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首页> 美国卫生研究院文献>Journal of Research of the National Institute of Standards and Technology >Microstructural Characterization of Cobalt-Tungsten Coated Graphite Fibers
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Microstructural Characterization of Cobalt-Tungsten Coated Graphite Fibers

机译：钴钨包覆石墨纤维的微观结构表征

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The present research concerns an electrodeposited cobalt-tungsten alloy coating on graphite fibers. Annealed and unannealed coated fibers were analyzed by scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The mole fraction of tungsten in the as-deposited cobalt-tungsten coating was found to be (7.10 ± 0.82) %, and the crystalline lattice was determined to be hexagonal close-packed. Note: The uncertainties reported here are expanded uncertainties (i.e., 2 standard deviation estimates). After annealing at 1100 °C for 1.5 h, the lattice was found to be a cobalt-tungsten-carbon (Co-W-C) alloy with a face centered cubic lattice. The mole fraction of tungsten in the annealed coating was shown to be (5.30 ± 0.66) %. XRD analysis revealed that the annealed coating contained regions having three slightly different lattice parameters. The lattice parameters in the three regions of the Co-W-C alloy coating corresponded to a mole fraction of carbon of 0.66 %, 0.40 %, and 0.19 % (± 0.18 %). These compositions are discussed with respect to the Co-W-C phase diagram. Various tungsten carbide species were identified in the coating and fiber, and a network of overlapping WC crystals was found at the coating-fiber interface. This network appeared to serve as a protective barrier to extend the lifetime of the fibers at elevated temperatures.
机译：本研究涉及石墨纤维上的电沉积钴钨合金涂层。通过扫描电子显微镜/能量色散X射线光谱仪（SEM / EDS），X射线衍射（XRD）和透射电子显微镜（TEM）分析退火和未退火的涂层纤维。发现在沉积的钴-钨涂层中钨的摩尔分数为（7.10±0.82）％，并且确定晶格为六方密堆积。注意：此处报告的不确定性是扩展的不确定性（即2个标准差估算值）。在1100°C下退火1.5小时后，发现该晶格是具有面心立方晶格的钴钨碳（Co-W-C）合金。钨在退火涂层中的摩尔分数显示为（5.30±0.66）％。 XRD分析表明，退火的涂层包含具有三个略有不同的晶格参数的区域。 Co-W-C合金涂层的三个区域中的晶格参数对应于碳的摩尔分数，分别为0.66％，0.40％和0.19％（±0.18％）。关于Co-W-C相图讨论了这些组成。在涂层和纤维中发现了各种碳化钨物质，并且在涂层-纤维界面处发现了重叠的WC晶体网络。该网络似乎是在高温下延长纤维寿命的保护性屏障。

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