高温处理对PCS裂解SiC基体的微晶形态及C/C-SiC材料性能的影响

采用聚碳硅烷(PCS)作为先驱体,通过浸渍裂解法制备C/C-SiC材料,分别经过1 400、1 500、1 600℃高温处理,研究了不同处理温度对SiC基体的微晶形态及C/C-SiC材料力学性能和抗氧化性能的影响。结果表明,3种处理温度下,SiC的晶型主要为β-SiC。温度升高,晶粒尺寸增大,1 500℃以后生长速度减缓;SiC微晶优先沿着(111)晶面生长,(220)和(311)晶面的生长取向逐渐增加。处理温度升高,C/C-SiC材料的弯曲强度和剪切强度不断下降。1 400℃处理后,C/C-SiC材料的断裂方式呈现出非常明显的韧性断裂。C/C-SiC材料在1 500℃静态空气中的氧化失重率随高温处理温度的升高而逐渐增大,氧化程度越来越严重,断面典型区域的氧化形貌由"尖笋状"成为"梭形"。

Effects of high temperature treatment on crystallite morphology of SiC matrix pyrolyzed from PCS and properties of C/C-SiC composites

C/C-SiC composites were fabricated with polycarbosilane(PCS) as precursor by infiltration and pyrolysis via high temperature treatment at 1 400 ℃,1 500 ℃ and 1 600 ℃ respectively.The effects of different treatment temperature on crystallite morphology of SiC matrix and mechanical property and oxidation-resistance property of C/C-SiC composites were investigated.The results show that β-SiC mainly forms at 1 400 ℃,1 500 ℃ and 1 600 ℃.With temperature rising,crystal size increases,and growth velocity decreases when temperature is above 1 500 ℃.The crystallite of SiC grows firstly along(111) plane,and the orientation of(220) plane and(311) plane gradually increase.Flexural strength and shear strength of C/C-SiC composites gradually decrease with temperature rising.Fracture mode of C/C-SiC composites exhibites obviously toughness fracture after high temperature treatment at 1 400 ℃.The oxidation weight loss rate gradually increases at 1 500 ℃ in air while treatment temperature rises.Oxidation degrees become increasingly severe.Oxidation morphology of typical region of fracture surface becomes from "bamboo shoot" to "shuttle".