V. G. Kuryavyi

Radiation-chemical synthesis of tetrafluoroethylene telomers and their use for preparation of thin protective fluoropolymer coatings

The specific features and possibilities of preparation of protective coatings and composite materials based on fluoromonomers using high-energy rays (60Co γ-rays, fast electrons) were analyzed. The emphasis was placed on synthesis and application of tetrafluoroethylene telomers in acetone. The structure and properties of telomers were examined by IR and NMR spectroscopy, as well as by X-ray diffraction analysis and diathermy. The radiation initiation allows preparation of new products with a broad spectrum of functional properties and opens wider prospects for technological application of fluoromonomers.

Atomic force microscopy and X-ray photoelectron spectroscopy study of chitosan-carbon fiber materials

Chitosan-carbon materials produced by electrochemical deposition of chitosan on an activated carbon fiber (ACF) as an electrode have been studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM data demonstrate that the microstructure of the coating depends on whether chitosan is deposited in soluble or insoluble form. XPS data are used to evaluate the state of chitosan in the composites in relation to the deposition conditions.

Photochemical properties of mixed-ligand complexes europium carboxylates

The photochemical behavior of mixed-ligand complexes of europium carboxylates with nitrogen-and phosphorus-containing neutral ligands of island and dimer types, Eu(L)3 · xD · nH2O and [Eu(L)3 · xD]2 · nH2O (L is the trifluoroacetate, toluate, or cinnamate anion), was studied. During UV irradiation of the complexes of europium carboxylates with 1,10-phenanthroline and 2,2′-dipyridyl, a luminescence buildup was observed. EPR measurements demonstrated that the observed buildup of luminescence from europium occurs in parallel with the increase of the concentration of radical anions formed from neutral ligands.

Morphology and structure of micro- and nanosize polytetrafluoroethylene powders prepared by the gas-phase method

Formation of fluoropolymer nanoaerosols and micropowders in the gas products of polytetrafluoroethylene pyrolysis and the hierarchical self-organization of ultradispersed powders were revealed. The features of the molecular and supramolecular structures of powders were analyzed. Low- and high-molecular-weight fractions of the fluoropolymers, constituting the powder particles were identified, and a method for their partitioning was proposed.

Properties of silicon prepared from plant raw materials

High-purity X-ray amorphous silicon dioxide samples have been prepared by hydrolyzing siliconcontaining plants in a 0.1 N HCl solution, followed by calcination at 700°C in air. Reducing the silica with metallic magnesium, we obtained silicon, which was then purified by sequential washings with hydrochloric, hydrofluoric, and sulfuric acids and water. The fine silicon powder thus prepared, up to 97.6% in purity, ranging in color from light brown to dark brown, was characterized by X-ray diffraction and IR spectroscopy. According to total external reflection X-ray fluorescence, electron probe microanalysis, and chemical analysis data, the major impurities in the powder were silicon dioxide, iron (within 0.45%), titanium (within 0.10%), calcium (within 0.088%), and manganese (within 0.031%). According to scanning electron microscopy data, the silicon obtained has the form of spongy material ranging in pore size from 50 to 200 nm.

Surface morphology and dispersity of europium heteroligand compounds subjected to mechanical activation

The methods of scanning electron and atomic-force microscopy were used to study the surface shape, size, and morphology of the particles in a reaction mixture (rare-earth salts with organic ligands) before and after mechanical processing in a centrifugal planetary ball mill. It was established that, after mechanical treatment, the luminescent europium and terbium heteroligand carboxylates and β-diketonates with neutral nitrogen-containing ligands turn into 10–12-μm globules composed of smaller particles with sizes 0.3–0.01 μm.

Mechanochemical synthesis of mixed-ligand europium β-diketonates with nitrogen-containing neutral ligands

The solid-phase reaction between europium salts of β-diketones and nitrogen-containing neutral ligands in a planetary mill produces luminescent mixed-ligand compounds Eu(β-dic)3 · D, where β-dic stands for dibenzoylmethane (DBM), benzoylacetone (BA), thenoyltrifluoroacetone (TTA), or benzoyltrifluoroacetone (BTFA); and D stands for 1,10-phenanethroline (Phen), 2,2-dipyridyl (Dipy), or diphenylguanidine (DPG). The mechanosynthesis and yield of lanthanide β-diketonates are studied as affected by the treatment parameters and the nature of the reagents. Powder X-ray diffraction demonstrates a staged course of the mechanochemical synthesis. Examination of formation-rate curves shows that grinding/stirring is the rate-controlling stage of the process. Thermogravimetric analysis (TGA) shows that the mechanosynthesis can proceed in the self-propagation mode. The relative luminescence intensity is determined as a function of treatment time. Particles of the mechanically activated mixture have sizes of 10–100 μm.

The mechanochemical treatment of europium nitrate with 1,10-phenanthroline

The reactions that occur during the mechanochemical treatment of europium nitrate with 1,10-phenanthroline were studied by X-ray electron, infrared, and luminescent spectroscopy. Two minutes of mechanical activation resulted in the formation of europium nitrate, 1,10-phenanthroline, and water. According to the X-ray electron spectroscopy data, the coordination of 1,10-phenanthroline to europium nitrate was accompanied by a decrease in the Eu 4d5/2 binding energy. Intense mechanochemical transformations caused changes in the composition of the surface of samples. Changes in the shape and size of reaction mixture particles and the morphology of sample surfaces after mechanical treatment in a ball mill compared with the initial mixture were studied.

Morphological structure and dispersity of luminescent heteroligand europium cinnamates

The luminescence characteristics of heteroligand europium cinnamates are reported. As follows from the IR spectra, cinnamic acid coordinates with europium in these compounds in the bidentate fashion. The shape, size, and surface morphology of particles of heteroligand europium cinnamates were determined by scanning electron and atomic force microscopy. Heteroligand europium complexes usually form plate-like and needle-like microcrystals of size 0.1–15 μm.

Hybrid nickel oxide-carbon fiber composites obtained in the presence of surfactants

The composite material nickel hydroxide (oxide)/carbon fiber has been obtained by hydroxide deposition on the surface of the activated carbon fiber (ACF) via urea hydrolysis in the presence of a surfactant. The organomineral composite NiO/CHIT/carbon fiber has been obtained by electrochemical deposition of nickel hydroxide on the ACF surface in combination with chitosan as well as by cathode deposition on a carbon fiber electrode preliminarily modified by chitosan. The surface of the obtained hybrid materials has been investigated by means of the methods of X-ray photoelectron spectroscopy (XPS), atomic force and scanning electron spectroscopy (AFM and SEM), and cyclic voltamperometry. The composition and properties of the obtained composites have been discussed.