The solidification of molten metals requires the presence of nuclei. Impurities, foreign particles or the vessel wall can be very helpful in this process, as they provide part of the surface energy for nucleation. This is called heterogeneous nucleation. This video takes a closer look at this type of nucleation.
00:00 Homogeneous nucleation
01:17 Wetting
01:59 Young relation
03:07 Change in the Gibbs energy of a nucleus
04:00 Volume energy
05:03 Surface energy between nucleus and melt
05:58 Surface energy between melt and wall
07:09 Surface energy between nucleus and wall
08:51 Total change in Gibbs energy of the nucleus
10:11 Critical nucleus radius
11:29 Free energy barrier (activation energy)
12:46 Seeding
