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The Infiltration Process and Texture Transition of 2D C/C Composites

Journal of Materials Science & Technology 2009年第1期25卷 109-114页

作者： Hejun Li Guozhong Xu Kezhi Li Chuang Wang Wei Li Miaoling Li Carbon/carbon Composites Research Center Key Laboratory of Ultrahigh Temperature Composites Northwestern Polytechnical University Xi＇an 710072 China

2D needle-punched fiber felt was infiltrated by a kind of rapid isothermal chemical vapor infiltration technique. The infiltration process and texture transition of the infiltrated C/C composites were investigated. The porosity and the variations of the cumulative pore volume were determined by mercury porosimetry. The texture of matrix carbon was studied under a polarized light microscope. The results show that the relative mass gain of the sample increases directly as the infiltration time at the initial stage until 20 h, and subsequently the increasing rate of the relative mass gain decreases gradually with the prolonging of infiltration time. Three layers of pyrocarbon were formed around fibers. Low-textured pyrocarbon was obtained at the initial stage. With the densification going on, high-textured pyrocarbon was formed on the surface of low-textured pyrocarbon. Then, low-textured pyrocarbon was produced again during the final stage of densification. The texture transition is ascribed to the variation of the ratio of cumulative inner surface area to volume of pores and the gas partial pressure in pores.

关键词： C/C composites Isothermal chemical vapor infiltration (ICVI) Pyrocarbon mercury porosimetry Polarized light microscope

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Fractal Characteristics of Coal Pores Based on Classic Geometry and Thermodynamics Models

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Acta Geologica Sinica(English Edition) 2011年第5期85卷 1150-1162页

作者： CAI Yidong~1,LIU Dameng~(1,*),YAO Yanbin~1,LI Junqian~1 and LIU Junlai~2 1 School of Energy Resources,China University of Geosciences,Beijing 100083,China 2 School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China School of Energy Resources China University of Geosciences Beijing 100083 China School of Earth Science and Resources China University of Geosciences Beijing 100083 China

To better understand the characteristics of coal pores and their influence on coal reservoirs, coal pores in eight main coalfields of North China were analyzed by mercury porosimetry and scanning electron microscopy（SEM）.Fractal characteristics of coal pores（size distribution and structure） were researched using two fractal models:classic geometry and *** two models establish the relationship between fractal dimensions and coal pores *** results include:（1） SEM imaging and fractal analysis show that coal reservoirs generally have very high heterogeneity;（2） coal pore structures have fractal characteristics and fractal dimensions characteristic of pore structures are controlled by the composition（e.g.,ash,moisture,volatile component） and pore parameters（e.g.,pore diameter,micro pores content） of coals;（3） the fractal dimensions（D;and D;） of coal pores have good correlations with the heterogeneity of coal pore *** fractal dimensions correlate to higher heterogeneity of pore *** fractal dimensions（D;and D;） have strong negative linear correlations with the sorted coefficient of coals （R;=0.719 and 0.639,respectively） that shows the heterogeneity of coal pores;（4） fractal dimension D;and petrologic permeability of coals have a strong negative exponential correlation（R;=0.82）.However, fractal dimension D;and petrologic permeability of coals have no obvious correlation;and（5） the model of classic geometry is more accurate for fractal characterization of coal pores in coal reservoirs than that of thermodynamics by optimization.

关键词： coal pores mercury porosimetry fractal dimensions thermodynamics model classic geometry model

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