X-RAY-DIFFRACTION, THERMAL-EXPANSION, ELECTRICAL-CONDUCTIVITY, AND OPTICAL MICROSCOPY STUDIES OF COAL-BASED GRAPHITES

In this work, the properties of three graphites (WVU-1, WVU-2, WVU-3) produced from solvent-extracted coal feedstocks are reported. The techniques of x-ray diffraction, thermal expansion, electrical conductivity, and optical microscopy were used for these measurements. Parameters determined include crystallite sizes L(c) and L(perpendicular-to), crystalline parameter d(002), Bacon anisotropy parameter, lattice strain, degree of graphitization, longitudinal and transverse coefficients of thermal expansion (CTE), electrical conductivity and density. The long-range goal of this project is to produce a coal-based isotropic graphite comparable in properties to H-451, a commercially available graphite produced from petrocoke feedstocks. Therefore, the properties of the WVU graphites are compared to those of H-451, and a high-purity graphite powder is included in this study for reference. These comparisons show that the x-ray and the CTE anisotropy ratios of the WVU-1 and WVU-3 graphites are comparable to those of H-451. However, WVU-2 is more anisotropic because of the hydrogenation process used for the coal feedstock. The electrical conductivities of the three WVU graphites are about half that of H-451. The lower conductivities and lower densities of the WVU graphites are due to lack of impregnation, a step which needs to be included in future sample preparations.