硝酸酸沉四钼酸铵过饱和溶液的成核研究

Studies on the nucleation of supersaturated ammonium tetramolybdate solution

测量了不同温度和不同过饱和比下硝酸酸沉四钼酸铵过饱和溶液的成核诱导时间，讨论了温度及过饱和比对成核诱导时间和成核速率的影响．结果表明，四钼酸铵过饱和溶液的成核速率随着温度的升高和过饱和比的增大而增大．在实验温度范围内均匀成核和非均匀成核之间的临界过饱和比为3．0，6．0．根据均匀成核理论，计算了不同温度下的固液界面张力、临界半径和临界成核自由能．讨论了四钼酸铵结晶的条件，认为在成核阶段应采用较高的温度和过饱和比，而在晶核长大阶段应控制较小的过饱和比，以利于获得均匀、完整的晶体．

The nucleation of ammonium tetramolybdate in supersaturated solutions by nitric acid was investigated at temperatures from 295.15 K to 311.15 K under different levels of supersaturation. Effects of temperature and supersaturation on the induction period and nucleation of ammonium tetramolybdate were studied. According to classical nucleation theory, it was possible to distinguish the homogeneous and heterogeneous nucleation from the dependence of supersaturation. The interracial tension, critical radius and critical Gihbs free energy of formation of the crystal were estimated based on the homogeneous nucleation theory. The conditions of the crystallization process were discussed.