液相沉淀法制备纳米粒子的过程特征和原理

以制备纳米粒子为目的的液相沉淀过程 ,其成核、生长、聚结和老化等 ,均具有自身特征和规律。理想的沉淀过程是成核和生长分区或分期进行 ,在成核区或成核期 ,体系过饱和度高于均相成核临界过饱和度 ,为均相成核动力学所控制 ;在生长区或生长期 ,体系过饱和度小于成核临界过饱和度 ,为界面生长机理所控制。提出采用特征成核时间和特征扩散时间 ,判定反应沉淀过程的成核控制因素。提出粒度分布控制的技术关键 ,是将成核过程由微观混合控制转化为动力学控制

Process Characteristics and Principles of Synthesis of Nanosized Particles by Liquid Precipitation Methods

In the synthesis of nanosized particles by liquid precipitation methods,all the processes,including nucleation,growth,aggregation,and ripening,had special characteristics in contrast to the culturing of single crystal.Supersaturation and its distribution were the main factors in determining the particles size and distribution (PSD).The ideal processes should comprise two zones or periods,the nucleation one which was homogeneous nucleation kinetics controlled,and the growth one,controlled by surface growth.Characteristic nucleation time and characteristic diffusion time were employed to judge the controlling factor of the nucleation process.It was suggested that the key in the control of PSD was to convert the micromixing controlled nucleation process into the kinetics controlled one.