反応焼結により作製した酸窒化アルミニウム-窒化ホウ素(AION-BN)複合体の酸化

概要

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AION-BN composite was prepared by heating a mixed powder compact with Al_2O_3-AIN-20 mass% BN-3 mass% Y_2O_3(Al_2O_3/AIN=2.4 in molar ratio) at 1850℃ for 2 h in N_2. The relative density of the heated compact was 70%. Oxidation characteristics of AION-BN composite were investigated over the temperature range of 1000-1500℃ in air. AION and BN were oxidized to form Al_2O_3 and B_2O_3 at the initial stage, respectively. The reaction between the formed B_2O_3 and Al_2O_3 yielded Al_4B_2O_9 and Al_<18>B_4O_<33>. Below 1200℃, oxygen penetrated into the composite through the open pores and oxidation occurred since the surface layer was porous owing to an insufficient amount of the formed B_2O_3 liquid. At 1100 and 1200℃, volume expansion accompanied by the formation of Al_<18>B_4O_<33> caused the occurrence of cracks in the composite. At 1300℃, a relatively dense layer with B_2O_3 liquid surrounded the composite and suppressed the penetration of oxygen into it. At 1500℃, oxidation was promoted to cause the deformation of the composite.
2001-02-01