Carbon coatings on carbon micro-coils by pyrolysis of methane and their properties

Carbon micro-coils were coated with pyrolytic carbon films by the decomposi tion of methane in an argon atmosphere, and the coating conditions and some of their properties were examined. Carbon micro-tubes or micro-solenoids w ere obtained using very regular and densely-coiled carbon micro-coils as th e source under the optimum CH4 flow rate of 10 seem and Ar 50 seem at 1000- 1200 degrees C. The bulk electrical resistivity, density and surface area o f the carbon-coated coils were 1-0.1 Omega cm, 1.7090 g/cm(3) and 5 m(2)/g, respectively. The oxidation onset temperature of the carbon micro-tubes ob tained at 1200 degrees C for 1 h was 660 degrees C, which is comparable to that of the vapor grown carbon fibers. The carbon micro-pipes or micro-sole noids obtained using the long carbon micro-coils of 1-10 mm long as the sou rce could absorb a wide range of electromagnetic waves of 250-950 MHz, and the reflection loss (absorption) reached 90-95%. (C) 1999 Published by Else vier Science Ltd. All rights reserved.