Reduced graphene oxide supported high-entropy oxide, method of preparation and use

Abstract

The application discloses a reduced graphene oxide loaded high-entropy oxide and a preparation method and application thereof, and relates to the technical field of high-entropy oxides. The preparation method comprises the following steps: ultrasonic treatment is conducted on graphene and metal salt respectively in respective solvents to obtain a metal salt solution and a graphene suspension; the metal salt solution is added into the graphene suspension, urea is added and stirred, and then the obtained mixed solution is pretreated to obtain a precursor powder; and the precursor powder is subjected to plasma flow treatment to obtain the reduced graphene oxide loaded high-entropy oxide. The high-entropy oxide obtained by using the preparation method has the advantages of polycrystal face scattering, excellent impedance matching and strong wave absorption loss capacity, and has a wide application prospect in the electromagnetic field of consumer electronics, new energy vehicles and military weapons.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, and specifically relates to a high-entropy oxide supported on reduced graphene oxide, its preparation method, and its application. Background Technology

[0002] With the commercialization of 5G technology and the booming development of artificial intelligence, electronic devices carrying electromagnetic waves are widely used in fields such as communications, medicine, and energy, accompanying people's lives almost throughout their lives. While high-frequency communication technology has greatly facilitated the efficient transmission of information, its densely distributed electromagnetic radiation seriously interferes with the normal operation of equipment and endangers human health. High-entropy oxides, with their tunable dielectric properties and abundant lattice defects, hold promise as novel electromagnetic wave absorbers for applications in electronic communications, aerospace, and military fields.

[0003] Currently synthesized high-entropy oxides are basically irregular in shape due to long-term crystallization at high temperatures, and their particles often agglomerate into blocks. The input impedance and dielectric parameters of the material are basically adjusted by the composition and content of the high-entropy oxides. It is difficult to control the electromagnetic properties of high-entropy oxides by using microstructure to finely regulate them. In addition, the electromagnetic attenuation capability of single-phase high-entropy oxides is limited, and additional phases need to be added to form heterogeneous composite materials to meet the requirements of electromagnetic absorption. Summary of the Invention

[0004] (I) Purpose of the Invention

[0005] The purpose of this invention is to provide a high-entropy oxide supported on reduced graphene oxide, its preparation method, and its application. The high-entropy oxide obtained by the preparation method of this invention has the advantages of polycrystalline scattering, excellent impedance matching, and strong wave absorption loss capability, and has broad application prospects in the electromagnetic fields of consumer electronics, new energy vehicles, and military weapons.

[0006] (II) Technical Solution

[0007] To address the above problems, a first aspect of the present invention provides a method for preparing a high-entropy oxide supported on reduced graphene oxide, comprising the following steps:

[0008] S1, dissolve graphene and metal salt in their respective solvents and sonicate to obtain metal salt solution and graphene suspension respectively;

[0009] S2, the metal salt solution is added to the graphene suspension, urea is added and stirred, and then the resulting mixture is pretreated to obtain precursor powder.

[0010] S3, the precursor powder is subjected to plasma flow treatment to obtain a high-entropy oxide supported on reduced graphene oxide.

[0011] Furthermore, in step S2, the mass ratio between graphene, metal salt, and urea is controlled to be 1:(1-10):(5-50).

[0012] Furthermore, the metal salt is a soluble metal salt, including iron salts, cobalt salts, nickel salts, copper salts, and manganese salts.

[0013] Furthermore, the pretreatment includes centrifugation, washing, and freeze-drying in sequence.

[0014] Furthermore, in step S3, the plasma jet processing time is 0.5–10 s, and the current is 30–60 A.

[0015] Furthermore, the electrical conductivity of the high-entropy oxide is 0.45–10 S / cm.

[0016] A second aspect of the present invention provides a high-entropy oxide supported on reduced graphene oxide, said high-entropy oxide being obtained by any of the methods described above for preparing high-entropy oxide supported on reduced graphene oxide, wherein the structure of said high-entropy oxide includes tetrahedron, octahedron and truncated octahedron.

[0017] Furthermore, the particle size of the high-entropy oxide is 50–250 nm.

[0018] Furthermore, the high-entropy oxide includes iron, cobalt, nickel, manganese, and copper, and the high-entropy oxide particles account for 10% to 30% of the total mass.

[0019] Furthermore, a third aspect of the present invention provides the application of a high-entropy oxide supported on reduced graphene oxide as described in any of the above descriptions, or a high-entropy oxide supported on reduced graphene oxide prepared by any of the above descriptions, in the electromagnetic field.

[0020] (III) Beneficial Effects

[0021] The above-mentioned technical solution of the present invention has the following beneficial technical effects: The present invention provides a high-entropy oxide supported on reduced graphene oxide, its preparation method, and its application. The high-entropy oxide obtained by the preparation method of the present invention has uniformly loaded particles on the surface of the reduced graphene oxide without particle agglomeration, thereby enhancing impedance matching. The high-entropy oxide has a polyhedral structure, and the polycrystalline structure enhances the multiple scattering of electromagnetic waves. The preparation method is as follows: first, a metal salt solution and a graphene suspension are prepared; then, the metal salt solution is added to the graphene suspension, urea is added and stirred, and then the resulting mixture is pretreated to obtain a precursor powder. Finally, the precursor powder is subjected to plasma flow treatment to obtain the high-entropy oxide supported on reduced graphene oxide. The high-entropy oxide supported on reduced graphene oxide prepared by the present invention has advantages such as polycrystalline scattering, excellent impedance matching, and strong wave absorption loss capability, and has broad application prospects in the electromagnetic fields of consumer electronics, new energy vehicles, and military weapons. Attached Figure Description

[0022] Figure 1 This is a transmission electron microscope (TEM) image of the high-entropy oxide supported on reduced graphene oxide prepared in Example 1 of this invention.

[0023] Figure 2 This is a high-resolution electron microscope image of the high-entropy oxide supported on reduced graphene oxide prepared in Example 1 of this invention;

[0024] Figure 3 This is the energy spectrum of the high-entropy oxide supported on reduced graphene oxide obtained in Example 1 of this invention;

[0025] Figure 4 This is a comparison chart of the electrical conductivity of the high-entropy oxides supported on reduced graphene oxide prepared in Examples 1, 2, and 3 of this invention;

[0026] Figure 5 This is a diagram of the electromagnetic absorption loss of the high-entropy oxide supported on reduced graphene oxide obtained in Example 1 of this invention.

[0027] Figure 6 This is a transmission electron microscope (TEM) image of the high-entropy oxide supported on reduced graphene oxide obtained in Example 2 of this invention.

[0028] Figure 7 This is a high-resolution electron microscope image of the high-entropy oxide supported on reduced graphene oxide obtained in Example 2 of this invention;

[0029] Figure 8 This is the energy spectrum of the high-entropy oxide supported on reduced graphene oxide obtained in Example 2 of this invention;

[0030] Figure 9This is an electromagnetic absorption loss diagram of the high-entropy oxide supported on reduced graphene oxide obtained in Example 2 of the present invention.

[0031] Figure 10 This is a transmission electron microscope (TEM) image of the high-entropy oxide supported on reduced graphene oxide obtained in Example 3 of this invention.

[0032] Figure 11 This is a high-resolution electron microscope image of the high-entropy oxide supported on reduced graphene oxide obtained in Example 3 of this invention.

[0033] Figure 12 This is the energy spectrum of the high-entropy oxide supported on reduced graphene oxide obtained in Example 3 of this invention;

[0034] Figure 13 This is an electromagnetic absorption loss diagram of the high-entropy oxide supported on reduced graphene oxide obtained in Example 3 of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0036] Graphene, as a typical two-dimensional carbon material, possesses a large specific surface area, excellent electrical conductivity, and high stability. Furthermore, graphene can provide anchoring sites during the crystallization of high-entropy oxides, preventing particle agglomeration. Therefore, developing a simple and efficient method for preparing high-entropy oxides supported on reduced graphene oxide with a polyhedral structure is of great significance. To this end, the first aspect of this invention provides a method for preparing high-entropy oxides supported on reduced graphene oxide, comprising the following steps:

[0037] S1, graphene and metal salt are dissolved in their respective solvents and ultrasonically treated to obtain metal salt solutions and graphene suspensions, respectively. The graphene treatment is as follows: graphene serves as the source of reduced graphene oxide in the final preparation of reduced graphene oxide-supported high-entropy oxide. The graphene can be any commercially available type, preferably from Shanghai Aladdin, Titan Technology, or Xiamen Kaina, or several of these. The solvent is any one or several of water, ethanol, methanol, and isopropanol, preferably water. The mass-to-volume ratio of graphene to solvent is (0.25–1.5):1, preferably (0.25–0.75):1, more preferably 0.5:1, in mg / mL. Ultrasound refers to dispersing the graphene solution using an ultrasonic cell disruptor. The cell disruptor has an efficiency of 20–1000W, preferably 300–500W, more preferably 400W. The ultrasonic time is between 45–150 min, preferably 60–90 min, more preferably 60 min. The unique cavitation, mechanical, and thermal effects of ultrasound create localized high temperatures and pressures in the solvent, accompanied by a jet, which promotes the uniform dispersion of graphene into the solvent, forming a graphene suspension. The metal salt treatment is as follows: the metal salts are soluble metal salts, specifically including iron, cobalt, nickel, copper, and manganese salts, preferably ferric chloride, cobalt chloride hexahydrate, nickel chloride hexahydrate, copper chloride, and manganese chloride tetrahydrate. The molar ratio of the soluble metal salts is preferably equimolar, which helps reduce the generation of metal oxide impurities and ensures the formation of single-phase high-entropy oxides. The solvent in this step is the same as the solvent used in the graphene treatment process, preferably water. Ultrasound refers to the dispersion of the metal salt solution using an ultrasonic cleaner. The dispersion time does not need to be too long; it is only necessary to mix the soluble metal salts evenly in the solvent. The ultrasonic time is 3–10 min, preferably 3–5 min, for example, 6 min. The concentration of the corresponding metal ions in each soluble metal salt solution is 0.2–0.6 mol / L, for example, 0.2 mol / L.

[0038] S2, the metal salt solution is added to the graphene suspension, urea is added and stirred, and then the resulting mixture is pretreated to obtain precursor powder. In this step, the mass ratio of graphene, metal salt (metal ions), and urea is controlled at 1:(1-10):(5-50), preferably 1:(2-10):(5-30). Using different ratios will prepare reduced graphene oxide supported on high-entropy oxides with different geometric structures. For example, if the mass ratio of graphene, metal ions, and urea is 1:2.3:7.2, the prepared high-entropy oxide exhibits a tetrahedral structure with a particle size of 50 nm; if the mass ratio of graphene, metal ions, and urea is 1:4.6:14.4, the prepared high-entropy oxide exhibits an octahedral structure with a particle size of 100 nm; if the mass ratio of graphene, metal ions, and urea is 1:9.2:28.8, the prepared high-entropy oxide exhibits a truncated octahedral structure with a particle size of 200 nm. When the mass ratio of graphene, metal salt, and urea is 1:9.2:28.8, and based on the total mass of reduced graphene oxide loaded with high-entropy oxide, the high-entropy oxide accounts for 30% of the total mass, resulting in excellent microwave absorption performance. When adding urea, the stirring speed is 500 r / min to 800 r / min, for example, 600 r / min, and the stirring time is 1 to 2 hours, for example, 2 hours. Pretreatment includes sequential centrifugation, washing, and freeze-drying. The specific pretreatment steps are as follows:

[0039] (1) The mixture is centrifuged and washed multiple times to obtain a precipitate. The solvent is removed by centrifugation at a speed of 5000–10000 rpm, preferably 5000–8000 rpm, more preferably 6000 rpm; the centrifugation time is 5–10 minutes, preferably 8 minutes. After centrifugation, the mixture is washed with either deionized water or anhydrous ethanol, preferably deionized water. In this step, the number of centrifugation and washing cycles is 2–4 times, preferably 3 times. During the washing process, metal ions and chloride ions anchored to the graphene surface are washed away. Therefore, the number of washing cycles should not be too few or too many. Too few cycles result in excess metal ions not being washed away, while too many cycles result in excess metal ions anchored to the graphene surface being washed off.

[0040] (2) The precipitate is freeze-dried to obtain a precursor powder. The freeze-drying time is 24 to 72 hours, preferably 25 to 50 hours, and more preferably 36 hours, wherein the precursor is brownish-green in color.

[0041] S3, the precursor powder is subjected to plasma jet treatment to obtain a high-entropy oxide supported on reduced graphene oxide. Plasma jet treatment of the precursor powder can activate graphene to reduce graphene oxide; simultaneously, five metal ions nucleate and co-melt to form a high-entropy oxide. The plasma jet treatment time is 0.5–10 s, preferably 0.8–2.4 s, for example, 30 A; the current is 30–60 A, preferably 30–40 A, for example, 0.8 s. If the current used during plasma jet treatment is too low and / or the time is too short, the high-entropy oxide cannot be completely co-melted, resulting in metal oxide impurities; if the current used is too high and / or the time is too long, the lightweight graphene component will be instantaneously oxidized at high temperatures, leaving no product residue. The gas used during plasma jet treatment is an inert gas such as nitrogen or argon, which is mainly used to generate plasma and protect the graphene from oxidation at extremely high temperatures. The gas flow rate is 200–500 mL / min, preferably 500 mL / min. When the gas flow rate is too low, the plasma jet cannot completely crystallize and eutecticly melt the high-entropy oxide; however, if the gas flow rate is too high, the plasma jet ionization will be too strong, resulting in the vaporization of graphene with no product residue. The electrical conductivity of the prepared high-entropy oxide is 0.45–10 S / cm.

[0042] Furthermore, a second aspect of the present invention provides a high-entropy oxide supported on reduced graphene oxide, wherein the high-entropy oxide is obtained by any of the preparation methods described above for high-entropy oxide supported on reduced graphene oxide, wherein the particles of the high-entropy oxide are uniformly loaded on the surface of the reduced graphene oxide without particle agglomeration, and the particle size of the high-entropy oxide is 50–250 nm. The high-entropy oxide has a polyhedral structure, including tetrahedrons, octahedrons, and truncated octahedrons.

[0043] Furthermore, the high-entropy oxide comprises iron, cobalt, nickel, manganese, and copper, derived from soluble metal salts, and the high-entropy oxide particles account for 10% to 30% of the total mass. That is, based on the mass of the high-entropy oxide supported on the reduced graphene oxide, the high-entropy oxide loading is 10 to 30 wt%.

[0044] Furthermore, the high-entropy oxide has an electrical conductivity of 0.45–10 S / cm, a minimum reflection loss RLmin of -57 dB at room temperature, and a maximum effective absorption bandwidth (EAB) of 4.13 GHz.

[0045] Furthermore, a third aspect of the present invention provides the application of high-entropy oxides supported on reduced graphene oxide as described in any of the above descriptions, or high-entropy oxides supported on reduced graphene oxide prepared by any of the above descriptions, in the electromagnetic field.

[0046] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0047] Example 1

[0048] Weigh 25 mg of Shanghai Aladdin graphene and place it in 50 mL of water. Use an ultrasonic cell disruptor at 400 W for 60 minutes to obtain a graphene suspension. Prepare five metal salt solutions with water: ferric chloride, cobalt chloride hexahydrate, nickel chloride hexahydrate, copper chloride, and manganese chloride tetrahydrate. The concentration of each metal cation is 0.2 mol / L. Sonicate each metal salt solution under an ultrasonic cleaner for 6 minutes.

[0049] 4 ml of each metal salt solution was added to a 0.5 mg / mL graphene suspension, along with 720 mg of urea. The mass ratio of graphene, metal salt, and urea was 1:9.2:28.8. The metal salt consisted of the total mass of five metal ions (Fe, Co, Ni, Cu, and Mn), with each ion representing 1 mM and a total mass of 230 mg. The mixture was magnetically stirred for 2 hours at 600 rpm. The mixture was then centrifuged and washed three times before being freeze-dried for 36 hours to obtain a brownish-green precursor powder. The precursor powder was then placed directly under a plasma jet and subjected to plasma jet treatment under the following conditions to obtain high-entropy oxide supported on reduced graphene oxide: argon gas (flow rate 500 mL / min), current 30 A, and treatment time 0.8 seconds. The high-entropy oxide structure supported on reduced graphene oxide obtained in Example 1 was a truncated octahedron, accounting for 30 wt% of the total mass. The high-entropy oxide supported on reduced graphene oxide had an electrical conductivity of 0.48 S / cm. Figure 4 As shown.

[0050] The electromagnetic wave absorption performance of the high-entropy oxide supported on the reduced graphene oxide was tested as follows: The high-entropy oxide supported on the reduced graphene oxide was mixed with molten paraffin at a mass ratio of 3:7, and then pressed into a coaxial ring-shaped sample in a mold. The outer diameter of the ring was 7.01 mm and the inner diameter was 3.04 mm. The relative complex permittivity and relative complex permeability of the high-entropy oxide supported on the reduced graphene oxide were measured using a network vector analyzer in the range of 2-18 GHz. The three-dimensional electromagnetic wave absorption and reflection diagram was obtained using the following formula:

[0051]

[0052] In formulas (1) and (2), Z0 is the vacuum characteristic impedance, Z in ε represents the normalized input impedance of the electromagnetic absorbing material.r and μ r Let f represent the relative complex permittivity and relative complex permeability of the material, d represent the thickness of the electromagnetic absorbing material, c represent the speed of light in vacuum, Tanh represent the hyperbolic tangent function, and j represent the imaginary number. The obtained electromagnetic absorption loss and effective bandwidth diagrams are shown below. Figure 5 As shown, reduced graphene oxide loaded with high-entropy oxide exhibits excellent electromagnetic wave absorption performance, with a minimum reflection loss RLmin of -57dB and a maximum effective absorption bandwidth (EAB, the effective absorption bandwidth being the band where the reflection loss is less than -10dB) of 4.13GHz. This is compared with the electromagnetic wave absorption performance diagram of Example 2 (…). Figure 9 The electromagnetic absorption performance diagrams of Example 3 and Example 4 are shown. Figure 13 By comparison, it was found that Example 1 has the strongest electromagnetic wave absorption and reflection loss, and Example 1 is the optimal example. Figure 1 The image shows a transmission electron microscope (TEM) image of the reduced graphene oxide supported on high-entropy oxide. The scale bar is 100 nm. It can be seen that the high-entropy oxide has a truncated octahedral geometry and a particle size of 200 nm. Figure 2 High-resolution electron microscope image of the prepared reduced graphene oxide supported on high-entropy oxide. Figure 2 The morphology and lattice fringes of a single truncated octahedron were characterized. The lattice fringes of 0.484 nm represent the (111) crystal plane of the crystal, which indicates the successful preparation of the high-entropy oxide. Figure 3 The energy spectrum of the reduced graphene oxide supported on the high-entropy oxide is shown. Figure 3 It can be seen that the metallic elements Fe, Co, Ni, Cu, and Mn are uniformly distributed in the crystal without any elemental segregation or separation, further proving the successful synthesis of high-entropy oxides. Figure 4 The diagram shows a comparison of the conductivity of the prepared reduced graphene oxide supported on high-entropy oxide with that of Examples 2 and 3. Figure 5 The electromagnetic absorption loss diagram of the prepared reduced graphene oxide-supported high-entropy oxide is shown.

[0053] Example 2

[0054] Weigh 25 mg of Shanghai Aladdin graphene and place it in 50 mL of water. Use an ultrasonic cell disruptor to sonicate for 60 minutes at 400 W to obtain a suspension. Prepare five metal salt solutions with water: ferric chloride, cobalt chloride hexahydrate, nickel chloride hexahydrate, copper chloride, and manganese chloride tetrahydrate. The concentration of each metal cation is 0.2 mol / L. Sonicate the metal salt solutions for 6 minutes using an ultrasonic cleaner.

[0055] Add 2 ml of each metal salt solution to a 0.5 mg / mL graphene suspension, and add 360 mg of urea, ensuring a mass ratio of graphene, metal salt, and urea of ​​1:4.6:14.4. Stir magnetically for 2 hours at 600 rpm. Then, centrifuge and wash the mixture three times before freeze-drying for 36 hours to obtain a brownish-green precursor powder.

[0056] By placing the precursor powder directly below the plasma jet and performing plasma jet treatment under the following conditions, reduced graphene oxide loaded with high entropy oxide can be obtained: the gas used is argon (flow rate of 500 ml / min), the current is 30 A, and the treatment time is 0.8 seconds.

[0057] The high-entropy oxide supported on the prepared reduced graphene oxide has an octahedral geometry, accounting for 21 wt% of the total mass. The conductivity of the high-entropy oxide supported on the reduced graphene oxide is 2.5 S / cm. Figure 4 As shown. The reduced graphene oxide loaded with high-entropy oxide was subjected to electromagnetic wave absorption performance testing according to the procedure in Example 1. The testing procedure in Example 2 was the same as that in Example 1. Figure 6 The image shows a transmission electron microscope (TEM) image of the prepared reduced graphene oxide loaded with high-entropy oxide. It can be seen that the high-entropy oxide has an octahedral geometry and a particle size of 100 nm. Figure 7 This shows a high-resolution electron microscope image of the prepared reduced graphene oxide supported on high-entropy oxide. Figure 7 The morphology and lattice fringes of individual octahedrons were characterized. The 0.484 nm lattice fringes represent the (111) crystal plane, demonstrating the successful preparation of the high-entropy oxide. Figure 8 The energy spectrum of the reduced graphene oxide supported on the high-entropy oxide is shown. Figure 8 It can be seen that the metallic elements Fe, Co, Ni, Cu, and Mn are uniformly distributed in the crystal, without any elemental segregation or separation. Figure 9 The electromagnetic absorption loss diagram of the prepared reduced graphene oxide-loaded high-entropy oxide is shown. It can be seen that the minimum reflection loss RLmin is -18.1dB and the maximum effective absorption bandwidth is 5.1GHz.

[0058] Example 3

[0059] Weigh 25 mg of Shanghai Aladdin graphene and place it in 50 mL of water. Use an ultrasonic cell disruptor to sonicate for 60 minutes at 400 W to obtain a suspension. Prepare five metal salt solutions with water: ferric chloride, cobalt chloride hexahydrate, nickel chloride hexahydrate, copper chloride, and manganese chloride tetrahydrate. The concentration of each metal cation is 0.2 mol / L. Sonicate the metal salt solutions for 6 minutes using an ultrasonic cleaner.

[0060] Add 1 ml of each metal salt solution to a 0.5 mg / mL graphene suspension, and add 180 mg of urea. The mass ratio of graphene, metal salt, and urea should be 1:2.3:7.2. Stir magnetically for 2 hours at a speed of 600 r / min. Then, centrifuge and wash the mixture three times, and freeze-dry for 36 hours to obtain a brownish-green precursor powder. Place the precursor powder directly under a plasma jet and perform plasma jet treatment under the following conditions to obtain reduced graphene oxide supported on high-entropy oxide: argon gas (flow rate 500 mL / min), current 30 A, and treatment time 0.8 seconds. In Example 3, the high-entropy oxide in the reduced graphene oxide supported on high-entropy oxide has a tetrahedral geometry, accounting for 12 wt% of the total mass. The conductivity of the reduced graphene oxide supported on high-entropy oxide is 10.02 S / cm. Figure 4 As shown.

[0061] The reduced graphene oxide loaded with high-entropy oxide was subjected to electromagnetic wave absorption performance testing according to the procedure in Example 1. The testing procedure in Example 3 was the same as that in Example 1. Figure 10 The image shows a transmission electron microscope (TEM) image of the prepared reduced graphene oxide loaded with high-entropy oxide. It can be seen that the high-entropy oxide has a tetrahedral geometry and a particle size of 50 nm. Figure 11 This shows a high-resolution electron microscope image of the prepared reduced graphene oxide supported on high-entropy oxide. Figure 11 The morphology and lattice fringes of a single tetrahedron were characterized. The lattice fringes of 0.486 nm represent the (111) crystal plane of the crystal. Figure 12 The energy spectrum of the reduced graphene oxide supported on the high-entropy oxide is shown. Figure 12 It can be seen that the metallic elements Fe, Co, Ni, Cu, and Mn are uniformly distributed in the crystal, without any elemental segregation or separation. Figure 13 The electromagnetic absorption loss diagram of the prepared reduced graphene oxide loaded with high-entropy oxide is shown. It can be seen that the minimum reflection loss RLmin is -7dB and the maximum effective absorption bandwidth is 0GHz.

[0062] This invention proposes a high-entropy oxide supported on reduced graphene oxide, its preparation method, and its applications. In the preparation method, five metal salts and urea are placed in a graphene dispersion, and the high-entropy oxide supported on reduced graphene oxide is obtained by sequential centrifugation, freeze-drying, and plasma jet injection. In the obtained high-entropy oxide supported on reduced graphene oxide, the high-entropy oxide with a geometrical structure is uniformly loaded on the surface of the reduced graphene oxide, enhancing the multiple scattering of electromagnetic waves. This high-entropy oxide supported on reduced graphene oxide exhibits excellent impedance matching and strong absorption loss capabilities, showing huge market demand and broad application prospects in consumer electronics, medical devices, and automotive energy fields. This invention has the following advantages:

[0063] (1) The high-entropy oxide supported on reduced graphene oxide provided by the present invention has the advantages of polycrystalline surface scattering, excellent impedance matching and strong wave absorption loss capability, and has broad application prospects in the electromagnetic fields of consumer electronics, new energy vehicles and military weapons.

[0064] (2) The high-entropy oxide supported on reduced graphene oxide provided by the present invention has a polyhedral structure, including tetrahedrons, octahedrons and truncated octahedrons. The polycrystalline structure enhances the multiple scattering of electromagnetic waves.

[0065] (3) The present invention provides a high-entropy oxide with a particle size between 50 and 250 nm loaded on the surface of reduced graphene oxide, which enhances impedance matching and the electrical conductivity of the composite material is between 0.45 and 10 S / cm.

[0066] (4) The preparation method provided by the present invention utilizes plasma jet to promote the entropy forming process of metal elements and the transformation of graphene into reduced graphene oxide; at the same time, the extremely fast heating rate allows the reduced graphene oxide to retain the thin-layer microporous structure, avoiding high-temperature vaporization under oxygen.

[0067] (5) The preparation method provided by the present invention has a plasma heating duration in the range of 0.5 to 10 seconds, which improves the preparation efficiency of high entropy oxides and makes it easy to realize industrial production.

[0068] Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention. In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. It should be understood that the above specific embodiments of this invention are merely illustrative or explanatory of the principles of this invention and do not constitute a limitation on this invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this invention should be included within the scope of protection of this invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries. The invention has been described above with reference to embodiments thereof. However, these embodiments are merely for illustrative purposes and are not intended to limit the scope of this invention. The scope of this invention is defined by the appended claims and their equivalents. Without departing from the scope of this invention, those skilled in the art can make various substitutions and modifications, all of which should fall within the scope of this invention. Although embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and modifications can be made to the embodiments of the present invention without departing from the spirit and scope of the invention. Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A method for preparing a high-entropy oxide supported on reduced graphene oxide, characterized in that, Includes the following steps: S1, dissolve graphene and metal salt in their respective solvents and sonicate to obtain metal salt solution and graphene suspension respectively, wherein the metal salt is a soluble metal salt, including iron salt, cobalt salt, nickel salt, copper salt and manganese salt. S2, the metal salt solution is added to the graphene suspension, urea is added and stirred, and then the resulting mixture is pretreated to obtain precursor powder. During mixing, the mass ratio between graphene, metal salt and urea is controlled as 1:(1~10):(5~50); the pretreatment includes centrifugation, washing and freeze drying in sequence; S3, the precursor powder is subjected to plasma jet treatment to obtain high-entropy oxide supported on reduced graphene oxide. In the plasma jet treatment process, the gas used is nitrogen or argon inert gas, the gas flow rate is 200~500 ml / min, the plasma jet treatment time is 0.5~10s, and the current is 30~60 A.

2. The method for preparing high-entropy oxide supported on reduced graphene oxide according to claim 1, characterized in that, The high-entropy oxide has an electrical conductivity of 0.45~10 S / cm.

3. A high-entropy oxide supported on reduced graphene oxide, characterized in that, The high-entropy oxide is obtained by the preparation method of high-entropy oxide supported on reduced graphene oxide according to claims 1-2, and the structure of the high-entropy oxide includes tetrahedron, octahedron and truncated octahedron.

4. The high-entropy oxide supported on reduced graphene oxide according to claim 3, characterized in that, The particle size of the high-entropy oxide is 50~250nm.

5. The high-entropy oxide supported on reduced graphene oxide according to claim 3, characterized in that, The high-entropy oxides include iron, cobalt, nickel, manganese and copper, and the high-entropy oxide particles account for 10% to 30% of the total mass.

6. The application of the high-entropy oxide supported on reduced graphene oxide prepared by the preparation method according to any one of claims 1-2 or the high-entropy oxide supported on reduced graphene oxide according to any one of claims 3-5 in the electromagnetic field.

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