Synthesis of flower-like La or Pr-doped mesoporous ceria microspheres and their catalytic activities for methane combustion

La or Pr-doped flower-like mesoporous ceria microspheres were prepared by a unique calcination of La or Pr-doped Ce(OH)CO₃ microspheres hydrothermally synthesized with the aid of glucose and acrylic acid. Prepared flower-like ceria-based materials have a novel hierarchical architecture with mesoporous structure and high surface area, which can obviously facilitate the catalytic combustion of methane, compared with general La or Pr-doped ceria. The presence of La or Pr can promote the production of oxygen vacancies and improve oxygen mobility, which result in enhancing the oxygen-storage capacity of the flower-like ceria and its catalytic performance for the methane combustion.     

Luminescence of Co-doped SrTiO3:Pr3+

The SrTiO3:Pr3+ material, co-doped with monovalent Li+, divalent Mg2+, and trivalent Al3+ was prepared by a new sol-gel method. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction(XRD) and scanning electron microcopy(SEM). Among the co-doped ion, Al3+ incorporation caused the least lattice change and had the best crystallinity. Photoluminescence spectra were taken to investigate the luminescence characteristics. We observed a red luminescence change of SrTiO3:Pr3+ after being co-doped, and a best enhancement on the red luminescence with the trivalent Al3+ was observed. The present results indicated that the charge defect associated with Al3+ has led to charge compensation of Pr+Sr and also implied that the charge defects(usually the second dopant ions replacing the A or B sites in the lattice) which are closer to Pr+Sr contribute more to the red luminescence enhancement.     

弧形底梯形渠道的实用经济断面计算

文中推导了有关弧形底梯形渠道水力最佳断面的一套计算公式。在此基础上进一步导出了其实用经济断面的计算公式，给出了相应的计算数据表格，并对《渠道防渗工程技术规范》SLl8—91中有关该内容论述的不足和不妥提出了意见。     

镅(Ⅲ)、锔(Ⅲ)、镨(Ⅲ)和钕(Ⅲ)与2-羟基-2,4-二甲基戊酸络合物稳定常数

本文研究了三价镅、锔、镨和钕与2-羟基-2,4-二甲基戊酸的络合作用。在pH=4.00,μ=0.5(NaClO_4)和25℃条件下,用静态阳离子交换法得到了各级稳定常数。指出了2-羟基-2,4-二甲基戊酸(HDMVA)可望成为三价镅、锔分离的优良淋洗剂。     

用稀土皂化有机相技术在轻稀土分离工艺中的新应用

采用Ｐ＿（２０４）萃取剂，氮化轻稀士为原料，应用稀土皂化有机相技术，连续、稳定地生产出９９～９９．５％的Ｎｄ＿２Ｏ＿３、镧铈谱富集物及部分９９～９９．５％Ｌａ＿２Ｏ＿３。且富集物ＬａＣｅＰｒ溶液稀土浓度提高了２～３倍，使下步工序的Ｃｅ－ｐｒ、Ｌａ－Ｃｅ分离段，在相同设备、萃取参数条件下，较原设计工艺提高处理量近５０％。     

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确定储油气层岩石的物性参数是油气田勘探与开发中的一个重要问题，而岩心分析是获得储层岩石资料的一种基本手段。对于低渗透致密岩石的物性参数，由于流体流动速率很小，采用常规的岩心分析方法难以测量和解释。为测定岩心物性参数，在瞬时脉冲技术基础上，通过测试岩石样品两端的压力变化，提出了自动拟合岩石样品两端实测压力的模型及其数值解法,研制了岩心物性参数解释软件，配合实验装置，实现了岩心分析实验数据的自动采集与解释。由于实验是通过测量岩样上、下流压力随时间的变化而不需要测量流量来测定岩心物性参数，从而避免了用常规方法测量致密岩石时的困难，同时在高压下测定的岩心物性参数更接近于矿场实际。最后，通过例子说明了实验简单易行，方法稳定可靠，结果准确，具有推广应用价值。     

Structural and Electrical Properties of Bi 3.25 La 0.75 Ti 3 O 12 and Bi 3.25 Pr 0.75 Ti 3 O 12 Thin Films for Memory Applications

In this work, Bi 3.25 La 0.75 Ti 3 O 12 (BLT) and Bi 3.25 Pr 0.75 Ti 3 O 12 (BPT) thin films were prepared by chemical solution deposition and characterized by X-ray diffraction, scanning electron microscope and electrical measurements. Layered perovskite BLT and BPT films can be achieved by 180 s annealing at a temperature as low as 650 C. Both BPT and BLT films are composed of closely packed spherical grains. BPT shows larger remnant polarization ( Pr ) and smaller coercive field. The Pr values of 700 C annealed BLT and BPT films are 18.3 w C/cm 2 and 20.5 w C/cm 2 , respectively, while BLT films show better-saturated hysteresis loops. The leakage current density of BPT films is significantly (about one order) lower than that of BLT. The dielectric properties of BLT and BPT films were measured and compared. Both films exhibit large dielectric constant and small loss tangent. Under bipolar switching cycles, BLT films showed little polarization reduction but a 30% polarization loss was observed for BPT films after 2 2 10 9 cycles.     

Pr~(3+)离子及Na_5Pr(WO_4)_4晶体的光谱性质

本文报道了新型发光晶体Na_5Pr(WO_4)_4的生长及Pr~(3+)离子的光谱性质。测定了该晶体的结构以及吸收光谱、荧光光谱和激发光谱。研究表明,该晶体有可能成为继Na_5Nd(WO_4)_4晶体之后又一激光晶体新品种。     

Zr对Pr-Fe-B非晶合金晶化形成纳米晶合金的作用

从非晶合金化激活能的角度，分析了Pr-Fe-B非晶合金在退火过程中晶粒粗大的原因，揭示了Zr元素在其晶化过程中的作用，结果表明，Zr能改变Pr-Fe-B非晶合金中α－Fe相的晶化行为，有助于形成尺寸细小的α-Fe相。