Nucleation at the contact line observed on nanotextured surfaces

It has been conjectured that roughness plays a role in surface nucleation, the tendency for freezing to begin preferentially at the liquid-gas interface. Using high speed imaging, we sought evidence for freezing at the contact line on catalyst substrates with imposed characteristic length scales (texture). Length scales consistent with the critical nucleus size and with δ∼τ/σ, where τ is a relevant line tension and σ is the surface tension, range from nanometers to micrometers. It is found that nanoscale texture causes a shift in the nucleation of ice in supercooled water to the three-phase contact line, while microscale texture does not.

On the Probability of Nucleation at the Surface of Freezing Drops

Recent publications have proposed that nucleation in the freezing of supercooled drops occurs at the drop surface, an idea supported by statistical thermodynamic arguments by Cahn [J. Chem. Phys. 1977, 66, 3667] coupled with thermodynamic arguments by Tabazadeh et al. [Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 15873]. Whether this phenomenon is general is examined by molecular dynamics simulations of the freezing of deeply supercooled liquid clusters of SeF6. It is found for this model system that while nucleation occurs not infrequently at the surface, it more often takes place in the interior. The probability for surface nucleation increases with the depth of supercooling. How this relates to theories of Cahn and Tabazadeh et al. is discussed briefly.