A reusable lightweight heat-insulating material and its preparation method and application

Abstract

The present invention discloses a reusable lightweight heat-insulating material and its application. The heat-insulating material is designed based on the thermal environment profile of reusable aircraft and follows the gradient concept of anti-radiation / heat protection / heat insulation. The surface of the material is a ceramic-based heat-proof coating with high emissivity, which reduces the penetration of radiant heat flow from the surface of the material; the interior of the material is a silicon-based heat-proof material with no ablation / low ablation effect; the innermost layer of the material is a lightweight heat-insulating material, which reduces the temperature of the aircraft structure. The present invention solves the problem of one-piece spraying molding of heat-proof materials. The material has a strong bonding force with the metal substrate surface, a stable interface, good process feasibility, and the ability to be reused a certain number of times, meeting the heat-insulating requirements of reusable aircraft.

Description

Technical Field

[0001] The present invention relates to the field of aerospace vehicle heat-insulating materials, and in particular to a reusable lightweight heat-insulating material and a preparation method and application thereof. Background Art

[0002] The thermal environment profile of reusable aircraft is complex, which places higher demands on heat-resistant materials. The current mainstream heat-resistant materials are resin-based and silicon-based heat-resistant materials. After being heated, the ablated surface of such materials becomes carbonized, loose, and the strength is weakened. The residual layer can only play a heat-insulating role and cannot be reused. The heat-resistant materials that can currently meet the requirements of reuse are connected to the side wall structure of the aircraft by bonding or mechanical snap-fit ​​connection. The bonding reliability is not high, the mechanical snap-fit ​​connection is relatively cumbersome, the process efficiency is not high, and it also brings additional interface reliability issues. Therefore, it is of great significance to develop a lightweight heat-resistant insulation material that has strong bonding with the metal substrate surface, stable interface, good process feasibility, and is reusable. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a reusable lightweight heat-insulating material and its preparation method and application. The material is oriented towards the thermal environment profile of reusable aircraft and adopts an anti-radiation / heat-proof / heat-insulating gradient design. Its surface is a high-emissivity ceramic-based heat-proof coating that can reduce the penetration of radiant heat flow; the interior is a silicon-based heat-proof material with no ablation or low ablation effect; the innermost layer is a heat-insulating material that can reduce the temperature of the aircraft structure, thereby enabling the material to be reused a certain number of times. The heat-insulating material is an integrated gradient material, which is integrally formed by spraying. The anti-radiation, heat-proof and heat-insulating layers are co-prepared and co-cured, and the system is compatible. In addition, the material has strong bonding with the surface of the metal substrate, a stable interface, and good process feasibility.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] <First Aspect>

[0006] A method for preparing a reusable lightweight heat-insulating material comprises the following steps:

[0007] S1. Preparation of thermal insulation layer;

[0008] S2. preparing a heat-proof layer on the heat-insulating layer;

[0009] S3, preparing an anti-radiation layer on the heat protection layer;

[0010] S4, performing densification treatment on the surface of the anti-radiation layer.

[0011] As an embodiment, the steps for preparing the thermal insulation layer are:

[0012] S11, mixing a silicone rubber-containing solvent, expanded particles, porous ceramic microspheres, a coupling agent, a dispersant, and a process solvent to obtain a uniform first slurry;

[0013] S12, adding a diluent to the first slurry to adjust the viscosity to 1000-2000 mPa·s to obtain a second slurry;

[0014] S13, applying the second slurry to the surface of the metal substrate in a wet film by multi-layer spraying, and then drying the surface.

[0015] As an embodiment, the steps for preparing the heat protection layer are:

[0016] S21, mixing a silicone rubber solvent, an inorganic ablation-resistant flame-retardant filler, a high-performance chopped fiber, a silicon-based reinforcing material, a coupling agent, a dispersant, and a process solvent to obtain a uniform third slurry;

[0017] S22, adding a diluent to the third slurry to adjust the viscosity to 1000-2000 mPa·s to obtain a fourth slurry;

[0018] S23, applying the fourth slurry in a multi-layer spraying manner to a wet film on the surface of the thermal insulation layer, and allowing the surface to dry.

[0019] As an embodiment, the steps for preparing the anti-radiation layer are:

[0020] S31, mixing the emission material, high-performance chopped fibers, inorganic ablation-resistant flame-retardant filler, and ceramic gel to obtain a uniform fifth slurry;

[0021] S32. Spray the fifth slurry on the surface of the heat-proof layer in a multi-layer spraying manner and allow the surface to dry.

[0022] As an embodiment, in step S11, the mass ratio of the silicone rubber solvent, expanded particles, porous ceramic microspheres, coupling agent, dispersant, and process solvent is: 25~35: 12~18: 21~35: 0.8~1.2: 0.8~1.2: 42~58.

[0023] In some embodiments, in step S11, the mass ratio of the silicone rubber solvent, the expanded particles, the porous ceramic microspheres, the coupling agent, the dispersant, and the process solvent is 30:15:25 to 30:1:1:50.

[0024] As an embodiment, in step S21, the mass ratio of the silicone rubber solvent, the inorganic ablation-resistant flame-retardant filler, the high-performance chopped fiber, the silicon-based reinforcing material, the coupling agent, the dispersant, and the process solvent is: 25~35: 10~14: 8~12: 1.5~2.5: 0.8~1.2: 0.8~1.2: 40~60.

[0025] In some embodiments, in step S21, the mass ratio of the silicone rubber solvent, the inorganic ablation-resistant flame-retardant filler, the high-performance chopped fiber, the coupling agent, the dispersant, and the process solvent is 30:10~12:10:2:1:1:50.

[0026] As an embodiment, in step S31, the mass ratio of the emissive material, the high-performance chopped fiber, the inorganic ablation-resistant flame-retardant filler, and the ceramic gel is: 4~6: 8~12: 4~6: 12~18.

[0027] In some embodiments, in step S31, the mass ratio of the emitting material, the high-performance chopped fiber, the inorganic ablation-resistant flame retardant filler, and the ceramic gel is 5:10:5:15.

[0028] As an embodiment, the silicone rubber-containing solvent is selected from one or more of 107 and GD-401 liquid methyl silicone rubber.

[0029] In some embodiments, the silicone rubber-containing solvent is 107 silicone rubber.

[0030] As an embodiment, the coupling agent is selected from one or more of KH-550 and KH-560.

[0031] In some embodiments, the coupling agent is KH-550.

[0032] As an embodiment, the dispersant is selected from one or more of mica powder with a particle size of 10-50 μm and boron nitride with a particle size of 1-10 μm.

[0033] In some embodiments, the dispersant is mica powder with a particle size of 30 to 45 μm.

[0034] As an embodiment, the process solvent is one or more of acetone, ethyl acetate, cyclohexanone, and xylene solvents.

[0035] As an embodiment, the process solvent is a mixture of acetone and ethyl acetate in a mass ratio of 3 to 1:1.

[0036] In some embodiments, the process solvent is a mixture of acetone and ethyl acetate in a mass ratio of 3:1.

[0037] As an embodiment, the diluent is selected from one or more of ethyl acetate and acetone.

[0038] In some embodiments, the diluent is ethyl acetate.

[0039] As an embodiment, the expanded particles are selected from one or more of expanded perlite, expanded vermiculite, and expanded graphite.

[0040] As an embodiment, the expanded particles are a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2 to 3:1.

[0041] In some embodiments, the expanded particles are a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2:1.

[0042] As an embodiment, the porous ceramic microspheres are selected from one or more of zirconia, silicon oxide, mullite, and hollow glass microspheres.

[0043] As an embodiment, the porous ceramic microspheres are a mixture of zirconium oxide and silicon oxide in a mass ratio of 2 to 3:1, the zirconium oxide has a particle size range of 1 to 10 μm, and the silicon oxide has a particle size range of 10 to 40 nm.

[0044] In some embodiments, the porous ceramic microspheres are a mixture of zirconium oxide and silicon oxide in a mass ratio of 3:1.

[0045] In some embodiments, the zirconium oxide has a particle size of 3-4 μm, and the silicon oxide has a particle size of 25-30 nm.

[0046] As an embodiment, the silicon-based reinforcing material is selected from one or more of white carbon black, SiC particles, and silicone resin reinforcing fillers.

[0047] In some embodiments, the silicon-based reinforcing material is white carbon black.

[0048] As an embodiment, the inorganic ablation-resistant flame-retardant filler is selected from one or more of iron oxide, montmorillonite, wollastonite, alumina fiber, and graphite.

[0049] As an embodiment, the inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, montmorillonite and alumina fiber in a mass ratio of 2.5~3.5: 0.8~1.2: 1.6~2.4.

[0050] In some embodiments, the inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, montmorillonite, and aluminum oxide fiber in a mass ratio of 3:1:2.

[0051] As an embodiment, the inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, wollastonite, and alumina fiber in a mass ratio of 2.5-3.5: 0.8-1.2: 1.6-2.4.

[0052] In some embodiments, the inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, wollastonite, and alumina fiber in a mass ratio of 3:1:2.

[0053] As an embodiment, the high-performance chopped fibers are selected from a ceramic fiber mixture.

[0054] As an embodiment, the high-performance chopped fibers are a mixture of alumina and silica fibers in a mass ratio of 6 to 8:4.

[0055] As an embodiment, the high-performance chopped fibers are ceramic fibers with a monofilament diameter of 5-15 μm and a chopped length of 50-200 μm.

[0056] As an embodiment, the emitting material is one or more of silicon carbide, zirconium boride, zirconium oxide, molybdenum disilicide, and high entropy ceramics with a particle size of 0.4 to 2 μm.

[0057] In some embodiments, the emitting material comprises silicon carbide with a particle size of 0.4-1 μm.

[0058] In some embodiments, the emitting material comprises zirconium boride with a particle size of 0.5-2 μm.

[0059] In some embodiments, the emitting material comprises zirconium oxide with a particle size of 0.5-1 μm.

[0060] In some embodiments, the emitting material comprises molybdenum disilicide with a particle size of 0.5-1 μm.

[0061] As an embodiment, the emitting material is a mixture of silicon carbide, zirconium boride and zirconium oxide in a mass ratio of 2~3:5~6:1~2.

[0062] In some embodiments, the emissive material is a mixture of silicon carbide, zirconium boride, and zirconium oxide in a mass ratio of 3:5:2.

[0063] As an embodiment, the emitting material is a mixture of molybdenum disilicide, zirconium boride and zirconium oxide in a mass ratio of 3~4:5~6:1~2.

[0064] In some embodiments, the emitting material is a mixture of molybdenum disilicide, zirconium boride, and zirconium oxide in a mass ratio of 4:5:2.

[0065] As an embodiment, the ceramic gel is one or more of alumina ceramic aerogel, tetraethyl orthosilicate sol, and zirconium oxychloride sol.

[0066] In some embodiments, the ceramic gel is an alumina ceramic aerogel.

[0067] As an embodiment, the multi-layer spraying is performed by plasma spraying.

[0068] As an embodiment, the parameters of the plasma spraying are: plasma power 30-80 kW, spraying distance 80-140 mm, spray gun speed 0.3-1 m / s, and path overlap of 25%-50% during repeated spraying.

[0069] As an embodiment, in step S1, the parameters of the plasma spraying are: plasma power 50-60 kW, spraying distance 80-120 mm, spray gun speed 0.3-1 m / s, and path overlap of 25%-40% during repeated spraying.

[0070] As an embodiment, in step S2, the parameters of the plasma spraying are: plasma power 60-70 kW, spraying distance 90-140 mm, spray gun speed 0.3-1 m / s, and path overlap of 25%-40% during repeated spraying.

[0071] As an embodiment, in step S3, the parameters of the plasma spraying are: plasma power 50-60 kW, spraying distance 80-150 mm, spray gun speed 0.3-0.8 m / s, and path overlap of 30%-50% during repeated spraying.

[0072] As an embodiment, in the multi-layer spraying, the thickness of a single layer is 30-150 μm, one layer is sprayed every 5-25 minutes, and the thickness of the multi-layer spraying is 0.2-7 mm.

[0073] As an embodiment, in step S1, in the multi-layer spraying, the thickness of a single layer is 50-150 μm, one layer is sprayed every 5-10 minutes, and the thickness of the multi-layer spraying is 3-7 mm.

[0074] As an embodiment, in step S2, in the multi-layer spraying, the thickness of a single layer is 100-150 μm, one layer is sprayed at an interval of 10-15 minutes, and the thickness of the multi-layer spraying is 2-5 mm.

[0075] As an embodiment, in step S3, in the multi-layer spraying, the thickness of a single layer is 30-50 μm, one layer is sprayed every 5-15 minutes, and the thickness of the multi-layer spraying is 200-500 μm.

[0076] As an embodiment, the surface drying is: drying at 10-40° C. and ≤30% humidity for 2-3 days.

[0077] As an embodiment, the densification treatment step is: coating a nano-ceramic sol on the surface of the anti-radiation layer, and performing a heat treatment to convert the sol into a gel, and repeating the coating and heat treatment steps until the porosity is less than 5%.

[0078] As an embodiment, the heat treatment temperature is 300-350°C.

[0079] As an embodiment, the ceramic sol is one or more of silica sol, alumina sol, zirconia sol, and zirconium boride sol.

[0080] In some embodiments, the ceramic sol is a silica and alumina sol.

[0081] As an embodiment, the concentration of the ceramic sol is 5-25 wt%.

[0082] As an embodiment, the mass ratio of silicon dioxide to aluminum oxide in the ceramic sol is 1.5-3:1, the concentration of SiO2 sol is 10wt.%-15wt.%, and the concentration of Al2O3 sol is 5wt.%-10wt.%.

[0083] In some embodiments, the mass ratio of silicon dioxide to aluminum oxide in the ceramic sol is 2:1, the concentration of SiO2 sol is 10 wt.%, and the concentration of Al2O3 sol is 5 wt.%.

[0084] <Second Aspect>

[0085] The invention provides a reusable lightweight heat-insulating material, which is prepared by adopting the method.

[0086] As an embodiment, the heat-insulating material includes a heat-insulating layer, a heat-protective layer and an anti-radiation layer arranged in sequence.

[0087] As an embodiment, the thermal insulation layer is a silicon-based thermal insulation material with low thermal conductivity.

[0088] As an embodiment, the heat protection layer is an ablation-resistant silicon-based heat protection material.

[0089] As an embodiment, the anti-radiation layer is a ceramic-based heat-resistant material.

[0090] As an embodiment, the heat-insulating material further comprises using nano-ceramic gel to fill the pores on one side of the anti-radiation layer as a local densification treatment.

[0091] As an embodiment, the thermal insulation layer contains expanded particles and porous ceramic microspheres.

[0092] As an embodiment, the heat-proof layer contains inorganic ablation-resistant flame-retardant fillers and high-performance chopped fibers.

[0093] As an embodiment, the anti-radiation layer contains an emitting material, high-performance chopped fibers, and an inorganic ablation-resistant flame-retardant filler.

[0094] As an embodiment, the anti-radiation layer further contains nano-ceramic gel.

[0095] <Third Aspect>

[0096] The present invention provides application of the above-mentioned reusable lightweight heat-insulating material on the surface of aerospace vehicle structures.

[0097] Compared with the prior art, the present invention has the following beneficial effects:

[0098] 1) Break through the limitations of semi-passive thermal protection systems to achieve high efficiency, ablation resistance, and reusability

[0099] This invention incorporates an inorganic, ablation-resistant, flame-retardant filler and a chopped, porous ceramic fiber reinforcement system into the heat-resistant layer, creating a high-temperature-resistant skeleton-layered barrier-fiber-reinforced composite structure. Compared to traditional resin-based and silicon-based materials, which rely on ablation phase transitions for passive heat protection, this material inhibits surface carbonization and porosity when heated, maintaining the structural integrity and mechanical strength of the residual layer. This prevents thermal degradation due to material loss, allowing for multiple reuse and addressing the core drawbacks of semi-passive materials, which suffer from ablation failure and non-reusability.

[0100] 2) Integrate heat protection and insulation functions to simplify the design of multi-layer heat protection systems

[0101] The radiation-resistant and thermal insulation layers are designed through the collaborative design of high-performance emissive materials and a porous ceramic microsphere / expanded particle composite structure, forming an integrated thermal protection mechanism combining radiative heat dissipation, high-temperature resistance, and ultra-low thermal conductivity. Compared to traditional ceramic-based thermal protection materials that require the complex structure of an additional thermal insulation layer, this invention combines optimized material composition with a multi-layer structure to achieve a thermal protection layer that combines high ablation resistance (withstands temperatures of 1200°C) with the ultra-low thermal conductivity of the thermal insulation layer (significantly reduced thermal conductivity at room temperature). This eliminates the need for a separate thermal insulation layer on the back of the ceramic material, simplifying the overall thermal protection architecture, reducing system weight, and improving reliability.

[0102] 3) Optimize the compatibility of materials and structural interfaces to improve connection reliability and process efficiency

[0103] The material system of this invention (particularly the composite design of a silicone-based adhesive and inorganic filler) can be integrated with the aircraft sidewall structure through an in-situ molding process, achieving integrated bonding or structural integration, avoiding the reliability risks of traditional bonding processes. Furthermore, the material's inherent high flexibility (synergistically enhanced by chopped fibers and a silicone rubber base) and structural adaptability simplify complex connection methods such as mechanical snap-fits, reducing interfacial stress concentration, enabling efficient assembly and long-term reliable connections, addressing the challenges of traditional connection methods, including cumbersome processes and a high risk of interfacial failure.

[0104] 4) Comprehensive performance improvement and application expansion

[0105] By combining the gradient functional design of the thermal insulation layer, heat protection layer, and radiation protection layer with the coordinated materials, the thermal protection system constructed by this invention combines: 1. Wide temperature range adaptability: Withstands extreme temperatures from -50°C to 1500°C; 2. Lightweight: Density significantly lower than traditional ceramic-based materials; 3. Multifunctional integration: Heat protection, insulation, radiation protection, and structural load-bearing are all integrated. This provides a highly efficient, reliable, and easy-to-maintain thermal protection solution for reusable aircraft, high-temperature industrial equipment, and other applications, breaking through the technical bottlenecks of traditional materials, which suffer from single functions, complex systems, and poor reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0107] Figure 1 The heat-proof performance attenuation of the heat-insulating materials prepared in Example 1 and the comparative example of the present invention under repeated thermal tests. DETAILED DESCRIPTION

[0108] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0109] For ease of understanding, the abbreviations or nouns mentioned below are first explained:

[0110] 107 silicone rubber: α,ω-dihydroxy polysiloxane is the base rubber for two-component and one-component condensation silicone rubbers, commonly known as 107 rubber on the market. In the present invention, the viscosity is selected to be 5000~15000mPa·s;

[0111] High-performance chopped fiber: a ceramic fiber mixture with a mass ratio of Al2O3:SiO2=3:2, a single fiber diameter of 5–15 μm, and a chopped length of 50–200 μm;

[0112] Expanded perlite: particle size 50–100 μm, thermal conductivity 0.05 W / (m·K);

[0113] Expanded vermiculite: 75μm~200μm, thermal conductivity 0.08 W / (m·K);

[0114] Nano-ceramic sol (SiO2 and Al2O3 sol): mass ratio of SiO2 and Al2O3 is 2:1, concentration of SiO2 sol is 10wt.%, and Al2O3 sol is 5wt.%.

[0115] Example 1

[0116] This embodiment provides a method for preparing a reusable lightweight heat-insulating material, comprising the following steps:

[0117] S1. Preparation of thermal insulation layer

[0118] The raw materials required are:

[0119] Containing silicone rubber solvent: 107 silicone rubber;

[0120] Expanded particles: a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2:1;

[0121] Porous ceramic microspheres: A porous hollow ceramic microsphere mixture composed of ZrO2 and SiO2 in a mass ratio of 3:1, with a zirconium oxide particle size range of 3-4 μm and a silicon oxide particle size range of 25-30 nm;

[0122] Coupling agent: KH-550;

[0123] Dispersant: mica powder with a particle size of 30-45 μm;

[0124] Process solvent: acetone and ethyl acetate in a mass ratio of 3:1.

[0125] The preparation method is:

[0126] By weight, 30 parts of silicone rubber solvent, 15 parts of expanded particles, 25 parts of porous ceramic microspheres, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniform slurry;

[0127] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0128] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 50-150 μm (100 μm in this embodiment), and the next layer is sprayed after an interval of 5-10 minutes (8 minutes in this embodiment). A wet film with a thickness of 3-7 mm (5 mm in this embodiment) is coated on the surface of the aluminum metal substrate. The spraying parameters are a plasma power of 50-60 kW (50 kW in this embodiment), a spraying distance of 80-120 mm (100 mm in this embodiment), a spray gun speed of 0.3-1.0 m / s (0.5 m / s in this embodiment), an overlap rate of 25%-40% (30% in this embodiment), and then the wet film is surface-dried to obtain a thermal insulation layer with a thickness of 5±0.5 mm.

[0129] S2. Preparation of heat protection layer

[0130] The raw materials required are:

[0131] Containing silicone rubber solvent: 107 silicone rubber;

[0132] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), montmorillonite (10-20 μm, 85% purity, layered), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0133] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0134] Silicon-based reinforcing filler: fumed silica;

[0135] Coupling agent: KH-550;

[0136] Dispersant: mica powder with a particle size of 30-45 μm;

[0137] Process solvent: acetone and ethyl acetate in a mass ratio of 3:1.

[0138] The preparation method is:

[0139] By weight, 30 parts of silicone rubber solvent, 12 parts of inorganic ablation-resistant flame-retardant filler, 10 parts of high-performance chopped fibers, 2 parts of silicon-based reinforcing filler, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniformly mixed slurry;

[0140] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0141] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 100-150 μm (120 μm in this embodiment), and the next layer is sprayed at an interval of 10-15 minutes (12 minutes in this embodiment), forming a wet film 2-5 mm thick (4 mm in this embodiment) on the surface of the thermal insulation layer. The spraying parameters are plasma power 60-70 kW (60 kW in this embodiment), spraying distance 90-140 mm (110 mm in this embodiment), spray gun speed 0.3-1.0 m / s (0.8 m / s in this embodiment), overlap rate 25%-40% (30% in this embodiment), and then the wet film is surface dried to obtain a thermal insulation layer with a thickness of 4±0.4 mm.

[0142] S3. Preparation of anti-radiation layer

[0143] The raw materials are:

[0144] High-performance emission material: a combination of 0.4-1 μm SiC, 0.5-2 μm ZrB2, and 0.5-1 μm ZrO2, with a mass ratio of 3:5:2.

[0145] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0146] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), montmorillonite (10-20 μm, 85% purity, layered), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0147] Ceramic gel: Alumina ceramic aerogel prepared by sol-gel method, with a pore size of 20 nm and a compressive strength of 2 MPa.

[0148] The preparation method is:

[0149] 5 parts of high-performance emission material, 10 parts of high-performance chopped fibers, 5 parts of inorganic ablation-resistant flame-retardant filler, and 15 parts of ceramic gel were mixed by mass and stirred thoroughly to obtain a spraying raw material;

[0150] The spraying raw materials are sprayed on the outside of the heat protection layer using a plasma spraying device in a multi-layer spraying manner. The parameters are: plasma power 50-60 kW (50 kW in this embodiment), spraying distance 80-150 mm (100 mm in this embodiment), spray gun speed: 300-800 mm / s (500 mm / s in this embodiment), path overlap 30%-50% (45% in this embodiment) during repeated spraying, single layer thickness 30-50 μm (30 μm in this embodiment), and the next layer is sprayed after an interval of 5-15 minutes (10 minutes in this embodiment) to obtain a wet film with a thickness of 200-500 μm (300 μm in this embodiment). The wet film is then surface-dried to obtain an anti-radiation layer with a thickness of 0.3±0.05 mm.

[0151] S4. Local densification treatment

[0152] Sol-gel sealing assisted densification is used, and nano-ceramic sol (SiO2 and Al2O3 sol) is dip-coated or sprayed onto the surface of the anti-radiation layer. Heat treatment is performed at 300-350°C (300°C in this embodiment) to convert the sol into gel and fill the micropores.

[0153] Repeat this step for densification until the porosity is <5%.

[0154] It should be noted that the parameters of the surface drying treatment are: drying for 2-3 days (3 days in this embodiment) at 10-40° C. (room temperature in this embodiment) and humidity ≤30%.

[0155] It should be noted that when the prepared heat-insulating material is connected to the substrate, the innermost side (heat-insulating layer) is treated with a coupling agent to prepare an interface layer for connection with the substrate.

[0156] Example 2

[0157] This embodiment provides a method for preparing a reusable lightweight heat-insulating material, comprising the following steps:

[0158] S1. Preparation of thermal insulation layer

[0159] The raw materials required are:

[0160] Containing silicone rubber solvent: 107 silicone rubber;

[0161] Expanded particles: a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2:1;

[0162] Porous ceramic microspheres: A porous hollow ceramic microsphere mixture composed of ZrO2 and SiO2 in a mass ratio of 3:1, with a zirconium oxide particle size range of 3-4 μm and a silicon oxide particle size range of 25-30 nm;

[0163] Coupling agent: KH-550;

[0164] Dispersant: mica powder with a particle size of 30-45 μm;

[0165] Process solvent: acetone and ethyl acetate in a mass ratio of 3:1.

[0166] The preparation method is:

[0167] By weight, 30 parts of silicone rubber solvent, 15 parts of expanded particles, 30 parts of porous ceramic microspheres, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniform slurry;

[0168] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0169] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 50~150 μm (100 μm in this embodiment), and the next layer is sprayed after an interval of 5~10 minutes (8 minutes in this embodiment), and a wet film with a thickness of 3-7 mm (5 mm in this embodiment) is coated on the surface of the aluminum metal substrate. The spraying parameters are plasma power 50~60 kW (50 kW in this embodiment), spraying distance 80~120 mm (100 mm in this embodiment), spray gun speed 0.3-1.0 m / s (0.5 m / s in this embodiment), overlap rate 25%~40% (30% in this embodiment), and then the wet film is surface dried to obtain a thermal insulation layer with a thickness of 5±0.5 mm.

[0170] S2. Preparation of heat protection layer

[0171] The raw materials required are:

[0172] Containing silicone rubber solvent: 107 silicone rubber;

[0173] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), wollastonite (40-60 μm, 85% purity, 90% layered, fibrous), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0174] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0175] Silicon-based reinforcing filler: fumed silica;

[0176] Coupling agent: KH-550;

[0177] Dispersant: mica powder with a particle size of 30-45 μm;

[0178] Process solvent: acetone and ethyl acetate in a mass ratio of 3:1.

[0179] The preparation method is:

[0180] By weight, 30 parts of silicone rubber solvent, 10 parts of inorganic ablation-resistant flame-retardant filler, 10 parts of high-performance chopped fibers, 2 parts of silicon-based reinforcing filler, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniformly mixed slurry;

[0181] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0182] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 100~150 μm (120 μm in this embodiment), and the next layer is sprayed at an interval of 10~15 minutes (12 minutes in this embodiment), forming a wet film 2-5 mm thick (4 mm in this embodiment) on the surface of the thermal insulation layer. The spraying parameters are plasma power 60~70 kW (60 kW in this embodiment), spraying distance 90~140 mm (110 mm in this embodiment), spray gun speed 0.3-1.0 m / s (0.8 m / s in this embodiment), overlap rate 25%~40% (30% in this embodiment), and then the wet film is surface dried to obtain a thermal insulation layer with a thickness of 4±0.4 mm.

[0183] S3. Preparation of anti-radiation layer

[0184] The raw materials are:

[0185] High-performance emission material: a combination of 0.5-1 μm MoSi2, 0.5-2 μm ZrB2, and 0.5-1 μm ZrO2, with a mass ratio of 4:5:2.

[0186] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0187] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), wollastonite (40-60 μm, 85% purity, 90% layered, fibrous), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0188] Ceramic gel: Alumina ceramic aerogel prepared by sol-gel method, with a pore size of 20 nm and a compressive strength of 2 MPa.

[0189] The preparation method is:

[0190] 5 parts of high-performance emission material, 10 parts of high-performance chopped fibers, 5 parts of inorganic ablation-resistant flame-retardant filler, and 15 parts of ceramic gel were mixed by mass and stirred thoroughly to obtain a spraying raw material;

[0191] The spraying raw materials are sprayed on the outside of the heat protection layer using a plasma spraying device in a multi-layer spraying manner. The parameters are: plasma power 50-60 kW (50 kW in this embodiment), spraying distance 80-150 mm (100 mm in this embodiment), spray gun speed: 300-800 mm / s (500 mm / s in this embodiment), path overlap 30%-50% (45% in this embodiment) during repeated spraying, single layer thickness 30-50 μm (30 μm in this embodiment), and the next layer is sprayed after an interval of 5-15 minutes (10 minutes in this embodiment) to obtain a wet film with a thickness of 200-500 μm (300 μm in this embodiment). The wet film is then surface-dried to obtain an anti-radiation layer with a thickness of 0.3±0.05 mm.

[0192] S4. Local densification treatment

[0193] Sol-gel sealing assisted densification was used, and nano-ceramic sol (SiO2 and Al2O3 sol) was dip-coated or sprayed onto the surface of the anti-radiation layer, and then heat-treated at 300-350°C (300°C in this embodiment) to convert the sol into gel to fill the micropores;

[0194] Repeat this step for densification until the porosity is <5%.

[0195] Example 3

[0196] This embodiment provides a method for preparing a reusable lightweight heat-insulating material, comprising the following steps:

[0197] S1. Preparation of thermal insulation layer

[0198] The raw materials required are:

[0199] Containing silicone rubber solvent: 107 silicone rubber;

[0200] Expanded particles: a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2:1;

[0201] Porous ceramic microspheres: A porous hollow ceramic microsphere mixture composed of ZrO2 and SiO2 in a mass ratio of 3:1, with a zirconium oxide particle size range of 3-4 μm and a silicon oxide particle size range of 25-30 nm;

[0202] Coupling agent: KH-550;

[0203] Dispersant: mica powder with a particle size of 30-45 μm;

[0204] Process solvent: 3:1 acetone and ethyl acetate.

[0205] The preparation method is:

[0206] By weight, 30 parts of silicone rubber solvent, 15 parts of expanded particles, 25 parts of porous ceramic microspheres, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniform slurry;

[0207] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0208] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 50~150 μm (100 μm in this embodiment), and the next layer is sprayed after an interval of 5~10 minutes (8 minutes in this embodiment), and a wet film with a thickness of 3~7 mm (3 mm in this embodiment) is coated on the surface of the substrate. The spraying parameters are plasma power 50~60 kW (50 kW in this embodiment), spraying distance 80~120 mm (100 mm in this embodiment), spray gun speed 0.3-1.0 m / s (0.5 m / s in this embodiment), overlap rate 25%~40% (30% in this embodiment), and then the wet film is surface dried to obtain a thermal insulation layer with a thickness of 3±0.3 mm.

[0209] S2. Preparation of heat protection layer

[0210] The raw materials required are:

[0211] Containing silicone rubber solvent: 107 silicone rubber;

[0212] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), montmorillonite (10-20 μm, 85% purity, layered), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0213] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0214] Silicon-based reinforcing filler: fumed silica;

[0215] Coupling agent: KH-550;

[0216] Dispersant: mica powder with a particle size of 30-45 μm;

[0217] Process solvent: acetone and ethyl acetate in a mass ratio of 3:1.

[0218] The preparation method is:

[0219] By weight, 30 parts of silicone rubber solvent, 12 parts of inorganic ablation-resistant flame-retardant filler, 10 parts of high-performance chopped fibers, 2 parts of silicon-based reinforcing filler, 1 part of coupling agent, 1 part of dispersant, and 50 parts of process solvent were mixed at 25±3°C for 0.5h to obtain a uniformly mixed slurry;

[0220] Then, 30 to 50 phr (30 phr in this embodiment) of ethyl acetate is added to the slurry to adjust the viscosity to 1000 to 2000 mPa·s (the viscosity in this embodiment is 1200 mPa·s);

[0221] Then, a multi-layer spraying method is adopted: the thickness of a single layer is 100~150 μm (1200 μm in this embodiment), and the next layer is sprayed at an interval of 10~15 minutes (12 minutes in this embodiment), forming a wet film 2~5 mm thick (2 mm in this embodiment) on the surface of the thermal insulation layer. The spraying parameters are plasma power 60~70 kW (60 kW in this embodiment), spraying distance 90~140 mm (110 mm in this embodiment), spray gun speed 0.3-1.0 m / s (0.8 m / s in this embodiment), overlap rate 25%~40% (30% in this embodiment), and then the wet film is surface dried to obtain a thermal insulation layer with a thickness of 2±0.2 mm.

[0222] S3. Preparation of anti-radiation layer

[0223] The raw materials are:

[0224] High-performance emission material: a combination of 0.4-1 μm SiC, 0.5-2 μm ZrB2, and 0.5-1 μm ZrO2, with a mass ratio of 3:5:2.

[0225] High-performance chopped fiber: ceramic fiber (Al2O3-SiO2) mixture;

[0226] Inorganic ablation-resistant flame-retardant filler: a combination of iron oxide (5 μm particle size, 95% purity, granular), montmorillonite (10-20 μm, 85% purity, layered), and alumina fiber (6 μm diameter, 50-200 μm length, 95% purity, fibrous), with a mass ratio of 3:1:2;

[0227] Ceramic gel: Alumina ceramic aerogel prepared by sol-gel method, with a pore size of 20 nm and a compressive strength of 2 MPa.

[0228] The preparation method is:

[0229] 5 parts of high-performance emission material, 10 parts of high-performance chopped fibers, 5 parts of inorganic ablation-resistant flame-retardant filler, and 15 parts of ceramic gel were mixed by mass and stirred thoroughly to obtain a spraying raw material;

[0230] The spraying raw materials are sprayed on the outside of the heat protection layer using a plasma spraying device in a multi-layer spraying manner. The parameters are: plasma power 50-60 kW (50 kW in this embodiment), spraying distance 80-150 mm (100 mm in this embodiment), spray gun speed: 300-800 mm / s (500 mm / s in this embodiment), path overlap 30%-50% (45% in this embodiment) during repeated spraying, single layer thickness 30-50 μm (30 μm in this embodiment), and the next layer is sprayed after an interval of 5-15 minutes (10 minutes in this embodiment) to obtain a wet film with a thickness of 200-500 μm (300 μm in this embodiment). The wet film is then surface-dried to obtain an anti-radiation layer with a thickness of 0.3±0.05 mm.

[0231] S4. Local densification treatment

[0232] Sol-gel sealing assisted densification is used, and nano-ceramic sol (SiO2 and Al2O3 sol) is dip-coated or sprayed onto the surface of the anti-radiation layer. Heat treatment is performed at 300-350°C (300°C in this embodiment) to convert the sol into gel and fill the micropores.

[0233] Repeat this step for densification until the porosity is <5%.

[0234] Comparative Example

[0235] In this comparative example, the heat-insulating material is prepared by the method provided in Reference Implementation 1, except that the inorganic ablation-resistant flame-retardant filler is replaced with a metal hydroxide (Al(OH)3). However, during the preparation process, it was found that the metal hydroxide decomposes and releases water vapor while absorbing heat at high temperatures. Although it can reduce temperature and flame retardancy, it will cause the internal pores of the heat-insulating material to increase sharply, affecting the internal bonding strength of the heat-insulating material, and further affecting the internal interface stability of the heat-insulating material.

[0236] Performance testing:

[0237] (1) Combine with metal substrate and detect interface bonding strength

[0238] The test method for the interfacial adhesion of heat-resistant coatings adopts the commonly used authoritative test method in the industry: GB / T 5210 "Determination of adhesion of coatings - Pull-off method".

[0239] (2) Heat flow assessment

[0240] Single ablation: ablation of the outer layer of the thermal protection coating, with a peak heat flux of 500kW / m 2 Continue for 30 seconds, then continue with a heat flux of 80kW / m 2 Ablation was continued for 200 s.

[0241] Multiple ablation: The above ablation steps were repeated 5 times.

[0242] Under the above-mentioned test heat flux, the surface temperature of the heat-resistant material reaches a maximum of about 1200°C.

[0243] Monitor the back temperature and comprehensive thermal conductivity of 10mm thick heat-resistant materials.

[0244] Back temperature of 10mm thick heat-proof material: Arrange 5 temperature sensor measuring points on the back temperature of the heat-proof material, and take the average of the 5 temperature measuring points as the back temperature of the heat-proof material.

[0245] Comprehensive thermal conductivity: The comprehensive thermal conductivity of thermal protection coatings is tested and calculated using the industry's commonly used authoritative test method: GB / T 10295 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - Heat flow meter method". The thermal conductivity is calculated by measuring the steady-state heat flow and temperature difference (λ = Q·d / (A·ΔT)).

[0246] Thermal performance degradation: The thermal performance degradation is calculated by counting the changes in the back temperature and comprehensive thermal conductivity of the material during multiple thermal assessment tests.

[0247] (3) Compressive strength

[0248] The test method for the compressive strength of the heat-resistant coating adopts the commonly used authoritative test method in the industry: GB / T 5072 "Test method for compressive strength of refractory materials at room temperature".

[0249] Table 1 Comparison of heat-resistant material parameters

[0250]

[0251] (1) Excellent heat insulation performance

[0252] The heat protection layer adopts an effective combination of inorganic ablation-resistant flame retardant filler and high-performance short-cut fiber, which has high stability below 800℃. Combined with the anti-radiation layer coated on the surface and local densification treatment, it can effectively resist the radiation heat flow of aerospace engine. It can withstand a peak heat flow of 500kW / m 2 (lasting 30s) and long-term heat flow 80kW / m 2The combined effect of the heat transfer (lasting 200 seconds) results in a back temperature of ≤150°C at a thickness of 10mm, and a comprehensive thermal conductivity of ≤0.3W / mK. Compared to traditional thermal insulation materials, which achieve a back temperature of 200-300°C at a thickness of 10mm under the same test heat flux, this invention significantly enhances the thermal insulation effect and better protects the base material.

[0253] (2) Excellent reusability

[0254] like Figure 1 As shown, under a predetermined heat flux, the thermal insulation material provided by the present invention (Example 1) experienced a 16% decrease in thermal insulation performance after five repeated tests. However, the conventional thermal insulation material (Comparative Example) experienced a >50% decrease in thermal insulation performance after one test. This ensures stable and reliable performance in repeated use, significantly reducing operating costs and improving resource utilization.

[0255] (3) Good system compatibility

[0256] The material components of the thermal insulation layer, heat protection layer, and anti-radiation layer do not chemically react with each other during the curing process, and the raw material properties will not deteriorate. The interfaces between the metal substrate, thermal insulation layer, and heat protection layer are treated with a coupling agent to achieve a strong bond and prevent delamination or peeling. The surface densification material of the anti-radiation layer is composed of the same system as the raw material components of the anti-radiation layer and similarly does not chemically react. This excellent system compatibility ensures the stability and reliability of the overall material performance and extends the material's service life.

[0257] (4) Scientific gradient design

[0258] The thermal conductivity and thermal expansion coefficient of the insulation, heat protection, and radiation protection layers are designed with a coordinated gradient. The outer layer has a high thermal conductivity, while the inner layer has a low thermal conductivity, decreasing from the inside out. This gradient thermal conductivity design allows the outer layer to dissipate heat quickly while the inner layer effectively blocks heat, extending the substrate's endurance and improving heat protection efficiency. The gradient thermal expansion coefficient design prevents stress concentration or cracking within the heat protection material caused by temperature fluctuations (20°C to 800°C at the interface), thereby enhancing the material's structural stability and durability.

[0259] (5) Efficient spray molding process

[0260] The use of spray coating for integrated molding reduces interface processing, avoids the complex process and instability of gluing, and achieves a strong interface bond. Furthermore, spray coating is highly adaptable to complex surfaces, eliminates the need for molds, reduces losses, and achieves high efficiency. Compared to traditional processes, this reduces process complexity, improves production efficiency, and reduces production costs.

[0261] (6) Low-cost co-preparation and co-curing process

[0262] The three layers of radiation protection, heat protection, and insulation are sprayed using the same or similar methods, eliminating the need for changes in spraying equipment, site, or personnel. Furthermore, the next layer can be sprayed only after the surface is dry, rather than having the previous one fully cured. The heat protection and insulation materials can be cured together. This co-preparation and co-curing process significantly reduces process costs, improves implementation efficiency, and facilitates large-scale industrial production.

[0263] (7) Lightweight

[0264] The comprehensive density of the heat-insulating material provided by the present invention is 0.5g / cm 3 The density of traditional thermal insulation materials is about 0.7~1.0g / cm 3 While ensuring excellent performance, it also achieves lightweight, and can be widely used in fields with strict weight requirements, such as aerospace, etc., to reduce the overall equipment mass, reduce energy consumption, and improve operating efficiency.

[0265] (8) Strong bonding and stable interface

[0266] The thermal insulation material provided by this invention exhibits a bonding strength and interfacial bonding strength of at least 0.5 MPa with metal substrates (such as aluminum alloys and magnesium alloys), exceeding the cross-sectional bonding strength of 0.3 MPa for conventional thermal insulation materials. This strong bonding and stable interface ensure a secure connection between the material and the substrate, making it less susceptible to delamination and shedding in complex environments such as high temperatures and vibrations, thereby improving the reliability and safety of the overall structure.

[0267] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a reusable lightweight heat-insulating material, characterized in that: The following steps are involved: S1. Preparation of a thermal insulation layer, wherein the thermal insulation layer contains expanded particles and porous ceramic microspheres; Step S1 comprises: mixing a silicone rubber solvent, expanded particles, porous ceramic microspheres, a coupling agent, a dispersant, and a process solvent to obtain a uniform first slurry; adding a diluent to the first slurry to adjust the viscosity to 1000-2000 mPa·s to obtain a second slurry; and applying the second slurry to the surface of the metal substrate by multi-layer spraying to form a wet film, and drying the film to obtain the thermal insulation layer. The mass ratio of silicone rubber solvent, expanded particles, porous ceramic microspheres, coupling agent, dispersant, and process solvent is: 25~35:12~18:21~35:0.8~1.2:0.8~1.2:42~58; The expanded particles are selected from one or more of expanded perlite, expanded vermiculite, and expanded graphite; S2. preparing a heat-proof layer on the heat-insulating layer, wherein the heat-proof layer contains an inorganic ablation-resistant flame-retardant filler and high-performance chopped fibers; Step S2 comprises: mixing a silicone rubber solvent, an inorganic ablation-resistant flame-retardant filler, high-performance chopped fibers, a silicon-based reinforcing material, a coupling agent, a dispersant, and a process solvent to obtain a uniform third slurry; adding a diluent to the third slurry to adjust the viscosity to 1000-2000 mPa·s to obtain a fourth slurry; and applying the fourth slurry to the surface of the thermal insulation layer in a multi-layer spraying manner to form a wet film, and allowing the surface to dry to obtain the thermal insulation layer. The mass ratio of silicone rubber solvent, inorganic ablation-resistant flame-retardant filler, high-performance chopped fiber, silicon-based reinforcing material, coupling agent, dispersant, and process solvent is: 25-35: 10-14: 8-12: 1.5-2.5: 0.8-1.2: 0.8-1.2: 40-60; The inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, montmorillonite, and alumina fiber in a mass ratio of 2.5-3.5: 0.8-1.2: 1.6-2.4; or the inorganic ablation-resistant flame-retardant filler is a mixture of iron oxide, wollastonite, and alumina fiber in a mass ratio of 2.5-3.5: 0.8-1.2: 1.6-2.4; The high-performance chopped fibers are selected from a ceramic fiber mixture; S3. Preparing an anti-radiation layer on the heat protection layer, wherein the anti-radiation layer contains an emissive material, high-performance chopped fibers, and an inorganic ablation-resistant flame-retardant filler; Step S3 comprises: mixing an emitting material, high-performance chopped fibers, an inorganic ablation-resistant flame-retardant filler, and a ceramic gel to obtain a uniform fifth slurry; spraying the fifth slurry on the surface of the heat-resistant layer by multi-layer spraying, and drying the slurry to obtain the radiation-resistant layer; The mass ratio of the launch material, high-performance chopped fiber, inorganic ablation-resistant flame-retardant filler, and ceramic gel is: 4~6:8~12:4~6:12~18; The emission material is one or more of silicon carbide, zirconium boride, zirconium oxide, molybdenum disilicide, and high entropy ceramics with a particle size of 0.4 to 2 μm; S4, performing densification treatment on the surface of the anti-radiation layer; Step S4 is: coating the surface of the anti-radiation layer with nano-ceramic sol, and performing heat treatment to convert the sol into gel, and repeating the coating and heat treatment steps until the porosity is less than 5%.

2. The method according to claim 1, characterized in that Also includes at least one of the following technical features: A2. The silicone rubber-containing solvent is selected from one or more of 107 and GD-401 liquid methyl silicone rubber; B2. The dispersant is selected from one or more of mica powder with a particle size of 10-50 μm and boron nitride with a particle size of 1-10 μm; D2, the porous ceramic microspheres are selected from one or more of zirconia, silicon oxide, mullite, and hollow glass microspheres; E2. The silicon-based reinforcing material is selected from one or more of white carbon black, SiC particles, and silicone resin reinforcing fillers; I2. The ceramic gel is one or more of alumina ceramic aerogel, ethyl orthosilicate sol, and zirconium oxychloride sol.

3. The method according to claim 1, characterized in that Also includes at least one of the following technical features: A3. The coupling agent is selected from one or more of KH-550 and KH-560; B3, the process solvent is one or more of acetone, ethyl acetate, cyclohexanone, and xylene solvents; C3. The diluent is selected from one or more of ethyl acetate and acetone.

4. The method according to claim 1, wherein Also includes at least one of the following technical features: A4, the expanded particles are a mixture of expanded perlite and expanded vermiculite in a mass ratio of 2-3:1; B4, the porous ceramic microspheres are a mixture of zirconium oxide and silicon oxide in a mass ratio of 2-3:1, the zirconium oxide has a particle size range of 1-10 μm, and the silicon oxide has a particle size range of 10-40 nm; E4, the high-performance chopped fibers are a mixture of alumina and silica fibers in a mass ratio of 6 to 8:4; F4, the emitting material is a mixture of silicon carbide, zirconium boride and zirconium oxide in a mass ratio of 2-3:5-6:1-2; G4, the emitting material is a mixture of molybdenum disilicide, zirconium boride and zirconium oxide in a mass ratio of 3-4: 5-6: 1-2; H4. The mass ratio of silicon dioxide to aluminum oxide in the ceramic sol is 1.5-3:1, the concentration of SiO2 sol is 10wt.%-15wt.%, and the concentration of Al2O3 sol is 5wt.%-10wt.%.

5. The method according to claim 1, wherein Also includes at least one of the following technical features: A5. The multi-layer spraying adopts plasma spraying method with the following parameters: plasma power 30-80 kW, spraying distance 80-140 mm, spray gun speed 0.3-1 m / s, and path overlap of 25%-50% during repeated spraying; B5. In the multi-layer spraying, the thickness of a single layer is 30-150 μm, one layer is sprayed every 5-25 minutes, and the thickness of the multi-layer spraying is 0.2-7 mm.

6. The method according to claim 1, wherein The heat treatment temperature is 300-350°C.

7. A heat-insulating material, characterized in that: It is prepared according to the method according to any one of claims 1 to 6, and comprises a heat insulation layer, a heat protection layer and an anti-radiation layer arranged in sequence, and the anti-radiation layer is locally densified.

8. Use of the heat-insulating material according to claim 7 on the surface of aerospace structures.

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