Kamm, P.H.; Yin, K.; Neu, T.R.; Schlepütz, C.M.; García-Moreno, F.; Wegst, U.G.K.: X-Ray Tomoscopy Reveals the Dynamics of Ice Templating. Advanced Functional Materials 33 (2023), p. 2304738/1-11
10.1002/adfm.202304738
Open Access Version
Abstract:
Little 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 approximate to 270 s with a spatial resolution of 6 mu m, 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 mu m s(-1) for applied cooling rates of C\dot{C} = 1-10 degrees 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.