Zn-SiC nanocomposite coatings are successfully produced by galvanostatic electrodeposition from aqueous citrate solutions, using SiC nanoparticles (NPs) with an average size of 56 nm. The optimal parameters of the zinc-citrate bath are chosen on the basis of analysis of a thermodynamic model. The effect of applied current density, bath composition, and hydrodynamic conditions are studied. The kinetics and mechanism of zinc reduction in the presence of SiC NPs are investigated using cyclic voltammetry. The surface charge of SiC NPs suspended in the electrolyte solutions is examined by the dynamic light scattering technique. The electrodeposited Zn-SiC coatings are characterized by wavelength dispersive X-ray fluorescence and scanning electron microscopy. It is shown that SiC codeposition with Zn proceeds through the entrapment of ceramic NPs during the reduction of citrate-zinc ions that are first adsorbed on the surface of the ceramic NPs. A maximal content of 6.4 wt% SiC incorporated into the Zn matrix is obtained at the lowest applied current density of j =-0.5 A dm-2 , with a nearly constant faradaic efficiency of 90%.

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A comparison is made between the codeposition behavior of Zn with SiC nanoparticles (NPs) of two average sizes: 56 nm and 90 nm. The SiC NPs are first characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Dynamic light scattering (DLS) is used to compare the surface charge of both kinds of SiC NPs suspended in aqueous citrate electrolytes. The effect of applied current density, hydrodynamic conditions, and total charge passed on the SiC content in the coating and electrodeposition rate is studied. The electrodeposited Zn-SiC coatings are characterized by wavelength dispersive X-ray fluorescence (WDXRF), scanning electron microscopy (SEM), and XRD. The results obtained confirm that Cit-Zn complexes are adsorbed on the surface of the SiC NPs, which are transported to the cathode and are codeposited with Zn during reduction. Zn-SiC incorporation may proceed also by mechanical entrapment of SiC agglomerates in the cavities and pores that are formed in the deposit under condition of relatively fast Zn deposition, which is accompanied by fast hydrogen evolution.

Zn–SiC nanocomposite coatings were electrodeposited from aqueous citrate electrolytes using either direct current deposition (DCD) or pulsed electrodeposition (PED). The effects of various surface-active organic compounds (SDS, gum arabic, gelatin, CTAB, PEG 20000, and Triton X–100) on the coatings’ surface morphology and chemical composition were studied. The influence of pulse frequency and duty cycle on the percentage of the SiC nanoparticles (NPs) incorporated and on the quality of the deposits was also investigated. The amount of SiC NPs incorporated in the Zn matrix was similar for layers obtained by DCD compared to PED. The Zn–SiC coating deposited by PED exhibited a more fine-grained surface morphology. The percentage of SiC co-deposited with Zn was mainly affected by the type of surfactant used. The ionic surfactants (cationic gelatin and CTAB or anionic gum arabic) allowed the co-deposition of considerably higher amounts of SiC NPs with Zn, compared to the non-ionic compounds PEG 20000 and Triton X–100. However, the use of high molecular weight organic compounds such as gelatin and gum arabic led to aggregation of SiC NPs within the Zn matrix.

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Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.