Search Results (14,199)

The purpose of this study was to investigate the effect of annealing temperature on the structural, morphological, and electrochemical properties of tungsten trioxide (WO₃) films, fabricated via electrodeposition and annealed at 50 °C, 250 °C, and 450 °C. Structural analysis using X-ray diffraction (XRD) revealed temperature-induced modifications, transitioning from amorphous to crystalline phases. Morphological studies by field emission scanning electron microscopy (FESEM) demonstrated an increase in grain size with temperature (31 nm, 48 nm, and 53 nm) and the formation of cracks at higher annealing temperatures. Electrochemical characterization showed that the WO₃ film annealed at 250 °C exhibited superior redox activity, enhanced ion diffusion, and excellent reversibility. Optical studies highlighted its exceptional performance, with 79.35% optical modulation, a coloration efficiency of 97.91 cm²/C, and rapid switching times (9.8 s for coloration and 7.5 s for bleaching). Furthermore, long-term cycling tests confirmed minimal degradation after 5000 cycles, demonstrating durability. This work provides a comprehensive understanding of the annealing temperature’s impact on WO₃ films and underscores the novelty of achieving optimal electrochromic (EC) performance through temperature tuning, advancing the design of energy-efficient smart materials. Full article

The objective of this paper is to develop assessment models to quantitatively evaluate the seismic damage caused to resilient concrete columns intended for buildings located in strong-earthquake-prone regions such as Japan and China. The proposed damage assessment models are based on the fractal analysis of crack patterns on the surface of damaged concrete columns and expressed in the form of a fractal dimension (FD) versus transient drift ratio relationship. To calibrate the proposed damage assessment models, a total of eighty images of crack patterns for eight concrete columns were utilized. All the columns were reinforced by weakly bonded ultra-high-strength (WBUHS) rebars and tested under reversed cyclic loading. The experimental variables covered the shear span ratio of the column, the concrete strength, the axial load ratio, and the amount of steel in the WBUHS rebars. A box-counting algorithm was adopted to calculate or derive the FD of the crack pattern corresponding to each transient drift ratio. The test results reveal that the FD is an efficient image-based quantitative indicator of seismic damage degree for resilient concrete columns and correlates strongly with the transient drift ratio and is subjected to the influence of the shear span ratio. The influence of the other experimental variables on the derived FDs is, if any, little. Based on the test results, a linear equation was developed to define the relationships between the FD and transient drift ratio, and a multi-linear equation was formulated to relate the transient drift ratio to the residual drift ratio, an important index adopted in current design guidelines to measure the repairability of damaged concrete structures. To further verify the efficiency of the drift ratio-based FD in seismic damage assessment, the correlation between the FD and relative stiffness loss (RSL), an indicator used to measure the overall damage degree of concrete structures, was also examined. The driven FD exhibited very strong correlation with RSL, and an empirical equation was developed to reliably assess the overall seismic damage degree of resilient concrete columns with an FD. Full article

In industries spanning manufacturing to software development, defect segmentation is essential for maintaining high standards of product quality and reliability. However, traditional segmentation methods often struggle to accurately identify defects due to challenges like noise interference, occlusion, and feature overlap. To solve these problems, we propose a cross-hierarchy feature fusion network based on a composite dual-channel encoder for surface defect segmentation, called CFF-Net. Specifically, in the encoder of CFF-Net, we design a composite dual-channel module (CDCM), which combines standard convolution with dilated convolution and adopts a dual-path parallel structure to enhance the model’s capability in feature extraction. Then, a dilated residual pyramid module (DRPM) is integrated at the junction of the encoder and decoder, which utilizes the expansion convolution of different expansion rates to effectively capture multi-scale context information. In the final output phase, we introduce a cross-hierarchy feature fusion strategy (CFFS) that combines outputs from different layers or stages, thereby improving the robustness and generalization of the network. Finally, we conducted comparative experiments to evaluate CFF-Net against several mainstream segmentation networks across three distinct datasets: a publicly available Crack500 dataset, a self-built Bearing dataset, and another publicly available SD-saliency-900 dataset. The results demonstrated that CFF-Net consistently outperformed competing methods in segmentation tasks. Specifically, in the Crack500 dataset, CFF-Net achieved notable performance metrics, including an Mcc of 73.36%, Dice coefficient of 74.34%, and Jaccard index of 59.53%. For the Bearing dataset, it recorded an Mcc of 76.97%, Dice coefficient of 77.04%, and Jaccard index of 63.28%. Similarly, in the SD-saliency-900 dataset, CFF-Net achieved an Mcc of 84.08%, Dice coefficient of 85.82%, and Jaccard index of 75.67%. These results underscore CFF-Net’s effectiveness and reliability in handling diverse segmentation challenges across different datasets. Full article

Structural health monitoring (SHM) is essential for ensuring the safety and longevity of laminated composite structures. Their favorable strength-to-weight ratio renders them ideal for the automotive, marine, and aerospace industries. Among various non-destructive testing (NDT) methods, ultrasonic techniques have emerged as robust tools for detecting and characterizing internal flaws in composites, including delaminations, matrix cracks, and fiber breakages. This review concentrates on recent developments in ultrasonic NDT techniques for the SHM of laminated composite structures, with a special focus on guided wave methods. We delve into the fundamental principles of ultrasonic testing in composites and review cutting-edge techniques such as phased array ultrasonics, laser ultrasonics, and nonlinear ultrasonic methods. The review also discusses emerging trends in data analysis, particularly the integration of machine learning and artificial intelligence for enhanced defect detection and characterization through guided waves. This review outlines the current and anticipated trends in ultrasonic NDT for SHM in composites, aiming to aid researchers and practitioners in developing more effective monitoring strategies for laminated composite structures. Full article

Conventional polypropylene fibers, characterized by their smooth surfaces, exhibit relatively weak bonding with cement-based materials, limiting their effectiveness in enhancing these materials’ mechanical properties. This study investigates a graft-modified approach to activating polypropylene fibers, introducing amide groups onto their surfaces to improve fiber–matrix interaction. The active polypropylene fibers were produced using an ultraviolet (UV) grafting technique, where maleic anhydride was first used to graft carboxyl groups onto the fiber surfaces, followed by acylation with diethylenetriamine to introduce amide bonds. The optimal experimental conditions were identified by using the degree of amidation as the response metric. Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed successful amination and surface activation, with a marked increase in specific surface area. The water contact angle of the active polypropylene fibers decreased significantly from 106.3° to 39.9°, indicating greatly improved wettability by the cement slurry and enhanced bonding strength between the fibers and the cement matrix. To evaluate the effects of the modified fibers, cement-stabilized macadam specimens incorporating various fiber contents were prepared and tested to determine their mechanical properties and shrinkage performance. The results indicated that, compared to conventional polypropylene fibers, the activated polypropylene fibers increased the 28-day compressive strength of CSM by 6.56%, enhanced tensile strength by 4.94%, reduced the rebound modulus by 7.42%, decreased the drying shrinkage coefficient by 25.55%, and lowered the thermal shrinkage coefficient by 13.16%. These findings demonstrate that the chemical bonding between the active polypropylene fibers and the cement matrix is significantly enhanced, leading to improved overall performance in crack resistance, material toughening, and shrinkage mitigation. Full article

Experimental and computational research on the behavior of small-scale and large-scale fiber-reinforced concrete (FRC) beams is presented in this paper. The experimental part included the small-scale bending tests, which were conducted on three 1.3 m long by 0.1 m wide by 0.15 m high rectangular simply supported beams, and the large-scale test that was conducted on 12.8 m long by 0.2 m wide by 1.3 m two-chords girder. The concrete mixture in the large-scale test was designed with environmentally more justifiable supplementary materials (binder and fibers), striving for sustainable excellence. To accurately predict the mechanical behavior of tested models, a numerical model incorporating the real nonlinear materials laws is used. A numerical model based on finite element analysis (FEA) is developed. The FEA model is created using a smeared crack approach with a constitutive law for the tensile behavior of FRC derived from an inverse analysis based on prism bending tests. The numerical model is validated against experimental results and the accuracy of numerical predictions based on finite element modeling showed a good correlation with the test data. The FEA-based model makes it easier to predict how FRC structures fail under transversal loading and can serve as a foundation for creating new design processes. Additionally, the presented research is aimed at the feasibility of recycled steel FRC field application in building structures. The usage of recycled steel fibers could achieve environmental benefits through the adoption of sustainable materials. The present study showcased the possibility of modeling reinforced concrete structural building parts made with recycled steel fibers using available software. Full article

Miniature patch antenna sensors have great potential in the field of structural health monitoring for crack propagation detection due to their small size and high sensitivity. A primary research focus has been achieving efficient miniaturization, with the performance of the dielectric layer playing a pivotal role. Studies have demonstrated that increasing the relative dielectric constant (ε_r) of the dielectric layer can reduce antenna size, but higher dielectric losses (tanδ) can lower radiation efficiency. This study identifies the optimal dielectric properties by examining the interplay between ε_r and tanδ to balance size reduction and radiation efficiency. Additionally, while increasing the dielectric layer’s thickness improves bandwidth and radiation efficiency, a thinner layer is preferred to maintain overall performance without compromising radiation efficiency. Furthermore, the resonant frequency of the smaller-sized patch antenna sensor exhibits greater detection sensitivity to crack propagation. These insights provide useful guidance for selecting effective dielectric layers and assist in the miniaturization design of antenna sensors. Full article

This review analyzes the use of magnetite-based catalysts in various oxidation reactions. It is shown that magnetite-based catalysts are the most promising candidates from the standpoint of easy separation from the reaction zone and reusability. Diverse examples of the use of magnetite-based composites are discussed, including the following reactions: partial oxidation of methane to formaldehyde; the oxidation of cycloalkanes into alcohols and ketones; the oxidation of alkenes and alcohols with the major focus made on benzylic alcohol oxidation; oxidative cracking of alkenes; Fenton-type reactions with H₂O₂ as a benign oxidant; the removal of dyestuff in water (including wastewater by oxidation); reactions of sulfides and thiols; the oxidation of 5-hydroxymethylfurfural as a platform chemical to 2,5-diformylfuran; the oxidation of D-glucose to D-gluconic acid; and the electrocatalytic oxidation of methanol and ethanol. The most important and best-studied applications of magnetic nanoparticles in the oxidation reactions are believed to be the oxidation of diverse benzylic alcohols and D-glucose, and Fenton-like reactions aiming at the removal of S- and N-compounds from ware and fuels. Magnetic nanocomposites are determined as the materials meeting a range of criteria: (1) they should be magnetic, (2) they contain nanoparticles, and (3) they consist of two (or more) nanocomponents. The core–shell materials with magnetic nanoparticles used as a core or as decorating nanoparticles are discussed in the review. Three main types of magnetic nanocomposites can be distinguished: (1) the systems where the magnetic phase is active in the considered reaction, for instance, Fenton-like oxidation; (2) the systems containing active metal nanoparticles supported onto the magnetic nanoparticles; and (3) materials with magnetic nanoparticles as a core coated with one or two shells (porous or non-porous), with the magnetic nanoparticles being active or not in the title reaction. Magnetic nanoparticles exhibit a number of advantages compared with supported non-magnetic catalysts of oxidation reactions. The advantages include the possibility of separation from the reaction medium (5–10 times) without a significant loss of the activity, their non-toxicity, low cost, and availability, and the easy preparation of these materials. The drawbacks may include the leaching of active components; a decrease in saturation magnetization in comparison with the bulk magnetite; a limited accessibility of active sites due to diffusion through the shells; the complicated composition and structure of the nanomaterials; a decrease in the activity and specific surface area; and a limited number of magnetic compounds with acceptable characteristics. Nevertheless, the advantages of magnetic nanocatalysts stimulate their wide use in liquid-phase oxidation reactions, which will be discussed in the review. Future perspectives on the use of magnetic composites are considered. Full article

Myrrh has unique medicinal properties: it is an anti-inflammatory, antifungal, and antibacterial material. The aim of this study was to assess the influence of ethanolic myrrh extract on the production and properties of modified PP and PLA melt spun yarns. In this work, multifilament yarns of polylactide (PLA) and polypropylene (PP) containing 10 wt% myrrh resin at different melt-spinning drawing ratios (DRs) were prepared. The results of scanning electron microscopy revealed that the multifilament yarns from polymers covered by myrrh resin extract had a smooth surface without cracks or visible myrrh derivatives. The influence of myrrh resin on the mechanical properties of PP and PLA multifilament yarns was analyzed, and it was found that the presence of myrrh (PP/M, PLA/M) increased tenacity (cN/tex) and decreased the tensile strain (%) of melt spun yarns obtained at different draw ratios (DRs). During optical analysis, it was found that the absorbance of yarns increased in the entire UV region of the spectra, which was most likely determined by the presence of myrrh. The degree of crystallinity and the wetting angle of PP/M and PLA/M multifilament yarns increased compared with the pure PLA and PP multifilament yarns. This study concludes that the presence of myrrh derivatives influences PLA yarns degradation rate and antibacterial effects against Gram-positive bacteria. Full article

Introducing a second phase has been an effective way to solve the brittleness of boron carbide (B₄C) for its application. Though reduced graphene oxide (rGO) is an ideal candidate for reinforcing the B₄C duo’s two-dimensional structure and excellent mechanical properties, the toughness is less than 6 MPa·m^1/2, or the hardness is lower than 30 GPa in B₄C–graphene composites. A barrier to enhancing toughness is the weak interface strength between rGO and B₄C, which limits the bridging and pull-out toughening effects of rGO. In this work, internal stress was introduced using a high-pressure and high-temperature (HPHT) method with B₄C–rGO composites. The optimal hardness and toughness values for the B₄C-2 vol% rGO composite reached 30.1 GPa and 8.6 MPa·m^1/2, respectively. The improvement in toughness was 4 times higher than that of pure B₄C. The internal stress in the composite increased gradually from 2.3 GPa to 3.3 GPa with an increase in rGO content from 1 vol% to 3 vol%. Crack deflection, bridging, and rGO pull-out are responsible for the improvement in toughness. Moreover, the high internal stress contributed to the formation of good interface strength by embedding rGO into the B₄C matrix particles, which further enhanced the dissipation of the crack energy during the pull-out process and led to high toughness. This work provides new insights into synthesizing high-toughness B₄C matrix composites. Full article

The advantages of asphalt pavement in terms of driving comfort, construction efficiency, and ease of maintenance have established it as the predominant choice for high-grade pavements at present. However, being highly sensitive to temperature and stress, asphalt performance is significantly influenced by external environmental conditions and loading, making it susceptible to various distress phenomena. Particularly in high-latitude regions, asphalt pavement cracking severely limits asphalt pavement’s functional performance and service lifespan under cold climatic conditions. To enhance the low-temperature cracking resistance of asphalt pavement in cold regions, tools such as VOS viewer 1.6.20 and Connected Papers were utilized to systematically organize, analyze, and summarize relevant research from the past 40 years. The results reveal that temperature shrinkage cracks and thermal fatigue cracks represent the primary forms of asphalt pavement distress in these regions. Cracking in asphalt pavement in cold regions is primarily influenced by structural design, pavement materials, construction technology, and climatic conditions. Among these factors, surface layer stiffness, base layer type, and the rate of temperature decrease exert the most significant impact on cracking resistance, collectively accounting for approximately 45.4% of all cracking-related factors. The low-temperature performance of asphalt pavement can be effectively improved through several strategies, including adopting full-thickness asphalt pavement with a skeleton-dense structure or reduced average particle size, incorporating functional layers, appropriately increasing the thickness of the upper layer and the compaction temperature of the lower layer, utilizing continuous surface layer construction techniques, and applying advanced materials. High-performance modifiers such as SBR and SBS, nanomaterials with good low-temperature performance, and warm mixing processes designed for cold regions have proven particularly effective. Among various improvement methods, asphalt modification has demonstrated superior effectiveness in enhancing the deformation capacity of asphalt and its mixtures, significantly boosting the low-temperature performance of asphalt pavements. Asphalt modification accounts for approximately 50% of the improvement methods evaluated in this study, with an average improvement in low-temperature performance reaching up to 143%. This paper provides valuable insights into the underlying causes of cracking distress in asphalt pavements in cold regions and offers essential guidance for improving the service quality of such pavements in these challenging environments. Full article

Digital light processing (DLP) 3D-printed Si₃N₄ ceramics, known for their exceptional performance, offer distinct advantages in meeting the high-strength and complex structural demands of industries such as aerospace, semiconductors, healthcare, automotive, energy, and machinery. However, due to Si₃N₄’s strong chemical stability, low diffusion rate, low self-sintering ability, and high melting point, achieving densification under conventional sintering conditions is challenging. As a result, sintering additives are essential to promote the sintering process, lower the sintering temperature, improve densification, and enhance performance. In this study, 45 vol% Si₃N₄ slurries were prepared using DLP 3D printing technology, incorporating nine different combinations of sintering additives, including aluminum oxide (Al₂O₃), yttrium oxide (Y₂O₃), and aluminum nitride (AlN), in various ratios with Si₃N₄. The slurries were then sintered at 1800 °C for 2 h under a 1 MPa N₂ atmosphere. Additionally, the phase composition, microstructure, grain distribution, and crack propagation of the materials. The results showed that a Si₃N₄ to Al₂O₃ and Y₂O₃ ratio of 95:2.5:2.5 produced elongated β-Si₃N₄ grain structures and enhanced density, achieving a maximum Vickers hardness of 12.88 ± 0.52 GPa. Additionally, the synergistic toughening effect of the rod-like β-Si₃N₄ grains and sintering aids significantly improved the fracture toughness of the Si₃N₄ ceramic matrix, with a flexural strength of 540.63 ± 10.05 MPa and a fracture toughness of 4.92 ± 0.07 MPa·m^1/2. This study lays the foundation for the future application of 3D-printed Si₃N₄ ceramics, optimization of sintering aid combinations at different ratios, and performance enhancement in extreme environments. Full article

The growth of diamond film with texture on stainless steel can significantly improve its wear properties, while conventional methods such as laser etching and ultrasonic vibration superimposed machining suffered from complex processes and extra equipment. Here, we propose a simple new method to prepare textured diamond film on stainless steel without any special apparatus. In this method, a W/W-N interlayer was first deposited on the stainless steel surface, and then the sample with the interlayer was put into a hot filament chemical vapor deposition (HFCVD) chamber to grow diamond films. The interlayer becomes cracked during the warm-up stage due to the large tensile stress formed by the thermal expansion coefficient difference between the interlayer and the steel. Then the deposited diamond films copy the morphology of the interlayer, forming the textured diamond film. The textured diamond film exhibits a small amount of stress, ~3.4 GPa, and greatly improved wear resistance. Our results provide a way to prepare textured diamond films with good wear resistance. Full article

To accurately assess the temperature action and effect of steel-concrete composite girder bridges in plateau and cold areas, this paper investigated nearly 50 years of historical meteorological data from 26 meteorological observation stations in the Tibet region of China. Based on the most unfavorable extreme meteorological data at each meteorological station, a finite element model was used to analyze the temperature field of the composite girder. The most unfavorable values of temperature were obtained. The regional differences in temperature actions at different meteorological stations were analyzed, and the isotherm maps of the extreme values of the uniform temperature and thermal gradients were further obtained based on spatial interpolation methods in the ArcGIS program. The study shows that the uniform temperature is significantly affected by the climatic environment, and the isotherm maps provide a visual representation of the geographic distribution pattern of temperature extremes. The maximum and minimum uniform temperatures in Tibet range from 18.28 °C to 42.27 °C and from −41.07 °C to 4.71 °C respectively. The maximum regional difference of positive and negative thermal gradient reaches 11.32 °C and 7.69 °C respectively. The temperature effects calculated using the most unfavorable values of the isotherm map are all more unfavorable than the specification calculations. In particular, the tensile stress of the concrete under the positive thermal gradient reaches 2.91 MPa, which exceeds the standard value of the tensile strength of concrete. This is a significant risk factor for cracking. The compressive stress of the steel girder under a negative thermal gradient reaches 19.35 MPa, which represents a 136% increase compared to the specified value. This increase elevates the risk of instability in the steel girder. Full article

To enhance the tribological properties of the coatings and to inhibit cracking, sandwich-structured composite coatings were fabricated, consisting of a Ni60CuMo/IN718 transition layer and a Ni60CuMo/Ni-coated Cu wear-resistant layer with four different Ni-coated Cu contents. The results indicate that the transition layer inhibits the crack formation in the coating, and the refined grain structure stabilizes its average hardness at approximately 485 HV_0.5. Increasing the Cu content in the wear-resistant layer exacerbates the segregation of the Cu-rich solid solution phases and refines the in situ-generated Cr₇C₃, TiC, and NbC phases. The average hardness of the wear-resistant layer decreases from 474 HV_0.5 to 408 HV_0.5 as the Ni-coated Cu content increases from zero to 75%. The coating with 50% Ni-coated Cu has the best Cu self-lubricating properties and exhibits the best wear resistance at both room and high temperatures. At room temperature, abrasive wear is the primary wear mechanism in the coatings. Although the ductility of the coatings is improved with increasing Cu content, excessive Cu reduces the hardness and load-bearing capacity. At 300 °C, oxidation wear becomes the dominant wear mechanism, accompanied by plastic deformation and three-body wear as the Cu content increases. At 500 °C, severe oxidation wear is the dominant mechanism, with excessive Cu leading to oxidation film failure. Full article