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采用天然气为前躯体在不同压力下使用化学气相渗积法制备炭/炭复合材料。利用甲烷分解热力学与沉积动力学研究了渗积压力对渗积速率和热解炭组织结构的影响。采用偏光显微镜观察热解炭的组织结构。结果表明:随着渗积压力的增加,初始渗积速率增大;但在渗积后期,渗积速率随着渗积压力的增大而降低,导致在高渗积压力下相同时间制备样品的最终密度降低。热解炭组织结构对渗积压力具有很强的依赖性。在低压(1 kPa)下渗积得到的热解炭基体全部为粗糙层结构。在适中的压力(3kPa,5 kPa,10 kPa)下,以炭纤维为圆心由内到外依次得到各向同性和粗糙层热解炭,整个基体以粗糙层为主。在15 kPa下,得到的热解炭组织结构为各向同性和光滑层组织。
Carbon / carbon composites were prepared by chemical vapor phase infiltration using natural gas as a precursor at different pressures. The effect of percolation pressure on the rate of percolation and the microstructure of pyrolytic carbon was studied using methane decomposition thermodynamics and sedimentation kinetics. Polarized microscope was used to observe the microstructure of pyrolytic carbon. The results show that the initial infiltration rate increases with the increase of the infiltration pressure, but decreases with the increase of the infiltration pressure in the late stage of infiltration, resulting in that the sample preparation at the same time under the hypertonic pressure The final density is reduced. Pyrolytic carbon organization structure has a strong dependence on the pressure of percolation. The pyrolytic carbon matrix obtained by infiltrating at low pressure (1 kPa) is all of rough layer structure. Under the moderate pressure (3kPa, 5kPa, 10kPa), the isotropic and rough pyrolytic carbon was obtained from the inside to the outside with the carbon fiber as the center. The whole substrate was mainly rough. At 15 kPa, the pyrolytic carbon structure obtained is isotropic and smooth layer structure.