Development of continuous preparation process of the coiled-carbon fiber by CVD process

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1) Micro-coiled carbon fibers were prepared by a metal catalyst activated pyrolysis of acetylene using a batch-type reactor (23 mm I.D,horizontal -type). The preparation conditions were examined in detail, and the growth mechanism was discussed.(1) It was found that Fe and NIs powders, those were reported so far to have no catalytic effects for the preparation of the carbon coils, have some catalytic effects under restricted conditions, and gave a coil yield of 10-20%.(2) Among transition metal carbides, TiC powder exclusively gave the carbon coils. Among titanium oxides, Ti203 powder and oxidized Ti plate gave the carbon coils (coil yield : 13-27%).(3) Deposition behaviors of total carbon and carbon coils on the crystal faces of a Ni single crystal were examined. The catalytic activity of respective crystal faces were as follows ; Ni(100) > (11) > (110). The coil yield for the Ni(100) was three time of that of the Ni(110). It was supposed that a driving force of coiling of the carbon fibers was this anisotropic behavior for the carbon deposition on the respective crystal faces of the catalysts.2) Micro-coiled carbon fibers were prepared using a intermittent or contimuous preparation apparatus (60 mm I.D.x1,000 mm long), and growth conditions were examined in details.(1) The carbon coils exclusively grew on the upper part of the source gas inlet.(2) The coil yield lineary increased with increasing reaction time, and the coils with 1-2 mm long were obtained.(3) The layr thickness of the hard deposits increased with increasing reaction time, especially after 10 min.(4) Ni powder was the most effective catalyst.(5) Powder-like coils having 1-5 micron in coil length were obtained by abrading bulk-coils using emery papers. The distribution of coil length depended on the grain size of the used emery papers.3) Designing of a mini plant (capacity : few hundred grams/month) for the praparation of large samples have been accomplished, and now in preparing the apparatus.