油水自组装制备Ag@AgCl/K_4Nb_6O_(17)及其光催化降解有机污染物的研究

在高温固相法制备K4Nb6O17的基础上,采用油水自组装合成复合光催化剂Ag@Ag Cl/K4Nb6O17,利用XRD、SEM、TEM、EDX、UV-Vis、PL、BET等多种手段对复合光催化剂的微观结构、形貌和性能进行了表征,并研究了可见光下降解亚甲基蓝(MB)的催化性能。研究表明,Ag@Ag Cl的粒径约为20 nm,均匀分散在二维层状结构K4Nb6O17的表面上;贵金属Ag纳米粒子的表面等离子体效应显著,对可见光的吸收范围从400 nm拓展到800 nm;Ag@Ag Cl(25%(质量分数))/K4Nb6O17在可见光照射60 min对亚甲基蓝的降解率为88.2%,远远高于单体Ag@Ag Cl和K4Nb6O17的活性。循环实验证明催化剂具有较好的稳定性,同时对苯酚和罗丹明B(Rh B)也具有一定的催化降解活性。淬灭实验表明自由基和空穴均为活性物种,并在此基础上提出降解机理。     

Porphyrin intercalation into a layered niobate derived from K4Nb6O17

The incorporation of guest species into two-dimensional inorganic structures can lead to materials with interesting chemical, catalytic, electronic, optical or mechanical properties. Concerning porphyrins and metalloporphyrins intercalation compounds, nanostructured materials have been obtained and evaluated in studies about photoprocess and catalytic reactions in confined media. The intercalation of bulky species such porphyrins into layered niobates is not easy to perform due to their high layer charge densities when compared to other layered materials. In this work we describe a method for TMPyP [5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H, 23H-porphyrin] intercalation into a layered niobate derived from K₄Nb₆O₁₇. The potassium precursor was converted into the acidic-exchanged form and then intercalated with n-butylamine to produce an expanded material that was later used in the production of a dispersion containing exfoliated niobate sheets. The niobate dispersion was dropped into a porphyrin solution originating an organic-inorganic hybrid composite of formula TMPyP_0.35H_0.6K₂Nb₆O₁₇·3H₂O. XRD data suggest a tilted arrangement of the TMPyP ring with respect to the layers. Spectroscopic data (uv-visible absorption, fluorescence and resonance Raman) showed that TMPyP is intercalated in a non protonated form and that the interaction with the niobate layers surface is weak, corroborating with the proposed tilted orientation in the interlayer region.     

Intercalation of substituted alkylammonium ions into layered potassium niobate K4Nb6O17

Substituted alkylammonium ions (protonated hydroxy amine and diamine) were intercalated into layered niobate K₄Nb₆O₁₇in order to introduce functional substituents into the interlayer spaces of the niobate. In the case of reaction with 3-hydroxypropylammonium ion, the intercalation compound incorporated the ammonium ions in a bilayer arrangement, by which the hydroxyl substituents were located in the middle of the interlayer spaces to form intermolecular hydrogen bonding. For the intercalation compounds with alkyldiammonium ions, the intercalated alkyldiammonium ions were present in monolayer and oriented transversally with respect to the niobate layers.     

K4Nb6O17光催化分解水产氢活性的研究

通过高温固相反应法合成了层状K4Nb6O17,采用X射线衍射、比表面积测定、扫描电镜等对K4Nb6O17进行了结构和形貌表征.在I-为电子给体、RuO2为助催化剂的情况下研究了RuO2的负载量、I-离子浓度和溶液pH值对K4Nb6O17光催化分解水产氢活性的影响.研究结果表明,表面负载RuO2可以显著提高K4Nb6O17光催化产氢速度.当I-浓度为15mmol/L,pH=9,RuO2负载量为0.7%时,约400nm紫外光辐射下K4Nb6O17光催化产氢的活性最佳,氢气生成的速度为798.9μmol/L·h.     

K2Ta2O6光催化剂的水热法制备及其光催化性能

以Ta2O5和KOH为原料采用水热法系统地制备了钽酸钾光催化剂。通过XRD、SEM、UV-Vis漫反射等测试手段对样品进行表征,探讨了反应时间、温度、KOH浓度等实验条件对结晶性能和形貌的影响。实验结果表明,水热温度为180℃,反应时间为24h,KOH浓度0.5mol/L条件下合成了结晶完善、粒径200nm左右的焦绿石相K2Ta2O6,其形貌是正八面体形;这种结构能有效地提高K2Ta2O6对藏红T溶液的光催化降解效率。     

Sm掺杂K_4Nb_6O_(17)的制备及其光催化性能

以KOH、Nb_2O_5和Sm(NO_3)_3为原料,采用水热合成法制备掺杂不同物质的量的Sm的片层状K_4Nb_6O_(17)光催化剂;采用X射线衍射、扫描电子显微镜、能量色散X射线光谱,高分辨率透射电子显微镜和X射线光电子能谱等测试技术对其结构和形貌进行表征,考察Sm掺杂K_4Nb_6O_(17)复合材料对有机染料罗丹明的降解性能。结果表明,Sm的掺杂提高了K_4Nb_6O_(17)的结晶度,Sm以Sm_2O_3的形式高度分散在K_4Nb_6O_(17)中;当Sm与Nb的物质的量比为0.01时,K_4Nb_6O_(17)具有最佳的光催化活性,在80 min内能使质量浓度为20 mg/L的罗丹明染料溶液100 mL完全脱色。     

NiFe2O4纳米粒子的水热合成及表征

以Ni(NO3)2·6H2O和Fe(NO3)3·9H2O为主要原料,在聚乙二醇(PEG)存在下,采用水热法制备了磁性NiFe2O4纳米粒子,用X射线衍射仪(XRD)、透射电子显微镜(TEM)和振动样品磁场计(VSM)等分析方法对样品进行了表征.结果表明:水热法合成的NiFe2O4纳米粒子为尖晶石结构,粒度分布均匀,为方形形貌,粒子直径范围在50～60nm;比饱和磁化强度为25.83emu/g,剩磁为6.167emu/g,矫顽力达85.87Oe.     

Ni、Co、Mn、Cu掺杂对K4 Nb6 O17光催化活性的影响

通过高温固相反应合成了铌酸盐K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 (5.0%mol)掺杂的K4Nb6O17并采用X射线衍射、紫外可见漫反射光谱、扫描电镜、比表面积分析等对其进行了结构和形貌表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 掺杂的K4Nb6O17作为催化剂在约400nm紫外辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因.     

Microwave synthesis and sintering of Mg4Nb2O9 nanoceramics

Mg₄Nb₂O₉ nanopowders were prepared from MgO and Nb₂O₅ mixtures by using a high energy ball milling method, combined with subsequent annealing at low temperatures by microwave heating. After milling for 20 h, pure phase Mg₄Nb₂O₉ nanopowders with an average grain size of 127 nm were obtained at 850, 130 °C lower than that required by a conventional solid state reaction process. Mg₄Nb₂O₉ ceramics sintered at a low temperature of 1,300 °C using microwave heating showed almost full density and excellent microwave dielectric properties (ε_r = 12.9, Q × f = 174,200 GHz and τ_f = ?68).     

Preparation and characterization of K-substituted NaCa4Nb5O17 microwave dielectric ceramics

The effect of K substitution for Na on the phase, microstructure and microwave dielectric properties of the Na_1?x K _x Ca₄Nb₅O₁₇ (x = 0–1) composition series was investigated. The compositions with x = 0, 0.5 and 1 formed single-phase Na_1?x K _x Ca₄Nb₅O₁₇ ceramics within the detection limit of the in-house XRD facility when sintered at 1,200–1,300 °C. At x = 0.25 and 0.75, the major Na_1?x K _x Ca₄Nb₅O₁₇ phase formed but along with a secondary CaNb₂O₆ phase. Relative permittivity (ε _r ) and temperature coefficient of resonant frequency (τ_f) increased from 45 to 51 and ?120 to +473 ppm/ °C respectively while the quality factor (Q × f _o ) decreased from 13,838 to 2,374 GHz with an increase in x from 0 to 1. Optimum microwave dielectric properties (i.e. ε _r  = 47, Q × f _o  = 5,047 GHz and τ_f = ? 23 ppm/ °C) were achieved for the x = 0.5 (i.e. Na_0.5K_0.5Ca₄Nb₅O₁₇) composition. Further investigations are required to improve the density and hence microwave dielectric properties of Na_1?x K _x Ca₄Nb₅O₁₇ ceramics.     

Hydrothermal synthesis and phase stability of CoNb2O6 with a rutile structure

CoNb₂O₆ was prepared by hydrothermal synthesis with polyvinyl alcohol as an additive. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to investigate the lattice parameters and the particle morphology. The products were observed as irregular particles with an average particle size of ca. 500 nm, which agglomerated from thin slices. Compared with the common columbite CoNb₂O₆, which was obtained by a traditional solid-state reaction, the product obtained by the hydrothermal method crystallized into a rutile structure. The rutile CoNb₂O₆ was metastable and it could transform into the columbite structure after calcining at 800 °C in air for 4 h.     

水热法制备花状纳米片簇Li4Ti5O12及其储锂性能

以氢氧化锂和钛酸四丁酯为原料,采用水热法制备出花状纳米片簇Li4Ti5O12粉体,研究了不同原料配比对产物晶体结构的影响。采用XRD、SEM对Li4Ti5O12的晶体结构和形貌进行了分析,结果表明所得产物是由Li4Ti5O12纳米片层组成的花状微球,所得晶体为尖晶石型结构。恒电流充放电实验表明,Li4Ti5O12在充放电倍率为0.1、1和2C下首次放电比容量分别为160、141和128mAh/g。     

花状Co3O4-NiO复合材料的水热合成及电化学性能

采用免模板水热法和500℃下的热处理过程制备了Co3O4-NiO复合材料.通过TG-DSC、XRD和SEM对复合材料的物相结构和形貌进行了表征,结果表明:复合材料中Co3O4和NiO的晶型分别为立方相和菱形结构,而且还具有特殊的花状结构.采用循环伏安、恒流充放电以及交流阻抗法测试了复合材料在6mol·L-1的KOH电解液中的电化学性能,结果表明:水热法制备的Co3O4-NiO复合材料具有很好的赝电容储能特性,比电容可达362.5F·g-1.     

Hydrothermal Synthesis of K2ZrSi6O15 , K2ZrSi3O9 , K2ZrSi2O7, and ZrSiO4 in the System KOH–ZrO2–SiO2–H2O

The phase relations in the KOH–ZrSiO₄–H₂O, KOH–ZrO₂(cr)–SiO₂–H₂O, and KOH–ZrO₂(nanocr)–SiO₂–H₂O systems were studied at 400°C, 0.1 GPa, and KOH concentrations from 2 to 46 wt %. The crystallization fields of K₂ZrSi₆O₁₅, K₂ZrSi₃O₉, K₂ZrSi₂O₇, and ZrSiO₄ were located. The potassium zirconosilicates have open-framework structures made up of corner-shared ZrO₆ octahedra and SiO₄ tetrahedra. The composition of the crystallizing silicates is shown to depend on the nature of the starting Zr- and Si-containing materials.     

Bi_8Nb_2O_(17)材料的电传导率测定

δ-Bi2O3是性能优异的氧离子导体,但是相变制约了它的应用。本研究利用固相烧结法制备Bi8Nb2O17材料,使之在低温下仍能保持传导性能好的立方相,采用X射线衍射分析表征了该材料的组成和结构,并利用交流阻抗技术测定了材料的电导率。结果表明,这种材料从室温到832℃不发生相变,但电导率随着温度的升高有较大的提升,832℃时达6.16S·m-1。另外,不同氧分压(20kPa~91.2kPa)条件下测定电导率,发现Bi8Nb2O17材料的氧离子电导率不随氧分压而变化,700℃和800℃下分别稳定于2.30S·m-1和3.89S·m-1,表明该材料在高温环境中是一种优良的氧离子导体,具有较大的应用潜能。     

Hydrothermal synthesis of NaEuF4 spindle-like nanocrystals

NaEuF₄ spindle-like nanocrystals have been synthesized through a simple hydrothermal method. The nanocrystals were well crystallized and exhibited fine morphology, as indicated by X-ray diffraction, transmission electron microscope and selected area electron diffractometer. The luminescence properties of these NaEuF₄ products were investigated.     

Hydrothermal synthesis and properties of NiFe2O4@BaTiO3 composites with well-matched interface

NiFe₂O₄@BaTiO₃ multiferroic composite particles were produced by a simple hydrothermal method in two steps: preparing NiFe₂O₄ nanoparticles and then synthesizing core-shell nanocomposites. Multiferroic composite ceramics were sintered from these powders. X-ray diffraction, Raman scattering and energy dispersive x-ray analyses indicated that the core-shell composites with a NiFe₂O₄ core and BaTiO₃ shell were formed in the hydrothermal environment. Different types of sharp interfaces were self-assembled owing to the minimization of direct elastic energy. The saturation magnetization of the composites linearly increased with the NiFe₂O₄ content while the dielectric constant decreased. A dielectric peak appeared at around 460 °C because of the oxygen vacancies in the BaTiO₃ ceramics. It resulted in an enhancement of magnetic permeability in the composites, indicating magnetoelectric coupling that was also observed by direct magnetoelectric measurements.