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Title: Testing thermal gradient driving force for grain boundary migration using molecular dynamics simulations

Strong thermal gradients in low-thermal-conductivity ceramics may drive extended defects, such as grain boundaries and voids, to migrate in preferential directions. In this work, molecular dynamics simulations are conducted to study thermal gradient driven grain boundary migration and to verify a previously proposed thermal gradient driving force equation, using uranium dioxide as a model system. It is found that a thermal gradient drives grain boundaries to migrate up the gradient and the migration velocity increases under a constant gradient owing to the increase in mobility with temperature. Different grain boundaries migrate at very different rates due to their different intrinsic mobilities. The extracted mobilities from the thermal gradient driven simulations are compared with those calculated from two other well-established methods and good agreement between the three different methods is found, demonstrating that the theoretical equation of the thermal gradient driving force is valid, although a correction of one input parameter should be made. The discrepancy in the grain boundary mobilities between modeling and experiments is also discussed.
Authors:
 [1] ;  [1] ;  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
1177645
Report Number(s):
INL/JOU--14-32912
Journal ID: ISSN 1359-6454; TRN: US1500184
DOE Contract Number:
AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 85; Journal Issue: C
Publisher:
Elsevier
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CRYSTAL DEFECTS; VELOCITY; VOIDS; GRAIN BOUNDARIES; MOLECULAR DYNAMICS METHOD; TEMPERATURE GRADIENTS; COMPUTERIZED SIMULATION; URANIUM DIOXIDE; MOBILITY; COMPARATIVE EVALUATIONS; EQUATIONS; TESTING; CERAMICS; CORRECTIONS COMPUTER MODELING OF GRAIN BOUNDARTY MIGRATION IN U; GRAIN BOUNDARY MIGRATION; THERMAL GRADIENT DRIVING FORCE; MOLECULAR DYNAMICS; OXIDES