| 摘要 |
PURPOSE:To obtain the subject sintered material having improved strength by forming a powdery raw material composed mainly of Si3N4, heat-treating in a non-oxidizing atmosphere under specific condition and sintering the product. CONSTITUTION:Powdery raw material composed of Si3N4 having an average particle diameter of <=0.8mum, a particle size distribution (3sigma) of <=0.4mum and a surface oxygen content of 1.5-2.5wt.% and a sintering assistant is mixed, dried and formed to obtain a formed article. The article is heat-treated at 1300-1500 deg.C in a non-oxidizing atmosphere under 1-100atm, at 1450-1600 deg.C in a non-oxidizing atmosphere under 100Torr to 10atm and then at 1600-1650 deg.C in a non-oxidizing atmosphere under 1-2,000atm to form >=85% of beta-Si3N4 and increase the relative density to >=80%. The total heat-treatment time is >=2hr. The heat-treated product is sintered at 1700-2000 deg.C. |
