汽车尾气用NO_x传感器

汽车尾气中的有害物主要有CO,HC,NOx,SOx以及一些微粒物质,给人类赖以生存的大气环境带来了严重的危害。汽车尾气用NOx传感器开发主要是为了解决NOx(包括NO,NO2)的排放问题,能够实现准确、快速地测定NOx含量,从而满足大气质量检测和环境保护的要求。目前,NOx气体传感器主要有半导体型、电位型和电流型。主要介绍了这3种汽车用NOx传感器的原理、结构及应用,并简要分析了其向微型化、集成化和智能化等方向发展的趋势。     

氧化锆基片式NO_x气体传感器的研制

采用具有自主知识产权的制备工艺流程,制备了氧化锆基NOx气体传感器。首先配制了性能良好的5mol%-ZrO2浆料,流延成型得到了氧化锆陶瓷素坯基片,经过剪裁、冲孔、开槽、丝网印刷等工艺,制备了传感器素坯,经过1450℃2h烧结得到了氧化锆基NOx传感器。应用线性伏安法初步测试了该NOx气体传感器的性能。制备的NOx气体传感器具有良好的NOx气体响应性能。初步性能测试结果表明,传感器的电流值和NO2气体浓度之间存在着强的线性相关性,线性相关系数99.27%,电流值在0.136A~0.142A之间,传感器的线性范围为:200ppm~2000ppm。     

氧气对NOx传感器气敏特性的影响

实验采用丝网印刷技术制作了以钇稳定氧化锆固体电解质(YSZ)为固体电解质、NiO为敏感电极和Pt为参考电极的混合电位型NOx传感器,并在高温(450～750 ℃)含NO和O2气氛中测试其气敏性能.测试结果显示该传感器在450～500 ℃和550～750 ℃时分别表现为电势幅值随温度升高而减小的正电势和负电势;同一NO浓度下,电势和半圆弧型阻抗谱只是随着O2含量在一定范围内的增大而分别增大和缩小.考虑到O2会把NO氧化成NO2,同时结合对传感器的理化性能、响应电势和阻抗谱及工作机理的的分析,研究了O2对NOx传感器气敏性能的影响.     

汽车智能传感器自动测试系统的设计和建立

NOx传感器的开发是出于对环境的保护,它用于检测汽车尾气排放的氮氧化物浓度。在传感器的开发过程中,传感器输出信号的自动测试是一个重要的步骤。设计了一种基于LabVIEW的友好的用户测试软件,用于传感器数据的实时测试、评估和错误检测,该数据通过CAN总线传输。CAN总线是汽车领域中应用最广泛的通信协议之一。基于LabVIEW建立的自动测试系统具有配置功能、CAN总线数据帧的显示和解码、CAN总线错误的检查、解码信息的测试和评估、报表的生成、信号的设置和验证等功能。     

基于IC卡的汽车尾气排放检测数据管理信息系统的设计与实现

虽然国家已经制定了严格的汽车尾气排放标准,尾气检测依然是目前我国环保的薄弱环节,尾气检测方式和尾气排放检测数据管理方式都有待提高。本文利用接触式IC卡和管理信息系统技术设计并实现了一套汽车尾气排放检测数据管理信息系统,主要完成对CO、NO、烟度等汽车排放的尾气信息进行采集、入库、写卡、读卡、查询、导入导出及权限、用户管理等功能。该系统有助于提高我国汽车尾气排放检测和数据管理水平,为实现汽车尾气排放检测管理的科学化、信息化和现代化打下坚实的基础。     

基于La0.9Sr0.1Ga0.8Mg0.2O3−δ固体电解质的电流型NO2传感器敏感特性的研究

采用丝网印刷技术制备了以La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM,Sr、Mg双掺杂的LaGaO3)为固体电解质、NiO为敏感电极(SE)材料的电流型NO2传感器。用X射线衍射仪和扫描电镜对该传感器进行了理化分析;通过测量其在不同温度和不同NO2浓度气氛中的I-V曲线和时间响应曲线,研究了传感器的电流输出信号和NO2浓度的关系、时间响应特性以及稳定性。结果显示:在400℃～650℃测试温度范围内,传感器响应电流的变化幅值ΔI和NO2浓度之间存在较好的线性关系。传感器的稳定性测试结果表明:传感器样品的响应电流幅值出现了一定程度的下降,稳定性有待进一步提高。     

非分光红外车辆尾气传感器系统设计

非分光红外( NDIR)是一种利用气体对红外光的选择性吸收原理进行气体浓度检测的方法.利用NDIR分析方法,设计一种车辆尾气检测传感器系统,实现对大气中存在的汽车尾气进行检测与分析.该系统使用多窗口红外传感器组合,采用v支持向量回归进行传感器建模.实验结果证明:该检测系统具有测量精度高、稳定性好和便于携带的特点,能够满足车辆尾气测量分析的需求.     

基于不分光红外法的汽车尾气检测传感器的设计

为实现对汽车尾气中CO、CO2、HC化合物的测量,提出了一种新型汽车尾气检测传感器的设计方案。该方案根据不分光红外法（NDIR）检测原理,讨论了汽车尾气检测传感器的整体结构和软硬件的实现方法;传感器采用新型的红外光源和四通道红外探测器,可以同时测量汽车尾气中CO、CO2、HC化合物的浓度;采用双进双出的圆柱形气室结构,可以提高系统的检测灵敏度和测量精度。实验结果表明,传感器的相对误差在±3%之内,具有良好的精度和稳定性,能够满足汽车尾气浓度测量分析的需求。     

基于ARM9的车载尾气监测系统的设计与实现

本文针对目前汽车尾气检测是在专业的监测和维修机构进行,车载尾气监测系统市场上还很少出现,提出了一套可在汽车运行时能自动进行尾气监测系统的设计方案。车载尾气监测系统硬件平台采用S3C2410X嵌入式微处理器和尾气传感器为主。本文更详细地介绍了车载尾气监测系统的软件系统的设计与实现,并进行了整体的系统测试。     

PPB级锆基安培型NO气体传感器性能的研究

采用丝网印刷技术制备了以In2O3为敏感电极的锆基安培型三电极NO传感器用以探测10-9级NO气体。用X射线衍射仪（XRD）和扫描电镜（SEM）对该传感器进行了理化分析;通过测量其在不同温度和不同NO浓度的气氛中的伏安特性曲线和时间响应曲线,研究了传感器的电流输出信号和NO浓度的关系以及时间响应特性。实验表明：在350℃~500℃测试温度范围内,极化电压为-60 mV,NO浓度变化为0~900×10-9时传感器响应电流的变化值Δcurrent和NO浓度之间存在较好的线性关系并且传感器在400℃时响应值最大。在被测气体总流量为100 cm3/min时,传感器信号90%的响应和恢复时间分别为18 s和12 s。传感器信号不受CO2浓度变化的影响,传感器的响应信号在测试时间里具有较好短期稳定性,但长期稳定性有待进一步提高。本文还采用阻抗谱分析方法对传感器的响应机理进行了初步的探索。     

Titania NOx sensors for exhaust monitoring

Oxide semiconductors have been examined to develop NO_x sensors for exhaust monitoring. Titania doped with trivalent elements, such as Al³⁺, Sc³⁺, Ga³⁺ or In³⁺, has a good sensitivity and selectivity to NO between 450 and 550 °C, and shows rapid response. A sensor probe for monitoring exhaust NO_x has been fabricated. Many kinds of interference gases, such as C₃H₆, CO and SO₂, have been found to have only a slight influence on the sensor response to NO. The influence of O₂ and H₂O is also negligible, except for the cases of 0% H₂O and fuel-rich conditions. In accordance with these results, the sensor probe operates satisfactority in the exhaust gas of various combustion conditions without interference from the various kinds of gas species in the exhaust gases.     

SF6设备检测用小型尾气回收装置研制及应用

现场预防性试验和检查性试验中,SF6设备检测尾气总量较大,进行尾气回收但不影响仪器检测的准确性是个难题。根据差压传感器测量大气与缓存气室压差,通过微控制单元控制缓存气室保持在限值压力范围。尾气回收装置控制部分以DSP核心控制芯片为核心,下位机控制板通过DSP程序进行装置的控制,人机交互界面设计美观实用,且对压力传感器进行了校准,线性度良好。保证在回收SF6检测尾气的同时,不影响SF6气体检测数据的准确性,且容量大,可多次回收检测用尾气,该装置可在现场与多种SF6气体检测仪器配套使用,包含SF6气体分解物检测仪、SF6纯度检测仪和SF6露点检测仪（SF6湿度检测仪）。所研制装置已在现场实现应用,验证了装置的可靠性,环保效益突出。     

Improvement of the NOx selectivity for a planar YSZ sensor

In recent years planar yttria-stabilized zirconia (YSZ) based electrochemical gas sensors for automotive exhaust applications have become a major source of interest. The present work aims to develop a sensor for industrialisation. For this reason planar YSZ-based electrochemical sensors using two metallic electrodes (platinum and gold) were fabricated using screen-printing technology and tested in a laboratory test bench for different concentrations of pollutant gas such as CO, NO, NO₂ and hydrocarbons in oxygen rich atmosphere. It was furthermore shown that the selectivity towards NO_x could be highly reinforced by deposing a catalytic filter consisting of 1.7-4.5 wt.% Pt dispersed on alumina directly on the sensing elements. This filter was characterized by the use of SEM, TPD and XRD.     

四烷氧基酞菁铜(Ⅱ)旋涂膜的气敏特性

设计合成了可溶性的四 a (2.2.4 三甲基 3 戊氧基)酞菁铜(C64H80N8O4Cu),利用旋涂技术制备了四 a (2.2.4 三甲基 3 戊氧基)酞菁铜旋涂膜,研究了配合物旋涂膜的红外光谱、电子吸收光谱、对NO2和乙醇蒸汽的敏感特性以及气敏机理。结果表明:可溶性的四 a (2.2.4 三甲基 3 戊氧基)酞菁铜可制得较理想的旋涂膜,与溶液相比较旋涂膜的电子吸收光谱明显变宽,且Q带的2个吸收峰分别红移了16nm和12nm。室温下配合物旋涂膜对较低体积分数NO2呈现出良好的气敏性,在NO2为1.0～5.0×10-6体积分数范围内表现出较好的线性关系,而薄膜对乙醇蒸汽响应的体积分数为3.0×10-5。动力学研究表明:四 a (2.2.4 三甲基 3 戊氧基)酞菁铜旋涂膜对气体的吸附和脱附分2个过程完成。     

光闪烁法在火电厂烟气测量中的应用

光闪烁法对湿烟气下小浓度烟尘含量检测的测量原理及装置实现过程。通过样机在实验锅炉上校核,并与电称低压冲击器(ELPI)及滤膜称重法的同步测试数据进行比对,拟合相关系数为0.994。实验结果证明,光闪烁法对烟气中颗粒物浓度的测量是可行的,并具有较高的准确性及灵敏度。同时给出了光闪烁法独有的信号及数据处理办法。     

用气相反应法制备纳米WO3气敏材料

材料的制备是研制半导体气敏传感器的关键环节.用气相反应法,以纯钨丝为原料,制备了WO3粉末,又以此WO3粉末为基材,制作了NO2气敏传感元件.在性能测试中发现,该元件对低浓度(10-10)NO2灵敏,灵敏度可达10倍左右,而且响应迅速,响应时间为1.5 s.文中从材料的微观结构入手,对材料的敏感机理作了分析.     

Vanadia doped tungsten-titania SCR catalysts as functional materials for exhaust gas sensor applications

Urea-SCR systems (selective catalytic reduction) are required to meet future NO_x emission standards of heavy-duty and light-duty vehicles. It is a key factor to control the SCR systems and to monitor the catalysts’ functionalities to achieve low emissions. The novel idea of this study is to apply commercially available SCR catalyst materials based on vanadia-doped tungsten-titania as gas sensing films for impedimetric thick-film exhaust gas sensor devices. The dependence of the impedance on the surrounding gas atmosphere, especially on the concentrations of NH₃ and NO₂, is investigated, as well as cross interferences from other components of the exhaust. The sensors provide a good NH₃ sensitivity at 500 °C. The sensor behavior is explained in light of the literature combining the fields of catalysts and semiconducting gas sensors.     

Impedancemetric gas sensor based on Pt and WO3 co-loaded TiO2 and ZrO2 as total NOx sensing materials

Pt-loaded metal oxides [WO₃/ZrO₂, MO_x/TiO₂ (MO_x = WO₃, MoO₃, V₂O₅), WO₃ and TiO₂] equipped with interdigital Au electrodes have been tested as a NO_x (NO and NO₂) gas sensor at 500 °C. The impedance value at 4 Hz was used as a sensing signal. Among the samples tested, Pt-WO₃/TiO₂ showed the highest sensor response magnitude to NO. The sensor was found to respond consistently and rapidly to change in concentration of NO and NO₂ in the oxygen rich and moist gas mixture at 500 °C. The 90% response and 90% recovery times were as short as less than 5–10 s. The impedance at 4 Hz of the present device was found to vary almost linearly with the logarithm of NO_x (NO or NO₂) concentration from 10 to 570 ppm. Pt-WO₃/TiO₂ showed responses to NO and NO₂ of the same algebraic sign and nearly the same magnitude, while Pt/WO₃ and WO₃/TiO₂ showed higher response to NO than NO₂. The impedance at 4 Hz in the presence of NO for Pt-WO₃/TiO₂ was almost equal at any O₂ concentration examined (1–99%), while in the case of Pt/WO₃ and WO₃/TiO₂ the impedance increased with the oxygen concentration. The features of Pt-WO₃/TiO₂ are favorable as a NO_x sensor that can monitor and control the NO_x concentration in automotive exhaust. The effect of WO₃ loading of Pt-WO₃/ZrO₂-based sensor is studied to discuss the role of surface W-OH sites on the NO_x sensing.     

A low-power micromachined MOSFET gas sensor

This paper reports on the design, fabrication, and characterization of the first low-power consumption MOSFET gas sensor, The novel MOSFET array gas sensor has been fabricated using anisotropic bulk silicon micromachining. A heating resistor, a diode used as temperature sensor, and four MOSFETs are located in a silicon island suspended by a dielectric membrane. The membrane has a low thermal conductivity coefficient and, therefore, thermally isolates the electronic components from the chip frame. This low thermal mass device allows the reduction of the power consumption to a value of 90 mW for an array of four MOSFETs at an operating temperature of 170°C. Three of the MOSFETs have their gate covered with thin catalytic metals and are used as gas sensors. The fourth one has a standard gate covered with nitride and could act as a reference. The sensor was tested under different gaseous atmospheres and has shown good gas sensitivities to hydrogen and ammonia. The low-power MOSFET array gas sensor presented is suitable for applications in portable gas sensor instruments, electronic noses, and automobiles