Processing of Advanced Materials

Spray forming of hierachical metal-metal composites

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.

Novel processing of nanostructured films for energy storage

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.

Read more about our work in: 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.

Control of microstructure by grain multiplication

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.