High-temperature radar stealth silicate modified material and preparation method thereof

Abstract

The application discloses a high-temperature radar stealth silicate modified material and a preparation method thereof, and belongs to the technical field of high-temperature electromagnetic protection. 10‑x Sr x Si6O 27‑x / 2 , wherein RE is one or any multiple elements in a lanthanide series in an equal proportion combination, and x<=0.5. The preparation method comprises the following steps: according to RE: Sr: Si=10-x: x: 6 and x<=0.5, a proper amount of RE2O3, SrCO3 and SiO2 powders are weighed according to their molar proportions, and are put into a ball mill tank, anhydrous ethanol is added for ball milling, and after being uniformly mixed, the mixture is dried and sieved; after being sieved, the mixed powder is cold isostatic pressed, is placed in an alumina ceramic boat, and is subjected to high-temperature calcination, so that the RE 10‑x Sr x Si6O 27‑x / 2 material with high-temperature radar stealth performance is prepared. The RE 10‑x Sr x Si6O 27‑x / 2 material with high-temperature radar stealth performance prepared by the application has the excellent characteristics of good chemical stability, high-temperature resistance, oxidation resistance, thin thickness, large bandwidth and strong reflection loss performance.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature electromagnetic protection technology. Specifically, it relates to a high-temperature radar stealth silicate modified material and its preparation method. Background Technology

[0002] In the context of modern warfare and the development of hypersonic vehicles, weaponry faces increasingly stringent requirements for both thermal environments and electromagnetic stealth. Especially during hypersonic flight (Mach 5 and above), the surface temperature of the aircraft can reach 1000°C or even higher. Traditional radar-absorbing materials, such as carbon-based materials and ferrites, suffer severe performance degradation at high temperatures, making them unsuitable for the stealth requirements of future equipment in extreme environments. Therefore, developing novel stealth materials that combine high-temperature stability with excellent electromagnetic wave absorption capabilities has become a key research direction in materials science and defense technology.

[0003] In recent years, researchers have gradually focused their attention on ceramic matrix composites, MAX phase materials, and rare-earth-doped oxide materials. For example, ZrB2-SiC ceramic composites, which exhibit excellent high-temperature oxidation resistance, can maintain structural stability at 1500℃. Furthermore, by doping with rare-earth elements such as Gd and Y, they demonstrate superior dielectric loss characteristics and microwave absorption capabilities in the 2–18 GHz frequency band, with a reflection loss (RL) as low as -35 dB or higher and an effective absorption bandwidth exceeding 5 GHz. Meanwhile, the composite of two-dimensional materials such as MXene with conductive ceramics has also shown potential for controlling dielectric constant and enhancing impedance matching, providing new ideas for achieving high-performance broadband microwave absorption.

[0004] However, the aforementioned materials inevitably undergo oxidation under high-temperature conditions, causing changes in their composition and resulting in irreversible damage to the stability of their radar stealth performance.

[0005] To overcome the instability of radar stealth performance under high-temperature conditions, developing new oxide radar stealth materials with high-temperature stability, adjustable electromagnetic parameters, and structural designability is not only one of the key technologies for achieving electromagnetic compatibility and stealth performance of hypersonic vehicles, but also represents the future direction of material innovation for intelligent weapon platforms. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-temperature radar stealth silicate modified material and its preparation method. Compared with radar stealth materials currently under research, this material has excellent high-temperature stability, strong oxidation resistance, thin and light structure, and outstanding low radar reflection loss. It can effectively alleviate the performance degradation of hot-end components under extreme thermal environments and has excellent electromagnetic stealth capabilities, providing technical support for future aerospace electronic warfare.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A high-temperature radar stealth silicate modified material, wherein the material is RE 10-x Sr x Si6O 27-x / 2 , where RE is one or any combination of lanthanide elements in equal proportions, and x≤0.5.

[0009] Preferably, the material is La. 9.6 Sr 0.4 Si6O 26.8 .

[0010] A method for preparing a high-temperature radar stealth silicate modified material includes the following steps:

[0011] (1) Weigh appropriate amounts of RE2O3, SrCO3 and SiO2 powders according to the molar ratio, ball mill and mix them evenly, dry them and sieve them.

[0012] (2) The mixed powder in step (1) is pre-calcined, ground, and sieved;

[0013] (3) The powder sieved in step (2) is subjected to uniaxial compression to form a preform, and the preform is subjected to high-temperature sintering to form the required RE. 10-x Sr x Si6O 27-x / 2 Material.

[0014] Further, in step (1), the RE source is RE2O3 (RE is one or any combination of multiple elements in equal proportions from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu); the molar ratio of each raw material is RE:Sr:Si = 10-x:x:6, and x ≤ 0.5. Place the above raw materials in a ball mill jar and add anhydrous ethanol. To ensure uniform ball milling, the ball-to-powder ratio is controlled at 5:1-10:1; the mass ratio of the solvent anhydrous ethanol to the mixed powder is 2:1-5:1; the ball milling speed is maintained at 300-400 rpm, and the mixing time is no less than 12 hours.

[0015] Furthermore, in step (2), the pre-firing temperature is 800-1400℃, the sintering time is 12-36h, and a 100-300 mesh sieve is used for sieving.

[0016] Furthermore, in step (3), the uniaxial pressure is 5-50 MPa, the holding time is 10-20 min, the high-temperature sintering temperature is 1400-1800℃, and the sintering time is 12-36 h.

[0017] Mechanism of the invention:

[0018] The material of this invention possesses high-temperature radar stealth performance, primarily because doping with divalent alkaline earth elements and rare earth elements can induce lattice distortion and break the original structural symmetry, generating a large number of oxygen vacancies. These oxygen vacancies can form localized states under the influence of electromagnetic waves, which is beneficial for carrier transitions and polarization processes, thereby improving dielectric loss capability and effectively enhancing radar wave absorption efficiency, especially maintaining stable absorption performance at high temperatures.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The preparation process is simple and controllable, and is suitable for large-scale production;

[0021] (2) The modified silicate material maintains excellent chemical and structural stability in high-temperature (>1000℃) environments and can resist high-temperature oxidation and thermal shock. At the same time, by introducing conductive or polarization-enhancing components, its complex permittivity can be effectively controlled to achieve strong absorption of millimeter-wave band and multi-band radar wave loss, thereby achieving excellent radar stealth performance;

[0022] (3) The material not only has excellent radar wave absorption capability, but also has certain mechanical properties and thermal insulation capability, making it suitable as a structural-functional integrated protective layer for high-temperature parts of aircraft. Compared with traditional multi-layer composite stealth materials, this material system has a higher degree of lightweighting and better interface thermal stability, which is conducive to improving overall service reliability and service life. Detailed Implementation

[0023] To make the objectives and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, any modifications or equivalent substitutions to the technical solutions of this invention that do not depart from the spirit and scope of the invention should be covered within the protection scope of this invention.

[0024] Example 1

[0025] A high-temperature radar stealth silicate modified material (La 9.6 Sr 0.4 Si6O 26.8 The specific steps are as follows:

[0026] (1) Using La2O3, SrCO3 and SiO2 powders as raw materials, weigh the powders according to the molar ratio La2O3:SrCO3:SiO2=4.8:0.4:6;

[0027] (2) Place the three raw materials weighed in step (1) into a ball mill jar and add anhydrous ethanol. To ensure uniform ball milling, the ball-to-material ratio is controlled at 7:1. The mass ratio of the solvent anhydrous ethanol to the mixed powder is 5:1. The ball milling speed is maintained at 400 rpm and the mixing time is 24 hours.

[0028] (3) Place the mixed powder anhydrous ethanol solution from step (2) in an 80°C forced-air drying oven for 12 hours to dry;

[0029] (4) The dried powder from step (3) is sieved using a 300-mesh sieve;

[0030] (5) Place the sieved powder from step (4) evenly in an alumina ceramic boat and pre-sinter at a high temperature of 1200℃ for 12 hours. After sintering, grind and sieve the powder using a 300-mesh sieve. Repeat this heat treatment at least three times.

[0031] (6) After the powder that has been pre-sintered in step (5) is sieved through a 300-mesh sieve, it is subjected to uniaxial compression. Under a uniaxial pressure of 50 MPa and a holding time of 10 min, it is pressed into a blank with a diameter of 30 mm and a thickness of 2 mm.

[0032] (7) The pressed preform in step (6) is placed in a muffle furnace for high-temperature sintering at a temperature of 1550°C for 12 hours.

[0033] (8) The radar stealth performance of the block material sintered in step (7) and machined is tested and evaluated using a high-temperature electromagnetic parameter testing system.

[0034] The La prepared in Example 1 of this embodiment 9.6 Sr 0.4 Si6O 26.8 The radar reflection loss performance of the material at 1000℃ is shown in Table 1.

[0035] Table 1

[0036]

[0037] Comparative Example 1

[0038] La 10 Si6O 27 The materials and their preparation method, specifically the following steps:

[0039] (1) Using La2O3 and SiO2 powders as raw materials, weigh the powders according to the molar ratio of La2O3:SiO2=5:6;

[0040] (2) Place the two raw materials weighed in step (1) into a ball mill jar and add anhydrous ethanol. To ensure uniform ball milling, the ball-to-material ratio is controlled at 7:1. The mass ratio of the solvent anhydrous ethanol to the mixed powder is 5:1. The ball milling speed is maintained at 400 rpm and the mixing time is 24 hours.

[0041] (3) Place the mixed powder anhydrous ethanol solution from step (2) in an 80°C forced-air drying oven for 12 hours to dry;

[0042] (4) The dried powder from step (3) is sieved using a 300-mesh sieve;

[0043] (5) Place the sieved powder from step (4) evenly in an alumina ceramic boat and pre-sinter at a high temperature of 1200℃ for 12 hours. After sintering, grind and sieve the powder using a 300-mesh sieve. Repeat this heat treatment at least three times.

[0044] (6) After the powder that has been pre-sintered in step (5) is sieved through a 300-mesh sieve, it is subjected to uniaxial compression. Under a uniaxial pressure of 50 MPa and a holding time of 10 min, it is pressed into a blank with a diameter of 30 mm and a thickness of 2 mm.

[0045] (7) The pressed preform in step (6) is placed in a muffle furnace for high-temperature sintering at a temperature of 1550°C for 12 hours.

[0046] (8) The radar stealth performance of the block material sintered in step (7) and machined is tested and evaluated using a high-temperature electromagnetic parameter testing system.

[0047] The La prepared in Comparative Example 1 10 Si6O 27 The radar reflection loss performance of the material at 1000℃ is shown in Table 2.

[0048] Table 2

[0049]

[0050] A comparison between Example 1 and Comparative Example 1 revealed that doping with divalent alkaline earth elements and RE elements can effectively improve La 10 Si6O 27 The inherent high-temperature radar stealth performance of the material is mainly due to the fact that doping with divalent alkaline earth elements and rare earth elements can cause lattice distortion and break the original structural symmetry, inducing a large number of oxygen vacancies. These oxygen vacancies can form localized states under the action of electromagnetic waves, which is conducive to the transition and polarization process of charge carriers, thereby improving dielectric loss and effectively enhancing radar wave absorption efficiency, especially maintaining stable absorption performance at high temperatures.

Claims

1. A high-temperature radar stealth silicate modified material, characterized in that, The material is La. 9.6 Sr 0.4 Si6O 26.8 .

2. A method for preparing a high-temperature radar stealth silicate modified material according to claim 1, characterized in that, Includes the following steps: (1) Weigh appropriate amounts of La2O3, SrCO3 and SiO2 powders according to the molar ratio; (2) Add the three raw materials weighed in step (1) into the ball mill jar in sequence, add an appropriate amount of anhydrous ethanol, and then mix them in the ball mill. (3) Place the anhydrous ethanol solution of the mixture obtained in step (2) into an oven for drying; (4) Sift the dried mixed powder from step (3); (5) Spread the sieved powder from step (4) evenly in an alumina ceramic boat and perform high-temperature pre-sintering; (6) Repeat step (5) of the pre-sintering process at least three times; (7) The powder after pre-sintering in step (6) is uniaxially pressed to obtain a green body; (8) The blank from step (7) is sintered at high temperature to form the desired La. 9.6 Sr 0.4 Si6O 26.8 Material.

3. The preparation method according to claim 2, characterized in that: In step (2), to ensure uniform ball milling, the ball-to-powder ratio is controlled at 5:1-10:1; the mass ratio of the ball milling solvent anhydrous ethanol to the mixed powder is 2:1-5:

1.

4. The preparation method according to claim 2, characterized in that: The ball mill speed should be maintained at 300-400 rpm, and the mixing time should be no less than 12 hours.

5. The preparation method according to claim 2, characterized in that: In step (5), the powder pre-firing temperature is 800-1400℃ and the sintering time is 12h-36h.

6. The preparation method according to claim 2, characterized in that: In step (7), the uniaxial pressure is 5-50 MPa and the pressure holding time is 10-20 min.

7. The preparation method according to claim 2, characterized in that: In step (8), the high-temperature sintering temperature is 1400-1800℃ and the sintering time is 12-36h.

8. The preparation method according to claim 2, characterized in that: In step (6), each time step (5) is repeated, grinding and sieving should be performed.

9. The preparation method according to claim 8, characterized in that: In steps (4) and (5), a 100-300 mesh sieve is used for screening.

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