Lightweight high-entropy perovskite wave-absorbing material and preparation method thereof

Abstract

The invention relates to the technical field of wave-absorbing materials, and discloses a lightweight high-entropy perovskite wave-absorbing material and a preparation method thereof, and the lightweight high-entropy perovskite wave-absorbing material is a high-entropy perovskite oxide. The chemical formula of the high-entropy perovskite oxide is Srx (AyMnyCryByCy) O3, x is equal to 1 to 3, and y is equal to 0.2 to 0.6; a, B and C are selected from any three of Fe, Co, Ni, Ti, Zn, Cu, Zr, Ga, Sn, Yb, Eu, Mo, Rh and Ru. According to the invention, the light high-entropy perovskite oxide is synthesized at a low temperature by using a one-step firing process and adopting a pure oxide as a raw material through proper doping elements and firing temperature. The high-entropy synthesized half-shell hexagonal prism high-entropy perovskite oxide structure with the large length-diameter ratio is beneficial to multiple reflection of electromagnetic waves in the material, reflection is reduced, the wave absorbing performance is improved, and the application range of the high-entropy perovskite oxide is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of absorbing materials, and in particular to a lightweight high-entropy perovskite absorbing material and a preparation method thereof. Background Art

[0002] Traditional magnetic metal materials have poor antioxidant ability, the electromagnetic wave absorption frequency of semiconductor materials is concentrated in high frequency, and the frequency band is relatively single. Carbon and iron absorbers have problems such as narrow absorption frequency band and weak absorption intensity.

[0003] At present, the design methods of absorbing materials mainly include the preparation of nanocomposite materials and doping modification. The coupling of two loss mechanisms can be achieved by combining dielectric loss type and magnetic loss type materials at the nanoscale, but the complex preparation process, the difficulty in accurately controlling the dispersion of nanofillers, and the poor thermal stability and oxidation resistance are the main factors restricting the application of nanocomposite materials.

[0004] Perovskite raw materials are abundant and easy to synthesize, with excellent photoelectric properties and a short production process. Perovskite has a unique crystal structure, especially the crystal defect structure and performance formed after doping, which may be used in many fields such as solid fuel cells, solid electrolytes, sensors, high-temperature heating materials, solid resistors and redox catalysts that replace precious metals, becoming a research hotspot in the fields of chemistry, physics and materials.

[0005] Perovskite oxides have excellent and diverse physical properties and are applicable to many different fields, but there is little research in the field of microwave absorption. High entropy oxides, as a new type of oxide system developed in recent years, have broken the design concept of traditional doped oxides and have attracted widespread attention from researchers at home and abroad due to their simple structure and excellent performance.

[0006] High entropy absorbing materials can be regulated through the lattice distortion effect of the structure and the high entropy effect of the components. Not only can the dielectric and magnetic properties of high entropy ceramic absorbing materials be regulated, their impedance matching characteristics and absorbing performance regulation can be achieved, but also their high-temperature thermal stability and oxidation resistance can be improved. However, the preparation process of high entropy perovskite absorbing materials in the prior art mostly adopts a two-step method to sinter ceramics or powders, which has complicated overall steps and takes a long time; the density of the sintered product is relatively large, and the required sintering temperature is high, and the process is complicated.

[0007] Therefore, a lightweight high entropy perovskite absorbing material and its preparation method are urgently needed to solve the above technical problems. Summary of the invention

[0008] The present invention aims to simplify the synthesis process in view of the deficiencies in the prior art, and to synthesize a lightweight perovskite material having a large aspect ratio and a half-shell hexagonal prism by a one-step method using pure oxide as a raw material.

[0009] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0010] A light high entropy perovskite absorbing material, wherein the light high entropy perovskite absorbing material is a high entropy perovskite oxide; the chemical formula of the high entropy perovskite oxide is Sr x (A y Mn y Cr y B y C y ) 3 , wherein x=1-3, y=0.2-0.6; A, B, and C are selected from any three of Fe, Co, Ni, Ti, Zn, Cu, Zr, Ga, Sn, Yb, Eu, Mo, Rh, and Ru.

[0011] Further preferably, A, B, and C are selected from Fe 2+ 、Co + 、Ni + 、Ti 2+ 、Zn 2+ , Cu 2+ 、Zr 4+ , Ga 2+ Sn 2+ , Yb 3+ 、Eu 3+ 、Mo 4+ , Rh 4+ 、Ru 4+ Any three of the .

[0012] The present invention firstly considers the elements that realize the coupling of the two loss mechanisms, so that the composition obtains the best balance of performance; selects non-isometric crystal system and alkali metal elements so as to have a lower melting point oxide for low temperature synthesis of high entropy perovskite oxide; selects doped MnO 2 Manganese dioxide is an octahedral structure, with oxygen atoms at the corners of the octahedron and manganese atoms in the octahedron. The octahedrons are connected to form single or double chains with common edges. These chains share the same top with other chains to form a tunnel structure with gaps, forming a cubic close packing; secondly, the overall tolerance factor of the high entropy element is ensured to be closer to 1; at the same time, elements with oxides of lower melting points are selected to synthesize high entropy perovskite oxides at low temperatures; finally, considering multiple factors such as ionic radius with similar substitution positions, the same crystal structure, similar electronegativity, the same valence state, entropy formation ability, size disorder factor and valence electron concentration, different raw materials are selected, and components with different atomic sizes and crystal structures are solid-dissolved together to obtain the specific composition of the high entropy perovskite oxide of the present invention.

[0013] The high entropy perovskite oxide of the present invention is actually a perovskite having a chemical formula of SrCrO 3The B site of the perovskite is doped in an equimolar ratio.

[0014] Preferably, the structure of the lightweight high entropy perovskite absorbing material is a half-shell hexagonal prism. Specifically, the structure here refers to the crystal structure.

[0015] Further preferably, the structure of the lightweight high entropy perovskite absorbing material is a half-shell hexagonal prism with a large aspect ratio.

[0016] Further preferably, the aspect ratio of the large aspect ratio half-shell hexagonal prism is 2:1.

[0017] Preferably, the density of the lightweight high entropy perovskite absorbing material is 2.25-3.3 g / cm 3 ; Further preferably, the density of the lightweight high entropy perovskite absorbing material is 2.45 to 3.13 g / cm 3 .

[0018] The present invention also includes a method for preparing a lightweight high entropy perovskite absorbing material, comprising the following steps:

[0019] S1, according to the chemical formula Sr x (A y Mn y Cr y B y C y ) 3 Calculate the required amount of Sr oxide, A oxide, Mn oxide, Cr oxide, B oxide and C oxide according to the ratio;

[0020] S2, weighing the pre-treated raw materials, and then wet-grinding them to obtain a mixture;

[0021] S3, drying and crushing the solid material obtained after centrifugation of the mixture to obtain a crushed raw material;

[0022] S4, adding a binder to the crushed raw material and then pressing and molding to obtain a molded sample;

[0023] S5, the formed sample is sintered at a sintering temperature of 800-1300° C. After sintering, a finished product of a lightweight high entropy perovskite absorbing material is obtained.

[0024] Preferably, in step S1, the oxide of Sr is SrO; the oxide of Mn is MnO 2 ; Cr oxide is Cr 2 O 3 ; The oxide of A, the oxide of B, and the oxide of C are selected from Fe according to the chemical formula 2 O 3 , Fe 3 O4 , CoO, NiO, TiO 2 、ZnO、CuO、ZrO 2 、GaO、SnO、Yb 2 O 3 、Eu 2 O 3 、MoO 2 , RhO 2 、RuO 2 Any three of the .

[0025] Preferably, in step S2, the ball-to-material ratio in the wet grinding process is 3:1, the liquid used in the wet grinding process is deionized water or anhydrous ethanol; the mass ratio of the liquid to the material being ball-milled is 3:1; the wet grinding time is 6 to 12 hours, and the rotation speed is set at 150 to 300 rpm.

[0026] Preferably, in step S2, the pretreatment process is: placing the raw material in a drying oven for drying. The dried raw material can also be crushed using a pulverizer before wet grinding.

[0027] Further preferably, in step S2, a planetary ball mill is used for wet grinding.

[0028] Specifically, the process of step S2 is as follows:

[0029] The raw materials are placed in a drying oven for drying. After drying, the raw materials are weighed according to the calculated amount and then crushed by a pulverizer. Subsequently, the raw materials are placed in a ball mill and liquid (deionized water or anhydrous ethanol) is added. The mass ratio of the liquid to the material to be ball milled in the ball mill is 3:1. Zirconia balls or high manganese steel balls with a ball-to-material ratio (mass ratio) of 3:1 are added. A rubber ring is placed on the sealing portion of the ball mill and the ball mill cover is sealed. The ball milling time of the planetary ball mill is adjusted to 6 to 12 hours and the rotation speed is set to 150 to 300 rpm. The ball mill is placed in the ball mill for ball milling.

[0030] Preferably, in step S3, the drying temperature is 50-80° C., and the drying time is 6-8 hours.

[0031] Specifically, the process of step S3 is as follows:

[0032] After the ball milling is completed, the ball mill is transferred to the glove box, the ball mill is opened, and the mixture in the ball mill is sucked into a centrifuge tube for centrifugal separation. The centrifugal speed is 3000-5000r / min, and the centrifugal time is 3-5min. After the centrifugal separation is completed, the upper liquid is sucked out, and the bottom is transferred to a tray, and then the tray is placed in a drying oven for drying. The drying temperature is 50-80°C and the drying time is 6-8h. After the drying is completed, the dried material is taken out and placed in a pulverizer for grinding into powder.

[0033] Preferably, in step S4, the adhesive is a 5wt% PVA solution or deionized water; the mass ratio of the adhesive to the crushed raw material is 1:10;

[0034] During the compression molding process, the molding pressure is 10-30 MPa, and the pressure holding time during molding is 30 seconds.

[0035] Specifically, the process of step S4 is as follows:

[0036] Take a certain amount of crushed raw materials, add 5% PVA solution or deionized water as a binder, mix well and place in a circular mold with a diameter of 30 mm, press and mold at a pressure of 10-30 MPa for 30 seconds, and then demold to obtain the molded sample.

[0037] Preferably, in step S5, the atmosphere used in the sintering process is O 2 .

[0038] Preferably, in step S5, the sintering temperature of the sintering process is changed as follows: firstly, the temperature is raised to the pre-sintering temperature of 750-1250°C for a heat preservation, then the temperature is raised to the sintering temperature of 800-1300°C for a second heat preservation; then the temperature is lowered to 500°C and then cooled with the furnace;

[0039] The pre-sintering temperature is lower than the sintering temperature; the insulation time of the first insulation is 1 to 5 hours; the insulation time of the second insulation is 0.5 to 4 hours; the heating and cooling rates are both 4 to 10°C / min.

[0040] The pre-sintering of the present invention is a heat preservation sintering performed before approaching the sintering temperature, which is helpful for the growth of perovskite along the c-axis to form a lightweight half-shell hexagonal prism with a large aspect ratio.

[0041] Preferably, in step S5, during the sintering process, the formed sample is placed in a crucible, the crucible is raised to half the height of the furnace chamber, and is placed in a furnace with O 2 The sintering is carried out in a high temperature box furnace with a low atmosphere.

[0042] Specifically, the process of step S5 is as follows:

[0043] The formed sample is placed in a crucible, and the crucible with a certain height (the crucible is raised to half the height of the furnace chamber) is placed in a furnace with O 2 The sintering is carried out in a high-temperature box furnace with a sintering temperature of 800-1300°C and a heating rate of 4-10°C / min. When the temperature is close to the sintering temperature, the temperature is kept warm, and then the temperature is raised to the sintering temperature and kept warm. During this period, the high entropy perovskite will grow along the c-axis, and the growth in other directions will be inhibited, eventually forming a half-shell hexagonal prism.

[0044] To be more specific, the temperature changes during the sintering process are as follows:

[0045] First, the temperature is raised to the pre-sintering temperature of 750-1250°C for a heat preservation, and then the temperature is raised to the sintering temperature of 800-1300°C for a second heat preservation; then the temperature is lowered to 500°C and cooled with the furnace;

[0046] The pre-sintering temperature is 50°C lower than the sintering temperature; the insulation time of the first insulation is 4h; the insulation time of the second insulation is 2h; the heating and cooling rates are both 10°C / min.

[0047] Working principle:

[0048] The present invention is compatible with two loss mechanisms; the tolerance factor is close to 1; non-isometric crystal system and alkaline earth metal with low melting point oxide are selected. By controlling the sintering process, pure oxide is used as raw material to synthesize high entropy perovskite oxide with large aspect ratio and half shell hexagonal prism with excellent wave absorption performance in one step.

[0049] The present invention studies the performance of perovskite in wave absorption, obtains excellent wave absorption performance, combines perovskite with high entropy, and prepares high entropy perovskite oxide with excellent wave absorption performance. The present invention studies its phase composition and reaction mechanism by improving the process, adopting different raw materials and ratios, synthesis process and sintering system, further discusses the influence on its performance and doping other materials in perovskite to improve the wave absorption performance. By doping some materials in perovskite, the sintering of perovskite can be promoted, and its wave absorption and other properties can be improved.

[0050] The present invention can make the material have both broadband absorption and strong absorption and high-efficiency wave absorbing performance by designing and preparing high-entropy oxide containing magnetic components. The high-entropy design method can simultaneously adjust the conductivity and enhance the magnetic loss capacity, and can also reduce the eutectic point and thus reduce the sintering temperature, providing a new idea for regulating impedance matching for wave absorbing materials with good conductivity.

[0051] Since the high entropy system is highly disordered and has multiple components, and the lattice distortion caused by the high entropy effect allows the high entropy ceramic to remain in a single phase under extreme temperature, pressure and chemical environment, making it stable under various service conditions. The present invention uses a one-time firing process to synthesize high entropy perovskite oxides, which reduces the sintering temperature and improves the synthesis efficiency. The synthesized large aspect ratio half-shell hexagonal prism structure is beneficial to the multiple reflections of electromagnetic waves inside, improving the wave absorption performance.

[0052] The advantages of the present invention are as follows: (1) a high-entropy perovskite oxide with excellent wave absorption performance is synthesized by a one-step solid-phase sintering process, which simplifies the process and enhances stability; (2) for the selection of raw materials for synthesizing the B-site high-entropy perovskite oxide, elements that can achieve the coupling of two loss mechanisms are firstly used, so that the composition obtains the best balance of performance; non-isometric crystal system and alkali metal elements are selected so as to have oxides with lower melting points, so that the high-entropy perovskite oxide can be synthesized at low temperature; MnO is selected for the B site. 2 , manganese dioxide is an octahedral structure, with oxygen atoms at the corners of the octahedron and manganese atoms in the octahedron. The octahedra are connected to form single or double chains. These chains share the same top with other chains to form a tunnel structure with gaps, forming a cubic close packing; secondly, the overall tolerance factor of the high entropy element is ensured to be closer to 1; finally, by comprehensively considering factors such as similar ionic radius at the substitution position, the same crystal structure, similar electronegativity, the same valence state, entropy formation ability, size disorder factor and valence electron concentration, different raw materials are selected to dissolve components with different atomic sizes and crystal structures together to synthesize high entropy perovskite oxides; (3) The synthesized high entropy perovskite material is different from ordinary Compared with perovskite materials, on the one hand, the performance is better, and on the other hand, the eutectic temperature can be reduced, the sintering temperature can be reduced, and the synthesis efficiency is improved; (4) a variety of improved process flows such as planetary ball milling, raising the molded sample (the crucible is raised to half the height of the furnace chamber), introducing oxygen atmosphere during sintering, and keeping warm at a temperature close to the sintering temperature are used. Planetary ball milling allows the raw materials to be fully mixed, and raising the molded sample and keeping warm at a temperature close to the sintering temperature (the pre-sintering process of the present invention) are beneficial to the growth of perovskite along the c-axis, forming a lightweight half-shell hexagonal prism with a large aspect ratio. The perovskite is a half-shell hexagonal prism with a low density (2.25-3.3 g / cm 3 The theoretical density of oxide is 4.5~5.5g / cm 3 );(5) The half-shell hexagonal prism structure with large aspect ratio formed by high entropy effect is beneficial to the multiple reflection of electromagnetic waves inside the material, reducing reflection and improving the wave absorption performance.

[0053] Compared with pure perovskite, the present invention synthesizes perovskite from pure oxide, selects different doping raw materials that can achieve coupling of two loss mechanisms, and synthesizes high entropy perovskite in one step by doping at the B position, simplifies the synthesis process as a whole, improves the synthesis efficiency, reduces the sintering temperature, and synthesizes a high entropy perovskite with a lightweight, large aspect ratio, half-shell hexagonal prism structure and excellent wave absorption performance. In addition, a large amount of organic solvent is not used in the synthesis process, thereby reducing environmental pollution. By synthesizing high entropy perovskite, the application range of ordinary perovskite is expanded, providing a scientific basis for the subsequent research and development and application of high entropy perovskite in the military field.

[0054] The sintering temperature of the present invention is 800-1300°C, and the corresponding light high entropy perovskite can be generated at a minimum temperature of 800°C; the light high entropy perovskite obtained by the present invention has a low density of 2.25-3.3 g / cm 3 .

[0055] Beneficial effects:

[0056] The present invention uses pure oxide as raw material and a one-step sintering process to synthesize a lightweight high-entropy perovskite oxide at low temperature by using appropriate doping elements and sintering temperature. The high-entropy synthesized half-shell hexagonal high-entropy perovskite oxide structure with a large aspect ratio is beneficial to multiple reflections of electromagnetic waves inside the material, reducing reflections, improving wave absorption performance, and expanding the application range of high-entropy perovskite oxides, so that it can be better applied to life and military-related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a preparation flow chart of Example 1 of the present invention;

[0058] Figure 2 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 XRD pattern of

[0059] Figure 3 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 XRD pattern of

[0060] Figure 4 The Sr(Co0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 XRD pattern of

[0061] Figure 5 The magnification of Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 SEM images of

[0062] Figure 6 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 SEM images of

[0063] Figure 7 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 SEM images of

[0064] Figure 8 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 SEM images of

[0065] Fig. 9 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 RL diagram at different thickness and frequency:

[0066] Fig.10 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3RL diagram at different thickness and frequency:

[0067] Fig.11 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 RL diagram at different thickness and frequency:

[0068] Fig.12 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 RL diagram at different thickness and frequency:

[0069] Fig.13 The Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 Density comparison chart of

[0070] Fig.14 The high entropy perovskite oxide with large aspect ratio half-shell hexagonal prisms in Example 1 of the present invention

[0071] Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 Diagram of wave absorption mechanism. DETAILED DESCRIPTION

[0072] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0073] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0074] There is no particular limitation on the purity of all raw materials in the present invention, and the present invention preferably adopts the conventional purity used in the art.

[0075] The devices used in the present invention are not particularly limited and can be any of the commonly used devices in the art.

[0076] Embodiment 1:

[0077] A method for preparing a lightweight high entropy perovskite absorbing material comprises the following steps:

[0078] Weigh 1 mol of SrO, 0.2 mol of MnO 2 , CoO, NiO, 0.1 mol of Cr 2 O 3 , Fe 2 O 3 Doping is performed at the B position.

[0079] The weighed raw materials were pretreated and then placed in a ball mill, anhydrous ethanol was added, the mass ratio of anhydrous ethanol to the material to be ball-milled in the ball mill was 3:1, and zirconium oxide balls with a ball-to-material ratio of 3:1 were added, a rubber ring was placed at the sealing of the ball mill, and the ball mill cover was sealed; the ball milling time of the planetary ball mill was adjusted to 12h, the speed was set at 260rpm, and the ball mill was placed in the ball mill for ball milling;

[0080] After the ball milling is completed, the ball mill is transferred to the glove box, the ball mill is opened, and the mixture in the ball mill is sucked into a centrifuge tube for centrifugal separation at a speed of 3800r / min and a centrifugal separation time of 5min; after the centrifugal separation is completed, the upper liquid is sucked out and the bottom is transferred to a tray, and then the tray is placed in a drying oven for drying at a drying temperature of 70°C and a drying time of 6h; after the drying is completed, the dried material is taken out and placed in a household pulverizer, and the pulverizer is used to grind it into powder;

[0081] Take 3g of the crushed raw material, add 5wt% PVA solution as a binder (the ratio of the crushed raw material to the binder is 10:1), mix well and place in a circular mold with a diameter of 30mm, dry press the crushed raw material under a pressure of 30MPa, hold the pressure for 30s and then demold to obtain the molded sample;

[0082] The formed sample is placed in a zirconia crucible, and the crucible with a certain height (the crucible is raised to half the height of the furnace chamber) is placed in a chamber filled with O 2 The sintering temperature is 1100°C in a high-temperature box furnace with a high-temperature atmosphere. When the sintering temperature is close to the sintering temperature, the temperature is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1050°C and keep warm for 4 hours, then sinter to 1100°C and keep warm for 2 hours, cool to 500°C and cool with the furnace, and the heating and cooling rates are 10°C / min), and the holding time is 6 hours. During this period, the high entropy perovskite will grow along the c-axis, and the growth in other directions will be inhibited, and finally a half-shell hexagonal prism will be formed.

[0083] The chemical formula of the finished lightweight high entropy perovskite absorbing material obtained in this embodiment is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 .

[0084] Embodiment 2:

[0085] The sintering temperature of this embodiment is 900°C. When it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 850°C and keep warm for 4 hours, then sinter to 900°C and keep warm for 2 hours, cool to 500°C and cool with the furnace, and the heating and cooling rates are 10°C / min), and the insulation time is 6 hours; the remaining steps are the same as Example 1.

[0086] The chemical formula of the finished lightweight high entropy perovskite absorbing material obtained in this embodiment is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 .

[0087] Embodiment 3:

[0088] The sintering temperature of this embodiment is 1300°C. When it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1250°C and keep warm for 4 hours, then sinter to 1300°C and keep warm for 2 hours, cool down to 500°C and cool with the furnace, and the heating and cooling rates are all 10°C / min), and the insulation time is 6 hours; the remaining steps are the same as Example 1.

[0089] The chemical formula of the finished lightweight high entropy perovskite absorbing material obtained in this embodiment is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 Comparative Example 1-1:

[0090] Weigh 1 mol of SrO, 0.2 mol of MnO, CoO, ZnO, 0.1 mol of Cr 2 O 3 , Fe 2 O 3Doping is performed at position B. The weighed raw materials are pretreated, then put into a ball mill, anhydrous ethanol is added, the water-to-material ratio is 3:1, and zirconium oxide balls with a ball-to-material ratio of 3:1 are added, a rubber ring is placed at the sealing of the ball mill, and the ball mill cover is sealed; the sintering temperature is 1100°C, and when it is raised to a temperature close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1050°C and keep warm for 4 hours, then sinter to 1100°C and keep warm for 2 hours, cool to 500°C and then cool with the furnace, and the heating and cooling rates are all 10°C / min), and the rest is consistent with Example 1.

[0091] The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 .

[0092] Comparative Example 1-2:

[0093] In this comparative example, the sintering temperature is 1200°C, and when it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1150°C and keep warm for 4 hours, then sinter to 1200°C and keep warm for 2 hours, cool to 500°C and then cool with the furnace, and the heating and cooling rate is 10°C / min), and the steps are the same as those of comparative example 1-1. The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 .

[0094] Comparative Examples 1-3:

[0095] In this comparative example, the sintering temperature is 1300°C, and when it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1250°C and keep warm for 4 hours, then sinter to 1300°C and keep warm for 2 hours, cool to 500°C and then cool with the furnace, and the heating and cooling rate is 10°C / min), and the steps are the same as those of comparative example 1-1. The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 .

[0096] Comparative Example 2-1:

[0097] Weigh 1 mol of SrO, 0.2 mol of MnO, CoO, TiO, 0.1 mol of Cr 2 O 3 , Fe 2 O 3 Doping is performed at position B. The weighed raw materials are pretreated, then put into a ball mill, anhydrous ethanol is added, the water-to-material ratio is 3:1, and zirconium oxide balls with a ball-to-material ratio of 3:1 are added, a rubber ring is placed at the sealing of the ball mill, and the ball mill cover is sealed; the sintering temperature is 1100°C, and when it is raised to a temperature close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1050°C and keep warm for 4 hours, then sinter to 1100°C and keep warm for 2 hours, cool to 500°C and then cool with the furnace, and the heating and cooling rates are all 10°C / min), and the rest is consistent with Example 1.

[0098] The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 .

[0099] Comparative Example 2-2:

[0100] In this comparative example, the sintering temperature is 1200°C, and when it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1150°C and keep warm for 4 hours, then sinter to 1200°C and keep warm for 2 hours, cool down to 500°C and cool with the furnace, and the heating and cooling rate is 10°C / min), and the steps are the same as those of comparative example 2-1. The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 .

[0101] Comparative Example 2-3:

[0102] In this comparative example, the sintering temperature is 1300°C, and when it is close to the sintering temperature, it is kept warm, and then the temperature is raised to the sintering temperature and kept warm (the specific sintering process is: first sinter to 1250°C and keep warm for 4 hours, then sinter to 1300°C and keep warm for 2 hours, cool down to 500°C and cool with the furnace, and the heating and cooling rate is 10°C / min), and the steps are the same as those of comparative example 2-1. The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 )3 .

[0103] Comparative Example 3:

[0104] This comparative example is the same as Example 1 except for the sintering temperature and the holding time. The sintering temperature is 700°C, and the temperature is kept when it is close to the sintering temperature, and then the temperature is increased to the sintering temperature and kept (the specific sintering process is: first sinter to 650°C and keep it for 4 hours, then sinter to 700°C and keep it for 2 hours, cool down to 500°C and cool with the furnace, and the heating and cooling rates are all 10°C / min), the rate is 10°C / min, and the temperature is kept when it is close to the sintering temperature, and the holding time is 6h.

[0105] The chemical formula of the product obtained in this comparative example is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 .

[0106] like Figure 1 Shown is a preparation flow chart of Example 1 of the present invention.

[0107] like Figure 2 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 XRD diagram of Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 The broken lines in the figure with temperatures of 1100°C, 900°C, and 1300°C represent the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 .Depend on Figure 2 It can be seen that the 700°C broken line represents the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 Perovskite cannot be synthesized.

[0108] like Figure 3 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 XRD diagram of the Sr(Co)2O3 obtained in Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3. 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 .Depend on Figure 3 It can be seen that the chemical formula is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 The lowest synthesis temperature of the high entropy perovskite is 1100°C, and the corresponding high entropy perovskite cannot be synthesized below 1100°C. The lowest temperature of the high entropy perovskite synthesized by the present invention is 800°C.

[0109] like Figure 4 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 XRD diagram. The broken lines representing the temperatures of 1100°C, 1200°C, and 1300°C in the figure are respectively the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 .Depend on Figure 4 It can be seen that the chemical formula is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 The lowest synthesis temperature of the high entropy perovskite is 1100°C, and the corresponding high entropy perovskite cannot be synthesized below 1100°C. The lowest temperature of the high entropy perovskite synthesized by the present invention is 800°C.

[0110] By the above Figures 2 to 4 It can be understood that the sintering temperature of the present invention is 800-1300° C. to synthesize lightweight high-entropy perovskite, and the sintering temperature is low.

[0111] like Figure 5 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 SEM image of Figure 5 It can be understood that the obtained structure is not a half-shell hexagonal prism, so the lightweight high-entropy perovskite absorbing material of the half-shell hexagonal prism of the present invention cannot be synthesized at the temperature of Comparative Example 3.

[0112] like Figure 6 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 SEM image of . Figure 6 It is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe .2 Ni 0.2 ) 3 SEM image of Figure 6 It can be seen that the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 It is a half-shell hexagonal prism. After measurement, its aspect ratio is 2:1, which is a half-shell hexagonal prism with a large aspect ratio.

[0113] like Figure 7 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 SEM image of . Figure 7 It is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3SEM image of Figure 7 It can be seen that using MnO as a raw material doping cannot synthesize the corresponding half-shell hexagonal high-entropy perovskite.

[0114] like Figure 8 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 SEM image of . Figure 8 It is Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 SEM. Figure 8 It can be seen that using MnO as a raw material doping cannot synthesize the corresponding half-shell hexagonal high-entropy perovskite.

[0115] like Fig. 9 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 RL diagrams at different thicknesses and frequencies. (a) The diagram is a 3D diagram; (b) The diagram is a 2D plane mapping diagram. Fig. 9 It can be seen that the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 No wave absorbing performance.

[0116] like Fig.10 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 RL diagrams at different thicknesses and frequencies. (a) The diagram is a 3D diagram; (b) The diagram is a 2D plane mapping diagram; (c) The diagram is the reflection loss at different thicknesses. Fig.10It can be seen that when the thickness is 4.8mm, the minimum reflection loss is -45.95dB; when it is 1.80mm, the minimum reflection loss is -43.34dB, and the EAB is 3.60GHz. It has effective electromagnetic wave absorption performance in the thickness range of 1 to 5mm, and it is wide-band in multiple frequency ranges. Its effective absorption bandwidth can effectively cover 3 to 18GHz.

[0117] like Fig.11 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Zn 0.2 ) 3 RL diagrams at different thicknesses and frequencies. (a) The diagram is a 3D diagram; (b) The diagram is a 2D plane mapping diagram; (c) The diagram is the reflection loss at different thicknesses. Fig.11 It can be seen that when the thickness is 1.50mm, the minimum reflection loss is -34.88dB, the EAB is 2.10GHz, and the effective absorption bandwidth is narrow. Fig.12 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ti 0.2 ) 3 RL diagrams at different thicknesses and frequencies. (a) The diagram is a 3D diagram; (b) The diagram is a 2D plane mapping diagram; (c) The diagram is the reflection loss at different thicknesses. Fig.12 It can be seen that when the thickness is 1.00mm, the minimum reflection loss is -30.91dB and the EAB is 0.85GHz; when the thickness is 1.6mm, the EAB is 1.955GHz. It has effective electromagnetic wave absorption performance in the thickness range of 1 to 3mm, and the effective absorption bandwidth effectively covers 8.5 to 11.5GHz.

[0118] By the above Figures 9 to 12 It can be seen that the large aspect ratio half-shell hexagonal prism structure of Example 1 of the present invention is beneficial to multiple losses of electromagnetic waves inside, reducing reflections and improving wave absorption performance. It has effective electromagnetic wave absorption performance in the thickness range of 1 to 5 mm, and its effective wave absorption bandwidth can effectively cover 3 to 18 GHz. At the same time, the effective absorption bandwidth is wide at multiple frequencies.

[0119] like Fig.13 As shown, the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 )3 Density comparison diagram; the temperature in the figure is 700°C, which represents the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 ; The temperatures of 1100°C, 900°C, and 1300°C in the figure represent the Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 ; Before sintering refers to the density of the sample before sintering, and after sintering refers to the density of the corresponding finished product Sr(Co 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 The density of Fig.13 It can be understood that the high entropy perovskite oxide formed has a relatively light density due to its half-shell hexagonal prism structure with a large aspect ratio.

[0120] like Fig.14 As shown, the high entropy perovskite oxide Sr(Co) with a half-shell hexagonal prism with a large aspect ratio is shown in Example 1 of the present invention. 0.2 Mn 0.2 Cr 0.2 Fe 0.2 Ni 0.2 ) 3 Diagram of wave absorption mechanism.

[0121] Depend on Fig.14 It can be understood that the excellent electromagnetic wave absorption performance of high entropy samples is attributed to the combined effect of dielectric loss and magnetic loss. Dielectric loss is mainly conductive loss, interface polarization and dipole polarization.

[0122] Transition metal cations exhibit different valence states and severe lattice defects in high entropy perovskite oxides, and the lattice distortion significantly affects the structure of transition metal ions, leading to the polarization of solid dipoles and the generation of defect dipoles, thereby promoting the polarization relaxation process of dipoles. During the movement of free charges, these charges are blocked by grain boundaries, resulting in continuous accumulation at the grain boundaries, forming interfacial polarization, and the half-shell hexagonal prisms with a large aspect ratio are beneficial to the multiple reflections of electromagnetic waves inside the material, reducing reflections and improving wave absorption performance. The large aspect ratio half-shell hexagonal prisms have a large surface area, which is beneficial to the formation of a conductive current in the material under an external electric field, converting the energy of the incident electromagnetic wave into heat energy, and generating conductive losses.

[0123] High entropy perovskites contain magnetic elements and will produce magnetic losses under alternating conditions.

[0124] The synthesized high-entropy perovskite forms a large number of aggregates composed of nanoparticles, which means that there are multiple grains inside the sample. When electromagnetic waves interact with the material, the interface effect between these crystals helps to attenuate the electromagnetic waves.

[0125] In summary, good impedance matching enables electromagnetic waves to enter the interior of the material, and the material itself also has a good electromagnetic wave loss path and a good electromagnetic wave loss effect.

[0126] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A lightweight high entropy perovskite absorbing material, Features: The lightweight high entropy perovskite absorbing material is a high entropy perovskite oxide; the chemical formula of the high entropy perovskite oxide is Sr x (A y Mn y Cr y B y C y ) 3 , wherein x=1-3, y=0.2-0.6; A, B, and C are selected from any three of Fe, Co, Ni, Ti, Zn, Cu, Zr, Ga, Sn, Yb, Eu, Mo, Rh, and Ru.

2. A lightweight high entropy perovskite absorbing material according to claim 1, Features: The structure of the lightweight high entropy perovskite absorbing material is a half-shell hexagonal prism with a large aspect ratio.

3. A method for preparing a lightweight high entropy perovskite absorbing material according to claim 1 or 2, It is characterized in that The following steps are involved: S1, according to the chemical formula Sr x (A y Mn y Cr y B y C y ) 3 Calculate the required amount of Sr oxide, A oxide, Mn oxide, Cr oxide, B oxide and C oxide according to the ratio; S2, weighing the pre-treated raw materials, and then wet-grinding them to obtain a mixture; S3, drying and crushing the solid material obtained after centrifugation of the mixture to obtain a crushed raw material; S4, adding a binder to the crushed raw material and then pressing and molding to obtain a molded sample; S5, the formed sample is sintered at a sintering temperature of 800-1300° C. After sintering, a finished product of a lightweight high entropy perovskite absorbing material is obtained.

4. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S1, the oxide of Sr is SrO; the oxide of Mn is MnO 2 ; Cr oxide is Cr 2 O 3 ; The oxide of A, the oxide of B, and the oxide of C are selected from Fe according to the chemical formula 2 O 3 , Fe 3 O 4 , CoO, NiO, TiO 2 、ZnO、CuO、ZrO 2 、GaO、SnO、Yb 2 O 3 、Eu 2 O 3 、MoO 2 , RhO 2 、RuO 2 Any three of the .

5. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S2, the ball-to-material ratio in the wet grinding process is 3:1, the liquid used in the wet grinding process is deionized water or anhydrous ethanol; the mass ratio of the liquid to the material being ball-milled is 3:1; the wet grinding time is 6 to 12 hours, and the rotation speed is set at 150 to 300 rpm.

6. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S3, the drying temperature is 50-80° C., and the drying time is 6-8 hours.

7. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In the step S4, the adhesive is a 5wt% PVA solution or deionized water; the mass ratio of the adhesive to the crushed raw material is 1:10; During the compression molding process, the molding pressure is 10-30 MPa, and the pressure holding time during molding is 30 seconds.

8. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S5, the atmosphere used in the sintering process is O 2 .

9. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S5, the sintering temperature of the sintering process is changed as follows: firstly, the temperature is raised to the pre-sintering temperature of 750-1250°C for a heat preservation, then the temperature is raised to the sintering temperature of 800-1300°C for a second heat preservation; then the temperature is lowered to 500°C and then cooled with the furnace; The pre-sintering temperature is lower than the sintering temperature; the insulation time of the first insulation is 1 to 5 hours; the insulation time of the second insulation is 0.5 to 4 hours; the heating and cooling rates are both 4 to 10°C / min.

10. The method for preparing a lightweight high entropy perovskite absorbing material according to claim 3, Features: In step S5, during the sintering process, the formed sample is placed in a crucible, the crucible is raised to half the height of the furnace chamber, and a stream of O is passed through the crucible. 2 The sintering is carried out in a high temperature box furnace with a low atmosphere.

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