Defect and Diffusion Forum Vols. 323-325

Abstract: Nanoscale systems show a wide variety of physical properties that cannot be observed in the bulk. Using atom probe tomography, it is possible to study nanostructured materials with almost atomic resolution in all three dimensions. In this article, we will present a short review of the latest atom-probe measurements carried out at University of Münster with particular focus on diffusion and segregation measurements in triple junctions and interface analysis.

Abstract: We present here an overview of native point defects calculations in silicon carbide using Density Functional Theory, focusing on defects energetics needed to understand self-diffusion. The goal is to assess the availability of data that are necessary in order to perform kinetic calculations to predict not only diffusion properties but also the evolution of defect populations under or after irradiation. We will discuss the spread of available data, comment on the main defect reactions that should be taken into account, and mention some of the most recent promising developments.

Abstract: The paper reviews the advantages of diffusion coating and the parameters deciding an optimum coating performance. Furthermore, innovative coating approaches are presented which have a significant potential beyond existing diffusion coating solutions.

Abstract: A short review of the most important reliable, as well as doubtful, in authors opinion points in a wide field of grain boundary diffusion, stresses and segregation.

Abstract: A general, consistent with linear irreversible thermodynamics, theory of stress and elastic deformation during interdiffusion is shown. Special consideration is given to the entropy balance and its production rate during diffusion in Cu-Fe-Ni alloys. The entropy produced during diffusion does not depend on the reference frame and is always positive. The paper spans the gap between the Darken method, linear irreversible thermodynamics and treatments by Stephenson and Svoboda.

Abstract: We consider the kinetics of chemical interdiffusion along the grain boundaries in stressed thin metal film attached to inert substrate. We show that the kinetics of stress relaxation in the film can be either accelerated or slowed down if compared with the same kinetics in a single-component film, depending on the difference of intrinsic GB diffusion coefficients of the two components. In the case of faster matrix atoms the tensile stress in the film significantly increases beyond its initial value at the beginning of interdiffusion process, while in the case of faster diffuser atoms the compressive stresses develop in the film at the intermediate stages of stress evolution.

Abstract: The problem of phase competition during reactive diffusion is revisited. Nucleation of an intermediate phase at an interface under external fluxes in the neighboring phases is considered in the frame of kinetic Fokker-Planck approach. Effective nucleation barrier depending on the divergence of external fluxes is introduced. New suppression/growth criteria are obtained.

Abstract: This paper present the determination of concentration profiles of an Mg Al diffusion couple that was obtained with a high resolution field emission scanning electron microscope, the Hitachi SU-8000 equipped with a SDD EDS detector. From these concentration profiles, the inter-diffusion coefficient is determined with the Boltzmann-Matano technique. The advantages and disadvantages of working at high and low beam energy for quantitative x-ray microanalysis are highlighted. The f ratio method is used in this work to convert the x-ray intensities into composition.

Abstract: We investigated lithium self-diffusion in amorphous and single crystalline lithium niobate at low temperatures of 323, 423 and 623 K. The diffusivity was studied by secondary ion mass spectrometry (SIMS), using ion beam sputtered ⁶LiNbO₃ as a tracer source. Our intention was to get information how structural disorder influences ionic diffusivity, while chemical composition remains unchanged. The results indicate an increase of the Li diffusivity by about eight orders of magnitude in the amorphous state.