N. Spyrellis, E.A. Pavlatou, S. Spanou, A. Zoikis – Karathanasis
Proceedings of the NPS 08 Nanoscale Phenomena and Structures in Bulk and Surface Phases (2008), 26/02-02/03/2008, Prof. Marin Drinov Academic Publishing House (Ed. by D. Kashchiev), Sofia, p. 221-228 (oral)
Composite coatings were obtained by electrochemical co-deposition (i) of TiO2 nanoparticles (mean diameter 21 nm) with nickel, from an additive-free Watts type bath by applying direct current (DC) and (ii) NiP composite coatings with tungsten carbide (WC) nanoparticles (mean diameter 200 nm) from a modified organic-free Watts bath under direct, as well as pulse, current conditions. For comparison, pure Ni and NiP deposits were also produced under the same experimental conditions. The influence of the variable electrolysis parameters (type of current, frequency, pH and current density) and the reinforcing particles properties (type, size, shape, concentration and dispersion in the bath) on the surface morphology, the structure and properties of the deposits will be demonstrated. In the case of Ni/TiO2 composite coatings the observed textural modifications of composite coatings are associated with specific structural modifications of Ni crystallites provoked by the absorption-desorption phenomena occuring on the metal surface, induced by the presence of TiO2 nanoparticles. Regarding the NiP-WC composite coatings, the experimental findings proved that the imposition of pulse current conditions leads to more compact coatings with increased embedded particles, more homogenous distribution of the nanoparticle and increased micro-hardness, compared to those produced under direct current conditions.