【作者】 于勤勤；

【导师】 崔得良；

【作者基本信息】 山东大学 ， 材料物理与化学， 2011， 博士

【摘要】 随着经济和工业的发展,人们的生活水平得到了很大提高,但是随之而来的是各种有毒有害气体对环境的破坏和对人们健康的危害。其中,CO气体是一种易燃易爆的有毒气体,少量的CO即能给人体造成伤害。由于它无色无味,难于被发现,以致中毒及爆炸事件时有发生。近年来,金属氧化物半导体型CO传感器因为在耐热性、耐蚀性、材料成本、元件制作工艺等方面的优势,成为研究较多的一种传感器。但是,对于金属氧化物半导体型CO传感器的研究大多是实验室产物,制备条件的限制使它们很难产业化。因此,我们致力于开发新的简单易行的方法,研制具有更高性能的CO传感器,以推动其达到实用化目标。我们利用溶剂热压方法,以SnO2纳米颗粒为原料,制备了SnO2及SnO2-MOx (MOx=CuO、Co3O4、ZrO2、CeO2、TiO2)多孔纳米固体。在此基础上,利用传统的厚膜制备工艺制备了SnO2及SnO2-MOx多孔纳米固体厚膜CO传感器,并对它们的气敏性能进行了测试分析。为了进一步改善CO传感器的性能,我们首次直接采用SnO2多孔纳米固体作为气敏元件,制备了双功能高气敏响应的SnO2多孔纳米固体CO传感器。在此基础上,利用压差交换法制备了微量Pt担载的SnO2多孔纳米固体CO传感器。利用Pt对CO的催化氧化作用实现了对低浓度CO的室温探测,而且传感器的气敏响应和选择性都很好。(1)我们分别以商品化SnO2纳米粉和经过溶剂热压法制备的SnO2多孔纳米固体为原料,制备了SnO2纳米粉厚膜以及SnO2多孔纳米固体厚膜CO传感器,对比了两者的气敏性能。实验结果表明：SnO2多孔纳米固体的多孔结构有利于提高CO传感器的气敏响应。另外,我们探讨了SnO2多孔纳米固体厚膜传感器制备过程中的参数(造孔剂用量、热压温度、热压压力和烧结温度)对CO传感器气敏性能的影响。实验结果证实：通过改变造孔剂用量、热压温度、热压压力和烧结温度,可以在一定范围内调控SnO2多孔纳米固体的孔径分布、孔容和比表面积,从而找到SnO2多孔纳米固体厚膜CO传感器的最佳制备条件。其中,当造孔剂用量、热压温度、热压压力和烧结温度分别为10ml、200℃、60MPa和700℃时,传感器的气敏响应最大。(2)为了进一步改善SnO2多孔纳米固体厚膜传感器的气敏性能,我们对SnO2纳米粉进行了少量掺杂,制备了SnO2-MOx多孔纳米固体厚膜传感器。结果表明：掺杂少量的金属氧化物后,传感器的气敏响应在一定程度上得到了提高。当掺杂少量的p型半导体金属氧化物CuO和Co3O4时,CuO (Co3O4)与SnO2之间发生电子的相互交换,导致气敏性能发生变化；掺杂少量CeO2、ZrO2和TiO2后,多孔固体的孔径分布发生了很大变化,这可能是掺杂后传感器气敏响应提高的原因。其中,当SnO2纳米粉中掺入10wt.%TiO2时,传感器的气敏响应最大。(3)为了探索改善CO传感器气敏性能的新方法,我们利用SnO2多孔纳米固体制备了新型传感器,避免了厚膜传感器制备过程中工艺复杂的问题,提出了一种制备CO传感器的新方法。实验表明：SnO2多孔纳米固体传感器的气敏性能得到了很大提高,与厚膜型CO传感器相比,电阻率降低、气敏响应明显增大、工作温度降低了100℃。另外,传感器在高温下对CH4有很好的响应,可以作为CO和CH4双功能传感器使用。(4)在成功研制SnO2多孔纳米固体传感器的基础上,我们用压差交换法制备了微量Pt担载的SnO2多孔纳米固体CO传感器。由于Pt的催化作用,其在室温下对50ppm CO就有很好的响应,并且对CO的选择性很好。当所用氯铂酸溶液的浓度为0.003mol/L (10ml)时,Pt-SnO2多孔纳米固体CO传感器的气敏响应最大。另外,我们也探讨了烧结温度和湿度对Pt-SnO2多孔纳米固体CO传感器气敏性能的影响。结果表明：随着烧结温度的升高,Pt的催化活性降低,气敏响应减小,当烧结温度达到700℃时,传感器对CO无响应；随着湿度的增加,H2O和CO在SnO2表面竞争吸附,使传感器的气敏响应降低。更多还原

【Abstract】 With the development of economy and industry, our living situation has been improved at the expense of environmental pollution and health deterioration. Many kinds of toxic and harmful gases exist in our circumstance. Among them, CO is a kind of inflammable, explosive and poisonous gas, which may do serious harm to human body. CO is very difficult to detect due to its colorless and odorless characteristic, so poisoning and explosion incidents often take place. In recent years, metal oxide semiconductor CO sensors attract more attentions due to their advantages in thermal stability, corrosion resistance, low cost etc. However, almost all the sensing materials are prepared in lab scale, and the harsh preparation conditions limit their applications to a large extent. Here we focused on the developing a new facile route to prepare new sensing materials with excellent sensing performances, and investigating the sensing mechanisms of these new materials.SnO2 and Sn02-MOx (M=CuO、Co3O4、ZrO2、CeO2、TiO2) porous nanosolids were prepared by a solvothermal hot-press (SHP) method using SnO2 nanoparticle as raw materials. Subsequently, we fabricated SnO2 and Sn02-MOx thick film CO sensors from SnO2 and Sn02-MOx porous nanosolids following a conventional process. In order to further improve the gas-sensing performances of CO sensors, we fabricated dual-functional highly responsive CO sensors by directly using SnO2 porous nanosolid as the gas-sensing elements. Furthermore, CO sensors based on Pt-loaded SnO2 porous nanosolids were prepared using a pressure-driven exchange route. Because of the catalytic effect of Pt, a CO sensor that can be used to detect low level CO at room temperature was prepared.(1) The gas-sensing performances of two thick film sensors fabricated from SnO2 nanoparticles and SnO2 porous nanosolid were compared, and the results show that the latter possesses lower resistance and higher sensor response due to its porous nature. In addition, all the parameters during fabricating thick film CO sensors, including the solvent volume, hot-pressing temperature, sintering temperature etc., influence the gas-sensing properties of the sensor. It is proved that by varying these parameters, all the pore diameter distribution, pore volume and specific surface area of SnO2 porous nanosolid are changed. The results demonstrate that optimum values for the solvent volume, hot-pressing temperature, pressure and sintering temperature are 10 ml,200℃,60 MPa and 700℃, respectively.(2) For enhancing the gas-sensing performances of CO sensors, a series of metal oxides were doped into SnO2 nanoparticles and thick film CO sensors based on SnO2-MOx (M=metal atom) porous nanosolids were fabricated. The results show that, the sensor responses of SnO2 to CO are all improved to a certain extent by doping. When p-type metal oxide semiconductors CuO and Co3O4 are doped into n-type SnO2, the electronic interactions between CuO/Co3O4 and SnO2 is the major reason for the improvement of sensing performances. However, when CeO2、ZrO2 and TiO2 are added into SnO2, the pore diameter distributions of SnO2 porous nonsolid are changed, this phenomenon may be responsible for the improvement of the sensor responses. The thick film CO sensor doping with 10wt.% TiO2 has the largest sensor response.(3) In order to explore new routes for improving gas-sensing performances of CO sensors, the novel CO sensors were fabricated by directly using SnO2 porous nanosolids as sensitive elements. The results reveal that the novel CO sensor based on SnO2 porous nanosolid possesses lower intrinsic resistivity and higher sensor response by comparing with that fabricated from SnO2 nanoparticles. Furthermore, the SnO2 porous nanosolid sensor also has much lower working temperature, and it can be used as a dual functional gas sensor, i.e., as CO sensor at 300℃and as CH4 sensor at 400℃, respectively.(4) For further increase the sensor response while decrease the operation temperature of CO sensors, CO sensors were fabricated by using Pt-loaded SnO2 porous nanosolids, which were prepared by a pressure-driven exchange method. With the help of catalytic effect of Pt, the sensors exhibit rather high sensor response to 50 ppm CO at room temperature. Besides, the sintering temperature and the humidity have influences on the sensor response. When the sintering temperature and humidity increase, the sensor response of the sensors deteriorates to some extent. After being sintered at above 700℃, the sensors have no response to CO at all.更多还原