Research On Thermal Conductivity Of Oriented Filled Epoxy Resin Composites

As technology advances,the performance of various electronic products has been continuously improved,and the volume has been reduced.If the heat generated by electronic products cannot be discharged in time,it will greatly reduce the service life of electronic products and even cause safety problems.Polymers are preferred as a new generation of thermal interface materials due to their light weight,anti-corrosion and easy processing.Nevertheless,the inherent low thermal conductivity limits its further development.An effective solution is to add highly thermal conductive fillers inside the polymer,so that the formation of an internally interconnected thermally conductive network between the fillers is the key to effective heat transfer.In addition,due to the synergistic effect between different thermally conductive fillers,hybrid fillers are increasingly used in composites in order to improve the thermal conductivity of composites,but how to achieve better enhancement is still a problem to be solved.In this paper,we realized the oriented arrangement of boron nitride sheets by the directional freeze-drying method,and used this as a template to realize the oriented arrangement of diamond by the vacuum infiltration method,and constructed a pod-like3 D interconnected thermal conductivity network inside the epoxy resin matrix.In order to prepare 3D boron nitride honeycomb structures with adjustable pore size,the effects of freezing solvent,dispersant,binder,freezing temperature,solute concentration,sheet diameter,heat treatment temperature and heat treatment time on the microscopic morphology of 3D boron nitride skeletons were investigated in this paper.The relationships of freezing temperature,solute concentration,sintering temperature and sheet diameter to the thermal conductivity of 3D boron nitride/epoxy composites were also investigated.The results show that the pore size of 3D boron nitride skeleton decreases with the decrease of freezing temperature and the increase of solute concentration.However,heat treatment and particle size have little effect on the pore size of 3D boron nitride skeleton.The thermal conductivity of 3D boron nitride/epoxy resin composites increases with the decrease of freezing temperature and the increase of solute concentration.In order to realize the directional arrangement of boron nitride and diamond at the same time,the 3D boron nitride/diamond/epoxy composite was prepared by vacuum infiltration method using the 3D boron nitride honeycomb structure after heat treatment as the secondary template.The arrangement of boron nitride and diamond in the composites was determined by SEM and CT,and the thermal conductivity,mechanical properties and electrical properties of 3D boron nitride/diamond/epoxy resin composites were tested.The outcomes show that the 3D boron nitride/diamond/epoxy composites have the highest thermal conductivity,elastic modulus,and resistivity compared to pure epoxy and 3D boron nitride/epoxy composites.The mechanism of thermal conductivity enhancement of 3D boron nitride/diamond/epoxy composites is explained by parallel structure modeling.The effective thermal conductivity of 11.318W/(m·K)in the partially filled diamond portion of the 3D boron nitride/diamond/epoxy composite is much higher than the thermal conductivity of 1.210 W/(m·K)in the diamond/epoxy composite with dense filling of diamond only.The results show that there is a synergistic effect between fillers inside the 3D boron nitride/diamond/epoxy composites,and the bridging effect of boron nitride walls on diamond particles also helps to improve the thermal conductivity of the composites.