Study On Organic/Inorganic Hybrid Modified High Thermal Conductivity Silica Gel Material

With the rapid development of the 5G era,electronic and electrical devices are developing towards high power density,miniaturization and integration,while their efficient heat dissipation has also become a crucial and urgent problem to be solved.As a commonly used electronic potting glue,silicone gel(SG)has the advantages of good electrical insulation,adhesion and sealing,but its lower thermal conductivity limits its application in more fields.Therefore,it has become a hot spot to develop potting compounds that can meet the requirements of today's electronic packaging.The main purpose of this thesis is to prepare a highly thermally conductive silicone gel composite material,and the composite material uses two-component room temperature vulcanized silicon gel as the matrix,flake graphite(FG)as the main thermal conductive filler,and silicon nitride(Si₃N₄)as the auxiliary thermal conductive filler,and studied in detail the influence of FG content,size,FG modification,FG and Si₃N₄ compounding,and FG orientation on the thermal conductivity,thermal stability,electrical insulation and other properties of the composites.First,the influence of FG addition amount and size on composites is studied.The results show that with the increase of FG addition,the thermal conductivity,thermal stability and heat resistance of the composite have been significantly improved;in addition,the size of FG also has an important influence on the thermal conductivity of the composite.Below,the FG sheet with a larger particle size has a better effect on improving the thermal conductivity of the composite.This is because the FG sheet with a larger size has a greater probability of contacting each other,and thus it is easier to form a heat conduction path in the matrix.When the amount of FG added is40%and the size is 50 mesh,the thermal conductivity of FG/SG composite has a maximum value of 1.101 W/(m·k),which is higher than pure SG(0.1641 W/(m·k))671%,and the thermal stability and mechanical properties of the composite are higher than pure SG.Three coupling agents KH550,KH560 and NDZ-311w were used to modify 50mesh?40%FG,and the effect of the type and concentration of the coupling agent on the properties of the composite was studied.The results show that as the concentration of the coupling agent increases,the thermal conductivity of the composite first increases and then decreases,but the thermal conductivity of the modified composite is higher than that of the unmodified composite,and KH550 modification has the best effect.When the concentration of KH550 is 1.5%,the thermal conductivity of the composite has a maximum value of 1.507 W/(m·k),which is 9.18 times and 1.37times higher than the thermal conductivity of pure SG and unmodified FG/SG composites,respectively This is because the coupling agent can improve the interface compatibility between the polymer and the graphite and strengthen the matrix-filler interface bonding force to reduce the interface thermal resistance and obtain higher thermal conductivity.Compared with single filler FG,FG/Si₃N₄ compound filler shows better reinforcement effect and higher thermal conductivity when filled with SG.When filled with 30%FG/10%Si₃N₄,the thermal conductivity of the composite is 1.35 W/(m·k),which is 1.23 times and 5.03 times higher than that of a single-filled 40%FG or 40%Si₃N₄ composite,respectively.This is due to the synergy between the two different shapes and sizes of fillers.In addition,the thermal conductivity of the composite modified by the three coupling agents KH550,KH560 and NDZ-311w is higher than that of the unmodified FG/Si₃N₄/SG composite.The 30%FG/10%Si₃N₄/SG composite modified by KH550 has the best thermal conductivity of 1.627 W/(m·k),which is 9.9 times and 1.21 times higher than that of pure SG and unmodified FG/Si₃N₄/SG composites.The composite material prepared after the FG is oriented along the direction of the magnetic field strength by applying an external magnetic field has a higher thermal conductivity.When the magnetic field strength is 0.65T and the addition amount of FG is 40%,the thermal conductivity of the composite has a maximum value of 1.849W/(m·k),which is 11 times and 1.7 times higher than that of pure SG and unoriented FG/SG composites.This is because FG has anisotropic thermal conductivity,and the thermally conductive composite prepared after it is oriented along a certain direction tends to have higher thermal conductivity in the orientation direction.