A core-shell nanocomposite thin film material, its preparation method and application

Abstract

This invention discloses a core-shell nanocomposite thin film material, its preparation method, and its application. The material is composed of polyvinylidene fluoride (PVDF) and BaTiO3. A first spinning solution is obtained by mixing PVDF, acetone, and N-N-dimethylformamide (DMF); a second spinning solution is obtained by mixing BaTiO3 and DMF. Using the first spinning solution as the outer core layer and the second spinning solution as the inner core layer, PVDF-encapsulated BaTiO3 composite nanofibers are obtained through coaxial electrospinning, successfully preparing a core-shell nanocomposite thin film. This invention achieves optimal piezoelectric performance by encapsulating BaTiO3 particles of different sizes. The preparation method is simple and low-cost, exhibiting excellent piezoelectric properties. Its application in piezoelectric energy harvesters can improve energy harvesting efficiency.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation technology, specifically relating to a core-shell nanocomposite thin film material and its preparation method and application. Background Technology

[0002] In recent years, significant progress has been made in energy harvesting to meet the growing demand for portable, sustainable, and renewable energy. Devices have been designed to capture ambient energy and convert it into usable electricity. Piezoelectric energy harvesters, capable of directly harvesting various forms of mechanical energy and converting them into electrical energy, are considered a viable alternative to traditional rechargeable batteries for powering various electronic devices. Among piezoelectric materials, polyvinylidene fluoride (PVDF) and its copolymers are considered promising candidates for energy harvesters due to their unique electroactivity, high flexibility, good processability, and long-term stability. However, the piezoelectric response produced by their harvesters remains low and cannot power most electronic devices. Therefore, attempts have been made to dope piezoelectric polymers to improve the piezoelectric response; however, the doping process involves the agglomeration of inorganic fillers at the interface, reducing interfacial polarization and thus limiting the performance improvement.

[0003] In recent years, with the rise of coaxial electrospinning technology, the coating of inorganic fillers has been achieved to prepare core-shell materials, which helps to increase the piezoelectric crystal structure, dipole arrangement, charge transfer, etc., and improve the piezoelectric output response. However, due to the non-uniform size of inorganic fillers, the performance of the prepared core-shell nanocomposite films is unstable. Therefore, improving the piezoelectric performance of prepared core-shell nanopiezoelectric materials remains a challenge. Summary of the Invention

[0004] Purpose of the invention: In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a core-shell nanocomposite thin film material with good piezoelectric properties, uniform distribution of internal inorganic fillers and almost uniform particle size.

[0005] Another technical problem that this invention aims to solve is to provide a method for preparing the composite material.

[0006] The final technical problem to be solved by this invention is that applying this composite material to an energy harvester can effectively improve the energy conversion efficiency and piezoelectric output response of the energy harvester.

[0007] Technical Solution: To solve the above-mentioned technical problems, the present invention provides a method for preparing core-shell nanocomposite thin film materials, comprising the following steps:

[0008] (1) Preparation of mixed solution of NaOH and Ba(CH3COO)2: Prepare mixed solution of NaOH and Ba(CH3COO)2, stir at room temperature to obtain clear and transparent mixed solution;

[0009] (2)C4H 10 O and C 16 H 36 Preparation of O4Ti mixed solution: Preparation of C4H 10 O and C 16 H 36 When the O4Ti mixed solution is stirred at room temperature, a milky white turbid mixed solution is obtained.

[0010] (3) Preparation of PEG20000 aqueous solution: Prepare PEG20000 aqueous solution and stir at room temperature to obtain clear and transparent PEG20000 aqueous solution;

[0011] (4) Preparation of precursor: Take the NaOH and Ba(CH3COO)2 mixed solution from step (1) and the C4H from step (2) 10 O and C 16 H 36 After mixing and vigorously stirring the O4Ti mixed solution, a milky white gel-like suspension was obtained. The mixed solution in step (3) was added, and then stirred to make the mixed solution evenly dispersed. The sample was then subjected to high-temperature hydrothermal synthesis to obtain a white precursor.

[0012] (5) Coaxial electrospinning: PVDF is dispersed in a mixed solution of DMF and acetone to obtain the first spinning solution, and the white precursor from step (4) is dispersed in a DMF solution to obtain the second spinning solution. The first spinning solution is used as the outer core layer and the second spinning solution is used as the inner core layer by coaxial electrospinning to obtain a core-shell nanocomposite thin film material.

[0013] In step (1), the concentration of Ba(CH3COO)2 in the mixed solution of NaOH and Ba(CH3COO)2 is 10-20 wt%, and the concentration of NaOH is 2-10 wt%. Preferably, the concentration of Ba(CH3COO)2 in the mixed solution of NaOH and Ba(CH3COO)2 in step (1) is 17 wt%.

[0014] Among them, the C4H mentioned in step (2) 10 O and C 16 H 36 In the O4Ti mixed solution, C 16 H 36 The O4Ti concentration was 30–40 wt%, and the C4H concentration was 30–40 wt%. 10 The O concentration is 60–70 wt%. Preferably, in step (2), C4H 10 O, C16 H 36 In the O4Ti mixed solution, C 16 H 36 The O4Ti concentration was prepared at 33 wt%.

[0015] In step (3), the concentration of PEG20000 in the PEG20000 aqueous solution is 0.1-1 wt%. Preferably, the concentration of the PEG20000 aqueous solution in step (3) is 0.49 wt%.

[0016] Among them, the mixed solution of NaOH and Ba(CH3COO)2 and C4H in step (4) 10 O and C 16 H 36 The O4Ti mixed solution was 10-30 ml, the stirring time was 0.5-1.5 h, the PEG20000 aqueous solution was 20-40 ml, the stirring time was 0.5-1.5 h, the hydrothermal temperature was 180-200℃, and the time was 1-26 h, resulting in BaTiO3 particles with a diameter of 20-150 nm.

[0017] In step (4), the hydrothermal reaction time is 1 to 5 hours, and the resulting BaTiO3 particles have a diameter of 20 to 50 nm.

[0018] In step (4), the hydrothermal reaction time is 10-14 h, and the BaTiO3 particles with a diameter of 70-100 nm are obtained.

[0019] In step (4), the hydrothermal reaction time is 22-26 h, and the resulting BaTiO3 particles have a diameter of 90-150 nm.

[0020] Preferably, in step (4), the mixed solution of NaOH and Ba(CH3COO)2 and C4H 10 O and C 16 H 36 The O4Ti mixed solution was 20 ml each, and the stirring time was 1 h. Then, 30 ml of PEG20000 aqueous solution was added, and the stirring time was 1 h. The hydrothermal reaction temperature was 190℃ and the time was 3 h, resulting in a precursor with an average particle size of 25 nm.

[0021] Preferably, in step (4), the solutions from steps (1) and (2) are 20 ml each, the stirring time is 1 h, and the PEG20000 aqueous solution from step (3) is 30 ml. The stirring time is then 1 h, the hydrothermal reaction temperature is 190 °C, and the time is 12 h, resulting in a precursor with an average particle size of 86 nm.

[0022] Preferably, in step (4), the solutions from steps (1) and (2) are 20 ml each, the stirring time is 1 h, and 30 ml of the PEG20000 aqueous solution from step (3) is added. The stirring time is then 1 h, the hydrothermal reaction temperature is 190 °C, and the reaction time is 24 h, resulting in a precursor with an average particle size of 105 nm.

[0023] In step (5), the mass ratio of PVDF to DMF and acetone mixed solution is 1:(5-20), the solution is mixed and stirred at 50-70℃ for 3-12 hours, the mass ratio of white precursor to DMF solution is 1:(5-20), the solution is mixed and stirred at 50-70℃ for 3-12 hours.

[0024] In step (5), the spinning conditions of the first and second spinning solutions are as follows: spinning rate of 1.0 to 2.0 mL / h, electrospinning voltage of 15 to 25 kV, temperature of 20 to 40 °C, humidity of 20 to 40%, and spinning distance of 10 to 20 cm. Preferably, the film obtained after spinning is dried at 50 to 70 °C for 6 to 24 h.

[0025] In step (5), the piezoelectric properties of BaTiO3 / PVDF with a particle size of 20-50 nm are 40-60 V.

[0026] In step (5), the piezoelectric properties of BaTiO3 / PVDF with a particle size of 70-100 nm are 30-40 V.

[0027] In step (5), the piezoelectric properties of BaTiO3 / PVDF with a particle size of 90-150 nm are 20-30 V.

[0028] Preferably, in step (5), the mass ratio of PVDF to DMF and acetone mixed solution is 1:5, the solution is mixed and stirred at 60°C for 6 hours, the mass ratio of white precursor to DMF solution is 1:19, and the solution is mixed and stirred at 60°C for 6 hours.

[0029] Preferably, the spinning conditions of the first spinning solution in step (5) are: spinning rate of 1.2 mL / h, voltage of 20 kV, temperature of 30 °C, humidity of 30%, and spinning distance of 15 cm.

[0030] Preferably, the spinning conditions of the second spinning solution in step (5) are: spinning rate of 0.3 mL / h, voltage of 20 kV, temperature of 30 °C, humidity of 30%, and spinning distance of 15 cm.

[0031] Preferably, the film obtained after spinning in step (5) is dried at 60°C for 12 hours.

[0032] The present invention also includes the core-shell nanocomposite thin film material obtained by the preparation method described above.

[0033] The present invention also includes the application of the core-shell nanocomposite thin film material in the preparation of piezoelectric energy harvesters.

[0034] Technical principle of the invention: The invention selects C 16 H 36 O4Ti and Ba(CH3COO)2 were used as titanium and barium sources, respectively. PEG20000 was used as a stabilizer, and NaOH was used as a mineralizing agent to adjust the pH value, ensuring the pH of the mixed solution after the reaction was greater than 11. The solvents were deionized water and n-butanol. The particle size of the product was adjusted by controlling the type of stabilizer, reaction time, and hydrothermal temperature. The prepared BaTiO3 precursor particles were encapsulated in PVDF by coaxial electrospinning, and after drying, a core-shell structured nanomaterial was obtained. Finally, it was assembled into a piezoelectric energy harvester to convert mechanical energy into electrical energy and store it in a capacitor for application in a wireless alarm system.

[0035] Beneficial Effects: Compared with existing technologies, this invention has the following advantages: This invention obtains a core-shell nanocomposite film with optimal piezoelectric performance by encapsulating BaTiO3 particles of different sizes. The composite material prepared by this invention, used as a film material for piezoelectric energy harvesters, utilizes a PVDF-encapsulated BaTiO3 nanoparticle core-shell structure, which helps increase piezoelectric crystal structure, dipole arrangement, charge transfer, etc., thereby improving piezoelectric output response. Simultaneously, it reduces the agglomeration of inorganic fillers and increases interfacial polarization. The preparation method of this invention is simple, economical, efficient, environmentally friendly, and low-cost, exhibiting excellent piezoelectric performance. Its application in piezoelectric energy harvesters can improve energy harvesting efficiency. Attached Figure Description

[0036] Figure 1 The X-ray diffraction (XRD) patterns of BaTiO3 with different particle sizes prepared in Examples 1, 2, and 3 of this invention are shown.

[0037] Figure 2 The bar chart shows the cubic phase content in BaTiO3 with different particle sizes prepared in Examples 1, 2, and 3 of this invention.

[0038] Figure 3 The Fourier transform infrared diffraction (FT-IR) pattern of the composite film obtained by coaxial electrospinning in Example 1 of this invention;

[0039] Figure 4 The image shows the X-ray diffraction (XRD) pattern of the composite film obtained by coaxial electrospinning in Example 1 of this invention.

[0040] Figure 5 The images show columnar crystal structures inside the composite films obtained by coaxial electrospinning in Examples 1, 2, and 3 of this invention.

[0041] Figure 6 SEM image of the BaTiO3 particles (average particle size of 25 nm) prepared in Example 1 of the present invention;

[0042] Figure 7 SEM image of the BaTiO3 particles (average particle size of 86 nm) prepared in Example 2 of the present invention;

[0043] Figure 8 SEM image of BaTiO3 particles (average particle size of 105 nm) prepared in Example 3 of the present invention;

[0044] Figure 9 This is a TEM image of PVDF-encapsulated BaTiO3 prepared in Example 1 of the present invention;

[0045] Figure 10 The piezoelectric properties of the composite piezoelectric films prepared in Examples 1, 2, and 3 of this invention are shown in the diagram.

[0046] Figure 11 This is a circuit diagram of the wireless alarm system prepared according to the present invention.

[0047] Figure 12 This is a module assembly diagram of the wireless alarm system prepared according to the present invention. Detailed Implementation

[0048] Example 1

[0049] A core-shell nanocomposite thin film material and its preparation method, comprising the following steps:

[0050] (1) Accurately weigh 0.5g NaOH and 4.468g Ba(CH3COO)2 solid and dissolve them in 20ml of deionized water to obtain a 17wt% Ba(CH3COO)2 mixed solution.

[0051] (2) Accurately weigh 5.98 ml of C 16 H 36 O4Ti solution was dissolved in 14.02 ml of n-butanol solution to obtain 33 wt% C. 16 H 36 O4Ti mixed solution.

[0052] (3) Accurately weigh 0.15g of PEG20000 solid (Sinopharm Group, catalog number 25322-68-3) and dissolve it in 30ml of deionized water to obtain a 0.49wt% PEG20000 solution.

[0053] (4) Take 20 ml of the mixed solution from step (1) and 20 ml of the mixed solution from step (2) and mix them vigorously for 1 h to obtain a milky white gel suspension. Add 30 ml of the mixed solution from step (3) and stir for another 1 h to make the mixed solution evenly dispersed. The sample is then subjected to high-temperature hydrothermal synthesis at a temperature of 190℃ for 3 h to obtain BaTiO3 with an average particle size of 25 nm.

[0054] (5) Take PVDF (Arkema, France, CAS#24937-79-9) and disperse it in a mixed solution of DMF and acetone (4:6). The mass ratio of PVDF to the mixed solution of DMF and acetone is 1:5. The solution is mixed and stirred at 60°C for 6 hours to obtain the first spinning solution. Take the white precursor (0.05g) from step (4) and disperse it in pure DMF solvent (>99.8%). The mass ratio of the white precursor to the DMF solution is 1:19. The solution is mixed and stirred at 60°C for 6 hours to obtain the second spinning solution. An experimental electrospinning machine (HZ-12) was used to spin coaxially, with the first spinning solution as the outer core layer and the second spinning solution as the inner core layer. The spinning rate of the first spinning solution was 1.2 mL / h, the voltage was 20 kV, the temperature was 30℃, the humidity was 30%, and the spinning distance was 15 cm. The spinning rate of the second spinning solution was 0.3 mL / h, the voltage was 20 kV, the temperature was 30℃, the humidity was 30%, and the spinning distance was 15 cm. The resulting film was dried at 60℃ for 12 h to obtain a core-shell BaTiO3 nanofiber film material, which was assembled into a piezoelectric energy harvester, and its output voltage was measured to be 49 V.

[0055] Example 2

[0056] The process was essentially the same as in Example 1, except that in step (1), 0.5 g of NaOH and 1.111 g of Ba(CH3COO)2 solid were weighed and dissolved in 10 ml of deionized water to prepare a 10 wt% Ba(CH3COO)2 mixed solution. In step (3), 0.02 g of PEG20000 solid was weighed and dissolved in 20 ml of deionized water to obtain a 0.1 wt% PEG20000 solution. In step (4), the time for hydrothermal treatment of the mixed solution was increased to 12 h, resulting in BaTiO3 with an average particle size of 86 nm. In step (5), the electrospinning voltage was 25 kV, and a piezoelectric energy harvester was assembled, with its output voltage measured at 36 V.

[0057] Example 3

[0058] The process was essentially the same as in Example 1, except that in step (1), 0.5 g of NaOH and 12.857 g of Ba(CH3COO)2 solid were weighed and dissolved in 30 ml of deionized water to prepare a 20 wt% Ba(CH3COO)2 mixed solution. In step (3), 0.04 g of PEG20000 solid was weighed and dissolved in 40 ml of deionized water to obtain a 1 wt% PEG20000 solution. In step (4), the time for hydrothermal treatment of the mixed solution was increased to 24 h, resulting in the preparation of BaTiO3 with an average particle size of 105 nm. In step (5), the electrospinning voltage was 15 kV, and a piezoelectric energy harvester was assembled, with its output voltage measured at 27 V.

[0059] Application example:

[0060] The piezoelectric energy harvesters prepared in Embodiments 1, 2, and 3 of this invention are connected to a Wi-Fi module, a buzzer module, a circuit board, etc., via a pre-drawn circuit diagram and assembled into a wireless alarm system. (See [link to documentation]). Figure 11 and Figure 12 The piezoelectric energy harvester prepared in Example 1 can be used to convert mechanical energy into electrical energy by applying a single 2.5 kPa tap, which is then stored in a 10 μF capacitor as an independent power source to power the alarm system.

[0061] The properties of the core-shell BaTiO3 nanofibers prepared in Examples 1-3 were characterized. Figure 1 The X-ray diffraction (XRD) patterns of the core-shell BaTiO3 nanomaterials prepared in Examples 1-3 show that the diffraction peaks of the samples are located at 22.1°, 31.5°, 38.8°, 45.1°, 56.1° and 65.7°, respectively, which correspond one-to-one with the (100), (110), (111), (200), (211) and (220) crystal planes of BaTiO3 (PDF#05-0626). This indicates that the samples are all BaTiO3 and there is no double peak at 45°, thus proving that the crystal mainly contains a cubic phase.

[0062] Figure 2 The bar chart shows the cubic phase content in the core-shell BaTiO3 nanomaterials prepared in Examples 1-3. Compared with Example 1, the cubic phase content in Examples 2-3 is significantly lower than that in Example 1, indicating that the cubic phase content gradually decreases as the size of BaTiO3 increases.

[0063] Figure 3 The Fourier transform infrared (FT-IR) spectra of the core-shell structured nanocomposite thin film materials prepared in Examples 1-3 are shown. The FT-IR spectrum of the sample in Example 1 shows a peak at 1396 cm⁻¹. -1 1184cm -1 1072cm-1 875cm -1 and 840cm -1 The adsorption peak belongs to the β phase of PVDF in the composite film, at 971 cm⁻¹. -1 779cm -1 and 605cm -1 The weak adsorption peak at 1396 cm⁻¹ belongs to the α phase of PVDF in the composite film. Compared with Example 1, in Examples 2-3, as the particle size of the core-shell material gradually increases, the adsorption peak at 1396 cm⁻¹ increases. -1 and 1072cm -1 The weakening of the peak at this point indicates that the β phase of PVDF in the composite film is weakened due to the increase in the particle size of the cubic phase BaTiO3. In other words, the increase in the particle size of the cubic phase BaTiO3 during electrospinning is not conducive to the formation of β phase PVDF.

[0064] Figure 4 The X-ray diffraction (XRD) patterns of the core-shell structured nanocomposite thin film materials prepared in Examples 1-3 show a strong plane (020) and a prominent plane (110) at 18.8° and 20.5°, respectively, which belong to the α-crystalline phase of the composite film. Simultaneously, an orthorhombic β-phase diffraction peak is observed on the (200) crystal plane at 20.5°. Compared to Example 1, in Examples 2-3, the β-phase PVDF in the composite film gradually decreases as the size of the encapsulated BaTiO3 particles gradually increases.

[0065] Figure 5 The histograms of the internal crystalline phase content distribution of the composite films prepared by coaxial electrospinning in Examples 1, 2, and 3 are shown. Compared with Example 1, the β phase content in Examples 2 and 3 is significantly reduced. As the particle size of the encapsulated BaTiO3 gradually increases in Examples 2 and 3, the cubic phase content in BaTiO3 decreases, thus the β phase content decreases.

[0066] Figure 6 SEM image of the average particle size (25 nm) of BaTiO3 prepared in Example 1; Figure 6 SEM image of the average particle size (86 nm) of BaTiO3 prepared in Example 2; Figure 7 The image shows the average particle size (105 nm) of BaTiO3 prepared in Example 3. The size of the generated BaTiO3 varies with the increase of hydrothermal time and the concentration of the reaction solution.

[0067] Figure 9 The image shows a TEM image of the PVDF-encapsulated BaTiO3 prepared in step (5) of Example 1.

[0068] Figure 10The figures show the performance of piezoelectric energy harvesters encapsulated in the core-shell structured nanocomposite films prepared in Examples 1-3. When the average particle size of the composite film in Example 1 is 25 nm, the output voltage of the piezoelectric energy harvester can reach 49 V. When the average particle size of Example 2 is 86 nm, the piezoelectric performance reaches 36 V, which is significantly lower than that of Example 1. When the average particle size of Example 3 is 105 nm, the piezoelectric performance reaches 27 V, which is also significantly lower than that of Example 1.

Claims

1. A method for preparing a core-shell nanocomposite thin film material, characterized in that, The method comprises the following steps: (1) Preparation of a mixed solution of NaOH and Ba(CH3COO)2: prepare a mixed solution of NaOH and Ba(CH3COO)2, and stir at room temperature to obtain a clear and transparent mixed solution; (2) C4H 10 O and C 16 H 36 Preparation of C4H 10 O and C 16 H 36 O4Ti mixed solution, stirred at room temperature to obtain a milky white turbid mixed solution; (3) Preparation of a PEG20000 aqueous solution: prepare a PEG20000 solution, and stir at room temperature to obtain a clear and transparent PEG20000 aqueous solution; (4) Preparation of the precursor: the mixed solution of NaOH and Ba(CH3COO)2 in step (1) and the mixed solution of C4H 10 O and C 16 H 36 O4Ti in step (2) are mixed and stirred strongly, then the aqueous solution of PEG20000 in step (3) is added, and the mixed solution is stirred again to make it uniformly dispersed. The sample is subjected to high-temperature hydrothermal synthesis to obtain a white precursor; (5) Coaxial electrospinning: take PVDF dispersed in a mixed solution of DMF and acetone to obtain a first spinning solution, take the white precursor of step (4) dispersed in a DMF solution to obtain a second spinning solution, and perform spinning by a coaxial electrospinning method to obtain a core-shell nanocomposite film material, in which the first spinning solution is used as an outer core layer and the second spinning solution is used as an inner core layer. In step (1), the concentration of Ba(CH3COO)2 in the mixed solution of NaOH and Ba(CH3COO)2 is 10-20 wt%, and the concentration of NaOH is 2-10 wt%; in step (2), the concentration of C4H... 10 O and C 16 H 36 In the O4Ti mixed solution, C 16 H 36 The O4Ti concentration is 30~40 wt%, C4H 10 The concentration of O is 60~70 wt%; in the PEG20000 aqueous solution in step (3), the concentration of PEG20000 is 0.1~1 wt%; in step (4), the mixed solution of NaOH and Ba(CH3COO)2 and C4H 10 O and C 16 H 36 The O4Ti mixed solution was 10~30 ml, the stirring time was 0.5~1.5 h, the PEG20000 aqueous solution was 20~40 ml, the stirring time was 0.5~1.5 h, the hydrothermal temperature was 180~200℃, and the time was 1~26 h, resulting in BaTiO3 with an average particle size of 20~150 nm.

2. The method of claim 1, wherein the core-shell nanocomposite thin film material is prepared by a process comprising: In step (5), the mass ratio of PVDF to the mixed solution of DMF and acetone is 1: (5-20), the solution is mixed and stirred at 50-70 ℃ for 3-12 h, and the mass ratio of the white precursor to the DMF solution is 1: (5-20), the solution is mixed and stirred at 50-70 ℃ for 3-12 h.

3. The method for preparing core-shell nanocomposite thin film material according to claim 1, characterized in that, In step (5), the spinning conditions of the first spinning solution and the second spinning solution are as follows: the spinning rate is 1.0-2.0 mL / h, the voltage is 15-25 kV, the temperature is 20-40 ℃, the humidity is 20-40%, and the spinning distance is 10-20 cm; and the obtained film is dried at 50-70 ℃ for 6-24 h.

4. The core-shell nanocomposite film material obtained by the preparation method of any one of claims 1-3.

5. Application of the core-shell nanocomposite film material of claim 4 in the preparation of a piezoelectric energy harvester.

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