Combination of Functional Nanoengineering and Nanosecond Laser Texturing for Design of Superhydrophobic Aluminum Alloy with Exceptional Mechanical and Chemical Properties

Abstract

Industrial application of metallic materials is hindered by several shortcomings, such as proneness to corrosion, erosion under abrasive loads, damage due to poor cold resistance, or weak resistance to thermal shock stresses, etc. In this study, using the aluminum-magnesium alloy as an example of widely spread metallic materials, we show that a combination of functional nanoengineering and nanosecond laser texturing with the appropriate treatment regimes can be successfully used to transform a metal into a superhydrophobic material with exceptional mechanical and chemical properties. It is demonstrated that laser chemical processing of the surface may be simultaneously used to impart multimodal roughness and to modify the composition and physicochemical properties of a thick surface layer of the substrate itself. Such integration of topographical and physicochemical modification leads to specific surface nanostructures such as nanocavities filled with hydrophobic agent and hard oxynitride nanoinclusions. The combination of superhydrophobic state, nano- and micro features of the hierarchical surface, and the appropriate composition of the surface textured layer allowed us to provide the surface with the outstanding level of resistance of superhydrophobic coatings to external chemical and mechanical impacts. In particular, experimental data presented in this study indicate high resistance of the fabricated coatings to pitting corrosion, superheated water vapor, sand abrasive wear, and rapid temperature cycling from liquid nitrogen to room temperatures, without notable degradation of superhydrophobic performance.

Pulsed Laser Induced Triple Layer Copper Oxide Structure for Durable Polyfunctionality of Superhydrophobic Coatings

“…This alloy melts at T = 1083 °C. As discussed in recent studies, laser surface treatment provides ample opportunities for modifying the surface properties of materials. Thus, the interaction of high power radiation with metal surface in the presence of atmospheric gases is accompanied by the chemical reactions leading to variation of the physicochemical properties of surface layers.…”

“…An ablation of the material results in the formation of a surface texture, whose characteristics are controlled by the parameters of laser treatment. Finally, the controlled combination of grain refinement with high stresses (induced by rapid cooling of the surface layer after laser heating) allows obtaining the desired mechanical properties of the surface …”

“…The additional heat treatment at T = 375 °C in an oven for 1–3 h was used to increase the fraction of surface cupric oxide with respect to cuprous oxide. To obtain a superhydrophobic state of the laser treated surface, the surface energy of the samples was reduced by chemisorption of fluorooxysilane onto the surface hydroxyl groups serving as chemisorption centers . Exposure of the samples in the sealed vessel with saturated vapors of methoxy‐{3‐[(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8‐pentadecafluorooctyl)oxy]‐propyl}‐silane for 1 h at T = 95 °C, followed by drying for 1 h in an oven at 130 °C resulted in the formation of a crosslinked layer of hydrophobic agent atop the laser textured surface and in the encapsulation of excess fluorooxysilane in the porous structures, formed upon laser treatment.…”

“…Abrasive wear of the fabricated samples was studied according to American Society for Testing and Materials (ASTM) Standard F735 in an oscillating sand abrasion test using the method, described in detail in our recent study …”

“…At the same time, for the majority of designed superhydrophobic coatings, a poor abrasive resistance restricts the practical application of these coatings. However, it was shown recently that a strategy, combining the laser chemical modification of metal's surface layer and laser texturing, followed by chemisorption of low energy compounds, can be effectively used to control the mechanical and chemical properties of a superhydrophobic layer on aluminum substrate.…”