Application Of Mg Alloys Research Articles

A fluorine-free bioinspired multifunctional slippery coating for ultra-long-term anticorrosion of Mg alloy, static/dynamic anti-icing, antibacterial and antifouling

Poor corrosion resistance limits the application of Mg alloy and it is meaningful to explore a surface coating technology for ultra-long-term corrosion protection of Mg alloy. Superhydrophobic surface (SHS) and smooth liquid-injected porous surface (SLIPS) have shown important application value in the field of Mg alloy corrosion protection. However, the unstable special interface of air layer or lubricant cannot act as stable corrosion barrier for the long term. Inspired by frog skin, a bionic fluorine-free multifunctional slippery coating (MSC) is prepared by one-step spraying a mixture of epoxy resin, silicone oil, modified nano TiO2 and modified micron mica powder. MSC exhibits a microstructure similar to frog skin, excellent slippery (sliding angle ∼ 3°) and strong lubricant retention. Different from anticorrosion mechanism of SHS and SLIPS by their special interface, MSC, storing silicone oil on the surface and inside the coating, demonstrates ultra-long-term anticorrosion to Mg alloy (both neutral salt spray and 3.5 wt% NaCl solution immersion for 60 days) due to excellent barrier effect throughout coating, and the scratch defect area of MSC is not significantly eroded after 14 days of salt spray. Moreover, MSC exhibits excellent static/dynamic anti-icing ability and low ice adhesion in a −20℃ environment, outstanding adhesion (level 4B), high hardness (3H), antibacterial (>94 %), antifouling, chemical stability and resistance to boiling water, ice water and UV radiation. All these excellent properties can promote the application of Mg alloy in a wider range of fields.

Biomimetic hydrogel coatings for improving the corrosion resistance, hemocompatibility, and endothelial cell growth of the magnesium alloy

The fast biodegradation and poor biocompatibility of Mg alloys in physiological environments are still the main problems restricting their application in cardiovascular stents. In this study, the hydrogel coatings (SBMA-AAM) with different proportions of methacryloyl ethyl sulfobetaine (SBMA) and acrylamide (AAM) were built on the surface of AZ31B magnesium alloy through ultraviolet (UV) polymerization. The corrosion degradation behavior, hemocompatibility, and endothelial cell (EC) growth performance of the samples were studied in detail. The findings revealed that the uniform and dense SBMA-AAM coatings could significantly enhance the corrosion resistance. In addition, the hydrogel coatings showed excellent hydrophilicity, which increased the albumin adsorption while inhibiting the fibrinogen adsorption, and thus reduced the platelet adhesion and activation and hemolysis rate, accordingly significantly enhancing their anticoagulant performance. Furthermore, SBMA-AAM hydrogel coating promoted the EC adhesion and proliferation and the vascular endothelial growth factor (VEGF) and nitric oxide (NO) secretion of ECs, which is conducive to promoting endothelialization. When the concentration ratio of SBMA and AAM was 1: 2, the modified magnesium alloy showed the best corrosion resistance and biocompatibility. Therefore, the SBMA-AAM hydrogel coating could effectively regulate the corrosion degradation performance and biocompatibility of Mg alloys, laying a foundation for the application of Mg alloys in cardiovascular stents.

Improvement in adhesion and corrosion resistance of Ce-based coating on micro-arc oxidized AZ31B Mg alloy via employing graphene oxide as an effective interlayer

Ce-based coatings are often used as protective coatings on Mg alloy because of their excellent self-healing and anticorrosion properties. However, poor adhesion of Ce coating can easily cause it peel off and thus lose its protective effect. In this work, for the first time, the graphene oxide (GO) was employed as an interlayer between micro-arc oxidation (MAO) and Ce-based coatings to improve their adhesion strength. The results show that the addition of GO layer can effectively improve the adhesion strength and hardness of the composite coating. The MAO/GO/Ce composite coating not only significantly enhance the corrosion resistance of the substrate, but also has self-healing ability. According to the molecular dynamics calculations, the GO interlayer can form a good bond with the inner MgO layer and the outer CeO2 layer. The MAO/GO/Ce composite coating with high adhesion and self-healing property may extend the practical application of Mg alloys.

The influence of rolling on the corrosion and wear resistance of the MAO coating on ZM5 alloy

PurposeThe impact of rolling on the performance of micro arc oxidation (MAO) coatings on ZM5 alloy has been underreported. The purpose of this study is to explore the correlation between rolling and the failure mechanism of MAO coatings in greater depth.Design/methodology/approachThe influence of rolling on the corrosion and wear properties of MAO coating was investigated by phase structure, bond strength test (initial bond strength and wet adhesion), electrochemical impedance spectroscopy and wear test. The change of the surface electrochemical properties was studied by first principles analysis.FindingsThe results showed that the MAO coating on rolled alloy had better corrosion and wear resistance compared to cast alloy, although the structure and component content of two kinds of MAO coating are nearly identical. The difference in interface bonding between MAO coating and Mg substrate is the primary factor contributing to the disparity in performance between the two types of samples. Finally, the impact of the rolling process on MAO coating properties is explained through first-principle calculation.Originality/valueA comprehensive explanation of the impact of the rolling process on MAO coating properties will provide substantial support for enhancing the application of Mg alloy anticorrosion.Graphical abstract

Mechanical responses and deformation mechanisms in the AZ31 magnesium alloy during cyclic bending

Cyclic loading behavior, such as cyclic bending, is unavoidably involved in various forming processes and the service of end products. Understanding the mechanical behavior of magnesium (Mg) alloys under cyclic bending is essential for promoting their application. Despite existing research, the microscopic mechanisms at play during cyclic bending, specifically the slip and twinning-de-twinning (TDT), warrant further exploration, which is the innovative focus of our study. To address this need, cyclic bending tests were performed on an extruded AZ31 Mg plate with the in-situ digital-image-correlation (DIC) technology. And the texture evolution was determined through electro backscattered diffraction (EBSD) measurements. Concurrently, the crystal-plasticity-based bending-specific approach, EVPSC-BEND, incorporating the TDT scheme, is utilized to interpret the mechanisms involved in cyclic bending. The impact at the macroscopic level is manifested in asymmetric cyclic moment-curvature curves, stress-strain distribution, and shifting of the neutral layer. The developed textures at different regions of the beam and the twin volume fraction distribution further directly illustrate twinning-de-twinning behaviors. Particularly, the upper and lower halves of the beam experience very distinct cyclic behaviors simultaneously. The upper half experiences a twinning, detwinning, and twinning cycle, while the lower half experiences a twin-free, twinning, and detwinning cycle. Additionally, through modeling the cyclic bending with different initial textures, the strong texture dependence has been revealed. The behaviors of magnesium alloy beam under cyclic bending discovered in this work can shed light on the application of Mg alloys, such as forming processes and service of end product.

Mechanically propelled ion exchange regulates metal/bioceramic interface characteristics to improve the corrosion resistance of Mg composite for orthopedic applications

The orthopedic application of Mg alloys suffers from excessive degradation. In this study, hydroxyapatite (HAP) nanoparticles are doped with MgO by high-energy ball milling, and then the obtained powders are compounded with WE43 powders and prepared into implants by laser powder bed fusion. During milling process, Mg2+ ions on MgO exchange some Ca2+ in HAP by mechanical collision and friction, which forms covalent bonds on the MgO/HAP interface. Subsequently, TEM observation showed that MgO on HAP forms semi-coherent interfaces with α-Mg, contributing to good bonding on the Mg/MgO interface. In this manner, strong bonding interfaces between ceramic particles and α-Mg were established, thereby preventing the agglomeration of nanoparticles. The well-dispersed ceramic particles provided more nucleation sites for apatite deposition, which benefits the formation of the passivation layer and thereby improves corrosion resistance. As a consequence, the composite exhibited a low corrosion density (20.1 ± 1.3 μA/cm2), high corrosion resistance (752.8 ± 19.7 Ω cm2), and low carrier concentration (1.28 ± 0.01 cm−3), indicating the formation of a more protective passivation layer. These findings suggested that the mHAP incorporated Mg composite may be a potential candidate for orthopedic implant.

In vitro degradation and dual responsively antibacterial zeolitic imidazolate frameworks-8@Rhein composite coating on magnesium alloy

Magnesium alloys attract wide attention as bone implant materials due to their outstanding biodegradable and biocompatible properties. However, its rapid degradation rate and bacterial infections after implanting limit its applications. Herein, a self-sacrificing Mg(OH)2 coating was formed on the MAO coated samples to avoid the dissolution of the MAO coating, promoting the in-situ growth of zeolitic imidazolate frameworks-8@Rhein coating on the MAO coated AZ31 alloys (defined as MAO/ZIF-8@Rhein coating). Results displayed that the MAO/ZIF-8@Rhein coating provides favorable corrosion resistance due to the physical barriers of ZIF-8@Rhein NPs and inner MAO coating. Rhein is one-step loaded by ZIF-8 NPs and released in response to both pH changes and near-infrared light (NIR) irradiation to kill bacteria. Additionally, the antibacterial rate of MAO/ZIF-8@Rhein coating reaches to 99.95 % (E. coli) and 99.90 % (S. aureus) under the synergy of contact-killing of Rhein and its photothermal effect by irradiation of 808 nm NIR light, and the photothermal conversion efficiency comes up to 53.4 %. Therefore, this dual responsively antibacterial composite coating with good corrosion resistance will promote the applications of Mg alloys in the biomedical field.

Effect of MgO Contents on the Microstructure, Mechanical Properties and Corrosion Behavior of Low-Alloyed Mg-Zn-Ca Alloy

The effects of different MgO contents (0.3 wt.%, 0.5 wt.%, 0.7 wt.% and 1.0 wt.%) on the microstructure and properties of Mg-1Zn-0.5Ca alloy (ZX) were systematically investigated to promote the clinical application of Mg alloys. The results showed that a MgO addition promoted the precipitates of Ca2Mg6Zn3 and Mg2Ca after hot extrusion. Meanwhile, the average grain size of the ZX alloy decreased abruptly from 17.73 μm to 5.54 μm after the addition of 0.3 wt.% MgO and then reduced slowly as further increasing the MgO contents to 1.0 wt.%. The microhardness and yield strength (YS) increased gradually from 59.43 HV and 102.0 MPa in ZX to 69.81 HV and 209.5 MPa in ZX1.0, respectively. However, the elongation to failure (EL) decreased from 26.7% in ZX to 21.2% in ZX1.0 due to the increase of volume fraction of the second phase and decrease of grain size as increasing the MgO. The corrosion result showed that ZX alloy exhibited local corrosion while ZX composites (ZX0.3, ZX0.5 and ZX0.7) displayed relatively uniform corrosion owing to the fine grain size, dispersed fine second and the protective effect of corrosion product after MgO hydrolyzation. However, excessive MgO (ZX1.0) easily caused the aggregation of itself and the precipitates and deteriorated the corrosion resistance of the material.

Magnesium Alloy Composite Water‐Repellent Surface with Durable Corrosion Resistance and Self‐Cleaning Behavior

Magnesium (Mg) alloys have poor corrosion resistance, higher requirements for corrosion resistance of the coating, and the changes in the environment in the actual application are complicated and diverse. Therefore, it is urgent to develop bio‐inspired water‐repellent surfaces (WRSs) with long‐lasting corrosion resistance and multiple excellent properties for Mg alloys. In this study, a composite water‐repellent surface (CWRS) with long‐lasting corrosion resistance and self‐cleaning behavior is prepared by combining laser processing, hydrothermal treatment, and immersion method on the Mg alloy surface. The effect of ambient temperature changes on the wettability and corrosion resistance of the CWRS is investigated. The experimental results showed that a uniform and dense CWRS with a film thickness of 36 μm could be prepared on the Mg alloy surface at an ambient temperature of 180 °C, demonstrating excellent corrosion resistance and self‐cleaning behavior. In addition, in the harsh salt spray test, it is found that even if the superhydrophobicity of the CWRS was lost, the surface still has good corrosion resistance. Multifunctional CWRSs have become a research hotspot, and it is of great significance to promote the application of Mg alloys in actual working conditions.

Mutual Impact of Four Organic Calcium Salts on the Formation and Properties of Micro-Arc Oxidation Coatings on AZ31B Magnesium Alloys

Calcium phosphate (Ca–P) coatings provide an effective approach in current research and the clinical application of Mg alloys by endowing them with improved corrosion resistance, biocompatibility, and even bioactivity. Ca-containing coatings were prepared on AZ31B magnesium alloys using the micro-arc oxidation (MAO) technique and a combination of ethylenediaminetetraacetic acid calcium disodium (EDTA–Ca), calcium glycerophosphate (GP–Ca), calcium gluconate (CaGlu2), and calcium lactate (CaLac2) as the Ca source in a near-neutral solution. The respective and mutual impacts of the four calcium salts on the formation and properties of the coatings were investigated. Experimental results indicated that GP–Ca was more decisive than EDTA–Ca, CaGlu2, and CaLac2 in the formation, morphology, and, therefore, the corrosion resistance of the coatings. GP–Ca alone could not effectively incorporate Ca2+ ions into the coatings but it could combine with EDTA–Ca, CaGlu2, and CaLac2 to bring a synergistic effect in improving the Ca content of the coatings. The bifunctional structure of CaGlu2 and CaLac2, containing hydroxyl groups and carboxylic groups with anchoring effects, enabled them to enhance the Ca content of the coatings. However, due to minor differences in functional group orientation, CaGlu2 was a little more efficient than CaLac2 in increasing Ca content, while CaLac2 was a little more efficient than CaGlu2 in improving the corrosion resistance of the coatings. Finally, the total concentration of the four calcium salts, [Ca2+]T, should be controlled at a proper level; otherwise, excessively high [Ca2+]T would produce localized microbumps originating from coating ablation, eventually deteriorating the corrosion resistance of the coatings.

Influence of Interlayers on Adhesion Strength of TiN Film on Mg Alloy

The wide application of Mg alloys has been restricted because of their poor corrosion and wear resistance. Titanium nitride ceramic films prepared via magnetron sputtering can improve the corrosion and wear resistance of Mg alloys. However, residual stress produced at the interface between the film and the Mg alloy substrate causes the TiN film to spall off and reduces its service life. One potential approach to mitigating residual stress involves enhancing the adhesive strength between the film and the substrate, thereby potentially extending the service life of the film. To increase the adhesion strength between the TiN film and the Mg alloy substrate, a Ti or Al interlayer was deposited on the Mg alloy by magnetron sputtering. Subsequently, the adhesion strengths of TiN/Ti and TiN/Al were determined under a single high shear force by scratch tests and were determined under multiple low shear forces by friction and wear tests. The results of scratch tests show that TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under a single high shear force. And the results of friction and wear tests show that both the TiN/Al and TiN/Ti films provided protection to the Mg alloy substrate against friction and wear, and TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under multiple low shear forces. This work can provide guidance for the selection of interlayers between Mg alloy substrates and hard ceramic films.

Effect of induced screw twisted strain on the twin orientation regulation and the ductility of pre-twined ZM21 Mg alloys

A novel twist strain-induced twin orientation regulation (TITOR) has been developed to modify the basal texture of Mg alloys. Firstly, the {10–12} tensile twins are pre-set by pre-compression on the ZM21 Mg alloy along the extrusion direction (ED), and then the TITOR process is adjusted to regulate the twins’ orientation. The results show that the orientation of some twins deviated by 30° from the ED direction to the transverse direction (TD) direction after introducing twist strain. The introduction of multiple passes of twist strain will result in almost all grains transforming into dynamic recrystallization (DRX) grains. And the generation of DRX behavior will be updating the microstructure. The mechanism in the TITOR process is continuous dynamic recrystallization (CDRX), which does not alter the orientation of the grains. When the PT samples undergo multiple passes TITOR treatments, the orientation of the DRX grains shifts towards the twisted plane (grain c-axis deviates by ∼ 30° from ED to TD direction). The formation of twist texture results in a larger value of SF, which is beneficial for the basal slip. Compared with the extruded Mg alloys, the TITOR-8P sample fracture elongation (FE) has been increased from 14.3 % to 30.6 % due to the promotion of basal slip activities and grain refinement. The ultimate tensile strength (UTS) has been increased from 243.5 MPa to 375.5 MPa. The newly proposed TITOR scheme is of great significance for promoting the application of Mg alloys.

Magnesium Alloys in Orthopedics: A Systematic Review on Approaches, Coatings and Strategies to Improve Biocompatibility, Osteogenic Properties and Osteointegration Capabilities.

There is increasing interest in using magnesium (Mg) alloy orthopedic devices because of their mechanical properties and bioresorption potential. Concerns related to their rapid degradation have been issued by developing biodegradable micro- and nanostructured coatings to enhance corrosion resistance and limit the release of hydrogen during degradation. This systematic review based on four databases (PubMed®, Embase, Web of Science™ and ScienceDirect®) aims to present state-of-the-art strategies, approaches and materials used to address the critical factors currently impeding the utilization of Mg alloy devices. Forty studies were selected according to PRISMA guidelines and specific PECO criteria. Risk of bias assessment was conducted using OHAT and SYRCLE tools for in vitro and in vivo studies, respectively. Despite limitations associated with identified bias, the review provides a comprehensive analysis of preclinical in vitro and in vivo studies focused on manufacturing and application of Mg alloys in orthopedics. This attests to the continuous evolution of research related to Mg alloy modifications (e.g., AZ91, LAE442 and WE43) and micro- and nanocoatings (e.g., MAO and MgF2), which are developed to improve the degradation rate required for long-term mechanical resistance to loading and excellent osseointegration with bone tissue, thereby promoting functional bone regeneration. Further research is required to deeply verify the safety and efficacy of Mg alloys.

Anodization and Plasma Electrolytic Oxidation Treatments of AZ91D Mg Alloy in Alkaline Aqueous Solutions

Mg alloys, such as AZ91 (Mg-9mass%Al-1mass%Zn), are lightweight materials with excellent mechanical properties. The applications of Mg alloys in automobiles could significantly contribute to reducing carbon dioxide emissions. Mg alloys are fully recyclable and abundantly available, which increases their desirability in light of rising environmental consciousness. However, the low corrosion resistance of Mg alloys is one of the major limitations to further applications.In Mg alloys, corrosion behavior is known to be related to the microstructure. During the real-time in situ observation of the corrosion process under galvanostatic polarization, filiform corrosion proceeded along the outside of the β phase (in lamellar α + β microstructure and along the α-mother phase 1. Furthermore, the β phase exhibited a higher potential in the OCPs of each phase and a small area with the boundary in 0.1 M NaCl at pH 8.0 2. Thus, the surface films of β phases was thought to suppress the corrosion of Mg alloys. Mg alloys can be treated by anodic oxidation or plasma electrolytic oxidation to obtain excellent corrosion resistance. The latter is similar to anodic oxidation but applies a higher voltage, which causes a discharge on the electrode surface and the resulting plasma modifies the oxide film significantly.In this study, anodic oxidation and plasma electrolytic oxidation were performed on AZ91D Mg alloy in alkaline solutions such as sodium phosphate. This study aims to compare the two methods in the same solution and to produce an Al-rich surface film with excellent corrosion resistance.In anodic oxidation, the size of the electrode area was approximately 1 cm2. The surface of the specimen was coated with epoxy resin, followed by paraffin. The reference electrode was Ag / AgCl (3.33 M KCl). The experiments were performed at 25 ℃. The scan rate of potentiodynamic polarization was set at 23 mV min-1. The starting potential was set at 20 mV lower than the open-circuit potential. The anodic oxidation treatments were terminated at 0 V, 3 V, and 5 V. Plasma electrolytic oxidation was performed with a liquid volume of 500 mL. The sample was mounted on a resin holder. The electrode surface was approximately 50 mm2. A Pt plate was used as the counter electrode. The sample and the counter electrode were fixed at a distance of 0.5 cm. A plasma-generating power supply was used. The solution was cooled down to 20 ℃ while the voltage was applied. The frequency and the pulse interval were adjusted. The voltage and type of solution were changed to produce the film. Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Corrosion Science, 192, 109834 (2021).Z. Shao, M. Nishimoto, I. Muto, and Y. Sugawara, Journal of Magnesium and Alloys, 11, 137-153 (2023).

Experimental study on temperature-dependent ratchetting-fatigue interaction of extruded AZ31 magnesium alloy

The variations in the plastic deformation mechanisms of extruded AZ31 magnesium (Mg) alloy at elevated temperature and the temperature-dependence of its ratchetting-fatigue interaction were revealed by a series of uniaxial stress-control low-cycle fatigue experiments. The experimental results elucidate that: (1) The tension-compression asymmetry and the S-shaped inflection point in the stress-strain hysteresis loops are gradually attenuated with elevating the temperature, and the evolution of ratchetting is also remarkably affected by the elevated temperature due to the activation of abundant non-basal plane slipping; (2) The fatigue life of the alloy exhibits a pronounced temperature-dependence, and specifically, the fatigue life is greater at 100°C compared to that at room temperature, but sharply decreases at 150°C and 200°C due to the significant ratchetting deformation at these two temperatures. Moreover, the dependence of fatigue life on the applied mean stress is also different at different temperatures; (3) Due to the significant ratchetting deformation in the alloy at elevated temperature, a transition from a brittle fatigue fracture mode to a ductile one also occurs as the temperature increases. This research provides valuable experimental data that serve as an important reference for the practical application of Mg alloys.

Multifunctional poly(allylamine hydrochloride)/bioactive glass layer by layer surface coating on magnesium alloy for biomedical applications

The present study reports on a novel multilayer coating for biodegradable magnesium (Mg) alloy substrates. This coating contains soy protein hydrolysate (SPH), poly(allylamine hydrochloride) (PAH), and folic acid (FA) templated bioactive glass (BG) nano particles. The multilayer, designated as SPH/(PAH/BG)n, was coated onto an alkaline-treated Mg alloy surface (AMgS) through a dip-coating process with various numbers of cycles (n = 5and 7) using a layer-by-layer (LbL) assembly. The BG particles had an average diameter of 12.53 ± 2.22 nm and were embedded with therapeutic FA molecules. Scratch testing, wettability, and roughness tests showed excellent adherence of the SPH/(PAH/BG)7 coating on AMgS, making it suitable for cell attachment. Electrochemical measurements in Hanks balanced salt solution (HBSS) demonstrated that the SPH/(PAH/BG)7 coating improved the corrosion resistance of the Mg alloy. SPH/(PAH/BG)7 coated substrate showed a maximum protective efficacy of 98.4041 %, thanks to the bioactive nature of BG. High-resolution XPS and XRD analyses on SPH/(PAH/BG)7/AMgS confirmed the corrosion deposition of Mg(OH)2, MgHPO4.H2O, CaHPO4.H2O, SiO2, MgCO3 and CaCO3 on the substrate surface after immersion in HBSS for 10 d at 37 °C. The LbL coated Mg substrate also showed excellent cytocompatibility by hemolysis assay These results suggest that the SPH/(PAH/BG)7/AMgS material has multifunctional properties and can be a possible alternative for biomedical applications of Mg alloys.

Influence of pH on corrosion resistance of slippery liquid-infused porous surface on magnesium alloy

A slippery liquid-infused porous surface (SLIPS) was developed on the AZ31 Mg alloy to provide corrosion protection. A layered double hydroxide (LDH) was applied to providing accommodation for liquid lubricants. The electrolyte pH was adjusted to obtain the best LDH film for the development of a SLIPS. The surface morphology, surface wettability, and electrochemical behavior of the SLIPS formed at different pH values were investigated. The results indicated that the MgAl-LDH film synthesized at a pH of 10.5 had a maximum thickness of 3.51 μm to accommodate the most silicone oil, with a mass of 0.22 mg/mm2, which provided the best corrosion protection, with the lowest corrosion current density of 3.72×10−9 A/cm2. On the other hand, compared with the superhydrophobic surface, the SLIPS imparted better corrosion resistance for the AZ31 substrate in both electrochemical behavior and long-term immersion test. The improved corrosion resistance of the SLIPS can further accelerate the application of Mg alloys in practice.

A non-fluorinated, in-situ self-healing electrothermal/superhydrophobic coating on Mg alloy for anti-icing and anti-corrosion

The superhydrophobic surface has become a smart strategy for boosting the application of Mg alloy due to its anti-icing and anti-corrosion abilities. However, its application has been limited due to some drawbacks, such as harmful fluorinated materials, poor mechanochemical robustness, and unsatisfactory anti-icing performance in extreme environments. Herein, a non-fluorinated electrothermal/superhydrophobic coating, including bottom insulation and top superhydrophobic films, is prepared on Mg alloy by spray method. The superhydrophobic coating exhibits good mechanical robustness, chemical stability, and in-situ electrothermal-healing ability against plasma and chemical etchings. The electrothermal characteristic and superhydrophobicity endow the coating with excellent static and dynamic anti-icing, de-frosting, and de-icing performances. Moreover, the superhydrophobic coating exhibits a long-term anti-corrosion effect due to a durable air layer and organic coating, and can recover the coating's corrosion resistance by repairing superhydrophobicity. We expect that this research provides a wise strategy for designing superhydrophobic coating with good mechanical robustness, good chemical stability, electrothermal, in-situ self-healing, outstanding anti-icing, and long-term corrosion protection abilities to meet functional needs of Mg alloy as well as other metal materials.

Electrophoretic Deposition of Nanohydroxyapatite on Homogenized Magnesium Based Alloy for Biomedical Applications

Magnesium (Mg) alloys are promising biodegradable implant materials. If successful, they do not require second surgical operation for their removal. However, the focus of this study is to address the limitation of fast degradation rate (DR) which hinders the clinical application of Mg alloys. The bio-corrosion rate of any intermetallic alloy is related to its beta (β) phase volume fraction. Thus, homogenization heat treatment (HHT) was carried out to reduce the β phase. The influence of β phase and the hydroxyapatite powders (HAp) was employed to slow down the initial DR of Mg AZ91 alloy. Samples were cut from Mg grade AZ91 alloy ingot in 10mm x 10mm x 3mm dimension. The samples were prepared and divided into two; the first part was classified as as-received sample (sample a) while the second one was processed for HHT. HHT was carried out at 410°C/10h, cooled inside the furnace and named as homogenized sample (sample b). The HAp was synthesized using a simple wet chemical precipitation technique (SWCPT) and deposited on sample b via electrophoretic deposition (EPD) at different voltages with different deposition times. The HAp, uncoated and coated samples were characterized. Potentiodynamic polarization (PP) and immersion tests were carried out in stimulated body fluid (SBF) to estimate the DR and in vitro bioactivity of Mg AZ91 respectively. The results revealed a significant drop in DR from sample a (1.421 mm per year) to coated sample h (3.73 x 10-4 mm per year). Keywords: Magnesium alloy, biodegradable implants, beta phase, homogenization heat treatment, hydroxyapatite, electrophoretic deposition.

Transcriptome analysis of hydrogen inhibits osteoclastogenesis of mouse bone marrow mononuclear cells.

Hydrogen (H2) is a major biodegradation product of implanted magnesium (Mg) alloys that are commonly used in the healing of bone fractures. Our earlier study showed that H2 can inhibit mouse bone marrow mononuclear cell (BMMC) osteoclastogenesis during the differentiation of these cells into osteoclasts, thereby facilitating fracture healing. However, the way by which H2 inhibits osteoclastogenesis remains to be elucidated. The present study used RNA-sequencing to study the transcriptome of H2-exposed BMMCs in an osteoclast-induced environment and identified the target genes and signaling pathways through which H2 exerts its biological effects. Several upregulated genes were identified: Fos, Dusp1, Cxcl1, Reln, Itga2b, Plin2, Lif, Thbs1, Vegfa and Gadd45a. Several downregulated genes were also revealed: Hspa1b, Gm4951, F830016B08Rik, Fads2, Hspa1a, Slc27a6, Cacna1b, Scd2, Lama3 and Col4a5. These differentially expressed genes were mainly involved in osteoclast differentiation cascades, as well as PI3K-AKT, Forkhead box O (FoxO), MAPK, peroxisome proliferator-activated receptor (PPAR), TNF, TGF-β, JAK-STAT, RAS, VEGF, hypoxia-inducible factor (HIF-1) and AMPK signaling pathways. In summary, the present study revealed the key genes and signaling pathways involved in the H2-mediated inhibition of osteoclastogenesis, thereby providing a theoretical basis for the significance of H2 and an experimental basis for the application of Mg alloys in the treatment of osteoporosis.