The role of iron carbide in multiwalled carbon nanotube growth

Schaper, Andreas; Hou, Haoqing; Greiner, Andreas; Phillipp, F.

doi:10.1016/j.jcat.2003.11.011

Cited by 179 publications

(132 citation statements)

References 39 publications

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“…In addition, carbon-saturated metallic nanoparticles melt at temperatures far below the bulk melting point of the metal [26,27]. Schaper et al [27] observed the motion of liquid/quasi liquid metal particle in the core of nanotube along the tube axis. They accounted this to the surface tensional forces buildup at the core material/tube interface and the compressive stress during thickness growth of the graphitic wall.…”

Section: Resultsmentioning

confidence: 99%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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The effect of hydrogen plasma treatment of iron oxide films on the growth and microstructure of carbon nanotubes (CNTs) by microwave plasma enhanced chemical vapor deposition process has been investigated. Microwave plasma was characterized in-situ using optical emission spectrometer. Morphology of the films was examined by scanning electron microscopy. Structural analysis was carried out by high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDS) and micro-diffraction attachments. It is found that oxide films without H 2 plasma pretreatment or treated for lesser time resulted in CNT films with high percentage of carbonaceous particles and with embedded particles/nanorods distributed discontinuously in the cavity of the nanotubes. The embedded particles were found to be of iron carbide (Fe-C) as confirmed by HRTEM, EDS and micro-diffraction analysis. Experimental observations suggested that the iron oxide particles had poor catalytic action for CNT growth and in-situ reduction of oxide clusters to Fe by hydrogen plasma plays a key role in discontinuous filling of the nanotubes by the catalytic particles. [12][13][14] have been used to synthesize CNTs. CVD methods (both thermal and plasma enhanced) are reliable in producing multiwalled CNTs (MWNTs) with proper control over the process parameters. Plasma enhanced CVD, however, can produce CNTs with a higher growth rate, at low temperature, and with better reproducibility. The plasma not only ionizes the gas but also causes a local surface heating [15]. Consequently, growth temperature could be significantly decreased compared to non-plasma CVD processes. In addition, the plasma atmosphere may also influence the detailed catalyst surface kinetics in many ways [16] and hence the growth of carbon nanostructures.Growth of CNTs and their microstructures depend on several parameters such as growth technique, feed gases, growth temperature, catalyst, and catalyst preparation method as well as their state (solid, liquid or vapor). In plasma assisted CVD processes, dilution gases play a critical role in the growth of CNTs and the structure of CNTs can be tailored by judicious control over gas composition [17]. In our earlier report, we investigated the effect of different dilution gases such as H 2 , NH 3 and N 2 and their different composition on the growth and microstructure of CNTs by microwave plasma enhanced CVD (MPECVD) process on Fe coated Si substrates using C 2 H 2 as feed gas [17]. Plasma pretreatment of catalyst film can also affect the growth and structure of CNTs significantly especially in a high frequency plasma process such as MPECVD. To the best of our knowledge, effect of H 2 plasma pretreatment of iron oxide films on the growth and structure of CNTs by MPECVD process have not been reported. Therefore, the motivation for the present

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Section: Resultsmentioning

confidence: 99%

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Srivastava

Kumar

2010

Nano-Micro Lett

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“…The consequence of this trend, which is observed for all systems, is that under equilibrium conditions, the CNT will act as a sink for C atoms available in the cluster. Hence, if a CNT is grown from a metal carbide [47] the growth process will not only be aborted when the addition of the external feedstock is stopped but the Ni carbide will be drained of C atoms and a pure Ni cluster will remain at the CNT end. This is of relevance to CNT growth, regrowth and CNT-electrode contacts where excess dissolved carbon atoms will diffuse from the metal to the CNT.…”

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confidence: 99%

First Principles Studies of the Effect of Nickel Carbide Catalyst Composition on Carbon Nanotube Growth

Börjesson

Bolton

2010

J. Phys. Chem. C

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Density functional theory calculations were used to investigate the stability of single walled carbon nanotubes (CNTs) attached to nanoparticles. The total energies and the adhesion energies between the CNTs and the nanoparticles were calculated for systems where the nanoparticles were either pure Ni or Ni carbide. It was found that the adhesion between the CNT and a pure Ni cluster is stronger than between the same CNT and a Ni-carbide cluster although the energy difference was small compared to the total adhesion energies. This adhesion strength implies that CNTs are likely to remain attached to both pure Ni and Ni-carbide clusters and that either pure Ni or Ni-carbide clusters may be docked onto the open CNT ends to achieve continued growth or electronic contacts between CNTs and electrode materials. The system with a CNT attached to a pure Ni cluster was found to be energetically favoured compared to a system containing the same CNT attached to a Ni carbide. The difference in total energy implies that a CNT should act as a sink for C atoms dissolved in the Ni-carbide cluster which means that the dissolved C atoms will be drained from the cluster, yielding a pure metal in the zero Kelvin thermodynamic limit. It is argued that this draining procedure is likely to occur even if carbon is added to the cluster at a proper rate, e.g. during CNT growth.

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“…In this experiment, the particles observed in CNCs and CNTs were Fe 3 C. When the carbon concentration of the particles at coagulation exceeds 25 at%, Fe 3 C particles can be formed in the CNCs and CNTs. Schaper et al showed from in situ TEM that graphene layers precipitate from Fe 3 C particles at 1143 K [28]. This temperature is 30 K lower than the heating temperature used in this study.…”

Section: Resultsmentioning

confidence: 64%

“…The melting Fe particles are mobile and fuse together. Fe-carbides with a carbon concentration of more than 50 at% are formed when the melting Fe particles contact with carbon [28]. During cooling, the solubility limit of carbon in the particles decreases and is followed by the precipitation of graphene layers on the particle surfaces.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Carbon Nanocapsules and Nanotubes Using Fe-Doped Fullerene Nanowhiskers

Kizuka

Miyazawa

Matsuura

2012

Journal of Nanotechnology

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We synthesized iron-(Fe-)doped C 60 nanowhiskers (NWs) by applying the liquid-liquid interfacial precipitation method that employs a C 60 -saturated toluene solution and a solution of 2-propanol containing ferric nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O). Fe particles of 3-7 nm in diameter were precipitated in the NWs. By heating at 1173 K, the NWs were transformed into hollow and Fe 3 C-encapsulated carbon nanocapsules and carbon nanotubes.

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The role of iron carbide in multiwalled carbon nanotube growth

Cited by 179 publications

References 39 publications

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

First Principles Studies of the Effect of Nickel Carbide Catalyst Composition on Carbon Nanotube Growth

Synthesis of Carbon Nanocapsules and Nanotubes Using Fe-Doped Fullerene Nanowhiskers

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