基于金属氧化物的二甲苯气体传感器的制备及其气敏性能研究

发布时间：2018-04-02 03:08

本文选题：金属氧化物　切入点：二甲苯　出处：《吉林大学》2017年硕士论文

【摘要】：社会的发展带来了物质的极大丰富,然而金无足赤,大多数材料都是利弊并存的,例如二甲苯,作为一种重要的化工原料和有机溶剂,可用于生产染料、涂料、树脂和油墨等,但其本身的毒性也使它成为一种典型的挥发性有机化合物污染源,同时其可燃性,也决定了它在生产过程中的危险性。因此,无论在日常生活中还是工业生产中,对二甲苯的实时监测都关系到人们的身体健康和生命安全。可以监测二甲苯的方法和工具有很多,但是相比之下,半导体式气体传感器以其小巧便携、响应迅速、廉价易得的优点,获得了人们越来越多的关注。而作为半导体式气体传感器的关键部分——半导体气敏材料的敏感特性对传感器的性能起着决定性的作用。从起初的SnO_2和ZnO,到后来的WO_3、Fe_2O_3、In_2O_3、Co_3O_4、NiO等等,再到后来的LaFeO_3、ZnCo_2O_4,以及一些硫化物,目前,被研究和应用于气敏领域的材料种类纷繁复杂,但作为气敏材料的主流,金属氧化物依然是研究气敏规律的热门选择。本文针对二甲苯气体检测,以金属氧化物为基体材料,通过掺杂、复合手段,旨在制备出性能优良的气体传感器。实验思路和研究内容如下:1.发现了一种制备具有孔隙的Co_3O_4棒状材料的方法。孔隙可以提高材料的比表面积,改变材料的表面状态,同时,棒状大结构可以使材料保持较好的稳定性。在气敏性能方面,对甲苯、甲醛、乙醇等都表现出响应,虽然对二甲苯的响应最高,但依然表现出单一材料选择性不够好的缺点,同时对二甲苯的响应恢复速度较慢也说明了其结构有待进一步改善,因此,开展了第二个实验。2.采用水热法制备了具有分等级结构的Co_3O_4微球,并对其进行了不同比例的Cr掺杂,研究了它们对挥发性有机化合物的气敏性能,尤其是对二甲苯的敏感特性。Cr掺杂的Co_3O_4材料相对于纯相的Co_3O_4材料,对甲醛、乙醇等响应变化不大,但对二甲苯的响应有了明显的提高,且在掺杂比例为5 at%的时候提高的最多(5 ppm二甲苯气体氛围中响应为6.38,相对与纯相Co_3O_4对5 ppm二甲苯的响应1.29,提高了近4倍),这种提高也改善了材料的选择性,降低了检测过程中其它气体带来的信噪比,并且响应和恢复过程进行速度很快,在30 s之内均可完成。但对于Cr掺杂的作用,根据表面电阻控制理论,认为在接近表面位置的作用可能更大,因此设计成适当的异质结型材料,应该会有更好的气敏表现,故而进行了第三个实验。3.设计并制备了以WO_3为基体材料,在其表面生长Cr_2O_3粒子,进而形成异质结型结构的气敏材料。制备方法采用了两步水浴法,其中,制备的WO_3呈具有分等级结构的花状粒子,其片状结构有较长的宽度,给二次生长的粒子提供了附着点,同时又有较薄的厚度,有利于更好地发挥出异质结的作用。对比由Cr_2O_3-WO_3制得的气体传感器和由WO_3材料制得的气体传感器,异质结构显著提高了材料对二甲苯气体的响应,且响应恢复速度依然较快,响应过程和恢复过程分别在5 s和20 s内就可完成。
[Abstract]:The development of society has brought abundant materials, however, most of the materials are None is perfect, both advantages and disadvantages, such as xylene, as an important chemical raw material and organic solvent, can be used in the production of dyes, paints, inks and resins, but its toxicity also makes it become a kind of typical volatile organic compounds pollution at the same time, the source of combustible, it also determines the risk in the production process. Therefore, both in daily life and industrial production, real time monitoring of p-xylene is related to people's health and life safety. There are many methods and tools for monitoring xylene, but compared to semiconductor gas the sensor with its compact and portable, fast response, the advantages of cheap, get more and more attention. As a key part of semiconductor gas sensors, semiconductor gas The sensitive characteristics of sensitive materials and the performance of the sensor plays a decisive role. From the beginning of the SnO_2 and ZnO, then WO_3, Fe_2O_3, In_2O_3, Co_3O_4, NiO and so on, then later LaFeO_3, ZnCo_2O_4, and some sulfides, at present, are numerous kinds of material research and application in gas field is complex, but as the mainstream of gas sensitive materials, metal oxide is still a popular choice of gas sensitive rules. In this paper the xylene gas detection, using metal oxide as base material, by means of doping, composite, in order to prepare gas sensor with excellent performance. The ideas and research contents are as follows: 1. it is found that the method of Co_3O_4 rod material the preparation has a pore. Pore can increase the surface area of the material, changing the surface state of the material at the same time, rodlike structure can make the materials to maintain stability better. In the gas sensing performance Formaldehyde, ethanol, toluene, etc. have shown a response, although the highest response of p-xylene, but still showed the single material selectivity problems at the same time, the slow recovery of p-xylene response also shows that the structure needs to be further improved, therefore, carried out second experiments with.2. Co_3O_4 microspheres prepared graded structure by hydrothermal method, and has carried on the different proportion of Cr doping were studied on the gas sensing properties of volatile organic compounds, especially the sensitive characteristics of.Cr doped Co_3O_4 materials for p-xylene phase pure Co_3O_4 material of formaldehyde, ethanol response changed little, but the response has been significantly xylene to improve, and when the doping amount is 5 at% when the maximum increase (5 ppm xylene gas atmosphere response was 6.38, compared with pure phase Co_3O_4 5 ppm two tnu-9 response 1.29,. The high of nearly 4 times), this increase also improved material selectivity, reduce the other gas detection process to bring the signal-to-noise ratio, and the response and recovery process is very fast, can be completed within 30 s. But the effects of doping Cr, according to the control theory of surface resistance, in that position close to the surface the effect may be greater, so the design of appropriate heterostructure materials, gas sensing performance should be better, therefore conducted third experiments on.3. was designed and fabricated with WO_3 as matrix material, growing on the surface of Cr_2O_3 particles, thus forming gas sensitive material heterojunction structure. Preparation the method adopts two step water bath, the prepared WO_3 was with flower shaped particle graded structure, the lamellar structure of long width, provides two times the growth of particle attachment point, and a thinner thickness, is conducive to better play A heterojunction. By comparing the Cr_2O_3-WO_3 gas sensor and gas sensor prepared by WO_3 material prepared by heterogeneous structure significantly improves the material response to xylene gas, and the response and recovery speed is still fast, the response and recovery process were 5 s and 20 s can be finished.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP212

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