【作者】 吴娜；

【导师】 王兢；

【作者基本信息】 大连理工大学 ， 测试计量技术及仪器， 2006， 硕士

【摘要】 本文介绍了关于甲醛气敏元件的制备及其灵敏度特性提高方面的研究,应用化学共沉淀法制备了二氧化锡（SnO₂）纳米材料,应用柠檬酸盐法制备了铁酸锶镧(La_xSr_1-xFeO₃)以及氧化镍（NiO）纳米材料,并对不同的敏感材料的气敏性能进行了比较。通过实验结果得出结论,SnO₂对甲醛的气敏性能最好,在相同条件下的灵敏度最高。应用制备的纳米敏感材料制作了厚膜型气敏元件以及旁热式气敏元件,对两种结构进行比较得出结论,在现有的工艺条件下,旁热式结构元件的性能要优于厚膜型元件的性能。 对制作的旁热式甲醛气敏元件的灵敏度特性等性能进行了测试,结果表明,SnO₂甲醛气敏元件灵敏度最高时的加热功率为0.4W;元件的响应时间约为25s,恢复时间约为40s;随着气体浓度的增加,元件的灵敏度逐渐增加,在高浓度阶段趋于饱和。同时测试了乙醇气体以及湿度对制作的旁热式甲醛气敏元件的干扰。发现在高浓度段,相同气体浓度的条件下,元件对乙醇气体的灵敏度要高于对甲醛气体的灵敏度,但是在低浓度段,出现了元件对甲醛气体的灵敏度要高于元件对乙醇气体的灵敏度的趋势。湿度的存在对制作的元件的影响很小。 组建了一套气敏元件自动测试系统,利用D/A卡实现对质量流量控制器的控制,该系统能够自动控制待测试气体的流量和浓度。在通气过程中,保证总体的气体流量不变,将流量对气敏元件的影响排除在外。同时,应用A/D卡使该系统能够自动采集气敏元件的动态响应,并绘制出动态响应曲线。 针对半导体氧化物气敏元件对甲醛气体以及乙醇气体的选择性不好的特点,从理论角度进行分析。以La_0.7Sr_0.3FeO₃元件为例,应用复阻抗法提出等效电路模型,在此基础上分析了元件的吸附机理。更多还原

【Abstract】 In this paper, the method about the fabrication of the formaldehyde gas sensor and the study of its sensitivity property were introduced. The SnO2 nanocrystalline material was prepared by chemical co-deposit method, La_xSr₁-xFeO₃ and NiO nanocrystalline material were prepared by citrate method respectively. The comparison between the different sensing materials has been taken. The sensing property of the SnO₂ gas sensor was better than the others, and the sensitivity of the SnO₂ gas sensor was the highest. Different structure has been compared, including the thick-film gas sensor and the indirect-heat gas sensor, the experiment results showed that the indirect-heat gas sensor was better than the thick film under the current techniques.The sensitivity of the formaldehyde gas sensor that we fabricated has been measured. It was showed that the heating power corresponding to the highest sensitivity was about 0.4W. The response time is about 25 seconds, and the recover time is about 40 seconds. Along with the increase of the gas concentration, the sensitivity of the gas sensor increased. The influence of ethanol to the formaldehyde gas sensor has also been tested. The results shows that the sensitivity of the gas sensor to ethanol is higher than its sensitivity to formaldehyde when the gas concentration is high, but when the gas concentration is much lower, the sensitivity trend towards higher for formaldehyde than for ethanol. This means the gas sensor we made is suitable for the detection of formaldehyde in lower concentration. The influence of the humidity was weak and may be neglected.An automatic test system for gas sensors was designed. D/A card was used to control the Mass Flow Controller （MFC）, so that the flow and the concentration of the gas could be controlled automatically. During the afflux of the gas, the total flow of the gas remains invariable, so that the influence of the flow to the gas sensor can be eliminated. A/D card was used to collect the real-time response signals.Due to disturb of ethanol to formaldehyde, we try to analysis the reason theoretically. Using the La₀.7Sr₀.3FeO₃ gas sensor as an example, an equivalent circuit model was built to analysis the adsorption theory of the formaldehyde gas.更多还原