Theses and Dissertations

Permanent URI for this collection

https://ir.ua.edu/handle/123456789/508

Browse

Browsing Theses and Dissertations by Subject "2D Materials"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    The Role of Texture on the Stability of Layered Materials
    (University of Alabama Libraries, 2024) Sakib, Nuruzzaman; Momeni, Kasra
    The role of grain boundaries (GBs) in determining the structural, mechanical, and thermal properties of two-dimensional materials, focusing on tungsten diselenide (WSe2) and graphene was investigated using molecular dynamics simulations. The phase transformation, mechanical failure, and thermal conductivity in these materials are explored. Exploring the kinetics of the phase transformation from graphene to diamane reveals that the transformation stress is significantly influenced by the thickness and temperature of the precursor graphene layer, whereas the transformation strain remains independent of these factors. Heterogeneous nucleation at GBs as a crucial mechanism differing from transformations in pristine graphene was also unveiled . The effects of GB misorientation angles and interlayer configurations on the shear-assisted transformation of multilayer graphene into diamane revealed that external shear aids the formation of ABC stacked graphene layers, which subsequently transforms into a few-layer diamond structure. Transformation is optimized by halting shear at an interlayer distance of 2.3 Å. Higher misorientation angles increased defect density, influencing diamond phase stability post-decompression. A computational toolkit for generating GB structures in transition metal dichalcogenides (TMDs) such as WSe2 is developed. This toolkit enables the replication of experimentally observed GBs and examine their impacts. Validation with high-resolution transmission electron microscopy confirmed that simulated structures closely represent experimental observations. In studying the mechanical properties of WSe2 monolayers with symmetric tilt GBs, the tensile strength and fracture strain decrease with increasing temperature, with brittle cracking as the dominant failure mode. The influence of topological defects, loading rates, and temperature on the mechanical behavior of monolayer WSe2 was also revealed. Finally, the impact of GBs on the thermal transport properties of monolayer WSe2 was studied using non-equilibrium molecular dynamics (NEMD) simulation. Higher defect density reduced thermal conductivity and Kapitza conductance due to increased phonon scattering at GBs. Both Kapitza resistance and thermal conductance are adversely affected by higher defect densities, underscoring the importance of GB characteristics in thermal management applications. Overall, this dissertation provides comprehensive insights into the influence of GBs on the properties of two-dimensional materials, offering valuable implications for the design and optimization of electronic and thermal management systems in nanodevices.