Study On The Hydrothermal Synthesis Of SnO₂ Nanoparticles And Fabrication Of SnO₂ Thick-film Gas Sensor

This paper includes three parts. The fabrication of SnO2 nanoparticles through the hydrothermal method is introduced in the first part. By many testing methods which include the investigation and the analysis of XRD,SEM and TEM, we find the best conditions. Meanwhile, the particle size of the SnO2 nanoparticles made on best conditions are measured and given a further analysis. The experiment results show that the average crystalline size of SnO2 particles obtained at hydrothermal temperature (200℃) for 10h is 3.7nm when the pH value is 7 and the nanoparticles are spherical, uniform, and well-dispersed. Furthermore, we study the relation between the particle size and the heat treatment temperature. The average grain sizes of SnO2 particles heat treated at 400℃,500℃,600℃,800℃separately for 2h, are 4.1nm,5.2nm,7.1nm,10.1nm, which shows that the particle size slightly increases with the heat treatment temperature.The investigation of fabricating CuO-SnO2 nanoparticles by the hydrothermal method is introduced in the second part. Through a lot of experiments combined with the investigation and analysis of XRD, we get the best technology process. In this process, we use the ion doping technique through the solution instead of the solid phase doping technique. The hydrothermal process remains the same, keeping at 200℃for 10h when the pH value is 7. The obtained solution is dried by the water bath to ensure the doping content. Then the powder is heat treated at 550℃for 2h to remove the crystallization water. The grain size of the obtained CuO-SnO2 nanoparticles is 5.5nm.The fabrication process and primary discussion of the thick-film H2S gas sensor is described in the third part, the characteristics of the sensor are also studied. During the fabrication process, many factors affect the characteristics of the gas sensor, which involve the proportion of CuO powder, the composition and proportion of glass glaze, the sintering temperature, and the time of heat preservation. The experiment results show that the slurry gets the best adhesive strength when the proportion of the thick film resistance materials to the glass glaze is 8:1. The film is sintered at 800℃for 2h. The gas sensing element has the best performance when doping 5wt% CuO. The gas sensitivity is 30 to 300ppm H2S, the response time is 100s and the best working temperature province is 150℃to 250℃.