Planar, impedance- metric NO_x sensor with spinel- type SE for high temperature applications

This study displays the results obtained with a planar, impedance- metric sensors having a NiCr2O4- SE and a special FSZ electrolyte. The sensing characteristics to NO and to O2/NO gas mixtures were analyzed at temperatures up to 700 °C. The cross-selectivity to other flue gases was tested. As a new capable type of sensing parameter the total impedance was applied

Schichtentwicklung für Hochtemperatur- NOx Gassensoren

Übersichtsvortrag zu den Aktivitäten des Instituts für Werkstoff-Forschung auf dem Gebiet der Hochtemperatur NOx Gasensorik

Characterization of MnO-doped lanthanum hexaluminate (LaMnAl11O19) in terms of selective catalytic reduction of NOx by addition of hydrocarbon reductant (HC-SCR)

Environmental pollution by vehicles, turbines and aircrafts has enormously increased in the last decade. New generation lean-burn combustion engines which are more effective and require less fuel consumption will raise the emission of nitrogen oxides (NOX) even more. Thus, especially in urban areas, more stringed environmental regulations are to release which can only be met by development of new catalytic materials and concepts. Rare earth oxide catalysts are reported to offer highly effective conversion of NOX by methane (CH4) in the terms of selective catalytic reduction (HC-SCR). Especially La2Oa is reported to have a high NO reduction by CH4 to N2, although its technical realization as catalyst material has not yet reported and can be challenging due to the hydroscopic property of La2O3. Complex oxide compounds containing La2Oa however can be suitable alternatives and promising candidates for technical application as catalysts. In this study, LaMnAlnOi9 is characterized in terms of HC-SCR with methane. Phase and morphological characterization of the powder synthesized by sol-gel route and coatings by electron-beam physical vapor deposition (EB-PVD) deposition was presented. LaMnAlnOi9 crystallizes to the magnetoplumbite phase at about 1000°C and is then thermally stabile up to 1400°C. FTIR spectra of pressed sol-gel powder showed that NO is adsorbed superficially and oxidized by the surface. The addition of oxygen led to changes of the spectrum in the nitritenitrate region and the formation of NO+ and N2O4 species. The EB-PVD coated LaMnAlnOi9 layer was catalytically characterized at 200°, 400° and 600 °C and showed catalytic activity towards NO depending on temperature

PLANAR, IMPEDANCE-METRIC NO_x SENSOR WITH NIO SENSING ELECTRODE FOR HIGH TEMPERATURE APPLICATIONS

In this study, an innovative type of sensor configuration is used which contains an electrolyte constructed of quasi-single crystalline columns, a porous NiO sensing electrode (SE) and a conductive Pt reference electrode (RE) deposited on the backside. As electrolyte EB-PVD manufactured discs of FYSZ and PYSZ composition were used. Gas sensing characterization of the sensors was carried with typical flue-gas mixtures in various concentrations. Impedance and potential analysis were done at a frequency range of 100 kHz and 0.005 Hz. Sensors with FYSZ electrolyte could be operated at higher temperatures compared to those with PYSZ electrolytes. The highest achieved sensing temperature in this study was 600°C. NO was successfully detected under the presence of 5%vol. O2 at the maximum operating temperature

Planar, impedance- metric NO_x sensor with spinel- type SE for high temperature applications

This study displays the results obtained with planar, impedance- metric sensors having a NiCr2O4- SE and a specially manufactured FSZ and PYSZ electrolytes. The fabrication of the sensor devices and their micro structural properties are analysed and their gas sensing properties under lean-burn conditions towards NOx are characterized. Therefore the sensing characteristics to NO and to O2/NO-gas mixtures are analysed at temperatures up to 700°C and at NO concentrations between 0 and 1000 ppm at the presents of different O2 concentrations. The cross-selectivity to other flue-gases, like CO2, CO and CH4 and mixtures of those with O2 are also analysed. The analysis shows that the total impedance is a new and capable type of sensing parameter for the characterisation of NO-gas sensors. This study applies the total impedance to demonstrate the principal applicability of impedance metric sensor concept for the detection of NOx in lean atmospheres and under harsh conditions. The tested sensor device is able to monitor NO up to 1000 ppm at 650°C