脉冲FCVI制备炭/炭复合材料的微观结构及力学性能

Microstructures and mechanical properties of carbon/carbon composites prepared by impulse forced flow thermal gradient chemical vapor infiltration

采用脉冲强制流动热梯度化学气相渗透（IFCVI）法制备了毡基炭／炭复合材料。借助偏光显微镜及扫描电子显微镜观察了基体热解炭的微观组织结构及断口形貌特征；用弯曲实验测定了材料的力学性能。结果表明：采用脉冲FCVI，经1000℃～1250℃，100h致密化，2300℃热处理后，炭／炭复合材料的密度可达1．7g／cm^3，弯曲强度为125．4MPa，挠度为0．61mm。该工艺致密化速率快，所制备材料的密度分布均匀、力学性能好。研究表明，温度是影响材料组织结构的主要因素，高温条件下有利于粗糙层热解炭组织的生成，而低温有利于光滑层热解炭组织的生成，一般因沉积环境复杂多变，常得到混合型组织。

Felt-based C/C composites were fabricated by an impulse forced flow thermal gradient chemical vapor infiltration technique The micro-morphologies and textural characteristics of the pyrocarbon and fracture surfaces were observed by polarized light microscopy and SEM. The mechanical properties of the composites were tested by bending experiments. Results showed that the density of the composites could be up to 1.7 g/cm^3 after 100 h densification at 1 000-1 250℃. Further heat treatment at 2 300 ℃ was carded out following densification. The flexural strength of the composites could reach 125.4 MPa with a deflection of 0.61 mm. The advantages of this technique were a high densification rate, uniform density and good mechanical properties. Densification temperature had a great impact on the microstructure. A higher temperature favored rough layer pyrocarbon while a lower temperature favored for smooth layer pyrocarbon, but a mixture was obtained in most cases because of complicated densification conditions.