DEVELOPMENT OF NOVEL PREPARATION PROCESS OF MICRO-COILED CARBON FIBERS AND TiC FIBERS

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Micro-coiled carbon fibers were prepared by the metal catalytic pyrolysis of acetylene containing small amounts of thiophene as an impurity using various type reactors. The reaction conditions and some properties of the obtained carbon coils were examined. And then, micro-coiled TiC fibers were obtained by the vapor phase titanizing of the carbon coils, and the reaction conditions and some properties were examined. The obtained results can be summarized as follows(A) Preparation and properties of carbon micro-coils :(1) New reactor with multiple source gas inlets were devised to obtain large amount of carbon coil samples. Coil yield of 20 mg/cm^2-substrate could be obtained for 2-hr reaction time.(2) Using the reactor made by lnconel, large amounts of carbonaceous deposits were formed on the surface of the reactor, and the coil yield was only 1-3mg/cm^2-substrate. Iron metal showed the negative effects the growth of carbon coils.(3) Using novel large reactor of 100 mm diam. and 1,000 m … More m long with multuple source gas inlets, the coil samples of 50g/day could be obtained(4) Acetylene was an exclusive source gas for obtaining carbon coils. Using propane as the source gas, small amounts of carbon coils with irregular coiling patterns was obtained via formation of acetylene by the pyrolysis of propane.(5) Metal oxides, such as Ta205, Nb205, NiO, as well as metal elements showed catalytic activities for growing carbon coils.(6) Application of vias voltage to the substrate showed strong effects the growth of carbon coils, and the coil yield increased to 1.5-2 times that of without vias voltage.(7) Carbon coils were an amorphous, but could be graphitized by the heat treatment at 3000 "*"C for 6-hr in CO+CO2 atmosphere.(B) Preparation of micro-coiled TiC fibers and some properties :(1) Carbon coils could be easily titinized at 800-1200"*"C under TiCI4+H2 atmosphere with full preservation of the coiling morphology.(2) Using very regular-coiled carbon fibers as a source coils, coiling patterns of the coils gradually disappeared with increasing reaction, and then disappeared to form straight fibers with continuous pores of submicron diameters in the fiber axis.(3) TiC micro-coils/micro-tubes have a bulk electrical resisitivity of 0.1-0.01 0cm depending on the bulk density and Ti/C ratio. Less