The work presented here describes two major problems: 1) Structural evolution of graphene oxide layers during thermal reduction using combined numerical methods and experimental measurements, and 2) Molecular dynamics simulations of thermal transport in polycrystalline graphene. The atomistic simulations reveal that thermal annealing of GO leads to the formation of highly stable carbonyl and ether residual oxygen functional groups that hinder the complete regraphitization of reduced GO, even when annealed at very high temperatures. The thermally activated interplay between carbon and oxygen, responsible for incorporation of oxygen in- and out-of-plane, has been elucidated. Defects and crystallographic distortion of the hexagonal graphene structure are also studied as a function of the chemical composition and the heating temperature. The calculations are supported by infrared and X-ray photoelectron spectroscopy measurements on GO at different stages of reduction. Finally, several more effective reduction treatments towards achieving complete regraphitization are proposed based on our detailed theoretical analysis. In second part of this thesis, we have studied the thermal conductance of tilt grain boundaries in graphene using non-equilibrium molecular dynamics simulations. When a constant heat flux is imposed, we observe sharp jumps in temperature at the grain boundaries. Based on the magnitude of these jumps, we have computed the Kapitza conductance of twin grain boundaries as a function of their misorientation angles. We find the boundary conductance to be in the range 1.5x1010-4.5x1010 W/m2K, which is significantly higher than that of any other thermoelectric interfaces reported in literature. Using the computed values of boundary conductances, we have identified a critical grain size of 0.1 microns below which the contribution of the tilt boundaries to the conductivity becomes comparable to that of the contribution from the grains themselves.
Bagri, Akbar,
"Topics in Mechanics of Two Dimensional Crystalline Materials"
(2013).
Mechanics of Solids Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0Z899Q2
