Last updated April 2013

Processing of advanced metallics

Processing of oxide dispersion strengthened alloys for fission and fusion power
Z. Hong, 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.

Microstructural control of Al alloys using intrinsic oxides
A. Verma, Dr. K.A.Q. O'Reilly, Professor P.S. Grant

Oxide particles exist in nearly all liquid metals and alloys exposed to air or even under protective atmospheres. Oxide particles are often considered harmful inclusions. However, recent research work has demonstrated that by using liquid metal engineering, the harmful effects of oxides might be reduced and they may even be contrived to play a useful role in nucleation. Work in Oxford has demonstrated that grain refiners not only nucleate the Al grains, but also control intermetallic selection in Al alloys, hence modifying mechanical properties. This project is investigating the potency of oxide particles for heterogeneous nucleation of intermetallics. The nucleation sequence of various intermetallic phases due to unavoidable oxides and their control is being studied during solidification of Al-alloys. A phase extraction technique is being used to facilitate the detailed characterisation of intermetallic phases and their interaction with extrinsic and intrinsic alloy additions. Special reference is being made to inclusions and impurity elements in recycled materials. (Funded by EPSRC)

Spray forming of Ni superalloys for high temperature applications
Dr A. Sato, Professor P.S. Grant

We are developing a novel variant of the spray forming process in order to produce Ni superalloy components with enhanced functionality for the power generation industry. Funded by Mitsubishi Heavy Industry, Japan.

Modelling and experiments concerning dendrite fragementation
Dr. Z. Guo*, Dr. E. Liotti 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.

Bulk nanostructured Al based alloys
H. Begg, Professor P.S. Grant

We are researching fibrular and laminate nanocomposites manufactured either by spray forming, casting, plasma spraying or powder processing, followed by high strain processing by extrusion. Systems of interest are primarily aluminium base and include both ultrahigh strength nanoquasicrystalline alloys ductilised with other Al alloy fibres and immiscible systems. Characterisation includes electron microscopy and X-ray diffractometry. Funded by EPSRC.

Lead free solder development and analysis for aerospace applications
S. Godard-Desmarest, Dr. C. Johnston, Professor P.S. Grant

This project builds 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. We are also developing a new meso-scale approach to testing single balls and entire BGAs at different temperatures. 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.

Development of high performance products comprising dissimilar metals by spray forming
S. Zhao, Professor P.S. Grant

Spray forming is being researched in order to produce clad tubes and cylinders with different interior and external prperties. Critical to these materials is control of the interface between the materials in terms of its strength and toughness, inter-diffusion, phase formation, and response to downstream processing. Successful development of this approach will facilitate a range of unusual products optimised for niche, high value applications in a number of industries. In collaboration with Dr. J. Mi, University of Hull. Funded by Baosteel, China.

Processing of energy storage and related materials

Novel high energy density high reliability capacitors
A. Mahadevegowda, 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)

Energy storage for low carbon grids
Dr C. Fu, Professor P.S. Grant

We are developing novel approaches for the fabrication of electrochemical energy storage devices that are relevant to grid-scale energy storage applications as part of the EPSRC Grand Challenge Project: Energy Storage for Low Carbon Grids that is a large scale, multi-partner project led by Imperial College London. We aim to address the many aspects of integrating energy storage into future energy networks. Our current focus is on spray processed electrodes in new materials for grid applications, and we will later apply some of our process developments to battery, fuel cell and device manufacture. Funded by EPSRC.

Structure-property relationships in graded nanocomposites for microwave applications
Q. Lei, Professor C. Grovenor, Professor P.S. Grant

There has been a great deal of international interest in the exciting electro-magnetic properties that can be achieved in metamaterials but very little work has been undertaken on how to process them in the large volume, techniques required for engineering applications. This project will focus on using a range of microstructural analysis techniques to investigate how the morphology and chemistry of conducting phases in dielectric matrices develop during scalable synthesis techniques, and how these microstructures control the properties. Funded by China Government scholarship and by EPSRC grant EP/I034548. In collaboration with partners in Queen Mary London and Exeter Universities.

The Quest for Ultimate Electromagnetics using Spatial Transformations (QUEST)
Dr E. Edwards, Professor C.R.M. Grovenor, Professor P.S. Grant

Recent UK-led breakthroughs in the theory of STs, such as the possibilities concerning cloaking and invisibility, have caught both the scientific and popular imagination, and have stimulated a huge growth in related research around the world. The potential of the underlying ST approaches, however, have much wider applicability than cloaking alone, in arguably more important applications that span communications, energy transfer, sensors and security. However, theory and concepts are outstripping practical demonstration and testing, leading to a mismatch in what may be theorised and computed and what can be realised for impact in society and commerce. We contend that the timing is now ideal for UK theorists, modellers, manufacturers and engineers to work together to maintain the UK strength in this field, with a clear focus on the reduction to practice and demonstration of potentially radical new concepts and devices. Collaboration with the University of Exeter, University of St Andrews, and Queen Mary, University of London.

Processing and properties of nanocomposite materials for electromagnetic applications
Y. Wang, Professor P.S. Grant

We are using novel processing of polymers to create materials with anisotropic electrical and magnetic properties, and arranging these according to designs that allow unusual and previously unattainable manipulations of microwaves. A mixture of processing for coatings, strip and bulk are being used, and these methods are being combined in order to achieve the required designs. Funded by DSTL.

Development of flexible energy storage and generation systems based on nano-hybrid materials
Professor J-M Kim, Professor P.S. Grant

The focus of the research is the development of sub-components and devices for energy storage and environmental energy harvesting based on functional nanostructures and novel fabrication approaches. The core of the research is the exploitation of layer-by-layer approaches for the fine scale arrangement and control of nanomaterials over large areas. This ambitious research builds on key know-how developed in Oxford on LbL processing of suspensions and is directed to both energy storage (primarily supercapacitors) and energy harvesting (piezo-based), and the exploration of processing strategies for their combination in flexible devices. Funded by KETEP, S. Korea.

Nanostructures for energy applications
L. O'Neill, C.A. Huang, M. Jiang, 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.

 

 

Other

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).