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Thermal property and microstructure contrast of three kinds of carbon/silicon carbide composites

机译：三种碳/碳化硅复合材料的热性能和微观结构对比

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One of the key technologies for the high performance reconnaissance satellites and large-scale space telescopes with reflectors is fabrication of a very lightweight material with high specific stiffness, low thermal expansion and high thermal conductivity. As the most preferential candidate at present, carbon/silicon carbide (C/SiC) composite has many special advantages, such as: no toxicity, easy assembly, ultra-light weight capability. Several preparation methods can be utilized to make the C/SiC composites green bodies, which are discussed respectively. Thermal property and microstructure contrast of C/SiC via reactive molten infiltration (RMI) , chemical vapor reaction (CVR) and RMI-CVR are depicted in this article. It is shown that C/SiC made by RMI possess of lower coefficient of thermal expansion and high thermal conductivity. And after microstructure observation, it was found that C/SiC made by CVR and RMI-CVR has different levels of micro pores. Carbon fibers in the composites mentioned above have been damaged at the same time, while similar state was not found in C/SiC made via RMI. In order to get an isotropy composite and to meet the optical and opto-mechanical requirements, two kinds of carbon fiber preforms, integrated felt and needled batton-woven fabric, were selected and desified firstly to a proper density using chemical vapor infiltration (CVI) to form carbon layers around carbon fibers. Upon completion of the preparation of carbon/carbon (C/C) composites green bodies, they had been high temperature treated and then been light-weight machined to form complicated ribs in the backs. Ultra-light weight capability of the two C/C greenbodies was evaluated. Thermal properties of C/C composites were evaluated too. It was found that both of two C/C greenbodies can been light-weight machined to form ribs with 2 mm thickness in each directions, and C/C greenbody with integrated felt preform has a higher isotropy level than the other one.
机译：高性能侦察卫星和带有反射镜的大型太空望远镜的关键技术之一是制造一种具有非常高的比刚度，低热膨胀和高导热率的轻质材料。作为目前最优先的候选材料，碳/碳化硅（C / SiC）复合材料具有许多特殊优势，例如：无毒，易于组装，超轻量。可以采用几种制备方法制备C / SiC复合材料生坯，分别进行讨论。本文描述了通过反应性熔渗（RMI），化学气相反应（CVR）和RMI-CVR的C / SiC的热性能和微观结构对比。结果表明，由RMI制成的C / SiC具有较低的热膨胀系数和较高的导热性。并且通过观察微观结构，发现由CVR和RMI-CVR制成的C / SiC具有不同水平的微孔。上述复合材料中的碳纤维同时被损坏，而通过RMI制成的C / SiC中未发现类似状态。为了获得各向同性复合材料并满足光学和光机械要求，选择了两种碳纤维预成型件，即集成毡和针刺棉/无纺布，并首先使用化学气相渗透法将其设计成适当的密度（ CVI）在碳纤维周围形成碳层。碳/碳（C / C）复合材料生坯的制备完成后，将其进行高温处理，然后轻量化以在背面形成复杂的肋条。评价了两个C / C生坯的超轻重量能力。还评估了C / C复合材料的热性能。结果发现，两个C / C生坯都可以进行轻量化加工，以形成在每个方向上厚度为2 mm的肋条，并且集成毛毡预成型件的C / C生坯具有比其他生坯更高的各向同性水平。

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