ABSTRACT

A novel large family of low dimensional materials, 2D transition metal carbides (MXenes), have shown excellent electronic and optical properties that are often superior compared to other 2D materials. Importantly and in contrast to other 2D materials, these properties can be systematically varied and studied within the same family, without changing elemental composition and type of interatomic bonds in the material. These unique features make MXenes equally interesting for fundamental science and application development, where they can be used in new planar and flexible devices, leading to new technologies and significant economic impacts. Some of these applications that are researched now include health monitoring sensors, high performance energy harvesting and storage systems, and chemo-photothermal cancer therapy. However, the adhesion of MXenes, which is critical in many of these applications, has yet to be systematically investigated. To date, there have only been a few theoretical studies of the adhesive behavior of MXenes, with little to no experimental data. In a broader sense, experimental determination of adhesive properties of MXenes will contribute to our understanding of the fundamental relationships between adhesion and atomic structures for low dimensional materials. This could revolutionize the modern materials and manufacturing industries in harnessing the adhesion for coatings and planar devices made of low dimensional materials.

The goals of the project are to: (i) systematically investigate the adhesive interactions of MXenes at the atomistic, nano- and micrometer scales, (ii) using the unique advantages provided by MXenes, systematically and separately examine the effects of surface functional groups and monolayer thickness of 2D materials on their adhesive interactions, and (iii) explore the environmental effects on the adhesion of MXenes including surface water and oxidation process. To achieve the goals, we intend to: (1) utilize the atomistic scale contact-based experiments to investigate the effect of atomic structures and surface terminations on the adhesion, (2) employ nanoindentation to understand the interfacial traction-separation relations of MXenes with themselves and other materials, (3) explore the potential use of in-situ nano-shear-lag experiments to investigate the shear interactions of MXenes, (4) combine the multiscale modeling and the experimental results to understand the coupled adhesive mechanisms involving the surface defects, terminations, monolayer thickness, and (5) explore the possible evaluation of the effects of surface water and oxidation process on the adhesion of MXenes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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