High-temperature heat treatment of carbon microcoils obtained by chemical vapor deposition process and their properties

Carbon microcoils obtained by the catalytic pyrolysis of acetylene at 770 °C were heat treated at 3000 °C for 6 h in a CO + CO2 atmosphere. The effect of the heat treatment on the morphology, microstructure, and properties was examined. The coiling morphology of the carbon coils was almost preserved even after the heat treatment, though it became brittle. The ruptured cross section of the two fibers, which form the coils, generally has either a trigonal pyramidlike form or negative pyramidal hollow. These characteristic ruptured patterns demonstrate the growth mechanism of the carbon coils. Distinct graphite layers (d = 0.339 nm) were developed by the heat treatment with an inclination of 10–40° versus the fiber axis to form a “herringbone” structure. The bulk electrical resistivity, density, and specific surface area were 10–0.1 Ωcm, 2.2077–2.087 g/cm3, and 6–8 m2/g, respectively.