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Research Papers: Micro/Nanoscale Heat Transfer

The Solid-State Neck Growth Mechanisms in Low Energy Laser Sintering of Gold Nanoparticles: A Molecular Dynamics Simulation Study

[+] Author and Article Information
Heng Pan, Seung H. Ko

Laser Thermal Laboratory, Department of Mechanical Engineering, University of California-Berkeley, Berkeley, CA 94720-1740

Costas P. Grigoropoulos1

Laser Thermal Laboratory, Department of Mechanical Engineering, University of California-Berkeley, Berkeley, CA 94720-1740cgrigoro@me.berkeley.edu

1

http:∕∕www.me.berkeley.edu∕ltl∕ltl.html

J. Heat Transfer 130(9), 092404 (Jul 11, 2008) (7 pages) doi:10.1115/1.2943303 History: Received July 05, 2007; Revised October 11, 2007; Published July 11, 2008

Molecular dynamics (MD) simulations were employed to investigate the mechanism and kinetics of the solid-state sintering of two crystalline gold nanoparticles (4.410.0nm) induced by low energy laser heating. At low temperature (300K), sintering can occur between two bare nanoparticles by elastic and plastic deformation driven by strong local potential gradients. This initial neck growth occurs very fast (<150ps), and is therefore essentially insensitive to laser irradiation. This paper focuses on the subsequent longer time scale intermediate neck growth process induced by laser heating. The classical diffusion based neck growth model is modified to predict the time resolved neck growth during continuous heating with the diffusion coefficients and surface tension extracted from MD simulation. The diffusion model underestimates the neck growth rate for smaller particles (5.4nm) while satisfactory agreement is obtained for larger particles (10nm). The deviation is due to the ultrafine size effect for particles below 10nm. Various possible mechanisms were identified and discussed.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Sintering geometry and atom movement pathways for different sintering mechanisms

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Figure 2

Extracted diffusion coefficients (a) and surface tension (b) from MD simulation

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Figure 3

Initial neck growth with respect to time (a), the temperature dependence of the radius of gyration. The transitions points are labeled as B, C, D for each size particle. The blue, purple, and red labels and curves represent 2633-, 5053-, and 3,1077-atom particles, respectively (b). and configurations of the 2633-atom particle pair at different temperature, with atoms colored according to their local structure (c).

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Figure 4

Motion of atoms during the transition from A to B for 2633 atoms (a), from A to B (b), and B to C (c) for 5053-atom particle; figures subtitled (d) and (e) represent the motion of atoms for 31,077-atom particles during the transition between the two points indicated by arrows in Fig. 5 and in Fig. 5, respectively

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Figure 5

The comparison between analytical model and MD simulations for 5053 atoms (a) and (b) and 31,066 atoms (c) and (d). The solid line is the analytical model and circle is the MD simulations.

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