Inorganic Materials: Applied Research最新文献

Abstract—The impurity composition of diborane synthesized by the hydrogenation reaction of boron chloride was studied for the first time with the chromatography–mass spectrometry method. A GS-GasPro 60 m × 0.32 mm capillary column with silica gel as a sorbent, a GS-CarbonPLOT 25 m × 0.32 mm × 0.25 μm column with a carbon sorbent, and a DB-5MS 30 m × 0.32 mm × 0.25 μm column with methylsiloxane were used to separate impurities. The impurities were identified by comparing their mass spectra with those from published data. The impurities of B₄–B₁₀ higher boranes, cyclohexane, and toluene were identified in diborane. B₆–B₁₀ boranes, cyclohexane, and toluene were found for the first time. The mass spectrum of B₉H₁₅, which was not found in the literature, was obtained and described.

Abstract

A method for quantitative evaluation of the porosity in carbon fiber reinforced plastic (CFRP) structures based on laser excitation of probe ultrasonic pulses is presented. The technique of estimating the porosity level in a material has been proposed using the experimentally measured phase velocity of longitudinal acoustic waves propagating in this material. By the example of control samples and actual CFRP structures, the possibility of obtaining maps of the local porosity distribution in the studied region of the structure has been demonstrated. It has been shown that in the structures studied, there are regions with a significant variation in the local porosity level. The proposed method can be used for quality monitoring of manufactured composite structures, as well as for studying the structural changes during operation of the structure.

Abstract

This article focuses on the process of producing ceramics based on the commercial Si₃N₄ powder of various dispersions (<5 μm and <1 μm) by spark plasma sintering (SPS). The powder mixtures of 97 wt % Si₃N₄ + 3 wt % additive of the Y₂O₃–Al₂O₃ composition are synthesized by the Pechini method. The SPS technology is used to obtain ceramic samples of ∅20 mm. The sintering is carried out in a vacuum at a heating rate of 50°C/min and a load of 70 MPa until the end of the shrinkage. The microstructure and phase composition of the ceramic samples are investigated. Mechanical properties are measured: Vickers hardness, Palmquist fracture toughness, and flexural strength according to the B3B (ball-on-three-balls test) method. Tribological tests are also carried out. It is established that the lower the dispersion of the powder mixtures based on Si₃N₄, the lower the end temperature of shrinkage. The relative density achieved is 96%. Ceramic materials based on Si₃N₄ powder with the dispersion of <1 μm are difficult to machine; they have the hardness of 19.0 ± 0.7 GPa and the crack resistance of 5.1 ± 0.4 MPa m^1/2. The flexural strength of the ceramics evaluated by the B3B method depends on the dispersion of Si₃N₄ powder; it is more than two times higher for the ceramics based on the commercial Si₃N₄ powder with the dispersion of <1 μm.

Abstract

A thermodynamic analysis of the chlorination of aluminum oxide was performed for the main possible reactions of interaction with chlorine. The process can only proceed in the direction of decreasing Gibbs energy (ΔG). The condition ΔG < 0 determines the fundamental possibility of carrying out the process under the given conditions and is determined only by the initial and final state of the system. The calculated Gibbs energy and the equilibrium constant in the temperature range of 400–1000 K show that, in the presence of a reducing agent, the reaction equilibrium is shifted towards the formation of aluminum chloride. It has been established that changes in the Gibbs energy of the chlorination reactions of Al₂O₃ polymorphs increase in the series γ-Al₂O₃, amorphous Al₂O₃, δ-Al₂O₃, and α-Al₂O₃. It is possible to assess efficiently the main principles of obtaining anhydrous aluminum chloride in a reacting system by assessing the change in the ratio of the starting components. A thermodynamic analysis of the Al–O–C–Cl and Al–O–C–Cl–Si–Na systems was performed at different component ratios. The latter system is a rough alumina containing sodium aluminosilicate. It has been shown that 100% yield of target products with the complete use of chlorine corresponds to the stoichiometry of their chemical interaction. The possibility of selective chlorination of Al₂O₃ and SiCl₄ has been determined. Sodium oxide, as demonstrated by calculations, is completely converted into chloride, which makes it possible to use the residue from chlorination to produce aluminum silicon alloys without sodium impurities.

Abstract

The mineral composition, petrographic structure, and magnetic properties of artificial glasses obtained from high-temperature melting of mixtures of rocks of various geneses (volcanic–sedimentary rocks, quartzite–shales, and psammite–silt–pelite complexes) are studied. When glasses were synthesized, cooling and glass transition conditions of various durations were used. The formation of ferrimagnetic minerals is due to the composition of the stock and the cooling rate of the melt. The resulting magnetic particles during “fast” cooling are mainly in the superparamagnetic state (up to 90% or more of the total amount of the magnetic phase in a sample). A mixture of particles of different sizes is formed during “slow” cooling and, as a result, in different magnetic states: from superparamagnetic to the low-domain state. The ferrimagnetic phase that crystallizes in artificial glasses is as chemically heterogeneous iron oxide aggregates, mainly non-stoichiometric magnetite.

Abstract

The sorption capacity of a highly porous carbon material obtained via high-temperature alkaline activation and activation with additional steam treatment was found. The resulting activated highly porous carbon material possessed a specific surface area of 2600–2700 m²/g and a pore volume of more than 1.3 cm³/g. High sorption activity was revealed relative to methylene blue (1075, 1865, and 2010 mg/g for carbonizate, AC-1, and AC-2, respectively) and the sunset (66, 934, and 972 mg/g for carbonizate, AC-1, and AC-2, respectively) organic dyes. The time to reach sorption equilibrium for the sorbents was found to be from 15 to 30 min. The resulting kinetic data were processed with pseudo-first-order and pseudo-second-order, Elovich, and intraparticle diffusion models. The pseudo-second-order model provided the highest correlation coefficients R² (when methylene blue dye molecules are removed, R² for AC-2, AC-1, and carbonizate are 1, 1, and 0.9999, respectively; when sunset dye molecules are removed, R² for AC-2, AC-1, and carbonizate are 1, 0.9999, and 0.9994, respectively). It was found that the chemical interaction proceeds between dye molecules and functional groups of a sorbent. It was revealed that the activated carbon material can serve as a highly effective absorber of organic pollutants from aqueous solutions.

Abstract—The effect of heat treatment (diffusion annealing, quenching, low-temperature and high-temperature tempering) on the structure, phase composition, and corrosion resistance of high-entropy 35Fe–30Cr–20Ni–10Mo–5W and 30Fe–30Cr–20Ni–10Mo–10W alloys has been studied. High-entropy alloys of the Fe–Cr–Ni–Mo–W system with different concentrations of tungsten are obtained by sintering mechanically alloyed powders in a vacuum furnace. It is revealed that the total and pitting resistance of the obtained high-entropy alloys to aqueous solutions of NaCl is higher than that of industrially produced austenitic corrosion-resistant steel 316L used in the oil and gas industry.

Abstract

The issues of synthesis of highly dispersed chemically homogeneous powders based on glaserite-like phases in the CaO–Na₂O–P₂O₅–SiO₂ (GeO₂) systems by a cryochemical method, including rapid freezing of a total salt solution, sublimation removal of ice, and subsequent thermolysis of a dehydrated salt precursor, are considered. The complex chemical composition of powders is necessary to create bioceramics from them with improved osteoplastic characteristics. Results of the synthesis of powders with submicron granulometry from solutions with different anionic composition are presented; the behavior of such powders during the sintering process is described.

Abstract—A method for producing tungsten powder consisting of spherical microparticles with dimensions of 20–50 μm is considered when processing granular tungsten nanopowder in a flow of argon electric arc thermal plasma. Experimental studies of plasma chemical synthesis of tungsten nanopowder in a plasma reactor with a limited jet flow during the interaction of tungsten trioxide with a flow of hydrogen-containing plasma generated in an electric arc plasma torch were carried out. The conditions of spray drying and the properties of a suspension consisting of tungsten nanoparticles were determined experimentally, ensuring the production of mechanically strong nanopowder microgranules of rounded shape with a homogeneous internal nanostructure that does not contain cavities, with the yield of microgranules with a size of less than 60 μm at the level of 65%. The influence of the parameters of the plasma processing of nanopowder microgranules in the thermal plasma flow on the degree of spheroidization and the microstructure of the resulting particles was established.

Abstract

Samples of unalloyed titanium VT1-0 with high strength characteristics (ultimate tensile strength of 820 MPa), which exceed the values for this material manufactured using conventional technologies, are produced by selective laser melting. To solve the problem of replacement of titanium alloys with commercially pure titanium in medical applications, unalloyed titanium VT1-0 with record mechanical characteristics (ultimate tensile strength of 1350 MPa) is processed by selective laser melting and rotary swaging. This value exceeds the characteristics of the high-strength Ti–6% Al–4% V alloy. The finely dispersed martensite formed as a result of high crystallization rates under the optimal mode of selective laser melting is the reason for the strength characteristics increase of unalloyed titanium VT1-0.