Research On Preparation Of Miniature Ceramic Heater

Using automotive oxygen sensor combined with three-way catalytic system to control the air-gas ratio can greatly reduce vehicle exhaust emissions. Thimble-type oxygen sensors need to take a long time to get to their minimum working temperature. So it is important to introduce a ceramic heater inserted into the thimble ceramic as a separate component. The application of domestic oxygen sensor in automobile is limited due to the disability to produce the heater. In this paper, the preparation of the ceramic heater was studied on the basis of previous work in the lab.75 alumina was selected for the material of the heater, further study of the preparation of the heater's protect layer was made. And main factors affecting the quality of the green tape were explored. The mechanism of the binder used in tape casting was studied and how the binder influenting on the quality of green tape was discussed by the viscosity test, visual observation and SEM testing. What's more, the influence of the ratio of binder and plasticizer on the quality of green tape was studied. The green tape casting process which was used to prepare for the protect layer was stabilized ultimately.Tungsten heating membrane is an important part of the preparation of the heater. Tungsten slurry formulation and preparation process of tungsten thick film were studied. The inorganic binder of tungsten thick film-glass frit formulation was determined. Glass formulation was analyzed and optimized by thermal analysis tests and X-ray diffraction. Microstructure of the sintered heating membrane and the substrate was analyzed. Influence of glass addition on characteristics of thick-film paste printing, debinding and co-sintering of heating membrane and 75 alumina substrate, and sheet resistance of sintered membrane were studied.The co-sintering behavior of the assembled green body was studied. Proper binder for assembling was determined. How protect layer and Hot Press Injection green body affecting each other's thrinkage during sintering was discussed, and the loadings of tape casting green tape and Hot Press Injection green body were determined. The influence of sintering atmosphere on 75 alumina sintering was studied, and influence of reducing atmosphere (H₂) on densification machenism of 75 alumina was discussed. Finally, sintering process in reducing atmosphere was optimized.