Synthesis of nanocomposite, (CdxZn1-x)S by gamma-irradiation in an aqueous system

Gamma-irradiation has been applied to synthesize the nanocomposite semiconductor constituted of zinc and cadmium sulfide Cd_1-xZn_xS ultra fine particles at room temperature by utilizing homogeneous release of S^2– ions from the decomposition of sodium thiosulfate. The structure, morphology, size and optical properties of that compound have been studied by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible spectrometer (UV-visible). The product obtained from irradiated solutions containing zinc ions, cadmium ions and the sulfur source has been characterized as a composite of (Cd_xZn_1-x)S, with spherical morphology and with a diameter of average size of about 5.3 nm. The possible mechanism of formation of the composite is proposed.The financial support of Shanghai Science and Technology Foundation through No. 0252nm 095 is gratefully acknowledged.The authors would thank the staff of Shanghai Applied Radiation Institute of Shanghai University for their valuable contributions.     

Li2+2xZn1-xSiO4水基溶胶-凝胶法合成及其离子导电性

用水基溶胶凝胶法制备了锂离子导体Li_2+2xZn_1-xSiO₄(0≤x≤0.5)。实验中对干凝胶的热稳定性进行了TG-DTG分析。XRD谱结果表明形成了与Li₃PO₄结构相关的固溶体Li_2+2xZn_1-xSiO₄。TEM结果则显示晶粒尺寸为50nm左右,并应用交流阻抗谱技术进行了样品烧结体的电性能测试。     

Networks of icosahedra in the sodium-zinc-stannides Na16Zn13.54Sn13.46(5), Na22Zn20Sn19(1), and Na34Zn66Sn38(1)

The three new ternary phases Na₁₆Zn_13.54Sn_13.46(5) (I), Na₂₂Zn₂₀Sn₁₉₍₁₎ (II), and Na₃₄Zn₆₆Sn₃₈₍₁₎ (III) were obtained by direct fusion of the pure elements and characterized by single crystal X-ray diffraction experiments: I, Ibam, Z=8, a=27.401(1), b=16.100(1), c=18.431(1) Å, R₁/wR₂ (all data)=0.051/0.088; II, Pnma, Z=4, a=16.403(1), b=15.598(1), c=22.655(6) Å, R₁/wR₂ (all data)=0.038/0.071; III, R3¯m, Z=3, a=16.956(1), c=36.861(1) Å, R₁/wR₂ (all data)=0.045/0.092. The structures consist of complex 3D cluster networks made of Zn and Sn atoms with the common motif of Kagomé nets of icosahedra. Additionally to the new heteroatomic {Zn_12−xSn_x} icosahedra that are omnipresent, triangular units, cages, and pairs of triply fused icosahedra fill the cavities of the Kagomé nets in compounds I, II, and III, respectively. Whereas I crystallizes in a new structure type, II and III have structural analogs in trielide chemistry. All three compounds closely approach the electron numbers expected for valence compounds according to the extended 8-N rule. The concept of achieving an isovalent situation to triel elements by combination of electron poorer and richer elements and the readily mixing of Zn and Sn allow the formation of icosahedral and triangular clusters without the participation of a group 13 element.     

Ce1-xCaxO2-x的溶胶-凝胶法的合成及其性质

固体电解质;氧离子导体;Ce1-xCaxO2-x的溶胶-凝胶法的合成及其性质     

Synthesis of 5S,12S - diHETE (LTBx)

The total synthesis of 5S, 12S-diHETE (LTB_x) was completed. The Wittig reaction of phosphorane 8 and chiral aldehyde 9 provided the key step to from the C-20 chain.     

低温合成超导体Ba1-xKxBiO3

先以BaCO₃和Bi₂O₃为原料由传统的固相反应制备纯BaBiO₃,然后在低温下将用KOH-KF熔盐处理这样的拓扑反应合成了Ba_1-xK_xBiO₃超导体. 所有样品均进行了粉末X射线衍射（XRD）和磁性表征. XRD结果表明,所得Ba_1-xK_xBiO₃样品均为纯相,且均可用赝立方晶胞指标化. 磁性测量表明所有样品具有超导电性,最高超导转变温度（T_c）为30.6 K. 讨论了反应时间、前驱体与熔盐质量比对超导转变温度的影响. 最佳的反应条件为：反应温度450 ℃,反应时间4 h,BaBiO₃：KOH：KF质量比1：5：2.5.     

Synthesis, structure and dielectric properties of Ba1-xSrxMyTi1-yO3 (M = Zr, Sn)

A series of Ba_1-xSr_xM_yTi_1-yO₃ (M = Zr, Sn, 0⩽x⩽0.4, 0⩽y⩽0.3) solid solutions were synthesized with the soft chemical method below 100 °C. XRD pattern and cell parameters-composition figures of the prepared powder demonstrate that they are completely miscible solid solutions based on BaTiO₃. Furthermore, TEM shows that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of the powder doped with Sr²+and Zr⁴⁺ or Sn⁴⁺ have dielectric constant eight times higher and dielectric loss thirty per cent lower than those of pure BaTiO₃ phase at room temperature.     

(ZrO2)1-x(Yb2O3)x纳米晶的水热法合成及其烧结体的电性能

(ZrO₂)_1-x(Yb₂O₃)_x (x=0.07, 0.09, 0.11) nanocrystallites were hydrothermally prepared in basic media by using co-precipitated Zr(OH)₄ and Yb(OH)₃ as precursor. The nanocrystallites have small particle sizes of 5.8~7.5 nm, narrow size distribution, less agglomeration and high sinterability. The oxide-ionic conduction properties of the prepared ceramics were investigated by means of AC impedance spectroscope, oxygen concentration cell at 600~1 000 ℃. The results show that the ceramic with x=0.09 is superior to the ceramics with x=0.07 and 0.11 in oxide-ionic conduction.     

Ba1-xSrxTi1-yMyO3固溶体的湿化学法合成与介电特性

A series of Ba_1-xSr_xTi_1-yM_yO₃ (M=Zr,Sn, 0≤ x≤ 0.5,0≤ y≤ 0.3) solid solutions were synthesized by chemical method at below 100℃ . XRD and cell parameters component figures of the series of the solid solutions powder demonstrated that the compounds are mutually miscible in the solid solutions. The particls size is about 70nm with spherical shape and uniform distribution. The result of preparing ceramics showed that after adulterating with Sr²⁺ and Zr⁴⁺ or Sn⁴⁺ in pure BaTiO₃ phase, the dielectric constant increased eight times while the dielectric loss decreased three times at room temperature.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

Preparation of MnxNi0.5-xZn0.5Fe2O4 Nanorods by the Co-precipitation Method

Mn_xNi_0:5-xZn_0:5Fe₂O₄ nanorods were successfully synthesized by the thermal treatment of rod-like precursors that were fabricated by the co-precipitation of Mn²⁺, Ni²⁺, and Fe²⁺ in the lye. The phase, morphology, and particle diameter were examined by the X-ray diffrac-tion and transmission electron microscopy. The magnetic properties of the samples were stud-ied using a vibrating sample magnetometer. The results indicated that pure Ni_0:5Zn_0:5Fe₂O₄ nanorods with a diameter of 35 nm and an aspect ratio of 15 were prepared. It was found that the diameter of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ (0≤x≤0.5) samples increased, the length and the aspect ratio decreased, with an increase in x value. When x=0.5, the diameter and the aspect ratio of the sample reached up to 50 nm and 7～8, respectively. The coercivity of the samples first increased and then decreased with the increase in the x value. The coer-civity of the samples again increased when the x value was higher than 0.4. When x=0.5,the coercivity of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ sample reached the maximal value (134.3 Oe)at the calcination temperature of 600 oC. The saturation magnetization of the samples first increased and then decreased with the increase in the x value. When x=0.2, the satura-tion magnetization of the sample reached the maximal value (68.5 emu/g) at the calcination temperature of 800 oC.     

Structural and Magnetic Properties of Bi(Fe1-xMnx)O3

Bi(Fe_1-xMnx)O₃ bulk ceramics with Mn concentration x up to 0.3 were prepared by rapid sintering using sol-gel derived fine powders. Structure transformation is found to depend on the Mn doping concentration by X-ray diffraction and Raman spectroscopy. Bi(Fe_1-xMnx)O₃ maintains the rhombohedral structure of BiFeO3 with x=0.05 and 0.1, but changes to the orthorhombic structure with x=0.3. Weak ferromagnetism is observed for Bi(Fe_1-xMnx)O₃ with x=0.05 and 0.1, but stronger paramagnetism is observed for Bi(Fe_1-xMnx)O₃ with x=0.3 indicating a magnetic phase change from antiferromagnetic to paramagnetic with the structure changing from R3c to C222. Two anomalies at 30 and 140 K are observed for Bi(Fe_1-xMnx)O₃ with x=0.05 and 0.1. The anomaly at 30 K is concluded to be related to the freezing of cluster spin glass from dc magnetic memory and relaxation measurements.     

Enantioselective Synthesis of (1R,2S) and (1S,2S) Dehydrocoronamic Acids

Thanks to the successive use of two esterases with different regioselectivities and conventional organic chemistry we have synthesized (1R,2S) and (1S,2S) dehydrocoronamic acids.     

(Ce0.9Nd0.1)1-xMoxO2-δ (0.00≤x≤0.10)的合成、表征与电性能

采用溶胶-凝胶法合成(Ce0.9Nd0.1)1-xMoxO2-δ(x=0.00、0.02、0.05、0.10)氧化物, 通过X射线衍射(XRD)、场发射扫描电镜(FESEM)等手段对氧化物进行结构表征, 交流阻抗谱测试电性能. 结果表明: 所有样品均为单一萤石立方结构; 少量MoO3的加入提高了材料的致密性, 降低了材料的总电阻、晶界电阻和晶界电阻在总电阻中所占比例, 提高了材料的电导率. 1200 ℃烧结样品24 h, 测试温度700 ℃时, (Ce0.9Nd0.1)1-xMoxO2-δ(x=0.00)总电导率和晶界电导率分别为0.05和0.19 S·m-1, 掺Mo材料(Ce0.9Nd0.1)1-xMoxO2-δ(x=0.02)的总电导率和晶界电导率分别为2.42 和3.96 S·m-1.     

AgGa(S1-xSex)2固溶体的电子结构和光学性质

采用基于赝势平面波基组的密度泛函理论方法, 对一系列具有黄铜矿结构的AgGa(S_1-xSe_x)₂固溶体的构型、电子结构、线性和二阶非线性光学性质进行了系统研究. 结果表明, 各固溶体具有类似的能带结构, 体系带隙随x值增加而逐渐减小. 当所引入的Hartree-Fock交换项贡献为22.56%时, 对应的杂化PBE泛函得到的带隙值与实验结果相近. 固溶体的各种光学性质, 包括折射率、双折射率、反射率、吸收系数和二阶倍频系数等均随着组成的改变呈现出有规律的变化趋势, 变化范围介于AgGaS₂和AgGaSe₂二者之间. 因此, 利用固溶体光学性质的变化规律, 可从中寻找出具有特定光学性能的晶体材料.     

金属间化合物Y（Fe1—xCox）11.3Nb0.7的磁性能机制研究

通过X射线衍射和磁笥测量方法研究了金属间化合物Y（Fe1-xCox)11.3Nb0.7（x=0,0.05,0.10,0.20）的结构与磁性能。粉末样品的X射线衍射和热磁曲线测量表明,所有Y（Fe1-xCox)11.3Nb0.7（x=0,0.05,0.10,0.20）化合物具有ThMn12型结构,具有良好的单相性,Co替代Fe引起居里温度显著提高和晶格常数的单调减小,室温下的饱和磁化强度M。随Co含量的增加在x=0.1-0.2之间呈现极大值,各向异性场Ba随x的增加,先增加而后减小。     

(CeO2)x-(La-Al2O3)1-x复合氧化物对柴油车尾气中可溶性有机成分的催化氧化

采用共沉淀法制备了一系列(CeO₂)_x-(La-Al₂O₃)_1-x复合氧化物(其中x为质量分数, x=0.00, 0.25, 0.50, 0.75, 1.00), 以其为催化剂. 采用热重-差热分析(TG-DTA)法模拟测试该系列催化剂对柴油车尾气中可溶性有机成分(SOF)的催化氧化性能. 结果表明, 当x=0.75时, 催化剂活性最高, 可使SOF在125℃起燃, 355℃完全转化. 并用低温N₂吸附-脱附, 储氧量(OSC)测试, X射线衍射(XRD), X射线光电子能谱(XPS)和H₂程序升温还原(H₂-TPR)等手段对催化剂进行了表征. 研究结果表明, 适量La 和Al 共掺杂增大了氧化铈的比表面积和催化剂中Ce³⁺所占的比例, 从而提高了催化剂对SOF的低温吸附能力和催化剂的储释放氧能力, 因而提高了催化剂对SOF的氧化活性. 所制备的(CeO₂)_0.75-(La-Al₂O₃)_0.25复合氧化物适合应用到柴油车尾气净化催化剂中.     

Synthesis of nanocrystalline zinc sulfide in a non-aqueous system by gamma-irradiation

Summary Gamma-irradiation has been applied to synthesize nanocrystalline ZnS with average size of 38 nm in a non-aqueous system at room temperature by utilizing homogeneous release of S^2- ions from the decomposition of carbon disulfide under γ-irradiation. The structure, morphology, size and optical properties have been studied by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectrometer (UV-visible). The product containing zinc ions and the sulfur source has been characterized as β-ZnS, sphalerite phase, with spherical morphology and with a diameter average size of about 38 nm.The possible mechanism of formation of the product is suggested in accord with the experiment.     

Synthesis and characterization of poly(vinyl phosphonic acid) (PVPA)-Fe3O4 nanocomposite

Poly(vinyl phosphonic acid) (PVPA)-Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of PVPA. Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA and conductivity measurements respectively. The capping of PVPA around the Fe₃O₄ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the phosphate and the nanoparticle surface. The crystallite and particle size were obtained as 6 ± 2 and 8.7 ± 0.1 nm from XRD line profile fitting and TEM image analysis respectively, which reveal nearly single crystalline nature of the Fe₃O₄ nanoparticles. Magnetic characterization of the bulk magnetite and (PVPA)-Fe₃O₄ nanocomposite reveals that both are in the superparamagnetic state at room temperature. The average magnetic domain size of the nanoparticles has been calculated using the Langevin function, which was fitted to the measured M-H hysteresis curves as 7.6 nm for the nanocomposite. In the nanocomposite, the reduction is due to the adsorption of PVPA onto the magnetite surface, which cancels some of the free spins at the surface causing a magnetically dead layer. Analysis of the conductivity and permittivity measurements revealed the coupling of ionic and polymer segmental motions and strong temperature dependency in the nanocomposite.