Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: I. Effect of O2

Oxidation of Cr(III) hydroxides, double Fe(III)-Cr(III) hydroxides, and some examples of spinel phases NiCr₂O₄ and Fe(Cr,Fe)₂O₄ in alkaline suspensions (0.2-0.5 M NaOH) under the action of air and pure oxygen (1-3 atm) was studied. The reaction rate increases with increasing concentration of alkali, temperature, and oxygen pressure. Under these conditions, Pu(IV) sorbed on chromium hydroxides is not oxidized with oxygen and remains in the precipitate.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: II. Effect of H2O2

Oxidation of various Cr(III) hydroxides and mixed Cr(III)-Ni(II) and Cr(III)-Fe(III) hydroxides with hydrogen peroxide was studied. The initial reaction rate increases as the Cr(III) content in the suspension and H₂O₂ concentration are increased and nonmonotonicaly decreases with increasing NaOH concentration within the 0.2-2.0 M range. The activation energy in 0.5 M NaOH is equal to 82 kJ mol^{- 1} (30-90°C). The oxidant consumption substantially exceeds the stoichiometry.     

Effect of annealing on d.c. conductivity of V2O5-SnO-TeO2 glasses

The d.c. conductivity (σ) of V₂O₅-SnO-TeO₂ glasses prepared by the press-quenching method was studied at temperatures from room temperature (RT) to 473 K, and the effect of annealing on σ was investigated. The conductivity of 50V₂O₅·20SnO·30TeO₂ glass was determined to be 3.98×10⁻⁴ Scm⁻¹ at 473 K and was unchanged for annealing (6–48 h) at 493 K, lower than T_g = 501 K, while its density increased with annealing time. These glasses were found to be n-type semiconductors, and the conduction was confirmed to be due to adiabatic small polaron hopping for V₂O₅ ≧ 50 mol%, and non-adiabatic for V₂O₅ < 50 mol%. The activation energy for conduction, W, decreased with annealing time. Variations in oxygen molar volume of the glasses with annealing time inferred a change in glass structure, from loosely to closely packed, resulting in a decrease in vanadium ion spacing with annealing. This caused an increase in the polaron band width, producing a decrease in polaron hopping energy and W. The effect of annealing time on the density of 50V₂O₅·20SnO·30TeO₂ glass was explained adequately by Winter's formula.     

Lower Oxidation States of f Elements: I. Preparation and Identification of Actinides and Lanthanides in Lower Oxidation States

Studies on the title subject, published mainly in the second half of the XX century and made both with macroamounts of lanthanides (Ln) and actinides (An) and with micro- and ultramicroamounts of radionuclides of these elements, are considered. Procedures for preparing f elements in lower oxidation states in solutions, melts, and solid matrices and methods for identifying these states (electrochemistry, spectrometry, high-temperature extraction, cocrystallization, etc.) are discussed.     

S2O2-8/Al-Zn-O固体酸的制备及表征

用溶胶-凝胶法制备了S2O82-/Al-Zn-O固体酸,考察了制备条件对其催化乙酸-正丁醇合成乙酸正丁酯催化性能的影响,并借助XRD、IR、TG/DSC、SEM等多种测试技术对其结构进行了表征。实验结果表明,制备条件对S2O28-/Al-Zn-O固体酸的催化性能有一定的影响,在最佳制备条件下,其酯化率可达98.06%。     

Optical and electrical properties of reactively d.c. magnetron-sputtered In2O3:Sn films

The deposition of transparent conductive indium oxide doped with tin is investigated. Characterization of the d.c. magnetron-sputtered films shows that it is possible to obtain transparent conductive films from an InSn alloy by sputtering in a reactive atmosphere. This deposition method in combination with an appropriate anneal results in a very low light absorption and a high electrical conductivity of the films. In this paper the two-step deposition technique and the electrical and optical properties of the deposited transparent and conductive layers are described.     

Recovery of Pd from Spent Fuel: 2. Sorption Recovery of Pd from Nitric Acid Solutions on Anion-Exchange Resins

Recovery of Pd from nitric acid solutions on various anion-exchange resins is studied. The effects of the HNO₃ concentration, temperature, and aminoacetic acid on the desorption of Pd are examined. Results of the experiments on Pd recovery from actual solutions from spent fuel reprocessing are reported.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 339–342.Original Russian Text Copyright © 2005 by Korolev, Pokhitonov, Gelis, Milyutin.     

Infrared Luminescence of Y2O2S:Er3+ and Y2O3:Er3+

The diffuse reflectance and luminescence spectra of Y₂O₂S:Er³⁺ and Y₂O₃:Er³⁺ are studied under selective and polarized laser excitation. The results indicate that the Er³⁺ luminescence bands of yttrium oxysulfide in the 1.54-m region are one order of magnitude stronger and broader than those of yttria. Y₂O₂S:Er³⁺ is shown to contain two types of Er-related emission centers differing in the anion environment of the Er³⁺ ion.     

基于腐蚀时间效应的含H_2S/CO_2环境中的腐蚀速率预测模型

高含H_2S/CO_2高温高压气井中井筒油管、套管的腐蚀已成为制约井筒完整性的主要因素,一旦井筒完整性失效将会给油气田的开发造成重大影响,并可能导致严重的人员安全、环境及经济损失。由于高温高压H_2S/CO_2环境腐蚀机理较为复杂,国际上使用较为广泛和经典的DE Waard腐蚀速率计算模型已不能预测类似高温高压复杂环境下井筒的腐蚀速率。目前,实验室通常开展短期的腐蚀测试试验,并以此数据预测长期的腐蚀速率,但长期的腐蚀速率与短期腐蚀速率差异甚大。因此,为了准确地预测服役寿命周期内油套管的腐蚀状况,采用自主设计制造的高温高压材料损伤试验平台,模拟气井井筒的实际腐蚀环境,开展CO_2、H_2S腐蚀环境中的电化学腐蚀速率测试试验,研究了不同测试时间下的腐蚀速率,分析了腐蚀速率的时间效应。结果表明:在管柱服役早期,其腐蚀速率较大,随着服役时间的延长,由于形成了腐蚀产物膜以及腐蚀性气体浓度的降低,腐蚀速率逐渐降低直至稳定于某一较低值。最后,利用数理统计方法建立了考虑腐蚀时间效应的腐蚀速率预测模型,可为合理选择油套管材质和油气井的安全评价提供依据。     

Decay time characteristics of La2O2S:Eu and La2O2S:Tb for use within an optical sensor for human skin temperature measurement

We focus on the development of a remote temperature sensing technology, i.e., an optical laser-based sensor, using thermographic phosphors for medical applications, particularly within an electromagnetically hostile magnetic resonance imaging (MRI) environment. A MRI scanner uses a strong magnetic field and radio waves to generate images of the inside of the body. The quality of the image improves with increasing magnetic resonance; however, the drawback of applying a greater magnetic strength is the inducement of heat into the body tissue. Therefore, monitoring the patient's temperature inside MRI is vital, but until now, a practical solution for temperature measurement did not exist. We show europium doped lanthanum oxysulphide (La(2)O(2)S:Eu) and terbium doped lanthanum oxysulphide (La(2)O(2)S:Tb) are both temperature sensitive to a low temperature range of 10-50 degrees C when under ultraviolet (UV) excitation. The emission spectra and decay time characteristics of these phosphors were demonstrated. The results indicate that La(2)O(2)S:Eu has a quenching rate of 13.7 m degrees C(-1) and 4 m degrees C(-1) at 512 nm and 538 nm, respectively. In addition, La(2)O(2)S:Tb has a lower quenching rate of 4.19 m degrees C(-1) at 548 nm due to its faster decay time.     

（Sb2O3）1—x（Sb2S3）x系新型氧硫混合红外玻璃的研究

首次制备了一类新型的（Ｓｂ２Ｏ３）１－ｘ（Ｓｂ２Ｓ３）ｘ的氧硫混合体系玻璃,测定了玻璃的组成,形成区域,并用ＤＴＡ,ＩＲ,ＵＶ光谱对其性能进行了研究,同时与Ｓｂ２Ｏ３单组份玻璃,Ｓｂ２Ｏ３－ＲＸ２（Ｒ＝二价金属离子）系玻璃进行了比较,该玻璃易于制备,化学稳定性好,透光区０．７～７．０μｍ,Ｔｃ－Ｔｇ〉９０℃,通过远红外光谱的分析,对玻璃的结构进行了初步研究。     

Crystal chemistry of lithium in octahedrally coordinated structures III. A new structure-type in the system K2O:Li2O:TiO2 (KxLixTi4−x2O8)

A new compound in the system K₂O:Li₂O:TiO₂ corresponding to the formula $\text{K}{}_{\mathrm{<mtext>x</mtext>}}\text{Li}{}_{\mathrm{<mtext>x</mtext>}}\text{Ti}{}_{\mathrm{<mtext>4?</mtext><mtext>x</mtext><mtext>2</mtext>}}\text{O}{}_8$ was found to be orthorhombic with a=3.821, b=15.921, c=2.973A space group Cmcm. The similarity between this unit cell and those of Rb_xMn_xTi_2?xO₄ and FeO(OH) has been used to predict the structure of this new phase. From the composition of this phase and that of the hollandite and ramsdellite phases in this system, it can be deduced that some of the Li⁺ ions occur in the tunnels as well as in octahedral coordination substituting for titanium.     

纳米Y2O2S:Tb X射线发光粉的合成及发光性质

以EDTA为螯合剂、尿素为沉淀剂,采用络合沉淀法制备了Y2O2S:Tb纳米X射线发光粉.通过X射线衍射(XRD)、光致发光(PL)光谱和X射线激发发光(XEL)光谱对纳米发光粉进行了表征,并研究了纳米晶的发光性能及Tb3+离子的能量传递过程.研究表明:所制备样品显示了单一的六角结构,其一次粒径约为32 nm.在254 nm紫外光和X射线激发下,Y2O2S:Tb X射线发光粉都显示了Tb3+离子的特征发射峰,分别起源于5D3和5D4能级到基态能级的跃迁.     

Effect of powder bed on the microstructure and electrical properties of Bi2O3- and Sb2O3-doped ZnO

The effects of powder bed on the microstructure and electrical properties of Bi₂O₃- and Sb₂O₃-doped ZnO specimens are investigated in the present study. By using a sufficient amount of powder bed, the weight loss of Bi₂O₃ reduces from >95 to <20%. The reduction of weight loss enhances significantly the densification and grain growth of ZnO. Furthermore, the use of powder bed can also reduce the size distribution of ZnO grains. Nevertheless, the presence of Bi₂O₃ residue results in the formation of a pyrochlore phase (Zn₂Bi₃Sb₃O₁₄) during the cooling down stage; its presence is detrimental to the nonlinear characteristics of ZnO–Bi₂O₃–Sb₂O₃ system.     

Facile synthesis of Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distribution and photoluminescence

Suppressing the crystallization and plate-like crystallite growth of RE₂(OH)₄SO₄·2H₂O compound by low-temperature (~4 °C) precipitation produced an amorphous RE₂(OH)_3.3(CO₃)_0.35SO₄·2H₂O precursor (RE = Gd_1-xTb_x) that can be decomposed to Gd₂O₂SO₄:Tb and Gd₂O₂S:Tb green phosphor nanopowders of unimodal size distributions upon calcination in air at 1000 °C (average particle size ~156.9 nm) and in hydrogen at 800 °C (average particle size ~130.2 nm), respectively. The optimal RE³⁺ concentration for precursor synthesis was determined to be ~0.10 mol/L. Through detailed characterization by XRD, FTIR, DTA/TG, FE-SEM, TEM and particle sizing, the courses of phase/morphology evolution were clarified. Photoluminescence study found that the (Gd_0.99Tb_0.01)₂O₂SO₄ and (Gd_0.98Tb_0.02)₂O₂S representative phosphors have quantum efficiencies of ~16.8% (λ_ex = 275 nm) and 38.5% (λ_ex = 286 nm), fluorescence lifetimes of ~3.70 and 1.75 ms and activation energies for thermal quenching of ~0.552 and 0.385 eV, respectively. The values are remarkably larger than those reported for Gd₂O₂S:Tb, which are considered to be due to higher purity, better crystallization and fewer luminescence-quenching defects of the product. Particularly, the (Gd_0.99Tb_0.01)₂O₂SO₄ phosphor has negative thermal quenching up to ~150 °C and can retain over 85% of its room temperature emission intensity at 250 °C, which may enlighten its application in high-power LEDs.     

Medicament Release from Suppository Bases: III. Ibuprofen - Physicochemical Characteristics and Bioavailability in Rabbits

Abstract

This investigation was designed to determine the invitro release of ibuprofen from suppository bases, and their invivo bioavailability in rabbits. Suppositories containing ibuprofen were made by the fusion method with Theobroma oil, Witepsol H-15 and PEG 1540. In order to produce an exact dosage form, the displacement value was determined. The suppository hardness was determined by utilizing the SBT (Erweka) apparatus and it was found that the Witepsol H-15 allows the formation of brittler suppositories. The release rates were determined with the USP dissolution apparatus and with cellophane membrane and it was found to be: PEG 1540 > Witepsol H-15 > Theobroma oil. The bioavail-ability of Indomethacin after rectal administration was: PEG 1540 > Witepsol H-15 > Theobroma oil which correlates with the invitro release.     

Electrical conductivity of Sc2O3-ZrO2 compositions by 4-probe d.c. and 2-probe complex impedance techniques

The ionic conductivities of several samples in the Sc₂O₃-ZrO₂ system (Sc₂O₃: ～ 8 mol %) have been measured using 4-probe d.c. and 2-probe complex impedance dispersion techniques. Samples which contained monoclinic zirconia showed hysteresis effects and S-shaped Arrhenius conductivity plots. This behaviour was assigned to the m-ZrO₂ ? t-ZrO₂ transformation. In samples which were free of monoclinic ZrO₂, contributions from the grain boundary resistance were relatively small. The Arrhenius plots of their conductivity showed a distinct change in the slope around 600° C towards higher activation energy and this was attributed to vacancy trapping. The 4-probe d.c. data could be fitted to an equation of the formρ=A ₁ T exp (E ₁/RT)+A ₂ T exp (E ₂/RT). The process which dominated the conduction mechanism at lower temperatures had an activation energy of 130 to 140 kJ mol^?1. The activation energy for the migration of oxygen ion vacancies within the bulk of the grain was 64 to 70 kJ mol^?1.     

Crystallization of AlPo4-5 from a system-1.5 (C3H7)3N.1.0Al2O3.1.0 P2O5. 40.0 H2O : Characterization of the products of crystallization

Crystallization of AlPO₄-5 from a gel of composition 1.5 Pr₃N (tripropylamine)· 1.0 Al₂O₃· 1.0 P₂O₅· 40.0 H₂O has been investigated by carrying out the hydrothermal synthesis of the crystalline aluminophosphate in a closed stainless steel pressure bomb at 423 K for different durations of the crystallization (0–48 h). The solid products obtained during the course of crystallization have been characterized thoroughly for their crystallinity (as AlPO₄-5), crystal size and morphology, N₂-sorption capacity (at 78 K and relative pressure of 0.3), thermal analysis, site energy distribution by TPD of pyridine, acidity by chemisorption of pyridine at 673 K and also for their catalytic activity in cumene cracking and o-xylene isomerization reactions at 673 K. The aluminophosphate formed at the different crystallization periods differ from each other largely in these properties. The optimum crystallization period for the synthesis of AlPO₄-5 is about 24 h.