In Fig. 1 the results of performing the standard X-ray absorption microtomography of the paint multilayer samples are shown. A series of eight sharply defined paint layers is clearly visible. The thickness of each layer derived from this tomogram is listed in Table 3 as the ‘absorption value’. Apart from showing, e.g. that layers 3 and 5 are the least X-ray absorbing while layer 7 absorbs the most X-rays, no information other than their shape/thickness can be derived from this tomogram.
In Fig. 3 the resulting XRD sinograms of titanium dioxide (rutile) and barium sulfate (barite) are shown together with the corresponding tomograms obtained via the MLEM reconstruction method. The tomograms show the rutile and barite distributions in a virtual, horizontal cross section of the sample. As shown in Fig. 2, this cross section is oriented perpendicular to the individual paint layers. It is clear that rutile is present in three of the layers while barite appears in two of them.