Preparation method and application of double-network cellulose-doped aramid aerogel enhanced by tetrapod zinc oxide whisker crystals

Abstract

The invention discloses a preparation method and application of tetrapod-like zinc oxide whisker-reinforced double-network cellulose-doped aramid aerogel, and relates to the field of aerogels, the preparation method comprises the following steps: S1, tetrapod-like zinc oxide whiskers are mixed and dispersed in an organic silicon prepolymer and an organic solvent to form an organic silicon prepolymer wrapping layer, and the organic silicon prepolymer wrapping layer is used as a core layer; the modified T-ZnOw is obtained; s2, mixing an aramid fiber dispersion liquid, a cellulose dispersion liquid, a polyvinyl alcohol solution, lauryl sodium sulfate and the modified T-ZnOw, homogenizing and foaming to obtain a composite emulsion; s3, directionally freezing the composite emulsion, and performing vacuum freeze drying to obtain primary aerogel; s4, performing heat treatment to obtain the double-network cellulose aramid-doped aerogel. According to the invention, the multi-dimensional acoustic energy dissipation structure, the thermal barrier property and the high-frequency vibration dissipation effect of the aerogel are optimized, so that not only is the problem of multi-dimensional interference in a precise instrument environment solved, but also a new application path is provided for a lightweight multifunctional material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogels, in particular to a preparation method of a double-network cellulose aramid aerogel reinforced by tetrapod-shaped zinc oxide whiskers and application thereof. BACKGROUND

[0002] The continuous development of industrial production and transportation is accompanied by increasing energy consumption and increasingly serious social noise pollution. The World Health Organization and clinical research show that noise pollution seriously affects human physical and mental health, and high-efficiency thermal insulation materials are crucial to reducing building energy consumption. Porous aerogels, with their ultra-low density, high porosity and high specific surface area, are ideal materials with sound absorption and thermal insulation functions. Aerogels dissipate sound energy through the friction between sound waves and pore walls by internal interconnected pores, and their porous structure can effectively block heat conduction.

[0003] Although traditional aramid aerogels (ANFs) have excellent thermal stability and chemical resistance, the pure aramid structure lacks effective cross-linking points, and the mechanical properties are limited. The introduction of cellulose nanofibers (CNF) can improve the strength by constructing a double-network structure through hydrogen bonds, but the effect of hydrogen bond interaction is limited. In addition, in the running process of various precision instruments such as optical platforms and spacecraft, not only are they disturbed by external noise, but they are also affected by the inevitable high-frequency micro-vibration generated by internal components. If the micro-vibration with a frequency exceeding 5,000 Hz cannot be effectively suppressed, it will directly affect the measurement accuracy, imaging quality and long-term running stability of the instrument.

[0004] Therefore, it is necessary to improve the prior art to solve the above problems. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides a preparation method of a double-network cellulose aramid aerogel reinforced by tetrapod-shaped zinc oxide whiskers and application thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In a first aspect, the present application provides a preparation method of a double-network cellulose aramid aerogel reinforced by tetrapod-shaped zinc oxide whiskers, comprising the following steps:

[0007] S1, mixing tetrapod-shaped zinc oxide whiskers in an organic silicon prepolymer and an organic solvent and performing ultrasonic dispersion, volatilizing the organic solvent, forming an organic silicon prepolymer wrapping layer on the surface of the tetrapod-shaped zinc oxide whiskers, and obtaining modified T-ZnOw; wherein the thickness of the wrapping layer is 10-50 nm;

[0008] S2, mixing aramid fiber dispersion liquid, cellulose dispersion liquid, polyvinyl alcohol solution, sodium dodecyl sulfate and modified T-ZnOw, and performing high-speed homogenization foaming to obtain a composite emulsion;

[0009] S3, injecting the composite emulsion into a mold for directional freezing, and then vacuum freeze-drying to obtain a primary aerogel;

[0010] S4, heat-treating the primary aerogel to crosslink the organosilicon prepolymer, thereby obtaining a dual-network cellulose aramid aerogel.

[0011] In a preferred embodiment of the present application, in the step of S1, the organosilicon prepolymer is a polydimethylsiloxane prepolymer, and accounts for 3-8% of the mass of the four needle-shaped zinc oxide whiskers; and the organic solvent is one of n-hexane, cyclohexane or petroleum ether.

[0012] In a preferred embodiment of the present application, in the step of S1, the power of the ultrasonic dispersion is 200-300 W, the frequency is 20-30 KHz, and the time is 25-35 min.

[0013] In a preferred embodiment of the present application, in the step of S2, the preparation of the aramid fiber dispersion solution comprises: dissociating aramid fibers in an organic solvent with alkali in a mass ratio of 1-1.5:1 to obtain a dispersion solution with a concentration of 0.8-1.2 wt%, and then inducing self-assembly by an ethanol solution to form aramid hydrogel, and performing solvent replacement and ultrasonic crushing treatment to obtain an aramid fiber dispersion solution.

[0014] The concentration of the ethanol solution is 25-30 wt%, and the ethanol solution is replaced at a time interval of 6-7 h; the solution replacement is selected from one of tert-butyl alcohol solution and deionized water, and the solution is replaced at a time interval of 6-8 h; the power of the ultrasonic crushing treatment is 100-150 W, the frequency is 20-30 KHz, and the time is 20-30 min.

[0015] In a preferred embodiment of the present application, in the step of S2, the preparation of the cellulose dispersion solution comprises: dispersing cellulose raw materials in an alkaline aqueous solution, adding a crosslinking agent after freeze-thaw treatment, and crosslinking at 40-60 ℃ for 2-4 h.

[0016] The cellulose raw materials are one of bamboo cellulose, cotton cellulose or wood cellulose; the alkaline aqueous solution is sodium hydroxide, urea and water in a mass ratio of 6-8:10-14:78-84; and the crosslinking agent is one of epichlorohydrin, glutaraldehyde or citric acid, and the addition amount is 5-15% of the mass of the cellulose.

[0017] In a preferred embodiment of the present application, in the step of S2, the concentration of the polyvinyl alcohol solution is 10-15 wt%; the rotation speed of the high-speed homogenization is 7000-9000 r / min, and the homogenization time is 10-20 min.

[0018] In a preferred embodiment of the present application, in the step of S2, the solid mass ratio of aramid fiber dispersion liquid, cellulose dispersion liquid, polyvinyl alcohol solution, sodium dodecyl sulfate and modified T-ZnOw is 1:0.8-1.2:0.9-1.3:1.8-2.1:0.7-1.1.

[0019] In a preferred embodiment of the present application, in the step of S3, the temperature of the directional freezing is-196 ℃, and the time is 10-20 min; the temperature of the freeze-drying is-50 ℃ to-20 ℃, the vacuum degree is 20-100 Pa, and the time is 36-48 h.

[0020] In a preferred embodiment of the present application, in the step of S4, the temperature of the heat treatment is 100-140 ℃, and the time is 0.5-1.5 h.

[0021] The second aspect of the present application provides a dual-network cellulose doped aramid aerogel prepared by the preparation method of any one of the preceding aspects, and the application of the dual-network cellulose doped aramid aerogel as a lightweight sound-absorbing, heat-insulating and vibration-damping material in the fields of aerospace, building and transportation.

[0022] The present application solves the defects in the background art, and has the following beneficial effects:

[0023] (1) The present application provides a preparation method of a dual-network cellulose doped aramid aerogel reinforced by four-pin zinc oxide whisker crystals and the application thereof. The four-pin zinc oxide whisker crystals are compounded with an interface modified by polydimethylsiloxane and a dual-network aramid cellulose matrix. The four-pin zinc oxide whisker crystals serve as a skeleton to provide support, and the polydimethylsiloxane modification layer can interact with the molecular chains in the polymer matrix, thereby enabling efficient conversion of energy within the material. The multi-dimensional sound energy dissipation structure, thermal resistance performance and high-frequency vibration dissipation effect of the aerogel are optimized, thereby not only solving the problem of multi-dimensional interference in a precision instrument environment, but also further providing a new application path for lightweight multifunctional materials.

[0024] (2) In the present application, by introducing a polydimethylsiloxane modification layer on the surface of the tetrapod-shaped zinc oxide whisker, an interfacial transition layer with excellent viscoelasticity can be constructed. The flexibility of the polydimethylsiloxane molecular chain and the interaction between the whisker and the matrix enable the interface to undergo reversible deformation and recovery under high-frequency vibration. When the vibration energy is transmitted to the whisker, its unique tetrapod-shaped structure acts as a nanometer vibrator to produce micro-bending and torsion. The viscoelastic interface converts mechanical energy into heat energy through the internal friction of the molecular chain segments, thereby greatly improving the vibration loss factor of the material in the high-frequency range. It can actively dissipate high-frequency micro-vibration, enabling it to change from passive reflection to active dissipation of energy management mode, thereby maintaining the integrity of the aerogel structure and achieving excellent acoustic and thermal performance while providing excellent vibration dissipation effect.

[0025] (3) In the present application, by utilizing the high-temperature resistance of aramid nanofiber and the hydrogen bond network of cellulose nanofiber, and by cross-linking reaction of polydimethylsiloxane to strengthen the structural stability at high temperature, the benzene ring structure of aramid gives the material excellent thermal stability, and the synergistic effect of the hydroxyl group of cellulose nanofiber and the silicon-oxygen bond of polydimethylsiloxane can hinder the heat transfer path, thereby making the composite aerogel have low thermal conductivity and the structure is not easy to collapse in high temperature environment, thereby effectively balancing the thermal insulation performance and thermal stability, which can be applied to extreme environments such as high-temperature industrial equipment, aerospace, etc., effectively reducing heat loss and energy consumption.

[0026] (4) In the present application, by adjusting the content and distribution of tetrapod-shaped zinc oxide whiskers in the aramid cellulose double network, the three-dimensional spatial structure of the tetrapod-shaped zinc oxide whisker forms a multi-level pore and a complex sound wave propagation path inside the aerogel. The needle-shaped branches can effectively increase the contact area and friction times of sound waves and pore walls, effectively promoting the eddy current loss and viscous dissipation of low-frequency sound waves. The whisker and the interface formed by the matrix constitute additional phonon scattering centers, greatly hindering the heat conduction path, thereby making the material exhibit excellent sound absorption performance in a wide frequency range while maintaining extremely low thermal conductivity, thereby realizing the synergistic optimization of sound and thermal performance and further expanding the application prospect of the material. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings;

[0028] Figure 1is a flow chart of a method for preparing a dual-network cellulose aramid hybrid aerogel reinforced by four-needle zinc oxide whiskers according to a preferred embodiment of the present application.

[0029] Figure 2 are axial (a) and radial (b) scanning electron microscope images of the dual-network cellulose aramid hybrid aerogel according to Embodiment 1 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0031] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in other manners different from those described herein. Therefore, the scope of the protection of the present application is not limited by the specific embodiments disclosed below.

[0032] It should be noted that the raw materials, equipment and reagents used in the present application can be purchased from the market or prepared by the prior art.

[0033] As shown in Figure 1 is a method for preparing a dual-network cellulose aramid hybrid aerogel reinforced by four-needle zinc oxide whiskers, comprising the following steps:

[0034] S1, mixing the four-needle zinc oxide whiskers in the organosilicon prepolymer and the organic solvent and performing ultrasonic dispersion, volatilizing the organic solvent, and forming an organosilicon prepolymer wrapping layer on the surface of the four-needle zinc oxide whiskers to obtain modified T-ZnOw; wherein the thickness of the wrapping layer is 10-50 nm;

[0035] S2, mixing aramid fiber (ANF) dispersion, cellulose (CNF) dispersion, polyvinyl alcohol (PVA) solution, sodium dodecyl sulfate (SDS) and modified T-ZnOw, and performing high-speed homogenization foaming to obtain a composite emulsion;

[0036] S3, injecting the composite emulsion into a mold for directional freezing, and then performing vacuum freeze drying to obtain a primary aerogel;

[0037] S4, performing heat treatment on the primary aerogel to crosslink the organosilicon prepolymer, and obtaining a dual-network cellulose aramid hybrid aerogel.

[0038] In some specific embodiments, in the step of S1, the organic silicon prepolymer is a polydimethylsiloxane prepolymer, and accounts for 3-8 % of the mass of the four acicular zinc oxide whiskers; the organic solvent is one of n-hexane, cyclohexane or petroleum ether.

[0039] In some specific embodiments, in the step of S1, the power of ultrasonic dispersion is 200-300 W, the frequency is 20-30 KHz, and the time is 25-35 min.

[0040] In some specific embodiments, in the step of S2, the preparation of the aramid fiber dispersion solution comprises: dissociating aramid fibers with an alkali in an organic solvent at a mass ratio of 1-1.5:1 to obtain a dispersion solution with a concentration of 0.8-1.2 wt%, and then inducing self-assembly by an ethanol solution to form aramid hydrogel, and performing solvent replacement and ultrasonic crushing treatment to obtain the aramid fiber dispersion solution; the concentration of the ethanol solution is 25-30 wt%, and the ethanol solution is replaced at a time interval of 6-7 h; the solution replacement is selected from one of tert-butyl alcohol solution and deionized water, and the solution is replaced at a time interval of 6-8 h; the power of ultrasonic crushing treatment is 100-150 W, the frequency is 20-30 KHz, and the time is 20-30 min.

[0041] In some specific embodiments, in the step of S2, the preparation of the cellulose dispersion solution comprises: dispersing cellulose raw materials in an alkaline aqueous solution, adding a crosslinking agent after freeze-thaw treatment, and crosslinking at 40-60 ℃ for 2-4 h; the cellulose raw material is one of bamboo cellulose, cotton cellulose or wood cellulose; the alkaline aqueous solution is sodium hydroxide, urea and water at a mass ratio of 6-8:10-14:78-84; the crosslinking agent is one of epichlorohydrin, glutaraldehyde or citric acid, and the addition amount is 5-15 % of the mass of the cellulose.

[0042] In some specific embodiments, in the step of S2, the concentration of the polyvinyl alcohol solution is 10-15 wt%; the rotation speed of high-speed homogenization is 7000-9000 r / min, and the homogenization time is 10-20 min.

[0043] In some specific embodiments, in the step of S2, the solid mass ratio of the aramid fiber dispersion solution, the cellulose dispersion solution, the polyvinyl alcohol solution, sodium dodecyl sulfate and modified T-ZnOw is 1:0.8-1.2:0.9-1.3:1.8-2.1:0.7-1.1.

[0044] In some specific embodiments, in the step of S3, the temperature of directional freezing is -196 ℃, and the time is 10-20 min; the temperature of freeze-drying is -50 ℃ to -20 ℃, the vacuum degree is 20-100 Pa, and the time is 36-48 h.

[0045] In some specific embodiments, in the step of S4, the temperature of the heat treatment is 100-140 ℃, and the time is 0.5-1.5 h.

[0046] The application provides application of the double-network cellulose aramid fiber aerogel prepared by the preparation method in any of the above in the field of lightweight sound absorption, heat insulation and vibration reduction materials in aerospace, building and transportation.

[0047] In order to further make the purpose and effect of the application simple and easy to understand, the application is further described in combination with the following specific examples and comparative examples, and the application is not limited in the scope of the examples.

[0048] It should be noted that in the examples and comparative examples, the preparation of raw materials is as follows: aramid fiber: short fiber form, length 5.6 mm, thickness 5D, specific gravity 1.38 g; tetrapod-shaped zinc oxide whisker (T-ZnOw): molecular weight 81.7, diameter 0.5-5 μm, length 10-50 μm, purchased from Wuhan Kemike Biomedicine; polydimethylsiloxane (PDMS): model JN-201, purity ≥99.9 %, purchased from Shandong Gengneng Chemical; dimethyl sulfoxide (DMSO): purity ≥99.9 %, purchased from Jinan Zhengkang Chemical; SDS: model dr-09, purity ≥99.9 %, purchased from Jinan Daorong Chemical; PVA: purity ≥99.9 %, purchased from Jinan Yuanlian Chemical;

[0049] The preparation of the aramid fiber dispersion solution includes: dissolving 2 g of aramid fiber and 2 g of potassium hydroxide in 196 mL of DMSO and 4 mL of water, magnetically stirring at room temperature for 36 h to obtain a dispersion solution with a concentration of 1.0 wt%, then pouring into a glass culture dish with a diameter of 10 cm, gradually adding a 25 wt% ethanol solution until the liquid completely covers the upper surface of the mold, replacing the ethanol solution every 6 h, and storing at room temperature for 24 h to form aramid hydrogel, crushing the aramid hydrogel and immersing it in a 25 wt% tert-butanol solution for solvent replacement, replacing the tert-butanol solution every 6 h, and storing at room temperature for 48 h, and finally ultrasonically dispersing the replaced aramid hydrogel at a power of 100 W and a frequency of 25 KHz for 30 min to obtain an aramid fiber dispersion solution;

[0050] The preparation of the cellulose dispersion solution includes: dissolving 3 g of bamboo cellulose powder in a mixture of sodium hydroxide (NaOH), urea and water with a mass ratio of 7:12:81, freezing at -12 ℃ for 24 h, adding 10 mL of epoxy chloropropane for crosslinking, and reacting at 50 ℃ for 3 h, immersing the obtained cellulose hydrogel in water to remove residual sodium hydroxide and urea, and performing the same ultrasonic crushing treatment as the aramid hydrogel to obtain a cellulose dispersion solution.

[0051] Example 1

[0052] A method for preparing a double-network cellulose aramid fiber doped aerogel reinforced by four-needle zinc oxide whisker crystals, comprising the following steps:

[0053] S1, disperse T-ZnOw in a n-hexane solution containing 5% PDMS prepolymer, the solid-liquid ratio of T-ZnOw to n-hexane solution is 1:3, after ultrasonic dispersion for 30 min at a power of 250 W and a frequency of 25 KHz, volatilize the solvent, form a wrapping layer with a thickness of 33 nm on the surface of T-ZnOw, and obtain modified T-ZnOw;

[0054] S2, mix the ANF dispersion, CNF dispersion, PVA solution, SDS and modified T-ZnOw with a solid mass ratio of 1:1:1.2:2:0.9, and homogenize and foam for 20 min at a speed of 8000 r / min by a high-speed homogenizer, to obtain a composite emulsion;

[0055] S3, inject the composite emulsion into a cylindrical silica gel mold, place it on a copper column, and put it into a dewar bottle as a whole, then perform directional freezing for 15 min with liquid nitrogen at-196℃, transfer the sample into a freeze dryer, and dry it at-45℃ under a vacuum degree of 30 Pa for 48 h, to obtain a primary aerogel;

[0056] S4, heat treat the primary aerogel in an air circulation oven at 120℃ for 1 h to completely crosslink the PDMS, and obtain a double-network cellulose aramid fiber doped aerogel.

[0057] To verify the successful preparation of the double-network cellulose aramid fiber doped aerogel in Example 1, see Figure 2 the axial 30 μm ( Figure 2 a) and radial 2 μm ( Figure 2b) SEM image; From the microscopic morphology, the internal structure of the aerogel exhibits a directional, layered network morphology, and the aerogel walls show a large number of tightly interconnected spherical pores. Among them, the tips of T-ZnOw contact the polymer matrix (ANF / CNF / PVA). The unique three-dimensional four-legged structure not only expands the internal volume of the aerogel, but also enhances the connectivity between the axial and radial directions, enabling it to have good acoustic and thermal properties. Furthermore, the surface of T-ZnOw is also coated with a layer of PDMS prepolymer, which optimizes the interfacial viscoelasticity between T-ZnOw and the polymer matrix. From the working principle, when high-frequency vibration is transmitted to the aerogel, the three-dimensional four-needle structure of rigid T-ZnOw acts as a nano-oscillator, like countless nano-springs and friction pairs. Its tips and bodies undergo micro-elastic bending and torsion. This process converts the macroscopic vibration energy into the deformation energy of T-ZnOw itself and the heat energy generated by friction with the viscoelastic interface (PDMS / PVA), thereby achieving efficient energy dissipation.

[0058] Example 2:

[0059] This embodiment is basically the same as Example 1, except that the thickness of the coating layer formed on the surface of modified T-ZnOw is different. The specific steps of S1 are as follows: T-ZnOw is dispersed in a hexane solution containing 3% PDMS prepolymer, the solid-liquid ratio of T-ZnOw to the hexane solution is 1:3, and ultrasonically dispersed at 250 W power and 25 KHz frequency for 30 min, and then the solvent is evaporated to form a coating layer with a thickness of 10 nm on the surface of T-ZnOw, thus obtaining modified T-ZnOw.

[0060] Example 3:

[0061] This embodiment is basically the same as Example 1, except that the thickness of the coating layer formed on the surface of modified T-ZnOw is different. The specific steps of S1 are as follows: T-ZnOw is dispersed in a hexane solution containing 8% PDMS prepolymer, the solid-liquid ratio of T-ZnOw to the hexane solution is 1:3, and ultrasonic dispersion is performed at 250 W power and 25 KHz frequency for 30 min. The solvent is then evaporated to form a coating layer with a thickness of 50 nm on the surface of T-ZnOw, thus obtaining modified T-ZnOw.

[0062] Example 4:

[0063] This embodiment is basically the same as embodiment 1, except that the amount of modified T-ZnOw is different. The specific steps of S2 are as follows: ANF dispersion, CNF dispersion, PVA solution, SDS and modified T-ZnOw with a solid mass ratio of 1:1:1.2:2:0.7 are mixed and homogenized and foamed at 8000 r / min for 20 min using a high-speed homogenizer to obtain a composite emulsion.

[0064] Example 5:

[0065] This embodiment is basically the same as Embodiment 1, except that the amount of modified T-ZnOw is different. The specific steps of S2 are as follows: ANF dispersion, CNF dispersion, PVA solution, SDS and modified T-ZnOw in a solid mass ratio of 1:1:1.2:2:1.1 are mixed and homogenized and foamed at 8000 r / min for 20 min using a high-speed homogenizer to obtain a composite emulsion.

[0066] Comparative Example 1:

[0067] This comparative example is basically the same as Example 1, except that: PDMS prepolymer was not introduced to modify T-ZnOw. Specifically: step S1 was omitted, and step S2 used unmodified T-ZnOw mixing.

[0068] Comparative Example 2:

[0069] This comparative example is basically the same as Example 1, except that the thickness of the coating layer formed on the surface of modified T-ZnOw is different. The specific steps of S1 are as follows: T-ZnOw is dispersed in a hexane solution containing 2% PDMS prepolymer, the solid-liquid ratio of T-ZnOw to the hexane solution is 1:3, and ultrasonically dispersed at 250 W power and 25 KHz frequency for 30 min, and then the solvent is evaporated to form a coating layer with a thickness of 4 nm on the surface of T-ZnOw, thus obtaining modified T-ZnOw.

[0070] Comparative Example 3:

[0071] This comparative example is basically the same as Example 1, except that the thickness of the coating layer formed on the surface of modified T-ZnOw is different. Specifically, step S1 is as follows: T-ZnOw is dispersed in a hexane solution containing 10% PDMS prepolymer, the solid-liquid ratio of T-ZnOw to the hexane solution is 1:3, and ultrasonic dispersion is performed at 250 W power and 25 KHz frequency for 30 min. The solvent is then evaporated to form a coating layer with a thickness of 69 nm on the surface of T-ZnOw, thus obtaining modified T-ZnOw.

[0072] Comparative Example 4:

[0073] This comparative example is basically the same as Example 1, except that the primary aerogel was not subjected to heat treatment, specifically, step S4 was omitted.

[0074] Comparative Example 5:

[0075] This comparative example is basically the same as Example 1, except that the amount of modified T-ZnOw is different. The specific steps of S2 are as follows: ANF dispersion, CNF dispersion, PVA solution, SDS and modified T-ZnOw in a solid mass ratio of 1:1:1.2:2:0.5 are mixed and homogenized and foamed at 8000 r / min for 20 min using a high-speed homogenizer to obtain a composite emulsion.

[0076] Comparative Example 6:

[0077] This comparative example is basically the same as Example 1, except that the amount of modified T-ZnOw is different. The specific steps of S2 are as follows: ANF dispersion, CNF dispersion, PVA solution, SDS and modified T-ZnOw in a solid mass ratio of 1:1:1.2:2:1.5 are mixed and homogenized and foamed at 8000 r / min for 20 min using a high-speed homogenizer to obtain a composite emulsion.

[0078] Performance testing: The aerogels obtained in Examples 1-5 and Comparative Examples 1-6 were tested for acoustic performance, thermal performance and vibration reduction performance in sequence. The results are shown in Table 1.

[0079] Acoustic Performance: Aerogel samples were cut into cylindrical specimens with diameters matching the impedance tubes and installed in the sample holder of the impedance tubes, ensuring a tight fit between the sample and the inner wall of the tube without gaps or leaks. The impedance tube testing system was turned on, and the dual-microphone transfer function method was used. The test frequency range was set to 100-6300 Hz, with a 100 mm diameter impedance tube used for the low-frequency range of 100-1600 Hz, and a 30 mm diameter impedance tube used for the mid-to-high frequency range of 1600-6300 Hz. Each sample was tested three times under the same conditions, and the sound absorption coefficient at different frequencies was recorded. The average of the three tests was taken as the final result. Furthermore, based on the sound absorption coefficient curves obtained from the tests, the sound absorption coefficients at four frequency points—250 Hz, 500 Hz, 1000 Hz, and 2000 Hz—were selected, and their arithmetic mean was calculated as the noise reduction coefficient (NRC), with the result rounded to three decimal places.

[0080] Thermal properties: The aerogel samples were cut into 100 mm × 100 mm × 10 mm cubes. The thermal conductivity was tested using the steady-state heat flow method. The samples were placed between the hot and cold plates of the thermal conductivity meter. The hot plate temperature was set to 35 ℃ and the cold plate temperature was set to 15 ℃ to form a stable temperature gradient. After the system reached thermal equilibrium, the heat flux density and temperature difference through the samples were measured. The thermal conductivity was calculated according to Fourier's law of heat conduction. During the test, insulation material was applied around the samples to reduce edge heat loss, and the ambient temperature fluctuations were monitored to ensure that the test was carried out under constant temperature conditions of 20-25 ℃. Each sample was measured three times, and the average value was taken as the final thermal conductivity result.

[0081] Vibration damping performance: Aerogel samples were processed into strip specimens of 50 mm × 10 mm × 2 mm. The vibration loss factor was tested using a dynamic mechanical analyzer. A three-point bending fixture was used, with the sample placed horizontally on two support points with a support point distance of 30 mm. The loading head was positioned directly above the midpoint of the sample. The test environment temperature was 25 ± 1 ℃, and the humidity was 50 ± 5 %RH. A frequency scanning mode was used, with a test frequency range of 5000-10000 Hz. The strain amplitude was set to 0.01% (to ensure the sample was in the linear viscoelastic region), and the dynamic force to static force ratio was 1:10. Starting from 5000 Hz, the frequency was gradually increased to 10000 Hz in 500 Hz intervals, and each frequency point was held for 2 minutes. The storage modulus E' and loss modulus E'' were recorded. The vibration loss factor tanδ was calculated using the formula tanδ = E'' / E'. Each sample was tested three times, and the average value of tanδ at each frequency point was taken.

[0082] Table 1: Performance test results of aerogels in Examples 1-5 and Comparative Examples 1-6

[0083] Performance test Sound absorption coefficient Noise reduction coefficient Thermal conductivity (W / (m-K)) Vibration loss factor Example 1 0.974 0.612 0.025 0.15 Example 2 0.915 0.583 0.027 0.11 Example 3 0.903 0.559 0.028 0.12 Example 4 0.921 0.565 0.029 0.10 Example 5 0.897 0.578 0.030 0.13 Comparative Example 1 0.872 0.534 0.041 0.05 Comparative Example 2 0.884 0.551 0.038 0.07 Comparative Example 3 0.891 0.559 0.039 0.06 Comparative Example 4 0.713 0.449 0.037 0.08 Comparative Example 5 0.805 0.512 0.035 0.09 Comparative Example 6 0.782 0.498 0.036 0.08

[0084] As shown in Table 1:

[0085] A comparison between Example 1 and Comparative Example 1 reveals that: Comparative Example 1 did not introduce PDMS prepolymer to modify T-ZnOw. The absence of the PDMS modification layer resulted in the lack of flexible segments on the surface of T-ZnOw, forming a rigid interface between T-ZnOw and the polymer matrix. Lacking a viscoelastic transition, when sound waves or vibrations are transmitted, effective friction cannot be formed between the T-ZnOw tip and the matrix. The elastic deformation energy of the nanooscillator is difficult to be converted into heat energy through the internal dissipation of the PDMS segments, causing the vibration loss factor to decrease from 0.15 to 0.05. In the heat conduction path, due to the lack of phonon scattering effect of PDMS at the interface, the thermal conductivity increases to 0.041 W / (m·K).

[0086] A comparison of Examples 1-3 and Comparative Examples 2-3 reveals that: in Examples 1-3, by adjusting the amount of PDMS prepolymer to control the coating thickness within the range of 10-50 nm, a suitable viscoelastic interface can be formed. The 33 nm coating in Example 1 maximizes the contact area between the needle tip and the substrate, and the rotation of the -Si-O- bonds in the PDMS chain segments can dissipate high-frequency vibrational energy. However, in Comparative Example 2, the coating thickness is too thin, resulting in insufficient coverage of the PDMS molecular chains, weak interfacial viscoelasticity, and inability to adequately buffer vibrational energy. Stress concentration between T-ZnOw and the substrate easily induces microcracks, reducing energy dissipation efficiency and causing the vibration loss factor to drop to 0.07. In Comparative Example 3, the coating thickness is too thick, reaching 69 nm, which hinders the direct contact between T-ZnOw and the substrate, reduces interfacial interaction, obstructs the vibrational energy transmission path, and further reduces the vibration loss factor to 0.06.

[0087] A comparison between Example 1 and Comparative Example 4 reveals that Comparative Example 4 was not heat-treated. Heat treatment allows the PDMS prepolymer to crosslink and form a stable three-dimensional network, strengthening the interfacial bonding between T-ZnOw and the matrix. Without heat treatment, the PDMS molecular chains are in an uncrosslinked state and remain linear. Under high-frequency vibration, they are prone to slippage or peeling, failing to dissipate energy continuously, and the vibration loss factor decreases from 0.15 to 0.08. Furthermore, the uncrosslinked PDMS segments have poor thermal stability and are easily decomposed at high temperatures, leading to the collapse of the aerogel pore structure. The thermal conductivity increases from 0.025 to 0.037, while the sound absorption coefficient decreases to 0.713.

[0088] A comparison of Examples 1 and 4-5 with Comparative Examples 5 and 6 reveals that: in Examples 1 and 4-5, the amount of modified T-ZnOw relative to the solid mass ratio of the ANF dispersion was 0.7-1.1, resulting in a uniform dispersion of its three-dimensional four-needle structure in the matrix, forming a nano-oscillator network; however, in Comparative Example 5, the amount was too low, resulting in an incomplete T-ZnOw network that could not effectively construct multi-level pores and energy dissipation paths, with the vibration loss factor dropping to 0.09; in Comparative Example 6, the amount was too high, causing T-ZnOw to easily agglomerate, with the needle tips intertwining to form rigid agglomerates, disrupting the double-network structure of the matrix. Sound waves were reflected rather than dissipated on the surface of the agglomerates, and the sound absorption coefficient decreased from 0.974 to 0.782. Simultaneously, the internal thermal conductivity of the agglomerates was enhanced, with the thermal conductivity increasing to 0.036.

[0089] The above description is based on the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0090] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker-like crystals, characterized in that, Includes the following steps: S1. Tetranexamon oxide whiskers are mixed in an organosilicon prepolymer and an organic solvent and ultrasonically dispersed. The organic solvent is evaporated, and an organosilicon prepolymer coating layer is formed on the surface of the tetranexamon oxide whiskers to obtain modified T-ZnOw. The thickness of the coating layer is 10-50 nm. S2. Aramid fiber dispersion, cellulose dispersion, polyvinyl alcohol solution, sodium dodecyl sulfate and modified T-ZnOw are mixed and foamed at high speed to obtain a composite emulsion; S3. Inject the composite emulsion into a mold and freeze it in a directional manner, then freeze-dry it under vacuum to obtain a primary aerogel; S4. The primary aerogel is heat-treated to crosslink the organosilicon prepolymer, resulting in a double-network cellulose-doped aramid aerogel.

2. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S1, the organosilicon prepolymer is a polydimethylsiloxane prepolymer, accounting for 3-8% of the mass of the tetraneedle-shaped zinc oxide whiskers; the organic solvent is one of n-hexane, cyclohexane, or petroleum ether.

3. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S1, the ultrasonic dispersion power is 200-300 W, the frequency is 20-30 KHz, and the time is 25-35 min.

4. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S2, the preparation of the aramid fiber dispersion includes: dissociating aramid fibers with an alkali in an organic solvent at a mass ratio of 1-1.5:1 to obtain a dispersion with a concentration of 0.8-1.2 wt%, then inducing self-assembly of aramid hydrogels through ethanol solution, and performing solvent replacement and ultrasonic pulverization to obtain the aramid fiber dispersion. The concentration of the ethanol solution is 25-30 wt%, and the ethanol solution is replaced every 6-7 hours. The solution replacement is selected from either tert-butanol solution or deionized water, and the solution is replaced every 6-8 hours. The ultrasonic pulverization process has a power of 100-150 W, a frequency of 20-30 kHz, and a time of 20-30 min.

5. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S2, the preparation of the cellulose dispersion includes: dispersing the cellulose raw material in an alkaline aqueous solution, adding a crosslinking agent after a freeze-thaw treatment, and crosslinking at 40-60 °C for 2-4 h; The cellulose raw material is one of bamboo cellulose, cotton cellulose or wood cellulose; the alkaline aqueous solution is sodium hydroxide, urea and water in a mass ratio of 6-8:10-14:78-84; the crosslinking agent is one of epichlorohydrin, glutaraldehyde or citric acid, and the amount added is 5-15% of the mass of cellulose.

6. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S2, the concentration of the polyvinyl alcohol solution is 10-15 wt%; the high-speed homogenization speed is 7000-9000 r / min, and the homogenization time is 10-20 min.

7. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S2, the solid mass ratio of the aramid fiber dispersion, cellulose dispersion, polyvinyl alcohol solution, sodium dodecyl sulfate and modified T-ZnOw is 1:0.8-1.2:0.9-1.3:1.8-2.1:0.7-1.

1.

8. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S3, the directional freezing temperature is -196 ℃ and the time is 10-20 min; the freeze-drying temperature is -50 ℃ to -20 ℃, the vacuum degree is 20-100 Pa, and the time is 36-48 h.

9. The method for preparing a double-network cellulose-doped aramid aerogel reinforced with tetraneedle zinc oxide whisker crystals according to claim 1, characterized in that: In step S4, the heat treatment temperature is 100-140 °C and the time is 0.5-1.5 h.

10. The application of a dual-network cellulose-doped aramid aerogel prepared by any one of claims 1-9 as a lightweight sound-absorbing, heat-insulating, and vibration-damping material in the fields of aerospace, construction, and transportation.

Images