A method for preparing a stretchable piezoelectric composite
By preparing piezoelectric composite materials through co-foaming and polar polymer coating, the problem of the inverse coupling between flexibility and piezoelectric properties is solved, and high-performance flexible piezoelectric composite materials are prepared, which are suitable for ultrasonic sensors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TSINGHUA UNIVERSITY
- Filing Date
- 2022-03-17
- Publication Date
- 2026-07-21
AI Technical Summary
Existing piezoelectric composite materials exhibit an inverse coupling relationship between maintaining flexibility and increasing the piezoelectric coefficient, leading to deterioration of mechanical properties and making it difficult to simultaneously obtain high-performance flexibility and piezoelectric properties.
Dense piezoelectric composite materials are prepared by co-foaming piezoelectric ceramic particles with a pore-forming agent, sintering them, coating them with a polar polymer or a composite medium based on a polar polymer, and then compounding them with silicone rubber.
It achieves high piezoelectric coefficient, low acoustic impedance and good mechanical flexibility. The piezoelectric properties are stable under 20% uniaxial tensile strain. The electrostrain performance is comparable to that of commercial piezoelectric ceramics. It is suitable for ultrasonic sensors without an acoustic matching layer.
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Figure CN116828960B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of piezoelectric composite materials, and particularly relates to a method for preparing a flexible and stretchable piezoelectric composite material. Background Technology
[0002] Piezoelectric composites are composite materials made of ferroelectric ceramics and polymers such as rubber or resin, capable of converting mechanical energy into electrical energy. Ferroelectric ceramics typically possess good piezoelectric properties but lack flexibility, while polymers usually possess excellent mechanical flexibility but often lack or only have weak piezoelectricity. By combining polymers with a certain degree of flexibility with piezoelectric ceramic particles, fibers, or structured piezoelectric ceramic frameworks, it is possible to obtain piezoelectric composite materials that achieve both good piezoelectric properties and a certain degree of flexibility.
[0003] Compared with traditional piezoelectric ceramic materials, piezoelectric composite materials have advantages such as lower acoustic impedance and higher hydrostatic pressure sensitivity, thus showing broad application prospects in ultrasonic transducers and other fields. In recent years, piezoelectric composite materials based on ferroelectric polymers or linear polymers have been extensively studied. Among them, the "0-3" type piezoelectric composite material (a polymer-based composite material with randomly filled ceramic particles. When the ceramic particles are not connected in any direction, its connectivity is defined as "0"; when the ceramic particles are connected in a certain direction, its connectivity is defined as "1". The polymer matrix is a three-dimensional connected structure, so its connectivity is defined as "3") has become a hot topic in scientific research due to its excellent flexibility and simple preparation process.
[0004] However, the polarization shielding and discontinuity in "0-3" type piezoelectric composites significantly affect their piezoelectric properties, resulting in a large gap in piezoelectric coefficient compared to traditional ceramics or ferroelectric polymers such as polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE). These types of piezoelectric composites typically require high filler content to achieve only a limited improvement in piezoelectric performance, at which point their mechanical properties deteriorate. While "1-3" type piezoelectric composites possess relatively high piezoelectric coefficients, even approaching those of piezoelectric ceramics with high ceramic content, they exhibit poor flexibility and complex manufacturing processes. The high ceramic content also contributes to their macroscopic brittleness and relatively high acoustic impedance. Piezoelectric composites with a certain degree of interconnected skeleton structure prepared using methods such as freeze-drying and template sacrificial methods still struggle to simultaneously achieve good mechanical flexibility and a high piezoelectric coefficient.
[0005] Because the maintenance of mechanical flexibility and the improvement of piezoelectric coefficient in piezoelectric composites have an inverse coupling relationship, obtaining a high piezoelectric coefficient in composites is often accompanied by a deterioration in mechanical properties. This hinders the development of high-performance flexible piezoelectric composites and their sensors. Therefore, developing piezoelectric composites that combine good mechanical properties with comprehensive piezoelectric properties is a current research focus and challenge. Summary of the Invention
[0006] The purpose of this invention is to overcome the defects of the aforementioned piezoelectric composite materials and provide a high-performance piezoelectric composite material with high stretchability, low acoustic impedance, and high piezoelectric coefficient. This method involves co-foaming piezoelectric ceramic particles with a pore-forming agent, sintering them, coating them with a polar polymer or a composite medium based on a polar polymer, and then laminating them with silicone rubber to form a dense piezoelectric composite material.
[0007] The piezoelectric composite material provided by the present invention is prepared by a method including the following steps: piezoelectric ceramic particles are co-foamed with a pore-forming agent, sintered, coated with a polar polymer or a composite medium based on a polar polymer, and then composited with silicone rubber to obtain the final product.
[0008] The present invention also provides a method for preparing the above-mentioned piezoelectric composite material, comprising the following steps:
[0009] (1) A slurry obtained by mixing piezoelectric ceramic particles with a pore-forming agent was used as a co-foaming precursor, and a piezoelectric ceramic porous framework was prepared by a surfactant-assisted rapid stirring co-foaming-high temperature sintering process.
[0010] (2) Impregnate the piezoelectric ceramic porous framework with a polymer solution or a polymer-conductive filler mixture to obtain a polymer-coated or polymer composite medium-coated composite porous framework material.
[0011] (3) Silicone rubber is used to infuse the porous composite skeleton material and then cured at high temperature to obtain a stretchable flexible piezoelectric composite material.
[0012] In step (1) of the above method, the types of surfactants used in the co-foaming process include, but are not limited to, any one or a mixture of several of sodium dodecyl sulfate (SDS), sodium linear alkylbenzene sulfonate (LAS) (such as sodium dodecylbenzene sulfonate (SDBS)), sodium fatty alcohol polyoxyethylene ether sulfate (AES), and ammonium fatty alcohol polyoxyethylene ether sulfate (AESA).
[0013] The stirring speed in the stirring co-foaming process can be 1200 rpm to 2500 rpm;
[0014] The piezoelectric ceramics include, but are not limited to, any one or a mixture of two of lead zirconate titanate (PZT) and barium titanate (BT);
[0015] The mass ratio of surfactant to piezoelectric ceramic can be 1:1000-1:500, specifically 1:1000;
[0016] The pore-forming agent used in the co-foaming process includes, but is not limited to, any one or a mixture of several of carbon nanotubes, graphene, and carbon black particles.
[0017] The mass ratio of pore-forming agent to piezoelectric ceramic particles can be 1:500-1:10, specifically 1:200;
[0018] The operation of rapid stirring co-foaming with surfactant assistance is as follows: dissolve piezoelectric ceramic powder, surfactant and pore-forming agent in water, stir at low speed until uniform, and then stir at high speed.
[0019] The low-speed stirring rate can be 400 rpm, and the time can be 30 min;
[0020] The high-speed stirring rate can be 1500 rpm, and the time can be 10 minutes;
[0021] After co-foaming but before high-temperature sintering, the process may further include drying the resulting ceramic foam.
[0022] The high-temperature sintering temperature can be 1000℃-1400℃, and the sintering time can be 0.5 hours-3 hours, such as sintering at 1200℃ for 2 hours.
[0023] In step (2) of the above method, the polymer includes, but is not limited to, any one or a mixture of several of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (P(VDF-TrFE-CTFE)), and polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene (P(VDF-TrFE-CFE)).
[0024] The polymer is P(VDF-TrFE), in which the molar ratio of the two copolymer units VDF and TrFE in P(VDF-TrFE) includes, but is not limited to, 50:50, 60:40, 70:30, 80:20, and 90:10; the molecular weight of P(VDF-TrFE) can be 50,000 to 1,000,000, such as 470,000.
[0025] The polymer is P(VDF-TrFE-CFE), and the molar ratio of the three copolymer units VDF, TrFE and CFE in P(VDF-TrFE-CFE) is including but not limited to 60:30:10.
[0026] In step (2) of the above method, the conductive filler may be carbon nanotubes and / or graphene;
[0027] The mass ratio of conductive filler to polymer can be any ratio within the range of 0-1:50, such as 1:1000.
[0028] The solvent used in the polymer solution or the polymer-conductive filler mixture is N,N-dimethylformamide (DMF) or a mixture of acetone and DMF, wherein the volume ratio of DMF to acetone in the mixture of acetone and DMF can be any ratio in the range of 4:1 to 1:4, such as 1:1.
[0029] The mass fraction of the polymer in the polymer solution or polymer-conductive filler mixture can be 1%-70%, such as 30%.
[0030] In step (2) of the above method, the immersion time is greater than 1 minute, such as 1 hour.
[0031] Step (2) of the above method may further include drying the obtained material after impregnation. The drying may specifically be blower drying, and the temperature of the blower drying is not lower than 30°C and not higher than 250°C, such as 140°C.
[0032] In step (3) of the above method, the silicone rubber can be any grade of silicone rubber, such as polydimethylsiloxane (PDMS).
[0033] The high-temperature curing temperature can be 30℃-150℃, such as 110℃; the high-temperature curing time can be 0.5 hours-24 hours, such as 1 hour of curing at 110℃.
[0034] The above method may further include (4) coating the obtained piezoelectric composite material with electrode material and polarizing it under high voltage, and attaching a backing layer to the polarized piezoelectric composite material to obtain the operation of the piezoelectric composite material sensor device.
[0035] In step (4) of the above method, the electrode material can be prepared by coating with silver paste or magnetron sputtering of gold electrodes;
[0036] The electric field strength of high-voltage polarization can be 20-50 kV / cm, and the polarization temperature can be 20-60℃;
[0037] The backing layer can be made from any commercially available backing material.
[0038] The piezoelectric composite material prepared by the above method is also within the scope of protection of this invention.
[0039] Sensing / transducer devices containing piezoelectric composite materials prepared by the above method are also within the scope of protection of this invention.
[0040] As can be seen from the above technical solution, this invention achieves the synthesis of a functional ceramic skeleton coated with a polymer composite dielectric layer through a simple co-foaming and impregnation process. After infusion and curing, a flexible piezoelectric composite material can be prepared. After mounting, a piezoelectric sensor can be fabricated. The entire process is suitable for automated, mechanized, and large-scale production. The resulting piezoelectric composite material has a piezoelectric coefficient far exceeding that of traditional ferroelectric polymers and "0-3" type piezoelectric composite materials. The positive piezoelectric coefficient of the piezoelectric composite material can reach 110 pC N. -1 The above electrostriction can reach 200 pm V. -1 The above requirements include an acoustic impedance of less than 4 Mrayl and a hydrostatic pressure sensitivity of more than 10 pm. 2 N -1 Meanwhile, the piezoelectric performance indicators remain essentially stable under uniaxial tensile strain within 20%. While maintaining flexibility and stretchability, its positive piezoelectric coefficient is comparable to BT piezoelectric ceramics, its electrostriction is comparable to commercial piezoelectric ceramics (PZT-5), and it exhibits a much lower acoustic impedance level than piezoelectric ceramics. When used as an acoustic wave receiver, the fabricated piezoelectric composite sensor can achieve a relative bandwidth of over 40% and a high pulse output signal at -6dB without the need for an acoustic matching layer.
[0041] Compared with the prior art, the present invention has the following beneficial effects:
[0042] The piezoelectric composite material prepared by this invention has excellent piezoelectric properties. The positive piezoelectric coefficient is improved by an order of magnitude compared with the ferroelectric polymer P (VDF-TrFE) and reaches the same order of magnitude as commercial piezoelectric ceramics.
[0043] The piezoelectric composite material prepared by this invention has excellent electro-strain properties, and its electro-strain under power frequency testing conditions is comparable to that of commercial piezoelectric ceramics.
[0044] The piezoelectric composite material prepared by this invention achieves good mechanical flexibility and stretchability by effectively controlling the ceramic content, with a maximum tensile strain of over 30%.
[0045] The piezoelectric composite material prepared by this invention exhibits excellent tensile stability within a 20% uniaxial tensile strain range.
[0046] The piezoelectric composite material prepared by this invention has a low acoustic impedance, which is about an order of magnitude lower than that of commercial piezoelectric ceramics and close to that of ferroelectric polymer P(VDF-TrFE).
[0047] The piezoelectric composite material prepared by this invention can be used in the receiver of an ultrasonic sensor without the need for an acoustic matching layer, and has a large response bandwidth and strong output signal. Attached Figure Description
[0048] Figure 1 This is a schematic diagram of the process for preparing the piezoelectric ceramic framework of the present invention.
[0049] Figure 2 This is a schematic diagram of the process for preparing the piezoelectric ceramic composite material of the present invention.
[0050] Figure 3 The images show the morphology of the PZT ceramic framework obtained in Example 1 of this invention. (a)(b) Scanning electron microscope images of the microstructure, and (c) Macroscopic sample image.
[0051] Figure 4 The images show the morphology of the BT ceramic skeleton obtained in Example 2 of this invention. (a) and (b) are scanning electron microscope images of the microstructure, and (c) is a macroscopic sample image.
[0052] Figure 5 The images show the morphology of the piezoelectric composite material obtained in Example 3 of this invention. (a) Scanning electron microscope (SEM) image of the composite PZT ceramic skeleton microstructure, and (b) Scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material.
[0053] Figure 6 The images show the morphology of the piezoelectric composite material obtained in Example 4 of this invention. (a) Scanning electron microscope (SEM) image of the composite PZT ceramic skeleton microstructure, and (b) Scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material.
[0054] Figure 7 The images show the morphology of the piezoelectric composite material obtained in Example 5 of this invention. (a) Scanning electron microscope (SEM) image of the composite BT ceramic skeleton microstructure, and (b) Scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material.
[0055] Figure 8 The following are the dielectric property test results of piezoelectric composite materials with different structures in Example 7 of this invention. (a) The dielectric constant of piezoelectric composite materials with different structures based on PZT at room temperature as a function of frequency; (b) The dielectric constant of piezoelectric composite materials with different structures based on PZT as a function of temperature within the temperature range of 15-120℃. Frequency sweep tests were performed on the piezoelectric composite materials every 5℃ within the test temperature range while maintaining relatively stable temperatures. (c) The dielectric constant of the BT-based piezoelectric composite material at room temperature as a function of frequency; (d) The dielectric constant of the BT-based piezoelectric composite material within the temperature range of 50-140℃ as a function of temperature.
[0056] Figure 9The following are the ferroelectric test results for piezoelectric composites with different structures based on PZT and BT in Example 8. During the ferroelectric tests, an electric field of 3-6 kV / mm was applied to the piezoelectric composites, and the frequency of the applied electric field was 10 Hz. (a) Ferroelectric loops of piezoelectric composites with different structures under static conditions, (b) Ferroelectric loops of PZT-based piezoelectric composites after different strain compression cycles.
[0057] Figure 10 The results of the piezoelectric performance test of the piezoelectric composite material in Example 9 are shown. (a) Quasi-static piezoelectric coefficient of the piezoelectric composite material in Example 4, (b) Electroinduced strain.
[0058] Figure 11 The mechanical property test results are shown in Example 10. (a) Tensile stress-strain curve of the PZT-based piezoelectric composite material. The tensile loading rate was 0.3 mm / min. (b) Cyclic compressive stress-strain curve of the PZT-based piezoelectric composite material. The compressive loading rate was 0.05 mm / min, and the number of compression cycles was 5.
[0059] Figure 12 The fatigue performance test results of the PZT-based piezoelectric composite material in Example 11 are as follows: (a) Change in piezoelectric coefficient under cyclic tensile stress. The cyclic tensile strain was kept at 20%, and the maximum number of cycles was 100,000. The piezoelectric coefficient of the piezoelectric composite material was tested using the quasi-static method after the 1st, 10th, 100th, 1000th, 10000th, and 100000th cycles, respectively. (b) Change in piezoelectric coefficient under cyclic bending stress. The radius of curvature was kept at 5 mm during cyclic bending, and the maximum number of cycles was 100,000. The piezoelectric coefficient of the piezoelectric composite material was tested using the quasi-static method after the 1st, 10th, 100th, 1000th, 10000th, and 100000th cycles, respectively.
[0060] Figure 13 The results of the ultrasonic sensing performance test of the piezoelectric composite material in Example 12 are shown. (a) Output amplitude, (b) Frequency domain characteristics. Detailed Implementation
[0061] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.
[0062] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.
[0063] Example 1: Preparation of PZT piezoelectric ceramic framework
[0064] according to Figure 1 The schematic diagram shown illustrates the preparation of the PZT ceramic framework. The specific steps are as follows:
[0065] (1) Weigh 10g of PZT ceramic powder (Tongxiang Qingfeng Technology Co., Ltd.), 0.01g of surfactant (sodium dodecyl sulfate, Sinopharm Chemical Reagent Co., Ltd., product code: 30166428) and 0.05g of pore-forming agent (carbon nanotubes, Nanjing Xianfeng Nano, item number: 100221), measure 6ml of deionized water and dissolve the ceramic powder, surfactant and pore-forming agent in the deionized water at the same time.
[0066] (2) Stir the resulting mixture at a speed of 400 rpm until homogeneous. Stirring time is approximately 30 minutes.
[0067] (3) Slowly increase the stirring speed to 1500 rpm and maintain it for 10 minutes to obtain PZT ceramic foam.
[0068] (4) After drying the PZT ceramic foam at room temperature for about 48 hours, it is sintered at high temperature. The temperature is raised to 1200℃ at a rate of 5-10℃ per minute and held for 2 hours before being cooled in the furnace to obtain the PZT ceramic skeleton.
[0069] The microstructure scanning electron microscope image of the PZT ceramic framework prepared in this embodiment is shown below. Figure 3 As shown in (a) and 3(b), macroscopic sample photographs are as follows. Figure 3 As shown in (c).
[0070] Example 2: Preparation of BT piezoelectric ceramic framework
[0071] according to Figure 1 The schematic diagram shown illustrates the fabrication of the BT ceramic framework. The specific steps are as follows:
[0072] (1) Weigh 10g of BT ceramic powder (Shandong Guoci), 0.01g of surfactant (sodium dodecyl sulfonate, Sinopharm Chemical Reagent Co., Ltd., product code: 30166428) and 0.05g of pore-forming agent (carbon nanotubes, Nanjing Xianfeng Nano, item number: 100221), measure 6ml of deionized water and dissolve the ceramic powder, surfactant and pore-forming agent in the deionized water at the same time.
[0073] (2) Stir the resulting mixture at a speed of 400 rpm until homogeneous. Stirring time is approximately 30 minutes.
[0074] (3) Slowly increase the stirring speed to 1500 rpm and maintain it for 10 minutes to obtain BT ceramic foam.
[0075] (4) After drying the PZT ceramic foam at room temperature for about 48 hours, it was sintered at high temperature. The temperature was increased to 1200℃ at a rate of 5-10℃ per minute and held for 2 hours before being cooled in the furnace to obtain the BT ceramic skeleton.
[0076] The scanning electron microscope image of the microstructure of the BT ceramic framework prepared in this embodiment is shown below. Figure 4 As shown in (a) and 4(b), macroscopic sample photographs are as follows. Figure 4 As shown in (c).
[0077] Example 3: Preparation of piezoelectric composite materials based on polymer-coated composite PZT ceramic skeletons
[0078] according to Figure 2 The schematic diagram shown illustrates the preparation of piezoelectric composite materials. The specific steps are as follows:
[0079] (1) Measure 0.6g of polymer P (VDF-TrFE-CFE) (molecular weight of 400,000, molar ratio of VDF, TrFE and CFE copolymer units of 60:30:10) (Arkema), add it to 15mL of DMF solvent (Sinopharm Group), and stir until a clear solution is obtained.
[0080] (2) The PZT ceramic skeleton prepared in Example 1 was immersed in the blending solution and soaked for about 30 minutes before being taken out and dried to obtain a polymer-coated composite PZT ceramic skeleton.
[0081] (3) The composite PZT ceramic skeleton was immersed in uncrosslinked silicone rubber (polydimethylsiloxane, Dow Corning), kept under a vacuum of 5 Pascals for 12 hours, and then cured at normal pressure and 110°C for about 30 minutes to obtain the piezoelectric composite material.
[0082] The scanning electron microscope image of the composite PZT ceramic framework microstructure prepared in this embodiment is shown below. Figure 5 As shown in (a), the scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material is as follows. Figure 5 As shown in (b).
[0083] Example 4: Preparation of piezoelectric composite materials based on polymer composite dielectric-coated composite PZT ceramic skeletons according to... Figure 2 The schematic diagram shown illustrates the preparation of a composite piezoelectric material. The specific steps are as follows:
[0084] (1) Measure 0.6g of polymer P (VDF-TrFE-CFE) (molecular weight of 400,000, molar ratio of VDF, TrFE and CFE copolymer units of 60:30:10), add it to 15mL of DMF solvent, and stir until a clear solution is obtained.
[0085] (2) Weigh 0.0005 g of carbon nanotubes and add them to the aforementioned polymer solution to form a blend solution. Use an ultrasonic instrument to sonicate the blend solution for 30 minutes to uniformly disperse the carbon nanotubes.
[0086] (3) The PZT ceramic skeleton prepared in Example 1 was immersed in the blending solution and soaked for about 30 minutes before being taken out and dried to obtain a polymer-coated composite PZT ceramic skeleton.
[0087] (4) The composite PZT ceramic skeleton is immersed in uncrosslinked silicone rubber, kept under a vacuum of 5 Pascals for 12 hours, and then cured at normal pressure and 110°C for about 30 minutes to obtain the piezoelectric composite material.
[0088] The scanning electron microscope image of the composite PZT ceramic framework microstructure prepared in this embodiment is shown below. Figure 6 As shown in (a), the scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material is as follows. Figure 6 As shown in (b).
[0089] Example 5: Preparation of piezoelectric composite materials based on polymer-dielectric-coated composite BT ceramic framework
[0090] according to Figure 2 The schematic diagram shown illustrates the preparation of a composite piezoelectric material. The specific steps are as follows:
[0091] (1) Measure 0.6g of polymer P (VDF-TrFE-CFE) (molecular weight of 400,000, molar ratio of VDF, TrFE and CFE copolymer units of 60:30:10), add it to 15mL of DMF solvent, and stir until a clear solution is obtained.
[0092] (2) The BT ceramic skeleton prepared in Example 2 was immersed in the blending solution and soaked for about 30 minutes, then removed and dried. A polymer-coated composite BT ceramic skeleton was obtained.
[0093] (3) The composite BT ceramic skeleton is immersed in uncrosslinked silicone rubber, kept under a vacuum of 5 Pascals for 12 hours, and then cured at normal pressure and 110°C for about 30 minutes to obtain the piezoelectric composite material.
[0094] The scanning electron microscope image of the composite BT ceramic framework microstructure prepared in this embodiment is shown below. Figure 7 As shown in (a), the scanning electron microscope image of the cross-sectional microstructure of the piezoelectric composite material is as follows. Figure 7 As shown in (b).
[0095] Example 6: Fabrication of a piezoelectric sensor device
[0096] (1) The piezoelectric composite material based on PZT prepared in Example 4 was coated with gold electrodes at both ends by magnetron sputtering.
[0097] (2) The piezoelectric composite material of the coated electrode was placed in an oil bath and polarized at 50°C with an electric field of 3 kV / mm for 30 minutes.
[0098] (3) Lead out the polarized piezoelectric composite electrodes with wires, and attach a backing layer to one of the sections.
[0099] Example 7: Dielectric property testing
[0100] Dielectric property tests were conducted on the piezoelectric composite materials with different structures in Examples 3 and 4 above. The relationship between the dielectric constant and frequency of the piezoelectric composite materials with different structures at room temperature can be obtained as follows: Figure 8 As shown in (a), the dielectric constant of piezoelectric composite materials with different structures varies with temperature within the temperature range of 15-120℃. Figure 8 As shown in (b). Dielectric property tests were performed on the piezoelectric composite material in Example 5 above, and the relationship between the dielectric constant of the piezoelectric composite material and frequency at room temperature was obtained as follows: Figure 8 As shown in (c), the dielectric constant of the piezoelectric composite material varies with temperature within the temperature range of 15-120℃. Figure 8 As shown in (d).
[0101] Depend on Figure 8 (a) It can be seen that the dielectric constants of the piezoelectric composite material based on the polymer composite dielectric layer and the polymer dielectric layer at a frequency of 1000 Hz are approximately 95 and 85, respectively. The dielectric constant of the composite material modified with the composite dielectric layer is improved compared with that of the composite material modified with the simple polymer dielectric layer. Figure 8 The dielectric constant temperature spectrum test in (b) shows that both piezoelectric composite materials in Examples 3 and 4 exhibit certain relaxation characteristics at room temperature, indicating that the relaxation characteristics of the polymer and its composite medium have been reflected in the piezoelectric composite material. Figure 8 (c) indicates that the piezoelectric composite material prepared in Example 5 has a dielectric constant of approximately 44 at a frequency of 1000 Hz. Figure 8 (d) indicates that the piezoelectric composite material in Example 5 exhibits the dielectric constant peak corresponding to the Curie transition of barium titanate ceramics near 120°C.
[0102] Example 8: Ferroelectric Performance Testing
[0103] Ferroelectric tests were performed on the piezoelectric composite materials with different structures in Examples 3, 4, and 5 above. The hysteresis loops of the piezoelectric composite materials with different structures under static conditions were obtained as follows: Figure 9 As shown in (a), the hysteresis loops of the PZT-based piezoelectric composite material in Example 4 after different strain compression cycles are as follows: Figure 9 As shown in (b).
[0104] Depend on Figure 9 (a) It can be seen that the piezoelectric composite materials in Examples 3, 4 and 5 achieved a polarization value much higher than that of the traditional 0-3 type composite materials by introducing foam ferroelectric ceramics. Among them, the piezoelectric composite material based on lead zirconate titanate (PZT) ceramic foam and polymer composite medium in Example 4 has the maximum polarization. Figure 9 (b) indicates that the polarization characteristics of the piezoelectric composite material in Example 4 remain stable after 20% strain cycling, and decrease slightly after 30% strain cycling.
[0105] Example 9: Piezoelectric Performance Test
[0106] The piezoelectric properties of the piezoelectric composite materials in Examples 3, 4, and 5 above were tested, and the quasi-static piezoelectric coefficients of the piezoelectric composite materials were obtained as follows: Figure 10 As shown in (a), the electro-strain curve is as follows: Figure 10 As shown in (b). Wherein, Figure 10 (a) represents the quasi-static piezoelectric coefficient of the piezoelectric composite material corresponding to Example 4 at different PZT volume fractions (8%, 11%, 14%, 25%).
[0107] Depend on Figure 10 (a) It can be seen that the quasi-static piezoelectric coefficient of the piezoelectric composite material in Example 4 increases with the increase of PZT content, reaching 251 pC N at a PZT volume fraction of 25%. -1 .Depend on Figure 10 (b) It can be seen that the 0-3 type piezoelectric composite material hardly exhibits significant field-induced strain under the action of an electric field, indicating that it does not have observable piezoelectricity. In contrast, the piezoelectric composite materials in Examples 3, 4, and 5 all exhibit typical butterfly curves, showing strong piezoelectricity. Among them, the piezoelectric composite material based on the polymer composite dielectric layer in Example 4 has the largest electro-induced strain.
[0108] Example 10: Mechanical Property Testing
[0109] Mechanical property tests were performed on the piezoelectric composite material in Example 4 above, and the tensile stress-strain curve of the piezoelectric composite material was obtained as follows: Figure 11 As shown in (a), the cyclic compressive stress-strain curve of the piezoelectric composite material is as follows: Figure 11 As shown in (b).
[0110] Depend on Figure 11 It can be seen that the piezoelectric composite material corresponding to Example 4 can withstand nearly 60% tensile elastic deformation and still maintain a certain elasticity under 50% compression cycle.
[0111] Example 11: Fatigue Performance Test
[0112] Fatigue performance tests were performed on the piezoelectric composite material in Example 4 above, and the tensile fatigue properties of the piezoelectric composite material were obtained as follows: Figure 12 As shown in (a), the bending fatigue properties are as follows: Figure 12 As shown in (b).
[0113] Depend on Figure 12 It can be seen that the piezoelectric composite material corresponding to Example 4 is at 10 6 The quasi-static piezoelectric coefficient remains relatively stable after several stretching and bending cycles.
[0114] Example 12: Performance Testing of Ultrasonic Sensors
[0115] The performance of the ultrasonic sensor in Example 6 above was tested, and the output amplitude was obtained as follows: Figure 13 As shown in (a), the frequency domain characteristics are as follows: Figure 13 As shown in (b).
[0116] Depend on Figure 13 It can be seen that the unmatched layer ultrasonic sensor in Example 6 exhibits a large output amplitude and good frequency domain characteristics.
[0117] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.
Claims
1. A piezoelectric composite material, prepared by a method comprising the following steps: co-foaming piezoelectric ceramic particles with a pore-forming agent, sintering and then coating them with a polar polymer or a composite medium based on a polar polymer, and then compounding them with silicone rubber to obtain the composite material. The polar polymer is any one or a mixture of several of polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene, and polyvinylidene fluoride-trifluoroethylene-chlorofluoroethylene.
2. A method for preparing the piezoelectric composite material according to claim 1, comprising the following steps: (1) A slurry obtained by mixing piezoelectric ceramic particles with a pore-forming agent was used as a co-foaming precursor, and a surfactant-assisted rapid stirring co-foaming-high temperature sintering process was used to prepare a piezoelectric ceramic porous framework. (2) The piezoelectric ceramic porous framework is impregnated with a polar polymer solution or a polar polymer-conductive filler mixture to obtain a composite porous framework material coated with a polar polymer or coated with a polar polymer composite medium. (3) Silicone rubber is used to infuse the coated composite porous skeleton material and then cured at high temperature to obtain a stretchable flexible piezoelectric composite material.
3. The method according to claim 2, characterized in that: In step (1), the piezoelectric ceramic is any one or a mixture of two of lead zirconate titanate and barium titanate; The mass ratio of surfactant to piezoelectric ceramic is 1:1000-1:
500.
4. The method according to claim 2 or 3, characterized in that: The pore-forming agent is any one or a mixture of several of carbon nanotubes, graphene, and carbon black particles. The mass ratio of pore-forming agent to piezoelectric ceramic particles is 1:500-1:
10.
5. The method according to claim 2, characterized in that: The high-temperature sintering temperature is 1000°C. o C-1400 o C, sintering time is 0.5 hours to 3 hours.
6. The method according to claim 2, characterized in that: In step (2), the conductive filler is carbon nanotubes and / or graphene; In the polar polymer-conductive filler mixed solution, the mass ratio of conductive filler to polar polymer is 0-1:50; In step (2), the immersion time is greater than 1 minute.
7. The method according to claim 2, characterized in that: Step (3), the high-temperature curing temperature is 30°C. o C-150 o C; The high-temperature curing time is 0.5 hours to 24 hours.
8. The method according to claim 2, characterized in that: Step (3) further includes (4) coating the obtained piezoelectric composite material with electrode material and polarizing it under high voltage, then attaching a backing layer to the polarized piezoelectric composite material to obtain the operation of the piezoelectric composite material sensor device.
9. The method according to claim 8, characterized in that: In step (4), the electrode material is prepared by coating with silver paste or magnetron sputtering of gold electrodes; The electric field strength for high-voltage polarization is 20-50 kV / cm, and the polarization temperature is 20-60°C. o C.
10. A sensing / transducer comprising the piezoelectric composite material of claim 1 or the piezoelectric composite material prepared by any one of claims 2-9.