| Piezoelectric polymer materials are widely used in the electronic field due to their unique electroactivity and flexibility.However,the shortcomings of polymer piezoelectric materials such as single category,complex processing technology and narrow operating temperature range limit their application in some high-tech fields.In view of many defects of piezoelectric polymer materials,the piezoelectric properties of polyacrylonitrile(PAN)nanofiber membrane were studied in this paper.The high piezoelectric properties of PAN nanofiber membrane were realized by electrospinning method for the first time,which broke through the limitation of piezoelectric properties of polymer in ultra-high temperature environment.The main research results are as follows:(1)The design idea of changing the piezoelectric properties of PAN material by adjusting the molecular conformation of PAN was proposed and realized.A new type of PAN nanofiber membrane piezoelectric material was prepared by electrostatic spinning.It was found that PAN nanofiber membranes have higher piezoelectricity than PVDF.A piece of PAN nanofiber membrane(working area 5×5 cm~2)can generate 2.0V and 1.1μA electrical output under the compressive impact.Its voltage output was1.67 times higher than PVDF nanofiber membrane under the same conditions,which proves that the piezoelectric properties of PAN are derived from its high content of planar zigzag conformation.The research upgrades our understanding of PAN piezoelectric properties.(2)A new type of high temperature resistant PAN nanofiber membrane piezoelectric material was prepared by thermal stabilization technique.The effect of the molecular structure of the material on its high temperature piezoelectric properties was studied,and the piezoelectric conversion mechanism was clarified.A 2.5×2.5 cm~2 thermally stabilized PAN device compressed at 450°C can generate a voltage of 9.7 V(current output 4μA)with a maximum output power density of 26.4 m W/m~2.This ultrahigh temperature piezoelectricity originates from the fact that thermally stabilized PAN has the conjugated trapezoidal structure,which makes polar groups unaffected by high-temperature environments.This research establishes a new record of high-temperature piezoelectric polymer materials,which solves the problem that polymer piezoelectric materials cannot be used in extreme high temperature environments.(3)The thermally stabilized PAN nanofiber membrane has excellent acoustoelectric conversion capability,which can convert acoustic wave into electric energy in the temperature range from room temperature to 450℃,and its performance is almost not affected by the ambient temperature.An acoustoelectric device made of a 3×3 cm~2thermally stabilized PAN nanofiber membrane can generate 118 V output voltage(current output 12μA)with a peak power density output of 392 m W/m~2.Compared with the non-thermally stabilized PAN nanofiber membrane,the thermally stabilized PAN had higher acoustoelectric conversion ability,a larger frequency response range,and stronger high-temperature stability.(4)The possibility of converting portable thermal energy into electricity has been demonstrated by combining a micro thermoacoustic engine with a PAN nanofiber acoustoelectric device.Under flame heating,the thermoacoustic waves generated by the thermoacoustic engine can be converted into electricity by a thermally stabilized PAN acoustoelectric device.A 3×3 cm~2 acoustoelectric device can generate 112 V electrical output with a peak power density of 324 m W/m~2.Gas torch,alcohol lamp flame,focused sunlight,and candle flame can all be used to drive thermoacoustic engines to generate thermoacoustic waves,which are converted into electricity by thermally stabilized PAN.This opens up a new way for emergency power supply in various outdoor scenarios. |
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