Microstructure and electrical resistivity of carbon/carbon composites prepared by thermal gradient chemical vapor infiltration

Abstract

Carbon/carbon composites were prepared by thermal gradient chemical vapor infiltration with kerosene as precursor. The microstructure and electrical resistivity were examined by polarized light microscopy and low-resistance instrument, respectively. The effects of processing parameters on microstructure as well as the influences of sample density, processing parameters, and needle punch on electrical resistivity of carbon/carbon composites were analyzed. The results show that besides rough laminar, smooth laminar and isotropic pyrocarbon occur at temperatures of 1000 C and 1200 C, respectively. The graphitization degree of composites increases from 16.28% to 63.95% as the heat treatment temperature increases from 2100 C to 2500 C. The electrical resistivity of carbon/carbon composites decreases with increasing heat treatment temperature and sample density but increases as the texture of pyrocarbon varies from rough laminar to smooth laminar. The main mechanism for influencing the electrical resistivity of carbon/carbon composites can be changing carrier concentration, altering grain scattering, or both actions.

Effects of carbon black content on the microstructure and properties of carbon/ceramic conductive composites

“…This means that the percolation threshold of CB is much lower than that of graphite. 25 Thus, doping CB is better than doping graphite when preparing conductive composites with a certain resistivity.…”

Quantitative characterization of the carbon/carbon composites components based on video of polarized light microscope

“…In particular, the components that including carbon fiber (CF), pyrocarbon, and pores have serious influence for the mechanical, thermal, tribological, and electrical properties of C/C composites. Such as the porosity of C/C composites is the major influencing factor of shear strength, and electrical resistivity (Barbosa, Pardini, & Botelho, 2015;Casal, Granda, Bermejo, Bonhomme, & Men endez, 2001), the increase of CF fraction would raise the internal friction of C/C composites (Hou, Li, Wang, Zhu, & Shen, 2000), and the structure and content of matrix are all closely related to mechanical, tribological, and electrical properties (Jia, Li, Zhang, Li, & Ren, 2014;Reznik, Guellali, Gerthsen, Oberacker, & Hoffmann, 2002;Wu, Du,, Fang, & Mei, 2012;Xu, Li, Bai, Wei, & Zhai, 2008;Yu et al, 2013).It means that we could enhance the properties through controlling the microstructure of C/C composites. Thus, the quantitative calculation of components is an essential prerequisite for studying the microstructure, and can provide a scientific guidance for improving the macroscopic properties.…”