Langmuir最新文献

The effect of embedded graphitic carbon nitride (g-C₃N₄) nanosheets on hydration and thermal response behavior of cross-linked thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate), abbreviated as P(MA-co-MA₃₀₀), thin films is probed by white light interferometry. Compared with that of the cross-linked pure P(MA-co-MA₃₀₀) films, the surface roughness of the cross-linked hybrid films is slightly increased, which is caused by the minor aggregation of g-C₃N₄ nanosheets during the spin-coating process. After exposure to a water vapor atmosphere, both cross-linked pure and hybrid films can absorb water and swell. However, the introduction of g-C₃N₄ not only induces a larger hydration extent but also triggers a nonlinear transition behavior upon heating. This prominent difference might be related to the residual hydrophilic groups (-NH₂ and N-H) on the surface of g-C₃N₄ nanosheets, which enhance the interaction and absorption capability for water molecules in the hybrid films. Upon further increasing the amount of embedded g-C₃N₄ nanosheets in films, more hydrogen bonds are formed and a larger hydration extent of films is observed. To break all of the hydrogen bonds in films, a higher transition temperature (TT) is required. The observed hydration and transition behaviors of hybrid films can be used to design hydrogel-based films for hydrogen evolution or wastewater treatment.

Superhydrophobic coatings are increasingly recognized as a promising approach to enhancing power generation efficiency and prolonging the operational lifespan of wind turbines. In this research, a durable superhydrophobic perfluoroalkoxy alkane (PFA) coating was developed and specifically designed for spray application onto the surface of wind turbine blades. The PFA coating features a micronano hierarchical structure, exhibiting a high water contact angle of 167.0° and a low sliding angle of 1.7°. The optimal PFA coating exhibits stability and maintains a superhydrophobic performance during mechanical and chemical tests. The findings of this study establish a positive association between the surface energy of the coating and its effectiveness in anti-icing. The delayed icing time for the PFA-coated surface is 46.83 times longer than that of an uncoated surface, and the ice adhesion strength is only 1.875 kPa. Additionally, the PFA coating demonstrates remarkably high ice suppression efficiencies of 94.7 and 99.5% in anti-icing experiments at ambient temperatures of -6 and -10 °C, respectively. It is anticipated that this stable superhydrophobic PFA coating will be a candidate for anti-icing applications in wind turbine blades.

Laser-assisted electrochemical machining (ECM) is an ideal manufacturing method for Inconel 718 (IN718) because of the method's high efficiency and good surface quality, and the basis for and key to laser-assisted ECM is its anodic electrochemical dissolution behavior. In this study, IN718 in a 10 wt % NaNO₃ solution was subjected to innovative electrochemical testing and laser-assisted ECM experiments to investigate its corrosion properties and the passive film characteristics formed on its surface. The passivation-related behaviors and structures of the passive film were investigated based on open-circuit potentials, dynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy. It was found that there was obvious active-passive-transpassive transition behavior, and the structure of the passive film in laser-assisted ECM exhibited pores and defects, resulting in weak corrosion resistance, compared with IN718 under ECM without laser irradiation. The chemical composition of the passive film was obtained by X-ray photoelectron spectroscopy. The results showed that the passive film was composed mainly of a mixture of NiO, Ni(OH)₂, Cr₂O₃, CrO₃, Fe₂O₃, α-Fe₂O₃, α-FeOOH, Nb₂O₅, NbO, MoO₃, MoO₂, and TiO₂. The passive film formed by laser-assisted ECM was rich in NiO and TiO₂ and lacked Cr₂O₃ and MoO₃, which validated its pores and defect structures. A corresponding schematic model was also proposed to characterize the interface structure between the IN718 substrate and the passive film. Laser-assisted ECM tests were performed under different current densities and machining times, and the corrosion morphology of IN718 was identified. Corrosion pits and a loose product layer appeared on the machined surface at low current densities, and the dissolution mechanism was pitting. The quantity and depth of the corrosion pits dispersed on the machined surface clearly decreased as the current density increased. Finally, a quantitative corrosion model was established to characterize the dissolution behavior of IN718 in NaNO₃ solution during laser-assisted ECM.

Surface texturing of manufactured products tailors their properties, such as friction, adhesion, biocompatibility, or fluid interactions. However, advancements in this area are largely the result of trial-and-effort testing and generally lack a science-guided framework for determining the surface topography that will optimize performance. The present investigation explores grayscale electron-beam lithography as a means to create multiscale surface patterns to control surface performance. Here, we created and characterized a set of surface textures on a silicon wafer; the textures were superpositions of sine waves of varying wavelengths and amplitudes. First, the multiscale topography of the patterned surface was characterized, using profilometry and atomic force microscopy, to understand its fidelity to the designed-in pattern. The results of this analysis demonstrated how grayscale lithography accurately controlled the lateral size of features but was less precise on the vertical height of the surface, and also introduced inherent roughness below the scale of patterning. Second, a micromechanical tester was used to characterize the adhesion of the surfaces with large-scale polished silicon spheres. The results showed that adhesion could be tailored, with significant contribution from all of the designed-in length scales of topography. The strength of adhesion did not correlate with conventional roughness parameters but could be accurately modeled using simple numerical integration. Taken together, this investigation demonstrates the promise and challenges of grayscale e-beam lithography with multiscale patterns as a method for the tailoring of surface performance.

Thermoresponsive microgels experience a volume phase transition triggered by temperature changes, a phenomenon often analyzed using dynamic light scattering to observe overall size alterations via the diffusion coefficient. However, local structural changes are typically assessed using more intricate and expensive techniques like small-angle neutron or X-ray scattering. In our research, we investigate the volume phase transition of poly-N-isopropylacrylamide (PNIPAM)-based microgels by employing a combination of temperature-dependent dynamic light scattering and simpler, faster, and more efficient attenuation measurements. We utilize attenuation at a fixed wavelength as a direct measure of dispersion turbidity, linking the absolute changes in hydrodynamic radius to the absolute changes in turbidity. This approach allows us to compare "classical" PNIPAM microgels from precipitation polymerization, charged copolymer microgels from precipitation copolymerization, and core-shell microgels from seeded precipitation polymerization. Our study includes a systematic analysis and comparison of 30 different microgels. By directly comparing data from dynamic light scattering and attenuation spectroscopy, we gain insights into structural heterogeneity and deviations from the established fuzzy sphere morphology. Furthermore, we demonstrate how turbidity data can be converted to swelling curves.

In this paper, CH₄, C₂H₂, H₂, and CO adsorbed on intrinsic MoTe₂ monolayer and transition metal atom (Ta, V)-doped MoTe₂ monolayer have been investigated with density functional theory based on first-principles study. The adsorption energy, geometries, band structures, and density of states of four gases (CH₄, C₂H₂, H₂, and CO) adsorbed on the MoTe₂ and doped MoTe₂ surfaces were analyzed. The results shown that the gas adsorption performance of transition metal atom (Ta, V)-doped MoTe₂ monolayers is more superior than that of intrinsic MoTe₂, and the adsorption energy and charge transfer of the adsorbed gases on the TM-MoTe₂ monolayer are significantly increased in comparison with both sides. Among them, Ta-MoTe₂ has the largest E_ads value in the adsorbed CO system with a very small adsorption distance, as well as a more suitable recovery time of CO at room temperature, so Ta-MoTe₂ can be a candidate material for CO detection. New atoms were introduced during the doping process, which increased the carrier density and carrier mobility of the material, thus improving the charge transfer at the surface of the material. which provides a direction for the gas-sensitive properties of metal Ta-modified MoTe₂ materials.

A critical constraint impeding the utilization of Mn-based oxide catalysts in NH₃ selective catalytic reduction (NH₃-SCR) is their inadequate resistance to water and sulfur. This vulnerability primarily arises from the propensity of SO₂ to bind to the acidic site in manganese oxide, resulting in the formation of metal sulfate and leading to the irreversible deactivation of the catalyst. Therefore, gaining a comprehensive understanding of the detrimental impact of SO₂ on the acidic sites and elucidating the underlying mechanism of this toxicity are of paramount importance for the effective application of Mn-based catalysts in NH₃-SCR. Herein, we strategically modulate the acidity of the manganese oxide catalyst surface through the incorporation of Ce and Nb. Comprehensive analyses, including thermogravimetry, NH₃ temperature-programmed desorption, in situ diffused reflectance infrared Fourier transform spectroscopy, and density functional theory calculations, reveal that SO₂ exhibits a propensity for adsorption at strongly acidic sites. This mechanistic understanding underscores the pivotal role of surface acidity in governing the sulfur resistance of manganese oxide.