The Effect of the Thickness of the Sensitive Layer on the Performance of the Accumulating NOx Sensor

Sensors

Andrea Groß²  Miriam Richter²  David J. Kubinski¹  Jacobus H. Visser¹ 

[1] Ford Research and Advanced Engineering, Dearborn, MI 48124, USA;University of Bayreuth, Zentrum für Energietechnik, Lehrstuhl für Funktionsmaterialien, Bayreuth 95440, Germany

关键词: lean NO_x trap (LNT);    NO_x storage and reduction catalyst (NSR);    low ppm-level NO_x sensing;    semiconducting gas sensor;    linear measurement range adaption;    carbonate nitrate conversion;   

DOI  :  10.3390/s120912329

来源: mdpi

【 摘 要 】

A novel and promising method to measure low levels of NO_x utilizes the accumulating sensor principle. During an integration cycle, incoming NO_x molecules are stored in a sensitive layer based on an automotive lean NO_x trap (LNT) material that changes its electrical resistivity proportional to the amount of stored NO_x, making the sensor suitable for long-term detection of low levels of NO_x. In this study, the influence of the thickness of the sensitive layer, prepared by multiple screen-printing, is investigated. All samples show good accumulating sensing properties for both NO and NO₂. In accordance to a simplified model, the base resistance of the sensitive layer and the sensitivity to NO_x decrease with increasing thickness. Contrarily, the sensor response time increases. The linear measurement range of all samples ends at a sensor response of about 30% resulting in an increase of the linearly detectable amount with the thickness. Hence, the variation of the thickness of the sensitive layer is a powerful tool to adapt the linear measurement range (proportional to the thickness) as well as the sensitivity (proportional to the inverse thickness) to the application requirements. Calculations combining the sensor model with the measurement results indicate that for operation in the linear range, about 3% of the LNT material is converted to nitrate.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.