论文标题:无机纳米材料的液相合成、生成机制与性能研究
Study on the Solution-Based Chemical Synthesis, Growth Mechanism and Physical Properties of Inorganic Nanomaterials
论文作者
论文导师 钱逸泰,论文学位 博士,论文专业 无机化学
论文单位 中国科学技术大学,点击次数 124,论文页数 109页File Size7186K
2006-04-01论文网 http://www.lw23.com/lunwen_663795827/
本论文主要研究目的在于利用基于液相的化学线路来制备无机纳米材料；通过对反应过程的研究，提出一些合理的模型来解释制备纳米材料的生长机制；对合成的纳米材料进行性能测试，以期待制备的材料具有特别的物理性质。论文的主要内容总结如下： 1．在类软模板的辅助下，利用溶剂热／水热法来控制合成不同形貌的纳米材料。Fe_3O_4纳米片和分型通过溶剂热线路在PEG-20000辅助下实现了选择性的合成。其中N_2H_4和表面活性剂PEG-20000在反应过程中起到重要的作用，它们分别从热力学和动力学控制了纳米晶的生长。试验过程中一个重要的事实被发现，二茂铁的浓度对产品的形貌起到关键性影响。限制分散聚集和限制成核聚集模型很好的解释纳米晶的生长过程。PbTe空心球和单晶纳米管也在溶剂热线路和类软模板辅助下被选择性的合成。其中乙醚—甘油微乳体系和乙醇—甘油均相体系是它们形成的关键。类软模板辅助的溶剂热／水热路线期望能便利的控制合成各种形貌的纳米材料。 2．通过寻找合适的原料和反应，溶剂热反应用来在较低的温度下制备功能性的纳米材料。利用Mg_3N_2和SiCl_4为原料，通过直接化合的溶剂热过程在600℃下成功合成大量单晶纯alpha Si_3N_4纳米线。这里SiCl_4不仅作为反应原料而且还作为溶剂来控制反应容器的压力。调查试验发现纳米线的生长经历了VLS过程。深入检测其发光性能，纳米线展示了红外波段的红移和光致发光的蓝移，这些光学性质都是由K中心和N中心的点缺陷引起。利用了类似的溶剂热过程，2H-SiC纳米片第一次在温度为180℃下成功制备。这一系列的试验结果说明了，在合适条件下溶剂热线路可以用来在较低的温度下合成通常在很高温度下才能得到的功能纳米材料。 3．在溶剂热基础上，一种共催化裂解方法被建立用来合成碳实心纳米材料。在Fe和Mg共催化下，C_6H_6和C_5H_6裂解生成产量高达90％碳纳米棒。更有趣的是在产品中发现了大量的Y型纳米棒。经过对反应物，催化剂，及其温度的调查，试验结果发现Fe和Mg共催化作用在碳纳米棒形成中起到了重要的作用；原料比例(C_5H_6和C_6H_6)的在产品形成过程中起到及其关键的作用；碳原子在催化剂表面的分散速度影响了碳材料的最终形貌。Gamaly和Ebbesen
In this dissertation, solution-based chemical routes were developed to synthesize inorganic nanomaterials; through investigating experimental process, some proper models are referred to discuss growth mechanism of as-prepared nanomaterials; as-prepared nanomaterials are applied in different fields to check their performance, and it is expected that nanomaterials possess some novel physical properties. The main points are summarized as follows:1. Solvothermal/hydrothermal methods with the help of quasi- (soft template) are developed to controllably synthesize nanomaterials with various morphologies. Fe_3O_4 nanoflakes and nanofractals have been controllably synthesized through solvothermal route under PEG-20000 assistance. The roles of surfactant PEG-20000 and N_2H_4 have been discussed in detail. One key fact has been found that the ferrocene concentrations have vital effect on the morphologies of the products. The sidebranching process and the oscillation of the concentration have been proposed to illustrate the formation mechanisms of the fractal nanocrystals. And diffusion-limited aggregation and nucleation-limited aggregation models have also described the process of fractals growth. Searching a proper model to discuss their growth mechanism, it is significant to find a general route to synthesize the nanomaterials we expect. Furthermore, the PbTe hollow nanospheres and single-crystalline nanotubes have been prepared using an ether-glycerol microemulsion system and an ethanol-glycerol homogeneous system as quasi- (soft template), respectively. This kind of solvothermal/hydrothermal route under quasi soft-template assistance is expected to controllably synthesize the nanomaterials with various morphologies.2. Through searching proper starting materials and reactions, solvothermal route is introduced to prepare functional nanomaterials (such as Si_3N_4, SiC) at lower temperature. Single-crystalline alpha silicon nitride nanowires have been achieved with large scale by the reaction of Mg_3N_2 and SiCl_4 at 600℃. As-obtained nanowires exhibit the quantum size effect in optical properties, showing the red
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