Preparation And Characterization Of Graphene And Its Resin-based Thermally Conductive Composite Materials

With the miniaturization and integration of electronic devices,heat dissipation has become a crucial problem which affects its service life.Therefore,thermal interface materials(TIMs)with high thermal conductivity between the heating elements and the radiators are needed to rapidly remove heat to reduce hot spot temperature.Due to the influence of the surface roughness of traditional polymer matrix composites,the mismatch between the electronic devices and the radiators increases the thermal interface resistance.Graphene has caused much attention due to its many superior performances,since its successful exfoliation in 2004.Especially,the high in plane thermal conductivity(5300W/m?k)and large specific surface area(2630 m~2/g)of graphene make it become the most suitable filler to enhance the thermal conductivity of polymer-based composite.This thesis mainly studied the different advantages and problems of the preparation of graphene,and preparated graphene/silicone and graphene/epoxy-resin thermal conductive composite.The thermal conductivity composite has a significantly increase in relatively low amount of graphene.In this work,we employ different methods to prepare graphene thermal conductive filler,graphene oxide(GO),redued graphene oxide(rGO),ball mill graphene nanoplatelet(BM-GNPs),homogeneous graphene nanoplatelets(H-GNPs)respectively.They were characterized by SEM,Raman and Four probe resistance tester and so on.Above four kinds of graphene thermal conductive filler were prepared into thermal conductivity sheets with silicone and epoxy,and thermal conductivity curves were measured by Laser flash diffusivity apparatus,the cross section morphology was observed by SEM and XRD analysis of the composition.We also use a different piece of analog electronic device in the actual work of thermal conductivity structure was prepared by simple cooling deviceResults show that BM-GNPs gel sheets(GNPs-GS),thermal conductivity reaching0.38 W/(m·k)with 10 wt.%,it has an increase by 90%compared with Pure gel sheet(Pure-GS).In addition,the thermal conductivity of gel sheet made by H-GNPs was 0.43W/(m·k)with 5wt.%,which was increased by 110%and 50%compared with the Pure-SGS and GPs-SGS with the same loading.Meanwhile,the simple heat dissipation devices constructed by these two kinds of gel sheets are used in the heat sink.In addition,H-GNPs/epoxy resin composite was prepared into electronic packaging TIMs.Magnetic field was used to order the direction of GNPs to prepare the thermal conductivity of anisotropy.Based on the parallel to the magnetic field direction and perpendicular to the direction and without magnetic field,thermal conductivity diminishing the existence of a regular,specific as follows:the horizontal>none>vertical magnetic field.This indicates that GNPs can turn to uniform direction,which changes the thermal conductivity of the composite in all directions.It benefit by anti-magnetic properties of GNPs,we have also observed the deflection process in solution through an optical microscope.XRD is used to analyze its composition,and the diffraction peaks of the resin matrix and the characteristic peaks of graphene can be clearly observed.Meanwhile,SEM and AFM images confirmed all graphene thermal conductive filler for single layer,less layer and few layer,and SEM observed the distribution of graphene in the matrix.Raman spectra show that the different graphene has different features,among them are qualitative method and the ball mill of GNPs defects is less,and the chemical preparation of GO and RGO have more defects relatively.