M. R. Reda, CanadElectrochim, Saskatoon, SK, Canada
Mike Reda Consultant Visiting prof. Engineering Physics Dept. University of Saskatchewan Canada Thermal insulation materials for sharp leading edges on hypersonic vehicles must be stable at very high temperatures (near 2000ºC). The materials must resist evaporation, erosion, and oxidation, and should exhibit low thermal diffusivity to limit heat transfer to support structures. The effect of the surface shear stresses is to induce high temperature and pressure surface oxidation. Surface oxidation can be considered as solid /gas heterogeneous chemical reaction.The high inter-facial temperature and pressure ( similar to hot working of the material) and in the presence of impurities which act as a dopant, a situation similar to doping of oxide at high temperature and pressures will subsequently induce phase change of the inter-facial layer and degradation. However, if the inter-facial layer is chosen properly so that the anticipated doping of impurities during high speed operation will lead to a phase change that have much lower thermal diffusivity. This can be done by dividing the inter-facial layer into two parts. In the interior part which will undergo a pseudo-liquid heterogeneous catalytic ( catalysis in the micro andnanochannels ) reaction which occurs at room temperature while at the exterior layer a high temperature and pressures non catalyzed heterogeneous reaction issimultaneously occurring.
Summary: Mike Reda
Consultant
Visiting prof.
Engineering Physics Dept.
University of Saskatchewan
Canada
Thermal insulation materials for sharp leading edges on hypersonic vehicles must be stable at very high temperatures (near 2000ºC). The materials must resist evaporation, erosion, and oxidation, and should exhibit low thermal diffusivity to limit heat transfer to support structures.
The effect of the surface shear stresses is to induce high temperature and pressure surface oxidation. Surface oxidation can be considered as solid /gas heterogeneous chemical reaction.The high inter-facial temperature and pressure ( similar to hot working of the material) and in the presence of impurities which act as a dopant, a situation similar to doping of oxide at high temperature and pressures will subsequently induce phase change of the inter-facial layer and degradation. However, if the inter-facial layer is chosen properly so that the anticipated doping of impurities during high speed operation will lead to a phase change that have much lower thermal diffusivity. This can be done by dividing the inter-facial layer into two parts. In the interior part which will undergo a pseudo-liquid heterogeneous catalytic ( catalysis in the micro andnanochannels ) reaction which occurs at room temperature while at the exterior layer a high temperature and pressures non catalyzed heterogeneous reaction issimultaneously occurring.
