Preparation, thermal stability and deflection of a density gradient thermally-conductive carbon foam material derived from phenolic resin

A density (rho) gradient thermally-conductive (lambda) phenolic foam material was initially prepared and it was used as a precursor to prepare a carbon foam (CF) material (rho-lambda-CF). The precursor was carbonized at the temperature between 900 and 1100 degrees C under the protection of N-2 gas and graphitized between 2100 and 2500 degrees C under the protection of Ar gas, respectively. The thermogravimetric analysis was carried out to investigate the influence of temperature on the thermal stability of the achieved rho-lambda-CF during carbonization and graphitization. The deflection of rho-lambda-CF reinforced with different types of carbon fibers by mass fractions of 0 wt%, 3 wt%, 6 wt%, and 9 wt% was investigated. The microstructure of the composites was observed and analyzed by scanning electron microscopy. The results show that the prepared rho-lambda-CF consisted of three parts: reticulated carbon, carbon microspheres, and voids. It had the graphite structure and exhibited a well structured obturator microsphere shape. The toughening mechanism of rho-lambda-CF reinforced with carbon fibers was preliminarily discussed.