Computational Studies of Catalytic Particles for Carbon Nanotube Growth

Bolton, Kim; Ding, Feng; Börjesson, Arne; Zhu, Wanfu; Duan, Haojie; Harutyunyan, Avetik R.; Curtarlo, S.

doi:10.1166/jctn.2009.1001

Cited by 28 publications

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“…For simplicity, we consider floating particles. The substrate−Fe nanoparticle interaction was shown to change the melting depression, , which can be parametrized in the GT equation through an effective radius. , The Fe−Fe interactions are described as a sum of a Born−Mayer-type repulsive and many-body attractive energy terms, where the coefficients are obtained by fitting the cohesive energy, lattice parameter, and elastic constant of γ-Fe . The potential landscape was shown to be adequate to reproduce CNT growth, the melting depression, and the Fe−C eutectic point .…”

Section: Methodsmentioning

confidence: 99%

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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Section: Methodsmentioning

confidence: 99%

Viscous State Effect on the Activity of Fe Nanocatalysts

Cervantes‐Sodi

McNicholas²,

Simmons³

et al. 2010

ACS Nano

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“…In fact, CVD experiments of SWCNT growth from small (∼0.6-2.1 nm) particles indicate that the diameter of the nanotube is similar to the diameter of the catalyst particle from which it grows. In some experiments where the growth mechanism is thought to be root-growth, the ratio of the catalyst particle diameter to SWCNT diameter is ∼1.0, whereas in experiments involving pre-made floating catalyst particles this ratio is ∼1.6 48 . Formation energies are calculated with respect to decomposition into the nearby stable elements or phases, depending the position in the ternary phase diagram as described later.…”

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confidence: 99%

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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Development of Coarse‐Grained Force Field by Combining Multilinear Interpolation Technique and Simplex Algorithm

Wan

Song

et al. 2019

J Comput Chem

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A fast, reasonable, and transferable coarse-grained (CG) molecular dynamics force field (FF) is essential to combine experimental and simulation data. However, the parameterization of CG FF usually requires massive computation, which hinders its rapid development. Here, we presented an efficient optimization protocol by combining multilinear interpolation technique with simplex algorithm. In this preliminary work, taking the experimental properties as the benchmark, we constructed a new set of CG FF for water and n-alkanes by adopting piecewise Morse function to describe the nonbonded interactions. This CG FF has a delicate balance between efficiency, accuracy, and transferability and well reproduced the correct structural and thermodynamics properties of pure water and alkane liquids. More importantly, optimized Morse potential was also successfully applied to describe the interactions between water and n-alkanes. It nicely predicted the phase separation, interface tension, hydration free energy, and formation of microemulsions of water/oil mixtures.

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Computational Studies of Catalytic Particles for Carbon Nanotube Growth

Cited by 28 publications

References 0 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

Development of Coarse‐Grained Force Field by Combining Multilinear Interpolation Technique and Simplex Algorithm

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