Near-field Radiative Heat Transfer Between Graphene-based Anisotropic Materials

According to the well-known Stefan-Boltzmann law,the radiative heat transfer between two parallel media is controlled by propagating electromagnetic waves,which ideally achieve blackbody radiative.However,the feasibility of this theory is limited to the far field.In recent years,with the rapid development of nanotechnology,researchers have found that many physical phenomena exhibit new physical properties under nanometer size.When the distance between the parallel media is smaller than the characteristic wavelength of the thermal radiation at the nanometer scale,the control of the radiative heat transfer by the propagated electromagnetic waves gradually fails.The evanescent waves and the surface polaritons play a leading role in the heat transfer process.Due to the coupling of surface waves at the interface of the parallel medium,near-field radiative heat transfer can exceed several orders of magnitude of blackbody radiation.In this thesis,the theory of fluctuation dissipation is used to quantitatively calculate and qualitatively analyze the near-field radiative heat transfer between graphene-based anisotropic materials.The main research contents are:First,the physical properties of graphene were analyzed,including the basic structure,photoelectric properties and graphene surface plasmons.The hyperbolic dispersion properties of anisotropic metamaterials studied in this paper are introduced.The dispersion relation of anisotropic materials is derived.The Fresnel reflection coefficient of the medium-graphene-medium structure surface is also derived.It shows that anisotropic metamaterial plays an important role in near-field radiative heat transfer.The heat transfer coefficient is calculated based on the fluctuation electrodynamics and fluctuation dissipation theory of near-field heat radiation.Secondly,by constructing a semi-infinite graphene-covered SiC nanowire arrays(SiC NWAs)composite structure,the surface Fresnel reflection coefficient and conductivity of the structure are derived.Using the theory of fluctuation dissipation theory,it is found that the surface plasmon excited by graphene and the hyperbolic phonon polaritons supported by SiC NWAs are coupled with each other and generate a new oscillation mode.The strong coupling of this different mode in the near field enhances near-field radiative heat transfer.At the same time,the periodic perforated structure of graphene covered SiC is proposed,and the near-field radiative heat transfer effects of the two structures are compared.Thirdly,a multi-layer waveguide composite structure of graphene-hexagonal boron nitride(hBN)-silicon carbide is proposed,which has different thermal conductivity coefficients for different parameters such as graphene chemical potential,silicon carbide thickness,hBN thickness and near-field distance.The impact was analyzed and discussed.At the same time,the radiative heat transfer intensity of the composite structure is compared with the radiative heat transfer intensity of the graphene-silicon carbide-hBN recombination structure.Through the theoretical calculation and comparison,the reasons for the difference between the two combined structures are analyzed,and the optimal structure for enhancing the near-field radiative heat transfer is obtained.