Because of long life, reliability and durability many kinds of titania coatings are used as part of bone implants [1]; intelligent protective coatings require low friction and wear [2]. Application of nanocomposites consisting of organic lubricant molecules in the form of thin film onto inorganic surface considerably lowers friction and wears [3].

In this approach, the organic-inorganic nanocomposites were created by deposition of di(n-alkyl)ditiophosphate acids (HDDP) on TiO₂ substrates with the use of dip-coating (DC), self-assembled (SA) and Langmuir-Blodgett (LB) methods. Ultra thin TiO₂ films prepared by dip-coating sol-gel method on Si (100) wafers were used as amorphous, anatase and rutile substrates.

The surface morphology, hydrophobicity and tribological behaviour, including the influence of alkyl chains length of HDDP (C12, C14 and C16), titania substrate phase and modification method, were characterized by surface probe microscopy (AFM/FFM), wetting contact angle and microtribometer measurements.

The surface morphology of modified TiO₂ substrates exhibit various morphologies from thin and smooth to closely-packed agglomerates of HDDP depending on the type of modifier and the deposition method. Smooth surfaces were obtained in LB method while thick agglomerates were observed for DC deposition.

Of amorphous and crystalline phases of TiO₂ (anatase and rutile) the lowest friction coefficient and wear is exhibited by rutile. However, HDDP/TiO₂ nanocomposite layers exhibit better antifrictional properties than unmodified titania surfaces. The best antiwear behavior and the lowest friction coefficient present C14 HDDP layers deposited by DC on rutile phase due to the formation of dense protective layer on hard substrate.

[1] H.F. Hildebrand, at al. , Surf. Coat. Technol., 2006, 200, 6318-6324

[2] C. Nistorica, at al. ,J. Vac. Sci. Technol. A 2005, 23, 836-840

[3] Y. Chen, W Liu, Ch. Ye, L. Yu, S. Qi Materials Research Biulletin 2001, 36, 2605-2612

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1. Mesoscopic objects, porous layers and nanocomposites - possibilities of sol-gel chemistry
2. Application of Atomic Force Microscopy (AFM) in imaging of sol-gel derived mesoscopic objects and thin structured layers
3. The influence of temperature, surface modification, deposition method and porosity on tribological properties of titanium dioxide thin films