Preparation Of Polyvinylidene Fluonde(PVDF)Nanogenerator Doped With Inorganic-salt

Nanogenerators prepared from nanoscale piezoelectric materials have a wide application prospect in micro self-powered systems such as implantable biosensor, environment monitor and portable electronics, which can convert the ambient mechanical or biomechanical energy directly into electrical energy. The self-powered ability can be expected to disaffiliate the heavy energy storage part of the system and the dependence on batteries.Piezoelectric polymer poly-vinylidene fluoride (PVDF) has been extensively studied because of its flexibility, lightweight, biocompatibility, long-term stability compared with normal inorganic piezoelectric materials. Considering the simultaneous stretching and poling in one step to form nanofibers, electrospinning is an ideal way to produce piezoelectric PVDF nanofibers with the β-phase formation. However, the piezoelectric property of electrospun PVDF nanofibers has to be improved. This thesis highlights a piezo-enhanced electrospun PVDF nanogenerator with a touch of inorganic-salt.Firstly, basic mechanism and hypothesis have been proposed by concluding the effects of various inorganic-salts doping on the piezoelectric property of electrospun PVDF nanogenerator in this work. Inorganic-salt which exists as electric dipoles in the spinning solution has the greatest promotion for the piezoelectric property of electrospun PVDF nanogenerator. The electric dipoles are oriented under the external electric field, which then act as nucleating agents that promote the formation of P phase during the crystallization of PVDF. Among them, FeCl3·6H2O shows the best performance.Secondly, PVDF nanofiber mats-based nanogenerators are prepared by electrospinning with a touch of ferric chloride hexahydrate(FeCl3·6H2O). The effect on the piezoelectric property of electrospun PVDF nanogenerator caused by various doping amount of FeCl3·6H2O are investigated. The piezoelectric output voltage of electrospun PVDF nanogenerator is highly enhanced with appropriate concentrations of FeCl3·6H2O dosages, which reflects a non-linear dependence of the response on the fraction of the β phase in the PVDF-FeCl3mats. However, the volume conductivity is sharply increased when excessive PVDF-FeCl3is added, which led to the induced positive and negative charges flowing longitudinally in the PVDF mats, causing serious neutralizing effects, which greatly lowered the piezoelectric output voltage. The optimal doping concentrations PVDF-FeCl3dosages is50.0(μmol/g PVDF).At last, well-aligned PVDF-FeCl3nanofiber mats-based nanogenerators are prepared via electrospinning using a high speed roller collector. The oriented fibers are greatly bent under the external pressure parallel to the winding direction, thus enhance the power output of nanogenerators. Compared to randomly distributed PVDF nanofiber mats, no significant change in β phase content is found, however the maximum generated peak piezo-voltage exhibited by oriented PVDF-FeCl3nanofiber mats is as high as-19/+19V, and the average capacitor charging power is202.8nW, which increases by494.7%. Meanwhile, the modifying methods above have a noticeable increase in the mechanical property of the electrospun PVDF nanofiber mats, one can expect wide applications in many areas.