Search Results (1,485)

Metal–organic bimetallic frameworks of Ni–Co, having metal content of 2:1 and 1:2 molar ratios, respectively, have been synthesized via a rapid laser method with a continuous-wave Nd:YVO₄ laser (λ = 975 nm) under 88–90 °C in a DMF/H₂O solution in 70 min. The structure, porosity, and photophysical, electrochemical, and dielectric characteristics of the frameworks and their reduced graphene oxide (rGO) composites in the form of powders and UV-cured PEGMEA/PEGDA films have been investigated. Framework Ni2Co1MOF demonstrated a BET surface area equal to 88.3 m² g⁻¹ and a total pore volume of 0.022 cm³ g⁻¹, whereas framework Ni1Co2MOF exhibited a BET surface area of 52.5 m² g⁻¹ and a total pore volume of 0.016 cm³ g⁻¹. The incorporation of rGO from 1 to 10 wt.% into the framework changed the charge transport and polarization properties of the materials. The electrochemical investigations of the 10 wt.% rGO-Ni1Co2MOF composite in 0.5 M HCl demonstrated a specific capacitance of 32.3 F g⁻¹ at 10 mV s⁻¹, and it preserved 98% of the electrochemical response after 400 cycles, in comparison with 96% for the 10 wt.% rGO-Ni2Co1MOF. The electrochemical responses consisted of both diffusion-controlled ion transport and pseudocapacitance. The introduction of rGO in 1 to 10 wt.% in the polymer composite improved the conductivity and Maxwell–Wagner–Sillars interface polarization at low frequencies in the case of low rGO concentrations, whereas overly high rGO content led to aggregation and the decreased influence of the conductive phase. The main contribution of the present work is the fast sub-100 °C synthesis approach for compositionally tunable Ni-Co frameworks/rGO materials and the relationships between the metal ratio, porous structure, interfacial charge transport, and dielectric response. Full article

CO₂ methanation is a promising power-to-gas technology that enables the conversion of carbon dioxide into methane. However, the development of efficient catalysts based on naturally abundant and inexpensive support remains an important challenge. In this work, metakaolin from natural kaolin was investigated as a novel support for high-loading (30 wt.%) Ni catalysts prepared using a melt infiltration method. The influence of CeO₂ and alkaline earth metal oxides (MgO, CaO) on the physicochemical properties and catalytic performance was systematically evaluated. It was evidenced that CeO₂ improved NiO reducibility, whereas MgO and CaO promoted Ni⁰ dispersion and modified textural and surface properties. In particular, Mg addition increased the S_BET from 23 to 39 m²/g and the total pore volume from 0.06 to 0.17 cm³/g compared with the Ni-MK sample. The promoted catalysts exhibited enhanced low-temperature activity and reached approximately 80% CO₂ conversion at 400 °C, close to thermodynamic equilibrium, maintaining CH₄ selectivity above 97%. Stable catalytic performance was preserved during 24 h time-on-stream tests. The results demonstrate that metakaolin is a promising sustainable support for Ni CO₂ methanation catalysts and that melt infiltration provides a simple and effective preparation route for obtaining high nickel loading. Full article

Mesoporous nanoscale HZSM-5 zeolites were prepared by alkali treatment and characterized by XRD, SEM, NMR, ICP-OES, N₂ adsorption/desorption, NH₃-TPD, Py-IR, and TG techniques. The effects of NaOH concentration on pore structure, acidity, and catalytic performance of nanoscale HZSM-5 zeolites were systematically investigated for selective conversion of aqueous ethanol to propylene. The results showed that the newly developed mesopores on HZSM-5 zeolite were enhanced with increasing NaOH concentrations. By treating nanoscale HZSM-5 zeolite using NaOH solutions with appropriate concentrations (0.2 mol/L), AZ-0.2 showed simultaneously higher propylene selectivity and better stability because of its larger mesopore volume, higher B/L ratios, and suitable acidity. However, excessive treatment by a high-concentration NaOH (0.4 mol/L) solution led to serious desilication, which remarkably increased the strength and amount of strong acid sites on AZ-0.4, resulting in a remarkable decrease in propylene selectivity and catalyst stability. Full article

The detection of triethylamine (TEA) at low concentrations requires sensing materials with high surface reactivity and efficient gas-transport capability. In this work, porous In₂O₃ nanostructures were successfully prepared through a mixed-solvent-regulated metal–organic framework-derived (MOF) strategy. Indium nitrate and terephthalic acid were used as the metal source and organic ligand, respectively. By adjusting the volume ratio of N,N-dimethylformamide and ethanol, the nucleation and growth of In-based MOF precursors were effectively regulated, followed by thermal conversion into porous MOF-derived In₂O₃ materials. Structural characterization confirms that all samples were completely transformed into cubic In₂O₃ after calcination and exhibited porous architectures assembled from In₂O₃ nanoparticles. The solvent composition was found to exert a pronounced influence on the pore structure, defect concentration, and surface oxygen species. Gas-sensing measurements reveal that the MOF-In₂O₃ sensor delivered the best TEA-sensing performance at 240 °C, with a response of 77 toward 100 ppm TEA, relatively fast response/recovery behavior, a detection limit down to 0.5 ppm, and good selectivity and long-term stability. The superior performance can be attributed to the continuous gas-diffusion channels constructed by nanoparticle assembly, abundant oxygen vacancies and chemisorbed oxygen species that promote surface oxidation reactions, and the effective catalytic oxidation capability of In₂O₃ toward TEA molecules. This study demonstrates that regulating the solvent composition during MOF precursor synthesis is a simple and effective route to optimize the microstructure and surface defects of In₂O₃ for improved TEA gas sensing. Full article

The growing volume of crustacean shell waste generated during seafood processing poses a serious environmental problem. However, this type of biowaste remains underutilized, despite being a promising renewable raw material for the production of functional carbon materials. This study aims to investigate how synthesis parameters influence the formation of a hierarchical porous structure in shrimp shell-based carbon materials and to optimize these parameters to improve CO₂ adsorption efficiency. Under optimal carbonization conditions (holding time: 2 h; temperature: 650 °C) and activation conditions (holding time: 2 h; temperature: 750 °C) with activator-to-carbon weight ratios (A/C) of 1/1, 2/1 and 4/1, the resulting porous carbon samples exhibited relatively high S_BET values (1175, 2708 and 3052 m²/g, respectively) and V_T (0.70, 1.55 and 2.60 cm³/g, respectively), as well as different pore size distributions. Notably, the resulting carbon materials demonstrated exceptional CO₂ adsorption performance at 298 K, reaching a maximum adsorption capacity of 40.03 mmol/g at 40 bar for sample SS_652_41752, 15.12 mmol/g at 15 bar for SS_652_21752, and 3.41 mmol/g at 1 bar for SS_652_11752. These values rank among the highest ever reported for biomass-derived porous carbon materials. The adsorption behavior of the most efficient sorbent, SS_652_41752, was further analyzed using Langmuir and Freundlich isotherm models over the temperature range of 298–318 K and at pressures up to 40 bar, and the isosteric heats of adsorption were calculated to elucidate adsorbent–adsorbate interactions. It was found that the differential molar isosteric heat of CO₂ adsorption decreased from approximately 20 to approximately 17 kJ/mol with increasing adsorption uptake, confirming the physisorption nature of the process. These results demonstrate that crustacean shell waste is a promising feedstock for producing carbon materials with tailored properties and significant potential for CO₂ adsorption applications. Full article

Inadequate cleaning of flexible endoscope channels remains a major cause of healthcare-associated infections despite established reprocessing protocols. We developed biomimetic carbon balls inspired by mustard seed surface features as a brush-free adjunct for endoscope channel cleaning, combining mild mechanical action with adsorption-based removal of organic debris. Activated carbon (AC) balls and carbon fiber (CF) balls with diameters of 1.8–3.0 mm were fabricated to fit 2.5–3.5 mm working channels and characterized by TGA, BET, SEM, and EDS. Cleaning performance was evaluated using tomato powder residue and microbiological validation, and computational fluid dynamics was used to assess flow behavior in a 2.7 mm channel containing a 2.6 mm ball under suction. CF balls showed more uniform thermal degradation (8.9% residual mass at 1000 °C) and a ribbed fibrous morphology. In contrast, AC balls exhibited porous, irregular structures with strong adsorption capacity, characterized by high thermal stability (86.4–89.3% residual mass) and pore volumes of 0.087–0.108 cm³/g and BET surface areas of 63.00 m²/g and 21.65 m²/g. After residue exposure, AC surfaces retained more particulate matter, while CF surfaces remained cleaner and promoted more pronounced wall interaction. Microbiological testing showed effective decontamination, with bacterial counts reduced below the detection limit. CFD analysis demonstrated pressure-driven gap flow, elevated local velocity, and vortex-induced wall shear stress sufficient to enhance debris removal without apparent channel damage. These results suggest that mustard seed-inspired carbon balls provide a promising brush-free strategy for endoscope reprocessing by integrating adsorption, hydrodynamic agitation, and gentle scouring to improve cleaning safety and efficacy. Full article

The article presents the results of systematic numerical studies on the efficacy of low-concentration nanoemulsions for enhanced oil recovery. A series of computational investigations was conducted to examine the displacement regimes of oil from digital core models with varying permeability using the developed low-concentration diesel fuel-based nanoemulsions. The volume fraction of diesel fuel in the emulsions was 1 vol.%. The volume fraction of the emulsifier ranged from 0.05% to 0.4%. The nanoemulsions demonstrated high efficiency across the entire range of permeabilities considered. It was shown that the behavior of the displacement front for water and for emulsions differs fundamentally. The waterflood front for emulsions is significantly more uniform and exhibits more complete cross-sectional saturation of pore channels compared to water flooding. With an increase in the capillary number, the oil displacement coefficient achieved by nanoemulsions increases. However, the maximum incremental effect from the use of nanoemulsions is observed at the minimum values of the capillary number. This finding indicates that the primary mechanisms underlying the positive impact of emulsions on oil displacement are the reduction in interfacial tension and the improvement of wettability. Full article

Cement–sodium silicate binary grout is widely used for water sealing and stratum reinforcement in deep underground engineering. Curing pressure profoundly affects the mechanical performance and microstructure of the hardened grout, whereas its pressure-dependent mechanical responses remain insufficiently understood. This study comprehensively investigates the grout’s workability, mechanical properties and water-loss degradation characteristics, combining scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) for microscopic analysis. The results show that the combined addition of 3% sodium bentonite and 1% polycarboxylate superplasticizer effectively mitigates slurry bleeding. An increased cement-sodium silicate volume ratio (C/S) improves fluidity and gel time, and C/S ratios of 0.4, 0.5 and 0.6 were adopted for mechanical tests. Under ambient conditions, grout compressive strength increases with curing age but declines at higher C/S ratios. Curing pressure presents a non-monotonic influence on strength: the strength reaches a minimum at 1.0 MPa and partially recovers at 2.0 MPa, which may result from the competition between pore compaction and hydration gel network damage. Water-loss-induced strength degradation undergoes three typical stages. Grout with lower C/S ratios cured under higher pressure possesses better crack resistance and residual strength. This study clarifies the pressure-adapted mechanism of the grout, providing guidance for its optimal proportioning and application in high-pressure underground engineering. Full article

Numerous studies have investigated the application of iron tailings as raw materials for cement concrete, while rare efforts have been devoted to developing epoxy pavement repair mortars where graded IT function simultaneously as fine aggregate and filler. This study prepared epoxy resin mortar for rapid repair of cement concrete pavement using graded iron tailings (IT) as fine aggregate and filler. All mixtures employed IT as fine aggregate, where the mass proportion of IT filler relative to the total IT mixture varied from 0% to 40%. The effects of IT filler content on workability, curing temperature, mechanical properties, volume stability, and bond strength were investigated, accompanied by microstructural analysis. Experimental results reveal that the incorporation of IT filler ameliorates the fresh workability and shortens the setting time of epoxy mortar, whereas the compressive strength, flexural strength and interfacial bond strength exhibit an initial ascending followed by a descending trend with the increasing IT filler fraction. The optimal IT filler content is determined to be 20%. For fresh-state performance, the modified mortar delivers a flowability of 176.8 mm (+29.7% relative to EM-0) and a setting time of 127 min. In terms of hardened mechanical and bonding properties, the 28-day compressive strength, 28-day flexural strength and 7-day flexural bond strength reach 113.2 MPa (+17.2%), 42.5 MPa (+34.0%) and 9.1 MPa (+75.0%), respectively, in comparison with the reference specimen EM-0. Microscopic characterizations deliver indirect evidence that appropriate IT filler may refine internal pore-size distribution, densify matrix microstructure and suppress crack propagation. The failure mode changed from pure interfacial debonding to cohesive failure in the cement substrate. This work provides a green scheme for resource utilization of iron tailings in high-performance pavement repair materials. Full article

Direct core-scale evidence remains insufficient for evaluating hydraulic fracture–natural fracture coupling and stimulation effectiveness in tight sandstone oil reservoirs. In this study, post-fracturing full-diameter cores from the Chang 8₁ tight oil reservoir in the Xi 119 well block, Xifeng Oilfield, Ordos Basin, were investigated using core observation, computed tomography (CT) scanning, fracture-source evidence and three-dimensional fracture-network reconstruction. A total of 87.56 m of core from 11 core runs was scanned at a voxel size of 50.62 μm. Natural fractures, hydraulic fractures and engineering-induced fractures were identified and distinguished based on fracture-surface features, CT expression, spatial continuity, proppant/tracer evidence and their relationship with bedding and lithological boundaries. The results show that lithological structure exerts a first-order control on hydraulic-fracture surface morphology. Massive sandstone tends to generate straight and continuous high-conductivity main fractures, argillaceous laminated sandstone promotes bedding-controlled discontinuous fractures with limited connectivity, and cross-bedded sandstone favors fracture diversion, branching and natural-fracture activation. Based on fracture assemblage, spatial connectivity and seepage behavior, three hydraulic fracture–natural fracture coupling types were classified: single hydraulic-fracture type, single main fracture–diverted fracture–natural fracture type, and dual main fractures–diverted fractures–natural fractures type. Their equivalent permeability increases stepwise from 155 mD to 345 mD and 586 mD, respectively, indicating a positive relationship between fracture-network complexity and seepage capacity. A CT-derived stimulation-effect evaluation framework was further established by integrating pore–fracture structural modification, fracture volume increase, aperture improvement and seepage-capacity enhancement. The dual main fractures–diverted fractures–natural fractures type shows the strongest stimulation response, with the largest reduction in small-aperture pore/fracture proportion, the greatest lamina-fracture aperture enlargement and the most significant permeability improvement. These results provide direct core-scale evidence for understanding fracture-network formation in continental tight sandstone reservoirs and support more targeted hydraulic-fracturing design and stimulation-effect evaluation. Full article

Accurate differentiation of in situ organic matter (IOM) from migrated organic matter (MOM) and their three-dimensional characterization are fundamental for understanding hydrocarbon generation, migration, and accumulation in shale reservoirs. However, conventional micro-computed tomography (micro-CT) cannot distinguish organic matter subtypes due to insufficient resolution. This study establishes a novel workflow integrating micro-CT with high-resolution scanning electron microscopy (SEM) through image registration. A cubic sample with parallel opposite faces facilitated ion milling and SEM-CT registration. Under SEM supervision, IOM, MOM, and pore–fracture space were interpreted in the micro-CT volume. Applied to the Chang 7 Member shale in the Ordos Basin, results reveal IOM occupies the largest volume fraction (6.96%), followed by MOM (0.94%), while pore–fracture space accounts for only 0.13%. MOM exhibits four morphological types interconnected by throat-like bridges at the ~3.7 μm scale. MOM and pore–fracture components share similar thickness distributions peaking at ~3.7 μm, reflecting their common inheritance from the pore–throat system, whereas IOM is controlled by sedimentary and compactional processes, favoring finer fractions (<3.5 μm). MOM volume far exceeds current pore space, indicating early hydrocarbons predominantly filled connected networks. This workflow overcomes conventional micro-CT limitations, providing a more objective approach for micro-component identification in shale micro-CT data. Full article

Deep low-rank coal from the Daqiang Mine in the Tiefa Basin was investigated using micro-CT imaging with a voxel size of 1 μm. The CT-resolved connected macropore structures of 12 representative elementary volumes (REVs) were reconstructed, and corresponding equivalent pore network models were established. Steady-state, isothermal, single-phase continuum methane flow was simulated under prescribed inlet and outlet pressures with no-flow lateral boundaries, which primarily represent the flow capacity of CT-resolved connected macropores under unstressed conditions. The results showed that: (1) the S1 group exhibited a relatively compact pore structure, smaller throats, stronger spatial heterogeneity, and poorer connectivity, whereas the S2 and S3 groups contained better-developed and more highly connected pore–throat networks; (2) the simulated mean absolute permeabilities of the S1, S2, and S3 groups were 0.781, 0.969, and 0.910 mD, respectively. These values were generally close to, but slightly higher than, the experimental measurements, mainly because the digital models retained only CT-resolved connected pores and did not account for stress-induced compression or the flow-limiting effects of unresolved fine throats; (3) permeability was positively correlated with pore radius, throat radius, and coordination number, but negatively correlated with throat length, pore-to-throat ratio, tortuosity, and fractal dimension. Among these parameters, throat radius showed the strongest correlation with permeability; and (4) an empirical regression model was further established: $K=-4.809+0.672 r_t+3.950 \tau .$ The model exhibited a high goodness of fit ($R^2=0.952$, $p<0.001$); however, its applicability is limited to the investigated coal samples from the Daqiang Mine. Overall, effective throat size and pore–throat connectivity provide more direct indicators of gas-transport capacity than total porosity alone, offering a pore-scale basis for identifying favorable CBM flow zones and optimizing reservoir stimulation strategies in the study area. Full article

Understanding pore-scale interactions among CO₂, the aqueous phase, and heavy oil is crucial for optimizing surfactant-assisted CO₂-enhanced oil recovery. In this study, a three-phase volume-of-fluid (VOF) framework is established in OpenFOAM to simulate immiscible displacement in two-dimensional porous media composed of circular solid grains. Two pore geometries are considered: a relatively uniform geometry and a preferential-channel geometry designed to promote early breakthrough. Sixteen injection schemes are compared, including pure CO₂ flooding, ordinary-water flooding, surfactant–water flooding, aqueous-phase preflush followed by CO₂ injection, and cyclic aqueous-phase/CO₂ injection with different aqueous-slug durations and switching frequencies. The effects of pore geometry, injection strategy, capillary number, viscosity ratio, interfacial tension, and wettability are evaluated using pore-volume-normalized oil recovery, breakthrough PV (the ratio of injected volume to pore volume), cumulative injected CO₂ PV at breakthrough, and phase-distribution indicators. The results show that pore geometry strongly affects macroscopic sweep and breakthrough behavior. In the preferential-channel geometry, pure CO₂ flooding and continuous ordinary-water flooding suffer from early breakthrough and poor sweep, whereas continuous surfactant–water flooding maintains high recovery because reduced oil–water interfacial tension and a more water-wet wall condition promote oil-film detachment and residual-oil mobilization. At 2.5 injected PV, the high-frequency short-slug and 1 s surfactant–water cyclic schemes give the highest or near-highest recovery in the relatively uniform geometry, while continuous surfactant–water flooding remains the highest-recovery scheme in the preferential-channel geometry. Considering the higher chemical demand of continuous surfactant injection and the carbon-utilization objective of CO₂-EOR, the combined surfactant–water/CO₂ schemes are evaluated to clarify the coupling between surfactant-induced oil mobilization and CO₂ displacement. Surfactant–water preflush followed by CO₂ injection becomes more effective as the preflush duration increases, and its recovery advantage over ordinary-water preflush is especially large in the preferential-channel geometry. However, the increase in CO₂ breakthrough PV in this geometry is limited compared with the recovery increment, indicating that the main benefit of surfactant–water is not only delayed gas breakthrough but also enhanced microscopic oil mobilization in poorly swept regions. Increasing the switching frequency slightly improves the cyclic response in the relatively uniform geometry under the tested schedules, whereas all cyclic schemes remain strongly constrained by reconnection with the dominant gas pathway in the preferential-channel geometry. Within the present idealized immiscible VOF model, these comparisons provide a controlled pore-scale comparison for distinguishing surfactant-induced residual-oil mobilization from CO₂ gas-channeling effects in heavy-oil porous media. Full article

Cover cracking induced by steel corrosion is a critical issue governing the durability degradation of reinforced concrete structures in marine environments. The crack initiation and propagation processes dominated by non-uniform rust expansion stress fields urgently require high-resolution continuous monitoring techniques. In this study, based on the principle of Rayleigh backscattering, distributed optical fibers were embedded along the upper surface of specimens to conduct in situ monitoring of surface strain in concrete. The effects of specimen length, biochar content, cover thickness, and rebar diameter were systematically investigated. The results indicate that the surface strain evolution follows a two-stage pattern—a slow growth stage followed by a rapid rise stage—corresponding respectively to the early-stage filling of interfacial pores and stress accumulation, and the later-stage propagation of macroscopic cracks. Increasing specimen length significantly amplifies the spatiotemporal non-uniformity of strain, characterized by “locally high peak strains but low overall mean values,” with the onset time of strain surges differing by more than 50 h across different cross-sections. The incorporation of 0.5% biochar reduces the average strain by approximately 17% and delays crack initiation to 260 h. Increasing cover thickness from 25 mm to 40 mm exhibits the most pronounced inhibitory effect, achieving a 39% reduction in strain and delaying crack initiation to 320 h, primarily attributed to the extended chloride transport path and enhanced hoop confinement stiffness. Reducing rebar diameter from 20 mm to 12 mm decreases the peak strain to 79% of that of the standard specimen, owing to reduced rust product volume and increased relative cover thickness. The macro-cell effect driven by chloride concentration gradient transition zones is identified as a key factor governing crack initiation locations. Theoretical crack widths derived from strain integration of optical fiber data are slightly lower than measured values, yet the overall trends remain consistent. This study provides a quantitative basis for continuous monitoring and durability assessment of corrosion-induced cracking in marine environments. Full article

Developing adsorbents with rapid kinetics and high adsorption capacity is essential for efficient CO₂ capture. Herein, oxygen-rich porous carbons were synthesized from phenolic resin through K₂CO₃ activation. By systematically varying the activation temperature and K₂CO₃/precursor ratio, the evolution of pore structure and its influence on CO₂ adsorption behavior were comprehensively investigated. The reaction between K₂CO₃ and the carbon matrix generated abundant micropores while preserving oxygen-containing surface functionalities, leading to enhanced adsorption affinity toward CO₂ molecules. The optimized carbon exhibited a high specific surface area of 1065 m² g⁻¹ and a narrow micropore volume of 0.54 cm³g⁻¹, delivering equilibrium CO₂ uptake capacities of 5.48 and 3.92 mmol g⁻¹ at 0 and 25 °C under 1 bar, respectively. In-depth analysis revealed that narrow microporosity played a more dominant role than total surface area in determining adsorption performance. Moreover, the optimized adsorbent showed a CO₂/N₂ selectivity of 15; rapid adsorption kinetics, with 90% of equilibrium capacity achieved within 4.5 min; and a dynamic CO₂ capture capacity of 0.91 mmol g⁻¹. The moderate isosteric heat of adsorption (20–36 kJ mol⁻¹) and excellent cyclic stability further confirmed the physisorption-dominated nature of the process. This work highlights the synergistic role of ultramicropore engineering and oxygen-containing surface functionalities in designing efficient porous carbon adsorbents for carbon capture. Full article