Inorganic Materials: Applied Research最新文献

Abstract

The production of homogeneous Ti–10Nb–(1–3)Mo (at %) alloys in the form of semifinished products (plates) was studied through multiple remeltings and homogenization annealing. Metallographic studies of the resulting materials in cast, rolled, and annealed states were carried out. The effect of annealing and composition on the structure, phase composition, and mechanical properties of the Ti–10Nb–(1–3)Mo alloy was revealed. Homogeneity after smelting was achieved by annealing at a temperature of 950°C for 12 h. An increase in the Mo content in the Ti–10Nb–(1–3)Mo alloy led to an increase in the strength of the alloys, while the ductility decreased. The achievement of high strength characteristics in selected alloys was associated with the development of annealing parameters after plastic deformation, namely, controlling the size of recrystallized grains and separating the α and β phases. In addition to α-Ti and β-Ti, the samples contained small amounts of ω-Ti, which led to a sharp increase in the hardness of the samples.

Abstract

γ'Ni₃Al-based casting alloys have a lower density, higher melting point and resistance to oxidation, and a higher ceiling of operating temperatures than modern heat-resistant nickel alloys. The article discusses the features of the electronic structure and crystallization of domestic (such as VKNA/VIN) and the most advanced foreign (γ' + γ) low-alloyed γ'Ni₃Al-based alloys (IC type), and experimental data on the nature of the structures formed during directional crystallization of alloys with different types of alloying and on the nature of the distribution of components in the γ'Ni₃Al and γNi phases and structural components in the cellular-dendritic structure of single crystals with 〈111〉 and 〈001〉 crystallographic orientation are presented. The influence of heat treatment on the microstructure, distribution of alloying elements, and mechanical properties of the VKNA type alloys is investigated in a wide range of temperature–time parameters. A comparative analysis of the effect of temperature and duration of heat treatment and cooling rate after heat treatment on the heat resistance of alloys showed that, unlike other Ni₃Al-based alloys, for single crystals from the VKNA type economically alloyed alloys and parts made from them (uncooled working blades of aviation gas turbine engines, nozzle apparatuses, jet nozzle spacers, and other parts of the hot path of gas turbine engines), a short-term heat treatment (1150°C/1 h) is necessary and sufficient to relieve casting stresses. The alloys demonstrate high heat resistance at 1100–1200°C and the ability to withstand short-term casting temperatures up to 1250–1300°C.

Abstract—A percutaneous delivery system for nicotinamide is developed and its functional properties are studied in vitro. Four compositions of the emulsion percutaneous delivery system for a nicotinamide transdermal therapeutic system (TTS) are suggested, in which the amount of the percutaneous carrier, docusate sodium, is varied. The performed studies of the diffusion of nicotinamide in vitro through unpreserved rabbit skin show that increasing the concentration of docusate sodium threefold (from 3.3 up to 9.8%) significantly increases the amount of the diffused drug substance by ~15% and decreases its residual concentration in the TTS. The amount of the antioxidant detected in the skin flap is lower than the therapeutic dose (~1.46% of its initial amount in the TTS) within 24 h after the start of the in vitro experiment, which indicates the absence of a possible aftereffect of the nicotinamide TTS in its clinical use after detaching from the patient’s skin.

Abstract

The content of oxygen and nitrogen in nickel-based powders and plasma coatings made of them has been studied. The Ni-based sprayed materials were divided into four groups according to the mechanism of their interaction with oxygen: (i) Ni; (ii) alloys alloyed with Cr; (iii) alloys additionally alloyed with Al; and (iv) alloys with more complex alloying with Cr, C, B, and Si, which actively interact with oxygen, including the formation of gaseous oxides. Alloying with 20% Cr (hereinafter in wt %) reduces the oxygen content in the coating by 35%, alloying with 17% Cr–10% Al reduces the oxygen content by 57%, and more complex alloying with 13.5% Cr–2.7% Si–1.65% B–0.36% C reduces the oxygen content by 92%. Increasing the plasma jet power increases the oxygen content in the Ni–20% Cr coating from 0.55 to 1.6%. Increasing the plasma jet power and preheating a substrate before spraying results in a limited increase in the oxygen content in the Ni–17% Cr–10% Al–1% Y and Ni–15% Cr–4% Fe–0.8% C–4.1% Si–3.1% B coatings using a plasma nozzle, which eliminates the thermal effects of the plasma jet and restricts the supply of atmospheric oxygen in the formation zone of the coating on the substrate. The Ni–17% Cr–10% Al–1% Y coating sprayed with the nozzle contains 0.48% O and 0.14% N instead of 2.31% O and 0.37% N when sprayed without the nozzle. An increase in the content of oxygen and nitrogen in the Ni, Ni–20% Cr, and Ni–40% Cr coatings together with the formation of a liquid-hardened structure in these coatings determines an increase in microhardness relative to that of the powder by 1.6–1.9 times.

Abstract

The progress in making macro- and mesoporous layers of porous silicon formed through Pd-assisted etching is analyzed. Different formation times and etching solution temperatures (varying from 25 to 75°C) are taken as the parameters. The layers of porous silicon obtained exhibit ethanol electro-oxidation properties. High values of the dissolution rate of the porous silicon are confirmed at a temperature of 75°C resulting in dramatic thinning and decreasing the specific surface area of the macro- and mesoporous layers, respectively. The resulting porous layers have different surface energies and surface areas. The samples exhibit different rates of ethanol dehydrogenation and differ in the number of dehydrogenated ethanol molecules. This is promising to control the activity of the electrode material in ethanol fuel cells.

Abstract

Co–Mg alloys have not been studied in sufficient detail. Information available in the literature relates to the study of changes in the Co–Mg system in composition–temperature coordinates. However, this does not take into account the significant difference in the vapor pressure values of Mg and Co in the alloy, which significantly reduces the accuracy of the results obtained. It is proposed to analyze the Co–Mg system in the coordinates composition–temperature–pressure. A detailed description of the state diagram of the system in pressure–temperature coordinates is given, projections of three-phase equilibrium lines are determined, individual isobaric and isothermal sections of the spatial p–T–x state diagram of the Mg–Co system are constructed, and the state diagram of the Co–Mg system in temperature–partial pressure of Mg coordinates is presented. The results obtained can be successfully used in the development of ternary and more alloys containing cobalt and magnesium.

Abstract

Influence of various organic and modifying additives on the technological properties (fluidity, bulk density, and compactibility) of G13 powder steel, with different mixing options, is considered. It has been found that the compaction of G13 powder mixture with copper stearate and nickel stearate is the most effective. Of the carbon-containing components considered, the best compaction occurs with the introduction of graphite. The most acceptable technological properties in terms of fluidity and bulk density have been obtained from a powder mixture of composition Fe + 14 wt % FeMn + 1.1 wt % C + 0.2 wt % WC(nano). Introduction of organic additives worsens the fluidity of a mixture, but increases its density.

Abstract

Granules of a chitosan–titanium dioxide composite material with different concentrations of titanium dioxide nanoparticles for agricultural use are obtained. The average diameter of the granules is 35 mm. It is shown that varying the concentration of titanium dioxide nanoparticles in the composite material within the studied limits does not affect the structure of its surface. Experiments are carried out in situ on the seeds of cucumber (Cucumis sativus). It is noted that, during the first three weeks, the composite material has an inhibitory effect on plant growth, and then, after the onset of dissolution of the granules, it has a growth-stimulating effect. The best growth rates are observed when two granules of a composite material with a ratio of chitosan to titanium dioxide of 3 to 1 are added to the soil. It is concluded that the obtained granules of a chitosan–titanium dioxide composite material can have a positive effect on the processes of plant growth and formation.

Abstract

A new macroporous cryogenically structured biomimetic of the extracellular matrix (ECM) was prepared on the basis of a commercially available concentrated collagen-containing solution, and the possibility of its use in tissue engineering was assessed. Spongy collagen-containing material was fabricated by sequential freezing of a concentrated collagen-containing solution, its subsequent lyophilization, followed by chemical tanning by treatment with an alcohol solution of carbodiimide. The morphology of the cryostructured multicomponent collagen-containing material was studied by optical and scanning electron microscopy (SEM) using lanthanide contrast. The cytotoxicity of the matrix was studied in a culture of human adipose tissue-derived mesenchymal stromal cells (hADSCs). Adhesion and proliferation of hADSCs on the surface of the matrix were studied on the seventh day of cultivation. The compression modulus of elasticity of the resulting collagen-containing material in a water-swollen state was 35.3 ± 2.2 kPa, the total water-holding capacity of the material was 45.80 ± 0.46 mL/g of polymer, and the degree of swelling of the macropore walls was 3.99 ± 0.31 mL/g. During SEM examination and histological staining with hematoxylin and eosin, a large-pored structure was observed on the surface and cross section of the disk. The pores in the upper part are larger (average diameter at least ~30 µm) than the pores in the lower part of the sponge (average diameter at most ~30 µm) owing to the occurrence of a vertical temperature gradient. The matrix did not have cytotoxicity toward hADSCs. In the sample, active proliferation of hADSCs was observed on the surface of the matrix. The lack of cytotoxicity and the ability to support the adhesion and proliferation of hADSCs indicate the possibility of using cryogenically structured extracellular matrix biomimetic in tissue engineering and regenerative medicine.

Abstract

The electrocatalytic activity of a new composite material based on η-carbide Nb₃(Fe, Al)₃C in the hydrogen evolution reaction from acidic and alkaline solutions is studied. The composite was obtained by spark plasma sintering of mechanically alloyed niobium, aluminum, and graphite powders in steel containers in petroleum ether, followed by etching in an alkaline solution or in a hydrofluoric acid solution. The composite consists of 78 wt % Nb₃(Fe, Al)₃C, 19 wt % Nb₅Al₃C_x, and 3 wt % graphite; it has a layered structure with a layer thickness of the Nb₅Al₃C_x phase of 50–70 nm. In terms of the magnitudes of overpotential in the hydrogen evolution reaction, the resulting composite is superior to undoped Nb₂CT_x and Nb₄C₃T_x.