Magnesium-Carbonate Apatite (Mg-xCA) is one of the potential magnesium composites to be developed as an alternative biodegradable implant material. Several attempts were made to optimize its characteristics. In this study, Mg-xCA (x = 0, 5, 10, and 15% wt) was prepared by powder metallurgy through warm compaction (WC) and further densified by 2 sintering process methods, namely conventional sintering (CS) and spark plasma sintering (SPS). The characterization included density test, XRD test, microstructure test (OM and SEM-EDS-Mapping), microhardness test, and electrochemical test. The SPS process improves the characteristics of Mg-xCA better than the CS process. The SPS process can increase the relative density by about 0.7-2.4%, increase the hardness by about 2-13%, and reduce the corrosion rate by about 32-49% compared to the initial condition before sintering (WC). The SPS structure has a lower oxygen elemental content than the CS structure. The sintered process with SPS is considered effective for the fabrication of Mg-xCA powder-based composites compared to the CS process.

Magnesium-based composites with carbonate apatite reinforcement are attractive biodegradable implant materials. In this study, we observed the effect of carbonate apatite content (5, 10, and 15% wt.) and milling time (3, 5, and 7 h) on the microstructure and microhardness of magnesiumcarbonate apatite composites fabricated by powder metallurgy. The consolidation process involved warm compaction without sintering. Characterization was achieved through density testing, x-ray diffraction (XRD), optical microscopy, SEM-energy dispersive x-ray spectroscopy (EDS), and microhardness testing. The powder milling time affects the distribution of apatite carbonate; adding carbonate apatite can increase the hardness of magnesium-based composites. In the XRD spectrum, we identify the dominant magnesium peak but not the magnesium oxide peak. Carbonate apatite powder is distributed at the grain boundaries. The hardness range is 40.26-44.82 Hv or increase by 8.21%-20.23% compared to the hardness of consolidated pure magnesium. The relative density is around 95.92%-98.71%, whereas the relative density of pure magnesium is 99.58%. The obtained optimal conditions for fabricating magnesium composites are the following: content of 10 wt% carbonate apatite (milled for 5 h) with a hardness of 43.58 Hv.

The development of magnesium-based materials, applied for a biodegradable implant, attracted the attention of many researchers. In this research, the initial development of the Mg/carbonate apatite (CA) miniplate was carried out. The miniplate Mg/5CA is fabricated through powder metallurgy and is followed by a sintering process. Pure magnesium is also fabricated with the same process and is used as a reference. The visual form, microstructure (OM), bending test and corrosion test of miniplate were investigated. The results showed that the visual form of the Mg/5CA miniplate is still not perfect. Flexural stress, flexural strain, and elasticity modulus were obtained at 34.02 MPa, 0.9%, and 3.53 GPa, respectively. The corrosion rate is obtained at 12.64 mm/year. The compaction process of Mg/5CA powder followed by sintering is considered to be less appropriate. The addition of the extrusion process and/or the ECAP process in fabrication can be an option to improve its properties.

Suitable biomechanical properties with a degradation rate parallel to normal bone healing time are vital characteristics for biodegradable implant material in orthopaedics. Magnesium (Mg) is a natural micronutrient as well as biodegradable metal with biomechanical characteristics close to that of the human bone, while carbonate apatite (CO3Ap) is a biological apatite with good osteoconductivity which allows bone healing without forming fibrotic tissue. We fabricated a Mg-CO3Ap composite with various content ratios by powder metallurgy, various milling times (3, 5, and 7 hours) at 200 RPM, warm compaction at 300°C and pressure of 265 MPa, sintering at 550°C, holding time of 1 hour, heating rate of 5°C/minutes, and room atmosphere cooling. Specimens were successfully created and had a density comparable to that of the human bone (1.95-2.13 g/cm3). Good biocompatibility was found on Mg-10% CO3Ap composite (66.67% of viable cells). Nevertheless, its biomechanical properties and corrosion resistance were inferior to the human bone. Additionally, the materials of the composites make the surrounding environment alkaline. Interparticle consolidation and grain size were dissatisfactory due to microstructural pores presumably formed by the Mg(OH)2 layer and oxidation process during sintering. However, alkaline condition caused by the material corrosion by-product might be beneficial for bone healing and wound healing process. Modifications on fabrication parameters are needed to improve interparticle consolidation, refine grain size, improve biomechanical strength, reduce corrosion products, and improve the degradation rate.