An amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material and its preparation method

Abstract

The application discloses an amorphous Co@Nd(BO2)3 / rGO nano-composite electromagnetic wave absorbing material and a preparation method thereof, and belongs to the field of magnetic functional materials. The application adopts a chemical reduction method to co-reduce divalent cobalt ions and trivalent neodymium ions, utilizes the difference in reduction properties of the two kinds of metal ions, and forms the completely amorphous Co@Nd(BO2)3 core-shell structure nano-composite particles after selective reduction of the divalent cobalt ions in the reaction process, and the nano-composite particles are uniformly pinned on the surface of reduced graphene oxide (rGO), so that a novel Co@Nd(BO2)3 / rGO nano-composite structure is prepared. The preparation process is simple, and the amorphous Co@Nd(BO2)3 / rGO nano-composite electromagnetic wave absorbing material can be prepared in large quantities. The amorphous Co@Nd(BO2)3 / rGO nano-composite electromagnetic wave absorbing material has excellent electromagnetic wave absorbing performance and good structural and performance stability, and is suitable for wide application.

Description

Technical Field

[0001] This invention belongs to the field of magnetic functional materials, specifically an amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material with excellent electromagnetic wave absorption properties such as low density, high absorption intensity, wide absorption bandwidth and high frequency absorption, and its preparation method. Background Technology

[0002] Electromagnetic wave absorbing materials can completely absorb or significantly reduce the electromagnetic wave energy projected onto their surface, and can eliminate or reduce the radiation or interference of electromagnetic waves to the human body and devices. As an indispensable and important type of electromagnetic functional material, they have a wide range of applications in modern society, including daily life and production, medical protection, and many dual-use industrial fields.

[0003] Research and development of electromagnetic wave absorbing materials has been booming for a long time, with a vast amount of literature and materials available. Electromagnetic wave absorbing materials can be broadly classified into three categories: resistive absorbing materials, which mainly include various conductive carbons or carbides, high-conductivity polymers, conductive fibers, and composite materials based on the aforementioned materials; dielectric absorbing materials, which mainly include barium titanate ceramics and their composite materials; and magnetic dielectric absorbing materials, which mainly include elemental metals or oxide particles such as iron, cobalt, and nickel, alloy particles of the three magnetic elements, and composite materials based on the aforementioned magnetic materials.

[0004] Although there are many types of electromagnetic wave absorbing materials, their use and device fabrication are primarily through coatings. This makes it difficult for some materials to simultaneously meet the requirements of mass production and maintaining effective electromagnetic wave absorption in coated or composite states. Many materials with electromagnetic wave absorption properties are not suitable for fabricating effective electromagnetic wave absorbing coatings or devices. Currently, the most practically applicable electromagnetic wave absorbing materials are soft magnetic composite materials based on magnetic media. Among these, the most commonly used in both military and civilian applications are electromagnetic wave absorbing coatings with carbonyl iron powder and iron oxide micro / nano particles as the core absorbers. While most conventional magnetic absorbing materials exhibit high electromagnetic wave absorption intensity in the 2–18 GHz frequency range, their strongest absorption frequency band is generally below the X-band, with an absorption bandwidth typically below 5 GHz. Furthermore, their high material density limits their application in high-frequency, broadband, and lightweight absorbing coatings and devices. In addition, conventional magnetic metal-based and iron oxide-based electromagnetic wave absorbing materials have poor oxidation resistance, resulting in poor performance stability of the fabricated absorbing coatings and devices. Because electromagnetic devices that emit electromagnetic radiation are used in diverse environments, the development of electromagnetic wave absorbing materials with excellent electromagnetic wave absorption performance, such as low density, high absorption intensity, wide absorption bandwidth and high frequency absorption band, and stable structure has always been the research and development goal of high-performance electromagnetic wave absorbing materials. Summary of the Invention

[0005] To address the problem of poor electromagnetic wave absorption performance of existing electromagnetic wave absorbing materials under conditions such as high frequency, wide bandwidth, and low density, this invention provides an amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material and its preparation method, which has excellent electromagnetic wave absorption performance such as low density, high absorption intensity, wide absorption bandwidth, and high frequency absorption.

[0006] An amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material is disclosed, comprising an amorphous Co / amorphous Nd(BO2)3 / rGO nanocomposite structure. High-purity amorphous Nd(BO2)3 completely coats the surface of high-purity amorphous Co, forming Co@Nd(BO2)3 core-shell structured nanocomposite particles. These Co@Nd(BO2)3 nanocomposite particles are uniformly anchored to the rGO surface, forming the Co@Nd(BO2)3 / rGO nanocomposite structure. The average particle size of the Co@Nd(BO2)3 is 20–80 nm. In the Co / Nd(BO2)3 nanocomposite particles, the mass fraction of Co is 20–80%, with the remainder being Nd(BO2)3. In the Co@Nd(BO2)3 / rGO nanocomposite structure, the mass fraction of rGO is 2–10%.

[0007] A method for preparing an amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material includes the following steps:

[0008] (1) Weigh an appropriate amount of the compound containing divalent Co ions and neodymium trichloride hexahydrate (NdCl3·6H2O), dissolve them fully in deionized water to obtain an aqueous solution containing Co ions and Nd ions, called solution one, wherein the molar ratio of Co ions to Nd ions is (3–7):1, and the concentration of NdCl3·6H2O is 0.010–0.020 mol / L.

[0009] (2) Add polyvinylpyrrolidone (PVP) to solution one with a mass of 4–8 times that of NdCl3·6H2O in step (1), and stir it to dissolve it completely to obtain solution two.

[0010] (3) Weigh an appropriate amount of monolayer graphene oxide (GO), dissolve it fully in deionized water, and then use an ultrasonic dispersion device to ultrasonically disperse it for 0.5–3 hours to prepare a uniformly dispersed GO dispersion with a concentration of 0.5–2.0 mg / ml.

[0011] (4) Under the protective atmosphere of flowing nitrogen, take an appropriate amount of GO dispersion and add it to solution two at once. After the addition is complete, stir at a stirring speed of 500–1000 r / min for 5–20 minutes to obtain mixed solution one.

[0012] The volume of the GO dispersion is determined by the specific proportion of graphene and the concentration of GO.

[0013] (5) Weigh an appropriate amount of NaBH4 and dissolve it fully in deionized water to prepare a NaBH4 solution with a concentration of 0.5–2.0 mol / L, wherein the amount of NaBH4 is 12–24 times the amount of NdCl3·6H2O added in step (1);

[0014] (6) Add NaBH4 solution dropwise to mixed solution one using a constant flow pump at a dropping rate of 0.5–2 ml / min until the NaBH4 solution is completely added. Then continue to react at a stirring speed of 500–1000 r / min for 40–90 minutes to obtain a mixed solution containing black precipitate, which is called mixed solution two.

[0015] (7) The mixed solution was centrifuged at 4000–10000 r / min to obtain a black precipitate. The black precipitate was then washed alternately with deionized water and anhydrous ethanol 2–5 times. The thoroughly washed product was placed in a vacuum drying oven and dried at 25–70℃ for 10–30 hours to obtain amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material.

[0016] Amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing materials are used to prepare high-performance electromagnetic wave absorbing coatings or devices for use in high-frequency environments, marine environments, or other corrosive environments. In the range of 2–18 GHz, the maximum absorption intensity of electromagnetic waves ranges from -60.14 to -84.09 dB, the maximum effective absorption bandwidth ranges from 6.13 to 7.24 GHz, and the electromagnetic wave absorbing plate ranges from 8 to 18 GHz.

[0017] The advantages and beneficial effects of this invention are as follows:

[0018] (1) The preparation method of the amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material of the present invention has the advantages of abundant raw material sources, simple process and environmental friendliness, and is suitable for mass production of electromagnetic wave absorbing materials.

[0019] (2) The amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material prepared by the present invention is a novel Co-based amorphous nanocomposite structure. It has excellent electromagnetic wave absorption performance and good structural and performance stability. It can be used to prepare high-performance electromagnetic wave absorbing coatings or devices for use in high-frequency environments, marine environments or other corrosive environments. It is suitable for medical protection, aerospace, electronics and electrical engineering, marine engineering and precision instruments and other fields. Attached Figure Description

[0020] Figure 1 The images show the X-ray diffraction patterns of the original amorphous Co@Nd(BO2)3 / rGO nanocomposite material and the Co@Nd(BO2)3 / rGO nanocomposite material annealed at 850℃ in Example 1; where... Figure 1 (a) is the XRD pattern of the original amorphous material. Figure 1 (b) is the XRD pattern of the sample after vacuum annealing at 850℃;

[0021] Figure 2 The images shown are scanning electron microscope (SEM) images of the original amorphous Co@Nd(BO2)3 / rGO nanocomposite material in Example 1 and transmission electron microscope (TEM) images of the Co@Nd(BO2)3 / rGO nanocomposite material annealed at 850℃; wherein, Figure 2 (a) is the SEM image of the original sample. Figure 2 (b) is a TEM image of the sample after vacuum annealing at 850℃;

[0022] Figure 3 The image shows the reflection loss curve of the amorphous Co@Nd(BO2)3 / rGO nanocomposite material in Example 1. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] This invention employs a chemical reduction method to co-reduc divalent cobalt ions and trivalent neodymium ions. Utilizing the difference in the reducibility of the two metal ions, only divalent cobalt ions are selectively reduced during the reaction process to form completely amorphous Co@Nd(BO2)3 core-shell structured nanocomposite particles. These particles are then uniformly anchored onto the surface of reduced graphene oxide (rGO), thus preparing a novel Co@Nd(BO2)3 / rGO nanocomposite structure.

[0025] In this invention, the compounds or hydrates containing divalent Co ions are commercially available analytical grade CoCl2·6H2O, CoSO4·H2O, Co(NO3)2·6H2O, [Co(NH3)6]Cl3, and C. 10 H 14 O4Co, etc.

[0026] Example 1

[0027] An amorphous Co@Nd(BO2)3 / rGO nanocomposite material exhibits excellent electromagnetic wave absorption properties, including low density, high absorption intensity, wide absorption bandwidth, and high-frequency absorption range. The average particle size of Co@Nd(BO2)3 is 40 nm; the mass fraction of Co in the Co@Nd(BO2)3 nanocomposite particles is 52%, and the mass fraction of Nd(BO2)3 is 48%; the mass fraction of rGO in the Co@Nd(BO2)3 / rGO nanocomposite structure is 3.2%. The preparation steps are as follows:

[0028] (1) Weigh 0.7138g CoCl2·6H2O and 0.2152g NdCl3·6H2O and dissolve them in 50ml of deionized water. After stirring, the solution containing Co ions and Nd ions with a concentration of 0.012mol / L is obtained by dissolving the solution.

[0029] (2) Add 1.2912 g of polyvinylpyrrolidone (PVP) to the solution containing Co ions and Nd ions in step (1) and stir it to dissolve it completely.

[0030] (3) Weigh an appropriate amount of monolayer graphene oxide (GO), dissolve it fully in deionized water, and then use an ultrasonic dispersion device to ultrasonically disperse it for 1 hour to prepare a uniformly dispersed GO dispersion with a concentration of 1 mg / ml.

[0031] (4) Under the protective atmosphere of flowing nitrogen, take 11 ml of the GO dispersion in step (3) and add it to the mixed solution containing Co ions and Nd ions in step (2) in which PVP is dissolved. After the addition is complete, stir at a stirring speed of 650 r / min for 10 minutes.

[0032] (5) Weigh 0.4540g of NaBH4 and dissolve it completely in deionized water to prepare a NaBH4 solution with a concentration of 1mol / L;

[0033] (6) Add the sodium borohydride aqueous solution from step (5) to the mixed solution from step (4) at a constant flow pump at a dropping rate of 1.0 ml / min until the NaBH4 solution is completely added. Then continue to react at a stirring speed of 650 r / min for 60 minutes to obtain a mixed solution containing precipitate.

[0034] (7) The mixed solution containing precipitate obtained in step (6) was centrifuged at 7000 r / min to obtain a black precipitate. The black precipitate was then washed three times alternately with deionized water and anhydrous ethanol. After thorough washing, the product was placed in a vacuum drying oven and dried at 45°C for 20 hours to obtain an amorphous Co@Nd(BO2)3 / rGO nanocomposite material with excellent electromagnetic wave absorption performance and good structural and performance stability.

[0035] Figure 1 (a) is the X-ray diffraction (XRD) spectrum of the original Co@Nd(BO2)3 / rGO nanocomposite material. Figure 1 (a) It can be seen that the sample exhibits a completely amorphous state; Figure 1 (b) is the XRD pattern of the sample after vacuum annealing at 850℃. Figure 1 (b) It can be seen that the sample annealed at 850℃ exhibits diffraction peaks of high-purity fcc-Co and Nd(BO2)3. Combined with the structural changes of the sample before and after annealing, it indicates that the original amorphous sample contained amorphous Co, amorphous Nd(BO2)3, and rGO.

[0036] Figure 2 (a) is a scanning electron microscope (SEM) image of the original amorphous Co@Nd(BO2)3 / rGO nanocomposite material. Figure 2 (a) It can be seen that Co@Nd(BO2)3 particles are uniformly anchored on the surface of rGO; Figure 2 (b) is a transmission electron microscope (TEM) image of the sample after vacuum annealing at 850℃. Figure 2 (b) It can be seen that Co@Nd(BO2)3 has a core-shell structure, with Nd(BO2)3 completely encapsulating the surface of Co particles as a shell, which gives Co@Nd(BO2)3 good antioxidant properties and structural stability.

[0037] Figure 3 The reflection loss curve of the amorphous Co@Nd(BO2)3 / rGO nanocomposite material shows that the Co@Nd(BO2)3 / rGO nanocomposite material has excellent electromagnetic wave absorption performance. In the range of 2–18 GHz, the maximum absorption intensity of electromagnetic waves is -84.09 dB, the maximum effective absorption bandwidth is 7.24 GHz, and the frequency range of electromagnetic wave absorption is 10–16 GHz.

[0038] Example 2

[0039] An amorphous Co@Nd(BO2)3 / rGO nanocomposite material exhibits excellent electromagnetic wave absorption properties, including low density, high absorption intensity, wide absorption bandwidth, and high-frequency absorption range. The average particle size of Co@Nd(BO2)3 is 20 nm; the mass fraction of Co in the Co@Nd(BO2)3 nanocomposite particles is 20%, and the mass fraction of Nd(BO2)3 is 80%; the mass fraction of rGO in the Co@Nd(BO2)3 / rGO nanocomposite structure is 10%. The preparation steps are as follows:

[0040] (1) Weigh 0.4283g CoCl2·6H2O and 0.2152g NdCl3·6H2O, dissolve them in 30ml of deionized water, and stir until fully dissolved to obtain an aqueous solution containing Co ions and Nd ions with a concentration of 0.020mol / L of NdCl3·6H2O.

[0041] (2) Add 0.8608 g of polyvinylpyrrolidone (PVP) to the solution containing Co ions and Nd ions in step (1) and stir it to dissolve it completely.

[0042] (3) Weigh an appropriate amount of monolayer graphene oxide (GO), dissolve it fully in deionized water, and then use an ultrasonic dispersion device to ultrasonically disperse it for 3 hours to prepare a uniformly dispersed GO dispersion with a concentration of 2.0 mg / ml.

[0043] (4) Under the protective atmosphere of flowing nitrogen, measure 14 ml of the GO dispersion in step (3) and add it all at once to the mixed solution containing Co ions and Nd ions in which PVP is dissolved in step (2). After the addition is complete, stir at a stirring speed of 500 r / min for 5 minutes.

[0044] (5) Weigh 0.2724g of NaBH4 and dissolve it completely in deionized water to prepare a NaBH4 solution with a concentration of 0.5mol / L;

[0045] (6) Add the sodium borohydride aqueous solution from step (5) to the mixed solution from step (4) at a constant flow pump at a dropping rate of 2 ml / min until the NaBH4 solution is completely added. Then continue to react at a stirring speed of 500 r / min for 40 minutes to obtain a mixed solution containing precipitate.

[0046] (7) The mixed solution containing precipitate obtained in step (6) was centrifuged at 10,000 r / min to obtain a black precipitate. The black precipitate was then washed twice alternately with deionized water and anhydrous ethanol. After thorough washing, the product was placed in a vacuum drying oven and dried at 25°C for 30 hours to obtain an amorphous Co@Nd(BO2)3 / rGO nanocomposite material with excellent electromagnetic wave absorption performance and good structural and performance stability.

[0047] In this embodiment, the Co@Nd(BO2)3 / rGo nanocomposite material has excellent electromagnetic wave absorption performance. In the range of 2–18 GHz, the maximum electromagnetic wave absorption intensity is -72.3 dB, the maximum effective absorption bandwidth is 6.13 GHz, and the electromagnetic wave absorption frequency range is 7–14 GHz.

[0048] Example 3

[0049] An amorphous Co@Nd(BO2)3 / rGO nanocomposite material exhibits excellent electromagnetic wave absorption properties, including low density, high absorption intensity, wide absorption bandwidth, and high-frequency absorption range. The average particle size of Co@Nd(BO2)3 is 80 nm; the mass fraction of Co in the Co@Nd(BO2)3 nanocomposite particles is 80%, and the mass fraction of Nd(BO2)3 is 20%; the mass fraction of rGO in the Co@Nd(BO2)3 / rGO nanocomposite structure is 2%. The preparation steps are as follows:

[0050] (1) Weigh 0.9993g CoCl2·6H2O and 0.2152g NdCl3·6H2O and dissolve them in 60ml of deionized water. After stirring, the solution containing Co ions and Nd ions with a concentration of 0.010mol / L is obtained.

[0051] (2) Add 1.7216 g of polyvinylpyrrolidone (PVP) to the solution containing Co ions and Nd ions in step (1) and stir it to dissolve it completely.

[0052] (3) Weigh an appropriate amount of monolayer graphene oxide (GO), dissolve it fully in deionized water, and then use an ultrasonic dispersion device to ultrasonically disperse it for 30 minutes to prepare a uniformly dispersed GO dispersion with a concentration of 0.5 mg / ml.

[0053] (4) Under the protective atmosphere of flowing nitrogen, measure 16 ml of the GO dispersion in step (3) and add it all at once to the mixed solution containing Co ions and Nd ions in which PVP is dissolved in step (2). After the addition is complete, stir at a stirring speed of 1000 r / min for 20 minutes.

[0054] (5) Weigh 0.5448g of NaBH4 and dissolve it completely in deionized water to prepare a NaBH4 solution with a concentration of 2mol / L;

[0055] (6) Add the sodium borohydride aqueous solution from step (5) to the mixed solution from step (4) at a constant flow pump at a dropping rate of 0.5 ml / min until the NaBH4 solution is completely added. Then continue to react at a stirring speed of 1000 r / min for 90 minutes to obtain a mixed solution containing precipitate.

[0056] (7) The mixed solution containing precipitate obtained in step (6) was centrifuged at 4000 r / min to obtain a black precipitate. The black precipitate was then washed 5 times alternately with deionized water and anhydrous ethanol. The thoroughly washed product was then placed in a vacuum drying oven and dried at 70°C for 10 hours to obtain an amorphous Co@Nd(BO2)3 / rGO nanocomposite material with excellent electromagnetic wave absorption performance and good structural and performance stability.

[0057] In this embodiment, the Co@Nd(BO2)3 / rGo nanocomposite material has excellent electromagnetic wave absorption performance. In the range of 2–18 GHz, the maximum electromagnetic wave absorption intensity is -60.14 dB, the maximum effective absorption bandwidth is 7.02 GHz, and the electromagnetic wave absorption frequency range is 14–18 GHz.

Claims

1. A method for preparing an amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material, characterized in that, Includes the following steps: (1) Weigh an appropriate amount of the compound containing divalent Co ions and neodymium trichloride hexahydrate (NdCl3∙6H2O), dissolve them fully in deionized water to obtain an aqueous solution containing Co ions and Nd ions, called solution one, wherein the molar ratio of Co ions to Nd ions is in the range of (3–7):1, and the concentration range of NdCl3∙6H2O is 0.010–0.020 mol / L; (2) Add polyvinylpyrrolidone (PVP) to solution one with a mass of 4–8 times that of NdCl3∙6H2O in step (1), and stir it to dissolve it completely to obtain solution two; (3) Weigh an appropriate amount of monolayer graphene oxide (GO), dissolve it fully in deionized water, and then use an ultrasonic dispersion device to ultrasonically disperse it for 0.5–3 hours to prepare a uniformly dispersed GO dispersion with a concentration of 0.5–2.0 mg / ml. (4) Under the protective atmosphere of flowing nitrogen, take an appropriate amount of GO dispersion and add it to solution two at once. After the addition is complete, stir at a stirring speed of 500–1000 r / min for 5–20 minutes to obtain mixed solution one. The volume of the GO dispersion is determined by the specific proportion of graphene and the concentration of GO. (5) Weigh an appropriate amount of NaBH4 and dissolve it completely in deionized water to prepare a NaBH4 solution with a concentration of 0.5–2.0 mol / L, wherein the amount of NaBH4 is 12–24 times the amount of NdCl3∙6H2O added in step (1); (6) Add NaBH4 solution dropwise to mixed solution one using a constant flow pump at a dropping rate of 0.5–2 ml / min until the NaBH4 solution is completely added. Then continue to react at a stirring speed of 500–1000 r / min for 40–90 minutes to obtain a mixed solution containing black precipitate, which is called mixed solution two. (7) Centrifuge the mixed solution at 4000–10000 r / min to obtain a black precipitate. Wash the black precipitate alternately with deionized water and anhydrous ethanol 2–5 times. Place the thoroughly washed product in a vacuum drying oven at 25–70°C. o Amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material was obtained by drying at C temperature for 10–30 hours.

2. The method for preparing an amorphous Co@Nd(BO2)3 / rGO nanocomposite electromagnetic wave absorbing material according to claim 1, characterized in that, The compounds containing divalent Co ions are analytical grade CoCl2∙6H2O, CoSO4∙H2O, Co(NO3)2∙6H2O, [Co(NH3)6]Cl3, or C. 10 H 14 O4Co.

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