Effect of external electromagnetic field and bias voltage on the chemical vapor growth of the carbon micro-coils and their properties

Carbon micro-coils were obtained by the chemical vapor deposition using a N i-catalytic pyrolysis of acetylene at 770 degreesC with hydrogen sulfide as impurity, with and without an external electromagnetic field (EM) and appl ying a DC and/or AC bias voltage to the substrate. The effects of the EM fi eld and bias voltage on the growth rate, morphology and properties of the a s-grown carbon micro-coils were examined. A pale red-purple light emission was observed during the reaction. The EM field resulted in full decompositi on of acetylene and coil yield of 1.6-2.3 times higher than that without th e external EM field was obtained. The coil yield obtained by the applicatio n of bias voltage increased linearly with the increasing of bias voltage. T he coil yield obtained with 400 V DC bias and 1000 V AC bias with the exter nal EM field were 2.2 and 2.3 times higher than that without the EM field a nd no applied bias, respectively. The very regular-coiled carbon fibers wit h a flat fiber cross-section and irregular-coiled carbon fibers with a circ ular fiber cross-section were obtained with the EM field and without the EM field irrespective of the bias voltage, respectively, (C) 2001 Elsevier Sc ience B.V. All rights reserved.