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

Abstract

Carbon micro-coils were coated with pyrolytic carbon films by the decomposition of methane in an argon atmosphere, and the coating conditions and some of their properties were examined. Carbon micro-tubes or micro-solenoids were obtained using very regular and densely-coiled carbon micro-coils as the source under the optimum CH4 flow rate of 10 sccm and Ar 50 sccm at 1000–1200°C. The bulk electrical resistivity, density and surface area of the carbon-coated coils were 1–0.1 Ω cm, 1.7090 g/cm3 and 5 m2/g, respectively. The oxidation onset temperature of the carbon micro-tubes obtained at 1200°C for 1h was 660°C, which is comparable to that of the vapor grown carbon fibers. The carbon micro-pipes or micro-solenoids obtained using the long carbon micro-coils of 1–10 mm long as the source could absorb a wide range of electromagnetic waves of 250–950 MHz, and the reflection loss (absorption) reached 90–95%.