等离子喷涂氧化钨涂层的制备及二氧化氮气敏性能研究

发布时间：2018-08-31 10:14

【摘要】：二氧化氮(NO2)是一种典型大气污染物,可导致光化学烟雾与酸雨等环境问题,也是大气污染物PM 2.5(粒径小于2.5微米的固态颗粒)的成因之一,因此研发一种快速、稳定、可靠的N02气体传感器具有重要的现实意义。n型宽禁带半导体材料,如三氧化钨(W03),被认为是高效气敏材料,在检测N02气体方面表现出巨大的应用潜力。本文采用大气等离子喷涂(APS)、溶液前驱体等离子喷涂(SPPS)和复合等离子喷涂(APS+SPPS)三种工艺方法,以WO3粉末和钨酸铵水溶液作为喷涂原料沉积W03单个粒子和涂层,研究喷涂工艺参数(基体温度、喷涂距离和氢气流量)对单个粒子和涂层微观结构的影响规律,最后对W03的N02气敏性能进行评价与分析。首先,对比APS和SPPS两种工艺,研究基体温度和喷涂距离对单个粒子沉积形貌的影响。实验结果表明,基体未预热时,APS粒子飞溅严重;随着基体温度的增加,微米粒子形貌从飞溅状向圆盘状转变,转变温度在200℃左右。对于SPPS纳米粒子而言,形貌更加复杂。基体温度为200℃时,出现泡沫状颗粒;当基体温度为250℃时,出现中空球状沉积粒子。随后,研究了喷涂距离和氢气流量对沉积粒子的影响规律,实验结果显示,喷涂距离为100 mm,氢气流量为4 L/min时,粒子的扁平化程度最好。然后,采用三种工艺,在带有金电极的氧化铝(A1203)传感器基体上制备了 W03涂层。扫描电镜分析发现,所有W03涂层都呈多孔、层状特征,其中SPPS涂层孔隙率最高,APS涂层最低,APS+SPPS涂层居中。经研究发现,APS制备WO3涂层毛孔粗大,涂层由微米粒子堆积而成;SPPS制备W03涂层毛孔细小,涂层比表面积大;APS+SPPS具有独特的微观形貌,在粗大的微米级W03粒子表面附着许多纳米级W03颗粒,形成独特的微纳结构。最后,对三种涂层进行气敏测试。结果显示,SPPS涂层灵敏度最高,APS灵敏度最低。这是因为SPPS涂层呈现多孔结构,且比面积最高。涂层形貌对气敏性能有重要影响,当采用SPPS沉积涂层时,喷涂距离为100 mm时,涂层气敏性能最佳;当采用APS+SPPS沉积涂层,氢气流量为2 L/min时,涂层灵敏度最佳。本文还测试了传感器工作温度和环境湿度对灵敏度的影响规律,当工作温度从150℃增加到250℃时,所有试样灵敏度均呈下降趋势,但响应恢复时间缩短;环境湿度从0%增加到100%时,传感器的基准电阻降低,但灵敏度变化却较为复杂。
[Abstract]:Nitrogen dioxide (NO2) is a typical atmospheric pollutant, which can cause environmental problems such as photochemical smog and acid rain. It is also one of the causes of atmospheric pollutant PM 2.5 (solid particles with particle size less than 2.5 microns). Therefore, it is of great practical significance to develop a fast, stable and reliable N02 gas sensor. Tungsten trioxide (W03) is considered as a highly efficient gas sensitive material. It has great potential in detecting N02 gas. In this paper, three process methods, atmospheric plasma spraying (APS), solution precursor plasma spraying (SPPS) and composite plasma spraying (APS + SPPS), were used to deposit single W03 with WO3 powder and ammonium tungstate aqueous solution as spraying materials. The influence of spraying parameters (substrate temperature, spraying distance and hydrogen flow rate) on the microstructure of single particle and coating was studied. Finally, the gas sensitivity of W03 N02 was evaluated and analyzed. Firstly, the influence of substrate temperature and spraying distance on the deposition morphology of single particle was studied by comparing APS with SPPS. The results showed that APS particles splashed seriously when the substrate was not preheated, and the morphology of micron particles changed from splashing to disc with the increase of substrate temperature, and the transition temperature was about 200. For SPPS nanoparticles, the morphology was more complex. Foam particles appeared when the substrate temperature was 200, and hollow spheres appeared when the substrate temperature was 250. Subsequently, the effects of spraying distance and hydrogen flow rate on the deposition particles were studied. The experimental results showed that the flattening degree of the particles was the best when the spraying distance was 100 mm and the hydrogen flow rate was 4 L/min. Then, W03 coating was prepared on the aluminum oxide (A1203) sensor substrate with gold electrode by three processes. Microscopic analysis showed that all W03 coatings were porous and layered, of which the porosity of SPPS coating was the highest, APS coating was the lowest, and APS + SPPS coating was the middle. The results show that the SPPS coating has the highest sensitivity and the APS sensitivity is the lowest. This is because the SPPS coating has the porous structure and the highest specific area. When the spraying distance is 100 mm and the hydrogen flow rate is 2 L/min, the gas sensitivity of the coating is the best. The influence of working temperature and ambient humidity of the sensor on the sensitivity is also tested. Sensitivity is decreasing, but response recovery time is shortened. When ambient humidity is increased from 0% to 100%, the reference resistance of the sensor decreases, but the change of sensitivity is more complex.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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