爆轰法合成超小TiO2的光催化性能分析

颗粒尺寸是影响TiO2光催化活性的重要因素,颗粒越小其光催化效率越高.在密闭的反应釜内引爆用含钛前驱体、硝酸铵、黑索金与一定量的聚苯乙烯小球制备的浆状混合炸药制备了超小的TiO2纳米颗粒.研究了炸药配比对TiO2的形貌、分散性、颗粒尺寸的影响,并通过降解甲基橙溶液表征超小TiO2的光催化性能.结果发现:制备的TiO2由金红石相与锐钛矿相组成,大部分颗粒呈球形或不规则四边形,尺寸在10nm左右,少量颗粒尺寸大于20nm,结晶度较好.炸药配比对TiO2的结晶度、颗粒大小、分散性等有较大影响.TiO2的禁带宽度在2.8eV左右,低于锐钛矿相与金红石相的禁带宽度,能够提高太阳光的利用率.爆轰制备的超小TiO2催化降解甲基橙溶液50min时,甲基橙的降解率为30;,明显高于爆轰法制备的颗粒较大的TiO2与铜粒子掺杂的纳米TiO2的光催化速率,光催化性能得到明显提高.     

(001)晶面主导的TiO2纳米片表面的F-对其光催化性能的影响

采用水热法以HF为晶面控制剂制备了TiO2纳米片,并用NaOH溶液对其处理,以甲基橙、甲基紫、罗丹明B和亚甲基蓝四种染料为降解对象,研究了处理前后TiO2纳米片的光催化性能并提出了机理.通过X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)等测试对处理前后TiO2纳米片的结构、形貌以及表面组成进行了表征.结果表明用NaOH溶液处理前后,样品均为边长24 nm、厚度6～7 nm、(001)晶面含量为84;的锐钛矿TiO2纳米片,但是处理后的样品表面F-、表面羟基和吸附水的数量都减少了,而且处理后样品的光催化活性降低.未经NaOH溶液处理的样品具有更高的光催化活性,归因于氟较氧更强的电负性可使TiO2表面吸附更多的水,促进了价带空穴对水的氧化,从而生成更多的羟基自由基.     

胶原纤维为模板制备Gd掺杂纤维状二氧化钛及光催化性能研究

以胶原为模板剂、硫酸钛为钛源、硝酸钆为掺杂源制备了钆掺杂纤维结构TiO2(Gd-TiO2).通过扫描电镜(SEM)、X射线衍射仪(XRD)、紫外可见漫反射光谱(UV-Vis-DRS)、X射线光电子能谱(XPS)对样品的表面形貌、晶相组成、紫外吸收带、元素组成及化合价态进行了分析.以甲基橙为目标降解物,研究了样品的光催化性能并确定钆的最佳掺杂量.结果表明:600℃煅烧温度下2;Gd-TiO2纤维结构完好、光催化效果最好,光反应30 min后其降解率达到91.89;,比起未掺杂试样大大提高.钆掺杂会改变TiO2的晶粒尺寸并能够抑制TiO2从锐钛矿相向金红石相转变,掺杂后紫外吸收带发生蓝移.     

热处理过程对纳米TiO2结构和性能的影响

以钛酸丁酯为钛源,采用溶胶-凝胶法制备纳米TiO2,结合TG-DTA,XRD,TEM等分析了不同热处理温度对纳米TiO2的晶型结构、晶粒粒径及微观形貌的影响.以甲基橙溶液为目标降解物,探讨了热处理温度对纳米TiO2光催化活性影响.利用Eastman的粒子生长理论对晶粒生长的动力学过程进行初步分析.研究表明:随着热处理温度升高,TiO2粒径逐渐从11.2 nm增大到78.6 nm;热处理温度为450～ 550℃时,纳米TiO2晶粒以锐钛矿为主,温度升至650℃时,出现了锐钛矿和金红石的混合相(质量比A∶R =9∶1),此时晶粒对甲基橙的降解率达到97.75;.而煅烧温度高于850℃后,TiO2几乎完全为金红石相,光催化活性显著下降.50;锐钛矿型TiO2转变金红石型TiO2的温度约为730℃,锐钛矿和金红石相晶粒表观活化能分别18.15 kJ/mol和42.56 kJ/mol;晶粒生长最快温度分别为546℃和1280℃.     

不同形貌的钨酸铋纳米材料的制备及其光催化性能

利用水热法通过调节溶液pH值和表面活性剂CTAB浓度制备了不同结构与形貌的钨酸铋纳米材料,用X射线衍射(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)等测试方法对产物进行了结构与形貌的表征,并研究了不同结构与形貌的钨酸铋样品对甲基橙的可见光催化降解性能.结果表明,在低pH值时样品为Bi2WO6相纳米片,随着pH值的增加,样品中出现了Bi3.84W0.16O6.24相八面体纳米颗粒,高pH值时,样品则为纯Bi3.84W0.16O6.24相八面体颗粒.随着表面活性剂浓度的增加,Bi2WO6纳米片有自组装的趋势,最终形成花瓣状结构.光催化甲基橙实验结果表明不同形貌的钨酸铋样品对甲基橙有不同的催化降解活性,片状Bi2WO6相纳米片高于Bi3.84W0.16O6.24相八面体颗粒.     

炭黑吸附水热法制备纳米TiO2粉体及其光催化降解甲基橙

利用炭黑吸附钛酸异丙酯水热法制得锐钛矿型TiO2纳米粉体.采用热重/差热分析(TG-DTA)、X-射线衍射(XRD)、扫描电镜(SEM)、比表面积吸附(BET)和紫外-可见光谱(Uv-vIS)等分析方法对不同煅烧机制下所得粉体的物相、颗粒度、分散性和光吸收性能进行表征.同时利用纳米TiO2粉体对甲基橙进行了光催化降解,研究了其光催化性能.结果表明,炭黑的吸附阻止了纳米TiO2超细颗粒的团聚和烧结,制得的颗粒分散均匀、具有单一锐钛矿晶型结构的TiO2纳米粉体.经500℃煅烧获得的TiO2粉体粒径约为15 nm,比表面积为76.31 g/m2.在紫外灯照射下,由于炭黑的吸附和纳米TiO2的光催化形成协同效应,甲基橙的光催化降解率在6min达到99;.     

表面活性剂辅助法制备纳米Z nO及光催化性能研究

以Zn(NO3)2·6H2 O、氨水和不同的表面活性剂为原料,采用沉淀法制备了具有不同微观形貌和尺寸的纳米ZnO,研究表面活性剂对纳米ZnO光催化降解甲基橙性能的影响.通过X射线衍射仪(XRD)、扫描电镜(SEM)和紫外可见分光光度计(UV-Vis)等对所制备纳米ZnO的物相、形貌及光吸收性能进行表征,并对其进行光催化性能测试.结果表明,以CTAB为表面活性剂所制备的纳米ZnO,粒径均匀、分散性良好、无明显团聚现象,并且对甲基橙的光催化降解性能最好,在2 h内降解率可达90.6;.     

水热法制备Nd3+-介孔TiO2/GO复合材料及光催化性能研究

采用水热法首先制备稀土Nd3+掺杂介孔TiO2,进而复合氧化石墨烯(GO)合成了系列Nd3+-介孔TiO2/GO复合材料.通过X射线衍射(XRD)、透射电镜(TEM)、孔结构分析(BJH与BET)、X射线光电子能谱(XPS)和紫外-可见漫反射(UV-vis)等测试手段对样品的微观结构、形貌、样品表面各元素价态及谱学性质进行表征,并以甲基橙模拟污染物测试其光催化性能.结果表明,所制样品均为锐钛矿结构TiO2,晶粒尺寸在3~4 nm之间;从UV-vis测试结果分析可知,与Nd3+-介孔TiO2和TiO2/GO相比,稀土Nd3+和GO的协同效应更能有效减小TiO2半导体禁带宽度,从而增加其对可见光的吸收.此外,不同光照射下光催化降解甲基橙的实验表明,所制备样品均有较强的紫外及可见光光催化性能,其中系列Nd3+-介孔TiO2/GO复合体系可见光光催化性能更为显著.     

TiO2-ZnTiO3纳米复合薄膜的制备及光催化性能

将ZnO粉末加入TiO2溶胶中制备出TiO2/ZnTiO3复合薄膜.利用X射线衍射仪、扫描电子显微镜、X射线光电子能谱、紫外-可见吸收光谱对其形貌、晶体结构、化学组成和光谱响应特征进行了表征.以亚甲基蓝(MB)溶液的脱色降解为模型反应,考察了不同ZnO掺入比例对复合薄膜光催化性能的影响.结果表明,所得材料的光催化性能与复合结构中TiO2的结晶结构有关.Ti/Zn=6∶1时,所得复合薄膜由锐钛矿相TiO2与钙钛矿相ZnTiO3构成,薄膜中晶粒尺寸较小(约为30 nm)、结晶度较高、催化性能最好.在紫外光下5h可使亚甲基蓝(MB)溶液脱色降解率达到94;,明显高于纯TiO2薄膜(87;).     

Ce/TiO2纳米管阵列的制备及光催化性能的研究

采用电化学阳极氧化法在钛表面制备TiO2纳米管阵列,并用稀土铈对其修饰改性.以甲基橙为目标降解物,考察了Ce3+溶液浓度、甲基橙溶液的初始浓度和初始pH对铈改性的TiO2纳米管光催化活性的影响.结果表明:Ce3+溶液的浓度存在一个最佳值,当Ce3+溶液浓度为0.01 mol/L,在10 mg/L,pH =3的甲基橙溶液中光催化活性最好.光照4h后,甲基橙的降解率达83％.     

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。