X-ray phase contrast imaging study of activated carbon/carbon composite

We have obtained the x-ray phase contrast images of the activated carbon/carbon (AC/C) composite used as electrodes in an electric double-layer capacitor (EDLC). To improve the spatial resolution, the beam size of x-ray transmitted from a sample were expanded by using asymmetric Bragg diffraction (asymmetric factor b) of analyzer crystal. Since the analyzer crystals were placed in (+, -) arrangements in both vertical and horizontal directions, the total magnification factor was 1/b2 for each direction. By using the 511 asymmetric Bragg diffraction of Si (100) analyzer with an asymmetric factor of 0.207, we could obtain the magnification factor of about 23.3. We applied this optical system to the AC/C composite. The phase contrast image corresponding to the carbon particles with the diameter of about 10 μm could be detected with the spatial resolution of 5 μm. Furthermore, we also obtained realtime images of bubble formation and movement during the overcharging of an EDLC with the time resolution of 30 frames number per second.