A porous ceramic / piezoelectric polymer aerogel composite for sound absorption noise reduction and a preparation method thereof

Abstract

The application belongs to the field of sound absorption and noise reduction materials, and discloses a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction and a preparation method thereof.The preparation method is as follows: (1) preparing ceramic slurry; (2) taking porous polymer as a precursor template, mounting the ceramic slurry, and drying to obtain a green body; (3) heating and sintering to obtain a porous ceramic matrix; (4) preparing a homogeneous solution of piezoelectric polymer material; (5) pouring the solution into the porous ceramic matrix and freeze casting; (6) freeze drying and quenching to obtain the porous ceramic / piezoelectric polymer aerogel composite material.The microstructure of the composite material is improved, the piezoelectric polymer aerogel component with secondary pore structure is introduced into the first-stage pore structure, and an additional sound-electricity conversion energy loss mechanism is introduced, so that the composite material obtained by the application has excellent absorption effect on noise in a wide frequency range of 250 Hz to 6400 Hz.

Description

Technical Field

[0001] This invention belongs to the field of sound-absorbing and noise-reducing materials, and more specifically, relates to a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction and its preparation method. Background Technology

[0002] With the continuous development of transportation industries and equipment, the resulting noise pollution has become a significant concern, and long-term exposure to noise can seriously harm human physical and mental health. Currently, mainstream sound-absorbing materials typically have high absorption coefficients in the high-frequency range (generally above 2kHz), but their absorption effect on mid- and low-frequency sound waves with strong penetration and long propagation distances is poor. Mid- and low-frequency noise (typically 1kHz–2kHz for mid-frequency and below 1kHz for low-frequency) is ubiquitous in daily life and often imperceptible, originating from various engines, compressors, household appliances, and vehicles. Therefore, it is crucial to focus on and prevent the potential harm caused by mid- and low-frequency noise to the human body.

[0003] The sound-absorbing materials on the market are mainly porous materials, such as sponge foam and fiber felt. However, their simple pore structure makes them have poor low-frequency sound absorption performance. At the same time, their temperature resistance and mechanical strength are also low, making it difficult to use them under complex and harsh working conditions. For micro-perforated plates and acoustic metamaterials with good low-frequency sound absorption, there is a disadvantage of narrow sound absorption frequency range (for example: [1] Xing Tuo, Li Xianhui, Gai Xiaoling, et al. Low-frequency sound absorption of micro-perforated plate composite acoustic metamaterials [J]. Acta Acustica, 2020, 45(06): 878-884., the frequency range of their sound absorption coefficient greater than 0.6 is 396~892Hz; [2] Ji Yanlu, Lü Haifeng, Liu Jibin. Influence of surface tension on the sound insulation performance of thin film acoustic metamaterials [J]. Functional Materials, 2019, 50(01): 1120-1125., the frequency range of their sound absorption coefficient greater than 0.6 is 700~920Hz), which limits their practical application. Porous ceramics, as a type of multifunctional ceramic material with high porosity, high mechanical strength, high temperature resistance and excellent chemical stability, have also shown great potential in the field of sound absorption and noise reduction. However, simply adjusting the pore structure of porous ceramics can only slightly improve the sound absorption performance of the material and cannot achieve excellent broadband sound absorption. Therefore, it is necessary to propose a new type of sound-absorbing material that can achieve effective sound absorption and noise reduction over a wide frequency range, while also taking into account good mechanical and physical properties for better applications. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction, and its preparation method. By improving the microstructure of the composite material and designing the overall process flow accordingly, a piezoelectric polymer aerogel component with a secondary pore structure is introduced into the first-order pore structure (obtained by replicating the precursor template). This results in a composite material with a multi-level pore structure. Furthermore, the piezoelectric polymer aerogel introduces an additional acoustic-electric conversion energy loss mechanism. These combined effects enable the porous ceramic / piezoelectric polymer aerogel composite material obtained by the present invention to exhibit excellent noise absorption over a wide frequency range (i.e., good overall absorption of sound waves with frequencies from 250Hz to 6400Hz), while also possessing lightweight, high strength, hydrophobic, and thermal insulation properties. This allows for wide application in sound absorption and noise reduction in transportation, industry, and construction.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction is provided, characterized by comprising the following steps:

[0006] (1) The ceramic raw material powder and additives are added together to the solvent and mixed evenly to obtain a ceramic slurry; wherein the additives include thickener, binder, dispersant and defoamer.

[0007] (2) Using a porous polymer as a precursor template, immerse it in the ceramic slurry obtained in step (1), and squeeze out the excess slurry after full immersion, so that the surface of the mesh skeleton of the precursor template is coated with ceramic slurry, and then dry it to obtain a green body.

[0008] (3) The green body obtained in step (2) is subjected to step heating sintering. The template material is removed first and then sintered to obtain a porous ceramic matrix.

[0009] (4) Add the piezoelectric polymer material to the organic solvent, stir and dissolve evenly to obtain a homogeneous solution;

[0010] (5) Pour the solution obtained in step (4) into the porous ceramic matrix obtained in step (3) to fully impregnate it so that the solution completely fills the pores of the porous ceramic, and then freeze-cast it.

[0011] (6) The frozen body obtained in step (5) is freeze-dried to obtain an aerogel structure. After the freeze-drying is completed, it is quenched to obtain a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction.

[0012] As a further preferred embodiment of the present invention, in step (1), the ceramic raw material powder is selected from one of zirconium oxide, alumina, silicon dioxide, silicon carbide, silicon nitride, aluminum nitride, boron carbide and boron nitride powder;

[0013] The solvent is water or ethanol;

[0014] The mass ratio of the thickener to the solvent is (0.2-1.0 wt%): 1.

[0015] The mass ratio of the adhesive to the solvent is (0.2-1.5 wt%): 1;

[0016] The mass ratio of the dispersant to the solvent is (0.3-1.0 wt%): 1;

[0017] The mass ratio of the defoamer to the solvent is (0.1-0.3 wt%): 1;

[0018] The solid content of the ceramic slurry obtained in step (1) is 60-80 wt%.

[0019] As a further preferred embodiment of the present invention, in step (2), the porous polymer is selected from at least one of polyurethane, polystyrene, polyvinyl chloride and cellulose;

[0020] The porous polymer has undergone pretreatment to improve surface roughness and remove inter-network membranes; preferably, the pretreatment is carried out by alkaline immersion method; specifically, the porous polymer is immersed in a sodium hydroxide solution with a mass fraction of 10-20 wt% for 4-8 hours at a temperature of 40-80°C to achieve pretreatment.

[0021] The porous polymer has a porosity of 30 PPI to 80 PPI, preferably 30 PPI, 35 PPI, 40 PPI, 45 PPI, 50 PPI, 60 PPI or 80 PPI.

[0022] As a further preferred embodiment of the present invention, in step (2), the extrusion method is selected from flat plate pressing and roller pressing, and the number of extrusions is 2 to 6 times;

[0023] The drying process specifically involves first drying at room temperature for 12–24 hours, and then drying at 60–90°C for 6–12 hours.

[0024] As a further preferred embodiment of the present invention, in step (3), the stepped heating sintering specifically involves first holding at temperature T1 to remove the solvent; then raising to temperature T2 to remove the template material; then raising to temperature T3 to completely remove the additives; and then raising to temperature T4 to sinter a porous ceramic matrix.

[0025] Among them, T1 is above 100℃, T2 is greater than or equal to the decomposition temperature of the template material, T3 is greater than or equal to the maximum value of the decomposition temperatures of the thickener, binder, dispersant and defoamer, and T4 is greater than or equal to the sintering temperature of the ceramic raw material powder.

[0026] As a further preferred embodiment of the present invention, in step (4), the piezoelectric polymer material is selected from: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and trifluoroethylene, a copolymer of polyvinylidene fluoride and tetrafluoroethylene, and a copolymer of polyvinylidene fluoride and hexafluoropropylene.

[0027] The organic solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone;

[0028] The stirring is carried out under heating conditions, preferably at a temperature of 50–70°C, and the stirring time is greater than 4 hours.

[0029] As a further preferred embodiment of the present invention, in step (5), the cryogenic casting is performed using a low-temperature freezing source of -196 to -20°C for 5 min to 12 h.

[0030] As a further preferred embodiment of the present invention, in step (6), the freeze-drying is carried out for 2 to 5 days under conditions of a temperature of -70 to -50°C and a vacuum degree of ≤40Pa;

[0031] The quenching process involves first holding the sample at 120–170°C for 1–8 hours, followed by cooling.

[0032] Specifically, the cooling method is one of the following: air cooling, room temperature water cooling, ice water cooling, and liquid nitrogen cooling.

[0033] Furthermore, when the cooling method is room temperature water cooling or ice water cooling, the product undergoes a drying process after cooling.

[0034] According to another aspect of the present invention, the present invention provides a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction obtained by the above preparation method.

[0035] According to another aspect of the invention, the invention provides the application of the above-described porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction in sound waves with absorption frequencies from 250 Hz to 6400 Hz.

[0036] Preferably, the sound wave frequency is 856-6400Hz and the sound absorption coefficient reaches 0.8 or higher.

[0037] Compared with the prior art, the present invention first uses a template replication method to prepare porous ceramics (where the pores are the first-order pore structure), and then uses a freeze-drying method to form piezoelectric polymer aerogels (where the pores are the second-order pore structure) in the pores of the porous ceramic matrix. The resulting composite material has a multi-level pore structure. At the same time, the piezoelectric polymer aerogel will also introduce an additional acoustic-electric energy conversion loss mechanism. The combined effect of these factors makes the porous ceramic / piezoelectric polymer aerogel composite material obtained by the present invention have excellent noise absorption effect over a wide frequency range, and at the same time have good compressive strength, thermal insulation performance and hydrophobic properties, which can be used for a wide range of sound absorption and noise reduction applications.

[0038] Specifically, the present invention can achieve the following beneficial effects:

[0039] (1) The preparation method provided by this invention utilizes a template replication method to prepare porous ceramics, resulting in porous ceramics with a porous structure (wherein the pores are the first-order pore structure). This invention preferably uses a porous polymer with a porosity of 30 to 80 PPI (PPI stands for Pores Per Inch) as a template, which has high porosity and uniform pore size. Furthermore, it can preferably be combined with an alkaline solution soaking pretreatment to further optimize the pore structure details of the template (the alkaline solution soaking pretreatment can, on the one hand, improve the surface roughness of the template, and on the other hand, remove some inter-network membranes, further connecting the pores). The porous ceramics prepared based on the template replication method have a highly interconnected pore structure, which is beneficial for sound waves to enter the material without being reflected away. Compared with other preparation methods (such as foaming methods), the method of this invention can control the pore structure of the porous ceramics by adjusting the porosity of the porous polymer template, and has the advantages of adjustable pore size and simplicity and speed.

[0040] (2) The preparation method provided by this invention forms a piezoelectric polymer aerogel as a secondary porous structure in the pores of a porous ceramic matrix through freeze-drying. The obtained aerogel has high porosity and small pore size, increasing the specific surface area inside the material, thereby enhancing the reflection and friction of sound waves with the material and improving the viscous heat loss of sound energy. At the same time, the weak vibration generated by the piezoelectric polymer aerogel under sound wave excitation can convert part of the vibration mechanical energy into electrical energy based on the local piezoelectric effect, further consuming the sound waves. Therefore, the porous ceramic / piezoelectric polymer aerogel composite material prepared by this invention has excellent broadband sound absorption performance, as described below. Figure 3 As shown, the composite material obtained by the method of the present invention has good sound absorption effect for sound waves with frequencies from 250Hz to 6400Hz; especially when the sound wave frequency is from 856Hz to 6400Hz, the sound absorption coefficient reaches more than 0.8.

[0041] (3) The preparation method provided by the present invention yields a porous ceramic / piezoelectric polymer aerogel composite material that also has the characteristics of low density, high strength, heat resistance and thermal insulation and hydrophobicity, which enables it to maintain structural and performance stability under complex and harsh working conditions and has broad application prospects.

[0042] (4) This invention innovatively combines porous ceramics and piezoelectric polymer aerogels through structural and process design. To achieve a more complete integration between the piezoelectric polymer aerogel and the porous ceramic, this invention uses a template method and a porous polymer as a template to prepare a porous ceramic with a high open porosity. This allows the polymer solution to easily and quickly fill the pores of the porous ceramic, avoiding the adverse effects of other preparation methods (such as foaming methods) that result in porous ceramics with more closed-pore structures on polymer filling. Secondly, this invention fills a porous ceramic matrix with piezoelectric polymer aerogel. This aerogel structure has a large pore size and low density, which is beneficial for the transmission of sound waves and enhances the vibration of the aerogel under sound wave excitation, thereby improving the acoustic-thermal and acoustic-electric conversion efficiency. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the porous ceramic prepared in Comparative Example 1 of this invention.

[0044] Figure 2 This is a comparison chart of the sound absorption coefficient curves of the porous ceramics prepared in Comparative Examples 1, 2, and 3 of this invention.

[0045] Figure 3 This is a scanning electron microscope image of the porous ceramic / piezoelectric polymer aerogel composite material prepared in Example 1 of the present invention.

[0046] Figure 4 The graph shows a comparison of the sound absorption coefficient curves of the porous ceramic / piezoelectric polymer aerogel composite materials prepared in Examples 1, 2, and 3 of this invention and the porous ceramic prepared in Comparative Example 1.

[0047] Figure 5 The thermal conductivity coefficients are those of the porous ceramic / piezoelectric polymer aerogel composite materials prepared in Examples 1, 2, and 3 of this invention and the porous ceramic prepared in Comparative Example 1.

[0048] Figure 6 The water contact angle is the porous ceramic / piezoelectric polymer aerogel composite material prepared in Examples 1, 2, and 3 of this invention.

[0049] Figure 7 The density and compressive strength of the porous ceramic / piezoelectric polymer aerogel composite materials prepared in Examples 1, 4, 5, and 6 of this invention are shown. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0051] The sound absorption coefficient was tested in the comparative examples and embodiments described below in accordance with GB / T18696.2-2002 "Measurement of sound absorption coefficient and acoustic impedance in acoustic impedance tubes - Part 2: Transfer function method". The sound absorption coefficient of the prepared samples was tested using an impedance tube. The frequency range of the sound wave f was 200Hz to 6400Hz, and the detection step size Δf = 8Hz.

[0052] The following are specific examples:

[0053] Comparative Example 1 (only the first-order pore structure was obtained)

[0054] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose (as thickener), 0.72g of polyvinyl alcohol (as binder), 0.3g of ammonium polyacrylate (as dispersant) and 0.12g of tributyl phosphate (as defoamer) were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0055] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0056] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry can completely enter the interior of the sponge, then take the sponge out of the slurry, squeeze the sponge 5 times with two flat plates, and discharge the excess slurry to obtain the green body.

[0057] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0058] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter (i.e., thoroughly remove thickener, binder, dispersant and defoamer); finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0059] Figure 1 This is a scanning electron microscope image of the porous ceramic prepared in the comparative example, which shows that it has a uniform network porous structure.

[0060] Comparative Example 2

[0061] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0062] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 45 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0063] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry can completely enter the interior of the sponge, then take the sponge out of the slurry, squeeze the sponge 5 times with two flat plates, and discharge the excess slurry to obtain the green body.

[0064] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0065] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter (i.e., thoroughly remove thickener, binder, dispersant and defoamer); finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0066] Comparative Example 3

[0067] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0068] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 40 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0069] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry can completely enter the interior of the sponge, then take the sponge out of the slurry, squeeze the sponge 5 times with two flat plates, and discharge the excess slurry to obtain the green body.

[0070] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0071] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter (i.e., thoroughly remove thickener, binder, dispersant and defoamer); finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0072] Figure 2 The graphs show a comparison of the sound absorption coefficient curves of the porous ceramics prepared in Examples 1, 2, and 3. It can be seen that the overall sound absorption performance of the porous ceramics improves with increasing PPI of the template material. However, adjusting the pore size of the porous ceramics alone has a limited effect on improving the sound absorption coefficient, and it is still impossible to achieve high sound absorption across a wide frequency range, especially in the mid-to-low frequency sound wave range.

[0073] Example 1

[0074] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0075] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0076] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the sponge, and then take the sponge out of the slurry; then squeeze the polyurethane sponge template soaked in slurry five times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0077] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0078] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0079] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0080] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0081] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0082] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0083] Figure 3 This is a scanning electron microscope image of the porous ceramic / piezoelectric polymer aerogel composite material prepared in this embodiment. It can be seen that the aerogel with a small pore structure was successfully formed in the large pores of the porous ceramic.

[0084] Example 2

[0085] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0086] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0087] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry can completely enter the interior of the sponge, then take the sponge out of the slurry, squeeze the sponge 5 times with two flat plates, and discharge the excess slurry to obtain the green body.

[0088] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0089] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0090] (6) Mix 0.619g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 450r / min for 6h to obtain a P(VDF-TrFE) solution with a mass fraction of 3wt%.

[0091] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0092] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0093] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0094] Example 3

[0095] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0096] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0097] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry can completely enter the interior of the sponge, then take the sponge out of the slurry, squeeze the sponge 5 times with two flat plates, and discharge the excess slurry to obtain the green body.

[0098] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0099] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0100] (6) Mix 0.833g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 500r / min for 8h to obtain a P(VDF-TrFE) solution with a mass fraction of 4wt%.

[0101] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0102] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0103] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0104] Figure 4 This is a comparison of the sound absorption coefficient curves of the sound-absorbing materials prepared in Comparative Example 1 and Examples 1, 2, and 3. It can be seen that compared to the porous ceramic prepared in Comparative Example 1, the sound absorption performance of the composite materials prepared in Examples 1, 2, and 3 was significantly improved after introducing the piezoelectric polymer aerogel structure. The average sound absorption coefficient of Comparative Example 1 in the range of 250Hz to 6400Hz was 0.72, while the average sound absorption coefficients of Examples 1, 2, and 3 were 0.88, 0.84, and 0.85, respectively. Compared to Comparative Example 1, the average sound absorption coefficient of Example 1 increased by 22%.

[0105] The noise reduction coefficient was obtained by calculating the average sound absorption coefficient at frequencies of 250Hz, 500Hz, 1500Hz, and 2000Hz. The noise reduction coefficient of Comparative Example 1 was 0.38, while the noise reduction coefficients of Examples 1, 2, and 3 were all 0.54, representing an improvement of 42%. This indicates that the mid-to-low frequency sound absorption performance of the porous ceramic / piezoelectric polymer aerogel composite material was significantly improved.

[0106] Furthermore, for low-frequency sound waves (below 1kHz) and high-frequency sound waves (above 2500Hz), the sound absorption coefficients of Examples 1, 2, and 3 are all higher than those of Comparative Example 1. In the low-frequency range, Example 3 shows the best effect; in the mid-to-high frequency range, Example 1 shows the best effect.

[0107] Figure 5 The figures show the thermal conductivity values ​​of the sound-absorbing materials prepared in Comparative Example 1 and Examples 1, 2, and 3. It can be seen that all of them have low thermal conductivity, with Example 3 exhibiting a thermal conductivity as low as 0.1658 W / m. -1 K -1 This indicates that the prepared sound-absorbing material has good heat insulation and temperature resistance properties.

[0108] Figure 6 The water contact angles of the porous ceramic / piezoelectric polymer aerogel composites prepared in Examples 1, 2, and 3 are 113°, 115°, and 117°, respectively, indicating that the composites have good hydrophobic properties.

[0109] Example 4

[0110] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0111] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0112] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the sponge, and then take the sponge out of the slurry; then squeeze the polyurethane sponge template soaked in slurry 6 times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0113] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0114] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0115] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0116] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0117] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0118] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0119] Example 5

[0120] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0121] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0122] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the interior of the sponge, and then remove the sponge from the slurry; then squeeze the polyurethane sponge template soaked in slurry four times using two flat plates to remove excess slurry and obtain a green body (in this green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0123] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0124] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0125] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0126] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0127] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0128] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0129] Example 6

[0130] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0131] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0132] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the interior of the sponge, and then remove the sponge from the slurry; then squeeze the polyurethane sponge template soaked in slurry three times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0133] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0134] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0135] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0136] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0137] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0138] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0139] Figure 7 The compressive strength and density values ​​of the porous ceramic / piezoelectric polymer aerogel composite materials prepared in Examples 1, 4, 5, and 6 are shown. Composite sound-absorbing materials of different densities were prepared by adjusting the number of extrusion cycles after the sponge template was fully impregnated with the slurry. All materials exhibited a density less than 1 g / cm³. -3 Its low density characteristic. At the same time, the composite sound-absorbing material also possesses a certain compressive strength; for example, when the density is 0.58 g / cm³. -3 At that time, its compressive strength was 1.24 MPa.

[0140] Example 7

[0141] (1) 210g of zirconium oxide powder, 90g of deionized water, 0.45g of sodium carboxymethyl cellulose, 0.9g of polyvinyl alcohol, 0.45g of ammonium polyacrylate and 0.18g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 70wt%.

[0142] (2) Cut a sponge template with a diameter of 130 mm and a thickness of 26 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0143] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the sponge, and then take the sponge out of the slurry; then squeeze the polyurethane sponge template soaked in slurry five times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0144] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0145] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 99 mm and a thickness of 20 mm.

[0146] (6) 3.265g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder was mixed with 160g of dimethyl sulfoxide solvent and magnetically stirred at 60℃ and 500r / min for 8h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0147] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 30 minutes. After demolding, a columnar frozen block is obtained.

[0148] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 4 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0149] (9) The composite material obtained in step (8) is kept at 140°C for 6 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 8 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0150] Example 8

[0151] (1) 180g of alumina powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconia grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0152] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0153] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the sponge, and then take the sponge out of the slurry; then squeeze the polyurethane sponge template soaked in slurry five times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0154] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0155] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1600°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0156] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0157] (7) Place the porous ceramic obtained in step (5) into the mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place the flat metal block into liquid nitrogen for 15 minutes to cool it fully, place the mold on the metal block and freeze for 20 minutes. After demolding, a columnar frozen block is obtained.

[0158] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0159] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0160] Example 9

[0161] (1) 180g of zirconium oxide powder, 60g of deionized water, 0.3g of sodium carboxymethyl cellulose, 0.72g of polyvinyl alcohol, 0.3g of ammonium polyacrylate and 0.12g of tributyl phosphate were mixed and added into a ball milling jar with zirconium oxide grinding beads. The mixture was ball milled at 200r / min for 6h to obtain a uniform ceramic slurry with a solid content of 75wt%.

[0162] (2) Cut a sponge template with a diameter of 38 mm and a thickness of 40 mm from a polyurethane sponge block with a pore size of 50 PPI. Soak it in a 20 wt% sodium hydroxide solution and soak it in a water bath at 60°C for 6 hours. After soaking, rinse the sponge template with clean water and dry it at 80°C for 4 hours to obtain a template for slurry impregnation.

[0163] (3) Immerse the sponge template obtained in step (2) in the ceramic slurry obtained in step (1), squeeze the sponge template fully so that the ceramic slurry completely enters the sponge, and then take the sponge out of the slurry; then squeeze the polyurethane sponge template soaked in slurry five times with two flat plates to remove excess slurry and obtain a green body (in the green body, the surface of the mesh skeleton of the porous template is coated with a uniform layer of slurry).

[0164] (4) The green body obtained in step (3) is placed at room temperature for 12 hours and then dried at 80°C for 8 hours.

[0165] (5) Place the dried green body obtained in step (4) into a muffle furnace, raise the temperature to 100°C at 1°C / min and hold for 30 min to remove residual moisture; then raise the temperature to 350°C at 1°C / min and hold for 2 h to remove the sponge template; continue to raise the temperature to 500°C at 1°C / min and hold for 60 min to remove residual organic matter; finally raise the temperature to 1500°C at 3°C / min and hold for 2 h; cool the furnace to room temperature to obtain a sound-absorbing porous ceramic with a diameter of 29 mm and a thickness of 30 mm.

[0166] (6) Mix 0.408g of polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) powder with 20g of dimethyl sulfoxide solvent, and stir magnetically at 60℃ and 400r / min for 4h to obtain a P(VDF-TrFE) solution with a mass fraction of 2wt%.

[0167] (7) Place the porous ceramic obtained in step (5) into a mold, and then pour the solution obtained in step (6) into the porous ceramic so that the pores of the porous ceramic are completely filled by the solution. Place it in a freezer at -20°C for 12 hours to freeze and cast. After demolding, a columnar frozen block is obtained.

[0168] (8) The frozen block obtained in step (7) was placed in a freeze dryer and freeze-dried at -60℃ and 20Pa for 3 days to obtain a preliminary porous ceramic / piezoelectric polymer aerogel composite material.

[0169] (9) The composite material obtained in step (8) is kept at 140°C for 5 hours, then immediately taken out and placed in an ice water bath to cool, and after cooling, it is dried at 80°C for 6 hours to obtain a porous ceramic / piezoelectric polymer aerogel composite material with excellent sound absorption performance.

[0170] The above embodiments are merely examples. Besides using a mesh polyurethane sponge as a precursor template, other porous polymer materials (such as polystyrene, polyvinyl chloride, and cellulose) can also be used. Thickeners, binders, dispersants, and defoamers, in addition to the specific materials used in the above embodiments, can also be other additive materials with similar functions, and their dosages can be flexibly adjusted. Furthermore, the pore size of the first-stage pores can be flexibly adjusted according to actual needs, i.e., different pore sizes can be obtained by adjusting the pore structure parameters of the template (such as PPI parameters). Similarly, the pore size of the secondary pores can be flexibly adjusted according to actual needs, i.e., different pore sizes can be obtained by adjusting the concentration of the piezoelectric polymer homogeneous solution (the higher the concentration, the smaller the pore size of the secondary pores; that is, in addition to the solution with a concentration less than or equal to 4 wt% used in the above embodiments, other concentrations can also be used) or by adjusting the freeze-drying conditions (the lower the freeze-casting temperature, the smaller the pore size of the secondary pores).

[0171] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction, characterized in that, Includes the following steps: (1) The ceramic raw material powder and additives are added together to the solvent and mixed evenly to obtain a ceramic slurry; wherein the additives include thickener, binder, dispersant and defoamer; (2) Using a porous polymer as a precursor template, immerse it in the ceramic slurry obtained in step (1), and squeeze out the excess slurry after full immersion, so that the surface of the mesh skeleton of the precursor template is coated with ceramic slurry, and then dry it to obtain a green body. (3) The green body obtained in step (2) is subjected to step heating sintering. The template material is removed first and then sintered to obtain a porous ceramic matrix. (4) Add the piezoelectric polymer material to the organic solvent, stir and dissolve evenly to obtain a homogeneous solution; (5) Pour the solution obtained in step (4) into the porous ceramic matrix obtained in step (3) to fully impregnate it so that the solution completely fills the pores of the porous ceramic, and then freeze-cast it. (6) The frozen body obtained in step (5) is freeze-dried to obtain an aerogel structure. After the freeze-drying is completed, it is quenched to obtain a porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction.

2. The preparation method according to claim 1, characterized in that, In step (1), the ceramic raw material powder is selected from one of zirconium oxide, alumina, silicon dioxide, silicon carbide, silicon nitride, aluminum nitride, boron carbide and boron nitride powder; The solvent is water or ethanol; The mass ratio of the thickener to the solvent is (0.2-1.0 wt%): 1, The mass ratio of the binder to the solvent is (0.2-1.5wt%): 1; The mass ratio of the dispersant to the solvent is (0.3-1.0 wt%): 1; The mass ratio of the defoamer to the solvent is (0.1-0.3wt%): 1; The solid content of the ceramic slurry obtained in step (1) is 60-80 wt%.

3. The preparation method according to claim 1, characterized in that, In step (2), the porous polymer is selected from at least one of polyurethane, polystyrene, polyvinyl chloride and cellulose; The porous polymer has been pretreated to increase surface roughness and remove inter-network membranes. The porous polymer has a porosity of 30 PPI to 80 PPI.

4. The preparation method according to claim 3, characterized in that, The pretreatment adopts an alkaline immersion method, in which the porous polymer is immersed in a sodium hydroxide solution with a mass fraction of 10~20wt% for 4~8h at a temperature of 40~80℃ to achieve pretreatment; The porous polymer has a porosity of 30 PPI, 35 PPI, 40 PPI, 45 PPI, 50 PPI, 60 PPI, or 80 PPI.

5. The preparation method according to claim 1, characterized in that, In step (2), the extrusion method is selected from flat plate pressing and roller pressing, and the number of extrusions is 2 to 6 times; The drying process specifically involves first drying at room temperature for 12-24 hours, and then drying at 60-90°C for 6-12 hours.

6. The preparation method according to claim 1, characterized in that, In step (3), the stepped heating sintering specifically involves first holding at temperature T1 to remove the solvent; then raising the temperature to T2 to remove the template material; then raising the temperature to T3 to completely remove the additives; and finally raising the temperature to T4 to sinter a porous ceramic matrix. Among them, T1 is above 100℃, T2 is greater than or equal to the decomposition temperature of the template material, T3 is greater than or equal to the maximum value of the decomposition temperatures of the thickener, binder, dispersant and defoamer, and T4 is greater than or equal to the sintering temperature of the ceramic raw material powder.

7. The preparation method according to claim 1, characterized in that, In step (4), the piezoelectric polymer material is selected from: polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and trifluoroethylene, a copolymer of polyvinylidene fluoride and tetrafluoroethylene, and a copolymer of polyvinylidene fluoride and hexafluoropropylene. The organic solvent is at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; The stirring is carried out under heating conditions, with a temperature of 50~70℃ and a stirring time of more than 4 hours.

8. The preparation method according to claim 1, characterized in that, In step (5), the cryogenic casting is performed using a low-temperature freezing source of -196 to -20°C for 5 min to 12 h.

9. The preparation method according to claim 1, characterized in that, In step (6), the freeze drying is carried out at a temperature of -70~-50℃ and a vacuum degree of ≤40Pa for 2~5 days; The quenching process involves first holding the sample at 120-170°C for 1-8 hours, followed by cooling. Specifically, the cooling method is one of the following: air cooling, room temperature water cooling, ice water cooling, and liquid nitrogen cooling. Furthermore, when the cooling method is room temperature water cooling or ice water cooling, the product undergoes a drying process after cooling.

10. A porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction obtained by the preparation method according to any one of claims 1-9.

11. The application of the porous ceramic / piezoelectric polymer aerogel composite material for sound absorption and noise reduction as described in claim 10 in sound waves with absorption frequencies from 250 Hz to 6400 Hz.

12. The application as described in claim 11, characterized in that, The sound wave frequency is 856~6400 Hz, and the sound absorption coefficient reaches 0.8 or higher.

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