Search

The synthesis of barium hexahydroxostannate BaSn(OH)6 and its thermal destruction leading to the barium stannate BaSnO3 have been studied. It is shown that the most intensive decomposition of BaSn(OH)6 occurs in the temperature range of 200–650°C. Crystallization of BaSnO3 proceeds in a narrow temperature range (650–675°C), and the maximum of the corresponding exo-effect is located at 667°C. It was found that at 500°C (within 60 min) BaSn(OH)6 completely decomposes with the formation of X-ray amorphous powder. When the material is kept at 600°C (60 min), crystallization of barium stannate BaSnO3 with perovskite structure takes place. The crystalline impurity of barium carbonate contained in the semiproduct is preserved up to 600°C, and at temperatures from 700°C the single-phase BaSnO3 is formed. The crystallization temperature of barium stannate can be reduced by 50–75°C due to thermal exposure of the powder for 40–60 min. Holding the semiproduct at 600°C for 60 min forms barium stannate with an average crystallite size of 21 ± 2 nm, and at 700°C there is a slight increase in this parameter (up to 22 ± 2 nm). With increasing temperature up to 1000°C there is intensification of crystallite enlargement process (up to 34 ± 3 nm). The obtained BaSnO3 powder, according to scanning electron microscopy data, consists of microrods (average length is about 85 μm; average diameter is about 10 μm). The surface of the rods is partially covered with spherical particles formed from smaller primary particles of about 30 nm in size. [ABSTRACT FROM AUTHOR]

A nanosized powder and nanostructured fibers of nickel–zinc ferrite Ni0.5Zn0.5Fe2O4 have been synthesized. Using X-ray diffraction analysis, it has been proven that the synthesized samples correspond to the nickel–zinc ferrite phase. It has been found that the fibers based on nickel–zinc ferrite have higher crystal lattice parameter and crystallite size values than those of the synthesized nanosized powder. Scanning electron microscopy data have shown that the studied samples consist of nanosized particles with a size of 20–60 nm for the powder and 20–40 nm for the fibers. The optical diffuse reflectance method has been used to determine the band gap for the Ni0.5Zn0.5Fe2O4 samples: 1.58 and 1.67 eV for the fibers and the powder, respectively. The photocatalytic degradation of methylene blue under the action of Ni0.5Zn0.5Fe2O4 samples of the different morphologies has been studied. It has been found that the nanostructured Ni0.5Zn0.5Fe2O4 fiber sample exhibits a higher photocatalytic activity, because the degree of degradation of methylene blue is 26% for the nanofibers and 18% for the nanopowder. [ABSTRACT FROM AUTHOR]

The formation of nanocrystalline Co3O4 by chemical precipitation has been studied. The validation of the obtained semiproduct has been carried out using simultaneous thermal analysis, infrared spectroscopy, and X-ray powder diffraction analysis. The process of thermal decomposition of the semiproduct with the formation of the target oxide, which is a highly dispersed powder (the average CSR size was about 17 ± 2 nm), free of impurities has been investigated. An approach to microplotter printing of miniature planar Co3O4 nanostructures of different geometries on the surface of silicon substrates with the use of functional inks made on the basis of the obtained nanopowder has been proposed. The features of the morphology of the formed thin-film structures have been investigated. It is shown that there is practically no "coffee ring" effect. As part of the local electrophysical characteristics study of the obtained samples, the distribution maps of surface potential and capacitance contrast have been built, and the value of the electronic work function has been calculated. As a result of the study, the possibility of using the developed technology for the manufacturing of electrode structures Co3O4 for supercapacitors of planar type has been shown. [ABSTRACT FROM AUTHOR]

The process of forming planar electrodes of the composition NiCo2O4 using high-performance high-resolution microplotter printing technology with functional inks based on nanopowders (average size of the coherent scattering region 14 nm) of a similar composition obtained by the method of programmable chemical coprecipitation of metal hydroxides has been studied. The thermal and spectral characteristics of the intermediate and the target oxide, as well as the features of their crystal structure and microstructure, have been studied using a set of methods of physicochemical analysis. According to X-ray phase analysis and Raman spectroscopy, the resulting coatings are single-phase and are characterized by a cubic spinel-type crystal structure. The results of scanning electron microscopy show that the resulting hierarchically organized coatings are homogeneous and contain no defects in the form of gaps or delaminations. The prospects of the developed technology for the manufacture of modern electrode materials of the composition NiCo2O4 are shown. [ABSTRACT FROM AUTHOR]

The features of the process of glycol-citrate synthesis of highly dispersed oxide La0.6Sr0.4Co0.2Fe0.8O3 – δ with varying concentrations of the oxidizing agent (nitro group) and reducing agent (ethylene glycol) in the reaction system have been studied. The effect of the parameters indicated on the thermal behavior, spectral characteristics, phase composition, and microstructure of the obtained nanopowders has been determined. It is shown that the proposed synthesis conditions make it possible to reduce the formation temperature of single-phase highly dispersed oxides of a given composition, which are promising as cathode materials for medium-temperature solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

Hydrothermal synthesis of V2O5 using ammonium vanadate and oxalic acid as the starting reactants was studied. The hydrothermal treatment of a solution at 200°C (6 h) gave a dark blue precipitate of vanadium dioxide consisting mainly of the monoclinic (B) phase. Further heat treatment at 350°C for 2 h resulted in vanadium dioxide oxidation to V2O5. The V2O5 particles thus obtained were 1–1.2 µm-long nanorods of 10–20 nm in diameter. The obtained powder was used to form a coating on an aluminum substrate. The distribution of local electrophysical properties over the surface of V2O5 particles was studied using scanning Kelvin probe microscopy and scanning capacitance microscopy. [ABSTRACT FROM AUTHOR]

Triethanolamine-assisted hydrothermal synthesis of hierarchical nickel oxide particles was studied. The thermal behavior, crystal structure, and spectral characteristics of α-Ni(OH)2 obtained by the hydrothermal treatment of the reaction system and subsequent drying of the solid phase were investigated. It was shown that the thermal treatment at 350°C for 1 h results in the decomposition of the obtained intermediate product to form the desired nanocrystalline oxide (average coherent scattering region size of about 6 nm). Kelvin probe force microscopy was used to construct the maps of the potential distribution over the surface of particles of the studied material and to determine the work function of its surface. [ABSTRACT FROM AUTHOR]

The production of a NiCo2O4 nanopowder using hydrolytically active heteroligand complexes [M(C5H7O2)x(C4H9O)y] (where M = Ni and Co) as precursors was investigated. A simultaneous thermal analysis was used to study the synthesis of a xerogel by the hydrolysis of the complexes, their polycondensation, and drying of the synthesized gel and the transformation of the produced xerogel to an oxide powder of the desired composition. Advantages were demonstrated for the proposed method of pen plotter printing using the obtained solution of the heteroligand complexes as a functional ink in the production of NiCo2O4 thin films on the surface of substrates of various types. The results of X-ray powder diffraction analysis and scanning and transmission electron microscopy confirmed that the proposed synthesis conditions and printing parameters ensure the efficient synthesis of the oxide of the desired composition as both a nanopowder (with an average size of coherent scattering regions of about 20 nm), and thin films (with an average particle size of 12–15 nm). [ABSTRACT FROM AUTHOR]

The synthesis of nanoscale WO3 by chemical precipitation with oxalic acid was studied. The obtained powder was characterized by IR-spectroscopy and powder X-ray diffraction, while its thermal behavior was investigated by simultaneous TGA/DSC analysis. It was found that before heat treatment, the precipitate is a mixture of WO3⋅2H2O and tungsten oxalate. The heat treatment at 400°C results in oxalate decomposition, while treatment at 500°C gives single-phase WO3 with monoclinic crystal structure (mean CSR of 36 ± 4 nm, particle length of 50 ± 5 nm, and particle width of 40 ± 4 nm). The electron work function of the surface of prepared WO3 particles in air was measured using Kelvin-probe force microscopy. It was shown that chemical precipitation of tungsten(VI) oxide using oxalic acid is a promising method for producing the corresponding nanopowder. [ABSTRACT FROM AUTHOR]

Abstract—The synthesis of NiMoO4 hierarchical nanostructures using the hydrothermal method has been studied. The decomposition of NiMoO4·xH2O crystalline hydrate formed during the synthesis has been studied using synchronous thermal analysis upon heating in a stream of air and argon. According to X-ray diffraction as well as scanning and transmission electron microscopies, the proposed conditions allow one to synthesize single-phase nanosized (average CSR size of about 25 ± 2 nm) nickel(II) molybdate, which has a spinel-type monoclinic structure (space group C2/m) without impurity inclusions. [ABSTRACT FROM AUTHOR]

The formation of CoMoO4 anisotropic nanostructures has been studied with a combination of programmed co-precipitation of metal hydroxides and the hydrothermal method. The thermal behavior, phase composition, and microstructure features of the obtained nanopowder have been investigated. Using a set of physicochemical methods of analysis, it has been shown that the proposed synthesis conditions make it possible to form a single-phase nanodispersed (average CSR size of about 30 ± 3 nm) oxide with a monoclinic spinel-type structure (space group C2/m) that does not contain impurity inclusions. [ABSTRACT FROM AUTHOR]

MnOx thin films on various types of substrates (glass, quartz, alumina, and Pt/Al2O3/Pt) were prepared by a combination of the sol–gel method and pen plotter printing, using the hydrolytically active heteroligand complex [Mn(C5H7O2)2 –x(C4H9O)x] as the precursor. The effect of synthesis parameters and printing modes on the microstructure, optical and electrophysical properties of the manufactured planar nanomaterials was studied. The electron work function of the MnOx film surface was assessed by Kelvin probe force microscopy (KPFM). Impedance spectroscopy was used to determine the temperature-dependent electrical conductivity of the prepared films in the temperature range 325–500°С. The proposed synthetic method and printing technology show promise for the formation of thin-film manganese oxide nanostructures for supercapacitor electrodes and optical devices. [ABSTRACT FROM AUTHOR]

Abstract—The preparation of zinc sulfide nanoparticles by chemical deposition was studied. The thermal behavior of the thus-prepared nanopowder in air at temperatures in the range 25–500°C was examined by simultaneous thermal analysis. The product was identified using X-ray powder diffraction and IR spectroscopy. Transmission electron microscopy (TEM) was used to determine the sizes of the product nanoparticles. Functional ink based on the prepared zinc sulfide was used to form thick-film ZnS nanostructures by microextrusion printing. Scanning electron microscopy was used to study the microstructure of the thus-formed coatings, and their electrophysical properties were assessed by impedance spectroscopy. Microextrusion printing was found to be effective not only in bioprinting, but also in the formation of semiconductor coatings. [ABSTRACT FROM AUTHOR]

The effect of the temperature of carbonization of xerogels on the chemical activity of the obtained materials in the Ta2O5–HfO2–C system was studied to create an energy-efficient method for producing ceramic materials based on the TaC–HfC system using reactive hot pressing or spark plasma sintering. A new method was developed to form a tantalum–hafnium–polymer-containing gel by creating interpenetrating organic–inorganic networks with the simultaneous initiation of hydrolysis of metal–containing precursors and polymerization of furfuryl alcohol (acid catalysis with formic acid). Samples of the Ta2O5–HfO2–C system with different reactivities in the carbothermal synthesis of complex carbides were obtained based on the xerogel produced after drying using carbonization under dynamic vacuum conditions at various temperatures (400, 700, and 1000°C). Their elemental and phase composition, microstructure and thermal behavior in an air flow were investigated. The powder synthesized at a minimum temperature of 400°C had the maximum reactivity but also contained rather much (3–4 wt %) unpyrolyzed organic fragments, which should be taken into account in planning high-temperature consolidation of carbide ceramics. [ABSTRACT FROM AUTHOR]

Nano-sized magnetite powders with addition of iron nitrides were synthesized via pulsed laser ablation (PLA) of an iron target in atmospheric air. A series of iron oxide nanopowders with various phase compositions (ranging from magnetite to hematite) and structures (from 2D lamellas and spherical nanoparticles to continuous 3D structures) were prepared via heat treatment of the initial (as-synthesized) powder at temperatures in the range 200–500°C. The powders were introduced into the composition of carbon paste electrodes (CPEs). The capacitive characteristics of the electrodes prepared were studied in comparison to a commercial electroexplosive iron oxide powder. The capacitances of electrodes were matched to the structural characteristics of the materials and their phase compositions. With the chosen electrode-preparation method, the powder heat-treated at 500°С (sample Fe/500) showed the highest capacitance. The potential of the studied ultrafine materials based on ablative iron oxide was shown for use in electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]