Formation of BaTiO 3 thin films from (110) TiO 2 rutile single crystals and BaCO 3 by solid state reactions

Abstract The formation of BaTiO 3 thin films from (110) TiO 2 rutile single crystals and BaCO 3 was investigated experimentally by solid -solid and gassolid reactions in vacuum. X-ray diffraction revealed the formation of an intermediate Ba 2 TiO 4 phase before BaTiO 3 is formed. According to our calculations the formation of Ba 2 TiO 4 is associated with a maximum decrease in the Gibbs energy at a CO 2 pressure lower than 10 À 4 mbar. Reactions at 600 -900 -C showed different processes to occur in the solid -solid and gas -solid reactions. The observations are interpreted in terms of the different mass transport mechanisms involved. The results shed new light on the phase sequence during BaTiO 3 formation; in particular a dissociation of BaCO 3 prior to its participation in the reaction has become rather unlikely.

Heat accumulation during femtosecond laser treatment at high repetition rate – A morphological, chemical and crystallographic characterization of self-organized structures on Ti6Al4V

This study presents a detailed characterization of self-organized nano- and microstructures on Ti6Al4V evoked by different scanning strategies and fluences with a 300 fs laser operating at a laser wavelength of 1030 nm. The resulting surface morphology was visualized via field emission scanning electron microscopy (FEG-SEM) images of the surface and cross-sections. X-ray diffraction (XRD)-analysis was performed to analyse changes in crystal structures. The chemical surface composition of the near-surface layer was determined by X-ray photoelectron spectroscopy (XPS). Results show a significant influence of heat accumulation while processing with high laser repetition rates on the formation, crystallinity and chemical composition of self-organized structures depending on the scanning strategy. The ablation with different laser scanning strategies led to varying dynamics of growth-mechanisms of self-organized structures, formation of intermetallic phases (Ti3Al), sub-oxides and oxides (Ti6O, TiO) as well as ions (Ti3+, Ti4+) in surface layer reliant on applied fluence. Furthermore, investigations revealed a heat-affected zone up to several micrometers in non-ablated material. © 2021 The Author

Friction stir welding Ti-al alloys with ultrasonic impact

High performance and reduced weight and cost are gaining importance in the aviation industry. There are different approaches to meet these requirements. In this study, titanium and aluminum alloys were welded using friction stir welding. The samples were divided into two groups, one of which was welded using ultrasound. Studies have shown that the strength of samples is influenced by many factors that are usually not taken into account. For example, the complexity of the interface between dissimilar materials and its roughness. It was found that the application of ultrasound during welding often increases the complexity of the interface and decreases its roughness, which generally leads to strengthening. This effect can neutralize the increase in the volume fraction of intermetallic compounds during the intensification of the welding process. The final strength consists of the number of defects, the volume fraction of intermetallics and the complexity of the interface

Binary systems and their nuclear explosions

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