Y-α/β-sialon的气压烧结

Gas-pressure Sintering of Y-α/β-sialon Composites

研究了Ｓｉ３Ｎ４粉末粒度、相组成、ＡＩＮ粉末的粒度及分阶段烧结工艺对气压烧结α／β－ｓｉａｌｏｎ的致密化、产物相组成和力学性能影响．采用三阶段保温烧结（１７００℃，１ｈ，１８００℃，１ｈ及１９５０℃，１．５ｈ）减少了Ｓｉ３Ｎ４与液相在高温反应促进了材料致密．适当的烧结工艺下及用适当的埋粉；细ＡｌＮ原料有利于材料致密．细Ｓｉ３Ｎ４原料（０．３μｍ）中氧杂质增加导致复合材料中α－ｓｉａｌｏｎ相减少．实验中采用β－Ｓｉ３Ｎ４原料时，产物中没有发现α－ｓｉａｌｏｎ．当Ａｌ２Ｏ３添加量发生较小变动时（如从３．７ｍｏｌ％变为５．１ｍｏｌ％），产物显微形貌发生明显变化．当以ＹＡＧ代替等量的Ａｌ２Ｏ３和Ｙ２Ｏ３作为添加剂时，产物中含有更丰富的长柱状β－ｓｉａｌｏｎ晶粒，１３００～１９００℃相动力学过程研究表明：ＹＡＧ延缓α－ｓｉａｌｏｎ的生成．较少的α－ｓｉａｌｏｎ空间限制及较多的液相促进β－ｓｉａｌｏｎ晶粒的生长．

The effects of sizes and phases contents of the starting materials Si3N4 and AlN, YAG additive and preheating conditions on the gas-pressure sintering behavior, phase compositions and properties of Y-α/β-sialon composites were investigated. Three stages of sintering (1700'℃ for 1h, 1800℃ for 1h and 1950℃ for 1.5h) are necessary for the densification of Y-α/β-sialon composites as the reaction between Si3N4 and liquid phases at high temperature is minimized. Fine AIN powder is beneficial for the densification with proper sintering schedule and embedding powder, Amount of α-sialon phase in the product is decreased when very fine Si3N4 (0.3μm) is used because of increased oxygen content in the powder. No α-sialon phase was found in the product when pure β-Si3N4 was used as raw material in our experiment. By adjusting the Al2O3 amount such as from 3.7mol% to 5.1mol%, the morphologies of the samples varies greatly. The amount of elongated grains increases obviously in the sample with YAG instead of Y2O3 and Al2O3 as additive. Phase development study at the temperatures between 1300℃ to 1900℃ shows that YAG additive postpones the formation of α-sialon.