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％.     

TiO2/P3HT纳米复合材料光催化降解甲基橙的动力学研究

用化学氧化聚合法制备了导电聚合物聚3-己基噻吩(P3HT).用聚3-己基噻吩改性纳米二氧化钛,合成TiO2/P3HT纳米复合微粒.对其光催化降解甲基橙的反应动力学进行了分析,测定了反应的表观活化能.结果表明,纯纳米TiO2和TiO2/P3HT纳米复合微粒光催化降解甲基橙的反应均为一级反应;纳米TiO2经聚3-己基噻吩(P3HT)修饰后在可见光下的光催化活性得到提高,且提高降解温度有利于提高甲基橙的降解率,纳米TiO2经P3HT修饰后降解甲基橙的表观活化能由23.44 KJ/mol下降到19.36 kJ/mol.     

氟改性TiO2的制备及光催化性能研究

以钛酸丁酯为钛源,氟化铵为氟源,采用溶胶凝胶法制备氟改性二氧化钛光催化剂,并用扫描电镜(SEM)、X射线衍射(XRD)、紫外可见光分度计(UV-Vis)、X射线光电子能谱(XPS)、光致发光荧光光谱仪(PL)、氮气吸附-脱附等方法对样品进行表征.以甲基橙(MO)为模拟污水,研究其光催化活性.结果 表明:F改性TiO2为纳米锐钛矿相,比表面积为141 m2/g.F以化学吸附态存在于TiO2的表面,形成(=)Ti-F基团,F的加入使得TiO2的吸收带边发生了红移,在甲基橙浓度为20 mg/L,紫外光照射时间为80 min时,F改性TiO2的脱色率最大达到了97;,具有较高的光催化活性.     

MoO3/TiO2复合催化剂的制备及光活性

以商业锐钛矿TiO2和钼酸铵水溶液作为前驱体,利用浸渍-焙烧的方法制备了MoO3与TiO2不同质量比率的MoO3/TiO2复合光催化剂.采用X射线衍射、高分辨透射电镜和紫外-可见漫反射对其进行了表征.以甲基橙为光催化反应的模型化合物,评价了其紫外光催化活性和MoO3/TiO2复合光催化剂的紫外产氢活性.通过添加各种自由基清除剂研究了甲基橙在光催化反应过程中的活性物种.结果表明:与纯的MoO3和TiO2相比,20; MoOJTiO2光催化剂在400 ～ 700 nm区域具有更强的光吸收性能并且吸收带边向长波方向移动.在所有MoO3/TiO2样品中,20; MoO3/TiO2光催化剂具有最高的紫外光活性.·OH,h+,·O2-和H2O2,特别是h+,共同支配了甲基橙的光催化降解过程.     

镧掺杂混晶结构TiO2纳米粉体的制备及其光催化性能

以钛酸四丁酯为Ti源,采用溶胶-凝胶自蔓燃法制备了镧掺杂的La-TiO2(简写为LT)纳米粉体.利用X射线粉末衍射(XRD)、红外光谱(FIIR)、透射电子显微镜(TEM)等对掺杂型TiO2粉体的晶型结构与颗粒尺寸等进行表征.利用紫外-可见光吸收光谱(UV-vis)研究了H2O2改性、镧掺杂量以及混晶结构对TiO2纳米粉体降解甲基橙的影响.结果表明:镧掺杂混晶TiO2粉体的光催化活性明显优于未掺杂的锐钛矿TiO2粉体.当La3+掺杂量为0.5;,合成温度为475℃(金红石相含量为26.0;)时,得到的TiO2粉体光催化活性最好.H2O2的加入有助于TiO2光催化剂表面的电子-空穴对生成,提高光催化剂对甲基橙的降解率,当H2O2浓度为6;时,光照3h后,降解率达到了91.97;.     

Ce掺杂TiO2纳米粉体的制备及其光催化性能研究

以钛酸丁酯为前驱体,冰醋酸为螫合剂,以硝酸铈为掺杂剂,采用溶胶.凝胶法制备了铈掺杂TiO2纳米粉体.研究了铈掺杂对TiO2相组成和晶粒尺寸的影响及不同掺杂量对TiO2光催化活性的影响,确定了Ce的最佳掺杂量.结果表明:Ce掺杂缩小了TiO2的锐钛矿相→金红石相(A→R)的相变温区范围,抑制了TiO2的晶粒增长.热处理温度升高,二氧化钛的比表面积下降.掺杂适量的铈提高了TiO2的光催化活性,Ce掺杂为0.05;摩尔分数时Ce-TiO2的光催化活性达到最佳,甲基橙降解率可达90;左右.     

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;.     

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℃.     

Ag/TiO2的制备及光催化性能研究

以钛酸丁酯为钛源,采用溶胶-凝胶法制备了Ag掺杂纳米TiO2,结合XRD、TEM、Uv-vis等测试手段,对样品的结构和性能进行了表征.以甲基橙溶液为目标降解物,探讨了Ag掺杂纳米TiO2的光催化活性,分析了Ag掺杂纳米TiO2提高光催化性能的机理.结果表明,Ag掺杂使TiO2晶粒减小,拓展了TiO2的光谱响应范围,降低了光生电子和空穴的复合几率;Ag掺杂后,TiO2光催化剂的吸收光谱向可见光区发生红移.Ag掺杂量为n(Ag)∶n(TiO2)=0.08;,紫外光下240 min,Ag掺杂纳米TiO2前后材料对甲基橙溶液去除率由60.3;提高到83.1;.     

TiO2/α-Fe2O3和TiO2/叶FeOOH纳米复合材料的制备与表征

以TiCl4为前驱体,α- Fe2O3、α-FeOOH为载体,采用水解沉淀法制备TiO2/α-Fe2O3和TiO2/α-FeOOH两种纳米复合光催化材料.采用X射线衍射分析(XRD)和透射电子显微镜(TEM)等对样品的晶相组成、形貌和微结构进行表征.结果表明,TiO2/α-Fe2O3复合材料由赤铁矿和金红石相TiO2组成;TiO2/α-FeOOH复合材料由水合氧化铁和金红石相TiO2组成.TiO2/α-Fe2O3复合材料中颗粒状TiO2能包覆在粒状氧化铁红表面,形成厚度范围在5～20 nm左右的薄层;TiO2/α-FeOOH复合材料是一种核壳结构,厚度范围在100～150 nm的针状TiO2聚集体为壳,能完整的包覆核层氧化铁黄.采用UV-vis光谱和甲基橙降解对其光催化活性进行评价,结果表明纳米TiO2与α-Fe2O3、α-FeOOH分别构成复合材料后,两者之间存在协同效应.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.     

Optical properties of the germanate melilites Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7

Refractive indices and their dispersion in the wavelength range from 365 nm to 2325 nm and transmission ranges of the tetragonal melilite‐type germanates Sr₂MgGe₂O₇, Sr₂ZnGe₂O₇ and Ba₂ZnGe₂O₇ were determined. The uniaxial positive crystals Sr₂MgGe₂O₇ and Ba₂ZnGe₂O₇ both offer the possibility for phase matched second harmonic generation, a detailed analysis of phase matching conditions is given. The refractive indices of Sr₂ZnGe₂O₇ show an isoindex (isotropic) point at 467 nm. The investigation was performed on Czochralski grown large single crystals. The crystal structure of all three germanates were determined by means of X ‐ray diffraction. The results corroborate unmodulated melilite‐type structures at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate, [C6H5CH2CHCH2CH2NH2CH2CH2]2HPO4·5H2O

The salt bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate is orthorhombic with the following unit cell dimensions: a = 11.235(2) Å, b = 27.924(6) Å, c = 9.321(4) Å space group Pca2₁ with Z = 4. The structure was solved by the Patterson method and refined to final R value of 0.049 for 1802 independent reflections. The flack parameter is 0.14 with an e.s.d. of 0.23. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O—H,...,O and N—H,...,O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical Properties of MnIn2S2Se2 Single Crystals

Optical transmittance and reflectance spectra of MnIn₂S₂Se₂ single crystals are measured in the wavelength range from 0.5 to 30 μm. The interference method is used to determine the refractive index of the compound for wavelengths between 0.8 and 12 μm. From an analysis of the absorption spectrum it follows that the fundamental edge is due to forbidden indirect transitions between parabolic bands for the polarization E ⊥ c with a gap energy of 1.50 eV at room temperature.     

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.