Staggered arrangement type 1-1 piezoelectric composite material and preparation method thereof

Abstract

The invention provides a staggered arrangement similar 1-1 type piezoelectric composite material and a preparation method thereof, the working procedure steps of cutting, arranging and bonding forming are adopted, thickness-polarized piezoelectric composite material strips which are staggered in the polarization direction are utilized, and a length vibration mode under width polarization of piezoelectric ceramics is utilized, so that the piezoelectric composite material is obtained. According to the piezoelectric composite material, the voltage applying direction is perpendicular to the vibration direction during working, a polarization electric field is separated from the working frequency, the thick piezoelectric composite material can be prepared through a relatively simple technology, and the piezoelectric composite material meets the requirement of an underwater acoustic transducer working at low frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric composite materials, and is applied to the transducer materials of medium and low frequency transducers operating in an underwater working environment. It is mainly a 1-1 type-like piezoelectric composite material with staggered arrangement and its preparation method. Background Art

[0002] A sonar device is a device that uses acoustic signals to obtain the azimuth and motion information of underwater targets or water body characteristics. The working principle of a sonar device is to transmit and receive acoustic wave signals through a sound generating device and a receiving device, and then perform echo signal calculation through an underwater acoustic signal processing algorithm to complete corresponding functions. An underwater acoustic transducer is a component in an underwater acoustic emission and reception device that completes the conversion of acoustic energy and electrical energy, and its performance directly affects the performance of the sonar device. Since the attenuation of sound propagation in water increases with the increase of the frequency of the acoustic signal, underwater acoustic transducers for long-distance detection have the working characteristics of low frequency and high power. Underwater acoustic transducers can be classified into piezoelectric, electromagnetic, electro-dynamic and other types according to their working principles. Among them, piezoelectric transducers are the most commonly used type of underwater acoustic transducers. The main transducer materials used in piezoelectric transducers are piezoelectric ceramics, piezoelectric single crystals, and piezoelectric composite materials, etc.

[0003] A piezoelectric composite material is a piezoelectric material formed by combining piezoelectric ceramics with another material in a specific connectivity in space. At present, the common material composition in practical applications is piezoelectric ceramics and polymer materials. At present, most of the existing patents in the field of piezoelectric composite materials are of 1-3 type, 2-2 type piezoelectric composite material configurations and derivative configurations, such as 1-1-3 type, 1-3-2 type, etc. For example: CN107170882.B, CN100401545.C, CN103456878.B, CN116973458.B, etc. The basic principles of the above patents are relatively similar. They all divide piezoelectric ceramics into a two-dimensional discrete piezoelectric fine column array in a plane, apply an electric field to the upper and lower ends of the slender columns, and the piezoelectric ceramics excited by the electric field generate a thickness expansion and contraction vibration form.

[0004] Generally speaking, the main feature of the above solutions is to use a combination of piezoelectric ceramics and polymers, utilize the thickness vibration mode of rectangular columns of piezoelectric ceramics, with the polarization direction of the ceramics being the same as the vibration direction and the electrode surface being perpendicular to the vibration direction. These types of configurations are unified in terms of the vibration form of the piezoelectric ceramics used, and all utilize the thickness vibration of the piezoelectric ceramics. The characteristic is that when working, the direction of the applied electric field is the same as the vibration direction, and the thickness vibration resonance frequency of the piezoelectric ceramics is inversely proportional to the thickness of the piezoelectric ceramics.

[0005] The disadvantage of this structure is that it is difficult to apply the piezoelectric composite material prepared by the above method to low-frequency underwater acoustic transducers. For low-frequency transducers, when a relatively thick piezoelectric composite material is used as the transducer material, if the transducer material is not laminated and a single-layer piezoelectric composite material is used, regardless of whether the composite material is prepared by the arrangement casting method or the cutting and filling method, a very high polarization voltage is required to polarize the piezoelectric ceramics; and if a multi-layer composite material is used as the transducer material, it is necessary to align the ceramic phase and polymer phase of each layer as much as possible with other layers, otherwise it will seriously affect the vibration mode and electro-acoustic characteristics of the piezoelectric transducer. Both of the above methods seriously increase the difficulty of process implementation.

[0006] In addition, when the transducer operates at low frequencies, it has a large strain. Since the applied electric field direction, polarization direction, and main vibration direction are all the same, the electrodes must be arranged in the radiation direction, and on this plane, there are two components: the actively vibrating piezoelectric ceramics and the passively vibrating polymers. When vibrating, the electrode surface is subjected to uneven forces in the normal direction, resulting in a large shear force at the interface between the piezoelectric phase and the polymer phase. Under the action of shear, once the electrode surface breaks, the piezoelectric phase loses the excitation electric field. Considering the above factors, piezoelectric composite materials are rarely used as driving materials for piezoelectric transducers operating at low frequencies. Summary of the Invention

[0007] The object of the present invention is to overcome the deficiencies existing in the prior art, and to provide a staggered 1-1 type piezoelectric composite material and its preparation method. By adopting staggered thickness-polarized length-elongation vibration composite piezoelectric strips to form a 1-1 type piezoelectric composite material, and making the working electric field perpendicular to the vibration direction, the problem of difficult preparation when the piezoelectric composite material is applied to low-frequency transducers is solved.

[0008] The object of the present invention is achieved by the following technical solutions. A staggered 1-1 type piezoelectric composite material includes a piezoelectric material, a polymer, and a metal diaphragm. The piezoelectric material and the polymer are arranged in a staggered distribution in the plane rows and columns, and there is a layer of metal diaphragm as an electrode sheet between every two columns; in the piezoelectric composite material, the polarization directions of the two adjacent layers of piezoelectric materials to the electrode sheet are opposite, and when opposite voltages are applied to two adjacent electrode sheets, the piezoelectric material in the piezoelectric composite material mainly vibrates in the length-elongation vibration mode.

[0009] Preferably, the piezoelectric material is a piezoelectric material such as piezoelectric ceramics and relaxor ferroelectric single crystals.

[0010] Preferably, the polymer is a passive material such as epoxy resin, polyurethane, polyester, polycarbonate, and polypropylene.

[0011] Preferably, the metal diaphragm is a low-resistivity metal sheet such as a copper sheet, an aluminum sheet, and a silver-plated copper sheet.

[0012] The present invention also provides a method for preparing the interleaved 1-1 type piezoelectric composite material. By using a two-step cutting and forming method and a pressure bonding method, the 1-1 type piezoelectric composite material is prepared. The specific steps are as follows:

[0013] S1. Cut the piezoelectric material along the polarization direction to prepare a rectangular column of the piezoelectric material. At the same time, cut the polymer with the same size to prepare a rectangular column of the polymer.

[0014] S2. Alternately arrange the cut rectangular columns of the piezoelectric material and the polymer along the short side direction.

[0015] S3. Bond or weld a metal diaphragm on one side of the alternately arranged structure as an electrode plate to form a composite body. Among them, the composite body with the positive electrode covered with the electrode plate is composite body A, and the composite body with the negative electrode covered with the electrode plate is composite body B.

[0016] S4. Repeat steps S1-S3 to prepare multiple composite bodies A and composite bodies B.

[0017] S5. Rotate 90 degrees to make the extension direction of the piezoelectric material perpendicular to the horizontal plane and use a fixture for positioning, so that the piezoelectric material and the polymer are alternately distributed in space. At the same time, the polarization directions of the two piezoelectric ceramics connected to one electrode plate are opposite, that is, one electrode plate connects one composite body A and one composite body B.

[0018] S6. Apply force along the direction perpendicular to the normal of the composite body plane to assist in bonding to form a spatially interleaved 1-1 type composite material.

[0019] The beneficial effects of the present invention are as follows: The present invention uses the transverse field length expansion and contraction of the piezoelectric material (piezoelectric ceramic) to replace the longitudinal field expansion and contraction mode of the thickness-polarized piezoelectric material as the main vibration mode of the piezoelectric composite material, so that the electrode surface direction is separated from the main vibration direction. When preparing a relatively thick piezoelectric composite material, it is not necessary to use a relatively thick piezoelectric ceramic, which greatly reduces the requirement for the polarization voltage and the technical difficulty.

[0020] At the same time, since there is no electrode surface on the main vibration surface, when using this type of piezoelectric composite material to prepare a transducer, general polishing and other means can be used on the upper and lower surfaces to increase the roughness of the vibration surface. When additional structures such as a matching layer need to be added, the mechanical bonding force of the radiation surface is increased, and the risk of debonding failure between the radiation surface and the additional structure or the sound-transmitting layer is reduced.

[0021] In addition, some new materials, such as partially oriented polarized relaxor ferroelectric single crystal materials, have a large d32 piezoelectric constant. The present invention can make full use of the characteristic of large length strain when applying voltage in the thickness direction of such materials to prepare an acoustic transducer with a new driving form. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those skilled in the art or ordinary technicians, other accompanying drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 Schematic diagram of the staggered type 1-1 piezoelectric composite material of the present invention.

[0024] Figure 2 Schematic diagram of the preparation steps of the present invention.

[0025] Figure 3 Schematic diagram of the difference between the repeating unit of the present invention and the prior art.

[0026] Figure 4 Schematic diagram of the difference in the vibration direction between the present invention and the prior art.

[0027] Figure 5 Schematic diagram for explaining the connectivity of the composite material.

[0028] Explanation of reference numerals in the drawings: piezoelectric material 1, polymer 2, metal diaphragm 3, positive electrode surface 3-1, negative electrode surface 3-2. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0030] As Figure 1 shown, a staggered type 1-1 piezoelectric composite material includes a piezoelectric material 1, a polymer 2, and a metal diaphragm 3. Among them, the piezoelectric material 1 is a piezoelectric material such as piezoelectric ceramics and relaxor ferroelectric single crystals, the polymer 2 is a passive material such as epoxy resin, polyurethane, polyester, polycarbonate, and polypropylene, and the metal diaphragm 3 is a low-resistivity metal sheet such as a copper sheet, an aluminum sheet, and a silver-plated copper sheet. The piezoelectric material 1 and the polymer 2 are arranged in a staggered distribution in the plane rows and columns, and there is a layer of metal diaphragm 3 as an electrode sheet between every two columns; in the piezoelectric composite material, the polarization directions of the two adjacent layers of piezoelectric material 1 are opposite. When opposite voltages are applied to the adjacent two electrode sheets, the piezoelectric material 1 in the piezoelectric composite material mainly vibrates in the length elongation vibration mode.

[0031] As Figure 2As shown, a method for preparing the staggered 1-1 type piezoelectric composite material is to prepare the 1-1 type piezoelectric composite material by a two-step cutting and molding and pressurizing bonding method, and specifically includes the following steps:

[0032] S1, such as Figure 2 (a) Pre-cutting shown: piezoelectric material 1 is cut along the polarization direction to prepare piezoelectric material rectangular prisms, and polymer 2 is cut with the same size to prepare polymer rectangular prisms;

[0033] S2, such as Figure 2 (b) Arrangement and bonding as shown: the cut piezoelectric material rectangular pillars and polymer rectangular pillars are arranged alternately along the short side direction;

[0034] S3, such as Figure 2 (c) The electrode covering shown: the metal film 3 is bonded or welded to one side of the alternately arranged surface as an electrode sheet to form a composite body, wherein the positive electrode covering the electrode sheet is composite body A, and the negative electrode covering the electrode sheet is composite body B;

[0035] S4, repeating steps S1-S3 to prepare multiple complexes A and B;

[0036] S5, such as Figure 2 (d) The flip arrangement shown: rotate 90 degrees, so that the extension direction of the piezoelectric material is perpendicular to the horizontal plane and the auxiliary tooling is positioned, and the piezoelectric material and the polymer are staggered in space, and the polarization directions of the two piezoelectric ceramics connected by an electrode sheet are opposite, that is, an electrode sheet connects a composite A and a composite B;

[0037] S6, such as Figure 2 (e) The pressure bonding shown and Figure 2 (f) Curing molding shown: force is added along the direction perpendicular to the normal line of the composite plane to assist bonding to form a spatially staggered 1-1 type composite material.

[0038] like Figure 3 As shown, a schematic diagram of the difference between the repeating unit of the present invention and the prior art is given. The left figure is a schematic diagram of the repeating unit of the prior art, and the right figure is a schematic diagram of the repeating unit of the present invention. In one repeating unit, a negative electrode surface 3-2 formed by two electrode sheets and a positive electrode surface 3-1 formed by one electrode sheet are included. The piezoelectric material 1 and the polymer 2 are staggered in the plane rows and columns, and the two layers of piezoelectric material 1 adjacent to the positive electrode surface 3-1 have opposite polarization directions.

[0039] After preparation, the piezoelectric material phase and the polymer phase in the piezoelectric composite material are arranged in a periodic and symmetric manner in the xoy plane. Each piezoelectric material is adjacent to the polymer in the x-direction and the y-direction, and each polymer is adjacent to the piezoelectric material in the x-direction and the y-direction. The material connectivity is in the form of 1-1 connectivity. The thin electrode sheets are arranged on a plane parallel to the xoz plane to connect the piezoelectric materials distributed along the x-direction. After applying an electric field excitation, the thickness polarization length expansion and contraction mode of the piezoelectric material (also known as the 31 / 32 mode) is mainly utilized. The direction of the external electric field is the same as the polarization direction, and the vibration direction is orthogonal to the polarization direction. As Figure 4 shown, a schematic diagram showing the difference in the vibration direction between the present invention and the prior art is given.

[0040] Mechanism of the present invention: The present invention adopts the process steps of cutting - arranging - bonding and forming. Through the thickness-polarized piezoelectric composite strips with staggered polarization directions, using the length vibration mode of the piezoelectric ceramic under width polarization, the direction of the applied voltage during operation is perpendicular to the vibration direction, realizing the separation of the polarization electric field and the working frequency, and being able to prepare a relatively thick piezoelectric composite material with a relatively simple process, so that the piezoelectric composite material meets the requirements of a low-frequency working underwater acoustic transducer.

[0041] Glossary of related technical terms

[0042] (1) Piezoelectric composite material and connectivity of piezoelectric composite material

[0043] Newnham et al. established a method to describe the connectivity properties of each phase of the piezoelectric composite material in geometric dimensions using symbols. According to Newnham's classification method, the first serial number representing a two-phase piezoelectric composite material represents the geometric connectivity dimension of the piezoelectric phase, and the second serial number represents the geometric connectivity dimension of the polymer phase. There are a total of 10 types of two-phase piezoelectric composite materials, and the morphological schematic is as Figure 5 shown.

[0044] (2) Expansion and contraction vibration modes of piezoelectric ceramics: Refer to Lin Shuyu's "Principles and Design of Ultrasonic Transducers" P22 and IEC60483 standard. In "Principles and Design of Ultrasonic Transducers", for piezoelectric ceramic materials, the expansion and contraction vibration modes can be divided into transverse field vibration expansion and contraction vibration modes and longitudinal field expansion and contraction vibration modes. Among them, the transverse field vibration modes include the radial vibration of a thin circular plate, the radial vibration of a thin circular ring, the radial vibration of a thin spherical shell, and the length expansion and contraction vibration mode of a thin strip, etc., while the longitudinal field expansion and contraction vibration modes include the thickness expansion and contraction vibration of a thin sheet and the length expansion and contraction vibration of a slender rod. Among them, the transverse field means that the polarization direction of the piezoelectric ceramic is perpendicular to the vibration direction, and the longitudinal field means that the polarization direction of the piezoelectric ceramic is parallel to the vibration direction.

[0045] In IEC 60483, the transverse field vibration modes correspond to unstiffened modes, where the radial vibration of a thin disk, the radial vibration of a thin ring, the radial vibration of a thin spherical shell, and the length expansion vibration mode of a thin strip respectively correspond to (g), (d), (f), and (a) in the standard Schedule II. The longitudinal field vibration modes correspond to stiffened modes, where the thickness expansion vibration of a thin sheet and the length expansion vibration of a slender rod respectively correspond to (a) and (c) in the standard Schedule III.

[0046] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. An interleaved 1-1 type piezoelectric composite material, characterized in that: It includes a piezoelectric material (1), a polymer (2) and a metal diaphragm (3). The piezoelectric material (1) and the polymer (2) are arranged in a staggered pattern on a plane row and column, and there is a layer of metal diaphragm (3) as an electrode sheet between every two columns; in the piezoelectric composite material, the polarization directions of two adjacent layers of piezoelectric material (1) are opposite. When opposite voltages are applied to two adjacent electrode sheets, the piezoelectric material (1) in the piezoelectric composite material mainly vibrates in a length elongation mode.

2. The interleaved type 1-1 piezoelectric composite material according to claim 1, characterized in that: The piezoelectric material (1) is a piezoelectric ceramic, a piezoelectric material related to relaxor ferroelectric single crystal.

3. The interdigitated 1-1 type piezoelectric composite material according to claim 1, characterized in that: The polymer (2) is a passive material related to epoxy resin, polyurethane, polyester, polycarbonate, polypropylene.

4. The interleaved Class 1-1 piezoelectric composite according to claim 1, characterized in that: The metal diaphragm (3) is a metal sheet with low resistivity related to copper sheet, aluminum sheet, silver-plated copper sheet.

5. A method for preparing the staggered 1-1 type piezoelectric composite material as described in any one of claims 1 to 4, characterized in that: It includes the following steps: S1. Cut the piezoelectric material (1) along the polarization direction to prepare a rectangular column of piezoelectric material. At the same time, cut the polymer (2) with the same size to prepare a rectangular column of polymer. S2. Arrange the cut rectangular columns of piezoelectric material and polymer alternately along the short side direction. S3. Bond or weld the metal diaphragm (3) on one side of the alternately arranged structure as an electrode sheet to form a composite body. Among them, the composite body with the positive electrode covered with the electrode sheet is composite body A, and the composite body with the negative electrode covered with the electrode sheet is composite body B. S4. Repeat steps S1 - S3 to prepare multiple composite bodies A and composite bodies B. S5. Rotate 90 degrees to make the extension direction of the piezoelectric material perpendicular to the horizontal plane and use a fixture for positioning, and make the piezoelectric material and the polymer staggered in space. At the same time, the polarization directions of two piezoelectric ceramics connected to one electrode sheet are opposite, that is, one electrode sheet connects one composite body A and one composite body B. S6. Apply a force along the direction normal to the plane of the composite body to assist bonding to form a spatially staggered 1 - 1 type composite material.

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