Synthesis and study of compounds of the general formula MITh2(VO4)3 (MI = Li, Na, Ag, K, Rb, Cs, Tl)

Double vanadates of thorium and univalent metals with r(M^I) < 1.6 Å were prepared by high-temperature solid-phase reactions. Representatives of this series with larger M^I atoms were prepared by the solgel method. The compounds crystallize in three structural types: zircon for Li and Na derivatives, scheelite for AgTh₂(VO₄)₃, and potassium thorium vanadate for the compounds containing K, Rb, Cs, and Tl. Thus, two morphotropic transitions are observed in the series of the compounds studied. The bands in the IR spectra were assigned, and the effect of the site symmetry of the VO₄ tetrahedra on the number of absorption bands was revealed. The incongruent melting points of the compounds were determined by differential scanning calorimetry.     

Thermal and luminescent properties of M2Zn(VO3)4 (M = Rb, Cs)

We have developed processes for the synthesis of the Rb₂Zn(VO₃)₄ and Cs₂Zn(VO₃)₄ tetrametavanadates. Rb₂Zn(VO₃)₄ has been prepared by solid-state reaction (350°C) between presynthesized RbVO₃ and ZnV₂O₆ powders, and Cs₂Zn(VO₃)₄ has been prepared by the Pechini method (sol-gel process). Both metavanadates crystallize in monoclinic symmetry (sp. gr. P2₁/m). Thermochemical characterization results demonstrate that the vanadates undergo complex transformations during heating to 450°C and subsequent cooling. As a result, the materials are in a nonequilibrium state at room temperature and consist of both the parent double metavanadates and their peritectic decomposition products. We believe that the formation of the structure of the M₂Zn(VO₃)₄ compounds from their melts is a kinetically hindered process. These compounds are structurally stable only at temperatures below 369 (Rb₂Zn(VO₃)₄) or 420°C (Cs₂Zn(VO₃)₄). We have measured for the first time the diffuse reflectance and photoluminescence excitation spectra of the two tetrametavanadates in their emission range and their photoluminescence spectra at various excitation wavelengths and determined their chromaticity coordinates. Their X-ray luminescence and scintillation decay characteristics have been determined for the first time under pulsed electron beam excitation. The electron excitation dissipation processes in the cesium and rubidium compounds are shown to be similar. We discuss the origin of the emission bands in the mixed vanadates and their potential application areas.     

钒酸锰负极材料的制备及其性能

本研究通过流变相反应-热解法制备了碳包覆钒酸锰锂离子电池负极材料,通过XRD、TEM和电化学测试对材料进行了表征.所制备的材料微观组织呈不规则的短圆柱形和球形,其直径分布在30～50 nm之间,短圆柱形颗粒长度在200 nm左右.在充放电电压为3.0 V到0.02 V范围内,当充放电电流为0.1 A/g时,钒酸锰负极材料首次可逆充电容量为876 mAh/g,经过100次充放电循环后,可逆充电容量为843 mAh/g;以2.0 A/g的大电流充放电时,可逆充电容量仍然保持在334 mAh/g左右,表现出较优秀的大电流充放电能力.     

聚(苯胺-邻六氟羟基苯胺)共聚物的合成及其性能表征

采用过硫酸铵作为引发剂,通过化学氧化聚合法制备了一系列可溶性的聚(苯胺-邻六氟羟基苯胺)(PAH)的共聚物。利用傅里叶红外光谱(FTIR)、核磁共振氟谱(19F-NMR)、核磁共振氢谱(1H-NMR)、凝胶渗透色谱(GPC)、紫外光谱(UV)和场发射扫描电子显微镜(FESEM)等对共聚物的化学结构和形貌等进行了表征和分析。结果表明,邻六氟羟基苯胺(HAFIP)成功导入了共聚物主链中,共聚物的数均分子量Mn介于6.51×10~4与9.04×10~4之间。HAFIP的存在抑制了共聚物的醌式结构n→π*跃迁,随着共聚物中邻六氟羟基苯胺(HAFIP)摩尔分数的增大,共聚物形貌逐渐由纳米纤维向纳米颗粒变换。与聚苯胺难于溶解于一般有机溶剂不同的是,当邻六氟羟基苯胺(HAFIP)的摩尔分数超过0.5时,共聚物可以完全溶解于四氢呋喃、乙醇、N-甲基吡咯烷酮、N,N-二甲基甲酰胺等有机溶剂中,表明HAFIP的导入,可以大幅改善聚苯胺的溶解性能,从而扩展聚苯胺的应用范围。     

二氧化钒超薄纳米片的制备及其光学性能研究

采用V2O5作为钒源,以乙二醇(EG))为还原剂,在190℃的条件下,通过简单的水热途径制备出了VO2 (B)超薄纳米片晶.并利用X射线衍射(XRD)、扫描电镜(SEM)、荧光分光光度计(PL)对样品的结构、形貌及荧光性能进行表征.研究结果表明:以乙二醇(EG)为还原剂制备出的晶体为纳米VO2 (B),长180～350...     

Hydrothermal synthesis of W and Mo co-doped VO2(B) nanobelts

W and Mo co-doped VO₂(B) nanobelts which used formic acid as reduction acid, NH₄VO₃ as vanadium source, (NH₄)₆W₇O₂₄?·?6H₂O and (NH₄)₆Mo₇O₂₄?·?4H₂O as doped sources were synthesised by the hydrothermal method. The samples were characterised by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). TEM and HRTEM images showed the samples had a length of 1?µm and a width of 100?nm. XRD, FTIR and XPS spectra revealed that Mo⁶⁺ and W⁶⁺ incorporated into the VO₂(B) lattice and formed solid-solution phases with VO₂(B).     

Synthesis and characterization of Dy(OH)3 and Dy2O3 nanotubes

Dy(OH)3 nanotubes with high aspect ratios of up to about 50 were synthesized in the presence of poly(ethylene glycol) via a hydrothermal method. Poly(ethylene glycol), as a nonionic surfactant, plays an important role in the formation of morphologies. Subsequent thermal treatment of Dy(OH)3 nanotube precursors at 450 degrees C for 6 h led to Dy2O3 nanotubes, during which the precursor tubular morphology was maintained. Selected-area electron diffraction and high-resolution transmission electron microscopy reveal the single-crystal nature of the Dy(OH)3 and Dy2O3 nanotubes. The morphologies and crystalline structure of the as-obtained products were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, respectively. By this method, we can obtain a mass of products.     

Electrochemical synthesis and physicochemical study of lanthanum(III) acetylacetonate complexes

Anodic dissolution of lanthanum metal in the presence of acetylacetone in ethanol, acetonitrile, and water was studied. Adducts of lanthanum tris--diketonates [La(EtOH)_0.5(AA)₃], [La(HAA)(AA)₃], and La(AA)₃(H₂O)₄, respectively, were isolated from these solutions. Electrochemical oxidation of lanthanum in the course of electrolysis is accompanied by its chemical dissolution. The compositions of the compounds obtained were confirmed by IR spectroscopy, mass spectrometry, thermal gravimetric analysis, isothermal heating, and elemental analysis for metal.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 510–512.Original Russian Text Copyright © 2004 by Kostyuk, Dik, Tereshko, Trebnikov.     

Synthesis and physicochemical properties of titanium(IV)- and cobalt(II)-Based photocatalytic oxide composites

We have studied the phase transitions, morphology, and photocatalytic activity of composites based on titanium(IV) and cobalt(II) oxides at Co doping levels from 0.5 to 60 wt % and heat-treatment temperatures from 80 to 1150°C. The highest photocatalytic activity under illumination in the spectral range λ ≥ 670 nm is offered by mesoporous X-ray amorphous and multiphase (X-ray amorphous phase, anatase, rutile, and CoTiO₃) nanomaterials containing 5–20 wt % Co, whereas two-phase materials (rutile + CoTiO₃) have the lowest photocatalytic activity.     

Synthesis and structural study of new potassium uranyl selenates K2(H5O2)(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)4 and K3(H3O)[(UO2)2(SeO4)4(H2O)2](H2O)5

Single crystals of new uranyl selenates K₂(H₅O₂)(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₄ (1) and K₃(H₃O)[(UO₂)₂(SeO₄)₄(H₂O)₂](H₂O)₅ (2) were prepared by isothermal evaporation at room temperature. The crystal structure of 1 was solved by the direct method [C2/c, a = 17.879(5), b = 8.152(5), c = 17.872(5) Å, β = 96.943(5)°, V = 2585.7(19) ų, Z = 4] and refined to R ₁ = 0.0449 (wR ₂ = 0.0952) for 2600 reflections with |F _o| ≥ 4σ _F . The structure of 2 was solved by the direct method [P2₁/c, a = 17.8377(5), b = 8.1478(5), c = 23.696(1) Å, β = 131.622(2)°, V = 2574.5(2) ų, Z = 4] and refined to R ₁ = 0.0516 (wR ₂ = 0.1233) for 4075 reflections with |F _o| ≥ 4σ _F . The structures of 1 and 2 are based on [(UO₂)₂(SeO₄)₄(H₂O)₂]^4? layers. The charge of the inorganic layer is compensated by potassium and oxonium ions arranged in the interlayer space. Each K ion is surrounded by seven O atoms belonging to uranyl selenate layers and water molecules, so that it binds with each other the adjacent uranyl selenate structural elements.     

纳米片钠铝石结构KAl(OH)2CO3的水热合成

用水热法制备出了纳米级粒径的纤维状KAl(OH)2CO3,并研究了不同水热反应条件对KAl(OH)2CO3的形成、颗粒度以及形态的影响.研究表明,不同条件下合成的晶粒均呈纤维状,随着温度的升高,长度和粒径均有所增大.在120℃制备得到的纤维平均直径为30nm,且分布均匀;KHCO3和Al(OH)3之比对KAl(OH)2CO3的形貌有显著的影响,KHCO3用量越大,晶粒直径越细;随着介质碱性的增强,晶粒直径在pH为9.5时出现极小值,且粉体的均匀性最好.在特定的反应体系中,当反应时间达到2h后,合成反应基本达到平衡,进一步延长合成时间对粉体的形貌和颗粒尺寸没有明显的影响.