My research group work on understanding the behaviour of materials under extreme environments, such as radiation damage, high temperatures or high stresses. By developing an understanding of the mechanical behaviour and defects which control materials behaviour we then try and develop materials better able to operate under extreme conditions. We are now working to take technqiues we have developed for traditional engineering materials and apply them to questions in other areas such as solid state batteries for energy storage and geological materials.
Much of our work is centred on developing mechanical testing techniques at the nano and micro scale. We have a state of the art high temperature nanoindentation system which allows us to perform tests up to temperature above 1000K. These techniques are being used to study a range of important materials for both nuclear power and aerospace applications. We also work with leading groups in Oxford and elsewhere to use understanding gained from our experiments to process new materials better suited to working under extreme conditions.
Materials systems being studied include; ceramic composites, high entropy alloys, refractory alloys, high strength steels and zirconium alloys. This is carried out with a range of partners including, UKAEA, General Atomics, Rolls Royce, Karlsruhe Institute of Technology, Germany and UC Berkeley, and University of Wisconsin-Maddison, USA, as well as many collaborators within Oxford. Particular areas of current research include:
Sodium/Na β″ Alumina Interface: Effect of Pressure on Voids.
ACS applied materials & interfaces
Three-electrode studies coupled with tomographic imaging of the Na/Na-β″-alumina interface reveal that voids form in the Na metal at the interface on stripping and they accumulate on cycling, leading to increasing interfacial current density, dendrite formation on plating, short circuit, and cell failure. The process occurs above a critical current for stripping (CCS) for a given stack pressure, which sets the upper limit on current density that avoids cell failure, in line with results for the Li/solid-electrolyte interface. The pressure required to avoid cell failure varies linearly with current density, indicating that Na creep rather than diffusion per se dominates Na transport to the interface and that significant pressures are required to prevent cell death, >9 MPa at 2.5 mA·cm-2.
Effects of neutron irradiation on the brittle to ductile transition in single crystal tungsten
JOURNAL OF NUCLEAR MATERIALS
Decoration of voids with rhenium and osmium transmutation products in neutron irradiated single crystal tungsten