Effect of substrate deformation on functional properties of atomic-layer-deposited TiO2 coatings on stainless steel

Changes in the functional properties of 50 and 100 nm thick anatase-type and of 100 and 150 nm thick rutile-type atomic-layer-deposited TiO2 coatings with increasing tensile deformation of AISI 304 stainless steel substrate up to 40% strain were studied. All as-received coatings exhibited good photoelectrochemical and photocatalytic activity as well as photohydrophilicity, but the photocatalytic activity of the rutile-type coatings was only one third of that of the anatase-type coatings. The deformation induced changes in the functional properties depended strongly on the type and thickness of the coating. For the 50 nm anatase-type coating, all the monitored functional properties were severely reduced when the applied strain was 1.4% and higher. Rest of the coatings showed also considerable, but more gradual, decrease of the photoelectrochemical and photocatalytic activity with increasing strain. Least affected was the photohydrophilicity which remained approximately constant until 30% applied strain for the 100 nm coatings, and showed some variation for the 150 nm coating. The possible reasons for the observed behavior are discussed.