氧化锌纳米粒子形态与制备条件的关系

通过一步法和二步法两种制备方法的主要制备条件的变化,探讨了氧化锌纳米粒子形态与制备条件的关系。温度对一步法直接合成纳米氧化锌的影响较大,当温度较低时,可以得到纤维状粉体,随温度升高,其形貌也逐渐向短棒状、类球状转变,在100℃反应时可以获得近球状颗粒;二步法的热分解反应为固相反应,粒度受反应温度和反应时间的影响,随热分解温度的升高和反应时间的延长,晶粒逐渐变大,但温度的变化影响最为显著。试验与理论分析表明,纳米氧化锌的粒度与形貌除受其晶核的形成与生长机制的影响外,在很大程度上还受到制备方法和制备条件的影响。一步法制备纳米氧化锌时,粉体的晶粒粒度与粉体的成核速度有关,成核速度越快,得到的粉体粒度越小;提高反应温度或增大反应物浓度都能使成核速度增快,因而制得的粉体粒度减小;同时伴有取向连生现象出现,这表明了氧化锌极性晶体的生长习性。

RELATION BETWEEN SHAPE OF NANO-ZnO CRYSTAL AND ITS PREPARATION CONDITIONS

In this paper the relation between configuration of nano-ZnO particles and preparation conditions is discussed by changing the main conditions in preparation with one-step and two-step method. The temperature has significant influence on the nano-ZnO synthesis reaction process by one-step method. Fibre powder can be prepared at lower temperature. As the temperature rises, the shapes of nano-ZnO particles changes from fibre- like to shortened prismatic-like and sphere-like, and at the temperature of 100℃transforms to approximative sphere-like. The thermal decomposition in the two-step mehod is solid-state reaction. The temperature and time of the solid-state reaction have effect on the particles size and patterns of nano-ZnO. Prolonging the reaction time and raising the reaction temperature, the particles size is gradually enlarged, and the change of the reaction tem- perature is more prominence. The test results and theoretical analysis indicate that the particles size and patterns of nano-ZnO are affected by the preparation method and preparation conditions to a large extent besides the effect factors as the formation of crystal nuclear and its growth mechanism. The nucleation rate of nano-ZnO influences the particle size, the rapider nucleation rate, the smaller the particle size. With the reaction temperature rising or reactant concentration increasing, the nucleation rate become rapider, and the particle size of nano-ZnO tend to be smaller. Oriented intergrowth occurs accompanying thecrystal formation, indicating the fact of the nature of polar ZnO crystal growth.