催化剂对B4C-SiC-Si复合材料组织与性能的影响

Effect of Catalysts on Microstructure and Properties of B4C-SiC-Si Composites

摘要:

采用环境友好型间苯二酚甲醛水基凝胶体系,应用凝胶注模成形法制备B₄C/C坯体,结合反应渗Si烧结工艺制备B₄C-SiC-Si复合材料。重点考察Na₂CO₃、NaOH、KOH、Na₂SiO₃和NaHCO₃五种不同碱性催化剂对B₄C-SiC-Si复合材料组织与力学性能的影响。结果表明：催化剂主要影响复合材料的组织均匀性及游离Si的尺寸。添加五种不同催化剂时复合材料主要由B_xC、B₁₂(B,C,Si)₃、SiC和Si组成,以NaOH、KOH或NaHCO₃为催化剂时,复合材料中游离Si的分布较均匀、尺寸较小；以NaOH作为催化剂时,B₄C-SiC-Si复合材料的综合力学性能最佳,其硬度、抗折强度和断裂韧性分别达到16.9 GPa、296 MPa和4.15 MPa.m^_1/2。

Abstract:

The B₄C/C preforms were prepared by the gel-casting and the B₄C-SiC-Si composites were fabricated based on liquid silicon infiltration process. The effects of different catalysts (Na₂CO₃, NaOH, KOH, Na₂SiO₃ and NaHCO₃)on the microstructure and mechanical properties of B₄C-SiC-Si composites were investigated. The results showed that the catalyst mainly affected the microstructural uniformity of composites and the size of residual Si. The composites were mainly composed of B₄C, B₁₂(B,C,Si)₃, SiC and Si. When NaOH, KOH or NaHCO₃as catalyst, the distribution of residual Si was uniform. With the NaOH as catalyst, the mechanical properties of B₄C-SiC-Si composites were the best：the hardness, flexural strength and fracture toughness were 16.9 GPa, 296 MPa and 4.15 MPa.m^_1/2, respectively.