Thermal behavior and effect of heat treatment in an inert gas on oxidized carbon microcoils

Abstract Vapor-grown carbon micro-coils were oxidation-treated under a low O2 flow rate at 450–820°C to enhance the chemically activated sites on the surface. The thermal characteristics of the oxidation-treated carbon coils were then examined. The starting temperature of weight loss in air was decreased by the oxidation treatment. The lowest starting temperature at which weight loss was observed was 420°C under the following conditions; (a) a mixed gas flow rate of O2=5 sccm (sccm means standard cubic centimetre/min) and Ar=50 sccm, (b) an oxidation treatment temperature of 600°C, and (c) a treatment time of 120 min. This lowest temperature was 120°C lower than that of the source carbon coils observed at 540°C. The band area of the endothermic peak on the DTA analysis significantly increased due to the post-heat treatment in Ar+N2 after oxidation treatment of the source carbon coils and attained a maximum value of 290 mV s/g, which was about 15 times that of the as-oxidized carbon coils without post-heat treatment. The microstructures, such as pits, holes, etc., present on the surface of the post-heat treated carbon coils after oxidation treatment were changed to more complex morphologies with the occurrence of more numerous pits, holes, etc., than that of the as-oxidized carbon coils.