High-resolution X-ray Computed Tomography Research Articles

Contact area analysis of an asphalt-concrete boundary layer with X-ray computed tomography imaging

This study focusses on the bond between asphalt and concrete. The bond is a decisive factor for the transfer of traffic loads. A lack of bond between the layers can quickly reduce the load-bearing behavior and thus lead to pavement failure. In the literature, the bond between asphalt pavements and concrete substrates is usually analyzed using mechanical test methods. With mechanical test methods, the effects of interlocking, glue adhesion and friction, which have an effect at the layer boundary, are not considered individually. Based on previous findings, the aim of this study is to carry out a precise analysis of the bonding at the layer interface between concrete and asphalt using bitumen emulsion by means of measurements with a high-resolution X-ray computer tomography (CT). To determine the effect of the surface texture of the substrate, the investigations were carried out on milled and smooth surface textures. In addition to the variation of the substrate profiles, the influence of the application quantity of the bitumen emulsions C40 B5-S and C60 BP4-S was analyzed by spraying quantities of 90 g/m² and 180 g/m² bitumen after breaking. A newly developed method was used to determine the effective degree of gluing at the layer boundary, which allowed the bonding efficiency to be determined. The results of the calculated degree of gluing for the individual variants show that the highest degree of gluing of 61.94% is achieved with the smooth texture variant and high application quantity of bitumen emulsion. The lowest degree of gluing of 17.01% was achieved with the milled texture variant without the application of bitumen emulsion. Overall, the results showed that the degree of gluing was increased for both surface textures by applying the bitumen emulsion. Compared to the smooth texture, the milled textures exhibit a lower degree of gluing for both bitumen quantities, which could be explained by the distribution of the bitumen emulsions on the substrate profiles.

Cranial anatomy of the "round-headed" Amphisbaenian Zygaspis quadrifrons (Squamata, Amphisbaenia) based on high-resolution x-ray computed tomography.

Amphisbaenians are a poorly understood clade of fossorial lizards. Because of their derived anatomy and relative scarcity, the systematics of the clade and its placement within squamates has long been controversial. Traditional approaches grouped species into four assemblages according to burrowing behavior and cranial morphology, resulting in the recognition of "shovel-headed," "round-headed," "keel-headed," and "spade-headed" morphotypes. Recent phylogenetic analyses do not support the monophyly of the taxa that share those morphotypes. Detailed analyses of cranial osteology were previously accomplished using high-resolution x-ray computed tomography (HRXCT) for the "shovel-headed" Rhineura hatcherii (Rhineruidae) and the "spade-headed" Diplometopon zarudnyi (Trogonophidae). A detailed description of the "round-headed" Amphisbaena alba was previously completed based upon traditional "dry" skeletal specimens. Seven species of the "round-headed" Blanus (Blanidae) were also analyzed using HRXCT. The goal of that project was a comparative analysis of all extant species of Blanus rather than a detailed, bone-by-bone description of one species, but certainly is useful for comparison with another "round-headed" taxon. The "round-headed" morphotype is by far the most common among amphisbaenians and is much in need of further documentation. We use HRXCT imagery to provide additional data about the disparity in cranial morphology among amphisbaenians. Those data allow us to provide another detailed description of a "round-headed" amphisbaenian, the poorly known southern African species Zygaspis quadrifrons. HRXCT is ideal for this relatively rare and diminutive species. We are able to visualize and describe a detailed reconstruction of the entire skull as well as individual cranial elements. Comparisons with other species that were described in similar detail-D. zarudnyi, Spathorhynchus fossorium, R. hatcherii, and A. alba-and to a lesser degree with Blanus, reveal a complex mosaic of morphological features of the skull in Zygaspis. Preliminary data suggest that intraspecific variation is present within Z. quadrifrons, and interspecific variation among other species of Zygaspis may be sufficient for species-level recognition based on cranial osteology. Our description is, therefore, also intended to serve as a baseline for comparative analysis of other specimens of Z. quadrifrons and of other species within the genus.

Percolation of sulfide liquid through semi-consolidated silicate cumulates: Textural evidence from breccia ores in the Kalatongke Cu-Ni sulfide deposit, NW China

The Kalatongke Cu-Ni sulfide deposit is an important Ni producer in China and contains abundant breccia ores which are especial in that the silicate fragments enclosed within the sulfide matrix have similar mineral assemblages to the host norite body. Using a combination of microbeam X-ray fluorescence (μ-XRF) and Tescan integrated mineral analyzer (TIMA) mapping, and 3D morphology by high-resolution X-ray computed tomography (HRXCT), we show that the breccia ores are of magmatic origin, as there are no foliation and fabrics of silicate fragments in the sulfide matrix. The 3D morphology of the breccia ores reveal that large silicate fragments are continually connected, whereas small silicate fragments are sub-spheric to spheric with sphericity values close to 1 and commonly rimed by magnetite. All these textures can be explained by that semi-consolidated silicate cumulates were percolated by sulfide liquid from replenished sulfide-bearing magma pulse in the magma conduits. The sulfide liquid from the replenished magma may have accumulated to form a sulfide pool overlying the semi-consolidated cumulates. Due to its high density, the sulfide liquid in the pool could percolate downward and infill the fracture network in the semi-consolidated cumulates, forming sulfide networks in the breccia ores. The sulfide liquid may also trap the interstitial, silicate melts on its way downward throughout the semi-consolidated cumulates, forming small sub-spheric to spheric silicate fragments in the breccia ores. Such a process revealed by the texture of breccia ores indicates that replenished magma pulses and degrees of percolation of sulfide liquid through semi-consolidated cumulates essentially control the distribution of ore bodies in the Kalatongke deposit.

Multiscale modeling of particle-induced damage in AA7075 aluminum sheet at large plastic strains

Large plastic deformation and ductile damage in precipitation hardening aluminum alloy AA7075 is driven by plastic flow in the vicinity of particles as well as fracture and decohesion of second phase particles embedded in the matrix. The current work investigates the deformation and damage characteristics of Fe-rich intermetallic particles, and η and θ precipitates in AA7075-O sheet. A multiscale model simulation methodology is presented and applied to analyze large-scale plastic deformation and damage characteristics. The methodology utilizes nanoscale molecular dynamics simulation to obtain matrix-particle interface strength properties and Weibull statistics to capture experimental fracture characteristics of particles. The above sub-models are incorporated within a 2-D real particle microstructure-based finite element model to conduct a comparative study of the roles of decohesion and fracture in the development of plasticity and void damage in AA7075-O sheet. In addition, in-situ SEM uniaxial tensile tests are carried out to assess the effectiveness of the simulation methodology and to compare the experimental and numerical results. Post-test high resolution X-ray computed tomography (HR-XCT) was also carried out to qualitatively observe particle-induced voiding in the material. The numerical methodology is shown to capture well the experimental trends in damage evolution of the individual particles. It is observed that particle damage is a function of inherent particle properties, their morphological features, and matrix strain localization characteristics. Larger-size Fe-rich particles are observed to undergo damage at an earlier stage, and consequently, affect the strain localization characteristics the most. In contrast, η precipitates are found to be most resistant to particle damage, followed by θ precipitates. Higher stresses inside strain localization bands, caused increased void damage initiation and growth of η and θ precipitates. Overall, particle fracture is observed to be marginally higher compared to particle decohesion, irrespective of the particle type.

Geochemical changes in Eastern Canadian lake sediment cores spanning the last ∼150 years highlight a relative shift towards increased metals and erosive materials

Since the start of the Industrial Revolution, the chemical cycling of numerous elements has been fundamentally altered. Using 210Pb-dated sediment cores from 37 Eastern Canadian lakes situated in 4 ecozones, we quantified the geochemical change experienced across this region since ca. 1850 CE using high-resolution computed X-ray Tomography and micro-X-ray fluorescence (µ-XRF) ITRAX scanners. Independent calibrations of µ-XRF ITRAX intensities using ICP-MS and -AES found strong correlations for numerous elements. Using relative abundance measures and absolute concentration estimates, we observed that most of our study lakes recorded temporal enrichments of metals, with several sites exceeding Canadian sediment quality guidelines. Using principal component analysis, we identified that parameters commonly associated with erosion (strontium and titanium), organic matter (molybdenum incoherence to coherence scattering ratio), and metals (zinc and lead) were key variables structuring within and among-lake variation since ca. 1850 CE. Calcium was identified as an additional variable, particularly for lakes in the Mixedwood Plains (MWP) ecozone, which may be linked to catchment activities including land-use changes. Temporally, many lakes shifted towards greater accumulation of inorganic sediment, coeval with higher Pb and Zn concentrations, reaching maxima ca. 1970 CE before decreasing rapidly. These results suggest that most lakes in the region were subjected to environmental pollution but that controls on key atmospheric pollutants in North America were effective across a large part of the country.

A new species of the genus Liotyphlops Peters, 1881 (Serpentes, Anomalepididae) from Colombia and the synonymization of Liotyphlopsbeui (Amaral, 1924) with Liotyphlopsternetzii (Boulenger, 1896).

A new species of Liotyphlops Peters, 1881, Liotyphlopspalauophissp. nov., is described from the neighborhoods of Bogota, Colombia from a previous syntype of L.anops, and a lectotype is designated for the latter species. The new species is readily distinguished from congeners by having the frontal scale divided (vs single), and a central foramen in the parabasisphenoid (vs foramen absent). High-resolution x-ray computed tomography (HRXCT) was used to study and present data on the skull of the holotype of the new species, the lectotype of L.anops, and the holotype of L.ternetzii. Additionally, extensive study of skull characters and external morphology failed to find diagnostic characters to differentiate L.beui and L.ternetzii, and the former is here considered a junior synonym of L.ternetzii, which is also redescribed.

Gemstone Inclusion Study by 3D Raman-Mapping and High-Resolution X-ray Computed Tomography: The Case of Trapiche Emerald from Swat, Pakistan

Gemstones usually contain inclusions as the natural hallmark of their formation. Studies on inclusions may contribute to our understanding of the gem and better adapt to the gems and jewelry industry. In this study, we applied advanced 3D Raman mapping and high-resolution X-ray computed tomography (HRXCT) and conducted a thorough experiment on one emerald with a special trapiche pattern containing a colorless core, solid minerals, and fluids. Hematite and magnetite were identified as metallic minerals by the Raman spectrum. The hexagonal core is beryl, and the voids are primarily filled with CO2 and N2. HRXCT demonstrated a visualized distribution of these inclusions within the gem host by reconstructing a 3D illustration. Further calculation of the volume of inclusions regarding the host showed that the minerals take up 0.07%, void 0.03%, and the hexagonal core 8.25%. The combined application of Raman-Mapping and X-ray Micro Computed Tomography proved to be a very promising technique for tracing the gemstones by characterizing the unique inclusions (identification and morphology) within the gem host.

A flat petal as ancestral state for Ranunculaceae.

Ranunculaceae comprise ca. 2,500 species (ca. 55 genera) that display a broad range of floral diversity, particularly at the level of the perianth. Petals, when present, are often referred to as “elaborate” because they have a complex morphology. In addition, the petals usually produce and store nectar, which gives them a crucial functional role in the interaction with pollinators. Its morphological diversity and species richness make this family a particularly suitable model group for studying the evolution of complex morphologies. Our aims are (1) to reconstruct the ancestral form of the petal and evolutionary stages at the scale of Ranunculaceae, (2) to test the hypothesis that there are morphogenetic regions on the petal that are common to all species and that interspecific morphological diversity may be due to differences in the relative proportions of these regions during development. We scored and analyzed traits (descriptors) that characterize in detail the complexity of mature petal morphology in 32 genera. Furthermore, we described petal development using high resolution X-Ray computed tomography (HRX-CT) in six species with contrasting petal forms (Ficaria verna, Helleborus orientalis, Staphisagria picta, Aconitum napellus, Nigella damascena, Aquilegia vulgaris). Ancestral state reconstruction was performed using a robust and dated phylogeny of the family, allowing us to produce new hypotheses for petal evolution in Ranunculaceae. Our results suggest a flat ancestral petal with a short claw for the entire family and for the ancestors of all tribes except Adonideae. The elaborate petals that are present in different lineages have evolved independently, and similar morphologies are the result of convergent evolution.

A New Method to Visualize the Internal Morphology of Crude Drugs Using High-Resolution X-Ray Computed Tomography.

The microscopic test method (microscopic examination) used to identify crude drugs is a common method in the identification of the original plant source by determining the characteristics from a small sample quantity. However, in recent years, the number of examiners who are familiar with the microscopic examination technique has decreased. In recent years, high-resolution X-ray computed tomography (HRXCT) has been used to visualize the internal structure of plants. HRXCT scans an object using X-rays and enables visualization of the internal structure of the crude drug using a computer. Therefore, in this report, HRXCT was used to easily observe the internal morphology of crude drugs using the Ephedra Herb as an example. The same internal morphological characteristics were observed using both, microscopic examination and HRXCT methods. Image analysis using HRXCT did not require specific techniques, such as sectioning, and the same tissue could be observed from any orientation using a single scan. It afforded remarkable technical simplification and reduction in time to inspect the organization's characteristics. Therefore, image analysis using HRXCT is a useful method for crude drug identifications.

Comparison of two ancient Egyptian Middle Kingdom statuettes from the Museo Egizio of Torino through computed tomographic measurements

X-ray Computed Tomography (CT) has a significant role as investigation tool not only in medical and industrial applications, but also in cultural heritage studies. One of the main reasons for such broad adoption of this method is its non-destructive capability to investigate the inner structure of precious and unique artefacts that would instead be damaged by traditional sampling procedures. Ordinary X-ray radiography is limited and gives only 2D images, while high-resolution X-ray CT imaging gives non-invasive access to three-dimensional (3D) information. This article focuses on the comparison of micro-CT results obtained from the analysis of two ancient Egyptian wooden statuettes representing offering bearers. The artefacts belong to the collection of the Museo Egizio of Torino as part of the funerary assemblage of Minhotep, discovered in the Asyut necropolis. For the analysis, an upgraded version of the X-ray imaging apparatus located in the Centro Conservazione e Restauro “La Venaria Reale” (CCR) was used, in order to reach a higher final resolution than the one already present and used at CCR. Thanks to this investigation, much information on the artistic technique was obtained and it was possible to highlight differences and similarities in the technical features of the two statuettes, acquiring elements to understand the specific contribution of micro-tomography in studying the finds and hypothesizing a common production method.

Simulation of micro-crack initiation and propagation under repeated load in asphalt concrete using zero-thickness cohesive elements

The fracture resistance of asphalt materials under repeated traffic loads significantly influences the service life of asphalt pavements. The numerical simulation of asphalt materials based on a form of fracture mechanics is considered as an efficient way to model fracture damage. Unlike traditional fracture mechanics approaches assuming the existence of infinitely sharp crack tips leading to stress singularities preceding the crack tips, an alternative approach, called Cohesive Zone Modelling (CZM), is presented to model crack initiation and propagation. To make the CZM more consistent with reality and thus yield more reliable results, a heterogeneous model was developed to explicitly model the different material phases (aggregate and asphalt mastic) captured by X-ray Computed Tomography (CT) (with a resolution of 0.014 mm3). A Two-Dimensional (2D) Finite Element (FE) model was reconstructed; the model embedded zero-thickness cohesive elements both in asphalt mastic and at interfaces between mastic and aggregates, in conjunction with viscoelastic material properties. Crack paths in asphalt mixture samples at different deformation levels in the Indirect Tensile Fatigue Test (ITFT) were compared to simulation results. The 2D model was then applied to predict crack initiation and propagation at 25 ℃. It is found that high resolution X-ray CT applied on small-size samples is a suitable method to visualize detailed crack geometry of asphalt concrete and reconstruct realistic aggregate morphology for simulations. The 2D FEM developed can approximately model the whole cracking process. Based on the model, it is found that factors such as aggregate size and distance between aggregates can affect crack initiation. At 5 ℃ microcracks tend to initiate predominantly at aggregate-binder interfaces. At 25 ℃ microcracks tend to initiate and propagate within the mastic; as the microcracks propagate. At both temperatures, microcracks were observed develop continuously throughout the modelling fatigue process.

On Acquisition Parameters and Processing Techniques for Interparticle Contact Detection in Granular Packings Using Synchrotron Computed Tomography.

X-ray computed tomography (XCT) is regularly employed in geomechanics to non-destructively measure the solid and pore fractions of soil and rock from reconstructed 3D images. With the increasing availability of high-resolution XCT imaging systems, researchers now seek to measure microfabric parameters such as the number and area of interparticle contacts, which can then be used to inform soil behaviour modelling techniques. However, recent research has evidenced that conventional image processing methods consistently overestimate the number and area of interparticle contacts, mainly due to acquisition-driven image artefacts. The present study seeks to address this issue by systematically assessing the role of XCT acquisition parameters in the accurate detection of interparticle contacts. To this end, synchrotron XCT has been applied to a hexagonal close-packed arrangement of glass pellets with and without a prescribed separation between lattice layers. Different values for the number of projections, exposure time, and rotation range have been evaluated. Conventional global grey value thresholding and novel U-Net segmentation methods have been assessed, followed by local refinements at the presumptive contacts, as per recently proposed contact detection routines. The effect of the different acquisition set-ups and segmentation techniques on contact detection performance is presented and discussed, and optimised workflows are proposed.

Three-dimensional strain evaluation of short-fiber-reinforced natural rubber using micro X-ray computed tomography

The vibration damping appears as a macroscopic material property due to the energy dissipation caused by the plastic deformation of the microstructure in the material, but the detailed mechanism is still unknown. This study prepared a damping material based on natural rubber (NR) and investigated its deformation behavior with/without fiber-shaped particles using synchrotron X-ray computed tomography (CT). High-resolution submicron X-ray CT was performed to evaluate the local strain in the microstructure from feature points scattered inside the NR. When the strain distribution changed under stepwise tensile loading, the NR-alone material deformed uniformly at the microscale, whereas the fiber composite rubber deformed nonuniformly. Furthermore, the number and volume of voids increased significantly with the compounding of fiber particles, and their values continued to increase depending on the strain amplitude and the loss factor. Controlling of non-uniform local strain and void formation will enable the design of damping characteristics.

Characterizing the effects of laser control in laser powder bed fusion on near-surface pore formation via combined analysis of in-situ melt pool monitoring and X-ray computed tomography.

Near-surface or sub-surface pores are critical to the structural integrity of additively manufactured (AM) metal parts, especially in fatigue failure applications. However, their formation in laser powder bed fusion is not well-understood due to the complex processes happening near the surface, which are challenging to monitor. A lack of high-fidelity data hinders understanding of the process and its effects. It is not well-known that problems with laser control parameters such as galvanometer acceleration and laser power on/off delay can form near-surface pores in laser powder bed fusion (LPBF) AM processes, and we investigated the characteristics of these pores in this research. We also demonstrate the capabilities and processes of combined studies using in-situ melt pool images and ex-situ X-ray computed tomography (XCT) images. Using the National Institute of Standards and Technology (NIST) Additive Manufacturing Metrology Testbed (AMMT), varying laser control schemes were implemented while in-situ coaxial melt pool images were acquired during the build of Nickel superalloy parts. A combination of time-stepped digital commands, in-situ coaxial melt pool monitoring images (≈ 8 μm/pixel), and ex-situ high-resolution XCT images (≈ 3.63 μm/voxel) were demonstrated. Advanced image analysis methods were used to characterize the pores found in terms of size and shape distribution and spatial location. XCT images, in high correspondence to melt pool images, clearly show the effects of the laser control parameters. We present the complete analysis chain of AM command, in-situ melt pool imaging, ex-situ XCT acquisition, and image analysis. Possible near-surface pore formation mechanisms are explained through the comparative image analysis. The approach of compiling combined analyses based on time-stepped digital commands, in-situ monitoring results, and ex-situ XCT measurement through image analysis enables observation and categorization of the different near-surface pore formation mechanisms stemming from laser and scan control.

Orogenic gold ores in three-dimensions: A case study of distinct mineralization styles at the world-class Cuiabá deposit, Brazil, using high-resolution X-ray computed tomography on gold particles

Ore studies using conventional petrographic methods have an intrinsic limitation that spatial (three-dimensional, 3-D) distribution, orientation, shape and mineral associations have to be inferred by 2-D observations and measurements. Further, developing statistically significant data sets is particularly difficult for gold ores, given the fine grain size and low gold abundance even in high-grade ores. We use high-resolution X-ray computed tomography (HRXCT) and improved processing methods to provide 3-D data of ore textures and in-situ gold particles to discern mineralization styles and improve ore recovery. This is a case study of the Archean, world-class Cuiabá orogenic gold deposit in the Quadrilátero Ferrífero province, the largest underground mine in Brazil.Selected samples represent distinct mineralization styles at the Cuiabá mine: BIF-hosted ore from the Fonte Grande Sul (FGS) orebody, and gold-bearing quartz-carbonate veins hosted in a metamafic unit from the Veio de Quartzo (VQZ) orebody. This study characterizes shape, size, orientation and mineral associations of over 16,000 gold particles. Segmentation and quantitative measurements of gold particles are particularly challenging due to their small grain size. This issue is addressed using the recently formalized partial volume and blurring (PVB) method. Gold mineralization styles differ in 3-D textural and quantitative aspects including size and spatial distribution. Analysis of the VQZ sample shows that gold particles are mainly free in the quartz-carbonate matrix, with many particles in direct contact with a diverse sulfide mineral assemblage. Gold particles in the BIF-hosted FGS ore form bands in association with high pyrrhotite zones within iron carbonate-rich bands. PVB analysis show that the long axis of measured particles in both ore types ranges from ∼25 μm to 1.4 mm, with median values around 115 μm. Larger particles dominantly are sub-equant to prolate spheroids, with smaller particles appearing to be dominantly sub-equant to equant grains. The HRXCT data reveal that the kinematic processes affect gold shape and orientation and indicate the influence of deformation at the grain scale.

High-Resolution X-Ray Computed Tomography: A New Workflow for the Analysis of Xylogenesis and Intra-Seasonal Wood Biomass Production.

Understanding tree growth and carbon sequestration are of crucial interest to forecast the feedback of forests to climate change. To have a global understanding of the wood formation, it is necessary to develop new methodologies for xylogenesis measurements, valid across diverse wood structures and applicable to both angiosperms and gymnosperms. In this study, the authors present a new workflow to study xylogenesis using high-resolution X-ray computed tomography (HRXCT), which is generic and offers high potential for automatization. The HXRCT-based approach was benchmarked with the current classical approach (microtomy) on three tree species with contrasted wood anatomy (Pinus nigra, Fagus sylvatica, and Quercus robur). HRXCT proved to estimate the relevant xylogenesis parameters (timing, duration, and growth rates) across species with high accuracy. HRXCT showed to be an efficient avenue to investigate tree xylogenesis for a wide range of wood anatomies, structures, and species. HRXCT also showed its potential to provide quantification of intra-annual dynamics of biomass production through high-resolution 3D mapping of wood biomass within the forming growth ring.

MicroCT as a Useful Tool for Analysing the 3D Structure of Lichens and Quantifying Internal Cephalodia in Lobaria pulmonaria

High-resolution X-ray computer tomography (microCT) is a well-established technique to analyse three-dimensional microstructures in 3D non-destructive imaging. The non-destructive three-dimensional analysis of lichens is interesting for many reasons. The examination of hidden structural characteristics can, e.g., provide information on internal structural features (form and distribution of fungal-supporting tissue/hypha), gas-filled spaces within the thallus (important for gas exchange and, thus, physiological processes), or yield information on the symbiont composition within the lichen, e.g., the localisation and amount of additional cyanobacteria in cephalodia. Here, we present the possibilities and current limitations for applying conventional laboratory-based high-resolution X-ray computer tomography to analyse lichens. MicroCT allows the virtual 3D reconstruction of a sample from 2D X-ray projections and is helpful for the non-destructive analysis of structural characters or the symbiont composition of lichens. By means of a quantitative 3D image analysis, the volume of internal cephalodia is determined for Lobaria pulmonaria and the external cephalodia of Peltigera leucophlebia. Nevertheless, the need for higher-resolution tomography for more detailed studies is emphasised. Particular challenges are the large sizes of datasets to be analysed and the high variability of the lichen microstructures.

SULFUR DISPERSION QUANTITATIVE ANALYSIS IN ELASTOMERIC TIRE FORMULATIONS BY USING HIGH RESOLUTION X-RAY COMPUTED TOMOGRAPHY

ABSTRACT Good dispersion of compounded ingredients in a rubber formulation is important for mechanical performance. After mixing, certain materials can remain undispersed within the rubber matrix, which could lead to critical flaws, influencing performance according to the Griffith failure criteria. High resolution X-ray computed tomography (XCT) offers a unique opportunity to measure phase domain size and distributions. Fillers such as carbon black or silica can be differentiated from sulfur or zinc oxide, providing an opportunity to determine dispersion characteristics of the various phases. The XCT technique has become an important characterization tool for three-dimensional and higher dimension material science due to the availability of polychromatic micro-focus X-ray sources and efficient high spatial resolution detectors with superior scintillators. High resolution XCT provides very rich data quantifying mixing efficiency of particulates in a matrix, such as insoluble sulfur or silica particles in rubber. Imaging with X-rays provides attenuation, phase, or scattering contrast and will prove to be a critical method for evaluating the field of rubber crosslinking, considering realistic environments in situ. This paper highlights methodology development and validation and provides insight on the dispersion of polymeric (insoluble) sulfur in rubber formulations. Dispersion assessment is compared using three techniques: high resolution XCT, population survival analysis in tensile testing, and optical microscopy.

X-ray CT and porosity mapping to determine the effect of ‘Fuji’ apple morphological and microstructural properties on the incidence of CO2 induced internal browning

There is considerable variability in the distribution of porosity within a fruit, hence non-destructive methods to map porosity of the entire fruit are essential. The objective of this study was to use X-ray computed tomography (CT) to map the porosity of ‘Fuji’ apple and help determine the extent to which different fruit morphological and microstructural properties influence the susceptibility of the fruit to CO2 stress-induced internal browning (IB). X-ray CT based porosity mapping and high-resolution X-ray CT were used to determine porosity changes in fruit tissue following exposure to an atmosphere enriched with 50 % CO2 at room temperature (21 °C) for 3 d after harvest. Low-resolution X-ray CT scans enabled the construction of porosity maps for intact fruit based on a linear regression model and a juice scan which acted as a 0 % porosity reference. Short-term exposure of fruit to a high level of CO2 markedly induced IB in the core region of the fruit. Axial porosity profiles measured before the CO2 stress treatment showed that porosity along the axial plane was usually lower in fruit that developed IB. Larger sized fruit were more susceptible to the CO2 stress-induced IB disorder. The porosity in the IB affected fruit tissue declined from 8.6 to 5.4 % following the CO2 stress treatment. It is recommended to ensure that levels of CO2 and O2 in the controlled atmosphere (CA) storage environment are carefully controlled to minimize the risk of IB incidence.

Determination of the Filler Distribution in an Epoxy Molding Compound Using High-Resolution X-Ray Computed Tomography

In this article, the filler distribution in an epoxy molding compound (EMC), used in IC packaging, is studied across a wafer using high-resolution X-ray computed tomography (HR-XCT). It is widely assumed that the fillers are uniformly distributed across the wafer. However, it is demonstrated that the distribution of the filler deviates across the wafer and that filler sizes affect the distribution on edge and center of wafer too. Quantitative HR-XCT of the filler distribution provides accurate data for simulation. Based on this approach, the differences between the coefficient of thermal expansion (CTE) and Young's modulus values of the filler material for the center and edge of the wafer are explained. Furthermore, compression simulations are conducted by applying an XCT-based finite element method (FEM) model to understand the role of EMC for the mechanical behavior of advanced IC packages. These findings are validated by in situ and stand-alone compression experiments. The accurate simulation results demonstrate that the use of an XCT-based FEM model provides insight into the mechanical behavior of the EMC itself and, furthermore, of the whole IC package.