Preparation method of cobalt-based composite particles with adjustable multilayer structure

Abstract

The present invention discloses a method for preparing cobalt-based composite particles with adjustable multilayer gaps, comprising the following steps: first, preparing a Co core; second, coating with SiO2; third, coating with Fe; fourth, coating with Co; and fifth, removing the Fe intermediate layer. This method utilizes structural design of the particles to increase the material's microwave absorption loss, resulting in composite particles with excellent microwave absorption properties. Furthermore, the gaps between the spherical shells can be tailored to the microwave frequency range in which the material is intended to operate, achieving enhanced absorption and effectively improving the material's microwave absorption loss performance.

Description

Technical Field

[0001] The invention belongs to the technical field of wave absorbing material preparation, and mainly relates to a method for preparing multi-layer gap-adjustable magnetic composite particles. Background Art

[0002] Absorbing materials refer to a type of functional material that can absorb and attenuate incident electromagnetic waves, convert electromagnetic energy into heat or other forms of energy and consume it, or cause the electromagnetic waves to disappear due to interference.

[0003] Today's electronic devices are trending towards miniaturization and multifunctionality. However, when the size of a device is reduced to a certain level, we have to consider the damage to the working environment and the impact of electromagnetic radiation generated during operation. High-tech equipment and medical equipment have extremely high requirements for stable operation, which requires high-performance microwave absorbing materials to ensure stable operation.

[0004] Numerous studies have shown that the hollow structure within hollow magnetic particles can effectively enhance their microwave absorption. This is primarily due to the reflection of electromagnetic waves at the hollow locations within the particles, accelerating their attenuation. However, a single-layer hollow structure has limited effect on electromagnetic wave reflection and attenuation. Multi-layer structures can increase electromagnetic wave absorption through multiple attenuations. Furthermore, by adjusting the interlayer spacing, multiple levels of reflection, refraction, and electromagnetic interference can be introduced to modify the absorption properties, improving them and enabling specialized absorption of electromagnetic waves in specific frequency bands.

[0005] Cobalt is a typical magnetic metal with a high Curie temperature (1150°C) and excellent electromagnetic properties, and is a good magnetic wave absorbing material; silicon oxide is a typical dielectric stealth material with good dielectric loss performance. Combining the two with multi-layer adjustable gaps can effectively achieve the combination of magnetic loss, dielectric loss and internal reflection loss.

[0006] Therefore, in order to effectively improve the microwave absorption loss performance of the material, this patent is proposed in this context, and a multilayer cobalt-based magnetic composite particle with adjustable gap is designed. Summary of the Invention

[0007] The present invention aims to provide a multilayer cobalt-based composite particle with adjustable gap structure. By utilizing the structural design of the particles, the material's loss absorption of microwaves is increased to obtain composite particles with excellent microwave absorption performance. At the same time, the gap between each layer of spherical shell can be specifically changed according to the microwave frequency range in which the material serves, thereby achieving a better absorption effect.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing multilayer structured cobalt-based composite particles with adjustable gaps comprises the following steps:

[0010] The first step is to prepare the Co core: a certain amount of Co salt solution is prepared with deionized water, and a certain amount of complexing agent is prepared. After lightly stirring and mixing with the Co salt solution, it is placed in an ultrasonic water bath and heated to a certain temperature. A certain amount of reducing agent is also prepared. Under the action of ultrasound and stirring, the reducing agent and salt solution are mixed and the reaction begins. After a certain period of time, the reaction is stopped and the central Co core particles are washed using a centrifuge to obtain;

[0011] The second step is to coat SiO2: the Co powder prepared in the first step is dispersed in deionized water, a certain amount of ethanol is added, and ammonia water is added dropwise to make the solution reach a certain pH value. After a period of time under ultrasonic and stirring conditions, a certain amount of ethyl orthosilicate is taken and added dropwise into the mixed solution at a certain rate using a constant flow pump. After a period of time, the reaction is stopped, and the coated SiO2 particles are collected after being washed with deionized water.

[0012] The third step is Fe coating: a certain amount of Fe salt solution is prepared, a certain concentration of complexing agent is added and mixed, and the mixture is heated to a certain temperature. The particles in the second step are then dispersed with deionized water, a certain amount of ethanol and ammonia water are added, and ultrasonic stirring is performed for a period of time. The two solutions are mixed, and a certain amount of sodium borohydride solution is prepared and added to the mixed solution under ultrasonic stirring conditions. The mixture is reacted at a certain temperature for a period of time. The product is washed with deionized water and collected to obtain Fe-coated particles.

[0013] The fourth step is to coat Co: a certain amount of Co salt solution and a certain amount of complexing agent are prepared. After lightly stirring and mixing with the Co salt solution, the mixture is placed in an ultrasonic water bath and heated to a certain temperature. The particles in the third step are dispersed in deionized water, and a certain amount of hydrazine hydrate reducing agent is prepared. The reducing agent, salt solution, and the mixed solution containing the particles in the third step are mixed and reacted for a period of time under the action of ultrasound and stirring. The product is taken out, cleaned, and collected. According to the design requirements, the second, third, and fourth steps are repeated until the desired multilayer structure with adjustable gap cobalt-based composite particles are obtained;

[0014] The fifth step is to remove the Fe intermediate layer: prepare an acid solution of a certain concentration, place the multilayer cobalt-based composite particles obtained in the fourth step into it, and slowly stir for a period of time to allow the acid to corrode the Fe intermediate layer to obtain multilayer structure gap-adjustable cobalt-based magnetic composite particles.

[0015] As a further improvement of this technical solution: in the first step, the Co salt solution is specifically a CoSO4 solution.

[0016] As a further improvement of the present technical solution: in the first step, a certain amount of complexing agent is prepared, specifically: trisodium citrate and potassium sodium tartrate are prepared into a complexing agent solution.

[0017] As a further improvement of this technical solution: in the first step, the reducing agent is NaOH.

[0018] As a further improvement of the present technical solution: in the second step, ammonia water is added dropwise to make the solution reach a certain pH value, specifically: ammonia water is added dropwise to make the solution pH value reach 10.

[0019] As a further improvement of this technical solution: in the third step, the Fe salt solution is specifically FeSO4 solution.

[0020] As a further improvement of the present technical solution: in the fourth step, the multilayer structure gap-adjustable cobalt-based composite particles include Co-SiO2-large gap-Co-SiO2-small gap-Co-SiO2-large gap-Co-SiO2 composite particles.

[0021] As a further improvement of the present technical solution: in the fourth step, the multilayer structured gap-adjustable cobalt-based composite particles include Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2 composite particles.

[0022] As a further improvement of the technical solution, it also includes characterizing and testing the wave absorption performance of the obtained multilayer composite particles to analyze the wave absorption performance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention utilizes the structural design of particles to increase the material's loss absorption of microwaves, thereby obtaining composite particles with excellent microwave absorption performance. At the same time, the gaps between the spherical shells of each layer can be specifically changed according to the microwave frequency range in which the material serves, thereby achieving a better absorption effect and effectively improving the microwave absorption loss performance of the material.

[0025] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and to implement it according to the contents of the description, the following preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. The specific implementation methods of the present invention are given in detail by the following embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 This is a schematic structural diagram of a multi-layer structured gap-adjustable cobalt-based composite particle proposed by the present invention. DETAILED DESCRIPTION

[0028] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. The following paragraphs describe the present invention in more detail by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in exact proportions. They are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0029] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a central component. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Example 1

[0032] Preparation of Co-SiO2-large gap-Co-SiO2-small gap-Co-SiO2-large gap-Co-SiO2 composite particles includes the following steps:

[0033] 1.1. Preparation of the central Co core:

[0034] Dissolve 20g of CoSO₄ in deionized water to make a 100ml solution. Add 10g of trisodium citrate and 10g of potassium sodium tartrate to make a 100ml complexing agent solution. After gently stirring the solution with the CoSO₄ solution, heat the mixture to 60°C in an ultrasonic water bath. Weigh 25g of NaOH to make a 100ml solution, add 50ml of hydrazine hydrate and stir to make a reducing agent. The reducing agent and mixture are mixed under 800Hz ultrasonication and 150rpm stirring to initiate the reaction. The reaction is terminated after 30 minutes, and the Co particles are washed and recovered using a centrifuge.

[0035] 1.2 Preparation of Co@SiO2

[0036] Take 5g of Co metal powder, add 40ml of ethanol and 10ml of deionized water, and stir at 800Hz ultrasonic speed and 100r / min. Add ammonia water dropwise to bring the solution pH to 10 and continue stirring for 30 minutes. Then, add 50ml of ethyl orthosilicate dropwise to the mixed solution at a rate of 5ml / min using a constant flow pump. Stop the reaction after 1 hour, rinse with deionized water, and collect.

[0037] 1.3 Preparation of Co@SiO2@Fe

[0038] Take 40g FeSO4 and prepare it into 200ml solution, and take 10g trisodium citrate and 10g potassium sodium tartrate to prepare 100ml complexing agent solution, heat to a certain temperature, then disperse Co@SiO2 nanoparticles into a mixed solution of 40ml ethanol and 100ml deionized water, add ammonia water dropwise until the solution pH is 10, mix for 30min under 800HZ ultrasound and 150r / min stirring conditions, take 25g sodium borohydride and dissolve it into 50ml solution, add it into the Co@SiO2 mixed solution together with ferric sulfate solution, react at 60℃ for 1h, wash the product with deionized water and collect it to obtain Co@SiO2@Fe particles.

[0039] 1.4 Preparation of Co@SiO2@Fe@Co:

[0040] Dissolve 10g of CoSO4 in 100ml of solution, and prepare 100ml of a complexing agent solution with 8g of trisodium citrate and 8g of potassium sodium tartrate. Add the complexing agent to the nickel sulfate solution and gently stir to mix. Then, heat the mixed solution to 60°C in an ultrasonic water bath. Weigh 25g of NaOH to make a 100ml solution, add 100ml of hydrazine hydrate and stir to prepare the reducing agent. Add the reducing agent to the mixture under 800Hz ultrasonication and 150r / min stirring to initiate the reaction. After 30 minutes, rinse the product with deionized water and collect it.

[0041] 1.5. Re-coating with SiO2 and a small amount of Fe:

[0042] Repeat step 1.2 to coat the particle surface with a layer of SiO2. Prepare another 50ml solution of FeSO4 with 5g of FeSO4, and prepare another 50ml complexing agent solution with 3g of trisodium citrate and 3g of potassium sodium tartrate. Heat to a certain temperature, then disperse the SiO2-coated particles in deionized water. Add ammonia dropwise until the solution has a pH of 10. Mix for 30 minutes under 800Hz ultrasonication and 150r / min stirring. Dissolve 2.5g of sodium borohydride in 30ml of solution, and add this solution, along with the ferric sulfate solution, trisodium citrate, and potassium sodium tartrate complexing solution, to the mixed solution coated with SiO2 again. React at 60°C for 10 minutes to obtain a relatively thin Fe layer.

[0043] Repeat steps 1.4 / 1.2 / 1.3 and 1.4 / 1.2 to obtain Co-SiO2-thicker Fe layer-Co-SiO2-thinner iron layer-Co-SiO2-thicker iron layer-Co-SiO2 composite particles.

[0044] 1.6. Remove the Fe intermediate layer to obtain Co-SiO2-large gap-Co-SiO2-small gap-Co-SiO2-large gap-Co-SiO2 composite particles:

[0045] Prepare 50 ml of 0.5% hydrochloric acid solution, place the Co-SiO2-thicker Fe layer-Co-SiO2-thinner iron layer-Co-SiO2-thicker iron layer-Co-SiO2 composite particles prepared in 1.5, and stir slowly for 60 minutes to allow the acid to corrode the Fe intermediate layer to obtain Co-SiO2-large gap-Co-SiO2-small gap-Co-SiO2-large gap-Co-SiO2 composite particles.

[0046] Example 2

[0047] Preparation of Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2 composite particles includes the following steps:

[0048] 2.1. Preparation of the central Co core:

[0049] Dissolve 20g of CoSO₄ in deionized water to create a 100ml solution. Add 10g of trisodium citrate and 10g of potassium sodium tartrate to create a 100ml complexing agent solution. After gently stirring the solution with the CoSO₄ solution, heat the mixture to 60°C in an ultrasonic water bath. Weigh 25g of NaOH to create a 50ml solution, then add 50ml of hydrazine hydrate and stir to create a reducing agent. The reducing agent and the mixture are mixed under 800Hz ultrasonication and 150rpm stirring to initiate the reaction. The reaction is terminated after 45 minutes, and the Co nanoparticles are washed using a centrifuge to obtain the Co nanoparticles.

[0050] 2.2 Preparation of Co@SiO2

[0051] Take 5g of Co metal powder, add 40ml of ethanol and 10ml of deionized water, and stir at 800Hz ultrasonic speed and 100r / min. Add ammonia water dropwise to bring the solution pH to 10 and continue stirring for 30 minutes. Then, add 50ml of ethyl orthosilicate dropwise to the mixed solution at a rate of 2ml / min using a constant flow pump. Stop the reaction after 1 hour, rinse with deionized water, and collect.

[0052] 2.3 Preparation of Co@SiO2@Fe

[0053] Take 3g FeSO4 and prepare it into 50ml solution, and take 2g trisodium citrate and 2g potassium sodium tartrate to prepare 50ml complexing agent solution, heat to a certain temperature, then disperse the particles prepared in 2.2 into a mixed solution of 40ml ethanol and 10ml deionized water, add ammonia water dropwise until the solution pH is 10, mix for 30min under 800HZ ultrasound and 150r / min stirring conditions, take 2.5g sodium borohydride and dissolve it into 30ml solution, add it into the Co@SiO2 mixed solution together with the ferric sulfate solution, react at 60℃ for 0.2h, wash the product with deionized water and collect it to obtain Co@SiO2@Fe particles.

[0054] 2.4 Preparation of Co@SiO2@Fe@Co:

[0055] Dissolve 10g of CoSO4 in 100ml of solution, and prepare 100ml of a complexing agent solution with 8g of trisodium citrate and 8g of potassium sodium tartrate. Add the complexing agent to the nickel sulfate solution and gently stir to mix. Then, heat the mixed solution to 60°C in an ultrasonic water bath. Weigh 25g of NaOH to make a 100ml solution, add 100ml of hydrazine hydrate and stir to prepare the reducing agent. Add the reducing agent to the mixture under 800Hz ultrasonication and 150r / min stirring to initiate the reaction. After 30 minutes, rinse the product with deionized water and collect it.

[0056] 2.5. Further coating with SiO2, Fe, and Co

[0057] Repeat steps 2.2 / 2.3 / 2.4 / 2.2 until Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2 composite particles are obtained.

[0058] 2.6 Remove the Fe intermediate layer to obtain Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2 composite particles:

[0059] Prepare 50 ml of 0.5% hydrochloric acid solution, place Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2-thinner iron layer-Co-SiO2 composite particles therein, and stir slowly for 60 minutes to allow the acid to corrode the Fe intermediate layer to obtain Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2 composite particles.

[0060] Characterization and testing of Example 1 and Example 2:

[0061] Characterization and microwave absorption performance test of the obtained multilayer composite particles

[0062] The performance test results of the samples obtained in the above examples 1 and 2 are shown in Table 1 below, including the reflection loss values ​​(RL), bandwidth (GHz) of different samples.

[0063] sample RL(dB) GHz(<-10dB) Example 1 -63 1.8GHz Example 2 -57 2.2GHz

[0064] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing multilayer structured cobalt-based composite particles with adjustable gaps, characterized in that: The following steps are involved: The first step is to prepare the Co core: a certain amount of Co salt solution is prepared with deionized water, and a certain amount of complexing agent is prepared. After lightly stirring and mixing with the Co salt solution, it is placed in an ultrasonic water bath and heated to a certain temperature. A certain amount of reducing agent is also prepared. Under the action of ultrasound and stirring, the reducing agent and salt solution are mixed and the reaction begins. After a certain period of time, the reaction is stopped and the central Co core particles are washed using a centrifuge to obtain; The second step is to coat SiO2: the Co powder prepared in the first step is dispersed in deionized water, a certain amount of ethanol is added, and ammonia water is added dropwise to make the solution reach a certain pH value. After a period of time under ultrasonic and stirring conditions, a certain amount of ethyl orthosilicate is taken and added dropwise into the mixed solution at a certain rate using a constant flow pump. After a period of time, the reaction is stopped, and the coated SiO2 particles are collected after being washed with deionized water. The third step is Fe coating: a certain amount of Fe salt solution is prepared, a certain concentration of complexing agent is added and mixed, and the mixture is heated to a certain temperature. The particles in the second step are then dispersed with deionized water, a certain amount of ethanol and ammonia water are added, and ultrasonic stirring is performed for a period of time. The two solutions are mixed, and a certain amount of sodium borohydride solution is prepared and added to the mixed solution under ultrasonic stirring conditions. The mixture is reacted at a certain temperature for a period of time. The product is washed with deionized water and collected to obtain Fe-coated particles. The fourth step is to coat Co: a certain amount of Co salt solution and a certain amount of complexing agent are prepared. After lightly stirring and mixing with the Co salt solution, the mixture is placed in an ultrasonic water bath and heated to a certain temperature. The particles in the third step are dispersed in deionized water, and a certain amount of hydrazine hydrate reducing agent is prepared. The reducing agent, salt solution, and the mixed solution containing the particles in the third step are mixed and reacted for a period of time under the action of ultrasound and stirring. The product is taken out, cleaned, and collected. According to the design requirements, the second, third, and fourth steps are repeated until the desired multilayer structure with adjustable gap cobalt-based composite particles are obtained; The fifth step is to remove the Fe intermediate layer: prepare an acid solution of a certain concentration, place the multilayer cobalt-based composite particles obtained in the fourth step into it, and slowly stir for a period of time to allow the acid to corrode the Fe intermediate layer to obtain multilayer structure gap-adjustable cobalt-based magnetic composite particles.

2. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the first step, the Co salt solution is specifically a CoSO4 solution.

3. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the first step, a certain amount of complexing agent is prepared, specifically, trisodium citrate and potassium sodium tartrate are prepared into a complexing agent solution.

4. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the first step, the reducing agent is NaOH.

5. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the second step, ammonia water is added dropwise to make the solution reach a certain pH value, specifically: ammonia water is added dropwise to make the solution pH value reach 10.

6. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the third step, the Fe salt solution is specifically a FeSO4 solution.

7. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: In the fourth step, the multilayer structured gap-adjustable cobalt-based composite particles include Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2-small gap-Co-SiO2 composite particles.

8. The method for preparing a multilayer structured gap-adjustable cobalt-based composite particle according to claim 1, characterized in that: It also includes characterizing the obtained multilayer composite particles and testing their wave absorption performance, and analyzing their wave absorption performance.

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