Near-field Radiative Heat Transfer Based On Electric And Magnetic Modulation In Graphene

For a long time,the understanding of thermal radiation has been based on Planck Theory: there is a maximum radiative heat flux between two blackbody at different temperatures.However,some studies have found that in some special cases,the classical theory of thermal radiation dominated by propagating wave is no longer applicable when the separation is comparable to or even smaller than the peak wavelength of radiation.Then the evanescent wave becomes the leading role in radiative heat transfer,which makes the heat flux much larger than the blackbody radiation limit.The radiatve heat transfer phenomenon is called near field radiative heat transfer(NFRHT).At room temperature,the peak position of the electromagnetic wave emitted by the object overlaps with th e frequency of the plasmon excited by graphene.Moreover,the surface plasmon polaritons(SPP)and magneto-plasmon polaritons(MPP)can be excited by graphene in the near-field regime.Therefore,graphene can be used to improve the heat transfer efficiency of near-field radiation.By regulating the graphene with electrical(grid voltage)and magnetic(external magnetic field)method,flexible,accurate and efficient micro-nano scale thermal management can be realized.However,there are still many problems to be solved in the research of near-field thermal radiation based on graphene modulation,such as simple radiation heat transfer model,complex heat transfer mechanism,unclear evolution rules and action mechanism of graphene SPP and MPP in complex structure,and lack of near-field thermal radiation research based on graphene magnetic control.Based on the above problems,the near-field thermal radiation of graphene in two body structure,three-body structure,many-body structure,two-dimensional twisted grating structure and plate-particle interaction structure were systematically studied from the electrical and magnetic aspects.The main contents are as follows:Based on the introduction of the optical conductivity model and the magneto-optical conductivity model of graphene,the characteristics of SPP and MPP of graphene were analyzed respectively from the aspects of energy transmission coefficient,reflection coefficient and dispersion relation,and the control effect of SPP and MPP on thermal radiation is studied.The near-field thermal radiation control mechanism based on the coupling effect of graphene MPP and surface phonon polaritons(SPh Ps)was studied.The contributions of MPP and SPh Ps in the coupling thermal radiation control were clarified.It w as found that MPP can couple with SPh Ps in the near-field regime.The coupling mode is affected by the magnetic field intensity,which can be flexibly controlled by the MPP sphps coupling effect.Based on the tunable properties of graphene and the three-body thermal photon tunneling effect,a flexible control method of temperature and heat flux was proposed.The control ability of equilibrium temperature under different geometric parameters was studied,and the mechanism of flexible regulation of thermal radiation was analyzed.It was found that the tunable graphene SPP is the fundamental reason for the flexible modulation of thermal radiation.In addition,based on the multi-body radiation theory,heat transfer model of graphene many-body structure considering the equilibrium temperature distribution was proposed.According to the many-body energy transfer coefficient,transient and steady heat transfer coefficient,the heat transfer mechanism of the structure was revealed.It was found that for the more dense structure,there exists strange temperature steps at the two sides of the boundary.The NFRHT between the isotropic materials covered by graphene grating was studied.The regulation effects under different twisted angles and graphene filling factors were studied respectively.Through the analysis of the energy transmission coefficient and dispersion relationship,it was found that graphene grating and substrate materials couple and form three different modes.They can evolve with the change of twist angle,so that the flexible regulation of thermal radiation can be realized by twisting.Based on the graphene MPP,a new method of NFRHT modulation was proposed by combining the twisted graphene grating and the external magnetic field.The effects of magnetic field intensity,graphene chemical potential and filling factor on the regulation effect were analyzed respectively.The effects of thermal radiation regulation of twisting were compared under the condition of zero magnetic field and magnetic field application.It was found that the twisting effect of grating was more obvious with the addition of magnetic field.The combined regulation of twisting-magnetic field owns a higher degree of freedom in regulation than the simple twisting control.By embedding multi-layer graphene film in the substrate and adopting core-shell particle structure,the method of long-distance heat transfer was proposed.It was found that the local phonon polarization near the core-shell particles can be strongly coupled with the multiple SPP excited by the multilayer graphene embedded in the substrate.It improved the thermal photon transmission efficiency of the particle substrate particle scattering interaction heat transfer channel.Therefore,the the long-distance heat transfer was realized without introducing any extra thermal sources.Based on the graphene-particle interaction structure,the giant thermal magnetoresistance effect based on the tunable MPP was proposed by means of external magnetic field,and the physical mechanism of the giant thermal magnetoresistance effect was analyzed and explained.It was found that the radiative heat flux can be modulated about three orders of magnitude by adjusting the intensity of magnetic field.Both the positive and negative relative ther mal magnetic resistances could be achieved.The above phenomenon was due to the enhancement and inhibition of the particle graphene particle scattering interaction by the graphene MPP.The overall radiation of the structure can be controlled by affecting t he scattering effect of the heat exchanger.