Coiled carbon fibers were prepared by pyrolysis of acetylene activated using a Ni catalyst and a small amount of impurities at 600–800 °C. It was found that the addition of a small amount of sulfur or phosphorus compound impurities in acetylene was indispensable for the growth of coiled carbon fibers. Among the sulfur compounds used, thiophene was the most effective for growing coiled carbon fibers with uniform coil diameter and producing a high yield (about 50% coils). Similar results were obtained with phosphorus trichloride.

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Microcoiled carbon fibers were obtained by the Ni catalyzed pyrolysis of acetylene at 600-800°C.The presence of small amounts of a sulfur compound impurity was indispensable for the growth of the coiled carbon fibers in high yield with good reproducibility. The optimum growth temperature was 750°C irrespective of the kind of sulfur compounds used as the impurity. The optimum impurity gas flow rate was restricted to a very narrow range depending on the impurity type. The maximum yield (about 50 %) of the coiled carbon fibers was obtained using thiophene. Some properties of the coiled carbon fibers were examined. A new growth mechanism for the coiled carbon fibers will be presented.

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