Jeff Gelb

Using Synchrotron X-Ray Nano-CT to Characterize SOFC Electrode Microstructures in Three-Dimensions at Operating Temperature

In recent years, developments in tomography tools have provided unprecedented insight into the microstructure of electrodes for solid oxide fuel cells, enabling researchers to establish direct links between electrode microstructure and electrochemical performance. Here we present results of high resolution, synchrotron X-ray nano computed tomography experiments, which have enabled microstructural characterisation of a mixed ionic electronic conducting lanthanum strontium cobalt iron oxide (LSCF) cathode with sub-50nm resolution at operating temperature. Using the uniquely non-destructive nano-CT platform, it is possible to characterise microstructural evolution processes associated with heating and operation in-situ

Nanoscale X-Ray Microscopic Imaging of Mammalian Mineralized Tissue

A novel hard transmission X-ray microscope (TXM) at the Stanford Synchrotron Radiation Lightsource operating from 5 to 15 keV X-ray energy with 14 to 30 microm2 field of view has been used for high-resolution (30-40 nm) imaging and density quantification of mineralized tissue. TXM is uniquely suited for imaging of internal cellular structures and networks in mammalian mineralized tissues using relatively thick (50 microm), untreated samples that preserve tissue micro- and nanostructure. To test this method we performed Zernike phase contrast and absorption contrast imaging of mouse cancellous bone prepared under different conditions of in vivo loading, fixation, and contrast agents. In addition, the three-dimensional structure was examined using tomography. Individual osteocytic lacunae were observed embedded within trabeculae in cancellous bone. Extensive canalicular networks were evident and included processes with diameters near the 30-40 nm instrument resolution that have not been reported previously. Trabecular density was quantified relative to rod-like crystalline apatite, and rod-like trabecular struts were found to have 51-54% of pure crystal density and plate-like areas had 44-53% of crystal density. The nanometer resolution of TXM enables future studies for visualization and quantification of ultrastructural changes in bone tissue resulting from osteoporosis, dental disease, and other pathologies.

Multi-scale method of Nano(Micro)-CT study on microscopic pore structure of tight sandstone of Yanchang Formation, Ordos Basin

Abstract Multi-scale (nano-to-micro) three-dimensional CT imaging was used to characterize the distribution and texture of micro-scale pore throats in tight sandstone reservoirs of the Triassic Yanchang Formation, Ordos Basin. First, the low-resolution Micro-CT was used to reflect the micro-pore texture of the core column with a diameter of 2.54 cm. Then, some samples with a diameter of 65 μm was derived from different areas according the different characteristics of micro-pore texture of the core scanned by low-resolution Micro-CT and scanned by high-resolution Nano-CT. Thus, a three-dimensional texture model of nano-scale micro-pores was reestablished and the permebility and porosity data of the sample could be obtained. On a micrometer scale, the size of the micro-pores varies, and their diameters range from 5.4 to 26.0 μm. The micro-pores are isolated, locally in the shape of a band. On a nanometer scale, the quantity of nanoscale micropores increases, the diameter of which ranges from 0.4 to 1.5 μm. The pore throats are arranged in the shape of tube and ball inside or on the surface of mineral particles(crystals). The ball-shaped micropores in nanoscale, often isolated in the three-dimensional space, show the poor connectivity and consequently act as the reservoir space. By contrast, the tube-shaped micropores in nanoscale show certain connectivity with micro-scale tube-shaped micropores and adjacent isolated ball-shaped micropores in nanoscale. Therefore, these tube-shaped micropores in nanoscale serve as throats and pores. Based on the calcution, the permeability of the samples is 0.843×10 −3 μm 2 and porosity is 10%.

A 30 nm-resolution hard X-ray microscope with X-ray fluorescence mapping capability at BSRF

A full-field transmission X-ray microscope (TXM) operating continuously from 5 keV to 12 keV with fluorescence mapping capability has been designed and constructed at the Beijing Synchrotron Radiation Facility, a first-generation synchrotron radiation facility operating at 2.5 GeV. Spatial resolution better than 30 nm has been demonstrated using a Siemens star pattern in both absorption mode and Zernike phase-contrast mode. A scanning-probe mode fluorescence mapping capability integrated with the TXM has been shown to provide 50 p.p.m. sensitivity for trace elements with a spatial resolution (limited by probing beam spot size) of 20 µm. The optics design, testing of spatial resolution and fluorescence sensitivity are presented here, including performance measurement results.

A high resolution, hard x-ray bio-imaging facility at SSRL

The old saying that seeing is believing has particular resonance for studying biological cells and tissues. Since 1677, when Anton van Leeuwenhoek used a simple light microscope to discover single cell organisms, scientists have relied on structural information obtained from microscopes with improving capabilities to advance the understanding of how biological systems work. Optical and electron microscopes are essential for many of these important discoveries and have been widely employed in biomedical research laboratories. However, various limitations exist in these microscopy techniques. We describe below how the new X-ray imaging facility at the Stanford Synchrotron Radiation Laboratory (SSRL), based on an Xradia nano-XCT full-field transmission X-ray microscope (TXM), can provide complementary and unique capabilities to the current microscopy methods for studying complex biological systems.

High resolution hard x-ray microscope on a second generation synchrotron source

A full-field, transmission x-ray microscope (TXM) operating in the energy range of 7-11 keV has been installed at the U7A beamline at the National Synchrotron Radiation Laboratory, a second generation synchrotron source operating at 0.8 GeV. Although the photon flux at sample position in the operating energy range is significantly low due to its relatively large emittance, the TXM can get high quality x-ray images with a spatial resolution down to 50 nm with acceptable exposure time. This TXM operates in either absorption or Zernike phase contrast mode with similar resolution. This TXM is a powerful analytical tool for a wide range of scientific areas, especially studies on nanoscale phenomena and structural imaging in biology, materials science, and environmental science. We present here the property of the x-ray source, beamline design, and the operation and key optical components of the x-ray TXM. Plans to improve the throughput of the TXM will be discussed.

Laboratory-based cryogenic soft x-ray tomography with correlative cryo-light and electron microscopy.

Here we present a novel laboratory-based cryogenic soft X-ray microscope for whole cell tomography of frozen hydrated samples. We demonstrate the capabilities of this compact cryogenic microscope by visualizing internal subcellular structures of Saccharomyces cerevisiae cells. The microscope is shown to achieve better than 50 nm half-pitch spatial resolution with a Siemens star test sample. For whole biological cells, the microscope can image specimens up to 5 μm thick. Structures as small as 90 nm can be detected in tomographic reconstructions following a low cumulative radiation dose of only 7.2 MGy. Furthermore, the design of the specimen chamber utilizes a standard sample support that permits multimodal correlative imaging of the exact same unstained yeast cell via cryo-fluorescence light microscopy, cryo-soft X-ray microscopy, and cryo-transmission electron microscopy. This completely laboratory-based cryogenic soft X-ray microscope will enable greater access to three-dimensional ultrastructure determination of biological whole cells without chemical fixation or physical sectioning.

Full-field transmission x-ray microscopy for bio-imaging.

A full-field hard-x-ray microscope at SSRL has successfully imaged samples of biological and environmental origin at 40 nm resolution. Phase contrast imaging of trabeculae from a female mouse tibia, loaded in vivo to study the effects of weight-bearing on bone structure, revealed a complex network of osteocytes and canaliculi. Imaging of cordgrass roots exposed to mercury revealed nanoparticles with strong absorption contrast. 3D tomography of yeast cells grown in selenium rich media showed internal structure.

The study of the reconstructed three-dimensional structure of a solid-oxide fuel-cell cathode by X-ray nanotomography.

The microstructure and morphology of solid-oxide fuel-cell electrodes are very complex but important because they strongly affect the electrical performance of the cell. In this work the high-resolution X-ray nanotomography technique is applied to reconstruct the three-dimensional microstructure of a (La(0.8)Sr(0.2))(0.95)MnO(3) yttria-stabilized zirconia composite cathode. Some key microstructural parameters, such as the porosity, representative elementary volume, connected pore volume and pore phase tortuosity, were obtained based on the three-dimensional reconstruction volume data with a spatial resolution of sub-60 nm. These parameters bear intimate correlation with the efficiency of the electrochemical conversion process, and provide valuable information for optimizing the manufacturing processes and improving the devices reliability.

Nanoscale Visualization of Gas Shale Pore and Textural Features

Characterization of gas shale pore topology and composition supports efforts to produce methane as well as assess the feasibility of using depleted organic-rich shale reservoirs for carbon dioxide sequestration. Imaging performed with Full-field Transmission X-Ray Microscopy technology to characterize gas shale structure and heterogeneity was conducted on a set of Barnett and Haynesville gas shale samples to help determine how the physical and chemical processes associated with CO2 in organic-rich shales affect injectivity and storage capacity (over long periods of time), and the ability of the shale to sequester CO2 (as both a free and adsorbed phase). The images show the presence of density-differentiated areas that might be an indication of predominantly organic and inorganic matter matrices, along with lowest-density lineal pathways that point to the potential presence of micro cracks. Using an innovative imaging technique at the nanoscale, high X-ray contrast gas was applied to the sample and the images obtained show visual enhancement of particular rock features, such as available porous space and microcracks.