Characterization and Manipulation of Interfacial Activity for Aqueous Galinstan Dispersions

Abstract

AbstractRoom temperature liquid eutectic metals have the potential to maintain electrical and thermal conductivity during deformation, a combination of properties difficult to obtain. Two such metals, eutectic gallium–indium (EGaIn) and galinstan (eutectic gallium–indium–tin), exhibit similar flow behavior attributed to a thin oxide shell. Understanding the oxide shell is critical for understanding the interactions that influence mixing and stability of the liquid metals in other media. In this paper, the effect of aqueous HCl on the interfacial tension (IFT), interfacial rheology, and dispersibility of galinstan are systematically evaluated. It is determined that the IFT of galinstan/water and galinstan/1 m HCl are similar (≈530 mN m−1), but at 0.001 to 0.5 m HCl IFT decreases to 160 mN m−1. Similar discontinuous behavior is observed in the interfacial rheology. The low IFT coupled with a mechanically strong interface at intermediate acid concentrations suggests a change in interface composition. This is supported by SnO2 particles, present during the dispersion process, producing more stable galinstan dispersions than Ga2O3 or In2O3. Interestingly, SnO2 also improves the dispersion of EGaIn despite its lack of tin. This new interfacial manipulation method enables galinstan dispersions in a range of aqueous and nonaqueous phases to enhance the electrical and thermal properties.