稀土金属在氯化物熔体中溶解损失的研究

目前,工业上广泛采用氯化物体系熔盐电解法制取稀土金属,但电流效率低,一般只有40％左右。稀土金属在熔盐中的溶解损失是电流效率低的重要原因之一,关于这方面的研究虽有些报道,但多限于单一稀土金属在自身熔盐中的溶解。在文献的基础上,我们进一步研究了混合稀土金属(RE)在RECl_3-KCl熔体中的溶解损失及LiCl、NaCl、     

氯化物熔盐体系中铀的化学种态研究进展

乏燃料后处理是未来先进核燃料循环体系的中心环节, 基于高温熔盐电解的干法后处理技术具有一定优势. 该技术通常在高温氯化物熔盐体系中进行, 采用电化学技术回收锕系元素, 并实现其与镧系元素的电解分离. 其中铀的分离回收是研究的重点之一. 为更好实现铀在熔盐中的分离与回收, 需要深入理解铀的电化学性质与其在熔盐中的配位化学性质的联系. 因此, 开展铀在氯盐体系中的化学种态研究至关重要. 本Review对国际上氯化物熔盐体系中针对铀化学种态的研究进展进行了总结归纳和提炼, 并对未来锕系元素在高温熔盐介质中的化学种态研究进行了展望.     

熔盐电化学低碳冶金新技术研究

本文重点介绍“氯化物熔盐体系电解还原固态氧化物冶金过程的高效化”和“氯化物熔盐体系电裂解硫化物及熔融碳酸盐与熔融氧化物体系电分解氧化物无温室气体排放冶金”的研究进展,结合武汉大学的部分代表性工作阐述了相关技术的原理,以期揭示熔盐电解技术在节能减排和资源高效利用上的优势及其发展前景,为发展短流程、低碳高效的电化学冶金工业提供理论和技术支持。     

Mo在NaCl·KCl熔盐体系中腐蚀的电化学研究

本文包括四个方面的工作:(1)通过热力学数据,计算了有关电极反应的电极电位,制作了NaCl-Mo,KCl-Mo体系的E-PO~(-2)图。(2)提出了一种熔盐腐蚀的电化学测量方法——弱极化曲线拟合。(3)研究了Mo在NaCl·KCl熔盐体系中的腐蚀行为。(4)研究了Mo在NaCl·KCl熔盐体系中的钝化形为。     

RECl_3-KCl体系电解稀土金属电流效率问题的讨论

本文综述了稀土熔盐电解的工艺技术现状和问题,分析了造成RECl_3-KCl体系电解稀土金属时电流效率低的原因,其中包括电解工艺条件、原料中的杂质、变价稀土元素和稀土金属溶解等,并对提高稀土熔盐电解制取稀土金属电流效率的途径进行了讨论。     

稀土元素氯化物水合物的脱水过程与水解反应的机理

熔盐电解法制取稀土金属时,所用的无水稀土氯化物是由相应的水合物在减压下加热脱水而制得的。弄清楚脱水过程的机理,避免氯化物水解生成氯氧化物,以期制得纯净的无水氯化稀土,这对于提高电解时的电流效率,降低金属产品中的含氧量,是很重要的。为此我们研究了全部稀土元素氯化物水合物的脱水过程和气相水解反应的机理,确定了一些中间水合     

较低温度下熔盐电解RE-Al合金的物化性质研究

本文对RE-Al合金体系相图的富铝部分以及混合轻稀土氯化物与等摩尔氯化钾、氯化钠所组成的熔盐混合物的物化性质与电化学性质进行了研究。     

LnCl_3-KCl-NaCl体系粘度的研究

目前关于熔盐体系粘度的研究报道甚少,这是由于熔体粘度的测量,技术上难度较大,尤其是当温度超过773K以后。稀土金属及其合金的生产,国内外多采用KCl-LnCl_3熔盐电解法。近年来,科学工作者系统地研究了LnCl_3-KCl-NaCl(Ln=La、Ce、Pr、Nd、Sm)熔盐体系。这一体系在生产中可以降低电解温度,减少材料腐蚀,降低电解质的挥发损失。因此研究该体系的物理化学性质,将有重要的意义。本工作是通过对熔体粘度的研究,为稀土熔盐化学和生产实践提供基础数据。     

Cr2O3粉末在CaCl2熔盐中直接电化学还原的金属通腔电极研究

应用金属通腔电极研究Cr2O3粉末于熔盐中的电化学行为,验证了900℃下Cr2O3粉末在含镁量<0.005%氯化钙熔盐中的分步还原机理,估算其电化学还原动力学参数;并由扫描电镜观察产物形貌,分析电解电位和时间对金属颗粒尺寸的影响.     

熔盐电化学的新进展

本文主要介绍熔盐体系、熔盐电池、熔盐电沉积金属以及合金、电合成化合物材料等方面的新进展 ,预期熔盐电化学在能源、环境保护和资源利用等领域中的应用 .     

Heavy Metal Concentrations in Water,Sediment and Fish from Izmit Bay,Turkey

Abstract

Mercury, cadmium and lead levels in water, sediment and fish samples from Izmit Bay, Turkey have been determined. Sampling and analysis methods are described. Variations of heavy metal concentrations from different sampling stations are discussed. Results indicate that the levels of mercury and cadmium were highest in the vicinity of a chlor-alkali plant while the highest concentration of lead was near a metallic pipe factory. The amounts of heavy metals found in the shoreline sediment samples were similar to those found in fish species from the bay.     

Complexation of common metal cations by cyanins: Binding affinity and molecular structure

The ability of diverse metal cations to form complexes with cyanin has been investigated by means of Density Functional Theory (DFT) and the Quantum Theory of Atoms in Molecules (QTAIM). The strongest preference is shown by trivalent metals which exceed that of Mg(II), indicating that ion replacement processes are suitable detoxification mechanisms for plants. Molecular structure analysis indicates that the larger the metal affinity of Cy⁻ the longer the C2-C1’ bond length and smaller ρ_b value. This is understood as upon metal complexation the Cy⁻ ligand molecular structure is more compatible with a dienolate-like structure rather than the 4′-keto-quinoidal-like structure. The weight of the former increases as stronger the binding. QTAIM charges indicate that the stronger the binding energy the larger the charge transfer from Cy⁻ to the metal, reducing its positive charge below the values indicated by the corresponding Lewis structure.     

Spectral and thermal studies on new hydrazinium metal sulfite dihydrates

Some new hydrazinium transition metal sulfite dihydrate complexes of the formula (N₂H₅)₂M(SO₃)₂(H₂O)₂ where M=Fe, Co, Ni, Cu and Zn have been prepared and characterized by hydrazine and metal analyses, magnetic studies, electronic and infrared spectra and thermal analysis. The magnetic studies coupled with electronic spectra of iron, cobalt, nickel and copper complexes indicate their high spin octahedral nature. However the zinc complex is diamagnetic and show only the charge transfer transition. The infrared spectra shows that both the hydrazinium ions are coordinated to the metal ions, the sulfite ions are present as bidentate ligand. The simultaneous TG-DTA of these complexes were investigated in air and nitrogen atmospheres. In air, cobalt, nickel and zinc complexes give respective metal sulfate as the final residue while iron and copper complexes give the mixture of respective metal oxide and sulfate as the decomposition product. In nitrogen atmosphere respective metal sulfites are formed as the end residue.     

SmartMetals: a new method for metal identification based on fuzzy logic

This paper presents a method of searching, identifying and cross‐referencing metal alloys based on their chemical composition and/or mechanical properties, typically obtained by analysis and tests. The method uses a general pattern similar to the approach of a human expert, and relies on a classification of metals based on metallurgical expertise and fuzzy logic for identifying metals and comparing their chemical and mechanical properties. The algorithm has been tested and deployed in real applications for fast metal identification and finding of unknown equivalents, by the leading companies in the field. The same principles can also be used in other domains for similar problems, such as organic and inorganic materials identification and generic drugs comparison. Copyright © 2009 John Wiley & Sons, Ltd.     

Dynamic PdII/CuI Multimetallic Assemblies as Molecular Models to Study Metal–Metal Cooperation in Sonogashira Coupling

Cooperation between two different metals plays a crucial role in many synergistic catalytic reactions, such as the Sonogashira C−C cross-coupling reaction, where an interaction between the Pd and Cu centers is proposed in the transmetalation step. Although several heterobimetallic Pd/Cu complexes were proposed as structural models of the active species in Sonogashira coupling, the detailed understanding of the metal–metal cooperation in transmetalation is still lacking in current systems. In this work, we report a stepwise and systematic approach to building heteromultimetallic Pd/Cu assemblies as a tool to study metal–metal cooperativity. We obtained fully characterized Pd/Cu multimetallic assemblies that show reactivity in alkyne activation, formation of catalytically relevant aryl/acetylide species, and C−C elimination, serving as functional models for Sonogashira reaction intermediates. The combined experimental and DFT studies highlight the importance of ligand-controlled coordination geometry, metal–metal distances and dynamics of the multimetallic assembly for transmetalation step.     

Methane conversion by various metal, metal oxide and metal carbide catalysts

The progress in the field of methane conversion into higher hydrocarbons including aromatics and oxygenated compounds in the recent five years will be reviewed shortly, together with a new type of the methane conversion reaction with carbon monoxide at lower temperatures (600–700 K) by supported group VIII metal catalysts. Benzene was formed selectively among hydrocarbons in the CH₄–CO reaction over silica-supported Rh, Ru, Pd and Os catalysts under atmospheric pressure. Both CH₄ and CO were required for benzene formation, and only ethane and ethylene were formed besides benzene. The amount of C₃–C₅ hydrocarbons was negligible, which suggests that a completely different mechanism from the CO–H₂ reaction may be operating over these catalysts despite of the similarity in the reaction conditions with the CO–H₂ reaction. The mechanism of benzene formation was studied deeply by means of kinetical investigation as well as infrared spectroscopy and isotopic tracer method in connection with that of CO hydrogenation.     

New hydrazinium lanthanide sulphite hydrates

Some new hydrazinium lanthanide sulphite hydrates of the formula N₂H₅Ln(SO₃)₂(H₂O)₂ where Ln=La, Pr, Nd and Sm and N₂H₅Ce(SO₃)₂ have been prepared and characterized by chemical analyses, magnetic studies and electronic and infrared spectroscopy. Thermal degradation of these complexes has been investigated by simultaneous TG-DTA techniques. These complexes decompose in air after dehydration to give the respective lanthanide sulphate as the final residue. However, cerium complex gives a mixture of cerium sulphate and ceric oxide as the end products. Cerium and neodymium complexes have also been subjected to thermal degradation in nitrogen atmosphere and the dehydration of neodymium complex was observed at a higher temperature than in air. The anhydrous neodymium and cerium complexes decompose in one step to give the respective sulphate in nitrogen atmosphere.     

Theoretical study of the first transition row oxides and sulfides

Summary The first transition row oxides and sulfides are studied using several different levels of theory. The calculations show the bonding mechanism in the sulfides and oxides to be very similar. For the oxides, accurate experimental data allow the theoretical methods to be calibrated. The same level of theory is used to study the sulfides where there is far less experimental information. For ScO through MnO and CuO the coupled cluster singles and doubles technique including a perturbational estimate of the connected triple excitations [CCSD(T)] yields spectroscopic constants (_e, _e, andD ₀) in good agreement with experiment. The triple excitations are found to be very important in achieving this accuracy. For FeO to NiO, the self-consistent-field (SCF) approach yields orbitals that are localized on the metal or oxygen. This appears to cause problems for the single reference techniques; this is discussed in detail for NiO. The complete-active-space SCF/internally contracted averaged coupled pair functional approach (CASSCF/ICACPF) works well for FeO to NiO. The calculation of accurate dipole moments is found to be very difficult.     

热电池正极材料的研究进展

热电池是一种热激活贮备式电池,由于其优良的贮存稳定性、放电可靠性等特点,广泛应用于多种军用武器的内部电源。为了满足当前不同军用武器装备的需求,热电池的发展趋于在提高电化学性能的同时实现小型化、微型化。热电池电化学性能的提高主要取决于正极材料的发展,目前对现有正极材料的优化改性和新型正极材料的开发是提高热电池性能的主要方法。本文从合成和改性方法的角度综述了近年来硫化物、氯化物、氟化物热电池正极材料的研究进展,并对其材料特性和放电性能进行了综合评估。最后,基于热电池特殊的应用场景,从热稳定性、放电电压、电导率等方面对热电池正极材料未来的发展方向进行了总结与展望。     

A novel method for making ultra-fine metal fibers and particles

A novel method based on plastic processing and equipment for preparing ultra-fine metal fibers and particles is reported. With this new method, metal fibers and particles can both be produced on the same equipment and the surfaces of the fibers and particles can be protected from oxidation by the polymers or solvents during the preparation process. Metal-alloy powders with lower melt point were filled into polymer by an extruder, followed by a die-drawing process at a temperature lower than the melt temperature of the metal alloy. Metal fibers or particles were obtained after the polymer matrix was washed away. Metal alloy fibers can be obtained when a polymer that strongly interacts with metal alloy, such as a special polyvinyl alcohol with a low alcoholysis degree, is used as the polymer matrix. Metal-alloy particles can be obtained when a polymer with weak interaction with metal alloy, such as polyethylene (PE), is used as the polymer matrix. Based on the principle of this new method, it is possible to produce finer or even nano-sized metal fibers and particles with higher melting points.