| In recent years,with the increasing development of technology,miniaturisation and ultra-high integration of precision instruments have become more and more common,such as the aerospace industry,semiconductor devices,defence industry,etc.As a result,the increasingly prominent problem of thermal conductivity and heat dissipation has severely restricted the development of these areas of industry,which has put forward more stringent requirements for thermal management materials.Currently commonly used thermal management materials include thermally conductive rubber gaskets,thermally conductive silicone grease,graphite phase thermal management materials,etc.Silicone grease is a polymer which consists of silicone bonds linked to hydrocarbon groups of silane.It can be used as an insulating medium in electronic assemblies to prevent short circuits between electronic components and as a sealant during mechanical assembly.Hexagonal boron nitride（h-BN）is a representative ceramic filler with ideal thermal conductivity.h-BN is relatively stable,with only small amounts of amino and hydroxyl functional groups on the defective parts of its surface,making it less reactive and difficult to disperse at room temperature.Based on this,in order to improve the dispersion of h-BN in the base material,the h-BN was modified by chemical bonding to improve the interfacial capacitance between the filler and the base material,and a thermal interface management material with silicone grease as the base material was prepared.The main contents and results are as follows:（1）Direct chemical grafting of the silane coupling agents KH550,KH560 and KH570 with h-BN by chemical modification resulted in a poorly formed thermally conductive filler,and the thermal conductivity filler formed after grafting was not effective.Considering that there were few active sites on the surface of h-BN,the experimental scheme was improved to functionalize the surface of h-BN.Under the action of sodium hydroxide,the reaction forms hydroxyl boron nitride（h-BN-OH）.h-BN-OH was chemically grafted with the silane coupling agents KH550,KH560 and KH570,respectively.Compared with the unmodified h-BN,the grafted filler had lower viscosity and higher thermal conductivity.The viscosity reduction effect of boron nitride modified by silane coupling agent KH550 is not obvious,and the thermal conductivity is almost the same as that directly filled with the same content of boron nitride in silicone grease.Compared with unmodified boron nitride,KH560 modified boron nitride can reduce the viscosity of silicone grease by about 23%,and KH570 modified boron nitride can reduce the viscosity of silicone grease by about 17%.It is found that KH560 has the best viscosity reduction and thermal conductivity.（2）Thermal conductive grease with high thermal conductivity（TC）was prepared by chemical modification.10-60 wt%h-BN-OH was chemically grafted with carboxyl terminated silicone oil.The grafted products were thermal conductive filler,dimethyl silicone oil as matrix material,and vapor phase nano Si O2 as thickener.The modified thermal conductivity filler was filled in the base silicone grease at 30 wt%.After the modification,the TC value of the silicone grease increased from 0.219 Wm-1K-1to 1.324 Wm-1K-1,and the thermal resistance of the interface decreased from 11.699℃W-1 to 1.889℃W-1.After testing,the modified thermal conductivity filler can effectively reduce the interface thermal resistance,has excellent thermal conductivity effect.（3）10-60 wt%amine-modified hexagonal boron nitride（h-BN-NH2）and carboxyl terminated silicone oil were also used for chemical grafting.After modification,the TC value of silicone lipid increased from 0.219 Wm-1K-1 to 0.928 Wm-1K-1,and the interfacial thermal resistance decreased from 11.699℃W-1 to 2.514℃W-1.After SEM,TEM and FTIR characterization,the microscopic characterization of the modified h-BN graft was analyzed.The formed amide bond could form a thermal conduction pathway and reduce the thermal resistance of the interface. |
