SnO2-Zn2SnO4复合陶瓷的介电性质研究

通过传统陶瓷制备工艺制备了致密的SnO2-Zn2SnO4复合陶瓷,研究了不同SnO2、Zn2SnO4复合比例对陶瓷介电性质的影响及其高介电性质产生的机理。研究发现,40Hz时,该复合陶瓷的相对介电常数高达104,远高于SnO2、Zn2SnO4陶瓷,且样品的相对介电常数、导纳随组分的变化规律一致。进一步研究发现,样品的电容随着施加偏压的变化满足肖特基势垒电容公式,这表明,SnO2-Zn2SnO4复合陶瓷的高介电行为起源于晶界处的双肖特基势垒。     

Microstructural investigation and SnO nanodefects in spray-pyrolyzed SnO2 thin films

Spray pyrolysis is one of the most cost-effective methods to prepare SnO₂ films due to its ability to deposit large uniform area, low fabrication cost, simplicity and low deposition temperature. Conventionally, scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) are routinely used to investigate microstructure and crystal structure of the SnO₂ films. In the present study, the SnO₂ films were deposited by spray pyrolysis at 300, 400 and 500 °C and the microstructure of the 500 °C film was further examined by using transmission electron microscopy (TEM) and convergent beam electron diffraction (CBED). It was found that large grain-size vertically-aligned columnar SnO₂ grains were formed after a few layers of small grain-size randomly oriented SnO₂ grains. Moreover, CBED showed the presence of SnO nanodefects that had not been reported before and could not be detected by SEM or XRD.     

Luminescence efficiency of SnO2:Eu and rate of SnO oxidation

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

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…     

Nanofibers Comprising Yolk–Shell Sn@void@SnO/SnO2 and Hollow SnO/SnO2 and SnO2 Nanospheres via the Kirkendall Diffusion Effect and Their Electrochemical Properties

Nanofibers with a unique structure comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres are prepared by applying the nanoscale Kirkendall diffusion process in conventional electrospinning process. Under a reducing atmosphere, post‐treatment of tin 2‐ethylhexanoate‐polyvinylpyrrolidone electrospun nanofibers produce carbon nanofibers with embedded spherical Sn nanopowders. The Sn nanopowders are linearly aligned along the carbon nanofiber axis without aggregation of the nanopowders. Under an air atmosphere, oxidation of the Sn–C composite nanofibers produce nanofibers comprising Sn@void@SnO/SnO₂ yolk–shell nanospheres and hollow SnO/SnO₂ and SnO₂ nanospheres, depending on the post‐treatment temperature. The mean sizes of the hollow nanospheres embedded within tin oxide nanofibers post‐treated at 500 °C and 600 °C are 146 and 117 nm, respectively. For the 250th cycle, the discharge capacities of the nanofibers prepared by the nanoscale Kirkendall diffusion process post‐treated at 400 °C, 500 °C, and 600 °C at a high current density of 2 A g^?1 are 663, 630, and 567 mA h g^?1, respectively. The corresponding capacity retentions are 77%, 84%, and 78%, as calculated from the second cycle. The nanofibers prepared by applying the nanoscale Kirkendall diffusion process exhibit superior electrochemical properties compared with those of the porous‐structured SnO₂ nanofibers prepared by the conventional post‐treatment process.     

Growth of IrO2, SnO2, and SnO2:IrO2 crystals

Crystals of IrO₂, SnO₂, and SnO₂:IrO₂ have been grown by chemical vapor transport. The IrO₂ crystals are larger than any previously reported. The SnO₂ and SnO₂:IrO₂ crystals are optically clear and are suitable for optical properties studies. This is the first report on the growth of SnO₂:IrO₂ crystals.     

Properties of SnO2-based ceramics

Some SnO₂-based ceramics of the ternary and binary systems SnO₂-Sb₂O₃-CuO have been prepared and some of their properties have been measured. It was observed that most of their properties, which include density, porosity, d.c. electrical conductivity, as well as the crystal occurrence, were dependent on the presence of CuO. Crystal phase occurrence was investigated using the X-ray diffraction technique and it was found that the phases were predominantly SnO₂ and Sb₂O₄ crystals. The d.c. conductivity at different sintering temperatures was found to be enhanced by the simultaneous presence of Sb₂O₃ and CuO.     

二氧化锡纳米线的生长机理研究

使用水平石英管式电炉，以二氧化锡和石墨的混合物为原材料、高纯氮气为载气，在850℃温度下用直接热蒸发法制备二氧化锡纳米线．衬底硅片的直径为10mm，其上覆盖一层5nm厚的金催化剂．原材料放在石英舟中，离原材料30mm的下风口处放置硅衬底，原材料和硅衬底都放置在石英管的中部电炉的恒温区内．用扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察到二氧化锡的纳米线结构；X射线衍射（XRD）表明二氧化锡纳米线具有四方金红石结构；选区电子衍射（SAED）照片表明二氧化锡纳米线具有完善的晶体结构．不同生长时间下制备样品的扫描电子显微镜和透射电子显微镜照片再现了二氧化锡纳米线的生长过程，该纳米线的生长符合传统的VLS生长机制．     

纳米晶SnO2粉末的制备

采用常规溶液化学沉淀法,通过仔细控制沉淀速率以类独石状Ｓｎ（ＯＨ）４沉积物。采用两种不同的煅烧工艺制备ＳｎＯ２粉,即：常规的将沉淀物磨成粉末后煅烧和将灰独石状沉淀物直接煅烧。选取４５０、６００,７５０。９００和１０５０℃个温度条件,保温２ｈ煅烧。结果表明直接煅烧法得到的ＳｎＯ２粉末的晶粒平均尺度较常规煅烧工艺得到的ＳｎＯ２粉末（１２￣５０ｎｍ）小,从晶化动力学角度对该现象给予了解释。     

纳米SnO_2及分子筛封装纳米SnO_2簇的湿敏性能研究

本文以液相法制备的纳米ＳｎＯ２微粉和分子筛封装的纳米ＳｎＯ２簇微粉为原料，采用涂膜法制作成湿敏元件，并且分别对这两种元件进行了湿敏性能的测试。研究表明纳米ＳｎＯ２微粉和分子筛封装的纳米ＳｎＯ２簇微粉，其湿敏元件灵敏度明显高于普通ＳｎＯ２微粉，阻湿线性关系良好，具有较好的湿敏性能。     

纳米SnO2、ZnO及ZnO／SnO2复合材料的气敏性能研究

以ZnO、S如纳米颗粒及ZnO／SnO2复合纳米材料分别作为气敏基料制成旁热式气敏元件,运用扫描电镜观察产物的形貌,用静态配气法对浓度为100ppm的甲烷气体进行气敏性能的测试。结果表明,这几类元件的最佳工作温度及灵敏度差异较大,当工作温度为350℃时SnO2纳米颗粒的气敏性能最佳。此温度下,SnO2响应时间和恢复时间也比纯ZnO纳米颗粒分别缩短了2S和3S。     

Microwave-assisted hydrothermal synthesis of nanocrystalline SnO powders

Tin oxide (SnO) powders were obtained by the microwave-assisted hydrothermal synthesis technique using SnCl₂·2H₂O as a precursor. By changing the hydrothermal processing time, temperature, the type of mineralizing agent (NaOH, KOH or NH₄OH) and its concentration, SnO crystals having different sizes and morphologies could be achieved. The powders were characterized by X-ray diffraction (X-ray), Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HR-TEM) and Selected Area Electron Diffraction (SAED). The results showed that plate-like form is the characteristic morphology of growth and the TEM analyses indicate the growth direction as (200).