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 .     

熔盐电精炼硅制备多晶硅的NaF-KCl熔盐净化及净化作用

采用预电解净化方法,研究了温度、电压、时间等对NaF-KC1熔盐净化的影响,结果发现温度800℃,预电解电压2.5V,预电解时间4h为熔盐净化合适条件.采用四电极法测量了800℃,净化前后NaF-KCl混合熔盐的电导率,计算了活化能,结果发现熔盐净化后电导率提高.进行了恒电位电精炼法制备多晶硅,采用XRD,SEM,EDS和ICP-ms对熔盐净化前后获得的多晶硅进行了表征,发现熔盐净化使多晶硅产品纯度明显改善,纯度达到99.99％.     

LiF-KCl-KBr系和KF-NaCl-NaBr系熔盐相图研究

用目测变温法和X-射线相分析研究了LiF-KCl-KBr系和KF-NaCl-NaBr系熔盐相图.并在此基础上估算了熔盐溶液的正、负偏差情况,结合熔盐溶液的MonteCarlo法研究结果进行了讨论.     

超增溶胶团自组装体原位合成纳米微粒

提出了一种原位合成纳米粒子的方法, 熔盐/超增溶胶团自组装法. 发现了熔盐的超增溶现象, 并提出了超增溶自组装机理. 在5%VB值小于1的表面活性剂和烃类组分形成连续相的反相胶束中超增溶自组装95%的熔盐, 熔盐形成多面体立方相, 并与表面活性剂的亲水基以静电吸附方式组装. 以超增溶胶团为纳米反应器, 熔盐与沉淀剂在胶团中进行原位合成. 该原位合成法具有不用水为溶剂、最大的沉淀量、粒子呈纳米级粒子和粒径分布范围窄等特点.     

基于机器学习势函数的熔盐体系分子动力学研究进展

熔盐是一类具有重要应用价值的熔融态材料,然而其微观结构与宏观性质之间的关系尚未完全探明,因此开展针对熔盐体系的分子动力学研究具有重要意义.针对高温熔盐体系的分子动力学研究以往主要依赖于传统分子动力学中力场的开发和第一性原理分子动力学的发展.近年来得益于机器学习和神经网络的加速发展,针对熔盐体系的机器学习势函数的开发工作取得了显著进展,其在探索熔盐配位化学和预测物理性质方面表现优异.本文首先梳理了熔盐领域内常用的分子动力学方法,重点介绍了机器学习势函数的发展现状;然后总结了机器学习势函数在熔盐研究方面的应用进展;最后展望了机器学习势函数在该领域的应用前景,并对可能存在的问题给出了建议.     

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.     

制备方法对LaFeO3纳米粉体的影响

分别采用熔盐法和溶液燃烧法合成了钙钛矿型LaFeO3纳米粉体,系统研究了两种制备方法对粉体相结构、形貌的影响,用XRD、SEM和TG/DSC对纳米粉体进行了表征.结果表明:熔盐体系、煅烧温度、燃料类型和燃料/氧化剂的摩尔比对合成LaFeO3有重要的影响.450-750℃的熔盐NaNO2体系及650-800℃的熔盐NaN...     

熔盐电解法制备稀土合金研究进展

熔盐电解法制备稀土合金具有成本低、成份均匀且容易控制、质量较好、易实现连续化生产等优势.本文结合稀土合金在金属结构材料、磁性材料和贮氢材料中的应用,在介绍熔盐电解的知识进展的基础上,综述了稀土分别与镁、铝、铁、钴、镍、铜等组成的合金的熔盐电解制备研究进展,并对以后的研究工作进行展望.     

熔盐技术的应用

本文阐述熔盐技术在工业及科技领域中的应用。着重介绍熔盐电解冶金、表面处理，制取半导体、超导体单晶、氟化锆系玻璃，熔盐燃料电池、锂电池，原子能体系中应用的熔盐技术，以及熔盐氟化、氯化等实例和发展动向。     

熔盐电解法制备纳米碳管及纳米线

以LiCl、LiCl+SnCl2等为熔盐电解质,采用电解石墨的方法制备了纳米碳管和纳米线,并运用TEM、XRD、EDS等分析手段对产物的形貌和结构进行了表征.结果表明,熔盐成分对电解产物的形态和性质有显著影响.在LiCl熔盐中可得到直径为75～100nm的纳米碳管;在LiCl+1.0%SnCl2熔盐中可生成β-Sn填充的纳米碳管.XRD测试表明,电解制备的β-Sn纳米线经氧化处理后在碳管内可转变为SnO2,其晶体结构为四方晶系,直径为20～50 nm.电解过程中Li+在石墨阴极上反应生成的LiC6化合物对纳米碳结构的形成具有重要作用.     

The Coordination Chemistry of f-Block Elements in Molten Salts

The coordination chemistry of f-block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f-block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f-block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties.     

Inorganic Molten Salts as Solvents for Cellulose

Inorganic molten salts can be used as efficient solvents for cellulose in a wide range of degrees of polymerization. Furthermore, molten salts can be applied as reaction medium for the derivatization of cellulose. For both dissolution and derivatization of cellulose, knowledge of the solution state as well as information about chemical interactions with the solvent system is essential. Using the melts of LiClO₄·3H₂O, NaSCN/KSCN/LiSCN·2H₂O and LiCl/ZnCl₂/H₂O as cellulose solvents, factors which determine the dissolving ability will be discussed. Besides the specific structure of the molten salt hydrate, the cation and the water content of the melt are the most important factors for the dissolving capability of a molten salt hydrate system. FT-Raman spectroscopy, ⁷Li and ¹³C NMR spectroscopy were applied to describe solvent–cellulose interactions and the state of cellulose dissolved in the molten salts. Using Raman and solid state NMR spectroscopy it was proved that cellulose is amorphous in the frozen solvent system. The application of inorganic molten salts as a medium for cellulose functionalization is demonstrated for cellulose carboxymethylation and acetylation.     

熔盐电化学创新研究——武汉大学电化学研究中心熔盐电化学研究工作简介

简要介绍近3年武汉大学电化学研究中心在熔盐电化学方面的若干研究进展:1)熔盐电解固态化合物制备单质硅及其合金以及无机功能材料;2)适于高温熔盐的全密封长寿命Ag/AgCl参比电极和可负载微量粉末的金属腔(坑)工作电极新技术;3)“三相界线电化学”新概念以及描述三相界线在薄层固态化合物电解还原过程中扩展变化的薄层模型.     

锕系元素在熔盐体系中的电化学及萃取特性研究进展

熔融盐是一类非水溶剂,分为高温熔盐、室温熔盐和低温熔盐。 作为反应介质和电解介质,因其优良性能,可以溶解很多难溶于水的活泼金属。 近年来,该领域的研究热点是将熔盐作为干法后处理的电解质分离和回收锕系元素。 本文综述了锕系元素在高温熔盐中的电化学行为、热力学等物理特性,介绍了近几年室温离子液体(RTILs)的研究进展及锕系元素在RTILs中萃取特性的最新研究成果,展望了熔盐体系未来的研究方向。     

新型室温熔盐二(三氟甲基磺酸酰)亚胺锂-乙酰胺/乙烯脲体系的研究

制备了二(三氟甲基磺酸酰)亚胺锂[LiN(SO₂CF₃)₂,LiTFSI]与乙酰胺和乙烯脲形成的新型室温熔盐,分析了其热学和电化学性能.LiTFSI-乙酰胺体系的热学稳定性好,低共熔温度为-62.18℃.电化学测试表明,LiTFSI-乙酰胺体系的电导率较高,n(LiTFSI):n(Acetamide)=1:6.5样品的室温电导率为1.08×10^-3S/cm,60℃时电导率为5.35×10^-3S/cm;摩尔比为1:4.0样品的电化学稳定电位窗为3V左右.     

新型高温、长寿命氯化物熔盐参比电极的制备与研究

本文介绍一种全固态离子导电玻璃盐桥制备方法,并以此设计新型的Ag/AgCl高温参比电极.该电极制作简单, 具有电位稳定,重现性好,使用寿命长,不污染研究体系等特点.可在多种氯化物熔盐体系中反复使用,适用温度范围 400~900℃.     

Electrochemical synthesis of ammonia in molten salts

Ammonia is important feedstock for both fertilizer production and carbon-free liquid fuel.Many techniques for ammonia formation have been developed,hoping to replace the industrial energy-intensive Haber-Bosch route.Electrochemical synthesis of ammonia in molten salts is one promising alternative method due to the strong solubility of N~(3-) ions,a wide potential window of molten salt electrolytes and tunable electrode reactions.Generally,electrochemical synthesis of ammonia in molten salts begins with the electro-cleavage of N_2/hydrogen sources on electrode surfaces,followed by diffusion of N~(3-)/H~+-containing ions towards each other for NH_3 formation.Therefore,the hydrogen sources and molten salt composition will greatly affect the reactions on electrodes and ions diffusion in electrolytes,being critical factors determining the faradaic efficiency and formation rate for ammonia synthesis.This report summarizes the selection criteria for hydrogen sources,the reaction characteristics in various molten salt systems,and the preliminary explorations on the scaling-up synthesis of ammonia in molten salt.The formation rate and faradaic efficiency for ammonia synthesis are discussed in detail based on different hydrogen sources,various molten salt systems,changed electrolysis conditions as well as diverse catalysts.Electrochemical synthesis of ammonia might be further enhanced by optimizing the molten salt composition,using electrocatalysts with well-defined composition and microstructure,and innovation of novel reaction mechanism.     

Determination of the Thermal Conductivities of Several Molten Alkali Halides by Means of a Sheathed Hot-Wire Technique

Abstract

A modification of the transient hot-wire method has been used for the measurement of the thermal conductivities of electrically conducting fluids. Although the method is probably not as accurate as the concentric-cylinder method in similar applications, it avoids radiation problems which hamper studies with many molten salts. We report here hot-wire measurements of the thermal conductivity values for molten alkali halides. These results indicate that, as was noted by White and Davis⁽¹⁾ for alkali nitrates, the temperature dependence of the thermal conductivities for those substances is positive. Such a temperature dependence seems to be an intrinsic property of ionic liquids and is not associated with the internal degrees of freedom of the ions constituting a molten salt.     

Evaluating physical properties of molten salt reactor fluoride mixtures

In the last years, interest in the use of high-temperature molten fluoride salts as fluid fuels and coolants in nuclear power systems has been increasing. The comprehensive information on the properties of molten fuel and coolant salts is necessary for development of new designs. Experimental data on physical properties of some prospective molten salt mixtures of Li, Na, Be, Zr fluorides containing fertile and fissile materials as well as soluble fission products are unknown. At the first stage of the conceptual development estimation of the required properties from the known experimental data can be useful for selection of suitable molten salt compositions. In this paper the approaches for estimation of the physicochemical properties such as density (ρ), dynamic viscosity (η), isobaric heat capacity (c_p), and thermal conductivity (λ) for molten salt fluoride mixtures are proposed. The calculation algorithm was based on the additivity principle for the properties (P_x) of multi-component molten salt mixtures, which can be found from the relationship P_x = ΣN_iP_i. Here N_i and P_i denote mole fraction and corresponding property of individual molten salts or their binary mixtures as constituents of the more complex systems. The empirical expressions connecting the property with molar volume and molecular mass of selected fluoride compositions are also derived and tested. Estimated values are compared with each other and available experimental data.