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CVI pyrocarbon microstructure significant impact on the performance of the C / C composites , and how to control the the CVI process parameters C / C composites rapid densification required structure pyrocarbon domestic and foreign research one of the hot topics . C / C composite materials commonly used in the production of carbon source of propylene, but its gas utilization , expensive , high production costs , and to some extent hindered the development and application of C / C composites . Therefore , to improve the market competitiveness of the C / C composites , the need to develop new carbon source to reduce the production cost of the product . Based on this goal, using natural gas as a carbon source , using temperature CVI prepared C / C composites , respectively preparation of deposition temperature , deposition pressure and gas residence time of isothermal CVI C / C composites densification and microstructure the impact the main results obtained are as follows : (1) the deposition temperature is an important process parameter, CVI densification at a deposition pressure of 10KPa , when the deposition temperature was raised to 1100 ° C by 1000 ℃ deposition 100h, the sample density increased 1.38g/cm3, continue to improve the deposition temperature to 1150 ° C , the density decreases 1.32g/cm3 . Deposition temperature of 1100 ° C , sample internal RL structure . (2) In the deposition temperature of 1100 ℃ , as the deposition pressure is increased from 1KPa to 15KPa, After deposition 100h , the density of the sample from 1.08g/cm3 to 1.58g/cm3 , elevated pressure densification is advantageous . Deposition pressure to 15Kpa , the sample heat pyrocarbon for RL and SL composed Banded structure , the pressure is obtained when RL structure 10KPa and 12kPa . (3) , when the residence time increased 0.32s 0.13 s , the density of the sample from 1.20g/cm3 to 1.46g/cm3 , continue to increase the residence time under the process conditions of a deposition temperature of 1100 ° C and the deposition pressure of 10KPa 0.39s when the density is reduced to 1.05g/cm3. RL structure is obtained when the residence time was 0.22s and 0.32s . ( 4) by orthogonal experimental design , data processing and analysis , that the deposition pressure is the most important factor to determine the C / C composite density , residence time is decided pyrolysis of the carbon microstructure of the most important factors , the present experimental conditions under optimal conditions . Under the conditions of this study , the optimal process parameters of deposition temperature of 1100 ° C , the deposition pressure 12KPa and the residence time of 0.32s .
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