Controllable Preparation And Thermal Conductivity Of Al₂O₃/EP Composites

With the continuous increase of integration and power density of electronic equipment,heat dissipation efficiency has become one of the main factors restricting the development of electronic components.Polymer matrix composites with thermal conductive fillers have been widely concerned by researchers because of their high thermal conductivity,good corrosion resistance and light weight.In order to obtain polymer matrix composites with high thermal conductivity,the method of increasing thermal conductivity filler is usually used,but its high proportion will affect the mechanics and machining properties of polymer matrix.Therefore,it is urgent to develop polymer matrix composites with low duty thermal conductivity fillers.The ice template method can be used to construct the ceramic 3D network skeleton,which can be used as the thermal conduction network of polymer matrix composite materials,to achieve a large increase in thermal conductivity under low filling capacity.In this paper,the ice template method was used to construct the Al₂O₃ 3D network skeleton,and the influence of different technological conditions on the microstructure of the Al₂O₃ 3D network skeleton was studied.The Al₂O₃/EP composite was prepared by vacuum impregnation technology,and the influence of different microstructure on the thermal conductivity of the Al₂O₃/EP composite was analyzed.The main research work is as follows:（1）Using gelatin and PVA as binder,ice template method was used to construct the Al₂O₃ 3D network skeleton.It was found that the type of binder significantly affected the microstructure of the Al₂O₃ 3D network skeleton.When gelatin was used as binder,honeycomb pore structure was obtained when the solid content was 5vol.%and 10vol.%.When the solid content increased to 15vol.%,the structure of the Al₂O₃ 3D network skeleton began to appear sheet structure,and when the solid content was 20vol.%,it became sheet.When PVA was used as binder,the local ordered lamellar pore structure was obtained.With the increase of binder content,the brush protrusion appeared on the pore wall.The temperature field distribution in the slurry was changed by adding the wedge Angle of silicone rubber,so that the anisotropic pore structure was oriented,and the layered Al₂O₃ 3D network skeleton with high order was obtained when the wedge Angle of silicone rubber was 10°and 15°.（2）Al₂O₃/EP composites were prepared by vacuum impregnation method using lamellar Al₂O₃ skeleton with different layer spacing and wall thickness as thermal conductivity network.The thermal conductivity analysis showed that the thermal conductivity of Al₂O₃/EP composites was anisotropic,and the thermal conductivity improvement in parallel to freezing direction was obviously better than that in vertical direction.The thermal conductivity of Al₂O₃/EP composite increases with the decrease of laminate spacing.When the laminate spacing reaches 45μm,the thermal conductivity of Al₂O₃/EP composite is 0.52W/（m·K）,which is 159.7%higher than that of pure epoxy resin.At the same time,the dielectric constant of Al₂O₃/EP composite increases with the decrease of lamellar spacing,while the volume resistivity decreases,but still remains above 10¹²Ω·cm.（3）The Al₂O₃/EP composite was prepared by sintering the Al₂O₃ 3D network skeleton and composite with EP.The thermal conductivity of the composite reached 3.69 W/（m·K）at the lamellae spacing of 123μm,which was 19 times higher than that of the pure epoxy resin.