Comparative investigation of three types of ethanol sensor based on NiO-SnO2 composite nanofibers

NiO-SnO2 composite nanofibers were synthesized via electrospinning techniques and characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy.Three types of sensor were applied to investigate the sensing properties of these nanofibers.Sensors A were fabricated by mixing the nanofibers with deionized water,and then grinding and coating them on ceramic tubes to form indirect heated gas sensors.Microsensors B(with an area of 600 μm×200 μm) were formed by spinning nanofibers on Si substrates with Pt signal electrodes and Pt heaters.Sensors C were fabricated by spinning nanofibers on plane ceramic substrates(with a large area of 13.4 mm×7 mm) with Ag-Pd signal electrodes only.The operating temperatures of sensors A and B were controlled by adjusting heater currents,and the operating temperatures of sensors C were controlled by adjusting an external temperature control device.Experimental results show that sensors C possess the highest sensing properties,such as high response values(about 42 to 100 μL/L ethanol),quick response/recovery speeds(the response and recovery times were 4 and 7 s,respectively),and excellent consistencies.These phenomena were explained by the retained fiber morphology and suitable sensor area.The presented results can provide some useful information for the design and optimization of one-dimensional nanomaterial-based gas sensors.     

Improved and excellent CO sensing properties of Cu-doped TiO<Subscript>2</Subscript> nanofibers

Cu-doped TiO2 nanofibers with an average diameter of about 80 nm are synthesized through an electrospinning method. Both anatase and rutile crystallographic structures are found in the fibers based on XRD results. Compared with pure TiO2 nanofibers, the Cu-doped TiO2 nanofibers exhibit improved CO sensing properties at 300°C. The sensitivity of Cu-doped TiO2 nanofibers is up to 3 when the sensor is exposed to 5 ppm CO, and the response and recovery times are about 4 and 8 s, respectively. Good selectivity i...     

Micro-structure sensors based on ZnO microcrystals with contact-controlled ethanol sensing

ZnO microcrystals are synthesized through a facile solution method and characterized by field-emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and X-ray diffraction. The ethanol sensing properties of these microcrystals are investigated by spin-coating them on a silicon substrate with Pt electrodes to fabricate a micro-structure sensor. The sensitivity is up to 8 when the sensor is exposed to 50 ppm ethanol, and the response time and recovery time are 10 s and 20 s, respectively. A contact-controlled model is established to explain the sensing properties of the microcrystals, which provides another approach to realize high-performance gas sensors.     

Improved ethanol, acetone and H2 sensing performances of micro-sensors based on loose ZnO nanofibers

Both one-dimensional nanostructures and porous nanostructures are benefit to the sensing enhancement of semiconducting functional materials.The present paper shows an effective route to combining the advantages of these two nanostructures for a novel type of ZnO nanomaterials.Basically,a pore-forming material is employed in an electrospinning method,and the products are characterized by X-ray powder diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),and transmission electron microscopy(TEM).The obtained materials are loose ZnO nanofibers,which own both porous and one-dimensional nanostructures.Micro-sensors are fabricated by sputtering and etching techniques,and the as-prepared nanofibers are used as the functional materials in them.The sensors show improved sensing properties both in sensitivity and response-speeds.The sensitivity is enhanced from 4 to 8 and the response time is shortened from 14 to 10 s when the sensors are exposed to 100 μL/L ethanol at 260℃.Similar results are also observed in acetone and H2 sensing tests.These enhancements are based on the one-dimensional and porous nanostructures of the nanofibers.     

静电纺丝法制备YAG-ZrO2复合纳米纤维

运用静电纺丝技术结合热处理工艺成功制备了形貌光滑、尺寸均匀的YAG-ZrO₂复合纳米纤维.采用XRD、FT-IR和SEM探索了电压与浓度对复合纤维物相及形貌的影响.结果表明:电压为25 kV、PVA质量分数为11%时得到表面光滑、尺寸均一的复合纤维前躯体.前驱体纤维经过1 200 ℃煅烧5 h后,具有较高的结晶度,直径约为500 nm且比较均匀.为了使YAG-ZrO₂纤维增强的复合材料具有自检性,研究了YAG-ZrO₂纤维的发光性能,发现用290 nm紫外光激发YAG-ZrO₂:Tb³⁺复合纳米纤维,在581 nm处出现明显的发射峰,并发出绿光,这一现象属于Tb³⁺的⁴D₄→⁷F₄跃迁.应力-发光实验结果表明,YAG-ZrO₂:Tb³⁺纤维可以实现对铝基复合材料应力-应变的检测.     

Improved and excellent ethanol sensing properties of SnO2/multiwalled carbon nanotubes

SnO₂/multiwalled carbon nanotubes (MWNTs) have been studied as gas sensing materials. Compared with pure SnO₂, SnO₂/MWNTs exhibit improved ethanol sensing properties such as higher sensitivity and quicker response/recovery at 300°C. The sensitivity is 35, 65, 166 and 243 to 500, 1000, 2000 and 3000 ppm ethanol, respectively. The response time is about 1 s, and the recovery time is about 5 s. The sensing improvement is explained in terms of the appropriate basal resistance and enhanced signal transfer brought by MWNTs.     

MISiC肖特基二极管式气体传感器响应特性分析

分析了金属－绝缘体－SiC(MISiC)结构肖特基二极管（SBD）气体传感器敏感机理，通过将热电子发射理论与隧道理论结构，建立了器件物理模型。模拟结果表明，响应特性与金属电极类型，绝缘层厚度，气体吸收效率和温度有关。模型结果与实验符合较好。通过模拟，得到MISiC结构最佳绝缘层（SiO2)厚度应为１nm左右。     

基于半导体陶瓷技术的二氧化碳传感器研究

采用硬质酸盐方法制备出纳米BaTiO3粉末,利用半导体陶瓷技术掺杂CeO-AgNO3制造出对CO2气体敏感的功能材料.基于CaCO3和RuO2制作电极,NiCr丝加热.CO2气体传感器当加热到400~450℃时,CO2体积分数为100×10-6~2 000×10-6,传感器的特征阻值由600 kΩ变化到150 kΩ,函数关系呈良好的全对数线性,同时测定了元件的温度特性和湿度特性,提出了此种传感器工作时,为提高传感器测试准确性,应考虑环境温湿度补偿技术.     

电纺CoFe2O4纳米纤维及其磁性研究

采用溶胶-凝胶过程和静电纺丝技术,以三氯化铁(FeCl3·6H2O)、醋酸钴(Co(CH3COO)2·4H2O)和聚乙烯醇(PVA)为前驱物,制得PVA/FeCl3/Co(CH3COO)2复合纳米纤维.经高温煅烧,制备了CoFe2O4纳米纤维.利用扫描电镜(SEM)、红外光谱(FT-IR)、差热-热重(TG-DTA)和X射线衍射(XRD)等分析测试手段对样品进行了表征,并研究了其磁性质.结果表明:静电纺丝技术制备的CoFe2O4纳米纤维为规则的一维结构,直径分布均匀,具有良好的铁磁性.     

纳米碳纤维复合材料的阻温特性研究

采用超声波分散的方法制备了纳米碳纤维/环氧树脂复合材料,研究了纳米碳纤维含量对复合材料导电性能的影响,并对其伏安特性及阻温特性进行了探讨.研究结果表明:复合材料的电阻率随纳米碳纤维质量分数的增加呈几何级数递减,其渗滤区域在0.1%~0.2%之间;其电流-电压关系基本符合欧姆定律;复合材料在升温和降温过程中均呈现出正温度效应和负温度效应,并具有较好的回复稳定性.     

PVPZn(Ac)_2复合纳米纤维的制备及其参数优化

采用静电纺丝法制备了PVP/Zn(Ac)2复合纳米纤维,利用扫描电子显微镜对其表面形貌进行了表征.研究了PVP含量、纺丝电压、乙酸锌含量等因素对纺丝过程和纤维形貌的影响,同时分析了不同参数引起纤维形貌变化的原因.结果表明,当2mL乙醇中PVP的含量为0.248g,2.5mL DMF中乙酸锌的含量为0.501g,纺丝电压为17kV时,可以得到平均直径为180nm、表面光滑而且连续性很好的PVP/Zn(Ac)2复合纳米纤维,实现了ZnO前驱体纳米纤维的可控制备.     

贵金属掺杂纳米偏锡酸锌气敏性能及其机理分析

运用共沉淀法制备出纳米ZnSnO3粉末,X射线衍射仪(XRD)分析为纯的ZnSnO3相,透射电镜(TEM)分析表明粒度达到纳米级.利用传统的旁热厚膜制备工艺制备了纯ZnSnO3及其掺杂贵金属的气敏传感器,测试了气敏性能.通过对气体吸附机理和扫描电子显微镜(SEM)对敏感层的分析解释气敏性能提高的原因.结果表明: Ag+、Pd2+的掺杂可提高器件对C2H5OH的灵敏度,对H2敏感度的提高达到15倍以上.掺杂阻碍了基体晶粒的长大,使其表面不规则且有较多气孔,这是气敏性能提高的主要原因.     

Influence of acetone on nanostructure and electrochemical properties of interfacial synthesized polyaniline nanofibers

The growth of polyaniline(PANI) nano fi bers through interfacial polymerization can be well controlled by adding a small amount of acetone in the water/chloroform system. It was found that the polymerization rate became slower in the presence of acetone, yielding PANI nano fi bers with larger aspect ratios. The in fl uences of the acetone addition on the morphology, microstructure and properties of as-prepared PANI nano fi bers were studied by scanning electron microscope(FE-SEM), ultraviolet–visible spectra(UV–vis), Fourier transform infrared(FT-IR) and Raman spectroscopy, X-ray diffraction(XRD), thermogravity analysis(TGA), and electrical and electrochemical measurements. The experimental results showed that PANI nano fi bers prepared by using ammonium persulfate(APS) as an oxidant with acetone exhibited slower growth, the larger ratio of length to diameter, and higher crystallinity(2θ=6℃, 19℃, 26℃) than that without acetone, meanwhile remained larger yield of 11.23% and higher conductivity 1.8*10-2S/cm compared with that obtained by replacing APS with Fe Cl3. More importantly, these PANI nano fi bers exhibited better electrochemical behaviors, which bene fi tted from their high crystallinity and good conductivity.     

Nb2O5纳米纤维的尺寸与物相调控研究

采用静电纺丝技术制备不同晶体结构的Nb2O5纳米纤维,利用SEM和XRD技术对产物的形貌和结构进行表征.结果表明:所得Nb2O5纳米纤维晶化良好、尺寸分布均匀、长径比高且连续性好.通过调整静电纺丝的电压,可对纳米纤维的直径进行调控.调整退火温度和退火气氛,可分别获得伪六方、正交、单斜和正交/单斜混合相的纳米纤维.     

H2 sensing properties of modified silicon nanowires

It has been found that the silicon nanowires modified with noble metals can be used to fabricate an effective H2 gas sensor in the present study.The preparation and surface modification of silicon nanowires(Si NWs) were carried out by chemical methods. The morphology of the silicon nanowires unmodified and modified with nanoparticles of platinum, palladium, silver and gold was investigated using scanning electron microscopy(SEM). The chemical composition of the silicon nanowire layers was studied by secondary ion mass spectroscopy(SIMS) and energy dispersive X-ray analysis(EDX). The structures of type metal/Si NWs/p-Si/Al were fabricated. The electrical characterization(I–V) was performed in primary vacuum and H2 at different concentrations. It was found that the metal type used to modify the Si NWs strongly influenced the I–V characteristics. The response of these structures toward H2 gas was studied as a function of the metal type. Finally, the sensing characteristics and performance of the sensors were investigated.     

基于可靠性的框架结构作动器/传感器最优配置

建立在模态可控度及最小费用函数的基础上，针对目前因使用组合优化来布置作动器计算量大的缺点，采用遗传算法来确定振动主动控制中作动器的最优配置．为适于框架结构的具体计算，对常规遗传算法约束条件的处理进行了改进．考虑到主动控制系统的可靠性，为了进一步确定作动器／传感器的最优配置，本文定义了一个可靠性指标，采用常规的Monte-Carlo法计算各种配置的可靠性，在可靠性基础上最终确定最优配置方案．本文最后给出了计算实例。     

静电纺再生纤维素复合纳米纤维的制备及其性能研究

利用静电纺丝制备聚丙烯腈/醋酸纤维素(PAN/CA)复合纳米纤维膜,并依次用0.05mol/L、0.1mol/L NaOH溶液对其进行水解处理,制得聚丙烯腈/再生纤维素(PAN/RC)复合纳米纤维膜.研究表明:纺丝液流量为0.5mL/h,所施加的电压为17kV,接收距离为18cm时,制得的PAN/CA复合纳米纤维直径更均匀,成丝形态更稳定.对PAN/CA复合纳米纤维膜及PAN/RC复合纳米纤维膜分别进行电镜扫描、红外光谱分析及静态接触角测定.结果表明:水解后的复合纳米纤维形态保持稳定,PAN/CA复合纳米纤维中的醋酸纤维素的酯基在碱处理后得到有效水解,复合纳米纤维膜的静态接触角由水解前的124.7°降低为10.1°,亲水性能得到大幅提升.     

基于Labview的热敏电阻温度传感系统设计

在简要阐述虚拟仪器技术Labview和热敏电阻测温原理的基础上,介绍一种基于虚拟仪器技术的温度传感系统。重点说明如何利用虚拟仪器工作平台来实现数据的采集、处理、显示和保存等功能。通过对温度传感系统进行标定,进而得到准确的被测对象温度曲线。该系统具有界面形象、操作方便、可靠性高等优点。     

Sensitivity dependence of surface plasmon resonance based sensors on prism refractive index

We theoretically and experimentally demonstrate that refractive index of the prism used to load metal film has significant influence on sensitivity of surface plasmon resonance based sensors. The prism with lower refractive index gives the sensors a higher sensitivity in detecting refractive index variations of a sample. We attribute this effect to the fact that a prism with low refractive index will increase coupling distance between surface plasmons and the medium under investigation. Foundation item: Supported by Wuhan University and National Education Ministry of China Biography: Wang Guo-ping (1964-), male, Professor, research direction: bolographic materials, diffractive optical elements, optical properties of metallic nanopracticles and metal-dielectric nanostructures     

一种基于无源传感器的数据采集传输系统设计

无线无源传感器的设计是传感器网络应用中关注的焦点.传统温湿压数据采集系统是单参数封装系统,针对此系统输出单一、可靠性低的特点,基于多参数混合封装技术,设计一种基于无源传感器的数据采集传输系统.该系统由基于STC(system chip)89C52的定时计数采集、基于ZigBee协议栈无线自组网传输及上位机3部分构成.结合实际应用对系统软硬件进行设计,实际测试结果表明该系统具有有效性和可行性.