Diffusion Fundamentals (E-Journal)
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Computing Transport Properties in Solid-State Materials from the Shapes of Potential Energy Landscapes
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Two-Step Reaction in Oxides: Nucleation and Growth Kinetics of ZnAl2O4 Spinel in ZnO/Al2O3 Bilayers
No full textLow-Temperature, Ultra-Giant Blistering of Atomic Layer Deposited Barrier Coatings on Polymer Films Caused by Additive Segregation
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Interdiffusion and Internal Stress Effects in Closed Geometry
No full textThis study examines how cylindrical geometry influences interdiffusion and stress development during the formation of ZnAl₂O₄ in nanoscale Pt/Al₂O₃/ZnO structures. Double-layered nanopillars with different diameters were annealed to induce reactive diffusion, and STEM imaging was used to measure intermetallic growth. Smaller pillars exhibited thinner ZnAl₂O₄ layers due to stronger diffusion-inhibiting stresses that cannot relax in closed geometries. At longer times parabolic growth behavior was observed. These results show that curvature-dependent stress fields play a key role in regulating diffusion kinetics at the nanoscale
Computer Simulations of Self-Diffusion of Adsorbed Water in a Model for Microporous Portland Cement
No full textMicroporous cement materials such as some types of Portland cement show swelling and shrinkage with strong hysteresis depending on the humidity. A quantitative theoretical explanation is based on the existence of strong forces mediated by adsorbed water between the pore walls and the resulting elastic response of the solid. We have performed Monte-Carlo simulations of the adsorption equilibrium in the microcapillaries. The microcapillary structure of cementitious materials has been modelled using Tobermorite slit pores. We have found huge pressures and pressure anisotropy within the adsorbed water layers. Accordingly, we obtained self-diffusion coefficients on the surfaces that correspond in magnitude to coefficients in liquid water under high pressure in a three-dimensional bulk volume. Significant differences were observed in lateral diffusion (parallel to the walls) and normal diffusion (perpendicular to the walls). The diffusion kinetics strongly depends on the width of the slit pores. The diffusion coefficients were determined by tracking the mean square displacement of water molecules during the simulations. The pressure and diffusion curves are in accordance with density profiles and radial distribution functions calculated from our simulations
Reaction-Diffusion in Co2Si/Zn Diffusion Couple
No full textPeriodic layered structures were examined in the Co₂Si/Zn diffusion couple annealed at 390 °C. SEM, TEM, EPMA, and XRD analyses revealed alternating Co–Si–rich and Zn–rich layers composed of CoSi, γ₁, and γ₂ phases with cell-to-cell variations in wavelength. The reaction zone thickness followed a parabolic time dependence, confirming diffusion-controlled growth governed by the Kirkendall effect. Three-dimensional FIB reconstruction showed complex layer morphologies, including branching and misalignment influenced by local diffusion pathways and grain orientations. EBSD measurements suggested no clear correlation between Co₂Si grain orientation and layer periodicity. These findings provide insight into multiphase reaction-diffusion mechanisms and the origin of periodic microstructures in the Co–Si–Zn system