Investigation On High Performance Piezoelectric Composites

Energy harvesting technology can convert energy in the environment into electrical energy which can be a reliable and endless resource for portable and low-power devices.To date,enormous energy harvesting devices have been developed based on different ambient power sources.Poly?vinylidene fluoride??PVDF?is an important polymer for energy harvesting devices based on vibrations,which is a widely used polymer with excellent flexibility and formability.However,since the piezoelectric coefficient of PVDF is relatively lower compared with inorganic piezoelectric materials,different methods were used to enhance the piezoelectricity of PVDF.In this study,different hybrid nanofillers were added into PVDF copolymer i.e.,poly?vinylidene fluoride-co-hexafluoropropylene??PVDF-HFP?to fabricate hybrid composite films.The electrical experiments of the composite films are conducted.The morphology,phase transformation,crystallization of composite films were also studied.The following works are contained in this study:?1?The prepararion process of solution casting method was improved.A portable device was manufactured to ensure stable temperature during mechanical stretching.The optimum temperature for mechanical stretching was verified.?2?Carbon black?CB?,few-layer graphene?FLG?and CB/FLG hybrid fillers were used to fabricate composite films.The piezoelectricity of composite films were studied.The characterization of composite films were carried out by scanning electron microscope,Fourier transform infrared spectroscopy analysis and other methods.It is founded that the output voltage and the harvesting power density were 81%and 229%higher than pure PVDF-HFP film,the relative fraction of?-phase were raised to 99%.?3?Two different hybrid fillers of carbon black?CB?/manganese dioxide?MnO₂?were synthesized using in situ method.Characterizations were conducted by transmission electron microscope,scanning electron microscope,X-ray diffraction and Raman spectrum.It is found that MnO₂ nano sheets grew on the CB and formed a coral like structure.?4?CB/MnO₂/PVDF-HFP hybrid composite films were fabricated.The open circuit voltage was measured,the dispersibility of the nano fillers,phase transformation and crystallinity of the composite films were also investigated.Though the improvement of open circuit voltage for composite was limited,the hybrid fillers perform uniform distribution in PVDF-HFP.And the relative fraction of ?-phase were raised to a high level with low concentration of hybrid fillers.