Turning the heat on - the Centre for Structural Ceramics
The Departments of Materials and Mechanical Engineering at Imperial College London, UK, have been awarded roughly £5.5m by the UK’s Engineering and Physical Sciences Research Council (EPSRC) to set up a national Centre for Structural Ceramics. The first five years funding comes from a Science and Innovation Award, which aims to build new activity in areas of national strategic importance.
Formally started in July 2008, the Centre aims to develop strong links to the energy, aerospace and defence, transport and healthcare industries. There have been four main activities since it opened – recruiting staff, creating an infrastructure, refurbishing premises and specifying equipment.
Support from the EPSRC includes £1.5m for state-of-the-art experimental facilities at Imperial’s South Kensington Campus. This will include the design and construction, in conjunction with equipment manufacturers, of instruments to measure structural properties in ceramics at temperatures (up to 2,400°C) higher than those achieved in current commercial units. Equipment to characterise high-temperature mechanical properties such as fracture, fatigue and nanoindentation is being specified.
The Centre plans to be an inclusive focus for national and international research based on a hub-and-spoke model with other universities, forging links to international centres of excellence.
An industrial consortium is planned, giving UK and international companies input into the research programme. The Centre will host extended visits by world leaders to London as well as national and international conferences.
The five-year funding package includes support for three PhD students based at other UK universities – the first of which has already been awarded to Bill Clegg of Cambridge University, who will supervise work on hardness loss in the ultra-high temperature ceramic titanium carbide.
Key research areas will include –
• High temperature processing of composites and non-oxides. These materials are difficult to process by conventional pressureless sintering because of differential constrained shrinkage in the case of composites, or the lack of atom mobility in non-oxides. The challenge is to overcome these problems using novel strategies to increase green density, driving force or mobility.
The focus will be on bulk thermo-mechanical properties, including hardness, elastic modulus, strength, toughness, specific heat, thermal conductivity, thermal expansion and creep, and fracture toughness, to temperatures above 2,000°C. These will be applied particularly to refractories, composites and laminated materials for ultra-high temperature composites or armour protection. Facilities are planned to study small-scale mechanical and fracture properties of ceramics and interfaces in thin films, coatings, porous materials and laminated structures.
• Characterisation and modelling of nanocomposites. Nanostructured composites, encompassing ceramic matrix composites (CMCs), porous materials and nanobonded composites offer a broad spectrum of advantageous mechanical and functional properties. New techniques such as focused ion beam tomography, nanoindentation and scanning probe microscopy enable characterisation of microstructure and local properties at an unprecedented level of detail. This will allow accurate modelling and design of macroscopic properties.
• Ultra-high temperature and hard non-oxide ceramics. There is enormous scope for novel non-oxide ceramics that have exceptional high temperature strength and creep properties and are harder than oxides in low temperature applications. These include carbides such as zirconium carbide and hafnium carbide, layered compounds such as titanium silicocarbide, nitrides, borides such as hafnium boride and zirconium boride, and non-oxide composites. Key challenges for these materials are processing and environmental protection for high temperature applications in air.
Developing a capability for high temperature (2,500°C) hot pressing will help to improve mechanical properties in CMCs, ultra-high temperature composites and functional gradient materials by understanding the sintering and densification mechanisms.
• Porous ceramics with controllable pore networks. These materials are required for applications in biomaterials, catalysis and filtration. Optimised pore networks are now feasible by combining the advances in processing, microstructural characterisation and property modelling.
• Interfaces. The mechanical and functional properties of ceramic/ceramic and ceramic/metal interfaces offer a rich field for novel fundamental scientific investigation with practical relevance. The analytical power of a Titan transmission electron microscope and the atomistic modelling capability of the Thomas Young Centre, both at Imperial, will be exploited.
• Thin films and coatings. These have wide applications as wear coatings and functional thin films. Film-substrate strain engineering will be used to control functional properties. Fundamental understanding is essential for optimisation.
Three new permanent academic positions – two lectureships and one at professor level – have been advertised. Two of these posts are joint between the two departments. Funding for a post-doctoral researcher and a PhD student is associated with each academic position.
There is also a need to develop expertise in the theories and non-linear, time dependent multi-scale modelling of fracture and damage in monoliths, composites, functionally graded materials, films and coatings, finite element analysis of elastic, plastic and creep deformation and fracture, bonding at interfaces and graded properties at coatings and interfaces, dependence of material properties on microstructure, fabrication processes and mulitaxial stress state, and micromechanisms of deformation over a temperature range.
A local management team, comprising key staff from both departments, has been formed to make tactical decisions and mentor new staff. A steering group, chaired by Professor John Wood and with membership from key industrial and academic partners, is being assembled to provide strategic guidance.
Major funding for laboratory and office refurbishment is available from Imperial College to house the Centre’s equipment and staff. Plans have been drawn up and building work will start in early 2009.