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

A density (ρ) gradient thermally-conductive (λ) phenolic foam material was initially prepared and it was used as a precursor to prepare a carbon foam (CF) material (ρ-λ-CF). The precursor was carbonized at the temperature between 900 and 1100 °C under the protection of N₂ gas and graphitized between 2100 and 2500 °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 ρ-λ-CF during carbonization and graphitization. The deflection of ρ-λ-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 ρ-λ-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 ρ-λ-CF reinforced with carbon fibers was preliminarily discussed.