Personal Homepages

Research interests concern developing understanding of the complex underlying physics during materials processing in order to develop new manufacturing techniques and advanced materials for industrial application. Much of the research is focused on detailed investigations of novel manufacturing routes and materials utilising liquid droplets, using a combination of experimentation on near industrial scale, on-line process diagnostics, numerical simulation, and close collaboration with industry.

Novel high energy density high reliability capacitors
A. Mahadevegowda, Dr. A. Cook, Dr. C. Johnston, Dr. H.E. Assender, Professor P.S. Grant
Current capacitor technology significantly limits the temperature capability and electrical performance of power electronics relative to the "More Electric Airframe" systems requirements, which are emerging rapidly as a key priority for both aeroengine and airframe manufacturers. Novel capacitor materials combining high dielectric ceramics and high performance polymers are being developed for aero-engine applications, particularly within the more electric aircraft concept. Investigations include characterisation of the fundamental material properties using advanced analytical instruments, clean room characterisation of the electrical properties, development of fabrication routes, and modelling of behaviour for lifetime prediction. (Funded by MoD/dstl and a Felix Scholarship)

Nanostructured Al-based Alloys for high strength applications
Dr. M.L. Galano, Professor P.S. Grant, Professor F. Audebert*, Professor G.D.W. Smith
Al-based nanostructured materials containing high volume fractions of quasicrystalline dispersoids are being produced by rapid solidification techniques. Particular emphasis is being placed on studying the microstructure stability and the mechanical properties leading to the manufacturing of the alloy in bulk shape. This project forms part of a collaboration agreement between the University of Oxford and University of Buenos Aires. (*University of Buenos Aires, Argentina)(Partially funded by Niobium Products Company CBMM)

Modelling and experiments concerning dendrite fragementation
Dr. Z. Guo* and Professor P.S. Grant
This project concerns the control of nucleation and subsequent microstructural evolution during solidification by intrinsic grain multiplication using external physical means such as acoustic/shock waves and pulsed magnetic fields. Fragments from broken dendrites are well-known to multiply the number of final grains in a casting, and so provide grain refinement and attendant improvements in quality and performance. The central idea of this project is to enhance dramatically this effect by disrupting continuously the thermal conditions in the melt and at growing solid/liquid interface, without any melt contamination. While various external field approaches have been developed, there remains some uncertainty in the mechanism of dendrite fragmentation, and this project will study both the underlying physics of grain multiplication as well as a new approach for its enhancement. Critical to the work is the use of phase field modelling and fluid flow modelling to explore the conditions that promote grain multiplication. (* Royal Society Newton Fellow, Tsinghua University, China)

EPSRC Centre for Innovative Manufacturing in Liquid Metal Engineering
Dr. E. Liotti, Dr. K. Sundaram, Professor P.S. Grant, Dr. K.A. Q. O'Reilly
Patrick Grant and Keyna O'Reilly have secured funding to establish a new £4.5M EPSRC Centre for Innovative Manufacturing in Liquid Metal Engineering. The Centre is led by BCAST at Brunel University and also involves Birmingham University together with 15 industrial partners who will contribute a further £4.6M. The new EPSRC Centre will work with industrial partners to develop innovative technologies for liquid metal processing that will allow for increased reuse and recycling of metals. This will lead to substantial conservation of natural resources, and a reduction in energy consumption and CO2 emissions. The work at Oxford will be based at the University's Begbroke Science Park, making use of the large scale processing facilities and microstructural characterisation capabilities. Oxford is investigating the nucleation of solid from liquid alloys in advanced solidification processes, and how to control the resulting microstructure to make manufacturing more tolerant to recycled source material. Current projects include the effects of ultrasound and other external fields during solidification and the control of AlFeSi intermetallics.

Nanostructures for energy applications
L. O'Neill, C.A. Huang, M. Jiang, B. Mendoza, Professor P.S. Grant
Nano-structured materials are attractive for some energy related applications because they can provide very high surface areas per unit mass, leading to high energy densities in various storage applications. A supercapacitor (electrochemical capacitor) stores electrical energy either in the form of ions at an electrode/electrolyte interface (electrical double-layer capacitor, EDLC) or by faradic redox reactions at the electrode (pseudo-capacitors). Both types offer high power density (rapid discharge), excellent reversibility, and long cycle life. Supercapacitors usually use activated (meso-porous) graphite for their electrodes, but alternatives with higher power capability are being studied intensively, including entangled, meso-porous carbon nanotube (CNT) films - an application that makes use of the "natural" tendency of the CNTs to entangle and percolate current at low volume fractions. We are fabricating comparatively large amounts of both multi-walled CNTs (by chemical vapour deposition) or single wall CNTs (by arc discharge) in-house, purifying them, functionalizing their surface to improve their ion storage capability, and then processing them into large area films or buckypaper - on a variety of flexible or stiff substrates. In some cases, other process steps can add nanoparticles to provide a superimposed pseudo-capacitance. Our goal is to demonstrate the potential benefits of this approach over existing materials at the laboratory scale, and also to ensure that we develop processing technologies that at all stages offer the potential for cost-effective scaling to the near-industrial, and then full industrial use. The ability to process and characterize fully these materials in-house is key to this strategy. Funded by EPSRC Grant: Supergen Energy Storage.

Advanced electronic packaging for harsh environment applications
M. Sousa, Dr. C. Johnston, Professor P.S. Grant
Down oil and gas well temperatures of 250C and pressures of more than 1,000bar provide the harshest environment that electronics must endure. Even though the very expensive electronics placed down-well are protected by thermal barriers and other technologies, the time that the electronics can spend down hole is limited. This project seeks to develop new technology so that electronics may operate under these extreme conditions for up to 10 years. The project forms part of a larger project, and brings together specialists in electronic materials, high reliability assembly and a well-logging instrumentation manufacturer. The project is making use of both in-house and industrial manufacture, assembly, testing and microstructural examination of novel multi-material combinations. Finite element modelling is being used to predict and understand behaviour under extreme environments. Materials under investigation include novel insulated metal substrates and various high temperature die attach and interconnect materials and processes. (Funded by the UK Technology Strategy Board and an industrial consortium).

Materials Knowledge Transfer Network - Transport and Sustainability
Dr. C. Johnston, Dr. R.M.K. Young, Professor. P.S. Grant
As part of the Materials KTN, we are running a comprehensive network and business programme focused future lightweight and high temperature materials for low pollution, high efficiency transport. New materials, their manufacturing technologies and their integration into engineering systems are critical if UK aerospace, automotive rail and marine sectors are to meet global technical drivers. We are helping UK transport and technology businesses to meet these requirements through a range of scientific and technical products and services focused on: lightweight materials, materials technologies for reduced emission, end of life technologies (disassembly, re-use, recycling), and more electric technologies. We also lead the Sustainability theme within the Materials KTN(Funded by UK Technology Strategy Board)

Lead free solder development and analysis for aerospace applications
S. Godard-Desmarest, Dr. C. Johnston, Professor P.S. Grant.
Due to safety considerations, the aerospace industry is largely exempt from legislation prohibiting the use of lead in interconnects in electronic assemblies, and lead continues to be used in avionics. This situation is unlikely to continue because of further legislation and difficulties in sourcing lead-containing materials and assemblies from suppliers. In contrast to domestic electronics where lead free solders are now standard and reliable, there are no current widely accepted "drop-in" replacement materials for lead solders that meet the more stringent and hostile aerospace standards for reliability. There is now a pressing need to develop underpinning scientific understanding of the factors governing lifetime of existing and future lead free solder materials for critical aerospace applications. Previous work at Oxford has shown that nanoindentation can be used to measure the mechanical properties and constitutive behaviour of ball grid array solders as a function of temperature, and that with careful interpretation, this data can be used in simulations of stress-strain that in turn can be correlated to reliability performance. The significance of the approach is that unlike previous approaches that have relied on time-consuming and costly mechanical testing of bulk materials to obtain basic property data, the nanoindentation and modelling route offers the potential to identify more rapidly promising lead free alloys that meet aerospace requirements, usually quick methods and very small amounts of candidate materials. The project will build on the approach established at Oxford to study a variety of promising new lead free solder compositions for aerospace applications. Ball grid array joints are made in-house so that full process history data can be captured and reproducibility assured. These assemblies are probed by nanoindentation and the key mechanical behaviour (yield, temperature dependent creep, etc) captured and interpreted in a form suitable for input into a numerical model of stress-strain accumulation. In this way, the potential of alloys can be firstly ranked qualitatively, and then the most promising alloys studied in more detail by further probing and modelling, and thermal cycling or assemblies using equipment at Oxford and at industrial partners. This project is sponsored by EPSRC, Goodrich and Oxatech

Bulk nanostructured Al based alloys
H. Begg, A. Kelly, C. Banjongprasert, N. Rounthwaite, Dr. M.L. Galano, Professor F. Audebert*, Professor G.D.W. Smith, Professor P.S. Grant
Development and processing of Al based nanocomposites alloys for high strength applications in bulk shape by several processing techniques, in particular spray forming. Alloys including Al-Fe-Cr-Ti are being produced in billet form and their microstructures and properties compared with those produced by rapid solidification and mechanical alloying. Characterisation includes electron microscopy and X-ray diffractometry using synchrotron radiation at Diamond. Downstream processing includes forging and extrusion, with mechanical properties studied as a function of temperature. Scaled-up billet sizes are being used for specific component trials. (Funded by EPSRC and industrial consortium, *University of Buenos Aires, Argentina)

Processing of oxide dispersion strengthened alloys for fission and fusion power
M. Gorley, Dr. H. Zhang, Professor S.G. Roberts, Professor P.S. Grant
Oxide dispersion strengthened alloys comprise a metallic alloy with a dispersion of sub-micron oxide particles. The fine scale dispersion of the ceramic particles gives rise to strain fields around the particles, which can confer strength and other properties by interaction with dislocations in a manner similar to that of fine scale precipitates produced by ageing heat treatments in conventional metallurgical alloys. The particles also have the potential to stabilize microstructural features such as grain size at intermediate temperature. A further potential benefit of these particles in steels for nuclear applications is that they or the interface between the particles and the matrix may act as a 'sink' for vacancies and He induced by a neutron flux environment, partially mitigating otherwise severely damaging effects such as embrittlement. It is known that the type (size, volume fraction, chemistry, etc) of particles and the homogeneity of their dispersion in the matrix is influential on the final ODS alloy properties and the extent to which potential benefits are realised in practice. However, there are few systematic studies that allow the detail of the oxide particle mixing/dissolution and re-precipitation behaviour to be reconciled in terms of the processing parameters of practical interest. In part, this derives from the long times associated with the design-make-characterise-irradiate-test cycle. In this project we combine in-house processing of high quality ODS steel powders by mechanical means, the subsequent manufacture of consolidated ODS alloys. The study focusses on the dynamics of the critical metallic-ceramic mixing process and aims to develop ideas for identifying and assuring the "quality" of milled powders so that downstream properties are evolved optimally. Alternative processes to mechanical mixing are also being explored. Funded by EPSRC.

10 public active projects

Colloidal synthesis of lead oxide nanocrystals and their optoelectronic properties, C.A. Cattley, A. Stavrinadis, R. Beal, J. Moghal, A.C. Cook, P.S. Grant, J.M. Smith, H.E. Assender and A.A.R. Watt, Chem. Comm., 46 (2010), 2802–2804. doi: 10.1039/b926176a.

SnS/PbS nanocrystal heterojunction photovoltaics, A. Stavrinadis, J.M. Smith, C.A. Cattley, A.C. Cook, P.S. Grant and A.A.R. Watt, Nanotechnology, 21 (2010), 185202 (7pp). doi: 10.1088/0957-4484/21/18/185202.

Fabrication and electrical properties of bulk textured LiCoO2, H. Zhang, P.J. Baker and P.S. Grant, J. Am. Ceram. Soc., (2010), doi: 10.1111/j.1551-2916.2010.03634.x

Modelling the deposition dynamics of a twin-atomizer spray forming system, G. Zhang, Z. Li, Y. Zhang, J. Mi and P. S. Grant, Mat. Trans. B, (2010) doi: 10.1007/s11663-009-9333-0

A novel hybrid supercapacitor with a carbon nanotube cathode and an iron oxide/carbon nanotube composite anode, X. Zhao, C. Johnston and P. S. Grant, J. Mater. Chem., 19 (2009), 8755-8760, doi: 10.1039/b909779a

Arc sprayed steel: microstructure in deep substrate features, A.P. Newbery and P.S. Grant, J. Thermal Spray Techn., 18 (2009), 256-271. doi: 10.1007/s11666-009-9300-y

Spray deposition of steam treated and functionalized single and multi-walled carbon nanotube films for supercapacitors, X. Zhao, W. Wang, B.T. Chu, B. Ballesteros, W. Wang, C. Johnston, J.M. Sykes and P.S. Grant, Nanotechnology, 20 (2009), 065605, doi:10.1088/0957-4484/20/6/065605.

Spray deposited fluoropolymer/multi-walled carbon nanotube composite films with high dielectric permittivity at low percolation threshold, X. Zhao, A.A. Koos, B.T.T. Chu, C. Johnston, N. Grobert, P.S. Grant, Carbon, 47 (2009), 561-569. doi:10.1016/j.carbon.2008.10.042.

Spray deposition of polymer nanocomposite films for dielectric applications X. Zhao, C. Hinchliffe, C. Johnston, P.J. Dobson and P.S. Grant, Mat. Sci. Eng. B, 151 (2008), 140–145. doi:10.1016/j.mseb.2008.05.024.

Modelling the shape and thermal dynamics during the spray forming of Ni superalloy rings. Part 1: droplet deposition, splashing and re-deposition J. Mi and P.S. Grant, Acta Mat., 56 (2008), 1588-1596, doi:10.1016/j.actamat.2007.12.021.

Modelling the shape and thermal dynamics during the spray forming of Ni superalloy rings. Part 2: heat flow and solidification, J. Mi and P.S. Grant, Acta Mat., 56 (2008), 1597-1608, doi:10.1016/j.actamat.2007.12.022.

An electrochemical study of repassivation of aluminium alloys with SEM examination of the pit interiors using resin replicas, K.L. Moore, J.M. Sykes and P.S. Grant, Corros. Sci., 50 (2008), 3233-3240. doi:10.1016/j.corsci.2008.08.027.

Pitting corrosion of spray formed Al–Li–Mg alloys, K.L. Moore, J.M. Sykes, S.C. Hogg and P.S. Grant, Corros. Sci., 50 (2008), 3221-3226. doi:10.1016/j.corsci.2008.08.012

The use of interfacial 3D geometry to control stress distributions in W coatings for fusion armour applications, G. Thomas, R. Vincent, G. Matthews, B. Dance and P.S. Grant, Mat. Sci. Eng. A, 477 (2008), 35–42. doi:10.1016/j.msea.2007.05.120

Multiphysics modelling of the spray forming process, J. Mi, U. Fritsching, O. Belkessam, I. Garmendia, A. Landaberea and P.S. Grant, Mat. Sci. Eng. A, 477 (2008), 2–8. doi:10.1016/j.msea.2007.08.083

Solidification in spray forming, P.S. Grant, Mat. Trans. A, 38A (2007), 1520—1529. doi:10.1007/s11661-006-9015-3

Processing, microstructure and property aspects of a spray cast Al-Mg-Li-Zr alloy, S.C. Hogg, I.G. Palmer, L.G. Thomas and P.S. Grant, Acta Mat., 55 (2007), 1885–1894. doi:10.1016/j.actamat.2006.10.057

Optimal robot path for minimizing thermal variations in a spray deposition process, P.D.A. Jones, S.R. Duncan, T. Rayment and P.S. Grant, IEEE Trans. Control Systems Techn., 15 (2007), 1-11. doi:10.1109/TCST.2006.883196

Evolution of percolation properties in nanocomposite films during particle clustering, T.K.H. Starke, C. Johnston and P.S. Grant, Scripta Mat., 56 (2007), 425-428. doi:10.1016/j.scriptamat.2006.10.034.

Microstructure evolution of vacuum plasma sprayed CoNiCrAlY coatings after heat treatment and isothermal oxidation, P. Poza and P.S. Grant, Surf. Coatings Techn., 201 (2006), 2887-2896. doi:10.1016/j.surfcoat.2006.06.001

Scientific, technological and economic aspects of rapid tooling by electric arc spray forming, A. Roche, S.R. Duncan and P.S. Grant, J. Thermal Spray Tech., 15 (2006), 796-801. doi:10.1361/105996306X1468794

The effect of particle distribution inhomogeneities on the dielectric properties of polymer/ceramic films, T.K.H. Starke, C. Johnston, S. Hill, P.D. Dobson and P.S. Grant, J. Phys. D: Appl. Phys., 39 (2006), 1305-1311.

Microstructural characterisation of spray formed Si-30Al for thermal management applications, S. Hogg, A. Lambourne, A. Ogilvy and P.S. Grant, Scripta Mat., 55 (2006), 111-114.

Oxidation during the electric arc spray forming of steel, A.P. Newbery and P.S. Grant, J. Mat. Processing Techn., 178 (2006), 259-269.

An investigation of novel spraycast Al-Mg-Li-Zr-(Sc) alloys, S.C. Hogg, I.G. Palmer and P.S. Grant, Mat. Sci. Forum, 519-521 (2006), 1629-1633.

Applied periodic l-infinity control: presenting prototype designs for a real spray form tooling process, V.A. Tsachouridis, P.D.A. Jones, S.R. Duncan and P.S. Grant, Control Eng. Practice, 14 (2006), 1477-1493.

Modelling the heat flow in spray formed steel shells for tooling applications, T. Rayment and P.S. Grant, Met. Mat. Trans. B, 37B (2006), 1037-1047.

Materials for fission and fusion power
S G Roberts / A J Wilkinson / P Bagot / P S Grant

Do you want to help to solve the future energy crisis? Are you interested in doing novel and exciting experimental work? Would you like opportunities for international collaborations and travel?

Fusion reactors potentially offer a complete solution to the problem of future energy supply, and are environmentally friendly: they emit no greenhouse gases, and so would not contribute to global warming. The recent success of the JET project at Culham in the south of Oxfordshire, which proved that plasma could be heated and controlled to produce fusion, has demonstrated the feasibility of the concept. The next step is to construct a prototype reactor (ITER) which is now the focus of a major international project. This will be followed by a prototype commercial reactor (DEMO).

So far relatively little demand has been made on the properties of the materials used for JET and other prototype reactors, since they had only to contain an operating plasma for very short times. For actual fusion power plants, materials issues will be crucial to success.

In the closer future, advanced fission reactors will be needed to meet some at least of the world energy demand, as fossil stocks dwindle and as their use become less environmentally acceptable. Materials degradation by radiation damage is a serious issue in current-generation reactors, and the new “generation IV” reactors currently being proposed will place even heavier demands on materials.

The materials needed will operate at temperatures of 600ºC or more, will need to withstand stresses up to 300MPa, and will accumulate over their lifetime radiation damage from fast neutrons amounting to ~100 displacements per atom. In fusion reactors, an additional problem will arise due to the high levels of helium and hydrogen produced in transmutation reactions. It is essential that any material used maintains adequate strength and toughness, while suffering minimal dimensional change through swelling and creep. These are very demanding requirements, which cannot be met by conventional structural materials. It will be necessary to develop and evaluate new materials.

Ion irradiation is currently the only non-activating method of mimicking the fast neutron damage produced in nuclear fission and fusion reactors (with or without co-implantation with He or H, to mimic the effects of fusion by-products). Implanted layers are ~2-3 microns deep or less.  We have developed micromechanical test methods, using ion beam machining to make specimens only a few microns in size, for determination of the elastic, plastic and fracture properties of candidate materials. This is linked with parallel electron microscopy and atom-probe microscopy studies of the development and nature of the radiation damage, and of the interactions between radiation damage and mobile dislocations which give rise to hardening and embrittlement.The experimental work is closely linked to the development and verification of computer models of radiation defects and their interactions.

A new large research project in this area, an EPSRC programme grant centred at Oxford University, started in early 2010. It involves UK and European partners (especially Liverpool University, CCFE Culham laboratory, the Commissariat à l'Énergie Atomique (CEA), and Rolls Royce). It aims at providing a thorough understanding of the mechanical properties and irradiation response of materials with potential for fusion and advanced fission reactor applications, including low-activation ferritic-martensitic steels, oxide-dispersion strengthened steels, model Fe-Cr alloys and tungsten alloys.

Individual research student projects started in 2009, 2010 and 2011 in the areas of:

• Tungsten-based alloys,
• Radiation hardening and embrittlement, 
• Grain boundary irradation embrittlement,
• Grain boundary stress-corrosion cracking,
• Processing & properties of Oxide Dispersion Strengthened alloys

Further projects will be available, to start October 2012. Applications for studentships in these areas from well-qualified applicants of all nationalities are welcome, but the note that available funding covers fees and stipend of UK and EU nationals only.

Also see homepages: Paul Bagot Patrick Grant Steve Roberts Angus Wilkinson

Spray forming of hierachical metal-metal composites
P S Grant

Spray forming is a high technology casting process for producing large scale advanced alloys with unmatched quality and performance. This project will explore spray forming for the processing of “designer” alloys by co-spraying a second (or more) liquid or metal phase into the primary sprayed alloy so that co-deposition and mixing occur to produce unusual and potentially highly useful structures and properties. This project will make use of the leading spray forming facilities at Oxford to manufacture and study hierachical metal-metal composites in which microstructural features at the nano, micro and meso scale are attempted to be controlled separately by co-spraying of different materials, from the simplest mixture of two pure metals that are then heavily deformed to produce nanofibrils, through to the co-injection of nanoscale powders and mixing of different liquid sprays to produce in-situ reactions and otherwise difficult to process compositions and phases. The microstructure and mechanical properties will be studied for the most promising combinations, together with the effect of downstream processing operations.

Also see homepages: Patrick Grant

Control of microstructure by grain multiplication
P. Grant

This project concerns the control of nucleation and subsequent microstructural evolution during solidification by intrinsic grain multiplication using external physical means such as acoustic/shock waves and pulsed magnetic fields. Fragments from broken dendrites are well-known to multiply the number of final grains in a casting, and so provide grain refinement and attendant improvements in quality and performance. The central idea of this project is to enhance dramatically this effect by disrupting continuously the thermal conditions in the melt and at growing solid/liquid interface, without any melt contamination. While various external field approaches have been developed, there remains some uncertainty in the mechanism of dendrite fragmentation, and this project will study both the underlying physics of grain multiplication as well as a new approach for its enhancement.

Also see homepages: Patrick Grant

Novel processing of nanostructured films for energy storage
P S Grant

This project will study a new and scaleable spray deposition technology developed at Oxford that can produce thin films (0.5micron up to 10’s of microns) from aqueous and non-aqueous suspensions of nanomaterials over areas of (currently) up to 750cm2. In particular, the processing of 1D nanostructures (rods and wires) of transition metal oxides into large area meso-porous films for supercapacitors and battery/photovoltaic hybrids will be studied. As well as the synthesis of nanostructures and their suspension, the project will focus on the manufacture of the films themselves with a particular emphasis on the scaleability and reproducibility of any developed approaches. Both single material meso-porous films formed from rods, wires and tubes, and hybrid or composite structures comprising mixtures of materials, for example to optimise energy storage and mechanical stability, will be studied in terms of their processability, microstructure and energy and power performance in real supercapacitor configurations.

Also see homepages: Patrick Grant

Also see a full listing of New projects available within the Department of Materials.