Compacted MX-80 bentonite is a potential backfill material in radioactive-waste repositories. Pore space in MX-80 has been the subject of considerable debate. 3D reconstructions of the pore space based on tomographic methods could provide new insights into the nature of the pore space of compacted bentonites. To date, few such reconstructions have been done because of problems with the preparation of bentonite samples for electron microscopy. The nanoscale intergranular pore space was investigated here by cryo-Focused Ion Beam nanotomography (FIB-nt) applied to previously high-pressure frozen MX-80 bentonite samples. This approach allowed a tomographic investigation of the in situ microstructure related to different dry densities (1.24, 1.46, and 1.67 g/cm3). The FIB-nt technique is able to resolve intergranular pores with radii >10 nm. With increasing dry density (1.24–1.67 g/cm3) the intergranular porosity (>10 nm) decreased from ~5 vol.% to 0.1 vol.%. At dry densities of 1.24 and 1.46 g/cm3, intergranular pores were filled with clay aggregates, which formed a mesh-like structure, similar to the honeycomb structure observed in diagenetic smectite. Unlike ‘typical’ clay gels, the cores of the honeycomb structure were not filled with pure water, but instead were filled with a less dense material which presumably consists of very fine clay similar to a colloid. In the low-density sample this honeycomb-structured material partly filled the intergranular pore space but some open pores were also present. In the 1.46 g/cm3 sample, the material filled the intergranular pores almost completely. At the highest densities investigated (1.67 g/cm3), the honeycomb-structured material was not present, probably because of the lack of intergranular pores which suppressed the formation of the honeycomb framework or skeleton consisting of clay aggregates.

A multiscale approach combining phase-contrast X-ray micro- and nanotomography is applied for imaging a Cretaceous fossil inflorescence in the resolution range from 0.75 μm to 50 nm. The wide range of scale views provides three-dimensional reconstructions from the external gross morphology of the inflorescence fragment to the finest exine sculptures of in situ pollen. This approach enables most of the characteristics usually observed under light microscopy, or with low magnification under scanning and transmission electron microscopy, to be obtained nondestructively. In contrast to previous tomography studies of fossil and extant flowers that used resolutions down to the micron range, we used voxels with a 50 nm side in local tomography scans. This high level of resolution enables systematic affinities of fossil flowers to be established without breaking or slicing specimens.

A new technique that allows direct three-dimensional (3D) investigations of mesopores in carbon materials and quantitative characterization of their physical properties is reported. Focused ion beam nanotomography (FIB-nt) is performed by a serial sectioning procedure with a dual beam FIB-scanning electron microscopy instrument. Mesoporous carbons (MPCs) with tailored mesopore size are produced by carbonization of resorcinol-formaldehyde gels in the presence of a cationic surfactant as a pore stabilizer. A visual 3D morphology representation of disordered porous carbon is shown. Pore size distribution of MPCs is determined by the FIB-nt technique and nitrogen sorption isotherm methods to compare both results. The obtained MPCs exhibit pore sizes of 4.7, 7.2, and 18.3 nm, and a specific surface area of ca. 560 m2/g.

We have demonstrated that structures down to 150 nm can be visualized in X-ray projection images using nanofocus X-ray sources. Due to their unlimited depth of focus, they do not possess a limit on the specimen size. This is essential for three-dimensional tomographic imaging of samples with a diameter larger than a few microns. Further simulation studies have shown that optimization of the detector response curve and switching from a reflective X-ray target to a transmission target should allow us to reach sub-100-nm resolutions.

Due to the extraordinary beam characteristics of the new PETRA III synchrotron, i.e., the high brilliance, the extremely low emittance of 1 nm rad, and the high fraction of coherent photons even in the hard X-ray range, the imaging beamline (IBL) at PETRA III will provide state of the art imaging and tomography capabilities with resolution well into the nanometer range. Novel applications of tomographic techniques allow for high speed in situ measurements as well as highest spatial and density resolutions. Additionally, the highly coherent beam enables the application of phase contrast methods in an exceptional way. Since the focus is on the energy range between 5 and 50 keV, the IBL will among others be ideally suited for microtomography and nanotomography on small engineering materials science samples as well as for studying soft matter, bones, medical implants, and biomatter.

Focused ion beam nanotomography (FIB-nt) is a novel method for high resolution three-dimensional (3D) imaging. In this investigation we assess the methodological parameters related to image acquisition and data processing that are critical for obtaining reproducible microstructural results from granular materials and from complex suspensions. For this purpose three case studies are performed: (1) The precision of FIB-nt is evaluated by analyzing a reference sample with nanospheres. Due to the implementation of an automated correction procedure, drift phenomena can be removed largely from the FIB data. However, at high magnifications remaining drift components can induce problems for 3D-shape reconstructions. (2) Correct object recognition from densely packed microstructures requires specific algorithms for splitting of agglomerated particles. To establish quantitative criteria for the correct degree of splitting, a parametric study with dry portland cement is performed. It is shown that splitting with a k-value of 0.6 leads to accurate results. (3) Finally, the reproducibility of the entire cryo-FIB analysis is investigated for high pressure frozen cement suspensions. Reproducible analyses can be obtained if the magnification is adapted to the particle size. At low magnifications the small particles and their surface area are underestimated. At high magnifications representativity is questioned because local inhomogeneities can become dominant.