Pressure-induced shear and interlayer expansion in Ti<sub>3</sub>C<sub>2</sub> MXene in the presence of water.

Ghidiu, Michael; Kota, Sankalp; Drozd, Vadym; Barsoum, Michel W · Sci Adv · 2018

basic_science · Level V

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Abstract

Pseudo-negative compressibility in layered materials is a phenomenon typically limited to in situ high-pressure experiments in some clay minerals and carbon-based materials. We show that the MXene Ti<sub>3</sub>C<sub>2</sub>T <sub><i>x</i></sub> expands along its crystallographic <i>c</i> direction when compressed in the presence of H<sub>2</sub>O. This expansive effect occurs when a mixture of powders and excess water is quasi-hydrostatically compressed in a diamond anvil cell; it also occurs to a much larger extent when powders are pressed uniaxially into discs and, notably, persists after pressure is released. We attribute the expansion to the insertion of H<sub>2</sub>O molecules and have identified shear-induced slipping of the nanosheets comprising multilayered MXene particles as a possible cause of this behavior in the latter case. This both has implications for the processing of MXenes and contributes to the field of materials with pseudo-negative compressibility by adding a new member for further investigation.