SiC ceramic composite aerogel as well as preparation method and application thereof

Abstract

The invention provides SiC ceramic composite aerogel as well as a preparation method and application thereof, and belongs to the technical field of functional clothing. The preparation method comprises the following steps: mixing silicon carbide with a silicon source precursor, carrying out sol-gel reaction, and drying to obtain aerogel; and then preparing the infrared radiation coating containing the hydrophobic layer and having high reflection performance. The prepared SiC ceramic composite aerogel comprises a silicon carbide aerogel layer prepared from silicon carbide and an infrared shielding layer on the surface of the silicon carbide aerogel layer. The SiC ceramic composite aerogel prepared by the invention has high temperature resistance, wave absorption, thermal insulation and infrared shielding properties, is suitable for extreme environments, can effectively prevent radar and infrared detection, can improve the toughness of the aerogel layer, has excellent comprehensive performance, and can be widely applied to the field of microwave-assisted imaging. The problem that an existing garment material cannot meet the requirements for high temperature resistance, radar and infrared stealth, heat preservation and the like at the same time can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of functional clothing, and in particular to a SiC ceramic composite aerogel and a preparation method and application thereof. Background Art

[0002] In some special fields, such as military, aerospace, and high-temperature industrial environment operations, extremely stringent requirements are placed on the clothing worn by personnel. Traditional clothing is difficult to simultaneously meet multiple requirements such as high temperature resistance, resistance to extreme cold, and prevention of radar detection and infrared detection. For example, in a high temperature environment, ordinary clothing is easily burned or loses its protective function; when covert actions are required, it is easy to be detected by radar or infrared equipment to expose the target. At present, the Kevlar aerogel film prepared by the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, has high porosity and high specific surface area, and low thermal conductivity [G.Li, L.Wang, X.Ji, X.Zhang, Suspending Light-Absorbing Nanoparticles in SilicaAerogel Enables Numerous Superblacks. Adv.Mater.2025,37,2412385.]. The phase change composite film compounded with polyethylene glycol and hydrophobized has a high phase change enthalpy, infrared emissivity that matches the environmental background, and ultra-low infrared transmittance in the 3-15μm infrared band, which can achieve infrared invisibility of non-heat-generating objects. Secondly, the team led by Academician Xu Weilin of Wuhan Textile University used waste cotton fibers and alkaline lignin to prepare a "toast-like" regenerated cellulose composite aerogel. By atomic layer deposition of titanium dioxide, it has an interference effect on thermal imaging detection equipment in the mid-infrared band of 8-14μm. The thermal camouflage capability in a simulated desert environment can meet the needs of military stealth [Z.Huang, A.Tong, T.Xing, A.He, Y.Luo, Y.Zhang, M.Wang, S.Qiao, Z.Shi, F.Chen, W.Xu, Regenerated Cellulose / Lignin Composite Aerogel with Unique Toast-Like Structure and Their Potential Applicationsin Thermal Camouflage. Adv.Funct.Mater.2025, 35, 2414696.].In addition, the multifunctional Co-N co-doped carbon-containing aerogel manufactured by the team of Associate Professor Zhao Rui and Professor Xue Weidong of the University of Electronic Science and Technology of China has multiple properties such as hydrophobicity, corrosion resistance, heat insulation and infrared stealth. Its surface temperature remains almost unchanged after 1h at 100°C, showing a good infrared stealth effect [K.Cao, W.Ye, Y.Zhang, R.Zhao, W.Xue, X.Yang, Fabrication of multifunctionalCo,N co-doped UIO-rGO aerogel with properties of hydrophobic, anti-corrosion, heat insulation, infrared stealth and electromagnetic wave absorption, Chem.Eng.J, 2024, 492, 152275]. However, although aerogel materials have many excellent properties, they have poor toughness and are prone to cracking in practical applications. In addition, they can only be used for a single function, which limits their effective application in functional clothing. Therefore, it is of great significance to develop a multifunctional integrated flexible aerogel material. Summary of the invention

[0003] The object of the present invention is to provide a SiC ceramic composite aerogel and a preparation method and application thereof. The SiC ceramic composite aerogel has high temperature, wave absorption, heat preservation and infrared shielding properties, is used in extreme environments and can effectively prevent radar and infrared detection, while improving the toughness of the aerogel layer.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a SiC ceramic composite aerogel, comprising the following steps:

[0006] The silicon carbide raw material, the silicon source precursor, the nano absorber, the high molecular polymer and the organic solvent are mixed to obtain a mixed material;

[0007] The mixed material is mixed with an acid catalyst, subjected to a sol-gel reaction, and then dried to obtain a silicon carbide aerogel;

[0008] The silicon carbide aerogel is immersed in an organic silane coupling agent solution to perform surface treatment to obtain an aerogel containing a hydrophobic layer;

[0009] The infrared shielding agent, the binder, the dispersant and water are mixed by ball milling to obtain a slurry;

[0010] After applying the slurry to the surface of the aerogel containing the hydrophobic layer, heat treatment is performed to obtain a SiC ceramic composite aerogel;

[0011] The nano absorber includes ferrite; the infrared shielding agent includes TiO2 or Ag.

[0012] Preferably, the silicon carbide raw material is silicon carbide fiber or silicon carbide whisker; the diameter of the silicon carbide raw material is 0.1-1 μm, and the aspect ratio is 30-100;

[0013] The silicon source precursor includes tetraethyl orthosilicate (TEOS) or methyl orthosilicate (TMOS); the mass ratio of the silicon source precursor to the silicon carbide raw material is 1:10-20.

[0014] Preferably, the average particle size of the nano absorber is 20 to 100 nm; the ferrite includes one or more of nickel ferrite, zinc ferrite and nickel zinc ferrite; the mass ratio of the nano absorber to the silicon carbide raw material is 5 to 10:1;

[0015] The high molecular polymer includes polyimide or polyetheretherketone; the mass of the high molecular polymer is 10-40% of the mass of the silicon carbide raw material.

[0016] Preferably, the acid catalyst comprises hydrochloric acid; the temperature of the sol-gel reaction is 50 to 90° C., the pH value is 3 to 6, and the reaction time is 6 to 24 hours.

[0017] Preferably, in the step of preparing silicon carbide aerogel, the drying method is atmospheric pressure drying or freeze drying, the atmospheric pressure drying temperature is 70 to 80°C, and the time is 6 to 8 hours; the freeze drying temperature is -40 to -60°C, and the time is 48 to 96 hours.

[0018] Preferably, the organosilane coupling agent in the organosilane coupling agent solution includes one or more of KH550, KA200, KH570 and KH792; the mass fraction of the organosilane coupling agent solution is 5-20%; the temperature of the surface treatment is 25-110° C., and the time is 12-24 hours.

[0019] Preferably, the particle size of the infrared shielding agent is 20 to 100 nm;

[0020] The binder includes one or more of aluminum sol, silica sol and aluminum dihydrogen phosphate; the dispersant includes sodium hexametaphosphate, sodium hexametaphosphate or sodium pyrophosphate;

[0021] The mass ratio of the infrared shielding agent, the binder, the dispersant and the water is 40:10-20:1-2:38-49;

[0022] The ball milling mixing conditions include: a ball mill speed of 300 to 400 rpm, a ball milling time of 12 to 24 hours, and a ball-to-material ratio of 1 to 5:1.

[0023] Preferably, the slurry is applied to the surface of the aerogel containing the hydrophobic layer by dipping;

[0024] The moving speed of the spray gun used for spraying is 5-10 cm / s, the number of spraying is 1-2 times, and the thickness of each spraying is independently 10-50 μm;

[0025] The immersion time is 10 to 30 minutes;

[0026] The heat treatment temperature is 500-800° C. and the time is 1-3 hours.

[0027] The present invention provides a SiC ceramic composite aerogel prepared by the preparation method described in the above technical solution.

[0028] The present invention provides application of the SiC ceramic composite aerogel described in the above technical solution in the field of multifunctional high-performance protective clothing.

[0029] The invention provides a method for preparing a SiC ceramic composite aerogel. The material comprises a silicon carbide aerogel layer prepared from silicon carbide and an infrared shielding layer on the surface of the silicon carbide aerogel layer, wherein the silicon carbide aerogel layer is prepared by a sol-gel process combined with a drying process, silicon carbide is selected as a skeleton, a nano absorber is added to improve the absorbing performance to achieve radar stealth, a high molecular polymer is mixed in and the silicon carbide aerogel is surface treated to enhance toughness, and then a highly reflective infrared shielding layer is applied in a specific band (3-5 μm and 8-14 μm) to improve the infrared shielding performance. The material has high porosity, low density and excellent thermal insulation properties, and can effectively block a large amount of dynamic cold and hot air from flowing in. The SiC ceramic composite aerogel prepared by the present invention has the properties of high temperature resistance, wave absorption, heat preservation and infrared shielding, is suitable for extreme environments and can effectively prevent radar and infrared detection, while improving the toughness of the aerogel layer, and has excellent comprehensive performance. It can solve the problem that existing clothing materials are difficult to simultaneously meet the multiple requirements of high temperature resistance, radar and infrared stealth, and heat preservation, and has broad application prospects in the field of clothing for operations in extreme environments such as military, aerospace, etc.

[0030] Furthermore, the silicon carbide aerogel layer of the present invention is prepared by a sol-gel process, high-quality silicon carbide fibers or whiskers are selected as the skeleton material, and are evenly dispersed in a silicon source precursor solution, and an aerogel structure is formed after drying. In order to enhance the wave absorbing performance, a nano-ferrite wave absorber is added during the preparation process; at the same time, the aerogel is surface-modified and an organic silane coupling agent is used to improve the hydrophobicity.

[0031] In order to improve the toughness of the aerogel layer, the present invention adds a high molecular polymer (such as polyimide (PI) or polyetheretherketone (PEEK)) to the precursor of the aerogel. These flexible high molecular polymers can form a structure similar to a "buffer network" in the skeleton structure of the aerogel. When the aerogel is subjected to external force, the flexible high molecular polymer can absorb and disperse energy through its own deformation, thereby effectively reducing the generation and expansion of cracks inside the aerogel.

[0032] In order to significantly improve the infrared shielding effectiveness of silicon carbide materials, the present invention prepares a layer of infrared radiation material with high reflective properties on the surface of silicon carbide aerogel. The infrared shielding layer formed can effectively reduce radiation heat dissipation and have a positive impact on the thermal cycle inside the aerogel material, thereby achieving the expected purpose of strengthening the thermal insulation performance of the fiber and preventing infrared detection. It not only optimizes the overall thermal insulation mechanism of the material, so that it can more effectively maintain the internal temperature stability under extreme ambient temperature conditions, but also greatly enhances the material's ability to resist infrared detection, expands its applicability and reliability in application scenarios with strict requirements for infrared stealth, and lays a solid foundation for the in-depth application of this material in related fields such as multifunctional high-performance protective clothing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a microscopic surface morphology of the coating in the composite aerogel prepared in Example 1;

[0034] Figure 2 The infrared radiation performance results of the composite aerogel coating prepared in Example 3;

[0035] Figure 3 The high temperature resistance results of the composite aerogel prepared in Example 3;

[0036] Figure 4 The microwave absorption performance results of the composite aerogel prepared in Example 3 are shown. DETAILED DESCRIPTION

[0037] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0038] The present invention provides a method for preparing a SiC ceramic composite aerogel, comprising the following steps:

[0039] The silicon carbide raw material, the silicon source precursor, the nano absorber, the high molecular polymer and the organic solvent are mixed to obtain a mixed material;

[0040] The mixed material is mixed with an acid catalyst, subjected to a sol-gel reaction, and then dried to obtain a silicon carbide aerogel;

[0041] The silicon carbide aerogel is immersed in an organic silane coupling agent solution to perform surface treatment to obtain an aerogel containing a hydrophobic layer;

[0042] The infrared shielding agent, the binder, the dispersant and water are mixed by ball milling to obtain a slurry;

[0043] After applying the slurry to the surface of the aerogel containing the hydrophobic layer, heat treatment is performed to obtain a SiC ceramic composite aerogel;

[0044] The nano absorber includes ferrite; the infrared shielding agent includes TiO2 or Ag.

[0045] The present invention mixes silicon carbide raw materials, silicon source precursors, nanometer wave absorbers, high molecular polymers and organic solvents to obtain a mixed material.

[0046] In the present invention, the silicon carbide raw material is preferably silicon carbide fiber or silicon carbide whisker; the diameter of the silicon carbide raw material is preferably 0.1-1 μm, more preferably 0.3-0.5 μm, and the aspect ratio is preferably 30-100, more preferably 40-60.

[0047] In the present invention, the silicon source precursor preferably includes tetraethyl orthosilicate (TEOS) or methyl orthosilicate (TMOS); the mass ratio of the silicon source precursor to the silicon carbide raw material is preferably 1:10-20, more preferably 1:11-12.5.

[0048] In the present invention, the average particle size of the nano absorber is preferably 20 to 100 nm, more preferably 30 to 60 nm; the nano absorber includes ferrite; the ferrite preferably includes one or more of nickel ferrite, zinc ferrite and nickel-zinc ferrite; when the ferrite is two or more of the above, the present invention has no special restrictions on the ratio of different types of ferrites, and any ratio is acceptable. The present invention has no special restrictions on the source of the ferrite, and commercially available products known in the art can be used; in the embodiments of the present invention, it is specifically purchased from Gaoke Magnetic Technology Co., Ltd.

[0049] In the present invention, the mass ratio of the nano absorber to the silicon carbide raw material is preferably 5 to 10:1, more preferably 8 to 10:1.

[0050] In the present invention, the high molecular polymer preferably includes polyimide or polyetheretherketone; the high molecular polymer preferably exists in the form of nanofibers or nanoparticles; the mass of the high molecular polymer is preferably 10-40% of the mass of the silicon carbide raw material, more preferably 12-30%, and further preferably 15-25%. The present invention has no special limitation on the source of the high molecular polymer, and any commercially available product known in the art can be used; in the embodiment of the present invention, it is specifically sourced from Jiangxi Xiancai Nanofiber Technology Co., Ltd.

[0051] In the present invention, the organic solvent is preferably ethanol; the present invention preferably dissolves the silicon source precursor in an organic solvent, adds silicon carbide raw material, nano absorber, and high molecular polymer to the obtained silicon source precursor solution, and stirs and mixes for 6 to 12 hours, more preferably 7 to 10 hours, and further preferably 8 to 9 hours; the concentration of the silicon source precursor solution is preferably 0.2 to 1 mol / L, more preferably 0.3 to 0.8 mol / L, and further preferably 0.4 to 0.6 mol / L.

[0052] After obtaining the mixed material, the present invention mixes the mixed material with an acid catalyst, performs a sol-gel reaction, and then dries to obtain silicon carbide aerogel.

[0053] In the present invention, the acid catalyst preferably includes hydrochloric acid; the concentration of the hydrochloric acid is preferably 0.1 mol / L; the amount of the acid catalyst preferably reaches the pH value required for the reaction.

[0054] In the present invention, the temperature of the sol-gel reaction is preferably 50-90°C, more preferably 60-80°C, and more preferably 65-75°C, the pH value is preferably 3-6, more preferably 3.5-5.5, and more preferably 4.0-4.5, and the reaction time is preferably 6-24h, more preferably 10-20h, and more preferably 15h; the sol-gel reaction is preferably carried out in a constant temperature water bath. During the sol-gel reaction, stirring is continued and the stirring speed is adjusted to 300-400rpm, more preferably 320-350rpm, until a gel is formed.

[0055] After the sol-gel reaction is completed, the present invention preferably transfers the obtained gel to a drying device for drying to obtain silicon carbide aerogel.

[0056] In the present invention, in the step of preparing silicon carbide aerogel, the drying method is preferably atmospheric pressure drying or freeze drying, the atmospheric pressure drying temperature is preferably 70 to 80°C, and the time is preferably 6 to 8h; the freeze drying temperature is preferably -40 to -60°C, more preferably -45 to -50°C, and the time is preferably 48 to 96h, more preferably 56 to 84h, and further preferably 60 to 72h.

[0057] After obtaining the silicon carbide aerogel, the present invention immerses the silicon carbide aerogel in an organic silane coupling agent solution and performs surface treatment to obtain an aerogel containing a hydrophobic layer.

[0058] In the present invention, the organosilane coupling agent in the organosilane coupling agent solution preferably includes one or more of KH550, KA200, KH570 and KH792; the mass fraction of the organosilane coupling agent solution is preferably 5-20wt%, more preferably 6-16wt%, and further preferably 8-10wt%; the solvent used in the organosilane coupling agent solution is preferably ethanol or acetone. The present invention has no special restrictions on the amount ratio of the silicon carbide aerogel to the organosilane coupling agent solution, as long as it is completely impregnated.

[0059] In the present invention, the surface treatment temperature is preferably 25 to 110° C., more preferably 25 to 60° C., and the time is preferably 12 to 24 hours, more preferably 15 to 18 hours.

[0060] After completing the surface treatment, the present invention preferably dries the obtained product to obtain an aerogel containing a hydrophobic layer; the drying temperature is preferably 60 to 110° C., more preferably 70 to 80° C., and the drying time is preferably 6 to 8 hours, more preferably 7 to 7.5 hours.

[0061] The invention ball-mills an infrared shielding agent, a binder, a dispersant and water to obtain a slurry; applies the slurry to the surface of an aerogel containing a hydrophobic layer, and then performs heat treatment to obtain a SiC ceramic composite aerogel.

[0062] In the present invention, the infrared shielding agent includes TiO2 or Ag; the particle size of the infrared shielding agent is preferably 20 to 100 nm, more preferably 30 to 60 nm. The infrared shielding agent of the present invention has high reflectivity in the 3 to 5 μm and 8 to 14 μm bands.

[0063] In the present invention, the binder preferably includes one or more of aluminum sol, silica sol and aluminum dihydrogen phosphate, more preferably aluminum sol or silica sol, and the concentration of the aluminum sol or silica sol is preferably 30wt%; the dispersant preferably includes sodium hexametaphosphate or sodium pyrophosphate.

[0064] In the present invention, the mass ratio of the infrared shielding agent, the binder, the dispersant and the water is preferably 40:10-20:1-2:38-49, more preferably 40:20:2:38.

[0065] In the present invention, the conditions for ball milling mixing preferably include: a ball mill speed of 300-400 rpm, more preferably 350-390 rpm, a ball milling time of 12-24 h, more preferably 18-22 h, and a ball-to-material ratio of 1-5:1, more preferably 2:1.

[0066] In the present invention, the slurry is applied to the surface of the aerogel containing the hydrophobic layer preferably by spraying or dipping; the moving speed of the spray gun used for spraying is preferably 5 to 10 cm / s, more preferably 6 to 7 cm / s, the number of spraying is preferably 1 to 2 times, and the thickness of each spraying is preferably 1 to 5 μm, more preferably 3 to 4 μm; the dipping time is preferably 10 to 30 min, more preferably 15 to 20 min.

[0067] The present invention preferably adds an infrared shielding agent, a binder, a dispersant and water into a ball mill for ball milling and mixing to obtain a slurry; the ball-milled slurry is evenly applied to the surface of the silicon carbide aerogel by a spraying or dipping process; the aerogel coated with the slurry is dried in a vacuum oven and then heat-treated to make the coating firmly adhere to the fiber layer, thereby obtaining a material with integrated functions of high temperature resistance, wave absorption, heat preservation and infrared shielding.

[0068] In the present invention, before heat treatment, the drying temperature is preferably 60-110°C, more preferably 80-100°C; the time is preferably 6-12h, more preferably 9-11h; the heat treatment temperature is preferably 500-800°C, more preferably 650-780°C, and the time is preferably 1-3h, more preferably 2-2.8h.

[0069] The present invention provides a SiC ceramic composite aerogel prepared by the preparation method described in the above technical solution.

[0070] The present invention provides the application of the SiC ceramic composite aerogel described in the above technical solution in the field of multifunctional high-performance protective clothing. The present invention has no special limitation on the application method, and the application can be carried out according to methods well known in the art.

[0071] The present invention first prepares a silicon carbide aerogel layer: silicon carbide fibers or whiskers are mixed with a silicon source precursor, and a sol-gel reaction is carried out under specific temperature and pressure conditions. After the reaction is completed, the aerogel is dried at normal pressure or freeze-dried to obtain aerogel. During the mixing process, a nano-ferrite absorber and a flexible high molecular polymer (such as polyimide nanofibers or polyetheretherketone nanoparticles) are added simultaneously. After the aerogel is prepared, an organic silane coupling agent is used to coat its surface. The coating thickness is controlled within the range of 1 to 5 μm and the uniformity of the coating by the number of spraying times.

[0072] After the silicon carbide fiber or whisker aerogel layer is prepared, an infrared radiation coating with high reflective performance is further prepared. First, the highly reflective TiO2 or Ag powder, binder (silicon sol or aluminum sol) and dispersant are mixed and placed in a ball mill for ball milling. The ball milling time is controlled at 12 to 24 hours to ensure that the components are evenly mixed and reach an ideal dispersion state. After that, the above-mentioned slurry is evenly applied to the surface of the aerogel by spraying or dipping. During the operation, the coating thickness is precisely controlled within a suitable range of 1 to 5 μm. Subsequently, the aerogel coated with the slurry is dried to remove the moisture and volatile components therein, and then sintered to make the coating firmly attached to the fiber layer, thereby successfully preparing an infrared radiation coating @ silicon carbide aerogel material, forming a complete material with high temperature resistance, wave absorption, heat preservation and infrared shielding integrated functions. This material can effectively protect users from the threats of high temperature, low temperature, radar and infrared detection in extreme environments, greatly expanding its application potential in military, aerospace, special industries and other fields with extremely high requirements for environmental adaptability and concealment.

[0073] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0074] In the following examples, ferrites were purchased from Gaoke Magnetic Technology Co., Ltd.

[0075] Both polyetheretherketone and polyimide are sourced from Jiangxi Xiancai Nanofiber Technology Co., Ltd.

[0076] Example 1

[0077] 1) Raw material preparation

[0078] 10g of silicon carbide fiber with a diameter of 0.5μm and an aspect ratio of 60 was selected; 1g of tetraethyl orthosilicate (TEOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.6mol / L; nickel zinc ferrite powder with an average particle size of 60nm was weighed according to a nickel zinc ferrite to silicon carbide fiber mass ratio of 10:1; polyimide nanofiber was weighed as a flexible polymer according to 25% of the mass of the silicon carbide fiber;

[0079] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 300 rpm for 9 hours to obtain a mixed material.

[0080] 2) Sol-gel reaction

[0081] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 4.5, and the mixture was placed in a constant temperature water bath at 70°C for reaction for 15 hours. Stirring was continued during the reaction and the stirring speed was adjusted to 350 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -50°C, and the freeze drying time was 72 hours to obtain silicon carbide aerogel.

[0082] 3) Surface treatment

[0083] The commercially available organosilane coupling agent KH-550 was prepared into an organosilane coupling agent KH-550 solution with 12% by mass using ethanol, and the obtained silicon carbide aerogel was soaked at room temperature for 18 hours, and then placed in an oven at 80°C for 7 hours to obtain an aerogel with a hydrophobic layer.

[0084] 4) Preparation of infrared radiation coating

[0085] Weigh 40wt% of TiO2 powder with a particle size of 60nm, 20wt% of silica sol (concentration of 30wt%), 2wt% of dispersant sodium hexametaphosphate and 38wt% of deionized water, add them into a ball mill, the ball mill speed is 350rpm, the ball milling time is 18h, and the ball-to-material ratio is 2:1 to obtain a slurry;

[0086] The slurry was evenly applied on the surface of the silicon carbide fiber aerogel layer by a spraying process. The spray gun moved at a speed of 7 cm / s, sprayed once, and the spraying thickness was controlled to be 3 μm. The aerogel coated with the slurry was placed in a vacuum oven, dried at 80°C for 9 hours, and then sintered at 650°C for 2 hours to obtain a composite aerogel material.

[0087] Example 2

[0088] 1) Raw material preparation

[0089] 10g of silicon carbide whiskers with a diameter of 0.3μm and an aspect ratio of 40 were selected; 0.9g of tetraethyl orthosilicate (TEOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.4mol / L; zinc ferrite powder with an average particle size of 30nm was weighed according to a mass ratio of nickel zinc ferrite to silicon carbide whiskers of 10:1; polyetheretherketone nanofibers were weighed as flexible polymers according to 15% of the mass of silicon carbide whiskers;

[0090] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 320 rpm for 8 hours to obtain a mixed material.

[0091] 2) Sol-gel reaction

[0092] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 3.5, and the mixture was placed in a constant temperature water bath at 60°C for reaction for 10 hours. During the reaction, stirring was continued and the stirring speed was adjusted to 320 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -45°C, and the freeze drying time was 60 hours to obtain silicon carbide aerogel.

[0093] 3) Surface treatment

[0094] The commercially available organic silane coupling agent KA200 was prepared into an organic silane coupling agent KA200 solution with ethanol having a mass fraction of 8%. The obtained silicon carbide aerogel was soaked at room temperature for 15 hours and then dried in an oven at 70° C. for 6 hours to obtain an aerogel with a hydrophobic layer.

[0095] 4) Preparation of infrared radiation coating

[0096] Weigh 40wt% of Ag powder with a particle size of 30nm, 20wt% of silica sol (concentration of 30wt%), 2wt% of dispersant sodium hexametaphosphate and 38wt% of deionized water, add them into a ball mill, the ball mill speed is 320rpm, the ball milling time is 15h, and the ball-to-material ratio is 2:1 to obtain a slurry;

[0097] The silicon carbide whisker aerogel was impregnated into the slurry by an impregnation process for 20 min. The aerogel coated with the slurry was placed in a vacuum oven, dried at 70°C for 7 h, and then sintered at 700°C for 1.5 h to obtain a composite aerogel material.

[0098] Example 3

[0099] 1) Raw material preparation

[0100] 10g of silicon carbide fiber with a diameter of 0.8μm and an aspect ratio of 80 was selected; 0.8g of methyl orthosilicate (TMOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.8mol / L; nickel ferrite powder with an average particle size of 80nm was weighed according to a mass ratio of nickel zinc ferrite to silicon carbide fiber of 10:1; polyimide nanofiber was weighed as a flexible polymer according to 30% of the mass of the silicon carbide fiber;

[0101] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 380 rpm for 10 hours to obtain a mixed material.

[0102] 2) Sol-gel reaction

[0103] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 5.5, and the mixture was placed in a constant temperature water bath at 80°C for reaction for 20 hours. Stirring was continued during the reaction and the stirring speed was adjusted to 380 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -55°C, and the freeze drying time was 84 hours to obtain silicon carbide aerogel.

[0104] 3) Surface treatment

[0105] The commercially available organosilane coupling agent KH570 was prepared into an organosilane coupling agent KH-570 solution with a mass fraction of 16% by ethanol, and the obtained silicon carbide aerogel was soaked at room temperature for 20 hours, and then placed in a 90° C. oven for drying for 8 hours to obtain an aerogel with a hydrophobic layer.

[0106] 4) Preparation of infrared radiation coating

[0107] Weigh 40wt% of TiO2 powder with a particle size of 80nm, 20wt% of aluminum sol (concentration of 30wt%), 2wt% of dispersant sodium hexametaphosphate and 38wt% of deionized water, add them into a ball mill, the ball mill speed is 380rpm, the ball milling time is 20h, and the ball-to-material ratio is 2:1 to obtain a slurry;

[0108] The slurry was evenly applied on the surface of the silicon carbide fiber aerogel layer by a spraying process. The movement speed of the spray gun was 9 cm / s. The spraying thickness was controlled to be 4 μm after one spraying. The aerogel coated with the slurry was placed in a vacuum oven, dried at 90°C for 10 h, and then sintered at 750°C for 2.5 h to obtain a composite aerogel material.

[0109] Example 4

[0110] 1) Raw material preparation

[0111] 10g of silicon carbide whiskers with a diameter of 0.2μm and an aspect ratio of 35 were selected; 0.5g of methyl orthosilicate (TMOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.3mol / L; mixed ferrite powder with an average particle size of 40nm (nickel oxide and zinc oxide were mixed in a mass ratio of 1:1) was weighed according to a mass ratio of nickel zinc ferrite to silicon carbide whiskers of 10:1; polyetheretherketone nanoparticles were weighed as a flexible polymer according to 12% of the mass of the silicon carbide whiskers;

[0112] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 330 rpm for 7 hours to obtain a mixed material.

[0113] 2) Sol-gel reaction

[0114] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 4.0, and the mixture was placed in a constant temperature water bath at 55°C for reaction for 8 hours. Stirring was continued during the reaction and the stirring speed was adjusted to 330 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -42°C, and the freeze drying time was 56 hours to obtain silicon carbide aerogel.

[0115] 3) Surface treatment

[0116] The organosilane coupling agent KH-570 produced by Nanjing Sysbo Organic Silicone Co., Ltd. was prepared into a 6% by mass organosilane coupling agent KH-570 solution using ethanol. The obtained silicon carbide aerogel was soaked at room temperature for 13 hours and then dried in an oven at 65°C for 6.5 hours to obtain an aerogel with a hydrophobic layer.

[0117] 4) Preparation of infrared radiation coating

[0118] Weigh 40wt% of TiO2 powder with a particle size of 40nm, 20wt% of aluminum sol (concentration of 30wt%), 2wt% of dispersant sodium pyrophosphate and 38wt% of deionized water, add them into a ball mill, the ball mill speed is 330rpm, the ball milling time is 16h, and the ball-to-material ratio is 2:1 to obtain a slurry;

[0119] The silicon carbide whisker aerogel was impregnated into the slurry by an impregnation process for 15 min. The aerogel coated with the slurry was placed in a vacuum oven, dried at 65°C for 8 h, and then sintered at 550°C for 1.2 h to obtain a composite aerogel material.

[0120] Example 5

[0121] 1) Raw material preparation

[0122] 10g of silicon carbide fiber with a diameter of 0.9μm and an aspect ratio of 90 was selected; 0.5g of methyl orthosilicate (TMOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.9mol / L; nickel ferrite powder with an average particle size of 90nm was weighed according to a mass ratio of nickel zinc ferrite to silicon carbide fiber of 10:1; polyimide nanoparticles were weighed as a flexible polymer according to 35% of the mass of the silicon carbide fiber;

[0123] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 390 rpm for 11 hours to obtain a mixed material.

[0124] 2) Sol-gel reaction

[0125] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 5.0, and the mixture was placed in a constant temperature water bath at 85°C for reaction for 22 hours. Stirring was continued during the reaction and the stirring speed was adjusted to 390 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -58°C, and the freeze drying time was 90 hours to obtain silicon carbide aerogel.

[0126] 3) Surface treatment

[0127] The commercially available organosilane coupling agent KH-792 was prepared into an organosilane coupling agent KH-792 solution with a mass fraction of 18% using ethanol. The obtained silicon carbide aerogel was soaked at room temperature for 22 hours and then dried in an oven at 100°C for 7.5 hours to obtain an aerogel with a hydrophobic layer.

[0128] 4) Preparation of infrared radiation coating

[0129] 40 wt % of Ag powder with a particle size of 90 nm, 20 wt % of silica sol (concentration of 30 wt %), 2 wt % of dispersant sodium pyrophosphate and 38 wt % of deionized water were weighed and added into a ball mill at a speed of 390 rpm for 22 h and a ball-to-material ratio of 2:1 to obtain a slurry;

[0130] The slurry was evenly applied to the surface of the silicon carbide fiber aerogel layer by a spraying process. The spray gun moved at a speed of 6 cm / s. The spraying was performed once so that the spraying thickness was 5 μm. The aerogel coated with the slurry was placed in a vacuum oven, dried at 100°C for 11 hours, and then sintered at 780°C for 2.8 hours to obtain a composite aerogel material.

[0131] Example 6

[0132] 1) Raw material preparation

[0133] 10g of silicon carbide whiskers with a diameter of 0.1μm and an aspect ratio of 30 were selected; 1g of tetraethyl orthosilicate (TEOS) was dissolved in ethanol to prepare a silicon source precursor solution with a concentration of 0.2mol / L; zinc ferrite powder with an average particle size of 20nm was weighed according to a mass ratio of nickel zinc ferrite to silicon carbide whiskers of 10:1; polyetheretherketone nanoparticles were weighed as a flexible polymer according to 10% of the mass of the silicon carbide whiskers;

[0134] All the above raw materials were placed in a stirring device, and stirred and mixed at a rotation speed of 300 rpm for 6 hours to obtain a mixed material.

[0135] 2) Sol-gel reaction

[0136] Hydrochloric acid (concentration of 0.1 mol / L) was added dropwise to the mixture, the pH value of the solution was adjusted to 3.0, and the mixture was placed in a constant temperature water bath at 50°C for reaction for 6 hours. Stirring was continued during the reaction and the stirring speed was adjusted to 300 rpm until a gel was formed. The gel was then transferred to a freeze drying device, the freeze drying temperature was set to -40°C, and the freeze drying time was 48 hours to obtain silicon carbide aerogel.

[0137] 3) Surface treatment

[0138] The commercially available organosilane coupling agent KH-792 was prepared into a 5% by mass organosilane coupling agent KH-792 solution using ethanol, and the obtained silicon carbide aerogel was soaked at room temperature for 12 hours and then dried in a 60°C oven for 6 hours to obtain an aerogel with a hydrophobic layer.

[0139] 4) Preparation of infrared radiation coating

[0140] 40 wt% of Ag powder with a particle size of 30 nm, 20 wt% of silica sol (concentration of 30 wt%), 2 wt% of sodium pyrophosphate (dispersant) and 38 wt% of deionized water were weighed and added into a ball mill at a speed of 300 rpm for 12 h and a ball-to-material ratio of 2:1 to obtain a slurry;

[0141] The silicon carbide whisker aerogel was impregnated into the slurry by an impregnation process for 10 min. The aerogel coated with the slurry was placed in a vacuum oven, dried at 60°C for 6 h, and then sintered at 500°C for 1 h to obtain a composite aerogel material.

[0142] Structural characterization and performance testing

[0143] 1) Figure 1 The microscopic surface morphology of the coating in the composite aerogel prepared in Example 1; Figure 1 It can be seen that the infrared radiation coating is well bonded to the aerogel matrix, indicating that there is a high interfacial compatibility between the coating and the matrix. The coating surface is uniform, and this uniformity helps to enhance the infrared stealth effect of the coating and reduce the reflection and scattering of infrared radiation.

[0144] 2) Figure 2 The infrared radiation performance results of the composite aerogel coating prepared in Example 3 show that the material exhibits low infrared radiation performance, indicating that it has excellent infrared stealth capability and is suitable as an infrared stealth material.

[0145] 3) The high temperature resistance, wave absorption, and infrared shielding properties of the composite aerogel prepared in Example 3 were tested using a sol-gel method.

[0146] Figure 3 The high temperature resistance results of the composite aerogel prepared in Example 3 are as follows: Figure 3 The results show that the aerogel material prepared by the above method has excellent high temperature resistance.

[0147] High temperature resistance: The material shows good stability in high temperature environment and is suitable for extreme high temperature environment.

[0148] Figure 4 The microwave absorption performance results of the composite aerogel prepared in Example 3 are as follows: Figure 4 The results show that: Radar absorbing performance: the material can effectively absorb radar waves and prevent radar detection.

[0149] 3. The toughness of the aerogel layer was tested using the method described in the national standard GB / T 1041-2008. The results showed that the aerogel prepared by the above method has excellent toughness of 0.23Mpa. The toughness is mainly attributed to the organic matter in the material, which provides good support for the aerogel, making it suitable as a wearable material.

[0150] Summarize

[0151] Microscopic morphology: The infrared radiation coating is well combined with the aerogel matrix, and the surface is uniform, which enhances the infrared stealth effect.

[0152] Comprehensive performance: The material has excellent high temperature resistance, wave absorption, heat preservation and infrared shielding properties, suitable for extreme environments and multi-functional needs.

[0153] Toughness: The aerogel layer has excellent toughness, which is mainly attributed to the organic matter and is suitable for use in wearable materials.

[0154] These test results indicate that the SiC ceramic composite aerogel provided by the present invention has broad application prospects in the field of functional clothing and can meet the needs of high temperature resistance, radar and infrared stealth, and thermal insulation.

[0155] In summary, the present invention successfully prepares a unique aerogel by mixing silicon carbide with a silicon source precursor, and further constructs an infrared radiation coating with high reflectivity by sol-gel reaction and drying. The composite aerogel is composed of a silicon carbide aerogel layer and an infrared shielding layer, showing excellent comprehensive performance. It not only has high temperature resistance, can stably play a role in extreme environments, but also has excellent wave absorption and heat preservation performance, and can effectively resist the interference of external heat and electromagnetic waves. More importantly, the presence of the infrared shielding layer enables it to effectively prevent radar and infrared detection, greatly improving its concealment in special scenes. At the same time, the composite aerogel can also enhance the toughness of the aerogel layer, overcoming the limitations of traditional materials. Compared with existing clothing materials, the SiC composite aerogel of the present invention successfully solves the problem of being difficult to simultaneously meet the requirements of high temperature resistance, radar and infrared stealth, and heat preservation, and provides a new and high-performance material selection for the field of functional clothing, with broad application prospects and huge market potential, and is expected to promote the further development and innovation of the functional clothing industry.

[0156] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a SiC ceramic composite aerogel, characterized in that: The following steps are involved: The silicon carbide raw material, the silicon source precursor, the nano absorber, the high molecular polymer and the organic solvent are mixed to obtain a mixed material; The mixed material is mixed with an acid catalyst, subjected to a sol-gel reaction, and then dried to obtain a silicon carbide aerogel; The silicon carbide aerogel is immersed in an organic silane coupling agent solution to perform surface treatment to obtain an aerogel containing a hydrophobic layer; The infrared shielding agent, the binder, the dispersant and water are mixed by ball milling to obtain a slurry; After applying the slurry to the surface of the aerogel containing the hydrophobic layer, heat treatment is performed to obtain a SiC ceramic composite aerogel; The nano absorber includes ferrite; the infrared shielding agent includes TiO2 or Ag.

2. The preparation method according to claim 1, characterized in that: The silicon carbide raw material is silicon carbide fiber or silicon carbide whisker; the diameter of the silicon carbide raw material is 0.1-1 μm, and the aspect ratio is 30-100; The silicon source precursor includes ethyl orthosilicate or methyl orthosilicate; the mass ratio of the silicon source precursor to the silicon carbide raw material is 1:10-20.

3. The preparation method according to claim 1, characterized in that: The average particle size of the nano absorber is 20 to 100 nm; the ferrite includes one or more of nickel ferrite, zinc ferrite and nickel zinc ferrite; the mass ratio of the nano absorber to the silicon carbide raw material is 5 to 10:1; The high molecular polymer includes polyimide or polyetheretherketone; the mass of the high molecular polymer is 10-40% of the mass of the silicon carbide raw material.

4. The preparation method according to claim 1, characterized in that: The acid catalyst includes hydrochloric acid; the temperature of the sol-gel reaction is 50 to 90° C., the pH value is 3 to 6, and the reaction time is 6 to 24 hours.

5. The preparation method according to claim 1, characterized in that: In the step of preparing silicon carbide aerogel, the drying method is atmospheric pressure drying or freeze drying. The atmospheric pressure drying temperature is 70 to 80° C. and the time is 6 to 8 hours; the freeze drying temperature is -40 to -60° C. and the time is 48 to 96 hours.

6. The preparation method according to claim 1, characterized in that: The organic silane coupling agent in the organic silane coupling agent solution includes one or more of KH550, KA200, KH570 and KH792; the mass fraction of the organic silane coupling agent solution is 5-20%; the temperature of the surface treatment is 25-110° C., and the time is 12-24 hours.

7. The preparation method according to claim 1, characterized in that: The particle size of the infrared shielding agent is 20 to 100 nm; The binder includes one or more of aluminum sol, silica sol and aluminum dihydrogen phosphate; the dispersant includes sodium hexametaphosphate or sodium pyrophosphate; The mass ratio of the infrared shielding agent, the binder, the dispersant and the water is 40:10-20:1-2:38-49; The ball milling mixing conditions include: a ball mill speed of 300 to 400 rpm, a ball milling time of 12 to 24 hours, and a ball-to-material ratio of 1 to 5:

1.

8. The preparation method according to claim 1 or 7, characterized in that: The slurry is applied to the surface of the aerogel containing the hydrophobic layer by spraying or dipping; The moving speed of the spray gun used for spraying is 5-10 cm / s, the number of spraying is 1-2 times, and the thickness of each spraying is 1-5 μm; The immersion time is 10 to 30 minutes; The heat treatment temperature is 500-800° C. and the time is 1-3 hours.

9. The SiC ceramic composite aerogel prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the SiC ceramic composite aerogel according to claim 9 in the field of multifunctional and high-performance protective clothing.

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