Preparation And Properties Of Cobalt Oxide Semiconductor Gas Sensors

Due to the increase in car exhaust,industrial waste gas and living gas,air pollution is becoming more and more serious,and it is more and more important to develop a low-cost,high-performance gas sensor to monitor the atmosphere.Among them,the semiconductor metal oxide sensor because the synthesis cost is very low,high sensitivity,fast response time / recovery time is short,the device is simple to create friendly interface,easy maintenance,detection and other factors become the most potential gas sensor.At present,Co₃O₄ as a P-type metal oxide,used as a gas sensor sensitive film has been widely studied.In this paper,Co₃O₄ was used as the research object,and the cobalt oxide nanometer materials with different morphologies were synthesized by hydrothermal method.The effect of the morphology of the materials on the sensor performance was studied.Finally,the gas sensing mechanism of the gas sensor was discussed in detail.The main research work of this paper is divided into:1.The Co₃O₄ nanoparticles were prepared by hydrothermal method using cobalt nitrate and sodium hydroxide as raw materials,ethanolamine as the dispersant and hydrogen peroxide as the oxidant at 160 ℃.The results of XRD showed that the precursor before sintering was Co（OH）2 and Co₃O₄,and Co（OH）2 was completely transformed into Co₃O₄ after sintering.The SEM observation showed that Co₃O₄ was a kind of nano-particles with irregular morphology,and the size of Co₃O₄ was about 20 nm.To produce the gas sensor,with the resulting Co₃O₄ powder and anhydrous ethanol mixed into a paste,and then evenly drip on the ceramic tube to form a sensitive film,and at room temperature for its gas-sensing test,the material on the gas The results show that the sensor has a good response to NH3,the lowest detection concentration of NH3 at room temperature is below 20 ppm,and it shows good reproducibility and long-term stability when tested for the same concentration of gas.Finally,The sensor’s gas sensing mechanism provides an effective theoretical basis for improving sensor performance in the future.2.An Co₃O₄ nanosheet was prepared by hydrothermal method using cobalt nitrate,urea and ammonium fluoride as raw materials.The morphology of Co₃O₄ nanosheets was analyzed by SEM and TEM.The porosity of nanosheets was calculated by BET method.The elemental analysis of nanosheets was carried out by XPS and discussed.The growth mechanism.Finally,the gas sensing performance of gas sensor based on Co₃O₄ nanosheets at room temperature was studied.The results show that the sensor has a fast response-recovery rate of 200 ppb or less at room temperature,and has a good linear relationship between the detection concentration and the responsiveness.In addition,the sensor has good reproducibility and long-term stability.3.First,cobalt nitrate,urea and copper nitrate as raw materials,the use of hydrothermal high temperature sintering to get both CuO and Co₃O₄ powder material,and its soluble in ethanol made into a paste as a side heat-type gas sensor And the gas sensitivity of the sensor to NH3 was also detected.The experimental results show that the sensor has good gas-sensing performance for NH3,the best working temperature is 200 ° C,the minimum detection concentration of NH3 is less than 1ppm,and has a fast response-recovery time,at the optimum working temperature The response of the NH3 at the same concentration indicates that the sensor has good reproducibility for NH3 and that the response to the same gas during the course of more than 20 days is substantially unchanged,indicating that the response to the same gas is less than 1 min.The sensor has reliable stability,the response of the sensor to NH3 is much higher than that of other gases,which proves that the sensor has good selectivity to NH3 and has a very good application prospect.