Structural Integrity Research Articles

Application of Artificial Neural Networks to a Model of a Helicopter Rotor Blade for Damage Identification in Realistic Load Conditions.

Monitoring the integrity of aeronautical structures is fundamental for safety. Structural Health Monitoring Systems (SHMSs) perform real-time monitoring functions, but their performance must be carefully assessed. This is typically done by introducing artificial damages to the components; however, such a procedure requires the production and testing of a large number of structural elements. In this work, the damage detection performance of a strain-based SHMS was evaluated on a composite helicopter rotor blade root, exploiting a Finite Element (FE) model of the component. The SHMS monitored the bonding between the central core and the surrounding antitorsional layer. A damage detection algorithm was trained through FE analyses. The effects of the load's variability and of the damage were decoupled by including a load recognition step in the algorithm, which was accomplished either with an Artificial Neural Network (ANN) or a calibration matrix. Anomaly detection, damage assessment, and localization were performed by using an ANN. The results showed a higher load identification and anomaly detection accuracy using an ANN for the load recognition, and the load set was recognized with a satisfactory accuracy, even in damaged blades. This case study was focused on a real-world subcomponent with complex geometrical features and realistic load conditions, which was not investigated in the literature and provided a promising approach to estimate the performance of a strain-based SHMS.

Exploring the mechanical potential of 3D woven solid structures for car seat cover

Seats serve as the primary connection point between humans and cars. To meet consumer expectations, the seat cover must possess mechanical durability. This is crucial due to the significance and expense associated with the assembling car seat cover. The mechanical durability of a material can be assessed by testing its tensile strength, tearing strength, stretchability, abrasion resistance, and pilling resistance. Many researchers conducted analyses on the mechanical performance of traditional seat covers. This study aims to explore the mechanical potential of 3D woven solid structures for car seat covers. Air-texturized polyester yarn (ATY) was utilized to produce various 3D woven solid structures and compared to benchmark 2D fabric seat covers with equivalent areal density. Placing three sets of yarn in the x, y, and z axes enhanced the structural integrity and distributed the stress evenly, which helped to boost the mechanical performance of 3D structures. The study concluded that 3D woven structures have the potential for mechanical performance and are expected to be utilized as car seat covers in the near future.

Controlled Crystallization and Enhanced Performance of γ-CsPbI3 Perovskite Through Methylammonium Iodide-Assisted Coevaporation.

Cesium lead triiodide (CsPbI3) perovskites have garnered significant attention owing to their suitable bandgap for tandem silicon substrates and excellent chemical stability. However, γ-CsPbI3 prepared via low-temperature co-evaporation is limited by a narrow black phase processing window and random crystal orientation, hindering its optoelectronic performance and industrial applications. This study introduced trace amounts of methylammonium iodide (MAI) into the co-evaporation system, enhancing the crystallization process, promoting columnar grain growth, and stabilizing the γ-phase perovskite, resulting in films with improved structural integrity and reduced defect density. The optimal Pb/Cs ratio for achieving the best photoelectric performance shifted from 1:1 to 1.1:1 in the presence of MAI. Additionally, the incorporation of MAI allowed for more efficient longitudinal carrier transport, as evidenced by the enhanced photoluminescence (PL) intensity. The bandgap of CsPbI3 remained approximately at 1.7eV before the δ-phase transition, ensuring suitability for photovoltaic applications. Ultimately, a photovoltaic device with 12% efficiency is achieved in the p-i-n structure without additional post-annealing of the CsPbI3 perovskite films, demonstrating the practical benefits of MAI incorporation.

Multi-Load Topology Optimization Design for the Structural Safety Maintenance of Low- and Intermediate-Level Radioactive Waste Packaging Containers in the Case of a Collision.

This paper presents an optimized design approach using nonlinear dynamic analysis and finite element methods to ensure the structural integrity of square-shaped containers made from ductile cast iron for intermediate- and low-level radioactive waste packaging. Ductile cast iron, with its spherical graphite structure, effectively distributes stress throughout the material, leading to a storage capacity increase of approximately 18%. Considering the critical need for containers that maintain integrity under extreme conditions like earthquakes, the design focuses on mitigating stress concentrations at the corners of square structures. Nonlinear dynamic analyses were conducted in five drop directions: three specified by ASTM-D5276 standards and two additional directions to account for different load patterns. Fractures were observed in four out of the five scenarios. For each direction where fractures occurred, equivalent loads causing similar displacement fields were applied to linear static models, which were then used for multi-load topology optimization. Three optimized models were derived, each increasing the volume by 1.4% to 1.6% compared to the original model, and the design that best met the structural integrity requirements during drop scenarios was selected. To further enhance the optimization process, weights were assigned to different load conditions based on numerical analysis results, balancing the impact of maximum stress, average stress, and plastic deformation energy. The final model, with its increased storage capacity and enhanced structural integrity, offers a practical solution for radioactive waste management, overcoming limitations in previous designs by effectively addressing complex load conditions.

High mixing enhancement for continuous uniformity Li/Al-LDHs in lithium extraction from low grade salt lakes

The enhancement of lithium extraction from low grade salt lake through the development of advanced adsorbents has become a primary focus in current research. A new method was developed in this work for the continuous fabrication of ultra-highly uniform lithium-aluminum layered double hydroxides (H-LDHs), used as lithium adsorbents, through a high mixing reactor. These H-LDHs featured a more consistent particle size distribution, which facilitated an enhanced vibrational density. This not only significantly increased the powder content in granules but also improved lithium adsorption efficiency. Computational fluid dynamics (CFD) modeling showed that the reactor reached peak mixing efficiency with a minimal gap size of 1 mm. The analysis further indicated that a Reynolds number of 75 led to enhanced mixing effects and stronger flow dynamics. Experiments with Qarhan salt lake brine demonstrated that the H-LDHs powders reached a lithium adsorption capacity of up to 7.27 mg/g, while the volumetric adsorption capacity of these H-LDHs granules exceeded that of traditional granules by 1.179 times. Subsequent desorption and cycling experiments verified the material’s enduring lithium adsorption efficacy and structural integrity, underscoring its considerable potential for industrial use.

Modeling the effect of material heterogeneity on the thermo-mechanical behavior of concrete using mesoscale and stochastic field approaches

The adverse impact of high temperatures on concrete is a well-recognized issue that can lead to significant mechanical deterioration and structural integrity loss. Factors such as aggregate type, cement composition, temperature, duration of exposure, and moisture content can substantially influence the fire resistance of concrete. To simulate and better understand the effects arising from the heterogeneity of concrete in a fire situation, a mesoscale approach is proposed, using the Mesh Fragmentation Technique (MFT) to assess the complex thermo-mechanical behavior of concrete. The MFT introduces high aspect ratio interface elements to model crack propagation and interfacial transition zones by means of an appropriated tensile damage constitutive law. In this extended framework, a fully-coupled thermo-mechanical model is proposed. The modeling approach includes considerations of both macroscopic and mesoscopic scales, in which the coarse aggregate, mortar matrix and interfacial transition zones are represented. Besides, a stochastic distribution is assumed for the material properties to account for the lower scale heterogeneity. The main novelty proposed in this study consists in the synergy of mesoscale and stochastic approaches that are herein combined to model the effect of heterogeneity on the concurrent macro-mesoscale thermo-mechanical behavior of concrete. To validate the numerical model’s capabilities in capturing thermally induced cracks, benchmark cases and a simulation of a bending beam exposed to elevated temperatures are presented. The results demonstrate the potential of the proposed approach in predicting the behavior of concrete subjected to thermal loading and the role played by heterogeneity in the thermally induced cracking.

Insights into thermomechanical behavior and design parameters of alumina calciner refractory lining

This study investigated the thermomechanical behavior of an alumina calciner’s lining, a critical component in alumina processing, often susceptible to maintenance issues arising from refractory failure due to erosion and cracking. Based on numerical analyses via the finite element method, the design of a refractory panel was modeled. Furthermore, the influence of geometric parameters and friction level between lining layers on the thermal and mechanical behavior of the system was evaluated. Key findings highlighted how the curvature changed the stress profiles, resulting in particular cracking patterns, where curved panels showed higher stress concentrations at the center of their edges. Empirical validation through in-situ crack pattern observations further validated the model’s predictive capability. Additionally, the study evaluated the influence of friction coefficients on resulting stresses, showing their small effect relative to other factors. Analyses on design parameters indicated that stress levels generally increased with the size-to-thickness ratio, highlighting the trade-off between reducing installation time and ensuring structural integrity in panel design and application. An alternative for enhancing lining performance was explored by selecting the material, where decreasing the insulating thermal conductivity reduced the likelihood of failure of the castable layer. Ultimately, the computational numerical method developed in this study offers a robust framework for exploring various geometries and materials, providing engineers with a versatile tool for optimizing lining designs in various operational scenarios.

Fabrication of green composite made by Cannabis sativa fiber reinforced granite filler blended epoxy matrix composite – Antimicrobial and structural analysis

The main novelty of this research lies in combining natural fibers and mineral fillers to create a sustainable material with enhanced antimicrobial and structural properties, offering promising applications in various industries requiring eco-friendly and high-performance materials. This study investigates the fabrication and analysis of a green composite made from Cannabis sativa fiber reinforced (CSFR) with granite filler in an epoxy matrix, focusing on antimicrobial properties and structural integrity. Various amounts of granite powder (0, 3, 6, 9, 12, and 15 g) were incorporated into the epoxy matrix. The composite exhibited significant antibacterial activity was observed against E. coli. Mechanical testing revealed that the composite with 12 g of granite powder showed the best performance, with tensile strength improving by 11.4%, flexural strength by 12.3%, impact strength by 29% and hardness is improved by 17.5%. SEM analysis highlighted well-dispersed particulates and strong fiber-matrix bonding at optimal filler levels. TGA showed enhanced thermal stability, with the decomposition onset shifting from 240 °C to 280 °C and weight retention improving 90% at 350 °C. This study underscores the potential of Cannabis sativa fiber reinforced granite filler epoxy matrix composites as sustainable materials with excellent antimicrobial and structural properties for advanced applications.

Strain and stress responses of the springback and rerounding processes of dented pipelines

Denting, a common geometric defect in oil and gas pipelines, can threaten the structural integrity and safety of pipelines. A pipeline dent is usually caused by the collision or extrusion of hard objects during the pipeline construction and service stages. Some rebound occurs in the dented zone when the external load is removed. In actual engineering, unconstrained dents tend to reround with increasing internal pressure of the pipeline. This study experimentally and numerically investigated the processes of springback and rerounding of a dented pipeline. First, full-scale testing was carried out to simulate the springback and rerounding processes, and the strain variations at the dent were measured. Then, a 3-dimensional numerical model was developed and then validated against the experimental results. According to the experimental and numerical results, the stress and strain responses of the pipeline during the springback and rerounding processes were studied in detail. Furthermore, the factors influencing the springback and rerounding coefficients were discussed. Finally, equations for predicting the springback and rerounding coefficients of dented pipelines were proposed on the basis of a nonlinear regression analysis. The results show that mainly elastic recovery occurs during springback. After a dent is unloaded, the elastic strain and von Mises stress of the pipeline decrease greatly, while the plastic strain remains unchanged. The elastic strain increases with increasing internal pressure. The springback and rerounding coefficients increase with increasing indenter diameter and diameter-to-wall thickness, while the loading depth has a negative effect on these coefficients. The proposed formulas can be used as a reference for estimating the ratios of dent springback and rerounding of dented pipelines.

2d van der Waal SiC/borophene heterostructure as a promising anode for high-capacity Li ion battery: First principles study

We constructed SiC/borophene heterostructure based on the method of commensurate lattice with supercell approach and studied the structural, electronic and electrochemical properties using density functional theory (DFT). The interfacial binding energy of SiC/borophene is as high as −26.07 meV/Å2. Significant amounts of charge were found to drift from SiC to borophene, resulting in interfacial charge redistribution and increased Li binding affinity on the surfaces. The electronic properties of SiC/borophene showed pronounced metallic conductivity, a trait conducive to anodic applications in electrochemical cells. The calculated Li adsorption energy at the interface of SiC/borophene is −2.23 eV. Multiple layer adsorption is also observed, with the heterostructure retaining much of its structural integrity after adatom adsorption, indicating possible good cycling stability. At the maximum concentration, the Li storage capacity for SiC/borophene is 1980.63 mAh/g, surpassing a large variety of other reported 2D complexes. Also, an overall average operating voltage of 1.06 V is maintained in the structure, which is in proximity of the optimal 1.5 V threshold requisite for anodic operations. The diffusion energy barriers associated with lithium ion migration across the three distinct adsorption sites of the heterostructure all reveal a nominal magnitude with the lowest barrier energy of 0.54 eV at the top of borophene adsorption layer and site. These findings show that SiC/borophene could be used as an anode in very high-capacity lithium-ion batteries.

The effect of supplementing freezing extender with Mn2+-, Zn2+- or Cu2+-nanosuccinate on select post-thaw characteristics of ram semen

The effects of Mn2+-, Zn2+- or Cu2+-nanosuccinate added to freezing extender on select post-thaw semen characteristics were determined in six Texel rams (aged 2–4 years) during seasonal anestrus (April-May). Ejaculates (n = 6 per ram) collected into an artificial vagina were divided into ten isovolumetric fractions each. Semen was diluted in lactose-yolk-tris-citrate-glycerin medium and nanosuccinates (Mn2+- and Zn2+-nanosuccinate: 0.0 (control), 2.5, 5.0 and 7.5 μg/l; Cu2+-nanosuccinate: 0.0 (control), 1.25, 2.5 and 3.75 μg/l) were added to semen extender. Extended semen was loaded into 0.25-ml straws and frozen in liquid nitrogen. After thawing, sperm motility parameters were determined with computer assisted semen analysis (CASA), and the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) was measured with a spectrophotometric technique. The addition of 5.0 μg/l of Mn2+- and Zn2+-nanosuccinate significantly increased the sperm progressive motility and both 2.5 and 5.0 μg/l improved sperm motion kinetics. Further, both nanosuccinates at a dose of 5.0 μg/l significantly decreased SOD activity and stimulated an increase in GPx and CAT activity in semen samples. Alternatively, the addition of Cu2+-nanosuccinate (highest dose) significantly reduced the progressive motility and velocity of ram spermatozoa, increased the percentage of sperm with acrosomal/head defects and seminal SOD activity, and depressed CAT (highest dose) and GPx (all doses) activity. In summary, the addition of Mn2+- and Zn2+-nanosuccinate to semen extender had beneficial effects on sperm motility/motion kinetics and structural integrity, whereas Cu2+-nanosuccinate generally had debilitating effects on the post-thaw semen characteristics in rams.

3D analysis of crack propagation in nuclear graphite using DVC coupled with finite element analysis

The initiation and propagation of cracks within nuclear graphite components compromise the lifespan of advanced gas-cooled reactors and even lead to safety incidents. A thorough understanding of fracture properties in nuclear graphite is crucial for the effective management and design of graphite structural components. In this work, an in-situ test of a double cleavage drilled compression (DCDC) specimen was conducted using X-ray tomographic imaging to fully analyze the 3D crack propagation behavior in IG-11 nuclear graphite. “Subvolume Splitting” digital volume correlation (SS-DVC) was employed to accurately quantify the displacement fields surrounding the crack. The entire 3D crack propagation and crack surface around the crack front were precisely captured through 3D imaging processing of the gray level residual (GLR) field. Additionally, crack opening displacements (CODs) and stress intensity factors (SIFs) were determined using finite element (FE) analysis with extended finite element method (XFEM). Experimental results indicate that although mode I crack remains predominant throughout the whole process, complex crack propagation exists around the crack front. The utilization of irregular crack surfaces in FE analysis helps to obtain refined displacement fields and accurate SIFs of the crack front. This work provides comprehensive insights into crack propagation and reveals the influence of complex crack morphology on SIF calculations, facilitating accurate prediction of structural integrity and rational design of graphite components.

Structural integrity assessment of CANDU pressure tubes using Sobol indices for global sensitivity analysis

CANDU11CANDU is a registered trademark of Atomic Energy of Canada Limited. reactors are a channel-type design where up to 480 zirconium alloy pressure tubes (PTs) act as the reactor pressure boundary. Fitness-for-service standards such as CSA N285.8 (CSA Group, 2015) have been established to prescribe the requirements of pressure tube evaluations to maintain their integrity throughout their lifetime. Probabilistic leak-before-break (LBB) assessments can be used in evaluations to demonstrate that the likelihood of a flaw growing past the stability point while undetected (or before a safe shutdown can be achieved) is below regulatory limits. The assessments typically require a ranking of model parameters based on their influence. The ranking process traditionally uses expert judgment and local sensitivity analysis methods. There has been recent interest in implementing global methods for LBB assessments as they can manage large numbers of variables and extensive sampling spaces. However, their adoption is hindered by the computational cost of the models involved.The current study proposes a method for performing global sensitivity parameter rankings during probabilistic LBB assessments. The study is the continuation of the CANDU nuclear power plant (NPP) pressure tube (PT) case study in El Bouzidi et al., (2024) where a probabilistic approach was implemented in RAVEN (Rabiti and Alfonsi, 2019) to estimate whether the probability of unstable crack growth in PTs is within acceptable limits. This follow-up work proposes surrogate modeling using a high-dimensional model representation to derive Sobol indices and establish a parameter influence ranking. The methodology is demonstrated in a Monte Carlo simulation campaign of a pressure tube inlet rolled joint. The implemented approach successfully identified and quantified critical parameters of the model while efficiently ranking and quantifying the interactions between input variables.

Electrospun three dimensional TiO2@N/P co-doped carbon nanofibers framework as high-performance anode materials for lithium-ion batteries

Electrospinning combined with heating treatment is employed to fabricate N/P co-doped carbon nanofibers encapsulating homogenous ultrafine TiO2 nanoparticles (TiO2@N/P-CNFs). Characterization results reveal that one-dimensional electrospun composite nanofibers with high electronic conductivity and structural integrity are interconnected with each other to construct a three-dimensional conductive nanofiber network as efficient ion/electron transport channels. Specifically, the Li//TiO2@N/P-CNFs coin cell delivers an initial discharge specific capacity of 754.9 mAh/g at 100 mA/g and maintains the reversible specific capacity of 486.1 mAh/g after 100 cycles. Moreover, the cell expresses the exceptional rate capability with discharge specific capacity of 272.2 mAh/g at 2000 mA/g, whose capacity can be restored to 474.3 mAh/g as soon as the current density is returned to 100 mAh/g. Furthermore, Li//TiO2@N/P-CNFs cell demonstrates a significant pseudocapacitive contribution of 78% at 1.0 mV/s. The excellent electrochemical performance can be explained by the fact that the N/P co-doping strategy is promising strategy for facilitating Li+ ions storage and transfer by broadening interlayer distance and increasing the distribution of defects and active sites. Besides, ultrafine TiO2 nanoparticles with diameter of about 7 nm harness excellent mechanical strength to maintain structural stability upon cycling. Therefore, easily fabricated TiO2@N/P-CNFs composite nanofibers with excellent electrochemical properties may be served as a promising option for advanced anode materials for lithium-ion batteries.

A Magneto-Electric Device for Fluid Pipelines with Vibration Damping and Vibration Energy Harvesting.

This study introduces an innovative energy harvesting system designed for industrial applications such as fluid pipelines, air conditioning ducts, sewer systems, and subsea oil pipelines. The system integrates magneto-electric flow coupling and utilizes a dynamic vibration absorber (DVA) to mitigate the vibrations induced by fluid flow while simultaneously harvesting energy through magnetic dipole-dipole interactions in a vibration energy harvester (VEH). The theoretical models, based on Hamilton's Principle and the Biot-Savart Law, were validated through comprehensive experiments. The results indicate the superior performance of the small-magnet system over the large-magnet system in both damping and power generation. The study analyzed the frequency response and energy conversion efficiency across different parameters, including the DVA mass, spring constant, and placement location. The experimental findings demonstrated significant vibration reduction and increased voltage output, validating the theoretical model. This research offers new avenues for energy harvesting systems in pipeline infrastructures, potentially enhancing energy efficiency and structural integrity.

Identification of hanger damage based on deflection influence matrix

Tied-arch bridges, a vital component of modern infrastructure, are susceptible to various forms of damage, particularly hangers. The detection and identification of such damages are crucial for maintaining structural integrity and safety. However, traditional methods face challenges in terms of accuracy and efficiency. This study aims to develop a refined method for hanger damage identification in tied-arch bridges, to address the limitations of existing techniques. By focusing on deflection changes at the anchoring points between the hangers and tie beams, we sought to enhance the precision of damage detection. We propose an innovative approach based on the concept of influence lines, introducing the ‘generalized deflection difference influence line'and the ‘deflection difference influence matrix’. Then proposed a new identification index for identifying the damaged hanger after matrix. An actual tied-arch bridge was used to validate the proposed approach. A detailed three-dimensional finite element model of the bridge was developed and calibrated using dynamic and static response data. Thirty different hanger-damage conditions were simulated to evaluate the effectiveness of the proposed method. Our findings reveal that the deflection difference influence matrix offers more detailed and comprehensive information on bridge distribution points than traditional methods. Our method proved effective in identifying hanger damage, irrespective of its location on the bridge. In additionally, the identification efficiency of the method can be improved by adjusting the magnitude of the applied load, with larger loads amplifying the detectability of damage. This study highlights the potential of the deflection difference influence matrix to revolutionize hanger damage identification for tied-arch bridges. Its adaptability, accuracy, and efficiency are significant advancements over existing methods. This study successfully demonstrates an innovative and reliable method for hanger damage identification.

Digital twins-boosted intelligent maintenance of ageing bridge hangers exposed to coupled corrosion–fatigue deterioration

The corrosion–fatigue coupled deterioration of ageing steel bridge hangers presents significant structural challenges, demanding rigorous condition assessments and timely maintenance interventions. This paper introduces a framework of digital twins-boosted intelligent maintenance (DTIM) tailored for ageing hangers, integrating the prediction model, monitoring data and inspection results. The DTIM features a suite of algorithms adaptation and innovations, including dynamic Partially Observable Markov Decision Processes (POMDP), Asynchronous Advantage Actor Critic (A3C), and Bayesian Dynamic Linear Models (BDLM). The DTIM emphasises regular early-life repairs, strategic inspections, and timely replacements towards life-end, tailored to the condition of specific bridge hangers in the case study presented. By coordinating actions across hangers, the DTIM enables opportunistic maintenance to further optimise resource allocation. The output highlights digital twins in exploring the add-on value of monitoring and inspection for the proactive and sustainable maintenance of ageing infrastructure, promising enhanced structural integrity and serviceability in a cost-effective and well-informed manner.

Extracellular vesicle-encapsulated microRNAs and respiratory health among American Indians in the Strong Heart Study

American Indian populations have experienced marked disparities in respiratory disease burden. Extracellular vesicle-encapsulated microRNAs (EV-miRNAs) are a novel class of biomarkers that may improve recognition of lung damage in indigenous populations. Are plasma EV-miRNAs viable biomarkers of respiratory health in American Indian populations? The Strong Heart Study is a prospective cohort study that enrolled American Indians aged 45-74 years. EV-miRNA expression was measured in plasma (1993-1995). Respiratory health outcomes including pre-bronchodilator forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and respiratory symptom burden were ascertained in the same study visit. Club cell secretory protein (CC-16), an anti-inflammatory pneumoprotein implicated in COPD pathogenesis, was measured in serum. Linear and logistic regression were used for statistical analyses. Biological pathway analyses were used to elucidate gene targets of significant EV-miRNAs. Among 853 American Indian adults, three EV-miRNAs were associated with FEV1, four EV-miRNAs were associated with FVC, and one EV-miRNA was associated with FEV1/FVC (P<0.05). Increased miR-1294 expression was associated with higher odds of airflow limitation (OR 1.29, 95% CI 1.07-1.55), while increased expression of miR-1294 (OR 1.32, 95% CI 1.07-1.63) and miR-532-5p (OR 1.57, 95% CI 1.02-2.40) was associated with higher odds of restriction. Increased miR-451a expression was associated with lower odds of exertional dyspnea (OR 0.71, 95% CI 0.59-0.85). Twenty-two EV-miRNAs were associated with serum CC-16 levels (q<0.05), suggesting EV-miRNAs may play a role in the pathway linking CC-16 to COPD pathogenesis. A pathway analysis showed key EV-miRNAs targeted biological pathways that modulate inflammation, immunity, and structural integrity in the lungs. Circulating EV-miRNAs are novel mechanistic biomarkers of respiratory health and may facilitate the early detection and treatment of lung damage in American Indian populations that have been disproportionately affected by chronic lung diseases.

Confining WS2 hierarchical structures into carbon core-shells for enhanced sodium storage

The growing demand for clean energy has heightened interest in sodium-ion batteries (SIBs) as promising candidates for large-scale energy storage. However, the sluggish reaction kinetics and significant volumetric changes in anode materials present challenges to the electrochemical performance of SIBs. This work introduces a hierarchical structure where WS2 is confined between an inner hard carbon core and an outer nitrogen-doped carbon shell, forming HC@WS2@NCs core–shell structures as anodes for SIBs. The inner hard carbon core and outer nitrogen-doped carbon shell anchor WS2, enhancing its structural integrity. The highly conductive carbon materials accelerate electron transport during charge/discharge, while the rationally constructed interfaces between carbon and WS2 regulate the interfacial energy barrier and electric field distribution, improving ion transport. This synergistic interaction results in superior electrochemical performance: the HC@WS2@NCs anode delivers a high capacity of 370 mAh g−1 at 0.2 A/g after 200 cycles and retains261 mAh g−1 at 2 A/g after 2000 cycles. In a full battery with a Na3V2(PO4)3 cathode, the Na3V2(PO4)3//HC@WS2@NC full-cell achieves an impressive initial capacity of 220 mAh g−1 at 1 A/g. This work provides a strategic approach for the systematic development of WS2-based anode materials for SIBs.

Highly efficient and water-resistant BaGa4S7:Eu2+ phosphor prepared by a self-reduction method

The development of eco-friendly luminescent materials is imperative for the advancement of phosphor-based technologies. This study corroborates the self-reduction of Eu3+ to Eu2+ through analyses utilizing photoluminescence (PL), excitation spectroscopy (PLE), and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations demonstrate that Eu2+ ions can efficaciously substitute Ba2+ ions within the BaGa4S7 lattice, preserving its structural integrity. Upon blue light excitation, BaGa4S7:Eu2+ manifests a robust green emission attributed to Eu2+ ions, showcasing a peak wavelength near 526 nm. The quantum yield (QY) of BaGa4S7:Eu2+ is remarkably high, registering at 74.8 %. Moreover, the temperature-dependent luminescence properties of BaGa4S7:Eu2+ phosphor were subjected to thorough investigation. Water resistance assays indicate that the sample preserves 76 % of its initial luminous intensity following 40 days of aqueous immersion. Additionally, BaGa4S7:Eu2+ based phosphor-converted white light-emitting diodes (WLEDs) demonstrate emission of high-quality white light. This unique water-resistant green emission sulfide phosphor is expected to have potential applications in lighting fields.