【作者】 冯欣；

【导师】 施利毅；

【作者基本信息】 上海大学 ， 材料学， 2007， 博士

【摘要】 低维结构纳米材料因其独特的光、电、磁和机械性能，在纳米器件和功能材料等领域具有潜在的应用前景。通过大量文献调研发现，低维纳米材料的结构、维度、形貌、尺寸等因素对其性能有着直接影响。本文探索通过液相法，选择适当的反应体系和工艺，避免加入常用的表面活性剂、有机溶剂等模板或诱导剂，仅仅利用晶体自身结构的生长特性或在煅烧体系中加入易于去除的无机熔盐作为液相介质以实现对纳米材料结构的有效调控。1．通过水相化学沉淀法，不加入任何有机添加剂，利用晶体自身的结构特征，成功合成出一维ZnO纳米棒。以氨水作为沉淀剂，通过控制反应温度80℃或以上直接沉淀反应，不经煅烧就得到了直径为120nm、长度为800nm～1μm、截面为六边形的ZnO纳米棒。研究了反应条件如反应温度、氨水用量和煅烧温度等对产物形貌和性能的影响。同时在一定的氨水用量和煅烧温度范围内，产物呈现人体肤色。对一维ZnO纳米棒的生长机理和着色机理进行了讨论。2．采用熔盐辅助技术，分别在纯水体系或醇水混合体系中，制备了粒径可控、分散性较好的零维ZnO颗粒。以氨水作为沉淀剂，纯水体系中70℃以下合成了不同粒径的Zn0颗粒，研究了不同反应条件对ZnO颗粒尺寸大小影响的规律；添加低共熔混合物可以有效减小颗粒粒径，提高产物的分散性。讨论了水相中ZnO的形成机理；通过反应体系中加入一定配比低介电常数的乙醇，在醇水混合体系中获得的前驱物辅以不同熔盐进行煅烧，可以对ZnO纳米颗粒形貌进行有效调控，研究表明纳米ZnO颗粒粒径随着乙醇和熔盐配比的增大而减小，同时分散性更好。对醇水体系和熔盐辅助在ZnO颗粒合成中的作用机理进行了探讨。3．采用硬脂酸和硅烷偶联剂KH-570分别对纳米ZnO颗粒进行有机表面修饰，ZnO表面由亲水性变为疏水性，且疏水性随修饰量的增加而增强。对修饰后的表面键合状态和表面性质进行了分析。硬脂酸与纳米ZnO的表面羟基发生类似于羧酸与醇的酯化反应，并以桥连的形式结合在ZnO表面；KH-570以化学键结合方式接枝在ZnO表面。4．基于零维ZnO颗粒的形貌可控合成，深入研究了熔盐辅助这一共性技术在纳米材料制备中的应用，取得了一定的新颖性结果。采用不同一元熔盐、低共熔混合物或反应副产物熔盐辅助煅烧，成功合成了In₂O₃、ZrO₂、NiO、Al₂O₃、MgO、Mg（OH）₂、TiCN及BP等其它多种纳米材料。在常压下，不添加任何表面活性剂和有机溶剂，创新性地采用无机ZnCl₂熔盐辅助煅烧得到了高压相六方刚玉型纳米In₂O₃，并采用低共熔混合物KCl-ZnCl₂辅助制备了高温稳定相立方纳米ZrO₂，同时研究了熔盐辅助煅烧对前驱物分解的影响规律。讨论了熔盐辅助技术在纳米材料合成中的作用机理。更多还原

【Abstract】 Low-dimensional nanostructured materials have received a worldwide interest because of their unique electronic, optical, and mechanical properties and their potential applications in nanodevices and functional materials. We find that the structure, dimension, shape and size of dimensional nanomaterials have important effects on their performances according to a lot of literatures. In the thesis, structure-controlled products were synthesized using a simple solution method according to the crystals growth behavior or inorganic molten salts as reaction media. The approach required neither complex apparatus and sophisticated procedures nor metal catalysts, templates or regulating surfactants.1. 1D ZnO nanorods were successfully synthesized by a simple chemical precipitation method in aqueous solution at 80℃using ammonia water as precipitant. The method utilized the crystals growth behavior and hexagonal ZnO nanorods with 120 nm in diameter and 800 nm～1μm in length were achieved without subsequent calcinations in oven. The effects of reaction conditions on the morphologies and performances of ZnO nanorods, including reation temperature, ammonia water amount, calcination temperature and so on, were studied. Furthmore, skin-colored ZnO nanorods were obtained with appropriate amounts of ammonia water or in a certain range of calcination temperature. The growth mechanisms and pigmentation mechanisms of ZnO nanorods were finally developed.2. The size-controlled and better-dispersed ZnO nanoparticles were obtained in aqueous solution and water-ethanol mixed solvent using molten salts assisted approach, respectively. Submicron- and nano-sized ZnO were synthesized in aqueous solution below 70℃using ammonia water as precipitant. The effects of reaction conditions on the diameter size of ZnO nanoparticles were studied, and the addition of eutectic could improve the dispersibility of the products. The formation mechanisms of ZnO nanoparticles in aqueous solution were also discussed. ZnO nanoparticles were synthesized in water-ethanol mixed solution. The diameter size and dispersion of the products were easy to control with the addition of low dielectric constant ethanol and subsequently calcination with an appropriate amount of molten salts. And the formation mechanisms in mixed solution and the effect of molten salts were investigated.3. ZnO nanoparticles were grafted by steric acid and silane coupling agent, respectively. The surface of nanosized ZnO changed from hydrophilicity to hydrophobicity after organic modification, and the hydrophobicity was impoved with the increase of agent amount. Surface bonding characteristics and surface characteristics were analyzed. The reaction of steric acid with surface hydroxyl of ZnO was similar to esterification reaction between carboxylic acids and alcohol. And steric acid could bridge with ZnO nanoparticles. KH570 silane coupling agent grafted onto the surface of ZnO nanoparticles in the form of chemical bond.4. Based on the general molten salts assisted technique, the others nanomaterials were also prepared and many novel achievements were developed. Different nanomaterials, such as In₂O₃, ZrO₂, NiO, Al₂O₃, MgO, Mg（OH）₂, TiCN and BP, were successfully prepared with adding molten salts or by-products. Under ambient pressure, the so-called high pressure phase, corundum type In₂O₃ nanocrystals were firstly prepared using ZnCl₂ as additive, the method required neither surfactants nor organic solvents. And the high temperature phase, c-ZrO₂, was also obtained in the presence of KCl-ZnCl₂ eutectic. Furthermore, the decomposition of precursor was adjusted with the addition of molten salts. Finally, the formation mechanisms of molten salts in the synthesis of nanomaterials were investigated in detail.更多还原