PhC-2021

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S.S. Nalimova¹, Z.V. Shomakhov², K.N. Punegova¹, A.A. Ryabko¹, A.I. Maximov^1
1 Saint Petersburg Electrotechnical University «LETI»
² Kabardino-Balkarian State University

Abstract: Zinc oxide nanorods were synthesized by the hydrothermal method. The obtained samples were processed in an aqueous-alcohol solution of potassium stannate and urea at 170 °C during different times. As a result, Zn–Sn–O nanostructures were obtained. The surface chemical composition of ZnO and Zn–Sn–O was studied using the X-ray photoelectron spectroscopy. Its sensitivity to vapors of isopropyl alcohol (1000 ppm) at 120 °C, 180 °C, 250°C was analyzed. The electron density redistribution during the Zn–Sn–O composite nanostructures formation manifests itself in the chemical shift of the O1s and Zn2p peaks. It confirm the rearrangement of chemical bonds when zinc atoms are replaced by tin ones. It was found that the sensitivity of composite structures to isopropyl alcohol vapors significantly exceeds that of ZnO in the entire temperature range under study. The improvement of gas-sensitive properties is associated with the presence of various types of surface centers in the Zn–Sn–O samples that participate in the adsorption and oxidation of isopropyl alcohol.
Keywords: zinc oxide, zinc stannate, gas sensors, nanorods, X-ray photoelectron spectroscopy

I.S. Medyankina, V.M. Skachkov, L.A. Pasechnik
Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: A method for producing amorphous silica from the enrichment wastes of low-titanium vanadium containing titanomagnetites of JSC «EVRAZ ZSMK» – wet magnetic separation tailings is proposed. The use of a NH₄HF₂ solution makes it possible to practically selectively extract silicon into the solution in the form of ammonium hexafluorosilicate. The extraction of silicon with 1,0–2,5 wt.% NH₄HF₂ solution for 6 hours reached 46 %. The diffusion process of the silicon extraction is described by the kinetic equation   1–(1–α)^1/3=0,0043·exp(–5230 / RT)·τ. Amorphous silica obtained by the sol-gel method from a fluoride silicon-containing solution has a highly developed surface 320 m2/g, the particle size calculated from the average density of «white carbon black» is of 10 nm. The increase in concentration to 20 wt. % NH₄HF₂ leads to the rise of the silicon solubility and of other tailings components, which are unwanted impurities in the final product. In general, it is shown that the hydrochemical leaching of silicon-containing industrial waste – tailings with weak solutions of ammonium hydrofluoride is promising for the synthesis of pure amorphous silica.
Keywords: wet magnetic separation tailings, amorphous silica, ammonium hydrofluoride, fluorination, kinetics of the process

Yu.A. Malkanduev¹, A.A. Kokoevа¹, A.T. Dzhalilov^2
1 Kabardino-Balkarian State University named after H.M. Berbekov
² Tashkent Research Institute of Chemical Technology

Abstract: The results of spontaneous polymerization of α -chloroacrylic and α -bromoacrylic acids with tertiary amines at a low temperature are presented. As a result of spontaneous polymerization during the interaction of α -halodacrylic acids with tertiary amines, polymers containing quaternary ammonium groups are formed. In order to confirm this assumption, nuclear magnetic resonance and infrared spectroscopic studies of the products of the spontaneous polymerization were carried out. Spontaneous polymerization proceeds, consisting of two stages: the quaternization reaction and the polymerization reaction. The kinetic regularities of the polymerization reaction were studied and it was shown that the quaternization reaction, which is the limiting stage of the spontaneous polymerization process, proceeds according to the S_N2–mechanism. It has described the first attempts to obtain new nanocomposite materials based on synthesized copolymers and modified montmorillonite. Analysis of the literature data shows that the features of the preparation of nanocomposites based on Na⁺–montmorillonite and water-soluble copolymers have not been previously studied.
Keywords: polyelectrolytes, chloroacrylic acid, bromoacrylic acid, spontaneous polymerization, polymerization kinetics, quaternary ammonium salts, composite

T.V. Kryukov, M.A. Feofanova, M.I. Skobin, A.I. Ivanova
Tver State University

Abstract: In this work, a team of authors obtained and isolated in solid form a metal complex compound by the interaction of aqueous solutions of trivalent cerium chloride and sodium salt of cefazolin. Its elemental composition was determined using the X-ray spectral electron probe analysis. The thermal characteristics of this compound, the temperature of its decomposition, the composition and the method of coordination of the inner sphere of this metal complex were clarified by the methods of thermogravimetry, differential scanning calorimetry and IR spectroscopy. Based on the data obtained, the inner sphere of the metal complex contains three molecules of cefazolin and three molecules of inner-sphere water. The composition of the inner sphere corresponds to the formula [CeCzl3(H2O)3]. Taking into account IR spectroscopy data, the authors concluded that the most likely way of coordination of cefazolin to the central ion is through the amide and carboxyl groups.
Keywords: coordination compounds of rare earth elements, cefazolin, cefazolin complexes, cephalosporins

V.K. Krut’ko¹, L.Yu. Maslova¹, O.N. Musskaya¹, T.V. Safronova², A.I. Kulak^1
1 Institute of General and Inorganic Chemistry of the National Academy of Sciences of Belarus
² Lomonosov Moscow State University

Abstract: The multiphase calcium phosphate foam ceramics, represented by β -tricalcium phosphate ( 65%) and β -calcium pyrophosphate ( 25 %),including hydroxyapatite (5 %) and α -tricalcium phosphate (5 %), with 60–64 % porosity and a through architecture of polyurethane foam was obtained. The application of a layer of hydroxyapatite led to an increase in the content of hydroxyapatite to 25 %, α -tricalcium phosphate to 40%, and an increase in static strength to 0,03 MPa with a decrease in porosity to 49%. The application of the second layer of hydroxyapatite promoted an increase in the content of hydroxyapatite to 40%, the static strength reached 0,05 MPa at a porosity 40 %. The bioapatite formation in the shape of «foam spheres» with a size from 2 to 10 μm occurred in the process of modifying all types of foam ceramics in a SBF solution during 21 – 28 days. The modified calcium phosphate foam ceramics enriched with α -tricalcium phosphate and hydroxyapatite, was characterized by the maximum static strength 0,08 MPa at a porosity 38%.
Keywords: calcium phosphate foam ceramics, hydroxyapatite, polyurethane foam, tricalcium phosphate, SBF (Simulated body fluid), bioapatite

V.K. Krut’ko¹, A.E. Doroshenko¹, O.N. Musskaya¹, S.M. Rabchynski², A.I. Kulak^1
1 Institute of General and Inorganic Chemistry, National Academy of Sciences of Belarus
² Belarusian State University

Abstract: Calcium phosphate coatings on titanium plates were obtained by electrochemical deposition at room temperature in a two-electrode cell at a constant current density of 30 mA/sm2 and a deposition time of 10 min, and brushite coatings from Ca(NO₃)₂/NH₄H₂PO₄ system at pH = 4, and composite (brushite/calcite/apatite) coatings from the CaCO₃/Ca(H2PO₄)₂ system at pH = 5. The apatite-forming ability (bioactivity) was determined by soaking both types of calcium phosphate coatings in a model SBF solution during month. The newly formed amorphized apatite layer after heat treatment at 800 °С crystallized into β –tricalcium phosphate/hydroxyapatite on brushite coatings and hydroxyapatite on composite coatings due to the presence of calcite, whose carbonate ions initiate formation of hydroxyapatite, as well as apatite nanoparticles in the initial coating. The obtained calcium phosphate coatings are promising as biocoatings capable to increase osseointegration of metal implants.
Keywords: calcium phosphate coatings, brushite, calcite, SBF model solution, apatite, hydroxyapatite

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

Abstract: The influence of organic vapors (isopropanol, ethanol, and acetone) with different concentrations in air on a response gas sensor based on nanostructured tin dioxide films synthesized by the sol-gel method was studied. It was found experimentally that inject of the gas mixtures containing organic vapors into measure chamber results to an increase of the conductivity of nanostructured tin dioxide films. In the area of high concentrations (more than 50% of saturated vapor), the concentration dependence of conductivity trends to saturation. The recognizing possibility of species gas admixture by using statistical processing of response only single sensor at different analyzed gas mixture concentrations is validated. The surface donor level of gas-reducing relative to acceptor level oxygen and desorption heat of gas particle were determined. A new method based multiparametric recognition gas mixtures is proposed based on using concentration-independent physical and chemical parameters of analyzed gases as classification properties. It is shown that proposed multiparametric recognition method has higher reliability in comparison with standard methods based on the analysis gas sensor response.
Keywords: gas sensor, sol-gel method, signals preprocessing, adsorption center parameters, multiparametric recognition of gas mixtures