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

Vapor-grown carbon micro-coils were oxidation-treated under a low O-2 flow rate at 450-820 degreesC to enhance the chemically activated sites on the s urface. The thermal characteristics of the oxidation-treated carbon coils w ere then examined. The starting temperature of weight loss in air was decre ased by the oxidation treatment. The lowest starting temperature at which w eight loss was observed was 420 degreesC under the following conditions: (a ) a mixed gas flow rate of O-2 = 5 sccm (sccm means standard cubic centimet re/min) and Ar=50 seem, (b) an oxidation treatment temperature of 600 degre esC, and (c) a treatment time of 120 min, This lowest temperature was 120 d egreesC lower than that of the source carbon coils observed at 540 degreesC . The band area of the endothermic peak on the DTA analysis significantly i ncreased due to the post-heat treatment in Ar+N-2 after oxidation treatment of the source carbon coils and attained a maximum value of 290 mV s/g, whi ch was about 15 times that of the as-oxidized carbon coils without post-hea t treatment. The microstructures, such as pits, holes, etc., present on the surface of the post-heat treated carbon coils after oxidation treatment we re changed to more complex morphologies with the occurrence of more numerou s pits, holes, etc., than that of the as-oxidized carbon coils. (C) 2001 El sevier Science Ltd. All rights reserved.