CN115295714B - Flexible piezoelectric nanofiber net film and preparation method and application thereof - Google Patents
Flexible piezoelectric nanofiber net film and preparation method and application thereof Download PDFInfo
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- CN115295714B CN115295714B CN202210906991.4A CN202210906991A CN115295714B CN 115295714 B CN115295714 B CN 115295714B CN 202210906991 A CN202210906991 A CN 202210906991A CN 115295714 B CN115295714 B CN 115295714B
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F1/00—General methods for the manufacture of artificial filaments or the like
- D01F1/02—Addition of substances to the spinning solution or to the melt
- D01F1/09—Addition of substances to the spinning solution or to the melt for making electroconductive or anti-static filaments
Abstract
The invention belongs to the field of electrostatic spinning, and particularly relates to a preparation method of a flexible piezoelectric nanofiber web membrane and application of the flexible piezoelectric nanofiber web membrane in a piezoelectric transducer. At present, most partial voltage electric energy conversion device electrodes are two-dimensional electrodes, and conductive electrodes are directly attached on the basis of original piezoelectric materials, and the extraction of conductive charges is limited on the surfaces of the piezoelectric materials. Therefore, the invention coats the conductive nano material on the surface of the PVDF nanofiber by utilizing an electrostatic spraying method to form the electrode with a three-dimensional structure, and the high conductivity of the conductive nano material and the high contact area between the piezoelectric nanofiber and the three-dimensional electrode are utilized to improve the piezoelectric charge migration efficiency, and the electric signal output and the piezoelectric performance are improved under the condition of unchanged pressure and stress area.
Description
Technical Field
The invention belongs to the field of electrostatic spinning, and particularly relates to a flexible piezoelectric nanofiber web membrane, and a preparation method and application thereof.
Background
With the aggravation of energy crisis and the deterioration of natural environment, the development and utilization of clean renewable energy have been paid attention to worldwide, and piezoelectric materials have the ability to convert mechanical strain energy into electric charge, the principle being that if pressure is applied to the piezoelectric materials, the charge centers of cations and anions are separated and form electric dipoles, which generate potential differences, and if dynamic strain phenomenon is applied to continuously change the pressure potential, stable pulse current flows through external circuits. The method can be applied to the artificial skin of the robot and can be used for various intelligent applications such as pulse detection, voice recognition and the like. Polyvinylidene fluoride (PVDF) is favored in the research of the fields of electromechanical transduction, sensors, human-computer interfaces and the like because of the characteristics of high-voltage coefficient, flexibility, light weight, good molding performance and the like. The PVDF nano fiber film has the advantages of high piezoelectric coefficient, good biocompatibility, light weight, softness and the like, and can be used for piezoelectric transduction and sensing devices in future.
At present, the way of improving the voltage output of the piezoelectric nanofiber is to polarize through an electric field, such as electrostatic spinning, so that the piezoelectric nanofiber is favored by virtue of simple equipment, convenient operation and low cost, and can continuously prepare the superfine fiber with the diameter of tens of nanometers to several micrometers, and the beta-phase crystallization content in PVDF can be effectively promoted through the polarization of an electrostatic field, so that the piezoelectric performance is improved. No additional high voltage polarization and mechanical stretching is required, which is an economically viable and relatively simple method.
The electrostatic spinning process and the spinning condition are optimized, and the composite nanofiber with better piezoelectric performance can be prepared by adding the functional nanomaterial into the spinning solution. By addition of nanofillers, the negative surface charge fillers can be combined with the-CH of PVDF 2 The positive surface charge filler can interact with the-CF of PVDF 2 The interaction of the groups enhances the interface coupling effect, thereby being beneficial to inducing the generation of polar beta phase and improving the piezoelectric performance. In addition, the use of filler particles (e.g. BaTiO 3 ZnO) itself can also enhance the piezoelectric response of the composite. Common nano-filler materials are graphene, carbon nanotubes, baTiO 3 ZnO and MnO 2 Etc.
CN101314869a (a device for preparing polymer nanofibers and a spinning method) prepares polymer nanofibers such as polyvinylidene fluoride (PVDF) by utilizing the drafting action of electrostatic field force. The high polymer solution prepared by the high polymer material is contained in a spinneret tube, and the high polymer solution is heated to a preset temperature through a temperature feedback controller; and loading voltage to make the polymer nano fiber flow out from the nozzle under the action of electric field force, and collecting the polymer nano fiber on the receiving plate. Similarly, CN105037761a (a preparation method of polyvinylidene fluoride nano film with beta crystalline phase) prepares a PVDF nano film with enhanced beta crystalline phase by doping graphene oxide GO, and firstly, dissolves graphene oxide and polyvinylidene fluoride in an organic solvent, and then, obtains a film-making solution with uniform dispersion by ultrasonic and magnetic stirring; standing and defoaming the film-forming solution; preparing a wet film by adopting a spin coating method; finally, the film is dried and crystallized by heat treatment in the atmospheric environment, and the polyvinylidene fluoride nano film with beta crystalline phase is prepared. On one hand, the content of beta crystalline phase in PVDF is improved by doping GO, and on the other hand, a spin coating process is adopted to prepare the PVDF nano film; the preparation process is simple and the cost is low.
It is worth noting that although the piezoelectric performance of PVDF can be improved by electric field polarization of electrostatic field force or by filler doping, in order to ensure good compatibility between nanoparticles and PVDF, a complex and elaborate particle surface modification process is generally required, which is not beneficial to realizing large-scale industrial production of composite materials. In addition, the introduction of conductive particles such as carbon nanotubes and graphene can also greatly reduce the electric field breakdown strength of the composite material, so that the polarized electric field of the composite material is smaller, and sufficient polarization cannot be obtained, thereby limiting the improvement range of the piezoelectric performance. And electrodes commonly used in piezoelectric transduction and sensing devices are metal or carbon materials with two-dimensional structures and can only contact with fibers on the surface of the piezoelectric nanofiber web. Thus, when the nanofiber web generates piezoelectric charges, only charges generated by nanofibers on the surface of the web can be transferred to the electrode to output a piezoelectric signal. At the same time, the majority of the internal fibers comprising the nanofiber web are also capable of simultaneously generating piezoelectric charges, but these charges cannot migrate effectively without contacting the electrodes, thereby greatly limiting the output of the piezoelectric signal. Therefore, another method is needed to construct a three-dimensional electrode structure capable of contacting the surface layer of the omentum to press the piezoelectric nanofibers, and more effectively realize charge migration after the piezoelectric charge is generated, thereby improving the energy conversion efficiency.
Disclosure of Invention
In order to solve the technical problems, the invention provides a flexible piezoelectric nanofiber web, which comprises a conductive film layer, a composite nanofiber web layer and a spinning polymer nanofiber web layer; the composite nanofiber web layer is arranged between the spinning polymer nanofiber web layer and the conductive film layer to form a laminated structure, as shown in fig. 4;
the composite nanofiber net film layer comprises a spinning polymer and a conductive substance, and is obtained by simultaneously carrying out electrostatic spinning of the spinning polymer and electrostatic spraying of the conductive substance;
the conductive substance and the conductive film layer are made of Ti 3 C 2 One or more of graphene oxide, silver, and carbon nanotubes.
Preferably, the spinning polymer is polyvinylidene fluoride, poly (vinylidene fluoride-trifluoroethylene) copolymer, polyvinyl fluoride, polyvinyl chloride, poly-gamma-methyl-L-glutamate or nylon-11.
Preferably, a composite laminate structure is shown in FIG. 5; the composite nanofiber net film layer consists of a composite film I and a composite film II, and the conductive film layer consists of a conductive film I and a conductive film II; the composite film I is arranged between the conductive film I and the spinning polymer nanofiber net film layer, the composite film II is arranged between the conductive film II and the spinning polymer nanofiber net film layer, and the spinning polymer nanofiber net film layer is arranged between the composite film I and the composite film II.
Preferably, the thickness ratio of the conductive film layer, the composite nanofiber web layer and the spun polymer nanofiber web layer is as follows: 0.01-0.1:0.2-3:1.
the invention also provides a preparation method of the flexible piezoelectric nanofiber web, which comprises the following steps:
s1: preparing conductive substance dispersion liquid and spinning polymer electrospinning liquid respectively;
s2: carrying out electrostatic spinning on the spinning polymer electrospinning liquid to obtain a spinning polymer nanofiber web membrane layer;
s3: simultaneously carrying out electrostatic spinning and electrostatic spraying on the surface of the spinning polymer nanofiber net film layer to obtain a perfectly coated continuous conductive layer on the nanofiber surface; the raw material of electrostatic spinning is spinning polymer electrospinning liquid, and the raw material of electrostatic spraying is conductive substance dispersion liquid;
s4: and continuing to electrostatically spray the conductive substance dispersion liquid on the surface of the multilayer film structure to obtain the flexible piezoelectric nanofiber web.
Preferably, the dispersion medium in the conductive substance dispersion liquid is one or more of ethanol, acetone, tetrahydrofuran, methanol and trichloroethylene.
Preferably, the conductive material dispersion is prepared by adding a conductive material to a corresponding solvent and performing ultrasonic treatment until the conductive material is uniformly dispersed.
Preferably, the solvent of the spinning polymer electrospinning liquid is one or more of dimethylformamide, water, tetrahydrofuran, ethanol and acetone.
Preferably, in the step S3, the conditions of electrospinning are as follows: the voltage is 8-18kV, and the injection speed is 1-2mL/h.
Preferably, in the step S3, the electrostatic spraying conditions are as follows: the voltage is 12-25kV, and the injection speed is 10-50mL/h.
Specifically, in the step S3, the electrostatic spinning is that the electrostatic spinning solution is sucked into an injector and put into a micro injection pump for electrostatic spinning, a needle point of a solution supply device is connected with a direct-current high-voltage positive electrode, and a receiving device connected with a direct-current high-voltage negative electrode is placed at a position 10 cm to 20cm away from the vertical direction of the needle point; under high voltage electric field, the electrospun liquid drops overcome the surface tension to form jet trickles, further forming fiber membranes, and collecting the fiber membranes to a receiving roller, wherein the rotating speed of the receiving roller is 400-1000r/min.
Specifically, in the step S3, the electrostatic spraying is to suck the conductive material dispersion liquid at the other end into a syringe, put the syringe into a micro injection pump, spray the conductive material dispersion liquid, and connect the needle point of the liquid supply device with the direct current high voltage positive electrode, wherein the spraying direction of the needle point is 5-8cm away from the roller receiving device, and the concentration of the conductive material dispersion liquid is 5-20mg/mL.
The invention also provides a piezoelectric transducer which comprises the flexible piezoelectric nanofiber web.
Preferably, the device also comprises a bottom copper foil electrode and a top copper foil electrode; the bottom copper foil electrode and the top copper foil electrode are respectively arranged on two sides of the flexible piezoelectric nanofiber net film.
At present, most of electrodes are two-dimensional electrodes, and conductive electrodes are directly attached on the basis of original piezoelectric materials, and the extraction of conductive charges is limited by the surfaces of the piezoelectric materials. Therefore, the conductive nano material is coated on the periphery of the PVDF nanofiber by using an electrostatic spraying method on the surface of the PVDF nanofiber, and the charges generated in the PVDF piezoelectric material are conducted out by using the high conductivity of the conductive nano material, so that the output voltage is increased under the condition of unchanged pressure and stress area, and the piezoelectric performance is improved.
Compared with the prior art, the technical scheme of the invention has the following advantages:
(1) The MXene nano-sheets are synchronously and controllably tightly coated on the surfaces of the nano-fibers through a synchronous electrostatic spinning/electrostatic spraying process, and a three-dimensional electrode structure is constructed on the piezoelectric nano-fiber net film;
(2) The piezoelectric nanofiber structure has the advantages that the energy conversion efficiency of the piezoelectric nanofiber is improved from different angles of the electrode, the effective contact between the piezoelectric nanofiber and the electrode of the transducer is optimized by utilizing the three-dimensional electrode structure constructed on the nanofiber net film, and the mobility of piezoelectric static charges and the output of piezoelectric signals are improved.
Drawings
FIG. 1 is an SEM image of (a) PVDF/MXene composite nanofibers and (b) PVDF nanofibers.
Fig. 2 is a cross-sectional SEM picture of a three-dimensional electrode structure.
Fig. 3 is a diagram of a three-dimensional flexible electrode electrospinning apparatus.
Fig. 4 is a schematic structural diagram of a single-sided three-dimensional electrode piezoelectric nanofiber transducer.
Fig. 5 is a schematic structural diagram of a two-sided three-dimensional electrode piezoelectric nanofiber transducer.
FIG. 6 is a piezoelectric output result of a single-sided three-dimensional electrode PVDF/MXene composite nanofiber web nanofiber piezoelectric transducer.
Fig. 7 shows the piezoelectric output result of a pure PVDF fiber piezoelectric transducer.
FIG. 8 shows the piezoelectric output result of a single-sided three-dimensional electrode PVDF/CNT composite nanofiber web nanofiber piezoelectric transducer.
FIG. 9 shows the piezoelectric output result of a single-sided three-dimensional electrode PVDF/GO composite nanofiber web nanofiber piezoelectric transducer.
FIG. 10 is a two-sided three-dimensional electrode PVDF/MXene composite nanofiber web nanofiber piezoelectric transducer.
Reference numerals illustrate: the electrode comprises a 1-top copper foil electrode, a 2-conductive film layer, a 3-composite nanofiber net film layer, a 4-spinning polymer nanofiber net film layer and a 5-bottom copper foil electrode.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
The invention provides a piezoelectric transducer of PVDF/MXene composite flexible piezoelectric nanofiber web, as shown in figure 4, comprising a top copper foil electrode 1, a bottom copper foil electrode 5, a conductive film layer 2, a composite nanofiber web layer 3 and a spinning polymer nanofiber web layer 4 for better connection with test equipment, wherein a three-dimensional electrode structure exists in the composite nanofiber web layer 3 so as to improve electrode contact effect; finally, the device can be fixed and packaged on two sides by utilizing PET films and the like.
The invention also provides a piezoelectric transducer of the PVDF/MXene composite flexible piezoelectric nanofiber web, as shown in figure 5, which comprises a top copper foil electrode 1 and a bottom copper foil electrode 5, wherein the two sides of the spinning polymer nanofiber web layer 4 are respectively provided with a composite nanofiber web layer 3; and the outer side of the composite nanofiber net film layer 3 is also provided with a conductive film layer 2.
Example 1
1. Preparation of MXene (Ti) 3 C 2 ) And adding the MAX precursor and lithium fluoride into 9mol of hydrochloric acid in the dispersion liquid, wherein the ratio of the MAX precursor to the lithium fluoride is 1:1.6. Placed in a polytetrafluoroethylene beaker and magnetically stirred at 40 ℃ for heating reaction for 24-18h. Washing with deionized water to neutrality, manually oscillating, dispersing, centrifuging to obtain MXene, and adding ethanol as solvent to obtain Ti 3 C 2 And (3) electrostatic spraying of the dispersion liquid.
2.4 mL of DMF and 6mL of acetone are taken and added into a beaker to be uniformly mixed, 2.2g of PVDF is added into the solution, the solution is magnetically stirred for 3 hours, the rotating speed is 800rpm, the temperature is 60 ℃, and the PVDF electrostatic spinning solution is prepared.
3. Spraying PVDF electrostatic spinning solution on an electrostatic spinning machine roller aluminum foil collecting device. The rotating speed is 400r/min, the distance between the needle head and the collecting device is about 15cm, the high-voltage power supply is 8.5kV, the spraying liquid amount is 2mL, and the pushing speed of the injection pump is 1mL/h.
4. After 2 hours, continuing spraying PVDF electrostatic spinning solution, and introducing Ti at the other side of the collecting roller 3 C 2 Carrying out electrostatic spraying on the dispersion liquid to form PVDF/Ti 3 C 2 The composite nanofiber net film layer has a needle tip which is about 6cm away from the collecting device, a high-voltage power supply is 18kV, the spraying liquid amount is 30mL, and the pushing speed of an injection pump is 30mL/h.
5. After the spraying of the composite nanofiber net film layer is finished, temporarily closing the electrostatic spinning of the PVDF end, and continuously spraying Ti 3 C 2 The dispersion was sprayed for 10 minutes at a high voltage power supply of 18kV to form an MXene film.
6. To treat Ti 3 C 2 After the coating is finished, closing Ti 3 C 2 And (5) end electrostatic spraying, and closing the electrostatic spinning device.
7. Cutting the piezoelectric fiber membrane to 3 x 3cm 2 Copper sheets are used as electrodes on two sides of the piezoelectric transducer, a lead is used for connecting, then the piezoelectric transducer is packaged by a PET film, the thickness of the PET film is 38 mu m, and finally the single-sided three-dimensional electrode PVDF/MXene composite nanofiber mesh film nanofiber piezoelectric transducer is obtained, the piezoelectric output result is shown in figure 6, the open circuit voltage reaches 2.43V, and the short circuit current reaches 0.29 mu A. The open circuit voltage of pure PVDF in FIG. 7 was 1.61V and the short circuit current was 0.18. Mu.A, measured under the same conditions.
Example 2
1. Preparing a CNT dispersion liquid, firstly adding a multiwall carbon nanotube into 1mol of HCl to remove impurities for 24 hours at a temperature of 60 ℃, then oxidizing the mixture with a mixed solution of nitric acid (69%) +concentrated sulfuric acid (90%) with a volume ratio of 1:3 at the temperature of 60 ℃ for 3 hours, and then washing, filtering and drying the mixture with a large amount of deionized water to obtain the pickled CNT powder. Adding 100mg of the pickled CNT into 50mL of ethanol solution, preparing a CNT dispersion liquid with the concentration of 2mg/mL, magnetically stirring for 10min, and then putting into an ultrasonic cleaner for ultrasonic treatment for 40min.
2.4 mL of DMF and 6mL of acetone are taken and added into a beaker to be uniformly mixed, 2.2g of PVDF is added into the solution, the solution is magnetically stirred for 3 hours, the rotating speed is 800rpm, the temperature is 60 ℃, and the PVDF electrostatic spinning solution is prepared.
3. Spraying PVDF electrostatic spinning solution on an electrostatic spinning machine roller aluminum foil collecting device. The rotating speed is 400r/min, the distance between the needle head and the collecting device is about 15cm, the high-voltage power supply is 8.5kV, the spraying liquid amount is 2mL, and the pushing speed of the injection pump is 1mL/h.
4. After 2 hours, continuing spraying PVDF electrostatic spinning solution, introducing CNT dispersion liquid to the other side of the collecting roller for electrostatic spraying to form a PVDF/CNT composite nanofiber net film layer, wherein the needle point is about 6cm away from the collecting device, the high-voltage power supply is 20kV, the spraying liquid amount is 40mL, and the pushing speed of the injection pump is 40mL/h.
5. After the spraying of the composite nanofiber net film layer is finished, temporarily closing the electrostatic spinning of the PVDF end, continuously spraying the CNT dispersion liquid, and spraying for 15min by using a high-voltage power supply of 18kV to form a pure CNT film layer.
6. And after the CNT layer is sprayed, closing the electrostatic spraying of the CNT end, and closing the electrostatic spinning device.
7. Cutting the piezoelectric fiber membrane to 3 x 3cm 2 Copper sheets are used as electrodes on two sides, a lead is used for being connected, then a PET film is used for packaging, the thickness of the PET film is 38 mu m, and finally the single-sided three-dimensional electrode PVDF/CNT composite nano fiber net film nanofiber piezoelectric transducer is obtained. As shown in FIG. 8, the piezoelectric output results in an open circuit voltage of 2.37V and a short circuit current of 0.42. Mu.A.
Example 3
1. Preparation of Graphene Oxide (GO) dispersion, 50mg of GO powder was first added to 10mL of an aqueous solution, and after 10min of probe ultrasound was performed using a cell pulverizer, 40mL of an ethanol solution was added to prepare 1mg/mL of graphene oxide dispersion.
2. Adding 4m DMF and 6mL acetone into a beaker, uniformly mixing, adding 2.2g PVDF into the solution, magnetically stirring for 3 hours, and obtaining PVDF electrostatic spinning solution at the rotating speed of 800rpm and the temperature of 60 ℃.
3. Spraying PVDF electrostatic spinning solution on an electrostatic spinning machine roller aluminum foil collecting device. The rotating speed is 400r/min, the distance between the needle head and the collecting device is about 15cm, the high-voltage power supply is 8.5kV, the spraying liquid amount is 2mL, and the pushing speed of the injection pump is 1mL/h.
4. After 2 hours, continuing spraying PVDF electrostatic spinning solution, introducing GO dispersion liquid to the other side of the collecting roller for electrostatic spraying to form a PVDF/GO composite nanofiber net film layer, wherein the needle tip is about 6cm away from the collecting device, the high-voltage power supply is 20kV, the spraying liquid amount is 40mL, and the pushing speed of the injection pump is 40mL/h.
5. After the spraying of the composite nanofiber net film layer is finished, temporarily closing the electrostatic spinning of the PVDF end, continuously spraying the GO dispersion liquid, and spraying for 15min by using a high-voltage power supply of 18kV to form the GO film layer.
6. And after the GO layer is sprayed, closing the GO end electrostatic spraying, and closing the electrostatic spinning device.
7. Cutting the piezoelectric fiber membrane to 3 x 3cm 2 Copper sheets are used as electrodes on two sides, the electrodes are packaged by PET films after being connected by leads, the PET film thickness is 38 mu m, and finally the single-sided three-dimensional electrode PVDF/GO composite nanofiber mesh film nanofiber piezoelectric transducer is obtained. As shown in FIG. 9, the piezoelectric output results in an open circuit voltage of 2.01V and a short circuit current of 0.27. Mu.A.
Example 4
1. Preparation of MXene (Ti) 3 C 2 ) And adding the MAX precursor and lithium fluoride into 9mol of hydrochloric acid in the dispersion liquid, wherein the ratio of the MAX precursor to the lithium fluoride is 1:1.6. Placed in a polytetrafluoroethylene beaker and magnetically stirred at 40 ℃ for heating reaction for 24-18h. Washing with deionized water to neutrality, manually oscillating, dispersing, centrifuging to obtain MXene, and adding ethanol as solvent to obtain Ti 3 C 2 And (3) electrostatic spraying of the dispersion liquid.
2.4 mL of DMF and 6mL of acetone are taken and added into a beaker to be uniformly mixed, 2.2g of PVDF is added into the solution, the solution is magnetically stirred for 3 hours, the rotating speed is 800rpm, the temperature is 60 ℃, and the PVDF electrostatic spinning solution is prepared.
3. Ti is firstly carried out on a roller aluminum foil collecting device of an electrostatic spinning machine 3 C 2 Dispersion liquidAnd (3) electrostatic spraying, wherein the high-voltage power supply is 18kV, and spraying is carried out for 10min to form the MXene film.
4. Then simultaneously opening an electrostatic spinning and electrostatic spraying device to prepare PVDF/Ti 3 C 2 The composite nanofiber net film layer has a needle tip which is about 6cm away from the collecting device, a high-voltage power supply is 18kV, the spraying liquid amount is 30mL, and the pushing speed of an injection pump is 30mL/h. The distance between the needle and the collecting device is about 15cm, the high-voltage power supply is 8.5kV, the spraying liquid amount is 1mL, and the pushing speed of the injection pump is 1mL/h.
5. After 1h, turn off Ti 3 C 2 And (3) end electrostatic spraying, namely continuing PVDF electrostatic spinning, wherein the rotating speed is 400r/min, the distance between the needle head and the collecting device is about 15cm, the high-voltage power supply is 8.5kV, the spraying liquid amount is 2mL, and the pushing speed of the injection pump is 1mL/h.
6. After 2h, continue to open Ti 3 C 2 End electrostatic spraying to prepare PVDF/Ti on the other side 3 C 2 The composite nanofiber net film layer has a needle tip which is about 6cm away from the collecting device, a high-voltage power supply is 18kV, the spraying liquid amount is 30mL, and the pushing speed of an injection pump is 30mL/h.
5. After the spraying of the composite nanofiber net film layer is finished, temporarily closing the electrostatic spinning of the PVDF end, and continuously spraying Ti 3 C 2 The dispersion was sprayed for 10 minutes at a high voltage power supply of 18kV to form an MXene film.
6. To treat Ti 3 C 2 After the coating is finished, closing Ti 3 C 2 And (5) end electrostatic spraying, and closing the electrostatic spinning device.
7. Cutting the piezoelectric fiber membrane to 3 x 3cm 2 Copper sheets are used as electrodes on two sides, a lead is used for being connected, then a PET film is used for packaging, the thickness of the PET film is 38 mu m, and finally the nano fiber piezoelectric transducer with the double-sided three-dimensional electrode PVDF/MXene composite nano fiber net film layer is obtained. The piezoelectric output results are shown in fig. 10, and the open circuit voltage and the short circuit current are measured to be 4.28V and 0.47 μa, respectively.
Effect evaluation 1
According to the invention, the three-dimensional conductive electrode is constructed by pasting the conductive nano material on the surface of the PVDF nano fiber, so that charges generated by deformation of the flexible piezoelectric material due to mechanical external force are collected, and charge transfer is realized more effectively, so that the energy conversion efficiency and the piezoelectric performance are improved under the condition of the same thickness. The single-sided three-dimensional electrode PVDF/MXene composite nanofiber web layer nanofiber web is prepared by spraying a conductive nanomaterial MXene on the surface of PVDF nanofiber, the measured output voltage is 1.61V, the output current is 0.29 mu A, the output voltage is 50.9% higher than that of pure PVDF under the same conditions, and the output current is 61.1% higher than that of pure PVDF under the same conditions. And designing and preparing a nano fiber net film of a double-sided three-dimensional electrode PVDF/MXene composite nano fiber net film layer, and measuring the open circuit voltage and the short circuit current of the nano fiber net film to be 4.28V and 0.47 mu A respectively.
Effect evaluation 2
The method comprises the steps of taking conductive nano materials (MXene) and PVDF as raw materials, adopting a synchronous electrostatic spinning/electrostatic spraying device (figure 3), carrying out PVDF electrostatic spinning at one end of the synchronous device, and carrying out MXene two-dimensional nano sheet electrostatic spraying at the other end of the synchronous device so as to realize uniform coating of the MXene nano sheet on the surface of a single nanofiber, and forming a conductive path to obtain the electrode (figure 1) with a three-dimensional structure. The optimal parameters can be found by controlling the size, concentration and distribution of the MXene sheets, and the transducer can respond to the change of different pressures and display different electric signals at different pressures and frequencies. FIG. 1 is an SEM image of PVDF electrospun nanofibers without the MXene highly conductive nanoplatelets coated thereon.
In order to better observe the three-dimensional electrode structure constructed by the two-dimensional MXene nano-sheets, the three-dimensional electrode structure is formed by the two-dimensional MXene nano-sheets in the N 2 And (3) removing PVDF nanofibers by high-temperature treatment in the atmosphere tube furnace to obtain a pure MXene three-dimensional structure which is independent of sheets. As shown in the SEM pictures of the cross-section of the three-dimensional electrode in fig. 2, it can be seen that the three-dimensional electrode structure has a large number of round hole structures, and the MXene coated nanofibers are formed after being removed by high temperature treatment. The MXene nano-sheets in the three-dimensional structure are mutually communicated to construct a novel porous electrode.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (9)
1. The flexible piezoelectric nanofiber web is characterized by comprising a conductive film layer (2), a composite nanofiber web layer (3) and a spinning polymer nanofiber web layer (4); the composite nanofiber web layer (3) is arranged between the spinning polymer nanofiber web layer (4) and the conductive film layer (2);
the composite nanofiber web membrane layer (3) comprises a spinning polymer and a conductive substance, and is obtained by simultaneously carrying out electrostatic spinning of the spinning polymer and electrostatic spraying of the conductive substance; the composite nanofiber net film layer (3) is of a three-dimensional electrode structure;
the conductive substance and the conductive film layer (2) are made of Ti 3 C 2 The method comprises the steps of carrying out a first treatment on the surface of the The composite nanofiber web membrane layers (3) are symmetrically arranged on two sides of the spinning polymer nanofiber web membrane layer (4); the conductive film layers (2) are symmetrically arranged on two sides of the integral structure of the composite nanofiber net film layer (3), the spinning polymer nanofiber net film layer (4) and the composite nanofiber net film layer (3).
2. The flexible piezoelectric nanofiber web according to claim 1, wherein the thickness ratio of the conductive film layer (2), the composite nanofiber web layer (3) and the spun polymer nanofiber web layer (4) is: 0.01-0.1:0.2-3:1.
3. a method of making a flexible piezoelectric nanofiber web as recited in claim 1, comprising the steps of:
s1: preparing conductive substance dispersion liquid and spinning polymer electrospinning liquid respectively;
s2: carrying out electrostatic spinning on the spinning polymer electrospinning liquid to obtain a spinning polymer nanofiber web membrane layer;
s3: simultaneously carrying out electrostatic spinning and electrostatic spraying on the surface of the spinning polymer nanofiber web layer to obtain a composite nanofiber web layer (3); the raw material of electrostatic spinning is spinning polymer electrospinning liquid, and the raw material of electrostatic spraying is conductive substance dispersion liquid;
s4: and continuously carrying out electrostatic spraying on the conductive substance dispersion liquid on the surface of the composite nanofiber web layer (3) to obtain the flexible piezoelectric nanofiber web.
4. The method according to claim 3, wherein the dispersion medium in the conductive substance dispersion liquid is one or more of ethanol, acetone, tetrahydrofuran, methanol and trichloroethylene.
5. The method of claim 3, wherein the solvent of the spinning polymer electrospinning liquid is one or more of dimethylformamide, water, tetrahydrofuran, ethanol and acetone.
6. The method according to claim 3, wherein in the step S3, the conditions for electrospinning are as follows: voltage 8-18kV, injection speed 1-2mL/h.
7. The method according to claim 3, wherein in the step S3, the electrostatic spraying conditions are as follows: voltage 12-25kV, injection speed 10-50mL/h.
8. A piezoelectric transducer comprising the flexible piezoelectric nanofiber web of claim 1 or 2.
9. The piezoelectric transducer of claim 8, further comprising a bottom copper foil electrode and a top copper foil electrode; the bottom copper foil electrode and the top copper foil electrode are respectively arranged on two sides of the flexible piezoelectric nanofiber net film.
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