Fabrication of Magnesium-Carbonate Apatite by Conventional Sintering and Spark Plasma Sintering for Orthopedic Implant Applications

Abstract

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.

Composite of Magnesium and Carbonate Apatite for Biodegradable Bone Implants: A Comparative Study on Sintering and Extrusion Techniques

“…The results of experimental density measurements and calculation of the relative density of Mg and Mg/5CA of the extrusion process (Extr) compared to the warm compaction process (WC), sintering process (Sint) in the previous study [19] are presented in Table 1. The relative density is calculated from the relationship between the experimental density (ρexp.)…”

“…Figure 5 shows the microstructure of pure Mg and Mg/5CA samples after the extrusion process (Extr) compared to the warm compaction (WC) and sinter processes (Sint) in previous studies [19]. Each process is observed in the center and the edges.…”

“…The densification process after compacting was conducted with two different processes, sintering and extrusion, as shown in Figure 2. The sintering process (Sint) was conducted in a tube furnace at 450ºC and held for 60 minutes under a vacuum (P = -0.1 MPa) with an oxygen content below 150 ppm [19]. The hot extrusion process (Extr) was carried out at 350ºC with the extrusion ratio (R) of 1.44, where the initial diameter of the rod was 12 mm, and the final diameter was 10 mm.…”

“…At a temperature of 450ºC, carbonate (CO3 -2 ) in CA can decompose into CO2 gas. This gas is thought to be trapped and form microporosity, so that it can weaken the binding strength of Mg/xCA [19], [37]. On the other hand, the morphology of the sintered grains is still in the form of equilibrium, relatively the same as the initial compaction (WC) conditions, and there is no strain hardening.…”

“…However, the carbonate (CO3 2-) present in CA starts to decompose into CO2 gas at 50°C. There is a tendency to increase at 450-650°C, causing the product to decompose and weakening the mechanical properties [14], [16], [19], [22]. Therefore, the extrusion process is introduced to prevent carbonate decomposition [10], [11], [23], [24].…”