Search

In articles first time to presents approach to obtaining of ultrafine defective composite α-FeOOH/α-Fe2O3 by hydrothermal synthesis and investigated the influence of post-processing on phase transformations, magnetic microstructure and elecroconductivity. The X-ray analysis, Mossbauer spectroscopy, IR spectroscopy and impedance spectroscopy used to analyzed the structural-morphological and elecroconductivity. It was established that the selection of the parameters of the synthesis to possible the control of the processes of nucleation, aggregation and restructuring of the formed defective composite. Theories of thermo-induced reorganization of different phase structures and the formation of the intrinsic semiconductorness as a result of internal activation are updated. [ABSTRACT FROM AUTHOR]

In articles first time to presents approach to obtaining of ultrafine defective composite α-FeOOH/α-Fe2O3 by hydrothermal synthesis and investigated the influence of post-processing on phase transformations, magnetic microstructure and elecroconductivity. The X-ray analysis, Mossbauer spectroscopy, IR spectroscopy and impedance spectroscopy used to analyzed the structural-morphological and elecroconductivity. It was established that the selection of the parameters of the synthesis to possible the control of the processes of nucleation, aggregation and restructuring of the formed defective composite. Theories of thermo-induced reorganization of different phase structures and the formation of the intrinsic semiconductorness as a result of internal activation are updated. [ABSTRACT FROM AUTHOR]

Potentiodynamic and galvanostatic investigations of hybrid electrochemical capacitor (HEC) models formed on the base of nanoporous carbon material (NCM) are performed. NCM is obtained from raw materials of plant origin (hemp fire) and modified lithium–manganese spinel Li1.2Mn1.8O4 . The influence of the surface morphology of carbon material on the electric capacity of the HEC is revealed. The total electric capacitance of the HEC models is determined, and its distribution is carried out on the capacitance, which is ensured by the formation of a double electric layer (DEL), and the redox capacitance due to the passage of Faraday reverse reactions. [ABSTRACT FROM AUTHOR]

In this work, the crystal structure of alpha-MnO2 has been obtained by the hydrothermal method. It was determined that the obtained material has a tunnel structure with average particle sizes of 12-15 nm. The electrochemical performances of α-MnO2 in an aqueous solution of 30 % KOH based electrolyte have been investigated by cyclic voltammetry and galvanostatic cycling methods. At the same time, it was determined that the specific capacity of the α-MnO2/electrolyte system decreased from 90 F/g to 55 F/g with an increase of the scan rate from 2 to 10 mV/s. Thus, the maximum values of specific capacitance about 104 F/g were obtained at 0.5 mV/s. The Coulomb efficiency of the electrochemical system is constant and independent of the cycle number under the charge/discharge process. Therefore, the total capacity of the material under investigation can be divided into the capacity of the double electric layer and the diffusioncontrolled redox capacity due to the Faraday reverse redox reactions. It was determined that the contribution of pseudocapacity is 90 % of the total specific capacity. In addition, it has been determined that the α-MnO2/KOH electrochemical system is stable under long-term cycling process. [ABSTRACT FROM AUTHOR]

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The structural-adsorption characteristics of nanoporous carbon materials (NСMs), obtained by thermochemical activation of vegetable raw materials by orthophosphoric acid with different mass ratio, are investigated in the article using the method of low temperature nitrogen sorption and scanning electron microscopy. Calculations of the specific surface area and pore size distribution allowed to determine the optimal parameters of the mass ratio of the activator and the raw materials, in which the obtained material has the highest parameters of the porous structure. The optimum conditions for NCMs obtaining are established, which can be used as electrodes of electric energy storage devices. [ABSTRACT FROM AUTHOR]

The nickel ferrite NiFe2O4 obtained by ceramic technology has been widely studied due to its tremendous properties like high electromagnetic performance, excellent chemical stability and mechanical hardness, and moderate saturation magnetization, making it a good contender for the application as soft magnets and low loss materials at high frequencies. The structure, mechanical, magnetic, electrical and dielectric properties of nickel ferrite are dependent upon several factors including the method of preparation, sintering time and temperature, chemical composition, type and amount of dopant, grain structure. The sol-gel with participation of auto-combustion (SGA) technique was used for the synthesis of Ni1-xMnxFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) nanoparticle ferrites. The mixed solution was dried at a temperature around 403 K. During evaporation the solution became viscous and finally formed a xerogel. At further temperature rise, the organic constituents are decomposed with the generation of gases such as CO2, N2 and H2O; therefore the xerogel automatically ignited. The auto-combustion was completed within a few seconds, yielding the nanopowders of ferrites. Structural parameters, morphology and optical properties were investigated. The XRD results confirm single-phase formation of the as-prepared samples with 0.0 ≤ x ≤ 0.4 having the Fd3m space group. The Ni0.5Mn0.5Fe2O4 and Ni0.4Mn0.6Fe2O4 powders except the spinel phase contain also additional FeO and Ni phases. The crystallite sizes (27-43 nm) decrease and the lattice parameters (0.8343-0.8459 nm) increase, while the Mn concentration increases. Morphological observations reveal that the crystallinity decreases significantly with increasing Mn content meanwhile the particle size becomes more uniform. It was found that the optical band gap increases with increasing concentration of Mn2+ ions in the ferrite structure. The band gap is in the range from 2.00 eV to 3.26 eV. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The results of electrochemical studies of nanoporous carbon as an electrode material for electrochemical capacitors are presented in the work. Nanoporous carbon material (NCM) is obtained from raw materials of plant origin by its carbonization and subsequent activation in potassium hydroxide. It is established that there is an optimal ratio 1 : 1 between content of KOH and carbon material at chemical activation, while the maximum specific capacity of NCM is 180 F/g. An equivalent electrical circuit, which allows modeling the impedance spectra in the frequency range of 10 – 3-105 Hz, is proposed and a physical interpretation of each element of the electrical circuit is presented. [ABSTRACT FROM AUTHOR]

The adsorption activity of activated carbon was found to depend on conditions of chemical treatment of precursor with orthophosphoric acid. As a precursor, dried apricot seeds were milled to a fraction of 0.25-1 mm. The surface area and value of pore capacity of carbon material increase with H3PO4 concentration. As a result, a mesoporous carbon with 0.9-1.23 cm3/g pores value was prepared, giving adsorption activity for methylene blue 310-350 mg/g and methyl orange 365-370 mg/g. [ABSTRACT FROM AUTHOR]

Chemical activation of nanoporous carbon material with nitric acid, followed by activation in a stream of argon at different temperatures, initiates formation on the surface of the material of amide, pyrrole and pyridine nitrogen compounds that improves the hydrophilic properties and increases its electrical conductivity. Value of the specific capacity of N-enriched carbon material in KOH aqueous solution increases by 30 % and an additional heat treatment in the temperature range of 440-460°C increases it by 10 %. [ABSTRACT FROM AUTHOR]

The structural characteristics and phase composition of substitutional solid solutions of (1−&#x03B3)LiFe5O8 + (&#x03B3)LiAl5O8 synthesized by ceramic technology are explored. The effect of the cooling method on the structural properties, cation distribution, and phase composition of the material is discussed. The order– disorder phase transition, existence of spinel saturation areas, and reduction of the unit cell parameter with increase of the substitution degree are found. Mössbauer spectroscopy measurements are consistent with this structural model. The γ-spectrum of absorption of Fe57 of the synthesized samples confirms both the multiphase composition of the studied systems revealed by the X-ray phase analysis and the existence of mesoscopic formations. [ABSTRACT FROM AUTHOR]