High-entropy oxide wave-absorbing ceramic powder material as well as preparation method and application thereof

Abstract

The invention relates to a high-entropy oxide wave-absorbing ceramic powder material as well as a preparation method and application thereof, belongs to the technical field of electromagnetic wave absorbing materials, and solves the problems of poor high-temperature resistance and oxidation resistance and low absorption efficiency on low-frequency wave bands of an existing electromagnetic wave absorbing material. The high-entropy oxide ceramic material has a perovskite structure, the molecular structure is ABO3, A comprises La and Sr, and B is at least five elements of Cr, Ni, Mn, Fe, Co, Zr, Hf and Ti. According to the invention, the high-entropy oxide is combined with the perovskite structure, the electromagnetic function of the high-entropy oxide ceramic material is accurately regulated and controlled, and effective absorption of low-frequency electromagnetic waves is realized; the material has oxidation resistance and thermal stability under a high-temperature condition, and excellent electromagnetic function strength of the material at a high temperature is maintained. According to the high-entropy oxide ceramic powder material, the range of an electromagnetic wave absorbing material is widened, the environmental adaptability is improved, and higher requirements of development of a communication technology on the electromagnetic wave absorbing material are met.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing ceramic materials, and in particular to a high entropy oxide absorbing ceramic powder material and a preparation method and application thereof. Background Art

[0002] Ideal electromagnetic functional materials should have the following characteristics: light and thin for easy carrying and installation; wide bandwidth coverage to adapt to electromagnetic waves of different frequencies, efficient absorption to reduce reflection and scattering; and high temperature resistance and antioxidant capabilities to maintain performance in extreme environments.

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

[0004] Therefore, there is an urgent need for an electromagnetic wave absorbing material that can be used for a long time in a high-temperature environment. It not only has the electromagnetic function at room temperature, but also has good electromagnetic function strength and wide-band coverage in a high-temperature extreme environment 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, an embodiment of the present invention aims to provide a high entropy oxide absorbing ceramic powder material and a preparation method and application thereof, so as to solve at least one of the problems of existing electromagnetic wave absorbing materials, namely, poor high temperature resistance and oxidation resistance, and low absorption efficiency in low frequency bands.

[0006] In the first aspect, an embodiment of the present invention provides a high entropy oxide absorbing ceramic material, which has a perovskite structure and a molecular structure of ABO3, wherein A includes La and Sr, and B is at least 5 elements of Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti.

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

[0008] Furthermore, the A includes La and Sr, and 1-3 elements among Ba, Y, Gd, and Ce.

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

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

[0011] Furthermore, the ceramic material is a ceramic powder material with a particle size of 120-230 mesh and a 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; Wherein, the raw materials of A are lanthanum trioxide and strontium carbonate; The raw materials of B are oxides of B, which are at least five selected from the group consisting of nickel oxide, manganese dioxide, ferric oxide, cobalt oxide, hafnium dioxide, titanium dioxide, and zirconium dioxide.

[0013] Furthermore, the sintering conditions include: maintaining the temperature at 1295-1405° C. for 10-15 hours under a vacuum degree of 8-20 Pa.

[0014] Furthermore, after the sintering, the process further includes crushing and screening the sintered product, and the mesh number of the sieve for the screening is 120-230 meshes.

[0015] Furthermore, 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 300-400rpm, and the time is 10-15h.

[0016] In a third aspect, an embodiment of the present invention provides an electromagnetic wave absorbing coating, wherein the electromagnetic wave absorbing coating includes the above-mentioned ceramic material.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. The high entropy oxide 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, which distorts the lattice structure of the oxide and generates defects. These distortions and defects not only improve the absorbing efficiency of the material, but also improve the chemical stability and thermal stability of the absorbing material at high temperature, enhance the cycle stability and extend the service life; the high entropy oxide with a perovskite structure has a solid solution phase that is originally not easy to stabilize thermodynamically, inhibits the phase separation and ordering process, and promotes the prepared high entropy oxide to have a uniform and dense microstructure, which is beneficial to the absorption and loss of electromagnetic waves, reduces the penetration depth of electromagnetic waves in the material, and makes the absorbing material thin and light, easy to carry and install; the synergistic effect between the various elements in the high entropy oxide can achieve strong absorption and broadband absorption of electromagnetic waves; by adjusting the types and proportions of A-site and B-site ions, the electromagnetic properties of the perovskite material can be precisely controlled, thereby optimizing its electromagnetic wave absorption performance to meet different application requirements.

[0018] The present invention combines the concept of high entropy with the perovskite structure, accurately regulates the electromagnetic function of high entropy oxide ceramic materials, and realizes effective absorption of low-frequency electromagnetic waves; it has oxidation resistance and thermal stability under high temperature conditions, and maintains the excellent electromagnetic functional strength of the material at high temperature; 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.

[0019] 2. In the molecular structure ABO3 of the high entropy oxide 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, thereby improving the electrical conductivity of the high entropy oxide ceramic material, achieving wide-band coverage to absorb electromagnetic waves of different frequencies, and making it have a complete and stable perovskite structure, further improving the material's absorbing performance and temperature resistance.

[0020] 3. In order to improve the electromagnetic functional strength and high temperature resistance of high entropy oxide ceramics, the present invention further limits the molar ratio of different B elements. 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.

[0021] 4. The particle size of the high entropy oxide absorbing ceramic powder material is controlled to be 120-230 mesh, and the bulk density is 1.0-1.4 g / cm 3 , in order to improve the fluidity of powder in actual thermal spraying applications, reduce the amount of element evaporation loss, and ensure that the powder can be fully melted during the thermal spraying process to prepare electromagnetic functional coatings, thereby improving the coating quality.

[0022] 5. The present invention adopts a solid phase synthesis method to prepare high entropy oxide absorbing ceramic materials. The raw materials are metal oxide powders, which are easy to obtain and low in cost. High-purity high entropy oxide ceramic materials with a perovskite structure can be obtained by directly sintering the metal oxide raw materials. The sintering temperature is 1295-1405°C and the time is 10-15h. 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.

[0023] 6. The method of the present invention adopts wet ball milling to mix the metal oxide powder raw materials. Wet ball milling has good heat dissipation effect, can effectively control the particle size and distribution of materials, and has low energy consumption and low cost, which is conducive to large-scale production of materials.

[0024] 7. The high entropy oxide absorbing ceramic material of the present invention is applied to the electromagnetic wave absorption coating, which not only absorbs electromagnetic waves in a wider frequency band, but also has a higher electromagnetic functional intensity in the lower frequency band (8-12GHz), such as Figure 5 As shown; when the prepared coating thickness is in the range of 1-2mm, not only the absorption bandwidth of the X-band at room temperature is above 1.5GHz, but also the absorption bandwidth of the X-band at 1000℃ is above 1.0GHz, as shown in Table 1. Compared with the prior art, it is more adaptable to new equipment and effectively avoids the detection of electromagnetic waves; at the same time, the perovskite structure of the high entropy oxide ceramic material of the present invention has good temperature resistance. The results of thermogravimetric analysis show that when heated to 1200℃ in an air atmosphere, the quality of the ceramic material remains stable, and it has good thermal stability and antioxidant properties. It still maintains good electromagnetic function at high temperature, stable cycle performance and long service life; in addition, the ceramic material of the present invention has a higher electromagnetic function strength for lower frequency bands (8-12GHz), which can reduce the thickness of the electromagnetic functional coating, realize the lightweight application of the absorbing material in electronic equipment, and is easy to carry and install. It is particularly suitable for equipment such as aircraft with strict weight requirements.

[0025] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components; Figure 1XRD diffraction patterns of high entropy oxide ceramic powder materials prepared in Examples 1 and 4-7; Figure 2 XRD diffraction patterns of high entropy oxide ceramic powder materials prepared in Example 1, Example 10, Comparative Example 1 and Comparative Example 2; FIG3 (a) is a SEM image of the high entropy oxide ceramic powder material prepared in Example 1; FIG3( b ) is an EDS spectrum of the high entropy oxide ceramic powder material prepared in Example 1; 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; Figure 5 This is a curve showing the change of electromagnetic loss at room temperature with frequency for electromagnetic functional coatings of different thicknesses prepared using the high entropy oxide ceramic powder material of Example 1. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0028] Ideal electromagnetic functional materials should have the following characteristics: light and thin for easy carrying and installation; wide bandwidth coverage to adapt to electromagnetic waves of different frequencies, efficient absorption to reduce reflection and scattering; and high temperature resistance and antioxidant capabilities to maintain performance in extreme environments.

[0029] However, existing electromagnetic functional materials are mostly magnetic materials. Although these materials perform well at room temperature, they are prone to lose their magnetism in high-temperature environments, resulting in a significant reduction in the electromagnetic function effect. On the other hand, although absorbing materials based on dielectric absorbing materials have the advantage of being able to be used at high temperatures, their electromagnetic function strength and bandwidth are often unsatisfactory.

[0030] Therefore, the present invention provides a high entropy oxide absorbing ceramic material, which has a perovskite structure and a molecular structure of ABO3, wherein A includes La and Sr, and B is at least five elements selected from Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti. According to a preferred embodiment of the present invention, La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) The XRD diffraction spectrum, SEM image and EDS spectrum of O3 powder are shown as follows: Figure 1 , as shown in Figure 3(a) and Figure 3(b).

[0031] On the one hand, the high entropy oxide has unique physical and chemical properties: high mixing entropy effect, hysteresis diffusion effect, lattice distortion effect and "cocktail" effect.

[0032] Specifically, the various elements in high-entropy oxides have different atomic sizes and are randomly distributed, which distorts the lattice structure of the oxide and generates defects. These distortions and defects can increase the number of scattering and reflections of electromagnetic waves inside the material, thereby extending the propagation path of electromagnetic waves in the material and improving the absorption efficiency. In addition, these distortions and defects also cause the material to have an atomic hysteresis diffusion effect, which increases the resistance of atomic diffusion when the material is subjected to changes in the external environment (such as temperature changes), which not only improves the chemical stability and thermal stability of the absorbing material at high temperatures, but also improves the material's cycle stability and extends its service life.

[0033] Specifically, high mixing entropy can stabilize solid solution phases that are originally difficult to form thermodynamically, inhibit phase separation and ordering processes, and promote the obtained high-entropy oxide to have a uniform and dense microstructure. The uniformity makes the electromagnetic properties throughout the interior consistent, avoiding the enhancement of electromagnetic wave reflection and scattering due to 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 areas of the material, making the absorbing material thinner and lighter, and easier to carry and install.

[0034] Specifically, the synergistic effect between the various elements in the high entropy oxide can significantly enhance the wave absorption performance of the material. Different elements have different corresponding characteristics to electromagnetic waves. Through reasonable element combination and ratio, strong absorption and broadband absorption of electromagnetic waves can be achieved.

[0035] 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 the advantages of adjustable elements, unique electronic conductivity, and adjustable concentration of oxygen vacancies, so that the high entropy oxide has good thermodynamic stability and high tolerance to the constituent elements, so that the ions at the A and B positions can be replaced individually or in combination by ions with different valences and radii within a fairly wide concentration range to form a solid solution; by adjusting the types and proportions of ions at the A and B positions, the electromagnetic properties of the perovskite material can be precisely controlled, thereby optimizing its electromagnetic wave absorption performance and meeting different application requirements.

[0036] The present invention combines the concept of high entropy with the perovskite structure, which not only realizes the precise regulation of the electromagnetic function of the high entropy oxide ceramic material and maintains the electromagnetic function strength of the material at high temperature, but also broadens the range of materials used for electromagnetic wave absorption.

[0037] Furthermore, the molecular structure of the high entropy oxide ceramic material provided by the present invention is ABO3, and the molar ratio of the two elements La and Sr as A is 3:7-7:3, which improves the electrical conductivity of the high entropy oxide ceramic material, achieves wide-band coverage to absorb electromagnetic waves of different frequencies, and makes it have a structurally complete and stable perovskite structure, further improving the material's wave absorption performance and temperature resistance.

[0038] According to some preferred embodiments of the present invention, the molar ratio of the two elements La and Sr as A is 3:7, 4:6, 5:5, 6:4 or 7:3 respectively.

[0039] Further, the A includes La and Sr, and 1-3 elements among Ba, Y, Gd, and Ce. Among the elements of A, except 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 in a molar ratio of 2:2:1, or La, Sr, and Ba in a molar ratio of 2:2:1, or La, Sr, Ba, and Ce in a molar ratio of 4:4:1:1.

[0040] Furthermore, the present invention further limits the molar ratio of different B elements in order to improve the electromagnetic functional strength and high temperature resistance of the high entropy oxide ceramic.

[0041] According to some preferred embodiments of the present invention, the B element is Fe, Co, Ni, Cr and Mn in a molar ratio of 1:1:1:1:1 or 1:1:1:1:2; or the B element is Zr, Hf, Ti, Fe and Cr in a molar ratio of 1:1:1:1:1; or the B element is Zr, Fe, Co, Ni, Cr and Mn in a molar ratio of 1:1:1:1:1:1.

[0042] The present invention controls the particle size of the high entropy oxide ceramic powder material to 120-230 meshes and the bulk density to 1.0-1.4 g / cm 3 , in order to improve the fluidity of powder in actual thermal spraying applications, reduce the amount of element evaporation loss, and ensure that the powder can be fully melted during the thermal spraying process to prepare electromagnetic functional coatings, thereby improving the coating quality.

[0043] Specifically, calculated according to molar percentage (mol%), the elements constituting the high entropy oxide absorbing 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, wherein A includes La and Sr, and B contains at least 5 transition metal elements.

[0044] According to a preferred embodiment of the present invention, the high entropy oxide absorbing 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、La 0.5 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 G 0.2 (Fe 0.2 Co0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3.

[0045] The present invention provides a method for preparing a high entropy oxide ceramic powder material, the method comprising: sintering the mixed raw materials; Wherein, the raw materials of A are lanthanum trioxide and strontium carbonate; The raw materials of B are oxides of B, which are at least five selected from the group consisting of nickel oxide, manganese dioxide, ferric oxide, cobalt oxide, hafnium dioxide, titanium dioxide, and zirconium dioxide.

[0046] Specifically, calculated according to molar percentage, the raw material ratio is as follows: 0 mol% to 7 mol% chromium oxide, 0 mol% to 15 mol% nickel oxide, 0 mol% to 22 mol% manganese dioxide, 0 mol% to 7 mol% iron oxide, 0 mol% to 7 mol% cobalt 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, and 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.

[0047] According to a preferred embodiment of the present invention, the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide, and nickel oxide are 17mol%, 34mol%, 7mol%, 7mol%, 14mol%, 7mol%, 14mol%, or 26mol%, 23mol%, 7mol%, 7mol%, 15mol%, 7mol%, 15mol%, or 9mol%, 45mol%, 7mol%, 7mol%, 13mol%, 6mol%, 13mol%, or 20mol%, 30mol%, 7mol%, 7mol%, 15mol%, 7mol%, 14mol%, or 13mol%, 40mol%, 7mol%, 7mol%, 13mol%, 7mol%, 13mol%, or 17mol%, 33mol%, 6mol%, 5mol%. The molar percentages of lanthanum trioxide, strontium carbonate, gadolinium trioxide, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide and nickel oxide are 14mol%, 26mol%, 13mol%, 7mol%, 6mol%, 13mol%, 7mol%, 14mol%; the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, zirconium dioxide, manganese oxide, cobalt trioxide and nickel oxide are 16mol%, 34mol%, 6mol%, 6mol%, 11mol%, 5mol%, 11mol%, 11mol%; the molar ratios of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, zirconium dioxide, hafnium dioxide and titanium dioxide are 16mol%, 33mol%, 6mol%, 6mol%, 13mol%, 13mol%, 13mol%.

[0048] The present invention adopts a solid phase synthesis method to prepare a high entropy oxide ceramic material. The raw material adopts metal oxide powder, which is easy to obtain and has low cost. The high-purity high entropy oxide ceramic material with a perovskite structure can be obtained by directly sintering the metal oxide raw material. The sintering temperature is 1295-1405°C and the time is 10-15h. 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.

[0049] 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 effect, can effectively control the particle size and distribution of materials, and has low energy consumption and low cost, which is conducive to large-scale production of materials.

[0050] Specifically, the conditions for wet ball milling include: the mixed medium is anhydrous ethanol, the ball material is zirconium balls, and 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.

[0051] Furthermore, the liquid surface of the anhydrous ethanol should immerse the zirconium ball.

[0052] Furthermore, the slurry obtained after the wet ball milling is filtered, the grinding balls are filtered out, and the remaining slurry after the filtration is dried.

[0053] Specifically, the tray containing the remaining slurry is placed in an oven for drying at a temperature of 80-110° C. for 10 hours.

[0054] Furthermore, in order to ensure that the mixed raw materials are heated evenly during the subsequent sintering process and to improve the product yield and quality, it is necessary to control the particle size of the mixed raw materials.

[0055] Specifically, the dried mixed raw material is sieved, and the mesh number of the sieve is 120-230 meshes.

[0056] Furthermore, in order to control the degree of solid phase synthesis reaction and the purity of the perovskite phase of the high entropy oxide ceramic, the sintering conditions include: in an argon atmosphere, at a temperature of 1295-1405°C, maintaining for 10-15 hours, preferably at a temperature of 1395-1400°C, maintaining for 10 hours.

[0057] 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.

[0058] Furthermore, in order to improve the electromagnetic wave absorption efficiency and high temperature resistance of the material, the product obtained by high temperature sintering needs to be crushed and screened to obtain a high entropy oxide ceramic material with a target size.

[0059] Specifically, the crude product after high-temperature sintering is broken into pieces, fully ground until there is no obvious block powder, and then poured into a ball mill for ball milling; the ball-to-material ratio in the ball milling crushing process is (5-7):1, and the ball stone material is zirconium oxide. 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 2mm, 5mm and 12mm respectively. In the ball milling crushing process of the product, the mass ratio of grinding balls with different diameters is 1:1:1, the rotation speed is 300-400r / min, and the time is 3-5min.

[0060] Specifically, the crushed product is sieved, and the mesh number of the sieve is 120-230 meshes.

[0061] Specifically, the bulk density of the ceramic powder material prepared by the method of the present invention is 1.0-1.4 g / cm 3 .

[0062] The present invention also provides an application of a high entropy oxide ceramic material in an electromagnetic wave absorption coating, wherein the frequency of the electromagnetic wave is 8-18 GHz, the thickness of the electromagnetic wave absorption coating is 1-2 mm, and the operating temperature is as high as 1200-1350° C., or even higher.

[0063] The high entropy oxide ceramic material of the present invention is applied to the electromagnetic wave absorption coating, which not only realizes the absorption of electromagnetic waves in a wider frequency band, but also has a higher electromagnetic functional strength in the lower frequency band (8-12GHz). Compared with the prior art, it can better adapt to new equipment and effectively avoid the detection of electromagnetic waves. At the same time, the perovskite structure of the high entropy oxide ceramic material of the present invention has good temperature resistance. The results of thermogravimetric analysis show that when heated to 1200°C in an air atmosphere, the quality of the ceramic material remains stable, and it has good thermal stability and antioxidant properties. It still maintains good electromagnetic function at high temperature, stable cycle performance, and long service life. In addition, the ceramic material of the present invention has a higher electromagnetic functional strength in the lower frequency band (8-12GHz), which can reduce the manufacturing thickness of the electromagnetic functional coating, realize the lightweight application of the absorbing material in electronic equipment, and is easy to carry and install. It is particularly suitable for equipment such as aircraft with strict weight requirements.

[0064] The technical solution of the present invention is further explained below in conjunction with specific embodiments.

[0065] The raw materials used in the present invention are all commercially available products in powder form with a particle size range of 100-800nm ​​and a purity of 99.99%.

[0066] Example 1 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 preparation method, comprising: (1) Weigh 20 mol of 17 mol% lanthanum trioxide, 34 mol% strontium carbonate, 7 mol% chromium trioxide, 7 mol% iron trioxide, 14 mol% manganese oxide, 7 mol% cobalt trioxide, and 14 mol% nickel oxide, and put them into a ball mill. Add zirconium oxide 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; add anhydrous ethanol while stirring until the powder surface is submerged; and mix by ball milling at a speed of 400 r / min for 10 h; (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, put it into an oven, and dry it at 100°C for 6 hours; (3) The powder dried in step (2) is sieved through a 150-mesh screen to obtain a mixed powder, which is placed in a zirconia crucible and sintered in a high-temperature sintering furnace at a temperature of 1400°C for 10 hours and a vacuum degree of 10 Pa, wherein the heating rate is 5°C / min; (4) The ceramic block sintered in step (3) is broken into pieces and ground until there is no obvious blocky powder. The pieces are then poured into a ball mill. Zirconia grinding balls with diameters of 12 mm, 5 mm, and 2 mm are added at a ball-to-material ratio of 6:1 and a mass ratio of 1:1:1. The balls are crushed at a speed of 350 r / min for 20 min. The powder is poured into 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 ) 3。

[0067] To La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was tested by XRD, SEM, EDS, TG and electromagnetic functional parameters. The results are as follows 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 body are evenly distributed, and the product purity is high; when heated to about 1250°C in an air atmosphere, a mass surge inflection point appears, indicating that the ceramic material has good thermal stability and oxidation resistance; in the 8-18GHz wave frequency range, it has good electromagnetic loss, especially in the low frequency band (8-12GHz), when the prepared coating thickness is less than 2mm, it has a wide electromagnetic wave absorption bandwidth at room temperature and 1000°C.

[0068] Example 2 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 the same preparation method as in Example 1, except that the raw materials manganese oxide, cobalt oxide and nickel oxide in step (1) of Example 1 are replaced by zirconium dioxide, hafnium dioxide and titanium dioxide, and the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, zirconium dioxide, hafnium dioxide and titanium dioxide are 16 mol%, 33 mol%, 6 mol%, 6 mol%, 13 mol%, 13 mol% and 13 mol%, respectively.

[0069] To 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 test, and the results are shown in Table 1. The ceramic powder prepared in Example 2 has good thermal stability and oxidation resistance.

[0070] Example 3 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)O3 is prepared by the same method as in Example 1, except that the raw materials and their amounts in step (1) of Example 1 are changed to: the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, iron trioxide, zirconium dioxide, manganese oxide, nickel oxide and cobalt trioxide are 16 mol%, 34 mol%, 6 mol%, 6 mol%, 11 mol%, 11 mol%, 11 mol% and 5 mol%, respectively.

[0071] To 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 was 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.

[0072] Example 4 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 trioxide, strontium carbonate, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide, 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.

[0073] To La 0.7 Sr 0.3 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 1 As shown in Table 1, the ceramic powder obtained in Example 4 has a single-phase perovskite structure, a high product purity, and good thermal stability and oxidation resistance.

[0074] Example 5 High entropy oxide ceramic powder La 0.3 Sr 0.7 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn0.2 )O3 is prepared by 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 9 mol%, 45 mol%, 7 mol%, 7 mol%, 13 mol%, 6 mol%, and 13 mol%, respectively.

[0075] To La 0.3 Sr 0.7 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 1 As shown in Table 1, the ceramic powder obtained in Example 5 has a single-phase perovskite structure, a high product purity, and good thermal stability and oxidation resistance.

[0076] Example 6 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 prepared by 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 20 mol%, 30 mol%, 7 mol%, 7 mol%, 15 mol%, 7 mol%, and 14 mol%, respectively.

[0077] To La 0.6 Sr 0.4 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 1 As shown in Table 1, the ceramic powder obtained in Example 6 has a dual-phase perovskite structure, a high product purity, and good thermal stability and oxidation resistance.

[0078] Example 7 High entropy oxide ceramic powder La 0.4 Sr 0.6 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2Mn 0.2 )O3 is prepared by 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.

[0079] To La 0.4 Sr 0.6 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 1 As shown in Table 1, the ceramic powder obtained in Example 7 has a dual-phase perovskite structure, a high product purity, and good thermal stability and oxidation resistance.

[0080] Example 8 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 is prepared by 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.

[0081] To La 0.5 Sr 0.5 (Fe 1 / 6 Co 1 / 6 Ni 1 / 6 Cr 1 / 6 Mn 1 / 3 )O3 ceramic powder was subjected to TG test, and the results are as follows Figure 4 As shown in Table 1, the ceramic powder obtained in Example 8 has good thermal stability and oxidation resistance.

[0082] Example 9 High entropy oxide ceramic powder La 0.4 Sr 0.4 G 0.2 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2Mn 0.2 )O3 is prepared by the same method as in Example 1, except that the molar percentages of lanthanum trioxide, strontium carbonate, gadolinium trioxide, chromium trioxide, iron trioxide, manganese oxide, cobalt trioxide, and nickel oxide are 14 mol%, 26 mol%, 13 mol%, 7 mol%, 6 mol%, 13 mol%, 7 mol%, and 14 mol%, respectively.

[0083] To La 0.4 Sr 0.4 G 0.2 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to TG test, and the results are shown in Table 1. The ceramic powder obtained in Example 9 has good thermal stability and oxidation resistance.

[0084] Example 10 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 prepared by the same method as in Example 1, except that the sintering temperature in step (1) of Example 1 is set to 1300°C.

[0085] Example 10: La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are shown in Table 1. The ceramic powder obtained in Example 10 has a single-phase perovskite structure, the product has high purity, and has good thermal stability and oxidation resistance.

[0086] Comparative Example 1 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 prepared by the same method as in Example 1, except that the sintering temperature in step (1) of Example 1 is set to 1150°C.

[0087] Comparative Example 1 obtained La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 2 As shown in Table 1, the ceramic powder obtained in Comparative Example 1 has a perovskite structure, but has a high impurity content and low product purity.

[0088] Comparative Example 2 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 prepared by the same method as in Example 1, except that the sintering temperature in step (1) of Example 1 is set to 1200°C.

[0089] Comparative Example 2 prepared La 0.5 Sr 0.5 (Fe 0.2 Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 )O3 ceramic powder was subjected to XRD and TG tests, and the results are as follows Figure 2 As shown in Table 1, the ceramic powder obtained in Comparative Example 2 has a perovskite structure, but has a high impurity content and low product purity.

[0090] Comparative Example 3 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 )O3 is prepared by 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 are 36 mol%, 8 mol%, 8 mol%, 8 mol%, 16 mol%, 8 mol%, and 16 mol%, respectively.

[0091] Comparative Example 3 prepared La 0.9 Sr 0.1 (Fe 0.2 Co 0.2 Ni 0.2 Cr0.2 Mn 0.2 )O3 ceramic powder was subjected to TG test, and the results are shown in Table 1.

[0092] Application Examples After the high entropy oxide ceramic powders prepared in Examples 1-10 and Comparative Examples 1-3 were mixed with wave-transmitting materials respectively, electromagnetic wave absorption coatings of different thicknesses were prepared by high-energy plasma spraying, and the electromagnetic functional parameters of the coatings at room temperature and 1000°C were determined by a waveguide method. The electromagnetic functional intensity of the high entropy oxide ceramic material was simulated based on the obtained electromagnetic functional parameters to obtain the electromagnetic wave absorption bandwidth, as shown in Table 1.

[0093] Table 1

[0094] It can be seen from Table 1 that when the thickness of the prepared electromagnetic functional coating is less than 2 mm, the coating prepared using the high entropy oxide ceramic powder of Examples 1-10 has a high absorption intensity for the X-band at room temperature and 1000°C, not only the absorption bandwidth for the X-band at room temperature is above 1.5 GHz, but also the absorption bandwidth for the X-band at 1000°C is above 1.0 GHz; while the coating prepared using the high entropy oxide ceramic powder of Comparative Examples 1-3, compared with the electromagnetic functional intensity at room temperature, has a sudden decrease in the electromagnetic functional intensity for the X-band at high temperature, or even zero, indicating that the ceramic material prepared in Examples 1-10 has good high-temperature absorbing performance.

[0095] from Figure 4 It can be seen that increasing the content of Mn element can significantly improve the heat resistance of the material, and the TG inflection point does not appear below 1400℃.

[0096] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high entropy oxide absorbing ceramic material, characterized in that: The ceramic material has a perovskite structure, and the molecular structure is ABO3, wherein A includes La and Sr, and B is at least five elements of Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti.

2. The ceramic material according to claim 1, characterized in that In the molecular structure ABO3, the molar ratio of La to Sr is 3:7-7:

3.

3. The ceramic material according to claim 1, characterized in that The A includes La and Sr, and 1 to 3 elements among Ba, Y, Gd, and Ce.

4. The ceramic material according to claim 1, characterized in that In the molecular structure ABO3, B is Fe, Co, Ni, Cr and Mn.

5. The ceramic material according to claim 4, characterized in that The molar ratio of Fe, Co, Ni, Cr and Mn is 1:1:1:1:1 or 1:1:1:1:

2.

6. The ceramic material according to claim 1, characterized in that The ceramic material is a ceramic powder material with a particle size of 120-230 meshes and a loose density of 1.0-1.4 g / cm 3 .

7. A method for preparing the ceramic material according to any one of claims 1 to 6, characterized in that: The method comprises: sintering the mixed raw materials; Wherein, the raw materials of A are lanthanum trioxide and strontium carbonate; The raw materials of B are oxides of B, which are at least five selected from the group consisting of nickel oxide, manganese dioxide, ferric oxide, cobalt oxide, hafnium dioxide, titanium dioxide, and zirconium dioxide.

8. The method according to claim 7, characterized in that The sintering conditions include: maintaining the temperature at 1295-1405° C. for 10-15 hours under a vacuum degree of 8-20 Pa; And / or, after the sintering, the method further comprises the steps of crushing and screening the sintered product, and the mesh number of the sieve for the screening is 120-230 meshes.

9. The method according to claim 7, characterized in that: 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 300-400rpm, and the time is 10-15h.

10. An electromagnetic wave absorbing coating, characterized in that: The electromagnetic wave absorbing coating comprises the ceramic material according to any one of claims 1 to 6 or the ceramic material obtained by the method according to any one of claims 7 to 9.

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