稀土金属掺杂WO3的气敏性能研究

采用H2O2氧化-水热结晶法制备掺杂La（NO3）3（La（NO3）3与WO3的摩尔比为1％、3％、5％、7％、9％）的WO3粉体,测试了不同比例掺杂La所得元件的气敏性能,得出结论：掺杂量为5％的时候气敏性能最佳。采用同样的方法制得掺杂量为5％La、Ce、md、Sm、Eu和Gd的WO。气敏元件,并测试了其气敏性能,掺杂5％Gd的WO3气敏元件相比其他稀土金属元素掺杂的WO3气敏元件对50ppmNO2和Cl2的灵敏度是最好的,分别为305．667和416．233。     

溶胶-凝胶法纳米WO3材料的合成、表征及气敏性能

采用溶胶-凝胶法制备了一系列掺杂有SiO2的WO3纳米粉体,通过TEM、XRD等分析手段对产物粉体的粒度、晶相结构进行了表征,测试了材料的气敏性能,探讨了煅烧温度、掺杂量、工作温度对材料气敏性能的影响。结果表明：适量SiO2的掺杂有利于提高WO3对NO2气体的灵敏度,其中掺杂量为3％（质量分数）的气敏元件在较低的工作温度下气敏性能突出。     

SiO2-WO3纳米粉体的合成及其气敏特性

采用化学沉淀法制备了xwt％SiO2-WO3(x=0，3，5，10，15)粉体材料，利用X射线衍射仪、透射电镜等测试手段分析了材料的微观结构，探讨了掺杂量、元件工作温度与W03气敏性能的关系.研究发现：SiO2的掺杂提高了WO3粉体材料对H2S气体的灵敏度，其中掺杂量为5％的烧结型气敏元件在180℃下对H2S气体有较高的灵敏度和选择性；本文还对WO3的H2S气敏机理进行了探讨．     

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．     

少量氧化锡掺杂提高三氧化钨探测H2S气体的气敏性能

为改善WO3基敏感材料的气敏性能,先采用液相还原法制备得到WO3粉体,再通过微波辅助液相法制备了SnO2掺杂量为0.5%、1%、3%、5%、10%(质量分数,下同)的SnO2-WO3复合材料。采用XRD和SEM对材料的物相、形貌进行了表征,并研究了掺杂SnO2对WO3气敏性能的影响。结果表明,掺杂3%的SnO2可显著提高WO3对H2S的灵敏度和选择性,在工作温度为160℃时,元件对体积浓度为10×10-6 H2S的灵敏度达65,对体积浓度为50×10-6 H2S的灵敏度高达169,且灵敏度与气体浓度呈现良好的线性关系。此外,纯WO3和SnO2(3%)-WO3材料在相对湿度RH=22%～64%时有良好的抗湿性。     

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.     

Fe掺杂NiO纳米花状微球的制备及其气敏性能研究

采用水热法成功制备了Fe掺杂NiO纳米花状微球,研究了Fe掺杂量对微球结构、形貌和气敏性能的影响。气敏实验结果表明:Fe掺杂NiO纳米微球基气敏元件对丙酮的气敏性能较纯相NiO显著提高;当Fe掺杂量为0.03g时,气敏器件在工作温度为280℃,丙酮质量浓度为3.7×10~(-4) mg/L条件下,气体灵敏度为41.8,是相同条件下未掺杂NiO基气敏元件的12倍,该气敏元件在检测低浓度丙酮气体时也表现出优异的性能。     

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。     

纳米结构Pt/WO3薄膜的制备、表征及氢敏性能

以钨粉和双氧水为主要原料,采用溶胶 - 凝胶法制备了WO3纳米薄膜,并用磁控溅射法在该WO3薄膜表面溅射掺杂了催化剂Pt.研究了该Pt/WO3纳米薄膜的结构和氢敏性能,结果表明,用此种方法制备的WO3基掺Pt薄膜具有良好的氢敏特性;平均膜厚160nm;薄膜经400℃以下退火处理后是非晶态结构,表面疏松多孔,氢敏效果好;经400℃以上退火处理后呈晶态结构,表面粗糙致密,氢敏效果差;Pt掺杂量对薄膜的氢敏效果有影响,掺杂量越多,氢敏效果越差.     

MnWO_4-Li_2WO_4系厚膜湿敏元件的性能

本文采用溶胶凝胶法制备WO3纳米粉体,再与MnCO3固相反应合成MnWO4,掺杂得到不同配比的MnWO4一Li2WO4湿敏材料,通过丝网印刷工艺制备厚膜湿敏元件.实验研究表明在适当的工艺条件下,MnWO4中掺杂30m01%Li2WO4的材料,所制备的元件具有低湿电阻小、灵敏度高、响应速度快、湿滞小的特点,这些特点为产品的实用化提供了有利条件.SEM照片和复阻抗分析.表明,该方法制备的材料具有纳米晶粒和优良的晶界微结构,是改善元件性能的重要原因.     

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.     

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。     

Preparation of gold/polyaniline/multiwall carbon nanotube nanocomposites and application in ammonia gas detection

Composites of multiwall carbon nanotubes (MWNTs), polyaniline (PANI), and gold nanoparticles were prepared by one pot synthesis. Based on the interaction between aniline monomers and MWNTs, aniline molecules were adsorbed and polymerized on the surface of MWNTs. The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoemission spectroscopy (XPS). The sensors based on Au/PANI/MWNT nanocomposites were tested for on-line monitoring of ammonia gas. The results show that the as-prepared sensors have superior sensitivity, and good repeatability upon repeated exposure to ammonia gas.     

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.     

Single-wall carbon nanotubes/epoxy elastomers exhibiting high damping capacity in an extended temperature range

In nanocomposites containing single-wall or multi-wall carbon nanotubes (SWCNT and MWCNT) high damping can be achieved by taking advantage of the weak bonding and interfacial friction between individual nanotubes and the matrix. The increase in damping capacity has already been proved for stiff epoxies and in this study it is extended to epoxy elastomers. Variable amounts (0.5–3 wt%) of oxidized SWCNT were dispersed by ultrasonication in precursors of an epoxy elastomer based on the reaction of diglycidylether of bisphenol A (DGEBA) and a polyoxypropylene with average molar mass of 2000, end-capped with primary amine groups. The quality of the initial dispersion was assessed by the constancy of the storage modulus with frequency in the low-frequency range. A rheological percolation threshold of 0.41 wt% SWCNT was found. Cured elastomers exhibited a large increase of the loss modulus with increasing amounts of SWCNT. For 3 wt% SWCNT, the increase in loss modulus was 1400% at room temperature. When temperature was increased up to 140 °C the loss modulus of the nanocomposite was practically constant while the one of the matrix dropped to a negligible value. The damping capacity at high temperatures opens important practical applications.     

基于Si-NPA的WO_3薄膜电容湿敏性能

采用匀胶旋涂技术将WO3溶胶沉积在硅纳米孔柱阵列(si-NPA)衬底上,经500℃退火制得WO3/Si-NPA复合薄膜.场发射扫描电镜和x射线衍射的表面形貌和结构分析表明,WO3在Si-NPA表面形成连续薄膜,且复合薄膜保持了Si-NPA规则阵列结构的特点.湿敏测试结果显示:在11%到95%的相对湿度范围内,WO3/Si-NPA湿敏元件输出电容强,且随测试频率的增加而单调降低;随着WO3薄膜厚度的增加,湿敏元件灵敏度明显增大,但元件相应的响应/恢复时间却延长.     

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.     

Direct-write fabrication of freestanding nanocomposite strain sensors

This paper deals with the design and microfabrication of two three-dimensional (3D) freestanding patterned strain sensors made of single-walled carbon nanotube (SWCNT) nanocomposites with the ultraviolet-assisted direct-write (UV-DW) technique. The first sensor consisted of three nanocomposite microfibers suspended between two rectangular epoxy pads. The flexibility of the UV-DW technique enables the sensor and its housing to be manufactured in one monolithic structure. The second sensor was composed of a nanocomposite network consisting of four parallel microsprings, which demonstrates the high capability of the technique when compared to conventional photolithographic technologies. The performances of the sensors were assessed under tension and compression, respectively. The sensors' sensitivities were evaluated by correlating their measured resistivities to the applied displacements/strains. Electrical conductivity measurements revealed that the manufactured sensors are highly sensitive to small mechanical disturbances, especially for lower nanotube loadings when compared to traditional metallic or nanocomposite films. The present manufacturing method offers a new perspective for manufacturing highly sensitive 3D freestanding microstructured sensors.