调幅分解及形核对相分离作用机理研究

任群; 王楠; 张莉; 王建元; 郑亚萍; 姚文静

调幅分解及形核对相分离作用机理研究

西北工业大学理学院空间应用物理与化学教育部重点实验室,西安,710072

The effects of spinodal decomposition and nucleation on phase separation

摘要: 以SCN-30wt％H2O，SCN-50wt％H2O和SCN-80wt％H2O三组透明体系，在恒温场下实现了形核和调幅分解两种过程；在此基础上，施加温度梯度，研究了第二相液滴的迁移运动规律．结果表明，相分离在临界成分体系以调幅分解方式进行，在另外两种体系中以形核长大方式进行；调幅分解与形核过程相比，反应进行得更快，液滴长大到同一尺寸所需时间仅为形核所需时间的1／3—1／2．且临界成分体系有更大的不混溶间隙，所以第二相液滴具有更多迁移时间，揭示了偏晶体系相分离过程中在临界成分处易获得壳．核组织的内在机理．在单向温度场中，测量了不同半径的液滴迁移速率，并且与理论Marangoni迁移速率值作比较，发现液滴迁移速率和Marangoni理论迁移速率符合较好．说明了在较好地抑制自然对流条件下Marangoni迁移对于相分离过程起主要作用．

关键词:

Abstract: Spinodal decomposition and nucleation process are realized by using three transparent solutions: SCN-30 wt%H2O, SCN- 50 wt%H2O, and SCN-80 wt%H2O, and the migration characteristics of minor phase droplets (MPDs) was investigated when uni- direction temperature field is applied. It is find that spinodal decomposition takes place in SCN-50 wt%H2O system and nucleation processes occur in SCN-30 wt%H2O and SCN-50 wt%H2O systems. The period during which the minor droplets of the same size in spinodal decomposition are formed is 1/3--1/2 of that in nucleation process. Moreover, the temperature interval in the system with critical composition is larger than those in other systems, therefore, the minor phase droplet formed in spinodal decomposition is longer than that in nucleation process. Under uni-direction temperature field conditions, the migration velocity of MPDs in SCN-80 wt%H2O system is measured experimentally. It is revealed that the experimental results agree well with the calculated Marangoni velocity, indicating that the Marangoni migration plays a key role in the motion of MPDs.

调幅分解及形核对相分离作用机理研究

西北工业大学理学院空间应用物理与化学教育部重点实验室,西安,710072

关键词:

The effects of spinodal decomposition and nucleation on phase separation

西北工业大学理学院空间应用物理与化学教育部重点实验室,西安,710072

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