题目: Ultra-high Temperature Ceramics for Thermal Protection of Hypersonic Flight
Professor Luc Vandeperre is a Professor of Structural Ceramics at Imperial College London, UK. He is the director of the EPSRC Centre for Doctoral Training in Nuclear Energy and the deputy director of the Centre for Advanced Structural Ceramics. He is a Fellow of the Institute of Materials, Minerals and Mining (IoM3) and of the Higher Education Academy of the UK. His research interests are in processing and properties of advanced ceramics and alternative cements, including ultra-high temperature ceramics for hypersonic flight, shaping of ceramics for turbine engines, ceramics for armour, 3D printing of ceramics, and novel sorbents for uranium for the safety case of geological disposal.
Hypersonic vehicles experience very high temperatures and heat fluxes due to the extreme gas temperatures encountered. These conditions lead to complex flow fields with real gas effects such as non-equilibrium thermochemistry, dissociation and ionisation. For re-entry vehicles, radiative cooling and ablative materials are used to cope with these extreme heat loads. Ultra high temperature ceramics with melting points above 3000 °C are the leading candidates for this application and their ability to withstand high heat inputs will be demonstrated by discussing the results of laser heating. However, for prolonged exposure to high temperature in oxygen containing environments, their poor oxidation resistance and the lower melting point of the oxides, eventually leads to a loss of shape stability of the surfaces crucial for flight. Therefore work is now focussing on transpiration cooling, not only as a technology capable of cooling the components, but more importantly as a technology to offer oxidation protection. Early tests results confirm that this will be possible provided a range of porous materials can be fabricated with designable permeability to the gas. The use of 3D printing to realize this will be the final topic of the seminar.