Abstract
In this study, nc-TiO2/Ni–Fe composite coatings, and Ni–Fe alloys as equivalents to their matrices, were obtained from citrate-sulphate baths in the electrodeposition process using direct current and pulse current conditions. The aim of the study was to examine the effects of TiO2 nanoparticles and current conditions on the chemical composition, surface morphology, microstructure, microhardness and magnetic properties of the electrodeposited coatings. The results show that the concentration of Fe in Ni–Fe alloys is related to the current conditions and is higher in the case of pulse current electrodeposition, while such a relationship was not observed for composites. The reinforcement of composites with TiO2 nanoparticles results in a more developed surface topography with many nodule-like structures. Composites and equivalent alloys deposited in pulse current are characterized by a finer grain size than those obtained in direct current. TiO2 nanoparticles and their agglomerates, several tens of nanometres in size, are distributed randomly in the Ni–Fe matrix of composites deposited in both current conditions used. Incorporation of a high volume fraction of nc-TiO2, exceeding over a dozen percent, and decreasing the nanograin size in nc-TiO2/Ni–Fe composites electrodeposited under pulse current conditions, allow a higher hardness to be achieved than in their counterparts obtained using direct current. Magnetic measurements showed ferromagnetic ordering of pristine TiO2 nanoparticles, however, the introduction of TiO2 nanoparticles into the Ni–Fe matrix resulted in a decrease in coercivity and saturation magnetization.Graphic
Highlights
Electrodeposition methods are used on a large scale for manufacturing alloy and composite coatings [1]
New nc-TiO2/Ni–Fe composites and analogical Ni–Fe alloys were electrodeposited from a single citratesulphate bath under DC and PC current conditions
Examinations of the chemical composition, surface morphology, microstructure, microhardness and magnetic properties allowed the differences in the characteristics of composites and alloys to be determined
Summary
Electrodeposition methods are used on a large scale for manufacturing alloy and composite coatings [1]. Electrodeposition is a suitable method for obtaining nanostructured composites, which are characterized by improved mechanical properties when compared to coarse-grained counterparts [2]. Electrodeposited metal-matrix composites (MMC) strengthened by ceramic particles are of considerable. The co-deposition of Fe and Ni is a typical anomalous deposition, where less noble Fe is deposited preferentially before nobler Ni in most electrochemical conditions [3, 4]. Using a single-bath electrochemical process with different deposition parameters, it is possible to obtain materials characterized by various chemical compositions [1, 5]. The mechanical properties of such alloys are often insufficient, but can be improved through reinforcement by ceramic particles, such as TiO2
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