The complex flow of liquid metal in evolving metallic foams is still poorly understood due to difficulties in studying hot and opaque systems. We apply X-ray tomoscopy –the continuous acquisition of tomographic (3D) images– to clarify key dynamic phenomena in liquid aluminium foam such as nucleation and growth, bubble rearrangements, liquid retraction, coalescence and the rupture of films. Each phenomenon takes place on a typical timescale which we cover by obtaining 208 full tomograms per second over a period of up to one minute. An additional data processing algorithm provides information on the 1 ms scale. Here we show that bubble coalescence is not only caused by gravity-induced drainage, as experiments under weightlessness show, and by stresses caused by foam growth, but also by local pressure peaks caused by the blowing agent. Moreover, details of foam expansion and phenomena such as rupture cascades and film thinning before rupture are quantified. These findings allow us to propose a way to obtain foams with smaller and more equally sized bubbles.

The structure and constitution of opaque materials can be studied with X‐ray imaging methods such as 3D tomography. To observe the dynamic evolution of their structure and the distribution of constituents, for example, during processing, heating, mechanical loading, etc., 3D imaging has to be fast enough. In this paper, the recent developments of time‐resolved X‐ray tomography that have led to what one now calls “tomoscopy” are briefly reviewed A novel setup is presented and applied that pushes temporal resolution down to just 1 ms, that is, 1000 tomograms per second (tps) are acquired, while maintaining spatial resolutions of micrometers and running experiments for minutes without interruption. Applications recorded at different acquisition rates ranging from 50 to 1000 tps are presented. The authors observe and quantify the immiscible hypermonotectic reaction of AlBi10 (in wt%) alloy and dendrite evolution in AlGe10 (in wt%) casting alloy during fast solidification. The combustion process and the evolution of the constituents are analyzed in a burning sparkler. Finally, the authors follow the structure and density of two metal foams over a long period of time and derive details of bubble formation and bubble ageing including quantitative analyses of bubble parameters with millisecond temporal resolution.

When solutions and slurries are directionally solidified, complex dynamics of solvent crystal growth and solvent templating determine the final hierarchical architecture of the freeze-cast material. With continuous X-ray tomoscopy, it is now possible to study in situ intricate and otherwise elusive ice crystal growth and solvent-templating phenomena. Quantifying these phenomena both time-resolved and in three dimensions provides novel insights into the formation of performance-defining features of freeze-cast cellular solids at several length scales: the material’s pore morphology (first hierarchical level), the molecular, fibrillar and particle self-assembly of components in the cell walls (second level) and the cell wall surface structures (third level). The freeze casting process is attractive because the features of the final hierarchical material architecture — which determine the material’s structural, mechanical and physical properties — can be custom designed for a given application. Overall porosity, pore size, geometry, orientation, particle packing in cell walls and cell wall surface features can be tailored for applications in, for example, biomedicine, environmental engineering, catalysis, power conversion, and energy generation and storage.