Titanium dioxide (TiO 2) with a rutile structure is known for its useful physical, chemical, mechanical and biomedical properties. Increasing efforts have been made to fabricate this material in the form of thin films for various applications, like chemical catalysts, optical devices and electromagnetic devices. More recently, it has been discovered that rutile has good biocompatibility and is a potential friction-reducing and wear resistant material, and thus it has a great potential for applications in human implants, medical devices and other tribological applications. In the present work, efforts have been made to produce protective rutile-TiO 2 films. This has been achieved by three routes: 1) thermal oxidation of bulk titanium 2) thermal oxidation of titanium film and 3) sputter deposition of rutile-TiO 2 with the aid of Ti underlayers. In order to understand the thermal oxidation mechanism and kinetics, a systematic study was carried out on bulk titanium. The effect of cooling rate on the adhesion of the oxide layer on titanium has been investigated. Efforts have been made to deposit titanium films onto AISI 316L stainless steel by magnetron sputtering, and then to partially convert the titanium films to titanium oxide by thermal oxidation. The resultant coating has a layered structure, comprising of rutile-TiO 2 layer at the top, an oxygen and nitrogen containing α-Ti layer in the middle and a diffuse-type interface. Such a hybrid coating system showed good adhesion with the substrate, improved corrosion resistance, and significantly enhanced surface hardness and tribological properties compared to stainless steel in terms of much reduced friction coefficient and increased wear resistance. Attempts have been made to fabricate TiO 2 films on 316L stainless steel by nonreactive magnetron sputtering of a rutile TiO 2 target, with and without a titanium underlayer. The effect of titanium underlayer thickness has been investigated in terms of phase evolution, film morphology, corrosion resistance, adhesion strength, hardness and tribological characteristics. Results showed that a titanium underlayer has a significant effect on the phase evolution in the TiO 2 film. Without this underlayer, an anatase-TiO 2 film is produced, in consistence with many other investigations. However, it is found for the first time that with a titanium underlayer, a rutile-TiO 2 film can be formed on the ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library v substrate. The underlayer characteristics play vital role in oxide film phase formations. The resultant rutile films show much improved friction, wear and corrosion properties, which vary with the thickness of the titanium underlayer.
