Mechanical and biomedical properties of hydroxyapatite-based gradient coating on α-Al2O3 ceramic substrate

A hydroxyapatite--based gradient coating on alpha--Al2O3 ceramic substrate is prepared by a multi--layer slurry--dipping and sintering process, on the basis of the glass binder with the chemical composition Na2O 8*0, K2O 7*0, Al2O3 3*0, ZnO 1*5, B2O3 15*0, SiO2 65*5 (wt%). The coating component varies gradually, in which hydroxyapatite increases and glass decreases gradually from the interface (between the coating and alumina substrate) to surface layer. The microstructure and mechanical properties of the coating layer can be effectively improved by the present design. The obtained gradient composite possesses a high hydroxyapatite concentration and porous surface, which thus leads to a good biocompatibility and bioactivity (e.g., the good biodegradation).