Anatase/rutile dual layer deposition due to hydrolysis of titanium oxysulfate with hydrogen peroxide solution at low temperature

Anatase/rutile dual layers were deposited on titanium and polyethylene substrates when they were soaked in TiOSO4/H2O2 solution and aged in hot water: The dense bottom layer predominantly consisted of rutile, while the upper layer consisted of loosely packed aggregation of anatase particles. The titania deposition was the results of compromise among three conflicting processes: (1) hydrolysis of TiOSO4 to yield either soluble titania- H2O2 complexes or titania, (2) dissolution of the titania layer under the presence of H2O2, and (3) corrosive reactions between titanium substrates and H2O2 to yield similar complexes or compounds. The dissolution–deposition equilibrium was found associated with pH of the sulfate solution and changed with soaking time. Thus, proper pH value and soaking time in the treating solution were the two key factors to control the formation of dense titania layers. The resulted titania layers were easily covered with fine apatite particles when soaked in a solution supersaturated with its component ions.