Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles

Jiang, Aiqin; Awasthi, Neha; Kolmogorov, Aleksey N.; Setyawan, Wahyu; Börjesson, Anders; Bolton, Kim; Harutyunyan, Avetik R.; Curtarolo, Stefano

doi:10.1103/physrevb.75.205426

Cited by 91 publications

(114 citation statements)

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“…At the nanoscale, the macroscopic dichotomy liquid/solid is not well-defined, and the issue of size-induced viscosity arises. This affects the catalyst activity by changing its melting point, 15,16 solubility, 17,18 and tendency to coarsen. 19 Kinetic properties, such as diffusion coefficients 20 and viscosity, can be used to study the particle state as a function of temperature and size.…”

Section: ϫ16mentioning

confidence: 99%

“…After an oscillating behavior of the precursors at T Ϸ 800Ϫ840 K, long-range disorder is reached at T ϭ 850 K. Owing to the finite size of the particle, melting in a single-species cluster is not a zerodimensional invariant point, unlike in the case of bulk materials, 15,19 as it occurs in a range ⌬T m . In our case ⌬T m is 840Ϫ850 K, where the solid and liquid phases co- exist in different fractions and time frames (dynamic coexistence 15,16,22,31,32,37,38 ). We thus introduce two definitions: T f , the minimum-liquid point (solidus), below which the particle is only solid, 15 and T m , the maximum-solid point (liquidus), above which the particle is only liquid.…”

mentioning

confidence: 99%

“…In our case ⌬T m is 840Ϫ850 K, where the solid and liquid phases co- exist in different fractions and time frames (dynamic coexistence 15,16,22,31,32,37,38 ). We thus introduce two definitions: T f , the minimum-liquid point (solidus), below which the particle is only solid, 15 and T m , the maximum-solid point (liquidus), above which the particle is only liquid. 15 Between T f and T m the nanoparticle fluctuates between the solid and liquid states 32,37,38 and overall resembles a viscous droplet of atoms.…”

mentioning

confidence: 99%

“…We thus introduce two definitions: T f , the minimum-liquid point (solidus), below which the particle is only solid, 15 and T m , the maximum-solid point (liquidus), above which the particle is only liquid. 15 Between T f and T m the nanoparticle fluctuates between the solid and liquid states 32,37,38 and overall resembles a viscous droplet of atoms. 26,27 ), the T range of dynamic coexistence enhances this diffusion, Figure 2.…”

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confidence: 99%

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Viscous State Effect on the Activity of Fe Nanocatalysts

Cervantes‐Sodi

McNicholas²,

Simmons³

et al. 2010

ACS Nano

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C atalytic chemical vapor deposition (CVD) is an effective site/sizeselective synthesis technique. 1Ϫ7The properties of the catalytic particle play a key role in the nucleation and growth processes, as well as in the final nanostructure morphology. 7Ϫ11 At the nanoscale, two aspects are inter-related: the possibility of bulk and surface diffusion of the feedstock in and on the nanoparticles 12Ϫ14 and the thermody- Here, we analyze the nanoparticles near the melting point by investigating, as functions of size, the melting depression and the self-diffusion coefficient D leading to viscosity ( ϰ 1/D). RESULTS AND DISCUSSIONIn nanoparticles, the melting point is inversely proportional to the diameter through the GibbsϪThomson (GT) relation. 9,19,21,22 We describe this by using classical molecular dynamics (MD) (see Methods for details). We characterize the melting by the change in internal energy, with associated latent heat, and by the variation in the Lindemann index statisticalbond-length order parameter, ␦, with respect to the temperature T.

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Viscous State Effect on the Activity of Fe Nanocatalysts

Cervantes‐Sodi

McNicholas²,

Simmons³

et al. 2010

ACS Nano

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“…Efficient catalysts must have long active lifetimes (with respect to feedstock dissociation and nanotube growth), high selectivity and be less prone to contamination 19,20,21,22,23 . Common factors that lead to reduction in catalytic activity are deactivation (i.e.…”

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Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

et al. 2008

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We explore the role of Mo in Fe:Mo nanocatalyst thermodynamics for low-temperature chemical vapor deposition growth of single walled carbon nanotubes (SWCNTs). By using the size-pressure approximation and ab initio modeling, we prove that for both Fe-rich (∼ 80% Fe or more) and Mo-rich (∼ 50% Mo or more) Fe:Mo clusters, the presence of carbon in the cluster causes nucleation of Mo2C. This enhances the activity of the particle since it releases Fe, which is initially bound in a stable Fe:Mo phase, so that it can catalyze SWCNT growth. Furthermore, the presence of small concentrations of Mo reduce the lower size limit of low-temperature steady-state growth from ∼0.58nmf orpureF eparticlesto ∼ 0.52nm. Our ab initio-thermodynamic modeling explains experimental results and establishes a new direction to search for better catalysts.Critical factors for the efficient growth of single walled carbon nanotubes (SWCNTs) via catalytic chemical vapor deposition (CCVD) 1,2,3 are the compositions of the interacting species (feedstock, catalyst, support 4,5,6,7,8,9,10 ), the preparation of the catalysts, and the synthesis conditions 11,12,13,14,15,16,17,18 . Efficient catalysts must have long active lifetimes (with respect to feedstock dissociation and nanotube growth), high selectivity and be less prone to contamination 19,20,21,22,23 . Common factors that lead to reduction in catalytic activity are deactivation (i.e. chemical poisoning or coating with carbon), thermal sintering (e.g. caused by highly exothermic reactions on the clusters surface 13,14,24 with insufficient heat transfer 25,26 ) and solid-state reactions (nucleation of inactive phases in the cluster 22,23,25 ).Metal alloy catalysts, such as Fe:Co, Co:Mo and Fe:Mo, improve the growth of CNTs 4,10,20,27,28,29,30,31 , because the presence of more than one metal species can significantly enhance the activity of a catalyst 20,32,33,34 , and can prevent catalyst particle aggregation 20,31,32,33 . In the case of Fe:Mo nanoparticles supported on Al 2 O 3 substrates, the enhanced catalyst activity has been shown to be larger than the linear combination of the individual Fe/Al 2 O 3 and Mo/Al 2 O 3 activities 20,27,28 . This is explained in terms of substantial inter-metallic interaction between Mo, Fe and C 20,35,36 which is congruent with previously observed solid-state reactions between these elements. In fact, the addition of Mo in mechanical alloying of powder Fe and C mixtures 38 promotes solid state reactions even at low Mo concentrations by forming ternary phases, such as the (Fe,Mo) 23 C 6 type carbides 38 .The way in which carbon interacts with transition metals depends on the metal species. Fe and Co belong to the "carbon dissolution-precipitation mechanism" group, where relatively large fractions of carbon dissolve into the cluster before stable carbides are formed, while Mo belongs to the "carbide formation-decomposition" group where carbide formation occurs rapidly at low carbon concentrations 39 . These mechanisms are governed by the interplay between solub...

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Carbon Nanomaterials: Synthetic Approaches

Tessonnier

2011

Nanotechnologies for the Life Sciences

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The sections in this article are Introduction General Concepts on the Synthesis of Carbon (Nano‐)Materials Uncatalyzed Synthesis of Carbon (Nano‐)Materials Catalyzed Synthesis of Carbon (Nano‐)Materials Synthesis from Solid Precursors Nanodiamonds Turning Graphite into Diamond Explosive Detonation Synthesis Fullerenes, Nanohorns, Single‐ and Multi‐Wall Carbon Nanotubes Catalytic Chemical Vapor Deposition Definitions Mechanistic Aspects Single‐ and Multi‐Wall Carbon Nanotubes Floating Catalyst CCVD Immobilized Catalyst CCVD Aligned Carbon Nanotubes Carbon Nanotubes Synthesized from Biocompatible Catalysts Metal‐ and PAH ‐Induced Toxicity of Carbon Nanotubes Purification Techniques Importance of Defects and Curvature for Further Functionalization Functionalization: Creating Anchoring Points for Bioactive Molecules Functionalization by Oxidation Functionalization by Coupling Reactions Noncovalent Functionalization Conclusion and Outlook

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Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles

Cited by 91 publications

References 116 publications

Viscous State Effect on the Activity of Fe Nanocatalysts

Viscous State Effect on the Activity of Fe Nanocatalysts

Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for single-walled carbon nanotube growth

Carbon Nanomaterials: Synthetic Approaches

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