The current study was intended to synthesize and characterize the physical, chemical, and mechanical properties of carbon/ carbon (C/C) composites using the chemical vapor infiltration (CVI) process. To that end, carbon fiber felt (CF) was used as a preform, and methane and hydrogen were employed as reactive and carrier gases, respectively. After deciding on the optimum temperature (1050 °C), the composite samples were produced at different times (0–195 h). Then the samples were studied for their phase and microstructure characteristics using XRD, SEM, FESEM, FTIR, and Raman spectroscope. The results showed that by increasing the CVI process time up to 195 h, the density of the produced samples increased from 0.20 to 1.62 g/cm3, and the specific surface area decreased from 58.78 to 0.23 m2/ g. Also, by increasing the process duration, the deposition rate decreased due to the reduction of the available surface for carbon deposition. In other words, due to the increase in density, and decrease in both porosity and specific surface area, the thermal conductivity coefficient and the bending strength of the samples increased. The composite specimens’ SEM images of the fracture surface indicated a weak interface between the carbon fibers and the carbon layer developed by the CVI process. The structural analyses showed that the morphology of carbon growth during the CVI process was initially laminar, but changed to rough-laminar (RL) with the higher duration of the CVI process.

The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.

The “Film boiling” Chemical Vapor Infiltration (CVI) process is a rapid densification one developed in particular for theelaboration of carbon/carbon composite materials. In order to optimize this new thermal gradient process, we have carried outseveral studies, on one hand, about the nature of the complex chemical reactions in a confined medium, and on the other hand,relative to the role of heat and mass transfers inside the preform. We show in this study that the introduction of a permeablesheath around the preform leads to hybrid liquid/gas CVI process which presents the advantages of very high densificationrates associated with a moderate input energy.

프로판(C3H8)을 반응가스로 사용하여 등온 저압화학기상침투법(low-pressure chemical vapor infiltration)으로 탄소/탄소 복합재료를 치밀화 할 때 반응온도, 반응가스농도, 가스유량, 반응압력 등의 제조공정변수들이 치밀화에 미치는 영향을 알아보기 위하여 실험계획법(Rdbust design method)에 의한 실험을 행하였다. 1회의 등온 저압화학기상침투 실험으로 탄소/탄소 복합재료의 부피 밀도와 표면과 내부의 부피 밀도의 차이를 특성치(characteristic value)로 한 실험계획법의 분산분석(analysis of variance)에 의하면 반응온도, 반응가스농도, 가스유량 등의 제고공정변수가 치밀화에 기여도가 높으며, 반응압력의 기여도와 제조공정변수들의 교호작용(interaction)에 의한 기여도는 낮은 것으로 나타났다. 반응온도가 1100˚C, 반응가스농도가 100% C3H8, 가스유량이 100 SCCM, 반응압력이 5torr인 조건에서 탄소/탄소 복합재료는 가장 높은 부피 밀도값을 나타내었으나 시편의 표면과 내부의 부피 밀도 차이값은 컸다.