B Chen, Professor G Ungar and Dr X Zeng

Graphene, an atom-thick layer of carbon atoms, demonstrated great potential to be used in next-generation molecular devices, nanomedicine, composites,etc. Since 2004 it has attracted substantial interest from Materials Scientists, Physicists and Chemists, and it won its discoverers the Nobel Prize for Physics in 2010. However, many of the fundamental issues in relation to this highly promising material remain unresolved. This project aims to investigate surface chemistry and properties of functionalized graphene nanosheets for manipulating their engineering or functional properties. It involves preparation and functionalization of graphene nanosheets, surface adsorption of nanosheets and characterization of surface properties at the molecular level by using a range of advanced techniques such as grazing incidence small-angle X-ray diffraction, transmission electron microscopy, atomic force microscopy and nanoindentation, in combination with molecular simulation.

90 POLYMER/GRAPHENE NANOCOMPOSITES
Supervisor: Dr B Chen

Polymers and Polymer Composites represent two important classes of materials and can be found in a wide variety of applications including transportation, construction, energy and healthcare. Based on the extraordinary intrinsic properties of graphene (i.e., an atom-thick layer of carbon atoms) such as high strength, stiffness and specific surface area, this project aims to develop graphene-reinforced polymer nanocomposites including biodegradable materials for enhancing the performance and application of existing polymers and composites. It will address two main challenges: (a) scale-up production of high-performance nanocomposites by using cost-effective approaches; and (b) tailing engineering properties according to end-product requirements. The potential candidate will receive training in a broad spectrum of techniques in relation to polymer processing, nanomaterials engineering, micro- and nano- structural characterization, evaluation of processing and engineering properties and beyond.

91 NANOMECHANICAL PROPERTIES OF POLYMERS
Supervisor: Dr S A Hayes

Nanomechanical testing or polymers is not as straightforward as for hard elastic materials, due to their inherent viscoelasticity. They are also frequently used as thin coatings on much harder substrates, and thus it can be difficult to determine the properties of the polymer independently from those of the substrate. Projects under this heading will therefore seek to facilitate a better understanding of the mechanical performance of polymeric materials under nanoindentation, either in the bulk or as thin coatings. The eventual aim is to allow the obtention of a full master curve of the polymers properties using conventional nanoindentation techniques.

92 IMPROVING THE TOUGHNESS OF COMPOSITES
Supervisor: Dr S A Hayes

Laminates produced from unidirectional composite pre-preg are well-known to be susceptible to impact damage, which produces extensive delaminations between layers with different orientation. While there are methods of reducing damage, it is still a major concern when designing composite components, and prevents full optimisation of the mechanical properties. This project will employ patterned interleaves between plies, with controlled mechanical properties, in order to dissipate the impact energy though mechanisms other than fracture. Optimum interleaf patterns will be established using modelling techniques, and the predictions of the model assessed experimentally. The toughness of new systems will be compared with traditional composites to assess the degree of toughness control that the new approach provides.

93 MECHANICAL PROPERTIES OF ALIGNED NANOCOMPOSITE MATERIALS
Supervisor: Dr S A Hayes

This project seeks to manufacture nanocomposite materials with controlled orientation of the reinforcement phase, in order to maximise the influence of the reinforcement on the mechanical properties. In conventional fibre reinforced composites, the maximum mechanical advantage is obtained when the fibres lie in the loading axis. However, with nanocomposites this is difficult to achieve. Currently nanocomposites have been shown to give significant improvement in the mechanical properties of rubbery polymers, but in glassy systems, success has been more elusive. This could be due to the misorientation of the reinforcement, meaning that it effectively acts as a flaw in the polymer, initiating the fracture process. By controlling the orientation it is hoped that such problems can be eliminated and the mechanical properties of nano-scale reinforcements fully exploited.

94 SELF-HEALING POLYMERS AND COMPOSITES
Supervisors: Dr S A Hayes

This project will continue development of recently patented self-healing technologies, which can currently enable an epoxy resin to recover 70% of pre-fracture load upon healing without the addition of new material. It is the aim to apply this technology in the field of advanced composites and also in adhesive resins. Projects are available in both of these areas depending on the applicants’ interests and experience. Typically, projects would involve the development and characterisation of new healing resins using guidelines that exist, followed by investigations into the technology to further our understanding of these novel functional resin systems and facilitate their adoption in commercial applications.

95 RENEWABLE RESOURCES
Supervisors: Prof. G. Ungar, Dr. X. Zeng

Aliphatic polyesters and copolyesters have green credentials both because they are biodegradable and because they can be synthesized from renewable resources such as vegetable oils. However, the mechanical properties do not match those of aromatic polyesters such as PET. Furthermore, aliphatic polyesters are highly susceptible to degradation during processing. For this reason hybrid aliphatic-aromatic copolyesters are being investigated, that would combine the best of aliphatic and aromatic polyesters. It is however important to retain a high level of crystallinity, a property not normally associated with random copolymers. This project will try to help solve this problem by investigating the distribution of aliphatic and aromatic units between the different crystal forms and between crystalline and amorphous domains. In addition to optical and electron microscopy, X-ray diffraction, thermal techniques, and computer modeling, a new technique of neutron fibre diffraction on selectively labeled copolymers will be developed.

96 CONTROLLING SELF-ASSEMBLY OF METAL NANOPARTICLES, QUANTUM DOTS AND GRAPHENE BY DIRECTED MORPHOLOGY OF SEMICRYSTALLINE POLYMERS
Supervisors: Prof. G. Ungar, Dr. X. Zeng

Controlling spatial arrangement of nano-objects is one of the primary concerns of nanotechnology. For example, by ordering gold or silver nanoparticles into strings, layers or 3d superlattices one can tune plasmonic resonance and potentially create negative dielectric permittivity, negative magnetic permeability, or even negative refractive index for applications including “invisible” metamaterials. Similarly embedding semiconductor quantum dots and coupling them with a periodic structure of the surrounding matrix can create new types of lasers and other optoelectronic devices. Attempts to achieve these goals often involve blends of nano-objects with block copolymers or, more recently, liquid crystals. In contrast, this project will focus on utilizing the natural tendency of semicrystalline polymers to create periodic structures on different length scales and harness this property to create controlled ordered arrays of nanoparticles, quantum dots and grapheme layers in novel types of nanocomposite.

97 PERIODIC AND QUASIPERIODIC MOLECULAR HONEYCOMBS AND NANOFRAMEWORKS
Supervisors: Dr. X.B. Zeng and Prof. G. Ungar

It has been shown recently that by combining incompatible rigid and flexible segments in one molecule, and adding weakly interacting groups, one can create novel self-assembled organic structures resembling honeycombs and scaffold-like frameworks. These can have different symmetries and can be modified to serve as catalysts, control-release materials or templates for nanoporous ceramics. Furthermore, there are indications (X.B. Zeng et al., Science 2011, 331, 1302) that some of the honeycombs may be quasicrystals, i.e. having symmetries beyond those achievable by periodic lattices, similar to those recently discovered in supramolecular dendrimers (X.B. Zeng et al. Nature 2004, 428, 157). The discovery of first quasicrystals has earned D. Shechtman the Nobel Prize in 2011. If successful, the new quasicrystalline honeycombs could act as a model for materials with very wide photonic bandgap, acting as media for creating photonic integrated circuits. These new structures will complement those comprised of molecular networks, also being studied in Sheffield (see Zeng et al., Nature Materials 2005, 4, 562). In the projects these emerging materials will be investigated using X-ray (synchrotron) and neutron scattering and atomic force microscopy – see also Chen et al. Science 2005, 307, 96.

(iv) Nanomaterials

CHARACTERISING THE NANOSCALE MORPHOLOGY OF POLYMER: FULLERENE PHOTOVOLTAIC BLENDS
Supervisors: Dr C Rodenburg (Materials Science & Engineering) and Prof. D. G Lidzey (Physics & Astronomy)

A fully funded studentship is available (for UK, EU nationals only) to join the Shine Centre for Doctoral Training starting in October 2013 with a project focused on advancing the development of Organic photovoltaic devices (OPV) through pioneering microscopy techniques in order to understand the complex structures which are critical to OPV operation. OPV could contribute substantially to clean electricity generation, provided devices can be made to operate with high efficiency, have extended lifetime and to be manufacturable at low-cost with high volume. Your task will be in advancing existing microscopy techniques to extract structural and chemical information on multiple length scales, and combine this with electrical measurements on device structures to address issues such a lifetime and high volume manufacturing of OPV. This cross faculty project is jointly funded and supervised the Faculty of Engineering and the Faculty of Science.

Please contact Dr Cornelia Rodenburg ( c.rodenburg@shef.ac.uk ) for more details or submit applications www.sheffield.ac.uk/postgraduate/research/apply by the end of February 2013.

98 SIMULATING MAGNETIC NANOPARTICLES
Supervisor: Professor J Harding with Dr C L Freeman

There are increasing numbers of exciting and dynamic uses for magnetic iron-oxide nanoparticles; for example in magnetic resonance imaging and high density media storage. New methods are needed to produce regularly-sized and shaped particles. Current methods are not simple or cheap and require the use of organic solvents or very high temperatures. However, nature has been producing ordered magnetic particles for two billion years. This project will investigate the methods used by magnetotactic bacteria to control the growth of iron oxide particles using computational modelling in collaboration with experimental groups at Leeds. Computational methods will be used to build up models of the magnetite-water interface which will explain the stability of the observed crystal morphologies. The effect of proteins on this interface can then be simulated. How do these molecules bind to the iron oxide surfaces? Do they stabilise particular crystal surfaces? Understanding and control of growth is an ambitious and exciting project which will improve scientific methods and offer benefits to healthcare and technological systems.

99 STABILITY OF NANOSTRUCTURED BATTERIES
Professor B J Inkson

Many machines vital for modern-day living, including computers, phones and cars, rely on batteries for their function. The development of improved portable energy storage, in the form of batteries, has several key issues including improving capacity and durability whilst simultaneously shrinking battery size. A key problem for battery electrodes is their microstructural stability; high surface area nanomaterials such as nanorod arrays have great potential for electrode and energy applications, however potential problems include nanorod coarsening or dissolution, deformation due to stress (poor mechanical properties), and electrically-induced breakdown.

This project will examine the stability of nanorod arrays for lithium batteries. Nanoelectrodes will be characterised before and after functional testing to determine key stability parameters. In particular, Sheffield NanoLAB technology will enable unique assembly of nanoscale battery circuits, and real-time in-situ imaging of Li loading and electrical nanotesting of the nanoscale functional units within the battery architechtures (such as individual nanorods), enabling dynamical nanoscale break-down mechanisms to be evaluated. This project will be a collaboration with Prof Xiang Yang Kong, Institute of Materials for Mobile Energy, at Shanghai Jiao Tong University (SJTU).

100 NANOSCALE FRICTION EVALUATED BY DYNAMICAL in-situ TEM
Professor B J Inkson

Tribology processes such as friction and wear affect all technology with moving parts. Although many friction (loss of energy) and wear (loss of material) processes occur at the nanoscale, it is extremely difficult to characterise the dynamics of these non-uniform events. Here at Sheffield NanoLAB we have built a new mechanical triboprobe miniaturized to fit inside an electron microscope which will enable two surfaces to be videoed as they rub against each other, and enable real-time evaluation of nanofriction and nanowear.

In three available PhD projects the TEM triboprobe will be used for ground-breaking research into
(a) friction of graphene
(b) friction of carbon nanoparticles including nanodiamond
(c) dynamical friction of ultrathin surface coatings systems

The microstructural changes and conversion of energy occurring during nanoscale impacts of individual particles, and frictional nanocontacts between rubbing surfaces, will be characterised in real-time using high resolution advanced ion and electron microscopy techniques. See www.nanolab.org.uk.

101 NEW MATERIALS FOR WELDING AND SOLDERING AT THE NANOSCALE
Professor B J Inkson

One of the central challenges for the construction, integration and repair of nanoscale systems is to develop reliable methods and materials for joining individual nanoobjects together and to substrates. Although a number of localized joining methods suitable for individual nanoscale objects have recently been proposed, including thermal & laser heating and ion beam deposition of material, they generally lead to some degradation of the nanostructure involved.

In this project nanoscale welding, using nanovolumes of metal solder, will be developed which should radically improves the spatial resolution, flexibility and controllability of nanoscale joins and welds. The use of solder to bond nanoobjects together should offer the opportunity to tailor the mechanical and functional properties of weld by controlling the chemistry, structure and volume of solder material used. A range of nanoscale solder materials will be fabricated, and the influence of solder particle size and chemistry on melting behavior and joining/welding performance will be evaluated using advanced microscopy methods including 3D tomography and in-situ functional testing.

102 3D IMAGING OF TEETH AND TOOTHPASTES
Professor B J Inkson

Our teeth are highly complex structures, engineered at the nanoscale. But they are also under constant attack by oral bacteria and acids from modern foods and fizzy drinks. Using toothpaste is our first line of defence against damage, so it is of great interest to evaluate how toothpaste materials interact with tooth enamel and dentine to reduce bacteria and staining, and manage tooth sensitivity.

This project will use a range of advanced 3D microscopy techniques including X-ray, ion and electron tomography to evaluate the 3D structure of teeth. The interaction of a range of toothpaste particles with the tooth nanostructure will be investigated in 3D to quantify and improve the functionality of toothpastes. In particular it will be systematically investigated whether a reduction in particle size to the nanoscale influences abrasion, surface modification and dentine tubule occlusion processes.

103 LOOKING INSIDE MATERIALS: NANOTOMOGRAPHY AND 3D NANOMETROLOGY
Supervisor: Dr G Möbus

Nanomaterials are intrinsically 3-dimensional materials, as their properties depend on surface-proximity and confinement of electronic or mechanical properties as low dimensional matter. Imaging of surfaces or planar cross-sections is no longer sufficient. In this project we develop new acquisition sequences and new data reconstruction procedures for applying the established technique of computed axial tomography (CAT) to nanomaterials, with special emphasis on 3D chemical and structural mapping. State-of-the-art aberration corrected electron microscopy is available for projection imaging. Applications will e.g. comprise nanoparticles, nanoparticle composites, functional nanotips and nanoporous materials.

104 NANOPATTERNING FOR ENGINEERING OF NOVEL DEVICES AND SURFACES
Supervisor: Dr G Möbus

We use electron beams to drill or cut patterns with sub 5nm dot resolution into inorganic substrates. The research concentrates especially on the physical origins of the ultimate resolution limit of this technique and the chemical processes taking place during ablation of atoms. A second central aim of the project is to study sublattice depletion (such as to remove anions only from a compound) to leave conductive or magnetic purely metallic material behind. Another aspect is the analysis of freshly milled patterns via nanoscale spectroscopy inside the transmission electron microscope. Prospective applications include nano-circuitry, nano-optics, patterns for nanoscale templating.

105 COMPUTATIONAL SIMULATION OF ATOMIC RESOLUTION IMAGING OF NANOPARTICLES WITH ABERRATION CORRECTED TEM
Supervisor: Dr G Möbus

Using latest equipment in the field of transmission electron microscopy, small particles can be mapped for structural and morphology changes down to a single monolayer or atom. The interpretation of images however often requires the understanding of the image formation process from a viewpoint of electron waves. In this project existing computer simulation software shall be used to predict and model the formation of images and diffraction patterns for the new Sheffield aberration corrected TEM facility (Kroto Institute). The project is complemented by post-processing computational evaluation of digital experimental micrographs of nanoparticles, and the student will participate in assisted imaging sessions to generate test data.

106 SELF-ASSEMBLED MOLECULAR WIRES AND LIQUID CRYSTALS IN INORGANIC NANOTEMPLATES
Supervisors: Prof. G. Ungar, Dr. X. Zeng

Straight one-dimensional electronic conductors of nanometre thickness can be produced by self-assembly of conjugated organic molecules or macromolecules. The idea is to incorporate them into molecular-scale electronic circuits. This project will utilize columnar and other types of liquid crystals and incorporate them into nanochannels and nanogrooves produced by electrochemical etching of alumina or ion etching of silicon. The diverse orientation patterns of these high charge mobility “molecular wires” will be investigated. Potentially these composited could result in new materials for molecular electronic and near-field optical devices. Small-angle X-ray diffraction, electron microscopy and high-resolution AFM will be the key characterization techniques, including collaboration on 3D electron tomography.

107 HOLLOW NANOPARTICLES AND NANOFIBRES
Supervisors: Prof. G. Ungar, Dr. X. Zeng

In this project inorganic and organic nanoparticles and their assemblies will be studied, including silica and titania hollow nanoparticles, as well as core-shell particles with conducting polymer shells. Furthermore, novel perforated (hollow) silica nanofibres will be studied, both on their own and enclosed in nanochannels in anodized alumina membranes. Among the potential applications of these materials are controlled drug release, optoelectronic devices, special catalysts, biomedical and environmental sensors and quantum dots. This project spans the areas of inorganic nanoparticles, polymers and liquid crystals. Analytical techniques based on X-ray, neutron and electron diffraction, as well as electron microscopy and AFM will be applied, in combination with molecular simulation. A particularly important technique will be grazing incidence small-angle X-ray scattering (GISAXS) using synchrotron radiation.

108 ARRANGING METAL NANOPARTICLES WITH LIQUID CRYSTALS
Supervisors: Dr. X. Zeng and Prof. G. Ungar

Nanoparticles based on metals, metal oxides or sulphides are currently of great scientific and technological interest. The coverage of nanoparticles with organic groups not only enhances the processability (e.g. solubility) of such systems, but, where suitable functional groups are included, it also allows applications in areas ranging from optics, electronics, and catalysis to biomedical research and medical diagnostics. The novelty of this project is in that the metal nanoparticles will be coated with liquid crystal molecules of different design, so as to achieve previously unavailable modes of 2d and 3d ordering on surfaces and in the bulk. Such use of directed self-assembly would produce arrays and gratings with novel electronic, magnetic and photonic properties. Preliminary studies have already produced several new nanolattices, containing ordered strings of gold nanoparticles with controllable particle spacings (see Zeng et al., Adv. Mater. 2009, 21, 1746). The project is part of the European network NANOGOLD, aiming at generating metamaterials for advanced optical applications.

(E) MULTISCALE MATERIALS MODELLING

109 SIMULATING THE GROWTH OF BIOMATERIALS
Supervisor: Professor J Harding

Minerals in biological systems (such as shells, teeth and bones) grow into complex shapes, often nothing like the shapes expected from conventional crystal chemistry. Somehow, organic molecules in the environment where the mineral grows are controlling this. It is likely that the mineral begins as a soft, hydrated, amorphous material and only later becomes a hard, crystalline materials. This project will use a range of simulation techniques to investigate how a variety of organic molecules can control the growth of carbonates and phosphates. This project is linked to collaborations with experimental groups both in the UK and elsewhere. Most of the codes required to do this have already been written, but there will be possibilities for people to develop programming skills if they so wish.

110 SIMULATING DIFFUSION IN CERAMICS AND MINERALS
Supervisor: Professor J Harding

How fast atoms move and where they end up is a major issue in understanding (and so controlling the properties of ceramics). The first is the problem of diffusion; the second the problem of segregation. This project will investigate the mechanisms of diffusion for a range of ceramics from perovskites to pyrochlores and garnets. It will also consider the segregation of atoms and ions to surfaces and grain boundaries and what difference this makes to the properties of these structures. A range of static and dynamic simulation methods will be used including ab initio methods. Depending on the materials chosen, the project could link to a range of experimental work in the Department: from batteries and ferroelectric materials to nuclear waste disposal. The codes to do the calculations are already exist, but there will be opportunities for writing scripts and codes if people are interested.

111 NUMERICAL MODELLING APPLIED TO DEEP GEOLOGICAL DISPOSAL OF NUCLEAR WASTE
Supervisors: Dr K P Travis and Professor F G F Gibb

Disposal in deep boreholes is emerging as a potentially better alternative to mined repositories for the geological disposal of heat-generating high-level nuclear wastes. In order to predict the behaviour of the waste forms and materials involved, and make performance assessments of the disposal, it is necessary to combine sophisticated numerical modelling studies with a programme of experimental work.

This project will build on our existing work which has concentrated on modelling the conductive flow of heat in realistic waste disposal scenarios using finite difference methods, extending it to cover heat transfer by convection and modelling container failure. The project requires a high competency in mathematics and would suit students whose first degree is in Physics/Applied Mathematics/materials Science/Chemistry or an appropriate engineering discipline.

112 MODELLING MATERIALS FAILURE USING SMOOTH PARTICLE APPLIED MECHANICS (SPAM)
Supervisor: Dr K P Travis

Smooth Particle Applied Mechanics (SPAM) is a quite general simulation method which uses particles to solve problems in continuum mechanics. The basic idea is to express all of the continuum field variables (density, stress, heat flux etc) on a grid composed of moving particles. SPAM is best suited to solving problems which present extreme difficulty for the more usual continuum methods such as Finite Elements (FE), Finite Differences (FD); The FE approach has problems when large scale irregular deformations are involved while the FD approach runs into difficulty when there are moving boundaries resulting from materials flow. SPAM has been used in a wide variety of applications such as cutting and machining, understanding the stability of naval vessels to waves, the dynamics of ice in the Arctic Ocean and even problems in Astrophysics. It also shows great potential for solving problems in Materials Engineering, particularly material failure.

(F) NUCLEAR MATERIALS

113 VITRIFICATION AND RE-USE OF WASTE MATERIALS
Supervisors: Dr R J Hand and Dr H Kinoshita

There are a number of industrial wastes that can potentially be vitrified so that can be safely immobilized, such as municipal waste incinerator ash, sewage sludge ash and asbestos. Although vitrification is attractive in principle it is an energy intensive process and thus secondary re-use of the product is required to make vitrification an attractive proposition. Secondary re-use requires us to have a detailed knowledge both of the materials produced by this process and of the process variables that can affect their final properties. We have ongoing research in this area and projects on a variety of wastes are available. All the projects will involve the study of the network structure and redox state of the vitrified wastes, with other aspects including chemical durability, viscosity, crystallisation, melting behaviour and refractory corrosion. All the projects will involve a substantial glass melting programme. Actual wastes will be studied where it is safe to do so, and surrogates where it is not, for example with asbestos. Analysis techniques to be used will include thermal analysis, FT-IR and Raman spectroscopy, viscometry and electron microscopy. Some projects may involve collaboration with Dr S Forder of Sheffield Hallam University for Mössbauer studies. Other properties of the wasteforms, such as the mechanical properties, will be investigated as required. If a project on toxic waste immobilization interests you please contact Dr RJ Hand to discuss details of the projects currently available.

114 SIMULATING DIFFUSION IN CERAMICS AND MINERALS
Supervisor: Professor J Harding

How fast atoms move and where they end up is a major issue in understanding (and so controlling the properties of ceramics). The first is the problem of diffusion; the second the problem of segregation. This project will investigate the mechanisms of diffusion for a range of ceramics from perovskites to pyrochlores and garnets. It will also consider the segregation of atoms and ions to surfaces and grain boundaries and what difference this makes to the properties of these structures. A range of static and dynamic simulation methods will be used including ab initio methods. Depending on the materials chosen, the project could link to a range of experimental work in the Department: from batteries and ferroelectric materials to nuclear waste disposal. The codes to do the calculations are already exist, but there will be opportunities for writing scripts and codes if people are interested.

115 CERAMIC WASTEFORMS FOR IMMOBILISATION OF FISSION PRODUCTS, MINOR ACTINIDES AND PLUTONIUM
Supervisors: Prof N C Hyatt and Dr E R Maddrell (National Nuclear Laboratory)

Background. Nuclear fuel reprocessing produces separated plutonium and a radio-toxic waste comprising fission products (e.g. cesium and iodine) and minor actinides (e.g. neptunium and americium). Excess plutonium requires immobilisation to safeguard against misuse and proliferation, whereas the waste components require immobilisation to prevent dispersal in the environment. Immobilisation of plutonium, fission products and minor actinides in crystalline ceramics may be achieved by targeting the substitution of these species on specific cation / anion sites with appropriate charge compensation. PhD top-up awards are available to support projects in this area – please ask for details.

Projects. The common aims of projects in this area are: firstly, to understand the substitution and charge compensation mechanisms required to immobilise fission products, minor actinides or plutonium in crystalline ceramics; and secondly, to identify the reactions leading to release of these species in accelerated corrosion experiments. Projects in this area will focus on one of the following topics:

1. Cesium immobilisation in hollandite ceramics, based on: BaxTi8-2xM2xO16
2. Minor actinide immobilisation in zirconolite ceramics, based on CaZrTi2O7
3. Plutonium immobilisation in pyrochlore and apatite ceramics, based on Gd2Ti2O7 and Ca2Y8Si6O26
4. Iodine immobilisation in iodo-apatite ceramics, based on Pb5(VO4)3I

Work involving plutonium and minor actinides will initially use non-radioactive simulants (e.g. lanthanide elements) or low activity α - isotopes (U, Th), with the aim of extending this work using Pu and Np through collaboration with the Institute of Trans-Uranics at Forschungszentrum Karlsrhue and Centre for Radiochemistry Research at The University of Manchester.

Training. Projects in this area will involve solid and liquid based ceramic processing methods and the use of a range of characterisation techniques, including: X-ray, neutron and electron diffraction, electron microscopy, and Raman, X-ray absorption and solid state nuclear magnetic resonance spectroscopies. Full training for working with radioisotopes will be provided. German language tuition would be provided for placement at ITU Karlsrhue. There is also the opportunity to take relevant MSc level modules in nuclear science and engineering, and a programme of professional skills development activities, offered by the Nuclear First Doctoral Training Centre.

PhD top-up awards are available to support projects in this area – please ask for details.

116 RADIATION DAMAGE EFFECTS IN NUCLEAR WASTE GLASSES STUDIED BY MULTI-ELEMENT X-RAY ABSORPTION SPECTROSCOPY
Supervisors: Prof N C Hyatt

Background. Alkali borosilicate glasses are currently employed for the immobilisation of UK high level (heat generating) nuclear waste, comprising the fission products separated by nuclear fuel reprocessing. Understanding of the effect of radiation damage (from β,γ and α decay) on the long term stability of nuclear waste glasses is currently lacking. However, such an understanding is critical in order to accurately predict the long term behaviour of waste loaded glasses under disposal conditions. Preliminary studies have demonstrated that, radiation enhanced diffusion of alkali cations, may lead to depolymerisation of the glass network. Ultimately this could lead to radiation induced phase separation, with a detrimental effect on glass durability.

Project. The aim of this project is to develop an holistic understanding of structure-composition-radiation damage effects in alkali borosilicate glasses. This study will take a systematic approach using electron and swift ion implantation of non-radioactive specimens, to simulate the effects β and α decay in a range of different glass compositions. A combination of nuclear magnetic resonance, Mossbauer and X-ray absorption spectroscopies will be applied to quantify the changes in the local structure (i.e. oxidation state, co-ordination number, and nearest neighbours) of key glass elements (B, Si, alkali, fission product and actinide surrogate elements). The results of this study will be compared with the results of modelling simulations of radiation damage effects undertaken by collaborating research groups.

Training. This project will involve melting and laboratory characterisation of nuclear waste glass compositions, combined with the use ion implantation facilities and synchrotron radiation sources in the UK, USA and Europe. Training will be provided in the theoretical and basis of spectroscopic techniques and analysis of data. There is also the opportunity to take relevant MSc level modules in nuclear science and engineering, and a programme of professional skills development activities, offered by the Nuclear First Doctoral Training Centre.

PhD top-up awards are available to support projects in this area – please ask for details.

117 THE NANOSCALE CHEMISTRY AND MICROSTRUCTURE OF HYDROTHEMALLY ALTERED MATERIALS FOR NUCLEAR WASTE IMMOBILISATION
Supervisors: Prof N C Hyatt and Prof. W M Rainforth

Background. Geological waste disposal in a mined repository is now accepted as the “best available approach” for long term management of the UK nuclear waste legacy, following the report of CoRWM. Wasteform dissolution is a key contributor to the source term in the performance assessment model for a Geological Disposal Facility (GDF). Hence, an understanding of the mechanism of wasteform dissolution underpins both prediction of disposal site evolution and public confidence in the safety of the chosen disposal option.

Project. Dissolution involves reaction between the exposed surface area of the wasteform material and the alteration fluid, resulting in an reaction interface between altered surface and pristine bulk. Characterisation of such alteration microstructures is essential in differentiating, for example, between diffusion controlled vs. dissolution – re-precipitation mechanisms of alteration, characterised by chemical gradient or discontinuity on the nano-scale at the alteration interface. This project will apply a combination of TEM techniques to investigate the microstructure and chemistry of hydrothermally altered ceramics, glasses and natural mineral analogues of relevance to nuclear waste immobilisation and disposal. In particular, we will develop FIB preparation methods to extract TEM specimens in the location of etch pits, phase separated regions, and grain boundaries to develop an understanding of the role of local microstructure and composition on alteration behaviour.

Training. This project will involve solid and liquid based ceramic processing methods and the use of a range of characterisation techniques, including: electron microscopy, focussed ion beam milling, and Raman and X-ray absorption spectroscopies. There is also the opportunity to take relevant MSc level modules in nuclear science and engineering, and a programme of professional skills development activities, offered by the Nuclear First Doctoral Training Centre.

PhD top-up awards are available to support projects in this area – please ask for details.

118 ELECTROCHEMICAL LEACHING OF RADIOACTIVE WASTE FORMS
Supervisor: Dr H Kinoshita

This project aims to establish a new technique to predict the integrity of radioactive waste forms in the future. Because a long-term safety and integrity is the key for the storage of radioactive materials, such technique would have a large impact world widely in this field. Electrochemical aging is a process that accelerates diffusion of ionic species in porous matrices. This technique developed at Tokyo Institute of Technology is capable of simulating the aging process over 100 years. We are aiming to apply this technique to predict the integrity of the radioactive waste forms in the future. In this project, we focus on (i) initial investigation and establishment of the electrochemical aging process, (ii) application of the technique to investigate integrity of radioactive waste forms in the future. There is also a possibility of collaboration with Tokyo Institute of Technology.

119 CO2 STORAGE IN RECYCLED CEMENTITIOUS MATERIALS
Supervisor: Dr H Kinoshita

This project aims to immobilise CO2 using recycled cementitious materials, to reduce the concentrations of this greenhouse gas in the atmosphere. Most of cementitious materials have very high concentration of Ca, which would readily form stable carbonates reacting with CO2 without any energy input and thus, they have a great potential for CO2 immobilisation and storage. Effective utilisation of recycled cementitious materials would benefit our society not only in reduction of wastes but also in reduction of CO2 in the environment.

In this project, we focus on (i) experimental investigation on various conditions of carbonation processes for different cementitious materials, and (ii) study on the physico-chemical properties of the carbonated materials. This experimental study complements with a theoretical study by thermodynamic modelling to investigate the optimal condition for CO2 capturing and storage.

120 BEHAVIOUR OF URANIUM IN CEMENTITIOUS MATRICES
Supervisor: Dr H Kinoshita

Understanding of the behaviour of uranium metal in cementitious system is crucially important in substantiating the performance of the radioactive waste products. It is known that uranium metal reacts with cementitious materials. However, the chemistry behind the reaction is still unclear, which makes it difficult to identify whether the reaction is advantageous or disadvantageous for the encapsulation of uranium and how to modify it in case the reaction is a disadvantage.

In this project, we focus on (i) thermodynamic stability/reaction of uranium metal in cementitious systems via thermodynamic modelling and supporting experimental works and (ii) identify the possible problems and scientific background to them and the corresponding solutions for the immobilisation of uranium.

121 SPECTROSCOPIC AND 3D-IMAGING CHARACTERISATION OF GLASS-NANOCOMPOSITES FOR VITRIFICATION OF RADIONUCLIDES
Supervisors: Dr G Möbus and Prof R J Hand

Physical and chemical properties of glasses and ceramics often depend on the coordination and valence states of spurious elements or other functional cations. A particular example is the multi-element glass matrix used to immobilise radioactive elements. In this project, the emphasis is on glass-compositions with high load of extra cations (non-radioactive simulants, e.g. lanthanides), such that solubility limits are exceeded, and precipitation of small crystals occurs. The technique of electron energy loss spectroscopy in the electron microscope is used to spatially map the distribution of coordination and valence parameters in a selection of such glass nanocomposites. Solubility limits, crystallisation sequences, and annealing processes of multi-component borosilicate glasses will be explored. Metrological analysis of the three-dimensional particle distribution in the glass matrix will form another essential part of the project.

122 STEEL CORROSION IN PORE SOLUTIONS OF ALKALI-ACTIVATED CONCRETES
Supervisor: Professor J Provis

The most fundamental factor required for the durability of any steel-reinforced concrete is the ability to develop and maintain an environment with appropriate chemical (and in particular electrochemical) conditions to enable the embedded steel to remain in a passive state. Steel corrosion is, on a worldwide basis, the predominant cause of premature failure of reinforced concrete elements; when steel rusts, it expands, and the resulting tensile stresses cause cracking and loss of performance in a structural sense. The chemistry of steel corrosion in the pore solution environment of concrete is complex, and far from fully understood, even for traditional Portland cement-based concretes. With the development and introduction of less environmentally-damaging binders, in particular alkali-activated/”geopolymer” concretes, the situation becomes even more complex. These materials can have pore solution environments which are very different (in both chemical and electrochemical senses) from the pore solution environments within Portland cement concretes, but are similarly required to hold the steel in a passive state if they are to act successfully as reinforced concretes. Decades of in-service observations of steel-reinforced alkali-activated concretes in various parts of the world have shown that they are able to provide a high degree of protection for embedded steel components, and on this basis, commercialization of these materials is proceeding. However, given that the chemical environment within a geopolymer binder is so different from that which is observed within Portland cement, detailed scientific investigation in this area is necessary to answer durability-related questions from a fundamental standpoint. This project will address this question in detail. Suitable chemical environments to simulate alkali-activated binder pore solutions will be developed and validated, and in-situ and ex-situ determination of the factors controlling corrosion will be conducted through the use of standard and advanced analytical tools.

123 THE ROLE OF MINOR ELEMENTS IN GEOPOLYMER FORMATION
Professor J.L. Provis

While a good deal of attention has been paid in recent years to the roles played by the silicon, aluminium and calcium supplied to the geopolymer formation reaction by different (solid and solution) mix components, there has been much less detailed investigation of the (often very important) roles of “minor” elements in geopolymer gel formation. This project will be focused on important “minor” elements (present at levels of 1-10% in fly ash and slag), in particular iron (ferric and ferrous), sulfur (in various oxidation states), boron and magnesium. Speciation and reactivity studies on each of these elements under conditions simulating geopolymer-forming reaction mixes will be conducted.

Iron in particular is generally supplied by fly ash particles, and its role in geopolymer formation is as yet unclear; some researchers have claimed that it has no influence on geopolymer formation, others have identified it as playing a key role in immobilisation of specific toxic species when geopolymer binders are used to immobilise hazardous wastes, and yet others have claimed that it shows a strongly deleterious effect on geopolymer gel formation. The effect of the form in which iron is supplied, including its availability from the different glassy phases which are present in fly ash, will be analysed in detail through the development and study of model systems, with a view towards developing a more detailed understanding of how these phases interact with aluminosilicates during geopolymer formation.

124 ENVIRONMENTAL CYCLING RESISTANCE OF GEOPOLYMER BINDERS
Supervisor: Professor J L Provis

Geopolymers have been proposed, and are currently being commercialised, as an environmentally-friendly alternative to Portland cement as a binder material in concretes. Concrete production is currently responsible for around 5-8% of worldwide human-derived CO2 emissions, and geopolymer technology provides the potential to reduce this by around 80-90% per ton of concrete, for comparable or better performance.

Determining and analysing the durability of geopolymer binders and concretes exposed in a cyclic manner to aggressive environments (in particular wet/dry cycling and ‘normal’ environmental exposure, as well as chloride and freeze/thaw conditions) has been identified as being important in the wider commercial acceptance of geopolymer technology. This project will form part of a major international research effort directed at determining the durability, degradation mechanisms and expected lifetimes of geopolymer concretes, and will be conducted with key input and collaboration from industrial geopolymer producers.

The project will involve analysis of geopolymers by a variety of experimental techniques, ranging from straightforward gravimetric analysis and strength testing to the use of advanced synchrotron beamline instruments to study areas such as tomography and phase evolution over time. The outcomes will provide for the first time detailed descriptions of the nanostructural and microstructural evolution of geopolymer binders and concretes during cyclic exposure to aggressive environments.

125 TETRAGONAL TUNGSTEN BRONZE STRUCTURED CERAMICS AS POTENTIAL NEW IMMOBILISATION MATRICIES FOR ACTINIDE RICH WASTE STREAMS
Supervisor: Dr M C Stennett

The tetragonal tungsten bronze (TTB) structure is a derivative of the perovskite structure (ABO3) but unlike simple perovskites, which are composed of a simple cubic array of corner sharing octahedral, sharing occurs in such a way as to create an arrangement of pentagonal, square and triangular sites in projection down the c-axis. As a result of the presence of these different sites the TTB structure is potentially suitable for the immobilisation of a wide variety of different size radionuclides. The TTB structure can be described by the formula [A12A2]C2B5O15 where the A sites will accomodate large monovalent (K+, Rb+), divalent (Ba2+, Sr2+) and trivalent (La3+, Ce3+) cations and the B sites will accommodate smaller cations such as Nb5+, Ti4+, Zr4+, Al3+, and Fe3+. The aim of the project is to synthesis TTB structured compounds and investigate the solubility limits of actinide analogues such as Ce3+/Ce4+ (and time permitting U4+/U6+) by a solid state ceramic route. The project will involve the application of solid state ceramic synthesis techniques to investigate the solid solution limits of actinide analogues in the TTB structure. A range of techniques, including X-ray diffraction, electron diffraction and electron microscopy will be employed to characterise the materials produced.

126 MOLTEN SALT SYNTHESIS OF CERAMICS FOR THE IMMOBILISATION OF RADIONUCLIDES
Supervisors: Dr M C Stennett

Crystalline ceramic phases are promising hosts for radionuclides arising from the nuclear fuel cycle. Single phase ceramics are usually produced by solid-state synthesis (SSS) which consists of solid-state reaction between oxide and/or carbonate precursors via repeated cycles of milling and reaction at high temperature. Repeated cycling at high temperature can lead to unwanted volatilisation / decomposition of reactants / product phases and is expensive. Molten salt synthesis (MSS) is an alternative to SSS and used low melting point water soluble salts as fluxes to promote diffusion of constituent components and improve homogeneity. MSS promotes phase formation at lower temperatures and can yield high surface area reactive powders which when consolidated will densify at relatively low temperatures compared to powders derived by SSS. The aim of this project is to explore the use of MSS to prepared single phase ceramics phases and demonstrate the suitability of the route for the incorporation of radionuclides. This project will involve the synthesis of ceramic phases by solid state and molten salt synthesis routes. A range of techniques, including: X-ray diffraction, electron microscopy, particle size and surface area analysis will be employed to characterise the materials produced.

127 RADIATION DAMAGE EFFECTS
Supervisors: Dr K Whittle and Prof W M Rainforth

For future nuclear technologies to be viable, the effects of high levels of radiation damage need to be quantified, understood, and mitigated. Materials currently being proposed, e.g. ODS materials, oxide and carbide based ceramics are poorly understood to high levels of damage, e.g. 400 dpa. This project will address these issues by using both in-situ and ex-situ irradiations. These irradiations will be undertaken with characterisation before and after irradiation, e.g. TEM, XRD, Raman spectroscopy, XAFS etc, on a range of specific model materials developing models to predict long term radiation damage effects. This work will involve collaborations with Argonne National Laboratory, USA, the Australian National University (ANU), and ANSTO (Australian Nuclear Science and Technology Organisation).

128 RADIATION DAMAGE AND RECOVERY PROCESSES
Supervisors: Dr K Whittle and Prof N C Hyatt

Understanding the processes involved, and the factors that influence, radiation damage and recovery are vital in understanding the long-term effects of damage and how it can be mitigated. This is difficult to do experimentally but can be modelled using a range of techniques. The project will use a range of simulation techniques examining specific systems for which there are experimental damage results. The results can then be used to potentially develop new materials with higher immunity to damage.

129 NEW WASTE FORMS FOR A NEW GENERATION
Supervisors: Dr K Whittle and Prof N C Hyatt

Development of new materials, primarily for use as Inert Matrix Fuels, and problematic waste streams is an important component in the future development of GenIV fission reactors. However, there are still important questions that need answering in the basic materials science, e.g. what is the structure adopted by the waste form, and where would the radioactive species go? This question directly impacts the future acceptance of a material, both in regulatory and predictive modelling for a repository. This project, using a range of experimental techniques, on both active and inactive materials will study both new and proposed waste forms, to more fully understand the structure and how it can be improved in the next generation of materials.

130 LONG RANGE DISORDER – SHORT RANGE ORDER
Supervisors: Dr K Whittle and Prof W M Rainforth

In many systems there is the potential for long-range disorder, but which retains short-range order. The short-range order is visible in electron diffraction, but poorly visible in X-ray and neutron diffraction. This observation has two potential uses, firstly it can be used to develop new materials with nuclear applications, e.g. fluorites as both a fuel and waste form. While at the same time the diffuse scattering can be used to study the effects of damage. This project will use ion beam irradiation, coupled with actinide doping to investigate this observation further and use it to develop further the models that exist in predicting radiation damage effects. Predominantly this work will examine ceramics, but ceramic-metallic hybrids are possible. This work will involve collaborations with ANSTO (Australian Nuclear Science and Technology Organisation), and the Australian National University.

(G) STRUCTURAL MATERIALS

131 THE MECHANICAL PROPERTIES OF GLASSES AS A FUNCTION OF COMPOSITION
Supervisor: Prof R J Hand

The effects of composition on the mechanical properties of silicate glasses are not well understood. Recent work both at Sheffield and elsewhere suggests that composition does have an effect on the mechanical properties of silicate glasses. Similar compositional dependence is expected with other glass types. Projects are available to look at the mechanical properties of silicate, borosilicate or iron phosphate glasses as a function of composition. All of the projects will utilise the glass-making facilities available at Sheffield to produce a range of glass compositions of the chosen glass type. A variety of mechanical properties including strength and toughness will be measured. Nanoindentation will be used to assess the near surface mechanical properties of the glasses after exposure to different environments. The flaws that cause failure in these glasses will also be investigated by optical and electron microscopy. The overall aim of the project will be to elucidate links between the mechanical properties and composition with a specific aim of trying to understand what compositional parameters control the ease of Griffith flaw formation in glasses. If a project on the mechanical properties of glasses interests you please contact Dr RJ Hand to discuss details of the projects currently available.

(H) SURFACE ENGINEERING AND TRIBOLOGY

132 WEAR PROPERTIES AND THERMAL STABILITY OF NEW PVD COATING COMPOSITIONS BASED ON TITANIUM WITH COMBINED METALLIC, METALLOID AND NON-METALLIC ALLOYING ADDITIONS
Supervisors: Dr A Leyland and Professor A Matthews

Titanium nitride and chromium nitride PVD ceramic coatings are now used widely in manufacturing industry to protect cutting and forming tools against wear. Both coatings possess certain technical advantages and disadvantages, which lend themselves to specific (and different) applications. For example, TiN behaves well in sliding wear against steel and against mild abrasion; CrN often performs well in impact wear and when some measure of corrosion protection is also needed (eg. in polymer injection moulding). However, with new requirements for dry, or minimally-lubricated, machining (where contact temperatures are high) and for machining and forming of non-ferrous alloys (where tribochemical interactions can be severe), more sophisticated (and preferably ‘adaptive’) coating systems are needed. Alloyed coatings such as TiAlN and CrAlN are now used commercially, where the aluminium additions provide improved oxidation resistance by promoting the formation of a protective alumina film in service. Such coatings can also, with careful selection of composition and/or processing route, exhibit ‘nanocomposite’ structures with two- or multi-phase compositions that are claimed to improve both hardness and toughness. For extreme hardness and high temperature stability, there has for many years been an interest in boron based coatings (eg. cubic boron nitride, boron carbide and transition-metal borides such as TiB2 and, more recently, CrB2). However, such films tend to be brittle and exhibit poor adhesion to many substrate materials. On the other hand, the addition of metalloid elements such as boron or silicon to TiN coatings has shown that ‘pseudo-binary’ nanocomposite structures (eg. TiN/TiB2, TiN/BN, TiN/Si3N4) can be generated, with exciting combinations of high hardness, improved toughness, chemical inertness and – particularly in the case of TiSiN – impressive thermal stability, to temperatures in excess of 1200°C. This project aims to explore the combined addition of metallic (eg. Cr, Al) and metalloid (eg. Si, B) elements to the Ti-N metal/non-metal binary system, with a view to developing new, adaptive, nanostructured coatings to satisfy future industrial requirements for the machining and forming of non-ferrous alloys and composites.

133 LOW TEMPERATURE DIFFUSION TREATMENTS FOR STAINLESS STEEL
Supervisors: Dr A Leyland and Professor A Matthews

Austenitic stainless steels are used widely in structural applications and for functional devices where good corrosion resistance is required. The tribological behaviour of such materials is however poor, preventing their use in mechanical devices where (for example) sliding or impact wear may occur.

Attempts to apply conventional diffusion treatments (such as gas nitriding) on such materials to improve wear behaviour show limited success - due both to the surface oxide film present and to the reduction in corrosion resistance which chromium nitride precipitation tends to cause. Recent attempts to apply plasma nitriding processes at treatment temperatures below 450°C have been shown to suppress nitride formation and reveal the development of a so-called 'expanded austenite' phase (with extreme interstitial nitrogen supersaturation) - which exhibits high hardness and wear resistance. The exact structure and composition of this phase is a matter of some debate; further detailed analytical work is required to understand more about both the nanostructure of this phase and the influence of process parameters on its formation. There is also literature evidence to suggest that carbon-expanded austenite is similarly wear-resistant and can be obtained at higher temperatures (ie. 500°C+) whilst still avoiding the formation of other phases damaging to corrosion resistance - with positive commercial implications for the depth and rapidity of treatment attainable. Low-pressure, high-intensity plasma processing techniques (pioneered in Physical Vapour Deposition of wear-resistant thin films) show excellent promise for the application of such diffusion layers on stainless steels and other candidate materials; further studies of the treatment parameters are however required to achieve process optimisation.

134 PHYSICAL VAPOUR DEPOSITION OF METAL NANOCOMPOSITE FILMS FOR WEAR AND CORROSION PROTECTION
Supervisors: Dr A Leyland and Professor A Matthews

Chemical inertness, they are difficult to deposit at a thickness sufficient to provide adequate corrosion protection of a metal substrate. This is often due to a combination of high compressive stress within the deposited film and practical/commercial considerations - whereby the synthesis of stoichiometric films of high structural integrity is difficult to achieve at rates of more that 2-3µm/hr, whilst maintaining an acceptable substrate temperature (ie. <500°C).

Both factors tend to impose a practical thickness limit of ~5-7µm on many PVD ceramic films, such that through-coating porosity remains high - and corrosive media can rapidly attack the coating-substrate interface. The relative chemical inertness of the PVD ceramic film serves only to accentuate this effect. PVD metallic coatings are however generally not subject to the thickness limitations described above; lightly-stressed films in excess of 10µm thick, with negligible porosity, can be produced at a rate of 10µm/hr, or higher. Taking advantage of the low miscibility of certain transition metal alloy pairings - eg. chromium/copper - and the ability, with the selection of appropriate deposition parameters, to supersaturate the chromium with nitrogen (or other interstitially-locating elements), thick metallic nanocomposite coatings can be produced which exhibit 'ceramic' hardness (ie. 20GPa+) and thus excellent wear resistance, yet possess many other potentially desirable properties (eg. toughness, corrosion protection) inherent to a metallic film. An improved understanding of how deposition parameters influence the structure-property relationships in such films is required; studies of coating composition and structure 'as-deposited' (and, for example, heat-treated at various temperatures above the deposition temperature) will provide valuable information which may be correlated to wear and corrosion behaviour.

135 HYBRID AND DUPLEX PROCESSES FOR IMPACT RESISTANCE
Supervisors: Professor A Matthews and Dr A Leyland

Many practical situations of contact between surface involve condition of repetitive impact. These include automotive (engine and transmission) systems, and many other applications in fields as diverse as printer technologies to metal forming processes. In order to resist surface failure under such impact conditions, coatings are often used. However, it has been found that in such situations fatigue-related failure mechanisms ensue, leading to coating cracking and delamination. Several approaches exist to try to mitigate such failures. For example, the mechanical properties of the coating can be modified, by structural and compositional changes, in order to prevent cracking, and to ensure that the coating can accommodate substrate deformations induced by the loading. Also, the substrate itself can be modified, to provide greater support to the coating. These approaches usually involve plasma-based coating and treatment methods, and the project aims to further develop such processes and to characterise the coatings and treatments produced, and evaluate their performance under repetitive dynamic impact conditions.

136 THERMAL BARRIER AND BOND COAT TECHNOLOGIES USING PHYSICAL VAPOUR DEPOSITION
Supervisors: Professor A Matthews and Dr A Leyland

Gas turbine engines are used in jet engines and in land-based power generation plant. The application of advanced thermal barrier coatings (TBCs) to components within the engine allow it to operate hotter, under controlled conditions of corrosion and thermal degradation, and thus with greater fuel efficiency and power output. Also, the turbine can last longer, thus reducing the frequency of maintenance and overhaul. However, the demands placed on the TBC are extreme, and include a need for excellent adhesion even after extended thermal cycling and hot corrosion conditions. Usually “bond coats” are applied between the TBC and the turbine component (eg the turbine blade) to try to mitigate these effects. A range of processes exist to apply the TBC and the bond coat. These often differ in terms of process characteristics and hardware, and are often carried out separately. The project aims to investigate a sequential bond coat and TBC deposition system to be carried out in a single coating cycle, and based on Physical Vapour Deposition (PVD) methods. The project involves coating characterisation and testing, as well as process development research.

137 PULSED PLASMA ELECTROLYTIC PROCESSES FOR COATING AND SURFACE TREATMENTS
Supervisors: Professor A Matthews and Dr A Yerokhin

Plasma electrolytic processes combine conventional electrolysis with a plasma discharge which can under certain conditions be generated at the metal-electrolyte interface. This allows effective modification of metal surfaces and deposition of coatings with unique properties. The project objectives are to develop novel processes of plasma electrolytic surface treatment, which can be used in a wide range of industrial applications. These include oxide ceramic coatings for wear and corrosion protection of lightweight metals (e.g. Mg, Al, Ti, and their alloys), environmentally friendly surface cleaning/coating processes for Cd replacement, new coating materials and structures for biomedical applications, etc. The investigations are focused on achieving an improved insight into the nature of electrolytic plasma discharges, with both plasma-metal and plasma-electrolyte interactions being considered. Various spectroscopic methods are employed for the discharge characterisation, along with current/voltage probing, video imaging and other techniques. Particular emphasis is given to the studies of pulsed bipolar modes of electrolysis, for which the effects of electrolyte composition and current pulse parameters are investigated, with an outlook to the process control and optimisation.

The coatings are characterised using advanced methods of SEM, TEM, EDX, XRD, etc. Testing will also be carried out to evaluate the performance of the modified surfaces.

138 WEAR BEHAVIOUR OF HIGH PERFORMANCE MATERIALS AND COATINGS
Supervisor: Professor W M Rainforth

Replacement of worn out components is a major cost to the world economy. In addition, it is being increasingly recognised that a reduction in friction between contacting components can make a direct contribution to a reduction in energy consumption, reducing environmental impact. Failure of components through wear can have major consequences, for example, a failed hip prosthetic results in severe pain and the requirement for immediate replacement. Wear behaviour depends on the dynamic changes to surface microstructure, which can either enhance or degrade wear resistance. Therefore, to understand how to improve the wear behaviour it is essential that evolution of surface microstructure as a result of frictional contact be understood. A number of projects can be run depending on the exact interest. Projects can be concerned with (a) friction and wear behaviour of biomedical ceramic materials (b) wear of advanced hard coatings, (c) high temperature degradation mechanisms. A number of advanced techniques will be required in order to characterise surface microstructure, including high resolution SEM, state-of-the-art TEM, focused ion beam (FIB) microscopy, atomic force microscopy (AFM) nanoindentation and Glow Discharge Optical Emission Spectroscopy (GDOES).

139 CHARACTERISATION AND IN-VITRO EVALUATION OF NOVEL BIOACTIVE COATINGS FOR Ti INTRABONE IMPLANTS
Supervisors: Dr A Yerokhin and Dr G Reilly

There are many clinical situations which necessitate implantation of an orthopaedic device including osteoporosis, osteoarthritis, sports injuries and congenital defects. Because many of these diseases are related to age and the increasing average age of the population is rising the numbers of patients needing implants are increasing rapidly, leading to a growing market for orthopaedic materials and devices. However a routine problem is that the patient’s own bone does not integrate well with the implant material and so the implant loosens and fails. 10-20% of hip and knee replacement operations worldwide are revisions due to implant failure through loosening. Considerable research is ongoing on modifications of the implant surface aimed at improving how the patient’s bone grows around the implant (osseointegration) to reduce the need for implant revision surgery. Integration of an implant with bone involves several process, first bone-forming cells (osteoblasts) must be induced to differentiate from mesenchymal stem cells (MSCs) present in the bone marrow. Then the osteoblasts synthesise a mixture of matrix proteins (mostly collagen) and bone mineral (carbonated hydroxyapatite). Therefore, for an implant to induce bone formation at its surface MSCs and osteoblasts should be able to attach and differentiate ultimately producing a matrix that adheres well to the implant. To address these requirements a new type of coating has been developed based on plasma electrolytic oxidation process of Ti alloys. Specially formulated electrolytes and current regimes employed allow formation of 15 to 30 micron thick ceramic surface layers that are hard, uniform and well adhered to the Ti substrate. The coating phase composition comprises titania matrix nesting various Ca and P containing compounds (both amorphous and crystalline) to ensure accelerated osseoinduction and integration on the implant surface. In depth characterisation of the coating morphology, chemical and phase composition will be carried out using optical microscopy, XRD, SEM, TEM, EDX and GDOES techniques. In-vitro tests will include seeding osteoblasts and MSCs onto the coated surfaces and examining cell proliferation and matrix production using histological staining methods. Cell morphology and attachment will be examined by immunostaining for matrix proteins and integrins and imaging the cells by confocal microscopy. A new method of testing osseointegration will be used in which cylindrical test samples of coated implants will be placed into a 3 dimensional tissue engineered bone matrix. The tissue engineered bone will be grown in a bioreactor and the growth of bone-like matrix around the implant analysed with histology confocal microscopy and CT scanning.