Search Results (638)

To address the susceptibility of traditional concrete to explosive spalling and the lack of in situ damage-monitoring methods at high temperatures, in this study, a novel self-sensing, high-temperature-resistant Engineered Cementitious Composite (ECC) was developed. The matrix contains eco-friendly glass sand reinforced with a hybrid system of polypropylene fibers (PPFs) and carbon fibers (CFs). The evolution of mechanical properties and the multimodal self-sensing characteristics of the ECC were systematically investigated following thermal treatment from 20 °C to 800 °C. The results indicate that the hybrid system exhibits a significant synergistic effect: through PFFs’ pore-forming mechanism, internal vapor pressure is effectively released to mitigate spalling, while CFs provide residual strength compensation. Mechanically, the compressive strength increased by 51.32% (0.9% CF + 1.0% PPF) at 400 °C compared to ambient temperature, attributed to high-temperature-activated secondary hydration. Regarding self-sensing, the composite containing 1.1% CF and 1.5% PPF displayed superior thermosensitivity during heating (resistivity reduction of 49.1%), indicating potential for early fire warnings. Notably, pressure sensitivity was enhanced after high-temperature exposure, with the 0.7% CF + 0.5% PPF group achieving a Fractional Change in Resistivity of 31.1% at 600 °C. Conversely, flexural sensitivity presented a “thermally induced attenuation effect” primarily attributed to high-temperature-induced interfacial weakening. This study confirms that the “pore-formation” mechanism, combined with the reconstruction of the conductive network, governs the material’s macroscopic properties, providing a theoretical basis for green, intelligent, and fire-safe infrastructure. Full article

This study examines how both the nature of the carbon support and the palladium precursor influence catalytic performance in acetylene hydrogenation. Six Pd-based catalysts were prepared on four carbon materials—high-heat-treated fibers (HHTs), carbon nanotubes, activated carbon and high surface area graphite—using either sulfate or chloride precursors. Catalytic tests performed in a continuous fixed-bed reactor reveal that HHT-supported catalysts achieve the highest ethylene selectivity and long-term stability, while in general catalysts derived from sulfate precursors exhibit enhanced selectivity compared to their chloride-derived counterparts. These improvements are consistent with the formation of sulfur, which may be incorporated as sub-stoichiometric sulfide species (S²⁻) interacting with metallic Pd, as revealed by the XPS results, rather than to palladium dispersion alone. The role of the carbon support in stabilizing these sites was further assessed by complementary characterization techniques, including transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The combined results indicate that highly graphitic supports such as HHT fibers favor sulfur retention at the catalyst surface, thereby promoting the stability and catalytic performance of Pd–S active motifs during acetylene hydrogenation. Full article

Electrical curing is a viable alternative to traditional thermal curing for geopolymer materials due to its capability for rapid and internal geopolymerization. In this research, reinforced geopolymer-based composite beams were successfully fabricated at a macroscale using a binary system of fly ash (FA) and granulated blast furnace slag (GBFS). The mixture was activated with a solution of sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH) with a fixed molar ratio of 2:1 for both, and aggregate-to-binder and activator-to-binder (A/B) ratios of 2.5 and 0.7, respectively. To ensure electrical conductivity, individual fiber systems were employed, including carbon fiber (CF), steel fiber (SF), and waste wire erosion (WWE), each incorporated at a dosage of 0.5 vol.% of the total mix volume. In addition, carbon black (CB) was introduced as a conductive filler at a constant dosage of 2.0 vol.% of the binder content in selected specimens. Each beam specimen contained only one type of conductive reinforcement or filler. A total of twelve reinforced geopolymer-based composite beams with a 150 mm square section and a span of 1300 mm, with a clear span of 1200 mm, were successfully cast and reinforced based on reinforced concrete beam designs and standards, with a dominant goal of enhancing beam behavior under flexure. The beams were cured in ambient curing conditions, or using thermal curing at 80 °C for 24 h, and using electrical curing from the fresh states with a fixed voltage of 25 V. Notwithstanding a common beam size and reinforcement pattern, distinct curing methods significantly influenced beam structure properties. Peak loads were between 20.8 and 31.5 kN, initial stiffness between 1.75 and 6.09 kN/mm, and total energy absorption between 690 and 1550 kN/mm, with a post-peak energy component of between 0.12 and 0.55. Displacement-based ductility measures spanned from 3.2 to 8.1 units with a distinct improvement in electrical curing regimes, especially in the SF-reinforced specimens; this indicates that electrical curing in reinforced geopolymer composite materials works as a governing mechanism in performance rather than simply a method for enhancing the strength of materials. Full article

Pitch-based activated carbon fibers, recognized for their excellent electrical conductivity, mechanical strength and durability, offer a compelling electrode alternative in the development of next-generation supercapacitors. In this review, we provide insight into the critical role of porosity in enhancing pitch-based carbon fiber performance in supercapacitors, with a focus on the processes and enhancements employed for pore introduction. The background and theoretical underpinnings for the necessity of porosity are briefly introduced, providing a rationale for the optimization of pore distribution. Moreover, the practical outcomes of these treatments are explored in supercapacitor applications, demonstrating the energy storage capabilities of pitch-based activated carbon fibers. In preparing this review, we surveyed the literature and found that pore introduction onto pitch-based carbon fibers is achieved almost solely through activation, which invites future research into alternative techniques. Additionally, it is apparent that future comparisons will benefit from the establishment of a standardized protocol for the reporting of supercapacitor performance. Full article

Background and Objectives: Inadvertent perioperative hypothermia is a common and clinically significant complication during laparoscopic surgery, leading to pain, agitation, shivering, and delayed recovery. This randomized controlled trial evaluated the effect of peri-induction active warming with an electric resistive blanket on postoperative pain and agitation—the primary outcomes—compared with passive insulation. Materials and Methods: This study was registered at ClinicalTrials.gov (Identifier: NCT06022926; date of registration: 15 August 2023) prior to the enrollment of the first patient. One hundred and thirty-two American Society of Anesthesiologists I–II adults undergoing laparoscopic cholecystectomy were randomly allocated (1:1) to two groups: one received active warming with a resistive carbon fiber underbody blanket (Group 1), and the other received passive insulation (Group 2). The tympanic core temperature was measured at four perioperative time points (TT1–TT4). Postoperative agitation (Riker Sedation–Agitation Scale, RSAS) and pain (Numerical Rating Scale, NRS) were assessed 20 min after extubation in the post-anesthesia care unit (PACU). Secondary outcomes included intraoperative and postoperative temperature, postoperative shivering, adverse events (bradycardia, tachycardia, hypotension, hypertension, postoperative nausea and vomiting, and respiratory depression), and the PACU length of stay. Results: Baseline core temperatures (TT1) were similar between the groups (36.5 ± 0.55 °C vs. 36.6 ± 0.54 °C; p = 1.00). However, mean core temperatures at TT2, TT3, and TT4 were significantly higher in the active warming group compared with the control group (TT2: 36.7 ± 0.53 °C vs. 36.5 ± 0.54 °C; TT3: 36.6 ± 0.49 °C vs. 36.4 ± 0.54 °C; TT4: 36.6 ± 0.51 °C vs. 36.2 ± 0.52 °C; all p < 0.001). Active warming markedly reduced postoperative agitation (RSAS ≥ 5: 3.1% vs. 19.4%, p = 0.004) and pain (NRS ≥ 4: 15.4% vs. 49.3%, p < 0.001). The incidence of shivering was lower (20.0% vs. 46.3%, p = 0.006), and the PACU stay was shorter (24 [23–28] min vs. 35 [30–40] min, p < 0.001) with active warming. No significant differences in adverse events were observed between groups. Logistic regression identified the intraoperative fentanyl dose as a predictor of agitation and identified shivering and the PACU duration as predictors of pain. Conclusions: Peri-induction active warming effectively maintained normothermia and improved recovery quality by reducing postoperative agitation, pain, shivering, and PACU stays without increasing adverse events. It should be considered a standard component of thermal management in short- and medium-duration laparoscopic surgeries. Full article

Hydrogen, as an alternative energy carrier, presents significant prospects for the transition to more environmentally friendly energy solutions. However, its efficient and safe storage remains a challenge, as materials with high adsorbent capacity and long-term storage capability are required. This study focuses on the synthesis and characterization of a composite material comprising carbon fiber and manganese dioxide (MnO₂/CFs), for the purpose of hydrogen storage. Carbon fiber was chosen as the basis for the composition of the composite material due to its large active surface area and its excellent mechanical, thermal, and electrochemical properties. The deposition of MnO₂ on the surface of carbon fibers took place through two different synthetic pathways: electrochemical deposition and chemical synthesis under different conditions. The electrochemical method enabled the production of a greater amount of oxide with optimized structural and chemical properties, whereas the chemical method was simpler but required more time to achieve comparable or lower-capacity performance. Elemental analysis of the electrochemically produced composites showcased an average of 40.5 ± 0.05 wt% Mn presence, which is an indicator of the quantity of MnO₂ on the surface responsible for hydrogen storage, while the chemically produced composites showcased an average of 7.6 ± 0.05 wt% Mn presence. Manganese oxide’s high specific capacity and reversible redox reaction participation make it suitable for hydrogen storage applications. The obtained results of the hydrogenated samples through physicochemical characterization indicated the formation of the MnOOH intermediate. Regarding these findings it may be remarked that carbon fiber/MnO₂ composites are promising candidates for hydrogen storage technologies. Finally, the fabricated carbon fiber/MnO₂ composites were applied successfully as working electrodes for analysis of the [Fe(CN)₆]^3−/4− redox system in aqueous KCl solutions. Full article

The escalating release of synthetic dyes from textile and allied industries has become a pressing global environmental issue due to their toxicity, persistence, and resistance to biodegradation. Among the various treatment strategies, adsorption has emerged as one of the most efficient, economical, and sustainable techniques for dye removal from aqueous environments. This review highlights recent advances in bio-derived adsorbents—particularly raw biomass powders, biochars, and activated carbons—developed from renewable waste sources such as agricultural residues, fruit peels, shells, and plant fibers. It systematically discusses adsorption mechanisms, the influence of process parameters, kinetic and thermodynamic models, and regeneration performance. Furthermore, the review emphasizes the superior adsorption efficiency and cost-effectiveness of biomass-derived carbons compared to conventional adsorbents. The integration of surface modification, magnetization, and nanocomposite formation has further enhanced dye uptake and reusability. Overall, this study underscores the potential of biomass-derived materials as sustainable alternatives for wastewater treatment and environmental remediation. Full article

Pecan (Carya illinoinensis) cultivation generates a substantial number of byproducts, particularly nutshells, which are often discarded despite being rich in bioactive and structural compounds. These agro-industrial residues, comprising nearly 50% of the total nut mass, contain high levels of phenolics, flavonoids, dietary fiber, and lignocellulosic matter, making them suitable for circular economy applications. This review critically evaluates the potential of pecan shell waste for value-added applications in environmental remediation, food and pharmaceutical formulations, and green materials production. It explores innovative green extraction techniques, such as ultrasound-assisted, microwave-assisted, and subcritical water extraction, to recover valuable compounds like ellagic acid and tannins with high efficiency and minimal environmental impact. Moreover, the review highlights the conversion of pecan shells into activated carbon for wastewater treatment and soil remediation. Pecan byproducts have been used as sustainable feedstocks for catalyst support, contributing to energy conversion and biomass catalysis. The bioactive compounds also offer therapeutic properties, including antioxidant, anti-inflammatory, and antimicrobial effects, supporting their inclusion in nutraceutical and cosmetic applications. Through a comprehensive synthesis of recent studies, this work highlights the role of pecan shell valorization in reducing waste, improving public health, and increasing economic resilience within agro-industrial systems. By aligning with sustainable development and circular economies, the utilization of pecan byproducts provides a low-cost, eco-innovative pathway to mitigate environmental pollution and promote sustainable development. Full article

Kombucha is a millennia-old beverage crafted from green or black tea and saccharides and fermented with a symbiotic culture of bacteria and yeast (SCOBY). This functional drink boasts health benefits, such as improved intestinal flora function, hepatoprotection and inhibition of amyloid fibers. It contains bioactive antioxidants, such as catechins, ascorbic acid, vitamins and other polyphenolic compounds. With kombucha’s rising popularity, the Food and Drug Administration (FDA) has implemented control procedures to ensure the quality and safety of this food product. Due to the antioxidant properties of the major bioactive compounds in kombucha, feasible and low-cost electroanalytical methods emerge as promising alternatives. The objective of this study was to evaluate the voltammetric behavior of kombucha samples to establish and compare their redox profiles and antioxidant activities. Thus, 18 kombucha samples were used, comprising commercial samples and samples prepared in the laboratory from different SCOBYs purchased from different countries, and analyzed by differential pulse voltammetry (DPV) and square wave voltammetry (SWV) on a carbon paste electrode (CPE). The electrochemical index (EI) values determined from the samples were used to establish their antioxidant activities. The EI values were also compared with spectrophotometric data from Folin–Ciocalteu (FC) and Ferric Reducing Antioxidant Power (FRAP) assays. Full article

Glued laminated timber (glulam) is increasingly adopted as a sustainable structural material; however, its performance under bending can be limited by brittle tensile failures and variability caused by natural defects. This study examines the flexural behavior of glulam beams strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. A four-point bending experimental program was carried out on glulam beams with varying CFRP bonded lengths, including unreinforced control beams. The results demonstrate that CFRP reinforcement enhanced load–carrying capacity by up to 48%, increased stiffness, and shifted failure modes from brittle tension–side ruptures to more favorable compression–controlled mechanisms. A nonlinear finite element (FE) model was developed using DIANA software 10.5 to simulate the structural response of both unreinforced and CFRP–strengthened beams. The numerical model accurately reproduced the experimental load–deflection behavior, stress redistribution, and failure trends, with deviations in ultimate load prediction generally within ±16% across all reinforcement configurations. The simulations further revealed the critical influence of CFRP bonded length on stress transfer efficiency and failure mode transition, mimicking experimental observations. By integrating experimental findings with numerical simulations and simplified analytical predictions, the study demonstrates that reinforcement length and bond activation govern the effectiveness of CFRP strengthening. The proposed combined methodology provides a reliable framework for evaluating and designing CFRP strengthened glulam beams. Full article

The extensive application of carbon fibers (CFs) and their composites in aerospace and electronics has established the optimization of their electrical conductivity as a critical research priority. Conventional electrodeposition techniques are limited by CF inherent chemical inertness and low surface energy, which increase the energy barrier for copper deposition, leading to defective coatings and weakened interfacial bonding. This study demonstrated that sodium hypophosphite (NaH₂PO₂) enhances CF copper deposition efficiency through concentration gradient experiments (0–30 g/L), revealing its modulation of deposition kinetics, crystallographic evolution, and interfacial adhesion strength. Electrochemical analysis showed that NaH₂PO₂ accelerates initial copper nucleation by reducing activation energy without forming complexes. Increasing its concentration expanded monofilament diameter from 8.55 to 9.26 μm post-deposition, with copper loading rising 28.89%. XRD analysis identified 20 g/L as the optimum for crystallinity, producing maximal grain size (8.27 nm) and predominant (111) orientation. This structure achieved a conductivity of 1.63 × 10³ S·cm⁻¹ (55.24% enhancement) and improved breaking force from 13.54 to 14.57 cN. Adhesion tests showed that the 20 g/L group maintained stability comparable to the control. These results suggest that 20 g/L is the preferred concentration balancing conductivity enhancement with mechanical stability. This approach offers a novel strategy for fabricating highly conductive CF composites. Full article

This research examines the influence of various concentrations (0%, 1%, 1.4% and 1.8% by weight) of activated carbon nanoparticles (AC NPs) on the performance of Elium biocomposites reinforced with hemp fibers. Unidirectional [0°/0°] laminates with 20% fiber volume fraction were fabricated via hand layup using two layers of 150 GSM hemp fabric and compression molded to achieve 0.9 mm cured thickness. Quasi-static tensile testing (ASTM D3039, 2 mm/min, 100 mm gauge length) revealed a pronounced non-monotonic relationship between AC NPs loading and mechanical properties, with optimal performance at 1.0 wt.% fillers and catastrophic degradation at 1.8 wt.%. AC NPs filled composites, which were then characterized by their electrical and thermal behavior. Electrically, it also achieved minimum resistivity (1.62 Ω·m) and maximum conductivity (0.62 S·m⁻¹), in contrast to the elevated resistance (42.5 kΩ) found in samples with a higher filler content. Thermal analysis showed a slight effect on the degradation of the onset temperature (300 °C) and a higher charring after addition of AC NP. Finite element analysis (FEA) provided a corroboration for these experimental findings, with simulations verification. Microscopy revealed cohesive fractures in the 1.0 wt.% composite whereas voids and brittle failure were evident in samples with higher loading. Hence, the concentration of 1.0 wt.% AC NP offers the best trade off of mechanical, electrical, and thermal properties. Full article

Distributed fiber-optic photoacoustic non-destructive testing (DFP-NDT) represents a paradigm shift from passive sensing to active probing, fundamentally transforming structural health monitoring through integrated fiber-based ultrasonic generation and detection capabilities. This review systematically examines DFP-NDT’s evolution by following the technology’s natural progression from fundamental principles to practical implementations. Unlike conventional approaches that require external excitation mechanisms, DFP-NDT leverages photoacoustic transducers as integrated active components where fiber-optical devices themselves generate and detect ultrasonic waves. Central to this technology are photoacoustic materials engineered to maximize conversion efficiency—from carbon nanotube-polymer composites achieving 2.74 × 10⁻² conversion efficiency to innovative MXene-based systems that combine high photothermal conversion with structural protection functionality. These materials operate within sophisticated microstructural frameworks—including tilted fiber Bragg gratings, collapsed photonic crystal fibers, and functionalized polymer coatings—that enable precise control over optical-to-thermal-to-acoustic energy conversion. Six primary distributed fiber-optic photoacoustic transducer array (DFOPTA) methodologies have been developed to transform single-point transducers into multiplexed systems, with low-frequency variants significantly extending penetration capability while maintaining high spatial resolution. Recent advances in imaging algorithms have particular emphasis on techniques specifically adapted for distributed photoacoustic data, including innovative computational frameworks that overcome traditional algorithmic limitations through sophisticated statistical modeling. Documented applications demonstrate DFP-NDT’s exceptional versatility across structural monitoring scenarios, achieving impressive performance metrics including 90 × 54 cm² coverage areas, sub-millimeter resolution, and robust operation under complex multimodal interference conditions. Despite these advances, key challenges remain in scaling multiplexing density, expanding operational robustness for extreme environments, and developing algorithms specifically optimized for simultaneous multi-source excitation. This review establishes a clear roadmap for future development where enhanced multiplexed architectures, domain-specific material innovations, and purpose-built computational frameworks will transition DFP-NDT from promising laboratory demonstrations to deployable industrial solutions for comprehensive structural integrity assessment. Full article

This research highlights the mechanical performance of alkali-activated polypropylene fiber (PPF) mortar containing natural pozzolan (NP) and waste glass powder (WGP) as partial replacements for cement. A total of 45 mix combinations and 405 samples were prepared by varying the levels of NP, WGP, PPF, and sodium silicate (SS), with sodium hydroxide (SH) as an alkali activator. The levels for these variables are NP (0%, 10%, and 20%) and WGP (0%, 10%, 20%, and 30%) by weight of the cement; PPF (0%, 0.5%, and 1.5%) by volume of mortar; and SS + SH (30%, 40%, and 50%) by weight of the binder. The molarity of the SH solution was kept at 10 M, while the SS/SH ratio was maintained at 2.5. Compressive (f’c), flexural (fr), and split tensile strength (ft) were evaluated at 7, 28, and 90 days. The results showed that strength development is strongly age-dependent, with 85–90% of the total strength achieved at 28 days and continued moderate gains to 90 days. SS + SH was the most significant variable, with 50% of activator content achieving the highest f’c, fr, and ft values. Within the tested ranges of NP (0–20%) and WGP (0–30%), strength showed a decreasing trend with increasing replacement due to dilution. PPF had a very minute effect on f’c but significantly improved fr and ft at 0.5% dosage because of crack-bridging. Correlation analysis confirmed that cement and SS + SH are the most dominant strength-controlling factors. The results suggest that the combined use of NP, WGP, and PPF maintains mechanical performance while reducing cement consumption, highlighting the feasibility of this hybrid alkali-activated mortar as a low-carbon construction material. Full article

Sodium-ion batteries (SIBs) present a sustainable alternative to lithium-ion systems due to the abundance and low environmental impact of sodium. However, their integration into multifunctional structural battery systems that combine electrochemical and mechanical properties remains unexplored. This work investigates the electrochemical performance of sodium-ion chemistry within a structural battery framework using unsized carbon fiber (UCF) as both a structural substrate and active electrode material. Ultrasonic spray coating was employed to deposit Mesocarbon Microbeads (MCMB) and NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) on UCF to form hybrid anode and cathode half-cells, respectively, with 1 M NaPF₆ in diglyme electrolyte. The MCMB on UCF hybrid anode demonstrated dual graphitic and carbon fiber storage mechanisms, achieving 50 mAh g⁻¹ capacity over 500 cycles at 1C with excellent Coulombic efficiency. The NFM–UCF cathode exhibited an initial capacity of 27.5 mAh g⁻¹ and maintained over 80% capacity retention for 230 cycles, continuing to cycle stably beyond 400 cycles. Post-cycling SEM imaging revealed surface cracking, particle expansion, and gas-pocket formation in both electrodes. These results demonstrate the electrochemical viability of sodium-ion chemistry in a multifunctional structural configuration and establish ultrasonic coating as a scalable, precise method for fabricating carbon fiber electrodes toward future sodium-ion structural batteries. Full article