WO3薄膜气敏光学传感特性研究

WO3薄膜是良好的光学气敏传感器材料.采用溶胶凝胶法制备了WO3掺杂薄膜,对样品在不同浓度氢气气氛中的气敏光学性质、敏感度及响应时间进行了测试、分析和计算,并结合光传输理论给出了气敏薄膜的光学变化机制,理论分析与实验结论吻合.     

基于磁控溅射的金属氧化物气敏薄膜的研究进展

气体传感器的应用越来越广泛,对气敏材料的研究也越来越深入。磁控溅射法是生产气敏薄膜的一种主要方法,本文重点介绍了用磁控溅射法制备的几种金属氧化物薄膜(SnO2、WO3、ZnO、TiO2、In2O3和NiO等)的气敏性能及其研究进展,对其它薄膜做了简要概述,并提出了目前在气敏薄膜研究中存在的问题。     

介孔硅基WO3纳米颗粒薄膜室温气敏元件特性

采用双槽电化学腐蚀法在p＋单晶硅片表面制备介孔硅层（meso-PSlayer）,然后用对向靶磁控反应溅射法在介孔硅表面沉积WO3纳米颗粒薄膜,在干燥空气中于400℃下保温4h进行退火热处理,制备出介孔硅基WO3纳米颗粒薄膜（WO3-PS）室温气敏元件.利用扫描电子显微镜（SEM）分析介孔硅层及WO3-PS的表面形貌,通过X射线衍射（XRD）研究WO3的结晶状态,测试WO3-PS气敏元件在室温下对NO2、NH3的气敏性能,并探讨了WO3-PS气敏元件的工作机理.实验结果表明,在介孔硅表面沉积WO3纳米颗粒薄膜可使介孔硅的气敏性能显著提高,其中在室温下对10×10^-6NO2的灵敏度由5提高至56,大大提高了介孔硅的灵敏度,并降低了其响应/恢复时间,提高了对NO2的选择性.     

纳米WO3薄膜

综述了纳米WO3薄膜的制备、表征及其在电致变色、气敏材料、共催化剂等方面的应用和作用原理.     

磁控溅射WO_3薄膜的制备及其NO_2气敏特性研究

采用直流反应磁控溅射法,在室温条件下通过改变放电气体压强制备出具有不同膜密度的WO3薄膜。结构表征结果表明,由单斜晶WO3纳米颗粒组成的薄膜具有层状结构,随着放电气体压强的增加,膜密度呈下降趋势。气敏特性研究结果表明,由WO3薄膜制备而成的气体传感器在工作温度为200℃时获得对NO2气体的最大灵敏度,并在50~300℃的工作温度范围内对NO2气体均展现出良好的气敏特性。在相同的检测条件下,气体灵敏度随着膜密度的减少而增加。     

WO3纳米微粒的制备及气敏特性研究进展

综述了近年来国内外对WO3纳米微粒作为气敏材料时的制备方法进展,对WO3的气敏机理进行了探讨,并总结了不同化合物的掺杂对其气敏性能的影响。     

碳纳米管掺杂纳米WO3气敏材料的制备及其应用

为降低WO3气敏元件的工作电压,改善WO3基敏感材料的气敏性能,采用化学吸附沉淀-水热法合成WO3和WO3/SWCNT复合材料,并研究矿化剂用量和SWCNT掺杂量对其气敏性能的影响.结果表明,大剂量矿化剂的使用会降低WO3的气敏性能;碳纳米管掺杂可以使WO3在较低的工作温度下有较高的灵敏度.SWCNT掺杂量为1％的元件...     

SiO2纳米复合稳定WO3薄膜气致变色特性研究

以钨粉为主要原料,采用过氧化法及提拉技术制备WO3薄膜,通过SiO2纳米颗粒复合改性提高了WO3薄膜的气致变色稳定性.测试并研究了SiO2复合掺杂对溶胶颗粒分布、气致变色稳定性等的影响,通过测试薄膜循环中红外振动吸收的演变,深入研究了SiO2纳米复合对WO3薄膜气致变色性能影响的内在机制.研究结果表明,SiO2的掺杂抑制了WO3薄膜内的共角聚合,将薄膜的致/褪色循环次数由20次提高到500次以上,WO3-SiO2复合薄膜的稳定网络结构是提高其气致变色循环稳定性的主要原因.     

CNT-WO3元件的氨敏性能研究

以碳纳米管（CNT）为掺杂剂制成CNT—WO3旁热式气敏元件．采用混酸氧化法对碳纳米管进行纯化，化学沉淀法制备了纳米WO3微粉，并用TEM、FT—IR、TG—DSC、XRD等方法进行了表征．测试了元件在室温条件下对NH3的气敏性能．结果表明，碳纳米管掺杂元件在室温下对NH3的灵敏度远远高于纯WO3元件，其中0．8wt％的掺杂元件对NH3具有最高的灵敏度．另外，掺杂元件还具有检测浓度低、检测范围宽、选择性好等优点，是一种较为理想的氨敏元件．     

纳米掺钯WO3薄膜及气致变色性能研究

以钨粉和双氧水为原料，采用溶胶-凝胶技术结合提拉镀膜法，制备了纳米结构掺钯气致变色WO3薄膜；分析了薄膜的折射率、厚度、结晶度、红外特性和表面形貌随温度变化特性；研究了薄膜的气致变色性能。研究结果表明，纳米掺钯气致变色WO3薄膜有着良好的气致变色特性。重点讨论了薄膜结构、薄膜水含量以及薄膜钯含量对薄膜变色效率的影响。     

纳米WO3制备方法的研究进展

将新型气敏材料ＷＯ３制成纳米级粒子,会大大提高其灵敏度。指出了纳米三氧化钨在气敏材料领域的应用前景,并着重对纳米三氧化钨的制备方法进行了评述。     

Structural and gas-sensing properties of WO/sub 3/ nanocrystalline powders obtained by a sol-gel method from tungstic acid

WO/sub 3/ nanocrystalline powders were obtained from tungstic acid following a sol-gel process. Evolution of structural properties with annealing temperature was studied by X-ray diffraction and Raman spectroscopy. These structural properties were compared with those of WO/sub 3/ nanopowders obtained by the most common process of pyrolysis of ammonium paratungstate, usually used in gas sensors applications. Sol-gel WO/sub 3/ showed a high sensor response to NO/sub 2/ and low response to CO and CH/sub 4/. The response of these sensor devices was compared with that of WO/sub 3/ obtained from pyrolysis, showing the latter a worse sensor response to NO/sub 2/. Influence of operating temperature, humidity, and film thickness on NO/sub 2/ detection was studied in order to improve the sensing conditions to this gas.     

NH3 sensing characteristics of nano-WO3 thin films deposited on porous silicon

The NH3 sensing characteristics of nano-tungsten trioxide (WO3) thin films deposited on porous silicon (PS) were investigated in the present study. Porous silicon layer was first prepared by electrochemical etching in an HF-based solution on a p(+)-type silicon substrate. Then, WO3 nano-films were deposited on the porous silicon layer by DC magnetron sputtering. Pt electrodes were deposited on the top surface of the WO3 films to obtain the WO3/PS gas sensor. The WO3 films deposited on PS were characterized by SEM, XRD and XPS. The NH3 sensing characteristics for WO3/PS gas sensor were tested at room temperature and 50 degrees C. The results showed that the NH3 sensing characteristics of WO3/PS were superior to WO3/Al2O3 at room temperature. The sensing mechanism of the nano-WO3 thin films based on PS was also discussed.     

Room-temperature resistive H₂ sensing response of Pd/WO₃ nanocluster-based highly porous film

Hydrogen- (H?-) induced resistive response of palladium (Pd) coated tungsten oxide (WO?) films prepared by using supersonic cluster beam deposition (SCBD) was investigated. An SCBD WO? film is found to be constructed of WO? nanoclusters of diameters of 3-5 nm. The nanoclusters are loosely connected to form a structure of high porosity around 66%. With this structure, the film exhibits many excellent room-temperature H? sensing properties, including high sensitivity, broad detectable range of H? concentration, low detection limit, fast response rate, excellent cyclic stability (>2400 cycles), high selectivity against vapor of many organic compounds, mild ambient pressure dependence and many other advantages such as low power consumption, miniaturizability and high batch-to-batch reproducibility. These findings are useful for making new high-quality H? sensors for monitoring the leakage of H? and ensuring safe use of this gas.     

氧化钨基半导体气体传感器的研究进展

近年来,氧化钨(WO_3)基半导体气体传感器由于可用来检测低浓度二氧化氮、二氧化硫、臭氧和氨气等气体而受到广泛关注。将WO_3基材料分为4类:纯WO_3材料、氧化物-WO_3复合材料、贵金属-WO_3复合材料和有机物-WO_3复合材料,总结近年来中外文献中WO_3基材料对不同气体的响应性能,展现近年来国内外WO_3基半导体气体传感器的研究进展。最后根据已有的工作进展,提出合成新型纳米材料、降低工作温度、提高传感器选择性应成为WO_3基半导体气体传感器下一阶段的研究重点。     

基于WO_3薄膜的双声路声表面波型SO_2气体传感器

以金属钨粉,H2O2,CH3OH和PVP(聚乙烯吡咯烷酮)为原料,利用热喷射方法在双声路声表面波器件的测量声路上制作了细微多网孔状WO3薄膜,提出并实现了一种在常温下可以实现对二氧化硫(SO2)气体进行物理吸附和解吸附的基于WO3薄膜的双声路声表面波型SO2气体传感器.声表面波器件的双声路结构消除了由于外界测量条件改变引起的测量误差,也进一步提高了传感器的可靠性和准确性.实验结果表明,该传感器具有好的重复性,在测量范围内对各种浓度的SO2气体具有好的响应特性;传感器在0.5ppm到20ppm浓度范围内的线性灵敏度大约为6.8KHz/ppm.     

Size-controlled synthesis and gas sensing application of tungsten oxide nanostructures produced by arc discharge

Several different synthetic methods have been developed to fabricate tungsten oxide (WO(3)) nanostructures, but most of them require exotic reagents or are unsuitable for mass production. In this paper, we present a systematic investigation demonstrating that arc discharge is a fast and inexpensive synthesis method which can be used to produce high quality tungsten oxide nanostructures for NO(2) gas sensing measurements. The as-synthesized WO(3) nanostructures are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), finger-print Raman spectroscopy and proton induced x-ray emission (PIXE). The analysis shows that spheroidal-shaped monoclinic WO(3) crystal nanostructures were produced with an average diameter of 30?nm (range 10-100?nm) at an arc discharge current of 110?A and 300?Torr oxygen partial pressure. It is found that the morphology is controlled by the arc discharge parameters of current and oxygen partial pressure, e.g.?a high arc discharge current combined with a low oxygen partial pressure results in small WO(3) nanostructures with improved conductivity. Sensors produced from the WO(3) nanostructures show a strong response to NO(2) gas at 325?°C. The ability to tune the morphology of the WO(3) nanostructures makes this method ideal for the fabrication of gas sensing materials.     

Material and sensing properties of Pd-deposited WO3 thin films

The physicochemical and electrical properties of Pd-deposited WO3 thin films were investigated as a function of Pd thickness, annealing temperature, and operating temperature for application as a hydrogen gas sensor. WO3 thin films were deposited on an insulating material using a thermal evaporator. X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the crystal structure, microstructure, surface roughness, and chemical property of the films, respectively. The deposited films grew into polycrystalline WO3 with a rhombohedral structure after annealing at 500 degrees C. Adding Pd had no effect on the crystallinity, but suppressed the growth of WO3 grains. The Pd was scattered as isolated small spherical particles of PdO2 on the WO3 thin film after annealing at 500 degrees C, while it agglomerated as irregular large particles or diffused into the WO3 after annealing at 600 degrees C. PdO2 reduction under H2 and reoxidation under air were dependent on both the Pd deposition thickness and annealing conditions. The WO3 thin film with a 2-nm-thick Pd deposit showed a good response and recovery to H2 gas at a 250 degrees C operating temperature.     

Faster response of NO₂ sensing in graphene-WO₃ nanocomposites

Graphene-based nanocomposites have proven to be very promising materials for gas sensing applications. In this paper, we present a general approach for the preparation of graphene-WO(3) nanocomposites. Graphene-WO(3) nanocomposite thin-layer sensors were prepared by drop coating the dispersed solution onto the alumina substrate. These nanocomposites were used for the detection of NO(2) for the first time. TEM micrographs revealed that WO(3) nanoparticles were well distributed on graphene nanosheets. Three different compositions (0.2, 0.5 and 0.1 wt%) of graphene with WO(3) were used for the gas sensing measurements. It was observed that the sensor response to NO(2) increased nearly three times in the case of graphene-WO(3) nanocomposite layer as compared to a pure WO(3) layer at room temperature. The best response of the graphene-WO(3) nanocomposite was obtained at 250?°C.