Three-component wave-absorbing powder based on effective medium theory and preparation method thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
- Filing Date
- 2026-02-06
- Publication Date
- 2026-06-09
Smart Images
Figure CN122168231A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave absorbing materials technology; in particular, it relates to a three-component microwave absorbing powder based on the effective medium theory and its preparation method. Background Technology
[0002] With the rapid development of radar detection technology, stealth performance has become a core element of an aircraft's battlefield survivability. Reducing the radar cross section (RCS) of an aircraft is the most direct and effective way to achieve radar stealth. Currently, the main technical means to reduce RCS fall into two categories: one is to reduce specular reflection and diffraction of radar waves through stealth design; the other is to use radar absorbing materials (RAM) to significantly attenuate the reflected energy of incident electromagnetic waves. Among these, developing broadband, strong-absorbing, and lightweight absorbing materials has always been a key focus and challenge in the field of aircraft stealth.
[0003] The main mechanism of radar absorbing materials is to convert incident electromagnetic wave energy into heat or other forms of energy, thereby significantly reducing radar echo intensity. Their absorption performance mainly depends on the material's electromagnetic parameters, particularly the complex permittivity (ε = ε' - jε'') and complex permeability (μ = μ' - jμ''). The real parts (ε', μ') determine the impedance matching characteristics between the material and free space, while the imaginary parts (ε'', μ'') characterize the loss capacity for electromagnetic waves. Existing radar absorbing materials mostly employ single-component materials (such as magnetic materials like ferrites and carbonyl iron, or carbon-based conductive materials like carbon nanotubes, graphene, and carbon fibers) or simple composite systems. Although carbon-based materials possess excellent conductivity and dielectric loss capabilities, effectively converting electromagnetic wave energy into Joule heat, their impedance matching characteristics are poor, and they are prone to strong surface reflection when used alone. To improve impedance matching and achieve broadband absorption, it is usually necessary to introduce matrix materials and carry out multi-component composite design so that the overall material approaches the free space wave impedance over a wider frequency band, while also taking into account integration with the background environment.
[0004] In the design of multi-component composite absorbing materials for radar, the effective medium theory provides an important solution: through this theory, a microscopically inhomogeneous multi-component composite system can be equivalent to a macroscopically homogeneous medium, obtaining the equivalent complex permittivity and complex permeability. Thus, without depending on the specific microscopic morphology, the influence of different components and volume ratios on macroscopic absorbing performance can be quickly predicted and optimized, providing theoretical guidance for the precise design of broadband strong absorption, thin and light absorbing materials. Summary of the Invention
[0005] The purpose of this invention is to provide a three-component microwave absorbing powder based on the effective medium theory and its preparation method.
[0006] This invention is achieved through the following technical solution:
[0007] This invention relates to a three-component microwave absorbing powder based on the effective medium theory, which is composed of a carbon black-silicon carbide mixed microwave absorbing agent and a cyanine bluestone matrix; wherein the volume fraction of the carbon black-silicon carbide mixed microwave absorbing agent in the three-component microwave absorbing powder is 55 vol% to 75 vol%; the volume fraction of the carbon black-silicon carbide mixed microwave absorbing agent and the volume fraction of cyanine bluestone are determined by a reverse solution method.
[0008] Preferably, the volume fraction of the carbon black-silicon carbide mixed microwave absorbing agent in the three-component microwave absorbing powder is 65 vol.
[0009] Preferably, the absorbing powder has a reflection loss of ≤-5 dB in the 8-12 GHz frequency band when the thickness is 1-4 mm.
[0010] Preferably, the carbon black-silicon carbide mixed microwave absorber is prepared by mechanically stirring carbon black and silicon carbide in anhydrous ethanol until homogeneous and then drying.
[0011] This invention also relates to a method for preparing the aforementioned three-component microwave absorbing powder based on the effective medium theory, comprising the following steps:
[0012] Step 1: Select carbon black and silicon carbide as the absorbing components, and determine or call up the complex permittivity and complex permeability of carbon black and silicon carbide.
[0013] Step 2: Based on the effective medium theory, establish an equivalent electromagnetic parameter calculation model for the carbon black-silicon carbide mixed absorber. Using the volume fractions of carbon black and silicon carbide as variables, calculate the equivalent complex permittivity and equivalent complex permeability of the mixed absorber under different ratios using MATLAB programming.
[0014] Step 3: Determine cyanite as the matrix material and measure or retrieve its electromagnetic parameters;
[0015] Step 4: Set the target absorption frequency band, reflection loss, and coating thickness, and construct the absorption performance evaluation function;
[0016] Step 5: Using the microwave absorption performance evaluation function as the optimization objective, the two-step dielectric function calculation method combined with programming is used to solve the problem in reverse, and the carbon black volume fraction, silicon carbide volume fraction, and the total integral of the carbon black-silicon carbide mixed microwave absorber in the final powder are obtained.
[0017] Step 6: Add the carbon black-silicon carbide mixed microwave absorbing agent and the cyanite matrix to anhydrous ethanol for ball milling or equivalent mechanical stirring. After stirring evenly, dry to remove the anhydrous ethanol to obtain a three-component microwave absorbing powder.
[0018] Preferably, in step 3, the average particle size of the cyanite is <10 μm.
[0019] Preferably, in step 4, the setting of the target absorption frequency band, reflection loss, and coating thickness specifically refers to:
[0020] Target: Reflection loss ≤-5 dB or ≤-10 dB in the 8-12 GHz band, coating thickness 1-4 mm; construct a comprehensive evaluation function: score = a × effective bandwidth + b × |average reflection loss| – c × thickness + penalty term, where a, b, and c are weighting coefficients.
[0021] Preferably, in step 5, the two-step dielectric function calculation method is: genetic algorithm, particle swarm optimization algorithm, or grid search optimization algorithm.
[0022] Preferably, in step 6, the preparation method of the carbon black-silicon carbide mixed microwave absorbing agent powder is as follows:
[0023] Carbon black and silicon carbide were added to a certain volume of anhydrous ethanol at a mass ratio of 12:1, magnetically stirred for 2 h, and dried at 60℃ to obtain a carbon black-silicon carbide mixed microwave absorbing agent powder.
[0024] Preferably, in step 6, the mass ratio of the carbon black-silicon carbide mixed microwave absorber powder to the cyanite matrix powder is 13:7.
[0025] The present invention has the following advantages:
[0026] This invention, based on the theory of effective media, involves the uniform blending of complex multi-component absorbing powders. By setting target absorption performance parameters, including reflection loss and absorbing layer thickness, the ratio of each absorbing component to the matrix material is derived and calculated in reverse. This significantly reduces the cycle of repeated testing and debugging required for traditional multi-component absorbing materials, enabling rapid and efficient preparation of multi-component absorbing powders with excellent absorption performance. This method is suitable for the rapid development of broadband, thin-layer, high-performance stealth absorbing powders. Attached Figure Description
[0027] Figure 1 This is a reflection loss diagram of the absorbing powder prepared in Example 1;
[0028] Figure 2 This is a magnified image of the morphology of the microwave absorbing powder prepared in Example 1. Detailed Implementation
[0029] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are merely further illustrations of the present invention, but the scope of protection of the present invention is not limited to the following embodiments.
[0030] Example 1
[0031] This embodiment relates to a method for preparing a three-component microwave absorbing powder based on the effective medium theory, including the following steps:
[0032] Step 1: Select carbon black and silicon carbide as the absorbing components. The complex permittivity of these components is obtained by referring to the data in the published literature or by actual measurement: ε_CB = 10 – 0.1i, μ_CB ≈ 1; ε_SiC = 10 – 0.1i, μ_SiC ≈ 1.
[0033] Based on the effective medium theory, an equivalent electromagnetic parameter calculation model for a carbon black-silicon carbide hybrid absorber is established. The volume fractions of carbon black and silicon carbide are used as variables (v_silicon carbide, v_carbon black), and the volume fractions of silicon carbide (v_SiC) and carbon black (v_CB) (v_SiC + v_CB = 1) are used as variables. The equivalent complex permittivity ε_mix and equivalent complex permeability μ_mix of the hybrid absorber under different ratios are calculated by MATLAB programming.
[0034] High-purity cordierite (average particle size <10 μm) was selected as the matrix material, with complex dielectric constants of ε_Cor = 4.7 – 0.02i and μ_Cor ≈ 1.
[0035] In this invention, all raw materials used are commercially available products well-known in the art.
[0036] The optimization objective is to maximize the effective bandwidth with a reflection loss RL ≤ -5 dB in the 8–12 GHz frequency band, and a coating thickness ranging from 1.0 to 4.0 mm. A comprehensive evaluation function is constructed as follows:
[0037] Score = 2 × Δf (GHz) + 0.2 × |RL_avg| – 0.8 × d (mm) – Penalty
[0038] Penalty = 0.3 × max(0, |RL_avg| – 5) / d is used to penalize schemes that do not reach –5 dB.
[0039] With the goal of maximizing the score, a set of optimal volume fraction combinations was obtained by using particle swarm optimization combined with electromagnetic simulation for inverse problem-solving:
[0040] The mixed absorber contains: v_SiC = 5 vol%, v_CB = 60 vol% (normalized percentages of 8% and 92%).
[0041] In the final absorbing powder: the total volume percentage of the mixed absorbing agent is 65 vol%, and that of cordierite is 35 vol%; the corresponding optimal matching thickness d = 1.45 mm, and the reflection loss results are as follows. Figure 1 As shown.
[0042] The preparation method of carbon black-silicon carbide mixed microwave absorbing agent powder is as follows: weigh 6.0 g of carbon black and 0.5 g of silicon carbide, add them to 30 mL of anhydrous ethanol, stir magnetically for 2 h, and then dry at 60 ℃ to obtain carbon black-silicon carbide mixed microwave absorbing agent powder.
[0043] The preparation method of the three-component microwave absorbing powder is as follows: The obtained mixed microwave absorbing agent and 3.5 g cordierite powder are added together into a ball mill jar containing 30 mL of anhydrous ethanol. Zirconia balls are used as the grinding medium, the ball-to-material ratio is 10:1, and the milling speed is 400 r / min for 6 h. After discharge, the powder is dried at 80 ℃ and passed through a 200-mesh sieve to obtain the multi-component microwave absorbing powder. The microstructure is shown in the figure below. Figure 2 As shown.
[0044] The above three-component microwave absorbing powder was mixed with epoxy resin at a mass ratio of 4:1 and then sprayed to form a thickness of 1.45 mm. After testing with a vector network analyzer (coaxial method), the RL was ≤ -5 dB in the full frequency band of 8-12 GHz and the bandwidth reached 3.2 GHz, showing excellent performance.
[0045] Example 2
[0046] This embodiment relates to a method for preparing a three-component microwave absorbing powder based on the effective medium theory, including the following steps: The method of this embodiment is the same as that of Embodiment 1, except that the target frequency band is changed to 12-18 GHz (Ku band), while the other materials and process conditions are the same.
[0047] The optimal component was obtained through the same reverse optimization process:
[0048] v_SiC = 0.5 vol%, v_CB = 60 vol% (approximately 0.8% and 99.2% after normalization); the total volume percentage of the mixed microwave absorber in the final powder is 65 vol%, cordierite is 35 vol%; the optimal matching thickness d = 0.98 mm.
[0049] Actual test results: Full bandwidth coverage with RL ≤ -5 dB in the 12–18 GHz range, and a bandwidth of -10 dB up to 4.1 GHz.
[0050] Examples 3-5
[0051] The same process as in Example 1 was used, except that the total volume percentage of the mixed microwave absorber in the final powder was changed to 55 vol%, 70 vol%, 75 vol%, with the remainder being cordierite.
[0052] The results show that the optimal thickness gradually decreases with increasing absorber content, but excessive thickness will lead to increased impedance mismatch. The overall performance is best at 65 vol%.
[0053] This invention, based on the theory of effective media, involves the uniform blending of complex multi-component absorbing powders. By setting target absorption performance parameters, including reflection loss and absorbing layer thickness, the ratio of each absorbing component to the matrix material is derived and calculated in reverse. This significantly reduces the cycle of repeated testing and debugging required for traditional multi-component absorbing materials, enabling rapid and efficient preparation of multi-component absorbing powders with excellent absorption performance. This method is suitable for the rapid development of broadband, thin-layer, high-performance stealth absorbing powders.
[0054] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.
Claims
1. A three-component microwave absorbing powder based on the effective medium theory, characterized in that, It is composed of a carbon black-silicon carbide mixed microwave absorbing agent and a cyanobryllium matrix; wherein the volume fraction of the carbon black-silicon carbide mixed microwave absorbing agent in the three-component microwave absorbing powder is 55 vol% to 75 vol%. The volume fractions of the carbon black-silicon carbide mixed microwave absorber and the volume fraction of cyanide were determined by inverse solving method.
2. The three-component microwave absorbing powder based on the effective medium theory as described in claim 1, characterized in that, The volume fraction of the carbon black-silicon carbide mixed microwave absorbing agent in the three-component microwave absorbing powder is 65 vol.
3. The three-component microwave absorbing powder based on the effective medium theory as described in claim 1, characterized in that, The absorbing powder has a reflection loss of ≤-5 dB in the 8-12 GHz frequency band when the thickness is 1-4 mm.
4. The three-component microwave absorbing powder based on the effective medium theory as described in claim 1, characterized in that, The carbon black-silicon carbide mixed microwave absorber is prepared by mechanically stirring carbon black and silicon carbide in anhydrous ethanol until homogeneous and then drying.
5. A method for preparing a three-component microwave absorbing powder based on the effective medium theory as described in claim 1, characterized in that, Includes the following steps: Step 1: Select carbon black and silicon carbide as the absorbing components, and determine or call up the complex permittivity and complex permeability of carbon black and silicon carbide. Step 2: Based on the effective medium theory, establish an equivalent electromagnetic parameter calculation model for the carbon black-silicon carbide mixed absorber. Using the volume fractions of carbon black and silicon carbide as variables, calculate the equivalent complex permittivity and equivalent complex permeability of the mixed absorber under different ratios using MATLAB programming. Step 3: Determine cyanite as the matrix material and measure or retrieve its electromagnetic parameters; Step 4: Set the target absorption frequency band, reflection loss, and coating thickness, and construct the absorption performance evaluation function; Step 5: Using the microwave absorption performance evaluation function as the optimization objective, the two-step dielectric function calculation method combined with programming is used to solve the problem in reverse, and the carbon black volume fraction, silicon carbide volume fraction, and the total integral of the carbon black-silicon carbide mixed microwave absorber in the final powder are obtained. Step 6: Add the carbon black-silicon carbide mixed microwave absorbing agent powder and the cyanite matrix powder to anhydrous ethanol, and ball mill or equivalent mechanical stirring. After stirring evenly, dry to remove the anhydrous ethanol to obtain the three-component microwave absorbing powder.
6. The method for preparing three-component microwave absorbing powder based on the effective medium theory as described in claim 5, characterized in that, In step 3, the average particle size of the cyanite is <10 μm.
7. The method for preparing three-component microwave absorbing powder based on the effective medium theory as described in claim 5, characterized in that, In step 4, the setting of the target absorption frequency band, reflection loss, and coating thickness specifically refers to: Target: Reflection loss ≤-5 dB or ≤-10 dB in the 8-12 GHz band, coating thickness 1-4 mm; construct a comprehensive evaluation function: score = a × effective bandwidth + b × |average reflection loss| – c × thickness + penalty term, where a, b, and c are weighting coefficients.
8. The method for preparing three-component microwave absorbing powder based on the effective medium theory as described in claim 5, characterized in that, In step 5, the two-step dielectric function calculation method is: genetic algorithm, particle swarm optimization algorithm, or grid search optimization algorithm.
9. The method for preparing three-component microwave absorbing powder based on the effective medium theory as described in claim 5, characterized in that, In step 6, the preparation method of the carbon black-silicon carbide mixed microwave absorbing agent powder is as follows: Carbon black and silicon carbide were added to a certain volume of anhydrous ethanol at a mass ratio of 12:1, magnetically stirred for 2 h, and dried at 60℃ to obtain a carbon black-silicon carbide mixed microwave absorbing agent powder.
10. The method for preparing three-component microwave absorbing powder based on the effective medium theory as described in claim 5, characterized in that, In step 6, the mass ratio of the carbon black-silicon carbide mixed microwave absorber powder to the cyanite matrix powder is 13:7.