碳化硅和氧化铝陶瓷的热等静压氮化

Nitridation of SiC and Al_2O_3 Ceramics by Hot Isostatic Pressing

通过对无压烧结、热压烧结和热等静压烧结ＳＩＣ陶瓷以及热压烧结的ＳｉＣ粒子补强Ａｌ２Ｏ３基复相陶瓷（ＳｉＣｐ－Ａｌ２Ｏ３）和ＳｉＣ粒子与ＳｉＣ晶须共同增强的Ａｌ２Ｏ３基复合材料（ＳｉＣｐ－ＳｉＣｗ－Ａｌ２Ｏ３）在氮气氛中进行高温氮化处理，成功地实现了这些材料的开口气孔表面裂纹的愈合。研究表明：热等静压氯化工艺可以显著提高ＳｉＣ和Ａｌ２Ｏ３陶瓷的抗弯强度，对断裂韧性也有较大的改善作用。对于热等静压烧结ＳｉＣ陶瓷，在１８５０℃和２００ＭＰａ氮气压力下氯化处理１小时后，其抗弯强度和断裂韧性分别由５８２ＭＰａ和５．７ＭＰａ·ｍ１／２提高到９０７ＭＰａ和８．４ＭＰａ·ｍ１／２；对于热压烧结的ＳｉＣｐ－Ａｌ２Ｏ３复相陶瓷和ＳｉＣｐ－ＳｉＣｗ－Ａｌ２Ｏ３复合材料，在１７００℃和１５０ＭＰａ氮气压力下氮化处理１小时后，其室温抗弯强度分别由４６０和７０５ＭＰａ提高到８９５和１０３３ＭＰａ。

Pressureless sintered, hot pressed and hot isostatically pressed SiC monolithic ceramics as well as hot pressed SiC particle-reinforced A12O3 bssed multiphase ceramics(SiCp-Al2O3) and SiC particle and whiskerreinforced A12O3matrix composites(SiCp- SiCw- A12O3 ) are nitrided by hot isostatic pressing in a N2atmosphere at high temperatures. The results have shown that the surface cracks and open POres can be healed and the mechanical properties can be obviously improved by nitridation. For hot isestutically pressed SiC ceramics with an A12O3 addition, when the nitriding process is performed under 200 MPa in N2 at 1850℃ for I h, the fie-cural strength and fracture toughness are increased 582 MPa and 5.7 MPa.m1/2tO 907 MPa and 8. 4 MPa. m1/2, respectively. For hot pressed SiCp-Al2O3and SiCp-SiCw-Al2O3, afternitridation under a N2-pressure of 150 MPa at a temperature of 1700℃ for 1 h, the room-temperaturestrengths are increased from 460 and 705 MPa to 895 and 1033 MPS, respectively.