载气对碳/碳复合材料致密化过程及微观结构的影响

Effect of Carrier Gas on the Densification Process and Microstructure of Carbon / Carbon Composites

以天然气作为碳源,以H_2和N_2为载气,采用等温化学气相沉积工艺制备碳/碳复合材料。采用偏光显微镜、SEM、万能试验机等表征所制备碳/碳复合材料的微观结构、密度变化和力学性能等。研究了碳源气体与载气比例对碳/碳复合材料致密化速率和热解碳微观结构以及力学性能的影响。结果表明:载气对碳/碳复合材料的致密化速率以及微观结构有重要影响(相对于不添加载气的情况,添加H_2和N_2的混合气体后,碳/碳复合材料的最终密度从1.42g/cm^3提高到1.71g/cm^3,而密度梯度Δρ从0.15g/cm^3降到0.04g/cm^3)。H2对优化气相裂解成分,抑制致密化初期的表面结壳、促进高织构热解碳的形成有显著影响,而N_2则对抑制致密化后期的表面结壳效果显著。

Carbon/carbon composites were prepared by isothermal chemical vapor deposition process using natural gas as carbon source and N2 and H2 as carrier gas. The microstructure, density and mechanical properties of carbon/carbon composites were characterized by polarizing optical microscope, SEM and universal testing machine. The effects of the ratio of carbon source gas and carrier gas on the densification rate and microstructure and mechanical properties of carbon/carbon composites were studied. The results showed that carrier gas had an important influence on the densification rate and microstructure of carbon/carbon composites. Compared with the situation without carrier gas ,after adding mixed gas of H2 and N2 ,the final density of carbon/carbon composites increased from 1.42g/cm^3 to 1.71g/cm^3 ,and the density gradient was reduced from 0. 15g/cm^3 to 0.04g/cm^3. H2 had significant effect on gas phase component and the promoting the formation of high texture pyrolysis carbon,but N2 suppressed surface crusting of later process of CVI.