【作者】 倪小敏；

【导师】 ??；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2006， 博士

【摘要】 本论文中的工作主要可分为两个部分： 一．进一步发展了以液相化学合成和同步组装的路线制备纳米组装结构的技术，提出了一种在无表面活性剂和无外磁场诱导的条件下制备磁性纳米组装结构的方法，在合成磁性金属镍和钴的纳米组装结构的实践上取得了较大的进展。在液相还原一步法中，通过选择各种配位剂控制纳米晶的生长过程，同时利用磁性纳米粒子之间的磁相互作用，制备得到了多种不同形貌的金属镍和钴的纳米组装结构。在前驱体—氢气固相还原两步法中，首先利用配位剂控制合成具有组装结构的金属氢氧化物前驱体，然后通过氢气还原，在前驱体形貌保持的条件下获得了金属镍和钴的纳米组装结构。详细内容归纳如下： 1．利用柠檬酸钠作配位剂辅助控制金属镍纳米晶在水热体系中的各向异性生长和同步组装，制备出由刺状纳米晶组装而成的镍微米线。通过调节柠檬酸钠的浓度、体系的碱度和反应温度等条件参数，实现了对镍微米线的微结构控制。对比实验研究发现该组装结构的形成是受反应动力学和磁性粒子的内在磁相互作用的共同影响。将此配位剂辅助合成法推广应用到其它配位剂体系，可得到类似的具有组装结构的镍微米线，证实了该反应路线的普适性。该镍纳米组装结构的磁学性质和催化碳氢化合物热解生成碳纳米管的性能均与其微结构密切相关。以此多刺镍微米线为原位模板，通过简单的金属置换反应，在其表面修饰一层金属银，可以在保持其形貌和磁性质基本不变的条件下有效地提高材料的抗氧化性能，同时屏蔽其催化碳纳米管生成的特性。 2．利用氨水和丁二酮肟作配位剂，在水合肼—镍盐的体系中，通过对反应物浓度和反应温度的调节，在低温水热的条件下分别制备出两种由面心立方结构金属镍的单晶六方片组装而成的花状多级结构。对比实验研究表明，配位剂的配位作用和结构导向作用以及磁性粒子内在的磁相互作用共同决定了纳米晶的各项异性生长和自发同步组装。 3．同时选择丁二酮肟和水合肼两种配位剂和镍离子配位形成的两种配合物组成混合镍源，利用这两种配合物的结构和稳定性差异，实现镍纳米晶的分步生长，合成了一种以球状颗粒为花心，剑状纳米晶为花瓣的镍纳米组装结构。两种更多还原

【Abstract】 The work in this dissertation could be divided into two parts.In the first part, solution-based routes assisted by complexants were developed to realize the chemical synthesis and simultaneous assembly of isolated nanoparticles into hierarchical nanostructures. We established a new route for the synthesis of magnetic assembly nanostructures without any surfactants or external magnetic field, which was successfully used in the fabrication of metallic nickel and cobalt hierarchical nanostructures. In the one-step solution chemical reduction method, nickel and cobalt assembly nanostructures with different-shapes were created by controlling the crystal growth with various complexants, together based on the magnetic interactions of magnetic particles. In the hydrogen reduction route, metallic nanoarchitectures were fabricated by hydrogen reduction of the hydroxides precursors, which were prepared first with the assistance of different complexant agents. The details are summarized as follows.1. Prickly nickel microwires assembled by nanothorns were fabricated from the anisotropic growth of metallic nickel nanocrystals and their simultaneous assembly assisted by citrate. By adjusting the reagent concentrations and temperature, microstructures of the nickel wires were modulated. Formation of the assembly nanostructures could be ascribed to the kinetic control of the reaction process and the inherent magnetic interactions between the magnetic particles. Such a complexant-assisted method could be extended to the other complexing systems, which was proved as a general route for the synthesis of nickel microwires. As-prepared nickel assembly nanostructures showed microstructure-dependent magnetic properties and catalysis for the growth of carbon nanotubes in pyrolyzing acetone. Using the nickel wires as in-situ reductant, prickly Ag_shell-Ni_core wires were obtained through a simple transmetallation reaction. The surface modification with silver showed little influence on the morphology and magnetic properties of the nickel wires, while greatly improved their oxidation-resistance and blocked their catalysis for the growth of carbon nanotubes in pyrolyzing acetone.更多还原