Quantifying the solid–fluid interfacial tensions depending on the substrate curvature: Young’s equation holds for wetting around nanoscale cylinder

Abstract

By extending the theoretical framework derived in our previous study [Imaizumi et al., J. Chem. Phys. 153, 034701 (2020)], we successfully calculated the solid–liquid (SL) and solid–vapor (SV) interfacial tensions of a simple Lennard-Jones fluid around solid cylinders with nanometer-scale diameters from single equilibrium molecular dynamics systems in which a solid cylinder was vertically immersed into a liquid pool. The SL and SV interfacial tensions γSL − γS0 and γSV − γS0 relative to that for bare solid surface γS0, respectively, were obtained by simple force balance relations on fluid-containing control volumes set around the bottom and top ends of the solid cylinder, which are subject to the fluid stress and the force from the solid. The theoretical contact angle calculated by Young’s equation using these interfacial tensions agreed well with the apparent contact angle estimated by the analytical solution to fit the meniscus shape, showing that Young’s equation holds even for the menisci around solids with nanoscale curvature. We have also found that the curvature effect on the contact angle was surprisingly small while it was indeed large on the local forces exerted on the solid cylinder near the contact line. In addition, the present results showed that the curvature dependence of the SL and SV interfacial free energies, which are the interfacial tensions, is different from that of the corresponding interfacial potential energies.

Effect of Alloying Elements in Steels on the Interfacial Structure and Mechanical Properties of Mg to Steel by Laser-GTAW Hybrid Direct Lap Welding

“…Studies have shown that Cr [18] promoted the formation of a smooth passivation film on the surface of the steel, and a smooth surface on the steel meant that the surface tension of the solid steel was greater. According to Young's equation [19,20]:…”

(Invited) Nanoscale Wetting and Its Connection with Macroscopic Young's Equation

“…where 〈•〉 denotes the ensemble average. Equation [10] means that if the system Hamiltonian H is analytically differentiable with respect to 𝜆, the integrand 〈𝜕𝐻/𝜕𝜆〉 in the right-most hand side can be obtained for each microscopic system with a given 𝜆 as the ensemble average. Hence, by numerically integrating Eq.…”

“…Hence, by numerically integrating Eq. [10], the free energy difference Δ𝐹 can be calculated. Similarly, by substituting the NVT partition function with NpT partition function Y as 𝐺(𝑁, 𝑝, 𝑇, 𝜆) = −𝑘 𝑇 ln 𝑌(𝑁, 𝑝, 𝑇, 𝜆)…”

“…Molecular dynamics (MD) analysis is a powerful tool to investigate and predict wetting from a microscopic point of view, with which various combinations of liquid and solid surface can be tested in silico. We have carried out MD simulations on the liquid behavior especially around the solid surface including static wetting (2)(3)(4)(5)(6)(7)(8)(9)(10)(11), dynamic wetting (12,13), liquid diffusivity (14-16) around the solid, and solid-liquid friction (17)(18)(19)(20)(21)(22)(23), where the fluid-solid pairs ranged from Lennard-Jones fluid to water, methanol, iso-propyl-alcohol and their mixture as fluids and from simple fcc crystal to OH-terminated Silica as the solid surfaces. In this series of studies, we have developed and adopted several methods for the calculation of the solid-related interfacial tensions from mechanical and thermodynamic viewpoints.…”