X‐Ray Tomoscopy Reveals the Dynamics of Ice Templating

Abstract

AbstractLittle experimentally explored and understood are the complex dynamics of microstructure formation by ice‐templating when aqueous solutions or slurries are directionally solidified (freeze cast) into cellular solids. With synchrotron‐based, time‐resolved X‐ray tomoscopy it is possible to study in situ under well‐defined conditions the anisotropic, partially faceted growth of ice crystals in aqueous systems. Obtaining one full tomogram per second for ≈270 s with a spatial resolution of 6 µm, it is possible to capture with minimal X‐ray absorption, the freezing front in a 3% weight/volume (w/v) sucrose‐in‐water solution, which typically progresses at 5–30 µm s−1 for applied cooling rates of = 1–10 °C min−1. These time and length scales render X‐ray tomoscopy ideally suited to quantify in 3D ice crystal growth and templating phenomena that determine the performance‐defining hierarchical architecture of freeze‐cast materials: a complex pore morphology and “ridges”, “jellyfish cap”, and “tentacle”‐like secondary features, which decorate the cell walls.