Corrosion of stainless steels in NaCl-KCl based melts

Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 was studied at 750 °C in NaCl-KCl equimolar melts. Iron, chromium and manganese species constitute the major corrosion products. The following mechanism of stainless steel corrosion in molten chlorides was proposed: 1) chemical interaction between the alloy and the salt intensified by the formation of microgalvanic pairs; 2) formation of chromium and molybdenum carbide-containing phases in steel as a result of heating to 750 °C; 3) additional formation of galvanic pairs between the grains of austenitic alloys and the carbide phases at the grain boundaries resulting in enhanced intergranular corrosion. ©The Electrochemical Society.Physical and Analytical Electrochemistry;Electrodeposition;Energy Technolog

STABILITY OF NIOBIUM PENTACHLORIDE SOLUTIONS IN CHLORIDE MELTS

Dissolution of niobium pentachloride in molten alkali chlorides was studied in NaCl-KCl, NaCl-CsCl, NaCl-KCl-CsCl and LiCl-KCl based melts and the progress of the dissolution was followed by in situ spectroscopy measurements and oxidimetry. The obtained results indicate that NbCl6- species constituted the main product of this reaction. At relatively high niobium concentrations in the melt NbCl6-, however, partly decomposed yielding NbCl62- and chlorine gas. The influence of temperature and average radius of solvent cation on concentration of formed niobium (IV) species were investigated

INVESTIGATION OF THE PROCESESSES IN CONTACT OF NIOBIUM-CONTAINING CHLORIDE MELTS WITH NIOBIUM METAL

In the current study we found that upon contacting metallic niobium with a melt containing higher oxidation state niobium ions the average oxidation state of niobium in the salt phase, mass of the metal and potential difference between niobium and indicator electrodes decrease. After certain period of time these parameters tend to achieve certain constant values. This moment corresponds to the stationary state of the system. Analysis of the experimental data showed that the mixture of niobium (III) and (IV) ions is the final product of interaction of niobium-containing chloride melts with niobium metal and, therefore, a mixture of niobium ions in two oxidation states is present in equilibrium with the metal. The average oxidation state of niobium in the obtained melts (after contacting with Nb metal) increases with increasing niobium concentration. This observation correlates with the results of cathodic current efficiency measurements during niobium electrorefining. Thermodynamic calculations were performed using niobium red-ox and equilibrium electrode potentials in NaCl-KCl based melts at 700 0C. The results confirmed that equilibrium oxidation state of niobium in the fused chloride can increase with increasing total concentration of niobium in the melt

REACTION OF NIOBIUM-CONTAINING CHLORIDE MELTS WITH NIOBIUM METAL

In the current study, we found that upon contacting metallic niobium with a melt containing higher oxidation state niobium ions the average oxidation state of niobium in the salt phase, mass of the metal and potential difference between niobium and an indicator electrodes decrease. Analysis of the experimental data showed that the mixture of niobium (III) and (IV) ions is the final product of interaction of niobium-containing chloride melts with niobium metal and, therefore, a mixture of niobium ions in two oxidation states is present in equilibrium with the metal. The average oxidation state of niobium in the obtained melts (after contacting with Nb metal) increases with increasing niobium concentration. Thermodynamic calculations were performed using niobium red-ox and equilibrium electrode potentials in NaCl-KCl based melts at 700 0C. The results confirmed that equilibrium oxidation state of niobium in the fused chloride could increase with increasing total concentration of niobium in the melt

DEPENDING ELECTRODE POTENTIAL OF U-Pd ALLOYS IN 3LiCl–2KCl–UCl3 MELTS AT DIFFERENT TEMPERATURES

Electrode potential of U-Pd alloys in 3LiCl–2KCl–UCl3 melts were studied at different temperatures

Temperature Dependence of the Potential U-Pd Alloys in 3LiCl-2KCl-UCl3 Melts

Temperature dependence of the potential U-Pd alloys in 3LiCl–2KCl–UCl3 melts were studied at different temperatures and concentrations using a variety of electrochemical techniques

SAMARIUM AND YTTERBIUM METAL PRODUCTION USING LANTANOTHERMIC REDUCTION

The method of lantanothermic reduction was proposed for production of metallic samarium and ytterbium. Their oxides were used as a crude material. The optimal conditions of the processes were determined. The enlarged lots of metals were produced using specially designed set-up

PRODUCTION OF METALLIC SAMARIUM AND YTTERBIUM BYLANTHANUM REDUCTION

The method of lantanothermic reduction was proposed for production of metallic samarium and ytterbium. Their oxides were used as a crude material. The optimal conditions of the processes were determined. The enlarged lots of metals were produced using specially designed set-up.The study was financially supported by the Ministry of Education and Science of the Russian Federation within the framework of subsidizing agreement of September 29, 2014 (no. 14.581.21.0002, unique agreement identifier RFMEFI58114X0002) of the Federal Target Program “Research and Development in Priority Directions of the Progress of the Scientific and Technological Complex of Russia for the Years 2014–2020.

LANTANOTHERMIC METHOD OF SAMARIUM AND YTTERBIUM REDUCTION

The method of lantanothermic reduction was proposed for production of metallic samarium and ytterbium. Their oxides were used as a crude material. The optimal conditions of the processes were determined. The enlarged lots of metals were produced using specially designed set-up.The study was financially supported by the Ministry of Education and Science of the Russian Federation within the framework of subsidizing agreement of September 29, 2014 (no. 14.581.21.0002, unique agreement identifier RFMEFI58114X0002) of the Federal Target Program “Research and Development in Priority Directions of the Progress of the Scientific and Technological Complex of Russia for the Years 2014– 2020.

EXPRESS SEMI-QUANTITATIVE ANALYSIS METHOD OF KALCL₄ BY DIFFUSION REFLECTION FOURIER-IR SPECTROMETRY

Applicability of IR diffusion reflection method was investigated for semi-quantitative determination of oxygen containing impurities in KAlCl₄