A high-entropy oxide-based wave-absorbing material, a preparation method and application thereof
By preparing core-shell structured high-entropy oxide absorbing materials, the problem of low absorption efficiency of existing absorbing materials in a wide frequency band was solved, achieving efficient, lightweight, and corrosion-resistant electromagnetic wave absorption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA THREE GORGES UNIV
- Filing Date
- 2026-05-14
- Publication Date
- 2026-07-14
Smart Images
Figure CN122395926A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microwave absorbing materials technology, specifically to a microwave absorbing material based on high-entropy oxides, its preparation method, and its applications. Background Technology
[0002] With the rapid development of electronic information technology, electromagnetic waves have been widely used in communications, radar, aerospace, and civilian electronic devices. However, the extensive use of electromagnetic waves has also brought about problems such as electromagnetic interference and electromagnetic radiation pollution, which not only affect the normal operation of precision equipment but also pose a potential threat to human health. Therefore, the development of high-performance electromagnetic wave absorbing materials has become a research hotspot in the field of materials science.
[0003] Ideal microwave absorbing materials should meet the requirements of being "thin, light, wide-bandwidth, and strong," meaning they should have thin coatings, light weight, wide absorption bandwidth, and high absorption intensity, while also possessing good thermal stability and environmental adaptability. Traditional microwave absorbing materials mainly include ferrites, magnetic metal powders, silicon carbide, and carbon-based materials. However, these materials have significant shortcomings in practical applications: ferrites have high density and their magnetic loss decreases sharply at high temperatures; magnetic metal powders are easily oxidized and have poor corrosion resistance; carbon-based materials, although low in density, have poor impedance matching characteristics, easily leading to surface reflection rather than absorption. Furthermore, single-component microwave absorbing materials are often limited by their fixed electromagnetic parameters, making it difficult to achieve efficient absorption over a wide frequency range, and the potential for adjustment through simple composite modification is limited.
[0004] In recent years, high-entropy materials, as a novel materials design concept, have shown great potential in the fields of energy, catalysis, and structural ceramics due to their unique "cocktail effect" and severe lattice distortion. High-entropy oxides typically contain five or more metallic elements with similar concentrations, forming a stable single-phase solid solution structure through multi-element synergistic effects. This highly mixed multi-element lattice configuration endows high-entropy materials with excellent tunable dielectric properties, high-temperature phase stability, and abundant defect dipoles.
[0005] Traditional microwave absorbing materials mainly include ferrites, magnetic metal powders, silicon carbide, and carbon-based materials. However, these materials have significant shortcomings in practical applications: ferrites have high density and their magnetic loss decreases sharply at high temperatures; magnetic metal powders are easily oxidized and have poor corrosion resistance; carbon-based materials, although low in density, have poor impedance matching characteristics, easily leading to surface reflection rather than absorption. High-entropy oxides (HEOs), as emerging multi-principal-element ceramic materials, have been proven to have microwave absorbing potential in recent years due to their unique lattice distortion effect, abundant oxygen vacancies, and multi-component synergistic polarization loss mechanism. However, single HEOs often fail to achieve efficient absorption due to low dielectric constants or poor impedance matching.
[0006] Therefore, developing a microwave absorbing material based on high-entropy oxides that also possesses broadband and strong absorption properties is of significant research importance and engineering application value. Summary of the Invention
[0007] To address the aforementioned problems, this invention provides a microwave absorbing material based on high-entropy oxides, which has a core-shell structure comprising a 90wt%-95wt% high-entropy oxide core and a 5wt%-10wt% graphene shell; the high-entropy oxides contain five metallic elements: iron, chromium, cobalt, aluminum, and manganese.
[0008] This invention also provides a method for preparing a microwave absorbing material based on high-entropy oxides, comprising the following steps:
[0009] (1) Preparation of high-entropy oxide precursor: Dissolve at least five metal salts in water to prepare a salt mixture, add sodium hydroxide solution to the salt mixture, and perform a hydrothermal reaction to obtain the high-entropy oxide precursor; (2) Preparation of high-entropy oxides: High-entropy oxide precursors are calcined at high temperature to obtain high-entropy oxides; (3) Preparation of microwave absorbing material: Disperse high entropy oxide in water or PDDA aqueous solution and stir to mix, then add graphene and stir to mix to obtain microwave absorbing material.
[0010] Furthermore, the five metal salts are nitrates or carbonates of iron, chromium, cobalt, aluminum, and manganese salts; the molar ratio of iron, chromium, cobalt, aluminum, and manganese salts is 1:(0.7-1.5):(0.7-1.5):(0.7-1.5):(0.7-1.5) based on the molar amount of the metals.
[0011] Furthermore, the sodium hydroxide solution has a mass concentration of 5%-10%; the OH- in the sodium hydroxide... - The mass ratio of the total metal elements in the iron salt, chromium salt, cobalt salt, aluminum salt and manganese salt is (4-6):1, preferably 5:1.
[0012] Furthermore, the hydrothermal reaction conditions are: holding at 160-200℃ for 8-12 hours; preferably, holding at 180℃ for 10 hours.
[0013] Furthermore, the high-temperature calcination conditions are: holding at 500-700℃ for 2-5 hours, with a heating rate of 2-4℃ / min; preferably, holding at 600℃ for 3 hours.
[0014] Furthermore, in step (3), the mass ratio of high-entropy oxide to water is 1:(60-100).
[0015] Further, in step (3), the mass concentration of the PDDA aqueous solution is 0.3wt%-1wt%; the mass ratio of the high-entropy oxide to the PDDA aqueous solution is 1:(150-250).
[0016] Furthermore, in step (3), the graphene is reduced graphene oxide, and the reduced graphene oxide accounts for 3%-8.5% of the total mass of the reduced graphene oxide and the high entropy oxide powder, preferably 7%.
[0017] The aforementioned microwave absorbing materials are used in the fields of electromagnetic absorption and protection.
[0018] The beneficial effects of this invention are as follows: This invention uses a high-entropy oxide composed of five elements—iron, chromium, cobalt, aluminum, and manganese—as the core and graphene powder as the shell. By modifying the surface of the high-entropy oxide in a PDDA solution to give it a positive charge, and since the graphene powder carries a negative charge after dissolving, the two substances are mixed to achieve a stable core-shell structure through electrostatic adsorption. The resulting composite material has the characteristics of broadband and strong absorption and can effectively absorb electromagnetic waves. Attached Figure Description
[0019] Figure 1 The XRD pattern is shown for the microwave absorbing materials prepared in Examples 1-5.
[0020] Figure 2 The image shows the reflection loss (RL) of the absorbing material prepared in Example 1.
[0021] Figure 3 The reflection loss diagram (RL) of the absorbing material prepared in Example 2 is shown.
[0022] Figure 4 The image shows the reflection loss (RL) of the absorbing material prepared in Example 3.
[0023] Figure 5 The image shows the reflection loss (RL) of the absorbing material prepared in Example 4.
[0024] Figure 6 The image shows the reflection loss (RL) of the absorbing material prepared in Example 5.
[0025] Figure 7 The image shows the reflection loss (RL) of the absorbing material prepared in Example 6.
[0026] Figure 8 This is a SEM image of the microwave absorbing material prepared in Example 3.
[0027] Figure 9 SEM image of the microwave absorbing material prepared in Example 6. Detailed Implementation
[0028] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.
[0029] Example 1 (1) Dissolve 0.56 g of solid ferric nitrate, 0.56 g of solid chromium nitrate, 0.41 g of solid cobalt nitrate, 0.52 g of solid aluminum nitrate, and 0.35 g of solid manganese carbonate in 35 ml of deionized water to obtain a metal suspension; dissolve 1.4 g of solid sodium hydroxide in 20 ml of deionized water to obtain a sodium hydroxide solution; place the metal suspension on a magnetic stirrer and stir for 10 min; slowly add the sodium hydroxide solution dropwise into the metal suspension to obtain hydrothermal reaction raw materials.
[0030] (2) Transfer the hydrothermal reaction raw materials to a 100ml hydrothermal reactor, place it in an oven, keep it at 180℃ for 10h, and after heating, let it cool naturally to obtain a solid-liquid separated sample. Pour off the supernatant and wash the precipitate several times. Filter and dry the washed precipitate, and finally grind it to obtain the powder, which is the high-entropy oxide precursor.
[0031] (3) Pour the high-entropy oxide precursor into a ceramic mold and spread it evenly. Place it in a muffle furnace for heating. Keep it at 600℃ for 3 hours. The heating rate is 3℃ / min. After heating, let it cool naturally. The resulting powder is the high-entropy oxide.
[0032] (4) Disperse the high-entropy oxide powder in water, add 35 ml of deionized water for every 0.5 g of powder, stir at 500 rpm for 20 min, then add 3 wt% (the ratio of reduced graphene oxide to the total mass of reduced graphene oxide and high-entropy oxide powder) of reduced graphene oxide (rGO), stir at 500 rpm for 20 min, then filter and dry to obtain the microwave absorbing material. XRD analysis is shown in [reference needed]. Figure 1 HEO / G-3.
[0033] Example 2 The difference from Example 1 is that 3 wt% reduced graphene oxide was replaced with 5 wt% reduced graphene oxide, while the rest remained the same as in Example 1, resulting in a microwave absorbing material. XRD analysis is shown below. Figure 1 HEO / G-5.
[0034] Example 3 The difference from Example 1 is that 3 wt% reduced graphene oxide was replaced with 7 wt% reduced graphene oxide, while the rest remained the same as in Example 1, resulting in a microwave absorbing material. XRD analysis is shown below. Figure 1 HEO / G-7.
[0035] Example 4 The difference from Example 1 is that 3 wt% reduced graphene oxide was replaced with 9 wt% reduced graphene oxide, while the rest remained the same as in Example 1, resulting in a microwave absorbing material. XRD analysis is shown below. Figure 1 HEO / G-9.
[0036] Example 5 The difference from Example 1 is that 3 wt% reduced graphene oxide was replaced with 0 wt% reduced graphene oxide, i.e., no reduced graphene oxide was added. The rest is the same as in Example 1, resulting in a microwave absorbing material. XRD analysis is shown below. Figure 1 HEO / G-0.
[0037] Example 6 (1)~(3) Same as Example 1.
[0038] (4) Disperse the high-entropy oxide powder in a 0.5 wt% PDDA aqueous solution. Add 100 ml of 0.5 wt% PDDA aqueous solution to every 0.5 g of high-entropy oxide powder, stir at 500 rpm for 30 min, then add 7 wt% (the ratio of reduced graphene oxide to the total mass of reduced graphene oxide and high-entropy oxide powder) of reduced graphene oxide (rGO), stir at 500 rpm for 30 min, and obtain the microwave absorbing material. PDDA is polydiallyldimethylammonium chloride, purchased from Maclean's.
[0039] The microwave absorption performance of the microwave absorbing materials prepared in Examples 1-6 was tested. The specific method was as follows: solid paraffin was melted, mixed with the microwave absorbing material at a mass ratio of 4:6, and then pressed into a ring to obtain a reflection loss test sample. The results are shown below. Figure 2-7 As shown, SEM observations were performed on the microwave absorbing materials prepared in Examples 3 and 6, and the results are shown in the figure. Figure 8 and Figure 9 .
[0040] Depend on Figure 2-6 It can be seen that among Examples 1-5, Example 3 (7wt% reduced graphene oxide) exhibits the best microwave absorption performance, achieving a minimum reflection loss of -32.52dB at a thickness of 2.5 mm, and an effective absorption bandwidth (RL ≤ -10 dB) of up to 5.27 GHz (10~15.27 GHz). Further analysis... Figure 8 As can be seen, in the microwave absorbing material obtained in Example 3, only a small portion of the graphene powder adheres to the surface of the high-entropy oxide, failing to form a uniform core-shell structure. This limits further improvement in the material's microwave absorption performance. To further enhance the microwave absorption performance, Example 6 of this invention makes a further innovation by using PDDA to modify the surface of the high-entropy oxide, such as... Figure 7 and Figure 9 As shown, when the graphene content is 7wt%, the graphene powder can completely coat the high-entropy oxide and significantly improve the wave absorption performance. The minimum reflection loss reaches -37.82dB near 16GHz. With a matching thickness of 2mm, the maximum effective absorption bandwidth can reach 4.63GHz.
Claims
1. A microwave absorbing material based on high-entropy oxides, characterized in that, It has a core-shell structure, consisting of a 90wt%-95wt% high-entropy oxide core and a 5wt%-10wt% graphene shell; the high-entropy oxide contains five metallic elements: iron, chromium, cobalt, aluminum, and manganese.
2. A method for preparing a microwave absorbing material based on high-entropy oxides, characterized in that, Includes the following steps: (1) Preparation of high-entropy oxide precursor: Dissolve at least five metal salts in water to prepare a salt mixture, add sodium hydroxide solution to the salt mixture, and perform a hydrothermal reaction to obtain the high-entropy oxide precursor; (2) Preparation of high-entropy oxides: High-entropy oxide precursors are calcined at high temperature to obtain high-entropy oxides; (3) Preparation of microwave absorbing material: Disperse high entropy oxide in water or PDDA aqueous solution and stir to mix, then add graphene and stir to mix to obtain microwave absorbing material.
3. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, The five metal salts are nitrates or carbonates of iron, chromium, cobalt, aluminum, and manganese; the molar ratio of iron, chromium, cobalt, aluminum, and manganese salts is 1:(0.7-1.5):(0.7-1.5):(0.7-1.5):(0.7-1.5).
4. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, The mass concentration of sodium hydroxide solution is 5%-10%; the OH- in sodium hydroxide - The mass ratio of the total metal elements in the iron salt, chromium salt, cobalt salt, aluminum salt and manganese salt is (4-6):1, preferably 5:
1.
5. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, The hydrothermal reaction conditions are 160-200℃ for 8-12 hours; preferably 180℃ for 10 hours.
6. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, The high-temperature calcination conditions are 500-700℃ for 2-5 hours, with a heating rate of 2-4℃ / min; preferably, 600℃ for 3 hours.
7. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, In step (3), the mass ratio of high-entropy oxide to water is 1:(60-100).
8. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, In step (3), the mass concentration of the PDDA aqueous solution is 0.3wt%-1wt%; the mass ratio of high entropy oxide to PDDA aqueous solution is 1:(150-250).
9. The method for preparing a microwave absorbing material based on a high-entropy oxide according to claim 2, characterized in that, In step (3), the graphene is reduced graphene oxide, and the reduced graphene oxide accounts for 3%-8.5% of the total mass of the reduced graphene oxide and high entropy oxide powder, preferably 7%.
10. The microwave absorbing material based on a high-entropy oxide according to claim 1, or the microwave absorbing material based on a high-entropy oxide according to any one of claims 2-9, is used for electromagnetic absorption and protection.