Ceramic coatings containing hydroxyapatite (HA) were fabricated on a biodegradable Mg₆₆Zn₂₉Ca₅ magnesium alloy through micro-arc oxidation by adding HA particles into the electrolytes. The phase composition and surface morphology of the coatings were characterized by X-ray diffraction and scanning electron microscopy analyses, respectively. Electrochemical experiments and immersion tests were performed in Hank’s solution at 37 °C to measure the corrosion resistance of the coatings. Blood compatibility was evaluated by in vitro blood platelet adhesion tests and static water contact angle measurement. The results show that the typical ceramic coatings with a porous structure were prepared on the magnesium alloy surface with the main phases of MgO and MgSiO₃ and a small amount of Mg₃(PO₄)₂ and HA. The optimal surface morphology appeared at HA concentration of 0.4 g/L. The electrochemical experiments and immersion tests reveal a significant improvement in the corrosion resistance of the ceramic coatings containing HA compared with the coatings without HA or bare Mg₆₆Zn₂₉Ca₅ magnesium alloy. The static water contact angle of the HA-containing ceramic coatings is 18.7°, which is lower than that of the coatings without HA (40.1°). The in vitro blood platelet adhesion tests indicate that the HA-containing ceramic coatings possess improved blood compatibility compared with the coatings without HA. Utilizing HA-containing ceramic coatings may be an effective way to improve the surface biocompatibility and corrosion resistance of magnesium alloys.

In recent years, biodegradable magnesium alloys have attracted considerable attention in medical devices, such as permanent implants and stents. However, poor corrosion resistance is a major problem limiting the practical application of magnesium alloys. In this study, Mg₆₇Zn₂₈Ca₅ alloys were prepared via two different methods, namely, vacuum induction melting and ulfur hexafluoride shielded melting. The effect of melting method on the bio-corrosion resistance of MgZnCa cast magnesium alloy was also studied. The microstructure and phase composition of Mg₆₇Zn₂₈Ca₅ alloys were investigated by optical microscopy and X-ray diffraction. The element distribution and surface morphology of Mg₆₇Zn₂₈Ca₅ alloys were examined by scanning electron microscopy and energy-dispersive spectroscopy. The corrosion resistance of Mg₆₇Zn₂₈Ca₅ alloys was measured via electrochemical and immersion tests. Results showed uniform composition of the Mg₆₇Zn₂₈Ca₅ alloy melted by vacuum induction. Immersed in the simulated body fluid, the corrosion rate of Mg₆₇Zn₂₈Ca₅ by vacuum induction melting (0.2618 mm/a) was lower than that by ulfur hexafluoride shielded melting (0.9686 mm/a); the corrosion potential of Mg₆₇Zn₂₈Ca₅ melted by vacuum induction (−1313 mV) was nobler than that by ulfur hexafluoride shielded melting (−1483 mV); the corrosion current of Mg₆₇Zn₂₈Ca₅ by vacuum induction melting (1.202 × 10⁻⁵ A) was lower than that by ulfur hexafluoride shielded melting (4.332 × 10⁻⁵ A). The Mg₆₇Zn₂₈Ca₅ by vacuum induction melting showed uniform corrosion behavior.

This paper presents a simple approach to preparing copper–matrix composites (CMCs) by using self-propagating high-temperature synthesis technique. The dry sliding friction behavior of CMCs was systematically investigated. Results showed that the strengthening layer presented a compact metallurgical joint to copper substrate without a distinct boundary. The running-in period for copper substrate at any load was approximately 125 s but decreased to less than 30 s for CMCs. Increasing the applied load resulted in shorter running-in periods. The average friction coefficients for pure copper substrate and CMCs presented slight variation at the steady state, with minor enhancement in CMCs. The wear loss rates of the two different sections in CMCs rapidly increased with increased load, and the wear loss rate of CMCs was always lower than that of pure copper substrate at any load. Typical adhesion wear character was observed according to the wear scar of pure copper substrate; the wear mechanism of CMCs was dominated by abrasive wear, accompanied by oxidized wear with increased applied load.