Carbon shells in flames

Nature (Impact Factor: 41.46). 07/1994; 370:603.
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    • "In particular, chemical vapour deposition is able to provide quick, efficient, high yield and cost effective production of carbon nanomaterials [1]. Non-catalytic processes also provide a means of producing carbon nanomaterials, in particular laser ablation and flame pyrolysis have successfully resulted in nanoscale carbons without involving catalytic particles [2]. The quality of the sample and the individual materials depend on numerous factors that govern the reordering of carbon atoms into nanoscale structures, which is comparatively random when occurring through a non-catalysed process. "
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    ABSTRACT: Non-catalysed growth methodologies of carbon nanomaterial synthesis can represent lower costs and greener approaches and cause less damage to the nanomaterial. During the carbonisation of a polyacrylonitrile-based co-polymer, carbon nanofibres (CNFs) and single- and multi-layer graphenes (SLG and MLG) are generated. The accumulated fragmentation products of the co-polymer coalesce to form CNFs that radiate away from the monolith, whose dimensions are linked to their template growth along crests, which were formed from the out-gassing of volatile products of the polymer during the stabilisation step. The slight shrinkage of the carbonising monolith also leads to exfoliation of larger areas of the surface yielding single- and multi-layered graphenes. These results reveal a potentially useful process for the facile production of carbon nanomaterials.
    Full-text · Article · Apr 2012 · Carbon
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    ABSTRACT: Carbon nanotubes in the form of multiwalled fullerenes are shown here to self-assemble under homogeneous gas-phase conditions of carbon condensation in an inert atmosphere heated to 1200$DGR@C-conditions previously thought to be optimal only for the annealing and growth of Cââ and other spheroidal shells. Tubular fullerenes are known to be less stable than their spheroidal counterparts and have thus far been reported only in circumstances where some extrinsic factor (e.g., high electric fields, catalytic metal particles, hydrogen atoms, or a surface at low temperature) was available to help keep the fullerene structure open at its growing end. The experimental evidence reported here now indicates that multiwalled tube growth is inherent in the condensation of pure carbon vapors. Adatoms bonded between edge atoms of adjacent layers at the growing end are proposed to be the crucial intrinsic factor facilitating tube growth by stabilizing the open conformation against closure. This new view of the growing nanotube tip structure is likely to impact on nanotube growth mechanisms under other conditions, particularly the arc. 32 refs., 4 figs.
    Full-text · Article · Jul 1995 · The Journal of Physical Chemistry
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    ABSTRACT: This paper reports the flame synthesis of WO3/C organic/inorganic octagonal nanoplatelets and nanorods. A high-purity tungsten wire inserted into the oxygen-rich region of the flame was used as a material source. The growth of the formed nanostructures starts with the oxidation of the metal probe, and evaporation of the oxide layer which is followed by the transport of the tungsten oxide vapors from the oxygen-rich to the hydrocarbon-rich zone of the flame. In the oxygen-rich zone, tungsten oxide vapors are crystallized into well-defined single crystal octagonal nanoplatelets. The continuous vapor deposition leads to the nanoplatelet growth in a preferred direction resulting in elongated rod-like nanostructures. The tungsten oxide structures entering the hydrocarbon-rich zone of the flame are coated with carbon layers forming hybrid WO3/C nanomaterials. The ideal conditions for the rapid and direct formation of these novel nanostructures are attributed to the synergy of the strong thermal and chemical gradients present in the flame volume. The entire process takes only a few seconds. A proposed mechanism of the hybridization process of the WO3 nanorods and nanoplatelets to WO3/C is described.
    No preview · Article · Dec 2012 · Journal of Nanoparticle Research
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