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262 results on '"Voorhees, P.W."'

31. Grain Boundary Formation Through Particle Detachment During Coarsening of Nanoporous Metals

Author

Elder, K.L.M., Beck Andrews, W., Ziehmer, M., Mameka, N., Kirchlechner, C., Davydok, A., Micha, J.-S., Chadwick, A.F., Lilleodden, E.T., Thornton, K., and Voorhees, P.W.

Abstract

Grain boundary formation during coarsening of nanoporous gold (NPG) is investigated wherein a nanocrystalline structure can form by particles detaching and reattaching to the structure. MicroLaue and electron backscatter diffraction measurements demonstrate that an in-grain orientation spread develops as NPG is coarsened. The volume fraction of the NPG sample is near the limit of bicontinuity, at which simulations predict that a bicontinuous structure begins to fragment into independent particles during coarsening. Phase-field simulations of coarsening using a computationally generated structure with a volume fraction near the limit of bicontinuity are used to model particle detachment rates. This model is tested by using the measured NPG structure as an initial condition in the phase-field simulations. We predict that up to ∼5% of the NPG structure detaches as a dealloyed Ag75Au25 sample is annealed at 300 °C for 420 min. The quantity of volume detached is found to be highly dependent on the volume fraction and volume fraction homogeneity of the nanostructure. As the void phase in the experiments cannot support independent particles, they must fall and reattach to the structure, a process that results in the formation of new grain boundaries. This particle reattachment process, along with other classic processes, leads to the formation of grain boundaries during coarsening in nanoporous metals. The formation of grain boundaries can impact a variety of applications, including mechanical strengthening; thus, the consideration and understanding of particle detachment phenomena are essential when studying nanoporous metals.

Published
2021
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44. Morphological instability in epitaxially strained dislocation-free solid films: linear stability theory

Author

Spencer, B.J., Voorhees, P.W., and Davis, S.H.

Subjects
Thin films -- Research, Stability -- Research, Physics
Abstract

Morphological instability in epitaxially-strained dislocation-free solid thin films was studied in terms of the linear stability theory. The results showed that the lattice mismatch between the film and the substrate resulted in instability. However, low temperatures and substrate elasticity helped offset the effects of lattice mismatch. The rowth rate of the film determined the critical film thickness.

Published
1993

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