We demonstrate a spray pyrolysis method to grow carbon nanotubes (CNTs) with high degree of crystallinity, aspect ratio and degree of alignment on a variety of different substrates, such as conventional steel, carbon fibres (CF) and ceramics. The process consists in the chemical vapour deposition of both a thin SiO2 layer and CNTs that subsequently grow on this thin layer. After CNT growth, increases in specific surface by factors of 1000 and 30 for the steel and CF samples, respectively, are observed. CNTs growth on ceramic surfaces results in a surface resistance of 37.5 Ohm/sq. When using conventional steel as a rector tube, we observed CNTs growth rates of 0.6 g/min. Details of nanotube morphology and the growth mechanism are discussed. Since the method discussed here is highly versatile, it opens up a wide variety of applications in which specific substrates could be used in combination with CNTs.
Phone: þ52 55 5950 4275, Fax: þ 52 55 5950 4284Double-helix microstructures consisting of two parallel strands of hundreds of multi-walled carbon nanotubes (MWCNTs) have been synthesized by chemical vapour deposition of ferrocene/toluene vapours on metal substrates. Growth of coiled carbon nanostructures with site selectivity is achieved by varying the duration of thermochemical pretreatment to deposit a layer of SiO x on the metallic substrate. Production of multibranched structures of MWCNTs converging in SiO x microstructure is also reported.In the abstract figure, panel (a) shows a coloured micrograph of a typical double-helix coiled microstructure of MWCNTs grown on SiO x covered steel substrate. Green and blue show each of the two individual strands of MWCNTs. Panel (b) is an amplification of a SiO x microparticle (white) on the tip of the double-stranded coil (green and blue). The microparticle guides the collective growth of hundreds of MWCNTs to form the coiled structure.
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