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In the manufacture of integrated circuits (ICs), copper is used primarily as the multilevel interconnect material, which is manufactured with a dual damascene technique utilizing chemical mechanical polishing (CMP) to planarize overburdened materials. However, there are many challenges for copper CMP technique to produce a surface with a superior planarity and local device surface finish with minimal dishing and erosion while achieving uniform copper blanket film under specific thickness. Considering these challenges, this study pioneered the development of a three-dimensional microstructural model for polishing pads, which is based on image processing algorithms to construct the porous feature structure of polishing pad in conjunction with generating a layer of surface asperities, allowing for an accurate assessment of the effect of downward pressure during CMP on the microstructure of polishing pads. Moreover, this study also develop the new calibration method based on finite element simulation method for determining the mechanism of material removal by abrasive particles as well as the passivation of thin copper blanket film in polishing slurry. Results of this study include not only investigations of the copper blanket wafer's surface roughness after CMP process but also the development of a new methodology of calibrating the material removal rates (MRRs) validated through comparison with CMP experiments. These findings can be further applied for developing CMP process model, and for advanced applications. [ABSTRACT FROM AUTHOR]

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-μCT). In situ formed 3D structures at different in vitro drug release states were characterized comprehensively. A distinct movement pattern of NaCl crystals from the push layer to the drug layer was observed, beneath the semi-permeable coating in the desiccated tablet samples. The 3D structures at different dissolution time revealed that the pushing upsurge in the bilayer osmotic pump tablet was directed via peripheral “roadways”. Typically, different regions of the osmotic front, infiltration region, and dormant region were classified in the push layer during the dissolution of drug from tablet samples. According to the observed 3D microstructures, a “subterranean river model” for the drug release mechanism has been defined to explain the drug release mechanism.

A novel protocol utilizing a phase-field model was used to process the reconstruction of a polycrystalline microstructure from synchrotron-based high-energy X-ray diffraction microscopy. This approach is an intuitive and standardized alternative to typical image processing routines. It preserves high-confidence regions by deploying a completeness-based mobility parameter in the phase-field model. Phase-field governing equations result in a space-filling grain map that adheres to the physics of the microstructure, i.e. , it penalizes high-energy grain shapes and configurations and promotes grain boundary (GB) smoothing. We quantify GB smoothing by measuring, in 2D, the circularity of interior grains and the tortuosity of individual GBs. Results are also presented in 3D. This post-processing protocol can be applied to any X-ray diffraction microscopy reconstruction that consists of a spatial map of grains and corresponding confidence values. Furthermore, it can be adapted to accommodate other types of microstructures, including those that are polyphase. [Display omitted] [ABSTRACT FROM AUTHOR]

Freestanding nanomembranes fabricated by lift-off technology have been widely utilized in microelectromechanical systems, soft electronics, and microrobotics. However, a conventional chemical etching strategy to eliminate nanomembrane adhesion often restricts material choice and compromises quality. Herein, we propose a nanomembrane-on-graphene strategy that leverages the weak van der Waals adhesion on graphene to achieve scalable and controllable release and 3D construction of nanomembranes. This fragile adhesion allows for precise delamination under stimulations, such as surface tension, thermal treatment, and mechanical bending. This strategy is compatible with various inorganic materials, including oxides, semiconductors, and metals, and allows for precise control of rolling and folding into 3D microstructures. Demonstrations include tubular microrobots with diverse locomotion and biodegradable nerve scaffolds based on facile delamination. Our nanomembrane-on-graphene strategy offers a versatile platform for the fabrication of functionalized microstructures.

• Multi-modal synchrotron µ-computed tomography (Sr-µCT) of neutron irradiated U-Mo. • Absorption and phase contrast Sr-µCT measured 3D porosity, swelling and composition. • A multilayered pore structure forms parallel to U-Mo/Zr interface at high-burnup. • Large interconnected and oriented pores form ∼5 µm from the U-Mo/Zr interface, which can lead to delamination. • Average local thickness of the Zr diffusion barrier was reduced by 53 %. The three-dimensional (3D) microstructure of neutron-irradiated uranium-10 wt.% molybdenum (U-10Mo) fuel with a burn-up of 9.8 × 1021 fissions/cm3 was characterized using a novel, multi-modal synchrotron micro-computed tomography approach combining propagation-based phase-contrast enhanced and absorption contrast techniques. The porosity development, porosity interconnectedness, swelling, composition, local thickness of the zirconium (Zr) diffusion barrier, and the influence of the fuel–cladding interaction on the local composition and pore morphology, were uniquely determined in 3D. Two cuboids were produced using a focused ion beam-scanning electron microscope at the Zr diffusion barrier–fuel interface and in the bulk fuel. The bulk fuel sample swelled by 53.3 [+9.7/−3.1]%, while the fuel near the Zr–fuel interface swelled by 63.3 [+14.7/−7.2]%. The average local thickness of the Zr diffusion barrier decreased by 53 %, compared to the expected pre-irradiated thickness. Four pore morphology regions were identified initiating parallel to the fuel–Zr interaction region: (1) an interaction layer of suppressed porosity, (2) a layer of elongated and interconnected porosity, (3) a transition zone of low porosity, and (4) a layer of unoriented porosity representative of the bulk fuel behavior. The increase in porosity near the diffusion barrier corresponded to a higher U concentration compared to that in the bulk fuel. The interconnected porosity in the fuel near the diffusion barrier was extensive and oriented parallel to the diffusion barrier, while the bulk fuel had more compact and isolated pore networks. The interaction layer, despite having suppressed porosity, was nearly 100 wt.% U. Porosity suppression at the diffusion barrier corresponds to the expected reduction in radiation-driven diffusion of Xe at the interface despite the anticipated increase in fission product nucleation originating from a higher U concentration. The novel 3D insights of the porosity, swelling, and compositional variations characterized herein can improve the fidelity of fuel performance codes for proliferation-resistant fuels for research and test reactors. [Display omitted] [ABSTRACT FROM AUTHOR]

Triple junctions (TJs) are line defects in three-dimensional (3D) polycrystalline materials where three grains meet. Transport along the TJs depends on the connectivity between them. Here, we investigate the connectivity of more than 6000 TJs in a 3D microstructure of pure iron (Fe) through the lens of bond percolation. Our efforts are made possible by synchrotron-based x-ray diffraction tomography, which allows us to resolve the TJ network both temporally and spatially, during grain growth. In the framework of standard percolation theory, we determine a percolation threshold of the TJs, above which there exists a continuous pathway of TJs that travels infinitely far. Our experimental results indicate a surprisingly different percolation threshold (by 16%) compared to models and theories. The reason for the discrepancy is that the real TJ network has a topological disorder that is not present in the idealized microstructures considered in prevailing models and theories. Leveraging the wealth of time-resolved data we trace the origin of this disorder by following the topological transitions that accompany grain growth. Overall, the insights obtained in this study can help guide the design of polycrystalline materials via defect engineering. [Display omitted] [ABSTRACT FROM AUTHOR]

Loess has a loose metastable structure, which is not difficult to destroy under loading. As the core of loess structures, the current main research directions of loess engineering properties are studying their microscopic behaviours and then interpreting and predicting macroscopic mechanical properties. In this study, based on the analysis of the basic physical properties of loess samples from seven different places, each sample is scanned using X-ray with continuous slice computed tomography (CT), and the three-dimensional microstructure of loess samples is established. According to the computer graphics method, each particle is equivalent to an ellipsoid, and the flattening rate and elongation rate of particles in each sample are quantitatively counted. Taking the particle size distribution (PSD) and shape parameters (flatness and elongation) of each sample as the control factors for generating discrete element method (DEM) samples, a series of triaxial compression simulation tests are conducted, and the microscopic behaviours of each sample are studied within the entire test framework. Comparing the results of seven different samples, it is shown that both PSD and particle shape have effects on the stress–strain relationship, dry density and normal contact force of loess samples. Most of the sand particles (> 0.075 mm) are flat particles, while the clay particles (< 0.005 mm) are mainly near spheres. When the volume fraction of sand particles is large, the dry density of the sample is the lowest. However, when the content of near-spherical clay particles is large and the PSD is good, the average coordination value is large, which shows that it has a strong normal contact force and thus a higher shear strength. [ABSTRACT FROM AUTHOR]

Defining and visualizing the three-dimensional (3D) structures of pharmaceuticals provides a new and important tool to elucidate the phenomenal behavior and underlying mechanisms of drug delivery systems. The mechanism of drug release from complex structured dosage forms, such as bilayer osmotic pump tablets, has not been investigated widely for most solid 3D structures. In this study, bilayer osmotic pump tablets undergoing dissolution, as well as after dissolution in a desiccated solid state were examined, and visualized by synchrotron radiation micro-computed tomography (SR-μCT). In situ formed 3D structures at different in vitro drug release states were characterized comprehensively. A distinct movement pattern of NaCl crystals from the push layer to the drug layer was observed, beneath the semi-permeable coating in the desiccated tablet samples. The 3D structures at different dissolution time revealed that the pushing upsurge in the bilayer osmotic pump tablet was directed via peripheral "roadways". Typically, different regions of the osmotic front, infiltration region, and dormant region were classified in the push layer during the dissolution of drug from tablet samples. According to the observed 3D microstructures, a "subterranean river model" for the drug release mechanism has been defined to explain the drug release mechanism. [Display omitted] Based on the observed three-dimensional (3D) structures of bilayer osmotic pump tablets in different release states, a "subterranean river model" for representing the drug release mechanism is proposed. [ABSTRACT FROM AUTHOR]

Multiple consolidation-permeability tests were performed on loess samples from the South Jingyang Plateau in northwest China to analyze permeability under actual stresses. Three-dimensional microstructures for loess samples under each consolidation stress were established based on high-resolution computed tomography images to thoroughly interpret the permeability variation in terms of the loess microstructures including the pores and throats. With increasing consolidation pressure, the permeability decreased greatly at the beginning and tended to become stable. In the stage of dramatic decrease in permeability, pore coordination number decreased slightly under pressure, indicating little influence of connectivity among pores on permeability. The pores in the range of 14 to 25 μm decreased by 10.1% in volume percentage, and the pores larger than 13 μm decreased by 19.6% in number. Accordingly, throats larger than 6 μm decreased by 13.1% in area percentage, and throats larger than 2 μm decreased by 14.9% in number. Throat size distribution played a decisive role in permeability, pore size distribution acted as a bridge to influence permeability, and only the spaced pores and some interaggregate or intergrain pores larger than 13 μm that allowed free water to pass were related to permeability. The decreases in these relatively large pores and throats caused considerable decreases in permeability. However, the existence of large throats, even large numbers of such throats, does not mean high permeability, which can be verified in the stable stage of permeability. This research provides a better understanding of loess permeability in terms of three-dimensional microstructure and further insights into the stability analysis of loess slopes and the control of other hazards in loess regions. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis (OA) is one of the most common musculoskeletal diseases and osteophytes area frequent radiographic feature of knee OA. The osteophyte structure in knee OA, however, is not well elucidated. This study aimed to clarify the three-dimensional microstructural characteristics of osteophytes in the medial compartment of the knee in knee OA patients using micro-computed tomography (micro-CT). We hypothesized that the morphology of osteophytes would differ from that of the neighboring normal cancellous bones. Ten medial compartment knee OA patients with Kellgren-Lawrence grade 4 severity were enrolled in the study, and all patients underwent total knee arthroplasty. Osteophytes and cancellous bones were obtained from the medial femoral condyle. The three-dimensional trabecular bone microstructure was analyzed by quantitative micro-CT using image analysis software. The trabecular bone volume fraction and trabecular number were significantly lower in osteophytes than in cancellous bones. Consistently, trabecular separation was significantly higher in osteophytes. Osteophytes exhibited disorganized trabecular orientation, trabecular perforation, disruption, and complete disconnection. These findings suggest that osteophytes are functionally fragile. [ABSTRACT FROM AUTHOR]

Nano-stereolithography, also known as two-photon direct writing is widely used for fabrication of the three-dimensional microstructure with submicron resolution. Heirarchical three-dimensional meshed microstructures are crucial for microelectromechanical systems (MEMS), photonics and biotechnological applications. Routine study for various applications using such structures requires fabrication of many sets of structures. Conventionally such meshed microstructures are constructed through layer-by-layer accumulation with discrete point-to-point laser scanning. This technique is time consuming, leading to long fabrication times placing constraints on practical applications as well as optimization of structures. In this work we propose continuous longitudinal laser scanning method as an effective means for direct writing of hierarchical three-dimensional meshed microstructures. The advantages of continuously longitudinal laser scanning method are explored for its time economy and fabrication effectiveness; a fabrication window is suggested to determine the fabrication parameter easily according to laser power and structural design. [ABSTRACT FROM AUTHOR]

The spinal cord is the primary neurological link between the brain and other parts of the body, but unlike those of the brain, advances in spinal cord imaging have been challenged by the more complicated and inhomogeneous anatomy of the spine. Fortunately with the advancement of high technology, phase-contrast synchrotron radiation microtomography has become widespread in scientific research because of its ability to generate high-quality and high-resolution images. In this study, this method has been employed for nondestructive imaging of the internal microstructure of rat spinal cord. Furthermore, digital virtual slices based on phase-contrast synchrotron radiation were compared with conventional histological sections. The three-dimensional internal microstructure of the intramedullary arteries and nerve fibers was vividly detected within the same spinal cord specimen without the application of a stain or contrast agent or sectioning. With the aid of image post-processing, an optimization of vessel and nerve fiber images was obtained. The findings indicated that phase-contrast synchrotron radiation microtomography is unique in the field of three-dimensional imaging and sets novel standards for pathophysiological investigations in various neurovascular diseases. [ABSTRACT FROM AUTHOR]

The mechanical and thermal properties of a particulate composite are generally dependent on its microstructure. In the present work, statistical synthetic structures are built to represent three-dimensional microstructure of SiC particle-reinforced Al composites. The statistical parameters are referred to the previous literature and our experimental data. Thermo-mechanical finite element analysis is performed to predict the Young’s modulus and thermal expansion coefficient, which are in good agreement with the experimental results. Furthermore, the irregular distribution of stress and strain from statistical synthetic models provides better qualitative description compared to other artificially synthesized models, such as unit cell models. Considering the accuracy, flexibility, and cost of the statistical synthetic model, we confirm that this model has high potential as an efficient modeling scheme for a wide range of materials. [ABSTRACT FROM AUTHOR]

Bimodal nanostructured (NS) metals composed of coarse-grained (CG) and nano-/ultrafine-grained phases possess high strength and good ductility. In this paper, three-dimensional (3D) microstructure-based numerical simulations via the mechanism-based strain gradient plasticity and the Johnson–Cook failure model are performed to study the effects of the shape and distribution of CG inclusions on the strength and ductility of bimodal NS Cu. Our results show that both the shape and distribution of CG inclusions significantly affect the overall ductility, while the former has more prominent influences than the latter. Spherical CG inclusions result in excellent overall ductility under all considered spatial distributions, while CG inclusions with sharp edges and corners facilitate microcrack initiation. However, the earlier microcrack initiation does not necessarily lead to a lower ductility since proper combinations of the shape and distribution of CG inclusions may retard microcrack propagation and thus enhance the overall ductility. These 3D microstructure-based simulations are helpful for the design of bimodal NS metals with improved mechanical properties. [ABSTRACT FROM AUTHOR]

High-energy diffraction microscopy (HEDM) constitutes a suite of combined X-ray characterization methods, which hold the unique advantage of illuminating the microstructure and micromechanical state of a material during concurrent in situ mechanical deformation. The data generated from HEDM experiments provides a heretofore unrealized opportunity to validate meso-scale modeling techniques, such as crystal plasticity finite element modeling (CPFEM), by explicitly testing the accuracy of these models at the length scales where the models predict their response. Combining HEDM methods with in situ loading under known and controlled boundary conditions represents a significant challenge, inspiring the recent development of a new high-precision rotation and axial motion system for simultaneously rotating and axially loading a sample. In this paper, we describe the initial HEDM dataset collected using this hardware on an alpha-titanium alloy (Ti-7Al) under in situ tensile deformation at the Advanced Photon Source, Argonne National Laboratory. We present both near-field HEDM data that maps out the grain morphology and intragranular crystallographic orientations and far-field HEDM data that provides the grain centroid, grain average crystallographic orientation, and grain average elastic strain tensor for each grain. Finally, we provide a finite element mesh that can be utilized to simulate deformation in the volume of this Ti-7Al specimen. The dataset supporting this article is available in the National Institute of Standards and Technology (NIST) repository (). [ABSTRACT FROM AUTHOR]

Quantitative microstructure information is critical to modeling and prediction of mechanical properties of structural components. In this study, the microstructure characteristics of aged squeeze-cast AZ91 alloy were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) analyses. Particularly, a study of the three-dimensional morphology of continuous precipitation during heat treatment was carried out using a combination of TEM and AFM. The results showed that a typical precipitate consisted of three kinds of faces, namely, broad, side, and end faces. The precipitate also presented a lath-shaped morphology with lozenge ends. Combined SEM and TEM analyses revealed quantitative information on the sizes and area number densities of precipitates after aging at different temperatures with different times. In general, the length and width of precipitates increased more rapidly than thickness during aging. The area number density initially increased and then slowly decreased because of coarsening. Furthermore, a special microstructure characteristic of the non-uniform continuous precipitation during aging was investigated using electron probe microanalysis (EPMA). The relationship between hardness response and yield strength was established. [ABSTRACT FROM AUTHOR]

The macroscopic properties of loess soils are significantly controlled by their microstructure. However, researches on the microstructure of loess soils at micrometer scale are inadequate, especially in the aspect of quantitative analysis of three-dimensional (3D) microstructure. This study systematically investigates the micrometer-scale microstructure of loess soils from Jingyang, Shaanxi province, China, via X-ray computed tomography and explored image segmentation method. The microstructural characteristics, including size, shape, and arrangement of particle and pore, were discussed from the real 3D view and quantitatively analyzed by statistical method. Results showed that the representative elementary volume obtained through porosity is applicable to microstructural parameters of size distribution, shape factor, orientation angle, and pore connectivity. Sectional analysis revealed that the two-dimensional (2D) results of size, shape, arrangement, and pore connectivity cannot adequately represent the corresponding 3D characteristics. These works may provide insight for researches on the microstructure of similar particulate materials. [Display omitted] • The micrometer-scale microstructure of loess soils was analyzed from real 3D view. • REV obtained from porosity is applicable to quantitative microstructure analysis. • 2D size, arrangement, shape, and pore connectivity cannot represent 3D characteristics. [ABSTRACT FROM AUTHOR]

A method based on the kinetics of crystal growth has been developed and applied to the computation of three-dimensional microstructure in austenite–martensite steels. The detailed crystallography of the transformation is used to model a realistic martensitic microstructure during the transformation without an external system of stresses. The interaction energy based on the plastic work model is taken into account to compute the variant selection in an austenitic stainless steel and formation of martensite under externally applied stress. [ABSTRACT FROM AUTHOR]

Abstract: Electrically conductive graphene-filled polystyrene nanocomposites with well-organized three dimensional (3D) microstructures were simply prepared by electrostatic assembly integrated latex technology. First, positively charged polystyrene was synthesized via disperse polymerization in ethanol/water medium by using a cationic co-monomer, and then directly co-assembled with graphene oxide. Eventually, a honeycomb-like graphene 3D framework was embedded in polystyrene matrix after in situ chemical reduction and hot compression molding. Due to the 3D conductive pathway derived from graphene based network evidenced by morphology studies, the fabricated nanocomposites show excellent electrical properties, i.e. extremely low percolation threshold of 0.09vol% and high saturated conductivity of 25.2S/m at GNs content of 1.22vol%. [Copyright &y& Elsevier]

This paper presents a three-dimensional (3D) image-based microstructural computational modeling framework to predict the thermoviscoelastic, thermoviscoplastic, and thermoviscodamage response of asphalt concrete. X-ray computed tomography is used to scan dense-graded asphalt concrete (DGA) to obtain slices and planar images, from which the 3D microstructure is reconstructed. Image processing techniques are used to enhance the quality of images in terms of phase identification and separation of particles. This microstructure is divided into two phases: aggregate and matrix. The aggregate phase is modeled as an elastic material and the matrix phase is modeled as a thermoviscoelastic, thermoviscoplastic, and thermodamage material. Stress-strain response, damage propagation, and the distributions of the viscoelastic and viscoplastic strains are predicted by performing virtual uniaxial and repeated creep-recovery tests of the developed 3D model of asphalt concrete. The effects of loading rate, temperature, and loading type on the thermomechanical response of asphalt concrete are investigated. In addition, the microscopic and macroscopic responses of DGA are compared with those of stone matrix asphalt (SMA). The results demonstrate that SMA can sustain higher strain levels at the microscopic level and higher macroscopic ultimate strength. The damage in SMA is more localized than in DGA. The microstructure-based framework presented in this paper can be used to offer insight on the influence of the distribution and properties of microscopic constituents on the macroscopic behavior of asphalt concrete. [ABSTRACT FROM AUTHOR]

Highlights: [•] We present a smoothing algorithm termed “level-set smoothing”. [•] The method can be applied to any voxel-based data describing a two-phase structure. [•] It allows quantitative characterization of morphology and its evolution. [ABSTRACT FROM AUTHOR]

This paper describes a method that contains a series of processes for producing three-dimensional (3-D) microstructures with a feature size in the submicrometer scale. It starts from using a metal contact printing lithography to pattern a thin metal film on the surface of a (100) silicon substrate. The metal film has a hole-array pattern with a hole diameter ranging from 300 nm to 800 nm and is used as an etching mask for silicon bulk machining to create concave pyramid-shaped surface microstructures. Using this bulk-machined silicon substrate as a template, polymer 3-D microstructures are replicated on top of a silicon dioxide (SiO2) layer. Finally, through a dry etching process, 3-D microstructures with a profile similar to the replicated polymer microstructures are formed on the SiO2 layer. Potential applications of these fabricated SiO2 microstructures in the light-emitting diode industry will be addressed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Apply the scanning electron microscope (SEM) imaging techniques to study pore microstructure and capture frost damage. [•] Apply cohesive fracture model for fracture simulation with 3D sample. [•] Construct 3D digital sample with imaging processing. [•] Compare model prediction with detected frost damage in tested samples and validate ice crystallization pressure mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Psychological stress plays an important role in the occurrence and development of temporomandibular joint disorder (TMD). The correlation between psychological factors and TMD has been clinically shown, but the influence of psychological stress on the temporomandibular joint (TMJ) structure still lacks direct evidence. Here, we used communication box to establish the rat model of psychological stress. The stress level of animals was estimated by the elevated plus maze (EPM) test and hormonal assays. The histomorphology and three-dimensional microstructure of the rat condyles were observed by hematoxylin–eosin (HE) staining and Micro-CT, respectively. Compared with control rats, the anxious state of the stressed rats was evidenced by higher plasma adrenocorticotropic hormone (ACTH) and corticosterone (CORT), as well as lower ratios of open arm entries and time and lower time spent in open arms after 1, 2, 3, 4 and 5week(s) post-exposure to psychological stimuli. HE staining and histomorphometric data analysis showed decreased thicknesses of the central and posterior condylar cartilages in stressed rats at weeks 3, 4 and 5, with the most obvious changes in the posterior part characterized by debonding and thinned fibrous layer, thickened proliferative layer, thinned mature layer and hypertrophic layer. Moreover, Micro-CT scanning revealed local lesion of the subchondral bone in the posterior condylar cartilages of stressed rats at week 5. Our findings indicate that pathologic changes of the histomorphology and three-dimensional microstructure occur in the condyles of stressed rats, hinting us a potential link between psychological factors and the pathogenesis or progression of TMD. [Copyright &y& Elsevier]

Abstract: The senescence-accelerated mouse strain P6 (SAMP6) is a model of senile osteoporosis, which possesses many features of senile osteoporosis in humans. So far, little is known about the systemic bone microstructural changes that occur at the cervical, thoracic, and lumbar vertebrae. In this study, we therefore investigated segmental variations of vertebral trabecular bone mineral density (BMD) and three-dimensional microstructure in SAMP6 and the normal control mouse (SAMR1) at 12months of age using quantitative micro computed tomography (micro-CT) and image analysis software. The vertebral height and vertebral cross-sectional area (CSA) increased, while vertebral trabecular BMD and trabecular bone volume fraction (BV/TV) decreased from the cervical to lumbar spine both in SAMR1 and SAMP6. As compared with SAMR1, the thoracic vertebral CSA had a tendency to be low and the lumbar vertebral CSA was significantly declined in SAMP6. The vertebral trabecular BMD, BV/TV, trabecular thickness (Tb.Th), and trabecular number (Tb.N) significantly decreased in cervical, thoracic and lumbar spine of SAMP6. Trabecular bone pattern factor (TBPf) was higher at the lumbar spine and the structure model index (SMI) of the lower thoracic and lumbar spine was higher in SAMP6. These results indicate that vertebral trabecular bone microstructures are remarkably heterogeneous throughout the spine in both SAMR1 and SAMP6. The decrease of vertebral trabecular bone density in SAMP6 advanced faster caudally than cranially within the spine, similar phenomena were observed in humans. These findings highlight the relevance of SAMP6 for studies of vertebral fragility associated with senile osteoporosis. [Copyright &y& Elsevier]

The purpose of this study was to develop the methods needed to enable the application of Immunofluorescent Array Tomography (IAT), a novel three-dimensional (3D) microscopy technique, to murine blood vessels. The anterior and posterior regions of the infrarenal aorta of 8-10 week old C57BL6 mice were evaluated. Staining and image analysis methods were developed. Antibody selection, primary antibody concentration, co-staining with multiple primary antibodies, and the multi-cycle staining design were optimized to produce positive and specific staining of elastin (1:50 dilution), smooth muscle cell actin (SMCA, 20 μg mL), and collagen type I (10 μg mL). Non-specific interactions were limited by optimizing secondary antibody staining conditions (1:200 dilution, 30 min). SMCA and collagen type I were stained in the first cycle, elastin was stained in the second cycle, and nuclei were stained in both cycles. Algorithms were developed to quantify volume fractions of medial elastin, SMCA, and nuclei, as well as adventitial collagen type I. Elastin thickness, spacing between elastin lamellae, elastin fragmentation, media wall thickness, nuclei aspect ratio, and nuclei amount were also quantified. We have qualitatively and quantitatively characterized the 3D microstructure and cellular morphology of the anterior and posterior infrarenal murine aorta using IAT. [ABSTRACT FROM AUTHOR]

Three-dimensional electron backscatter diffraction data, obtained by serial sectioning a nickel-base superalloy, has been analysed to measure the geometric arrangement of grain boundary planes at triple junctions. This information has been used to calculate the grain boundary character distribution (GBCD) and the grain boundary energy distribution (GBED). The twin content from the three-dimensional GBCD calculation compares favourably with the twin content estimated by stereology. Important factors in the analysis are the alignment of the parallel layers, the ratio of the out-of-plane to in-plane spacing of the discrete orientation data and the discretisation of the domain of grain boundary types. The results show that grain boundaries comprised of (111) planes occur most frequently and that these grain boundaries have a relatively low energy. The GBCD and GBED are inversely correlated. [ABSTRACT FROM AUTHOR]

We investigated age- and gender-related variation of both cortical and trabecular microstructure in human femoral neck. We found that age-related change of cortical porosity is more noticeable than that of trabecular parameter. Our data may help to gain more insight into the potential mechanism of osteoporotic femoral neck fractures. Variations in the microstructure of cortical and trabecular bone contribute to decreased bone strength. Age- and gender-related changes in cortical and trabecular microstructure of femoral neck is unclear. The aim of this study was to identify three-dimensional (3D) microstructural changes of both cortical and trabecular bone simultaneously in human femoral neck with age and gender, using micro-computed tomography (micro-CT). We hypothesized that there would be differences in age-related changes of cortical and trabecular bone for both women and men. We used 56 femoral necks of 28 women and men (57–98 years of age) from a Japanese population. The subjects were chosen to give an even age and gender distribution. Both women and men were divided into three age groups: middle (57–68 years), old (72–82 years), and elderly (87–98 years) groups. We examined cortical bone specimen from the inferior sector of femoral neck and trabecular bone specimen from the middle of femoral neck using micro-CT and 3D bone analysis software. Cortical thickness (Ct.Th) decreased by 10–15%, cortical porosity (Ca.V/TV) almost doubled, and canal diameter (Ca.Dm) increased by 65–77% between the middle-aged and elderly groups for both women and men. The trabecular bone volume fraction (BV/TV) decreased by around 20%; trabecular thickness (Tb.Th), trabecular number (Tb.N), and connectivity density (Conn.D) decreased; and trabecular separation (Tb.Sp) and structure model index (SMI) increased with age for both women and men. As compared with women, men had higher Ct.Th and BV/TV and lower Ca.V/TV and Ca.Dm among three age groups. There was a significant inverse correlation between Ca.V.TV and BV/TV for both women and men. Our findings indicate that Ct.Th and BV/TV decreased, and Ca.V/TV and Ca.Dm increased in femoral neck with age for both women and men. The most obvious age-related change is the increase of Ca.V/TV. The decrease of BV/TV with age is more noticeable than that of Ct.Th. This is the first study that has provided both cortical and trabecular microstructural data simultaneously in a Japanese sample. These data may help us to gain more insight into the potential mechanism of osteoporotic femoral neck fractures. [ABSTRACT FROM AUTHOR]

Abstract: The senescence-accelerated mouse strain P6 (SAMP6) is a model of senile osteoporosis, which possesses many features of senile osteoporosis in humans. So far, little is known about the systemic bone microstructural changes that occur at multiple skeletal sites. In this study, we therefore, investigated site (vertebra, femur and tibia) dependence of bone microstructure and bone mineral density (BMD) in SAMP6 and the normal control mouse (SAMR1) at 5 and 12months of age using quantitative micro computed tomography (micro-CT) and image analysis software. As compared with SAMR1, the most prominent change in SAMP6 was the reduction of vertebral trabecular bone volume fraction (BV/TV) and trabecular BMD. Moderate decrease of trabecular bone mass was observed in the proximal tibia and distal femur. Increased marrow area and periosteal perimeter were investigated, though the cortical area and cortical thickness had no marked changes in the mid-tibial and mid-femoral cortical bones. These results indicate that bone microstructural properties in SAMP6 are remarkably heterogeneous throughout the skeleton, which is analogous to changes that occur in human bones. These findings further validate the relevance of SAMP6 as a model of senile osteoporosis. [Copyright &y& Elsevier]

Abstract: Three-dimensional (3D) microstructures of TiB reinforcement in two discontinuously reinforced Ti–6Al–4V (Ti64) alloy composites produced via blended elemental (BE) powder metallurgy are reconstructed from large-area high-resolution optical montage serial sections. The TiB phase in both composites shows whisker morphology with roughly hexagonal cross-sections, a unimodal size distribution, and uniform random morphological orientations. The TiB whiskers in these composites are significantly coarser compared to similar materials produced via pre-alloyed powder metallurgy but did not contain coarse primary TiB particles. [Copyright &y& Elsevier]

How to improve the acquisition efficiency of electron back scatter diffraction (EBSD) and meanwhile avoid the drifting of images caused by the charge effect is still an issue that needs to be solved urgently for three-dimensional (3D) EBSD characterization of non-conductive ceramic materials. The purpose of this study is to solve the problem based on an experimental and theoretical basis using the yttria-stabilized zirconia (YSZ) coating as the research subject. To eliminate the charge effect, the charge equilibrium point of the YSZ coating was determined using the Duane–Hunt limit method. When the incident energy is equal to the E 2 value (3.06 keV), the charge effect on the scanning electron microscopy images of the YSZ coating disappears. However, the incident energy of 3.06 keV exhibits lower EBSD collection efficiency for a 3D EBSD result because of the long exposure time; therefore, increasing the incident energy to 7 keV under the large beam current is a practical way to improve EBSD collection efficiency, which inevitably results in the charge problem again. Furthermore, Ga ion implantation caused the charge effect on the YSZ coating at 7 keV under the large beam current to disappear, which can be attributed to the decrease in bandgap widths and the improvement of electrical conductivity of the t-YSZ phase after Ga ion implantation based on first principles. Calculations of the cohesive energies reveal that Ga ions are more likely to occupy the lattice positions of the YSZ coating after Ga ion implantation. Finally, a high-resolution 3D EBSD image of the YSZ coating was obtained. • This study provides a method to avoid the drifting of EBSD images for YSZ coatings. • The acquisition efficiency of EBSD images for YSZ coatings was improved. • A high-resolution 3D EBSD result of the YSZ coating was obtained. [ABSTRACT FROM AUTHOR]

Abstract: Age-related bone loss, which is poorly characterized, is a major underlying cause of osteoporotic fractures in the elderly. In order to identify the morphological feature of age-related bone loss, we investigated sex and site (tibia, femur and vertebra) dependence of bone microstructure in aging hamsters from 3 to 24 months of age using micro-CT. In the proximal tibia and distal femur, trabecular bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th) and bone mineral density (BMD) increased to a maximum at 6 or 12 months and then declined progressively from 12 to 24 months of age. Trabecular separation (Tb.Sp), trabecular bone pattern factor (TBPf) and structure model index (SMI) increased with age. As compared with male hamsters, BV/TV and Tb.N were significantly lower in females at 18 and 24 months of age. Age-related decrease of trabecular BV/TV in the vertebral body was less than that of the femoral and tibial metaphyses. In the mid-femoral diaphysis, cortical bone area remained constant from 3 to 24 months of age. Cortical thickness decreased from 12 to 24 months and cortical BMD declined significantly from 18 to 24 months of age. These findings indicate that skeletal site and sex differences exist in hamster bone structure. Age-related bone changes in hamsters resemble those in humans. We conclude that hamster may be a useful model to study at least some aspects of bone loss during human aging. [Copyright &y& Elsevier]

Abstract: Visualization of three-dimensional (3D) microstructure is useful for understanding microstructural geometry. In this contribution, 3D microstructures of TiB whiskers in two powder metallurgy processed Ti–6Al–4V–1B alloys are reconstructed and visualized using large-area high-resolution montage serial sections and digital image processing to study the effects of processing route on the morphology and anisotropy of the TiB phase. The microstructures consisted of eutectic TiB in Ti-64 and are free from coarse primary phase TiB. The eutectic TiB phase has whisker morphology in both the compacted and compacted plus extruded conditions. The orientations of TiB whiskers are uniformly random in the compacted condition and highly aligned anisotropic in the extruded condition. The spatial distributions of TiB are uniform in both cases without any clustering. The large volumes of reconstructed 3D microstructures are useful for incorporation into finite element-based computations. [Copyright &y& Elsevier]

Abstract: Visualization and representation of three-dimensional (3D) pore morphologies in the high-pressure die-cast Mg alloys are of significant interest for understanding and modeling processing–microstructure–properties relationships. In this contribution, an efficient and unbiased montage serial sectioning technique is applied for reconstruction of large volume (∼1.24×109 μm3) high-resolution (∼1μm) 3D microstructure of a high-pressure die-cast AM50 Mg alloy containing gas (air) and shrinkage pores. The reconstruction of 3D microstructure from montage serial sections enables visualization and characterization of detailed 3D morphologies and spatial correlations of gas (air) and shrinkage pores. The reconstructed 3D microstructure is implemented in a 3D finite elements (FE) computational framework to illustrate how realistic complex microstructural feature morphologies can be incorporated in the simulations of micromechanical response of these high-pressure die-cast cast microstructures. [Copyright &y& Elsevier]

Abstract: Three-dimensional (3D) microstructures of TiB phase in a powder metallurgy Ti–6Al–4V–1.7B alloy processed using two different routes are reconstructed from large-area high-resolution montage serial sections. Visualizations of the 3D microstructures are used to determine the effects of the processing route on the morphology, anisotropy, and spatial distributions of TiB particles. [Copyright &y& Elsevier]

Abstract: This paper reviews microscale processes to fabricate three-dimensional structures, in particular, high-aspect-ratio arrayed structures, using precise electrochemical etching process. Array of sharp micropits were pre-formed on the front side surface of Si wafer and the electrochemical etching was carried out using aqueous HF solution, with the back side illumination to generate holes, which diffused to the edge of the micropits to proceed the dissolution of Si with fluoride species. In order to form high-aspect-ratio pores at selected areas, a shade mask pattern was fabricated on the back side surface to align the illumination to the pre-patterned area on the front side surface. The parameters, such as HF concentration, current density and hole diffusion length, were optimized and uniform array of straight pores was formed into the designed area of Si wafer. Subsequently the surface of the pores was thermally oxidized to form SiO2 layers, and arrayed glass tubes with picoliter volume were fabricated. On the other hand, the pore filling with metal was attempted using electrodeposition to obtain array of the metal needles. For this, the “single batch” process was developed to form the pore array and metal filling with single electrolyte, and array of metal micro needles was successfully formed. These processes demonstrated capability and possibility of the electrochemical processes for microscale fabrication, and further precise processes can be developed using these approaches. [Copyright &y& Elsevier]

Abstract: We report on three-dimensional (3D) microstructure visualization and finite-element method modeling of deformation in Sn–3.5Ag alloy. The 3D virtual microstructure accurately represented the alignment, aspect ratio, and distribution of the Ag3Sn second phase. The 3D microstructure-based approach is more accurate than unit cell models for simulating and understanding material behavior. [Copyright &y& Elsevier]

Three-dimensional (3D) microstructures were formed using a wet process consisting of the formation of a multilayered microstructure and selective etching of the other layers of the structure. Cylindric Cu/Ni multilayered microstructures of 50 μm in diameter and 30 μm in height were formed by electroplating and photolithography. Cu layers were then etched selectively in acidic thiourea solution. The redox reaction of the multilayered microstructure in the solution was investigated electrochemically. The shapes of three-dimensional microstructures were affected by the surface morphology of the deposited films. Various three-dimensional microstructures having controlled geometric unevenness were obtained using films having smooth surface morphology. [Copyright &y& Elsevier]

Sn electrodeposition was employed for fabricating an array of microabsorbers with a ‘mushroom-shaped’ microstructure for a precision X-ray microdetector, the so called X-ray microcalorimeter. A deposition process for flat and smooth Sn films, which was suitable for the use of the absorber material, was developed by optimizing the conditions of additives such as o-cresol-4-sulfonic acid and polyethyleneglycol (PEG) to the Sn bath. The Sn films exhibited suitable properties, i.e. a higher superconducting transition temperature than the operating temperature of the X-ray microcalorimeter. The mushroom-shaped absorber array was successfully fabricated by Sn electrodeposition in combination with a photolithographic technique. [Copyright &y& Elsevier]

• A soft and compressible 3D liquid metal/elastomer foam was facilely prepared. • The foam presents super durability and stability when subjected to repeated use. • Compress-induced rises of electrical/thermal conductivity and EMI SE were obtained. • The foam can serve as soft EMI shields and heat transfer materials in electronics. With the development of 5G wireless technology and Internet of Things, electromagnetic interference (EMI) and heat generation in electronic devices and interconnects are becoming increasingly ubiquitous due to the proliferation of wearable electronics. It raises great concerns that EMI and elevated heat degrade device performance and also cause detrimental effects on human health. The soft and deformable materials that are capable of simultaneously shielding EMI and dissipating heat effectively are thus in high demand. Herein, a flexible composite material exhibiting substantial increases of electrical/thermal conductivities and EMI shielding effectiveness (SE) under compression was developed by introducing three-dimensional (3D) liquid metal (LM) network into an elastomer foam. The electrical conductivity, thermal conductivity, and EMI SE of the 3D LM/elastomer foam increase more than 14, 8.3, and 1.8 times, respectively, when compressed to a strain of 60% due to the compress-induced improvement in percolation of the LM. Moreover, neither microstructure damage nor performance degradation was observed in the foam during 10,000 compress-release cycles under 50% strain. Furthermore, we have demonstrated the proof-of-concept applications of the 3D LM/elastomer foam used as soft EMI shields and heat spreaders in wearable electronics. [ABSTRACT FROM AUTHOR]

A three-dimensional (3D) microstructure of Fe-intermetallic compounds (Fe-IMCs) was analyzed by means of x-ray tomography. 3D images were obtained to understand the internal structure of the Fe-IMCs in Al-Si-Mg-Fe alloys. A needle-shaped β phase appears in two-dimensional (2D) observations while platelet and irregular morphologies of the Fe-IMCs are identified in 3D investigations. The reconstructed microstructure was roughly crushed with 20% reduction rates and less broken parts of Fe-IMCs are observed, showing platelet and blunt morphologies. The combination of a large- and small-volume of the Fe-IMCs remained after a 60% reduction rate. The needle- and lateral-shaped of the Fe compounds were finely fragmented into the micro- and/or nano-scale at a 80% reduction rate. The average size of the Fe-IMCs is refined from 20.3 to 2.9 μm at the 80% reduction rate. The largest size of the Fe-IMCs is shortened from 85.5 to 21.3 μm. It is considered that fracture is affected by the length of the Fe-IMCs. Rapid cracks initiated around the fragmented Fe-IMCs at the reduction rate of 40% because the number of the Fe-IMCs is increased due to fragmentation. On the other hand, the harmful influence of Fe-IMCs on elongation becomes positive when the length of the Fe-IMCs decreases to less than a critical size. [ABSTRACT FROM AUTHOR]

In order to fabricate three-dimensional metal microstructures, a combined machining process based on 3D printing technology and electroforming technology is proposed. Firstly, a substrate with microstructures is fabricated by 3D printing technology, and then the microstructures were fabricated by electroforming technology. The influence of process parameters such as current density, distance between electrodes and pulse current duty cycle on the electroformed layer were studied and analyzed. It was determined that the peak current density 6A/dm2, the void ratio 20%, and the distance between electrodes 40 mm were the optimum process conditions of electroforming experiment. The electroforming experiments of different microstructures were carried out with the optimum process parameters. [ABSTRACT FROM AUTHOR]

Loess has a loose metastable structure that easily collapses during wetting and loading. Microstructure analysis is essential for a better understanding of the engineering properties of loess; however, two-dimensional (2D) methods cannot fully demonstrate the geometric microstructural characteristics of loess particles. The three-dimensional (3D) loess microstructure is reconstructed based on an improved serial sectioning technique. Point, edge and face contacts are observed from the 3D reconstructed microstructure of natural loess. The 3D microstructural features of particles and pores are also quantitatively studied by analyzing statistical parameters, including the equivalent diameter, sphericity, aspect ratio and orientation index. The particle size distribution (>10 μm) obtained from the microstructural analysis is validated via a comparison with the results of a laser particle size analysis. In total, 92% of the particles have a sphericity that lies between 0.5 and 0.9, and the aspect ratio of 93% of the particles is between 0.3 and 0.7. Additionally, 67% of the particles are oriented from 0° to 45°, whereas approximately 64% of the pores (>2 μm) are oriented from 45° to 90°. Each 3D parameter has a unique value and can reflect the true spatial morphology of the particles, avoiding the influence of the observation angle and section. The 3D characterization of the loess microstructure will provide insights into the underlying collapse mechanisms and could provide realistic 3D parameters for use in numerical simulations. • Serial sectioning was modified and applied to 3D microstructure reconstruction of loess. • 3D features of loess particles were quantified by diameter, morphology and orientation index. • Point, edge and face contacts were observed in 3D reconstructed loess microstructure. [ABSTRACT FROM AUTHOR]