常圧焼結窒化ケイ素セラミックスの機械的及び耐アルカリ腐食特性に対する粒界結晶化の効果

概要

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To evaluate an effect of grain boundary crystallization on corrosion characteristics of sintered silicon nitride in alkaline, weight-loss was measured during corrosion test in boiling 30 mass% NaOH aqueous solution up to 200h for as-sintered and heat-treated Si_3N_4(1100℃, 3h+1400℃, 6h). As-sintered and heat-treated Si_3N_4 showed 0.8 mass% and 0.1mass% weight decrease after 200h, respectively. The grain boundary crystallization was effective to improve the corrosion resistance of Si_3N_4. This could be attributed that quarternary oxynitrides Y_8Si_4N_4O_<14> and Y_<20>Si_<12>N_4O_<18>called as J-phase and H-phase, respectively, crystallized in intergranular liquid by the heat treatment, resulting in a decrease of residual secondary glass phase in grain boundaries. Mechanical characteristics including crushing load of Si_3N_4 ball, fracture toughness and hardness were evaluated, and the grain boundary crys-tallization improved these properties slightly.
社団法人日本セラミックス協会の論文
1995-02-01