An ultralow thermal conductivity silicon oxide aerogel insulation felt and a preparation method thereof

Abstract

The application discloses an ultralow-thermal-conductivity silicon oxide aerogel heat insulation felt and a preparation method thereof. Polycarbosilane is used to wrap carbon black powder, and then pyrolysis is carried out to obtain silicon carbide wrapped carbon powder. The powder is added to sol for preparing the aerogel heat insulation felt as a light shielding agent. The carbon is prevented from being oxidized at high temperature through the wrapping of the silicon carbide, so that the strong absorption and scattering performance of carbon to infrared radiation is retained. The silicon oxide aerogel heat insulation felt obtained by the method has the advantages of ultralow high-temperature thermal conductivity, low density and the like.

Description

Technical Field

[0001] This invention belongs to the technical field of silica aerogel insulation felt, specifically relating to an ultra-low thermal conductivity silica aerogel insulation felt and its preparation method. Background Technology

[0002] Aerogels are a type of solid material with a continuous, irregular network structure. Both the colloidal particles and the pore structure are on the nanoscale. This unique nanoporous network structure endows them with properties such as low density, low thermal conductivity, and high specific surface area. They are currently the solid materials with the lowest thermal conductivity at room temperature.

[0003] Currently, silica aerogel insulation felts are widely used in oil pipelines, heating networks, buildings, nuclear power, storage tank equipment, tank armor, rail transportation, and ships. Related research exists, for example, CN202311147343.6, which describes a composite aerogel felt containing organic-inorganic hybrid hollow microspheres, its preparation method, and its application. The preparation process employs atmospheric pressure drying, including: adding a silicon source, solvent, and phytic acid to water for hydrolysis, then adjusting the pH to obtain a silica sol solution; adding organic-inorganic hybrid hollow microspheres to the silica sol solution and stirring to obtain a sol solution containing organic-inorganic hybrid hollow microspheres; immersing a fiber felt in the sol solution containing organic-inorganic hybrid hollow microspheres, allowing it to stand, and drying to obtain the composite aerogel felt. This invention provides a composite aerogel felt with a more stable structure, better thermal insulation performance, no agglomeration or powder shedding, no need for multiple washing and replacement, a simpler process, and is more suitable for large-scale production.

[0004] However, silica aerogel insulation felt prepared by existing methods has strong transmittance to near-infrared thermal radiation with wavelengths of 3μm-8μm, so its ability to block infrared radiation at high temperatures is poor and its thermal conductivity increases rapidly.

[0005] To improve the thermal insulation performance of silica aerogel at high temperatures, light-blocking agents are typically added to enhance its infrared radiation blocking ability and improve its high-temperature insulation performance. Commonly used infrared light-blocking agents include carbon black, TiO2 powder, B4C powder, and SiC particles. Carbon black has strong absorption and scattering properties for infrared radiation, resulting in the best light-blocking effect. However, carbon black is easily oxidized at high temperatures (>300℃) and has poor thermal stability, which limits its application to some extent. SiC particles, as a ceramic material, have stable performance at high temperatures, but their light-blocking effect is relatively inferior to that of carbon black. Summary of the Invention

[0006] To address the issues of high thermal conductivity at high temperatures in existing silica aerogel insulation felts and the easy oxidation of carbon black as a light-blocking agent at high temperatures, this invention provides an ultra-low thermal conductivity silica aerogel insulation felt and its preparation method. The ultra-low thermal conductivity aerogel insulation felt prepared using this invention has ultra-low high-temperature thermal conductivity and has broad application prospects in aerospace, shipbuilding, tank armor, petroleum, chemical and other fields.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing an ultra-low thermal conductivity silica aerogel insulation felt includes the following steps:

[0009] S1. Preparation of silicon carbide / carbon powder materials:

[0010] S1-1. Mix polycarbosilane and xylene in a mass ratio of 1:(2-5), stir to dissolve, and obtain a uniform mixture 1.

[0011] S1-2. Prepare commercially available carbon black powder, add xylene and surfactant I, stir evenly to obtain mixture 2;

[0012] The ratio of carbon black powder to xylene is 1g:(10-20)mL, and the amount of surfactant I added is 5%-10% of the mass of xylene;

[0013] S1-3: Add mixture 2 to mixture 1, heat and stir, and cool to obtain a mixed slurry;

[0014] The addition ratio of the mixture 1 to the mixture 2 is 1:(1-2) by mass ratio of polycarbosilane to toner.

[0015] S1-4: The mixed slurry is placed in a tube furnace and subjected to high-temperature pyrolysis under a nitrogen atmosphere. The resulting powder is washed with xylene and dried to obtain silicon carbide-coated carbon powder (i.e., silicon carbide / carbon powder material).

[0016] S2, Sol preparation:

[0017] S2-1, Component A: The organosilicon source, ethanol, and H2O are stirred at room temperature in a molar ratio of 1:(1-3):(2-6). Then, an acid catalyst is slowly added to adjust the pH of the solution to 4-6. After hydrolysis at room temperature, a silicon-based hydrolysate is obtained.

[0018] S2-2, Component B: Ethanol and concentrated ammonia water are stirred at room temperature in a mass ratio of 1 kg:(0.5-6) ​​g to obtain an alkaline catalyst solution;

[0019] S2-3, C components: Stir silane coupling agent, surfactant II, ethanol, and H2O at a mass ratio of 1:(0.2-0.5):(5-20):(0.1-1) for 30 min, then slowly add acid catalyst, adjust the pH of the solution to 4-6 to obtain a sol, and add the silicon carbide / carbon powder material obtained in S1 and mix evenly.

[0020] The ratio of the silicon carbide / carbon powder material to the sol (silane coupling agent + surfactant II + ethanol + H2O + acid catalyst) in component C is (0.5-3) kg: 100 L;

[0021] S3. Prepare a whole roll of fiber felt;

[0022] S4. The fiber mat passes through the impregnation tank at a constant speed via the conveyor line. Components A, B, and C are mixed in the pipeline at a volume ratio of 1:(4-10):(0.5-2) and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel mat.

[0023] S5. The wet gel mat is transported to the microwave cavity via a conveyor line for rapid gelation and curing by microwave heating. The temperature inside the microwave cavity is maintained at 40℃-55℃.

[0024] S6: After the wet gel mat leaves the microwave cavity, it undergoes room temperature aging.

[0025] S7: Ethanol is added to replace the wet gel mat after it has aged at room temperature;

[0026] S8: After supercritical drying, the replaced wet gel felt is used to obtain ultra-low thermal conductivity silica aerogel insulation felt, which has the following properties:

[0027] The typical density is 0.14 g / cm³. 3 -0.18 g / cm 3 Typical thermal conductivity values ​​at room temperature are 0.01504 W / (m·K)-0.01877 W / (m·K), at 300℃ are 0.02011 W / (m·K)-0.02451 W / (m·K), and at 500℃ are 0.03367 W / (m·K)-0.03812 W / (m·K).

[0028] A 30mm thick ultra-low thermal conductivity silica aerogel insulation felt, after being heated to 900℃ on one side for 3600s, has a cold surface temperature of ≤85℃.

[0029] Furthermore, the carbon black powder mentioned in S1-2 is spherical carbon powder with a particle size of 20 nm-50 nm; surfactant I is one of Span 20, Span 40, Span 60 and Span 80.

[0030] Furthermore, in S1-3, stirring is carried out at a temperature of 40℃-60℃.

[0031] Furthermore, the high-temperature pyrolysis procedure described in S1-4 is as follows: the room temperature is raised to 80℃-120℃ and held for 2h-4h; then the temperature is raised to 1600℃ and held for 4h-6h; then the temperature is lowered to 600℃ and then allowed to cool naturally, wherein the heating rate is 1℃ / min and the cooling rate is 5℃ / min.

[0032] Furthermore, the purity of the ethanol in S2-1 is ≥95%; the stirring at room temperature is carried out for 20 minutes; and the hydrolysis at room temperature is carried out for 2-24 hours.

[0033] The organosilicon source is one or a combination of two or more of tetraethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, and polyethyl orthosilicate; the acid catalyst is one or a combination of two or more of hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

[0034] Furthermore, the stirring described in S2-2 is performed at room temperature for 30 minutes;

[0035] Furthermore, in S2-3, the silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-mercaptopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and the surfactant II is sodium dodecylbenzenesulfonate or sodium stearate.

[0036] Furthermore, the fiber felt described in S3 is one of glass fiber felt, high silica fiber felt, aluminum silicate fiber felt, and mullite fiber felt; the fiber felt has a width of 0.5m-1.5m.

[0037] Furthermore, the rapid gel described in S5 has a gelation time of 3-8 minutes.

[0038] Furthermore, the aging process described in S6 at room temperature lasts for 4-12 hours.

[0039] Furthermore, the supercritical drying described in S8 is performed using either CO2 supercritical drying or ethanol supercritical drying. The CO2 supercritical drying process involves drying the aerogel under CO2 gas protection at a temperature of 40℃-75℃, controlling the pressure in the autoclave at 8MPa-20MPa, and the reaction time at 4h-24h. The ethanol supercritical drying process involves drying the aerogel under nitrogen gas protection at a temperature of 260℃-320℃, controlling the pressure in the autoclave at 8MPa-14MPa, and the reaction time at 4h-10h.

[0040] This invention also relates to an ultra-low thermal conductivity silica aerogel insulation felt, obtained by the above-mentioned preparation method of an ultra-low thermal conductivity silica aerogel insulation felt, and has the following properties:

[0041] The typical density is 0.16 g / cm³. 3 -0.18 g / cm 3 Typical thermal conductivity values ​​at room temperature are 0.01504 W / (m·K)-0.01877 W / (m·K), at 300℃ are 0.02011 W / (m·K)-0.02451 W / (m·K), and at 500℃ are 0.03367 W / (m·K)-0.03812 W / (m·K).

[0042] A 30mm thick ultra-low thermal conductivity silica aerogel insulation felt, after being heated to 900℃ on one side for 3600s, has a cold surface temperature of ≤85℃.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] 1. The poor high-temperature thermal stability of carbon black limits its application in existing technologies, and it is rarely used in the preparation of low thermal conductivity silica aerogel insulation felt. The present invention describes a method for preparing ultra-low thermal conductivity silica aerogel insulation felt, which involves encapsulating carbon black powder with polycarbosilane, followed by high-temperature pyrolysis to obtain silicon carbide-encapsulated carbon powder. This powder is then added as a light-shielding agent to the sol used to prepare the aerogel insulation felt, preventing carbon oxidation at high temperatures and preserving carbon's strong absorption and scattering properties for infrared radiation, thus achieving ultra-low high-temperature thermal conductivity.

[0045] 2. Existing technologies typically use a single surfactant to treat the powder. This method only physically modulates the interface between the powder and the liquid through the surfactant, which can improve the wettability of the powder and the liquid to a certain extent, but cannot fundamentally solve the problem of powder agglomeration, thus making it difficult to achieve stable mass production. The preparation method of ultra-low thermal conductivity silica aerogel insulation felt described in this invention adopts powder surface treatment technology and uses silane coupling agent and surfactant II in synergy. Surfactant II assists in the dispersion of silane coupling agent and powder, while silane coupling agent undergoes a hydrolysis reaction in a weakly acidic environment. The hydrolysis intermediate reacts chemically with the powder, bridging the liquid and powder through chemical bonds, improving the interface between the two phases, and allowing the powder to be better dispersed in the liquid. At the same time, the organic long chain of silane coupling agent is grafted onto the powder surface, effectively improving the agglomeration between powder particles.

[0046] 3. The preparation method of the ultra-low thermal conductivity silica aerogel insulation felt of the present invention uses silane coupling agent and surfactant II in synergy. Surfactant II assists in the dispersion of silane coupling agent and powder, while silane coupling agent undergoes hydrolysis reaction in a weakly acidic environment. The hydrolysis intermediate product reacts chemically with the powder, bridging the liquid and powder through chemical bonds, improving the interface between the two phases, and allowing the powder to be better dispersed in the liquid. At the same time, the organic long chain of silane coupling agent is grafted onto the surface of the powder, effectively improving the agglomeration between powders, thereby obtaining a silica aerogel insulation felt with stable thermal conductivity, which can be mass-produced.

[0047] 4. The ultra-low thermal conductivity silica aerogel insulation felt described in this invention has an ultra-low high-temperature thermal conductivity because silicon carbide-encapsulated carbon powder is added as a light-shielding agent. This not only retains the strong absorption and scattering properties of carbon for infrared radiation, but also prevents the oxidation of the light-shielding agent at high temperatures through the protection of the outer surface silicon carbide, thereby improving the high-temperature thermal stability of the light-shielding agent. As a result, the prepared silica aerogel insulation felt stably possesses an ultra-low high-temperature thermal conductivity. Attached Figure Description

[0048] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0049] Figure 1 Photograph of the ultra-low thermal conductivity silica aerogel insulation felt prepared in Example 1;

[0050] Figure 2 SEM image of the ultra-low thermal conductivity silica aerogel prepared in Example 1;

[0051] Figure 3 This is a flowchart illustrating the preparation process of the ultra-low thermal conductivity silica aerogel insulation felt of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] like Figure 3 The diagram shown is a flowchart of the preparation process of ultra-low thermal conductivity silica aerogel insulation felt in the following embodiments;

[0054] Example 1:

[0055] A method for preparing an ultra-low thermal conductivity silica aerogel insulation felt includes the following steps:

[0056] S1. Preparation of silicon carbide / carbon powder materials:

[0057] S1-1. Mix polycarbosilane and xylene in a mass ratio of 1:2, stir to dissolve, and obtain a uniform mixture 1.

[0058] S1-2. Prepare commercially available carbon black powder, add xylene and surfactant I, stir evenly to obtain mixture 2;

[0059] The carbon black powder is spherical with a particle size of 20 nm; surfactant I is Span 20; the ratio of carbon black powder to xylene is 1 g: 10 mL, and the amount of surfactant I added is 5% of the mass of xylene;

[0060] S1-3: Add mixture 2 to mixture 1, stir at 40°C, and obtain a mixed slurry after cooling;

[0061] The addition ratio of mixture 1 to mixture 2 is 1:1 by mass of polycarbosilane to toner.

[0062] S1-4: The mixed slurry is placed in a tube furnace and subjected to high-temperature pyrolysis under a nitrogen atmosphere. The resulting powder is washed with xylene and dried to obtain silicon carbide-coated carbon powder (i.e., silicon carbide / carbon powder material).

[0063] The high-temperature pyrolysis procedure is as follows: the room temperature is raised to 80°C and held for 4 hours; then the temperature is raised to 1600°C and held for 4 hours; then the temperature is lowered to 600°C and then allowed to cool naturally; wherein the heating rate is 1°C / min and the cooling rate is 5°C / min.

[0064] S2, Sol preparation:

[0065] S2-1, Component A: The organosilicon source, ethanol, and H2O are stirred at room temperature for 20 minutes in a molar ratio of 1:1:2. Then, the acid catalyst is slowly added to adjust the pH of the solution to 4. After hydrolysis at room temperature for 10 hours, a silicon-based hydrolysate is obtained.

[0066] The purity of the ethanol is ≥95%; the organosilicon source is tetraethyl orthosilicate; the acid catalyst is nitric acid; S2-2, Component B: Ethanol and concentrated ammonia are mixed at a mass ratio of 1 kg: 6 g and stirred at room temperature for 30 min.

[0067] An alkaline catalyst solution was obtained;

[0068] S2-3, C components: Stir silane coupling agent, surfactant II, ethanol and H2O in a mass ratio of 1:0.2:5:0.1 for 30 min, then slowly add nitric acid to adjust the pH of the solution to 4 to obtain a sol, and add the silicon carbide / carbon powder material obtained in S1 and mix evenly.

[0069] The ratio of the silicon carbide / carbon powder material to the sol (silane coupling agent + surfactant II + ethanol + H2O + acid catalyst) in component C is 0.5 kg: 100 L.

[0070] The silane coupling agent is γ-aminopropyltriethoxysilane, and surfactant II is sodium dodecylbenzenesulfonate;

[0071] S3. Prepare a whole roll of fiber felt, 1.5m wide;

[0072] The fiber mat is a glass fiber mat;

[0073] S4. The fiber mat passes through the impregnation tank at a constant speed via the conveyor line. Components A, B, and C are mixed in the pipeline at a volume ratio of 1:4:0.5 and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel mat.

[0074] S5. The wet gel mat is transported to the microwave cavity via a conveyor line for rapid gelation and curing by microwave heating. The gelation time is 3 minutes and the temperature inside the microwave cavity is maintained at 55°C.

[0075] S6: After the wet gel mat leaves the microwave cavity, it is aged at room temperature for 4 hours;

[0076] S7: Ethanol is added to replace the wet gel mat after it has aged at room temperature;

[0077] S8: The replaced wet gel felt was subjected to supercritical ethanol drying. The drying process was as follows: the aerogel was dried at 260℃ under nitrogen protection, the pressure in the autoclave was controlled at 14MPa, and the reaction time was 4h, thus obtaining the ultra-low thermal conductivity silica aerogel insulation felt. The SEM image of this ultra-low thermal conductivity silica aerogel is shown below. Figure 2 .

[0078] Example 2:

[0079] A method for preparing an ultra-low thermal conductivity silica aerogel insulation felt includes the following steps:

[0080] S1. Preparation of silicon carbide / carbon powder materials:

[0081] S1-1. Mix polycarbosilane and xylene at a mass ratio of 1:5, stir to dissolve, and obtain a uniform mixture 1.

[0082] S1-2. Prepare commercially available carbon black powder, add xylene and surfactant I, stir evenly to obtain mixture 2;

[0083] The carbon black powder is spherical with a particle size of 50 nm; surfactant I is Span 80; the ratio of carbon black powder to xylene is 1 g: 20 mL, and the amount of surfactant I added is 10% of the mass of xylene.

[0084] S1-3: Add mixture 2 to mixture 1, stir at 50°C, and obtain a mixed slurry after cooling;

[0085] The addition ratio of the mixture 1 to the mixture 2 is 1:2 by mass of polycarbosilane to carbon powder;

[0086] S1-4: The mixed slurry is placed in a tube furnace and subjected to high-temperature pyrolysis under a nitrogen atmosphere. The resulting powder is washed with xylene and dried to obtain silicon carbide-coated carbon powder (i.e., silicon carbide / carbon powder material).

[0087] The high-temperature pyrolysis procedure is as follows: the room temperature is raised to 100°C and held for 3 hours; then the temperature is raised to 1600°C and held for 6 hours; then the temperature is lowered to 600°C and then allowed to cool naturally; wherein the heating rate is 1°C / min and the cooling rate is 5°C / min.

[0088] S2, Sol preparation:

[0089] S2-1, Component A: The organosilicon source, ethanol, and H2O are stirred at room temperature for 20 minutes in a molar ratio of 1:3:6. Then, the acid catalyst is slowly added to adjust the pH of the solution to 5. After hydrolysis at room temperature for 24 hours, a silicon-based hydrolysate is obtained.

[0090] The purity of the ethanol is ≥95%; the organosilicon source is methyl orthosilicate or methyltrimethoxysilane; the acid catalyst is oxalic acid.

[0091] S2-2, Component B: Ethanol and concentrated ammonia water were mixed at a mass ratio of 1 kg: 0.5 g and stirred at room temperature for 30 min to obtain an alkaline catalyst solution;

[0092] S2-3, C components: Stir silane coupling agent, surfactant II, ethanol and H2O in a mass ratio of 1:0.5:10:1 for 30 min, then slowly add oxalic acid to adjust the pH of the solution to 6 to obtain a sol, and add the silicon carbide / carbon powder material obtained in S1 and mix evenly.

[0093] The ratio of the silicon carbide / carbon powder material to the sol (silane coupling agent + surfactant II + ethanol + H2O + acid catalyst) in component C is 3 kg: 100 L.

[0094] The silane coupling agent is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and the surfactant II is sodium dodecylbenzenesulfonate;

[0095] S3. Prepare a whole roll of fiber felt, 1.5m wide;

[0096] The fiber felt is a high-silica fiber felt;

[0097] S4. The fiber mat passes through the impregnation tank at a constant speed via the conveyor line. Components A, B, and C are mixed in the pipeline at a volume ratio of 1:10:2 and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel mat.

[0098] S5. The wet gel mat is transported to the microwave cavity via a conveyor line for rapid gelation and curing by microwave heating. The gelation time is 8 minutes and the temperature inside the microwave cavity is maintained at 40°C.

[0099] S6: After the wet gel mat leaves the microwave cavity, it is aged at room temperature for 12 hours;

[0100] S7: Ethanol is added to replace the wet gel mat after it has aged at room temperature;

[0101] S8: The replaced wet gel felt is subjected to supercritical ethanol drying. The drying process is as follows: the aerogel is dried at 300℃ under the protection of nitrogen gas, the pressure of the autoclave is controlled at 8MPa, and the reaction time is 8h, thus obtaining ultra-low thermal conductivity silica aerogel insulation felt.

[0102] Example 3:

[0103] A method for preparing an ultra-low thermal conductivity silica aerogel insulation felt includes the following steps:

[0104] S1. Preparation of silicon carbide / carbon powder materials:

[0105] S1-1. Mix polycarbosilane and xylene in a mass ratio of 1:3, stir to dissolve, and obtain a uniform mixture 1.

[0106] S1-2. Prepare commercially available carbon black powder, add xylene and surfactant I, stir evenly to obtain mixture 2;

[0107] The carbon black powder is spherical with a particle size of 40 nm; surfactant I is Span 60; the ratio of carbon black powder to xylene is 1 g: 12 mL, and the amount of surfactant I added is 6% of the mass of xylene.

[0108] S1-3: Add mixture 2 to mixture 1, stir at 60°C, and obtain a mixed slurry after cooling;

[0109] The addition ratio of the mixture 1 to the mixture 2 is 1:1.5 by mass of polycarbosilane to toner.

[0110] S1-4: The mixed slurry is placed in a tube furnace and subjected to high-temperature pyrolysis under a nitrogen atmosphere. The resulting powder is washed with xylene and dried to obtain silicon carbide-coated carbon powder (i.e., silicon carbide / carbon powder material).

[0111] The high-temperature pyrolysis procedure is as follows: the room temperature is raised to 120°C and held for 2 hours; then the temperature is raised to 1600°C and held for 5 hours; then the temperature is lowered to 600°C and then allowed to cool naturally; wherein the heating rate is 1°C / min and the cooling rate is 5°C / min.

[0112] S2, Sol preparation:

[0113] S2-1, Component A: The organosilicon source, ethanol, and H2O are stirred at room temperature for 20 minutes in a molar ratio of 1:2:6. Then, the acid catalyst is slowly added to adjust the pH of the solution to 6. After hydrolysis at room temperature for 2 hours, a silicon-based hydrolysate is obtained.

[0114] The purity of the ethanol is ≥95%; the organosilicon source is polyethyl silicate or methyltrimethoxysilane; the acid catalyst is sulfuric acid.

[0115] S2-2, Component B: Ethanol and concentrated ammonia water were mixed at a mass ratio of 1 kg: 2 g and stirred at room temperature for 30 min to obtain an alkaline catalyst solution;

[0116] S2-3, C components: Stir silane coupling agent, surfactant II, ethanol and H2O in a mass ratio of 1:0.4:20:1 for 30 min, then slowly add sulfuric acid to adjust the pH of the solution to 5 to obtain a sol, and add the silicon carbide / carbon powder material obtained in S1 and mix evenly.

[0117] The ratio of the silicon carbide / carbon powder material to the sol (silane coupling agent + surfactant II + ethanol + H2O + acid catalyst) in component C is 1.2 kg: 100 L.

[0118] The silane coupling agent is γ-mercaptopropyltriethoxysilane, and the surfactant II is sodium stearate;

[0119] S3. Prepare a whole roll of fiber felt, 1.2m wide;

[0120] The fiber felt is aluminum silicate fiber felt;

[0121] S4. The fiber mat passes through the impregnation tank at a constant speed via the conveyor line. Components A, B, and C are mixed in the pipeline at a volume ratio of 1:6:2 and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel mat.

[0122] S5. The wet gel mat is transported to the microwave cavity via a conveyor line for rapid gelation and curing by microwave heating. The gelation time is 6 minutes and the temperature inside the microwave cavity is maintained at 50°C.

[0123] S6: After the wet gel mat leaves the microwave cavity, it is aged at room temperature for 8 hours;

[0124] S7: Ethanol is added to replace the wet gel mat after it has aged at room temperature;

[0125] S8: The replaced wet gel felt is subjected to supercritical CO2 drying. The drying process is as follows: the aerogel is dried at 50°C under the protection of nitrogen gas, the pressure of the autoclave is controlled at 20MPa, and the reaction time is 24h, thus obtaining ultra-low thermal conductivity silica aerogel insulation felt.

[0126] Example 4:

[0127] A method for preparing an ultra-low thermal conductivity silica aerogel insulation felt includes the following steps:

[0128] S1. Preparation of silicon carbide / carbon powder materials:

[0129] S1-1. Mix polycarbosilane and xylene in a mass ratio of 1:4, stir to dissolve, and obtain a uniform mixture 1.

[0130] S1-2. Prepare commercially available carbon black powder, add xylene and surfactant I, stir evenly to obtain mixture 2;

[0131] The carbon black powder is spherical with a particle size of 30 nm; surfactant I is Span 40; the ratio of carbon black powder to xylene is 1 g: 15 mL, and the amount of surfactant I added is 8% of the mass of xylene.

[0132] S1-3: Add mixture 2 to mixture 1, stir at 55℃, and obtain a mixed slurry after cooling;

[0133] The addition ratio of mixture 1 to mixture 2 is 1:1.2 by mass of polycarbosilane to toner.

[0134] S1-4: The mixed slurry is placed in a tube furnace and subjected to high-temperature pyrolysis under a nitrogen atmosphere. The resulting powder is washed with xylene and dried to obtain silicon carbide-coated carbon powder (i.e., silicon carbide / carbon powder material).

[0135] The high-temperature pyrolysis procedure is as follows: the room temperature is raised to 90°C and held for 2 hours; then the temperature is raised to 1600°C and held for 4 hours; then the temperature is lowered to 600°C and then allowed to cool naturally; wherein the heating rate is 1°C / min and the cooling rate is 5°C / min.

[0136] S2, Sol preparation:

[0137] S2-1, Component A: The organosilicon source, ethanol, and H2O were stirred at room temperature for 20 minutes in a molar ratio of 1:2:4. Then, the acid catalyst was slowly added to adjust the pH of the solution to 4.5. After hydrolysis at room temperature for 8 hours, a silicon-based hydrolysate was obtained.

[0138] The purity of the ethanol is ≥95%; the organosilicon source is polyethyl silicate or methyltrimethoxysilane; the acid catalyst is sulfuric acid.

[0139] S2-2, Component B: Ethanol and concentrated ammonia water were mixed at a mass ratio of 1 kg: 1 g and stirred at room temperature for 30 min to obtain an alkaline catalyst solution;

[0140] S2-3, C components: Stir silane coupling agent, surfactant II, ethanol, and H2O in a mass ratio of 1:0.3:10:0.8 for 30 minutes, then slowly add sulfuric acid to adjust the pH of the solution to 4.5 to obtain a sol, and add the silicon carbide / carbon powder material obtained in S1 and mix evenly.

[0141] The ratio of the silicon carbide / carbon powder material to the sol (silane coupling agent + surfactant II + ethanol + H2O + acid catalyst) in component C is 2 kg: 100 L.

[0142] The silane coupling agent is N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and the surfactant II is sodium stearate;

[0143] S3. Prepare a whole roll of fiber felt, 1.2m wide;

[0144] The fiber felt is a mullite fiber felt;

[0145] S4. The fiber mat passes through the impregnation tank at a constant speed via the conveyor line. Components A, B, and C are mixed in the pipeline at a volume ratio of 1:8:1 and then sprayed into the ultrasonic impregnation tank to mix the fiber and the sol, thus obtaining a wet gel mat.

[0146] S5. The wet gel mat is transported to the microwave cavity via a conveyor line for rapid gelation and curing by microwave heating. The gelation time is 5 minutes and the temperature inside the microwave cavity is maintained at 50°C.

[0147] S6: After the wet gel mat leaves the microwave cavity, it is aged at room temperature for 6 hours;

[0148] S7: Ethanol is added to replace the wet gel mat after it has aged at room temperature;

[0149] S8: The replaced wet gel felt is subjected to supercritical CO2 drying. The drying process is as follows: the aerogel is dried at 75°C under the protection of nitrogen gas, the pressure of the autoclave is controlled at 8MPa, and the reaction time is 12h, thus obtaining ultra-low thermal conductivity silica aerogel insulation felt.

[0150] Comparative Example 1:

[0151] The difference between Comparative Example 1 and Example 1 is that silicon carbide / carbon powder material is not added to component C in steps S2-3, otherwise it is the same as Example 1.

[0152] Comparative Example 2:

[0153] The difference between Comparative Example 2 and Example 1 is that in steps S2-3, component C is replaced with 20nm carbon black powder instead of silicon carbide / carbon powder material; otherwise, it is the same as Example 1.

[0154] Comparative Example 3:

[0155] The difference between Comparative Example 3 and Example 1 is that in steps S2-3, component C does not add a silane coupling agent to treat the opaque agent; otherwise, it is the same as Example 1.

[0156] Performance testing:

[0157] The performance of the thermal insulation felts prepared in the examples and comparative examples was tested:

[0158] Density: Tested according to GB / T34336-2017.

[0159] Thermal conductivity test at room temperature: Tested according to GB / T10295-2008.

[0160] Thermal conductivity test at 300℃ / 500℃: Tested according to GB / T10294-2008.

[0161] The results are shown in Table 1:

[0162] Table 1: Performance Test Table for Thermal Insulation Felt

[0163]

[0164] One roll (30m) of ultra-low thermal conductivity silica aerogel insulation felt obtained in Example 1 and Comparative Example 3 above. 2 Four groups of samples were randomly selected from the sample, and the properties of the composite material were tested as shown in Table 2.

[0165] Table 2: Test Table for Performance Stability of Thermal Insulation Felt

[0166]

[0167] Results and Discussion:

[0168] By comparing Example 1 and Comparative Example 1 (Table 1), the addition of the light-blocking agent in the examples can effectively suppress high-temperature radiative heat transfer and improve the high-temperature heat insulation performance of aerogel insulation felt.

[0169] By comparing Example 1 and Comparative Example 2, it was found that in the Comparative Example, the addition of carbon black powder as a light-blocking agent caused oxidation of the carbon black powder at 500°C, resulting in unstable thermal conductivity of the material. In the Example 1, polycarbosilane was used to encapsulate carbon black powder, which was then subjected to high-temperature pyrolysis to obtain carbon powder encapsulated in silicon carbide. This powder was added to the sol for preparing aerogel insulation felt as a light-blocking agent, which improved the high-temperature thermal stability of carbon, prevented carbon oxidation at high temperatures, and preserved the strong absorption and scattering properties of carbon for infrared radiation, thereby giving the aerogel insulation felt an ultra-low high-temperature thermal conductivity.

[0170] Comparing Example 1 and Comparative Example 3 (Table 2), the sample in Example 1 showed stable performance, while Comparative Example 3, which only used surfactant to modify the powder, produced a material with excellent thermal conductivity, but the material's performance stability was poor. This is because surfactants typically rely on adsorption at the interface between two phases to reduce surface energy through directional arrangement, thus assisting in dispersion. However, due to the fine particle size of the powder and the influence of the sol pH, relying solely on physical adsorption makes it difficult for the powder surface to reach the minimum concentration required for surfactant micelle formation, resulting in minimal improvement. In Example 1, a silane coupling agent and a surfactant were used synergistically. The surfactant assisted in the dispersion of the silane coupling agent and the powder through physical adsorption. The silane coupling agent underwent hydrolysis in a weakly acidic environment, and its hydrolysis intermediates reacted chemically with the powder, bridging the liquid and powder through chemical bonds, improving the interface between the two phases, and allowing the powder to be better dispersed in the liquid. Simultaneously, the organic long chains of the silane coupling agent were grafted onto the powder surface, effectively improving the agglomeration between powder particles, thereby obtaining a stable aerogel insulation felt.

[0171] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method of making an ultralow thermal conductivity silica aerogel insulation batt, characterized by, The method comprises the following steps: S1, preparation of silicon carbide / carbon powder material: S1-1, mix polycarbosilane and xylene according to a mass ratio of 1:(2-5), stir and dissolve to obtain a uniform mixture 1; S1-2, prepare commercially available carbon black powder, add xylene and surfactant I, stir to obtain a mixture 2; The ratio of the carbon black powder to xylene is 1g:(10-20)mL, and the addition amount of the surfactant I is 5%-10% of the mass of the xylene; S1-3: add the mixture 2 to the mixture 1, heat and stir, and then cool to obtain a mixed slurry; The mass ratio of the polycarbosilane to the carbon black powder is 1:(1-2); S1-4: place the mixed slurry in a tube furnace, perform high-temperature pyrolysis under a nitrogen atmosphere, wash the obtained powder with xylene, dry, and obtain a silicon carbide-coated carbon powder, i.e., the silicon carbide / carbon powder material; S2, sol preparation: S2-1, A component: mix an organic silicon source, ethanol and H2O according to a molar ratio of 1:(1-3):(2-6), stir at room temperature, slowly add an acid catalyst, adjust the pH value of the solution to 4-6, hydrolyze at room temperature, and obtain a silicon-based hydrolysis solution; S2-2, B component: mix ethanol and concentrated ammonia water according to a mass ratio of 1kg:(0.5-6)g, stir at room temperature, and obtain an alkaline catalyst solution; S2-3, C component: mix a silane coupling agent, a surfactant II, ethanol and H2O according to a mass ratio of 1:(0.2-0.5):(5-20):(0.1-1), stir for 30 min, slowly add an acid catalyst, adjust the pH value of the solution to 4-6, obtain a sol, and mix the obtained sol with the silicon carbide / carbon powder material obtained in S1; The ratio of the silicon carbide / carbon powder material to the sol in the C component is (0.5-3)kg:100L; S3, prepare a whole roll of fiber felt; S4: the fiber felt passes through the glue dipping pool at a constant speed through the conveying line, A component, B component and C component are mixed in the pipeline according to a volume ratio of 1:(4-10):(0.5-2), and then sprayed into the ultrasonic glue dipping pool to mix the fiber and the sol, and obtain a wet gel felt; S5: the wet gel felt is sent to a microwave cavity for microwave heating, rapid gelation and solidification, and the temperature in the microwave cavity is kept at 40-55℃; S6: after the wet gel felt leaves the microwave cavity, normal temperature aging is performed; S7: the wet gel felt after normal temperature aging is replaced with ethanol; S8: after the replaced wet gel felt is subjected to supercritical drying, an ultra-low thermal conductivity silicon oxide aerogel heat insulation felt is obtained, and the ultra-low thermal conductivity silicon oxide aerogel heat insulation felt has the following properties: The typical density is 0.16 g / cm³. 3 -0.18 g / cm 3 Typical thermal conductivity values ​​at room temperature are 0.01504 W / (m·K)-0.01877 W / (m·K), at 300℃ are 0.02011 W / (m·K)-0.02451 W / (m·K), and at 500℃ are 0.03367 W / (m·K)-0.03812 W / (m·K). The ultra-low thermal conductivity silicon oxide aerogel heat insulation felt with a thickness of 30mm has a cold face temperature of ≤85℃ after single-side heating at 900℃ for 3600s.

2. The method of claim 1, wherein the method further comprises the step of: The carbon black powder in S1-2 is spherical carbon powder with a particle size of 20-50nm; and the surfactant I is one of Span 20, Span 40, Span 60 and Span 80.

3. The method of claim 1, wherein the method further comprises the step of: In S1-3, stirring is carried out at a temperature of 40℃-60℃; the high-temperature pyrolysis described in S1-4 is performed as follows: the temperature is raised from room temperature to 80℃-120℃ and held for 2h-4h; then the temperature is raised to 1600℃ and held for 4h-6h; then the temperature is lowered to 600℃ and then allowed to cool naturally, wherein the heating rate is 1℃ / min and the cooling rate is 5℃ / min. ​ 4. The method of claim 1, wherein the method further comprises: The purity of the ethanol mentioned in S2-1 is ≥95%; the stirring at room temperature is carried out for 20 min; the hydrolysis at room temperature is carried out for 2 h-24 h. The organosilicon source is one or a combination of two or more of tetraethyl orthosilicate, methyl orthosilicate, methyltriethoxysilane, methyltrimethoxysilane, and polyethyl orthosilicate; the acid catalyst is one or a combination of two or more of hydrochloric acid, oxalic acid, nitric acid, sulfuric acid, acetic acid, and hydrofluoric acid.

5. The method of claim 1, wherein the method further comprises: The stirring as described in S2-2 is performed at room temperature for 30 minutes. In S2-3, the silane coupling agent is one of γ-aminopropyltriethoxysilane, γ-mercaptopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and the surfactant II is sodium dodecylbenzenesulfonate or sodium stearate.

6. The method of claim 1, wherein the method further comprises: The fiber felt described in S3 is one of glass fiber felt, high silica fiber felt, aluminum silicate fiber felt, and mullite fiber felt; the fiber felt has a width of 0.5m-1.5m.

7. The method of claim 1, wherein the method further comprises the step of: The rapid gel described in S5 has a gelation time of 3-8 minutes. ​ 8. The method of claim 1, wherein the method further comprises: The aging process described in S6 at room temperature takes 4-12 hours.

9. The method for preparing an ultra-low thermal conductivity silica aerogel insulation felt according to claim 1, characterized in that, The supercritical drying described in S8 is performed using either CO2 supercritical drying or ethanol supercritical drying. The CO2 supercritical drying process involves drying the aerogel under CO2 gas protection at a temperature of 40℃-75℃, controlling the pressure in the autoclave at 8MPa-20MPa, and the reaction time at 4h-24h. The ethanol supercritical drying process involves drying the aerogel under nitrogen gas protection at a temperature of 260℃-320℃, controlling the pressure in the autoclave at 8MPa-14MPa, and the reaction time at 4h-10h.

10. An ultralow thermal conductivity silica aerogel insulation batt characterized by, The ultra-low thermal conductivity silica aerogel insulation felt obtained according to any one of claims 1-9 has the following properties: Density typical values are 0.16 g / cm 3 - 0.18 g / cm 3 - Thermal conductivity at room temperature typical values are 0.01504 W / (m.K) - 0.01877 W / (m.K), at 300°C typical values are 0.02011 W / (m.K) - 0.02451 W / (m.K), at 500°C typical values are 0.03367 W / (m.K) - 0.03812 W / (m.K); A 30mm thick ultra-low thermal conductivity silica aerogel insulation felt, after being heated to 900℃ on one side for 3600s, has a cold surface temperature of ≤85℃.

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