Study On The Performance Enhancement And Mechanism Of BaTiO₃ Nanometer Materials On PVDF Triboelectric Generator

Triboelectric phenomenon has been discovered for thousands of years,but it is hard to collect the electricity generated,until recently,the triboelectric generator?TEG?has begun to develop.Triboelectric generator is an energy collecting device that is based on the principle of triboelectric phenomenon and electrostatic induction to collect and utilize the mechanical energy in the friction process of two objects.For TEG,the most important factors are the choice of two kinds of triboelectric materials with different electronegativity,the design of device structure and the realization of circuit that collects electric energy.The manufacture technology of TEG is simple,low cost and suitable for mass production,and various types of energy can be collected by TEG such as the human body mechanical vibration,bridge and sea water fluctuation.TEG can be used as a micropower source for power supply or as a self-energized sensor.In this thesis,two kinds of materials with different electronegativity were used to manufacture a triboelectric generator.The positive material was polyamide 6?PA6?,and the negative material was polyvinylidene fluoride?PVDF?.We mix barium titanate?BTO,BaTiO₃?with PVDF to improve the piezoelectric coefficient and relative dielectric constant of the film,thus enhancing the output performance of TEG.The influence of barium titanate concentration and different PVDF-BTO film thickness on TEG output performance was analyzed in detail.Based on the theoretical analysis,the theoretical basis of the influence of barium titanate and PVDF-BTO film thickness on TEG performance was studied.The results show that the output voltage and current performance of the TEG was mainly affected by three factors:material piezoelectric coefficient,dielectric constant and the surface roughness.Blending a certain concentration of BTO nano materials and making the PVDF-BTO composite film have a certain thickness is a simple and effective method to enhance the surface roughness,piezoelectric and dielectric constant of the film,so as to enhance the properties of TEG.The research results of this thesis have positive significance for promoting the mechanism,experiment and application of TEG.The main work and achievements of this thesis are as follows:1.PVDF with different concentration of BTO and PA6 films were prepared by spin coating.In PVDF films,BaTiO₃ was mixed with different concentrations to get PVDF-BTO films,and the concentration was 5%,10%,15%,20%and 30%respectively.The surface roughness of different concentration films was observed by scanning electron microscope.With the increase of concentration,the surface roughness increases,and BaTiO₃ powder is agglomerated.The piezoelectric properties of thin films were tested by piezoelectric microscope.The piezoelectric coefficient of the film increases with the increase of concentration,and then decreases.When the concentration of BaTiO₃ is 10%,the piezoelectric coefficient of PVDF-BTO film achieves the highest value of 30 pm/V.The relative dielectric constant of PVDF-BTO films were measured by wide temperature broadband impedance analyzer.The relative dielectric constant of the films increases first and then decreases with the increase of the concentration.When the concentration of BaTiO₃ is 10%,the relative dielectric constant of the PVDF-BTO film reaches the maximum value of 19.2.2.The vertical contact-separation mode TEG is prepared.The PVDF/PVDF-BTO films and PA6 films were respectively applied to the glass substrate by conductive aluminum double-side adhesive,and the wires were connected to the structure of the triboelectric generator.We adopt the vertical contact separation structure,and the dynamic fatigue test machine is used to control the two plates of TEG to produce periodic contact and separation.In this process,TEG can generate periodic voltage and current.Results show that the output voltage and current of TEG increase with the contact pressure and plate spacing.In the same test condition,the TEG system composed of PVDF-BTO film has higher output voltage and current than that of PVDF film TEG.When the plate distance is set to 10mm and the force is set to 180N,the peak voltage of PVDF-BTO/PA6 TEG is as high as 900 V,which is 2.34 times of the peak voltage of PVDF/PA6 TEG in the same condition.3.The influence of BaTiO₃ concentration on the electrical properties of PVDF-BTO/PA6 TEG was studied.The PVDF-BTO films of different BaTiO₃ concentrations and PA6 films respectively constitute TEG system and then their output performance was tested.Results show that the effect of BaTiO₃ concentration on TEG performance is very large.With the increase of concentration of BaTiO₃,the peak voltage and current increase first and then decrease.When the concentration of BaTiO₃ is 10%,the output voltage and output current reaches the maximum value of 432 V and 13?A,respectively.4.The effect of PVDF-BTO film thickness on the electrical properties of PVDF-BTO/PA6 TEG was studied.The thickness of the films was measured by the alpha step instrument.The PVDF-BTO films with different thickness and PA6 films constitute TEG system and their output performance was tested.Results show that the film thickness has great influence on TEG performance.With the increase of PVDF-BTO film thickness,the output voltage and current generally show the trend of first increase and then decrease.When the thickness of PVDF-BTO film is 3 6?m,the voltage and current reaches the maximum,and the output voltage and current are 432 V and 13 ?A,respectively.5.By theoretical modeling,we can get the TEG output voltage expression.Through analysis and calculation,the relative dielectric constant and charge density change with the different concentrations of BaTiO₃,which is the key of the change of the TEG output voltage.The increase of relative dielectric constant and piezoelectric coefficient of PVDF-BTO films can increase the surface charge density,thus increasing the output voltage of TEG.In the thickness range selected by the experiment,the film thickness significantly affects the charge density,thus affecting the output voltage of TEG.6.SAW devices were prepared on PVDF-BTO piezoelectric flexible film as substrate.The appropriate experimental parameters and experimental methods were obtained through several experiments,and a good shape IDT was prepared on the PVDF-BTO substrate.However,due to the large surface roughness of PVDF-BTO film,the acoustic loss is too large to obtain resonance performance.Using lithium niobate as substrate,the same technological process was tested,and the SAW device produced had good resonance performance.