高效锂离子筛吸附剂MnO2·0.5H2O的软化学合成及吸附性能研究

以MnCl2·4H2O,LiOH·H2O等试剂为初始原料,采用溶胶-凝胶、水热处理、固化等软化学合成步骤制备了锂离子筛前驱体Li1.6Mn1.6O4,并经稀盐酸抽锂后得到了高选择性锂离子筛吸附剂MnO2·0.5H2O.着重对合成过程中锂锰比,氧化剂用量等因素影响进行了探讨,并对所制备吸附剂的吸附性能进行了研究.结果表明,经软化学合成步骤制备的锂离子筛对Li 有良好的吸附量和选择性,在未来从海水、卤水等液态锂资源富集或提取锂的应用中具有很大的潜力.     

直接沉积法制备棒状ZnO

在溶液体系中90 ℃下, 以三乙醇胺与醋酸锌为反应试剂, 用直接沉积法合成了微米及纳米尺寸的棒状ZnO粒子, 并对粒子进行了透射电镜(TEM)、X射线衍射(XRD)、热重(TG)和差热扫描量热分析(DSC)等表征. 通过晶体的成核和生长理论初步解释了棒状ZnO粒子的形成过程.     

(Zn，M)TiO3(M=Co，Ni，Co0.5Ni0.5)固溶体的溶胶-凝胶法合成

通过改进的溶胶-凝胶工艺在低温(800 ℃)下合成了基于钛酸锌(ZnTiO₃)体系的(Zn_1-xCo_x)TiO₃、(Zn_1-xNi_x)TiO₃和[Zn_1-x(Co_0.5Ni_0.5)_x]TiO₃陶瓷固溶体。采用X射线衍射分析(XRD)和差示扫描量热法(DSC)等测量技术对产物进行了物相和热稳定性分析。XRD结果表明，获得单一六方相(Zn_1-xCo_x)TiO₃、(Zn_1-xNi_x)TiO₃和[Zn_1-x(Co_0.5Ni_0.5)_x]TiO₃时各自的固溶稳定区间为0.5 ≤ x ≤ 1.0, 0.9 ≤ x ≤ 1.0和0.8 ≤ x ≤ 1.0。与此同时，热分析结果证实，伴随钛酸锌基陶瓷体系掺杂钴量的增加，其六方相的热稳定性提高，且效果比掺杂镍更加显著。     

Sonochemical synthesis and luminescence properties of single-crystalline BaF2:Eu nanospheres

BaF₂ nanocrystals doped with 5.0 mol% Eu³⁺ has been successfully synthesized via a facile, quick and efficient ultrasonic solution route employing the reactions between Ba(NO₃)₂, Eu(NO₃)₃ and KBF₄ under ambient conditions. The product was characterized via X-ray powder diffraction (XRD), scanning electron micrographs (SEM), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra. The ultrasonic irradiation has a strong effect on the morphology of the BaF₂:Eu³⁺ particles. The caddice-sphere-like particles with an average diameter of 250 nm could be obtained with ultrasonic irradiation, whereas only olive-like particles were produced without ultrasonic irradiation. The results of XRD indicate that the obtained BaF₂:Eu³⁺ nanospheres crystallized well with a cubic structure. The PL spectrum shows that the BaF₂:Eu³⁺ nanospheres has the characteristic emission of Eu^{3+ 5}D₀-⁷F_J (J=1-4) transitions, with the magnetic dipole ⁵D₀-⁷F₁ allowed transition (590 nm) being the most prominent emission line.     

6/7Li NMR study of the Li1-zNi1+zO2 phases

A series of Li1-zNi1+zO2 materials have been synthesised by the coprecipitation route. An X-ray diffraction study was carried out on these materials using the Rietveld method to determine the departure from the ideal stoichiometry z, which ranges from 0 to 0.138. The actual Li/Ni ratio was also checked by chemical analyses using inductively coupled plasma (ICP) for each sample. The stoichiometric sample (z approximately 0) was obtained using a 15% Li excess. (6/7)Li NMR results from LiNiO2 (z approximately 0) show that the asymmetric shape of the NMR signal is due to anisotropy. Calculations give evidence that the paramagnetic dipolar interaction from the electron spins carried by Ni is anisotropic but does not completely explain the experimental anisotropy. (6)Li MAS NMR (magic angle spinning NMR) experiments and temperature standardisation NMR measurements unambiguously assign the isotropic position at +726 ppm. The static-echo NMR spectra of the non-stoichiometric Li1-zNi1+zO2 phases also exhibit an asymmetric shape whose width increases with the departure from the ideal stoichiometry z. (6/7)Li static and MAS NMR show that the 2zNi(2+) ions thus formed modify the dipolar interaction within the materials and also affect the Fermi contact interaction, since a distribution of Li environments is observed using (6)Li NMR for non-stoichiometric samples.     

Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions

Mn₂O₃ calcined at 450 ℃ by a simple template-free oxalate route gave 96.2% selectivity of imine at 100% conversion of benzylamine. The high selectivity of the imines clearly depended on the Mn³⁺/Mn⁴⁺ ratio. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time. This catalytic process was carried out under milder conditions, no base additives, and air as the only oxidant.     

Comparative study of the synthesis of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> in silica through the polymerized complex route of the sol–gel method

In this work the synthesis of CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors, without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe₂O₄ and NiFe₂O₄ in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C.     

The thermal conversion of the tetrahydrothiophene‐precursor polymer to poly(p‐phenylene vinylene)

This paper reports the thermal conversion of the tetrahydrothiophene (THT)‐precursor to poly(p‐phenylene vinylene) (PPV). Detailed investigations of the conversion process show that the leaving groups THT and HCl do not eliminate simultaneously. Moderate temperatures (≤125 °C) are sufficient to eliminate the THT while a higher temperature of ≈150 °C is necessary for the leaving group HCl. Furthermore, the THT groups split off at two characteristic temperatures. Our investigations have shown that a consistent picture of the reaction mechanism can only be obtained if the configuration of the polymer chain is considered. For the total reaction of the THT‐precursor to PPV a reaction mechanism is suggested that consists of at least four steps. Copyright © 1999 John Wiley & Sons, Ltd.     

一种合成平面双核金属酞菁的新方法

A new planar binuclear bisphthalocyaninato-metal-planar hexa-tert-butylbisphthalocyaninato dicobalt (Ⅱ) was synthesized by the reaction of 4-tert-butylphthalic anhydride with pyromellitic dianhydride, urea and CoCl₂·6H₂O. This is a new synthesis method (phthalic route). The total yield reaches up to 15%. The synthetic reaction conditions are as follows: appropriate molar ratio of the reactant, reaction in solid phase and without ammonium molybdate as catalyst.