Search Results (2,919)

To achieve the large-scale, high-value utilization of vanadium–titanium slag (VTS) in the metallurgical industry, this study replaces blast furnace slag (BFS) with VTS to construct a quaternary all-solid-waste cementitious system composed of VTS, BFS, steel slag (SS), and desulfurization gypsum (DG). It systematically investigates the effects of VTS content (0–60%) on the mechanical properties, leaching toxicity, and hydration heat behavior of the system. XRD, TG–DSC, and SEM–EDS techniques are employed to explore the influence of VTS on hydration behavior and microstructural evolution. The results show that when VTS replaces 30% of the BFS (A3, VTS:BFS:SS:DG = 3:3:3:1), the 28-day compressive strength reaches 31.33 MPa. The leaching concentrations of heavy metals in all specimens are far below the standards for drinking water quality. Hydration heat analysis reveals that the incorporation of VTS advances the acceleration period of hydration. The A3 specimen maintains a relatively high heat release rate in the middle and later stages (after 72 h), and its cumulative heat release is significantly higher than that of the system without VTS, revealing the “slow hydration” mechanism of VTS at later stages. The [SiO₄]–[AlO₄] bonds in VTS undergo a depolymerization–repolymerization process. In addition, an appropriate amount of VTS promotes the deposition of hydration products such as ettringite (AFt), C–S–H, and C–A–S–H gels through micro-filling effects and heterogeneous nucleation, thereby improving the microstructure of the system. However, excessive VTS (≥45%) significantly inhibits the hydration reaction and reduces gel formation due to the decrease in highly reactive BFS components and the increased TiO₂ content. This study provides new insights into the resource utilization of VTS in multi-solid-waste cementitious materials. In addition, VTS-based cementitious materials are suitable for practical scenarios with low early strength requirements, such as goaf backfilling. Therefore, future studies should further investigate the long-term sulfate resistance and carbonation resistance of these materials under real application conditions. Full article

Coal gangue (CG) ranks among China’s most significant industrial solid by-products. In response to China’s carbon neutrality commitments and the growing emphasis on resource recycling, finding effective ways to valorize CG has emerged as a pressing concern. Based on the mineral composition and chemical composition characteristics of CG, this study systematically investigated the enhancement effects of three alkali activators (Na₂SiO₃, NaOH, and Ca(OH)₂) on the cementitious properties of CG. Through different dosage and compressive strength tests, the efficiency ranking of the three activators was determined as follows: Na₂SiO₃ > Ca(OH)₂ > NaOH. A 10% Na₂SiO₃ dosage combined with 28-day curing was identified as the optimal condition for achieving sufficient reaction and structural densification. Under these conditions, the compressive strength of CG cementitious material reached 6.4 MPa, representing an increase of 190.9% compared to the blank group (2.2 MPa), significantly superior to Ca(OH)₂ (69.55%) and NaOH (62.27%). X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analyses revealed that alkali activators function primarily by disrupting the crystalline framework of CG, promoting the cross-linking polymerization of silicon–aluminum monomers to generate dense cementitious products, thereby improving material performance. The Na₂SiO₃ is attributed to its “dual activation effect”, providing OH⁻ to create an alkaline environment while supplying reactive silicate ions (SiO₃²⁻) to accelerate N-A-S-H gel and C-A-S-H gel formation. These findings offer guidance for optimizing CG-based cementitious formulations for formula optimization and large-scale utilization of CG cementitious materials. Full article

The hydrogeochemical characterization of shallow volcanic lakes at the Sete Cidades Volcano (São Miguel, Azores) provides new insights into the processes controlling water chemistry in low-depth lacustrine systems within active volcanic environments. Fourteen lakes (0.6–4 m deep) were sampled during two campaigns (winter 2024 and spring/summer 2025), combining in situ physicochemical measurements and major ion analyses along vertical profiles. The lakes are holomictic, cold (11.3–17.6 °C), slightly acidic (pH 5.66–5.95), and weakly mineralized (EC ~65–69 µS/cm), indicating dilute waters of predominantly meteoric origin. Hydrochemical facies are dominated by Na–Cl type, with strong correlations between chloride and conductivity (r = 0.857), supporting a major contribution from marine atmospheric deposition. To move beyond correlation-based interpretation, Gibbs diagrams and saturation indices (PHREEQC) were applied to constrain the dominant geochemical processes. Most samples plot within the precipitation dominance field, while all calculated saturation indices are negative (SI < 0), indicating undersaturation with respect to carbonate, evaporite, and silicate minerals. These results demonstrate that water chemistry is primarily controlled by atmospheric inputs, with only minor contributions from water–rock interaction and negligible influence of evaporation or mineral equilibrium processes. Seasonal increases in HCO₃⁻ and dissolved CO₂ at depth suggest enhanced organic matter decomposition during warmer periods, highlighting the role of biogeochemical processes in modulating carbon dynamics in shallow systems. The absence of a clear hydrothermal signature further distinguishes these lakes from deeper volcanic systems in the Azores. This study provides the first integrated hydrogeochemical framework for shallow volcanic lakes in the region, combining classical hydrochemistry with process-based tools. The results establish a quantitative baseline for assessing environmental change and improve the interpretation of external (atmospheric) versus internal (geochemical and biological) controls in volcanic lake systems. Full article

Background/Objectives: Influenza A virus (IAV) infection triggers robust inflammation and acute lung injury. Andrographolide, a primary active compound from Andrographis paniculata, can mitigate IAV-induced inflammation; however, its precise mechanisms remain poorly elucidated. This study aimed to define its host-directed protective effects and molecular mechanisms. Methods: We used a lethal IAV (H1N1, PR8) model in BALB/c mice and infected A549 cells. Survival, lung pathology, cytokines, and viral titers were measured. Lung RNA sequencing identified dysregulated signaling pathways. PI3K/AKT and pyroptosis pro-teins were analyzed by Western blot. The PI3K/AKT axis was functionally validated with the AKT inhibitor in vivo and AKT1 siRNA in vitro. Results: Andrographolide improved survival, attenuated body weight loss, and reduced lung pathology and inflammatory cytokine levels in IAV-infected mice, without exhibiting direct antiviral activity. Consistent with the in vivo findings, andrographolide enhanced cell viability and suppressed cytokine secretion in infected cells. RNA sequencing revealed marked upregulation of the PI3K/AKT signaling pathway in the lungs of treated mice, as confirmed by increased PI3K and AKT phosphorylation. Furthermore, andrographolide downregulated the expression of key pyroptosis-executing proteins, including cleaved caspase-3 and the gasdermin E (GSDME) N-terminal fragment. These protective effects were substantially abrogated by an AKT inhibitor and AKT1 siRNA. Conclusions: These findings reveal a novel host-directed mechanism by which andrographolide alleviates IAV-induced immunopathology by activating the PI3K/AKT pathway, thereby suppressing caspase-3/GSDME-dependent pyroptosis. Thus, this axis represents a promising target for controlling excessive inflammation in severe influenza. Full article

In this study, polysiloxane-containing polyimide (si-PI) composite coatings containing hexagonal boron nitride (hBN) particles of four different sizes and at different contents were prepared, and their mechanical and tribological properties were investigated. The coatings were deposited on steel substrates via dip coating and cured at 160 °C. Their tribological properties were measured using reciprocating sliding tests under unlubricated conditions against a steel ball. The composite coatings containing nano-hBN with the smallest mean primary particle size of 0.05 μm exhibited the lowest wear. Subsequently, coatings containing 1–15 wt% nano-hBN were prepared to examine the effect of filler content. The results showed that the coatings with low nano-hBN contents (1–2 wt%) had relatively high friction coefficients and significantly reduced wear on both the coating and the counterpart. Cross-sectional scanning electron microscopy (SEM) observations revealed that dispersed small hBN aggregates suppress crack propagation through dispersion strengthening. Coatings with low nano-hBN contents (1–2 wt%) also exhibited sufficient electrical insulation. However, as the hBN content increased further, hBN agglomeration was promoted, weakening the crack-propagation suppression effect and increasing wear. These findings indicate that low-content nano-hBN/si-PI composite coatings are promising electrical erosion-resistant coatings for the outer rings of the bearings used in electric vehicle motors. Full article

First-principles calculations based on density functional theory (DFT) are performed to investigate the interfacial properties and fracture behavior of 3C-SiC(111)/Al(111) and 4H-SiC(0001)/Al(111) interfaces. To mitigate surface effects through adequate slab thickness, the interface models are constructed by positioning a seven-layer Al(111) slab atop eight-layer 3C-SiC(111) and 14-layer 4H-SiC(0001) slabs, respectively. Accounting for the distinct surface terminations and stacking sequences of each polytype, six interface configurations are established: C-top, -center, and -hollow; Si-top, -center, and -hollow. Based on the simulation results of surface energy, work of separation, and electron density distribution, the C-top configuration yields the most stable SiC/Al interface structure, exhibiting the highest work of separation. The ultimate tensile strengths of the C-top interfaces are 6.603 GPa (3C-SiC/Al) and 6.851 GPa (4H-SiC/Al), with corresponding tensile strains of 10% and 12%, respectively. Tensile fracture initiates exclusively within the Al slab for all C-top interfaces, but at distinct atomic layers: fracture occurs between the second and third Al layers (Al2–Al3) for 3C-SiC/Al; and between the first and second Al layers (Al1–Al2) for 4H-SiC/Al. This distinction reflects the influence of different interfacial configurations on the bonding strength between aluminum atomic layers. In summary, an atomic-scale investigation of the interfacial properties and fracture behavior of SiC/Al interfaces provides critical insights for the design and fabrication of novel ceramic/metal composites. Full article

The global demand for biodiesel production is steadily increasing. Conventional homogeneous basic catalysts, while widely used in the industry, face significant drawbacks, such as the requirement for high-quality feedstock, excessive waste generation, and multiple purification steps. In this study, an acidic silane (IM-CPTMS-BS-H₂SO₄) containing imidazolium and sulfonic groups was synthesized. Heterogeneous catalysts were then prepared by anchoring varying proportions of the silane onto SBA-15 mesoporous solids. These materials were characterized by FTIR, ¹³C and ²⁹Si NMR, TGA, XRD, CHNS and acidity measurements. The catalysts were evaluated in the transesterification of methyl acetate with ethanol, with increasing catalytic conversions with the amount of grafted IM-CPTMS-BS-H₂SO₄. Furthermore, increasing the catalyst loading (from 2% to 5% wt.) and the reaction temperature (from 50 °C to 65 °C) led to higher methyl acetate conversion rates. Full article

Pyrrolo[2,3-d]pyrimidine is a privileged fused heterocyclic scaffold that has attracted considerable attention in medicinal chemistry due to its diverse biological activities. Herein, we report an efficient synthesis strategy for the preparation of the pyrrolo[2,3-d]pyrimidine-based natural toyocamycin aglycone and pyrrolo[2,3-d]pyrimidine derivatives. The synthesis of toyocamycin aglycone features a key benzylamine nucleophilic substitution followed by a palladium-catalyzed cyanation reaction. From a key intermediate derived from this route, nineteen new pyrrolo[2,3-d]pyrimidine derivatives were rapidly synthesized via key Suzuki–Miyaura coupling and amine nucleophilic substitution reactions. Their cytotoxic activities were evaluated against Huh-7 and HepG liver cancer cell lines. Most derivatives were inactive after 24 h. However, 28a–28c, 28e and 28f exhibited moderate cytotoxicity with IC₅₀ values ranging from 5.7 to 62.6 μM. Among them, compound 28e displayed the highest potency against HepG cells, with IC₅₀ values of 5.7 μM. Compared with normal HEK293 cells, it showed a selectivity index (SI) of 3.60 against HepG cells. Preliminary structure-activity relationship analysis suggested that incorporation of a cyclopropyl group further improves antitumor activity. Full article

Due to the high water absorption of coal gangue aggregate, concrete prepared with a high content of this material exhibits a significantly reduced service life under freeze–thaw conditions. This study evaluates the frost resistance of gel-enhanced coal gangue aggregate concrete modified by incorporating nano-SiO₂ and polypropylene fibre (PPF) to generate more C-S-H gel and form a dense structure with different dosages of air-entraining agent (0, 0.004%, 0.008%, 0.012%, and 0.016%). The research results show that when the admixture content is 0.012%, the concrete still exhibits excellent frost resistance after 100 freeze–thaw cycles. The mass loss is only 4.7%, compressive strength loss is 37%, and dynamic elastic modulus loss is 39%, while the specimen maintains the best apparent integrity. In addition, the capillary water absorption rate, initial capillary water absorption rate, and cumulative water absorption all reach their lowest values under this condition, indicating optimal frost resistance performance. Finally, through regression analysis, a highly accurate predictive model for capillary water absorption was established, providing a theoretical basis for further research on the durability and frost resistance of coal gangue aggregate concrete. Full article

To develop a high-performance inorganic fireproof coating suitable for steel structures, this study utilized magnesium phosphate cement (MPC) as the matrix and introduced expanded perlite (EP) as a lightweight aggregate. The effects of EP content (40–55%) and magnesium-to-phosphorus ratio (M/P = 4:1–7:1) on the dry density, compressive strength, bond strength, and fire resistance of the coating were systematically investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to reveal the phase evolution and microstructure evolution mechanisms at high temperatures. The results indicate that increasing EP content significantly reduces the dry density and thermal conductivity of the coating, enhancing thermal insulation performance. However, excessive incorporation leads to the deterioration of mechanical properties, with an optimal EP content of 45%. The M/P ratio influences the interfacial bond strength and high-temperature structural stability by regulating the proportion of the hydration product K-struvite (KMgPO₄·6H₂O) and residual MgO. Compressive strength peaked at M/P = 6:1 (0.80 MPa), while bond strength was optimal at M/P = 5:1 (0.097 MPa), corresponding to the best fire resistance (back-side temperature of 180.4 °C). At high temperatures, K-struvite dehydrates and transforms into anhydrous KMgPO₄, which, together with residual MgO and crystallized SiO₂ from EP, forms a dense ceramic skeleton, ensuring the structural integrity of the coating. Comprehensive performance evaluation determined the optimal mix ratio as M/P = 5:1 and EP content = 45%. The coating with this ratio exhibits a dry density of approximately 560 kg/m³, a 14-day compressive strength of 0.53 MPa, a bond strength of 0.097 MPa, and a back-side temperature of 180.4 °C under flame exposure, demonstrating a favorable balance of lightweight character, mechanical integrity, and thermal insulation performance suitable for steel structure fire protection applications. Full article

To obtain ultrahigh strength Cu alloy strip for board-to-board connectors, a CuNiSiMgMn multi-element high-solute alloy was designed, and high-temperature short-time solid solution was utilized to optimize the properties of this alloy. The evolution in microstructure and properties of the cold-rolled CuNiSiMgMn alloy strip during high-temperature short-time solid solution, aging, and further cold-rolling are investigated. The results reveal that there are high-density Ni_xSi precipitates and deformation defects in the original cold-rolled CuNiSiMgMn alloy strip. During a solid solution at 1000 °C, recrystallization primarily occurs between 15 and 30 s, while precipitate decomposition starts at a solid solution time of ~30 s and is almost complete 10 s later. With further increase in the solid solution time, the grain size of the alloy grows rapidly, but the residual precipitate particles exhibit little change. Upon aging at 500 °C for 2 h and a further 80% cold-rolling, nano-sized precipitates are formed, yielding high-strength alloy strips. The 80% cold-rolling increases the microhardness by 12% and decreases the electrical conductivity by 3% IACS. The strip solid solution-treated for 35 s exhibits the maximum strength, with a tensile strength of >950 MPa and a conductivity of >30% IACS. Further extension of the solid solution time decreases both the tensile strength and elongation. This work clarifies the critical time of recovery, recrystallization, and precipitate decomposition of the CuNiSiMgMn alloy during high-temperature solid solution and provides guidance for industrial production. Full article

Calcium–silicate–hydrate (C-S-H), the primary binding phase governing cement paste cohesion, undergoes progressive physicochemical transformation upon carbonation—a process that critically dictates concrete durability in atmospheric environments. When CO₂ penetrates the porous cement matrix, it triggers a cascade of degradation mechanisms: calcium leaching decalcifies the C-S-H structure, inducing polymerization of silicate chains from dimeric to longer-chain configurations, while concurrent precipitation of calcium carbonate and amorphous silica gel fundamentally reconstitutes the nanoscale architecture. These nanoscale alterations propagate to macroscopic property evolution, manifesting as initial strength and stiffness gains due to pore-filling carbonation products followed by eventual deterioration as the cohesive binding network deteriorates. This review synthesizes current understanding of carbonation-induced structural evolution, examining the coupled influences of environmental parameters—CO₂ concentration, relative humidity, and temperature—alongside C-S-H intrinsic chemistry (Ca/Si ratio, aluminum substitution, and alkali content) on reaction kinetics and material performance. However, significant knowledge gaps persist: predictive models for in-service carbonation rates remain elusive due to the disconnect between idealized laboratory conditions and the heterogeneous, cracked reality of field concrete; the causal linkage between nanoscale C-S-H alteration and macroscale cracking patterns along with physical performance is poorly resolved, and most mechanistic studies rely on synthetic C-S-H, neglecting the compositional complexity of real Portland cement systems. We further propose emerging protection strategies, including surface barrier coatings and low-carbon alternative binders (geopolymers, calcium sulfoaluminate cements, carbon-negative materials such as recycled cement), which demonstrate enhanced carbonation resistance. Future research priorities include developing effective coating barriers for carbonation protection, developing operando characterization techniques for real-time reaction monitoring, deploying machine learning algorithms to bridge atomistic simulations with structural-scale predictions, and establishing long-term field performance databases to validate laboratory-derived degradation models. Full article

Wollastonite-1A from Băița Bihor occurs in distal calcic skarns developed in the contact zone of a mainly granodioritic batholith, of Upper Cretaceous age, with Mesozoic limestones and dolostones. Wollastonite generally occurs in the inner part of metasomatic columns, in monomineralic skarns or associated with grossular and molybdenite-2H as ore mineral. The physical properties (i.e., refraction indices α = 1.616, β = 1.629, and γ = 1.631, 2V_α = 39° and density D_m = 2.922(3) g/cm³) are typical for a term close to the stoichiometry, which is confirmed by the chemical analysis. The chemical structural formula of the analyzed wollastonite-1A is (Ca_1.000Mg_0.002Mn_0.001Fe_0.001)(Al_0.004Ti_0.001Si_0.994)O₃, which closely approximates the ideal CaSiO₃. The Gladstone–Dale compatibility indices account for an excellent agreement between physical and chemical data. The mineral can be satisfactorily refined as triclinic, space group $P\overline{1}$, with R₁ = 0.0678 and cell parameters a = 7.9233(3) Å, b = 7.3203(3) Å, c = 7.0651(3) Å, α = 90.053(3)°, β = 95.208(3)°, γ = 103.384(3)°. Both the IR and Raman spectra principally reveal bands related to vibrations of bridged and non-bridged oxygens pertaining to SiO₄ structural tetrahedra. At Băița Bihor, wollastonite-1A is part of the prograde paragenesis, marked by a peak temperature of 550–600 °C. Full article

The persilylated Si₃–Si₇ analogues of the C₃–C₇ aromatic molecules and ions with all hydrogen or all fluorine atoms at silicon have been calculated at high levels of theory, up to MP2/aug-cc-pVTZ for all species and CCSD/6-311++G** for Si₃ and Si₄ species, both in the gas phase and in a polar solvent (water). The aromaticity of the calculated species was estimated using structural, energetic, and NMR criteria. (SiF)₃⁺ cations are more aromatic than (SiH)₃⁺ by the NICS (nuclear-independent chemoical shift) but less aromatic by the ASE (aromatic stabilization energy) criterion. Dications (SiX)₄²⁺ are planar (X = H) or slightly puckered (X = F); the ASE decreases by 4–5 kcal/mol upon going from gas to solution, or from X = H to X = F. Dianions (SiX)₄²⁻are nonplanar and antiaromatic. The ASE for the slightly distorted-from-planarity anion Si₅H₅⁻ is ~53 kcal/mol, vs. 85 kcal/mol for its carbon analogue. The structure of Si₆X₆ molecules strongly depends on the level of calculations. The NICS and ASE values have been calculated for planar Si₆H₆ and (SiH)₇⁺ but not for strongly distorted Si₆F₆ and (SiF)₇⁺ species. Full article

This study employed a metakaolin-based geopolymer (GP) to solidify potassium copper hexacyanoferrate after its saturation with adsorbed Cs⁺. The experiment was designed using response surface methodology (RSM) in the Design–Expert 13 software, targeting the compressive strength and cumulative leaching fraction of the solidified form. A regression model was developed to achieve the multi-objective optimization of the comprehensive performance of the GP solidified product. Regression analysis identified the optimal mix proportion as Na₂O/Al₂O₃ = 0.84, SiO₂/Al₂O₃ = 2.8, and H₂O/Na₂O = 10.23. Under these conditions, the experimentally measured compressive strength was 23.41 MPa. The 42-day cumulative leaching fractions at 25 °C and 40 °C were 7.906 × 10⁻⁴ cm and 1.5923 × 10⁻³ cm, respectively, both significantly below the national standard threshold (Standard Code GB7023-2011) of 2.6 × 10⁻¹ cm. The percentage error remained within 10%, indicating strong agreement with predicted values. These results suggest that metakaolin-based GP exhibits promising potential for the immobilization of radionuclides. Full article