Surface Engineering and Applied Electrochemistry最新文献

Palladium is commonly used as a catalyst in the process of surface metallization of acrylonitrile-butadiene-styrene (ABS), but since palladium is expensive, alternatives are sought. In this study, colloidal silver was used as the catalyst to metallize an ABS surface, and the effect of colloidal silver on the electroless copper plating of the ABS surface under different conditions was studied. The average bonding strength was 1.37 kN/m, which is much higher than that of palladium colloid. The experimental results show that colloidal silver has good catalytic activity, and it is expected to be used in metallization of industrial non-conductive surfaces.

The (1E)-benzylidene hydrazine was tested as a corrosion inhibitor for mild steel in 0.5 M HCl by using polarization and electrochemical impedance spectroscopy measurements at temperatures 303, 313, 323, and 333 K. The data obtained from those two methods were in good agreement with each other. The effect of an increase in temperature and a change in the concentration of the inhibitor were studied. The inhibition efficiency was found to increase with an increase in the inhibitor concentration. The maximum inhibition efficiency of 92% was observed for 500 ppm of the inhibitor at 323 K. Polarization measurements showed that the Schiff base acts as a mixed type of inhibitor involving both physisorption and chemisorption. Temperature studies revealed that the inhibition efficiency increased at temperatures up to 323 K, but, beyond that, the inhibitor efficiency decreased due to the desorption of the inhibitor. The adsorption of (1E)-benzylidene hydrazine on a mild steel surface is an endothermic process and was best described by the Langmuir adsorption isotherm. Both kinetic and thermodynamics adsorption parameters were calculated and discussed. The surface morphology of the uninhibited and inhibited mild steel samples was analyzed using scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results obtained from the quantum chemical analysis are well correlated with other experimental ones.

This work deals with the influence of the parameters of the working fluid (hydrostatic pressure, temperature, specific electrical conductivity) and the geometry of the electrode system (the length of the interelectrode gap and the uninsulated part of the anode) on the prebreakdown characteristics of an electric discharge in a liquid aqueous electrolyte (breakdown voltage and breakdown delay time) and the minimum charging voltage, which provides a stable high-voltage breakdown of the interelectrode gap. The research has shown that an increase in the hydrostatic pressure leads to an increase in most of the characteristics under study. At the same time, an increase in the specific electrical conductivity and temperature was observed to lead to their decrease. It was suggested that the effect of temperature on the prebreakdown characteristics is associated with a change in the specific electrical conductivity of the working fluid during its heating. The data obtained showed no effect of the length of the interelectrode gap on the breakdown voltage and its breakdown delay time as well as the minimum charging voltage. The results of the experimental studies made it possible to develop a criterion for determining the charging voltage that provides a stable high-voltage breakdown of the water interelectrode gap. Its experimental verification has shown that it can be applied to the design of electric discharge equipment and to the choice of technological modes of operation in the specified range of parameters.

Composite insulators are popular choice in contemporary power industry due to their numerous advantages. When these insulators are subject to various stresses, their performance gets affected due to the material degradation. One of the methods to improve the material property is to incorporate inorganic nanofillers. In this work, aluminum oxide nanofillers, synthesized in the laboratory using a solution combustion process were used and studied. The nano range was ascertained with X-ray diffraction. Those fillers were mixed in the silicone rubber specimens in 0, 1, 3, and 5 wt % concentrations. They were more rapidly aged under UV radiation, temperature, humidity and electric stresses. Dry and wet flashover tests were carried out on both virgin and aged samples, and the results showed that the concentration of 3 wt % offered a better breakdown voltage. Fourier transform infrared spectroscopy revealed percentage variations in the properties of the aged specimens, the aging resistance, degradation resistance, hydrophobicity, oxidation resistance, and erosion resistance were significantly better in 3 wt % Al₂O₃ filled samples. Scanning electron microscopy with energy dispersive X-ray spectroscopy images showed that at 3 wt % concentration there was a fairly uniform distribution of nanofillers in the silicone base and there was the least ingress of water at same weight percentage of specimens. Their improvements in the insulation property is primarily attributed to the fair distribution of nano Al₂O₃ fillers into the silicone base, a good Si–CH₃ bond structure, a low carbon cross linking and good percolation, which makes them the best candidates for outdoor insulation of power systems.

The X-ray diffraction, infrared spectroscopy, chemical analysis, and cation exchange capacities are the most common techniques used for the physico-chemical study and characterization of clays. All of these used in the present study showed that the Tunisian clay samples collected from Zaghouan area (Zg₁, Zg₂, and Zg₃) and Hawaria area (Ha1, Ha₂, and Ha₃) consisted of illite, kaolinite, and smectite associated with quartz, K-feldespar, calcite, and dolomite. The chemical analysis revealed that Al₂O₃ is relatively high in the Ha₂ sample. The CaO rate was high (5.08 and 7.16 wt %) for Ha₃ and Zg₃ samples. To demonstrate the impact of clay mineralogical composition on the rheological properties, six samples were used to prepare the mixed clay aqueous suspension. Its effect depends on the proportion of the 2:1 phyllosilicate, especially smectite, as well as on the rheological properties of the blank clay suspensions and of Na₂CO₃ treated ones. Calcite forms large agglomerations with clays minerals, which prevents flocculation. The negative charges in the tetrahedral layers were generated by the substitution of Si⁴⁺ with Al³⁺, and they were compensated by the interlayer exchangeable cations. Therefore, the interlayer hydration leads to an increase of the dispersion of clay particles and rheological properties.