A general approach to grain growth driven by energy density differences among the grains, associated with curvature and/or extraneous driving forces (e.g. external fields) is developed. A mean field approximation leads to the definition of a threshold energy density, E∗, which depends on moments of the current distributions of grain diameters, a, and grain energy densities, E, such that the rat...

Recent research on the buildup of rocks from small dust grains has reaffirmed that grain growth in protoplanetary disks should occur quickly. Calculation of growth rates have been made for a variety of growth processes and generally predict high probabilities of sticking in low-velocity collisions that may be brought about in a number of ways in protoplanetary disks. Laboratory experiments have...

Na is found to improve the performance of Cu(In,Ga)Se2 (CIGS) solar cells although the mechanism is not clear. This paper briefly reviews some of the observations on Na in CIGS polycrystalline and epitaxial films. Experiments suggest weak electrical effects of Na within grains, primarily by reducing compensation and in some cases by enhancing acceptor concentrations. As it segregates to surface...

This work addresses two transitions in material behavior: one, the initial peak in stress response associated with dynamic recrystallization and two, the rapid increase in grain growth rate associated with pore separation from grain boundaries. A criterion is derived that predicts the initial peak in stress response associated with dynamic recrystallization, and another criterion is derived tha...

The structure evolution characteristics of NdF3 thin films has been analysed concerning texture and grain morphology. The structure could be classified according to the structure zone models, and the growth mode could be related to zone T and zone II. Contamination of the films by residual gases was found to inhibit the migration of grain boundaries and therefore, zone II does not appear even a...

The three-dimensional microstructure of Ni, observed after five annealing intervals, was compared to simulations grain growth using the threshold dynamics method with assumption capillarity as only driving force. A grain-by-grain comparison made it possible identify sources differences between simulation and experiment. most significant difference for grains smallest sizes, which predicted woul...

An apparatus has been developed to study the nucleation, growth, and morphology of water–ice grains spontaneously generated in a weakly ionized plasma having very cold neutral particles. Nucleation of water–ice grains in the laboratory experiment occurs only when plasma exists but the plasma density is not too high. Nonspherical, fast growth occurs when the mean free path of water molecules exc...

The effect of austenite grain size on the evolution of the bainite transformation in steels is not yet certain in spite of many investigations.1–7 Barford and Owen1 reported that the reaction rate was accelerated by decreasing the grain size, because of an increase in the number density of grain boundary nucleation sites. Umemoto et al.2 reported similar results and proposed an equation that de...

The study of microstructural evolution in polycrystalline materials has been active for many decades so it is interesting to illustrate the progress that has been made and to point out some remaining challenges. Grain boundaries are important because their long-range motion controls evolution in many cases. We have some understanding of the essential features of grain boundary properties over t...