自由取向炭/炭复合材料的新型制备及工艺优化

Preparation and process optimization of randomly oriented C/C composites by a novel method

  • 摘要: 采用在炭纤维束的内部浸润熔融沥青的传统方法制备得到的炭/炭(C/C)复合材料难以实现细旦化水平,这是因为单束丝中含有数千根丝,经浸渍后沥青附着,从而引起沥青局部渗出,以及因不均匀沥青稳定性而导致微观结构不均匀。本文通过稳定的中间相沥青和分散的短切炭纤维混合、热压和炭化过程制备出细旦化水平的C/C复合材料。探讨了工艺参数对中间相沥青残炭率的影响。通过残炭率/工艺时间、残炭率×(表观密度/实密度)来优化工艺参数。结果表明,通过此法得到了细旦化水平的中间相沥青与炭纤维复合材料。中间相沥青的残炭率随加热升温速率、沥青/炭纤维质量比的增加而降低;随热压压力而增加。在高压力和高质量比下,发生沥青局部渗出。通过调控得到最佳的C/C复合材料制备工艺参数为:热压压力15 MPa,升温速率0.2℃/min及沥青/炭纤维质量比1:1。

     

    Abstract: Conventional ways of fabricating C/C composites are unable to achieve wetting in the core of the carbon fiber tow by molten pitch because a single tow has thousands of fibers. Pitch stabilization after infiltration into the carbon fiber preform results in local oozing of the pitch and a non-uniform microstructure due to non-uniform pitch stabilization in the preform. The objective of this research was to devise a method by which complete wetting of fibers in the tow with mesophase pitch is attained by mixing stabilized pitch and chopped and scattered carbon fibers, followed by hot-pressing and carbonization. The influence of process parameters on the carbon yield of the stabilized mesophase pitch is evaluated. The carbon yield divided by processing time and the carbon yield multiplied by the ratio of the apparent density to real density of the C/C composites are used to optimize process parameters. Results show that complete wetting of fibers with mesophase pitch is attained by this method. The carbon yield of the stabilized mesophase pitch decreases with heating rate and the mass ratio of stabilized pitch to carbon fibers, and increases with hot-pressing pressure. At high pressures and high mass ratios, local oozing of the stabilized pitch occurs. The optimum C/C composite was prepared under a hot-pressing pressure of 15 MPa, a heating rate of 0.2℃/min and a mass ratio of stabilized pitch to carbon fibers of 1:1.

     

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