An impact mill has been developed to produce powders from shavings of refractory metals using the impact grinding method for reuse in electrometallurgy in devices with screw feed, for example, in 3D printers. The proposed device provides high uniformity of grinding with a minimum content of dust fraction and impurity content at low technical and economic costs. The result is achieved using a Laval nozzle, which operates in the supersonic jet formation mode. In the area of the first Mach disk, there are rod fenders arranged in a cascade, and the impact plate is located in the turbulence zone and is equipped with winglets with holes for separating crushed metal.

Hollow submicrometer-sized SiO 2 particles are synthesized, and changes in the structure and morphology of their shells during heat treatment are studied. The dependences of the shrinkage of silica shells on the temperature of annealing of particles are studied. It is found the shells of hollow particles are pore-free and impervious to liquids after annealing at 600°C.

Hollow SiO2 particles of submicron size were synthesized and changes in the structures and morphology of their shells during heat treatment were investigated. The dependences of the shrinkage of silica shells on the annealing temperature of the particles were studied. It has been found that after annealing at 600°C, shells of hollow particles become non-porous and impermeable to liquid media.

Terahertz (THz) technology offers a variety of applications in medical spectroscopy and imaging. In such applications, tissues are commonly assumed to be optically homogeneous at the THz-wavelength scale, while the THz-wave-tissue interactions are described (in a simplified manner) within the effective medium theory (EMT). Meanwhile, recent studies of tissues from human, animal, and plants involving emerging modalities of superresolution (beyond the Abbe diffraction limit) THz microscopy, have found tissue inhomogeneities with dimensions comparable to the THz wavelength (approximately lambda), which can lead to THz-wave scattering effects. This poses a problem of studying an interplay between the THz-wave absorption and the scattering phenomena in soft turbid tissues. To mitigate this challenge, in this paper, a tissue-mimicking phantom is developed that has the form of a gelatin slab, as a highly absorbing hydrated matrix, into which silicon dioxide (SiO2) microparticles are embedded, with their lower refractive index and loss and subwavelength or mesoscale diameters. The analytical methods of Lorenz-Mie scattering theory have predicted a nonisotropic differential extinction cross section for such scatterers, which results in the non-Rayleigh scattering regime and casts doubt on the applicability of EMT for such tissues. Surprisingly, we have found theoretically, using the radiative transfer theory (RTT), and confirmed experimentally, using THz pulsed spectroscopy, that the effective optical properties of the proposed phantom are still determined by EMT over wide ranges of the diameters (d <= 0.47 lambda) and volume fractions (f(v)<= 0.2) of the scatterers. This effect was attributed to the strong THz-wave loss in a host medium and, therefore, should be general for a variety of soft tissues in the THz range. Thus, our findings hopefully broaden the applicability of EMT for describing the interactions between THz radiation and soft turbid tissues.

Hollow silica particles are obtained by the template method using previously synthesized particles of polymethyl methacrylate. The effect of the type of catalyst (ammonium hydroxide, L-arginine) on the shrinkage and mechanical strength of silica shells during heat treatment is established. Their initial porosity is assessed. The dependence of the shrinkage of hollow particles on the temperature of calcination in the range of 100–900°C is shown. It is found that the particles obtained using ammonium hydroxide as the catalyst have a higher mechanical strength and are less susceptible to deformation during calcination.

The protection of DC power circuits against short circuits in the load is considered and a possibility of preventing emergencies is demonstrated during operation of pulse power supplies feeding the AC electric arc, which is a complex load for output stages of an inverter. The proposed scheme was implemented and tested in an arc power supply for the development of 3D-printing technology using local segregation electric arc melting.

Carbon structures with an inverted opal lattice was synthesized. Comparative studies of the electrochemical properties of lithium–sulfur cells with sulfur electrodes based on the samples and other carbon materials have been carried out. The synthesized material showed a good stability when cycling in the range of more than 300 cycles. That says about the prospects for the use of such structures in lithium–sulfur batteries.

This review, for the first time, summarizes the results of studies of the defect formation mechanisms in mixed crystals grown from aqueous solutions. The general mechanism of interaction of a crystal with a foreign solution is described (reaction of isomorphous replacement). As a result of this reaction, the crystal surface turns into a mosaic of local areas where multidirectional processes (dissolution and growth) occur simultaneously. Data on mosaic microinhomogeneity, which is a new type of composition inhomogeneity inherent solely to multicomponent crystals, is presented. A new mechanism for the mismatch stress relaxation in heterocompositions of brittle crystals grown from low-temperature solutions is described; in this case, the formation of misfit dislocations is impossible and stress relaxation occurs due to the formation of numerous inclusions at the interface. The general concept of growing high-quality mixed crystals from solutions is described, using the example of K2(Co, Ni)(SO)2 · 6H2O (KCNSH) mixed crystals.

Mixed crystals of potassium‒cobalt sulfate hexahydrate/potassium‒nickel sulfate hexahydrate (K 2 Co(SO 4 ) 2 · 6H 2 O/K 2 Ni(SO 4 ) 2 · 6H 2 O (KCNSH)) have been grown from a solution with an isomorphic-component ratio of KCSH : KNSH = 1 : 2. The presence of mosaic microheterogeneity in KCNSH crystals at a level of ∼2 at % is confirmed, and its dependence on supercooling is studied. The radial heterogeneity of KCNSH crystals is investigated as a function of the growth direction and rate. The heterogeneity of Co concentration in different samples is shown to vary from 0.2 to 0.8 wt %.

In this work, we synthesized C-8 cubic carbon microcrystals by carbonization of anthracene. Gas products of carbonization were trapped at the outlet of the pipe in distilled water. By the methods of SEM, HRTEM and electron diffraction the morphology and structure of the obtained nanocrystals were studied. It is shown that carbonization of anthracene vapors leads to the formation of plate-like C-8 crystals of up to 0.5 microns in size. The unit cell parameter within the bce lattice is a = 4.08 (0.02) angstrom.

— The original equipment has been developed and the feasibility has been shown of manufacturing shaped products from refractory metals by 3D printing using a high-pressure electric arc in a protective gas atmosphere. The proposed technique is performed using layer-by-layer metal deposition using local electric arc skull melting. In experiments aimed at manufacturing molybdenum crucibles, it has been shown that the speed of 3D printing is higher by 2–3 orders of magnitude than the speed of printing by selective laser sintering.

K2Ni(SO4)2 · 6H2O (KNSH), K2Co(SO4)2 · 6H2O (KCSH), and K2NixCo(1 – x)(SO4)2 · 6H2O (KCNSH) crystals have been grown by traditional and accelerated techniques. The microhardness and crack lengths were measured by indentation with a Vickers pyramid in dependence of the crystal growth conditions in order to improve the crystal structure and properties. It was shown that, with an increase in the growth rate, the stress intensity factor of the crystals (which characterizes the fracture toughness) changes in dependence of the composition: it decreases for KCSH (due to the rise in inhomogeneity) but increases for KCNSH, which is explained by lowering the level of both the mosaic and radial inhomogeneity. In the case of KNSH crystals, the fracture toughness of the {110} sector decreases, whereas the changes in the sector {001} of “slow” crystal are differently directed, which is explained by the high inhomogeneity of its composition.