FeSiAl-siC wave-absorbing composite material, preparation method and application thereof

Abstract

The application provides a FeSiAl-SiC wave-absorbing composite material and a preparation method and application thereof, relates to the technical field of wave-absorbing material preparation, and the method comprises the following steps: FeSiAl alloy powder and SiC powder are ball-milled and mixed according to a first preset mass ratio to obtain FeSiAl-SiC composite powder; the FeSiAl-SiC composite powder and high-temperature inorganic glue are uniformly ground and mixed according to a second preset mass ratio, and then are formed by die pressing to obtain a blank; the blank is solidified at room temperature, and then is solidified by programmed temperature rising to obtain the FeSiAl-SiC wave-absorbing composite material. The preparation process is simple, the material is light, thin and has excellent low-frequency absorption performance, and the material has wide-temperature-zone stability and is suitable for S-band, C-band and high-temperature electromagnetic wave absorption.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing material preparation technology, specifically to a FeSiAl-SiC microwave absorbing composite material, its preparation method, and its application. Background Technology

[0002] Electromagnetic wave absorbing materials have important applications in fields such as stealth, electromagnetic radiation protection, and anti-interference for civilian electronic equipment. As radar detection technology develops towards lower frequency bands (such as S-band and C-band), there is an urgent need for absorbing materials that can achieve efficient absorption at low frequencies while meeting the requirements of lightweight, thinness, and high-temperature stability.

[0003] Currently, commonly used microwave absorbing materials mainly include dielectric absorbing agents (such as SiC and carbon materials). However, single SiC-based microwave absorbing materials generally suffer from bottlenecks such as a single dielectric loss mechanism, insufficient absorption efficiency at low frequencies (such as S-band and C-band), large matching thickness, and narrow effective absorption bandwidth, making it difficult to meet the needs of modern equipment for thin, wide, lightweight, and strong microwave absorbing materials.

[0004] In existing technologies, SiC-based composite materials (Al2O3 or rare-earth modified SiC composite materials, such as SiC+Al2O3+Y2O3) are generally used. However, their bandwidth with reflection loss RL < -5dB in the S-band is limited, and the thickness corresponding to the low-frequency absorption peak is relatively large. More importantly, the magnetic properties of most microwave absorbing composite materials decrease sharply in high-temperature environments (such as 400℃-600℃), making it difficult to meet the application requirements of high-temperature stealth or high-temperature electromagnetic absorption. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a FeSiAl-SiC microwave absorbing composite material, its preparation method and application, and to solve at least one technical problem in the background art.

[0006] A first aspect of the present invention is to provide a method for preparing a FeSiAl-SiC microwave absorbing composite material, the method comprising: FeSiAl alloy powder and SiC powder are ball-milled and mixed at a first preset mass ratio to obtain FeSiAl-SiC composite powder. The FeSiAl-SiC composite powder and high-temperature inorganic adhesive are ground and mixed evenly according to a second preset mass ratio, and then molded to obtain a blank. The preform was cured at room temperature and then cured by programmed temperature increase to obtain the FeSiAl-SiC microwave absorbing composite material.

[0007] According to one aspect of the above technical solution, the first preset mass ratio is (2-3):1, the particle size of the FeSiAl alloy powder is 8μm-12μm, and the particle size of the SiC powder is 0.5μm-2μm.

[0008] According to one aspect of the above technical solution, the ball mill adopts a planetary ball mill with a ball milling speed of 200r / min-400r / min and a ball milling time of 3h-5h.

[0009] According to one aspect of the above technical solution, the high-temperature inorganic adhesive includes silicic acid and alumina, and the mass ratio of silicic acid to alumina is (1-3):1.

[0010] According to one aspect of the above technical solution, the second preset mass ratio is (7-9):(3-2).

[0011] According to one aspect of the above technical solution, the compression molding pressure is 12MPa-20MPa, and the holding time is 20s-40s.

[0012] According to one aspect of the above technical solution, the curing time at room temperature is 12h-24h.

[0013] According to one aspect of the above technical solution, the programmed temperature-curing step includes: Heat to 70℃-90℃ and hold for 1.5h-2.5h; Raise the temperature to 140℃-160℃ and hold for 1.5h-2.5h.

[0014] A second aspect of the present invention is to provide a FeSiAl-SiC microwave absorbing composite material, wherein the FeSiAl-SiC microwave absorbing composite material is prepared by the above-described method for preparing FeSiAl-SiC microwave absorbing composite material, and the density of the FeSiAl-SiC microwave absorbing composite material is 2.9 g / cm³. 3 -3.1g / cm 3 .

[0015] A third aspect of the present invention is to provide an application of the FeSiAl-SiC microwave absorbing composite material as described above, wherein the FeSiAl-SiC microwave absorbing composite material is used for electromagnetic wave absorption at the lower end of the S-band, C-band or X-band, or for electromagnetic wave absorption in high-temperature environments above 500°C.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention uses FeSiAl alloy, which possesses excellent oxidation resistance and low-frequency resonance, as the magnetic component to prepare FeSiAl-SiC microwave absorbing composite material with SiC. This material can achieve low-band microwave absorption performance in thin materials. In terms of absorption performance, this material can effectively absorb in the S-band even at a thin thickness and has a good absorption effect over a wide frequency range, improving the absorption efficiency per unit thickness. In addition, this material has excellent thermal stability and high-temperature magnetic properties. Its mass change is minimal over a wide temperature range, and it still retains considerable magnetic loss capacity at high temperatures. After wide-temperature aging treatment, its absorption performance does not decrease but increases. Moreover, its absorption performance under high-temperature in-situ testing is better than that at room temperature, exhibiting stable absorption characteristics that are almost unaffected by temperature changes. It is suitable for electromagnetic wave absorption in the S-band, C-band, low-end X-band, and high-temperature environments.

[0017] 2. The preparation process of FeSiAl-SiC microwave absorbing composite material is simple, requiring only ball milling, pressing and low-temperature curing, without the need for high-temperature sintering, resulting in low cost and easy large-scale production; the resulting material has low density and light weight, meeting the requirements for lightweighting. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a SEM image of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention; Figure 2 The room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention is shown. Figure 3 The room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Example 2 of this invention is shown. Figure 4 The room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Example 3 of this invention is shown. Figure 5 This is a room temperature reflectance curve of the SiC microwave absorbing material prepared in Comparative Example 1 of this invention; Figure 6 The room temperature reflectance curve of the FeSiAl microwave absorbing material prepared in Comparative Example 2 of this invention is shown. Figure 7 This is a room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Comparative Example 3 of this invention; Figure 8 This is a room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Comparative Example 4 of this invention; Figure 9This is a room temperature reflectance curve of the FeSiAl-SiC microwave absorbing composite material prepared in Comparative Example 5 of this invention; Figure 10 This is a room temperature reflectance curve of the pure SiC material prepared in Comparative Example 6 of this invention; Figure 11 This is a room temperature reflectance curve of the pure FeSiAl material prepared in Comparative Example 7 of this invention. Figure 12 The graph shows the complex permeability of the FeSiAl-SiC microwave absorbing composite material prepared in Example 2 of this invention. Figure 13 The TGA curve of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention; Figure 14 The MT curve of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention; Figure 15 The reflectance curves of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention after aging at different temperatures for 4 hours are shown. Figure 16 The graph shows the reflectance curves of the FeSiAl-SiC microwave absorbing composite material prepared in Example 1 of this invention at different temperatures. Detailed Implementation

[0019] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] This invention provides a method for preparing FeSiAl-SiC microwave absorbing composite material, the method comprising: steps S1-S3.

[0021] Step S1: FeSiAl alloy powder and SiC powder are ball-milled and mixed at a first preset mass ratio to obtain FeSiAl-SiC composite powder; Among them, Fe, Si, and Al elements easily form a dense oxide protective layer at high temperatures, which has better oxidation resistance than pure Fe or FeCo alloys, and its magnetic permeability is well matched with the dielectric constant of SiC.

[0022] Specifically, the first preset mass ratio is (2-3):1, the particle size of FeSiAl alloy powder is 8μm-12μm, and the particle size of SiC powder is 0.5μm-2μm. By combining specific ratios and particle sizes, the synergy between magnetic loss and dielectric loss is achieved, and the absorption peak is tuned to the S-band.

[0023] The ball milling process employs a planetary ball mill with a milling speed of 200 r / min-400 r / min and a milling time of 3 h-5 h. Ball milling ensures thorough dispersion of the FeSiAl and SiC phases, preventing agglomeration and guaranteeing the microscopic uniformity of the subsequent composite material.

[0024] Step S2: Grind and mix the FeSiAl-SiC composite powder and high-temperature inorganic adhesive at a second preset mass ratio until uniform, and then mold the mixture to obtain a blank. The high-temperature inorganic adhesive comprises silicate and alumina in a mass ratio of (1-3):1. As a binder, the high-temperature inorganic adhesive forms a ceramic phase framework during subsequent curing without significantly affecting electromagnetic parameters. The optimized ratio of silicate to alumina provides sufficient bond strength without compromising microwave absorption performance.

[0025] The second preset mass ratio is (7-9):(3-2).

[0026] The compression molding pressure is 12MPa-20MPa, and the holding time is 20s-40s.

[0027] Step S3: The preform is cured at room temperature and then cured by programmed temperature rise to obtain FeSiAl-SiC microwave absorbing composite material.

[0028] The curing time at room temperature is 12h-24h.

[0029] The process of temperature-curing includes: Heat to 70℃-90℃ and hold for 1.5h-2.5h; Raise the temperature to 140℃-160℃ and hold for 1.5h-2.5h.

[0030] Compression molding within a specific pressure range combined with a stepped temperature curing process is employed. The pressure is applied to achieve high density and optimize electromagnetic parameters, while the specific low-temperature curing process is used to avoid damaging the magnetism of FeSiAl at high temperatures and to ensure that the binder is fully cured, thereby improving strength.

[0031] Accordingly, the present invention also provides a FeSiAl-SiC microwave absorbing composite material, which is prepared by the above-mentioned preparation method of FeSiAl-SiC microwave absorbing composite material, and the density of the FeSiAl-SiC microwave absorbing composite material is 2.9 g / cm³. 3 -3.1g / cm 3 .

[0032] In addition, the present invention also provides an application of the FeSiAl-SiC microwave absorbing composite material as described above, wherein the FeSiAl-SiC microwave absorbing composite material is used for electromagnetic wave absorption at the low end of the S-band, C-band or X-band, or for electromagnetic wave absorption in high temperature environments above 500°C.

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0034] Example 1 The present invention provides a method for preparing FeSiAl-SiC microwave absorbing composite material, the method comprising: steps S1-S3.

[0035] Step S1, take FeSiAl (FeSi) particles with a diameter of 10 μm. 9.6 Al 5.4‌ Alloy powder and SiC powder with a particle size of 1μm were weighed at a mass ratio of 3:1, poured into a nylon ball mill jar, and milled for 4 hours using a planetary ball mill at a speed of 300r / min (ball-to-material ratio of 4:1). The ball milling medium was ethanol. After being removed, the powder was placed in an oven and dried in air at 80℃ until the ethanol was completely evaporated. The powder was then passed through an 80-mesh sieve to obtain FeSiAl-SiC composite powder. Step S2: 50g of FeSiAl-SiC composite powder and 12g of high-temperature inorganic adhesive are thoroughly stirred, then poured into a mortar and ground further until uniformly mixed. The mixture is then loaded into a mold, and a powder tablet press is used to apply a pressure of 20MPa for 30s to press and form a blank. The high-temperature inorganic adhesive includes silicic acid and alumina, with 8g of silicic acid and 4g of alumina (silicic acid: alumina = 2:1).

[0036] Step S3: Place the blank at room temperature for 16 hours, then put it into an oven, heat it to 80°C, keep it at that temperature for 2 hours, then heat it to 150°C, keep it at that temperature for 2 hours, and then let it cool naturally to room temperature to obtain the FeSiAl-SiC microwave absorbing composite material.

[0037] The process involves initial solidification of the high-temperature inorganic adhesive in the green body at room temperature, followed by heat treatment at 80℃ to remove residual solvent and initiate cross-linking, and finally, heat treatment at 150℃ to complete curing and form a stable ceramic binder phase. Press molding densifies the material, achieving a density of 3.1 g / cm³.3 This improves impedance matching and mechanical strength.

[0038] through Figure 1 SEM observations showed that SiC particles were uniformly attached to the surface of FeSiAl particles, forming a heterogeneous interface, which is beneficial to interfacial polarization loss.

[0039] Example 2 The difference between Embodiment 2 and Embodiment 1 is that the first preset mass ratio is 2:1, and the pressing molding process densifies the material, achieving a density of up to 3.0 g / cm³. 3 The other steps are the same.

[0040] Example 3 The difference between Embodiment 3 and Embodiment 1 is that the pressing pressure of 20MPa is replaced with 12MPa, while the other steps are the same.

[0041] Comparative Example 1 The difference between Comparative Example 1 and Example 1 of the present invention is that in step S1, SiC (90%) + Al2O3 (5%) + Y2O3 (5%) replaces FeSiAl-SiC composite powder, and FeSiAl alloy powder is not added. The other steps are the same, and SiC microwave absorbing material is obtained.

[0042] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in step S1, SiC powder is removed and FeSiAl alloy powder is used entirely, while the other steps are the same, to obtain FeSiAl microwave absorbing material.

[0043] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the molding process in step S2 is removed, the mixed powder is directly poured into a mold with adjustable thickness, gently vibrated to make the surface roughly flat, and then manually applied with a pressure of 0.25 MPa for 30 seconds to flatten it. The other steps are the same.

[0044] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the first preset mass ratio is 1:1, while the other steps are the same.

[0045] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the first preset mass ratio is 1:2, while the other steps are the same.

[0046] Comparative Example 6 In Comparative Example 6 of this invention, SiC powder and paraffin wax were mixed in a mass ratio of 8:2. The mixed powder was poured into a mold with adjustable thickness, and the surface was gently vibrated to make it roughly flat. A pressure of 0.25 MPa was applied manually for 30 seconds to flatten it, thus obtaining pure SiC material. Solid paraffin wax is an insulating and non-magnetic substance, and it is a transparent material for electromagnetic waves, only acting as a binder. Therefore, the electromagnetic loss of the composite material can be attributed to the role of SiC powder.

[0047] Comparative Example 7 Comparative Example 7 of this invention uses FeSiAl alloy powder mixed with paraffin wax at a mass ratio of 8:2. The mixed powder is directly poured into a mold with adjustable thickness, gently vibrated to make the surface roughly flat, and then manually pressed flat with a pressure of 0.25MPa for 30s to obtain pure FeSiAl material.

[0048] 1. Electromagnetic parameter testing By using a waveguide cavity electromagnetic parameter testing system and a coaxial method testing system to test its electromagnetic parameters, and based on the formula for calculating the magnetic loss tangent, the magnetic loss versus frequency curve can be obtained; the reflection loss RL of composite materials of different thicknesses versus frequency curves can be calculated based on transmission line theory (see...). Figures 2-11 ).

[0049] Comparative Example 1 uses SiC absorbing material (SiC+Al2O3+Y2O3), requiring a thickness of over 3.5 mm in the S-band to achieve a point-frequency reflectivity (RL) < -10 dB, with an extremely narrow effective bandwidth (< 0.5 GHz). Comparative Example 2 uses FeSiAl absorbing material, which has almost no effective absorption performance in the S-band. Comparative Example 6 uses pure SiC material with very poor absorption performance. Comparative Example 7 uses pure FeSiAl material, which is beneficial for low frequencies, but is still not ideal when used alone (eddy current loss causes it to fail). In contrast, Example 1 achieves a continuous frequency band RL < -10 dB (bandwidth 0.2 GHz - 0.53 GHz) with a thinner thickness (2.2 mm - 3.0 mm), and the RL < -5 dB bandwidth is significantly increased (1.38 GHz vs < 0.5 GHz).

[0050] Furthermore, when the thickness of Example 3 (molding pressure of 12 MPa) is 2.2 mm, there is no effective absorption frequency band below -10 dB; effective absorption (RL < -10 dB) begins to appear from a thickness of 2.5 mm. As the thickness increases, the effective absorption frequency band shifts to lower frequencies, and the bandwidth gradually widens. When the thickness increases from 2.5 mm to 2.9 mm, the effective absorption bandwidth increases from 0.25 GHz to 1.0 GHz, demonstrating good thin-layer S-band absorption potential. Compared with Example 1 (molding pressure of 20 MPa), only a thickness of 2.2 mm is required to achieve effective absorption, indicating that increasing the molding pressure can significantly reduce the minimum thickness required for the material to achieve effective absorption. This is because the increased pressure enhances the loss capability of the FeSiAl-SiC absorbing composite material against electromagnetic waves, while simultaneously shifting the resonant absorption peak to lower frequencies.

[0051] Furthermore, in Comparative Example 3 (artificially flattened by applying 0.25 MPa pressure), the thickness needs to be increased to 4.0 mm to achieve a resonance point with RL < -10 dB at 4.0 GHz. In contrast, Example 1, with a thickness of only 2.2 mm, achieves RL < -10 dB in the 3.4 GHz–3.6 GHz frequency range and RL < -5 dB in the 2.62 GHz–4.00 GHz frequency range. This indicates that compression molding improves the material's density, optimizes the matching of dielectric constant and permeability, and significantly enhances absorption efficiency, thereby achieving low-frequency absorption with thin materials.

[0052] Furthermore, in Example 2 (FeSiAl:SiC=2:1), when the thickness is 2.5 mm, the frequency corresponding to the absorption peak is located in the S-band (2GHz-4GHz); when the thickness is increased to 3.0 mm, RL < -10 dB in the 2.79GHz-3.32GHz frequency band, and the effective absorption bandwidth is approximately 0.53GHz. This demonstrates that the position of the absorption peak and the effective absorption bandwidth can be flexibly controlled by adjusting the thickness.

[0053] Furthermore, when the thickness of Comparative Example 4 (FeSiAl:SiC=1:1) was increased to 2.8 mm, effective absorption only occurred at a frequency of 4.0 GHz (RL < -10 dB); when the thickness was 3.0 mm, the effective absorption peak appeared at 3.70 GHz, corresponding to a peak frequency of 3.94 GHz; when the thickness was further increased to 3.5 mm, the effective absorption bandwidth broadened to 0.9 GHz. Compared with Example 2 (FeSiAl:SiC=2:1), under the same thickness conditions, the absorption peak frequency of Comparative Example 4 was significantly higher, indicating that appropriately increasing the FeSiAl content in the SiC system is beneficial to extending the absorption performance to lower frequency bands. Therefore, if the composition of Comparative Example 4 is to achieve effective absorption in the S-band (2 GHz-4 GHz), a larger thickness is required.

[0054] Furthermore, when the thickness of Comparative Example 5 (FeSiAl:SiC=1:2) was increased to 3.3 mm, effective absorption only occurred at a frequency of 4.0 GHz (RL < -10 dB). This compositional system requires a significantly larger thickness to achieve effective absorption in the S-band (2 GHz - 4 GHz).

[0055] 2. Complex permeability test Compared to pure SiC (a non-magnetic material), the complex permeability has a real part of 1 and an imaginary part of 0, such as... Figure 12 As shown, Figure 12 (a) and Figure 12 In Figure (b), the curves of the real part and imaginary part of the complex permeability of Example 2 at different frequencies are respectively. The complex permeability of Example 2 increases significantly (the real part of the complex permeability is close to 1.9 at 2.6 GHz) and has good magnetic loss capability (the magnetic loss tangent increases), indicating that FeSiAl provides magnetic response.

[0056] 3. Thermal stability test The thermal stability of the material was analyzed using the differential scanning calorimetry method. Figure 13 The TGA curve for Example 1 is shown. The curve indicates that the percentage change in material mass is less than 1% from room temperature to 1200°C, with no obvious endothermic or exothermic peaks. This demonstrates that the FeSiAl-SiC microwave absorbing composite material possesses excellent thermal stability and oxidation resistance, maintaining structural and compositional stability over a wide temperature range.

[0057] 4. Magnetic test The magnetization intensity of the material as a function of temperature was measured using the Quantum Design Magnetic Measurement System (MPMS3) to characterize the changes in its magnetic properties with temperature. Figure 14 The MT curve is shown in Example 1. The curve shows that when the temperature rises to 500℃, the FeSiAl-SiC absorbing composite material still retains approximately 30% of its room temperature saturation magnetization, indicating that it still possesses a certain magnetic loss capacity at high temperatures. Therefore, this FeSiAl-SiC absorbing composite material can be used for electromagnetic wave absorption in an environment of 500℃.

[0058] 5. Aging tests at different temperatures Using Example 1 with a thickness of 2.20 mm as a sample, at 5.38 GHz - 8.2 GHz ( Figure 15 (a) and 3.94GHz-5.99GHz Figure 15 Within the frequency band (b) in the figure, after aging in air at different temperatures (-50℃, 25℃, 200℃, 400℃, 600℃) for 4 hours and then cooling to room temperature, the electromagnetic parameters were measured, and the reflectivity curve was calculated. The comparison frequency is 3.94GHz. See [reference needed]. Figure 15.

[0059] -50℃ treatment: The maximum reflection loss decreased slightly from -7.48dB (3.94GHz) of the sample at 25℃ to -6.08dB, but still maintained a certain absorption capacity.

[0060] Treatment at 200℃: The maximum reflection loss increased to -8.56dB, which is 114.4% of that of the sample at 25℃, indicating an improvement in absorption performance.

[0061] Treatment at 400℃: The maximum reflection loss further increased to -9.52dB, which is 127.2% of that of the sample at 25℃.

[0062] Treatment at 600℃: The maximum reflection loss reached -9.60dB, which is about 128% of that of the sample at 25℃, and the absorption performance remained good.

[0063] The above results show that the absorption performance of the FeSiAl-SiC microwave absorbing composite material not only did not significantly decrease after aging within the range of -50℃ to 600℃, but was actually optimized after treatment at 200℃-600℃. This indicates that the material can be used for electromagnetic wave absorption in the low end of the C-band (4GHz-8GHz) and X-band (8GHz-12GHz) at 600℃.

[0064] 6. Reflectivity test at different temperatures Using Example 1 with a thickness of 2.16 mm as a sample, at 3.94 GHz - 5.99 GHz ( Figure 16 (a) and 5.38GHz-8.2GHz ( Figure 16 Within the frequency band (b) in the diagram, electromagnetic parameters were tested at different temperatures. The reflectivity curves calculated from the electromagnetic parameters using transmission line theory are shown in the figure. Figure 16 .

[0065] Treatment at 25℃ (room temperature): The maximum reflection loss is approximately -8.5dB.

[0066] 200℃ treatment: Maximum reflection loss increases to -9.49dB, corresponding to a frequency of 3.94GHz.

[0067] Treatment at 400℃: The maximum reflection loss is -9.35dB, which is slightly lower than that at 200℃ but still better than that at room temperature.

[0068] 500℃ treatment: The absorption performance is significantly improved, with the maximum reflection loss reaching -15.65dB, corresponding to a frequency of 4.66GHz.

[0069] Within the 3.94GHz-5.99GHz (S-band to C-band) and 5.38GHz-8.2GHz (C-band to the lower end of the X-band) frequency bands, and within the temperature range of 25℃ to 400℃, the absolute value of the maximum reflection loss of the FeSiAl-SiC absorbing composite material fluctuates slightly, but increases significantly at 500℃; the frequency corresponding to the absorption peak shifts slightly to higher frequencies with increasing temperature. Comparison curves show that the absorption performance is superior at 500℃ compared to room temperature, making it suitable for high-temperature electromagnetic wave absorption applications (such as engine exhaust nozzles and missile compartments).

[0070] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a FeSiAl-SiC microwave absorbing composite material, characterized in that, The method includes: FeSiAl alloy powder and SiC powder are ball-milled and mixed at a first preset mass ratio to obtain FeSiAl-SiC composite powder. The FeSiAl-SiC composite powder and high-temperature inorganic adhesive are ground and mixed evenly according to a second preset mass ratio, and then molded to obtain a blank. The preform was cured at room temperature and then cured by programmed temperature increase to obtain the FeSiAl-SiC microwave absorbing composite material.

2. The preparation method of the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The first preset mass ratio is (2-3):1, the particle size of the FeSiAl alloy powder is 8μm-12μm, and the particle size of the SiC powder is 0.5μm-2μm.

3. The preparation method of the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The ball milling process uses a planetary ball mill with a milling speed of 200 r / min-400 r / min and a milling time of 3 h-5 h.

4. The preparation method of the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The high-temperature inorganic adhesive comprises silica and alumina, with a mass ratio of silica to alumina of (1-3):

1.

5. The method for preparing the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The second preset mass ratio is (7-9):(3-2).

6. The method for preparing the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The compression molding pressure is 12MPa-20MPa, and the holding time is 20s-40s.

7. The method for preparing the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The curing time at room temperature is 12h-24h.

8. The method for preparing the FeSiAl-SiC microwave absorbing composite material according to claim 1, characterized in that, The process of temperature-curing includes: Heat to 70℃-90℃ and hold for 1.5h-2.5h; Raise the temperature to 140℃-160℃ and hold for 1.5h-2.5h.

9. A FeSiAl-SiC microwave absorbing composite material, characterized in that, The FeSiAl-SiC microwave absorbing composite material is prepared by the method described in any one of claims 1-8, and the density of the FeSiAl-SiC microwave absorbing composite material is 2.9 g / cm³. 3 -3.1g / cm 3 .

10. An application of the FeSiAl-SiC microwave absorbing composite material as described in claim 9, characterized in that, The FeSiAl-SiC microwave absorbing composite material is used for electromagnetic wave absorption in the lower end of the S-band, C-band, or X-band, or for electromagnetic wave absorption in high-temperature environments above 500℃.

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