N. A. Mel’nikova

Solid electrolytes with predominant chloride conductivity

The ionic transport features were studied in PbCl2 and SnCl2 single crystals and in KPb2Cl5, K2PbCl4, PbCl2-Al2O3, CsSnCl3, and SnCl2 - 6 mol % MCl (M = Li, Na, Ag, K, Tl, Rb, Cs) ceramic materials. A reference data review on electroconductivity of chloride-conducting solid electrolytes was made. A conclusion was made on application prospects of ionic conductors with predominant chloride conductivity as sensitive membranes in solid state electrochemical devices.

Synthesis of carbon nanotubes from a cobalt-containing aerosilogel

At present carbon nanotubes are one of the most demanded products of carbon nanotechnologies [1–3]. The principal industrial technologies for manufacture of carbon nanotubes are arc discharge, laser ablation, and chemical vapor deposition (CVD) onto the surface of catalysis. The fluidized-bed CVD is used to success for large-scale manufacture of carbon nanotubes [2]. However, thin carbon nanotubes with a narrow size distribution are fairly difficult to synthesize by this technology. Apparently, this problem can be solved not by optimization of synthesis conditions, but also by selection of catalysts with appropriate porous and active-center structures.

Nafion-based composite solid electrolytes containing carbon nanotubes

Nafion-based composite solid electrolytes containing multiwalled carbon nanotubes have been studied by impedance spectroscopy. The effect of carbon nanotube morphology on the proton conductivity of the composites has been estimated at low relative humidity. Surface modification of carbon nanotubes with acidic groups increases the proton conductivity.

Study of the effect of methods for liquid-phase synthesis of nanopowders on the structure and physicochemical properties of ceramics in the CeO 2 –Y 2 O 3 system

Two alternative chemical synthesis methods—cryotechnological coprecipitation of hydroxides and cocrystallization of salts—were used for preparing (CeO2)1–x(Y2O3)x nanopowders (x = 0.10, 0.15, 0.20) with a mean coherent scattering domain size of ~7–11 nm and Ssp = 2.1–97.5 m2/g. From these nanopowders, ceramic nanomaterials with mean coherent scattering domain sizes of ~61–85 nm were synthesized. It was studied how the phase composition, microstructure, and electrical transport properties of the produced samples depend on the Y2O3 content of a CeO2-based solid solution and on the synthesis method. It was shown that, in the series (CeO2)1–x(Y2O3)x (x = 0.10, 0.15, 0.20), the solid solution (CeO2)0.90(Y2O3)0.10 has the highest ionic conductivity with the ion transport number ti = 0.73 (600°C). In its physicochemical characteristics, this ceramic can be used as a solid electrolyte of intermediate-temperature fuel cells.

Ag2S-As2S3-TlI chalcogenide glasses as perspective material for solid-state chemical sensors

Modern research techniques with radioactive isotopes were used to study the transport characteristics, (conductivity and diffusion) in chalcogenide membrane materials of the Ag2S-As2S3-TlI system. It was demonstrated that, on raising the silver sulfide concentration in a glass, the total electrical conductivity grows by two orders of magnitude, which is due to the pronounced change of the band structure and to the increase in the electronic component of the conductivity. New chemical sensors for determination Tl ions in solutions were developed on the basis of these solid-state studies.

Proton conductivity of composites based on Nafion and silica matrices with a chemically modified surface

The surface of aerosilogel and macroporous and microporous glasses was modified with aromatic sulfo groups (≡Si(CH2)2-C6H4-SO3H) by the chemical assembly method. Composite solid electrolytes containing Nafion were prepared from the silica matrices with a chemically modified surface. The proton conductivity of the materials was studied by impedance spectroscopy. Composite materials based on Nafion and aerosilogel matrices and macroporous glasses with grafted ≡Si(CH2)2-C6H4-SO3H groups showed the highest proton conductivity.

Electrical conductivity of potassium titanyl phosphate KTiOPO4 pure crystals and those doped with Na+, Rb+, and F– ions

KTiOPO4 crystals, both pure and doped with rubidium Rb+ and fluorine F– ions, were grown in temperature range from 1060 to 846°С from salt solvent containing potassium metaphosphate КРО3 and potassium orthophosphate К3РО4 by using a Czochralski modified method. Potassium–sodium titanyl phosphate crystals were obtained from KTiOPO4 crystals by the potassium isomorphic replacement with sodium; to this purpose, sodium chemical diffusion from NaNO3 melt was used. Their ionic conductivity was studied by the electrochemical impedance spectroscopy method. The KTiOPO4 crystal doping with rubidium and sodium ions was shown to lower the conductivity, whereas the doping with fluorine ions results in increased conductivity.

Nafion-based composite solid electrolytes containing water-soluble fullerene C60 derivatives

Nafion-based composite solid polyelectrolytes containing fullerene C60 and its water-soluble derivatives fullerenol-C60 and tris-malonate-C60 were studied by the impedance spectroscopy method. It was found that introduction of these dopants in Nafion leads to a substantial increase in proton conductivity of the composites in the region of low relative humidity. The reasons for the influence of dopants on proton conductivity of composites were discussed.

Synthesis of Composite Solid Electrolytes Based on Polyacrylic Acid via Radical Polymerization Initiated from Silica Surface

A procedure has been developed for the synthesis of silica-supported polymerization initiators, which includes chemisorption of (3-aminopropyl)triethoxysilane, hydrolysis of the alkoxy groups, and chemisorption of 4,4′-azobis(4-cyanopentanoic acid). It has been found that the reaction of 4,4′-azobis(4-cyanopentanoic acid) with immobilized amino groups in the presence of N,N′-dicyclohexylcarbodiimide involves only one functional group in the former. The effect of the solid support porosity on the composition of organosilica obtained by surface-initiated radical polymerization of acrylic acid has been studied. The best yield of grafted polyacrylic acid is obtained on aerosilogel with large mesopores in combinations with developed surface. The dependence of the impedance of polyacrylic acid-modified aerosilogel on the relative air humidity has been studied, and the possibility of using this material in humidity sensors has been shown.

Nafion- and aquivion-based nanocomposites containing detonation nanodiamonds

Nafion- and Aquivion-based composite solid polyelectrolytes containing deagglomerated detonation nanodiamonds were studied by the impedance spectroscopy method. It was found that introduction of these dopants leads to a substantial increase in proton conductivity of hybrid membranes with low relative humidity.