PhC-2021

S.M. Masloboeva
I.V. Tananaev Institute of Chemistry – Subdivision of the Federal Research Centre «Kola Science Centre of the Russian Academy of Sciences»

Abstract: Known methods of a boron doped lithium niobate charge synthesis were analyzed. Such a charge is applied for the growth by Czochralski of single crystals with high optical quality. Homogeneous doping (the charge is obtained from precursor Nb₂O₅ : B and Li₂CO₃ ) was compared with solid phase doping (the charge is obtained from the mixture Li₂CO₃ : Nb₂O₅ : H₃BO₃). Homogeneous doping was determined to help produce LiNbO₃ : B crystals with a more uniform distribution of a boron dopant, boron distributes more uniform in the melt volume; technological regimes established during crystal growth become easier. For the first time the paper considers liquidphase charge synthesis method; the method excludes the stage of annealing of homogenized mixture of niobium pentoxide and lithium carbonate. Results are crucial for the choice of technology at growing of boron doped lithium niobate crystals for exact areas of technics.
Keywords: lithium niobate, charge synthesis, single crystal, doping, boron, optical quality

O.V. Malyshkina, G.S. Shishkov, A.I. Ivanova
Tver State University

Abstract: It is shown in the work that as a result of sintering of composite samples of barium titanate (80 vol. %) – barium ferrite ( 20 vol. %) in a porcelain crucible at a temperature of 1300 °C, a eutectic appears. As a result of comparing the properties of the samples obtained at different sintering temperatures, it was found that the samples sintered at 1250 °C have optimal properties. The structure and dielectric properties of barium titanate ceramic samples and barium titanate (80 vol. %) – barium ferrite ( 20 vol. %) composite sintered at a temperature of 1250 °C are compared. It has been shown that the addition of 20% barium ferrite to the composition of barium titanate increases the dielectric constant, pyroelectric coefficient, and piezoelectric modulus d₃₃ of the composite of 1,5–2 times compared to barium titanate ceramics, while the value of the piezoelectric modulus d₃₁ remains unchanged. The introduction of 20 % barium ferrite into the barium titanate ceramics is sufficient for the resulting composite to have magnetic characteristics corresponding to pure barium ferrite.
Keywords: multiferroic, barium ferrite, barium titanate, magneto-electric composite, piezoelectric ceramic structure

E.D. Kurbanova, R.M. Belyakova, V.A. Polukhin
Institute of Metallurgy, Ural Branch of the Russian Academy of Science

Abstract: With unique mechanical and functional properties, amorphous, nanocrystalline and matrix duplex microstructure membrane alloys based on group V elements actively contribute to the development of hydrogen energy. There are still not completely resolved problems for these new alloys – their low thermal stability, insufficient mechanical strength (plasticity, hardness), and intermetallic and hydride embrittlement. For effective use, alloys with a triple composition are being developed – which, in addition to the elements of group V, also include nickel and titanium as alloying metals. Not only amorphous and nanocrystalline alloys are obtained that are applicable in electronics and power engineering, as well as membrane alloys with a duplex matrix structure that combines amorphous, nano- and quasicrystalline dendritic-hardening phases strengthening the amorphous matrix. In specialized membrane ternary alloys, NiTi and NiTi₂ compounds are formed, which stabilize and protect nano- and crystalline membranes from brittle destruction. It has been found that the intense formation of hydrides in these alternative membrane alloys is as undesirable as for palladium-based compounds. The alloys under consideration actually make it possible to obtain high-purity gaseous hydrogen using new compositions instead of expensive membranes based on Pd–Au/Ag/Cu alloys.
Keywords: amorphous and nanocrystalline alloys, nickel, titanium, zirconium, niobium, structurization, membrane gas separation, hydrogen purification, solubility, hydrogen permeability, accumulation, thermal stability, fragility, crystallization, modeling, diffusion, nanophases, Me–H hydrides, embrittlement, duplex matrix microstructure

A.I. Kovtun, A.G. Mysyura
Institute of Applied Problems of Physics and Biophysics of National Academy of Sciences of Ukraine

Abstract: Nanotechnologies using biopolymers are widely used in biomedical applications. In this work, nanocomposite hydrogels based on natural (chitosan, carboxymethylcellulose) and synthetic (polyvinyl alcohol) polymers with silver nanoparticles for application to a textile carrier have been developed. Carboxymethylcellulose dialdehyde and boric acid were used as crosslinking reagents in the creation of hydrogels. Physicochemical properties (sorption capacity in unilateral contact with the model medium, degree of swelling, vapor permeability, capillarity) of hydrogel coatings on a textile carrier, and the kinetics of the drugs release (lidocaine, dioxidine) included in the hydrogels were determined. It is shown that materials with a two-layer coating are characterized by higher sorption properties relative to saline and a longer release of drugs than materials with a single-layer coating. The release of drugs from the two-layer coatings occurs in two stages with a maximum release within two days. The obtained textile materials with a film nanocomposite hydrogel coating can be used as dressings in the treatment of wounds.
Keywords: hydrogel, silver nanoparticles, textile, chitosan, polyvinyl alcohol, carboxymethylcellulose dialdehyde, drug release kinetics, dressing, wound treatment

N.A. Klychkov, V.V. Simakov, I.V. Sinev, D.A. Timoshenko
Saratov State University

Abstract: Nanostructured gas-sensitive tin dioxide films have been synthesized by sol-gel technology. A conductivity vs temperature dependence of a gas sensor into atmosphere of synthetic air has been investigated. A response vs temperature dependence of a gas sensor into atmosphere of isopropanol vapors with various concentrations has been investigated. Local minimum on the temperature dependence of the tin dioxide film conductivity in clean air atmosphere were observed. A decrease in conductivity with increase temperature in the range of 300…350 °C can be associated with a dissociation molecular form of the adsorbed oxygen. At temperatures above 350 °C, conductivity increases because of desorption of the atomic form of the adsorbed oxygen on the surface of gas-sensitive tin dioxide film. The greatest response value is achieved at a sensor temperature equal to 350 °C. It is proposed that the reason is a domination of the atomic form of the chemisorbed oxygen on the surface. The analysis of response time vs concentration and response time vs temperature of gas sensor has been carried out. Sensor response time decreases monotonically with increase admixture substance in gas-probes, apparently because of increase in adsorption rate admixture particles on the surface of gas-sensitive film. It was found that the dependence of the response time on the operating temperature has an Arrhenius form. This may be associated with thermally activated adsorption-desorption processes and heterogeneous chemical reactions on the surface of sensor active layer.
Keywords: sol-gel method, nanostructured films, tin dioxide, gas sensor response time

Yu.F. Ivanov¹, Yu.A. Abzaev², A.A. Klopotov², N.A. Prokopenko¹, O.S. Tolkachev¹, P.Yu. Nikitin⁴, V.V. Shugurov¹, A.D. Teresov¹, M.S. Petyukevich^3
1 Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences
² Tomsk State University of Architecture and Building
³ National Research Tomsk Polytechnic University
⁴ National Research Tomsk State University

Abstract: This paper presents the results of structural studies of films with a thickness of up to 5 microns of high-entropy alloys of the AlNbTiZrCu system. The films were synthesized on metal and cermet substrates by deposition of a multielement metal plasma created by electric arc plasma assisted simultaneous independent sputtering of several cathodes. It is shown that the films are a layered material and have an amorphous-crystalline structure. It was found that irradiation of films with a pulsed electron beam (18 keV, 20 J/cm2, 50 μs, 3 imp., 0,3 s-1) is accompanied by crystallization of the material. It is shown that the resulting films are dominated by the compound of the AlNbTiZr composition with the lattice parameter of 0,32344 nm. On the basis of theoretical calculations, the structural data of the crystal AlTi_0,86Zr_0,95Nb lattice were obtained, mechanical and thermodynamic characteristics of this compound were determined.
Keywords: high-entropy alloy, low-pressure gas discharge plasma, film/substrate system, pulsed electron beam, phase composition, structure

D.A. Zernitsa¹, V.G. Shepelevich^2
1 Mozyr State Pedagogical University named after I.P. Shamiakin
² Belarusian State University

Abstract: The results of studies of the effect of ultrahigh melt cooling rates, equal to at least 10⁵ K/s, on the properties of rapidly solidified alloys of the Zn–Sn system are presented. The upper region of the foil, in contact with the crystallizer during solidification, had more dispersed particles of the second phase, and as the distance from the upper layers increased, the particle sizes increased. At room temperature, the decomposition of a supersaturated solid solution proceeds with the release of dispersed particles. Additional heat treatment leads to the coarsening of the particles of the second phase, and helps to reduce the microhardness. Rapidly solidified foils with a maximum zinc concentration are characterized by the presence of a (0001) texture, which weakens as the tin content in zinc increases, and upon alloying up to 30 wt. % Sn is rearranged to (1010) texture. Heat treatment up to 160 °C does not change the texture.
Keywords: rapidly solidification, lead-free solders, Zn–Sn alloy, microhardness, unit cell, isochronous annealing, decomposition, solid solution

E.A. Bogdanova, V.M. Skachkov
Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: Nanoscale hydroxyapatite and fluorapatite powders were synthesized by precipitation from solutions. Food gelatin is used as a binder. This composition has a high adhesion on materials of different nature and porosity. Porous films and granules with a developed specific surface area were also obtained. Their microstructures are considered. The possibility of using a colloidal suspension and an aqueous suspension of crystalline apatite in combination with a gelatin solution as a bioactive material, both for creating coatings and obtaining granules, has been studied. It is established that the use of apatite powder together with gelatin can significantly reduce the time of formation of a bioactive coating and significantly increase its adhesive strength. The obtained apatite granules are compared in size depending on the concentration of gelatin in an aqueous solution. Patent applications have been filed for the developed bioactive coatings and granular material based on nanoscale apatite with a binding agent.
Keywords: hydroxyapatite, fluorsubstituted hydroxyapatite, gelatin, collagen, biomaterial, bioactive coatings, adhesion, granules

E.A. Bogdanova, V.M. Skachkov, I.M. Giniyatullin, D.I. Pereverzev, K.V. Nefedova
Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: The article discusses the possibility of obtaining a hardened composite material with a porous structure based on nanostructured hydroxyapatite (HAP) synthesized by precipitation from a solution. The new material was obtained by the mechanochemical synthesis of HAP with reinforcing additives of zirconium dioxide and silicic acid. The synthesized samples are certified using modern physico- chemical methods of analysis. The influence of the qualitative and quantitative composition of the composite on the sintering processes, porosity, strength characteristics, the degree of dispersion and morphology of the studied samples is shown. It has been experimentally established that the sample has the maximum strength characteristics and a constant composition of Ca₁₀(PO₄)₆(OH)₂–15%SiO₂·nH₂O–5%ZrO₂. The composite material has a dense uniform structure with a high degree of crystallinity, with a developed porosity, is a promising material for further research in order to introduce it into medical practice. A patent application has been filed for the developed composite material.
Keywords: hydroxyapatite, zirconium oxide, silicon oxide, composite biomaterials, crystallinity, microhardness

E.S. Bakhvalova¹, A.V. Bykov², L.Zh. Nikoshvili², L. Kiwi-Minsker^1
1 Tver State University
² Tver State Technical University

Abstract: In this paper, the density functional theory calculations were carried out in order to find the adsorption energies of a benzene ring on small Pd⁰ clusters consisting of four or nine atoms. The adsorption of benzene on palladium clusters was found to result in a noticeable energy gain of the system: –146 kJ/mol in the case of Pd₄, and –117 kJ/mol in the case of Pd₉ . The adsorption energies of chloro-, bromo- and iodoanisole on Pd4⚹C6H6 were also calculated. The adsorption of iodoanisole was characterized by the highest energy gain of the system (–278 kJ/mol) and occurred dissociatively without activation, that fundamentally distinguished it from chloro- and bromoanisole. The data obtained can be used to explain the differences in the behavior of catalysts based on hyper- cross-linked polystyrene in cross-coupling reactions of various aryl halides and phenylboronic acid, and also the fact that aryl iodides can favor the formation of homogeneous forms of palladium.
Keywords: palladium, clusters, aryl halides, Suzuki cross-coupling, density functional theory