Thermal properties of chemical vapour-deposition SiC-C nanocomposites
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- Wang, Y., Sasaki, M. & Hirai, T. J Mater Sci (1991) 26: 5495. doi:10.1007/BF02403948
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The relationship between the thermal properties and the microstructure of chemical vapour-deposition (CVD) SiC-C nanocomposites, covering the entire composition range from SiC to C, was investigated after measuring thermal conductivity and thermal expansion. The samples were prepared under deposition temperatures (Tdep) of 1673 and 1773 K and total gas pressure (Ptot) of 40 kPa. The thermal conductivity of CVD SiC-C nanocomposites decreased as C content increased. For the deposits containing 24.3 to 71 mol % C prepared atTdep = 1773 K, some parts of the C phase formed a layered structure having its plane parallel to the deposition surface. This arrangement reduced the thermal conductivity in the direction perpendicular to the deposition surface to a much lower value. The CVD C and CVD C-SiC containing < 1.5 mol % SiC showed strong anisotropic thermal expansion. However, the thermal expansion of CVD SiC-C nanocomposites having a C content up to about 70 mol % was isotropic and nearly equal to that of CVD SiC. The low preferred orientation and the low modulus of elasticity of the C phase may be reasons for these results.