Atomistic analyses of the effect of temperature and morphology on mechanical strength of Si-C-N and Si-C-O nanocomposites

摘要

3-D molecular dynamics (MD) analyses of SiC-Si_3N_4 nanocomposite deformation and SiCO nanocomposite deformation are performed at 300 K,900 K, and 1500 K. In SiC-Si_3N_4 nanocomposites, distribution of second phase SiC particles, volume fraction of atoms in GBs, and GB thicknessplay an important role in temperature dependent mechanical behavior. The deformation mechanism is a trade-off between the stress concentrationcaused by SiC particles and Si_3N_4-Si_3N_4 GB sliding. The temperature increase tends to work in favor of GB sliding leading to softening of structures.However, microstructural strength increases with increase in temperature when GBs are absent In the case of SiCO nanocomposites, findingsindicate that temperature change dependent amorphization of nanodomains, the nanodomain wall placement, the nanodomain wall thickness, and nanodomain size are important factors that directly affect the extent of crystallinity and the strength against mechanical deformation.