Nowadays, X-ray tube-based high-resolution CT systems are widely used in scientific research and industrial applications. But the potential, convenience and economy of these lab systems is often underestimated. The present paper shows the comparison of sophisticated conventional µCT with synchrotron radiation-based µCT (SRµCT). The different aspects and characteristics of both approaches like spatial and density resolution, penetration depth, scanning time or sample size is described in detail. The tube-based µCT measurements were performed with a granite-based phoenix nanotom CT system (GE Sensing & Inspection Technologies, Wunstorf, Germany) equipped with a 180 kV -15 W high-power nanofocus tube with tungsten or molybdenum targets. The tube offers a wide range of applications from scanning low absorbing samples in nanofocus mode with voxel sizes below 500 nm and strong absorbing objects in the high power mode with focal spot and voxel sizes of a few microns. The SRµCT measurements were carried out with the absorption contrast set-up at the beamlines W 2 and BW 2 at HASYLAB/DESY (Hamburg, Germany), operated by the GKSS Research Center. The range of samples examined covers materials of very different absorption levels and related photon energies for the CT scans. Both quantitative and qualitative comparisons of CT scans using composites from the field of materials science are shown.

Impact of processing-induced structural defects on the electrical properties of a graphene monolayer has been investigated using scanning microwave microscopy (SMM). Graphene sheets grown on copper foil by chemical vapor deposition were transferred to a silicon wafer covered with a 300 nm thick thermal SiO2 layer and then patterned into a grating structure using the standard lithography technique. Raman spectroscopy and SMM were employed to monitor the defect generation and the induced surface impedance change on graphene. Correlation of the SMM image contrast shows that the etching-induced defects cause a decrease of the electrical conductivity and permittivity of the graphene monolayer. In addition, the SMM image contrast shows a frequency dependency: at higher frequencies, the permittivity of the graphene monolayer plays an important role, resulting in the SMM phase imaging contrast reversed from the low frequency measurements. Numerical simulations were performed, which are in very good agreement with the experimental results.

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