Phase–Property Diagrams for Multicomponent Oxide Systems toward Materials Libraries

Exploring the vast compositional space offered by multicomponent systems or high entropy materials using the traditional route of materials discovery, one experiment at a time, is prohibitive in terms of cost and required time. Consequently, the development of high-throughput experimental methods, aided by machine learning and theoretical predictions will facilitate the search for multicomponent materials in their compositional variety. In this study, high entropy oxides are fabricated and characterized using automated high-throughput techniques. For intuitive visualization, a graphical phase–property diagram correlating the crystal structure, the chemical composition, and the band gap are introduced. Interpretable machine learning models are trained for automated data analysis and to speed up data comprehension. The establishment of materials libraries of multicomponent systems correlated with their properties (as in the present work), together with machine learning-based data analysis and theoretical approaches are opening pathways toward virtual development of novel materials for both functional and structural applications

Potentiodynamic Polarization Studies and Surface Chemical Composition of Bismuth Titanate (BixTiyOz) Films Produced through Radiofrequency Magnetron Sputtering

The applications of Bismuth Titanate (BixTiyOz) materials have been focused on their electronic and optical properties, but with respect to the use of these compounds in applications like corrosion resistance, have been very few or nonexistent. For this reason, in the present investigation BixTiyOz thin films were deposited using RF magnetron sputtering onto silicon wafers, stainless steel 316L, and titanium alloy (Ti6Al4V) substrates, in order to carry out a study of the corrosion behavior of this compound. The structural properties of the coatings were studied through X-ray diffraction (XRD), the morphology was determined using Scanning Electron Microscopy (SEM), the corrosion resistance behavior of the coated and uncoated substrates was evaluated via the Potentiodynamic Polarization technique, and surface chemical composition was evaluated through X-ray photoelectron spectroscopy (XPS). The XRD results indicated that the films were amorphous. The SEM micrographs showed that the deposited films were homogeneous, but in some cases there were cracks. The potentiodynamic polarization technique showed that the corrosion current in the coated substrates decreased by an order of two magnitudes with respect to the uncoated substrates, but in both cases the corrosion mechanism was pitting due to the pores in the film. The XPS analysis shows that the deposited films contain both Bi3+ and Ti4+

A Microstructural and Wear Resistance Study of Stainless Steel-Ag Coatings Produced through Magnetron Sputtering

This paper presents a study of the tribological properties of stainless steel coatings with varying Ag contents, deposited via magnetron sputtering. The growth of the coatings was done in Ar and Ar + N2 atmospheres in order to change the crystalline phase in the coating. The analysis of the chemical composition was performed using energy-dispersive X-ray spectroscopy (EDS) and the structural analysis was performed via X-ray diffraction (XRD). The adhesive wear resistance and the friction coefficient were evaluated using the ball-on-disk test with a ball of alumina. The coatings’ adhesion was measured with a scratch tester and the mechanical properties were evaluated with a nanoindenter. The morphology of the films and the wear track were characterized via scanning electron microscopy (SEM). By means of XRD, phases corresponding to the body-centred cubic (BCC) structure were found for the coatings deposited in an inert atmosphere and face-centred cubic (FCC) for those deposited in a reactive atmosphere. A more compact morphology was observed in coatings with a higher silver content. The values of the hardness increased with an increase in the silver content and the presence of nitrogen in the coatings. In the wear traces, mainly mechanisms of oxidative and adhesive wear and plastic deformation were found. The coefficient of friction decreased with an increase of silver in the coatings, whereas the wear rate decreased

Annealing Effect on the Structural and Optical Properties of Sputter-Grown Bismuth Titanium Oxide Thin Films

The aim of this work is to assess the evolution of the structural and optical properties of BixTiyOz films grown by rf magnetron sputtering upon post-deposition annealing treatments in order to obtain good quality films with large grain size, low defect density and high refractive index similar to that of single crystals. Films with thickness in the range of 220–250 nm have been successfully grown. After annealing treatment at 600 °C the films show excellent transparency and full crystallization. It is shown that to achieve larger crystallite sizes, up to 17 nm, it is better to carry the annealing under dry air than under oxygen atmosphere, probably because the nucleation rate is reduced. The refractive index of the films is similar under both atmospheres and it is very high (n =2.5 at 589 nm). However it is still slightly lower than that of the single crystal value due to the polycrystalline morphology of the thin films