Fast densification of thick-walled carbon/carbon composite tubes using electrically coupled chemical vapor infiltration

• Published in: Carbon (New York) 2013-06, Vol.57, p.371-379
• Main Authors: Xiaojun, Wu, Wen, Cheng, Shengru, Qiao, Yan, Li, Lianfeng, Wei, Lin, Cheng, Kangjian, Wu
• Format: Article
• Language: English
• Subjects: Carbon; Carbon-carbon composites; Chemical vapor infiltration; Chemistry; Colloidal state and disperse state; Densification; Density; Exact sciences and technology; General and physical chemistry; Laminar; Porosity; Porous materials; Tubes
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2013.01.085

Rapid densification of thick-walled carbon/carbon (C/C) composite tubes by electrically coupled chemical vapor infiltration (EC-CVI) was investigated. The bulk densities and pore sizes of the C/C composites after different densification periods were measured. The results show that C/C composites were able to be densified by EC-CVI rapidly and efficiently. A thick-walled C/C composite tube, whose outer diameter, inner diameter and height was 240, 60 and 200mm, respectively, was able to be densified to 1.71g/cm3 after a densification time of 400h. If the outer diameter and inner diameter were increased to 400 and 100mm, respectively, the final density of the component reached 1.50g/cm3 under the same experimental condition. After densified by EC-CVI, the amount of the pores with a size larger than 100μm decreased significantly, and the porosity was even close to zero for the composites with a density of 1.62g/cm3. It indicates that EC-CVI can effectively fill the large pores in the composites. In the densified composite by EC-CVI, the pyrocarbon on the carbon fibers presented a rough laminar and smooth laminar morphology dominantly. Finally, the densification mechanism of the C/C composites by EC-CVI was simulated by the fractal method.