In this paper, electrodeposition of nano-and micro-crystalline copper films and thin-layers with direct and pulse periodic currents is effectively controled. Electrical and physico-chemical characterizations of the copper films are realized, and the optimized electrodeposition parameters are so determined. Next, they are applied to micromolding. The attention is focused on microstructure, surface roughness, hardness, and on process parameters leading to major differences in final products. The obtained results show that the addition of a spike and a decrease in forward current can improve the throwing power in plating quality. Decrease in the grains dimension of the copper layers results in an increase of both the corrosion rate and the double layer capacitance but then charge transfer resistance decreases.

This paper presents a one-period energy method of studying the electrochemical corrosion phenomena that occur on metal surfaces. The method employs the energy state variables (time functions) to determine whether the material is susceptible to corrosion. The main feature of this approach is the elimination of the frequency analysis, and thereby gives significant simplifications of the corrosion rate measurement. Another important feature is that the method is based on an analysis of the appropriate loops on the energy phase plane which results in the corrosion process being easily estimated through the evaluation of the loop area. The physical results obtained by this method are easily interpretable with robust properties. The usefulness of the proposed technique was examined in microcrystalline and nanocrystalline copper layers deposited on a polycrystalline substrate by the electrocrystallization method. The quantitative results obtained from the measurements of the one-period energy loops are used for controlling the corrosion resistances of the micro-and nano-copper thin-layer coatings. Several experiments performed on real specimens verified the effictiveness of the method as used for analysing the electrochemical corrosion in many practical systems. We have shown that the corrosion resistance of the nanocrystalline copper layers is worse than that of microcrystalline copper layers even when the layers of the two types are produced by the same electrochemical method.

A nickel-boron (Ni-B)/graphene composite coatings were produced using chemical reduction method on a steel substrate. These composites were compared to NiB coatings without graphene embedded into the matrix. Graphene in the form of an aqueous suspension of graphene oxide flakes was used. Graphene was characterized by single-layered flakes about 0.5 lm in size. The coatings produced were characterized by an amorphous structure. The incorporation of graphene into the NiB matrix affects the surface topography and morphology of the coatings produced. The addition of graphene strengthened the coating material. An increase in the hardness ($ 1100 HK0.025) was noted for Ni-B/graphene composite coatings compared to the hardness ($ 950 HK0.025) of the NiB coatings without a built-in dispersion phase. Composite coatings also exhibited a better corrosion resistance than the coatings without embedded graphene.

Purpose: The paper presents the results of investigations of Ni-B/Si3N4 composite layers produced on steel substrate by electroless method. Design/methodology/approach: Amorphous silicon nitride powder (Si3N4) with nanometric particle sizes was used as a dispersion phase for the production of composite layers. Ni-B/Si3N4 composite layers were produced in baths of varying Si3N4 powder content. For comparative purposes, the study also includes results related to a Ni-B layer. The Si3N4 powder and the structure of the produced layers were characterized. The topography and morphology of the surface of the produced layers are presented. The adhesion of the layers to the substrate material was determined. Microhardness and tribological properties of test materials were determined. Findings: The results of the studies show that Ni-B/Si3N4 composite layers and Ni-B composite layers are characterized by compact structures and good adhesion to the substrate material. The incorporation of Si3N4 particles into the Ni-B layers increases the degree of surface development of the layers. The Ni-B/Si3N4 composite layer material exhibits less microhardness and less abrasive wear compared to Ni-B layers. However, the extent of wear damage of the Ni-B/Si3N4 is relatively small comparing to Ni-B layers.

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