Study On The Thermal Conductivity Of Carbon-based Composites

With the continued miniaturization of electronic devices,the heat dissipation of smart electronics is crucial to maintain the devise worked with proper performance and lifespan.Smart electronic devices will generate excess heat when they work.If the generated heat from smart electronics could not be dissipated as quickly and effectively,the performance and reliability of these devices will be reduced with the temperature rising.High thermal conductive material could reduce the local hot spot temperature in smart electronics quickly and the temperature of electronics can be maintained at a relatively low level.Because of their corrosion resistance,lightweight,ease of processing and low cost,polymers are wildly used in electronics.However,a limiting property of polymeric materials in electronics is their low thermal conductivity,most of which are under 0.5W·m^-1·k^-1.Therefore,it is of great importance and urgent to improve the thermal conductivity of polymers.Many kinds of high thermal conductive fillers have been added into polymer to improve the thermal conductivity of polymers.Recently,carbon nanotube（CNT）and graphene have gained considerable interest to improve thermal conductivity of polymer due to their superior thermal conductivity.To fully utilize the potentials of high thermal conductive filler,multi-walled carbon nanotubes（MWCNTs）and expanded graphite were added into epoxy resin to improve the thermal conductivity of epoxy resin.The experimental results indicated that the maximum thermal conductivity of MWCNTs/epoxy resin composite was 0.3448 W·m^-1·k^-1by adding 0.5wt%of MWCNTs into epoxy resin.Compared with epoxy resin,the thermal conductivity of MWCNTs/epoxy resin composite was improved 30%.When 0.75 wt%MWCNTs-COOH was added into epoxy resin,the maximum thermal conductivity of MWCNTs-COOH/epoxy resin composite was 0.3813 W·m^-1·k^-1,which was improved by 40%compared with epoxy resin.Modification of carbon nanotubes can reduce the thermal resistance of carbon nanotubes and epoxy resin,thereby further improving the thermal conductivity of epoxy resin.The thermal conductivity of epoxy resin could reach up to 0.4039 W·m^-1·k^-1 by adding hybrid filler（MWCNTs-COOH/expanded graphite）.Because of the synergistic effect of the composite fillers,it can inhibit the aggregation of the fillers in the polymer,which makes the fillers form a uniform dispersion system in the polymer and thus significantly improves the thermal conductivity of the polymer composites.At the same time,the connection between the carbon nanotube and the expanded graphite makes the composite fillers form a complete thermal conduction network in the polymer,and the heat conduction network can further improve the thermal conductivity of the epoxy resin.In addition,the super graphene film was grown on the foamed nickel base,and the composite filler of nickel foam-graphene was added to the epoxy resin to improve its thermal conductivity.Nickel foam inhibits the agglomeration of graphene in epoxy resin,and graphene forms a three-dimensional heat conduction network in epoxy resin with foam nickel as the skeleton.For graphene-nickel three-dimensional filler which graphene was grown on nickel foam for 45 min,the thermal conductivity of graphene-nickel/epoxy composite can reach up to 2.6549 W·m^-1·k^-1,which was 9 times greater than that of raw epoxy resin(0.2617 W·m^-1·k^-1).