The one-dimensional (1-D) nanomaterials (e.g., carbon nanotubes, silver nanowires, zinc oxide nanofibers) and two-dimensional (2-D) nanomaterials (e.g., graphene, boron nitride, molybdenum disulfide, black phosphorus) have exhibited overwhelming excellent properties over their bulk counterpart underpinned by their extremely large specific surface area at the single strip/layer level, yet the broad applications and explorations of their unprecedented properties require a diversity of their geometric morphologies, beyond their inherently straight or planar structures. As an example, crumpled graphene particles that are converted and assembled from 2-D planar graphene sheets create a subtle material platform for widespread applications of graphene. However, such crumpled particles are suffered from small spatial availabilities in geometry, high electrical resistance, and low strength in mechanical deformation due to the limited numbers and stabilities of connections among individual deformed graphene. In this study, we present a facile approach for converting the 1-D/2-D nanomaterials to 3-D architected structures through the evaporation of their liquid solutions. When the 1-D/2-D nanomaterials are suspended in a liquid droplet, once the liquid evaporation occurs at elevated temperatures, the system equilibrium will break, leading to large deformation, instability, and self-assembly of the 1-D/2-D materials. We report, in both theoretical analysis and large-scale coarse-grained molecular dynamics simulations, that a crumpled graphene/carbon nanotubes(CNTs) composite nanoparticle with large accessible space and high-mechanical strength can be achieved by encapsulating folded CNTs inside via a solvent evaporation-induced assembly approach. Here we develop a theoretical framework that can describe the liquid evaporation-driven deformation and self-folding of 1-D/2-D materials. A unified energy-based theoretical model is developed to address the kinetic migration of both CNTs and graphene suspended in a liquid droplet and their crumpling and assembling mechanism into a composite particle by solution evaporation. The contact probability, surface ridge densities, and geometric size in assembled graphene/CNTs composite nanoparticles are quantitatively extracted after the complete evaporation of liquid, and are further correlated with their accessible space including accessible surface area and volume and mechanical strength. Coarse-grained models of 1-D and 2-D materials are developed and their dynamic interaction with liquid molecules during evaporation is mimicked by proposing a controllable virtual van der Waals force field. The structural and morphological evolution of assembling graphene/CNTs composite nanoparticles with solution evaporation are uncovered by the simulations, and the results show remarkable agreement with theoretical predictions. This study offers a foundation for synthesizing highly connected, mechanically enhanced, crumpled particles with tunable spatial porous structures by tailoring graphene and CNTs for applications in functional structures and devices.


Liquid Evaporation-Assisted Crumpling and Assembling of One- and Two-Dimensional Nanomaterials

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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