A cluster-derived rare earth-based composite electromagnetic wave absorbing material and preparation method thereof

Abstract

The present invention relates to the technical field of wave absorbing materials, and in particular to a cluster-derived rare earth-based composite electromagnetic wave absorbing material and a preparation method thereof. The rare earth-based composite electromagnetic wave absorbing material is obtained by compounding carboxylated multi-walled carbon nanotubes and cluster compound crystals; the composite is obtained by calcining the composite at 400°C to 700°C. The present invention uses rare earth-based coordinated cluster crystals as precursors, and compounds them with carbon-based materials, and performs high-temperature pyrolysis and carbonization to prepare cluster-derived rare earth-based composite electromagnetic wave absorbing materials. While using carbon-based materials to enhance the dielectric properties of composite materials, the electromagnetic properties of rare earth metal ions are utilized to greatly improve the magnetic loss performance of the material, and finally the material has good wave absorbing performance, which not only further expands the application of rare earth elements in wave absorbing materials, but also solves the problem of poor wave absorbing performance of the material caused by the single loss mechanism and impedance mismatch of traditional single-component carbon-based / magnetic metal wave absorbing materials.

Description

Technical Field

[0001] The present invention relates to the technical field of wave absorbing materials, and in particular to a cluster-derived rare earth-based composite electromagnetic wave absorbing material and a preparation method thereof. Background Art

[0002] Today, electromagnetic wave technology is widely used, bringing convenience to people's lives while also causing serious electromagnetic pollution. Electromagnetic pollution mainly includes electromagnetic radiation and electromagnetic interference, which pose a potential threat to human health and the normal operation of electronic equipment. Wave-absorbing materials, abbreviated as MAMs, are materials that can absorb most incident electromagnetic waves and minimize the reflection of electromagnetic waves on the surface. This type of material can convert electromagnetic waves that enter the material into a variety of other energies for dissipation and attenuation, avoiding the reflection and transmission of electromagnetic waves as much as possible, thereby reducing electromagnetic pollution and maintaining the stability and safety of electronic equipment. Therefore, the development of high-efficiency electromagnetic wave absorbing materials is a key strategy to effectively reduce electromagnetic pollution.

[0003] Currently, researchers have discovered a variety of materials that can be used to prepare absorbing materials, such as carbon materials, magnetic metal materials, semiconductor materials, and polymer materials. However, single-component absorbing materials have certain drawbacks and limitations in terms of electromagnetic properties and performance. For conductive lossy absorbing materials, their high conductivity greatly limits their application. The presence of the skin effect can lead to enhanced surface reflection and poor impedance matching. Magnetic lossy materials, likewise, are limited in practical application due to the shortcomings of their single component. Magnetic lossy materials generally have a high density, resulting in heavy materials that are not conducive to practical application.

[0004] Rare earth elements, due to their excellent physical properties, such as high magnetic susceptibility, high saturation magnetization, and large magnetocrystalline anisotropy, are increasingly being used in microwave absorbing materials. Research has shown that doping with rare earth elements can effectively adjust the impedance matching properties of materials, resulting in improved electromagnetic wave absorption performance. However, the large radius, high charge, and complex and variable coordination patterns of rare earth ions make the preparation of porous rare earth complexes challenging. Summary of the Invention

[0005] To address the poor absorption performance of traditional single-component carbon-based and magnetic metal absorbers, which suffer from a single loss mechanism and impedance mismatch, the present invention provides a cluster-derived rare earth-based composite electromagnetic wave absorber and a method for its preparation. This method provides a theoretical foundation for further expanding the application of rare earth elements in absorbers.

[0006] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0007] A first aspect of the present invention provides a method for preparing a cluster-derived rare earth-based composite electromagnetic wave absorbing material, comprising the following steps:

[0008] The carboxylated multi-walled carbon nanotubes and cluster crystals are compounded to prepare a composite; the mass ratio of the carboxylated multi-walled carbon nanotubes to the cluster crystals is 10 to 20:1; the cluster crystals are {Ni 120 Sm 96}Crystal, {Ni 120 Gd 96}Crystal, {Ni 120 Nd 96 Any one of the crystals;

[0009] The composite is calcined at 400-700 DEG C to obtain a cluster-derived rare earth-based composite electromagnetic wave absorbing material.

[0010] Preferably, the crystal parameters of the cluster compound crystal are: {Ni 120 Nd 96 The crystal parameters of the crystal are: crystallized in the triclinic system, the space group is P-1, and the unit cell parameters are α=71.29deg, β=66.63deg, γ=77.07deg, {Ni 120 Sm 96 The crystal parameters of the crystal are: crystallized in the triclinic system, the space group is P-1, and the unit cell parameters are α=71.15deg, β=66.62deg, γ=77.32deg, {Ni 120 Gd 96 The crystal parameters of the crystal are: crystallized in the triclinic system, the space group is P-1, and the unit cell parameters are α=71.15deg, β=66.24deg, γ=77.00deg,

[0011] Preferably, the cluster compound crystals are prepared by the following method: uniformly mixing a nickel salt, a rare earth salt, N-methyliminodiacetic acid, potassium bromide, and methanol, then adding triethylamine and reacting at 140°C. After the reaction is complete, cluster compound crystals are prepared; the nickel salt is Ni(CH3COO)2·4H2O; the rare earth salt is any one of Nd(NO3)3·6H2O, Sm(NO3)3·6H2O, and Gd(NO3)3·6H2O. Preferably, the ratio of the nickel salt, rare earth salt, N-methyliminodiacetic acid, potassium bromide, and methanol is 1.2 mmol to 1.3 mmol: 1.2 mmol to 1.3 mmol: 0.1 mmol: 0.4 mmol to 0.5 mmol: 9 mL; and the ratio of triethylamine to methanol is 9 mL to 300 μL. The corresponding cluster compound crystals can be prepared within this ratio range.

[0012] Preferably, the dimensions of the carboxylated multi-walled carbon nanotubes are: inner diameter 2 nm to 5 nm, outer diameter 5 nm to 15 nm, and length 10 μm to 30 μm.

[0013] Preferably, the composite is prepared by ultrasonically dispersing carboxylated multi-walled carbon nanotubes in water to obtain a carboxylated multi-walled carbon nanotube solution; ultrasonically dispersing cluster compound crystals in water to obtain a cluster compound crystal solution; mixing the carboxylated multi-walled carbon nanotube solution and the cluster compound crystal solution, then ultrasonically treating the mixture. After the ultrasonic treatment is completed, the mixture is filtered and dried to obtain the composite. Preferably, the ultrasonic treatment is continued for 8 to 12 hours. Preferably, the temperature of the ultrasonic treatment is controlled at ≤60°C. Preferably, the calcination time is 2 hours. Preferably, the calcination is carried out under inert gas protection.

[0014] The second aspect of the present invention further provides a cluster-derived rare earth-based composite electromagnetic wave absorbing material prepared by the preparation method described in the first aspect.

[0015] Beneficial effects of the present invention:

[0016] 1. The present invention uses cluster compound crystals as precursors, composites them with carbon-based materials, and performs high-temperature pyrolysis and carbonization to prepare cluster-derived rare earth-based composite electromagnetic wave absorbing materials. While using carbon-based materials to enhance the dielectric properties of the composite materials, the electromagnetic properties of rare earth metal ions are utilized to significantly improve the magnetic loss performance of the material, ultimately giving the material excellent wave-absorbing performance. This not only further expands the application of rare earth elements in wave-absorbing materials, but also solves the problem of traditional single-component carbon-based / magnetic metal wave-absorbing materials, which have a single loss mechanism and impedance mismatch, resulting in poor wave-absorbing performance of the material.

[0017] 2. The present invention's rare earth-based composite electromagnetic wave absorbing material, prepared by combining carbon-based materials with cluster crystals in a mass ratio of 10:1, achieves a minimum reflection loss of -58.85 dB at a thickness of 3 mm. The rare earth-based composite electromagnetic wave absorbing material prepared in a mass ratio of 15:1 achieves a minimum reflection loss of -40.04 dB at a thickness of 4 mm. The rare earth-based composite electromagnetic wave absorbing material prepared in a mass ratio of 20:1 achieves a minimum reflection loss of -23.79 dB. The effective absorption bandwidth reaches 16.85 GHz. Compared to the performance of materials not combined with the aforementioned materials, the absorption performance of the material obtained by combining carbon-based materials with cluster crystals and then subjecting them to high-temperature pyrolysis and carbonization is three times higher. This is primarily attributed to the increased electrical loss caused by the increased carbon content in the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Figures 1 and 3 show the absorption performance of the samples prepared in Examples 1 to 3. (a) shows the reflection loss of Gd / Ni@C-500; (b) shows the reflection loss of Sm / Ni@C-500; (c) shows the reflection loss of Nd / Ni@C-500; (d) shows the three-dimensional relationship between the reflection loss of Gd / Ni@C-500, frequency, and thickness; (e) shows the three-dimensional relationship between the reflection loss of Sm / Ni@C-500, frequency, and thickness; and (f) shows the three-dimensional relationship between the reflection loss of Nd / Ni@C-500, frequency, and thickness.

[0019] Figure 2 The powder X-ray diffraction patterns of the samples prepared in Examples 3 to 6 are shown in FIG. 1 , where (b) is a partial enlarged view of the portion selected by the dotted line in (a).

[0020] Figure 3 The following are scanning electron micrographs of Sm / Ni@C-500: (a) is a scanning electron micrograph before high-temperature carbonization; (b) is a scanning electron micrograph at low magnification after high-temperature carbonization; (c) is a scanning electron micrograph at high magnification after high-temperature carbonization; (d) to (i) are transmission electron micrographs after high-temperature carbonization.

[0021] Figure 4 In the figure, (j) is a high-resolution transmission electron microscopy image of Sm / Ni@C-400; (k) is a high-resolution transmission electron microscopy image of Sm / Ni@C-500.

[0022] Figure 5 XPS spectra of Sm / Ni@C-700. (a) is the C1s spectrum; (b) is the O 1s spectrum; (c) is the Sm 3d spectrum; and (d) is the Ni 2p spectrum.

[0023] Figure 6In the figure, (a) is the XPS total spectrum of Sm / Ni@C-500; (b) is the C1s spectrum of Sm / Ni@C-500; (c) is the O1s spectrum of Sm / Ni@C-500; (d) is the Sm 3d spectrum of Sm / Ni@C-500; (e) is the Ni 2p spectrum of Sm / Ni@C-500; (f) is the Raman spectra of Sm / Ni@C-400, Sm / Ni@C-500, Sm / Ni@C-600, and Sm / Ni@C-700.

[0024] Figure 7 Figures 2 and 3 show the microwave absorption performance of Sm / Ni@C-400, Sm / Ni@C-500, Sm / Ni@C-600, and Sm / Ni@C-700. (a) shows the real part of the dielectric constant versus frequency; (b) shows the imaginary part of the dielectric constant versus frequency; (c) shows the dielectric loss tangent versus frequency; (d) shows the real part of the magnetic permeability versus frequency; (e) shows the imaginary part of the magnetic permeability versus frequency; and (f) shows the magnetic loss tangent versus frequency.

[0025] Figure 8 The reflection loss of Sm / Ni@C-400 varies with frequency. (a) is a two-dimensional graph, and (b) is a three-dimensional graph.

[0026] Figure 9 The reflection loss of Sm / Ni@C-500 varies with frequency. (a) is a two-dimensional graph, and (b) is a three-dimensional graph.

[0027] Figure 10 The reflection loss of Sm / Ni@C-600 varies with frequency. (a) is a two-dimensional graph, and (b) is a three-dimensional graph.

[0028] Figure 11 The reflection loss of Sm / Ni@C-700 varies with frequency. (a) is a two-dimensional graph, and (b) is a three-dimensional graph.

[0029] Figure 12 This is the transmission electron microscope image of the sample SmNi / C@CNTs-10:1.

[0030] Figure 13 The powder X-ray diffraction patterns and Raman spectra of three samples, SmNi / C@CNTs-10:1, SmNi / C@CNTs-15:1, and SmNi / C@CNTs-20:1, are shown in Figure 1. (a) is the powder X-ray diffraction pattern; (b) is the Raman spectrum.

[0031] Figure 14Figure 2 is a graph showing the microwave absorption performance of carboxylated multi-walled carbon nanotubes when the doping ratio is 50%. Figure (b) is a partial enlarged view of part A in Figure (a).

[0032] Figure 15 Figures 2 and 3 show the microwave absorption performance of SmNi / C@CNTs-10:1, SmNi / C@CNTs-15:1, and SmNi / C@CNTs-20:1. (a) shows the real part of the dielectric constant versus frequency; (b) shows the imaginary part of the dielectric constant versus frequency; (c) shows the dielectric loss tangent versus frequency; (d) shows the real part of the magnetic permeability versus frequency; (e) shows the imaginary part of the magnetic permeability versus frequency; and (f) shows the magnetic loss tangent versus frequency.

[0033] Figure 16 In the figure, (a) is a two-dimensional graph of the reflection loss value of SmNi / C@CNTs-10:1 changing with frequency; (b) is a two-dimensional graph of the reflection loss value of SmNi / C@CNTs-15:1 changing with frequency; (c) is a two-dimensional graph of the reflection loss value of SmNi / C@CNTs-20:1 changing with frequency; (d) is a three-dimensional graph of the reflection loss value of SmNi / C@CNTs-10:1 changing with frequency; (e) is a three-dimensional graph of the reflection loss value of SmNi / C@CNTs-15:1 changing with frequency; (f) is a three-dimensional graph of the reflection loss value of SmNi / C@CNTs-20:1 changing with frequency. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0035] Unless otherwise specified, the methods described in the following examples are all conventional methods; the reagents and materials described are all commercially available unless otherwise specified.

[0036] RL min is the minimum reflection loss. SEM is a scanning electron microscope. TEM is a transmission electron microscope. HRTEM is a high-resolution transmission electron microscope. XPS is an X-ray photoelectron spectroscopy.

[0037] In the following examples, carboxylated multi-walled carbon nanotubes were purchased through commercial channels. The product supplier is Shanghai Haohong Biomedicine Technology Co., Ltd., the brand is Leyan, the purity is >99%, the inner diameter is 2nm~5nm, the outer diameter is 5nm~15nm, and the length is 10μm~30μm.

[0038] Example 1

[0039] Cluster {Ni 120 Nd 96 A method for preparing a carbon-based composite material comprises the following steps:

[0040] Step 1, {Ni 120 Nd 96 Preparation of} crystals: Mix 1.24mmol of Ni(CH3COO)2·4H2O, 1.24mmol of Nd(NO3)3·6H2O, 0.10mmol of N-methyliminodiacetic acid, and 0.42mmol of potassium bromide, and dissolve them in 9mL of pure methanol. Then add 300μL of triethylamine to adjust the pH of the solution. Finally, add the mixed solution to a 12mL polyethylene reactor. The temperature is raised to the target temperature of 140℃ within 1 hour, and the temperature is maintained at 140℃ for 72 hours, and then cooled to room temperature within 36 hours. After washing with ethanol at room temperature, regular light blue block crystals are obtained, which are recorded as {Ni 120 Nd 96} crystal. Based on Nd calculation, {Ni 120 Nd 96 The yield of crystals was about 60%.

[0041] Step 2, cluster {Ni 120 Nd 96 Preparation of carbon-based composite materials: Prepared {Ni 120 Nd 96 The crystals were washed with anhydrous ethanol, filtered through filter paper, and then placed in a fume hood to air dry. After drying, they were fully ground in a mortar to obtain a powder sample. The obtained powder sample was then loaded into a high-temperature resistant quartz boat and placed in a tube furnace filled with nitrogen gas. The temperature was increased to 500°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. The cluster compound {Ni 120 Nd 96}Carbon-based composite material, denoted as Nd / Ni@C-500, has a product yield of about 50%.

[0042] Example 2

[0043] Cluster {Ni 120 Gd 96 A method for preparing a carbon-based composite material comprises the following steps:

[0044] Step 1, {Ni 120 Gd 96Preparation of} crystals: Mix 1.24mmol of Ni(CH3COO)2·4H2O, 1.24mmol of Gd(NO3)3·6H2O, 0.10mmol of N-methyliminodiacetic acid, and 0.42mmol of bromide, and dissolve them in 9mL of pure methanol. Then add 300μL of triethylamine to adjust the pH of the solution. Finally, add the mixed solution to a 12mL polyethylene reactor. The temperature is raised to the target temperature of 140℃ within 1 hour, and kept heated at 140℃ for 72 hours, and then cooled to room temperature within 36 hours. After washing with ethanol at room temperature, regular light blue block crystals are obtained, which are recorded as {Ni 120 Gd 96} crystal, calculated based on Gd, {Ni 120 Gd 96 The yield of crystals was about 60%.

[0045] Step 2, cluster {Ni 120 Gd 96 Preparation of carbon-based composite materials: Prepared {Ni 120 Gd 96 The crystals were washed with anhydrous ethanol, filtered through filter paper, and then placed in a fume hood to air dry. After drying, they were fully ground in a mortar to obtain a powder sample. The obtained powder sample was then loaded into a high-temperature resistant quartz boat and placed in a tube furnace filled with nitrogen gas. The temperature was increased to 500°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. The cluster compound {Ni 120 Gd 96}Carbon-based composite material, denoted as Gd / Ni@C-500, with a product yield of about 50%.

[0046] Example 3

[0047] Cluster {Ni 120 Sm 96 A method for preparing a carbon-based composite material comprises the following steps:

[0048] Step 1, {Ni 120 Sm 96Preparation of} crystals: Mix Ni(CH3COO)2·4H2O 1.24mmol, Sm(NO3)3·6H2O 1.24mmol, N-methyliminodiacetic acid 0.10mmol, and potassium bromide 0.42mmol, and dissolve them in 9mL of pure methanol. Then add 300μL of triethylamine (about 2.14mmol) to adjust the pH of the solution. Finally, add the mixed solution to a 12mL polyethylene reactor. The temperature is raised to the target temperature of 140℃ within 1 hour, and kept heated at 140℃ for 72h, and then cooled to room temperature within 36h. After washing with ethanol at room temperature, regular light blue block crystals are obtained, which are recorded as {Ni 120 Sm 96} crystal, calculated based on Sm, {Ni 120 Sm 96 The yield of crystals was about 60%.

[0049] Step 2, cluster {Ni 120 Sm 96 Preparation of carbon-based composite materials: Prepared {Ni 120 Sm 96 The crystals were washed with anhydrous ethanol, filtered through filter paper, and then placed in a fume hood to air dry. After drying, they were fully ground in a mortar to obtain a powder sample. The obtained powder sample was then loaded into a high-temperature resistant quartz boat and placed in a tube furnace filled with nitrogen gas. The temperature was increased to 500°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. The cluster compound {Ni 120 Sm 96}Carbon-based composite material, denoted as Sm / Ni@C-500, has a product yield of about 52%.

[0050] In order to explore the suitable experimental conditions for preparing microwave absorbing materials using different clusters as self-sacrificial templates, {Ni 120 Nd 96}、{Ni 120 Gd 96}、{Ni 120 Sm 96 Three crystals were used as precursors. Three samples were initially obtained at an experimental temperature of 500°C: Nd / Ni@C-500, Gd / Ni@C-500, and Sm / Ni@C-500. The absorption properties of the three samples were investigated. The results are shown in Figure 2. Figure 1 shown.

[0051] from Figure 1It can be seen that when the thickness is 7mm, the minimum reflection loss of Gd / Ni@C-500, Sm / Ni@C-500, and Nd / Ni@C-500 can reach -39.59dB, -40.65dB, and -21.85dB respectively; compared with the reported absorbing materials, the RL of the three is min The reflection loss absorption of Sm / Ni@C-500 and Gd / Ni@C-500 is close and strong, but the overall effective absorption frequency range of Gd / Ni@C-500 is the lowest. Therefore, through preliminary research, it is found that among the three different rare earth samples, {Ni 120 Sm 96} is the best precursor for preparing carbon-based composite materials, so {Ni 120 Sm 96}crystals are used as precursors for subsequent experiments to conduct further experiments to explore the effects of factors such as temperature on material properties. It should be noted that since the three samples prepared in Examples 1 to 3 have a high magnetic metal content and less carbon material with electrical loss, the effective absorption frequency range of the three samples is narrow, approximately 2 GHz, and is only distributed in the second half of the frequency range. This is because magnetic loss will be enhanced under high-frequency conditions. In addition, when testing the samples using a vector network analyzer, the samples are required to be mixed with the paraffin matrix in a certain proportion before testing. Here, the doping ratio of all samples is 70%. Obviously, this is a relatively high ratio. Therefore, a key to subsequent testing is to reduce the doping ratio of the samples from 70% to 50% for experimental exploration.

[0052] Example 4

[0053] Cluster {Ni 120 Sm 96 The method for preparing the carbon-based composite material is different from that of Example 3 in that the temperature is increased to 400°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. 120 Sm 96}Carbon-based composite material, denoted as Sm / Ni@C-400, with a product yield of about 55%.

[0054] Example 5

[0055] Cluster {Ni 120 Sm 96 The method for preparing the carbon-based composite material is different from that of Example 3 in that the temperature is increased to 600°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. 120 Sm 96}Carbon-based composite material, denoted as Sm / Ni@C-600, with a product yield of about 50%.

[0056] Example 6

[0057] Cluster {Ni 120 Sm 96 The method for preparing the carbon-based composite material is different from that of Example 3 in that the temperature is increased to 700°C at a rate of 5°C / min and continued for 2 hours, and then cooled naturally to room temperature. 120 Sm 96}Carbon-based composite material, denoted as Sm / Ni@C-700, with a product yield of about 48%.

[0058] Powder X-ray diffraction analysis: with {Ni 120 Sm 96 The carbon-based composite materials were prepared by high-temperature carbonization at different temperatures using} crystals as precursors: Sm / Ni@C-400, Sm / Ni@C-500, Sm / Ni@C-600, and Sm / Ni@C-700. The four samples were characterized by powder X-ray diffractometer for phase and structure analysis. The results are shown in Figure 2. Figure 2 shown.

[0059] Comparing the powder diffraction peaks of the precursor, the phase composition of the cluster crystals changed after high-temperature carbonization, and the samples obtained at different calcination temperatures had similar spectra. Figure 2 It can be seen that Sm / Ni@C-700 has obvious and sharp diffraction peaks. The strong diffraction peaks at 44.5°, 51.8° and 76.4° correspond to the diffraction peaks of metallic nickel, PDF#04-0850; they correspond to the (111), (200) and (220) crystal planes of face-centered cubic nickel respectively; four strong diffraction peaks appear at 28.42°, 32.92°, 47.04° and 58.53°, which correspond to the diffraction peaks of Sm2O3, PDF#42-1461; this proves that pure metallic Ni and rare earth oxide Sm2O3 exist in the sample.

[0060] For the three samples Sm / Ni@C-400, Sm / Ni@C-500, and Sm / Ni@C-600, the spectra of the three samples show two steamed bun peaks, which may be due to the poor crystallinity of the three samples. Figure 2 It can be seen that as the experimental temperature increases, the peak intensity continues to increase, and the diffraction peaks gradually become sharper, indicating that the crystallinity of the samples is continuously improving. In addition, no diffraction peaks of carbon substances are observed in the powder X-ray diffraction patterns. This may be due to the high metal content and low carbon content in the four samples. The composition of the samples can be further analyzed by combining Raman spectroscopy and X-ray photoelectron spectroscopy.

[0061] Scanning electron microscopy and transmission electron microscopy analysis: In order to observe the microscopic morphology of the sample, the morphological changes of the sample Sm / Ni@C-500 were characterized by scanning electron microscopy and transmission electron microscopy, such as Figure 3 and Figure 4 shown.

[0062] like Figure 3 , cluster {Ni 120 Sm 96 Before high-temperature carbonization, the sample Sm / Ni@C-500 exhibited regular, smooth blocks. After carbonization, the Sm / Ni@C-500 sample exhibited a "flower-like" morphology with relatively uniform particles and a rough, wrinkled surface, indicating that the precursor's skeleton collapsed during high-temperature pyrolysis. Figure 3 Figures (d) to (i) show that the samples after high-temperature carbonization have a loose structure, and Figure (f) shows that the samples may have agglomerated during the calcination process. The dark black and gray parts represent the metal components and the carbon components after carbonization, respectively.

[0063] In order to further obtain the specific composition of samples Sm / Ni@C-400, Sm / Ni@C-500, and Sm / Ni@C-600, the local interplanar spacing of the lattice fringes in the high-resolution transmission electron microscopy images of Sm / Ni@C-400 and Sm / Ni@C-500 samples was analyzed and calculated to assist in determining the composition and structure of the materials. Figure 4 In the high-resolution transmission electron micrographs of both samples, lattice fringes of metallic Ni and NiO can be observed, further demonstrating that, in addition to pure metallic Ni, the samples also contain other oxides or other Ni-containing compounds. However, no striped regions of metallic Sm compounds were observed in the electron micrographs. This may be because the experimental temperature was not high enough, preventing the material from forming regular lattice fringes, or because there was no metallic Sm distributed in the selected area.

[0064] X-ray photoelectron spectroscopy analysis: X-ray photoelectron spectroscopy test was performed on the sample Sm / Ni@C-700. X-ray photoelectron spectroscopy, referred to as XPS. Peaks of four elements, C, O, Sm, and Ni, can be observed in the total XPS spectrum of the sample Sm / Ni@C-700, proving the presence of the four elements in the sample. The C1s peak with a binding energy of 284.8eV was used to correct and process the peak positions of other spectra, and the chemical states of each element in the sample Sm / Ni@C-700 were determined by the positions of the peaks corresponding to different binding energies in the element spectra. Figure 5In the C1s spectrum, the peaks at binding energies of 284.41eV, 286.44eV, and 289eV correspond to CC / C=C, polar groups CO, and C=O bonds, respectively. These polar groups are also the source of polarization resonance in the sample. In the O1s spectrum, the peaks at binding energies of 532.60eV and 531eV correspond to CO and C=O bonds, respectively; while the peak at 529.60eV corresponds to the metal oxide Sm-O bond, indicating that Sm oxides and compounds exist in the sample Sm / Ni@C-700. In the Sm3d spectrum, there are two peaks at binding energies of 1084eV and 1110.22eV, which correspond to Sm 3+ Sm 3d 5 / 2 and Sm 3d 3 / 2 orbital, which is consistent with the results of powder X-ray diffraction of Sm2O3. Finally, in the Ni 2p spectrum, the two peaks with binding energies of 854.50eV and 855.81eV correspond to the Ni 2p 3 / 2 orbital, while the peak at 871 eV corresponds to the 2p 1 / 2 orbit; in addition, two satellite peaks are present at binding energies of approximately 860 eV and 880 eV. This result indicates that in addition to Sm2O3 and elemental Ni, Ni oxides or other metal compounds may also be present in the Sm / Ni@C-700 sample. This is consistent with the results of the powder X-ray diffraction test. Some components are not reflected in the powder X-ray diffraction pattern due to their low content.

[0065] In order to further confirm the composition of the sample surface and the valence state of the metal elements, the sample Sm / Ni@C-500 was subjected to XPS test. XPS is X-ray photoelectron spectroscopy. Figure 6 As shown in the XPS total spectrum, the appearance of the corresponding peaks of the four elements C, O, Ni, and Sm proves the presence of these four elements in the sample Sm / Ni@C-500. Similarly, the peak position of the other spectra is corrected using the C1s peak with a binding energy of 284.80eV. The chemical state of each element is determined by the position of the peak corresponding to different binding energies in the spectrum of each element. Figure 6 , the spectra of the four elements C, O, Ni, and Sm were subjected to peak separation. In the C1s spectrum, the three peaks corresponding to the binding energies of 284.56eV, 286.21eV, and 289.43eV correspond to CC / C=C, polar groups CO, and C=O bonds, respectively. In the O1s spectrum, the two peaks with binding energies of 532.83eV and 531.40eV correspond to CO and C=O bonds, respectively, while the peak at 529.25eV corresponds to the metal oxide bond Sm-O. In the Sm 3d spectrum, there are two peaks with binding energies of 1083.82eV and 1109.41eV, which correspond to the rare earth ion Sm3+ Sm 3d 5 / 2 and Sm 3d 3 / 2 orbital, which is consistent with the presence of Sm2O3 in the phase results of powder X-ray diffraction. Finally, in the Ni 2p spectrum, the three peaks with binding energies of 854eV, 855.60eV, and 856.71eV correspond to the Ni 2p 3 / 2 orbital, the peaks at 871.21eV, 875eV, and 872.61eV correspond to the 2p 1 / 2 orbit. In addition, there are two satellite peaks at two positions with binding energies of approximately 860eV and 880eV. Combined with the results of powder X-ray diffraction, it can be shown that in addition to the presence of elemental metal Ni, the sample Sm / Ni@C-500 also contains Ni oxides or other metal compounds, which may not be reflected in the powder spectrum due to their low content. This is also consistent with the phenomenon that the crystallinity of the precursor is not high at low temperatures, and obvious peaks gradually appear as the temperature rises to 700°C. Comparing the results of Sm / Ni@C-500 and Sm / Ni@C-700, the types of components of the two are approximately the same, but may differ in content.

[0066] Raman spectroscopy analysis: Raman testing can detect the degree of graphitization of materials. Figure 6 Figure (f) shows that all samples have a peak at 1356 cm -1 and 1610cm -1 There are two obvious bands at the two locations, namely D band and G band. G band represents graphite carbon or ordered carbon, and D band represents defects or disordered carbon. The ratio of the two intensities is I G / I D It is a physical quantity used to evaluate the degree of graphitization of materials. The larger the ratio, the higher the degree of graphitization of the sample. After calculation, it was found that the I G / I D The values ​​are 0.99, 1.04, 1.07 and 1.09 respectively. This shows that the higher the calcination temperature, the more orderly the arrangement of carbon atoms and the higher the degree of graphitization of the material; accordingly, the conductivity of the sample will also increase, which is conducive to the improvement of the conductivity loss in the sample and will affect the dielectric constant of the material. In addition, the I G / I DThe values ​​are all small, indicating that their degree of graphitization is not high, which is consistent with the absence of obvious carbon peaks in the powder X-ray diffraction pattern. Therefore, the conductivity of the sample is also low, which is consistent with the electromagnetic parameter data measured by subsequent samples. According to the theoretical law of impedance matching of electromagnetic wave absorbing materials, a unilateral increase in conductivity is not conducive to the impedance matching of the material, so a single increase in conductivity does not necessarily make the material have good performance. This is also the reason why the sample Sm / Ni@C-700 has the highest carbon content and dielectric loss, but the performance is not the best. In summary, it can be concluded that the sample Sm / Ni@C-500 is composed of Sm2O3, metal Ni and its metal oxide and carbon complexes. Due to its poor crystallinity, it does not show obvious diffraction peaks in the powder X-ray diffraction pattern.

[0067] Analysis of electromagnetic wave absorption performance: The real part of the dielectric constant, denoted as ε', represents the material's ability to store external electric field energy; the imaginary part of the dielectric constant, denoted as ε", represents the corresponding loss capacity. The real part of the magnetic permeability, denoted as μ', represents the material's ability to store external magnetic field energy; the imaginary part of the magnetic permeability, denoted as μ", represents the loss capacity of the external magnetic field. The tangent value of the dielectric constant is denoted as tanδε; the tangent value of the magnetic permeability is denoted as tanδμ. The size of tanδε and tanδμ can reflect the loss capacity of the material. Generally speaking, tanδε is positively correlated with the material's ε", and the size of tanδμ is positively correlated with the material's μ". The larger the values ​​of these two imaginary parts, the stronger the material's loss capacity.

[0068] Depend on Figure 7 The results show that ε' for the four samples increases slightly with increasing frequency, while ε" decreases with decreasing frequency. Several multiple resonance peaks appear in the ε' and ε" versus frequency curves, indicating the occurrence of polarization resonances in the samples, corresponding to polarization losses in the absorber material loss mechanism. The resonances in the high-frequency and low-frequency regions can be attributed to interface polarization and dipole polarization, respectively. Furthermore, the values ​​of ε' and ε" increase with increasing temperature, indicating that higher calcination temperatures lead to greater dielectric loss potential. This is consistent with the temperature-dependent variation of tanδε, likely due to the higher carbonization degree at higher temperatures. Among them, Sm / Ni@C-700 has the largest tanδε value, indicating the highest dielectric loss potential. Similarly, the real part μ' and imaginary part μ" of the magnetic susceptibility both show a slight downward trend, while increasing with increasing temperature. This phenomenon indicates that calcination temperature also affects the magnetic properties of the materials, which is consistent with the phase transformation of the metallic elements in the materials. The magnetic permeability tangent value tanδμ of the four samples is slightly higher than the dielectric constant tangent value tanδε, indicating that magnetic loss slightly dominates the entire loss attenuation process.

[0069] In order to study the electromagnetic wave absorption performance of four samples Sm / Ni@C-400, Sm / Ni@C-500, Sm / Ni@C-600, and Sm / Ni@C-700, the two-dimensional and three-dimensional graphs of the reflection loss value of the four samples Sm / Ni@C-400, Sm / Ni@C-500, Sm / Ni@C-600, and Sm / Ni@C-700 as a function of frequency are shown. Figures 8 to 11 As shown. Figures 8 to 11 The results show that the Sm / Ni@C-400 and Sm / Ni@C-700 samples have almost no absorption effect. While the Sm / Ni@C-500 and Sm / Ni@C-600 samples have some absorption effect, overall their performance is less than ideal. At a frequency of 15.2 GHz and a matching thickness of 8 mm, the minimum reflection loss values ​​of the Sm / Ni@C-500 and Sm / Ni@C-600 samples are -14.09 dB and -11.90 dB, respectively. The maximum effective absorption band is around 2 GHz and is located in the high-frequency region. This suggests that the magnetic loss effect of all four samples is strong, as it is enhanced at high frequencies.

[0070] According to the above analysis, the absorption performance of the four samples is not ideal, which may be due to the precursor {Ni 120 Sm 96 The magnetic metal content in the structure is too high, while the carbon content is low and the dielectric constant is low, resulting in an unbalanced impedance matching. In addition, between 400℃ and 700℃, the performance of the sample shows a trend of first increasing and then decreasing. At 500℃, the sample's absorption performance reaches its best. Further in-depth analysis shows that the various electromagnetic parameters of the sample Sm / Ni@C-500 are not the best, but it has the best performance. This may be because its electromagnetic parameters just achieve a good balance. Therefore, 500℃ was selected as the calcination temperature for subsequent exploratory experiments to carry out the next step of performance optimization experiments.

[0071] Example 7

[0072] {Ni 120 RE 96 A method for preparing a CNTs-derived carbon-based composite material comprises the following steps:

[0073] Step 1, {Ni 120 Sm 96}Crystal preparation: The preparation process is the same as that in Example 3.

[0074] Step 2, {Ni 120 RE 96Preparation of carbon-based composite materials derived from} / CNTs: Carboxylated multi-walled carbon nanotubes were ultrasonically dispersed in 10 mL of deionized water to obtain a carboxylated multi-walled carbon nanotube solution; 120 Sm 96} crystals were ultrasonically dispersed in 10 mL of deionized water to obtain {Ni 120 Sm 96} solution.

[0075] The carboxylated multi-walled carbon nanotube solution and {Ni 120 Sm 96} solution was mixed and ultrasonicated for 10 h; wherein, carboxylated multi-walled carbon nanotubes and {Ni 120 Sm 96 The mass ratio of the crystals is 10:1. In order to avoid the influence of the water temperature increase on the experiment during the ultrasonic process, the cold water should be replaced intermittently. The obtained mixture was centrifuged and washed three times, and the obtained precipitate was placed in a vacuum drying oven and vacuum dried at 60°C for 24 hours. The dried sample was loaded into a high-temperature resistant quartz boat, and then placed in a tubular furnace with nitrogen gas, and heated to 500°C at a heating rate of 5°C / min. After heating for 2 hours, it was naturally cooled to room temperature. Obtained {Ni 120 RE 96} / CNTs-derived carbon-based composites, denoted as SmNi / C@CNTs-10:1.

[0076] Example 8

[0077] {Ni 120 RE 96 A method for preparing a CNTs-derived carbon-based composite material comprises the following steps:

[0078] Step 1, {Ni 120 Sm 96}Crystal preparation: The preparation process is the same as that in Example 3.

[0079] Step 2, {Ni 120 RE 96 Preparation of carbon-based composite materials derived from} / CNTs: The difference from Example 7 is that the carboxylated multi-walled carbon nanotubes and {Ni 120 Sm 96 The mass ratio of the crystals is 15:1. 120 RE 96} / CNTs-derived carbon-based composites, denoted as SmNi / C@CNTs-15:1.

[0080] Example 9

[0081] {Ni 120 RE 96A method for preparing a CNTs-derived carbon-based composite material comprises the following steps:

[0082] Step 1, {Ni 120 Sm 96}Crystal preparation: The preparation process is the same as that in Example 3.

[0083] Step 2, {Ni 120 RE 96 Preparation of carbon-based composite materials derived from} / CNTs: The difference from Example 7 is that, in which, carboxylated multi-walled carbon nanotubes and {Ni 120 Sm 96 The mass ratio of the crystals is 20:1. In order to avoid the influence of the water temperature increase on the experiment during the ultrasonic process, the cold water should be replaced intermittently. The obtained mixture was centrifuged and washed three times, and the obtained precipitate was placed in a vacuum drying oven and vacuum dried at 60°C for 24 hours. The dried sample was loaded into a high-temperature resistant quartz boat, and then placed in a tubular furnace with nitrogen gas, and heated to 500°C at a heating rate of 5°C / min. After heating for 2 hours, it was naturally cooled to room temperature. Obtained {Ni 120 RE 96} / CNTs-derived carbon-based composites, denoted as SmNi / C@CNTs-20:1.

[0084] High-resolution transmission electron microscopy analysis: In order to verify whether the cluster precursor and carbon nanotubes are successfully composited, high-resolution transmission electron microscopy is used for characterization, such as Figure 12 As shown in Figure 2, it can be seen that the two were successfully composited, and this composite method mainly relies on the electrostatic interaction between ions.

[0085] Powder X-ray diffraction analysis: Powder X-ray diffraction analysis was performed on three samples, SmNi / C@CNTs-10:1, SmNi / C@CNTs-15:1, and SmNi / C@CNTs-20:1, to characterize the phase composition and structure of the three samples. Figure 13 As shown in Figure (a), the diffraction peak positions of the three samples are essentially identical, with two peaks appearing around 30° and 45°, with slightly different peak intensities. Because the carbonization temperature was 500°C, the three samples exhibit the same diffraction peaks as Sm / Ni@C-500.

[0086] Laser Raman spectroscopy analysis: Laser Raman spectroscopy was performed on three samples of SmNi / C@CNTs-10:1, SmNi / C@CNTs-15:1, and SmNi / C@CNTs-20:1 to characterize the degree of graphitization of the samples. Figure 13 As shown in Figure (b). At 1356cm -1 and 1610cm -1There are two obvious bands at two locations, with a ratio of I G / I D The degree of graphitization of the three samples was not high, which was consistent with the low content of composite carbon materials in the samples.

[0087] Analysis of electromagnetic wave absorption performance: The absorption performance of carboxylated multi-walled carbon nanotubes was tested when the doping ratio was 50%. MWCNTS-COOH is carboxylated multi-walled carbon nanotubes, such as Figure 14 As shown, a single carboxylated carbon nanotube does not exhibit the property of absorbing electromagnetic waves, and the property does not change with the change of matching thickness.

[0088] In order to study the microwave absorption performance of the composite material prepared by combining cluster compound 5 with carbon nanotubes, the electromagnetic parameter data curves in the frequency range of 2GH~18GHz were also obtained, as shown in Figure 2. Figure 15 As shown. The results show that compared with the materials without carbon nanotubes, the ε' and ε" values ​​of the three samples after carbon nanotubes are greatly improved, among which SmNi / C@CNTs-10:1 has the largest ε' and ε" values. The maximum value of ε' changes from 4.65 to 13, and the maximum value of ε" changes from 1.8 to 3.6, which shows that the dielectric loss of the material has also increased. In addition, the tanδε value of SmNi / C@CNTs-10:1 is also the largest, because it has the highest carbon content, which also shows that when the temperature is the same, the carbon content of the material directly affects its electrical loss. Similarly, many strong multiple resonance peaks appear in the graph of ε' and ε" versus frequency, indicating the existence of polarization resonance. Compared with the uncompounded derivative carbon-based material, it is found that the polarization resonance intensity of the material after carbon nanotubes is greater than that of the uncompounded derivative material, the polarization loss of the material is improved, and the performance of the material is enhanced. Compared with the uncompounded carbon-based materials, it is not difficult to find that the μ' and μ" values ​​of the three composite samples have not changed much, and the tangent value tanδμ is still slightly higher than the tanδε value, which indicates that in the entire loss attenuation process of the sample, the effect of magnetic loss is still slightly greater than that of dielectric loss.

[0089] The microwave absorption performance of SmNi / C@CNTs-10:1, SmNi / C@CNTs-15:1 and SmNi / C@CNTs-20:1 was tested. Figure 16As shown. The results show that all three samples have certain absorbing properties, and the properties have been greatly improved compared to the uncomposite materials. Among them, the minimum reflection loss of SmNi / C@CNTs-10:1 reaches -58.85dB at a thickness of 3mm. The minimum reflection loss of SmNi / C@CNTs-15:1 at a thickness of 4mm is -40.04dB, and the corresponding effective absorption bandwidth is 14.27GHz. The minimum reflection loss value of SmNi / C@CNTs-20:1 is -23.79dB, and the effective absorption bandwidth reaches 16.85GHz. In the frequency range of 2GHz to 18GHz, not only the matching thickness of the absorbing material is reduced and the minimum reflection loss value is improved, but the effective absorption bandwidth is also greatly improved.

[0090] Table 1 Performance comparison of samples with a loading ratio of 50 wt%

[0091] sample <![CDATA[RL min / dB]]> <![CDATA[f m / GHz]]> <![CDATA[d1 / mm]]> <![CDATA[d2 / mm]]> Absorption bandwidth / GHz References ZnO / N-doped C -39.7 8.5 4.0 4.0 4.3 1 <![CDATA[ZrO2 / C]]> -58.7 16.8 1.5 1.7 5.5 2 CuO / C -57.5 14.9 1.6 1.6 4.7 3 <![CDATA[CoS2N-CNTs]]> -65.0 16.4 1.6 1.6 4.2 4 waxberty-like Ni / C -73.2 12.3 2.2 1.8 4.8 5 <![CDATA[Co@NPC@TiO2]]> -51.7 13.8 1.7 5.0 3.0 6 <![CDATA[Co / C@V2O3]]> -40.1 15.2 1.5 1.5 4.6 7 <![CDATA[Co / ZrO2 / C]]> -57.2 15.8 3.3 4.6 6.9 8 <![CDATA[CoFe@C@MnO2]]> -64.0 15.6 1.3 1.6 9.2 9 SmNi / C@CNTs-10∶1 -58.9 7.4 3.0 2.0 4.1 Example 7 SmNi / C@CNTs-15∶1 -40.1 5.8 4.0 2.0 3.8 Example 8

[0092] Note: RL min is the minimum reflection loss; f m is the matching frequency; d1 is the thickness corresponding to the minimum reflection loss; d2 is the thickness corresponding to the maximum absorption bandwidth.

[0093] Reference 1: Wu QL, JinhH, Chen Wei, et al. Graphitized nitrogen-doped porous carbon composites derived from ZIF-8 as efficient microwave absorption materials[J]. Materials Research Express, 2018, 3(6): 065602. Reference 2: Zhang X, Qiao J, Liu C, et al. A MOF-derived ZrO2 / C nanocomposite for efficient electromagnetic wave absorption[J]. Inorganic Chemistry Frontiers, 2020, 7(2): 385-393. Reference 3: Ma JN, Zhang XM, Liu W, et al. Direct synthesis of MOF-derived nanoporous CuO / carbon composites for high impedance matching and advanced microwave absorption[J]. Journal of Materials Chemistry C, 2016, 4(48):11419-11426. Reference 4: Yan J,huang Y,han XP, et al. Metal organic framework(ZIF-67)-derived hollow CoS2 / N-doped carbon nanotube composites for extraordinary electromagnetic wave absorption[J]. Composites Part B: Engineering, 2019, 163: 67-76. Reference 5: Liu DW, Du YC, X P, et al. Waxberry-like hierarchical Ni@C microspheres with high-performance microwave absorption[J]. Journal of Materials Chemistry C, 2019, 7(17): 5037-5046. Reference 6: Zhang XM, Ji GB, Liu W, etal.A novel Co / TiO2nanocomposite derived from a metal-organic framework:synthesis and efficient microwave absorption[J].Journal of MaterialsChemistry C,2019,4(9):1860-1870. Reference 7: Zhou CH,WC,Liu D,et al.Metal-Organic framework derivedhierarchical Co / C@V2O3hollow spheres as a thin,lightweight,andhigh-efficiency electromagnetic wave absorber[J]. Chemistry-AEuropean Journal, 2019, 25(9):2234-2241. Reference 8: Zhang Materials&Interfaces, 2019, 11(39): 35959-35968. Reference 9: Zhang Y, Yang ZH, Li M, et al. heterostructured CoFe@C@MnO2nanocubes for efficient microwave absorption[J]. Chemical Engineering Journal, 2020, 382: 123039.

[0094] The SmNi / C@CNTs-10:1 and SmNi / C@CNTs-15:1 prepared in the present invention exhibit excellent absorption performance, while the matching thickness and absorption bandwidth require further optimization and improvement. This demonstrates that the combination of cluster compounds and carbon nanotubes effectively improves the material's performance. It also verifies the electromagnetic imbalance problem caused by the high magnetic metal content and low carbon content of cluster-derived carbon-based materials. This fully demonstrates that the combination of magnetic metal particles and oxides with carbon materials can achieve electromagnetic synergy, resulting in an excellent electromagnetic wave absorption material.

[0095] The above results show that rare earth elements can improve the wave absorption performance of materials by affecting the resistivity, grain size and other factors of the materials. 120 RE 96} as a precursor, and a carbon-based composite material was prepared by high-temperature pyrolysis and carbonization. Multi-walled carbon nanotubes and clusters were then compounded in different mass ratios and carbonized at 500°C. The results showed that when the mass ratio of the two was 10:1, the composite material had the minimum reflection loss RL at a thickness of 3mm. min Reaching -58.85dB, when the mass ratio is 15:1 and the material thickness is 4mm, the minimum reflection loss RL min Reach -40.04dB; when the mass ratio is 20:1, the minimum reflection loss RL min The composite material's effective absorption bandwidth reaches -23.79dB, and its absorption performance is 16.85GHz. Compared with the performance of the uncomposite material, the material's absorption performance is improved by 3 times, which is mainly attributed to the increased electrical loss caused by the increased carbon content in the material.

[0096] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cluster-derived rare earth-based composite electromagnetic wave absorbing material, characterized in that: The following steps are involved: The carboxylated multi-walled carbon nanotubes and cluster crystals are compounded to prepare a composite; the mass ratio of the carboxylated multi-walled carbon nanotubes to the cluster crystals is 10-20:1; the cluster crystals are {Ni 120 Sm 96 }Crystal; {Ni 120 Sm 96 The crystal parameters of the crystal are: crystallized in the triclinic system, with a space group of P -1, the unit cell parameters are a = 34.53 Å, b = 35.70 Å, c =37.25 Å, α = 71.15 deg, β = 66.62 deg, γ = 77.32 deg, V = 39675 Å 3 ; The composite is calcined at 500° C. to obtain a cluster-derived rare earth-based composite electromagnetic wave absorbing material.

2. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 1, characterized in that: The cluster compound crystal is prepared by the following method: Nickel salt, rare earth salt, N-methyliminodiacetic acid, potassium bromide and methanol are uniformly mixed, and then triethylamine is added to react at 140° C. After the reaction is complete, a cluster compound crystal is prepared; The nickel salt is Ni(CH3COO)2·4H2O; and the rare earth salt is Sm(NO3)3·6H2O.

3. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 1, characterized in that: The usage ratio of nickel salt, rare earth salt, N-methyliminodiacetic acid, potassium bromide and methanol is 1.2mmol~1.3mmol:1.2mmol~1.3mmol:0.1mmol:0.4mmol~0.5mmol:9mL; the usage ratio of triethylamine and methanol is 9mL:300μL.

4. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 1, characterized in that: The dimensions of the carboxylated multi-walled carbon nanotubes are: an inner diameter of 2nm to 5nm, an outer diameter of 5nm to 15nm, and a length of 10μm to 30μm.

5. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 1, characterized in that: The specific preparation process of the composite is as follows: Ultrasonic dispersion of carboxylated multi-walled carbon nanotubes in water to obtain a carboxylated multi-walled carbon nanotube solution; dispersing the cluster compound crystals in water by ultrasonication to obtain a cluster compound crystal solution; The carboxylated multi-walled carbon nanotube solution and the cluster compound crystal solution are mixed and then subjected to ultrasonic treatment. After the ultrasonic treatment is completed, the mixture is filtered and dried to obtain the composite.

6. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 5, characterized in that: The ultrasonic treatment is continued for 8 h to 12 h.

7. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 5, characterized in that: The temperature of the ultrasonic treatment was controlled at ≤ 60 °C.

8. The method for preparing the cluster-derived rare earth-based composite electromagnetic wave absorbing material according to claim 1, characterized in that: The calcination time is 2h.

9. A cluster-derived rare earth-based composite electromagnetic wave absorbing material prepared by the preparation method according to any one of claims 1 to 8.

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