预置粒子对均匀胶体粒子形成的影响

研究预置粒子对于均匀胶体粒子形成的影响,对深入了解均匀粒子的形成机理以及开拓覆盖技术的应用具有重要意义.所谓预置粒子就是在经升温陈化能够生成均匀胶体粒子的溶液中,于陈化前加入的具有一定形态(组成、形状和大小),一定浓度的胶体粒子,新形成的沉淀物因预置粒子的表面性质、形态和浓度的不同而变化.据文献报导,新沉淀的形成过程有:①新粒子的形成与预置粒子的存在无关,新沉淀物独立成核并成长为独立的稳定

THE EFFECTS OF PRE-EXSISTING PARTICLES ON THE FORMATION OF UNIFORM COLLOIDAL PARTICLES

The presence of pre-exsisting foreign particles will strongly affect the formation, morphology and even the crystal types of colloidal particles formed by the hydrolysis of concerned salts at elevated temperature, depending on the shape, size, surface charge and number concentration of pre-exsisting particles. The nucleation of new materials usally varies in different ways: (1) independent nucleation; (2) local nucleation on the active sites of pre-exsiting particles; (3) nucleation on the full surfaces of pre-exsisting particles. Our new finding is that the morphology, chemical compostion and even crystal types of new precipitation change with the number concentration of pre-exsisting particles. For example, the aging solution for preparing β-FeOOH, a mixture of β-FeOOH and hematite in the presence of pre-exsisting spherical or spindle hematite will be obtained. Accompanying with the presence of the foreigners, the content of hematite obviously. When the number of foreign particles is equal to or more than that of β-FeOOH formed without foreigners, the product is pure hematite. It indicates that the saturated concentration of the components may be redueed by foreign particles.