Influence of Mechanical and the Corrosion Characteristics on the Surface of Magnesium Hybrid Nanocomposites Reinforced with HAp and rGO as Biodegradable Implants

Abstract

Magnesium composites stay relevant for the applications of biodegradable implant as they are harmless and possess characteristics such as density and elastic modulus analogous to the cortical bone in humans. But corrosion is one major issue associated with magnesium when the biomedical applications are contemplated. Moreover, load bearing abilities are also required in case of an orthopedic implant. In this study, to achieve the desired implant characteristics, hybrid nanocomposites (HNCs) of Mg–2.5Zn binary alloys such as metal matrix, hydroxyapatite (HAp), and reduced graphene oxide (rGO) as reinforcements were fabricated via the vacuum-assisted stir casting method. The overall weight percentage of the reinforcements was fixed at 3% and both the reinforcements varied in compositions by weight to prepare the samples S0 (Pure Magnesium), S1 (Mg–2.5Zn–0.5HAp–2.5rGO), S2 (Mg–2.5Zn–1.0HAp–2.0rGO), S3 (Mg–2.5Zn–1.5HAp–1.5rGO), S4 (Mg–2.5Zn–2.0HAp–1.0rGO), and S5 (Mg–2.5Zn–2.5HAp–0.5rGO), respectively. The influence of mechanical characteristics such as tensile strength, compressive strength, and microhardness as well as the corrosion over the surface of the nanocomposite in simulated body fluid (SBF) have been assessed for their suitability as biodegradable orthopedic implants. Results suggest that the fabricated nanocomposites exhibit superior characteristics in comparison to pure magnesium. Increasing the HAp from 0.5 wt.% to 2.5 wt.% enhanced the compressive strength and reduced the corrosion rate. On the other hand, increasing the rGO from 0.5 wt.% to 1.5 wt.% increased the tensile strength. The formation of apatite layer over the composites is observed in the SBF solution. Among all the fabricated hybrid nanocomposite samples, the sample S3 (Mg–2.5Zn–1.5HAp–1.5rGO) with equal wt.% of HAp and rGO exhibited 209.60 MPa of ultimate tensile strength, 300.1 MPa of ultimate compressive strength, and a corrosion rate of 0.91 mm/year thus making it the best suited and a prospective material for biodegradable implant application.