Electrochemical synthesis of titanium diboride in the dispersed state from halide melts

A study is made of the electrolytic deposition of titanium boride powders from halide melts. The conditions required for the deposition of different phases are determined. On the whole, the synthesis process is controlled by interrelated factors: electrolyte composition, current density, and the temperature and duration of the electrolysis operation.     

Electrochemical Removal of AlCl3 from LiCl-KCl Melts

In order to remove impurity AlCl₃ from LiCl-KCl melts before Li electrolysis, the Al³⁺ reduction potential on a tungsten electrode and the relation between Al³⁺ reduction peak current and AlCl₃ concentration in LiCl-KCl-AlCl₃ melts were determined by cyclic voltammetry (CV). Constant potential electrolysis at –1.6 V vs Cl₂/Cl^– on both solid Fe and liquid Zn cathodes was performed to remove AlCl₃ impurity from the LiCl-KCl-AlCl₃ melts. The removal rate of Al³⁺ from the melts was analyzed by both electrochemical methods and inductively coupled plasma–atomic emission spectrometry (ICP-AES) analysis. The results showed that 96.11 wt pct of Al were removed on a Fe cathode and 99.90 wt pct on a Zn cathode through 10 hours electrolysis, respectively. While stirring the melts by argon gas, 99.21 wt pct of Al³⁺ was separated from the melts by 4 hours of electrolysis at 723 K (450 °C), which effectively expedited the Al³⁺ electrochemical reduction rate and shortened the electrolysis time.     

Preparing different phases of Mg-Li-Sm alloys by molten salt electrolysis in LiCl-KCl-MgCl2-SmCl3 melts

Different phases of Mg-Li-Sm alloys were prepared by galvanostatic electrolysis in LiCl-KCl-MgCl2-SmCl3 melts at 670 °C.The electrolysis process and phase control of Mg-Li-Sm alloys were studied.The microstructures of α,α+β,β phases of Mg-Li-Sm alloys were characterized by X-ray diffraction(XRD) and optical microscope(OM).Analysis of scanning electron microscopy(SEM) and EDS mapping analysis showed that Mg distributed homogeneously in Mg-Li-Sm alloys.EDS result showed that the distribution of Sm was more at...     

二氧化硫膜电解制备硫磺机理与应用研究

研究了利用316L不锈钢做阴极时,二氧化硫电化学还原制备硫磺过程的机理和影响因素。利用循环伏安法、计时电量法研究了二氧化硫在316L不锈钢电极上的还原机理,提出二氧化硫经历了4个电子4个质子的还原过程。通过离子膜反应器分别考察了电流密度、阴极液酸浓度对二氧化硫电化学还原制备硫磺过程的影响。当二氧化硫浓度5 g/L、硫酸浓度0.5 mol/L、电流密度126.98 A/m^2、电解时间3 h时,二氧化硫转化为硫磺的转化率为73.42%,空时产量0.64 kg/(m^3·h),单位能耗9.64 kWh/kg。     

Electrocapillarity in the aluminum reduction cell

The effect of the current density on the interfacial tension between aluminum and cryolite containing melts was measured based on the sessile drop method and an X-ray radiographic technique. The experiments were carried out under constant current densities in graphite crucibles with BN lining. When the aluminum drop was the cathode, the interfacial tension was almost independent of the current density. During electrolysis, the interfacial tension increased with decreasing NaF/AlF₃ ratio in a similar manner to that observed when no electrolysis was performed. The interfacial tension between aluminum and an electrolyte containing between 5 to 10 wt pct A1F₃, 5 wt pct CaF₂, and 5 wt pct A1₂O₃ is 690 ± 60 mN/m for cathodic current densities between 0.1 and 0.6 A/cm₂. Interruption of electrolysis caused an instantaneous decrease in the interfacial tension followed by a slow increase with time. This sudden drop together with a decrease in interfacial tension with reversal of cell polarity indicate that the metallic side of the interface has an excess positive charge. The interface was enriched with NaF during electrolysis as indicated by the slow recovery of the interfacial tension after current interruption. T. UTIGARD, formerly Graduate Student, is now Research Engineer, Alusuisse, CH-3965 Chippis, Switzerland     

The current efficiency of barium during the electrolysis of chloride and oxide-chloride melts with liquid cadmium and zinc cathodes

The influence of the current density (i) and the duration of electrolysis on the current efficiency of barium (CE_Ba) in the alloy with zinc and cadmium has been investigated during the electrolysis of melts (K-Na)Cl_eq-26 mol % BaCl₂ containing up to 0.4 mol % BaO dissolved at T = 973 K. It is determined that the dependence of CE_Ba on the current density passes through a maximum: at i = 0.18 A/cm², the value of CE Ba in the alloy with Zn is 86%; with cadmium it is 74%. An increase in the electrolysis time and the presence of barium oxide in the melt decrease the current efficiency of barium in melts.     

Electrochemical study on preparation of Mg-Li-Yb alloys in LiCl-KCl-KF-MgCl2-Yb2O3 melts

This paper presented a novel study on electrochemical codeposition of Mg-Li-Yb alloys in LiCl-KCl-KF-MgCl2-Yb2O3 melts on molybdenum. The factors of the current efficiency were investigated. Electrolysis temperature had great influence on current efficiency; the highest current efficiency was obtained when electrolysis temperature was about 660 oC. The content of Li in Mg-Li-Yb alloys increased with the high current densities. The optimal electrolytic temperature and cathodic current density were around 660 oC and 9.3 A/cm2, respectively. The chemical content, phases, morphology of the alloys and the distribution of the elements were analyzed by X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry, respectively. The intermetallic of Mg-Yb was mainly distributed in the grain boundary of the alloys, presented as reticulated structures, and refined the grains. The lithium and ytterbium contents in Mg-Li-Yb al-loys could be controlled by changing the concentration of MgCl2 and Yb2O3 and the electrolysis conditions.     

氯化钕熔盐电解制取钕铁中间合金

本文简要评述了制取Nd及富Nd合金的方法,分析讨论了用消耗性Fe阴极电解NdCl_3-KCl熔盐制取Nd-Fe合金的原理及选择技术条件的原则。实验室电解试验获得了含Fe仅13％的优质Nd-Fe合金,69％的合金电流效率(按纯Nd计为60％),Nd直收率大于90％。试验结果表明,本法是技术上合理、经济上有利的制取Nd-Fe合金的简便有效方法。     

Corrosion of Zinc Ferrite Based Inert Anodes in AlF3-NaF-Al2O3 Melts Under Conditions of Anodic Polarization

ZnFe2O4-based inert anodes were made to conduct the aluminum electrolysis tests. The corrosion behaviors of the inert anodes were examined and discussed. Experiment results prove that: (1) ZnFe2O4-based inert anodes are good corrosion resistant to AlF3-NaF-Al2O3 melts under the conditions of anodic polarization; (2) High anodic current density(＞1.5 A·cm-2), high alumina concentration and low ratio of NaF/AlF3 in the molten salts will be the most important conditions for using inert anode.     

氟化物体系熔盐电解制备YNi合金

以Y2O3为电解原料,以金属镍棒为自耗阴极、石墨板为阳极,在常规的石墨电解槽中采用氟化物体系熔盐电解法制备了YNi合金.研究了电解时间、电解温度、电解质组成、阴极电流密度等主要技术参数对电解过程的影响,并对所制备的钇镍合金进行了表征.结果表明,熔盐电解制备钇镍合金的较优工艺条件为:电解温度1000℃,电解质YF3与Li...     

Electrochemical Production of Tungsten Powders from Tungsten Hardmetal Waste

Hardmetals intended to perform in harsh operating conditions are developed with the use of metallic powders, in particular, tungsten powders. The growing consumption of tungsten in industry necessitates the improvement of techniques employed to produce it from industrial waste. The objective of this research effort was to reduce metallic tungsten (as a powder) from chloride and chloride–fluoride melts and determine the factors influencing its particle size. The starting material was tungsten oxide (WO3) produced electrochemically from processed raw material (VK-6 tungsten carbide pseudoalloy). The melts were KCl–NaCl–CsBr and NaCl–KCl–CsBr–Na3WO3F3 eutectic mixtures. When the melt with a high WO2F42− content was subjected to electrolysis, tungsten precipitated as a superfine powder. The precipitate morphology showed that the tungsten particle size was dependent on electrolysis conditions. A relatively inexpensive and effective method of producing tungsten powders was developed upon the research.     

Selection of the Optimum Electrolysis Bath Composition for the Synthesis of Holmium–Iron Triad Metal Intermetallics

The results of high-temperature electrochemical synthesis of holmium–iron triad metal intermetallics in chloride melts are presented. The influence of the current density, the composition of an electrolysis bath, and the synthesis time on the electrolysis processes and the composition of the end product is studied. The electrolysis of the molten KCl–NaCl mixture containing 0.5–2.5 mol % holmium trichloride and 0.1–2.5 mol % nickel (cobalt) dichloride at a current density of 0.5–2.0 A/cm², a temperature of 973–1073 K, and an electrolysis time of 30–90 min is shown to cause the formation of a cathode deposit in the form of a “metal–salt pear” on a tungsten electrode. This pear consists of a mixture of metallic nickel (cobalt) and HoNi, HoNi₅, and HoNi₃ (HoCo₂, HoCo₃, HoCo₅, Ho₂Co₁₇) intermetallics. The intermetallic compound content in the cathode deposit is found to increase at a constant current density (1.2 A/cm²) and when the holmium chloride content in a melt or the ratio of the holmium chloride concentration to the nickel (cobalt) chloride concentration increases. Only a mixture of holmium–nickel (cobalt) intermetallics can exist in the cathode deposit if the electrolysis bath composition and the electrolysis parameters are controlled. The electrochemical synthesis of holmium–iron intermetallics was performed under galvanostatic conditions in molten KCl–NaCl–HoCl₃. Iron ions are introduced in a melt via the anodic dissolution of metallic iron. The results of X-ray diffraction analysis of the electrolysis products demonstrate the fundamental possibility of synthesizing holmium–iron intermetallics. The optimum conditions of electrosynthesis of holmium–iron triad metal intermetallics are determined.     

高电流密度银电解新工艺的研究与应用

在现有银电解工艺的基础上,借鉴贵溪冶炼厂高电流密度铜电解生产经验,通过试验研究,确定了高电流密度(700A/m2)电解条件下电解液最佳组分、净化工艺、循环控制模式、搅拌方式等关键技术,自行设计出适合高电流密度生产的银电解槽,开发出具有自主知识产权的高电流密度银电解新工艺,电流密度由原来的350A/m2提高至700A/m2。     

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。     

熔盐电解生产Al-Sr合金的新工艺及其加料周期

研究了以SrCO3为原料熔盐电解法生产Al-Sr合金新工艺,采用连续脉冲-示波器法测定电解过程的反电动势.结果发现:(1)延长电解时间,合金中锶的质量分数逐渐增加,最高可达18.54%;(2)增加电流密度,反电动势亦随之增加,而升高温度反电动势则有所降低;(3)在电解过程中,反电动势逐渐增加,但向熔体中加入SrCO3后,反电动势明显降低.因此确定在正常电解时是SrCO3在分解.以此规律制定了正常生产的加料周期和加料量,保证了生产的稳定进行.以SrCO3为原料生产Al-Sr合金,不但减少了环境污染,也降低了Al-Sr合金的生产成本.     

电解法制备高锰酸钾试验研究

电解法制备高锰酸钾一般采用间歇式和敞开式工艺。通过试验,考察试验装置和各非平衡态非线性耦合因素(离子浓度、阳极电流密度、电解温度、电解时间等)对制备高锰酸钾的影响。结果表明,在电解温度65.0～70.0℃、电流密度65.0～75.0A/m2、电解时间12h条件下,电流效率仍能维持在40.0%以上,而传统的间歇式电流效率最高仅35%。在封闭式反应装置中连续电解可达到清洁生产、节能减排的目地。     

5Cu/(10NiO-NiFe2O4)金属陶瓷惰性阳极钠钾混合电解质电解腐蚀研究

采用传统粉末冶金技术制备了铝电解用5Cu/(NiFe2O4-10NiO)金属陶瓷惰性阳极,对其在钠钾冰晶石混合冰晶石中进行电解腐蚀。研究结果表明,从微观来看,阳极存在腐蚀现象。电解过程的槽电压波动剧烈。Fe、Ni和Cu组元的平衡浓度分别为150×10-6、42×10-6及40×10-6,腐蚀速率比常规电解条件下的低。     

熔盐电解法制取钬铁合金试验研究

在氟化物熔盐体系中采用自耗阴极进行氧化物的熔盐电解,通过电解温度、阴极电流密度和熔盐配比等主要技术条件进行正交设计试验,对电解过程中电解质组成、电解温度、阴极电流密度和加料速度等因素对合金成分、稀土收率影响进行了试验研究。获得了较佳的工艺技术条件,为钬铁合金的规模化生产提供了切实可行的途径。     

Influence of crystallization conditions on the structure and modifying ability of Al–Sc alloys

The influence of the modes of thermal-and-temporal treatment and cooling rate of metallic alloys on crystallization regularities of Al–Sc alloys and their structure, properties, and modifying ability are established. Castings of Al–Sc alloy, which were prepared by the electrolysis of salt melts KF–NaF–AlF₃–Sc₂O₃ at 820–850°C, are used as the initial charge for casting. It is established that, by varying the magnitude of melt overheating and casting temperature, it is possible to vary the crystal shape, amount, and size in wide limits. The modifying action of cast and rapidly quenched master alloys, as well as the master alloy produced by electrolysis, is tested for Al–4.5% Cu alloy. The largest effect of milling the structure of the Al–4.5% Cu–0.4% Sc alloy is attained when using the rapidly quenched master alloy.     

Extraction of Scandium and Zirconium from Their Oxides during the Electrolysis of Oxide–Fluoride Melts

The main features of scandium and zirconium extraction from their oxides to aluminum during the aluminothermic and electrolytic preparation of Al–Sc and Al–Zr alloys and master alloys in the KF–AlF₃, NaF–AlF₃, and KF–NaF–AlF₃ oxide–fluoride melts with Sc₂O₃ and ZrO₂ additives are studied. The influence of the melt composition and temperature, the synthesis time, the contents of oxides Sc₂O₃ and ZrO₂ in the melts, the mechanical stirring of aluminum, and the cathodic current density on the contents of scandium and zirconium in aluminum and on their extraction from the oxides is determined. The average values of scandium and zirconium extraction are 20–75 and 40–100%, respectively, depending on the synthesis parameters. The electrolytic decomposition of the oxides in the KF–AlF₃, NaF–AlF₃, and KF–NaF–AlF₃ melts results in the enhancement of scandium and zirconium extraction to aluminum. The parameters of the preparation of Al–Sc and Al–Zr alloys and master alloys with the scandium content to 10 wt % and zirconium content to 15 wt % during the electrolysis of oxide–fluoride melts are chosen as a result of the results obtained.