Custom precision rotary table enables fastest 3D x-ray tomographic images
Captured at the BESSY II synchrotron, the images are of aluminum granules becoming a metallic foam.
|The experimental setup has a fast-rotation stage, an IR heating lamp (temperature up to 800 °C), a boron nitrids crucible transparent to x-rays, a 200-µm-thick scintillator, a white-beam optical system, and a Dimax CMOS camera made by PCO (Kelheim, Germany). The incident (red) and transmitted (green) X-ray beams as well as the light path from the scintillator to the camera (blue) are shown. (Image: HZB)|
As a first example, the team investigated granules of aluminum alloys that become a metallic foam when heated. To do this, they mounted an infrared lamp above the metal granulate to heat the sample to about 650 °C. A complete 3D tomographic image with spatial resolution of 2.5 µm (the pixel size) was generated every 40 ms. The nearly 400 tomographic 3D images allow detailed, time-resolved analysis of the process as it occurs.
"We wanted to develop a better understanding of how pores form in the grains -- whether they also reach the granule surfaces and to what extent this process varies in different granules," says Garcia-Moreno.
Data is useful for industry
This is a question of practical relevance to industry, as granules of metallic compounds could fill complicated shapes better while foaming than foams manufactured from a block of metal. However, the molded part will only be able to withstand stress if the grains also bond closely with one another during foaming. With the ultrafast 3D tomography developed at BESSY II, this can now be observed very precisely.
Since the EDDI beamline must be dismantled for an upgrade from BESSY II to BESSY-VSR, Garcia-Moreno is in contact with other x-ray sources and plans to establish this method at those locations.
1. Francisco García-Moreno et al., Journal of Synchrotron Radiation (2018); https://doi.org/10.1107/S1600577518008949