Spherical hollow piezoelectric composite material and preparation method thereof

Abstract

The invention provides a spherical hollow piezoelectric composite material and a preparation method thereof, and belongs to the technical field of piezoelectric materials. According to the method disclosed by the invention, the precise manufacturing of the complex three-dimensional structure of the piezoelectric composite material is realized, and the controllability of the structure can be realized; a 1-3 type (namely a two-phase piezoelectric composite material composed of one-dimensionally arranged piezoelectric phases and three-dimensionally communicated polymer phases) piezoelectric composite material is of a periodic array structure formed by embedding piezoelectric ceramic columns into a resin matrix, and precise arrangement and complex three-dimensional shape control of the ceramic columns are difficult to realize by a traditional process. According to the 3D photocuring printing technology, liquid photosensitive resin is cured layer by layer, so that the diameter, spacing and spatial distribution of piezoelectric materials (such as ceramic columns) can be accurately controlled, complex structures such as a spherical polymer hollow frame are formed, and the degree of freedom of material design is remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of piezoelectric materials, and particularly relates to a spherical hollow piezoelectric composite material and a preparation method thereof. BACKGROUND

[0002] The piezoelectric composite material is composed of PZT piezoelectric ceramic phase and polymer phase in a certain spatial geometric distribution according to a certain connection mode, volume or weight. The connection mode of the piezoelectric composite material is represented by m-n, wherein m refers to the dimension of the ceramic phase, and n refers to the dimension of the polymer. Common piezoelectric composite materials include 0-0, 0-1, 0-2, 0-3, 1-1, 1-2, 1-3, 2-2, 2-3 and 3-3 type piezoelectric composite materials. These materials have the characteristics of high piezoelectricity, high compressive strength and high temperature stability.

[0003] The traditional preparation method (such as the cutting-filling method and the injection molding method) of the piezoelectric composite material is complicated. In addition, due to the high hardness and brittleness of the piezoelectric ceramic, the piezoelectric ceramic is difficult to process, which increases the difficulty of arranging the ceramic rods, and makes the preparation of the piezoelectric composite material more difficult. SUMMARY

[0004] Therefore, the purpose of the application is to provide a spherical hollow piezoelectric composite material and a preparation method thereof. The spherical hollow piezoelectric composite material provided by the application has excellent piezoelectric performance and a simple preparation method.

[0005] In order to achieve the above purpose, the application provides the following solutions:

[0006] The application provides a preparation method of a spherical hollow piezoelectric composite material, which comprises the following steps:

[0007] The polymer is used as a raw material, and light curing 3D printing is performed based on the size and pore structure of a preset spherical polymer hollow frame to obtain two hemispherical polymer hollow frames. The polymer comprises a photosensitive resin.

[0008] The piezoelectric material and the two hemispherical polymer hollow frames are assembled to obtain two hemispherical hollow piezoelectric composite materials. The piezoelectric material is assembled into the large pores of the two hemispherical polymer hollow frames, respectively.

[0009] The two hemispherical hollow piezoelectric composite materials are assembled to obtain the spherical hollow piezoelectric composite material.

[0010] Preferably, the conditions of the light curing 3D printing include: the accuracy is 0.01 mm, the laser spot is 0.00184 mm, the printing speed is 30 mm / h, the layer thickness is 0.1 mm, and the printing laser power is 75%. 2

[0011] ​Preferably, before the assembling, the inner and outer surfaces of the two hemispherical hollow piezoelectric composite materials are coated with conductive paste respectively to form inner and outer electrode surfaces.

[0012] Preferably, the conductive paste comprises silver paste; and the coating thickness is 0.1 mm.

[0013] Preferably, the assembling comprises the following steps:

[0014] The piezoelectric material is inserted into the large holes of the two hemispherical polymer hollow frames in sequence, the side surface of the piezoelectric material is coated with silicone rubber, and the piezoelectric material is assembled and bonded with the hole positions in the two hemispherical polymer hollow frames, and then cured.

[0015] The application provides a spherical hollow piezoelectric composite material prepared by the preparation method, comprising a spherical polymer hollow frame and a piezoelectric material.

[0016] Preferably, the volume of the piezoelectric material is 30-70% of the volume of the spherical hollow piezoelectric composite material.

[0017] Preferably, the large hole is a rectangular hole, the rectangular hole is a through hole, the length is 1.02-2.02 mm, and the width is 1.02-2.02 mm.

[0018] Preferably, the piezoelectric material is a cuboid, the length of the cuboid is 1-2 mm, the width is 1-2 mm, and the height is 3 mm.

[0019] Preferably, the outer diameter of the spherical polymer hollow frame is 30 mm, and the inner diameter is 27 mm.

[0020] The application provides a preparation method of a spherical hollow piezoelectric composite material, comprising the following steps: taking a polymer as a raw material, performing light-cured 3D printing based on a preset size and pore structure of a spherical polymer hollow frame to obtain two hemispherical polymer hollow frames; the polymer comprises a photosensitive resin; assembling piezoelectric material and the two hemispherical polymer hollow frames to obtain two hemispherical hollow piezoelectric composite materials; the piezoelectric material is assembled into macropores of the two hemispherical polymer hollow frames, respectively; and assembling the two hemispherical hollow piezoelectric composite materials to obtain the spherical piezoelectric composite material. The preparation method provided by the application simplifies the preparation process of a traditional piezoelectric composite material, and the method can be used to design a piezoelectric composite material with an arbitrary complex curved surface. Specifically, the method of the application realizes accurate manufacturing of a piezoelectric composite material with a complex three-dimensional structure, and the piezoelectric composite material can be controlled in structure. A 1-3 type (i.e., a two-phase piezoelectric composite material composed of one-dimensional arranged piezoelectric phase and three-dimensional connected polymer phase) piezoelectric composite material is formed by embedding piezoelectric ceramic columns into a resin matrix to form a periodic array structure, and it is difficult for a traditional process to realize accurate arrangement of the ceramic columns and control of a complex three-dimensional shape. The 3D light-cured printing technology can accurately control the diameter, spacing and spatial distribution of the piezoelectric material (such as the ceramic column) by layer-by-layer curing of liquid photosensitive resin, and can form complex structures such as a spherical polymer hollow frame, thereby significantly improving the degree of freedom of material design.

[0021] The preparation method provided by the application can optimize the piezoelectric performance of the piezoelectric material, and the spherical polymer hollow frame structure further optimizes the stress transmission path, i.e., all the pores in the spherical polymer hollow frame (such as a resin frame) limit the positions of the piezoelectric material (such as piezoelectric ceramic columns) embedded therein, so that each piezoelectric ceramic column is embedded in the radial direction of the spherical hollow piezoelectric composite material, and each piezoelectric ceramic column can vibrate in the thickness direction along the radial direction when excited by ultrasonic vibration, i.e., the stress direction of vibration is the radial direction of the sphere, i.e., there is no deviation, so that the spherical hollow piezoelectric composite material can more efficiently convert mechanical energy into electrical energy under the action of an electric field.

[0022] The present application can precisely control the volume fraction of piezoelectric material (such as ceramic column) by 3D printing technology (such as the volume ratio of resin frame and ceramic column, such as the volume ratio of ceramic column is 30-70%), while ensuring high electromechanical coupling coefficient (the electromechanical coupling coefficient of the thickness vibration of ordinary piezoelectric ceramic material is between 0.45-0.55, and the electromechanical coupling coefficient of the spherical hollow piezoelectric composite material of the present application is 0.732), reducing dielectric loss and reducing heat dissipation of energy in the material, and improving energy conversion efficiency. High sensitivity transducer design can be realized, in 1-3 type structure, the periodic arrangement of piezoelectric material enhances the anisotropy of piezoelectric effect, so that the material is more sensitive to the change of mechanical stress or electric field in a certain direction. The symmetry of the spherical polymer hollow frame further improves the isotropic response ability of the material, which is suitable for the manufacture of high sensitivity sensors and transducers.

[0023] The present application allows rapid adjustment of the geometric parameters (such as diameter, spacing) of piezoelectric material (such as ceramic column) and the composition ratio of spherical polymer hollow frame (such as resin frame) by modifying the digital model through 3D photocuring printing, realizing the customized design of material performance. The research and development cycle can also be shortened, and the traditional process of preparing 1-3 type piezoelectric composite material needs to go through multiple processing (such as preparation, arrangement, resin filling of ceramic column, etc.), which is long in cycle and high in cost. 3D printing technology can realize the integrated process from design to manufacturing, significantly shorten the research and development cycle, and reduce the development cost. Finally, 3D printing technology adopts additive manufacturing method, and the material utilization rate can reach more than 90%, which significantly reduces the material waste in traditional process.

[0024] The present application is based on the preparation of spherical hollow piezoelectric composite material by photocuring 3D printing. In terms of performance, by adjusting the continuous gradient change of the side length of the spherical polymer hollow frame, specifically, by adjusting the size of the large hole in the spherical polymer hollow frame, the size can be gradually increased or decreased from the radius direction to the top hole, forming a gradient change of the hole size, which can be gradually decreased from 2mm square hole side length to 1mm square hole side length in the present application, each time by 0.2mm; taking the hemispherical polymer hollow frame as an example, from bottom to top (placement direction and Figure 6The length of the side of the large hole of the second row is 0.2mm smaller than that of the first row, the length of the side of the large hole of the third row is 0.2mm smaller than that of the second row, and so on, which is gradually reduced to the top, that is, the periodic arrangement of the large hole is formed, so that the space ratio between the piezoelectric material and the spherical polymer hollow frame is changed, and the piezoelectric composite material with a suitable matching ratio (the volume of the piezoelectric material is 30-70% of the volume of the spherical hollow piezoelectric composite material) is efficiently achieved, so as to control the acoustic impedance of the material and reduce the reflection loss of the ultrasonic transmission interface; the damping characteristic is enhanced, the viscoelasticity of the spherical polymer hollow frame matrix and the scattering effect of the piezoelectric material are synergistically acted, the acoustic energy attenuation is significantly improved, and the spherical polymer hollow frame is suitable for wideband sound absorption or vibration suppression. (That is, the addition of the polymer hollow frame can reduce the acoustic impedance performance of the whole material, and different proportions present different acoustic impedance performance regulation, and the reduction of the acoustic impedance can improve the acoustic matching of the transducer and the propagation medium (such as water or biological tissue), reduce the interface reflection, and improve the energy transmission efficiency); in terms of preparation efficiency and precision, the spherical polymer hollow frame is directly generated by 3D printing, the complex processes such as mold development, cutting / arrangement of ceramics in the traditional method are omitted, the preparation period is shortened (from several weeks to several hours), in terms of precision control, the printing layer thickness can be as low as 0.01m, the error of the cuboid ceramic spacing is less than 5%, the high-frequency resonance consistency of the piezoelectric material (such as piezoelectric ceramic small columns) is ensured, compared with the ceramic utilization rate (only 50-70%) of the traditional cutting-filling method, and the utilization rate of the 3D printing frame+ceramic small column filling can be improved to more than 90%. The 3D printing spherical polymer hollow frame provides the core advantages of high design freedom, performance adjustability and preparation efficiency for the spherical piezoelectric composite material, and is especially suitable for the development of small-batch, customized high-performance acoustic devices. The preparation method provided by the application is simple. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0026] Figure 1 Structure diagram of the spherical hollow piezoelectric composite material;

[0027] Figure 2 Process flow diagram of the spherical hollow piezoelectric composite material;

[0028] Figure 3 Physical diagram of the spherical hollow piezoelectric composite material;

[0029] Figure 4 Physical diagram of the spherical hollow piezoelectric composite material with silver paste electrodes on the inner and outer surfaces;

[0030] Figure 5 A ball-shaped hollow piezoelectric composite material electrode with silver paste coated on both inner and outer surfaces;

[0031] Figure 6 A resin hollow frame model. DETAILED DESCRIPTION

[0032] The application provides a preparation method of a ball-shaped hollow piezoelectric composite material, comprising the following steps:

[0033] Polymer is used as raw material, and light curing 3D printing is performed based on preset size and pore structure of a spherical polymer hollow frame to obtain two hemispherical polymer hollow frames; the polymer comprises photosensitive resin.

[0034] The piezoelectric material and the two hemispherical polymer hollow frames are assembled to obtain two hemispherical hollow piezoelectric composite materials; the piezoelectric material is assembled into the large pores of the two hemispherical polymer hollow frames, respectively.

[0035] The two hemispherical hollow piezoelectric composite materials are assembled to obtain the spherical piezoelectric composite material.

[0036] Unless otherwise specified, the raw materials and equipment used in the application are commercially available.

[0037] Polymer is used as raw material, and light curing 3D printing is performed based on preset size and pore structure of a spherical polymer hollow frame to obtain two hemispherical polymer hollow frames; the polymer comprises photosensitive resin.

[0038] In the application, the photosensitive resin preferably comprises general standard resin, high-toughness resin, flexible resin or heat-resistant high-temperature resin; the general standard resin preferably comprises Standard Black, Standard Grey, UV-650 or Elegoo Grey; the high-toughness resin preferably comprises Liqcreate Tough-X, DSM Taurus TM or Formlabs Tough Resin; the flexible resin preferably comprises Formlabs Flexible Resin, SirayaTech Blu or Liqcreate Flex; and the heat-resistant high-temperature resin preferably comprises Formlabs High Temp Resin, DSM or Liqcreate High Temp. In the embodiment of the application, specifically, the general standard resin UV-650 has the characteristics of low cost and good strength.

[0039] The present invention preferably uses 3D modeling software to design the size and pore structure of the spherical polymer hollow frame. In the present invention, the conditions of the light-curing 3D printing preferably include: an accuracy of 0.01mm, a laser spot of 0.00184mm 2 , the printing speed is 30mm / h, the layer thickness is 0.1mm, the printing laser power is 75%, and the printing time of 6 hemispherical polymer hollow frames requires 83min.

[0040] After obtaining the hemispherical polymer hollow frame, the present invention assembles the piezoelectric material and the two hemispherical polymer hollow frames to obtain two hemispherical hollow piezoelectric composite materials; the piezoelectric materials are respectively assembled into the macropores of the two hemispherical polymer hollow frames.

[0041] In the present invention, the raw material for preparing the piezoelectric material is preferably a piezoelectric single crystal, more preferably a piezoelectric ceramic square. The piezoelectric material is preferably prepared using a cutting machine; the cutting machine preferably has an accuracy of 0.001 mm. After cutting, the resulting piezoelectric material is preferably cleaned and dried.

[0042] Piezoelectric ceramics are mainly composed of metal oxides (such as lead oxide, zirconium oxide, titanium oxide, niobate, barium / titanate, etc.) formed into a polycrystalline structure through high-temperature sintering, and exhibit a piezoelectric effect after polarization treatment. In the present invention, the piezoelectric ceramic preferably includes lead-based piezoelectric ceramics or lead-free piezoelectric ceramics; the lead-based piezoelectric ceramics preferably include lead zirconate titanate PZT or lead magnesium niobate PMN-PZT; the lead-free piezoelectric ceramics preferably include barium titanate BaTiO3, potassium sodium niobate KNN, or bismuth layered structure BNT. In the embodiment of the present invention, the piezoelectric ceramic is specifically a lead zirconate titanate PZT5A piezoelectric ceramic.

[0043] The present invention adopts a high-precision cutting machine to prepare the piezoelectric material, thereby being able to obtain a high-precision piezoelectric material that is fully matched with the hemispherical polymer hollow frame.

[0044] In the present invention, the assembly (referred to as the first assembly) preferably includes the following steps:

[0045] The piezoelectric material is sequentially inserted into the large holes of the two hemispherical polymer hollow frames, the side surfaces of the piezoelectric material are coated with silicone rubber, and assembled and bonded to the holes in the two hemispherical polymer hollow frames, and then cured (referred to as the first curing).

[0046] The present invention has no particular limitation on the method of inserting the piezoelectric material into the macropore, and any method known in the art can be used. In the present invention, the first curing temperature is preferably room temperature, and the first curing time is preferably 2 hours.

[0047] In the present application, the position of the one-dimensionally arranged piezoelectric phase is determined by the hole position reserved by the printed polymer phase.

[0048] The silicone rubber has mechanical flexibility, which endows the spherical hollow piezoelectric composite material with good flexibility and mechanical adaptability; meanwhile, the silicone rubber has low acoustic impedance, and the low acoustic impedance property of the silicone rubber makes it have good matching with water or other low impedance medium; the silicone rubber has good environmental adaptability, and has good temperature resistance, humidity resistance and chemical corrosion resistance, which can protect the piezoelectric material (such as the piezoelectric ceramic small column) from environmental factors and prolong the service life of the device.

[0049] After obtaining the two hemispherical hollow piezoelectric composite materials, the two hemispherical hollow piezoelectric composite materials are assembled to obtain the spherical hollow piezoelectric composite material.

[0050] In the present application, the assembling preferably comprises: bonding the two hemispherical hollow piezoelectric composite materials by using epoxy resin, and performing second curing, in which the temperature of the second curing is preferably 45 DEG C, and the time is preferably 4h.

[0051] In the present application, when the two hemispherical hollow piezoelectric composite materials are assembled, the large holes on the maximum circumferences of the two hemispherical hollow piezoelectric composite materials need to be one-to-one corresponding.

[0052] In the present application, when the admittance curve test is performed, the first assembly is preferably further comprising: coating the inner and outer surfaces of the two hemispherical hollow piezoelectric composite materials with conductive paste respectively to form inner and outer electrode surfaces, and then performing second assembly on the two hemispherical hollow piezoelectric composite materials with the inner and outer electrode surfaces to obtain the spherical hollow piezoelectric composite material with the inner and outer electrode surfaces.

[0053] In the present application, the conductive paste preferably comprises silver paste; and the thickness of the coating is preferably 0.1mm.

[0054] After the coating is completed, the surface conductive paste is preferably blown dry, and then the two hemispherical hollow piezoelectric composite materials coated with the conductive paste are bonded by using epoxy resin, and then third curing is performed.

[0055] In the present application, the temperature of the blowing is preferably 300 DEG C, the blowing distance is preferably 10cm, and the blowing time is preferably 10min; the temperature and time of the third curing are the same as those of the second curing, which will not be repeated here.

[0056] The silver paste has good electrical conductivity, and can form electrodes on the inner and outer surfaces of the spherical hollow piezoelectric composite material, helping the piezoelectric material to absorb and convert electrical energy. This is crucial for the application of piezoelectric materials, as the electrodes are the key part of connecting the external circuit to the piezoelectric material, enabling the mutual conversion of electrical and mechanical energy. The electrical conductivity of the silver paste can reduce the resistance of the electrode and improve the efficiency of current transmission. In the spherical hollow piezoelectric composite material, the reduction of electrode resistance helps to reduce energy loss and improve the overall performance of the material. The electrical conductivity and stability of the silver paste help to ensure accurate and efficient transmission of signals between the spherical hollow piezoelectric composite material and the external circuit. The silver paste has good corrosion resistance and stability, and can maintain its electrical conductivity for a long time under various environmental conditions. This helps to prolong the service life of the spherical hollow piezoelectric composite material and ensure its reliability in different application scenarios.

[0057] The present application provides a spherical hollow piezoelectric composite material prepared by the preparation method described in the above scheme, which comprises a spherical polymer hollow frame and a piezoelectric material; the spherical polymer hollow frame has a large pore structure, and the piezoelectric material is located in the large pore of the spherical polymer hollow frame; the polymer in the spherical polymer hollow frame comprises a photosensitive resin.

[0058] In the present application, the volume of the piezoelectric material is preferably 30-70% of the volume of the spherical hollow piezoelectric composite material, and in the embodiments of the present application, it can be specifically 30%, 40%, 45%, 50%, 60%, 65% or 70%. Among them, the optimal ratio range of piezoelectric material and spherical polymer hollow frame needs to be determined according to the specific application requirements and material performance requirements, and the piezoelectric material volume fraction between 30% and 70% can achieve better comprehensive performance, if a higher electromechanical coupling coefficient is required, the volume fraction of the piezoelectric material can be appropriately increased; if lower acoustic impedance or better flexibility is required, the volume fraction of the piezoelectric material can be appropriately reduced.

[0059] In the present application, the large pore is preferably a rectangular hole, the rectangular hole is preferably a through hole, the length is preferably 1.02-2.02 mm, and in the embodiments of the present application, it can be specifically 1.02 mm or 2.02 mm; the width is preferably 1.02-2.02 mm, and in the embodiments of the present application, it can be specifically 1.02 mm or 2.02 mm; the piezoelectric material is preferably a rectangular cuboid, the length of the rectangular cuboid is preferably 1-2 mm, and in the embodiments of the present application, it can be specifically 1 mm or 2 mm; the width is preferably 1-2 mm, and in the embodiments of the present application, it can be specifically 1 mm, 1.5 mm or 2 mm; the height is preferably 3 mm. In the present application, the outer diameter of the spherical polymer hollow frame is preferably 30 mm, and the inner diameter is preferably 27 mm.

[0060] When the large holes are arranged periodically, it is preferred that the side length of the square hole gradually decreases from 2 mm to 1 mm, each time by 0.2 mm; taking the hemispherical polymer hollow frame as an example, from bottom to top (the placement direction and Figure 6 the same), the side length of the large hole in the second row is 0.2 mm smaller than that in the first row, the side length of the large hole in the third row is 0.2 mm smaller than that in the second row, and so on, gradually decreasing to the top.

[0061] In the present application, the shape of the hollow piezoelectric composite material can also be designed as a two-dimensional curved surface, i.e., a hemicylindrical or cylindrical curved surface, and applied to an arc surface transducer. It can also be designed as a wavy curved surface, simulating the wavy shape in nature, and designed as a continuously undulating curved surface. It can also be designed as a spiral curved surface, similar to a spring or vortex structure. It can also be designed as a honeycomb-shaped curved surface, similar to the porous shape of a honeycomb.

[0062] In order to further illustrate the present application, a spherical hollow piezoelectric composite material and a preparation method thereof provided by the present application are described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0063] Example 1

[0064] The preparation process of the spherical hollow piezoelectric composite material is shown in Figure 2 Fig. 1, and a pure piezoelectric single crystal sheet (specifically, a pure piezoelectric ceramic square sheet) is selected. In this example, a lead zirconate titanate PZT5A piezoelectric ceramic square sheet is used. A high-precision cutting machine is used to cut the sheet-shaped piezoelectric material into small columns, and the cut small columns are ultrasonically cleaned and dried. The thickness of the sheet-shaped piezoelectric ceramic square sheet is 3 mm, and the length and width are 35 mm.

[0065] Specifically, the high-precision cutting machine has a precision of 0.001 mm. The cutting machine cuts along the X and Y axes of the square piezoelectric material. The cut piezoelectric ceramic small columns are cuboids, and the length and width of the bottom surface of the piezoelectric ceramic small columns are both 2 mm, and the height is 3 mm. The piezoelectric ceramic small columns are ultrasonically cleaned with pure water as the cleaning liquid. After cleaning, a drying oven is used for drying at a temperature of 45°C for 2 hours.

[0066] A three-dimensional modeling is used to design a spherical resin hollow frame model, as shown in Figure 6 Fig. 2. Model parameters: the outer diameter of the hemispherical resin hollow frame is 30 mm, the inner diameter is 27 mm, the length and width of the hole are both 2.02 mm, and the depth is 3 mm. The model is directly exported to generate an STL text input to a light-curing printer.

[0067] The general standard resin UV-650 photosensitive resin is used as raw material to carry out light curing 3D printing, the pore diameter on the resin frame is just capable of assembling with the piezoelectric ceramic small column, and two half-spherical resin hollow frames are obtained; wherein, the precision of the light curing 3D printing is 0.01mm precision motion control platform, the laser spot is 0.00184mm 2 , the printing speed is 30mm / h, the layer thickness is 0.1mm, the printing laser power is 75%, the printing time is 27.67min, the length and width of the pore in the two half-spherical resin hollow frames are both 2.02mm, and the depth is 3mm; the outer diameter of the two half-spherical resin hollow frames is 30mm, and the inner diameter is 27mm.

[0068] The piezoelectric ceramic small column after cleaning and drying is sequentially inserted into the large holes of the two half-spherical resin hollow frames, the side surface of the piezoelectric small column is coated with Nandai 704 silicone rubber, and the two half-spherical resin frames are assembled and bonded, after the silicone rubber is cured at room temperature for 2h, two half-spherical hollow piezoelectric composite materials are obtained; the volume ratio of the piezoelectric phase is 45%.

[0069] The two half-spherical hollow piezoelectric composite materials are bonded using epoxy resin, and are cured in a 45℃ oven for 4h to obtain a spherical hollow piezoelectric composite material.

[0070] The spherical hollow piezoelectric composite material is composed of a spherical polymer hollow frame and a piezoelectric material; the spherical polymer hollow frame has a large hole structure, and the piezoelectric material is located in the large hole of the spherical polymer hollow frame; the polymer in the spherical polymer hollow frame is a photosensitive resin, Figure 1 is a structure diagram of the spherical hollow piezoelectric composite material, Figure 3 is a physical diagram of the spherical hollow piezoelectric composite material.

[0071] When performing admittance curve testing, the inner and outer surfaces of the two half-spherical hollow piezoelectric composite materials are respectively coated with a thin layer of silver paste to form inner and outer electrode surfaces, wherein the thickness of the silver paste thin layer is 0.1mm, the surface silver paste is blown dry using a hot air gun, the temperature of the hot air gun is 300℃, the blowing distance is 10cm, and the blowing dry time is 10min, then the two half-spherical hollow piezoelectric composite materials plated with silver paste are bonded using epoxy resin, and are cured in a 45℃ oven for 4h to obtain a spherical hollow piezoelectric composite material with inner and outer electrode surfaces, as shown in Figure 4 .

[0072] Performance test

[0073] The impedance analyzer is used to test the admittance curve of the spherical hollow piezoelectric composite material with inner and outer electrode surfaces, and in the frequency scanning range of 100kHz-800kHz, the resonant frequency is 445kHz, and there is only one resonant peak.

[0074] As Figure 5 shown. The spherical hollow piezoelectric composite material provided by the application has the following advantages compared with pure piezoelectric ceramic spherical piezoelectric material: the spherical hollow piezoelectric composite material takes low-density resin as a hollow frame, significantly reduces the overall weight, and is suitable for applications sensitive to weight; the toughness of the resin compensates for the brittleness of the ceramic, improves impact resistance and fatigue life, and reduces the risk of brittle fracture. By adjusting the ratio of resin and piezoelectric phase, different media (such as human tissues or water) can be matched to improve the efficiency of acoustic energy transmission. The stress concentration effect of the spherical resin hollow frame can more efficiently convert mechanical energy into electrical energy, improving piezoelectric output; 3D printing allows complex spherical structures (such as gradient porosity, multi-stage cavities), achieving functional design that traditional ceramic processes cannot achieve. Reduce the amount of high-cost piezoelectric ceramic, and light-cured forming is faster and more energy-saving than ceramic sintering process.

[0075] Although the above embodiment describes the present application in detail, it is only a part of the embodiment of the present application, not all embodiments, and other embodiments can be obtained according to the present embodiment without creativity, which belongs to the protection scope of the present application.

Claims

1. A method for preparing a spherical hollow piezoelectric composite material, comprising the following steps: performing light-cured 3D printing based on a preset size and pore structure of a spherical polymer hollow frame to obtain two hemispherical polymer hollow frames, wherein the polymer comprises a photosensitive resin; assembling a piezoelectric material and the two hemispherical polymer hollow frames to obtain two hemispherical hollow piezoelectric composite materials, wherein the piezoelectric material is assembled into a large hole of each of the two hemispherical polymer hollow frames; assembling the two hemispherical hollow piezoelectric composite materials to obtain the spherical hollow piezoelectric composite material.

2. The production method according to claim 1, characterized by, The conditions of the light-cured 3D printing include: precision is 0.01mm, laser spot is 0.00184mm 2 , printing speed is 30mm / h, layer thickness is 0.1mm, and printing laser power is 75%.

3. The preparation method according to claim 1, characterized in that Before the assembling, the method further comprises coating an inner surface and an outer surface of the two hemispherical hollow piezoelectric composite materials with a conductive paste to form inner and outer electrode surfaces.

4. The production method according to claim 3, characterized by, The conductive paste comprises silver paste, and the coating thickness is 0.1 mm.

5. The preparation method according to claim 3, characterized in that The assembling comprises the following steps: inserting the piezoelectric material into the large hole of each of the two hemispherical polymer hollow frames in sequence, smearing the side surface of the piezoelectric material with silicone rubber, and assembling and bonding the piezoelectric material with the hole in each of the two hemispherical polymer hollow frames, and then curing. 6.The spherical hollow piezoelectric composite material prepared by the method of any one of claims 1 to 5, comprising a spherical polymer hollow frame and a piezoelectric material, wherein the spherical polymer hollow frame has a large hole structure, the piezoelectric material is located in the large hole of the spherical polymer hollow frame, and the polymer in the spherical polymer hollow frame comprises a photosensitive resin.

7. The spherical hollow piezoelectric composite of claim 6, wherein, The volume of the piezoelectric material is 30-70% of the volume of the spherical hollow piezoelectric composite material.

8. The spherical hollow piezoelectric composite of claim 6, wherein, The large hole is a rectangular hole, the rectangular hole is a through hole, the length of the rectangular hole is 1.02-2.02 mm, and the width of the rectangular hole is 1.02-2.02 mm.

9. The spherical hollow piezoelectric composite of claim 6 or 7, wherein, The piezoelectric material is a cuboid, the length of the cuboid is 1-2 mm, the width of the cuboid is 1-2 mm, and the height of the cuboid is 3 mm.

10. The spherical hollow piezoelectric composite of claim 6 or 7, wherein, The outer diameter of the spherical polymer hollow frame is 30 mm, and the inner diameter of the spherical polymer hollow frame is 27 mm.

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