Vol 90, No 11 (2017)

The progress of the biodiesel industry throughout the world led to the overproduction of glycerol, which, in turn, led to a drastic decrease in the glycerol price. This makes glycerol an attractive raw material for preparing various products and intermediates. Procedures for converting glycerol into high value added products are considered in this review.

Effect of synthesis conditions on the formation and dielectric characteristics of materials based on the La_0.33Ca_0.67Al_0.33Ti_0.67O₃ phase was studied. It is shown that the new approach suggested in the study to obtaining ceramic materials based on the LaAlO₃–CaTiO₃ system via introduction of an excess amount of Al₂O₃ over the stoichiometry of L_a0.33Сa_0.67Ti_0.67Al_0.33O₃ results in that a finely grained material is formed with relative permeability ε = 45, temperature coefficient of the relative permittivity τ_ε =–66 × 10^–6 K^–1, dielectric losses tan δ = 2 × 10^–4, and quality factor Q = 4700 at f = 9 GHz. The functional characteristics of the resulting material are comparable with the parameters of the materials synthesized by chemical coprecipitation and indicate that its use in elements of microwave electronics is promising.

It was demonstrated experimentally that the spatial separation of two processes of chemical vapor deposition, one of which provides synthesis of filler (MoS₂) nanoparticles and the other yields the matrix (SiO₂) of the nanocomposite coating, performed ina common reactor, enables an independent control over two process rates and makes it possible to widely vary the composition of the films deposited in this way. The deposition was performed in a double-zone vertical tubular quartz reactor. Molybdenum disulfide particles were produced by pyrolysis of aerosols of ammonium thiomolybdate solutions in dimethylformamide in the upper zone of the reactor, and the plasma-chemical deposition of a nanocomposite coating occurred in the lower zone into which MoS₂ nanoparticles were transported by the gas flow and tetraethoxysilane was delivered. It was shown that the nanocomposite coatings composed of molybdenum disulfide (filler) and silicon oxide (matrix) possess improve the antifriction properties as compared with the matrix (SiO₂ layers), these properties being determined by the relative amounts of MoS₂ nanoparticles in the layer and by their average size.

Lithium-vanadium bronze Li_1+xV₃O₈ was produced by the solid-phase method and its electrical conductivity was measured with silver and platinum electrodes. X-ray diffraction and thermal analyses demonstrated that Li_1+xV₃O₈ interacts at a temperature of 480°C with metallic silver to give AgV₂O₅ and AgV₃O₈, which is responsible for the poor reproducibility of results in electrical conductivity measurements with silver electrodes.

Polycondensation of a mixture of diamines, 3,3'-dihydroxy-4,4'-diaminodiphenylmethane and bis-(3-aminopropyl)dimethylsiloxane taken in a 3: 2 molar ratio, with isophthaloyl chloride was used to synthesize a silicon-containing poly(ortho-hydroxyamide) POA-Si exhibiting an increased adhesion to such substrates as Si, SiO₂, quartz, glass, and glass-ceramics. The polymer was separated by the fractional precipitation method into seven fractions and its polydispersity was evaluated. The degree of intramolecular orientation ordering (Kuhn segment) was determined and Mark–Kuhn–Houwink equations were derived, which can be used to determine the molecular masses of the newly synthesized samples.

To characterize the stability of the filtration combustion (FC) front, a dimensionless coefficient that describes the spatial distortions of the combustion front and is equal to the ratio between the maximum and minimum front width is suggested. It was shown for the example of bidisperse fuel mixtures of hard coal that, with an inclined rotating reactor, the gasification process can be stabilized as compared with the vertical reactor. A stable combustion front was observed at any content of the fine fraction in experiments of gasification of a fuel composed of 5–7- and 3–5-mm fractions. A stable combustion front was observed in experiments with a fine (1–2 mm) fraction up to its content of 60%.

Nonionic surfactants added in concentrations significantly exceeding the critical micelle concentration in water increase by a factor of 1.5–2 the content of nanotubes in the dispersion volume upon ultrasonic dispersion of carbon nanotubes and enhance the stability of the system. Homologs with the mean degree of oxyethylation n = 10–12 exhibit the strongest dispersing and stabilizing properties. The electrokinetic properties of carbon nanotube dispersions are influenced by the concentration and degree of oxyethylation of the surfactants. The dispersions obtained can be used for modification of butadiene–styrene latexes and vulcanized rubbers based on them.

The influence of impregnation of aluminum oxide desiccants prepared by centrifugal thermal activation of hydrargillite with alkali (KОН and NaOH) and carbonate (Na₂CO₃ and K₂СО₃) solutions on the physicochemical properties of the products was studied. Impregnation with alkali solutions increases the dynamic capacity of the desiccants by a factor of 2 and more, whereas impregnation with carbonate solutions decreases the sorption characteristics of the desiccants at similar texture characteristics. Introduction of alkaline modifiers leads to a considerable decrease in the concentration of Lewis acid sites on the surface and to an increase in the concentration of strong base sites. Linear correlation was revealed between the concentration of strong base sites on the surface of the desiccants and their dynamic capacity in drying of humid air. The desiccants modified by impregnation exhibit not only high static and dynamic capacity, allowing improvement of the drying efficiency, but also considerably enhanced mechanical strength.

The influence of the solution ionic strength (up to 1.89 M), temperature (up to 413 K) and acidity (pH down to 1.65) on the drag reduction DR and flow rate increment ΔQ of an aqueous solution of the terpolymer containing 71.6 mol % acrylamide, 10.5 mol % acrylonitrile, and 17.9 mol % sodium 2-acrylamido-2-methylpropanesulfonate was studied by capillary turbulent viscometry. The intrinsic performance and the optimum concentrations of the terpolymer under these conditions were determined. The temperature dependence of the flow rate increment for the terpolymer solution passes through a maximum. The turbulence drag reduction for water flows at temperatures exceeding 373 K was demonstrated.

A new three-dimensionally cross-linked plasticized elastomer filled with polyfractional silicon dioxide was developed on the basis of a frost-resistant high-molecular-mass divinyl–isoprene copolymer. A quinol ether was suggested as an effective cross-linking agent. The envelopes of the experimental and calculated energies of mechanical failure at different temperatures as applied to uniaxial extension were constructed. The composite was recommended as a structural material for the development of wear-resistant parts and units of automobile and aviation transport intended for operation in a wide temperature range, including the Russian Extreme North and Arctic.

Well-crystallized and nano-sized LiFePO₄/graphene composite have been successfully synthesized by in-situ disperse graphene oxide (GO) in precursor via a rapid microwave-solvothermal process at 200°C within 10 min. In spite of the low synthesis temperature, the structural and morphological properties of as-prepared composites are of high specific capacity, an excellent high rate capability, and stable cycling performance. In comparison with LiFePO₄/grahite soft-packed full-cell, the assembled soft-packed full-cell with solvothermally synthesized LiFePO₄/graphene composite and graphite electrode show better cycle performances prepared at higher temperature.

Self-Assembled porous micro-spherical LiFePO4 have been successfully obtained through spray drying route. The prepared LiFePO₄ is higher tap of 1.4 g cm^–3 thank to its self-assembled porous structure. The studies of electrochemical performances were conducted at full cell level. The results show that the assembled pouch-typed full-cells with as-obtained LiFePO4 are of excellent rate capability and cycle life. As a result, the as-prepared LiFePO₄ cathode material with self-assembled porous structure is capable of large-scale applications.

A method of adding graphene oxide (GO) and further reinforcing by the treatment of gamma-irradiation was used to enhance the properties of ultrahigh molecular weight polyethylene (UHMWPE). The effects of GO and irradiation on UHMWPE, particularly the influence of irradiation on UHMWPE/GO nanocomposites, were investigated from the aspects of thermal and mechanical properties. The results show that the thermal stability of UHMWPE/GO nanocomposites was slightly decreased by irradiation. But both GO doping and irradiation increased the crystallinity of UHMWPE. A similar variation tendency was appeared between compressive properties and crystallinity. A postulated mechanism was established to explain how GO doping and irradiation actually improved the properties of UHMWPE.

Page 843, Fig. 7. “G, g cm^–2 s^–1” should be replaced by “G × 10⁵, g cm^–2 s^–1.”