Synchrotron Radiation X-ray Micro-computed Tomography Research Articles

Assessment of soil aggregate pore structure after 8 years of cultivation from the parent material of a Mollisol

Soil erosion exposes the underlying parent material (PM) to the surface and an appropriate soil restoration approach is required to maintain soil quality. However, the current knowledge on soil restoration (e.g., improvement of soil aggregate structure) is mainly obtained from studies on well-developed soils. It remains unclear how aggregate pore structure of soils can be improved following different agricultural practices during the early stage of pedogenesis. The present study quantified the effects of 8 years of different agricultural practices (land use types, mineral fertilizers, and different amounts of organic inputs) on the aggregate stability, aggregate pore morphology, and surface properties of a topsoil (0–20 cm) and compared the findings with those of a prior PM and a long-cultivated Mollisol (MO). The results showed that clay content and the specific surface area of soil aggregates decreased, while soil organic carbon, aggregate stability, and surface fragment structure increased for all treatments as compared to those for the PM. Mineral fertilization alone did not increase aggregate stability; however, the combination of mineral and organic fertilization increased aggregate stability by 117%. Compared to the PM, the treated soils showed an increase in porosity as determined by synchrotron radiation X-ray micro-computed tomography (SR-µCT). Compared to naturally restored grasslands, the soil under crop rotation with tillage showed a decrease in pore roundness by 15%; however, supplementation with a large amount of organic input during cultivation increased pore roundness. The principal component analysis using all the indicators showed that the soil structure after 8-year cultivation was not comparable to that of the well-developed MO. Our results revealed the development of PM structure under various agricultural practices and highlighted the co-interaction effects of mineral fertilizers and organic inputs on the properties of soil aggregates during the early stage of pedogenesis.

In situ X-ray tomography of fracture behaviour in low-porosity L-PBF AlSi10Mg alloy with laser shock peening

ABSTRACT In this study, we employed a novel hybrid AM process, in which periodic laser shock peening (LSP) treatments were added to the standard laser powder bed fusion (L-PBF) process, for fabricating the AlSi10Mg alloy. As a result, the porosity of the alloy was reduced by approximately 90%. To monitor damage evolution, we conducted in situ tensile tests using high-resolution synchrotron radiation X-ray micro-computed tomography. The results indicate that in the LSP-treated L-PBF AlSi10Mg alloy, with a porosity of around 0.05%, the plasticity of vertical tensile samples significantly increases, and the fracture strain closely resembles that of the horizontal sample. The reduction in porosity results in increased spacing between adjacent defects, which decreases the interaction between defects. Consequently, the rapid fracture caused by the merge of large defects is prevented. Notably, micro-cracks observed in the vertical samples before tensile fracture primarily originates at the molten pool boundaries rather than from defects.

The role of internal defects on anisotropic tensile failure of L-PBF AlSi10Mg alloys

This paper investigates the effects of defects on tensile failure of additive manufactured AlSi10Mg alloy focusing particularly on the role of large pancake shaped loss of fusion (LOF) defects lying perpendicular to the build direction (BD). Time-lapse in situ synchrotron radiation X-ray micro-computed tomography during straining reveals how, when tested parallel to the BD, the LOF defects extend laterally with straining connecting to other defects and giving rise to low plasticity and an essentially brittle failure mode. When they are aligned edge-on to the straining direction, failure is characterised by a ductile cup-cone failure with significant elongation of the defects axially and extensive necking prior to failure. The soft fish-scale melt pool boundaries were also found to affect the fracture path. These results highlight the anisotropic effect of loss of fusion defects in controlling tensile ductility and the need to minimize their size and aspect ratio. In cases where these cannot be fully eliminated the component should be fabricated such that the BD is not aligned with the dominant in-service loading direction.

Morphology of Palaeospondylus shows affinity to tetrapod ancestors.

Palaeospondylus gunni, from the Middle Devonian period, is one of the most enigmatic fossil vertebrates, and its phylogenetic position has remained unclear since its discovery in Scotland in 1890(ref.1). The fossil's strange set of morphological features has made comparisons with known vertebrate morphotype diversity difficult. Here we use synchrotron radiation X-ray micro-computed tomography to show that Palaeospondylus was a sarcopterygian, and most probably a stem-tetrapod. The skeleton of Palaeospondylus consisted solely of endoskeletal elements in which hypertrophied chondrocyte cell lacunae, osteoids and a small fraction of perichondral bones developed. Despite the complete lack of teeth and dermal bones, the neurocranium of Palaeospondylus resembles those of stem-tetrapod Eusthenopteron2 and Panderichthys3, and phylogenetic analyses place Palaeospondylus in between them. Because the unique features of Palaeospondylus, such as the cartilaginous skeleton and the absence of paired appendages, are present in the larva of crown tetrapods, our study highlights an unanticipated heterochronic evolution at the root of tetrapods.

Characterization of oxidation behavior of 3D needled C/C composite by Synchrotron radiation X-ray micro-computed tomography

C/C composite has been considering to be used as structural components in the field of nuclear energy. However, the material will be subjected to rapid oxidation in the air. This paper presents the microstructure evolutions of a type of high density C/C composites at 550 °C in the air. Synchrotron radiation X-ray micro-computed tomography (SR-µCT, resolution: 0.65 µm) was used to characterize the microstructure in different oxidation stages. The results showed that the material was oxidized nearly homogeneous. The large pores played great rule in the oxidation behavior. The pores in the material started to extend quickly in initial stage and the number of pores and porosity were rapidly increased. Then the oxidation rate decreased as defective graphite in the composition exhausted. In addition, it also can be seen that SR-µCT is a perspective tool for microstructural characterization, especially structure evolution in 3D in the materials.

Synchrotron radiation analysis of root dentin: the roles of fluoride and calcium ions in hydroxyapatite remineralization.

Although the use of fluoride for root caries control is reported to be effective, the mechanism of maintaining hydroxyapatite is still unclear. This study elucidates the roles of fluoride in the recrystallization of hydroxyapatite, and the impact of calcium to maintain the abundance of hydroxyapatite on acid-challenged root dentin with a novel approach - using synchrotron radiation. Root dentin samples obtained from 40 extracted human premolars were subjected to pH challenge in combination with fluoride treatment. The effect of fluoride on hydroxyapatite regeneration on the root was investigated by using a range of fluoride concentrations (1000-5000 p.p.m.) and the EDTA-chelation technique in vitro. Synchrotron radiation X-ray micro-computed tomography and X-ray absorption spectroscopy were utilized to characterize the chemical composition of calcium species on the surface of prepared samples. The percentage of hydroxyapatite and the relative abundance of calcium species were subsequently compared between groups. The absence of calcium or fluoride prevented the complete remineralization of hydroxyapatite on the surface of early root caries. Different concentrations of fluoride exposure did not affect the relative abundance of hydroxyapatite. Sufficient potency of 1000 p.p.m. fluoride solution in promoting hydroxyapatite structural recrystallization on the root was demonstrated. Both calcium and fluoride ions are prerequisites in a caries-prone environment. Orchestration of F- and Ca2+ is required for structural homeostasis of root dentin during acid attack. Sustainable levels of F- and Ca2+ might thus be a strict requirement in the saliva of the population prone to root caries. Fluoride and calcium contribute to structural homeostasis of tooth root, highlighting that routine fluoride use in combination with calcium replenishment is recommended for maintaining dental health. This study also demonstrates that utilization of synchrotron radiation could provide a promising experimental platform for laboratory investigation especially in the dental material research field.

Bridging the structure gap between pellets in artificial dissolution media and in gastro-intestinal tract in rats

Changes in structure of oral solid dosage forms (OSDF) elementally determine the drug release and its therapeutic effects. In this research, synchrotron radiation X-ray micro-computed tomography was utilized to visualize the 3D structure of enteric coated pellets recovered from the gastrointestinal tract of rats. The structures of pellets in solid state and in vitro compendium media were measured. Pellets in vivo underwent morphological and structural changes which differed significantly from those in vitro compendium media. Thus, optimizations of the dissolution media were performed to mimic the appropriate in vivo conditions by introducing pepsin and glass microspheres in media. The sphericity, pellet volume, pore volume and porosity of the in vivo esomeprazole magnesium pellets in stomach for 2 h were recorded 0.47, 1.55 × 108 μm3, 0.44 × 108 μm3 and 27.6%, respectively. After adding pepsin and glass microspheres, the above parameters in vitro reached to 0.44, 1.64 × 108 μm3, 0.38 × 108 μm3 and 23.0%, respectively. Omeprazole magnesium pellets behaved similarly. The structural features of pellets between in vitro media and in vivo condition were bridged successfully in terms of 3D structures to ensure better design, characterization and quality control of advanced OSDF.

Deformation mechanisms and mechanical performances of architected mechanical metamaterials with gyroid topologies: Synchrotron X-ray radiation in-situ compression experiments and 3D image based finite element analysis

Synchrotron radiation X-ray micro-computed tomography (SR-μCT) is a robust non-destructive 3D imaging technique that has been widely used to characterize defects in advanced materials and structures, which demonstrates great advantages for defects characterizations and microstructures evolution process investigations of mechanical metamaterials at micro- and nano-scales. In this study, the internal features and damage evolution of the periodic architected mechanical metamaterials manufactured with projection micro litho stereo exposure (PμLSE) are investigated by combining SR-μCT 3D imaging techniques and in-situ compression experiments. The results show that the failure process of periodic architected mechanical metamaterials under compression loading is characterized by the curved surface fracture and curved surface buckling through the damage evolution process. Afterwards, reconstructed geometrical model based on SR-μCT 3D tomography images is proposed to analyze the relationship between the manufactured sample and the mechanical behavior, and the in-situ experiments and numerical simulation results were compared for verification.

Defect evolution during high temperature tension-tension fatigue of SLM AISi10Mg alloy by synchrotron tomography

Lack of fusion defects and porosity are inevitable characteristics of additive manufacturing and these are expected to play a key role in determining fatigue life and fatigue failure when excluding the influence of inhomogeneous microstructures. This work followed damage accumulation under tension-tension cyclic loading at 250 °C in situ by time-lapse synchrotron radiation X-ray micro-computed tomography (SR-μCT) for AlSi10Mg test-pieces, produced by selective laser melting (SLM) over their complete fatigue lives (ranging from 180 to 38,000 cycles). These samples were found to accumulate widespread plastic strain each cycle in common with ultra-low cycle fatigue (UCLF) at low levels of triaxial constraint. The defects were found to elongate plastically at a rate approximately 10 times larger than their growth rate laterally. This elongation behaviour at room and elevated temperature fatigue is proportional to the accumulated longitudinal strain increment each cycle. Rotation under the influence of shear is also observed for those defects close to the surface of samples. Some defect coalescence was observed, but final failure was found to be associated with the nucleation of a high density of secondary microvoids (occurring at eutectic Si platelets) that form just prior to failure and link up by microvoid coalescence. These steps may take up approximate 90% of the fatigue life. The final stage of cyclic plasticity occurs when the longitudinal strain exceeds ~ 0.9. Our results are in line with previous models of strain accumulation and defect growth under ULCF conditions.

Micro and nanolattice fabrication using projection micro litho stereo exposure additive manufacturing techniques and synchrotron X-ray 3D imaging-based defect characterization

Synchrotron radiation X-ray micro-computed tomography (SR-µCT) is a 3D imaging technique that is widely employed for the characterization of defects in advanced materials and structures. In this study, we characterize several typical defects in octettruss and re-entrant 3D lattice structures by using SR-µCT. The 3D micro-lattice structures are manufactured using projection micro litho stereo exposure (PµLSE) additive manufacturing technology. The as-fabricated 3D lattice samples are characterized using optical microscopy, and subsequently, by SR-µCT. Further more, a statistical analysis is performed to characterize the surface roughness and internal defects qualitatively, whereby the statistical geometrical parameters of struts along different directions and strut joints are analyzed and classified. Consequently, several typical defects are identified: (1) holes at the joints of the strut and irregular diameter deviations of the strut in the octet-truss lattice structure; (2) irregular diameter variations, bulges, dislocations, grooves, accumulations, and torsion in the re-entrant lattice structure. All of these defects are related to the building direction, the weight of the structure, bubbles, dust, and impurities during the PµLSE additive manufacturing process.

Gamma-irradiation-induced micro-structural variations in flame-retardant polyurethane foam using synchrotron X-ray micro-tomography.

Flame-retardant polyurethane foams are potential packing materials for the transport casks of highly active nuclear materials for shock absorption and insulation purposes. Exposure of high doses of gamma radiation causes cross-linking and chain sectioning of macromolecules in this polymer foam, which leads to reorganization of their cellular microstructure and thereby variations in physico-mechanical properties. In this study, in-house-developed flame-retardant rigid polyurethane foam samples were exposed to gamma irradiation doses in the 0-20 kGy range and synchrotron radiation X-ray micro-computed tomography (SR-µCT) imaging was employed for the analysis of radiation-induced morphological variations in their cellular microstructure. Qualitative and quantitative analysis of SR-µCT images has revealed significant variations in the average cell size, shape, wall thickness, orientations and spatial anisotropy of the cellular microstructure in polyurethane foam.

Consolidation of building materials with a phosphate-based treatment: Effects on the microstructure and on the 3D pore network

Inorganic-mineral treatments are commonly applied to decayed stone substrates in order to slow down the decay processes, through the partial transformation of the original stone material into newly-formed crystalline phases. The purpose of this study is to explore the effects induced by a promising consolidating treatment based on diammonium hydrogenphosphate (DAP) solutions on Noto limestone, a porous carbonatic matrix used as ornamental stone in the south of Italy. The research findings, obtained combining water absorption by capillarity measurements, mercury intrusion porosimetry (MIP) and synchrotron radiation X-ray micro-computed tomography (SR-μCT), demonstrate that the DAP consolidation induces microstructural modifications of the stone in terms of porosity and pore size distribution, changing the capillarity absorption values and decreasing the sorptivity speed. This study paves the way to a deeper investigation of the effects induced by a wider range of conservation treatments to the 3D microstructural features of porous geomaterials, by using an innovative multi-scale approach.

Multi-dimensional visualization for the morphology of lubricant stearic acid particles and their distribution in tablets

The shapes of particles and their distribution in tablets, controlled by pretreatment and tableting process, determine the pharmaceutical performance of excipient like lubricant. This study aims to provide deeper insights to the relationship of the morphology and spatial distribution of stearic acid (SA) with the lubrication efficiency, as well as the resulting tablet property. Unmodified SA particles as flat sheet-like particles were firstly reprocessed by emulsification in hot water to obtain the reprocessed SA particles with spherical morphology. The three-dimensional (3D) information of SA particles in tablets was detected by a quantitative and non-invasive 3D structure elucidation technique, namely, synchrotron radiation X-ray micro-computed tomography (SR-µCT). SA particles in glipizide tablets prepared by using unmodified SA (GUT), reprocessed SA (GRT), as well as reference listed drug (RLD) of glipizide tablets were analyzed by SR-µCT. The results showed that the reprocessed SA with better flowability contributed to similarity of breaking forces between that of GRT and RLD. SA particles in GRT were very similar to those in RLD with uniform morphology and particle size, while SA particles in GUT were not evenly distributed. These findings not only demonstrated the feasibility of SR-µCT as a new method in revealing the morphology and spatial distribution of excipient in drug delivery system, but also deepened insights of solid dosage form design into a new scale by powder engineering.

Homogenization of cortical bone reveals that the organization and shape of pores marginally affect elasticity.

With ageing and various diseases, the vascular pore volume fraction (porosity) in cortical bone increases, and the morphology of the pore network is altered. Cortical bone elasticity is known to decrease with increasing porosity, but the effect of the microstructure is largely unknown, while it has been thoroughly studied for trabecular bone. Also, popular micromechanical models have disregarded several micro-architectural features, idealizing pores as cylinders aligned with the axis of the diaphysis. The aim of this paper is to quantify the relative effects on cortical bone anisotropic elasticity of porosity and other descriptors of the pore network micro-architecture associated with pore number, size and shape. The five stiffness constants of bone assumed to be a transversely isotropic material were measured with resonant ultrasound spectroscopy in 55 specimens from the femoral diaphysis of 29 donors. The pore network, imaged with synchrotron radiation X-ray micro-computed tomography, was used to derive the pore descriptors and to build a homogenization model using the fast Fourier transform (FFT) method. The model was calibrated using experimental elasticity. A detailed analysis of the computed effective elasticity revealed in particular that porosity explains most of the variations of the five stiffness constants and that the effects of other micro-architectural features are small compared to usual experimental errors. We also have evidence that modelling the pore network as an ensemble of cylinders yields biased elasticity values compared to predictions based on the real micro-architecture. The FFT homogenization method is shown to be particularly efficient to model cortical bone.

Optimization of taste-masking on ibuprofen microspheres with selected structure features

The microsphere was a primary particulate system for taste-masking with unique structural features defined by production process. In this article, ibuprofen lipid microspheres of octadecanol and glycerin monostearate were prepared to mask the undesirable taste of ibuprofen via three kinds of spray congealing processes, namely, air-cooling, water-cooling and citric acid solution-cooling. The stereoscopic and internal structures of ibuprofen microspheres were quantitatively analyzed by synchrotron radiation X-ray micro-computed tomography (SR-µCT) to establish the relationship between the preparation process and microsphere architectures. It was found that the microstructure and morphology of the microspheres were significantly influenced by preparation processes as the primary factors to determine the release profiles and taste-masking effects. The sphericity of ibuprofen microspheres congealed in citric acid solution was higher than that of other two and its morphology was more regular than that being congealed in air or distilled water, and the contact angles between congealing media and melted ibuprofen in octadecanol and glycerin monostearate well demonstrated the structure differences among microspheres of three processes which controlled the release characteristics of the microspheres. The structure parameters like porosity, sphericity, and radius ratio from quantitative analysis were correlated well with drug release behaviors. The results demonstrated that the exterior morphology and internal structure of microspheres had considerable influences on the drug release behaviors as well as taste-masking effects.

Macroscopic anisotropic bone material properties in children with severe osteogenesis imperfecta

Children with severe osteogenesis imperfecta (OI) typically experience numerous fractures and progressive skeletal deformities over their lifetime. Recent studies proposed finite element models to assess fracture risk and guide clinicians in determining appropriate intervention in children with OI, but lack of appropriate material property inputs remains a challenge. This study aimed to characterize macroscopic anisotropic cortical bone material properties and investigate relationships with bone density measures in children with severe OI. Specimens were obtained from tibial or femoral shafts of nine children with severe OI and five controls. The specimens were cut into beams, characterized in bending, and imaged by synchrotron radiation X-ray micro-computed tomography. Longitudinal modulus of elasticity, yield strength, and bending strength were 32–65% lower in the OI group (p<0.001). Yield strain did not differ between groups (p≥0.197). In both groups, modulus and strength were lower in the transverse direction (p≤0.009), but anisotropy was less pronounced in the OI group. Intracortical vascular porosity was almost six times higher in the OI group (p<0.001), but no differences were observed in osteocyte lacunar porosity between the groups (p=0.086). Volumetric bone mineral density was lower in the OI group (p<0.001), but volumetric tissue mineral density was not (p=0.770). Longitudinal OI bone modulus and strength were correlated with volumetric bone mineral density (p≤0.024) but not volumetric tissue mineral density (p≥0.099). Results indicate that cortical bone in children with severe OI yields at the same strain as normal bone, and that their decreased bone material strength is associated with reduced volumetric bone mineral density. These results will enable the advancement of fracture risk assessment capability in children with severe OI.

Classification of microcrystalline celluloses via structures of individual particles measured by synchrotron radiation X-ray micro-computed tomography

Microcrystalline cellulose (MCC) is one of the most important excipients due to its outstanding binding and tableting properties. Owing to the absence of high resolution characterization techniques at the single particle scale, 3D (three dimension) microstructure of MCC and its effects on formulation performance remain unexamined. The aim of this work was to establish a methodology for single particles of MCC type 102 based on synchrotron radiation X-ray micro computed tomography (SR-μCT), principal component analysis (PCA) and partial least square discriminant analysis (PLSDA). Scanning electron microscopy, SR-μCT, powders properties together with tensile strength (TS), disintegration time (DT), Kawakita plots and force/displacement profiles of tablets were measured. PCA-PLSDA was applied to evaluate the structural classification of MCC particles on the basis of 2D and 3D SR-μCT derived images. The studied MCCs were found to differ in the TS, DT, Kawakita plot and force/displacement, while box ratio and Feret ratio had major influence on the principal components, but the angle of repose, bulk and tapped density did not exhibit significantly. These findings verified that different samples of MCCs from alternative suppliers have morphological diversity when assessed at the individual particle level, which could result into variation in powder properties and tableting performance.

Characterization of the pore structure and cementing substances of soil aggregates by a combination of synchrotron radiation X‐ray micro‐computed tomography and scanning electron microscopy

Pore characteristics and chemical composition of soil aggregates from two contrasting soil types (Fe‐rich Alisol and SOM‐rich Phaeozem) were determined with synchrotron radiation X‐ray micro‐computed tomography (SR‐mCT) and scanning electron microscopy coupled with an energy‐dispersive X‐ray spectrometer (SEM–EDS). Data fusion to combine 3‐D SR‐mCT images and 2‐D SEM–EDS data was used to establish the relation between pore structure and cementing substances within the soil aggregates. The SR‐mCT analysis showed that Phaeozem aggregates had greater total measurable porosity and were more anisotropic (DA) than Alisol aggregates. Soil aggregates of 5–10, 2–5 and 0.5–2 mm diameter were measured and found to have a similar pore‐size distribution (PSD) across a range of pore sizes for the Alisol, but not for the Phaeozem. The SEM–EDS mapping revealed that Fe‐rich areas in Alisol aggregates were connected, whereas the carbon‐rich areas in Phaeozem aggregates were isolated. Wavelet analysis suggested that the Alisol aggregates might have been formed by global interactions among microaggregates and iron oxides, whereas the Phaeozem aggregates were formed by localized interactions among microaggregates and carbon, the main cementing agent. The heatmap analysis showed that iron oxide not only acts as a binding agent in Alisol aggregates, but also affects the pore size in addition to the pore shapes, whereas carbon functions only as a binding agent and has little effect on pore structure of the Phaeozem aggregates. The combination of SR‐mCT and SEM–EDS techniques provides a powerful tool for quantifying the pore characteristics of soil aggregates and investigating the interactions between the pore structure and cementing substances within the aggregates.HighlightsThe effects of different cementing substances on the pore structure of Fe‐rich and SOM‐rich soil aggregates. A multi‐scale analysis and data fusion method were applied to data from synchrotron imaging and SEM. Iron oxides affected only the pore structure of the Fe‐rich soil aggregates. The data fusion method has potential for understanding the key features of soil at the aggregate scale.

Non-destructive analysis of in situ ammonoid jaws by synchrotron radiation X-ray micro-computed tomography

Non-destructive analysis of in situ ammonoid jaws by synchrotron radiation X-ray micro-computed tomography

Bone dynamics in the upward direction after a maxillary sinus floor elevation procedure: serial segmentation using synchrotron radiation micro-computed tomography.

ObjectiveMaxillary sinus floor augmentation has been shown to be the most predictable surgical technique for enhancing the bone volume in the posterior area of the maxilla. The purpose of this study was to analyze the serial slice image segmentation of newly formed bone and bone substitutes after sinus floor elevation using synchrotron radiation X-ray micro-computed tomography (SR-μCT).Materials and methodsBone biopsy specimens were collected after 6 months of sinus floor augmentation. From the six bone biopsy specimens, the cross-sectional images at every 8 μm along the apical direction from the inferior border using serial segmentation from three-dimensional reconstructed X-ray images were analyzed. The amount of new bone and bone substitutes were measured at each slicing image (300–430 images per specimen).ResultsThe bone dynamics between the new bone and bone substitutes along the inferior–superior direction in humans after maxillary sinus floor elevation (MSFE) were analyzed using the whole sample region. Although these observations suggest that the specimens are structurally inhomogeneous, sinus floor elevation was confirmed to be a reliable surgical procedure for increasing the amount of bone.ConclusionSR-μCT is highly effective for obtaining high-resolution images. An analysis of biological specimens using SR-μCT is quite reliable and this technique will be an important tool in the wide field of tissue engineering.