Search Results (2,547)

Red mud-based backfill containing circulating fluidized bed (CFB) ash and reactive MgO must maintain adequate mechanical integrity and environmental stability under moisture and alkaline exposure. This study investigated the durability of carbonation-solidified red mud-based backfill subjected to wetting–drying cycles and alkaline red mud liquor (RML) immersion. Specimens carbonated for 0, 2, 4, 6, 8, and 10 h were evaluated in terms of macroscopic morphology, mass loss, linear shrinkage, unconfined compressive strength (UCS), electrical resistivity, pH, hazardous-element leaching, scanning electron microscopy, and X-ray diffraction. Increasing carbonation duration generally reduced mass loss and linear shrinkage while improving UCS and electrical resistivity within the investigated exposure range. Wetting–drying cycling resulted in progressive surface erosion, shrinkage, and strength deterioration. By contrast, RML immersion produced an initial increase in UCS and resistivity, followed by stabilization or a slight decline at later ages. The observed changes were consistent with pore filling by carbonate-bearing products and low-crystallinity reaction products, followed by local pore development and disruption of the cemented structure during prolonged exposure. At a UCS threshold of 0.8 MPa, the response-surface models yielded estimated threshold exposures of 6.92–13.98 cycles under wetting–drying conditions and 45.69–75.05 d under RML immersion, with the RML estimates extrapolated from the 28 d dataset. Within the tested conditions, carbonation improved the resistance of the backfill material to cyclic moisture disturbance and alkaline immersion, with the 8–10 h groups retaining relatively higher mechanical and dimensional performance. Full article

Pitting corrosion is a more insidious and dangerous failure mode than uniform corrosion for protective coatings in marine environments, especially when sulfide ions (S²⁻) are present. In this work, Inconel 625 (IN625) and IN625-5 wt.% yttria-stabilized zirconia (YSZ) composite coatings were fabricated on 20G steel by laser-directed energy deposition (LDED) using optimized parameters. The coatings exhibit dense microstructures, with porosities of 1.87% ± 0.10% and 1.67% ± 0.10%, respectively. The pitting resistance was systematically evaluated by cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution without and with 20 ppm Na₂S. The CPP results show that the addition of YSZ decreases the pitting potential (E_pit) and protection potential (E_prot), indicating reduced resistance to pit initiation, while the smaller hysteresis loop suggests an improved tendency for repassivation. S²⁻ induces a notable drop in E_prot and impairs repassivation for both coatings, yet the IN625-YSZ coating retains a slightly higher E_prot than IN625. EIS analysis reveals that the IN625-YSZ coating in S²⁻-containing solution shows an increased R_ct of 2.738 × 10⁵ Ω·cm² compared with its counterpart in 3.5 wt.% NaCl solution, while the corresponding R_L decreases to 2.513 Ω·cm², suggesting a weakened outer barrier layer despite partial interfacial blocking. Post-corrosion morphology shows that YSZ particles act as preferential pitting nucleation sites; in sulfide-free solution they produce numerous shallow pits, whereas in S²⁻-containing solution they lead to larger and deeper pits. The results may provide a reference for the future design and evaluation of LDED-manufactured composite coatings under sulfide-containing marine environments. Full article

Be–Al alloys are attractive for aerospace and precision-engineering applications because of their low density, high specific stiffness, and excellent dimensional stability. However, their broader application is constrained by multiscale defects arising from the low mutual solubility of Be and Al, their large melting-point difference, and the high reactivity of the Be/Al interface. This review critically examines defect formation and microstructural evolution in Be–Al alloys produced by casting, powder metallurgy, pressure infiltration, thermomechanical processing, and additive manufacturing, with particular emphasis on additive manufacturing. Rapid solidification can refine the Be-rich phase and suppress coarse segregation, but unstable melt-pool behavior, restricted gas escape, cyclic thermal loading, and insufficient interfacial diffusion may also promote porosity, compositional heterogeneity, residual stress, and interfacial degradation. The mechanical properties of Be–Al alloys depend strongly on Be-phase morphology, continuity of the Al matrix, interfacial integrity, and the spatial distribution of processing-induced defects. Recent progress in alloy design, process optimization, interfacial engineering, and post-processing is evaluated, together with the limitations of the available evidence. Future research should establish quantitative processing–defect–microstructure–property relationships through in situ monitoring, multiscale characterization, predictive modeling, and standardized mechanical validation. These advances are essential for the reliable manufacture of complex, high-performance Be–Al components. Full article

This work presents the use of an unmodified fluorine-doped tin oxide (FTO) electrode as an electrochemical sensor for the stable and highly reproducible detection of cannabidiol (CBD) in an oral pharmaceutical formulation (CBD-OS). This was achieved using an electrochemical methodology with 0.1 M LiClO₄ in acetonitrile as the electrolyte medium. The oxidation process of CBD on the FTO was extensively studied using cyclic voltammetry to analyze the influence of forced convection during the experiment. Quantification was performed by differential pulse voltammetry with standard addition to the dissolved CBD oral oil (CBD-OS), which allowed for the determination of a detection limit of 4.8 µM and a correlation coefficient R² = 0.9989. Statistical tests indicated no significant differences between the proposed electrochemical methodology and HPLC. The FTO electrode exhibited high reproducibility, withstanding more than 20 consecutive additions to the same electrode without loss of response, thanks to its intrinsic stability and the strategic use of forced convection. The use of an unmodified electrode enabled the development of a simple, reproducible, robust, and cost-effective analytical methodology for CBD analysis in pharmaceutical samples. 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

To address the critical limitations of traditional photothermal–responsive epoxy–based shape memory polymers (ESMPs), such as poor compatibility and cyclical instability, a series of side–chain azobenzene (Azo)–functionalized linear ESMPs (EPDm) were successfully synthesized via chemical bonding. Highly rigid 4–aminoazobenzene (Azodm) units were covalently integrated into the Bisphenol A–type epoxy backbone as functional photo–responsive side chains. Systematic characterizations confirmed that the glass transition temperature (T_g) of the EPDm polymers could be precisely tuned from 41.53 °C to 53.26 °C by adjusting the Azodm content. Benefiting from the proposed homogeneous covalent architecture, the EPDm films exhibited superior photothermal sequential behavior and remarkable shape memory stability despite a slight reduction in tensile strength (≈10–12 MPa). Under 365 nm UV irradiation, the pre–stretched EPDm₁₀ specimen achieved a rapid macroscopic bending angle of over 150° within 15 s, driven exclusively by the trans–to–cis molecular photoisomerization of the Azo side chains well below the matrix T_g. Furthermore, standard shape memory cycles demonstrated excellent shape fixity (R_f > 98%) and recovery (R_r > 95%) ratios, alongside exceptional anti–fatigue performance with minimal strain variance (≈5%) over consecutive cycles. This work establishes a robust and high–efficiency molecular design strategy for photo–thermally sequentially responsive shape memory polymers, offering immense potential for smart actuators and flexible electronics. Full article

The positional arrangement of BN and CC units in B₆C₆N₆ cyclic nanorings profoundly influences their stability, electronic structure, optical response, and reactivity. Here, we comparatively investigate eight positional isomers (C1–C8) using DFT and TD-DFT calculations. Among C1–C8, C1 is the most stable, and C8 is the most unstable in the range of 200–1000 K. Their relative stability is governed by B-N charge separation, homonuclear B-B and N-N defects (charge repulsion), and bond-angle distortion (ring tension). The HOMO–LUMO gaps range from 4.40 eV (C3) to 8.45 eV (C2), indicating distinct kinetic stability. Aromaticity analysis reveals that all isomers are nonaromatic. In the gas phase, the lowest-energy absorption bands of C1 and C3 are located at about 429 nm and 606 nm, respectively. Due to different transition mechanisms, namely locally excited (LE) for the former and charge-transfer (CT) for the latter, solvent polarity has dramatically different influence on these two absorption bands. Compared to their positions in the gas phase, these absorption bands are blue-shifted about 20 nm and 220 nm in water, respectively. Reactivity analysis identifies the B-B bond in C7 as the strongest electrophilic site (LEAE = −2.93 eV), with the surrounding framework serving as nucleophilic domains, endowing C7 with the strongest bifunctional reactivity. This work establishes a comprehensive structure–property map for B₆C₆N₆ isomers, providing guidance for designing BCN-based nanorings for catalysis, molecular recognition, and optoelectronics. Full article

A high-performance Z-scheme Ho₂BiNbO₇/ZnBiTmO₄ heterojunction (HZ) photocatalyst was prepared for the first time using a wet impregnation method. The HZ photocatalyst significantly improved the separation efficiency of the photoinduced electrons and the photoinduced holes; meanwhile, the HZ photocatalyst could effectively broaden the visible light spectrum via a specific mechanism of the Z-scheme heterojunction structure. The experimental results displayed that the HZ photocatalyst had strong catalytic activity when the brilliant green (BLG) was degraded. In particular, the degradation rate of BLG when using the HZ photocatalyst was found to be 99.47%, and the mineralization efficiency of the total organic carbon (TOC) concentration was found to be 98.26% when using the HZ photocatalyst under visible light irradiation (VILIIR). The HZ photocatalyst possessed higher photocatalytic activity compared with Ho₂BiNbO₇, ZnBiTmO₄, or N-doped TiO₂ (N-T). The degradation rate of BLG when using the HZ photocatalyst was 1.27 times higher than that when using Ho₂BiNbO₇, 1.15 times higher than that when employing ZnBiTmO₄, or 2.91 times higher than that when using N-T under VILIIR. The mineralization efficiency of the TOC concentration after catalytic degradation of BLG when employing the HZ photocatalyst was 1.31 times higher than that when employing Ho₂BiNbO₇, 1.19 times higher than that when employing ZnBiTmO₄, or 3.14 times higher than that when using N-T under VILIIR. The experimental generating radicals confirmed that the HZ photocatalyst might produce diverse reactive radicals, which contained superoxide anions (•O₂⁻), hydroxyl radicals (•OH) and photogenerated holes (h⁺) after catalytic degradation of BLG. The descending order of oxidizing capacity for above three radicals was as follows: •OH > •O₂⁻ > h⁺. The descending order of the photocatalytic activity for the four photocatalysts was as follows: HZ > ZnBiTmO₄ > Ho₂BiNbO₇ > N-T. The intermediate degradation products of BLG were detected by employing the HZ photocatalyst during the photocatalytic degradation process of BLG; the reliability, reusability, and stability of the HZ photocatalyst were proven by quintic cyclical degradation experiments of BLG. This study developed the degradation pathways and degradation mechanism of BLG when using the HZ photocatalyst under VILIIR. This work supplies novel thought for the design and manufacture of Z-scheme heterojunction catalysts, and it provides a basis for developing an efficient environmental remediation technique for BLG pollution. Full article

Groundwater-related weakening and repeated low-strain-rate disturbances can jointly affect the long-term stability of soft surrounding rock. In this study, a PFC3D model was developed by combining a cumulative residual-strain damage variable with a Weibull statistical damage variable. Water effects were represented indirectly through water-content-dependent mesoscopic parameters and contact-strength degradation, thereby linking macroscopic irreversible deformation to progressive mesoscopic bond degradation. The cyclic responses of mudstone specimens with water contents of 0%, 3%, 5%, and 7.04% were simulated under a roadway-like three-directional, five-face boundary condition, consisting of axial loading, lateral pressure, one laterally constrained side, and one free face. The model reproduced the main stress–strain trends and failure characteristics. From the dry to saturated state, the experimental and simulated peak strengths decreased by 68.51% and 67.44%, respectively. Increasing water content also promoted earlier crack initiation, weakened strong force-chain continuity, and shifted failure from localized shear instability to distributed tensile–shear damage. Energy dissipation became increasingly important as water content increased. These findings clarify the mesoscopic damage mechanism of water-bearing mudstone under coupled water-induced softening and low-strain-rate cyclic loading, providing a reference for stability assessment and support design in underground soft-rock engineering. Full article

In this study, a lanthanum-modified MgAl double-layer hydroxide (La-LDH) was synthesized and investigated as a novel inorganic consolidant for gypsum, lime and cement-based mortars. The material was characterized by X-ray diffraction, WDXRF, SEM, dispersion stability analyses and DLS. XRD confirmed the formation of a hydrotalcite-like structure with secondary phases of lanthanum carbonate and hydroxylcarbonate, while SEM observations revealed a platelet-like morphology, typical of LDH materials. DLS analysis revealed a polydisperse granular distribution, with particle populations centered at approximately 99 and 383 nm, indicating the coexistence of nanometer sized LDH particles and larger aggregates within the consolidant dispersion. The prepared material (0.5 g/L) was dispersed in ethanol–water solution (40%:60%) and applied by brushing onto the specimens made for this purpose. The treatment resulted in minor chromatic variations (ΔE* < 1.5 for all substrates). No surface crusting, visible deposits or adverse aesthetic changes after treatment or accelerated ageing were observed. Of the substrates investigated, lime mortar showed the most pronounced response, indicating a 26.4% increase in surface cohesion, together with a substantial improvement in water permeability (up to 87%). In contrast, gypsum and cement mortars showed only limited improvements. Artificial ageing tests demonstrated good visual stability of the treated surfaces, while freeze–thaw tests indicated only minor changes in frost resistance. Salt crystallization tests showed that the treatment did not negatively affect the strength of any of the substrates investigated and, in several cases, delayed crack propagation and material loss during cyclic exposure to sodium sulphate solution. Full article

Ex situ hydrogen biomethanation represents a promising approach to converting surplus renewable electricity into CH₄-rich gas through the biological reduction in CO₂ with H₂, mediated by hydrogenotrophic methanogens. In this study, an ex situ H₂ biomethanation process was investigated in a lab-scale mesophilic anaerobic reactor operated in fed-batch mode. The system followed a cyclic operational strategy comprising sequential gas feeding, reaction, and discharge phases. Hydrogen was supplied through a pressure-controlled feeding strategy, whereas CO₂ injection maintained dissolved CO₂ concentrations at 25, 17, and 2 mg L⁻¹ during the initial, intermediate, and final stages, respectively. During early operation, volatile fatty acids (VFAs) temporarily accumulated to 3 g L⁻¹, accompanied by a decrease in pH. Progressively lowering the dissolved CO₂ target restored process stability, reduced the VFA concentration to 618 mg L⁻¹, and increased the pH to 7.6. Under stable final-stage conditions, the reactor achieved an average CH₄ concentration of 93.3%, a hydrogen utilization efficiency of 99%, and a methane evolution rate (MER) of 3.95 NL CH₄ L_VR⁻¹ d⁻¹. These results show that combining pressure-controlled hydrogen injection with dissolved CO₂ regulation enhances methane production and maintains stable ex situ biomethanation. Full article

Financial systems are highly nonlinear and often influenced by investment cycles, market fluctuations, and external financing activities, which can generate complex dynamic behaviors. This paper proposes a new three-dimensional chaotic financial firm model by extending the classical Bouali financial system through the inclusion of a cyclic reinvestment perturbation represented by a sinusoidal nonlinear term. The proposed modification aims to capture state-dependent nonlinear reinvestment feedback in reinvestment decisions caused by changing economic conditions and business cycles. The dynamical characteristics of the model are investigated using equilibrium analysis, local stability theory, Lyapunov exponents, the Kaplan–Yorke dimension, bifurcation analysis, and multistability analysis. Numerical results show that the system possesses three equilibrium points, all of which are unstable under the selected parameter setting. The system exhibits chaotic dynamics confirmed by a positive maximum Lyapunov exponent and a fractal attractor characterized by a Kaplan–Yorke dimension greater than two. Comparative results indicate that the new model demonstrates richer nonlinear dynamical behavior than existing financial firm systems reported in the literature. Furthermore, bifurcation and Lyapunov spectrum analyses disclose multiple transitions between periodic and chaotic states as system parameters vary, while multistability analysis reveals the coexistence of symmetric periodic and chaotic attractors under identical parameter values but different initial conditions. Finally, total amplitude control and offset boosting techniques are implemented to regulate attractor size and position while preserving the underlying chaotic behavior. These findings demonstrate that cyclic reinvestment perturbations significantly enrich the nonlinear dynamics and symmetry properties of financial firm systems, providing a useful framework for studying complex financial behaviors and chaos control. Full article

The extreme temperature cycling (−196 °C to 125 °C) and intense ultraviolet radiation on the lunar surface pose significant degradation risks to polymeric materials and their fibrous reinforcements. This work presents a comparative durability assessment between basalt fiber fabric and basalt rock powder after accelerated cyclic thermal shock treatments and UV exposure, aiming to establish a fundamental durability database for basalt fibers as candidate reinforcements for future polymer-matrix composites in lunar exploration. Multiscale characterizations reveal that regardless of the number of treatment cycles, the fiber surface morphology remains intact without cracking or etching. X-ray diffraction and Fourier-transform infrared spectroscopy confirm that the amorphous silicate network of the basalt fibers is well preserved, with no thermally induced recrystallization or compositional alteration. Thermogravimetric analysis further demonstrates that the treated fabrics retain the inherent thermal stability of pristine basalt, indirectly evidencing structural integrity. Importantly, the tensile strength of basalt yarns does not exhibit a cycle-dependent degradation trend, and the K/S colorimetric values remain stable even under combined thermal and UV exposure. Collectively, these findings confirm that basalt fiber fabric possesses exceptional resistance to lunar-mimetic aggressive environments, and its durability is comparable to that of natural basalt rock. Full article

Under cyclic loading, anchorage interfaces in anti-floating anchors may degrade, weakening bond strength and reducing bearing capacity, thereby compromising structural safety. Accordingly, understanding the mechanical behavior of anti-floating anchors while accounting for interface degradation is essential for ensuring the safety of underground structures. This study employs an elastic–plastic shear stress–shear displacement model that incorporates cyclic interface degradation, in which the degradation of interface strength and stiffness is governed by the number of loading cycles and the cyclic degradation parameters. By combining the load transfer method with the finite difference method, a mechanical analysis framework was developed for anti-floating anchors subjected to cyclic loading. The model was validated against published experimental data and then used to investigate interface stress distributions, load transfer mechanisms, and the effects of the number of loading cycles, load amplitude, and mean load. The results show that (1) under initial loading, the stress distribution along the anchoring interface progressively shifts toward the anchor tip as the load increases; (2) under cyclic loading, the bearing capacity of anti-floating anchors decreases continuously with increasing cycle numbers and stabilizes after reaching a certain number of cycles; (3) different initial interface strengths significantly influence the load transfer mechanism. High-strength interfaces can complete load transfer within a shorter anchorage length with more concentrated stress distribution, while low-strength interfaces enter the stable degradation stage earlier with more uniform stress distribution. The cyclic degradation parameter determines the degradation process and ultimate strength state of the interface. These findings provide practical guidance for controlling the long-term uplift deformation of underground structures, thereby helping to reduce the risk of basement upheaval and structural cracking in coastal environments with high groundwater levels. Full article

In this study, warm shot peening was applied to Ti-Al coatings to investigate its effect on high-temperature oxidation behavior at 800–1000 °C. WSP induced severe plastic deformation and thermal effects, resulting in grain refinement, increased lattice distortion, and TiAl-to-Ti₃Al phase transformation, thereby enhancing the structural stability of the coating matrix. Cyclic oxidation kinetics revealed a two-stage process transitioning from reaction-controlled to diffusion-controlled behavior. WSP delivered prominent protective effects at intermediate temperatures, substantially reducing oxidation weight gain and rate constants by promoting the formation of dense, stable Ti₂O₃ and Al₂O₃ protective layers with finer, more uniform oxide-scale morphology. However, this beneficial effect progressively weakened with increasing temperature and sharply diminished at 1000 °C, where massive generation of porous, thermally unstable TiO₂ dominated the oxidation process. The loose TiO₂ structure provided channels for inward oxygen diffusion, offsetting the microstructural optimization advantages of WSP and compromising oxide-scale barrier effectiveness. These findings establish a clear structure–performance correlation for WSP-modified Ti-Al coatings and elucidate the temperature-dependent failure mechanism of surface modification under ultra-high-temperature oxidation conditions. Full article