In2O3纳米材料的制备及其气敏特性的研究

文中采用溶胶－凝胶法合成了In2O3纳米粉体,确定其晶体结构并掺入Co3O4、Au等掺杂剂制成烧结式器件,该器件对CO气体具有较高的灵敏度,良好的响应恢复特性和选择性。     

金掺杂氧化铪薄膜的电阻转变性能研究

采用射频磁控溅射法在ITO基底上制备了Hf O2和Hf O2:Au薄膜,并对Cu/Hf O2/ITO和Cu/Hf O2:Au/ITO三明治结构进行了电阻转变性能测试。结果表明:两者均展现出可逆双极电阻转变性能,但Cu/Hf O2:Au/ITO器件的SET电压较小,电压分布更加集中并且性能更稳定。通过对器件双对数I-V曲线拟合分析,发现其电阻转变机制为空间电荷限制电流效应。金的掺入增加了薄膜中的缺陷,提高了基于氧空位的导电通道的均一性,从而优化了器件的电阻转变性能。     

孔深孔径对多孔湿度传感器灵敏度的影响

湿度传感器有电阻和电容等类型,由此可以从电阻和电容等方面分析湿度的变化.根据多孔Al2O3电容湿度传感器微观结构,建立了该器件的等效电路模型,利用此模型讨论了孔深和孔径对多孔Al2O3 湿度传感器性能的影响.根据孔深孔径的合理取值范围,通过仿真,找出孔高比与面积占空比的最佳值,提高了湿度传感器的灵敏度.     

NiO基厚膜NO_2传感器的研制

文中分别以化学沉淀法、柠檬酸法和均相沉淀法制备了NiO纳米材料,通过XRD方法对所制备材料的晶体结构进行分析表征.并以上述不同方法制备的NiO为基体材料,Cr2O3、WO_3为掺杂剂制作了电导型厚膜NO_2气体传感器.研究了工作温度、掺杂剂等对器件气敏性能的影响.结果表明:掺杂WO_3的NiO基厚膜传感器对NO_2有较高的灵敏度、良好的选择性及响应特性,并且对器件的敏感机理做了初步的分析.     

MCS-48单片机I/O扩展技术

MCS-48单片机有27根I/O线,能满足一般场合的应用,但是当应用系统需配备各种外设(如键盘、显示器等)时,或进行工业控制(工业控制需相当数量的I/O点数)时,芯片的I/O线就不够用了,此时就需要进行扩展。MCS-48单片机允许四种I/O扩展方式:一、使用一个特别的廉价扩展器8243;二、用标准的MCS-0185 I/O器件扩展;三、可用存贮器、I/O组合扩展器件进行扩展(如8155、8355等);四、也可用标准TTL(74系列)器件扩展。一、通过扩展器8243进行扩展对于小系统,最有效的I/O扩展方法是使用8243扩展器。8243是专门为MCS-48单片机设计的一种廉价的4位I/O扩展芯片,可以扩展4个4位I/0口,MCS-48单片机     

基于稀土荧光材料的光纤温度传感器

本文采用稀土荧光材料,设计了一套荧光光纤测温系统。系统选取经济实用的发光二极管作为光源,以稀土材料Y2O2S:Eu Fe2O3作为敏感材料,通过一套荧光信号检测装置,对荧光寿命进行测量。利用产生的荧光的周期与激励光相同,但在相位上滞后于激励光这一特性,对微弱荧光信号进行检测,有效抑制系统噪声,提高了系统的信噪比。通过实验对几种敏感材料进行光谱测试,Y2O2S:Eu Fe2O3与光源相匹配,且对器件的要求较低,微弱信号检测装置利用光电放大器、带通滤波器、异或电路等有效消除噪声,提高了系统信噪比。光谱实验证明,Y2O2S:Eu Fe2O3波峰的强度比Y2O2S:Eu高近一个数量级的紫外激发效率,且与LED光源及探测器相匹配,其测温范围从室温到450℃,分辨率为0.5℃,从而证明了系统的可行性。     

基于PLC控制的搬运机械手的应用

论述了搬运机械手的功能、结构原理及软件设计.结合大蒜根须切除设备中大蒜的搬运,详细介绍了PLC的选择、I/O的分配、PLC与器件的逻辑电路连接及系统的气动原理.     

基于PLC控制的气动机械手系统

本文论述了基于PLC控制的气动机械手装置的功能、结构、原理及软件设计。文中详细介绍了PLC的选择,I／O点分配,PLC与器件的逻辑电路连接及系统的气动原理与工作原理等具体内容。     

TiNi形状记忆薄膜的光刻新工艺

TiNi形状记忆薄膜光刻工艺是此类MEMS器件制作的关键技术之一。研究了剥离工艺(lift\|off)用于TiNi薄膜图形化的可行性,并首次利用溅射的金属Pt作掩膜进行TiNi薄膜湿法腐蚀。结果表明溅射的Pt在HF/HNO3/H2O腐蚀TiNi过程中,具有抗腐蚀力强、与TiNi结合致密、不漂起的特点,是TiNi薄膜长时间腐蚀的理想掩膜材料。     

电路在线维修测试仪的原理和技术特点(三)

2 3改进数字器件状态测试我们知道,状态测试是对逻辑器件在线功能测试的重要扩充。用于对非逻辑类数字器件、功能未知的数字器件、以及器件库中尚没有的逻辑器件的故障检测。它通过把好板上的器件的各种在线状态,与故障板上的相应器件的在线状态进行比较的办法来发现故障,是测     

常温甲烷气敏元件的研制

采用掺有Pd活性SnO_2-InO_3-TiO_2敏感材料,再掺入MgO等金属氢化物,制成复合基体材料,采用直热式气敏元件制造工艺,经表面修饰改性,研制成功常温CH_4气敏元件,给出了常温下的气敏特性,并探讨其机理。     

贵金属修饰纳米In2O3的制备及应用

以金属铟粒为铟源制备硝酸铟溶液,采用水热法合成纳米In<,2>O<,3>,粉体,并通过贵金属Pd和Ag掺杂对In<,2>O<,3>粉体进行修饰.利用X射线衍射仪(XRD),比表面积测试仪(BET)等分析手段对材料进行表征,并且研究了气敏性能.结果表明:制得的In<,2>O<,3>粉体属于立方晶型,晶粒度为25.08 nm.In<,2>O<,3>气敏元件对丙酮、乙醇汽油及H<,2>S气体有较高的灵敏度和较好的响应恢复特性.Pd掺杂In<,2>O<,3>对ψ(乙醇汽油)为100×10<'-6>和ψ(H<,2>S)为50×10<'-6>的灵敏度分别高达36.70和87.96.     

Further laboratory studies and stratospheric flight of a mass spectrometer beam system

A gas expansion system combined with a mass spectrometer has been tested and flown successfully in the stratosphere. Through a sequence of orifices and high speed pumping, gas particles were formed into a molecular beam and analyzed by a sensitive mass spectrometer. During two balloon flights, vertical profiles of all major atmospheric constituents as well as O(3), CO(2), H(2)O and others were obtained. Gases such as (38)Ar and (16)O(17)O provided in-flight calibration standards. The sensitivity of the system was such that gases with mixing ratios of 10 ppb at an ambient pressure of about 10 mbar were detectable.     

Zn_2SnO_4气敏材料的共沉淀法制备及其氧化物掺杂改性

新型复合材料Zn_2SnO_4具有良好的气敏性,文献鲜有报道Zn_2SnO_4材料的制备以及氧化物掺杂改性;因此采用液相共沉淀法制备了Zn_2SnO_4粉体材料,利用X射线衍射仪(XRD)对合成的材料的结构进行了表征;通过固相反应制备了MnO_2,Li_2O掺杂的Zn_2SnO_4粉体,对旁热式气敏元件的性能进行了测试.实验发现Zn_2SnO_4是一种性能优良的酒敏材料,氧化物掺杂剂MnO_2和Li_2O的加入明显提高了材料对乙醇气体的灵敏度和选择性,质量百分含量为0.5%的Li_2O的掺杂量可以使元件对于体积分数为50×10-6的乙醇气体灵敏度达到150.     

A catalytic reactor for the trapping of free radicals from gas phase oxidation reactions

A catalytic reactor for the trapping of free radicals originating from gas phase catalytic reactions is described and discussed. Radical trapping and identification were initially carried out using a known radical generator such as dicumyl peroxide. The trapping of radicals was further demonstrated by investigating genuine radical oxidation processes, e.g., benzaldehyde oxidation over manganese and cobalt salts. The efficiency of the reactor was finally proven by the partial oxidation of cyclohexane over MoO(3), Cr(2)O(3), and WO(3), which allowed the identification of all the radical intermediates responsible for the formation of the products cyclohexanol and cyclohexanone. Assignment of the trapped radicals was carried out using spin trapping technique and X-band electron paramagnetic resonance spectroscopy.     

新型镍基药芯焊丝熔敷金属的高温氧化行为

采用增重法测定了自制新型镍基药芯焊丝熔敷金属在800℃和1000℃空气中的高温氧化行为。采用扫描电镜（SEM）对氧化产物表面和横截面形貌进行了观察,X射线衍射仪（XRD）对氧化膜层的物相进行了分析。结果表明,熔敷金属在800℃氧化时,氧化增重与氧化时间遵从抛物线规律,表面氧化膜无剥落,氧化速率较稳定;在1000℃氧化时,氧化增重与氧化时间近似遵从抛物线规律,表面氧化膜出现少量剥落,且氧化膜增厚,氧化增重是800℃氧化时的4倍左右。氧化过程中,氧化膜主要由Cr2O3组成。     

Study on the radiative transfer through non-gray gas mixtures within an irregular 3-D enclosure by using the modified weighted sum of gray gas method

In this study the modified weighted sum of gray gases model (WSGGM) using the gray gas regrouping technique and the discrete ordinates interpolation method (DOIM) are applied to analyze the radiative transfer within an irregular 3-D enclosure filled with non-gray gas mixture of CO₂, H₂O and N₂. The computer code developed in this study is successfully applied for solving the non-gray gas radiation within a 3-D rectangular enclosure and the gray gas radiation within an irregular 3-D enclosure by showing fairly good agreements with the existing results. In this paper the radiative transfer within an irregular 3-D enclosure filled with non-isothermal non-gray gases with uniform mixtures of CO₂, H₂O and N₂ is studied to demonstrate the applicability of the modified sum of gray gases model for irregular systems and to examine the effect of the concentrations of CO₂ and H₂O on the radiative transfer within modern combustors. Results show that the wall heat fluxes and the radiative heat source terms are increased as the concentrations of CO₂ and H₂O are increased. Results also show that the radiative fluxes caused by the mixture gases with high concentrations CO₂ and H₂O which can be observed in oxy-fuel combustion systems can reach up to nearly twice of those found in ordinary air-fuel combustion systems.     

A momentum imaging microscope for dissociative electron attachment

We describe an experimental approach to image the three-dimensional (3D) momentum distribution of the negative ions arising from dissociative electron attachment (DEA). The experimental apparatus employs a low energy pulsed electron gun, an effusive gas source and a 4π solid-angle ion momentum imaging spectrometer consisting of a pulsed ion extraction field, an electrostatic lens, and a time- and position-sensitive detector. The time-of-flight and impact position of each negative ion are measured event by event in order to image the full 3D ion momentum sphere. The system performance is tested by measuring the anion momentum distributions from two DEA resonances, namely H(-) from H(2)O(-) ((2)B(1)) and O(-) from O(2)(-) ((2)Π(u)). The results are compared with existing experimental and theoretical data.     

新型固体电解质基氮氧化物传感器的制备与性能研究

氮氧化物(NO_x,NO+NO₂)是我国首要的气体污染源之一,其对自然环境和人类健康均造成了严重的威胁,因此开发原位检测NO_x的高效检测设备势在必行。NO_x的排放源主要为工业废气和汽车尾气,其气体温度较高、成分比较复杂,而固体电解质基气体传感器可以实现在高温下对NO_x的高选择性、高灵敏度检测。本研究以Co₃O₄/Cr₂O₃/YSZ的复合材料为敏感电极,以YSZ为固体电解质构建了阻抗型NO_x传感器。采用XRD、SEM和EDX对传感器进行了表征,并系统研究了传感器在高温下对NO的敏感特性。结果表明：Co₃O₄/Cr₂O₃/YSZ敏感电极材料呈颗粒状,粒径约为200 nm,并且敏感电极以疏松多孔的状态覆盖在电解质表面,有利于气体的扩散和传质。传感器对NO_x具有良好的响应...     

Characteristics of Sputter-deposited Gadolinia-doped Ceria Thin Films on Al2O3/SiO2/Si Systems

Metal oxide films prepared by thin film technology have been reported for the potential applications on thin solid electrolyte layers for solid oxide fuel cells(SOFCs). Gadolinia-doped ceria(GDC) thin films and Al2O3 layers on SiO2/Si substrates are successively deposited by RF reactive magnetron sputtering from a cerium-gadolinium (90:10 at.%) alloy target and Al target in O2/Ar gas mixture and then perform post-thermal treatments at 300-700 ℃ and 900 ℃ for 2 h, respectively. Materials characteristics and chemical compositions of GDC films and Al2O3 layers are investigated by X-ray photoelectron spectroscopy(XPS), cross-sectional scanning electron microscopy(SEM), X-ray diffraction(XRD), and atomic force microscopy(AFM). Stoichiometric Al2O3 layers with polycrystalline structures are firstly prepared onto SiO2/Si substrates. A cubic fluorite structure with columnar crystallites of GDC films is successfully deposited on Al2O3/SiO2/Si systems. The chemical composition of 700 ℃-annealed GDC films is (Ce0.91Gd0.09)O1.94 and possesses a higher film density of 7.257 g/cm3. As a result, GDC thin films prepared by RF reactive magnetron sputtering and post-thermal treatments can be used as thin solid electrolyte layers for intermediate temperature SOFCs system as compared to the well-known yttria-stabilized zirconia(YSZ).