Research On Preparation Process And Temperature Characteristics Of ZrO₂-based NO_x Sensor

Nitrogen oxides?NO_X?have a great impact on urban air pollution,most countries have put nitrogen oxides and ammonia nitrogen into binding targets,the most important of which is the emission of nitrogen oxides from motor vehicles.The ZrO₂-based NO_X sensor can detect the content of NO_X in the exhaust gas and meet the requirements of atmospheric quality detection.At present,only a few foreign companies have mastered the preparation technology of NO_X sensors which can be commercialized,but its structure is complex,and a comprehensive technical blockade is carried out in China.Therefore,it is extremely urgent to develop a kind of ZrO₂-based NO_X sensor with excellent structure and stable performance independently.Based on the existing preparation process of ZrO₂-based NO_X sensor in the laboratory,combined with the problems encountered in the experiment and the actual application process,the technology of making zirconia cast lamination with excellent overlap and the laminated co-firing technology between zirconia and alumina were studied and discussed in this paper,and the influence of operating temperature on the pump current of ZrO₂-based NO_X sensor was tested and analyzed.The research contents are as follows:?1?The effects of different laminating activators on the superposition properties of zirconia cast substrates were studied.The results show that under the same laminating conditions,0.5wt%PVB+99.5wt%ethanol solution and 0.5wt%PVB+99.5wt%terpineol solution can be used as laminating activator to improve the superposition of zirconia cast substrate and obtain good superposition effect,which can improve the strength and toughness of substrate material in NOX sensor chip.?2?The effects of different formulations of alumina printed sheets on the co-firing results of zirconia and alumina which are two kinds of heterogeneous materials were studied.The results show that when alumina printed sheet is prepared by mixing powder with organic carrier using PVB as binder at a mass ratio of 1:1,zirconia-alumina-zirconia co-firing samples will have smooth surface,good interface bonding and the strongest thermal shock resistance after printing,laminating and sintering.Thus,the lamination and co-firing of zirconia and alumina in NO_X sensor chip can be realized,the working stability and service life of NO_X sensor chip can be improved.?3?The effects of different operating temperatures on the pump current signal of ZrO₂-based NO_X sensor were studied by single-pump method.The results show that the operating temperature of ZrO₂-based NO_X sensor has an effect on the pump current signal.The relationship between the main pump current and temperature is consistent with the theoretical formula,while the pump current signals of the auxiliary pump and the measuring pump have inconsistent fluctuations with the theoretical relationship when the temperature changes.The reasonable operating temperature range is1003.15¹063.15 K so that the NO_X sensor has more accurate output signal.