The effects of spinodal decomposition and nucleation on phase separation

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.