Effect of Nanopillars on the Wetting State and Adhesion Characteristics of Molten Aluminum Droplets

Abstract

To solve the adhesion problem between molten aluminum and vacuum ladle liner during the electrolytic aluminum production process, the wetting state and adhesion properties of molten aluminum droplets on substrate surfaces with different nanopillars are investigated based on molecular dynamics. The results show that the adhesion strength of molten aluminum droplets in different wetting states has the pattern Young state > Wenzel state > Cassie state. Effects of increasing nanopillar height or interval are poles apart in the wetting state and adhesion characteristics of aluminum molten droplets. The critical height and critical interval of the nanopillar where the wetting state transition occurs are obtained. The increase of the nanopillar width can induce the wetting state transition from the Cassie state to the Wenzel state. In addition, the phantom wall method is applied to study the variation of the separation force. It is found that a peak in the separation force curve occurs when the molten droplet separates from the bottom of the nanopillar interval or the top of the nanopillar. The separation force curves of the droplets in the Young state and the Cassie state have single peaks, while the droplets in the Wenzel state have double peaks.

The effect of crystallographic orientation of α-Al2O3 on the wetting behavior and adhesion characteristics of aluminum droplets

“…In order to reveal the influence of substrate crystallographic orientation on the diffusion characteristics of Al droplets on the substrate surface, MD simulations are used to calculate the mean-square displacement (MSD) and the diffusion coefficient (D) of aluminum droplets [30]. And MSD can be obtained by the formula below [4,31]:…”

“…The diffusion coefficients of Al droplets on the C, M, and R surfaces at 1073 K can be obtained from equation (4). The diffusion coefficients are 1.64 × 10 −8 m 2 s −1 , 1.60 × 10 −8 m 2 s −1 , and 1.62 × 10 −8 m 2 s −1 before 200 ps, and 6.17 × 10 −9 m 2 s −1 , 4.08 × 10 −9 m 2 s −1 and 4.67 × 10 −9 m 2 s −1 on the C, M, and R surfaces in the second stage (200-600 ps), respectively.…”

“…Since alumina (α-Al 2 O 3 ) makes up the majority of the inner wall material of the vacuum ladle [1], the issue with adhesion between aluminum fluid and the inner wall of the vacuum ladle that occurs during aluminum fluid transport is essentially one between liquid Al and solid α-Al 2 O 3 . There are many factors affecting the wetting behavior at the solid-liquid interface, such as alloying elements [2], surface morphology [3,4], temperature [5], and substrate dissolution [6]. The surface of single-crystal α-Al 2 O 3 can be created by a variety of crystal surfaces [7].…”

1000 °C High-Temperature Wetting Behaviors of Molten Metals on Laser-Microstructured Metal Surfaces

“…Recently, molten metals have also been proposed to be potential novel materials in various fields, such as newly developed batteries and nuclear fusion. − The wetting of molten metals on various substrate surfaces has a great impact on related processes and applications, significantly affecting the processing feasibility and product performance. However, only few literature studies focused on the wettability of molten metals at high temperatures (e.g., 1000 °C) compared with the wettability studies on more common liquids under more gentle conditions, such as water and low-melting-point liquid metals at room temperature. − Various simulations have been performed to predict the probable wetting behaviors of molten metals on various substrates, − but practical observations remain scarce due to the availability of materials and the strict environmental requirements. Among the restricted experimental work, researchers prefer to improve the wettability of molten metals with several kinds of solid surfaces for better performance in welding, brazing, metal-based composite formation, and lithium battery preparation. − ,− For example, Wu et al proposed a method to enhance the wettability of a kind of room-temperature gallium-based liquid metal on polyacrylate surfaces for a better connection, Fan et al modified the wetting and spreading behaviors of Sn on the SiC surface by changing the content of the alloying element Cr, Li et al enhanced the wettability of molten high manganese steel with Ni–Co-coated ZTA ceramic particles to strengthen the abrasive wear resistance of the composites, and Sui et al studied the wetting ability of molten Ce and Cu–Ce alloy on various carbon materials.…”

“…On the other hand, limited publications studied the effect of surface microstructures on the wetting behaviors of molten metals on substrates at high temperatures, while most of them concerned about the composition of the melts and the substrate surfaces or the periphery conditions. − ,,− , Lai et al found that a microporous copper substrate enhanced the wetting of molten Sn, while Zhou et al structured the steel mold surfaces to weaken the adhesion of the molten and resolidified Al alloys with the mold by preventing their full wetting. Liu et al discussed the effect of laser-textured stainless steel surface structures on the wetting and spreading behaviors of the Al–Si alloy in the presence of flux, and Lin et al observed that rough silica surfaces improved the spreading of the Sn–Ag–Ti alloy.…”