Polyvinylidene fluoride / graphene oxide composite material as well as preparation method and application thereof

Abstract

The invention relates to a polyvinylidene fluoride / graphene oxide composite material as well as a preparation method and application thereof. The preparation method of the polyvinylidene fluoride / graphene oxide composite material comprises the following steps: dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution; performing hydrothermal reaction on the first mixed solution, and standing to obtain a second mixed solution; spin-coating and casting the second mixed solution to obtain a thin film; and annealing the film to obtain the polyvinylidene fluoride / graphene oxide composite film material. The invention also provides the polyvinylidene fluoride / graphene oxide composite material prepared by the preparation method. The invention also provides application of the polyvinylidene fluoride / graphene oxide composite material prepared by the preparation method. The polyvinylidene fluoride / graphene oxide composite material is applied to a multifunctional intelligent sensor. The problem that an existing PVDF composite material does not have piezoelectric and thermoelectric properties at the same time or has poor electrical properties is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyvinylidene fluoride composite materials, and in particular to a polyvinylidene fluoride / graphene oxide composite material and a preparation method and application thereof. Background Art

[0002] With the advent of the intelligent era, people's daily lives have generated a large demand for sensors, especially multifunctional smart sensors, which have become the current key research object. At the same time, new composite materials that can achieve multifunctional sensing have also become a major exploration hotspot.

[0003] Polyvinylidene fluoride (PVDF) organic material belongs to ferroelectric materials. Under certain conditions, it has unique piezoelectric and thermoelectric properties, making it an important candidate for multifunctional composite materials. Polyvinylidene fluoride is a fluorine-containing polymer, mainly composed of vinylidene fluoride homopolymer or copolymer of vinylidene fluoride and other small amounts of fluorine-containing vinyl monomers. Due to the special crystal structure of polyvinylidene fluoride, it contains at least five crystal forms (α, β, γ, δ, ε). The common crystal forms are α, β, γ, such as Figure 1 As shown. Among them, the α crystal form is the most common and the easiest to obtain crystal form in the preparation process, but the α crystal form is a monoclinic system with a configuration of TGTG', the crystal chain dipole polarity is opposite, and it does not show polarity; the β crystal form is an orthorhombic system with a configuration of all-trans TTTT, and the crystal chain contained in the unit cell is zigzag, so the β crystal form shows polarity. The higher the β crystal content in the prepared PVDF material, the stronger the electrical properties it presents under specific conditions, and it can be used in the manufacture of multifunctional chemical sensors, actuators and biomedical materials. Therefore, how to prepare PVDF films with high β content has become a research focus.

[0004] CN 106432753 A discloses a method for preparing PVDF extended chain crystals, comprising the following steps: (1) blending: adding PVDF and an organic solvent to a high-speed mixer according to a weight ratio for premixing; (2) dissolving: placing the mixed material into a specified mold, then loading the mold filled with the material into a heating furnace, turning on the heating power supply, controlling the heating rate to be 10°C / min, heating and heating the mixture to completely dissolve it, and keeping it warm for 10 to 60 minutes; (3) cooling: cooling the mold to a certain temperature and then keeping it warm for a certain time; (4) desorption: heating the sample obtained in step (3) to a certain temperature and keeping it warm, controlling the heating rate to be 1°C / min, desorbing and removing the solvent, and obtaining PVDF extended chain crystals. This preparation method uses common organic solvents for preparation, has high requirements on the equipment (spin coater) for preparing the solution, requires high insulation temperature and annealing temperature, takes a long preparation time, and the content of the obtained PVDF extended chain crystals is uncontrollable and greatly affected by accidental factors.

[0005] CN 112614933 A discloses a preparation method of PVDF piezoelectric material and PVDF piezoelectric material, the method comprising the following steps: preparing a PVDF original solution, and preparing a mixed solution of charged modified molecules and PVDF; forming a first PVDF layer from the PVDF original solution, forming a second PVDF layer and a third PVDF layer from the mixed solution of charged modified molecules and PVDF, and making the second PVDF layer and the third PVDF layer respectively located on two surfaces of the first PVDF layer to form a PVDF material matrix, when forming the PVDF matrix, making the modified molecules in the second PVDF layer and the third PVDF layer form a charged cross-linked network with PVDF; applying a charged electrode catalyst solution on the second PVDF layer and the third PVDF layer, the type of charge carried by the electrode catalyst solution being opposite to the type of charge in the mixed solution of modified molecules and PVDF; performing chemical plating treatment on the PVDF material matrix to which the charged catalyst solution is applied, so that electrodes are formed on the second PVDF layer and the third PVDF layer. The two electrodes of the PVDF piezoelectric material can have good signal transmission performance. However, the preparation method is complicated, involving not only solution preparation, but also the use of electrode catalyst solution and chemical plating, etc. Moreover, the PVDF piezoelectric material prepared by this method does not have thermoelectric properties. Summary of the invention

[0006] The purpose of the present invention is to provide a polyvinylidene fluoride / graphene oxide composite material and a preparation method and application thereof, so as to solve the problem that the existing PVDF composite materials do not have both piezoelectric and thermoelectric properties or have poor electrical properties, and can also solve the problem that the preparation process of the existing PVDF composite materials is complicated and the conditions are harsh.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0009] S1, dissolving polyvinylidene fluoride (PVDF) and graphene oxide in an organic solvent to obtain a first mixed solution;

[0010] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution;

[0011] S3, spin-coating and casting the second mixed solution to obtain a thin film;

[0012] S4. Annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0013] According to the above technical means, by dissolving polyvinylidene fluoride (PVDF) and graphene oxide in an organic solvent and then conducting a hydrothermal reaction, it is not only effective to prevent the agglomeration problem of graphene oxide, but also to promote the nucleation and crystallization of PVDF, effectively improving the nucleation rate and crystallinity. Annealing treatment is then performed after the hydrothermal reaction to ensure the effective formation of the β crystal form in the composite material.

[0014] Preferably, in S1, the mass ratio of polyvinylidene fluoride to the first mixed solution is 1:7-20; the mass ratio of graphene oxide to the first mixed solution is 1:5-1000.

[0015] Preferably, the molecular weight of the polyvinylidene fluoride is between 10,000 and 60,000.

[0016] By selecting polyvinylidene fluoride with a molecular weight between 10,000 and 60,000, the concentration of the prepared second mixed solution is effectively guaranteed to be appropriate, thereby avoiding the problems of rapid crystallization before spin coating and failure to form a film during spin coating.

[0017] Preferably, in S1, the organic solvent is selected from at least one of dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO) and acetone.

[0018] Preferably, the step S1 specifically includes: dissolving polyvinylidene fluoride and graphene oxide in an organic solvent, and ultrasonically vibrating to obtain a first mixed solution.

[0019] Preferably, in S2, the temperature of the hydrothermal reaction is 60° C. to 110° C., and the time of the hydrothermal reaction is 12 to 24 hours.

[0020] By limiting the temperature of the hydrothermal reaction to between 60°C and 110°C, the problem of PVDF denaturation due to high temperature is effectively avoided.

[0021] Preferably, in S4, the annealing temperature is 30° C. to 80° C., and the annealing time is 20-60 min.

[0022] After research, it was found that controlling the annealing temperature between 30°C and 80°C is more conducive to the formation of β crystal, and also helps to remove organic solvents and moisture in the film.

[0023] The present invention also provides a polyvinylidene fluoride / graphene oxide composite material prepared by the preparation method of the present invention.

[0024] Preferably, the content of β crystal in the polyvinylidene fluoride / graphene oxide composite material is above 49%, and the polyvinylidene fluoride / graphene oxide composite material has both thermoelectric and piezoelectric properties.

[0025] The present invention also provides an application of the polyvinylidene fluoride / graphene oxide composite material prepared by the preparation method described in the present invention. The polyvinylidene fluoride / graphene oxide composite material is applied to multifunctional intelligent sensors, such as pressure detection sensors, thermoelectric sensors, composite sensors, etc.

[0026] Beneficial effects of the present invention:

[0027] 1) The preparation method of the polyvinylidene fluoride / graphene oxide composite material of the present invention, by taking polyvinylidene fluoride and graphene oxide as raw materials, dissolving them together in an organic solvent, and undergoing hydrothermal treatment, spin coating and annealing treatment, not only effectively increases the nucleation rate and crystallinity of PVDF, but also increases the content of β crystal in the polyvinylidene fluoride / graphene oxide composite material, so that the prepared polyvinylidene fluoride / graphene oxide composite material has excellent PVDF piezoelectric and thermoelectric properties, as well as higher electrochemical properties, has the advantages of simple preparation method, mild conditions and low cost, and has promotion and application value in the technical field of polyvinylidene fluoride composite materials;

[0028] 2) The polyvinylidene fluoride / graphene oxide composite material of the present invention has excellent electrochemical properties through a simpler preparation method, and can be used in the fields of pressure detection sensors, thermoelectric sensors, composite sensors, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of different crystal forms in the PVDF molecular chain;

[0030] Figure 2 The present invention is a flow chart of a method for preparing the polyvinylidene fluoride / graphene oxide composite material. DETAILED DESCRIPTION

[0031] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0032] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0033] Example 1

[0034] like Figure 2 As shown, a method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0035] S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution, specifically comprising:

[0036] S11, raw material preparation: weigh graphene oxide: PVDF and DMF according to a mass ratio of 1:100:1000, so as to obtain a first mixed solution in which the mass fraction of graphene oxide is 0.1%wt and the mass fraction of PVDF is 10%wt;

[0037] S12, dissolving and blending: dissolving the weighed PVDF and graphene oxide in DMF, and performing ultrasonic oscillation to accelerate the dissolution of PVDF and graphene oxide, the oscillation time is 30 minutes, and obtaining a first mixed solution;

[0038] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution, specifically comprising:

[0039] S21, placing the first mixed solution in a hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature is 80° C., the hydrothermal reaction time is 16 h, so that the graphene oxide is completely dispersed in DMF;

[0040] S22, placing the first mixed solution after complete dispersion in a vacuum box and letting it stand for 20 minutes to remove bubbles in the solution, thereby obtaining a second mixed solution;

[0041] S3, spin-coating and casting the second mixed solution to obtain a thin film, specifically comprising:

[0042] The second mixed solution was spin-coated at a spin-coating speed of 1000 rpm to obtain a thin film;

[0043] S4, annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material, specifically comprising:

[0044] The film formed by spin coating was annealed at a temperature of 50° C. to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0045] Example 2

[0046] like Figure 2 As shown, a method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0047] S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution, specifically comprising:

[0048] S11, raw material preparation: weigh graphene oxide: PVDF and DMF according to a mass ratio of 5:100:1000, so as to obtain a first mixed solution in which the mass fraction of graphene oxide is 0.5%wt and the mass fraction of PVDF is 10%wt;

[0049] S12, dissolving and blending: dissolving the weighed PVDF and graphene oxide in DMF, and performing ultrasonic oscillation to accelerate the dissolution of PVDF and graphene oxide, the oscillation time is 30 minutes, and obtaining a first mixed solution;

[0050] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution, specifically comprising:

[0051] S21, placing the first mixed solution in a hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature is 80° C., the hydrothermal reaction time is 16 h, so that the graphene oxide is completely dispersed in DMF;

[0052] S22, placing the first mixed solution after complete dispersion in a vacuum box and letting it stand for 20 minutes to remove bubbles in the solution, thereby obtaining a second mixed solution;

[0053] S3, spin-coating and casting the second mixed solution to obtain a thin film, specifically comprising:

[0054] The second mixed solution was spin-coated at a spin-coating speed of 1000 rpm to obtain a thin film;

[0055] S4, annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material, specifically comprising:

[0056] The film formed by spin coating was annealed at a temperature of 50° C. to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0057] Example 3

[0058] like Figure 2 As shown, a method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0059] S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution, specifically comprising:

[0060] S11, raw material preparation: weigh graphene oxide: PVDF and DMF according to a mass ratio of 10:100:1000, so as to obtain a first mixed solution with a mass fraction of graphene oxide of 1%wt and a mass fraction of PVDF of 10%wt;

[0061] S12, dissolving and blending: dissolving the weighed PVDF and graphene oxide in DMF, and performing ultrasonic oscillation to accelerate the dissolution of PVDF and graphene oxide, the oscillation time is 30 minutes, and obtaining a first mixed solution;

[0062] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution, specifically comprising:

[0063] S21, placing the first mixed solution in a hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature is 80° C., the hydrothermal reaction time is 16 h, so that the graphene oxide is completely dispersed in DMF;

[0064] S22, placing the first mixed solution after complete dispersion in a vacuum box and letting it stand for 20 minutes to remove bubbles in the solution, thereby obtaining a second mixed solution;

[0065] S3, spin-coating and casting the second mixed solution to obtain a thin film, specifically comprising:

[0066] The second mixed solution was spin-coated at a spin-coating speed of 1000 rpm to obtain a thin film;

[0067] S4, annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material, specifically comprising:

[0068] The film formed by spin coating was annealed at a temperature of 50° C. to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0069] Example 4

[0070] like Figure 2 As shown, a method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0071] S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution, specifically comprising:

[0072] S11, raw material preparation: weigh graphene oxide: PVDF and DMF according to a mass ratio of 1:100:1000, so as to obtain a first mixed solution in which the mass fraction of graphene oxide is 0.1%wt and the mass fraction of PVDF is 10%wt;

[0073] S12, dissolving and blending: dissolving the weighed PVDF and graphene oxide in DMF, and performing ultrasonic oscillation to accelerate the dissolution of PVDF and graphene oxide, the oscillation time is 30 minutes, and obtaining a first mixed solution;

[0074] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution, specifically comprising:

[0075] S21, placing the first mixed solution in a hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature is 80° C., the hydrothermal reaction time is 16 h, so that the graphene oxide is completely dispersed in DMF;

[0076] S22, placing the first mixed solution after complete dispersion in a vacuum box and letting it stand for 20 minutes to remove bubbles in the solution, thereby obtaining a second mixed solution;

[0077] S3, spin-coating and casting the second mixed solution to obtain a thin film, specifically comprising:

[0078] The second mixed solution was spin-coated at a spin-coating speed of 1000 rpm to obtain a thin film;

[0079] S4, annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material, specifically comprising:

[0080] The film formed by spin coating was annealed at a temperature of 30° C. to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0081] Example 5

[0082] like Figure 2 As shown, a method for preparing a polyvinylidene fluoride / graphene oxide composite material comprises the following steps:

[0083] S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution, specifically comprising:

[0084] S11, raw material preparation: weigh graphene oxide: PVDF and DMF according to a mass ratio of 1:100:1000, so as to obtain a first mixed solution in which the mass fraction of graphene oxide is 0.1%wt and the mass fraction of PVDF is 10%wt;

[0085] S12, dissolving and blending: dissolving the weighed PVDF and graphene oxide in DMF, and performing ultrasonic oscillation to accelerate the dissolution of PVDF and graphene oxide, the oscillation time is 30 minutes, and obtaining a first mixed solution;

[0086] S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution, specifically comprising:

[0087] S21, placing the first mixed solution in a hydrothermal reactor for hydrothermal reaction, the hydrothermal reaction temperature is 80° C., the hydrothermal reaction time is 16 h, so that the graphene oxide is completely dispersed in DMF;

[0088] S22, placing the first mixed solution after complete dispersion in a vacuum box and letting it stand for 20 minutes to remove bubbles in the solution, thereby obtaining a second mixed solution;

[0089] S3, spin-coating and casting the second mixed solution to obtain a thin film, specifically comprising:

[0090] The second mixed solution was spin-coated at a spin-coating speed of 1000 rpm to obtain a thin film;

[0091] S4, annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material, specifically comprising:

[0092] The film formed by spin coating was annealed at a temperature of 80° C. to obtain a polyvinylidene fluoride / graphene oxide composite film material.

[0093] Comparative Example 1

[0094] (1) Raw material preparation: graphene oxide: PVDF and DMF are weighed in a mass ratio of 1:100:1000, so that the mass fraction of graphene oxide in the first mixed solution is 0.1%wt and the mass fraction of PVDF is 10%wt;

[0095] (2) Ultrasonic dissolution: The first mixed solution was placed in an ultrasonic cleaner and ultrasonicated for 1 hour; then, the solution was placed in a magnetic stirrer and stirred for 1 hour to obtain a second mixed solution.

[0096] (3) Standing: The second PVDF / graphene oxide mixed solution after ultrasonic stirring was stood in a vacuum box for 20 min to remove bubbles in the solution.

[0097] (4) Spin coating: Spin coating was performed at a spin coating speed of 1000 rpm.

[0098] (5) Annealing: The thin film formed by spin coating is annealed at 50° C. to obtain a PVDF / graphene oxide composite thin film material.

[0099] Detection and analysis

[0100] 1. Differential Scanning Calorimetry (DSC) Test

[0101] The specific operation is as follows: 9 mg of each sample of the PVDF / graphene oxide composite film material prepared in Examples 1 to 5 and Control Example 1 are weighed and placed in a sample crucible, and a differential scanning calorimeter (DSC) is used to perform a differential scanning calorimetry test starting from 25°C and a heating rate of 10°C to 300°C to obtain a differential scanning calorimeter (DSC) thermogram, and the crystallinity of each sample is observed and calculated through each thermogram. The calculation results are shown in Table 1.

[0102] The calculation formula for melting enthalpy is: Xc = ΔHm / ΔH0m

[0103] Wherein, ΔHm represents the melting enthalpy of the sample measured by DSC, ΔH0m represents the theoretical melting enthalpy value of 100% crystalline PVDF (ΔH0m=102.5 J / g), and Xc represents the crystallinity of the sample.

[0104] Table 1 Crystallinity results in samples

[0105]

[0106]

[0107] From the analysis in Table 1, it can be seen that with the increase of the added graphene oxide content, the PVDF crystallinity in the obtained vinylidene fluoride / graphene oxide composite material is higher, indicating that graphene oxide helps the crystallization of PVDF; at the same time, the annealing temperature will also affect the crystallization of PVDF, and the crystallinity is highest at 50°C.

[0108] 2. Fourier transform infrared spectroscopy (FTIR) test

[0109] The specific operation is: the PVDF / graphene oxide composite film material samples prepared in Examples 1 to 5 and Control Example 1 are respectively subjected to Fourier transform infrared spectroscopy detection to obtain Fourier transform infrared spectrum (FTIR) graphs, and the percentage content of β crystal in the PVDF / graphene oxide composite film material samples is calculated by the Fourier transform infrared spectrum (FTIR) graph, and the calculation results are shown in Table 2.

[0110] The calculation formula for the percentage content of β crystal is: F(β)=A 839 / (1.26A 763 +A 839 )

[0111] Among them, A 763 represents the characteristic peak absorption intensity of the non-electroactive phase α, A 839 It represents the characteristic peak absorption intensity of the electroactive phase β, and F(β) represents the relative content of the electroactive β crystal.

[0112] Table 2 Results of the percentage content of β crystal in the samples

[0113] Fβ(％) Example 1 49.4 Example 2 60.5 Example 3 78.5 Example 4 58.7 Example 5 62.1 Comparative Example 1 45.6

[0114] As can be seen from Table 2, the β-crystal content in the PVDF / graphene oxide composite film materials prepared in Examples 1 to 5 is basically 60% or more, and has a high β-crystal content. The all-trans configuration of the β-crystal makes its spontaneous polarization intensity higher, so that the PVDF film material has better piezoelectric and thermoelectric properties.

[0115] 3. Thermoelectric test

[0116] The specific operation is as follows: the PVDF / graphene oxide composite film material samples prepared in Examples 1 to 5 and Comparative Example 1 are subjected to thermoelectric tests at a temperature of 40°C to 50°C.

[0117] When the pyroelectric current I changes, it will output p , the relationship between pyroelectric current and temperature change is shown below:

[0118] Ip=A*α*(dT / dt)

[0119] Where A represents the area of ​​the sample, unit: cm 2 , α represents the pyroelectric coefficient of the sample, unit: uc / cm 2 K, dT / dt represents the rate of temperature change, the area and temperature change rate are known quantities, I p It represents the pyroelectric current. By measuring the pyroelectric current, the corresponding pyroelectric coefficient can be calculated. The test results are shown in Table 3.

[0120] Table 3 Pyroelectric coefficient results of samples

[0121] <![CDATA[α(uc / cm 2 K)]]> Example 1 1.56 Example 2 1.95 Example 3 2.73 Example 4 1.88 Example 5 1.92 Comparative Example 1 1.02

[0122] From the analysis in Table 3, it can be seen that under the experimental conditions, when the graphene oxide content is 1%wt, the pyroelectric coefficient obtained by sample testing is the highest, that is, the graphene oxide completely dispersed and dissolved in the PVDF organic solvent contributes to the formation of β crystal, thereby improving the thermoelectric performance of the material.

[0123] 4. Piezoelectric test

[0124] Using a d33 piezoelectric tester, the polyvinylidene fluoride / graphene oxide composite film materials prepared in Examples 1 to 5 and Control Example 1 were polarized and then subjected to a piezoelectric test. The d33 tester can directly display the piezoelectric coefficient. The test results are shown in Table 4.

[0125] Table 4 Piezoelectric coefficient results of samples

[0126]

[0127]

[0128] It can be seen from Table 4 that the d33 piezoelectric reading under the hot water method is significantly higher than that in the comparative example, which proves that the PVDF / graphene oxide composite material prepared by the hydrothermal method has better piezoelectric properties.

[0129] In summary, the preparation method of the polyvinylidene fluoride / graphene oxide composite material of the present invention uses polyvinylidene fluoride and graphene oxide as raw materials, dissolves them together in an organic solvent, and undergoes hydrothermal treatment, spin coating and annealing treatment, which not only effectively increases the nucleation rate and crystallinity of PVDF, but also improves the content of crystal forms in the polyvinylidene fluoride / graphene oxide composite material, so that the prepared polyvinylidene fluoride / graphene oxide composite material has excellent PVDF piezoelectric and thermoelectric properties, higher electrochemical properties, and has the advantages of simple preparation method, mild conditions and low cost. In the technical field of polyvinylidene fluoride composite materials, it has promotion and application value.

[0130] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride / graphene oxide composite material, characterized in that: The following steps are involved: S1, dissolving polyvinylidene fluoride and graphene oxide in an organic solvent to obtain a first mixed solution; S2, subjecting the first mixed solution to a hydrothermal reaction, and allowing the solution to stand to obtain a second mixed solution; S3, spin-coating and casting the second mixed solution to obtain a thin film; S4. Annealing the film to obtain a polyvinylidene fluoride / graphene oxide composite film material.

2. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: In S1, the mass ratio of polyvinylidene fluoride to the first mixed solution is 1:7-20; the mass ratio of graphene oxide to the first mixed solution is 1:5-1000.

3. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: The molecular weight of the polyvinylidene fluoride is between 10,000 and 60,000.

4. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: In S1, the organic solvent is selected from at least one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and acetone.

5. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: The step S1 specifically includes: dissolving polyvinylidene fluoride and graphene oxide in an organic solvent, and ultrasonically vibrating to obtain a first mixed solution.

6. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: In S2, the temperature of the hydrothermal reaction is 60° C. to 110° C., and the time of the hydrothermal reaction is 12 to 24 hours.

7. The method for preparing the polyvinylidene fluoride / graphene oxide composite material according to claim 1, characterized in that: In S4, the annealing temperature is 30° C. to 80° C., and the annealing time is 20 to 60 minutes.

8. A polyvinylidene fluoride / graphene oxide composite material obtained by the preparation method according to any one of claims 1 to 7.

9. The polyvinylidene fluoride / graphene oxide composite material according to claim 8, characterized in that: The content of the β-crystal in the polyvinylidene fluoride / graphene oxide composite material is above 49%, and the polyvinylidene fluoride / graphene oxide composite material has both thermoelectric and piezoelectric properties.

10. An application of a polyvinylidene fluoride / graphene oxide composite material obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The polyvinylidene fluoride / graphene oxide composite material is applied to a multifunctional intelligent sensor.

Images