https://www.surfacesciencewestern.com/wp-content/uploads/2012/01/ass11_biesinger.pdf

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn

https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

Microstructures and properties of high-entropy alloys

Open literature publications, in the period from 2010 to the end of January 2018, on refractory high entropy alloys (RHEAs) and refractory complex concentrated alloys (RCCAs) are reviewed. While RHEAs, by original definition, are alloys consisting of five or more principal elements with the concentration of each of these elements between 5 and 35 at.%, RCCAs can contain three or more principal elements and the element concentration can be greater than 35%. The 151 reported RHEAs/RCCAs are analyzed based on their composition, processing methods, microstructures, and phases. Mechanical properties, strengthening and deformation mechanisms, oxidation, and corrosion behavior, as well as tribology, of RHEA/RCCAs are summarized. Unique properties of some of these alloys make them promising candidates for high temperature applications beyond Ni-based superalloys and/or conventional refractory alloys. Methods of development and exploration, future directions of research and development, and potential applications of RHEAs are discussed.

Development and exploration of refractory high entropy alloys—A review

Disordered multicomponent systems, occupying the mostly uncharted centres of phase diagrams, were proposed in 2004 as innovative materials with promising applications. The idea was to maximize the configurational entropy to stabilize (near) equimolar mixtures and achieve more robust systems, which became known as high-entropy materials. Initial research focused mainly on metal alloys and nitride films. In 2015, entropy stabilization was demonstrated in a mixture of oxides. Other high-entropy disordered ceramics rapidly followed, stimulating the addition of more components to obtain materials expressing a blend of properties, often highly enhanced. The systems were soon proven to be useful in wide-ranging technologies, including thermal barrier coatings, thermoelectrics, catalysts, batteries and wear-resistant and corrosion-resistant coatings. In this Review, we discuss the current state of the disordered ceramics field by examining the applications and the high-entropy features fuelling them, covering both theoretical predictions and experimental results. The influence of entropy is unavoidable and can no longer be ignored. In the space of ceramics, it leads to new materials that, both as bulk and thin films, will play important roles in technology in the decades to come. The valuable combination of disorder and non-metallic bonding gives rise to high-entropy ceramics. This Review explores the structures and chemistries of these versatile materials, and their applications in catalysis, water splitting, energy storage, thermoelectricity and thermal, environmental and wear protection.

High-entropy ceramics

Multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings were deposited on C45 and M2 steel substrates by co-sputtering of pure metallic Ti, Zr, Nb, Hf and Ta targets in Ar + N2 and Ar + CH4 reactive atmospheres, respectively TiN, TiC and TiZrNbHfTa metallic coatings were also prepared as reference All the films were comparatively investigated for elemental and phase composition, texture, microstructure, hardness, friction and wear behavior X-ray structural analysis revealed the formation of single-solution phases ((111) texture) As compared to the reference binary coatings (TiN and TiC), the multi-component films exhibited significantly higher hardnesses (a difference in hardness of about 10 GPa in the case of nitrides) and also superior wear performance The best friction and wear behavior was found for the (TiZrNbHfTa)C film, for which the friction coefficient and wear rate were of 015 and 08 × 10− 6 mm3 N− 1 m− 1, respectively

Nanostructured multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C hard coatings

Multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings were deposited on Ti6Al4V alloy by co-sputtering of Ti, Zr, Nb, Hf and Ta metallic targets in reactive atmosphere. The coatings were analyzed for elemental and phase compositions, crystalline structure, morphology, residual stress, hardness, friction performance, wear–corrosion resistance and cell viability. For all the films, only simple fcc solid solutions with (111) preferred orientations were found, with crystallite sizes in the range 7.2–13.5 nm. The coatings were subjected to compressive stress, with values ranging from 0.8 to 1.6 GPa. The carbide coating with the highest carbon content (carbon/metal ≈ 1.3) exhibited the highest hardness of about 31 GPa, the best friction behavior ( μ = 0.12) and the highest wear resistance (wear rate K=0.2×10−6mm3N−1m−1), when testing in simulated body fluids (SBFs). Cell viability tests proved that the osteoblast cells were adherent to the coated substrates, and a very high percentage of live cells were observed on sample surfaces, after 72 h incubation time.

Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications.

Preparation and characterization of titanium oxy-nitride thin films

(TiAlCrNbY)C multi-component carbide coatings were prepared by reactive co-sputtering of Ti, Al, Cr, Nb and Y targets in an Ar + CH 4 atmosphere. The films were investigated for elemental and phase composition, chemical binding state, texture, morphology, residual stress, roughness, hardness, friction and wear using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), surface profilometry, hardness measurements, and tribological tests. The metals in the carbide films were found in an almost equiatomic ratio, whereas the carbon content varied from about 46 to 82 at.%. For film composition close to stoichiometry, a single fcc solid solution phase with an (111) preferred orientation was detected. The coatings with higher carbon concentrations (69–82 at.%) exhibited an amorphous structure. Fine grained and smooth surface morphologies were observed by AFM. While the metallic film exhibited a low tensile stress (∼ 0.240 GPa), the carbides coatings were subjected to compressive stress, with values (from 0.200 to 1.950 GPa) strongly depending on CH 4 flow rate. The hardness values (13–23 GPa) were found to be lower than those usually reported for binary carbides (30–35 GPa), while the dry friction coefficients were in the range 0.05–0.25.

Characteristics of (TiAlCrNbY)C films deposited by reactive magnetron sputtering

ZrCN single layer and Zr/ZrCN multilayered hard coatings, deposited by reactive magnetron sputtering, were investigated as possible candidates to be used as protective layers on medical implants. The elemental composition, hardness and adhesion of the coatings were analyzed. “In vivo” investigations on rats were carried out in order to examine the biomedical effects of coated implants. After 8 weeks of periosseous implantation, the blood parameters and the reaction of the surrounding tissues to the implants were evaluated. For comparison, uncoated stainless steel 316L implants were also investigated. Biological tests revealed that the best humoral immune response was obtained for the multilayer coated implants. Also, hematological analysis showed no significant differences in any of the blood parameters (red and white blood cell counts, hemoglobin concentration, and hematocrit) between the control group (sham operated rats) and the experimental groups formed by rats with coated implants.

Mihai Balaceanu

Papers

Nanostructured multi-element (TiZrNbHfTa)N and (TiZrNbHfTa)C hard coatings

Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications.

Preparation and characterization of titanium oxy-nitride thin films

Characteristics of (TiAlCrNbY)C films deposited by reactive magnetron sputtering

Characterization of Zr-based hard coatings for medical implant applications