由聚碳硅烷生成纳米SiC颗粒增强B4C基复相陶瓷的结构与性能

制备了由聚碳硅烷（PCS）为先驱体裂解形成的纳米SiC增强的B₄C基复合材料,并与直接球磨混合法制备的纳米SiC增强的B₄C基复合材料进行了对比研究.实验结果表明,先驱体法制备的复合材料形成一种复杂的晶内/晶间结构;B₄C内部的纳米SiC和Al₂O₃内部的少量纳米SiC、晶界处的层片状SiC、B₄C晶粒内部的SiC亚晶界结构.材料的断裂方式以穿晶断裂为主,形成晶内裂纹扩展路径,增强了材料的韧性.采用PCS为先驱体工艺制备高性能的纳米复相陶瓷,其组织均匀性、致密度和力学性能均优于直接机械混合制备的纳米复合材料.

Microstructure and Properties of Polycarbosilane Transferred Nano SiC Reinforced B4C Matrix Composites

Nano-sized SiC reinforced B₄C matrix composites were fabricated through a pyrolysis route from polycarbosilane(PCS) precursor. The microstructure and properties of the materials, compared with the materials sintered by direct mixed powders, were investigated. It shows that, the composites fabricated via precursor form a kind of complicated intra-intergranular structure: nano SiC within the grains of B₄C and Al₂O₃, sharp angle-layered SiC precipitating in the grain boundaries, and SiC substructures within the grains of B₄C. The crack deflection within the crystal grains is caused by intragranular fracture, increasing the fracture toughness significantly. The homogenization, relative density and mechanical properties of the composites fabricated by polycarbosilane precursor are higher than those of the composites made by directly mixed powders.