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。     

阳极氧化TiN薄膜制备N掺杂纳米TiO2薄膜及其可见光活性

室温下通过电泳沉积(EPD)的方法在Ti片表面制备TiN薄膜, 然后对TiN薄膜进行阳极氧化得到N掺杂多孔纳米结构的TiO2薄膜. 利用X射线衍射(XRD), X射线光电子能谱(XPS), 扫描电子显微镜(SEM)及光电化学方法对得到的薄膜进行表征. XRD测试结果表明, 经过阳极氧化并在350 ℃空气气氛中退火1 h的薄膜中存在锐钛矿晶型的TiO2. XPS的结果表明, 样品中的N元素取代部分O, 且N的摩尔分数为0.95%. SEM显示, 经阳极氧化后薄膜表面出现多孔纳米结构. 光电化学测试结果显示, 阳极氧化提高了N掺杂TiO2薄膜在可见光下的光电响应. 经阳极氧化并热处理的薄膜在0 V电位及可见光照射下光电流密度为2.325 μA·cm-2, 而单纯热处理的薄膜在相同条件下光电流密度仅为0.475 μA·cm-2. 阳极氧化得到纳米多孔结构提高了N掺杂纳米TiO2薄膜的表面积, 从而对可见光的响应增大.     

氧化钛-氧化石墨插层结构及其光催化性能(英文)

采用氧化石墨(GO)和硫酸钛作为初始反应物,在低温下(80℃)制备了纳米级的氧化钛-氧化石墨插层(TiO2-GO)复合材料,研究了这一复合材料的紫外光催化性能.结果表明,在采用TiO2-GO插层复合材料对甲基橙溶液进行紫外光催化降解时,其降解效率η=1.17mg·min-1·g-1,明显优于德固赛P25氧化钛粉.通过对TiO2-GO插层复合材料进行X射线衍射(XRD)、傅里叶红外(FT-IR)光谱、X射线光电子能谱(XPS)和场发射扫描电子显微镜(FESEM)等测试,表征了产物的晶相结构、界面状况及其显微结构.结果表明:插层结构中的TiO2晶粒为锐钛矿和金红石的混合相,且锐钛矿相含量大于金红石相含量;氧化石墨层间的含氧基团如C襒O,基本被还原.对TiO2-GO插层复合材料的形成机理以及该材料具有优越光催化性能的原因进行了探讨.     

氧化铁磁性纳米粒子的表面配体交换及相转移

以苯甲醇为单一溶剂, 通过常压、高温热解乙酰丙酮铁, 制备了尺寸单分散的四氧化三铁磁性纳米粒子. 采用透射电镜(TEM), X射线衍射(XRD), 动态光散射(DLS)等方法对粒子形貌和结构进行了表征. 利用傅里叶变换红外(FT-IR)光谱和热重分析(TGA)研究了所制备纳米粒子的表面化学, 结果表明稳定四氧化三铁粒子的是苯甲酸分子, 且表面覆盖度小于20%. 所制备的磁性纳米粒子可以在室温下方便地进行表面配体交换, 从而为氧化铁磁性纳米粒子的功能化提供新的途径.     

阳极氧化TiN薄膜制备N掺杂纳米TiO2薄膜及其可见光活性

室温下通过电泳沉积(EPD)的方法在Ti片表面制备TiN薄膜,然后对TiN薄膜进行阳极氧化得到N掺杂多不孔纳米结构的TiOz薄膜.利用x射线衍射(XRD),X射线光电子能谱(XPS),扫描电子显微镜(SEM)及光电化学方法对得到的薄膜进行表征.XRD测试结果表明,经过阳极氧化并在350℃空气气氛中退火1 h的薄膜中存在锐钛矿晶犁的TiO2.xPs的结果表明,样品中的N元素取代部分O,且N的摩尔分数为O.95%.SEM显示,经阳极氧化后薄膜表面出现多孔纳米结构.光电化学测试结果显示,阳极氧化提高了N掺杂TiO2薄膜在可见光下的光电响应.经阳极氧化并热处理的薄膜在0 V电位及可见光照射下光电流密度为2.325μ.cm2,而单纯热处理的薄膜在相同条件下光电流密度仅为0.475μA·cm-2.阳极氧化得到纳米多孔结构提高了 N 掺杂纳米 Ti02 薄膜的表面积,从而对可见光的响应增大.     

Mg3(VO4)2的环己烷氧化脱氢性能与X射线光电子能谱分析

采用X射线光电子能谱对柠檬酸法制备的Mg3( VO4)2催化剂表面物种进行了研究,并结合X射线衍射(XRD)、扫描电镜(SEM)、傅立叶红外光谱(FT-IR)和氢气程序升温还原(H2 - TPR)对催化剂的表征结果及其在环己烷氧化脱氢反应中的催化性能,进一步探讨了Mg3( VO4)2催化剂表面物种与其催化性能之间的关系...     

金红石/锐钛矿混晶结构的TiO2薄膜光催化活性

采用磁控溅射法制备出一组金红石/锐钛矿混晶结构的纳米TiO2薄膜催化剂,并通过光催化降解苯酚实验考察该薄膜的催化性能.光催化实验证明,随着催化剂中金红石含量减少,催化剂的光催化活性逐渐提高.X射线衍射(XRD)、X射线光电子能谱(XPS)、表面光电压谱(SPS)和原子力显微镜(AFM)结果表明,催化剂为金红石和锐钛矿混晶结构,并随着金红石含量减少,催化剂的表面羟基(OH)和桥氧(-O-)的含量逐渐增加,而且费米能级逐渐提高.表面羟基和桥氧是有利于光催化的"活性物种";费米能级的提高使TiO2/H2O界面处TiO2的表面带弯增大,导致了价带光生空穴参加光催化反应的几率增大,有效地促进了光生载流子的分离;这些因素是催化剂光催化活性逐渐提高的主要原因.     

金红石/锐钛矿混晶结构的TiO2薄膜光催化活性

采用磁控溅射法制备出一组金红石/锐钛矿混晶结构的纳米TiO2薄膜催化剂,并通过光催化降解苯酚实验考察该薄膜的催化性能. 光催化实验证明, 随着催化剂中金红石含量减少, 催化剂的光催化活性逐渐提高. X射线衍射(XRD)、X射线光电子能谱(XPS)、表面光电压谱(SPS)和原子力显微镜(AFM)结果表明, 催化剂为金红石和锐钛矿混晶结构, 并随着金红石含量减少, 催化剂的表面羟基(OH)和桥氧(—O—)的含量逐渐增加, 而且费米能级逐渐提高. 表面羟基和桥氧是有利于光催化的“活性物种”; 费米能级的提高使TiO2/H2O 面处TiO2的表面带弯增大, 导致了价带光生空穴参加光催化反应的几率增大, 有效地促进了光生载流子的分离; 这些因素是催化剂光催化活性逐渐提高的主要原因.     

低温静电自组装法制备贵金属修饰TiO_2纳米结构薄膜及其增强的光催化性能(英文)

以碱-水热法在金属Ti片上原位生长了TiO2纳米结构(纳米花和纳米线)薄膜,并采用低温静电自组装方法将超细贵金属(金、铂、钯)纳米颗粒均匀沉积于多孔TiO2薄膜上.负载于Ti片上的贵金属/TiO2纳米结构薄膜具有一体化结构、多孔架构和高光催化活性.超高分辨率场发射扫描电子显微镜(FESEM)直接观察表明贵金属纳米颗粒在TiO2表面分布均匀,且颗粒之间相互分离,金、铂、钯纳米颗粒的平均粒径分别约为4.0、2.0和10.0nm.俄歇电子能谱(AES)纵深成分分析表明贵金属不仅沉积于薄膜表面,且大量分布于TiO2纳米结构薄膜内部,其深度超过580 nm.X射线光电子能谱(XPS)分析表明,经300°C下在空气中热处理后,纳米金仍保持金属态,纳米铂部分被氧化成PtOabs,而钯粒子则完全被氧化成氧化钯(PdO).以低温静电自组装法沉积贵金属,贵金属负载量可通过调节组装时间与溶胶pH值来控制.光催化降解甲基橙的结果表明,沉积的纳米金和铂能显著增加TiO2纳米结构薄膜的光催化活性,说明金和铂粒子可促进光生载流子的分离;但负载的PdO对TiO2薄膜的光催化性能增强几乎无作用.     

静电纺丝制备YVO4:Sm3+纳米纤维及其荧光光谱性能

采用静电纺丝技术与高温煅烧工艺相结合,以氧化钐、氧化钇、偏钒酸铵和聚丙烯腈为主要原料,制备稀土离子掺杂的YVO4:Sm3+纳米纤维。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、傅立叶变换红外(FT-IR)、热重-差热(TG-DTA)和荧光光谱(PL)等分析测试手段对所得样品的结构、形貌和荧光光谱性能进行表征。研究结果表明:静电纺丝制备的有机-无机复合纤维的直径在200~250 nm之间,经过900℃热处理后,所得YVO4:Sm3+样品纤维状结构保持完好,直径减至100 nm。掺杂的稀土Sm3+离子在YVO4纤维中显示出特征发射,同时VO3-4和稀土Sm3+离子之间存在能量传递;Sm3+的掺杂浓度为2%(摩尔分数)时发光强度最大。     

Optical Switching in VO2 Thin Films

Vanadium dioxide thin films have been deposited from vanadium alkoxides VO(OR)3. An amorphous film is formed that transforms into crystalline VO2 upon heating at 500°C under a reducing atmosphere. Optically transparent VO2 thin films are then obtained that exhibit both electrical and optical switching around 70°C. The switching temperature together with the shape of the hysteresis loop can be modified by doping VO2 films with foreign cations. Doped MxVO2 (M = W6+, Nb5+, Ti4+, Cr3+ or Al3+) thin films have been prepared under the same conditions by mixing the vanadium alkoxide and a metal salt in an alcoholic solution. The switching temperature decreases when the film is doped with high-valent cations (W6+) and increases with low-valent cations (Al3+, Cr3+). The transition temperature first decreases and then increases when TiIV is added to the VO2 film while the width of the hysteresis loop is significantly reduced.     

Preparation and Magnetic Properties of Submicron CrO2 Thin Film on Poly-crystal TiO2 Film

The submicron chromium dioxide(CrO₂) thin film was fabricated on a poly-crystal titania(TiO₂) film using Si wafers as substrates by atmospheric pressure chemical vapor deposition(CVD) method. X-Ray diffraction patterns show that the CrO₂ films were pure rutile structure. Scanning electron microscopy(SEM) images indicate that the CrO₂ films consisted of submicron grains with a grain size of 250―750 nm. The magnetic researches reveal that the magnetic easy axis is parallel to the films, and at room temperature, the CrO₂ films show linear magnetoresistance.     

The effects of oxygen concentration on ultraviolet luminescence of ZnO films by sol–gel technology and annealing

ZnO thin films were successfully deposited on SiO₂/Si substrate using the sol–gel technique and annealed in various annealing atmospheres at 900 °C by rapid thermal annealing (RTA). X-ray diffraction revealed the (002) texture of ZnO thin films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the grains of the ZnO thin film were enlarged and its surface was smoothed upon annealing in oxygen. PL measurement revealed two ultraviolet (UV) luminescence bands at 375 and 380 nm. The intensity of the emission peak at 380 nm became stronger as the concentration of oxygen in the annealing atmosphere increased. The X-ray photoelectron spectrum (XPS) demonstrated that a more stoichiometric ZnO thin film was obtained upon annealing in oxygen and more excitons were generated from the radiative recombination carriers consistently. Additionally, the UV intensity increased with the thickness of ZnO thin film.     

Optical and structural characteristics of yttrium doped ZnO films using sol–gel technology

Yttrium-doped ZnO gel was spin-coated on the SiO₂/Si substrate. The as-prepared ZnO:Y (YZO) thin films then underwent a rapid thermal annealing (RTA) process conducted at various temperatures. The structural and photoluminescence characteristics of the YZO films were discussed thereafter. Our results indicated that the grain size of YZO thin films being treated with various annealing temperatures became smaller as compared to the ones without being doped with yttrium. Furthermore, unlike other ZnO films, the grains of YZO thin films appeared to separate from one another rather than aggregating together as both types of the films were annealed under the same environment. The photoluminescence characteristic measured showed that the UV emission was the only radiation obtained. However, the UV emission intensity of YZO thin film was much stronger than that of the ZnO thin film after annealing them with the same condition. It was also found that the intensity increased with an increase in the annealing temperature, which was caused by the exciton generated and the texture surface of the YZO thin film.     

Templated growth of smart nanocomposite thin films: Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition of vanadyl acetylacetonate,auric acid and tetraoctyl ammonium bromide

Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised to produce nanocomposite thin films of gold nanoparticles and vanadium dioxide from vanadyl acetylacetonate and auric acid. The addition of tetraoctyl ammonium bromide (TOAB) to the precursor solution gave control of the size and distribution of gold nanoparticles in the vanadium oxide matrix. These reactions led to vanadium dioxide films with reduced crystallite sizes and enhanced thermochromic properties. The films were analysed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Their optical and thermochromic behaviour was also determined. This hybrid method shows great potential for the production of nanocomposite thin films with good physical properties.     

The Influence of Heat Treatment Mode on the Properties of Bi4Ti3O12 Thin Films by Chemical Solution Deposition Technique

Bi₄Ti₃O₁₂ thin films were prepared by chemical solution deposition technique on n-Si(lOO). Bismuth nitrate and titanium butoxide were used as starting materials. In this paper, we used this technique to prepare Bi₄Ti₃O₁₂ thin films heat treated by both rapid annealing for 30 seconds in a rapid annealing heater and annealing in a furnace for 30 minutes, and found that the heat treat mode greatly influences the properties of the films. The crystallization temperature of the film made from rapid annealing is about 500℃, while that of the film prepared by heating in a furnace is about 550℃. X-ray diffraction pattern of the film heat treated by the former has stronger (004), (006), (008), (0010) peaks than that of the film heat treated by the latter, which suggests that the rapid annealing heat treat mode favors preferential c-oriental film. The grain size of the film obtained by rapid annealing is smaller than that of the film prepared by heating in a furnace. When the films were both annealed at 600℃,the coercive field of the film heat treated by the former is 45 kV/cm, while that of the film heat treated by the latter is 87 kV/cm.     

Ceramic Films via Organometallic Complex as Single Source Precursor

Fe2(CO)6(μ-S2) was used as a single source precursor in attempt to produce FeS film via MOCVD. Pyrolysis of Fe2(CO)6(μ-S2) at temperature below 500℃ produced Fe1-xS or Fe7S8 powder as indicated by its powder X-ray spectra. At 750 ℃, polycrystalline FeS powder was obtained. In film deposition, polycrystalline Fe1-xS or Fe7Ss films were obtained on Si(100) and Ag/Si(100) substrates below 500 ℃. SEM micrographs showed the film on Si(100) substrate containing whisker like grains. However, pillar like grains were obtained on Ag/Si(100) substrate.Deposition rates are also different for different substrates as evaluated by the thickness of the films, which were obtained by SEM micrographs of the cross section of the films. At 750℃, similar polycrystalline Fe1-xS or Fe7S8 film was obtained.     

Influence of rapid thermal annealing on structure and interfacial characteristic of ZnO thin films

Highly C‐axis oriented ZnO thin film was manufactured by radio‐frequency magnetron sputtering technique on Si (111) substrate. The main objective was to study the influence of rapid thermal annealing (RTA) temperature on the structure and interfacial characteristic of ZnO thin films. X‐ray diffraction results showed that the ZnO thin films annealed at 600 °C by RTA technique had a perfect C‐axis preferred orientation compared to the other ZnO thin films, and the full width at half maximum of ZnO (002) rocking curve measurements indicted that the RTA‐annealed ZnO thin films possessed better crystal structure. Atom force microscopy displayed that the grain size of RTA‐annealed ZnO thin films was fine and uniform compared with the as‐deposited ZnO thin films, although the grains grew in RTA process and the root meant square roughness was smaller than that of as‐deposited films. High‐resolution transmission electron microscopy showed that there was an obvious amorphous layer between ZnO thin films and Si substrate, but the RTA‐annealed ZnO thin films exhibited larger and denser columnar structure and a preferred orientation with highly c axis perpendicular to the amorphous layer. Copyright © 2012 John Wiley & Sons, Ltd.     

X-Ray Analysis of Multi-Films for Electrochromic Device Application

Multilayer films based on tungsten oxide (WO₃), ITO (indium tin oxide) and CdS were deposited mainly by reactive dc magnetron sputtering onto glass substrates for electrochromic application. The thin films were analyzed by means of XPS (X-ray photoelectron spectroscopy), GIXD (grazing incidence X-ray diffraction) and XRD (X-ray diffraction). XRD and XPS results confirmed that the films were WO₃, CdS and ITO, respectively. The surface and interface of the CdS/ITO bi-layered film was studied by GIXD in different incidence angles. Detailed results about the amorphous characterization of the films during room temperature growth and post annealing are given.     

Influence of sputter power on structural and electrical properties of TiO2 films for Al/TiO2/Si gate capacitors

Titanium dioxide (TiO₂) thin films were deposited onto p‐Si substrates held at room temperature by reactive Direct Current (DC) magnetron sputtering at various sputter powers in the range 80–200 W. The as‐deposited TiO₂ films were annealed at a temperature of 1023 K. The post‐annealed films were characterized for crystallographic structure, chemical binding configuration, surface morphology and optical absorption. The electrical and dielectric properties of Al/TiO₂/p‐Si structure were determined from the capacitance–voltage and current–voltage characteristics. X‐ray diffraction studies confirmed that the as‐deposited films were amorphous in nature. After post‐annealing at 1023 K, the films formed at lower powers exhibited anatase phase, where as those deposited at sputter powers > 160 W showed the mixed anatase and rutile phases of TiO₂. The surface morphology of the films varied significantly with the increase of sputter power. The electrical and dielectric properties on the air‐annealed Al/TiO₂/p‐Si structures were studied. The effect of sputter power on the electrical and dielectric characteristics of the structure of Al/TiO₂/p‐Si (metal‐insulator‐semiconductor) was systematically investigated. Copyright © 2014 John Wiley & Sons, Ltd.