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Energetics of the formation of Cu-Ag core-shell nanoparticles

Modelling and Simulation in Materials Science and Engineering

Chandross, M.

This work presents molecular dynamics and Monte Carlo simulations aimed at developing an understanding of the formation of core-shell Cu-Ag nanoparticles. The effects of surface and interfacial energies were considered and used to form a phenomenological model that calculates the energy gained upon the formation of a core-shell structure from two previously distinct, non-interacting nanoparticles. In the majority of cases, the core-shell structure was found to be energetically favored. Specifically, the difference in energy as a function of the radii of the individual Cu and Ag particles was examined, with the assumption that a core-shell structure forms. In general, it was found that the energetic gain from forming such a structure increased with increasing size of the initial Ag particle. This result was interpreted as a result of the reduction in surface energy. For two separate particles, both Cu and Ag contribute to the surface energy; however, for a core-shell structure, the only contribution to the surface energy is from the Ag shell and the Cu contribution is changed to a Cu-Ag interfacial energy, which is always smaller.

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TYPE Journal Article YEAR 2014
ScopusOSTIDOI

Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression

Sarobol, Pylin S.; Chandross, M.; Carroll, Jay D.; Mook, William M.; Boyce, Brad B.; Kotula, Paul G.; McKenzie, Bonnie B.; Bufford, Daniel C.; Hall, Aaron C.

The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and significant plastic deformation during compressi on . On the other hand, the micron sized Al 2 O 3 particles exhibited brittle f racture in compression. In situ compression experiments showed 3um Al 2 O 3 particles fractured into pieces without observable plastic deformation in compression. Particle deformation behaviors will be used to inform Al 2 O 3 coating deposition parameters and particle - particle bonding in the consolidated Al 2 O 3 coatings.

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TYPE SAND Report YEAR 2014
OSTIDOI

Competitive Wetting in Active Brazes

Welding Journal

Chandross, M.

We found that the wetting and spreading of molten filler materials (pure Al, pure Ag, and AgAl alloys) on a Kovar ™ (001) substrate was studied with molecular dynamics simulations. A suite of different simulations was used to understand the effects on spreading rates due to alloying as well as reactions with the substrate. Moreover, the important conclusion is that the presence of Al in the alloy enhances the spreading of Ag, while the Ag inhibits the spreading of Al.

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TYPE Journal Article YEAR 2014
OSTI
Results 101–125 of 149
Results 101–125 of 149