三氧化二铟基复合纳米材料的制备及其气敏性能研究

【作者】 高军；

【导师】 史克英；

【作者基本信息】 黑龙江大学 ， 物理化学， 2016， 博士

【摘要】 一维金属氧化物半导体纳米功能材料因其独特的物理性质和潜在的应用价值,成为材料科学研究的焦点。目前,已经有包括水热法、模板法、静电纺丝法、气相法等在内的多种技术手段被用来合成一维金属氧化物纳米功能材料。其中,静电纺丝法作为一种非常灵活的材料合成方法,能够自由地调控一维材料的结构、组成甚至宏观外貌（管径、棒、多通道等）。然而单一组分静电纺丝法所合成的材料难以满足人类社会发展的需要,因此,为了进一步改善一维纳米材料的性能并拓展其应用范围,人们开始尝试通过表面修饰与掺杂制备复合物,以及使用模板剂等手段来调控产物的形貌和结构,从而制得能够在多种领域发挥重要作用的新型一维纳米功能材料。基于上述考虑,本论文在In₂O₃纳米材料的形貌和结构方面做了有益的探索,设计并合成了In₂O₃基一维纳米材料,构建NO_x气敏元件并对其进行了气敏性能的研究。此外,也探讨了材料的结构、形貌与其性能的关系。首先,利用静电纺丝法制得PVP/In（NO3）3复合纳米纤维前驱体,经过700 o C高温煅烧得到In₂O₃纳米纤维。随后将所合成的纳米纤维组装成气敏元件检测室温下NO_x气敏性能。通过对In₂O₃基气敏传感器的气敏机理研究,发现所合成材料良好的气敏性能主要归因于:所合成的In₂O₃纳米纤维具有独特的形貌和结构,有利于气体分子的扩散、吸附和脱附;小尺寸的纳米粒子具有较大的表面/体积比,In₂O₃纳米粒子间形成强相互作用,能够为电子的转移提供有效的通道。该实验的方法简单,操作容易,为合成其他类型气敏传感器的方法提供了有利的理论和实际的经验。其次采用一步静电纺丝法合成了介孔Al2O3-In₂O₃复合纳米纤维。通过调节加入Al2O3的量改变一维复合材料的结构:当加入量增加时,产物的形貌会从Al2O3-In₂O₃复合纳米管变化为纳米棒。其中20AI介孔纳米管在室温条件下对NO_x气体具有优异的气敏传感性能:97 ppm时对NO_x气体的灵敏度为100,最低检测限高达291 ppb。此外,在35天内,气敏元件对0.97⁹.7 ppm的NO_x气体具有稳定的灵敏度和响应时间。该材料在室温下增强的气敏性能可以归因于一维介孔的管状结构和氧化铝之间的协同效应:介孔和独特的一维中空结构具有较高的比表面积,可以作为气体的吸附-脱附和扩散的通道。此外,这种独特的结构还为NO_x与表面吸附的氧离子反应提供了更多的化学活性位点。另外20AI介孔纳米管传感器高灵敏度可能归因于氧化铝的改性作用,即添加的Al2O3可以增加氧空位或者缺陷,控制晶粒长大,调控材料电阻率,并提供更多的化学活性位点（O-,O2-）。然后利用静电纺丝法合成了Ti O2-In₂O₃复合纳米纤维,并将其组装为气敏元件室温下进行了NO_x气敏性能的检测。其中PVP作为表面活性剂和模板对纳米纤维的生长机理起到了至关重要的作用。大的In₂O₃单晶纳米粒子可以与Au电极形成良好的肖特基接触,易于电子的传输。纤维中的Ti O2纳米粒子作为电子供体可以增加In₂O₃复合纳米纤维的载流子密度。同时,使复合纤维表面的吸附氧量增加。上述协同作用使该气敏传感器具有高的灵敏度、快速响应和恢复响应。Ti O2-In₂O₃复合纳米纤维为制备出性质优异的气敏传感器提供了参考。最后使用SBA-16粉末作为硬模板剂,通过水热法首先合成In（OH）3前驱体,再经过高温煅烧制得介孔的In₂O₃。利用0.3 mol·L-1的In（NO3）3为前驱体溶液合成的无论是In（OH）3中间体还是介孔In₂O₃为疏松多孔结构,In₂O₃纳米晶相互叠加形成多孔结构,比表面积增加。此外,介孔In₂O₃纳米晶及孔的边缘,含大量的缺陷位。这种独特的结构为目标气体与样品表面之间的反应提供了丰富的化学活性中心。将所合成材料构建气敏元件并在室温下对NO_x进行检测,发现该元件室温下具有超高的响应和极强的选择性,对于97 ppm的NO_x气体响应可达到158.7,最低检测限达到970 ppb。更多还原

【Abstract】 In recent years, one-dimensional metal-oxide-semiconductor nano-functional materials become the focus of research due to its unique physical properties and potential application values, and it gradually developed into a new research focus. At present, there are variety of techniques having been used to synthesis of one-dimensional metal oxides nano-functional materials, including hydrothermal method, template method, electrostatic spinning method, gas phase method, and so on.Among them, as a kind of flexible synthesis method, the electrostatic spinning method can freely control the morphology（pipe diameter, rod, multichannel and so on）,structure, composition and macroscopic appearance of one-dimensional material.However, simply using electrospinning method to synthesize the single-compound nanomaterials can not meet the needs of social development, therefore, in order to further improve the performance of one-dimensional nanomaterials and expand their range of applications, people began to experiment with the doped by surface modification, preparation complexes, and the use of template agents and other means to control the morphology and structure of the product, in order to obtain new 1D functional nanomaterials that can play an important role in a variety of areas.Based on the above consideration, the paper has made beneficial exploration in terms of morphology and structure of In₂O₃ nanomaterials. In this paper,one-dimensional In₂O₃ nanomaterials were designed and synthesized, and they had been used for NO_x gas sensitive element. In addition, the relationship between morphology and structure of the material with gas sensing performance was also discussed. The main content of this paper are as follows:（1） At first, PVP/In（NO3）3·4.5H2 O composite nanofibers precursor was synthesized by electrostatic spinning method, subsequently, the precursor was calcined at the high temperature of 700 oC, and In₂O₃ nanofibers formed after cooling down to the roomtempreture. Then assemble the synthesis of nanofibers into a gas sensitive element and to explore its operating temperature, the comparisons of the results shows that the element showed the best gas sensitive performance for NO_x gas. Through researching the gas-sensing mechanism of In₂O₃ gas sensors found that the good gas-sensing properties of synthesis can be attributed to the following two points:（a） The synthesized In₂O₃ nanofibers have unique morphology and structure, which are advantageous to the gas molecular diffusion and stripping absorption;（b） Small size of nanoparticles have larger specific surface area, which can provide effective channel for electron transfer.The whole process of synthesis is very easy to operate and provides beneficial theory and practical experience for synthesis of other types of gas sensor.（2） Using one-step electrostatic spinning method synthesized mesoporous Al2O3-In₂O₃ composite nanofibers. By adjusting the quantity of Al2O3,We found that with the addition amount increasing, the product’s morphology will change. Thereinto,mesoporous Al2O3-In₂O₃ nanotubes with 20 AI Al2O3-containing has the excellent properties of gas sensitive sensor with NO_x at the room temperature: other gas sensitivity for NO_x at 97 ppm is 100, and the minimum detection limit is up to291 ppb.In addition, the gas sensitive element keeps constant sensitivity and response time for0.97 to 9.7 ppm of NO_x in 35 days. The enhanced gas-sensing properties of materials at room temperature can be attributed to one-dimensional mesoporous tubular structure and synergies between alumina:（a） The mesoporous structure and unique one-dimensional hollow structure has higher specific surface area which can be used as a channel for gas adsorption-desorption and diffusion. In addition, the unique structure provides more chemical active site for surface adsorption.（b） The high sensitivity of 20 AI mesoporous nanotubes gas sensor could be attributed to the modification effects of Al2O3, namely the add of Al2O3 can increase the oxygen vacancy or defect and control the grain growth, resistivity, and provide more chemical active sites（O-,O2-）.（3） TiO2-In₂O₃ composite nanofibers were synthesized by electrostatic spinning method. As a surfactant and a template, PVP play a crucial role in the growth process of nanofibers. In₂O₃ nanoparticles that contact with Au electrode can control an electronic go through the gas sensor. As the electron donor, TiO2 particles in Nanofiber can increase the carrier density of In₂O₃ nanofibers. Therefore, TiO2-In₂O₃ composite nanofibers gas sensors have high sensitivity, fast response and recovery time.TiO2-In₂O₃ composite nanofibers provide a reference for preparing gas sensors with excellent properties.（4） In（OH）3 precursors was synthesized through hydrothermal method by using the SBA-16 powder as hard template agent, after that, the In（OH）3 was calcined at high temperature, and the mesoporous In₂O₃ nanosheets formed after cool down to tempreture. Results show when using 0.3 mol·L- 1 In（NO3） 3 for the precursor solution,the product would have the most loosen structure, and the nanofiber superposition with each other, but the interlayer will be separated by a certain gap, which makes the specific surface area of sample increase significantly. In addition, In₂O₃ crystal is rich in a large number of defects due to porous structure of product. This unique structure provides abundant chemical activity center for the target between the gas and the surface reaction. Besides, the gas sensitive materials showed ultra high response and strong selectivity for NO_x at room temperature: response sensitivity can reach 158.7 at97 ppm of NO_x, and the lowest detection limit can reach 970 ppm.更多还原