Synchrotron X-ray Micro Research Articles

Experimental investigation of dynamic drying in single pharmaceutical granules containing acetaminophen or carbamazepine using synchrotron X-ray micro computed tomography

Drying time, velocity, and temperature are important aspects of the drying process for pharmaceutical granules observed during tablet manufacturing. However, the drying mechanism of single granules is often limited to modelling and simulation, with the internal and physical changes difficult to quantify at an experimental level. In this study, in-situ synchrotron-based X-ray imaging techniques were used for the first time to investigate the dynamic drying of single pharmaceutical granules, quantifying internal changes occurring over the drying time. Two commonly used excipients (lactose monohydrate (LMH) and microcrystalline cellulose (MCC)) were used as pure components and binary mixtures with one of either two active pharmaceutical ingredients of differing hydrophilicity/hydrophobicity (acetaminophen (APAP) and carbamazepine (CBZ)). Water was used as a liquid binder to generate single granules of 25 % to 30 % moisture content. Results showed that for most samples, the drying time and composition significantly influences the pore volume evolution and the moisture ratio, with the velocity and temperature of the drying air possessing mixed significance on increasing the rate of pore connectivity and moisture removal depending on the sample composition. Effects of active ingredient loading resulted in minimal influence on the drying of CBZ and generated binary mixtures, with APAP and its respective mixtures’ drying behaviour dominated by the material’s hydrophilic nature.

Nondestructive geochemical characterization of fossil hominin taphonomy and burial history

To date, only three Homo habilis specimens have been discovered that have associated craniodental and postcranial elements, providing a limited fossil record of the ontogeny and morphology of early members of the genus Homo. Recently, a nearly complete dentition, likely attributable to H. habilis, was discovered and excavated from early Pleistocene-age fluvial-lacustrine sediments of the upper Burgi Member of the Koobi Fora Formation at site F25787 in Area 13, near Ileret, Kenya. On the surface less than 15 m away, at site F25966, postcranial elements were found, which, if from the same individual as the nearby dentition, would represent the fourth associated craniodental and postcranial assemblage of this species. We developed a geochemical taphonomic history of these ca. 2 Ma hominin fossils using nondestructive X-ray based microanalytical tools (synchrotron and benchtop X-ray fluorescence chemical imaging and micro- and nano-computed tomography volumetric reconstruction), bulk analyses of sediments and paleosols at the excavation sites, and sedimentologic and stratigraphic observations. We integrate the chemical and physical taphonomic histories to test whether teeth (excavated in situ) and postcranial bones (eroded onto the outcrop surface) derive from a single individual. Minor differences in taphonomic history are attributable to the different biomineral properties of the dental and osseous components and to differences in physical damage during early post-mortem scavenging, dispersal, and burial in adjacent depositional settings. Microscale geochemical mapping enabled the temporal ordination of chemical and physical events in the specimens’ chemical taphonomic histories. Specifically, authigenic Fe- and K-bearing clays and Y, U, and Sr uptake occurred in post-burial fractures in bones and were also incorporated pervasively throughout dentin in teeth. Barite mineralization occurred along the latest fractures in both materials, and as a coating on tooth roots. The stratigraphic, taphonomic, and geochemical evidence supports the interpretation that the hominin fossils represent a single individual. Successful application of these nondestructive sample characterization methods demonstrates capabilities for thorough interrogation of the taphonomic histories of other potential hominin fossil associations, enabling more robust and accurate palaeontologic constraints using those relationships.

4D study of liquid binder penetration dynamics in pharmaceutical powders using synchrotron X-ray micro computed tomography

The properties of pharmaceutical powders, and the liquid binder, directly influence the penetration behavior in the wet granulation process of the pharmaceutical industry. Conventional methods encounter challenges in understanding this fast process. In this work, an emerging synchrotron-based X-ray imaging technique (having fast imaging capability) was employed to investigate the internal process from 2D and 3D to real-time (in-situ with ms time intervals) 3D (also considered 4D) perspectives. Two commonly used excipients (lactose monohydrate (LMH) and microcrystalline cellulose (MCC)) were used to make binary mixtures with acetaminophen (APAP) as the active pharmaceutical ingredient (API). Isopropanol and water were employed as liquid binders in the single droplet impact method. Results showed that for most of the mixtures, the porosity increased at higher fractions of APAP. MCC mixtures experienced less agglomeration and more uniform pore distribution than LMH ones, resulting in a faster droplet penetration with isopropanol. Moreover, the imbibition-spreading studies showed that isopropanol penetration in MCC powders followed more unidirectional vertical movement than horizontal spreading. Our results also demonstrated that simultaneous granulation of LMH with water resulted in much slower penetration. This study revealed that synchrotron X-ray imaging can investigate 3D internal pore structures and how they affect the quantitively real-time internal penetration dynamics.

Influence of microdefects in rust layer of weathering steel on corrosion resistance from 3D observation by synchrotron X-ray micro tomography

Microdefects in the rust layer of conventional steel and weathering steel were investigated by synchrotron X-ray micro tomography to understand the effect of defects on corrosion resistance. The rust layer of the weathering steel contained fewer and smaller defects than that of the conventional steel. A good correlation existed between the volume of defects and ion permeation of the rust layer obtained by EIS. In comparison with the conventional steel, the tomography results indicated that a protective layer formed on the weathering steel.

Evolution of propped fractures in shales: The microscale controlling factors as revealed by in situ X-Ray microtomography

The behavior of proppant at the microscale during fracture closure in oil and gas shales is not yet well understood. In this context, we used a combination of dynamic synchrotron X-ray micro computed tomography with morphometric analysis and flow modeling to provide new insight into the dominant physical processes acting at the microscale during fracture closure, and understand their impact on hydraulic properties of the fracture. The roles of three variables have been investigated in proppant monolayers: i) Shale mineralogy and microstructure; ii) Shale bedding orientation with respect to the fracture plane; iii) Proppant characteristics. Unsurprisingly, all three variables have an impact on the permeability evolution during closure and their extent has been quantified via Stokes flow simulations. For the fracture geometry considered, proppant rearrangement during loading is the leading cause of permeability loss. The mechanical strength of proppant and shale becomes important at the later stages of the fracture closure. Bedding orientation has an impact on the mechanical response of the proppant-shale contact areas. The more regular morphology and higher mechanical strength of ceramic proppant allows to maintain a better permeability throughout the whole fracture evolution cycle when compared to quartz sand. This combined analysis approach allowed us to understand and quantify the processes involved during the closure of a propped fracture and to directly link them to the evolution of morphology and hydraulic properties. A better understanding of the contributions of these processes could ultimately help in the design and optimization of proppants, enabling more efficient extraction of hydrocarbons from unconventional systems.

Ex-situ visualization of the wet domain in the microporous layer in a polymer electrolyte fuel cell by X-ray computed tomography under water vapor supply

The wet domain in a microporous layer (MPL) in a polymer electrolyte fuel cell (PEFC) was visualized in order to clarify water accumulation in the MPL. The performance of PEFC is affected by accumulation of liquid water in the cathode gas diffusion layer (GDL). The liquid water hinders oxygen transport to the catalyst layer, resulting in increased mass-transport loss. Although MPLs suppress water accumulation in the GDL, this mechanism has not yet been fully clarified. The present study used synchrotron X-ray micro computed tomography (CT) to visualize water accumulation in the MPL. The experiment was conducted while supplying water vapor to the MPL side of the GDL. The MPL was visualized to be wetted heterogeneously, and liquid water movement from the MPL to the GDL substrate was visualized. These observations were supported by plotting the volume fraction of either the wet domain of the MPL or the water cluster as a function of through-plane distance.

Dynamics of enhanced gas trapping applied to CO2 storage in the presence of oil using synchrotron X-ray micro tomography

During CO2 storage in depleted oil fields, under immiscible conditions, CO2 can be trapped in the pore space by capillary forces, providing safe storage over geological times - a phenomenon named capillary trapping. Synchrotron X-ray imaging was used to obtain dynamic three-dimensional images of the flow of the three phases involved in this process - brine, oil and gas (nitrogen) - at high pressure and temperature, inside the pore space of Ketton limestone. First, using continuous imaging of the porous medium during gas injection, performed after waterflooding, we observed chains of multiple displacements between the three phases, caused by the connectivity of the pore space. Then, brine was re-injected and double capillary trapping - gas trapping by oil and oil trapping by brine - was the dominant double displacement event. We computed pore occupancy, saturations, interfacial area, mean curvature and Euler characteristic to elucidate these double capillary trapping phenomena, which lead to a high residual gas saturation. Pore occupancy and saturation results show an enhancement of gas trapping in the presence of both oil and brine, which potentially makes CO2 storage in depleted oil reservoirs attractive, combining safe storage with enhanced oil recovery through immiscible gas injection. Mean curvature measurements were used to assess the capillary pressures between fluid pairs during double displacements and these confirmed the stability of the spreading oil layers observed, which facilitated double capillary trapping. Interfacial area and Euler characteristic increased, indicating lower oil and gas connectivity, due to the capillary trapping events.

Stress Relaxation Related to Spontaneous Thin Film Buckling: Correlation between Finite Element Calculations and Micro Diffraction Analysis

Compressive residual stresses generated during thin film deposition may lead to undesirable film damage, such as delamination, buckling, and flaking, ultimately leading to the failure of the device employing the film. Understanding the residual stress generation and role in these damage mechanisms is necessary to preserve thin film integrity and optimize its functional properties. Thin shell theory has been used for decades to predict buckling but the results have not yet been correlated with experimental data since the techniques used to measure stress in metallic films were not able to do so at the required micron scale until recently. Micro scanning X-ray diffraction now enables the direct mapping of the local stress of metallic films. In this paper, finite element method based on thin shell theory and synchrotron X-ray micro diffraction have been used to determine stress maps of thin film buckling patterns. Calculations of the stress distribution in the metallic films have been performed taking into account the buckling geometry determined from optical measurements. Stress distributions over gold blisters and tungsten wrinkles obtained with the two techniques are in fair agreement and allow for the accurate determination of the stress relaxation profile from the bottom to the top of the buckling, validating the thin shell theory model.

Synchrotron-Based Micro-CT Investigation of Oxic Corrosion of Copper-Coated Carbon Steel for Potential Use in a Deep Geological Repository for Used Nuclear Fuel

Within the multi-barrier system proposed for the permanent disposal of used nuclear fuel, the primary engineered barrier is the sealed metallic container. The present Canadian container design utilizes a carbon steel vessel coated with Cu for corrosion protection. In the event of a defect in the Cu coating that exposes the steel substrate, galvanically accelerated corrosion of steel is, in principle, possible. In this work, the progression of corrosion at a simulated through-coating defect in 3.0 mol/L NaCl solution containing dissolved O2 was monitored using electrochemical measurements and imaged non-destructively using synchrotron X-ray micro computed tomography (micro-CT). The damage volume at the base of the simulated defect was measured from the 3D micro-CT data and used to calculate the amount of O2 used to drive steel corrosion. The results demonstrate that the availability of O2 determines the rate and overall extent of corrosion, while the coatings produced using different deposition and treatment methods (cold spray deposition, heat-treated cold spray deposition, electrodeposition) lead to different corrosion propagation geometries, with the distribution of damage depending on the quality of the Cu/steel interface.

The measurement of internal surface characteristics of fuel nozzle orifices using the synchrotron X-ray micro CT technology

The design of fuel nozzle orifices at micrometer scales is crucial for generating desired fuel spray patterns, and consequently optimizing fuel combustion and emission in internal combustion engines. Although there have been several recent advancements in the characterization of orifice internal geometries, quantitative studies on the orifice internal wall surface characteristics are still challeges due to the lack of effective measuring methods. A new method for quantifying the internal wall surface characteristics of fuel nozzle micro-orifices is presented in this study to achieve a better understanding and prediction of spray characteristics: Firstly, by using the synchrotron X-ray micro CT technology, a three-dimensional digital model of the fuel nozzle tip was constructed. Secondly, a data post-processing technique was then applied to unfold the orifice internal wall surface to a flat base plane. Finally, the conventional surface characteristic quantification techniques can be used to evaluate the wall surface characteristics. Two diesel nozzles with identical orifice geometry design but different hydraulic grinding time were measured using this method. One nozzle was hydro-ground for 2 s while the other was not. The internal wall surfaces of the two orifices were successfully unfolded to base planes and their surface characteristics were respectively analyzed. The surface fluctuation data were perfectly reproduced by a Gaussian distribution function. The standard deviations of the distribution demonstrate the fluctuation range and the distribution of the entire surface fluctuation profiles. As an effective parameter to evaluate the hydraulic grinding process and the spray behaviors, the standard deviation was considered feasible for the analysis of the orifice internal wall surface characteristics.

Synchrotron X-ray Micro Tomography at the Advanced Light Source: In-Situ Sample Environments for Advanced Aerospace Materials

Synchrotron X-ray Micro Tomography at the Advanced Light Source: In-Situ Sample Environments for Advanced Aerospace Materials

A sparsity-based iterative algorithm for reconstruction of micro-CT images from highly undersampled projection datasets obtained with a synchrotron X-ray source.

Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.

Liquid-Water Distribution in Compressed Gas-Diffusion Layers Using X-Ray Computed Tomography

Effective liquid-water management is essential for commercializing polymer-electrolyte fuel cells (PEFCs). At lower operating temperatures, there is a need to remove liquid water from the cathode electrode to ensure optimal reactant transport1. To achieve maximum water permeation, it is necessary to optimize the gas-diffusion layers (GDLs). Currently, there is a lack of understanding of water transport, especially under in-situ conditions wherein the GDLs are selectively compressed under lands to provide good electrical conductivity but remain uncompressed under the gas flow channels. In this study, we use synchrotron X-ray micro computed tomography (CT) to study the water distribution in commercially available GDL materials under various levels of compression. We correlate the GDL’s morphological properties such as local spatially-resolved porosity and void-size distribution to local liquid-water distribution and water-transport capability. Water imbibition through the GDL driven by a static water column was imaged in a sample holder with a grooved stomp. Controlled levels of GDL compression were achieved by tuning an ultra-fine pitch threaded bolt on top of the stomp. Liquid-water profiles were resolved as local averages in in-plane and through-plane directions. Figure 1 shows local liquid-water distributions for three GDLs under different levels of compression as local averages through the GDL depth. Narrowing of the liquid front was observed with increasing compression (decreasing thickness), where most of the liquid is transported under the channel. It appears that at lower compressions the advance of the liquid front is uniform; this is due to uniform porosity and due to availability of void space at the GDL|injection plate interface that allows liquid-water redistribution. At high compressions, porosity and liquid saturation are directly correlated, something that was not observed for the uncompressed sample. This finding is relevant for the design of GDL architectures with modulated porosity, where liquid-water removal can be directed through controlled porosity levels. Figure 1 Average YZ liquid saturation as a function of X position for three compressions at capillary pressure of 1.4 kPa Acknowledgement This work was funded by Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy. References A. Steinbach, “High Performance, Durable, Low Cost Membrane Electrode Assemblies for Transportation Applications”, DOE Annual Merit Review (2014). Figure 1

미세 X선 단층촬영 기법의 개발과 적용

The objective of this study is to elucidate the feasibility of synchrotron X-ray micro CT as a non-destructive imaging method to visualize the three-dimensional morphological structures of biological and non-biological samples. The experiments were conducted in 7B2 X-ray micro CT beamline in Pohang Accelerate Laboratory (PAL). A rotational 3-axis stage was specially designed for <TEX>$0^{\circ}-180^{\circ}$</TEX> scanning of test samples. Preliminary tests were performed for opaque samples including a mosquito head, a plant seed and gas diffusion layer (GDL) of polymer electrolyte fuel cell to verify the feasibility of the X-ray micro CT. It visualized clearly the internal structure of all the test samples, supporting its usefulness.

About microcracking due to leaching in cementitious composites: X-ray microtomography description and numerical approach

Chemical shock of cement based materials leads to significant degradation of their physical properties. A typical scenario is a calcium leaching due to water (water with very low pH compared with that of pore fluid). The main objective of this paper is to evaluate the evolution of microstructure induced by leaching of a cementitious composite using synchrotron X-ray micro tomography, mainly from an experimental point of view. In this particular case, it was possible to identify cracking induced by leaching. After a description of the degradation mechanism and the X-ray synchrotron microtomographic analysis, numerical simulations are performed in order to show that cracking is induced by an initial pre-stressing of the composite, coupled with decalcification shrinkage and dramatic decrease in tensile strength during leaching. X-ray microtomography analysis allowed to make evidence of an induced microcracking in cementitious material submitted to leaching.

Application of synchrotron X-ray micro tomographic microscopy at low temperature

Application of synchrotron X-ray micro tomographic microscopy at low temperature

Transcrystallinity in aramid and carbon fiber reinforced nylon 66: determining the lamellar orientation by synchrotron X-ray micro diffraction

This paper presents the structural details of nylon 66 transcrystallinity induced by aramid (kevlar 29, 49 and 149) and carbon (pitch based) fibers, as determined by high spatial resolution X-ray diffraction. Using stepwise scanning, the orientation of the lamellae in the transcrystalline layer was measured as a function of distance from the fiber. The main observation is that this orientation is distinct for each system and almost independent of distance from the fiber. Of particular interest is the bi-layered transcrystallinity formed on a surface treated kevlar 49 fiber, in which the lamellar a * axis is nearly perpendicular and at an angle of ∼12° to the fiber in the outer and inner layer, respectively. The crystallographic analysis generates grids of oriented lamellae with respect to the fiber axis.

Synchrotron X-ray 미세영상기법을 이용한 식물 목질부 내부 수액 유동의 계측

Synchrotron X-ray micro imaging technique was employed to non-invasively monitor the water flow inside xylem vessels in a bamboo leaf. The phase contrast X-ray images clearly visualized plant anatomy and the rise of a water front inside the vessels. Consecutive X-ray images taken for 60 seconds revealed water rise kinetics against gravity in the xylem of a cut dry leaf taken from a bamboo tree. For the first time, traces of water rise, variation of contact angle between water and xylem wall as well as the internal structure of xylem were obtained. In xylem vessels, a repeating flow pattern has a typical flow velocity of 30.7/s and faster flow is established intermittently. It is concluded that the transmission type of X-ray micro imaging can be used as a powerful tool to investigate the ascent of sap in the xylem vessels at a resolution higher than that of MRI.

Local Layer Structures in Ferroelectric Liquid Crystal Cells Filled with a Material Which Exhibits Cholesteric-Chiral Smectic C Phase Transition

We investigated the local layer structures in ferroelectric liquid crystal (FLC) cells which have a monostable switching mode using synchrotron X-ray micro diffraction. The monostable switching mode is realized by the FLC cells filled with a material which has cholesteric–chiral smectic C (Ch–SmC*) phase transition sequences. On cooling these cells from the isotropic phase to the SmC* phase, the texture of domains and stripes was observed. The X-ray micro diffraction study revealed that the smectic layer bending with the layer shrinkage generate the texture.

Dynamic Layer Response under Electric Field in Antiferroelectric Liquid Crystal Cells Measured by Synchrotron Microbeam Time Resolved X-Ray Diffraction

Direct observation of the local layer response of an antiferroelectric liquid crystal to the step form electric field has been carried out by a time resolved synchrotron X-ray micro diffraction measurement. When an electric field was changed from high voltage to OV, corresponding to the ferroelectric to antiferroelectric phase transition, the local layer transformed from the bookshelf to the quasi-bookshelf structure within 0.3 ms. The horizontal chevron structure was found in both the phases, though the decrease in the horizontal chevron angle was observed during a period of 0.2 ms after turning off the electric field. In the antiferroelectric to ferroelectric phase transition process (from OV to high voltage), the layer structure transformed to the bookshelf within 0.04 ms.