| In recent years,with the development of microelectronics technology,electronic components have become more integrated and miniaturized.In order to ensure the long-term reliable operation of electronic components,the requirements for their thermal conductivity and insulation performance are higher.However,the thermal conductivity of most polymers is very low,which can not meet the heat dissipation requirements of electronic components.The preparation of composite materials with high thermal conductivity fillers has become a hot topic in the research of electronic packaging materials.In this paper,silicon dioxide coated sulfonated graphene(Si O2@SGO),spherical alumina coated sulfonated graphene(α-Al2O3@SGO)and spherical alumina composite carbon nanotubes(α-Al2O3@CNT)were used as thermal conductive fillers to prepare a series of high thermal conductive composites,which were cured in epoxy resin,and their thermal conductivity,dielectric property,insulation property and thermal stability were studied.(1)A layer of silica insulation(Si O2@SGO)was coated on the surface of sulfonated graphene by sol-gel method.The Si O2@SGO hybrids were characterized by X ray diffraction(XRD),fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TG)and scanning electron microscope(SEM).Si O2@SGO/EP and SGO/EP composites were prepared by adding Si O2@SGO and SGO into epoxy resin(EP)with mass fractions of 5wt%-25wt%,respectively.The results show that the thermal conductivity of the composites increases with the increase of Si O2@SGO content.When the filling content is 25wt%,the thermal conductivity of the composites reaches 0.71W/(m·K),which is 3.4 times higher than that of the matrix EP resin.This is because the presence of Si O2@SGO improves the phonon transport channel in EP resin.The thermal stability of the composites was increased from 300 oC to 340 oC,and the glass transition temperature was also increased by 10 oC.The composites also maintained excellent dielectric properties(dielectric constant was 8,dielectric loss was 0.25)and electrical insulation properties(volume resistivity was 1.06×1010 ?·cm).(2)A hybrid of α-Al2O3@SGO was prepared by electrostatic self-assembly method,and then epoxy resin matrix composites were prepared by solution blending method.The effects of the ratio and content of alumina-coated sulfonated graphene(α-Al2O3@SGO)hybrids on the thermal conductivity,thermal stability,glass transition temperature,dielectric properties and insulation properties of epoxy resin matrix composites were systematically studied.The results show that the thermal conductivity of α-Al2O3@SGO/EP composite is the best when the ratio of α-Al2O3: SGO is 20:1.When the content of hybrid filler is 30wt%,the thermal conductivity of α-Al2O3@SGO/EP is 1.49 W/(m·K),which is 7.1 times of that of epoxy resin.The thermal stability and glass transition temperature are increased by 56 oC and 10 oC,and the dielectric properties(dielectric constant is 7.5,dielectric loss is 0.25)and insulation properties(volume resistivity is 1.86×1010 ?·cm)are also improved.(3)Carboxyl functionalization of carbon nanotubes was carried out in concentrated sulfuric acid and nitric acid mixed solution.A spherical alumina-coated carbon nanotube(α-Al2O3@CNT)hybrid filler was prepared by electrostatic self-assembly method.Then it was added to epoxy resin to compound and α-Al2O3@CNT/EP composite was prepared.The results show that the optimum ratio of CNT:α-Al2O3 is 1:10.When the filler of α-Al2O3@CNT is added to 30wt%,the thermal conductivity of α-Al2O3@CNT/EP composites reaches 1.53 W/(m·K),which is 7.3 times that of pure epoxy resin.The thermal stability of the composites increases from 300 oC to 385.7oC,the glass transition temperature increases by nea rly 10 oC,the dielectric properties(dielectric constant is 6.1,dielectric loss is 0.25)and insulation properties(volume resistivity is 2.02×1010 ?·cm),which met the requirements. |
PDF Full Text Request