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卷 2017, 编号 2 (2017)
- 年: 2017
- 文章: 15
- URL: https://journals.rcsi.science/0036-0295/issue/view/10425
Article
Relation between the thermal expansion coefficient and the heat capacity in halide melts
摘要
The thermal expansion coefficients of molten halides have been analyzed. This parameter has been found to be a constant for all halides except for lithium halides. Since the thermal expansion coefficient and the molar heat capacity of halides change symbatically, the ratio of the molar heat capacity to the thermal expansion coefficient is also a constant.
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Thermodynamic analysis of the lead oxide dissolution in the alkali–carbonate NaOH + 30 wt % Na2CO3 melt
摘要
An isothermal saturation method was used to study the PbO solubility in the NaOH + 30 wt % Na2CO3 melt. A model dissolution mechanism is considered. Thermodynamic parameters have been calculated.
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Liquidus temperatures and phase equilibria in the BaCl2–MCl–BaO systems
摘要
The liquidus temperatures of the BaO–BaCl2–MCl systems (with M = alkali metal) are determined by thermal analysis. The caloric effects observed during melting of the barium-containing chloride eutectic with barium oxide additions are studied. A chemical mechanism of barium oxide dissolution in the melts is confirmed. X-ray diffraction patterns taken for the melt solidified after experiment indicate the presence of barium oxychloride Ba4OCl6 in the solid phase. It is shown that the significant increase in the liquidus temperature in adding the barium oxide to barium-containing chloride molten mixtures is related to substantial changes in their composition and structure.
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Raman spectra and conductivity of PbO–PbCl2–CsCl melts
摘要
The structure and the conductivity of homogeneous CsCl–PbCl2–PbO melts with different compositions are studied. The Raman spectra (RS) of the chloride and oxide–chloride melts containing lead oxide have been measured. It is found that the CsCl (71.3 mol %)–PbCl2 (28.7 mol %) system with the addition of 12 mol % PbO and the CsCl (18.3 mol %)–PbCl2 (81.7 mol %) system with the addition of 18 mol % PbO contain Pb3O2Cl+ oxide–chloride groups. The temperature dependences of the electrical conductivity are measured in the PbCl2–CsCl chloride melts containing 28.7 and 81.7 mol % lead chloride and in homogeneous molten mixtures CsCl (71.3 mol %)–PbCl2 (28.7 mol %) with the addition of 12 mol % PbO and the CsCl (18.3 mol %)–PbCl2 (81.7 mol %) with the addition of 18 mol % PbO. Significant degradation of the ion conductive properties of the PbO–PbCl2–CsCl oxide–chloride melts as compared to those of the PbCl2–CsCl chloride electrolytes has been revealed. It is shown that the decrease in the electrical conductivity of the PbCl2–CsCl oxide–chloride melts as lead oxide is added is due to the presence of Pb3O2Cl+ oxide–chloride groups.
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Effect of the electrolyte composition on the corrosion of 12Kh17 steel in molten alkali metal carbonates
摘要
The corrosion of 12Kh17 steel in the melts of alkali metal carbonates containing additions of various chemical types is studied using anodic potentiostatic polarization. The morphology of the 12Kh17 steel surface is analyzed by electron-probe microanalysis. The introduction of corrosion passivators and activators affects the mechanism of local corrosion damages. The corrosion of the steel proceeds according to an electrochemical mechanism. Carbonate anions serve as oxidizers of the steel along with oxygen dissolved in the melt. Treatment of a corrosive medium can be used to protect metallic constructions against corrosion in high-temperature salt electrolytes. Combined introduction of corrosion activators and passivators in a salt phase makes it possible to form protective layers with a high corrosion resistance.
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Electrical conductivity of KAlCl4–ZrCl4 molten mixtures
摘要
The electrical conductivity of commercially challenging KAlCl4–ZrCl4 molten mixtures has been studied as a function of temperature (in the range from 345°C to 500°C) and the ZrCl4 concentration (0‒32.5mol %) using cells of a unique design. It is found to vary in the range from 0.41 to 0.80 S cm–1, increasing with temperature or when the mole concentration of zirconium tetrachloride in molten mixtures decreases.
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Influence of alkaline earth metal cations on the charge transfer kinetics for the redox couple Ti(IV)/Ti(III) in a chloride–fluoride melt
摘要
The influence of strongly polarizing cations Mg2+, Ca2+, Sr2+, and Ba2+ on the charge transfer kinetics of the redox couple Ti(IV)/Ti(III) is studied. The standard rate constants of charge transfer (ks) for the Ti(IV)/Ti(III) redox couple in the (NaCl–KCl)eq–NaF (10 wt %)–K2TiF6 melt upon the addition of the strongly polarizing cations into the starting melt are determined. The dependence of the charge transfer rate constants on the ionic potential of the cations is established. The activation energies of the charge transfer process are calculated for the fluoride complexes of the Ti(IV)/Ti(III) redox couple with the outer-sphere cations Mg2+, Ca2+, Sr2+, and Ba2+.
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Electrochemical synthesis of an iridium powder with a large specific surface area
摘要
The synthesis of iridium powder in a molten NaCl–KCl medium at 700°C is carried out for the first time. The influence of the ratio of the cathode to the anode current density (ic/ia) on the structure and the morphology of the iridium powder is investigated. Single-phase and polycrystalline iridium powders with a specific surface of 16.8 m2/g are produced. The phase composition and the surface texture of the deposits are studied. The specific surface and the particle size of iridium powders as functions of the ratio ic/ia are analyzed.
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Analytical representation of the concentration dependences of the thermodynamic functions of liquid binary metallic systems with negative deviations from ideal behavior
摘要
The application of a number of algebraic expressions for describing the concentration dependences of the thermodynamic functions in liquid binary metallic systems with negative deviations from ideal behavior is considered.
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Stability, atomic dynamics, and thermal destruction of the d metal/graphene interface structure
摘要
The results of molecular dynamics simulation performed using multiparticle potentials have been analyzed. The thermally activated processes of relaxation, diffusion, and formation of metal/graphene (M = Cu, Ru/G) interface structures have been considered, and their disordering and destruction have been analyzed as an analog to melting of a low-dimensional system upon heating.
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Solidification of ternary systems with a nonlinear phase diagram
摘要
The directional solidification of a ternary system with an extended phase transition region is theoretically studied. A mathematical model is developed to describe quasi-stationary solidification, and its analytical solution is constructed with allowance for a nonlinear liquidus line equation. A deviation of the liquidus equation from a linear function is shown to result in a substantial change in the solidification parameters.
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Thermodynamic simulation of the oxidation of radioactive graphite in the Na2CO3–K2CO3–NiO and Na2CO3–K2CO3–CuO melts
摘要
The oxidation of radioactive graphite in the Na2CO3–K2CO3–NiO and Na2CO3–K2CO3–CuO melts in the temperature range 373–3273 K is subjected to a thermodynamic simulation. The behavior of radionuclides is studied and the equilibrium constants of the reactions occurring in these systems are calculated.
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Simulation of the potentiodynamic and galvanostatic phase formation in melts
摘要
A general scheme is used to consider the initial stages of electrocrystallization under potentiodynamic and galvanostatic conditions. Proposed theoretical models are shown to agree well with the experimental results obtained during the electrodeposition of silver crystals on an iridium microelectrode from nitrate melt containing an excess background electrolyte.
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Electrochemical synthesis of tetragonal oxide tungsten bronze nanofilms on platinum
摘要
We are the first to synthesize nanofilms of tetragonal oxide tungsten bronze (OTB) on a Pt(110) substrate by the electrolysis of the K2WO4–Na2WO4–WO3 melt at 700 and 750°C. The composition and the morphology of OTB are shown to depend on the deposition potential and the WO3 concentration in the melt. The laws of formation of tetragonal OTB films are discussed. The synthesized OTB samples are found to have a good thermal stability in the temperature range 20–800°C.
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Formation of nanocrystalline tetragonal oxide tungsten bronzes on platinum
摘要
Cyclic voltammetry is used to study the formation of tetragonal oxide tungsten bronze of the composition KxNayWO3 on a Pt(110) substrate during electrodeposition from a K2WO4–Na2WO4–WO3 melt. The potential ranges in which cathode products of various compositions and morphologies form are found. KxNa(0.66–x)WO3 crystals are shown to form according to the nucleation/growth mechanism. A general scheme is proposed and used to write equations for cathode reactions.
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