以炭毡为预制体,甲烷为炭源前驱体,沉积温度为1000℃～1150℃的工艺条件下,从温度梯度,密度梯度和沉积动力学方面,研究了制备炭/炭复合材料的微波热解CVI工艺特点,分析了微波热解CVI工艺的沉积机理.结果表明:采用微波热解CVI工艺可制备出体积密度为1.84g·cm-3的炭/炭复合材料,平均致密化速率达0.063g·cm-3·h-1.温度梯度的存在,使预制体实现了从内至外逐步沉积;微波的引入,增加了纤维表面的有效活性点,提高了表面反应速率;微波对化学反应具有一定的催化作用.
Microwave assisted chemical vapor infiltration for the rapid fabrication of carbon/carbon (C/C) composites was investigated at 1000-1150℃ for different times using carbon felts as substrates and methane as carbon precursor. The temperature and density distribution in the felts were measured and the densification kinetics were investigated. It is found that the highest density of the C/C composite prepared by this method is 1.84 g/cm3 with a densification rate of 0.063 g·cm-3·h-1. The mechanism of the effective and rapid densification is accounted for by a densification from the inside to the outside of the felts under an inverted temperature gradient, an increase of the available active sites for carbon deposition, an increase of conision probability between hydrocarbon species and carbon fibers, and a catalytic effect of microwaves for the pyrolysis of methane.
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