Porous Structure of Acetylene Black after Heat Treatment

The porous structure of acetylene black samples obtained by decomposition of acetylene at various pressures in a constant-volume tube reactor and subsequent heat treatment in an inert medium at temperatures of 200, 400, 600, 800, 1000, 1200, and 1400°C has been studied. Nitrogen adsorption isotherms at 77 K were obtained by the low-temperature adsorption method, and the textural characteristics of carbon black were calculated from them. It was found that at a pressure increased from 2.5 to 5 bar during the decomposition of pure acetylene, the surface area of acetylene black did not change and amounted to 88 and 83 m2/g (according to BET), respectively. As a result of heat treatment in the inert medium, the specific surface area obtained at 2.5 bar decreased relative to that of the starting carbon black not subjected to heat treatment. The average pore radius determined by the Barrett–Joyner–Halenda (BJH) method did not change at different temperatures and pressures and amounted to 1.62 nm. A scanning electron microscopy study shows that the average particle size decreased from 53 to 40 nm at increased initial pressure of acetylene. Based on the results, it can be concluded that subsequent heat treatment does not lead to an appreciable change in the particle shape and size, nor in the overall structure of the carbon black surface. A thermogravimetric analysis (TGA) of the original carbon black sample in an inert medium was performed. It shows that the mass of carbon black increased by 4% when the sample was heated to 400°C, did not change on heating from 400 to 1150°C, and decreased by 1% on heating from 1150 to 1400°C.