Preparation And Application Of β-phase PVDF Films Based On Multi-field Coupling Technology

The ability of piezoelectric materials to harvest available mechanical energy from the surrounding environment and convert it into electrical energy is a property that makes them play an important role in self-powered devices and flexible smart wearable devices,as well as in energy harvesting,biomedical and smart sensing fields.Piezoelectric materials mainly include piezoelectric ceramics,piezoelectric crystals and piezoelectric polymers.Compared with traditional piezoelectric ceramics and piezoelectric crystals,piezoelectric polymer materials have the advantages of high flexibility,good impact resistance and fatigue resistance,which are compatible with the characteristics of flexible smart wearable devices.Polyvinylidene fluoride(PVDF)piezoelectric thin film is a piezoelectric polymer material with wide scientific value and technical application prospects.PVDF thin film has been widely used and concerned in the fields of energy harvesting,new smart sensors,biomedicine and battery diaphragm because of its unique piezoelectric effect and soft texture,high sensitivity and wide frequency response range,however,the quality of PVDF piezoelectric films produced in China is still not high,and there is still a gap compared with foreign countries,so this paper carried out a study related to the preparation process of β-phase PVDF films..In this paper,PVDF films were first prepared using different preparation methods,then the phase transition law of β phase and the properties of PVDF films were comprehensively investigated under multi-field coupling conditions,and finally the applications of PVDF piezoelectric films were explored The specific research contents are as follows:1.The PVDF films were prepared using different preparation processes such as solution casting,spin coating and hot pressing,and the properties of the PVDF films prepared by different methods were compared,and then the advantages and disadvantages of each preparation method were analyzed to find a suitable preparation process for this study.2.To characterize the crystalline shape and morphology of the prepared PVDF films by X-ray diffractometer,Fourier infrared spectrometer and scanning electron microscope under multi-field coupling conditions,and to explore the β-crystalline phase transition law of PVDF films under multi-field coupling conditions.3.characterize the key parameters in the preparation of PVDF piezoelectric films,characterize the piezoelectric properties of PVDF piezoelectric films by piezoelectric coefficient tester,and find the best process method and conditions for the preparation of PVDF piezoelectric films with high voltage electrical properties under the current experimental environment.4.To fabricate piezoelectric nanogenerators based on the high-voltage electrical performance PVDF piezoelectric films prepared by ourselves and to investigate the application of PVDF piezoelectric films.The piezoelectric nanogenerators was fabricated using the high-voltage electrical performance PVDF piezoelectric films prepared by ourselves,and the preliminary exploration of the application of PVDF piezoelectric films was carried out.The experimental results show that high temperature,high stretching multiplicity and high polarization field strength conditions can promote the increase ofβ-crystalline content inside PVDF films.The highest piezoelectric coefficient(30p C/N)can be obtained for PVDF piezoelectric films prepared by the hot pressing process when the hot pressing temperature is 180°C,the stretching multiplicity is 4times,and the polarization field strength is 150 MV/m.The piezoelectric properties of PVDF piezoelectric films prepared by the hot pressing process are basically comparable to those of commercial PVDF piezoelectric films in the market.The piezoelectric nanogenerators prepared from PVDF piezoelectric films based on the hot pressing process have also shown remarkable performance in energy storage applications and wearable applications.