Preparation of carbon foam-reinforced carbon aerogels and their copyrolysis mechanism

Abstract

This paper reports a copyrolysis strategy for preparing carbon foam-reinforced carbon aerogels with low thermal conductivity. Three types of precarbonized foams derived from commercial (0.03 g/cm 3 ), low-density (0.03 g/cm 3 ), and medium-density (0.06 g/cm 3 ) phenolic resin foams were impregnated with resorcinol-formaldehyde (RF) sol, aged at 50 °C, exchanged with ethanol, dried supercritically, and finally carbonized by copyrolysis at temperatures ranging from 600 to 900 °C. The linear shrinkage characteristics during the pyrolysis of the aerogels, foams, and composites at different temperatures were measured to analyze the formation process of the gap at the composite interface. The compressive strength of the composites was found to be higher than that of the carbon foam components. The thermal conductivity of the three composites was gauged at temperatures ranging from 25 to 1900 °C. The CCH-900 (commercial carbon foam-reinforced carbon aerogels after copyrolysis at 900 °C) composite exhibited the lowest high-temperature thermal conductivity (λ 1900 °C = 0.25 W/m·K). Finally, the copyrolysis mechanism of the RF aerogels and phenolic resin foams was analyzed through XPS, TG-MS, and Fourier transform infrared spectrometer. • A novel co-pyrolysis strategy is proposed to reduce the interfacial gap of carbon foam-reinforced carbon aerogel composites. • The composites constructed by the phenolic resin foams with wall film exhibit low high temperature thermal conductivity. • The co-pyrolysis mechanism between phenolic aerogels and phenolic resin foams are proposed.