Vitrification of Liquid Metal‐in‐Oil Emulsions Using Nano‐Mineral Oxides

Abstract Ga and Ga‐based alloys have recently received significant attention as “liquid metals (LMs)” with the combined advantages of a low toxicity, low melting point, high fluidity, and high conductivity. An important method for modifying LMs for enhanced processabilities and new applications is to tailor them into colloidal microdroplets suspended in a liquid medium. In this study, the unique vitrification behavior of oil‐based colloidal systems is shown with suspended LM microdroplets induced by various mineral oxide (MO) nanoparticles that are added as solid rheology modifiers. MOs exhibit a high affinity for the surfaces of suspended LM droplets in an apolar oil medium due to the polar interaction between the MO surface and the oxide skin of the LM. Thus, even minute amounts of added MOs (Φ_MO < 0.01) transform a free‐flowing LM suspension (Φ_MO ≈ 0.55) into a highly viscoelastic fluid that enables advanced processing (e.g., 3D printing). At high MO loadings (Φ_MO ≥ 0.1), an emulsion with unprecedentedly high rheological strength is obtained, characterized by a yield stress of ≈10⁴ Pa. In highly vitrified emulsions, partial sintering effects are induced by high internal sample stress, which improves the thermophysical properties of emulsions that may be useful for several practical applications.