Material Systems for Extreme Environments

The conditions in which materials are required to operate are becoming ever more challenging. Operating temperatures and pressures are increasing in all areas of manufacture, energy generation, transport and environmental clean-up. Often the high temperatures are combined with severe chemical environments and exposure to high energy and, in the nuclear industry, to ionising radiation. The production and processing of next-generation materials capable of operating in these conditions will be non-trivial, especially at the scale required in many of these applications. In some cases, totally new compositions, processing and joining strategies will have to be developed. The need for long-term reliability in many components means that defects introduced during processing will need to be kept to an absolute minimum or defect-tolerant systems developed, e.g. via fibre reinforcement. Modelling techniques that link different length and time scales to define the materials chemistry, microstructure and processing strategy are key to speeding up the development of these next-generation materials. Further, they will not function in isolation but as part of a system. It is the behaviour of the latter that is crucial, so that interactions between different materials, the joining processes, the behaviour of the different parts under extreme conditions and how they can be made to work together, must be understood.

Our vision is to develop the required understanding of how the processing, microstructures and properties of materials systems operating in extreme environments interact to the point where materials with the required performance can be designed and then manufactured. Aligned with the Materials Genome Initiative in the USA, we will integrate hierarchical and predictive modelling capability in fields where experiments are extremely difficult and expensive.

The team have significant experience of working in this area. Composites based on 'exotic' materials such as zirconium diborides and silicon carbide have been developed for use as leading edges for hypersonic vehicles over a 3 year, DSTL funded collaboration between the 3 universities associated with this proposal. World-leading achievements include densifying them in <10 mins using a relatively new technique known as spark plasma sintering (SPS); measuring their thermal and mechanical properties at up to 2000oC; assessing their oxidation performance at extremely high heat fluxes and producing fibre-reinforced systems that can withstand exceptionally high heating rates, e.g. 1000oC s-1, and temperatures of nearly 3000oC for several minutes.

The research planned for this Programme Grant is designed to both spin off this knowledge into materials processing for nuclear fusion and fission, aerospace and other applications where radiation, oxidation and erosion resistance at very high temperatures are essential and to gain a deep understanding of the processing-microstructure-property relations of these materials and how they interact with each other by undertaking one of the most thorough assessments ever, allowing new and revolutionary compositions, microstructures and composite systems to be designed, manufactured and tested. A wide range of potential crystal chemistries will be considered to enable identification of operational mechanisms across a range of materials systems and to achieve paradigm changing developments. The Programme Grant would enable us to put in place the expertise required to produce a chain of knowledge from prediction and synthesis through to processing, characterisation and application that will enable the UK to be world leading in materials for harsh environments.

New technologies are demanding ever increasing performance from materials, particularly for components used at very high temperatures in oxidising, high radiation flux and other extreme environments; increasingly, this means turning to ceramic materials for solutions. The work to be done under this proposal will directly address the needs of a number of sectors, including those of the energy and defence industries, where new materials are required. In all sectors of the energy industry, for example, there is clear evidence that materials technology will play a vitally important role in meeting future needs arising from higher temperatures and more demanding environments. Increasing emphasis is also evident for the need to model materials, both to be able to predict their properties before they are made and to develop an understanding of how they will change over time with use. This proposal seeks to address these concerns. The defence sector also places very significant demands on materials and again effective modelling is required across the materials continuum. There is an even greater need to understand how materials behave under extreme conditions of temperature, pressure, high strain rate and shock; a particularly demanding application being leading edges for hypervelocity flight, where temperatures in excess of 2500oC occur during flight in the upper atmosphere where atomic oxygen is present and with very significant mechanical stresses. This proposal will directly address all of these issues.

Both academic and industrial organisations will benefit. Details of the former were outlined earlier; the primary impact on industry will be to provide both new materials and the ability to design enhanced materials to organisations that require materials for components that need to operate under extreme environments, and those that are involved in developing them. An important measure of impact will be the development of an active, connected academic and industrial community. There are a number of organisations who have seen the potential of our proposal and provided letters of support; our research will be generating enabling technology for each of these organisations and many others. All the investigators have strong backgrounds in interacting with industry and are committed to facilitating increased engagement between academia and industry as part of this role. Two way secondments and training are also key components of the strategy. Although exploitation in the UK is a priority, where this is not practical, the team is well connected to the world-wide industry to generate income streams from IPR through licensing deals.

The consortium will use the _Connect portal to establish a dedicated group web site that is capable of delivering webinars and other web based information dissemination. The Materials KTN will assist with cross-linking this with their other relevant interest groups and help to network the Project with other relevant communities. The Thomas Young Centre (TYC) also offers a wide range of opportunities for networking and dissemination. Outreach to the wider community will also be assisted by a self-funding summer school and international conference on composites for extreme environments and a series of two way knowledge exchange workshops and public engagement activities held in years 3 - 5, each focused on a different target audience. Further outreach to the wider scientific communities will be organized by the PI and Co-I's through organizations such as the IOM3, IOP and the RSC. We will also aim to network directly with Government agencies such as DSTL and AWE and will encourage applied research through TSB collaborative projects. Of particular interest will be to get strongly involved with the US Materials Genome Initiative and to interact more with leading teams in the US (e.g. the National Hypersonic Science Centre for Materials & Structures and AFRL), ISTEC in Italy and teams in Australia.