Metallic foams characterization with X-ray microtomography using Medipix2 detector

The objective of the paper is to present characterization tools for specific metallic foams objects. As a first step, the objective is to obtain the geometric model of the foam as an input for computed fluid dynamics code. In a second stage, the water behavior in foam samples is studied in free conditions. To address these objectives, an X-ray microtomograph system based on a microfocus X-ray generator and the Medipix2 detector has been implemented. Such X-ray generator has a focal spot size in the magnitude of 1 μm that allows a geometric magnification of the sample without blurring images. Experimental constraints are details to observe in the foams in the magnitude of a few tens of micrometers or less, which implies very low contrast. For these reasons the Medipix2 detector is well suited as a very low noise detector. Two-dimensional images are acquired for 360 projections of the foam. The three-dimensional image is obtained by using an algebraic algorithm Ordered Subset Expectation Maximization (OSEM). Two spatial scales are studied in dry and wet conditions for the foams. Images acquired on a 10 mm2 sample of foam with pixel size equal to 50 μm are used to make the analysis at a macroscopic scale of geometry and water kinetics. Images acquired on a 1 mm2 sample of foam with pixel sizes equal to 5 μm are used for a thin characterization of the geometry and to reconstruct the water distribution along the struts of the foam.