Subjects -> CHEMISTRY (Total: 928 journals)
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INORGANIC CHEMISTRY (45 journals)

Showing 1 - 36 of 36 Journals sorted alphabetically
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9)
Advances in Polymer Technology     Open Access   (Followers: 14)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 5)
Bioinorganic Chemistry and Applications     Open Access   (Followers: 5)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 1)
Communication in Inorganic Synthesis     Open Access  
European Journal of Inorganic Chemistry     Hybrid Journal   (Followers: 10)
European Polymer Journal     Hybrid Journal   (Followers: 42)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Indian Journal of Chemistry - Section A     Open Access   (Followers: 9)
Inorganic and Nano-Metal Chemistry     Hybrid Journal   (Followers: 1)
Inorganic Chemistry     Hybrid Journal   (Followers: 31)
Inorganic Chemistry Communications     Hybrid Journal   (Followers: 13)
Inorganic Chemistry Frontiers     Hybrid Journal   (Followers: 4)
Inorganic Materials     Hybrid Journal   (Followers: 5)
Inorganic Materials: Applied Research     Hybrid Journal   (Followers: 1)
Inorganica Chimica Acta     Hybrid Journal   (Followers: 6)
Inorganics     Open Access   (Followers: 1)
International Journal of Bio-Inorganic Hybrid Nanomaterials     Open Access   (Followers: 2)
International Journal of Inorganic Chemistry     Open Access   (Followers: 3)
JBIC Journal of Biological Inorganic Chemistry     Hybrid Journal   (Followers: 2)
Journal of Inorganic and Organometallic Polymers and Materials     Hybrid Journal   (Followers: 8)
Journal of Inorganic Biochemistry     Hybrid Journal   (Followers: 4)
Journal of Inorganic Chemistry     Open Access   (Followers: 3)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Progressive Research in Chemistry     Open Access  
Journal of Separation Science     Hybrid Journal   (Followers: 10)
Materials Today Chemistry     Hybrid Journal   (Followers: 2)
Open Journal of Inorganic Chemistry     Open Access   (Followers: 1)
Polymer Bulletin     Hybrid Journal   (Followers: 6)
Polymer Composites     Hybrid Journal   (Followers: 18)
Russian Journal of Inorganic Chemistry     Hybrid Journal  
Separation Science plus (SSC plus)     Hybrid Journal  
Zeitschrift für anorganische und allgemeine Chemie     Hybrid Journal   (Followers: 1)
Similar Journals
Journal Cover
Inorganic Materials: Applied Research
Journal Prestige (SJR): 0.207
Number of Followers: 1  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2075-1133 - ISSN (Online) 2075-115X
Published by Springer-Verlag Homepage  [2469 journals]
  • Synthesis of a Highly Porous Material Based on Mechanically Alloyed Cu and
           Zn Powders by Chemical Dealloying

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      Abstract: In this work, we obtained porous materials based on Cu–Zn alloy with high permeability and developed surface. This was achieved by creating multilevel porosity in the material by a combined method that combined the use of a removable pore former and chemical etching. The effect of synthesis conditions on the structure and properties of the obtained materials is investigated. The material structure is a system of interconnected pores with a size of 300–400 μm, as well as pores with a size of less than 15 μm. On samples subjected to chemical etching, an increase in the specific surface area was observed from 0.11 to 4.12 m2/g when the pore-forming agent was ammonium bicarbonate and from 0.88 to 1.60 m2/g when the blowing agent was potassium carbonate. The multilevel porous material had a permeability of more than 12 × 10–12 m2 and a porosity of 83–87%. It was found that the sintering of the material was accompanied by the evaporation and condensation of zinc on the surface of the pores.
      PubDate: 2022-04-01
       
  • High-Temperature Oxidation of the Copper–Nickel Alloys Synthesized
           by Spark Plasma Sintering

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      Abstract: The article presents data on heat resistance high-temperature tests of powder materials based on copper–nickel. The features of oxidation of samples of copper–nickel alloys with various alloying elements have been studied. Compaction of samples of copper–nickel alloys was performed by spark plasma sintering (SPS). The dependence of the growth rate of the oxide film on the temperature of high-temperature oxidation was established, and the effect of alloying elements in the composition of the samples on their heat resistance was considered. On the basis of the results of studies, the dependence of the oxide film growth rate on high-temperature oxidation and the influence of alloying elements in the composition of sintered copper–nickel alloys on their heat resistance was considered. It was determined that, for all the considered compositions of copper–nickel alloys synthesized by spark plasma sintering, the temperature of 1000°C of 20-h test for heat resistance is not the limiting one, since the samples retain their integrity. It is shown that simultaneous alloying of copper–nickel alloys with aluminum and chromium provides the highest heat resistance. The rate of growth of scale for composition Cu–Ni–Cr–Al is 1.49 × 10–3 g/cm3, which is lower than the oxidation rate of pure nickel of 3.78 × 10–3 g/cm3 at 1000°C. These two samples demonstrate the lowest weight gain after testing at 1000°С; for compositions Cu–Ni–Al, Cu–Ni–Cr–Si, and 50 wt % Cu–50 wt % Ni, the oxidation rate increases by two orders of magnitude; for compositions Cu–Ni–Si and Ni, it increases by three orders of magnitude.
      PubDate: 2022-04-01
       
  • Thermal Deformation Properties of Dynamically Vulcanized Thermoplastic
           Elastomers Based on Random Polypropylene and Nitrile Butadiene Rubber

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      Abstract: The thermal deformation properties of dynamically vulcanized thermoplastic elastomers based on random polypropylene and nitrile butadiene rubber (NBR) are studied. Exxelor PO1200, a graft polypropylene copolymer with a maleic anhydride, was used as a compatibilizer to improve the compatibility of polymer mixtures. The concentration of maleic anhydride in the grafted copolymer was 3.0 wt %. We showed that it is possible to improve the compatibility of bipolar mixtures through the incorporation of a compatibilizer, when there is no separation between the components of the mixture. We found that the polymer composition exhibits the properties of thermoplastic elastomers upon the introduction of 30 wt % NBR-18 and 40 wt % NBR‑26 or NBR-40 into random polypropylene, so that the plastic deformation changes to a highly elastic one typical of rubbers. The temperature regions of the solid, highly elastic, and viscous-flow states are found. The polymer mixtures were vulcanized with crosslinking agents (dicumyl peroxide and sulfur) to exhibit the properties of rubber. We showed that the thermomechanical properties of dynamically vulcanized thermoplastic elastomers change significantly with an increase in concentration of dicumyl peroxide from 0.25 to 1.0 wt %. The vulcanized materials almost completely lose their ability to flow, and they transform from a highly elastic state to a glassy one after the introduction of 1.0 wt % of dicumyl peroxide. The melt flow index (MFI) of vulcanized thermoplastic elastomers remains unchanged after the introduction of sulfur in an amount from 1.0 to 10 wt %.
      PubDate: 2022-04-01
       
  • Hybrid Carbon–Hydrocarbon Structure

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      Abstract: New hybrid carbon-hydrocarbon structure was found and studied after pumping a gas mixture of methane and hydrogen through a synthetic diamond powder sample with a size of 314–400 μm. The experiment was performed with a microwave plasma-chemical system for the deposition of polycrystalline diamond films. The power of the microwave generator was 3.5 kW, the consumption of hydrogen was 400 mL/min, the consumption of methane was 20 mL/min, and the pressure in the reactor chamber was 63 mmHg. The diamond powder was placed into molybdenum cups inserted into a copper holder placed on a water-cooled copper table. The gas mixture was pumped at a pressure drop of 13 mmHg. The unidirectional filament formations, some of which ended as spherical ones, were found in the space between diamond particles of the surface layer. Such a structure called “dandelion” is a composition of filamentous (with a length of 100–500 μm and a diameter of 2 μm) and spherical formations (with average diameter of 18 μm). Raman spectroscopy was used to find the features of these formations. The filamentous formation is single-crystal graphite. The surface of the spherical formation is spindle-shaped structures of nanocrystalline graphite 2 μm in length and 200 nm in thickness and nanodiamond grains with trans-polyacetylene chains [C2H2]n.
      PubDate: 2022-04-01
       
  • Composites Based on Isotactic Polypropylene and High-Pressure Polyethylene
           with Zinc-Containing Nanofillers

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      Abstract: The effect of nanofiller (NF) additives containing zinc oxide nanoparticles stabilized by a polymer matrix of high pressure polyethylene obtained by the mechanochemical method on the structure and properties of metal-containing nanocomposites based on isotactic polypropylene (PP) and high pressure polyethylene (PE) using differential thermal (DTA) and X-ray phase (XRD) analyses was studied. The improvement of strength, deformation, and rheological parameters, as well as thermal-oxidative stability of the obtained nanocomposites, was revealed, which, apparently, is associated with the synergistic effect of interfacial interaction of zinc-containing nanoparticles in the PE matrix with the components of the PP/PE polymer composition. It is shown that nanocomposites based on PP/PE/NF can be processed both by the pressing method and by the injection molding and extrusion methods, which expands the scope of its application.
      PubDate: 2022-04-01
       
  • Effect of Artificial Aging on Crack Resistance of Sheets of High-Strength
           Aluminum-Lithium Alloy V-1469

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      Abstract: In this paper, we study the effect of artificial aging modes on the structure, mechanical properties, and crack resistance of high-strength aluminum-lithium alloy V-1469 sheets. Kinetic curves of changes in mechanical properties at various temperatures and long exposures are plotted. To establish the possibility of increasing the crack resistance, one-stage and multistage modes of artificial aging are selected in the study. As a result, a mode that allows increasing crack resistance at a slight decrease in strength and maintaining high corrosion resistance and fatigue life is chosen. The structural-phase state and the complex of properties of sheets processed according to the selected mode with sheets processed according to the mode providing maximum strength are compared. Crack resistance determined for large-sized (750 mm wide) samples from V‑1469T1 alloy sheets processed according to the selected aging mode is at the level of plating sheets of alloy 1163AT. Unlike high-strength aluminum alloys with strength and fracture toughness achievable by overaging, the same properties in aluminum-lithium alloy V-1469 can be achieved by aging with short exposures.
      PubDate: 2022-04-01
       
  • Effect of Liquid-Phase Synthesis Method of Nanopowders on Microstructure
           and Physicochemical Properties of Ceramics in CeO2–Sm2O3 System

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      Abstract: Nanopowders of the composition of (СeO2)1 – x(Sm2O3)x (x = 0.02, 0.05, 0.10, and 0.20) were synthesized by two methods of chemical liquid-phase synthesis: coprecipitation of hydroxides with freezing and co-crystallization of salts with an average CSR size of ~8–11 nm and Ssp = 40–83 m2/g. On their basis, ceramic nanomaterials with a cubic crystal structure of the fluorite type, with a CSR of ~65–81 nm (1300°C), were obtained. The dependence of the phase composition, microstructure, and electric transport properties of the obtained samples on the content of Sm2O3 in a solid solution based on CeO2 and the synthesis method is revealed. It is shown that, in the series (СeO2)1 – x(Sm2O3)x (x = 0.02, 0.05, 0.10, and 0.20), a solid solution of the composition (CeO2)0.80(Sm2O3)0.20 has the highest ionic conductivity σ700°C = 2.7 × 10–2 S/cm. The resulting ceramic can be used as a solid electrolyte for intermediate-temperature fuel cells owing to its physical and chemical characteristics.
      PubDate: 2022-04-01
       
  • Influence of Technological Conditions in the Formation of Electrically
           Conductive Thermoplastic Polymer-Graphite Composites

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      Abstract: The article discusses the synthesis and properties of electrically conductive polymer composite materials based on low-ash graphite grade GSM-1, modified with acids using bisulfate technology. Investigations of the influence of such technological methods as pressing and rolling on rollers with a variable gap on the conductivity of composite materials based on thermally expanded graphite and thermally expanded polymer-graphite compositions containing acid-modified graphite have been carried out. It is shown that, by applying to polymer composites the technological methods of thermal expansion, pressing, and rolling on rollers, it is possible, firstly, to combine fillers of different nature, shapes, and sizes and, secondly, to obtain composites with the required conductivity of an electrically conductive polymer composite. The paper shows the advantage of using thermally expanded graphite in comparison with other forms of graphite to obtain highly conductive polymer compositions.
      PubDate: 2022-04-01
       
  • Features of Damageability and Modification of Surface Layers of Al and Its
           Alloys by Powerful Energy Fluxes in a Plasma Focus Facility

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      Abstract: The results of the analysis of damageability and modification of the structural-phase state of the surface layers of aluminum and its alloys by powerful fluxes of fast high-energy ions and high-temperature plasma in plasma focus facilities as well as using pulsed laser radiation are presented. Pure Al, an alloy of the Al–Mg–Li system, a duralumin alloy, and a composition of a ceramic coating Al2O3 on an Al substrate are considered. It is shown that, in the regime of Al irradiation with a power density of q ≈ 106–107 W/cm2 in the nano- and microsecond range of pulse durations, ultrafast crystallization of melted surface layer occurs with the formation of a wavy surface relief and structural fragments of submicrocrystalline and nanoscale size. After the action of deuterium plasma fluxes on a duralumin alloy tube located along the axis of the plasma focus facility, a modification of the structural-phase state of the alloy is observed: the initial two-phase state of an αAl-solid solution of copper in aluminum and inclusions of the second phase of CuAl2 became fine-grained and single-phase owing to the dissolution of CuAl2 particles in the melt. Irradiation of an alloy of the Al–Mg–Li system containing 2 wt % Li and 5 wt % Mg at q = 5 × 106 W/cm2 and τ = 50–100 ns after four pulsed impacts of fast ions and deuterium plasma led to the modification the structural-phase state of the surface layer of the alloy associated with an increase in the content of magnesium oxide and a decrease in the crystal lattice parameter of the Al-based solid solution. The formation of spherical cavities due to the evaporation of lithium into the internal micropores of the surface layer is also found. The low damageability and structural stability of Al2O3 ceramic on an Al substrate under beam-plasma impacts in the plasma focus facility with a radiation power density q ≤ 108–109 W/cm2 in the nano- and microsecond range of pulse duration is noted. At the same time, the Al2O3/Al composition was unstable to pulsed laser radiation in the free-running mode (q = 105–106 W/cm2, τ = 0.7 ms) and Q-switch mode (q = 107–108 W/cm2, τ = 80 ns). In both cases, the coating peeled off from the substrate.
      PubDate: 2022-04-01
       
  • Kinetic Study of Lithium–Zinc Ferrite Synthesis under Electron Beam
           Heating Conditions

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      Abstract: In this paper, we consider the kinetic regularities of lithium–zinc ferrite synthesis under conditions of heating by a high-energy electron beam of mixtures of initial reagents Fe2O3–Li2CO3–ZnO of bulk density and pressed in a hydraulic press. Radiation-thermal synthesis of the samples was performed using an ILU-6 pulsed electron accelerator by heating them with a 2.4-MeV high-energy electron beam. The samples were heated to 600, 700, and 750°C and held at these temperatures for up to 120 min. For comparison with radiation-thermal synthesis, similar studies were carried out with traditional thermal annealing under the same conditions. An X-ray diffraction analysis of the synthesized samples was performed. The rate of ferrite formation was found to depend on both the heating method and the density of the mixture. Heating the mixture with an electron beam is shown to significantly accelerate the process of obtaining ferrite, which manifests itself in a decrease in the values of the kinetic parameters of the ferrite synthesis. An increase in the rate of ferrite formation under the effect of electrons is due to a significant decrease in the activation energy of the synthesis and a decrease in the pre-exponential factor in the temperature dependence.
      PubDate: 2022-04-01
       
  • Prediction of Space Groups for Perovskite-Like
           $${\text{A}}_{{\text{2}}}^{{{\text{II}}}}$$ BIIIB'VO6 Compounds

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      Abstract: The prediction of new compounds having such composition as \({\text{A}}_{{\text{2}}}^{{{\text{II}}}}\) BIIIB'VO6 was carried out, the type of distortion of their perovskite-like lattice and the space group were predicted, and the crystal lattice parameters of the predicted compounds were estimated. For the prediction, only the property values of the chemical elements were used. The programs based on machine learning algorithms for different variants of neural networks, a linear machine, the formation of logical regularities, k-nearest neighbors, and support vector machine showed the best results when predicting the type of distortion of a perovskite-like lattice. When evaluating the lattice parameters, programs based on algorithms for orthogonal matching pursuit and automatic relevance determination regression were the most accurate methods. The prediction accuracy for the type of distortion of perovskite-like lattice was no less than 74%. The accuracy of estimating the lattice linear parameters was within ±0.0120–0.8264 Å, and the accuracy of angles β for the monoclinic distortion of the lattice amounted to ±0.08°–0.74°. The calculations were carried out using systems based on machine learning methods. To evaluate the prediction accuracy, an examination recognition in the cross-validation mode was used for the compounds included in the sample for machine learning. The predicted compounds are promising for searching for novel magnetic, thermoelectric, and dielectric materials.
      PubDate: 2022-04-01
       
  • Numerical Evaluation of Subcritical Crack Growth Kinetics in Structural
           Adhesive Joints under Long-Term Static Loads Using Cohesive Zone Model and
           Experimental Data

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      Abstract: A numerical method for the simulation and calculation the subcritical crack growth kinetics and for plotting kinetic G–V diagrams for structural adhesive junctions under prolonged static loading is proposed. The load has been set by the global subcritical crack opening according to mode I. The simulation and calculations have been carried out using a cohesive zone model implanted into the finite element method in the environment of the ANSYS software package. The parameters of the cohesive zone law and the subcritical crack growth kinetics have been experimentally determined for samples in the form of a double cantilever beam made of aluminum alloy plates glued using industrial grade epoxy adhesive. Comparison of the calculated and experimental data has shown a good correlation.
      PubDate: 2022-04-01
       
  • Solvatochromic Effects in Absorption and Luminescence Spectra and
           Stability of the Emission Quantum Yield of Carbon Nanoparticles: Part I

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      Abstract: We studied the features of the solvatochromic effects of absorption and photoluminescence spectra and the emission quantum yield of carbon nanoparticles synthesized by various methods from a mixture of citric acid and nitrogen-containing precursors in protic and aprotic solvents. The parameters of absorption and photoluminescence spectra and the value of the quantum yield of emission of particle solutions largely depend on the method, conditions, and modes of synthesis, the method of modification and separation of carbon nanoparticles, types and composition of precursors, and fundamental properties of solvents and their pH. In solvents with a dielectric constant of 4.5–109.5, the quantum yield of particle emission varies in a wide range of 10.8 to 100.0%, and the peak of the photoluminescence band shifts from 466.4 to 536.8 nm. There are strong solvatochromic effects of the absorption and photoluminescence spectra of particles, and the contribution of the protonation and deprotonation of surface groups of carbon nanoparticles is rather significant. The effect of universal and specific interactions on the spectroscopic parameters of carbon nanoparticles is investigated, and a significant contribution to the solvatochromic effects of specific interactions is demonstrated.
      PubDate: 2022-04-01
       
  • Selective Hydrogen Absorption by Ti–Ni Powders near Equiatomic
           Composition after High-Intensity Mechanical Treatment

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      Abstract: The Ti–Ni powder having a composition close to the equiatomic one after its high-intensity mechanical treatment and hydrogenation with the use of an electrochemical method has been studied. It is shown that the powder in its initial state consists of a mixture of TiNi (austenite, martensite), Ti2Ni, and TiNi3 phases, whereas after the mechanical treatment (ball milling), an X-ray amorphous phase is formed. It has been shown that the dislocation density estimated on the basis of X-ray data after the treatment changes differently in all the phases. For the Ti2Ni phase, this parameter is significantly greater than that for TiNi and Ni3Ti. It has been found that the lattice parameters of TiNi (austenite) Ni3Ti do not change in the course of electrochemical hydrogenation after the treatment and they agree with the published data. The lattice parameter of the Ti2Ni phase exhibits an increase, which indicates prevailing interaction between hydrogen and Ti2Ni phase owing to a high dislocation density and a high concentration of rather large octahedral/tetrahedral voids. It has been shown that there is an “incubation period” in the hydrogenation of Ti2Ni phase amounting to 90 min for the mechanical treatment for10 s. It is shown that the lattice parameter of the Ti2Ni‑based phase corresponds to such hydrides as Ti2NiH0.5 and Ti2NiH0.8 depending on the duration of milling and on the hydrogenation time. For example, the lattice parameter of the Ti2Ni-based phase can correspond to such hydrides as Ti2NiH0.5 and Ti2NiH0.8 after 30 and 300 s of milling after 90 min of hydrogenation and can correspond to Ti2NiH0.5 after 10 s of milling and 140–180 min of hydrogenation.
      PubDate: 2022-04-01
       
  • Heat-Resistant RuAl-Based Alloys: III. Powder Alloys—Mechanical
           Alloying

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      Abstract: Refractory (melting point Tm = 2100°C), heat-resistant ruthenium monoaluminide RuAl, lighter (ρ = 7.97 g/cm3) than Ni superalloys, is considered as a promising material for operation at a high temperature and under relatively low loads in high-velocity gas oxidizing flows. This alloy can be used not only at a temperature higher than operating temperature tw inherent in both nickel superalloys and nickel and titanium aluminides, but also at a temperature higher than the melting point of the latter. RuAl is also an ideal candidate for potential use in protective coatings. In the first part of the paper, RuAl-based cast alloys have been considered. In the second part of the paper, the potentialities of obtaining alloys based on RuAl directly from the initial powders of ruthenium and aluminum by combining the temperature–time modes of reactive alloying (RA), as well as the sequence and intensity of pressure application in the course of RA, are considered. The third part of the paper is devoted to studying the potentialities of powders doped with RuAl (NiAl, TiAl) with a preset composition obtained by means of mechanical alloying used as a starting material.
      PubDate: 2022-04-01
       
  • Poisson Ratio of TiNi

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      Abstract: A review of the published data and methods for calculating the Poisson ratio of the TiNi intermetallic compound in the poly- and single-crystal state is performed. The results of our own research are also presented. Significant variability of the presented data is noted, which is due to differences in the thermomechanical processing of the alloys and the measurement and calculation methods used. By averaging the matrices of elastic constants and compliance coefficients using the Voigt, Reuss, and Hill approximations, we obtained the values of the parameters of the effective elastic properties of TiNi polycrystals and calculated the Poisson ratio. Using analytical expressions to calculate the values of the extreme values, the extrema of the Poisson ratio of cubic TiNi crystals are determined for standard orientations. On the basis of a number of data, TiNi crystals are auxetics (materials having negative Poisson ratio values); on the basis of other data, they are not. We found that TiNi crystals belong to the so-called partial auxetics; in this case, the signs of the inequalities (s12 < 0, s = s11 + s12 – s44/2 > 0 or s12 > 0, s = s11 + s12 – s44/2 < 0) are opposite. The values of the Poisson ratio TiNi averaged over the transverse directions of deformation are analyzed. Isosurfaces of the Poisson ratio and their sections are presented using the ELATE computer graphics package and the M-ATHCAD computer algebra program. Aspects of TiNi elastic anisotropy, its parameters, and their relationship to martensitic transformations in TiNi and alloys based on it are discussed.
      PubDate: 2022-04-01
       
  • Obtaining of Low-Flammable Sorbent Based on Polyurethane Foam for Trapping
           Radioactive Iodine Forms

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      Abstract: The composite sorption material based on a highly porous polyurethane foam matrix with a layer of impregnated activated carbon powder applied to its surface has been developed. The reticulated polyurethane foam Regicell was used as a base for the sorbent samples. The compounds that most effectively inhibit the combustion process were phosphates, sulfates, borates and pyrosulfates. The selection of the optimal amount of the fire retardant was carried out and the sorption capacity of the material samples in relation to radioactive methyl iodide was studied. It became clear that the sorbent treated with a 20% solution of ammonium sulfate can be classified as a material with low combustibility. The study of the sorption capacity was carried out on a certified stand under conditions corresponding to the standard test method for iodine sorbents applied to nuclear power plants. During the tests, more than 99.9% radioactive methyl iodide trapping efficiency was achieved, which exceeds that for the industrial granular sorbent as a reference. It was found that the gas flow hydraulic resistance corresponding to the manufactured samples is lower than that of the industrial one. The relative sorption capacity index was used as a criterion for comparing the sorption capacity of materials characterized by different free volume fractions.
      PubDate: 2022-04-01
       
  • Study of Rheological and Structural Properties of Modified Carboxymethyl
           Cellulose Solutions Using Crosslinking Agents Based on Substituted
           Oxyranes

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      Abstract: Modified carboxymethyl cellulose (CMC) biopolymer materials are widely used in various fields of medicine. For different medical purpose and therapeutic goals, it is required to regulate the degree of biodegradation of implanted biopolymers by synthesizing modified gels using substituted oxyrane crosslinkers—1,4-butanediol diglycidyl ether (BDDE) and polyethylene glycol diglycidyl ether (PEGDE). However, their high cost dictates the urgency of investigation of new crosslinking agents that will be cheaper and at the same time will not require a change in the technological process. So, the crosslinking agent polypropylene glycol diglycidyl ether (PPGDE) was chosen. In this work the rheological and structural properties of modified CMC gels with a new crosslinking agent—polypropylene glycol diglycidyl ether (PPGDE)—were investigated and compared with the properties of both unmodified CMC and modified CMC using BDDE and PEGDE. It is shown the modified samples have a 2–3 times higher viscosity in comparison with unmodified CMC. The sample modified with PPGDE showed high viscosity and shear force; however, the difference in comparison with the other samples is small. The degree of modification of all gels is similar, but the degree of crosslinking of PPGDE is practically absent. However, owing to the low degree of crosslinking in the rest of the samples, this parameter has no effect on the viscosity of the solution. The cytotoxicity of all gels was also tested, which confirmed their low toxicity. Thus, gels using a new crosslinking agent—PPGDE—exhibit properties similar to both BDDE and PEGDE, which makes it possible to predict other properties and effects in practical use.
      PubDate: 2022-04-01
       
  • Gas Extrusion Treatment of Thermally Hardened Steel and Alloys in the Mode
           of Deformation-Thermal Hardening

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      Abstract: Thermally hardened alloys based on iron (50KhFA steel), titanium (VT-14), and aluminum (D16) were subjected to deformation by gas extrusion with local heating in the mode of deformation-thermal hardening with high degrees of deformation 90% or more to obtain a thin wire at the output. Gas extrusion was performed at various combinations of processing parameters–gas pressure, deformation temperature, extrusion speed. The wire deformed under various combinations of processing parameters was cooled in air and subjected to tempering or aging and a tear test. The mechanical properties obtained as a result of the tests were compared with the data on the mechanical properties of the initial undeformed alloys and heat-treated and non-heat-treated alloys. On all gas-extruded alloys, the mechanical properties exceeded the initial ones in both strength and plasticity. The combination of gas extrusion parameters (gas pressure, deformation temperature, extrusion speed) has a decisive influence on the combination of strength and ductility of alloys treated by gas extrusion.
      PubDate: 2022-04-01
       
  • Synthesis and Characterization of NaYF4:Yb3+:Er3+/NaYF4 Upconversion
           Nanophosphors

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      Abstract: The NaYF4:Yb3+:Er3+/NaYF4 upconversion nanophosphors (UCNPs) containing ions of rare-earth elements with a core/shell structure were synthesized solvothermally, and their photoluminescent properties were analyzed depending on the size of nanoparticles and preparative synthesis conditions. We showed that the intensity and lifetime of photoluminescence of the upconversion nanoparticles depend on the intensity of laser excitation, the size of the nanoparticles, and the presence of an inert shell. When an inert shell is formed on the surface of NaYF4:Yb3+:Er3+ nanoparticles, the conversion coefficient of visible and near-IR radiation in different spectral regions can increase by an order of magnitude owing to the shielding of luminescent centers from nonradiative losses at surface defects.
      PubDate: 2022-04-01
       
 
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