热解碳沉积温度对增强石墨力学性能的影响

Effect of densification temperature on mechanical properties of graphite reinforced by pyrolytic carbon

采用化学气相沉积增密技术制备热解碳增强普通石墨材料。研究沉积温度对增强石墨力学性能的影响,并探讨热解碳增强普通石墨材料的沉积机理。结果表明:随沉积温度升高,增强石墨的抗弯强度提高,在1 600℃沉积时达到最大值39.33 MPa,比石墨基体提高21.7%。其主要原因是随沉积温度升高,热解沉积由CVI过程变为CVD过程。当温度低于1 600℃时,化学气相渗透过程占主导;温度高于1 600℃后热解碳极易沉积在基体表面,形成热解碳膜,化学气相沉积过程占主导。在1 600℃温度下,其抗弯强度随沉积时间的变化不大,这证明高温下(1 600℃)化学气相沉积主要发生在石墨块体表面。

The common graphite materials reinforced by pyrolytic carbon were prepared by chemical vapor deposition. The effect of deposition temperature on the mechanical properties of the common graphite materials reinforced by pyrolytic carbon were studied. The deposition mechanism of pyrolytic carbon was studied, too. The results show that： the flexural strength of graphite rises gradually, with the increase of deposition temperature, until to the deposition temperature of 1 600℃. The main reason is that the pyrolytic process changed from CVI into CVD process with the deposition temperature increased from low to high. When the temperature is lower than 1 600℃, the chemical vapor infiltration process dominated. When the temperature is higher than 1 600℃, the deposition of pyrolytic carbon on the matrix surface is extremely easy and forms pyrolytic carbon film, as well as chemical vapor deposition process is dominated. The variation of flexural strength with the deposition time changes little at the temperature of 1 600℃, which proves that chemical vapor deposition occurs mainly in the graphite block surface at the high temperature.