Preparation And Properties Of Thermally Conductive Epoxy Resin Composites Based On The Modified Al₂O₃

With the continuous advancement of technology,Various electronic devices and components are gradually miniaturized and integrated.However,this leads to the rapid accumulation of heat,which is difficult to transfer to the outside.Therefore,the heat generated by the device must be emitted from the packaging materials in time.The normal operation of the device can be guaranteed by improving the thermal conductivity of the packaging materials to speed up the dissipation of heat.At present,the common method is to increase the thermal conductivity of composites by adding thermally conductive fillers.This method can not only effectively improve the thermal conductivity of materials,but also select different thermally conductive fillers according to requirements to meet different applications.Epoxy resin（EP）composites have received widespread attention due to their low price and excellent comprehensive properties.Alumina（Al₂O₃）can be used as filler to prepare thermal conductive epoxy resin composites because of their excellent electrical insulation and thermal stability.However,the improvement of the thermal conductivity of the epoxy resin by unmodified Al₂O₃is limited.Therefore,it is necessary to improve the thermal conductivity of epoxy resin composites by surface modification of Al₂O₃.In this paper,Al₂O₃was used to prepare Al₂O₃@BN and Al₂O₃@Ni hybrid particles with boron nitride（BN）and nickel（Ni）respectively,which can be used to construct the heat conduction channel in the composites and improve the thermal conductivity of epoxy resin composites.The main research contents are as follows:（1）The surface of Al₂O₃was modified with 3-aminopropyl triethoxysilane（APTES）coupling agent and connected to amino groups.The problem of lack of group activity on BN surface was solved by hydroxylation of BN with strong alkali under heating condition.Al₂O₃@BN hybrid particles were prepared by electrostatic assembly of hydroxylated BN and Al₂O₃with amino groups,which were used to improve the thermal conductivity of epoxy resin composites.The morphologies and structures of Al₂O₃,BN and Al₂O₃@BN hybrid particles before and after modification were characterized by SEM,FTIR and XRD.Then the epoxy resin composites were prepared and the thermal conductivity of the composites was studied.The thermal stability,fracture morphology,electrical insulation properties,tensile properties and dynamic thermo-mechanical properties of the composites were studied.The results show that when the ratio of Al₂O₃to BN in hybrid particles is 4:1 and the filling amount is 35vol%,the thermal conductivity of Al₂O₃@BN/EP composites reached1.25 W/（m·K）,which was 525%higher than that of pure epoxy resin.And the composites still maintain excellent thermal stability,electrical insulation,dynamic thermo-mechanical properties and mechanical properties.（2）Hydrazine hydrate（N₂H₄·H₂O）is used as reducing agent,the Ni²⁺in nickel sulphate（Ni SO₄）was chemically reduced by the method of liquid phase reduction,and the nano-Ni particles were reduced to the surface of Al₂O₃to prepare Al₂O₃@Ni hybrid particles.The surface morphology and structure of Al₂O₃@Ni hybrid particles were characterized by XPS,XRD,FTIR,SEM and EDS.Al₂O₃@Ni/EP composites were prepared by adjusting the content of Al₂O₃hybrid particles and adding to epoxy resin,and the thermal conductivity of Al₂O₃@Ni/EP composites was studied.Then the thermal stability,fracture morphology,electrical insulation properties and dynamic thermo-mechanical properties of Al₂O₃@Ni/EP composites were characterized and tested.The experimental results show that when the Al₂O₃@Ni content is 50vol%,the thermal conductivity of the Al₂O₃@Ni/EP composites are relatively highest,reaching1.2 W/（m·K）,which is 500%higher than that of pure epoxy resin.And the composites still maintain the excellent thermal stability,electrical insulation and dynamic thermo-mechanical properties of epoxy resin.