Search Results (57,529)

Structural analysis using X-rays and electron beams has long provided the average arrangement of atoms and molecules—that is, “structural information”—with high precision. By contrast, static measurements cannot directly yield dynamic information on how a material changes over time; instead, information on motion is convolved into a single numerical value such as the B-factor (atomic displacement parameter). Taking this limitation as its starting point, this review surveys the recent trend of introducing a time axis into measurements to observe material dynamics directly. First, we outline the technological foundations that have made the transition from static to time-resolved measurement possible. It rests on the dramatic shortening of exposure times, enabled by the increased brilliance of X-ray and electron sources and by advances in detection technology such as direct photon-counting detectors. Next, we survey dynamic measurement techniques, including time-resolved X-ray crystallography, coherent X-ray scattering, neutron scattering, and time-resolved electron microscopy. We also point out the essential limitation that most of them still return ensemble or volume averages. Building on this, we systematically describe diffracted X-ray tracking (DXT), diffracted X-ray blinking (DXB), small-angle X-ray blinking (SAXB), transmitted X-ray blinking (TXB), and electron-beam molecular dynamics (EBMD), which use gold nanocrystals and gold nanoparticles as motion probes. We distinguish throughout between methods that follow individual objects—DXT and EBMD, which yield trajectories of single labeled molecules or single particles—and methods that analyze intensity fluctuations arising from many contributors within one pixel or illuminated volume—DXB, SAXB and TXB. The latter are not single-molecule measurements; rather, they replace a global ensemble average by a spatially localized statistical one, retaining local heterogeneity that a bulk measurement would average away. Finally, we discuss the implementation and prospects of the large-volume data analysis—principal component analysis, Bayesian inference, machine learning, and autonomous measurement—needed to handle the explosively increasing amount of information that the time axis introduces. We close with the outlook that time-resolved measurement incorporating AI and big-data analysis will become established as a new measurement platform that complements and extends conventional static structural analysis. Full article

In rock reinforcement systems, bond stress at the joint between rock bolts and grout exerts a crucial influence on determining the bonding capacity of rock bolts. However, much less research has been conducted to study the joint bond stress (JBS) distribution with analytical deduction. Therefore, this paper adopted an analytical model to evaluate JBS distribution. The novelty of this paper is that the JBS distribution under different grouting conditions can be quantitatively studied. Based on variable controlling techniques, the influence of different parameters on JBS distribution state was studied. These studied parameters included joint strength, joint remaining strength and relative slide at joint remaining strength. Results showed that after rock bolts were loaded, the loading process can be basically divided into five different stages. Joint strength exerts a crucial influence on determining the JBS distribution state before the joint fully disconnected. After the joint started disconnecting, larger joint strength led to a slower propagation speed of the maximum JBS. When the remaining strength of the joint increased, after the whole joint deformed plastically, the disconnected length became longer, and frictional resistance in the disconnected section became larger. This led to an increase in the bonding capacity of rock bolts. Compared with joint strength and joint remaining strength, relative slide at joint remaining strength had a slightly smaller influence on JBS distribution. Before the joint disconnected, increasing relative slide at joint remaining strength was likely to improve the propagation speed of the maximum JBS. This study is valuable for further understanding the stress-transferring mechanism in rock reinforcement systems. Full article

Defect calculations for semiconductors demand both large supercells and accurate electronic structures, posing a significant challenge to first-principles methods. Conventional density functional theory (DFT) with local or semi-local exchange-correlation functionals severely underestimates the band gap, whereas hybrid functionals such as HSE06 provide higher accuracy but at a substantially increased computational cost. In this work, we demonstrate that shell DFT-1/2, a self-energy correction method for electronic structure calculations, may be used jointly with HSE06 to reach the optimal efficiency as well as accuracy. In particular, indium phosphide (InP) was taken as an example. The shell DFT-1/2 method was utilized to yield accurate band structures with a 1.44 eV direct gap, without any empirical parameter. Subsequently, the portion of exact exchange was tuned to match the shell DFT-1/2 electronic structure in HSE06 calculations. The charge transition levels of various point defects in InP were derived using HSE06, and HSE06 and shell DFT-1/2 may be employed alternatively to yield the density of states for the defective supercells. Their consistency proves the feasibility of the complementary employment of the two methods, and this strategy is readily extendable to other semiconductor research. Full article

Fe-based amorphous soft magnets have long been investigated with respect to alloy design and processing strategies to enhance saturation polarization (J_s) while preserving the amorphous phase essential for excellent soft magnetic properties and superior performance. This study demonstrates that Fe80B13Si7 melt-spun ribbons, containing a moderately high ferromagnetic fraction (~80 at%), display excellent amorphous stability, impressive soft magnetic behavior, and extremely low energy losses when processed under a highly efficient quenching atmosphere provided by helium. With the identical processing parameters, soft magnetic ribbons produced in helium gas provide a fully amorphous structure, whereas the ribbons synthesized in nitrogen undergo partial crystallization. The helium-quenched samples exhibit an exceptionally low mean coercivity (H_c) of ~1.3 A/m, in contrast to the nitrogen-quenched ones (mean H_c~14 A/m). The attained maximum permeability (μ_max) in helium (28.4 ± 1.3 (×10³)) is even comparable with commercial Metglas 2605SA1 (33.3 ± 4.8 (×10³)). The average saturation polarization (J_s) of the ribbons fabricated in both helium (~1.63 T) and nitrogen (~1.61 T) gases exceeds the commercial reference (~1.55 T). The helium environment showcases an excellent surface profile relative to nitrogen-induced quenching, which even shows a lower arithmetic mean surface height (S_a) than the reference material. Furthermore, the optimum annealing window for minimizing coercivity is found to lie approximately 15 to 20 K below the Curie temperatures (T_c) of the respective specimens. Core loss (P_core) measurements reveal substantial loss reduction in helium-quenched ribbons relative to nitrogen-quenched ones and even slightly lower than Metglas 2605SA1 at a lower polarization level (J~0.5 T). Therefore, this work establishes a comprehensive understanding of how helium and nitrogen gases, as quenching environments, influence the amorphous formation, magnetic softness, surface morphology, and energy losses of an alloy with a relatively high Fe content from the Fe-B-Si family to harness the material’s maximum potential. Full article

Bacterial cellulose (BC) has been used as a renewable support for the development of photocatalytic nanocomposites due to its three-dimensional nanofibrillar network and large surface area. BC-based photocatalytic systems have been investigated for environmental applications, including the degradation of organic pollutants in wastewater. BC is commonly considered a passive scaffold. However, there is evidence suggesting that the strategy used to immobilize photocatalysts may influence the physicochemical characteristics of the resulting nanocomposites and their photocatalytic performance. This work investigates the effect of the TiO₂ immobilization strategy on the photocatalytic performance of BC/TiO₂ nanocomposites. Two simple immobilization approaches, namely agitation-assisted deposition and vacuum filtration-assisted deposition, were compared to evaluate how catalyst loading and immobilization routes influence the photocatalytic degradation of tartrazine as a model organic pollutant. The materials were characterized by FTIR, XRD, and UV–Vis, and their photocatalytic activity was evaluated through degradation kinetics. The results showed that photocatalytic performance is not only dependent on the amount of immobilized TiO₂ but also on the immobilization strategy employed. FTIR tests revealed differences in the O-H stretching region, suggesting changes in the local chemical environment of cellulose surface hydroxyl groups, whereas XRD and UV–Vis analyses indicated that the crystalline structure and optical band gap of TiO₂ remained essentially unchanged. These findings indicate that controlling the TiO₂ immobilization strategy provides a simple strategy for tailoring the photocatalytic performance of BC-based nanocomposites. Full article

Ce³⁺-activated Gd₃(Al,Ga)₅O₁₂:Ce scintillation ceramics have been widely studied due to their excellent scintillation properties. However, the relatively long radiative lifetime and slow decay components limit their applications in X-ray imaging. To address these issues, Lu³⁺ ions were introduced to partially substitute Gd³⁺ ions, thereby weakening the role of self-trapped states in the excitation process of Ce³⁺ and reducing the negative effects caused by shallow electron traps. As a result, the scintillation decay time was, overall, shortened, and an average decay time of 63 ns was obtained when x = 0.997. Meanwhile, the afterglow behavior induced by shallow electron traps was significantly suppressed (for the sample with x = 0.5, the afterglow intensity was measured to be approximately 0.48% of the initial intensity at 100 ms after the X-ray excitation was turned off). Meanwhile, an X-ray imaging spatial resolution comparable to that of commercial CsI:Tl (10 lp mm⁻¹) was achieved for the (Gd,Lu)₃Ga₂Al₃O₁₂:Ce³⁺ scintillation ceramics. Full article

Although ceramic materials exhibit excellent thermal stability, high melting points, and chemical inertness, their intrinsic brittleness restricts their application across various fields. To address this challenge, ceramic fibers possessing the flexibility and functionality demanded by advanced applications have emerged. This review provides an overview of recent progress in ceramic fibers, emphasizing four major spinning techniques, including melt spinning, electrospinning, solution blow spinning, and wet spinning, along with their underlying fabrication mechanisms and process–structure relationships. The fibrous architectures (including aerogels, textiles, and membranes) demonstrate exceptional performance in thermal protection, extreme environment, wave absorption, thermoelectric energy conversion, and wearable electronic textiles and high-temperature catalysis. Despite these advancements, challenges remain in scalable continuous production, long-term stability under realistic service conditions, multifunctional integration, and cost-effective sustainability. This review provides a roadmap for translating laboratory innovations into practical, large-scale deployment in aerospace, energy, and electronic systems. Full article

Ti-6Al-4V titanium alloy is extensively employed in deep-sea structural applications owing to its excellent corrosion resistance, while its extra-low-interstitial (ELI) variant provides higher fracture toughness and is commonly presumed to exhibit even better stress corrosion cracking (SCC) resistance. In this work, displacement-rate-dependent fracture toughness (K_Q) measurements and failure analysis were performed for compact tension specimens machined from an engineering Ti-6Al-4V ELI plate with different orientations, tested in air and 3.5 wt.% NaCl solution over displacement rates of 0.0012–1.2 mm/min. In air, K_Q exhibits a pronounced loading-rate dependence, decreasing by more than 20% at low displacement rates relative to maximum rate, accompanied by quasi-cleavage features on the fracture surfaces indicative of hydrogen-assisted damage, likely arising from environmental or processing-related hydrogen uptake. In 3.5 wt.% NaCl solution, the minimum K_Q within the low-rate regime (0.0012–0.12 mm/min) is 58 MPa·m^0.5, comparable to values reported for conventional Ti-6Al-4V under similar conditions. The pronounced rate dependence and transition toward cleavage-like fracture reveal a strong coupling between loading kinetics and environmental degradation. This work demonstrates that enhanced intrinsic toughness does not necessarily translate into superior SCC resistance and establishes loading rate as a critical factor governing the environmental fracture of Ti-6Al-4V ELI under marine conditions. Full article

We investigate the dynamic magnetic properties of an epitaxial Co₂₅Fe₇₅ thin film grown on a MgAl₂O₄ (001) substrate using broadband ferromagnetic resonance (VNA-FMR). The film exhibits a pronounced fourfold symmetry of the resonance field, characteristic of cubic magnetocrystalline anisotropy. By combining broadband and angular-dependent FMR measurements, we determined a spectroscopic g-factor of 2.083 ± 0.017, an effective magnetization of 1655 ± 31 kA/m, and a cubic magnetocrystalline anisotropy field of 28.25 ± 0.22 mT. Beyond the expected angular dependence of the resonance field, we experimentally demonstrated a pronounced flattening of the frequency versus magnetic field dependence for magnetic field direction located between the principal crystallographic axes. The effect, predicted by conventional ferromagnetic resonance theory but not previously investigated in detail, originates from the equilibrium rotation of the magnetization and is quantitatively described within the Stoner–Wohlfarth framework. For ${\varphi }_H$ = 34°, the resonance frequency remained nearly constant over the magnetic field interval from 6.8 to 26.2 mT at room temperature. A comparison with other (001)-oriented epitaxial magnetic films revealed that similar frequency plateaus can occur over frequencies ranging from 0.9 to 12.35 GHz and over magnetic field intervals from 0.5 to 63 mT. These findings establish a route toward microwave devices that are insensitive to fluctuations in the applied magnetic field and motivate further studies of spin-wave dynamics in this regime. Full article

This study systematically explores the impacts of germanium (Ge) substitution for aluminium (Al) on the structure and properties of calcium fluoro-alumino-silicate glass (4.5SiO₂-3Al₂O₃-1.5P₂O₅-3CaO-2CaF₂) and its derived glass-ceramics, aiming to mitigate Al-induced biological toxicity in the materials. Glass samples with 0–60 mol% Ge substitution were prepared via melting–quenching, and comprehensively characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS). Results show that the base glass contains three crystalline phases: fluorapatite (FAp, Ca₅(PO₄)₃F), anorthite (CaAl₂Si₂O₈), and aluminium phosphate (AlPO₄). Ge⁴⁺ integrates into the glass network as [GeO₄] tetrahedra without forming independent Ge-based phases; with rising Ge substitution ratio, FAp mass fraction increases from 36% to 65%, anorthite decreases from 46% to 18%, and glass transition temperature (Tg) drops from 678 °C to 617 °C. High Ge substitution (≥40 mol%) triggers network relaxation and spherical particle formation, and local Ca/P ratio reduction drives FAp morphological reconstruction, while low Ge content (≤20 mol%) promotes regular phase crystallisation. The optimal Ge substitution level is 20 mol%, which cuts Al content by 20% to alleviate toxicity, moderately reduces enthalpy for improved sinterability, and realises synergistic mechanical reinforcement via FAp, anorthite and AlPO₄. This material integrates low toxicity, favourable sinterability and excellent bioactivity, providing a novel strategy for developing low-Al, high-bioactivity glass-ceramics for dental and bone repair applications. Full article

Taking the repair of prefabricated hole defects in 2024 aluminum alloy thin-walled components
by friction stir spot welding (FSSW) as the research object, the evolution laws
of microstructure and mechanical properties of FSSW-repaired joints of thin-walled components
were clarified through process experiments and numerical simulations. The
collaborative effect of the temperature field and material flow field during the FSSW repair
process and their regulation laws on the microstructure and properties were revealed. The
results show that as the repair speed increases, the macroscopic surface quality of the FSSW
joint improves. When the repair speed reaches 2000 r/min, a high-quality repaired joint
with a smooth and flat surface and no porosity defects can be obtained. Meanwhile, within
the repair speed range of 800 to 2000 r/min, the grains undergo dynamic recrystallization
(DRX) due to the combined effect of heat and mechanical forces, eventually forming a
uniform equiaxed grain structure in the weld core area. ABAQUS 2023 simulation verifies
the temperature distribution during the FSSW repair process. When the repair speed is
2000 r/min, the maximum temperature obtained from the simulation is 431.1 ◦C, which
agrees with the measured value from the experiment. The simulation results further reveal
that when the repair speed increases from 1200 r/min to 2000 r/min, the material fluidity
significantly enhances, and the flow velocity on the advancing side is always higher than
that in other areas. At the rotational speed of 2000 r/min, the plastic material flows continuously
from the periphery and eventually fills the defect area completely. The fracture
mode of the FSSW-repaired joint is mainly ductile fracture. With the increase in the repair
speed, the number of dimples at the fracture surface increases significantly. When the
rotational speed reaches 2000 r/min, the joint achieves the best mechanical properties, and
the FSSW-repaired joint reaches the maximum tensile strength of 169 MPa. Full article

Triboelectric nanogenerators (TENGs) are promising for harvesting low-frequency mechanical energy, but rotating TENGs (R-TENGs) driven by low-speed water flow remain constrained by limited driving torque, sliding-contact losses, and rotating-system stability. Here, a three-dimensional (3D) riveted complementary-structure rotating triboelectric nanogenerator (RCSR-TENG) is proposed for low-speed water-flow energy harvesting. A semi-analytical formulation incorporating a force-dependent real-contact fraction is developed to describe the coupled relationships among output voltage, transferred charge, rotation angle, and contact force. Because the contact parameters were not independently calibrated, the formulation is used for sensitivity and trend analysis rather than as a quantitatively validated predictive model. For the single prototype tested for each configuration, at 1000 rpm under the fixed effective measurement load of 9 MΩ, the RCSR-TENG produced a peak output power of 544 μW, compared with 304 μW for the flat R-TENG, representing an increase of approximately 79%. The same RCSR-TENG prototype maintained a stable voltage amplitude of over 150,000 rotation cycles. When coupled to a fully passive flapping-foil collector in a 0.55 m s⁻¹ water flow, the system generated periodic electrical output with a peak area-normalized power exceeding 5000 μW m⁻². These results demonstrate the structural-performance advantage of the riveted complementary design and its proof-of-concept applicability to low-speed water-flow energy harvesting. Full article

Surface roughening is a common defect in plastic deformation processing, directly affecting product surface quality and service performance. This study investigates the mechanisms of surface roughness evolution during plastic deformation by considering both intrinsic and extrinsic factors. A macro–meso-scale modelling framework is developed by coupling crystal plasticity finite element modelling, fluid–solid interaction modelling, and macro–meso boundary conditions. The crystal plasticity model incorporates a constitutive model based on crystal plasticity theory, a Voronoi-based geometric model, and a real rough-surface topography model to capture non-uniform grain-scale plastic deformation. Fluid–solid interaction modelling is introduced to analyze the influence of liquid lubricant on the deforming solid material. Boundary interpolation and continuous displacement theories are then used to transfer macro-scale boundary constraints to the meso scale. The proposed framework is numerically implemented and applied to the aluminum alloy tube drawing process. The effects of intrinsic factors, including grain size, grain orientation, and initial surface roughness, and extrinsic factors, including deformation path, strain rate, and lubrication condition, are systematically examined. From a practical point of view, effective strategies to improve surface quality are by reducing grain size, lowering initial surface roughness, decreasing the strain rate and using low-viscosity lubricants. Full article

In the era of global energy transition, the development of third-generation photovoltaic technologies, such as dye-sensitized solar cells, has emerged as a paramount challenge in materials engineering. This study is dedicated to the synthesis and implementation of graphene quantum dots as eco-friendly sensitizers within DSSC architectures. The GQDs were synthesized via a microwave-assisted hydrothermal route using biodegradable organic precursors, providing a “green” alternative to conventional, toxic heavy-metal-based materials. The nanocrystalline structure and optoelectronic properties of the sensitizer were verified through UV-Vis and visual photoluminescence assessment. A focal point of this research was the optimization of the GQD concentration on the mesoporous surface of the titanium dioxide photoanode. Measurements were conducted utilizing a custom-designed experimental setup integrated with 3D-printed (FDM) components and an Arduino microcontroller, ensuring precise data acquisition under controlled illumination conditions (405–625 nm). The results indicated an optimal operational point at a fivefold dilution of the stock solution (0.4 g/dm³), which yielded the highest open-circuit voltage ($V_{\mathrm{oc}}$) of 545.4 mV under UV irradiation. The decline in photovoltaic performance observed at higher concentrations was attributed to excessive nanostructure agglomeration, which effectively blocked the mesopores of the semiconductor. Furthermore, the demonstrated high chemical capacitance of the system imparts electrochemical capacitor-like characteristics to the cell, enabling energy stabilization under fluctuating illumination. To elucidate the underlying sensitization mechanisms at the atomic level, computational simulations were conducted utilizing the MACE machine-learning potential and the GFN2-xTB semi-empirical method. The theoretical models revealed that the formation of stable covalent Ti–O–C bridges (chemisorption) is imperative for establishing strong interfacial electronic coupling. Solvation models and molecular dynamics (MD) at 300 K confirmed the thermodynamic and operational robustness of the hybrid system in an aqueous electrolyte. Ultimately, this combined experimental and theoretical work conclusively demonstrates that graphene quantum dots represent an efficient, highly stable, and non-toxic alternative to classic molecular dye sensitizers. Full article

Unidirectionally macrochanneled tetragonal zirconia polycrystals (TZP) scaffolds, comprising elongated microporous frameworks, were fabricated via vat photopolymerization (VP) using a solution of 75 wt% camphene and 25 wt% 1,6-hexanediol diacrylate (HDDA) as a phase-separable, photopolymerizable vehicle. The camphene/HDDA solution underwent phase separation at 5 °C, accompanied by the recrystallization and dendritic growth of camphene, thereby generating three-dimensionally interconnected camphene crystal networks enclosed by HDDA. Following the photopolymerization of HDDA, the scaffolds were freeze-dried to remove the camphene crystals and subsequently heat-treated for debinding to eliminate organic phases, including photopolymerized HDDA, the dispersant, and the photoinitiator. The effect of sintering temperature on the geometry of the micropores and the densification of the TZP walls was examined. The optimum sintering condition (1500 °C for 3 h) enabled the creation of elongated micropores with a volume fraction of 61.17 ± 0.90 vol%, surrounded by highly densified TZP walls. The fabricated scaffolds exhibited well-defined macrochannels arranged in a hexagonal pattern, separated by microporous frameworks. Their overall porosity was as high as 74.65 ± 0.73 vol%, owing to the high framework microporosity. Despite their high porosity, the scaffolds achieved a compressive strength of 53.10 ± 8.19 MPa and a compressive modulus of 364.38 ± 70.90 MPa. Full article