CN119528572A - A high entropy oxide microwave absorbing ceramic powder material and its preparation method and application - Google Patents
A high entropy oxide microwave absorbing ceramic powder material and its preparation method and application Download PDFInfo
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Abstract
本发明涉及一种高熵氧化物吸波陶瓷粉体材料及其制备方法和应用，属于电磁波吸收材料技术领域，解决了现有电磁波吸收材料的耐高温性和抗氧化性差、对低频波段的吸收效率低的问题。所述高熵氧化物陶瓷材料具有钙钛矿结构，分子结构为ABO3，A包括La和Sr，B为Cr、Ni、Mn、Fe、Co、Zr、Hf、Ti中的至少5种元素。本发明将高熵氧化物与钙钛矿结构相结合，精准调控高熵氧化物陶瓷材料的电磁功能，实现对低频电磁波的有效吸收；具有高温条件下的抗氧化性及热稳定性，并保持材料在高温下优异的电磁功能强度。本发明高熵氧化物陶瓷粉体材料拓宽了电磁波吸收材料的范围，提高环境适应性，满足通讯技术的发展对电磁波吸收材料提出的更高要求。
The present invention relates to a high entropy oxide absorbing ceramic powder material and a preparation method and application thereof, belonging to the technical field of electromagnetic wave absorbing materials, and solving the problems of poor high temperature resistance and oxidation resistance of existing electromagnetic wave absorbing materials and low absorption efficiency in low frequency bands. The high entropy oxide ceramic material has a perovskite structure, and the molecular structure is ABO 3 , A includes La and Sr, and B is at least 5 elements of Cr, Ni, Mn, Fe, Co, Zr, Hf, and Ti. The present invention combines high entropy oxide with perovskite structure, accurately controls 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 function strength of the material at high temperature. The high entropy oxide ceramic powder material of the present invention broadens the scope of electromagnetic wave absorbing materials, improves environmental adaptability, and meets the higher requirements of electromagnetic wave absorbing materials put forward by the development of communication technology.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorbing ceramic materials, in particular to a high-entropy oxide wave absorbing ceramic powder material, a preparation method and application thereof.
Background
The ideal electromagnetic functional material should have the characteristics of light weight, portability and installation, broadband coverage to accommodate electromagnetic waves of different frequencies, efficient absorption to reduce reflection and scattering, and high temperature and oxidation resistance that can maintain performance in extreme environments.
However, the existing electromagnetic functional materials are mainly magnetic materials, which are good at normal temperature, but are easy to lose magnetism in a high-temperature environment, so that the electromagnetic functional effect is greatly reduced, on the other hand, the dielectric wave absorbing material is mainly used as a wave absorbing material, which has the advantage of being capable of being used at high temperature, but the electromagnetic functional strength and the frequency bandwidth are often unsatisfactory, and the thickness of an electromagnetic functional coating actually applied to electronic equipment is required to be below 2mm by taking the coating as an example, and according to the quarter-wavelength theory, the electromagnetic functional coating can show ideal electromagnetic functional strength at high frequency (Ku wave band) and can not show ideal electromagnetic functional strength at relatively low frequency (such as X wave band) due to the limitation of the thickness of the coating.
Therefore, there is an urgent need for an electromagnetic wave absorbing material suitable for a long time in a high temperature environment, which not only has an electromagnetic function at normal temperature, but also has good electromagnetic function strength and broadband coverage in a high temperature extreme environment, so as to meet the higher requirements of development of communication technology on the electromagnetic wave absorbing material.
Disclosure of Invention
In view of the above analysis, the embodiment of the invention aims to provide a high-entropy oxide wave-absorbing ceramic powder material, and a preparation method and application thereof, which are used for solving at least one of the problems of poor high temperature resistance and oxidation resistance and low absorption efficiency to a low-frequency band of the existing electromagnetic wave absorbing material.
In a first aspect, an embodiment of the present invention provides a high-entropy oxide wave-absorbing ceramic material, where the ceramic material has a perovskite structure and a molecular structure of ABO 3, where a includes La and Sr, and B is at least 5 elements in Cr, ni, mn, fe, co, zr, hf, ti.
Further, in the molecular structure ABO 3, the molar ratio of La to Sr is 3:7-7:3.
Further, the A comprises La and Sr, and 1-3 elements in Ba, Y, gd, ce.
Further, in the molecular structure ABO 3, the B is Fe, co, ni, cr and Mn.
Further, the molar ratio of Fe, co, ni, cr, mn is 1:1:1:1:1 or 1:1:1:1:2.
Further, the ceramic material is ceramic powder material, the grain diameter is 120-230 meshes, and the apparent density is 1.0-1.4g/cm 3.
In a second aspect, embodiments of the present invention provide a method of preparing the above ceramic material, the method comprising sintering the mixed raw materials;
Wherein the raw materials of A are lanthanum oxide and strontium carbonate;
the raw material of the B is oxide of the B, and is at least 5 selected from nickel oxide, manganese dioxide, ferric oxide, cobaltic oxide, hafnium oxide, titanium dioxide and zirconium dioxide.
Further, the sintering condition comprises maintaining at a temperature of 1295-1405 ℃ for 10-15 hours under a vacuum degree of 8-20 Pa.
Further, the sintering process further comprises the steps of crushing and screening the sintered product, wherein the number of the screening meshes is 120-230 meshes.
Further, the mixing method is wet ball milling, and specific conditions include anhydrous ethanol as medium, ball-to-material ratio of (2-4): 1, rotation speed of 300-400rpm and time of 10-15h.
In a third aspect, embodiments of the present invention provide an electromagnetic wave absorbing coating comprising the above ceramic material.
Compared with the prior art, the invention has at least one of the following beneficial effects:
1. The high-entropy oxide wave-absorbing ceramic material provided by the invention has a perovskite structure, a plurality of elements in the high-entropy oxide have atomic size difference and are randomly distributed, so that the lattice structure of the oxide is distorted and generates defects, the distortion and defects not only improve the wave-absorbing efficiency of the material, but also improve the chemical stability and thermal stability of the wave-absorbing material at high temperature, enhance the circulation stability and prolong the service life, the high-entropy oxide with the perovskite structure has a solid solution phase which is not easily stabilized in thermodynamics, inhibits the phase separation and ordering process, promotes the prepared high-entropy oxide to have a uniform and compact microstructure, is favorable for the absorption and loss of electromagnetic waves, reduces the penetration depth of the electromagnetic waves in the material, enables the wave-absorbing material to tend to be light and thin, is convenient to carry and install, can realize the strong absorption and broadband absorption of the electromagnetic waves, and can realize the accurate regulation and control of the electromagnetic property of the perovskite material by adjusting the types and the proportions of A-site and B-site ions, thereby optimizing the electromagnetic wave-absorbing performance of the perovskite material and meeting different application requirements.
The high-entropy oxide ceramic powder material combines the high-entropy concept with the perovskite structure, accurately regulates and controls the electromagnetic function of the high-entropy oxide ceramic material, realizes effective absorption of low-frequency electromagnetic waves, has oxidation resistance and thermal stability under high temperature conditions, maintains excellent electromagnetic function strength of the material at high temperature, widens the range of the electromagnetic wave absorbing material, improves the environmental adaptability, and meets the higher requirements of development of communication technology on the electromagnetic wave absorbing material.
2. In the molecular structure ABO 3 of the high-entropy oxide wave-absorbing ceramic material provided by the invention, the molar ratio of La to Sr serving as A is controlled to be 3:7-7:3, so that the conductivity of the high-entropy oxide ceramic material is improved, broadband coverage is realized to absorb electromagnetic waves with different frequencies, and the high-entropy oxide wave-absorbing ceramic material has a perovskite structure with complete and stable structure, and the wave-absorbing performance and the temperature resistance of the material are further improved.
3. In order to improve the electromagnetic functional strength and the high temperature resistance of the high-entropy oxide ceramic, the invention further defines the molar ratio of different B elements, and according to some preferred embodiments of the invention, when B is Fe, co, ni, cr and Mn, the molar ratio of each element is 1:1:1:1:1:1 or 1:1:1:1:2.
4. The particle size of the high-entropy oxide wave-absorbing ceramic powder material is controlled to be 120-230 meshes, and the apparent density is 1.0-1.4g/cm 3, so that the fluidity of powder in practical thermal spraying application is improved, the element evaporation loss is reduced, the powder can be fully melted in the process of preparing an electromagnetic functional coating by thermal spraying, and the coating quality is improved.
5. The high-entropy oxide wave-absorbing ceramic material is prepared by adopting a solid-phase synthesis method, adopts metal oxide powder as raw materials, is easy to obtain and low in cost, can be prepared by directly sintering the metal oxide raw materials, has a perovskite structure, is safe and environment-friendly, does not need extremely toxic solvents in the preparation process, has a short preparation period, and is expected to be produced in a large scale, wherein the sintering temperature is 1295-1405 ℃ and the sintering time is 10-15 h.
6. The method mixes the metal oxide powder raw materials by adopting a wet ball milling method, has good heat dissipation effect, can effectively control the granularity and the distribution of the materials, has low energy consumption and low cost, and is beneficial to the mass production of the materials.
7. The high-entropy oxide wave-absorbing ceramic material is applied to an electromagnetic wave adsorption coating, realizes electromagnetic wave absorption in a wider wave frequency band, has higher electromagnetic functional strength in a lower frequency band (8-12 GHz), as shown in figure 5, has an absorption bandwidth of more than 1.5GHz for an X wave band at room temperature and an absorption bandwidth of more than 1.0GHz for the X wave band at 1000 ℃ when the prepared coating thickness is in a range of 1-2mm, is more suitable for novel equipment to effectively avoid detection of electromagnetic waves, has high temperature resistance in a perovskite structure, has better heat stability and oxidation resistance when being heated to 1200 ℃ in an air atmosphere, has higher electromagnetic function and long cycle performance stability when being heated to high temperature, has higher functional strength for the lower frequency band (8-12 GHz), can be used for manufacturing lightweight flight equipment, has the electromagnetic wave-absorbing function, is more suitable for being used for manufacturing lightweight flight equipment, has the requirements of the electromagnetic wave-absorbing function, is more convenient to install, and the weight is more limited by the requirements of the electromagnetic wave-absorbing ceramic material.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to designate like parts throughout the drawings;
FIG. 1 is an XRD diffraction pattern of the high entropy oxide ceramic powder materials prepared in examples 1 and 4-7;
FIG. 2 is an XRD diffraction pattern of the high entropy oxide ceramic powder materials prepared in example 1, example 10, comparative example 1 and comparative example 2;
FIG. 3 (a) is an SEM image of the high entropy oxide ceramic powder material prepared in example 1;
FIG. 3 (b) is an EDS spectrum of the high entropy oxide ceramic powder material prepared in example 1;
FIG. 4 is a graph showing TG measurement at a temperature increase rate of 10℃per minute of the high-entropy oxide ceramic powder materials prepared in example 1 and example 8;
Fig. 5 is a plot of electromagnetic loss versus frequency at room temperature for various thicknesses of electromagnetic functional coatings prepared using the high entropy oxide ceramic powder material of example 1.
Detailed Description
The following detailed description of preferred embodiments of the invention is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the invention, are used to explain the principles of the invention and are not intended to limit the scope of the invention.
The ideal electromagnetic functional material should have the characteristics of light weight, portability and installation, broadband coverage to accommodate electromagnetic waves of different frequencies, efficient absorption to reduce reflection and scattering, and high temperature and oxidation resistance that can maintain performance in extreme environments.
However, the conventional electromagnetic functional materials are mainly magnetic materials, which are excellent in normal temperature performance but tend to lose magnetism in a high temperature environment, so that the electromagnetic functional effect is greatly impaired, while the dielectric wave absorbing materials are mainly used at high temperature, but the electromagnetic functional strength and the frequency bandwidth are often unsatisfactory.
Therefore, the invention provides a high-entropy oxide wave-absorbing ceramic material, which has a perovskite structure and a molecular structure of ABO 3, wherein A comprises La and Sr, and B is at least 5 elements in Cr, ni, mn, fe, co, zr, hf, ti. According to a preferred embodiment of the present invention, XRD diffractograms, SEM images and EDS energy spectra of La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 powder are shown in fig. 1, fig. 3 (a), fig. 3 (b), respectively.
In one aspect, the high entropy oxide has unique physicochemical properties such as high mixed entropy, delayed diffusion, lattice distortion, and "cocktail" effects.
Specifically, the multiple elements in the high-entropy oxide have atomic size difference and are randomly distributed, so that the lattice structure of the oxide is distorted and defects are generated, and the distortion and defects can increase the scattering and reflection times of electromagnetic waves in the material, thereby prolonging the propagation path of the electromagnetic waves in the material and improving the wave absorbing efficiency. In addition, the distortion and the defects also cause the material to have an atomic retardation diffusion effect, so that the resistance of atomic diffusion when the material is subjected to external environment changes (such as temperature changes) is improved, the chemical stability and the thermal stability of the wave-absorbing material at high temperature are improved, the cycle stability of the material is improved, and the service life of the material is prolonged.
Specifically, the high mixing entropy can stabilize a solid solution phase which is not easy to form in thermodynamics, inhibit phase separation and ordering processes, promote the prepared high entropy oxide to have a uniform and compact microstructure, ensure that electromagnetic properties of all parts in the high entropy oxide are consistent, avoid enhancement of electromagnetic wave reflection and scattering caused by nonuniform electromagnetic properties, and are beneficial to absorption and loss of electromagnetic waves.
Specifically, the synergistic effect among multiple elements in the high-entropy oxide can obviously enhance the wave absorbing performance of the material, and the corresponding characteristics of different elements on electromagnetic waves are different, so that the strong absorption and broadband absorption of the electromagnetic waves are realized through reasonable element combination and proportioning.
On the other hand, the high-entropy oxide ceramic material provided by the invention has a perovskite structure, and the perovskite structure (ABO 3) of the high-entropy oxide has the advantages of adjustable elements, unique electronic conductivity, adjustable concentration of oxygen vacancies and the like, so that the high-entropy oxide has good thermodynamic stability and high tolerance to constituent elements, ions on A site and B site can be independently or compositely replaced by ions with different electricity valence and radius in a quite wide concentration range to form a solid solution, and the electromagnetic property of the perovskite material can be accurately regulated and controlled by adjusting the types and the proportion of the ions on A site and B site, thereby optimizing the electromagnetic wave absorption performance of the perovskite material and meeting different application requirements.
The invention combines the high entropy concept with the perovskite structure, not only realizes the accurate regulation and control of the electromagnetic function of the high entropy oxide ceramic material, but also maintains the electromagnetic function strength of the material at high temperature, and widens the material range applied to electromagnetic wave absorption.
Further, the molecular structure of the high-entropy oxide ceramic material provided by the invention is ABO 3, the molar ratio of La to Sr serving as A is 3:7-7:3, the conductivity of the high-entropy oxide ceramic material is improved, broadband coverage is realized to absorb electromagnetic waves with different frequencies, the high-entropy oxide ceramic material has a perovskite structure with complete and stable structure, and the wave absorbing performance and the temperature resistance of the material are further improved.
According to some preferred embodiments of the 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.
Further, the A comprises La and Sr, and 1-3 elements in Ba, Y, gd, ce. Among the elements as a, the content of other elements other than La and Sr is 20mol% or less of the total amount of a elements, and if the content of other elements is too high, the conductivity of the ceramic material is affected, thereby affecting the electromagnetic functionality thereof. Illustratively, 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.
Furthermore, the invention further defines the molar ratio of different B elements for the electromagnetic functional strength and the high temperature resistance of the high-entropy oxide ceramic.
According to some preferred embodiments of the invention, the B element is Fe, co, ni, cr and Mn in a molar ratio of 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 1:1:1:1:1:1, or the B element is Zr, fe, co, ni, cr and Mn in a molar ratio of 1:1:1:1:1:1.
The particle size of the high-entropy oxide ceramic powder material is controlled to be 120-230 meshes, and the loose packing density is 1.0-1.4g/cm 3, so that the fluidity of powder in practical thermal spraying application is improved, the element evaporation loss is reduced, the powder can be fully melted in the process of preparing an electromagnetic functional coating by thermal spraying, and the coating quality is improved.
Specifically, elements constituting the high-entropy oxide wave-absorbing ceramic material ABO 3 comprise, calculated according to mole percent (mol%), 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 comprises La and Sr, and B contains at least 5 transition metal elements.
According to a preferred embodiment of the present invention, the high entropy oxide wave-absorbing ceramic material of the present invention is La0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3、La0.5Sr0.5(Zr0.2Hf0.2Ti0.2Fe0.2Cr0.2)O3、La0.5Sr0.5(Zr1/6Fe1/ 6Co1/6Ni1/6Cr1/6Mn1/6)O3、La0.7Sr0.3(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3、La0.3Sr0.7(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3、La0.6Sr0.4(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3、La0.4Sr0.6(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3、La0.5Sr0.5(Fe1/6Co1/6Ni1/6Cr1/6Mn1/3)O3、La0.4Sr0.4Gd0.2(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3.
The invention provides a method for preparing high-entropy oxide ceramic powder material, which comprises the steps of sintering mixed raw materials;
Wherein the raw materials of A are lanthanum oxide and strontium carbonate;
the raw material of the B is oxide of the B, and is at least 5 selected from nickel oxide, manganese dioxide, ferric oxide, cobaltic oxide, hafnium oxide, titanium dioxide and zirconium dioxide.
Specifically, according to mole percentage, the raw materials comprise 0mol% -7 mol% of chromium oxide, 0mol% -15 mol% of nickel oxide, 0mol% -22 mol% of manganese dioxide, 0mol% -7 mol% of ferric oxide, 0mol% -7 mol% of cobalt oxide, 0mol% -15 mol% of zirconium dioxide, 0mol% -15 mol% of hafnium oxide, 0mol% -15 mol% of titanium dioxide, 0mol% -30 mol% of lanthanum oxide and 0mol% -50 mol% of strontium carbonate, wherein the raw materials contain lanthanum oxide and strontium carbonate as sources of A, and the raw materials contain at least 5 transition metal oxides as sources of B.
According to a preferred embodiment of the invention, the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, iron oxide, manganese oxide, cobalt oxide, nickel oxide are 17mol%, 34mol%, 7mol%, 14mol%, or 26mol%, 23mol%, 7mol%, 15mol%, or 9mol%, 45mol%, 7mol%, 13mol%, 6mol%, 13mol%, or 20mol%, 30mol%, 7mol%, 15mol%, 7mol%, 14mol%, or 13mol%, 40mol%, 7mol%, 13mol%, or 17mol%, 33mol%, 6mol%, 5mol%, 22mol%, 6mol%, 11mol%; the mole percentages of lanthanum oxide, strontium carbonate, gadolinium oxide, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide are 14 mole percent, 26 mole percent, 13 mole percent, 7 mole percent, 6 mole percent, 13 mole percent, 7 mole percent and 14 mole percent, and the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, zirconium oxide, manganese oxide, cobalt oxide and nickel oxide are 16 mole percent, 34 mole percent, 6 mole percent, 11 mole percent, 5 mole percent, 11 mole percent and 11 mole percent, and the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, zirconium dioxide, hafnium oxide and titanium dioxide are 16 mole percent, 33 mole percent, 6 mole percent, 13 mole percent and 13 mole percent.
The high-entropy oxide ceramic material is prepared by adopting a solid-phase synthesis method, adopts metal oxide powder as raw materials, is easy to obtain and low in cost, can be prepared by directly sintering the metal oxide raw materials, has a perovskite structure, is sintered at 1295-1405 ℃ for 10-15 hours, does not need a highly toxic solvent in the preparation process, is safe and environment-friendly, has a simple process and a short preparation period, and is expected to be produced in a large scale.
Furthermore, the method mixes the metal oxide powder raw materials by adopting a wet ball milling method, has good heat dissipation effect, can effectively control the granularity and the distribution of the materials, has low energy consumption and low cost, and is beneficial to the mass production of the materials.
Specifically, the wet ball milling conditions comprise that the mixing medium is absolute ethyl alcohol, the ball stone material is zirconium balls, and grinding balls with different diameters and proportions can influence the crushing efficiency and the particle size distribution of powder, so that grinding balls with the diameters of 2mm, 5mm and 12mm are respectively selected, and in the wet ball milling process, the mass ratio of the grinding balls with the different diameters is 1:1:1, the rotating speed is 300-400 r/min, and the time is 10-15 h.
Further, the liquid level of the absolute ethyl alcohol is used for immersing the zirconium balls.
Further, filtering the slurry obtained after wet ball milling, filtering away grinding balls, and drying the residual slurry after filtering.
Specifically, a tray containing the residual slurry is put into an oven for drying, wherein the drying temperature is 80-110 ℃ and the drying time is 10 hours.
Further, in order to uniformly heat the mixed raw materials in the subsequent sintering process and improve the product yield and quality, the particle size of the mixed raw materials needs to be controlled.
Specifically, the dried mixed raw materials are subjected to screening treatment, and the mesh number of a screening screen is 120-230 meshes.
Further, in order to control the extent of the solid phase synthesis reaction and the perovskite phase purity of the high entropy oxide ceramic, the sintering conditions include maintaining at a temperature of 1295-1405 ℃ for 10-15 hours, preferably at a temperature of 1395-1400 ℃ for 10 hours under an argon atmosphere.
According to some preferred embodiments of the invention, the high temperature sintering has a vacuum of 10Pa, a temperature of 1400 ℃ or 1300 ℃ for a period of 10 hours.
Further, 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 having a target size.
Specifically, the coarse product after high-temperature sintering is crushed, fully ground to no obvious blocky powder, and then poured into a ball milling tank for ball milling treatment, wherein the ball material ratio in the ball milling crushing process is (5-7): 1, and the ball stone material is zirconia. The grinding balls with different diameters and proportions can influence the crushing efficiency and the particle size distribution of the powder, so the diameter of the grinding balls is 2mm, 5mm and 12mm respectively, the mass ratio of the grinding balls with different diameters is 1:1:1 in the ball milling and crushing process of the product, the rotating speed is 300-400 r/min, and the time is 3-5 min.
Specifically, the crushed product is subjected to screening treatment, and the mesh number of the screening screen is 120-230 meshes.
Specifically, the loose packing density of the ceramic powder material prepared by the method is 1.0-1.4g/cm 3.
The invention also provides application of the high-entropy oxide ceramic material in an electromagnetic wave adsorption coating, wherein the frequency of electromagnetic waves is 8-18GHz, the thickness of the electromagnetic wave adsorption coating is 1-2mm, and the use temperature is as high as 1200-1350 ℃ or even higher.
The high-entropy oxide ceramic material is applied to an electromagnetic wave adsorption coating, not only realizes the absorption of electromagnetic waves at wider wave frequency, but also has higher electromagnetic functional strength at lower frequency band (8-12 GHz), and can be more suitable for the detection of novel equipment to effectively avoid electromagnetic waves, meanwhile, the perovskite structure of the high-entropy oxide ceramic material has good temperature resistance, and the quality of the ceramic material is always stable, has better thermal stability and oxidation resistance when the ceramic material is heated to 1200 ℃ in an air atmosphere, and has better electromagnetic function and stable cycle performance and long service life at high temperature, and in addition, the ceramic material has higher electromagnetic functional strength at lower frequency band (8-12 GHz), can reduce the manufacturing thickness of the electromagnetic functional coating, realizes the light weight of the wave absorbing material applied in electronic equipment, is convenient to carry and install, and is particularly suitable for aircraft equipment with strict weight limiting requirements.
The technical scheme of the invention is further explained below by combining specific examples.
The raw materials used in the invention are all commercial products, are in powder form, have the particle size range of 100-800nm and have the purity of 99.99%.
Example 1
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 comprises the following steps:
(1) Weighing 20mol of lanthanum oxide, 34mol of strontium carbonate, 7mol of chromium oxide, 7mol of ferric oxide, 14mol of manganese oxide, 7mol of cobalt oxide and 14mol of nickel oxide which are all added into a ball milling tank, adding zirconia grinding balls with diameters of 2mm, 5mm and 12mm respectively, wherein the mass ratio is 1:1:1, the ball material ratio is 4:1, adding absolute ethyl alcohol while stirring until the powder surface is submerged, and ball milling and mixing for 10 hours under the rotating speed of 400 r/min;
(2) Pouring the slurry uniformly mixed in the step (1) into a 120-mesh screen to filter out grinding balls, pouring the rest slurry into a tray, putting into a baking oven, and drying for 6 hours at the temperature of 100 ℃;
(3) Sieving the dried powder in the step (2) through a 150-mesh screen to obtain a mixture powder, putting the mixture powder into a zirconia crucible, and sintering in a high-temperature sintering furnace at 1400 ℃ for 10 hours and 10Pa, wherein the temperature rising rate is 5 ℃ per min;
(4) Knocking the ceramic blocks sintered in the step (3), grinding until no obvious block powder exists, pouring the ceramic blocks into a ball milling tank, pouring zirconia grinding balls with diameters of 12mm, 5mm and 2mm respectively in a ball-material ratio of 6:1, and crushing the ceramic blocks for 20min under the condition that the rotating speed of the ball mill is 350r/min, wherein the mass ratio of the zirconia grinding balls is 1:1:1;
pouring the powder into a 120-mesh screen mesh, and sieving to obtain the high-entropy electromagnetic functional oxide ceramic powder material La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3.
As shown in the results of XRD, SEM, EDS, TG and electromagnetic function parameter tests on La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder, as shown in the figures 1, 3 (a), 3 (b), 4, 5 and table 1, the ceramic powder obtained in the example 1 has a single-phase perovskite structure, the elements in the components are uniformly distributed, the purity of the product is high, a quality shock inflection point appears when the ceramic powder is heated to about 1250 ℃ in an air atmosphere, which indicates that the ceramic material has better heat stability and oxidation resistance, and has better electromagnetic loss in the 8-18GHz wave frequency range, especially in the low-frequency range (8-12 GHz), and the prepared coating thickness is smaller than 2mm, and has wider electromagnetic wave absorption bandwidth at room temperature and 1000 ℃.
Example 2
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Zr0.2Hf0.2Ti0.2Fe0.2Cr0.2)O3 adopts the same preparation method as in example 1, except that the raw materials of manganese oxide, cobalt oxide and nickel oxide in step (1) of example 1 are replaced by zirconium dioxide, hafnium oxide and titanium dioxide, and the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, zirconium dioxide, hafnium oxide and titanium dioxide are respectively 16 mole%, 33 mole%, 6 mole%, 13 mole% and 13 mole%.
TG test was carried out on La 0.5Sr0.5(Zr0.2Hf0.2Ti0.2Fe0.2Cr0.2)O3 ceramic powder, and the results are shown in Table 1, and the ceramic powder prepared in example 2 has better thermal stability and oxidation resistance.
Example 3
The preparation method of the high-entropy oxide ceramic powder La0.5Sr0.5(Zr1/6Fe1/6Co1/6Ni1/6Cr1/6Mn1/6)O3 adopts the same method as in example 1, except that the raw materials and the amounts thereof in step (1) of example 1 are changed, and the molar percentages of lanthanum trioxide, strontium carbonate, chromium trioxide, ferric oxide, zirconium dioxide, manganese oxide, nickel oxide and cobalt trioxide are 16mol%, 34mol%, 6mol%, 11mol% and 5mol%, respectively.
The ceramic powder La0.5Sr0.5(Zr1/6Fe1/6Co1/6Ni1/6Cr1/6Mn1/6)O3 was subjected to TG test, and the results are shown in table 1, and the ceramic powder prepared in example 3 has good thermal stability and oxidation resistance.
Example 4
The preparation method of the high-entropy oxide ceramic powder La 0.7Sr0.3(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide in the step (1) of example 1 are 26 mole percent, 23 mole percent, 7 mole percent, 15 mole percent, 7 mole percent and 15 mole percent respectively.
XRD and TG tests are carried out on La 0.7Sr0.3(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder, and the results are shown in figure 1 and table 1, and the ceramic powder obtained in example 4 has a single-phase perovskite structure, high product purity, and good thermal stability and oxidation resistance.
Example 5
The preparation method of the high-entropy oxide ceramic powder La 0.3Sr0.7(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide in the step (1) of example 1 are respectively 9 mole percent, 45 mole percent, 7 mole percent, 13 mole percent, 6 mole percent and 13 mole percent.
XRD and TG tests are carried out on La 0.3Sr0.7(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder, and the results are shown in figure 1 and table 1, and the ceramic powder obtained in example 5 has a single-phase perovskite structure, high product purity, and good thermal stability and oxidation resistance.
Example 6
The preparation method of the high-entropy oxide ceramic powder La 0.6Sr0.4(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide in the step (1) of example 1 are respectively 20 mole percent, 30 mole percent, 7 mole percent, 15 mole percent, 7 mole percent and 14 mole percent.
XRD and TG tests are carried out on La 0.6Sr0.4(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder, the results are shown in figure 1 and table 1, and the ceramic powder obtained in example 6 has a biphase perovskite structure, high product purity, and good thermal stability and oxidation resistance.
Example 7
The preparation method of the high-entropy oxide ceramic powder La 0.4Sr0.6(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide in the step (1) of example 1 are respectively 13 mole percent, 40 mole percent, 7 mole percent, 13 mole percent, 7 mole percent and 13 mole percent.
XRD and TG tests are carried out on La 0.4Sr0.6(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder, the results are shown in figure 1 and table 1, and the ceramic powder obtained in example 7 has a biphase perovskite structure, high product purity, and good thermal stability and oxidation resistance.
Example 8
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Fe1/6Co1/6Ni1/6Cr1/6Mn1/3)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide in the step (1) of example 1 are 17 mole percent, 33 mole percent, 6 mole percent, 5 mole percent, 22 mole percent, 6 mole percent and 11 mole percent respectively.
The results of TG tests on La 0.5Sr0.5(Fe1/6Co1/6Ni1/6Cr1/6Mn1/3)O3 ceramic powders are shown in fig. 4 and table 1, and the ceramic powder obtained in example 8 has good thermal stability and oxidation resistance.
Example 9
The preparation method of the high-entropy oxide ceramic powder La0.4Sr0.4Gd0.2(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, gadolinium oxide, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide are respectively 14 mole percent, 26 mole percent, 13 mole percent, 7 mole percent, 6 mole percent, 13 mole percent, 7 mole percent and 14 mole percent.
The ceramic powder La0.4Sr0.4Gd0.2(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 was subjected to TG test, and the results are shown in table 1, and the ceramic powder obtained in example 9 has good thermal stability and oxidation resistance.
Example 10
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 was the same as in example 1, except that the sintering temperature in step (1) of example 1 was set to 1300 ℃.
The La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder prepared in example 10 was subjected to XRD and TG tests, and the results are shown in table 1, and the ceramic powder prepared in example 10 has a single-phase perovskite structure, high product purity, and good thermal stability and oxidation resistance.
Comparative example 1
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 was the same as in example 1, except that the sintering temperature in step (1) of example 1 was set to 1150 ℃.
XRD and TG tests were carried out on the La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder prepared in comparative example 1, and the results are shown in FIG. 2 and Table 1, and the ceramic powder obtained in comparative example 1 has a perovskite structure, and has high impurity content and low product purity.
Comparative example 2
The preparation method of the high-entropy oxide ceramic powder La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 was the same as in example 1, except that the sintering temperature in step (1) of example 1 was set to 1200 ℃.
XRD and TG tests were carried out on the La 0.5Sr0.5(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder prepared in comparative example 2, and the results are shown in FIG. 2 and Table 1, and the ceramic powder prepared in comparative example 2 has a perovskite structure, and has high impurity content and low product purity.
Comparative example 3
The preparation method of the high-entropy oxide ceramic powder La 0.9Sr0.1(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 adopts the same method as in example 1, except that the mole percentages of lanthanum oxide, strontium carbonate, chromium oxide, ferric oxide, manganese oxide, cobalt oxide and nickel oxide are 36 mole percent, 8 mole percent, 16 mole percent, 8 mole percent and 16 mole percent respectively.
The La 0.9Sr0.1(Fe0.2Co0.2Ni0.2Cr0.2Mn0.2)O3 ceramic powder prepared in comparative example 3 was subjected to TG test, and the results are shown in table 1.
Application example
The high-entropy oxide ceramic powders prepared in examples 1 to 10 and comparative examples 1 to 3 were mixed with a wave-transmitting material, respectively, and then electromagnetic wave absorption coatings of different thicknesses were prepared by a high-energy plasma spraying method, electromagnetic functional parameters of the coatings at normal temperature and 1000 ℃ were measured by a waveguide method, and electromagnetic functional strength of the high-entropy oxide ceramic material was simulated according to the obtained electromagnetic functional parameters, thereby obtaining electromagnetic wave absorption bandwidths, as shown in table 1.
TABLE 1
As can be seen from Table 1, the coating prepared from the high-entropy oxide ceramic powder of examples 1 to 10 has higher absorption strength to the X-band at room temperature and 1000 ℃ under the condition that the thickness of the prepared electromagnetic functional coating is less than 2mm, and the absorption bandwidth to the X-band at room temperature is more than 1.5GHz, and the absorption bandwidth to the X-band at 1000 ℃ is more than 1.0GHz, while the coating prepared from the high-entropy oxide ceramic powder of comparative examples 1 to 3 has better high-temperature wave absorption performance compared with the electromagnetic functional strength at normal temperature, and the electromagnetic functional strength to the X-band at high temperature is suddenly reduced, even is zero.
As can be seen from fig. 4, 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 ℃.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (10)
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| CN116589264A (en) * | 2023-04-25 | 2023-08-15 | 郑州大学 | Perovskite ceramic material and preparation method and application thereof |
| CN117747312A (en) * | 2023-12-26 | 2024-03-22 | 云南大学 | High-entropy oxide super capacitor electrode material, preparation method and energy storage device |
| CN117809987A (en) * | 2023-12-26 | 2024-04-02 | 云南大学 | Transition metal high-entropy oxide, preparation method and application thereof |
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| CN115304373A (en) * | 2022-07-25 | 2022-11-08 | 云南大学 | Perovskite-like rare earth doped high-entropy oxide fluorescent ceramic material and preparation method thereof |
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| CN116282214A (en) * | 2023-02-17 | 2023-06-23 | 郑州大学 | A high-entropy perovskite type electromagnetic wave absorbing material and its preparation method |
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