Materials最新文献

Surface collisions at Pyrex walls limit the spin coherence in nuclear magnetic resonance gyroscopes (NMRG) vapor cells, while the cavity-stem junction introduces geometry dependent exchange that perturbs the transverse spin relaxation time T2 of ¹²⁹Xe atoms. We combine T2 measurements with Monte Carlo simulations of confined diffusion and surface collisions to decompose the relaxation of Xe atoms and derive a cavity-stem geometry correction for wall relaxation. A structural coupling factor (SCF) is introduced to compress stem length and aperture diameter into a dimensionless metric for diffusion-limited mixing, enabling prediction of the transverse relaxation rate versus geometry. Across eight simulated configurations, the model yields R2=0.982 and agrees with experiments within 7-9%, comparable to the measurement uncertainty (±0.015s-1). Using the validated framework, geometry optimization reduces the relaxation rate from 0.225 to 0.131s-1 (a 41.8% improvement). This Pyrex surface-collisional analysis provides an in-situ, T2-based route to compare effective surface depolarization across fabrication and surface-treatment protocols while accounting for cavity-stem coupling.

Adiabatic shear banding (ASB) is a critical failure mechanism in titanium alloys subjected to high-strain-rate deformation, and its initiation is strongly influenced by the initial crystallographic texture. The dynamic response and ASB sensitivity of extruded and annealed Ti-6Al-4V (TC4) alloy rods were investigated under dynamic compression of cubic specimens along the extrusion direction (ED) and the transverse direction (TD) at a strain rate of 2500 s^-1. Split Hopkinson pressure bar (SHPB) tests combined with digital image correlation (DIC) were employed to obtain the stress-strain response and the evolution of strain localization. A dislocation density-based crystal plasticity finite element model (CPFEM), incorporating the measured texture, was established to elucidate the correlation between texture and ASB behavior. The experimental results show that TD specimens exhibit a yield strength approximately 100 MPa higher than that of ED specimens, while both orientations display comparable post-yield hardening behavior. ASB initiation occurs earlier in TD (compressive strain ~0.13) than in ED (~0.23), indicating greater ASB sensitivity in the TD orientation. The CPFEM successfully reproduces the directional stress-strain responses and the observed localization morphology, enabling mechanistic interpretation in terms of slip activity and thermomechanical coupling. The simulations indicate that ED loading is dominated by prismatic ⟨a⟩ slip, resulting in lower flow stress and more dispersed strain localization. In contrast, TD loading is governed primarily by pyramidal ⟨c + a⟩ slip, leading to elevated flow stress and intensified localization. The higher ASB sensitivity in the TD orientation is therefore attributed to texture-controlled slip-mode partitioning, enhanced thermomechanical coupling, and a more concentrated crystallographic orientation distribution that facilitates intergranular slip transfer. These findings provide guidance for tailoring microtexture to mitigate dynamic failure in titanium alloys subjected to high-strain-rate loading.

Duplex-phase low-density steels are attracting interest for lightweight structural applications, as reducing vehicle mass is an effective route to lower fuel consumption and emissions. This review summarizes recent progress in alloy design, processing, microstructure control, and performance of duplex-phase low-density steels. The roles of major alloying elements are discussed in terms of phase stability and precipitation tendency, followed by an overview of typical processing routes from melting to hot and cold rolling and subsequent heat treatments used to tailor phase fractions and defect structures. Strengthening mechanisms are reviewed with emphasis on precipitation control, including the beneficial contribution of fine intragranular κ' precipitates and the ductility penalty associated with coarse intergranular κ* films, as well as the use of B2-based particles for high specific strength. Deformation behavior is then discussed in terms of transformation-/twinning-induced plasticity (TRIP/TWIP), planar versus wavy slip, and strain partitioning between ferrite and austenite. Finally, key challenges are outlined, including quantitative interface-based mechanism description, gaps in service property data, stable industrial production and compositional uniformity, and the development of forming and welding windows for engineering implementation.

Wood used in construction varies in density, leading to differences in strength and rigidity. Wood densification has recently emerged as a promising technique to address these limitations and enhance material performance. This study explores the potential of two abundant and low-cost invasive hardwood species in South Africa-Prosopis glandulosa (Honey Mesquite) and Acacia mearnsii (Black Wattle)-as sources for producing densified wood. A range of strengthening methods, including chemical, pressure, and heat treatments, were applied and compared. After partial delignification and hot pressing, sample thicknesses were reduced by 40% for Prosopis and 50% for Acacia, yielding substantial increases in flexural strength of 216% (22.61 MPa) for Prosopis and 334% (24.65 MPa) for Acacia. In addition to anatomical imaging, analyses of lignosulphonate content, and thermogravimetric profiling, the study also evaluated several practical, carpentry-relevant mechanical properties. These included comparative tests for flexural and compressive strength, nailing and sanding performance, as well as assessments of water absorption, electrical resistivity, and flame-holding capacity.

Polystyrene (PS) is widely used yet highly flammable, and developing halogen-free flame retardants that ensure both high fire safety and mechanical performance remains a challenge. A green intumescent system comprising ammonium dihydrogen phosphate (ADP) and phytic acid-triethylenetetramine (PA-TETA) was incorporated into PS powder via sequential solution grinding and hot pressing. The optimal formulation, PS/10ADP/15PA-TETA, achieved a limiting oxygen index of 28.5% with a UL-94 V-0 rating, and reduced the peak heat release rate and total heat release by 73.8% and 46.2%, respectively, while retaining 78.4% of the tensile strength of neat PS. The ADP/PA-TETA system operates via a cooperative condensed-phase charring and gas-phase dilution mechanism, achieving superior flame retardancy in PS composites. This work provides an effective and eco-friendly strategy for fabricating high-performance PS composites with balanced flame retardancy and mechanical properties.

Nickel-titanium (NiTi) alloys are attractive for functional and biomedical applications due to their shape memory effect, superelasticity, and favorable corrosion resistance and biocompatibility. In this work, the influence of strut size on the compressive response of laser-based powder bed fusion (PBF-LB/M) fabricated NiTi ortho-octahedral porous scaffolds was systematically investigated using combined experiments and finite element simulations. Four scaffold designs with identical unit-cell size (2 mm) but different strut sizes (280, 320, 360, and 400 μm) were fabricated, and their forming quality and deformation behaviors were examined. The as-built scaffolds exhibited high geometric fidelity to the CAD models and stable manufacturability across the investigated parameter range. Quasi-static compression tests revealed a typical three-stage response (linear-elastic regime, plateau/collapse regime, and densification), with both elastic modulus and compressive strength increasing markedly with strut size. Specifically, the modulus increased from 1.17 to 4.28 GPa and the compressive strength increased from 155 to 564 MPa as the strut size increased from 280 to 400 μm. A pronounced oscillatory plateau was observed for the 280 μm scaffolds, indicating progressive layer-by-layer collapse, whereas larger struts promoted a shear-band-dominated failure mode characterized by an approximately 45° fracture zone. Explicit quasi-static simulations reproduced the experimentally observed collapse sequence and demonstrated that stress preferentially concentrates at nodal junctions, with load transfer dominated by struts aligned with the loading direction. The agreement between experiments and simulations confirms the predictive capability of the proposed modeling framework and provides mechanistic insights into geometry-controlled failure. These findings establish a structure-property-failure relationship for PBF-LB/M-fabricated NiTi octahedral scaffolds and offer practical guidance for tailoring stiffness, strength, and collapse mode through strut-size design.

Given the increasingly stringent environmental standards mandated today, the functionalization of textile materials using natural biopolymers and plant extracts represents an environmentally acceptable alternative to traditional synthetic agents. To obtain functionalized viscose fabric, a pretreatment process involving periodate oxidation followed by chitosan deposition was performed. Chitosan provides enhanced biological properties due to the presence of amino groups, which enable its deposition and the application of pomegranate peel (Punica granatum L.) extract during functionalization. Pomegranate peel extract contains a large number of bioactive compounds that further enhance the antibacterial and antioxidant activities of the functionalized viscose fabric. Changes in surface chemistry, morphology, and biological properties after functionalization and up to five washing cycles were followed by FTIR spectroscopy, zeta potential measurements, SEM, and determination of antibacterial and antioxidant activities, respectively. The results showed a 100% bacterial reduction against Staphylococcus aureus up to five washing cycles, and 100% before and 99% after one washing cycle against Escherichia coli. The antioxidant activity of functionalized viscose (70.5% and 60.1% for 60 min and 120 min pre-oxidized fabrics, respectively) decreased after washing, while the obtained color remained stable after five washing cycles. The results indicate that viscose fabric functionalized with pomegranate peel extract can be used in the production of bioactive clothing for individuals with sensitive skin, as well as household and healthcare textile products.

Biocompatible thin films are essential for advancing biomedical devices, as they enhance integration with biological tissues, improve device longevity, and reduce complications. The rapid evolution of both medical needs and materials science has led to a diverse array of deposition techniques, each offering unique advantages and challenges for tailoring surface properties without compromising the bulk characteristics of implants and sensors. While laser-based methods-such as pulsed laser deposition (PLD) and Matrix-Assisted Pulsed Laser Evaporation (MAPLE)-are renowned for their precision, ability to preserve complex material stoichiometry, and suitability for low-temperature processing, the broader landscape includes several other important approaches. Physical Vapor Deposition (PVD) techniques, including magnetron sputtering and pulsed electron deposition, are widely used for their ability to create uniform, adherent coatings with controlled thickness and composition, making them suitable for both hard and soft biomedical substrates. Chemical Vapor Deposition (CVD) and its plasma-enhanced variant (PECVD) offer conformal coatings and excellent control over film chemistry, which is particularly valuable for functional polymer and ceramic films. Other methods, such as sol-gel processing, ion beam deposition, and electrophoretic deposition, provide additional flexibility in terms of coating composition, adhesion, and processing temperature, allowing for the fabrication of films with tailored mechanical, chemical, and biological properties. Despite these advances, the field faces ongoing challenges in optimizing film properties for specific clinical applications, ensuring reproducibility, and scaling up production for widespread use. The necessity of this review lies in its comprehensive comparison of laser-based techniques with alternative deposition methods, providing critical insights into their respective strengths, limitations, and suitability for different biomedical scenarios. By synthesizing recent developments and highlighting current gaps, this review aims to guide researchers and clinicians in selecting the most appropriate thin-film deposition strategies to meet the evolving demands of next-generation biomedical devices.

This study used finite element simulation and theoretical analysis to predict the crack distribution patterns that may occur during the shrinkage cracking process of rectangular timber beams. Based on the predictions, experimental specimens with six typical crack distribution patterns (I-VI) were designed. Subsequently, a four-point bending test method was employed to conduct large-sample size fracture tests on a total of 1200 small-sized Pinus sylvestris var. mongolica specimens, quantifying the effects of the crack depth, location, and distribution patterns on the specimens' load-bearing capacity. The results indicate that when multiple cracks exist in a timber beam, their collective effect is not a simple superposition of individual cracks but a spatial distribution coupling effect. Both the depth and location of the cracks play crucial roles in their interaction. This study introduces three coefficients for evaluating the influence of cracks on timber beams, namely the load-bearing capacity coefficient (R), the decline ratio of load-bearing capacity (D), and the comprehensive crack-influence coefficient (β), which can effectively quantitatively evaluate crack damage effects. The framework established in this study, which links shrinkage crack characteristics with the load-bearing capacity of timber beams, along with the experimental data provided, can serve as a reference for the safety evaluation and scientific maintenance of historical timber components and modern timber structures with shrinkage cracks.

Objective: This systematic review aimed to evaluate material-based modifications of resorbable root canal filling materials for primary teeth, assessing how compositional changes-including bioactive additives, antimicrobial agents, and alternative base matrices-influence antimicrobial performance. Methods: A systematic search of PubMed, Scopus, Web of Science (WoS), and Embase was performed in October 2025. Search terms included (primary teeth OR deciduous teeth) AND (root canal filling materials OR root canal filling OR canal obturation) AND (antibacterial agents OR antibacterial OR antimicrobial). Study selection adhered to PRISMA 2020 standards and was systematically organized through the PICO framework. From 199 identified records, 18 studies met the eligibility criteria. Results: Most studies evaluated modified zinc oxide-based materials. Additives such as propolis, Morinda citrifolia extract, Aloe vera, and olive oil enhanced antimicrobial activity or improved clinical and radiographic outcomes compared with conventional zinc oxide-eugenol. Triclosan-containing formulations consistently demonstrated strong antibacterial effects. In contrast, chlorhexidine yielded variable results, with some calcium hydroxide-based pastes showing superior performance in its absence. Antibiotic-enriched materials exhibited high antimicrobial efficacy; however, several studies raised concerns regarding the potential development of bacterial resistance. Conclusions: Most of the introduced modifications of resorbable root canal filling materials for primary teeth enhance antimicrobial activity and their physicochemical properties in vitro. Clinical evidence is limited and heterogeneous, and therefore, its superiority over conventional materials cannot be definitively determined. Further long-term, randomized clinical trials on large patient groups, evaluating the same modifications, are needed to confirm the effects observed in laboratory studies.