Pyrolysis behavior and chemical composition of the precursors influence on structure and properties of coal-tar-pitch-based carbon foams

Carbon foams with high compressive strength and low thermal conductivity were produced using coal tar pitches (CTPs) obtained from low-temperature coal tar (LTCT), after thermal treatment combined with vacuum distillation technology and selective solvents. Pyrolysis behavior and the chemical composition of CTPs were investigated by elemental analysis, thermogravimetric analysis, Fourier transform infrared and X-ray photoelectron spectroscopy. Investigation of the relationship between the properties of the precursors and the structure of the obtained foams indicated that the pyrolysis behavior and composition of the precursors significantly affected the foaming process, and the structure and thermal conductivity of the foam. The experimental results showed that the structures and characteristics of the carbon foams could be controlled by adjusting the chemical composition of the precursors. In addition, carbon foams with honeycomb-type, open-cell structures, and ordered lamellar ligaments were produced from CTPs with the lowest HS and TI contents by treatment with toluene, and showed a low thermal conductivity of 0.039 W/m.K. Carbon foam without microcracks was obtained from CTPs with the highest HS contents produced from LTCT modified by N, N-dimethyl formamide, which showed a compressive strength of 6.580 MPa.