Chameleon Metals: Autonomous Nano‐Texturing and Composition Inversion on Liquid Metals Surfaces

Abstract

Studies on passivating oxides on liquid metals are challenging, in part, due to plasticity, entropic, and technological limitations. In alloys, compositional complexity in the passivating oxide(s) and underlying metal interface exacerbates these challenges. This nanoscale complexity, however, offers an opportunity to engineer the surface of the liquid metal under felicitous choice of processing conditions. We inferred that difference in reactivity, coupled with inherent interface ordering, presages exploitable order and selectivity to autonomously present compositionally biased oxides on the surface of these metals. Besides compositional differences, sequential release of biased (enriched) components, via fractal‐like paths, allows for patterned layered surface structures. We, therefore, present a simple thermal‐oxidative compositional inversion (TOCI) method to introduce fractal‐like structures on the surface of these metals in a controlled (tier, composition, and structure) manner by exploiting underlying stochastic fracturing process. Using a ternary alloy, a three‐tiered (in structure and composition) surface structure is demonstrated.

Gallium‐Based Liquid Metal Composites and the Continuous Forming Methods

“…Recently, Martin Thuo's team explored GaInSn's LM surface oxide structure in detail, demonstrating its layered and controllable surface oxide, which has been described as a "chameleon". [34,48] The oxide layer of galliumbased liquid metal is directly defined as the gallium oxide Table 2. Physical properties of several LMs and water (H 2 O).…”

“…Recently, Martin Thuo's team explored GaInSn's LM surface oxide structure in detail, demonstrating its layered and controllable surface oxide, which has been described as a “chameleon”. [ 34,48 ] The oxide layer of gallium‐based liquid metal is directly defined as the gallium oxide component in most of the previous studies. In this study, the process of its oxidation formation was described in detail from the microscopic level, which found that the thermal oxidation component inversion phenomenon, taking GaInSn for example, when the LM is exposed to air, according to the rules of the Gibbs free energy, due to the low Gibbs free energy of gallium oxide (as shown in Figure 3b), The Ga component is the first to be oxidized, that is, the outer oxide is Ga oxide.…”

Mechanistic Understanding of Speciated Oxide Growth in High Entropy Alloys

“…1f). [27][28][29] The use of APT illuminates further details about the growth of outer oxides, especially the formation of Co islands on the surface layer, which might not be visible in two dimensions (Fig. 1g).…”

Compositional Design of Surface Oxides in Gallium–Indium Alloys

“…Presently, a number of techniques have been developed to moderate, accelerate, functionalize, remove (via etchants), or augment the existence of such native oxide layers on liquid metals. − ,,− Despite these efforts, the existence and identity of the native oxide under ambient conditions have been treated as inevitable, rather than as additional tunable parameters of these already highly versatile systems. Notably, rheological results published by Jacob et al suggest that surface oxide replacement occurs for liquid metal systems in which a small piece of aluminum is placed into a bath of Ga, EGaIn, or Galinstan .…”