Development and Implementation of a Nanotomography Setup at the PETRA III Beamline P05

X-ray nanotomography is used to analyze materials on the sub-micrometer scale. Many soft biological materials, i.e. most organic tissues, can be imaged with soft X-rays. For materials with a higher electron density, such as bone or teeth, metals, and ceramics, X-ray energies of more than 10 keV need to be used. All these setups require X-ray optics for either direct imaging of the object in question or for preparing a magnified projection. The P05 Imaging Beamline for X-ray micro- and nanotomography is situated at the newly refurbished PETRA III 3rd generation storage ring at DESY. A dedicated experiment for X-ray nanotomography at higher energies was built in one of the two experimental hutches. An X-ray optics concept tailored for this experiment was specified and an accompanying mechanics concept was devised. Based on these concepts, the experiment was designed and installed. In addition to testing the nanotomography experimental components, the beamline front end was commissioned and the influence of these components on the nanotomography experiment was investigated. Higher harmonics from the undulator and monochromator as well as beam position drifts caused by mechanical drifting the monochromator were investigated to analyze their influence on the nanotomography. The X-ray optics were tested in detail and an operational setup was achieved for both the X-ray microscopy and the cone-beam setup. The achieved resolution of the hard X-ray microscope is better than 100 nm line and space. Nanotomographies were performed on a nanoporous gold sample and a photonic glass sample. Image correlation and correction allowed to perform a reconstruction of the photonic glass sample using a filtered backprojection algorithm. The packing fraction of the photonic glass could be successfully extracted from the 3D-dataset

Opportunities and challenges for digital morphology

Advances in digital data acquisition, analysis, and storage have revolutionized the work in many biological disciplines such as genomics, molecular phylogenetics, and structural biology, but have not yet found satisfactory acceptance in morphology. Improvements in non-invasive imaging and three-dimensional visualization techniques, however, permit high-throughput analyses also of whole biological specimens, including museum material. These developments pave the way towards a digital era in morphology. Using sea urchins (Echinodermata: Echinoidea), we provide examples illustrating the power of these techniques. However, remote visualization, the creation of a specialized database, and the implementation of standardized, world-wide accepted data deposition practices prior to publication are essential to cope with the foreseeable exponential increase in digital morphological data

Aging of a Pt/Al₂O₃ exhaust gas catalyst monitored by quasi in situ X-ray micro computed tomography

Catalyst aging effects were analyzed using X-ray absorption micro-computed tomography in combination with conventional characterization methods on various length scales ranging from nm to [small mu ]m to gain insight into deactivation mechanisms. For this purpose, a 4 wt% Pt/Al2O3 model exhaust gas catalyst was coated on a cordierite honeycomb and subjected to sequential thermal aging in static air at 950 [degree]C for 4, 8, 12 and 24 hours. The aging was followed on the one hand by traditional methods, i.e. CO-oxidation activity, scanning and transmission electron microscopy (SEM, TEM), and X-ray diffraction (XRD). On the other hand, all intermediate aging steps were captured by X-ray absorption micro-computed tomography ([small mu ]-CT) with 1.27 [small mu ]m voxel size using a quasi in situ approach as complementary tool. The [small mu ]-CT data allowed comparing exactly the same position after each treatment using a special alignment procedure during data analysis which took into account that the sample was remounted on the sample holder. A growth of the initially nanometer-sized Pt particles into larger crystals as well as its agglomeration was found, preferentially in voids between support grains. Sintering occurred especially around the larger particles, which is in line with the Ostwald ripening mechanism reported for this system on a nanometer scale. The distribution of chemical elements in an embedded and mechanically cross-sectioned honeycomb was additionally mapped by an electron probe micro analyzer (EPMA), which in agreement to the [small mu ]-CT results shows no diffusion of Pt into the cordierite. Together with studies on the nanometer scale, these results allow a more thorough multi-scale modeling of exhaust gas catalysts, especially also during aging

Determination of the packing fraction in photonic glass using synchrotron radiation nanotomography

Photonic glass is a material class that can be used as photonic broadband reflectors, for example in the infrared regime as thermal barrier coating films. Photonic properties such as the reflectivity depend on the ordering and material packing fraction over the complete film thickness of up to 100 μm. Nanotomography allows acquiring these key parameters throughout the sample volume at the required resolution in a non-destructive way. By performing a nanotomography measurement at the PETRA III beamline P05 on a photonic glass film, the packing fraction throughout the complete sample thickness was analyzed. The results showed a packing fraction significantly smaller than the expected random close packing giving important information for improving the fabrication and processing methods of photonic glass material in the future

Development and Implementation of a Nanotomography Setup at the PETRA III Beamline P05

X-ray nanotomography is used to analyze materials on the sub-micrometer scale. Many soft biological materials, i.e. most organic tissues, can be imaged with soft X-rays. For materials with a higher electron density, such as bone or teeth, metals, and ceramics, X-ray energies of more than 10 keV need to be used. All these setups require X-ray optics for either direct imaging of the object in question or for preparing a magnified projection. The P05 Imaging Beamline for X-ray micro- and nanotomography is situated at the newly refurbished PETRA III 3rd generation storage ring at DESY. A dedicated experiment for X-ray nanotomography at higher energies was built in one of the two experimental hutches. An X-ray optics concept tailored for this experiment was specified and an accompanying mechanics concept was devised. Based on these concepts, the experiment was designed and installed. In addition to testing the nanotomography experimental components, the beamline front end was commissioned and the influence of these components on the nanotomography experiment was investigated. Higher harmonics from the undulator and monochromator as well as beam position drifts caused by mechanical drifting the monochromator were investigated to analyze their influence on the nanotomography. The X-ray optics were tested in detail and an operational setup was achieved for both the X-ray microscopy and the cone-beam setup. The achieved resolution of the hard X-ray microscope is better than 100 nm line and space. Nanotomographies were performed on a nanoporous gold sample and a photonic glass sample. Image correlation and correction allowed to perform a reconstruction of the photonic glass sample using a filtered backprojection algorithm. The packing fraction of the photonic glass could be successfully extracted from the 3D-dataset

Modified x-ray polymer refractive cross lens with adiabatic contraction and its realization

A refractive x-ray lens with reduced focal length, due to continuous reduction in the designed aperture over the length of the lens, is presented. The lens elements have refractive parabolic sidewalls like geometrical prisms, with a varying cross section over the length of the lens, in accordance with the x-ray propagation law. The focusing effect occurs directly in the lens due to the fact that the initial x-ray beam is directed toward the focal point, and due to the phase retardation caused by the refractive properties of the sidewall surfaces. An array of such adiabatic lens elements with different optical parameters, arranged in a number of rows, represented by polymer microstructures, has been produced using x-ray lithography. Preliminary testing of the lenses has resulted in a focal spot of 67 nm at a photon energy of 18.6 keV

Evolution of a Novel Muscle Design in Sea Urchins (Echinodermata: Echinoidea)

The sea urchin (Echinodermata: Echinoidea) masticatory apparatus, or Aristotle's lantern, is a complex structure composed of numerous hard and soft components. The lantern is powered by various paired and unpaired muscle groups. We describe how one set of these muscles, the lantern protractor muscles, has evolved a specialized morphology. This morphology is characterized by the formation of adaxially-facing lobes perpendicular to the main orientation of the muscle, giving the protractor a frilled aspect in horizontal section. Histological and ultrastructural analyses show that the microstructure of frilled muscles is largely identical to that of conventional, flat muscles. Measurements of muscle dimensions in equally-sized specimens demonstrate that the frilled muscle design, in comparison to that of the flat muscle type, considerably increases muscle volume as well as the muscle's surface directed towards the interradial cavity, a compartment of the peripharyngeal coelom. Scanning electron microscopical observations reveal that the insertions of frilled and flat protractor muscles result in characteristic muscle scars on the stereom, reflecting the shapes of individual muscles. Our comparative study of 49 derived “regular” echinoid species using magnetic resonance imaging (MRI) shows that frilled protractor muscles are found only in taxa belonging to the families Toxopneustidae, Echinometridae, and Strongylocentrotidae. The onset of lobe formation during ontogenesis varies between species of these three families. Because frilled protractor muscles are best observed in situ, the application of a non-invasive imaging technique was crucial for the unequivocal identification of this morphological character on a large scale. Although it is currently possible only to speculate on the functional advantages which the frilled muscle morphology might confer, our study forms the anatomical and evolutionary framework for future analyses of this unusual muscle design among sea urchins

Aging of a Pt/Al2O3\mathrm{Pt/Al_2O_3} Exhaust Gas Catalyst Monitored by Quasi in Situ X-ray Micro Computed Tomography

Catalyst aging effects were analyzed using X-ray absorption micro-computed tomography in combination with conventional characterization methods on various length scales ranging from nm to μm to gain insight into deactivation mechanisms. For this purpose, a 4 wt% Pt/Al2O3 model exhaust gas catalyst was coated on a cordierite honeycomb and subjected to sequential thermal aging in static air at 950 °C for 4, 8, 12 and 24 hours. The aging was followed on the one hand by traditional methods, i.e. CO-oxidation activity, scanning and transmission electron microscopy (SEM, TEM), and X-ray diffraction (XRD). On the other hand, all intermediate aging steps were captured by X-ray absorption micro-computed tomography (μ-CT) with 1.27 μm voxel size using a quasi in situ approach as complementary tool. The μ-CT data allowed comparing exactly the same position after each treatment using a special alignment procedure during data analysis which took into account that the sample was remounted on the sample holder. A growth of the initially nanometer-sized Pt particles into larger crystals as well as its agglomeration was found, preferentially in voids between support grains. Sintering occurred especially around the larger particles, which is in line with the Ostwald ripening mechanism reported for this system on a nanometer scale. The distribution of chemical elements in an embedded and mechanically cross-sectioned honeycomb was additionally mapped by an electron probe micro analyzer (EPMA), which in agreement to the μ-CT results shows no diffusion of Pt into the cordierite. Together with studies on the nanometer scale, these results allow a more thorough multi-scale modeling of exhaust gas catalysts, especially also during aging