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%H ₂O, SCN-50 wt%H ₂O, and SCN-80 wt%H ₂O, and the migration characteristics of minor phase droplets (MPDs) was investigated when unidirection temperature field is applied. It is find that spinodal decomposition takes place in SCN-50 wt%H ₂O system and nucleation processes occur in SCN-30 wt%H ₂O and SCN-50 wt%H ₂O 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%H ₂O 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.