Search Results (2,128)

Lithium slag (LS), a solid waste generated during lithium smelting, exhibits significant potential for geopolymer preparation. However, the high shrinkage of lithium slag geopolymer mortar (LSGM) severely restricts its engineering application. Currently, research on the effects of mix proportions (GBFS-LS mass ratio, water–binder ratio, and binder–sand ratio) on LSGM’s shrinkage, and the correlation between shrinkage behavior and microstructures (pore structure and thermal behavior), remains insufficient. Additionally, there is a lack of targeted shrinkage prediction models for LSGM. To address these research gaps, this study systematically investigates the shrinkage characteristics of LSGM and develops a modified prediction model. Thermogravimetric analysis–differential thermal gravimetric analysis (TG-DTG) results show that a lower GBFS-LS ratio promotes the formation of dense sodium-alumino-silicate hydrate (N-A-S-H) gels. Meanwhile, mercury intrusion porosimetry (MIP) tests demonstrate that optimizing the water–binder ratio and binder–sand ratio refines the pore structure of LSGM, where the average pore size is reduced from 53.5 nm at a GBFS-LS ratio of 3 to 28.75 nm at a GBFS-LS ratio of 1.5.Quantitatively; compared with the group with a GBFS-LS ratio of 3, the 90-day shrinkage strain of the group with a GBFS-LS ratio of 1.5 decreases by 25.8%. When the water–binder ratio decreases from 0.57 to 0.27, the 90-day shrinkage strain reduces by 36.7%; in contrast, increasing the binder–sand ratio from 0.21 to 0.39 leads to a 39.8% increase in 90-day shrinkage strain. Based on the experimental data and the fundamental framework of the American Concrete Institute (ACI) model, this study introduces mix proportion influence coefficients and constructs a novel shrinkage prediction model tailored to LSGM. The coefficient of determination (R²) of the proposed model exceeds 0.98. This model provides a reliable quantitative tool for the mix proportion optimization and engineering application of LSGM. Full article

Magnetic biochar (Zn/Fe-BC) was prepared from jujube branches via an impregnation pyrolysis–coprecipitation technique to eliminate Cr(VI) from water. ZnFe₂O₄ was introduced through ZnCl₂-based impregnation and pyrolysis, which can regulate the microstructure of hydrocarbon frameworks. Furthermore, FeSO₄·7H₂O was used as the precursor for co-precipitation to embed Fe₃O₄ into the material, improving its reducibility and magnetism. The results demonstrated that Zn/Fe-BC exhibited excellent Cr(VI) removal efficiency. Under optimal conditions (an initial Cr(VI) concentration of 50 mg/L, pH 2, and an adsorbent dosage of 2 g/L), the maximum adsorption capacity of Zn/Fe-BC reached 27.85 mg/g, which was significantly higher than that of unmodified biochar (23.20 mg/g). Following five cycles of adsorption and desorption, the desorption efficiency was still higher than 60.35%. The following were the inhibitory effects of coexisting anions on the elimination of Cr(VI): CO₃²⁻ > PO₄³⁻ > SO₄²⁻ > NO₃⁻. According to kinetic and isothermal adsorption experiments, the adsorption process adhered to the Freundlich isotherm and followed a pseudo-second-order kinetic model, indicating a multilayer adsorption process. Cr(VI) removal by Zn/Fe-BC was driven by physical adsorption and chemical reduction, involving a synergistic combination of electrostatic attraction, reduction, complexation, precipitation, and pore filling. These findings demonstrate the potential of the Zn/Fe-BC magnetic biochar as an effective adsorbent for Cr(VI) remediation in water treatment applications. Full article

The pore structure of cocopeat-based substrates critically influences their hydraulic properties, directly affecting water use efficiency in soilless cultivation systems. Previous macroscopic modeling approaches infer pore structures indirectly from water retention curves and rely on empirical parameterization of pore geometry and connectivity, overlooking microscale features that directly control fluid pathways and permeability. To address this gap, this study employed micro-CT imaging to reconstruct the three-dimensional pore structures of coarse cocopeat and a fine cocopeat–perlite mixture. Nine regions of interest (ROIs), representing three typical pore types in each substrate, were selected for quantitative pore structure analysis and pore-scale saturated flow simulations. Results show that over 90% of pore diameters in both substrates fall within the 0–400 μm range, and variations in cocopeat particle size and perlite addition significantly affect average pore diameter, porosity, fractal dimension, and tortuosity, thereby influencing permeability and local flow distribution. This study provides new insights into the microscale mechanisms governing water movement in cocopeat-based substrates and reveals key structural factors regulating hydraulic behavior in soilless cultivation systems. Full article

To overcome the limitations imposed by the anisotropy and heterogeneity of natural loess, this study establishes a novel quantitative macro–micro correlation framework for investigating the deformation mechanisms of artificial structural loess (ASL). ASL samples were prepared by mixing remolded loess with cement (0–4%) and NaCl (0–16%), followed by static compaction (95% degree) and 28-day curing (20 ± 2 °C, >90% RH) to replicate the structural properties of natural loess under controlled conditions. An integrated experimental methodology was employed, incorporating consolidation/collapsibility tests, particle size analysis, X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). A three-dimensional nonlinear model was proposed. The findings show that intergranular cementation, particle size distribution, and pore architecture are the main factors influencing loess’s compressibility and collapsibility. A critical transition from medium to low compressibility was observed at cement content ≥1% and moisture content ≤16%. A strong correlation (Pearson |r| > 0.96) was identified between the mesopore volume ratio and the collapsibility coefficient. The innovation of this study lies in the establishment of a three-dimensional nonlinear model that quantitatively correlates key microstructural parameters (fractal dimension value (D), clay mineral ratio (C), and large and medium porosity (n)) with macroscopic deformation indicators (porosity ratio (e) and collapsibility coefficient (δ_s)). The measured data and the model’s output agree quite well, with a determination coefficient (R²) of 0.893 for porosity and 0.746 for collapsibility, verifying the reliability of the model. This study provides a novel quantitative tool for loess deformation prediction, offering significant value for engineering settlement assessment in controlled cementation and moisture conditions, though its application to natural loess requires further validation. Full article

In this article, a Nd₂Fe₁₄B_p/2024Al composite was prepared using high-energy ball milling, magnetic field cold isostatic pressing, and microwave sintering. The influence of powder particle size on microstructure and mechanical properties was discussed. The experimental results demonstrated that a ball milling duration of 10 h yielded powders with an average particle size of 5 μm, resulting in a refined and homogeneous microstructure, with a hardness value of 115 HV. Additionally, the densification process of the microwave-sintered sample was analyzed. When the sintering temperature was 490 °C, in-depth analysis was conducted on the effect of Nd₂Fe₁₄B addition on the microstructure and properties of the composite. The results showed that when the addition of Nd₂Fe₁₄B was 15 wt.%, the microstructure of the composite was uniform with fewer pores, and the Nd₂Fe₁₄B phase was evenly distributed on the matrix. At the same time, the compactness, microhardness, yield strength, and compressive strength of the composite also reached their optimal values, which were 94.3%, 136 HV, 190.5 MPa, and 248.9 MPa, respectively. When the addition of Nd₂Fe₁₄B reached 20 wt.%, the magnetic properties of the composite were slightly better than those of 15 wt.% Nd₂Fe₁₄B addition. However, based on the goal of preparing a high-magnetic and high-performance aluminum-based composite, considering the microstructure, mechanical properties, and magnetic properties comprehensively, it is believed that 15 wt.% is the optimal addition amount of Nd₂Fe₁₄B. Full article

Biomass-derived hard carbon (BHC) has attracted considerable attention as a sustainable and cost-effective anode material for sodium-ion batteries (SIBs), owing to its natural abundance, environmental friendliness, and promising electrochemical performance. This review provides a detailed overview of recent progress in the synthesis, structural design, and performance optimization of BHC materials. It encompasses key fabrication routes, such as high-temperature pyrolysis, hydrothermal pretreatment, chemical and physical activation, heteroatom doping, and templating techniques, that have been employed to control pore architecture, defect density, and interlayer spacing. Among these strategies, activation-assisted pyrolysis and heteroatom doping have shown the most significant improvements in sodium (Na) storage capacity and long-term cycling stability. The review further explores the correlations between microstructure and electrochemical behavior, outlines the main challenges limiting large-scale application, and proposes future research directions toward scalable production and integration of BHC anodes in practical SIB systems. Overall, these advancements highlight the strong potential of BHC as a next-generation anode for grid-level and renewable energy storage technologies. Full article

Concrete structures are vulnerable to sulfate attacks during their service life, as sulfate ions react with cement hydration products to form expansive phases, generating internal stresses that cause mechanical degradation. In this study, a cementitious capillary crystalline waterproofing material (CCCW) was incorporated into concrete to mitigate sulfate ingress and enhance sulfate resistance. The evolution of compressive strength, ultrasonic pulse velocity, dynamic elastic modulus, and the microstructure of concrete was investigated in sulfate-exposed concretes with varying CCCW dosages and strength grades; the sulfate ion concentration profiles were also analyzed. The results indicate that the enhancement effect of CCCW on sulfate resistance declines progressively with increasing concrete strength. The formation of calcium silicate hydrate and calcium carbonate fills the pores of concrete, hindering the intrusion of sulfate solution. Moreover, the self-healing effect of concrete further inhibits the diffusion of sulfate ions through cracks, improving the sulfate resistance of concrete. These findings provide critical insights and practical guidance for improving concrete resistance to sulfate-induced deterioration. Full article

This study introduces an innovative approach to addressing the plastic shrinkage of ultra-high-performance concrete (UHPC) using an azodicarbonamide (ADC) expansive agent. The influence of ADC on the workability, mechanical properties, and plastic shrinkage of UHPC were systematically investigated. The findings reveal that the addition of ADC generates a substantial number of bubbles within the UHPC slurry, thereby reducing internal frictional resistance and cohesion of the mixture. Consequently, the fluidity and setting time of UHPC were enhanced to varying degrees with increasing ADC content. However, the introduction of these bubbles also reduced the density, leading to a noticeable decline in both compressive and flexural strength, particularly at later stages. Notably, ADC effectively mitigated early shrinkage and increased the vertical expansion rate within the first 24 h. When the ADC dosage ranged from 0.04% to 0.1%, the UHPC remained in an expanded state within 24 h, with a notable difference in expansion rate exceeding 0.02% from 3 to 24 h. Microstructural and pore structure analysis revealed that the ADC generated considerable gas during the mixing process, forming numerous micropores within the UHPC matrix. These dispersed pores contributed to reduced compactness of the UHPC hydrates, resulting in increased pore area, porosity, and average pore diameter. Full article

This study explores the influence of vibration timing on the performance of high early-strength cement-based composites used in bridge wet joints. A series of experimental techniques, including SEM, MIP, and RCM tests, were employed to evaluate microstructural evolution, mechanical properties, and durability. The results indicate that vibration applied between the initial and final setting phases has a critical impact, significantly reducing early-age compressive, flexural, and bond strengths. This deterioration is mainly attributed to micro-crack formation and enhanced pore connectivity, as confirmed by SEM and MIP analyses. Moreover, vibration markedly increases the chloride diffusion coefficient, particularly in mixtures with higher water-to-binder ratios, thereby raising long-term durability concerns. These findings underscore the necessity of optimizing mix proportions and strictly controlling vibration timing to ensure both the mechanical performance and service life of high early-strength cement composites in bridge construction. The study provides practical insights for the design and application of durable, resilient bridge wet joints. Full article

This study investigates the air filtration capabilities of fibrous membranes fabricated via electrospinning, with a focus on optimizing processing parameters. Specifically, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a well-characterized biodegradable polyester, was electrospun to produce membranes exhibiting precisely controlled surface microstructures. The optimal fiber morphology was attained under conditions of a 20 kV applied electric field, a solution flow rate of 0.5 mL·h⁻¹, a polymer concentration of 13 wt.%, and a needle inner diameter of 0.21 mm. The microstructural features of the electrospun PHBV membranes were characterized using scanning electron microscopy (SEM). Complementary analysis via ¹³C nuclear magnetic resonance (NMR) spectroscopy confirmed that the membranes comprised pure 3-hydroxyvalerate (3HV) copolymerized with 3-hydroxybutyrate (3HB) terminal units, with 3HV mole fractions ranging from 17% to 50%. The incorporation of different molar percentages of 3HV in PHBV membrane significantly enhances its durability, as evidenced by Ball Burst Strength (BBS) measurements, with an elongation at burst that is 65–86% greater than that of ASTM F2100 level 3 mask. The nanofibrous membranes exhibited a controlled pore size distribution, indicating their potential suitability for air filtration applications. Particle filtration efficiency (PFE) assessments under standard atmospheric pressure conditions showed that the optimized electrospun PHBV membranes achieved filtration efficiencies exceeding 98%. Additionally, the influence of 3HV content on biodegradation behavior was evaluated through soil burial tests conducted over 90 days. Results indicated that membranes with lower 3HV content (17 mol.%) experienced the greatest weight loss, suggesting accelerated degradation in natural soil environments. Full article

Nanomaterials play a beneficial role in regulating the function of cement-based materials. The effects and mechanism of graphene oxide (GO) on foam behavior in solutions and air-entraining behavior of cement mortar were studied, and its effect on the microstructure of cement mortar was also investigated. The results show that a synergy between GO’s hydrophobicity and the air-entraining agent’s hydrophobic chains drove more agent molecules to adsorb onto the GO surface, subsequently spreading and aggregating across the bubbles. GO effectively assisted the air entraining agent to refine the bubble size, improved the bubble stability of aqueous solutions, and had excellent air entraining performance in the fresh cement mortar, as well as the optimum air-void adjustment performance of hardened cement mortars. With the addition of 0.4‰ GO, the loss rate of gas content in the GO mixed mortar was 10.3%, which was 55.8% lower than that when only using AEA. The addition of 0.4‰ of GO effectively increased the volume fraction of the cement mortar system. GO reduced the pore volume in the mortar through the filling effect and nucleation effect to reduce the total porosity and refine the microstructure of the mortar. Full article

Metal/composite interfacial interactions are critical to the mechanical performance of Fiber Metal Laminates (FMLs). In this study, the feasibility of successively combining Vacuum-Assisted Resin Transfer Molding (VARTM) and Vacuum Bagging (VB) was investigated, a strategy that has not been reported in the literature for the fabrication of FMLs with 2/1 stacking configuration, using low-cost 3003-H14 aluminum alloy. The substrate was surface modified through mechanical abrasion and chemical etching in an ultrasonic bath with a 0.1 M NaOH solution, varying the exposure time (20, 40, and 60 min). These surfaces were characterized by optical microscopy and atomic force microscopy (AFM), conducting both qualitative and quantitative analyses of the two- and three-dimensional surface features associated with pore morphology. Additionally, their effects on interlaminar strength and Mode I failure modes of the adhesive joint at the metal/composite interface were evaluated. Micrographs of the surface variants revealed a systematic evolution of the metallic microstructure. The T-peel tests demonstrated that the microstructural features influenced the interlaminar behavior. The 40 min treatment exhibited the highest initial peak force (26.4 N) and the highest average peel force (12.4 N), with a predominantly cohesive mixed-mode failure, representing the most favorable configuration for maximizing adhesion at the metal/composite interface. Full article

The increasing demand for reliable, sensitive, and cost-effective gas sensors drives ongoing research in this field. Ideal gas sensors must demonstrate high sensitivity and selectivity, stability, rapid response and recovery times, energy efficiency, and affordability. One-dimensional (1D) metal oxide semiconductors (MOSs) are prominent candidates due to their excellent sensing properties and straightforward fabrication processes. The sensing efficacy of 1D MOSs is heavily dependent on their surface area and porosity, which influence gas interaction and detection efficiency. Polymeric templates serve as effective tools for enhancing these properties by enabling the creation of uniform, porous nanostructures with high surface area, thereby improving gas adsorption, sensitivity, and dynamic response characteristics. This review systematically examines the role of polymeric templates in the construction of 1D MOSs for gas sensing applications. It discusses critical factors influencing polymer template selection and how this choice affects key microstructural parameters, such as grain size, pore distribution, and defect density, essential to sensor performance. The recent literature highlights the mechanisms through which polymer templates facilitate the fine-tuning of nanostructures. Future research directions include exploring novel polymer architectures, developing scalable synthesis methods, and integrating these sensors with emerging technologies. Full article

Geopolymers, as a novel class of low-carbon and eco-friendly cementitious material, exhibit outstanding durability and promote the resource utilization of industrial solid wastes. However, as a promising alternative to ordinary Portland cement, its susceptibility to carbonation-induced degradation may limit its widespread application. To address this challenge, this study systematically examined the effects of magnesium oxide (MgO) content and the metakaolin-to-fly ash ratio on the carbonation performance, mechanical properties, pH value, and microstructures of metakaolin–fly ash-based (MF-based) geopolymer pastes. The findings revealed that an increase in the fly ash ratio correlated with a decline in the compressive strength of MF-based geopolymer pastes. Conversely, the incorporation of MgO significantly enhanced the compressive strength, with higher fly ash ratios leading to more substantial improvements in strength. Furthermore, the addition of MgO and fly ash effectively mitigated the penetration of carbonation and the associated decrease in the pH value of the MF-based geopolymer pastes. Specifically, compared to the control group without MgO (M8F2-0%), MF-based geopolymer pastes with 4% and 8% MgO additions exhibited reductions in carbonation depth of 69.4% and 80.4%, respectively, after 28 days of carbonation, while pH values were observed to be 1.22 and 1.15 units higher, respectively. Additionally, microscopic structural analysis revealed that the inclusion of MgO resulted in a reduction in pore size, porosity, and mean pore diameter within the geopolymer pastes. This improvement was mainly attributed to the promotion of hydration processes by MgO, leading to the formation of fine Mg(OH)₂ crystals within the high-alkalinity pore solution, which enhances microstructural densification. In conclusion, the incorporation of MgO significantly improves the carbonation resistance and mechanical performance of MF-based geopolymers. It is recommended that future studies explore the long-term performance under combined environmental actions and evaluate the economic and environmental benefits of MgO-modified geopolymers for large-scale applications. Full article

Well cementing is an important step in oil and gas development. It uses cement to seal the formation and the casing, preventing fluid leakage. However, when conducting offshore oil well cementing operations, deep-water formations are usually weakly consolidated soils, and it is difficult to form a good cementation between the cement and formation. Therefore, enhancing the strength of the formation is one of the effective measures. This study uses the microbial-induced carbonate precipitation technology to cement sandy formations containing clay minerals. The triaxial tests were conducted to evaluate the consolidation effectiveness in the presence of three clay minerals: montmorillonite, illite, and kaolinite. X-ray computed tomography was utilized to characterize microscopic pore parameters, while thermogravimetric analysis, X-ray diffraction, and surface potential measurements were applied to analyze the mechanisms of clay minerals affecting microbial consolidation. The results showed that microbial mineralization mainly affects the cohesion of the samples. The cohesion of the montmorillonite sample increased from 20 kPa to 65.4 kPa, an increase of up to 3.27 times. The other two samples (illite and kaolinite) had increases of only 0.33 times and 1.82 times. Although the strength of the montmorillonite sample increased the most, unexpected large pores appeared with a diameter of over 120 µm, accounting for 7.1%. This is mainly attributed to the mineral expansion property. The expansion of the minerals will trap more microorganisms in the sample, thereby generating more calcium carbonate. And it also reduced the gaps between sand particles, creating favorable conditions for the connection of calcium carbonate. Although the surface charge of the minerals also affects the attachment of microorganisms, all three minerals have negative charges and a difference of no more than 0.84 mV (pH = 9). Therefore, the expansion property of the minerals is the dominant factor affecting the mechanical and microstructure of the sample. Full article