Synchrotron-based Tomographic Microscopy Research Articles

Evolutionary convergence in conodonts revealed by Synchrotron-based Tomographic Microscopy

Evolutionary convergence in conodonts revealed by Synchrotron-based Tomographic Microscopy

Synchrotron-based tomographic microscopy (SbTM) of wood: development of a testing device and observation of plastic deformation of uniaxially compressed Norway spruce samples

Abstract To understand better the structure-property relationships of wood in situ, nondestructive synchrotron-based tomographic microscopy (SbTM) with subcellular resolution is useful. In this context, an in situ testing device was developed to determine the cellular response of wood to mechanical loading. Different rotationally symmetric specimens were tested to synchronize the failure areas to the given scanning areas. Norway spruce samples were uniaxially compressed in the longitudinal direction and scanned in situ at several increasing relative forces ending up in the plastic deformation regime. A sufficiently high quality in situ tomography was demonstrated. The reconstructed data allowed the observation of the load-dependent development of failure regions: cracks and buckling on the microstructure were clearly visible. Future investigations with SbTM on different wood species, loading directions, and different moisture contents are promising in terms of the micromechanical behavior of wood.

High-throughput full-automatic synchrotron-based tomographic microscopy.

At the TOMCAT (TOmographic Microscopy and Coherent rAdiology experimenTs) beamline of the Swiss Light Source with an energy range of 8-45 keV and voxel size from 0.37 µm to 7.4 µm, full tomographic datasets are typically acquired in 5 to 10 min. To exploit the speed of the system and enable high-throughput studies to be performed in a fully automatic manner, a package of automation tools has been developed. The samples are automatically exchanged, aligned, moved to the correct region of interest, and scanned. This task is accomplished through the coordination of Python scripts, a robot-based sample-exchange system, sample positioning motors and a CCD camera. The tools are suited for any samples that can be mounted on a standard SEM stub, and require no specific environmental conditions. Up to 60 samples can be analyzed at a time without user intervention. The throughput of the system is dependent on resolution, energy and sample size, but rates of four samples per hour have been achieved with 0.74 µm voxel size at 17.5 keV. The maximum intervention-free scanning time is theoretically unlimited, and in practice experiments have been running unattended as long as 53 h (the average beam time allocation at TOMCAT is 48 h per user). The system is the first fully automated high-throughput tomography station: mounting samples, finding regions of interest, scanning and reconstructing can be performed without user intervention. The system also includes many features which accelerate and simplify the process of tomographic microscopy.

Determination of Local GDL Saturation on the Pore Level by In Situ Synchrotron Based X-ray Tomographic Microscopy

In-situ synchrotron-based tomographic microscopy (SRXTM) with a spatial resolution in the order of 1μm and sensitivity for carbon and liquid water, has the potential to provide fundamental information for the understanding of the wetting properties of gas diffusion layer (GDL) materials on the pore level. This is important for the understanding of the solid-water interactions in the porous structures since water transport in GDLs is considered a key transport mechanism polymer electrolyte fuel cells (PEFC). However SRXTM of PEFC is a major experimental challenge. To obtain quantitative results, a complete cell needs to be operated under realistic conditions in the constrained space of the small field of view on the beamline sample stage without disturbing the sample rotation.

Connectivity of Phases and Growth Mechanisms in Peritectic Alloys Solidified at Low Speed: an X-Ray Tomography Study of Cu-Sn

The variety of microstructures that form at low solidification speed in peritectic alloys, bands, and islands, or even coupled (or cooperative) growth of the primary α and peritectic β phases, have been previously explained by nucleation-growth mechanisms. In a recent investigation on Cu-Sn, a new growth mechanism was conjectured on the basis of two-dimensional (2-D) optical microscopy and electron backscattered diffraction (EBSD) observations made in longitudinal sections. In the present contribution, synchrotron-based tomographic microscopy has been used to confirm this mechanism: α and β phases totally interconnected in three dimensions and bands (or islands) can result from an overlay mechanism, rather than from a nucleation events sequence. When the lateral growth of a new layer is too fast, an instability can lead to the formation of a lamellar structure as for eutectic alloys.