Y2Co 17 @Nitrogen-doped graphite-carbon nanocomposite electromagnetic wave absorbing materials and their preparation methods

Abstract

This invention discloses a highly stable Y₂Co with tunable electromagnetic wave absorption performance. 17 @Nitrogen-doped graphite carbon (NGC) nanocomposite soft magnetic materials and their preparation methods. A combination of co-precipitation, dopamine self-polymerization, and controlled heat treatment processes was employed to first completely coat graphite carbon (C) onto the surface of CoO-Co-Y₂O₃-containing composite particles to form a CoO-Co-Y₂O₃ / C core-shell structured composite precursor. Then, a series of highly stable Y₂Co nanocomposite materials with tunable electromagnetic wave absorption properties were prepared by co-reduction of the precursor using a controlled calcium reduction method. 17 @NGC nanocomposite electromagnetic wave absorbing material, in which dense NGC with a nanometer thickness is completely and uniformly coated with high-purity Y2Co by a surface modification layer. 17 The surface of nanoparticles greatly enhances Y2Co 17 Due to its antioxidant properties and structural stability, this phase is widely applicable as an electromagnetic wave absorbing material, suitable for numerous electromagnetic compatibility and protection technologies. This invention offers advantages such as abundant raw material sources, simple preparation process, and low production cost.

Description

Technical Field

[0001] This invention belongs to the field of rare earth-based metal functional materials and their preparation technology, and specifically relates to a highly stable Y₂Co with tunable electromagnetic wave absorption. 17 @NGC nanocomposite soft magnetic materials and their preparation methods. Background Technology

[0002] High-performance rare-earth-based metal materials, based on rare-earth-metal alloys or compounds, are among the core materials in modern high-tech fields such as electronics, electrical engineering, mechanical manufacturing, and aerospace. The exploration and development of novel rare-earth-based metal materials has always been an important research area in materials science and engineering. In recent years, nanostructured rare-earth-metal alloys or compounds prepared using various advanced nanotechnologies have shown great promise in cutting-edge fields such as nanocatalysis, low-carbon energy, artificial intelligence, and next-generation electronic communications due to their diverse material structures and superior physicochemical properties, which are significantly different from conventional rare-earth-based metal materials.

[0003] Rare earth metals, due to their generally reactive chemical properties, exhibit strong oxidizing activity compared to other metals in various application environments, including air, humidity, acids, alkalis, and high temperatures. Nanostructured rare earth-based metal materials, with their large specific surface area and high surface energy, are more easily oxidized than conventional rare earth-based metal materials, facing bottlenecks in their preparation and application, such as compositional changes and poor structural stability caused by easy oxidation. Furthermore, nanostructured rare earth-based metal materials also face pressing technical challenges, including easy decomposition, difficulty in alloying, and the inability to form a single alloy phase. Research indicates that employing appropriate material composite methods (such as coating nanoparticles with antioxidant layers and multiphase composites) can improve the oxidation resistance and structural stability of nano-rare earth-metal alloys or compounds to some extent, but this also leads to significant changes in the composition and structure of rare earth-based metal materials, affecting their intrinsic physicochemical properties and reducing their actual material performance. Therefore, it is necessary to develop new methods for preparing rare earth-based metal nanomaterials that enhance their oxidation resistance and structural stability, obtaining high-purity and highly stable nanostructured rare earth-based metal alloys or compounds while maintaining their intrinsic physicochemical properties to meet the requirements of practical applications.

[0004] This invention provides a highly stable Y2Co 17 @NGC Nanocomposite Electromagnetic Wave Absorbing Materials and Their Preparation Methods. This paper describes a method that combines co-precipitation, DA self-polymerization coating, and controlled heat treatment to first completely coat C (graphite carbon) using DA and GO as carbon sources onto the surface of composite particles with a phase composition of CoO, Co, and Y2O3, forming a CoO-Co-Y2O3 / C core-shell structure composite precursor. Then, a series of Y2Co nanocomposite materials with tunable electromagnetic wave absorption properties are prepared by co-reduction of the precursor using a controlled calcium reduction method.17 @NGC nanocomposite electromagnetic absorbing material. This material encapsulates Y2Co with an ultrathin graphite carbon nanolayer. 17 The nanoparticle method greatly improves Y2Co 17 The phase exhibits antioxidant properties and structural stability, while maintaining Y2Co. 17 The high purity of rare earth alloys in NGC nanocomposites endows them with excellent intrinsic magnetism and electromagnetic wave absorption properties. By adjusting the ratio of DA and GO, the carbon defects in the NGC-modified layer can be altered, thereby controlling the Y₂Co content. 17 Electromagnetic wave absorption properties of @NGC nanocomposites. This invention effectively solves the bottleneck problems such as poor oxidation resistance and structural stability that limit the research and application of nanostructured rare earth alloys, and helps to promote the practical application of high-performance rare earth-based metal nanomaterials; it also provides a new technology for surface modification of easily oxidized metal nanomaterials, and provides new ideas for the research and application of novel metal-based nanomaterials. Summary of the Invention

[0005] The purpose of this invention is to provide a highly stable Y₂Co with tunable electromagnetic wave absorption. 17 @NGC nanocomposite soft magnetic materials and their preparation methods, the material composition and structural characteristics of which are: Y2Co 17 The average particle size of the NGC nanocomposite particles is 100–450 nm; the NGC surface modification layer with a thickness of 1–4 nm is completely and uniformly coated with high-purity Y₂Co. 17 The surface of nanoparticles greatly enhances Y2Co 17 The antioxidant properties and structural stability of the phase; adjusting the ratio of DA and GO in the precursor can obtain a DGC surface modification layer with more carbon defects, thus obtaining Y2Co rich in surface carbon defects. 17 @DGC nanocomposite particles. Their material properties include Y2Co... 17 @NGC nanocomposites have high saturation magnetization (M s =112.1~113.3 emu / g) and high coercivity ( i H c =242.9~294.6Oe); Y2Co 17 @NGC nanocomposite soft magnetic materials exhibit a maximum electromagnetic wave absorption intensity range of -69.69 to -80.16 dB within the 2–18 GHz range, corresponding to an absorption frequency range of 4.30–7.49 GHz. This makes them suitable for fabricating absorbers that absorb electromagnetic waves in the C-band frequency range; Y2Co 17@DGC nanocomposite soft magnetic materials exhibit a maximum electromagnetic wave absorption intensity range of -20.19 to -68.67 dB within the 2–18 GHz range, corresponding to an electromagnetic wave absorption frequency range of 13.40–16.71 GHz. This makes them suitable for preparing absorbers that absorb electromagnetic waves in the Ku-band frequency range. As a high-performance electromagnetic wave absorbing material, they have broad application prospects in fields such as electronic communications and aerospace.

[0006] To achieve the above objectives, the technical solution of the present invention includes the following steps:

[0007] (1) Preparation of Y2O3-Co3O4 composite oxide@GO composite precursor: Dissolve an appropriate amount of GO in deionized water and disperse it by ultrasonication to prepare a 0-2 mg / mL GO aqueous solution; Dissolve commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate in a molar ratio of 2:14-2:19 in 10-30 mL of the above-prepared GO aqueous solution and stir for 5-30 minutes; Then, quickly pour a mixed alkaline solution of sodium hydroxide with a concentration of 0.2-0.4 mol / L and sodium carbonate with a concentration of 0.1-0.3 mol / L into the above mixed solution containing yttrium ions, cobalt ions and GO, adjust its pH value to 9-11, and continue stirring for 10-30 minutes to allow the two metal ions to fully precipitate and obtain a flocculent precipitate. The above precipitate was collected by centrifugation and washed 6 to 11 times with deionized water. It was then dried in an oven at 30 to 80°C and ground to obtain amorphous Y-Co hydroxide@GO composite powder. The powder was then placed in a muffle furnace and calcined in air for 2 to 5 hours at a temperature of 300 to 600°C. After cooling in the furnace, the Y2O3-Co3O4 composite oxide@GO composite precursor was obtained.

[0008] (2) Preparation of CoO-Co-Y2O3 / C composite precursor: Dissolve 0.3-0.8 g of Y2O3-Co3O4@GO composite precursor prepared in step (1) in 50-200 mL of commercially available Tris-HCl buffer (1.0 M, pH = 8.5), disperse by ultrasonication for 0.5-2 hours, then add 10-100 mg of dopamine hydrochloride, continue magnetic stirring for 12-24 hours, and centrifuge to collect composite particles coated with PDA; wash the PDA-coated particles 3-5 times with deionized water and anhydrous ethanol, and dry them in a vacuum drying oven at 30-80℃; anneal the dried powder under an argon atmosphere for 1-4 hours at a temperature of 600-800℃ and a heating rate of 2℃ / min-5℃ / min, and obtain the CoO-Co-Y2O3 / C composite precursor after furnace cooling.

[0009] (3) Preparation of Y2Co 17@NGC Nanocomposite Soft Magnetic Material: The CoO-Co-Y2O3 / C composite precursor obtained in step (2), commercially available high-purity calcium particles, and analytical grade potassium chloride are uniformly mixed in a mass ratio of 1:1:5 to 1:3:1 and placed in a crucible. The mixture is then transferred to a controlled atmosphere heat treatment furnace. Under the protective atmosphere of high-purity argon, the temperature is increased from room temperature to 850 to 1000°C at a rate of 2°C / min to 8°C / min. After reacting for 1 to 3 hours, the furnace is cooled to obtain the reaction product. The calcium oxide and unreacted calcium particles in the reaction product are washed away with deionized water, and then washed several times with anhydrous ethanol to remove excess water. The product is then dried in a vacuum drying oven at 30 to 80°C for 3 to 12 hours to obtain Y2Co. 17 @NGC nanocomposite soft magnetic particles.

[0010] This invention has the advantages of simple preparation process, low production cost and wide applicability. Attached Figure Description

[0011] Figure 1 Y2Co in Example 1 17 X-ray diffraction (XRD) spectra of / DGC nanocomposites

[0012] Figure 2 Y2Co in Example 1 17 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the / DGC nanocomposite material, including:

[0013] Figure 2 (a) is Y2Co 17 SEM morphology of / DGC nanocomposite material;

[0014] Figure 2 (b) is Y2Co 17 TEM image of / DGC nanocomposite material;

[0015] Figure 2 (c) is Y2Co 17 High-resolution HRTEM image of / DGC nanocomposite material;

[0016] Figure 3 Y2Co in Example 1 17 X-ray photoelectron spectroscopy (XPS) of Co element in DGC nanocomposites and samples after 2 nm surface etching.

[0017] Figure 4 Y2Co in Example 1 17 / DGC and Y2Co in Example 2 17 Raman spectrum of / NGC nanocomposite material

[0018] Figure 5Y2Co in Example 1 17 The hysteresis loop of / DGC nanocomposite material at a maximum applied magnetic field of 20 kOe

[0019] Figure 6 Y2Co in Example 1 17 / DGC nanocomposite material reflection loss curve

[0020] Figure 7 Y2Co in Example 1 17 Thermogravimetric (TG) curves of / DGC nanocomposites from room temperature to 800℃

[0021] Example 1

[0022] Y₂Co exhibits absorption of electromagnetic waves in the Ku-band frequency range 17 @DGC nanocomposite materials, in which Y2Co 17 The average particle size is 199.2 nm, and the DGC thickness is approximately 2.8 nm. The preparation steps are as follows:

[0023] (1) 24.84 mg GO was dissolved in 18 mL of deionized water and ultrasonically dispersed to prepare a 1.38 mg / mL GO aqueous solution. Commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate in a molar ratio of 2:16.5 were dissolved in 18 mL of the above-prepared GO aqueous solution and stirred for 20 minutes. Then, a mixed alkaline solution of 0.35 mol / L sodium hydroxide and 0.15 mol / L sodium carbonate was quickly poured into the above mixed solution containing yttrium ions, cobalt ions and GO, and the pH value was adjusted to 10. The mixture was stirred for another 20 minutes to allow the two metal ions to fully precipitate and obtain a flocculent precipitate. The precipitate was collected by centrifugation and washed 9 times with deionized water. It was then dried in an oven at 60°C and ground to obtain amorphous Y-Co hydroxide@GO composite powder. The powder was then placed in a muffle furnace and calcined in air for 3 hours at a calcination temperature of 450°C. After cooling in the furnace, a Y2O3-Co3O4 composite oxide@GO composite precursor was obtained.

[0024] (2) 0.4 g of the Y2O3-Co3O4@GO composite precursor prepared in step (1) was poured into 100 mL of commercially available Tris-HCl buffer (1.0 M, pH = 8.5). After ultrasonic dispersion for 1 hour, 50 mg of dopamine hydrochloride was added. After magnetic stirring for 24 hours, the product was collected by centrifugation. The product was washed 5 times with deionized water and anhydrous ethanol and then dried in a vacuum drying oven at 45 °C. The dried powder was annealed under an argon atmosphere for 2 hours at a temperature of 700 °C and a heating rate of 2 °C / min. After furnace cooling, the CoO-Co-Y2O3 / C composite precursor was obtained.

[0025] (3) The CoO-Co-Y2O3 / C composite precursor obtained in step (2), commercially available high-purity calcium granules, and analytical grade potassium chloride were uniformly mixed in a mass ratio of 1:2:3 and placed in a crucible. The mixture was then transferred to a controlled atmosphere heat treatment furnace. Under the protective atmosphere of high-purity argon, the temperature was increased from room temperature to 850°C at a rate of 5°C / min. After reacting for 2 hours, the furnace was cooled to obtain the reaction product. The calcium oxide and unreacted calcium granules in the reaction product were washed away with deionized water, and then washed several times with anhydrous ethanol to remove excess water. The product was then dried in a vacuum drying oven at 45°C for 12 hours to obtain Y2Co. 17 @DGC nanocomposite soft magnetic particles.

[0026] from Figure 1 It can be seen that only Y2Co appears in the XRD pattern of the product obtained by controlled calcium reduction of the CoO-Co-Y2O3 / C composite precursor using DA and GO as carbon sources. 17 The diffraction peaks of the Y2Co phase did not show those of other elements, alloys, or oxides containing Y or Co. Therefore, high-purity single-phase Y2Co can be prepared by controlled calcium reduction of CoO-Co-Y2O3 composite particles. 17 Combined with other material structure research data presented later, it can also be found that ultrathin graphitic DGC is coated on high-purity Y2Co in the form of a surface modification layer. 17 On the surface of the phase, therefore no DGC diffraction peaks appeared in the XRD spectrum of the product.

[0027] Combination Figure 2 (a) SEM, Figure 2 (b) TEM topography and Figure 2 (c) The HRTEM high-resolution image shows that a dense DGC-modified layer with a thickness of approximately 2.8 nm completely encapsulates the nearly spherical Y2Co. 17 Y₂Co nanoparticles with an average particle size of approximately 199.2 nm are formed on the surface of the nanoparticles. 17 / DGC nanocomposite particles.

[0028] from Figure 3 Y2Co 17 XPS spectra of Co elements in the / DGC nanocomposite material and its surface after 2nm etching show that in Y2Co 17 Co was observed not only in the DGC nanocomposite material 2+ XPS characteristic peaks were observed for Y₂Co, and also for metallic Co. The XPS characteristic peak intensity of metallic Co in the sample etched by 2 nm was significantly higher than that in the unetched sample. The XPS results indicate that Y₂Co... 17 Y2Co in DGC nanocomposites 17The phase has extremely high purity and weak surface oxidation, with its surface oxide layer not exceeding 2 nm.

[0029] contrast Figure 4 Y2Co 17 / DGC and Y2Co 17 Raman spectra of carbon in / NGC reveal that both DGC and NGC modified layers exhibit characteristics of graphitic carbon, but they also show distinctly different carbon defects.

[0030] from Figure 5 It can be seen that, due to Y2Co 17 @DGC nanocomposite materials contain ultra-high purity Y2Co 17 Nanoparticles and ultrathin DGC modification layer, Y2Co 17 / DGC nanocomposite material M s The value is as high as 112.1 emu / g; due to Y2Co 17 The flower-like microstructure and surface modification effect of DGC, Y2Co 17 @DGC nanocomposites have high... i H c Value (242.9Oe).

[0031] from Figure 6 It can be seen that Y2Co 17 / DGC nanocomposite materials exhibit excellent electromagnetic wave absorption performance: in the range of 2 to 18 GHz, the maximum absorption intensity of electromagnetic waves is -52.59 dB, corresponding to an electromagnetic wave absorption frequency of 16.71 GHz.

[0032] from Figure 7 The TG curve in the image shows that Y2Co 17 The weight of the DGC nanocomposite material hardly increased when heated in air from room temperature to 200°C; upon further heating to 300°C, its weight increased slowly. TG testing results indicate that this is due to the dense DGC modification layer completely coating the high-purity Y₂Co. 17 The surface of nanoparticles thus makes Y2Co 17 / DGC nanocomposite structures exhibit excellent antioxidant properties and temperature stability.

[0033] The Y2Co prepared in this embodiment 17 / DGC nanocomposite materials have excellent oxidation resistance and structural stability. In the range of 2 to 18 GHz, the maximum absorption intensity of electromagnetic waves is -52.59 dB, corresponding to an absorption frequency of 16.71 GHz. They are suitable for preparing absorbers for electromagnetic wave absorption in the Ku band frequency range.

[0034] Example 2

[0035] Y₂Co exhibits absorption of electromagnetic waves in the C-band frequency range 17 @NGC nanocomposite materials, in which Y2Co 17 The average particle size is 114.7 nm, and the NGC thickness is approximately 1.5 nm. The preparation steps are as follows:

[0036] (1) Commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate in a molar ratio of 2:16.5 were dissolved in 18 mL of deionized water and stirred for 20 minutes until fully dissolved. Then, a mixed alkaline solution of 0.35 mol / L sodium hydroxide and 0.15 mol / L sodium carbonate was quickly poured into the above aqueous solution containing yttrium and cobalt ions, and the pH was adjusted to 10. The mixture was stirred for another 20 minutes to allow the two metal ions to fully precipitate and obtain a flocculent precipitate. The precipitate was collected by centrifugation and washed 9 times with deionized water. It was then dried in an oven at 60°C and ground to obtain amorphous Y-Co hydroxide composite powder. The powder was then placed in a muffle furnace and calcined in air for 3 hours at a temperature of 450°C. After cooling in the furnace, a Y2O3-Co3O4 composite oxide precursor was obtained.

[0037] (2) 0.4 g of the Y2O3-Co3O4 composite precursor prepared in step (1) was poured into 100 mL of commercially available Tris-HCl buffer (1.0 M, pH = 8.5). After ultrasonic dispersion for 1 hour, 50 mg of dopamine hydrochloride was added. After magnetic stirring for 24 hours, the product was collected by centrifugation. The product was washed 5 times with deionized water and anhydrous ethanol and then dried in a vacuum drying oven at 45 °C. The dried powder was annealed under an argon atmosphere for 2 hours at a temperature of 700 °C and a heating rate of 2 °C / min. After furnace cooling, the CoO-Co-Y2O3 / C composite precursor was obtained.

[0038] (3) The CoO-Co-Y2O3 / C composite precursor obtained in step (2), commercially available high-purity calcium granules, and analytical grade potassium chloride were uniformly mixed in a mass ratio of 1:2:3 and placed in a crucible. The mixture was then transferred to a controlled atmosphere heat treatment furnace. Under the protective atmosphere of high-purity argon, the temperature was increased from room temperature to 850°C at a rate of 5°C / min. After reacting for 2 hours, the furnace was cooled to obtain the reaction product. The calcium oxide and unreacted calcium granules in the reaction product were washed away with deionized water, and then washed several times with anhydrous ethanol to remove excess water. The product was then dried in a vacuum drying oven at 45°C for 12 hours to obtain Y2Co. 17 @DGC nanocomposite soft magnetic particles.

[0039] The Y2Co prepared in this embodiment 17 / NGC nanocomposites exhibit excellent oxidation resistance and structural stability. In the range of 2–18 GHz, the maximum absorption intensity of electromagnetic waves is -80.16 dB, corresponding to an absorption frequency of 4.30 GHz. They are suitable for preparing absorbers for electromagnetic wave absorption in the C-band frequency range.

[0040] Example 3

[0041] Y₂Co exhibits absorption of electromagnetic waves in the Ku-band frequency range 17 @DGC nanocomposite materials, in which Y2Co 17 The average particle size is 100 nm, and the DGC thickness is approximately 1 nm. The preparation steps are as follows:

[0042] (1) 15 mg GO was dissolved in 30 mL of deionized water and ultrasonically dispersed to prepare a 0.5 mg / mL GO aqueous solution. Commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate with a molar ratio of 2:14 were dissolved in 30 mL of the above-prepared GO aqueous solution and stirred for 30 minutes. Then, a mixed alkaline solution of 0.2 mol / L sodium hydroxide and 0.3 mol / L sodium carbonate was quickly poured into the above mixed solution containing yttrium ions, cobalt ions and GO, and the pH value was adjusted to 9. The mixture was stirred for another 10 minutes to allow the two metal ions to fully precipitate and obtain a flocculent precipitate. The precipitate was collected by centrifugation and washed 6 times with deionized water. It was then dried in an oven at 30 °C and ground to obtain amorphous Y-Co hydroxide@GO composite powder. The powder was then placed in a muffle furnace and calcined in air for 5 hours at a calcination temperature of 300 °C. After cooling in the furnace, a Y2O3-Co3O4 composite oxide@GO composite precursor was obtained.

[0043] (2) 0.3 g of the Y2O3-Co3O4@GO composite precursor prepared in step (1) was poured into 50 mL of commercially available Tris-HCl buffer (1.0 M, pH = 8.5). After ultrasonic dispersion for 0.5 hours, 10 mg of dopamine hydrochloride was added. After magnetic stirring for 12 hours, the product was collected by centrifugation. The product was washed three times with deionized water and anhydrous ethanol and then dried in a vacuum drying oven at 30 °C. The dried powder was annealed under an argon atmosphere for 1 hour at a temperature of 600 °C and a heating rate of 2 °C / min. After furnace cooling, the CoO-Co-Y2O3 / C composite precursor was obtained.

[0044] (3) The CoO-Co-Y2O3 / C composite precursor obtained in step (2), commercially available high-purity calcium granules, and analytical grade potassium chloride were uniformly mixed in a mass ratio of 1:1:5 and placed in a crucible. The mixture was then transferred to a controlled atmosphere heat treatment furnace. Under the protective atmosphere of high-purity argon, the temperature was increased from room temperature to 900℃ at a rate of 2℃ / min. After reacting for 3 hours, the furnace was cooled to obtain the reaction product. The calcium oxide and unreacted calcium granules in the reaction product were washed away with deionized water, and then washed several times with anhydrous ethanol to remove excess water. The product was then dried in a vacuum drying oven at 30℃ for 12 hours to obtain Y2Co. 17 @DGC nanocomposite soft magnetic particles.

[0045] The Y2Co prepared in this embodiment 17 / DGC nanocomposite materials have excellent oxidation resistance and structural stability. In the range of 2 to 18 GHz, the maximum absorption intensity of electromagnetic waves is -68.67 dB, corresponding to an absorption frequency of 13.52 GHz. They are suitable for preparing absorbers for electromagnetic wave absorption in the Ku band frequency range.

[0046] Example 4

[0047] Y₂Co exhibits absorption of electromagnetic waves in the Ku-band frequency range 17 @DGC nanocomposite materials, in which Y2Co 17 The average particle size is 450 nm, and the DGC thickness is approximately 4 nm. The preparation steps are as follows:

[0048] (1) 20 mg GO was dissolved in 10 mL of deionized water and ultrasonically dispersed to prepare a 2 mg / mL GO aqueous solution; commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate in a molar ratio of 2:19 were dissolved in 10 mL of the above-prepared GO aqueous solution and stirred for 5 minutes; then, a mixed alkaline solution of 0.4 mol / L sodium hydroxide and 0.1 mol / L sodium carbonate was quickly poured into the above mixed solution containing yttrium ions, cobalt ions and GO, the pH value was adjusted to 11, and stirring was continued for 30 minutes to allow the two metal ions to fully precipitate and obtain a flocculent precipitate. The above precipitate was collected by centrifugation and washed 11 times with deionized water and dried in an oven at 80℃. After grinding, amorphous Y-Co hydroxide@GO composite powder was obtained; the above powder was further placed in a muffle furnace and calcined in air for 2 hours at a calcination temperature of 600℃. After cooling with the furnace, Y2O3-Co3O4 composite oxide@GO composite precursor was obtained.

[0049] (2) 0.8 g of the Y2O3-Co3O4@GO composite precursor prepared in step (1) was poured into 200 mL of commercially available Tris-HCl buffer (1.0 M, pH = 8.5). After ultrasonic dispersion for 2 hours, 100 mg of dopamine hydrochloride was added. After magnetic stirring for 24 hours, the product was collected by centrifugation. The product was washed 5 times with deionized water and anhydrous ethanol and then dried in a vacuum drying oven at 80 °C. The dried powder was annealed under an argon atmosphere for 4 hours at a temperature of 800 °C and a heating rate of 5 °C / min. After furnace cooling, the CoO-Co-Y2O3 / C composite precursor was obtained.

[0050] (3) The CoO-Co-Y2O3 / C composite precursor obtained in step (2), commercially available high-purity calcium granules, and analytical grade potassium chloride were uniformly mixed in a mass ratio of 1:3:1 and placed in a crucible. The mixture was then transferred to a controlled atmosphere heat treatment furnace and heated from room temperature to 1000℃ at a rate of 8℃ / min under the protective atmosphere of high-purity argon. After reacting for 1 hour, the furnace was cooled to obtain the reaction product. The calcium oxide and unreacted calcium granules in the reaction product were washed away with deionized water, and then washed several times with anhydrous ethanol to remove excess water. The product was then dried in a vacuum drying oven at 80℃ for 3 hours to obtain Y2Co. 17 @DGC nanocomposite soft magnetic particles.

[0051] The Y2Co prepared in this embodiment 17 / DGC nanocomposite materials have excellent oxidation resistance and structural stability. In the range of 2 to 18 GHz, the maximum absorption intensity of electromagnetic waves is -20.19 dB, corresponding to an absorption frequency of 13.40 GHz. They are suitable for preparing absorbers for electromagnetic wave absorption in the Ku band frequency range.

Claims

1. A highly stable Y₂Co with tunable electromagnetic wave absorption properties 17 The method for preparing nitrogen-doped graphite carbon (NGC) nanocomposite soft magnetic materials is characterized by... Includes the following steps: Step 1: An amorphous Y-Co hydroxide@graphene oxide (GO) composite precursor is prepared by co-precipitation, dried, and ground into powder. This powder is then calcined in air to obtain a Y2O3-Co3O4 composite oxide@GO composite precursor. Step 2: Polymerized dopamine (PDA) is coated onto the surface of the Y2O3-Co3O4@GO composite structure using a DA self-polymerization reaction in an alkaline buffer solution containing dopamine (DA), forming Y2O3-Co3O4@GO / PDA composite particles. These particles are then subjected to appropriate heat treatment to obtain a CoO-Co-Y2O3 / graphite carbon (C) composite precursor. Step 3: The CoO-Co-Y2O3 / C composite precursor is co-reduced using a controlled calcium reduction method to obtain Y2Co. 17 @NGC Nanocomposite Soft Magnetic Materials: A combined co-precipitation method, DA self-polymerization coating, and controlled heat treatment process are used to first completely coat C, using DA and GO as carbon sources, onto the surface of composite particles with a phase composition of CoO, Co, and Y2O3, forming a CoO-Co-Y2O3 / C core-shell structure composite precursor. Then, a controlled calcium reduction method is used to co-reduce the precursor to prepare Y2Co with tunable electromagnetic wave absorption properties. 17 @NGC nanocomposite soft magnetic materials; Y2Co 17 The average particle size of the NGC nanocomposite particles is 100–450 nm; the NGC surface modification layer with a thickness of 1–4 nm is completely and uniformly coated with high-purity Y₂Co. 17 The surface of nanoparticles greatly enhances Y2Co 17 The antioxidant properties and structural stability of the phase; adjusting the ratio of DA and GO in the carbon source in the precursor can obtain an NGC surface modification layer (Defect-rich Graphite Carbon, or DGC for short) with more carbon defects, thereby obtaining Y2Co rich in surface carbon defects. 17 @DGC nanocomposite particles.

2. A highly stable Y₂Co with tunable electromagnetic wave absorption performance as described in claim 1. 17 The preparation method of @NGC nanocomposite soft magnetic material is characterized by: Step one is achieved as follows: A suitable amount of GO is dissolved in deionized water and ultrasonically dispersed to prepare a 0–2 mg / mL GO aqueous solution; commercially available yttrium chloride hexahydrate and cobalt chloride hexahydrate in a molar ratio of 2:14–2:19 are dissolved in 10–30 mL of the prepared GO aqueous solution and stirred for 5–30 minutes; then, a mixed alkaline solution of 0.2–0.4 mol / L sodium hydroxide and 0.1–0.3 mol / L sodium carbonate is rapidly poured into the above mixed solution containing yttrium ions, cobalt ions, and GO, and the pH is adjusted to 9–11. Stirring continues for 10–30 minutes to allow the two metal ions to fully precipitate, obtaining a flocculent precipitate; the precipitate is collected by centrifugation and washed 6–11 times with deionized water, then placed at 30–80 °C. The powder was dried in an oven at °C and then ground to obtain amorphous Y-Co hydroxide@GO composite powder. The powder was then placed in a muffle furnace and calcined in air for 2 to 5 hours at a temperature of 300 to 600 °C. After cooling in the furnace, the Y2O3-Co3O4 composite oxide@GO composite precursor was obtained.

3. A highly stable Y₂Co with tunable electromagnetic wave absorption performance as described in claim 1. 17 The preparation method of @NGC nanocomposite soft magnetic materials is characterized by: Step two is achieved as follows: 0.3–0.8 g of the Y2O3-Co3O4@GO composite precursor prepared in step one is poured into 50–200 mL of commercially available 1.0 M Tris-HCl buffer solution with a pH of 8.

5. After ultrasonic dispersion for 0.5–2 hours, 10–100 mg of dopamine hydrochloride is added, and magnetic stirring is continued for 12–24 hours. The PDA-coated composite particles are then collected by centrifugation. The PDA-coated particles are washed 3–5 times with deionized water and anhydrous ethanol and then dried in a vacuum drying oven at 30–80 °C. The dried powder is then annealed under an argon atmosphere for 1–4 hours at a temperature of 600–800 °C at a heating rate of 2–5 °C / min. After furnace cooling, the CoO-Co-Y2O3 / C composite precursor is obtained.

4. A highly stable Y₂Co with tunable electromagnetic wave absorption performance as described in claim 1. 17 The preparation method of @NGC nanocomposite soft magnetic materials is characterized by: Step 3 is achieved as follows: The CoO-Co-Y2O3 / C composite precursor obtained in Step 2, commercially available high-purity calcium granules, and analytical grade potassium chloride are uniformly mixed in a mass ratio of 1:1:5 to 1:3:1 and placed in a crucible. The mixture is then transferred to a controlled atmosphere heat treatment furnace. Under a protective atmosphere of high-purity argon, the temperature is increased from room temperature to 850–1000 °C at a rate of 2 °C / min to 8 °C / min. After reacting for 1–3 hours, the furnace is cooled to obtain the reaction product. The product is then washed with deionized water to remove calcium oxide and unreacted calcium granules, followed by multiple washes with anhydrous ethanol to remove excess water. Finally, the product is dried in a vacuum drying oven at 30–80 °C for 3–12 hours to obtain Y2Co. 17 @NGC nanocomposite soft magnetic particles.

5. A highly stable Y₂Co with tunable electromagnetic wave absorption properties prepared by the method according to any one of claims 1 to 4. 17 @NGC nanocomposite soft magnetic materials have the following intrinsic magnetic properties: due to Y2Co 17 @NGC nanocomposites contain ultra-high purity Y2Co 17 Nanoparticles and an ultrathin NGC modification layer, Y2Co 17 @NGC nanocomposites exhibit high saturation magnetization, ranging from 112.1 to 113.3 emu / g, slightly lower than that of Y₂Co. 17 corresponding M s The theoretical value of Y2Co; due to 17 The flower-like microstructure and the surface modification effect of NGC, Y2Co 17 @NGC nanocomposites exhibit high coercivity, ranging from 242.9 to 294.6 Oe; their electromagnetic wave absorption properties can be tunable by adjusting the carbon defects in NGC: Y₂Co 17 @NGC nanocomposite soft magnetic materials exhibit a maximum electromagnetic wave absorption intensity range of -69.69 to -80.16 dB in the 2–18 GHz range, corresponding to an electromagnetic wave absorption frequency range of 4.30–7.49 GHz. This makes them suitable for fabricating absorbers for C-band frequency range electromagnetic wave absorption; Y2Co 17 @DGC nanocomposite soft magnetic materials exhibit a maximum electromagnetic wave absorption intensity range of -20.19 to -68.67 dB in the 2–18 GHz range, corresponding to an electromagnetic wave absorption frequency range of 13.40–16.71 GHz, making them suitable for preparing absorbers for electromagnetic wave absorption in the Ku-band frequency range.

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