Search Results (123)

Concrete pavements frequently develop subsurface voids between surface and base layers during long-term service due to cyclic loading, environmental effects, and subgrade instability, which compromise structural integrity and traffic safety. Ground-penetrating radar (GPR) has been widely used as a non-destructive method for detecting such voids. However, the presence of coarse aggregates with strong electromagnetic scattering properties often introduces pseudo-reflection signals in radar images, hindering accurate void identification. To address this challenge, this study develops a high-fidelity three-phase concrete model incorporating aggregates, mortar, and the interfacial transition zone (ITZ). The Finite-Difference Time-Domain (FDTD) method is used to simulate electromagnetic wave propagation in both voided and intact structures. Simulation results reveal that aggregate-induced scattering can blur or distort reflection interfaces, generating pseudo-hyperbolic anomalies even in the absence of voids. In cases of thin-layer voids, real echo signals may be masked by aggregate scattering, leading to missed detections. GPR systems can be broadly classified into impulse, continuous-wave, and multi-frequency types. To validate the simulations, field tests using multi-frequency 2D/3D GPR systems and borehole verification were conducted. The results confirm the consistency between simulated and actual radar anomalies and validate the proposed model. This work provides theoretical insight and modeling strategies to enhance the interpretation accuracy of GPR data for subsurface void detection in concrete pavements. Full article

Solid-state lithium batteries (SSLBs) have emerged as a promising alternative to conventional lithium-ion systems due to their superior safety profile, higher energy density, and potential compatibility with lithium metal anodes. However, a major challenge hindering their widespread deployment is the formation and growth of lithium dendrites, which compromise both performance and safety. This review provides a comprehensive and structured overview of recent advances in dendrite suppression strategies, with special emphasis on the role played by the nature of the solid electrolyte. In particular, we examine suppression mechanisms and material innovations within the three main classes of solid electrolytes: sulfide-based, oxide-based, and polymer-based systems. Each electrolyte class presents distinct advantages and challenges in relation to dendrite behavior. Sulfide electrolytes, known for their high ionic conductivity and good interfacial wettability, suffer from poor mechanical strength and chemical instability. Oxide electrolytes exhibit excellent electrochemical stability and mechanical rigidity but often face high interfacial resistance. Polymer electrolytes, while mechanically flexible and easy to process, generally have lower ionic conductivity and limited thermal stability. This review discusses how these intrinsic properties influence dendrite nucleation and propagation, including the role of interfacial stress, grain boundaries, void formation, and electrochemical heterogeneity. To mitigate dendrite formation, we explore a variety of strategies including interfacial engineering (e.g., the use of artificial interlayers, surface coatings, and chemical additives), mechanical reinforcement (e.g., incorporation of nanostructured or gradient architectures, pressure modulation, and self-healing materials), and modifications of the solid electrolyte and electrode structure. Additionally, we highlight the critical role of advanced characterization techniques—such as in situ electron microscopy, synchrotron-based X-ray diffraction, vibrational spectroscopy, and nuclear magnetic resonance (NMR)—for elucidating dendrite formation mechanisms and evaluating the effectiveness of suppression strategies in real time. By integrating recent experimental and theoretical insights across multiple disciplines, this review identifies key limitations in current approaches and outlines emerging research directions. These include the design of multifunctional interphases, hybrid electrolytes, and real-time diagnostic tools aimed at enabling the development of reliable, scalable, and dendrite-free SSLBs suitable for practical applications in next-generation energy storage. Full article

Tidal seashell waste represents an abundant, underutilized marine resource that poses environmental disposal challenges but offers potential as a sustainable bio-filler in epoxy composites. This study investigates its incorporation into bio-based epoxy systems to reduce reliance on non-renewable materials and promote circular economy objectives. Processed seashell powder was blended into epoxy formulations, and response surface methodology was applied to optimize filler loading and resin composition. Comprehensive characterization included tensile strength, impact resistance, hardness, density, and thermal conductivity testing, along with microscopy analysis to evaluate filler dispersion and interfacial bonding. The optimized composites demonstrated improved hardness, density, and thermal stability while maintaining acceptable tensile and impact strength. Microscopy confirmed uniform filler distribution at optimal loadings but revealed agglomeration and void formation at higher contents, which can reduce interfacial bonding efficiency. These findings highlight the feasibility of valorizing marine waste as a reinforcing filler in sustainable composite production, supporting environmental goals and offering a scalable approach for the development of durable, lightweight materials suitable for structural, coating, and industrial applications. Full article

Void defects, manifested as distributed porosity, are common in metal additive manufacturing (AM) and can significantly degrade the mechanical performance and reliability of fabricated components. To enable real-time quality control during fabrication, this study proposes a grating laser ultrasonic method for the online evaluation of porosity in AM parts. Based on the theoretical relationship between surface acoustic wave (SAW) velocity and material porosity, a non-contact detection approach is developed, allowing the direct inference of porosity from the measured SAW velocities without requiring knowledge of the exact source–detector distance. Numerical simulations are conducted to analyze SAW propagation under varying porosity conditions and to validate the inversion model. Experimental measurements on aluminum alloy specimens with different porosity levels further confirm the sensitivity of SAW signals to internal voids. The results show consistent waveform and spectral trends between the simulation and experiment, supporting the feasibility of the proposed method for practical applications. Overall, the findings demonstrate the potential of this approach for the accurate online monitoring of void defects in metal AM components. Full article

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) have attracted significant interest as hybrid reinforcements in epoxy (Ep) composites for enhancing mechanical performance in structural applications, such as aerospace and automotive. These 1D and 2D nanofillers possess exceptionally high aspect ratios and intrinsic mechanical properties, substantially improving composite stiffness and tensile strength. In this study, epoxy nanocomposites were fabricated with 0.1 wt.% and 0.3 wt.% of CNTs and GNPs individually, and with 1:1 CNT:GNP hybrid fillers at equivalent total loadings. Scanning electron microscopy of fracture surfaces confirmed that the CNTGNP hybrids dispersed uniformly, forming an interconnected nanostructured network. Notably, the 0.3 wt.% CNTGNP hybrid system exhibited minimal agglomeration and voids, preventing crack initiation and propagation. Mechanical testing revealed that the 0.3 wt.% CNTGNP/Ep composite achieved the highest tensile strength of approximately 84.5 MPa while maintaining a well-balanced stiffness profile (elastic modulus ≈ 4.62 GPa). The hybrid composite outperformed both due to its synergistic reinforcement mechanisms and superior dispersion despite containing only half the concentration of each nanofiller relative to the individual 0.3 wt.% CNT or GNP systems. In addition to mechanical performance, electrical conductivity analysis revealed that the 0.3 wt.% CNTGNP hybrid composite exhibited the highest conductivity of 0.025 S/m, surpassing the 0.3 wt.% CNT-only system (0.022 S/m), owing to forming a well-connected three-dimensional conductive network. The 0.1 wt.% CNT-only composite also showed enhanced conductivity (0.0004 S/m) due to better dispersion at lower filler loadings. These results highlight the dominant role of CNTs in charge transport and the effectiveness of hybrid networks in minimizing agglomeration. These findings demonstrate that CNTGNP hybrid fillers can deliver optimally balanced mechanical enhancement in epoxy matrices, offering a promising route for designing lightweight, high-performance structural composites. Further optimization of nanofiller dispersion and interfacial chemistry may yield even greater improvements. Full article

The growing demand for low-cost biosensors has stimulated the study of new technologies and materials like molybdenum disulfide (MoS₂). Due to its electroconductive nature and high surface-to-volume ratio, it allows for the ultra-sensitive detection of biomarkers. The crystal structure of MoS₂ provides it with a unique micrometer thickness, making it appropriate for biosensing in healthcare, environmental monitoring, and food safety. As compared to traditional materials, MoS₂ can work without labels (through field-effect transduction or plasmonic shifts) while maintaining biocompatibility and low-cost fabrication, which fill significant voids in the early diagnosis of diseases. This paper provides an overview of the recent advancements in MoS₂-based biosensors, which are primarily focused on the field-effect transistors and surface plasmon resonance techniques and fabrication methods for MoS₂-based biosensors like mechanical exfoliation, liquid-phase exfoliation, physical vapor deposition, chemical vapor deposition, and chemical exfoliation, applications in various industries, and their characterization techniques to evaluate the quality and functionality of MoS₂ nanosheets in biosensors. While certain challenges remain like improving conductivity and scalability, MoS₂-based biosensors serve as a powerful tool for the precise and reliable detection of biomarkers in environmental, food, and healthcare industries. Full article

Soil treatment with natural materials is an effective method to improve the mechanical properties of the original soil for recycling engineering construction. This research aims to evaluate the synergistic effects of lignin fiber and cement on sandy clayey silt stabilization. A factorial experimental design was employed, testing five lignin fiber contents (0%, 2%, 4%, 6%, and 8%) and three cement contents (0%, 2%, and 4%) across four curing periods (1, 7, 14, and 30 days). Unconfined compressive strength (UCS) tests were conducted in triplicate for each combination (total *n* = 180 samples), and failure surfaces were analyzed using Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX). Results indicate a critical lignin fiber threshold of 4%, beyond which UCS decreased by 15–20% due to increased void ratios. Statistical analysis (ANOVA, *p* < 0.05) confirmed significant interactions between lignin fiber, cement content, and curing time. For instance, 4% lignin fiber and 4% cement yielded a 139% UCS increase after 30-day curing compared to untreated soil. SEM-EDX revealed that lignin fiber networks enhance ductility by bridging soil particles, while cement hydration reduced particle detachment. These findings provide a quantitative framework for optimizing lignin fiber-cement stabilization in sustainable geotechnical applications. Full article

This study explores the correlation between road surface texture, including microtexture (texture depth) and macrotexture (wavelength) in asphalt pavement, and suspended dust generation on asphalt pavements. A detailed analysis of various pavement types, including Hot Mix Asphalt (HMA) and porous pavement, was conducted to assess their impact on dust load and concentration. For HMA pavements, deeper texture depths led to a higher dust load and concentration, attributed to the impermeable nature of the material, which causes dust to become easily suspended in the air. Conversely, porous pavements, which have air gaps in their surface layers, showed reduced dust suspension despite a higher dust load, due to the ability of these voids to trap dust and minimize air-pumping effects from tire–road contact. The study found that a macrotexture depth (MTD) exceeding 1.7 mm stabilized dust concentration, while higher surface wavelengths and silt load (sL) values above 0.1 g/m² significantly contributed to dust suspension. These findings suggest that optimizing road surface texture and aggregate size, considering the voids and depth, can help reduce suspended dust, providing a balance between road safety and environmental management. This research offers valuable insights for designing pavements that mitigate air pollution while maintaining functional performance. Full article

Frost resistance of pavement concrete is closely related to air void structure. Traditionally, such a structure is assessed by measuring chord lengths according to the guidelines provided in the PN-EN 480-11 standard. In recent years, increased attention has been given to analyzing pore diameters (2D) on the surface of concrete samples. The measurement procedure employed in the surface method should enable accurate identification of small pores formed by modern air-entraining admixtures. Researchers suggest only pores under 300 µm significantly impact frost resistance, raising the question of whether pores over 1000 µm should be considered in measurements. This study attempts to define the measurement frame parameters required to obtain satisfactory results. Additionally, a comparative analysis of air void structure parameters from 2D and 1D methods was conducted. Geometrical models of air voids distributed within cement paste using the Monte Carlo method based on air void structure data derived from real concrete were created. Analysis of these models demonstrated good agreement between the 2D and 1D results. It was concluded that satisfactory results require the analysis of either three measurement frames of 50 × 50 mm or four frames of 40 × 40 mm, with a resolution of at least 3 µm/px. Full article

Unregulated underground group mining in China has led to problems such as unclear locations and complex shapes of mine goafs in mineral engineering, posing serious safety hazards for subsequent mining operations. This paper takes mineral engineering with complex mine goafs as the research object, integrates multi-survey data from surface deformation remote sensing monitoring and 3D laser scanning measurement to survey the area where the surface deformation rate reaches 14cm/ year, accurately identifies the location of risky mine goafs, and constructs detailed representations of the real shapes of the complex mine goafs inside the mineral engineering. The FLAC^3D 6.0 software is used to establish a 3D numerical simulation model of the mine goafs, fully considering the mining process, and conducting characteristic analysis of the stress distribution, failure range and surface deformation response of the mine goafs, revealing the impact of void deformation on the stability of the mine. The numerical simulation results are combined with on-site investigations to verify whether geological disasters have been caused by mine goafs. The research methods and results can provide effective technical means for the detailed survey and stability assessment of mineral engineering with complex mine goafs, which can help to reduce the risk of geological disasters in mines and improve the safety of mineral engineering. Full article

During pipe-roof construction using pipe-jacking technology, lubricants are injected into the tail void to reduce pipe–soil friction and minimize soil loss. However, research on ground settlement caused by multiple adjacent pipe jackings remains limited, and the influence of lubricant Young’s modulus on ground settlement control is not clear. To address these gaps, this study conducts a comprehensive investigation using a Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D). Initially, the research model is validated against a pipe-roof case in Japan. Subsequently, ground response characteristics are simulated under lubricants with different Young’s moduli, considering four burial depths, two pipe-roof arrangements (“gate-shaped” and “horseshoe-shaped”), and two tail voids. The results indicate that low-stiffness lubricants mobilize greater surface settlement, while increasing the lubricant Young’s modulus more markedly optimizes the interaction among adjacent pipelines, thereby greatly alleviating the settlement. Nonetheless, the control effectiveness of lubricant on the settlement is influenced by other factors. Increasing burial depths and tail voids weaken the lubricant’s capacity to mitigate surface settlement. In contrast, the horseshoe-type arrangement is more conducive to the lubricant’s control effect on surface settlement than the gate-type system. Moreover, under these three cases, an increase in the lubricant Young’s modulus can more substantially reduce surface settlement. These findings provide valuable insights for controlling ground settlement during pipe-roof construction. Full article

A highly redox-active ternary nickel sulfide and cobalt-anchored carbon nanocomposite (NiS-Co@C) electrochemical electrode is synthesized by a two-step pyrolysis-hydrothermal method using biomass-derived carbon. The high-crystalline hierarchical porous nanostructure provides abundant voids and cavities, along with a large specific surface area, to improve the interfacial properties. The as-synthesized electrode achieved a specific capacity of 640 C g⁻¹ at 1 A g⁻¹, with a capacity retention of 93% over 5000 cycles, revealing outstanding electrochemical properties. Nickel sulfide nanoparticles embedded in the cobalt-anchored carbon framework improved redox activity, ion transport, and conductivity, resulting in a dominant diffusion-controlled battery-type behavior. Moreover, a hybrid supercapattery, based on battery-type NiS-Co@C as the positrode and capacitive-type activated carbon as the negatrode, achieved a maximum specific energy/power of 33 Wh kg⁻¹/7.1 kW kg⁻¹ with a 91% capacity retention after 5000 cycles. The synergistic effect of the combinatorial battery–capacitor behavior of the hybrid supercapattery has improved the specific energy–power considerably, leading the development of next-generation energy storage technologies. Full article

The surface topology and fractal dimension of ultrathin silver and gold films have been investigated utilizing atomic force microscopy. These films were formed at the early stages of metal deposition through thermal evaporation and have pre-percolation thicknesses. They contain both metallic and insulating (void) phases, making them metal–dielectric composites. We identified the main parameters of the microstructure, such as the size of the metallic particles and surface roughness, as well as the dependence of these parameters on the film thickness and substrate parameters. Approaches to processing data, including correlation analysis, were employed. An analysis of dependencies and an explanation of their appearance were conducted. The discussion also addressed the limitations of using atomic force microscopy for studying ultrathin metal films. We determined the various types of fractal dimensions, considering the film topology for two- as well as three-dimensional objects. Depending on the actual dimensions of the phase boundary for silver films, a maximum was found. Different approaches to determining the fractal dimensions in 3Ds case show a similar dependence, but different values. Full article

The quality of newly constructed pavement depends mostly on compaction, which is essential for ensuring the pavement’s longevity and performance. Traditional methods of evaluating pavement compaction and density, such as core sampling and nuclear gauge measurements, are often time-consuming and invasive and provide only a limited amount of data at a low spatial resolution on the potential air void content of the asphalt layers. The present study aimed to assess the specific gravity (G_mb) of a dolomitic asphalt mixture at different degrees of compaction using GPR techniques. Relative density (RD) maps were generated to visualize the spatial homogeneity of the asphalt density. Nuclear density gauging was applied for the calibration, and cores were used to validate the results. The survey was conducted on two recently paved roads in Szeged, Hungary. After testing various approaches, it was found that applying horn antennas and the surface reflection (SR) method is the most feasible way to obtain reliable and accurate dielectric permittivity (ε) data. Based on the measurements, clear relationships were found between dielectric constants, G_mb, and aggregate size. The findings highlight that it is possible to indirectly determine the G_mb of asphalts composed of dolomite and limestone aggregates using GPR, with aggregate sizes ranging from 11 mm to 25 mm and G_mb values between 2.43 and 2.57 g/cm³. Consequently, a robust function was developed, which can be applied to other asphalts with similar compositions. Full article

The effects of abrasion on the heating performance of carbon nanotube (CNT)/epoxy composites were investigated in terms of Joule’s heat, convective heat, and radiative heat under moderate-to-severe and localized abrasive conditions. While the overall heating behavior was characterized by the heating rate and the curvature of the transient response, a numerical solution of the heat equation was used to quantify convective and radiative heat transfers, incorporating the specific heat of each component, the convective heat transfer coefficient, and the Biot number. CNT reinforcement significantly improved wear resistance at a CNT concentration of 0.31 vol. %, but the presence of micro-voids led to a slight increase in wear rate with additional CNT inclusion. Using an equivalent circuit model, local and severe abrasion scenarios were analyzed to determine the variation in electrical conductivity with temperature at different degrees of abrasion, indicating the impact of scattering effects. This analysis provides valuable insights for estimating both wear resistance and the heating performance of self-heated surface materials, with potential applications in future space technologies. Full article