稀土石膏常压酸化法制备硫酸钙晶须的研究

以含稀土的石膏为原料运用常压酸化法合成硫酸钙晶须,探讨了不同工艺条件对生成的硫酸钙晶须形貌的影响,同时还考察了晶型助长剂的种类和晶型助长剂的含量对硫酸钙晶须生长的影响,利用SEM和XRD分别对硫酸钙晶须的表面形貌、物相特征做了表征分析。实验得到制备硫酸钙晶须的最佳的反应条件：稀土石膏质量浓度为0.22 g/mL、反应时间为25 min、盐酸浓度为2.8 mol/L、反应温度为70 ℃、陈化时间为4 h,在此条件下合成的硫酸钙晶须平均长度为61 μm,平均长径比为30.5;通过对比实验选出了CuCl₂作为促进硫酸钙晶须生长的助长剂,在添加5%（质量分数）的CuCl₂的情况下可使硫酸钙晶须长径比从30.5增至41,长度从61 μm增至81 μm。     

四川某稀土矿选矿试验研究

针对四川某稀土矿选矿工艺存在的稀土回收率低的问题，开展了一系列选矿试验研究。试验结果表明，在矿浆质量浓度为30%，粗选NaOH用量为600g/t，水玻璃用量为3000g/t，EF1106用量为3500g/t，起泡剂用量为60g/t情况下，采用一粗、三精、两扫、中矿按顺序返回的选矿流程，可获得稀土REO的品位和回收率分别为66.32%和79.88%的稀土浮选精矿。与该选厂的生产指标相比，稀土回收率提高了13.93%。     

Protection of power transformer using multi criteria decision-making

Power transformers are protected by different relays that operate independently. Malfunction of each relay has a major role in reducing the reliability of the protection system. In order to mitigate the main drawbacks of the power transformer relays, an overall protection scheme is presented in this paper. This scheme proposes a novel multi criterion algorithm using decision-making based on fuzzy logic. In this paper the outputs of restricted earth fault relay and a directional check unit, are combined with the output of the differential protection relay. Therefore, problems that are pertaining to independent operation of each relay have been mitigated and the relays cover protection blind spots of each other. The improved power transformer protection (IPTP) scheme enhances the sensitivity and reliability of the power transformer protection. Extensive simulations are used to measure the effectiveness and merit of the proposed IPTP relay. The above efforts result in a multi criteria approach for protection of power transformers.     

高路堤预应力锚索桩板墙承载特性分析

以昆明—曼谷国际公路k70路堤加固工程为背景,采用原位测试方法,完成了不同工况下预应力锚索桩板墙承载特性的现场试验。通过观测结构位移、土压力、桩身内力以及锚索预应力等,系统分析了预应力锚索桩板墙的受力特性与力学行为。锚索桩板墙对高路堤的加固效果显著,填筑初期结构位移随填土高度线性增加,锚索施工后增速有所减缓;初始填筑阶段,抗滑桩变形以刚性倾斜为主,随着锚索张拉和桩后填土不断增高桩身产生了较为明显的弯曲变形。作用在抗滑桩后的土压力大致呈三角形分布,板后土压力大致呈抛物线型分布;相同埋深条件下作用在抗滑桩上的土压力明显大于挡板,原因在于相邻抗滑桩间产生了明显的土拱效应,下部相邻抗滑桩间的土拱效应更强;与解析解的对比结果表明,实测最大桩后土压力与滑坡推力接近,远小于被动土压力;实测板后土压力与主动土压力接近,工程设计中可选取Rankine主动土压力作为挡板的设计荷载,在不利位置采取增大板厚等措施避免挡板发生破坏。采用弹性弯曲梁理论对锚索桩板墙内力计算的结果与实测结果基本一致。张拉锁定初期锚索预应力损失较大,约为设计荷载的10%,后期锚索预应力逐渐趋于稳定,锚索预应力长期损失约为设计荷载值的12%~15%。     

Radiation damage behavior of carbon/carbon composite in Low Earth Orbit environment

To understand the degradation behavior of Carbon/Carbon(C/C) composite in LEO radiation environment, groups of 2D-C/C composites samples were exposed to ground-based Low Earth Orbit(LEO) simulating facilities. The LEO radiating environment covers part of Van Allen inner belt, which contains atomic oxygen(AO) and high-energy proton radiating regions. These two kinds of radiating sources were arranged for simulating the real LEO radiating conditions regarding to the first orbit movement speed of serving space shuttles. Changes of micro-structure, mass loss, surface roughness, chemical construction and thermal physical properties after environmental assessment were analyzed and compared to understand the damage behavior of LEO radiation on C/C composite. It was found that AO is the main factor of mass loss in LEO radiating particles. The charged high-energy protons have an aggravating damage ability with energetic AO, damage situations of degree in orbit down process is more serious than in orbit rising process. The LEO radiation damage mechanisms of C/C composite are revealed and expounded either.     

Luminescence and energy transfer of color-tunable Lu_2MgAl_4SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+) phosphors

Energy transfer among the co-doped activators is an efficient route to achieve color-tunable emission in inorganic phosphors.Herein,photoluminescence tuning from blue to cyan has been achieved in the Lu_2MgAl_4 SiO_(12);Eu~(2+),Ce~(3+)phosphors by varying the Ce~(3+) concentration with a fixed Eu~(2+)content.With the further introduction of a Mn~(2+)-Si4+couple into the host lattice,the emission color can be tuned to red through the energy transfer of Eu~(2+)and Mn~(2+).The luminescence properties and the energy transfer mechanism were studied in detail.The energy transfer from Eu~(2+)to Ce~(3+)is certified as a dipolequadrupole interaction with the energy transfer efficiency of 41.4% and Eu~(2+)to Mn~(2+)belongs to a dipole-dipole interaction with the energy transfer efficiency of 94.3%.The results imply that this singlephased Lu_2MgAl4 SiO_(12):Eu~(2+),Ce~(3+),Mn~(2+)phosphor has a potential prospect for application in near-UV chip pumped white light emitting diodes.     

Sensitivity of a solid Eu(III) complex towards acetonitrile vapor: Structural and spectroscopic characterization

The Eu(III) nitrate complex of the meso- N,N′-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine ligand was synthesized and characterized by single crystal and powder X-ray diffraction. The crystal lattice of the complex is capable of absorbing and desorbing selectively acetonitrile molecules, at 293 K upon an acetonitrile vapor pressure of ∼0.1 × 10⁵ Pa. This process, which is partially reversible, can be easily followed by both powder X-ray diffraction (P-XRD) and Eu(III) luminescence spectroscopy. The acetonitrile molecule, located in the outer coordination sphere of the metal ion, does not affect the radiative transition probability of ⁵D₀ level of Eu(III) and also it does not activate further non-radiative channels from this level. On the other hand, this molecule is capable of affecting the energy position and intensities of the crystal field components of the ⁵D₀→⁷F₂ transition. The complex in solid form can be considered a promising material for the optical sensing of acetonitrile vapors.     

The variation of microstructures,spectral characteristics and catalysis effects of Fe~(3+) and Zn~(2+) co-doped CeO_2 solid solutions

Fe~(3+)and Zn~(2+)ions were doped into the lattice of CeO_2 via the hydrothermal method.The micro structure and spectra features were analyzed systemically.XRD results show that the solid solubility of Fe~(3+)and Zn~(2+)ions in Ce_(1-x)(Fe_(0.5)Zn_(0.5))_xO_2 can be identified as x=0.16.The cell volumes are decreased by increasing the doped content.The TEM graphs prove that the grain size of the sample is about 10 nm,and the EDS result indicates that the doped contents are in accordance with that of the theory concentrations.Meanwhile,the doping also causes the increasing concentrations of the defects and oxygen vacancies which are supported by the XPS,Raman,UV and PL characterizations.The samples exhibit better catalytic activities for improving the hydrogen storage properties and the electrochemical kinetics of the ball milled Mg_2Ni based composites.Further,the catalysis effects are improved by increasing the doped contents,which can be ascribed to the increasing contents of the oxygen vacancies,defects,the special electron transition states and the nature of the doped ions in CeO_2-based solid solutions.     

Kinetics and thermodynamics modeling of Nd(III) removal from aqueous solution using modified Amberlite XAD7

New adsorbent material was obtained by modification of commercial Amberlite XAD7 with thiourea that represents a non-toxic, cheap and environmentally friendly extractant. Prepared adsorbent was used for removal of neodymium ions from aqueous solutions. Thiourea modified Amberlite involved in this study shows good adsorption capacities (74.3 mg/g) and excellent efficiency during Nd removal process. In order to elucidate the mechanism of the Nd adsorption process kinetic, thermodynamic and equilibrium studies were performed, establishing this way which kinetic model better describes the Nd adsorption process. Moreover the thermodynamic studies prove that the Nd adsorption on thiourea modified Amberlite XAD7 is an endothermic and spontaneous process.     

A series of Er~(3+)-activated SrLaGa_3O_7 single crystal fibers for mid-infrared laser application

A multidisciplinary approach for the production and characterization of a series of high concentration Er~(3+)activated SrLaGa_3 O_7(abbreviated as Er:SLGO) crystal fibers is shown to have a great promise for implementation in mid-infrared laser applications.The current approach includes the design and formation of unique layered tetrahedral network structures with several kinds of rare earth(RE) ions including Er ions distributing statistically between layers,such as Er:SLGO,Er,Nd:SLGO,Er,Yb,Ho:SLGO,Er,Eu:SLGO and Er,Ho:SLGO.Five kinds of Er:SLGO crystal fibers were designed to grow via a micropulling down method.Spectroscopic analyses show that Er,Yb,Ho:SLGO and Nd,Er:SLGO crystal fibers were superiorly endowed with inhomogeneous broadening absorption and strong emission.The unique structural components design enables the generation of improved absorption and emission recombination,and the inhibition of self-termination as well.Generally,the use of structural components design may warrant high-efficiency emissions in RE-doped crystal fibers.