Pore Structure Evolution Research Articles

Recovery of lithium from spent cathode carbon from aluminium electrolysis based on ultrasound-assisted acid leaching

ABSTRACT Spent cathode carbon from aluminum electrolysis (SCC) is a typical fluorinated hazardous solid waste generated by the aluminium industry, and its safe disposal and efficient recovery of valuable metals (lithium) are dual challenges for resource recycling and environmental protection. An innovative coupled ultrasound-assisted hydrochloric acid leaching (UHAL) process is proposed for the first time for the efficient recovery of lithium from SCC with complex components. The multi-parameter dynamic model based on Box-Behnken design was developed to regulate the HCl concentration (1 mol/L), time (60 min), temperature (40 °C) and power (20 W). The multi-scale solid-phase evolution analyses, such as surface reconstruction by scanning electron microscopy (SEM), phase transformation by X-ray diffraction (XRD), pore structure evolution by Brunauer-Emmett-Teller (BET), and particle fragmentation by laser particle size analysis, reveal the synergistic mechanism of the dissociation of LiF inclusions and enhancement of lithium ion diffusion, under the effect of ultrasonic field.

Hypoxic preparation of solid wastes derived ceramsite for enhanced Cd(II) removal.

Hypoxic preparation of solid wastes derived ceramsite for enhanced Cd(II) removal.

Investigation of the Evolutionary Patterns of Pore Structures and Mechanical Properties During the Hydration Process of Basalt-Fiber-Reinforced Concrete

Recent studies primarily focus on how the fiber content and curing age influence the pore structure and strength of concrete. However, The interfacial bonding mechanism in basalt-fiber-reinforced concrete hydration remains unclear. The lack of a long-term performance-prediction model and insufficient research on multi-field coupling effects form key knowledge gaps, hindering the systematic optimal design and wider engineering applications of such materials. By integrating X-ray computed tomography (CT) with the watershed algorithm, this study proposes an innovative gray scale threshold method for pore quantification, enabling a quantitative analysis of pore structure evolution and its correlation with mechanical properties in basalt-fiber-reinforced concrete (BFRC) and normal concrete (NC). The results show the following: (1) Mechanical Enhancement: the incorporation of 0.2% basalt fiber by volume demonstrates significant enhancement in the mechanical performance index. At 28 days, BFRC exhibits compressive and splitting tensile strengths of 50.78 MPa and 4.07 MPa, surpassing NC by 19.88% and 43.3%, respectively. The early strength reduction in BFRC (13.13 MPa vs. 22.81 MPa for NC at 3 days) is attributed to fiber-induced interference through physical obstruction of cement particle hydration pathways, which diminishes as hydration progresses. (2) Porosity Reduction: BFRC demonstrates a 64.83% lower porosity (5.13%) than NC (11.66%) at 28 days, with microscopic analysis revealing a 77.5% proportion of harmless pores (<1.104 × 107 μm3) in BFRC versus 67.6% in NC, driven by densified interfacial transition zones (ITZs). (3) Predictive Modeling: a two dimensional strength-porosity model and a three-dimensional age-dependent model are developed. The proposed multi-factor model demonstrates exceptional predictive capability (R2 = 0.9994), establishing a quantitative relationship between pore micro structure and mechanical performance. The innovative pore extraction method and mathematical modeling approach offer valuable insights into the micro-structural evolution mechanism of fiber concrete.

Structural and Sorption Characteristics of Nanocellulose Aerogel-Based Composite Materials Doped with Mefenamic and Flufenamic Acids: Insights from Magic Angle Spinning and High-Pressure NMR Spectroscopy.

Our research, which employs a comprehensive approach combining high-pressure and magic angle spinning (MAS) NMR spectroscopy methods, investigates the structural and sorption characteristics of composite materials based on cellulose aerogels. The 13C NMR studies, conducted in supercritical CO2, revealed kinetic parameters for the sorption processes that significantly differ from those of silica-based analogs. The analysis of chemical shifts from 19F MAS NMR spectra led to the first identification of two stable phase states of flufenamic acid within the cellulose aerogel: an amorphous phase within the pore volume (-62.15 ppm) and a liquid-like phase on the surface of the pores (-65.09 ppm), with a ratio of 2:1. These findings, which contrast starkly with previous data for silica systems, where only a liquid-like state was observed, underscore the unique three-dimensional architecture and highly developed porous structure of cellulose aerogels. These features appear to stabilize metastable amorphous phases of active pharmaceutical ingredients (APIs), opening up new perspectives for the use of cellulose aerogels in the controlled stabilization of metastable phases of APIs in composite materials.

Pore Structure Evolution in Long-Term Water-Flooding Unconsolidated Sandstone Reservoirs

Pore Structure Evolution in Long-Term Water-Flooding Unconsolidated Sandstone Reservoirs

Real-time NMR investigation of water infiltration mechanisms and pore structure evolution in fractured sandstone near-wellbore regions

Real-time NMR investigation of water infiltration mechanisms and pore structure evolution in fractured sandstone near-wellbore regions

Multiscale Modeling of Compressive Strength Degradation in Manufactured Sand Concrete: Linking Pore Structure Evolution to Salt Freeze-Thaw Damage

Multiscale Modeling of Compressive Strength Degradation in Manufactured Sand Concrete: Linking Pore Structure Evolution to Salt Freeze-Thaw Damage

Preparation of ultramicroporous carbon for gas adsorption through oxygen-rich precursor-enhanced chemical activation.

Preparation of ultramicroporous carbon for gas adsorption through oxygen-rich precursor-enhanced chemical activation.

Clogging Modes of Microbially Induced Calcium Carbonate Precipitation Under Continuous Flow Conditions and Mode Transitions

Abstract Microbially induced calcium carbonate precipitation (MICP) holds vast potential for soil reinforcement, material repair, and permeability control. However, the pore structure evolution and clogging modes under continuous flow conditions remain elusive, which limits the optimization of MICP technology. Through microfluidic experiments, we investigate the effects of porosity, particle size, injection rate, and cementation solution concentration on the clogging and migration of precipitates during the MICP process. We perform the spatial correlation analysis to characterize the pore structure evolution and identify three MICP clogging modes under continuous flow conditions, ranging from selective channel clogging to pore bridging clogging and to homogeneous clogging. Two dimensionless parameters are calculated to characterize the pore structure and reaction kinetics. Combining these parameters with the observed clogging morphologies, we construct a clogging mode phase diagram to predict MICP clogging mode transitions, which reveals the complex influence of pore structure and solution state on MICP. This work elucidates the clogging modes of MICP and their transitions under continuous flow conditions, providing theoretical support for solving the problem of uneven clogging in MICP and the prediction of clogging behavior, and is of practical significance for enhancing the controllability and applicability of this technology.

Pore Structure and Fractal Characteristics of Coal Rocks Under Variable Moisture Content Increment Cycles Using LF-NMR Techniques

The spatiotemporal heterogeneity of moisture distribution causes the coal pillar dams in underground water reservoirs to undergo long-term dry–wet cycles (DWCs) under varying moisture content increments (MCIs). Accurately measuring the pore damage and fractal dimensions (Df) of coal rock by different MCIs under DWCs is a prerequisite for in-depth disclosure of the strength deterioration mechanism of underground reservoir coal pillar dams. This study employed low-field nuclear magnetic resonance (LF-NMR) to quantitatively characterize the pore structural evolution and fractal dimension with different MCI variations (Δw = 4%, 6%, 8%) after one to five DWCs. The results indicate that increasing MCIs at constant DWC numbers (NDWC) induces significant increases in pore spectrum area, adsorption pore area, and seepage pore area. MRI visualization demonstrates a progressive migration of NMR signals from sample peripheries to internal regions, reflecting enhanced moisture infiltration with higher MCIs. Total porosity increases monotonically with MCIs across all tested cycles. Permeability, T2 cutoff (T2C), and Df of free pores exhibit distinct response patterns. A porosity-based damage model further reveals that the promoting effect of cycle numbers on pore development and expansion outweighs that of MCIs at NDWC = 5. This pore-scale analysis provides essential insights into the strength degradation mechanisms of coal pillar dams under hydro-mechanical coupling conditions.

The Impact of Sulphate Erosion Formation Products on the Pore Structure of Cementitious Materials during Dry and Wet Cycling- Based on Thermodynamic Simulations

Experimental techniques like X-ray diffraction (XRD) and pore size distribution determination (MIP), in conjunction with thermodynamic simulation (GEMS) and kinetic modeling of cement hydration (PK), were used to analyze the microstructures and phase compositions of cementitious materials under the coupling effect. This allowed researchers to study the evolution of formation products and pore structure of cementitious materials under the coupling of long-term wet and dry cycling and sulphate erosion. The findings demonstrate that the cement pastes with varying w/b ratios formed the expansion products calcium alumina and gypsum after 180 days of dry and wet cycling by 5% sodium sulphate solution; however, the specimens with lower water-ash ratios had denser structures, fewer erosion products, and better resistance to sulphate erosion. The following illustrates how sulphate erosion products affect the pore structure: during the early stages of erosion, the pore structure becomes more refined and has an increase in the number of transition pores between 10-100 nm due to the erosion products such calcium alumina and sodium sulphate crystals filling the pores. The degree of sulphate erosion is exacerbated by the formation of new cracks and larger macropores, which result in an increase in the number of erosion products, an increase in the average pore size, and a looser pore structure. However, the calcite growing in the transition pores is more destructive, and the crystallisation pressure keeps building up, leading to the destruction of some of the transition pores.

Tensile Resistance and Fracture Mechanisms of Silica Aerogels Reinforced by Nanotube-Graphene Hybrid Networks.

Despite their outstanding thermal insulation and ultralight structure, silica aerogels suffer from inherent mechanical fragility, making the investigation of their mechanical behavior crucial for expanding their practical utility in advanced applications. To enhance their mechanical performance, this study introduces a dual-phase reinforcement strategy by anisotropically incorporating carbon nanotubes (CNTs) and graphene oxide (GO) sheets into the aerogel matrix. Using molecular dynamic simulations, we systematically investigate the tensile behavior and pore structure evolution of these hetero-structured composites. The results reveal a non-monotonic dependence of tensile strength on loading ratio, distinguishing three strain-dependent reinforcement regimes. High loading content (11.1%) significantly improves strength under low strain (0-26%), whereas low loading levels (1.8%) are more effective at preserving structural integrity under large strain (44-50%). Moderate loading (5.1%) yields balanced performance in intermediate regimes. While increasing carbon content reduces initial pore size by partially filling the framework, tensile deformation leads to interfacial debonding and the formation of larger pores due to CNT-GO hybrid structure interactions. This work elucidates a dual reinforcement mechanism-physical pore confinement and interfacial coupling-highlighting the critical role of nanostructure geometry in tuning strain-specific mechanical responses. The findings provide mechanistic insights into anisotropic nanocomposite behavior and offer guidance for designing robust porous materials for structural and functional applications.

Promoting Effects of Zr on CO2 Hydrogenation over Porous Co/CexZr1-xO2-δ Catalyst.

The porous Co/CexZr1-xO2-δcatalysts were prepared by using a template agent-impregnation method. The physicochemical properties of the prepared catalysts were studied by using the XRD, BET, H2-TPR, and H2-TPD. The effects of the catalyst structure and Zr dosage on CO2hydrogenation performances were also investigated. The porous CexZr1-xO2support prepared by the hard-template method has a large specific surface area and developed pore structure. With the increment of Zr dosage, the crystal phase structure of the prepared porous CexZr1-xO2support transforms from cubic phase to tetragonal phase. The Co-Ce-O-Zr solid solution was formed in the corresponding catalyst by introducing an appropriate amount of Zr and significantly improved the reducibility of the Co3O4/CexZr1-xO2precursors, by which the interaction between the active Co0 and support was enhanced. At the same time, it is conducive to the formation of oxygen vacancies and highly dispersed Co0to promote the hydrogenation active sites to be formed in the corresponding catalyst, and thus promoting the CO2hydrogenation. The porous CoCe0.99Zr0.01catalyst with the Zr content of 1.0 mol% has the best catalytic performances. At 400 °C and atmospheric pressure, the CO2hydrogenation conversion and CH4selectivity on the CoCe0.99Zr0.01catalyst reached 59.8% and 94.7%, respectively.

Study on Freeze-Thaw Cycle Performance and Regional Service Life Prediction of Hydrophobic Aerogel-Modified ACEPS Boards.

The aim of this study is to systematically investigate the influence of hydrophobic aerogel on the performance of aerogel cement-based expanded polystyrene (EPS) insulation board (ACEPS board) under freeze-thaw cycles (FTCs) and to predict its service life in four typical climate zones: Beijing, Harbin, Urumqi, and Nanjing. The effects of aerogel content on compressive strength, volumetric water absorption, thermal conductivity, and pore structure evolution of ACEPS were thoroughly analyzed through FTC testing. The results demonstrated that aerogel significantly reduced the volumetric water absorption of ACEPS due to its excellent hydrophobicity, thereby decreasing the compressive strength attenuation from 40% to 24%, suppressing the increase in thermal conductivity from 0.0130 to 0.0055 W/(m·K), and mitigating pore structure degradation. In the regional service life prediction, aerogel-modified ACEPS exhibited significantly improved freeze-thaw resistance in the cold climates of Harbin and Urumqi, as well as in the high freeze-thaw frequency environment of Beijing. Notably, specimens with high aerogel content demonstrated outstanding structural and functional durability. This study provides a theoretical foundation and practical guidance for incorporating aerogel in the optimized designs and applications of thermal insulation building materials in cold regions.

Investigating encroachment behaviour of pore water on pore structure of unsaturated loess using continuous NMR technique

Abstract To study the influence of the evolution of pore structure and pore fluid state on the loading effect of unsaturated loess, a series of oedometer tests were carried out on intact and remoulded loess, supplemented by low‐field nuclear magnetic resonance (NMR) tests at different consolidation stages of the same specimens for the first time. The results show that the deformation of intact loess lags behind that of remoulded loess during mechanical wetting. The pore water gradually encroaches on the pore structure, which increases the debonding effect of soil and the behaviour of loess gradually converges to that of saturated loess. Under the same vertical pressure, unsaturated loess maintains a higher void ratio than saturated. The decrease in the relaxation time span predicts the compression of the pore structure and the gradual encroachment of water. Deformation caused by consolidation enhances the water retention performance of unsaturated loess. The results provide guidance for understanding the evolution of micropore fabrics in the compaction process of loess.

Effects of crumb rubber particles on the evolution of pore structure in steam-cured concrete under freeze-thaw cycles

Effects of crumb rubber particles on the evolution of pore structure in steam-cured concrete under freeze-thaw cycles

Evolution of pore structure in bituminous coal during in-situ supercritical water gasification: Experimental study and mechanistic understanding

Evolution of pore structure in bituminous coal during in-situ supercritical water gasification: Experimental study and mechanistic understanding

Seepage starting pressure gradient of leaching solution under microscopic pore structure evolution of uranium-bearing sandstone by acid in situ leaching

To investigate the influence of pore structure evolution under physicochemical reaction stimulation on the variation of seepage pressure gradient in percolation systems. The study conducted seepage experiments under three different flow rates, employing computed tomography scanning to characterize sandstone samples during leaching. The relationship between pressure gradient and migration capacity of the leaching solution was established through the pore radius and fractal dimension obtained after three-dimensional reconstruction. The results indicated that minerals in sandstone were continuously dissolved and eroded during leaching, and the number of pores and throats increased with the leaching time. The pores were predominantly sub-nanoscale pores with a small proportion of micrometer-scale pores, while the throats mainly consisted of sub-nanoscale and nanoscale throats. The proportions of micrometer-scale pores, sub-nanoscale pores, and nanoscale pores were different under different flow rates, while throat channel distributions within the same range differed. Sandstone exhibited more effective leaching at flow rate of 0.8 ml/min, with the number of pores and throats increasing and the radius also expanding over time. Furthermore, the pore fractal dimension (Df) of sandstone increased with permeability enhancement, whereas the tortuosity fractal dimension (Dt) decreased with permeability increase. Based on reconstructed pore parameters, a predictive model correlating pressure gradient with mobility coefficient of leaching solution was established using mechanical equilibrium and fractal theory, demonstrating satisfactory model performance. The research provided a theoretical foundation for real-time adjustment of injection pressure based on pressure gradient monitoring when encountering pore clogging during leaching, offering significant practical implications for improving leaching efficiency.

Structural Evolution and Pore Enhancement of Coal under Acid Corrosion, Assisting in the Selection of Enhanced Coalbed Methane Parameters for Acidizing Stimulated Reservoirs

Summary Reservoir acidizing stimulation is among the commonly adopted methods for increasing natural gas production. With the effect of acid, the structural properties of coal change, which directly affects the gas storage and transportation behaviors within the reservoir. Understanding these structural evolutions and their corresponding control mechanisms is crucial. This work determined the optimal acid concentration through acidification experiments and characterized the structural evolution laws of samples before and after optimal acid treatment using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), mercury intrusion porosimetry (MIP), low-temperature N2 (LTG-N2), and low-temperature CO2 (LTG-CO2) methods. The results showed that acid treatment altered the physical and chemical structure of coal, reducing the effective gas adsorption sites. This effect also increases average pore size and changes pore proportions, with micropores and mesopores evolving towards macropores, improving the gas transport properties. The control mechanism of pore structure evolution and migration enhancement is clarified from the micro level. A full-range characterization method for pore FD (fractal dimension) is proposed. The decrease in sample FD indicates that the pore network transforms into a simpler form after acidification, and the connectivity of pores and gas fluidity is improved. In engineering practice, it is necessary to comprehensively consider the marginal effect of mining, cost, environmental issues, etc., and to pay attention to matching the reservoir properties when optimizing the acidizing process parameters. The research results can provide theoretical guidance for the selection of acid stimulation reservoirs and enhanced coalbed methane (ECBM) process parameters.

Computer analysis of the influence of preparation conditions on the porous structure development of nitrogen-doped activated carbons

Computer analysis of the influence of preparation conditions on the porous structure development of nitrogen-doped activated carbons