Molecular dynamics simulation of the wetting characteristics of a nanofluid droplet on rough substrate

Temperature dependence of adhesion properties at liquid-aluminum/solid interfaces

The adhesion problem of the liquid aluminum (Al) and solid surfaces in the production process has not been completely solved. In this paper, by performing the molecular dynamic simulations, we first establish models composed of liquid-Al/Al and liquid-Al/silicon (Si) systems, in which the region of solid temperature is from 100 K to 800 K. Then, the dependence between the adhesion force and the solid temperature is qualitatively investigated. The adhesion mechanism of liquid atoms is explored in terms of their diffusion behavior. The results show that there is an opposite effect of the temperature on adhesion properties between the liquid-Al/Al interface and the liquid-Al/Si interface. The thermal excitation effect induces enlargement of the probability of atomic collisions, which accounts for the increase of the adhesion force at the liquid-Al/Al interface. Conversely, the thermal excitation effect leads to the detachment of the atoms in contact with each other, which reduces the adhesion force at the liquid-Al/Si interface. Our findings reveal that the solid Al surface is aluminophilic but the solid Si surface is aluminophobic. In addition, the adhesion between liquid-Al and solid surfaces can be explained by the variation of the interfacial potential.

Shape Optimization of a Microhole Surface for Control of Droplet Wettability via the Lattice Boltzmann Method and Response Surface Methodology

The chief aim is to explore the wetting state on a microhole surface and to optimize the shape parameters of a microhole surface. A two-dimensional pseudopotential model was established, and the effects of shapes on the wetting behavior were explored. The shape parameters were optimized via the response surface methodology. The results reveal that the microhole surface can achieve a superhydrophobic state. When the diameter varies from 25 to 200 μm, the droplet is gradually lifted. However, when the diameter of the microhole is too large, the contact angle decreases rapidly. When the microhole diameter increases, relative radii of the x- and y-directions exhibit increasing trends. With the increase of the spacing, the gaps between the microholes are gradually filled with the droplet. When spacing increases, relative radii of x- and y-directions exhibit decreasing trends. The largest contact angle of 171.246° at the diameter of 76 μm and the spacing of 48 μm is observed.