Complexity and Opportunities in Liquid Metal Surface Oxides

Martin, Andrew; Du, Chuanshen; Chang, Boyce S.; Thuo, Martin M.

doi:10.1021/acs.chemmater.0c02047

Cited by 49 publications

(50 citation statements)

References 90 publications

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“… [8, 14] The passivating oxide espouses a complex compositional gradient that has, until recently, been ignored [13a, 15] . This complex autonomously organized gradient, over a very short distance (a Guggenheim interface), [16] complicates the definition of surface stress and its effect in bulk properties. In the absence of a passivating oxide, the surface energy of a solid metal surface is defined as

γ_{metal} = A_{H} / 24 π D_{0}^{2}

, where A H is Hamaker's constant and D 0 is distance between atoms [17] .…”

Section: Resultsmentioning

confidence: 99%

“…Ambient removal of an oxide layer is, therefore, not merely a separation as inferred in definition of γ metal above. In liquid metal alloys, therefore, γ metal is at the very least a third rank tensor that captures the contribution of 1) compositional gradient across the thickness of the oxide, [13a, 15c, 16] 2) shape, [18] 3) component flux/diffusivity, [19] and iv) metal‐oxide interface plasticity [20] . Surface speciation, thickness, and packing density across the oxide thickness induces asymmetry in chemical potential across the oxide thickness rendering the interfacial energy a tensor,

\hat{T} \propto \nabla^{2} γ

[21] .…”

Section: Resultsmentioning

confidence: 99%

“…3) Scalable and accessible synthesis of stable undercooled system enables a distinct class of functional material with unique properties, akin to that of metastable metallic glasses or other amorphous solids. The nature of this frustrated kinetic state creates an opportunity for unprecedented and unique low‐energy and low‐temperature metal processing pathways (soft lithography, heat‐free solders, additive manufacturing, among others) [8, 14c,d, 16, 28, 35] …”

Section: Resultsmentioning

confidence: 99%

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Stabilization of Undercooled Metals via Passivating Oxide Layers

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Undercooling metals relies on frustration of liquid–solid transition mainly by an increase in activation energy. Passivating oxide layers are a way to isolate the core from heterogenous nucleants (physical barrier) while also raising the activation energy (thermodynamic/kinetic barrier) needed for solidification. The latter is due to composition gradients (speciation) that establishes a sharp chemical potential gradient across the thin (0.7–5 nm) oxide shell, slowing homogeneous nucleation. When this speciation is properly tuned, the oxide layer presents a previously unaccounted for interfacial tension in the overall energy landscape of the relaxing material. We demonstrate that 1) the integrity of the passivation oxide is critical in stabilizing undercooled particle, a key tenet in developing heat‐free solders, 2) inductive effects play a critical role in undercooling, and 3) the magnitude of the influence of the passivating oxide can be larger than size effects in undercooling.

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γ_{metal} = A_{H} / 24 π D_{0}^{2}

, where A H is Hamaker's constant and D 0 is distance between atoms [17] .…”

Section: Resultsmentioning

confidence: 99%

\hat{T} \propto \nabla^{2} γ

[21] .…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Stabilization of Undercooled Metals via Passivating Oxide Layers

et al. 2021

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“…[8,14] Thep assivating oxide espouses ac omplex compositional gradient that has,u ntil recently,b een ignored. [13a,15] This complex autonomously organized gradient, over avery short distance (a Guggenheim interface), [16] complicates the definition of surface stress and its effect in bulk properties.I nt he absence of ap assivating oxide,the surface energy of asolid metal surface is defined as g metal ¼ A H 24pD 2 0 ,w here A H is Hamakersc onstant and D 0 is distance between atoms. [17] A speciated passivating oxide diverges surface tension (rg)asthe system equilibrates.…”

Section: Resultsmentioning

confidence: 99%

Stabilization of Undercooled Metals via Passivating Oxide Layers

et al. 2021

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“…The surface is a type of interface, which specifically refers to the gas phase substance in interfacial behavior. In the processes of thermodynamics, [ 16,17 ] surface absorption, [ 18,19 ] controllable wetting, [ 6,13,20 ] material catalysis, [ 21,22 ] redox, and other physical and chemical reactions, [ 23,24 ] RTLMs inevitably contact with other substances with different phase states. Even the pure liquid metal would contact with oxygen in the air to yield a thin protective film.…”

Section: Introductionmentioning

confidence: 99%

Interfacial Engineering of Room Temperature Liquid Metals

Liu

Cui

et al. 2021

Adv Materials Inter

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and formed spontaneously and instantaneously upon exposure to atmospheric oxygen. [1-3] The thin film or "protective skin" covering the surface of RTLMs, generally dominated the physical properties and applications of the materials. This thin film is composed of a majority fraction of gallium oxides with a much smaller amount of indium and tin oxides. [4] When immersed in acidic or alkaline electrolytes, the oxidic films of RTLMs will be dissolved. [5-8] Due to the disorder of internal structure, the surface of the spherical liquid metal droplet is smooth and removable under the function of surface tension. [9,10] According to the size and structure of the solid substrate, the contact areas between the liquid metal and the solid substrate shows various wetting phenomena and corresponding application scenarios. [11-14] Surface chemical composition plays the primary role in dominating various phenomena and practical applications of RTLMs, which possessed the technologically important and scientifically interesting parameter. Gallium-based liquid metal is similar in structure to conventional solid metal, except for some covalent bonds inside, and the physicochemical properties have the commonality of both metallic solid and fluid properties. [15] The composition of gallium-based alloys can be assumed as made up of several atomic groups, within which the permutation of the solid remains, the binding energy between the liquid atoms remains strong, but the binding force between the groups was broken. The interface refers to the contact area between the different phases, which is the transition layer from one phase to another. The binding force of electrons that are relatively far away from the inner core is related to their energy, causing the interface behavior between different phases to be incompletely consistent. The surface is a type of interface, which specifically refers to the gas phase substance in interfacial behavior. In the processes of thermodynamics, [16,17] surface absorption, [18,19] controllable wetting, [6,13,20] material catalysis, [21,22] redox, and other physical and chemical reactions, [23,24] RTLMs inevitably contact with other substances with different phase states. Even the pure liquid metal would contact with oxygen in the air to yield a thin protective film. [17,25,26] Therefore, the investigation of interfacial behaviors between RTLMs and different surrounding mediums is helpful to renovate and broaden the understanding and applications of liquid metal. So far, there gradually appeared literature on phenomena and mechanism of the interfacial effect of RTLMs, such as synthesis of low-dimensional materials in the gas atmosphere, [27,28] Room temperature liquid metals (RTLMs), especially those made of galliumbased alloys belong to an emerging versatile material with fascinating characteristics derived from its simultaneous metallic and inherent fluidic natures. The interfacial effects of liquid metal involved in diverse surfaces thus play critical roles in explaining many fundamental phenomena....

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Complexity and Opportunities in Liquid Metal Surface Oxides

Cited by 49 publications

References 90 publications

Stabilization of Undercooled Metals via Passivating Oxide Layers

Stabilization of Undercooled Metals via Passivating Oxide Layers

Stabilization of Undercooled Metals via Passivating Oxide Layers

Interfacial Engineering of Room Temperature Liquid Metals

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