Inorganic Materials: Applied Research最新文献

Yttrium-doped titanium dioxide nanoparticles are synthesized using a hydrothermal method. Titanium dioxide nanoparticles with different yttrium content are characterized using infrared Fourier spectroscopy, diffuse reflectance spectroscopy, transmission electron microscopy, scanning electron microscopy, X‑ray diffraction, and small-angle X-ray scattering. Optimal processing modes (washing with solvents and subsequent thermal annealing) are selected to obtain particles with improved photocatalytic properties and minimal carbon content of residual organic derivatives. Yttrium-doped titanium dioxide nanoparticles demonstrate higher photocatalytic activity compared to the undoped sample, which is explained by the formation of additional energy levels within the band gap that reduces the intensity of the reverse recombination process. The results obtained facilitate the selection of the most optimal modes and methods for obtaining titanium dioxide nanoparticles with high photocatalytic activity.

The mechanism of transition of colloidal nanoparticles of metallic zinc obtained by pulsed laser ablation (PLA) of a metal target in liquid with different pH into zinc oxide directly during PLA and their storage has been considered. It is shown that the rate of oxidation of metallic zinc particles in solution depends on the rate of two partial electrochemical reactions interconnected by the electron balance, namely, the rate of formation of the ionized form of zinc and the ionization discharge of oxygen dissolved in water. It has been revealed that the rate of oxygen delivery through the Prandtl boundary layer is the limiting stage of the zinc oxide phase formation process. As well, a number of powder samples are obtained using the PLA of metallic zinc in weakly acidic, neutral, and alkaline aqueous media and drying of the resulting colloidal solutions; their composition has been analyzed. According to X-ray phase analysis, exposure to atmospheric oxygen leads to significant further oxidation of the obtained powders; however, a metallic phase was detected in the sample after PLA in an alkaline medium. Thus, varying the conditions of the PLA provides wide opportunities for obtaining a final product with a specific composition and properties.

The microstructure and microhardness of a Ni + WC–12 wt % Co + Ni + WC–12 wt % Co + Ni plasma-enhanced layered coating on a cylindrical titanium substrate after friction treatment (FT) with simultaneous pressure by two high-speed steel tools has been analyzed. The experiments were performed with substrate rotation and tool movement along the generatrix of the substrate. The main FT parameters, that is, the linear velocity of the coating during its rotation and the shear force of tools on the coating, determine the power of the process of up to 0.77 kW. This work on the coating, as related to its area of 34 J/mm², determines the process temperature of up to 1391°C. Local deformation of the coating during FT on substrates with smooth and threaded surface profiles with a height of 89–371 μm compacts the coating to a greater extent in its upper part and above the ridges. The microhardness of the layer (WC–12 wt % Co) of the coating in the state after plasma spraying with an indenter load of 200 G was 6.91 GPa and 12.09 GPa at P = 20 G; after FT the microhardness increased to 18.92 GPa with an indenter load of 200 G and to 21.56 GPa with a load of 20 G, which corresponds to the microhardness of the sprayed powder.

The heat capacity of the AlBe1 aluminum alloy (Al + 1 wt % Be) with magnesium additives in the cooling mode has been determined using the known heat capacity of a copper reference sample. Processing the cooling rate curves of samples of AlBe1 alloy with magnesium and the reference (Cu grade M00) resulted in deriving equations to describe the temperature dependence of the cooling rate. Based on the experimental finding the cooling rates of alloy samples and the reference and knowing the sample mass the polynomials of the temperature dependence of the heat capacity have been determined. The polynomials are described using a four-term equation. The integrals of the specific heat capacity allow one to find the temperature dependencies of the change in enthalpy, entropy, and the Gibbs energy for the AlBe1 aluminum alloy containing magnesium. Using the polynomial dependencies we obtained, it is shown that with increasing temperature the heat capacity, enthalpy, and entropy increase in alloys, whereas the Gibbs energy decreases. Adding magnesium in the studied concentration range (0.05–1.0 wt %) leads to an increase in the heat capacity, enthalpy, and entropy in the initial AlBe1 alloy, while the Gibbs energy decreases.

Abstract—The influence of tantalum on the microstructure and properties of AISI 316L stainless steel produced by direct metal laser deposition was investigated. A powder mixture for direct metal laser deposition was prepared by adding tantalum powder to AISI 316L alloy powder at 5 and 95%, respectively. Metal samples were printed at laser power settings of 180 and 200 W. A comparison of height and width in longitudinal and transverse cross-sections was carried out, along with analyses of microstructure, microhardness, friction tests, and elemental composition for the two types of samples that were produced. The effect of tantalum on the dendritic structure was demonstrated. It was established that the tantalum content in the alloy during laser metal deposition significantly influences the volumetric shrinkage of the samples and promotes the formation of secondary arms on the primary arms of dendritic crystals. Tantalum particles act as nucleation centers and also contribute to grain refinement of AISI 316L stainless steel. During direct metal laser deposition, tantalum particles do not melt completely and partially retain their original structure, as confirmed by elemental analysis.

Abstract—Laser-acoustic method of spot heating of stainless steel AISI 316L is under consideration. Equipment for carrying out experiments with and without the application of ultrasonic vibrations with a frequency of 40 kHz and a power of 100 W is developed. The microstructure of weld spots is analyzed based on the obtained optical images. A globular form of dendrites during processing with ultrasonic exposure is revealed in contrast to the columnar form of dendrites obtained during processing in the traditional way. An algorithm is developed for determining the percentage content of phase components of the obtained microstructure—austenite and the conventionally introduced “X” phase, which takes into account ferrite and other possible new formations in the structure of the weld spot. Comparative analysis shows that the content of the X-phase on the fusion line is almost the same, while in the central and mixed zones of the weld spot, its percentage content is 51 and 41% higher in the experiments carried out with ultrasonic exposure. The analysis shows an increase in the hardness of weld spots within 5%. A conclusion is made about the advisability of developing and using a laser-acoustic processing method.

The effect of ultrahigh frequency (microwave) curing on the microstructure and mechanical properties of three-component epoxy resins (ER) and glass fiber reinforced polymer (GFRP) has been studied. A comparative analysis of the manufactured samples of ER and GFRP cured by both traditional thermal and microwave methods was carried out. The optimal parameters of the microwave curing process for ER and GFRP were determined, which made it possible to obtain samples with high strength properties under standard tensile and bending tests. Comparative fractographic and microstructural studies of transverse fracture surfaces for ER samples cured by thermal and microwave methods were carried out using scanning electron microscopy (SEM). It has been established that the curing of ER by the microwave method leads to an increase in the size of globules and the number of pores in the material, a more pronounced local plastic deformation during the destruction of the sample, and to a greater variation in the ratio of the propagation velocities of the main and secondary cracks. Comparative studies of the microstructure of the cross-section surfaces and longitudinal cleavage surfaces were also carried out for GFRP samples cured by thermal and microwave methods. It was found that for GFRP samples cured by the microwave method the fracture during longitudinal cleavage is mainly cohesive, caused by the propagation of a crack through the matrix material.

Abstract—The effect of low-pressure direct current discharge on polyphenylene oxide films was studied. Filtered atmospheric air was used as the working gas. It was shown that plasma treatment leads to significant hydrophilization of the polymer surface during treatment at the cathode and anode. The storage of modified films in air leads to a decrease in hydrophilicity, which is more characteristic of films treated at the anode. The change in the chemical structure of plasma-modified samples was studied by X-ray photoelectron spectroscopy and the formation of a significant amount of oxygen-containing groups was shown during plasma treatment of films. The atomic content of oxygen increased to a greater extent after treatment at the anode. Using atomic force microscopy, the change in film morphology after exposure by plasma was studied and a significant increase in their roughness was established. The modified films had significantly higher selectivity of gas permeability for CO₂/CH₄, CO₂/N₂ and O₂/N₂ vapors without reducing the flow of CO₂ and O₂ relative to the initial values.

Abstract—Methods of introducing hydrogen isotopes into organic compounds without the use of solvents are described. Inorganic carriers, including nanomaterials, that are used to prepare reaction mixtures are given. The possibilities of a solid-phase method for introducing a deuterium or tritium label into organic compounds, including unsaturated and thermolabile compounds are shown. The influence of reaction conditions on the yield and degree of inclusion of the hydrogen isotope into labeled preparations is considered. An attempt was made to explain the obtained data by the processes that occur in the system hydrogen isotope–catalyst–carrier–nature of the compound.

This article studies nickel-based metal-ceramic materials with the addition of nanoparticles of refractory compounds in order to improve their mechanical properties and wear resistance. It is shown that aluminum-magnesium spinel nanoparticles and yttrium oxide microparticles play a key role in strengthening of material and blocking grain growth during sintering, which improves the mechanical properties. Nanoparticles help reduce friction and wear. X-ray and microscopic analyses of the cermets based on the NiAl–Al₂O₃ system are performed. The influence of sintering on the quality of composites is considered. The mechanical and tribological properties of composites with the addition of yttrium oxide and aluminum-magnesium spinel are determined. The influence of the structure and composition on the wear and friction of composites at different temperatures is considered. The microstructure and composition of wear tracks are analyzed, showing the improvement in the characteristics of composites with the addition of nanoparticles of refractory compounds. The importance of adding nanoparticles to improve the properties of nickel-based metal-ceramic materials in high-temperature applications is shown.