High-resolution X-ray Computed Tomography Research Articles

Age and growth assessment of western North Atlantic spiny butterfly ray Gymnura altavela (L. 1758) using computed tomography of vertebral centra

Life history strategies of batoid fishes have evolved within dynamic marine ecosystems. Adaptations in reproductive and developmental biology are paramount to the survival of species, and therefore knowledge of growth rates to maturity is fundamental for identifying constraints on the conservation of populations. The butterfly rays (Myliobatiformes: Gymnuridae) are highly derived batoids with generally low reproductive potentials for which age and growth information remains unknown. In this study we applied high-resolution X-ray computed tomography (HRXCT) to vertebral centra from a stingray for the first time to estimate age, and used a multimodel approach to investigate growth of spiny butterfly ray, Gymnura altavela. Estimated ages of the oldest male and female were 11 and 18 yrs. at disk widths (WD) 1355 mm and 2150 mm, respectively. Disk width-at-age data were analyzed using three growth models (von Bertalanffy, logistic, Gompertz), and the most parsimonious and empirically supported model was the logistic function with sex treated as a fixed effect on asymptotic disk width (WD ∞ ) and k parameters. Model parameter estimates were (males) WD ∞ = 1285.46 ± 67.27 mm, k = 0.60 ± 0.10, and (females) WD ∞ = 2173.51 ± 129.78 mm, k = 0.27 ± 0.04. Results indicated sexually dimorphic growth patterns, with males growing faster and reaching asymptotic size at earlier ages than females. These age and growth results are the first reported for the genus, and suggest that G. altavela grows at a similar rate as some teleosts and batoids, and relatively fast among chondrichthyans.

Use of high-resolution X-ray computed tomography and 3D image analysis to quantify mineral dissemination and pore space in oxide copper ore particles

Mineral dissemination and pore space distribution in ore particles are important features that influence heap leaching performance. To quantify the mineral dissemination and pore space distribution of an ore particle, a cylindrical copper oxide ore sample (ϕ4.6 mm × 5.6 mm) was scanned using high-resolution X-ray computed tomography (HRXCT), a nondestructive imaging technology, at a spatial resolution of 4.85 μm. Combined with three-dimensional (3D) image analysis techniques, the main mineral phases and pore space were segmented and the volume fraction of each phase was calculated. In addition, the mass fraction of each mineral phase was estimated and the result was validated with that obtained using traditional techniques. Furthermore, the pore phase features, including the pore size distribution, pore surface area, pore fractal dimension, pore centerline, and the pore connectivity, were investigated quantitatively. The pore space analysis results indicate that the pore size distribution closely fits a log-normal distribution and that the pore space morphology is complicated, with a large surface area and low connectivity. This study demonstrates that the combination of HRXCT and 3D image analysis is an effective tool for acquiring 3D mineralogical and pore structural data.

Gas scintillation glass GEM detector for high-resolution X-ray imaging and CT

A high-spatial-resolution X-ray-imaging gaseous detector has been developed with a single high-gas-gain glass gas electron multiplier (G-GEM), scintillation gas, and optical camera. High-resolution X-ray imaging of soft elements is performed with a spatial resolution of 281µm rms and an effective area of 100×100mm. In addition, high-resolution X-ray 3D computed tomography (CT) is successfully demonstrated with the gaseous detector. It shows high sensitivity to low-energy X-rays, which results in high-contrast radiographs of objects containing elements with low atomic numbers. In addition, the high yield of scintillation light enables fast X-ray imaging, which is an advantage for constructing CT images with low-energy X-rays.

Inspection of geometry influence and fiber orientation to characteristic value for short fiber reinforced ceramic matrix composite under bending load

For use of short fiber reinforced ceramics the knowledge of the influence of coupon geometry on the failure mode and the determined resistance in bending tests is necessary. In contrast to the continuous fiber reinforced ceramic matrix composites (CMC), for short fiber reinforced CMC there are only few studies and no standard on consideration of size effects. In the present work, the influence of coupon geometry and test conditions on the average value and distribution of flexural strength has been investigated. Two short fiber CMCs with different fiber length were examined under four point bending load. Moreover, the relationship between fiber orientation in the loaded area, failure location and measured flexural strength was investigated through high resolution X-ray computer tomography (μCT) and SEM. The presented outputs will be proposed to a future standard for bending test of short fiber reinforced CMC materials with different fiber length.

Nucleation rates of spherulites in natural rhyolitic lava

The rates of nucleation and crystal growth from silicate melt are difficult to measure because the temperature–time path of magma is often unknown. We use geochemical gradients around spherulites in obsidian glass to estimate the temperature–time interval of spherulite crystallization. This information is used in conjunction with new high-resolution X-ray computed tomography (HRXCT) data on the size distributions of spherulites in six samples of rhyolite obsidian lava to infer spherulite nucleation rates. A large data set of geochemical profiles indicate that the lavas cooled at rates of 10 −2.2 to 10 −1.2 °C/h, and that the spherulites grew at rates that decreased exponentially with time, with values of 10 −0.70 to 10 0.30 μm/h at 600 °C. Spherulites are estimated to have begun nucleating when undercooling [Δ T , = liquidus T (≈800 °C) minus nucleation T ] reached 100–277 °C, and stopped when Δ T = 203–365 °C, with exact values dependent on assumed cooling and growth rates. Regardless of rates, we find that spherulites nucleated within a ~88–113 °C temperature interval and, hence, began when Δ T ≈ 0.65–0.88 × T L , peaking when Δ T ≈ 0.59–0.80 × T L . A peak rate of nucleation of 0.072 ± 0.049 cm −3 h −1 occurred at 533 ± 14 °C, using cooling and growth rates that best fit the data set of geochemical profiles. While our inferred values for Δ T overlap those from experimental studies, our nucleation rates are much lower. That difference likely results from experimental studies using hydrous melts; the natural spherulites grew in nearly anhydrous glass.

Satan's skeleton revealed: a tomographic and comparative osteology of Satan eurystomus, the subterranean Widemouth Blindcat (Siluriformes, Ictaluridae)

The Widemouth Blindcat, Satan eurystomus Hubbs and Bailey 1947, was the second of four stygobitic species of Ictaluridae discovered in the subterranean waters of southern Texas and northeastern Mexico. The skeletal anatomy of Satan has been scarcely known from a few, dated radiographs. Using additional radiographs and high resolution CT-datasets for two well-ossified specimens, we applied high-resolution X-ray computed tomography (HRXCT) to visualize, illustrate and describe the bony skeleton of Satan. We also provide an online archive of still and animated tomographic images of the skeletal anatomy of this little-known species.The skeleton and soft anatomy of Satan are distinctive. Twelve skeletal autapomorphies are described that singularly distinguish Satan within Ictaluridae and, probably in combination, from all other catfishes. Some of these are reductive losses or simplifications of skull bones (e.g. loss of one infraorbital bone; reduced ornamentation of the pterotic bone) and joint complexity (e.g. simple overlapping frontal-lateral ethmoid articulation; loosely ligamentous interopercle-posterior ceratohyal joint). Some of the autapomorphies are anatomically and perhaps developmentally complex (e.g. a novel series of three midline joints closing a middle span of the posterior cranial fontanel; a deeply excavated temporal fossa and an unusually enlarged interhyal bone). The tiny dorsal-fin spinelet (first lepidotrich) of Satan has a novel peaked and twisted shape.Ten apparent and exclusive synapomorphies within Ictaluridae gathered from this and previous studies suggest that Satan and Pylodictis are closest relatives. Most of these are functionally related to prey detection and suction feeding: fusion of the symphyseal mandibular sensory pores and increase in the number of preoperculo-mandibular canal pores; depressed, flattened heads and wide transverse mouths; prominent posterior process of the lateral ethmoid alongside and below the frontal bone margin; vertical and blade-like supraoccipital posterior process; unique arrangement of the parasagittal and occipital muscleattachment crests on the skull roof; large triangular panel of integument within the operculum framed by the opercle, preopercle and interopercle bones; elongated posterior ceratohyal; and, form of the fourth supraneural and loss of its anterior nuchal plate.In contrast, 15 synapomorphies recovered by Arce-H. et al. 2016, are confirmed suggesting that Satan is one of the four stygobitic ictalurids comprising a “Troglobites” subclade within the family: (Trogloglanis, Satan, Prietella phreatophila, P. lundbergi). These features include three stygomorphic and reductive apomorphies that are exclusive within Ictaluridae: loss of fully developed eyes and pigmentation, and simplification of the fifth vertebra and its joint with the Weberian apparatus. Twelve other synapomorphies shown by the Troglobites are also apparent homoplasies of character states shared with various other ictalurids. These include reductive characters such as shortened lateral line canal, reduced infraorbitals and underdeveloped or incomplete ossifications of the pterotic, supraoccipital, hyoid arch bones and transcapular ligament. Also, the Troglobites and various other ictalurids have: an adnate adiposecaudal fin, foreshortened anterior cranial fontanelle, reduced ventral wings of the frontal bone, replacement of bone by cartilage in hypohyal joints; incompletely ossified transcapular ligament, and consolidation of some hypural bones.Completing a full morphological character dataset across the Troglobites has been impeded by incomplete specimen preparations and study of P. lundbergi and to a lesser extent, P. phreatophila and Trogloglanis.

Aligning Microtomography Analysis with Traditional Anatomy for a 3D Understanding of the Host-Parasite Interface - Phoradendron spp. Case Study.

The complex endophytic structure formed by parasitic plant species often represents a challenge in the study of the host-parasite interface. Even with the large amounts of anatomical slides, a three-dimensional comprehension of the structure may still be difficult to obtain. In the present study we applied the High Resolution X-ray Computed Tomography (HRXCT) analysis along with usual plant anatomy techniques in order to compare the infestation pattern of two mistletoe species of the genus Phoradendron. Additionally, we tested the use of contrasting solutions in order to improve the detection of the parasite’s endophytic tissue. To our knowledge, this is the first study to show the three-dimensional structure of host-mistletoe interface by using HRXCT technique. Results showed that Phoradendron perrottetii growing on the host Tapirira guianensis forms small woody galls with a restricted endophytic system. The sinkers were short and eventually grouped creating a continuous interface with the host wood. On the other hand, the long sinkers of P. bathyoryctum penetrate deeply into the wood of Cedrela fissilis branching in all directions throughout the woody gall area, forming a spread-out infestation pattern. The results indicate that the HRXCT is indeed a powerful approach to understand the endophytic system of parasitic plants. The combination of three-dimensional models of the infestation with anatomical analysis provided a broader understanding of the host-parasite connection. Unique anatomic features are reported for the sinkes of P. perrottetii, while the endophytic tissue of P. bathyoryctum conformed to general anatomy observed for other species of this genus. These differences are hypothesized to be related to the three-dimensional structure of each endophytic system and the communication stablished with the host.

Skull osteology of the Eocene amphisbaenian Spathorhynchus fossorium (Reptilia, Squamata) suggests convergent evolution and reversals of fossorial adaptations in worm lizards.

The fossorial amphisbaenians, or worm lizards, are characterized by a suite of specialized characters in the skull and postcranium, however fossil evidence suggests that at least some of these shared derived traits evolved convergently. Unfortunately the lack of detailed knowledge of many fossil taxa has rendered a more precise interpretation difficult. Here we describe the cranial anatomy of the oldest-known well-preserved amphisbaenian, Spathorhynchus fossorium, from the Eocene Green River Formation, Wyoming, USA, using high-resolution X-ray computed tomography (HRXCT). This taxon possesses one of the most strongly reinforced crania known among amphisbaenians, with many dermal bones overlapping each other internally. In contrast to modern taxa, S.fossorium has a paired orbitosphenoid, lacks a true compound bone in the mandible, and possesses a fully enclosed orbital rim. The last feature represents a highly derived structure in that the jugal establishes contact with the frontal internally, reinforcing the posterior orbital margin. S.fossorium also possesses a strongly modified Vidian canal with a previously unknown connection to the ventral surface of the parabasisphenoid. Comparison with the closely related fossil taxon Dyticonastis rensbergeri reveals that these derived traits are also shared by the latter species and potentially represent synapopmorphies of an extinct Paleogene clade of amphisbaenians. The presence of a reinforced orbital rim suggests selection against the loss of a functional eye and indicates an ecology potentially different from modern taxa. Given the currently accepted phylogenetic position of Spathorhynchus and Dyticonastis, we predict that supposedly 'unique' cranial traits traditionally linked to fossoriality such as a fused orbitosphenoid and the reduction of the eye show a more complex character history than previously assumed, including both parallel evolution and reversals to superficially primitive conditions.

Evaluating Soil Tillage Practices Using X-Ray Computed Tomography and Conventional Laboratory Methods

<abstract> Using x-ray computed tomography (CT) for non-destructive 3-D imaging and analysis of soil physical properties has been investigated for over 30 years. However, applying this system in soil science has remained a specialized research area using primarily low-resolution medical-grade x-ray CT units that were not designed for soil analysis applications. The main research objectives were to characterize and compare physical properties of soil core samples from long-term chisel plow (CP) and no-till (NT) agricultural field management sites using a high-resolution industrial-grade x-ray CT unit and two conventional soil laboratory method (SLM) soil macroporosity analysis procedures. Field research activities during 1999 included collecting four soil columns for each CP and NT soil management practice at the Iowa State University Northeast Research and Demonstration Farm at Nashua, Iowa. Findings from this study indicate that percent macroporosity and soil bulk density values were significantly higher and lower, respectively, for annual CP rowcrop (corn and soybean) versus annual NT rowcrop systems. Since the soil structure of perennial NT vegetation (native grasses and trees) is similar to CP, rowcrop practices could explain inconsistent soil hydraulic conductivity values from NT cropping systems. These results underscore the potential of x-ray CT as an effective soil porosity analysis tool and suggest the development of an online database of x-ray CT 3-D soil core images based on soil type and tillage system. This readily available information could aid scientists in soil structural analysis applications, potentially avoiding the limitations of x-ray CT unit cost and system availability issues.

3D textural evidence for the formation of ultra-high tenor precious metal bearing sulphide microdroplets in offset reefs: An extreme example from the Platinova Reef, Skaergaard Intrusion, Greenland

The Platinova Reef in the Skaergaard Intrusion, east Greenland, is an example of a type of layered-intrusion-hosted, precious metal-enriched, stratiform, disseminated sulphide deposit referred to as “offset reefs”. These typically show platinum-group element (PGE) enrichment immediately below a major increase in the abundance of Cu-rich sulphides, with a prominent peak in Au enrichment exactly at that transition between the PGE-rich and the Cu-sulphide-rich zones. The reasons for the relative sequence of offsets in metal peaks, and the occasionally very high metal tenors have been subject to great debate. Here we use an integrated approach of high-resolution X-ray computed tomography (HRXCT), SEM, synchrotron and desktop microbeam XRF mapping, and thin section petrography to comprehensively classify the textural relations of the precious metal-bearing sulphides of the Platinova Reef as an extreme end member example of an exceedingly high tenor offset deposit. Our results show that in the zones of PGE enrichment, precious metal minerals (PMMs) are intimately associated with Cu sulphide globules, mostly located at, or close to, silicate and oxide boundaries. The textures are identical in zones enriched in Pd and Au, and thus we do not see any evidence for different processes forming the different zones. The PMM:Cu sulphide ratio in each globule varies significantly but overall the size of the globules increases from the Pd-rich, through the Au-rich, and into the Cu zone, with a significant corresponding decrease in PM tenor. As such, this records a progression of exceedingly high tenor, microdroplets of sulphide, which progressively get larger up through the section, and decrease in tenor proportionally to their size. Cumulus droplets of Cu sulphide became enriched in metals, and were trapped in situ without significant transport from their point of nucleation. The transition to larger sulphides represents a change from sulphides nucleated and trapped in situ, to larger ones that liquated from magma devoid of crystals, and that were able to grow and sink. This feature is common in all offset reef deposits, and is marked by the major enrichment in Au. Although the metal ratios of PGE to Au in the Pd- and Au-rich offset zones differ, the identical textures and comparable mineralogy show the physical mechanisms of concentration are the same, indicating a similar physical method of concentration. The relative position of the Pd, Au and Cu peaks in the Platinova Reef is essentially the same as that in numerous other offset reefs, suggesting that common overarching processes are responsible for the enrichment in metals, and relative offsets in peak metal concentrations in all such deposits. The most important of these processes are their relative Dsul/sil values and the diffusivities of the metals, which determine the order of offsets and the high tenors of the smallest sulphide droplets. The Platinova Reef therefore records the extreme enrichment via equilibrium and diffusive partitioning into sulphide liquid microdroplets very close to their point of nucleation.

Modern theoretical and technical approaches in plant morphology

Morphology is deeply rooted in organismal biology, which in recent years has gone through a steady decline in interest both at research institutions and funding agencies. In parallel with this development, morphology as a discipline has been marginalized and nowadays many think of it as just a classical and largely obsolete field of research. However, this is far from the truth. Thanks to modern theoretical concepts and novel technical applications, plant morphology has much to contribute to modern botanical and evolutionary research.In our presentation, we will first outline the application of High Resolution X-Ray Computed Tomography (HRXCT) to the study of plant structure. The ideal way to describe the morphological phenotype of a given organism is to build a three dimensional (3D) model, which may then be interpreted with respect to other types of data, e.g., metabolite content or functional groups of pollinators. We have developed simple but efficient lab protocols using contrasting agents such as phosphotungstate and bismuth tartrate that allow for the streamlined acquisition of high resolution phenotypic data and 3D-representations even of soft plant tissues such as floral organs, ovules, and meristematic tissues. To illustrate this, we will outline selected ongoing studies in comparative plant science that make use of high resolution tomography.In the second part of our talk, we will present a project on the floral morphospace. A striking feature of morphological variation is that due to developmental, functional, and phylogenetic constraints, not all theoretically possible architectures have been explored during evolution. A modern approach to studying the evolution of realized forms among possible ones is to construct morphospaces, i.e. theoretical, mathematical spaces describing and relating organismal phenotypes. Although widely applied in zoology, morphospace analyses and related approaches have so far been largely disregarded in botany, with notable exceptions in the field of pollination biology. Here, we use a morphospace approach to describe and quantify the morphological diversity (disparity) of flowers in the asterid order Ericales. To do so, we have built a dataset containing 37 floral characters for more than 380 species (275 genera) representative of the entire order. We have used non-parametric representations and statistics methods based on distance matrices to build and analyze a morphospace, in which we compare the relative positions of the different ericalean families. We quantify and interpret the disparity among these groups in the light of their taxonomic diversity, their evolutionary history, and their ecology. In addition, we analyze patterns of disparity between sterile, male, and female floral organs.

Wettability measurement under high P‐T conditions using X‐ray imaging with application to the brine‐supercritical CO2 system

AbstractWe present a new method for measuring wettability or contact angle of minerals at reservoir pressure‐temperature conditions using high‐resolution X‐ray computed tomography (HRXCT) and radiography. In this method, a capillary or a narrow slot is constructed from a mineral or a rock sample of interest wherein two fluids are allowed to form an interface that is imaged using X‐rays. After some validation measurements at room pressure‐temperature conditions, we illustrate this method by measuring the contact angle of CO2‐brine on quartz, muscovite, shale, borosilicate glass, polytetrafluoroethylene (PTFE or Teflon), and polyether ether ketone (PEEK) surfaces at 60–71°C and 13.8–22.8 MPa. At reservoir conditions, PTFE and PEEK surfaces were found to be CO2‐wet with contact angles of 140° and 127°, respectively. Quartz and muscovite were found to be water‐wet with contact angles of 26° and 58°, respectively, under similar conditions. Borosilicate glass‐air‐brine at room conditions showed strong water‐wet characteristics with a contact angle of 9°, whereas borosilicate glass‐CO2‐brine at 13.8 MPa and 60°C showed a decrease in its water‐wetness with contact angle of 54°. This method provides a new application for X‐ray imaging and an alternative to other methods.

Interior 3D-Strain Mapping in Opaque Materials Using Digital Volumetric Speckle Photography and X-Ray Micro Computer Tomography

Developing a true 3D experimental stress analysis technique has been the holy grail of solid mechanics researchers since the genesis of the field. Combined the high-resolution x-ray computer tomography (Micro CT) with the 2D speckle photography technique developed by one of us (Chiang), we recently proposed a new 3D strain analysis technique called Digital Volumetric Speckle Photography (DVSP). The elements of DVSP technique are as follows. A reference volumetric image of the specimen is recorded by a Micro-CT scan and stored as a reference. Under load the deformed CT image of the specimen is also recorded. Both volume images are divided into subimages of certain voxel arrays. Each corresponding pair of the subimages are ‘compared’ via a two-step 3D Fourier Transform analysis. The result is a 3D map of displacement vectors representing the collective displacement experienced by all the speckles within the subset of voxels. Strain distribution of the entire specimen can then be calculated using appropriate displacement strain relations. Application of this technique to strain mapping of red sandstone and composite are presented.

High-resolution X-ray computed tomography of through silicon vias for RF MEMS integrated passive device applications

This paper presents our exploration of microfocus and high-resolution X-ray computed tomography (CT) on open high-aspect ratio through Silicon via (TSV) test structures, the interior wall covered with a ~10μm thick conformal Cu plating, using state-of-the-art and commercially available X-ray systems. Goal of our research is to better understand the physical failure mechanisms of defective open TSVs, in order to further improve the yield of TSV production for integrated passive devices (IPD) to be used in radio frequency microelectromechanical system (RF MEMS) applications.Micrometer-sized defects were non-destructively identified in some of the open TSVs (i.e. Cu plating thickness deviations, incomplete plating and large voids) using microfocus X-ray CT, which were then verified by destructive mechanical cross-sectioning. With high-resolution X-ray CT, which has almost an order of magnitude better resolution, (sub) micron-sized defects in TSVs were directly non-destructively identified and localized, without the need for further destructive inspection techniques for confirmation. The Cu plating thickness variations, in TSVs all connected to a large-area redistribution layer, were found to be design related; based on these failure analysis findings, a new electroplating procedure has been established.

Conservation studies of cultural heritage: X-ray imaging of dynamic processes in building materials

High-resolution X-ray computed tomography (HRXCT) is a 3 D -imaging and analysis technique frequently used for the investigation of internal structures of a large variety of objects, including building materials. The 3 D information is important for the characterisation of internal dynamic processes ( e.g ., water and salt migration, the influence of temperature and/or relative humidity changes) in natural stone, mortars, bricks and concrete. One of the main advantages of HRXCT is the fact that it is a non-destructive characterization technique, which allows 3 D monitoring of internal structural changes at resolutions in the (sub)micrometre scale. Because of its non-destructive nature, it is possible to measure changes in porosity, evolution of micro-cracks, crystallization of salts and migration paths of liquids in the same rock sample over a specific time period. Driven by the technological and computational progress, the technique is continuously growing as an analysis tool in the Geosciences and is becoming an important method in the field of Cultural Heritage. In this manuscript, a short summary of the principle, the advantages and limitations of X-ray computed tomography are presented. In addition, an overview of some current applications of imaging dynamic processes (such as liquid migration, artificial stone weathering and treatment) is provided by means of HRXCT. This is demonstrated in studies related to conservation of Cultural Heritage.

Reidentification of avian embryonic remains from the cretaceous of mongolia.

Embryonic remains within a small (4.75 by 2.23 cm) egg from the Late Cretaceous, Mongolia are here re-described. High-resolution X-ray computed tomography (HRCT) was used to digitally prepare and describe the enclosed embryonic bones. The egg, IGM (Mongolian Institute for Geology, Ulaanbaatar) 100/2010, with a three-part shell microstructure, was originally assigned to Neoceratopsia implying extensive homoplasy among eggshell characters across Dinosauria. Re-examination finds the forelimb significantly longer than the hindlimbs, proportions suggesting an avian identification. Additional, postcranial apomorphies (strut-like coracoid, cranially located humeral condyles, olecranon fossa, slender radius relative to the ulna, trochanteric crest on the femur, and ulna longer than the humerus) identify the embryo as avian. Presence of a dorsal coracoid fossa and a craniocaudally compressed distal humerus with a strongly angled distal margin support a diagnosis of IGM 100/2010 as an enantiornithine. Re-identification eliminates the implied homoplasy of this tri-laminate eggshell structure, and instead associates enantiornithine birds with eggshell microstructure composed of a mammillary, squamatic, and external zones. Posture of the embryo follows that of other theropods with fore- and hindlimbs folded parallel to the vertebral column and the elbow pointing caudally just dorsal to the knees. The size of the egg and embryo of IGM 100/2010 is similar to the two other Mongolian enantiornithine eggs. Well-ossified skeletons, as in this specimen, characterize all known enantiornithine embryos suggesting precocial hatchlings, comparing closely to late stage embryos of modern precocial birds that are both flight- and run-capable upon hatching. Extensive ossification in enantiornithine embryos may contribute to their relatively abundant representation in the fossil record. Neoceratopsian eggs remain unrecognized in the fossil record.

The application of high resolution X-ray computed tomography on naturally deformed rock salt: Multi-scale investigations of the structural inventory

X-ray computed tomography (CT) represents a useful technique providing new perspectives and insights for the structural investigation of naturally-deformed rock salt. Several samples of Permian rock salt from Gorleben, Asse and Teutschenthal (Germany) were investigated by exploiting the non-destructive nature of μCT and nCT techniques particularly for salt rocks. CT imaging enabled the visualization and quantification of anhydrite impurities, pore space and fluid phases located along grain-boundaries or trapped as intracrystalline inclusions. Disseminated grains and aggregates of anhydrite in rock salt of the Gorleben salt dome have been visualized and quantified by μCT for the first time in order to portray their spatial occurrence. The visualization of anhydrite aggregates and pore space shows no correlation between their spatial distributions. This independence excludes the anhydrite to be responsible for elevated porosity (0.87 ± 0.07 vol.-%). High-resolution nCT scans (≤1 μm voxel size) of single intracrystalline and grain-boundary fluid inclusions from Gorleben and Asse rock salt allowed the visualization and quantification of their various phase components. A major achievement is the detailed description of the morphology and shape of the fluid inclusions and of their phase components, which has not been conducted in rock salt research by high-resolution X-ray CT imaging before.

Evaluation of a combined HRXCT/EBSD method for detecting epitaxial nucleation of garnet porphyroblasts

The combination of high-resolution X-ray computed tomography (HRXCT) with electron backscattered diffraction (EBSD) analysis has the potential to reveal evidence for epitaxial nucleation of garnet porphyroblasts containing an included fabric. HRXCT measures the fabric orientation near the inferred nucleation site at the crystal centre, whereas EBSD establishes the crystallographic orientation of the porphyroblast relative to the attitude of the included fabric. Using the orientation of the central fabric as a proxy for the attitudes of the basal planes of micas on which the garnet may have nucleated, one can determine if low-index planes in garnet—(100), (110), or (111)—are parallel to (001) of mica, which would correspond to known epitaxial relationships between the two minerals. We test the feasibility of this approach with a set of exploratory measurements for six garnet porphyroblasts from Passo del Sole (Switzerland) and five from the Nevado Filabride Complex (Spain); we also report unsuccessful attempts at such measurements in rocks from Harpswell Neck (USA). The results do not deviate appreciably from those expected of a set of measurements drawn from a parent population with a random distribution of orientations. However, considering the size of the present measurement uncertainties in relation to the precision required to recognize an epitaxial relationship unambiguously, it is not possible in this data set to exclude epitaxy as a nucleation mechanism. The principal limitation to this approach is the need for high precision in determining the attitude of the included fabric at the site of nucleation, which depends largely upon the choice of suitable samples. Crystals ideal for such studies would contain a non-crenulated, planar (not helicitic) foliation, defined by numerous small, well-aligned inclusions. With careful sample selection, this approach could be a viable technique for evaluating the prevalence in nature of epitaxial nucleation of garnet porphyroblasts.

Investigation of cutting-induced damage in CMC bend bars

Ceramic matrix composites (“CMC”) with a strong fibre-matrix interface can be made damage-tolerant by introducing a highly porous matrix. Such composites typically have only a low interlaminar shear strength, which can potentially promote damage when preparing specimens or components by cutting. In order to investigate the damage induced by different cutting methods, waterjet cutting with and without abrasives, laser-cutting, wire eroding and cutoff grinding were used to cut plates of two different CMCs with a matrix porosity up to 35 vol.-%. For each combination of cutting method and composite, the flexural and interlaminar shear strength of the resulting specimens was determined. Additionally, the integrity of the regions near the cut surfaces was investigated by high-resolution x-ray computer tomography. It could be shown that the geometrical quality of the cut is strongly affected by the cutting method employed. Laser cut and waterjet cut specimens showed damage and delaminations near the cut surface leading to a reduced interlaminar shear strength of short bend bars in extreme cases.

Measurement of fiber orientation distribution in injection-molded short-glass-fiber composites using X-ray computed tomography

Being able to measure the fiber orientation distribution in the injection-molded composite parts is of considerable importance, since the distribution locally affects the mechanical and physical properties of the final part such as its strength, impact toughness, internal stress, and fatigue properties. In this study, we experimentally measured the fiber orientations in two injection-molded specimens produced from 30wt% short-glass-fiber-reinforced polyamide 6 using plate-shaped cavities with and without a weld-line. The fiber orientation distributions were observed directly using a high-resolution three-dimensional (3D) X-ray computed tomography (CT) system XVA-160α. A simple method based on a series of X-ray CT images was developed to measure the orientation angles of the individual fibers. Further, precise 3D calculations of the fiber orientations related to the second-order orientation tensor components were performed to obtain a consistent description of the observed behavior. Consequently, this study explored a potential application of X-ray CT imaging, a novel and powerful technique for observing and measuring fiber orientation. Further, the software CIMP-PACK3DM was employed to analyze the resin flow in the mold cavity using the finite element method (FEM). The filling patterns of the injection-molded plates with and without a weld-line as determined using FEM were in good quantitative agreement with the X-ray CT imaging analysis results. It was found that the fiber 3D orientation distributions of the injection-molded plates with and without a weld-line could be obtained with precision by combining the high-resolution 3D X-ray CT system XVA-160α with the resin flow analysis software CIMP-PACK3DM using FEM.