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以双峰碳化硅粉末、碳黑、短碳纤维为原料,采用注浆成型、反应烧结法制备了力学性能优异的碳化硅复合材料。研究了硅化反应对碳纤维表面形貌及组分的影响。结果表明:硅化反应在碳纤维表面生成致密β-SiC层,反应过程伴随的体积膨胀增加了纤维表面的粗糙度。混合酸HNO3+HF腐蚀实验表明纤维表面由直径2～5 m的β-SiC晶粒构成。提出了硅化纤维的双层结构模型:外层由微米、亚微米尺度β-SiC晶粒构成,内层由Si–C基团组成的混合物组成。碳短纤维体积分数为30%时,复合材料的弯曲强度、断裂韧性分别达到最大值416MPa、5.1MPa m0.5,相比单一反应烧结碳化硅陶瓷分别提高102%、78%。
Using bimodal silicon carbide powder, carbon black and short carbon fiber as raw materials, a silicon carbide composite material with excellent mechanical properties was prepared by slip casting and reaction sintering. The effect of silicidation on the surface morphology and composition of carbon fiber was studied. The results show that the silicification reaction produces a dense β-SiC layer on the surface of carbon fiber, and the volume expansion accompanying the reaction increases the roughness of the fiber surface. The mixed acid HNO3 + HF corrosion experiments show that the fiber surface is composed of β-SiC grains with a diameter of 2 ~ 5 m. A two-layer structure model of the silicided fiber is proposed: the outer layer is composed of β-SiC grains with micrometer and submicron scales, and the inner layer is a mixture with Si-C groups. The flexural strength and fracture toughness of the composites reached the maximum value of 416MPa and 5.1MPa m0.5, respectively, when the volume fraction of short carbon fibers was 30%, which was increased by 102% and 78% respectively compared with the single reaction sintered silicon carbide ceramic.