Porous Structure Research Articles

Comparison of Different Additives and Ages on Mechanical and Acoustic Behavior of Coal Gangue Cemented Composite

Cemented backfill represents a significant trend in mine filling methods; however, it often exhibits high brittleness and limited resistance to failure, which can restrict its practical application. This study investigates the mechanical properties and damage evolution of fiber-reinforced coal gangue cemented materials (CGCMs) at various curing times using uniaxial compressive tests, acoustic emission (AE) analysis, and scanning electron microscopy (SEM). Specimens were created with different fillers, including carbon fibers (CFs), steel fibers (SFs), and carbon black (CB), and subjected to uniaxial compression until failure. Control specimens without fillers were also tested for comparison. The microstructure of the specimens was examined using scanning electron microscopy (SEM). The findings indicate that (1) the compressive strength of filler-reinforced CGCMs increases between 7 and 14 days of curing but decreases thereafter, with CB significantly improving early-age strength; (2) specimens reinforced with CFs and SFs exhibit significantly enhanced toughness in their post-cracking response; (3) AE events during specific stages can effectively identify the reinforcing effects of CFs and SFs; (4) the presence of fillers improves resistance to shear cracks, with CFs and SFs being more effective than CB; and (5) adding CB results in a denser and more stable hydration product structure, while CFs and SFs lead to a more porous structure with increased cracking.

Multifunctional Electromagnetic Responsive Porous Materials Synthesized by Freeze Casting: Principles, Progress, and Prospects

AbstractFreeze casting is a solidification technique utilized in the fabrication of porous materials. However, the freeze casting process is quite complex, and significant challenges remain in precisely controlling the pore size and shape of porous structures. This study aims to investigate the customization of multifunctional electromagnetic wave (EMW) absorbers with 3D porous structures via freeze casting. This review initially presents the fundamental principles underlying the freeze casting technique and examines the correlation between internal and external factors during the preparation process and porosity. The emerging trends in constructing novel and intricate macroscopic structures through freeze casting are subsequently outlined. Furthermore, this review focuses on the fabrication of composites with various porous microstructures through freeze casting of low‐dimensional building blocks, and their EMW response and multifunctional properties. By regulating the internal and external influencing mechanisms of freeze casting, porous EMW absorption materials exhibit outstanding advantages such as electromagnetic property manipulation, controllable structure, high porosity, high specific surface area, lightweight, and flexibility. These features broaden their applications in electromagnetic shielding, mechanical property, radar stealth, thermal insulation and fire prevention, flexible sensors, antifreeze ability, etc. In addition, we discuss the challenges and prospects of high‐performance EMW absorbers using freeze casting techniques.

Effect of Synthesis Temperature on Performance of Phenazine-Based Cathode for Sodium Dual-Ion Batteries.

Organic materials have attracted much attention in the field of electrochemical energy storage due to their ecological sustainability, abundant resources and structural designability. However, low electrical conductivity and severe agglomeration of organic materials lead to poor discharge capacity and reaction kinetics in batteries. Herein, the morphology of the phenazine-based organic polymer poly(5,10-diphenylphenazine) (PDPPZ) was modified by varying the synthesis temperature. PDPPZ-165 °C with an exceptional porous structure provides abundant reaction channels for rapid charge transfer and diffusion that improves the reaction kinetics in sodium dual-ion batteries. Therefore, PDPPZ-165 °C cathode possesses excellent rapid charge-discharge capability delivering a specific capacity of 119.2 mAh g-1 at 40 C. Furthermore, a high specific capacity of 124.7 mAh g-1 can be provided even at a high loading of 16 mg cm-2 at 0.5 C with a capacity retention of 86.4 % after 500 cycles. This work could afford new insights for optimizing the performance of organic cathode materials in sodium dual-ion batteries.

Fabrication of Mesoporous SiO<sub>2</sub> Shells for Dye Adsorption Studies

The present work focuses on the fabrication of novel hybrid materials for toxic dye removal from an aqueous environment. Nanocarbon template (20-30 nm) was coated with tri-ethyl-orthosilicate (TEOS). The core-shell structure developed was further air pyrolyzed at 600 °C to produce mesoporous silica shells. The pore structures and characteristics of the material were evaluated using XRD, nitrogen adsorption studies, SEM, and TEM. Owing to the hierarchical porosity in range of 1-4 nm and 10-20 nm their adsorption studies were investigated for Phenol-Red. Dye adsorption studies performed revealed 98% removal efficiency with only 20 mg of adsorbent dose within 15 minutes.

Mullite Synthesis Using Porous 3D Structures Consisting of Nanofibrils of Aluminum Oxyhydroxide Chemically Modified with Ethoxysilanes

Nanocrystalline mullite was synthetized by annealing a highly porous 3D structure consisting of nanofibrous aluminum oxyhydroxides treated with ethoxysilanes. The chemical, structural, and phase transformations in the aluminosilicate nanosystem were studied in the temperature range between 100 and 1600 °C. The features of the solid-phase synthesis of mullite at the interface of crystalline alumina with a liquid silica layer are discussed. It was established that chemical modification of the alumina surface with ethoxysilanes significantly limits the interphase mass transport and delays the phase transformation of the amorphous oxide into γ-Al2O3, which begins at temperatures above 1000 °C, while the basic structural nanofibrils are already crystallized at ~850 °C. The formation of mullite was completed at temperatures ≥ 1200 °C, where the fraction of γ-Al2O3 sharply decreased.

Double Carbon-Species Coated Porous Silicon Anode Induced by Interfacial Energy Reduction for Lithium-Ion Batteries.

The rapid development of electric vehicles necessitates high-energy density Li-ion batteries for extended range. Silicon is a promising alternative to graphite anodes due to its high capacity; however, its substantial volume expansion during cycling leads to continuous growth of the solid electrolyte interphase and significant capacity fading. This study addresses these issues by designing a porous Si structure combined with a double carbon-species coating layer, induced by low interfacial energy in a scalable process. Carbon and graphene are located on Si surfaces, forming a close interface that maintains electrical contact, suppresses lithium consumption, and enhances charge transfer properties. The composite anode with a double carbon-species coating on Si demonstrates rapid stabilization with increasing coulombic efficiency, achieving a specific capacity of 1,814 mAh g-1 at 0.2 C and a high-rate capability of 1,356 mAh g-1 at 10C. Additionally, in a full-cell configuration with LiFePO4, it recorded a specific capacity of 161 mAh g-1 at 0.2 C. These results show the potential of porous Si with a carbon-graphene coating for stable, high-capacity operation in Li-ion batteries, offering new insights into high-performance electrochemical systems. Moreover, the double carbon-species coating derived from a scalable surface chemistry-based process presents a realistic alternative for industrial applications.

Inverse Identification of Constituent Elastic Parameters of Ceramic Matrix Composites Based on Macro–Micro Combined Finite Element Model

Accurate material performance parameters are the prerequisite for conducting composite material structural analysis and design. However, the complex multiscale structure of ceramic matrix composites (CMCs) makes it extremely difficult to accurately obtain their mechanical performance parameters. To address this issue, a CMC micro-scale constituents (fiber bundles and matrix) elastic parameter inversion method was proposed based on the integration of macro–micro finite element models. This model was established based on the μCT scan data of a plain-woven CMC tensile specimen using the chemical vapor infiltration (CVI) process, which could reflect the real microstructure and surface morphology characteristics of the material. A BP neural network was used to predict the multiscale stiffness, considering the influence of the porous structure on the macroscopic stiffness of the material. The inversion process of the constituent elastic parameters was established using the trust-region algorithm combined with an improved error function. The inversion results showed that this method could accurately invert the CMC constituent elastic parameters with excellent robustness and anti-noise performance. Under four different degrees of deviation in the initial iteration conditions, the inversion error of all parameters was within 1%, and the maximum inversion error was only 2.16% under a 10% high noise level.

Tailoring of the Properties of Amorphous Mesoporous Titanosilicates Active in Acetone Condensation

Amorphous mesoporous materials are promising as catalysts for processes involving or forming bulk molecules. In a reaction such as acetone condensation to form mesitylene, an effective catalyst should not only have a developed porous structure but also have active centers of acidic and basic types. The sol–gel approach allows one to obtain titanosilicates with such characteristics. This work demonstrates the possibility of controlling their properties by varying the conditions for the synthesis of titanosilicate gels. It has been established that controlling hydrolysis allows one to increase the activity of amorphous mesoporous titanosilicates by 10 times: from acetone conversion of 6% to 60%. It has been shown that the use of titanium acetylacetonate complexes in the synthesis of gels leads to an increase in the content of tetracoordinated Ti in the structure and contributes to an increase in the acidity of titanosilicates. During the condensation of acetone on the obtained mesoporous titanosilicates, high acetone conversion (60–79%) and mesitylene selectivity of up to 83% were achieved.

Controlling the Polarity of Metal–Organic Frameworks to Promote Electrochemical CO2 Reduction

AbstractThe addition of polar functional groups to porous structures is an effective strategy for increasing the ability of metal–organic frameworks (MOFs) to capture CO2 by enhancing interactions between the dipoles of the polar functional groups and the quadrupoles of CO2. However, the potential of MOFs with polar functional groups to activate CO2 has not been investigated in the context of CO2 electrolysis. In this study, we report a mixed‐ligand strategy to incorporate various functional groups in the MOFs. We found that substituents with strong polarity led to increased catalytic performance of electrochemical CO2 reduction for these polarized MOFs. Both experimental and theoretical evidence indicates that the presence of polar functional groups induces a charge redistribution in the micropores of MOFs. We have shown that higher electron densities of sp2‐carbon atoms in benzimidazolate ligands reduces the energy barrier to generate *COOH, which is simultaneously controlled by the mass transfer of CO2. Our research offers an effective method of disrupting local electron neutrality in the pores of electrocatalysts/supports to activate CO2 under electrochemical conditions.

Phytic Acid Functionalized Hierarchical Porous Metal-Organic Framework Microspheres for Efficient Extraction of Uranium from Seawater.

Uranium is a critical resource in the development of nuclear energy, and its extraction from natural seawater has been identified as a potential solution to address uranium resource shortages. In this study, hierarchical meso-/micro- porous metal-organic framework functionalized with phytic acid (PA) microspheres (denoted H-UiO-66-PA) are rationally synthesized for efficient uranium extraction. This unique design allowed for a large adsorption capacity and fast adsorption kinetics, making it a promising material for uranium extraction. Due to the hierarchically porous structure, H-UiO-66-NH2 materials not only provide more sites for grafting PA, and thus enhance the adsorption capacity, but also facilitate the rapid diffusion of uranyl ions which can quickly and effectively access the interior of the H-UiO-66-PA adsorbent. Therefore, the obtained H-UiO-66-PA can achieve an impressive absorption efficiency of 6.76mgg-1 in actual seawater within 15 days. Meanwhile, the H-UiO-66-PA possesses a good adsorption capacity for uranyl ions in the five adsorption/desorption cycles. This work proposes a feasible strategy for constructing functional hierarchical porous MOFs for uranium removal.

Zeolite‐Based “Particle Board” Membranes for Rapid and Selective Hydrogen Permeation

AbstractZeolites, with their well‐defined pore sizes and outstanding stability, are regarded as the quintessential material for precise molecular separation tasks. However, the leap from easily produced zeolite powders to synthesizing free‐standing zeolite membranes, which can fully leverage their ordered porosity, presents substantial technical hurdles. Addressing this challenge, this study introduces polymers of intrinsic microporosity (PIM‐1) as adhesives through a wrapping‐compression method for the facile fabrication of high‐performance and free‐standing zeolite (FAU) “particle board” membranes. The 3D tomogram reconstruction from the focused ion beam‐scanning electron microscope images reveals the “particle board” membranes exhibit hierarchical porous structures. The non‐interconnecting macropores between zeolite particles facilitate the rapid H2 permeation, and the zeolites’ ordered micropores sieve the gas molecules. The optimized FAU@PIM‐1 free‐standing membrane with hierarchically pore structures demonstrated hydrogen permeance (2240 GPU) alongside H2/CH4 selectivity (31.68) for mixed gas and maintained this performance level under pressure ranges from 1.2 to 4.0 bar and over protracted operational periods (up to 3200 h). Meanwhile, EMT and MFI‐type zeolites have also been successfully applied to validate the versatility of this method, demonstrating its widespread potential for the fabrication of various free‐standing zeolite membranes.

Boosting Dendrite‐Free Zinc Anode with Strongly Polar Functional Group Terminated Hydrogel Electrolyte for High‐Safe Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries (AZIBs) have become a promising energy storage device due to their low cost and high security. However, the severe dendrite growth and side reactions on metallic zinc (Zn) anode hamper their commercial implementation. Herein, a strongly electronegative trifluoroborate anion (─BF3−) functionalized polyacrylamide hydrogel (PAME) is well‐designed and constructed as the quasi‐solid‐state electrolyte to overcome these obstacles. The PAME chain segments terminated with strongly polar functional groups promote the conversion of water molecules from free water to bound water through the enhanced hydrogen bonding interaction to alleviate the side reactions. Furthermore, the PAME electrolyte featured with hierarchically porous structure and enhanced electrostatic interaction among the ─BF3− groups, and Zn2+ ions homogenizes the high‐flux Zn ion transport and induce the uniform deposition to restrain dendrite growth. Consequently, the assembled Zn‖PAME‖Zn batteries deliver remarkable cycling stability over 1800 h at 1 mA cm−2 and 900 h at 15 mA cm−2. Additionally, the constructed Zn‖PAME‖MnO2 full cells achieve a reversible capacity of 202 mAh g−1 at 2.0 A g−1 with a capacity retention rate of 91.4% over 500 cycles. This work sheds light on constructing the strongly polar hydrogel electrolyte to boost free‐dendrite Zn anodes for long‐lifespan AZIBs.

Static-spun mesoporous silica-coated CsPbBr3 blue fibres: synthesis and fluorescence properties.

Due to their excellent properties, blue CsPbBr3 quantum dots show great promise for full-colour display and lighting applications. This study used acetonitrile, a polar solvent, to post-treat CsPbBr3 quantum dots, resulting in a blue shift to 453nm. To enhance stability, these quantum dots were encapsulated within the pore structure of mesoporous silica. A flexible luminescent fiber material was prepared using poly (lactic acid) (PLA) as the substrate, demonstrating improved hydrophobicity and stable optical properties. The material exhibited a contact angle of 99.7° and maintained 82.2% of its fluorescence intensity after 30days at room temperature. These findings highlight its significant potential for optical applications.

Research on mechanical properties and pore structure evolution process of steam cured high strength concrete under freeze thaw cycles.

With the widespread use of high-strength concrete structures (HC), the impact of pore structure on their performance has become a current research focus. The mechanism by which different curing conditions and freeze-thaw cycles influence the evolution of pore structure remains unclear. Therefore, this study systematically investigated the frost resistance of high-strength concrete under different curing conditions, measured the mass loss rate, compressive strength, and relative dynamic elastic modulus of concrete under freeze-thaw cycles. Utilizing low-field nuclear magnetic resonance (NMR) technology, this study analyzed the evolution of pore structure in HC under freeze-thaw cycles. Additionally, the fractal dimension was used to evaluate the change of concrete internal pore structure, so as to reflect the influence of pore structure on the mechanical properties of concrete subjected to freeze-thaw cycles, and then evaluated the freeze-thaw damage of HC. The experimental results indicated that the steam curing regimes led to an increase in the porosity of HC, thereby influencing its frost resistance. Steam-cured high-strength concrete (SMHC) exhibited a higher degradation rate under freeze-thaw cycles, resulting in a greater level of deterioration compared to standard curing high-strength concrete (SDHC), even under the same number of freeze-thaw cycles.

Achieving Ultra-High Heat Flux Transfer in Graphene Films via Tunable Gas Escape Channels.

Graphene films have been applied in the thermal management of electronic devices due to their high thermal conductivity. However, the ever-increasing power and local heat flux density of electronic chips require graphene films with excellent heat flux carrying capacity. Enhancing the heat flux carrying capacity is highly challenging, and the key is to maintain high thermal conductivity while increasing film thickness. Gases released during film assembly and the resulting catastrophic structural destruction should be responsible for the trade-off between film thickness and thermal conductivity. Herein, the evolution of the pore structure is investigated during the assembly of graphene films and propose the construction of gas escape channels for the preparation of thick graphene films. The process involves using humidification treatment and freeze-drying GO films to pre-construct the ordered flat pore structure. The microstructure optimization of graphene films with more order, fewer wrinkles and defects, and larger grain size is achieved. After optimization, graphene films with ultra-high thermal conductivity (1781Wm-1K-1) and a thickness over 100µm are realized. These films exhibit exceptional heat dissipation and cooling capabilities in high heat flux density (≈2000Wcm-2). This finding holds significant potential for guiding the thermal management of high-power devices.

Ingrown Leading to Hierarchical SAPO‐34 with High Catalytic Activity

AbstractIntroduce meso/macro‐pore to the crystal of SAPO‐34 is an efficient way to overcome its inherent diffusion resistance. Porogen, formation hierarchical structure by inhibiting the growth of the crystals, would increase the costs of SAPO‐34 and is usually not friendly to environment. In this work, an ingrowth route to synthesize hierarchical SAPO‐34 is developed by secondary silica addition via hydrothermal method. Hierarchical porous SAPO‐34 was synthesized without adding any pore‐generating agent. Secondary silica addition put off the Si and P transferring from the mother liquid to gel phase, leading to the chemical composition of surface first meeting to the crystallization conditions. Then the crystallization started from the surface to the inside of the amorphous particles. The hierarchical SAPO‐34 showed numerous meso/macro pore structure and weaker acid strength. So the hierarchical SAPO‐34 showed better catalytic activity than the conventional SAPO‐34 in MTO reaction.

The Mesoscopic Damage Mechanism of Jointed Sandstone Subjected to the Action of Dry–Wet Alternating Cycles

The effect of the dry–wet cycle, characterized by periodic water level changes in the Three Gorges Reservoir, will severely degrade the bearing performance of rock formations. In order to explore the effect of the dry–wet cycle on the mesoscopic damage mechanism of jointed sandstone, a list of meso-experiments was carried out on sandstone subjected to dry–wet cycles. The pore structure, throat features and mesoscopic damage evolution of jointed sandstone with the action of the dry–wet cycle were analyzed using a-low-field nuclear magnetic resonance (NMR) technique. Subsequently, the impact on the mineral content of dry–wet cycles was studied by small angle X-ray scattering (SAXS). Based on this, the mesoscopic damage mechanism of sandstone subjected to dry–wet cycles was revealed. The results show that the effects of the drying–wetting cycle can promote the development of porous channels within sandstone, resulting in cumulative damage. Besides, with an increase in dry–wet cycles, the proportion of small pores and pore throats decreased, while the proportion of medium and large pores and pore throats increased. The combined effects of extrusion crush, tensile fracture, chemical reaction and dissolution of minerals inside the jointed sandstone contributed to the development of mesoscopic pores, resulting in the increase of porosity and permeability of rock samples under the dry–wet cycles. The results provide an important reference value for the stability evaluation of rock mass engineering under long-term dry–wet alternation.

Multifractal Methods in Characterizing Pore Structure Heterogeneity During Hydrous Pyrolysis of Lacustrine Shale

By using gas physisorption and multifractal theory, this study analyzes pore structure heterogeneity and influencing factors during thermal maturation of naturally immature but artificially matured shale from the Kongdian Formation after being subjected to hydrous pyrolysis from 250 °C to 425 °C. As thermal maturity increases, the transformation of organic matter, generation, retention, and expulsion of hydrocarbons, and formation of various pore types, lead to changes in pore structure heterogeneity. The entire process is divided into three stages: bitumen generation stage (250–300 °C), oil generation stage (325–375 °C), and oil cracking stage (400–425 °C). During the bitumen generation stage, retained hydrocarbons decrease total-pore and mesopore volumes. Fractal parameters ΔD indicative of pore connectivity shows little change, while Hurst exponent H values for pore structure heterogeneity drop significantly, indicating reduced pore connectivity due to bitumen clogging. During the peak oil generation stage, both ΔD and H values increase, indicating enhanced pore heterogeneity and connectivity due to the expulsion of retained hydrocarbons. In the oil cracking stage, ΔD increases significantly, and H value rises slowly, attributed to the generation of gaseous hydrocarbons further consuming retained hydrocarbons and organic matter, forming more small-diameter pores and increased pore heterogeneity. A strongly negative correlation between ΔD and retained hydrocarbon content, and a strongly positive correlation with gaseous hydrocarbon yield, highlight the dynamic interaction between hydrocarbon phases and pore structure evolution. This study overall provides valuable insights for petroleum generation, storage, and production.

Investigation on the transmission of Love waves due to an impulsive line source in a heterogeneous double porous rock structure.

The region around the reservoir sometimes encounters the seismic response of ground. The phenomena of Love waves propagation also caused by seismic activity which can further significantly influenced by an impulsive line source present in the rock structures of ground. The current study elucidates the propagation behavior of Love waves induced by an impulsive line source within the anisotropic layered heterogeneous double porous rock structures commonly found in proximity to the reservoir areas. The expression of the dispersion relation for the Love waves propagation due to an impulsive line source has been derived by using the Fourier transformation and Green's function technique. The above-mentioned rock composite structure is consisted of two different portions: upper transversely isotropic double porous (TIDP) layer medium and lower heterogeneous isotropic double porous half-space (IDP) medium. In the aforesaid half-space medium, both types of heterogeneities viz. linear and quadratic have been considered. The impacts of heterogeneity parameters associated with the lower heterogeneous IDP half-space, porosity parameter (corresponds to both upper TIDP layer and lower IDP half-space) and anisotropic parameter of TIDP layer on Love waves phase velocity have also been studied. Some special outlines have also been depicted graphically.

Innovative COF@MXene composites for high performance energy applications

AbstractAs a new type of composite two-dimensional material formed by the combination of Covalent Organic Frameworks (COFs) and two- dimensional (2D) MXenes, COF/MXene heterostructures (COF@MXene) inherit the stable porous two-dimensional structure of COFs and the excellent electrochemical performance and catalytic activity of MXenes, thus attracting widespread attention. Additionally, COF@MXene possesses various elemental affinity sites, efficient ion channels, and the ability to append various functional groups, which endow them with tremendous potential in electrochemical energy storage, energy conversion, and catalysis. Currently, there is a lack of extensive literature discussing the utilization of COF@MXene. The quest for enhanced physicochemical attributes through tailored modifications and composite strategies for COF@MXene is still a noteworthy hurdle. Furthermore, discovering novel application contexts that can harness the exceptional capabilities of these materials presents a formidable task. This review initiates with an exploration of the primary methodologies for synthesizing COF and MXene composites. Subsequently, it outlines the diverse applications of COF and MXene in energy storage, energy conversion, and environmental conservation. Lastly, it discusses the primary obstacles and future trajectories within these domains.