Design And Study On Performance Of Multi-dimensional Nanofiller/polydimethylsiloxane Thermal Management Composites

The rising of the fifth generation of mobile communication technology has led to the rapid development of modern electronic devices in ultra-miniaturization,high concentration,and multi-functionalization.Traditional thermal conductive materials can not meet the thermal management of modern electronic equipment.Thermal conductive composites with polymer matrix have become the preferred solution to heat dissipation problems of electronic devices due to their excellent electrical insulation,and the ability to bring new performance.In this work,inspired by the electrical conductive networks,two-dimensional(2D)boron nitride(BN)and one-dimensional(1D)silver nanowires(Ag NW)were chosen to construct three-dimensional(3D)thermal conductive networks.It was expected to eliminate complicated processes and template methods.Firsty,two-dimensional boron nitride nanosheets(BNNS)were prepared by cell crushing-assisted liquid phase exfoliation and 1D silver nanowires were prepared by polyol method.Then,the prepared BNNS and Ag NW were used as fillers and polydimethylsiloxane(PDMS)was used as matrix to prepare three multi-dimensional composites,BNNS/PDMS,Ag NW/PDMS and Ag NW/BNNS/PDMS,respectively.The effects of different filler contents on the microscopic morphology,thermal management properties,mechanical properties,and electrical insulation properties of the multi-dimensional nanofiller/PDMS composites systems were investigated by various characterization,and the effects of interfacial thermal resistance(ITR)on the thermal conductivity of the composites systems were further investigated by different theoretical thermal conductivity models.It was observed by SEM that BN would make the interface between BN and PDMS rough,while the addition of Ag NW would improve the interface between BN and PDMS.and resulted in enhanced thermal conductivity.In comparison with the thermal conductivities of BNNS/PDMS,Ag NW/PDMS and Ag NW/BNNS/PDMS composites systems,it was found that the thermal conductivity of 2 wt%Ag NW/20 wt%BNNS/PDMS composite reached 0.64 W m^-1K^-1,an enhancement of 237%of neat PDMS.The interfacial thermal resistances of BNNS/PDMS,Ag NW/PDMS and Ag NW/BNNS/PDMS were calculated by the effective medium theoretical model as well as the Foygel model.It was found that the interfacial thermal resistance of the Ag NW/BNNS/PDMS composite system decreased from 5.47×10^-7 m~2 K W^-1,3.07×10^-7 m~2 K W^-1 of composites BNNS/PDMS and Ag NW/PDMS to 1.96×10^-8 m~2 K W^-1.Compared with the neat PDMS matrix,filling the PDMS matrix with either 2D BNNS or 1D Ag NW enhanced the tensile strength at break,but the rigid fillers result in a decrease in the tensile elongation at break of the composites.When filled with both 1D Ag NW and2D BNNS filler,the tensile strength at break and tensile elongation at break decreased with the increase of Ag NW/BNNS content in composites.Despite the addition of highly electrically conducting filler Ag NW in composites Ag NW/PDMS and Ag NW/BNNS/PDMS,the composites have high volume resistivities.The addition of Ag NW did not help the formation of electrical conductive networks but the thermal conductive networks.Their volume resistivities were all in the range of electrical insulators.The synergistic effect of 1D Ag NW and 2D BNNS on the performance enhancement of the composites was fully demonstrated.