Mechanical Properties of СeF3 Single Crystals

Crystallography Reports - The anisotropy of the mechanical characteristics of CeF3 crystals (sp. gr. $$P\bar {3}c1$$) grown from the melt by the Bridgman technique has been studied for the first...     

Reduction Processes in the Course of Mechanochemical Synthesis of Li1+xV3O8

Mechanical activation (MA) of the LiOH+V₂O₅ and Li₂CO₃+V₂O₅ mixtures followed by brief heating at 673 K was used to prepare dispersed Li_1+xV₃O₈. It was shown that structural transformations during MA are accompanied by reduction processes. EPR spectra of Li_1+xV₃O₈ are attributed to vanadyl VO²⁺ ions with weak exchange interaction. The interaction of localized electrons (V⁴⁺ ions) with electron gas (delocalized electrons), which is exhibited through the dependence of EPR line width of vanadium ions versus measurement temperature (C–S–C relaxation), is revealed. It is shown that C–S–C relaxation is different for intermediate and final products. The properties of mechanochemically prepared Li_1+xV₃O₈ are compared with those of HT-Li_1+xV₃O₈, obtained by conventional solid state reaction. Mechanochemically prepared Li_1+xV₃O₈ is characterized by a similar amount of vanadium ions, producing electron gas, but a higher specific surface area.     

Effect of porous structure of LiCoPO4 on its performance in hybrid supercapacitor

Journal of Solid State Electrochemistry - Hybrid supercapacitors (HSCs) based on the mechanochemically prepared LiCoPO4 samples with different specific surface area and porosity as cathodes and the...     

The character of interactions of CO,H<Subscript>2</Subscript>, and CH<Subscript>3</Subscript>OH with the surface of γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Cu-Zn oxide catalyst

The thermal desorption of CO, H₂, and CH₃OH from the surface of Katalco-58 industrial catalyst for the synthesis of methanol and γ-Al₂O₃ was studied. Weak interaction of the gases with the surface of samples was observed over the temperature range 75–400°C. The desorption of the gases obeyed the second-order Wigner-Polyani equation. The desorption energies of the gases were calculated. The mechanism of dimethyl ether synthesis was studied.     

Lithium conductivity and lithium diffusion in NASICON-type Li<Subscript>1+x</Subscript>Ti<Subscript>2–x</Subscript>Al<Subscript>x</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> (x= 0; 0.3) prepared by mechanical activation

LiTi₂(PO₄)₃ (LTP) and Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) (S. g. R-3c) have been prepared using conventional ceramic and mechanical activation (MA) methods. It has been shown that preliminary mechanical activation of initial mixtures leads to different nature and amount of dielectric admixtures in the final product after heat treatment at 800–1000 °C as compared with ceramic method. Transport properties of as prepared materials have been studied by lithium ionic conductivity at d.c. and a.c. (complex impedance method), and ⁷Li NMR spin-lattice relaxation rate T₁ ^–1 measurements. Lithium ionic conductivity of mechanochemically prepared LTP and LATP was characterized by significant reduction of grain boundary resistance, especially for LTP, while the bulk conductivity and Li ion diffusion does not noticeably change. The activation energy of bulk conductivity and Li ion diffusion, i.e. short-range motion, appeared to be almost the same for all samples and was equal to ~0.20 eV. On contrary, the activation energy of d.c.-conductivity, i.e. long-range Li ion motion decreases from ~0.6 eV for ceramic samples to ~0.4 eV for samples prepared via mechanochemical route. It was proposed that MA leads to formation of nano-particulate high-conductive grain boundaries both in LTP and LATP. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007.     

On the possibility of using interferometry in the study of arc in the combustion plasma flow

The use of holographic interferometry in the visible spectral region and interferometry in the submillimeter region for diagnostics of arc in the combustion plasma flow is discussed. The experimental arrangement and results are presented. The use of these two methods enables to determine the gas temperature and the electron concentration in the arc.     

Comparative structural analysis of LiMPO<Subscript>4</Subscript> and Li<Subscript>2</Subscript>MPO<Subscript>4</Subscript>F (M = Mn,Fe, Co,Ni) according to XRD,IR, and NMR spectroscopy data

A comparative structural study of LiMPO₄ (M = Mn, Fe, Co, Ni) orthophosphates and Li₂MPO₄F (M = Co, Ni) fluorophosphates obtained by mechanochemically assisted solid-state synthesis is performed using powder XRD, IR, and NMR spectroscopy methods. It is shown that all compounds crystallize in the orthorhombic symmetry (space group Pnma). Lattice parameters decrease on passing from Mn to Ni, which is due to the decrease in the ionic radius of the d metal. According to the IR spectroscopy data, in this series an increase in the covalency of the P–O bond is observed along with a decrease in the covalency of the M–O bond. On passing to fluorophosphates, the symmetry of PO₄ tetrahedra increases. ⁶Li and ³¹P NMR spectra of all compounds are characterized by the dependence of the contact shift on the nature of metal M and the degree of distortion of the MO₆ coordination polyhedron. ⁶Li MAS NMR line width is noticeably affected by the concentration of structural defects. Unlike orthophosphates with equivalent lithium ions, fluorophosphates contain lithium ions in three different positions.     

The mixed boundary-value problem for a transtropic layer with a cavity

Using superposition of solutions and Fourier series we study the stressed state in a transversally isotropic layer with a cavity. We describe the results of numerical studies as functions of the elastic properties of the material, the geometric characteristics of the body, and the nature of the load variation. Four figures. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 25, 1995 pp. 8–15.