Homepage
  • Molecular Dynamics Study
  • Molecular Dynamics Study
  • Molecular Dynamics Study
  • Molecular Dynamics Study
  • Molecular Dynamics Study
backback
main > scientific publications > e15 > molecular dynamics study
Molecular Dynamics Study
of the Change of Silicon Carbide Thermal Conductivity with Irradiation Damage and Grain Size

J. P. Crocombette, L. Gélébart, F. Gao, W. Weber

The high thermal conductivity of silicon carbide is a key property in view of its possible use for future fusion or fission nuclear reactors. However concerns exist about its degradation, as compared to the perfect monocrystalline reference material, due to the conditions of operation and the microstructure of the material. In this work we studied, mainly with molecular dynamics simulations, two sources of deterioration of the thermal conductivity of cubic SiC : the irradiation damage and the polycrystallinity of the material.
SiC thermal conductivity is known to exhibit a huge decrease with irradiation. To understand this effect, we calculated the variation of the thermal conductivity produced by the accumulation of defects induced by displacement cascades [1]. The conductivity is found to decrease with dose, in very good quantitative agreement with low temperature irradiation experiments. The calculated values at lower doses (below 0.1 dpa) are close to the smallest measured values after high temperature irradiation, indicating that the decrease of the conductivity observed at these low doses is related to the creation of point defects. The  subsequent decrease that takes place upon further cascade accumulation is characteristic of the amorphization of the material and is experimentally observed for low temperature irradiation only.
To tackle the change in thermal conductivity due to the grain size of the SiC material, we first calculated the interfacial (Kapitza) thermal resistance of series of grain boundaries, focusing on [111] tilt grain boundaries of various angles. The interfacial resistance is found to increase with the disorientation for low angles and to saturate for angles larger than 10°. Strong variations of the resistance are found for boundaries of comparable angles and energies due to changes in their atomic structures. The obtained interfacial resistances were then included in a finite element modelling which enabled us to calculate the global thermal conductivity of a polycrystalline sample as a function of the size of its grains.

Molecular Dynamics Study Molecular Dynamics Study
Download complete paper
Logo ExtreMat is funded within the Sixth Framework
Programme of the European Community.
Logo
© 2007 Bayern Innovativ GmbH. Imprint / Disclaimer