Correlation between Pitch Impregnation Pressure and Pore Sizes of Graphite Block

This study aimed to investigate the effect of impregnation pressure on the decrease in porosity of impregnated bulk graphite. The correlation between pitch impregnation behavior and the pore sizes of the bulk graphite block was studied to determine the optimal impregnation pressure. The densities and porosities of the bulk graphite before and after pitch impregnation under various pressures between 10 and 50 bar were evaluated based on the Archimedes method and a mercury porosimeter. The density increased rates increased by 1.93–2.44%, whereas the impregnation rate calculated from the rate of open porosity decreased by 15.15–24.48%. The density increase rate and impregnation rate were significantly high when the impregnation pressures were 40 and 50 bar. Compared with impregnation pressures of 10, 20, and 30 bar, the minimum impregnatable pore sizes with impregnation pressures of 40 and 50 bar were 30–39 and 24–31 nm, respectively. The mercury intrusion porosimeter analysis results demonstrated that the pressure-sensitive pore sizes of the graphite blocks were in the range of 100–4500 nm. Furthermore, the ink-bottle-type pores in this range contributed predominantly to the effect of impregnation under pressure, given that the pitch-impregnated-into-ink-bottle-type pores were difficult to elute during carbonization.

A Convenient and Reliable Method of Manufacturing Inclined Bulk Graphite for Measuring Thermal Conductivity With TDTR

In this work, in order to study the thermal transport along arbitrary direction in bulk graphite, we develop a simple and convenient method to manufacture inclined bulk graphite applying Focused Ion beam (FIB). Then, we measure the thermal conductivity of inclined bulk graphite with the time-domain thermoreflectance (TDTR) technique and the measured results show that our processing method is reliable. Based on the TDTR measurement of inclined bulk graphite with a tilt angle of 90°, the in-plane thermal conductivity is on the order of 2030 Wm−1 K−1 and the cross-plane thermal conductivity is on the order of 5.5 Wm−1 K−1 at room temperature, which is close to the previously reported results. Our processing and measurement methods provide a new perspective on the study of the intrinsic mechanism of anisotropic thermal transport in anisotropic layered materials.