Search Results (17,443)

The temporal effects associated with surface plasmon polaritons (SPP) in a slab of conductive quantum material (metal, graphene, or semiconductor) are described as a quantum plasma. Exchange potentials associated with quantum degeneracy are included. We derive a new dispersion relation of SPP modes in a quantum plasma slab with finite size, which reduces to the previously known cases of a single plasma boundary and of a two-dimensional slab in the appropriate limits. A new SPP instability regime due to exchange quantum effects is demonstrated. The phenomenology of time refraction and time reflection is extended to SPP, and the frequency shifts and amplitude transformations due to a time boundary are derived. Finite time boundary effects and arbitrary temporal changes of the medium are also considered. Full article

Single point incremental forming (SPIF) represents a flexible manufacturing process capable of producing complex sheet metal parts without the need for dedicated forming dies. However, achieving high dimensional accuracy remains a major challenge due to phenomena such as elastic springback and localized deformation. In this context, the present study investigates the influence of tool-axis orientation on the dimensional accuracy of parts manufactured through robot-based single point incremental sheet forming (RB-SPIF). The experimental analysis considered two toolpath strategies (contour and spiral), two vertical step sizes (0.5 mm and 1 mm), and two tool-axis configurations (fixed tool-axis and wall-normal tool-axis orientation), resulting in eight experimental cases. The dimensional accuracy of the manufactured parts was evaluated using optical 3D scanning and cross-sectional profile analysis. The results show that the vertical step size has a significant influence on the resulting geometry, with smaller step sizes generating profiles closer to the nominal geometry. The toolpath strategy also affects the geometry, with spiral trajectories generally producing slightly improved profiles compared to contour strategies; however, this effect was not found to be statistically significant under the investigated conditions. Furthermore, the use of a wall-normal tool-axis configuration improves the agreement between the measured and nominal profiles by enhancing the contact conditions between the tool and the metal sheet surface. These findings indicate that adaptive tool-axis orientation represents a promising strategy for improving the dimensional accuracy of parts produced by robot-based incremental sheet forming systems. Full article

Agmatinase (SpeB) catalyzes the hydrolysis of agmatine to produce putrescine, a key step in bacterial polyamine biosynthesis. Here, we report the crystal structure of SpeB from Klebsiella pneumoniae (kpSpeB) and characterize its oligomeric and active-site architecture. SEC–MALS analysis demonstrates that kpSpeB forms a canonical hexamer in solution. Structural comparison reveals high similarity to Escherichia coli SpeB and other members of the arginase superfamily, including proclavaminic acid amidino hydrolase (PAH) and guanidine hydrolase (GdmH). Despite strong conservation of residues coordinating the binuclear Mn²⁺ center, subtle differences in metal positioning and cavity geometry were observed. Surface analysis indicates variations in active-site cavity volume among homologues, with partial occlusion in GdmH due to a bulky tryptophan residue. These findings suggest that minor adjustments in metal coordination and cavity architecture may fine-tune substrate selectivity while preserving the conserved catalytic framework of the arginase superfamily. Full article

The disposal of waste tyres presents a significant environmental challenge, necessitating sustainable, high-value recycling solutions. This study explores the incorporation of waste tyre metal fibre (WTMF) into hot mix asphalt (HMA) to enhance mechanical performance while reducing its electrical resistivity as well as the landfill burden. The primary goal of this research is to apply response surface methodology (RSM) to experimental data for modelling and optimizing WTMF-modified HMA mixes by capturing the coupled effects of fibre reinforcement and binder content on mechanical and functional performance. The microstructural characteristics of WTMF were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). WTMF-modified mixes containing five WTMF dosages (from 0% to 1.50%) and bitumen contents from 4% to 6% were prepared and tested in the laboratory. The resulting dataset was used for RSM modelling, with WTMF and bitumen contents as input factors and Marshall stability, flow, porosity, and electrical resistivity as response variables. The central composite design (CCD) technique was employed to quantify interaction effects and to identify statistically significant trends. The developed models were validated using statistical indicators, and optimal mixture compositions were determined and experimentally verified. Microstructural analysis revealed WTMF’s irregular, rough surface with microcracks and pits, aiding crack-bridging and stress transfer. RSM results indicated 0.71% WTMF and 5.1% bitumen as an optimal combination of factors. Furthermore, high R² (>0.80) and adequate precision (>4.0) values from analysis of variance (ANOVA) underscore the significance of the proposed models, revealing a robust correlation between experimental and predicted data. This study demonstrated WTMF’s potential to be used in conventional HMA mixes, offering a sustainable recycling pathway for waste tyres. Full article

Corn processing waste represents an abundant, renewable, and low-cost lignocellulosic resource with considerable potential for environmental remediation applications. Large quantities of residues generated during corn processing, including cobs, husks, bran, and other by-products, are produced annually and can be utilized directly as native biomass or converted through thermochemical processes into hydrochars and biochars. This systematic review provides a comparative analysis of native corn processing biomass, hydrochars produced via hydrothermal carbonization, and biochars obtained through pyrolysis, with a focus on their potential as adsorbents for the removal of organic and inorganic pollutants from soil and water systems. Particular attention is given to the influence of thermochemical conversion processes on the physicochemical properties of the materials, including surface chemistry, porosity, functional groups, and structural characteristics, which govern adsorption mechanisms such as ion exchange, electrostatic interactions, surface complexation, hydrogen bonding, and π–π interactions. Furthermore, the advantages and limitations of each material type are discussed, together with key environmental and techno-economic considerations related to their production and practical application, including indicative production costs (USD per kg of adsorbent) and cost–performance relationships in terms of adsorption capacity. By linking biomass conversion processes, material properties, and adsorption performance, this review aims to provide a comprehensive overview of corn processing waste valorization and to support the development of sustainable adsorbent materials for soil and water remediation. A total of 36 studies were included in the qualitative synthesis following PRISMA guidelines. Full article

This work investigates the behavior of carbon dioxide (CO₂) near the surface of different single-atom alloys to evaluate their potential as catalysts for decarbonization processes. Specifically, 26 transition metals from the first three transition series, alloyed with three low Miller index copper supports, were considered. Adsorption energies and distances of linear CO₂, trigonal CO₂, and CO* + O* on the surfaces were calculated using the semiempirical computational method MOPAC-PM7. Additionally, activation energies were determined from previously published research. The proposed methodology is less computationally demanding than DFT studies, and results show good agreement with both experimental and simulated data. This approach provides a computationally efficient methodology for screening promising materials that convert CO₂ into valuable products, such as methane and methanol. Full article

This study uses a bismuth ferrite (BiFeO₃) and MXene (Ti₃C₂Tx) to design a surface plasmon resonance (SPR) biosensor for the sensitivity enhancement at a 633 nm wavelength. Here, MXene serves as a biorecognition element (BRE) layer to ensure stable and reliable biomolecule adsorption. The MXene is a family of two-dimensional (2D) materials with metallic-like conductivity, a large surface area that can attach biomolecules, and improve biocompatibility. The addition of a conductive 2D MXene layer and a high-index BiFeO₃ dielectric layer greatly improves light–matter interaction and evanescent field penetration at the sensing interface. Strong plasmonic coupling is indicated by the reflectance analysis, which shows a distinct and consistent shift in the resonance angle as analyte RI increases. This study examined the sensitivity at optimized Ag and BiFeO₃ layer thickness. At an Ag of 39 nm and BiFeO₃ of 3 nm thickness, the maximal sensitivity of 340.68°/RIU with a remarkable figure of merit (FoM) of 47.38/RIU is obtained. The overall detection accuracy (DA) and FoM are significantly improved by the large sensitivity enhancement, despite a slight increase in full width at half maximum (FWHM). Furthermore, the penetration depth (PD) of 198.50 nm (at RI:1.330) and 199.52 nm (at RI:1.335) is attained with the proposed structure. Due to its high sensitivity, reusability, and reproducibility, the SPR biosensor has the potential to be used in biochemical, environmental, and medical detection. Full article

This study focuses on the evaluation of eco-friendly corrosion inhibitors derived from extracts of Rhus typhina L. leaves, collected in August during the summer season, on OLC45 metal surfaces in a 0.5 M H₂SO₄ corrosive environment. The extracts were obtained using the microwave extraction technique and characterized by HPLC. The protective properties of OLC45 coated with LESRT (leaf extract collected in summer from Rhus typhina L.) were examined by potentiostatic and potentiodynamic polarization procedures and electrochemical impedance spectroscopy (EIS) in 0.5 M H₂SO₄. The application of the Langmuir isotherm revealed high values of the adsorption constant and standard free energies (ΔG°_ads), suggesting a possible mixed adsorption process with an increased tendency toward chemisorption. The influence of temperature on the electrochemical behavior of OLC45 samples in H₂SO₄, both in the absence and presence of two extracts derived from Rhus typhina leaves at a concentration of 1000 ppm, was investigated over the temperature range of 293–333 K. A comparison of the two inhibitors’ effectiveness revealed high inhibitory efficiency, up to 91% at 1000 ppm LESRT₁ (methanol/double-distilled water (50%:50%, v/v)) and 92% for LESRT₂ (ethanol/double-distilled water (50%:50%, v/v)) at 1000 ppm LESRT₂. Full article

Monitoring air quality is crucial for understanding and improving public health. There is interest in developing ultra-sensitive, low-power, cost-effective sensors. This work demonstrates that structural modulation of Sn nanoparticles through controlled deposition and oxidation enables a transition from metallic to semiconducting percolative networks, significantly enhancing NO₂ sensing performance at room temperature. The proposed percolation-driven sensing mechanism provides a new framework for understanding charge transport and gas interaction in nanostructured metal oxide systems. The nanoparticles are deposited near the percolation threshold for electrical conduction and, upon exposure to air, consist of a tin core and an amorphous Sn₃O₄ surface. Post-deposition heating in air at 320 °C for two hours forms SnO and Sn₃O₄ on top of the gold electrodes and polycrystalline SnO in the tetragonal litharge phase, known as Romarchite, on the glass between the electrodes. Both as-deposited and heat-treated sensors were capable of detecting NO₂ at room temperature, with a limit of detection in the parts-per-billion range. A percolation model is used to explain their operating currents, in which NO₂ reacts at nanoparticle gaps and intra-grain boundaries to form charge-depletion regions that primarily determine their resistance. Heat treatment has also been found to cause disproportionation of SnO, resulting in tin-rich precipitates and increasing the operating current to the milliampere range. These precipitates, although oxidized on their surfaces when exposed to air, may serve as bridges that reduce the total resistance of the percolating paths. Full article

High-entropy alloys (HEAs) are typically produced using high-temperature metallurgical routes; however, alternative synthesis approaches based on wet-chemical processing remain relatively unexplored. In this study, a compositionally complex two-phase AgCuCoNiFe high-entropy alloy was synthesized using a precipitation–reduction strategy involving co-precipitation of mixed metal carbonates followed by thermal reduction in a reducing atmosphere. The objective of the work was to evaluate the feasibility of this hydrometallurgical route for preparing compositionally complex alloys and to investigate the structural evolution of the material as a function of reduction time. Quantitative MP-AES analysis confirmed efficient co-precipitation of all five elements, enabling the preparation of a precursor with near-equimolar metal composition. Structural characterization using SEM, EDS, and XRD revealed the presence of surface compositional heterogeneity in the as-reduced state, characterized by Ag-enriched domains. After controlled surface abrasion, the internal material exhibited significantly more uniform elemental distribution, although the obtained composition was not equimolar. X-ray diffraction patterns showed a transition from multiple sharp reflections at the surface to broadened peaks in the bulk, consistent with enhanced alloying within the bulk compared to the surface, while still revealing a two-phase character. Microhardness measurements indicated moderate hardness with mean values in the range of 187–221 HV with no significant dependence on reduction time, while wettability analysis revealed moderately hydrophilic behavior with contact angles in the range of approximately 75–83°. The results suggest that precipitation–reduction can be a viable alternative route for the synthesis of multicomponent HEAs, enabling the formation of chemically mixed alloy structures without the use of conventional melting-based processing. However, the obtained alloy exhibits incomplete chemical homogeneity, indicating that further optimization of the synthesis conditions is required to achieve a fully uniform composition. Full article

Environmentally friendly radiation shielding materials for medical institutions require lightweight characteristics and high flexibility as key performance indicators. One promising approach is the incorporation of lead-free materials that combine high-density shielding fillers with polymer matrices. High filler loading is necessary to maintain shielding performance while preserving the inherent flexibility of the polymer. However, during the mixing of shielding materials with polymers, microvoids may form. Therefore, strategies are required to enhance structural densification of the composite by reducing microvoid formation. This study aims to investigate the effects of interfacial design using an anchor–chain dispersant (APTES: 3-aminopropyltriethoxysilane) on micropore formation, effective density, and X-ray shielding performance in highly filled tungsten/thermoplastic polyurethane (TPU) composites. TPU-based composite shielding sheets containing 75–90 wt% tungsten were fabricated. The dispersant (APTES) can adsorb onto the surface of metal particles and form a stabilization layer. In this study, the observed reduction in particle agglomeration and porosity upon addition of the dispersant suggests that interfacial stabilization was induced. As a result, in the 85 wt% composite sheet, the porosity decreased from 5.89% without the dispersant to 0.56% with the dispersant, leading to an improvement in the densification level and effective density of the sheet. Under the same thickness condition (0.25 mm), the dispersant-containing sheet exhibited a shielding efficiency that was 3–4% p higher than that of the sheet without dispersant in the 100–120 kVp range. Meanwhile, as the tungsten content increased, the overall density and shielding efficiency of the sheets also increased. At 90 wt% tungsten loading, the composite demonstrated shielding performance approaching that of conventional lead shielding even at a reduced thickness. These results indicate that interfacial design using an anchor–chain dispersant is an effective processing strategy for improving density uniformity and radiation shielding performance in highly filled tungsten/TPU composite shielding materials by controlling microvoid formation. Full article

Diamond-like carbon (DLC) coatings are widely used as protective and self-lubricating surfaces in metal–metal contacts. Their frictional behavior is governed by the formation and evolution of carbon-rich transfer layers (TLs), which can be tailored through functionalization with carbon nanomaterials. Recent studies have shown that graphene sheets (GSs) and nanodiamonds (NDs) act synergistically to achieve ultra-low friction in microrough (~0.2 μm) metal–DLC contacts under dry N₂ at a 1 N load. Here, we probe how this lubrication mechanism evolves with increasing load from 1 to 10 N—corresponding to local contact pressures up to ~11–16 GPa—respectively, in dry N₂ and humid air conditions. Ball-on-disk experiments are performed on an industrial hydrogenated DLC coating sliding against stainless-steel. In dry N₂, GS–ND functionalization yields a low and stable coefficient of friction across the entire load range, reaching a minimum of about 0.05. In humid air, higher friction levels are observed across all loads (CoF ~0.10–0.15), accompanied by oxidation-driven modifications of both wear debris and the counterface contact region, with oxygen content increasing by more than a factor of three compared to dry N₂. Detailed microscopy and spectroscopy analyses indicate that enhanced lubricity in dry N₂ arises from TLs incorporating GSs, NDs, and nanoscroll-like structures, whereas humid air promotes interfacial amorphization and oxidation, leading to load-insensitive friction and boundary lubrication effects through physisorbed water molecules. Full article

Water is one of the most valuable resources on the planet; without it, life as we know it could not exist. Consequently, its increasing scarcity and pollution, which are mainly due to industrialization and changing consumption patterns, intensify the stress on water resources. At the same time, industrial activities contribute to water contamination with pollutants such as heavy metals, further reducing water availability. Due to their risks to human health and ecosystems, effective removal strategies are essential. Among the emerging approaches, polymer-based additive manufacturing (AM), commonly known as 3D printing (3DP), has gained attention for water treatment due to its versatility, precise control over structure and porosity, and ease of processing, while remaining at a low cost. Additionally, the polymers used have interesting adsorbent properties and allow for the incorporation of functional additives, further enhancing their performance. This review analyses the recent advances in 3D-printed polymeric materials for the removal of heavy metals and dyes, focusing on material composition, manufacturing technologies, geometry, removal mechanisms, performance, and regeneration. It was concluded that metal ions and cationic dyes are primarily removed through adsorption, due to interactions with negatively charged surfaces that are often enhanced by high-affinity additives. Anionic dyes are generally less effectively removed by adsorption and often rely on degradation mechanisms. However, adsorption of anionic dyes can occur, for instance when the adsorbent surface is modified to introduce positively charged functional groups. The ability of 3DP to create hierarchical porous structures combining micro-, meso-, and macropores improves fluid flow and contact area, thereby enhancing the removal efficiency. Full article

In the Philippines’ agricultural setup, pre-harvest cacao (Theobroma cacao) fruits are wrapped with low-density polyethylene (LDPE) for moisture retention and damage protection. Responding to the growing concern for its waste volume and scarcity of treatment, this research explores the co-hydrothermal carbonization (co-HTC) of cacao shells (CS) and LDPE as a method to convert agricultural waste with plastic into hydrochar for potential energy applications. Thus, observations on the thermal, physicochemical, and morphological changes from feedstocks to hydrochar are carried out. Optimal conditions of 200 °C for 60 min resulted in hydrochar with 21.11 MJ/kg and appreciable thermal properties. SEM micrographs show that hydrochar had increased surface area, a good fuel characteristic, and surface flaking on oversized LDPE film, suggesting relative LDPE degradation. EDX analysis reveals C, K, Ca, and Zn metals that affect chemical pathways. FTIR analysis further supports chemical synergy by preservation of functional groups innate from both parent materials. Kinetic and thermal evolutions are also investigated to reveal the influence of pretreatment on the stability of cacao shell-dominated hydrochar and the effectivity of biomass integration to facilitate relatively easier cracking of LDPE. The findings support co-HTC as a viable technology to enhance the circular economy by valorizing LDPE and cacao shells while promoting energy recovery and solid fuel production. Full article

For cable compound manufacturers, accurate formulation fine-tuning is essential to ensure safety, long-term durability, and compliance with international standards for dielectric strength, volume resistivity, and environmental and thermal ageing. This work presents an experimental study demonstrating how minor additives can critically affect the performance of complex flame-retardant elastomeric formulations. The investigation focuses on the role of small amounts of zinc oxide (ZnO) in commercial cable compounds based on a crosslinked elastomeric matrix composed of ethylene–propylene monomer (EPM), ethylene–propylene–diene monomer (EPDM), and thermoplastic polyolefin elastomer (POE). The formulations contain aluminium trihydroxide (ATH) as the major filler, together with several minor additives. Among these, a phenolic antioxidant (AN01) acting as a metal deactivator is also present. The addition of ZnO in low amounts (2–5 phr) allowed the compounds to maintain a volume resistivity ≥ 10¹² Ω·cm in water at 100 °C. To elucidate the role of ZnO, a systematic set of formulations was prepared by varying the type and content of selected additives. The compounds were prepared by melt mixing in an internal mixer (Banbury type), followed by peroxide crosslinking via compression molding. Electrical characterization results indicate that ZnO interacts with the phenolic additive through surface adsorption, forming a coated particle with significantly reduced electrical conductivity. Optimal electrical performance was achieved when the ZnO-to-additive ratio corresponded to the minimum amount required for complete surface complexation. Full article