Grain size control in polycrystalline colloidal solids

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Abstract
Recent experiments on the static and dynamic properties of polycrystalline colloidal solids show a pronounced influence of morphological details. Here we investigate several possibilities to vary systematically one key morphological parameter, namely the average crystallite radius rc of polycrystalline solids. We report measurements of rc as observed by microscopy in well-characterized Yukawa model suspensions. The pair energy of interaction is systematically varied through precise experimental adjustment of the suspension parameters packing fraction Φ, number of ionic surface groups N, and concentration of screening ions c. The average size is found to systematically decrease with increasing interaction. At fixed suspension parameters we performed solidification under shear, i.e., in the presence of alternating electric fields. We report preliminary results in dependence on both the electric field strength and frequency. The grain size increases with increasing shear rates. It shows a complex behavior as a function of the frequency and the wave form of the applied field. Qualitative explanations are discussed and a first application is presented.