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Designing highly osteogenic and effective antibacterial biomaterials with a prolonged service life for oral implants remains an ongoing challenge. In this work, the multi-element (TiZrTaNbMo)N high entropy nitride (HEN), with different concentrations of Ag, was co-deposited onto surgical grade commercially pure titanium by a reactive sputter-deposition technique using a double cathode glow discharge plasma system. The effects of Ag concentration on the microstructure and mechanical properties of the HEN-Ag nanocomposite coatings were investigated by various testing methods. Potentiodynamic polarization measurements were used to evaluate the corrosion resistance of the coatings in simulated body fluid. The antibacterial activity of the HEN-Ag nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The cytocompatibility and osteogenesis activity of the HEN nanocomposite coatings using MC3T3-E1 cells were evaluated by a CCK-8 assay and an alkaline phosphatase quantitative assay. These studies demonstrate that the Ag-free HEN coating was composed of a face-centered-cubic (FCC) nitride phase, which displays good mechanical properties, anti-corrosion performance and osteogenic function, but no antibacterial properties were observed. In contrast, the HEN 0.9 Ag 0.1 coating, composed of amorphous/nanocrystalline high-entropy nitride embedded with silver nanoparticles ∼10 nm in diameter, displays good mechanical and anti-corrosion performance, together with the excellent cell compatibility and antibacterial performance, which offer potential for providing outstanding protective efficiency for dental implants. Although the HEN 0.8 Ag 0.2 nanocomposite coating exhibited superior antibacterial efficacy, potential for in vitro cytotoxicity was identified. • The size and distribution of Ag nanoparticles were determined as a function of Ag content. • The HEN 0.9 Ag 0.1 nanocomposite coating improved the corrosion/wear resistance of CP-Ti. • The HEN 0.9 Ag 0.1 nanocomposite coating exhibited antibacterial behaviour against a spectrum of microbial and fungal species. • The HEN 0.9 Ag 0.1 nanocomposite coating enhanced the cytocompatibility and in vitro bioactivity of CP-Ti. [ABSTRACT FROM AUTHOR]

To improve the tribocorrosion performance of mechanical components applied in marine environments, a (TiZrNbTaMo)C refractory high entropy alloy carbide (RHEAC) coating was deposited using a sputtering deposition technique onto a commercial purity Ti substrate. The as-synthesized RHEAC coating, with an average thickness of approximately 22 µm, exhibited a single-phase face-centered cubic (FCC) crystal structure, composed of equiaxed grains with an average diameter of approximately 9 nm. The tribocorrosion performance of the RHEAC coating was investigated by both open circuit potential (OCP) and potentiodynamic polarization measurements in 3.5 wt% NaCl solution. Under both static corrosion and tribocorrosion conditions, the RHEAC coating showed higher OCP values relative to the uncoated substrate. Similarly, the potentiodynamic polarization measurements revealed that the RHEAC coating exhibited more noble corrosion potential values and a lower corrosion current density under both static and tribocorrosion conditions, in comparison with uncoated Ti. After application of the RHEAC coating, the specific wear rate of commercially pure Ti was lowered by two orders of magnitude under conditions of both tribocorrosion and dry sliding wear. Moreover, Mott-Schottky and point of zero charge (PZC) measurements suggested that the passive film present on the RHEAC coating exhibited a smaller donor density as well as a higher capacity to impede Cl − ions adsorption than the passive film grown on uncoated substrate. • The potential drop of the RHEAC coating is significantly lower than CP-Ti substrate. • The RHEAC coating possesses a larger E corr and a lower i corr than CP-Ti substrate. • The specific wear rate of bare CP-Ti has improved by two orders of magnitude after coated with RHEAC. • The RHEAC coating exhibits lower donor densities than uncoated CP-Ti. [ABSTRACT FROM AUTHOR]

In this work, the structural stability, mechanical properties and electronic structure of β-Ta 5 Si 3 with different Al additions were first predicted by first-principles density functional calculations. The binary and ternary β-Ta 5 Si 3 are thermodynamically and mechanically stable, but their thermodynamic stability slightly decreases with Al additions. The elastic constants, bulk modulus (B), shear modulus (G) and Young's modulus (E) of Al-alloyed β-Ta 5 Si 3 were calculated. According to the criteria involving the bulk/shear modulus (B/G ratio) and Poisson's ratio, the D8 m -structured ternary Ta 5 Si 3 , where two Si 4a atoms are replaced by two Al atoms, shows improved ductility. Based on the theoretical analysis, the β-Ta 5 (Si 0.83 Al 0.17 ) 3 nanocrystalline coating was deposited onto polished Ti-6Al-4V alloy substrates by double cathode glow discharge plasma method. The phase constitution, microstructure and composition of the coating were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The as-deposited coating was composed of nearly rounded D8 m -β-Ta 5 Si 3 grains with an average size of ∼4 nm and exhibited strong (002) and (400) preferred orientation. After Al alloying, the hardness and the compressive residual stress of the β-Ta 5 Si 3 decreased, and the contact damage resistance and adhesion strength increased. The electrochemical corrosion properties of the β-Ta 5 (Si 0.83 Al 0.17 ) 3 nanocrystalline coating were compared to the binary β-Ta 5 Si 3 coating and Ti-6Al-4V in 3.5 wt% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. It was shown that the corrosion resistance of the β-Ta 5 Si 3 was improved through the substitution of Al for Si. [ABSTRACT FROM AUTHOR]

A novel wear and corrosion resistant β-Ta 5 Si 3 coating was deposited onto a Ti-6Al-4V substrate using a double glow discharge plasma method. The structure of the coating was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), and its mechanical properties were determined by a combination of nanoindentation and scratch testing. Dry sliding wear behavior of the β-Ta 5 Si 3 coating was evaluated using a ball-on-disc tribometer. Further, the electrochemical behavior of the β-Ta 5 Si 3 coating was assessed through immersion in a 3.5 wt% NaCl solution. The as-deposited coating consisted of equiaxed tetragonal D8 m -structured Ta 5 Si 3 exhibiting a ∼4 nm grain size with a pronounced (400) preferred orientation. The specific wear rates of the β-Ta 5 Si 3 coating were ∼10 −6 mm 3 /(N m), which is two orders of magnitude better than that of the uncoated substrate under the same test conditions. This is because the coating exhibits higher values of H/E. Finally, the corrosion resistance of the coating was improved relative to bare alloy in this solution. Mott-Schottky analysis showed that the passive film formed on the coating during corrosion testing behaved like an n-type semiconductor. The carrier density was one order of magnitude less than that formed on bare substrate in the same solution. In light of this, the β-Ta 5 Si 3 nanocrystalline coating is expected to provide protection to metallic components against wear and corrosion and as such extend their service life. [ABSTRACT FROM AUTHOR]

To improve the corrosion resistance, surface electrical conductivity and wettability of Ti–6Al–4V used in polymer electrolyte membrane fuel cell (PEMFC), a ZrCN nanocrystalline coating was deposited on Ti–6Al–4V substrate using double cathode glow discharge technique. The new coating exhibited a nanocomposite structure, consisting of amorphous C, CN x and nanocrystalline ZrCN. The effect of the HF concentrations on the corrosion behavior of the coating was investigated by potentiodynamic, potentiostatic polarizations and electrochemical impedance spectroscopy (EIS) in a simulated the operating conditions of a PEMFC. With increasing HF concentrations, the corrosion potential (E corr ) decreased and the corrosion current density (i corr ) of the ZrCN coating increased, indicating that corrosion resistance decreased with the increase of HF concentrations. However, at any given concentration of HF, the corrosion resistance of the ZrCN coating was significantly higher than that of uncoated Ti–6Al–4V. The results of EIS measurements showed that with increasing the concentration of HF, the resistance of the passive film (R b ) formed on the ZrCN coating decreased slightly, being of the order of magnitude of ∼10 7 Ω cm 2 , which was an improvement by four orders of magnitude compared to uncoated Ti-6A1-4V. At a compaction force of 140 N cm −2 , no perceptible difference in the interfacial contact resistance (ICR) of ZrCN-coated Ti-6A1-4V was observed before and after potentiostatic polarization for 120 min, and its ICR values were reduced by one order of magnitude in comparison to that of uncoated Ti-6A1-4V. Moreover, ZrCN-coated Ti-6A1-4V exhibited a much low surface wettability than uncoated Ti–6Al–4V alloy, which was beneficial for both water management and improving corrosion resistance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cr alloying leads to the change in preferred orientation from (210) to (200) of the coatings. [•] The hardness and elastic modulus of the coatings are reduced by Cr addition. [•] Cr alloying improves the corrosion resistance of the coatings. [•] Cr addition increases the Mulliken population of Mo–Mo bonds. [ABSTRACT FROM AUTHOR]

Abstract: Novel Cr-alloyed MoSi2-based nanocomposite coatings were successfully synthesized onto Ti–6Al–4V substrates by a double glow discharge plasma technique. The architecture of the nanocomposite coatings exhibited a hierarchical structure, consisting of equiaxed C40-MoSi2 with a bimodal grain size distribution and strip-shaped Mo5Si3 grains segregated to the boundaries of submicron MoSi2 grains. The results showed that the toughness of the MoSi2-based nanocomposite coatings depended strongly upon their hierarchical structure and the magnitude of compressive residual stresses in the nanocomposite coatings. [Copyright &y& Elsevier]