A piezoelectric composite material based on in-situ modified barium titanate, its preparation method and application

Abstract

This invention discloses a piezoelectric composite material based on in-situ modified barium titanate, its preparation method, and its application, belonging to the field of piezoelectric composite material technology. The invention first mixes barium titanate and 2-thienylacetonitrile in isopropanol solution to obtain a barium titanate modified material through in-situ modification. Then, it is ball-milled and mixed with polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate, and 819 photoinitiator to obtain the piezoelectric composite material through photocuring. The piezoelectric composite material utilizes the covalent chemical bond and physical interaction between 2-thienylacetonitrile and barium titanate to firmly attach the 2-thienylacetonitrile molecular chains to the surface of barium titanate particles, repairing surface defects and chemical inertness of barium titanate. Furthermore, the introduction of 1-ethyl-3-methylimidazolium sulfate enhances the polarization electric field in conjunction with the barium titanate modified material, resulting in a piezoelectric composite material with excellent piezoelectric properties, good stability, and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric composite material technology, specifically relating to a piezoelectric composite material based on in-situ modified barium titanate, its preparation method, and its application. Background Technology

[0002] Piezoelectric materials are functional materials capable of converting between mechanical and electrical energy. They possess unique properties in terms of force, heat, light, electricity, and sound, and are widely used in industrial, civilian, and defense applications, including ultrasonic transducers, sensors, non-destructive testing, ultrasonic motors, transformers, buzzers, and detectors. Based on their crystal structure, piezoelectric materials can be classified into piezoelectric single crystals, polycrystalline piezoelectric ceramics, piezoelectric thin films, polymer piezoelectric materials, polymer-piezoelectric ceramic composites, and novel piezoelectric materials.

[0003] Perovskite ferroelectrics possess the ability to convert mechanical energy into electrical energy, making them a fundamental material for piezoelectric sensors and transducers. Among these, high-performance lead zirconate titanate [Pb(Zr,Ti)O3,PZT]-based piezoelectric ceramics are widely used in piezoelectric devices due to their superior piezoelectric coefficient and high Curie temperature. However, the application of lead-containing piezoelectric materials is detrimental to ecological protection and sustainable human development, thus prompting focused research on the development of lead-free piezoelectric materials.

[0004] Barium titanate (BaTiO3, BT)-based ceramics have been extensively studied due to their excellent piezoelectric properties and lead-free structure. Barium titanate is a white powder and, as a typical ABO3-type functional material, mainly exists in two crystal forms: cubic (paraelectric) and tetragonal (ferroelectric). Cubic barium titanate has a highly symmetrical structure, exhibiting paraelectricity and acting as an isotropic dielectric. Tetragonal barium titanate, due to the spontaneous polarization of its tetragonal structure, possesses significant ferroelectric, piezoelectric, thermoelectric, and energy harvesting properties, making it widely used in various electronic devices in the ceramics industry, such as multilayer ceramic capacitors, dynamic random access memory (DRAM), and thermistors. Barium titanate is hailed as the "pillar of the electronic ceramics industry" and is one of the most widely used and consumed raw materials in electronic ceramics.

[0005] Barium titanate is the earliest discovered lead-free piezoelectric ceramic and can be used in various energy conversion, sound conversion, signal conversion, and oscillation, microwave, and sensor devices based on piezoelectric equivalent circuits. However, due to the relatively low piezoelectric properties of the prepared barium titanate-based ceramic materials, its application examples are currently limited. Firstly, surface defects and inhomogeneities of barium titanate affect its bonding with the polymer matrix, leading to unstable electrical and mechanical properties of the composite material. Secondly, barium titanate has a weak polarization electric field, which cannot fully utilize its piezoelectric properties.

[0006] Chinese patent CN118851745A, filed on September 25, 2024, discloses a barium titanate ceramic piezoelectric thin film and its preparation method. By selecting raw materials containing a specific mass ratio of titanium source and barium source to prepare barium titanate ceramic piezoelectric thin film, the barium titanate ceramic piezoelectric thin film obtained after calcination directly possesses piezoelectric catalytic performance without further polarization treatment, simplifying the preparation process of barium titanate ceramic piezoelectric thin film and improving the preparation efficiency of ceramic piezoelectric thin film. However, this preparation method focuses on improving the grain boundary density of barium titanate ceramic piezoelectric thin film at the microscopic level, without fundamentally repairing the surface defects of barium titanate.

[0007] Chinese patent CN114262222A, filed on December 31, 2021, discloses a method for regulating the resistivity and polarization intensity of bismuth ferrite-barium titanate-based piezoelectric ceramic materials. This method controls the stoichiometry of the bismuth ferrite-barium titanate-based piezoelectric ceramic materials to regulate their resistivity and polarization intensity. However, this method requires the ceramic powder to undergo granulation, blanking, plasticizing, and sintering, followed by air quenching to regulate the polarization intensity. This process is not only complex but also fails to disclose any technical features related to improving electrical stability.

[0008] With the increasing demand for lead-free materials and the rapid development of smart wearable devices and flexible electronics, piezoelectric materials are being used more and more widely in sensors, thin films and coatings. Barium titanate-based ceramics, as a promising alternative to PZT, have regained attention. Therefore, it is urgent to study a barium titanate-polymer composite material that can simultaneously possess excellent piezoelectric properties, good stability and mechanical properties. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a piezoelectric composite material based on in-situ modified barium titanate, its preparation method, and its application. Utilizing the covalent chemical bond and physical interaction between 2-thienylacetonitrile and barium titanate, the 2-thienylacetonitrile molecular chain is firmly attached to the surface of barium titanate particles, repairing surface defects and chemical inertness of barium titanate. Furthermore, 1-ethyl-3-methylimidazolium sulfate is introduced to enhance the polarization electric field in conjunction with the barium titanate modified material, resulting in a piezoelectric composite material with excellent piezoelectric properties, good stability, and mechanical properties.

[0010] The technical solution of the present invention is as follows: One objective of this invention is to provide a method for preparing a piezoelectric composite material based on in-situ modified barium titanate, the preparation steps of which are as follows: (1) Barium titanate and 2-thienylacetonitrile were mixed in isopropanol solution and stirred continuously to react, and barium titanate modified material was obtained by in-situ modification. (2) The barium titanate modified material is ball-milled with polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate ethyl ester and 819 photoinitiator until uniform, and then photocured to obtain the piezoelectric composite material.

[0011] Furthermore, in step (1), the mass ratio of 2-thienylacetonitrile to barium titanate is 1:2, the modification temperature is room temperature, and the stirring time is 24-26 h.

[0012] Furthermore, in step (1), the mass ratio of barium titanate to isopropanol is 1:100.

[0013] Further, in step (2), the mass ratio of polyurethane acrylate to barium titanate modified material is 1:1; the mass ratio of 1-ethyl-3-methylimidazolium sulfate to polyurethane acrylate is 0.05:1; and the mass ratio of 819 photoinitiator to polyurethane acrylate is 0.02:1.

[0014] Furthermore, in step (2), the ball milling time is 12-14 h and the ball milling speed is 300 rpm.

[0015] Furthermore, in step (2), the photocuring process uses ultraviolet light or laser curing technology, with a photocuring temperature of 50-80℃ and a curing time of 10 min.

[0016] The second objective of this invention is to provide a piezoelectric composite material based on in-situ modified barium titanate, wherein the piezoelectric composite material has a stable composite structure formed by barium titanate modified material, 1-ethyl-3-methylimidazolium sulfate, and polyurethane acrylate.

[0017] Furthermore, the piezoelectric coefficient d of the piezoelectric composite material 33 It is 35 pC / N. The third objective of this invention is to provide an application of a piezoelectric composite material based on in-situ modified barium titanate in the fabrication of wearable sensors.

[0018] The fourth objective of this invention is to provide an application of in-situ modified barium titanate piezoelectric composite material in the preparation of piezoelectric coatings.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention innovatively proposes a method for preparing piezoelectric composite materials without damaging the original properties of barium titanate and polymer composites. It utilizes 2-thienylacetonitrile to modify barium titanate, enabling a stable chemical bond between the two materials through coordination bonds or oxygen vacancies. This ensures that the 2-thienylacetonitrile molecular chains firmly adhere to the surface of the barium titanate particles, thereby repairing surface defects in barium titanate and enhancing the compatibility between barium titanate and the polymer matrix. This robust bonding not only enhances piezoelectric properties but also improves mechanical stability, temperature resistance, and chemical resistance. It overcomes the modification difficulties caused by surface defects and chemical inertness in conventional barium titanate materials, and solves the limitations imposed by surface defects on the piezoelectric properties of traditional barium titanate-based piezoelectric materials, as well as the impact of poor dispersibility and interfacial compatibility on material stability and overall performance.

[0020] 2. The piezoelectric composite material designed in this invention possesses excellent piezoelectric properties, good stability, and mechanical properties. It not only improves surface quality and enhances the polarization electric field but also improves the bonding force with the polymer matrix. This invention introduces 1-ethyl-3-methylimidazolium sulfate ionic liquid. Utilizing the dispersion of the ionic liquid in the polymer matrix, it can interact with modified barium titanate to increase the electric field strength of the piezoelectric composite material during polarization, further enhancing the piezoelectric properties. Simultaneously, the interaction between the ionic liquid and the polymer, especially the interaction between the cations of the ionic liquid and the negatively charged portion of the polymer matrix, also improves the material's conductivity and stability.

[0021] 3. This invention achieves efficient and low-energy preparation of piezoelectric composite materials through a simple ball milling and photocuring method without adding complex processes. Furthermore, the 1-ethyl-3-methylimidazolium sulfate ionic liquid used is environmentally friendly and non-toxic, ensuring the safety and sustainability of the material. In addition, the novel piezoelectric composite material obtained by this invention exhibits good mechanical and electrical stability, making it suitable for various practical applications such as high-performance wearable sensors and piezoelectric coatings. Attached Figure Description

[0022] Figure 1 The performance tests of this invention used pure barium titanate / polyurethane acrylate, barium titanate / polyurethane acrylate modified with 2-thienylacetonitrile, and barium titanate / polyurethane acrylate / ionic liquid were conducted to determine their d-values. 33 Test data graph; Figure 2The figures show the hysteresis loops of barium titanate / polyurethane acrylate composites modified with ionic liquid / 2-thienylacetonitrile at different filler mass fractions in the performance test of this invention. Among them, BTO-T20 is barium titanate / polyurethane acrylate modified with ionic liquid / 2-thienylacetonitrile at a mass fraction of 20%, BTO-T40 is barium titanate / polyurethane acrylate modified with ionic liquid / 2-thienylacetonitrile at a mass fraction of 40%, and BTO-T60 is barium titanate / polyurethane acrylate modified with ionic liquid / 2-thienylacetonitrile at a mass fraction of 60%. Figure 3 The diagram shows the open-circuit voltage of unmodified barium titanate and barium titanate modified with 2-thienylacetonitrile / ionic liquid in the performance test of this invention. BTO / PUA is pure barium titanate / polyurethane acrylate, and IL / 2-T-OACN modifiedBTO / PUA is barium titanate / polyurethane acrylate modified with ionic liquid / 2-thienylacetonitrile. Detailed Implementation

[0023] The present invention will be further described below with reference to preferred embodiments. The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values. These ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed herein. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0024] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. Example 1 This embodiment provides a method for preparing a piezoelectric composite material based on in-situ modified barium titanate, including the following steps: (1) 1g of barium titanate and 0.5g of 2-thienylacetonitrile were mixed in 100g of isopropanol solution and stirred continuously for 24 h to obtain barium titanate modified material by in-situ modification at room temperature. (2) The barium titanate modified material, polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate ethyl ester and 819 photoinitiator were ball-milled at a mass ratio of 1:1:0.05:0.02 until uniform. The ball milling time was 12 h and the ball milling speed was 300 rpm. (3) Using ultraviolet light curing technology, the mixture obtained in step (2) is cured at 50°C for 10 min. After light curing, it becomes the piezoelectric composite material.

[0025] Example 2 This embodiment provides a piezoelectric composite material based on in-situ modified barium titanate, the preparation method of which includes the following steps: (1) 1g of barium titanate and 0.5g of 2-thienylacetonitrile were mixed in 100g of isopropanol solution and stirred continuously for 25 h to obtain barium titanate modified material by in-situ modification at room temperature. (2) The barium titanate modified material, polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate ethyl ester and 819 photoinitiator were ball-milled at a mass ratio of 1:1:0.05:0.02 until uniform. The ball milling time was 13 h and the ball milling speed was 300 rpm. (3) Using ultraviolet light curing technology, the mixture obtained in step (2) is cured at 65°C for 10 min. After light curing, it becomes the piezoelectric composite material.

[0026] Example 3 This embodiment provides a method for preparing a piezoelectric composite material based on in-situ modified barium titanate, including the following steps: (1) 1g of barium titanate and 0.5g of 2-thienylacetonitrile were mixed in 100g of isopropanol solution and stirred continuously for 26 h to obtain barium titanate modified material by in-situ modification at room temperature. (2) The barium titanate modified material, polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate ethyl ester and 819 photoinitiator were ball-milled at a mass ratio of 1:1:0.05:0.02 until uniform. The ball milling time was 14 h and the ball milling speed was 300 rpm. (3) Using laser curing technology, the mixture obtained in step (2) is cured at 80°C for 10 min. After photocuring, it becomes the piezoelectric composite material.

[0027] Comparative Example 1 This embodiment provides a method for preparing a piezoelectric composite material based on in-situ modified barium titanate. The specific experimental steps are the same as in Example 1, except that the mass ratio of 2-thiophene acetonitrile to barium titanate is changed to 1:1.

[0028] Comparative Example 2 This embodiment provides a method for preparing a piezoelectric composite material based on in-situ modified barium titanate. The specific experimental steps are the same as in Example 1, except that the mass ratio of 2-thiophene acetonitrile to barium titanate is changed to 3:1.

[0029] Comparative Example 3 This embodiment provides a method for preparing a piezoelectric composite material based on in-situ modified barium titanate. The specific experimental steps are the same as in Example 1, except that the mass ratio of 2-thiophene acetonitrile to barium titanate is changed to 4:1.

[0030] Comparative Example 4 This embodiment provides a method for preparing a piezoelectric composite material, including the following steps: (1) 0.5g of 2-thienylacetonitrile, polyurethane acrylate, ionic liquid and 819 photoinitiator were added to a ball mill for ball milling and mixing. The ball milling time was 12 h and the ball milling speed was 300 rpm. (2) The mixture was cured by UV curing technology. The curing temperature was 75°C and the curing time was 10 minutes to obtain the piezoelectric composite material.

[0031] Performance testing 1. Piezoelectric properties d 33 test The piezoelectric properties of pure barium titanate / polyurethane acrylate, barium titanate / polyurethane acrylate modified with 2-thienylacetonitrile, and barium titanate / polyurethane acrylate / ionic liquid modified with 2-thienylacetonitrile as described in Example 1 were measured. 33 The test involved cutting the cured sample into Φ10 mm discs, coating the surface with gold electrodes, and then subjecting the samples to electric field polarization to activate their piezoelectric properties. Quasi-static d-axis polarization was then used. 33 The measuring instrument performs d 33 test.

[0032] Test results are as follows Figure 1 As shown, modification of barium titanate with 2-thienylacetonitrile alters its surface properties, enhancing the interfacial interaction between barium titanate and the polyurethane acrylate matrix. This improves stress transfer efficiency within the material and enhances the dispersion of barium titanate in the polyurethane acrylate matrix, leading to an increase in the piezoelectric coefficient. The addition of 1-ethyl-3-methylimidazolium sulfate ionic liquid creates ion migration channels within the material. Under mechanical stress, ions migrate, generating an additional electric field. This field superimposes with the piezoelectric material's own electric field, further enhancing the piezoelectric output signal and increasing the piezoelectric coefficient.

[0033] 2. Hysteresis loop test Hysteresis loop tests were performed on BTO-T20, BTO-T40, and BTO-T60. The test results are as follows: Figure 2 As shown, with the increase of the mass fraction of BTO filler, the polarization ability of the composite material is enhanced, and its polarization intensity becomes higher and higher.

[0034] 3. Open circuit voltage test Open-circuit voltage tests were performed on unmodified barium titanate and barium titanate modified with 2-thienylacetonitrile / ionic liquid. BTO / PUA was pure barium titanate / polyurethane acrylate, and IL / 2-T-OACN modified BTO / PUA was the barium titanate / polyurethane acrylate modified with the ionic liquid / 2-thienylacetonitrile described in Example 1. A combination of a mechanical vibration table and a high-impedance voltmeter was used. First, the sample was fixed on the surface of the vibration table, and the mechanical load conditions were simulated by adjusting the vibration frequency and amplitude. The high-impedance voltmeter was connected to both ends of the sample to record the transient voltage signal of the material in real time. During the experiment, the vibration table frequency ranged from 10 to 100 Hz.

[0035] Test results are as follows Figure 3 As shown, the open-circuit voltage of BTO / PUA is relatively low. With applied voltage, the voltage gradually increases, but the increase is small, eventually reaching a relatively stable value. The open-circuit voltage of IL / 2-T-OACN modified BTO / PUA is significantly higher than that of BTO / PUA. With applied voltage, the voltage increases rapidly and significantly, eventually reaching a higher stable value. 2-Thienylacetonitrile modification effectively repairs defects such as oxygen vacancies on the surface of barium titanate particles through chemical bonding and surface wetting effects, thereby improving the polarization electric field of the particles. Simultaneously, the modification significantly improves the dispersion and uniformity of the particles in the polymer matrix, avoiding agglomeration and thus improving the overall polarization capability of the material. The introduction of ionic liquid further optimizes the charge transport efficiency of the material. This improvement in interfacial electrical properties not only enhances the electrical response of the material but also significantly improves its signal stability. Through the synergistic effect of multiple mechanisms of 2-thienylacetonitrile and ionic liquid, the open-circuit voltage of the barium titanate / polyurethane acrylate composite material is effectively improved.

[0036] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a piezoelectric composite material based on in-situ modified barium titanate, characterized in that, The preparation steps are as follows: (1) Barium titanate and 2-thienylacetonitrile were mixed in isopropanol solution and stirred continuously to react, and barium titanate modified material was obtained by in-situ modification. (2) The barium titanate modified material is ball-milled with polyurethane acrylate, 1-ethyl-3-methylimidazolium sulfate ethyl ester and 819 photoinitiator until uniform, and then photocured to obtain the piezoelectric composite material.

2. The method for preparing a piezoelectric composite material based on in-situ modified barium titanate according to claim 1, characterized in that, In step (1), the mass ratio of 2-thienylacetonitrile to barium titanate is 1:2, the modification temperature is room temperature, and the stirring time is 24-26 h.

3. The method for preparing a piezoelectric composite material based on in-situ modified barium titanate according to claim 1, characterized in that, In step (1), the mass ratio of barium titanate to isopropanol is 1:

100.

4. The method for preparing a piezoelectric composite material based on in-situ modified barium titanate according to claim 1, characterized in that, In step (2), the mass ratio of polyurethane acrylate to barium titanate modified material is 1:1; the mass ratio of 1-ethyl-3-methylimidazolium sulfate to polyurethane acrylate is 0.05:1; and the mass ratio of 819 photoinitiator to polyurethane acrylate is 0.02:

1.

5. The method for preparing a piezoelectric composite material based on in-situ modified barium titanate according to claim 1, characterized in that, In step (2), the ball milling time is 12-14 h and the ball milling speed is 300 rpm.

6. The method for preparing a piezoelectric composite material based on in-situ modified barium titanate according to claim 1, characterized in that, In step (2), the photocuring process uses ultraviolet light or laser curing technology, with a photocuring temperature of 50-80℃ and a curing time of 10 min.

7. A piezoelectric composite material based on in-situ modified barium titanate prepared by the method according to any one of claims 1-6, characterized in that, The piezoelectric composite material has a stable composite structure formed by barium titanate modified material, ethyl 1-ethyl-3-methylimidazolium sulfate, and polyurethane acrylate.

8. The piezoelectric composite material based on in-situ modified barium titanate according to claim 7, characterized in that, The piezoelectric coefficient d of the piezoelectric composite material 33 It is 35 pC / N.

9. The application of a piezoelectric composite material based on in-situ modified barium titanate according to claim 7 or 8 in the fabrication of wearable sensors.

10. The application of a piezoelectric composite material based on in-situ modified barium titanate according to claim 7 or 8 in the preparation of a piezoelectric coating.

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