关键词: 预置粒子, 独立成核, 局部成核, 表面膜, 粒子形态

Abstract: 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.

Key words: Pre-exsisting particle, Independent nucleation, Local nucleation, Surface film nucleation, Particle morphology