|Budget Amount *help
¥3,200,000 (Direct Cost : ¥3,200,000)
Fiscal Year 1998 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1997 : ¥2,400,000 (Direct Cost : ¥2,400,000)
Micro-coils or micro-tubes of various metal nitrides were prepared by the vapor phase nitriding of metal carbide coils (indirect process or two step process) and metalizing/nitriding of carbon coils (one step process or direct process), and the preparation conditions, mechanism, microstructure, properties were examined. The obtained results can be summarized as follows.
(A) Indirect process or two step process :
(1) The carbon micro-coils was vapor phase titianized at 800-1200ﾟC under TiCl4 + H2 atmosphere to form TiC micro-coils. Using regular carbon coils, the obtained TIC micro-coils have micro-tube like morphology.
(2) The TiC micro-coils was nitrided at 800-1200ﾟC in N2 atmosphere. The TiC micro-coils was partly nitrided at 800ﾟC for 6-hr reaction times to form TiN/TiC micro-coils/tubes.
(3) TiC micro-coils was fully nitrided to the core at 1000ﾟC for 6-hr reaction time to form TiN micro-coils/micro-tubes.
(B) Direct process :
(1) The carbon coils was treated with MCI (M=Ti, Nb, Ta, Si)
+N2+H2 atmosphere in the temperature range of 800-1200ﾟC.
(2) The carbon coils changed to metal nitride with full preservation of the coiling pattern, without the formation of intermediate layers of metal carbides.
(3) Using very regular-coiled carbon fibers, the coiling pattern gradually disappeared with increasing reaction temperature and reaction times, and then fully disappeared to form apparent straight fibers of 3-10 mum diameter.
(4) The straight fibers have a continuous pore of submicrom diameter through the fiber axis. That is, this straight fibers obtained by the metarizing/nitriding of the regular carbon coils is a micro-tube of metal nitride.
(5) The carbon coils was fully titanized/nitride to the core at 1000ﾟC for 6 hrs, while partly titanized/nitrides from the surface at 800ﾟC for 6 hrs.
(6) The large specific surface area of carbon coils ; about 100m^2/g, was decreased to 10-20m^2/g by the metalizing/nitriding, depending on the reaction temperature and reaction time.
(7) The metal nitride micro-coils/micro-tubes have bulk electrical resistivities of 0.1-0.01 "0"cm depending on the bulk density and conversion ratio of the carbon coils to the metal nitride.
(8) The electromagnetic wave absorption of the metal nitride micro-coils/micro-tubes was about 90% in 800-900 MHz region for 20wt% in an epoxy resin. Less