Fabrication Of 0-3 Type PVDF Matrix Piezoelectric Composites Doped With Conductive Phase

In order to prepare a piezoelectric composite with flexibility and good piezoelectric properties,polyvinylidene fluoride?PVDF?was used as the matrix material and lead zirconate titanate?PZT?was used as the ceramic functional phase.The PZT/PVDF two-phase composite was prepared by casting method and the preparation process was optimized.PZT/PVDF/GR composites and PZT/PVDF/CNT composites were prepared by using KH550 modified graphene?GR?and carbon nanotubes?CNT?as conductive filling phases respectively.The effect of conductive phase addition on the electrical properties of composites was discussed.Graphene and carbon nanotubes were added to the composite as a conductive phase according to a certain ratio,and the optimal ratio of the two conductive phases was studied.The main research contents and results of the thesis are as follows:The best conditions for the polarization of the composites were studied:Polarization voltage:6kV/mm,polarization temperature:90°C,polarization time:20 min.Taking PZT/PVDF two-phase composite as the research object,the effect of PZT particle size on the electrical properties of composites was discussed.Experiments shows that the dielectric constant and piezoelectric constant of the composite are the largest when the ceramic particle size is 1.22?m.At this time,the dielectric constant and piezoelectric constant were the largest,72.5 and 23.48pC/N respectively,and the dielectric loss was the lowest,the value is0.0178.The PZT/PVDF two-phase composite prepared by casting method was studied,and the effects of subsequent hot pressing treatment on the morphology and electrical properties of the composites were discussed.The results show that the hot pressing treatment can make the composite material more compact and the piezoelectric constant is also improved.The piezoelectric strain constant after hot pressing is 24.94pC/N,which is 6.2%higher than that of the composites without hot pressing.PZT/PVDF/GR composites were prepared by using modified graphene as conductive phase.The results show that the content of graphene is positively correlated with the dielectric constant,dielectric loss and electrical conductivity of the composite.The piezoelectric constant increases first and then decreases with the increase of the graphene content,and the graphene content is0.6 wt%when the piezoelectric constant reaches the peak.At this time,the d₃₃3 of the composite material is 29.2pC/N,which is 24.3%higher than that of the PZT/PVDF two-phase composite material,and the dielectric loss is low at 0.0273,which has practical use value.PZT/PVDF/CNT composites were prepared by using modified carbon nanotubes as conductive phase.The results show that the content of carbon nanotubes is positively correlated with the dielectric constant,dielectric loss and electrical conductivity of the composite.The piezoelectric constant increases first and then decreases with the increase of the carbon nanotubes content,and the addition amount of carbon nanotubes is 0.5 wt%when the piezoelectric constant reaches the peak.At this time,the d₃₃3 of the composite material is31.6pC/N,which is 34.4%higher than that of the PZT/PVDF two-phase composite material,and the dielectric loss is low at 0.0325,which has practical use value.The use of modified graphene and modified carbon nanotubes as a conductive phase can effectively improve the performance of the composite,and it is concluded through experiments that the optimal ratio of carbon nanotubes to graphene is 4:1.At this time,d₃₃3 is the highest,34.7pC/N,and the dielectric loss is reasonable,which is 0.0232.