炭化珪素焼結体の酸化におよぼすK₂O-Al₂O₃-SiO₂系結合剤の影響

抄録

The principal purpose of this investigation was to make clear the oxidation behavior at 1200° to 1400°C of silicon carbide bodies containing 15% bonds in the system K₂O-Al₂O₃-SiO₂.
The oxidation resistance was determined using a small plate specimen 14mm in diameter and about 8mm thick. For most of work the specimen was oxidized at 1200° and 1400°C in a flowing atmosphere with controlled amounts of oxygen and water vapor. The weight gain, volume change, and porosity of the specimen were determined. The results obtained are summarized as follows:
(1) The bonds containing large amounts of K₂O and Al₂O₃ retarded the oxidation of silicon carbide. At 1200°C K₂O was more effective on reduction of the oxidation than Al₂O₃, but at 1400°C the effect of Al₂O₃ on the oxidation resistance became somewhat high.
(2) Silicon carbide was oxidized very strongly by the mixture of water vapor and oxygen when heated above 1200°C. It was observed that at such a high temperature the specimen swelled and cracked and permitted oxidation.
(3) The presence of Al₂O₃, K₂O in the bodies and water vapor in the atmosphere caused the formation of cracks, which had also been found in ceramic bonded silicon carbid refractories. The mechanism of formation of cracks was explained on the basis of reactions in the system K₂O-Al₂O₃-SiO₂-H₂O.
(4) After heating the specimen in air at 1400°C for 10 hrs the rate of oxidation by water vapor at 1200°C diminished considerably.