Ni-P coatings, with their high microhardness (HV) and wear resistance, have been proposed as a viable alternative to hard chromium. However, wear testing experiments on electroless Ni-P coatings were conducted under a variety of conditions, including test equipment, load, substrate materials and counterface materials, resulting in unreliable comparative evaluations of experimental results. Therefore, this article presents an analysis of experimental research on Ni-P and Cr coatings, as well as a statistical analysis of the results obtained under similar conditions. The results of simultaneous wear tests on Ni-P and Cr coatings published from 1958 to 2022 were used for evaluation and comparative analysis. The relative wear of Ni-P versus hard Cr was calculated from experimental data and analyzed using statistical methods such as Tukey's statistical methods, nonparametric and parametric statistics. This review found that the wear performance of electroless nickel coatings generally does not match that of hard chromium coatings. The results of this analysis indicate that: (i) Ni-P coating can be used as a protective and hardening coating; (ii) the wear resistance of the electroless Ni-P coating, being 1.9 +/- 0.4 times less, does not reach the same level of wear resistance as that of hard Cr; (iii) there is a tendency for the wear resistance of Ni-P to gradually approach the wear resistance of Cr; (iv) the dependence of the wear rate on the phosphorus content of the Ni-P alloy indicates that the minimum possible wear rate is achieved at a P content of about 4-7 wt%. The search for effective alternatives to hard chromium plating is ongoing, and this review has identified several areas where effective engineering solutions could be found.

Among the coatings used to ensure the operational and protective properties of products, a special place is occupied by coatings with metals, alloys and metal matrix composites based on them, which are obtained by electrodeposition or autocatalytic (chemical) reduction. Both types of coatings are complex systems in which the nature and the ratio of components play a decisive role. In the 80 years since the first publication, scientific and practical interest in chemical coatings has remained consistently high. Many works are devoted to the influence of the dispersed phase on the characteristics of composite coatings. However, a large number of possible combinations of dispersed phases to give the coating the desired properties remain outside the attention of researchers. Earlier, a review on composite electroplating coatings was published, in which a specially formed problem-oriented database was used. Taking into account the interest in the proposed information submission system, the developed technology was extended to the analysis of publications on electroless coatings based on available databases for the period 2015-2023. Ni-P is chosen as the matrix, and the dispersed phases are divided into classes (oxides, nitrides, carbides, polymers, etc.). The review covers 247 scientific articles. The results of the analysis are presented in the form of 8 tables with corresponding links. As in the case of electroplating coatings, it is shown that an insignificant part of the possible combinations in the matrix-dispersed phase system is described. The presented material can be used not only as a reference, but also as a basis for finding new research directions and innovative approaches in the development of this class of coatings, including using machine learning methods.

The surface roughness of coatings has a significant impact on their functional properties and efficiency. We present the results of studying the effect of the main technological parameters on the roughness of chemical coatings with Ni – P and Ni – Cu – P alloys. The key factors affecting the roughness of coatings were determined by the Taguchi method. Parameters of the coating process were varied in the experiments: concentration of components in solution, pH, temperature, and the time of deposition. It is found that the surface roughness increases linearly with the thickness of coatings. The concentration of sodium hypophosphite and pH value have the greatest influence on the development of roughness. It is shown that the lowest roughness is observed at concentrations of sodium hypophosphite and copper salt 0.358 and 0.0012 mol/liter, pH 5.8 and temperature 90 °C. The rate of the surface roughness development for Ni – P and Ni – Cu – P coatings under optimal conditions is 0.68 and 0.97 %/μm (before optimization — 6.72 %/μm). The obtained results can be used to improve the methodology for reducing the roughness of coatings with Ni – P and Ni – Cu – P alloys and, accordingly, to improve the functionality, wear resistance and quality of coatings.

An important chemical impurity in the composition of zirconium materials for nuclear power engineering is hafnium, the content of which should not exceed 0.05 and 0.01% for domestic and foreign alloy grades, respectively. Hafnium, being an analogue of zirconium in its chemical properties, is difficult to be analyzed using classical methods of analytical chemistry. Among the physical methods, the X-ray fluorescence method is the most expressive, which is important in conditions of continuous production. The method of X-ray fluorescence for measuring the content of hafnium in zirconium-containing material has been tested on the example of potassium fluorozirconate, a precursor for obtaining alloys. With various combinations of crystal analyzers, detectors, and collimators of the wave-dispersive spectrometer, the ratios of the intensities of the analytical lines of Hf and Zr in the second order of reflection were refined, and the degree of decrease in the fluorescence intensity of those lines was determined. The X-ray fluorescence spectra of hafnium lines in potassium fluorozirconate at the content characteristic of nuclear-pure zirconium are studied. The possibility of recording the intensity of the Hf analytical lines and methods of eliminating the interference from the Zr lines in the second order of reflection are considered. The metrological characteristics are calculated for Hf analytical lines. It is shown that the smallest error and the lowest detection limit (0.001%) is provided when using the HfLβ1 line at certain settings of the wave-dispersive spectrometer, including the X-ray tube operation mode, a combination of a crystal analyzer, a detector and a collimator, as well as the amplitude discriminator settings. The method of accounting for the background is recommended. The proposed method of hafnium determination is applicable to the materials with a constant content of zirconium.

In order to solve the problem of choosing the compositions of high-entropy alloys (HEAs) consisting of five or more elements, it is necessary to use methods that considers many variables and the complexity of estimating the relationships between them. Based on chemical-information approaches to the analysis of Web of Science databases, information on the frequency of use of chemical elements in the described HEAs has been obtained, which make it possible to identify trends in the research and development of new materials.

The article analyses opportunities for enhancing resource and environmental efficiency of modern electroplating processes. These parameters highly depend on metal and water use efficiency. Water is consumed primarily for washing details after the plating. Authors analyse reasons for changing water intensity of electroplating processes and opportunities for reducing water consumption while implementing Best Available Techniques (BAT). Data on solution carry-over published in the research literature, norms and standards are compared. Various periods of the technology development and environmental regulation are considered (1939 to date). Specific water consumption grows since 1970s which is caused both by the increase of concentrations of main components of technological solutions and by the introduction of GOST 9.047-75 standard. The standard sets an elevated solution carry-over value: if in 1959-1968, this value varied between 0.055 and 0.073 L/m(2), in 1972 the new value was set at 0.2 L/m(2). Authors assume that this decision was caused by the environmental regulation requirements which became more stringent at that time. Increased solution carry-over norms allowed using water to dilute wastewater and thereby to reduce concentrations of contaminants. The average solution carry-over value is 0.065 L/m(2), while the most probable values vary between 0.04 and 0.08 L/m(2) and may be considered as environmentally and resource sound when setting BAT requirements for designing electroplating processes. For the two-stage washing process, parameter (qK(1/2)) is calculated. This parameter characterises the specific washing water volume. Annual water consumption in the electroplating processes is assessed. The consumption calculated based on existing norms, varies from 3.4 to 6.2 mln m(3) per year; it is 2.5 times higher than the consumption reported in the research articles.

The deposition of bicomponent composite coatings containing both hard and soft particles is studied. Technologically important characteristics (deposition rate, coating composition) of electroless deposition of bicomponent Ni—Cu—P— Cr2O3—MoS2 composite coatings from slightly acidic baths are determined. Bath composition, mol/L: NiSO4 — 0,12; CuSO4 — 0,0016; NaH2PO2 — 0,37; NH2CH2COOH — 0,13; Succinic acid — 0,18; Pb (CH3COO)2 — 10–5; рН 6,5. A mixture of dispersed hard particles (Cr2O3) and soft particles (MoS2) was added to the solution for electroless deposition of a copper doped Ni—P alloy. It was found that when adding a mixture of dispersed Cr2O3 (40...25 % wt.) and MoS2 (60...75 % wt.) at a concentration of 10 g/L, the solution remains stable during deposition and allows the formation of Ni — Cu (1...1.5 wt.%) — P (4 wt.%) — Cr2O3(3 % wt.) — MoS2 (0.12— 0.16 % wt.) coatings at a rate of 15 mg/(cm2 •h). Deposited coatings after heat treatment at 400 °C has a microhardness of 11.1...11.2 GPA. It is concluded that the technology of electroless deposition of bicomponent composite coatings Ni—Cu—P—Cr2O3—MoS2 is promising for obtaining materials with increased hardness and wear resistance.

Composite coatings were obtained by electro-co-deposition of chromium with Graphite, TiN or wurtzite-like BN (w-BN). The content (vol.%) of the dispersed phase in the electrodeposits was equal to: Cr–Graphite – 10, Cr–TiN – 4, Cr–w-BN – 1. Cr-Graphite coatings showed no increase in the microhardness (HV), while their fracture toughness (K1c) and wear characteristics were better as compared to Cr deposits. The coefficient of friction in the tribopair “coating– steel” decreased from 0.32 (Cr) to 0.19 (Cr–Graphite) under conditions of dry friction and from 0.05 (Cr) to 0.03 (Cr–Graphite) in the presence of a lubricant. The inclusion of TiN particles into a Cr-matrix resulted in an improvement in both HV and wear resistance (WR) of the coatings. A significant increase in WR (70–170 %) was obtained for Cr–w-BN coatings with small content of the dispersed phase. Therefore, Cr–Graphite, Cr–TiN, Cr–w-BN electrodeposits may be considered as promising wear-resistant materials.

The distribution of coatings by the frequency of their application during surface treatment by electrochemical methods is considered. This is important not only for understanding the structure of the electrochemical surface treatment sector, but also for identifying priority areas of scientific and technical research. Nonparametric statistical methods show the uniformity of samples and reveal the relationship between the number of enterprises that sell a certain type of coating, i.e. the frequency of applying a certain type of coating in different countries (USA, Japan, Italy, France, Germany, Great Britain, Spain, Canada, Mexico, Russia, South Africa). The results of testing the hypothesis of a close relationship between the ranks of coatings showed that a significant correlation was found between the distribution of coatings by the frequency of their application (implementation) among all countries. For example, when comparing the United States and Canada, the rank correlation coefficient is 0.62 (the lowest value obtained), which is greater than the calculated critical value of 0.56; when comparing Italy and Spain, the correlation coefficient takes the highest value of 0.97, which is greater than the critical value of 0.19. The results obtained allowed us to use this data to compile a generalized rating of the frequency of use of all coatings based on data from different countries. Based on the analysis, metal coatings can be arranged in a row according to the descending frequency of their application: Cr > Ni > Zn > Cu > Cd. The results of the ranking of coatings showed that the most commonly used electrochemical methods for surface treatment are metal coatings with chromium and nickel, and among the inorganic non – metallic coatings-oxide and then phosphate, which allows us to highlight the research devoted to the application of these coatings as priority areas of scientific and technical research.

Citations are currently one of the most important indicators of scientific performance. In this work, we set out to analyse the dynamics of publication activity and the citations of Russian researchers in foreign journals in comparison with similar indicators for foreign researchers published in Russian journals. Using the methods of nonparametric statistics, we studied citation indicators for 5 journals from different research areas published in 4 foreign countries (Germany, the Netherlands, Great Britain and the USA) and Russia. An additional research instrument was the content analysis of scientific article reviews. A statistically significant decrease in the citation of Russian authors by both foreign (from 1,4 to 0,4%), and Russian scientists (from 21,8 to 11,2%) in foreign journals in the period under review was observed. If this trend persists over the following five years, the citation of authors affiliated with the Russian Federation will decrease to a minimal level, which may negatively affect the international ratings of Russian scientific organizations. Recommendations on curbing the identified negative dynamics include the need to improve the quality of scientific research and publications, as well as to stimulate reasonable citation of the works by Russian authors in translated editions included in international databases.

The paper proposes a method for the neutralization of mercury-containing waste, corresponding to the principles of green chemistry (carrying out reactions at normal pressure and temperature, the absence of wastewater formation), based on the quantitative binding of metallic mercury and its compounds into water-insoluble and insoluble in dilute acids, mercury sulfide (II). Solid-phase reactions in the system mercury-glass-sulfur (iron sulfide, pyrite) were studied to ensure the maximum complete conversion of metallic mercury contained in the waste into mercury (II) sulfide. As a reactor for carrying out such reactions, it has been proposed to use ball and / or vibrating mills, which help to disperse the mercury. On the basis of a series of experiments on the mechanochemical immobilization of mercury from imitation mercury-containing wastes, the most optimal conditions for the reaction are described in detail. The rest of the mercury, up to safe concentrations in the proposed approach, must be immobilized by adding oxidizing agents (for example, potassium permanganate, hydrogen peroxide). Provision of draining and pumping of reaction masses and reaction products is achieved by adding 10-15% bentonite (GNB-30 grade) and water to the reactors in the experimentally established solid: liquid ratio = 1:4. The level of migration of mercury sulfide from the resulting product into water bodies was also investigated, as well as the subsequent potential impact of mercury on plants. The results obtained indicate the possibility of using the proposed method of chemical demercurization, as a result of which mercury sulfide is formed. The resulting neutralized waste can be considered non-hazardous and subject to disposal at landfills (in accordance with the Federal Classification Catalog of Wastes).

In this paper the effect of parameters such as concentration of glycine, succinic acid and bath pH on the technological parameters of the electroless deposition of nickel-phosphorus alloy coatings (deposition rate, specific pH change during deposition), the composition of the coatings and their properties (microhardness after heat treatment) was studied. Experimental design of 23 central composite design (CCD) was used to evaluate the appearance of coating, rate, specific pH change, the chemical composition of alloys, and microhardness, as well as to optimize the electroless process of the alloy using Response Surface Methodology (RSM) associated with experimental design. The microhardness of the deposited coatings was 4.6 - 6.8 GPa and after heat treatment at 400 °C for 0.5 h increased to 9.7-11.6 GPa, which corresponds to hard chromium coatings obtained by electrodeposition from solutions of chromic acid. The Harrington desirability function was applied for optimization. The optimal composition of bath (in mol/l) and electroless conditions are proposed: NiSO4·6H2O – 0.12, NaH2PO2·H2O– 0.36, NH2CH2COOH – 0.30, (CH2)2(COOH)2 – 0.20, Pb(CH3COO)2 - 10-5; pH – 5.8. Temperature – 70 – 96 ºС. An acceptable rate deposition of 8 (70 ºС) and 34 (95 ºС) mg/(cm2∙h) was observed for an alloy obtained under optimal conditions from an solution of optimal composition. Under these conditions, the coating contained 6 wt.% of phosphorus. Therefore, the results of this work show the importance of using optimization techniques to obtain metallic coatings with controlled properties for different types of applications.

The production of purified sodium bicarbonate is accompanied by the formation of wastewater containing sodium carbonate and bicarbonate. Up to 1.5 m(3) of wastewater is formed per 1 t of purified sodium bicarbonate. Wastewater contains about 23.5 g/l sodium carbonate and about 40.4 g/l sodium bicarbonate. The article presents the results of studies related to the processing of wastewater generated in the production of purified sodium bicarbonate in a membrane electrolyzer with a cation exchange membrane. The waste water treatment process was carried out at a membrane current density of 30 mA/cm(2) to 60 mA/cm(2). It is shown that in the process of electrochemical processing of wastewater, sodium carbonate is extracted first, and then sodium bicarbonate is extracted. At the same time, during the electrolysis, sodium hydroxide is formed. The maximum concentration of sodium hydroxide achieved in the process was 362 g/l. The current efficiency of the electrolysis process calculated by changing the concentration of sodium hydroxide depends on the membrane current density. The maximum current efficiency is observed at a current density of 30 mA/cm(2) and equals 64.3%. The specific energy costs of sodium hydroxide producing increase with increasing current density. The minimum energy consumption was 2.2 kWh/kg.

In this paper the effect of parameters such as current density, temperature, electrolytic bath pH and concentration of chromium sulfate and sodium hypophosphite on the electrodeposition process of the Cr-P alloys was investigated. Chemical composition of the coatings was evaluated by scanning electron microscopy and X-ray diffraction. Experimental design 25-1 central composite design was used to evaluate the chemical composition of alloys, current efficiency and the appearance of coatings as well as to optimize the electrodeposition process of the alloy using Response Surface Methodology associated with experimental design. The Harrington desirability function was applied for optimization. The optimal composition of bath (in g/l) and electrolysis conditions are proposed: Cr2(SO4)3·6H2O – 285, Al2(SO4)3·12H2O – 120, Na2SO4 – 50, NaH2PO2·H2O – 20, CO(NH2)2 – 70, рН – 1.3, temperature – 35 ºС, current density – 46 А/dm2. An acceptable current efficiency 13-14 % was observed for an alloy obtained under optimal conditions of 46 A/dm2, 35 °C and pH 1.3 from an electrolyte of optimal composition. Under these conditions, the coating contained 16 wt.% phosphorus. The alloys were X-ray amorphous at a phosphorus content of about 6 wt.%. When the phosphorus content was 16 wt.% the alloys became nanocrystalline and the chromium phosphide – Cr3P phase was released, which can be seen from the peaks on X-ray diffractograms. This indicates the formation of Cr-Cr3P nanocrystalline composite coatings under nucleation conditions (in Statu Nascendi). Therefore, the results of this work show the importance of using optimization techniques to obtain metallic coatings with controlled properties for different types of applications.