A surface-modified cobalt-based microwave absorber, its preparation method and application

Abstract

This invention belongs to the field of microwave absorbing materials technology, specifically relating to a surface-modified cobalt-based microwave absorbing agent, its preparation method, and its application. The surface-modified cobalt-based microwave absorbing agent of this invention comprises a cobalt-based material and cobalt hydroxyl oxide coated on the surface of the cobalt-based material, wherein the cobalt hydroxyl oxide is obtained by in-situ conversion of the cobalt-based material surface. This invention addresses the shortcomings of existing cobalt-based electromagnetic wave absorbing materials by modifying the surface of the cobalt-based material through an electrochemical in-situ conversion method, transforming the cobalt surface into cobalt hydroxyl oxide. The cobalt hydroxyl oxide improves impedance matching, reduces electromagnetic wave reflection, and enhances the material's microwave absorption performance. The cobalt-based microwave absorbing agent with cobalt hydroxyl oxide surface modification exhibits good electromagnetic wave absorption performance and stability. Furthermore, this method requires simple equipment and procedures, is easily scalable, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, specifically relating to a surface-modified cobalt-based microwave absorbing agent, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Magnetic materials have wide applications in the field of electromagnetic wave absorption materials. Elemental cobalt, as a good magnetic material, has a high saturation magnetization, which is beneficial for achieving high permeability in the GHz range, thus enabling thinner absorption layers. However, single magnetic materials suffer from poor impedance matching and a single loss mechanism, which is not conducive to practical applications. Currently, a common solution is to combine carbon materials with metallic cobalt to improve impedance matching and increase dielectric loss capability. However, these carbon / cobalt composites often still exhibit excessively high dielectric constants and poor impedance matching, inevitably leading to excessive reflection of electromagnetic waves at the incident surface, which is detrimental to improving absorption performance. Furthermore, the metallic cobalt in carbon / cobalt composites still exists in elemental form, making it susceptible to oxidation and corrosion from the environment, causing damage to the material structure and a decrease in absorption performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a surface-modified cobalt-based microwave absorbing agent, its preparation method, and its applications. This invention addresses the deficiencies of existing cobalt-based electromagnetic wave absorbing materials by using an electrochemical in-situ conversion method to modify the surface of cobalt-based materials, transforming the cobalt surface into cobalt hydroxyl oxide. Cobalt hydroxyl oxide is used to improve impedance matching, reduce electromagnetic wave reflection, and enhance the material's microwave absorption performance. The cobalt-based microwave absorbing agent with cobalt hydroxyl oxide surface modification exhibits good electromagnetic wave absorption performance and stability. Furthermore, the method involves simple equipment and procedures, is easily scalable, and has broad application prospects.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, the present invention provides a surface-modified cobalt-based microwave absorber, comprising a cobalt-based material and cobalt hydroxyl oxide coated on the surface of the cobalt-based material, wherein the cobalt hydroxyl oxide is obtained by in-situ conversion on the surface of the cobalt-based material.

[0007] In a second aspect, the present invention provides a method for preparing the surface-modified cobalt-based microwave absorber described in the first aspect, comprising the following steps:

[0008] A slurry is obtained by uniformly mixing a cobalt-based metallic material and a binder in a solvent. The slurry is then coated onto a conductive substrate to form an electrode. The electrode is subjected to electrochemical treatment, and the material on the electrochemically treated electrode is separated from the conductive substrate to obtain the surface-modified cobalt-based microwave absorber.

[0009] Thirdly, the present invention provides an absorber composed of a surface-modified cobalt-based microwave absorber and a matrix material as described in the first aspect.

[0010] Fourthly, the present invention provides the application of the surface-modified cobalt-based microwave absorbing agent described in the first aspect and / or the microwave absorber described in the third aspect in radio communication systems, high-frequency protection, microwave heating equipment, construction of microwave anechoic chambers, or stealth technology.

[0011] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0012] (1) The surface coating of cobalt hydroxyoxide improves the impedance matching characteristics and increases the dielectric loss of the material, thus achieving excellent electromagnetic wave absorption performance.

[0013] (2) The surface-modified cobalt-based microwave absorber is uniformly coated with cobalt hydroxyl oxide nanostructures. The high valence state of cobalt hydroxyl oxide can effectively prevent cobalt metal from being oxidized and corroded, thus enhancing the overall antioxidant and corrosion resistance of the microwave absorber.

[0014] (3) The preparation process of surface-modified cobalt-based microwave absorbers is simple, easy to operate, has good controllability, short preparation cycle, and is easy to industrialize.

[0015] (4) In this invention, the surface-modified cobalt metallic material with hydroxyl oxide is mixed with paraffin at a filling rate of 50%. The effective absorption bandwidth at 2.7 mm is 5.2 GHz, and the maximum reflection loss at 3.0 mm is -60.2 dB. The absorber prepared by the surface-modified cobalt metallic absorbing agent has the characteristics of thin thickness, low density, wide absorption bandwidth, and high absorption intensity. It also has good impedance matching characteristics, good interference cancellation and loss attenuation capabilities, which can provide ideas for the design of electromagnetic wave absorbing materials in the future. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 The XRD diffraction patterns of metallic cobalt and cobalt hydroxyoxide-modified metallic cobalt in Example 1 are shown below.

[0018] Figure 2These are scanning electron microscope images of metallic cobalt (a) and cobalt hydroxyoxide-modified metallic cobalt (b) in Example 1;

[0019] Figure 3 The image shows the microwave absorption performance of cobalt modified with cobalt hydroxyl oxide in Example 1.

[0020] Figure 4 Scanning electron microscope images of Co / C fiber (a) and CoOOH / Co / C fiber (b) in Example 2;

[0021] Figure 5 This is a scanning electron microscope image of cobalt metal modified with cobalt hydroxyoxide in Example 3. Detailed Implementation

[0022] In a first typical embodiment of the present invention, a surface-modified cobalt-based microwave absorber comprises a cobalt-based material and cobalt hydroxyl oxide coated on the surface of the cobalt-based material, wherein the cobalt hydroxyl oxide is obtained by in-situ conversion on the surface of the cobalt-based material.

[0023] In one or more embodiments of this implementation, the cobalt-based material includes elemental cobalt or a composite containing elemental cobalt.

[0024] A second typical embodiment of the present invention, a method for preparing a surface-modified cobalt-based microwave absorber as described in the first typical embodiment, includes the following steps:

[0025] A slurry is obtained by uniformly mixing a cobalt-based metallic material and a binder in a solvent. The slurry is then coated onto a conductive substrate to form an electrode. The electrode is subjected to electrochemical treatment, and the material on the electrochemically treated electrode is separated from the conductive substrate to obtain the surface-modified cobalt-based microwave absorber.

[0026] In one or more embodiments of this implementation, the mass ratio of the cobalt-based material to the adhesive is 8.5-9.5:1, and the adhesive includes one or any combination of two or more of the following: polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylamide, ethylene-propylene-diene copolymer resin, styrene-butadiene rubber, polybutadiene, fluororubber, polyoxyethylene, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and hydroxypropyl cellulose.

[0027] In one or more embodiments of this implementation, the solvent includes one or any combination of two or more of the following: water, alcohols, polyols, terpenes, N-methyl-2-pyrrolidone, dimethyl carbonate, diethyl carbonate, ethyl acetate, and methyl propionate.

[0028] In one or more embodiments of this implementation, the coating includes one or any combination of two or more of the following methods: dip coating, scraping coating, spin coating, spraying coating, screen printing, and suspended particle dip coating.

[0029] In one or more embodiments of this implementation, the conductive substrate includes one of a metal substrate, a carbon material substrate, or conductive glass;

[0030] Preferably, the conductive glass comprises one of FTO, ITO, AZO, ZnO:B, ZnO:Ga, ZnO:In, Cd2SnO4, Zn2SnO4, TiO2:Nb, SrTiO3:Nb, CuS, CuAlO2, and CuAlS2.

[0031] In one or more embodiments of this implementation, the electrochemical treatment includes one or a combination of any two or more of the following methods: cyclic voltammetry, constant current charge-discharge, and variable current charge-discharge.

[0032] A third typical embodiment of the present invention provides an absorber composed of a surface-modified cobalt-based microwave absorber and a matrix material as described in the first typical embodiment.

[0033] Preferably, the matrix material is one or more of paraffin, rubber, resin or paint.

[0034] The fourth typical embodiment of the present invention is the application of a surface-modified cobalt-based microwave absorbing agent as described in the first typical embodiment and / or a microwave absorber as described in the third typical embodiment in radio communication systems, high-frequency protection, microwave heating equipment, construction of microwave anechoic chambers, or stealth technology.

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0036] Example 1

[0037] Cobalt nanomaterials and polyvinylidene fluoride were added to N-methyl-2-pyrrolidone and mixed evenly by grinding to form a slurry with a suitable viscosity. The slurry was then uniformly coated onto an FTO substrate using a blade coating method to form an electrode. The electrode was then subjected to constant current charge-discharge treatment. Finally, the electrode was immersed in acetone to separate the loaded material from the FTO substrate, resulting in a cobalt composite material with cobalt hydroxyl oxide surface modification.

[0038] The slurry contains a cobalt metal to polyvinylidene fluoride mass ratio of 9:1, a constant current charge-discharge voltage window of -0.5 to 0.5V, a charge-discharge current density of 100mA / g, an electrolyte solution of 6mol / L KOH, and 100 cycles.

[0039] like Figure 1 As shown, the diffraction peak positions in the X-ray powder diffraction (XRD) pattern of the obtained sample are consistent with the standard diffraction data for face-centered cubic cobalt (JCPDS No. 15-0806) and cobalt hydroxyoxide (JCPDF 26-0480), indicating that the synthesized cobalt hydroxyoxide-modified cobalt composite material contains both cobalt metal and cobalt hydroxyoxide. Furthermore, based on the peak intensity, cobalt metal is determined to be the main component, suggesting that only a small portion of the cobalt metal is converted into cobalt hydroxyoxide. Figure 2 As shown in the scanning electron microscope (SEM) images, metallic cobalt consists of spherical particles with a relatively smooth surface. After surface modification with cobalt hydroxyl oxide, the surface becomes a lamellar coating structure, indicating that electrochemical treatment can transform the surface of metallic cobalt into cobalt hydroxyl oxide.

[0040] Electromagnetic wave absorbers were fabricated using cobalt metal with a cobalt hydroxyl oxide surface modified as described above, and tested using an Agilent Technologies E5244A electromagnetic wave vector network analyzer. The absorbing material was mixed with paraffin at a 50% filling rate to form ring-shaped samples, and its electromagnetic parameters were measured in the 2-18 GHz frequency range. The electromagnetic wave absorption curves are shown below. Figure 3 As shown, the surface-modified cobalt with cobalt hydroxyl oxide has an effective absorption bandwidth of 5.2 GHz at 2.7 mm and a maximum reflection loss of -60.2 dB at 3.0 mm, indicating that it has excellent electromagnetic wave absorption performance.

[0041] Example 2

[0042] Unlike Example 1, the raw material cobalt nanoparticles were transformed into composite nanofibers (Co / C fibers) composed of cobalt and carbon, and the resulting material was denoted as CoOOH / Co / C fibers.

[0043] like Figure 4 As shown, scanning electron microscope (SEM) images reveal that the Co / C fiber surface is rough and exhibits a granular mosaic pattern. After surface modification with cobalt hydroxyoxide, the CoOOH / Co / C fiber surface becomes a lamellar coating structure, indicating that electrochemical treatment can convert metallic cobalt in the cobalt / carbon composite material into cobalt hydroxyoxide.

[0044] Example 3

[0045] Unlike Example 1, the electrochemical treatment method for the electrode after fabrication was changed from constant current charge-discharge method to cyclic voltammetry. Specific parameters are as follows: voltage window -0.5 to 0.5 V, scan rate 10 mA / g, electrolyte solution 6 mol / L KOH, and 100 cycles.

[0046] like Figure 5 As shown, scanning electron microscopy (SEM) characterization revealed that the surface of the cobalt particles after cobalt hydroxyl oxide surface modification became lamellar.

[0047] Comparative Example

[0048] Unlike Example 1, the electrode was only immersed in a 6 mol / L KOH electrolyte solution for 10 days without electrochemical treatment. Scanning electron microscopy (SEM) characterization showed that the microstructure of metallic cobalt did not change significantly, and it still maintained relatively smooth spherical particles, indicating that electrochemical treatment is a necessary condition for the transformation of metallic cobalt surface into cobalt hydroxyoxide.

[0049] Example 5

[0050] Unlike Example 1, the mass ratio of cobalt metal to polyvinylidene fluoride in the slurry is 8.5:1.

[0051] Example 6

[0052] Unlike Example 1, the mass ratio of cobalt metal to polyvinylidene fluoride in the slurry is 9.5:1.

[0053] Example 7

[0054] The difference from Example 1 is that polytetrafluoroethylene is used instead of polyvinylidene fluoride.

[0055] Example 8

[0056] Unlike Example 1, acetone was used instead of N-methyl-2-pyrrolidone.

[0057] Example 9

[0058] Unlike Example 1, cobalt foam was used instead of FTO glass.

[0059] Example 10

[0060] Unlike Example 1, polyethylene was used instead of polyvinylidene fluoride.

[0061] Example 11

[0062] The difference from Example 1 is that dimethyl carbonate is used instead of N-methyl-2-pyrrolidone.

[0063] Example 12

[0064] Unlike Example 1, carbon cloth was used instead of FTO glass.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An absorber, characterized in that, It consists of a surface-modified cobalt-based microwave absorber and a matrix material; The matrix material is one or more of paraffin wax, rubber, resin, or paint; The surface-modified cobalt-based microwave absorber includes cobalt-based nanomaterials and cobalt hydroxyl oxide coated on the surface of the cobalt-based nanomaterials, wherein the cobalt hydroxyl oxide is obtained by in-situ conversion on the surface of the cobalt-based nanomaterials.

2. The absorber as described in claim 1, characterized in that, The cobalt-based nanomaterials include elemental cobalt or composites containing elemental cobalt.

3. The absorber as described in claim 1, characterized in that, The preparation method of the surface-modified cobalt-based microwave absorber includes the following steps: A slurry is obtained by uniformly mixing cobalt-based nanomaterials and a binder in a solvent. The slurry is then coated onto a conductive substrate to form an electrode. The electrode is subjected to electrochemical treatment, and the material on the electrochemically treated electrode is separated from the conductive substrate to obtain the surface-modified cobalt-based microwave absorber.

4. The absorber as described in claim 3, characterized in that, The mass ratio of the cobalt-based nanomaterial to the binder is 8.5-9.5:

1. The binder includes one or any combination of two or more of the following: polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyacrylamide, ethylene-propylene-diene copolymer resin, styrene-butadiene rubber, polybutadiene, fluororubber, polyoxyethylene, polyvinylpyrrolidone, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and hydroxypropyl cellulose.

5. The absorber as described in claim 3, characterized in that, The solvent includes one or any combination of two or more of the following: alcohol, polyol, terpene, N-methyl-2-pyrrolidone, dimethyl carbonate, diethyl carbonate, ethyl acetate, and methyl propionate.

6. The absorber as described in claim 3, characterized in that, The coating includes one or any combination of two or more of the following methods: dip coating, scraping coating, spin coating, spray coating, screen printing, and suspended particle dip coating.

7. The absorber as described in claim 3, characterized in that, The conductive substrate includes one of a metal substrate, a carbon material substrate, or a conductive glass.

8. The absorber as described in claim 7, characterized in that, The conductive glass includes one of FTO, ITO, AZO, ZnO:B, ZnO:Ga, ZnO:In, Cd2SnO4, Zn2SnO4, TiO2:Nb, SrTiO3:Nb, CuS, CuAlO2, and CuAlS2.

9. The absorber as described in claim 3, characterized in that, The electrochemical treatment includes one or a combination of any two or more of the following methods: cyclic voltammetry, constant current charge-discharge, and variable current charge-discharge.

10. The application of an absorber as described in any one of claims 1-9 in radio communication systems, high-frequency shielding, microwave heating equipment, construction of microwave anechoic chambers, or stealth technology.

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