| 摘要 |
PURPOSE: To obtain a silicon nitride sintered compact excellent in heat resistance, high-temperature strength and abrasion resistance and improved in corrosion resistance to liquid sodium by constructing the sintered compact from silicon nitride grains and a crystalline grain boundary of a specific volume fraction and keeping the density of the sintered compact to a specific relative density. CONSTITUTION: Powder of rare earth oxide, aluminum oxide, aluminum nitride, silicon oxide, magnesium oxide, etc., which are sintering auxiliaries in an amount of <=10% as volume fraction of the sintering compact is added to fine grains of silicon nitride which is a hardly sintable material and the mixture is dried and formed. Then, the formed product is sintered at high temperature in an inert atmosphere and retained in a temperature range of 1,500-1,000 deg.C for >=4hr in the temperature-lowering step in sintering to crystallize boundary phase or gradually cooled at a temperature-lowering rate of 100 deg.C/hr in the same temperature range. |
