Crystal Growth of Composite Nanoparticles by Advanced Gas-Evaporation Technique

本研究旨在探讨气体蒸发法制备复合纳米粒子的晶体生长机理，即在低气压惰性气体中蒸发材料制备超细粒子的方法。样品的制备按以下程序进行。首先，将由气体蒸发技术制备的纳米级烟雾颗粒A引入石英管中，石英管由管式炉进行差动真空加热。然后，另一种材料B的蒸汽随后在管子中凝结到烟雾颗粒A的表面上。因此，A-B复合纳米粒子通过上述过程生长。这些颗粒被直接收集到电子显微镜微格上，并用透射电子显微镜进行观察。在工程方面，研究了不同制备条件对CuZu和CuC60&Gt；体系的晶体结构和形貌的影响。对于后一种体系，预先研究了C&lt；60&gt；纳米粒子的生长。主要研究结果如下：1.铜锌复合体系：在一定的制备条件下(主要是铜的蒸发温度T&lt；铜的蒸发温度Cu‘&Gt；Ar的压力P&lt；Ar&Gt；锌的加热温度T_F)下生长复合纳米颗粒。对于低T&lt；F‘&Gt；，由于锌的蒸气密度低，铜相颗粒长大。对于高T&lt；F‘&Gt；合金相颗粒是由于铜纳米颗粒与锌蒸气之间的合金化而长大的。为了获得足够的T&lt；F‘&gt；复合纳米颗粒，其形貌为铜锌合金相被锌层包裹。2.Cu-C&lt；60&gt；系统：本系统的主要目的是研究非金属材料C&lt；60&gt；因此，C_&lt；60&gt；不是以单分子形式存在，而是以团簇形式存在于管内。随着加热的进行，C&lt；60&gt；向石墨转变。

The aim of this study is to investigate a crystal growth mechanism of composite nanoparticles prepared by a gas-evaporation technique, that is, a method preparing ultrafine particles by evaporation of meterial in an atmosphere of inert gas at a low pressure. The sample preparation was carried out according to the following procedure. First, smoke particles A of nanometer size prepared by a gas-evaporation technique are introduced into a quartz tube which is differentially evacuated and heated by a tubular furnace. Then, the subsequent condensation of vapor of another material B onto the surface of the smoke particles A occurs in the tube. Thus, A-B composite nanoparticles grow through the above process. The particles are collected direstly onto TEM microgrids and observed using a transmission electron microscope. In the term of project, the crystal structure and morphology of Cu-Zu and Cu-C_<60> systems were studied in relation to the preparation conditions. For the latter system, the growth of C_<60> nanoparticles was studied in advance. The results are as the following.1.Cu-Zn composite system : Composite nanoparticles grew under the limited preparation conditions (mainly, evaporation temperature of copper T_<Cu'> argon pressure P_<Ar> and heating temperature of zinc T_F). For low T_<F'> Cu phase particles grew because of low vapor density of zinc. For high T_<F'> alloy phase particles grew due to alloying among Cu nanoparticles and zinc vapor. For adequate T_<F'> composite nanoparticles with the morpology of Cu-Zn alloy phase surrounded by zinc layr.2.Cu-C_<60> systems : The aim of this system is mainly to study the effect of nonmetallic material C_<60>. As a result, C_<60> existed not as single molecules but as clusters in the tube. And C_<60> transformed to graphite with the progress of heating.