原料配比对水热法合成纳米MnO2晶型及电化学性能的影响

本文采用水热法,通过调节高锰酸钾(KMnO4)和硫酸锰(MnSO4)原料配比控制MnO2的晶体结构和形貌.当KMno4与MnSO4物质的量比为6∶1时,制备出由纳米片构成的球形δ-MnO2,形似海胆,直径约为0.5-1μm;当两者物质的量比2∶3时,所得α-MnO2纳米线粗细均匀,直径约为30 ～50 nm,长度为1 μm;当两者物质的量比减小到1∶3时,则合成出直径约为50 ～ 100 nm,长度为2～4 μm的短棒状β-MnO2.采用循环伏安法和恒电流充放电法对上述电极材料进行电化学性能研究,结果表明海胆状δ-MnO2具有优良的超电容性能,1 A/g充放电时,其放电比电容为162 F/g,远高于α-MnO2(62F/g)纳米线和棒状β-MnO2(8 F/g)的比电容.     

KMnO4与醇类有机物制备MnOOH的研究

在140℃的条件下,用KMnO4分别与甲醇、乙醇、丙醇、丁醇、乙二醇、1,3-丙二醇以及1,4-丁二醇进行水热反应24 h。采用X射线粉末衍射(XRD)与环境扫描电子显微镜(SEM)对反应产物进行表征。结果表明,KMnO4与乙醇、丙醇、丁醇以及1,4-丁二醇反应均可以得到较纯的棒状MnOOH晶体。KMnO4与甲醇、1,3-丙二醇反应不仅得到了MnOOH晶体并且也得到Mn3O4晶体,而与乙二醇的反应只得到了Mn3O4晶体。并简单探讨了形成这种规律的原因。     

酸度控制的不同MnO2的水热制备及电化学性能

以KMnO4为锰源、CO(NH2)2为还原剂,通过水热反应制备MnO2,考察了体系酸度对产物结构和形貌的影响,应用X-射线衍射、扫描电镜和N2吸-脱附技术对产物进行表征.结果表明,在0～1 mol/L H2 SO4溶液中,制备了颗粒状、球形、纤维状和海胆状MnO2,前两种MnO2为层状结构,后两种MnO2具有隧道结构.海胆状MnO2的比表面积高达95 m2/g.电化学测试结果显示,在0.1 A/g的电流密度下,海胆状MnO2首次放电比容量达到1318.8 mAh/g.恒流充放电140次后,容量保持率为74;.     

熔盐热法制备ZnWO4纳米晶及其光催化性能

以Na2WO4·2H2O,Zn(NO3)2·6H2O为原料,LiNO3,NaNO3为熔盐介质,采用熔盐热法合成了ZnWO4纳米晶材料,对其相结构和纳米晶生长动力学进行了表征,对比传统水热法,研究了熔盐热剂与水溶剂两种介质类型对纳米晶形貌和光催化活性的影响.结果表明,晶体生长介质对ZnWO4纳米晶形貌会产生重要影响.采用熔盐热法在反应温度为180℃,保温时间为8 h条件下合成了形貌规则,分布均匀的四方板块层状等轴ZnWO4纳米粉体,晶粒尺寸在20～40 nm之间;在相同反应条件下,水热合成的纳米晶为棒状结构,其直径约25 nm,长度在100～200 nm之间;ZnWO4纳米晶的晶体完整度和晶体形貌对其光催化活性会产生重要影响,晶体发育完整的ZnWO4纳米晶具有更高的活性;在晶体发育完整的前提下,粉体的比表面积越大,相应的光催化活性也越高.     

棒状MnPO4·H2O单晶的生长及其形成机理研究

以MnCl2,NaNO3和H3PO4为原料,在温度为150℃的水热条件下反应12 h制备出了棒状MnPO4·H2O单晶.利用X射线粉末衍射(XRD)、场发射扫描电镜(FESEM)和透射电子显微镜等手段对产物进行表征.结果表明,合成的产物为MnPO4·H2O单晶棒,直径为0.78～1.9 μm,长度达几十微米.讨论了水热条件下反应时间对产物形貌的影响,并对棒状MnPO4·H2O单晶的生长机理进行了分析.     

微波法合成纳米MnO_2及其电化学性能研究

采用微波法制备了不同形貌的MnO2纳米粉体。通过X射线衍射、扫描电子显微镜对MnO2的微观结构和形貌进行了表征。结果表明:制备的MnO2为α-MnO2和γ-MnO2的混晶,随着微波反应时间的增加,其形状由花瓣状过渡为棒状,并且其晶型越来越完整。电化学测试结果表明,合成的MnO2在2 mol/L的(NH4)2SO4中具有较好的电化学性能,在2 mA/cm2的电流下放电时的比容量为240 F/g。     

磁性Fe3O4六方片状晶体和单晶纳米棒的水热合成

本文分别以FeSO4·7H2O、(NH4)2Fe(SO4)2·6H2O和NaOH、NH3·H2O为原料,以KClO4与KNO3为氧化剂,采用水热合成法分别合成出Fe3O4六角片状晶体和单晶纳米棒.产物分别用X射线衍射仪(XRD)谱图、透射电子显微镜(TEM)、选区电子衍射(SAED)谱图以及磁滞回线图谱加以表征.结果表明,反应物原料及氧化剂的选择对Fe3O4单晶的制备及其形态的影响至关重要.反应温度控制在110℃,时间为14h.室温下,Fe3O4六方片状晶体和单晶纳米棒的磁化率(Ms)和矫顽力(Hc)均有所区别.     

棒状MnPO4·H2O单晶的生长及其形成机理研究

以MnCl2,NaNO3和H3PO4为原料,在温度为150℃的水热条件下反应12h制备出了棒状MnPO4·H2O单晶。利用X射线粉末衍射（XRD）、场发射扫描电镜（FESEM）和透射电子显微镜等手段对产物进行表征。结果表明,合成的产物为MnPO4.H2O单晶棒,直径为0.78～1.9μm,长度达几十微米。讨论了水热条件下反应时间对产物形貌的影响,并对棒状MnPO4.H2O单晶的生长机理进行了分析。     

锐钛矿相TiO2纳米棒状晶体的水热合成

以TiCl3为前驱物,在前驱物中添加一定的钛酸钠纳米管,在水热条件下,合成了锐钛矿相TiO2纳米晶体.其工艺参数为:1.0 mol/L KF为矿化剂,填充度为68;,150 ℃恒温保持24 h.生成的晶体形貌为块状.当添加经400 ℃烧结过的钛酸纳米管时,合成了棒状锐钛矿晶体,晶体直径约为10 nm,长度约为30～100 nm,最大长径比约为5:1.研究了在前驱物中添加不同的纳米管时对生成物的影响.     

TiCl3水热合成纯金红相和锐钛相TiO2纳米晶体

本文采用水热法,以TiCl3为前驱物,在180℃反应24h,合成了金红相纳米TiO2棒状晶体,晶体直径为50~100nm,长度为100~200nm。当添加10mol/L NaCl作矿化剂时,晶体长度达到600~800nm。当溶液中添加KF浓度为0.05mol/L时,生成物仍为金红相,晶体直径约为50nm,长度约为100nm。当溶液中添加KF浓度为0.7mol/L时,生成纯锐钛相纳米TiO2,晶体颗粒均匀,呈四方形,边长100nm左右。当KF浓度为1mol/L时,生成物仍为锐钛相,但晶体边长降为50nm左右。实验结果表明氟离子对锐钛相的形成有很强的诱导作用。     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Photoluminescence characteristics of Mg- and Si-doped GaN thin films grown by MOCVD technique

We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains.     

Solubility of Ag2O into the Na2O–B2O3–Al2O3 system

The solubility of Ag₂O was measured for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag₂O for the Na₂O–B₂O₃ system above the melting point of Ag for the first time. It was found that the addition of Na₂O decreases the solubility of Ag₂O while the addition of Al₂O₃ had little effect on the solubility. The effect of Na₂O and Al₂O₃ on the solubility of Ag₂O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag₂O in Na₂O–B₂O₃–Al₂O₃ melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver.     

Considerations on the structure and physical properties of B2O3-SiO2 and GeO2-SiO2 glasses

Data of density, refractive index and thermal expansion coefficient for B₂O₃-SiO₂ and GeO_2-SiO₂ glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B₂O₃, GeO₂ and SiO₂. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO₃, GeO₄ and SiO₄ units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B₂O₃ or GeO₂ in the concerned glasses.     

Molecular structure and crystal packing of uncomplexed 1,6-bis(N-cyano-p-methoxy-anilino)-2,4-hexadiyne, C22H18N4O2

The X-ray crystal structure of 1,6-bis(N-cyano-p-methoxy-anilino)-2,4-hexadiyne, C₂₂H₁₈N₄O₂, is determined. The crystal packing is dominated by phenyl stacking interactions. Weak C–H···N hydrogen bonds help align the molecules. C–H··· hydrogen bonding is not apparent.     

Structural and electrical properties of vapour phase grown Cd1 − xFexTe single crystals

Cd_1 − xFe_xTe single crystals were prepared by vapour phase growth method in the composition range of 0 ≤ x ≤ 0.03. Chemical analysis, surface morphology, structural investigations and electrical properties were carried out by EDAX, SEM, XRD, TEM and transport technique, respectively. Microscopic variations between the target and actual compositions were noticed. Morphology studies revealed that dislocation aided growth is active in the present crystals. TEM and XRD studies confirmed that the samples of all compositions crystallized in zinc blende structure, and the lattice parameters varied almost linearly decreases with Fe content. At room temperature, the resistivity of the Cd_1 − xFe_xTe crystals of all compositions (x = 0.01, 0.015, 0.02, 0.025 and 0.03) lies in the range of 3.5-6.5 M Ω, the activation energies lie in the range of 63-133 meV, and the samples were show the ‘p’ type conductivity.     

空位浓度对纤锌矿CdS电子结构和光学性质影响的第一性原理研究

本文基于密度泛函理论的平面波超软赝势方法,采用第一性原理研究了含Cd空位缺陷CdS和含S空位缺陷纤锌矿CdS的几何结构、能带结构、电子态密度及光学性质。通过计算分析可知,含Cd空位缺陷的CdS体系均为p型半导体,含S空位缺陷的CdS体系跃迁方式均由直接跃迁变为间接跃迁。Cd、S空位缺陷的CdS体系的态密度总能量降低。空位CdS体系相较于本征CdS体系的静介电常数均有提高,并随着空位浓度的增大而增大,Cd空位缺陷体系更为明显,极化能力得到显著提升。空位Cd的CdS体系相较于本征CdS体系在红外波段存在明显的吸收,空位S的CdS体系相较于本征CdS体系在可见光波段存在明显的吸收。