Search Results (1,718)

This research presents a comprehensive evaluation of semi-elastic polyurethane adhesives used for bonding wooden flooring, with a particular focus on both domestic (oak) and exotic hardwood species (teak, iroko, wenge, merbau). Given the increasing interest in sustainable construction practices and the growing use of diverse wood species in flooring systems, this study aimed to assess the mechanical, morphological, and surface properties of adhesive joints under both standard laboratory and thermally aged conditions. Mechanical testing was conducted according to PN-EN ISO 17178 standards and included shear and tensile strength measurements on wood–wood and wood–concrete assemblies. Specimens were evaluated in multiple aging conditions, simulating real-world application environments. Shear strength increased post-aging, with the most notable improvement observed in wenge (21.2%). Tensile strength between wooden lamellas and concrete substrates remained stable or slightly decreased (up to 18.8% in wenge), yet all values stayed above the 1 MPa minimum requirement, confirming structural reliability. Surface properties of the wood species were characterized through contact angle measurements and 3D optical roughness analysis. Teak exhibited the highest contact angle (74.9°) and the greatest surface roughness, contributing to mechanical interlocking despite its low surface energy. Oak and iroko showed high wettability and balanced roughness, supporting strong adhesion. Scanning electron microscopy (SEM) revealed stable adhesive penetration across all species and aging conditions, with no signs of delamination or interfacial failure. The study confirms the suitability of polyurethane adhesives for durable, long-lasting bonding in engineered and solid wood flooring systems, even when using extractive-rich or dimensionally sensitive tropical species. The results emphasize the critical role of surface morphology, wood anatomy, and adhesive compatibility in achieving optimal bond performance. These findings contribute to improved material selection and application strategies in flooring technology. Future research should focus on bio-based adhesive alternatives, chemical surface modification techniques, and in-service performance under cyclic loading and humidity variations to support the development of eco-efficient and resilient flooring systems. Full article

Lignin, an abundant and renewable biopolymer, holds significant potential for asphalt modification owing to its unique aromatic structure and reactive functional groups. This review summarizes the main lignin preparation routes and key physicochemical attributes and assesses its applicability for enhancing asphalt performance. The physical incorporation of lignin strengthens the asphalt matrix, improving its viscoelastic properties and resistance to oxidative degradation. These enhancements are mainly attributed to the cross-linking effect of lignin’s polymer chains and the antioxidant capacity of its phenolic hydroxyl groups, which act as free-radical scavengers. At the mixture level, lignin-modified asphalt (LMA) exhibits improved aggregate bonding, leading to enhanced dynamic stability, fatigue resistance, and moisture resilience. Nevertheless, excessive lignin content can have a negative impact on low-temperature ductility and fatigue resistance at intermediate temperatures. This necessitates careful dosage optimization or composite modification with softeners or flexible fibers. Mechanistically, lignin disperses within the asphalt, where its polar groups adsorb onto lighter components to boost high-temperature performance, while its strong interaction with asphaltenes alleviates water-induced damage. Furthermore, life cycle assessment (LCA) studies indicate that lignin integration can substantially reduce or even offset greenhouse gas emissions through bio-based carbon storage. However, the magnitude of the benefit is highly sensitive to lignin production routes, allocation rules, and recycling scenarios. Although the laboratory research results are encouraging, there is a lack of large-scale road tests on LMA. There is also a lack of systematic research on the specific mechanism of how it interacts with asphalt components and changes the asphalt structure at the molecular level. In the future, long-term service-road engineering tests can be designed and implemented to verify the comprehensive performance of LMA under different climates and traffic grades. By using molecular dynamics simulation technology, a complex molecular model containing the four major components of asphalt and lignin can be constructed to study their interaction mechanism at the microscopic level. Full article

The solar-driven conversion of CO₂ into long-chain (C₃₊) products offers a sustainable pathway to mitigate climate change, produce carbon-neutral fuels and value-added chemicals. Over the past few decades, significant advances have been achieved in CO₂ photoreduction; however, most systems still favor C₁ products (CO, CH₄) or C₂ intermediates. However, the synthesis of C₃₊ products poses a formidable challenge due to the complex multi-electron transfer steps required for C–C bond formation. This review provides a concise overview of recent progress in solar-driven photocatalytic and photothermal CO₂ reduction, with a specific focus on the formation of C₃₊ products. The fundamental principles are discussed, including the critical role of C–C coupling mechanisms and the stepwise reaction pathways for C₃₊ products. It highlights how the extended carbon chain length significantly increases the complexity and reduces selectivity, with the suppression of side reactions being a primary research objective. Key catalytic strategies, such as the use of copper-based materials, are examined for their unique ability to facilitate these demanding transformations. Finally, the major challenges are outlined, and a future outlook for this field is provided, with an emphasis on the need for advanced catalyst design and in situ characterization to unlock the potential of solar fuels. Full article

Recent advances in nanotechnology have highlighted the transformative potential of carbon-based nanomaterials, such as carbon nanofibers, carbon nanotubes, and graphene, in cementitious systems. These materials have shown a remarkable ability to enhance the mechanical strength, fracture toughness, and overall functional performance of cementitious composites. Their nanoscale dimensions and exceptional intrinsic properties allow for effective stress bridging, crack arrest, and matrix densification. Despite these promising features, the current understanding remains limited, particularly regarding their application to concrete. Furthermore, literature lacks systematic, parallel evaluations of their respective effectiveness in improving both mechanical performance and long-term durability, as well as their potential to impart true multifunctionality to concrete structures. It is worth noting that significant and statistically significant improvements in fracture behavior were observed at specific nanofiller concentrations, suggesting strong potential for the material system in next-generation innovative infrastructure applications. Experimental results demonstrated that both CNTs and GNPs significantly enhanced the mechanical performance of concrete, with flexural strength increases of approximately 49% and 38%, and compressive strength improvements of 22% and 47%, respectively, at optimum contents of 0.6 wt.% CNTs and 0.8 wt.% GNPs. SEM analyses confirmed improved matrix densification and interfacial bonding at these concentrations, while higher dosages led to agglomeration and reduced performance. This gap highlights the need for targeted experimental studies to elucidate the structure-property relationships governing these advanced materials. Full article

A detailed understanding of interface degradation in humid environments is essential for improving the reliability of adhesive bonding technologies. Water absorption within the adhesive layer significantly affects joint strength, a factor considered to be long-term degradation. However, even if water does not approach the interface from the inside due to absorption, it can reach the interface from the outside through the crack tip and instantaneously affect the fracture behavior of the interface, highlighting the need to investigate short-term degradation mechanisms. In this study, the effect of water at the aluminum/epoxy resin interface on crack propagation was quantitatively evaluated by measuring the mode I energy release rate through double cantilever beam (DCB) tests. By changing the surface condition of the adherend, interfacial and cohesive failures were achieved, and DCB tests were conducted in air and underwater conditions to compare the effect of water on the fracture energy. Results showed that the interfacial fracture energy decreased by more than 50% when the crack propagated in water, but no significant reduction was observed in the cohesive fracture energy. The decrease in interfacial fracture energy in the presence of water indicates the immediate disruption of chemical bonding. Full article

Li/fluorinated carbon (CF_x) batteries have attracted considerable attention in the field of energy storage owing to their excellent energy density and long storage life. However, the development of CF_x cathodes is restricted by their poor conductivity at high degrees of fluorination. Herein, ZIF-8-based fluorinated carbon with a well-developed network structure was fabricated via gas-phase fluorination and acid treatment. Moreover, treatment at a low fluorination temperature of 180 °C for 4 h and acid washing endowed the obtained fluorinated carbon (HFG@ZIF-8) with a high F/C (1.62), favorable specific surface area (207 m² g⁻¹), unique porous channels, and highly electrochemically active C–F bonds, resulting in a maximum specific capacity (1143.4 mAh g⁻¹) and energy density (2614.8 Wh kg⁻¹) at 0.02 C. The superior Li⁺ transport efficiency, with diffusion coefficients ranging from 1.47 × 10⁻¹¹ to 1.93 × 10⁻¹⁷ cm² s⁻¹, enables HFG@ZIF-8 to deliver 453.4 mAh g⁻¹ at 5 C with no voltage delay. Therefore, this work provides an innovative strategy for the preparation of high-performance CF_x cathodes. Full article

This study identifies the technological signature of ancient and alternative “Chu” and “Kriab” gold glass mosaic mirrors from Thailand. Although these mirrors play an important role in Thai decorative heritage, their production routes and interfacial chemistry at the lead-to-glass interface have remained unclear. A survey of 154 sites across Thailand shows mosaic glass was widely distributed and likely produced during the Ayutthaya period (~300 years ago). Portable X-Ray Fluorescence (pXRF), Wavelength-Dispersive XRF (WD-XRF), scanning electron microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS) were used to examine the material properties of observed Chu mirrors. Most samples can be classified as a mixed lead–alkaline glass type, with a PbO content ranging from 4.28 to 48.17 wt%. Their yellow tone is controlled by iron and manganese redox states. Chemical and physical analyses distinguish between Chu from the northern part of Thailand and Kriab from the central part of Thailand, which share a silica source but rely on different fluxes, pointing to different glass workshops. Crucially, XPS depth profiling reveals a well-defined interfacial reaction zone extending to approximately 6 nm in the ancient mirrors, predominantly characterized by disordered, chain-like Pb–O–Pb linkages. These polymeric structures enable a “chemical bridging” mechanism that effectively accommodates interfacial strain arising from thermal expansion mismatch, thereby ensuring exceptional long-term adhesion. Furthermore, the depth-dependent distribution of hydrated lead species and the emergence of photoelectron energy-loss features beyond ~6 nm distinguish the superior metallic integrity of the ancient coatings from the alternative reproductions. This distinct stratification confirms that ancient artisans achieved a sophisticated balance between a chemically bonded interface and a coherent metallic bulk. These findings offer significant insights into the ingenuity of ancient Thai artisans, providing a scientific foundation for the conservation, restoration, and replication of these culturally significant artifacts. Full article

Background: Durable bonding to zirconia remains difficult because its chemically inert surface resists acid etching. Additive manufacturing (AM) enables controlled surface morphology, which may enhance micromechanical retention without additional treatments. Methods: Zirconia specimens with three AM-derived surface designs—(1) concave–convex hemispherical patterns, (2) concave hemispherical patterns, and (3) as-printed surfaces—were fabricated using a slurry-based 3D printing system and sintered at 1500 °C. Zirconia specimens fabricated by subtractive manufacturing using CAD/CAM systems, polished with 15 µm diamond lapping film and with or without subsequent alumina sandblasting, served as controls. Surface morphology was analyzed by FE-SEM, and shear bond strength (SBS) was tested after cementation with a resin-based luting agent. Results: SEM revealed regular layered textures and designed hemispherical structures (~300 µm) in AM specimens, along with step-like irregularities (~40 µm) at layer boundaries. The concave–convex AM group showed significantly higher SBS than both sandblasted and polished subtractive-manufactured zirconia (p < 0.05). Vertically printed specimens demonstrated greater bonding strength than those printed parallel to the bonding surface, indicating that build orientation affects resin infiltration and interlocking. Conclusion: AM-derived zirconia surfaces can provide superior and reproducible micromechanical retention compared with conventional treatments. Further optimization of printing parameters and evaluation of long-term durability are needed for clinical application. Full article

The interaction between small organic molecules and coal macerals plays a critical role in regulating fluid retention and transport in coal-related energy and environmental systems. However, the microscopic mechanisms governing adsorption selectivity and interfacial dynamics on different maceral surfaces remain insufficiently understood. In this study, molecular dynamics simulations were employed to investigate the adsorption and desorption behaviors of toluene (TOL) and tetrahydrofuran-2-ol (FUR) on inertinite (INE) and vitrinite (VIT) surfaces at the molecular level. Time-dependent variations in adsorption number, residence time, molecular mobility, interaction energies, and hydrogen-bond characteristics were systematically analyzed. The results reveal strong maceral- and molecule-dependent adsorption preferences. TOL exhibits the most stable adsorption on the INE surface, characterized by rapid surface accumulation, minimal desorption, and a long residence time of 0.43547 ns, which is mainly driven by strong van der Waals interactions and aromatic stacking effects. In contrast, TOL adsorption on VIT is highly dynamic, with frequent desorption events and a markedly reduced residence time of 0.1077 ns. FUR shows relatively weaker and more reversible adsorption on INE, accompanied by enhanced molecular mobility and a shorter residence time of 0.31354 ns. Notably, FUR demonstrates stronger surface retention on VIT, with an extended residence time of 0.34439 ns, which can be attributed to increased electrostatic contributions and intermittent hydrogen bonding. Hydrogen-bond analysis indicates that FUR forms longer-lived hydrogen bonds with VIT (22.05 ps) than with INE (17.86 ps), providing additional stabilization at the interface. These findings elucidate the distinct adsorption mechanisms of aromatic and polar molecules on heterogeneous coal macerals and offer molecular-scale insights into organic matter–coal interfacial processes relevant to energy extraction and subsurface transport. Full article

Polyurethane-based implantable devices (PUIDs) delivered via catheter are increasingly used in structural heart interventions; however, limited in vivo data exist regarding their long-term biostability and biological safety. This study evaluated a balloon-shaped implant made of Pellethane^®, a polyether-based polyurethane, designed as a three-dimensional intracardiac spacer and deployed via percutaneous femoral vein access. The device was chronically positioned adjacent to the tricuspid valve annulus in seven pigs for 24 weeks. Explanted devices and surrounding tissues were evaluated through material characterization (SEM, GPC, FT-IR, and ¹H-NMR) and histological analysis. SEM and FT-IR confirmed preserved surface morphology and chemical bonds, GPC showed stable molecular weight, and ¹H-NMR revealed intact urethane and ether linkages. Materials characterization revealed no evidence of hydrolytic or oxidative degradation, indicating structural stability of the devices. Histological analysis showed stable device positioning with minimal thrombosis or inflammatory response. Biocompatibility was confirmed via ISO 10993-1:2018 Standard (International Organization for Standardization (ISO): Geneva, Switzerland, 2018), and extractable substances were evaluated under exhaustive extraction conditions specified by ISO 10993-18:2020 (International Organization for Standardization (ISO): Geneva, Switzerland, 2020), with no toxicologically significant findings. These findings support the long-term biostability and biological safety of the PUIDs in dynamic cardiac environments, informing future design criteria for catheter-delivered cardiovascular devices. Full article

This study develops an integrated panel econometric framework for modeling investment–output dynamics in circular economy sectors, explicitly addressing dynamic propagation, long-run equilibrium relationships, endogeneity, and nonlinear responses. Building on the Samuelson–Hicks Multiplier–Accelerator model, the analysis combines two complementary approaches. A dynamic panel specification estimated by the Generalized Method of Moments (Arellano–Bond) is employed to capture output inertia, intertemporal transmission of investment shocks, and stability properties of the dynamic system. In parallel, a nonlinear panel ARDL model estimated using the Pooled Mean Group (PMG/NARDL) methodology is used to identify cointegration and to distinguish between the long-run and short-run effects of positive and negative investment variations. The empirical analysis relies on a balanced panel of 28 European economies (EU-27 and the United Kingdom) over the period 2005–2023, using sectoral circular economy data, with gross value added as the output variable and gross private investment as the main regressor. The results indicate the existence of a stable cointegrated relationship between investment and output, characterized by significant asymmetries, with expansionary investment shocks exerting larger and more persistent effects than contractionary shocks. Dynamic GMM estimates further confirm delayed investment effects and a stable autoregressive structure. Overall, the paper contributes to mathematical economic modeling by providing a unified dynamic–equilibrium panel framework and by extending the empirical relevance of Multiplier–Accelerator dynamics to circular economy systems. Full article

Carbon fibre-reinforced polymer (CFRP) bonded steel structures are increasingly adopted in offshore floating structures, yet their interfacial performance is highly susceptible to corrosion in marine environments. Corrosion-induced degradation of the CFRP–steel interface can significantly affect load transfer mechanisms and long-term structural reliability. This paper reports an experimental study on corrosion-induced degradation mechanisms and bond–slip behaviour of CFRP–steel double-strap joints. Controlled corrosion damage was generated using an accelerated electrochemical technique calibrated to ISO 9223 corrosivity categories. Tension tests were performed to examine the effects of corrosion degree, CFRP bond length, and the inclusion of glass fibre sheets (GFS) in the adhesive layer on failure modes, ultimate load capacity, and effective bond length. Digital image correlation (DIC) was employed to obtain strain distributions along the CFRP plates and to establish a bond–slip model for corroded interfaces. The results indicate that corrosion promotes a transition from CFRP delamination to steel–adhesive interface debonding, reduces interfacial shear strength to 17.52 MPa and fracture energy to 5.49 N/mm, and increases the effective bond length to 130 mm. Incorporating GFS mitigates corrosion-induced bond degradation and enhances joint performance. The proposed bond–slip model provides a basis for more reliable durability assessment and design of bonded joints in corrosive environments. Full article

This paper compares actively managed bond vs. equity mutual fund performance using modified False Discovery Rate ($q^{\ast }$) and percent simulated t(α) < Actual t(α). Bond funds are more likely to outperform than equity funds: $q^{\ast }$(%Sim < Act) shows 33.9% (30.0%) of bond funds generate positive t(α) on net excess returns vs. 1.8% (0.0%) for equity funds. $q^{\ast }$ shows percent simulated t(α) < Actual t(α)results are sensitive to Type II error. Bond fund outperformance is associated with long-term holdings, and corporate bond fund excess returns tend to decline with fund size. Full article

Conventional anticorrosive coatings suffer from limitations of low solid content and rigorous surface pretreatment, posing environmental and cost challenges in field applications. In this study, a novel high-solid-content (>95%) epoxy-polysiloxane (Ep-PSA) ceramic metal coating was prepared that enables low-surface-treatment application. The originality lies in the synergistic combination of nano-sized ceramic powders, high-strength metallic powders, polysiloxane resin (PSA), and solvent-free epoxy resin (Ep), which polymerize through an organic–inorganic interpenetrating network to form a dense shielding layer. The as-prepared Ep-PSA coating system chemically bonds with indigenous metal substrate via Zn₃(PO₄)₂ and resin functionalities during curing, forming a conversion layer that reduces surface preparation requirements. Differentiating from existing high-solid coatings, this approach achieves superior long-term barrier properties, evidenced by |Z|_0.01Hz value of 9.64 × 10⁸ Ω·cm², after 6000 h salt spray exposure—four orders of magnitude higher than commercial 60% epoxy zinc-rich coatings (2.26 × 10⁴ Ω·cm², 3000 h salt spray exposure). The coating exhibits excellent adhesion (14.28 MPa) to standard sandblasted steel plates. This environmentally friendly, durable, and easily applicable composite coating demonstrates significant field application value for large-scale energy infrastructure. Full article

The fate of a selection of linear and cyclic silicone oil formulations in heavy-duty fluid dampers is studied from molecular dynamics simulations. Mimicking cyclic agitation to all-atom simulation models, we elaborate oscillatory compression/decompression runs that feature degradation reactions within only hundreds of loading cycles. This enables the assessment of chain scission, reassembly and cyclization mechanisms from ns-scale molecular dynamics simulations. Using analogous testing scenarios, we compare the degradation reactions of linear and cyclic silicone chains and demonstrate the importance of silicone ring formation. In turn, cyclic silicone moieties show relative persistence in our compression/decompression runs. We conclude that long-term degradation finally leads to a manifold of cyclic silicone molecules, featuring rings of up to tens of monomeric units. The underlying molecules are not inert to Si-O bond cleavage and reformation, but feature reactivity in terms of the fusion of small to large rings and vice versa. Full article