Development of ceramic microcoils with 3D-herical/spiral structures

Abstract

Various modified CVD processes, such as modified hot filament method, vapor phase diffusion process, in-situ CVD process, catalytic CVD process, for the preparation of ceramics single crystals and fibers were developed. The preparation conditions, morphologies, microstructure and properties of transition metal carbides, nitrides, borides, silicides, sulfides, etc were examined. We have first found that various ceramic fibers with 3D-helical/spiral structure, such as Si3N4, carbon, TiC, TiO2, etc. were obtained using metal-catalyzed CVD and/or vapor phase diffusion processes under critically controlled reaction conditions. Carbon microcoils (CMC) with double-helical structure were obtained with high reproducibility by metal catalyzed pyrolysis of acetylene. The CMCs have many interesting and eminent characteristics, such as 3D-helical/spiral microstructure with μm orders in coil diameters, diverse microstructures from amorphous to graphite structure, changing in electrical parameters under the application of various stimuli, high microwave absorption and microwave heating abilities, breeding or anti-breeding effect on cells, fibrils of organisms, etc.

A review of shaped carbon nanomaterials

“…Studies performed by Chen et al 63 showed that as-synthesised carbon coils could be elongated by ~ 42% (Figure 19). Further studies by Motojima 50 revealed that helical fibres with circular cross section could be expanded to between 4.5 times and 15 times that of the original coil length. By contrast, a coil with flat cross section could only be extended to 1.5 times its original coil length.…”

“…However, helical material several microns in diameter has been synthesised, indicating that metal particle size was not the only factor that determined carbon morphology. 50,51 The catalyst particle shape has also been proposed to control the carbon growth. Motojima 50 showed that different crystal faces of a metal particle could show variable coil growth.…”

“…50,51 The catalyst particle shape has also been proposed to control the carbon growth. Motojima 50 showed that different crystal faces of a metal particle could show variable coil growth. From these results it was proposed that coiling could be related to unequal extrusion rates of carbon from different catalyst faces (Figure 17b).…”

“…50 Volodin et al 62 conducted the first AFM measurements of the mechanical properties of carbon nanocoils. The force modulation measurements agreed with the elasticity theory and showed a Young's modulus of ~ 0.7 TPa.…”

Wachstumsinduziertes Biegen und Verwinden von Einkristallen

“…[212][213][214] ZrS 2 bildet Rollen. [215,216] Natürlicher Rutil (TiO 2 ), Cosalit (Pb 2 Bi 2 S 5 ), Stibnit (Sb 2 S 3 ) und Chalcotrichit (Cu 2 O) bilden verwundene faserfçrmige Kristalle, [217] ebenso wie Magnesium-reicher Calcit. [218] Quarz [219][220][221][222][223][224][225] (Abbildung 9 a) gesellt sich als verwundener Makrokristall (100 mm < h < 3 cm) zum Phosgenit von Sowerby [57] und dem Stibnit von Wada (Abbildung 5).…”