微波CVI制备碳碳复合材料微观组织结构的研究

Study on Microstructure of C/C Composites Prepared by Microwave Chemical Vapor Infiltration

以甲烷为碳源气体,普通碳毡作为预制体,采用微波CVI方法制备了碳碳复合材料。考查了温度为1100℃时,气体浓度对碳碳复合材料微观结构的影响进行了研究,并用金相显微镜、扫描电子显微镜(SEM)等手段对热解碳组织结构进行观察和分析。结果表明,随着气体浓度的增加,热解碳的组织结构从中织构转变为高织构,最后又转变为中织构组织。同时,对沉积后的断口形貌与外观进行SEM分析,发现微波CVI下热解碳沉积形貌与其它CVI技术所得到的形貌明显不同,呈现一种漩涡状的圆包结构,提出了一种新的热解碳沉积模式:气相成核-液相融并-逐层生长模式。

With methane as carbon source gas,carbon felt as porous preforms,C/C composites were fabricated by microwave CVI process at 1100℃ with residue time of 0.2s.The effect of methane concentration on microstructure of the C/C composites was studied,and the microstructure of samples were observed and analyzed by polarized optical microscopy and scanning electron microscopy.Results show that the textures of the matrix carbon change from medium-textured to high-textured firstly,and then to medium-textured with the increasing of gas concentration.Simultaneously,the morphology of pyrolytic carbon by microwave CVI process shows a kind of circinate round-wrap structure through SEM observations,which is obviously different from that of other CVI processes.A new deposition mode of pyrocarbon is presented: gasous nuclei-liquid syncretism-lamellar growth pattern.