Search Results (477)

Rouaite (Cu₂(OH)₃NO₃) long hexagonal multilayered nanoplates with high purity and high crystallinity were prepared from acidic reaction solution (pH = 4.4–4.8) with the assistance of ZnO. The ZnO-assisted strategy is remarkably different from the conventional synthetic protocol that was regularly carried out in alkaline solution (pH > 11). The rouaite multilayer nanoplates displayed exceptionally high catalytic activity in the catalytic wet peroxide oxidation (CWPO) of Congo red (CR). The catalytic efficiency for CR decolorization achieved an impressive 96.3% in 50 min under near-neutral (pH = 6.76) and ambient conditions (T = 20 °C, p = 1 atm), without increasing the temperature and/or decreasing the pH value to acidic region (pH = 2–3) as is commonly employed in CWPO process for improved degradation efficiency. Full article

Carbon fiber (CF) and carbon fiber-reinforced polymers (CFRPs) are widely used in the aerospace, automotive, and energy sectors due to their high strength, stiffness, and low density. However, significant waste is generated during manufacturing and after the use of CFRPs. Traditional disposal methods like landfilling and incineration are unsustainable. CFRP machining processes, such as drilling and milling, produce fine chips and dust that are difficult to recycle due to their heterogeneity and contamination. This study investigates the oxidation behavior of CFRP drilling waste from two types of materials (tube and plate) under oxidative (non-inert) conditions. Thermogravimetric analysis (TGA) was performed from 200 °C to 800 °C to assess weight loss related to polymer degradation and carbon fiber integrity. Scanning electron microscopy (SEM) was used to analyze morphological changes and fiber damage. The optimal range for removing the polymer matrix without significant fiber degradation has been identified as 500–600 °C. At temperatures above 700 °C, notable surface and internal fiber damage occurred, along with nanostructure formation, which may pose health and environmental risks. The results show that partial fiber recovery is possible under ambient conditions, and this must be considered regarding the harmful risks to the human body if submicron particles are inhaled. This research supports sustainable CFRP recycling and fire hazard mitigation. Full article

Classical thermodynamics omits rigidity, which property distinguishes solids from gases and liquids. By accounting for rigidity (i.e., Young’s elastic modulus, ϒ), we recently amended historical formulae and moreover linked heat capacity, thermal expansivity, and ϒ. Further exploration is motivation by the importance of classical thermodynamics to various applied sciences. Based on heat performing work, we show here, theoretically, that density times sublimation enthalpy divided by the molar mass (ρΔH_sub/M, energy per volume), depends linearly on ϒ (1 GPa = 10⁹ J m⁻³). Data on diverse metals, non-metallic elements, chalcogenides, simple oxides, alkali halides, and fluorides with cubic structures validate this relationship at ambient conditions. Furthermore, data on hcp metals and molecular solids show that ρΔH_sub/M is proportional to ϒ for anisotropic materials. Proportionality constants vary only from 0.1 to 0.7 among these different material types (>100 substances), which shows that the elastic energy reservoir of solids is large. Proportionality constants depend on whether molecules or atoms are sublimated and are somewhat affected by structure. We show that ductility of refractory, high-ϒ metals affect high-temperature determinations of their ΔH_sub. Our results provide information on sublimation processes and subsequent gas phase reactions, while showing that elasticity of solids is the key parameter needed to assessing their energetics. Implications are highlighted. Full article

We studied the adsorption thermodynamics and mechanism behind the binding of nitric oxide (NO) in the interior surfaces and structural fragments of the high metal center density microporous Metal-Organic Framework (MOF) CPO-27-Cu, by gas sorption, at a series of temperatures. For the purpose of comparison, we also measured the corresponding CO₂ adsorption isotherms, and as a result, the isosteric heats of adsorption for the two studied adsorptives were derived, being in the range of 12–15 kJ/mol for NO at loadings up to 0.5 NO molecules per formula unit (f.u.) of the bare compound (C₄O₃HCu), and 23–25 kJ/mol CO₂ in the range 0–1 CO₂ per f.u. Microscopically, the mode of NO binding near the square pyramid Cu(II) centers was directly accessed with the use of in situ NO gas adsorption X-ray Absorption Spectroscopy (XAS). Additionally, during the vacuum/temperature activation of the material and consequent NO adsorption, the electronic state of the Cu-species was monitored by observing the corresponding X-ray Near Edge Spectra (XANES). Contrary to the previously anticipated chemisorption mechanism for NO binding at Cu(II) species, we found that at slightly elevated temperatures, under ambient, but also cryogenic conditions, only relatively weak physisorption takes place, with no evidence for a particular adsorption preference to the coordinatively unsaturated Cu-centers of the material. Full article

This work aims to study the catalytic properties of Fe, Cr, and Cu catalysts deposited on chitosan–silica (SBA-15) composites in liquid phase oxidation of cyclohexane (CH) with H₂O₂ and photocatalytic hydrogen evolution reaction. The catalysts were obtained by consecutive adsorption of chitosan (CS) and metal ions (Fe³⁺, Cr³⁺, Cu²⁺) on SBA-15 at ambient conditions. Characterization of the catalysts by XRD, IR spectroscopy, XPS, TEM, SEM, etc., showed the CS and metal ion adsorption on the solid support. Modification with CS provided better immobilization of the metal ions on SBA-15. The synthesized catalysts demonstrated different performance in liquid phase oxidation of cyclohexane with H₂O₂ under mild conditions at 40 °C and atmospheric pressure. Cyclohexane conversion on Fe–CS/SBA-15 (18.5%) and Cr–CS/SBA-15 (21.6%) was higher than on Cu–CS/SBA-15 (9.3%). The influence of different conditions of the reaction such as time, temperature, catalyst dosage, substrate and oxidant ratio on cyclohexane conversion in the presence of the most efficient Cr–CS/SBA-15 catalyst was also studied. The optimal reaction conditions were found to be the following: duration of reaction—4 h, temperature of reaction—50 °C, m_cat—0.03 g, a substrate/H₂O₂ ratio of 1:3. In addition, Cr–CS/SBA-15 and Fe–CS/SBA-15 catalysts were studied in a photocatalytic H₂ evolution reaction. The Fe-containing catalyst demonstrated superior efficiency in photocatalytic H₂ evolution. The total volume of hydrogen produced within 3 h was 103 mL/g. Thus, this study demonstrates that chitosan possesses promising potential in the design of the supported catalysts for cyclohexane oxidation and photocatalytic hydrogen evolution reactions. Full article

This work provides a comprehensive investigation into the synergistic effects of zirconium and oxygen on the microstructural evolution, high-temperature oxidation resistance, and mechanical properties of γ-phase Ti52AlxZr alloys (x = 0, 0.5, 1, and 2 at.%) under systematically controlled oxygen concentrations. Unlike prior studies that have examined these alloying elements in isolation, this study uniquely decouples the contributions of interstitial (oxygen) and substitutional (zirconium) solutes by employing low (LOx) and high (HOx) oxygen levels. Alloys were synthesized via vacuum arc melting and subsequently subjected to homogenization annealing at 1250 °C for 100 h to ensure phase and microstructural stability. Characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) were employed to elucidate phase constitution and grain morphology. Zirconium addition was found to stabilize the γ-TiAl matrix, suppress α₂-phase formation, and promote grain coarsening in LOx specimens. Conversely, elevated oxygen concentrations led to α₂-phase precipitation along grain boundaries. Mechanical testing, comprising Vickers hardness and uniaxial compression at ambient and elevated temperatures (800 °C), revealed that both zirconium and oxygen significantly enhanced strength and hardness, with Ti52Al2Zr delivering optimal mechanical performance. Moreover, zirconium substantially improved oxidation resistance by promoting the formation of a thinner, adherent Al₂O₃ scale while simultaneously inhibiting TiO₂ growth. Collectively, the findings demonstrate the critical role of zirconium in engineering advanced γ-TiAl-based intermetallics with superior high-temperature structural integrity and oxidation resistance. Full article

This study aims to comprehensively assess the suitability of post-processing annealing (at 900–1200 °C) for enhancing the key properties of 316L steel fabricated via laser powder bed fusion (LPBF). It adopts a holistic approach to investigate the annealing-driven evolution of microstructure–property relationships, focusing on tensile properties, nanoindentation hardness and modulus, impact toughness at ambient and cryogenic temperatures (−196 °C), and the corrosion resistance of LPBF 316L. Annealing at 900–1050 °C reduced tensile strength and hardness, followed by a moderate increase at 1200 °C. Conversely, ductility and impact toughness peaked at 900 °C but declined with the increasing annealing temperature. Regardless of the annealing temperature and testing conditions, LPBF 316L steel fractured through a mixed transgranular/intergranular mechanism involving dimple formation. The corrosion resistance of annealed steel was significantly lower than that in the as-built state, with the least detrimental effect being observed at 1050 °C. These changes resulted from the complex interplay of annealing-induced structural transformations, including elimination of the cellular structure and Cr/Mo segregations, reduced dislocation density, the formation of recrystallized grains, and the precipitation of nano-sized (MnCrSiAl)O₃ inclusions. At 1200 °C, an abundant oxide formation strengthened the steel; however, particle coarsening, combined with the transition of (MnCrSiAl)O₃ into Mo-rich oxide, further degraded the passive film, leading to a sharp decrease in corrosion resistance. Overall, post-processing annealing at 900–1200 °C did not comprehensively improve the combination of LPBF 316L steel properties, suggesting that the as-built microstructure offers a favorable balance of properties. High-temperature annealing can enhance a particular property while potentially compromising other performance characteristics. Full article

Marine transportation contributes approximately 2.5% of global greenhouse gas emissions. While previous studies have examined biodiesel effects on automotive engines, research on marine applications reveals critical gaps: (1) existing studies focus on single-parameter analysis without considering the complex interactions between biodiesel ratio, engine load, and operating conditions; (2) most research lacks comprehensive lifecycle assessment integration with real-time operational data; (3) previous optimization models demonstrate insufficient accuracy (R² < 0.80) for practical marine applications; and (4) no adaptive algorithms exist for dynamic biodiesel ratio adjustment based on operational conditions. These limitations prevent effective biodiesel implementation in maritime operations, necessitating an integrated multi-parameter optimization approach. This study addresses this research gap by proposing an integrated optimization model for fuel efficiency and emissions of marine diesel engines using biodiesel mixtures under diverse operating conditions. Based on extensive experimental data from two representative marine engines (YANMAR 6HAL2-DTN 200 kW and Niigatta Engineering 6L34HX 2471 kW), this research analyzes correlations between biodiesel blend ratios (pure diesel, 20%, 50%, and 100% biodiesel), engine load conditions (10–100%), and operating temperature with nitrogen oxides, carbon dioxide, and carbon monoxide emissions. Multivariate regression models were developed, allowing prediction of emission levels with high accuracy (R² = 0.89–0.94). The models incorporated multiple parameters, including engine characteristics, fuel properties, and ambient conditions, to provide a comprehensive analytical framework. Life cycle assessment (LCA) results show that the B50 biodiesel ratio achieves optimal environmental efficiency, reducing greenhouse gases by 15% compared to B0 while maintaining stable engine performance across operational profiles. An adaptive optimization algorithm for operating conditions is proposed, providing detailed reference charts for ship operators on ideal biodiesel ratios based on load conditions, ambient temperature, and operational priorities in different maritime zones. The findings demonstrate significant potential for emissions reduction in the maritime sector through strategic biodiesel implementation. Full article

Nickel (Ni) ultrathin films exhibit phase-dependent electrical, magnetic, and optical characteristics that are significantly influenced by deposition methods. However, these films are inherently prone to rapid oxidation, with the oxidation rate dependent on substrate, temperature, and deposition parameters. The focus of this research is to investigate the temporal oxidation of RF-sputtered Ni ultrathin films on Corning glass under ambient atmospheric conditions and its impact on their structural, surface, and optical characteristics. Controlled film thicknesses were achieved through precise manipulation of deposition parameters, enabling the analysis of oxidation-induced modifications. Atomic force microscopy (AFM) revealed that films with high structural integrity and surface uniformity are exhibiting roughness values (Rq) from 0.679 to 4.379 nm of corresponding thicknesses ranging from 4 to 85 nm. Scanning electron microscopy (SEM) validated the formation of Ni grains interspersed with NiO phases, facilitating SPR-like effects. UV-visible spectroscopy is demonstrating thickness-dependent spectral (plasmonic peak) shifts. Finite Difference Time Domain (FDTD) simulations corroborate the observed thickness-dependent optical absorbance and the resultant shifts in the absorbance-induced plasmonic peak position and bandgap. Increased NiO presence primarily drives the enhancement of electromagnetic (EM) field localization and the direct impact on power absorption efficiency, which are modulated by the tunability of the plasmonic peak position. Our work demonstrates that controlled fabrication conditions and optimal film thickness selection allow for accurate manipulation of the Ni oxidation process, significantly altering their optical properties. This enables the tailoring of these Ni films for applications in transparent conductive electrodes (TCEs), magneto-optic (MO) devices, spintronics, wear-resistant coatings, microelectronics, and photonics. Full article

This study investigates a novel approach to moderate-temperature carbon capture by examining the enhanced performance of thermally pre-treated dolomite. To obtain mixed oxides, dolomite samples were prepared via calcination in a quartz cylindrical furnace under an ambient atmosphere at 900 °C, and subsequently thermally pre-treated under an inert (argon) stream at 650 °C. Characterization of the as-prepared samples involved morphological, structural, textural, and optical features examined through XRD, BET, SEM-EDS, FT-IR, and RAMAN, XPS, and UV-vis spectroscopy, whereas TGA and subsequent multicyclic tests were used to study the CO₂ sorption. The dolomite sample calcined at 900 °C for 60 min, and after being activated under an inert atmosphere (argon), labeled PCD60Act, exhibited the highest CO₂ uptake of 0.477 g_CO2/g_sorbent; after 15 sorption–regeneration cycles, it still retained a CO₂ uptake of 0.38 g_CO2/g_sorbent at 650 °C, and it was also successfully regenerated at this moderate temperature, demonstrating 84% capture capacity retention. These remarkable results are explained by the crystalline defects generated during the thermal pre-treatments of the dolomite. This research offers valuable perspectives on the viability of employing thermally pre-treated dolomite as an inexpensive, thermally stable, and moderate-temperature regenerable CaO-based sorbent for applications in CO₂ removal in the context of integrated carbon capture and conversion (ICCC) for the production of high-purity hydrogen. Full article

Prolonged exposure to extreme humid heat can induce systemic inflammation, organ stress, and hormonal imbalance. While fluid replacement is commonly recommended, its mechanistic efficacy under humid heat stress remains unclear. This study investigated the impact of fluid intake on thermoregulation, inflammation, organ function, and stress signaling during 8 h of humid heat exposure (ambient temperature: 40 °C, relative humidity: 55%) in 32 healthy young adults (20 males and 12 females). Participants completed two randomized trials: limited fluid intake (LFI, 125 mL/h) and full fluid intake (FFI, 375 mL/h). Core temperature (T_core), inflammatory cytokines (IL-6, IL-1β, IFN-γ, TNF-α), organ stress markers (ALT, BUN), oxidative stress indices (MDA, SOD), and cortisol were assessed pre- and post-exposure. FFI significantly reduced post-exposure T_core (37.8 ± 0.3 °C vs. 38.1 ± 0.3 °C, p = 0.046), mitigated cytokine elevations, and decreased BUN (blood urea nitrogen), ALT (alanine aminotransferase), and cortisol levels. Western blot analysis of PBMCs revealed that LFI activated NF-κB p65, JNK2, p38, and STAT3α phosphorylation, whereas FFI suppressed these responses. These findings demonstrate that adequate hydration attenuates heat-induced systemic and molecular stress responses. Our results highlight hydration as a key modulator of inflammatory signaling pathways during prolonged heat stress, offering insights into preventive strategies for populations vulnerable to climate-induced extreme heat events. Full article

The Cr₂O₃ film on the outer surface of traditional cracking furnace tubes is prone to spalling, which shortens the tube life. Fe-Ni-Cr-based austenitic stainless steel (AFA alloy) with added Al has attracted attention because it can form a more stable Al₂O₃ film on the surface. However, the alloy’s mechanical performance and the stability and oxidation resistance of the oxide film need to be improved simultaneously. This investigation examined silicon concentration variations (0–1.5 wt.%) on AFA alloy’s ambient-temperature tensile performance and oxidation response under reduced oxygen partial pressures (10⁻¹⁸–10⁻¹⁶ bar). The findings demonstrate that the alloy was composed of the FCC, B2-NiAl, and M₂₃C₆ phases. With Si addition, the B2-NiAl phase volume fraction increased. Mechanical testing demonstrated progressive elevation in tensile strength and hardness coupled with reduced elongation, attributable to combined solid-solution hardening and B2-NiAl precipitation strengthening. At low oxygen pressure, a continuous multi-layer oxide film developed on the alloy’s surface: the outermost layer was composed of a continuous Cr₂O₃ layer, with a fraction of MnCr₂O₄ spinel phase enriched on the outer surface. The middle layer was SiO₂, which evolved from a particulate to a continuous layer with increasing Si content. The innermost layer was composed of Al₂O₃. Accelerated manganese diffusion through Cr₂O₃ facilitated MnCr₂O₄ spinel layer formation. Full article

An isocratic reverse-phase high-performance liquid chromatography (RP-HPLC) method, coupled with photodiode array detection (PDA), was developed for the identification and characterization of stress degradation products and an unknown process-related impurity of rivaroxaban in bulk drug form. Rivaroxaban, a selective and direct Factor Xa inhibitor, underwent forced degradation under hydrolytic (acidic, alkaline, and neutral), photolytic, thermal, and oxidative stress conditions, following the ICH’s guidelines. The drug displayed significant susceptibility to acid, base, and oxidative environments leading to the formation of eleven degradation products. All degradation products, along with process impurities and Rivaroxaban, were effectively separated using a (4.6 × 250 mm, 5 µm) C18 Thermo ODS Hypersil column at ambient temperature. The mobile phase composed of acetonitrile and monobasic potassium phosphate (pH 2.9) in a 30:70 (v/v) ratio, with a flow rate of 1.0 mL/min, and detection was carried out at 249 nm. The LC-PDA method was validated in accordance with the ICH’s guidelines and USP38-NF33, demonstrating specificity, linearity, accuracy, precision, and robustness. Recovery studies showed results within the range of 98.6–103.4%, with a % RSD LT 2%. The limits of detection (LOD) and quantitation (LOQ) for rivaroxaban were determined to be 0.30 ppm and 1.0 ppm, respectively. Stress studies confirmed that the degradation products did not interfere with rivaroxaban detection, establishing the method as stability-indicating. Specific impurities were identified, including impurity G at 2.79 min, impurity D at 3.50 min, impurity H at 5.32 min, impurity C at 6.14 min, impurity E at 8.36 min, impurity A at 9.03 min, and impurity F at 9.49 min. Additionally, several unknown impurities were observed at 3.20, 4.00, 4.59, and 4.77 min. Statistical evaluation confirmed the method’s reliability, making it suitable for routine analysis, quality control of raw materials, formulations of varying strengths, dissolution studies, and bioequivalence assessments of rivaroxaban formulations. Full article

The present study explores and verifies the chemical modifications achieved by grafting 4-formylcyclohexyl heptanoate (FH) and 4-(2,5-dioxopyrrolidin-1-yl) cyclohexane-1-carbaldehyde (CC) onto addition-curing silicone rubber (SiR). These modifications aim to enhance the electrical insulation performance, moisture resistance, and pyrolysis tolerance of the SiR material, thereby improving its suitability for reinforced insulation in power transmission systems. First-principles calculations demonstrate that both the chemical graft modifications can introduce shallow hole traps of 0.3~0.4 eV and deep electron traps of 0.9~1.0 eV into the polymer molecule of addition-curing SiR for inhibiting charge transport and injection. It is indicated from first-principles oxidation reaction pathways that the chemical grafting of FH or CC contributes positively, rather than impacts negatively, to the oxidative stability of addition-curing SiR. We also reveal how the two proposed species of organic molecules as grafting agents can act on modifying water adsorption uptake, heat capacity, molecular thermal vibration, and polymer pyrolysis of the SiR material, which are highly accountable for its resistances to high-temperature electrical breakdown, moisture aging, and thermal spikes of partial discharge. The comprehensive molecular simulations and material calculations demonstrate that both the grafted agents can significantly intensify polymer molecule aggregations, restrain molecular thermal vibrations, and reduce water adsorption uptakes. One of the preferable graft agents (CC) can also considerably improve polymer pyrolysis tolerance, while contributing to improved high-temperature electrical breakdown strength and moisture resistance of addition-curing SiR. This research highlights the significant potential of graft modification in molecular compositions to improve the electrical insulation, moisture resistance, ambient-temperature thermal stability, and pyrolysis tolerance of addition-curing SiR, offering valuable insights to develop competent elastomeric polymer applied for cable accessory insulation. Full article

Growing spinach year-round via greenhouse hydroponics in warm climates can be challenging because of the intolerance of many spinach cultivars to heat. Root-zone cooling in hydroponic systems in warm climates may be a promising cooling method to alleviate heat stress; however, its effectiveness is still unknown in spinach plants. This study aimed to investigate the impact of root-zone cooling on the growth and physiological responses of four spinach cultivars (‘Lakeside’, ‘Hammerhead’, ‘Mandolin’, and ‘SV2157’) grown in deep water culture hydroponic systems in a greenhouse during the summer season in two growing cycles. The experiment consisted of the following three root-zone temperatures (RZTs): Control (ambient water temperature), RZT24 (24 °C), and RZT21 (21 °C). Among the four cultivars, ‘SV2157’ performed equally regardless of the treatment, demonstrating superior heat tolerance versus the other three cultivars. ‘Mandolin’ exhibited the greatest benefit from root-zone cooling, with increases in shoot dry weights of 87% and 94% under RZT24 and RZT21, respectively, compared to those under control treatment. Additionally, total leaf areas significantly increased under the two root-zone cooling treatments. ‘Lakeside’ and ‘Hammerhead’ generally benefited from root-zone cooling, although the magnitude of growth increases was small or statistically insignificant. However, ‘Lakeside’ and ‘Hammerhead’ were highly responsive to lower ambient air temperatures, as evidenced by increases of 121% and 90%, respectively, in shoot fresh weights across the treatments in Cycle 2 (average air temperature of 24.7 °C) compared to those in Cycle 1 (29.3 °C). Physiological responses to root-zone cooling varied among cultivars, with ‘SV2157’ exhibiting the highest chlorophyll, carotenoid, and anthocyanin levels. Higher total phenolic contents under control treatment in Cycle 1 in all three cultivars except for ‘SV2157’ suggested greater reactive oxygen species production, indicating oxidative stress. Root-zone cooling reduced oxidative stress indicators, including mortality (%), hydrogen peroxide content, and malondialdehyde content, and minimized cell leakage. Based on plant growth, physiological and biochemical traits, and electricity consumption, cooling the root zone to 24 °C rather than 21 °C is recommended for hot summers with high air temperatures. Full article