Crystal Growth of Composite Nanoparticles by Advanced Gas-Evaporation Technique

本研究的目的是探讨气体蒸发技术制备复合纳米粒子的晶体生长机理，即在低压惰性气体气氛中通过蒸发材料制备超细粒子的方法。根据以下程序进行样品制备。首先，将通过气体蒸发技术制备的纳米尺寸的烟雾颗粒A引入到石英管中，该石英管通过管式炉进行差分抽真空和加热。然后，另一种材料B的蒸气随后在管中冷凝到烟雾颗粒A的表面上。因此，A-B复合纳米颗粒通过上述过程生长。将颗粒直接收集到TEM微网格上，并使用透射电子显微镜观察。本课题研究了Cu-Zn系和Cu-C_2系的晶体结构和形貌<60>与制备条件的关系。对于后一种体系，我们对碳纳米颗粒的生长<60>进行了研究。主要研究结果如下：1.Cu-Zn复合体系：在有限的制备条件（主要是铜的蒸发温度T_&lt;Cu '&gt;、氩气压力P_<Ar>和锌的加热温度T_F）下，复合纳米粒子生长。对于低T_&lt;F '&gt; Cu相，由于Zn的蒸气密度低，Cu相颗粒长大。对于高T_&lt;F '&gt;合金相颗粒的生长是由于Cu纳米颗粒与锌蒸气之间的合金化。2.Cu-C_2<60>体系：本体系主要研究非金属材料C_2对Cu_2/C_2复合纳米粒子的影响<60>。结果表明，C_2<60>在管内不是以单分子形式存在，而是以团簇形式存在.随着加热的进行，C_<60>2转变为石墨。

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.