A method and device for preparing porous piezoelectric ceramic material

Abstract

The present invention belongs to the technical field of functional ceramic materials, and discloses a method for preparing porous piezoelectric ceramic materials and a preparation device thereof. The method comprises: step S1: preparing a porous material forming slurry by mixing; step S2: using a power ultrasonic transducer to emit ultrasonic waves to generate a cavitation effect, generating microbubbles during the slurry forming process, and regulating the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer, thereby regulating the position and morphology of the microbubbles generated by cavitation; step S3: curing the slurry to obtain a porous material blank; step S4: heat-treating the porous material blank to obtain a porous material. The porous piezoelectric ceramic material prepared by the above method of the present invention has good performance, can realize customized production, has low production cost, high efficiency, and environmentally friendly production, and is conducive to the preparation of functional materials with specific acoustic properties and energy storage properties, and is also conducive to the preparation of porous composite materials with more complex external structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramic materials, and in particular relates to a method for preparing a porous piezoelectric ceramic material and a preparation device thereof. Background Art

[0002] Piezoelectric ceramics are functional materials that can convert mechanical energy into electrical energy through the piezoelectric effect. Piezoelectric ceramics can cause their domain walls to deflect under high-voltage electric fields. Polarized piezoelectric ceramics exhibit the piezoelectric effect and are widely used in ultrasonic transducers, underwater acoustic transducers, electroacoustic transducers, ceramic filters, and other fields.

[0003] Porous ceramic materials, particularly porous piezoelectric ceramics, offer low acoustic impedance, low density, excellent sound absorption, and high heat absorption capabilities. They are widely used in underwater acoustic transducers, energy harvesters, and biofunctional ceramics. Current methods for preparing porous piezoelectric ceramics primarily include pore-forming agent removal and sintering, freeze casting, and gel casting.

[0004] The current main method is the pore-forming agent removal sintering method. This method has the following disadvantages for preparing porous piezoelectric ceramics: first, this preparation method will use too much organic pore-forming agent; second, the organic pore-forming agent will produce more defects near the pore wall when burned out, resulting in a decrease in overall performance. This preparation method also makes it difficult to form pores of different sizes, shapes, or even gradients in the same ceramic, which will result in a lower overall density of the ceramic, larger defects, and unsatisfactory performance.

[0005] The freeze casting method is to form columnar ice crystals in the solvent of the slurry under low temperature conditions. The sublimation of ice will leave channels in the body. This method is mainly used for the preparation of lamellar and directional holes, and it is difficult to prepare circular holes. The gel injection molding method is to cross-link and polymerize the organic monomers of a low-viscosity, high-solid volume fraction suspension into a three-dimensional network structure under the action of a catalyst and initiator. Toxic chemical reagents are used in the preparation process of this method, which is relatively expensive.

[0006] Therefore, it is difficult for the porous piezoelectric ceramic materials prepared in the existing technology to simultaneously meet the requirements of pore size, shape, position control, low cost, and environmentally friendly production, and further innovative and effective solutions are needed. Summary of the Invention

[0007] The present invention aims to address the technical problems existing in the background technology and provide a preparation method and preparation device of porous piezoelectric ceramic materials. Power ultrasonic cavitation is used to generate microbubbles to prepare porous material molding slurry, and the position and shape of microbubble generation are regulated by adjusting the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer. The porous material green body is then obtained by a solidification slurry molding method, avoiding the defects between pores when pores are generated by using a pore-forming agent. The prepared porous piezoelectric ceramic material has good performance, can be customized, and has low production cost, high efficiency and environmentally friendly production.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] A method for preparing a porous piezoelectric ceramic material, comprising the following steps:

[0010] Step S1: Mixing to prepare porous material forming slurry;

[0011] Step S2: using a power ultrasonic transducer to emit ultrasonic waves to generate a cavitation effect, generating microbubbles during the slurry forming process, and regulating the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer to further control the position and morphology of the microbubbles generated by cavitation;

[0012] Step S3: solidifying the slurry and forming it into a porous material body;

[0013] Step S4: heat-treating the porous material blank to obtain a porous material.

[0014] Furthermore, the step S1 specifically includes:

[0015] Step S11: uniformly mixing the required material powder, dispersant and liquid forming slurry carrier to obtain porous material forming slurry;

[0016] Step S12: vacuuming the slurry to remove bubbles in the formed slurry.

[0017] Furthermore, in step S2, the power ultrasonic transducer adopts a single-element power transducer or a multi-element array power transducer.

[0018] Furthermore, the single-element power transducer controls the sound field distribution and focusing mode through an acoustic lens, and controls the sound power intensity and frequency to achieve the control of microbubble generation and movement.

[0019] The multi-element array power transducer adopts phased array technology, and realizes the control of microbubble generation and movement by regulating the array arrangement and focusing mode, combined with the control of sound power intensity and frequency.

[0020] Furthermore, the array arrangement of the multi-element array power transducer includes a linear array, a circular array, a concave array or a convex array.

[0021] Furthermore, in step S2, the calculation formula for regulating the size, shape and movement trajectory of microbubbles in the slurry by the acoustic power intensity and frequency of the power ultrasonic transducer is as follows:

[0022]

[0023] In the above formula, ρ is the density of the slurry; R is the radius of the microbubble; and are the vibration velocity and acceleration of the radial motion of the bubble wall of the microbubble; μ is the shear viscosity coefficient of the slurry; P g0 is the gas pressure inside the microbubble at static state, in is the surface tension when the microbubble radius is R0, σ is the surface tension coefficient, P0 is the ambient static pressure, P V is the vapor pressure inside the microbubble; γ is the specific heat ratio of the gas inside the microbubble; P A is the sound pressure amplitude; ω is the circular frequency of the sound wave, ω=2πf, f is the frequency of the sound wave; W is the sound power; v is the propagation speed of the sound wave in the slurry; A is the area passed by the sound wave per unit time; t is the excitation time of the ultrasonic transducer.

[0024] Furthermore, in step S2, the power ultrasonic transducers are in two groups, which are placed in the slurry and outside the slurry tank respectively;

[0025] The motion trajectories of the two groups of power ultrasonic transducers include circle, ellipse, square, triangle or polygon;

[0026] The two groups of power ultrasonic transducers can be used separately or in combination.

[0027] Furthermore, the power ultrasonic transducer placed outside the slurry tank transmits the ultrasonic wave generated by the power ultrasonic transducer to the slurry in the slurry tank through the coupling structure provided between the power ultrasonic transducer and the slurry tank;

[0028] The coupling structure is composed of soft package material, acoustic lens, coupling fluid or wedge block.

[0029] Furthermore, in step S2, the shape of the microbubbles includes: one or more combinations of spheroids, ellipsoids, tori, and polyhedrons; the size of the microbubbles ranges from 0.1 μm to 500 μm;

[0030] The frequency range of the power ultrasonic transducer is 20kHz-30MHz; the sound power intensity range of the power ultrasonic transducer is: 0W / cm 2<Sound power≤50000W / cm 2 .

[0031] At the same time, the present invention also provides a preparation device for porous piezoelectric ceramic materials, which is used to implement the preparation method as described in any of the above items, including an electronic control unit, a power ultrasonic control unit and a slurry forming unit; the power ultrasonic control unit and the slurry forming unit are both connected to the electronic control unit, and the electronic control unit is an external electronic control module;

[0032] The power ultrasonic control unit includes a power ultrasonic transducer, which is used to emit ultrasonic cavitation in the slurry to generate microbubbles, forming a porous material slurry with microbubbles, and by adjusting the array arrangement, sound power intensity and frequency of the power ultrasonic transducer, the position and shape of the microbubbles generated by cavitation are controlled;

[0033] The slurry forming unit is used for forming a porous material slurry having microbubbles.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The present invention uses high-power ultrasonic cavitation to generate microbubbles to prepare porous material forming slurry, avoiding the generation of defects between pores when using pore-forming agents to generate pores, and is more conducive to the generation of independent closed pores. In addition, no toxic chemical reagents are used in the production process, and the production meets environmental protection requirements;

[0036] (2) In the process of forming the porous material forming slurry, the present invention can generate microbubbles at specific locations by adjusting the array form, motion trajectory, and focusing mode of the power ultrasonic transducer; by regulating the sound power intensity and frequency of the power ultrasonic transducer, the size, shape, and motion position of the microbubbles generated by cavitation can be regulated; the above-mentioned regulation mode is more conducive to the preparation of functional materials with specific acoustic properties and energy storage properties;

[0037] (3) The present invention adopts a solidified slurry molding method to form porous materials, especially adopts a light-curing 3D printing molding technology, which is conducive to the preparation of porous composite materials with more complex appearance and structure, and can achieve low-cost, high-efficiency, and customized preparation of porous composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of a method for preparing a porous material according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic structural diagram of a preparation device in which a power ultrasonic control unit is placed in a slurry tank in an embodiment of the present invention;

[0040] Figure 3 for Figure 2Schematic diagram of the motion trajectory structure of the power ultrasonic control unit;

[0041] Figure 4 This is a schematic structural diagram of a preparation device in which the power ultrasonic control unit is placed outside the slurry tank in an embodiment of the present invention;

[0042] Figure 5 This is a graph showing the change in microbubble radius calculated theoretically in an embodiment of the present invention;

[0043] Figure 6 This is an SEM image of a porous barium titanate piezoelectric ceramic with a pore content of 12.5% ​​actually prepared in an embodiment of the present invention;

[0044] Explanation of the marks in the figure: 1-power ultrasonic control unit; 2-slurry tank; 3-printing platform; 4-printing parts; 5-laser; 6-coupling structure; 7-guide rail. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] In the description of the present invention, it should be understood that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0047] Example 1

[0048] The embodiment of the present invention provides a method for preparing a porous piezoelectric ceramic material, Figure 1 As shown, the method includes the following steps:

[0049] Step S1: Mixing and preparing porous material forming slurry; specifically comprising:

[0050] The required material powder, dispersant and liquid forming slurry carrier are mixed evenly to obtain porous material forming slurry;

[0051] The slurry is vacuumed to remove bubbles in the molding slurry.

[0052] Step S2: Use a power ultrasonic transducer to emit ultrasonic waves to produce a cavitation effect, generate microbubbles during the slurry forming process, and regulate the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer to further regulate the position and morphology of the microbubbles generated by cavitation (including the size, shape and motion position of the microbubbles).

[0053] In step S2, the power ultrasonic transducer is a single-element power transducer or a multi-element array power transducer.

[0054] If a single-vibration power transducer is used, the single-vibration power transducer can realize the regulation of the generation and movement of microbubbles after being focused by an acoustic lens. Specifically, the acoustic lens can adjust the sound field distribution of the single-vibration power transducer. By replacing different types of acoustic lenses, such as the acoustic focusing lens and acoustic holographic lens in the prior art, some acoustic lens designs may produce a uniformly distributed sound field, while other acoustic lens designs may produce a sound field with a specific pattern or shape. These different sound field distributions will affect the generation and movement of microbubbles. The type and parameters of the acoustic lens will affect the focusing and distribution of ultrasonic waves, thereby affecting the generation of microbubbles. By regulating the sound field of different types of acoustic lenses, combined with the regulation of sound power intensity and frequency, the generation and movement of microbubbles can be regulated.

[0055] If a multi-element array power transducer is used, the sound field distribution is controlled by regulating the array arrangement of the multi-element array power transducer, and the array arrangement includes but is not limited to array modes such as linear array, annular array, concave array and convex array; the multi-element array power transducer adopts phased array technology, and through focusing and array arrangement regulation, combined with the regulation of sound power intensity and frequency, microbubbles can be formed at different positions of the slurry and the movement of the microbubbles can be regulated.

[0056] The calculation formula for regulating the size, shape and movement trajectory of microbubbles in the slurry by the acoustic power intensity and frequency of the power ultrasonic transducer is as follows:

[0057]

[0058] In the above formulas (1)-(2), ρ is the density of the slurry; R is the radius of the microbubble; and are the vibration velocity and acceleration of the radial motion of the bubble wall of the microbubble; μ is the shear viscosity coefficient of the slurry; P g0 is the gas pressure inside the microbubble at static state, in is the surface tension when the microbubble radius is R0, σ is the surface tension coefficient, P0 is the ambient static pressure, P V is the vapor pressure inside the microbubble; γ is the specific heat ratio (or polytropic index) of the gas inside the microbubble; P Ais the sound pressure amplitude; ω is the circular frequency of the sound wave, ω=2πf, f is the frequency of the sound wave; W is the sound power; v is the propagation speed of the sound wave in the slurry; A is the area passed by the sound wave per unit time; t is the excitation time of the ultrasonic transducer.

[0059] The power ultrasonic transducers are arranged in two groups, one inside the slurry and one outside the slurry tank. Microbubbles are generated and their movement is regulated by controlling the movement of the two groups of power ultrasonic transducers, one inside the slurry tank and the other outside the slurry tank, around the slurry forming center. The movement trajectories of the two groups of power ultrasonic transducers include various shapes, such as circular, elliptical, square, triangular, or polygonal. The two groups of power ultrasonic transducers can be used individually or in combination. Furthermore, the power ultrasonic transducer placed outside the slurry tank can be coupled to the slurry tank via a soft packaging material, an acoustic lens, a coupling fluid, or a wedge, allowing ultrasonic waves to propagate through the slurry tank.

[0060] The shape and movement of the microbubbles formed by ultrasonic cavitation are affected by the properties of the medium, environmental conditions and sound field parameters. The shapes of the microbubbles include but are not limited to spheroids, ellipsoids, toroids and polyhedrons. The size of the microbubbles can be controlled by adjusting the frequency or sound power intensity of the power ultrasonic transducer. The size range of the microbubbles is 0.1μm-500μm, the frequency range of the power ultrasonic transducer is 20kHz-30MHz, and the sound power intensity range of the power ultrasonic transducer is: 0W / cm 2 <Sound power≤50000W / cm 2 .

[0061] Step S3: solidifying the slurry and forming it into a porous material body;

[0062] The methods used for solidifying the slurry include, but are not limited to, photocuring, thermosetting, acoustic curing, tape casting, extrusion, gel casting, or freeze casting. Photocuring can utilize photocuring 3D printing technology, which is advantageous for preparing porous composite materials with more complex shapes and structures, and can achieve low-cost, high-efficiency, and customized preparation of porous composite materials.

[0063] Step S4: heat-treating the porous material blank to obtain a porous material; the heat treatment includes but is not limited to degreasing, sintering and other treatment methods.

[0064] Example 2

[0065] An embodiment of the present invention provides a device for preparing porous materials, comprising an electronic control unit, a power ultrasonic control unit, and a slurry forming unit; the power ultrasonic control unit and the slurry forming unit are both connected to the electronic control unit, and the electronic control unit is an external electronic control module;

[0066] The power ultrasonic control unit includes a power ultrasonic transducer, which is used to emit ultrasonic cavitation in the slurry to generate microbubbles, forming a porous material slurry with microbubbles, and by regulating the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer, the position and shape of the microbubbles generated by cavitation are regulated;

[0067] The slurry forming unit is used for forming a porous material slurry having microbubbles.

[0068] As one example, Figure 2 As shown, the slurry tank 2 contains slurry, a power ultrasonic control unit 1, and a printing platform 3. The printing part 4 is located on the printing platform 3. The power ultrasonic control unit 1 is placed in the slurry in the slurry tank 2 and is located on the outer side of the printing platform 3. The laser 5 is located directly above the printing part 4 and is used to provide a laser light source. Figure 3 As shown, the motion trajectory of the power ultrasonic control unit 1 is a circle surrounding the printing platform 3.

[0069] As another embodiment, Figure 4 As shown, the slurry tank 2 contains slurry and a printing platform 3, the printed part 4 is located on the printing platform 3, the power ultrasonic control unit 1 is placed on the guide rail 7 outside the slurry tank 2, and the gap between the power ultrasonic control unit 1 and the slurry tank 2 is filled with a coupling structure 6, which is composed of soft package material, acoustic lens, coupling liquid or wedge block filling; through the conduction of the coupling structure 6, the ultrasonic wave emitted by the power ultrasonic control unit 1 passes through the slurry tank 2 and propagates in the slurry, and the laser 5 is located directly above the printed part 4 and is used to provide a laser light source.

[0070] Example 3

[0071] The present invention adopts the preparation device in Example 2 and the preparation method in Example 1 to prepare a porous barium titanate piezoelectric ceramic material. The preparation process is as follows:

[0072] Step S1: Mixing and preparing porous barium titanate piezoelectric ceramic forming slurry;

[0073] Specifically, barium titanate ceramic powder with a particle size of 500 nm, a photosensitive resin, a dispersant, and a photoinitiator are stirred and mixed in a homogenizer, and then the slurry is vacuumed to remove bubbles in the formed slurry;

[0074] Step S2: emitting ultrasonic waves through a power ultrasonic transducer to generate a cavitation effect, thereby generating microbubbles during the slurry forming process, and regulating the motion trajectory, acoustic power intensity, and frequency of the power ultrasonic control unit 1 to thereby control the position and morphology of the microbubbles generated by cavitation, thereby forming a porous barium titanate piezoelectric ceramic forming slurry having a certain number, size, and controllable motion position of microbubbles;

[0075] Specifically, an ultrasonic transducer with a sound wave frequency of 25kHz and a sound pressure amplitude of 0.15MPa-0.18MPa is used, and a ceramic slurry of a mixture of barium titanate and resin with a density of 1500kg / m 3 The shear viscosity coefficient of the slurry is 0.28kg / (ms) and the surface tension coefficient is 0.04kg / s 2 , the static pressure of the environment is 0.1013MPa, the specific heat ratio of the gas in the microbubble is 1.07, and the vapor pressure in the microbubble is 0.2Mpa;

[0076] The change of microbubble radius with time calculated according to formula (1)-(2) is shown in the figure below: Figure 5 As shown, the radius of the generated microbubbles is controlled to be in the range of 2.65 μm-3.65 μm;

[0077] Step S3: Obtain a porous barium titanate blank by photocuring printing of the slurry, specifically, combining Figure 2-3 As shown, the laser 5 excites the laser light source under the action of the galvanometer module to expose the porous barium titanate piezoelectric ceramic forming slurry with microbubbles, wherein the porous barium titanate piezoelectric ceramic forming slurry is attached to the printing platform 3, and the printing platform 3 is raised and lowered by the electronic control unit. Each time a layer is printed, the printing platform 3 moves down a layer, so that the porous barium titanate piezoelectric ceramic forming slurry is photocured under the exposure conditions to obtain a porous barium titanate piezoelectric ceramic green body with controllable microbubble quantity, size, and shape;

[0078] Step S4: Degrease the porous barium titanate piezoelectric ceramic body obtained above at 800°C and sinter at 1290°C to finally obtain a porous barium titanate piezoelectric ceramic. The SEM image of the ceramic is shown in FIG. Figure 6 As shown, the position pointed by the white arrow is the barium titanate ceramic microbubble, the pore content is 12.5%, the microbubble radius size is 2.5μm-5μm, and the ceramic porosity is 12.5%, which is consistent with Figure 5 The radius of the microbubbles produced by theoretical calculation is basically consistent with the range of 2.65μm-3.65μm.

[0079] The above description is only an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the scope of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing a porous piezoelectric ceramic material, characterized in that: The method comprises the following steps: Step S1: Mixing and preparing porous material forming slurry; Step S1 specifically includes: Step S11: uniformly mixing the required material powder, dispersant and liquid forming slurry carrier to obtain porous material forming slurry; Step S12: vacuuming the slurry to remove bubbles in the formed slurry; Step S2: using a power ultrasonic transducer to emit ultrasonic waves to generate a cavitation effect, generating microbubbles during the slurry forming process, and regulating the sound field distribution and motion trajectory, sound power intensity and frequency of the power ultrasonic transducer to further control the position and morphology of the microbubbles generated by cavitation; Step S3: solidifying the slurry and forming it into a porous material body; Step S4: heat treating the porous material body to obtain a porous material; In step S2, the acoustic power intensity and frequency of the power ultrasonic transducer are used to control the size, shape and movement trajectory of microbubbles in the slurry. The calculation formula is as follows: In the above formula, ρ is the density of the slurry; R is the radius of the microbubble; and are the vibration velocity and acceleration of the radial motion of the bubble wall of the microbubble; μ is the shear viscosity coefficient of the slurry; P g0 is the gas pressure inside the microbubble at static state, in is the surface tension when the microbubble radius is R0, σ is the surface tension coefficient, P0 is the ambient static pressure, P V is the vapor pressure inside the microbubble; γ is the specific heat ratio of the gas inside the microbubble; P A is the sound pressure amplitude; ω is the circular frequency of the sound wave, ω=2πf, f is the frequency of the sound wave; W is the sound power; v is the propagation speed of the sound wave in the slurry; A is the area passed by the sound wave per unit time; t is the excitation time of the ultrasonic transducer.

2. The preparation method according to claim 1, characterized in that In step S2, the power ultrasonic transducer is a single-element power transducer or a multi-element array power transducer.

3. The preparation method according to claim 2, characterized in that The single-element power transducer controls the sound field distribution and focusing mode through an acoustic lens, and controls the sound power intensity and frequency to achieve the control of microbubble generation and movement. The multi-element array power transducer adopts phased array technology, and realizes the control of microbubble generation and movement by regulating the array arrangement and focusing mode, combined with the control of sound power intensity and frequency.

4. The preparation method according to claim 3, characterized in that The array arrangement of the multi-element array power transducer includes a linear array, an annular array, a concave array or a convex array.

5. The preparation method according to claim 2, characterized in that In step S2, the power ultrasonic transducers are in two groups, which are placed in the slurry and outside the slurry tank respectively; The motion trajectories of the two groups of power ultrasonic transducers include circle, ellipse, square, triangle or polygon; The two groups of power ultrasonic transducers can be used separately or in combination.

6. The preparation method according to claim 5, characterized in that The power ultrasonic transducer is placed outside the slurry tank, and the ultrasonic wave generated by the power ultrasonic transducer is transmitted to the slurry in the slurry tank through the coupling structure provided between the power ultrasonic transducer and the slurry tank for propagation; The coupling structure is composed of soft package material, acoustic lens, coupling fluid or wedge block.

7. The preparation method according to claim 1, characterized in that In step S2, the shape of the microbubbles includes: one or more combinations of spheroids, ellipsoids, toroids, and polyhedrons; the size of the microbubbles ranges from 0.1 μm to 500 μm; The frequency range of the power ultrasonic transducer is 20kHz-30MHz; the sound power intensity range of the power ultrasonic transducer is: 0W / cm 2 <Sound power≤50000W / cm 2 .

8. A device for preparing a porous piezoelectric ceramic material, used for implementing the preparation method according to any one of claims 1 to 7, characterized in that: It includes an electronic control unit, a power ultrasonic control unit and a slurry forming unit; the power ultrasonic control unit and the slurry forming unit are both connected to the electronic control unit, and the electronic control unit is an external electronic control module; The power ultrasonic control unit includes a power ultrasonic transducer, which is used to emit ultrasonic cavitation in the slurry to generate microbubbles, forming a porous material slurry with microbubbles, and by adjusting the array arrangement, sound power intensity and frequency of the power ultrasonic transducer, the position and shape of the microbubbles generated by cavitation are controlled; The slurry forming unit is used for forming a porous material slurry having microbubbles.

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