| Polymer-based thermally conductive composite material is a new material with good heat dissipation performance,which is mainly used to solve the heat dissipation problems of various devices in the fields of electronic packaging,automobile manufacturing,LED lighting,battery thermal management and photovoltaic industry.As a new one-dimensional nanomaterial,metal nanowires not only inherit the excellent thermal conductivity of the metal itself,but also have high aspect ratio,which shows great potential for application in the field of thermal conductive materials.This paper is based on the research of polymer-based thermal conductive composites filled with metal nanowires.The silver nanowires（AgNW）were combined with zinc oxide（ZnO）nanoparticles,graphene oxide（GO）and graphene aerogels（GA）.The AgNW@ZnO filler with one-dimensional structure,the GO/AgNW hybrid filler with two-dimensional structure and the GA/AgNW porous hybrid filler with three-dimensional structure were prepared and added to the epoxy resin matrix,which effectively improved the thermal conductivity of composite materials.In addition,according to the characteristics of high aspect ratio and light transmittance of metal nanowires,copper nanowires（CuNW）and reduced graphene oxide（rGO）were combined to prepare surface coated polymer composite films,which greatly improved the plane thermal conductivity of the composite films.The specific research contents are as follows:1.One-dimensional AgNW with high aspect ratio was prepared.Then,ZnO nanoparticles were modified on the surface of the nanowires by precipitation method to prepare AgNW@ZnO composite filler with one-dimensional core-shell structure.The filler was added into the epoxy resin to prepare AgNW@ZnO/EP thermal conductive composite materials.The results showed that thermal conductivity of the composites containi ng AgNW is improved after ZnO surface modification.When the content of AgNW@ZnO was 8 wt%,the thermal conductivity of AgNW@ZnO/EP composite reached 0.77 W/（m·K）.The increase of thermal conductivity attributed to the fact that ZnO effectively improved the interface bonding between AgNW and epoxy matrix and strengthened the contact between AgNWs.The introduction of the ZnO coating effectively improved the electrical insulation of the composite material.When the filler content was 8 wt%,the volume resistivity of the composite material was higher than 1013Ω·cm.In addition,the composite material also had good thermal stability and low dielectric constant.2.A series of GO/AgNW hybrid fillers with two-dimensional layered structure were prepared by mixing GO nanosheets with AgNWs and adjusting their percentage（15%～90%）.The study found that the thermal conductivity of GO/AgNW/EP composites increased the most when the total amount of filler remained constant at 4wt%and the percentage of AgNW was 75%.The GO/AgNW hybrid filler was prepared according to the above percentage.When the filling amount was 10 wt%,the thermal conductivity of the composite material was 1.2 W/（m·K）,and the volume resistivity was 2.2×109Ω·cm.There was a synergistic effect between AgNW and GO in this hybrid filler.The gap between the AgNW network was filled by GO,forming a hybrid network structure,which can provide more phonon transmission channels.In addition,in the study of the mechanical properties of the prepared composite material,it was found that the filler also had a certain synergistic effect on improving the impact strength of the composite material.3.Graphene hydrogel was prepared by hydrothermal reduction of graphene oxide with ethylenediamine,and then graphene aerogel（GA）was prepared by freeze drying and high temperature thermal reduction.A series of GA/AgNW three-dimensional porous hybrid thermal conductive fillers with different AgNW contents were prepared by depositing AgNW onto the surface of the GA sheet by dipping.The study found that the mass fraction of graphene aerogel in the GA/AgNW/EP composite was 1.1 wt%.Depositing a small amount of AgNW significantly improved the thermal conductivity of the composite.When the content of AgNW was 4 wt%,thermal conductivity of GA/AgNW/EP composites was up to1.51 W/（m·K）.In addition,the comparative analysis found that the thermal conductivity of the GA/AgNW/EP composite was 2.6 times that of the rGO/AgNW/EP composite with the same composition and different structure prepared by the solution mixing method.The three-dimensional porous composite filler significantly improved the thermal conductivity of composite material at lower filling amount.This was because GA constructed a three-dimensional overall thermal conductivity framework,and AgNW was deposited on the surface of the GA nanosheets,which significantly improved the thermal conductivity of the filler framework.4.The copper nanowires（CuNW）with high aspect ratio were prepared.Polyvinylidene fluoride（PVDF）film was used as the matrix material,and CuNW and rGO coatings were bonded on the surface of PVDF film using acrylate UV curing technology.The rGO/CuNW/PVDF flexible transparent film was prepared,which the planar thermal conductivity of the film was achieved up to 103 W/（m·K）.The study found that the rGO coating could effectively prevent the oxidation of the inner layer CuNW and improved the thermal stability of the film.After the prepared composite film was bent 1000 times,the square resistance of the film did not change significantly.The light transmittance of the film at 550 nm was 73%,and it had good flexibility and light transmittance.The film was used for the lateral heat dissipation of high-power LEDs,which effectively reduced the phenomenon of heat accumulation inside the device.The composite film had excellent planar heat transfer performance. |
