Research on the preparation of highthermalconductivity carbon block by the ordered growth of self-assembled mesophase

Highthermalconductivity carbon material is a focus in the new carbon material research field. With few QIs coal tar pitch as raw material in this work, the thermoplastic mesophase pitch was prepared by the thermal polymerization processes. The effect of molding pressure on the development of ordered mesophase was studied. In our experiments, the mesophase pitch containing the same TI was molded respectively at 25°C to 600°C under 6.18MPa,9.24 MPa,13.84 MPa,20.05 MPa, carbonized at 1000°C and graphitized at 2800 °C. The results showed that the graphitization degree of the carbon blocks ranges from 48.8% to 72.1% by graphitized at 2800°C. With the increase of pressure, the apparent density increased from 1.47 g/cm3 to 1.58g/cm3 and the porosity decreased. It is shown by SEM that the regional mesophase displayed a sort of highly ordered structure with long fiber and the mesophase liquid crystal molecules were aligned perpendicular to the compressing in the molding process. The axial and radial direction of thermal conductivity range of the carbon blocks was 140.5-156W/m-K, 169.2-219.4W/W/m-K, respectively. The anisotropic ratio increased as the pressure increased and reached 1.41. It was proved that one-step hot press molding not only increased the density and decreased the porosity of the carbon blocks, but also promoted the growth of mesophase in order, formed the long-range ordered, fibrous structure which was similar to carbon fibers. Consequently, the phonons conducted along the long-range ordered structure, the hindrance of the conduction of phonons was reduced.