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

摘要

Carbon microcoils obtained by the catalyticpyrolysis of acetylene at 770 deg C were heat treated at 3000deg C for 6 h in a CO + CO_2 atmosphere. The effect of the heattreatment on the morphology, microstructure, and propertieswas examined. The coiling morphology of the carbon coils wasalmost preserved even after the heat treatment, though it becamebrittle. The ruptured cross section of the two fibers, which formthe coils, generally has either a trigonal pyramidlike form ornegative pyramidal hollow. These characteristic rupturedpatterns demonstrate the growth mechanism of the carbon coils.Distinct graphite layers (d = 0.339 nm) were developed by theheat treatment with an inclination of 10~40 deg versus the fiberaxis to form a "herringbone" structure. The bulk electricalresistivity, density, and specific surface area were 10-0.1 Item,2.2077-2.087 glem~3, and 6-8 m~2/g, respectively.