A growth mechanism of regularly coiled carbon fibers through acetylene pyrolysis

Kawaguchi, Masayuki; Nozaki, Koji; Motojima, Seiji; Iwanaga, Hiroshi

doi:10.1016/0022-0248(92)90077-v

Cited by 112 publications

(60 citation statements)

References 8 publications

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“…As a general practice, researchers all over the world have been synthesizing microcoiled carbon fibers using thin metal film, metal supported on fine ceramic powder, iron coated indium tin oxide ͑ITO͒, thin films of Fe, Ni, Cr, Ti, Zn, and their oxides coated on silicon or copper substrates; and studied the morphology, growth mode, and elongation lengths of the coiled nanostructures. [14][15][16][17][18][19][20] However, the synthesis of springlike CNFs employing ultrafine metal nanoparticles instead of usual micron-sized particles and observation of surface states by photoluminescence ͑PL͒ technique has not been examined so far. It is known that the morphology and size of catalyst are highly responsible for the growth of coiled CNFs.…”

Section: 2mentioning

confidence: 99%

Photoluminescence and electron paramagnetic resonance studies of springlike carbon nanofibers

Shanker

Arora

Haranath

2009

Applied Physics Letters

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Carbon nanofiber ͑CNF͒ with springlike and double-helix structures has been synthesized by catalytic thermal pyrolysis of an acetylene precursor at 850-950°C using iron nanopowder and thiophene as catalyst and promoter, respectively. High resolution electron microscopy revealed a higher d-spacing ͑ϳ3.46 Å͒ of ͑002͒ crystal plane than customary multiwalled carbon nanotube ͑MWCNT͒ ͑3.37 Å͒ that helps in sustaining mechanical shocks better than MWCNTs. The large surface to volume ratio of springlike CNF does provide many delocalized free electrons to enhance the photoluminescence activity. Electron paramagnetic resonance signal showed a single narrow line having g-value 2.0024Ϯ 0.0002 and spin contribution 3.4956ϫ 10 −16 spins/ g.

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Section: 2mentioning

confidence: 99%

Photoluminescence and electron paramagnetic resonance studies of springlike carbon nanofibers

Shanker

Arora

Haranath

2009

Applied Physics Letters

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“…CNCs [13][14][15][16][33][34][35][36][37] are nanocarbon materials with a coiled structure and are composed of nanometer-scale fibers. Compared with CNTs, CNCs have considerably more electron emission sites-not only at the tips but also at the numerous nanocrystallites embedded in the amorphous carbon body.…”

Section: Cncs As Electron Emitting Nanomaterialsmentioning

confidence: 99%

Fabrication and Simulation of Self-Focusing Field Emission X-ray Tubes

et al. 2015

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A self-focusing field emission (FE) X-ray tube with a large-area cathode design was simulated and fabricated. The designed X-ray tube had a cylindrically symmetric geometry; the diameter of the cathode and the anode was 15 mm, and the cathode-anode distance was 20 mm. Owing to the unique cup-shaped design of the cathode, the electron beam emitted from the large-area cathode was focused onto the anode without using magnetic lenses or extra biased electrodes. Carbon nanocoils, which were grown on the bottom of the circular cup-shaped cathode, were used as electron emitters because of their excellent FE properties. A simulation of the electron trajectories for various cup heights revealed that the optimal focal spot size (0.1 mm) was obtained at a cup height of 5 mm OPEN ACCESSAppl. Sci. 2015, 5 943 when a voltage of 50 kV was applied. To verify this result, an X-ray tube was fabricated and tested. An X-ray photograph of the tested tooth and electric circuits showed good resolution and X-ray intensity. The large cathode area effectively reduces the current density and thereby improves the lifetime of the cathode.

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“…From these results, we proposed the 3D-growth model of the carbon coils based on the catalytic anisotropy of the crystal faces of the catalyst grain. [16][17][18][19] Figure 9 shows the growth model of the circular carbon coils. In this model, the order of the catalytic activity for the carbon deposition among the three crystal faces is A > B > C. Basically, a carbon fiber is composed of fine carbon grains deposited from the three crystal faces of A, B, and C, and curls in such a way that the carbon grains deposited on crystal faces A and B are on the outer side of the coil, while the grains deposited on crystal face C are inside.…”

Section: Morphologymentioning

confidence: 99%

Preparation and Characterization of Carbon Microcoils (CMCs)

Motojima

Chen

2007

Bulletin of the Chemical Society of Japan

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Carbon micro-coils (CMCs) with 3D-helical/spiral structures and coil diameters on the order of micrometer were obtained by metal-catalyzed pyrolysis of acetylene at 700-800 C. The preparation conditions, morphology, growth mechanism, microstructure, and some properties of the CMCs were examined in detail. Two pieces of vapor grown carbon fibers grown from a metal catalyst grain curl and entwine each other due to the anisotropic catalytic activity between different crystal faces of the catalyst grain and thus form double-helix CMCs. CMCs have an almost amorphous structure but could be graphitized by high-temperature heat treatment with full preservation of the coiling morphology. The CMCs could effectively generate inductive electromotive force, inductive current and thus Joul's heat under microwave irradiation. The CMCs/elastic polymer composite elements showed high tactile sensing properties which are comparable to that of human skin. The CMCs are a possible candidate for electromagnetic wave absorbers, remote heating materials, visualization elements of microwaves, tactile sensor elements, micro-antennae, chiral catalysts, bio-activators or biodeactivators, energy converters, etc.

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A growth mechanism of regularly coiled carbon fibers through acetylene pyrolysis

Cited by 112 publications

References 8 publications

Photoluminescence and electron paramagnetic resonance studies of springlike carbon nanofibers

Photoluminescence and electron paramagnetic resonance studies of springlike carbon nanofibers

Fabrication and Simulation of Self-Focusing Field Emission X-ray Tubes

Preparation and Characterization of Carbon Microcoils (CMCs)

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