FEATURES OF APPLICATION OF GAS-THERMAL AND PLASMA METHODS FOR OBTAINING FUNCTIONAL COATINGS

The article provides recommendations for the modes and parameters of gas-thermal and plasma coating technologies in relation to flat friction pairs subject to uneven operational loads

High-efficiency 2D nanosheet exfoliation by a solid suspension-improving method

Two-dimensional (2D) materials with mono or few layers have wide application prospects, including electronic, optoelectronic, and interface functional coatings in addition to energy conversion and storage applications. However, the exfoliation of such materials is still challenging due to their low yield, high cost, and poor ecological safety in preparation. Herein, a safe and efficient solid suspension-improving method was proposed to exfoliate hexagonal boron nitride nanosheets (hBNNSs) in a large yield. The method entails adding a permeation barrier layer in the solvothermal kettle, thus prolonging the contact time between the solvent and hexagonal boron nitride (hBN) nanosheetand improving the stripping efficiency without the need for mechanical agitation. In addition, the proposed method selectively utilizes a matching solvent that can reduce the stripping energy of the material and employs a high-temperature steam shearing process. Compared with other methods, the exfoliating yield of hBNNSs is up to 42.3% at 150°C for 12 h, and the strategy is applicable to other 2D materials. In application, the ionic conductivity of a PEO/hBNNSs composite electrolytes reached 2.18×10−4 S cm−1 at 60°C. Overall, a versatile and effective method for stripping 2D materials in addition to a new safe energy management strategy were provided.

An imidazolium-based zwitterionic polymer for antiviral and antibacterial dual functional coatings

An imidazolium-based zwitterionic polymer is reported with dual functions of antivirus and antifouling with broad applicability.

A Review on Self-Cleaning Coatings for Tunnels

Self-cleaning coatings for tunnels can effectively remove dust and stains accumulated over the surface of tunnel linings and their appurtenances due to the closed environment and poor ventilation. This paper systematically introduces the current research status of self-cleaning coatings for tunnels, focusing on the development of super-hydrophobic self-cleaning coatings, superamphiphobic self-cleaning coatings, exhaust gas degradation coatings, fire retardant coatings, and tunnel de-icing coatings. The advantages and disadvantages of the five functional coatings are then briefly described, and the problems of self-cleaning coatings for tunnels at the present stage are pointed out. Finally, the development direction of self-cleaning coatings for tunnels is proposed to provide a reference for the research and application of self-cleaning coatings for tunnels.

Development of Porous Films Based on Polyanionic Cellulose to Form Functional Coatings

New porous films based on polyanionic cellulose with AlOOH nanoparticles have been developed. The morphology of the films has been studied by electron microscopy: the size of the formed pores is 1000-500 microns; the total surface porosity of the films is 30%. Using infrared microscopy, it was shown that during the formation of porous films, their chemical composition remains unchanged. Differential scanning calorimetry was used to determine the threshold for thermal destruction of porous films: 306 С. The possibility of using the obtained materials as antifriction coatings when filling the pores with solid lubricant MoS2 is considered. It is shown that for a steel sample protected by a porous coating with MoS2, the friction coefficient decreases by 50% compared to the friction coefficient for a steel surface under a load of up to 450 MPa.

Processes and technologies of cold gas dynamic spraying of products agricultural equipment

Modern equipment of processing industry, animal husbandry, bioenergy complexes is used for processing, storage or transportation of aggressive substances. Functional coatings made of inert materials do not enter into any chemical reactions with food, processed products, livestock waste, acids and other aggressive media. There is a question of protection of the equipment of the processing industry, animal husbandry, bioenergy complexes from aggressive environments by application of processes of a cold gas-dynamic spraying. This is an urgent problem for the development of protective technologies and appropriate equipment for the implementation of the process of creating functional coatings

Characterization of opportunity for upgrading of the system based on arc plasma torch for thermal spaying of ceramic materials, by means of use of fuel vortex intensifier. Part I: Thermodynamic modeling of the system efficiency parameters

One of the main trends in the field of improving the modern technologies of thermal spraying, including plasma one, for functional ceramic coatings formation is the reducing the energy consumption of the process. In this regard, one of the important directions for improving these technologies is the development of their new versions, using the principle of adding inexpensive fuel-oxidizer mixtures based on hydrocarbons with air. This type of plasma-fuel type of spraying will be promising for application at the present time, first of all, in order to obtain refractory functional coatings. For this purpose, we investigated the opportunity for upgrading an industrial unit/system for plasma spraying of ceramic powder materials with arc plasma torch of 25–40 kW power by the use of experimental variant of a fuel gas-vortex intensifier. The thermodynamic assessment of possible parameters of the generated mixed flow after the torch with this fuel intensifier was carried out to estimate the applicability of this system to optimize the spraying of oxide and carbide coatings (based on the examples of Al2O3, Cr3C2 and other powders). The analysis of possible parameters of the produced flow after the torch with intensifier was performed for the cases of main C–H–O–N–Ar–Me (Me = Al, Cr) systems and additional C–H–O–Al-system to assess the potential of this system to modify the technology of oxide and carbide ceramic coatings formation. New regimes, which were analyzed in our research as the simulants of Al2O3 spraying, surpass on calculated energy efficiency characteristics (by 10–20 %) one of the new prospective spraying methods with (СO2+СH4)-plasma, as well as the conventional method of powder heating during the spraying with N2-plasma. The case of our proposed fuel assisted process (FA-APS) with liquefied petroleum gas (LPG) fuel for the heating of ceramic powders (especially, Al2O3) demonstrates the advantage of the process (in particular, on the energy efficiencies and energy consumption) in a comparison with the conventional regimes of APS of the powders (in N2 plasma of the standard torch). For the variants of the FA-APS with Al2O3 and Cr3C2 feedstock powders it was established to be potentially possible to obtain (at the moderate values of total electric energy consumption for the torch and auxiliary equipment, – near 1.8 and 1.0 kWh/(kg of product)) such high level of the process productivity on the final product as approximately 17 and 28 kg/h, respectively; at the values of required power of the torch:  28.2 and  22.3 kW.

Sliding Wear Behavior of High-Temperature Vacuum-Brazed WC-Co-NiP Functional Composite Coatings

The present study aimed to investigate the tribological behavior of high-temperature vacuum-brazed WC-Co-NiP functional coatings deposited on 16MnCr5 case hardening steel. Dry sliding wear resistance was evaluated using a non-conformal ball-on-disk arrangement, at room temperature against 100Cr6 and WC-Co static partners, respectively. Morphological, microstructural, and chemical composition analyses showed a complex, phased structure composed of tungsten carbide, nickel, and hard cobalt-based η-structure. In the testing conditions, the coefficient of friction against 100Cr6 and WC-Co counterparts entered a steady-state value after approximately 1000 m and 400 m, respectively. The wear track analysis revealed phenomena of particles trapped between the sliding bodies, as well as gradual removal of asperities. The calculations of the wear rates proved that the values were strongly influenced by properties of the sliding system, such as crystal structure, stress discontinuities, hardness, and material homogeneity.

SELECTION AND ANALYSIS OF RAW MATERIALS FOR A PROTECTIVE AND DECORATIVE LAYER OF COMPOSITE MATERIAL

With modern housing construction, the cost of finishing work has increased significantly. The development of protective and decorative coatings is necessary, with architectural and artistic advantages and high performance properties with a slight increase in cost. It is necessary to develop a high-quality multilayer monolithic composite with a high degree of adhesion of functional layers to each other. Glass industry waste of various fractions and coloring salts of metals are proposed to be used for a decorative layer, which allows to obtain an almost unlimited color gamut of the coating during plasma chemical modification. The choice of application of high-alumina refractory and alumina cement in the protective layer is justified due to their high thermal resistance to sudden temperature changes. Compositions of a protective layer based on binders and a decorative layer using crushed colored container glass and coloring metal salts moistened with a 5% aqueous solution of liquid glass have been proposed, which makes it possible to significantly expand the raw material base for obtaining functional coatings on concrete. The melt heating temperature and the kinetics of its cooling are determined in order to identify rational rates and duration of high-temperature treatment for further coating creation. Rational rates of plasma processing of composite material for the formation of coatings of various textures are revealed