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A microscopic mechanism for the unipolar resistive switching phenomenon in nickel oxides is proposed based on the thermal decomposition of oxygen ions from oxygen-rich clusters and their recombination with electron-depleted vacancies induced by local electric field in conductive filaments. The proposed physical feature is confirmed by x-ray photoelectron spectroscopy, transmission electron microscopy and electrical measurements in the as-deposited NiO x samples. The deduced formulae under reasonable approximations directly demonstrate the relationships of switching parameters that were widely observed and questioned in different material systems, indicating the universal validity of the proposed mechanism.

A simple numerical scheme is presented to simulate partial equilibrium solidification with complete interstitial and negligible substitutional solute back diffusion in multi-component and multi-phase systems. Based on this scheme, a computing tool capable of using Thermo-Calc databases directly has been developed for the estimation of solidification behavior of steels and other interstitial-containing alloys. Agreements between calculated and experimental as well as DICTRA results have been obtained on the microsegregation, fraction of eutectic, and freezing range of several steels. This suggests that the partial equilibrium assumption and proposed numerical scheme are reasonable and satisfactory, and confirms that the carbon back diffusion plays a very important role in the solidification of steels.

A phenomenological model was utilized to describe diffusivities in the γ (fcc) /γü (L12) and A2/B2 phases of the NiüAl system. An effective strategy, which takes the homogeneity range and defect concentration into account, was developed in the present work to optimize the atomic mobilities of γü phase. Such a strategy results in a dramatic decrease in the number of atomic mobility parameters to be evaluated for the L12 phase. The measured composition- and temperature- dependent diffusivities in the NiüAl system have been well replicated by the present mobility descriptions. For the L12 phase, comprehensive comparisons show that with fewer model parameters the presently obtained mobilities yield a better fit to experimental diffusivities, compared with previous assessments. The mobility descriptions are further validated by comparing calculated and measured concentration profiles for various diffusion couples. The time-dependent Al composition profile for the annealed vapor Al / γ couple is accurately described for the first time.