Surface Engineering and Applied Electrochemistry最新文献

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.

Increasing the hardness and wear resistance of powder alloys and coatings through the use of ultrafine-grained powders and metastable phases is a promising way in powder metallurgy. This paper presents results of the studies of the process of obtaining ultrafine powders by the electrical discharge erosion of the cemented carbide waste WC–5TiC–10Co on a special installation. An empirical model that describes the dependence of the productivity of the process on the discharge energy and properties of a liquid is provided. The dependence of the chemical and phase compositions of the obtained powders on the compositions of the used liquids and the specific energy consumption was investigated. The effect of the discharge energy on the morphological composition and the average particle diameter was examined. It was revealed that the formation of a metastable solid solution (W,Ti)C and a decrease in the concentration of cobalt induce an increase in the hardness of the resulting spherical particles from 1410HV_0.05 to 2540HV_0.05.

In this paper, the concentration functions of electrical conductivity and pH are determined for aqueous solutions of an ionic liquid based on diethanolamine and boric acid (DEAB). Correlations between the physicochemical properties of an aqueous solution of DEAB and the processes of dissociation of the system components were established. Charge carriers in DEAB solutions are shown to be anions. It was established that an aqueous solution of DEAB has unipolar electrical conductivity and anion-exchange properties with an anion transfer number of 0.79.

It is experimentally shown that a meniscus is raised under the action of pulsed-periodic spark discharges between the electrode and the meniscus in a capillary formed by two vertically fixed cylindrical rods. The recorded effect can be applied, for example, to intensify technological processes of the fabric impregnation.

The anodic dissolution of type Kh18N10 (Cr18Ni10) chromium–nickel steel was performed in a nitrate solution (conductivity of 0.15 S/cm) under pulsed current conditions using pulse durations of 20–100 µs, current densities of 0.01–100 A/cm², and relative pulse durations of 10 to 1 (duty cycle from 10 to 100% (direct current), respectively). Different hydrodynamic conditions were implemented, and the surface temperature was measured. The results obtained are in line with the hypothesis that the process is mediated by the formation of a semiconducting anodic oxide film with point defects that can exhibit different types of conduction. The film is described within point defect model II, and the rate of its electrochemical formation is balanced under steady-state conditions by the rate of its chemical dissolution, which is why the mass decrease per unit charge reaches a limiting value of 0.16–0.18 mg/C (under the pulsed conditions), which corresponds to a current efficiency close to 100% (assuming the highest oxidation state for alloying components of the steel in solution). In going from pulsed current to direct current conditions, the thermokinetic instability of the film is observed, i.e., it forms and then undergoes breakdown due to thermal explosion. Under such circumstances, the current yield of anodic dissolution may not only reach 100%, assuming the lowest degree of oxidation of the alloying components (thermal activation), but exceeds this value as a result of chemical interaction between the film-free surface and the electrolyte.