Honeycomb filling aerogel thermal insulation material and preparation method thereof

Abstract

The method comprises the following steps: preparing an aluminum oxide nanowire precursor with a certain length-diameter ratio by a hydrothermal method, mixing the aluminum oxide nanowire precursor with silicon dioxide nano powder and ceramic fibers, filling the mixture into a honeycomb, and carrying out compression molding, curing, ethanol solvent replacement, subcritical drying and other process steps to obtain the honeycomb filled aerogel thermal insulation material. The honeycomb filled aerogel heat insulation material is successfully prepared. According to the preparation method disclosed by the invention, efficient preparation of the aerogel-filled honeycomb material with controllable filling density and excellent mechanical strength is realized by regulating and controlling a micro-nano hierarchical structure and mixed components. The aerogel is combined with the honeycomb, and the aluminum oxide nanowire cluster and the ceramic fiber are introduced as inorganic components, so that the shrinkage cracking of the aerogel at high temperature is inhibited, and the structural stability and the mechanical property of the material at high temperature are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology and discloses a honeycomb-filled aerogel thermal insulation material, which is particularly suitable for aerospace thermal protection materials that require lightweight, load-bearing, and high-efficiency thermal insulation performance. Background Technology

[0002] Spacecraft re-entry / atmospheric reentry generates severe aerodynamic heating, making thermal protection systems a crucial subsystem essential for ensuring the proper functioning of internal electronic components and crew space. Integrated thermal protection materials have been a hot research topic in the aerospace field, leading to the development of a range of materials including thermal insulation tiles, lightweight micro-ablation materials, and ceramic fiber felt. While these materials possess excellent thermal insulation properties, most are only suitable for single-use, experiencing varying degrees of performance degradation during repeated use.

[0003] Honeycomb sandwich structures are a traditional form of structural material. Combining a honeycomb sandwich architecture with aerogel, with the aerogel filling the pores of the honeycomb, creates a novel multifunctional integrated material that combines heat protection, insulation, and load-bearing capabilities. However, due to limitations of traditional processes, the silica aerogel traditionally filled in the honeycomb pores is prone to problems such as powder and flaking, affecting the honeycomb bonding performance. Furthermore, the brittle nature of aerogel materials also leads to insufficient reliability for repeated use in the development of integrated heat protection and insulation materials.

[0004] In view of the above shortcomings, it is an important task to develop an effective aerogel material for filling honeycomb cells and a method that can precisely control the height and precision of the filling cells according to the bonding requirements. Summary of the Invention

[0005] Based on the above analysis, in order to solve the technical problems existing in the prior art, the present invention provides a honeycomb-filled aerogel thermal insulation material and its preparation method.

[0006] The present invention provides a honeycomb-filled aerogel thermal insulation material in a first aspect, and provides a method for preparing the material, the method comprising the following steps:

[0007] (1) Using 0.1-2g of mixed acid solution as adsorbent and 0.02-0.2g of surfactant as auxiliary agent, alumina nanopowder is subjected to high-temperature hydrothermal reaction to obtain alumina nanowire clusters;

[0008] (2) Alumina nanoclusters are mixed with quartz fibers and silica nanoparticles and then dispersed uniformly using a mixer to obtain a wet gel.

[0009] (3) The wet gel is filled into the honeycomb, and the molding is performed twice. The filling accuracy of the honeycomb filling surface is adjusted to obtain a honeycomb filled wet gel block containing solvent.

[0010] (4) Soak the honeycomb-filled wet gel block containing solvent in ethanol solution for 6-9 days to replace the solvent and obtain the replaced honeycomb-filled wet gel block;

[0011] (5) The replaced honeycomb-filled wet gel block is placed in a dry container for subcritical treatment to obtain a honeycomb-filled aerogel thermal insulation material.

[0012] Further, the alumina nanopowder in step (1) has a particle size of 5-50 nm and a mass of 1-30 g. It is first dissolved in 10-200 mL of water, and then a mixed acid solution is added.

[0013] The mixed acid solution is prepared by mixing 0.001-1 mol / L sulfuric acid and 0.001-1 mol / L hydrochloric acid in a mass ratio of 1:1.

[0014] The surfactant comprises: 0.01-0.1g sodium dodecylbenzenesulfonate and 0.01-0.1g hexadecyltrimethylammonium bromide;

[0015] The high-temperature hydrothermal reaction conditions are: reaction at 100-300℃ for 1-24 hours;

[0016] The alumina nanowires have cluster diameters of 10-100 nm and lengths of 100-800 µm.

[0017] Further, in step (2), the silica nanopowder accounts for 5-30% of the mass of the alumina nanoclusters, and the quartz fiber accounts for 0.5-10% of the mass of the alumina nanoclusters;

[0018] The mixer speed is 100-1500 r / min.

[0019] Furthermore, the quartz fiber in step (2) is a short-cut fiber with a length of 2-100 mm.

[0020] Furthermore, the honeycomb in step (3) includes, but is not limited to: aramid honeycomb, glass fiber honeycomb, and metal honeycomb.

[0021] Furthermore, step (3) involves molding and shaping in two stages, including:

[0022] First, the filler is filled into the honeycomb under a pressure of 0.1-0.5 MPa, and preliminary molding is carried out in 10-30 minutes; then, with the assistance of a silicone rubber mold, it is shaped under a pressure of 0.05-0.2 MPa for 20 minutes.

[0023] Furthermore, in step (4), the amount of ethanol solution used is 5-15 times the honeycomb volume, and the number of replacements is 2-4 times.

[0024] Furthermore, the drying equipment described in step (5) is a subcritical drying equipment with a drying temperature of 25-80℃ and a drying pressure of 0.01-0.2Mpa.

[0025] This invention also discloses a honeycomb-filled aerogel thermal insulation material prepared according to any of the above preparation methods, wherein:

[0026] The density of this material is 0.15-0.5 g / cm³. 3 The compressive strength is 0.8-3.2MPa, the tensile strength after composite bonding is 2-6MPa, the thermal conductivity at room temperature is 0.038-0.068 W / m·K, and the heat resistance temperature range is 200-800℃.

[0027] The present invention also discloses the application of the above-mentioned honeycomb-filled aerogel thermal insulation material in the preparation of aerospace thermal protection materials.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) The aerogel precursor in this invention is different from traditional precursors such as silicon dioxide. In this study, long nanowires are used as the main unit for the assembly process. The precursor is a semi-solid. In typical examples, the nanowires prepared have a diameter as low as 10-100 nm and a length of 100-800 µm. The skeleton has high strength and does not flow randomly, which can ensure an efficient filling process and is suitable for filling large-sized irregular shapes.

[0030] (2) Nanowire clusters with large aspect ratios can achieve a physically cross-linked wet gel network structure instead of cross-linking through chemical bonds. The wet gel can also be reshaped after being filled into the honeycomb.

[0031] (3) A ternary interpenetrating network of “nanowire-fiber-powder” is constructed by using silica powder, quartz fiber and nanowire skeleton. Alumina nanowires provide rigid support, silica powder fills the pores to improve thermal insulation performance, and ceramic fiber bridges cracks to enhance toughness. The three are dispersed at the molecular level through high speed, which enhances the mechanical properties of composite aerogel.

[0032] (4) Alumina nanowires form a continuous ceramic skeleton at high temperature, which has a self-toughening effect, inhibits shrinkage and cracking during preparation and use, and ceramic fibers and nanowires reinforce each other. Through fiber pull-out effect, heat dissipation stress is dissipated, etc., so that the operating temperature range of the material is as low as -196℃.

[0033] (5) The use of customized soft molds for filling and molding processes can effectively control the honeycomb filling height and provide the necessary conditions for the bonding process of composite materials. Attached Figure Description

[0034] Figure 1 This is a flowchart of the preparation process of the present invention.

[0035] Figure 2 This is a physical image of the aerogel prepared in Example 1.

[0036] Figure 3 This is a SEM image of the aerogel prepared in Example 1. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] In a first aspect, this invention provides a honeycomb-filled aerogel thermal insulation material and a method for preparing the same, the method comprising the following steps:

[0039] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0040] Example 1

[0041] (1) 6 g of alumina nanopowder (particle size 20 nm) was dissolved in 100 mL of water, and 1 g of 0.02 mol / L hydrochloric acid and 0.02 mol / L sulfuric acid (mass ratio 1:1) were added as adsorbents. Sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide were added as adsorbents. The amount of each surfactant added was 0.01 g. The reaction was carried out at 230 °C for 7 h to obtain alumina nanowire clusters with a diameter of 50 nm and a length of 100-800 µm.

[0042] (2) The alumina nanoclusters obtained in step (1) are mixed with silica powder and quartz fiber, and a dispersant is used for homogenization dispersion at a speed of 100 r / min. The silica powder accounts for 15% of the mass of the alumina nanoclusters, and the quartz fiber accounts for 2% of the mass of the alumina nanoclusters. The quartz fiber is a short chopped fiber with a length of 30 mm, thereby obtaining a wet gel.

[0043] (3) The composite wet gel obtained in step (2) is filled into the aramid honeycomb. The filling is done by one side. After 30 minutes of initial molding, a pressure of 0.2 MPa for 20 minutes is applied. The filling accuracy of the honeycomb filling surface is controlled by a customized rubber soft mold to obtain a honeycomb filling wet gel block containing solvent.

[0044] (4) The composite gel obtained in step (3) was placed in 10 times the amount of ethanol solution for 3 days to perform solvent replacement;

[0045] (5) The honeycomb filling wet gel after replacement in step (4) is dried. The drying equipment is a subcritical drying equipment, the drying temperature is 60 ℃, and the drying pressure is 0.1 Mpa.

[0046] (7) The density of the prepared composite aerogel is 0.25 g / cm³. 3 It has a compressive strength of 1.2 MPa, a thermal conductivity of 0.075 W / m·K, a tensile strength of 4 MPa after bonding, and a temperature resistance of ≥200℃.

[0047] A physical image of the prepared aerogel is shown below. Figure 2 As shown, SEM images of the aerogel were also performed, and the results are as follows. Figure 3 As shown.

[0048] Example 2

[0049] Example 2 is basically the same as Example 1, except that the amount of alumina powder added in step 1 is 10g.

[0050] Performance tests were conducted on the honeycomb-filled aerogel material of Example 2. It was found that the precursor had a high viscosity, the strength after filling the honeycomb reached 1.6 MPa, and the tensile strength of the material after bonding the skin was 3.5 MPa. Other performance indicators are shown in Table 1.

[0051] Example 3

[0052] Example 3 is basically the same as Example 1, except that the quartz fiber in step 2 is a short-cut fiber with a length of 10 mm.

[0053] Performance tests on the honeycomb-filled aerogel material in Example 3 revealed that the aerogel material was uniform, and other performance indicators are shown in Table 1.

[0054] Example 4

[0055] Example 4 is basically the same as Example 1, except that the honeycomb type in step 3 is polyimide honeycomb.

[0056] Performance testing of the honeycomb-filled aerogel material in Example 4 showed that the temperature resistance of the honeycomb-filled aerogel was improved to 350°C.

[0057] Example 5

[0058] Example 5 is basically the same as Example 1, except that the quartz fiber content in step (2) is increased to 8%.

[0059] For the performance testing of the honeycomb-filled aerogel material in Example 5, the material density increased to 0.3 g / cm³, the compressive strength increased to 1.5 MPa, but the room temperature thermal conductivity increased to 0.085 W / m·K. Other performance indicators are shown in Table 1.

[0060] Example 6

[0061] Example 6 is basically the same as Example 1, except that the honeycomb type in step 3 is titanium alloy honeycomb.

[0062] Performance testing of the honeycomb-filled aerogel material in Example 6 showed that the material's temperature resistance was improved to over 600°C.

[0063] Comparative Example 1

[0064] Comparative Example 1 is basically the same as Example 1, except that the drying process in step (5) is performed under normal pressure instead of a subcritical drying process.

[0065] In Comparative Example 1, the performance of the honeycomb-filled aerogel material was tested. It was found that the aerogel was severely detached from the honeycomb wall and could not form an integral material structure. The thermal conductivity of the material increased to 0.15 W / m·K. Other performance indicators are shown in Table 1.

[0066] Comparative Example 2

[0067] Comparative Example 2 is basically the same as Example 1, except that: no quartz fiber was added in step (2), and the aerogel cracked and shed powder after drying.

[0068] Comparative Example 3

[0069] Comparative Example 3 is basically the same as Example 1, except that a rubber-based soft mold was not used for secondary molding.

[0070] The material obtained inside the honeycomb cannot be effectively bonded.

[0071] Comparative Example 4

[0072] Comparative Example 4 is basically the same as Example 1, except that the solvent replacement time in step (5) is shortened to 3 days.

[0073] After the honeycomb-filled aerogel dries, the material cracks, the insulation material deteriorates significantly from the honeycomb wall, and the thermal conductivity is as high as 0.10-0.12 W / m·K.

[0074] Comparative Example 5

[0075] Comparative Example 5 is basically the same as Example 1, except that silica powder was not added in step 2.

[0076] The performance of the honeycomb-filled aerogel material in Comparative Example 5 was tested, and its thermal conductivity was as high as 0.08 W / m·K.

[0077] Comparative Example 6

[0078] Comparative Example 6 is basically the same as Example 1, except that: in step (1), the alumina nanoclusters prepared in this invention were not used, but aluminum sol (sol particles are 10-50 nm and the solid content is 15%).

[0079] An observation and analysis of the honeycomb-filled aerogel material in Comparative Example 6 revealed that the aerogel had serious problems with powder shedding and cracking, and the tensile strength of the material after bonding the skin was less than 0.1 MPa.

[0080] The performance indicators of the honeycomb-filled aerogel materials in Examples 1-6 and the aerogel materials in Comparative Examples 1-6 are shown in Table 1.

[0081] Table 1 Performance indicators of the honeycomb-filled aerogel materials prepared in Examples 1-6 and the aerogel materials in Comparative Examples 1-6

[0082]

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a honeycomb-filled aerogel thermal insulation material, comprising the following steps: (1) Using 0.1-2g of mixed acid solution as adsorbent and 0.02-0.2g of surfactant as auxiliary agent, alumina nanopowder is subjected to high-temperature hydrothermal reaction to obtain alumina nanowire clusters; (2) Alumina nanoclusters are mixed with quartz fibers and silica nanoparticles and then dispersed uniformly using a mixer to obtain a wet gel. (3) The wet gel is filled into the honeycomb, and the molding is performed twice. The filling accuracy of the honeycomb filling surface is adjusted to obtain a honeycomb filled wet gel block containing solvent. (4) Soak the honeycomb-filled wet gel block containing solvent in ethanol solution for 6-9 days to replace the solvent and obtain the replaced honeycomb-filled wet gel block; (5) The replaced honeycomb-filled wet gel block is placed in a dry container for subcritical treatment to obtain a honeycomb-filled aerogel thermal insulation material.

2. The preparation method according to claim 1, wherein: The alumina nanopowder in step (1) has a particle size of 5-50 nm and a mass of 1-30 g. First, dissolve it in 10-200 mL of water, and then add the mixed acid solution. The mixed acid solution is prepared by mixing 0.001-1 mol / L sulfuric acid and 0.001-1 mol / L hydrochloric acid in a mass ratio of 1:

1. The surfactant comprises: 0.01-0.1g sodium dodecylbenzenesulfonate and 0.01-0.1g hexadecyltrimethylammonium bromide; The high-temperature hydrothermal reaction conditions are: reaction at 100-300℃ for 1-24 hours; The alumina nanowires have cluster diameters of 10-100 nm and lengths of 100-800 µm.

3. The preparation method according to claim 1, wherein: In step (2), the silica nanoparticles account for 5-30% of the mass of the alumina nanoclusters, and the quartz fibers account for 0.5-10% of the mass of the alumina nanoclusters. The mixer speed is 100-1500 r / min.

4. The preparation method according to claim 1, wherein: The quartz fiber mentioned in step (2) is a short-cut fiber with a length of 2-100 mm.

5. The preparation method according to claim 1, wherein: The honeycomb in step (3) includes: aramid honeycomb, glass fiber honeycomb, and metal honeycomb.

6. The preparation method according to claim 1, wherein: Step (3) involves molding and shaping in two stages, including: First, filler is applied into the honeycomb structure using a pressure of 0.1-0.5 MPa, and initial molding takes 10-30 minutes. Subsequently, with the assistance of a silicone rubber mold, it is shaped using a pressure of 0.05-0.2 MPa for 20 minutes.

7. The preparation method according to claim 1, wherein: In step (4), the amount of ethanol solution used is 5-15 times the volume of the honeycomb, and the number of replacements is 2-4 times.

8. The preparation method according to claim 1, wherein: The drying equipment mentioned in step (5) is a subcritical drying equipment with a drying temperature of 25-80℃ and a drying pressure of 0.01-0.2Mpa.

9. A honeycomb-filled aerogel thermal insulation material prepared by any one of the preparation methods according to claims 1 to 8, wherein: The density of this material is 0.15-0.5 g / cm³. 3 The compressive strength is 0.8-3.2MPa, the tensile strength after composite bonding is 2-6MPa, the thermal conductivity at room temperature is 0.038-0.068 W / m·K, and the heat resistance temperature range is 200-800℃.

10. The application of the honeycomb-filled aerogel thermal insulation material according to claim 9 in the preparation of aerospace thermal protection materials.

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