Search

Processing-induced defects affect the performance and reliability of multilayered ceramics. They are introduced from the raw powder, or during tape casting, drying, thermo-compression, binder burnout, and sintering. Using synchrotron X-ray multiscale tomography, we investigated how the microstructural heterogeneities and various defects evolve in the sintering of tape-cast alumina laminate. The strength-limiting defects were identified as large defects at the layer interface and peculiar crack-like defects formed around large inclusions contained in the raw powder. Although a slurry might be uniform in colloidal processing, the particle packing in the tape was heterogeneous. This heterogeneity determined the spatial distribution of pores and formed complex pores in later stages. Moreover, we found the formation of flake-like sheets in slurry due to the self-assembly of polyhedral alumina crystals. This phenomenon has the potential to be applied in the manufacture of 2D micro-sheets controlled to the thickness of a single particle. [ABSTRACT FROM AUTHOR]

Because the fabrication of three-dimensional (3D) microelectrodes is quite challenging, microelectrodes with a simple cross-section are usually used in micro-electro-discharge machining (micro-EDM) to perform layer-by-layer scanning machining for machining 3D microstructures. In this study, we used pure copper powder as the raw material to prepare 3D queue microelectrodes through selective laser melting (SLM). The influences of laser power and laser scanning speed on the densification rate of the 3D microelectrodes were investigated. Moreover, the effects of the temperature and temperature holding time on the conductivity and EDM performance of the 3D microelectrodes during heat treatment were also analyzed. In order to improve the geometric accuracy of the 3D microstructure, 3D microstructures were subjected to micro-EDM with 3D queue microelectrodes: the first microelectrode was used for rough machining and the remaining microelectrodes were used for fine machining. In addition, to ensure a high surface quality of the 3D microstructure, multiple EDM were conducted to eliminate unmelted copper powder and layer defects on the surface of the 3D queue microelectrode. Finally, by applying the 3D queue microelectrodes in micro-EDM, a 3D microstructure with a height error of 1 µm and surface roughness of 1.685 µm was obtained after three repeated discharges. [ABSTRACT FROM AUTHOR]

This paper demonstrates a non-destructive technique to evaluate the internal microstructure in the Sn-Ag-Cu (SAC) solder joint through synchrotron X-ray radiation tomography. Synchrotron X-ray tomography is increasingly utilized for characterizing the internal microstructure of materials in 3D images. A 3D model is reconstructed from a set of 2D projection images taken from different angles and angular position during the sample rotation, thus it could provide a more comprehensive description of the microstructure of an alloy compared to 2D images. In this paper, it is successfully observed and evaluated the internal microstructure of a 900 μm solder joint sample. The key principles and methods of synchrotron X-ray tomography are briefly described. Examples of quantitative and qualitative assessments on the grain refinement effect of Mg addition to SAC35 solder joint are also presented in this paper.

Ice cream is a multiphase frozen dessert that often melts during distribution and upon consumption. The meltdown phenomenon is one of the concerns in the quality preservation of ice cream for consumer convenience in the frozen food industry. In this context, X-ray tomography was used to visualise and quantify 3D ice crystal and air bubble evolution during the meltdown of ice cream. Two ice cream products, namely I and II, with varying air volume fractions, were evaluated for this study. The results indicated a small mean diameter of 66.43 ± 2.07 µm at 0 min and decreased to 45.74 ± 3.92 µm during 10 min of the meltdown of ice cream II. A large mean diameter of ice crystals of 75.02 ± 3.14 µm was found in ice cream I, at 0 min that decreased significantly (p < 0.05) to 54.30 ± 2.63 µm during 10 min of the meltdown. The air bubbles were also observed to decrease in mean diameter. The 3D datasets on the ice crystals and air bubbles described in this work provide more insight into the 3D microstructural evolution during the meltdown and are useful in controlling the sensory quality attributes of ice cream desserts. [ABSTRACT FROM AUTHOR]

This paper demonstrates a non-destructive technique to evaluate the internal microstructure in the Sn-Ag-Cu (SAC) solder joint through synchrotron X-ray radiation tomography. Synchrotron X-ray tomography is increasingly utilized for characterizing the internal microstructure of materials in 3D images. A 3D model is reconstructed from a set of 2D projection images taken from different angles and angular position during the sample rotation, thus it could provide a more comprehensive description of the microstructure of an alloy compared to 2D images. In this paper, it is successfully observed and evaluated the internal microstructure of a 900 µm solder joint sample. The key principles and methods of synchrotron X-ray tomography are briefly described. Examples of quantitative and qualitative assessments on the grain refinement effect of Mg addition to SAC35 solder joint are also presented in this paper. [ABSTRACT FROM AUTHOR]

Microstructural features such as voids, microcracks and interfaces play an important role in the mechanical properties of polymer‐bonded explosives, which significantly decide the performance, safety and reliability. A series of micron‐scale 3D models were constructed, and a 3D cohesive finite element method in a commercial software was used to study the elastic properties and fracture development of HMX/Estane polymer‐bonded explosives under quasi‐static tension. The predicted Young's modulus of HMX/Estane PBX with particle volume fraction of 92.7 % at 0.01 s−1 is 2.24 GPa, which is only 7.4 % different from the experimental result. 3D models perform better than 2D models in the prediction of Young's modulus and Poisson's ratio, and the difference between 2D and 3D results can be up to 40 %. In addition, the effect of particle size on the mechanical properties is investigated. It is shown that 3D models can correctly describe the relationship of particle size with stress‐strain curves and fracture development of PBX. Results demonstrate that a 3D model is necessary in the study to delineate the relationships between microstructural features and the mechanical behavior of polymer‐bonded explosives. [ABSTRACT FROM AUTHOR]

Abstract Two-photon lithography has emerged as a highly effective method for fabricating intricate three-dimensional (3D) microstructures. It enables the rapid fabrication of 3D microstructures, unlike conventional two-dimensional nanopatterning. Researchers have extensively investigated two-photon polymerization (TPP) for the fabrication of diverse 3D micro/nanodevices with high resolution. TPP can be applied in cell cultures, metamaterials, optical materials, electrical devices, and fluidic devices, to name a few. In this study, we investigate the applications and innovative research pertaining to TPP, which is an effective fabrication technique with significant advancement in various fields. In particular, we attempt to determine the reasons that cause the detachment or delamination of 3D microstructures during the development process and propose some solutions. A step-by-step fabrication process for a glass substrate, from photoresist deposition to laser scanning and the dissolution of the uncured photoresist, is presented. Defects such as pattern delamination are discussed, with emphasis on the cell scaffold structure and microlens array. Understanding and addressing these defects are vital to the success of 3D microstructure fabrication via TPP.

The advent of techniques enabling three-dimensional (3D) analysis of objects, defects, and fields has been key to discoveries and paradigm shifts in molecular biology, astrophysics, medicine, quantum physics, etc. In materials science, the 3D nature of materials microstructures remains largely hidden; leading to a fragmented understanding of microstructure-property linkages. Current tools cannot characterize large volumes of 3D microstructures at fine resolution. To this end, this study introduces a graph-theory-based framework to automatically extract 3D microstructures and statistics of electron-backscatter diffraction datasets. Further, leveraging network science, the study introduces a new approach to classify and compare microstructures; the keystone to materials taxonomy. The significance of this tool is demonstrated by studying deformation twin structures in Titanium. The study reveals extraordinarily complex and tortuous twin networks never observed via traditional two-dimensional analysis. This changes our perception of the ability of metals to withstand severe microstructure changes without failing.

Three-dimensional (3D) microstructured biomaterials are favorable in tissue engineering due to their superior guidance to cellular activities. Herein, we developed a 3D microstructured bacterial cellulose (BC) with arranged fibers by controlling Acetobacter xylinum through an electric field (EF) application. The real-time video analysis showed that EF directed the migration of A. xylinum and increased its migration speed with the increased EF. The bacteria quickly changed direction with high motility in response to the switch on/off of the EF. In the long-term electrical stimulation (ES), the growth of A. xylinum was influenced. Likewise, bacterial cells were oriented along the direction of EF while bacteria simultaneously produced nanocellulose, resulting in 3D networks with aligned fibers. The prepared 5 mA-BC hydrogels presented the ordered 3D microstructure with higher fiber alignment, diameter and flexibility than that of NO EF-BC hydrogels. The in vitro biological evaluation demonstrated that the 5 mA-BC hydrogels were biocompatible whereon NIH3T3 cells proliferated along the direction of fiber alignment. These findings demonstrate that ES provides a promising strategy for the natural fabrication of aligned 3D microstructured BC to guide cellular activities for tissue regeneration. [ABSTRACT FROM AUTHOR]

Two-photon lithography has emerged as a highly effective method for fabricating intricate three-dimensional (3D) microstructures. It enables the rapid fabrication of 3D microstructures, unlike conventional two-dimensional nanopatterning. Researchers have extensively investigated two-photon polymerization (TPP) for the fabrication of diverse 3D micro/nanodevices with high resolution. TPP can be applied in cell cultures, metamaterials, optical materials, electrical devices, and fluidic devices, to name a few. In this study, we investigate the applications and innovative research pertaining to TPP, which is an effective fabrication technique with significant advancement in various fields. In particular, we attempt to determine the reasons that cause the detachment or delamination of 3D microstructures during the development process and propose some solutions. A step-by-step fabrication process for a glass substrate, from photoresist deposition to laser scanning and the dissolution of the uncured photoresist, is presented. Defects such as pattern delamination are discussed, with emphasis on the cell scaffold structure and microlens array. Understanding and addressing these defects are vital to the success of 3D microstructure fabrication via TPP. [ABSTRACT FROM AUTHOR]

The blood–brain barrier (BBB) surrounds brain cells and prevents external substances from entering the brain through blood vessels. This complicates drug delivery to brain cells, but drugs that can cross the BBB have been developed recently, expanding the scope of treatment for brain diseases. However, traditional biological research typically relies on simple monolayer cell cultures that do not reflect the complex functional properties of human tissues and organs or their responses to external stimuli. Bioprinting technology is gradually overcoming the drawbacks of in vitro models by applying techniques, such as simulating 3D structures, which cannot be realized by biological models, utilizing biocompatible materials and mass cell culture at the tissue level; however, it has been limited to printing microstructural patterns. The in vitro model presented here printed the BBB microstructure in a liquid state, eliminating many defects inherent to printing on a flat surface in air. The aqueous two-phase printing (ATPP) material consisted of a composite matrix capable of phase separation, where three different cell types could be cultured to create a BBB model. The ATPP model will help in central nervous system disease research, drug screening, and drug discovery, because it provides an environment where the nutrient supply and drug concentration of cells can be controlled. [ABSTRACT FROM AUTHOR]

Two biopolyol-based foams derived from banana leaves (BL) or stems (BS) were produced, and their compression mechanical behavior and 3D microstructure were characterized. Traditional compression and in situ tests were performed during 3D image acquisition using X-ray microtomography. A methodology of image acquisition, processing, and analysis was developed to discriminate the foam cells and measure their numbers, volumes, and shapes along with the compression steps. The two foams had similar compression behaviors, but the average cell volume was five times larger for the BS foam than the BL foam. It was also shown that the number of cells increased with increasing compression while the average cell volume decreased. Cell shapes were elongated and did not change with compression. A possible explanation for these characteristics was proposed based on the possibility of cell collapse. The developed methodology will facilitate a broader study of biopolyol-based foams intending to verify the possibility of using these foams as green alternatives to the typical petrol-based foams. [ABSTRACT FROM AUTHOR]

Gas exchange mechanisms play crucial roles in maintaining fruit post-harvest quality in perishable fruit such as strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.). The internal oxygen concentration ([O2]) of strawberry and blueberry were measured using Clark-type oxygen sensing electrodes. The volume of intercellular voids in strawberry was obtained by micro-computed tomography (micro-CT). In both berries, internal [O2] was consistent and relatively high across measured tissues. The overall [O2] was well above the Michaelis constant (K m) for cytochrome c oxidase in both fruit and different from previously examined grape (Vitis vinifera L.) berry mesocarp with near zero minimum [O2]. In strawberry and blueberry, cell vitality was also maintained at full maturity in the mesocarp. Higher storage temperature (i.e. 20 vs 4°C) reduced internal [O2] of strawberry. Pedicel detachment in blueberry was associated with greater fruit dehydration and lower internal [O2] after short-term storage of 12 h. The results suggest that the intercellular voids of the fruit's mesocarp provide an efficient gas exchange route for maintaining high fruit internal [O2] post-harvest. Understanding the dynamics and factors regulating internal oxygen concentration ([O2]) of strawberry (Fragaria × ananassa Duch.) and blueberry (Vaccinium corymbosum L.) fruit can assist horticultural improvement and post-harvest management. This work has integrated oxygen sensing and non-destructive imaging techniques to provide insight into the 3D microstructure of the mesocarp of strawberries and blueberries. The results provide fundamental knowledge on how oxygen and tissue anatomy are interrelated in small soft fruit. The implications of the observed anatomical features on post-harvest fruit physiology (specifically internal [O2]) are discussed. [ABSTRACT FROM AUTHOR]

This study utilized 1D carbon nanotubes (CNTs) and 2D graphene nanosheets (GNs) in preparation of 3D microstructured polypropylene (PP) nanocomposites with improved anti-wear and nanomechanical responses. The nanocomposites fabricated through melt compounding using Haake Rheomixer showed well dispersed nanoparticles in the matrix due to the aid of PP grafted maleic anhydride (PP-g-MA) coupling agent. The developed PP-CNTs-GNs hybrid nanocomposite showed lower coefficient of friction compared to the pure PP and its nanocomposites containing individual CNTs and GNs. PP-1CNTs-1GNs hybrid nanocomposite had lower wear rate of about 1.01 × 10−5 mm3/mN compared to 8.9 × 10−5 mm3/mN, 4.2 × 10−5 mm3/mN, and 4.8 × 10−5 mm3/mN measured for the pure PP, PP-3CNTs and PP-3GNs nanocomposites, respectively. The PP-1CNTs-1GNs nanocomposite respectively showed reduction in mass loss of about 78.7%, 62.2%, and 69.1% when related to the pure PP, PP-3CNTs and PP-3GNs nanocomposites. Maximum hardness and elastic modulus of about 153 MPa and 2.7 GPa were measured for PP-3CNTs-1GNs hybrid nanocomposite, while about 86.4 MPa and 1.5 GPa were recorded for the pure PP, respectively. The enhanced properties of the hybrid nanocomposites are due to the good synergetic effect of CNTs-GNs and the formation of 3D microstructures in the PP matrix with relaxed molecular chains and network hardening of the PP matrix. [ABSTRACT FROM AUTHOR]

Graphene (Gr) and Graphene Oxide (GO) are graphene-based nanosheet (GNS) materials with ultrahigh mechanical properties. The addition of Gr/GO (from 0.01 % to 2 % in mass) to a cement-based material can significantly enhance its mechanical properties. GO has higher efficiency than Gr, but it is more costly. In this paper, a Gr-GO solution was developed by combining Gr and GO in water. The compressive strengths of the samples with and without Gr-GO were determined. Deep analyses were performed by applying several imaging techniques such as nano-tomography, SEM, and confocal Raman imaging to exploit the correlation between microstructural properties and mechanical properties and durability of cement-based materials. The microstructural properties were also quantified from the 3D images obtained by nano-tomography. The results showed that the GNS-added sample had a higher porosity (about 12.4 %) than that of the reference sample (about 6.1 %) but the GNS-added sample had a more homogeneous distribution of micropores. Raman imaging results explained the formation of hydration product and acceleration of hydration rate by Gr-GO in GNS-added samples. The mechanical properties showed that the addition of 0.03 % Gr-GO could increase the compressive strength of mortar samples by 28 %. [Display omitted] • A mixture combining Graphene (Gr) and Graphene Oxide (GO) was developed. • Addition of 0.03 % Gr-GO increased the compressive strength of mortar by 28 %. • 3D microstructural properties of samples were analyzed. • The correlation between microstructure and mechanical properties of samples was exploited. [ABSTRACT FROM AUTHOR]

Mo–Si–Ti alloys, like eutectic Mo–20Si–52.8Ti (at%), have previously been intensely investigated, owing to their excellent oxidation and creep resistance. To better understand high‐temperature mechanical behavior, a holistic assessment of microstructural features is necessary. Correspondingly, 3D‐focused ion beam tomography is carried out in Mo–20Si–52.8Ti. The results indicate a severely interconnected network of Mo solid solution (MoSS) and intermetallic (Ti,Mo)5Si3. Both phases retain similar network connectivity, lamellar sizes, etc. The brittle to ductile transition temperature (BDTT) is then determined through a series of bending tests and interpreted using the microstructural information. The BDTT is found to be ≈1100–1150 °C, different from Mo–9Si–8B with a continuous MoSS network. The BDTT is an immediate consequence of the continuous network of both MoSS and (Ti,Mo)5Si3. The MoSS network is instrumental in crack trapping and bridging, indicating that the present phase distribution maximized the mechanical performance over (Ti,Mo)5Si3. Having determined the network microstructure and BDTT, tensile creep behavior is evaluated and compared to previously published compressive creep results. The results show consistency in terms of strain rate, stress exponent, and microstructural features indicating a reliably good creep resistance for the network microstructure of Mo–20Si–52.8Ti regardless of loading direction. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is characterized by critical alterations of the subchondral bone microstructure, besides the well‐known cartilaginous changes. Clinical computed tomography (CT) detection of quantitative 3D microstructural subchondral bone parameters is applied to monitor changes of subchondral bone structure in different stages of human OA and is compared with micro‐CT, the gold standard. Determination by clinical CT (287 µm resolution) of key microstructural parameters in tibial plateaus with mild‐to‐moderate and severe OA reveals strong correlations to micro‐CT (35 µm), high inter‐ and intraobserver reliability, and small relative differences. In vivo, normal, mild‐to‐moderate, and severe OA are compared with clinical CT (331 µm). All approaches detect characteristic expanded trabecular structure in severe OA and fundamental microstructural correlations with clinical OA stage. Multivariate analyses at various in vivo and ex vivo imaging resolutions always reliably separate mild‐to‐moderate from severe OA (except mild‐to‐moderate OA from normal), revealing a striking similarity between 287 µm clinical and 35 µm micro‐CT. Thus, accurate structural measurements using clinical CT with a resolution near the trabecular dimensions are possible. Clinical CT offers an opportunity to quantitatively monitor subchondral bone microstructure in clinical and experimental settings as an advanced tool of investigating OA and other diseases affecting bone architecture. [ABSTRACT FROM AUTHOR]

At present, micro-shafts with complex structural feature have been widely used in the fields of micro-motors, micro-drives and micro-reducers. Complex microstructures on the micro-shaft can be obtained by layer-by-layer scanning micro-electrical discharge machining (EDM) and micro-reciprocated wire-EDM. However, the above-mentioned methods suffer from the disadvantages such as complex process flow and low machining efficiency. To address the above problems, this paper introduced the workpiece rotation into micro-EDM to machine 3D microstructures on the micro-shaft. First, the microstructure was obtained by micro-milling on the surface of copper plate. Then, the microstructure on the surface of copper plate was finished by milling cutter, so as to effectively remove burrs. The copper plate with the microstructure was used as the tool electrode, and the micro-shaft was used as the workpiece. Under the action of the moving platform, the high-speed rotating micro-shaft gradually approached the tool electrode, and complex 3D microstructures were gradually machined on the surface of the micro-shaft by micro-EDM. Finally, micro-EDM of the micro-shaft was carried out at voltage of 80 V, rotation speed of 3000 rad, pulse width of 1 μs, pulse interval of 5 μs and feed speed of 1.3 mm/min. A 3D microstructure with good shape accuracy and surface topography was obtained on the micro-shaft, and the surface roughness of the microstructure was 0.245 μm. [ABSTRACT FROM AUTHOR]

The modification of cell wall pectin is a major contributing factor to apple softening, associated with intensive variations of firmness and microstructure. Thus, a better understanding of the relationship between fruit optical properties, firmness, 3D microstructure and pectin is important for improving the optical detection of apple firmness. This work explored the optical properties in the wavelength range of 430 – 1650 nm related to cell wall pectin during apple softening, in order to better determine their firmness and 3D microstructural changes. An automatic single integrating sphere system was used to quantify absorption coefficient (μ a) and reduced scattering coefficient (μ s ′). Micro-CT imaging, SEM and TEM were used to quantify the porosity, cell numbers, cell volume, volume fraction and microstructure of Fuji apples during storage. Firmness, pectin fractions, soluble solids content (SSC), titratable acid content (TAC), and moisture content were also measured. Results showed that depolymerization of pectin substances induces an increase in porosity (r = 0.97) and modification of cellular structure, leading to a decrease in firmness (r = 0.90). The reduction in firmness and cell numbers exhibited a strong positive correlation with both μ a in the range of 1000 – 1650 nm and μ s ′ between 430 and 1000 nm with mean r of 0.88–0.96, whereas increases in covalent-soluble pectin (CSP) and porosity displayed a negatively correlated with these bands. The linear relationship indicates that Vis-NIRS at 980 nm could better predict apple firmness than μ a or μ s ′ alone, with a coefficient of determination R2 of 0.97. Our findings suggest that the mechanism of optical technology for detecting apple firmness may be the interaction between tissue structure and pectin on μ s ′ and μ a. • Micro-CT was used to quantify apple tissue 3D structural parameters. • Firmness was highly related to the porosity, cell number and CSP. • Porosity and cell number related well with scattering coefficient. • The μ a showed a high linear relationship with CSP. • Vis-NIRS at 980 nm could better predict apple firmness than μ a or μ s ′ alone. [ABSTRACT FROM AUTHOR]

Abstract Osteoarthritis (OA) is characterized by critical alterations of the subchondral bone microstructure, besides the well‐known cartilaginous changes. Clinical computed tomography (CT) detection of quantitative 3D microstructural subchondral bone parameters is applied to monitor changes of subchondral bone structure in different stages of human OA and is compared with micro‐CT, the gold standard. Determination by clinical CT (287 µm resolution) of key microstructural parameters in tibial plateaus with mild‐to‐moderate and severe OA reveals strong correlations to micro‐CT (35 µm), high inter‐ and intraobserver reliability, and small relative differences. In vivo, normal, mild‐to‐moderate, and severe OA are compared with clinical CT (331 µm). All approaches detect characteristic expanded trabecular structure in severe OA and fundamental microstructural correlations with clinical OA stage. Multivariate analyses at various in vivo and ex vivo imaging resolutions always reliably separate mild‐to‐moderate from severe OA (except mild‐to‐moderate OA from normal), revealing a striking similarity between 287 µm clinical and 35 µm micro‐CT. Thus, accurate structural measurements using clinical CT with a resolution near the trabecular dimensions are possible. Clinical CT offers an opportunity to quantitatively monitor subchondral bone microstructure in clinical and experimental settings as an advanced tool of investigating OA and other diseases affecting bone architecture.

Two biopolyol-based foams derived from banana leaves (BL) or stems (BS) were produced, and their compression mechanical behavior and 3D microstructure were characterized. Traditional compression and in situ tests were performed during 3D image acquisition using X-ray microtomography. A methodology of image acquisition, processing, and analysis was developed to discriminate the foam cells and measure their numbers, volumes, and shapes along with the compression steps. The two foams had similar compression behaviors, but the average cell volume was five times larger for the BS foam than the BL foam. It was also shown that the number of cells increased with increasing compression while the average cell volume decreased. Cell shapes were elongated and did not change with compression. A possible explanation for these characteristics was proposed based on the possibility of cell collapse. The developed methodology will facilitate a broader study of biopolyol-based foams intending to verify the possibility of using these foams as green alternatives to the typical petrol-based foams.

3D Cross-linked Ti 3 C 2 T x -Ca-SA films with expanded Ti 3 C 2 T x interlayer spacing prepared by a simple route and exhibit a superior electrochemical performance. The assembled all-solid-state symmetric pseudocapacitor shows good reliability and flexibility. [Display omitted] • 3D Cross-linked Ti 3 C 2 T x -Ca-SA films with expanded Ti 3 C 2 T x interlayer spacing are prepared. • Expanded interlayer spacing accelerates electrolyte ions transport and increases the intercalation pseudocapacitance. • The 3D cross-linked microstructure synchronously constructs a stable conductive network and maintains good flexibility. • The all-solid-state symmetric pseudocapacitor exhibits good reliability and flexibility under different bending states. Ti 3 C 2 T x , a member of the MXene, has attracted extensive interest because of its high conductivity, unique two-dimensional (2D) structure and intrinsic pseudocapacitance for supercapacitors. Flexible and freestanding Ti 3 C 2 T x films are promising electrodes for functioned supercapacitors used in wearable and portable electronic devices. However, the severe self-restacking of 2D Ti 3 C 2 T x nanosheets restraints their practical application. Herein, freestanding and flexible three-dimensional (3D) cross-linked Ti 3 C 2 T x -Ca-SA (sodium alginate) films with expanded Ti 3 C 2 T x interlayer spacing are reported. The expanded interlayer spacing allows more electrolyte ions to quickly intercalate providing more intercalation pseudocapacitance, while the 3D cross-linked microstructure ensures a continuous conductive network facilitating charges transport. Attributing to the unique structure, the Ti 3 C 2 T x -Ca-SA film delivers an outstanding areal capacitance (633 mF cm−2 at 5 mV s−1). Meanwhile, the assembled all-solid-state pseudocapacitor shows good flexibility and capacity stability under various bending conditions. The device exhibits a high energy density up to 12.6 µWh cm−2 at the power density of 375 µW cm−2 and excellent cycling stability, which are much better than prior reported state-of-the-art supercapacitors. This research exploits a simple method to optimize the structure of MXene as state-of-the-art electrodes for high-performance flexible energy-storage devices. [ABSTRACT FROM AUTHOR]

As a nontraditional processing technology, electrochemical discharge machining (ECDM) can process glass and engineering ceramics precisely. This technology has proven to be a potential process for glass 3D microstructure. However, the key to expanding the application of ECDM is how to improve machining accuracy. This research conducted micro-hole and microgroove machining. Power voltage and frequency influence on hole processing efficiency, hole entrance diameter, and hole limit depth was explored. We considered four factors affecting ECDM—the voltage and frequency of the pulse power supply, the tool electrode feed rate, and the rotation speed. We studied their influence on the roughness of the microgrooves. The results show that machining efficiency, entrance diameter, and limit depth of micro-holes increased with the increase in voltage but decreased with the increase in power frequency. The results show that the roughness of microgrooves has an apparent positive correlation with the power voltage. In contrast, it had an evident negative correlation with the power frequency and electrode speed. The bottom surface roughness of microgrooves can be as minor as 0.605 μm. Various complex 3D microstructures on the glass surface by layer-by-layer method proved the great potential of ECDM. [ABSTRACT FROM AUTHOR]

Hearing loss is a serious illness affecting people’s normal life enormously. The acoustic properties of a tympanic membrane play an important role in hearing, and highly depend on its geometry, composition, microstructure and connection to the surrounding annulus. While the conical geometry of the tympanic membrane is critical to the sound propagation in the auditory system, it presents significant challenges to the study of the 3D microstructure of the tympanic membrane using traditional 2D imaging techniques. To date, most of our knowledge about the 3D microstructure and composition of tympanic membranes is built from 2D microscopic studies, which precludes an accurate understanding of the 3D microstructure, acoustic behaviors and biology of the tissue. Although the tympanic membrane has been reported to contain elastic fibers, the morphological characteristic of the elastic fibers and the spatial arrangement of the elastic fibers with the predominant collagen fibers have not been shown in images. We have developed a 3D imaging technique for the three-dimensional examination of the microstructure of the full thickness of the tympanic membranes in mice without requiring tissue dehydration and stain. We have also used this imaging technique to study the 3D arrangement of the collagen and elastic fibrillar network with the capillaries and cells in the pars tensa-annulus unit at a status close to the native. The most striking findings in the study are the discovery of the 3D form of the elastic and collagen network, and the close spatial relationships between the elastic fibers and the elongated fibroblasts in the tympanic membranes. The 3D imaging technique has enabled to show the 3D waveform contour of the collagen and elastic scaffold in the conical tympanic membrane. Given the close relationship among the acoustic properties, composition, 3D microstructure and geometry of tympanic membranes, the findings may advance the understanding of the structure—acoustic functionality of the tympanic membrane. The knowledge will also be very helpful in the development of advanced cellular therapeutic technologies and 3D printing techniques to restore damaged tympanic membranes to a status close to the native.

Micro structuring of surfaces is of great interest for various applications, e.g. for the tooling industry, the printing industry and for consumer goods. In suitable mass production applications, such as injection molding or roll-to-roll processing for various markets, the final product could be equipped with new properties, such as hydrophilic behavior, adjustable gloss level, soft-touch behavior, light management properties etc. To generate functionalities at reasonable cost, embossing dies can be augmented with additional micro/nano-scale structure using laser ablation technologies. Despite the availability of ultrashort pulsed (USP) high power lasers (up to several hundred watts), it is still a challenge to structure large areas, as required on embossing rolls, in an acceptable processing time for industrial production. In terms of industrial implementation, direct digital transfer is a limiting factor for ultrahigh resolution. Shorter machining times by further increasing spot or workpiece motion are limited. Enlarging the ablation diameter, and thus the tool diameter, delivers a higher ablation rate with the comparable ablation quality, but entails a reduction in resolution. While maintaining the achieved state-of-the-art performance, upscaling of single modulated lasers provides a less demanding way to increase productivity. In the processing of steel surfaces, an increase in material removal can also be achieved by using pulse burst. In this work, the parallel process of single modulated multi laser sources is compared with a laser source split by diffractive optical elements (DOE) for applications in a cylinder micro patterning system. A newly developed highly compact ps laser with repetition rates up to 8 MHz and an average power of 300 or 500 W was divided into 8 or 16 parallel beamlets by a DOE. The ablation rate of each approach was investigated by typical microstructures on copper surfaces. At surface speeds of 10 m/s and a resolution of 5080 dpi, an ablation rate of up to 27 mm³/min was achieved. Different functional surface geometries were realized on an embossing roll as master, which is used for replication of the structures in roll-to-roll processes. Functional structures, such as friction reduction, improved soft touch or light guiding elements on large surfaces are demonstrated. [ABSTRACT FROM AUTHOR]

The objective of performing transmission electron microscopy (TEM) tomography (TEMT) on poly (lactic acid) (PLA)/clay samples is to characterize their 3D microstructure by obtaining the dispersion distribution and orientation of the dimensions of the clays. This information cannot be elucidated from a qualitative TEM analysis or from conventional characterization techniques such as X-ray diffraction. The nanocomposites are obtained by mixing PLA with Cloisite 20A and 30B at different extrusion shear rates which have been analyzed in 3D. Quantitative TEMT is performed to all the nanocomposites and the resulting 3D quantitative characterization (geometry of clay particles misalignment degree and distribution) is used for a more realistic comprehension of the mechanical behavior of the nanocomposites. [ABSTRACT FROM AUTHOR]

Aluminium alloys designed for additive manufacturing with Zr addition exhibit heterogeneous microstructures from the grain scale down to the atomic scale. Bimodal grain structures with submicron equiaxed grains near the melt pool boundaries and columnar grains at the melt pool interiors are observed. The regions consisting of submicron grains are interconnected in 3D. The tensile response of these alloys often shows the presence of a stress plateau or a yield drop phenomenon near the yield strength but the underlying mechanisms still need to be clarified. Herein we investigate the tensile response of a new Al-4Mn-3Ni-2Cu-1Zr alloy in various conditions: after a stress relief (SR=300 °C/4 h) as well as after ageing at 400 °C for 1 h, 4 h (peak-aged) and 96 h (overaged). Based on the plot of the work hardening rate vs true stress, we identify specific characteristics allowing to appreciate the evolution of the elastoplastic transition depending on the heat treatment. The presence of microyielding and a stress plateau near the macroscopic yield strength are evidenced. Microscale DIC based on the local contrast provided by the microstructure decorated by a high fraction of intermetallic particles turns out to be the relevant scale to clarify the mechanisms involved in the elastoplastic transition. Microyielding is related to the regions near the melt pool boundaries and to the columnar grains. The latter yields at lower stress in comparison with the submicron grains due to a reduced contribution of grain boundary strengthening. The stress plateau is attributed to the low work-hardening capacity of the submicron grains. [Display omitted] [ABSTRACT FROM AUTHOR]

To investigate the structural characteristics and mechanical properties of minerals in vanadium-titanium sinter, the 3D microstructures of the sinter were reconstructed by serial sectioning in conjunction with computer-aided 3D reconstruction techniques The results show that hematite and magnetite in vanadium-titanium sinter will grow along the longitudinal axis direction and act as a scaffold. The size of magnetite crystals in vanadium-titanium sinter is much smaller than that in traditional sinter. The calcium ferrite in vanadium-titanium sinter is columnar-like, while that in traditional sinter is needle-like. The decreasing order of the microhardness value of minerals in the two sinters is hematite, calcium ferrite, magnetite and silicate, while the fracture toughness value from highest to lowest is calcium ferrite, hematite, magnetite and silicate. The comprehensive hardness value and comprehensive fracture toughness value of vanadium-titanium sinter are both less than these of traditional sinter.

Electrochemical impedance spectroscopy (EIS) is a powerful technique for material characterization and diagnosis of the solid oxide fuel cells (SOFC) as it enables separation of different phenomena such as bulk diffusion and surface reaction that occur simultaneously in the SOFC. In this work, we simulate the electrochemical impedance in an experimentally determined, three-dimensional (3D) microstructure of a mixed ion-electron conducting (MIEC) SOFC cathode. We determine the impedance response by solving the mass conservation equation in the cathode under the conditions of an AC load across the cathode’s thickness and surface reaction at the pore/solid interface. Our simulation results reveal a need for modifying the Adler-Lane-Steele model, which is widely used for fitting the impedance behavior of a MIEC cathode, to account for the difference in the oscillation amplitudes of the oxygen vacancy concentration at the pore/solid interface and within the solid bulk. Moreover, our results demonstrate that the effective tortuosity is dependent on the frequency of the applied AC load as well as the material properties, and thus the prevalent practice of treating tortuosity as a constant for a given cathode should be revised. Finally, we propose a method of determining the aforementioned dependence of tortuosity on material properties and frequency by using the EIS data.

Abstract Background Sciuromorpha (squirrels and close relatives) are diverse in terms of body size and locomotor behavior. Individual species are specialized to perform climbing, gliding or digging behavior, the latter being the result of multiple independent evolutionary acquisitions. Each lifestyle involves characteristic loading patterns acting on the bones of sciuromorphs. Trabecular bone, as part of the bone inner structure, adapts to such loading patterns. This network of thin bony struts is subject to bone modeling, and therefore reflects habitual loading throughout lifetime. The present study investigates the effect of body size and lifestyle on trabecular structure in Sciuromorpha. Methods Based upon high-resolution computed tomography scans, the femoral head 3D inner microstructure of 69 sciuromorph species was analyzed. Species were assigned to one of the following lifestyle categories: arboreal, aerial, fossorial and semifossorial. A cubic volume of interest was selected in the center of each femoral head and analyzed by extraction of various parameters that characterize trabecular architecture (degree of anisotropy, bone volume fraction, connectivity density, trabecular thickness, trabecular separation, bone surface density and main trabecular orientation). Our analysis included evaluation of the allometric signals and lifestyle-related adaptation in the trabecular parameters. Results We show that bone surface density, bone volume fraction, and connectivity density are subject to positive allometry, and degree of anisotropy, trabecular thickness, and trabecular separation to negative allometry. The parameters connectivity density, bone surface density, trabecular thickness, and trabecular separation show functional signals which are related to locomotor behavior. Aerial species are distinguished from fossorial ones by a higher trabecular thickness, lower connectivity density and lower bone surface density. Arboreal species are distinguished from semifossorial ones by a higher trabecular separation. Conclusion This study on sciuromorph trabeculae supplements the few non-primate studies on lifestyle-related functional adaptation of trabecular bone. We show that the architecture of the femoral head trabeculae in Sciuromorpha correlates with body mass and locomotor habits. Our findings provide a new basis for experimental research focused on functional significance of bone inner microstructure.

In view of tlie current problem of low number of active sites and poor conductivity of materials when M0S2 is used as a hydrogen evolution catalyst，MoS^/PVP composite catalyst was prepared by li(_uid - phase ultrason¬ic strijDping metliod and centrifugal treatment in this study. PVP increased the concentration of MoS2 in the dispersion and increased the amount of catalytic active sites. 2H phase to 1T phase transition occurred during the process，which enhanced the catalytic activity. The PI substrate containing the conductive copper layer was selected as the electrode substrate，which improved the transmission efficiency of electrons between the catalyst and the electrode. The MoS3 PVP composite catalyst was immobilized on the surface of the PI - based electrode by inkjet printing technolog to prepare a catalytic hydrogen evolution electrode with an overpotential of 77 mV at 10 mA . cm-2 and a Tafel slope of 65 mV . dec-1. The above results indicated that the MoS2/PVP catalytic elecrode had axcellent catalytic activity. [ABSTRACT FROM AUTHOR]

This paper presents a new full-field, efficient and mesh-free numerical framework to model microstructure evolution, dynamic recrystallization (DRX) and formability in hexagonal closed-packed (HCP) metals such as magnesium alloys at warm temperatures. A rate tangent-fast Fourier transform-based elasto-viscoplastic crystal plasticity constitutive model for HCP metals (RTCP-FFT-HCP) is coupled with a probabilistic cellular automata (CA) approach to model DRX (CA-DRX). Furthermore, this new model is coupled with the Marciniak-Kuczynski (M-K) approach to model formability of magnesium alloys at elevated temperatures. The RTCP-FFT-HCP model computes macro stress-strain, twinning volume fraction, micromechanical fields, texture evolution and local dislocation density. Nucleation of new grains and their subsequent growth is modeled using the cellular automata approach with probabilistic state switching rule. First, the proposed RTCP-FFT-HCP model is validated by comparing the predicted stress-strain responses and texture evolution under uniaxial tension and compression with experimental measurements for AZ31 sheet alloy at room temperature. The coupled CA-RTCPFFT-HCP model is further validated by comparing the predicted stress-strain responses and texture evolution in uniaxial compression with experimental measurements at 100 °C, 200 °C and 300 °C for the AZ31 sheet alloy. Next, the forming limit diagrams (FLDs) with and without including the effects of DRX are simulated at 100 °C, 200 °C and 300 °C for AZ31 sheet alloy. The predicted FLDs with DRX show very good agreement with the experimental measurements and clearly demonstrate the need for an accurate DRX model. The study reveals that the DRX strongly affects the deformed grain structure, grain size and texture evolution and also highlights the importance accounting for DRX during FLD simulations at high temperatures. • First coupled MK-cellular automata-FFT-based crystal plasticity framework. • First framework that simulates the effects of DRX on the formability. • Demonstrating the effects of DRX on 3D grain structure, grain size and texture evolution. • Demonstrating the importance of accounting for DRX to model formability. • Accurate predictions of forming limit strains at elevated temperatures. [ABSTRACT FROM AUTHOR]

A one step functionalization of large surfaces and layers could be enabled by high power ultrashort pulsed lasers. Despite today's availability of high power ultrashort pulsed lasers (up to several hundred watts), it is still a challenge to structure large surface areas, which is required on embossing rollers, within an acceptable processing time for industrial roll-to-roll production. Furthermore, fluencies near the ablation threshold are necessary to provide the highest depth resolution with minor side effects. So, it is a challenge to convert the increasing high average laser power into a high processing speed by maintaining the well-known quality of ultrashort pulsed lasers constant. One approach is the combination of a high-speed application and several parallel ablating laser spots. In this contribution, a newly developed high compact picosecond laser with high pulse repetition rates and an average power of 500 W was distributed into 8 and 16 parallel beamlets by a diffractive optical element. The power was controlled by single acousto-optical modulators per beamlet. Different functional surface geometries have been realized on an embossing roller as a master, which is used for the replication of the structures in a roll-to-roll or a roll-to-plate process. Feature sizes from 2 μm to 10 μm in areas of 2 m2 could be processed. With this approach, functional structures such as reduction in friction, improved soft touch, or light guiding elements can be generated on large surfaces within short processing times. [ABSTRACT FROM AUTHOR]

High energy x-ray diffraction microscopy was used to image the microstructure of α-Fe before and after a 600 °C anneal. These data were used to determine the areas, curvatures, energies, and velocities of approximately 40,000 grain boundaries. The measured grain boundary properties depend on the five macroscopic grain boundary parameters. The velocities are not correlated with the product of the mean boundary curvature and grain boundary energy, usually assumed to be the driving force. The total migration of a boundary consists of both translations approximately normal to the boundary and lateral changes in area. Through the lateral changes in area, low energy boundaries tend to expand in area while high energy boundaries shrink, reducing the average energy through grain boundary replacement. The driving force for this process is not related to curvature and might disrupt the expected curvature – velocity relationship. [Display omitted] [ABSTRACT FROM AUTHOR]

Fluorescence-linked immunosorbent assay (FLISA) is a commonly used, quantitative technique for detecting biochemical changes based on antigen–antibody binding reactions using a well-plate platform. As the manufacturing technology of microfluidic system evolves, FLISA can be implemented onto microfluidic disk platforms which allows the detection of trace biochemical reactions with high resolutions. Herein, we propose a novel microfluidic system comprising a disk with a three-dimensional incubation chamber, which can reduce the amount of the reagents to 1/10 and the required time for the entire process to less than an hour. The incubation process achieves an antigen–antibody binding reaction as well as the binding of fluorogenic substrates to target proteins. The FLISA protocol in the 3D incubation chamber necessitates performing the antibody-conjugated microbeads’ movement during each step in order to ensure sufficient binding reactions. Vascular endothelial growth factor as concentration with ng mL−1 is detected sequentially using a benchtop process employing this 3D microfluidic disk. The 3D microfluidic disk works without requiring manual intervention or additional procedures for liquid control. During the incubation process, microbead movement is controlled by centrifugal force from the rotating disk and the sedimentation by gravitational force at the tilted floor of the chamber.

• Bi 2 S 3 /TiO 2 NTAs photoelectrode was fabricated by electrodeposition strategy. • Bi 2 S 3 /TiO 2 NTAs possessed high physicochemical properties. • Bi 2 S 3 /TiO 2 NTAs exhibited high visible PC efficiency of methylene blue. • The enhanced visible PC mechanism of Bi 2 S 3 /TiO 2 NTAs was confirmed. In the present study, Bi 2 S 3 /TiO 2 nano-tube arrays (Bi 2 S 3 /TiO 2 NTAs) photoelectrode was fabricated by anodization and electrodeposition strategy. Besides, the deposition time and electric current density during photoelectrode construction process was optimized as 90 min and −0.8 A⋅cm−2, MB removal and mineralization efficiency within 30 min was 82.3% and 57.4%, severally. Afterwards, physicochemical properties of the resulting Bi 2 S 3 /TiO 2 NTAs were studied through SEM, XRD, XPS and DRS measurements. Photoelectrochemical (PECH) performance was determined by transient photocurrent density (TPR) and electrochemical impedance spectroscopy (EIS). Results indicated that Bi 2 S 3 /TiO 2 NTAs photoelectrode was constructed successfully and with enhanced photocatalytic performance. Additionally, OH radical and e- played the dominant parts in the photocatalystic process confirmed via scavenging experiments. At last, enhanced photocatalytic mechanism of Bi 2 S 3 /TiO 2 NTAs reaction system was proposed. The consequence would be attributed to the special 3D microstructure formation and the construction of Z-scheme photocatalytic system of Bi 2 S 3 /TiO 2 NTAs, which both could improve photocatalytic performance via effective photogenerated electron-hole separation and electron transfer process. [ABSTRACT FROM AUTHOR]

• A simple and efficient PDMS double casting method using plasma treatment followed by alcohol passivation is described. • Two-step surface treatment ensures double casting performance at a single micron scale resolution. • The method is capable of micron level reproduction of objects featuring high aspect ratios and complex 3D microstructures. We propose a simple and efficient polydimethylsiloxane (PDMS) double casting method using plasma treatment followed by methanol or ethanol treatment. The plasma treatment oxidizes the functional groups on the surface of the PDMS mold, showing an increase in the concentration of hydroxyl functional groups (OH); subsequent exposure to the alcohols prevents adherence of the second PDMS casting. This process effectively passivates the surface of the PDMS master mold to suppress further chemical bonding. This two-step surface treatment ensures excellent double casting performance at a single micron scale resolution to yield micron level reproduction of objects featuring high aspect ratios, two-dimensional surface micropatterns, and complex three-dimensional microstructures. [ABSTRACT FROM AUTHOR]

Computational predictions of measures for macroscopic material attributes from the microstructure scale is a fundamental challenge in materials science. Data transfer across scales and physics-based models plays a central role in this highly material-specific process. Here, we present an approach for computationally establishing the probabilistic shock-to-detonation transition (SDT) threshold or "pop plot" (PP, the relation between run-to-detonation distance and applied pressure) of polymer-bonded explosives (PBXs) from three-dimensional (3D) simulations. The approach takes respective advantages of multiphysics Lagrangian and Eulerian modeling frameworks. The combined Lagrangian and Eulerian simulations provide an explicit account of 3D heterogeneous material microstructure at sizes up to tens of mm, mechanisms for the development of hotspots, and the coupled mechanical-thermal-chemical-transport processes which underlie the behaviors being predicted. Data transfers in the form of hotspot intensity fields from the Lagrangian simulations to the Eulerian simulations link the two frameworks. To capture the fundamental nature of the multiphysics processes, the source, and the propagation of the stochastic variations in material behavior, a 3D statistically equivalent microstructure sample set (SEMSS) is designed and used. The approach facilitates an efficient quantification of the probabilistic macroscopic detonation thresholds, leading to an analytical expression for the PP that accounts for both the microstructure effects and uncertainties. The material system modeled tracks the properties of PBX 9501 and the loading conditions studied involve shock pressure Ps in the range of 11–15 GPa. The results are in good agreement with available experimental data. [ABSTRACT FROM AUTHOR]

A typical Longmaxi (LMX) shale sample from Sichuan basin, China, is investigated in three dimensional through multiscale tomography methods spanning pixel sizes from 3.25 μm to 10 nm, combining X-ray computed tomography and focused ion beam-scanning electron microscopy imaging techniques. Pores, organic matter (OM) and pyrite were segmented and reconstructed at multiple scales and the representative elementary volume (REV) of each phase at different scales based on the convergence of error bars in the volume fraction are determined. Results show that REVs at each scale varied between different phases. The determination of REV defined the applicable scale of different methods as well as the appropriate scales of specific structures. Porosity of LMX shale determined at different scales shows significant difference at two orders of magnitude. This difference likely was caused by structural heterogeneity together with the limitations of methods. This study confirms that REV is a feasible and powerful approach in modeling shale using multiscale 3D imaging. The application of multiscale 3D imaging techniques to worldwide shale gas reservoirs could allow for significant insights into the assessment of migration mechanisms within low-permeability systems. Image 1 • Longmaxi shale is visualized in 3-D across the mm to nm scale using complementary methods. • Integrated imaging illustrates microstructural complexities of increasing heterogeneity at higher resolutions. • REVs at multiscale are determined, which defines the applicable scale of different methods. • The porosity changes with the observing scale and is likely to peak at about 250 μm within the mm scale. [ABSTRACT FROM AUTHOR]

Abstract Frozen vegetables are often exposed to dynamic temperature conditions during cold storage and distribution chain. The resulting ice recrystallization leads to microstructural changes, which is directly linked to the final vegetable quality. To this end, X-ray μCT was applied to visualize and quantify 3D ice crystal changes in carrot over a period of two months of frozen storage with dynamically changing temperature. The studied conditions revealed a significant increase in ice crystal size during the storage period. The mean equivalent diameter of the ice crystals increased from 246 ± 15.9 μm, to 342 ± 13.2 μm, 394 ± 18.5 μm, 525 ± 28.0 μm and 578 ± 27.6 μm at 0 d, 7 d, 14 d, 30 d and 60 d of storage, respectively, while the number of ice crystals decreased. The 3D data on the ice crystals and image analysis presented within this paper provide an insight making it possible to describe microstructure evolution, and for better control cold storage sector of frozen vegetables. Highlights • X-ray μCT imaging was performed to visualize the 3D ice crystal growth during storage. • Ice crystal size increases with increase storage time under dynamic temperatures. • Number of ice crystals decreased over a period of storage. • 3D image analysis to quantify ice crystal changes in carrot tissue during storage. [ABSTRACT FROM AUTHOR]

Abstract Complex 3D microstructure and mechanical properties can be precisely characterized and linked by employing the X-ray micro-tomography combined with EBSD serial sectioning. Global sensitivity and principal component analysis can be used to rank and coarsen the contributing features that control the mechanical response. Afterwards, by creating surrogate models, the relationship between the most contributing features and mechanical properties can be further analyzed via support vector machines. The aforementioned novel approach was applied to study the relationship between 3D microstructural features and short crack behavior in a Ti-6Al-4V alloy. It was revealed that short crack path, growth rate, and its variation are mainly affected by the interaction with neighboring grains; however, as the short crack front becomes larger, there is a decrease and a change in the importance of those interactions. A high number of grains in contact with long cracked α grains in the loading direction may impose a constraint on the crack opening resulting in low crack growth rates. For the larger crack front, the increase in the shear stress field around the cracked grains leads to crack bifurcations and to the formation of secondary cracks, resulting in a decrease in crack driving forces with low crack growth rates. It was concluded that short crack behavior is strongly affected by the shape, size, and crystallographic features of its neighboring grains, which cause variation in the shear and tensile stress fields resulting in crack growth rate variation. [ABSTRACT FROM AUTHOR]

Abstract Cast duplex stainless steels (CDSS) is being extensively used in many industries. The morphology and distribution of ferrite phase present, as well as the micropores defect, significantly influences the hot cracking susceptibility and corrosion resistance of CDSS. In this work, the microstructure and the micropores of the inner wall and outer wall position of a primary coolant pipe used in the pressurized water reactor (PWR) were characterized and compared using a lab scale X-ray microtomography approach. During centrifugal casting process, the local ferrite grains tend to grow in the same direction. Although the ferrite phases seem separated from each other in a two-dimensional (2D) image, most of them are connected in a three-dimensional (3D) view. Solution treatment can result in homogeneous distribution in both fraction and morphology of ferrite phase. Micropores always form along the ferrite/austenite interface and the inner wall position is more prone to porosity. Highlights • High number of projections, intermediate accelerating voltage, and exposure time were used for high quality scans in steel. • The "average dataset" method can improve the scan quality significantly. • Ferrite has a complex dendritic morphology, and local ferrite grains tend to grow in the same direction during centrifugal casting process. • The variations in cooling rate along radial direction and shrinkage porosity in the inner surface region affects microporosity along the radial direction. • Both in the inner wall and outer wall position, the micropores always form along the ferrite/austenite interface. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) microelectrodes used for processing 3D microstructures in micro-electrical discharge machining (micro-EDM) can be readily prepared by laminated object manufacturing (LOM). However, the microelectrode surface always appears with steps due to the theoretical error of LOM, significantly reducing the surface quality of 3D microstructures machined by micro-EDM with the microelectrode. To address the problem above, this paper proposes a filling method to fabricate a composite 3D microelectrode and applies it in micro-EDM for processing 3D microstructures without steps. The effect of bonding temperature and Sn film thickness on the steps is investigated in detail. Meanwhile, the distribution of Cu and Sn elements in the matrix and the steps is analyzed by the energy dispersive X-ray spectrometer. Experimental results show that when the Sn layer thickness on the interface is 8 μm, 15 h after heat preservation under 950 °C, the composite 3D microelectrodes without the steps on the surface were successfully fabricated, while Sn and Cu elements were evenly distributed in the microelectrodes. Finally, the composite 3D microelectrodes were applied in micro-EDM. Furthermore, 3D microstructures without steps on the surface were obtained. This study verifies the feasibility of machining 3D microstructures without steps by micro-EDM with a composite 3D microelectrode fabricated via the proposed method.