Vol 89, No 8 (2016)

Titania powders with anatase structure and crystallite size ranged from 20 to 27 nm were produced from titanium hydroxide by hydrothermal synthesis. The nanopowders and the initial hydroxide were isothermally heat-treated in a hydrogen flow at temperatures of 00–1000°C for times ranging from 1 to 27.5 h. It was found that the thermal treatment of titanium hydroxide in a reducing atmosphere at 800–900°C yields TiO₂ with rutile structure. An unusual thermal stability of the metastable structure of anatase was observed in the case of nanocrystalline TiO₂ powders up to a temperature of 900°C at which the anatase–rutile phase transition is observed. It was found that the nonstoichiometry of rutile and anatase powders changes upon a thermal treatment in a hydrogen flow. The heat-treatment in a hydrogen flow at 1000°C for 1 h was shown to lead to the formation of nanoparticles of the Magneli phase with the composition corresponding to Ti9O17 irrespective of the chemical nature of the precursor. The increase of the heat-treatment time at this temperature leads to the appearing of the Magneli phases with the compositions corresponding to Ti₈O₁₅ and Ti₉O₁₇ and Ti₂O₃ and Ti₃O₅ suboxides in addition to the Ti₉O₁₇ main phase.

Glycine-nitrate combustion method was used to obtain powders based on CeFeO₃ nanocrystals with average crystallite size in the range from 33 ± 3 to 51 ± 5 nm. The influence exerted by parameters of the glycine-nitrate combustion process and, in particular, by the glycine-nitrate ratio (G/N) on the composition and crystallite size of the synthesis products was determined. The optimal G/N ratio at which nanocrystalline cerium orthoferrite is formed with the minimum amount of impurity phases Fe₂O₃ and CeO₂ was found to be 0.8. It was demonstrated that the composition of the starting solution affects the nature of the phase heterogeneity in the resulting product, crystallite size, and porosity of the nanocrystalline powders being formed. The patterns determined in the study make it possible to optimize the technology of nanocrystalline powders based on CeFeO₃ in order to obtain powders with prescribed phase composition and crystallite sizes to enable their use as a basis for photocatalytic materials.

Carbon-enriched glass-like material was produced by pyrolysis of polymethylphenylsiloxane. The physicochemical (examined by X-ray powder diffraction analysis, photoelectron spectroscopy, Raman scattering method, and energy-dispersive X-ray analysis) and electrochemical (examined by galvanostatic/potentiostatic cycling of electrodes in an organic electrolyte) properties of this material make it possible to regard it as a silicon-doped hard carbon. A thin-film electrode made of this material is cardinally different from pasted powder electrodes in the small hysteresis of charge-discharge curves and high reversible and low irreversible capacity with respect to lithium ions.

Electrochemical deposition of molybdenum oxides from molybdate-containing solutions onto glassy carbon electrodes and the same electrodes coated with a film of poly(3,4-ethylenedioxythiophene) conducting polymer was studied. The morphology of the deposited molybdenum oxides was examined by scanning electron microscopy. The method of X-ray photoelectron spectroscopy was used to determine the state of molybdenum in surface molybdenum oxides and a conclusion was made that the oxide MoO₂ is mostly present.

Template two step electrodeposition method and atomic layer deposition were used to synthesize copper nanowires of varied length (1.2 to 26.2 μm) and copper nanowires coated with titanium dioxide. As a result of the atomic layer deposition of TiO₂, coated nanowires demonstrated an up to 10-fold decrease in the wetting angle, compared with uncoated nanowires. It was found the dissipation rate is substantially higher for nanowires coated by the atomic layer deposition method (100 s) as compared with the uncoated copper nanowires (400 s), which assumes the positive properties of water propagation along the surface, necessary for improving the heat transfer. It was also found that the water contact angle for uncoated nanowires and those coated with TiO₂ by the atomic layer deposition (ALD) gradually increases as the samples are kept in air. A gradual increase in wettability was also observed for smooth silicon wafers coated by ALD of TiO₂, which were exposed to air. On the coated silicon substrates, the wetting angle gradually increased from 10° to approximately 56° in the course of four days. In addition, it was shown that copper nanowires coated with TiO₂ by the atomic layer deposition method have an excellent corrosion resistance, compared with uncoated nanowires, when brought in contact with air and water.

The development of the catalytic properties of supported model catalysts СuO·ZnO·K₂O/SiO₂ with different component ratios in methanol dehydrogenation was studied. In the temperature interval 400–500°С, the formation of the target product, formaldehyde, is accompanied by the formation of surface polymeric hydrocarbons, which undergo gradual condensation to coke with the evolution of hydrogen and carbon dioxide. By properly combining the concentrations of the supported components and the sequence of the deposition of zinc, copper, and potassium oxides, it is possible to reduce the time in which the steady-state catalyst operation mode is reached and to improve the catalyst selectivity with respect to formaldehyde formation.

The possibility of modification of polyvinyl alcohol with epichlorohydrin was examined with the aim of preparing hemocompatible materials exhibiting high mechanical density at limited swellability. The conditions of modification and preparation of branched polyvinyl alcohol and of hemocompatible hydrogel systems with improved operation properties were determined.

The influence of the ratio of the acrylamide, acrylonitrile, and 2-acrylamido-2-methylpropanesulfonic acid monomeric units in the terpolymer on its resistance to elevated temperatures and sensitivity to calcium salts was studied. The influence of the terpolymer composition on the chemical transformations occurring under the conditions of thermal and hydrothermal treatment was studied by TGA and IR spectroscopy. The degree of hydrolysis of the terpolymers influences their resistance to CaCl₂. The resistance of the terpolymers to CaCl₂ additions at their concentrations of up to 7 wt % is preserved at the content of 2-acrylamido-2-methylpropanesulfonic acid units higher than 20 mol %. The revealed features allow optimization of the structure of polymer systems used in drilling lubricants.

The effect of COOH-functionalized multiwalled carbon nanotubes on the temperature–velocity conditions of the fabrication of composite glass fiber reinforced plastic rebars (so-called needletrusion) used in building was studied. EPIKOTE 862 epoxy oligomer (Bisphenol F diglycidyl ether) in combination with EPICUREW curing agent (aromatic diamine) in 100 : 26.4 ratio was used as binder. The use of functionalized multiwalled carbon nanotubes as additives to the unmodified epoxy binder for fabrication of composite materials by needletrusion allows production of high-quality items with the required characteristics without loss in the production capacity. It is preferable to introduce nanotubes in an amount of no more than 0.2 wt %.

Specific features of remote plasma chemical etching of photoresist layers based on diazonaphthoquinones in oxygen at reduced pressure was studied. The possibility of performing “soft” etching at rates of 4–10 nm min^–1 to obtain a photoresist layer surface with the root-mean-square roughness no higher than 0.2 nm was demonstrated.

In the present study, the effect of parameters, including microwave irradiation power, pH, dosage of chemical reagents (collector, depressant and activator) were studied by microflotation (in Hallimond tube) process. The mechanical flotation tests were carried out on optimum parameters obtained from microflotation tests. The software based on experimental design method (DX7) with the two-level full factorial design was applied to determine the parameter effects and to optimize the microflotation recovery. The optimum conditions were determined by analysis of variance (ANOVA), indicating that the irradiation power was the most effective parameter. The optimum values of parameters in the microflotation process are as follows: power of microwave (1000 W), pH (6.3), dosage of chemical reagents (sodium oleate 3.65 × 10^-4 M as a collector, acidified sodium silicate 2 g L^–1 as a depressant, and lead(II) nitrate 2.1 × 10^–5 M as an activator). By applying these optimized parameters, a product with ilmenite recovery of 83.26% was predicted by the software. The results of microflotation tests indicated that an ilmenite recovery of 82.35% was achieved being very close to the predicted value. The results of mechanical flotation based on optimized condition showed that the recovery and separation efficiency of irradiated ilmenite were improved up to 86.03% and 48.61%, respectively, indicating the positive effect of irradiation on ilmenite floatability.

The process of precipitation of ammonium ferric sulfate dodecahydrate (NH₄Fe(SO₄)₂·12H₂O) from waste solutions, obtained during autoclave oxidation of pyrite concentrate has been studied. A special feature of these solutions is the high concentration of Fe(III) ions (>60 g L^–1) and sulfuric acid (> 61 g L^–1). Based on comprehensive laboratory tests, the study determined the optimal conditions for the precipitation process of ammonium ferric sulfate dodecahydrate (AFS) by salting out with ammonium sulfate: reagent excess (100% over stoichiometric, temperature 276 K, time 1 h). The process should be conducted under continuous slow stirring which would not allow forming of large crystals that are difficult to remove from the reactor. The test work confirmed that high quality crystals can be produced by prior oxidation of Fe(II) to Fe(III) ions using hydrogen peroxide and copper removal from the solution.

In the paper, a shale inhibitor, glucose graft copolyammonium (GGPA), was prepared and evaluated by bentonite linear expansion test, anti-swelling experiments, mud ball experiments. The drilling fluid properties were evaluated. Anti-swelling results shows that anti-swelling rate of 0.8% GGPA reaches up to 94.5%. Mud ball experiment and drilling fluid evaluation showed that GGPA has strong inhibitive capability to bentonite hydration swelling. GGPA can control the particle size of bentonite. The inhibition mechanism of the polyamine salt was analyzed by thermogravimetric analysis and scanning electron microscope. The results demonstrate that the GGPA can be adsorbed on clay surface through electrostatic interaction and hydrogen bonds by an anchoring effect and a hydrophobic effect.

The NH₃–SCR of NO reaction has been studied using three different manganese containing catalysts supported on γ-Al₂O₃, ZSM-5, and SAPO-34. The nanocatalysts were prepared by homogeneous deposition precipitation (HDP) method and characterized via BET, TEM, H₂-TPR, and NH₃-TPD analysis. The activity of the catalysts varied significantly depending on the type of the support. The Mn-ZSM-5 and Mn/γ-Al₂O₃ catalysts were more active for NO conversion than Mn-SAPO-34 catalyst. The no correlation was found between surface area, strength and amount of acid sites, and NO conversion of the catalysts. The results of H₂-TPR revealed lower onset reduction temperatures of MnO_x species in Mn-ZSM-5 and Mn/γ-Al₂O₃ compared with Mn-SAPO-34, indicating easily reducibility of MnO_x species in these catalysts. The redox properties of catalysts are responsible for the SCR activity. The Mn-SAPO-34 catalyst contains low quantitative of access reducible MnO_x species, which is followed by considerable decrease in the activity. The NO conversion ability of Mn-supported catalysts has been correlated with support structure.

A procedure involving portionwise extractant feeding was suggested for improving the characteristics of selective extraction of metal ions from aqueous solutions. This procedure enhances the extraction of metal ions into the organic phase, reduces the extractant consumption, and increases the distribution ratio of metals between the organic and aqueous phases and the metal separation factor in extraction.