Plasma Electrolytic Oxidation and Characterization of Spark Plasma Sintered Magnesium/Hydroxyapatite Composites

Abstract

Magnesium (Mg)/hydroxyapatite (HA) (10 wt.% and 20 wt.%) composites were prepared by using pure Mg and as synthesized HA powders using the spark plasma sintering (SPS) method. The objective of the present study is to improve the corrosion resistance of spark plasma sintered Mg/HA composites and to ensure that the degradation time of these composites match with that of bone remodeling. Mg and HA powders were ball milled for 2 h and spark plasma sintered at a temperature of 475 °C and pressure of 40 MPa in vacuum. The sintered compacts were further treated by plasma electrolytic oxidation (PEO) in order to improve the corrosion resistance. The structural, microstructural and morphological studies were done using X-ray diffraction, optical microscopy and scanning electron microscopy, respectively. The corrosion resistance of as-sintered and PEO treated Mg/HA composites was studied by potentiodynamic polarization test in a 7.4 pH simulated body fluid (SBF) environment. The corrosion test results of as-sintered composites showed that the corrosion resistance decreases with the increase in percentage of HA in the composite. However, the PEO treated Mg/HA composites have shown delayed onset of degradation. Therefore, it can be hypothesized that the PEO treated Mg/HA composites would serve as bioactive and biodegradable orthopedic implant materials with low corrosion rates.

Magnesium-Based Bioactive Composites Processed at Room Temperature

“…It is worth noting that hardness and compression testing are not as effective as tensile testing in evaluating the soundness of the metallic matrix since internal defects propagate under tensile stresses, but these defects can effectively withstand compressive loading. While there are reports of the fabrication of magnesium-hydroxyapatite composites [12,15,16,17,18,19], tensile testing was seldom conducted and the ultimate stress observed in the present experiments is comparable to that observed in composites produced through hot-extrusion [14,15]. It is concluded, therefore, that HPT processing is effective in producing sound magnesium-based composites without the need to heat the composite components.…”

“…There are many reports on the fabrication of magnesium-based composites with hydroxyapatite using not only commercial purity Mg (CP-Mg) [12,13,14,15,16,17,18], but also Mg alloys such as AZ91 (Mg-9 wt% Al-1 wt% Zn) [19,20]. The usual fabrication methods involve heating, such as sintering [12,16,17] or hot extrusion [15,18,19,21]. The addition of HA within the Mg matrix, combined with mechanical processing, provides both grain refinement and a gain in strength.…”

Sintering Behavior and Mechanical Properties of Magnesium/β-Tricalcium Phosphate Composites Sintered by Spark Plasma Sintering

“…These discoveries regarding sintering behavior including densi cation and reaction are able to facilitate the design of not only Mg/β-TCP composites but also other Mg/calcium phosphate composites which also forms MgO as a reaction product. [22][23][24] 4.3 Relationship between microstructure and mechanical properties of Mg/β-TCP composites Mg/β-TCP composites fabricated at 793 K improved their mechanical properties compared with Mg, as shown in Fig. 10.…”

Differentialin vitrodegradation and protein adhesion behaviour of spark plasma sintering fabricated magnesium-based temporary orthopaedic implant in serum and simulated body fluid

“…However, the presence of Al in AZ series alloy is detrimental to the human body. Other studies also support the improvement of the corrosion and mechanical properties in HA containing Mg matrix [16][17][18]. Thus, HA with a chemical composition similar to cortical bone evinces to be the best choice for reinforcement of the composite.…”