【作者】 闫德；

【导师】 闫鹏勋；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2009， 博士

【摘要】 随着现代社会的飞速发展，能源与环境问题越来越突出。纳米科技的飞速发展为解决能源与环境危机提供了无尽的机遇与广阔的前景。锰氧化物的优异性质使得它在催化、吸附、离子交换、通讯、微波铁氧体、软磁铁氧体、气敏、湿敏等诸多领域都有广泛的应用。本文主要关注的是它在能源和环境领域的应用：以锰的氧化物作为锂离子二次电池的正极材料不仅具有造价低廉、能量密度高、安全性高等优点，而且对环境不会产生任何污染；锰氧化物作为微波吸收材料能消除或屏蔽电子设备所造成的电磁污染，净化人类的生存环境。本论文以倡导绿色环保为时代背景、以纳米科技的飞速发展为科学背景、以锰氧化物在二次电池和微波吸收领域的应用为着眼点，着重研究了各种不同形貌锰氧化物低维纳米材料的制备、生长机制及形貌控制，并初步研究了锰氧化物纳米材料的微波吸收特性，为进一步深入研究奠定基础。本论文的主要研究内容、研究成果及创新点如下：1、无需任何模板和表面活性剂的辅助，只用KMnO₄和H₂O为反应物，用水热法制备了分级结构的花状自组装MnO₂多孔微球和γ-MnOOH纳米带。我们对其微观形貌和结构进行了表征，首次提出了一个包含两个竞争因素，即温度和库仑相互作用的竞争机制，对其生长机理进行了很好的解释。根据我们所提出的生长机制，推论出了得到均一形貌及两种形貌在产物中所占比例的控制方法，并在实验中得到了验证，实现了产物形貌较为精确的控制。2、无需任何模板和表面活性剂的辅助，只用KMnO₄和H₂O为反应物，用水热法在硅基底上制备了锰氧化物多层膜。所制得的多层膜由一层单晶纳米片所组成的表面多孔层和一层或多层数目不等的底部非晶层组成。我们对其微观结构进行了深入表征，结果表明，表面多孔层是钠水锰矿结构的MnO₂，非晶底层中可能包含有γ-MnOOH、γ-Mn₃O₄、γ-MnO₂、α-MnO₂，在底层和基底的界面上可能存在SiO₂和结合了-OH的Mn离子和Si离子。为探索其生长机制，我们首次提出了一个包含内应力的产生、积累、释放和化学反应同时存在的复杂机制，成功的解释了这种多层膜的生长机制。3、用水热法结合后续热处理制备了黑水锰矿（β-MnOOH和γ-Mn₃O₄）和Mn₃O₄纳米颗粒及Mn₂O₃三维网状结构。研究了三维网状结构的形成过程。对产物的微波吸收性质进行了测试，着重研究了颗粒大小，热处理温度，热处理时间对它们微波吸收性能的影响，并跟相应的块体材料进行了对比。详细分析了产物微波吸收的机理，为锰氧化物在微波吸收领域的实际应用打下基础。更多还原

【Abstract】 With the rapid development of modern society, energy and environment problem havearoused more and more attention, however, new approaches and chances to solve theseproblems are provided by the fast development of nanoscience and nanotechnology.Manganese oxides with excellent properties have wide applications in various fields, forexample, catalysts, absorbers, ion exchange, communication, microwave ferrite, softmagnetic ferrite, gas sensor, humidity sensors and many other fields. Here, our attention isfocused on its applications in the following two fields, energy and environmental protectionIt does not only has the advantages of low prices, high energy density and high safety, butalso has no harm to the environment as the cathode material of lithium-ion secondarybatteries. It can also eliminate the electron magnetic pollution caused by various kinds ofelectronic devices as an microwave absorber, thus purifies the human living environment.Therefore, with the call for environmental protection as the times background, the rapiddevelopment of nanoscience and technology as the scientific background and the respect ofits applications in the fields of lithium-ion secondary batteries and microwave absorption,the preparation, growth mechanism and morphology control of the low dimensionalmanganese oxides nanomaterials were investigated. Moreover, its application as microwaveabsorber was primarily studied which lays a solid foundation for further investigations.The content, results and originalities of this research are as follows:1.3D self-assembled flowerlike hierarchical spheres of MnO₂ andγ-MnOOH nanobelts were prepared by a simple hydrothermal method, using KMnO₄ and H₂O as reactants, without any templates and surfactants. Morphology and structure of the product were characterized. A growth mechanism was proposed for the first time, which involved two competitive factors, temperature and Coulomb interaction, to understand the formation mechanism of the product. A simple morphology control method to obtain products of uniform morphology and their proportion in the product, which deduced from the proposed mechanism was supported by parallel experiments, thus the morphology of the product can be controlled.2. Manganese oxde film on Si substrate was obtained by hydrothermal method, using KMnO₄ and H₂O as reactants, without the assistance of any templates and surfactants. The as-prepared film consists of a porous surface layer which was composed of many single crystal nanosheets, and one or more amorphous bottom layers. In-depth characterization was carried out. Results showed that the porous surface layer was Birnessite MnO₂ and the amorphous bottom layers might containγ-MnOOH,γ-Mn₃O₄,γ-MnO₂,α-MnO₂, and -OH bonded Mn and Si ions and SiO₂ might existed in the interface between the substrate and bottom layers. To understand formation mechanism of the as-prepared manganese oxide film, a complex mechanism involved the coexistence of internal stress and chemical reaction was proposed, and the formation mechanism and process of the film were well understood.3. Hydrohausmannite （β-MnOOH andγ-Mn₃O₄）,Mn₃O₄ nanoparticles and 3D porous network were prepared by hydrothermal method and subsequent heat treatments. The formation process of the 3D porous network was studied. The microwave absorption properties of the samples were tested, and the effect of particles size, temperature and duration of the heat treatment were also investigated. Comparation of microwave absorption properties of nanomaterials and bulk materials were made. For the future application of manganese oxide in microwave absorption, microwave absorption mechanism of the samples was discussed in detail.更多还原