An oxide ceramic fiber composite aerogel material with infrared shielding and wave absorbing performance and a preparation method thereof

Abstract

The application discloses an oxide ceramic fiber-based composite aerogel material with infrared shielding and wave absorbing performance and a preparation method thereof. The ceramic fiber composite aerogel material takes oxide ceramic fiber as a basic component unit, takes SiO2 / C sol as a high-temperature binder, a silicon source and a carbon source, and grows a large number of SiC nanowires in the aerogel through a carbon thermal reduction reaction to form an oxide-based ceramic fiber composite aerogel material with infrared shielding and wave absorbing performance. The oxide ceramic fiber-based composite aerogel material has an infrared transmittance of less than 10%, has excellent high-temperature heat insulation effect, and has a compression strength under 10% strain of greater than 0.89 MPa. In addition, the oxide ceramic fiber-based composite aerogel material has excellent wave absorbing performance, and when the thickness is 3.6 mm, the minimum reflection loss is up to -46.2 dB at 7.7 GHz, and the effective absorption bandwidth is 2.83 GHz.

Description

Technical Field

[0001] This invention relates to the field of ceramic fiber materials technology, specifically to an oxide ceramic fiber-based composite aerogel material that simultaneously possesses infrared shielding and wave absorption properties, and its preparation method. Background Technology

[0002] With the continuous development of aerospace and military technologies, supersonic fighter jets, missiles, and other weapons systems flying at high Mach numbers not only have to face extremely harsh thermal environments, but also face the risk of being "detected and shot down" by increasingly advanced enemy radar detection devices. An effective way to solve this problem is to use lightweight high-temperature insulation and radar-absorbing materials to reduce the weight of weapons systems while meeting their requirements for high-temperature thermal protection and radar-absorbing stealth protection, thereby improving their flexibility.

[0003] Ceramic fiber aerogels exhibit extremely low density and excellent thermal insulation properties due to their extremely high porosity, making them potential candidate materials for high-temperature thermal protection in weaponry. Oxide ceramic fiber aerogels, particularly those constructed from oxide ceramic fibers such as mullite, alumina, and zirconia, which possess low thermal conductivity at room temperature, show the greatest application potential. However, because oxide ceramic fibers are transparent in the ~2.5-7μm infrared range, their thermal conductivity increases dramatically with temperature, severely impacting their high-temperature insulation performance. Furthermore, since oxide ceramic fiber aerogels lack electromagnetic wave absorption properties, they are currently only used as high-temperature thermal protection materials for weaponry. For stealth protection of weaponry, additional electromagnetic wave absorbing materials must be used, which undoubtedly increases the weight of the weaponry. Therefore, addressing the problem of the rapid increase in thermal conductivity at high temperatures while simultaneously endowing oxide ceramic fiber aerogels with electromagnetic wave absorption properties is crucial for the development of weaponry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an oxide ceramic fiber composite aerogel material and its preparation method that simultaneously possess infrared shielding and wave absorption properties. This invention not only solves the problem of the rapid increase in thermal conductivity of oxide ceramic fiber aerogel at high temperatures, but also endows it with a certain electromagnetic wave absorption effect, which can simultaneously provide high-temperature thermal protection and wave absorption stealth protection for weapons and equipment.

[0005] The present invention adopts the following technical solution:

[0006] An oxide-based ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties is proposed. The basic building block is oxide ceramic fiber, and SiO2 / C sol is used as a high-temperature binder, silicon source and carbon source. SiC nanowires are grown in large quantities inside the aerogel through carbothermal reduction reaction to form an oxide-based ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties.

[0007] A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and microwave absorption properties includes the following steps:

[0008] Step 1: Mix tetraethyl orthosilicate, glucose, ethanol, distilled water and acid in a molar ratio of 1:4:(16~32):(8~16):(0.01~0.10) and stir at 25℃~60℃ for 1~6h to obtain SiO2 / C sol;

[0009] Step 2: Mix ceramic fiber, distilled water, and SiO2 / C sol at a mass ratio of (5-30):1:(0.02-0.15), stir magnetically at 25℃-60℃ for 20-30 minutes, and then place in an ultrasonic device for ultrasonication for 10-20 minutes. Repeat the magnetic stirring and ultrasonication process 2-3 times.

[0010] Step 3: Freeze the above fiber dispersion in a refrigerator for 2-10 hours, and then place the sample in a freeze dryer and vacuum for 24-48 hours to obtain a ceramic fiber aerogel preform.

[0011] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and carry out a high-temperature carbothermic reduction reaction under an inert atmosphere to obtain a ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel.

[0012] Furthermore, in step 1, the acid is one of acetic acid, phosphoric acid, nitric acid, or hydrochloric acid.

[0013] Furthermore, in step 2, the ceramic fiber is one or more of mullite fiber, zirconia fiber, and alumina fiber; the length of the ceramic fiber is 15-200 μm.

[0014] Furthermore, in step 2, the ceramic fiber dispersion is magnetically stirred for 20-30 minutes, then placed in an ultrasonic device and ultrasonicated at a frequency of 20-25 kHz for 10-20 minutes; then the ultrasonically treated fiber dispersion is stirred again, and this cycle is repeated 2-3 times.

[0015] Furthermore, in step 3, the freezer temperature is -20℃ to -80℃.

[0016] Furthermore, in step 3, the vacuum level of the freeze dryer remains below 20 Pa throughout the freeze-drying process.

[0017] Furthermore, in step 4, the heating rate in the tube furnace is 1–5 °C / min, the reaction temperature is 1300 °C–1400 °C, and the holding time is 2–6 h.

[0018] Furthermore, in step 4, the inert atmosphere is either nitrogen or argon.

[0019] As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are:

[0020] First, the ceramic fiber composite aerogel material prepared by this invention uses oxide ceramic fibers as the main raw material, with SiO2 / C sol serving as the high-temperature binder, silicon source, and carbon source, respectively. It is prepared by freeze-drying combined with a high-temperature carbothermal reduction reaction. SiC nanowires are grown inside the oxide ceramic fiber composite aerogel material, which can endow it with infrared shielding and electromagnetic wave absorption properties. At the same time, the numerous SiC nanowires grow together and intertwine, which can fill the original large pores of the aerogel, enrich its pore structure, hinder heat transfer, and enhance the multiple reflection loss of electromagnetic waves. The prepared aerogel material is lightweight, has low thermal conductivity at room temperature and high temperature, and exhibits excellent infrared shielding and wave absorption properties. It can be used as a high-temperature thermal protection and wave absorption stealth protection material for weapons such as supersonic fighter jets and missiles.

[0021] Secondly, the SiC nanowires grown inside the ceramic fiber composite aerogel material can improve the infrared shielding performance of the aerogel, which is beneficial to reducing its high-temperature infrared thermal radiation, thereby solving the problem of the rapid increase in thermal conductivity of oxide ceramic fiber aerogel at high temperature; and it also has high toughness, which helps to improve the mechanical properties of oxide ceramic fiber aerogel.

[0022] Third, the oxide ceramic fiber-based composite aerogel material of the present invention has an infrared transmittance of less than 10%, exhibiting excellent high-temperature thermal insulation effect. At the same time, its compressive strength at 10% strain is greater than 0.89 MPa. In addition, it exhibits excellent wave absorption performance, with a minimum reflection loss of -46.2 dB at 7.7 GHz and an effective absorption bandwidth of 2.83 GHz at a thickness of 3.6 mm.

[0023] Fourth, the oxide ceramic fiber-based composite aerogel material of the present invention has a simple preparation process and low cost, and is of great significance for the development of integrated materials for high-temperature thermal protection and wave-absorbing stealth protection of weapons and equipment. Attached Figure Description

[0024] Figure 1 This is a photograph of the oxide ceramic fiber composite aerogel material prepared in Example 1;

[0025] Figure 2 SEM image of the oxide ceramic fiber composite aerogel material prepared according to the present invention in Example 2;

[0026] Figure 3 Infrared transmittance of the oxide ceramic fiber-based composite aerogel material prepared in Example 3 in the wavelength range of 2.5–7.0 μm;

[0027] Figure 4The electromagnetic wave reflection loss diagram is shown for the oxide ceramic fiber-based composite aerogel material prepared in Example 4. Detailed Implementation

[0028] The present invention will be further described below through specific embodiments.

[0029] An oxide-based ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties is proposed. The basic building block is oxide ceramic fiber, and SiO2 / C sol is used as a high-temperature binder, silicon source and carbon source. SiC nanowires are grown in large quantities inside the aerogel through carbothermal reduction reaction to form an oxide-based ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties.

[0030] Its preparation method includes the following steps:

[0031] Step 1: Mix tetraethyl orthosilicate, glucose, ethanol, distilled water and acid in a molar ratio of 1:4:(16~32):(8~16):(0.01~0.10) and stir at 25℃~60℃ for 1~6h to obtain SiO2 / C sol;

[0032] Step 2: Mix ceramic fiber with distilled water and SiO2 / C sol at a mass ratio of (5-30):1:(0.02-0.15), stir magnetically at 25℃-60℃ for 20-30 minutes, and then place it in an ultrasonic device and sonicate at a frequency of 20-25kHz for 10-20 minutes. Repeat the magnetic stirring and sonication process 2-3 times.

[0033] Step 3: Place the above fiber dispersion in a refrigerator and freeze at -20℃ to -80℃ for 2 to 10 hours. Then place the sample in a freeze dryer and evacuate it for 24 to 48 hours. The vacuum degree is always below 20 Pa during the freeze drying process to obtain ceramic fiber aerogel preform.

[0034] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and carry out a high-temperature carbothermic reduction reaction under an inert atmosphere to obtain a ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel. The heating rate in the tube furnace is 1-5℃ / min, the reaction temperature is 1300℃-1400℃, and the holding time is 2-6h.

[0035] Specifically, in step 1, the acid is one of acetic acid, phosphoric acid, nitric acid, or hydrochloric acid.

[0036] In step 2, the ceramic fiber is one or more of mullite fiber, zirconia fiber, and alumina fiber; and the length of the ceramic fiber is 15 to 200 μm.

[0037] In step 4, the inert atmosphere is either nitrogen or argon.

[0038] Example 1

[0039] A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and microwave absorption properties includes the following steps:

[0040] Step 1: Tetraethyl orthosilicate, glucose, ethanol, distilled water and phosphoric acid are mixed in a molar ratio of 1:4:16:8:0.01 and stirred at 25°C for 2 hours to obtain SiO2 / C sol.

[0041] Step 2: Mix mullite fiber, distilled water, and SiO2 / C sol at a mass ratio of 8:1:0.03, stir magnetically at 25°C for 20 minutes, and then sonicate in an ultrasonic device for 10 minutes. Repeat the magnetic stirring and ultrasonication process twice.

[0042] Step 3: Freeze the above fiber dispersion in a refrigerator for 3 hours, and then place the sample in a freeze dryer and vacuum for 24 hours to obtain a ceramic fiber aerogel preform;

[0043] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and, under nitrogen atmosphere protection, raise the temperature to 1350℃ at a heating rate of 2℃ / min and hold for 2 hours to obtain a mullite-based ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel.

[0044] Physical images of the materials prepared above are attached. Figure 1 As shown; the fiber has a thermal conductivity of 0.025 W·m at room temperature (25℃). -1 ·K -1 The high-temperature thermal conductivity at 1000℃ is 0.053 W·m. -1 ·K -1 The infrared transmittance is less than 10% in the band between 2.5 and 7.0 μm; at a thickness of 4.3 mm, the minimum reflection loss reaches -48.2 dB at 6.5 GHz, and the effective absorption bandwidth is 4.62 GHz.

[0045] Example 2

[0046] A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and microwave absorption properties includes the following steps:

[0047] Step 1: Mix tetraethyl orthosilicate, glucose, ethanol, distilled water and hydrochloric acid in a molar ratio of 1:4:20:8:0.03 and stir at 30°C for 3 hours to obtain SiO2 / C sol;

[0048] Step 2: Mix alumina fiber, distilled water, and SiO2 / C sol at a mass ratio of 15:1:0.05, stir magnetically at 30°C for 30 minutes, and then place in an ultrasonic device for ultrasonication for 20 minutes. Repeat the magnetic stirring and ultrasonication process 3 times.

[0049] Step 3: Freeze the above fiber dispersion in a refrigerator for 5 hours, and then place the sample in a freeze dryer and vacuum for 48 hours to obtain a ceramic fiber aerogel preform.

[0050] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and, under argon atmosphere protection, raise the temperature to 1300℃ at a heating rate of 5℃ / min and hold for 5 hours to obtain an alumina-based ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel.

[0051] SEM images of the materials prepared above are attached. Figure 2 As shown; the thermal conductivity at room temperature (25℃) is 0.016 W·m. -1 ·K -1 The high-temperature thermal conductivity at 1000℃ is 0.047 W·m. -1 ·K -1 The infrared transmittance is less than 3% in the band between 2.5 and 7.0 μm; at a thickness of 4.9 mm, the minimum reflection loss at 7.2 GHz reaches -52.3 dB, and the effective absorption bandwidth is 3.92 GHz.

[0052] Example 3

[0053] A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and microwave absorption properties includes the following steps:

[0054] Step 1: Tetraethyl orthosilicate, glucose, ethanol, distilled water and acetic acid are mixed in a molar ratio of 1:4:32:8:0.02 and stirred at 60°C for 1 hour to obtain SiO2 / C sol;

[0055] Step 2: Mix zirconium oxide fiber, distilled water, and SiO2 / C sol at a mass ratio of 20:1:0.10, stir magnetically at 60°C for 20 minutes, and then place in an ultrasonic device for ultrasonication for 10 minutes. Repeat the magnetic stirring and ultrasonication process twice.

[0056] Step 3: Freeze the above fiber dispersion in a refrigerator for 10 hours, and then place the sample in a freeze dryer and vacuum for 40 hours to obtain a ceramic fiber aerogel preform.

[0057] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and, under nitrogen atmosphere protection, raise the temperature to 1360℃ at a heating rate of 3℃ / min and hold for 3 hours to obtain a zirconia-based ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel.

[0058] The material prepared above has a thermal conductivity of 0.025 W·m at room temperature (25°C). -1 ·K -1 The high-temperature thermal conductivity at 1000℃ is 0.061 W·m. -1 ·K -1 The infrared transmittance is less than 6% in the wavelength range of 2.5–7.0 μm, as shown in the attached image. Figure 3 As shown, with a thickness of 3.3 mm, its minimum reflection loss reaches -43.1 dB at 6.5 GHz, and its effective absorption bandwidth is 4.75 GHz.

[0059] Example 4

[0060] A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and microwave absorption properties includes the following steps:

[0061] Step 1: Tetraethyl orthosilicate, glucose, ethanol, distilled water and nitric acid are mixed in a molar ratio of 1:4:16:8:0.05 and stirred at 30°C for 6 hours to obtain SiO2 / C sol.

[0062] Step 2: Mix mullite fiber, distilled water, and SiO2 / C sol at a mass ratio of 30:1:0.15, stir magnetically at 30°C for 30 minutes, and then sonicate in an ultrasonic device for 20 minutes. Repeat the magnetic stirring and ultrasonication process 3 times.

[0063] Step 3: Freeze the above fiber dispersion in a refrigerator for 10 hours, and then place the sample in a freeze dryer and vacuum for 48 hours to obtain a ceramic fiber aerogel preform.

[0064] Step 4: Place the ceramic fiber aerogel preform in a tube furnace and, under argon atmosphere protection, raise the temperature to 1400℃ at a heating rate of 2℃ / min and hold for 2 hours to obtain a mullite-based ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel.

[0065] The material prepared above has a thermal conductivity of 0.013 W·m at room temperature (25°C). -1 ·K -1 The high-temperature thermal conductivity at 1000℃ is 0.041 W·m. -1 ·K -1 Infrared transmittance is less than 1% in the 2.5–7.0 μm band; at a thickness of 3.6 mm, its minimum reflection loss at 7.7 GHz reaches -46.2 dB, with an effective absorption bandwidth of 2.83 GHz, and electromagnetic wave reflection loss is as follows: Figure 4 As shown.

[0066] In summary, the oxide ceramic fiber-based composite aerogel material of this invention has an infrared transmittance of less than 10%, exhibiting excellent high-temperature thermal insulation performance. Furthermore, its compressive strength at 10% strain is greater than 0.89 MPa. In addition, it demonstrates superior microwave absorption performance, achieving a minimum reflection loss of -46.2 dB at 7.7 GHz with an effective absorption bandwidth of 2.83 GHz at a thickness of 3.6 mm. Its preparation process is simple and low-cost, making it of great significance for the development of integrated materials for high-temperature thermal protection and microwave absorption stealth protection of weapon systems.

[0067] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing an oxide-ceramic fiber composite aerogel material possessing both infrared shielding and wave absorption properties, characterized in that: Using oxide ceramic fibers as the basic building blocks and SiO2 / C sol as a high-temperature binder, silicon source, and carbon source, SiC nanowires are grown in large quantities inside the aerogel through a carbothermal reduction reaction, forming an oxide-based ceramic fiber composite aerogel material that simultaneously possesses infrared shielding and wave absorption properties. The preparation method specifically includes the following steps: Step 1: Mix tetraethyl orthosilicate, glucose, ethanol, distilled water and acid in a molar ratio of 1:4:(16~32):(8~16):(0.01~0.10) and stir at 25℃~60℃ for 1~6h to obtain SiO2 / C sol; Step 2: Mix ceramic fiber, distilled water, and SiO2 / C sol at a mass ratio of (5~30):1:(0.02~0.15), stir magnetically at 25℃~60℃ for 20~30 min, and then place it in an ultrasonic device for 10~20 min. Repeat the magnetic stirring and ultrasonication cycle 2~3 times to obtain a fiber dispersion. Step 3: Freeze the above fiber dispersion in a refrigerator for 2-10 hours, and then place the sample in a freeze dryer and vacuum for 24-48 hours to obtain a ceramic fiber aerogel preform. Step 4: Place the ceramic fiber aerogel preform in a tube furnace and carry out a high-temperature carbothermic reduction reaction under an inert atmosphere to obtain a ceramic fiber composite aerogel material with SiC nanowires grown inside the aerogel. In step 2, the ceramic fiber is one or more of mullite fiber, zirconia fiber, and alumina fiber; the length of the ceramic fiber is 15~200µm. In step 4, the heating rate in the tube furnace is 1~5℃ / min, the reaction temperature is 1300℃~1400℃, and the holding time is 2~6h.

2. The method for preparing an oxide ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties according to claim 1, characterized in that: In step 1, the acid is one of acetic acid, phosphoric acid, nitric acid, or hydrochloric acid.

3. The method for preparing an oxide ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties according to claim 1, characterized in that: In step 2, the ceramic fiber dispersion is magnetically stirred for 20-30 minutes, then placed in an ultrasonic device and ultrasonicated at a frequency of 20-25 kHz for 10-20 minutes; then the ultrasonically treated fiber dispersion is stirred again, and this cycle is repeated 2-3 times.

4. The method for preparing an oxide ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties according to claim 1, characterized in that: In step 3, the freezer temperature is -20℃ to -80℃.

5. The method for preparing an oxide ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties according to claim 1, characterized in that: In step 3, the vacuum level of the freeze dryer remains below 20 Pa throughout the freeze drying process.

6. The method for preparing an oxide ceramic fiber composite aerogel material with both infrared shielding and wave absorption properties according to claim 1, characterized in that: In step 4, the inert atmosphere is either nitrogen or argon.

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