Modeling metallic nanoparticle synthesis in a magnetron-based nanocluster source by gas condensation of a sputtered vapor (original) (raw)
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Design of nanoparticle synthesis by inert-gas condensation process was studied according to the mechanisms and kinetics of nucleation and growth in the vapor phase. The effect of process parameters, e.g., source temperature, evaporation rate, and the inert-gas pressure, on the particle size and particle shape was examined at the example for silver and copper-tin alloy. The synthesized nanopowders had near spherical shape with particle size range from 10 to 60 nm dependent on the processing condition. Scanning and transmission electron microscopy (SEM and TEM) analyses showed that the crystallites are subunits of larger agglomerate particles, and relatively large particles display crystal habit. Based on the experimental results and theoretical principles, nucleation, growth, coagulation and coalescence of the particles were analyzed. Accordingly, the kinetics and mechanisms of nanoparticle synthesis in low-pressure gas phase was determined. A simple operating map for nanoparticle synthesis was presented. The results may serve as a guide for design of experimental studies on the effect of process parameters on nanoparticle characteristics.
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Chemical Engineering Science, 2002
A systematic engineering study on continuous synthesis of bismuth metal nanoparticles by vapor condensation in tube ows is presented. Simulations of aerosol nucleation, condensation and coagulation are cast in a design diagram format to guide experimental studies on the e ect of process parameters on product nanoparticle characteristics. Flow visualization, tracer gas analysis and computational uid dynamics are used to unravel the e ect of particle residence time distribution on product morphology during evaluation of alternate quenching designs for the metal vapor. Bismuth nanoparticles of average diameter 12-37 nm, as determined by nitrogen adsorption and X-ray di raction, were made by controlling the quenching gas ow rate, carrier gas ow rate and process pressure. ?
AIChE Journal, 2017
We present a free-energy driven kinetic Monte Carlo model to simulate homogeneous nucleation of metal nanoparticles (NPs) from vapor phase. The model accounts for monomer-cluster condensations, cluster-cluster collisions, and cluster evaporations simultaneously. Specifically, we investigate the homogeneous nucleation of Al NPs starting with different initial background temperatures. Our results indicate good agreement with earlier phenomenological studies using the Gibbs' free energy formulation from Classical Nucleation Theory (CNT). Furthermore, nucleation rates for various clusters are calculated through direct cluster observations. The steady-state nucleation rate estimated using two different approaches namely, the Yasuoka-Matsumoto (YM) and mean first passage time (MFPT) methods indicate excellent agreement with each other. Finally, our simulation results depict the expected increase in the entropy of mixing as clusters approach the nucleation barrier, followed by its subsequent drastic loss after the critical cluster formation resulting from first-order phase transitions.
In this paper we have reported the syntheses of copper and silicon nano-clusters by a sputtering-gas-aggregation type growth technique. The process involves typical magnetron sputtering vaporization of target materials followed by an inert gas condensation to form clusters of varying sizes. The size-distributions of the clusters typically follow a normaldistribution and the peak cluster sizes of the distributions depends on several factors, which include gas-flow rate, length of the growth region, deposition pressure etc. We have observed a variation in the peak cluster size with the variation of the gas (argon) flow rates. The experimental values are compared with the existing models and the results are found to be in good agreement. The results are significant since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster-size distributions.
Computational Materials Science, 2020
The fine bimetallic Cu-Ni integrated nanoparticles were obtained by the modified solution combustion synthesis in the air using glycine as a fuel. The synthesized nanoparticles were studied by XRD analysis using single-and two-phase approaches for Rietveld refinement simulation, by scanning TEM-EDX spectroscopy and HR TEM technics. The data analysis for nanoparticles' characteristics showed close integration of Cu and Ni crystalline structures, which tend to form a bimetallic alloy. The process of bimetallic nanoparticles' formation was computer simulated using the Monte Carlo method in the temperature range from 300 to 600 K. The simulation established the patterns of neck formation for two cases of the initial arrangement of copper and nickel nanoparticles: direct contact and relative displacement of 0.2 nm. It was established, that in the case of relative displacement in comparison with the case of the direct contact the coalescence process is «delayed» by 60-80 K upon heating. A description of the energy spectra of two particles during the neck forming has been provided.