Analysis of gas-phase condensation of nickel nanoparticles

Гафнер, С. Л.; Gafner, Yu. Ya.

doi:10.1134/s1063776108100191

Cited by 24 publications

(16 citation statements)

References 25 publications

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“…A more complete description of the approach to simulating the condensation process was given earlier. 8,11,15 An important point for simulations of condensation phenomena is the coupling of the system to a heat bath. Since considerable amounts of binding energy are released as clusters are formed, such a coupling is necessary in order to avoid unphysical temperature increases.…”

Section: Simulation Techniquementioning

confidence: 99%

The general mechanisms of Cu cluster formation in the processes of condensation from the gas phase

et al. 2015

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Technological applications of metallic clusters impose very strict requirements for particle size, shape, structure and defect density. Such geometrical characteristics of nanoparticles are mainly determined by the process of their growth. This work represents the basic mechanisms of cluster formation from the gas phase that has been studied on the example of copper. The process of Cu nanoclusters synthesis has been studied by the moleculardynamics method based on tight-binding potentials. It has been shown that depending on the size and temperature of the initial nanoclusters the process of nanoparticle formation can pass through different basic scenarios. The general conditions of different types of particles formation have been defined and clear dependence of the cluster shape from collision temperature of initial conglomerates has been shown. The simulation results demonstrate a very good agreement with the available experimental data. Thus, it has been shown that depending on the specific application of the synthesized particles or in electronics, where particles of a small size with a spherical shape are required, or in catalytic reactions, where the main factor of effectiveness is the maximum surface area with the help of temperature of the system it is possible to get the realization of a certain frequency of this or that scenario of the shape formation of nanocrystalline particles.

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Section: Simulation Techniquementioning

confidence: 99%

The general mechanisms of Cu cluster formation in the processes of condensation from the gas phase

et al. 2015

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“…The latter turned out to be the result of the agglomeration of two particles containing 2212 and 172 atoms, respectively. In the long run, the cluster of 4467 atoms turned out to be the result of the agglomeration of more than 20 individual primary particles with typical sizes from 1.0 to 2.0 nm [23]. However, most of these particles subsequently combined between themselves, so that only five particles separated by well defined interphase boundaries remained distinguishable in the internal structure of the Ni 4467 cluster at the final stage.…”

Section: Resultsmentioning

confidence: 97%

“…Subsequently, the system was cooled with some fixed rate to a pre specified final temperature. The synthesis simulation technique used is described in more detail in [23]. From the entire ensemble of produced clusters, we chose the nanoparticles with the maximum number of interfaces between the various structural phases.…”

Section: Resultsmentioning

confidence: 99%

“…Clearly, more com plex models similar to the ab initio method are more realistic, but it turns out to be just impossible to simu late clusters consisting of several hundred or thousand atoms by this method even in the current state of the art of computer technology. On the other hand, the potentials developed by Cleri and Rosato [21] were successfully applied in a number of cluster studies [22][23][24][25][26][27][28][29][30][31][32] and are currently among the main potentials for calculating the properties of metallic clusters.…”

Section: The Simulation Techniquementioning

confidence: 99%

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Molecular-dynamics simulation of the heat capacity for nickel and copper clusters: Shape and size effects

Гафнер

Redel

Gafner

2012

J. Exp. Theor. Phys.

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We have investigated the heat capacity of ideal Cu and Ni fcc clusters with diameters from 2 to 6 nm in the temperature range 200-800 K by the molecular dynamics method using a modified tight binding potential. Our analysis has shown consistency with the experimental results at temperatures of 200-300 K. The data obtained are also indicative of several regularities that are in agreement with the analytical calcula tions. We have concluded from the results of our computer simulations that the heat capacity in the case of isolated free clusters can exceed that of a bulk material, with this difference decreasing as the nanoparticle grows proportionally to the reduction in the fraction of surface atoms. The excess of the heat capacity for ideal copper and nickel nanoclusters with D = 6 nm at T = 200 K has been found to be 10% and 13%, respectively. Consequently, the large heat capacities of copper and nickel nanostructures observed in some real experi ments cannot be related to the characteristics of free clusters. We hypothesize that these properties of a nano material depend on the degree of agglomeration of its constituent particles, i.e., the surfaces and interphase boundaries of interconnected nanoclusters can have a strong effect. To test this hypothesis, we took nickel and copper clusters of various sizes (4000-7200 atoms) produced through the simulation of condensation from the gas phase. At high temperatures, we failed to adequately assess the role of the interphase boundaries in calculating the heat capacity of nanoparticles. The reason was the mass diffusion of Ni or Cu atoms to impart an energetically more favorable shape and structure to the synthesized clusters. At low temperatures, the heat capacity of such clusters exceeded that of clusters with an ideal shape and structure by a value from 3.2% to 10.6%. We have concluded that the Ni and Cu clusters produced in real experiments cannot be applied in devices using the thermal energy of such clusters without a preliminary optimization stage, because their external shape and interior structure are nonideal.

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“…Transitions from the fcc to Ih packing took place at 285 K (Ni 135 ) and at 352 K (Ni 177 ), i.e., the stability of the fcc structure increased with increase in the cluster size. 86 The thermal size effects are also manifested in the temperature dependences of other characteristics, for example, the internal pressure and internal stress (Figs 10 and 11) over a broad temperature range even when liquid-and solid-like states coexist (during quasi-melting). The non-monotonic temperature dependence of the internal pressure reflects complex structure transformations and modification of the cluster state on heating.…”

Section: Iv1 Isomerizationmentioning

confidence: 98%

Stability and thermal evolution of transition metal and silicon clusters

Полухин¹,

Vatolin²

2015

Russ. Chem. Rev.

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ContentsRussian Chemical Reviews 84 (5) 498 ± 539 (2015) # 2015 Russian Academy of Sciences and Turpion Ltd V A Polukhin, N A Vatolin Russ. Chem. Rev. 84 (5) 498 ± 539 (2015) 499 { Structure designations: Ih is icosahedral, fcc is face-centred cubic, hcp is hexagonal close-packed, bcc is body-centred cubic, pc is primitive cubic; sph is sphalerite type. V A Polukhin, N A Vatolin Russ. Chem. Rev. 84 (5) 498 ± 539 (2015) V A Polukhin, N A Vatolin Russ. Chem. Rev. 84 (5) 498 ± 539 (2015)

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Analysis of gas-phase condensation of nickel nanoparticles

Cited by 24 publications

References 25 publications

The general mechanisms of Cu cluster formation in the processes of condensation from the gas phase

The general mechanisms of Cu cluster formation in the processes of condensation from the gas phase

Molecular-dynamics simulation of the heat capacity for nickel and copper clusters: Shape and size effects

Stability and thermal evolution of transition metal and silicon clusters

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