熔盐电解中钛离子电化学沉积行为研究

对熔盐电解提钛工艺中钛离子的电化学沉积行为进行研究,首先通过调整TiCl_4和海绵钛的比例在NaClKCl熔盐中反应制备出不同电解质组分,然后在制备的电解质体系中研究钛离子的电化学沉积行为。低价钛电解质组分的XRD分析结果表明,在993 K的NaCl-KCl熔盐中,当TiCl_4与Ti摩尔比为1∶2时,反应产物主要为2价的TiCl_2,电解质形成NaCl-KCl-TiCl_2体系;当摩尔比为2∶1时,反应产物主要为2.57价的TiCl_2和K_3TiCl_6,电解质形成NaCl-KCl-TiCl_2-K_3TiCl_6体系。两种电解质体系的循环伏安研究结果表明,NaCl-KCl-TiCl_2体系中钛离子的还原历程为Ti~(2+)→Ti,主要受扩散影响,扩散系数为2.93×10~(-5)cm~2/s,而NaCl-KCl-TiCl_2-K_2TiCl_6体系中钛离子还原历程为Ti~(3+)→Ti~(2+)和Ti~(2+)→Ti两步。钛离子电化学沉积产物的SEM分析结果表明在NaCl-KCl-TiCl_2体系中,得到的钛粉产物呈现大颗粒的枝晶状,随着电流密度增大和钛离子浓度减小,钛粉产物颗粒逐步变细;而在NaCl-KCl-TiCl_2-K_2TiCl_6体系中获得产物为细颗粒的多孔状钛粉。     

Stability of complex molybdenum(III) ions in molten alkali metal chlorides

High-temperature absorption spectroscopy is used to study the effect of temperature in the range 550?C750°C and the cation composition of a solvent salt on the spectroscopic characteristics and stability of MoCl ₆ ^3? complex ions in melts based on alkali metal chlorides (LiCl; CsCl; LiCl-KCl, NaCl-CsCl, KCl-CsCl, and NaCl-KCl-CsCl eutectic mixtures; and equimolar NaCl-KCl mixture).     

Na2WO4-ZnO-WO3熔盐体系表面张力的研究

采用拉筒法测定了800～950℃范围内Na2WO4 ZnO WO3熔盐体系的表面张力。结果表明:该体系的表面张力与温度成线性关系,随着温度的升高而降低;在同一温度下,熔盐中的阴离子结构随着WO3摩尔含量的增加趋于复杂,表面张力降低,随ZnO摩尔含量的增加趋于简单,表面张力升高;组元ZnO对表面张力的影响比组元WO3大。     

The surface tensions and foaming behavior of melts in the system CaO-FeO-SiO2

The surface tensions of melts in the system CaO-FeO-SiO₂ have been measured in the temperature range 1573 to 1708 K using the hollow cylinder technique. The iron oxide content was maintained constant at 30 wt pct and the CaO/SiO₂ wt pct ratio was varied in the range 0.43 to 1.5. Surface tension increases with increasing basicity and with decreasing temperature. The data were used to test published correlations of slag foaming indexes with surface tension and viscosity. Foam life increases with increasing viscosity and with decreasing surface tension. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

Interfacial tension between aluminum and NaCl-KCl-based salt systems

Aluminum scrap is frequently remelted under a NaCl-KCl based salt flux cover to prevent oxidation, to aid in the stripping of oxide films, and to improve drop coalescence. In this process, the interfacial tension between the aluminum metal and the salt flux plays an important role. However, the measurement of interfacial tensions at high temperature is difficult and prone to errors. Therefore, an interfacial tension model, presented in this article, has been developed. The interfacial tension between aluminum and NaCl-KCl based melts does not change with the addition of chlorides or with variations in the composition of the NaCl-KCl melt. On the other hand, the addition of fluorides decreases the interfacial tension to various extents due to the adsorption of sodium and/or potassium at the interface. Addition of AlF₃ is the least effective; additions of LiF, MgF₂, CaF₂, BaF₂, or SrF₂ are moderately effective; and additions of NaF or KF are the most effective in lowering the interfacial tension.     

Measurement of the density and surface tension of Ni-based superalloys in the liquid and mushy states

The densities of three Ni-based superalloys have been measured in both liquid and mushy states by both a modified sessile drop method (MSDM) and a modified pycnometric method (MPM) for alloys CMSX-4 and CM186LC, and for CMSX-10 alloy by MSDM only. The surface tensions of liquid CMSX-4, CM186LC, and CMSX-10 superalloys were measured using the sessile drop method. All measurements were carried out in a highly purified argon atmosphere with the oxygen partial pressure of less than 10⁻¹⁹ MPa in the gas outlet. The densities of all superalloys in both liquid and mushy states were found to decrease with increasing temperature. The volume thermal expansion of each superalloy in the mushy state was found to be higher than that in the liquid state. The densities determined by different methods have been critically assessed and recommended values in both liquid and mushy states are given as a linear function of temperature for the three Ni-based superalloys. The surface tension of liquid CMSX-4 superalloy was found to decrease with increasing temperature, while that of liquid CMSX-10 superalloy increases with increasing temperature. The wetting behavior of liquid CM186LC on the alumina substrate was found (1) to differ significantly from that of CMSX-4 and CMSX-10 and (2) to vary with time. A HfO₂-rich layer was found in the contact area of CM186LC with the alumina substrate, which could lead to some uncertainty in the value obtained for the surface tension determined for CM186LC.     

The effect of temperature on the surface tension and adsorption functions of the Fe-S-O melts – an analysis based on interaction parameters

The present investigation analyses the thermodynamic behaviour of the surfaces and adsorption as a function of temperature and composition in the Fe-S-O melts based on the Butler's equations. The calculated values of the surface tensions exhibit an elevation or depression depending on the type of the added solute at a concentration which coincides with that already present in the system. Generally, the desorption of the solutes as a function of temperature results in an initial increase followed by a decrease in the values of the surface tension. The observations are analyzed based on the surface interaction parameters which are derived in the present research.     

NdF_3-LiF-Nd_2O_3体系表面张力数学模型的研究

用拉筒法研究了低NdF3 浓度下NdF3-LiF体系的表面张力 .采用二因子二次回归正交设计 ,得出表面张力 (σ)与NdF3 含量 (C)、温度 (t)的回归方程 ,讨论了NdF3含量、温度对表面张力的影响 ,并考察了加入Nd2 O3 对体系表面张力的影响     

Measurement of the surface tensions of Fe-saturated iron silicate and Fe-saturated calcium ferrite melts by Padday’s cone technique

Padday’s cone technique allows determination of the surface tension of a liquid from measurement of the maximum excess force exerted on a cone during its immersion in, or withdrawal from, the liquid and knowledge of the density of the liquid. As the technique does not require rupture of the meniscus, an equilibrium measurement is obtained. The surface tensions of Fe-saturated iron silicate melts and Fe-saturated calcium ferrites, measured at 1410 °C using iron cones, are in good agreement with values in the literature obtained using the hollow cylinder technique. The maximum excess forces exerted on Pt-Rh cones immersed in liquid iron oxides at 1460 °C in the composition range from saturation with iron toX _Fe2_O3 = 0.205 have been measured. The surface tensions of these melts cannot be determined unambiguously from the experimental measurements because of an uncertainty in the densities of the melts. However, it is shown that the literature values for the surface tension of liquid iron oxide are incorrect because of an error in the experimental procedures used.     

Surface Properties of Manganese – Tin Liquid Alloys

We used the sessile drop method to study the temperature and concentration dependences of the density and surface tension of melts in the manganese – tin system. The density polytherms are linear dependences which are consistent with those calculated by the additivity rule for the specific volumes of the pure components. The temperature dependences of the surface tension are also linear and their temperature coefficient changes from negative values for tin-rich melts to positive values for melts with high manganese content. The surface tension isotherm is satisfactorily described by the Popel-Pavlov equation. We calculated the composition of the surface layer of the studied melts as a function of the composition of the bulk phase. We have shown that the model for the surface layer of melts in the Mn – Sn system at 1300°C is close to monolayer.     

Interaction of exogenous refractory nanophases with antimony dissolved in liquid iron

The heterophase interaction of Al₂O₃ refractory nanoparticles with a surfactant impurity (antimony) in the Fe–Sb (0.095 wt %)–O (0.008 wt %) system is studied. It is shown that the introduction of 0.06–0.18 wt % Al₂O₃ nanoparticles (25–83 nm) into a melt during isothermal holding for up to 1200 s leads to a decrease in the antimony content: the maximum degree of antimony removal is 26 rel %. The sessile drop method is used to investigate the surface tension and the density of Fe, Fe–Sb, and Fe–Sb–Al₂O₃ melts. The polytherms of the surface tension of these melts have a linear character, the removal of antimony from the Fe–Sb–Al₂O₃ melts depends on the time of melting in a vacuum induction furnace, and the experimental results obtained reveal the kinetic laws of the structure formation in the surface layers of the melts. The determined melt densities demonstrate that the introduction of antimony into the Fe–O melt causes an increase in its compression by 47 rel %. The structure of the Fe–Sb–O melt after the introduction of Al₂O₃ nanoparticles depends on the time of melting in a vacuum induction furnace.     

Al2O3和Cr2O3对自蔓延冶金法制备 CuCr合金冶炼渣性能的影响

自蔓延冶金法制备CuCr合金时,合金中的Al₂O₃和Cr₂O₃夹杂物会在熔渣精炼过程中被冶炼渣溶解,改变熔渣成分,从而影响冶炼渣的熔点、黏度、密度和表面张力等性能,给精炼过程带来不利影响.使用熔体物性测定仪针对Al₂O₃和Cr₂O₃含量变化对冶炼渣的性能影响规律进行了研究,结果表明:Al₂O₃和Cr₂O₃含量的增加均可以提高熔渣的黏度、凝固温度和表面张力,Cr₂O₃对黏度和表面张力的影响较大,Al₂O₃对凝固温度的影响较大;Al₂O₃使熔体密度上升,Cr₂O₃使熔体密度先上升后下降.      

Surface properties of elastically deformed copper electrode in alkali metal chloride melts

The estans of a copper polycrystalline electrode in the NaCl, KCl, and CsCl melts and the NaCl-KCl and NaCl-CsCl eutectics is measured at various temperatures. The zero-charge potential of the elastically deformed electrode in these systems is determined. A mechanism is proposed for the interaction between salt-phase anions and the copper surface. It consists in the formation of a covalent bond between the atoms of a positively charged copper surface and the salt-phase anions with partial charge transfer to the metal.     

Ejection of steel and slag droplets from gas stirred steel melts

Abstract

Liquid ejections from gas stirred melts can be classified into small film and jet droplets caused by bubble bursting and larger splashes resulting from gas channels formed at higher exiting gas velocities. In view of the conditions in ladle metallurgy, experimental investigations were carried out at moderate to low gas flowrates in an arc heated, bottom stirred 150 kg steel melting furnace and an 80 L water tank. Droplets were collected at different heights above the melt level, while gas flowrates, viscosities, surface tensions, and slag layer thickness were varied. The number of steel droplets collected decreased greatly with height (in the range 30-110 mm) and with size (in the range 0·1-1·8 mm). Calculations showed that the entrainment of droplets is strongly influenced by the velocity of upward flowing gases. While at low flowrates typical for secondary metallurgy (0·1 m s ^-1), only droplets <50 μm will be entrained, BOF (basic oxygen furnace) typical flowrates (20-50 m s ^-1) will cause particles up to 500 μm to be carried into the dust removal systems. Higher surface tensions resulted in increased droplet ejection, while higher viscosities led to a decreasing quantity of ejected melt. Slag layers led to a decrease in the ejection of steel droplets and to an increase in ejected slag but they did not completely stop steel ejection, because gas bubbles appear to entrain steel drops when they rise through the slag layer. Bubble bursting in a pure slag system caused large but few slag droplets due to the high viscosity of the slag as compared to the steel melt.     

Thermodynamics of the oxygen solutions in iron-nickel melts

The oxygen solutions in Fe-Ni melts containing chromium, manganese, vanadium, carbon, silicon, titanium, or aluminum are studied thermodynamically. The equilibrium constants of the deoxidation of the melts by these elements are determined, and the activity coefficients for infinite dilution and the interaction parameters in alloys of various compositions are found. The oxygen solubilities in the alloys are calculated as a function of the nickel and deoxidizer contents. The deoxidizer contents at the minima in the oxygen solubility curves for the melts are determined, and the corresponding minimum oxygen concentrations are calculated. As the nickel content in the system increases, the deoxidizing capacities of chromium, manganese, and silicon are shown to increase substantially, and the deoxidizing capacity of carbon increases most strongly. As the nickel content in the melt increases, the deoxidizing capacities of vanadium and titanium first decrease insignificantly and then increase substantially. As the nickel content in the melt increases to 50%, the deoxidizing capacity of aluminum first decreases and then increases; in pure nickel, it is identical to that in pure iron.     

氧化钪-氯化-铝镁热还原法制备钪中间合金新工艺研究

本文介绍了利用Sc     

Study of the surface properties of nickel-based melts by the constrained drop method: I. Surface tension

The constrained drop method is used to study the surface tension σ of the following melts at 1773–1923 K and p _Ar = 0.1 MPa: nickel of various grades (with various oxygen contents), binary Ni-Al (Re) alloys, and a complex Ni-Re-(W, Mo, Co) alloy. The value of σ of liquid nickel is shown to decrease with increasing oxygen content in it. The additions of aluminum (6%) and rhenium (3–7%) to nickel in binary alloys weakly change its surface tension. Alloying elements (W, Mo, Co) in Ni-Re-(W, Mo, Co) alloys insignificantly affect σ of their melts.     

Volume and Surface Properties of a Bismuth-Containing Separating Nickel Melt

The influence of a bismuth impurity on the properties of solid and liquid alloys in the concentration range that obeys Henry’s law is considered. The structural and physicochemical properties, specifically, the density and the surface tension, of real melts are studied on relatively pure metals. The changes in the properties of the melts are estimated from changes in the temperature dependences of the density and the surface tension upon heating and cooling and in the concentration dependences of these parameters at a constant temperature. These dependences exhibit a correlation between the volume and surface properties of the melts: the density and the surface tension increase or decrease simultaneously. The introduction of bismuth in the nickel melt is accompanied by the appearance of a relatively strong compression effect (i.e., a decrease in the melt volume). At a certain bismuth content in the melt, the compression effect weakens because of the appearance of an excess phase or its associates and melt separation.     

Density and surface tension of a concentrated lead melt in nickel

The influence of a lead impurity on the properties of metallic melts in the composition range that obeys Henry’s law is studied. The formation of the structural and physicochemical properties of real concentrated melts can be traced from changes in the temperature and concentration dependences of structure-sensitive properties, namely, density and surface tension. The surface properties of a solution depend on its volume properties and differ from them in enhancement effect. The lead saturation of the nickel melt is found to be accompanied by a compression effect (decrease in the melt volume), which is enhanced to a certain lead concentration. As this concentration is exceeded, the compression effect weakens because of volume separation and the appearance of an excess lead phase. As the lead content in a nickel base increases, the surface tension decreases, a second phase forms, and the melt undergoes separation.     

Applicability of butler’s equation in interpreting the thermodynamic behavior of surfaces and adsorption in Fe-S-O melts

Expressions for various second-order derivatives of surface tension with respect to composition at infinite dilution in terms of the interaction parameters of the surface and those of the bulk phases of dilute ternary melts have been presented. A method of deducing the parameters, which consists of repeated differentiation of Butler’s equations with subsequent application of the appropriate boundary conditions, has been developed. The present investigation calculates the surface tension and adsorption functions of the Fe-S-O melts at 1873 and 1923 K using the modified form of Butler’s equations and the derived values for the surface interaction parameters of the system. The calculated values are found to be in good agreement with those of the experimental data of the system. The present analysis indicates that the energetics of the surface phase are considerably different from those of the bulk phase. The present research investigates a critical compositional range beyond which the surface tension increases with temperature. The observed increase in adsorption of sulfur with consequent desorption of oxygen as a function of temperature above the critical compositional range has been ascribed to the increase of activity ratios of oxygen to sulfur in the surface relative to those in the bulk phase of the system.