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Title: Phase-field simulations of pore migration and morphology change in thermal gradients

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1398662
Grant/Contract Number:
#151905
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 490; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-08 15:26:10; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Vance, Ian W., and Millett, Paul C.. Phase-field simulations of pore migration and morphology change in thermal gradients. Netherlands: N. p., 2017. Web. doi:10.1016/j.jnucmat.2017.04.027.
Vance, Ian W., & Millett, Paul C.. Phase-field simulations of pore migration and morphology change in thermal gradients. Netherlands. doi:10.1016/j.jnucmat.2017.04.027.
Vance, Ian W., and Millett, Paul C.. Sat . "Phase-field simulations of pore migration and morphology change in thermal gradients". Netherlands. doi:10.1016/j.jnucmat.2017.04.027.
@article{osti_1398662,
title = {Phase-field simulations of pore migration and morphology change in thermal gradients},
author = {Vance, Ian W. and Millett, Paul C.},
abstractNote = {},
doi = {10.1016/j.jnucmat.2017.04.027},
journal = {Journal of Nuclear Materials},
number = C,
volume = 490,
place = {Netherlands},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jnucmat.2017.04.027

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  • Pore migration in a temperature gradient (Soret effect) is investigated by a phase-field model coupled with a heat transfer calculation. Pore migration is observed towards the high temperature domain with velocities that agree with analytical solution. Due to the low thermal conductivity of the pores, the temperature gradient across individual pores is increased, which in turn, accelerates the pore migration. In particular, for pores filled with xenon and helium, the pore velocities are increased by a factor of 2.2 and 2.1, respectively. A quantitative equation is then derived to predict the influence of the low thermal conductivity of pores.
  • In this study, the collective migration behavior of pores and grain boundaries under a temperature gradient is studied for simple single crystal, bi-crystal and polycrystal configurations with a phase-field model formulism. For simulation of the microstructure of solids, composed of pores and grain boundaries, the results indicate that not only the volume fraction of pores, but also its spatial partitioning between the grain boundary junctions and the grain boundary segments appears to be important. In addition to various physical properties, the evolution kinetics, under given temperature gradients, will be strongly influenced with the initial morphology of a poly-crystalline microstructure.
  • Te precipitates are one of main defects that form during the cooling process of as–grown CdTe crystals. Many factors such as the kinetic properties of intrinsic point defects (vacancy, interstitial, and antisites), internal stresses around the precipitates associated with the lattice mismatch between the precipitate and matrix, thermal stresses due to temperature gradients, extended defects (dislocations, twin and grain boundaries), non-stoichiometric composition, and the thermal treatment processing might all affect the formation and growth/dissolution of Te precipitates. A good understanding of these effects on Te precipitate evolution kinetics is technically important in order to optimize the material process and obtainmore » high quality crystals. This work aims to develop a phase-field model for investigating the evolution of a Te-precipitate in a Te-rich CdTe crystal under cooling. Cd vacancies and Te interstitials are assumed to be the diffusion species in the system. We also assume that the system is in two phase equilibrium (matrix CdTe and liquid Cd-Te droplet) at high temperatures and three phase equilibrium (matrix CdTe, Te-precipitate, and void) at low temperatures. With the thermodynamic and kinetic properties from experimental phase diagrams and thermodynamic calculations, the effect of Te and vacancy mobility, cooling rates and internal stresses on Te-precipitate and void evolution kinetics are investigated.« less
  • Defects inside single crystals are an important concern because they directly affect the physical or chemical properties of the material, especially in sapphire used as substrates for semiconductors. We have investigated the thermally activated transformations of nanometer-scale cracks and phase transitions inside sapphire by femtosecond laser irradiation and successive heat treatments. The nanocracks transformed into periodic arrays of pores and dislocations that aligned along the (1102) planes after heat treatments above 1300 deg. C. The amorphous phase at the focal point recovered into the initial single crystalline phase after the heat treatments. Our study provides useful information on the recoverymore » behavior of nanometer-scale defects in a single crystal.« less