Chemical vapor deposition of coiled ceramics

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1) Preparation conditions of the coiled carbon fibers have been examined in detail.a) It was found that a small amount of impurities such as hydrogen sulfide, phosphorus trichloride, it was indispensable for the growth of the coiled carbon fibers. The optimum concentration of the H_2S impurity was determined to be 0.06-0.09 vo1%.b) The maximum yield of the coiled carbon fibers (about 30 %) was obtained at about 700^ﾟC under an optimum impurity concentration.c) The coil length increased linearly with increasing reaction time up to 60 min.d) The flow rate of acetylene and acetone impurities did not affected on the growth of the coiled carbon fibers.2) Growth mechanism of the coiled carbon fibers was discussed. It was observed that presence of nickel catalyst was indispensable for the growth of the coiled carbon fibers. We proposed a new growth mechanism "tip quasi-VLS mechanism" for the growth of the coiled carbon fibers.3) The coiled silicon carbide fibers have been prepared by the vapour phase siliconizing of the coiled carbon fibers, and also by the reaction of an organic presusrsor with carbon tetrachloride and hydrogen at 1300-1400^ﾟC.4) The coiled titanium carbide fibers have been prepared by the vapor phase titanizing of the coiled carbon fibers at 1100-1300^ﾟC.