| Piezoelectric materials can collect mechanical energy in the form of environmental vibration,fluid flow,machine rotation and biological movement by using piezoelectric effect,and apply it to all aspects of life through energy conversion.Compared with inorganic piezoelectric materials,PVDF and its copolymers have attracted extensive attention and research because of their excellent flexibility,biocompatibility and easy manufacturing process.By electrostatic spinning preparation of PVDF nanofiber membrane,can effectively improve PVDF piezoelectric properties and improve the energy utilization in electromechanical conversion,which makes it show excellent application prospects in the fields of flexible wearable and self powered electrical parts.In this paper,PVDF nanofiber membrane was prepared by electrostatic spinning method.By adding cellulose acetate（CA）and Mo S2@TNr nanoheterojunctions,the content ofβphase（piezoelectric phase）in PVDF was regulated to improve its piezoelectric properties,and then assembled into friction-piezoelectric nanogenerators.The main research contents are as follows:（1）With N,N dimethyl formamide（DMF）and acetone mixed solvent as dispersion medium,the preparation of nano fiber PVDF membrane electrostatic spinning technology,studied the mixing ratio of DMF and acetone,PVDF concentration,spinning voltage,spinning fluid velocity and collection device types of PVDF nanometer fiber under different experimental parameters,such as morphology,diameter size and distribution,The optimal spinning parameters were as follows:PVDF concentration 12%,DMF:acetone=6:4（mass ratio）,spinning voltage 18 k V,spinning fluid flow rate 0.4 m L/h and drum collector（diameter 5cm）.Under these conditions,piezoelectric test and structure analysis of PVDF nanofiber membranes with different concentrations were carried out.The results show that when PVDF concentration is12%,the content ofβphase reaches 63.65%,and the maximum output voltage reaches2.2V.（2）PVDF/CA composite nanofiber membranes were prepared by combining cellulose acetate（CA）with PVDF,and the effects of different proportions of PVDF/CA on the morphology,structure and piezoelectric properties of composite nanofiber membranes were investigated.The results showed that the average diameter and diameter dispersion of the composite nanofibers increased with the addition of CA.The fiber diameter increased from 0.24μm to 0.37μm,and the diameter dispersion increased from 0.05μm-0.40μm to 0.10μm-1.0μm.When the mass ratio of PVDF to CA was 9:1,the maximumβphase content was 69.31%,and the piezoelectric performance was the highest.Under a mechanical stress of magnitude 1 N and frequency 1 Hz,the output voltage reached 4.1 V and the current value reached 1.5μA.Compared with the pure PVDF membrane without CA,the voltage and current increased by 78.3%and 66.7%,respectively.Charging a 4.7μF capacitor for 15 minutes can instantly light up 9 LED lights.（3）On the basis of PVDF/CA=9/1（mass ratio）,the PVDF/CA/Mo S2@TNr composite nanofiber membrane was prepared by combining Mo S2@TNr nano-heterojunction with PVDF,and then assembled into friction-piezoelectric composite nanogenerator.The results show that after adding Mo S2@TNr,The average diameter of composite nanofibers decreased.When the amount of Mo S2@TNr is 0.5 wt%,theβphase content reaches 78.1%,and the output performance of the composite nanogenerator is also the largest.Under the action of periodic mechanical stress of 1 N and 2 Hz,the peak voltage and peak current reach 13.1 V and 3.8μA.When the mechanical force is 1 N 6 Hz,the output voltage and current of the nanogenerator reach71 V and 6.3μA,respectively.When the resistance value of external load is 10 MΩ,the output power reaches the maximum value of 6.25 m W/m2.After access to the full bridge rectifier circuit,it can drive 80 serial LED lights to light up,showing good mechanical energy collection performance. |
PDF Full Text Request