First Principles Calculations of Interfaces in Ultra High Temperature Ceramics

Abstract

This work focuses on understanding the influence of temperature on correlations between thermal conduction and mechanical strength in material interfaces including a high temperature material interface. Analyses examine single crystal ZrB2, single crystal SiC, and a <0001>-<111> ZrB2-SiC interface using a framework based on Car Parrinello molecular dynamics (CPMD) ab-initio simulation method from 500 K to 2500 K. Analyses indicate that the strength reduction with increase in temperature is strongly correlated to phonon and electron thermal diffusivity change. With increase in temperature, phonon thermal diffusivity increases in the case of ZrB2 and reduces in the cases of SiC as well as the interface. Electron contribution to thermal diffusivity increases with temperature increase in the case of interface. Examination of change in thermal properties at different mechanical strain levels reveals that the mechanisms of strength and thermal property change with increase in temperature may be similar to the mechanisms responsible for property change with change in applied strain.