| With the development of miniaturization,integration and lightweight of electronic components,it is urgent to harmoniously improve energy storage density and thermal conductivity of polymer-based dielectric composites.The dielectric constant and breakdown strength have an important influence on the energy storage density of dielectric materials.Under the background of device miniaturization and integration,the breakdown strength is considerably determined by the thermal breakdown caused by dielectric loss.Therefore,it is of great research value for the composite materials to effectively suppress dielectric loss and timely conduct the heat generated by the conducting loss while the improvement of dielectric constant is achieved.In this paper,based on 2D boron nitride nanosheets(BNNS)with high thermal conductivity prepared by an optimized laboratory process,a novel composite filler was designed and prepared by loading barium titanate@polyaniline(BT@PANI)core-shell particles on BNNS surface.The effect of the filler’s microstructure on the dielectric properties and thermal conductivity of the composites were investigated.This work can provide a new way for the development of energy storage polymer composite dielectrics and has great application value.Firstly,using Li~+as intercalator,hexagonal boron nitride nanosheets(BNNS)with a narrow distribution of the slice diameter were prepared by ultrasonic-assisted hydrothermal method and two-step centrifugation method.After the surface modification for BNNS were processed by in-situ polymerization,polydopamine-boron nitride nanosheets(PDA-BNNS)were prepared and morphology regulation was achieved.The results show that the PDA loading content in the direction of BNNS surface and thickness gradually reduces as the mass ratio of BNNS to DA-HCl decreases.When the mass ratio of BNNS to DA-HCl is 8:1,the edge of the products is smooth.PDA like spherical shape locally gathered on the surface of BNNS to form bumps.The special morphology can not only provide enough adhesive sites for other materials and also avoid destroying the rheological property of two-dimensional materials because of the over-sized slice diameter that can be get when other materials is adhered on the end face.In addition,the high conductivity loss due to the easy formation of free charge transport paths can also be blocked.Then,utilizing the adhesion property of PDA,a novel composite filler of BNNS/BT@PANI were prepared by loading BT@PANI on the surface of PDA-BNNS using a independently developed and simple method of cyclic sedimentation,and the polyvinylidene fluoride(PVDF)-based composites were investigated.The results show that the number of the BT@PANI particles loaded on the surface of BNNS arises with the increase in the mass ratio of BT@PANI to BNNS.In the BNNS/BT@PANI/PVDF composites,the composite fillers present an distribution tendency parallel to the surface of the PVDF-based composites.Dielectric constants of the composites with 20wt%filler loading undergo a decrease with the increasing loaded content of the BT@PANI particles.The maximum value reaches 20.55(10~3 Hz)which is more than twice that of PVDF film,while the dielectric loss maintains around 0.20.Especially within the frequency of 10~4～10~6 Hz,the dielectric loss is in the range of around 0.10.The values of thermal conductivity for the composites reduce form 0.64 W/m K to 0.92W/m K,which are much higher than that of the pure PVDF film(0.22 W/m K),and exhibit a declining tendency with the increasing loading content of the BT@PANI particle.The simultaneous improvement of the dielectric and heat-conducting properties in relatively low loading content can be ascribed to the strategy that the core-shell particles with conducting property are loaded on the surface of BNNS resulting in intercepting transport paths of free charge. |
