Abstract
Direct current electrodeposited Sn–Ni/TiO2 nanostructured coatings were produced by embedding two different doped types of TiO2 particles within the alloy matrix, a commercially available doped carbon-based and doped N,S-TiO2 particles. The structural characteristics of the composite coatings have been correlated with the effect of loading, type of particles in the electrolytic bath, and the applied current density. Regardless of the type of doped particles TiO2, increasing values of applied current density resulted in a reduction of the co-deposition percentage of TiO2 particles and an increase of Tin content into the alloy matrix. The application of low current density values accompanied by a high load of particles in the bath led to the highest codeposition percentage (~3.25 wt.%) achieved in the case of embedding N,S-TiO2 particles. X-ray diffraction data demonstrated that in composite coatings the incorporation of the different types of TiO2 particles in the alloy metal matrix modified significantly the nano-crystalline structure in comparison with the pure coatings. The best photocatalytic behavior under visible irradiation was revealed for the composite coatings with the highest co-deposition percentage of doped N,S-TiO2 particles, that also exhibited enhanced wear resistance and slightly reduced microhardness compared to pure ones.
Highlights
Over the last years, TiO2 as an n-type wide bandgap semiconductor has become one of the most widely known photocatalysts for supplying solutions to environmental issues
The objective of this study is twofold: (a) estimate the optimum electrodeposition parameters by tuning applied current density and particles’ loading in the bath that result to the production of composite Sn–Ni/doped-TiO2 nano-coatings with high co-deposition percentage of particles dispersed into alloy metal matrix, and (b) investigate the correlation between compositional and morphological characteristics of the produced surfaces with the observed photocatalytic performance under visible light, taking into consideration that the proposed coatings should preserve attractive appearance, high hardness and wear resistance in comparison with pure Sn–Ni ones
Pure Sn–Ni and composite Sn–Ni/doped-TiO2 coatings were deposited under direct current conditions (DC) from a commercial chloride fluoride-based Tin-nickel solution Galvaloy NS11 provided by Elplatek A/S (Espergærde, Denmark)
Summary
TiO2 as an n-type wide bandgap semiconductor has become one of the most widely known photocatalysts for supplying solutions to environmental issues. TiO2 photocatalytic products like self-cleaning glass and surface sterilization tools have been proven to be efficient and of great value for the applications that they are oriented [1]. The photocatalytic activity depends on the bandgap energy of materials [2]. TiO2 with anatase and rutile phases exhibits a bandgap value of 3.2 and 3.0 eV, respectively [1]. Despite the type of TiO2 (anatase and rutile TiO2 are most often reported as photocatalysts), bulk TiO2 has little photocatalytic ability. TiO2 nanocrystals have several advantages over their bulk counterparts in terms of potential applications due to their high surface-to-volume ratio, Coatings 2020, 10, 775; doi:10.3390/coatings10080775 www.mdpi.com/journal/coatings
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