The electrical conductivity of molten KAlCl4–ZrCl4 mixtures in a wide temperature range

A. B. Salyulev, V. A. Khokhlov, N. I. Moskalenko.

ABSTRACT:

In the cells of the original design, the specific electrical conductivity of promising industrial KAlCl4–ZrCl4 molten mixtures depending on the composition (0–32.5 mol % ZrCl4) and temperature (345–556°С) was measured for the first time. The conductivity is found to be rising with the increasing temperature and the decreasing zirconium tetrachloride content in salt mixtures. The refined equations of the temperature and concentration dependences of the melts electrical conductivity are derived taking into account the results of our previous studies.

KEYWORDS:

electrical conductivity, melts, low melting mixtures, ZrCl4, KAlCl4

DOI: 10.7868/S0235010618050134

Electrical conductivity of cryolite systems in molten and solid state

A. V. Rudenko, A. A. Kataev, O. Yu. Tkacheva, A. A. Redkin, Yu. P. Zaikov.

ABSTRACT:

The electrical conductivity of cryolite systems NaF–AlF3 with cryolite ratio 2.4–3.0 containing CaF2 3.0–7.0 wt %, MgF2 1.2–2.0 wt %, Al2O3 0–8.0 wt % in the temperature range of 700–1050°C has been studied by the impedance spectroscopy. Additions of CaF2 and MgF2 to the molten sodium cryolite reduce the electrical conductivity, but below the liquidus temperature in the twoEphase region of solid and liquid phases, the electrical conductivity increases with the fluoride salts concentration. The electrical conductivity of cryolite systems decreases with increasing Al2O3 content throughout the temperature range.

KEYWORDS:

sodium cryolite, electrical conductivity, liquidus temperature, solidus temperature

DOI: 10.7868/S0235010618050122

Electroconductivity of GdCl3–KCl–Gd2O3 system

E. V. Nikolaeva, I. D. Zakir’yanova, A. L. Bovet, T. V. Sosnovtseva.

ABSTRACT:

The temperature dependence of the electrical conductivity of the molten eutectic GdCl3(0.515)–KCl (0.485), containing up to 3.3 mol. % of gadolinium oxide have been investigated. The temperature dependences of the specific electrical conductivity of the molten GdCl3–KCl–Gd2O3 system were approximated by the second order polynomials. The formation of gadolinium oxychloride was confirmed by spectral studies of frozen melt.

KEYWORDS:

conductivity, gadolinium oxide, impedance

DOI: 10.1134/S0235010618060051

Nanostructuring of samples Eu2Ba3Cu5Oy

L. A. Klinkova, V. I. Nikolaychik, N. V. Barkovsky, V. K. Fedotov, A. F. Shevchun

ABSTRACT

The composition and structure of ceramic samples of Eu2Ba3Cu5Oy (Eu‑235) oxide of a tetragonal and orthorhombic structure were studied by X-ray diffraction (XRD) and chemical analysis, electron diffraction, elemental analysis (EA), and high-resolution electron microscopy (SEMM) in a transmission electron microscope (TEM). According to XRF data, samples annealed in air at a temperature of 1213 K and additionally in an oxygen atmosphere (P (O2) = 101 kPa, 723 K) are single-phase. However, according to EA data in TEM, these samples are inhomogeneous in the cationic composition, which corresponds to the process of disproportionation of 3Eu2Ba3Cu5Oy → Eu3Ba4Cu7Oy (Eu‑347) + Eu3Ba5Cu8Oy (Eu‑358). On the curve of the temperature dependence of the magnetic susceptibility = f (T) of the rhombic sample Eu‑235 with a diamagnetic response at Tc = 80 K, two more are observed at Tc = 40 and 30 K, indicating the presence of three superconducting phases. The tetragonal and rhombic Eu‑235 samples according to the STEM images are nanostructured and consist of coherently fused domains 2–5 nm in size.

KEYWORDS:

oxide Eu2Ba3Cu5Oy, disproportionation, nanostructure, superconductivity.

Electrical conductivity of molten alumophosphate and borosilicate glasses containing simulated high-level waste from nuclear fuel processing

O. Yu. Tkacheva, V. B. Remisov, P. V. Kozlov, E. A. Belanova, N. V. Vlasova, Yu. P. Zaikov

ABSTRACT

The electrical conductivity of the borosilicate and aluminophosphate glasses containing simulated high-level waste from the reprocessing of spent nuclear fuel VVER‑440 has been studied by the impedance spectroscopy method. It was found that the electrical conductivity of the aluminophosphate and borosilicate glasses was determined mainly by the sodium oxide concentration and significantly changes with temperature. An empirical equation of the electrical conductivity dependence on the sodium oxide content and temperature is obtained for the borosilicate glasses. The effect of the HLW simulators on the electrical conductivity of molten glasses was insignificant in the concentration range being studied.

KEY WORDS

spent nuclear fuel, high-level waste, aluminophosphate glass, borosilicate glass, melt, electrical conductivity

Electrical conductivity and raman spectra of the α-Al2O3 – molten Li2CO3-Na2CO3-K2CO3-NaCl disperse systems

D. Zakiryanova, Е. V. Nikolaeva, А. L. Bove, B. D. Antonov.

ABSTRACT

Information on the specific electric conductivity of the dispersed system a-Al2O3-molten carbonate-chloride mixture of Li2CO3-Na2CO3-K2CO3-NaCl in the temperature range of 455–550 °C is obtained. Using the method of Raman spectroscopy, it was shown that in the investigated temperature range a-Al2O3 does not enter into a chemical interaction with the carbonate-chloride melt. Data on the strength and energy characteristics of the CO32– anion in these systems are obtained.

KEY WORDS

Conductivity, Raman spectra, disperse system, melts.

The high-volage penonena in aluminum Molten chloride electrolytes

L. A. Kazieva, S. I. Suleymanov.

ABSTRACT

The electrical conductivity of the molten chloroaluminates NaAlCl4 and KAlCl4 increases with increasing of electrical field strength and reach the limiting values (the Wien effect) which surpass their usual low-voltage conductivity up to 200 and 700 percent respectively. These results have been obtained on the base of analysis of the microsecond high-voltage discharges in the melts (the Wien effect). After the high-voltage pulses discharges having been completed in the melts, their conductivity and electrolyze current have been found to rise up to 50% and their decomposition potentials has found to decrease more than 20% (the “memory effect”). The relaxation time of a non-equilibrium state reaches 5 minutes and more.
KEY WORDS

activation, melts, chloroaluminates, Wine effect, relaxation, structure, aluminum, conductivity.

LaCoO3-d as an Oxygen Electrode Material for the Molten Carbonate Fuel Cell. Part 2. Catalytic activity of LaCoO3-d for oxygen reduction in (Li0.62K0.38)2CO3 melt

S. I. Vecherskii, M. A. Konopelko, N. N. Batalov, M. A. Zvezdkin, I. V. Zvezdkina.

ABSTRACT

Kinetics of oxygen reduction on “in situ” lithiated LaCoO3-d electrode in (Li0.62K0.38)2CO3 melt has been studied. It has been shown that under the experimental conditions the main electroactive species are superoxide ions and molecular oxygen, which correlates with studies on a gold electrode. However, the observed mechanism of the electrode reaction differed from the mechanisms proposed for the gold electrode. A number of mechanisms accounting the peculiarities of the oxide electrode have been proposed. Exchange current densities were found to be independent on the oxygen partial pressure and varied in the range 220–290 mA/cm2, depending on the experimental conditions and the supposed mechanism.

KEY WORDS

molten carbonate, fuel cell, perovskite, lanthanum cobaltite, oxygen reduction, electrocatalytic activity.

LaCoO3-d as an Oxygen Electrode Material for the Molten Carbonate Fuel Cell. Part 1. Electrophysical Properties of lithiated LaCoO3-d.

S. I. Vecherskii, M. A. Konopelko, B. D. Antonov, N. N. Batalov, M. A. Zvezdkin, I. V. Zvezdkina.

ABSTRACT

Oxides LaCoO3-d + (z/2) Li2O (0 ≤ z ≤ 0.15) were synthesized and studied to elucidate variation of electrophysical properties of LaCoO3-d due to lithiation “in situ” in (Li0.62K0.38)2CO3 eutectic melt. It has been found that a perovskite-like solid solution (La1-хLix)(LiхСо1-х)O3-d, where х = z/(z + 2), forms as a result of doping by Li. The solid solution region does not exceed 2х = 0.072. At higher lithium content LiCoO2 appears along with the main perovskite-like phase. Single-phase samples exhibit a metallic type of conductivity and positive thermopower at the molten carbonate operating temperature 920 K. Electrical conductivity of Li-doped samples is 1.5 or less time smaller compared to LaCoO3-d, it varies in the range 3.2 × 104–3.8 × 104 S/m.

KEY WORDS

molten carbonate, fuel cell, perovskite, lanthanum cobaltite, electrical conductivity.