Interfacial Structure of Nanocrystalline SnO2 and SiO2-doped SnO2

Tindioxideisoneofthemostimp0rtantmaterialsforsens0rs.Inthisletter,theinterfacialstructuresofn-SnO2andn-Si-SnO2(d0pedwith5wtpctSiO2)samplespreparedbythesol-gelpr0cesshavebeenin-vestigatedbyX-raydiffraction(XRD),p0sitronlife-timespectr0sc0pyand119SnM6ssbauerspectr0scopy.Variati0nsofgrainsizeforn-SnO2andn-Si-SnO2sampleswithsinteringtemperatureshowthatthegrowthhastw0stageswithincreasingtempera-ture.Thecrystallizationtemperatureisab0ut5O0'C.Whenthesinteringtemperaturewaslowerthanthecrystall…     

半导体SnO2纳米晶态粉体显微结构对气敏传感器性能的影响

用ＸＲＤ、ＳＥＭ手段分析了共沉淀工艺和水热合成技术制备的半导体ＳｎＯ２纳米晶态粉体及其厚膜陶瓷材料的显微结构,结果表明两种粉体的晶粒尺寸大约７ｎｍ,但两种粉体的ＸＲＤ照片差异较大。用水热合成技术制备的粉体其颗粒是由纳米晶粒团聚而成,颗凿尺寸大约３００ｎｍ左右,具有较大的表面活性,而具有较大的表面活性,而用共沉淀工艺制备的粉体,颗粒分布较宽,活性差。两种粉体的显微结构对厚膜陶瓷材料显微结构的形成和Ｓ     

Structural,Optical and Photoluminescence Study of Nanocrystalline SnO2 Thin Films Deposited by Spray Pyrolysis

Undoped SnO₂ thin films prepared by spray pyrolysis method reveal polycrystalline nature with prominent peaks along (110), (101) and (211) planes. All the films are nanocrystalline with particle size lying in the range of 3·14–8·6 nm calculated by DS formula. Orientation along plane (200) decreases continuously as molar concentration of SnO₂ increases. Dislocation density along plane (110) also decreases as molar concentration increases except 0·4 M SnO₂ thin film. Scanning electron microscopy image of the films contain jelly structures along with agglomerated clusters of particles. SnO₂ synthesized successfully, which confirms by Fourier transform infra-red spectroscopy. The optical transmittance spectra of 0·2 M SnO₂ thin film shows transmittance about 50–60% transmission in visible and near infrared region with a sharp cut off in the ultraviolet region. The transmission decreases in visible and near infrared region as molar concentration increases. Broad UV emission at 398 nm is observed in photoluminescence spectra of the films along with a blue emission, when excited at 250 nm wavelength. Emission intensity randomly changed as SnO₂ molar concentration increases. When excited at 320 nm, one UV and two visible peaks appeared at 385, 460 and 485 nm, respectively.     

Photosensitization of Nanocrystalline SnO2 Films with a tris(2,2'-Bipyridine) Ruthenium(II)-Fullerene Dyad

A photoelectrochemical study of a tris(2,2'-bipyridine)ruthenium(II)-C₆₀ donor-acceptor dyad adsorbed on nanocrystalline semiconductor SnO₂ electrodes has been carried out. The results show that the incident photon-to-current conversion efficiency of dyad-based photoelectrochemical cells is ∼10%.     

Nanocrystalline SnO2 formation using energetic ion beam

Nanocrystalline tin oxide (SnO2) thin films grown by RF magnetron sputtering technique were characterized by UV-Visible absorption spectroscopy and Photoluminescence spectroscopy. From atomic force microscopic (AFM) and Glancing angle X-ray diffraction (GAXRD) measurements, the radius of grains was found to be approximately 6+/-2 nm. The thin films were bombarded with 250 keV Xe2+ ion beam to observe the stability of nanophases against radiation. For ion bombarded films, optical absorption band edge is shifted towards red region. Atomic force microscopy studies show that the radius of the grains was increased to approximately 8 +/- 1 nm and the grains were nearly uniform in size. The size of the grains has been reduced after ion bombardment in the case of films grown on Si. During this process, defects such as vacancies, voids were generated in the films as well as in the substrates. Ion bombardment induces local temperature increase of thin films causing melting of films. Ion beam induced defects enhances the diffusion of atoms leading to uniformity in size of grains. The role of matrix on ion beam induced grain growth is discussed.     

Hydrothermal Synthesis of Nanocrystalline SnO2 for Gas Sensors

Nanocrystalline SnO₂ is prepared by hydrothermal synthesis (130–250°C, 2–5 h) using three different precursors and is characterized by x-ray diffraction, transmission electron microscopy, and nitrogen BET measurements. The crystallite size of SnO₂ powders (d = 4–5 nm) prepared from amorphous stannic acid gels is found to vary very little with process temperature and duration. Air anneals at 500°C for 1–20 h demonstrate that the highest stability toward crystallite growth is offered by the samples prepared by oxidizing SnSO₄ with H₂O₂ (the crystallite size increases only slightly, from 4–5 to 5–7 nm), whereas the crystallite size of the samples prepared by high-temperature hydrolysis of SnCl₄ increases markedly, from 4–5 to 16–17 nm. Nanocrystalline NiO-doped SnO₂ is prepared by hydrothermal treatment, and its physicochemical properties are investigated. Both SnO₂ and SnO₂NiO exhibit gas sensitivity, as demonstrated by consecutively exposing the samples to different gaseous atmospheres: O₂ N₂ O₂ and O₂ N₂ + C₂H₅OH O₂.     

High Oxygen Nanocomposite Barrier Films Based on Xylan and Nanocrystalline Cellulose

Nano-Micro Letters - The goal of this work is to produce nanocomposite film with low oxygen permeability by casting an aqueous solution containing xylan, sorbitol and nanocrystalline cellulose. The...     

Photosensitization of Nanocrystalline SnO2 Films with a tris(2,2′‐Bipyridine) Ruthenium(II)‐Fullerene Dyad

Abstract

A photoelectrochemical study of a tris(2,2′‐bipyridine)ruthenium(II)‐C₆₀ donor–acceptor dyad adsorbed on nanocrystalline semiconductor SnO₂ electrodes has been carried out. The results show that the incident photon‐to‐current conversion efficiency of dyad‐based photoelectrochemical cells is ～10%.     

纳米TiO2粉晶的晶粒长大动力学及相转位动力学

用溶液胶－凝胶法制备了ＴｉＯ２纳米粉晶。对干凝胶做了ＤＴＡ、ＴＧ等热分析。利用ＸＲＤ微结构数据对粉晶长大行为及其相转位进行了分析了研究。结果表明,当热处理温度低于５００℃时,粉末粒径增长缓慢,而热处理温度高于５００℃时,粉末生长上变理论计算了晶粒长大激活能及相转位活化能,研究表明,高温区粒子生长激活能比低温区（５００℃以上）高出几倍,与粗晶粒相比,ＴｉＯ２的锐钛矿向金红石相转变的活化能要低得多。     

P型透明导电SnO2薄膜的研究进展

SnO2薄膜是一种应用广泛的宽禁带半导体材料.近几年来,随着对SnO2的光电性质及其在光电器件方面应用的开发研究,SnO2薄膜成为研究热点之一.制备掺杂的p型SnO2是形成同质p-n结以及实现其实际应用的重要途径.近年来,国内外在p型SnO2薄膜研究方面取得了较大的进展.目前报道的p型SnO2薄膜的最高电导率为5.952Ω-1cm-1.并且得到了具有较好非线性伏安特性的铟锡氧化物的透明p-n结.本文就其最新进展进行了综述.     

三维有序多孔SnO2膜的制备及表征

分别采用浸渍一提拉法和液相渗透(LPI)法用SnO2前驱物填充模板得到SnO2/PS复合膜,灼烧去除模板后,成功地制备了三维有序多孔SnO1膜.PS胶粒晶体模板是用乳液聚合法合成的单分散PS微球通过垂直沉积法在55℃组装而成.实验结果显示,由改进的LPI法制备的三维有序多孔膜质量相对较高,面积较大并且无"表皮"覆盖.在灼烧去除模板的过程中孔径有一定的收缩.     

SnO_2∶Sb电热膜的自限温特性

本文研究了掺锑量对ＳｎＯ２∶Ｓｂ电热膜电阻温度特性的影响。发现高掺锑量的电热膜具有自限流和自限温特性,并分析了该特性对电热膜寿命的影响。     

自持金刚石厚膜上沉积ZnO薄膜的研究

ZnO/金刚石结构的表面声学波滤波器的性能主要取决于沉积ZnO薄膜的质量.本文用金属有机化合物气相沉积两步生长法在自持化学气相沉积金刚石厚膜的成核面上制备了ZnO薄膜,并用X射线衍射谱,扫描电子显微镜和室温光荧光谱对薄膜质量进行了表征.结果表明得到的ZnO薄膜取向一致,表面较均匀,光学质量良好.     

Deformation Strength of Nanocrystalline Thin Films

The data of deformation strength and microstructure of thin films of nanocrystalline Pd recently provided by Colla et al. have been analysed. It is shown that the properties of the films with cylindrical grains of30 nm diameter extending over a significant portion of the film thickness(≈90 nm) are quantitatively comparable to what is known from nanocrystalline bulk material. This is explained in terms of boundarymediated processes governing emission, storage, and recovery of dislocations.     

Cu－TiC纳米晶复合薄膜的研究

本文采用多靶磁控溅射技术，通过分别控制Ｃｕ和ＴｉＣ靶的溅射功率制取了不同ＴｉＣ含量的复合薄膜，采用ＸＲＤ、ＸＰＳ和ＴＥＭ技术分析了薄膜的组织结构，并测定了薄膜的硬度和电阻率。研究结果表明：随ＴｉＣ含量的增加，Ｃｕ－ＴｉＣ复合薄膜的晶粒逐步细化，直至形成纳米晶，与此相应，薄膜的硬度提高，导电性降低。     

SnO_2复合薄膜甲烷气敏传感器研究进展

甲烷是具有稳定四面体分子结构的碳氢化合物,其键能大、分解困难且活性低,是煤矿安全生产的主要障碍及一种温室气体。SnO2半导体薄膜制备工艺简单、成本低廉、性能稳定,是甲烷传感器研发的主流气敏材料。科技人员进行了很多相关研究以提高传感器的性能,如新气敏材料的研究、催化剂/添加剂的使用、气敏机理的探索、传感器结构改进及气敏膜的表面修饰改性等。本文从气敏膜制备与改性、传感器结构设计及气敏机理研究三个方面,综述了近年来SnO2复合薄膜甲烷传感器的研究进展,结果表明:①应开发复合型金属氧化物半导体及高分子气敏材料,以提高灵敏度、选择性与稳定性;②研发微型智能传感器是未来发展的主要方向,而自组装技术应可用于制备金属氧化物半导体薄膜气体传感器微纳阵列;③气敏机理应与实验测试、材料设计及器件制备进行对照研究。     

Microstructures and Photocatalytic Properties of S Doped Nanocrystalline TiO2 Films

The nanocrystalline S doped titanium dioxide films were successfully prepared by the improved sol-gel process. Here TiO(C₄H₉O)₄ and CS(NH₂)₂ were used as precursors of titania and sulfur, respectively. The as-prepared specimens were characterized using x-ray diffraction (XRD), x-ray energy dispersive spectroscopy (EDS), high-resolution field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) surface area, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of organic dyes in aqueous solution. The results of XRD, FE-SEM, and BET analyses indicated that the TiO₂ films were composed of nanoparticles. S doping could obviously not only suppress the formation of brookite phase but also inhibit the transformation of anatase to rutile at high temperature. Compared with pure TiO₂ film, S doped TiO₂ film exhibited excellent photocatalytic activity. It is believed that the surface microstructure of the modified films is responsible for improving the photocatalytic activity.     

Sensor Properties of Pd-Doped SnO2 Films Deposited by Laser Ablation

Polycrystalline SnO₂ and SnO₂ films were surface-doped with palladium using laser ablation. The effect of the energy density of pulsed KrF laser radiation on the plasma generation process and Pd deposition rate was studied, and the depth profiles of Pd in the films were determined. The gas response of the Pd/SnO₂, SnO₂, and Pd/SnO₂ films was studied between 200 and 380°C using a mixture of 1 vol % H₂ with N₂. Surface doping with Pd was found to enhance the hydrogen sensitivity of SnO₂ by two orders of magnitude.     

膜厚对SnO2厚膜型气敏器件灵敏度的影响

本文通过制备不同膜厚的纳米SnO₂厚膜型气敏器件试样,测量试样对乙醇气体的灵敏度和试样的阻温曲线并进行复阻抗分析,研究了试样的膜厚对灵敏度的影响．SnO₂纳米材料由化学沉淀法制备,采用平面丝网印刷技术制作不同膜厚的气敏试样．结果表明,试样膜厚在65μm左右对乙醇气体具有最大灵敏度．膜厚对灵敏度的影响可能与膜层的晶粒接触状态如接触面积、气孔率、气孔宽度和深度等发生变化有关．