炭/炭复合材料中炭纤维的催化石墨化防护研究

Carbon/carbon (C/C) composites are widely used in aerospace and industrial fields due to their outstanding high temperature performance. However, the fabrication temperature of C/C composites is high, and the processing time of C/C composites is long, leading to high costs of C/C composites. Catalytic chemical vapor infiltration (CCVI) can shorten the processing time of C/C composites remarkably, but carbon fibers were catalytically graphitized by catalysts, and the structure of the carbon fibers was destroyed seriously, which will affect properties of the C/C composites. Therefore, a new concept that protection of carbon fibers from catalytic graphitization is introduced in this program, which is explorative and innovative.. In this program, pyrocarbon and pitch-based carbon protection layers will be coated on the surface of carbon fibers by chemical vapor deposition and pitch imgregnation-carbonization method respectively, and catalytic C/C composites and conventional C/C composites will be fabricated by CCVI method, using electroplated Ni as catalyst. Effect of the catalyst and the carbon protection layers on properties of the composites will be studied through thermophysical and mechanical properties comparison of the different C/C composites. Catalytic graphitization mechanism of the carbon fibers as well as protection mechanism of the carbon protection layers with different structures to the catalytic graphitization will be explored through detailed microstructure characterization of the C/C composites, for the purpose of providing a feasible approach for the fabrication of high performance C/C composites by CCVI method.

炭/炭（C/C）复合材料因其杰出的高温性能，已被广泛应用于航空和工业领域。然而，C/C复合材料制备温度高，工艺时间长，导致成本居高不下。催化化学气相渗透法（CCVI）能显著缩短C/C复合材料的工艺时间，但催化剂导致炭纤维被催化石墨化，结构遭到严重破坏，势必影响C/C复合的热物理和力学性能。因此，本课题提出炭纤维的催化石墨化防护的新概念，具有较强的探索性和创新性。. 本课题拟分别采用化学气相沉积和沥青浸渍炭化法在炭纤维表面披覆热解炭和沥青炭防护层，以电镀Ni为催化剂，通过CCVI制备催化C/C复合材料和常规C/C复合材料。通过不同C/C复合材料热物理和力学性能的对比，研究催化剂和炭防护层对复合材料性能的影响。通过对C/C复合材料详细的显微结构表征，揭示炭纤维的催化石墨化机理和不同结构炭防护层对催化石墨化的防护机理，以期为CCVI法制备高性能C/C复合材料提供一种切实可行的途径。

炭/炭（C/C）复合材料因其杰出的高温性能，已被广泛应用于航空和工业领域。然而，C/C复合材料制备温度高，工艺时间长，导致其制备成本居高不下。催化化学气相渗透法（CCVI）能显著缩短C/C复合材料的工艺时间，但催化剂会导致炭纤维被催化石墨化，结构遭到严重破坏，从而影响C/C复合材料的热物理和力学性能。因此，本课题提出了炭纤维的催化石墨化防护的新概念，具有较强的探索性和创新性。. 本课题采用化学气相沉积法在炭纤维表面披覆了不同厚度的炭防护层，采用电镀法在原始炭纤维和披覆炭防护层的炭纤维上加载均匀分布的Ni催化剂。然后，通过CCVI方法制备了无防护层催化C/C复合材料和有炭防护层催化C/C复合材料。根据不同防护层厚度的催化C/C复合材料的详细显微结构对比，表明（1）无防护的炭纤维被严重催化石墨化，Ni催化剂甚至迁移进入炭纤维芯部；（2）170nm厚度的炭防护层可以防止大部分催化剂向炭纤维迁移，但是仍有部分催化剂突破防护层并导致炭纤维皮层被催化石墨化；（3）当炭防护层厚度增加至320nm时，所有催化剂颗粒均被阻挡，炭纤维没有发生催化石墨化。. 因此，本项目研究证实了炭防护层对Ni催化剂导致的炭纤维催化石墨化的防护有效性，并且炭防护层的防护作用与其厚度密切相关，同时阐明了Ni催化剂对炭纤维的催化石墨化机理。本项目研究为CCVI法制备高性能C/C复合材料过程中炭纤维的催化石墨化防护提供了一种切实可行的方法。