We report on a very significant enhancement of the thermal, chemical, and mechanical stability of self-organized TiO2 nanotubes layers, provided by thin Al2O3 coatings of different thicknesses prepared by atomic layer deposition (ALD). TiO2 nanotube layers coated with Al2O3 coatings exhibit significantly improved thermal stability as illustrated by the preservation of the nanotubular structure upon annealing treatment at high temperatures (870 °C). In addition, a high anatase content is preserved in the nanotube layers against expectation of the total rutile conversion at such a high temperature. Hardness of the resulting nanotube layers is investigated by nanoindentation measurements and shows strongly improved values compared to uncoated counterparts. Finally, it is demonstrated that Al2O3 coatings guarantee unprecedented chemical stability of TiO2 nanotube layers in harsh environments of concentrated H3PO4 solutions.

Beneq Olarinluoma 9 02201 Espoo Finland

Center of Materials and Nanotechnologies Faculty of Chemical Technology University of Pardubice nam Cs legii 565 53002 Pardubice Czech Republic

Joint laboratory of Solid State Chemistry Faculty of Chemical Technology University of Pardubice Studentska 95 532 10 Pardubice Czech Republic

Laboratory of Nanostructures and Nanomaterials Institute of Physics of the CAS v v i Na Slovance 2 182 21 Prague 8 Czech Republic

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