核融合炉用高熱伝導性SiC繊維強化SiCマトリックス複合材料の開発(学位論文)

Development of high thermal conductive SiC fiber reinforced SiC matrix composites for fusion reactors (Thesis)

田口 富嗣

Taguchi, Tomitsugu

SiC/SiC複合材料の熱伝導率を予測するために、新たな3次元モデル(cubicモデル)を提案した。Cubicモデルを用いた理論解析の結果、複合材料内に存在する気孔を球状化すること,高熱伝導率を有する新たな相を熱の伝導方向に平行に導入することにより、複合材料の熱伝導率が著しく増加することがわかった。これら理論解析結果を検証するために、カーボンナノファイバー(CNF)を分散させたSiC/SiC複合材料を、反応焼結法を用いて作製した。熱伝導率測定の結果、室温で90W/mK程度の高熱伝導SiC/SiC複合材料が作製できた。Cubicモデルを用いたCNF分散SiC/SiC複合材料の熱伝導率の推定値と実測値は非常によく一致した。このことから、本研究で提案したCubicモデルの妥当性を実験的に示すことができた。

A 3 dimensional model (after cubic model) was developed to quantitively predict the thermal conductivity of SiC fiber-reinforced SiC matrix (SiC/SiC) composites. The cubic model showed that thermal conductivity of the composites increased by decreasing the porosity and ensphering the shape of pore. The SiC/SiC composites were fabricated by chemical vapor infiltration (CVI) and reaction bonding (RB) processes. The thermal conductivity of the composites by RB process was higher than that by CVI process. The reason is that the porosity of the composites by RB process was lower than that by CVI process and the shape of pore in the composites by RB process was almost sphere. The thermal conductivity of the SiC/SiC composite by RB process was consistent with the estimated value by the cubic model. The cubic model also showed that the thermal conductivity of the composites increased by introducing a high thermal conductive new phase parallel to the direction of heat flow. To verify the prediction, a SiC/SiC composite with carbon nano-fiber (CNF) were fabricated by RB process. The thermal conductivity of the SiC/SiC composite with CNF was approximately 90 W/mK at room temperature. The thermal conductivity of the SiC/SiC composite was coincided with the estimated value by the cubic model. They concluded that the cubic model was useful for predicting the thermal conductivity of fiber-reinforced composites.