Ta2O5空心球的制备及光催化性能

采用无皂乳液聚合法合成了粒径为500 nm的聚苯乙烯(PS)球。运用层层自组装技术在PS球表面交替沉积单分子层的TaO3纳米页与聚二烯丙基二甲基氯化铵(PDDA)多层膜,650℃煅烧除去PS模板和PDDA高分子层后,得到Ta2O5空心球。空心球的直径为500 nm左右,壁厚约10 nm。XRD结果显示该空心球为正交晶系Ta2O5。空心结构显著提高了Ta2O5的光催化活性,在紫外光照射60 min后,Ta2O5空心球降解亚甲基蓝达90%以上,而商品Ta2O5只能降解28%。     

中空Ta2O5/TiO2复合光催化剂的可控氧化制备及性能

以钛粉、钽粉为原料,炭黑作为反应性模板,通过熔盐法在炭黑表面原位生长了TaTiC₂纳米碳化物涂层,并以所得TaTiC₂/C复合物为碳化物前驱体,再经可控氧化制备出中空Ta₂O₅/TiO₂复合光催化剂。采用X射线粉末衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、紫外-可见（UV-Vis）漫反射（DRS）及N₂物理吸附等手段对所制备的光催化剂进行形貌、显微结构及孔结构表征。以高压汞灯为紫外光源,以亚甲基蓝为目标降解物,通过光催化降解实验评价中空Ta₂O₅/TiO₂复合光催化剂的光催化活性。结果表明,熔盐法生长碳化物涂层厚度均匀（20~30 nm）,碳化物主要以TaTiC₂晶相存在且具有纳米级的颗粒尺寸。中空Ta₂O₅/TiO₂复合光催化剂同时具有200 nm左右的中空大孔结构及壳层10 nm左右的介孔结构。中空大孔和介孔的存在提高了所制备催化剂对亚甲基蓝的吸附能力。此外,TiO₂与Ta₂O₅通过电子能带结构的耦合,有效提高了光生电子和空穴的分离效率,从而显著提高了光催化活性。n_Ti∶n_Ta=2.5∶1.5时,相应的中空Ta₂O₅/TiO₂复合光催化剂表现出最佳的光催化活性,对亚甲基蓝的紫外光催化降解率高达97%。     

中空Ta_2O_5/TiO_2复合光催化剂的可控氧化制备及性能

以钛粉、钽粉为原料,炭黑作为反应性模板,通过熔盐法在炭黑表面原位生长了TaTiC_2纳米碳化物涂层,并以所得TaTiC_2/C复合物为碳化物前驱体,再经可控氧化制备出中空Ta_2O_5/TiO_2复合光催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见(UV-Vis)漫反射(DRS)及N2物理吸附等手段对所制备的光催化剂进行形貌、显微结构及孔结构表征。以高压汞灯为紫外光源,以亚甲基蓝为目标降解物,通过光催化降解实验评价中空Ta_2O_5/TiO_2复合光催化剂的光催化活性。结果表明,熔盐法生长碳化物涂层厚度均匀(20~30 nm),碳化物主要以TaTiC_2晶相存在且具有纳米级的颗粒尺寸。中空Ta_2O_5/TiO_2复合光催化剂同时具有200 nm左右的中空大孔结构及壳层10 nm左右的介孔结构。中空大孔和介孔的存在提高了所制备催化剂对亚甲基蓝的吸附能力。此外,TiO_2与Ta2O5通过电子能带结构的耦合,有效提高了光生电子和空穴的分离效率,从而显著提高了光催化活性。nTi∶nTa=2.5∶1.5时,相应的中空Ta_2O_5/TiO_2复合光催化剂表现出最佳的光催化活性,对亚甲基蓝的紫外光催化降解率高达97%。     

Ta3N5@Ta2O5的可控制备及可见光催化分解水析氢性能

以水热法制备的Ta_2O_5纳米粒子为前驱体,利用高温氮化技术成功制备了核壳异质结构的Ta_3N_5@Ta_2O_5纳米光催化剂。采用XRD、XPS、TEM、N_2吸附-脱附测试、DRS及电化学测试等分析手段,考察了氮化温度和氮化时间对样品的表面组成、晶粒尺寸、晶面结构、能带结构及载流子分离效率的影响规律。在NH_3气流量50 mL·min~(-1)的条件下,当氮化温度为750℃,控制氮化时间能够对纳米Ta_2O_5样品的带隙结构在3.86~2.08 eV间有效调控,相应地样品逐渐从Ta_2O_5经TaON@Ta_2O_5转化为Ta_3N_5@Ta_2O_5;当氮化时间为3 h,氮化温度由750℃升高到900℃,Ta_3N_5@Ta_2O_5样品的带隙窄化至2.04 eV;当氮化温度为850℃,氮化时间延长至12 h,Ta_2O_5完全氮化为Ta_3N_5,带隙进一步窄化至2.02 eV。经850℃氮化3 h样品,壳层Ta_3N_5界面转化为高活性(110)晶面,光生载流子分离效率最大,在可见光(λ420 nm)照射下光解水析氢活性最高,达21.75μmol·g~(-1)·h~(-1)。     

The crystal chemistry of L-Ta2O5 and related structures

Single crystals of a new form of L-Ta₂O₅ with a 19×b superstructure have been synthesised by flux growth. The phase is most likely stabilised by the incorporation of a small amount of lithium (0.14 wt% Li) from the flux. The phase has C-centred monoclinic symmetry with , (), , γ=90.00(1)°. The structure was refined in space group C112/m to R₁=0.044 for 814 unique reflections with F>4σ(F). The structure can be described as comprising chains of edge-shared TaO₇ pentagonal bipyramids that are regularly folded at (010) planes to give sinusoidal chains along [010]. These chains are interconnected along [100] and [001] by corner sharing, creating inter-chain regions that are occupied by isolated TaO₆ octahedra and pairs of corner-shared octahedra. A comparison with published data for high-quality refinements of related structures has led to the development of a general model that can explain the structural chemistry variations in the known L-Ta₂O₅-related structures. A shorthand notation is presented for representing the structures, based on the sequence along [010] of the interchain octahedra.     

静电纺丝法制备V2O5微纳米棒及光催化性能

以聚乙烯吡咯烷酮(PVP)和偏钒酸铵(NH4VO3)为原料,利用静电纺丝技术结合溶胶过程制备PVP/NH4VO3纤维,对纤维缓慢控温处理制备V2O5微纳米棒。采用热重-差热分析(TG-DTA)、X射线衍射光谱(XRD)、傅立叶红外光谱(FT-IR)、场发射扫描电子显微镜(FE-SEM)、X射线光电子能谱(XPS)和紫外-可见漫反射光谱(UV-Vis)技术手段对V2O5微纳米棒的结构和表面形态进行表征。以亚甲基蓝(MB)的光降解为模型反应,研究V2O5微纳米棒的光催化性能。结果表明:热处理温度对催化剂表面形态和晶相的生长有明显影响,550℃煅烧的V2O5微纳米棒在可见光区对MB的光降解效率最高,并分析和探讨了可能的光催化机理。     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

High-pressure transitions in MgAl2O4 and a new high-pressure phase of Mg2Al2O5

Phase transitions in MgAl₂O₄ were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al₂O₃ corundum that are high-pressure dissociation products of MgAl₂O₄ spinel combines into calcium-ferrite type MgAl₂O₄ at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al₂O₃ corundum and a new phase with Mg₂Al₂O₅ composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg₂Al₂O₅ phase indicated that the phase represented a new structure type with orthorhombic symmetry (Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å³, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O₆ octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O₆ octahedra. The structure is related with that of ludwigite (Mg, Fe²⁺)₂(Fe³⁺, Al)(BO₃)O₂. The molar volume of the Mg₂Al₂O₅ phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al₂O₃ corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl₂O₄ among various A²⁺B³⁺₂O₄ compounds.     

V2O5/TiO2催化剂表面结构FT-IR发射光谱研究(II)

用傅里哀变换红外发射光谱原位考察了V_2O_5/TiO_2催化剂在制备焙烧过程中担载偏钒酸铵的热分解步骤及其形成的表面活性相结构。偏钒酸铵在200 ℃左右分解, 在300 ℃之前完全转化为晶相V_2O_5。担载于TiO_2上的偏钒酸铵在100 ℃左右与TiO_2已产生强的化学作用, 在200 ℃之前已完全分解。对于10%(质量分数)V_2O_5/TiO_2催化剂其担载偏钒酸分解后在1020 cm~(-1)附近出现晶相V_2O_5的特征峰。但在500 ℃进一步焙烧后晶相V_5O_5的峰减弱并在1025—900 cm~(-1)区出现宽峰, 表明部分晶相V_2O_5可能转化为二维高分散的VO_x物种。2%(质量分数)V_2O_5/TiO_2催化剂在焙烧过程中也显示晶相V_2O_5的弱峰, 但同时也观察到属于VO_x物种的宽峰。进一步降低钒担载量, V_2O_5晶相特征峰逐渐消失, 而在1025—900 cm~(-1)区出现二维VO_x物种的宽峰。结果还表明傅里哀变换红外发射光谱是表征氧化物催化剂表面相结构的一种有力的方法。     

Second order incommensurate phase transition in 25L-Ta2O5

A new structural state 25L-Ta₂O₅, obtained from sintering and annealing treatments of a Ta₂O₅ powder, is identified both by electron diffraction and high resolution imaging on a transmission electron microscope (TEM). According to general rules for the different L-Ta₂O₅ structures proposed by Grey et al. (J. Solid State Chem. 178 (2005) 3308), a structural model is derived from their crystallographic data on 19L-Ta₂O₅. This model yields simulated images in agreement with high resolution TEM observations of the structure oriented along its [001] zone axis, but only for a very thin crystal thickness of less than 1.2 nm. Such a limitation is shown to be due to a modulation of the structure along its [001] axis. Actually, from an analysis of a diffuse scattering and of its evolution into satellites reflections as a function of the cooling rate, a second order incommensurate phase transition can be assumed to occur in this compound. The property of single phase samples observed by TEM is also verified by X-ray powder diffraction. In a discussion about studies performed by different authors on incommensurate structures in the system Ta₂O₅-WO₃, it is noticed that TEM results, similar to ours, indicate that phase transitions could be expected in these structures.     

The crystal structure determinations and refinements of K2S2O7, KNaS2O7 and Na2S2O7 from X-ray powder and single crystal diffraction data

The crystal structures of K₂S₂O₇, KNaS₂O₇ and Na₂S₂O₇ have been solved and/or refined from X-ray synchrotron powder diffraction data and conventional single-crystal data. K₂S₂O₇: From powder diffraction data, monoclinic C2/c, Z=4, a=12.3653(2), b=7.3122(1), , β=93.0792(7)°, R_Bragg=0.096. KNaS₂O₇: From powder diffraction data; triclinic , Z=2, a=5.90476(9), b=7.2008(1), , α=101.7074(9), β=90.6960(7), γ=94.2403(9)°, R_Bragg=0.075. Na₂S₂O₇: From single-crystal data; triclinic , Z=2, a=6.7702(9), b=6.7975(10), , α=116.779(2), β=96.089(3), γ=84.000(3)°, R_F=0.033. The disulphate anions are essentially eclipsed. All three structures can be described as dichromate-like, where the alkali cations coordinate oxygens of the isolated disulphate groups in three-dimensional networks. The K-O and Na-O coordinations were determined from electron density topology and coordination geometry. The three structures have a cation-disulphate chain in common. In K₂S₂O₇ and Na₂S₂O₇ the neighbouring chains are antiparallel, while in KNaS₂O₇ the chains are parallel. The differences between the K₂S₂O₇ and Na₂S₂O₇ structures, with double-, respectively single-sided chain connections and straight, respectively, corrugated structural layers can be understood in terms of the differences in size and coordinating ability of the cations.     

CeO2改性Ag-V2O5/TiO2催化剂的甲基吡啶氧化脱甲基性能

以锐钛矿TiO_2为载体,考察了CeO_2改性对Ag-CeO_2-V_2O_5/TiO_2催化3-甲基吡啶氧化脱甲基性能的影响,并优化了催化剂组成与制备条件.结果表明:Ce掺杂改性不仅能够与V物种作用形成Ce VO_4,而且促进V_2O_5分散,改善活性组分的氧化还原性能,从而提高3-甲基吡啶脱甲基转化率与选择性,改善Ag-V_2O_5/TiO_2催化性能.适宜的催化剂组成为V_2O_5负载量15%,Ce/V的摩尔比0.33,Ag质量分数1.0%.过高的焙烧温度将导致TiO_2载体向金红石型转变,Ag-CeO_2-V_2O_5/TiO_2适宜制备条件为450℃焙烧4 h.     

Structural study of the NaCdVO4-Cd3V2O8 and CdO-V2O5 sections of the ternary system Na2O-CdO-V2O5

The NaCdVO₄-Cd₃V₂O₈ and CdO-V₂O₅ sections of the ternary system Na₂O-CdO-V₂O₅ have been studied and the crystal structures of Cd₃V₂O₈ and Cd₁₈V₈O₃₈ compounds were determined from single-crystal X-ray diffraction data. Cd₃V₂O₈ crystallizes with the maricite-type structure in space group Pnma, a=9.8133(10) Å, b=6.9882(10) Å, c=5.3251(10) Å and Z=4, whereas Cd₁₈V₈O₃₈ crystallizes in space group P1 with a new-type structure, a=8.5761(14), b=8.607(3), c=12.896(2) Å, α=95.64(1), β=102.45(1), γ=108.42(1)° and Z=1. The Cd₃V₂O₈ structure is made up of Cd1O₄ infinite chains of edge-sharing Cd1O₆ octahedra which are parallel to the b direction. The Cd1O₄ chains are linked together by VO₄ tetrahedra and strongly distorted Cd2O₄ tetrahedra. The structure of Cd₁₈V₈O₃₈ is based on an ordered three-dimensional framework of cadmium and vanadium polyhedra that share corners. The distorted CdO₆ octahedra, CdO₅ trigonal bipyramids and CdO₅ square pyramids share corners, edges or faces.     

Bi4O5Br2光催化剂的制备及可见光降解卡马西平的活性研究

采用水解法合成了Bi_4O_5Br_2光催化剂,并通过XRD、SEM和DRS等手段对催化剂的结构、形貌和光吸收性质进行了表征。结果表明,催化剂呈不规则片状结构,其带隙能为2.1eV,价带电位E_(VB)和导带电位E_(CB)分别为2.61和0.51 eV。基于反应原理和表征结果,提出了催化剂形成机理。在可见光照射下,Bi_4O_5Br_2对卡马西平表现出高效的光催化氧化活性,光照120min后,卡马西平的降解率超过90%,反应动力学速率常数k达到0.018min~(-1)。捕获剂实验结果表明卡马西平降解过程中的主要活性物质是光生空穴(h~+)和超氧自由基阴离子(·O~-_2)。致畸作用实验结果表明,可见光照射120min后,卡马西平溶液基本上没有污染。此外,Bi_4O_5Br_2光催化剂在光催化降解卡马西平过程中表现出较高的化学稳定性和可重复性,表明其具有实际应用的潜力。     

LiMn2O4表面包覆Li4Ti5O12的制备及倍率特性

采用固相法合成了尖晶石型LiMn₂O₄，并通过溶胶-凝胶法制备了不同物质的量的百分比含量Li₄Ti₅O₁₂包覆的正极材料。X-射线衍射和扫描电镜结果表明，Li₄Ti₅O₁₂微粒包覆在LiMn₂O₄的表面没有产生晶体结构的变化。实验电池在室温下，以1C，2C和5C倍率作充放电循环测试；结果表明，与未包覆的LiMn₂O₄相比，表面包覆Li₄Ti₅O₁₂微粒的正极材料在高倍率下具有更好的循环稳定性。     

一锅法制备S型异质结光催化剂Fe2O3/Fe2TiO5及其高效降解有机污染物性能

首次采用简单的一锅法制备了Fe₂O₃/Fe₂TiO₅异质结纳米材料。构建S型异质结后,与纯的Fe₂O₃和Fe₂TiO₅相比,Fe₂O₃/Fe₂TiO₅复合材料表现出更高的光催化降解速率和效率。经过2.5 h的光照后,Fe₂O₃/Fe₂TiO₅可以降解接近100%的亚甲基蓝（MB）。在Fe₂O₃/Fe₂TiO₅复合材料中,Fe₂O₃和Fe₂TiO₅之间形成了内建电场,可以促进光生电子-空穴对的分离。因此,具有更高能量的Fe₂TiO₅导带中的电子和具有更高能量的Fe₂O₃价带中的空穴可以得到有效的保留,从而使它们更加有效地扩散到催化剂表面,并参加降解反应。此外,Fe₂O₃/Fe₂TiO₅复合材料具有很好的光催化稳定性。     

Zn/V2O5水相二次电池的交流阻抗研究

The dependence of charge transfer resistances of electrodes in the aqueous Zn/V 2O 5 secondary battery on the Zn 2+ amount intercalated was studied by means of AC impedance experiments. The results showed that the electrode reaction on cathode was controlled by the diffusion of Zn 2+ at the beginning of the discharge process. With the increase of Zn 2+ amount intercalated into the cathode, the reaction became a kinetic controlled process, i.e.a process controlled by intercalation of Zn 2+ in V 2O 5.     

WS2/CuGa2O4复合材料的制备及其气敏性

采用共沉淀法制备了CuGa₂O₄纳米材料,并利用水热法制备了一系列WS₂/CuGa₂O₄复合材料。结合X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等对制备的材料进行了物相组成、表面形貌以及元素价态的分析。研究了WS₂的复合量对CuGa₂O₄材料检测乙醇气体敏感性能的影响。实验结果表明,当WS₂与CuGa₂O₄质量比为1%时,该复合材料制备的传感器在室温下对100μL·L^-1乙醇气体表现出345.3的灵敏度,响应时间和恢复时间分别为184和69 s,且最低检测限为0.1μL·L^-1。     

WS2/CuGa2O4复合材料的制备及其气敏性

采用共沉淀法制备了CuGa₂O₄纳米材料,并利用水热法制备了一系列WS₂/CuGa₂O₄复合材料。结合X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)等对制备的材料进行了物相组成、表面形貌以及元素价态的分析。研究了WS₂的复合量对 CuGa₂O₄材料检测乙醇气体敏感性能的影响。实验结果表明,当 WS₂与 CuGa₂O₄质量比为 1%时,该复合材料制备的传感器在室温下对 100 μL·L^-1乙醇气体表现出 345.3 的灵敏度,响应时间和恢复时间分别为 184 和 69 s,且最低检测限为 0.1μL·L^-1。     

V2O5-TiO2复合半导体光催化材料结构及光响应性能研究

采用溶胶凝胶法制备了V₂O₅-TiO₂复合半导体材料，通过Raman、XRD及UV-Vis DRS等实验方法研究了V₂O₅与TiO₂复合对材料表面组成、晶体结构以及光响应性能的影响。结果表明：钒加入后优先与TiO₂作用形成较为稳定的金红石型TiVO₄晶相，其中V⁴⁺是促进TiO₂发生相变的关键；随着钒加入量的增加，V₂O₅由表面高分散状态逐渐聚集形成晶相，并释放部分Ti⁴⁺使之形成锐钛矿型TiO₂晶相，使得体相中金红石型TiO₂的含量有所下降；复合后形成的TiVO₄晶相显著提高了材料对可见光的吸收率，并使其吸光域红移至460 nm左右。