【作者】 钭启升；

【导师】 杨德仁；

【作者基本信息】 浙江大学 ， 材料工程， 2007， 硕士

【摘要】 自1991年Iijima合成纳米碳管以来，纳米材料由于其新颖的物理、化学和生物学特性以及在纳米器件中的潜在用途成为当今纳米技术的研究热点。而纳米材料大量、低成本和简单有效地合成与组装无论从基础研究的角度，还是从性能与应用的角度来看，都有着特殊重要的意义。首先利用氧化锌种子辅助低温化学反应，合成百克级、直且细氧化锌纳米棒。研究表明下面几个因素对氧化锌纳米棒的尺寸和形貌起关键作用：（1）氧化锌种子与锌源的摩尔比。当氧化锌种子和锌源摩尔比为0．03时，得到的是直径为20nm，长度为800nm的氧化锌纳米棒。而当氧化锌种子和锌源摩尔比为0．003时，得到是直径100nm纳米棒和200nm纳米棒组成的标枪状氧化锌纳米结构；（2）反应试剂，如水合硝酸锌和二乙烯基三胺，反应前不会将氧化锌种子溶解；（3）分散剂，如聚乙烯醇（PVA），通过空间位阻效应控制氧化锌纳米棒的长度。其次利用异质形核种子（MnO₂或CdS纳米颗粒）辅助低温化学反应对氧化锌纳米结构进行裁剪，获得伞状氧化锌纳米结构。接着利用表面活性剂辅助水热法成功合成MnOOH纳米结构，并利用后续的热处理将其转化为MnO₂纳米结构。研究表明，当以十六烷基三甲基溴化铵为表面活性剂时，所得产物为MnOOH纳米棒，纳米棒的直径大约在10～50nm，并且通过热处理将其转化为MnO₂纳米棒。生长机理研究表明MnOOH纳米棒是由片状络合物卷曲而成。另外采用柠檬酸辅助水热法及后续热处理合成了MnO₂圆盘状纳米结构，圆盘的直径在200nm左右，厚度在10nm左右。进一步研究表明CA可以限制纳米结构的c轴方向的生长，从而获得圆盘状纳米结构。最后利用乙二醇辅助水热法制备氧化铁的纳米结构，系统研究了Fe³⁺和OH^-的比例、乙二醇的含量、不同碱源以及后续热处理对氧化铁纳米结构的影响，同时研究了不用形貌的氧化铁纳米结构对其磁性的影响．研究表明：当Fe³⁺和OH^-的摩尔比>1：4时，无论有无乙二醇的加入，所得样品都为六方相的α-Fe2O3纳米颗粒；当Fe³⁺和OH^-的摩尔比<1：4，有乙二醇辅助时，所得样品为正交相飞机状的FeOOH纳米结构；当Fe³⁺和OH^-的摩尔比<1：4，无乙二醇辅助时，所得样品为正交相的FeOOH纳米棒．经过600℃，1h热处理后，飞机状的FeOOH和FeOOH的纳米棒都可以转化为多孔的飞机状α-Fe₂O₃和α-Fe₂O₃的纳米棒。不同形貌和尺寸对材料的磁性能有很大的影响。更多还原

【Abstract】 Since the discovery of carbon nanotubes in early 1990’s, quasi one-dimensional nanomaterials have received intensive interests due to their novel physical, chemical, and biological properties as well as the potential applications in nanodevices. Large-scale, cost-effective, simple and practical synthesis and assembly of one-dimensional nanomaterials is of importance for the fundamental research and application.In the dissertation, we developed a simple approach to hectogram-scale synthesizing straight and thin ZnO nanorods at low temperature （95℃） by a seed-assisted chemical reaction. The following factors played the key role for the growth of ZnO nanostructures: （1） the molar ratio of ZnO seed and zinc source controled the growth of ZnO nanorods. At low molar ratio of ZnO seed and zinc source （0.003）, the javelin-like ZnO nanorods consisting of the thin ZnO nanorods with the diameter of 100 run and the thick ZnO nanorods with the diameter of 200 nm were obtained. In contrast, the straight ZnO nanorods with the diameter of about 20 nm were prepared. （2） Nearly neutral reactants including zinc nitrate hydrate and diethylenetriamine could not dissolve the ZnO seeds before the chemical reaction. （3） The dispersant such as poly（vinyl alcohol） （PVA） acted as a spatial obstructor to control the length of ZnO nanorods. Moreover, the ZnO nanostructures were tunably grown by the heterogeneous nucleation （CdS or MnO₂ nanoparticles） assisted chemical reaction at low temperature （95℃） and umbrella-like ZnO nanostructures were achieved.A surfactant assisted hydrothermal method was employed to prepare MnOOH nanostructures. Moreover, the MnO₂ nanostructures were obtained by the thermal conversion of MnOOH nanostructures. It was indicated that MnOOH nanorods with the diameter of about 10-50 nm were obtained by cetyltrimethylammonium bromide （CTAB） assisted hydrothermal process and MnO₂ nanorods were achieved from the thermal conversion of MnOOH nanorods. It was revealed that the formation mechanism of MnOOH nanorods was due to the rolling process of the flake-like complex. Moreover, the disc-like MnO₂ nanostructures with the diameter of about 200nm and the thickness of about 10 nm were prepared by citric acid （CA） assisted hydrothermal process and subsequently calcination. Further investigation indicated that the growth of MnOOH nanostructures along c axis was limited due to the preferential absorption.Finally, Fe₂O₃ nanostructures were prepared by the ethylene glycol （EG） assisted hydrothermal process. The effects of the molar ratio of Fe³⁺ and OH^-, the amount of EG, the concentration and annealing on the morphology and composition were investigated. Moreover, the effects of Fe₂O₃ nanostructures with different morphology and size on the magnetic properties were also investigated. The results indicated that only hexagonal -Fe₂O₃ nanoparticles can be obtained when the molar ratio of Fe³⁺ and OH" was less than 1:4 with or without the addition of EG; when the Fe³⁺ and OH" was more than 1:4, the orthorhombic airplane-like FeOOH nanostructures could be achieved with the assistance of EG; while the Fe³⁺ and OH^- is more than 1:4, the orthorhombic FeOOH nanorods could be achieved without the assistance of EG. The airplane-like FeOOH nanostructures and FeOOH nanorods were transformed into the porous airplane-like Fe₂O₃ nanostructures and Fe₂O₃ nanorods by caicination. The different size and morphology of Fe₂O₃ had great influence on their magnetic properties.更多还原