Radar and infrared compatible stealth material with high-entropy alloy / spinel core-shell structure and preparation method of radar and infrared compatible stealth material

Abstract

The invention discloses a radar and infrared compatible stealth material with a high-entropy alloy / spinel core-shell structure and a preparation method of the radar and infrared compatible stealth material, and belongs to the technical field of stealth materials. The stealth material is of a micro-nano-scale core-shell structure and comprises a high-entropy alloy solid solution which is used as a core, has a soft magnetic characteristic, contains Fe, Co and Ni and is of a face-centered cubic or body-centered cubic structure; and an in situ grown MnCr2O4-based spinel semiconductor layer as a shell. During preparation, FeCoNiCrMn series high-entropy alloy powder is used as a matrix, and an in-situ modification strategy that step-by-step low-oxygen-pressure grain boundary segregation is combined with vacuum quenching lock defects is adopted. According to the invention, perfect unification of microwave transmission loss and infrared high reflection functions is realized on the microscopic scale, the preparation process is simple and controllable, the problems of high emission and no corrosion resistance of the traditional wave-absorbing material are solved, and the material has a wide application prospect in the field of multi-spectrum stealth of aerospace and marine equipment.

Description

Technical Field

[0001] This invention relates to the field of stealth materials technology, and more specifically, to a radar-infrared compatible stealth material based on an oxygen vacancy engineering high-entropy alloy / spinel core-shell structure and its preparation method. Background Technology

[0002] With the rapid development of radar detection technologies (such as synthetic aperture radar and phased array radar) and infrared detection technologies (such as staring infrared thermal imagers and infrared-guided missiles), modern battlefield reconnaissance has evolved from single-band to multi-spectral joint detection using microwave, infrared, and visible light. Statistics show that among downed aircraft, losses caused by infrared-guided weapons and radar-guided weapons account for approximately 40% and 50%, respectively. Therefore, single-function stealth materials can no longer meet the battlefield survivability requirements of advanced weaponry (such as fifth-generation fighters, hypersonic vehicles, and stealth ships). Developing multi-spectral compatible stealth materials that can simultaneously absorb wideband radar waves and have low infrared emissivity has become a crucial area of ​​competition in the defense science and technology field.

[0003] However, achieving dual-mode stealth with both radar and infrared capabilities in a single material system faces inherent physical contradictions, which are known as the "Achilles' heel" of the stealth technology field:

[0004] Radar stealth requires "absorption": To reduce microwave reflection, absorbing materials must possess good impedance matching characteristics, allowing electromagnetic waves to enter the material and be converted into heat energy through magnetic or dielectric loss. Currently, mainstream absorbing agents (such as carbon nanotubes, graphene, and ferrites) are typically highly absorbent media. According to Kirchhoff's laws, high absorption inevitably leads to high emission. These materials typically have an emissivity of 0.85~0.95 in the 3-14µm infrared band, appearing as significant "hot spots" in the infrared field of view.

[0005] Infrared stealth requires "reflection": the core of reducing infrared emissivity lies in increasing the reflectivity of the material surface. According to the Hagen-Rubens relation, low-emissivity materials typically require extremely high electrical conductivity (such as metals like gold, silver, and aluminum). However, highly conductive surfaces produce strong "specular reflection" of radar waves, leading to a sharp increase in the radar cross section (RCS) and completely losing radar stealth capabilities.

[0006] To reconcile the above contradictions, researchers have tried various material design strategies, but significant technical bottlenecks still exist: Limitations of traditional core-shell structures: Existing technologies often employ a "magnetic metal core@dielectric shell" structure (such as Fe@SiO2, Ni@TiO2, or Fe@Polyaniline). Although the dielectric shell improves impedance matching and provides some corrosion protection, these shells are essentially electrical insulators or low-conductivity semiconductors, unable to provide enough free carriers to reflect infrared light, making it difficult to reduce their infrared emissivity below 0.6.

[0007] The complexity of multi-layer structures: Another strategy is to design "frequency selective surfaces (FSS)" or "multi-layer metamaterial structures," that is, a bottom layer that absorbs waves and a top layer that has high infrared reflectivity. Although such structures are theoretically feasible, they require extremely high processing precision, making them difficult to apply to large-area curved surface skins. Furthermore, the interlayer bonding is weak, making them prone to delamination and peeling under high-speed airflow or thermal shock.

[0008] The challenge of weather resistance in traditional magnetic metals: While Fe, Co, and Ni-based nanoparticles with high saturation magnetization exhibit excellent microwave absorption properties, their chemical stability is extremely poor. In marine salt spray or high-temperature, high-humidity environments, their surfaces are prone to uncontrolled oxidation, generating non-magnetic α-Fe₂O₃ or hydroxides, leading to irreversible degradation of their microwave absorption performance.

[0009] In recent years, high-entropy alloys, with their unique "high-entropy effect" and "hysteresis diffusion effect," have exhibited excellent corrosion resistance and soft magnetic properties, and are considered ideal candidates for next-generation high-performance microwave absorbing agents. Current research on the application of high-entropy alloys in microwave absorbing mainly focuses on optimizing magnetic loss by adjusting the composition (e.g., FeCoNiCrAl) or breaking the Snoek limit through ball milling and sheet formation. However, existing high-entropy alloy microwave absorbing materials generally neglect the band structure modulation of grain boundaries and surface oxide layers. In particular, no technology has yet been able to utilize defect engineering to construct, in situ, a semiconductor shell that can both dissipate microwaves and achieve low infrared emission through high carrier concentration, while maintaining the magnetic properties of high-entropy alloys. Summary of the Invention

[0010] To address the problems in existing technologies, such as the susceptibility of metallic radar absorbers to corrosion and failure under harsh environments, the increased mechanical brittleness of composite materials due to high filler content, and the difficulty of achieving non-equilibrium state control and in-situ interface reinforcement of multi-component nanoalloys using traditional preparation processes, this invention aims to provide a radar-infrared compatible stealth material and its preparation method based on low-oxygen-pressure grain boundary segregation and vacuum quenching defect-locking technology. This invention aims to solve the compatibility problem between electromagnetic loss and infrared reflection at the microscale by in-situ growing an oxygen-vacancy-rich spinel oxide shell, while simultaneously endowing the material with excellent corrosion resistance and anti-icing properties, thereby preparing a truly all-weather, multi-spectral compatible stealth material.

[0011] To solve the above problems, the technical solution adopted by the present invention is as follows: This invention uses FeCoNiCrMn-based high-entropy alloy powder as a matrix and proposes an in-situ modification strategy combining "stepwise low-oxygen-pressure grain boundary segregation" with "vacuum quenching to lock defects." Firstly, under a low oxygen partial pressure of 10... -1 Under an atmosphere of -100 Pa, the differences in Gibbs free energy, oxidation potential, and diffusion rate between Mn, Cr, and other elements are utilized. The active elements are driven to directionally segregate and pre-oxidize to the powder surface through a medium-temperature section (600-700℃). Subsequently, a high-temperature section (850-950℃) induces solid-state reaction and crystallization of the surface oxides, resulting in the in-situ growth of a continuous and dense Mn-Cr spinel oxide shell.

[0012] At the end of the heat treatment stage, a high-temperature vacuum rapid cooling process is used to block the backfilling path of oxygen in the crystal lattice, effectively "freezing" and retaining the high-concentration oxygen vacancies generated at high temperatures within the spinel shell lattice. The resulting powder exhibits a unique microscopic gradient core-shell structure: the core is a FeCoNi-based solid solution with high saturation magnetization, retaining the high magnetic permeability of the metal; the outer shell is a MnCr2O4-based spinel semiconductor layer rich in oxygen vacancies, with the band structure controlled by the Mn / Cr ratio.

[0013] Specifically, Stealth materials, with core-shell structures at the micro-nano scale, include: The core is a high-entropy alloy solid solution with soft magnetic properties containing Fe, Co, and Ni, and a face-centered cubic (FCC) or body-centered cubic (BCC) structure; and the shell is an in-situ grown MnCr2O4-based spinel semiconductor layer.

[0014] Furthermore, if we set the atomic percentages of Fe, Co, Ni, Cr, and Mn as a:b:c:d:e, then 20≤a,b,c, 10≤d≤20, 5≤e≤15, and a+b+c+d+e=100.

[0015] Furthermore, the thickness of the MnCr2O4-based spinel semiconductor layer is 10 nm to 100 nm.

[0016] Furthermore, the spinel semiconductor shell contains a high concentration of oxygen vacancy defects: in the X-ray photoelectron spectroscopy spectrum, the area of ​​the oxygen vacancy peak located at 531.0-532.0 eV accounts for more than 30%, indicating that the shell has a high carrier concentration, which makes its infrared emissivity in the 3-14 μm band less than 0.6.

[0017] The aforementioned method for preparing stealth materials includes, S1 (precursor preparation): Metal powder raw materials are weighed according to atomic percentage, and five metal powders of Fe, Co, Ni, Cr and Mn are prepared into high-entropy alloy precursor powders with a single solid solution phase through high-energy mechanical alloying process. S2 (stepwise low-oxygen pressure pre-oxidation treatment): The precursor powder is placed in a low-oxygen partial pressure atmosphere and heat-treated in a stepwise heating method of "medium-temperature segregation-high-temperature crystallization". By utilizing the difference between the oxidation potential and diffusion rate of the elements, Mn and Cr elements are induced to segregate to the powder surface and undergo selective oxidation, and spinel oxide shell is grown in situ. S3 (vacuum quenching lock defect): After the high-temperature crystallization stage of heat treatment is completed, the atmosphere is immediately stopped and the vacuum is drawn to a negative pressure state. Then, rapid cooling is performed to retain oxygen vacancies in the spinel oxide shell. After cooling to room temperature, the stealth material is obtained.

[0018] Furthermore, in S1, if the atomic percentages of Fe, Co, Ni, Cr, and Mn are set as a:b:c:d:e, then 20≤a,b,c, 10≤d≤20, 5≤e≤15, and a+b+c+d+e=100.

[0019] Furthermore, when weighing the Mn powder raw material, an additional 2 wt.%~5 wt.% of the theoretical mass of Mn powder is added to compensate for the volatilization loss during the subsequent heat treatment process.

[0020] Furthermore, the low oxygen partial pressure atmosphere refers to an oxygen partial pressure (PO2) controlled at 10. -1 The atmosphere environment is in the range of Pa-100Pa. The atmosphere environment is achieved by adjusting the vacuum degree or introducing an inert gas containing trace amounts of oxygen. For example, a CH4+Ar mixed gas with a CH4 content of 2-4% is introduced for atmosphere control. CH4 is a reducing gas and can be used as a C source to form a C layer on the surface, which further enhances the ability to absorb waves and reflect infrared light.

[0021] Furthermore, the step-by-step heating method is specifically as follows: The first stage (surface segregation): the temperature is increased to 600-700℃ at a rate of 3-5℃ / min and held for 1-3 hours. This stage is used to drive the migration of Mn and Cr elements inside the matrix to the surface and form a metastable oxide precursor film. The second stage (in-situ phase formation): continue heating to 850-950℃ at a rate of 2-5℃ / min and hold for 1-3 hours. This stage is used to promote the solid-phase reaction of the surface oxides and transform them into a dense Mn-Cr spinel structure.

[0022] Furthermore, in S3, evacuating to a negative pressure state means reducing the gas pressure inside the furnace to below 1 Pa; rapid cooling means a cooling rate greater than 10℃ / min until the temperature drops below 200℃.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention successfully resolves the physical mechanism contradiction between radar absorption and infrared stealth. This invention introduces a high concentration of charge carriers into a spinel shell with dielectric properties through "oxygen vacancy defect engineering." According to Drude's free electron theory, this high carrier concentration endows the shell with metallic-like high reflectivity in the infrared band (3-14 μm), thereby reducing the infrared emissivity to below 0.6. Simultaneously, the shell maintains suitable dielectric loss characteristics in the microwave band, and combined with the magnetic loss of the metal core, achieves broadband strong absorption. This invention achieves a perfect balance between "microwave transmission loss" and "high infrared reflectivity" at the microscale.

[0024] (2) This invention constructs a unique gradient dual magnetic core-shell structure, breaking through the traditional Snoek limit. Unlike traditional "magnetic core@non-magnetic insulating shell" (such as Fe@SiO2) structures where the non-magnetic shell dilutes the overall magnetic properties, the Mn-Cr spinel shell grown in situ in this invention possesses ferrimagnetism or paramagnetism. This gradient magnetic structure of "high Ms metal core-low Ms oxide shell" not only effectively suppresses high-frequency eddy current losses but also enhances the magnetic loss capability in the low-frequency band through multiple magnetic exchange coupling effects, significantly broadening the effective absorption bandwidth.

[0025] (3) The in-situ growth process endows the material with excellent interfacial bonding and weather resistance. Existing chemical coating methods (such as the sol-gel method) typically produce core-shell interfaces based on physical adsorption, resulting in weak bonding and susceptibility to peeling under thermal shock. This invention utilizes low-oxygen-pressure grain boundary segregation technology to grow a continuous, dense spinel oxide layer in situ based on chemical bonding forces. This dense shell layer blocks the diffusion path of oxygen and chloride ions to the metal core, enabling the material to pass a 720-hour neutral salt spray test and exhibiting excellent anti-icing / self-cleaning properties, significantly extending the service life of stealth materials in harsh environments such as the ocean and high-altitude low-temperature environments.

[0026] (4) The innovative “vacuum quenching and defect locking” process enables precise control of the band structure. This invention abandons the conventional furnace-based cooling process and creatively introduces a high-temperature vacuum quenching step. This process effectively blocks the backfilling of lattice vacancies by ambient oxygen during cooling, successfully "freezing" the thermodynamically non-equilibrium oxygen vacancies formed at high temperatures within the room-temperature shell. This not only significantly improves infrared stealth performance but also further enhances electromagnetic wave absorption capabilities through defect polarization relaxation.

[0027] (5) Compared with complex atomic layer deposition or multi-step wet chemical coating processes, the present invention adopts the "ball milling + one-step graded heat treatment" route, which does not require the use of expensive organic solvents or precursors, has no "three wastes" emissions, and has low equipment requirements (a conventional tube furnace is sufficient), and has extremely high process stability and large-scale industrial production potential.

[0028] The material prepared by this invention has the characteristics of broadband microwave absorption, low infrared emissivity and excellent environmental adaptability (corrosion resistance and anti-icing), and is particularly suitable for multi-spectral compatible stealth and all-weather protection of weapon systems such as aerospace vehicles, marine ships and ground heavy equipment. Attached Figure Description

[0029] Figure 1 The X-ray diffraction (XRD) spectra of the products obtained in Examples 1-2 and Comparative Example 1 of this invention are shown below. Figure 2 These are comparison images of the microstructure of the products obtained in Examples 1-2 and Comparative Example 1 using scanning electron microscopy (SEM). Figure 3 The infrared reflectance curves of the products obtained in Examples 1-2 and Comparative Example 1 of this invention are shown in the 8-14 μm band. Figure 4 The radar reflection loss (RL) curves of the products obtained in Examples 1-2 and Comparative Example 1 of the present invention in the 2-18 GHz frequency band are shown. Figure 5 These are comparative photographs showing the surface macromorphology of the coatings in Example 1 and Comparative Example 1 after undergoing a 720-hour neutral salt spray test. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Example 1 A method for preparing a stealth material, specifically: 1. Precursor powder preparation: Select metal powder with a purity >99.9% and a particle size of 200 mesh. According to the atomic percentage of Fe... 25 Co 25 Ni 25 Cr 15 Mn 10Weighing was performed. To compensate for the volatilization loss under the subsequent high-temperature vacuum environment, an additional 3 wt.% of the theoretical mass of Mn powder was added when weighing the Mn powder.

[0032] Ball milling: The mixed powder was loaded into a stainless steel ball mill jar with a ball-to-powder ratio (BPR) of 15:1, and 1.5 wt.% anhydrous ethanol was added as a process control agent. After sealing in an argon-protected glove box, the mixture was ball milled for 45 hours at 350 r / min using a planetary ball mill (with a 15-minute pause every 1 hour of operation).

[0033] Product: After ball milling, a single solid solution high-entropy alloy precursor powder with uniform particle size distribution (D50 ≈ 2-5 μm) was obtained.

[0034] 2. Stepwise low-oxygen pressure heat treatment and vacuum quenching sample loading: The precursor powder is spread evenly in a corundum ceramic boat and placed in the constant temperature zone of a tube furnace.

[0035] Atmosphere control: A 2% CH4+Ar mixed gas (flow rate 100 sccm) is introduced, and the oxygen partial pressure in the furnace is controlled to be approximately 10 Pa by utilizing the trace amount of residual oxygen in the gas path.

[0036] Heating program: Exhaust section: Increase the temperature to 400°C at 5°C / min and hold for 30 min to remove adsorbed ethanol and moisture.

[0037] Segregation stage (critical): Increase the temperature to 650°C at 5°C / min and hold for 2 hours. This stage drives the Mn / Cr elements to accumulate on the surface and form a metastable oxide film.

[0038] Crystallization stage (phase formation): The temperature is increased to 900°C at a rate of 3°C / min and held for 2 hours. This stage promotes the transformation of surface oxides into a dense spinel structure.

[0039] Vacuum quenching (core): 5 minutes before the end of the 900°C heat preservation period, stop the gas supply and turn on the vacuum pump to quickly evacuate the gas pressure inside the furnace tube to <0.5Pa. After the heat preservation period ends, immediately remove the quartz tube from the heating zone for rapid air cooling (cooling rate >50°C / min) until the temperature drops to room temperature.

[0040] 3. Post-treatment after hydrophobic modification: The sintered powder was immersed in an ethanol solution containing 1 wt.% stearic acid, ultrasonically dispersed for 10 min, filtered and dried to obtain “oxygen vacancy engineered high entropy alloy / spinel core-shell microwave absorbing powder” used as a stealth material.

[0041] Example 2 The purpose of this embodiment is to verify that the process can still stably generate target stealth materials under different temperature windows, thus proving the universality of the method in this application.

[0042] Compared with Example 1, this embodiment only adjusts the heat treatment parameters, while the other steps remain the same: Segregation section temperature: Adjust to 700℃ and hold for 1.5 hours.

[0043] Crystallization section temperature: Adjust to 850℃ and hold for 2 hours.

[0044] The final product was “oxygen vacancy engineered high-entropy alloy / spinel core-shell microwave absorbing powder”, which was used as a stealth material.

[0045] Comparative Example 1 This comparative example did not use the "stepwise heating" process (to verify corrosion resistance and shell quality). The only difference from Example 1 is the heating procedure; the other steps remain the same. The 650℃ insulation step was eliminated, and sintering was carried out directly from room temperature to 900℃ at a rate of 5℃ / min.

[0046] Result: Fe / Co / Ni and Mn / Cr compete for oxidation simultaneously, resulting in an impure shell composition (containing iron oxides) and a loose structure, making it impossible to form a dense spinel protective layer.

[0047] The products obtained in Examples 1-2 and Comparative Example 1 were tested respectively, specifically as follows: Phase composition was determined using X-ray diffraction (XRD) with Cu Kα radiation to characterize the crystal structure and phase composition of the material. The results are shown in [Figure number missing]. Figure 1 .

[0048] Microscopic morphology testing was performed using a scanning electron microscope (SEM). The method involved uniformly dispersing the powder sample and adhering it to a conductive adhesive for high-vacuum observation. The results are shown in [Figure number missing]. Figure 2 .

[0049] Infrared reflectance was measured using an infrared spectrometer. The method involved measuring the hemispherical reflectance within a wavelength range of 8-14 μm at room temperature. The results are shown in [reference needed]. Figure 3 .

[0050] Radar absorption performance was tested using a vector network analyzer (VNA). The method employed was the coaxial transmission line method to measure the complex permittivity and complex permeability, and to calculate the reflection loss (RL). The results are shown in [Figure number missing]. Figure 4 .

[0051] Corrosion resistance (neutral salt spray) test: Refer to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test" standard. The method is as follows: The stealth powder obtained in each example and comparative example is mixed with epoxy resin at a 1:1 mass ratio, uniformly coated onto the surface of an aluminum alloy substrate (coating thickness approximately 1 mm), and placed in a salt spray test chamber after curing. The test chamber temperature is set to 35℃, and a 5wt.% NaCl solution is used for continuous spraying for 720 hours. The results are shown in Table 2. Figure 5 .

[0052] Anti-icing and self-cleaning (hydrophobicity) tests: The static water contact angle (WCA) and roll-off angle (SA) of the coating surface were measured at room temperature using a contact angle meter (Kruss DSA100 equipment, Germany) to characterize the self-cleaning performance. The anti-icing test method was as follows: The substrate coated with the stealth material was placed on a semiconductor cooling stage at -15°C, and 10 μL of deionized water was added. The time it took for the water droplet to completely transform from a transparent liquid state to an opaque solid ice state (icing delay time) was recorded using a high-speed camera. The results are shown in Table 2.

[0053] from Figure 1 It can be seen that in the spectra of Examples 1 and 2, in addition to the characteristic peaks corresponding to the high-entropy matrix alloy (1-Matrix), the spinel phase (3-Spinel) was successfully generated. However, Comparative Example 1, which did not undergo the stepwise process, showed a significant impurity phase (2-M2O3). This indicates that the stepwise low-oxygen-pressure process effectively induced the directional segregation of active elements, resulting in the in-situ growth of the target spinel shell.

[0054] from Figure 2 It can be seen that a uniform and dense nanoscale rough shell structure was grown in situ on the surface of the particles in Examples 1 and 2 (clear Coke adhesion is visible). In contrast, the sample surface of Comparative Example 1 was relatively smooth and dry, and failed to form a continuous and dense active core-shell structure.

[0055] from Figure 3 It can be seen that: Example 1 feature: The curve remains above 40% overall.

[0056] Physical significance: This demonstrates that the high concentration of oxygen vacancies retained through "vacuum quenching" successfully makes the spinel shell exhibit "metal-like" high reflectivity, with an infrared emissivity as low as below 0.6, thus meeting the requirements for stealth.

[0057] Features of Example 2: The curve shape is the same as that of Example 1, but the overall curve has shifted downward by about 10%.

[0058] Physical meaning: This indicates a slight deviation in process parameters (such as a slightly lower temperature or a slightly shorter holding time). Although the oxygen vacancy concentration is increased, it has not reached its maximum. The stealth effect is good, but not as good as the optimal group.

[0059] Comparative Example 1 characteristics: The curve is very low, remaining at around 10%-15% (which is the typical reflectance of ordinary oxides).

[0060] Physical significance: Due to the use of "slow cooling in the furnace," oxygen vacancies are filled (healed) by oxygen in the environment, and the shell becomes ordinary insulating ceramic. The insulator has strong absorption and weak reflection of infrared light, resulting in extremely high emissivity (e≈0.86), thus rendering infrared stealth ineffective.

[0061] from Figure 4 It can be seen that: Example 1 (Best of the Invention): Peak absorption: -48.5 dB at 10.4 GHz.

[0062] Bandwidth: Extremely wide effective bandwidth of RL<-10 dB, extending from 5.6 GHz to 15.4 GHz, perfectly covering the X-band and most of the Ku-band.

[0063] Curve shape: The absorption peak is deep and wide, indicating that the polarization relaxation loss caused by oxygen vacancies is very strong.

[0064] Example 2 (Process Fine-tuning): Peak value: approximately -32.3 dB at 10.8 GHz.

[0065] Bandwidth: Still good (7.2 GHz - 14.2 GHz), but slightly reduced compared to Example 1, and the absorption intensity is also slightly weaker. This reflects the fine-tuning effect of process parameters (such as temperature window) on performance.

[0066] Comparative Example 1 (no vacuum quenching - slow cooling in the furnace): Peak: -18.4 dB at 11.2 GHz.

[0067] Bandwidth: Effective only in the 10.0 - 12.4 GHz range, very narrow.

[0068] Cause: The oxygen vacancy "healed", and the dielectric loss was greatly reduced, resulting in a sharp drop in the overall wave absorption capacity.

[0069] Table 1 compares the electromagnetic parameters at the X-band center frequency (10 GHz). As can be seen from Table 1, Example 1 achieves a high imaginary part of the complex permittivity of 9.67, while maintaining a relatively high imaginary part of the complex permeability (0.70). In contrast, Comparative Example 1 has an extremely low (μ′′) of only 1.09, with (μ′′) as low as 0.11. This clearly demonstrates that the high concentration of oxygen vacancies significantly enhances dielectric loss, while the high-entropy alloy core maintains excellent magnetic loss, achieving broadband strong absorption.

[0070] Table 1 Comparison of electromagnetic parameters at the center frequency (10 GHz) of the X-band

[0071] Table 2 shows the results of corrosion resistance and hydrophobic anti-icing tests. Figure 5 The three figures, from left to right, correspond to Example 1, Example 2, and Comparative Example 1, respectively. (See Table 2 and...) Figure 5 It can be seen that the corrosion resistance and hydrophobic anti-icing properties of Examples 1-2 are significantly better than those of Comparative Example 1.

[0072] Table 2 Results of corrosion resistance and hydrophobic anti-icing tests

Claims

1. A stealth material, characterized in that, Core-shell structures at the micro / nano scale include: High-entropy alloy solid solutions containing Fe, Co, and Ni with face-centered cubic or body-centered cubic structures, exhibiting soft magnetic properties as the core; and MnCr2O4-based spinel semiconductor layer grown in situ as a shell.

2. The stealth material according to claim 1, characterized in that, If the atomic percentages of Fe, Co, Ni, Cr, and Mn are set as a:b:c:d:e, then 20≤a,b,c, 10≤d≤20, 5≤e≤15, and a+b+c+d+e=100.

3. The stealth material according to claim 1, characterized in that, The thickness of the MnCr2O4-based spinel semiconductor layer is 10 nm to 100 nm.

4. The stealth material according to claim 1, characterized in that, In the X-ray photoelectron spectroscopy (XPS) spectrum of the spinel semiconductor shell, the oxygen vacancy peak at 531.0-532.0 eV accounts for more than 30% of the area.

5. The method for preparing the stealth material according to any one of claims 1 to 4, characterized in that, include, S1, five metal powders, Fe, Co, Ni, Cr and Mn, are prepared into high-entropy alloy precursor powders with a single solid solution phase; S2, the precursor powder is placed in a low oxygen partial pressure atmosphere and heat-treated in a stepwise heating manner. S3. After the heat treatment is completed, the atmosphere is immediately stopped and the vacuum is drawn to a negative pressure state. Then, rapid cooling is performed. After cooling to room temperature, the stealth material is obtained.

6. The preparation method according to claim 5, characterized in that, In S1, the atomic percentages of Fe, Co, Ni, Cr, and Mn are set as a:b:c:d:e. Then, 20≤a,b,c, 10≤d≤20, 5≤e≤15, and a+b+c+d+e=100.

7. The preparation method according to claim 6, characterized in that, When weighing the Mn powder raw material, add an additional 2 wt.%~5 wt.% of the theoretical mass of Mn powder.

8. The preparation method according to claim 5, characterized in that, The low oxygen partial pressure atmosphere refers to an oxygen partial pressure (PO2) controlled at 10. -1 Atmosphere environment in the range of Pa-100Pa.

9. The preparation method according to claim 5, characterized in that, The step-by-step heating method is as follows: First stage: Increase the temperature to 600-700℃ at a rate of 3-5℃ / min and hold for 1-3 hours; Second stage: Continue to heat to 850-950℃ at a rate of 2-5℃ / min, and hold for 1-3 hours.

10. The preparation method according to claim 5, characterized in that, In S3, evacuating to a negative pressure state means reducing the gas pressure inside the furnace to below 1 Pa; rapid cooling means a cooling rate greater than 10℃ / min until the temperature drops below 200℃.

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