Application of annexation principle of thermodynamic property of In-Pb-Sb and In-Bi-Pb melts

Based on the principle of annexation and phase diagrams, the structural units of In-Pb-Sb and In-Bi-Pb melts were determined, and their calculating models of mass action concentrations were formulated. Calculated results agree well with practical values, which in turn show that the models deduced can reflect the structural realities of corresponding melts and the principle of annexation is applicable not only to some binary metallic melts, but also to ternary metallic melts.     

橡胶熔体在不同生产工艺下流动的数值分析

膨胀干燥机是橡胶后处理的重要设备,可脱去橡胶熔体中质量分数为90%的水分。基于FLUENT软件,对橡胶熔体在膨胀干燥机流道中的流动进行数值分析,在不同进出口压力差、螺杆转速等生产工艺条件下,根据速率分布云图、压力分布云图,分析橡胶熔体在膨胀干燥机流道中的流动规律,从而改善橡胶质量。     

LiCl-KCl-LaCl3熔盐体系中La3+的反应动力学机理

在LiCl-KCl共晶盐中,研究了在不同温度下La³⁺的反应动力学机理。首先,在723～873 K范围内,利用循环伏安法(CV)测得La³⁺的扩散系数D为3.06×10^-5～6.08×10^-5 cm²/s,并根据Arrhenius方程计算了La³⁺在电解质中的扩散活化能E_D=34.51 kJ/mol。随后,利用电化学阻抗谱技术(EIS)研究了La³⁺在电极上的动力学参数并测得交换电流密度i₀为0.48～1.39 A/cm²、反应速率常数k₀=2.04×10^-4～5.90×10^-4 cm/s及反应活化能E_a=35.04 kJ/mol。通过Nyquist图和拟合的等效电路图研究La³⁺在W电极上的反应动力学机理,发现在LiCl-KCl共晶盐中La³⁺     

Ni基高温合金在LiCl-KCl熔盐中的腐蚀行为研究

熔盐电解精炼是乏燃料干法后处理的核心工艺单元,其反应容器需在高温、LiCl-KCl熔盐环境下长期服役,活泼合金元素Cr的选择性溶解使得钝化Cr2O3保护膜难以生成,结构材料面临严重的腐蚀问题,严重阻碍了干法后处理技术的工程化应用.Ni基高温合金在高温氯化物熔盐中的热力学性质稳定,是电解精炼反应容器潜在的候选材料,然而目前Mo、W等关键合金元素对Ni基高温合金在LiCl-KCl熔盐中的耐腐蚀性能影响暂不明确.采用浸泡腐蚀的方法,研究了Haynes 230、Inconel 625、GH 3535、Inconel 690和GH 4169五种Ni基高温合金在550℃、氩气气氛下LiCl-KCl熔盐中的腐蚀行为,采用X射线衍射、扫描电子显微镜及能谱分析对腐蚀产物的组成和形貌进行了分析.研究结果表明,五种Ni基高温合金在与LiCl-KCl熔盐相互作用的过程中均发生腐蚀失重,失重情况为Inconel 625＞GH 3535＞Haynes 230＞Inconel 690＞GH 4169.其中Inconel 625和GH 4169合金在基体近表层生成了富Mo氧化膜,导致外层(Cr,Fe)2O3与基体的热相容性变差,有明显的脱落趋势.相比高Cr含量的Inconel 690合金发生严重的电化学溶解,低Cr的GH 3535合金外层(Cr,Fe)2O3 含量低,抗氧化能力也明显降低,使得氧向基体内部渗入.而Haynes 230合金外表面生成了富W的氧化物,有效地阻挡了Cl-的侵蚀,在以上五种Ni基高温合金中具有最好的耐腐蚀性能.     

铌硼酸盐玻璃熔体的高温红外光谱

本文首次采用高温红外光谱及DSC—7差热分析技术研究了Nb₂O₅—B₂O₃—K₂O系统玻璃熔体结构,并建立了该系统玻璃和高温熔体结构模型。     

Simulation study on molecular relaxation in ionomer melts

Relaxation behavior of ionomer molecule in melt state was investigated by Brownian simulation where motion of a bead-rod chain representing a linear ionomer molecule was calculated in two-dimension. Entanglement between the other molecules was assumed by a repulsive interaction between the chain and randomly located entanglement points. Effect of ion aggregates was also introduced by an attractive interaction between the chain and attractive sites randomly dispersed in the simulation box. Relaxation spectra of end-to-end motion and local bond orientation were obtained in equilibrium calculation for various chain lengths. The effect of the attractive site was discussed on the spectrum. It was found that on the end-to-end motion, the longer the chain was, the more discrepant the spectrum was, while on the bond orientation, the shorter it was, the more discrepant the spectrum was. On the basis of these results, a picture to describe the experimental phenomena was proposed.     

Equilibrium Distributions of Actinides and Fission Products in Pyrochemical Separation Systems, (II) LiCl-KCl/Cd System

Equilibrium distributions of actinides and fission products were determined in a LiCl-KCl/Cd system at 800–973 K. The redox potential of the system was controlled with the addition of reductant Li. Different distribution behaviors due to different group elements were observed. The group partitioning in this system was thus supported to be feasible. On reduction, however, the actinide and lanthanide elements were found to be less soluble in the Cd phase and to remain at the interface in the form of their solid intermetallics. A group partitioning process in which reductive extraction is combined with filtration was proposed on the basis of the present observations.     

Oxidation–reduction processes in halide and oxohalide niobium containing melts. Part I: Interaction of fluoride–chloride and oxofluoride–chloride Nb(V) melts with niobium oxides

The interaction between the K2NbF7–KCl–NaCl melt widely used for niobium electrolysis and niobium oxides of higher (Nb2O5) and lower (NbO2 and NbO) oxidation states was studied by linear sweep voltammetry and analysis of the dissolution time dependences. Three monooxofluoride complexes, NbOF4–, NbOF2–5 and NbOF63–, may form at the mole ratio of Nb2O5:K2NbF7=1:3. No significant difference was found in the electrochemical behaviour of the complexes, but their discharge potentials become more negative with increasing number of fluorine anions in the complex. Due to the interaction of K2NbF7 with NbO2 and NbO, oxofluoride Nb(v) and fluoride Nb(iv) complexes form simultaneously in the KCl–NaCl melt. Thus, the content of the latter increase until the molar ratios in the melt become NbO2dissolv.:K2NbF7init.=1:2 and NbOdissolv.:K2NbF7init.=1:3 and decrease with further dissolution of oxides in the melt. Dissolution of lower niobium oxides in melts containing oxofluoride Nb(v) complexes was also studied.     

Properties of Nitrogen-Containing Yttria—Alumina—Silica Melts and Glasses

The viscosity and solubility of nitrogen in Y₂O₃–Al₂O₃–SiO₂ melts have been systematically examined. The effects of nitrogen content on viscosity for Y-Al-Si-O-N melts and on Vickers hardness of oxynitride glasses also have been examined. Although the viscosity of Y₂O₃–Al₂O₃–SiO₂ melts was decreased, the solubility of nitrogen into the melts was increased with increased Y₂O₃ content. These results indicated that the yttrium ion behaved as a network modifier. Therefore, the structural units for viscous flow became small, and the amount of nonbridging oxygen increased in the melts when the Y₂O₃ content increased. The viscosity of Y-Al-Si-O-N melts and Vickers hardness of oxynitride glasses remarkably increased with increased nitrogen content. These results suggested that the substitution of nitrogen for oxygen in the melts may have led to a high average coordination of nonmetal atoms and that the increased cross-linking produced a more rigid glass network.     

On the development of metallic inert anode for molten CaCl2–CaO System

Some fundamental aspects related to inert anode development in molten CaCl₂–CaO were investigated based on thermodynamic analysis, electrochemistry of metals and solubility of oxide measurements. The Gibbs free energy change of several key anodic reactions including electro-stripping of metals, electro-formation of metallic oxides, electro-dissolution of metallic oxides as well as oxygen and chlorine evolution was calculated and documented, for the first time, as a reference to develop metallic inert anode in chloride based melts. The anodic behaviors of typical metals (Ni, Fe, Co, Mo, Cu, Ag, and Pt) in the melt were investigated. The results confirmed the thermodynamic stability order of metals in the melts and revealed that surface oxide formation can increase the stability of the electrodes in CaO containing melt. Furthermore, solubility of several oxides (NiO, Fe₂O₃, Cr₂O₃, Co₃O₄, NiFe₂O₄) in pure CaCl₂ or CaCl₂–CaO melts was measured to evaluate the stability of oxide coating or a cermet inert anode in the melt. It was found that the solubility of NiO decreased with increasing CaO concentration, while that of Fe₂O₃ increased. Ni coated with NiO film had much higher stability during anodic polarization.