Langmuir最新文献

This study employed reactive force field molecular dynamics simulations to investigate the mechanisms underlying the ultrasonic vibration-assisted polishing of 4H-SiC in hydrogen peroxide (H₂O₂) solutions. A model was developed to simulate scratching with a single diamond abrasive particle in an aqueous H₂O₂ environment to systematically examine the effects of vibration amplitude and frequency on friction forces, surface chemical reactions, material removal, surface morphology, and crystal structure. The results revealed that ultrasonic vibrations significantly influenced the fluctuation characteristics of the friction forces. Specifically, the frequency primarily determined the period of these fluctuations, whereas the amplitude determined their magnitude. Increasing both the amplitude and frequency promoted the formation of oxidation bonds, with the amplitude having a more pronounced influence. Ultrasonic vibrations promoted oxidation by increasing the number of dangling bonds on the surface, resulting in more oxidation bonds. Additionally, higher amplitudes facilitated the removal of atoms from silicon carbide (SiC) substrate, whereas variations in frequency had a marginal impact on atomic displacement. Lower frequencies and smaller amplitudes reduce amorphization, thereby preserving the crystalline structure of the SiC surface. However, high-frequency vibrations improve surface smoothness by shortening the single-cycle interaction time. These findings provide theoretical insights into the fundamental mechanisms of ultrasonic vibration-assisted polishing, guiding its optimized application in precision processing of SiC materials.

A novel melamine-derived quaternary ammonium salt corrosion inhibitor (Me-B) was synthesized using melamine and benzyl bromide as raw materials. Systematic evaluation of its corrosion inhibition performance for N80 carbon steel in a 15 wt % HCl solution was conducted via weight loss measurements and electrochemical techniques. Experimental results demonstrate that Me-B exhibits outstanding performance. At 363 K, the addition of 0.1 wt % Me-B significantly reduced the corrosion rate of N80 steel from 1,258.36 g·m^-2·h^-1 to 19.75 g·m^-2·h^-1, corresponding to an inhibition efficiency of 98.4%. Even at elevated temperatures up to 383 K, Me-B retained measurable corrosion inhibition capability. Adsorption of Me-B on the N80 steel surface follows a mixed physical-chemical mechanism consistent with the Langmuir adsorption model, which elevates the energy barrier for corrosion reactions and impedes their progression. Theoretical calculations elucidated the inhibition mechanisms of both neutral Me-B and protonated Me-B (Me-BH⁺), revealing that Me-BH⁺ possesses superior reactivity and enhanced adsorption affinity toward the metal surface compared to neutral Me-B. This facilitates the formation of a compact protective film that effectively blocks corrosive medium penetration, thereby mitigating acid-induced metal corrosion.

This study employs density functional theory to investigate the adsorption and sensing behaviors of characteristic decomposition gases from lithium-ion battery thermal runaway (CO, CO₂, and C₂H₄) on pristine and Ag-cluster modified MoS₂, MoSe₂, and Janus MoSSe monolayers. The structural, electronic, and adsorption properties were systematically analyzed to elucidate the influence of Ag_n (n = 1-3) clusters on the gas sensing performance. Results indicate that Ag doping enhances the thermodynamic formation energy, charge transfer, and electronic coupling between gas molecules and substrates, converting weak physisorption into stronger chemisorption, particularly for CO and C₂H₄. Among all configurations, Ag₃-MoSSe exhibits the highest adsorption energy and the most significant modulation of the Fermi level, accompanied by band gap narrowing and improved conductivity. Coadsorption of CO and C₂H₄ demonstrates a synergistic effect, leading to quasi-metallic characteristics and stronger hybridization between the Ag-4d and C-2p orbitals. Furthermore, the weak interaction of H₂O with the Ag-modified surfaces indicates good humidity resistance and selectivity. Work function and sensitivity analyses reveal that Ag₃-MoSSe possesses the highest sensitivity to C₂H₄ with moderate recovery capability, making it a promising candidate for real-time detection of characteristic gases generated during lithium-ion battery thermal runaway.

To develop high-performance air filters with integrated antimicrobial functionality, this study employed electrospinning to fabricate polysulfone (PSF)-based filters incorporating two efficient photocatalysts: Ph-C≡C-Cu and 4-F-Ph-C≡C-Cu. The resulting composite materials were systematically evaluated for their antibacterial and particulate filtration properties. Among them, the 2% 4-F-Ph-C≡C-Cu@PSF filter exhibited an antibacterial rate of 95.2% against Gram-positive Staphylococcus aureus, while the 2.5% Ph-C≡C-Cu@PSF filter showed an antibacterial rate of 86.6% against Gram-negative Escherichia coli, which also achieved a high PM 2.5 filtration efficiency of 97.5%. In terms of the balance between filtration and breathability, the 1% 4-F-Ph-C≡C-Cu@PSF filter showed the best quality factor (0.05). Mechanistic investigation revealed that the superior antibacterial activity of 4-F-Ph-C≡C-Cu composites is primarily attributable to their enhanced superhydrophobicity. This work successfully prepared dual-functional filters via electrospinning, presenting a promising strategy for developing advanced materials for antimicrobial air filtration applications.

An in-depth understanding of the adsorption and energy storage mechanism of a zeotropic working fluid in metal-organic framework materials is significant for the application of nanomaterials in thermodynamic cycles. In this study, the adsorption behavior and energy storage properties of R32, R1234yf, and their mixtures in MOF-5 were investigated using the grand canonical Monte Carlo (GCMC) method. The adsorption characteristics and adsorption heat were revealed under different pressure, temperature, and composition conditions. In addition, the rationality of the ideal adsorbed solution theory (IAST) used in the present models was also verified. The study showed that the uptake of R32 was sensitive to both temperature and pressure while that of R1234yf was sensitive to pressure below 1000 kPa but insensitive in the range of 1000-6000 kPa and insensitive to temperature. During the adsorption of R32/R1234yf mixtures, the adsorption of R1234yf also exhibits a similar trend. The selective adsorption coefficient of MOF-5 for R32 in comparison to R1234yf decreased with an increase in temperature and increased with an increase in pressure. By adding MOF-5 to the R32/R1234yf zeotropic mixtures, the enthalpy change of the zeotropic/MOF-5 nanofluid could be improved.

The urgent need for sensitive, selective, and rapid detection of nerve agents (NAs), a class of highly toxic organophosphorus compounds, has motivated the development of advanced fluorescent sensing materials. Herein, a series of interpenetrated luminescent metal-organic frameworks (MOFs) with 2,6-naphthalenedicarboxylic acid (NDC) and naphthalenediimide (NDI) or perylenediimide (PDI) ligands were reported, specifically targeting the detection of diethyl chlorophosphate (DCP), a nerve agent simulant. Among them, the 3D Zn-PDI-NDC framework demonstrates a pronounced fluorescence "turn-on" response to DCP with an ultra-low detection limit of 3.6 ppb and high selectivity, even in the presence of potential interferents, which is mainly attributed to ligand conformational reorganization accompanied by host-guest ground-state interactions. On the other hand, Zn-NDI-NDC and Zn-NDC MOFs with similar interpenetrated architectures display distinct fluorescence response behaviors, including fluorescence quenching or weak enhancement, reflecting differences in ligand electronics and host-guest interactions. Such comparative sensing behaviors in structurally related MOF sensors highlight the crucial role of ligand electronics and geometry. Overall, this work presents a PDI-based interpenetrated MOF platform with excellent DCP sensing performance and offers insights into MOF design strategies for organophosphorus nerve agent detection.

Commercial separators face significant challenges in mitigating lithium dendrite growth, primarily due to non-uniform lithium ion deposition, which leads to battery performance degradation and raises safety concerns related to separator failure. To address these issues, this study proposes a novel composite separator incorporating two-dimensional (2D) X-type molecular sieves as a functional coating for lithium metal battery separators. The primary objective is to achieve uniform lithium-ion distribution across the surface of the lithium metal anode, thereby effectively inhibiting the formation of lithium dendrites. The results indicate that in comparison to conventional polypropylene (PP) separators, the 2D-X-PP composite separators exhibit substantially improved physical properties, such as enhanced thermal stability, wettability, and tensile strength. In terms of electrochemical performance, cells incorporating the 2D-X-PP separators retained an outstanding 70% of their initial capacity after 1000 cycles, while those employing PP separators retained less than 50% of their capacity after only 500 cycles. These findings provide strong evidence of the exceptional performance of 2D-X-PP and further pave the way for the development of molecular-sieve-functionalized separators in lithium metal batteries.