Proton conductivity in TaH(PO4)2 · 2H2O + SiO2 composite electrolytes

The composite electrolytes of composition (1 ? x)TaH(PO₄)₂ · 2H₂O/xSiO₂ (x = 0.2–0.4) are synthesized, and their transport properties are characterized over a wide temperature range. Doping with highly dispersed silica only insignificantly changes the proton conductivity of tantalum hydrogenphosphate below 370 K; above 820 K, the conductivity increases. The evolution of the phase composition of TaH(PO₄)₂ · 2H₂O and its base materials during thermolysis is studied.     

Ion transport in MF-4SK cation-exchange membranes modified with acid zirconium phosphate

An MF-4SK cation-exchange membrane has been modified to obtain composite materials containing acid zirconium phosphate particles. It is demonstrated by electron microscopy and X-ray diffraction that acid zirconium phosphate in the resulting membrane is in the crystalline state. As compared to the initial MF-4SK membrane, the modified membrane shows a somewhat lower diffusion permeability and a higher ion selectivity.     

Polarization Characteristics of Composite Electrodes in Electrochemical Cells with Solid Electrolytes Based on CeO<Subscript>2</Subscript> and LaGaO<Subscript>3</Subscript>

For two types of electrochemical cells with oxygen-conducting solid electrolytes based on lanthanum gallate (LSGM) and cerium oxide (SDC) studied are the temperature dependences of the polarization conductivity of air electrodes prepared from lanthanum-strontium manganite (LSM) and composites LSM-LSGM, LSM-SDC, and LSM-SSZ (SSZ is zirconium dioxide-based electrolyte). Effect of praseodymium oxide, added into these electrodes as a modifier, on their electrochemical properties is examined. Electrochemical systems with an LSM/LSGM interface exhibit low electrochemical activity toward the oxygen reaction, because during the formation of electrodes, LSM interacts with LSGM to form a poorly conducting product.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 602–606.Original Russian Text Copyright © 2005 by Yaroslavtsev, Kuzin, Bronin, Bogdanovich.     

Specific features of magnetic properties of ferrihydrite nanoparticles of bacterial origin: A shift of the hysteresis loop

The results of the experimental investigation into the magnetic hysteresis of systems of superparamagnetic ferrihydrite nanoparticles of bacterial origin have been presented. The hysteresis properties of these objects are determined by the presence of an uncompensated magnetic moment in antiferromagnetic nanoparticles. It has been revealed that, under the conditions of cooling in an external magnetic field, there is a shift of the hysteresis loop with respect to the origin of the coordinates. These features are associated with the exchange coupling of the uncompensated magnetic moment and the antiferromagnetic “core” of the particles, as well as with processes similar to those responsible for the behavior of minor hysteresis loops due to strong local anisotropy fields of the ferrihydrite nanoparticles.     

Behavior of manganite electrodes in contact with LSGM electrolyte: the nature of low electrochemical activity

The electrochemical cells with electrodes based on La_0.8Sr_0.2MnO₃ (LSM) and supporting solid electrolytes La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 (LSGM) and Ce_0.80Sm_0.20O_1.90 (SDC) were studied comparatively. Characteristics of LSM electrodes and composite electrodes comprising a mixture of LSM and electrolytes of different origins [LSGM, SDC, and Zr_0.82Sc_0.18O_1.91 (SSZ) in the mass ratio of 1:1] were analyzed. It was shown that: 1) the electrode polarization conductivity and the ohmic resistance of the cells with the LSM–LSGM composite electrodes on the LSGM and SDC electrolytes had very similar values, while they were largely different from all the other electrodes, 2) the electrochemical activity of the electrodes on the SDC electrolyte was much higher than on the LSGM electrolyte, and 3) the ohmic resistance of the cells with the SDC electrolyte corresponded to the electrolyte resistance, whereas, the ohmic resistance of the cells with the LSGM electrolyte was much larger than the electrolyte resistance. The obtained results are due to the interaction between the LSM and LSM-containing electrodes with the LSGM electrolyte during sintering, leading to the formation of a product with a very low conductivity.     

Expansion of capabilities of the short-duration wind tunnel with an opposing pressure multiplier

A method for raising the maximum settling-chamber pressure in a short-duration wind tunnel equipped with pressure multipliers arranged in opposition to each other for stabilization of test gas parameters is proposed. For this purpose, a wind-tunnel design with an additional third pressure multiplier attached to the body of the second pressure multiplier was developed. The rod of the additional multiplier contacts the large-area piston stage of the second multiplier, and the pre-piston space being connected to the receiver. The inclusion of an additional pressure multiplier in the wind-tunnel design at the maximum attainable driver-gas pressure of 150?170 bar, defined by the standard industrial pressure of air used for filling wind-tunnel receivers with the driver gas, allows a two-fold increase in the maximum settling-chamber pressure, from 1100 to 2000?2200 bar. For raising the maximum settling-chamber pressure above 2000–2200 bar, the use of one additional pressure multiplier proved to be insufficient because, in the latter case, its becomes necessary to simultaneously raise the driver-gas pressure over 150?170 bar.     

Kinetics of H+/Na+ Ion Exchange on H1 ± xZr2 − xMx(PO4)3 (M = Y or Nb) NASICON Materials

The thermodynamic parameters of ion exchange have been estimated for HZr₂(PO₄)₃ · H₂O and the products of its aliovalent doping. Ion exchange occurs via formation of the (H₃O_{1 ? x}Na_x)Zr₂(PO₄)₃ solid-solution series. As in the case of ion exchange on layered zirconium phosphate (Zr(HPO₄)₂ · H₂O), the interdiffusion coefficient and the major interfacial defect generation processes are considerably affected by the contact-solution pH.     

Effect of ultrasonication on the formation and properties of zirconium hydrogen phosphate HZr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O with NASICON structure

We compare ionic conductivity in zirconium hydrogen phosphate samples with NASICON structure prepared by various methods. Hydrothermal and hydrothermal/ultrasonic treatment reduces the crystallite size and increases ionic conductivity in HZr₂(PO₄)₃ · nH₂O samples at low temperatures. At high temperatures, the conductivity of the anhydrous phase HZr₂(PO₄)₃ is higher in the material prepared by ion exchange. Ultrasonication does not considerably improve the properties of hydrothermally prepared samples.