Facile bioactive transformation of magnesium alloy surfaces for surgical implant applications

The market for orthopedic implant alloys has seen significant growth in recent years, and efforts to reduce the carbon footprint of medical treatment (i.e., green medicine) have prompted extensive research on biodegradable magnesium-based alloys. Magnesium alloys provide the mechanical strength and biocompatibility required of medical implants; however, they are highly prone to corrosion. In this study, Mg-9Li alloy was immersed in cell culture medium to simulate degradation in the human body, while monitoring the corresponding effects of the reaction products on cells. Variations in pH revealed the generation of hydroxyl groups, which led to cell death. At day-5 of the reaction, a coating of MgCO3 (H2O)3, HA, and α -TCP appeared on sample surfaces. The coating presented three-dimensional surface structures (at nanometer to submicron scales), anti-corrosion effects, and an altered surface micro-environment conducive to the adhesion of osteoblasts. This analysis based on bio-simulation immersion has important implications for the clinical use of Mg alloys to secure regenerated periodontal tissue

The Effect of Lithium Ion Leaching from Calcined Li–Al Hydrotalcite on the Rapid Removal of Ni²⁺/Cu²⁺ from Contaminated Aqueous Solutions

A layered double hydroxide (LDH) calcined-framework adsorbent was investigated for the rapid removal of heavy metal cations from plating wastewater. Li–Al–CO3 LDH was synthesized on an aluminum lathe waste frame surface to prepare the sorbent. The calcination treatment modified the LDH surface properties, such as the hydrophilicity and the surface pH. The change in surface functional groups and the leaching of lithium ions affected the surface properties and the adsorption capacity of the heavy metal cations. A zeta potential analysis confirmed that the 400 °C calcination changed the LDH surface from positively charged (+10 mV) to negatively charged (−17 mV). This negatively charged surface contributed to the sorbent instantly bonding with heavy metal cations in large quantities, as occurs during contact with wastewater. The adsorption isotherms could be fitted using the Freundlich model. The pseudo-second-order model and the rate-controlled liquid-film diffusion model successfully simulated the adsorption kinetics, suggesting that the critical adsorption step was a heterogeneous surface reaction. This study also confirmed that the recovered nickel and/or copper species could be converted into supported metal nanoparticles with a high-temperature hydrogen reduction treatment, which could be reused as catalysts

Crystallization of a chemical conversion layer that forms on AZ91D magnesium alloy in carbonic acid

This investigation studied the crystallization of a chemical conversion layer that formed on AZ91D Mg alloy in carbonic acid. The layer was an amorphous precursor to a crystalline Mg-Al layered double hydrotalcite, which improved the corrosion resistance of the alloy. The precursor must be treated with a strongly alkaline solution, causing the leaching out of amphoteric Al3+. The leaching step evidently caused crystallization from an amorphous precursor layer to a crystalline coating. Nuclear magnetic resonance analysis indicated that Al3+, which was originally randomly coordinated with surrounding OH− in the precursor, coordinated octahedrally with OH− groups in the crystalline conversion coating

Microstructural and Corrosion Characteristics of Alloying Modified Layer on 5083 Al Alloy by Electrical Discharge Alloying Process with Pure Silicon Electrode

This study examines the surface modification of 5083 Al alloy by electrical discharge alloying (EDA) process, using pure Si as an electrode. Al alloy surface was modified by the EDA process to explore the effect of machining parameters (discharge current, pulse duration and duty factor) on the thickness, hardness and roughness of the alloyed layer. Samples were analyzed by scanning electron microscopy (SEM), electron probe analysis (EPMA) and X-ray diffraction. Since pure Si was used as an electrode, the alloyed layer had high concentration of Si from 2 mass% (the position in the layer at substrate side) to 12 mass% (the position in the layer close to surface side). Experimental results reveal that the thickness of the alloyed layer had a concave downward relationship with the discharge current and pulse duration. High hardness (� Hv 250) of the alloyed layer was obtained. The results of X-ray diffraction indicate that the primary phase in the substrate was �-Al, while there were composite phases containing �-Al and Si particles in the alloyed layer. Additionally, the alloyed layer exhibited as good corrosion resistance as 5083 Al alloy in aqueous NaCl

Synthesis, microstructure,andphotocatalysisofIn2O3 hollowparticles

Indium oxide (In2O3) microspheres with hollow interiors have been prepared by a facile implantation route which enables indium ions released from indium-chloride precursors to implant into nonporous polymeric templates in C2Cl4 solvent. The templates are then removed upon calcination at 500 °C in air atmosphere, forming hollow In2O3 particles. Specific surface area (0.5-260 m2 g−1) and differential pore volume (7 × 10−9 to 3.8 × 10−4 m3 g−1 Å−1) of the hollow particles can be tailored by adjusting the precursor concentration. For the hollow In2O3 particles with high surface area (260 m2 g−1), an enhanced photocatalytic efficiency (up to ∼one-fold increase) against methylene blue (MB) dye is obtained under UV exposure for the aqueous In2O3 colloids with a dilute solids concentration of 0.02 wt.%