Архив

The article discusses the results of mathematical modeling of the one-sided pressing technological process of powder fluoropolymer materials. The peculiarity of the theoretical description is the consideration of rheodynamics, structuring and kinetics of compaction of the compressed medium. An important point of such a description is the choice of rheological equations. In what follows, it is assumed that the compaction of the material occurs according to the mechanism of viscous flow of the mass into pores (according to the theory of Ya.I. Frenkel). The rheological properties of such a medium, i.e. the ability to deform and flow, are determined by the properties of the solid phase, the presence and degree of porosity. Two variants of the technological process of pressing are considered depending on the externally specified conditions for the movement of the press plunger: modes of a constant specified force or its constant speed. The analysis of numerical calculations for each of these modes made it possible to identify their fundamental features. It was found that in the mode of a specified force, progressive autobraking of the compaction process occurs over time. It is shown that for pressing materials in both modes it is necessary to select such parameters when the time of structural transformations is longer than the compaction time. The conducted analysis allowed to develop specific recommendations for forecasting rational modes of one-sided pressing of powder materials.

This paper presents the aspects of the formation of multilayer composite material (MCM) consisting of aluminium-magnesium alloy AlMg6, titanium VT1-0 and austenitic stainless steel 12Cr18Ni10Тi during explosive welding. This MCM has promising properties for use in various industries such as shipbuilding and automobile manufacturing. However, the production of this material presents certain difficulties due to different properties of the initial materials. In this paper, the effect of residual stresses occurring in MCM after explosive welding on the continuity of the joint was investigated. Using metallographic studies and electron microscopy, it was found that the high velocity impact process between different materials comprising MCM formed weld interfaces with straight and wavy profiles. There was also evidence of dynamic recrystallisation at the 12Cr18Ni10Ti–VT1-0 weld interface and the formation of vortex zones in wave crests. The microhardness of the layers was also measured. The measurement showed that hardening occurred in MCM layers with the maximum value in the 12Cr18Ni10Ti steel layer. The evaluation of tear strength revealed that the formation of cracks occurred at the interface between the VT1-0–AlMg6 weld interface, with an average strength of 160 MPa. The results of the study may be useful to specialists in materials science, mechanical engineering and other related fields

The aim of this study is to develop nanostructured protective coatings with high chemical resistance for metal surfaces. To modify paints and varnishes, compositions based on carbon nanotubes (CNTs), bismuth oxide nanoparticles, silicon dioxide, titanium dioxide, magnesium hydroxide and aluminum hydroxide were used. The introduction of nanomaterials into acrylic paint and varnish material helps to increase the adhesive strength of coatings, so the best effect was determined with the introduction of CNTs in the amount of 0.1 % – the adhesive strength increased from 2.0–2.2 MPa to 2.9–3.1 MPa with a change in the nature of the separation of the paint and varnish coating from the substrate from fully adhesive (100 %) to adhesive-cohesive. Evaluation of the chemical resistance of nanostructured paint and varnish coatings modified with CNTs showed that when the coatings were exposed to an herbicide solution, they retained their weight regardless of the concentration of the modifier, while their hardness did not change (H). Evaluation of the equilibrium swelling rate made it possible to determine that paint and varnish coatings modified with bismuth oxide nanoparticles and CNTs are resistant to solvents and acquire a more mesh structure in relation to coatings without additives. Scanning of various sections of the sample surfaces on atomic force microscope (AFM) showed that when modified with bismuth oxide and CNT nanoadditives, the surface becomes smoother, and the nanometer roughness decreases from 50–60 nm to 20–30 nm. A more significant reduction in protrusions is observed in coatings modified with CNTs, which indicates that the coating is strengthened by reducing the size of depressions and pores.

In this paper, we study the capabilities and some features of direct electron-beam lithography using a layer of silicon dioxide SiO2 (grown by thermal oxidation) as a resist sensitive to the action of the electron beam and a developing composition based on an aqueous solution of dilute buffered hydrofluoric acid. Additional factors influencing the lithography result (the existence of an initial period of exposure effect enhancement) are found. To explain this feature, a hypothesis about the mechanism of the influence of the electric charge introduced into the SiO2 layer (during exposure) on the process of further development of the latent image is proposed. As a measure eliminating the manifestations of contamination phenomena, an approach using a sacrificial copper layer applied during the exposure period is proposed. A rationale for choosing the metal of the sacrificial layer is given based on experimental observations and a hypothesis about the possible chemical composition of contamination spots in the exposed areas. The parameters of the direct lithography process on SiO2 known from the literature are clarified. The nonlinear nature of the effect of the electron beam on the silicon dioxide layer is found and simple empirical dependencies that allow a quantitative description of the result of the lithography process for the case of large-scale structures are proposed. It is shown that even when using a sacrificial copper layer, it is possible to achieve a lithographic process resolution of no worse than 30 nm.

The paper presents a theoretical study of the sorption mechanisms of tripropylamine, triisopropylamine, trihydroxypropylamines, and tetrapropylammonium chloride on the surface of copper phthalocyanine containing a metal atom, using density functional theory. The critical points of QTAIM, IRI, and charge distributions in sorbate-sorbent complexes were analyzed to investigate the interaction mechanism between the sorbate molecule and the surface. It was found that trialkylamines exhibit a higher binding energy with the surface than trialkylaminoalcohols due to their lower interaction energy with the solvent. In all cases, the binding of sorbate molecules to the surface is primarily driven by electrostatic and dispersion interactions; however, the presence of bonds with orbital overlap significantly enhances the stability of the complexes. The complex with the quaternary ammonium salt is the most stable due to a combination of electrostatic and orbital interactions. In the complex with a quaternary ammonium cation, significant polarization of the surface toward the crystal interior is observed, which may increase the interaction energy between molecules in the surface layers and reduce the solubility of modified particles in polar solvents. In all complexes with orbital overlap, the 3 2 z d -orbitals of the copper atom contribute from the surface side.

This study synthesized nanocomposite activated carbon (AC) from plant raw materials (peach production waste), modified with carbon nanotubes (CNTs). The first stage in obtaining all samples involved hydrothermal carbonization (HTC) of peach pomace in an aqueous environment with the addition of a specific amount of CNTs, after which the biomass was gradually carbonized and activated using an alkali (KOH) in an inert atmosphere. The aim of the study was to evaluate the effect of CNTs on the structure and physicochemical and functional properties of the nanocomposite AC. It was established that the carbon obtained from the initial mixture containing 0.05 wt. % CNTs showed a specific surface area according to the BET model of 2876 m2⋅g–1 and a total pore volume of 1.643 cm3⋅g–1. It is presumed that the interaction of the biomass with the nanotubes occurs at sites on the surfaces of the samples after HTC, where functional groups are located. The sample with 0.05 wt. % CNTs exhibited minimal ID/IG and d100 values, indicating a higher order of the carbon structure. For all carbons, the sorption capacity relative to synthetic dyes – malachite green (MG) and Congo red (CR) – was determined. A general correlation was found between the changes in the ID/IG and d100 values and the activity of the AC samples. The AC with 0.05 wt. % CNTs demonstrated the highest capacity for both dyes in static mode: 2987 mg⋅g–1 for MG and 1201 mg⋅g–1 for CR, respectively. For this particular sample, an assessment of the sorption kinetics was conducted

This article explores a modern approach to the design of carbon dioxide (СО2) sorbents based on the concept of the potential energy landscape (PEL). The authors analyze the relationship between PEL characteristics and СО2 sorption efficiency. The article demonstrates how the manipulation of PEL parameters enables the development of optimized materials with desired sorption properties. The article examines the influence of the depth and distribution of energy minima on the selectivity, capacity, and kinetics of СО2 sorption. Various strategies for modifying the PEL, including surface functionalization and the targeted introduction of defects, to achieve the desired sorption characteristics are highlighted. Examples of different types of sorbents, such as MOFs, zeolites, and activated carbons, designed within the framework of the PEL concept are presented. Potential applications of the developed sorbents in carbon capture and storage technologies, as well as the synthesis of chemically valuable products have been considered. This review will be of interest to materials science and energy specialists involved in the development of new sorption materials.