連続, 不連続気孔径分布を有する黒鉛上に気相化学反応により生成したSiC層の微構造評価と残留応力分布

抄録

β-SiC conversion layers have been prepared on two different graphites with the “continuous” and “discontinuous” pore size distribution by the solid-solid (SS) and vapor-solid (VS) reactions in SiO₂-C system. X-ray diffraction patterns of converted specimens showed the noticeable differences in the conversion extent to SiC according to pore size distribution. It was thought that the high infiltration and high conversion rate of “continuous” (CBY) graphite were due to the continuous pore distribution in the range of 0.01-10.0μm. In cross-sectional morphology, the converted “continuous” graphites showed the SiC layer with the interlayer with the average SiC:C ratio of 1:3, but the converted “discontinuous” graphites showed the conversion layer and an interface boundary with the SiC:C ratio in the range of 1:3 to 1:4. The interlayer of converted “continuous” graphite seems to be responsible for the high SiO gas infiltration rate, the resultant active SiC nucleation behavior and the conversion behavior over limited volume of surface. The FEM stress field diagrams of the converted graphites revealed the residual stress fields associated with the thermal mismatch between the conversion layer and the substrate. It was assumed that the stress values of SiC conversion layers measured by X-ray method originated from the additional constraining effects by the stress relaxation across boundaries and the grain growth or grain combination effect in conversion area.