Construction of porous micro/nano structures on the surface of Ti–Mo–Zr alloys by anodic oxidation for biomedical application

Ti–Mo–Zr alloys have attracted increasing interest for biomedical applications, due to their outstanding properties such as low elastic modulus. To improve the bioactivity of alloys, this study utilized the anodic oxidation method to fabricate porous micro/nano structures on the surface of a series of Ti–Mo–Zr alloys, including the Ti–12Mo-AO, Ti–10Zr-AO, and Ti–12Mo–10Zr-AO groups. The morphology, composition, phase, microhardness, roughness, wettability, adhesion strength, corrosion resistance, bioactivity, and biocompatibility of each group were systematically investigated. The formation mechanism of surfaces was discussed from the perspective of thermodynamics. Our results demonstrated that, Ti–12Mo-AO showed the structure of single-layer regularly arranged nanotubes, while Ti–10Zr-AO and Ti–12Mo–10Zr-AO exhibited a double-layer porous structure with a nano-filamentous upper layer and a densely arranged nanotube lower layer. With low crystallinity, these surfaces showed an amorphous structure and were composed of the oxides of corresponding matrix element. After anodizing, the microhardness and wettability of surfaces increased, while their corrosion resistance decreased. Compared with Ti–12Mo-AO, Ti–10Zr-AO and Ti–12Mo–10Zr-AO possessed a higher degree of roughness, better wettability, stronger interface bonding, and higher apatite forming ability. Furthermore, the biocompatibility of Ti–12Mo–10Zr-AO was superior to that of the other groups. Taken together, our results revealed that, under the same anodic oxidation condition, Ti–Mo–Zr alloys formed different porous micro/nano structures on the surface. Particularly, due to its favorable properties, Ti–12Mo–10Zr-AO is very attractive for future biomedical application.