Use Of X-ray CT Research Articles

A Review of Particle Size Analysis with X-ray CT.

Particle size and morphology analysis is a problem common to a wide range of applications, including additive manufacturing, geological and agricultural materials' characterisation, food manufacturing and pharmaceuticals. Here, we review the use of microfocus X-ray computed tomography (X-ray CT) for particle analysis. We give an overview of different sample preparation methods, image processing protocols, the morphology parameters that can be determined, and types of materials that are suitable for analysis of particle sizes using X-ray CT. The main conclusion is that size and shape parameters can be determined for particles larger than approximately 2 to 3 μm, given adequate resolution of the X-ray CT setup. Particles composed of high atomic number materials (Z > 40) require careful sample preparation to ensure X-ray transmission. Problems occur when particles with a broad range of sizes are closely packed together, or when particles are fused (sintered or cemented). The use of X-ray CT for particle size analysis promises to become increasingly widespread, offering measurements of size, shape, and porosity of large numbers of particles within one X-ray CT scan.

Assessment of spatial representativity of X-ray tomography to study Vertical Flow Treatment wetlands

French Vertical Flow (VF) treatment wetlands receive raw wastewater and provide simultaneous sludge and wastewater treatment. For proper sludge handling, the treatment wetland must be designed adequately and specific operational conditions must be maintained. When these conditions are not met, accumulation of biosolids may lead to clogging. Filtration in French VF Treatment wetlands is governed by mechanisms at the pore-scale. They must be better understood to predict reliably biosolid accumulation. X-ray Computed Tomography (Xray-CT) is a promising technique to characterize in detail the morphology of the filtering media in treatment wetlands. In order to set a solid basis for the use of Xray-CT, the spatial representativity of measurements must be assessed. This issue is addressed in this study by successively analyzing spatial properties at the filter scale using Frequency Domain Electromagnetic Measurements (FDEMs), and at the pore scale using Xray-CT. A map of the electric conductivity at the surface of a French VF Treatment wetland is obtained by FDEM that indicates a homogeneous distribution of biosolids to which electrical conductivity is highly correlated. Different morphological properties were computed from Xray-CT after phase segmentation: phase volume fraction profiles, Specific Surface Area profiles and pore size distributions. Samples show several similarities of pore scale properties obtained by Xray-CT independently of the sampling region and especially the same vertical gradients. FDEM measurements and Xray-CT analysis are in agreement to indicate a good influent distribution at the surface of a full-scale mature French VF Treatment wetland. A criterion to define the limits of the deposit layer and gravel layer is introduced. This division allows to compare layers independently. Finally, a 2D-REV analysis suggests that the selected sample diameter of 5 cm is large enough to be representative of the heterogeneous distribution of phases at the pore-scale as long as no Phragmites are present.

Developments in X-ray tomography characterization for electrochemical devices

Over the last century, X-ray imaging instruments and their accompanying tomographic reconstruction algorithms have developed considerably. With improved tomogram quality and resolution, voxel sizes down to tens of nanometers can now be achieved. Moreover, recent advancements in readily accessible lab-based X-ray computed tomography (X-ray CT) instruments have produced spatial resolutions comparable to specialist synchrotron facilities. Electrochemical energy conversion devices, such as fuel cells and batteries, have inherently complex electrode microstructures to achieve competitive power delivery for consideration as replacements for conventional sources. With resolution capabilities spanning tens of microns to tens of nanometers, X-ray CT has become widely employed in the three-dimensional (3D) characterization of electrochemical materials. The ability to perform multiscale imaging has enabled characterization from system-down to particle-level, with the ability to resolve critical features within device microstructures. X-ray characterization presents a favorable alternative to other 3D methods, such as focused ion beam scanning electron microscopy, due to its non-destructive nature, which allows four-dimensional (4D) studies, three spatial dimensions plus time, linking structural dynamics to device performance and lifetime. X-ray CT has accelerated research from fundamental understanding of the links between cell structure and performance, to the improvement in manufacturing and scale-up of full electrochemical cells. Furthermore, this has aided in the mitigation of degradation and cell-level failures, such as thermal runaway. This review presents recent developments in the use of X-ray CT as a characterization method and its role in the advancement of electrochemical materials engineering.

Structural Characterization of Membrane-Electrode-Assemblies in High Temperature Polymer Electrolyte Membrane Fuel Cells

In high temperature polymer electrolyte fuel cells, polybenzimidazole membranes doped in phosphoric acid are used as electrolyte material. The membrane thickness directly relate to the amount of absorbed acid which relate to performance. In this study, we compare scanning electron microscopy and X-ray micro-computed tomography (CT) regarding suitability for determining the structure of electrolyte membranes. Semi-automated layer identification and thickness estimation was used to reduce human errors and data processing time. Scanning electron microscopy was found reliable for membrane thickness characterization despite necessary destructive sample preparation. With X-ray CT it was possible to study the cells non-destructively before and after cell test. This made it possible to identify, so-called hot pressing, as the step in which the membrane lost most of its thickness. After cell operation, the use of X-ray CT at large field of view and a recently developed layer detection algorithm made it possible to visualize compression of the membrane in a pattern identical to that of the flow plate channels. This compression pattern would have been difficult to determine with conventional electron microscopy or X-ray CT without semi-automated layer detection.

X-ray CT in the detection of palm weevils

Early detection of the red palm weevils (RPW) is a major challenge in agriculture among all kinds of palm trees due to the nature of the insect and the difficulty to trace them through their life stages associated with the tree life. Many methods have been applied for the weevil detection such as X-ray diffraction techniques, fluoroscopy and ultrasound. On the other hand, the idea of tomography has been used for other purposes such as the determination of the age of the tree and for applied environmental studies. Such technology can also reveal the weevil in principle. In this study, we explore the use of X-ray CT for weevil detection with the Monte Carlo method. A model of the stem of a palm tree is developed for simulations. MCNPX is chosen to carry out the simulations for the radiography tally in the code. The tally records the 2D data of the X-ray beams irradiating the tree model. An iterative reconstruction method for cone beam CT is applied to obtain the 3D slices of the tree model. We are exploring the minimum number of projection angles and the detectability of the weevil. We shall also report the sensitivity of weevil detection using X-ray CT with a large set of simulations with different weevil sizes and tree diameters.

Introduction of X-ray CT application in geotechnical engineering – theory and practice

In this paper, fundamental issues on the use of X-ray CT to geomaterials were discussed, which were the contents of what you have to know about the use of X-ray CT, especially for geomaterials or granular materials. Then, two of our recent studies were introduced, which are 1) the use of X-ray CT data to quantitative measurements such as deformation and strains and 2) comparison of X-ray CT results with numerical analysis. Here, the triaxial compression test on sand was conducted and the image analysis technique called "Digital Image Correlation" was used to measure displacement and strain fields in the soils using a large number of CT images. For the second topic, one of the advantages on the use of X-ray CT is to investigate the behavior in three dimensions. Here, so called trap door test was conducted with the materials of glass beads and the shape of the square door. DEM analysis was also conducted for the simulation of this behaviour and both results were compared. Based on all the results in this paper, the effectiveness of the use of X-ray CT in geomechanics and geotechnical engineering was revealed.

OBSERVATION OF FIBERS IN LONG FIBER REINFORCED METAL MATRIX COMPOSITES BY X-RAY COMPUTED TOMOGRAPHY USING SYNCHROTRON RADIATION

Abstract Four types of MMC reinforced with B and SiC fibers were observed by X-ray CT using synchrotron radiation. Use of X-ray CT made possible the direct observation of fibers and defects in them. On the basis of X-ray coefficients of the elements in the composites the energy values of 21 and 29 KeV were selected for Al alloy and Ti alloy, respectively. The inner fiber and debonding parts of the interface between fiber and matrix were clearly observed for the composites used in this study. In the case of the silicon carbide reinforced aluminum composites, the core carbon fibers of 30 μm in diameter were also observed. The resolution of X-ray CT scanner used in this study was about 10μm. 3-dimensional images were reconstructed from several CT images. The 3-dimensional images visually displayed the inner structure and were very useful in discussing the model of the fracture process of the fibers contained in the metal matrix composites.