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The fabrication of bioactive polymer nanocomposite coatings with enhanced biocompatibility and surface protection has been a topic of abundant concern in orthopaedic implant applications. Herein, we electrochemically prepared a novel poly (3,4-ethylenedioxythiophene) (PEDOT) based nanocomposite coatings with different contents of fluoro hydroxyapatite (FHA) nanoparticles on a newly developed Ti-Nb-Zr (TNZ) alloy; an appropriate approach to advance the surface features of TNZ implants. FTIR, XRD, and Raman analyses of the coating confirm the successful preparation of PEDOT/FHA nanocomposite, and XPS validate the chemical interaction between FHA and PEDOT matrix. SEM and TEM examination show the uniform distribution of spherical FHA nanoparticles inside the PEDOT matrix. Hardness and contact angle measurement results showed improving in the hardness and surface wettability of the coated samples respectively. Electrochemical corrosion tests specified that the PEDOT/FHA coatings exhibit higher corrosion protection than the pure PEDOT coatings. The fabricated nanocomposite coating supports the cell adsorption and proliferation of MG-63 cells. Moreover, antibacterial studies against Gram positive and negative bacteria reveal the enhanced antibacterial performance of the coated TNZ substrates. Our results show the potential applications of PEDOT/FHA nanocomposite as a most viable coating for the orthopaedic implants., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A biocompatible dicalcium phosphate dihydrate (DCPD) brushite coating of flake-like crystals was developed on AZ91D and AZ31 magnesium (Mg) surfaces to control and slow down the rapid degradation rate of the substrates. The electrochemical behavior of the DCPD-coated substrates was examined in a simulated body fluid (SBF) with uncoated substrates as the control. Fabrication of the coating was achieved via chemical immersion technique by modifying the surfaces with Ca(NO3)2·4H2O and KH2PO4 in addition to heat treatment. The morphology of the DCPD coating is uniform and dense with a flake-like crystal structure. After in vitro tests, the DCPD coating would have exhibited excellent corrosion resistance with more biomineralization of the active calcium phosphate (CaP). Moreover, the DCPD coating induced CaP formation after immersion in the SBF, indicating excellent bioactivity upon increasing the coating. Hence, the two-step chemical treatment enhances the bioactivity of DCPD coatings on Mg alloys, making them better implant materials. [ABSTRACT FROM AUTHOR]

Despite the widespread application of Ti alloy in the biomedical field, surface treatments are typically applied to improve its resistance to corrosion and wear. A newly developed biomedical Ti-20Nb-13Zr at.% alloy (TNZ) was laser-treated in nitrogen environment to improve its surface characteristics with corrosion protection performance. Surface modification of the alloy by laser was performed through a Nd:YAG laser. The structural and surface morphological alterations in the laser nitrided layer were investigated by XRD and a FE-SEM. The mechanical properties have been evaluated using nanoindentation for laser nitride and as-received samples. The corrosion protection behavior was estimated using electrochemical corrosion analysis in a physiological medium (SBF). The obtained results revealed the production of a dense and compact film of TiN fine grains (micro-/nanosize) with 9.1 µm below the surface. The mechanical assessment results indicated an improvement in the modulus of elasticity, hardness, and resistance of the formed TiN layer to plastic deformation. The electrochemical analysis exhibited that the surface protection performance of the laser nitrided TNZ substrates in the SBF could be considerably enhanced compared to that of the as-received alloy due to the presence of fine grains in the TiN layer resulting from laser nitriding. Furthermore, the untreated and treated Ti-20Nb-13Zr alloy exhibited higher corrosion resistance than the CpTi and Ti6Al4V commercial alloys. The improvements in the surface hardness and corrosion properties of Ti alloy in a simulated body obtained using laser nitriding make this approach a suitable candidate for enhancing the properties of biomaterials. [ABSTRACT FROM AUTHOR]

Nanostructured Fe-18Cr-2Si alloys were developed by a combination of mechanically alloying (MA) and spark plasma sintering (SPS) process. SPS was carried out in vacuum at three different temperatures (900, 1000, and 1100 °C) with a fixed holding time of 10 min and an applied pressure of 50 MPa. Potentiodynamic polarization (PDP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were used to study the effect of sintering temperature on the electrochemical properties of newly developed nanostructured ferritic Fe-18Cr-2Si alloy. XRD results showed that, after sintering, crystallite size increased with increasing sintering temperature and maximum crystallite size was 23.64 nm. The results showed that with increasing sintering temperature, corrosion resistance was increased in terms of pitting potential (Epit), passive current density (ip), and polarization resistance (Rp). The improved corrosion resistance was found to be closely related with the densification of the sintered alloys. [ABSTRACT FROM AUTHOR]

A duplex treatment of laser gas assisted nitriding and TiN-PVD (physical vapor deposition) coating was carried out on the surface of Ti-6Al-4V alloy. The laser pulse frequency was varied between 2,000 and 1,000 Hz to identify the optimum test conditions. Moreover, nanoindentation technique was utilized to in-situ map mechanical properties and study the wear behavior of the developed dissimilar layers. It was observed that these alloys exhibited transitional properties by employing the duplex treatment; by obtaining the values of individual layers due to the sensitivity of the nanoindentation tests and the possibility of testing small volumes of materials. The hardness and modulus of elasticity values of the sample treated at 2,000 Hz were relatively higher compared to other samples which can be attributed to the increased thickness of the laser affected zone caused by the higher deposited energy per unit area with increased frequency. Wear tests were conducted on the upper TiN layer and the substrate of the alloy to evaluate the improvement in tribological properties. It was observed that the wear resistance of the surface layer was on average 20 times higher than the substrate and the adhesion of the TiN-PVD layer is expected to improve due to the introduction of the laser-irradiated layer underneath which acted like a transitional region. [ABSTRACT FROM AUTHOR]

Abstract: Titanium alloys find widespread applications in multiple industries owning to their remarkable combination of properties like high specific strengths and good corrosion resistance. Nevertheless, their use in wear resistance applications was limited due to their poor tribological properties. This characteristic is attributed to the low plastic shearing resistance and the low work hardening properties of the alloys. To combat this, several surface treatment procedures have been suggested and implemented in the past with variable successes. One of the promising methods for improving tribological characteristics of these alloys is duplex treatment. In the present study a duplex treatment of laser nitriding and TiN-PVD (physical vapor deposition) coating was employed on Ti-6Al-4V alloy with variable laser pulse frequencies. It was found that the laser affected zone expands in size at higher laser pulse frequency. For the sample treated at 2000Hz, the laser affected zone expands over a thickness of approximately 50μm. Additionally, it was found that the microstructure was mainly composed of dendrite and a needle-like structures underneath in all treated samples. Metallic α-Ti was found to exist as observed from the XRD results which was later confirmed by XPS analyses and this was attributed to the nature of the PVD process. [Copyright &y& Elsevier]

A combined program of experiments and simulations is used to study the problem of cyclic indentation loading on metallic glasses. The experiments use a spherical nanoindenter tip to study shear band formation in three glasses (two based on Pd and one on Fe), after subjecting the glass to cycles of load in the nominal elastic range. In all three glasses, such elastic cycles lead to significant increases in the load required to subsequently trigger the first shear band. This cyclic hardening occurs progressively over several cycles, but eventually saturates. The effect requires cycles of sufficient amplitude and is not induced by sustained loading alone. The simulations employed a new shear transformation zone (STZ) dynamics code to reveal the local STZ operations that occur beneath an indenter during cycling. These results reveal a plausible mechanism for the observed cyclic hardening: local regions of confined microplasticity can develop progressively over several cycles, without being detectable in the global load-displacement response. It is inferred that significant structural change must attend such microplasticity, leading to hardening of the glass. [ABSTRACT FROM AUTHOR]

Magnesium (Mg)-based biocomposites and bioalloys are used in biomedical applications such as bone fixation, cardiovascular stents, hip joints, screws/pins, and dental implants. This review focuses on the mechanical properties and corrosion behavior of magnesium-based biocomposites and alloys. These properties are critically discussed to evaluate the development of modern Mg-based biocomposites and alloys for biomedical applications. Metallic and ceramic reinforcements such as Ti, Zn, TiO 2 , MgO, ZnO, ZrO 2 , TiB 2, and Al 2 O 3 are bioactive, bioinert, have suitable mechanical properties and are highly dependent on the processing routes. Powder metallurgy and disintegrated melt deposition are promising approaches to develop Mg-based composites for biomedical applications. The corrosion resistance is related to the stability of deposits and their chemical stability in in vivo and in vitro environments. Ca, TiO 2 , hydroxyapatite (HA), and fluorapatite (FA) are inferred to exhibit better corrosion resistance. • Review of mechanical properties for Mg-based biomicrocomposites, Mg-based bionanocomposites. • Review on recent advance on mechanical properties for Mg-based bioalloys. • Review for Corrosion behavior of Mg-based biomicrocomposites, Mg-based bionanocomposites, and Mg-based bioalloys. • Critical Review for Corrosion behavior of Mg-based bioalloys. [ABSTRACT FROM AUTHOR]

Abstract Microalloying with multi-elements assist in the development of high performance alloys. In this study, a powder metallurgy processed light-weight microalloyed Mg6Zn0.4Ca0.5Cu was developed. Alloying elements were effectively diffused into commercially pure magnesium by high temperature sintering. Although there was some accumulation of non-diffused alloying element at magnesium inter-particle boundary, which were found to have well sintered among themselves and assisted in the enhancement of ductility in the Mg6Zn0.4Ca0.5Cu alloy. The developed alloy experienced simultaneous enhancement in the strength and ductility. The level of strength attained by the Mg6Zn0.4Ca0.5Cu was significant (81% higher than unalloyed magnesium) and similar was the ductility (76% higher than unalloyed magnesium). Solid solution and well-sintered inter-particle accumulated alloying elements induced ductile failure of the Mg6Zn0.4Ca0.5Cu alloy under tensile stress. Highlights • Blend-press-sinter powder metallurgy processed microalloyed lightweight alloy. • Alloying elements were added in nanoparticle form and distributed in magnesium by solid state diffusion during sintering. • The magnesium experienced simultaneous enhancement of strength and ductility due to the microalloying. • The microalloyed magnesium has significantly high strength and ductility. [ABSTRACT FROM AUTHOR]

• TiN coating was deposited on biomedical Ti20Nb13Zr alloy using CA-PVD. • The coating showed good corrosion protection in SBF and artificial saliva. • The coating showed a reduced coefficient of friction and wear rate. • The TiN coating showed potential for biomedical applications. Although Ti-based alloys have shown improved biocompatibility, the release of metal ions at long implantation times due to reduced surface hardness and wear resistance results in reduced service lifetimes of implants and cause implant loosening. To overcome these limitations and extend the lifetime of Ti-based implants, a TiN ceramic coating was deposited on the developed Ti20Nb13Zr (TNZ) alloy by using cathodic arc physical vapor deposition. The objective of this paper was to examine and assess the performance of the coating and its influence on surface hardness, in- vitro corrosion, wear rate and friction coefficient. The results exhibited that the TiN coating led to an enhancement of the surface hardness of 23.1 GPa and modulus of elasticity of 224.6 GPa. In-vitro corrosion investigations showed better corrosion protection for the coated alloy in both simulated body fluid and artificial saliva compared to the uncoated alloy. The coefficient of friction (~ 0.4) of the coated alloy was almost 30% less than that of the TNZ alloy, and the wear rate of the coated TNZ was 0.62 ± 0.07×10−5 mm3/Nm compared to 3.9 ± 0.8×10−5 mm3/Nm for the uncoated sample. The obtained results indicate that coating the TNZ alloy with TiN may be a promising option for biomedical uses. [ABSTRACT FROM AUTHOR]