| With the development of China’s aerospace industry,the electronic equipment to ensure the normal operation of aircraft is becoming more and more sophisticated and multifunctional.A large amount of heat generated by aerospace electronic equipment in the work is the main reason for the significant reduction of equipment performance and reliability.Therefore,the demand for heat management materials that can effectively dissipate heat is increasingly urgent,and the requirements for its thermal conductivity and thermal conductivity efficiency are also increasing.In recent years,polymer matrix composites have attracted extensive attention in the field of aerospace thermal management because of their outstanding comprehensive properties such as lightweight and designability.Improving the thermal conductivity and heat dissipation efficiency of polymer-based thermally conductive composites has always been an important direction for the development of high-performance thermally conductive composites.In this paper,polydimethylsiloxane（PDMS）is selected as the polymer matrix,and different methods are used to build an efficient heat conduction network to improve the thermal conductivity of PDMS.The main research contents and results of this paper are as follows:（1）The efficient construction of the thermally conductive network in the polymer matrix can be achieved by prefabrication.Using organic foam as raw material,silicon carbide foam（SF）was obtained by carbonization and vitrification,and silicon carbide foam with in-situ growth of nanowires（NWSF）was obtained by optimizing the preparation process.The morphology,composition and structure of foam were characterized by scanning electron microscope,X-ray diffraction,Fourier transform infrared spectroscopy and Raman spectroscopy;Furthermore,PDMS/SF and PDMS/NWSF composites were obtained by immersing polydimethylsiloxane into foam and curing by vacuum assisted impregnation.The thermal conductivity,tensile and compressive properties of the composites were compared.The results show that Si C foam,as a preformed filler network,can form a complete heat conduction network in PDMS,so it can effectively improve the thermal conductivity of PDMS;At the same time,the tensile properties of the composites are improved under the action of debonding-pullout,crack pinning and other toughening mechanisms;However,the weak interaction between the inorganic filler network and the polymer matrix makes it easier to deform/crack at the interface of the composite,and the broken Si C skeleton has a certain destructive effect on the matrix in the compression process,resulting in the reduction of the compressibility of the composite.（2）It is an effective means to obtain high thermal conductivity polymer matrix composites by improving the content of thermal conductivity components in the composites through component design,optimizing microstructure and adjusting size,so as to realize as many effective thermal conductivity paths as possible.In the study,composite filler systems with different sizes（alumina（Al2O3）and zinc oxide（Zn O））and composite filler systems with different dimensions（Al2O3 and graphene）were investigated respectively,and these composite fillers were dispersed in PDMS with low molecular weight to prepare thermal conductive silicone grease with high thermal conductivity.The results show that because the small-size filler can effectively fill the gap between the large-size filler,the composite filler composed of different sizes of filler can obtain a larger filling amount in the polymer matrix than a single filler;At the same time,due to the bridging effect of two-dimensional filler,Al2O3/graphene composite filler has more advantages than single filler in the preparation of high thermal conductivity composites. |
