氮化硅（Si3N4）微粉的超高压烧结研究

 氮化硅（Si₃N₄）是具有优良性能的陶瓷材料，具有广泛的工程应用前景。但由于这种化合物属于共价结合性质并具有很高的熔点，陶瓷的烧结需要在很高的温度下进行。本文探讨了在超高压力下这种材料的烧结行为的变化。对含有AlN、Al₂O₃及少量La₂O₃添加物的Si₃N₄微粉在3~7 GPa，800~2 000 ℃的压力温度范围内进行烧结，并应用X射线衍射、扫描电子显微镜观察及密度测量等方法研究了烧结样品。结果表明高压力可以大大促进Si₃N₄的α→β转变及固相反应，降低烧结温度。高压下烧结过程分为两个阶段：低温下以粉末粒子结合为主要内容的过程及高温下各物相间的相变和固相反应为主的过程。研究表明，超高压力下烧结没有改变所研究组份样品的复合相组成。

A STUDY ON SINTERING BEHAVIOR OF SILICON NITRIDE Si_3N_4 MICRO POWDER UNDER HIGH PRESSURES

Silicon nitride (Si₃N₄) is a series of ceramic material with outstanding technological properties and has been widely investigated for various engineering applications. On the other hand, these kinds of ceramics are of covalent bounding and are very difficult to sinter. This investigation was conducted for understanding the high pressure sintering behavior of Si₃N₄ micro-powder samples. Sintering was performed at high pressures ranging from 3 to 7 GPa and temperatures in a range of 800~2 000 ℃. The sintering samples are composed of Si₃N₄ and AlN, Al₂O₃ and La₂O₃ additives. The sintering compacts were characterized with the aid of X-ray diffraction, scanning electron microscopy and density measurement methods. The obtained results shows that the α→β conversion of Si₃N₄ phase is greatly promoted by highly compression and the powder samples could be sintered at quite lower temperatures. Additionally, the high pressure sintering process is observed to be consisting of two stages: at moderate temperatures the sintering process consists of only the joining of the composited particles, while at high enough temperatures, the solid state reactions between the composite powders can be greatly proceeded and resuled in a fully sintered compacts.