Cellulose fiber aerogel / porous aluminum sound-absorbing material and preparation method thereof

Abstract

The application discloses a preparation method of PMMA microsphere-pored cellulose fiber aerogel / porous aluminum composite sound-absorbing material, and belongs to the technical field of porous sound-absorbing materials. The application takes porous aluminum as a matrix, takes polymethyl methacrylate (PMMA) microspheres as a pore-forming agent for cellulose fiber aerogel, adds the porous aluminum filled with the microspheres into a deacetylated cellulose fiber suspension, performs vacuum suction, performs freeze drying, immerses into an ethyl acetate solution, and removes the PMMA microspheres after heating, so that finally the PMMA microsphere-pored cellulose fiber aerogel is obtained in the pores of the porous aluminum. The porous structure formed in the aerogel of the obtained composite sound-absorbing material significantly increases the interface contact area in the sound wave propagation path, promotes the dissipation and reflection of sound wave energy, and thus improves the overall sound-absorbing efficiency. In addition, the porous aluminum itself serves as a rigid skeleton and provides necessary mechanical support for the composite structure, so that the composite structure can meet the comprehensive application requirements of high strength and high efficient sound absorption.

Description

Technical Field

[0001] This invention relates to the field of porous sound-absorbing materials technology, specifically to a cellulose fiber aerogel / porous aluminum sound-absorbing material and its preparation method. Background Technology

[0002] Noise pollution is a typical problem accompanying rapid urbanization and industrialization. It not only disrupts daily life but also poses a long-term threat to public health. To effectively control noise, the development of high-performance sound-absorbing materials has become an important direction in the field of environmental functional materials. Ideal sound-absorbing materials should possess broadband and efficient sound absorption, excellent mechanical properties, environmental stability, and sustainability to meet the application needs of complex scenarios such as transportation, construction, and industrial equipment.

[0003] Currently, common sound-absorbing materials are mainly divided into two categories: porous sound-absorbing materials and resonant sound-absorbing structures. Porous materials, such as foamed metals, fiber felts, and porous polymers, rely on the frictional and viscous losses of sound waves after they enter the material to achieve sound absorption. Their performance is mainly affected by factors such as porosity, pore size distribution, and flow resistance. Among them, porous aluminum, due to its lightweight, high strength, high temperature resistance, non-hygroscopicity, and recyclability, exhibits significant advantages under mechanical loads and harsh environments, making it a highly regarded structural-functional integrated material in engineering applications. However, the sound absorption performance of porous aluminum is limited by its pore size and pore structure. In the mid-to-high frequency range (especially above 2500Hz), insufficient acoustic impedance matching often leads to a decrease in the sound absorption coefficient, limiting its application in broadband noise reduction.

[0004] To improve mid-to-high frequency sound absorption performance, low-density, high-porosity fiber-based aerogel materials (such as cellulose fiber aerogels) have been extensively studied. Cellulose fiber aerogels possess abundant micro-nano hierarchical pores and a large specific surface area, enabling efficient sound absorption by extending the sound wave propagation path and enhancing viscous loss. However, these materials typically exhibit low mechanical strength and high brittleness, making them prone to structural collapse under vibration or pressure conditions. They also lack durability and reliability, making it difficult for them to independently bear loads or long-term dynamic loads.

[0005] In recent years, composite material design has provided a feasible path to balance sound absorption and mechanical properties. For example, combining porous aluminum with polymer foam or fiber felt can complement each other's properties to some extent. However, existing composite methods mostly use simple filling or physical bonding, resulting in weak interfacial bonding and easy component separation; moreover, traditional fillers themselves still have problems such as narrow sound absorption bandwidth or insufficient strength. In addition, aerogel materials often generate internal stress and cracks due to drying shrinkage during the composite process, leading to uneven distribution and compromised integrity within the porous framework, affecting the stable performance of acoustic properties.

[0006] Therefore, developing a novel composite strategy that effectively integrates the broadband sound absorption advantages of cellulose fiber aerogel while maintaining the high mechanical properties of porous aluminum, and synergistically optimizing the internal structure and acoustic impedance matching of the material through micron-level pore-forming and stress-buffering techniques, is key to improving the overall performance of the composite material. Such materials are expected to achieve long-term, stable, broadband noise reduction in high sound pressure and high vibration environments such as rail transportation and heavy machinery, demonstrating significant engineering application prospects. Summary of the Invention

[0007] To address or partially address the problems existing in the prior art, the primary objective of this invention is to provide a cellulose fiber aerogel / porous aluminum composite sound-absorbing material, which mainly comprises: cellulose fiber aerogel and porous aluminum; wherein the porous aluminum contributes to the basic sound absorption performance, acts as a structural support and supports the aerogel; the cellulose fiber aerogel has micron-sized pores formed by PMMA microspheres inside, and the porosity reaches 95%~99%.

[0008] Another objective of this invention is to provide a method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material, the specific steps of which are as follows: (1) Deacetylation of cellulose fibers: Add a mixed solution of water and tert-butanol, disperse and cut to obtain a suspension of deacetylated cellulose fibers.

[0009] (2) PMMA microspheres are filled into porous aluminum and immersed in a deacetylated cellulose fiber suspension. After vacuuming and pressurizing in a defoaming tank, porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores is obtained.

[0010] (3) After freezing, freeze-drying, heating and decomposing the microspheres, the porous aluminum containing cellulose fiber suspension in the pores and PMMA microspheres are dried to obtain cellulose fiber aerogel / porous aluminum composite sound-absorbing material.

[0011] Preferably, in step (1) of the present invention, the cellulose fiber is an electrospun cellulose fiber with an average diameter of 1µm; the deacetylation condition is that the cellulose fiber is placed in a 0.5N KOH / ethanol solution and bathed in a water bath at 25°C for 2 hours.

[0012] Preferably, in step (1) of the present invention, the volume ratio of cellulose fiber to KOH / ethanol solution is 1:5; the dispersion and cutting conditions are dispersion and cutting at 13000 rpm for 30 min in a homogenizer.

[0013] Preferably, in step (1) of the present invention, the volume ratio of water to tert-butanol is 3:1.

[0014] Preferably, the porous aluminum in step (2) of the present invention has a porosity of 80-85% and an average pore size of 0.5 mm; the PMMA microspheres have a particle size of 50-200 μm and a filling rate of 70-80%.

[0015] Preferably, the conditions for vacuuming and pressurizing the defoaming tank in step (2) of the present invention are to vacuum to 23000Pa and pressurize for 1 minute.

[0016] Preferably, the freezing conditions in step (3) of the present invention are -65℃ to -20℃ for 6 hours; the freeze-drying conditions are vacuum freeze-drying in a cold trap at 1 Pa and -86℃ for 4 days; and the heating decomposition conditions for the microspheres are immersion in ethyl acetate solution and heating to 50℃ for 3 hours.

[0017] The principle of this invention: This invention is based on a strategy combining the "sacrificial template method" and "multi-level porous structure synergistic design." By precisely controlling the material composition and process, a cellulose fiber aerogel with high porosity and multi-scale pore structure is constructed inside porous aluminum, thereby achieving efficient absorption of broadband noise and synergistic improvement of material mechanical properties. The deacetylation treatment not only removes acetyl groups on the surface of cellulose, significantly improving its hydrophilicity and dispersion uniformity, laying the foundation for the formation of a stable three-dimensional aerogel network, but also eliminates ester bonds on the cellulose molecular chain, effectively avoiding the problem of softening and disintegration of the aerogel structure caused by the hydrolysis of cellulose ester bonds induced by ethyl acetate solution in subsequent steps.

[0018] Using polymethyl methacrylate (PMMA) microspheres as a removable pore-forming template, PMMA microspheres were first uniformly filled into the pores of porous aluminum. Then, a cellulose fiber suspension was introduced, allowing it to permeate and encapsulate the microspheres under vacuum assistance. After the suspension was freeze-dried to form a stable cellulose aerogel network, the PMMA microsphere template was removed by utilizing the property of ethyl acetate to effectively permeate, swell, and dissolve PMMA molecular chains. Furthermore, at different freezing temperatures, a mixed solvent of water and tert-butanol crystallized to produce ice crystals of different sizes and morphologies, which sublimated to form secondary pores, thus affecting the porosity of the aerogel. The relationship between the porosity of the cellulose fiber aerogel and the freezing temperature is as follows: in, Porosity (%) of cellulose fiber aerogel. T The freezing temperature is (°C).

[0019] Through the above process, a multi-level structure with macropores and mesopores is constructed. This structure exerts a multi-level, synergistic energy dissipation mechanism under the action of sound waves: the micron-sized main channels formed after the removal of PMMA microspheres serve as the main incident path of sound waves, significantly extending the sound wave propagation distance and increasing the number of frictions between the sound waves and the pore walls, thus efficiently dissipating mid-to-low frequency sound energy through the viscosity effect; the mesoporous structure composed of the cellulose aerogel network itself, with its huge specific surface area, promotes rapid and repeated heat exchange between air molecules and pore walls under the action of sound waves, thereby converting high-frequency sound energy into heat energy; and the porous aluminum skeleton not only provides mechanical support for the entire composite material, but its inherent pore structure also contributes to the basic broadband sound absorption performance; the three are coupled with each other, realizing the gradient transition of acoustic impedance and multi-mode dissipation of sound energy, breaking through the limitations of narrow sound absorption bandwidth or poor mechanical properties of single materials.

[0020] By fitting multiple linear regression, the average sound absorption coefficient (α) and porosity of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material were obtained. P ) and aperture ( D The functional relationship model of ) α = 1.0095 - 0.2382 × P -0.0000647× D Wherein, α is the average sound absorption coefficient of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material. P To improve the porosity of PMMA microsphere-porous cellulose fiber aerogel / porous aluminum composite materials, D The average pore size of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite material.

[0021] The beneficial effects of this invention are: (1) The PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material of the present invention has an average sound absorption coefficient of 0.795~0.829 in the frequency range of 800~6300Hz, which is 13.41%~18.26% higher than that of porous aluminum material with the same porosity (0.701).

[0022] (2) This invention achieves the composite of PMMA microsphere porous cellulose fiber aerogel and porous aluminum by completing the pore-forming, gelling and drying process of cellulose fiber aerogel suspension inside porous aluminum, and obtains a PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material with high sound absorption performance, so as to meet the requirements of a wider range of sound-absorbing materials. Attached Figure Description

[0023] Figure 1This is a macroscopic photograph of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material in Example 2.

[0024] Figure 2 The sound absorption coefficient versus frequency relationship of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material in Example 2.

[0025] Figure 3 The microporous structure of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material in Example 2 is shown. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, but the scope of protection of the present invention is not limited thereto.

[0027] Example 1 A method for preparing a PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material specifically includes the following steps: (1) Select cellulose electrospun fibers with an average diameter of 1µm, place them in a 0.5N KOH / ethanol solution and bathe them in a 25℃ water bath for 2 hours to deacetylate them. The volume ratio of cellulose electrospun fibers to KOH / ethanol solution is 1:5.

[0028] (2) Prepare a 50 mL mixed solution with a volume ratio of water to tert-butanol of 3:1. Add deacetylated cellulose electrospun fibers to the mixed solution and further disperse and cut them at 13000 rpm for 30 minutes using a homogenizer to obtain a suspension of deacetylated cellulose fibers.

[0029] (3) Fill porous aluminum with an average particle size of 50µm and a porosity of 80% and an average pore size of 0.5mm with microspheres, and the filling rate is 70%. Place it in a deacetylated cellulose fiber suspension until it is submerged and then place it in a defoaming tank. Vacuum the aluminum to 23000Pa and hold it for 1 minute. Then, draw the deacetylated cellulose fiber suspension into the porous aluminum filled with microspheres to obtain porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores.

[0030] (4) The porous aluminum containing cellulose fiber suspension and PMMA microspheres were placed in a refrigerator and frozen at -20°C for 6 hours, and then vacuum freeze-dried in a cold trap at 1 Pa and -86°C for 4 days.

[0031] (5) After drying the cellulose fiber / porous aluminum composite material containing PMMA microspheres, it was immersed in ethyl acetate solution and heated to 50°C for 3 hours to decompose and remove the PMMA microspheres. After drying, PMMA microsphere-porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material was obtained. The average pore size of the obtained aerogel was 50µm and the porosity was 95%.

[0032] The PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material obtained in this embodiment has an average sound absorption coefficient of 0.807 in the frequency range of 800~6300Hz, which is 15.12% higher than the average sound absorption coefficient of porous aluminum of 0.701.

[0033] Example 2 A method for preparing a PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material specifically includes the following steps: (1) Select cellulose electrospun fibers with an average diameter of 1µm, place them in a 0.5N KOH / ethanol solution and bathe them in a 25℃ water bath for 2 hours to deacetylate them. The volume ratio of cellulose electrospun fibers to KOH / ethanol solution is 1:5.

[0034] (2) Prepare a 50 mL mixed solution with a volume ratio of water to tert-butanol of 3:1. Add deacetylated cellulose electrospun fibers to the mixed solution and further disperse and cut them at 13000 rpm for 30 minutes using a homogenizer to obtain a suspension of deacetylated cellulose fibers.

[0035] (3) Fill the porous aluminum with an average particle size of 100µm and a porosity of 83% and an average pore size of 0.5mm with microspheres, and the filling rate is 75%. Place it in the deacetylated cellulose fiber suspension until it is submerged and place it in a defoaming tank. Vacuum the aluminum to 23000Pa and hold it for 1 minute. Then, draw the deacetylated cellulose fiber suspension into the porous aluminum filled with microspheres to obtain porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores.

[0036] (4) The porous aluminum containing cellulose fiber suspension and PMMA microspheres were placed in a refrigerator and frozen at -30°C for 6 hours, and then vacuum freeze-dried in a cold trap at 1 Pa and -86°C for 4 days.

[0037] (5) After drying the cellulose fiber / porous aluminum composite material containing PMMA microspheres, it was immersed in ethyl acetate solution and heated to 50°C for 3 hours to decompose and remove the PMMA microspheres. After drying, a PMMA microsphere-porosized cellulose fiber aerogel / porous aluminum composite sound-absorbing material was obtained. The aerogel had an average pore size of 100µm and a porosity of 96%. Its macroscopic photograph is shown below. Figure 1 As shown, the microporous structure is as follows Figure 3As shown.

[0038] The sound absorption coefficient of the PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material obtained in this embodiment is related to frequency in the frequency range of 800~6300Hz as follows: Figure 2 As shown, its average sound absorption coefficient in the frequency range of 800~6300Hz is 0.829, which is 18.26% higher than that of porous aluminum (0.701).

[0039] Example 3 A method for preparing a PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material specifically includes the following steps: (1) Select cellulose electrospun fibers with an average diameter of 1µm, place them in a 0.5N KOH / ethanol solution and bathe them in a 25℃ water bath for 2 hours to deacetylate them. The volume ratio of cellulose electrospun fibers to KOH / ethanol solution is 1:5.

[0040] (2) Prepare a 50 mL mixed solution with a volume ratio of water to tert-butanol of 3:1. Add deacetylated cellulose electrospun fibers to the mixed solution and further disperse and cut them at 13000 rpm for 30 minutes using a homogenizer to obtain a suspension of deacetylated cellulose fibers.

[0041] (3) Fill porous aluminum with an average particle size of 150µm into a porous aluminum with a porosity of 85% and an average pore size of 0.5mm, with a filling rate of 80%. Place it into a deacetylated cellulose fiber suspension until it is submerged and then place it in a defoaming tank. Vacuum the aluminum to 23000Pa and hold it for 1 minute. Then, draw the deacetylated cellulose fiber suspension into the porous aluminum filled with microspheres to obtain porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores.

[0042] (4) The porous aluminum containing cellulose fiber suspension and PMMA microspheres were placed in a refrigerator and frozen at -45°C for 6 hours, and then vacuum freeze-dried in a cold trap at 1 Pa and -86°C for 4 days.

[0043] (5) After drying the cellulose fiber / porous aluminum composite material containing PMMA microspheres, it was immersed in ethyl acetate solution and heated to 50°C for 3 hours to decompose and remove the PMMA microspheres. After drying, PMMA microsphere-porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material was obtained; the aerogel had an average pore size of 150µm and a porosity of 97%.

[0044] The PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material obtained in this embodiment has an average sound absorption coefficient of 0.809 in the frequency range of 800~6300Hz, which is 15.41% higher than the average sound absorption coefficient of porous aluminum of 0.701.

[0045] Example 4 A method for preparing a PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material specifically includes the following steps: (1) Select cellulose electrospun fibers with an average diameter of 1µm, place them in a 0.5N KOH / ethanol solution and bathe them in a 25℃ water bath for 2 hours to deacetylate them. The volume ratio of cellulose electrospun fibers to KOH / ethanol solution is 1:5.

[0046] (2) Prepare a 50 mL mixed solution with a water and tert-butanol volume ratio of 3:1. Add deacetylated cellulose electrospun fibers to the mixed solution and further disperse and cut them at 13000 rpm for 30 minutes using a homogenizer to obtain a deacetylated cellulose fiber suspension.

[0047] (3) Fill the porous aluminum with an average particle size of 200µm and a porosity of 83% and an average pore size of 0.5mm with microspheres, and the filling rate is 75%. Place it in the deacetylated cellulose fiber suspension until it is submerged and place it in a defoaming tank. Vacuum the aluminum to 23000Pa and hold it for 1 minute. Then, draw the deacetylated cellulose fiber suspension into the porous aluminum filled with microspheres to obtain porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores.

[0048] (4) The porous aluminum containing cellulose fiber suspension and PMMA microspheres were placed in a refrigerator and frozen at -65°C for 6 hours, and then vacuum freeze-dried in a cold trap at 1 Pa and -86°C for 4 days.

[0049] (5) After drying the cellulose fiber / porous aluminum composite material containing PMMA microspheres, it was immersed in ethyl acetate solution and heated to 50°C for 3 hours to decompose and remove the PMMA microspheres. After drying, PMMA microsphere-porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material was obtained; the aerogel had an average pore size of 200µm and a porosity of 99%.

[0050] The PMMA microsphere porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material obtained in this embodiment has an average sound absorption coefficient of 0.795 in the frequency range of 800~6300Hz, which is 13.41% higher than the average sound absorption coefficient of porous aluminum of 0.701.

[0051] In summary, by compositing PMMA porous cellulose fiber aerogel into porous aluminum, a PMMA porous cellulose fiber aerogel / porous aluminum composite sound-absorbing material is obtained, in which PMMA porous cellulose fiber aerogel fills the pores of porous aluminum, and the sound absorption performance of the material can be significantly improved.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cellulose fiber aerogel / porous aluminum composite sound-absorbing material, characterized in that, Mainly includes: Cellulose fiber aerogel and porous aluminum.

2. The cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 1, characterized in that, In the cellulose fiber aerogel / porous aluminum composite sound-absorbing material, the porous aluminum serves as a structural support and carries the aerogel; the interior of the cellulose fiber aerogel is formed by PMMA microspheres creating micron-sized pores.

3. The preparation method of the cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 1, characterized in that, The specific steps are as follows: (1) Deacetylation of cellulose fibers: Add a mixed solution of water and tert-butanol, disperse and cut to obtain a suspension of deacetylated cellulose fibers; (2) PMMA microspheres are filled into porous aluminum and immersed in a deacetylated cellulose fiber suspension. After vacuuming and pressurizing in a defoaming tank, porous aluminum containing cellulose fiber suspension and PMMA microspheres in the pores is obtained. (3) After freezing, freeze-drying, heating and decomposing the microspheres, the porous aluminum containing cellulose fiber suspension in the pores and PMMA microspheres are dried to obtain cellulose fiber aerogel / porous aluminum composite sound-absorbing material.

4. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, The average diameter of the cellulose fiber in step (1) is 1µm, and the deacetylation condition is that the cellulose fiber is placed in a 0.5N KOH / ethanol solution and bathed in a water bath at 25°C for 2 hours.

5. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, The volume ratio of cellulose fiber to KOH / ethanol solution in step (1) is 1:5, and the dispersion and cutting conditions are dispersion and cutting at 13000 rpm for 30 min in a homogenizer.

6. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, In step (1), the volume ratio of water to tert-butanol is 3:

1.

7. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, The porous aluminum in step (2) has a porosity of 80-85% and an average pore size of 0.5 mm; the PMMA microspheres have a particle size of 50-200 μm and a filling rate of 70-80%.

8. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, The conditions for vacuuming and pressurizing the defoaming tank in step (2) are to vacuum to 23000Pa and pressurize for 1 minute.

9. The method for preparing a cellulose fiber aerogel / porous aluminum composite sound-absorbing material according to claim 3, characterized in that, The freezing conditions described in step (3) are -65℃ to -20℃ for 6 hours; the freeze-drying conditions are vacuum freeze-drying in a cold trap at 1 Pa and -86℃ for 4 days; and the heating decomposition conditions for the microspheres are immersion in ethyl acetate solution and heating to 50℃ for 3 hours.

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