Abstract
It has been tried to design and prepare SiC/C Functionally Gradient Material (FGM) accompanying compositional gradient from SiC to C, for developing thermal-barrier materials for space plane. Thermal stresses in SiC monolith and SiC/C⋅FGM were calculated, based on one-dimensional linear analysis for a cylindrical model in infinite length, using Young's moduli, thermal expansion coefficients, thermal conductivities, densities, Poisson's ratios and fracture strength of SiC and C. It was found that that the thermal stress in SiC/C⋅FGM was considerably smaller than that of SiC monolith. According to the graded concentration predicted from the calculation, the possibility of preparation of SiC/C⋅FGM by CVD was investigated under the CVD conditions; a SiCl4-C3H8-H2 system, a deposition temperature of 1773K, total gas pressure of 6.7kPa. A plate (thickness of 1mm) having a compositional gradient from SiC to C was obtained on a graphite substrate by changing Si/C ratio in gas phase during deposition. Many pores were observed in the region of 40-60mol% C.
