Study Of The Thermal Conductivity Of Mesophase Pitch-based Carbon Foam Prepared With Supercritical Fluid

Mesophase pitch-based carbon foam, prepared from mesophase pitch, besides the low density, corrosion resistance and small thermal expansion coefficient like the carbon foams derived from other precursors, has high thermal conductivity for the anistropic structure of its precursor.In this paper, mesophase pitch was foamed in a high-pressure reactor with supercritical solvents which have good permeability and solubility with the pitch. The size and structure of the pores could be controlled through pressure releasing.After analyzing the law that different supercritical fluids effect the structure of the carbon foam, we could find the regulation of the carbon foam structure and ligament structure by mixed solvents. The pore and ligament structure of carbon foam formed under different conditions was studied: pressure, temperature, solvent sort and other factors. The changes of the thermal properties after carbonization and graphite were researched. The dependence of thermal properties of carbon foam on its pore and ligament structure was analyzed. It is found that the mixed solvents could have a good solubility with mesophase and improve the homogeneity. At the same time , the bubble diameter can be controlled easily . By choosing different mixing ratio of the supercritical fluid, we can get carbon foam with density in the range of 0.01～0.8g/cm~3, uniform size distribution between 150～1100μm, wall thickness of 15～100μm, porosity of 91% or more.The thermal properties of carbon foam have been investigated and the mechanism of the thermal conductivity was analyzed on the model of thermal conductivity related to different pore structure. The carbon foam thermal conductivity calculation model have been established to calculate the thermal conductivity which was compared with the experimental data.