Frequency Dispersion of Impedance in a Molten Electrolyte

<p>It is an experimental fact that the impedance of an electrolyte as usually measured (by conductance bridge in a two electrode cell) is dependent on the frequency of the applied voltage. A quantity of fundamental physical significance in the elucidation of the structure of an electrolyte is the mobility of the conducting species. In order to know the mobilities of conducting species it is necessary to know the resistance of the particular electrolyte. However in order to establish the nature of the electrolyte i.e. its structure, resistance measurements are required which are precise and accurate and the variation of resistance (conductance) with temperature must be accurately know.</p>

Frequency Dispersion of Impedance in a Molten Electrolyte

<p>It is an experimental fact that the impedance of an electrolyte as usually measured (by conductance bridge in a two electrode cell) is dependent on the frequency of the applied voltage. A quantity of fundamental physical significance in the elucidation of the structure of an electrolyte is the mobility of the conducting species. In order to know the mobilities of conducting species it is necessary to know the resistance of the particular electrolyte. However in order to establish the nature of the electrolyte i.e. its structure, resistance measurements are required which are precise and accurate and the variation of resistance (conductance) with temperature must be accurately know.</p>

Oxidation and electrical properties of chromium–iron alloys in a corrosive molten electrolyte environment

Chromium–iron (CrFe) binary alloys have recently been proposed to serve as the “inert” anode for molten oxide electrolysis (MOE). Herein, the effects of anodic polarization on physical and functional properties of CrFe anodes in the corrosive environment of MOE are studied via empirical observations and theoretical calculations. The findings indicate that the alloys form an inner chromia–alumina solid-solution covered by an MgCr2O4 spinel layer. A survey into the electrical properties of the detected oxides suggests that the layered oxide scale function as an efficient conductor of electricity at elevated temperature. The formation mechanism of the oxides is also investigated.

Surface Modification on Ti-6Al-4V Alloy During Corrosion in a High Temperature Ionic Liquid

Corrosion behavior of Ti-6Al-4V alloy was investigated by anodic polarization curves in LiF-NaF-KF molten salts mixture at 823K. The surface alloy (native composition and its modification and corrosion resistance after 4 hours immersion) was studied by XRD, SEM and XPS. XPS analysis shows TiO2 with small amount of V2O5, Al2O3 and TiF4, while in the electrolyte it was showed the presence of V in a very low concentration. AFM demonstrates that formation of a rough and non-protective oxide layer should be responsible for the weak protective properties of the alloy. The degradation mechanism of the alloy during corrosion is based on the formation of TiF4 and of the passing of vanadium in the molten electrolyte.

Oxidation and electrical properties of chromium-iron binary alloys in a corrosive molten electrolyte environment

Chromium-iron (CrFe) binary alloys have recently been proposed to serve as the ʺinertʺ anode for molten oxide electrolysis (MOE). Herein, the effects of anodic polarization on physical and functional properties of CrFe anodes in the corrosive environment of MOE are studied via empirical observations and theoretical calculations. The findings indicate that the alloys form an inner chromia-alumina solid-solution covered by an MgCr2O4 spinel layer. A survey into the electrical properties of the detected oxides suggests that the layered oxide scale function as an efficient conductor of electricity at elevated temperature. The formation mechanism of the oxides is also investigated.

MgO Modified with MgF2 as an Electrolyte Immobilizing Agent for the High-Temperature Cells

Magnesium oxide, generally applied as a filler in high-temperature cells (with an electrolyte melting point above 250 °C), was modified with magnesium fluoride to improve its mechanical and electrical properties. Samples containing 10 and 25 mol.% MgF2 were prepared and calcined at 500, 600, and 700 °C. They were characterized by low-temperature nitrogen adsorption and X-ray diffractometry (XRD). Moreover, the electrolyte absorption, mechanical strength of pellets made of filler and electrolyte, and volume of unfilled spaces were determined. It was shown that the introduction of MgF2 in the amount of 10 and 25 mol.% results in a considerable decrease in the surface area of the initial MgO, which testifies to the covering of MgO by the formed fluoride. However, no new crystalline phases were formed as concluded from the XRD analysis. The pellets consisting of electrolyte and MgF2/MgO filler (the electrolyte + 40 wt.% of the filler) had a higher mechanical strength compared to bare MgO filler. In particular, they outperformed MgO in the ionic conductivity of molten electrolyte. The latter was almost three times as high as that of MgO filler, when the filler containing 25 mol.% MgF2 was employed. The aforementioned properties of MgF2/MgO materials predispose them for use as fillers in high-temperature cells.

Corrosion and oxidation of silicon carbide on the nitride bond in the side lining of aluminum electrolysis cells

The main question for understanding the corrosion of silicon carbide on the nitride-silicon bond onboard linings is whether corrosion of Si3N4‒SiC material with gases (and, in particular, oxidation) is preceded by corrosion by molten electrolyte, or corrosion by molten electrolyte plays its own role in material degradation during service. It is more likely that the reactions of SiC and Si3N4 with cryolite melt pass through a preoxidation stage. Calculations show that most of the possible reactions of SiC and Si3N4 with oxygen and carbon monoxide and carbon dioxide have a positive volumetric effect, which reduces the porosity of the material, but may cause cracks in it. The resulting silicon oxide is dissolved in the electrolyte melt, and can also react with electrolyte components in the gas phase. Ill. 6. Ref. 24. Tab. 2.