2012/01/23 by Qin Xu, Nikolai Oudalov, Nikolai Qudalov +4 · 241 citations
Engineering · Materials Science · Physics and Astronomy · #Contact angle #Eutectic system #Fluid Dynamics and Thin Films #Nanomaterials and Printing Technologies #Oxide #Sessile drop technique #Surface Modification and Superhydrophobicity #Surface stress #Surface tension #Viscosity #Wetting #Yield (engineering) #cond-mat.mtrl-sci #cond-mat.soft #physics.flu-dyn
paper · pdf · doi:10.1063/1.4724313
published in Physics of Fluids 24(6) (American Institute of Physics) · 18 pages, 9 figures
arxiv created 2012/01/23 · openalex publication_date 2012/06/01 · arxiv updated 2013/05/06 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
Liquid metals exhibit remarkable mechanical properties, in particular large surface tension and low viscosity. However, these properties are greatly affected by oxidation when exposed to air. We measure the viscosity, surface tension, and contact angle of gallium and a eutectic gallium-indium alloy while controlling such oxidation by surrounding the metals with an acid bath of variable concentration. Rheometry measurements reveal a yield stress directly attributable to an oxide skin that obscures the intrinsic behavior of the liquid metals. We demonstrate how the intrinsic viscosity can be obtained with precision through a scaling technique that collapses low- and high-Reynolds number data. Measuring surface tension with a pendant drop method, we show that the oxide skin generates a surface stress that mimics surface tension and develop a simple model to relate this to the yield stress obtained from rheometry. We find that yield stress, surface tension, and contact angle all transition from solid-like to liquid behavior at the same critical acid concentration, thereby quantitatively confirming that the wettability of these liquid metals is due to the oxide skin.