ZrO2–Sc2O3 Solid Electrolytes Doped with Yb2O3 or Y2O3

Russian Journal of Electrochemistry - The effects of the Y2O3 and Yb2O3 co-doping impurities on the transport characteristics and stabilization of the cubic phase in solid solutions based on...     

Preparation of a library of unsymmetrical ureas based on 8-azabicyclo[3.2.1]octane scaffold

This paper reports the preparation of a library of unsymmetrical ureas based on 8-azabicyclo[3.2.1]octane scaffold. The reported synthetic route uses nortropane-8-carbonyl chlorides as key intermediates that, when treated with a slight excess of amine, give the corresponding ureas in high yield (129 examples).     

Synthesis,Self-Assembly in Crystalline Phase and Anti-Tumor Activity of 2-(2-/4-Hydroxybenzylidene)thiazolo[3,2-a]pyrimidines

A series of new thiazolo[3,2-a]pyrimidines different by aryl substituents in 2 and 5 positions are synthesized and characterized in solution as well as in the crystalline phase using ¹H and ¹³C NMR-, IR-spectroscopies, mass-spectrometry methods, and single crystal X-ray diffraction (SCXRD). The SCXRD study revealed the role of intermolecular H-bonding in the formation of supramolecular architectures (racemic monomers, centrosymmetric racematic dimers, or homochiral 1D chains) of obtained thiazolo[3,2-a]pyrimidines derivatives depending on solvents (aprotic DMSO or protic EtOH) used upon the crystallization process. Moreover, the in vitro study of cytotoxicity toward different tumor cells showed their high or moderate efficiency with moderate cytotoxicity against normal liver cells which allows to consider the obtained thiazolo[3,2-a]pyrimidine derivatives as promising candidates for application as antitumor agents.     

Coordination mode for turn-based phosphine ligands: the origin of selectivity in Pd catalysis

A series of experiments was performed to determine the nature of the catalyst in peptide-derived phosphine ligands. The selectivity of the catalyst system was determined with four ligands that are diastereomeric at the phosphine containing amino acid. Additionally, a series of monophosphine ligands was synthesized and screened to determine if the active catalysts are derived from a phosphine-amide complex.     

Effect of Heat Treatment on the Thermal Conductivity of Single Crystals of ZrO2-Based Solid Solutions Stabilized with Scandium and Yttrium Oxides

Physics of the Solid State - The effect of heat treatment at 1000°C for 400 h on the thermal conductivity of zirconium dioxide crystals stabilized with scandium oxide...     

Synthesis and properties of fuel cell anodes based on (La0.5 + x Sr0.5 − x )1 − y Mn0.5Ti0.5O3 − δ (x = 0–0.25, y = 0–0.03)

Results are presented of studying electrochemical properties of perovskite-like solid solutions (La_{0.5 + x} Sr_{0.5 ? x} )_{1 ? y} Mn_0.5Ti_0.5O_{3 ? δ} (x = 0–0.25, y = 0–0.03) synthesized using the citrate technique and studied as oxide anodic materials for solid oxide fuel cells (SOFC). X-ray diffraction (XRD) analysis is used to establish that the materials are stable in a wide range of oxygen chemical potential, stable in the presence of 5 ppm H₂S in the range of intermediate temperatures, and also chemically compatible with the solid electrolyte of La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05O_{3 ? δ} (LSGMC). It is shown that transition to a reducing atmosphere results in a decrease in electron conductivity that produced a significant effect on the electrochemical activity of porous electrodes. Model cells of planar SOFC on a supporting solid-electrolyte membrane (LSGMC) with anodes based on (La_0.6Sr_0.4)_0.97Mn_0.5Ti_0.5O_{3 ? δ} and (La_0.75Sr_0.25)_0.97Mn_0.5Ti_0.5O_{3 ? δ} and a cathode of Sm_0.5Sr_0.5CoO_{3 ? δ} are manufactured and tested using the voltammetry technique.     

Electron-induced radiation from C60 fullerene in the gas phase

The formation of radiating particles in the excitation of C₆₀ fullerene molecules by electrons with energies E _e<100 eV is investigated by the method of crossed molecular and electron beams. A quasicontinuous (with a spectral resolution of 3 nm) emission spectrum, close to the Planck emission spectrum of a heated body, is recorded in the wavelength range 300–800 nm. The temperature of the radiation corresponds to an internal energy of the C₆₀ molecule of approximately 40 eV. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 915–919 (25 June 1996)     

Preparation of membrane-electrode assemblies of solid oxide fuel cells by co-sintering of electrodes

The results of the development of procedures for forming membrane-electrode assemblies (MEAs) of solid oxide fuel cells (SOFCs) by co-sintering of electrodes and electrochemical tests of MEAs were described. Plates of Hionic? material (Fuel Cell Materials, United States) with an area of 50 × 50 mm² were used as a solid electrolyte membrane. The cathode layers were prepared from cation-deficient lanthanum-strontium manganite and the anion conductor 89 mol % ZrO₂–10 mol % Sc₂O₃–1 mol % CeO₂ (10Sc1CeSZ) with a carbon black addition for control over the microstructure. The anode layers were formed from the composite NiO/10Sc1CeSZ and by introducing rice starch as a pore-forming agent in the anode current-collecting layer. The thermal treatment mode was optimized based on thermogravimetry and scanning electron microscopy data and the results of testing the electrochemical characteristics of SOFCs to provide the formation of electrochemically active electrodes using one thermal cycle.     

Electrical, electrochemical, and thermomechanical properties of perovskite-type (La1?x Sr x )1?y Mn0.5Ti0.5O3?δ (x?=?0.15–0.75, y?=?0–0.05)

Strontium additions in (La_1?x Sr _x )_1?y Mn_0.5Ti_0.5O_3?δ (x?=?0.15–0.75, y?=?0–0.05) having a rhombohedrally distorted perovskite structure under oxidizing conditions lead to the unit cell volume contraction, whilst the total conductivity, thermal and chemical expansion, and steady-state oxygen permeation limited by surface exchange increase with increasing x. The oxygen partial pressure dependencies of the conductivity and Seebeck coefficient studied at 973–1223?K in the p(O₂) range from 10^?19 to 0.5?atm suggest a dominant role of electron hole hopping and relatively stable Mn³⁺ and Ti⁴⁺ states. Due to low oxygen nonstoichiometry essentially constant in oxidizing and moderately reducing environments and to strong coulombic interaction between Ti⁴⁺ cations and oxygen anions, the tracer diffusion coefficients measured by the ¹⁸O/¹⁶O isotopic exchange depth profile method with time-of-flight secondary-ion mass spectrometric analysis are lower compared to lanthanum–strontium manganites. The average thermal expansion coefficients determined by controlled-atmosphere dilatometry vary in the range 9.8–15.0?×?10^?6?K^?1 at 300–1370?K and oxygen pressures from 10^?21 to 0.21?atm. The anodic overpotentials of porous La_0.5Sr_0.5Mn_0.5Ti_0.5O_3?δ electrodes with Ce_0.8Gd_0.2O_2-δ interlayers, applied onto LaGaO₃-based solid electrolyte, are lower compared to (La_0.75Sr_0.25)_0.95Cr_0.5Mn_0.5O_3?δ when no metallic current-collecting layers are introduced. However, the polarization resistance is still high, ~2 Ω?×?cm² in humidified 10?% H₂–90?% N₂ atmosphere at 1073?K, in correlation with relatively low electronic conduction and isotopic exchange rates. The presence of H₂S traces in H₂-containing gas mixtures did not result in detectable decomposition of the perovskite phases.