N. G. Molchanova

Electron transfer in an electron ion molten mixture of CuCl-CuCl2-MeCl (Me = Li, Na, K, Cs)

Abstract Electron and ion transfer numbers, electroconductivity, density, and concentrations of Cu+ and Cu2+ in molten salt mixtures of CuCl–CuCl2–MeCl (Me=Li, Na, K, Cs) were measured at a partial pressure of chlorine over the melt equal to the atmospheric pressure in the temperature interval from 800 to 1000 K. Partial values of ion and electron transfers and the molar volume of the melts were determined. Mobility of electrons was estimated. The electron transfer number was a maximum in the CuCl–CuCl2 melt with tc equal to 0.9. When chlorides of alkali metals were added to the CuCl–CuCl2 melt, the electron component of electroconductivity was preserved up to 90, 65, 60, and 50 mol.% LiCl, NaCl, KCl, and CsCl, respectively. A mechanism of the electron transfer in the test melts was proposed.

Electrode processes at the glass carbon/LiCl-CuCl-CuCl2 melt interface

The kinetics of the electrode processes occurring at the glass carbon/LiCl-CuCl-CuCl2

Thermodynamic characteristics of Pb-Sb alloys

\left( {N_{CuCl - CuCl_2 } = 0 - 7.5 mol \% } \right)

Synthesis of new metal-matrix Al–Al2O3–graphene composite materials

melt interface is studied by the coulostatic method, single current pulse chronopotentiometry, and stationary voltammetry at a temperature of 950 K and the atmospheric pressure of chlorine over a melt. The exchange current densities in the molten mixtures are determined by the coulostatic method. These data are used to calculate the transfer coefficient (α = 0.54 ± 0.06) and the rate constant of the electrode reaction Cu2+ + e− ai Cu+ (kS = 0.26 ± 0.02 cm/s). The results of stationary voltammetry in the cathode potential region reveal pronounced limiting currents up to the precipitation of metallic copper on an electrode. The experimental data obtained by chronopotentiometry are used to find the transition times for various current densities over the entire concentration range under study. The dependences plotted in the iτ1/2 = f(i) coordinates suggest the presence of a chemical homogeneous reaction preceding the electrode process. The total value of the rate constants of the forward and back reactions is estimated to be ≈2. The copper mono- and dichloride concentrations are determined in the concentration range under study.

Formation of titanium diboride coatings during the anodic polarization of titanium in a chloride melt with a low boron oxide content

Glasses of the SiO2–Al2O3–BaO–MgO and SiO2–Al2O3–ZrO2–CaO–Na2O systems were synthesized in the perspective to apply them as sealants in SOFC at operating temperatures of 700–900 °C. Thermal properties of the chosen glass compositions and their compatibility with the SOFC materials (YSZ-electrolyte and alloy-interconnector Crofer22APU, 15×25T) were investigated by means of synchronic thermal analysis and high-temperature dilatometry. The elemental analysis was performed by atomic emission spectroscopy. The average values of the temperature coefficients of the linear extension are 10.0×10−6 °C−1 for glass 45%SiO2– 15%Al2O3–25%BaO–15%MgO and 9.5×10−6 °C−1 for glass 60%SiO2–10%Al2O3–10%ZrO2–5%CaO–15%Na2O. The gluing microstructure in YSZ/glass/Crofer22APU was studied by scanning electron microscopy. The crystallization process of silicate phases was revealed to occur in the SiO2–Al2O3–BaO–MgO glass. The analysis of the crystallization products was performed by Raman spectroscopy and X-ray diffraction. Glassy ceramics was proved to possess better parameters in comparison with amorphous glass to be used as a sealant in electrochemical sensors and oxygen sensors. The SiO2–Al2O3–ZrO2–CaO–Na2O low-temperature amorphous glass can be applied in SOFC.

An electron transfer in CuCl-CuCl2 melt at different Cl2 partial pressures

Thermodynamic properties of Pb-Sb alloys containing 20–95 mol % Pb are investigated by the method of measurement of equilibrium emf values in the range T = 723–873 K in a molten mixture of potassium and lead chlorides. The partial and integral thermodynamic characteristics of the system are calculated, and small negative deviations from ideality are revealed. The extremum of integral functions of mixing lies in the region of 0.55 mole fraction of Pb. The system could not be treated as a regular solution since the excess entropy introduces a considerable contribution to deviation from ideality, while the excess Gibbs energy differs considerably from the heat of mixing.

Electron transfer in the CuCl-CuCl2-LiCl melt

The main features of scandium and zirconium extraction from their oxides to aluminum during the aluminothermic and electrolytic preparation of Al–Sc and Al–Zr alloys and master alloys in the KF–AlF3, NaF–AlF3, and KF–NaF–AlF3 oxide–fluoride melts with Sc2O3 and ZrO2 additives are studied. The influence of the melt composition and temperature, the synthesis time, the contents of oxides Sc2O3 and ZrO2 in the melts, the mechanical stirring of aluminum, and the cathodic current density on the contents of scandium and zirconium in aluminum and on their extraction from the oxides is determined. The average values of scandium and zirconium extraction are 20–75 and 40–100%, respectively, depending on the synthesis parameters. The electrolytic decomposition of the oxides in the KF–AlF3, NaF–AlF3, and KF–NaF–AlF3 melts results in the enhancement of scandium and zirconium extraction to aluminum. The parameters of the preparation of Al–Sc and Al–Zr alloys and master alloys with the scandium content to 10 wt % and zirconium content to 15 wt % during the electrolysis of oxide–fluoride melts are chosen as a result of the results obtained.

Electrode Potentials of Bismuth in a Mixture of Potassium and Lead Chlorides

The mechanism of formation of ceramic microparticles (alumina) and graphene in a molten aluminum matrix is studied as a function of the morphology and type of precursor particles, the temperature, and the gas atmosphere. The influence of the composition of an aluminum composite material (as a function of the concentration and size of reinforcing particles) on its mechanical and corrosion properties, melting temperature, and thermal conductivity is investigated. Hybrid metallic Al–Al2O3–graphene composite materials with up to 10 wt % alumina microparticles and 0.2 wt % graphene films, which are uniformly distributed over the metal volume and are fully wetted with aluminum, are synthesized during the chemical interaction of a salt solution containing yttria and boron carbide with molten aluminum in air. Simultaneous introduction of alumina and graphene into an aluminum matrix makes it possible to produce hybrid metallic composite materials having a unique combination of the following properties: their thermal conductivity is higher than that of aluminum, their hardness and strength are increased by two times, their relative elongation during tension is increased threefold, and their corrosion resistance is higher than that of initial aluminum by a factor of 2.5–4. We are the first to synthesize an in situ hybrid Al–Al2O3–graphene composite material having a unique combination of some characteristics. This material can be recommended as a promising material for a wide circle of electrical applications, including ultrathin wires, and as a structural material for the aerospace industry, the car industry, and the shipbuilding industry.