Gradient-size magnetoelectric heterostructure and preparation method and application thereof

Abstract

The invention discloses a gradient-size magnetoelectric heterostructure and a preparation method and application thereof.The gradient-size magnetoelectric heterostructure comprises substrate carbon, composite carbon and nickel nanoparticles, the composite carbon and the nickel nanoparticles are composited on the substrate carbon, the nickel nanoparticles are coated with the composite carbon, the size of the nickel nanoparticles is in gradient distribution within the range of 0.25 nm to 27 nm, and the size of the nickel nanoparticles is larger than or equal to 20 nm. According to the gradient-size magnetoelectric heterostructure and the preparation method thereof, the defects in the prior art are overcome, the Ni particles in the gradient-size magnetoelectric heterostructure are distributed in a gradient size mode, multi-scale magnetoelectric interaction is constructed in the gradient-size magnetoelectric heterostructure, and the gradient-size magnetoelectric heterostructure has the advantages that the gradient-size magnetoelectric heterostructure is formed; and the low-frequency electromagnetic wave absorption capability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation and application, and in particular to a magnetoelectric heterostructure with gradient size and a preparation method and application thereof. Background Art

[0002] With the development of 5G communication technology and the advancement of military low- and medium-frequency (2GHz-8 GHz) detection technology, the importance of electromagnetic wave absorption in many fields has become increasingly prominent. By optimizing the composition and structure, magnetic elements can significantly enhance the dissipation capacity of incident EM waves in a specific frequency band, meeting the high requirements of 5G and military detection for material performance. At the same time, adjusting the magnetic component helps to achieve tuned absorption, ensuring that the material works effectively at different frequencies and adapts to different application scenarios. Multi-scale design allows precise control of the mechanical, electrical, magnetic, and thermal properties of functional materials at different scales (nano, micro, and macro). Therefore, the present invention constructs a magnetoelectric heterostructure with a gradient size that can be used for low-frequency electromagnetic wave absorption. Summary of the invention

[0003] The purpose of the present invention is to provide a magnetoelectric heterostructure with gradient size and a preparation method and application thereof, thereby overcoming the shortcomings of the prior art.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A magnetoelectric heterostructure with a gradient size includes a base carbon and composite carbon and nickel nanoparticles composited on the base carbon, wherein the nickel nanoparticles are encapsulated in the composite carbon, the size of the nickel nanoparticles is gradiently distributed in the range of 0.25nm-27nm, and the nickel nanoparticles are composed of at least one of single atoms, clusters and nanoparticles.

[0006] The method for preparing the above heterostructure comprises the following steps:

[0007] S1, 50 mg of the base carbon is uniformly dispersed in 100 mL of solvent, then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 100 mg-500 mg of a nickel source are added, and the mixture is stirred at room temperature for 10 h-20 h, and the obtained powder is washed and dried to obtain product A;

[0008] S2, heating the product A to 500°C-700°C in a reducing atmosphere for pyrolysis for 4h-6h, and obtaining a magnetoelectric heterostructure with gradient size after cooling.

[0009] Furthermore, the base carbon is flaky carbon.

[0010] Furthermore, the nickel source is nickel chloride hexahydrate.

[0011] Furthermore, the solvent is a mixed solution of water and ethanol in a volume ratio of 1:1.

[0012] Furthermore, the reducing atmosphere is a mixture of argon and hydrogen.

[0013] Application of gradient-size magnetoelectric heterostructures in electromagnetic wave absorbing materials.

[0014] Compared with the prior art, the implementation effects of the present invention are as follows:

[0015] 1. The present invention successfully prepared Ni-containing 2+ -Product A of PDA component, the surface of the base carbon is composited with Ni 2+ -PDA layer, the obtained product A (RC-Ni 2+ -PDA) has a smooth morphology; secondly, the synthesized product A powder is heated in H 2 / Ar atmosphere annealing to achieve Ni 2+ -PDA to Ni@C components; With the increase of nickel source addition, the number of nickel particles (Ni NPs) on the surface of the substrate carbon increased significantly, and the 2 In the range of 1.5 Å, the number of nickel nanoparticles increased from about 26 to more than 100. At the same time, the average sizes of Ni nanoparticles on the surface of RC-Ni@C-1, RC-Ni@C-2 and RC-Ni@C-3 were 34.1 nm, 42.6 nm and 48.2 nm, respectively, showing an increasing trend. In addition, the Ni particles inside the gradient-sized magnetoelectric heterostructure have a gradient size distribution, which enables the construction of multi-scale magnetoelectric interactions in the gradient-sized magnetoelectric heterostructure.

[0016] 2. During the pyrolysis process, due to the restricted reduction and Kirkendall diffusion effect, gradient-sized nickel nanoparticles can be positioned in the substrate carbon, where the substrate carbon is the core and the polymer PDA is the outer layer, which together restrict the growth direction of the Ni particles from the inside to the outside.

[0017] 3. The nickel nanoparticles with gradient size distribution in the magnetoelectric heterostructure produce unique magnetoelectric interactions, which improve its ability to absorb low-frequency electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 ac in the middle is RC@Ni 2+ -PDA-1(a), RC@Ni 2+ -PDA-2(b) and RC@Ni 2+ -PDA-3 (c) SEM image; d is the X-ray diffraction pattern of the base carbon and the gradient-sized magnetoelectric heterostructure of Examples 3-5; e is a schematic diagram of the internal structure of the gradient-sized magnetoelectric heterostructure;

[0019] Figure 2Where ac is the SEM image and related size distribution of the gradient-sized magnetoelectric heterostructures of Examples 3-5; dj is the transmission electron microscope photo of the gradient-sized magnetoelectric heterostructure RC-Ni@C-2 of Example 4 and the distribution diagram of nickel nanoparticles; k is the surface image with distance profile of RC-Ni@C-2, and L and n are element mapping images of RC-Ni@C-2;

[0020] Figure 3 a is the HAADF-STEM image of RC-Ni@C-2, b and d are the enlarged images of 1# and 2# regions in a, c and e are the GPA strain images of 1# and 2# regions corresponding to b and d, respectively;

[0021] Figure 4 Where ad is the electromagnetic wave absorption performance of RC, RC-Ni@C-1, RCNi@C-2, and RC-Ni@C-3;

[0022] Figure 5 Three-dimensional radar wave scattering signals of PEC substrate (a), RC (b), RC-Ni@C-1 (c), RC-Ni@C-2 (d), and RCNi@C-3 (e). (f) is a schematic diagram of the RCS reduction values ​​of PEC, RC, and RC-Ni@C-2 composites.

[0023] Figure 6 The magnetic properties test data of the gradient-sized magnetoelectric heterostructures of Examples 3-5. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] 50 mg of base carbon (RC) was uniformly dispersed in 100 mL of solvent, which was a mixed solution of water and ethanol in a volume ratio of 1:1; then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 100 mg of nickel chloride hexahydrate were added, and the mixture was stirred at room temperature for 10 h. The obtained powder was washed and dried to obtain product A; the obtained product A was heated in a reducing atmosphere (H 2 / Ar mixed gas, where H 2 The volume of the composite was 5% (5%) heated to 500°C for pyrolysis for 6 h, and a magnetoelectric heterostructure with gradient size was obtained after cooling.

[0027] Example 2

[0028] 50 mg of base carbon (RC) was uniformly dispersed in 100 mL of solvent, which was a mixed solution of water and ethanol in a volume ratio of 1:1; then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 500 mg of nickel chloride hexahydrate were added, and the mixture was stirred at room temperature for 20 h. The obtained powder was washed and dried to obtain product A; the obtained product A was heated in a reducing atmosphere (H 2 / Ar mixed gas, where H 2 The volume of the composite was 5%) heated to 700°C for pyrolysis for 4 h, and a magnetoelectric heterostructure with gradient size was obtained after cooling.

[0029] Example 3

[0030] 50 mg of RC was evenly dispersed in 100 mL of solvent, which was a mixed solution of water and ethanol in a volume ratio of 1:1. Then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 119 mg of nickel chloride hexahydrate were added, and the mixture was stirred at room temperature for 14 h. The obtained powder was washed and dried to obtain a composite Ni on the surface of RC. 2+ and polydopamine (PDA); the obtained product A is placed in a reducing atmosphere (H 2 / Ar mixed gas, where H 2 The volume of the Ni@C was 5% (5%) and heated to 600 °C for pyrolysis for 5 h. After cooling, a magnetoelectric heterostructure with gradient size was obtained, which was marked as RC-Ni@C-1.

[0031] Example 4

[0032] 50 mg of base carbon (RC) was uniformly dispersed in 100 mL of solvent, which was a mixed solution of water and ethanol in a volume ratio of 1:1; then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 238 mg of nickel chloride hexahydrate were added, and the mixture was stirred at room temperature for 14 h. The obtained powder was washed and dried to obtain a composite Ni on the surface of the base carbon (RC). 2+ and polydopamine (PDA); the obtained product A is placed in a reducing atmosphere (H 2 / Ar mixed gas, where H 2 The volume of the Ni@C was 5% (5%) heated to 600 °C for pyrolysis for 5 h, and after cooling, a magnetoelectric heterostructure with gradient size was obtained, which was marked as RC-Ni@C-2.

[0033] Example 5

[0034] 50 mg of base carbon (RC) was evenly dispersed in 100 mL of solvent, which was a mixed solution of water and ethanol in a volume ratio of 1:1; then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 475 mg of nickel chloride hexahydrate were added, and the mixture was stirred at room temperature for 14 h. The obtained powder was washed and dried to obtain a composite Ni on the surface of the base carbon (RC). 2+and polydopamine (PDA); the obtained product A is placed in a reducing atmosphere (H 2 / Ar mixed gas, where H 2 The volume of the prepared Ni@C-3 was 5% (5%) and heated to 600 °C for pyrolysis for 5 h. After cooling, a magnetoelectric heterostructure with gradient size was obtained, which was labeled as RC-Ni@C-3.

[0035] The gradient-sized magnetoelectric heterostructures prepared in Examples 3-5 were analyzed by the following detection methods: X-ray diffractometer (model: D8 Advance), vibrating sample magnetometer (model: LakeShore7404), X-ray photoelectron spectrometer (model: Thermo Kalpha), scanning electron microscope (model: S4800) and transmission electron microscope (model: JEM-2100F) were used to characterize the composition, structure, magnetization, morphology and chemical environment of RC and RC-Ni@C composites. HAADF-STEM and integrated differential phase contrast (iDPC) images were obtained on an aberration-corrected transmission electron microscope (model: Spectra 300). The electromagnetic parameters of RC and RCNi@C composites were measured using a vector network analyzer (model: E5071C).

[0036] like Figure 1 As shown in Figure 2, Ni was successfully prepared on the surface of the base carbon (RC) particles after in situ polymerization. 2+ and polydopamine (Ni 2+ -PDA) component, the base carbon is a lamellar structure with a size between 1um-5um, and the composite Ni 2+ -PDA layer, the obtained RC-Ni 2+ -PDA composite material has a smooth morphology. 2+ -PDA powder in H 2 / Ar atmosphere annealing to achieve Ni 2+ -PDA to Ni@C components, e.g. Figure 1 d-1e, The composite carbon derived from the thermal decomposition of polydopamine encapsulates the reduced nickel nanoparticles. Figure 2 As shown in a-2c, with the increase of nickel source content, the number of nickel nanoparticles on the surface of the substrate carbon has a significant increasing trend. 2 In the range of 100 Å, the number of nickel nanoparticles increased from about 26 to more than 100, and the average sizes of Ni nanoparticles on the surfaces of RC-Ni@C-1, RC-Ni@C-2, and RC-Ni@C-3 were 34.1 nm, 42.6 nm, and 48.2 nm, respectively, showing an increasing trend. Moreover, with the increase of nickel source content, the magnetic properties of RC-Ni@C-1, RC-Ni@C-2, and RC-Ni@C-3 also continued to increase (e.g. Figure 6 From the HAADF-STEM image (Figure 2 d) It can be found that the internal nickel nanoparticles have a gradient size distribution. Figure 2 The three typical areas marked in d are the center (RC-Ni@C-2), and the surface TEM image ( Figure 2 e-2g) and related spectral lines ( Figure 2 h-2j) confirm that nickel nanoparticles in the base carbon exist in a variety of forms (size distribution ranges from 0.25nm to 27nm), and the size distribution shows an obvious gradient distribution phenomenon, including single atoms, clusters and nanoparticles. Figure 2 k It can be seen that a selected Ni single atom on the substrate carbon is surrounded by a large number of Ni nanoparticles of different sizes, that is, a multi-scale magnetoelectric interaction is constructed in the magneto-dielectric heterostructure with gradient size. The nickel nanoparticles embedded in the substrate carbon were mapped by energy dispersive X-ray spectroscopy (EDS) ( Figure 2 L), further indicating its multi-size and multi-site distribution. In addition, the N element doped in the base carbon comes from the PDA-derived N source. Due to the restricted reduction and Kirkendall diffusion effect, during the pyrolysis process, gradient-sized nickel nanoparticles can be positioned in the base carbon, with RC as the core and polymer PDA as the outer layer, which jointly restrict the growth direction of the nickel nanoparticles from the inside to the outside. With the increase of Ni addition, the density of the surface nickel nanoparticles increases. In this RC-Ni@C system, nickel nanoparticles regulate metal support interactions, change the chemical environment, and locate strain distribution, thereby affecting its intrinsic electromagnetic wave absorption performance.

[0037] Geometric phase analysis (GPA) is used to study the interactions within magnetoelectric heterostructures with gradient sizes, such as Figure 3 As shown in a, two typical regions (1# and 2#) were selected for Ni-C interaction analysis, and it can be found that there are more strain mutation regions along the Exy direction ( Figure 3 c. Figure 3 e), which shows that the larger the size of nickel nanoparticles, the stronger the interaction. Based on the gradient distribution of nickel nanoparticles, the electronic state and geometric configuration between the nickel-carbon heterostructure interface can be further adjusted to control the magnetoelectric interaction. In the magnetoelectric heterostructure system with gradient size, the metal-support interaction is regulated as the chemical environment and positional strain distribution change, thereby affecting the inherent electromagnetic properties of the material and providing design space for low-frequency electromagnetic absorption.

[0038] According to the coaxial test principle, the electromagnetic parameters of the magnetoelectric heterostructure containing 50wt.% paraffin matrix carbon and gradient size were tested in the 2GHz-18GHz frequency band. The reflection loss (RL) value was further calculated by the following formula:

[0039]

[0040] In the formula, Z in is the input impedance, ε r and μ r are the complex permittivity and magnetic permeability, c is the speed of light, f is the frequency, and d is the thickness. The relationship between thickness (1mm-5mm), frequency (2GHz-18 GHz) and RL value (RL<-10dB) is mapped into a two-dimensional distribution ( Figure 4 a-4d), after inducing the Ni@C shell layer on the RC substrate, the effective absorption region (RL<-10dB) shows a trend of first weakening and then increasing. The minimum reflection loss RL of RC min The value is -20.8dB at 12.8GHz, which is the minimum reflection loss RL of RC-Ni@C-1. min The value is 27.2dB at 16.4GHz, and the minimum reflection loss RL of RC-Ni@C-2 is min The value is -35.9dB at 5.8GHz, and the minimum reflection loss RL of RC-Ni@C-3 min The value is -16.7 at 13.8 GHz. It can be seen that the multi-scale design of Ni nanoparticles in RC-Ni@C-2 composites provides a new strategy for obtaining excellent low-frequency (2 GHz-8 GHz) absorption performance, covering special detection and 5G communication frequency bands; Figure 4 When the thickness of the gradient-sized magnetoelectric heterostructures of RC in a-4d and Examples 4-6 was 3.0 mm-5.0 mm, the effective electromagnetic wave absorption (RL<-10 dB) changed significantly.

[0041] Based on the obtained electromagnetic parameters, thickness (3.5mm) and application frequency (5.8GHz), the relevant radar cross section (RCS) simulation was carried out, and the RCS value (σ) on the perfect electric conductor (PEC) plane (180cm*180cm) can be calculated. Figure 5 As shown in a-5e, the 3D radar scattering signal of the RC-Ni@C composite material is significantly weakened compared with the base carbon. Among these coating absorption layers, the scattering signal of the RC-Ni@C-2 composite material is the weakest, and the absorption capacity at low frequencies is the best, as shown in Fig. Figure 5 f. Compared with the RC plane, the RCS value of the RC-Ni@C-2 composite material is the smallest in the angle range of -90°<θ<90°, and the RCS scattering reduction effect is significant. Therefore, the regulation of the unique multi-scale interaction between magnetic Ni particles and metal loads in this RC-Ni@C composite material is of great significance in guiding the development of efficient electromagnetic wave absorption materials, especially in low-frequency performance.

[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A magnetoelectric heterostructure with gradient size, characterized in that: The invention comprises base carbon and composite carbon and nickel nanoparticles composited on the base carbon. The nickel nanoparticles are coated in the composite carbon, and the sizes of the nickel nanoparticles are distributed in a gradient within the range of 0.25nm-27nm.

2. A method for preparing the heterostructure according to claim 1, characterized in that: The following steps are involved: S1, 50 mg of the base carbon is uniformly dispersed in 100 mL of solvent, then 30 mg of dopamine hydrochloride, 3 mL of ammonia water, and 100 mg-500 mg of a nickel source are added, and the mixture is stirred at room temperature for 10 h-20 h, and the obtained powder is washed and dried to obtain product A; S2, heating the product A to 500°C-700°C in a reducing atmosphere for pyrolysis for 4h-6h, and obtaining a magnetoelectric heterostructure with gradient size after cooling.

3. The method for preparing a heterostructure according to claim 2, characterized in that: The base carbon is flaky carbon.

4. The method for preparing a heterostructure according to claim 2, characterized in that: The nickel source is nickel chloride hexahydrate.

5. The method for preparing a heterostructure according to claim 2, characterized in that: The solvent is a mixed solution of water and ethanol in a volume ratio of 1:

1.

6. The method for preparing a heterostructure according to claim 2, characterized in that: The reducing atmosphere is a mixture of argon and hydrogen.

7. A magnetoelectric heterostructure with gradient size according to claim 1, characterized in that: Application in electromagnetic wave absorbing materials.

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