| With the advent of the 5G era,the frequency and power consumption of electronic equipment have gradually increased,and the amount of heat generation has also gradually increased.This has caused the thermal risk of electronic devices to continue to increase.Therefore,the requirements for thermal conduction efficiency of thermal interface materials are also increasing.Two-dimensional materials such as graphene and boron nitride have excellent thermal conductivity and high thermal conductivity in the direction along the two-dimensional crystal plane,but the thermal conductivity is poor in the thickness direction perpendicular to the crystal plane.In this paper,by constructing these two-dimensional high thermal conductivity materials into a three-dimensional structure with high elasticity,an interface material with excellent thermal conductivity can be obtained by mechanical compression.The effects of pore structure and pore wall enhancement on the interface thermal conductivity of highly elastic three-dimensional graphene and the effect of resilience on the thermal conduction efficiency of three-dimensional boron nitride are mainly studied.The main research includes:(1)In the process of preparing high elastic three-dimensional graphene aerogel by ice template method,by adjusting the concentration of graphene oxide solution(1～6 mg/ml),three-dimensional graphene with different pore diameter,pore wall thickness and pore density is obtained.The mechanical property test shows that the three-dimensional graphene can withstand 90%compression deformation,and the structural integrity can still be maintained after 500 times of compression recovery.The thermal conductivity test proves that the thermal conductivity improves with the increase of density under compression.When the compression strain is 90%,the three-dimensional graphene with a density of 5.19 mg/cm~3 obtains the highest thermal conductivity of 46.55 W/(m·K),the lowest The interface thermal resistance is 25.06 mm~2·K/W.(2)In order to further improve the thermal conductivity of the material,polyimide is loaded in situ in the three-dimensional graphene wall layer,and further graphitization treatment is used to enhance the mechanical strength of the three-dimensional graphene pore wall.Through testing,it was found that the mechanical strength and performance of the enhanced three-dimensional graphene composite material were improved.In terms of thermal conductivity,under compression,the thermal conductivity of the composite after carbonization increased from the initial 32.62W/(m·K)to 38.36 W/(m·K),and the interface thermal resistance decreased from 30.29 mm~2·K/W to 25.59 mm~2·K/W.After graphitization,the thermal conductivity of the composite material is further enhanced,the thermal conductivity is increased to 50.71 W/(m·K),and the interface thermal resistance is reduced to 23.16 mm~2·K/W.(3)In order to solve the problems of high porosity and low thermal conductivity of three-dimensional boron nitride,an ice template method was used to prepare three-dimensional boron nitride aerogel,which was reinforced in situ by polydimethylsiloxane to make it have High elasticity.Mechanical performance tests show that the maximum compression deformation of the three-dimensional boron nitride composite material can reach 70%.The thermal conductivity test results show that with the increase in the size of the raw material(3～19μm),the internal contact thermal resistance of the three-dimensional boron nitride decreases and the thermal conductivity increases.However,when the size of the raw material layer exceeds 19μm,its excessive volume steric hindrance leads to an increase in the void volume of the internal pore wall of the three-dimensional boron nitride,resulting in a decrease in its thermal conductivity.The thermal conductivity of the composite material prepared with the raw material size of 19μm under 70%compression deformation can reach 5.84 W/(m·K),and the interface thermal resistance is 439.50mm~2·K/W. |
PDF Full Text Request