Vol 90, No 9 (2017)

Reduction of vanadium(III) oxide with boron carbide and nanofibrous carbon in an induction furnace in argon was used to obtain a highly dispersed vanadium diboride powder. The characteristics of vanadium diboride powders were studied by various analytical methods. It was found that the material obtained contains only a single phase, vanadium diboride, with powder particles mostly aggregated, the average size of particles and aggregates being 9.8 μm at a wide particle size distribution. The optimal synthesis parameters were determined: V₂O₃: B₄C: C ratio corresponding to the stoichiometry, temperature 1700°C, and keeping time 20 min.

Methods for providing stabilization of ammonium nitrate and expanding the application field of this oxidizing agent in gas-generating compositions used for various purposes were sought for. The results of a study of the physicochemical properties of ammonium nitrate with a melamine–potassium nitrate double additive introduced by mechanical mixing and crystallization from an aqueous (nonaqueous) solution at the boiling point are presented. The phase diagrams of the ammonium nitrate–melamine and ammonium nitrate–melamine–potassium nitrate systems, based on the results of a differential-thermal analysis, demonstrated that a phase-stable ammonium nitrate can be formed by using the method of crystallization from an aqueous (nonaqueous) solution at the boiling point. The resulting samples were examined by IR spectroscopy and X-ray diffraction analysis, and a conclusion was made that a new thermodynamically stable phase can be formed in the system with individual additives, and the introduction of a double additive leads to a combined effect: a thermodynamically stable crystal structure is formed, with the simultaneous slowing down of the nucleation and growth of a new phase in the course of a phase transformation.

Processes of hexanitrohexaazaisowurtzitane remodification were studied at various temperatures for three crystallization systems based on acetone, ethyl acetate, and acetonitrile. The remodification conditions of the α- and β-forms into the required ε-modification and also the conditions in which the γ-modification is formed were found. The crystal habits of crystals of the ε-polymorphic modification of hexanitrohexaazaisowurtzitane, obtained in the crystallization systems under study, are described.

Chemical compositions of electrically insulating coatings based on the Cr₂O₃–SiO₂–CaO–NiO system were developed. The coatings effectively protect modern devices in a wide range of positive and negative temperatures (from –60 to +250°C).

Microarc oxidation of aluminum in borate and silicate-alkaline electrolytes in order to form porous ceramic coatings that can be used as catalyst supports was subjected to an integrated study. The advantages of the technological modes of microarc oxidation of aluminum were analyzed. A catalytically active nickel oxide was deposited into pores of a ceramic coating.

X-ray diffraction analysis, synchronous-thermal analysis, and IR spectroscopy were used to confirm the possibility of obtaining a tin–molybdenum solid solution by the closed-cycle technology via joint mechanochemical activation of tin oxide (SnO₂) and molybdenum oxide (h-MoO₃), followed by a thermal treatment at 650°C. An analysis of the catalytic properties demonstrated that various target reaction products (methyl formate and formaldehyde) can be obtained by varying the temperature of the methanol dehydrogenation process. It was found that the selectivity toward methyl formate reaches a maximum of 99.88% at a temperature of 180°C. Raising the temperature further results in that the selectivity toward formaldehyde increases and reaches its maximum value at 260°C.

Differential scanning calorimetry and X-ray diffraction at wide and small angles were used to examine the biodegradable composites of poly-3-hydroxybutyrate with chitosan, produced by mixing of these polymers in a rotor disperser at 150°C. Samples of individual polymers and composites with 80, 40, and 20 wt % poly- 3-hydroxybutyrate were studied. It was found that the presence of chitosan in the composites leads to a change in the crystallite size of poly-3-hydroxybutyrate and to an increase in the large period in this polymer. Mixing of poly-3-hydroxybutyrate with chitosan affects the structural rearrangement in crystalline regions of poly-3-hydroxybutyrate under a high-temperature treatment. The effect of a high-temperature treatment of the composites via alternation of melting–crystallization cycles in the nonisothermal mode, when a sample is heated and cooled at the same constant rate of 8 deg min–1 in the range from 20 to 200°C and is annealed at a temperature of 150°C, was analyzed. This analysis suggests that, in composites of this kind, the intermolecular interaction between the components is a factor strongly affecting the structure of the crystalline regions and the mechanism of their rearrangement in the course of annealing. The mechanism of this interaction is discussed.

Thermoplastic polycarbonate (PC) and nylon 6 (NY) composites with cenosphere and hollow glass beads were prepared and their mechanical, rheological, thermal and flame retardency properties were studied. The flexural behavior of the composites increased after loading with cenosphere and hollow glass beads. The tensile strength of the PC composites was enhanced up to 80 N mm^–2 as compared to pure PC while no remarkable change was observed in case of nylon 6 composites. Study of thermogravimetric Analysis (TGA) showed that the thermal stability of all the composites (Polycarbonate/cenosphere, Polycarbonate/hollow glass beads, Nylon 6/cenosphere and Nylon 6/hollow glass beads) increased. It was concluded that both the fillers enhanced the non-flammability of the polymers. Limiting oxygen index (LOI) value of all the composites showed an increase with increase in the concentration of filler. The optimal results of LOI and UL 94 were observed in composites with 8% cenosphere and 12 % cenosphere in case of Nylon 6. Cenosphere led to superior mechanical properties of polycarbonate and nylon 6 in comparison to hollow glass beads which suggested the composites can find use in automotive, industrial, pump component and for manufacturing of light weight parts in aeronautic industry at lower economic value.

Layered lithium transition metal oxide LiNi_0.5Co_0.2Mn_0.3O₂ cathode materials were successfully obtained through a simple carbonate co-precipitation method. Monodispersed Li[Ni_0.5Co_0.2Mn_0.3]O₂ spherical agglomeration consisted of nanoscale secondary particles enable material to be higher energy and powder density. Pouch-typed cells were assembled to investigate electrochemical performance of Li[Ni_0.5Co_0.2Mn_0.3]O₂ at level of full-cell. The results show that the assembled pouch-typed full-cells present higher capacity, excellent rate capacity, and cycle life, which is due to its monodispersed uniform morphology with nanoscale secondary particles.

A study of nickel coatings electroplated from electrolytes of the compositions (M) NiSO₄ 0.5, NiCl₂ 0.3, and H₃BO₃ 0.404 (electrolyte 1) and NiSO₄ 0.5, NiCl₂ 0.3, and H₃BO₃ 0.404 with the addition of 2 mg L^–1 RADO (electrolyte 2) in the constant-current mode after preliminary potentiostatic treatment (underpotential deposition) of the support revealed the formation of Fe–Ni alloy in the initial moment of formation of the nickel coating. Pretreatment of the steel surface in the underpotential deposition mode allows preparation of uniform finely crystalline nickel coatings with enhanced levels of the wear resistance, microhardness, and corrosion resistance.

The reaction of magnesium hydroxide with a concentrated aqueous solution of iron(III) chloride yields a mixture of magnesium–iron layered double hydroxide and iron oxide–hydroxide in the akaganeite form. The content of these phases depends on the Mg/Fe atomic ratio in the starting reactant mixture. Iron oxide–hydroxide is the major reaction product at the Mg/Fe atomic ratio in the interval 1.5–1.75, and layered magnesium–iron layered double hydroxide, at Mg/Fe = 3–4. The ability of the synthesized products to take up As(III) from aqueous solutions was studied. These sorbents allow the arsenic concentration to be decreased from 3–5 mg L^–1 to values below MPC (0.01 mg L^–1).

A procedure was developed for recovery and concentration of residual palladium(II) from a “lean” refining solution by extraction with 1Н-1,2,4-triazole derivatives. Palladium(II) is extracted quantitatively from 1 M hydrochloric acid solutions and under optimum conditions is selectively separated from platinum(IV) and rhodium(III).

Terpolymers of acrylamide, acrylonitrile, and sodium 2-acrylamido-2-methylpropanesulfonate were prepared by radical copolymerization in aqueous solution. The terpolymers obtained are enriched in acrylamide units and depleted of acrylonitrile units relative to the initial monomer ratio. The acrylamide–acrylonitrile–sodium 2-acrylamido-2-methylpropanesulfonic acid terpolymers show high performance as drag reduction agents. Under the conditions of thermal, salt, and acid aggressions, the terpolymer containing 71.6 mol % acrylamide, 10.5 mol % acrylonitrile, and 17.9 mol % sodium 2-acrylamido-2-methylpropanesulfonate ensures drag reduction no less than 70%.

Nonwoven materials were prepared by electrospinning from solutions of polyethylene oxide in water and in a 0.1 M aqueous lithium perchlorate solution. Addition of lithium perchlorate increases the conductivity of the solutions but does not alter their viscosity. The mean diameter of the fibers obtained was 100–500 nm. The supramolecular structure of the polymer underwent no significant changes in the course of electrospinning. The materials obtained can be applied directly onto organic memristive devices and used as a polymer electrolyte.

New diffusion membranes were prepared by introducing endofullerenes with encapsulated iron atoms, Fe@C₆₀, into the poly-2,6-dimethyl-1,4-phenylene oxide matrix. The structure of transport channels in the films upon swelling in deuteromethanol was determined by small-angle neutron scattering. The mechanical and transport properties of the modified membranes were studied.