Differences In Microstructure Research Articles

Temperature effects on ribbon characteristics in soft gelatin capsule manufacture

In the manufacture of soft gelatin capsules using a rotary-die encapsulation machine, the formation of ribbons at the cooling drums and their subsequent mechanical performance are key attributes for a smooth machinability. In this paper we present the results of a comprehensive investigation of the intricate impact of the cooling drum temperature in the range between 5 and 25 °C on the mechanical and the microstructural properties of a highly concentrated gelatin formulation (40% w/w) typically used in soft capsule manufacture.The study demonstrates that the temperature at the cooling drums strongly affects the gelation kinetics, the gel elasticity and the tensile strength of the ribbons. The temperature correlates linearly with the storage modulus G′ under low shear deformation, i.e. the lower the temperature of the gel, the higher the gel elasticity. A reverse linear relationship was found for the temperature-dependent ultimate tensile strength (UTS) of the gelatin ribbons, i.e. a higher drum temperature leads to a higher UTS. This inverse effect of the ageing temperature on G′ and UTS can be explained by temperature-induced microstructural differences within the gel network, as indicated by FTIR spectroscopy and Differential Scanning Calorimetry (DSC) measurements. Lower ageing temperatures result in a higher number of triple helical junction zones with fewer and/or weaker hydrogen bonds, which translate into a higher gel elasticity under low shear deformation, but a lower resilience of the ribbons against rupture in tensile testing. At higher temperatures, fewer but longer and/or more thermostable triple helical links in the gel network enhance the stability of the ribbons against tensile stress.In summary, the results clearly reveal that a detailed understanding of the complex relationship between the drum temperature, the gel network structure and the mechanical properties of gelatin ribbons is essential for process optimization.

Fabrication of TC4 and Ti48Al bimetals by plasma arc additive manufacturing： Microstructure and mechanical properties

Plasma arc additive manufacturing (PAAM) was applied to fabricate TC4 and Ti48Al (gamma titanium aluminide) bimetals in this work. The impact of deposition sequence on the microstructure and mechanical properties of two groups of bimetals (TC4-Ti48Al, first deposited TC4, then Ti48Al; Ti48Al-TC4, first deposited Ti48Al, then TC4) was investigated. The results show that the ultimate tensile strengths of two groups of bimetals exhibit significant differences, with 158.4 MPa for TC4-Ti48Al and 232.3 MPa for Ti48Al-TC4, the reason for this disparity is the difference in microstructure at the transition zone, which is attributed to heat input and Marangoni convection. The phase transformation evolution of TC4-Ti48Al transition zone is (major α2 + minor α)→ (major α2 + minor γ) → (major γ + minor α2), and (major α2 + minor α) → (major α + minor α2) for Ti48Al-TC4. The formation mechanism of transition zones and relationship between the microstructure characteristics and mechanical properties of two groups of bimetals were further discussed. Overall, the property of Ti48Al-TC4 was superior, and this work provides a promising new method for the preparation of TC4 and Ti48Al bimetals.

Fatigue investigations of elastomers developed for high-pressure hydrogen gas environments

Hydrogen possesses many characteristics to be an ideal candidate as a more sustainable energy carrier, especially for the transport sector. For a proper optimization of this abundant resource, hydrogen needs to be compressed, and stored in high-pressure conditions, which demands improvement in technology and the development of appropriate materials. In this context, elastomeric sealing components play a critical role and they need to withstand harsh working conditions, for example, high-pressure, wide temperature range, cyclic exposure conditions, etc. In this work, eight different grades designed for this application were analyzed in terms of fatigue behavior and long-term performance. This was verified through fatigue crack growth experiments, the energy dissipation, and temperature increase during crack propagation were analyzed and correlated with micro-structural differences of materials. Furthermore, the materials were investigated at large and small deformations through uniaxial tensile tests and Dynamic Mechanical Analysis (DMA), respectively. It was found that only with the addition of a coupling agent can silica-filled NBR have properties similar to carbon black (CB) filled NBR, despite a reduction in both fatigue strength and energy dissipation. Coupling agents also involved an increase in bound rubber. Regarding CB-filled compounds, with peroxide crosslinking a reduction in fatigue strength was found, while no effect on the quantity of bound rubber was observed. Increased CB content in NBR grades led to decreased fatigue resistance and higher energy dissipation; higher bound rubber content was found as well. Also for EPDM grades, increased CB content resulted in reduced fatigue resistance. Despite an increase in energy dissipation, the content of bounded rubber was the same even with higher CB content.

Fracture toughness and microstructural analysis of rotary friction welded S355J2 and SS316L steels for critical applications

Dissimilar metal welding is seeing growing adoption across industries to enhance structural functionality and efficiency. Achieving high-quality, defect-free dissimilar weld joints requires a comprehensive understanding of the interrelationships between the welding-induced microstructural changes and the material's performance characteristics, particularly its fracture-related properties. This study investigates the impact of microstructural changes on the fracture toughness of dissimilar welds between structural low-carbon steel (S355J2) and austenitic stainless steel (SS316L) prepared using the Rotary Friction Welding (RFW) technique. Welding preforms were created from respective pipe pup pieces. The evaluation involves microstructural analysis, tensile testing, hardness testing, and fracture toughness testing using compact tension specimens derived from various zones of the weld joints. Results revealed significant microstructural differences across the weld joint. The weld region exhibited stable hardness with a maximum of 208 HV1 in S355J2′s thermo-mechanically affected zone (TMAZ). High tensile strength (Ultimate Tensile Strength 540 MPa, Yield Strength 367 MPa) with failures mainly on the S355J2 side. The fracture toughness (KQ) matched parent metal values, with the RFW weld centre line (WCL) showing superior crack tip opening displacement (CTOD) of 0.35 mm. Fractography generally indicates ductile failure.

Preparation of microgel particles from egg yolk components by combining phospholipase A2 with high-pressure homogenization: Physicochemical, structural properties and their effects on foaming, processing stability of egg white protein

In this study, two types of microgel particles from egg yolk components were prepared by combining enzymatic hydrolysis with high-pressure homogenization (HPH), and their differences in physicochemical properties, foaming properties, and microstructure were compared. Results showed that the particle size of both types of microgel particles had decreased from 2744.07 ± 408.26 nm (egg yolk, EY) to 144.97 ± 3.19 nm (PLA2 hydrolyzed egg yolk microgel particles, PYM) and 535.07 ± 46.07 nm (egg yolk microgel particles hydrolyzed by PLA2, YMP), from 736.24 ± 34.61 nm (EG) to 182.76 ± 4.12 nm (PLA2 hydrolyzed egg yolk granules microgel particles, PGM) and 443.98 ± 27.09 nm (egg yolk granules microgel particles hydrolyzed by PLA2, GMP). Besides, their interfacial adsorption abilities were significantly improved, reflected in the increase values in overrun, from161.90 % ± 9.84 % (EY) to 269.64 % ± 16.73 % (PMY) and 307.20 % ± 16.09 % (YMP), from 189.21 % ± 5.02 % (EG) to 280.38 % ± 36.05 % (PGM) and 261.91 % ± 34.03 % (GMP). Their structural properties showed higher stabilities after treatments. When the microgel particles are applied to cakes, the specific volume was increased from 2.05 ± 0.1 mL/g (EY) to 2.25 ± 0.13 mL/g (PYM) and 2.45 ± 0.03 mL/g (YPM), and from 2.00 ± 0.09 mL/g (EG) to 2.51 ± 0.13 mL/g (PGM) and 2.75 ± 0.21 mL/g (GMP), respectively. The hardness and chewiness were reduced with both types of microgel particles from egg yolk components, which indicated their potential value as edible foam stabilizers in the baking industry.

Effects of scanning strategy and scanning speed on microstructures and mechanical properties of NiTi alloys by laser powder bed fusion

In this work, the influence of processing parameter including laser scanning strategy and scanning speed on grain morphology and crystalline orientation of NiTi alloys fabricated by laser powder bed fusion (L-PBF) was comprehensively investigated from the perspective of crystal growth. The results show that as the interlayer rotation angle increases from 0 to 90°, the grain morphology changes from the coarse columnar to columnar-and-equiaxed shapes, accompanied by the texture intensity first rising then reducing. Besides, increasing the scanning speed leads to a transition in grain morphology from columnar to equiaxed crystals, as well as a reduction in grain size and texture intensity. The recovery mechanism caused by different thermal histories under various scanning speeds was discussed, with a particular focus on dislocation density and its distribution. The results demonstrate that the dislocation density gradually increases with the increase of scanning speed, leaving behind more dislocations within the matrix. Furthermore, the effects of scanning speed and building direction on the compressive behavior were investigated through identifying the difference of microstructure in the NiTi alloys by L-PBF. This study highlights the relationship among processing, microstructure, and mechanical performance, paving the way for tailoring and designing microstructures and mechanical properties for the NiTi alloys by L-PBF.

Comparison of Pore Structure Characteristics of Shale-Oil and Tight-Oil Reservoirs in the Fengcheng Formation in Mahu Sag

Despite the abundance of shale-oil and tight-oil reserves in the Fengcheng Formation within the Mahu Sag, exploration and development efforts for both types of reservoir are still in their early stages. A comprehensive examination and comparison of the pore structures of these reservoirs can establish rational classification and evaluation criteria. However, there is a dearth of comparative analyses focusing on the pore structures of shale-oil and tight-oil reservoirs within the Fengcheng Formation. This study addresses this gap by systematically analyzing and comparing the pore structures of these reservoirs using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), low-temperature nitrogen adsorption, and mercury intrusion capillary pressure experiments (MICP). The results show that the shale oil within the Fengcheng Formation exhibits a higher content of carbonic acid compared to the tight-oil samples. Furthermore, it demonstrates smaller displacement pressure and median pressure, a larger sorting coefficient, and superior permeability in contrast to tight oil. Notably, the shale oil within the Fengcheng Formation is characterized by abundant striated layer structures and micro-fractures, which significantly contribute to the microstructural disparities between shale-oil and tight-oil reservoirs. These differences in microstructures between shale oil and tight oil within the Fengcheng Formation in the Mahu Sag region delineate distinct criteria for evaluating sweet spots in shale-oil and tight-oil reservoirs.

Study on Thermophysical Properties and Phase Change Regulation Mechanism of Optically-Controlled Phase Change Materials: Synthesis, Crystal Structure and Molecular Dynamics.

Optically-controlled phase change materials, which are prepared by introducing molecular photoswitches into traditional phase change materials (PCMs), can convert and store solar energy into photochemical enthalpy and phase change enthalpy. However, the thermophysical properties of optically controlled PCMs, which are crucial in the practical, are rarely paid attention to. 4-(phenyldiazenyl)phenyl decanoate (Azo-A-10) is experimentally prepared as an optically-controlled PCMs, whose energy storage density is 210.0 kJ·kg-1, and the trans single crystal structure is obtained. The density, phase transition temperature, thermal conductivity, and other parameters in trans state are measured experimentally. Furthermore, a microscopic model of Azo-A-10 is established, and the thermophysical properties are analyzed based on molecular dynamics. The results show that the microstructure parameter (order parameters) and thermophysical properties (density, radial distribution function, self-diffusion coefficient, phase change temperature, and thermal conductivity) of partially or completely isomerized Azo-A-10, which are challenging to observe in experiments, can be predicted by molecular dynamics simulation. The optically-controlled phase change mechanism can be clarified according to the differences in microstructure. The optically-controlled switchability of thermophysical properties of an optically-controlled PCM is analyzed. This study provides ideas for the improvement, development, and application of optically-controlled PCMs in the future.

Recrystallization behavior and strengthening mechanism of friction stir welded T-joint of Ti80 titanium alloy

In this study, Ti80 titanium alloy T-joints were produced by friction stir welding (FSW), and the joint temperature and residual stress distribution of the joints were analyzed by numerical simulation based on the ABAQUS platform, and the correlation between microstructure and performance of FSWed T-joint was investigated. The results show that the SZ is lamellar α grains due to the fact that the peak temperature of all joints exceeds β phase transus. The deformation and dynamic recrystallization behavior take place in the β phase region. During the subsequent cooling stage, the acicular α/α' phase is precipitated from refined prior β phase. The non-uniform heating and cooling results in the significant microstructure differences in the weld thickness direction. The top and middle of the SZ are composed of basketweave structure, while the bottom of the SZ shows a bimodal structure. The microhardness distribution along the skin shows a higher value in the weld area, and the weakest area is located in the HAZ due to recovery, resulting in a significant reduction in dislocation density of the weld. The tensile specimen breaks in the HAZ when it is stretched along the skin direction, while it breaks in a direction parallel to the skin when it is stretched along the stringer. The fracture mechanism of the joint changes from a hybrid mode of ductile and brittle fracture to ductile fracture as the rotation speed increases from 600 rpm to 750 rpm.

The Effect of Silicon Nanoparticle Size on Cycle and Calendar Life

Lithium-ion batteries are now ubiquitous in modern electronics, electric vehicles, and many other applications. As the battery industry continues to push for better, longer lasting batteries, many have turned to using a different anode material that would provide higher-energy density and require less frequent charges. While graphite is the tried-and-true anode material for lithium-ion batteries, a silicon anode battery could provide up to ten times higher theoretical energy density than graphite. However, there are a lot of challenges standing in the way between silicon anode batteries and commercialization—the large volume expansion of silicon (around 200-300% expansion, compared to graphite at 10%) and the unstable solid-electrolyte-interface (SEI) of silicon results in anodes that mechanically degrade and calendar age faster than their graphite counterparts.Previous research has demonstrated that plasma-enhanced chemical vapor deposition (PECVD) silicon nanoparticles with a hydrophilic coating such as polyethylene oxide (PEO) results in silicon anodes with good cycle life [1, 2, 3, 4]. In this system, smaller particle sizes typically yielded better cyclability than larger particle sizes, which is contrary to conventional wisdom that more surface area is detrimental as it allows for more SEI formation and side reactions. However, since silicon anodes experience large volume changes during cycling, the surface area might not be the dominant contribution to capacity fade. Larger silicon particles result in larger total expansions of the electrode, which causes more mechanical damage like cracks to form, exposing fresh surface area to electrolyte and SEI formation.This research investigates the performances of PEO-coated PECVD Si electrodes with nanoparticles ranging from 3 to 27 nm in diameter. We measure the cycle life at a rate of 0.333C, as well as the calendar lifetimes of each electrode. We characterize each electrode with SEM imaging, tortuosity measurements, and electrochemical impedance spectroscopy to understand the differences in microstructure that contribute to capacity fade and impedance rise.

Investigation of fatigue crack growth behavior and crack tip plastic zone characteristics in welded structures based on local displacement fields

The fatigue crack growth behavior in welds is difficult to evaluate due to complex internal stresses and microstructural differences. This paper uses the CJP model based on displacement field variations to describe the fatigue crack growth behavior and the size of the crack tip plastic zone in welds. First, fatigue crack growth rate tests were conducted on base metal and as-welded specimens. The digital image correlation technique was used to capture the speckle pattern variations on the specimen surface during crack growth, obtaining the crack tip displacement field required by the CJP model. Based on this, by calculating the stress intensity factor ranges ΔK and ΔKCJP, two da/dN–ΔK(ΔKCJP) curves defined by the traditional and CJP models were obtained, proving the model’s applicability for describing fatigue crack growth behavior in welded joints. Finally, the CJP model was used to calculate and compare the crack tip plastic zones of base metal and as-welded specimens. It was found that the maximum error for the as-welded specimen was 37.84%, occurring at the initial stage of crack propagation and gradually decreasing with the fatigue process.

Sequencing-Dependent Impact of Carbon Coating on Microstructure Evolution and Electrochemical Performance of Pre-lithiated SiO Anodes: Enhanced Efficiency and Stability via Pre-Coating Strategy.

Silicon monoxide (SiO) has attracted considerable interest as anode material for lithium-ion batteries (LIBs). However, their poor initial Coulombic efficiency (ICE) and conductivity limit large-scale applications. Prelithiation and carbon-coating are common and effective strategies in industry for enhancing the electrochemical performance of SiO. However, the involved heat-treatment processes inevitably lead to coarsening of active silicon phases, posing a significant challenge in industrial applications. Herein, the differences in microstructures and electrochemical performances between prelithiated SiO with a pre-coated carbon layer (SiO@C@PLi) and SiO subjected to carbon-coating after prelithiation (SiO@PLi@C) are investigated. A preliminary carbon layer on the surface of SiO before prelithiation is found that can suppress active Si phase coarsening effectively and regulate the post-prelithiation phase content. The strategic optimization of the sequence whereprelithiation and carbon-coating processes of SiO exert a critical influence on its regulation of microstructure and electrochemical performances. As a result, SiO@C@PLi exhibits a higher ICE of 88.0%, better cycling performance and lower electrode expansion than SiO@PLi@C. The pouch-type full-cell tests demonstrate that SiO@C@PLi/Graphite||NCM811 delivers a superior capacity retention of 91% after 500 cycles. This work provides invaluable insights into industrial productions of SiO anodes through optimizing the microstructure of SiO in prelithiation and carbon-coating processes.

Gas tungsten arc welding of a multiphase CoCuxFeMnNi (x=20,30) high entropy alloy system: Microstructural differences and their consequences on mechanical performance

With the current advancements in materials science, the development of high entropy alloys (HEAs) is progressively increasing. Hence, research on their processability is essential to make them competitive alternatives to common engineering alloys that are widely used in structural applications. One manufacturing technique commonly employed in this sector is gas tungsten arc welding (GTAW). This technique allows to obtain single monolithic parts from separate components, often at the cost of local microstructural and mechanical properties variation across the joint. As such, GTAW processing is capable of supplying relevant knowledge regarding the feasibility of joining new materials and their potential industry uptake. In this study, we present a comparative analysis on the use of GTAW on two distinct multiphase high entropy alloys: CoCu20FeMnNi and the CoCu30FeMnNi. Firstly, microstructural observations coupled with CalPhaD-based calculations and synchrotron X-ray diffraction analysis, allowed to delve, and compare, the microstructural evolution across both welds. It was possible to observe the dual phase nature of the microstructure throughout the welded joint alongside the nucleation of a B2 BCC phase in the heat affected zone (HAZ) of both HEAs. Considering the mechanical properties of the welded materials, results evidenced a poorer, yet still acceptable mechanical performance. The observed decrease in mechanical strength is attributed to the residual stress conditions and large grain size that developed owing to the process thermal cycle, which contrasted deeply with the microstructure of each base material.

Mechanistic investigation on the influence of coating weights on the corrosion behaviour of hot-dip-galvanised Zn-Mg-Al coatings

Time-lapse Microscopy, scanning vibrating electrode technique and potentiodynamic methods were used to study the influence of increasing coating weight (80–310 gm–2) on microstructure, cut-edge and surface corrosion of Zn-Mg-Al coatings in 0.17 M NaCl. Cut-edge corrosion was similar for all coatings due to the oxygen reduction reaction becoming diffusion-limited. A 64% reduction in surface corrosion was observed for high coating weights through increases in eutectic volume fraction. Spatial and temporal corrosion mechanisms were controlled by microstructural morphological differences as coating weight varied. 80 g.m–2 coatings demonstrated lateral anodic spreading potentially reducing coating penetration rates despite their higher surface corrosion rate.

Impact of Sleeve Gastrectomy on Brain Structural Integrity.

Potential brain structural differences in people with obesity (PwO) who achieve over or less than 50% excess weight loss (EWL) after sleeve gastrectomy (SG) are currently unknown. We compared measures of gray matter volume (GMV) and white matter (WM) microstructural integrity of PwO who achieved over or less than 50% EWL after SG with a group of controls with obesity (CwO) without a past history of metabolic bariatric surgery. Sixty-two PwO underwent 1.5T MRI scanning: 24 who achieved more than 50% of EWL after SG ("group a"), 18 who achieved less than 50% EWL after SG ("group b"), and 20 CwO ("group c"). Voxel-based morphometry and tract-based spatial Statistics analyses were performed to investigate GMV and WM differences among groups. Multiple regression analyses were performed to investigate relationships between structural and psychological measures. Group a demonstrated significantly lower GMV loss and higher WM microstructural integrity with respect to group b and c in some cortical regions and several WM tracts. Positive correlations were observed in group a between WM integrity and several psychological measures; the lower the WM integrity, the higher the mental distress, emotional dysregulation, and binge eating behavior. The present results gain a new understanding of the neural mechanisms of outcome in patients who undergo SG. We found limited GMV changes and extensive WM microstructural differences between PwO who achieved over or less than 50% EWL after SG, which may be due to higher vulnerability of WM to the metabolic dysfunction present in PwO.

Assessment of location- and orientation- dependent fatigue behaviour for as-deposited LPBF Inconel 718 using miniaturized specimens

The location- and orientation-dependence of tensile properties and low/high cycle fatigue behaviour of additively manufactured IN718 were determined on as-deposited material with the use of miniaturized specimens. Local properties were determined throughout the build height for two orientations by using 39 fatigue samples and 32 tensile test coupons excised from bulk builds. The low cycle fatigue behaviour is described with the use of the Manson-Coffin approach while the high cycle regime was analysed using a Wohler-based assessment. Extensive microstructure characterization included optical microscopy, electron microscopy with EDX and EBSD analyses, fractography and computer tomography in order to rationalize the fatigue anisotropy in certain regimes. Significant anisotropy in the low cycle (i.e. high strain) fatigue regime is attributed to the differences in microstructure, UTS, and ductility in the as-deposited material. The fatigue behaviour in the high cycle (i.e. low strain) regime was worse in Z-oriented samples, partly due to its somewhat lower UTS and detrimental orientation of lack-of-fusion defects that served as fatigue initiation sites. The complete axial fatigue behaviour, which evaluated the whole range from uniaxial tension (i.e. one cycle) through the low cycle to high cycle regime, was attempted with the use of the Stussi model. While the various modelling approaches that used either uniaxial tension or cyclic tension data captured some of the observations, the detrimental effects of process-induced defects and their orientation with respect to the loading direction prevented a complete description of the fatigue behaviour in the high cycle fatigue regime. Nevertheless, the use of miniaturized samples provides a unique capability to examine both the location- and orientation-dependent fatigue behaviour relevant to many engineering structures.

Phase compositions, microstructures, and microwave dielectric properties of novel high-entropy spinel-structured MAl2O4 ceramics

High-entropy design for MgAl2O4 spinel has rarely been reported. In this study, six novel high-entropy spinel-structured (HES) MAl2O4 ceramics were prepared through the conventional solid-state reaction method. The effect of high-entropy design on the crystal structure, microscopic morphology, and microwave dielectric performance of HES ceramics was investigated based on X-ray diffraction (XRD), Raman spectra, and scanning/transmission electron microscopy (SEM/TEM). The analysis shows that the difference of one element among the high-entropy components can lead to an obvious variation in the lattice parameters, microstructures, and performance. The differences in microstructure, especially grain size, are the joint effects of particle size distribution, porosity, and composition. Specifically, (Mg0.2Mn0.2Co0.2Ni0.2Zn0.2)Al2O4 (HES04) ceramic sintered at 1625 °C for 4 h exhibits superior properties: εr=8.78 ± 0.03, Q×f=34,022 ± 910 GHz (@12.62 GHz), and τf=−29.3 ± 0.6 ppm/°C. These results suggest that the high-entropy strategy is an effective method to tune the dielectric properties of MgAl2O4 ceramic.

Effect of Annealing after Casting and Cold Rolling on Microstructure and Electrochemical Behavior of High-Entropy Alloy, Cantor

High-entropy alloys (HEAs), a relatively new class of materials, have attracted significant attention in materials science owing to their unique properties and potential applications. High entropy stabilizes the phase of a solid solution over a wide range of chemical compositions, yielding unique properties superior to those of conventional alloys. Therefore, this study analyzed the microstructure and electrochemical behavior of HEAs (Cantor) to evaluate their corrosion resistance, according to their manufacturing process (casting, cold rolling, and annealing). The microstructural morphologies and sizes were analyzed using electron backscatter diffraction. The electrochemical behavior was examined using open circuit potential measurements, electrochemical impedance spectroscopy, potentiodynamic polarization tests, and critical pitting temperature measurements using a potentiostat. The casting process formed a nonuniform microstructure (average grain size = 19 μm). The cold rolling process caused the formation of fine grains (size = 4 μm). A uniform microstructure (grain size > 151 μm) was formed after heat treatment. The corrosion resistance of the HEAs was determined from the passivation layer formed by Cr oxidation. These microstructural differences resulted in variations in the electrochemical behavior. Microstructural and electrochemical analyses are crucial because HEAs have diverse potential applications. Therefore, this study contributes to future improvements in HEA manufacturing processes.

Sex and mental health are related to subcortical brain microstructure

Some mental health problems such as depression and anxiety are more common in females, while others such as autism and attention deficit/hyperactivity (AD/H) are more common in males. However, the neurobiological origins of these sex differences are poorly understood. Animal studies have shown substantial sex differences in neuronal and glial cell structure, while human brain imaging studies have shown only small differences, which largely reflect overall body and brain size. Advanced diffusion MRI techniques can be used to examine intracellular, extracellular, and free water signal contributions and provide unique insights into microscopic cellular structure. However, the extent to which sex differences exist in these metrics of subcortical gray matter structures implicated in psychiatric disorders is not known. Here, we show large sex-related differences in microstructure in subcortical regions, including the hippocampus, thalamus, and nucleus accumbens in a large sample of young adults. Unlike conventional T1-weighted structural imaging, large sex differences remained after adjustment for age and brain volume. Further, diffusion metrics in the thalamus and amygdala were associated with depression, anxiety, AD/H, and antisocial personality problems. Diffusion MRI may provide mechanistic insights into the origin of sex differences in behavior and mental health over the life course and help to bridge the gap between findings from experimental, epidemiological, and clinical mental health research.

Enhanced thermal expansion with nanocrystalline Cu in SiO2 vias for hybrid bonding

The thermal expansion of copper pads within dielectric vias plays a crucial role during hybrid bonding. In this paper, we tailored the thermal expansion of Cu pads by modifying the grain size of Cu, and adopted in-situ heating atomic force microscopy (AFM) to measure their surface profiles at room temperature, 100, 150, and 200 °C. Results showed that by reducing the grain size from 2.5 μm to 0.15 μm, the expansion (8.4 nm) of nanocrystalline Cu pads at 200 ℃ increased to more than twice that of coarse-grained Cu counterparts (3.7 nm). This significant enhancement in Cu expansion is critical for enlarging the process window of hybrid bonding in 3D IC fabrication. Microstructural differences and significant plastic deformation in the nanocrystalline Cu pads further indicate the dominance of Coble creep, resulting in the discrepancy in total expansion. Additionally, the thermal expansion of nanocrystalline Cu pads with (111)-preferred orientation was investigated. Their higher-than-expected expansion offers the potential for high-quality hybrid bonding.