CN112251914B

CN112251914B - High-temperature-resistant composite nanofiber membrane for preparing piezoelectric material and preparation method thereof

Info

Publication number: CN112251914B
Application number: CN202011165254.0A
Authority: CN
Inventors: 刘忠柱; 陈嘉亮; 潘玮; 秦琦; 宋梦; 米立伟
Original assignee: Zhongyuan University of Technology
Current assignee: Zhongyuan University of Technology
Priority date: 2020-10-27
Filing date: 2020-10-27
Publication date: 2022-02-08
Anticipated expiration: 2040-10-27
Also published as: CN112251914A

Abstract

The invention belongs to the technical field of functional composite materials, relates to a composite nanofiber membrane, and particularly relates to a preparation method of a high-temperature-resistant composite nanofiber membrane for preparing a piezoelectric material. Adding graphene into a solvent, then adding a magneton, sealing, and performing ultrasonic treatment for 1h to obtain a graphene solution; adding PAN into the graphene solution, magnetically stirring at constant temperature until the PAN is completely dissolved, and then stirring at normal temperature until uniform spinning solution is formed; and (3) absorbing the spinning solution into an injector after vacuum defoaming, and performing electrostatic spinning to prepare the PVDF/graphene composite nanofiber membrane. The thermal property and the mechanical property of the PAN are improved by adding the graphene, so that the PAN/graphene composite nanofiber membrane has higher thermal stability and mechanical property. The PAN/graphene composite nanofiber membrane is subjected to piezoelectric performance test, and is found to have higher output voltage and output current.

Description

High-temperature-resistant composite nanofiber membrane for preparing piezoelectric material and preparation method thereof

Technical Field

The invention belongs to the technical field of functional composite materials, relates to a composite nanofiber membrane, and particularly relates to a high-temperature-resistant composite nanofiber membrane with good piezoelectric property and a preparation method thereof.

Background

With the rapid and continuous development of global economy and the continuous increase of world population, the energy crisis problem is intensified more and more. The environmental pollution problem caused by large-scale consumption of fossil energy such as petroleum, coal, natural gas and the like also causes great troubles to the health and life of people. Therefore, how to alleviate the energy crisis and not pollute the environment has become the core problem that needs to be solved for human sustainable development. From the long-term development, the gradual replacement of traditional energy sources by new green renewable energy sources is the most fundamental solution. The novel renewable energy mainly refers to mechanical energy, solar energy, hydroenergy, wind energy and the like. In the aspect of mechanical energy collection, the piezoelectric effect has extremely important and wide application value, such as a piezoelectric nano generator.

The piezoelectric material is a high-technology material with functional characteristics, can realize energy conversion of electric energy and mechanical energy, and is widely applied to the fields of biology, photoelectric information and renewable energy sources. Piezoelectric materials are mainly classified into the following: piezoelectric crystals (e.g., quartz), piezoelectric ceramics (e.g., barium titanate), piezoelectric polymers (e.g., polyvinylidene fluoride), and piezoelectric composites (e.g., flexible composites of polyvinylidene fluoride and barium titanate).

Conventional piezoelectric ceramics have high piezoelectric performance, but their inherent brittleness, hardness and poor flexibility limit their applications, which is also a major obstacle for their applications in flexible/wearable electronics. Among piezoelectric polymers, polyvinylidene fluoride (PVDF) is one of the most important commercial piezoelectric materials, and its good piezoelectric properties are derived from its trans-planar zigzag β -form. However, PVDF has a low softening temperature and high dielectric loss, and is expensive and not readily available. While PAN, one of the three synthetic fiber raw materials, is cheap and easy to obtain, has better environmental resistance and heat resistance, and the like, most importantly, PAN has a dipole moment larger than that of PVDF due to the existence of cyano group with a larger dipole moment, which directly affects the piezoelectric performance of the polymer material. The larger the dipole moment, the better the piezoelectric performance. Meanwhile, compared with the piezoelectric polymer PVDF which cannot be polymerized to form a copolymer, PAN is expected to replace PVDF to be used in the piezoelectric field.

Polyacrylonitrile (PAN) is obtained from acrylonitrile monomers by free radical polymerization. PAN has higher melting point, solvent resistance, weather resistance, aging resistance and insulativity and is often used for wastewater treatment; meanwhile, PAN also has the advantages of pollution resistance, easiness in cleaning and unique hydrophilic-hydrophobic property, and is very suitable for a separation material of dye wastewater. However, compared to conventional nanofiber membranes, PAN fibers are bulky, non-abrasion resistant, and have lower strength, thereby limiting their use as membrane materials. Based on this, it is necessary to modify it to improve its strength.

Wangbao, etc. [ Wangbao, Zhengying, Lifengmei, a reduced graphene oxide/polyacrylonitrile composite fiber and a preparation method thereof, the patent numbers are: CN 107956110A adopts self-assembly technology to prepare the reduced graphene oxide/polyacrylonitrile composite fiber. Compared with the traditional graphene/polyacrylonitrile composite material preparation technology, the composite nanofiber membrane prepared by the electrostatic spinning method has the advantages of simple process, easiness in operation and the like. And the fiber membrane of the composite nanofiber membrane prepared by the electrostatic spinning method is superior to other preparation methods in the aspects of pore diameter, fiber uniformity, stability and the like. Meanwhile, the composite nanofiber membrane also presents larger specific surface area and void ratio. Although there are research groups that have separately prepared polyacrylonitrile/graphene composite nano-yarn by wet-multi-needle electrostatic spinning technology and electrostatic spinning technology [ patent no: CN 105862142 a ] and oriented porous graphene/polyacrylonitrile composite nanofibers [ patent No.: CN 109468686 a ], but because the final product is a fiber yarn, it cannot be used to prepare bulk materials of large surface area. Meanwhile, the research group discusses the mechanical property and the conductivity of the polyacrylonitrile/graphene composite nano yarn, and does not deeply research the piezoelectric property of the polyacrylonitrile/graphene composite nano yarn as a piezoelectric sensor.

Disclosure of Invention

In order to solve the technical problems, the invention provides a high-temperature-resistant composite nanofiber membrane with good piezoelectric performance and a preparation method thereof.

The technical scheme of the invention is realized as follows:

the preparation method of the high-temperature-resistant composite nanofiber membrane with good piezoelectric performance comprises the following steps:

(1) adding graphene into a solvent, then adding a magneton, sealing, and performing ultrasonic treatment for 1h to obtain a graphene solution;

(2) adding PAN into the graphene solution obtained in the step (1), magnetically stirring at a constant temperature until the PAN is completely dissolved, and then stirring at a normal temperature until a uniform spinning solution is formed;

(3) and (3) absorbing the spinning solution obtained in the step (2) into an injector after vacuum defoaming, and performing electrostatic spinning to prepare the PVDF/graphene composite nanofiber membrane.

The solvent in the step (1) is a mixed solvent of DNF and acetone, wherein the volume ratio of DMF to acetone is (6-10): 2.

The mass concentration of the graphene solution in the step (1) is 1-5 wt%.

The mass fraction of PAN in the spinning solution in the step (2) is 10-12w t%.

The temperature of the constant-temperature magnetic stirring in the step (2) is 60-80 ℃.

The parameters of electrostatic spinning in the step (3) are as follows: spinning voltage is 16-18 kV, receiving distance is 15-20 cm, injection speed is 0.6-1.2 mL/h and spinning time is 5-6 h.

The thickness of the high-temperature resistant composite nanofiber membrane prepared by the method is 100-120 mu m, the output voltage is about 5-6V, and the current is 0.150-0.175 mu A.

The invention has the following beneficial effects:

the invention has the beneficial effects that:

1. the preparation process is simple, the equipment requirement is low, the operation is easy, the prepared PAN/graphene composite nano electrospun membrane has uniform appearance, and more than 80% of fiber diameter is concentrated between 300 and 500 nm. Meanwhile, the raw materials are light and high polymer materials with good flexibility, so that the composite fiber membrane also has good flexibility and can be cut into films with different sizes or complex shapes according to requirements.

2. The thermal property and the mechanical property of the PAN are improved by adding the graphene, so that the PAN/graphene composite nanofiber membrane has higher thermal stability and mechanical property.

3. The PAN/graphene composite nanofiber membrane has good piezoelectric performance, and the output voltage and the output current of the PAN/graphene composite nanofiber membrane are respectively as high as about 6V and 1.5 muA, so that the PAN/graphene composite nanofiber membrane is expected to be applied to the fields of personal health monitoring, disease treatment and prevention, electronics, measurement, military, traffic and the like as a sensor and an energy capturer.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is an SEM topography and fiber diameter distribution of the PAN nanofiber membrane prepared in example 1.

Fig. 2 shows mechanical property results obtained by performing mechanical property experiments on the PAN/graphene composite fiber membrane prepared in example 1.

Fig. 3 is a TGA plot of PAN/graphene composite nanofiber membranes of varying graphene content and pure PAN-based nanofiber membranes prepared in example 1.

Fig. 4 is a graph showing the results of the piezoelectric performance test performed on the PAN/graphene composite fiber membrane prepared according to the example, wherein (a) the output voltage and (b) the output current of the PAN fiber membrane are shown; and (c) output voltage and (d) output current of the PAN/graphene composite nanofiber membrane.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

The preparation method of the high-temperature-resistant composite nanofiber membrane with good piezoelectric performance in the embodiment comprises the following steps:

(1) preparing a PAN/graphene spinning solution: 0.03 g of graphene is respectively weighed by an electronic analytical balance, added into a mixed solvent of 8mL of N-N Dimethylformamide (DMF) and 2mL of acetone, put a magneton into the solution and sealed by a preservative film, and subjected to ultrasound for a certain time in an ultrasonic cleaner. Then, 1 g of PAN was added to the above solution and it was placed in 80 g^oStirring the mixture on a constant-temperature magnetic stirrer for 90 min to completely dissolve the PAN. And then, transferring the solution to a normal-temperature six-linkage magnetic stirrer, and stirring for 12 hours at normal temperature to prepare a uniform spinning solution with 10% of PAN (Polyacrylonitrile) and 3% of graphene. And finally, standing the uniform spinning solution in a vacuum environment for a period of time to remove air bubbles in the spinning solution.

(2) Preparing a PAN/graphene nanofiber membrane: and (2) sucking the spinning solution subjected to standing and defoaming in the step (1) into a syringe, removing air bubbles in the spinning solution, and fixing the spinning solution on a syringe pump to perform electrostatic spinning. The spinning process conditions are as follows: the spinning voltage is 18 kV, the spinning receiving distance is 20 cm, the spinning speed is 1 mL/h, and the spinning time is 6 h. And after spinning is finished, collecting the PAN/graphene composite nanofiber membrane, and drying the PAN/graphene composite nanofiber membrane in a vacuum drying oven for 4 hours to completely volatilize the solvent, and storing for later use.

(3) Preparing a PAN spinning solution and preparing a PAN nanofiber membrane: weighing 1 g of PAN with an electronic analytical balance, adding the PAN into a mixed solvent of 8mL of DMF and 2mL of acetone, adding a magneton into the solution, sealing the solution with a preservative film, and placing the solution at 80 DEG C^oStirring the mixture on a constant-temperature magnetic stirrer for 90 min to completely dissolve the PAN. And then, transferring the solution to a normal-temperature six-linkage magnetic stirrer, and stirring for 12 hours at normal temperature to prepare a uniform spinning solution with 10% PAN concentration. And finally, standing the uniform spinning solution in a vacuum environment for a period of time to remove air bubbles in the spinning solution. And sucking the spinning solution subjected to standing and defoaming into an injector, removing bubbles in the spinning solution, and fixing the spinning solution on an injection pump for electrostatic spinning. The spinning process conditions are the same as the steps（2）。

The SEM morphology and fiber diameter distribution of the PAN and PAN/graphene composite nanofiber membranes prepared in this example are shown in fig. 1. As can be seen in fig. 1a, the electrospun PAN fiber membrane has a uniform fiber morphology with few beaded structures. In addition, the fiber diameter distribution is relatively uniform (about 600-800 nm), while the diameter distribution of about 56% of the fibers is between 800-1000 nm, and the number of bent fibers is very small as can be seen from the SEM image. As can be seen from FIG. 1b, some fibers in the PAN/graphene composite nanofiber membrane are slightly bent, and meanwhile, compared with the PAN fiber membrane, the diameter of the single fiber is smaller, the diameter distribution is mainly between 300-500 nm, wherein 52% of the fiber diameter is distributed between 300-400 nm. In addition, it can be seen from the SEM picture that some graphene sheets are attached to the nanofiber surface (as indicated by red arrows), and no agglomeration of graphene is found.

The PAN and PAN/graphene composite fiber membranes prepared in this example were subjected to mechanical property tests, and the results are shown in fig. 2. From the figure, it can be seen that the tensile strength and the elongation at break of the pure PAN nanofiber membrane are respectively about 5 MPa and 100%, while the tensile strength and the elongation at break of the PAN/graphene composite nanofiber membrane are respectively 9.5 MPa and 110%, and therefore, the excellent mechanical properties of the graphene have a good reinforcing effect, because the larger specific surface area of the graphene increases the contact area of the matrix, and the resistance to the movement of PAN molecules is increased during the stretching process.

The PAN and PAN/graphene composite fiber membranes prepared in this example were subjected to thermal performance tests, and the results are shown in fig. 3. As can be seen from the figure, the initial decomposition temperature of the PAN and PAN/graphene nanofiber membranes is about 315 ℃, the PAN nanofiber membrane rapidly undergoes a large amount of decomposition between 315 ℃ and 375 ℃, and then the decomposition amount begins to be obviously reduced. The PAN/graphene composite nanofiber membrane has a high decomposition speed between 315 ℃ and 350 ℃, has a low decomposition speed between 350 ℃ and 450 ℃, and then tends to be balanced. Therefore, from the TG results, it can be seen that the addition of graphene improves the thermal performance of PAN fiber membranes.

The PAN and PAN/graphene composite fiber membranes prepared in this example were subjected to a piezoelectric performance test, and the results are shown in fig. 4. At a test frequency of 2 Hz and a pressure of 10N, the PAN fiber membrane has an output voltage of about 8V and an output current of 0.2 muA. The macromolecular structure of PAN mainly has a 31-helix conformation and a planar-sawtooth conformation, wherein the planar-sawtooth conformation has high piezoelectric properties. Based on this, it was demonstrated that the macromolecular chains in the PAN fiber membranes had a partially planar sawtooth conformation. And the output voltage of the PAN/graphene composite nano-fiber is about 6V, and the current is about 0.175 muA. Compared with the PAN fiber membrane, the PAN/graphene has the advantages that the piezoelectric performance is reduced, on one hand, the planar sawtooth conformation content in the PAN macromolecular chain is reduced slightly due to the addition of the graphene; on the other hand, under external stress, the distance between carbon atoms in the single-layer graphene is increased, and the energy of adjacent transition is lowered, so that the electronic fermi speed is reduced, the electric conductance is further reduced, a negative piezoelectric effect is generated, and finally the output voltage is slightly reduced.

Example 2

(1) preparing a PAN/graphene spinning solution: 0.01 g of graphene is respectively weighed by an electronic analytical balance, added into a mixed solvent of 8mL of N-N Dimethylformamide (DMF) and 2mL of acetone, put a magneton into the solution and sealed by a preservative film, and subjected to ultrasound for a certain time in an ultrasonic cleaner. Then, 1 g of PAN was added to the above solution and it was placed in 80 g^oStirring the mixture on a constant-temperature magnetic stirrer for 90 min to completely dissolve the PAN. And then, transferring the solution to a normal-temperature six-linkage magnetic stirrer, and stirring for 12 hours at normal temperature to prepare a uniform spinning solution with 10% of PAN (Polyacrylonitrile) and 3% of graphene. And finally, standing the uniform spinning solution in a vacuum environment for a period of time to remove air bubbles in the spinning solution.

Example 3

(1) preparing a PAN/graphene spinning solution: 0.05 g of graphene is respectively weighed by an electronic analytical balance, added into a mixed solvent of 8mL of N-N Dimethylformamide (DMF) and 2mL of acetone, put a magneton into the solution and sealed by a preservative film, and subjected to ultrasound for a certain time in an ultrasonic cleaner. Then, 1 g of PAN was added to the above solution and it was placed in 80 g^oStirring the mixture on a constant-temperature magnetic stirrer for 90 min to completely dissolve the PAN. And then, transferring the solution to a normal-temperature six-linkage magnetic stirrer, and stirring for 12 hours at normal temperature to prepare a uniform spinning solution with 10% of PAN (Polyacrylonitrile) and 3% of graphene. And finally, standing the uniform spinning solution in a vacuum environment for a period of time to remove air bubbles in the spinning solution.

Example 4

(1) preparing a PAN/graphene spinning solution: 0.03 g of graphene was weighed out by an electronic analytical balance, and added to a mixed solvent of 8mL of N-N Dimethylformamide (DMF) and 2mL of acetoneA magneton is put into the solution and sealed by a preservative film, and the solution is subjected to ultrasonic treatment in an ultrasonic cleaning instrument for a certain time. Then, 1.2 g of PAN was added to the above solution and it was placed in 80 g^oStirring the mixture on a constant-temperature magnetic stirrer for 90 min to completely dissolve the PAN. And then, transferring the solution to a normal-temperature six-linkage magnetic stirrer, and stirring for 12 hours at normal temperature to prepare a uniform spinning solution with the PAN concentration of 12% and the graphene content of 2.5%. And finally, standing the uniform spinning solution in a vacuum environment for a period of time to remove air bubbles in the spinning solution.

Example 5

(2) Preparing a PAN/graphene nanofiber membrane: and (2) sucking the spinning solution subjected to standing and defoaming in the step (1) into a syringe, removing air bubbles in the spinning solution, and fixing the spinning solution on a syringe pump to perform electrostatic spinning. The spinning process conditions are as follows: spinning voltage is 16 kV, spinning receiving distance is 20 cm, spinning speed is 1 mL/h, and spinning time is 6 h. And after spinning is finished, collecting the PAN/graphene composite nanofiber membrane, and drying the PAN/graphene composite nanofiber membrane in a vacuum drying oven for 4 hours to completely volatilize the solvent, and storing for later use.

Example 6

(2) Preparing a PAN/graphene nanofiber membrane: and (2) sucking the spinning solution subjected to standing and defoaming in the step (1) into a syringe, removing air bubbles in the spinning solution, and fixing the spinning solution on a syringe pump to perform electrostatic spinning. The spinning process conditions are as follows: the spinning voltage is 18 kV, the spinning receiving distance is 20 cm, the spinning speed is 0.6 mL/h, and the spinning time is 6 h. And after spinning is finished, collecting the PAN/graphene composite nanofiber membrane, and drying the PAN/graphene composite nanofiber membrane in a vacuum drying oven for 4 hours to completely volatilize the solvent, and storing for later use.

Comparative example

A preparation method of non-woven nano graphene/polyacrylonitrile non-woven fabric comprises the following steps:

weighing 0.1 g of graphene, 5 ml of N-dimethylformamide, uniformly mixing the graphene and the N-dimethylformamide, and then putting the mixture on a magnetic stirrer to stir for 30 minutes to uniformly mix the mixture; then, adding 0.5 g of polyacrylonitrile, stirring for 30 minutes, and carrying out ultrasonic crushing; crushing for 60 minutes, stirring again, heating and stirring for about 90 minutes, before experiment, ensuring that the solution is heated and stirred completely, then placing the solution on an electrostatic spinning device by using a needle cylinder as a container, wherein the voltage is 18 kV, the distance between an electrode plate and a needle head is adjusted to be 15 cm, spinning is carried out, a flat plate receiver is adopted for receiving, and the non-woven nano graphene/polyacrylonitrile non-woven fabric is obtained, the diameter of the obtained fiber is 50-100nm, and the thickness of the fiber film is 10-500 mu m. Tables 1 and 2 show the mechanical properties and resistivity results of the graphene/polyacrylonitrile nonwoven fabric, respectively.

TABLE 1 sample tensile test parameters

TABLE 2 resistivity measurements and parameters

The comparative example differs from example 1 of the present application in that:

1. the used raw materials of the graphene and the polyacrylonitrile are different in types and dosage, the graphene used in the invention is high-conductivity graphene, the dosage is 0.01-0.05 g, the molecular weight of the polyacrylonitrile is 15 ten thousand, and the dosage is 1 g. In the comparative example, the mass of the graphene is 0.1-1.0 g, and the mass of the polyacrylonitrile is 0.5-5.0 g. That is, the concentration of graphene was different from that prepared in the comparative example;

2. the raw materials are different, the organic solvent used in the invention is a mixed solution of N' N dimethylformamide and acetone, and the organic solvent used in the comparative example is one of N-N dimethylformamide and methanol.

3. The preparation methods are different, the preparation of the spinning solution in the step (1) in the comparative example is that the graphene is dissolved in the organic solvent and then only stirred without ultrasonic treatment, and then the polypropylene is added into the solution and then is stirred by magnetic force and crushed by ultrasound to be mixed uniformly;and the step (1) of the invention is to add graphene into a mixed solvent of N-N dimethylformamide and acetone, put a magneton into the solution, and only carry out ultrasonic treatment on the magneton for a certain time in an ultrasonic cleaning instrument. Then, polyacrylonitrile is added and then the mixture is placed at 80^oC, stirring for 90 min on a constant-temperature magnetic stirrer, and finally transferring the solution to a normal-temperature six-linkage magnetic stirrer and stirring for 12 h at normal temperature.

4. The difference in the preparation method is also shown in that the electrostatic spinning process parameter set in claim 5 of the comparative example is different from the parameter set in step (2) of the present invention. Claim 5 wherein the parameters are arranged differently

5. The prepared products have different performances, and the mechanical strength, the resistivity and the visible light absorptivity of the graphene/polyacrylonitrile composite nanofiber membrane are obtained in the comparative example, wherein the fiber diameter is 50-100nm, and the thickness of the fiber membrane is 10-500 mu m. In the polyacrylonitrile/graphene composite nanofiber membrane obtained in the finished product embodiment (1), more than 80% of the fiber diameters are distributed at 300-500 nm, and the thickness of the fiber membrane is at 100-120 μm. The piezoelectric property, the mechanical property and the thermal property of the finished product are mainly emphasized, and the finished product is expected to be used as a sensor and an energy capturer to be applied to the fields of personal health monitoring, disease treatment and prevention, electronics, measurement, military, traffic and the like.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The preparation method of the high-temperature-resistant composite nanofiber membrane for preparing the piezoelectric material is characterized by comprising the following steps of:

(1) adding graphene into a solvent, then adding a magneton, sealing, and performing ultrasonic treatment for 1h to obtain a graphene solution; wherein the solvent is a mixed solvent of N-N dimethylformamide and acetone, the volume ratio (6-10) of the N-N dimethylformamide to the acetone is 2, and the mass concentration of the graphene solution is 1-5 wt%;

(2) adding PAN into the graphene solution obtained in the step (1), magnetically stirring at a constant temperature until the PAN is completely dissolved, and then stirring at a normal temperature until a uniform spinning solution is formed; wherein the mass fraction of PAN in the spinning solution is 10-12 wt%;

(3) and (3) absorbing the spinning solution obtained in the step (2) into an injector after vacuum defoaming, and carrying out electrostatic spinning to prepare the PAN/graphene composite nanofiber membrane.

2. The method of claim 1, wherein: the temperature of the constant-temperature magnetic stirring in the step (2) is 60-80 ℃.

3. The method according to claim 1, wherein the parameters of the electrospinning in the step (3) are as follows: spinning voltage is 16-18 kV, receiving distance is 15-20 cm, injection speed is 0.6-1.2 mL/h and spinning time is 5-6 h.

4. The high temperature resistant composite nanofiber membrane prepared by the method of any one of claims 1 to 3, wherein: the thickness of the high-temperature resistant composite nanofiber membrane is 100-120 mu m, the output voltage is about 5-6V, and the current is 0.150-0.175 mu A.