Control for oriented growth of large size KCl crystals by the competition between spontaneous and induced nucleation/growth on a Langmuir-Blodgett film

Langmuir-Blodgett (LB) film of stearic acid was used as template to induce the nucleation and growth of KCl crystals when the KCl solution was cooled from 50 to 25 degrees C. When the LB film template was vertically dipped into the solution, only induced crystals with (1 1 0) orientation were formed. However, if the template was horizontally placed into solutions, both the induced nuclei at the solution/film interface and spontaneous nuclei formed in solution were simultaneously absorbed onto the LB film, and then grew further to form crystals. X-ray diffraction (XRD) patterns and optical microscopy images showed that the orientation and morphology of the crystals were controlled properly by changing the orientation and position of the LB films in the solutions.

Electrochemical behavior of Nd3+ and Ho3+ in LiCl-KCl eutectic melt

The electrochemical behavior of Nd3+ and Ho3+ ions on molybdenum electrode in the LiCl-KCl eutectic melts has been studied by cyclic voltammetry and open-circuit potentiometry. The results show that the reduction process of Nd3+ and Ho3+ ions on molybdenum electrode is one-step three electron reversible reaction. The diffusion coefficients of Nd3+ and Ho3+ ions are 1.13 x 10(-6) cm(2).s(-1)(450 degrees C) and 2.142 x 10(-5) cm(2).s(-1)(450 degrees C), respectively. The measured standard electrode potential of Ho3+/Ho is 2.987 V(vs. Cl/Cl-), being more negative than the theoretical one, the reason of which is also discussed.

KCl-LiCl共晶熔体中Nd~(3+)和Ho~(3+)的电化学行为

用循环伏安法和恒电流电解后的电位时间曲线法，研究了ＬｉＣｌＫＣｌ熔体中Ｎｄ３＋和Ｈｏ３＋在Ｍｏ电极上的电化学行为。结果表明，Ｎｄ３＋和Ｈｏ３＋在Ｍｏ电极上的还原都为一步３电子可逆过程。其扩散系数分别为：１１３×１０－６和２１４２×１０－５ｃｍ２·ｓ－１（４５０℃），４５０℃下Ｈｏ３＋／Ｈｏ电极对的标准氧化还原电位为２９８７Ｖ（ｖｓ·Ｃｌ／Ｃｌ－１），并讨论了实验值较理论值偏负的原因。

ELECTROCHEMICAL-BEHAVIOR OF YTTRIUM ION IN LICL-KCL-NACL EUTECTIC MELT

The electrochemical reduction of yttrium ion on a molybdenum electrode in a LiCl-KCl-NaCl eutectic melt at 723 K was found to be almost reversible and to proceed by a one-step three electron reaction. The diffusion coefficient D of the Y(III) ion was measured to be (3.3 +/- 0.4) x 10(-6) cm2 s-1 by cyclic voltammetry, (5.0 +/- 0.9) x 10(-6) cm2 s-1 by the rotating disk electrode method, and (7.1 +/- 0.7) x 10(-6) cm2 s-1 by chronopotentiometry. The D values obtained by the latter two methods are in fairly good agreement with each other. The rather low D value obtained by cyclic voltammetry might be attributed to the fact that yttrium metal can dissolve slightly in the chloride melt. The standard potential of Y(III)/Y(0) couple was determined to be (-3.174 +/- 0.006) V (vs. Cl2/Cl-) by open-circuit potentiometry, (-3.15 +/- 0.02) V (vs. Cl2/Cl-) by the rotating disk electrode method and (-3.16 +/- 0.02) V (vs. Cl2/Cl) by chronopotentiometry. These three values are in good agreement with each other. Several types of Ni-Y intermetallic compounds were found to be formed on a nickel electrode.

STRUCTURE-ANALYSIS OF MOLTEN CACL2-KCL SYSTEM BY X-RAY-DIFFRACTION

Radial distribution function of CaCl2-KCl (1:2 mol) melt was measured by X-ray scattering of high temperature liquid. The nearest neighbour distances of Ca2+-Cl-, K+-Cl- and Cl--Cl- ionic pairs are 0.278, 0.306 and 0.380 nm, respectively, Discussion on the relation between structure and physicochemical properties in the melt was simply done in this paper.

金属镧、钕分别在KCl+NaCl熔盐中的溶解行为

金属溶解于熔盐中的行为表现为溶解的金属与熔盐中的离子发生了不同程度的相互作用。稀土金属在含有自身熔盐中的溶解,前人已作了一些研究,其溶解机理归结起来主要有以下几种:生成了低价稀土离子;体系形成了胶体溶液以及离子-电子液

CaCl_2-KCl熔体结构的X射线衍射分析

用高温液态X射线衍射方法,测定了摩尔比为1∶2的CaCl_2-KCl熔体的径向分布函数。结果表明,熔体中Ca~(2+)-Cl~-、K~+-Cl~-和Cl~--Cl~-离子对间的最近邻距离分别为0.278,0.306和0.380nm.由于Ca~(2+)与Cl-间的强Coulomb作用,在熔融的摩尔比为1∶2的CaCl_2-KGl体系中,Cl~--Cl~-间的最近邻距离明显小于纯KCl熔体中Cl~--Cl~-间的最近邻距离。

La-LaCl_3-KCl熔体的计算机模拟研究

用Monte Carlo方法对La-LaCl_3-KC1体系在1223K时的结构进行了计算机模拟研究,得到了熔体中诸离子对的偏径向分布函数和体系在1223K的势能和内能。结果表明,在熔体中La(Ⅲ)有相当一部分以LaCl_6~3六配位形式存在,而La(Ⅱ)则主要以LaCl_4~2四配位形式存在。结果还表明,熔体中的自由体积分布不均匀,存在许多不规则的空孔和缝隙,其中XK~+·YC1~-集团内的缝隙比纯KC1熔体中的缝隙明显增多。

LiF-KCl熔体的X-射线结构分析

目前多采用径向分布函数来描述熔盐的结构,虽然这种一维统计描述给出的信息有限,但它是迄今为止较为成熟的一种方法。实验上获得熔体的径向分布函数主要通过衍射法。在国际上日本等国家的研究人员对纯熔盐的衍射结构分析已经进行了多年的研究,由于混合熔盐的结构比较复杂,所以近些年才有关于混合熔盐X-射线衍射结构分析的报道,但只限于相同阳离子或相同阴离子的体系,对于LiF-KCl体系至今未见报道。

LiF-KCl熔盐溶液的径向分布函数

本文利用X射线散射技术测定和Monte Carlo计算机模拟计算,获得了LiF-KCl熔体的径向分布函数。实验发现,在互易系LiF-KCl熔体中,小离子Li~+与F~-更易形成结合较为紧密的集团,而大离子K~+与Cl~-的结合相对较为松地,即出现“大大小小”效应。

STUDY ON FUSIBILITY DIAGRAMS CONTAINING LICL AND PHASE-DIAGRAM OF LICL-KCL-LIF TERNARY BY DIRECT CHLORINATION

In order to avoid the hygroscopicity of LiCl specimem, the method of directly chlorinating Li_2CO_3 with NH_4Cl was successfully introducing into the thermal analysis of the system containing LiCl. The three fusibility diagram of LiCl-KCl, LiClNaCl, LiCl-LiF were determined using the method. The results are in agreement wish the values reported in the literature, and phase diagram of LiCl-KCl-LiF ternary system was constructed based on these results. Temperature of the ternary eutectic, composed of 57.3mol％...

La在KCl-NaCl和LaCl_3-KCl-NaCl熔体中的溶解行为

本文利用透明槽技术、电化学循环V-A法及量子化学EHMO三种方法,研究了La在KCl-NaCl(1:1mol)及LaCl_3-KCl-NaCl熔体中的溶解行为。初步认为:溶解在KCl-NaCl熔体中的La是以中性金属状态存在。在LaCl_3-KCl-NaCl熔体中,溶解的La与La~(3+)作用生成低价La~(2+)离子,La~(2+)又与周围的La~(3+)作用形成原子簇离子La_m~(n+)赋存于熔体之中。