氧化铁基纳米结构的控制合成及其气敏性能研究
文献类型：学位论文
| 作者 | 李振民 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-21 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 王丹 |
| 关键词 | α-Fe2O3 纳米棒 空心球 气敏性能 纳米复合 |
| 其他题名 | Controlled Synthesis of α-Fe2O3-Based Nanostructures and Their Gas-Sensing Performances |
| 学位专业 | 化学工程 |
| 中文摘要 | α-Fe2O3是一种典型的环境友好的n型半导体，在室温下的禁带宽度为Eg = 2.1 eV；作为传统的金属氧化物气敏材料已经应用在可燃性气体、毒性气体的检漏报警、环境气体的监控等领域，并且具有无毒、低廉、耐腐蚀等优点，因此一直是半导体气敏材料领域研究的焦点。但是纯的α-Fe2O3结构稳定而导电性及气敏性较差，严重限制了其产品的应用推广。 α-Fe2O3的敏感机理属于表面控制型，其粒子尺寸、表面状态和氧气吸附量在材料灵敏度方面扮演着重要角色，所以氧化铁基纳米材料的结构对其气敏性能有很大的影响。因此氧化铁基纳米材料的结构调控及不同结构对其气敏性能的影响已经成为当前研究的热点。 本论文采液相合成手段，发展了纳米α-Fe2O3的结构调控工艺，制备了结构和形貌各异的α-Fe2O3基气敏材料，研究了其气敏性能，取得的研究结果如下： (1) 在SO42-辅助作用下，水热法合成了α-Fe2O3纳米棒，并通过调变SO42-的浓度实现了棒状产物的尺寸调控。产物的形貌和物相随水热反应时间变化的研究表明α-Fe2O3纳米棒是由α-FeOOH的纳米针经相转化而来。通过水热-焙烧两步法制备了具有大比表面积的α-Fe2O3纳米棒，该纳米棒的比表面积(89.1 m2/g)要远大于水热法直接得到的纳米棒的比表面积(12.9 m2/g)。气敏性能研究发现：水热-焙烧两步法合成的α-Fe2O3纳米棒由于尺寸小、比表面积大而比水热法合成的α-Fe2O3纳米棒具有高的灵敏度。 (2) 通过简单的1, 2-丙二胺辅助水热法一步合成了高长径比、单分散的α-Fe2O3单晶纳米棒。研究结果表明：纳米棒的生成经过了两步相转化，即：Fe(OH)3 → α-FeOOH → α-Fe2O3；1,2-丙二胺在α-Fe2O3纳米棒的生成过程中即提供碱源，又起到了形状控制剂的作用。该法合成的单分散的α-Fe2O3单晶纳米棒对乙醇和甲醛的灵敏度高，有望在气敏传感器上得到应用。 (3) 以碳球作为模板制备了具有核-壳结构的铁酸盐空心球(MFe2O4, M = Zn, Co, Ni, Cd)。通过控制初始溶液中金属盐的浓度可以调控核-壳结构铁酸盐空心球的核、壳尺寸和物相组成。气敏性质研究表明：由于ZnFe2O4空心球具有高的比表面积和多孔的结构，比ZnFe2O4纳米颗粒表现出更高的灵敏度和更好的响应恢复特性。 (4) 以碳球为模板合成了α-Fe2O3和Fe2TiO5/α-Fe2O3纳米复合的空心球。通过改变初始溶液中Ti/Fe的摩尔比，可以控制空心球的组成。气敏性能研究发现：该空心球的气敏性能并不简单的随着空心球比表面积的增加而提高，而随空心球表面Ti含量的增加，样品灵敏度逐渐增大，当在Ti/Fe = 0.28时达到最大值；继续增加Ti含量，灵敏度下降。空心球中的α-Fe2O3与Fe2TiO5纳米粒子形成纳米复合，降低了晶界电阻，这可能是材料气敏性能提高的主要原因。 |
| 英文摘要 | Hematite (α-Fe2O3), as conventional metal-oxide gas-sensing material, has been widely employed in detection of toxic and inflammable gases and monitoring of atmospheric gases. It is a typical environment friendly n-type semiconductor (Eg = 2.1 eV) and its nontoxicity, low cost, and high resistance to corrosion are definitely very attractive features for application in fabricating gas-sensor. Pure α-Fe2O3 has a poor electrical conductivity and gas sensitivity, which cause a big limit in more spread application of gas sensors. It is known that the sensing mechanism of α-Fe2O3 belongs to the surface-resistance controlled type, in which the grain sizes, surface states, and oxygen adsorption quantities play important roles in its gas sensitivity. Therefore, the nanostructural materials have great influences on their gas-sensing performaces. As a result, the controlled synthesis of α-Fe2O3 based nanoscale materials and the effects of the different nanostructure on their gas-sensing performaces have been becoming one of the hot topics. This study developed morphologically controllable routes to synthesize α-Fe2O3 via a solution synthesis approach and prepared various kinds of α-Fe2O3 based gas-sensing materials with different morphologies. Additionally, the gas-sensing properties of these materials were also studied. The results are as follows: (1) The size-controlled synthesis of hematite nanorods were conducted via a hydrothermal method with the assistance of SO42- ion. The diameters and lengths could be controlled by varying the SO42- concentration in the reaction system. The studies for time-dependent phase evolution showed that the α-Fe2O3 nanorods were transformed from α-FeOOH nanoneedles. The α-Fe2O3 nanorods with a high BET specific surface area were synthesized through a two-step method of hydrothermal process followed by calcination. The BET specific surface area of α-Fe2O3 nanorods from two-step method was about 89.1 m2/g, which was higher than that of the nanorods from hydrothermal method. The studies of gas-sensing properties for the different products showed that the nanorods from two-step method exhibited higher sensitivity to enthanol than those from hydrothermal method. (2) Monodispersed α-Fe2O3 single-crystalline nanorods with high aspect ratios were synthesized in large scale by a simple and direct 1, 2-propanediamine-assisted hydrothermal method. Hematite nanorods were obtained through a two-step phase transformation process as follows: Fe(OH)3 → α-FeOOH → α-Fe2O3. In the formation process of α-Fe2O3 nanorods, the 1, 2-propanediamine not only served as alkali source but also played a role of shape-control agent. These monodispersed α-Fe2O3 single-crystalline nanorods will be promising in the practical application in C2H5OH and HCHO gas sensors because of their good gas-sensing properties to ethanol and formaldehyde. (3) The homogeneous hollow core-shell microspheres of spinel ferrites (MFe2O4, M = Zn, Co, Ni, Cd) were synthesized by using carbonaceous saccharide microspheres as hard template. The composites, and core sizes and shell thicknesses of hollow spheres obtained could be manipulated by changing the concentration of metal salts. Compared with ZnFe2O4 nanoparticles, the ZnFe2O4 hollow spheres exhibited higher sensitivity and quicker responses to organic gases such as ethanol due to their high BET specific surface area and porous hollow structure. (4) The α-Fe2O3 and Fe2TiO5/α-Fe2O3 hollow spheres were prepared by using carbonaceous polysaccharide microspheres as hard template. The contents of the composites including α-Fe2O3 and Fe2TiO5 in the products could be adjusted by varying the ratios of Ti to Fe in the precursor solution. The studies of gas-sensing properties for the different samples showed that the sensitivity didn’t increase with the increasing of the BET specific surface area of the hollow spheres. While, the sensitivities of the hollow-sphere samples increased first and then decreased with the increasing of Ti content, and reached the maximum at Ti/Fe = 0.28. The improved gas-sensing performances of Fe2TiO5/α-Fe2O3 nanocomposite hollow spheres were attributed to the formation of α-Fe2O3-Fe2TiO5 nanocomposites in large quantities which may play an important role to reduce the grain boundary resistance. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 149 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1188]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 李振民. 氧化铁基纳米结构的控制合成及其气敏性能研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009. |
入库方式： OAI收割
来源：过程工程研究所
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