热压烧结氮化硅陶瓷的力学性能研究

Study on Mechanical Properties of Hot-Press Sintering Silicon Nitride Ceramics

采用Y2O3-La2O3和LiF-MgO-SiO22组烧结助剂,通过短切碳纤维增韧的方法,热压烧结制备了氮化硅陶瓷,并对所得氮化硅陶瓷的相组成、微观结构和力学性能进行了分析和讨论。结果表明:长柱状β-Si3N4晶粒有利于提高材料的力学性能;加入纤维不仅不能使材料的抗弯强度提高,反而有所下降,其原因是在高温制备过程中,碳纤维与氧发生反应,在氮化硅陶瓷中产生的缺陷所致。但是加入碳纤维能够提高氮化硅陶瓷的断裂韧性,其原因是碳纤维与氧反应形成的缺陷,使裂纹在断裂过程发生了偏转。

Silicon nitride ceramics were prepared by hot-press sintering method using α-Si3N4 power with short chopping carbon-fiber as starting materials, Y2O3-La2O3 and LiF-MgO-SiO2 as additives, respectively. The phase composition, microstructure and mechanical properties of the ceramics were studied and discussed. The results show that the rod-like β-Si3N4 grains improve the mechanical properties of the composites. The flexure strength decreased when the carbon fiber was incorporated. The main reason is that the defects of the ceramics formed from reaction of carbon and oxygen during the ceramics preparation at the high temperature. At the same time, the defects resulting in the cracks formed, cracks deflection and propagation resistance make the fracture toughness of the ceramics tougher.