CN111048659A - Piezoelectric film and preparation method thereof - Google Patents
Piezoelectric film and preparation method thereof Download PDFInfo
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- CN111048659A CN111048659A CN201811201761.8A CN201811201761A CN111048659A CN 111048659 A CN111048659 A CN 111048659A CN 201811201761 A CN201811201761 A CN 201811201761A CN 111048659 A CN111048659 A CN 111048659A
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Abstract
The invention relates to the technical field of piezoelectric materials, in particular to a piezoelectric film and a preparation method thereof. The preparation method comprises the steps of mixing and dispersing the vinylidene fluoride pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and further carrying out polarization treatment on the film to be treated to obtain the required piezoelectric film. The preparation method has high preparation process efficiency, the prepared piezoelectric film has good high-temperature resistance, the power-electricity conversion capability of the piezoelectric film is remarkably improved, and the piezoelectric film with the piezoelectric coefficient larger than 32pc/N can be obtained. The invention also provides a piezoelectric film which is prepared based on the piezoelectric film preparation method, and the piezoelectric coefficient of the piezoelectric film is larger than 32 pc/N.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of piezoelectric materials, in particular to a piezoelectric film and a preparation method thereof.
[ background of the invention ]
A piezoelectric material is a material that can convert mechanical energy and electrical energy into each other. Among them, piezoelectric polymers, particularly vinylidene fluoride piezoelectric polymers, have been widely used in the fields of sensors, chips, energy engineering, environmental purification, flaw detection, wearable, and the like, because of their high piezoelectric properties and their unique flexibility. However, due to the limitations of the existing preparation technology, the method cannot exert the characteristic of strong polarity of the polyvinylidene fluoride to the maximum extent. The piezoelectric coefficient (d) of the materials obtained up to now33) And is also lower.
[ summary of the invention ]
In order to solve the problems, the invention provides a piezoelectric film and a preparation method thereof.
The invention provides a piezoelectric film preparation method, which solves the technical problem and comprises the following steps: providing a vinylidene fluoride-trifluoroethylene copolymer, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent to form a vinylidene fluoride-trifluoroethylene pre-solution; providing graphene, and dissolving the graphene in a solvent to form a graphene suspension; mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and carrying out polarization treatment on the film to be treated to obtain the required piezoelectric film.
Preferably, the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer is 90/10-50/50; wherein the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.005-2%.
Preferably, the concentration of the vinylidene fluoride-trifluoroethylene pre-solution is 1-20 wt%, the concentration of the graphene suspension is 0.005-1.5 wt%, and the solvent comprises any one or a combination of more of butanone, N-dimethylpyrrolidone and N, N-dimethylamide.
Preferably, the graphene comprises exfoliated graphene sheets, the graphene comprises oxygen-containing functional groups, and the oxygen content of the graphene is 2% to 6%.
Preferably, the oxygen-containing functional group comprises one or a combination of carboxyl, carbonyl and hydroxyl; the graphene further includes a C-O dipole that matches the dipole of the vinylidene fluoride-trifluoroethylene copolymer.
Preferably, the coating mode comprises any one of spin coating, spray coating and overall coating; the thickness of the formed film to be treated is 2-20 μm.
Preferably, the substrate comprises any one of ITO glass, silicon wafer, copper plate, and aluminum plate.
Preferably, the drying treatment specifically includes the steps of: and drying the film to be processed for 1-8 min at room temperature under vacuum condition to form a dried film.
Preferably, the polarization treatment specifically comprises the following steps: and (3) polarizing the film to be treated for 1-20 min at the temperature of 20-30 ℃ by using a voltage of 3-20 KV, wherein the distance between the polarized electrode end and the surface of the film is 0.01-25 mm. The invention also provides a piezoelectric film for solving the technical problem, which is prepared by mixing and dispersing a vinylidene fluoride-trifluoroethylene pre-solution and a graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; further carrying out polarization treatment on the film to be treated to obtain the piezoelectric film; the piezoelectric coefficient of the piezoelectric film is larger than 32 pc/N.
Compared with the prior art, the system for testing the piezoelectric coefficient has the advantages. The piezoelectric film and the preparation method thereof provided by the invention are simple and feasible, and can form a preparation method of a polyvinylidene fluoride piezoelectric film with a strong piezoelectric effect.
The invention provides a preparation method of a piezoelectric film, which comprises the following steps: providing a vinylidene fluoride-trifluoroethylene copolymer, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent to form a vinylidene fluoride-trifluoroethylene pre-solution; providing graphene, and dissolving the graphene in a solvent to form a graphene suspension; mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and further carrying out polarization treatment on the film to be treated to obtain the required piezoelectric film. Based on the preparation method, the piezoelectric film with the piezoelectric coefficient larger than 32pc/N can be obtained, the preparation method is high in preparation process efficiency, the prepared piezoelectric film is good in high-temperature resistance, the piezoelectric film can be further processed conveniently, and the mechanical-electrical conversion capability of the piezoelectric film is remarkably improved.
The invention also provides a piezoelectric film, which is prepared by mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; further carrying out polarization treatment on the film to be treated to obtain the piezoelectric film; the piezoelectric coefficient of the piezoelectric film is larger than 32pc/N, and the piezoelectric film has excellent transparency and wide application range.
[ description of the drawings ]
Fig. 1 is a schematic flow chart of steps of a method for manufacturing a piezoelectric thin film according to a first embodiment of the present invention.
Fig. 2 is a schematic view of the main structure of the thin film polarization apparatus used in step S5 shown in fig. 1.
Fig. 3A is a TEM image of a piezoelectric thin film obtained when the vinylidene fluoride pre-trifluoroethylene solution was mixed with the graphene suspension, the mass percentage of graphene to the mass of vinylidene fluoride was 0.01%.
Fig. 3B is a TEM image of a piezoelectric thin film obtained when the vinylidene fluoride-trifluoroethylene pre-solution was mixed with the graphene suspension, and the mass percentage of graphene to the mass of vinylidene fluoride was 0.05%.
Fig. 3C is a TEM image of a piezoelectric thin film obtained when the vinylidene fluoride-trifluoroethylene pre-solution was mixed with the graphene suspension, and the mass percentage of graphene to the mass of vinylidene fluoride was 0.1%.
Fig. 3D is a TEM image of a piezoelectric film obtained when the vinylidene fluoride pre-trifluoroethylene pre-solution was mixed with the graphene suspension, and the mass percentage of graphene to the mass of vinylidene fluoride was 0.1%.
The attached drawings indicate the following:
10. a thin film polarization device; 11. an electric field assembly; 111. a high voltage electrode terminal; 112. a low voltage electrode terminal; 12. an article carrying platform; 90. a film to be treated; 901. a first surface; 902. a second surface.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The vinylidene fluoride can be crystallized into α, β, gamma and delta four crystal phases under different conditions, wherein the polar β crystal form of which the molecules are in all-trans conformation has piezoelectric characteristics.
Referring to fig. 1, in order to obtain the β crystal form with strong piezoelectric effect, a first embodiment of the present invention provides a method for preparing a novel piezoelectric film, which includes the following steps:
step S1, providing a vinylidene fluoride-trifluoroethylene copolymer, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent to form a vinylidene fluoride-trifluoroethylene pre-solution;
step S2, providing graphene, and dissolving the graphene in a solvent to form a graphene suspension;
step S3, mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; when the vinylidene fluoride-trifluoroethylene pre-solution is mixed with the graphene suspension, the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.005% -2% calculated by adding pure graphene and pure vinylidene fluoride;
step S4, coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be processed;
in step S5, the film to be processed is subjected to polarization processing to obtain a piezoelectric film.
The sequence of the above steps S1 and S2 can be interchanged, or the sequence of the above steps S1 and S2 can be performed synchronously, which is only an example and not a limitation of the present invention.
In the above step S1, the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer is 90/10 to 50/50. The copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer can also be 80/20-60/40, and specifically, the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer further comprises 85/15, 80/20, 75/25, 70/30, 65/35 or 60/40.
Further, the vinylidene fluoride-trifluoroethylene pre-solution is prepared by dissolving powder of a vinylidene fluoride-trifluoroethylene copolymer in a solvent, wherein the solvent comprises any one or a combination of more of butanone, N-dimethyl pyrrolidone and N, N-dimethyl amide.
The concentration of the vinylidene fluoride-trifluoroethylene pre-solution refers to the mass percentage of a polyvinylidene fluoride-trifluoroethylene copolymer in a mixture of the polyvinylidene fluoride-trifluoroethylene copolymer and a solvent, the concentration of the vinylidene fluoride-trifluoroethylene pre-solution is 1-20 wt%, and the concentration of the vinylidene fluoride-trifluoroethylene pre-solution can also be 1-5 wt%, 3-8 wt%, 1-15 wt%, 5-20 wt%, 5-10 wt%, 3-10 wt%, 6-20 wt% or 15-20 wt%. Specifically, the concentration of the vinylidene fluoride-trifluoroethylene pre-solution can also be 1 wt%, 3 wt%, 5 wt%, 9 wt%, 11 wt%, 13 wt%, 15 wt%, 17 wt%, 19 wt% or 20 wt%.
In the step S2, the graphene provided may be prepared by using a chemical vapor deposition method, an epitaxial growth method, a redox method, an arc discharge method, and a substrate-free vapor phase method.
In the step S2, the concentration of the graphene suspension refers to the mass percentage of graphene in the mixture of graphene and solvent, and the concentration of the graphene suspension is 0.005-1.5 wt%, and further, the concentration of the graphene suspension may also be 0.005-0.01 wt%, 0.008-0.2 wt%, 0.03-0.05 wt%, 0.03-1 wt%, 0.01-0.03 wt%, 0.03-1.5 wt%, 0.1-0.8 wt%, or 0.9-0.5 wt%. In particular, the concentration of the graphene suspension may also be 0.005 wt%, 0.008 wt%, 0.01 wt%, 0.03 wt%, 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.5 wt%, 0.7 wt%, or 1 wt%.
In some embodiments of the present invention, the desired graphene is prepared by a redox method. The graphene is pretreated in an oxidation-reduction mode, and the graphene oxide forms functional groups among graphene sheet layers so as to be beneficial to stripping the graphene sheet layers, and then redundant functional groups are removed by using a reduction reaction. Optionally, the graphene includes an oxygen-containing functional group, and an oxygen content of the graphene is 2% to 6%. Specifically, the graphene has an oxygen content of 2%, 2.5%, 3.5%, 4%, 4.6%, 5.1%, 5.4%, 5.9%, or 6%.
Because the oxygen-containing functional group on the graphene can form a hydrogen bond with the vinylidene fluoride-trifluoroethylene copolymer, the interface interaction is enhanced, and the oxygen content and the oxygen-containing functional group of the graphene can influence the electrical, mechanical and electrochemical properties of the graphene. Specifically, the oxygen-containing functional group comprises one or a combination of carboxyl, carbonyl and hydroxyl.
In the invention, the extra dipole provided by the addition of the graphene interacts with the dipole of the vinylidene fluoride-trifluoroethylene copolymer, which contributes to the orientation of the dipole of the vinylidene fluoride-trifluoroethylene, so that the polarization effect of β crystal phase in the polarization treatment process can be improved, and the piezoelectric effect of the crystal phase can be improved.
In the step S3, the vinylidene fluoride pre-solution is mixed with the graphene suspension, and dispersed to obtain a vinylidene fluoride-trifluoroethylene/graphene solution, wherein, in the mixing process, the addition amounts of the graphene and the vinylidene fluoride may be: 0.005 g-2 g of graphene is required to be added per 100g of vinylidene fluoride. Specifically, the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.01-1%, 0.005-0.15%, 0.005-0.05%, 0.04-0.08%, 0.005-0.08% or 0.005-1.5%. Specifically, the percentage of the mass of graphene to the mass of vinylidene fluoride may be 0.005%, 0.008%, 0.01%, 0.015%, 0.03%, 0.06%, 0.08%, 0.09%, 0.1%, 0.5%, 0.6%, 0.8%, 0.9%, 1.2%, 1.5%, or 2%.
In the step S3, the mixing temperature is 20 ℃ to 30 ℃, and the vinylidene fluoride-trifluoroethylene pre-solution is mixed with the graphene suspension and dispersed to obtain a vinylidene fluoride-trifluoroethylene/graphene solution, and the mixture is dispersed to form a uniform solution so as to be coated to form a film.
In the above step S4, the substrate includes any one of ITO (indium tin oxide) glass, a silicon wafer, a copper plate, and an aluminum plate. The coating mode comprises any one of spin coating, spray coating and overall coating, the thickness of the film to be treated formed by the coating mode is 2-20 μm, specifically, the thickness of the film to be treated formed by the coating mode can also be 5-15 μm, 5-8 μm, 7-10 μm, 9-13 μm or 11-15 μm, and also can be specifically 2.5 μm, 3 μm, 4.5 μm, 5.5 μm, 6 μm, 8 μm, 9.5 μm, 12 μm, 14 μm, 15 μm or 20 μm.
Specifically, the spraying is to form a thin film on the substrate in a point spraying mode; the overall coating is to form a film on the substrate by surface spraying.
In some embodiments of the present invention, the drying process includes drying at normal temperature and normal pressure, and the drying process may further include:
and drying the film to be processed for 1-8 min at room temperature under vacuum condition to form the film to be processed.
Wherein, the standard atmospheric pressure (101.325kPa) is taken as the reference pressure, the vacuum condition of solvent volatilization can be expressed as-0.02 MPa to-0.1 MPa, and the vacuum condition of solvent volatilization can also be-0.02 MPa, -0.01 MPa or-0.1 MPa.
Under the vacuum condition of solvent volatilization, the corresponding volatilization time is 3-5 min, 1-3 min, 5-8 min, 5-15 min, 7-15 min or 10-15 min, specifically 3min, 5min, 6min, 8min, 10min, 12min, 13min or 15min, etc. Compared with the existing heating drying, the drying time is short, and the transparency of the film cannot be influenced.
The polarization processing in step S5 includes the following steps: and polarizing the film to be treated for 1min to 20min at the temperature of 20 ℃ to 30 ℃ by using the voltage of 3KV to 20 KV. Wherein the distance between the polarized electrode end and the surface of the film is 0.01-25 mm.
The above step S5 is performed based on a thin film polarization apparatus 10. As shown in fig. 2 in detail, the thin film polarization apparatus 10 includes an electric field assembly 11 and an article carrier 12, wherein the article carrier 12 is used for carrying a thin film 90 to be processed, the thin film 90 to be processed includes a first surface 901 close to the article carrier 12 and a second surface 902 far from the article carrier 12, the article carrier 12 is grounded and makes the potential of the first surface 901 of the thin film 90 to be processed zero, the electric field assembly 11 includes a high voltage electrode 111 and a low voltage electrode 112, the high voltage electrode 111 is located above the article carrier 12, the low voltage electrode 112 is located between the high voltage electrode 111 and the article carrier 12 to be processed, the high voltage electrode 111 has a higher potential than the low voltage electrode 112, and ambient gas above the article carrier 12 can be ionized by the high voltage electrode 111 and move under an electric field formed by the electric field assembly 11 and gather on the second surface 902 of the thin film 90 to be processed, an intra-film electric field is formed in the film to be processed 90 along the thickness direction of the film to be processed 90, so as to polarize the film to be processed 90.
Preferably, the low voltage electrode terminal 112 is a grid electrode terminal or a flat plate electrode terminal having a penetrating portion. The low voltage electrode end 112 can determine the electric potential of the plane where the low voltage electrode end 112 is located and homogenize the electric field where the low voltage electrode end 112 is located. The plate electrode end is provided with a penetrating part for charged ions to pass through, for example, a plurality of mutually parallel metal wires and a certain distance are arranged at intervals to form the plate electrode, and the penetrating part of the plate electrode end is formed at intervals among the plurality of metal wires. Preferably, the low voltage electrode terminal 112 is a grid electrode terminal, which is a grid electrode, wherein the area of each grid on the grid electrode is preferably 1-100 mm2, that is, when the grid is square, the side length of the grid is 1-10 mm.
Preferably, the distance between the low voltage electrode end 112 and the article carrier 12 is 0.01-25 mm. Wherein, the distance between the low voltage electrode end 112 and the article bearing platform 12 is 0.01-5 mm, 4-10 mm, 7-16 mm, 10-25 mm or 1-3 mm. Specifically, the distance between the low voltage electrode tip 112 and the article carrier 12 is 0.01mm, 0.03mm, 0.15mm, 0.3mm, 0.5mm, 0.8mm, 1mm, 1.5mm, 1.8mm, 2mm, 2.5mm, 3mm, 5mm, 8mm, 10mm, 13mm, 16mm, 18mm, 19mm or 25 mm.
In the present invention, the intra-film electric field formed in the film 90 to be processed can be better controlled by determining the distance between the low voltage electrode terminal 112 and the article carrier 12, so that the intra-film electric field is in a high and stable state.
The electric potential of the high voltage electrode end 111 can be provided by an electric potential source, and preferably, the high voltage electrode end 111 comprises needle electrodes or linear electrodes distributed in an array, which can ensure that the high electric field is obtained. Among them, the wire electrode is preferably used, which can further improve the yield, and the wire electrode is preferably 30 to 100 μm in diameter. And the distance between the high voltage electrode end 111 and the low voltage electrode end 112 is greater than the distance between the low voltage electrode end 112 and the article carrier table 12.
Specifically, the polarization treatment may be performed at, for example, 20 ℃, 22 ℃, 24 ℃, 25 ℃, 27 ℃, 28 ℃ or 30 ℃.
The polarization voltage of the corresponding low-voltage electrode end 112 can be 3 KV-10 KV, 5 KV-15 KV, 8 KV-12 KV or 17 KV-20 KV. The corresponding polarization voltage can also be 3KV, 5KV, 8KV, 12KV, 15KV, 16KV, 17KV, 19KV or 20 KV.
The time for polarization treatment can also be 5-20 min, 1-3 min, 2-6 min, 5-9 min, 8-13 min, 12-15 min or 15-20 min. Specifically, the time for performing the polarization treatment can be 2min, 5min, 6min, 8min, 10min, 11min, 13min, 15min, 16min or 20 min.
A second embodiment of the present invention provides a piezoelectric thin film, which is obtained by preparing the piezoelectric thin film according to any one of the above-mentioned piezoelectric thin film preparation methods, and the piezoelectric coefficient of the prepared piezoelectric thin film may be greater than 32 Pc/N.
Specifically, the piezoelectric film is prepared by mixing and dispersing a vinylidene fluoride pre-trifluoroethylene solution and a graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and further carrying out polarization treatment on the film to be treated to obtain the piezoelectric film.
When the vinylidene fluoride-trifluoroethylene pre-solution is mixed with the graphene suspension, the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.005% -2%, and the relevant definition of the mass percentage of the graphene to the mass of the vinylidene fluoride is consistent with that in the first embodiment. In the mass percentage of the graphene to the vinylidene fluoride, the mass percentage of the graphene to the vinylidene fluoride is the mass percentage of the pure graphene to the mass percentage of the pure vinylidene fluoride, and the ratio is 0.05%, that is, it can be understood that 0.05g of graphene is correspondingly added to 100g of vinylidene fluoride.
The vinylidene fluoride-trifluoroethylene pre-solution is obtained by dissolving a vinylidene fluoride-trifluoroethylene copolymer in a solvent.
The graphene suspension is obtained by dissolving graphene in a solvent. The specific limitations regarding the manufacturing process are consistent with the specific step limitations in the first embodiment described above and are not limited herein.
In the invention, the adopted vinylidene fluoride-trifluoroethylene raw material is a vinylidene fluoride-trifluoroethylene copolymer, and compared with vinylidene fluoride, a trifluoroethylene copolymerization unit introduced by the vinylidene fluoride-trifluoroethylene copolymer can provide certain steric hindrance, so that the vinylidene fluoride is forced to be adjusted to an all-trans conformation, and an β crystal phase is more easily formed.
Further introducing graphene, and because oxygen-containing functional groups contained in the graphene can form hydrogen bonds with the vinylidene fluoride-trifluoroethylene copolymer, the interface interaction is enhanced; meanwhile, the addition of the graphene can provide additional dipoles which interact with the dipoles of the vinylidene fluoride-trifluoroethylene copolymer, so that the orientation of the dipoles of the vinylidene fluoride-trifluoroethylene is facilitated, and the piezoelectric effect of the prepared piezoelectric film is improved.
In the invention, in order to better show that the piezoelectric performance of the piezoelectric film prepared by the piezoelectric film preparation method is superior, the invention further provides the following experimental group and comparison group:
experimental group 1: providing a vinylidene fluoride-trifluoroethylene copolymer, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent N, N-dimethyl amide to form a vinylidene fluoride-trifluoroethylene pre-solution, wherein the concentration of the vinylidene fluoride-trifluoroethylene pre-solution is 5 wt%, and the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer is 80/20;
providing graphene, and dissolving the graphene in a solvent N, N-dimethyl amide to form a graphene suspension with the concentration of 0.1 wt%, wherein the oxygen content of the graphene is 4%, the oxygen-containing functional groups of the graphene are hydroxyl and carboxyl, and the graphene is a single-layer graphene layer stripped through redox operation;
mixing and dispersing a vinylidene fluoride-trifluoroethylene pre-solution and a graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution, wherein the mass of graphene accounts for 0.01% of that of the vinylidene fluoride in the mixing process;
coating the vinylidene fluoride-trifluoroethylene/graphene solution on ITO glass, and drying under room temperature and vacuum conditions (-0.1 MPa) to form a film to be treated, wherein the thickness of the film to be treated is 10 microns;
and (3) placing the thin film to be processed in an environment with the temperature of 25 ℃, and carrying out polarization processing for 5min by using the voltage of 15KV to obtain the piezoelectric thin film, wherein the distance between the polarization grid and the surface of the thin film is 2 mm.
Experimental group 2: it differs from the above experimental group 1 in that: the solvent for preparing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension is N, N-dimethyl pyrrolidone and N, N-dimethyl amide in a mass ratio of 1: 1, preparing a mixed solution.
Experimental group 3: it differs from the above experimental group 1 in that: the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer was 60/40.
Experimental group 4: it differs from the above experimental group 1 in that: vinylidene fluoride-trifluoroethylene pre-solution with the concentration of 20%.
Experimental group 5: it differs from the above experimental group 1 in that: the concentration of the graphene suspension was 1 wt%.
Experimental group 6: it differs from the above experimental group 1 in that: the oxygen content of the graphene is 2%.
Experimental group 7: it differs from the above experimental group 1 in that: the oxygen content of the graphene is 6%.
Experimental group 8: it differs from the above experimental group 1 in that: the oxygen-containing functional group includes a carboxyl group and a carbonyl group.
Experimental group 9: it differs from the above experimental group 1 in that: the thickness of the film to be treated was formed to be 5 μm.
Experimental group 10: it differs from the above experimental group 1 in that: the thickness of the film to be treated was 15 μm.
Experimental group 11: it differs from the above experimental group 1 in that: the substrate is a silicon wafer.
Experimental group 12: it differs from the above experimental group 1 in that: the drying treatment is natural drying treatment at normal temperature and normal pressure.
Experimental group 13: it differs from the above experimental group 1 in that: and carrying out polarization treatment on the film to be treated for 5min by using a 3KV voltage to obtain the piezoelectric film, wherein the distance between the polarization grid and the surface of the film is 1 mm.
Experimental group 14: it differs from the above experimental group 1 in that: and carrying out polarization treatment on the film to be treated for 5min by using a voltage of 20KV to obtain the piezoelectric film, wherein the distance between the polarization grid and the surface of the film is 3 mm.
Experimental group 15: it differs from the above experimental group 1 in that: and carrying out polarization treatment on the film to be treated for 5min by using a voltage of 3.5KV to obtain the piezoelectric film.
Experimental group 16: it differs from the above experimental group 1 in that: and carrying out polarization treatment on the film to be treated for 5min by using a voltage of 19.5KV to obtain the piezoelectric film.
Experimental group 17: it differs from the above experimental group 1 in that: the time for the polarization treatment was 10 min.
Comparative group 1: mixing vinylidene fluoride powder and graphene powder according to a mass ratio of 99: 1, adding the mixed material into a high-speed mixer for mechanical mixing to obtain a mixed material, and further adding the mixed material into a rheometer with the temperature of 200 ℃ and the rotating speed of 60r/min for melting and mixing for 15min to obtain a vinylidene fluoride/1% graphene composite material; placing the vinylidene fluoride/1% graphene composite material under a voltage of 220V, heating to 200 ℃, adjusting the voltage to 100V, keeping the temperature at about 200 ℃ for 10min, keeping the vinylidene fluoride/1% graphene composite material in a molten state, continuously raising the voltage to 175V, and adding a pre-pressure of 150MPa to obtain a high-pressure sample of the vinylidene fluoride/1% graphene composite material.
Comparative group 2: providing a vinylidene fluoride-trifluoroethylene copolymer with a copolymerization ratio of 80/20, dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent N, N-dimethyl amide to form a solution with the concentration of 5 wt%, and coating the solution on the ITO glass to form a film to be tested.
Comparative group 3: the differences from the above comparative group 2 are: and (3) placing the thin film formed on the ITO glass in an environment with the temperature of 25 ℃, carrying out polarization treatment for 5min by using the voltage of 15KV, and carrying out planning treatment to obtain the piezoelectric thin film, wherein the distance between a polarization grid and the surface of the thin film is 2 mm.
Comparative group 4: it differs from the above experimental group 1 in that: the film to be treated after drying treatment is the film to be measured, and polarization treatment is not needed.
Comparative group 5: it differs from the above experimental group 1 in that: the specific steps of carrying out polarization treatment on the film to be treated are as follows: and polarizing the film to be processed for 30min at the voltage of 2KV, wherein other specific steps are unchanged.
Comparative group 6: it differs from the above experimental group 1 in that: the specific steps of carrying out polarization treatment on the film to be treated are as follows: and polarizing the film to be processed for 1min at the voltage of 30KV, wherein other specific steps are unchanged.
Comparative group 7: it differs from the above experimental group 1 in that: the specific steps of carrying out polarization treatment on the film to be treated are as follows: heating to 200 ℃ under the experimental pressure of 400Mpa, keeping the temperature for 30min, and obtaining the piezoelectric film by utilizing heating polarization.
The films obtained in the above experimental groups 1 to 17 and comparative groups 1 to 7 were placed in a quasi-static D model ZJ-633The piezoelectric coefficient data detection is performed in the piezoelectric instrument, and the following detection data is obtained, and the corresponding detection data is summarized as the following table 1:
TABLE 1 comparison of results of piezoelectric coefficient test of films obtained in Experimental groups 1 to 17 and comparative groups 1 to 7
Based on the contents in table 1, it can be seen that, in the above experimental groups 1 to 17, compared to the case where vinylidene fluoride is used as a raw material alone, the trifluoroethylene copolymerization unit introduced into the vinylidene fluoride-trifluoroethylene copolymer can provide a certain steric hindrance, so that the vinylidene fluoride is forced to be adjusted to an all-trans conformation, and an β crystal phase is more easily formed.
The graphene is introduced, and oxygen-containing functional groups of the graphene can form hydrogen bonds with the vinylidene fluoride-trifluoroethylene copolymer, so that the interface interaction is enhanced; meanwhile, the addition of the graphene can provide additional dipoles, so that the orientation of the vinylidene fluoride-trifluoroethylene copolymer is consistent, and the piezoelectric effect of the vinylidene fluoride-trifluoroethylene copolymer is improved.
And when the thin film to be processed is polarized, the dipoles of the vinylidene fluoride-trifluoroethylene copolymer tend to be polarized, so that the piezoelectric effect of the prepared vinylidene fluoride-trifluoroethylene copolymer/graphene piezoelectric thin film is further improved.
Further comparing the experimental group 1 and the comparison groups 2-4, wherein the comparison group 2 and the comparison group 3 are two films obtained before and after polarization, the piezoelectric coefficients are 4pc/N and 23pc/N, and the comparison group 4 is based on the deformation of the experimental group 1, wherein the comparison group 4 is a film provided in the experimental group 1 and not before polarization, and the piezoelectric coefficients of the experimental group 1 and the comparison group 4 are 6.5pc/N and 34.1pc/N, which shows that the piezoelectric effect is greatly improved after adding graphene and performing polarization treatment.
In order to further verify that the piezoelectric film prepared by the preparation method of the piezoelectric film provided by the invention has better performance, the films obtained by the experimental group 1 and the comparative group 7 are further detected based on GB 2410-80 transparent plastic transmittance and haze test method to obtain the transmittance and haze of the corresponding piezoelectric film.
Among them, the transmittance of the experimental group 1 was 93%, and the transmittance of the comparative group 7 was only 90%.
Therefore, by utilizing the polarization method provided by the invention, better film light transmittance can be obtained.
Further, ultrathin sections of the piezoelectric thin films prepared and obtained based on the experimental group provided by the present invention are observed by a transmission electron microscope, and the dispersion condition of the graphene in the polyvinylidene fluoride-trifluoroethylene copolymer and the presence or absence of agglomeration can be observed by a TEM image, and specific TEM images can be seen in fig. 3A, fig. 3B, fig. 3C and fig. 3D.
The piezoelectric film corresponding to fig. 3A is prepared by the method described in experimental group 1, and the piezoelectric films corresponding to fig. 3B, 3C, and 3D are obtained by adjusting the mass of the graphene to 0.05%, 0.1%, and 0.5% of the mass of the vinylidene fluoride on the basis of experimental group 1.
As can be seen from the above four figures, the reduced graphene oxide sheets (black sheet structure in the figure) are uniformly dispersed in the vinylidene fluoride-trifluoroethylene matrix (floccules in the figure), so as to form an intercalation network structure, which can enhance the piezoelectric performance of the vinylidene fluoride-trifluoroethylene. Meanwhile, as the content of the reduced graphene oxide increases, as shown in fig. 3A, 3B, 3C and 3D, the percentage of the mass of the graphene to the mass of the vinylidene fluoride is respectively 0.01%, 0.05%, 0.1% and 0.5%, and it can be seen from the figure that as the addition ratio of the graphene increases, the dispersibility of the graphene in the vinylidene fluoride-trifluoroethylene matrix gradually decreases, and the agglomeration phenomenon occurs.
Compared with the prior art, the piezoelectric film and the preparation method thereof provided by the invention have the following beneficial effects:
the invention provides a preparation method of a piezoelectric film, which comprises the following steps: providing a vinylidene fluoride-trifluoroethylene copolymer, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in a solvent to form a vinylidene fluoride-trifluoroethylene pre-solution; providing graphene, and dissolving the graphene in a solvent to form a graphene suspension; mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and further carrying out polarization treatment on the film to be treated to obtain the required piezoelectric film. Based on the preparation method, the piezoelectric film with the piezoelectric coefficient larger than 32pc/N can be obtained, the preparation method is high in preparation process efficiency, the performance of the prepared piezoelectric film is good, and the power-electricity conversion capability of the piezoelectric film is remarkably improved.
In the invention, the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer is 90/10-50/50; wherein, in the mixing process, the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.005-2%; the concentration of the vinylidene fluoride-trifluoroethylene pre-solution is 1-20 wt%, the concentration of the graphene suspension is 0.005-1.5 wt%, and the solvent comprises any one or a combination of more of butanone, N-dimethyl pyrrolidone and N, N-dimethyl amide. The further limitation of the vinylidene fluoride-trifluoroethylene copolymer and the graphene can improve the piezoelectric property of the piezoelectric film prepared by the piezoelectric film preparation method. The dispersion degree of the graphene in the vinylidene fluoride-trifluoroethylene can be further improved by respectively premixing and then mixing, and the piezoelectric performance of the film is prevented from being influenced by agglomeration of the graphene.
In the invention, the graphene comprises an exfoliated graphene sheet layer, the graphene comprises an oxygen-containing functional group, and the oxygen content of the graphene is 2-6%. By limiting the oxygen content, the number of hydrogen bonds formed between the vinylidene fluoride-trifluoroethylene copolymer and the oxygen-containing functional group after the graphene is added can be further increased.
In the invention, the oxygen-containing functional group comprises one or a combination of carboxyl, carbonyl and hydroxyl. Based on different oxygen-containing functional groups, more types of interaction dipoles can be provided for the vinylidene fluoride-trifluoroethylene copolymer, so that the orientation of the dipoles of the vinylidene fluoride-trifluoroethylene copolymer can be better changed, and the piezoelectric effect can be provided.
In the present invention, the graphene further includes a C-O dipole matched to the dipole of the vinylidene fluoride-trifluoroethylene copolymer. To assist in the orientation of the dipoles of the vinylidene fluoride-trifluoroethylene copolymer, thereby providing the piezoelectric effect.
In the invention, the coating mode comprises any one of spin coating, spray coating and overall coating; the thickness of the formed film to be treated is 2-20 μm. The thickness of the coating film has great influence on the effect of polarization treatment, and the piezoelectric film preparation method provided by the invention can prepare and obtain a film with smaller thickness.
In the present invention, the substrate includes any one of ITO glass, a silicon wafer, a copper plate, and an aluminum plate. The substrate is selected to match with the coating mode, so that the uniformity and the flatness of the film formed by coating can be improved, and the piezoelectric effect of the piezoelectric film can be further improved.
In the present invention, the drying process specifically includes the steps of: and drying the film to be processed at room temperature under vacuum condition to form a dried film. Vacuum drying is adopted, and compared with heating drying, the time is short, and the transparency of the prepared film is better.
In the present invention, the polarization specifically comprises the steps of: and polarizing the film to be processed for 1-20 min at 20-30 ℃ by using a voltage of 3-20 KV, wherein the distance between the polarizing grid and the surface of the film is 1-3 mm. By using high-voltage polarization, heating is not needed, polarization can be completed in a short time, and the polarization efficiency can be improved.
The invention also provides a piezoelectric film, which is prepared by mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and further carrying out polarization treatment on the film to be treated to obtain the piezoelectric film, wherein the piezoelectric coefficient of the piezoelectric film is greater than 32pc/N, and the piezoelectric film has excellent transparency and wide application range.
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 and improvements made within the spirit of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A piezoelectric film preparation method is characterized in that: which comprises the following steps:
providing a vinylidene fluoride-trifluoroethylene copolymer and a solvent, and dissolving the vinylidene fluoride-trifluoroethylene copolymer in the solvent to form a vinylidene fluoride-trifluoroethylene pre-solution; providing graphene, and dissolving the graphene in a solvent to form a graphene suspension; mixing and dispersing the vinylidene fluoride-trifluoroethylene pre-solution and the graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; and carrying out polarization treatment on the film to be treated to obtain the required piezoelectric film.
2. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the copolymerization ratio of the vinylidene fluoride-trifluoroethylene copolymer is 90/10-50/50; wherein the mass percentage of the graphene to the mass of the vinylidene fluoride is 0.005-2%.
3. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the concentration of the vinylidene fluoride-trifluoroethylene pre-solution is 1-20 wt%, the concentration of the graphene suspension is 0.005-1.5 wt%, and the solvent comprises any one or a combination of more of butanone, N-dimethyl pyrrolidone and N, N-dimethyl amide.
4. A method for manufacturing a piezoelectric thin film as claimed in claim 3, wherein: the graphene comprises an exfoliated graphene sheet layer, the graphene comprises an oxygen-containing functional group, and the oxygen content of the graphene is 2% -6%.
5. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the oxygen-containing functional group comprises one or a combination of more of carboxyl, carbonyl and hydroxyl; the graphene further includes a C-O dipole that matches the dipole of the vinylidene fluoride-trifluoroethylene copolymer.
6. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the coating mode comprises any one of spin coating, spray coating and overall coating; the thickness of the formed film to be treated is 2-20 μm.
7. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the substrate comprises any one of ITO glass, a silicon wafer, a copper plate and an aluminum plate.
8. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the drying treatment specifically comprises the following steps: and drying the film to be processed for 1-8 min at room temperature under vacuum condition to form a dried film.
9. The method for manufacturing a piezoelectric thin film as claimed in claim 1, wherein: the polarization treatment specifically comprises the following steps: and (3) polarizing the film to be treated for 1-20 min at the temperature of 20-30 ℃ by using a voltage of 3-20 KV, wherein the distance between the polarized electrode end and the surface of the film is 0.01-25 mm.
10. A piezoelectric film, characterized in that: mixing and dispersing a vinylidene fluoride pre-solution and a graphene suspension to obtain a vinylidene fluoride-trifluoroethylene/graphene solution; coating the vinylidene fluoride-trifluoroethylene/graphene solution on a substrate, and drying to form a film to be treated; further carrying out polarization treatment on the film to be treated to obtain the piezoelectric film; the piezoelectric coefficient of the piezoelectric film is larger than 32 pc/N.
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