Fabrication of composite coating comprising bioactive calcium and sodium titanates on titanium using calcium hydroxide slurry containing sodium ions

We attempted to fabricate a composite coating comprising bioactive calcium and sodium titanates on titanium (Ti) using a calcium hydroxide (Ca(OH)2) slurry containing sodium ions (Na+). The coating procedure was as follows: a Ti substrate was buried in the slurry, which was prepared by mixing Ca(OH)2 powder with NaOH and/or NaCl solution, and the slurry was then heated at 923 K in air. This procedure resulted in the formation of a composite coating comprising CaTiO3 and Na4Ti5O12 with a thickness of ca. 430 nm on the substrate. When the composite coating was soaked in a simulated body fluid, calcium phosphate precipitated on the surface more rapidly than on a monolayer of CaTiO3. It is likely that dissolved Na+ from the coating promoted the formation of the calcium phosphate.