Search Results (1,740)

This study reports a binder-free, catalyst-free method for fabricating vertically aligned carbon nanotubes (VACNTs) directly on copper (Cu) foil using plasma-enhanced chemical vapor deposition (PECVD) for electrochemical double-layer capacitor (EDLC) applications. This approach eliminates the need for catalyst layers, polymeric binders, or substrate pre-treatments, simplifying electrode design and enhancing electrical integration. The resulting VACNTs form a dense, uniform, and porous array with strong adhesion to the Cu substrate, minimizing contact resistance and improving conductivity. Electrochemical analysis shows gravimetric specific capacitance (C_grav) and areal specific capacitance (C_areal) of 8 F g⁻¹ and 3.5 mF cm⁻² at a scan rate of 5 mV/s, with low equivalent series resistance (3.70 Ω) and charge transfer resistance (0.48 Ω), enabling efficient electron transport and rapid ion diffusion. The electrode demonstrates excellent rate capability and retains 92% of its initial specific capacitance after 3000 charge–discharge cycles, indicating strong cycling stability. These results demonstrate the potential of directly grown VACNT-based electrodes for high-performance EDLCs, particularly in applications requiring rapid charge–discharge cycles and sustained energy delivery. Full article

In the shift toward sustainable energy, there is a strong demand for efficient and durable energy storage solutions. Supercapacitors, in particular, are a promising technology, but they require high-performance materials that can be produced using simple, eco-friendly methods. This has led researchers to investigate new materials and composites that can deliver high energy and power densities, along with long-term stability. Herein, we report a green synthesis approach to create a composite material consisting of reduced graphene oxide and silver nanoparticles (rGO/Ag). The method uses ascorbic acid, a natural compound found in fruits and vegetables, as a non-toxic agent to simultaneously reduce graphene oxide and silver nitrate. To enhance electrochemical performance, the incorporation of silver nanoparticles into the rGO structures is optimized. In this study, different molar concentrations of silver nitrate (1.0, 0.10, and 0.01 M) are used to control silver nanoparticle loading during the synthesis and reduction process. A correlation between silver concentration, defect density in rGO, and the resulting capacitive behavior was assessed by systematically varying the silver molarity. The synthesized materials exhibited excellent performance as supercapacitor electrodes in a three-electrode configuration, with the rGO/Ag 1.0 M composite showing the best performance, reaching a maximum specific capacitance of 392 Fg⁻¹ at 5 mVs⁻¹. Furthermore, the performance of this optimized electrode material was investigated in a two-electrode configuration as a coin cell device, which demonstrates a maximum areal-specific capacitance of 22.63 mFcm⁻² and a gravimetric capacitance of 19.00 Fg⁻¹, which is within the range of commercially viable devices and a significant enhancement, outperforming low-level graphene-based devices. Full article

Carbon nanorods have been synthesized from acetylene and steam using europium oxide nanorods as a template. The resulting carbon exhibits a high conductivity of 4.66 × 10⁵ S/m and a surface area of 1226 m²/g. The Eu₂O₃ was partially or completely washed from the carbon, creating hollow nanorods. Hybrid supercapacitors were fabricated where the Eu₂O₃ contributes a redox pseudocapacitance. A gravimetric capacitance of 501.2 F/g for the hybrid cell and 202 F/g for the carbon-only cell was measured at 1 A/g using 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in propylene carbonate as an electrolyte. The hybrid supercapacitor exhibited an excellent energy density of 108 Wh/kg at 1 A/g compared to 43 Wh/g at 1 A/g for the carbon-only supercapacitor. Full article

The corrosion behavior of open-cell AlSn6Cu-based composites, one reinforced with SiC particles and the other with Al₂O₃ particles, was investigated. The composites were fabricated via liquid-state processing, employing both squeeze casting and the replication method, and they produced in two distinct pore size ranges (800–1000 µm and 1000–1200 µm). Corrosion performance was systematically evaluated through gravimetric (weight loss) measurements and electrochemical techniques, including open-circuit potential monitoring and potentiodynamic polarization tests. Comprehensive microstructural and phase analyses were conducted using X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The results revealed that both reinforcement type and pore architecture have a significant impact on corrosion resistance. Al₂O₃-reinforced composites consistently outperformed their SiC-containing counterparts, and pore enlargement generally improved performance for the unreinforced alloy and the Al₂O₃ composite but not for the SiC composite. Overall, the optimal corrosion resistance is achieved by pairing a coarser-pore architecture (1000–1200 µm) with Al₂O₃ reinforcement, which minimizes both instantaneous (electrochemical) and cumulative (gravimetric) corrosion metrics. This study addresses a gap in current research by providing the first detailed assessment of corrosion in open-cell AlSn6Cu-based composites with controlled pore architectures and different ceramic reinforcements, offering valuable insights for the development of advanced lightweight materials for harsh environments. Full article

Wood density is a key property since it affects almost every other property of wood such as its elasto-mechanical, acoustic, thermal, or electrical properties. Hence, it is essential to determine wood density for the interpretation of any other property test. Density measurements are usually carried out gravimetrically by measuring the wood specimens’ dimensions and taking their weight. In order to be independent of moisture, wood density is measured at an absolute dry state. However, depending on which wood properties shall be measured after the oven-dry density is determined, heating the wood up to 103 °C can be problematic because the volatile components of the wood can evaporate. For this reason, the drying conditions (temperature in °C (60, 80, 103 °C)), duration in h (8, 16, 24, 48 h)) required to achieve an absolute dry state inside wood specimens—being obligatory for the analysis of various physical, mechanical, or even biological properties—were examined for different softwood and hardwood species. Basically, oven-dry measurements (i.e., 48 h at 103 °C) themselves contained a significant error, which was considered to be the result of deviations in the handling of the specimens and the scales used. Using temperatures below 103 °C was critical for the determination of absolute dry mass and dimensions. Wood specimens with a high content of volatile ingredients led to an apparently increased residual MC (e.g., shown for Scots pine heartwood), thus volatile ingredients were considered an additional source of error during oven-dry measurements. Full article

Lithium–oxygen battery performance is limited by the instability of the electrolytes. Herein, it is shown that highly concentrated DMSO and DMF electrolytes improved resistance to degradation compared to lower electrolyte concentrations. Gravimetric capacities of DMSO-based electrolytes decreased modestly with increasing molar ratio up to 0.4, demonstrating the ability of highly concentrated electrolytes to perform relatively well at the higher concentrations needed to help reduce electrolyte degradation. These cells maintain their cycling lifetimes up to a molar ratio of 0.3 before a dramatic decrease is seen. Previously, DMF had been disregarded as a viable electrolyte in Li–O₂ batteries due to very low gravimetric capacities at low concentrations and a very short cycle life. Here, it is demonstrated for the first time that performance in DMF greatly improves with increasing the Li salt-to-solvent molar ratio, with the capacity peaking at 0.4 for LiTFSI–DMF electrolytes matching the best performance in DMSO at low concentrations. Furthermore, increasing the LiTFSI–DMF concentration greatly improves cycling lifetimes, with cycling lifetimes almost tripling when the LiTFSI–DMF molar ratio increases from 0.1 to 0.25, ~60% larger than that achieved with DMSO. These results suggest that other electrolyte solvents previously thought unusable should be reconsidered for use in Li–O₂ batteries at high concentrations. Full article

Moisture transport in building materials significantly influences their durability, mechanical integrity, and thermal performance. This study presents an experimental investigation of moisture permeability in a range of traditional and modern wall elements, including autoclaved aerated concrete (ACC), ceramic blocks, silicate blocks, perlite concrete blocks, and concrete units. Both vapor diffusion and capillary transport mechanisms were analyzed under controlled climatic conditions using gravimetric and hygrometric methods. Among the tested materials, autoclaved aerated concrete (AAC) was selected for detailed numerical modeling because of its high porosity, strong capillarity, and widespread use in modern construction, which make it especially vulnerable to moisture-related degradation. Based on the experimental findings, a digital twin was developed to simulate hygrothermal behavior of walls made of ACC under various environmental conditions. The model incorporates advanced moisture transport equations, capturing diffusion and capillary effects while considering real-world variables, such as relative humidity, temperature fluctuations, and wetting–drying cycles. Calibration demonstrated strong agreement with experimental data, enabling reliable predictions of moisture behavior over extended exposure scenarios. This integrated approach provides a robust engineering tool for assessing the long-term material performance of AAC, predicting degradation risks, and optimizing material selection in humid climates. The study illustrates how coupling experimental data with digital modeling can enhance the design of moisture-resistant and durable building envelopes. Full article

Asphalt fume emissions cause significant environmental hazards during the preparation of hot-mix asphalt. In this study, experimental investigations were conducted employing a reactor vessel to simulate asphalt fumes under controlled conditions. Asphalt fumes were obtained through an integrated system comprising glass fiber filter cartridges and an impinger absorption bottle. Quantitative analysis was then conducted using gravimetric analysis and UV-Vis spectrophotometry. Through systematic monitoring of compositional changes in asphalt binder fractions, the fume emission characteristics during in-plant mixing operations were quantitatively correlated with the following processing parameters: temperature, airflow rate, and mixing duration. Comparative evaluation revealed optimal performance from a ternary compound inhibitor containing cuprous chloride, ditert-butylhydroquinone, and ferric chloride in mass proportions of 4:4:2. At a critical dosage of 0.6 wt%, this compound inhibitor demonstrated significant reduction in total particulate matter emissions without compromising asphalt binder properties. In addition, comprehensive performance characterization through rheological testing and thin-film oven aging (TFOT) showed that the modified low-fume asphalt binder maintained equivalent or improved performances compared to a conventional asphalt binder. Full article

The influence of freeze–thaw (FT) cycling and fucoidan incorporation on the structural and digestive characteristics of lotus seed starch (LS) gels was systematically examined. Fucoidan–lotus seed starch (F-LS) gels were exposed to 0, 1, 3, and 5 FT cycles. Repeated FT treatments were found to disrupt the gel matrix and decrease thermal stability, whereas the addition of 1–2% fucoidan effectively alleviated these degradations. Crystallinity was significantly reduced from 37.62% to 26.38% (p < 0.05), indicating suppressed retrogradation. Thermal gravimetric and low-field NMR analyses revealed reinforced matrix cohesion. In vitro digestion assays demonstrated that fucoidan significantly retarded starch hydrolysis and promoted resistant starch (RS) formation. After five FT cycles, the RS content of 2% F-LS gels reached 29.03%, a 30.24% increase compared to the control. These findings suggest that fucoidan could serve as a natural and effective cryoprotectant and digestibility modulator in starch-based functional foods, offering both technological and nutritional benefits. Full article

This study evaluates the impact of incorporating lateral mass density variations into geoid models for Java, Indonesia, aiming to enhance the accuracy of regional geoid determinations. Geoid models have traditionally used a constant density assumption; however, Java’s varied topography and geological complexity suggest that density variability may significantly influence geoid accuracy. Employing the Stokes–Helmert method combined with the remove–compute–restore (RCR) technique, we calculated geoid models using both constant density and laterally variable density from the UNB TopoDens model. The models were validated against GNSS/leveling data, showing that while lateral density variations had limited effects along flat topographic profiles, they introduced notable discrepancies in regions with considerable elevation changes. Specifically, variable density models exhibited discrepancies of up to 30 cm in regions with complex terrain, underscoring the importance of selecting appropriate density models for precise geoid computations in heterogeneous landscapes. Nonetheless, a comprehensive validation using geometric geoid models is required to confirm the accuracy improvements across the entire region. Full article

This study presents a novel framework to assess the combined impact of soiling and thermal effects on rooftop PV systems through multi-seasonal, multi-site field campaigns in an industrial-urban environment. This work addresses key research gaps by providing a high-resolution, site-specific analysis that captures the synergistic effect of particulate accumulation and thermal stress on PV performance in an industrial-urban environment—a setting distinct from the well-studied arid climates. The study further bridges a gap by employing controlled pre- and post-cleaning performance tests across multiple sites to isolate and quantify soiling losses, offering insights crucial for developing targeted maintenance strategies in pollution-prone urban areas. Unlike previous work, it integrates gravimetric soiling measurements with high-resolution electrical (I–V), thermal, and environmental monitoring, complemented by PVSYST simulation benchmarking. Field data were collected from five rooftop plants in Bursa, Türkiye, during summer and winter, capturing seasonal variations in particulate deposition, module temperature, and PV output, alongside irradiance, wind speed, and airborne particulates. Soiling nearly doubled in winter (0.098 g/m²) compared to summer (0.051 g/m²), but lower winter temperatures (mean 19.8 °C) partially offset performance losses seen under hot summer conditions (mean 42.1 °C). Isc correlated negatively with both soiling (r = −0.68) and temperature (r = −0.72), with regression analysis showing soiling as the dominant factor (R² = 0.71). Energy yield analysis revealed that high summer irradiance did not always increase output due to thermal losses, while winter often yielded comparable or higher energy. Soiling-induced losses ranged 5–17%, with SPP-2 worst affected in winter, and seasonal PR declines averaged 10.8%. The results highlight the need for integrated strategies combining cleaning, thermal management, and environmental monitoring to maintain PV efficiency in particulate-prone regions, offering practical guidance for operators and supporting renewable energy goals in challenging environments. Full article

This study systematically investigated the dissolution equilibrium of lithium carbonate (Li₂CO₃) in mixed Na₂CO₃-NaCl aqueous solutions through isothermal dissolution experiments spanning 283.15–353.15 K. Precise solubility determinations were conducted using a gravimetric analysis under controlled thermodynamic conditions. The obtained solubility data were successfully correlated with the Extended Debye–Hückel (E-DH) model, yielding residual standard deviations below 0.09, which validates the model’s applicability in this ternary system. Both experimental observations and theoretical predictions confirmed that increasing the salt molality enhances the synergistic suppression of the Li₂CO₃ solubility through combined common-ion and salt effects. The thermodynamic analysis revealed the dissolution process to be exothermic (ΔH_d < 0), and entropy change dominates (ξ_S ≈ 78%), with negative entropy changes (ΔS_d < 0) indicating predominant hydration ordering effects. These mechanistic insights establish critical thermodynamic benchmarks for optimizing lithium carbonate precipitation processes in brine lithium extraction operations. Full article

The global insect farming sector is rapidly expanding, driven by rising demand for sustainable protein sources and its potential to contribute to food security solutions. This study focuses on the quantification of chitin by comparing two gravimetric methods (ADF-ADL and crude fiber estimation) with a purification method considered as a reference method. It also aims to use the near-infrared spectroscopy (NIRS) to rapidly assess the quality of insect meals, in particular the macronutrients (moisture, protein, fat) and chitin content in a large data set of insect samples. Both alternative methods overestimated chitin content compared to the enzymatic purification method, which is the most reliable but more complex and expensive. Given their advantages (fairly simple, no significant investment, higher sample throughput, relatively short time execution), they can serve for rapid screening when precise chitin determination is not required. Calibration models showed good performance, particularly for protein and fat determination, and satisfactory results for chitin prediction. The NIRS models show promises for rapid and reliable prediction of insect products, although the chitin assessment remains to be further validated. Its implementation could streamline chemical quality control in insect-based food and feed production, offering speed and flexibility for industrial applications. Full article

The rising demand for clean energy, especially hydrogen, has heightened the need for efficient storage materials. Perovskites, with their unique structures, show great promise for hydrogen storage and optical uses. To identify promising candidates for hydrogen storage materials, the mechanical, electronic, and optical properties of four ordered vacancy double perovskite structures X₂MH₆ (Ba₂BeH₆, Ba₂MgH₆, Ca₂BeH₆, and Sr₂MgH₆) were predicted using density functional theory. These materials were confirmed to be stable, and their hydrogen storage capacity, mechanical properties, electronic structures, and optical performance were thoroughly analyzed. Ca₂BeH₆ demonstrated the highest gravimetric (6.32%) and volumetric (32.29 g·H₂/L) hydrogen storage capacity, showcasing its exceptional potential. It should be noted that the hydrogen storage capacities reported here are theoretical estimates based solely on structural models, and this study does not assess the practical storage and delivery performance of these materials. Its mechanical stiffness and near-isotropic properties further enhance its practicality. Electrical studies revealed all four materials are semiconductors, all of them are direct semiconductors. Optical properties were analyzed via dielectric functions, offering key insights for designing advanced hydrogen storage and optical materials. Full article

Air pollution is one of the major environmental challenges worldwide. Settleable particulate matter (SPM), related to this environmental problem, contains metals capable of producing negative effects on human health (e.g., cardiovascular and respiratory illness). For this study, continuous monitoring was carried in the urban city of Loja (Ecuador), where 10 points were distributed based on different land uses. Samples were collected on a monthly basis using a passive method, by means of samplers built based on the 502 Method. The gravimetric method was then used in the laboratory to determine the concentration of SPM. The inductively coupled plasma–optical emission spectroscopy (ICP-OES) technique was used to identify the presence of metals as such as Copper (Cu), Lead (Pb), Cobalt (Co), Cadmium (Cd), Chromium (Cr), Silver (Ag), Arsenic (As), and Mercury (Hg) in SPM. The results obtained showed that SPM and As differed significantly between land uses, but most metals showed significant differences in relation to temporal changes. Although 90% of the sampling points show SPM concentrations within the limits established by environmental regulations, some of the points exceed the World Health Organization (WHO) limit of 0.5 mg/cm². Finally, the temporal changes in more metals were clearly observed, probably because of increased combustion processes (vehicular traffic), with a higher percentage of metals clearly observed during the April and August months. Furthermore, the highest levels of vegetation burning in Loja province, including the surroundings of the city of Loja, occurred in August. This analysis provides essential data to guide environmental monitoring and air quality management strategies, aiming to reduce health risks from long-term exposure to metal-enriched particulate matter. Full article