A preparation method of a BTO@PDMS fiber film

Abstract

The application relates to a preparation method of a BTO@PDMS fiber film, which comprises the following steps: in an ethanol solution, surface-modifying barium titanate nanoparticles with a vinyl silane coupling agent, ultrasonic dispersion of the barium titanate nanoparticles and polydimethylsiloxane prepolymer in n-hexane, reaction in the presence of tetrahydrofuran and a polydimethylsiloxane curing agent to obtain a BTO@PDMS core material solution; coaxial electrospinning of the BTO@PDMS core material solution and a PVP shell layer solution, aluminum foil paper collection, and PVP / BTO@PDMS fiber film obtaining; after stripping the PVP / BTO@PDMS fiber film from the aluminum foil paper, high-temperature crosslinking and curing and anhydrous ethanol washing are sequentially performed to obtain the BTO@PDMS fiber film. The vinyl silane coupling agent is used for surface modification of the barium titanate nanoparticles, the dispersibility of the barium titanate nanoparticles in the polydimethylsiloxane is improved, and the high-voltage electric field in the electrospinning is used to make the barium titanate internal dipole complete a step polarization from disorder to order in the preparation process of the film, so that the BTO@PDMS fiber film with piezoelectric properties is obtained.

Description

Technical Field

[0001] This invention relates to the technical field of piezoelectric thin films, and in particular to a method for preparing BTO@PDMS fiber films. Background Technology

[0002] With rapid industrialization and the increasing depletion of fossil fuels, people are forced to explore green energy sources to address the current energy crisis. Piezoelectric materials, based on the piezoelectric effect, have been widely studied in the field of mechanical energy harvesting due to their ability to convert mechanical energy into electrical energy. Currently, extensive research focuses on combining piezoelectric materials with high piezoelectric properties with flexible polymers to develop high-performance flexible piezoelectric sensors by leveraging the advantages of both. Barium titanate, with its high piezoelectric constant, low dielectric constant, and non-toxicity, is considered an ideal filler for preparing flexible piezoelectric sensors. However, directly doping piezoelectric nanoparticles into polymers currently leads to problems such as nanoparticle aggregation and uneven dispersion. Chemically modifying piezoelectric nanoparticles and bonding them to polymers through chemical bonds can effectively improve the aggregation problem. This not only benefits the flexibility of the film but also enhances its application flexibility in wearable devices.

[0003] Chinese Patent CN113150554B discloses a PDMS-based flexible energy storage composite membrane. The membrane uses PDMS as the matrix and inorganic dielectric nanoparticles or nanowires as fillers. The inorganic dielectric nanoparticles are barium titanate or barium strontium titanate nanoparticles, and the inorganic dielectric nanowires are also barium titanate or barium strontium titanate nanowires. When the filler is inorganic dielectric nanoparticles, the mass ratio of the filler to PDMS is 1:19 to 1:4; when the filler is inorganic dielectric nanowires, the mass ratio is 1:39 to 1:9. This flexible energy storage composite membrane, using PDMS as the matrix and inorganic dielectric nanomaterials as fillers, possesses both high energy storage density and ultra-high energy storage efficiency. In particular, when barium titanate nanoparticles are used as fillers, the energy storage density of PDMS reaches as high as 7.1 J / cm³. 3 The energy storage efficiency can reach up to 99%; when using barium strontium titanate nanowires as filler, its energy storage density reaches as high as 11.7 J / cm³. 3 At the same time, it can maintain an ultra-high energy storage efficiency of 99%.

[0004] Although the aforementioned PDMS-based flexible energy storage composite membranes have made some progress in improving energy storage density and efficiency, some problems still exist in practical applications. For example, due to the poor dispersion of barium titanate nanoparticles in the PDMS matrix, the piezoelectric and mechanical properties of the composite membrane cannot reach their optimal levels. Furthermore, the existing technology does not fully consider the impact of nanoparticle surface modification on the piezoelectric properties of the composite membrane, which limits the application potential of PDMS-based composite membranes in developing high-performance flexible piezoelectric sensors. Barium titanate has three crystal structures: orthorhombic, tetragonal, and cubic. The orthorhombic phase is a stable structure at room temperature but has no piezoelectric effect. The tetragonal and cubic phases are high-temperature phases; the tetragonal phase transforms into the cubic phase near the Curie temperature of approximately 120°C. The cubic phase mainly exhibits ferroelectric properties and weak piezoelectric properties. Only barium titanate with a tetragonal crystal structure possesses excellent piezoelectric properties at room temperature. Therefore, flexible piezoelectric sensors based on barium titanate with a tetragonal crystal structure can exhibit high piezoelectric performance.

[0005] Chinese Patent Publication No. CN116330773A discloses a method for preparing a composite nanogenerator for an intelligent monitoring system, comprising the following steps: S1: preparing barium titanate nanowires (BTO Ncs) via a two-step hydrothermal method and subjecting them to hydroxylation treatment to obtain hydroxylated barium titanate nanowires; S2: mixing the hydroxylated barium titanate nanowires obtained in step S1 with carboxylated carbon nanotubes, PVDF, and PDMS, and electrospinning to prepare a PVDF / PDMS-BTO-CNT nanofiber film; S3: sequentially bonding a PI film, copper tape, and the PVDF / PDMS-BTO-CNT nanofiber film obtained in step S2, and then attaching the PI film to the inside of a rubber hose to assemble the composite nanogenerator. In the above electrospun nanofiber film, the barium titanate nanowires are arranged approximately coaxially around the carbon nanotubes. The charge generated by triboelectricity helps to promote the polarization of dipoles inside the nanofiber film, thereby enhancing the piezoelectric properties, which in turn enhances the output of the composite nanogenerator. Therefore, its performance when used as a composite nanogenerator is better than the sum of its performance when used as a triboelectric nanogenerator and a piezoelectric nanogenerator.

[0006] The shortcomings of the aforementioned existing technologies lie in the fact that while the fabrication methods of composite nanogenerators improve piezoelectric performance to some extent, the fabrication process is complex, involving the mixing of multiple materials and multi-step processing, which not only increases production costs but also reduces production efficiency. Furthermore, the combination of multiple materials may lead to compatibility issues, affecting the stability and reliability of the composite nanogenerator. Currently, the polarization methods for inducing piezoelectric effects in flexible piezoelectric films mainly include electric field polarization, pressure polarization, and thermal polarization. Among these, pressure polarization and thermal polarization are relatively simple, but they can lead to stress concentration, film damage, or interface defects in the film. Electric field polarization, on the other hand, is highly controllable, efficient, and does not introduce stress that causes damage, thus it is widely used. However, the corona polarization method based on electric fields suffers from high energy consumption, long processing time, and susceptibility to electrical breakdown of the film. Summary of the Invention

[0007] The problem this invention aims to solve is to provide a method for preparing BTO@PDMS fiber films that addresses the aforementioned shortcomings of existing technologies. This method primarily addresses the limitations of piezoelectric particle dispersion in flexible polymers, high energy consumption during high-voltage polarization, and cumbersome procedures that restrict further applications. It employs a vinyl silane coupling agent to surface-modify barium titanate nanoparticles, improving their dispersion in polydimethylsiloxane. Furthermore, it utilizes a high-voltage electric field during electrospinning to achieve a one-step polarization process during film preparation, transforming the disordered dipoles within the barium titanate into an ordered arrangement, thus obtaining a BTO@PDMS fiber film with piezoelectric properties.

[0008] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0009] A method for preparing a BTO@PDMS fiber film includes the following steps:

[0010] In hydrogen peroxide, tetragonal barium titanate nanoparticles undergo a hydroxylation reaction. After the reaction is completed, post-treatment is performed to obtain surface-hydroxylated barium titanate nanoparticles.

[0011] In S2, the surface-hydroxylated barium titanate nanoparticles obtained in S1 are surface-modified under the action of a vinyl silane coupling agent in an ethanol solution. After modification, they are post-treated to obtain vinyl-modified barium titanate nanoparticles.

[0012] S3 involves ultrasonically dispersing the polydimethylsiloxane prepolymer and the vinyl-modified barium titanate nanoparticles obtained in S2 in n-hexane, and then reacting them in the presence of tetrahydrofuran and polydimethylsiloxane curing agent to obtain a BTO@PDMS core material solution.

[0013] S4 mixes anhydrous ethanol and polyvinylpyrrolidone to obtain a PVP shell solution;

[0014] S5 involves coaxial electrospinning of the BTO@PDMS core solution obtained in S3 and the PVP shell solution obtained in S4, and collecting them using aluminum foil to obtain a PVP / BTO@PDMS fiber film.

[0015] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is then subjected to high-temperature crosslinking curing and washing with anhydrous ethanol to obtain the BTO@PDMS fiber film.

[0016] Furthermore, in S1, the concentration of hydrogen peroxide is 70-80 wt%, and the ratio of hydrogen peroxide to tetragonal barium titanate nanoparticles is controlled to be 150-250 mL: 10-20 g.

[0017] Further, in S1, tetragonal barium titanate nanoparticles are first ultrasonically dispersed in hydrogen peroxide, and the dispersion time is controlled to be 25-35 min. Then, a hydroxylation reaction occurs, and the reaction temperature is controlled to be 100-110℃, the stirring speed is 700-900 r / min, and the reaction time is 5-7 h.

[0018] Further, in S2, the concentration of the ethanol solution is 70-80 wt%, and the ratio of the amount of ethanol solution, hydroxylated barium titanate nanoparticles and vinyl silane coupling agent is controlled to be 40-80 mL: 2.0-3.0 g: 1.5-2.5 g.

[0019] Further, in S2, the hydroxylated barium titanate nanoparticles and vinyl silane coupling agent are first ultrasonically dispersed in an ethanol solution, and the dispersion time is controlled to be 25-35 min. Then, surface modification is carried out, and the reaction temperature is controlled to be 70-80℃, the stirring speed is 700-900 r / min, and the reaction time is 15-17 h.

[0020] Furthermore, in S1 and S2, the post-treatment includes centrifugal washing with anhydrous ethanol 2-3 times and vacuum drying.

[0021] Further, in S3, the ratio of polydimethylsiloxane prepolymer, vinyl-modified barium titanate nanoparticles, polydimethylsiloxane curing agent and tetrahydrofuran is controlled to be 4.0~6.0g:0.50~0.60g:0.40~0.60g:0.4~0.6mL, and the concentration of BTO@PDMS core material solution is 8~12wt%.

[0022] Furthermore, in S3, the dispersion time is first controlled to be 25-35 min, the reaction temperature is controlled to be 30-50℃, the stirring speed is 500-700 r / min, and the reaction time is 1-2 h.

[0023] Further, in S4, the molecular weight of polyvinylpyrrolidone is 1200~1400kDa, the ratio of anhydrous ethanol to polyvinylpyrrolidone is controlled to be 15~20mL:1.5~2.0g, and the concentration of the PVP shell solution is 12~18wt%.

[0024] Furthermore, in step S4, the mixing temperature is controlled at 60~80℃, the stirring speed is 700~900r / min, and the stirring time is 1~3h.

[0025] Furthermore, in S5, the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15 cm, the injection rate of the BTO@PDMS core solution is 0.8~1.2 mL / h, the injection rate of the PVP shell solution is 2.0~2.8 mL / h, the rotation speed of the roller collector is 100~150 r / min, the positive electrode of the electrospinning machine is +13 kV and the negative electrode is -2 kV, the electrospinning temperature is 20~40℃, and the ambient humidity is 40~50%.

[0026] Furthermore, in S5, after electrospinning begins, a Taylor cone-shaped microjet can be observed under direct light. After the jet stabilizes, the direct light is turned off, and electrospinning continues for 2-3 hours.

[0027] Furthermore, in S6, the cross-linking curing temperature is controlled at 100~120℃, and the cross-linking curing time is 10~15h.

[0028] Specifically, the method includes the following steps:

[0029] S1 First, add 10-20g of tetragonal barium titanate nanoparticles (BTO NPs) to 150-250mL of 70-80wt% hydrogen peroxide (reaction solvent), and ultrasonically disperse for 25-35min. Then, set up a reflux reaction apparatus, control the oil bath temperature at 100-110℃, the stirring speed at 700-900r / min, and the reaction time at 5-7h. After the reaction, centrifuge and wash 2-3 times with anhydrous ethanol, and vacuum dry to obtain surface-hydroxylated barium titanate nanoparticles (BTO-OH NPs).

[0030] S2 is prepared by first adding 2.0-3.0g of the hydroxylated barium titanate nanoparticles (BTO-OH NPs) obtained in S1 and 1.5-2.5g of vinyl silane coupling agent (KH-171, vinyltrimethoxysilane) to 40-80mL of 70-80wt% ethanol solution (reaction solvent). The mixture is then ultrasonically dispersed for 25-35min. A reflux reaction apparatus is then constructed, and the oil bath temperature is controlled at 70-80℃, the stirring speed at 700-900r / min, and the reaction time at 15-17h. After the reaction is completed, the mixture is centrifuged and washed 2-3 times with anhydrous ethanol and then vacuum dried to obtain vinyl-modified barium titanate nanoparticles (BTO NPs@SCA).

[0031] S3 first adds 0.50-0.60g of the vinyl-modified barium titanate nanoparticles (BTO NPs@SCA) obtained in S2 to 4.0-6.0g of polydimethylsiloxane prepolymer (PDMS prepolymer, not limited to, for example, high molecular weight end-group vinyl polydimethylsiloxane), and 1.0-2.0mL of n-hexane (dispersant), and ultrasonically disperses for 25-35min. Then, 0.40-0.60g of polydimethylsiloxane curing agent (PDMS curing agent, not limited to, for example, DBP) and 0.4-0.6mL of tetrahydrofuran (THF, reaction solvent) are added. Then, a stirring reaction device is set up, and the oil bath temperature is controlled at 30-50℃, the stirring speed is 500-700r / min, and the reaction time is 1-2h. After the reaction is completed, a 10wt% BTO@PDMS core material solution is obtained.

[0032] S4 First, add 1.5-2.0g of polyvinylpyrrolidone (PVP) powder with a concentration of 1200-1400kDa to 15-20mL of anhydrous ethanol (AE, reaction solvent). Then, set up a stirring and mixing device, control the oil bath temperature at 60-80℃, the stirring speed at 700-900r / min, and the stirring time at 1-3h to obtain a PVP shell solution.

[0033] In step S5, a 5mL syringe is used to draw 8-12wt% of the BTO@PDMS core solution obtained in step S3 and 12-18wt% of the PVP shell solution obtained in step S4, respectively. A 15G / 21G coaxial electrospinning needle is attached to the syringe. The syringe is then mounted on the fixed platform of the electrospinning machine. Aluminum foil is used to collect the solution at the roller collector end of the electrospinning machine, and the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm. The injection rate of the BTO@PDMS core solution is 0.8-1.2mL / h, and the injection rate of the PVP shell solution is 2.0mL / h. The electrospinning rate was ~2.8 mL / h, the rotation speed of the drum collector was 100~150 r / min, a +13 kV voltage was applied to the positive electrode and a -2 kV voltage was applied to the negative electrode of the electrospinning machine, the electrospinning temperature was 20~40℃, and the ambient humidity was 40~50%. Then, electrospinning was started, and Taylor cone-shaped micro-jet could be observed under direct light. After the jet stabilized (there are three main types of instability in electrospinning: viscous instability, axisymmetric flexural instability, and non-axisymmetric tortuosity instability), the direct light was turned off, and electrospinning was continued for 2~3 hours to obtain PVP / BTO@PDMS fiber film.

[0034] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is first placed in an oven and baked at 100~120℃ for 10~15h to ensure that polydimethylsiloxane (PDMS) can be fully crosslinked and cured. Then, the cured PVP / BTO@PDMS fiber film is washed multiple times with anhydrous ethanol until the PVP shell is removed to obtain BTO@PDMS fiber film.

[0035] Preferably, the method includes the following steps:

[0036] S1 First, 15g of tetragonal barium titanate nanoparticles (BTONPs) were added to 200mL of 75wt% hydrogen peroxide (reaction solvent) and ultrasonically dispersed for 30min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 105℃, the stirring speed at 800r / min, and the reaction time was 6h. After the reaction was completed, the nanoparticles were washed three times by centrifugation with anhydrous ethanol and vacuum dried to obtain surface-hydroxylated barium titanate nanoparticles (BTO-OH NPs).

[0037] S2 was first prepared by adding 2.5g of the hydroxylated barium titanate nanoparticles (BTO-OH NPs) obtained in S1 and 2g of vinyl silane coupling agent (KH-171, vinyltrimethoxysilane) to 50mL of 80wt% ethanol solution (reaction solvent). The mixture was ultrasonically dispersed for 30min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 75℃, the stirring speed at 800r / min, and the reaction time was 16h. After the reaction was completed, the mixture was centrifuged and washed three times with anhydrous ethanol, and then vacuum dried to obtain vinyl-modified barium titanate nanoparticles (BTONPs@SCA).

[0038] S3 first adds 0.55g of the vinyl-modified barium titanate nanoparticles (BTO NPs@SCA) obtained in S2 and 1.5mL of n-hexane (dispersant) to 5g of polydimethylsiloxane prepolymer (PDMS prepolymer, not limited to, for example, high molecular weight end-group vinyl polydimethylsiloxane), and ultrasonically disperses for 30min. Then, 0.5g of polydimethylsiloxane curing agent (PDMS curing agent, not limited to, for example, DBP) and 0.5mL of tetrahydrofuran (THF, reaction solvent) are added. Then, a stirring reaction device is set up, and the oil bath temperature is controlled at 40℃, the stirring speed is 600r / min, and the reaction time is 1h. After the reaction is completed, a 10wt% BTO@PDMS core material solution is obtained.

[0039] The mass-to-volume ratio of polydimethylsiloxane prepolymer, polydimethylsiloxane curing agent and tetrahydrofuran is controlled to be 10g:1g:1mL.

[0040] S4 First, add 1.8g of 1300kDa polyvinylpyrrolidone (PVP) powder to 16mL of anhydrous ethanol (AE, reaction solvent), then build a stirring and mixing device, and control the oil bath temperature at 70℃, the stirring speed at 800r / min, and the stirring time at 2h to obtain a PVP shell solution.

[0041] S5 First, using a 5mL syringe, draw up the 10wt% BTO@PDMS core solution obtained in S3 and the 15wt% PVP shell solution obtained in S4, respectively. The syringe is fitted with a 15G / 21G coaxial electrospinning needle. The syringe is then mounted on the fixed platform of the electrospinning machine. Aluminum foil is used to collect the solution at the roller collector end of the electrospinning machine, and the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm. The injection rate of the BTO@PDMS core solution is 1.0mL / h, and the injection rate of the PVP shell solution is 2... The electrospinning rate was 0.4 mL / h, the rotation speed of the drum collector was 120 r / min, a voltage of +13 kV was applied to the positive electrode and a voltage of -2 kV was applied to the negative electrode of the electrospinning machine, the electrospinning temperature was 30℃, and the ambient humidity was 40~50%. Then the electrospinning was started, and Taylor cone-shaped micro-jet could be observed under direct light. After the jet stabilized (there are three main types of instability in electrospinning: viscous instability, axisymmetric flexural instability, and non-axisymmetric tortuosity instability), the direct light was turned off, and the electrospinning was carried out for 2 hours to obtain PVP / BTO@PDMS fiber film.

[0042] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is first placed in an oven and baked at 110°C for 12 hours to ensure that polydimethylsiloxane (PDMS) can be fully crosslinked and cured. Then, the cured PVP / BTO@PDMS fiber film is washed multiple times with anhydrous ethanol until the PVP shell is removed to obtain the BTO@PDMS fiber film.

[0043] Preferably, in the BTO@PDMS fiber film, the BTO@PDMS fibers are of uniform thickness and exhibit the 3D network structure unique to electrospinning. The fibers in the BTO@PDMS fiber form a three-dimensional multi-space structure, which is beneficial for stress concentration between fibers under load and for the output of piezoelectric charge.

[0044] In summary, the beneficial technical effects of the present invention are as follows:

[0045] This invention uses a vinyl silane coupling agent to modify the surface of barium titanate nanoparticles, thereby improving their dispersibility in polydimethylsiloxane.

[0046] By using coaxial electrospinning technology containing 10wt% BTO@PDMS core material solution and 15wt% PVP shell solution, this invention achieves the ordered arrangement of dipoles inside barium titanate under the action of a high voltage electric field, thereby completing the polarization process in one step and significantly enhancing the piezoelectric properties of BTO@PDMS fiber films.

[0047] By removing the PVP shell through a high-temperature crosslinking and curing reaction and a cleaning process with anhydrous ethanol, the BTO@PDMS fiber film prepared by this invention exhibits low Young's modulus, excellent piezoelectric constant and outstanding piezoelectric properties, making it an ideal material for preparing flexible piezoelectric sensors.

[0048] The BTO@PDMS fiber film prepared by this invention can be directly coated with electrodes and encapsulated into a piezoelectric flexible sensor that does not require an additional power source, and its application fields are extremely wide. Attached Figure Description

[0049] Figure 1 This is a SEM image of the PVP / BTO@PDMS fiber film prepared in Example 2 of the present invention;

[0050] Figure 2 This is a SEM image of the BTO@PDMS fiber film prepared in Example 2 of the present invention;

[0051] Figure 3 These are the FTIR spectra of the PVP / BTO@PDMS fiber film and the BTO@PDMS fiber film prepared in Example 2 of this invention;

[0052] Figure 4 This is a statistical graph of the piezoelectric coefficient of the BTO@PDMS fiber film prepared in Example 2 of the present invention;

[0053] Figure 5 This is a butterfly-shaped piezoelectric response amplitude diagram of the BTO@PDMS fiber film prepared in Example 2 of the present invention. Detailed Implementation

[0054] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0055] Example 1: A method for preparing a BTO@PDMS fiber film disclosed in this invention includes the following steps:

[0056] In hydrogen peroxide, tetragonal barium titanate nanoparticles undergo a hydroxylation reaction. After the reaction is completed, post-treatment is performed to obtain surface-hydroxylated barium titanate nanoparticles.

[0057] In ethanol solution, the surface-hydroxylated barium titanate nanoparticles obtained in S1 are surface-modified under the action of vinyl silane coupling agent. After modification, they are post-treated to obtain vinyl-modified barium titanate nanoparticles.

[0058] S3 involves ultrasonically dispersing the polydimethylsiloxane prepolymer and the vinyl-modified barium titanate nanoparticles obtained in S2 in n-hexane, followed by reaction in the presence of tetrahydrofuran and polydimethylsiloxane curing agent to obtain a BTO@PDMS core material solution.

[0059] S4 mixes anhydrous ethanol and polyvinylpyrrolidone to obtain a PVP shell solution;

[0060] S5 involves coaxial electrospinning of the BTO@PDMS core solution obtained in S3 and the PVP shell solution obtained in S4, and collecting the solutions using aluminum foil to obtain a PVP / BTO@PDMS fiber film.

[0061] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is then subjected to high-temperature crosslinking curing and washing with anhydrous ethanol to obtain the BTO@PDMS fiber film.

[0062] Example 2: This is a method for preparing a BTO@PDMS fiber film disclosed in this invention. The difference from Example 1 is that it includes the following steps:

[0063] S1 was first added to 200 mL of 75 wt% hydrogen peroxide, 15 g of tetragonal barium titanate nanoparticles were added and ultrasonically dispersed for 30 min. Then, a reflux reaction apparatus was set up and the oil bath temperature was controlled at 105 ℃, the stirring speed was 800 r / min, and the reaction time was 6 h. After the reaction was completed, the nanoparticles were centrifuged and washed three times with anhydrous ethanol and vacuum dried to obtain surface hydroxylated barium titanate nanoparticles.

[0064] First, in 50 mL of 80 wt% ethanol solution, add 2.5 g of hydroxylated barium titanate nanoparticles obtained from S1 and 2 g of vinyl silane coupling agent KH-171, and ultrasonically disperse for 30 min. Then, build a reflux reaction apparatus, control the oil bath temperature at 75 ℃, the stirring speed at 800 r / min, and the reaction time at 16 h. After the reaction is completed, centrifuge and wash three times with anhydrous ethanol, and vacuum dry to obtain vinyl-modified barium titanate nanoparticles.

[0065] S3 first added 0.55g of vinyl-modified barium titanate nanoparticles obtained from S2 and 1.5mL of n-hexane to 5g of polydimethylsiloxane prepolymer, and ultrasonically dispersed it for 30min. Then, 0.5g of polydimethylsiloxane curing agent and 0.5mL of tetrahydrofuran were added. Then, a stirring reaction device was set up, and the oil bath temperature was controlled at 40℃, the stirring speed was 600r / min, and the reaction time was 1h. After the reaction was completed, a 10wt% BTO@PDMS core material solution was obtained.

[0066] The mass-to-volume ratio of polydimethylsiloxane prepolymer, polydimethylsiloxane curing agent and tetrahydrofuran is controlled to be 10g:1g:1mL.

[0067] S4 First, add 1.8g of 1300kDa polyvinylpyrrolidone powder to 16mL of anhydrous ethanol, then build a stirring and mixing device, and control the oil bath temperature at 70℃, the stirring speed at 800r / min, and the stirring time at 2h to obtain a PVP shell solution.

[0068] S5 First, using a 5mL syringe, draw up the 10wt% BTO@PDMS core solution obtained in S3 and the 15wt% PVP shell solution obtained in S4, respectively. The syringe is fitted with a 15G / 21G coaxial electrospinning needle. The syringe is then mounted on the fixed platform of the electrospinning machine. Aluminum foil is used to collect the solution at the roller collector end of the electrospinning machine, and the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm. The injection rate of the BTO@PDMS core solution is... The injection rate was 1.0 mL / h, the injection rate of the PVP shell solution was 2.4 mL / h, the rotation speed of the roller collector was 120 r / min, the positive electrode of the electrospinning machine was +13 kV and the negative electrode was -2 kV, the electrospinning temperature was 30℃, and the ambient humidity was 40~50%. Then the electrospinning was started, and Taylor cone-shaped micro-jet could be observed under direct light. After the jet stabilized, the direct light was turned off, and the electrospinning was carried out for 2 hours to obtain the PVP / BTO@PDMS fiber film.

[0069] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is first placed in an oven and baked at 110°C for 12 hours to ensure that the polydimethylsiloxane can be fully crosslinked and cured. Then, the cured PVP / BTO@PDMS fiber film is washed multiple times with anhydrous ethanol until the PVP shell is removed to obtain the BTO@PDMS fiber film.

[0070] The PVP / BTO@PDMS fiber films and BTO@PDMS fiber films prepared using the above steps were subjected to performance testing.

[0071] 1. The surface morphology of the prepared PVP / BTO@PDMS fiber film was tested using scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, the PVP / BTO@PDMS fibers are found to be uniformly interwoven and exhibit a 3D network structure.

[0072] 2. The surface morphology of the prepared BTO@PDMS fiber film was tested using scanning electron microscopy (SEM), and the results are as follows: Figure 2 As shown, BTO@PDMS fibers are found to be more dense and exhibit a 3D network structure;

[0073] 3. FTIR infrared spectroscopy was performed on the PVP / BTO@PDMS fiber film and the BTO@PDMS fiber film. The results are as follows: Figure 3 As shown, it can be seen that the PVP / BTO@PDMS fiber film at 3410 cm⁻¹... -1 and 1652cm -1 Characteristic vibration peaks appeared at 3410 cm⁻¹, indicating the unique CH₂OH stretching and C=O stretching vibrations in the PVP rings. The BTO@PDMS fiber film obtained after washing with anhydrous ethanol showed these vibrations at 3410 cm⁻¹. -1 and 1652cm -1 The disappearance of the peak and the enhancement of the PDMS absorption peak indicate that the PVP shell has been completely removed.

[0074] 4. Cut five 2cm × 2cm pieces of BTO@PDMS fiber film, place them on a quasi-static instrument, select five points for testing, record the test data, and then take the average value to obtain the piezoelectric constant D. 33 The value, the result is as follows Figure 4 As shown, the D of the BTO@PDMS fiber film prepared by coaxial electrospinning can be seen. 33 The value remains at 5~6 pC / N;

[0075] 5. A 1cm × 1cm piece of BTO@PDMS fiber film was cut and subjected to piezoelectric microscopy (PFM) testing. The electroinduced changes of the BTO@PDMS fiber film under an applied excitation voltage were detected using a conductive probe of an atomic force microscope. The results are as follows: Figure 5 As shown, the piezoelectric response amplitude of the BTO@PDMS fiber film exhibits a typical butterfly-shaped curve in the range of -6V to 6V. This result once again verifies that the BTO@PDMS fiber film has piezoelectric properties and is expected to be widely used in piezoelectric flexible sensors, tactile sensors and other fields.

[0076] Examples 3-6: This invention discloses a method for preparing BTO@PDMS fiber films. The difference from Example 2 is that in S1, the amount of tetragonal barium titanate nanoparticles is controlled to be 10g, 12g, 18g, and 20g respectively.

[0077] By comparing Examples 2 and Examples 3-6, it was found that as the amount of tetragonal barium titanate nanoparticles increased, the surface hydroxylation effect was limited, and the van der Waals forces between barium titanate nanoparticles increased, leading to enhanced attraction between particles and agglomeration.

[0078] Examples 7-10: In S2, a method for preparing BTO@PDMS fiber film disclosed in this invention is presented. The difference from Example 2 is that the amount of hydroxylated barium titanate nanoparticles is controlled to be 2.0, 2.3, 2.8, and 3.0 g, respectively, and the amount of vinyl silane coupling agent is controlled to be 1.5, 1.8, 2.3, and 2.5 g, respectively.

[0079] By comparing Examples 2 and 7-10, the modification effect gradually increased with the increase of the amount of vinyl silane coupling agent KH-171, which improved the compatibility between barium titanate nanoparticles and polydimethylsiloxane. However, when the amount of coupling agent exceeded 2.5g, the excessive use of coupling agent caused some coupling agent to fail to react fully with barium titanate nanoparticles, and instead formed small agglomerates in the fiber film, affecting the uniformity and mechanical properties of the fiber.

[0080] Examples 11-14: This invention discloses a method for preparing BTO@PDMS fiber films. The difference from Example 2 is that in S3, the concentration of the BTO@PDMS core solution is controlled to be 8, 9, 11, and 12 wt% respectively; and in S4, the concentration of the PVP shell solution is controlled to be 12, 14, 16, and 18 wt%.

[0081] By comparing Example 2 and Examples 11-14, the tensile fracture rate of BTO@PDMS fiber film decreased as the BTO doping amount increased. The reason for this may be that the modified BTO reacted with some of the silane bonds in the PDMS prepolymer, resulting in insufficient silane bonds for crosslinking reaction after adding the same amount of curing agent.

[0082] By comparing Example 2 and Examples 11-14, as the PVP shell concentration increases, the uncured BTO@PDMS core solution is effectively coated under the action of the PVP spinning Taylor cone. After high-temperature curing in the later stage, BTO@PDMS fibers with uniform diameter are obtained.

[0083] In addition, BTO@PDMS fiber films prepared based on PVP with a molecular weight of 1500 kDa have good mechanical properties and porosity balance, while molecular weight that is too high or too low is not conducive to the overall performance of BTO@PDMS fiber films.

[0084] Examples 15-18: In S5, a method for preparing BTO@PDMS fiber film disclosed in this invention is presented. The difference from Example 2 is that the injection rates of the BTO@PDMS core solution are 0.8, 0.9, 1.1, and 1.2 mL / h, and the injection rates of the PVP shell solution are 2.0, 2.3, 2.6, and 2.8 mL / h, respectively.

[0085] By comparing Examples 2 and Examples 15-18, the injection speed of the BTO@PDMS core solution was controlled to be 0.8, 0.9, 1.1, and 1.2 mL / h, respectively. As the injection speed increased, the PVP shell could not form a coating on the core solution, which may lead to leakage of the core solution. This increased adhesion between fibers resulted in an increase in the Young's modulus of the BTO@PDMS fiber film and a decrease in piezoelectricity.

[0086] By comparing Example 2 and Examples 15-18, the injection rate of the PVP shell solution was controlled to be 2.0, 2.3, 2.6, and 2.8 mL / h, respectively. As the injection rate of the PVP shell solution increased, the solvent may not evaporate completely, and an effective coating may not be formed on the BTO@PDMS core material solution, which may have a certain impact on the morphology of the BTO@PDMS fiber film.

[0087] Example 19: This is a method for preparing a BTO@PDMS fiber film disclosed in this invention. The difference from Example 1 is that it includes the following steps:

[0088] S1 First, 10g of tetragonal barium titanate nanoparticles were added to 150mL of 70wt% hydrogen peroxide and ultrasonically dispersed for 25min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 100℃, the stirring speed at 700r / min, and the reaction time was 5h. After the reaction was completed, the nanoparticles were washed twice by centrifugation with anhydrous ethanol and vacuum dried to obtain surface-hydroxylated barium titanate nanoparticles.

[0089] S2 was first added to 40 mL of 70 wt% ethanol solution, along with 2.0 g of hydroxylated barium titanate nanoparticles obtained in S1 and 1.5 g of vinyl silane coupling agent KH-171. The mixture was ultrasonically dispersed for 25 min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 70 °C, the stirring speed at 700 r / min, and the reaction time at 15 h. After the reaction was completed, the mixture was centrifuged and washed twice with anhydrous ethanol and then vacuum dried to obtain vinyl-modified barium titanate nanoparticles.

[0090] S3 first added 0.500g of vinyl-modified barium titanate nanoparticles obtained in S2 and 1.0mL of n-hexane to 4.0g of polydimethylsiloxane prepolymer, and ultrasonically dispersed it for 25min. Then, 0.40g of polydimethylsiloxane curing agent and 0.4mL of tetrahydrofuran were added. Then, a stirring reaction device was set up, and the oil bath temperature was controlled at 30℃, the stirring speed was 500r / min, and the reaction time was 1h. After the reaction was completed, a 10wt% BTO@PDMS core material solution was obtained.

[0091] S4 First, add 1.5g of 1200kDa polyvinylpyrrolidone powder to 15mL of anhydrous ethanol, then build a stirring and mixing device, and control the oil bath temperature to 60℃, the stirring speed to 700r / min, and the stirring time to 1h to obtain a PVP shell solution.

[0092] S5 First, using a 5mL syringe, draw up the 8wt% BTO@PDMS core solution obtained in S3 and the 12wt% PVP shell solution obtained in S4, respectively. The syringe is fitted with a 15G / 21G coaxial electrospinning needle. The syringe is then mounted on the fixed platform of the electrospinning machine. Aluminum foil is used to collect the solution at the roller collector end of the electrospinning machine, and the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm. The BTO@PDMS core solution is then injected... The injection rate was 0.8 mL / h, the injection rate of the PVP shell solution was 2.0 mL / h, the rotation speed of the roller collector was 100 r / min, the positive electrode of the electrospinning machine was +13 kV and the negative electrode was -2 kV, the electrospinning temperature was 20℃, the ambient humidity was 40%, and then electrospinning was started. Taylor cone-shaped micro-jet could be observed under direct light. After the jet stabilized, the direct light was turned off, and electrospinning was carried out for 2 hours to obtain PVP / BTO@PDMS fiber film.

[0093] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is first placed in an oven and baked at 100°C for 10 hours to ensure that the polydimethylsiloxane can be fully crosslinked and cured. Then, the cured PVP / BTO@PDMS fiber film is washed multiple times with anhydrous ethanol until the PVP shell is removed to obtain the BTO@PDMS fiber film.

[0094] Example 20: This is a method for preparing a BTO@PDMS fiber film disclosed in this invention. The difference from Example 1 is that it includes the following steps:

[0095] S1 First, 20g of tetragonal barium titanate nanoparticles were added to 250mL of 80wt% hydrogen peroxide and ultrasonically dispersed for 35min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 110℃, the stirring speed at 900r / min, and the reaction time was 7h. After the reaction was completed, the nanoparticles were centrifuged and washed three times with anhydrous ethanol and vacuum dried to obtain surface hydroxylated barium titanate nanoparticles.

[0096] S2 was first added to 80 mL of 80 wt% ethanol solution, along with 3.0 g of hydroxylated barium titanate nanoparticles obtained in S1 and 2.5 g of vinyl silane coupling agent KH-171. The mixture was ultrasonically dispersed for 35 min. Then, a reflux reaction apparatus was set up, and the oil bath temperature was controlled at 80 °C, the stirring speed at 900 r / min, and the reaction time at 17 h. After the reaction was completed, the mixture was centrifuged and washed three times with anhydrous ethanol and then vacuum dried to obtain vinyl-modified barium titanate nanoparticles.

[0097] S3 first added 0.60g of vinyl-modified barium titanate nanoparticles obtained in S2 and 2.0mL of n-hexane to 6.0g of polydimethylsiloxane prepolymer, and ultrasonically dispersed it for 35min. Then, 0.60g of polydimethylsiloxane curing agent and 0.6mL of tetrahydrofuran were added. Then, a stirring reaction device was set up, and the oil bath temperature was controlled at 50℃, the stirring speed was 700r / min, and the reaction time was 2h. After the reaction was completed, a 10wt% BTO@PDMS core material solution was obtained.

[0098] S4 First, add 2.0g of 1400kDa polyvinylpyrrolidone powder to 20mL of anhydrous ethanol, then build a stirring and mixing device, and control the oil bath temperature to 80℃, the stirring speed to 900r / min, and the stirring time to 3h to obtain a PVP shell solution.

[0099] S5 First, using a 5mL syringe, draw up the 12wt% BTO@PDMS core solution obtained in S3 and the 18wt% PVP shell solution obtained in S4, respectively. The syringe is fitted with a 15G / 21G coaxial electrospinning needle. The syringe is then mounted on the fixed platform of the electrospinning machine. Aluminum foil is used to collect the solution at the roller collector end of the electrospinning machine, and the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm. The BTO@PDMS core solution is then injected... The injection rate was 1.2 mL / h, the injection rate of the PVP shell solution was 2.8 mL / h, the rotation speed of the roller collector was 150 r / min, the positive electrode of the electrospinning machine was +13 kV and the negative electrode was -2 kV, the electrospinning temperature was 40℃, the ambient humidity was 50%, and then electrospinning was started. Taylor cone-shaped micro-jet could be observed under direct light. After the jet stabilized, the direct light was turned off, and electrospinning was carried out for 3 hours to obtain PVP / BTO@PDMS fiber film.

[0100] S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is first placed in an oven and baked at 120°C for 15 hours to ensure that the polydimethylsiloxane can be fully crosslinked and cured. Then, the cured PVP / BTO@PDMS fiber film is washed multiple times with anhydrous ethanol until the PVP shell is removed to obtain the BTO@PDMS fiber film.

[0101] Comparative Example 1: This is a method for preparing BTO@PDMS fiber films disclosed in this invention. The difference from Example 2 is that in S1, barium titanate nanowires (BTO Ncs) are used instead of tetragonal barium titanate nanoparticles (BTO NPs).

[0102] Because barium titanate nanowires have a large aspect ratio, they are prone to semi-embedded in PDMS fiber membranes during electrospinning, resulting in uneven morphology of the PDMS fiber membranes and affecting the output of piezoelectric properties.

[0103] Comparative Example 2: This is a method for preparing BTO@PDMS fiber film disclosed in this invention. The difference from Example 2 is that, in S2, a vinyl silane coupling agent is not used.

[0104] Without the use of vinylsilane coupling agents, the surface-hydroxylated barium titanate nanoparticles cannot undergo hydrolysis to prevent vinyl groups from being grafted onto the BTO surface, thus affecting the dispersibility of BTO in PDMS.

[0105] Comparative Example 3: This is a method for preparing BTO@PDMS fiber film disclosed in this invention. The difference from Example 2 is that in S4, polyvinylidene fluoride (PVDF) is used instead of polyvinylpyrrolidone (PVP).

[0106] PVDF is an excellent piezoelectric polymer. Although using PVDF instead of PVP can improve the piezoelectricity of fiber films, PVDF has a high Young's modulus, resulting in poor film elongation, which is not conducive to its application in wearable devices and limits its application scenarios.

[0107] Comparative Example 4: This is a method for preparing BTO@PDMS fiber film disclosed in this invention. The difference from Example 2 is that, in S5, a PVP shell solution is not used.

[0108] Since PDMS is a non-polar polymer, and the PDMS prepolymer and curing agent require high temperature and time to complete cross-linking and curing, it cannot be directly electrospun.

[0109] Comparative Example 5: This is a method for preparing BTO@PDMS fiber film disclosed in this invention. The difference from Example 2 is that in S6, high-temperature cross-linking and curing are not performed.

[0110] Without high-temperature cross-linking and curing, the uncured core material solution will dissolve when anhydrous ethanol is used to remove the PVP shell, resulting in BTO@PDMS fibers not forming a film.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a BTO@PDMS fiber film, characterized by: Includes the following steps, In hydrogen peroxide, tetragonal barium titanate nanoparticles undergo a hydroxylation reaction. After the reaction is completed, post-treatment is performed to obtain surface-hydroxylated barium titanate nanoparticles. In S2, the surface-hydroxylated barium titanate nanoparticles obtained in S1 are surface-modified under the action of a vinyl silane coupling agent in an ethanol solution. After modification, they are post-treated to obtain vinyl-modified barium titanate nanoparticles. S3 involves ultrasonically dispersing the polydimethylsiloxane prepolymer and the vinyl-modified barium titanate nanoparticles obtained in S2 in n-hexane, and then reacting them in the presence of tetrahydrofuran and polydimethylsiloxane curing agent to obtain a BTO@PDMS core material solution. S4 mixes anhydrous ethanol and polyvinylpyrrolidone to obtain a PVP shell solution; S5 involves coaxial electrospinning of the BTO@PDMS core solution obtained in S3 and the PVP shell solution obtained in S4. The roller collector end of the electrospinning machine is collected with aluminum foil to obtain a PVP / BTO@PDMS fiber film. S6 After peeling the PVP / BTO@PDMS fiber film obtained in S5 from the aluminum foil, it is sequentially subjected to high-temperature cross-linking curing and washing with anhydrous ethanol to obtain the BTO@PDMS fiber film. In S2, the concentration of the ethanol solution is 70-80 wt%, and the ratio of ethanol solution, hydroxylated barium titanate nanoparticles, and vinyl silane coupling agent is controlled to be 40-80 mL: 2.0-3.0 g: 1.5-2.5 g. In step S3, the ratio of polydimethylsiloxane prepolymer, vinyl-modified barium titanate nanoparticles, polydimethylsiloxane curing agent, and tetrahydrofuran is controlled to be 4.0~6.0g:0.50~0.60g:0.40~0.60g:0.4~0.6mL, and the concentration of BTO@PDMS core material solution is 8~12wt%. 2.The method for preparing a BTO@ PDMS fiber film according to claim 1, characterized in that: In S1, the concentration of hydrogen peroxide is 70-80 wt%, and the ratio of hydrogen peroxide to tetragonal barium titanate nanoparticles is controlled to be 150-250 mL: 10-20 g.

3. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In S1, tetragonal barium titanate nanoparticles are first ultrasonically dispersed in hydrogen peroxide, and the dispersion time is controlled to be 25-35 min. Then, a hydroxylation reaction occurs, and the reaction temperature is controlled to be 100-110℃, the stirring speed is 700-900 r / min, and the reaction time is 5-7 h.

4. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In step S2, hydroxylated barium titanate nanoparticles and vinyl silane coupling agent are first ultrasonically dispersed in an ethanol solution, and the dispersion time is controlled to be 25-35 min. Then, surface modification is performed, and the reaction temperature is controlled to be 70-80℃, the stirring speed is 700-900 r / min, and the reaction time is 15-17 h.

5. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In step S3, the dispersion time is first controlled to be 25-35 min, then the reaction temperature is controlled to be 30-50℃, the stirring speed is 500-700 r / min, and the reaction time is 1-2 h.

6. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In S4, the molecular weight of polyvinylpyrrolidone is 1200~1400kDa, the ratio of anhydrous ethanol to polyvinylpyrrolidone is controlled to be 15~20mL:1.5~2.0g, and the concentration of the PVP shell solution is 12~18wt%.

7. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In step S5, the distance between the coaxial electrospinning needle and the roller collector is controlled to be 15cm, the injection rate of the BTO@PDMS core solution is 0.8~1.2mL / h, the injection rate of the PVP shell solution is 2.0~2.8mL / h, the rotation speed of the roller collector is 100~150r / min, the positive electrode of the electrospinning machine is +13kV and the negative electrode is -2kV, the electrospinning temperature is 20~40℃, and the ambient humidity is 40~50%.

8. The method for preparing a BTO@PDMS fiber film according to claim 1, characterized in that: In step S5, after electrospinning begins, a Taylor cone-shaped microjet can be observed under direct light. Once the jet stabilizes, the direct light is turned off, and electrospinning continues for 2-3 hours.

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