Search

In the article, the creation of electrically conductive composite ceramics based on facing tiles with the addition of SiC with specified electrodynamics’ characteristics was considered. To obtain a press powder, the raw materials in a predetermined amount were weighed, 10, 20 and 30 % silicon carbide were added and subjected to wet grinding in a ball mill. The resulting slip was dried in a drying oven and passed through a № 05 sieve. The finished press powder for facing ceramics with SiC, moistened to 8 %, was weighed and poured into a mold for pressing, the pressure force was 18—20 MPa. The resulting green was dried in a drying oven. The semi-finished product was burned in a sillite furnace at a firing temperature of 1120—1140 °C with a holding at a maximum temperature of 5—10 minutes. The chemical composition of obtained press powder and the technological scheme for obtaining samples were presented. The obtained data shown that the best sample was facing ceramics with 30 % SiC, which had the following properties: water absorption — 5.9 %, open porosity — 12.5 %, apparent density — 2.13 g/cm2, resistivity — 0.43 ⋅10-6 Ohm ⋅m. The obtained X-ray diffraction pattern indicated the presence of silicon carbide in the sample after firing, which was confirmed by the data on the study of specific volumetric resistance of the studied ceramics and the obtained practical results.

The electrolysis modes affect on the quantitative and phase composition of the ternary Fe-Co-W and Fe-Co-Mo coatings is studied. It was established that the distribution of refractory components over the thickness of the coating varies in the opposite way with increasing duration of electrolysis – the molybdenum content increases and the tungsten one decreases. Amorphous-crystalline structure of alloys has been visualized by X-ray spectroscopy, including inter-metallic phases Co7W6, Fe7W6, Fe7Mo, Fe7Co, FeCo along with α-Fe and Fe3C. The size of coherent-scattering region of the amorphous part is of 6–8 nm. The formation of metallic tungsten and molybdenum additional phases has been detected for alloys deposited at pulse current which contributes microhardness Hμ increase up to 700 compared with direct current mode. Magnetic characteristics of Fe-Co-W(Mo) films were measured depending of deposition time. It was concluded that the content of magnetic phases in upper layers of Fe-Co-W deposits is higher than in the bottom ones and superior Fe-Co-Mo coatings. It qualitatively corresponds to W(Mo) content changes over the thickness.

The process of ternary Co-W(Mo)-Zr alloys deposition on a copper substrate from pyrophosphate-citrate electrolytes in a pulsed mode was investigated. The effect of temperature, the pH of the electrolyte, and the current density on the composition, surface morphology, and current efficiency of ternary electrolytic cobalt alloys with refractory metals was studied. The resulting coatings are characterized by a uniformly developed surface without cracks, which provides a sufficiently high and reproducible microhardness. It was found that the size of the globules on the alloy surface decreases with increasing the current density up to 10 A/dm2. It was found that an increase in temperature favorably affects the current efficiency and microhardness of Co-W-Zr coatings. The regimes of the electrosynthesis of coatings by cobalt-tungsten-zirconium alloys with a given level of the surface development and microhardness were substantiated.

Ternary coatings Fe-Co-W with an iron content of 40–55 at.%, cobalt 39–44 at.%, and tungsten 4–12 at.% and Fe-Co-Mo with an iron content of 40–55 at.%, cobalt 39–44 at.%, and tungsten 4–12 at.% were obtained by galvanostatic and pulse electrolysis on the mild steel substrate from iron(III) citrate-based electrolyte. The influence of electrolysis mode and parameters on composition of deposited alloys was studied. The competing reduction of iron and tungsten in Fe-Co-W coatings as well as the competitive deposition of iron and cobalt in Fe-Co-Mo coatings at various current densities were defined. Simultaneously, the alloy enrichment with molybdenum is more marked at a pulse mode. Atomic force microscope analysis of the Fe-Co-W alloy coating morphology and surface topography indicates their globular structure with spherical grains in the range of 2.5–3.5 μm. The surface of Fe-Co-Mo is characterized by parts of a globular structure with an average conglomerate size of 0.3–0.5 μm and singly located cone-shaped hills with a base diameter of 3 μm. Sites with a developed surface were detected within the same scan area which topography is identical to the crystal lattice of cobalt with the crystalline conglomerate sizes in the range of 0.2–1.75 μm.

The study aims at the investigation of the morphology and topography of the ternary Fe-Co-Mo electrolytic coatings. Compositions and morphology of the alloys are examined by scanning electron microscopy and X-ray analysis. Both topography and surface roughness are studied by an atomic force microscopy AFM using a NT–206 microscope. The Fe-Co-Mo coatings with an iron content of 47 at.%, cobalt 28 at.% and molybdenum 25 at.% are deposited on mild steel substrate by pulse electrolysis mode from citrate bath with the ratio of concentrations с(Fe 3+ ):с(Co 2+ ):с(MoO 4 2– ) = 2.5:3:1. Atomic force microscope analysis topography of the coatings Fe-Co-Mo at the scanning area 39.9×39.9 μm show that their surface is more developed compared with the substrate material. Moreover the AFM analysis of the coatings morphology and surface topography indicates the parts with a globular structure with an average conglomerates size of 0.2–0.5 μm and singly located sharp grains. Within the same scan area, sites with a developed surface are detected the topography of which is identical to the crystal structure of cobalt with the crystallite size in the range of 0.2–1.75 μm. The parameters R a and R q for parts with different morphology as well as average characteristics of coatings demonstrated the low roughness of the surface. Electrolytic deposits Fe-Co-Mo can be attributed to 8–9-th class of roughness. The study tested the magnetic behavior of Fe-Co-Mo coatings. The coercive force of 7–10 Oe confirms the soft magnetic properties of materials which in combination with high microhardness open prospects for usage of Fe-Co-Mo systems in the production of magnetic head elements for recording and reproducing information .

This paper presents the results of studies on the electrochemical treatment characteristics of aluminum and alloys in alkaline electrolytes. It is shown that the heterogeneity of the alloys composition complicates the formation of the surface oxide layer. To homogenize the treated surface and obtain oxide coatings doped with manganese and cobalt, electrolytes based on KOH and K4P2O7 with the addition of KMnO4 and CoSO4 were used. Plasma electrolytic oxidizing (PEO) in these electrolytes in the range of current densities 5–20 A/dm2 allows to obtain mixed oxide coatings which contained both aluminum oxide matrix and doping metal oxides Al2O3·MnOx and Al2O3·CoOy. It is shown that an increase in the PEO current density and the concentration of manganate- and cobalt(II) ions in the solution leads to an increase the content of dopant metals in the coatings outer layer. The incorporation of manganese and cobalt oxides in the composition of the surface layers was confirmed by the results of X-ray structural analysis. The rational modes of aluminum alloys PEO treatment were substantiated to obtain coatings with manganese and cobalt contents up to 25–40 аt.%. Formed oxide systems have a developed surface and high adhesion to the base metal and show an increased corrosion resistance and catalytic activity. This allows us to view them as promising materials for air- and water-cleaning technologies and internal combustion engine waste gas purification systems.

The structure and properties of the oxide films formed on titanium alloys by means of plasma-electrolytic oxidizing in alkali electrolytes based on pyrophosphates, borates, or acetates of alkali metals with the addition of dopants’ oxides or oxoanions of varying composition have been studied. Anodic polarization in the spark discharge (microarc) mode at application of interelectrode potential 90 to 160 V has been used to obtain mixed-oxide systems TiOx·WOy, TiOx·MoOy, TiOx·ZrO2, and TiOx·V2O5. The possibility to obtain the oxide layers containing the alloying elements by the modification of the composition of electrolytes has been stated. The chemical and phase composition as well as the topography, the microstructure, and the grain size of the formed layers depend on the applied current, interelectrode voltage, and the layer chemical composition. The effect of formed films composition on the resistance of titanium to corrosion has been discussed. Catalytic activity of mixed-oxide systems was determined in the model reaction of methyl orange dye MO photodestruction.

Ti x Zn y O z coatings have been synthesized by anodic oxidation in alkaline solutions based on potassium pyrophosphate and hydroxide. The elemental composition and surface morphology of the resulting coatings have been examined; the photocatalytic properties of the coatings have been determined. It has been found that the highest photocatalytic activity in the degradation of the methyl orange azo dye under UV irradiation is exhibited by a Ti x Zn y O z coating on the VT1-0 alloy with a zinc content of about 1 wt %. Processrate constants, synergy factors, and quantum efficiency of the coatings have been determined.

Electrochemical synthesis of nickel-based composite coatings and foil reinforced with nanosized aluminum oxide is reported. Ni-Al₂O₃ composites with different content of the modifying phase were prepared by chemical dispersion of aluminum oxide using the “from above down” principle. The influence of the aluminum oxide concentration in the electrolyte on the physicomechanical properties of the reinforced foil was determined. Incorporation of reinforcing phase particles into the metal matrix leads to a decrease in the grain size and enhances by a factor of 2–6 the strength characteristics of the coatings and foil. The topography of the surface and the cross section profile of the composites were examined, and the influence of these characteristics on the properties of the materials was determined. Представлены результаты электрохимического формирования композиционных покрытий и фольг на основе никеля, армированных наноразмерным оксидом алюминия. Для получения композитов Ni-Al₂O₃ с различным содержанием модифицирующей фазы использован метод химического диспергирования оксида алюминия по принципу сверху вниз. Установлено влияние концентрации оксида алюминия в электролите на физико-механические свойства армированных фольг. Включение в основную матрицу металла частиц армирующей фазы приводит к уменьшению размеров зерен и повышает в 2-6 раз прочностные характеристики покрытий и фольг. Изучена топография поверхности и профиль сечения композитов и установлено их влияние на свойства материалов.

The study aims at the investigation of the influence of electrolyte composition and plasma electrolytic oxidation modes on the composition and morphology of a mixed aluminum and cobalt oxides at the AL25 alloy. Composition, morphology and surface roughness of the oxide systems are examined by scanning electron microscopy, X-ray analysis and atomic force microscopy. Mixed oxide coatings Al 2 O 3 ·CoO x formed from the diphosphate electrolytes at various concentration ratio diphosphate / cobalt sulfate contain cobalt of 8–30at. % (in terms of metal) in the matrix of alumina. Plasma electrolytic oxidation in a two-stage mode of the incident power provided formation of strongly adhered coatings characterized by non-stoichiometry ratio of cobalt and oxygen as well as low content of silicon in deposits. Obtained mixed oxide systems have developed surface with alternating the spheroid and torus-shaped structures which is associated with a large number of catalytic sites. They exhibit catalytic behavior in the model reactions of CO conversion to CO 2 and benzene oxidation not inferior to the contacts with noble metals . The coatings Al 2 O 3 ·CoO x contribute to fuel economy and improve the environmental performance of the internal combustion engine thus can be recommended for use in the neutralization of gas emissions systems and as coatings for pistons of combustion chamber.

Principles of plasma-electrolytic oxidation of the aluminum alloys in diphosphate electrolytes are discussed. It has been established that a variation in concentration of the electrolyte components and electrolysis parameters (current density and treatment time) provides the formation of oxide coatings consisting of the basic matrix materials and the cobalt oxides of different composition and morphology that are expected to affect their functional properties. Mixed oxide coatings formed in a plasma-electrolytic mode characterized by microglobular structure with reducing the conglomerate size have an increased abrasion and wear resistance and an intense catalytic activity. Thus, there is a prospect of using such coatings in the process of burning fuel in internal combustion engines and reduce the toxicity of emissions improving fuel efficiency and environmental performance of engines and in the industrial systems of catalytic purification of exhaust gases of industrial plants and power system facilities.

Method of electrosynthesis of composite coatings and foil composed of copper reinforced with nanosize aluminum oxide is described. A method for chemical dispersion of aluminum oxide by the top-down principle and an electrolyte composition are suggested, which provide synthesis of composite materials with varied content of the modifying phase. The results of mechanical tests indicate that the plasticity, strength, and a number of other physicomechanical properties of thus synthesized composite materials are improved.

Galvanic alloy coatings Fe-Mo (W) and Fe-Mo-W were deposited from citrate bath based on Fe (III) using both direct and pulsed current on substrates steel 3 and grey cast iron GC 18. It was shown that the alloying components content, their distribution on the surface, morphology and topography of the coatings are depended on the electrolysis mode. It was established that the functional properties of the binary and ternary alloys of iron (corrosion resistance, microhardness, antifriction et al.) exceed parameters of the substrate and are predetermined by the composition, structure, material and surface roughness. Электролитические покрытия сплавами Fe-Mo (W) и Fe-Mo-W получены из цитратного электролита на основе Fe (III) в гальваностатическом и импульсном режимах на подложках из стали 3 и серого чугуна СЧ 18. Показано, что содержание легирующих компонентов, их распределение по поверхности, морфология и топография покрытий зависят от режима нанесения. Установлено, что функциональные свойства бинарных и тернарных сплавов железа (коррозионная стойкость, микротвердость, антифрикционные и др.) превышают показатели подложки и предопределяются составом, структурой материала и шероховатостью поверхности.

Specifi c features of the electrodeposition of iron–molybdenum coatings from a citrate electrolyte based on iron(III) sulfate and sodium molybdate in dc and unipolar pulsed modes were studied. It was demonstrated that bright compact coatings with varied content of molybdenum can be produced by varying the relative concentrations of salts of the alloy-forming components and the solution pH. The current density ranges providing the high efficiency of the galvanostastic electrolysis were determined and it was shown that using the pulsed mode makes smaller the amount of nonmetallic impurities in a coating, diminishes its roughness and leads to formation of surface layers with a more uniform composition, The iron–molybdenum coatings exhibit a high corrosion resistance in corrosive media and physicomechanical properties improved as compared with the base metal, which makes it possible to recommend these coatings for protection from corrosive-mechanical disintegration and restoration of the surface of worn articles.

The adhesion failure area (n) at the polymer coating/steel interface in aggressive media was measured using an a.c. impedance technique. A n value of 0.2-5.0% of the total surface was found for different film-formers (epoxy, vinyl, divinyl acetylene) after 10 days' exposure in electrolyte. It was shown that the n value and its changes during exposure [n = f(τ)] depend on the nature of the film-former, the solution composition, and the dissolved oxygen (CO2) and chloride ion (CCl-) concentrations. It was found that the epoxy coating adhesion stability was much higher in comparison with the vinyl and divinyl acetylene coatings. An increase in the chloride ion concentration resulted in an increase of n for the coatings studied, i.e. destruction of adhesional bonds, but at the same time relative increments δn/δτ and δn/δCO2, were confined within the same range. The mechanism of the observed processes is explained from the point of view of competitive adsorption of hydroxide and chloride ions at the metal surf...

New types of cements with a high refractoriness (above 1800°C), ultimate compressive strength of 40–60 MPa, and insignificant loss of strength on heating (20–25%) have been obtained in the CaAl2O4-CaAl4,O7-MgCr2O4 system.