Effect of external electromagnetic field and bias voltage on the vapor growth, morphology and properties of carbon micro coils

Carbon microcoils were obtained by the Ni-catalyzed pyrolysis of acetylene at 770 degrees C using thiophene as an impurity with and without an external electromagnetic (EM) field and by applying or not applying a bias: voltage to the substrate. The effects of the external EM field and bias voltage on the growth rate, morphology and some properties of the carbon microtoils were examined, It was observed that the external EM field accelerated the decomposition of acetylene resulting in a coil yield of 1.3-1.7 times higher than that without the external EM held. The application of the bias voltage also resulted in an increase of the coil yield; the yield linearly increased with increasing bias voltage. The coil yield obtained with a DC bias of 600 V and an AC bias of 2000 V with an applied external EM field was 1.9 and 2.1 times higher than that without the EM field and bias voltage, respectively. The very regularly-coiled carbon fibers with Bat fiber cross-sections and irregularly-coiled carbon fibers with circular fiber cross-sections were obtained with the Ehl field and without the EM field irrespective of the bias voltage, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.