氮化硅粉添加剂对反应烧结氮化硅的影响

Effects of Si_3N_4 Powder Additives on the Reaction-Sintering Silicon Nitride

以Mg(OH)_2·4MgCO_3·6H_2O和Al(OH)_3为烧结助剂,在起始原料硅粉中添加等轴状α-Si_3N_4和纤维状β-Si_3N_4,通过调整原料配比,采用反应烧结制备了不同气孔率和抗弯强度的氮化硅陶瓷。考察了氮化硅粉体形貌和添加量对多孔氮化硅陶瓷微观组织和力学性能的影响。借助X射线衍射(XRD),扫描电子显微(SEM)和三点弯曲法对氮化硅陶瓷的微观组织和力学性能进行了研究。XRD分析表明适量氮化硅的添加有利于提高硅粉氮化率,但同时抑制了新生成的氮化硅从α相向β相的转变。SEM表明β-Si_3N_4纤维的添加造成了陶瓷显微结构不均匀,因而导致陶瓷抗弯强度下降。

Silicon nitride ceramics was fabricated by reaction sintering using Mg（OH）2·4MgCO3·6H2O and Ai（OH）3 as the sintering aids. The influence of amount of additional α-SigN4 and β-Si3N4 on their microstructures was investigated. The microstructures and mechanical properties of the ceramics were characterized by XRD, SEM and three-point bending measurement. The addition of Si3N4 increased the nitridation ratio of silicon powders and suppressed the phase transition from α-Si3N4 to β-Si3N4. The initial β-SigN4 grains grew abnormally generating stress and degrading the mechanical properties of the ceramics.