Enhancement of solid-state reaction rates by non-hydrostatic stress effects on polycrystalline diffusion kinetics

摘要: Reaction layer growth between two chemically different solids may be controlled by polycrystalline diffusion kinetics in the growing phase. The depend on interplay volume and grain boundary diffusion. Using spinel formation single crystals of periclase sapphire as an example, we quantify effects applied mechanical stress bulk-transport properties reaction layer. rate increases fourfold when normal to interface from 3 30 MPa due stress-induced changes structure. At low stress, low-index (i.e., ∑3) “coincidence site lattice” boundaries with slow coefficients dominate, related epitactic sapphire. Increasing triggers periclase, causes sapphire-grown grains rotate out epitaxy, fast dominate. This effect outweighs hitherto emphasized influence size bulk transport polycrystals.