Search Results (474)

High-performance thermoplastics are gaining increasing attention for space applications. However, the extreme lunar environment requires multifunctional materials that combine electrical conductivity for electrostatic charge dissipation with low thermal conductivity for thermal insulation. One promising strategy to achieve this balance is through conductive polymer nanocomposites with controlled morphology. In this study, the localization, migration, and network formation of carbon nanotubes (CNTs) in two-phase blends of polyetheretherketone/polyetherimide (PEEK/PEI) were systematically investigated to establish the relationships between processing, morphology, and the resulting electrical and thermal properties. Despite the strong thermodynamic preference of CNTs for the PEI phase, both PEEK/CNT and PEEK/PEI/CNT nanocomposites exhibit similar electrical percolation thresholds (0.25–0.5 wt.%), attributed to spatial confinement arising from PEEK crystallinity in PEEK/CNT and from phase-selective localization in the blend system, which limits the effective volume available for CNT dispersion. Morphological characterization confirmed co-continuous blend structures and complete CNT migration into the PEI phase in the PEEK/PEI/CNT system, while rheological studies revealed percolated networks forming below the electrical percolation threshold. Processing conditions strongly impacted conductivity: short mixing times preserved interconnected CNT agglomerates and enhanced conductivity, whereas prolonged mixing promoted dispersion but destroyed conductive pathways. Furthermore, thermal annealing induced agglomeration and weakened networks in PEEK/CNT systems but had a negligible effect on PEEK/PEI/CNT composites due to improved CNT–PEI compatibility. Finally, thermal conductivity remained low across all systems, maintaining the material’s insulating performance for the harsh thermal environment of the Moon. Full article

Climate change and irrigation expansion are expected to substantially alter hydrological processes and agricultural productivity in the semi-arid watersheds of northern Ethiopia; however, their combined impacts remain insufficiently quantified. This study evaluated the effects of future climate change and irrigation management on watershed hydrology and crop yield in the Geba watershed using the Soil and Water Assessment Tool Plus (SWAT+). The model was calibrated and validated using observed daily streamflow data for the 2006–2020 period and driven by an ensemble of five bias-corrected CORDEX Africa regional climate models (RCMs) under the RCP 4.5 and RCP 8.5 scenarios for the mid-century (2046–2060) and late-century (2086–2100) periods. Two agricultural management systems, namely rainfed and irrigation-rainfed integrated management, were evaluated. Model performance was satisfactory for streamflow simulation, with NSE values of 0.56 and 0.50 and KGE values of 0.64 and 0.54 during calibration and validation, respectively. The results indicate a progressive shift toward an evapotranspiration-dominated hydrological regime under future climate conditions. Under rainfed management, surface runoff and evapotranspiration increased by up to 60% and 30%, respectively, whereas groundwater recharge and lateral flow declined substantially. Irrigation scenarios intensified hydrological stress by reducing percolation, lateral flow, and water yield by up to 80%, 60%, and 55%, respectively. Statistical analyses revealed that climate forcing, management type, and their interactions significantly affected hydrological responses (p < 0.001), with emission pathways representing the dominant driver of variability. Crop responses varied considerably among management systems and crop types. Rainfed maize and wheat exhibited moderate yield increases under mid-century conditions, whereas teff consistently showed negative responses under most climate scenarios, indicating high vulnerability to warming and moisture stress. Under irrigation management, most crops experienced substantial yield reductions during late-century periods, although tomatoes showed localized gains under high-emission scenarios. Overall, the findings demonstrate that irrigation expansion alone may not provide sustainable adaptation under increasing climate stress because it intensifies evapotranspiration and reduces groundwater recharge. Integrated watershed management, climate-resilient crop selection, efficient irrigation practices, and soil-moisture conservation strategies are therefore essential for sustaining agricultural productivity and water availability in semi-arid Ethiopian watersheds. Full article

Sediment internal nutrient loading is a major cause of surface water eutrophication. Adding organic amendments to dredged sediments can improve reuse potential but risks enhancing nutrient leaching. This column study investigated the effect of adding compost (25% v/v), freshwater algae suspension (2.5% v/v), or their combination (22.5% compost + 2.5% algae) to reservoir bottom sediments on the leaching of orthophosphate (PO₄³⁻) and nitrate nitrogen (NO₃-N) under three simulated weekly rainfall events. Unamended sediment served as the control. Compost-amended sediment showed the highest PO₄³⁻ concentrations in the leachates, but these levels stabilized over time, whereas NO₃-N concentrations decreased rapidly. Algae alone reduced both PO₄³⁻ and NO₃-N leaching compared to the control. The combination of compost and algae enhanced the retention of several elements, though it did not fully mitigate phosphorus leaching. Furthermore, this combination effectively decreased overall leachate volume; it was a direct result of the progressive hydration of the organic material, which increased the mixture’s water-holding capacity and thereby reduced percolation. Chemically, compost promoted nitrogen transformation processes (e.g., immobilization or denitrification), while algae likely facilitated nutrient uptake. We conclude that organic amendments play a dual role: compost increases phosphorus availability but stabilizes its release, whereas algae reduce the leaching of both nutrients. The choice of amendment should therefore align with specific water quality targets. Longer-term and field-scale studies are needed to confirm these trends. Full article

Nanobubble-saturated water (NBSW) has gained prominence in agricultural research due to its ability to affect root-zone oxygenation and soil–plant interactions. This review aimed to analyze the available research on the impacts of NBSW on soil moisture storage, percolation, electrical conductivity (EC), microbial activity, and soil structural dynamics across different gas types and soil textures. Therefore, a systematic literature search was carried out, and the retrieved publications were synthesized with keyword co-occurrence and bibliometric analysis. This review fills the gap in the literature by integrating findings on root-zone oxygenation, nutrient dynamics, and soil structural responses into a single framework. Research showed that NBSW may influence water partitioning by increasing evaporation and lowering percolation, leading to different vertical moisture gradients. However, the effects could be impacted by the soil texture, as finer textures retained more moisture, while coarser soils increased oxygen penetration and microbial stimulation. Furthermore, increased oxygen availability under NBSW further changed microbial community activity, which could impact soil CO₂ emissions and nitrogen and phosphorus cycling. While repeated NBSW application may gradually increase soil compaction, particularly in finer-textured soils, overall, NBSW demonstrated versatile watering modifications that might influence soil physical, chemical, and biological processes. However, further research is needed to determine the appropriate gas types and application strategies for different soils under real field-scale agricultural conditions. Full article

This review comparatively analyzed MWCNT-reinforced thermoplastic polyester nanocomposites based on petroleum-derived (PET, PBT) and bio-based (PLA, PBS) matrices, focusing on processing methods, mechanical performance, thermal stability, electrical behavior, and recyclability. Optimal MWCNT loadings typically ranged from 0.3 to 3 wt.%; higher loadings induced nanotube agglomeration and deteriorated properties due to poor dispersion and stress concentration. Melt mixing, solution blending, direct compounding, and in situ polymerization were evaluated, and their influence on dispersion quality, interfacial bonding, and scalable manufacturability was discussed. PET exhibited the largest improvements in mechanical and thermal performance (tensile strength and modulus increases >300% in optimized systems); acid or compatibilizer functionalization of MWCNT improved PET thermal stability by approximately 20–50 °C and promoted heterogeneous nucleation. PBT reached optimal reinforcement at 0.3–1 wt.% MWCNT, yielding tensile strength increases up to ~57% alongside increased crystallinity and faster crystallization kinetics. PLA generally showed reduced tensile strength after MWCNT addition unless compatibilized (e.g., via plasticizers or grafting), whereas PBS consistently gained strength, modulus, and crystallinity but experienced reductions in ductility. Electrical percolation thresholds varied widely (0.25–14 wt.%), demonstrating that dispersion quality, nanotube functionalization, and processing route governed conductivity and percolation behavior more than matrix chemistry. Recyclability and circular economy aspects were assessed: while PET/MWCNT systems showed promise for mechanical recycling and property recovery, data on repeated reprocessing, CNT structural integrity, and long-term electrical performance were scarce; PBT recycling studies were limited, and PBS/PLA recycling with retained conductive networks remained underexplored. Based on the comparative analysis, key limitations, critical research gaps, and practical recommendations for processing, compatibilization, and end-of-life evaluation were identified to guide future work aimed at enhancing both performance and sustainability of polyester/MWCNT nanocomposites. Full article

The electrification of high-temperature industrial processes requires refractory materials that combine thermal stability with tailored electrical functionality. In this study, Ta/Nb-Al₂O₃ composites were prepared by spark plasma sintering (SPS) to investigate densification, metal-phase deformation, electrical conductivity and percolation behavior. Coarse, fine and superfine alumina powders were combined with tantalum or niobium and sintered at 1300–1600 °C for 5 min with 50 MPa uniaxial pressure. The results show that the alumina particle size and morphology strongly influence the formation of conductive metal networks. Coarse alumina promotes deformation and elongation of the metallic phase, thereby improving metal-phase connectivity and lowering the operational percolation threshold. Fine and superfine alumina enhance densification but can delay percolation by embedding metal particles in a dense ceramic matrix. Combining these fractions, both effects can be balanced, enabling improved densification while maintaining effective conductive pathways. An operational percolation threshold of 7.5 vol.-% was obtained for Ta/coarse alumina, indicating highly effective metal-phase connectivity after SPS. Microstructural analysis supports the interpretation that matrix-controlled metal-particle deformation and spatial distribution govern the electrical response. Tailored alumina matrix design can reduce the refractory metal content required for conductive ceramic–metal composites. Full article

Gallium (Ga)-based liquid metal (LM) composites, particularly those based on eutectic gallium–indium (EGaIn) and related alloys, have emerged as a promising materials platform for soft and deformable energy storage owing to their unique combination of metallic conductivity, fluidic deformability, and adaptive interfaces. Despite rapid advances in LM-enabled devices, binders remain insufficiently understood and are still commonly regarded as passive structural components. Here, we present a comprehensive binder-centered perspective for LM composites, establishing the binder as a key regulator of electro-chemo-mechanical coupling, interfacial stability, transport behavior, and processability in soft energy systems. We show that tailored binder chemistries in Ga-based LM systems—including stretchable batteries, printable conductors, and soft electrochemical devices—govern LM droplet dispersion, suppress coalescence and leakage, and preserve conductive percolation under large deformation, while enabling room-temperature fabrication and printability through rheological regulation and interfacial wetting. Beyond mechanical confinement, emerging binder functionalities—including dynamic bonding, supramolecular interactions, ionically conductive networks, and reversible polymer architectures—enable self-healing interfaces, adaptive transport pathways, and robust adhesion in deformable devices. By integrating recent advances in stretchable batteries, flexible supercapacitors, printable electronics, and multifunctional soft energy systems, we establish a unified multiscale framework linking binder molecular design to device-level electrochemical and mechanical performance. We further discuss sustainability and manufacturing considerations, including recyclable polymer networks, low-temperature fabrication, and scalable processing strategies. Finally, we outline current challenges and future opportunities toward programmable binder systems with tunable viscoelasticity, interfacial reactivity, and adaptive functionality. This Review establishes binder-centered engineering as a key pathway for transforming LM composites from proof-of-concept materials into resilient, manufacturable, and multifunctional soft energy technologies for wearable, stretchable, and biointegrated electronics. Full article

Land-use change from natural vegetation to agricultural systems significantly affects watershed hydrology and water quality. This study assesses the long-term effects of historical land-use change on hydrologic processes and nitrogen transport in the Straight River watershed, Minnesota, USA, using the Soil and Water Assessment Tool Plus (SWAT+) model. Three land-use scenarios were created to assess changes in water balance and nitrate levels. These scenarios represent the reconstructed pre-settlement conditions from 1855, established agricultural development from 2006, and current conditions from 2022. Results show a significant increase in water percolation and groundwater recharge. Percolation more than doubled, increasing from about 118 mm under reconstructed pre-colonial conditions to over 256 mm in 2022. Streamflow increased to 2.1 m³s⁻¹ in 2022, indicating improved hydrologic connectivity and groundwater contributions. Nitrate leaching increased from about 1.14 kg N ha⁻¹ to more than 32 kg N ha⁻¹ (1850s–2022), and nitrate export increased by >2000%, indicating strong nitrate loading. The significant increase in nitrate compared to water fluxes points to agriculture as the primary source of groundwater pollution and downstream nutrient loading. These findings highlight the importance of land-use change in affecting water balance and nutrient behavior. They also point out the need to include a historical baseline in watershed assessments. The results show the importance of better land and nutrient management strategies to reduce nitrate losses and protect water resources in intensively managed agricultural areas. Full article

Climate change is expected to significantly alter hydrological regimes in high-altitude tropical basins, where water availability strongly depends on precipitation variability and groundwater processes. The Ramis River basin, a major tributary of Lake Titicaca in the Peruvian Altiplano, is particularly vulnerable to hydroclimatic variability due to its dependence on seasonal water resources. This study evaluates the impacts of climate change on runoff, groundwater recharge, percolation, and renewable water resources using the SWAT hydrological model calibrated and validated for the period 1981–2024. Future projections were developed using the MPI-ESM-MR and ACCESS1-0 global climate models under RCP 4.5 and RCP 8.5 scenarios for the period 2025–2100, applying bias correction through CMhyd. The results indicate a strong sensitivity of basin hydrology to climate forcing. Under the MPI-ESM-MR model, runoff decreases by up to 68% under RCP 4.5, while extreme increases exceeding 130% are projected under RCP 8.5. In contrast, ACCESS1-0 shows moderate reductions in most scenarios. Renewable water resources exhibit a general declining trend (−23% to −41%), suggesting increasing water scarcity conditions. Additionally, the Standardized Precipitation Index (SPI) reveals a higher frequency and persistence of drought events toward the end of the century, particularly under high-emission scenarios. Overall, the findings indicate that the Ramis River basin may face a dual hydroclimatic risk characterized by reduced water availability and increased hydrological extremes. These results highlight the need to integrate climate projections into water resource management and to implement adaptive strategies to reduce future water vulnerability in high-Andean basins. Full article

Carbon/inorganic hybrid composites have evolved from filler-reinforced materials into design platforms for coupled electromagnetic, thermal, sensing, environmental, protective and energy-related functions. Their distinctive value lies in the possibility of combining a conductive, polarizable or porous carbon phase with an inorganic phase that contributes dielectric, magnetic, catalytic, ionic, thermally conductive or barrier behavior. This review examines carbon/inorganic hybrid multifunctional composites from the viewpoint of structure–property relationships, with emphasis on interfacial design, percolation, anisotropy, hierarchical architecture, processing and metrology. Selected graphitic composite studies are discussed as case studies for broadband dielectric spectroscopy, microwave shielding, high-frequency contact metrology, thermal diffusivity analysis and impedance-monitored graphene filters; these case studies are integrated with the broader international literature on CNT and graphene polymer composites, MXene films and foams, graphene/metal oxide photocatalysts, boron nitride/carbon thermal networks, biochar–graphene adsorbents, smart coatings, sensors, supercapacitors and water remediation systems. The central argument is that credible multifunctionality requires more than measuring several properties on the same material. It requires simultaneous or service-relevant co-optimization under constraints of thickness, density, processability, aging, humidity, corrosive media, regeneration, toxicity, economic feasibility and scalable fabrication. The review concludes with design rules and reporting recommendations intended to help move the field from impressive property demonstrations toward application-ready hybrid material systems. Full article

Electrically conductive polymer composites (ECPCs) have attracted growing interest in applications requiring lightweight, processable, and electrically functional materials. Their increasing use has created a strong need for reliable models capable of predicting electrical conductivity from component properties, composite composition, and microstructural features. Although classical percolation theory can describe the sharp increase in conductivity near the percolation threshold, it is often insufficient for predicting conductivity over a wider range of filler concentrations or for distinguishing the underlying conduction mechanisms. This review examines the main modeling approaches used for carbon-filled polymer composites, including percolation-centered, homogenization, network-based, and data-driven models. These approaches are compared in terms of their assumptions, required inputs, strengths, and limitations, with emphasis on how they account for filler morphology, orientation, dispersion, tunneling effects, and conductive-network formation. The review also identifies key challenges and future needs, particularly the development of integrated, orientation-sensitive, and physically informed models for predicting anisotropic electrical conductivity in processed ECPCs. Full article

This study aims to develop sustainable conductive nanocomposites based on poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends reinforced with multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelets (G), focusing on their multifunctional performance. The novelty lies in the production of hybrid nanocomposites based on PLA/PCL blends with MWCNT/G using conventional industrial processing techniques, enabling the development of eco-friendly nanocomposites with tailored electrical, mechanical, and electromagnetic properties. The nanocomposites were prepared by twin-screw extrusion followed by injection molding. Rheological, scanning electron microscopy (SEM), mechanical, thermal, thermomechanical, electrical conductivity, and electromagnetic shielding properties were systematically evaluated. From a rheological perspective, the PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites exhibited a plateau at low frequencies, associated with the formation of a percolated network. This was confirmed by the significant increase in electrical conductivity and electromagnetic shielding response. The morphology observed by SEM showed a refinement of the PCL phase in the PLA matrix with the incorporation of MWCNT. The PLA/PCL/MWCNT/G (4/2 parts per hundred resin, phr) nanocomposite showed a 309% increase in impact strength compared to neat PLA, while maintaining the heat deflection temperature (HDT). The elastic modulus exceeded 2300 MPa and accelerated the crystallization process by more than 15 °C compared to PLA, which makes it important to reduce injection molding time. Additionally, it exhibited the highest electrical conductivity level, around 6.79 × 10⁻⁵ S/cm, which resulted in improved electromagnetic shielding performance in the 8.2–18 GHz range, highlighting the synergistic effect between 1D and 2D fillers. The developed PLA/PCL/MWCNT and PLA/PCL/MWCNT/G nanocomposites demonstrate potential for antistatic applications, combining sustainability with multifunctional performance and industrial scalability. Full article

UV-curable polymer composites are attractive for fabricating complex components by digital light processing (DLP), but improving thermal transport while preserving printability remains challenging at high filler loadings. In this work, solvent-free UV-curable formulations filled with hexagonal boron nitride (h-BN) and h-BN/graphite hybrids were developed for DLP 3D printing using commercially available equipment. The effects of filler composition on viscosity, printability, microstructure, through-thickness thermal conductivity, electrical conductivity, and tensile behavior were investigated. Viscosity increased markedly with filler loading, yet reliable DLP printing was achieved up to 40 wt% h-BN through composition-dependent adjustment of build parameters. Thermal analysis supported negligible macroscopic sedimentation during printing, while optical and FE-SEM observations revealed generally uniform platelet dispersion, visible 50 μm layer stratification, and limited phase segregation in the hybrid systems. The through-thickness thermal conductivity increased from ~0.25 W/mK for the neat resin to ~1.95 W/mK at 40 wt% h-BN. At a fixed 20 wt% h-BN, graphite addition led to a smaller increase in thermal conductivity, up to ~1.16 W/mK, while increasing electrical conductivity and reducing mechanical performance. A phenomenological percolation-type model captured the thermal-conductivity trend of the h-BN series. Overall, h-BN-rich formulations provided the most effective route to enhance thermal conductivity while preserving electrical insulation. Full article

Carbon/polymer composites are increasingly designed as microstructure-engineered multifunctional materials that combine mechanical reinforcement with electrical/thermal transport, electromagnetic interference (EMI) shielding, and sensing. Performance is governed less by filler fraction than by the coupled control of network topology, junction resistance, and interfacial thermal boundary resistance under processing-induced shear and thermal histories. Electrical response follows percolation combined with tunneling/contact-controlled junctions, producing nonlinear σ(φ) behavior and high piezoresistive sensitivity near the percolation threshold. In contrast, thermal transport is commonly limited by Kapitza resistance and filler–filler junction resistance, restricting exploitation of the intrinsic conductivity of CNTs and graphene. Recent advances emphasize hybrid and 3D carbon architectures that densify connectivity, reduce junction losses, and enable programmable anisotropy via scalable routes such as masterbatch extrusion and additive manufacturing. However, translation remains constrained by dispersion-driven variability, transport–toughness trade-offs, and incomplete durability assessment under cycling, humidity, and reprocessing. This review consolidates mechanistic structure–processing–property relationships and provides application-driven design rules for sensors, EMI shielding, and thermal management. Full article

Seamount basalts undergoing long-term seawater immersion and percolation are subject to varying degrees of low-temperature alteration, causing a release of substantial amounts of Sr-Nd-Pb-Hf into seawater and thereby providing a sustained, long-term, mantle-derived source for marine material cycling. Such a mantle input mixes with crustal weathering material settled to the ocean via rivers and aeolian dust, resulting in crust-mantle mixing, altogether constraining the Sr-Nd-Pb-Hf isotopic compositions of seawater and polymetallic crusts. Among these, the isotopic compositions of Sr and Pb more closely resemble those of terrigenous input materials, while Nd isotopes indicate a roughly averaged mixing mechanism. The Hf isotopic composition approaches that of enriched mantle-derived Ocean Island Basalts (OIBs). Low-temperature-altered minerals in basalt, such as montmorillonite and phillipsite, possess both permanently negative and variable charges. This causes the formation of an electrostatic field, resulting in an adsorptive potential that facilitates the initial growth of charged Fe and Mn colloidal particles on the surfaces of altered basalt. Simultaneously, Fe, Mn, Co, Ni, and Rare-Earth Elements (REEs) released during the low-temperature alteration process contribute essential material for the growth of a polymetallic crust. Full article