Transmission electron microscopy study of the microstructure of carbon/carbon composites reinforced with in situ grown carbon nanofibers
Transmission electron microscopy study of the microstructure of carbon/carbon composites reinforced with in situ grown carbon nanofibers
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DOI：
10.1016/j.carbon.2012.01.063
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发表时间：
2012-06
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
在C/C复合材料中引入纳米碳纤维（CNFs）是提高C/C复合材料力学性能的有效方法。采用化学气相渗透法制备了原位生长碳纳米纤维增强C/C复合材料和不含碳纳米纤维的常规C/C复合材料。透射电子显微镜研究表明，缠结的CNF（30- 120 nm）在碳纤维（CF）表面形成互锁网络。此外，在CNF的生长过程中，在CF的表面上沉积了薄的高织构（HT）热解碳（PyC）层（约20 nm）。我们发现C/C复合材料的微观结构强烈地依赖于CNF的局部分布密度（LDD）。在低CNF LDD的区域中，形成三层结构。内层（附着于CF）是HT PyC（约20 nm），中间层（150- 200 nm）由HT PyC涂覆的CNF（HT/CNF）和中等织构的PyC组成，最外层（几微米）由HT/CNF和微孔组成。在高CNF LDD的区域中，形成双层结构。内层为HT PyC（~ 20 nm），外层由HT/CNFs、各向同性PyC和纳米孔组成。然而，只有中等织构的热解碳和微孔被发现在传统的C/C复合材料的基体。
Introduction of carbon nanofibers (CNFs) into carbon/carbon (C/C) composites is an effective method to improve the mechanical properties of C/C composites. In situ grown CNFs reinforced C/C composites as well as conventional C/C composites without CNFs were fabricated by chemical vapor infiltration. Transmission electron microscopy investigations indicate that the entangled CNFs (30–120nm) formed interlocking networks on the surface of carbon fibers (CFs). Moreover, a thin high-textured (HT) pyrocarbon (PyC) layer (∼20nm) was deposited on the surface of CFs during the growth of CNFs. We find the microstructure of C/C composites depends strongly on the local distribution density (LDD) of CNFs. In regions of low CNF LDD, a triple-layer structure was formed. The inner layer (attached to CF) is HT PyC (∼20nm), the middle layer (150–200nm) is composed of HT PyC coated CNFs (HT/CNFs) and medium-textured PyC, and the outmost layer (several microns) is composed of HT/CNFs and micropores. In regions of high CNF LDD, a double-layer structure was formed. The inner layer is HT PyC (∼20nm), and the outer layer is composed of HT/CNFs, isotropic PyC and nanopores. However, only medium-textured PyC and micropores were found in the matrix of the conventional C/C composites.