A high-temperature resistant and wave-transmitting silicon oxide aerogel composite material and its preparation method

Abstract

The present invention provides a high-temperature resistant, wave-transmitting silica aerogel composite material and a preparation method thereof, relating to the field of high-temperature thermal insulation materials. The preparation method of the high-temperature resistant, wave-transmitting silica aerogel composite material comprises adding an alkaline catalyst solution to an organosilane precursor to form a silica sol, which is then dehydrated through an alcohol-water separation membrane to produce a replaced silica sol. The silica sol is then combined with a composite ceramic fiber felt to form a gel, aged, and then subjected to supercritical drying to produce the high-temperature resistant, wave-transmitting silica aerogel composite material. The preparation method of the high-temperature resistant, wave-transmitting silica aerogel composite material of the present invention can improve the high-temperature stability, thermal insulation stability, and thermal insulation performance of the silica aerogel composite material while further improving the wave transmission performance of the silica aerogel composite material.

Description

Technical Field

[0001] The present invention relates to the field of high-temperature thermal insulation materials, and in particular to a high-temperature resistant and wave-transmitting silicon oxide aerogel composite material and a preparation method thereof. Background Art

[0002] Aerogels, with their unique nanoporous structure, currently possess the lowest room-temperature thermal conductivity among solid materials. Currently, silica aerogel composites are widely used in oil pipelines, heat distribution networks, nuclear power plants, storage tanks, tank armor, rail transit, shipbuilding, aerospace, and other fields. However, silica aerogel nanoparticles prepared using the existing acid-base two-step process exhibit uneven particle size and are prone to sintering, densification, and pore structure collapse at high temperatures, resulting in dimensional shrinkage and decreased thermal insulation performance. Consequently, the long-term operating temperature of silica aerogel insulation blankets is limited to below 700°C, making them incapable of meeting insulation requirements at higher temperatures. Existing silica aerogel composites shrink by over 5% after heat treatment at 900°C for 2 hours, and their thermal conductivity increases significantly at high temperatures. Although alumina aerogel exhibits good high-temperature resistance, it undergoes phase transitions with increasing temperatures, especially above 1000°C, significantly reducing its specific surface area. Furthermore, alumina aerogels exhibit poor wave transmission, limiting their application.

[0003] At the same time, existing silica aerogel composite materials have been widely used in certain high-end equipment fields due to their good wave-transmitting properties. However, due to the limitations of the aforementioned defects, their operating temperature can only be below 700°C, which cannot meet the performance requirements of high-end equipment with higher operating temperatures.

[0004] Furthermore, the silica particles and pore structure of existing silica aerogel composite materials that can withstand high temperatures above 600°C are uneven, resulting in their dielectric constant and dielectric loss still being relatively high and unable to be effectively reduced.

[0005] In order to improve the high-temperature stability and high-temperature thermal insulation performance of silica aerogel, the prior art discloses using a silica sol in an alcohol solvent system as a silicon source, adding a sunscreen to improve the high-temperature thermal insulation performance, and obtaining a silica aerogel composite material after drying. However, the addition of the sunscreen directly leads to the deterioration of the wave transmission performance of the aerogel insulation felt, and the sunscreen is prone to sedimentation during the sol process, making it unsuitable for mass production. Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a high-temperature resistant, wave-transmitting silica aerogel composite material and a preparation method thereof, which improves the high-temperature stability, thermal insulation stability and thermal insulation performance of the silica aerogel composite material while further improving the wave transmission performance of the silica aerogel composite material.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material comprises the following steps:

[0009] Step S001: adding an alkaline catalyst solution to an organosilane precursor under heating conditions to prepare a silica sol;

[0010] Step S002: placing the silica sol in a replacement box equipped with an alcohol-water separation membrane to remove water from the silica sol until the silica sol has a silica solid content of 5-30 wt% and a water content of less than 5 wt%, thereby obtaining a replaced silica sol;

[0011] Step S003: impregnating the ceramic fiber felt into a pre-impregnated slurry containing boron nitride and silicon nitride, and drying after impregnation to obtain a composite ceramic fiber felt;

[0012] Step S004: impregnating the composite ceramic fiber felt into the replaced silica sol, heating to gelate, and then aging to obtain a fiber felt / gel composite;

[0013] Step S005: The fiber felt / gel composite is subjected to supercritical drying to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

[0014] Preferably, in step S001, the heating temperature is 45-75°C;

[0015] The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate;

[0016] The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:1.

[0017] Preferably, in step S001, the molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:1.

[0018] Preferably, in step S002, the removal of water from the silica sol using an alcohol-water separation membrane is performed under normal pressure and a temperature of 30-50°C;

[0019] The alcohol-water separation membrane is an organic silicon membrane with a permeation flux of 3.3-3.5 kg·m -2 ·h -1 .

[0020] Preferably, in step S003, the prepreg slurry is composed of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether;

[0021] The weight ratio of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 12-13:6-6.5:100:2-2.3:0.9-1.1;

[0022] The ethanol volume concentration of the ethanol aqueous solution is 70-80%.

[0023] Preferably, in step S003, the impregnation pressure is controlled to be 1.5-2 MPa, the impregnation time is 2-3 hours; the ceramic fiber felt is quartz fiber felt, and the density is 0.15-0.3 g / cm 3 , fiber diameter is 1-5 μm;

[0024] The volume ratio of ceramic fiber felt to prepreg slurry is 0.2-0.25:1.

[0025] Preferably, in step S004, the heating gelation temperature is 40-60° C. and the time is 3-8 hours;

[0026] The aging time is 22-24h.

[0027] Preferably, in step S004, the volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.05-0.1:1.

[0028] Preferably, in step S005, the supercritical drying temperature is controlled to be 270-280° C., the pressure is controlled to be 8-10 MPa, the pressure reduction rate is controlled to be 2-3 MPa / h, and the supercritical drying time is controlled to be 2-4 hours.

[0029] A high temperature resistant and wave-transmitting silica aerogel composite material prepared by the above preparation method has a dielectric constant of 1.1-1.3 and a dielectric loss of (5-30)×10 -4 The thermal conductivity coefficient at room temperature is 0.025-0.027W / (m·K), and the thermal conductivity coefficient at 1000℃ is 0.054-0.055W / (m·K).

[0030] The preparation method of the high-temperature resistant and wave-transmitting silica aerogel composite material of the present invention uses an organosilane precursor as the main raw material and a high-temperature resistant ceramic fiber felt composited with boron nitride and silicon nitride as a reinforcement. The high-temperature resistant and wave-transmitting silica aerogel composite material is prepared through a simple and rapid process of fiber felt impregnation, composite aging, and supercritical drying. Compared with the existing technology, the following beneficial effects can be achieved:

[0031] 1) The present invention uses a composite organosilane precursor as the main raw material, adds an alkali as a catalyst to cause it to gel, and forms a silica sol with a nanoporous network structure; then the silica sol is separated and replaced by alcohol and water to obtain a replaced silica sol with a specific silica solid content and moisture content; the ceramic fiber felt is impregnated with a pre-impregnated slurry containing boron nitride and silicon nitride, and then further impregnated with the replaced silica sol to obtain a fiber felt / gel composite; finally, the composite material containing high-temperature resistant and wave-transmitting silica aerogel is obtained by supercritical drying; wherein, the composite ceramic fiber felt is used as a reinforcement and as a high-temperature resistant fiber skeleton, which, on the one hand, improves the high-temperature stability of the silica aerogel composite material, and on the other hand, improves the mechanical properties of the silica aerogel composite material; and the capillary force generated by the drying medium during the supercritical drying process is very small, and a silica aerogel with better blockiness and porous network structure can be obtained; through the combination of the aforementioned technical means, the high-temperature stability, thermal insulation stability, and thermal insulation performance of the silica aerogel composite material can be improved while further improving the wave transmission performance of the silica aerogel composite material.

[0032] 2) The high-temperature resistant and wave-transmitting silica aerogel composite material of the present invention can be used at 1000°C for a long time while having very low thermal conductivity and good mechanical properties. After being treated at 1100°C for 2 hours, there is no shrinkage in the thickness direction. The typical thermal conductivity values ​​at room temperature, 800°C, 1000°C, and 1100°C are 0.025W / (m·K), 0.046W / (m·K), 0.054W / (m·K), and 0.062W / (m·K), respectively, which are more than 50% lower than those of existing silica aerogel composite materials. The dielectric constant is 1.1-1.3, and the dielectric loss is (5-30)×10 -4 ; Bending strength is greater than 2MPa, and compressive strength (10%) is greater than 0.5MPa.

[0033] 3) The preparation method of the present invention has readily available raw materials, a simple process, and is easy to control. Raw materials are readily available, the preparation cycle is short, and it is conducive to large-scale production.

[0034] 4) The high-temperature resistant and wave-transmitting silica aerogel composite material prepared by the present invention has the advantages of high-temperature resistance of 1100°C, excellent thermal insulation performance, and good wave transmission performance. It has broad application prospects in the fields of aerospace high-temperature insulation, civil kiln insulation and heat insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a scanning electron microscope image of the high-temperature resistant and wave-transmitting silica aerogel of Example 2.

[0036] Figure 2 This is a 1000°C test background temperature diagram of the high-temperature resistant and wave-transmitting silica aerogel composite material of Example 2.

[0037] Figure 3 This is a scanning electron microscope image of the silicon oxide aerogel composite material prepared in Comparative Example 1.

[0038] Figure 4 This is a scanning electron microscope image of the silicon oxide aerogel composite material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0039] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described.

[0040] In order to provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described. It should be noted that the following detailed description is illustrative and is intended to further illustrate the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are intended only to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," and the like are used to distinguish similar objects and are not used to describe a specific order or precedence. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] An embodiment of the present invention provides a method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material, comprising the following steps:

[0043] Step S001: preparing silica sol using an organosilane precursor; specifically, adding an alkaline catalyst solution to the organosilane precursor under heating conditions of 45-75° C., and stirring the mixture for 6-24 hours to obtain silica sol.

[0044] In step S001, the organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; preferably, the ratio of methyltrimethoxysilane to ethyl orthosilicate (or methyl orthosilicate) is 1:0.3-0.4.

[0045] The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:1;

[0046] The molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:1.

[0047] Step S002: Place the silica sol in a replacement box equipped with an alcohol-water separation membrane, and separate and remove water from the silica sol at normal pressure and 30-50°C until the silica solid content is 5-30wt% and the water content is less than 5wt%, thereby obtaining the replaced silica sol for standby use.

[0048] In step S002, the alcohol-water separation membrane used is an organic silicon membrane with a permeation flux of 3.3-3.5 kg·m -2 ·h -1 .

[0049] Step S003: Put boron nitride and silicon nitride into an ethanol aqueous solution with a volume concentration of 70-80%, stir evenly, then continue to add polyvinyl alcohol and fatty alcohol polyoxyethylene ether, stir evenly and place in a ball mill, and ball mill for 2-3 hours to obtain a pre-impregnated slurry; immerse the ceramic fiber felt in the pre-impregnated slurry, control the immersion pressure to 1.5-2MPa, take it out after immersion for 2-3 hours, and dry it at 75-80°C to constant weight to obtain a composite ceramic fiber felt.

[0050] In step S003, the weight ratio of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 12-13:6-6.5:100:2-2.3:0.9-1.1;

[0051] Ceramic fiber felt is quartz fiber felt with a density of 0.15-0.3g / cm 3 , fiber diameter is 1-5 μm;

[0052] The volume ratio of ceramic fiber felt to prepreg slurry is 0.2-0.25:1.

[0053] Step S004: immerse the composite ceramic fiber felt in the replaced silica sol, heat to 40-60° C., keep warm for 3-8 hours for gelation, and allow to stand for aging for 22-24 hours to obtain a fiber felt / gel composite.

[0054] In step S004, the volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.05-0.1:1.

[0055] Step S005: supercritically dry the fiber felt / gel composite, controlling the supercritical drying temperature to 270-280°C, the pressure to 8-10 MPa, the pressure reduction rate to 2-3 MPa / h, and the supercritical drying time to 2-4 hours to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

[0056] The embodiment of the present invention also provides a high temperature resistant and wave-transmitting silica aerogel composite material prepared by the above method, with a dielectric constant of 1.1-1.3 and a dielectric loss of (5-30)×10 -4The thermal conductivity coefficient at room temperature is 0.025W / m·k, and the thermal conductivity coefficient at 1000℃ is 0.054W / m·k.

[0057] The present invention will be further described below with reference to some specific embodiments.

[0058] Example 1

[0059] This embodiment provides a method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material, specifically:

[0060] Step S001: adding an alkaline catalyst solution to a mixture of ethyl orthosilicate and methyltrimethoxysilane (i.e., an organosilane precursor) in a mass ratio of 0.6:1 under heating conditions at 50° C., and stirring the mixture for 20 hours to obtain a silica sol.

[0061] The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.25wt%, and the volume ratio of ethanol to water is 1.2:1;

[0062] The molar ratio of the base to the organosilane precursor (ethyl orthosilicate and methyltrimethoxysilane) in the alkaline catalyst solution is 0.3:1.

[0063] Step S002: Place the silica sol in a replacement box equipped with an alcohol-water separation membrane, and separate and remove water from the silica sol at normal pressure and 30°C until the silica solid content is 18wt% and the water content is less than 5wt%, thereby obtaining the replaced silica sol for standby use.

[0064] The alcohol-water separation membrane used is an organic silicon membrane with a permeation flux of 3.3 kg·m -2 ·h -1 .

[0065] Step S003: Put boron nitride and silicon nitride into an ethanol aqueous solution with a volume concentration of 80%, stir evenly, then continue to add polyvinyl alcohol and fatty alcohol polyoxyethylene ether, stir evenly and place in a ball mill, and ball mill for 2 hours to obtain a pre-impregnated slurry; immerse the ceramic fiber felt in the pre-impregnated slurry, control the immersion pressure to 1.5 MPa, take it out after immersion for 2 hours, and dry it at 75°C to constant weight to obtain a composite ceramic fiber felt.

[0066] The weight ratio of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 12:6:100:2:0.9;

[0067] Ceramic fiber felt is quartz fiber felt with a density of 0.2g / cm 3 , fiber diameter is 3 μm;

[0068] The volume ratio of ceramic fiber felt to prepreg slurry is 0.2:1.

[0069] Step S004: immerse the composite ceramic fiber felt in the replaced silica sol, heat to 45° C., keep warm for 8 hours for gelation, and allow to stand for aging for 24 hours to obtain a fiber felt / gel composite.

[0070] The volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.05:1.

[0071] Step S005: supercritically dry the fiber felt / gel composite, controlling the supercritical drying temperature to 270° C., the pressure to 10 MPa, the pressure reduction rate to 2 MPa / h, and the supercritical drying time to 2.5 h to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

[0072] This embodiment also provides a high-temperature resistant and wave-transmitting silica aerogel composite material prepared by the aforementioned method.

[0073] After testing, the dielectric constant of the high temperature resistant and wave-transmitting silica aerogel composite material is 1.25, and the dielectric loss is 6.1×10 -4 The thermal conductivity at room temperature is 0.027W / (m·k), the thermal conductivity at 800℃ is 0.049W / (m·k), the thermal conductivity at 1000℃ is 0.055W / (m·k), and the thermal conductivity at 1100℃ is 0.064W / (m·k); after treatment at 1100℃ for 2h, there is no shrinkage in the thickness direction, the flexural strength is 2.4MPa, and the compressive strength (10%) is 0.54MPa.

[0074] Example 2

[0075] This embodiment provides a method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material, specifically:

[0076] Step S001: adding an alkaline catalyst solution to a mixture of methyl orthosilicate and methyltrimethoxysilane (i.e., an organosilane precursor) in a mass ratio of 0.7:1 under heating conditions at 60° C., and stirring the mixture for 16 hours to obtain a silica sol.

[0077] The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.27 wt%, and the volume ratio of ethanol to water is 1.2:1;

[0078] The molar ratio of the base to the organosilane precursor (methyl orthosilicate, methyltrimethoxysilane) in the alkaline catalyst solution is 0.3:1.

[0079] Step S002: Place the silica sol in a replacement box equipped with an alcohol-water separation membrane, and separate and remove water from the silica sol at normal pressure and 40°C until the silica solid content is 18wt% and the water content is less than 5wt%, thereby obtaining the replaced silica sol for standby use.

[0080] The alcohol-water separation membrane used is an organic silicon membrane with a permeation flux of 3.3 kg·m -2 ·h -1 .

[0081] Step S003: Put boron nitride and silicon nitride into an ethanol aqueous solution with a volume concentration of 75%, stir evenly, then continue to add polyvinyl alcohol and fatty alcohol polyoxyethylene ether, stir evenly and place in a ball mill, and ball mill for 2.5 hours to obtain a pre-impregnated slurry; immerse the ceramic fiber felt in the pre-impregnated slurry, control the immersion pressure to 1.8 MPa, take it out after immersion for 2.5 hours, and dry it at 75°C to constant weight to obtain a composite ceramic fiber felt.

[0082] The weight ratio of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 12.7:6.2:100:2.1:1;

[0083] Ceramic fiber felt is quartz fiber felt with a density of 0.2g / cm 3 , fiber diameter is 3 μm;

[0084] The volume ratio of ceramic fiber felt to prepreg slurry is 0.22:1.

[0085] Step S004: immerse the composite ceramic fiber felt in the replaced silica sol, heat to 50° C., keep warm for 5 hours for gelation, and allow to stand for aging for 22 hours to obtain a fiber felt / gel composite.

[0086] The volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.08:1.

[0087] Step S005: supercritically dry the fiber felt / gel composite, controlling the supercritical drying temperature to 275°C, the pressure to 9 MPa, the pressure reduction rate to 2.5 MPa / h, and the supercritical drying time to 3 hours to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

[0088] like Figure 1 As shown, this embodiment also provides a high-temperature resistant and wave-transmitting silica aerogel composite material prepared by the above method.

[0089] After testing, the dielectric constant of the high temperature resistant and wave-transmitting silica aerogel composite material is 1.13, and the dielectric loss is 5.4×10 -4The thermal conductivity at room temperature is 0.025W / (m·k), the thermal conductivity at 800℃ is 0.046W / (m·k), the thermal conductivity at 1000℃ is 0.054W / (m·k), and the thermal conductivity at 1100℃ is 0.062W / (m·k); after treatment at 1100℃ for 2h, there is no shrinkage in the thickness direction, the flexural strength is 2.5MPa, and the compressive strength (10%) is 0.57MPa.

[0090] like Figure 2 As shown in the 1000℃ test back temperature graph of the high-temperature resistant and wave-transparent silica aerogel composite material, the back temperature-time curve in the figure is flat. After the heating temperature fluctuates and drops sharply, the back temperature-time curve has no obvious fluctuation, and the highest temperature on the back is only 119.85℃. The thermal insulation performance of the composite material is excellent, which is more than 40% higher than that of existing aerogel composite materials.

[0091] Example 3

[0092] This embodiment provides a method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material, specifically:

[0093] Step S001: adding an alkaline catalyst solution to a mixture of ethyl orthosilicate and methyltrimethoxysilane (i.e., an organosilane precursor) in a mass ratio of 0.8:1 under heating conditions at 70° C., and stirring the mixture for 10 hours to obtain a silica sol.

[0094] The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.28wt%, and the volume ratio of ethanol to water is 1.2:1;

[0095] The molar ratio of the base to the organosilane precursor (ethyl orthosilicate and methyltrimethoxysilane) in the alkaline catalyst solution is 0.3:1.

[0096] Step S002: Place the silica sol in a replacement box equipped with an alcohol-water separation membrane, and separate and remove water from the silica sol at normal pressure and 45°C until the silica solid content is 18wt% and the water content is less than 5wt%, thereby obtaining the replaced silica sol for standby use.

[0097] The alcohol-water separation membrane used is an organic silicon membrane with a permeation flux of 3.3 kg·m -2 ·h -1 .

[0098] Step S003: Put boron nitride and silicon nitride into an ethanol aqueous solution with a volume concentration of 80%, stir evenly, then continue to add polyvinyl alcohol and fatty alcohol polyoxyethylene ether, stir evenly and place in a ball mill, and ball mill for 3 hours to obtain a pre-impregnated slurry; immerse the ceramic fiber felt in the pre-impregnated slurry, control the immersion pressure to 2MPa, take it out after immersion for 3 hours, and dry it at 75°C to constant weight to obtain a composite ceramic fiber felt.

[0099] The weight ratio of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 13:6.5:100:2.3:1.1;

[0100] Ceramic fiber felt is quartz fiber felt with a density of 0.2g / cm 3 , fiber diameter is 3 μm;

[0101] The volume ratio of ceramic fiber felt to prepreg slurry is 0.25:1.

[0102] Step S004: immerse the composite ceramic fiber felt in the replaced silica sol, heat to 55° C., keep warm for 5 hours for gelation, and allow to stand for 24 hours for aging to obtain a fiber felt / gel composite.

[0103] The volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.1:1.

[0104] Step S005: supercritically dry the fiber felt / gel composite, controlling the supercritical drying temperature to 280° C., the pressure to 8 MPa, the pressure reduction rate to 3 MPa / h, and the supercritical drying time to 4 h to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

[0105] This embodiment also provides a high-temperature resistant and wave-transmitting silica aerogel composite material prepared by the aforementioned method.

[0106] After testing, the dielectric constant of the high temperature resistant and wave-transmitting silica aerogel composite material is 1.28, and the dielectric loss is 6.4×10 -4 The thermal conductivity at room temperature is 0.026W / (m·k), the thermal conductivity at 800℃ is 0.048W / (m·k), the thermal conductivity at 1000℃ is 0.055W / (m·k), and the thermal conductivity at 1100℃ is 0.063W / (m·k); after treatment at 1100℃ for 2h, there is no shrinkage in the thickness direction, the flexural strength is 2.4MPa, and the compressive strength (10%) is 0.55MPa.

[0107] Comparative Example 1

[0108] Comparative Example 1 adopts the technical solution of Example 2, except that: 1) step S003 is omitted, and the ceramic fiber felt is directly immersed in the replaced silica sol; 2) supercritical drying is replaced by atmospheric pressure drying.

[0109] The scanning electron microscope image of the silicon oxide aerogel composite material prepared in Comparative Example 1 is as follows: Figure 3 After testing, the dielectric constant of the high temperature resistant and wave-transmitting silica aerogel composite material is 2.10, and the dielectric loss is 12.3×10 -4 The thermal conductivity at room temperature is 0.069W / (m·k), the thermal conductivity at 800℃ is 0.085W / (m·k), the thermal conductivity at 1000℃ is 0.151W / (m·k), and the thermal conductivity at 1100℃ is 0.197W / (m·k); the flexural strength is 1.9MPa, and the compressive strength (10%) is 0.47MPa.

[0110] Comparative Example 2

[0111] Comparative Example 2 adopts the technical solution of Example 2, except that step S002 is omitted and the composite material is directly prepared using silica sol.

[0112] The scanning electron microscope image of the silicon oxide aerogel composite material prepared in Comparative Example 2 is as follows: Figure 4 As shown. After testing, the dielectric constant of the silica aerogel composite material of Comparative Example 2 is 1.52, and the dielectric loss is 8.5×10 -4 The thermal conductivity at room temperature is 0.035W / m·k, the thermal conductivity at 800℃ is 0.068W / (m·k), the thermal conductivity at 1000℃ is 0.088W / (m·k), and the thermal conductivity at 1100℃ is 0.117W / (m·k).

[0113] Unless otherwise specified, all percentages used in the present invention are by mass.

[0114] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant and wave-transmitting silica aerogel composite material, characterized in that: The following steps are included: Step S001: adding an alkaline catalyst solution to an organosilane precursor under heating conditions to prepare a silica sol; Step S002: placing the silica sol in a replacement box equipped with an alcohol-water separation membrane to remove water from the silica sol until the silica sol has a silica solid content of 5-30 wt% and a water content of less than 5 wt%, thereby obtaining a replaced silica sol; Step S003: impregnating the ceramic fiber felt into the prepreg slurry, and drying after impregnation to obtain a composite ceramic fiber felt; In step S003, the prepreg slurry is composed of boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether; The weight ratio of the boron nitride, silicon nitride, ethanol aqueous solution, polyvinyl alcohol, and fatty alcohol polyoxyethylene ether is 12-13:6-6.5:100:2-2.3:0.9-1.1; the volume concentration of ethanol in the ethanol aqueous solution is 70-80%; Step S004: impregnating the composite ceramic fiber felt into the replaced silica sol, heating to gelate, and then aging to obtain a fiber felt / gel composite; Step S005: The fiber felt / gel composite is subjected to supercritical drying to obtain a high-temperature resistant and wave-transmitting silica aerogel composite material.

2. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S001, the heating temperature is 45-75°C; The organosilane precursor is a mixture of methyltrimethoxysilane and ethyl orthosilicate, or a mixture of methyltrimethoxysilane and methyl orthosilicate; The alkaline catalyst solution is an ethanol / water solution of ammonia, the mass fraction of ammonia is 0.25-0.5wt%, and the volume ratio of ethanol to water is 1-1.2:

1.

3. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S001, the molar ratio of the alkaline component in the alkaline catalyst solution to the organosilane precursor is 0.1-0.5:

1.

4. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S002, water in the silica sol is removed by using an alcohol-water separation membrane under normal pressure and a temperature of 30-50°C; The alcohol-water separation membrane is an organic silicon membrane with a permeation flux of 3.3-3.5 kg·m -2 ·h -1 .

5. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S003, the impregnation pressure is controlled to be 1.5-2 MPa, and the impregnation time is 2-3 hours; the ceramic fiber felt is quartz fiber felt with a density of 0.15-0.3 g / cm 3 , fiber diameter is 1-5 μm; The volume ratio of ceramic fiber felt to prepreg slurry is 0.2-0.25:

1.

6. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S004, the heating and gelling temperature is 40-60° C., and the heating and gelling time is 3-8 hours; The aging time is 22-24h.

7. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S004, the volume ratio of the composite ceramic fiber felt to the replaced silica sol is 0.05-0.1:

1.

8. The method for preparing the high temperature resistant and wave-transmitting silica aerogel composite material according to claim 1, characterized in that: In step S005, the supercritical drying temperature is controlled to be 270-280° C., the pressure is controlled to be 8-10 MPa, the pressure reduction rate is controlled to be 2-3 MPa / h, and the supercritical drying time is controlled to be 2-4 hours.

9. A high temperature resistant and wave-transmitting silica aerogel composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The dielectric constant is 1.1-1.3, and the dielectric loss is (5-30)×10 -4 The thermal conductivity coefficient at room temperature is 0.025-0.027W / (m·K), and the thermal conductivity coefficient at 1000℃ is 0.054-0.055W / (m·K).

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