Fabrication of TiO2/SiO2 Composite Coating via a High-Temperature Self-Organizing Porous TiO2 Layer on Ti

We studied the fabrication of a TiO2/SiO2 composite coating on Ti. At a temperature above 1100 K with oxygen partial pressure, a self-organized coating of rutile phase TiO2 is formed on a Ti substrate. The thick TiO2 coating (>10 m) had a "piecrust-like" multilayer structure, which comprise TiO2 monolayers and gaps. A composite coating containing SiO2 was fabricated via a sol-gel method in vacuum to improve the exfoliation strength of the brittle, porous TiO2 coating. Cross-sectional SEM images revealed sufficient amounts of SiO2 in the gaps between the TiO2 monolayers in the TiO2/SiO2 composite coating, even at the interface between the oxide coating and the substrate. Exfoliation stress of the composite coating was up to 10-15 times higher than for the self-organized TiO2 coating alone, and the composite coating's failure mode was interfacial compared with cohesive for the self-organized TiO2 coating.