Search Results (370)

This investigation meticulously examines the influence of activation energy, thermophoresis, Brownian motion, and magnetic fields on the flow dynamics and heat transfer characteristics of a non-Newtonian hybrid nanofluid comprising aluminum oxide (Al₂O₃), copper (II) oxide (CuO), and ethylene glycol over a horizontally stretching porous wedge. This research addresses the imperative need for enhancing energy transfer and thermal management systems, which possess considerable technical significance and industrial relevance. The flow equations were formulated into ordinary differential equations through the use of similarity transformations, which in turn were solved numerically by employing the spectral relaxation (SR) scheme. The findings indicate that the Brownian motion, activation energy, wedge angle, and magnetic field intensity are pivotal determinants of the system’s flow and thermal behavior. In particular, an increase in the wedge angle correlates with an augmentation of the Nusselt number while concurrently diminishing the thermal and diffusion profiles. A comparative analysis of the current investigation and earlier scrutiny revealed that hybrid nanofluids enhance mass and energy transfer rates in both studies. The novelty of this investigation is anchored in its comprehensive exploration of magneto-flow dynamics and the characteristics of hybrid nanofluids within the context of porous wedge-shaped geometries and external magnetic influences. The findings of this study extend previous research by offering quantitative elucidation regarding how pivotal parameters, such as wedge angles, activation energy, thermophoresis, and Brownian motion, affect heat and mass transfer phenomena, thus laying a robust groundwork for the optimization of hybrid nanofluid applications in engineering and industrial environments. The results are in robust agreement with the existing body of literature, thereby affirming the contributions of this study to the academic discourse in the field. Full article

A simple and cost-effective graphite paste electrode modified with 5-(4-aminophenyl)-4-amino-1,2,4-triazole-3(2H)-thione was developed for the selective voltammetric determination of Cu(II) ions in environmental water samples. The N,S-donor ligand was incorporated into a graphite–polystyrene matrix without the use of nanomaterials, providing a reproducible and straightforward electrode fabrication route. Scanning electron microscopy revealed a rough, porous surface morphology with an enhanced electroactive surface area of 0.065 cm², approximately twice the geometric area. Electrochemical impedance spectroscopy confirmed diffusion-controlled mass transport, while cyclic voltammetry indicated quasi-reversible behaviour of the Cu(II)/Cu(0) redox system with a linear dependence of peak current on the square root of the scan rate. Differential pulse voltammetry under optimised conditions (0.1 mol·L⁻¹ H₂SO₄, pH 1.0–1.2) yielded a linear analytical response over the concentration range of 0.01–0.4 μmol·L⁻¹ (R² = 0.99507), with a limit of detection of 0.02 μmol·L⁻¹ and a limit of quantification of 0.06 μmol·L⁻¹—well below the WHO guideline for copper in drinking water. The sensing mechanism involves selective N,S-bidentate coordination of Cu(II) at the electrode surface, followed by electrochemical reduction, as supported by FT-IR spectroscopic evidence. The sensor demonstrated good selectivity toward Cu(II) in the presence of common interfering metal ions at up to 20-fold excess. The method was successfully validated against ICP-OES (recovery 99.8%, RSD < 0.33%) and confirmed by spike–recovery experiments (99.0–99.5%), confirming its practical applicability for trace-level environmental monitoring. The modified electrode retained approximately 93% of its initial response after 30 consecutive measurements and 91% after 14 days of storage, demonstrating good operational stability. Full article

Cu-Ni co-deposit electrodes were prepared and tested in an undivided cell for the electrochemical removal of nitrate from aqueous solutions. Pulsed electrodeposition (PED) under a dynamic hydrogen bubble template and direct electrodeposition (DE) techniques were used for synthetizing porous nickel- and copper-based cathodes. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses showed dendritic and cauliflower-like deposits with a uniform distribution of nickel and copper on the electrode surface, both using flat and foam nickel supports. The PED technique on nickel foam generated highly porous Cu-Ni coatings, with the largest electrochemical active surface area (ECSA) among all the investigated electrodes. Electrolysis in alkaline solutions containing nitrates was performed in an undivided cell in potentiostatic mode. The selectivity towards N₂ was strongly dependent on both copper loading and applied potential; in particular, the foam electrode containing about 23% Cu showed very low ammonia production even at the highest cathodic overpotential, evidencing its marked preference for nitrogen formation. The process performed in the undivided cell using foam-supported Cu-Ni cathodes enabled 100% of conversion of nitrate to molecular nitrogen within approximately 7 h, allowing the complete denitrification of the water. Full article

The escalating prevalence of bacterial infections has intensified the search for innovative antimicrobial strategies, particularly for infected wound management. Chondroitin sulfate (CS), a naturally occurring glycosaminoglycan with established biocompatibility, presents an attractive scaffold for developing metal ion-functionalized biomaterials. This study reports the fabrication of chondroitin sulfate–copper complex (CSCu) and chondroitin sulfate–zinc complex (CSZn) through an ion exchange method, wherein Cu²⁺ and Zn²⁺ ions bind to the groups of carboxylate, sulfate, or N-acetyl from the CS backbone. The resulting complexes exhibited copper or zinc loading capacities of about 6.6% and demonstrated potent antibacterial activity against E. coli and S. aureus. The integration of CSCu or CSZn with sodium alginate yielded a hydrogel system with a higher apparent viscosity, possessing injectability and spreadability on the skin surface and a porous three-dimensional internal structure conducive to wound healing applications. In a murine model of S. aureus-infected full-thickness wounds, topical application of CSCu and CSZn hydrogels substantially accelerated wound closure, achieving 97.46% and 98.11% healing, respectively, by day 10. Additionally, treatment with CSCu or CSZn hydrogels significantly attenuated systemic inflammatory responses, as reflected in lowered serum TNF-α, IL-1β, and IL-6 alongside increased IL-10. Histological evaluation confirmed enhanced re-epithelialization and stratum spinosum formation in treated wounds. These findings establish CSCu and CSZn as a promising bioactive agent for addressing bacterial wound infections through a dual mechanism of direct antibacterial action and immunomodulatory effects, offering a valuable alternative to conventional antibiotic therapies. Full article

Engineering multifunctional scaffolds that effectively promote bone regeneration while concurrently mitigating the risk of infection remains a significant challenge in the field of bone tissue engineering. In this study, we present the fabrication of electrospun poly(lactic acid) (PLA) nanofibrous composite scaffold (PLASrCu) incorporating strontium peroxide (SrO₂) and copper-doped hydroxyapatite (CuHA) particles. The resulting composite scaffold exhibited interconnected porous structures and extracellular matrix-like morphologies. Physicochemical characterization confirmed the preservation of PLA chemical structure and the successful incorporation of crystalline SrO₂ and CuHA phases, with the tensile strength increasing from 2.3 to 2.8 MPa. The PLASrCu scaffold exhibited sustained ion release of Sr and Cu (12.2 and 13.3 mg/L, respectively, over 14 days), together with controlled oxygen generation (10.2 mg/L within 30 min), particularly under hypoxic conditions. In vitro biological assessments demonstrated that the PLASrCu scaffold significantly enhanced cell proliferation and viability. Moreover, osteogenic differentiation and mineralization were markedly promoted, as evidenced by upregulated expression of COL1, OPN, and RUNX2 (5.1-, 2.6-, and 1.9-fold increases, respectively) and increased calcium deposition. Importantly, the Cu-containing scaffolds effectively inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa, resulting in antibacterial rates above 99.9%. Collectively, these results demonstrate that the PLASrCu nanofibrous scaffold integrates osteogenic, oxygen-generating, and antibacterial functions within a single platform, highlighting its strong potential for the regeneration of infected and oxygen-deficient bone defects. Full article

Porous silicate scaffolds represent a promising class of grafting materials for hard tissue engineering due to their superior bioactivity, adjustable degradation rates, and ability to stimulate both osteogenesis and angiogenesis. In this work, scaffolds based on an akermanite-targeted (Ca₂MgSi₂O₇) starting composition, including copper-doped variants, were synthesized using sol–gel and combustion routes, followed by 3D printing to achieve porous architectures with controlled pore size and interconnectivity. The powders were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermal analysis to evaluate their morphology, composition, and crystalline phases. The scaffolds were further assessed in terms of bioactivity by immersion in simulated body fluid (SBF), antibacterial activity, and in vitro cellular response. The results confirmed that copper doping enhanced antibacterial properties, while maintaining favorable biological behavior. Comparative analysis revealed differences between the two synthesis methods, with sol–gel providing more homogeneous structures and combustion leading to highly porous morphologies. These findings highlight copper-doped silicate scaffolds as promising candidates for bone tissue regeneration, combining architectural integrity with biological functionality. Full article

Fuzz buttons are formed by interweaving and compacting fine metallic wires, resulting in a highly porous architecture with complex internal contact interactions. Their compressive behavior is governed by the evolution of wire–wire contacts, frictional sliding, local bending, and plastic deformation, which cannot be adequately captured by conventional homogenized models. To address this limitation, a process-informed finite element modeling approach based on virtual fabrication is proposed. First, the spatial trajectories of 24 beryllium copper wires are generated using a parametric three-dimensional weaving algorithm and smoothed by cubic spline interpolation to obtain continuous wire centerlines. The resulting preform is then virtually compacted to reconstruct the densified wire network and its contact topology. The model employs a globally controlled solid-element mesh, a penalty-based general contact algorithm, a Coulomb friction model, and an explicit quasi-static solution scheme. The size-dependent plastic response of the fine wires is further incorporated through a Nix–Gao-based correction to the constitutive relation. The model is validated against quasi-static compression experiments at compressive strains of 15%, 20%, and 25%. The relative errors in the predicted peak forces are 2.12%, 5.65%, and 6.81%, respectively, while the corresponding coefficients of determination for the force–displacement curves are 0.984, 0.970, and 0.973. The model successfully reproduces the nonlinear loading–unloading response and hysteretic energy dissipation over the investigated strain range. The proposed approach provides a physically grounded numerical framework for predicting the compressive behavior of fuzz buttons and investigating the mesoscopic mechanics of complex interwoven wire networks. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

Thermoacoustic oscillations are excited sound waves in systems with large temperature gradients. Thermoacoustic engines and refrigerators can be constructed using porous materials to enhance the acoustic power produced and facilitate heat pumping for refrigeration. Porous materials can also be utilized as catalytic beds to convert between the two spin-isomers of hydrogen: orthohydrogen and parahydrogen. The conversion between ortho- and parahydrogen is either endothermic or exothermic, and the composition of the isomers manipulates the heat capacity of the fluid. This study experimentally investigates ortho-parahydrogen conversion in a thermoacoustic standing-wave engine with different oxidized catalytic materials. Recorded experimental measurements include the onset temperature ratio, acoustic pressure amplitude, and frequency of the thermoacoustic engine. The results depict a relationship between the oxidized materials and the acoustic amplitude. All oxidized materials promoted an increase in acoustic amplitude versus the pure metallic components. Steady-flow conversion was measured for brass oxide and iron oxide pellets; however, no conversion was detected for aluminum oxide or copper oxide pellets. The initial datapoints provide evidence that future cryogenic hydrogen thermoacoustic devices will need to account for the spin isomer conversion inside the stack. New flow-through regenerating liquefiers can also be constructed, which convert orthohydrogen to parahydrogen during liquefaction. Full article

To address the urgent demand for eco-friendly and low-cost catalysts to replace toxic heavy-metal additives in energetic materials, this work focuses on developing biomass-derived copper-doped porous carbon (CuPC) as a high-efficiency catalyst for the thermal decomposition and combustion of molecular perovskite energetic material (H₂dabco)NH₄(ClO₄)₃(DAP-4). Biomass carbonaceous material has garnered extensive attention in many fields, owing to the low cost, high utilization efficiency, and environment protection. Herein, the CuPC catalysts were rationally designed and fabricated via the high-temperature carbonization treatment of biomass carbonaceous material precursor. The catalytic effects of CuPC on the thermal decomposition and combustion characteristics of DAP-4 were systematically investigated. The results revealed that CuPC possessed inherent catalysis property on the decomposition and combustion reaction of DAP-4. Cu_xO_y nanoparticles were uniformly distributed on the surface of carbonized biomass substrates, endowing the catalysts with superior dispersibility. Thermal analysis results indicated that the addition of 5 wt% CuPC-3 reduced the thermal decomposition peak temperature from 378 °C of raw DAP-4 to 350 °C of DAP-4/CuPC-3. Moreover, the apparent activation energy of DAP-4 was notably decreased with the incorporation of CuPC catalysts. The combustion characterization results demonstrated that DAP-4 exhibited a more intense combustion process with the addition of CuPC, accompanied by elevated maximum combustion temperature and enhanced combustion heat. The catalytic mechanism of CuPC on the thermal decomposition and combustion of DAP-4 was further proposed. This work provides a targeted strategy for designing sustainable biomass-based catalysts to optimize the energy release performance of advanced molecular perovskite energetic materials. Full article

Primary aromatic amines (PAAs), such as 4,4′-methylenedianiline (MDA) and 4-chloroaniline (4-CA), are toxic, carcinogenic, and persistent pollutants widely detected in aquatic environments. To address this issue, UiO-66 was modified through nitro functionalization, copper doping, and defect regulation, and further integrated with chitosan (CS) to construct a composite aerogel (CS@CuUiO-66-NO₂) for the removal of MDA and 4-CA from wastewater. The adsorbent demonstrated relatively fast adsorption kinetics (MDA: 6 h; 4-CA: 4 h) and high adsorption capacities (MDA: 643.74 mg·g⁻¹; 4-CA: 491.54 mg·g⁻¹), showing improved performance compared to pristine UiO-66 and many previously reported adsorbents under similar conditions. The enhanced adsorption performance is likely attributed to the synergistic effects of multiple interactions, including hydrogen bonding, π-π interactions, and possible coordination interactions between functional groups of the adsorbent and PAAs. Moreover, the adsorbent maintained good adsorption performance after five adsorption–desorption cycles, with only a slight decrease in efficiency (~8%), and exhibited limited interference from coexisting anions. Overall, this study presents a feasible strategy for designing porous composite adsorbents with favorable reusability for potential applications in aqueous pollutant remediation. Full article

In this study, the in situ solvothermal synthesis of a copper-based metal–organic framework (Cu-BTC MOF) into two porous ceramic substrates with a 10 cm diameter and 2 cm thickness was reported. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, diffuse reflectance spectroscopy (DRS), Tauc plot analysis, optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were the techniques that were utilized to verify the formation and incorporation of the MOF into ceramics (two samples, with different SiO₂ particles; 500 µm (Ceramic 1), and 150 µm (Ceramic 2)). The synthesized Cu-MOF exhibited a crystalline structure. Both the composites and the Cu-MOF exhibited visible-light absorption, with optical band gaps of 2.5 eV and 2.4 eV, respectively, as determined by DRS. TEM images demonstrated that crystalline MOF domains were successfully included inside the ceramics. Methyl orange (MO), Congo red (CR), and methylene blue (MB) were used to assess the composites’ ability to remove dyes. Catalytic hydrogenation, powered by in situ hydrogen production from NaBH₄ hydrolysis, demonstrated high removal efficiencies of 91–97% after 60 min. Adsorption, on the other hand, was ineffective. Despite undergoing four consecutive cycles without performance degradation, the materials demonstrated remarkable recyclability. Cu-MOF@ceramic composites are effective, durable, and practically applicable for improved wastewater treatment. Full article

With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), zinc slag, lithium slag (LS), electrolytic manganese residue (EMR), phosphogypsum (PG), water treatment sludge (WTS), sewage sludge, blast furnace slag (BFS), steel slag (SS), coal fly ash (CFA), coal gasification slag (CGS), copper smelting slag (CSS), and lead smelting slag (LSS). Having been chemically processed, they exhibit complex compositions that pose challenges for further utilization. In this paper, we comprehensively review the preparation of adsorbents from IISWs as raw materials, the applications of IISW-derived adsorbents, and their adsorption mechanisms. The obtained adsorbents include modified IISWs, zeolites, porous ceramics, and composite and hybrid adsorbents. The adsorption mechanisms, such as van der Waals forces, electrostatic interactions, and π–π interactions, contribute to the rapid adsorption kinetics and high adsorption capacity observed in these adsorbents. Full article

To meet the miniaturized cooling demands of high-heat-flux electronic devices, metal foams—featuring high specific surface area and multiscale porous structures—are considered promising candidates for enhancing flow boiling evaporation. However, pore density (PPI) and grooved geometry (channel aspect ratio, AR) jointly regulate vapor–liquid distribution, rewetting, and flow resistance, thereby constraining overall performance. Here, flow boiling experiments were conducted on nickel and copper foams with pore densities of 100, 500, and 1000 PPI and AR values of 0.7, 1.0, and 1.3. Heat transfer coefficient (HTC), wall superheat ($\mathsf{\Delta }T$), and pressure drop ($\mathsf{\Delta }p$) were systematically evaluated, complemented by transient two-phase simulations revealing vapor fraction, temperature, and pressure drop distributions. A pronounced non-monotonic pore-density dependence is observed: 500 PPI achieves an optimal balance between heat-transfer enhancement and flow resistance, whereas 100 PPI suffers from vapor accumulation and temperature non-uniformity, and 1000 PPI is penalized by excessive permeability resistance and pore-scale confinement. An optimal AR of 1.0 promotes efficient vapor venting and stable rewetting. Under the optimal configuration (500 PPI, AR $=1.0$), a limiting heat flux of 348.6 W/cm², corresponding to the HTC of 55.4 kW/(m² · K), and a limiting HTC of 130.3 kW/(m² · K) are achieved, providing quantitative design guidelines for metal-foam two-phase evaporators. Full article

Mg-Zn-Ca bulk metallic glasses (BMGs) have attracted significant attention in the field of biodegradable metallic biomaterials due to their desirable in vivo degradability and high strength. However, their relatively high brittleness limits further practical applications. In this work, porous Fe skeleton-reinforced Mg-Zn-Ca bulk metallic glass composites (BMGCs) were fabricated by pressure infiltration using porous Fe skeleton as the toughening phase and Mg₆₆Zn₃₀Ca₃Sr₁ alloy as the matrix. It was found that electroless copper plating improved the interfacial wettability between molten Mg and Fe, as well as the infiltration-forming capability of the BMGCs. Quasi-static compression tests showed that the BMGC exhibited a compressive strength of 500 MPa, a plastic strain of 0.2%, and a yield strength of 420 MPa, representing a significant improvement over the matrix BMG alloy. The fracture surface displayed a vein-like pattern, indicating a noticeable transition from brittle to ductile fracture behavior. Thus, the porous Fe skeleton-reinforced Mg-Zn-Ca BMGC shows promise as a potential biodegradable biomedical material. Moreover, the preparation route presented here offers a new perspective for developing degradable Mg-Zn-Ca-based BMGCs. Full article