Radar wave-absorbing material with high emissivity as well as preparation method and application of radar wave-absorbing material
By preparing FexNi1-xCr2O4 absorbing material and forming a coating on a metal substrate, the problem of unstable coating structure at high temperature was solved, and the effects of high emissivity and radar stealth were achieved.
Patent Information
- Application Number
- CN202510839581.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-09-26
AI Technical Summary
Existing high-temperature resistant and high-infrared emissivity coating materials are easily oxidized in high-temperature environments, resulting in structural instability, reduced emissivity, and inability to effectively suppress the increase in aircraft surface temperature.
FexNi1-xCr2O4 material is used. Fe2O3, NiO and Cr2O3 are mixed by ball milling and pre-sintered to form a spinel structured absorbing material. A coating is formed on the metal substrate by plasma spraying to improve the high-temperature stability and emissivity of the material.
The material structure remains intact at high temperatures, and the emissivity reaches above 0.9, achieving effective radiation heat dissipation and meeting the needs of radar stealth and infrared radiation heat dissipation.
Smart Images
Figure CN120698516A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of radar wave absorbing materials, and in particular to a high-emissivity radar absorbing material, a preparation method, and an application thereof. Background Art
[0002] To address the problem of aerospace vehicles requiring radar absorption while significantly enhancing infrared radiation heat transfer, thereby suppressing surface temperature increases, one solution is to apply a high-temperature, high-emissivity infrared coating to the equipment surface as a radiation heat shield to enhance radiation and achieve heat dissipation. Existing methods for preparing high-temperature, high-emissivity infrared coatings use SiC and MoSi2 powder as the primary raw materials. However, the SiC material is susceptible to oxidation when exposed to high temperatures for extended periods, resulting in structural instability and reduced emissivity. Summary of the Invention
[0003] The main purpose of this application is to provide a high-emissivity radar absorbing material and its preparation method and application, aiming to solve the problem of reduced emissivity caused by structural instability of infrared radiation materials in high-temperature environments.
[0004] To achieve the above purpose, the present application provides a high emissivity radar absorbing material, the chemical formula of which is Fe x Ni 1-x Cr2O4, wherein x is 0.2-0.8; the absorbing material is obtained by ball-milling and mixing raw materials Fe2O3, NiO and Cr2O3, and pre-sintering; the absorbing material has a reflection loss of -27dB at 8-12GHz and an emissivity greater than 0.9 at a temperature of 25-30°C.
[0005] To achieve the above objectives, the present application also provides a method for preparing a high-emissivity radar absorbing material, comprising: ball-milling Fe2O3, NiO, and Cr2O3 according to the ratio of each element in the chemical formula of the absorbing material to obtain a uniform powder; and pre-sintering the uniform powder at 1200-1500°C for 12-24 hours to obtain the absorbing material.
[0006] Optionally, during the ball milling process, the sizes of the ball milling beads are 3 mm and 6 mm, respectively, and the mass ratio thereof is 2:1.
[0007] To achieve the above-mentioned objectives, the present application also provides a method for preparing a high-emissivity radar absorbing material coating, which uses absorbing material, including: ball milling the absorbing material, an adhesive and deionized water to obtain a viscous slurry; spray granulating the viscous slurry to obtain an absorbing powder; and spraying the absorbing powder onto a metal substrate by a plasma spraying method to obtain an absorbing material coating.
[0008] Optionally, during the plasma spraying process, the spraying voltage is 25-30 V, the spraying current is 300-350 A, the main gas flow rate is 1500-2000 L / h, the powder feeding rate is 150-180 L / h, and the spraying distance is 50-75 mm.
[0009] Optionally, the metal substrate is a stainless steel plate, a nickel-based alloy plate or an aluminum alloy plate.
[0010] To achieve the above objectives, the present application also provides an application of a high-emissivity radar absorbing material in an aircraft.
[0011] Compared with the prior art, the present invention has the following advantages: The high emissivity radar absorbing material of the present invention, Fe x Ni 1-x The structure of Cr2O4 is a spinel structure. The spinel structure has a rigid oxygen skeleton, and its oxygen ions are densely packed in a face-centered cubic pattern, forming a distortion-resistant three-dimensional skeleton. The thermal expansion stresses of its tetrahedral (A site) and octahedral (B site) voids offset each other, and can also prevent structural collapse. In addition, the spinel structure also has high bond strength and high coordination number dispersed bond energy, while strong ion-covalent bonds require high energy to break, so that its lattice can still remain intact at high temperatures. NiCr2O4 is doped with iron ions, resulting in changes in the lattice, further improving its emissivity, which can reach above 0.9 at room temperature, which is beneficial to the radiation heat dissipation of aircraft. It also has a low reflectivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 This is the XRD phase detection result diagram of the absorbing material obtained in Example 4; Figure 2 This is a diagram showing the dielectric test results of the absorbing material obtained in Example 4; Figure 3 This is a graph showing the magnetic permeability test results of the absorbing material obtained in Example 4; Figure 4 This is a graph showing the calculation results of the reflection loss of the absorbing material obtained in Example 4.
[0013] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0014] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.
[0015] The first embodiment of the present invention provides a high-emissivity radar absorbing material, the chemical formula of which is Fe x Ni 1-x Cr2O4, wherein x is 0.2-0.8; the absorbing material is obtained by ball-milling and mixing raw materials Fe2O3, NiO and Cr2O3, and pre-sintering; when the sample is 2.6 mm, the reflection loss of the absorbing material at 8-12 GHz can be as low as -27 dB, and the emissivity is greater than 0.9 at a temperature of 25-30°C.
[0016] In this embodiment, Fe x Ni 1-x The structure of Cr2O4 is a spinel structure. The spinel structure has a rigid oxygen skeleton, and its oxygen ions are densely packed in a face-centered cubic pattern, forming a three-dimensional skeleton that is resistant to distortion. The thermal expansion stress of its tetrahedral (A-site) and octahedral (B-site) voids offset each other, and can also prevent structural collapse. In addition, the spinel structure also has high bond strength, high coordination number, and dispersed bond energy. Strong ionic-covalent bonds require high energy to break, so its lattice can remain intact at high temperatures. Ni in NiCr2O4 2+ ions are located in the tetrahedral position in nickel-chromium spinel, Cr 3+ The ions are located in the octahedral position of nickel-chromium spinel. The spatial symmetry of spinel is smaller than that of other structures. There are a large number of vacancies in the NiCr2O4 spinel unit cell. By replacing these vacancies with iron ions, NiCr2O4 is doped and modified, which causes the lattice to change, further improving its emissivity, which can reach above 0.9 at room temperature, which is beneficial to the radiation heat dissipation of aircraft. Since spinel ferrite has a high Curie temperature and coercive force, it can show strong magnetism and high saturation magnetization at room temperature. Therefore, by doping NiCr2O4 with iron ions, the wave absorption performance of NiCr2O4 can be improved, thereby ensuring Fe x Ni 1-x Cr2O4 has a lower reflectivity at 8-12GHz, meeting the requirements of radar stealth.
[0017] A second embodiment of the present invention provides a method for preparing a high-emissivity radar absorbing material, which specifically includes the following steps: In step S1, Fe2O3, NiO, and Cr2O3 are ball-milled according to the ratio of the elements in the chemical formula of the absorbing material to obtain a uniform powder. During the ball-milling process, anhydrous ethanol is used as the milling medium, and the ball milling beads are 3 mm and 6 mm in size, with a mass ratio of 2:1. Using these two sizes of beads yields a smaller particle size of the raw material powder. To ensure the performance of the absorbing material, the ball-milled mixture is dried in a drying oven at a constant temperature. The dried powder is then sieved to select the smaller particles and obtain a uniform powder.
[0018] Step S2: placing the uniform powder in an alumina crucible and pre-sintering it at 1200-1500° C. for 12-24 hours to obtain a wave absorbing material.
[0019] A third embodiment of the present invention provides a method for preparing a high-emissivity radar absorbing material coating, using the above-mentioned absorbing material, comprising: Step S3, ball-milling the absorbing material, the adhesive, and deionized water to obtain a viscous slurry; wherein the adhesive is PVA, and the mass ratio of the adhesive to the absorbing material is 1:190-210; Step S4, spray granulating the viscous slurry to obtain a microwave-absorbing powder; Specifically, the viscous slurry is sent into the centrifugal atomizer and dispersed into small droplets. The small droplets enter the drying chamber. Under the action of high-temperature air at 1350-1450℃, the moisture in the flying droplets evaporates quickly. The dried powder gathers in the powder collector at the lower end under the action of its gravity, and the absorbing powder is obtained in the powder collector.
[0020] In step S5, the absorbing powder is sprayed onto the metal substrate using a plasma spraying method to form an absorbing material coating. During the plasma spraying process, the spraying voltage is 25-30 V, the spraying current is 300-350 A, the main gas flow rate is 1500-2000 L / h, the powder feed rate is 150-180 L / h, and the spraying distance is 50-75 mm. The metal substrate is a stainless steel plate, a nickel-based alloy plate, or an aluminum alloy plate.
[0021] Example 1Fe 0.2 Ni 0.8 Cr2O4 Step S1, according to the ratio of each element in the chemical formula of the absorbing material, Fe2O3, NiO and Cr2O3 are poured into a ball mill, and alumina ball milling beads of 3 mm and 6 mm in size are added, and anhydrous ethanol is added thereto for ball milling and mixing to obtain a mixed material; Step S2: placing the mixed material in a drying oven and drying it at a constant temperature, and sieving the dried powder to select powder with small particle size to obtain a uniform powder; Step S2: Place the uniform powder in an alumina crucible and pre-sinter at 1300°C for 14 hours to obtain the absorbing material Fe 0.2 Ni 0.8 Cr2O4; Step S3, the absorbing material Fe 0.2 Ni 0.8 Cr2O4, PVA and deionized water were ball-milled to obtain a viscous slurry; In step S4, the viscous slurry is fed into a centrifugal atomizer and dispersed into small droplets. The small droplets enter a drying chamber. Under the action of high-temperature air at 1400°C, the water in the flying droplets evaporates quickly. The dried powder is gathered in a powder collector at the lower end under the action of its gravity, and the absorbing powder is obtained in the powder collector; Step S5: spraying the absorbing powder onto the high-temperature nickel-based alloy plate by a plasma spraying method to obtain a absorbing material coating.
[0022] Example 2Fe 0.4 Ni 0.6 Cr2O4 The amount of raw materials added in this embodiment is different from that in Example 1, and the rest are the same.
[0023] Example 3Fe 0.6 Ni 0.4 Cr2O4 The amount of raw materials added in this embodiment is different from that in Example 1, and the rest are the same.
[0024] Example 4Fe 0.8 Ni 0.2 Cr2O4 The amount of raw materials added in this embodiment is different from that in Example 1, and the rest are the same.
[0025] Comparative Example The raw materials are NiO and Cr2O3 with a mass molar ratio of 1:1, and the preparation method is the same as that in Example 1.
[0026] The absorbing material obtained in step 2 of Example 4 was subjected to XRD phase detection, specifically as follows Figure 1 As shown in the figure, it can be seen that the material phase is NiCr2O4 phase (PDF#77-0008). The dielectric test and magnetic permeability test of the samples prepared in Example 4 and Comparative Example 1 are as follows. Figure 2 、 3 The real part of the dielectric constant is generally related to the polarization in the material, while the imaginary part of the complex dielectric constant is generally related to the conductivity and polarization relaxation of the material for electrical loss type absorbing materials. Figure 2 (a) The relationship between the real part of the dielectric constant of Example 4 and Comparative Example 1 shows that when iron ions are added, the real part of the dielectric constant increases from 6 to 12. Figure 2 (b, c) It can be seen that the real part of the dielectric constant increases from 0 to 3, and the dielectric loss tangent increases from 0 to 0.3, becoming a wave absorbing material. The reflection loss calculation of the sample prepared in Example 4 above is as follows Figure 4 As shown in the figure, the absorbing material exhibits high dielectric loss at low frequencies (8-12 GHz). When the sample thickness is 2.3 mm, the -10 dB effective absorption bandwidth reaches 8.66-10.91 GHz. The infrared emissivity of the samples prepared in Examples 1-4 and Comparative Example 1 was measured at room temperature. As shown in Table 1, the samples exhibit high emissivity in the 3-5 μm band at both room and high temperatures.
[0027] Table 1 Measurement results of infrared emissivity at room temperature
[0028] A fourth embodiment of the present invention provides a high-emissivity radar absorbing material for use in an aircraft. The absorbing material of this embodiment is used in an aerospace aircraft to facilitate radiation heat dissipation of the aircraft.
[0029] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.
Claims
1. A high emissivity radar absorbing material, characterized in that: The chemical formula of the absorbing material is Fe x Ni 1-x Cr2O4, where x is 0.2-0.8; The absorbing material is obtained by ball-milling and mixing raw materials Fe2O3, NiO and Cr2O3, and pre-sintering; The wave absorbing material has a reflection loss of -27 dB at 8-12 GHz and an emissivity greater than 0.9 at a temperature of 25-30° C.
2. A method for preparing the high-emissivity radar absorbing material according to claim 1, characterized in that: include: According to the ratio of each element in the chemical formula of the absorbing material, Fe2O3, NiO and Cr2O3 are ball-milled and mixed to obtain a uniform powder; The uniform powder is pre-sintered at 1200-1500° C. for 12-24 hours to obtain a wave absorbing material.
3. The method for preparing a high-emissivity radar absorbing material according to claim 2, wherein: During the ball milling process, the sizes of the ball milling beads were 3 mm and 6 mm, respectively, and the mass ratio thereof was 2:
1.
4. A method for preparing a high-emissivity radar absorbing material coating, characterized in that: The absorbing material according to claim 1, comprising: ball-milling the absorbing material, adhesive and deionized water to obtain a viscous slurry; spraying and granulating the viscous slurry to obtain microwave-absorbing powder; The microwave-absorbing powder is sprayed on the metal substrate by a plasma spraying method to obtain a microwave-absorbing material coating.
5. The method for preparing a high-emissivity radar absorbing material according to claim 4, characterized in that: During the plasma spraying process, the spraying voltage is 25-30V, the spraying current is 300-350A, the main gas flow rate is 1500-2000L / h, the powder feeding rate is 150-180L / h, and the spraying distance is 50-75mm.
6. The method for preparing a high-emissivity radar absorbing material according to claim 4, wherein: The metal substrate is a stainless steel plate, a nickel-based alloy plate or an aluminum alloy plate.
7. Use of the high-emissivity radar absorbing material according to claim 1 in an aircraft.