Composite systems of alternately electrodeposited nanocrystalline Ni and Cu films on cold-rolled polycrystalline copper substrates were fabricated. Highly-densified parallel interfaces which can give rise to high strength of composites are obtained by depositing layers at a very narrow spacing. The hardness properties of the composite systems were characterized using Vickers microhardness testing with loads ranging from 1.96 N down to 0.049 N. Above a certain critical penetration depth, a measured hardness value is not the hardness of the electrodeposited film, but the so-called ?composite hardness?, because the substrate also participates in the plastic deformations during the indentation process. Dependence of microhardness on layer thickness, Ni/Cu layer thickness ratio and total thickness of the film was investigated. Model of Korsunsky was applied to the experimental data in order to determine the composite film hardness. The microhardness increased with decreasing the layer thickness down to 30 nm and it is consistent with the Hall-Petch relation. Layer thickness and layer thickness ratio are the important parameters which are responsible for making decision of the total film thickness.

Fine-structured nickel coatings were electrodeposited from a sulfamate-based electrolyte onto different substrates: polycrystalline cold-rolled copper and single crystal silicon with (111) orientation. The influence of the substrate layers and chosen plating conditions on the mechanical and structural properties of these composite structures were investigated by Vickers microhardness testing for different loads. Above a certain critical penetration depth, the measured hardness value was not the hardness of the electrodeposited film, but the so-called 'composite hardness', because the substrate also participated in the plastic deformations during the indentation process. Two composite hardness models (Chicot-Lesage and Korsunsky), constructed on different principles, were chosen and applied to the experimental data in order to distinguish film and substrate hardness. The microhardness values of the electrodeposited nickel layers were mainly influenced by the current density. Increasing the current density led to a decrease in grain size, which resulted in higher values of the microhardness.

Purpose: The purpose of the study was to evaluate the surface characteristics of demineralized enamel after treatment with pastes containing casein phosphopeptide–amorphous calcium phosphate (CPP-ACP) or casein phosphopeptide–amorphous calcium fluoride phosphate (CPP-ACFP) and to compare their efficacy with that of 0.05% NaF. Methods: Following formation of the artificial carious lesion, enamel slabs were divided into 4 groups (CPP-ACP, CPP-ACFP, 0.05% NaF and control) and submitted to a chemical caries model. Remineralization potential was examined using scanning electron microscope, energy-dispersive spectroscopy (EDS) and microhardness test. Scanning electron microphotographs were analyzed for area, minimal, maximal and mean diameter, perimeter, roundness and number of enamel defects and percentage of tooth surface affected by defects. Results: Treatment with 0.05% NaF partly reduced the appearance of enamel defects when compared with irregular demineralized enamel. Treatment with CPP-ACP or CPP-ACFP resulted in occlusion of defects which produced more flattened enamel surface. Image analysis revealed reduction of the dimensions of the defects in the 3 experimental groups. Treatment with CPP-ACFP decreased the number of enamel defects when compared with demineralized enamel. The EDS analysis did not show differences in Ca/O, P/O and Ca/P ratios between the groups (P>0.05). Microhardness test revealed significant effects of CPP-ACP and CPP-ACFP (P<0.05). Conclusions: Pastes containing CPP-ACP or CPP-ACFP showed potential to remineralize enamel surface lesions.

In this study, a novel procedure, based on application of the Chicot?Lesage (C?L) composite hardness model, was proposed for the determination of an absolute hardness of electrolytically produced copper coatings. The Cu coatings were electrodeposited on the Si(111) substrate by the pulsating current (PC) regime with a variation of the following parameters: the pause duration, the current density amplitude and the coating thickness. The topography of produced coatings was characterized by atomic force microscope (AFM), while a hardness of the coatings was examined by Vickers microindentation test. Applying the C?L model, the critical relative indentation depth (RID)c of 0.14 was determined, which is independent of all examined parameters of the PC regime. This RID value separated the area in which the composite hardness of the Cu coating corresponded to its absolute hardness (RID <?0.14) from the area in which the application of the C?L model was necessary for a determination of the absolute coating hardness (RID ? 0.14). The obtained value was in a good agreement with the value already published in the literature.