Catalysis by Molten Metals and Molten Alloys

It appears pertinent for the opening of this review to cite the work of Ipatiew [1]. In 1901 he reported that certain metals catalyzed the decomposition of alcohols even above the melting points of the catalyst metals, However, he gave no special attention to the catalytic activity of the molten metal (liquid metal), and thus 20 years or more elapsed without any significant advances in the research on the catalysis of the liquid metal.     

Catalysis by Molten Metals and Molten Alloys

Abstract

It appears pertinent for the opening of this review to cite the work of Ipatiew [1]. In 1901 he reported that certain metals catalyzed the decomposition of alcohols even above the melting points of the catalyst metals, However, he gave no special attention to the catalytic activity of the molten metal (liquid metal), and thus 20 years or more elapsed without any significant advances in the research on the catalysis of the liquid metal.     

熔盐电镀铝合金的研究进展

熔盐中用电沉积法可得到具有良好物理性能,优异抗腐蚀性、装饰性等特性的合金镀层。本文综述了铝合金在氯化物体系中的熔盐电镀,介绍了影响合金镀层组成、结构及性能的因素,并着重介绍了Al-Cr合金和Al-Ni合金的研究,展望了铝合金熔盐电镀的发展前景。     

Influence of Magnesium-Aluminum Spinel on the Directed Oxidation of Molten Aluminum Alloys

The directed oxidation of some molten aluminum alloys was studied. Alloys containing Si, Zn, and Mg are readily converted into Al₂O₃/Al composites with the characteristic directed metal oxidation process (DIMOX) metal-channel structure. No reaction took place when alloys without Mg were used. However, when Mg-free melts containing Si and Zn were in contact with bulk spinel (MgAl₂O₄), the typical reaction product grew from the metal pool, although without formation of the spinel starter layer which was thought to be a prerequisite for DIMOX growth. Furthermore, the growth front was more planar than when Mg-containing alloys were used.     

BaZrO3坩埚的制备及与钛合金熔体的界面反应

以BaCO3和ZrO2为原料,采用固相法合成BaZrO3粉体,利用冷等静压成型技术结合固相烧结技术制备出BaZrO3坩埚,并将其用于TiNi合金真空感应熔炼实验。通过研究不同BaCO3和ZrO2摩尔比条件下合成产物的物相组成,分析了烧结温度和助熔剂TiO2对BaZrO3坩埚致密度及熔炼后界面反应的影响。结果表明,在BaCO3和ZrO2摩尔比接近1:1、BaZrO3粉体合成温度为1200℃、TiO2添加量(质量分数)为2%、烧结温度为1750℃条件下,坩埚致密度达到97%。将此坩锅用于TiNi合金熔炼实验,发现BaZrO3与TiNi合金熔体润湿性较差,二者间无过渡层,坩埚材料未向熔体扩散,也没有与BaZrO3反应生成中间相。     

Oxidation-Reduction Equilibria in Molten Na2O.2SiO2 Glass

The oxidation-reduction equilibria in molten glasses having a soda/silica ratio of 1/2 and containing small amounts of variable-valence ions of the transition elements titanium, vanadium, iron, cobalt, and nickel, the post-transition elements tin and antimony, and the rare-earth element cerium were obtained by equilibrating the melts with various atmospheres. The simple mass expression
was always applicable. In the expression, n is the number of electrons involved in the valence change of the metal M. The value of n is 1 for all systems except for the ions of antimony and tin where n is 2. The ions found are those generally accepted as existing in glass melts which are Ti³⁺, Ti⁴⁺; Fez+, Fe³⁺; Ce³⁺, Ce⁴⁺; Mn²⁺, Mn³; Co²⁺, Co³⁺; Ni²⁺, Ni³; Sb³⁺, Sb⁵⁺; and Sn²⁺, Sn⁴⁺. Two mass action expressions were needed for vanadium-containing glasses to describe the equilibria between 5+, 4+, and 3 f species.     

Structure Analysis of Molten Ba–Ge Alloys Using Electrostatic Levitation Technique Combined With High-Energy X-Ray Diffraction

High-energy synchrotron X-ray diffraction experiments were performed for clathrate-forming barium–germanium (Ba–Ge) alloys in the liquid state near the eutectic composition. The accurate structure information of highly reactive melts has been obtained by applying electrostatic levitation technique as a containerless method. The structure information obtained from the reverse Monte Carlo simulation suggests that the short-range ordering between the Ge atoms occurs with the addition of Ba atoms in the liquid Ba–Ge alloys. This can be associated with the formation of the cage-like structure composed of the Ge atoms in the liquid alloys near the eutectic composition.     

Ionic Equilibria in Liquid Silicates

Liquid silicates, in common with phosphates and probably other oxygen-containing inorganic polymers which are stable at high temperatures, contain in general a multitude of anionic species ranging in size and complexity from simple "monomeric" groupings such as SiO₄⁴⁻ and P0₄³⁻ to continuous, cross-linked networks of infinite molecular weight. The average size and distribution of these species in binary systems may be inferred, at least approximately, from thermodynamic data in combination with polymer theory on the assumption that the activity coefficients of the constituents are arrayed in geometric series. This is equivalent to assuming ideal mixing of polymeric segments. As anticipated, deviations from the theory become significant at the gel point, which varies with the nature of the cation. The significance of these concepts in relation to the constitution of glasses is discussed. In particular, it is indicated that a glass may consist of sol and gel portions, the complexity and relative proportions of which vary with the nature of the cation and the silica content. In theory, the ion SiO₄⁴⁻ is the most abundant single species of discrete silicate ion at all silica contents.     

Oxidation-Reduction Equilibria in Iron-Containing Glass

The oxidation-reduction equilibrium between ferrous and ferric iron in Na₂O · 2Si0₂ glass melts was studied by equilibrating melts with various oxygen partial pressures. Exceedingly long equilibration times were required to obtain meaningful results. The reaction appears to be diffusion-controlled and may be expressed as 20^2-+ 4Fe³⁺$4 4Fe²⁺+ O₂. Data are presented in which the valence of iron varies from predominantly +3 to predominantly +2.     

Defect Equilibria in Transition Metal Oxides

This paper assesses the importance of vacancy aggregates in transition metal oxides. It presents the predictions of quantitative atomistic calculations and discusses them in relation to observed structural, diffusion, thermodynamic, and other data. The results indicate that vacancy complexes constitute the major defect species at high nonstoichiometry. The commonly discussed vacancy-hole complexes appear to be unimportant except, perhaps, over a very limited composition range.     

Oxidation-Reduction Equilibria in Molten Na2O.2SiO2 Glass in Contact with Metallic Copper and Silver

The oxidation-reduction equilibrium in Na₂O-2SiO₂ glass melts containing either copper or silver was studied by systematically varying the oxygen partial pressure above the melt. For copper the two equilibria are
For silver the equilibrium is analogous to the second of the two copper reactions.     

Polarography in Molten Sodium Disilicate

Polarographic techniques using a rotating micro-electrode are given. Experimental results cover concentrations and valence states of metal oxides in a sodium disilicate solution.     

Experimental Phase Equilibria in the PbOx-CaO System

Phase equilibria in the PbO _x -CaO system at oxygen partial pressures of 1.01 10⁵ and 1.01 10³ Pa were experimentally investigated. The temperatures of the eutectic reaction between PbO and PbCa₂O₄ and of the peritectic melting of PbCa₂O₄ were measured via differential thermal analysis at five oxygen partial pressures. The phase transition in air between PbO and Pb₃O₄ was not affected by the coexistence of PbCa₂O₄.     

Ternary Phase Equilibria in the Zr-Si-C System

Phase equilibria in the ternary Zr-Si-C system at 1200°C are investigated in this work. A specific effort was made tofabricate a stable or metastable Zr₃SiC₂ phase, analogous to Ti₃SiC₂, but no evidence of such a compound was observed.The existence of the Zr₅Si₄ and Zr₃Si phases, which were previously described in analyses of the Zr-Si binary, isconfirmed in this study and their phase relationships withinthe ternary Zr-Si-C system are established by electronmicroprobe analysis and transmission electron microscopy.     

Low-Temperature Phase Equilibria in the Y-Ba-Cu-O System

Ultrasonically prepared freeze-dried nitrate precursors and high-precision solution calorimetry were used to investigate the low-temperature thermodynamic stabilities of compounds in the Y-Cu-O, Ba-Cu-O, Y-Ba-O, and Y-Ba-Cu-O pseudobinary and pseudoternary systems at 1 atm of oxygen. Y₂Cu₂O₅, Y₂BaCuO_s, and BaCuO₂ were found to be metastable below 682°, 728°, and 710°± 5°C, respectively. The only stable phases in the Y-Ba-Cu-O system at 298 K and 1 atm of oxygen are Ba₂Cu₃O₆, CuO, BaO₂, and Y₂O₃. By compiling the calorimetric and phase equilibria data, a series of Y-Ba-Cu-O isothermal phase diagrams were constructed between 25° and 900°C at 1 atm of oxygen.     

Phase Equilibria in the Quaternary System Ti-Al-C-N

The quaternary system Ti-Al-C-N and its binary and ternary boundary systems are investigated using powder methods and XRD analysis. Phase equilibria at 1375°C are presented in an isothermal network for alloys up to 50 at.% Ti. In the vertical section Ti₂AIC_1-x-Ti₂AlN_1-x a complete series of solid solutions exists at 1495°C, but a wide miscibility gap occurs at 1375°C. The vertical section Ti₃AlC_1-x-Ti₃AlN_1-x is more complex because of the occurrence of the quaternary, tetragonally distorted phase Ti₃Al(C,N)_1-x ( a = 0.41135(4) nm, c = 0.41366(5) nm) and the transformation of perovskite-type Ti₃AlN_1-x into filled Re₃B-type Ti₃AlN_1-x below 1200°C.