Electromagnetic wave absorbent based on CeFe-PBA and preparation method thereof

Abstract

The invention discloses an electromagnetic wave absorbent based on CeFe-PBA and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbents. The preparation method comprises the following steps: 1) adding polyvinylpyrrolidone into a cerium salt aqueous solution, uniformly mixing, and then sequentially mixing with ethanol and a potassium ferricyanide aqueous solution to prepare CeFe-PBA precursor powder; (2) the precursor powder is subjected to a carbon thermal reduction reaction, and Fe-CeO2 powder is obtained; (3) the Fe-CeO2 powder is dissolved in a Tris dilute solution, then dopamine hydrochloride is added, and Fe-CeO2 (at) PDA powder is prepared; 4, the Fe-CeO2 (at) PDA powder is subjected to a carbon thermal reduction reaction in the N2 atmosphere, and the CeO2 / Fe3C (at) C electromagnetic wave absorbent is prepared. The method is simple in technological operation, controllable in condition, stable in hollow structure, high in conversion rate and good in repeatability, and the obtained absorbent has excellent microwave absorption performance and has industrial application prospects.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic wave absorbers, and particularly relates to a CeFe-PBA-based electromagnetic wave absorber and a preparation method thereof. BACKGROUND

[0002] Electromagnetic wave absorbers can effectively overcome electromagnetic interference and are a key approach to addressing increasingly severe electromagnetic pollution problems. Metal-organic frameworks (MOFs) have the advantages of large specific surface area, high porosity, many active sites, and designable chemical composition, and are considered as a very promising precursor material for preparing electromagnetic wave absorbers.

[0003] Single-metal MOF materials can be derived into composite materials of metals, metal oxides, and metal carbides and carbon after high-temperature pyrolysis. However, single-metal MOF-derived composites have simple structures, single electromagnetic energy loss mechanisms, lack of synergistic effects of multiple mechanisms, and are difficult to achieve effective matching with the impedance of free space, making it difficult to meet the requirements of minimum reflection loss and effective frequency bandwidth for actual applications. To improve the impedance matching ability of the material, the magnetism synergistic effect can be used, that is, by simultaneously introducing magnetic metal materials and non-magnetic metal oxide materials, the high magnetic permeability of the magnetic metal and the low dielectric loss characteristics of the non-magnetic oxide are utilized to reduce the difference between the dielectric constant and the magnetic permeability, and improve the impedance matching performance of the material in a wide frequency band. However, during the high-temperature carbonization or pyrolysis process of the MOF material prepared by this method, the magnetic metal particles are prone to agglomeration, resulting in a decrease in active sites and a decrease in interface polarization effect. In addition, by preparing a microwave absorbing material with a hollow structure, electromagnetic waves can more easily enter the interior of the material, enhancing the impedance matching effect. At the same time, the hollow structure has a higher specific surface area and porosity, which can reduce the material filling amount, save costs, and make the material lighter in mass and smaller in volume. However, hollow structure materials are often unstable and prone to collapse. SUMMARY

[0004] The purpose of the present application is to provide a CeFe-PBA-based electromagnetic wave absorber and a preparation method thereof. The absorber has uniform shape and size, a stable hollow structure, excellent microwave absorption performance, simple process operation, controllable conditions, high conversion rate, good repeatability, low cost, and industrial application prospects.

[0005] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows: A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, comprising the following steps: 1) Polyvinylpyrrolidone is added to a cerium salt aqueous solution and stirred at a speed of 300-500 rpm for 10-25 min to obtain a solution A; the solution A is mixed with ethanol to obtain a solution B; the solution B is mixed with a potassium ferricyanide aqueous solution to obtain a solution C, which is stirred and then left to stand to obtain a CeFe-PBA precursor powder; wherein: the mass ratio of the cerium salt to polyvinylpyrrolidone is 1:10-15; the solid-liquid ratio in the cerium salt aqueous solution is 25-35 g / L; in the solution C, the volume ratio of water to ethanol is 1.5-4:1; 2) The CeFe-PBA precursor powder obtained in step 1) is subjected to a carbothermal reduction reaction to obtain a Fe-CeO2 powder; 3) The Fe-CeO2 powder obtained in step 2) is dissolved in a Tris dilute solution, and then dopamine hydrochloride is added, which is stirred and then left to stand to obtain a Fe-CeO2@PDA powder; wherein the mass ratio of the Fe-CeO2 powder to dopamine hydrochloride is 1-3:1; 4) The Fe-CeO2@PDA powder obtained in step 3) is subjected to a carbothermal reduction reaction under a N2 atmosphere to obtain a CeO2 / Fe3C@C electromagnetic wave absorber; wherein the carbothermal reduction reaction temperature is 700-900℃, and the time is 1-5 h.

[0006] According to the above scheme, in step 1), the cerium salt is one of cerium nitrate, cerium sulfate, cerium acetate, cerium oxalate and cerium fluoride.

[0007] According to the above scheme, in step 1), the mass ratio of the cerium salt to potassium ferricyanide is 1:1-5.

[0008] According to the above scheme, in step 1), the volume ratio of the solution A to ethanol is 1:2-6.

[0009] According to the above scheme, in step 1), the solution A is mixed with ethanol, and stirred for 10-20 min to obtain the solution B. Preferably, the stirring speed is 200-500 rpm.

[0010] According to the above scheme, in step 1), the solid-liquid ratio in the potassium ferricyanide aqueous solution is 8-15 g / L, i.e. 8-15 g of potassium ferricyanide corresponds to 1 L of water.

[0011] According to the above scheme, in step 1), the volume ratio of the solution B to the potassium ferricyanide aqueous solution is 1:1-3.

[0012] According to the above scheme, in step 1), the solution B is mixed with the potassium ferricyanide aqueous solution, which is stirred for 10-30 min and then left to stand for 8-12 h to obtain the CeFe-PBA precursor powder. Preferably, the stirring speed is 200-500 rpm.

[0013] According to the above scheme, in the step 1), the average particle size of the obtained CeFe-PBA precursor powder is 2.23-3.17 μm.

[0014] According to the above scheme, in the step 2), the temperature of the carbothermic reduction reaction is 600-800 ℃, and the time is 1-5 h; preferably, the heating rate is 1-5 ℃ / min.

[0015] According to the above scheme, in the step 3), the volume ratio of the Tris solution to water in the Tris dilute solution is 1:1-10. The Tris solution is a commonly used biochemical buffer, and the main component is Tris (tris(hydroxymethyl) aminomethane).

[0016] According to the above scheme, in the step 3), the solid-liquid ratio of the Fe-CeO2 powder to the Tris dilute solution is 2-12 g / L.

[0017] According to the above scheme, in the step 3), the stirring time is 10-30 min, and the standing time is 5-15 h. Preferably, the stirring speed is 200-500 rpm.

[0018] According to the above scheme, in the step 4), the heating rate is 1-5 ℃ / min.

[0019] Provided is a CeFe-PBA-based electromagnetic wave absorber prepared by the above preparation method.

[0020] According to the above scheme, the electromagnetic wave absorber has a spindle morphology, uniform particle size, and a hollow core-shell structure, wherein the core layer comprises CeO2 and Fe3C, and the outer shell is a carbon matrix.

[0021] Preferably, the average particle size of the electromagnetic wave absorber is 2.23-3.17 μm.

[0022] The application provides a preparation method of an electromagnetic wave absorber based on CeFe-PBA. First, potassium ferricyanide is used as an organic ligand, cerium in a cerium salt is used as a metal center, and water and ethanol are used as reaction solvents to prepare a CeFe-PBA precursor powder under the action of a surfactant polyvinylpyrrolidone. Appropriate polyvinylpyrrolidone is added to a cerium salt aqueous solution with a proper concentration, and stirring and dispersion are performed at a suitable rotating speed and for a proper time to promote uniform dispersion of the polyvinylpyrrolidone in the cerium salt aqueous solution. Then, a spindle-shaped CeFe-PBA precursor powder with controllable morphology and uniform particle size is obtained by combining a suitable feeding sequence and regulating the ratio of deionized water and ethanol, and the particle size is suitable, which is beneficial to subsequent construction of a hollow structure. Then, the CeFe-PBA precursor powder is subjected to a carbothermal reduction reaction to obtain Fe-CeO2 powder, and the Fe-CeO2 powder is reacted with hydrochloric acid dopamine with a proper ratio to effectively protect the structure and morphology of the template from being damaged and realize formation of a hollow structure in a subsequent step. Then, the carbothermal reduction reaction is performed at a suitable temperature and for a suitable time, and the spindle-shaped CeO2 / Fe3C@C electromagnetic wave absorber with a hollow core-shell structure is basically converted, the CeO2 / Fe3C is uniformly dispersed, the spindle-shaped structure is stable, the obtained hollow structure is not easy to collapse, the conversion rate is high, and the repeatability is good, which is beneficial to batch production.

[0023] The application has the following beneficial effects: 1. The application provides an electromagnetic wave absorber based on CeFe-PBA, which has a spindle-shaped morphology, uniform particle size, and a hollow core-shell structure. The core layer comprises CeO2 and Fe3C, and the shell is a carbon matrix. The uniform distribution of Fe magnetic metal, CeO2 non-magnetic metal oxide, and carbon layer synergistically realizes better impedance matching, and in combination with the stable hollow structure, multiple heterogeneous interfaces, and the layered conformation of the core-shell structure, the impedance matching is greatly improved, the effective bandwidth of the CeO2 / Fe3C@C electromagnetic wave absorber is improved, the reflection loss is strong, and the application prospect is important.

[0024] 2. The application provides a preparation method of an electromagnetic wave absorber based on CeFe-PBA. First, potassium ferricyanide is used as an organic ligand, cerium in a cerium salt is used as a metal center, and water and ethanol are used as reaction solvents to prepare a CeFe-PBA precursor powder under the action of a surfactant polyvinylpyrrolidone. Appropriate polyvinylpyrrolidone is added to a cerium salt aqueous solution with a proper concentration, and stirring and dispersion are performed at a suitable rotating speed and for a proper time to promote uniform dispersion of the polyvinylpyrrolidone in the cerium salt aqueous solution. Then, a spindle-shaped CeFe-PBA precursor powder with controllable morphology and uniform particle size is obtained by combining a suitable feeding sequence and regulating the ratio of deionized water and ethanol, and the particle size is suitable, which is beneficial to subsequent construction of a hollow structure. Then, the CeFe-PBA precursor powder is subjected to a carbothermal reduction reaction to obtain Fe-CeO2 powder, and the Fe-CeO2 powder is reacted with hydrochloric acid dopamine with a proper ratio to effectively protect the structure and morphology of the template from being damaged and realize formation of a hollow structure in a subsequent step. Then, the carbothermal reduction reaction is performed at a suitable temperature and for a suitable time, and the spindle-shaped CeO2 / Fe3C@C electromagnetic wave absorber with a hollow core-shell structure is basically converted, the CeO2 / Fe3C is uniformly dispersed, the spindle-shaped structure is stable, the obtained hollow structure is not easy to collapse, the conversion rate is high, and the repeatability is good, which is beneficial to batch production. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 shows the CeFe-PBA precursor powder prepared in Example 1 of this invention. Figure 1 a) and CeO2 / Fe3C@C electromagnetic wave absorber ( Figure 1 (b) Scanning electron microscope image; Figure 2 is a transmission electron microscope image of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present invention; Figure 3 is an X-ray diffraction pattern of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present invention; Figure 4 shows the reflection loss of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present invention at frequencies of 2~18GHz and thicknesses of 1~3 mm. Detailed Implementation

[0026] The present invention will be further described and explained below with reference to the accompanying drawings and specific embodiments. All embodiments herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0027] Example 1 A method for preparing an electromagnetic wave absorber based on CeFe-PBA is provided, comprising the following steps: Step 1: According to the mass ratio of cerium nitrate to polyvinylpyrrolidone of 1:12, the polyvinylpyrrolidone powder is placed in the aqueous solution of cerium nitrate, mixed, and stirred at 300 rpm for 10 min to obtain solution A; The solid-liquid ratio in the cerium nitrate aqueous solution is 30 g / L; Step 2: Mix the solution A and ethanol, and stir at 300 rpm for 10 min to obtain solution B; Step 3: Dissolve potassium ferricyanide in pure water at a solid-liquid ratio of 8.8 g / L, and stir at 300 rpm for 10 min to obtain a potassium ferricyanide solution. Step 4: Mix the solution B and the potassium ferricyanide solution to obtain solution C, stir at 300 rpm for 10 min, place at room temperature for 12 h, separate the solid and liquid, wash, and dry to obtain CeFe-PBA precursor powder; wherein: in solution C, the volume ratio of water to ethanol is 1.8:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:1. Step 5: The CeFe-PBA precursor powder is subjected to a carbothermic reduction reaction at 600℃ for 1 h to obtain Fe-CeO2 powder; wherein the heating rate is 2℃ / min.

[0028] Step 6: Dissolve the Fe-CeO2 powder in a dilute Tris solution at a solid-liquid ratio of 2 g / L to obtain solution D; The volume ratio of Tris solution in the Tris dilute solution and pure water is 1:9; Step 7, according to the mass ratio of Fe-CeO2 powder: dopamine hydrochloride 1.3:1, dopamine hydrochloride is placed in solution D, stirring at a speed of 200 rpm for 30 min, and placed at room temperature for 10 h, solid-liquid separation, washing, drying, to obtain Fe-CeO2@PDA powder; Step 8, the Fe-CeO2@PDA powder is placed in a N2 atmosphere, and a carbothermal reduction reaction is carried out at 750℃ for 1.5 h to prepare a CeO2 / Fe3C@C electromagnetic wave absorber, achieving a high conversion rate of more than 80% of the precursor into a hollow structure electromagnetic wave absorber; wherein the heating rate is 5℃ / min.

[0029] Comparative Example 1 The specific preparation process refers to Example 1, except that the mass ratio of cerium nitrate: polyvinylpyrrolidone is 1:20, and the polyvinylpyrrolidone agglomerates when dissolved, resulting in uneven final template size, leading to a decrease in the performance of the final wave absorber material.

[0030] Comparative Example 2 The specific preparation process refers to Example 1, except that in solution C, the volume ratio of water to ethanol is 1:3, and the amount of water added is less, resulting in a final template size that is too small, with an average particle size of about 1.5 μm, leading to a hollow structure that cannot be achieved after sintering of the final wave absorbing material.

[0031] Comparative Example 3 The specific preparation process refers to Example 1, except that the mass ratio of Fe-CeO2 powder: dopamine hydrochloride is 5:1, and the amount of dopamine hydrochloride coating is insufficient to protect the precursor template, resulting in structure collapse after sintering.

[0032] Example 2 A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, comprising the following steps: Step 1, according to the mass ratio of cerium sulfate: polyvinylpyrrolidone 1:12, the polyvinylpyrrolidone powder is placed in the cerium sulfate aqueous solution, mixed, and stirred at a speed of 400 rpm for 15 min to obtain solution A; The solid-liquid ratio in the cerium sulfate aqueous solution is 30 g / L; Step 2, the solution A and ethanol are mixed, and stirred at a speed of 400 rpm for 10 min to obtain solution B; Step 3, according to the solid-liquid ratio of 8 g / L, potassium ferricyanide is dissolved in pure water, and stirred at a speed of 400 rpm for 10 min to obtain a potassium ferricyanide solution; Step 4, mixing the solution B and the potassium ferricyanide solution to obtain a solution C, stirring at a speed of 400 rpm for 10 min, standing at room temperature for 10 h, solid-liquid separation, washing, and drying to obtain a CeFe-PBA precursor powder; wherein: in the solution C, the volume ratio of water to ethanol is 3.8:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:4.8; Step 5, performing a carbothermal reduction reaction on the CeFe-PBA precursor powder at 650℃ for 2 h to obtain a Fe-CeO2 powder; wherein the temperature rising rate is 2 ℃ / min Step 6, dissolving the Fe-CeO2 powder in a Tris dilute solution at a solid-liquid ratio of 2 g / L to obtain a solution D; The volume ratio of the Tris solution in the Tris dilute solution to pure water is 1:9; Step 7, putting dopamine hydrochloride into the solution D at a mass ratio of Fe-CeO2 powder to dopamine hydrochloride of 1:1, stirring at a speed of 400 rpm for 15 min, standing at room temperature for 10 h, solid-liquid separation, washing, and drying to obtain a Fe-CeO2@PDA powder; Step 8, placing the Fe-CeO2@PDA powder in a N2 atmosphere, and performing a carbothermal reduction reaction at 900℃ for 2 h to obtain a CeO2 / Fe3C@C electromagnetic wave absorber; wherein the temperature rising rate is 2 ℃ / min.

[0033] Example 3 A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, which comprises the following steps: Step 1, putting polyvinylpyrrolidone powder into a cerium acetate aqueous solution at a mass ratio of cerium acetate to polyvinylpyrrolidone of 1:10, mixing, and stirring at a speed of 300 rpm for 20 min to obtain a solution A; The solid-liquid ratio in the cerium acetate aqueous solution is 33 g / L; Step 2, mixing the solution A and ethanol, and stirring at a speed of 300 rpm for 10-20 min to obtain a solution B; Step 3, dissolving potassium ferricyanide in pure water at a solid-liquid ratio of 9 g / L, and stirring at a speed of 300 rpm for 10 min to obtain a potassium ferricyanide solution; Step 4, mixing the solution B and the potassium ferricyanide solution to obtain a solution C, stirring at a speed of 300 rpm for 20 min, standing at room temperature for 12 h, solid-liquid separation, washing, and drying to obtain a CeFe-PBA precursor powder; wherein: in the solution C, the volume ratio of water to ethanol is 3.5:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:1.6; Step 5, carbonthermal reduction reaction of the CeFe-PBA precursor powder at 700℃ for 2 h to obtain Fe-CeO2 powder; wherein the heating rate is 3 ℃ / min Step 6, dissolving the Fe-CeO2 powder in a Tris dilute solution at a solid-liquid ratio of 6 g / L to obtain solution D; The volume ratio of Tris solution to pure water in the Tris dilute solution is 1:6; Step 7, putting dopamine hydrochloride into solution D at a mass ratio of Fe-CeO2 powder to dopamine hydrochloride of 2:1, stirring at a speed of 300 rpm for 15 min, placing at room temperature for 6 h, solid-liquid separation, washing, and drying to obtain Fe-CeO2@PDA powder; Step 8, carbonthermal reduction reaction of the Fe-CeO2@PDA powder under N2 atmosphere at 750℃ for 2 h to obtain CeO2 / Fe3C@C electromagnetic wave absorber, wherein the heating rate is 3 ℃ / min.

[0034] Example 4 A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, comprising the following steps: Step 1, putting polyvinylpyrrolidone powder into cerium oxalate aqueous solution at a mass ratio of cerium oxalate to polyvinylpyrrolidone of 1:12, mixing, and stirring at a speed of 400 rpm for 20 min to obtain solution A; The solid-liquid ratio in the cerium oxalate aqueous solution is 32 g / L; Step 2, mixing solution A and ethanol, and stirring at a speed of 400 rpm for 15 min to obtain solution B; Step 3, dissolving potassium ferricyanide in pure water at a solid-liquid ratio of 10 g / L, and stirring at a speed of 400 rpm for 10 min to obtain a potassium ferricyanide solution; Step 4, mixing solution B and the potassium ferricyanide solution to obtain solution C, stirring at a speed of 400 rpm for 20 min, placing at room temperature for 12 h, solid-liquid separation, washing, and drying to obtain CeFe-PBA precursor powder; wherein: in solution C, the volume ratio of water to ethanol is 2.5:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:4.4; Step 5, carbonthermal reduction reaction of the CeFe-PBA precursor powder at 750℃ for 3 h to obtain Fe-CeO2 powder, wherein the heating rate is 5 ℃ / min; Step 6, dissolving the Fe-CeO2 powder in a Tris dilute solution at a solid-liquid ratio of 10 g / L to obtain solution D; The volume ratio of Tris solution to pure water in the Tris dilute solution is 1:7; Step 7, according to the mass ratio of Fe-CeO2 powder: dopamine hydrochloride 2:1, dopamine hydrochloride is placed into solution D, stirring at a speed of 400 rpm for 20 min, and placed at room temperature for 10 h, solid-liquid separation, washing, and drying to obtain Fe-CeO2@PDA powder; Step 8, the Fe-CeO2@PDA powder is placed in a N2 atmosphere, and a carbothermal reduction reaction is carried out at 800℃ for 3 h to obtain a CeO2 / Fe3C@C electromagnetic wave absorber, wherein the heating rate is 5 ℃ / min.

[0035] Example 5 A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, comprising the following steps: Step 1, according to the mass ratio of cerium fluoride: polyvinylpyrrolidone 1:15, the polyvinylpyrrolidone powder is placed in the cerium fluoride aqueous solution, mixed, and stirred at a speed of 450 rpm for 25 min to obtain solution A; The solid-liquid ratio in the cerium fluoride aqueous solution is 30 g / L; Step 2, the solution A and ethanol are mixed, and stirred at a speed of 450 rpm for 20 min to obtain solution B; Step 3, according to the solid-liquid ratio of 10 g / L, potassium ferricyanide is dissolved in pure water, and stirred at a speed of 450 rpm for 20 min to obtain a potassium ferricyanide solution; Step 4, the solution B and the potassium ferricyanide solution are mixed to obtain solution C, and stirred at a speed of 450 rpm for 30 min, and placed at room temperature for 12 h, solid-liquid separation, washing, and drying to obtain a CeFe-PBA precursor powder; wherein: in solution C, the volume ratio of water to ethanol is 2.6:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:4; Step 5, the CeFe-PBA precursor powder is subjected to a carbothermal reduction reaction at 800℃ for 3 h to obtain Fe-CeO2 powder, wherein the heating rate is 5 ℃ / min; Step 6, according to the solid-liquid ratio of 10 g / L, the Fe-CeO2 powder is dissolved in a Tris dilute solution to obtain solution D; The volume ratio of Tris solution to pure water in the Tris dilute solution is 1:9; Step 7, according to the mass ratio of Fe-CeO2 powder: dopamine hydrochloride 2.5:1, dopamine hydrochloride is placed into solution D, stirring at a speed of 450 rpm for 20 min, and placed at room temperature for 12 h, solid-liquid separation, washing, and drying to obtain Fe-CeO2@PDA powder; Step 8, the Fe-CeO2@PDA powder is placed in a N2 atmosphere, and a carbothermic reduction reaction is carried out at 900°C for 3h, to obtain a CeO2 / Fe3C@C electromagnetic wave absorber, wherein the temperature increasing rate is 5°C / min.

[0036] Example 6 A preparation method of a CeFe-PBA-based electromagnetic wave absorber is provided, comprising the following steps: Step 1, the polyvinylpyrrolidone powder is placed in the cerium nitrate aqueous solution, mixed, and stirred at a speed of 500 rpm for 20 min to obtain solution A, according to the mass ratio of cerium nitrate to polyvinylpyrrolidone being 1:13; The solid-liquid ratio in the cerium nitrate aqueous solution is 35 g / L; Step 2, the solution A and ethanol are mixed, and stirred at a speed of 500 rpm for 20 min to obtain solution B; Step 3, according to the solid-liquid ratio of 15 g / L, potassium ferricyanide is dissolved in pure water, and stirred at a speed of 500 rpm for 20 min to obtain a potassium ferricyanide solution; Step 4, the solution B and the potassium ferricyanide solution are mixed to obtain solution C, and stirred at a speed of 500 rpm for 30 min, and placed at room temperature for 12 h, and then solid-liquid separation, washing and drying are carried out to obtain a CeFe-PBA precursor powder; wherein: in the solution C, the volume ratio of water to ethanol is 1.7:1, and the mass ratio of cerium nitrate to potassium ferricyanide is 1:1.7; Step 5, the CeFe-PBA precursor powder is subjected to a carbothermic reduction reaction at 700°C for 5h to obtain a Fe-CeO2 powder, wherein the temperature increasing rate is 3°C / min; Step 6, according to the solid-liquid ratio of 12 g / L, the Fe-CeO2 powder is dissolved in a Tris dilute solution to obtain solution D; The volume ratio of the Tris solution to pure water in the Tris dilute solution is 1:10; Step 7, according to the mass ratio of Fe-CeO2 powder to hydrochloric acid dopamine being 2:1, the hydrochloric acid dopamine is placed into the solution D, and stirred at a speed of 500 rpm for 30 min, and placed at room temperature for 15 h, and then solid-liquid separation, washing and drying are carried out to obtain a Fe-CeO2@PDA powder; Step 8, the Fe-CeO2@PDA powder is placed in a N2 atmosphere, and a carbothermic reduction reaction is carried out at 900°C for 5h to obtain a CeO2 / Fe3C@C electromagnetic wave absorber, wherein the temperature increasing rate is 3°C / min.

[0037] Figure 1 is a scanning electron microscope picture of the CeFe-PBA precursor powder and the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present application; wherein Figure 1(a) is a scanning electron microscope picture of the CeFe-PBA precursor, and Figure 1(b) is a scanning electron microscope picture of the CeO2 / Fe3C@C electromagnetic wave absorber. As can be seen from Figure 1(a), the CeFe-PBA shows regular spindles, indicating smoothness, uniform shape and size; as can be seen from Figure 1(b), the prepared CeO2 / Fe3C@C inherits the spindle morphology of the CeFe-PBA template, and the particle surface becomes rough, and the precursor is converted into the CeO2 / Fe3C@C electromagnetic wave absorber.

[0038] Figure 2 Figure 2 is a transmission electron microscope picture of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present application; as can be seen from Figure 2, the prepared CeO2 / Fe3C@C electromagnetic wave absorber particle is a spindle, showing an obvious hollow structure, the inside is composed of CeO2 and Fe3C, and the shell is composed of a carbon matrix derived from polydopamine. The hollow spindle structure with a variety of heterogeneous components uniformly dispersed inside and outside the shell can provide multiple interface losses and multiple scattering, which is conducive to obtaining a CeO2 / Fe3C@C electromagnetic wave absorber material with excellent microwave absorption performance.

[0039] Figure 3 is an X-ray diffraction pattern of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present application; as can be seen from Figure 3, there are three characteristic peaks of CeO2 at 28.6°, 47.7° and 56.5° (JCPDS No. 75-0076), so the presence of CeO2 in the CeO2 / Fe3C@C electromagnetic wave absorber can be confirmed. There are two characteristic peaks of Fe3C at 37.7° and 43.0° (JCPDS No. 76-1877), so the presence of Fe3C in the CeO2 / Fe3C@C electromagnetic wave absorber can be confirmed.

[0040] Figure 4 is a reflection loss plot of the CeO2 / Fe3C@C electromagnetic wave absorber prepared in Example 1 of the present application at a frequency of 2-18 GHz and a thickness of 1-3 mm; as can be seen from Figure 4, the minimum reflection loss of the prepared CeO2 / Fe3C@C electromagnetic wave absorber material reaches -49.26 dB at a thickness of 2.82 mm, and the effective absorption bandwidth is 3.84 GHz at a thickness of 2.9 mm. The specific embodiment has simple operation, controllable morphology and operation process, and the prepared CeO2 / Fe3C@C electromagnetic wave absorber can effectively absorb electromagnetic waves, has strong reflection loss and large effective absorption bandwidth.

[0041] It is to be understood that the above description is intended to be illustrative and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the application should, therefore, be determined not with reference to the above description, but instead with reference to the appended claims, along with their full scope of equivalents.

Claims

1. A method for preparing an electromagnetic wave absorber based on CeFe-PBA, characterized in that, Includes the following steps: 1) Polyvinylpyrrolidone was added to a cerium salt aqueous solution and stirred at 300-500 rpm for 10-25 min to obtain solution A; solution A was mixed with ethanol and stirred until homogeneous to obtain solution B; solution B was mixed with a potassium ferricyanide aqueous solution to obtain solution C, stirred and allowed to stand to obtain CeFe-PBA precursor powder; wherein: the mass ratio of cerium salt to polyvinylpyrrolidone was 1:10-15; the solid-liquid ratio in the cerium salt aqueous solution was 25-35 g / L; the volume ratio of water to ethanol in solution C was 1.5-4:1; 2) The CeFe-PBA precursor powder obtained in step 1) is subjected to a carbothermic reduction reaction to obtain Fe-CeO2 powder; 3) Dissolve the Fe-CeO2 powder obtained in step 2) in a dilute Tris solution, then add dopamine hydrochloride, stir and let stand to prepare Fe-CeO2@PDA powder; wherein the mass ratio of Fe-CeO2 powder to dopamine hydrochloride is 1~3:1; 4) The Fe-CeO2@PDA powder obtained in step 3) is subjected to a carbothermal reduction reaction under N2 atmosphere to prepare CeO2 / Fe3C@C electromagnetic wave absorber; wherein the carbothermal reduction reaction temperature is 700~900℃ and the time is 1~5h.

2. The preparation method according to claim 1, characterized in that, In step 1), the cerium salt is one of cerium nitrate, cerium sulfate, cerium acetate, cerium oxalate, and cerium fluoride.

3. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of cerium salt to potassium ferricyanide is 1:1~5.

4. The preparation method according to claim 1, characterized in that, In step 1), the solid-liquid ratio in the potassium ferricyanide aqueous solution is 8~15g / L.

5. The preparation method according to claim 1, characterized in that, In step 1), solution B is mixed with potassium ferricyanide aqueous solution, stirred for 10-30 min and then allowed to stand for 8-12 h to obtain CeFe-PBA precursor powder.

6. The preparation method according to claim 1, characterized in that, In step 1), the average particle size of the obtained CeFe-PBA precursor powder is 2.23~3.17μm.

7. The preparation method according to claim 1, characterized in that, In step 2), the temperature of the carbothermic reduction reaction is 600~800℃ and the time is 1~5h.

8. The preparation method according to claim 1, characterized in that, In step 3), the stirring time is 10-30 min; the standing time is 5-15 h.

9. An electromagnetic wave absorber based on CeFe-PBA prepared by the preparation method according to any one of claims 1-8.

10. The electromagnetic wave absorber according to claim 9, characterized in that, The electromagnetic wave absorber has a spindle-shaped morphology, uniform particle size, and a hollow core-shell structure, wherein the core layer includes CeO2 and Fe3C, and the outer shell is a carbon matrix.

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