Title

In Situ Tensile Testing of Nanometer-Thick Two-Dimensional Transition-Metal Carbide Films: Implications for MXenes Acting as Nanoscale Reinforcement Agents

Abstract

In-plane mechanical behavior of stacks formed by titanium carbide MXenes (Ti2CTx, Ti3C2Tx) was investigated in a microscale uniaxial tensile experiment with the in situ scanning electron microscope (SEM) nanoindenter and a push-to-pull (PTP) micro-electro-mechanical system (MEMS). When the number of MXene monolayers in a stack varies from 9 to 26 (Ti2CTx with d-spacing of 1.36 nm) and 7 to 52 (Ti3C2Tx with d-spacing of 1.48 nm), the measured Young's moduli stay almost constant, averaging at 217.75 GPa (Ti2CTx) and 204.92 GPa (Ti3C2Tx). In the same experiment, the measured tensile strength monotonically decreases from 9.61 to 7.59 GPa (Ti2CTx) and 9.89 to 7.99 GPa (Ti3C2Tx). Notably, this dependence on the number of stacked MXene monolayers is much weaker than that previously observed in multilayer graphene and MoS2 stacks, which displayed a significant reduction of both tensile strength and Young's modulus, compared to what was expected from additivity, as the number of monolayers increased. This difference implies a better scaling-up of the mechanical properties of MXenes as compared to other multilayer two-dimensional (2D) materials. Furthermore, atomistic simulations show that defects in different layers in the multilayer MXenes give rise to the observed dependence of the tensile strength on the number of MXene monolayers in a stack. The atomic damage initiated in the weakest layer with the highest defect density promotes strain softening, leading to a reduced tensile strength of the MXenes. Our results show that multilayer MXenes could be used as excellent mechanical reinforcing agents for composite materials across scales and potentially in other applications where robust mechanical performance is essential.

Department(s)

Civil, Architectural and Environmental Engineering

Second Department

Chemistry

Comments

Y. Li, C. Wei, S. Huang, V. N. Mochalin, and C. Wu gratefully acknowledge financial support of this work by the National Science Foundation through Grant no. CMMI-1930881. The authors also acknowledge funding support from the Material Research Center at Missouri University of Science and Technology, Mid-America Transportation Center, and Missouri Department of Transportation.

Keywords and Phrases

In Situ Tensile Testing; MXenes; Number-Of-Layer Dependency; Tensile Strength; Young's Modulus

International Standard Serial Number (ISSN)

2574-0970

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2021 American Chemical Society (ACS), All rights reserved.

Publication Date

13 May 2021

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