The role of metal nanoparticles in the catalytic production of single-walled carbon nanotubes—a review

Moisala, Anna; Nasibulin, Albert G.; Kauppinen, Esko I.

doi:10.1088/0953-8984/15/42/003

Cited by 446 publications

(283 citation statements)

References 60 publications

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“…The high surface-to-volume ratio of nanoparticles has been predicted to cause a significant increase of the solubility [26][27][28][29][30][31][32][33]. However, lattice relaxation in very small particles can also reduce the stable interstitial carbon concentration [34]. There is a growing consensus that solid solutions as well as the phase behavior of alloys at the nanoscale remain poorly understood [30,31,35].…”

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confidence: 99%

Giant carbon solubility in Au nanoparticles

Sutter

2011

J Mater Sci

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Variable temperature transmission electron microscopy of individual 5 nm Au nanoparticles shows a striking increase in the particle size on raising the temperature from room temperature to 500°C in the presence of carbon from amorphous carbon support. Using the assembly of ordered graphene shells on the surface of individual nanoparticles at elevated temperatures-and the high pressures induced by such shells-as an experimental tool to study the origins of this swelling, we find that the volume increase is associated with the uptake of carbon to concentrations exceeding the bulk solubility by more than four orders of magnitude. The formation of stable metalcarbon nanostructures that have no bulk equivalent may have important implications on the functional properties of metal nanoparticles.The interaction of carbon with transition metals is key to processes for synthesizing the known sp 2 bonded carbon allotropes-fullerenes, nanotubes, and graphene-all of which are materials showing extraordinary properties and enormous potential for applications.Graphene, a planar two-dimensional honeycomb lattice of sp 2 bonded carbon atoms [1] Typically, transition metals catalytically dissociate hydrocarbons at their surfaces to set free carbon adatoms, which can be absorbed into the bulk at high temperature and segregate to the surface on subsequent cooling to form sp 2 -bonded structures. Planar graphene is synthesized by this process on bulk crystals or thin films of transition metals, such as Ru [16][17][18], Pt [19], Ir [20], and Ni [21], which can take up carbon into interstitial sites with solubilities up to a few atomic percent. Carbon nanostructures, such as fullerenes [22][23][24][25] are synthesized over transition metal (Fe, Ni, Co) nanoparticles, using the same steps of hydrocarbon dissociation, carbon intake into interstitial sites, and precipitation. It is generally assumed that the uptake of carbon in metal nanoparticles involves interstitial sites, similar to the bulk, but the stable concentrations (i.e., the carbon solubility) may be different at the nanoscale. The high surface-to-volume ratio of nanoparticles has been predicted to cause a significant increase of the solubility [26][27][28][29][30][31][32][33]. However, lattice relaxation in very small particles Electronic supplementary material The online version of this article

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confidence: 99%

Giant carbon solubility in Au nanoparticles

Sutter

2011

J Mater Sci

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“…The melting temperatures of the alloy-C system are lower than those of the metal-C system. Further, reduction in particle size results in lowering of melting temperature [21]. According to two widely accepted ''tip-growth'' and ''root-growth'' mechanisms, the hydrocarbon gas decomposes on the metal surfaces of the metal particle to release carbon, which dissolve in these metal particles.…”

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confidence: 99%

“…Carbon nanofibers possessing a platelet structure were obtained by Wang et al, by decomposition of methane over Ni-Cu-MgO catalyst [24]. Since the morphology of deposited carbon and the methane decomposition rate depend on the structure and nature of the active catalytic sites and the size of the catalyst particles [21], alloy hydride catalysts with low cost and active catalytic centres would be desirable for the catalytic decomposition of methane to produce pure hydrogen.…”

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Single step process for the synthesis of carbon nanotubes and metal/alloy-filled multiwalled carbon nanotubes

2007

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A single-step approach for the synthesis of multi-walled nanotubes (MWNT) filled with nanowires of Ni/ternary Zr based hydrogen storage alloy has been illustrated. We also demonstrate the generation of COfree hydrogen by methane decomposition over alloy hydride catalyst. The present work also highlights the formation of single-walled nanotubes (SWNT) and MWNTs at varying process conditions. These carbon nanostructures have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), Energy dispersive X-ray analysis (EDX) and Raman spectroscopy. This new approach overcomes the existing multi-step process limitation, with possible impact on the development of future fuel cell, nano-battery and hydrogen sensor technologies.

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“…It is known that CH 4 is the most stable hydrocarbon, which makes it the carbon source that goes to self-pyrolysis at the highest temperatures [42,43]. In studies of high temperature methane CVD growth at 1000°C using supported catalyst Kong et al [44] and Kang et al [45] obtained CNTs without H 2 and with H 2 , with diameters in quite a small range (1-6 nm) and (10-15 nm), respectively.…”

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confidence: 99%

Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

Aksak

Selamet

2010

Appl. Phys. A

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Carbon nanotubes (CNTs) were grown on thin iron (Fe) films on SiO 2 /Si substrates by chemical vapor deposition (CVD) at four different hydrogen (H 2 )/methane (CH 4 ) ratios at temperatures ranging from 925 to 1000°C. The effects of temperature and the amount of hydrogen gas on the mean diameter at increasing temperature were examined. We demonstrated that the mean diameter and its distribution depend not only on temperature but also on the H 2 amount. We showed that increasing H 2 amount strongly affects the structure of CNTs, especially at high growth temperature; the mean diameter at 1000°C reduced from about 383 to 34 nm by increasing H 2 amount from 24 to 50 sccm. We observed that at high temperature growth the mean diameter was decreasing very fast initially with increasing H 2 amount suggesting the dominance of H 2 over the growth temperature. A decrease in the slope of diameter vs. H 2 amount with further increment in H 2 amount implied that the temperature was, then, deciding the CNT diameter through catalyst particle coarsening. The statistical analysis presented implies that the H 2 amount has to be adjusted according to the growth temperature for given CH 4 amount to keep CNT diameter under control, and the large diameter distributions at high temperature and high H 2 amount can be associated with the large variation in the catalyst particle sizes.M. Aksak · Y. Selamet ( ) Carbon

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The role of metal nanoparticles in the catalytic production of single-walled carbon nanotubes—a review

Cited by 446 publications

References 60 publications

Giant carbon solubility in Au nanoparticles

Giant carbon solubility in Au nanoparticles

Single step process for the synthesis of carbon nanotubes and metal/alloy-filled multiwalled carbon nanotubes

Carbon nanotube diameter tuning using hydrogen amount and temperature on SiO2/Si substrates

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