Search Results (3,712)

Graphene can effectively enhance the impedance matching and dielectric loss capability in dielectric loss/magnetic loss dual-mechanism absorbers, and influences the overall magnetic loss capability of the material through various mechanisms. In this study, carbonyl iron/graphene composite absorbers with different graphene contents were prepared using the solution blending method. An absorbing honeycomb structure was fabricated using aramid honeycomb as the substrate via an impregnation process. The complex permittivity and complex permeability of the materials were tested within the 2–18 GHz frequency band. The absorption capability and mechanism were comprehensively analyzed alongside the reflection loss curves. Furthermore, the influence of graphene on the magnetic loss capability of the dual-mechanism absorbing material was investigated through VSM tests. Research indicates that the content and distribution of graphene can enhance the dispersion of CIP. In addition to a significant improvement in dielectric loss, it also exerts an influence on magnetic loss through a synergistic mechanism. Full article

In recent years CO₂ reforming of methane has attracted great interest as it produces high CO/H₂ ratio syngas suitable for the synthesis of higher hydrocarbons and oxygenated derivatives since it is a way for disposing and recycling two greenhouse gases with high environmental impact, CH₄ and CO₂, and because it is regarded as a potential route to store and transmit energy due to its strong endothermic effect. Along with noble metals, all the group VIII metals except for osmium have been studied for catalytic CO₂ reforming of methane. It was found that the catalytic activity of Ni, though lower than those of Ru and Rh, was higher than the catalytic activities of Pt and Pd. Although noble metals have been proven to be insensitive to coke, the high cost and restricted availability limit their use in this process. It is therefore valuable to develop stable Ni-based catalysts. In this contribution, we show how their activity and coking resistivity are greatly related to the size and dispersion of Ni particles. Well-dispersed Ni nanoparticles were achieved by multistep impregnation on a mesoporous silica support, namely SBA-15, obtained through a sol-gel method, using acetate as a nickel precursor and keeping the Ni loading between 5% and 11%. Significant catalytic activity was obtained at temperatures as low as 450 °C, a temperature well below their deactivation temperature, i.e., 700 °C. For the pre-reduced samples, a CO₂ conversion higher than 99% was obtained at approximately 680 °C. As such, their deactivation by sintering and coke formation was prevented. To the best of our knowledge, no Ni-based catalysts with complete CO₂ conversion at temperatures lower than 800 °C have been reported so far. Full article

Graphite, with its layered structure and weak van der Waals bonding between graphene nano layers, exhibits excellent self-lubricating properties. Natural graphite, characterized by high crystallinity, and artificial graphite, with relatively low crystallinity, exhibit distinct friction behaviors and structural differences, which significantly influence the performance of graphite–resin composites as solid lubricants. This study investigates the effects of natural/artificial graphite ratios and hydrophobic silane coupling treatment on the oil impregnation behavior, friction coefficient, wear stability, and microstructural changes in graphite–resin composites. Under a vertical load of 88,260 N and surface pressure of 50 MPa, the impregnated graphite–resin composites demonstrated low friction coefficients and stable wear behavior. SEM analysis revealed well-preserved microstructures, and Raman spectroscopy confirmed the formation of stable lubrication films through the I_D/I_G ratio, indicating graphene exfoliation. The results indicate that natural graphite provides dense structures and stable friction, while artificial graphite enhances oil impregnation but leads to unstable friction behavior. Full article

Industrial air pollution, particularly acidic gases such as hydrogen chloride (HCl), poses serious environmental and health hazards. Here, hopcalite catalysts were introduced into activated carbon fibers via the impregnation process to enhance HCl capture. The Cu/Mn molar ratio was fixed at 1:1 while the Cu precursor loading was varied with the weight of Cu (Cu 0.04–0.1). Structural and surface modifications were examined using scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometer, and Brunauer–Emmett–Teller analyses. Progressive CuMnOx deposition increased Cu and Mn contents up to 4 at.% and 3.7 at.%, respectively, but decreased the specific surface area from 1565.1 to 1342.7 m²/g owing to pore blocking. Fixed-bed breakthrough tests (50 ppm HCl, 1000 mL/min) showed that moderate catalyst addition (Cu 0.04) yielded the highest total removal (83.6%) and adsorption capacity (12,354.6 mg/g), benefiting from combined physical and catalytic chemisorption. Higher loadings (Cu 0.06–0.1) further reduced microporosity and led to lower removal efficiencies. These results demonstrate that an optimal CuMnOx level effectively promotes chemical adsorption without compromising the intrinsic microporous network of ACFs. Full article

This study aimed to develop a high-performance Modified Activated Carbon Fiber (ACF) filter for the effective removal of Volatile Organic Compounds (VOCs) generated in workplaces and for application in indoor VOCmitigation devices. ACF was modified with CuMnOx catalysts and evaluated for the removal of formaldehyde, acetaldehyde, and benzene. The modified ACF filter was prepared by introducing CuMnOx via an impregnation method using Cu(NO₃)₂⋅3H₂O and Mn(NO₃)₂⋅6H₂O precursors, followed by a crucial high-concentration oxygen plasma surface treatment (50 sccm gas flow) to effectively incorporate oxygen functional groups, thereby enhancing catalyst dispersion and activity. Characterization of the fabricated ACF/CuMnOx composite revealed that the optimized sample, now designated ACF-P-0.1 (representing both CuMnOx catalyst impregnation and O₂ plasma treatment), exhibited uniformly dispersed CuMnOx particles (<500 nm) on the ACF surface. This stability retained a high specific surface area (1342.7 m²/g) and micropore ratio (92.23%). H₂-TPR analysis demonstrated low-temperature reduction peaks at 140 °C and 205.8 °C, indicating excellent redox properties that enable high catalytic VOC oxidation near room temperature. The oxygen plasma treatment was found to increase the interfacial reactivity between the catalyst and ACF, contributing to further enhancement of activity. Performance tests confirmed that the ACF-P-0.1 sample provided superior adsorption–oxidation synergy. Benzene removal achieved a peak efficiency of 97.5%, demonstrating optimal interaction with the microporous ACF structure. For formaldehyde, a removal efficiency of 96.6% was achieved within 30 min, significantly faster than that of Raw ACF, highlighting the material’s ability to adsorb VOCs and subsequently oxidize them with high efficiency. These findings suggest that the developed ACF/CuMnOx composite filters can serve as promising materials for VOCs removal in indoor environments such as printing, coating, and conductive film manufacturing processes. Full article

The increasing demand for electricity and the requirement for transformers to operate under higher loads have driven the search for new insulating materials. On the one hand, papers with enhanced thermal resistance, such as thermally upgraded kraft (TUK) papers, are being introduced; on the other, the use of ester liquids is gaining attention due to their thermal and environmental advantages. This study investigates the thermal ageing behaviour of TUK paper impregnated with five ester liquids—four natural liquids of different origin and one synthetic—subjected to accelerated ageing at 130 °C, 150 °C, and 170 °C, and compared with mineral oil as impregnating fluid as a reference. The degradation of the paper, assessed through its degree of polymerisation, was monitored alongside the evolution of key chemical, physical, and dielectric properties of the liquids. In addition to the experimental analysis, this work also examines the current maintenance standards applied to transformers operating with different insulating fluids. The results showed that while the paper degradation was similar across most of the esters, the ageing behaviour of the fluids differed significantly in terms of acidity, moisture content, interfacial tension, and dielectric dissipation factor. These discrepancies strongly influence the interpretation of fluid condition based on existing transformer maintenance standards, which may lead to inconsistent assessments when applied to ester-filled transformers. The findings highlight both the suitability of natural esters for high-temperature operation and the need to revisit condition assessment criteria in standards that were originally developed for mineral oil systems. Full article

Synthesis of anionic metal–organic framework Na[Ce(BDC)₂(DMF)₂] based on cerium (III)–sodium terephthalate was performed. The crystal structure, studied by the Rietveld method, consists of anionic [Ce(BDC)₂]⁻ layers, connected by interlayer sodium cations in a 3D network. Variable-temperature PXRD, total X-ray scattering with pair distribution function analysis, and DFT calculations revealed framework structure stability upon DMF elimination and thermal treatment up to 300 °C. Modification with copper cations was performed using wetness impregnation with a Cu(NO₃)₂ methanol solution to obtain a catalyst for carbon monoxide oxidation. Cu²⁺@Na[Ce(BDC)₂(DMF)₂] in situ decomposition leads to the catalytic activity of the resulting CuO/CeO₂ composite during CO gas oxidation by air. Full article

High-performance self-powered ultraviolet (UV) photodetectors (PDs) based on mixed-dimensional 3D BiOCl nanosheet array/2D ZnO nanoparticle films heterojunction were fabricated via facile spin-coating and impregnation methods. Under zero bias, compared to the pristine ZnO PD exhibiting a large dark current (≈2 μA) and slow response time (>20 s/>20 s), the optimized 2-BiOCl-ZnO heterojunction PD demonstrated a dramatically suppressed dark current (≈1 nA), along with an ultrahigh on/off ratio (22,748) and a shorter response time (17.44 ms/14 ms) under 365 nm light illumination. This optimized device also achieved a remarkable responsivity of 1.08 A·W⁻¹ and a detectivity of 2.48 × 10¹³ Jones at 354 nm. The built-in electric field formed at the BiOCl-ZnO heterojunction interface, the improved light absorption enabled by the mixed-dimensional heterostructure, and the optimized charge carrier separation and transport within the device were responsible for the enhanced self-powered performance. Due to its fascinating photoelectric properties, this PD was applied as a self-powered signal receiver in a UV optical communication system, demonstrating the ability to achieve efficient and high-speed message transmission. The rational construction of BiOCl-based heterojunction has proved to be an efficient pathway to achieving self-powered photodetection. These results demonstrate that the rational construction of heterojunctions holds great potential for fabricating high-performance PDs. Full article

The growing emphasis on controlling sulfur-containing compounds in fuel oils has driven the development of numerous desulfurization technologies. Among these, catalytic oxidative desulfurization (CODS) has garnered considerable research interest due to its exceptional capability to efficiently remove refractory sulfur compounds, particularly dibenzothiophene (DBT), under relatively mild reaction conditions. However, the widespread application of CODS has been hindered by the high cost and complex preparation processes of the catalysts. To enhance the practical potential of CODS, in this study, a novel Zr@AC catalyst was developed by a facile “solution impregnation + high-temperature calcination” strategy, where zirconium species were effectively supported on activated carbon. Experimental results demonstrated that under optimized conditions of 0.1 g catalyst dosage, 2.0 O/S ratio, reaction temperature 100 °C and reaction time 50 min, the Zr@AC-mediated CODS system achieved a remarkable desulfurization efficiency of 97.24% for DBT removal. The removal efficiency of DBT increased by 9.0% compared with non-catalytic systems. The characterization techniques revealed that the Zr@AC catalyst possesses a hierarchically rough surface morphology, high specific surface area, abundant active sites, and distinctive Zr-O functional groups. Kinetic analysis indicated that the oxidation process follows second-order reaction kinetics. Furthermore, the catalyst maintained over 95% desulfurization efficiency after five consecutive regeneration cycles, confirming that the prepared catalyst has the exceptional recyclability and operational stability. Full article

This study assessed the effect of vacuum impregnation with antioxidants on the postharvest quality of Hass avocados. Fruits were treated with 1% calcium lactate + 1% ascorbic acid (T1) or 1% calcium lactate + 1% citric acid (T2), under 1 bar for 30 s, and compared with untreated controls. Physicochemical properties, enzymatic activity, color, texture, and sensory quality were monitored during 18 days at 12 °C (±1). Both treatments reduced weight and firmness loss, inhibited polyphenol oxidase activity, and delayed browning. Shelf life was extended to ~9.4 days (T1) and ~10.1 days (T2) compared with 6.99 days in controls. These results show that vacuum impregnation with organic acids moderately improves avocado preservation under refrigerated storage. Full article

Biofuels and value-added chemicals can be produced using biomass. These products can substitute the corresponding petroleum-based ones, reducing the carbon footprint, ensuring domestic production, and minimizing/exploiting organic wastes in a circular economy philosophy. Natural mineral-based catalysts seem to be a promising, eco-friendly, and low-cost approach for biomass valorization. This article attempts to highlight the potential of natural mineral-based catalysts for various processes targeting the above valorization. Natural zeolites and clays can be used as catalysts/CO₂ adsorbents and catalytic supports in various biorefinery processes (pyrolysis, gasification, hydrothermal liquefaction, esterification/transesterification, hydrotreatment, cracking, isomerization, oxidation, condensation, etc.). Acid/base, redox, and textural properties of these materials are key factors for their catalytic performance and can be easily regulated by suitable treatments, like calcination, acid/base-washing, metal impregnation, doping, etc., which are discussed in this article. The application of natural minerals in biorefinery processes makes them greener, cost-effective, and easily scalable. Full article

This study primarily focuses on the development and optimization of a high-efficiency catalyst for biodiesel production. Potassium carbonate-supported solid catalysts were synthesized using soot as the support material via an equal-volume impregnation method. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses confirmed the successful deposition of potassium carbonate onto the soot surface, resulting in uniformly dispersed spherical nanoparticles on the catalyst. The catalytic performance was evaluated through single-factor experiments, assessing the effects of catalyst loading, alcohol-to-oil molar ratio, reaction temperature, and reaction time on the transesterification reaction. The maximum biodiesel yield obtained from the Single-factor experiments was 95.29% under the optimal conditions of 6 wt% catalyst loading (relative to oil), alcohol-to-oil molar ratio of 14:1, reaction temperature of 60 °C, and reaction time of 3 h. Furthermore, response surface methodology (RSM) using a four-factor, three-level Box–Behnken design (BBD) was employed to systematically analyze the interaction effects of these variables on the biodiesel yield. The optimized conditions identified by RSM were 61.1 °C, 3.3 h, alcohol-to-oil molar ratio of 14.2:1, and 6.1 wt% catalyst dosage, yielding 95.37% biodiesel conversion. These findings demonstrate that the soot-supported potassium carbonate catalyst developed in this study exhibits excellent catalytic activity, offering a novel catalyst system for industrial biodiesel production with significant academic and practical potential. Full article

Dichlorodiphenyltrichloroethane (DDT), used in the 20th century to combat malaria, is considered harmful to health and the environment. As an alternative, insecticides such as pyrethroids have been used, especially alphacypermethrin, which is applied in mosquito nets impregnated with long-lasting insecticide (LLIN). This study analyzed the concentrations of DDT and alphacypermethrin in soils from three municipalities in the Legal Amazon (Mazagão, Porto Velho, and Cantá) using gas chromatography. The results showed the presence of DDT and metabolites, indicating slow degradation in the region, especially in Cantá, with an average of 2.694 mg/kg of total DDT. Alphacypermethrin stands out in Porto Velho, with an average of 0.364 mg/kg, possibly due to the use of LLINs. DDT did not represent a significant ecological risk in this study, but it did present risks to human health, mainly through food intake. The incremental lifetime cancer risk (ILCR) indicated potential danger, with values of up to 2.93 × 10⁻³ for DDT and 1.17 × 10⁻¹ for alphacypermethrin. The total non-carcinogenic risk index (HI) was extreme, with a maximum value of 336.61. The pesticides evaluated did not present an ecological risk, but they do pose risks to human health, indicating irregular use of LLINs and the need for continuous monitoring. Full article

This study aimed to evaluate the incorporation of graphene-based additives, graphene nanoplatelets (GNPs) and graphene oxide quantum dots (GOQDs), into polymeric fiber matrices used as biofilm supports in anaerobic digestion systems, determining additive specific effects by benchmarking the impregnated matrices against the same nylon carrier without additives under identical operational conditions. Modified matrices were assessed through BMP assays using the liquid fraction of fruit and vegetable waste (LF-FVW) as substrate. Intermediate GNP and GOQD loadings (FM50 and FMDOT50) achieved the highest methane yields (317.9 ± 20.2 and 348.4 ± 20.0 mL CH₄/g COD_(rem)) compared with the control fiber matrix (301.0 ± 20.1 mL CH₄/g COD_(rem)). Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analyses confirmed nanomaterial retention on the matrix surface and interaction with microbial aggregates. Embedding the nanostructures within the fiber enhanced biofilm formation and methane yield while minimizing nanomaterial washout. Future work will focus on advanced physicochemical characterization (XRD, XPS, BET, and EDX mapping), leaching tests to assess long term stability, and scale up evaluation for full scale anaerobic digestion applications. Full article

Recently, the resource utilization of agricultural biomass wastes for the preparation of a wide range of high-value-added chemicals and functional materials, especially heterogeneous catalysts, has received extensive attention from researchers. In this work, mesoporous WO₃/ZrO₂-SiO₂ catalysts are prepared by a two-step incipient-wetness impregnation method using agricultural biomass waste rice husk (RH) as both the silicon source and mesoporous template. The effects of different WO₃ and ZrO₂ loadings on the oxidative desulfurization (ODS) performance of samples are investigated, and the suitable WO₃ and ZrO₂ loadings are 11 and 30%, respectively. The relevant characterization results indicate that, compared to 11%WO₃/SiO₂, the introduction of ZrO₂ leads to the formation of stronger W-O-Zr bonds, which makes the tungsten species stabilized in the state of W⁶⁺. The strong preferential interaction between Zr and W facilitates the formation of stable and highly dispersed WO_x clusters on the mesoporous ZrO₂-SiO₂ carrier. Furthermore, it also prevents the formation of WO₃ crystallites, significantly reducing their content and thus inhibiting the loss of the WO₃ component during cycling experiments. Therefore, the 11%WO₃/30%ZrO₂-SiO₂ sample shows excellent catalytic activity and recycling performance (DBT conversion reaches 99.2% after 8 cycles, with a turnover frequency of 12.7 h^–1; 4,6-DMDBT conversion reaches 99.0% after 7 cycles, with a turnover frequency of 6.3 h^–1). The kinetics of the ODS reactions are further investigated. The mechanism of the ODS reaction is explored through experiments involving leaching, quenching, and the capture of the active intermediate. Finally, a possible reaction mechanism for the ODS process for the 11%WO₃/30%ZrO₂-SiO₂ sample is proposed. Full article