8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P5.58Wed 711:10-14:00Homogeneous and heterogeneous crystal nucleation incolloidal hard spheresMarkus Franke 1 and Hans Joachim Schöpe 11 University Mainz, Staudinger Weg 7, 55128, Mainz, GermanyWe investigated crystal nucleation and the microstructure evolution in suspensions of gravitymatched colloidal hard spheres (HS) in the presence of container walls using a combination oftime resolved light scattering and optical microscopy. We determined nucleation rate densities,characteristic times, crystal growth velocities and nucleation barrier heights for both homogeneousand heterogeneous nucleation as function of metastability Dµ. Extracting the surface tension ofthe critical nucleus, we surprisingly observe that the surface tension is a function of metastability.Within the coexistence region the surface tension increases approximately linear with Dµ andsaturates crossing the melting volume fraction. Comparing homogeneous nucleation and heterogeneousnucleation at the container walls we observe a decreasing barrier height with increasingparticle concentration for the bulk while the Barrier for heterogeneous nucleation nearly disappearsat all particle concentration due to complete wetting of the wall. This favours the formation of wallcrystals due to earlier nucleation and the microstructure evolution is given by an interplay of wallcrystal growth and homogeneous nucleation and growth of bulk crystals.58