Vol 91, No 2 (2018)

Industrial silicon carbide powder was consolidated with boron by the spark-plasma-sintering (SPS) method. It was shown that a preliminary mechanical activation is a promising method for introduction of high concentrations of boron into silicon carbide. The influence exerted by the boron concentration on the sintering and properties of the material based on silicon carbide was examined. A ceramic based on silicon carbide with 10 wt % amorphous boron was obtained with density of 3.12 g cm^–3, hardness of 31.9 GPa, and crack-resistance coefficient of 5.7 MPa m^1/2. The ceramic is promising as a construction ceramic for nuclear reactors and gas-turbine engines.

1 M solutions of NaClO₄ mixed with ethylene carbonate, dimethyl carbonate, and fluoroethylene carbonate were studied as electrolytes for a double-layer supercapacitor with electrodes made of Norit DLC Supra 30 activated carbon. It was shown that the specific capacity of activated carbon depends on the electrolyte composition, range of cycling voltages, and current density. The maximum specific capacitance of 40 F g^–1 was obtained in 1 M NaClO₄ mixed with ethylene carbonate: dimethyl carbonate: fluoroethylene carbonate (4: 5: 1) at a current density of 36 mA g^–1 in the range 10–2300 mV. The minimum specific capacitance was obtained under the same cycling conditions in the electrolyte with 1 M NaClO₄ + ethylene carbonate: dimethyl carbonate (1: 1). The variation of the specific capacitance with the electrolyte composition and range of cycling voltages is accounted for by the existence of a pseudocapacitance caused by the occurrence of side processes on the surface of activated carbon. The impedance spectroscopy was used to find that the introduction of fluoroethylene carbonate into the electrolyte positively affects the charge-transfer resistance and favors an increase in the specific capacitance of activated carbon.

Processes of deposition of multiwall carbon nanotubes in the synthesis by metal-organic chemical vapor deposition on hollow cylindrical substrates and the effect of the substrate area on the yield of the target product were studied. Making larger the tubular deposition reactor and the area of the cylindrical substrate enabled a substantial increase in the yield of carbon nanotubes. The technological synthesis parameters of the carbon material were optimized. Methods were developed for purification of carbon nanotubes by annealing in air, and materials were obtained with purity of no less than 98%. Physicochemical analysis methods were used to examine the structure and properties of the materials.

Specific features of the chemical vapor deposition of carbon-containing nanoparticles from aerosols of CH₅COOH–C₃H₇NO solutions, including the effect of the main technological parameters on the size characteristics, structure, and composition of the products being formed, are described. It is shown that the shape, size, and structure of the particles being formed are determined by processes occurring both in the downstream-first evaporation zone and in the main pyrolysis zone, and the temperatures of these zones are the most important technological parameters. It was found that the concentration of benzoic acid in solution can be used as a technological parameter making it possible to gradually vary the size characteristics of the carbon particles obtained. The results of the study form a basis for development of a technology and equipment for obtaining carbon-containing nanoparticles.

Efficiency of using detonation nanodiamonds is strongly affected by the amount and elemental composition of impurities. The study considers the possibility of affecting the yield of detonation nanodiamonds and diamond-containing stock and the content and composition of incombustible impurities in the stock and diamonds by varying the composition of the water armor (shell) of the classical TNT–hexogen (50/50) charge. As compounds affecting the above parameters were used hydrazine, urotropin, ammonia, urea, Trilon B (disodium salt of ethylene diamine tetraacetic acid), aminotetrazole, and boric acid. It was found that using urotropin was the optimal as regards a whole set of parameters. In this case, the maximum yield of detonation nanodiamonds (6.9%) and diamond-containing stock (13.4%) was obtained. A close yield of the diamond-containing stock and detonation nanodiamonds was provided by using hydrazine and urea in the armor. Use of boric acid in the armor can substantially diminish the variety of impurity elements in the diamond-containing stock and detonation nanodiamonds at an acceptable yield of the diamond-containing stock (11.1%) and detonation nanodiamonds (6.13%). Use of pure water as the armor is inefficient.

With the fast development of the biodiesel industry, the byproduced crude glycerol becomes excessive due to the limited demand for refined glycerol. This article provides a green and efficient route to produce acrylic acid from crude glycerol, which is a promising alternative and complement to the petroleum-based production of acrylic acid due to its economic and environmental benefits. Among all the impurities, only the alkaline metal ions in crude glycerol significantly decreased the yield of acrylic acid. After desalination of the plant crude glycerol with ion-exchange resin to remove the critical impurities, the sequential dehydration and oxidation system gave 86% acrylic acid yield, which was as high as that with pure glycerol. In addition, the system showed good thermal stability and regeneration ability after the reaction with desalted crude glycerol. Both the HPW/Cs–Nb and VMo–SiC catalysts were stable for at least 70 h. The activity and selectivity were well recovered after regeneration at the coke burning temperature of 500°C.

In this study, regular-shaped magnetic-activated carbon nanocomposite (m-Fe₃O₄@ACCs) was synthesized and characterized with X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and the vibrating sample magnetometer (VSM) and was used as adsorbents for the removal of nitrotoluene compounds (NTCs) from water and industrial wastewater. The effective parameters on adsorption process, such as solution pH, shaking speed, contact time, and adsorbent dosage were optimized and the optimum amounts were 7 300 rpm, 10 min, and 1.2 g L^–1, respectively. The contact time and adsorbent dosage are dependent parameters and hence were studied simultaneously. The results showed no significant loss in the adsorption capacity, and the adsorption efficiency of m-Fe₃O₄@ACCs could still be 90% in the 9th cycle. The equilibrium adsorption isotherm followed the Langmuir isotherm model describes the monolayer adsorption of NTCs on m-Fe₃O₄@ACCs, and the maximum adsorption capacities (q_m) for 2-nitrotolouene, 2,6-dinitrotoluene, 2,4-dinitrotoluene, and 3,4-dinitrotoluene were found to be 144.93, 142.86, 166.67, and 153.85 mg g^−l, respectively. The proposed process was successfully applied for the removal of NTCs from tap water and nitration process wastewater.

СоМоS/Sup catalysts were prepared from 12-molybdophosphoric heteropoly acid and cobalt citrate, with Al₂O₃, SiO₂, TiO₂, and ZrO₂ used as supports (Sup). The synthesized catalysts were studied by low-temperature nitrogen adsorption, X-ray diffraction, temperature-programmed ammonia desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The catalytic properties of the catalysts were studied in a flow-through installation at 260 and 340°С, pressure of 3.0 MPa, feed space velocity of 80 h^–1, and Н2/feed ratio of 500 L_n.c. L^–1. The guaiacol hydrodeoxygenation rate increases with a decrease in the mean length of the active phase particles, irrespective of the kind of the oxide support. As for the support effect, the catalyst activity decreases in the order SiO₂ > Al₂O₃ > ZrO₂ ~ TiO₂. On the other hand, the catalysts supported on ZrO₂ and Al₂O₃ exhibit the highest stability. The causes of the observed trends and the possible relationships between the characteristics of the catalysts and active phase nanoparticles are discussed.

Layered nanosized hydrosilicates of various morphologies were prepared by hydrothermal synthesis in the NiO–SiO₂–TiF₄–H₂O system. Hydrosilicate nanotubes of the pecoraite and Ni-montmorillonite structure with a small amount of impurity phases are formed in the examined interval of temperatures and times. These nanomaterials can be used as sorbents, catalysts, and componentes of composite materials for functional purposes.

A new sorbent for noble metal ions, ensuring selective recovery of Au(III) ions from aqueous solutions containing interfering 3d metal ions, was suggested. The new functional derivative, poly(thiocarbamoylsulfostyre ne), was prepared by treatment of poly(chlorosulfostyrene) with thiourea. At the total degree of functionalization with sulfo and thiourea groups of up to 1.0, the degree of thiocarbamoylation can be controlled in the range from 10 to 75%. The composition and structure of the polymer-analogous transformation products were characterized by elemental analysis, Fourier IR spectroscopy, and thermal gravimetric analysis with IR identification of the decomposition products. Evaluation of the sorption activity of poly(thiocarbamoylsulfostyrene) has shown that the sorbent takes up Au(III) ions virtually quantitatively with high selectivity from an aqueous solution containing Co(II), Fe(III), Pd(II), and Ni(II) ions.

A new polyfunctional monomer, 2-chloromethyl-1-(p-vinylphenyl)cyclopropane, was synthesized, and its radical copolymerization with styrene was performed. The copolymerization constants were determined, and the Alfrey–Price Q–e parameters were calculated. The photochemical cross-linking of the synthesized copolymer containing photosensitive groups (cyclopropane ring, chlorinated organic moiety) was studied. The copolymer exhibits relatively high photosensitivity (54 cm² J^–1) and can be used as a photosensitive base of negative photoresists.

Tetrablock polyurethane ureas with mixed soft segments and dissimilar hard urethane urea blocks, based on oligo(propylene oxide)diol, oligo(tetramethylene oxide)diol, 2,4-toluene diisocyanate, isophorone diisocyanate, and methylene-bis-o-chloroaniline as a low-molecular-mass chain extender were synthesized and studied. The fragmentary ordering of the polymer chains of the new polyurethane urea was proved by rheokinetic data. The structure–property relationship for the polymer was found. The new polyurethane ureas surpass in the true strength the available diblock polyurethane ureas with poly(propylene oxide) soft segments by a factor of 1.5. The strength properties of the new tetrablock polyurethane ureas only weakly depend on the strain rate varied in the range 0.56–0.006 s^–1.

Principal possibility of using a smart polymer, poly-N-vinylcaprolactam, for immobilization of biopharmaceuticals (antibodies and antigens) in the course of phase transition of a soluble coil into an insoluble globule was demonstrated. A procedure for preparing a hydrosol stable at room temperature in the presence of a stabilizer was examined. The hydrosol obtained, in which the collapsed polymer with the captured antigen acts as a solid support, can be used for agglutination with a complementary antibody, i.e., the immunochemical reaction can be evaluated visually.

The work is devoted to the study of the joint cathodic electrodeposition of copper with nickel and cadmium during the formation of the paint-and-varnish coating. It was determined that the reduction of nickel and cadmium occurs at the beginning of the electrodeposition process, while copper is deposited throughout the process. The influence of metals on the process of thermosetting of coatings and on their basic properties was defined. Bimetallopolymer coatings containing copper have a thermal conductivity 2 times greater than polymer coatings.