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The physicochemical properties of the (LiF (1) + MgF2 (2))eut + LaF3 (3) molten system have been investigated. The phase equilibria, density and volume properties, electrical conductivity, and surf...

Phase diagrams (solubility), density, electrical conductivity and viscosity of molten system (MgF2 – CaF2)eut – MgO have been investigated. The phase diagram of (MgF2 – CaF2 – LiF)eut – MgO and (MgF2 – BaF2)eut– MgO and the density of (MgF2 – CaF2 – LiF)eut – MgO have been also investigated. The solubility of MgO was measured by means of thermal analysis, the density by means of a computerized Archimedean method, electrical conductivity by means of a tube–cell (pyrolytic boron nitride) with stationary electrodes and the viscosity of the melt by computerized torsion pendulum method. It was found that the all investigated properties varied linearly with temperature in all investigated mixtures. On the basis of density values, the molar volume of the melts and partial molar volume have been calculated. The coordinates of the eutectic systems has been established as follows: (CaF2 – MgF2)eut – MgO as 0.30 mol% at 972 °C; (CaF2 – MgF2 – LiF)eut – MgO as 0.20 mol% at 941 °C; and (MgF2 – BaF2)eut. – MgO as 0.25 mol% at 883 °C. The density of the molten system of (CaF2 – MgF2)eut – MgO was found to be at 1000 °C: 2.687 g·cm−3 for the system with 0 mol% of MgO; 2.700 g·cm−3 for the system with 0.30 mol% of MgO and 2.728 g·cm−3 for the system with 0.50 mol% of MgO. The density of the molten system of (CaF2 – MgF2 – LiF)eut – MgO was found to be at 1000 °C: 2.875 g·cm−3 for the system with 0 mol% of MgO; 2.690 g·cm−3 for the system with 0.20 mol% of MgO and 2.650 g·cm−3 for the system with 0.30 mol% of MgO. The viscosity of basic eutectic mixture of (CaF2 – MgF2)eut at 1000 °C was found to be 7.806 mPa·s.

Precise research on the RbF-Al2O3 system was carried out by means of combining X-ray powder diffraction, high-field solid-state NMR spectroscopy, and thermal analysis methods. α-Rb3AlF6, RbAlO2, Rb2Al22O34, and new phase, Rb2Al2O3F2, were identified in the system. The structure of this new rubidium oxofluoroaluminate was determined. It is built up from single layers of oxygen-connected AlO3F tetrahedra, those layers beeing separated by fluorine atoms. This type of structure exhibits a decent ionic conductivity at ambient temperature, 1.74 × 10-6 S cm-1. The similar structural arrangement of O3Al-O-AlO3 and FO2Al-O-AlO2F tetrahedra of the conduction planes in Rb2Al22O34 and Rb2Al2O3F2 were confirmed by 27Al NMR measurements. A thermal analysis of the RbF-Al2O3 system revealed that it can be defined as a pseudobinary subsystem of the more general quaternary RbF-AlF3-Al2O3-Rb2O phase diagram. From a phase analysis of individual phase fields, the mutual metastable behavior of all founded phases can be considered. It was observed that fluoro- and oxoaluminates exist together. Rb2Al2O3F2 is more stable under high temperature. Rubidium fluoro- and oxoaluminates are metastable precursors of the thermodynamically more stable structure of rubidium oxofluoroaluminate.

We present a techno-economic analysis of a 17,000–18,000 metric tons per year electrolytic process for producing Mg from MgO with and without out a concentrated solar thermal input. The solar thermal input is delivered via power tower technology and the evaporation and condensation of sodium. Energy requirements for the process at scale were based on thermodynamics and an extrapolation of laboratory measurements of the electrochemical kinetic and mass transport parameters via a finite-element numerical model. While technically possible, integrating a solar thermal input does not make economic sense without crediting avoided CO 2 emissions. A solar thermal input reduces energy operational costs from $0.654/kg to as low as $ 0.481/kg, but it also lowers the Mg production rate of the electrolytic cells such that more cells are required to achieve production capacity, which, in turn, increases capital and maintenance costs. The net operational savings are negligible. The estimated operational costs to produce Mg are ∼$2.46/kg. At this cost, the process without a solar thermal input is economically tantalizing vis a vis the current commercial processes for producing Mg, and its CO 2 emission level is 46% lower than that of the Pidgeon process, currently the predominant method for producing Mg.

Coal fly ash from coal power plants is a potential raw material for the production of alumina. An objective aluminothermic reduction method for the preparation of Al-Si master alloy and alumina from coal fly ash was investigated. The kinetic analysis using non-isothermal differential scanning calorimetry indicated that the reduction of Al6Si2O13, Fe2O3, and TiO2 by aluminum in coal fly ash occurs at 1618 K, 1681 K, and 1754 K, respectively. Moreover, the influence of reaction temperature on product composition was studied. The phases and morphologies of the products obtained by the aluminothermic reduction of coal fly ash at 1373-1773 K were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, respectively. The results from X-ray diffraction show that no oxide reduction has taken place at 1373 K and 1473K, the compositions of the product obtained by aluminothermic reduction of fly ash at 1573K- 1673 K are Al2O3, mullite, Al and Si, while the compositions of the product at 1773 K are Al2O3, Al, and Si. In addition, the chemical compositions of Al-Si alloy obtained at 1773 K are 86.81 wt% Al and 13.19 wt% Si.

We examined the kinetic and transport processes involved in Mg production from MgO via electrolysis at ca 1250 K with in a eutectic mixture of MgF 2 –CaF 2 , using a Mo cathode, and carbon anode. Exchange current densities, transfer coefficients, and diffusion coefficients of the electroactive species were established using a combination of cyclic and linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The cathode kinetics are described by a concentration dependent Butler–Volmer equation. The exchange current density and cathodic transfer coefficient are 11±4 A cm −2 and 0.5±0.12 respectively. The kinetics of the anode are described by two Tafel equations: at an overvoltage below 0.4 V, the exchange current density is 0.81±0.2 mA cm −2 with an anodic transfer coefficient of 0.5±0.1; above 0.4 V overvoltage the values are 0.14±0.05 mA cm −2 and 0.7±0.2 respectively. The diffusion coefficients of the electroactive species are D (Mg 2+ )=5.2±0.6E−5 cm 2 s −1 and D ( Mg 2 OF 4 2 - )=7.2±0.2E−6 cm 2 s −1 . The ionic conductivity of the electrolyte is ca 2.6 S cm −1 . A 3D finite element model of a simple cell geometry incorporating these kinetic and transport parameters suggest that up to 27% of the energy required to drive the electrolysis reaction can be supplied thermally for a current density of 0.5 A cm −2 , enabling a reduction in operating cost if the thermal energy is substituted for valuable electric work.

The present paper is an attempt to critically review the relevant techniques for the laboratory measurement of interfacial tension of high-temperature liquid-liquid systems, mostly linked with metallurgy and pyrochemistry. Even if the present paper is preferably devoted to interfacial high-temperature measurements, the same information concerning surface tension will be implicitly provided, as well. There will be no report of the techniques related to dynamic interfacial tension, measurements of ultralow interfacial tension, and the techniques used in microtensiometry and nanotensiometry. These methods (often call nonclassical techniques) are very hard to employ at high temperature, even if they could be in general used at these conditions.

d ) Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, SK-845 36 Bratislava e ) Instituto de Ciencia de Materiales de Aragon, CSIC-University of Zaragoza, ES-50009 Zaragoza The rapid-solidification processing (by a cooling rate of 105 -1 06 K/s) was used for the preparation of deeply undercooled cryolite/alumina (Na3AlF 6/Al2O3) melts. We found a mass of nanotubes on the surface of these undercooled melts. The nanotubes were preferentially located on the defect places of the surface with the following approximate dimensions: base � 100 � 100 nm, length � 1000 nm. The solidified samples with the nanotubes on the surface were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and infrared spectroscopy (IR).

The interfacial tension (IFT) between aluminum and cryolite melts containing different salt additions (AlF3, NaF, Na2SO4, NaVO3) has been measured by the capillary depression method under the condi...