Si_3N_4セラミックスの焼結過程における固相-気相反応(第2報) : カーボン粉末中で熱処理したときのSi_3N_4のβ→α'転移

概要

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Monolithic β-Si_3N_4 ceramics with additives of 5 mass%Y_2O_3 and 5 mass%Al_2O_3 were prepared by gas-pressure sintering at 2023 K at a N_2 pressure of 1 MPa with 50 mass%Si_3N_4/50 mass%BN powder bed. When β-Si_3N_4 was heat-treated at 2023, 2073 and 2123 K at the N_2 pressures of 0.1 and 1 MPa with a carbon powder bed, a surface layer containing mainly SiC was generated. Inside the SiC layer, α-SiAlON was generated. Moreover, melilite(Y_2Si_3O_3N_4)was observed when the N_2 pressure was 0.1 MPa. The reasons for the generations of α-SiAlON and melilite were thought to be as follows. During the formation of the SiC layer, the liquid phase with Y- and Al-elements was excluded from the original surface layer. The liquid phase with Y- and Al-elements concentrated between the SiC layer and the β-Si_3N_4 bulk. Finally, Y and Al in the liquid phase reacted with β-Si_3N_4, and α-SiAlON and melilite were formed.
社団法人日本セラミックス協会の論文
2000-02-01