Preparation And Characterization Of BaTiO₃@PAN/PVDF Nanofiber Based Piezoelectric Materials

In recent years,the rapid development of portable wearable flexible electronic devices has been widely concerned by scholars.Piezoelectric sensors have been widely studied because of their advantages such as good flexibility,high sensitivity,low production cost and easy miniaturization.At present,the flexible sensor output piezoelectric signal is weak and strong problems,a single piezoelectric material can not meet the requirements of people,inorganic piezoelectric material has a high dielectric constant but brittle,organic piezoelectric material is flexible but low dielectric constant,so exploring the composite of organic and inorganic piezoelectric materials is the current research hotspot.In this paper,BaTiO₃@PAN/PVDF nanofiber wiki piezoelectric composite materials were prepared by electrostatic spinning technology.The nanofibers were oriented by drafting and the composite piezoelectric materials with different crystallinity were obtained by different cooling methods.Due to the low strength of the nanofiber film,the strength of the nanofiber film was improved by hot-pressing bonding,then the hot draft orientation was carried out,and different cooling methods were adopted.Finally,the nanofiber film was hot-pressing bonded according to the cross-layer composite Angle of 0°,45°and 90°,and the composite piezoelectric material was obtained.The main research results are as follows:（1）Firstly,BaTiO₃ was surface modified by DA,and its particle size was analyzed.The results showed that compared with BaTiO₃,the particle size distribution of PDA-BT after modification was smaller,which proved that its dispersion performance became better.XRD tests show that the crystal morphology of BaTiO₃ does not change before and after modification,and its piezoelectric properties are not affected.（2）Secondly,the effects of the mass fraction of PDA-BT on the properties of PAN nanofiber membranes were studied.FTIR test showed that the 3~1 helical conformation of PAN changed to the planar zigzag conformation after adding PDA-BT.When the mass fraction of PDA-BT is 5%,the maximum conformation content of planar sawteeth is 51.04%,the piezoelectric properties are significantly improved,the maximum open circuit voltage is 0.94 V,and the mechanical properties of PAN nanofiber membrane are the best:the fracture stress is 4.64 MPa,the fracture strain is 16.05%.（3）Then,the influence of the mass fraction of PDA-BT on the properties of PVDF nanofiber membrane was studied.XRD results showed that PVDF changed fromαcrystal toβcrystal after adding PDA-BT.When the mass fraction of PDA-BT was 9%,theβcrystal content of PVDF reached 90.4%.The piezoelectric properties of PVDF were significantly improved,and the maximum open circuit voltage was 1.14 V.At this time,the mechanical properties of PVDF nanofiber membrane were the best:the fracture stress was 11.79 MPa,and the fracture strain was 48.11%.（4）Response surface method（BBD）was further used to optimize the experimental conditions of hot pressing.The results showed that when the hot pressing temperature was 179.414,the hot pressing time was 2.595 min,and the hot pressing pressure was0.535 MPa,The maximum predicted fracture stress of PDA-BT@PAN/PVDF composite nanofiber membrane is 11.182 MPa.Experimental verification under the above conditions shows that the fracture stress of the nanofiber membrane increases from 6.02 MPa to 11.42 MPa by 89.70%.After drafting and cooling,the relative content ofβcrystal was increased to 91.8%.When cooled by liquid nitrogen,the crystallinity Xc reaches 49.44%,and the open-circuit voltage reaches 1.46 V.（5）Finally,the effects of different splicing angles on the orientation of PDA-BT@PAN/PVDF composite nanofiber membranes were studied.When the splicing Angle is 90°,the pore size distribution is the smallest,between 0.2-0.5 um,and the maximum open-circuit voltage reaches 1.66 V.