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INTRODUCTION: The inflammatory response triggered by orthopedic devices results in the generation of reactive oxygen species (ROS) and a decrease in pH, accelerating the corrosion rate of Mg implants. To address corrosion challenges, various strategies are explored, including alloying with zinc and calcium elements and surface modifications. Plasma electrolytic oxidation (PEO) emerges as a promising technology, forming porous MgO coatings on Mg surfaces [1]. The electrolyte composition and the incorporation of additives not only affect coating characteristics but also influence the thickness and porosity of PEO coatings, collectively playing crucial roles in determining and preventing corrosion [2]. This study underscores the potential use of additives with ROS-scavenging properties, such as manganesebased additives in the PEO electrolyte, and the synthesis of MgO-Mn3O4 coatings on Mg-Zn-Ca alloy, as a means to mitigate corrosion rates, especially in inflammatory conditions. EXPERIMENTAL: In this study, PEO coatings incorporating Mn3O4 were fabricated on Mg-Zn-Ca substrate using two distinct methods: the introduction of KMnO4 salt and the inclusion of Mn3O4 nanoparticles in the electrolyte composition. In the first approach, composite coatings were chemically synthesized within the plasma microdischarge area, while the second route involved physical processes through electrophoretic adsorption. The electrochemical and immersion corrosion tests were conducted under simulated normal conditions using a PBS solution (pH 7) and under inflammatory conditions, achieved by introducing H2O2 and HCl (pH 5.2) into the PBS solution. RESULTS AND DISCUSSION: The experimental results showed that the inclusion of KMnO4 into electrolyte led to a reduction in voltages, while Mn3O4 resulted in an elevation in process voltages, directly impacting the structural characteristics of the coatings. Importantly, incorporating these additives decreases surface porosity and increases PEO coating thickness. Electrochemical and immersion corrosion tests, conducted under both simulated normal and inflammatory conditions, underscored the vulnerability of uncoated Mg-Zn-Ca alloy to corrosion, particularly in inflammatory settings (with corrosion rates increasing from approximately 2 to 16 mm·y-1). Notably, the composite PEO coatings, incorporating Mn3O4 nanoparticles, displayed superior corrosion performance. This superiority manifested as a significant decrease in corrosion current density and an increase in total impedance resistance compared to basic PEO coatings. For instance, potentiodynamic polarization results indicated a substantial reduction in corrosion current density, decreasing from 73.9 μA·cm-2 for basic PEO coatings to 5.5 μA·cm-2 for Mn3O4-incorporated PEO coatings. The enhanced performance was attributed to the catalytic activity of Mn3O4 in scavenging H2O2 in simulated inflammatory conditions, as well as the greater thickness and lower porosity of the composite coatings compared to basic PEO. Collectively, these features hindered the penetration of corrosive agents to the substrate. Moreover, the coatings showed a controlled release of Mn ions into the surrounding environment within a safe concentration range for the human body. CONCLUSIONS: These findings suggest that PEO coatings incorporating Mn3O4 present promising protective solutions for Mg implants, showcasing improved corrosion behavior associated with inflammation. [ABSTRACT FROM AUTHOR]

The effects of rare earth element erbium (Er) additions on the microstructure and mechanical properties of Al-15Zn-2.5Mg-2.5Cu alloy have been investigated. This new high strength alloy with erbium additions (0.5, 1.0, 1.5 and 2.0 wt%) was synthesized by liquid metallurgy route followed by hot extrusion. Microstructural characterization was performed using scanning electron microscope and electron probe microanalysis. Significant annum! of grain refinement was observed with erbium addition in the hot extruded and heat treated alloy. Tensile test was performed to investigate the effect rare earth on mechanical behavior of alloy in as cast and hot extruded condition before and after 16 hfiif treatment The combined effect of erbium addition, hot extrusion and heat treatment significantly enhanced the tensile strength of alloy (602 MPa) when compared to the as cast alloy without erbium addition (225 MPa). The strengthening of the alloy was attributedto grain refinement caused by erbium along with hot extrusion and formation of precipitates after T6 heat treatment. Fractograhic investigations revealed that the hot extruded alloy with erbium addition after heat tieatment showed uniformly distributed deep dimples exhibiting ductile behavior. [ABSTRACT FROM AUTHOR]

A modified strain-induced melt activation (SIMA) process was applied and its effect on the structural characteristics and hardness of the aluminum alloy Al-12Zn-3Mg-2.5Cu was investigated. Specimens subjected to a deformation of 40% at 300℃ were heat treated at various times (10-40 min) and temperatures (550-600℃). Microstructural studies were carried out using optical and scanning electron microscopies (SEM). Results showed that the best microstructure was obtained at the temperature and time of 575℃ and 20 min, respectively. The hardness test results revealed superior hardness in comparison with the samples prepared without the application of the modified SIMA process. T6 heat treatment including quenching to 25℃ and aging at 120℃ for 24 h was employed to reach to the maximum strength. After the T6 heat treatment, the average tensile strength increased from 231 MPa to 487 and 215 MPa to 462 for samples before and after strain-induced melt activation process, respectively. Ultimate strength of globular microstructure specimens after SIMA process has a lower value than as-cast specimens without SIMA process. [ABSTRACT FROM AUTHOR]

Two kinds of biocompatible coatings were produced in order to improve the corrosion resistance of nickel titanium(NiTi) alloy. A titaniumoxide-titanium(TiO2-Ti) compositewas coated on NiTi alloy using electrophoreticmethod. After the coating process, the samples were heat-treated at 1000 °C in two tube furnaces, the first one in argon atmosphere and the second one in nitrogen atmosphere at 1000 °C. The morphology and phase analysis of coatings were investigated using scanning electron microscopy and X-ray diffraction analysis, respectively. The electrochemical behavior of the NiTi and coated samples was examined using polarization and electrochemical impedance spectroscopy tests. Electrochemical tests in simulated body fluid demonstrated a considerable increase in corrosion resistance of composite-coated NiTi specimens compared to the non-coated one. The heat-treated composite coating sample in nitrogen atmosphere had a higher level of corrosion resistance compared to the heat-treated sample in argon atmosphere, which is mainly due to having nitride phases. [ABSTRACT FROM AUTHOR]

In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the Seebeck coefficient with the addition of CNT. The electrical conductivity increased from 0.011 to 0.1345 S/cm with the increment of CNT from 0.5 to 10 wt%. The highest Seebeck coefficient of 11.4 μV/K was observed for the sample containing 5 wt% CNT at 338 K where the maximum power factor of 1.598×10−3 μWm−1K−2 was obtained for the fabric coated with nanocomposite containing 10 wt% CNT. [ABSTRACT FROM AUTHOR]

Silica-supported, metal-promoted MoS2 catalysts were prepared. Sol–gel method was used for providing the SiO2 support as well as for including the catalyst precursors and promoter in one single step of preparation. The general idea in this approach is to obtain the promoted MoS2 catalyst phase finely and uniformly distributed in the SiO2 support. Scanning electron microscopy of the obtained catalysts shows a fine and homogeneous distribution of the metal-promoted MoS2 particles on the SiO2 matrix with surface area between 62 and 104m2/g. Metal promoter affects the surface area, pore size distribution and the hydrodesulfurization (HDS) activity and selectivity. When different promoters were used at the same amount, the highest selectivity for direct C–S bound cleavage is observed for Ru/MoS2/SiO2 catalyst, and at different amounts of Co the highest selectivity was occurred with Co/MoS2/SiO2 at 12% of Co/MoS2, X-ray diffraction studies showed that the catalysts are poorly crystallized with a very weak intensity of the (002) line of 2H-MoS2. Comparison on the catalytic activities of the catalysts with different metal promoters was made. Catalytic activity results showed the method of preparation used in this study is successful in producing very efficient catalysts for the HDS of dibenzothiophene (DBT). Silica-supported, cobalt-promoted MoS2 catalyst showed the highest activity. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane (PEM) fuel cells are considered as the best choice for transportation applications due to their superb advantages such as low pollution, high efficiency and low cost. Metallic bipolar plates make up a prime component in the PEM fuel cells. As metallic bipolar plates, the corrosion resistance of stainless steel (SS-316L) and aluminum alloy (AA-6061) materials coated with graphite in different nanometer thicknesses were investigated. Corrosion tests were carried under simulated fuel cell operation conditions (1 M H2SO4, 70 °C). The results showed that the best thickness for SS-316L is 200 nm. For the AA-6061 material, however, the maximum graphite coating thickness of 600 nm examined in this study still seems inadequate protection for PEM bipolar plates. [ABSTRACT FROM AUTHOR]

Significance: Optical coherence tomography (OCT) has emerged as the standard of care for diagnosing and monitoring the treatment of various ocular disorders due to its noninvasive nature and in vivo volumetric acquisition capability. Despite its widespread applications in ophthalmology, motion artifacts remain a challenge in OCT imaging, adversely impacting image quality. While several multivolume registration algorithms have been developed to address this issue, they are often designed to cater to one specific OCT system or acquisition protocol., Aim: We aim to generate an OCT volume free of motion artifacts using a system-agnostic registration algorithm that is independent of system specifications or protocol., Approach: We developed a B-scan registration algorithm that removes motion and corrects for both translational eye movements and rotational angle differences between volumes. Tests were carried out on various datasets obtained from two different types of custom-built OCT systems and one commercially available system to determine the reliability of the proposed algorithm. Additionally, different system specifications were used, with variations in axial resolution, lateral resolution, signal-to-noise ratio, and real-time motion tracking. The accuracy of this method has further been evaluated through mean squared error (MSE) and multiscale structural similarity index measure (MS-SSIM)., Results: The results demonstrate improvements in the overall contrast of the images, facilitating detailed visualization of retinal vasculatures in both superficial and deep vasculature plexus. Finer features of the inner and outer retina, such as photoreceptors and other pathology-specific features, are discernible after multivolume registration and averaging. Quantitative analyses affirm that increasing the number of averaged registered volumes will decrease MSE and increase MS-SSIM as compared to the reference volume., Conclusions: The multivolume registered data obtained from this algorithm offers significantly improved visualization of the retinal microvascular network as well as retinal morphological features. Furthermore, we have validated that the versatility of our methodology extends beyond specific OCT modalities, thereby enhancing the clinical utility of OCT for the diagnosis and monitoring of ocular pathologies., (© 2024 The Authors.)