Transmission electron microscopy study of the microstructure of unidirectional C/C composites fabricated by catalytic chemical vapor infiltration
Transmission electron microscopy study of the microstructure of unidirectional C/C composites fabricated by catalytic chemical vapor infiltration
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DOI：
10.1016/j.carbon.2012.08.070
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发表时间：
2013
期刊：
影响因子：
10.9
通讯作者：
Yequn Liu;LianLong He;Xue-feng Lu;P. Xiao
中科院分区：
文献类型：
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作者：
Yequn Liu;LianLong He;Xue-feng Lu;P. Xiao
以化学镀镍-磷为催化剂，采用化学气相渗透法制备了单向碳/碳（C/C）复合材料。透射电镜（TEM）研究表明，热解炭（PyC）基体中100 ~ 800nm的催化剂颗粒由Ni3P相和Ni相组成，而碳纤维中微小的催化剂颗粒（<50nm）中只观察到Ni3P相。催化剂颗粒在基体中被高织构的PyC壳包裹，在壳中观察到开口。复合材料中中等织构PyC的厚度（720 ~ 850nm）大于常规C/C复合材料（660 ~ 740nm），但织构程度差异不显著。催化剂部分从PyC壳中挤出并迁移到碳纤维中，导致碳纤维的催化石墨化，破坏了碳纤维的结构均匀性。基于TEM观察，提出了碳纤维催化石墨化的溶解/沉淀机理，提出了催化剂颗粒的溶解/沉淀/包封/断裂/挤压机理。
Unidirectional carbon/carbon (C/C) composites were fabricated by catalytic chemical vapor infiltration, using electroless Ni–P as catalyst. Transmission electron microscopy (TEM) investigations indicate that the catalyst particles (100–800nm) in the pyrocarbon (PyC) matrix are composed of Ni3P and Ni phases, but only the Ni3P phase was observed in the tiny catalyst particles (<50nm) in carbon fibers. The catalyst particles in the matrix were encapsulated by high-textured PyC shells, in which openings were observed. The thicknesses of the medium-textured PyC in the composites (720–850nm) are greater than in conventional C/C composites (660–740nm), but have no significant difference in texture degree. Catalysts were partially extruded out of the PyC shells and migrated into the carbon fibers, leading to the catalytic graphitization of the carbon fibers, and their structural homogeneity was destroyed. Based on the TEM observation, a dissolution/precipitation mechanism was proposed for the catalytic graphitization of carbon fibers, and a dissolution/precipitation/encapsulation/fracture/extrusion mechanism was proposed for the encapsulation of catalyst particles.