Influence of Initial Surface Area / Volume Ratio of the Fiber Preform on Kinetics of Chemical Vapor Infiltration and Texture of Infiltrated Carbon(PDF)
MATERIALS CHINA[ISSN:1674-3962/CN:61-1473/TG]
Issue:
2013年第11期
Page:
33-42
Research Field:
特约研究论文
Publishing date:
Info
Title:
Influence of Initial Surface Area / Volume Ratio of the Fiber Preform on Kinetics of Chemical Vapor Infiltration and Texture of Infiltrated Carbon
(1. Institute of Chemical Technology and Polymer ChemistryKarlsruhe Institute of Technology, Karlsruhe 76131, Germany) (2.State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, CAS, Beijing 100190, China)
Keywords:
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CLC:
PACS:
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DOI:
10.7502/j.issn.1674-3962.2013.11.02
DocumentCode:
Abstract:
Isothermal, isobaric chemical vapor infiltration of carbon fiber felts with fiber volume fractions of 7.1% and 14.2% were investigated to analyze the influence of initial surface area / volume ratio, [A/V], of the fiber preform on infiltration kinetics and texture of infiltrated carbon. Experiments were performed at a temperature of 1095oC, a methane pressure of 22.5kPa, a residence time of 0.1s and infiltration times being stepwise increased from 20 to 120h. Global bulk density and bulk density, porosity as well as density of matrix carbon as a function of infiltration depth were determined. Carbon texture was analyzed with polarized杔ight microscopy. The results show that infiltration kinetics in the initial stage of infiltration are dominated by the nucleation mechanism and afterwards by the growth mechanism of carbon formation. These changes of deposition chemistry and kinetics lead to changes of carbon texture from low / medium to medium / high. All changes are caused by an increase of [A/V] ratio. They occur in a significantly earlier stage in the case of the felt with the higher initial [A/V] ratio, as to be expected. These results are a perfect confirmation of conclusions from earlier studies.