Study On Preparation Of C/C Composites With Thermal Conductivity By One-step Molding Under Thermal State

C/C composites with the most future development prospect have a series of good properties such as good temperature-resistant structural,high thermal conductivity,high tensile strength. There is an urgent need to explore an effective and simple method for preparation of C/C composites, which can be widely used in the field of aerospace field,military industry,mobile computer and household electric apparatus.This study based on mechanism of orderly growth of mesophase. Coal tar pitches were used as raw materials for mesophase pitches of thermal polymerization, then put synthetic mesophase pitch and short carbon fibers into kneading pan, agitated the mixture with electric heating.The carbon mixes were prepared to C/C composites after the process of hot press molding,carbonization graphitization. The test result indicated that when TI value of the mesophase pitch was 82.1% and mass fraction of SCFs was 7%, the hot pressed sample had higher strength and hardness with minimum porosity of 16.95%. There was no significant change in thermal conductivity of axial direction,while MSCF%>7%, the thermal conductivity decreased sharply; thermal conductivity of radial section was improved with increasing content of SCFs, when SCFm%=7%, the maximum value was 127.5W/(m-K).In order to reduce anisotropy ratio of two dimensional thermal conductivities of C/C composites, the bidirectional hydraulic machine and special mould were designed to prepare the carbon precursor. The graphitized samples examined by XRD indicated the distance between graphite layer decreased from 0.3389nm to 0.3379nm with a stepped pipeline of decreasing bore. In addition, thermal conductivity of axial direction increased to 115.5 W/(m-K), anisotropy ratio of two-dimensional thermal conductivity reduced from 1.62 to 1.22 for uniforming the thermal conductivity of C/C composites.