Heterogeneous nucleation during a phase transition

Most systems in everyday life are not perfectly clean, and dusts, particulates or several substrates provide a template for initial growth of a new phase. If the value of the interfacial tension between the new condensing phase and the particle (or the substrate) surface is low, then this property considerably decreases the energy requirement of nuclei formation (AGT)max so that heterogeneous nucleation occurs as an easier and preferable path for phase transformations. In addition, phase transformations take place at or very close to the equilibrium temperature. 

When 0= 0° this means that the liquid completely wets the solid, [(AGT)max]heterogeneous equals zero, and spontaneous heterogeneous nucleation occurs with no super-saturation at the equilibrium temperature. When 6 = 90° then [(AGT)max]heterogeneous is half the homogeneous value, and when 6= 180° both homo- and heterogeneous nucleation energy barriers are equal. 

(1968) The Physics and Chemistry of Surfaces. Dover, New York. 

Hirschfelder, J.O., Curtiss, C.F. and Bird, R.B. (1954) Molecular Theory of Gases and Liquids. Wiley, New York. 

Prausnitz, J.M., Lichtenthaler, R.N. and Azevedo E.G. (1999) Molecular Thermodynamics of Fluid-Phase Equilibria (3rd edn). Prentice Hall, Englewood Cliffs. 

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