Laser Sintering of SnO2 : Sb Sol-Gel Coatings

Sb doped sol-gel SnO2 single layers (thickness 100 nm) were prepared from alcoholic solution and deposited via a dip coating process on fused silica substrates. The coatings have been sintered at a typical rate of 10–15 cm2/s by CO2 laser irradiation. The laser spot was scanned in one direction at a speed of 15,000 cm/s and the sample was moved in a perpendicular one at a speed up to 250 mm/s. The temperature of the topmost 10 m layer was monitored by a fast pyrometer (s resolution). The following properties of the coatings have been determined: the electrical resistivity , the carrier density n, and mobility , the structure, the thickness, the mesoscopic and micromorphology and the density. The sintering by CO2 laser radiation is mainly a thermal driven process. At T 500°C it allows to obtain coatings with a smaller resistivity (6.8×10–3 cm) than those produced by conventional furnace firing (el2.9×10–2 cm). The results are discussed in terms of particle size and packing density.     

制备条件对Sb/SnO2超细粉水分散性的影响

制备条件对Sb/SnO2超细粉水分散性的影响     

Preparation and Optical Properties of Sb2S3 Microcrystallite Doped Silica Glasses by the Sol-Gel Process

The sol-gel process has been applied to the preparation of nano-size Sb2S3 crystallite doped silica glasses and thin films. Silica glasses containing 1–1.5 wt% Sb2S3 are prepared by hydrolysis of complex solution of Si(OC2H5)4, SbCl3 and SC(NH2)2, and subsequent heat treatment. The nano-size crystallite in the matrix is observed by means of TEM. The transmission spectra of the films show that the transmission valley shifts toward longer wavelengths with increasing heat treatment time and temperature. Second harmonic generation (SHG) has been observed in the glasses illuminated with intense 1.06 m and frequency-doubled laser beams from mode-locked Nd:YAG laser.     

Excimer Laser Crystallization of SnO2:Sb Sol-Gel Films

Instead of classical or rapid thermal annealing, KrF excimer laser irradiation has been successfully applied to crystallize dried SnO₂:Sb films elaborated by a sol-gel process. The penetration of the crystallization front below the film surface, as imaged by transmission electron microscopy, is controlled by the laser fluence and the number of pulses and can thus be confined in the film itself without affecting sensitive substrates. All films laser irradiated at fluences higher than 40 mJ/cm² become conductive. At constant laser fluence, the electrical sheet resistance goes through a minimum with increasing number of pulses. The consequence of film's densification and morphology on electrical properties is discussed.     

SnO2纳米薄膜的制备、显微结构及气敏性能

SnO2纳米薄膜的制备、显微结构及气敏性能;SnO2薄膜;溶胶-凝胶法     

共沉淀条件对纳米级Sb/SnO2粒度和电性能的影响

导电粉;共沉淀温度;pH值;微粉末特性;共沉淀条件对纳米级Sb/SnO2粒度和电性能的影响     

Optical Properties of Sol-Gel Coatings on Plastic Foils Embossed with Surface-Relief Gratings

A novel technique has been developed to fabricate surface-relief gratings using sol-gel derived porous coating on plastic foil substrates. Organically modified TiO₂ sol was prepared by roll-coating on OPP foil substrates. The plastic films coated with TiO₂ nano-particles were embossed to form surface-relief gratings with micro-structures. The morphology of the porous coatings and the micro-structures were investigated using electron scanning microscopy (SEM). Optical transmission of the films was measured using UV-VIS and IR spectroscopy. The diffraction efficiency of the gratings on the coated plastic foil was examined in terms of fabrication conditions. It was shown that special figures could be seen in the films when the angle of view was changed. The final products of the composite films are transparent and suitable for industry manufacture and applications.     

Synthesis of Nanocrystalline, Redispersable Antimony-Doped SnO2 Particles for the Preparation of Conductive, Transparent Coatings

Nanocrystalline, redispersable Sb-doped SnO2 with Sb contents from 0.1–10 mol% (with respect to Sn) and a primary particle size of about 5 nm was prepared from SnCl4 and SbCl3 in solution by a growth reaction. The aggregation of the particles was avoided by in situ surface modification with amino carbonic acids. The stabilizing effect of the surface modification could be maintained during the following hydrothermal crystallization step (150°C, 10 bar). The resulting nanocrystalline particles are fully redispersable in aqueous suspensions at pH 11; solid contents up to 40 wt% can be achieved.Such aqueous dispersions were used to prepare transparent, conductive coatings on glass by spin coating. After thermal densification (1 hour at 550°C) transparent coatings of 220 nm thickness were obtained. A minimum specific electrical resistance of 2.5 · 10–2 cm for Sb contents between 4 and 5 mol% was measured, the transparency in the visible range against air was 90%.     

纳米晶Sb掺杂SnO2(ATO)粉体的合成与表征

以Sn粉和Sb₂O₃为原料.采用共沉淀法制备了纳米ATO粉.TG-DSC及FTIR结果表明.450℃以前前驱体已失去全部水分.并完全转化为氧化物.XRD测量结果表明.所得ATO粉具有四方金红石结构.500℃焙烧后粉体的粒径为12nm.随着焙烧温度的升高.粉体的粒径增加.TEM测定结果表明,粉体的分散性很好.团聚很少.粉体的烧结性能良好,950℃时烧结5h即达到理论密度的97.3％.用霍尔系数法测定粉体的导电行为.表明该粉体具有良好的导电性能.     

柔性透明自支撑氧化锡锑电纺纳米纤维膜的制备与表征

以四氯化锡和三氯化锑为前驱体,通过静电纺丝技术制备了柔性透明的自支撑氧化锡锑(ATO)纳米纤维膜.研究结果表明,该柔性ATO纤维膜具有四方相金红石晶体结构,且呈无规的纤维网状分布.当前驱体煅烧温度分别为520℃和700℃时,纤维的平均直径为200和150 nm;组成纤维的颗粒的平均粒径为10和19 nm;可见光透过率为72%和80%;电阻率为5.23和2.20Ω·cm.该自支撑ATO纳米纤维膜还显示出优异的柔韧性,在弯曲500次后其电阻率基本不变.     

Influences of Heating Condition and Substrate-Surface Roughness on the Characteristics of Sol-Gel-Derived Hydroxyapatite Coatings

A prepared transparent HA solution was coated on Ti6Al4V substrates by a spin-coating technique. The crystallization of the sol-gel-derived HA coated on the metallic substrates could be done at relatively low firing temperatures (as low as 600°C). The characteristics of the HA-coated layer were dependent on the surface roughness of substrates and heating conditions such as firing temperature, holding time, heating rate, and atmosphere. The heat treatment at a slow heating rate (<2°C/min.) and a long heating time (>10 hrs) at 600°C in air produced the uniform surface and improved the crystallinity. The HA layer coated on 20 m grit-blasted substates was more uniform and had fever cracks after firing, compared with that coated on 100 m grit-blasted rougher substrates.     

Investigation of IrO2/SnO2 thin film evolution by thermoanalytical and spectroscopic methods

The formation mechanism of thermally prepared IrO₂/SnO₂ thin films has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry (TG-MS) and infrared emission spectroscopy (IRES). Mixtures of varying composition of the precursor salts (SnCl₂·2H₂O dissolved in ethanol and IrCl₃·3H₂O dissolved in isopropanol) were prepared onto titanium metal supports. Then the solvent was evaporated and the gel-like films were heated in an atmosphere containing 20% O₂ and 80% Ar to 600°C. The thermogravimetric curves showed that the evolution of the oxide phases take place in several decomposition stages and the final mixed oxide film is formed between 490 and 550°C, depending on the noble metal content. Mass spectrometric ion intensity curves revealed that below 200°C crystallization water, residual solvent, and hydrogen-chloride (formed as a result of an intramolecular hydrolysis) are liberated. The decomposition of surface species (surface carbonates, carbonyls and carboxylates) formed via the interaction of the residual solvent with the precursor salts takes place up to 450°C as evidenced by emission Fourier transform infrared spectrometry. This revised version was published online in July 2006 with corrections to the Cover Date.     

PdO,Au, CdO修饰SnO2纳米纤维的制备及其气敏特性

采用静电纺丝的方法制备了SnO₂纳米纤维,并分别用PdO、Au、CdO对该纳米纤维材料进行表面修饰.用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(EDX)、X射线光电子能谱(XPS)分析、Brunauer-Emmett-Teller (BET)比表面积测试对材料进行表征.修饰前后, SnO₂纳米纤维都是由约15 nm的纳米颗粒构成的直径约为200 nm的多级结构材料.采用静态测试系统对纯SnO₂及不同物质修饰的SnO₂的气敏特性进行测试,结果表明,未修饰的SnO₂纳米纤维气敏元件对甲醛具有较好的响应.修饰后的SnO₂材料的气敏特性都有明显的改善. CdO修饰的SnO₂气敏元件对甲醛的响应值最高,且响应恢复时间短,选择性好. Au修饰的SnO₂气敏元件对甲醛响应的最佳工作温度从300 ℃降到了200 ℃.经PdO修饰后, SnO₂纳米纤维对甲苯的响应值变得最高.初步分析了经过修饰的SnO₂气敏材料的敏感机理.     

Study of the Selectivity of SnO2 Supported Membranes Prepared by a Sol-Gel Route

In this work the sol-gel process was used to prepare SnO2 supported membranes with an average pore size of 2.5 nm. The effects of salt concentration (NaCl or CaCl2) and of the pH of the aqueous solutions used on the flux and selectivity through the SnO2 membrane were analyzed by permeation experiments and the results interpreted taking account of the zeta potential values determined from the electrophoretic mobility of the SnO2 powder aqueous dispersion. The results show that the ion flux (Na+, Ca2+ and Cl–) throughout the membrane is determined by the electrostatic repulsion among these species and the surface charge at the tin oxide-solution interface.     

Role of Organic Additives in the Sol-Gel Synthesis of Porous CaF2 Anti-Reflective Coatings

Porous CaF₂ anti-reflective coating films were prepared by the sol-gel method. Effects of organic additives on deposition and optical properties of the films were investigated. Amino alcohols (2-aminoethanol, 2-dimethylaminoethanol, and triethanolamine) and alcohols with larger molecular weights (ethyleneglycol, 2-methoxyethanol, cyclohexanol, and 2-(2-n-butoxyethoxy)ethanol) were chosen as the organic additives. Among these additives, cyclohexanol was the most effective to control the surface morphology and the optical properties of the films. By changing the amount of cyclohexanol in the coating solution, it was possible to control the optical thickness of the CaF₂ films. Accordingly, the wavelength giving the maximum transmittance could be changed in the UV region.     

Influence of Solvent Concentration on the Microstructure of SiO2-TiO2 Sol-Gel Films

Spin-coating is one of the possible methodsfor the fabrication of optical planar waveguides. These have several applications in integrated optical devices, provided that their optical losses are below ≈1 dB/cm. The attenuation is caused in part by surface and bulk scattering. The latter depends on the microstructure of the films and, more particularly, the porosity, which is studied here. A series of SiO₂−TiO₂ films were prepared from solutions containing different concentrations of ethanol. The influence of the ethanol/(Si+Ti)_alkoxides volume ratio on the porosity was investigated by Ellipsometry, Infrared Spectroscopy, and Scanning Electron Microscopy. The porosity volume fraction was found to reach a minimum when the ethanol volume ratio is near 4.     

聚苯胺对新型杂化透明导电薄膜制备和性能的影响

以聚苯胺和掺锑的氧化锡作为主要原料, 采用溶胶-凝胶法制备了新型有机-无机杂化透明导电薄膜. 薄膜的可见光透过率为85%以上, 电导率达到10⁰～10¹ S•cm^－1. 研究了聚苯胺含量的变化对浸涂液粘度、薄膜结构、光透过率、电导率的影响. 随着聚苯胺引入量的增加, 薄膜的电导率、可见光透过率均有所增大. 浸涂液的粘度可在长达25天的时间内保持稳定, 很适于浸涂工艺. 扫描电镜照片显示, 薄膜比较致密、均匀, 厚度为250 nm左右.     

Influence of Surfactant and Humidity on Sol-Gel Macroporous Organosilicate Coatings

In the preparation of macroporous hydrophobic organosilicate films using methyltriethoxysilane (MTES) as precursor, the effects of surfactant addition, surfactant properties and atmospheric humidity were explored. As films dried, preferential evaporation of the ethanol resulted in an increase of the relative water content. This led to development of phase separation between the hydrophobic gel and the aqueous liquid and ultimately the formation of macropores. In the presence of surfactant, surfactant adsorption at the aqueous phase/gel interface affected the extent of phase separation therefore the resulting pores. Span 20 surfactant (HLB = 8.6) has lower compatibility with the aqueous phase than Tween 20 (HLB = 16.7) and effectively increases the hydrophobicity of the gel phase leading to the formation of larger pores. An increase in Span 20 content from 2 wt.% to 5 wt.% also increased pore size. Film porosity also increased significantly with humidity inside the coating chamber. It would appear that the increased porosity is a result of increased phase separation caused by reduced water evaporation at the higher humidity. Highly macroporous (up to 80% porosity), reproducible and uniform films were obtained by incorporating Span 20 surfactant into the coating solutions and performing dip coating at 80% relative humidity.     

Sb2O3／TiO2纳米复合物的合成及性质研究

以改进的溶胶-凝胶法制备了Sb2O3／TiO2纳米复合物,用扫描电镜、X射线粉末衍射、傅立叶红外光谱、紫外-可见光谱以及荧光等测试技术对产物进行了分析和表征．结果表明：所得纳米复合物颗粒分散均匀,具有锐钛矿相结构,平均粒径约为10nm．还研究了所得产物的光催化性质、电化学性质及电化学发光行为．结果表明：Sb2O3的掺入可以提高TiO2的光催化效果,当反应物中m（Sb2O3）／m（TiO2）=10％时,所得纳米复合物对亚甲基蓝和罗丹明B的光催化效果最好．     

Synthesis of Silica Aerogels: Influence of the Supercritical CO2 on the Sol-Gel Process

The synthesis of silica aerogels was modified by addition of supercritical CO₂ during the sol-gel process. It was shown, that CO₂ acts as a catalyst and accelerates the gelation significantly. This effect was studied under a multitude of experimental conditions. The influence of the precursor concentration, temperature and the nature of the catalysts and solvent on the gel formation in presence of CO₂ was studied. Several gels obtained by this method were dried and transparent silica aerogels were produced.