Hydrothermal Microwave-Assisted Fabrication of Nanohydroxyapatite Powder and Optimization of Its Nanocomposite Coatings on Magnesium Alloy for Orthopedic Applications

Abstract

Developing appropriate protecting coatings for Mg alloy applications is a challenging issue. Herein, nanohydroxyapatite (nanoHAP) powder was first fabricated by the simple hydrothermal microwave-assisted method. A direct current electrophoresis deposition (EPD) of nanoHAP composite coatings on Mg-3Zn-0.8Ca magnesium alloy was successfully executed. Three suspensions with HAP-dispersive resin solution (ETELAC) ratios (in wt %) of 5-5, 5-2.5, and 2.5-2.5 were chosen for optimizing the effect of applied voltage, deposition time, and stirring mode and rates on the EPD process. NanoHAP composite coatings were applied on each sample in single- and double-run depositions. The results revealed that the maximum weight gain on the coated samples was obtained in 5-5 suspension at 50 V under 150 rpm mechanical stirring rate. Surface examination indicated crack-free coating formation with varying grain sizes. Adhesion tests demonstrated high interconnection between the obtained nanocomposite coatings and the alloy substrate. Electrochemical evaluation measurements in SBF at 37 °C indicated that the corrosion resistance of any coated sample is always superior compared to that of the uncoated bare substrate. It was suggested that the EPD of nanoHAP/ETELAC composite coatings on Mg-Zn-Ca alloy can be a good solution for protecting the alloy from the attack of the aggressive ions bound in the SBF environment.