A high-entropy oxide microwave-absorbing ceramic powder material, its preparation method and application

Abstract

The present invention relates to a high-entropy oxide microwave-absorbing ceramic powder material, its preparation method and application, belonging to the technical field of electromagnetic wave absorption materials, and solves the problems of poor high-temperature resistance and oxidation resistance of existing electromagnetic wave absorption materials and low absorption efficiency in the low-frequency band. The high-entropy oxide ceramic material has a perovskite structure, and the molecular structure is ABO3, where A includes La and Sr, and B is at least 5 elements among Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti. The present invention combines high-entropy oxides with a perovskite structure to precisely regulate the electromagnetic function of the high-entropy oxide ceramic material, achieving effective absorption of low-frequency electromagnetic waves; having oxidation resistance and thermal stability under high-temperature conditions, and maintaining excellent electromagnetic function intensity of the material at high temperatures. The high-entropy oxide ceramic powder material of the present invention broadens the scope of electromagnetic wave absorption materials, improves environmental adaptability, and meets the higher requirements for electromagnetic wave absorption materials put forward by the development of communication technology.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing ceramic materials, and particularly to a high-entropy oxide wave-absorbing ceramic powder material and its preparation method and application. Background Technique

[0002] Ideal electromagnetic functional materials should possess the following characteristics: being light and thin for easy carrying and installation; having wide-band coverage to adapt to electromagnetic waves of different frequencies, and efficient absorption to reduce reflection and scattering; and the ability to maintain performance under extreme environments, such as high temperature resistance and oxidation resistance.

[0003] However, most of the existing electromagnetic functional materials are mainly magnetic materials. Although these materials perform well at room temperature, they are prone to losing magnetism in high-temperature environments, resulting in a significant reduction in the electromagnetic functional effect. On the other hand, although wave-absorbing materials based on dielectric wave-absorbing materials have the advantage of being able to be used at high temperatures, their electromagnetic functional intensity and bandwidth are often not satisfactory. Taking coatings as an example, the thickness requirement of electromagnetic functional coatings actually applied to electronic devices is below 2 mm. According to the quarter-wavelength theory, due to the limitation of the coating thickness, they can exhibit ideal electromagnetic functional intensity at high frequencies (Ku band), but cannot exhibit ideal electromagnetic functional intensity at relatively low frequencies (such as X band).

[0004] Therefore, there is an urgent need for an electromagnetic wave absorbing material that can be applied for a long time in high-temperature environments, which not only has electromagnetic functions at room temperature but also has good electromagnetic functional intensity and wide-band coverage in high-temperature extreme environments to meet the higher requirements for electromagnetic wave absorbing materials put forward by the development of communication technology. Summary of the Invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a high-entropy oxide wave-absorbing ceramic powder material and its preparation method and application to solve at least one of the problems of poor high-temperature resistance and oxidation resistance of existing electromagnetic wave absorbing materials and low absorption efficiency for low-frequency bands.

[0006] In a first aspect, the embodiments of the present invention provide a high-entropy oxide wave-absorbing ceramic material. The ceramic material has a perovskite structure, and its molecular structure is ABO3. Among them, A includes La and Sr, and B is at least 5 elements selected from Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti.

[0007] Further, in the molecular structure ABO3, the molar ratio of La to Sr is 3:7 - 7:3.

[0008] Further, A includes La and Sr, and 1 - 3 elements selected from Ba, Y, Gd, and Ce.

[0009] Further, in the molecular structure ABO3, B is Fe, Co, Ni, Cr, or Mn.

[0010] Further, the molar ratio of Fe, Co, Ni, Cr, and Mn is 1:1:1:1:1 or 1:1:1:1:2.

[0011] Further, the ceramic material is a ceramic powder material with a particle size of 120 - 230 mesh and a loose bulk density of 1.0 - 1.4 g / cm 3 .

[0012] In a second aspect, an embodiment of the present invention provides a method for preparing the above-mentioned ceramic material, the method comprising: sintering the mixed raw materials;

[0013] Wherein, the raw material of A is lanthanum oxide and strontium carbonate;

[0014] The raw material of B is an oxide of B, selected from at least 5 of nickel oxide, manganese dioxide, iron(III) oxide, cobalt(III) oxide, hafnium dioxide, titanium dioxide, and zirconium dioxide.

[0015] Further, the sintering conditions include: under a vacuum of 8 - 20 Pa, at a temperature of 1295 - 1405 °C, for 10 - 15 h.

[0016] Further, after sintering, it further includes the steps of crushing and screening the sintered product, and the mesh number of the sieve for screening is 120 - 230 mesh.

[0017] Further, the mixing method is wet ball milling, and the specific conditions include: the medium is anhydrous ethanol, the ball-to-material ratio is (2 - 4):1, the rotation speed is 300 - 400 rpm, and the time is 10 - 15 h.

[0018] In a third aspect, an embodiment of the present invention provides an electromagnetic wave absorption coating, and the electromagnetic wave absorption coating includes the above-mentioned ceramic material.

[0019] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0020] 1. The high-entropy oxide microwave-absorbing ceramic material provided by the present invention has a perovskite structure. The various elements in the high-entropy oxide have atomic size differences and are randomly distributed, causing lattice distortion of the oxide and generating defects. These distortions and defects not only improve the microwave absorption efficiency of the material, but also enhance the chemical stability and thermal stability of the microwave-absorbing material at high temperatures, improve the cyclic stability and extend the service life; the high-entropy oxide with a perovskite structure has a solid solution phase that is thermodynamically unstable originally, inhibits the phase separation and ordering processes, promotes the obtained high-entropy oxide to have a uniform and dense microstructure, is conducive to the absorption and loss of electromagnetic waves, reduces the penetration depth of electromagnetic waves in the material, makes the microwave-absorbing material tend to be thin and light, and is convenient for carrying and installation; the synergistic effect between various elements in the high-entropy oxide can achieve strong absorption and broadband absorption of electromagnetic waves; by adjusting the types and ratios of A-site and B-site ions, precise regulation of the electromagnetic properties of the perovskite material can be realized, thereby optimizing its electromagnetic wave absorption performance and meeting different application requirements.

[0021] The present invention combines the high-entropy concept with the perovskite structure, precisely regulates the electromagnetic function of the high-entropy oxide ceramic material, and realizes effective absorption of low-frequency electromagnetic waves; it has antioxidant and thermal stability under high-temperature conditions and maintains excellent electromagnetic function intensity of the material at high temperatures; the high-entropy oxide ceramic powder material of the present invention broadens the range of electromagnetic wave absorption materials, improves environmental adaptability, and meets the higher requirements for electromagnetic wave absorption materials put forward by the development of communication technology.

[0022] 2. In the molecular structure ABO3 of the high-entropy oxide microwave-absorbing ceramic material provided by the present invention, the molar ratio of the two elements La and Sr as A is controlled to be 3:7 - 7:3, which improves the conductivity of the high-entropy oxide ceramic material, realizes broadband coverage to absorb electromagnetic waves of different frequencies, and enables it to have a complete and stable perovskite structure, further improving the microwave absorption performance and temperature resistance of the material.

[0023] 3. In order to improve the electromagnetic function intensity and high-temperature resistance of the high-entropy oxide ceramic, the molar ratios of different B elements are further limited. According to some preferred embodiments of the present invention, when B is Fe, Co, Ni, Cr, and Mn, the molar ratio of each element is 1:1:1:1:1 or 1:1:1:1:2.

[0024] 4. The particle size of the high-entropy oxide microwave-absorbing ceramic powder material of the present invention is controlled to be 120 - 230 mesh, and the loose bulk density is 1.0 - 1.4 g / cm 3 , so as to improve the fluidity of the powder in actual thermal spraying applications, reduce the evaporation loss of elements, and ensure that the powder can be fully melted during the preparation of the electromagnetic function coating by thermal spraying, improving the coating quality.

[0025] 5. The present invention prepares the high-entropy oxide microwave absorbing ceramic material by solid-phase synthesis method. The raw materials are metal oxide powders, which are easy to obtain and have low cost. By directly sintering the metal oxide raw materials, a high-purity high-entropy oxide ceramic material with perovskite structure can be obtained. The sintering temperature is 1295 - 1405 °C and the time is 10 - 15 h. The preparation process does not require highly toxic solvents, is safe and environmentally friendly, has simple process and short preparation cycle, and is expected to be mass-produced.

[0026] 6. The method of the present invention mixes the metal oxide powder raw materials by wet ball milling. Wet ball milling has good heat dissipation effect, can effectively control the particle size and distribution of the material, and has low energy consumption and low cost, which is beneficial to the large-scale production of the material.

[0027] 7. When the high-entropy oxide microwave absorbing ceramic material of the present invention is applied to the electromagnetic wave absorption coating, it can not only absorb electromagnetic waves in a relatively wide wave frequency band, but also has high electromagnetic function intensity especially in the lower frequency band (8 - 12 GHz), as Figure 5 shown; when the thickness of the prepared coating is in the range of 1 - 2 mm, it can not only have an absorption bandwidth of more than 1.5 GHz for the X-band at room temperature, but also have an absorption bandwidth of more than 1.0 GHz for the X-band at 1000 °C. Compared with the prior art in Table 1, it can better adapt to new equipment to effectively avoid electromagnetic wave detection; at the same time, the perovskite structure of the high-entropy oxide ceramic material of the present invention has good temperature resistance. Through the thermogravimetric analysis results, it can be known that when heated to 1200 °C in air atmosphere, the mass of the ceramic material remains stable all the time, having good thermal stability and antioxidant ability, still maintaining good electromagnetic function at high temperature, stable cycling performance and long service life; in addition, the ceramic material of the present invention has high electromagnetic function intensity for the lower frequency band (8 - 12 GHz), can reduce the production thickness of the electromagnetic function coating, realize the lightweight application of the microwave absorbing material in electronic equipment, and is convenient for carrying and installation, especially suitable for equipment such as aircraft with strict weight limit requirements.

[0028] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be obvious from the description, or can be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained from the content specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are only for the purpose of showing specific embodiments, and are not considered as a limitation of the present invention. Throughout the drawings, the same reference signs represent the same components;

[0030] Figure 1XRD diffraction patterns of the high-entropy oxide ceramic powder materials prepared in Examples 1, 4 - 7;

[0031] Figure 2 XRD diffraction patterns of the high-entropy oxide ceramic powder materials prepared in Example 1, Example 10, Comparative Example 1 and Comparative Example 2;

[0032] Figure 3(a) is the SEM image of the high-entropy oxide ceramic powder material prepared in Example 1;

[0033] Figure 3(b) is the EDS spectrum of the high-entropy oxide ceramic powder material prepared in Example 1;

[0034] Figure 4 TG measurement curves of the high-entropy oxide ceramic powder materials prepared in Example 1 and Example 8 at a heating rate of 10 °C / min;

[0035] Figure 5 Curves of the electromagnetic loss varying with frequency at room temperature for different thickness electromagnetic functional coatings prepared using the high-entropy oxide ceramic powder material of Example 1. Detailed implementation manners

[0036] The following will specifically describe the preferred embodiments of the present invention in conjunction with the drawings. Among them, the drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principle of the present invention, rather than to limit the scope of the present invention.

[0037] An ideal electromagnetic functional material should have the following characteristics: being lightweight and thin for easy carrying and installation; having a wide frequency band coverage to adapt to electromagnetic waves of different frequencies, being highly absorptive to reduce reflection and scattering; and having high temperature resistance and oxidation resistance to maintain performance in extreme environments.

[0038] However, most of the existing electromagnetic functional materials are mainly magnetic materials. Although these materials perform well at room temperature, they are prone to losing magnetism in high-temperature environments, resulting in a significant reduction in the electromagnetic functional effect. On the other hand, although the wave-absorbing materials based on dielectric wave-absorbing materials have the advantage of being able to be used at high temperatures, their electromagnetic functional intensity and frequency band width are often not satisfactory.

[0039] Therefore, the present invention provides a high-entropy oxide wave-absorbing ceramic material. The ceramic material has a perovskite structure, and the molecular structure is ABO3. Among them, A includes La and Sr, and B is at least 5 elements selected from Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti. According to the preferred embodiment of the present invention, La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn0.2 )The XRD diffraction pattern, SEM image, and EDS energy spectrum of the O3 powder are shown in Figure 1 Figure 2, Figure 3(a), and Figure 3(b), respectively.

[0040] On the one hand, the high-entropy oxide has unique physical and chemical properties: high mixing entropy effect, sluggish diffusion effect, lattice distortion effect, and "cocktail" effect.

[0041] Specifically, there are atomic size differences and random distributions among the various elements in the high-entropy oxide, which cause lattice structure distortion and generate defects in the oxide. These distortions and defects can increase the number of scattering and reflection times of electromagnetic waves inside the material, thereby extending the propagation path of electromagnetic waves in the material and improving the wave absorption efficiency. In addition, these distortions and defects also cause the material to have an atomic sluggish diffusion effect, increasing the resistance to atomic diffusion when the material undergoes external environmental changes (such as temperature changes). This not only improves the chemical stability and thermal stability of the wave-absorbing material at high temperatures but also enhances the cyclic stability of the material and extends its service life.

[0042] Specifically, the high mixing entropy can stabilize the solid solution phase that is thermodynamically difficult to form originally, inhibit the phase separation and ordering processes, and promote the prepared high-entropy oxide to have a uniform and dense microstructure. The uniformity enables the electromagnetic properties everywhere inside to be consistent, avoiding the enhancement of electromagnetic wave reflection and scattering caused by uneven electromagnetic properties, which is beneficial to the absorption and loss of electromagnetic waves. The dense microstructure reduces the penetration depth of electromagnetic waves in the material, making it easier for electromagnetic waves to be absorbed and lost on the surface and near-surface regions of the material, making the wave-absorbing material tend to be thin and light, facilitating carrying and installation.

[0043] Specifically, the synergistic effect among the various elements in the high-entropy oxide can significantly enhance the wave absorption performance of the material. Different elements have different corresponding characteristics for electromagnetic waves. Through reasonable element combination and ratio, strong absorption and broadband absorption of electromagnetic waves can be achieved.

[0044] On the other hand, the high-entropy oxide ceramic material provided by the present invention has a perovskite structure. The perovskite structure (ABO3) of the high-entropy oxide has advantages such as adjustable elements, unique electronic conductivity, and adjustable oxygen vacancies, enabling the high-entropy oxide to have good thermodynamic stability and high tolerance to constituent elements. Ions at the A-site and B-site can be individually or complexly substituted by ions with different valences and radii within a relatively wide concentration range to form a solid solution. By adjusting the types and ratios of A-site and B-site ions, precise control of the electromagnetic properties of the perovskite material can be achieved, thereby optimizing its electromagnetic wave absorption performance and meeting different application requirements.

[0045] The present invention combines the concept of high entropy with the perovskite structure, not only achieving precise regulation of the electromagnetic functions of high-entropy oxide ceramic materials and maintaining the electromagnetic function intensity of the materials at high temperatures, but also broadening the range of materials applied to electromagnetic wave absorption.

[0046] Further, the molecular structure of the high-entropy oxide ceramic material provided by the present invention is ABO3. The molar ratio of the two elements La and Sr as A is 3:7 - 7:3, which increases the conductivity of the high-entropy oxide ceramic material, realizes broadband coverage to absorb electromagnetic waves of different frequencies, and enables it to have a complete and stable perovskite structure, further improving the wave absorption performance and temperature resistance performance of the material.

[0047] According to some preferred embodiments of the present invention, the molar ratios of the two elements La and Sr as A are respectively 3:7, 4:6, 5:5, 6:4 or 7:3.

[0048] Further, A includes La and Sr, and 1 - 3 elements selected from Ba, Y, Gd, and Ce. Among them, among the elements as A, except for La and Sr, the content of other elements is less than or equal to 20 mol% of the total amount of A elements. If the content of other elements is too high, it will affect the conductivity of the ceramic material, thereby affecting its electromagnetic functionality. Exemplarily, A is La, Sr, and Gd with a molar ratio of 2:2:1, or La, Sr, and Ba with a molar ratio of 2:2:1, or La, Sr, Ba, and Ce with a molar ratio of 4:4:1:1.

[0049] Further, in order to improve the electromagnetic function intensity and high-temperature resistance performance of the high-entropy oxide ceramic, the present invention further defines the molar ratios of different B elements.

[0050] According to some preferred embodiments of the present invention, the B elements are Fe, Co, Ni, Cr, and Mn with a molar ratio of 1:1:1:1:1 or 1:1:1:1:2; or the B elements are Zr, Hf, Ti, Fe, and Cr with a molar ratio of 1:1:1:1:1; or the B elements are Zr, Fe, Co, Ni, Cr, and Mn with a molar ratio of 1:1:1:1:1:1.

[0051] The present invention controls the particle size of the high-entropy oxide ceramic powder material to be 120 - 230 mesh, and the loose bulk density is 1.0 - 1.4 g / cm 3 , in order to improve the fluidity of the powder in actual thermal spraying applications, reduce the evaporation loss of elements, and ensure that the powder can be fully melted during the process of preparing an electromagnetic function coating by thermal spraying, thereby improving the coating quality.

[0052] Specifically, calculated according to mole percentage (mol%), the elements constituting the high-entropy oxide microwave absorption ceramic material ABO3 include: Cr 0-10, Ni 0-10, Mn 1-10, Fe 0-10, Co 0-10, Zr 0-5, Hf 0-5, Ti 0-5, 0 < La < 50, 0 < Sr < 50, where A includes La and Sr, and B contains at least 5 transition metal elements.

[0053] According to a preferred embodiment of the present invention, the high-entropy oxide microwave absorption ceramic material of the present invention is La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, La 0.5 Sr 0.5 (Zr 0.2 Hf 0.2 Ti 0.2 Fe 0.2 Cr 0.2 )O3, La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6 )O3, La 0.7 Sr 0.3 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, La 0.3 Sr 0.7 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, La 0.6 Sr 0.4 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, La 0.4 Sr 0.6 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, La0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3, La 0.4 Sr 0.4 Gd 0.2 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3.

[0054] The present invention provides a method for preparing a high-entropy oxide ceramic powder material, the method comprising: sintering the mixed raw materials;

[0055] Wherein, the raw material of A is lanthanum trioxide and strontium carbonate;

[0056] The raw material of B is an oxide of B, selected from at least 5 of nickel oxide, manganese dioxide, iron(III) oxide, cobalt(III) oxide, hafnium dioxide, titanium dioxide, zirconium dioxide.

[0057] Specifically, calculated according to molar percentages, the proportions of the raw materials are as follows: 0 mol% to 7 mol% chromium(III) oxide, 0 mol% to 15 mol% nickel oxide, 0 mol% to 22 mol% manganese dioxide, 0 mol% to 7 mol% iron(III) oxide, 0 mol% to 7 mol% cobalt(III) oxide, 0 mol% to 15 mol% zirconium dioxide, 0 mol% to 15 mol% hafnium dioxide, 0 mol% to 15 mol% titanium dioxide, 0 mol% to 30 mol% lanthanum trioxide, 0 mol% to 50 mol% strontium carbonate; wherein, the added raw materials contain lanthanum trioxide and strontium carbonate as the source of A; the raw materials contain at least 5 transition metal oxides as the source of B.

[0058] According to a preferred embodiment of the present invention, the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide, and nickel oxide are 17 mol%, 34 mol%, 7 mol%, 7 mol%, 14 mol%, 7 mol%, 14 mol%, or 26 mol%, 23 mol%, 7 mol%, 7 mol%, 15 mol%, 7 mol%, 15 mol%, or 9 mol%, 45 mol%, 7 mol%, 7 mol%, 13 mol%, 6 mol%, 13 mol%, or 20 mol%, 30 mol%, 7 mol%, 7 mol%, 15 mol%, 7 mol%, 14 mol, or 13 mol%, 40 mol%, 7 mol%, 7 mol%, 13 mol%, 7 mol%, 13 mol%, or 17 mol%, 33 mol%, 6 mol%, 5 mol%, 22 mol%, 6 mol%, 11 mol%; the molar percentages of lanthanum sesquioxide, strontium carbonate, gadolinium sesquioxide, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide, and nickel oxide are 14 mol%, 26 mol%, 13 mol%, 7 mol%, 6 mol%, 13 mol%, 7 mol%, 14 mol%; the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, zirconium dioxide, manganese oxide, cobalt sesquioxide, and nickel oxide are 16 mol%, 34 mol%, 6 mol%, 6 mol%, 11 mol%, 5 mol%, 11 mol%, 11 mol%; the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, zirconium dioxide, hafnium dioxide, and titanium dioxide are 16 mol%, 33 mol%, 6 mol%, 6 mol%, 13 mol%, 13 mol%, 13 mol%.

[0059] The present invention uses a solid-phase synthesis method to prepare a high-entropy oxide ceramic material. The raw materials are metal oxide powders, which are easy to obtain and have low costs; by directly sintering the metal oxide raw materials, a high-purity high-entropy oxide ceramic material with a perovskite structure can be obtained. The sintering temperature is 1295 - 1405 °C, and the time is 10 - 15 h. The preparation process does not require highly toxic solvents, is safe and environmentally friendly, and has a simple process and a short preparation cycle, and is expected to be mass-produced.

[0060] Furthermore, the method of the present invention uses wet ball milling to mix the metal oxide powder raw materials. Wet ball milling has good heat dissipation effects, can effectively control the particle size and distribution of the materials, and has low energy consumption and low costs, which is beneficial to the large-scale production of the materials.

[0061] Specifically, the conditions for wet ball milling include: the mixing medium is anhydrous ethanol, and the ball material is zirconium balls. Since the use of grinding balls with different diameters and ratios can affect the crushing efficiency and particle size distribution of the powder, the present invention selects grinding balls with diameters of 2 mm, 5 mm, and 12 mm respectively. During the wet ball milling process, the mass ratio of the grinding balls with different diameters is 1:1:1, the rotation speed is 300 - 400 r / min, and the time is 10 - 15 h.

[0062] Furthermore, the liquid level of the anhydrous ethanol should submerge the zirconium balls.

[0063] Furthermore, filter the slurry obtained after wet ball milling, remove the grinding balls, and dry the remaining slurry after filtration.

[0064] Specifically, place the tray containing the remaining slurry into an oven for drying. The drying temperature is 80 - 110 °C, and the time is 10 h.

[0065] Furthermore, in order to make the mixed raw materials heat evenly during the subsequent sintering process and improve the product yield and quality, it is necessary to control the particle size of the mixed raw materials.

[0066] Specifically, perform screening on the dried mixed raw materials. The mesh number of the sieve for sieving is 120 - 230 meshes.

[0067] Furthermore, in order to control the degree of solid-phase synthesis reaction and the perovskite phase purity of the high-entropy oxide ceramics, the sintering conditions include: under the condition of an argon atmosphere, at a temperature of 1295 - 1405 °C, for 10 - 15 h, preferably at a temperature of 1395 - 1400 °C, for 10 h.

[0068] According to some preferred embodiments of the present invention, the vacuum degree of the high-temperature sintering is 10 Pa, the temperature is 1400 °C or 1300 °C, and the time is 10 h.

[0069] Furthermore, in order to improve the electromagnetic wave absorption efficiency and high-temperature resistance of the material, it is necessary to crush and screen the product obtained by high-temperature sintering in order to obtain a high-entropy oxide ceramic material with a target size.

[0070] Specifically, break the coarse product after high-temperature sintering, grind it sufficiently until there is no obvious blocky powder, and then pour it into a ball mill for ball milling treatment; the ball-to-material ratio during the ball milling and crushing process is (5 - 7):1, and the ball material is zirconia. Since the use of grinding balls with different diameters and ratios can affect the crushing efficiency and particle size distribution of the powder, the present invention selects grinding balls with diameters of 2 mm, 5 mm, and 12 mm respectively. During the ball milling and crushing process of the product, the mass ratio of the grinding balls with different diameters is 1:1:1, the rotation speed is 300 - 400 r / min, and the time is 3 - 5 min.

[0071] Specifically, the product after crushing treatment is subjected to screening treatment, and the mesh number of the sieve for screening is 120 - 230 meshes.

[0072] Specifically, the loose bulk density of the ceramic powder material prepared by the method of the present invention is 1.0 - 1.4 g / cm 3 .

[0073] The present invention also provides an application of a high-entropy oxide ceramic material in an electromagnetic wave absorption coating. The frequency of the electromagnetic wave is 8 - 18 GHz, the thickness of the electromagnetic wave absorption coating is 1 - 2 mm, and the use temperature is as high as 1200 - 1350 °C, or even higher.

[0074] Applying the high-entropy oxide ceramic material of the present invention to an electromagnetic wave absorption coating can not only achieve the absorption of electromagnetic waves in a relatively wide wave frequency range, especially having a high electromagnetic function intensity in a lower frequency band (8 - 12 GHz). Compared with the prior art, it can better adapt to new equipment to effectively avoid electromagnetic wave detection. At the same time, the perovskite structure of the high-entropy oxide ceramic material of the present invention has good heat resistance. Through thermogravimetric analysis results, it can be seen that when heated to 1200 °C in an air atmosphere, the mass of the ceramic material remains stable, having good thermal stability and antioxidant properties, still maintaining good electromagnetic functions at high temperatures, with stable cyclic performance and long service life. In addition, the ceramic material of the present invention has a high electromagnetic function intensity in the lower frequency band (8 - 12 GHz), which can reduce the production thickness of the electromagnetic function coating, realize the lightweight of the application of the wave-absorbing material in electronic devices, facilitate carrying and installation, and is especially suitable for equipment such as aircraft with strict weight limit requirements.

[0075] The following further explains and illustrates the technical solutions of the present invention in combination with specific embodiments.

[0076] All raw materials used in the present invention are commercially available products, in powder form, with a particle size range of 100 - 800 nm and a purity of 99.99%.

[0077] Example 1

[0078] Preparation method of high-entropy oxide ceramic powder La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3, comprising:

[0079] (1) Weigh 20 mol of 17 mol% lanthanum oxide, 34 mol% strontium carbonate, 7 mol% chromium(III) oxide, 7 mol% iron(III) oxide, 14 mol% manganese oxide, 7 mol% cobalt(III) oxide, and 14 mol% nickel oxide and put them into a ball mill jar. Then add zirconia grinding balls with diameters of 2 mm, 5 mm, and 12 mm respectively, with a mass ratio of 1:1:1 and a ball-to-material ratio of 4:1. While stirring, add absolute ethanol until the powder surface is submerged. Ball mill and mix at a rotation speed of 400 r / min for 10 h;

[0080] (2) Pour the slurry mixed evenly in step (1) into a 120-mesh sieve to filter out the grinding balls. Pour the remaining slurry into a tray and place it in an oven to dry at 100 °C for 6 h;

[0081] (3) Screen the powder dried in step (2) through a 150-mesh sieve to obtain a mixture powder. Put it into a zirconia crucible and sinter it in a high-temperature sintering furnace. The sintering temperature is 1400 °C, the time is 10 h, and the vacuum degree is 10 Pa. Among them, the heating rate is 5 °C / min;

[0082] (4) Break the sintered ceramic block in step (3) and grind it until there are no obvious lumps of powder. Then pour it into a ball mill jar and pour zirconia grinding balls with diameters of 12 mm, 5 mm, and 2 mm respectively at a ball-to-material ratio of 6:1, with a mass ratio of 1:1:1. Crush it for 20 min under the condition that the rotation speed of the ball mill is 350 r / min;

[0083] Pour the powder through a 120-mesh sieve to obtain a high-entropy electromagnetic functional oxide ceramic powder material La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O 3。

[0084] Perform XRD, SEM, EDS, TG, and electromagnetic function parameter tests on the La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder. The results are as shown in Figure 1 Figure 3(a), Figure 3(b), Figure 4 , Figure 5As shown in Table 1, it can be seen from the test results that the ceramic powder obtained in Example 1 has a single-phase perovskite structure, the elements inside the powder are evenly distributed, and the product has high purity; when heated to about 1250 °C in an air atmosphere, there will only be an inflection point of a sharp increase in mass, indicating that the ceramic material has good thermal stability and oxidation resistance; in the frequency range of 8 - 18 GHz, it has good electromagnetic loss, especially in the low-frequency band (8 - 12 GHz), when the prepared coating thickness is less than 2 mm, it has a wide electromagnetic wave absorption bandwidth at room temperature and 1000 °C.

[0085] Example 2

[0086] High-entropy oxide ceramic powder La 0.5 Sr 0.5 (Zr 0.2 Hf 0.2 Ti 0.2 Fe 0.2 Cr 0.2 )O3 is prepared by using the same preparation method as in Example 1, except that: in step (1) of Example 1, the raw materials manganese oxide, cobalt oxide and nickel oxide are replaced with zirconium dioxide, hafnium dioxide and titanium dioxide, and the molar percentages of lanthanum trioxide, strontium carbonate, chromium(III) oxide, iron(III) oxide, zirconium dioxide, hafnium dioxide and titanium dioxide are 16 mol%, 33 mol%, 6 mol%, 6 mol%, 13 mol%, 13 mol% and 13 mol% respectively.

[0087] For the La 0.5 Sr 0.5 (Zr 0.2 Hf 0.2 Ti 0.2 Fe 0.2 Cr 0.2 )O3 ceramic powder was subjected to TG testing, and the results are shown in Table 1. The ceramic powder prepared in Example 2 has good thermal stability and oxidation resistance.

[0088] Example 3

[0089] High-entropy oxide ceramic powder La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6)The preparation method of O3 is the same as that of Example 1, except that: the raw materials and their amounts in step (1) of Example 1 are changed and replaced with: the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, zirconia, manganese oxide, nickel oxide and cobalt sesquioxide are 16 mol%, 34 mol%, 6 mol%, 6 mol%, 11 mol%, 11 mol%, 11 mol% and 5 mol% respectively.

[0090] For La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6 )O3 ceramic powder is subjected to TG test, and the results are shown in Table 1. The ceramic powder prepared in Example 3 has good thermal stability and oxidation resistance.

[0091] Example 4

[0092] High-entropy oxide ceramic powder La 0.7 Sr 0.3 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 is prepared by the same method as in Example 1, except that: the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide and nickel oxide in step (1) of Example 1 are 26 mol%, 23 mol%, 7 mol%, 7 mol%, 15 mol%, 7 mol% and 15 mol% respectively.

[0093] For La 0.7 Sr 0.3 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 1 and shown in Table 1. The ceramic powder obtained in Example 4 has a single-phase perovskite structure, high product purity; and has good thermal stability and oxidation resistance.

[0094] Example 5

[0095] High-entropy oxide ceramic powder La 0.3 Sr 0.7 (Fe 0.2 Co 0.2 Ni0.2 Cr 0.2 Mn 0.2 ) The preparation method of O3 is the same as that of Example 1, except that: the molar percentages of lanthanum oxide, strontium carbonate, chromium oxide, iron oxide, manganese oxide, cobalt oxide, and nickel oxide in step (1) of Example 1 are 9 mol%, 45 mol%, 7 mol%, 7 mol%, 13 mol%, 6 mol%, and 13 mol% respectively.

[0096] For La 0.3 Sr 0.7 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) The O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 1 shown in Table 1. The ceramic powder obtained in Example 5 has a single-phase perovskite structure, high product purity; and has good thermal stability and oxidation resistance.

[0097] Example 6

[0098] The preparation method of the high-entropy oxide ceramic powder La 0.6 Sr 0.4 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 is the same as that of Example 1, except that: the molar percentages of lanthanum oxide, strontium carbonate, chromium oxide, iron oxide, manganese oxide, cobalt oxide, and nickel oxide in step (1) of Example 1 are 20 mol%, 30 mol%, 7 mol%, 7 mol%, 15 mol%, 7 mol%, and 14 mol% respectively.

[0099] For La 0.6 Sr 0.4 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) The O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 1 shown in Table 1. The ceramic powder obtained in Example 6 has a double-phase perovskite structure, high product purity; and has good thermal stability and oxidation resistance.

[0100] Example 7

[0101] The high-entropy oxide ceramic powder La 0.4 Sr 0.6 (Fe0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) Preparation method of O3, using the same method as in Example 1, except that: the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide, and nickel oxide in step (1) of Example 1 are 13 mol%, 40 mol%, 7 mol%, 7 mol%, 13 mol%, 7 mol%, and 13 mol% respectively.

[0102] For La 0.4 Sr 0.6 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 1 shown in Table 1. The ceramic powder obtained in Example 7 has a double-phase perovskite structure, high product purity; and has good thermal stability and oxidation resistance.

[0103] Example 8

[0104] Preparation method of high-entropy oxide ceramic powder La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3, using the same method as in Example 1, except that: the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide, and nickel oxide in step (1) of Example 1 are 17 mol%, 33 mol%, 6 mol%, 5 mol%, 22 mol%, 6 mol%, and 11 mol% respectively.

[0105] For La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3 ceramic powder is subjected to TG test, and the results are as Figure 4 shown in Table 1. The ceramic powder obtained in Example 8 has good thermal stability and oxidation resistance.

[0106] Example 9

[0107] High-entropy oxide ceramic powder La 0.4 Sr0.4 Gd 0.2 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) The preparation method of O3 is the same as that of Example 1, except that the molar percentages of lanthanum sesquioxide, strontium carbonate, gadolinium sesquioxide, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide, and nickel oxide are 14 mol%, 26 mol%, 13 mol%, 7 mol%, 6 mol%, 13 mol%, 7 mol%, and 14 mol% respectively.

[0108] For La 0.4 Sr 0.4 Gd 0.2 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) The O3 ceramic powder is subjected to TG testing, and the results are shown in Table 1. The ceramic powder obtained in Example 9 has good thermal stability and oxidation resistance.

[0109] Example 10

[0110] The preparation method of the high-entropy oxide ceramic powder La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 is the same as that of Example 1, except that the sintering temperature in step (1) of Example 1 is set to 1300 °C.

[0111] The La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder prepared in Example 10 is subjected to XRD and TG testing, and the results are shown in Table 1. The ceramic powder obtained in Example 10 has a single-phase perovskite structure, high product purity, and good thermal stability and oxidation resistance.

[0112] Comparative Example 1

[0113] The high-entropy oxide ceramic powder La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2Cr 0.2 Mn 0.2 ) The preparation method of O3 is the same as that in Example 1, except that: the sintering temperature in step (1) of Example 1 is set to 1150 °C.

[0114] For the La prepared in Comparative Example 1 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 2 shown in Table 1. In addition to having a perovskite structure, the ceramic powder obtained in Comparative Example 1 has a high impurity content and a low product purity.

[0115] Comparative Example 2

[0116] The preparation method of the high-entropy oxide ceramic powder La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 is the same as that in Example 1, except that: the sintering temperature in step (1) of Example 1 is set to 1200 °C.

[0117] For the La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder is subjected to XRD and TG tests, and the results are as Figure 2 shown in Table 1. In addition to having a perovskite structure, the ceramic powder obtained in Comparative Example 2 has a high impurity content and a low product purity.

[0118] Comparative Example 3

[0119] The high-entropy oxide ceramic powder La 0.9 Sr 0.1 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2)The preparation method of O3 is the same as that of Example 1, except that the molar percentages of lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide, and nickel oxide are 36 mol%, 8 mol%, 8 mol%, 8 mol%, 16 mol%, 8 mol%, and 16 mol% respectively.

[0120] For the La 0.9 Sr 0.1 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to TG testing, and the results are shown in Table 1.

[0121] Application Example

[0122] The high-entropy oxide ceramic powders prepared in Examples 1-10 and Comparative Examples 1-3 were respectively mixed with a wave-transparent material, and electromagnetic wave absorption coatings with different thicknesses were prepared by high-energy plasma spraying. The electromagnetic function parameters of the coatings at room temperature and 1000 °C were measured by the waveguide method, and the electromagnetic function strength of the high-entropy oxide ceramic materials was simulated based on the obtained electromagnetic function parameters, so as to obtain the electromagnetic wave absorption bandwidth, as shown in Table 1.

[0123] Table 1

[0124]

[0125] As can be seen from Table 1, when the thickness of the prepared electromagnetic function coating is less than 2 mm, at room temperature and 1000 °C, the coatings prepared from the high-entropy oxide ceramic powders of Examples 1-10 have relatively high absorption intensity for the X-band. Not only is the absorption bandwidth for the X-band above 1.5 GHz at room temperature, but also the absorption bandwidth for the X-band is above 1.0 GHz at 1000 °C. For the coatings prepared from the high-entropy oxide ceramic powders of Comparative Examples 1-3, compared with the electromagnetic function strength at room temperature, the electromagnetic function strength for the X-band decreases sharply at high temperature, even to zero, indicating that the ceramic materials prepared in Examples 1-10 have good high-temperature wave absorption performance.

[0126] From Figure 4 it can be seen that the increase in the content of Mn element can significantly improve the heat resistance of the material, and the TG inflection point does not appear below 1400 °C.

[0127] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high-entropy oxide wave-absorbing ceramic material applied to an electromagnetic wave absorption coating, characterized in that, The ceramic material has a perovskite structure with a molecular structure of ABO3, where ABO3 is La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6 )O3 or La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3 with a TG inflection point temperature > 1400°C. The method includes: (1) Put 20 mol of raw materials into a ball milling tank, and add zirconia grinding balls with diameters of 2 mm, 5 mm, and 12 mm respectively. The mass ratio is 1:1:1, and the ball-to-material ratio is 4:

1. Add anhydrous ethanol while stirring until the powder surface is submerged. Ball mill and mix for 10 h at a rotation speed of 400 r / min; (2) Pour the slurry mixed evenly in step (1) into a 120-mesh sieve to filter out the grinding balls. Pour the remaining slurry into a tray and place it in an oven. Dry it at a temperature of 100 °C for 6 h; (3) Screen the powder dried in step (2) through a 150-mesh sieve to obtain a mixture of powder materials. Put it into a zirconia crucible and sinter it in a high-temperature sintering furnace. The sintering temperature is 1400 °C, the time is 10 h, and the vacuum degree is 10 Pa. Among them, the heating rate is 5 °C / min; (4) Break the sintered ceramic block in step (3) and grind it until there is no obvious blocky powder, then pour it into a ball milling tank. Pour zirconia grinding balls with diameters of 12 mm, 5 mm, and 2 mm into the ball milling tank at a ball-to-material ratio of 6:1, and the mass ratio is 1:1:

1. Crush it for 20 min under the condition that the rotation speed of the ball mill is 350 r / min; Pour the powder into a 120-mesh sieve for sieving to obtain a high-entropy electromagnetic functional oxide ceramic powder material; When the molecular structure ABO3 is La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6 )O3, the raw materials in step (1) are lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, zirconium dioxide, manganese oxide, nickel oxide and cobalt sesquioxide, and the molar percentages are 16 mol%, 34 mol%, 6 mol%, 6 mol%, 11 mol%, 11 mol%, 11 mol%, 5 mol% respectively; When the molecular structure ABO3 is La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3, the raw materials in step (1) are lanthanum sesquioxide, strontium carbonate, chromium sesquioxide, iron sesquioxide, manganese oxide, cobalt sesquioxide, and nickel oxide, and their molar percentages are 17 mol%, 33 mol%, 6 mol%, 5 mol%, 22 mol%, 6 mol%, and 11 mol% respectively.

2. A high-entropy oxide wave-absorbing ceramic material, characterized in that, Prepared by the method described in claim 1, the ceramic material has a perovskite structure with a molecular structure of ABO3, and the ABO3 is La 0.5 Sr 0.5 (Zr 1 / 6 Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 6 )O3 or La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3 with a TG inflection point temperature > 1400 °C.

3. An electromagnetic wave absorbing coating, characterized in that, The electromagnetic wave absorption coating includes the ceramic material described in claim 2.

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