Materials with a three-dimensional (3D) microcoiled structure or with a microtube morphology are not industrially available. However, we could expect novel properties from the microcoiled materials which have morphologies similar to DNA or from a microtube morphology. The growth of microcoiled carbon fibers from the vapor phase has been reported by many researchers. [1][2][3][4][5][6][7][8][9] The vapor growth of the microcoils of SiC, [10][11][12] Si 3 N 4 , [13][14][15][16] etc. have also been reported. However, the growth of such coiled fibers was accidental and poorly reproducible. We have obtained regularly microcoiled carbon fibers (referred to as "carbon coils" hereafter) with high reproducibility by the catalytic pyrolysis of acetylene. 17-26 Furthermore, we have obtained various ceramic microcoils, such as SiC, 27 TiC, 19,27 and ZrC, 28 by vapor phase metallizing of the carbon coils with full preservation of the coiling morphology. The microcoiled fibers or microtubes of metal carbides and nitrides may be potential candidates for conductive fillers, reinforcing fibers, electromagnetic shielding materials or absorbers, microsensors, etc.In this work, TiN microcoils or microtubes were prepared by vapor phase nitriding of TiC microcoils (indirect process) and direct titanizing/nitriding of carbon microcoils (direct process). The preparation conditions and some properties were also determined. ExperimentalPreparation of source carbon coils.-The source carbon coils were prepared by the Ni-catalyzed pyrolysis of acetylene. A horizontal quartz tube (60 mm i.d.) was used as the reaction tube. The gas mixture of acetylene containing a small amount of thiophene as an impurity, hydrogen, and nitrogen were introduced into the reaction tube from an upper gas inlet and exhausted from a lower outlet. A graphite plate, on which Ni powder (about 5 m diam) was dispersed, was used as a substrate. Reaction temperature, reaction time, and total reaction gas pressure were fixed at 750ЊC, 2 h, and 1 atm, respectively. The obtained carbon coils have a coil diameter of 3-5 m, coil pitch of 0.3-2 m, and a coil length of 1-5 mm.

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