Using X-ray tomoscopy to explore the dynamics of foaming metal

Abstract

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.

High-speed x-ray tomography of silo discharge

“…Synchrotron x-ray tomography may provide sufficiently high beam intensity, but it has two drawbacks: conventional techniques are limited to approximately one tomogram per second or less, which is much too slow for the present task. Even with recent progress in sampling speeds for synchrotron microtomograms [52][53][54], the recording times of the order of hundred milliseconds per tomogram are insufficient for our purpose. More problematic, however, is the necessity of fast rotation of the sample during the measurement, which will disturb the discharge dynamics when the container size is of the order of centimeters.…”

Pushing the temporal resolution in absorption and Zernike phase contrast nanotomography: enabling fast in situ experiments

“…Fast nanotomography using an X-ray microscope has the potential to bridge the gap between ultra-fast microtomography with time resolution down to a few milliseconds (García-Moreno et al, 2019) and spatial resolution of down to 1 mm, and high-resolution imaging techniques such as focused ion-beam tomography and ptychography with spatial resolution down to a few tenths of a nanometre but several hours of acquisition time.…”

Characterization of metals in four dimensions

“…One can subsequently concatenate these 3D tomograms to yield a 4D reconstruction, see Figure 2(c). Another related approach that has recently caught traction in the community is incremental reconstruction [59]. Here, the tomograms have a floating start angle, i.e.…”