Chemical reaction process and densification mechanism ofChemical Vapor Infiltration (CVI) technology forCarbon/Carbon composites

摘要

C/C composites were fabricated using Pressure-Gradient CVI technology with Propene (C3H6) as the carbon precursorgas, N2 as the carrier gas. The CVI process was deduced from analyzing the component of molecules in gas phase andobserving the microstructure of deposition carbon. The results show that CVI process starts from the breakdown of C-C singlebond of Propene (C3H6), and form two kinds of active groups in the process of the homogeneous gas phase reaction.Afterwards, these active groups form many stable bigger aromatic molecules. These stable bigger aromatic molecules depositin carbon fiber surface immediately. At the same time, the hydrogen atoms of the bigger molecules deposited on the carbonfiber surface are eliminated and the solid pyrolytic carbon matrices are formed in the heterogeneous reaction process. Inaddition, the solid carbon powders formed in the homogeneous reaction process and deposited on the carbon fiber surface actas the crystallization centers.