Cryogenic EBSD reveals structure of directionally solidified ice–polymer composite

• Cryo-SEM of freeze-cast polymer solution reveals an ice-templated structure.
• Cryo-EBSD reveals the ice crystal a-axis to parallel the solidification direction.
• The honeycomb-like polymer phase favors columnar ridges only on one side.
• Combining cryo-SEM with EBSD links solidification theory with experiment.

Despite considerable research efforts on directionally solidified or freeze-cast materials in recent years, little fundamental knowledge has been gained that links model with experiment. In this contribution, the cryogenic characterization of directionally solidified polymer solutions illustrates, how powerful cryo-scanning electron microscopy combined with electron backscatter diffraction is for the structural characterization of ice–polymer composite materials. Under controlled sublimation, the freeze-cast polymer scaffold structure is revealed and imaged with secondary electrons. Electron backscatter diffraction fabric analysis shows that the ice crystals, which template the polymer scaffold and create the lamellar structure, have a-axes oriented parallel to the direction of solidification and the c-axes perpendicular to it. These results indicate the great potential of both cryo-scanning electron microscopy and cryo-electron backscatter diffraction in gaining fundamental knowledge of structure–property–processing correlations.

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