Heterogeneous nucleation of metals and colloids on templates - a comparative study

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It is envisaged to investigate heterogeneous nucleation of colloidal systems and metallic alloys on differently structured templates. The structure of the template is changed in crystallography and intermediate distance of lattice sites.The colloidal systems used are consisting of charged particles in a salty solution. By changing the surface charge density and/or the salt concentration the interaction potential between the colloids is tuned. Fused silica templates with simple bcc and fcc structured surfaces will be applied. For this the suspensions will be prepared with a continuous preparation technique which allows for the precise control of interaction parameters. Templates will be fixed in flat flow cells and investigated with microscopy and light scattering. Measurement will be carried out at low to moderate metastability. At higher metastability ultra small angle x-ray scattering is applied. Investigations will focus on the kinetics, the morphological changes and phase behaviour in dependence on structure and orientations of the templates.Also crystallization of metals in contact with templates of different structures is studied. Metallic melts of Fe-Ni are undercooled by containerless electromagnetic levitation and crystallization is externally stimulated by touching the undercooled melt drop at preselected undercooling temperature by different structured nucleation trigger. The effect of these changes on the nucleation barrier of heterogeneous nucleation of phase formation as well as the resulting microstructure formation will be investigated.