A bionic double-network nanofiber aerogel with integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant functions and its preparation method

Abstract

The present invention discloses a bionic double-network high-temperature heat insulation, low-frequency noise reduction, and fire-retardant integrated nanofiber aerogel and its preparation method, which belongs to the field of fiber aerogel technology. The preparation method of the bionic double-network high-temperature heat insulation, low-frequency noise reduction, and fire-retardant integrated nanofiber aerogel of the present invention comprises the following steps: mixing a silane precursor, water, and an acid catalyst to obtain a hydrolyzed silane sol; adding Laponite powder to the hydrolyzed silane sol to obtain a Laponite aqueous dispersion; mixing the Laponite aqueous dispersion with SiO2 nanofibers to obtain a Laponite mixed SiO2 nanofiber dispersion, directionally freezing, and then vacuum drying and sintering to obtain the bionic double-network high-temperature heat insulation, low-frequency noise reduction, and fire-retardant integrated nanofiber aerogel (LAPSNAs). Compared with the prior art, the material has a wide temperature range compression resilience with constant temperature, good high-temperature thermal insulation properties, excellent low-frequency noise reduction performance, and fire-retardant function.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber aerogels, and in particular to a bionic double-network nanofiber aerogel with integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant functions, and a preparation method thereof. Background Art

[0002] Aerogel materials, with their high porosity, high specific surface area, and low density, have been widely used in thermal insulation, sound absorption, and gas adsorption. However, their microstructure is a pearl-chain structure composed of nanoparticles connected by inter-necked connections. Nanoparticles have high surface energy and are easily sintered at high temperatures, causing structural collapse. This connection method also makes aerogels brittle, making them difficult to withstand the transient impacts and high external forces encountered in practical applications. It can easily cause structural cracks throughout the material, leading to serious consequences. The use of silicon sources containing organic groups (such as methyl and ethyl groups) can improve this situation, converting brittle aerogels into flexible aerogels. However, these materials still cannot withstand extreme strains, and the plastic deformation after rebound is high.

[0003] Nanofiber aerogels, based on one-dimensional nanofibers as their basic building blocks, transform the traditional aerogel's neck-type connection between microscopic nanoparticles into a fiber-stitched structure, significantly improving the stress transfer method and efficiency. The resulting nanofiber aerogels exhibit excellent resilience and are suitable for practical production applications. Nanofiber aerogels typically have interpenetrating pores, through which sound waves easily propagate, preventing them from being fully dissipated. By introducing nanosheets to seal these interpenetrating pores, the complex maze-like structure of one-dimensional nanofiber / two-dimensional nanosheet composite aerogels is expected to simultaneously impart excellent thermal insulation and noise reduction properties to nanofiber aerogels.

[0004] Existing techniques for preparing nanofiber aerogels require the introduction of room-temperature organic binders to achieve stable and uniform material preparation, which are then removed through sintering. This organic binder removal inevitably leads to sample shrinkage, affecting material uniformity and creating a cumbersome process. Furthermore, to achieve functional integration, researchers often employ more complex techniques such as 3D printing to construct aerogels with multi-level pore structures, increasing both time and process costs.

[0005] Patent CN202410918266.8 uses water as a solvent to mix one or more bacterial cellulose and its derivative nanofibers with a crosslinking agent, a crosslinking catalyst, a dispersant, and a thickener, and then freeze-drying to obtain a porous nanofiber aerogel. However, in order to ensure the uniformity and stability of the material, organic dispersants and thickeners are added. This not only increases the variety of raw materials, increases the preparation cost and process complexity, but also makes the prepared material not resistant to high temperatures. At the same time, due to the presence of organic matter, a certain amount of sample shrinkage will inevitably occur during the thermal crosslinking process, which is not conducive to maintaining the internal structure formed by freeze-drying.

[0006] Patent CN202411467854.0 mixes ceramic particles with a binder and uses in-situ freezing technology as an aid to prepare anisotropic ceramic aerogels using 3D printing technology. However, this technology requires strict control of the viscosity of the printing slurry and requires sintering at an ultra-high temperature of 2000°C. The process is cumbersome and the synthesis cost is high. In addition, its radial thermal conductivity at room temperature is as low as 0.09 W·m −1 ·k −1 , which is much larger than the thermal conductivity of air (0.027 W·m −1 ·k −1 ), which is still at a relatively high level; although its noise reduction coefficient (NRC) is relatively high, the frequency range corresponding to its sound absorption peak is relatively narrow, and the sound absorption coefficient of its anisotropic material is mostly lower than 0.6 below 2000 Hz, which is not conducive to absorbing noise of unknown frequencies.

[0007] Therefore, there is an urgent need to develop a simple, low-cost, functionally integrated nanofiber composite aerogel to enable high-temperature insulation, low-frequency sound absorption, and fire retardancy under extreme conditions. Summary of the Invention

[0008] The purpose of the present invention is to provide a bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated nanofiber aerogel and a preparation method thereof to solve the above-mentioned problems in the background technology.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] One of the technical solutions of the present invention is to provide a method for preparing a bionic double-network nanofiber aerogel with integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant functions, comprising the following steps:

[0011] mixing a silane precursor, water, and an acid catalyst to obtain a hydrolyzed silane sol;

[0012] adding Laponite powder to the hydrolyzed silane sol to obtain a Laponite aqueous dispersion;

[0013] The Laponite aqueous dispersion is mixed with SiO2 nanofibers to obtain a Laponite mixed SiO2 nanofiber dispersion, which is directionally frozen, then vacuum dried, and sintered to obtain the bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated nanofiber aerogel.

[0014] Preferably, the step of mixing the silane precursor, water and acid catalyst is: first adding water to the container, adding the acid catalyst after stable stirring, adding the silane precursor after stabilization, and fully stirring and hydrolyzing to obtain the hydrolyzed silane sol; the hydrolysis time is 0.5~3h.

[0015] Preferably, the Laponite aqueous dispersion is prepared by adding Laponite powder to the hydrolyzed silane sol, and then performing high-speed homogenous dispersion at a rotation speed of 8000-13000 r / min for 10-20 minutes.

[0016] More preferably, during the high-speed homogenous dispersion, an ice-water bath is used to ensure that the temperature of the slurry is within the range of 20-40° C. to prevent the solution temperature from rapidly rising and causing gelation, thereby obtaining a viscous and stable Laponite aqueous dispersion.

[0017] This process requires ensuring appropriate rotation speed and time to prevent the mixed slurry from shear thinning or rapid gelation.

[0018] Preferably, the silane precursor is one or more of methyltrimethoxysilane, methyltriethoxysilane, methyl orthosilicate and ethyl orthosilicate; and the acid catalyst is acetic acid and / or oxalic acid.

[0019] Preferably, the volume ratio of water, silane precursor and acid catalyst is 90:0.71-2.14:0.036.

[0020] Preferably, the mass ratio of water, SiO2 nanofibers and Laponite powder is 90:0.3-0.9:0.09-0.9.

[0021] Preferably, the preparation method of the SiO2 nanofiber is as follows: first, the SiO2 nanofiber non-woven fabric is cut into small pieces, and pre-cut using a wall breaker for 3 minutes to obtain a SiO2 nanofiber suspension without obvious SiO2 nanofiber non-woven fabric pieces, and then homogenized and cut at a speed of 13000 r / min for 20 minutes to obtain a homogenous liquid, and then dried at 120°C for 24 hours to obtain the SiO2 nanofiber.

[0022] Preferably, the directional freezing is as follows: the Laponite mixed SiO2 nanofiber dispersion is placed in a mold, and then the mold is placed in an ultra-low temperature preservation box with a unidirectional temperature gradient distribution for directional freezing; the bottom of the mold is in contact with the copper block of the ultra-low temperature preservation box, and the copper block plays a role of unidirectional freezing, the temperature of the copper block is -86°C, and the time of the directional freezing is 20 to 180 minutes.

[0023] Preferably, the internal ambient temperature of the dryer during vacuum drying is -50°C~50°C, the water supply cold trap temperature is -70°C~-45°C, the drying time is 24~96h, and the vacuum degree is 5~30Pa; the sintering is performed by heating to 900°C at a heating rate of 1~2°C / min and then keeping the temperature for 120 min, and the sintering atmosphere is air atmosphere.

[0024] The second technical solution of the present invention is to provide a method for preparing a biomimetic double-network high-temperature thermal insulation, low-frequency noise reduction, and fire-retardant integrated gradient density nanofiber aerogel, comprising the following steps:

[0025] (1) mixing a silane precursor, water, and an acid catalyst to obtain a hydrolyzed silane sol; adding Laponite powder to the hydrolyzed silane sol to obtain a Laponite aqueous dispersion;

[0026] (2) mixing the Laponite aqueous dispersion with SiO2 nanofibers to obtain a first Laponite-SiO2 nanofiber dispersion;

[0027] (3) Repeat step (2) to prepare N Laponite mixed SiO2 nanofiber dispersions with the same or different SiO2 nanofiber concentrations;

[0028] (4) Directional freezing the first Laponite mixed SiO2 nanofiber dispersion until it is completely frozen and solidified, and repeatedly adding N Nth Laponite mixed SiO2 nanofiber dispersions for directionally freezing;

[0029] (5) The product of step (4) is vacuum dried and sintered to obtain the bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated gradient density nanofiber aerogel.

[0030] The third technical solution of the present invention: provides a bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated nanofiber aerogel obtained according to the above-mentioned preparation method, wherein the nanofiber aerogel is composed of a bionic loofah network structure and a house-of-cards structure network. On a large scale, it is a bionic loofah network structure in which fibers are interlaced and fixed by silane sol, and on a small scale, it is a house-of-cards structure network composed of nanosheets between fiber holes.

[0031] Preferably, the density of the composite aerogel is 5-40 mg / cm 3 The porosity is 98.75~99.14%, and the thermal conductivity at room temperature is 0.027~0.032 W·m −1 ·k −1 The high temperature thermal conductivity at 800℃ is 0.0749~0.0886 W·m −1 ·k −1 , the noise reduction coefficient NRC value is 0.40~0.76.

[0032] The technical principles of the present invention are as follows:

[0033] Laponite, a synthetic hectorite nanoclay, forms a card-house structure during continuous stirring, achieving thickening without the need for an additional binder. After stirring, during the directional freezing process, the Laponite nanosheets in this card-house structure are squeezed into the fiber walls by the directional freezing ice crystals. This disordered arrangement of Laponite nanosheets fills the through-pores of the aerogel, potentially enhancing the reflection and dissipation of sound waves. Furthermore, during the reaction and molding process, various interactions between Laponite, the silane sol, and the SiO2 nanofibers ensure the structural stability of the formed LAPSNAs. The hydrolyzed silane sol is rich in hydroxyl groups, and the Laponite nanosheets are adsorbed and bonded to the silica sol through hydrogen bonding and electrostatic interactions between the positively charged Na ions and the silica sol. Furthermore, during high-speed stirring, the silica sol and Laponite nanosheets mix thoroughly and continuously approach each other. Electrostatic interactions between the free Na ions in the Laponite and the lone-pair O atoms in the silica sol promote the formation of numerous coordination bonds. Furthermore, hydrogen bonding between the hydroxyl groups in the SiO2 nanofibers, hydrolyzed silica sol, and Laponite nanosheets further enhances the interactions between the composite components. After high-temperature sintering, the hydroxyl groups in the SiO2 nanofibers, the silane sol, and the silane sol itself dehydrate to form a more stable Si-O-Si structure, further enhancing the composite's structural stability. This gives the prepared LAPSNAs exceptional structural stability, which is the foundation for their functional integration.

[0034] Natural loofahs have a labyrinthine structure with a network of through-holes. Within this structure, heat transfer must proceed along a complex path, significantly lengthening the heat transfer path and reducing heat transfer efficiency. Furthermore, the numerous through-holes and tortuous channels within this labyrinthine structure effectively impede air flow, reducing thermal convection. Furthermore, the inner walls of this labyrinthine structure absorb and reflect thermal radiation multiple times, reducing heat radiation. Furthermore, this structure strongly restricts the transmission of sound waves. When sound waves enter the labyrinthine structure of the through-holes, they cause vibrations in the air within the structure. This vibration causes friction with the walls, converting the sound energy into heat and dissipating it. Furthermore, this complex labyrinthine structure, with its various through-holes and cavities of varying sizes and shapes, has a natural frequency that may align with sound waves of varying frequencies, resulting in resonance. Therefore, this complex network structure may enhance the structure's broadband noise reduction performance. In summary, the labyrinthine structure of natural loofahs possesses inherent advantages in both thermal insulation and noise reduction, offering promise for the development of integrated thermal insulation and noise reduction materials. Inspired by this, the present invention uses a directional freeze-drying method, utilizing the squeezing effect of ice crystals on SiO2 nanofibers, to gradually assemble individual fibers into fiber bundles. The bundles are continuously connected and intertwined, gradually forming a complex network-like maze structure, creating a nanofiber aerogel with a bionic loofah network structure. This aerogel, composed of a primary, large-scale bionic loofah network structure and a secondary, house-of-cards network structure between the fiber bundles, is an excellent insulator of heat and sound waves.

[0035] Based on the above principles, the present invention designs and prepares a bionic double-network nanofiber aerogel, aiming to improve the high-temperature thermal insulation, low-frequency noise reduction and fire retardant properties of the aerogel and achieve functional integration.

[0036] The beneficial technical effects of the present invention are as follows:

[0037] This invention utilizes the house-of-cards network structure created by Laponite during high-speed homogenization and the biomimetic loofah structure formed during directional freeze-drying to construct a biomimetic dual-network nanofiber aerogel with integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant properties. The primary loofah network structure influences solid-state heat conduction and radiation reflection, the secondary house-of-cards network structure influences gaseous heat conduction and convection, and the tertiary nanosheet layered structure influences oxygen and heat diffusion, facilitating the formation of a physical insulation layer that prevents the transfer of heat, oxygen, and combustible volatiles. Laponite also exhibits high thermal stability, maintaining its structural integrity at high temperatures, thereby extending the material's fire resistance. Furthermore, when sound waves pass through the pores within the nanofiber aerogel, they experience frictional dissipation with the fiber walls. Simultaneously, they are reflected by the house-of-cards network structure between fiber bundles, extending the sound wave propagation path and allowing for sufficient dissipation within the house-of-cards structure, further enhancing the sound wave dissipation. Consequently, the resulting biomimetic dual-network nanofiber aerogel exhibits integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant properties, making it promising for material coating applications under extreme conditions.

[0038] The present invention utilizes the Laponite-formed house-of-cards structure to enhance the viscosity of the mixed slurry, maintaining a stable, uniform suspension for extended periods. During directional freezing and ice crystal extrusion, the aerogel will not settle due to its own gravity. This allows the process to produce ultra-low-density nanofiber aerogels with a uniform and stable structure without the need for room-temperature binders, reducing the use of additional raw materials and significantly reducing the weight of the material coating. This method is highly efficient and environmentally friendly. This stable preparation method easily produces large aerogel samples suitable for industrial production and offers strong scalability and customization. To meet the diverse needs of actual industrial production, the aerogels can be customized into shapes such as dumbbells, triangles, tubes, squares, circles, and any letter of the alphabet, and their size, thickness, and dimensions can be adjusted arbitrarily, demonstrating flexible scalability and potential for application in critical and complex equipment locations.

[0039] The density of the bionic double-network high-temperature thermal insulation, low-frequency noise reduction, and fire-retardant integrated nanofiber aerogel prepared by the present invention is 5-40 mg / cm 3 The porosity is 98.75~99.14%, and the thermal conductivity at room temperature is 0.027~0.032 W·m −1 ·k −1 The high temperature thermal conductivity at 800℃ is 0.0749~0.0886 W·m −1 ·k −1, the noise reduction coefficient NRC value is 0.40~0.76, and the maximum temperature resistance can reach 1000℃. At the same time, the aerogel has temperature-invariant superelasticity and can still maintain good compression rebound performance in liquid nitrogen and butane torch flames. In addition, the aerogel has better high-temperature thermal insulation performance and low-frequency sound absorption performance than commercial thermal insulation and sound absorption materials in actual high-temperature pipeline coating experiments and actual noise source noise reduction experiments. The preparation method of the present invention is simple, environmentally friendly, low-cost, and has a wide range of applications. It can meet the coating applications of various complex components in extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 The biomimetic structure, principle, and microstructure of the biomimetic dual-network aerogel of the present invention are shown in Figure 1. (a) shows a house-of-cards structure used in architecture; (b) shows a house-of-cards structure formed by nanosheets in the product of Example 1; (c) shows a Laponite nanosheet network structure in the product of Example 1; (d) shows a natural loofah structure; (e) shows an enlarged view of a natural loofah structure; and (f) shows a biomimetic loofah network structure in the product of Example 1.

[0042] Figure 2 The Laponite mixed SiO2 nanofiber dispersion in Example 1 and the aerogel sample prepared according to the method of Example 1 are real pictures. Among them, (a) is a real picture of the Laponite mixed SiO2 nanofiber dispersion; (b) is a real picture of the aerogel sample with a size of 2300 cm 3 Actual picture of the aerogel sample.

[0043] Figure 3 (a) is a physical picture of the ultralight aerogel prepared in Example 11, and (b) is a physical picture of aerogels of various sizes and shapes prepared according to the method of Example 1.

[0044] Figure 4 Microscopic morphologies of the products of Examples 1, 7-9. (a)-(d) are LAP0.1SNA; (e)-(h) are LAP0.4SNA; (i)-(l) are LAP0.7SNA; (m)-(p) are LAP1.0SNA.

[0045] Figure 5Microscopic morphologies of the products of Examples 1, 4-6. (a)-(d) are LAPSNA0.5; (e)-(h) are LAPSNA1.0; (i)-(l) are LAPSNA1.5; (m)-(p) are LAPSNA2.0.

[0046] Figure 6 The compression rebound performance of the product of Example 4 at extreme temperatures is shown in Figure 4. (a) shows the rebound performance of the product in a butane torch flame at 1000°C; (b) shows the rebound performance of the product in liquid nitrogen at -196°C.

[0047] Figure 7 The morphology and thermal insulation properties of the samples of Examples 1, 7-9 are shown. (a) is a photo of the sample; (b) is the density and room-temperature thermal conductivity of the sample; and (c) is the high-temperature thermal conductivity of the sample.

[0048] Figure 8 The morphology and thermal insulation properties of the samples of Examples 1, 4-6 are shown in Figure 1. (a) is a photo of the sample; (b) is the density and room-temperature thermal conductivity of the sample; and (c) is the high-temperature thermal conductivity of the sample.

[0049] Figure 9 Comparison of the high-temperature resistance of the sample from Example 1 with carbon fiber mat, glass fiber needle-punched mat, and glass fiber mat on a flat-plate heating instrument. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0050] Figure 10 The high-temperature resistance performance of the sample of Example 1 under the flame of an alcohol burner is shown in Figure 1. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0051] Figure 11 The high-temperature resistance performance of the sample of Example 1 in a butane torch flame is shown in Figure 1. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0052] Figure 12 This is a temperature difference diagram of the hot and cold surfaces of the sample in Example 1 under a butane torch.

[0053] Figure 13 The morphology and sound absorption performance of the samples of Examples 1 and 11-13 are shown in Figure 1. (a) is a photo of the actual product; (b) is a sound absorption coefficient curve; and (c) is the noise reduction coefficient (NRC).

[0054] Figure 14 The following are the sound absorption performance diagrams of samples with different thicknesses in Example 1. (a) is the sound absorption coefficient curve; (b) is the noise reduction coefficient (NRC).

[0055] Figure 15 The morphology and sound absorption performance of the samples of Examples 1, 4-6 are shown in Figure 1. (a) is a photo of the actual product; (b) is a sound absorption coefficient curve; and (c) is the NRC value.

[0056] Figure 16 The morphology and sound absorption performance of the samples of Examples 1, 7-9 are shown in Figure 1. (a) is the actual image; (b) is the sound absorption coefficient curve; and (c) is the NRC value.

[0057] Figure 17 The basic properties and air flow resistance diagrams of the samples of Examples 1, 7-9 are shown. (a) represents porosity and density; (b) represents air flow resistance.

[0058] Figure 18 Absolute sound pressure distribution diagram of the samples of Examples 1 and 7-9.

[0059] Figure 19 The following is a comparison of the sound absorption performance of the sample in Example 1 and other materials. (a) shows the sound absorption coefficient curve comparison of the sample and commercial sound-absorbing cotton; (b) shows the relationship between the NRC value and surface density of different sound-absorbing materials.

[0060] Figure 20 The morphology of the sample of Example 16 is shown in Figure 1. (a) is a macroscopic morphology; (b) is a microscopic morphology of the gradient density structure.

[0061] Figure 21 The sound absorption performance of the samples in Examples 16-20 is shown in Figure 1. (a) is the sound absorption coefficient curve; (b) is the NRC value.

[0062] Figure 22 is the absolute sound pressure distribution of the samples in Examples 16-20.

[0063] Figure 23 Comparison of the thermal insulation performance of the sample from Example 1 and the actual pipe wrapping performance of glass fiber mat. (a) is a photo of the semi-tubular sample; (b) is a photo of the sample wrapped around a high-temperature steam pipe; (c) is an infrared image of the sample wrapped around the high-temperature steam pipe; (d) is a photo of the semi-tubular glass fiber mat; (e) is a photo of the glass fiber mat wrapped around the high-temperature steam pipe; and (f) is an infrared image of the glass fiber mat wrapped around the high-temperature steam pipe.

[0064] Figure 24 The following are simulation diagrams of the actual pipe wrapping of the sample and glass fiber mat in Example 1. (a) shows the simulation result of the sample wrapping a high-temperature pipe; (b) shows the simulation result of the glass fiber mat wrapping a high-temperature pipe.

[0065] Figure 25This is a comparison chart of the coating thickness of the sample in Example 15 and the original glass wool product used for ship pipelines when maintaining the same outer surface temperature.

[0066] Figure 26 These are the sound intensity contours of the sample from Example 1 and commercial sound-absorbing cotton. (a) shows the sound intensity contour test setup; (b) shows the sound intensity contour without the material; (c) shows the sound intensity contour when covered with commercial sound-absorbing cotton; and (d) shows the sound intensity contour when covered with the prepared material.

[0067] Figure 27 Schematic diagram of the force mechanism between the components during the molding process of samples of Examples 1-20 of the present invention. DETAILED DESCRIPTION

[0068] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0069] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0071] The terms “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0072] The preparation method of SiO2 nanofibers used in the following embodiments and comparative examples of the present invention is as follows: first, the SiO2 nanofiber non-woven fabric is cut into small pieces, and pre-cut using a wall breaker for 3 minutes to obtain a SiO2 nanofiber suspension without obvious SiO2 nanofiber non-woven fabric pieces, and then homogenized and cut using a T25 easy clean high-speed homogenizer at a speed of 13000 r / min for 20 minutes to obtain a homogenous liquid, and then dried in a 120°C oven for 24 hours to obtain a single SiO2 nanofiber.

[0073] Unless otherwise specified, the "normal temperature" in the present invention is 20-30°C.

[0074] Unless otherwise specified, the raw materials in the present invention are of analytical grade.

[0075] The raw materials used in the following examples and comparative examples of the present invention are all commercially available products.

[0076] Example 1

[0077] Preparation of nanofiber aerogel:

[0078] In a 150mL beaker, 90g of deionized water and 0.036ml of acetic acid were added and stirred uniformly in a magnetic stirrer at 1200r / min. Then, 2.14ml of methyltrimethoxysilane solution was added, and the stirring speed was increased to 1800r / min and continued for 0.5h to obtain a stable hydrolyzed silane sol. Subsequently, 0.9g of Laponite powder was added to the hydrolyzed silane sol and homogenized and cut using a T18 easy clean high-speed homogenizer at 10,000r / min for 10 minutes to obtain a stable Laponite aqueous dispersion. The stable Laponite aqueous dispersion was then transferred to a magnetic stirrer and stirred continuously until stable. After 0.9g of SiO2 nanofibers were added, and stirring was continued at 1800r / min for 0.5h to obtain a stable Laponite-SiO2 nanofiber dispersion.

[0079] A stable Laponite-mixed SiO2 nanofiber dispersion is poured into a polytetrafluoroethylene mold, which is then placed in a -86°C cryogenic chamber. The bottom of the mold contacts a copper block in the directional freezing device, which acts as a directional freezing mechanism. Directional freezing is performed for 30 minutes at a -86°C temperature. During the directional freezing process, the mold is covered with thick insulation to isolate heat transfer from all sides and ensure unidirectional freezing.

[0080] After the entire slurry is completely frozen into a block, it is quickly transferred to a freeze dryer and dried by vacuum drying at a vacuum degree of 5.7 Pa and a water-filled cold trap temperature of -60°C for 24 hours to obtain the aerogel to be sintered. Then it is transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere. It is then kept warm for 120 minutes to obtain nanofiber aerogel (denoted as LAPSNA1.0 or LAP1.0SNA).

[0081] Example 2

[0082] The only difference from Example 1 is that methyltrimethoxysilane is replaced with an equal volume of methyltriethoxysilane, the stirring time in the preparation of the hydrolyzed silane sol is changed to 3 h, and the vacuum degree in the vacuum drying stage is changed to 10.2 Pa and the time is changed to 28 h.

[0083] Example 3

[0084] The only difference from Example 1 is that acetic acid is replaced by an equal volume of oxalic acid, methyltrimethoxysilane is replaced by an equal volume of ethyl orthosilicate, the vacuum degree of the vacuum drying stage is changed to 7.3 Pa, the time is changed to 36 h, and the heating rate of the sintering stage is changed to 2°C / min.

[0085] Examples 1-3 are about preparing LAPSNAs using different silane precursors and acid catalysts.

[0086] Example 4

[0087] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 1.07 ml of methyltriethoxysilane solution, and the vacuum degree in the vacuum drying stage is changed to 6.1 Pa. The obtained product is recorded as LAPSNA0.5.

[0088] Example 5

[0089] The only difference from Example 1 is that the amount of methyltrimethoxysilane solution added is changed to 3.20 ml, and the vacuum degree in the vacuum drying stage is changed to 5.8 Pa. The obtained product is recorded as LAPSNA1.5.

[0090] Example 6

[0091] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 4.27 ml of methyltriethoxysilane solution, and the vacuum degree in the vacuum drying stage is changed to 9.2 Pa. The obtained product is recorded as LAPSNA2.0.

[0092] Examples 1, 4-6 are for preparing LAPSNAs with different silane sol contents.

[0093] Example 7

[0094] The only difference from Example 1 is that methyltrimethoxysilane is replaced with an equal volume of methyltriethoxysilane, the amount of Laponite powder added is changed to 0.09 g, and the vacuum degree in the vacuum drying stage is changed to 11.3 Pa. The obtained product is recorded as LAP0.1SNA.

[0095] Example 8

[0096] The only difference from Example 1 is that methyltrimethoxysilane is replaced by an equal volume of methyltriethoxysilane, the amount of Laponite powder added is changed to 0.36 g, and the vacuum degree in the vacuum drying stage is changed to 14.4 Pa. The obtained product is recorded as LAP0.4SNA.

[0097] Example 9

[0098] The only difference from Example 1 is that methyltrimethoxysilane is replaced by an equal volume of methyltriethoxysilane, the amount of Laponite powder added is changed to 0.63 g, and the vacuum degree in the vacuum drying stage is changed to 11.3 Pa. The obtained product is recorded as LAP0.7SNA.

[0099] Examples 1, 7-9 are for preparing LAPSNAs with different Laponite contents.

[0100] Example 10

[0101] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 0.71 ml of methyltriethoxysilane solution, the added amount of Laponite powder is changed to 0.30 g, the added amount of SiO2 nanofiber is changed to 0.30 g, and the vacuum degree in the vacuum drying stage is changed to 12.7 Pa.

[0102] Example 11

[0103] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 1.07 ml of methyltriethoxysilane solution, the added amount of Laponite powder is changed to 0.45 g, the added amount of SiO2 nanofiber is changed to 0.45 g, and the vacuum degree in the vacuum drying stage is changed to 15.1 Pa.

[0104] Example 12

[0105] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 1.42 ml of methyltriethoxysilane solution, the added amount of Laponite powder is changed to 0.60 g, the added amount of SiO2 nanofiber is changed to 0.60 g, and the vacuum degree in the vacuum drying stage is changed to 13.2 Pa.

[0106] Example 13

[0107] The only difference from Example 1 is that 2.14 ml of methyltrimethoxysilane solution is replaced by 1.78 ml of methyltriethoxysilane solution, the added amount of Laponite powder is changed to 0.75 g, the added amount of SiO2 nanofiber is changed to 0.75 g, and the vacuum degree in the vacuum drying stage is changed to 13.4 Pa.

[0108] Examples 1, 10-13 are for preparing LAPSNAs of different densities.

[0109] Example 14 (Large-scale sample)

[0110] 800g of deionized water and 0.32ml of acetic acid were added to a 1000mL beaker and stirred at 1200r / min in a magnetic stirrer. Then, 18.99ml of methyltriethoxysilane solution was added, the stirring speed was increased to 1800r / min, and stirring was continued for 0.5h to obtain a stable hydrolyzed silane sol. 8g of Laponite powder was then added to the hydrolyzed silane sol and homogenized and cut using a T18 easy clean high-speed homogenizer at 10,000r / min for 10 minutes to obtain a stable Laponite aqueous dispersion. The stable Laponite aqueous dispersion was then transferred to a magnetic stirrer and stirred continuously until stable. 8g of SiO2 nanofibers were added and stirring was continued at 2000r / min for 0.5h to obtain a stable Laponite mixed with SiO2 nanofiber dispersion.

[0111] Repeat the above steps twice to obtain three cups of the same Laponite-SiO2 nanofiber dispersion. This is then poured into an oversized PTFE mold (34cm*34cm*2.5cm). The mold is then placed in a -86°C ultra-low temperature freezer. The bottom of the mold contacts the copper block in the directional freezing device, which acts as a directional freezing mechanism. The directional freezing process continues for 90 minutes at a -86°C temperature. During the directional freezing process, the mold is covered with thick insulation to isolate the surrounding heat and ensure unidirectional freezing.

[0112] After the entire slurry is completely frozen into a block, it is quickly transferred to a freeze dryer and dried by vacuum drying for 72 hours at a vacuum degree of 16.7 Pa and a water-filled cold trap temperature of -60°C to obtain the aerogel to be sintered. It is then transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain nanofiber aerogel.

[0113] Example 15 (High-temperature insulation pipe coating sample)

[0114] Preparation of nanofiber aerogel:

[0115] In a 500mL beaker, 270g of deionized water and 0.108ml of acetic acid were added and stirred uniformly in a magnetic stirrer at 1200r / min. Then, 6.41ml of methyltrimethoxysilane solution was added, and the stirring speed was increased to 1800r / min and continued for 0.5h to obtain a stable hydrolyzed silane sol. Subsequently, 0.27g of Laponite powder was added to the hydrolyzed silane sol and homogenized and cut using a T18 easy clean high-speed homogenizer at 10,000r / min for 10 minutes to obtain a stable Laponite aqueous dispersion. The stable Laponite aqueous dispersion was then transferred to a magnetic stirrer and stirred continuously until stable. After stabilization, 2.7g of SiO2 nanofibers were added and stirred at 1800r / min for 0.5h to obtain a stable Laponite-SiO2 nanofiber dispersion.

[0116] A stable Laponite-mixed SiO2 nanofiber dispersion is poured into a cylindrical polytetrafluoroethylene mold, which is then placed in a -86°C ultra-low temperature storage chamber. The bottom of the mold contacts a copper block in the directional freezing apparatus, which acts as a directional freezing mechanism. Directional freezing is performed for 180 minutes at a -86°C temperature. During the directional freezing process, the mold is covered with thick insulation to isolate heat transfer from all sides and ensure unidirectional freezing.

[0117] After the entire slurry is completely frozen into a block, it is quickly transferred to a freeze dryer and dried for 96 hours by vacuum drying at a vacuum degree of 10.2 Pa and a water-filled cold trap temperature of -60°C to obtain the aerogel to be sintered. Then it is transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain nanofiber aerogel.

[0118] Example 16

[0119] Preparation of gradient density nanofiber aerogels:

[0120] The Laponite mixed SiO2 nanofiber dispersions prepared in Example 1, Example 10 and Example 12 were taken respectively.

[0121] First, the Laponite mixed SiO2 nanofiber dispersion in Example 1 was poured into a polytetrafluoroethylene mold, and then the mold was placed in an ultra-low temperature storage box with a temperature of -86°C. The bottom of the mold was in contact with the copper block in the directional freezing device. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 10 minutes), the dispersion in Example 12 was poured in. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 12 minutes), the dispersion was poured in. ), pour the dispersion in Example 10 and continue the freezing process. After the entire slurry is completely frozen into a block (the required directional freezing time is 14 minutes), it is quickly transferred to a freeze dryer and dried for 32 hours by gradient heating vacuum drying at a vacuum degree of 8.2 Pa and a water-filled cold trap temperature of -60°C to obtain an aerogel to be sintered. Then, it is transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain a gradient density nanofiber aerogel (denoted as LG-LAPSNA-SL).

[0122] Example 17

[0123] Preparation of gradient density nanofiber aerogels:

[0124] Take the Laponite mixed SiO2 nanofiber dispersions prepared in Example 11, Example 12 and Example 13 respectively.

[0125] First, the dispersion in Example 13 was poured into a polytetrafluoroethylene mold, and then the mold was placed in an ultra-low temperature storage box at -86°C, with the bottom of the mold in contact with the copper block in the directional freezing device. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 10 minutes), the dispersion in Example 12 was poured in. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 12 minutes), the dispersion in Example 11 was poured in. The dispersion in the mixture continued to freeze until the entire slurry was completely frozen into a block (the required directional freezing time was 14 minutes), and then it was quickly transferred to a freeze dryer and dried for 32 hours by gradient heating vacuum drying at a vacuum degree of 17.1 Pa and a water-filled cold trap temperature of -60°C to obtain the aerogel to be sintered. It was then transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain a gradient density nanofiber aerogel (denoted as SG-LAPSNA-SL).

[0126] Example 18

[0127] Preparation of gradient density nanofiber aerogels:

[0128] Three portions of the Laponite mixed SiO2 nanofiber dispersion prepared in Example 12 were taken respectively.

[0129] First, pour the first cup of the dispersion in Example 12 into a polytetrafluoroethylene mold, then place the mold in an ultra-low temperature storage box at -86°C, with the bottom of the mold in contact with the copper block in the directional freezing device. Before the entire slurry is almost completely frozen into a block (only a layer of molten slurry remains on the surface, and the required directional freezing time is 10 minutes), pour the second cup of the dispersion in Example 12. Before the entire slurry is almost completely frozen into a block (only a layer of molten slurry remains on the surface, and the required directional freezing time is 12 minutes), pour the third cup of the dispersion in Example 12. The dispersion in Example 12 continued the freezing process until the entire slurry was completely frozen into a block (the required directional freezing time was 14 minutes), and then was quickly transferred to a freeze dryer, and dried for 32 hours by gradient heating vacuum drying at a vacuum degree of 10.8 Pa and a water-filled cold trap temperature of -60°C to obtain an aerogel to be sintered. Then, it was transferred to a muffle furnace, and the temperature was increased to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain a gradient density nanofiber aerogel (denoted as UG-LAPSNA).

[0130] Example 19

[0131] Preparation of gradient density nanofiber aerogels:

[0132] Take the Laponite mixed SiO2 nanofiber dispersions prepared in Example 11, Example 12 and Example 13 respectively.

[0133] First, the dispersion in Example 11 was poured into a polytetrafluoroethylene mold, and then the mold was placed in an ultra-low temperature storage box at -86°C, with the bottom of the mold in contact with the copper block in the directional freezing device. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 10 minutes), the dispersion in Example 12 was poured in. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 12 minutes), the dispersion in Example 13 was poured in. The dispersion in the mixture continued to freeze until the entire slurry was completely frozen into a block (the required directional freezing time was 14 minutes), and then it was quickly transferred to a freeze dryer and dried for 32 hours by gradient heating vacuum drying at a vacuum degree of 17.1 Pa and a water-filled cold trap temperature of -60°C to obtain the aerogel to be sintered. It was then transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain a gradient density nanofiber aerogel (denoted as SG-LAPSNA-LS).

[0134] Example 20

[0135] Preparation of gradient density nanofiber aerogels:

[0136] The Laponite mixed SiO2 nanofiber dispersions prepared in Example 1, Example 10 and Example 12 were taken respectively.

[0137] First, the dispersion in Example 10 was poured into a polytetrafluoroethylene mold, and then the mold was placed in an ultra-low temperature storage box at -86°C, with the bottom of the mold in contact with the copper block in the directional freezing device. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 10 minutes), the dispersion in Example 12 was poured in. Before the entire slurry was almost completely frozen into a block (only a layer of molten slurry remained on the surface, and the required directional freezing time was 12 minutes), the dispersion in Example 1 was poured in. The dispersion in the mixture continued to freeze until the entire slurry was completely frozen into a block (the required directional freezing time was 14 minutes), and then it was quickly transferred to a freeze dryer and dried for 32 hours by gradient heating vacuum drying at a vacuum degree of 18.8 Pa and a water-filled cold trap temperature of -60°C to obtain the aerogel to be sintered. It was then transferred to a muffle furnace and heated to 900°C at a heating rate of 1°C / min in an air atmosphere, and then kept warm for 120 minutes to obtain a gradient density nanofiber aerogel (denoted as LG-LAPSNA-LS).

[0138] Examples 16-20 are samples with different density gradients.

[0139] Effect verification

[0140] To better demonstrate the performance and cost advantages of the products in various examples (collectively referred to as LAPSNAs) in actual engineering applications, this paper conducted actual pipeline wrapping energy-saving calculations using LAPSNAs and glass wool, the original material used for high-temperature pipelines. The simulations simulated the required insulation thickness for a 1-meter-long main steam pipeline, assuming a steam pipeline diameter of 32 mm, an internal pipe temperature of 350°C, and an insulation surface temperature of 55°C.

[0141] (1) Thickness of insulation layer

[0142] According to GB 50264 "Design Code for Thermal Insulation Engineering of Industrial Equipment and Pipelines", the calculation method for the thickness of the insulation layer is as follows:

[0143] #timg# （1） #timg# （2） #timg# （3） #timg# （4） #timg# （5）

[0144] Where:

[0145] is the outer diameter of the insulation layer (m); is the outer diameter of the pipeline (m); λ is the thermal conductivity of the insulation layer (℃); is the outer surface temperature of the pipeline (℃); is the outer surface temperature of the insulation layer (℃); is the ambient temperature (℃); is the radiation heat transfer coefficient of the outer surface of the insulation layer (W / (m 2 K)); is the convection heat transfer coefficient of the outer surface of the insulation layer; is the heat transfer coefficient of the outer surface of the insulation layer; The blackness of the outer surface material of the thermal insulation layer. By comparing the blackness table of commonly used materials in the standard, it can be seen that the blackness of the fiber fabric is about 0.75.

[0146] (2) Weight of insulation layer per unit length

[0147] The weight of the insulation layer per unit length is calculated based on the thickness of the insulation layer and the density of the insulation material. The calculation formula is:

[0148] #timg# （6）

[0149] in, is the weight of the insulation layer per unit length, is the density of the insulation material.

[0150] (3) Heat loss per unit length of insulation layer

[0151] The heat loss per unit length is calculated based on the outer diameter of the insulation layer and the surface heat release coefficient. The calculation formula is:

[0152] #timg# （7）

[0153] in, is the heat loss per unit length of insulation layer.

[0154] Table 1 is a comparative analysis of the coating conditions of different insulation materials.

[0155] Table 1 Comparison of different insulation material coatings

[0156] parameter Glass wool (raw material) Product of Example 15 Decline Thermal conductivity <![CDATA[0.085(W·m −1 ·k −1 )]]> <![CDATA[0.046(W·m −1 ·k −1 )]]> 45.9% bulk density <![CDATA[140(kg / m 3 )]]> <![CDATA[18(kg / m 3 )]]> 87.1% Coating thickness per unit length 60.7 (mm) 37.1 (mm) 38.9% Envelope volume per unit length <![CDATA[0.018(m 3 )]]> <![CDATA[0.008(m 3 )]]> 55.6％ Wrapping weight per unit length 2.475 (kg) 0.145 (kg) 94.1％ Heat dissipation per unit length 100.5 (W / m) 71.2 (W / m) 29.2％

[0157] As can be seen from Table 1, the material prepared by the present invention has obvious advantages over the original glass wool products. The thermal conductivity of the prepared material is less than 3 / 5 of the original glass wool, and the density is only about 1 / 10 of the original glass wool. The unit length coating thickness of glass wool is 60.7 mm, and when the outer surface is lowered to the same temperature, the prepared material only needs 37.1 mm, which is reduced by about 2 / 5. Figure 25 At the same time, the unit length of the coating volume and unit length of the coating weight were reduced by 55.6% and 94.1%, respectively, and the unit length of the coating volume and weight were reduced by 0.008 m3 The heat dissipation per unit length of the pipe coated with the prepared material is 71.2 W / m, which is 29.2% lower than the 100.5 W / m of the original glass wool product, greatly reducing heat loss. In summary, compared with the original glass wool product, the prepared material has reduced the heat dissipation per unit length in terms of coating thickness, volume, and weight. In particular, the coating weight has been reduced by about 94.1% compared to the original, greatly reducing the use of raw materials and achieving significant energy-saving and economic benefits.

[0158] Figure 1 The biomimetic structure, principle, and microstructure of the biomimetic dual-network aerogel of the present invention are shown in Figure 1. (a) shows a house-of-cards structure used in architecture; (b) shows a house-of-cards structure formed by nanosheets in the product of Example 1; (c) shows a Laponite nanosheet network structure in the product of Example 1; (d) shows a natural loofah structure; (e) shows an enlarged view of a natural loofah structure; and (f) shows a biomimetic loofah network structure in the product of Example 1.

[0159] In the process of preparing biomimetic double network aerogel, various shapes can be prepared by replacing different molds. In order to verify this property, the present invention prepared a variety of samples by simply adjusting the shape of the polytetrafluoroethylene mold in Example 1. The actual figure is as follows Figure 2 and Figure 3 As shown in (b) in .

[0160] Figure 2 The Laponite mixed SiO2 nanofiber dispersion in Example 1 and the aerogel sample prepared according to the method of Example 1 are real pictures. Among them, (a) is a real picture of the Laponite mixed SiO2 nanofiber dispersion; (b) is a real picture of the aerogel sample with a size of 2300 cm 3 Actual picture of the aerogel sample.

[0161] Figure 2 This indicates that the product prepared by the method of the present invention can be used for large-scale preparation in industrial production and is expected to be used in coating applications for large equipment.

[0162] Figure 3 (a) is a physical picture of the ultralight aerogel prepared in Example 11, and (b) is a physical picture of aerogels of various sizes and shapes prepared according to the method of Example 1.

[0163] Figure 3 The prepared material is ultra-lightweight and exhibits flexible scalability, and is expected to be used in key and complex parts of equipment.

[0164] Figure 4Microscopic morphologies of the products of Examples 1, 7-9. (a)-(d) are LAP0.1SNA; (e)-(h) are LAP0.4SNA; (i)-(l) are LAP0.7SNA; (m)-(p) are LAP1.0SNA.

[0165] Figure 4 A typical double network structure is shown in the nanostructured samples. As the Laponite content increases, the complexity of the house-of-cards network increases, and more Laponite nanosheets fill the pores in the house-of-cards network, increasing the chances of reflection and dissipation of sound waves.

[0166] Figure 5 Microscopic morphologies of the products of Examples 1, 4-6. (a)-(d) are LAPSNA0.5; (e)-(h) are LAPSNA1.0; (i)-(l) are LAPSNA1.5; (m)-(p) are LAPSNA2.0.

[0167] Figure 5 It shows that excessive silane sol will be wrapped in the house-of-cards structure network composed of Laponite nanosheets, affecting the original morphology of the house-of-cards structure network, and will increase the wall thickness, affect the pore uniformity, and is not conducive to performance improvement.

[0168] Figure 6 The compression rebound performance of the product of Example 4 at extreme temperatures is shown in Figure 4. (a) shows the rebound performance of the product in a butane torch flame at 1000°C; (b) shows the rebound performance of the product in liquid nitrogen at -196°C.

[0169] Figure 6 It is shown that the prepared material can still maintain good compression resilience under extreme temperatures, and is expected to be used in the field of coating equipment subjected to complex loads at extreme temperatures.

[0170] Figure 7 The morphology and thermal insulation properties of the samples of Examples 1, 7-9 are shown. (a) is a photo of the sample; (b) is the density and room-temperature thermal conductivity of the sample; and (c) is the high-temperature thermal conductivity of the sample.

[0171] Figure 7 The effect of Laponite content on the thermal conductivity and density of the prepared materials is shown. The samples exhibit low density and low thermal conductivity. With the increase of Laponite content, the solid-phase heat conduction increases and the thermal conductivity coefficient rises. However, the thermal conductivity remains low at 800°C, only 0.08 W·m −1 ·k −1 nearby.

[0172] Figure 8The morphology and thermal insulation properties of the samples of Examples 1, 4-6 are shown in Figure 1. (a) is a photo of the sample; (b) is the density and room-temperature thermal conductivity of the sample; and (c) is the high-temperature thermal conductivity of the sample.

[0173] Figure 8 The effect of silane sol content on the thermal conductivity and density of the prepared materials was demonstrated. The results showed that silane sol had an adverse effect on the increase of thermal conductivity and density. However, the thermal conductivity of the sample with the highest silane sol content was still lower than 0.09 W·m at 800℃. −1 ·k −1 .

[0174] The high temperature resistance performance of the sample of Example 1 with a thickness of 12 mm was compared with that of the carbon fiber felt.

[0175] Figure 9 Comparison of the high-temperature resistance of the sample from Example 1 with carbon fiber mat, glass fiber needle-punched mat, and glass fiber mat on a flat-plate heating instrument. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0176] Figure 9 The results show that compared with fiber felt, glass fiber needle punched felt and glass fiber felt, the material prepared by the present invention has the best thermal insulation performance under the surface heat source heating of the flat plate heater. After 600s, the surface temperature is only 61.4℃ and remains stable.

[0177] The sample of Example 1 with a thickness of 12 mm was subjected to a high temperature resistance test on the flame of an alcohol lamp.

[0178] Figure 10 The high-temperature resistance performance of the sample of Example 1 under the flame of an alcohol burner is shown in Figure 1. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0179] Figure 10 The results showed that when heated by a point heat source like an alcohol lamp, the temperature distribution on the cold surface of the prepared material was uniform, with no apparent temperature concentration. This indicates that the material can diffuse heat from its center across the entire surface, further demonstrating the uniformity of the material's biomimetic dual-network structure. After 10 minutes, the surface temperature remained stable at only 64.3°C, demonstrating excellent thermal insulation properties.

[0180] The sample of Example 1 with a thickness of 12 mm was subjected to a high temperature resistance test in a butane torch flame.

[0181] Figure 11 The high-temperature resistance performance of the sample of Example 1 in a butane torch flame is shown in Figure 1. (a) is an optical image; (b)-(d) are infrared images after different heating times.

[0182] Figure 11 It shows that the prepared material also has fire-retardant properties. Under continuous heating by a 1000 high-temperature butane blowtorch flame, the temperature of its back can still be stabilized at 68.2°C.

[0183] A temperature difference test between the hot and cold surfaces of the sample of Example 1 with a thickness of 12 mm was conducted under a butane torch.

[0184] Figure 12 This is a temperature difference diagram of the hot and cold surfaces of the sample in Example 1 under a butane torch.

[0185] Figure 12 It shows that the prepared material has a freezing surface temperature difference of up to 932°C under the flame of a butane blowtorch, while the 12mm sample has a temperature gradient of up to 777°C / cm, further demonstrating its excellent complex thermal insulation network structure.

[0186] The morphology and sound absorption performance tests were performed on the samples of Examples 1 and 11-13 with a thickness of 30 mm.

[0187] Figure 13 The morphology and sound absorption performance of the samples of Examples 1 and 11-13 are shown in Figure 1. (a) is a photo of the actual product; (b) is a sound absorption coefficient curve; and (c) is the noise reduction coefficient (NRC).

[0188] Figure 13 It shows that with the increase of density, the sound absorption performance of the sample is improved, which is due to the increase of density in the complex structure inside the material.

[0189] By adjusting the shape of the polytetrafluoroethylene mold in Example 1, samples with different thicknesses (10, 20, 30, 40, 50 mm) were prepared and their morphology and sound absorption performance were characterized. The test results are shown in the figure. Figure 14 shown.

[0190] Figure 14 The following are the sound absorption performance diagrams of samples with different thicknesses in Example 1. (a) is the sound absorption coefficient curve; (b) is the noise reduction coefficient (NRC).

[0191] Figure 14 It shows that with the increase of thickness, the sound absorption performance of the sample is improved, the thickness extends the path of sound wave dissipation and enhances the dissipation of sound waves.

[0192] The morphology and sound absorption performance tests were performed on the samples of Examples 1 and 4-6 with a thickness of 30 mm.

[0193] Figure 15 The morphology and sound absorption performance of the samples of Examples 1, 4-6 are shown in Figure 1. (a) is a photo of the actual product; (b) is a sound absorption coefficient curve; and (c) is the NRC value.

[0194] Figure 15 This indicates that too much or too little silane sol is not beneficial to improving the sound absorption performance, and LAPSNA1.0 has the best sound absorption performance.

[0195] The morphology and sound absorption performance tests were performed on the samples of Examples 1 and 7-9 with a thickness of 30 mm.

[0196] Figure 16 The morphology and sound absorption performance of the samples of Examples 1, 7-9 are shown in Figure 1. (a) is the actual image; (b) is the sound absorption coefficient curve; and (c) is the NRC value.

[0197] Figure 16 It shows that with the increase of Laponite content, the sound absorption performance of the sample is improved. This is because the Laponite content affects the complexity of the card house network structure and improves the dissipation level of sound waves.

[0198] Figure 17 The basic properties and air flow resistance diagrams of the samples of Examples 1, 7-9 are shown. (a) represents porosity and density; (b) represents air flow resistance.

[0199] Figure 17 The results show that the prepared material has ultra-high porosity and low density, and the air flow resistance increases with the increase of Laponite content, which is consistent with the Figure 16 The results are consistent.

[0200] Figure 18 Absolute sound pressure distribution diagram of the samples of Examples 1 and 7-9.

[0201] Figure 18 The absolute sound pressure distribution of samples with varying Laponite content was simulated. LAP1.0SNA exhibited the greatest sound pressure drop, transitioning from red to dark green, indicating optimal sound absorption. However, the transmitted sound pressure of LAP0.1SNA remained high, indicating insufficient sound absorption.

[0202] Figure 19 The following is a comparison of the sound absorption performance of the sample in Example 1 and other materials. (a) shows the sound absorption coefficient curve comparison of the sample and commercial sound-absorbing cotton; (b) shows the relationship between the NRC value and surface density of different sound-absorbing materials.

[0203] Figure 19 In (a), the samples of Example 1 with a thickness of 30 mm and commercial sound-absorbing cotton were tested; in (b), the samples of Example 1, as well as straw fiber, glass fiber, porous ceramics, silica aerogel, phoenix orchid fiber, micron / nanofiber aerogel, sandwich foam, and polypropylene fiber mat were tested.

[0204] Figure 19The 30mm sample's sound absorption coefficient surpasses that of commercial sound-absorbing cotton. Compared with some commercial sound-absorbing materials and reported materials with excellent sound absorption performance, it exhibits the highest NRC value and extremely low surface density. Its NRC value, as high as 0.76, exceeds the results of several leading papers (DOI:10.1038 / s41467-021-26890-9, DOI:10.1021 / acsnano.2c06011, DOI:10.1002 / adfm.202301870). Its ultra-high NRC value meets the broadband noise reduction requirements of high-efficiency sound-absorbing materials (NRC ≥ 0.56), and it ranks among the second-tier sound-absorbing materials (0.8 > NRC ≥ 0.6), suggesting broad application prospects in industrial noise reduction.

[0205] Figure 20 The morphology of the sample of Example 16 is shown in Figure 1. (a) is a macroscopic morphology; (b) is a microscopic morphology of the gradient density structure.

[0206] Figure 20 The corresponding sample thickness is 36 mm, and the thickness of each density unit is 12 mm.

[0207] from Figure 20 The results show that the material becomes increasingly dense from top to bottom, with the pore size decreasing and the porosity decreasing. Furthermore, there is no obvious transition at the junction of each basic density unit, further demonstrating the uniform size of the gradient density material.

[0208] Figure 21 The sound absorption performance of the samples in Examples 16-20 is shown in Figure 1. (a) is the sound absorption coefficient curve; (b) is the NRC value.

[0209] Figure 21 The corresponding sample thickness is 36 mm, and the thickness of each density unit is 12 mm.

[0210] Figure 21 LG-LAPSNA-SL demonstrates the best sound absorption performance. This is because the low-density units on the surface allow more sound waves to enter, while the high-density units inside fully dissipate the sound waves, broadening the frequency range corresponding to sound absorption.

[0211] Figure 22 is the absolute sound pressure distribution of the samples in Examples 16-20.

[0212] Figure 22 The absolute sound pressure results also show that the smaller the density of the first unit on the surface, the more sound waves enter (corresponding to the red area), and the larger the density of the third unit inside, the faster the color changes, indicating that the dissipation of low-frequency sound waves is higher, which is consistent with Figure 21 Also corresponding.

[0213] A comparative test of the thermal insulation performance of actual pipe wrapping was conducted on the sample of Example 1 with a thickness of 25 mm and the glass fiber felt.

[0214] Figure 23 Comparison of the thermal insulation performance of the sample from Example 1 and the actual pipe wrapping performance of glass fiber mat. (a) is a photo of the semi-tubular sample; (b) is a photo of the sample wrapped around a high-temperature steam pipe; (c) is an infrared image of the sample wrapped around the high-temperature steam pipe; (d) is a photo of the semi-tubular glass fiber mat; (e) is a photo of the glass fiber mat wrapped around the high-temperature steam pipe; and (f) is an infrared image of the glass fiber mat wrapped around the high-temperature steam pipe.

[0215] Figure 23 It is shown that in actual pipe wrapping experiments, the prepared material has better actual high-temperature thermal insulation performance than commercial glass fiber felt, and is expected to be extended to the application of wrapping other complex equipment.

[0216] Figure 24 The following are simulation diagrams of the actual pipe wrapping of the sample and glass fiber mat in Example 1. (a) shows the simulation result of the sample wrapping a high-temperature pipe; (b) shows the simulation result of the glass fiber mat wrapping a high-temperature pipe.

[0217] Figure 24 The prepared materials and the actual pipe wrapping simulation results of glass fiber mat were simulated, and the results were compared with those of Figure 23 However, in the actual pipe coating experiment, the surface of the material is not only affected by the high temperature transfer from the inner pipe, but also by the radiation heat transfer from the surrounding pipes to the material surface. Therefore, its surface temperature is different from the experimental data.

[0218] Figure 25 This is a comparison chart of the coating thickness of the sample in Example 15 and the original glass wool product used for ship pipelines when maintaining the same outer surface temperature.

[0219] Figure 25 It can be intuitively demonstrated that the prepared material can significantly reduce the coating thickness compared with the original glass wool product, thereby reducing the cost.

[0220] The sound intensity cloud map test was performed on the sample of Example 1 with a thickness of 20 mm and commercial sound-absorbing cotton.

[0221] Figure 26 These are the sound intensity contours of the sample from Example 1 and commercial sound-absorbing cotton. (a) shows the sound intensity contour test setup; (b) shows the sound intensity contour without the material; (c) shows the sound intensity contour when covered with commercial sound-absorbing cotton; and (d) shows the sound intensity contour when covered with the prepared material.

[0222] from Figure 26The prepared material demonstrates superior noise reduction compared to commercial sound-absorbing cotton. The central sound pressure level before the material was approximately 74 dB, while after the commercial sound-absorbing cotton was added, it dropped to approximately 69 dB, a reduction of approximately 5 dB. After the prepared material was added, the central sound pressure level dropped to approximately 55 dB, a reduction of approximately 19 dB. This further demonstrates that the prepared material exhibits superior noise reduction compared to commercial sound-absorbing cotton in practical applications.

[0223] Figure 27 Schematic diagram of the force mechanism between the components during the molding process of samples of Examples 1-20 of the present invention.

[0224] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated nanofiber aerogel, characterized in that: The following steps are involved: mixing a silane precursor, water, and an acid catalyst to obtain a hydrolyzed silane sol; adding Laponite powder to the hydrolyzed silane sol to obtain a Laponite aqueous dispersion; The Laponite aqueous dispersion is mixed with SiO2 nanofibers to obtain a Laponite-mixed SiO2 nanofiber dispersion, which is directionally frozen, then vacuum-dried, and sintered to obtain the bionic double-network high-temperature thermal insulation, low-frequency noise reduction, and fire-retardant integrated nanofiber aerogel; The volume ratio of water, silane precursor and acid catalyst is 90:0.71-2.14:0.036; The mass ratio of the water, SiO2 nanofiber and Laponite powder is 90:0.3-0.9:0.09-0.

9.

2. The preparation method according to claim 1, characterized in that The silane precursor is one or more of methyltrimethoxysilane, methyltriethoxysilane, methyl orthosilicate and ethyl orthosilicate; and the acid catalyst is acetic acid and / or oxalic acid.

3. The preparation method according to claim 1, characterized in that The preparation method of the SiO2 nanofiber is as follows: first, the SiO2 nanofiber non-woven fabric is cut into small pieces, and pre-cut using a wall breaker for 3 minutes to obtain a SiO2 nanofiber suspension without obvious SiO2 nanofiber non-woven fabric pieces, and then homogenized and cut at a speed of 13000 r / min for 20 minutes to obtain a homogenous liquid, and then dried at 120°C for 24 hours to obtain the SiO2 nanofiber.

4. The preparation method according to claim 1, characterized in that The preparation method of the Laponite aqueous dispersion is as follows: Laponite powder is added to the hydrolyzed silane sol, and then high-speed homogenization and dispersion are performed at a rotation speed of 8000-13000 r / min for 10-20 minutes.

5. The preparation method according to claim 1, characterized in that The directional freezing is unidirectional freezing, the temperature is -196~-70°C, and the time is 20~180 minutes.

6. The preparation method according to claim 1, characterized in that The vacuum drying environment temperature is -50°C to 50°C, the time is 24 to 96 hours, and the vacuum degree is 5 to 30 Pa; the sintering is performed by heating to 900°C at a heating rate of 1 to 2°C / min and then keeping the temperature for 120 minutes. The sintering atmosphere is an air atmosphere.

7. A method for preparing a biomimetic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated gradient density nanofiber aerogel, characterized in that: The following steps are involved: (1) mixing a silane precursor, water, and an acid catalyst to obtain a hydrolyzed silane sol; adding Laponite powder to the hydrolyzed silane sol to obtain a Laponite aqueous dispersion; (2) mixing the Laponite aqueous dispersion with SiO2 nanofibers to obtain a first Laponite-SiO2 nanofiber dispersion; (3) Repeat step (2) to prepare N Laponite mixed SiO2 nanofiber dispersions with the same or different SiO2 nanofiber concentrations; (4) Directional freezing the first Laponite mixed SiO2 nanofiber dispersion until it is completely frozen and solidified, and repeatedly adding N Nth Laponite mixed SiO2 nanofiber dispersions for directionally freezing; (5) The product of step (4) is vacuum dried and sintered to obtain the bionic double-network high-temperature thermal insulation-low-frequency noise reduction-fire retardant integrated gradient density nanofiber aerogel.

8. A bionic double-network nanofiber aerogel with integrated high-temperature thermal insulation, low-frequency noise reduction, and fire retardant functions obtained according to the preparation method according to any one of claims 1 to 6.

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