A bio-based aerogel and a preparation method and application thereof

Abstract

The application discloses a kind of bio-based aerogel and its preparation method and application.The preparation method of bio-based aerogel of the application includes the following steps: 1) hydrolysis is carried out by adding organic alkoxysilane with hydrolysable group into acid solution, and organic silica sol is obtained;2) organic silica sol is added into biomass dispersion liquid to prepare mixed solution, then the mixed solution and functional nanomaterial dispersion liquid are mixed, and then freeze forming is carried out, and then freeze drying and heating drying are carried out, and bio-based aerogel is obtained.The bio-based aerogel of the application has excellent mechanical properties, strong hydrophobicity, excellent flame retardancy and thermal stability, good heat insulation, simple preparation method, mild preparation conditions, green environmental protection and other advantages, and also has sensitive fire early warning function, piezoresistive sensing function and self-cleaning function and other functions, and can be applied in intelligent fire fighting, building heat insulation, transportation, aerospace and other fields on a large scale.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel materials, in particular to a bio-based aerogel and a preparation method and application thereof. BACKGROUND

[0002] Bio-based aerogels have low density, high porosity, low thermal conductivity, biodegradability and other advantages, and show good application prospects in the field of thermal insulation. However, traditional bio-based aerogels are not only flammable, but also have poor size stability and thermal stability, poor elasticity, and high moisture absorption, which greatly limits their application range. At present, the flame retardant properties of bio-based aerogels are mainly improved by chemical modification (for example: CN 115216129 A and CN 114752115 A) or adding a large amount of inorganic flame retardant (for example: CN 113045792 A, CN 114292446 A and CN 113388151 A). Although the composite materials prepared by the above methods exhibit good flame retardancy, the chemical modification process is inefficient, which not only consumes a large amount of chemical reagents, but also requires a tedious post-treatment process, and the actual application is greatly limited. In addition, due to the weak interaction between inorganic flame retardants and biomass matrix materials, the mechanical properties of the composite materials are not ideal. In recent years, with the gradual improvement of people's safety awareness and the rapid development of the Internet of Things, people have higher requirements for the fire safety and multifunctionality of materials, that is, not only the flame retardant properties of materials should be good, but also they should have sensitive fire warning function. The existing aerogel materials cannot meet the growing actual application requirements.

[0003] Therefore, it is of great significance to develop a bio-based aerogel with excellent mechanical properties, strong hydrophobicity, excellent flame retardancy and thermal stability, good thermal insulation, and sensitive fire warning function. SUMMARY

[0004] The present application aims to provide a bio-based aerogel and a preparation method and application thereof.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A preparation method of a bio-based aerogel comprises the following steps:

[0007] 1) adding an organic alkoxysilane with hydrolysable groups to an acid solution to hydrolyze, to obtain a silica sol;

[0008] 2) adding the silica sol to a biomass dispersion liquid to prepare a mixed solution, mixing the mixed solution and a functional nanomaterial dispersion liquid, and then performing freeze forming, freeze drying and heating drying to obtain the bio-based aerogel.

[0009] Preferably, the organic siloxane having hydrolysable groups in step 1) is at least one of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, propyltrimethoxysilane, and methylphenyldimethoxysilane.

[0010] Preferably, the acid solution in step 1) is at least one of an aqueous acetic acid solution with a concentration of 3-15 mmol / L, an aqueous hydrochloric acid solution with a concentration of 3-10 mmol / L, and an aqueous sulfuric acid solution with a concentration of 0.5-3.5 mmol / L.

[0011] Preferably, the mass ratio of the organic alkoxysilane having hydrolysable groups and the acid solution in step 1) is 1:2-8.

[0012] Preferably, the hydrolysis in step 1) is carried out at room temperature (25℃±5℃) for 0.5-3 h.

[0013] Preferably, the biomass dispersion liquid in step 2) is prepared by mixing biomass and water at a mass ratio of 1:50-200.

[0014] Preferably, the biomass in the biomass dispersion liquid in step 2) is at least one of bacterial cellulose, microcrystalline cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, carboxymethyl chitosan, chitosan, hydroxypropyl chitosan, chitin, alginate, lignin, and gelatin.

[0015] Preferably, the specific preparation process of the biomass dispersion liquid in step 2) is mixing biomass and water, stirring at 30-60℃ for 1-6 h, and ultrasonic dispersion at 10-30℃ for 0.5-3 h.

[0016] Preferably, the functional nanomaterial dispersion liquid in step 2) is prepared by mixing functional nanomaterials and water at a mass ratio of 1:50-200.

[0017] Preferably, the functional nanomaterials in the functional nanomaterial dispersion liquid in step 2) are at least one of aminated carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, graphene oxide, aminated graphene oxide, carboxylated graphene oxide, titanium carbide, molybdenum carbide, and titanium nitride.

[0018] Preferably, the specific preparation process of the functional nanomaterial dispersion liquid in step 2) is mixing functional nanomaterials and water, and ultrasonic dispersion at 10-30℃ for 0.5-3 h at a power of 50-300 W.

[0019] Preferably, the mass ratio of the organic silica sol and the biomass dispersion liquid in step 2) is 1:5-25.

[0020] Preferably, the specific preparation process of the mixed solution in step 2) is as follows: the organosilicon sol is added dropwise to the biomass dispersion at a temperature of 30℃~60℃ and under stirring, the dropwise addition rate is 2mL / min~4mL / min, and the stirring speed is 200rpm~800rpm.

[0021] Preferably, the mass ratio of the mixed solution and the functional nanomaterial dispersion in step 2) is 5 to 20:1.

[0022] Preferably, the freeze-forming in step 2) is carried out at -18℃ to -10℃ for 8h to 12h.

[0023] Preferably, the freeze-drying time in step 2) is 24h to 48h.

[0024] Preferably, the heating and drying in step 2) is carried out at 70℃~90℃ for 3h~15h.

[0025] Preferably, the heating and drying in step 2) further includes a preheating process, which is carried out at 50°C to 60°C for 40 to 80 minutes.

[0026] A bio-based aerogel, which is prepared by the above-described method.

[0027] Preferably, the density of the bio-based aerogel is 5 mg / cm³. 3 ~100mg / cm 3 Specific surface area is 110m² 2 / g~500m 2 / g.

[0028] A bio-based aerogel as described above is used for applications such as fire early warning, flame retardant insulation, or piezoresistive sensing.

[0029] Principle of the present application: The present application prepares an organosilica sol by hydrolyzing an organic alkoxysilane, and uniformly mixes it with a biomass dispersion liquid and a functional nanomaterial dispersion liquid, and then freezes, in the process of ice crystal growth, the functional nanomaterials self-assemble with the biological macromolecules and the silica sol, in the freezing-drying and subsequent continuous heating process, the hydrolysis formed silanol dehydrates and condenses, also with the hydroxyl groups in the biological macromolecules and the functional fillers, forming a complete covalent bond, hydrogen bond network, and an organosilica mineralized modified bio-based aerogel is prepared. Due to the uniform assembly and strong interaction of the polysiloxane network with the biological macromolecules and the functional nanomaterials, the mechanical properties of the bio-based aerogel are greatly improved. The Si-O-Si network and the functional nanomaterials together endow the bio-based aerogel with efficient flame retardancy and excellent thermal stability. At the same time, the porous structure and electrical conductivity of the aerogel make it have sensitive piezoresistive sensing performance, which can monitor different human movements in real time. The hydrophobic groups of the polysiloxane network endow the aerogel material with excellent hydrophobicity. In addition, based on the thermal resistance or thermoelectric properties of the functional nanomaterials, the bio-based aerogel has sensitive temperature sensing and fire warning functions.

[0030] Application of the bio-based aerogel of the present application: connecting the bio-based aerogel with a digital multimeter and connecting a fire warning device in series, the threshold value can be set in advance according to different needs, and the warning device is triggered when the bio-based aerogel is subjected to a certain temperature, realizing the function of fire warning; connecting the bio-based aerogel with a digital multimeter and fixing it on different parts of the human body, the piezoresistive sensing detection of human movement can be realized; when the bio-based aerogel is subjected to external dust accumulation, it can be self-cleaning by rainwater washing away the dust.

[0031] The bio-based aerogel of the present application has excellent mechanical properties, strong hydrophobicity, excellent flame retardancy and thermal stability, good thermal insulation, simple preparation method, mild preparation conditions, green environmental protection and other advantages, and also has sensitive fire warning function, piezoresistive sensing function and self-cleaning function, etc. Multiple functions, can be widely used in intelligent fire fighting, building thermal insulation, transportation, aerospace and other fields.

[0032] Specifically:

[0033] 1) The bio-based aerogel of the present application has excellent mechanical properties and hydrophobicity, and the mineralization modification of organosiloxane overcomes the defects of inherent hygroscopicity and poor mechanical properties of bio-based aerogel;

[0034] 2) The bio-based aerogel of the present application has sensitive fire warning function, which can quickly trigger the fire alarm when subjected to flame burning, realizing "active fire prevention";

[0035] 3) The bio-based aerogel of the present application has excellent flame retardance and thermal stability, and the polyorganosiloxane network and functional nanomaterials have excellent barrier property and catalytic charring property, which can greatly improve the flame retardance and thermal stability of the bio-based aerogel;

[0036] 4) The preparation process of the bio-based aerogel of the present application is simple, green and environmentally friendly, and the raw materials are easy to obtain, which is suitable for large-scale popularization and application, and conforms to the concept of green and sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The FT-IR graph of polymethylsilsesquioxane, bacterial cellulose, titanium carbide MXene and the bio-based aerogel of Example 1.

[0038] Figure 2 The SEM graph and element distribution graph of the cross section of the bio-based aerogel of Example 1.

[0039] Figure 3 The real object photo of the resilience test process of the bio-based aerogel of Example 1.

[0040] Figure 4 The vertical combustion test video screenshot of the bio-based aerogel of Example 1.

[0041] Figure 5 The fire warning test video screenshot of the bio-based aerogel of Example 1.

[0042] Figure 6 The resistance change curve of the bio-based aerogel of Example 1 monitoring finger movement.

[0043] Figure 7 The self-cleaning test video screenshot of the bio-based aerogel of Example 1. DETAILED DESCRIPTION

[0044] The present application will be further explained and described below in conjunction with specific embodiments.

[0045] Example 1:

[0046] A bio-based aerogel, the preparation method thereof comprises the following steps:

[0047] 1) Mix methyltrimethoxysilane and 6mmol / L acetic acid aqueous solution according to the mass ratio of 1:3, then stir at room temperature for 2h to obtain a silicone sol;

[0048] 2) Mix titanium carbide MXene and deionized water according to the mass ratio of 1:100, then ultrasonic dispersion at 20℃ for 2h with the ultrasonic power of 100W to obtain a functional nanomaterial dispersion liquid;

[0049] 3) The bacterial cellulose and deionized water are mixed in a mass ratio of 1:100, stirred at 30°C for 5h, and ultrasonically dispersed at 20°C for 2h to obtain a biomass dispersion liquid;

[0050] 4) The silicone sol is added dropwise to the biomass dispersion liquid at a temperature of 40°C under stirring, the dropwise speed is 2mL / min, the stirring speed is 300rpm, the mass ratio of silicone sol to biomass dispersion liquid is 1:15, and a mixed solution is obtained;

[0051] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed in a mass ratio of 10:1, then injected into a mold, frozen at -18°C for 12h, freeze-dried in a freeze dryer for 48h, preheated at 50°C for 1h, and heated in an oven at 80°C for 8h to obtain the bio-based aerogel.

[0052] Example 2:

[0053] A bio-based aerogel, the preparation method comprising the following steps:

[0054] 1) Dimethyl dimethoxy silane and 3mmol / L hydrochloric acid aqueous solution are mixed in a mass ratio of 1:2, stirred at room temperature for 3h to obtain a silicone sol;

[0055] 2) Titanium carbide MXene and deionized water are mixed in a mass ratio of 1:150, ultrasonically dispersed at 10°C for 2h, and the ultrasonic power is 200W to obtain a functional nanomaterial dispersion liquid;

[0056] 3) Microcrystalline cellulose and deionized water are mixed in a mass ratio of 1:150, stirred at 30°C for 3h, and ultrasonically dispersed at 10°C for 3h to obtain a biomass dispersion liquid;

[0057] 4) The silicone sol is added dropwise to the biomass dispersion liquid at a temperature of 30°C under stirring, the dropwise speed is 3mL / min, the stirring speed is 300rpm, the mass ratio of silicone sol to biomass dispersion liquid is 1:10, and a mixed solution is obtained;

[0058] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed in a mass ratio of 15:1, then injected into a mold, frozen at -18°C for 12h, freeze-dried in a freeze dryer for 48h, preheated at 50°C for 1h, and heated in an oven at 70°C for 6h to obtain the bio-based aerogel.

[0059] Example 3:

[0060] A bio-based aerogel, the preparation method comprising the following steps:

[0061] 1) ethyl trimethoxysilane and an aqueous solution of acetic acid with a concentration of 10 mmol / L were mixed according to a mass ratio of 1:4, and stirred at room temperature for 3 h to obtain a silica sol;

[0062] 2) carboxylated carbon nanotubes and deionized water were mixed according to a mass ratio of 1:100, and ultrasonically dispersed at 20℃ for 3 h at an ultrasonic power of 100 W to obtain a functional nanomaterial dispersion liquid;

[0063] 3) alginate and deionized water were mixed according to a mass ratio of 1:100, stirred at 50℃ for 5 h, and ultrasonically dispersed at 20℃ for 2 h to obtain a biomass dispersion liquid;

[0064] 4) the silica sol was added dropwise to the biomass dispersion liquid at a temperature of 50℃ under stirring, the dropwise speed was 2 mL / min, the stirring speed was 400 rpm, and the mass ratio of the silica sol to the biomass dispersion liquid was 1:15 to obtain a mixed solution;

[0065] 5) the mixed solution and the functional nanomaterial dispersion liquid were mixed according to a mass ratio of 15:1, and then injected into a mold, and then frozen at -18℃ for 8 h, and then freeze-dried in a freeze dryer for 24 h, and then preheated at 60℃ for 1 h, and then heated in an oven at 90℃ for 6 h to obtain a bio-based aerogel.

[0066] Example 4:

[0067] A bio-based aerogel, the preparation method comprising the following steps:

[0068] 1) diethyldiethoxysilane and an aqueous solution of hydrochloric acid with a concentration of 4 mmol / L were mixed according to a mass ratio of 1:4, and stirred at room temperature for 0.5 h to obtain a silica sol;

[0069] 2) graphene oxide and deionized water were mixed according to a mass ratio of 1:100, and ultrasonically dispersed at 10℃ for 1 h at an ultrasonic power of 200 W to obtain a functional nanomaterial dispersion liquid;

[0070] 3) carboxymethyl cellulose and deionized water were mixed according to a mass ratio of 1:150, stirred at 30℃ for 1 h, and ultrasonically dispersed at 20℃ for 1 h to obtain a biomass dispersion liquid;

[0071] 4) the silica sol was added dropwise to the biomass dispersion liquid at a temperature of 50℃ under stirring, the dropwise speed was 4 mL / min, the stirring speed was 300 rpm, and the mass ratio of the silica sol to the biomass dispersion liquid was 1:20 to obtain a mixed solution;

[0072] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed according to a mass ratio of 20:1, and then injected into a mold, and then frozen at-18℃ for 10h, and then placed in a freeze dryer for freeze drying for 32h, and then preheated at 50℃ for 1h, and then placed in an oven for heating at 70℃ for 10h, to obtain the bio-based aerogel.

[0073] Example 5:

[0074] A bio-based aerogel, the preparation method comprising the following steps:

[0075] 1) Dimethyldimethoxysilane and a sulfuric acid aqueous solution with a concentration of 3mmol / L are mixed according to a mass ratio of 1:4, and then stirred at room temperature for 1h to obtain an organosilica sol;

[0076] 2) Molybdenum carbide MXene and deionized water are mixed according to a mass ratio of 1:200, and then ultrasonically dispersed at 20℃ for 2h, with an ultrasonic power of 200W, to obtain a functional nanomaterial dispersion liquid;

[0077] 3) Gelatin and deionized water are mixed according to a mass ratio of 1:150, and then stirred at 50℃ for 3h, and then ultrasonically dispersed at 20℃ for 2h to obtain a biomass dispersion liquid;

[0078] 4) The organosilica sol is added dropwise into the biomass dispersion liquid which is in a stirring state at a temperature of 50℃, with a dropwise adding speed of 2mL / min and a stirring speed of 600rpm, and the mass ratio of the organosilica sol to the biomass dispersion liquid is 1:20, to obtain a mixed solution;

[0079] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed according to a mass ratio of 15:1, and then injected into a mold, and then frozen at-18℃ for 9h, and then placed in a freeze dryer for freeze drying for 24h, and then preheated at 60℃ for 1h, and then placed in an oven for heating at 80℃ for 6h, to obtain the bio-based aerogel.

[0080] Example 6:

[0081] A bio-based aerogel, the preparation method comprising the following steps:

[0082] 1) Diethyldiethoxysilane and an acetic acid aqueous solution with a concentration of 8mmol / L are mixed according to a mass ratio of 1:6, and then stirred at room temperature for 1h to obtain an organosilica sol;

[0083] 2) Amino-functionalized graphene oxide and deionized water are mixed according to a mass ratio of 1:100, and then ultrasonically dispersed at 10℃ for 1h, with an ultrasonic power of 200W, to obtain a functional nanomaterial dispersion liquid;

[0084] 3) Hydroxypropyl chitosan and deionized water are mixed according to a mass ratio of 1:200, and then stirred at 40℃ for 3h, and then ultrasonically dispersed at 20℃ for 1h to obtain a biomass dispersion liquid;

[0085] 4) The organic silicon sol is added dropwise to the biomass dispersion liquid with a temperature of 40℃ and stirring, the dropwise speed is 4mL / min, the stirring speed is 500rpm, the mass ratio of the organic silicon sol and the biomass dispersion liquid is 1:20, to obtain a mixed solution;

[0086] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed according to the mass ratio of 5:1, then injected into a mold, frozen at-18℃ for 10h, then placed in a freeze dryer for freeze drying for 48h, preheated at 50℃ for 1h, and then placed in an oven for heating at 80℃ for 3h, to obtain the bio-based aerogel.

[0087] Example 7:

[0088] A bio-based aerogel, the preparation method comprising the following steps:

[0089] 1) The propyl trimethoxysilane and the hydrochloric acid aqueous solution with a concentration of 10mmol / L are mixed according to the mass ratio of 1:2, then stirred at room temperature for 1h, to obtain an organic silicon sol;

[0090] 2) The titanium nitride MXene and the deionized water are mixed according to the mass ratio of 1:150, then ultrasonic dispersed at 10℃ for 2h, the ultrasonic power is 100W, to obtain a functional nanomaterial dispersion liquid;

[0091] 3) The hydroxypropyl cellulose and the deionized water are mixed according to the mass ratio of 1:50, then stirred at 40℃ for 3h, and then ultrasonic dispersed at 20℃ for 1h, to obtain a biomass dispersion liquid;

[0092] 4) The organic silicon sol is added dropwise to the biomass dispersion liquid with a temperature of 50℃ and stirring, the dropwise speed is 3mL / min, the stirring speed is 300rpm, the mass ratio of the organic silicon sol and the biomass dispersion liquid is 1:20, to obtain a mixed solution;

[0093] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed according to the mass ratio of 15:1, then injected into a mold, frozen at-18℃ for 12h, then placed in a freeze dryer for freeze drying for 32h, preheated at 60℃ for 1h, and then placed in an oven for heating at 80℃ for 3h, to obtain the bio-based aerogel.

[0094] Example 8:

[0095] A bio-based aerogel, the preparation method comprising the following steps:

[0096] 1) The methyl phenyl dimethoxysilane and the sulfuric acid aqueous solution with a concentration of 3mmol / L are mixed according to the mass ratio of 1:4, then stirred at room temperature for 2h, to obtain an organic silicon sol;

[0097] 2) The amino-functionalized carbon nanotubes and deionized water are mixed in a mass ratio of 1:100, and then ultrasonic dispersion is carried out at 20°C for 2 hours, with an ultrasonic power of 300 W, to obtain a functional nanomaterial dispersion liquid;

[0098] 3) The chitin and deionized water are mixed in a mass ratio of 1:100, and then stirring is carried out at 50°C for 5 hours, and then ultrasonic dispersion is carried out at 20°C for 1 hour, to obtain a biomass dispersion liquid;

[0099] 4) The silicone sol is added dropwise to the biomass dispersion liquid in a stirring state at a temperature of 60°C, with a dropwise addition speed of 3 mL / min and a stirring speed of 600 rpm, and the mass ratio of the silicone sol to the biomass dispersion liquid is 1:15, to obtain a mixed solution;

[0100] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed in a mass ratio of 15:1, and then injected into a mold, and then frozen at -18°C for 8 hours, and then placed in a freeze dryer for freeze drying for 48 hours, and then preheated at 60°C for 1 hour, and then placed in an oven for heating at 90°C for 4 hours, to obtain a bio-based aerogel.

[0101] Example 9:

[0102] A bio-based aerogel, a preparation method thereof comprising the following steps:

[0103] 1) The ethyl trimethoxysilane and an acetic acid aqueous solution with a concentration of 6 mmol / L are mixed in a mass ratio of 1:6, and then stirring is carried out at room temperature for 2 hours, to obtain a silicone sol;

[0104] 2) The hydroxyl-functionalized carbon nanotubes and deionized water are mixed in a mass ratio of 1:150, and then ultrasonic dispersion is carried out at 20°C for 2 hours, with an ultrasonic power of 200 W, to obtain a functional nanomaterial dispersion liquid;

[0105] 3) The lignin and deionized water are mixed in a mass ratio of 1:100, and then stirring is carried out at 30°C for 5 hours, and then ultrasonic dispersion is carried out at 20°C for 2 hours, to obtain a biomass dispersion liquid;

[0106] 4) The silicone sol is added dropwise to the biomass dispersion liquid in a stirring state at a temperature of 50°C, with a dropwise addition speed of 3 mL / min and a stirring speed of 400 rpm, and the mass ratio of the silicone sol to the biomass dispersion liquid is 1:10, to obtain a mixed solution;

[0107] 5) The mixed solution and the functional nanomaterial dispersion liquid are mixed in a mass ratio of 10:1, and then injected into a mold, and then frozen at -18°C for 10 hours, and then placed in a freeze dryer for freeze drying for 24 hours, and then preheated at 50°C for 1 hour, and then placed in an oven for heating at 80°C for 8 hours, to obtain a bio-based aerogel.

[0108] Comparative Example 1:

[0109] A bio-based aerogel, the preparation method comprising the following steps:

[0110] 1) mixing bacterial cellulose and deionized water according to a mass ratio of 1:100, stirring at 30°C for 5h, and ultrasonic dispersion at 20°C for 2h to obtain a biomass dispersion liquid;

[0111] 2) injecting the biomass dispersion liquid into a mold, freezing at-18°C for 12h, freeze-drying in a freeze dryer for 48h, and heating at 80°C in an oven for 8h to obtain the bio-based aerogel.

[0112] Comparative Example 2:

[0113] A bio-based aerogel, the preparation method comprising the following steps:

[0114] 1) mixing titanium carbide MXene and deionized water according to a mass ratio of 1:100, and ultrasonic dispersion at 20°C for 2h to obtain a functional nanomaterial dispersion liquid, wherein the ultrasonic power is 100W;

[0115] 2) mixing bacterial cellulose and deionized water according to a mass ratio of 1:100, stirring at 30°C for 5h, and ultrasonic dispersion at 20°C for 2h to obtain a biomass dispersion liquid;

[0116] 3) mixing the functional nanomaterial dispersion liquid and the biomass dispersion liquid according to a mass ratio of 1:10, injecting into a mold, freezing at-18°C for 12h, freeze-drying in a freeze dryer for 48h, and heating at 80°C in an oven for 8h to obtain the bio-based aerogel.

[0117] Performance test:

[0118] Test method:

[0119] Fourier infrared spectroscopy (FT-IR) analysis: mix the sample powder with potassium bromide powder and press into a sheet, and use a Fourier infrared spectroscopy analyzer (Germany Bruker Company, model: TENSOR27) to detect the infrared spectrum information in the range of 400cm -1 ~ 4000cm -1 .

[0120] Scanning electron microscopy (SEM) test: use conductive glue to adhere the sample to the sample stage, and perform surface gold spraying treatment, and then use a scanning electron microscope (Germany Carl Zeiss Company, model: Merlin) to observe the surface morphology of the sample, and the acceleration voltage is 15kV.

[0121] Vertical combustion test: according to the ASTM D6413 standard, the length of the alcohol lamp flame is 40mm, the distance from the bottom of the sample to the wick is 20mm, the alcohol lamp is removed after burning for 20s, and the combustion phenomenon is recorded.

[0122] Fire warning test: The sample was connected to the voltage alarm using copper wires, and then the sample was burned with an alcohol lamp. The flame length of the alcohol lamp was 40mm, and the distance from the bottom of the sample to the lamp wick was 20mm. For thermal resistance warning, the warning resistance change rate was 90%, and for thermoelectric warning, the warning voltage was 1mV. The warning response time of the sample was recorded.

[0123] Human motion detection: The sample was connected to the human joint and a digital multimeter (Keithley, USA, model: DMM6500 6 1 / 2) using copper wires, and the resistance change curve was recorded.

[0124] Self-cleaning test: Place copper chloride powder on the aerogel surface, spray the surface with water, and observe and record the phenomenon.

[0125] Specific tests:

[0126] 1) Fourier transform infrared (FT-IR) spectra of polymethylsilsesquioxane (formed by hydrolysis and condensation of methyltrimethoxysilane), bacterial cellulose, titanium carbide MXene, and the bio-based aerogel of Example 1 are shown below. Figure 1 As shown.

[0127] Depend on Figure 1 It can be seen that the bio-based aerogel exhibits Si-OC and Ti-OC characteristic peaks that are not present in polymethylsilsesquioxane, bacterial cellulose, and titanium carbide MXene, indicating that bacterial cellulose combines with methyltrimethoxysilane and titanium carbide MXene through dehydration, and methyltrimethoxysilane successfully achieves mineralization modification of bacterial cellulose.

[0128] Furthermore, similar tests revealed that the organoalkoxysilanes with hydrolyzable groups in Examples 2-9 all achieved mineralization modification of biomass.

[0129] 2) Scanning electron microscopy (SEM) images and elemental distribution maps of the cross-section of the bio-based aerogel in Example 1 are shown below. Figure 2 As shown.

[0130] Depend on Figure 2 It can be seen that Si and Ti elements are uniformly distributed in the aerogel matrix, indicating that MXene is uniformly dispersed in the bio-based aerogel, and methyltrimethoxysilane is also uniformly mineralized.

[0131] Furthermore, the same tests revealed that the functional nanomaterials in the bio-based aerogels of Examples 2-9 were uniformly dispersed, and the organoalkoxysilanes with hydrolyzable groups were also uniformly mineralized.

[0132] 3) The rebound elasticity test of the bio-based aerogel of Example 1 (compress the bio-based aerogel with a weight about 9000 times of the weight of the bio-based aerogel, then remove the weight, and observe the deformation state of the bio-based aerogel) was carried out. The actual photos of the process are shown in Figure 3

[0133] As can be seen from Figure 3 , the bio-based aerogel of Example 1 can restore to its original shape after the weight is removed, and has excellent rebound elasticity.

[0134] In addition, the same test found that the bio-based aerogels of Examples 2-9 also have excellent rebound elasticity.

[0135] 4) The bio-based aerogels of Examples 1-9 and Comparative Examples 1-2 were subjected to vertical combustion test, fire warning test, human motion detection and self-cleaning test, and the test results are as follows:

[0136] a) The vertical combustion test video screenshot of the bio-based aerogel of Example 1 is shown in Figure 4

[0137] b) The fire warning test video screenshot of the bio-based aerogel of Example 1 is shown in Figure 5

[0138] c) The resistance change curve of the bio-based aerogel of Example 1 monitoring finger movement is shown in Figure 6

[0139] d) The self-cleaning test video screenshot of the bio-based aerogel of Example 1 is shown in Figure 7

[0140] e) The vertical combustion test and fire warning test results of the bio-based aerogels of Examples 1-9 and Comparative Examples 1-2 are shown in Table 1:

[0141] Table 1 Vertical combustion test and fire warning test results

[0142]

[0143] f) The self-cleaning test results of the bio-based aerogels of Examples 1-9 and Comparative Examples 1-2 are shown in Table 2:

[0144] Table 2 Self-cleaning test results

[0145]

[0146]

[0147] As can be seen from Figure 4 and Table 1, the bio-based aerogel of Example 1 exhibits excellent flame retardant performance and can achieve self-extinguishment in 1 second in the vertical combustion test.​​​​​

[0148] By Figure 5 and Table 1, it can be seen that when the flame ignites the bio-based aerogel of Example 1, part of the titanium carbide MXene is oxidized to generate titanium dioxide. Due to the semiconductor effect of titanium dioxide, the resistance decreases when it is subjected to high temperature, which makes the overall aerogel resistance drop rapidly, thereby triggering the thermal resistance early warning device within 1.8s, and having a sensitive fire thermal resistance early warning ability.

[0149] By Figure 6 It can be seen that the bio-based aerogel of Example 1 can be used for monitoring different human activities, thanks to its porous structure and good electrical conductivity.

[0150] By Figure 7 and Table 2, it can be seen that the bio-based aerogel of Example 1 exhibits excellent hydrophobicity. When the surface is sticky with dirt, the dirt can be carried away by the water flow without affecting the aerogel itself.

[0151] From Table 1 and Table 2, it can be seen that:

[0152] A) By comparing Example 2 with Example 1, it is found that the mineralization of dimethyl dimethoxysilane with functional nanomaterial titanium carbide MXene can also improve the flame retardant performance of microcrystalline cellulose aerogel. In the vertical combustion test, it self-extinguishes within 0.9s after the flame is removed 10s after ignition. At the same time, the thermal resistance early warning can occur within 2s, which can remind people to escape in time. In addition, the mineralized modified microcrystalline cellulose aerogel has better hydrophobicity, with a contact angle of 150°±5°. In addition, the bio-based aerogel of Example 2 also has excellent mechanical, thermal insulation and sensitive piezoresistive sensing properties;

[0153] B) By comparing Example 3 with Example 1, it is found that the mineralization of ethyl trimethoxysilane with carboxylated carbon nanotubes can also improve the flame retardant performance of alginate aerogel. In the vertical combustion test, it self-extinguishes within 1.2s after the flame is removed 10s after ignition. This is mainly because the mineralization modification of silane makes the aerogel form a more dense carbon layer with the generated silicon dioxide during combustion, and under the support of the carboxylated carbon tube skeleton, it exhibits excellent flame retardancy. At the same time, the thermal resistance early warning test also found that the early warning can occur within 1.5s, which is mainly because the carboxylated carbon tube loses carboxyl during heating, making the resistance drop rapidly, and its semiconductor properties further accelerate this process, so that more sensitive thermal resistance early warning can be achieved. In addition, the non-hydrolyzed ethyl also makes the mineralized modified alginate aerogel have good hydrophobicity, with a contact angle of 149°±1°. In addition, the bio-based aerogel of Example 3 also has good mechanical, thermal insulation and sensitive piezoresistive sensing properties;

[0154] C) By comparing Example 4 with Example 1, it is found that the mineralization of diethyl diethoxysilane and graphene oxide can also improve the flame retardant performance of carboxymethyl cellulose aerogel, which is self-extinguished within 2.0 s after the flame is removed 10 s after ignition in the vertical combustion test, mainly because the mineralization modification of silane makes the carboxymethyl aerogel form a more dense carbon layer together with the generated silicon dioxide during combustion, and under the skeleton support of graphene oxide, it shows excellent flame retardancy, and in the thermal electric fire warning test, it is also found that the warning can occur within 1.6 s, mainly because the reduction of graphene oxide to reduced graphene oxide under heat causes the resistance to decrease rapidly, so that sensitive thermal resistance warning can be achieved. In addition, compared with Example 3, the two non-hydrolyzed ethyl groups make the mineralized modified carboxymethyl cellulose aerogel have better hydrophobic performance, with a contact angle of 153°±4°. In addition, the biobased aerogel of Example 4 also has good mechanical, thermal insulation and sensitive piezoresistive sensing performance;

[0155] D) By comparing Example 5 with Example 1, it is found that the mineralization of dimethyl dimethoxysilane and molybdenum carbide MXene can also improve the flame retardant performance of gelatin aerogel, which is self-extinguished within 1.5 s after the flame is removed 10 s after ignition in the vertical combustion test, mainly because the mineralization modification of silane makes the aerogel form a more dense carbon layer together with the generated silicon dioxide during combustion, and under the catalytic carbonization and skeleton support of molybdenum carbide MXene, it shows excellent flame retardancy, and in the thermal electric fire warning test, it is also found that the warning can occur within 2.3 s, mainly because when one end of the aerogel is heated, the internal carriers move along the temperature gradient to output voltage changes, triggering the warning device to achieve more sensitive thermal electric warning. In addition, the two non-hydrolyzed methyl groups make the mineralized modified gelatin aerogel have better hydrophobic performance than Example 1, with a contact angle of 151°±2°. In addition, the biobased aerogel of Example 5 also has good mechanical, thermal insulation and sensitive piezoresistive sensing performance;

[0156] E) By comparing Example 6 with Example 1, it is found that the mineralization of diethyl diethoxysilane and aminated graphene oxide can also improve the flame retardant performance of hydroxypropyl chitosan aerogel, which is self-extinguished within 2.2 s after the flame is removed 10 s after ignition in the vertical combustion test, and in the thermal resistance fire warning test, it is also found that the warning can occur within 3.4 s, mainly because the amino group of aminated graphene oxide is removed and reduced to reduced graphene oxide during heating, causing the resistance to decrease rapidly, so that sensitive thermal resistance warning can be achieved. In addition, the two non-hydrolyzed ethyl groups make the mineralized modified hydroxypropyl chitosan aerogel have good hydrophobic performance, with a contact angle of 150°±2°. In addition, the biobased aerogel of Example 6 also has good mechanical, thermal insulation and sensitive piezoresistive sensing performance;

[0157] F) By comparing Example 7 with Example 1, it is found that the mineralization of propyl trimethoxysilane with titanium nitride MXene can also improve the flame retardant performance of hydroxypropyl cellulose aerogel. In the vertical combustion test, the flame is removed within 1.2 s after ignition for 10 s, and in the fire thermal electric warning test, the warning can occur within 1.6 s. This is mainly because when one end of the aerogel is heated, the internal carriers of titanium nitride MXene move along the temperature gradient, generating a voltage difference to trigger the warning device, so that sensitive thermal electric warning can be achieved. In addition, the non-hydrolyzed propyl group makes the mineralized modified hydroxypropyl cellulose aerogel have better hydrophobic performance, with a contact angle of 154°±5°. In addition, the biobased aerogel of Example 7 also has good mechanical, thermal insulation and sensitive piezoresistive sensing performance;

[0158] G) By comparing Example 8 with Example 1, it is found that the mineralization of methyl phenyl dimethoxysilane with aminated carbon nanotubes can also improve the flame retardant performance of chitin aerogel. In the vertical combustion test, the flame is removed within 1.6 s after ignition for 10 s. This is mainly because the mineralization modification of silane makes the aerogel form a more dense carbon layer together with the generated silicon dioxide during combustion, and under the support of the skeleton of aminated carbon tubes, it shows excellent flame retardancy. In the fire thermal resistance warning test, it is also found that the warning can occur within 1.9 s. This is mainly because the amino group of the aminated carbon nanotube is quickly removed during heating, causing the resistance to rapidly decrease, and its semiconductor property further accelerates this process, so that more sensitive thermal resistance warning can be achieved. In addition, the non-hydrolyzed methyl group also makes the mineralized modified chitin aerogel have good hydrophobic performance, with a contact angle of 153°±3°. In addition, the biobased aerogel of Example 8 also has good mechanical, thermal insulation and sensitive piezoresistive sensing performance;

[0159] H) By comparing Example 9 with Example 1, it is found that the mineralization of ethyl trimethoxysilane with hydroxylated carbon nanotubes can also improve the flame retardant performance of lignin aerogel. In the vertical combustion test, the flame is removed within 3.0 s after ignition for 10 s. This is mainly because the mineralization modification of silane makes the aerogel form a more dense carbon layer together with the generated silicon dioxide during combustion, and under the support of the skeleton of the carbon tube, it shows excellent flame retardancy. In the fire thermal resistance warning test, it is also found that the warning can occur within 2.9 s. This is mainly because the semiconductor property of the hydroxylated carbon nanotube causes the resistance to rapidly decrease when heated, so that sensitive thermal resistance warning can be achieved. In addition, the non-hydrolyzed ethyl group also makes the mineralized modified lignin aerogel have good hydrophobic performance, with a contact angle of 145°±3°. In Example 9, the hydroxyl group on the hydroxylated carbon nanotube forms a stronger interaction with the polysiloxane network, so the aerogel shows better mechanical performance. In addition, the biobased aerogel of Example 9 also has good thermal insulation and sensitive piezoresistive sensing performance;

[0160] From Table 1, it can be seen that the bio-based aerogels of Examples 1-9 all have excellent flame retardant properties and fire warning properties; when not modified by organosilicon mineralization (Comparative Example 1), the bacterial cellulose aerogel is extremely flammable and burns completely in the vertical burning test, so it cannot achieve the function of fire warning, and after adding functional nanomaterial MXene (Comparative Example 2), the flame retardant property is improved to a certain extent, but still does not have the function of fire warning; after modification by organosilicon mineralization (Examples 1-9), all the bio-based aerogels exhibit excellent flame retardant properties, and the flame can be quickly extinguished after leaving the fire source, which is mainly due to the catalysis of functional nanomaterials to form carbon during combustion, and the carbon layer formed by the further improvement of the Si-O-Si network effectively blocks the transmission of heat and flammable gas, thereby greatly improving the flame retardancy of the aerogel;

[0161] From Table 1, it can be seen that after modification by organosilicon mineralization, all the bio-based aerogels can quickly trigger the fire alarm after being burned by the flame, and for the bio-based aerogels of Examples 1-4, 6, 8 and 9, the output resistance changes rapidly due to the chemical change or semiconductor properties of the functional nanomaterials, thereby triggering the thermal resistance warning device, and for the bio-based aerogels of Examples 5 and 7, the carriers in the functional nanomaterials move from the hot end to the cold end after a temperature difference occurs in the aerogel, thereby generating a voltage and a reverse current between the two ends of the aerogel, triggering the thermoelectric fire alarm device.

[0162] In summary, the bio-based aerogel of the present application has excellent fire warning performance, flame retardant performance, self-cleaning ability and piezoresistive sensing ability, and can be applied to the fields of intelligent fire fighting, modern home and national defense and military industry.

[0163] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A method for preparing a bio-based aerogel, characterized in that, Includes the following steps: 1) Add an organoalkoxysilane with a hydrolyzable group to an acid solution for hydrolysis to obtain an organosilicon sol; 2) Add organosilicon sol to biomass dispersion to prepare a mixed solution, then mix the mixed solution with functional nanomaterial dispersion and freeze-shape, then freeze-dry and heat-dry to obtain bio-based aerogel; Step 1) The organosiloxane with a hydrolyzable group is at least one of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, propyltrimethoxysilane, and methylphenyldimethoxysilane. Step 2) The biomass in the biomass dispersion is at least one of bacterial cellulose, microcrystalline cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, chitosan, hydroxypropyl chitosan, carboxymethyl chitosan, chitin, alginate, lignin, and gelatin; Step 2) The functional nanomaterials in the functional nanomaterial dispersion are at least one of the following: aminated carbon nanotubes, carboxylated carbon nanotubes, hydroxylated carbon nanotubes, graphene oxide, aminated graphene oxide, carboxylated graphene oxide, titanium carbide, molybdenum carbide, and titanium nitride. Step 2) The freeze-forming process is carried out at -18℃ to -10℃ for 8 hours to 12 hours.

2. The preparation method according to claim 1, characterized in that: Step 1) The mass ratio of the organoalkoxysilane with hydrolyzable groups to the acid solution is 1:2 to 8; Step 2) The biomass dispersion is prepared by mixing biomass and water at a mass ratio of 1:50 to 200; Step 2) The functional nanomaterial dispersion is prepared by mixing functional nanomaterials and water at a mass ratio of 1:50 to 200; Step 2) The mass ratio of the organosilicon sol to the biomass dispersion is 1:5 to 25; Step 2) The mass ratio of the mixed solution to the functional nanomaterial dispersion is 5 to 20 to 1.

3. The preparation method according to claim 1 or 2, characterized in that: The acid solution in step 1) is at least one of the following: an aqueous solution of acetic acid with a concentration of 3 mmol / L to 15 mmol / L, an aqueous solution of hydrochloric acid with a concentration of 3 mmol / L to 10 mmol / L, or an aqueous solution of sulfuric acid with a concentration of 0.5 mmol / L to 3.5 mmol / L.

4. The preparation method according to claim 1 or 2, characterized in that: The hydrolysis described in step 1) is carried out at room temperature for 0.5 h to 3 h.

5. The preparation method according to claim 1 or 2, characterized in that: The specific preparation process of the mixed solution in step 2) is as follows: the organosilicon sol is added dropwise to the biomass dispersion at a temperature of 30℃~60℃ and under stirring, at a dropping rate of 2mL / min~4mL / min and a stirring speed of 200rpm~800rpm.

6. The preparation method according to claim 1 or 2, characterized in that: The freeze-drying time in step 2) is 24h to 48h.

7. The preparation method according to claim 1 or 2, characterized in that: The heating and drying in step 2) is carried out at 70℃~90℃ for 3h~15h.

8. A bio-based aerogel, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. An application of the bio-based aerogel as described in claim 8 for fire early warning, flame retardant insulation, or piezoresistive sensing.

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