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High shear in situ exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium.

ABSTRACT: A diversity of two-dimensional nanomaterials has recently emerged with recent attention turning to the post-transition metal elements, in particular material derived from liquid metals and eutectic melts below 330 °C where processing is more flexible and in the temperature regime suitable for industry. This has been explored for liquid gallium using an angled vortex fluidic device (VFD) to fabricate ultrathin gallium oxide (Ga₂O₃) sheets under continuous flow conditions. We have established the nanosheets to form highly insulating material and have electrocatalytic activity for hydrogen evolution, with a Tafel slope of 39 mV dec^-1 revealing promoting effects of the surface oxidation (passivation layer).

SUBMITTER: Vimalanathan K

PROVIDER: S-EPMC9419649 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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Publications

High shear in situ exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium.

Vimalanathan Kasturi K Palmer Timotheos T Gardner Zoe Z Ling Irene I Rahpeima Soraya S Elmas Sait S Gascooke Jason R JR Gibson Christopher T CT Sun Qiang Q Zou Jin J Andersson Mats R MR Darwish Nadim N Raston Colin L CL

Nanoscale advances 20210901 20

A diversity of two-dimensional nanomaterials has recently emerged with recent attention turning to the post-transition metal elements, in particular material derived from liquid metals and eutectic melts below 330 °C where processing is more flexible and in the temperature regime suitable for industry. This has been explored for liquid gallium using an angled vortex fluidic device (VFD) to fabricate ultrathin gallium oxide (Ga2O3) sheets under continuous flow conditions. We ...[more]

PMID: 36132680

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Project description:Liquid-phase deposition of exfoliated 2D nanosheets is the basis for emerging technologies that include writable electronic inks, molecular barriers, selective membranes, and protective coatings against fouling or corrosion. These nanosheet thin films have complex internal structures that are discontinuous assemblies of irregularly tiled micron-scale sheets held together by van der Waals (vdW) forces. On stiff substrates, nanosheet vdW films are stable to many common stresses, but can fail by internal delamination under shear stress associated with handling or abrasion. This "re-exfoliation" pathway is an intrinsic feature of stacked vdW films and can limit nanosheet-based technologies. Here we investigate the shear stability of graphene oxide and MoSe2 nanosheet vdW films through lap shear experiments on polymer-nanosheet-polymer laminates. These sandwich laminate structures fail in mixed cohesive and interfacial mode with critical shear forces from 40 - 140 kPa and fracture energies ranging from 0.2 - 6 J/m2. Surprisingly these energies are higher than delamination energies reported for smooth peeling of ordered stacks of continuous 2D sheets, which we propose is due to energy dissipation and chaotic crack motion during nanosheet film disassembly at the crack tip. Experiment results also show that film thickness plays a key role in determining critical shear force (maximum load before failure) and dissipated energy for different nanosheet vdW films. Using a mechanical model with an edge crack in the thin nanosheet film, we propose a shear-to-tensile failure mode transition to explain a maximum in critical shear force for graphene oxide films but not MoSe2 films. This transition reflects a weakening of the substrate confinement effect and increasing rotational deformation near the film edge as the film thickness increases. For graphene oxide, the critical shear force can be increased by electrostatic cross-linking achieved through interlayer incorporation of metal cations. These results have important implications for the stability of functional devices that employ 2D nanosheet coatings.

Dataset Information

High shear in situ exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium.

Publications

High shear <i>in situ</i> exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium.

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