Characterization and in-vitro activity of powder metallurgy magnesium-zinc/bioglass composite for biomedical applications

Abstract

In this study, bio-glass 45S5 powder was added into the mixture of Mg-Zn powders to produce biocomposite using powder metallurgy method for biomedical applications. The bio-glass composition was varied from 0, 5, 10, 15, 20, 25, to 30 wt. %. The objective of this works is to study the effect of bio-glass addition into Mg-Zn based biomaterials in terms of physical, mechanical, corrosion resistance and bioactivity properties. Optical microscope, Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) and X-Ray Diffraction (XRD) were used to characterize the microstructure and phases present in the composites. Microstructure result shows that bio-glass was distributed in the matrix Mg-Zn. EDS results show that Zn has not completely diffuse into the Mg matrix due to the effect of processing parameter. There is no evidence of bio-glass diffusion into the matrix. XRD diffraction patterns of as sintered samples show expected peak of Mg in all samples. Properties such as density and compressive strength were determined using the pycnometer and Instron machine respectively. Density of the composite was compared with the theoretical value and the result trends indicated that the density has increased as the amount of bio-glass increased. The trends are valid for the true, theoretical, and bulk densities. Increment of densities value could be subjected to the filling of interparticles spacing by bio-glass. However, the total porosity also increased as the bio-glass amount increased. It could be attributed to the segregation of bio-glass particles. As the amount of bio-glass increase, more bio-glass segregate and leads to bigger size of bio-glass inclusion size inside the composite. Since no reaction between magnesium and bio-glass, the bigger the size of bio-glass inclusions, the larger the voids form at the interface, which will eventually give raise to total porosity results. The compressive strength shows that as the amount of bio-glass increased, the compressive strength of the composites decreased. This also could be attributed to the voids left at the interface of bio-glass and matrix which acts as crack initiators. In vitro test was conducted, in which samples were immersed in Simulated Body Fluid (SBF) to determine the corrosion rate and bioactivity of the composites. The results showed that corrosion rate of the samples decreases with increasing content of bio-glass. The accumulation of corrosion products, alongside with the formation of apatite layer retarded the corrosion process. The apatite layer that used to indicate the bioactivity was also traced on the surface of composites. The apatite layer formed has a lower value of Ca/P ratio compared to the ideal crystalline hydroxyapatite, however it is still compliant with biomaterials requirement