High-temperature-resistant aerogel calcium silicate composite material and preparation method thereof

Abstract

The invention relates to the field of aerogel composite materials, in particular to a high-temperature-resistant aerogel calcium silicate composite material and a preparation method thereof, and solves the problems that the mechanical property of aerogel is reduced and the service life is shortened due to the fact that the interface bonding force between an existing aerogel phase and a reinforced phase is easily limited by the material and influenced by modified substances. The preparation method comprises the following steps: firstly, dispersing calcium salt in an aqueous solution of ethanol to form a calcium salt solvent, sequentially adding polymethylacrylic acid and 1, 4-butanediol diglycidyl ether to form a calcium salt gel precursor, placing activated fibers in a polyphenol chitosan solution for reaction, placing reinforced fibers in a molybdenum disulfide turbid solution for ultrasonic dispersion, and drying to obtain the composite material. Then carrying out hydrothermal reaction, immersing the composite fibers into a calcium salt gel precursor for negative pressure vacuum adsorption, and drying to form the high-temperature-resistant aerogel calcium silicate composite material. The interface bonding capacity and the heat resistance of the composite material can be enhanced, and the mechanical property and the heat insulation property of the material at high temperature are remarkably enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogel composite materials, and specifically relates to a high-temperature resistant aerogel calcium silicate composite material and a preparation method thereof. Background Art

[0002] An aerogel is a solid material with a nano-porous network structure. Its high porosity enables it to have excellent heat insulation ability. The preparation of actual products using aerogels is mainly composed of various inorganic fibers, nano-sized silica aerogel fillers and other materials as the main body, with water as the dispersion medium, adding special adhesives, and making a viscous slurry through fiber loosening and stirring. The composite material has low density and extremely light weight, with gases or air occupying most of its volume. Related aerogel composite materials are widely used in military aerospace, thermal pipelines, petrochemical industry, new energy and other fields, and show excellent heat insulation, fire prevention and mechanical properties in these fields. However, the strength of the aerogel itself is low, and most of them require composite reinforcement materials to improve their mechanical properties.

[0003] The development of composite materials is limited by the material properties between the aerogel phase and the reinforcing phase, resulting in insufficient interfacial bonding strength between the two phases, which may cause interfacial debonding during long-term use or in extreme environments, leading to a decrease in heat resistance or mechanical properties, and thus causing cracking or failure of the composite material.

[0004] In the development of related aerogel materials, silicon dioxide is mainly used as the main material of the aerogel. There are also aluminum oxide or polymer-based aerogels, but they all have the defects of weak absorbability and mechanical properties. With the development, calcium silicate is used as a reinforcing material, enabling the mechanical properties of the aerogel to be significantly improved. However, it is still impossible to completely avoid moisture absorption in a humid environment, and the performance of the material will decline after long-term use. In subsequent research and development, the aerogel material was hydrophobically modified. The introduced organic functional groups such as carboxyl and amino groups will change the interaction between nanoparticles, restricting the effective connection of the reinforcing phase, resulting in a loose aerogel skeleton. And the modified substances such as silane coupling agents will combine with the hydroxyl groups on the aerogel, forming a grid-like structure with increased rigidity, which is prone to cracking rather than deformation. Therefore, it is necessary to improve and adjust the combination of the aerogel phase and the reinforcing phase. Summary of the Invention

[0005] In order to solve the problem that the interfacial bonding force between the existing aerogel phase and the reinforcing phase is easily restricted by the material itself and the modified substances, resulting in a decrease in the mechanical properties and lifespan of the aerogel, the present invention provides a high-temperature resistant aerogel calcium silicate composite material and a preparation method thereof. The technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present application provides a method for preparing a high-temperature resistant aerogel calcium silicate composite material, including the following specific preparation steps:

[0007] S1. Preparation of a liquid sol: Prepare an aqueous solution of ethanol, disperse a calcium salt in the aqueous solution of ethanol to form a calcium salt solvent, and successively add polymethacrylic acid and 1,4-butanediol diglycidyl ether to the calcium salt solvent for reaction to form a calcium salt gel precursor;

[0008] S2. Pretreatment of the reinforcing phase: Place polyphenol chitosan in an acetic acid solution and stir to form a polyphenol chitosan solution. Then place the reinforcing fiber in an APTES toluene solution to form an activated fiber, and place the activated fiber in the polyphenol chitosan solution for reaction. After the combination is completed, a reinforcing fiber filament is obtained;

[0009] S3. Composite of the two-phase materials: Mix sodium molybdate and thiourea in deionized water, then heat for a hydrothermal reaction to form a molybdenum disulfide turbid solution. Place the reinforcing fiber filament in the molybdenum disulfide turbid solution for ultrasonic dispersion, and then perform a hydrothermal reaction to obtain a composite fiber filament;

[0010] S4. Post-treatment of the composite gel: Immerse the composite fiber filament in the calcium salt gel precursor for negative pressure vacuum adsorption, let it stand and then replace the solvent, and then dry to form a high-temperature resistant aerogel calcium silicate composite material.

[0011] In the present application, by using multi-shell chitosan to modify the surface of the reinforcing fiber, the interfacial bonding ability between the fiber and the matrix can be effectively enhanced, the mechanical properties of the composite material are improved, the tensile strength and compressive strength are increased, and good structural integrity performance can be maintained at high temperatures. When the two-phase components are combined in the present application, molybdenum disulfide is also added for in-situ modification, so that molybdenum disulfide grows on the surface of the reinforcing fiber filament. The operation of this step is reflected in the specific implementation manner, which can make the reinforcing fiber filament maintain the toughness of the three-dimensional grid after being affected by high temperature, and will not cause excessive cross-linking of functional groups and the skeleton, thereby reducing the increase in the rigidity of the micro-material and reducing the generation of cracks, and having better interfacial bonding ability.

[0012] In addition, the molybdenum disulfide introduced in the present application has excellent stability at high temperatures, and its lamellar structure can effectively prevent the conduction of heat, thereby significantly reducing the influence of temperature on the interfacial bonding between the composite materials therein, indirectly enhancing the mechanical properties of the composite material, and finally reflected in the thermal insulation stability of the material.

[0013] The present application uses acetic acid to disperse polyphenol chitosan, which can break the hydrogen bonds between chitosan molecules, so as to dissolve evenly. And acetic acid will relieve the degradation of chitosan at low temperature, stabilize the viscosity of the solution, improve the controllability of the process, and make polyphenol chitosan carry a positive charge, which is convenient for subsequent electrostatic adsorption with the fiber surface, so as to better combine.

[0014] Preferably, in step S1, the volume ratio of the aqueous ethanol solution is 8-12:1, the solid-liquid ratio of the calcium salt to the aqueous ethanol solution is 5-30 g:200 mL, the solid-liquid ratio of polymethacrylic acid to the aqueous ethanol solution is 1-10 g:100 mL, and the dosage of 1,4-butanediol diglycidyl ether is 0.5-2 times the added mass of polymethacrylic acid.

[0015] Preferably, in step S1, the temperature at which 1,4-butanediol diglycidyl ether is added to the calcium salt solvent is 0-10°C.

[0016] Preferably, the reinforcing fiber in step S2 is one of silica fiber, silica ceramic fiber, carbon nanofiber or hollow micro-nanofiber, the mass fraction of the polyphenol chitosan solution is 1 wt% - 8 wt%, the volume fraction of the glacial acetic acid solution is 2-6%, and the volume concentration of APTES in the APTES toluene solution is 1-10%.

[0017] In the selection of the above reinforcing fibers, silica fibers with a size of 9-11 microns are used, silica ceramic fibers with a size of 2-5 microns are used, carbon nanofibers with a diameter of about 100-400 nanometers and a length of 5-20 microns are used, and hollow micro-nanofibers with a diameter of 80-150 nanometers are used, which can greatly improve the comprehensive performance of the aerogel composite material.

[0018] Preferably, in step S2, the activation time of the reinforcing fiber in the APTES toluene solution is 1-2 h, the activation temperature is 60-80°C, the reaction time of the activated fiber in the polyphenol chitosan solution is 4-12 h, and the reaction temperature is 15-60°C.

[0019] Preferably, in step S3, the mixing mass ratio of sodium molybdate to thiourea is 5:5-12, the temperature of the hydrothermal reaction is 180-220°C, the reaction time is 12-24 h, the ultrasonic power of the ultrasonic dispersion is 200-400 W, the ultrasonic time is 5-30 min, and the temperature of the hydrothermal reaction of the reinforcing fiber filaments in the molybdenum disulfide turbid solution is 120-160°C, and the hydrothermal reaction time is 6-12 h.

[0020] Preferably, in step S4, the pressure of the negative pressure vacuum adsorption is -0.08 MPa to -0.10 MPa, the negative pressure vacuum adsorption time is 30-60 min, the standing time is 6-12 h, the replacement solvent is ethanol gradient replacement, the replacement time interval is 6 h, and the replacement times are 3-5 times.

[0021] Preferably, the solvent concentration for gradient replacement is 30% → 50% → 70% → 100% (v / v).

[0022] Preferably, in step S4, supercritical drying is used for drying. The supercritical drying medium is CO2, the temperature is 30 - 45 °C, the pressure is 6 - 12 MPa, and the time is 2 - 4 h.

[0023] On the other hand, the high-temperature resistant aerogel calcium silicate composite material prepared by the above preparation method of the present application has excellent high-temperature resistance, good mechanical properties, and a unique pore structure, and can be widely used in the fields of aerospace and high-temperature heat insulation.

[0024] The beneficial effects of the present invention are:

[0025] In the process of preparing the composite material of the present application, first, the reinforcing fibers are modified with polyphenol chitosan, which can initially enhance the interfacial bonding ability. Then, sodium molybdate and thiourea are used for hydrothermal reaction to form microscopic particles that can grow on the surface of the fiber filaments, and through a secondary hydrothermal reaction, they are grown and bonded to the surface of the fiber filaments. The introduction of molybdenum disulfide can greatly improve the interfacial bonding between the fiber filaments and the aerogel precursor. Its unique existence will weaken the bonding of temperature to the two-phase substances - the aerogel phase and the reinforcing fiber phase.

[0026] Molybdenum disulfide forms a nanoscale barrier. When a small number of cracks occur, the surface area of molybdenum disulfide and the van der Waals force between layers can deflect the propagation path of the cracks, reduce straight penetration, and effectively delay crack propagation; and after chitosan is combined with molybdenum disulfide, anchor points will be formed in the three-dimensional grid, and the segments of chitosan can also disperse stress through deformation to induce crack bypass; secondly, polyphenol chitosan can form a coordination bond with metals through surface chemical groups to form a cross-linked network on the surface of molybdenum disulfide, enhancing the stability of molybdenum disulfide while inhibiting interfacial separation.

[0027] Moreover, the surface roughness of the fibers modified with chitosan increases, forming a mechanical interlock with the matrix material. And when the fibers are pulled out, the fibers modified with chitosan and molybdenum disulfide will form interfacial friction in the pulling-out path, increasing the friction coefficient and enhancing the interfacial bonding ability. Description of the Drawings

[0028] Figure 1 It is a graph of the thermal conductivity data of the examples and comparative examples of the present invention.

[0029] Figure 2 It is a graph of the shrinkage rate data of the examples and comparative examples of the present invention at different temperatures. Detailed Embodiments

[0030] Below, reference will be made to the reference appendix Figures 1 to 2The embodiments of the present invention are described in detail. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and are not intended to limit the protection scope of the present invention.

[0031] Example 1

[0032] S1. Prepare an ethanol aqueous solution with a volume ratio of 10:1. Disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 15 g:200 mL to form a calcium salt solvent. Add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 3 g:100 mL, and then add 1,4-butanediol diglycidyl ether with a mass 1.2 times that of polymethacrylic acid, and react at 5 °C to form a calcium salt gel precursor.

[0033] S2. Select silica fiber as the reinforcing fiber. Prepare an acetic acid solution with a volume fraction of 4%. Dissolve polyphenol chitosan in it at a mass fraction of 4 wt% to form a polyphenol chitosan solution. Place the reinforcing fiber in an APTES toluene solution with a volume concentration of 8%, and activate it at 70 °C for 1.5 h to obtain an activated fiber. Immerse the activated fiber in the polyphenol chitosan solution and react at 45 °C for 8 h to obtain a reinforced fiber filament after the combination is completed.

[0034] S3. Mix sodium molybdate and thiourea in a mass ratio of 5:9, and place them in deionized water to form a mixed solution. The concentrations of sodium molybdate and thiourea in deionized water are 10 g / L. Perform a hydrothermal reaction at 200 °C for 18 h to form a molybdenum disulfide turbid solution. Place the reinforced fiber filament in the turbid solution, ultrasonically disperse it at a power of 300 W for 20 min, and then perform a hydrothermal reaction at 140 °C for 9 h to obtain a composite fiber filament.

[0035] S4. Immerse the composite fiber filament in the calcium salt gel precursor. The mass ratio of the composite fiber filament to the calcium salt gel precursor is 1:10, and vacuum adsorb it at a pressure of -0.09 MPa for 45 min. After standing for 9 h, perform gradient solvent replacement with ethanol, and the replacement concentration sequence is 30% → 50% → 70% → 100% (v / v), with an interval of 6 h for each stage and a total of 4 replacement times. Finally, perform supercritical drying with CO2 as the medium, with a drying temperature of 40 °C, a pressure of 9 MPa, and a duration of 3 h to obtain a high-temperature resistant aerogel calcium silicate composite material.

[0036] Example 2

[0037] S1. Prepare an ethanol aqueous solution with a volume ratio of 8:1. Disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 5 g:200 mL to form a calcium salt solvent. Add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 1 g:100 mL, and then add 1,4-butanediol diglycidyl ether with a mass 0.5 times that of polymethacrylic acid, and react at 0 °C to form a calcium salt gel precursor.

[0038] S2. Select silicon dioxide ceramic fiber as the reinforcing fiber; prepare an acetic acid solution with a volume fraction of 2%, dissolve polyphenol chitosan in it at a mass fraction of 1 wt% to form a polyphenol chitosan solution; place the reinforcing fiber in an APTES toluene solution with a volume concentration of 1%, activate it at 60 °C for 1 h to obtain activated fiber; immerse the activated fiber in the polyphenol chitosan solution and react at 15 °C for 4 h, and obtain the reinforced fiber filaments after the combination is completed.

[0039] S3. Mix sodium molybdate and thiourea in a mass ratio of 5:5, place them in deionized water to form a mixed solution, and the concentrations of sodium molybdate and thiourea in deionized water are 5 g / L; carry out a hydrothermal reaction at 180 °C for 12 h to form a molybdenum disulfide turbid solution; place the reinforced fiber filaments in the turbid solution, ultrasonically disperse them at a power of 200 W for 5 min, and then carry out a hydrothermal reaction at 120 °C for 6 h to obtain composite fiber filaments.

[0040] S4. Immerse the composite fiber filaments in the calcium salt gel precursor, and the mass ratio of the composite fiber filaments to the calcium salt gel precursor is 1:5. Carry out vacuum adsorption at a pressure of -0.08 MPa for 30 min; after standing for 6 h, carry out gradient solvent replacement with ethanol, and the replacement concentration sequence is 30% → 65% → 100% (v / v), with an interval of 6 h for each stage and a total of 3 replacement times; finally, carry out supercritical drying with CO2 as the medium, with a drying temperature of 30 °C, a pressure of 6 MPa, and a duration of 2 h to prepare a high-temperature resistant aerogel calcium silicate composite material.

[0041] Example 3

[0042] S1. Prepare an ethanol aqueous solution with a volume ratio of 12:1, disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 30 g:200 mL to form a calcium salt solvent; add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 10 g:100 mL, and then add 1,4-butanediol diglycidyl ether with a mass twice that of polymethacrylic acid, and react under the condition of 10 °C to form a calcium salt gel precursor.

[0043] S2. Select carbon nanofibers as the reinforcing fiber; prepare an acetic acid solution with a volume fraction of 6%, dissolve polyphenol chitosan in it at a mass fraction of 8 wt% to form a polyphenol chitosan solution; place the reinforcing fiber in an APTES toluene solution with a volume concentration of 10%, activate it at 80 °C for 2 h to obtain activated fiber; immerse the activated fiber in the polyphenol chitosan solution and react at 60 °C for 12 h, and obtain the reinforced fiber filaments after the combination is completed.

[0044] S3. Mix sodium molybdate and thiourea in a mass ratio of 5:12, place them in deionized water to form a mixed solution, and the concentrations of sodium molybdate and thiourea in deionized water are 12 g / L; carry out hydrothermal reaction at 220 °C for 24 h to form a molybdenum disulfide turbid solution; place the reinforcing fiber filaments in the turbid solution, ultrasonically disperse them at a power of 400 W for 30 min, and then carry out hydrothermal reaction at 160 °C for 12 h to obtain composite fiber filaments.

[0045] S4. Immerse the composite fiber filaments in the calcium salt gel precursor, and the mass ratio of the composite fiber filaments to the calcium salt gel precursor is 1:20. Carry out vacuum adsorption at a pressure of -0.10 MPa for 60 min; after standing for 12 h, carry out gradient solvent replacement with ethanol, and the replacement concentration sequence is 30% → 45% → 70% → 85% → 100% (v / v), with an interval of 6 h for each stage and a total of 5 replacement times; finally, carry out supercritical drying with CO2 as the medium, with a drying temperature of 45 °C, a pressure of 12 MPa, and a duration of 4 h to obtain a high-temperature resistant aerogel calcium silicate composite material.

[0046] Comparative Example 1 - The difference between this comparative example and Example 1 is that polyphenol chitosan is not used for reactive bonding with the reinforcing fiber.

[0047] S1. Prepare an ethanol aqueous solution with a volume ratio of 10:1, disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 15 g:200 mL to form a calcium salt solvent; add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 3 g:100 mL, and then add 1,4-butanediol diglycidyl ether which is 1.2 times the mass of polymethacrylic acid, and react at 5 °C to form a calcium salt gel precursor.

[0048] S2. Select silica fiber as the reinforcing fiber; place the reinforcing fiber in an APTES toluene solution with a volume concentration of 8%, and activate it at 70 °C for 1.5 h to obtain activated fiber.

[0049] S3. Mix sodium molybdate and thiourea in a mass ratio of 5:9, place them in deionized water to form a mixed solution, and the concentrations of sodium molybdate and thiourea in deionized water are 10 g / L; carry out hydrothermal reaction at 200 °C for 18 h to form a molybdenum disulfide turbid solution; place the activated fiber in the turbid solution, ultrasonically disperse it at a power of 300 W for 20 min, and then carry out hydrothermal reaction at 140 °C for 9 h to obtain composite fiber filaments.

[0050] S4. Immerse the composite fiber filaments in the calcium salt gel precursor. The mass ratio of the composite fiber filaments to the calcium salt gel precursor is 1:10. Perform vacuum adsorption at a pressure of -0.09 MPa for 45 min. After standing for 9 h, perform gradient solvent replacement with ethanol. The replacement concentration sequence is 30% → 50% → 70% → 100% (v / v), with a 6-h interval for each stage and a total of 4 replacement times. Finally, perform supercritical drying with CO2 as the medium at a drying temperature of 40 °C, a pressure of 9 MPa, and a duration of 3 h to obtain the high-temperature resistant aerogel calcium silicate composite material.

[0051] Comparative Example 2 - The difference between this comparative example and Example 1 is that molybdenum disulfide was not used for the hydrothermal reaction of the reinforcing fiber filaments.

[0052] S1. Prepare an ethanol aqueous solution with a volume ratio of 10:1. Disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 15 g:200 mL to form a calcium salt solvent. Add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 3 g:100 mL, and then add 1,4-butanediol diglycidyl ether which is 1.2 times the mass of the polymethacrylic acid. React at 5 °C to form the calcium salt gel precursor.

[0053] S2. Select silica fiber as the reinforcing fiber. Prepare an acetic acid solution with a volume fraction of 4%. Dissolve polyphenol chitosan in it at a mass fraction of 4 wt% to form a polyphenol chitosan solution. Place the reinforcing fiber in an APTES toluene solution with a volume concentration of 8%, and activate it at 70 °C for 1.5 h to obtain the activated fiber. Immerse the activated fiber in the polyphenol chitosan solution and react at 45 °C for 8 h. After the bonding is completed, obtain the reinforcing fiber filaments.

[0054] S3. Immerse the reinforcing fiber filaments in the calcium salt gel precursor. The mass ratio of the reinforcing fiber filaments to the calcium salt gel precursor is 1:10. Perform vacuum adsorption at a pressure of -0.09 MPa for 45 min. After standing for 9 h, perform gradient solvent replacement with ethanol. The replacement concentration sequence is 30% → 50% → 70% → 100% (v / v), with a 6-h interval for each stage and a total of 4 replacement times. Finally, perform supercritical drying with CO2 as the medium at a drying temperature of 40 °C, a pressure of 9 MPa, and a duration of 3 h to obtain the high-temperature resistant aerogel calcium silicate composite material.

[0055] Comparative Example 3 - The difference between this comparative example and Example 1 is that molybdenum disulfide was not combined by in-situ reaction, but by ultrasonic dispersion of crystals.

[0056] S1. Prepare an ethanol aqueous solution with a volume ratio of 10:1. Disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 15 g:200 mL to form a calcium salt solvent. Add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 3 g:100 mL, and then add 1,4-butanediol diglycidyl ether which is 1.2 times the mass of polymethacrylic acid. React at 5 °C to form a calcium salt gel precursor.

[0057] S2. Select silica fiber as the reinforcing fiber. Prepare an acetic acid solution with a volume fraction of 4%. Dissolve polyphenol chitosan in it at a mass fraction of 4 wt% to form a polyphenol chitosan solution. Place the reinforcing fiber in an APTES toluene solution with a volume concentration of 8%, and activate it at 70 °C for 1.5 h to obtain an activated fiber. Immerse the activated fiber in the polyphenol chitosan solution and react at 45 °C for 8 h. After the combination is completed, obtain the reinforced fiber filament.

[0058] S3. Put molybdenum disulfide powder into isopropanol to form a mixed solution. The concentration of molybdenum disulfide powder in deionized water is 15 g / L. Perform ultrasonic treatment for 1 h at an ultrasonic power of 400 W to carry out exfoliation to form a molybdenum disulfide dispersion. Place the reinforced fiber filament in the molybdenum disulfide dispersion, ultrasonically disperse it at a power of 300 W for 20 min, and then carry out a hydrothermal reaction at 140 °C for 9 h to obtain a composite fiber filament.

[0059] S4. Immerse the composite fiber filament in the calcium salt gel precursor. The mass ratio of the composite fiber filament to the calcium salt gel precursor is 1:10. Carry out vacuum adsorption at a pressure of -0.09 MPa for 45 min. After standing for 9 h, carry out gradient solvent replacement with ethanol. The replacement concentration sequence is 30% → 50% → 70% → 100% (v / v), with an interval of 6 h for each stage and a total of 4 replacement times. Finally, carry out supercritical drying with CO2 as the medium, with a drying temperature of 40 °C, a pressure of 9 MPa, and a duration of 3 h to obtain a high-temperature resistant aerogel calcium silicate composite material.

[0060] Comparative Example 4 - The difference between this comparative example and Example 1 is that deionized water is used instead of the acetic acid solution.

[0061] S1. Prepare an ethanol aqueous solution with a volume ratio of 10:1. Disperse the calcium salt in the ethanol aqueous solution at a solid-liquid ratio of 15 g:200 mL to form a calcium salt solvent. Add polymethacrylic acid to the calcium salt solvent at a solid-liquid ratio of 3 g:100 mL, and then add 1,4-butanediol diglycidyl ether which is 1.2 times the mass of polymethacrylic acid. React at 5 °C to form a calcium salt gel precursor.

[0062] S2. Select silicon oxide fiber as the reinforcing fiber; dissolve polyphenol chitosan in deionized water at a mass fraction of 4 wt% to form a polyphenol chitosan solution; place the reinforcing fiber in an APTES toluene solution with a volume concentration of 8%, and activate it at 70 °C for 1.5 h to obtain activated fiber; immerse the activated fiber in the polyphenol chitosan solution and react at 45 °C for 8 h. After the combination is completed, reinforcing fiber filaments are obtained.

[0063] S3. Mix sodium molybdate and thiourea in a mass ratio of 5:9, place them in deionized water to form a mixed solution, and the concentrations of sodium molybdate and thiourea in deionized water are 10 g / L; carry out a hydrothermal reaction at 200 °C for 18 h to form a molybdenum disulfide turbid solution; place the reinforcing fiber filaments in the turbid solution, ultrasonically disperse them at a power of 300 W for 20 min, and then carry out a hydrothermal reaction at 140 °C for 9 h to obtain composite fiber filaments.

[0064] S4. Immerse the composite fiber filaments in a calcium salt gel precursor, and the mass ratio of the composite fiber filaments to the calcium salt gel precursor is 1:10. Carry out vacuum adsorption at a pressure of -0.09 MPa for 45 min; after standing for 9 h, carry out gradient solvent replacement with ethanol, and the replacement concentration sequence is 30% → 50% → 70% → 100% (v / v), with an interval of 6 h for each stage and a total of 4 replacement times; finally, carry out supercritical drying with CO2 as the medium, with a drying temperature of 40 °C, a pressure of 9 MPa, and a duration of 3 h to obtain a high-temperature resistant aerogel calcium silicate composite material.

[0065] Experiments and Data

[0066] Carry out mechanical property and heat resistance tests on the high-temperature resistant aerogel calcium silicate composite materials prepared in the above examples and comparative examples. The specific test methods are as follows:

[0067] Tensile strength: Carry out tensile strength detection according to the standard of GB / T1040.1-2018, unit: MPa.

[0068] Aerogel density: Unit: g / cm3.

[0069] High-temperature stability test: Place the material at 1000 °C, 1100 °C, and 1200 °C for 2 h, and test its shrinkage rate, unit: %.

[0070] Thermal conductivity: Unit: W / (m·K).

[0071] The specific data are shown in Table 1 and Table 2 below:

[0072] Table 1

[0073] Tensile strength Aerogel density Thermal conductivity Example 1 24.5 0.47 0.025 Example 2 24.1 0.50 0.027 Example 3 24.4 0.49 0.029 Comparative Example 1 16.7 0.39 0.033 Comparative Example 2 19.2 0.48 0.082 Comparative Example 3 17.8 0.46 0.051 Comparative Example 4 18.1 0.44 0.030

[0074] The experimental data of the high-stability test are as follows:

[0075] Table 2

[0076]

[0077]

[0078] The thermal conductivity in Table 1 above is plotted as a broken line graph as Figure 1 shown. The shrinkage rate of Table 2 above is plotted as a broken line graph, as Figure 2 shown.

[0079] Analysis

[0080] From the analysis of the data in Table 1 and Table 2 above, it can be seen that the high-temperature resistant calcium silicate aerogel composite materials prepared in Example 1, Example 2 and Example 3 have good tensile strength and low thermal conductivity, and perform well in multi-stage temperature tests, with low shrinkage rate and stable structure.

[0081] From the analysis of the experimental data in Table 1 and Table 2, it can be seen that the degree of decline in the tensile strength of Comparative Example 1 is the largest, and it shows extremely poor tolerance in multi-stage temperature tests, is easily affected by temperature, and the structure is damaged most severely. The difference between Comparative Example 1 and Example 1 is that polyphenol chitosan is not used to bind the reinforcing fibers. Therefore, it can be confirmed that the use of polyphenol chitosan can maximize the binding strength between the aerogel material and the reinforcing phase material, thereby affecting the performance of the aerogel composite material.

[0082] From the analysis of the experimental data in Table 1 and Table 2, it can be seen that the tensile strength of Comparative Example 2 has decreased to a certain extent, and it shows poor tolerance in multi-stage temperature tests, is easily affected by temperature, and the structure is damaged relatively severely. The difference between Comparative Example 2 and Example 1 is that molybdenum disulfide is not used for the hydrothermal reaction of the reinforcing fiber filaments. Therefore, it can be confirmed that the modification of molybdenum disulfide on the reinforcing phase fibers can greatly alleviate the binding ability between the aerogel phase and the reinforcing phase under high-temperature influence, thereby indirectly affecting the performance of the aerogel composite material.

[0083] From the analysis of the experimental data in Table 1 and Table 2, it can be seen that the tensile strength of Comparative Example 3 has decreased significantly, and the shrinkage rate has decreased to a certain extent in multi-stage temperature tests, is affected by temperature, and the structure is damaged moderately. The difference between Comparative Example 3 and Example 1 is that in-situ reaction combination is not used, but crystal ultrasonic dispersion combination is used. Therefore, it can be confirmed that the microparticles formed by in-situ synthesis of molybdenum disulfide have the most efficient binding performance in the hydrothermal reaction, can maximize the protection ability for the aerogel phase, thereby improving the mechanical properties and heat resistance of the aerogel composite material.

[0084] From the analysis of the experimental data in Table 1 and Table 2, it can be seen that the tensile strength of Comparative Example 4 decreased slightly and decreased relatively gently in the multi-stage temperature test. It is affected by temperature and the structural damage is less. The difference between Comparative Example 4 and Example 1 is that glacial acetic acid was not used for the dispersion of polyphenol chitosan. Therefore, it can be confirmed that the use of glacial acetic acid can greatly enhance the binding effect between polyphenol chitosan and fibers, thereby improving the subsequent binding effect between the fiber-reinforced phase and the aerogel phase, and thus indirectly improving the mechanical properties of the aerogel composite material.

[0085] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A preparation method of a high-temperature resistant aerogel calcium silicate composite material, characterized in that, It includes the following specific preparation steps: S1. Preparation of liquid sol: Prepare an aqueous solution of ethanol, disperse a calcium salt in the aqueous solution of ethanol to form a calcium salt solvent, and successively add polymethacrylic acid and 1,4-butanediol diglycidyl ether to the calcium salt solvent for reaction to form a calcium salt gel precursor; S2. Pretreatment of the reinforcing phase: Place polyphenol chitosan in an acetic acid solution and stir to form a polyphenol chitosan solution. Then place the reinforcing fiber in an APTES toluene solution to form an activated fiber, and place the activated fiber in the polyphenol chitosan solution for reaction. After the combination is completed, a reinforcing fiber filament is obtained; S3. Composite of two-phase materials: Mix sodium molybdate and thiourea in deionized water, and then heat for hydrothermal reaction to form a molybdenum disulfide turbid solution. Place the reinforcing fiber filament in the molybdenum disulfide turbid solution for ultrasonic dispersion, and then carry out hydrothermal reaction to obtain a composite fiber filament; S4. Post-treatment of the composite gel: Immerse the composite fiber filament in the calcium salt gel precursor for negative pressure vacuum adsorption, let it stand and then replace the solvent, and then dry to form a high-temperature resistant aerogel calcium silicate composite material.

2. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, wherein In the step S1, the volume ratio of the aqueous solution of ethanol is 8-12:1, the solid-liquid ratio of the calcium salt to the aqueous solution of ethanol is 5-30 g:200 mL, the solid-liquid ratio of the polymethacrylic acid to the aqueous solution of ethanol is 1-10 g:100 mL, and the dosage of 1,4-butanediol diglycidyl ether is 0.5-2 times the added mass of the polymethacrylic acid.

3. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, characterized in that, In the step S1, the temperature at which 1,4-butanediol diglycidyl ether is added to the calcium salt solvent is 0-10 °C.

4. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, characterized in that, In the step S2, the reinforcing fiber is one of silica fiber, silicon dioxide ceramic fiber, carbon nanofiber or hollow micro-nano fiber. The mass fraction of the polyphenol chitosan solution is 1 wt%-8 wt%, the volume fraction of the acetic acid solution is 2-6%, and the volume concentration of APTES in the APTES toluene solution in toluene is 1-10%.

5. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, characterized in that, In the step S2, the activation time of the reinforcing fiber in the APTES toluene solution is 1-2 h, the activation temperature is 60-80 °C, the reaction time of the activated fiber in the polyphenol chitosan solution is 4-12 h, and the reaction temperature is 15-60 °C.

6. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, characterized in that, In the step S3, the mixing mass ratio of sodium molybdate and thiourea is 5:5-12, the temperature of the hydrothermal reaction is 180-220 °C, the reaction time is 12-24 h, the ultrasonic power of the ultrasonic dispersion is 200-400 W, the ultrasonic time is 5-30 min, and the temperature of the hydrothermal reaction of the reinforcing fiber filament in the molybdenum disulfide turbid solution is 120-160 °C, and the hydrothermal reaction time is 6-12 h.

7. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 1, characterized in that, In the step S4, the pressure of the negative pressure vacuum adsorption is -0.08 MPa to -0.10 MPa, the negative pressure vacuum adsorption time is 30-60 min, the standing time is 6-12 h, the solvent replacement is carried out by gradient replacement with ethanol, the replacement time interval is 6 h, and the replacement times are 3-5 times.

8. The preparation method of a high-temperature resistant aerogel calcium silicate composite material according to claim 7, characterized in that, The solvent concentration v / v of the gradient replacement is 30% → 50% → 70% → 100%.

9. A high-temperature resistant aerogel calcium silicate composite material and a preparation method thereof according to claim 1, characterized in that, In the step S4, supercritical drying is adopted, the supercritical drying medium is CO2, the temperature is 30-45 °C, the pressure is 6-12 MPa, and the time is 2-4 h.

10. A high-temperature resistant aerogel calcium silicate composite material prepared by the preparation method according to any one of claims 1-9.

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