Study On Three-phase Compound Of Polymer-based High Performance Dielectric Materials

With the development of microelectronic technology,electronic products increasingly require miniaturization and functional diversification.In recent decades,polymer-matrix composites have attracted extensive attention of reasearchers due to their good compatibility with printed circuit boards and relatively excellent dielectric properties.Many researchers focus their attention on the conductor/polymer composites and conductor/ceramic/polymer composites because of their excellent performance in improving the dielectric constant,but these materials also have high dielectric loss.Currently,a large number of researches have focused on the modification of the conductor fillers,the research directions include surface modification,compound modification and coating modification of conductor fillers,among which the research on the compounding and filling ways of multiple fillers is relatively rare.In this paper,barium titanate powder and carbon black-barium titanate?CB-BT?compound powder were prepared by hydrothermal method after surface treatment of carbon black with different surface modifiers.And carbon black/barium titanate?CB/BT?compound powder was prepared by ball-milling.Different compounding and filling ways of fillers were used to prepare carbon black/barium titanate/epoxy three-phase composites,namely incorporating CB-BT and CB/BT into the epoxy matrix separately,and filling CB and BT powder into epoxy matrix in sequence and reverse order,respectively.It was found that the phase of barium titanate synthesized by the hydrothermal method in the same system with carbon black in it is related to the surface properties of the carbon black,indicating that there were heterogeneous nucleation and growth of barium titanate on the surface of the CB particles.The carbon black paricles oxidized by concentrated HNO₃ is the best choice as the conductor fillers,and the temperature of 160°C and the concentration of Ba²⁺of 0.075 mol/L were the optimal conditions for the preparation of CB-BT composite powders.In the CB-BT composite powder prepared under the above conditions,CB and BT adhered to each other,which effectively blocked the direct contact of carbon black and formed a stable composite powder that is suitable fillers for polymer-matrix composites.Among different compounding and filling ways of carbon black and barium titanate,the CB-BT/Epoxy composites prepared by using the hydrothermally prepared CB-BT composite powder as the fillers exhibits the lowest dielectric loss and high permittivity.At the same time,the preparation process of the composites can be simplified by reducing the modification and addition steps of the fillers.In order to further investigate the influence of the phase of barium titanate on the dielectric properties of the composites,the CB-BT composite powder was burn-in at 600°C in a vacuum environment for 8 h.There was a transformation from cubic phase to tetragonal phase of barium titanate after burn-in,which improved the dielectric properties of the composites.At a frequency of 10 kHz,when the filler content was 5 vol%,the dielectric constant and dielectric loss of CB-BT/Epoxy and 600°C-CB-BT/Epoxy composites were 14.5,16.8,and 0.012,0.013,respectively;when the filler content was 20 vol%,the dielectric constant and dielectric loss of the composites were 22.1,30.3,and 0.022,0.019,respectively.