机械合金化与热压烧结法制备2Si-B-3C-N陶瓷

2Si-B-3C-N Ceramics Prepared by Mechanical Alloying and Hot-Pressing Consolidation

以Si3N4、B4C、C、Si等粉末为原料,采用机械合金化方法制备2Si-B-3C-N粉末,在氮气保护下1900℃,40MPa热压烧结30min获得2Si-B-3C-N陶瓷,研究了块体陶瓷微观组织结构与力学性能。高能球磨粉末在热压烧结后致密度达到了97.9%。热压烧结的2Si-B-3C-N陶瓷中主要含有等轴状的β-SiC和层片状的h-BCN相。BCN晶粒尺寸约为200nm,SiC晶粒尺寸约为400～500nm。BCN晶粒主要分布在SiC晶粒周围。2Si-B-3C-N陶瓷的室温抗弯强度、弹性模量、断裂韧性、硬度分别为446.6MPa、144.6GPa、5.10MPa·m1/2和5.53GPa。在高温空气状态下,2Si-B-3C-N陶瓷的抗弯强度随温度的升高而降低,1000和1400℃下的抗弯强度分别为358.7和202.1MPa。

2Si-B-3C-N powders were prepared by mechanical alloying with Si3N4, B4C, C and Si as starting materials and they were hot pressed at 1900 ℃ under 40 MPa for 30 min in N2 atmosphere to obtain 2Si-B-3C-N ceramic. Microstructure and mechanical properties of the bulk ceramic were studied. After hot pressing the density of the powder was up to 97.9%. The HPed ceramic was mainly composed of equiaxed β-SiC and lamellar h-BCN phase. The size of BCN grains was about 200 nm and that of SiC about 400-500 nm. BCN grains distributed around SiC grains. The flexural strength, elastic modulus, fracture tough and Vickers hardness were 446.6 MPa, 144.6 GPa, 5.10 MPa^1/2 and 5.53 GPa, respectively. In air atmosphere at high temperature, the flexural strength decreased as the temperature increasing, which was 358.7 MPa and 202.1 MPa at 1000 ℃ and 1400 ℃, respectively.