Development and characterization of micro-coil carbon fibers by amicrowave CVD system

Abstract

Nano- and micro-coiled carbon fibers find applications in electronicdevices, electromagnetic absorbers and filters. Smart devices can be conceivedusing tunable films on these fibers and tunable host materials. A new methodof producing helical carbon fibers with dimensions in the order of less than amicrometer has been developed using microwaves. The microwave CVD systempresented here eliminates the use of the toxic impurity gas, which is requiredin the conventional method. Both methods involve gas phase reactions over asubstrate seeded with an appropriate catalyst. Micro-coiled carbon fiber(MCCF) was grown by the catalytic pyrolysis of acetylene on a silicon carbidesubstrate on which nickel metal powder was dispersed as a catalyst. Variousfactors, for example flow rate of the gas, particle size of the catalyst,effect of reaction temperature and time, were studied in order to understandthe growth of the microwave synthesis of MCCF. MCCFs were also synthesized bya conventional method in the presence of thiophene as an impurity gas so thata comparison can be made with the materials obtained by the microwave system.The morphology of the final products were investigated by scanning electronmicroscopy. The carbon products obtained by traditional and microwave methodswere investigated with the help of x-ray diffraction. The effect of variousreaction conditions on the morphological development of a MCCF were examinedin detail. Furthermore, a brief study was made on the microwave absorbingproperty of the MCCF.