CeO2/SnO2纳米材料的制备与气敏性能研究

本文应用溶胶-凝胶法制备了7种不同成分和煅烧温度的CeO2/SnO2材料,应用X射线衍射方法对其中的3种进行了结构表征和粒度分析,运用自组装的气敏性能设备检测了该7种不同成分的CeO2/SnO2材料的气敏性能,简要分析了其气敏机理。结果表明:掺杂CeO2有利于SnO2晶粒的细化;掺杂CeO2和La2O3可改变或提高SnO2气敏材料对某些气体的气敏性能;煅烧温度在600℃~800℃之间,掺杂2?O2的CeO2/SnO2气敏材料,随煅烧温度上升,气敏性能下降;煅烧温度600℃、掺杂5?O2的CeO2/SnO2气敏材料,对乙醇具有较高的灵敏度和选择性,具有开发应用价值;CeO2/SnO2气敏材料的气敏机理为表面电导控制型。     

ZnO掺杂的SnO_2纳米纤维的制备、表征及气敏机理(英文)

以二水氯化亚锡(SnCl2·2H2O)为盐原料,采用静电纺丝的方法制备了SnO2纳米纤维.为了研究ZnO掺杂对SnO2形貌、结构及化学成分的影响,分别制备了不同含量ZnO掺杂的SnO2/ZnO复合材料.利用热重-差热分析(TG-DTA)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱仪、扫描电镜(SEM)及能量色散X射线(EDX)光谱对材料的结晶学特性及微结构进行了表征.制备的SnO2/ZnO复合材料是由纳米量级的小颗粒构成的分级结构材料.ZnO含量不同,对应的SnO2/ZnO复合材料结构不同.表征结果表明ZnO的掺杂量对SnO2材料的形貌及结构均起着重要作用.将制备的不同ZnO含量的SnO2/ZnO复合材料进行气敏测试,测试结果表明,Sn:Zn摩尔比为1:1制作的气敏元件对甲醇的灵敏度优于其它摩尔比的气敏元件.讨论了SnO2/ZnO复合材料气敏元件的敏感机理.同时针对Sn:Zn摩尔比为1:1时表现出最好的气敏响应,分析了其原因,包括Zn的替位式掺杂行为、ZnO的催化作用、过量ZnO对SnO2生长的抑制作用以及SnO2与ZnO晶粒界面处的异质结.     

热解法制备纳米SnO2及其气敏性能研究

作为一种n型金属氧化物半导体，SnO2由于具有寿命长、灵敏度高和成本低等特点而一直是电阻式气敏传感器研究的热点．由于SnO2材料的气敏效应是晶粒表面控制型的，因此，SnO2的传感性能对其粒径和比表面积的大小有很强的依赖性．改进SnO2制备方法，提高其气敏效应一直是气敏传感器研究的热点．目前，文献报道的方法大多是以SnCl4为原料制备SnO2，而以其它锡盐为原料的研究则很少。本文以SnC2O4为原料，通过低温直接热解SnC2O4制得SnO2．所得产物具有粒径小、分布均匀和比表面积大的特点，且具有良好的酒敏特性，该产物的红外吸收出现明显的红移现象。     

掺杂La2O3的SnO2纳米颗粒的制备及对三甲胺气敏性能的研究

采用均相沉淀法制备了SnO2以及掺杂不同La2O3质量比的SnO2纳米颗粒,对材料进行TG-DTA热分析、Zeta电位测定及XRD表征,将材料制作成烧结式La2O3-SnO2复合材料气敏元件,并测试了元件对三甲胺的气敏性能。研究表明:所得粉体粒径在4~10nm之间,且SnO2粉体粒径随La2O3掺杂量的增加而减小。少量La2O3的掺杂显著改善了SnO2对低浓度TMA的灵敏度,工作电压5V时,La2O3掺杂量为5wt%的SnO2纳米颗粒对12μg/L和173μg/L TMA的灵敏度分别达到6.4和120。     

超声喷雾共沉淀法制备纳米氧化锡粉体及其气敏性研究

采用超声波喷雾技术,以SnCl4·5H2O和CO(NH2)2为前驱体原料制备了氧化锡以及Ce稀土离子掺杂纳米粉体.详细地研究了超声喷雾条件、反应时间以及化学组分对纳米SnO2粉体的形貌和尺寸的影响规律,以及前驱体沉淀物脱水化学处理的条件.用XRD,TEM研究了所获纳米粒子的晶相和形貌.结果表明,制备的SnO2纳米粒子呈球状,尺寸在10～20 nm,纳米颗粒均匀,分散性好.以该粉体为基础制备了相应的气敏元件,测定了气体灵敏度与温度和稀土元素掺杂的关系.研究测试表明,纳米SnO2半导体气敏元件对NO2气体有着良好的响应-恢复特性,并且具有较高的灵敏度和较低的工作温度.稀土元素铈的掺杂能明显提高纳米SnO2粉体的气敏性能.     

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     

钛酸钠纤维表面自组织生长SnO2纳米晶体

SnO2是重要的宽禁带半导体材料之一,禁带宽度为3.6 eV,在透明导电膜、气敏传感器、光催化、太阳能转换等有广泛的应用.纳米尺度SnO,材料存在许多优异的物理化学性能,受到特别的关注.合成SnO2纳米材料的方法有气相法、溶胶凝胶法、液相沉淀法、固相法、水热法等,其中水热法是在高压釜里的高温、高压反应环境中,采用水作为反应介质的结晶过程.     

球形SnO2 纳米微粒的合成及形成机理分析

以SnCl4*5H2O为主要原料,用溶剂热技术在油酸体系中成功地合成了球形SnO2纳米微粒,在无水乙醇体系中合成了菱形的SnO2纳米微粒.通过X射线粉末衍射(XRD),选区电子衍射(SAED)和透射电镜(TEM)对两种产物进行了表征,并对两种产物的形成机理进行了分析.透射电镜(TEM)结果表明: 在油酸体系中得到了平均尺寸约为 3.5 nm的球形SnO2纳米微粒,此微粒趋向于特殊高的比表面积,适合于作气敏探测器材料方面的应用.     

热解法制备纳米sno2及气敏性能

在不同温度下热解SnC2O4制备出纳米SnO2。利用XRD、红外光谱测试技术研究了SnO2的形貌、结构及晶粒生长过程,对它们的气敏性能进行了研究。结果表明,随着热解温度的不同,获得的颗粒尺寸不同。机理研究显示:650℃以上或650℃以下SnO2颗粒生长的方式不同。当热处理温度<650℃时,晶核生长以表面扩散为主,晶粒生长缓慢;在650℃以上热解时,晶粒以晶界迁移进行粒子生长,生长比较迅速。热解温度对气敏灵敏度影响很大,对响应恢复时间影响不大。热解法合成的SnO2纳米材料具有较好的酒敏性能,650℃热处理所得样品的气敏性能最佳,在灵敏度、响应恢复时间上表现优良。     

介孔SnO2的结构表征及其湿敏性能

以十六烷基三甲基溴化铵、十二胺为模板剂, 采用双模板法及均相沉淀法, 分别制备了介孔结构的SnO2. BET测试结果表明, 双模板法制备的介孔SnO2平均孔径、孔容和比表面积分别为4.9 nm、0.213 m3·g-1和172.9 m2·g-1, 而均相沉淀法合成产物孔径分布的离散程度较大, 孔容和比表面积降至双模板法的66.0%和21.8%. 以叉指电极为工作电极集电体, 利用交流阻抗技术测定了所得SnO2的湿敏性能. 结果表明, 与均相沉淀法制备的SnO2 相比, 双模板法制得SnO2的双电层电荷传递阻抗、双电层电容及Warburg扩散系数随湿度变化的幅度更明显, 表明其具有较好的湿敏性能. 对介孔结构特征与湿敏性能相关性研究表明, 具有较大孔容和比表面的介孔SnO2可改善材料的感湿性能.     

Morphology and electrochemical properties of a composite produced by a peroxide method on the basis of tin dioxide and carbon black

Using peroxostannate as a precursor, a composite material based on tin dioxide and carbon black was obtained, in which tin dioxide forms a coating on the surface of carbon black nanoparticles. The synthesized material was characterized by electron microscopy and X-ray powder diffraction analysis, and also the electrochemical characteristics of this material as an anode material for lithium-ion batteries were studied. The material demonstrates good stability and rate performance, which is indicative of the efficiency of the peroxide method for producing promising inexpensive anode materials based on tin dioxide and carbon black.     

Graphene oxide supported tin dioxide: synthetic approaches and electrochemical characterization as anodes for lithium- and sodium-ion batteries

The review addresses synthetic approaches to composite materials based on graphene oxide and nano tin dioxide and their electrochemical properties as anodes for lithium- and sodiumion batteries. The introduction of a carbon matrix into the composite material improves the electrochemical characteristics of the anodes. In most methods, the synthesis of graphene oxide–tin dioxide composites is based on the use of tin(II,IV) chlorides as the starting compounds, and the most efficient electrode materials were obtained by the hydrothermal or solvothermal routes. Thermal processing is much more economic than the gas phase deposition protocols but requires heating of a large volume of dilute tin oxide dispersions in an autoclave. Mechanochemistry (ball milling) is also economically unfavorable for the synthesis of composite materials. In addition, large volumes of acidic wastes that should be neutralized and safely discarded are formed when tin chlorides are used. An alternative environmentally friendly technique based on the use of aqueous peroxide solutions can be applied for the production of efficient anode materials based on graphene oxide and tin dioxide. This process does not involve acidic wastes, uses hydrogen peroxide and ethanol as reagents, and accomplishes film deposition (coating) at room temperature. Final thermal treatment is required only for the active material, which minimizes energy expenses and equipment costs.     

Miniaturized chemical multiplexed sensor array

Miniaturized tin oxide semiconductor sensors are fabricated directly by site-specific dip-pen nanopatterning using precursor inks derived from the sol-gel method. The good flow characteristics and strong affinity of the sols to measurement electrodes enable intimate contact. The measurable, reproducible, and proportionate changes in the resistance of the sensors when exposed to trace quantities of oxidative and reducing gases constitute the basis for such sensors. These sensors show rapid response and ultrafast recovery for the detection of nitrogen dioxide and acetic acid. Furthermore, an array of eight miniaturized sensors is created by doping the pristine tin-based sol ink with different metal ions; the different responses of each sensor to certain gases constitute a reference response spectrum that can be used to recognize the gas. Such recognition ability, instant response and rapid recovery, compact size, and integration with the current microelectronics platform make the miniaturized sensor array a significant development for the on-site and real-time detection of life-threatening gases.     

Sensitivity to hydrogen of sensor materials based on SnO2 promoted with 3d metals

The sensitivity to hydrogen and the catalytic activity in the oxidation of hydrogen of sensor materials based on tin dioxide and doped with cobalt, nickel, iron, and copper have been studied. The sensitivity of the sensors and the degree of conversion of hydrogen pass symbatically through a maximum with increasing quantity of each of the dopants. The results are explained by the influence of grain boundaries between tin dioxide and the dopants applied during the course of the oxidation reaction of hydrogen on the sensor material and on the sensitivity of the sensor to H₂. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 121–125, March–April, 2008.     

Modeling of hydrocarbon sensors based on p-type semiconducting perovskites

In the scope of the present contribution, perovskite SrTi(1-x)Fe(x)O(3-delta) was investigated as a model material for conductometric hydrocarbon sensing at intermediate temperatures between 350 and 450 degrees C. To explain the observations made during sensor optimization in a quantitative way, a novel sensor model was proposed. At the microscopic scale, the local gas concentration affects local conductivity of the gas sensitive material. In the case of n-type tin oxide sensors, this interaction is commonly attributed to a redox reaction between the reducing analyte gas and adsorbed oxygen. In contrast, a reduction process affecting the entire bulk was assumed to govern gas sensitivity of SrTi(1-x)Fe(x)O(3-delta) films. Although very few variables needed to be assumed or fitted, the present bulk-type model was found to represent well sensor functionality of p-type conducting SrTi(0.8)Fe(0.2)O(3-delta) films. In addition to the temperature dependence of sensor response, the hydrocarbon sensitivity, m, was predicted with good accuracy. The different sensor responses towards hydrocarbons with a different chemical reactivity and other cross-interfering species, such as NO, was explained as well as the dependence on film thickness for screen printed films.     

Methodology for the selection of suitable sensors for incorporation into a gas sensor array

An investigation into suitable mathematical techniques which can be used to select sensor components for a gas sensor array is reported. Data from a tin dioxide Taguchi semiconductor sensor array were obtained individually for various organic solvents and analysed using multivariate techniques, including principal component analysis, cluster analysis and star symbol plots. It was shown that the array data produced a series of characteristic response patterns for the analytes. It was also found that analytes of similar chemical nature had similar response patterns, indicating a correlation between sensor interaction and the chemical functional groups of the analyte. The multivariate techniques used proved to be very useful in enabling a suitable selection of the components of the array to be made by identifying which of the components or sensors were acting independently.     

The optical and gas-sensitive properties of opal-like structures based on SnO<Subscript>2</Subscript>

Opal-like materials based on tin dioxide were prepared, and their structural and sensor characteristics were studied. The optical transmission spectra of opal-like structures based on SnO₂ were recorded, and the volume fraction occupied in them by tin dioxide was estimated. It was shown that structures based on SnO₂ contained a photon stop-zone in the visible spectrum range. The sensor properties of the materials toward CO and H₂ were studied over the temperature range 375−425°C. The SnO₂ samples studied had much higher sensitivity to CO compared with SnO₂ materials without opal-like structures.     

Lifetime-based optical sensor for high-level pCO2 detection employing fluorescence resonance energy transfer

An optical sensor for the measurement of high levels of carbon dioxide in gas phase has been developed. It is based on fluorescence resonance energy transfer (FRET) between a long-lifetime ruthenium polypyridyl complex and the pH-active disazo dye Sudan III. The donor luminophore and the acceptor dye are both immobilised in a hydrophobic silica sol–gel/ethyl cellulose hybrid matrix material. Tetraoctylammonium hydroxide (TOA-OH) is used as an internal buffering system. Fluorescence lifetime is measured in the frequency domain, using low-cost phase modulation measurement technology. The use of Sudan III as an acceptor dye has enabled the sensor to have a dynamic range up to 100% carbon dioxide. The sensor displays 11.2° phase shift between the limit of detection (LOD) of 0.06 and 100% CO₂ with a resolution of better than 2%. The encapsulation in the silica/polymer hybrid material has provided the sensor with good mechanical and chemical stability. The effect of molecular oxygen, humidity and temperature on the sensor performance was studied in detail.     

Synthesis and Gas-sensing Performance of Nanosized SnO2

Nanosized tin dioxide particles were prepared by sol-gel dialytic processes with tin(Ⅳ) chloride and alcohol as start materials. The nanoparticles of tin dioxide were charactered by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET. The results show that the average diameter of tin dioxide particles dried at 353 K was about 2nm. Even if the tin dioxide particles were calcined at 873 K, the average diameter of particles was less than 10 nm. The removal of Cl^- was solved by using this kind of method. The mechanism of the formation of tin dioxide nanosized particles was proposed and analyzed in this paper. We also measured the sensitivity of the sensor based on the tin oxide powder calcined at 673K to NH3, alcohol, acetone, hexane and CO. The gas-sensing performance results indicate that this sensor has a higher sensitivity to alcohol and acetone, and selectivity for NH3, hexane and CO at an operating temperature of 343 K.     

Semiconductor Detector for Gas Leakages from a Main Line without Digging Ground

A chromatographic semiconductor detector was developed for an instrument designed for finding main-line gas leaks without digging. The sensing element of the detector is an adsorption semiconductor sensor based on tin dioxide doped with antimony and containing palladium additives. The optimum operation conditions of the sensor as a chromatographic detector were determined. The detector was highly sensitive to hydrocarbons (to 0.5 ppm in terms of CH₄). The stability of the developed detectors was examined.