Fabrication of Advanced C/C Composites by a Hybrid Process of CVI/Liquid Precursor Impregnation

ABSTRACTFabrication process of advanced C/C composites was developed by combining the CVI and liquid impregnation-pyrolysis processes. Time-controlled temperature-gradient (TC-TG-) CVI process was developed to accelerate the carbon matrix deposition in the C-fiber preform within relatively short process-time. The temperature gradient in the preform was changed according to a controlled program. The present TC-TG-CVI process gave twice as much weight gain as that of the conventional steady TG-CVI process. The CVI process, however, showed limitation to fill up the large pores between the bundles. Liquid impregnation-pyrolysis was, therefore, carried out after the TC- TG-CVI process to improve the infiltration of these pores. Polycarbosilane (PCS) with the yield of about 50 wt% was used as the liquid precursor to form a SiC-rich matrix to improve the oxidation-resistance. SiC matrix was observed in the pores between bundles after pyrolysis of PCS. The weight gain after pyrolysis was found to be nearly saturated after 10 cycles of the impregnation-pyrolysis process.

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Effect of PCS Pyrolysis Process on C Fiber in Cf/SiC Composite

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.1284 ◽

2007 ◽

Vol 336-338 ◽

pp. 1284-1286

Author(s):

Yun Zhou Zhu ◽

Ming Yuan ◽

Zheng Ren Huang ◽

Shao Ming Dong ◽

Dong Liang Jiang

Keyword(s):

High Temperature ◽

Carbon Fiber ◽

Concentration Gradient ◽

Bending Strength ◽

Pyrolysis Process ◽

Fiber Preform ◽

Intrinsic Structure ◽

C Fiber ◽

The Matrix ◽

Polymer Infiltration

3-D braided C fiber preform was used to reinforce SiC matrix by polymer infiltration and pyrolysis (PIP). The effect of PCS pyrolysis process on the uncoated carbon fiber was studied. During the pyrolysis, amorphous SiCxOy and some free silicon yielded. The Si element diffused into the C fiber from the matrix because of the concentration gradient at high temperature and destroyed the intrinsic structure of the uncoated C fiber. At the same time, the free Si reacted with the uncoated C fiber. Thus, strong bonding between the fiber and matrix was formed. As a result, bending strength of the composite was decreased.

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Densification Behavior and Microstructure Evolution of SiCf/SiC Composites Incorporated with In Situ Grown SiC Nanowires

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.124-126.711 ◽

2007 ◽

Vol 124-126 ◽

pp. 711-714 ◽

Cited By ~ 1

Author(s):

Seok Min Kang ◽

Weon Ju Kim ◽

Ji Yeon Park ◽

Soon Gil Yoon ◽

Woo Seog Ryu

Keyword(s):

Growth Behavior ◽

Densification Behavior ◽

Fiber Preform ◽

Matrix Deposition ◽

Sic Nanowires ◽

Sic Fiber ◽

The Matrix ◽

Sic Composites ◽

Fiber Preforms

SiC nanowires could be grown homogeneously within SiC fiber preforms by controlling the concentration of a reactant gas. The morphology and the growth behavior of the SiC nanowires were largely dependent on the degree of the reactant supersaturation. The SiC nanowires incorporated in the fiber preform increased the surface area at which the matrix deposition could take place, enhancing an efficiency of the matrix infiltration and altering the remaining pore structure of the SiCf/SiC composite.

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