Densification Behavior of Thermal Gradient CVI of Large-scale C/C Composites

doi:10.15541/jim20140291

Abstract

Abstract:

Using integral carbon felt as reinforced perform, large-scale C/C composites were prepared by thermal gradient-chemical vapor infiltration (TG-CVI) with two temperature controlling ways, namely keeping constant temperature of the inner wall or outer wall of the samples. The results indicated that, for keeping constant temperature of the outer wall, the composite density was merely 0.64 g/cm³, showing high-low-high distribution across the wall. Meanwhile, its structure comprised rough laminar and smooth laminar. For keeping constant temperature of the inner wall, the density of the sample showed evenly distribution across the wall and increased to 0.98 g/cm³, and densification efficiency was 73.79%, higher than that of the former. Under this temperature controlling way, the composite comprised only rough laminar carbon with superior properties. Compared to the outer wall temperature controlling, the composite prepared by the inner wall temperature controlling, needed higher temperature and more appropriate temperature gradient during densification, which was consistent well with the ideal densification model. Moreover, the inner wall temperature controlling way enabled the large-scale C/C composite densification from inner side to outside wall, and achieved uniform density distribution, high densification efficiency and excellent microstructure.

Key words: large-scale C/C composite, thermal gradient-chemical vapor infiltration, densification efficiency

CLC Number:

TB332

LI Yan, CUI Hong, ZHANG Hua-Kun, JI A-Lin, JIE Yu-Jie. Densification Behavior of Thermal Gradient CVI of Large-scale C/C Composites[J]. Journal of Inorganic Materials, 2015, 30(2): 153-158.

Figures/Tables 8

Fig. 1 Schematic diagram of outerwall (a) and innerwall (b) temperature controlling ways of the sample A and B, respectively

Fig. 2 Densities of samples prepared under out (A) and inner (B) wall temperature controlling at different densification time

Fig. 3 Temperature changes of samples prepared under out (A) and inner(B) wall temperature controlling at different densification time

Fig. 4 SEM images of sample A and B at different positions after densification for 600 h (a, c and e): Inner wall, central section and outer wall of sample A, respectively, under outer wall temperature controlling; (b, d and f): Inner wall, central section and outer wall of sample B under inner wall temperature controlling

Fig. 5 PLM of pyrocarbon of samples A and B at different positions (a, c and e): Inner wall, central section and outer wall of sample A, respectively, under outer wall temperature controlling, and Ae values were 16°-18°; 16°-18° and 18°-20°, respectively. (b, d and f): Inner wall, central section and outer wall of sample B, respectively, under inner wall temperature controlling, and all Ae values were 18°-20°

Fig. 6 CT curves of sample A under outer wall temperature controlling after densification for 300 h (a) and 600 h (b)

Fig. 7 CT curves of sample B under inner wall temperature controlling after densification for 300 h (a) and 600 h (b)

Fig. 8 CT images on cross section of samples under out wall (a) and inner wall (b) temperature controlling after densification for 600 h

References 16

[1]	ZOU ZHI-QIANG, TANG ZHONG-HUA, XIONG JIE.The manufacturing of C/C composite brake disk by means of thermal gradient densification technique.New Carbon Materials, 2000, 15(2): 22-27.
[2]	DELHAES P.Chemical vapor deposition and infiltration processes of carbon materials. Carbon, 2002, 40: 641-657.
[3]	WANG JI-PING, QIAN JUN-MING, QIAO GUAN-JUN, et al.A rapid fabracation of composites by a thermal gradient chemical vapor infiltration method with vaporized kerosene as a precursor.Materials Chemistry and Physics, 2007, 101: 7-11.
[4]	LI HE-JUN.Carbon/carbon composites.New Carbon Materials, 2001, 16(2): 79-80.
[5]	ZHANG WEI-GANG, HU Z J, HÜTTINGRT K J. Chemical vapor infiltration of carbon fiber felt:optimization of densition and carbon microstruction.Carbon, 2002, 40: 2529-2545.
[6]	HU Z. J, ZHANG WEI-GANG, HÜTTINGRT K J, et al. Influence of pressure,temeperature and suface area/volume ratio on the texture of pyrolytic carbon deposited from methane.Carbon, 2003, 41: 749-758.
[7]	PAUW V D, COLLIN A, SEND W, et al.Deposition rates during the early stages of pyrolytic carbon deposition in a hot-wall reactor and the development of textrue.Carbon, 2006, 44: 3091-3101.
[8]	HU ZI-JUN, HÜTTINGR K J. Chemical vapor infiltration of carbon revised Part Ⅱ: Experimental results. Carbon, 2001, 39: 1023-1032.
[9]	ZHANG WEI-GANG, HÜTTINGR K J. Densification of a 2D carbon fiber perform by isothermal,isobaric CVI:Kinetics and carbon microstructurec CVI:Kinetics and carbon microstructure.Carbon, 2003, 41: 2325-2337.
[10]	WU XIAO-JUN, CHENG WEN, QIAO SHENG-RU, et al.Fast densification of thick-walled carbon/carbon composite tubes using electrically coupled chemical vapor infiltration. Carbon, 2013, 57: 371-379.
[11]	SUN GUO-LING, LI HE-JUN, QI LE-HUA, et al.Analysis of unstable temperature field for theraml gradient CVI densification process of C/C composite.Acta Metallurgica Sinica, 2006, 42(10): 1046-1050.
[12]	GUELLALI M, OBERACKER R, HOFFMANN M J, et al.Textures of pyrolytic carbon formed in the chemical vapor infiltration of capillaries.Carbon, 2003, 41: 97-104.
[13]	YIN JIAN, ZHANG HONG-BO, XIONG XIANG, et al.Influence of microstructure of pyrocarbon on ablation performances of C/C composites.Chinese Journal of Materials Research, 2007, 21(1): 10-14.
[14]	YAN GUI-SHEN, LI HE-JUN, ZHANG SHOU-YANG, et al.Densification mechanism of perform with thermal gradient CVI.Acta Materiae Compositae Silica, 2003, 20(2): 64-70.
[15]	DENG JING-YI,LIU WEN-CHUAN,DU HAI-FENG, et al. Control of the deposition temperature in thermal gradient CVI. Carbon Techniques, 1999(6): 22-24.
[16]	LI JIAN-LI,SU ZHE-AN,ZHANG MING-YU, et al.Mehanism of densification of C/C composites fabricated with high density perform.Journal of Inorganic Materials, 2011, 26(7): 711-714.