First principles computational studies of spontaneous reduction reaction of Eu(III) in eutectic LiCl‐KCl molten salt

Using first principles calculations, we study fundamental mechanism of spontaneous reduction reaction of Eu³⁺ to Eu²⁺ in eutectic LiCl‐KCl molten salt. We decouple the reaction Gibbs free energy into enthalpy and entropy contributions by using rigorous thermodynamic formalism. Key structural features of the solvation shell are characterized by the radial distribution function and the coordination number. Compared with Eu²⁺, the Eu³⁺ ion has a more rigid framework of the solvation shells, corroborating its stronger electrostatic interaction with neighboring ligands of Cl^? ions and a more favorable state on the aspect of enthalpy. Computations on vibrational frequency, however, pose significant contribution of vibrational entropy to the reaction Gibbs free energy for the reduction. Vibration frequency of Eu²⁺ is smaller than that of Eu³⁺, driving a more positive change of the entropy in the reduction reaction. Furthermore, an Eu²⁺ diffuses more quickly than an Eu³⁺ in the LiCl‐KCl molten salt with switching mechanism of ligand Cl^? ions in the solvation shell. Our results propose that the spontaneity of the reduction reaction is driven by the entropic contribution by overcoming the penalty of the reaction enthalpy.     

Impact of rare earth europium (RE-Eu3+) ions substitution on microstructural,optical and magnetic properties of CoFe2−xEuxO4 nanosystems

In this study, pure cobalt ferrite (CoFe₂O₄) nanoparticles and europium doped CoFe₂O₄ (CoFe_2−xEu_xO₄; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe³⁺) ions by trivalent rare earth europium (RE-Eu³⁺) ions on the microstructure, optical and magnetic properties of the produced CoFe₂O₄ nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu₂O₃ phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ₁ and υ₂) and tetrahedral A-site (υ₃) around 415 cm⁻¹, 470 cm⁻¹ and 600 cm⁻¹ respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu³⁺ ions within CoFe₂O₄ host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu³⁺ added to CoFe₂O₄ in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe_2−xEu_xO₄, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe₂O₄ have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu³⁺ in CoFe₂O₄ lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe₂O₄ samples. Substitution of Fe³⁺ ions in CoFe₂O₄ nanoparticles with RE-Eu³⁺ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications.     

克量级铀中微量铕和铽的放化分离方法研究

为提高中子诱发铀裂变时低产额裂变产物¹⁵⁶Eu和¹⁶¹Tb产额测量的精度，需获得放化纯的¹⁵⁶Eu和¹⁶¹Tb样品。本工作建立了氢氧化物共沉淀法除铝、氟化钙共沉淀法除铀、TRPO萃取法提取稀土元素、阳离子交换色谱法从混合稀土元素中分离Eu和Tb的流程，可用于大量铀、铝和裂变产物中微量Eu和Tb的分离。在待分离样品中含2 g铀、0.65 g铝和裂变产物的条件下，该流程对Eu、Tb的化学回收率均大于80%，对U、²³⁹Np、⁹⁵Zr、¹⁰³Ru、¹³¹I、¹³²Te、¹⁴⁰Ba、¹⁴⁰La、¹⁴¹Ce、¹⁴⁷Nd等主要干扰物质的去污因子达到106。该方法可满足中子诱发铀裂变时¹⁵⁶Eu和¹⁶¹Tb产额精确测量的要求。     

金属铕配合物的合成及其晶体结构

合成了席夫碱N-亚水杨基-2-氨基吡啶,并以此为有机配体与过渡金属铕反应,得到了相应的配合物,且在一定的条件下培养得到配合物的单晶,解析出其晶体结构,并对其进行了荧光性质研究。     

铕（III）-1-（氯苯基）-3-（2-羟基苯基）-丙二酮类配合物的合成与荧光性质

合成了1-(邻氯苯基)-3-(2-羟基苯基)-丙二酮(L1)、1-(间氯苯基)-3-(2-羟基苯基)-丙二酮(L2)和1-(对氯苯基)-3-(2-羟基苯基)-丙二酮(L3)3种配体,并将此3种配体分别与 Eu(III)反应生成3种新的稀土配合物。运用元素分析、红外光谱与荧光光谱等手段对配合物进行了表征。结果表明：3种配合物的组成分别为 Eu(L1)3·2H2O、Eu(L2)3·2H2O 和 Eu(L3)3·2H2O。荧光光谱显示,3种配合物的配体均能将吸收的能量有效地传递给三价铕离子,从而使配合物发射出强的铕离子的特征荧光。在3种配合物中,Eu(L1)3·2H2O 的荧光强度远大于 Eu(L2)3·2H2O 和 Eu(L3)3·2H2O 的荧光强度,这说明配体 L1与 Eu(III)离子的能级匹配较好,能量传递效率较高。     

白光LED用红色发光材料CaLa_2(MoO_4)_4:Eu~(3+)的微波辅助溶胶–凝胶法合成及发光特性

以柠檬酸为络合剂,采用微波辅助溶胶–凝胶法制备了CaLa2(MoO4)4:Eu3+红色荧光粉。研究了前驱体的热分解历程,分析表征了样品的结构、形貌和发光性能。探讨了焙烧温度、Eu3+掺杂量、柠檬酸与乙二醇摩尔比和硼酸用量等对样品发光性能的影响。结果表明:前驱体经700~900℃焙烧均能得到目标产物CaLa2–x(MoO4)4:x Eu3+,样品具有白钨矿结构,属于四方晶系。样品的激发光谱在250~350 nm处有一宽吸收带,对应于Mo–O,Eu–O电荷迁移带;在395和464 nm处存在很强的吸收峰,归属于Eu3+的4f–4f跃迁。发射光谱主峰位于616 nm处,归属于Eu3+的5D0→7F2电偶极跃迁发射。前驱体经800℃焙烧所得样品发光强度最大,且发光强度随着Eu3+掺杂量的增加而增大,在x=0.2~1.0范围内未出现猝灭现象。体系中加入适量乙二醇,可以起到细化晶粒、提高粉体分散性的作用,但浓度过高则会降低样品的发光强度;助熔剂硼酸的用量对样品发光强度影响较大,当用量为3%时,样品的发光性能较好。     

Comparative study on the extraction of trivalent americium and europium by CMPO in imidazolium-based ionic liquids and dodecane

The extraction of Am³⁺ and Eu³⁺ by octyl(phenyl)-N,N-diisobutyl carbamoylmethylphosphine oxide (CMPO) in eight imidazolium-based ionic liquids and in n-dodecane was studied and compared. Slope analysis indicates that the ligand/metal ratio in the extracted complexes in ionic liquids is much larger than that in n-dodecane. Nitric acid has different impacts on the extraction, depending greatly on the nature of the ionic liquids. A mixed-extraction mechanism, namely cation exchange plus the formation of neutral complexes (solvation), was proposed for the extraction in the ionic liquid systems. In addition, temperature was found to have a remarkable influence on the extraction. Highly exothermic enthalpy changes were obtained for the extraction in ionic liquid systems. This work provides further insight into the particular role played by the unique properties of ionic liquids in the extraction of metal ions from nitric acid media.     

Removal of Liquid and Solid Impurities from Uranyl Nitrate Hexahydrate Crystalline Particles in Crystal Purification Process

The purification behavior of uranyl nitrate hexahydrate (UNH) was investigated to evaluate the decontamination performance of liquid and solid impurities using a dissolver solution of mixed oxide (MOX) fuel in batch experiments. The UNH crystal recovered from the MOX fuel dissolver solution containing simulated fission products (FPs) was purified by a sweating and melt filtration process. Although the decontamination factors (DFs) of Pu, Cs, and Ba did not change in the sweating process, that of Eu increased with increases in temperature and time. These results indicate that liquid impurities such as Eu were effectively removed by the sweating method, but solid impurities such as Pu, Cs, and Ba were minimally affected in the batch experiments. On the other hand, the DF of Ba increased with 0.45 and 5.0 μ filters in the melt filtration process. Since Pu and Cs formed as Cs₂Pu(NO₃)₆ in the course of U crystallization and was accompanied with the UNH crystal, these behaviors were similar to each other. Although the DFs of Pu and Cs did not change with the 5.0 μ filter, it increased approximately twofold with the 0.45 μ filter. The particle size of Cs₂Pu(NO₃)₆ is relatively small and might pass through the 5.0 μ filter in the melt filtration process. The liquid impurities as Eu remained in the molten UNH crystal with some filters.