A CoMn metal oxide electromagnetic wave absorbing material and its preparation method and application

Abstract

The present invention relates to a CoMn metal oxide electromagnetic wave absorbing material and its preparation method and application. The composition of the CoMn metal oxide electromagnetic wave absorbing material is Co 3‑x Mn x O4, where 0

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and in particular to a CoMn metal oxide electromagnetic wave absorbing material and a preparation method and application thereof. Background Art

[0002] Human-computer interaction and virtual reality technologies have caused significant electromagnetic interference / pollution in smart electronic devices. Electromagnetic wave absorbing materials can convert incident electromagnetic energy into heat, effectively reducing electromagnetic radiation interference / pollution. Metal oxide-based materials stand out among sulfide-based, carbon-based and metal-based electromagnetic wave absorbing materials for their low cost, eco-friendliness, ability to achieve strong reflection loss and adjustable electromagnetic wave absorption frequency region. However, the narrow effective electromagnetic wave absorption bandwidth (EAB) limits application demand. One of the main reasons is that the wide band gap of metal oxides makes it difficult for electrons to escape confinement and become free carriers, resulting in a lack of effective polarization centers. The narrow EAB disadvantage of oxides has led to less attention paid to oxide-based electromagnetic wave absorbing materials. Therefore, the development of oxide absorption materials with wide EAB is of great significance.

[0003] Effective strategies for broadening EABs include adjusting composition, including chemical composition, crystal structure (e.g., defect engineering), phase transitions (e.g., multiphase coexistence to form heterostructures), and structural design (e.g., core-shell or multilayer structures). Based on the microwave length matching principle, the key to enhancing EABs in dielectric response-dominated systems (e.g., oxide- and sulfide-based systems) lies in generating sufficient dielectric relaxation responses across a wide range of electromagnetic wave frequencies to enhance electromagnetic wave energy dissipation. However, current vacancy engineering for EAB modulation has primarily focused on anion vacancies, while cation vacancies have received little attention. Furthermore, the mechanisms of cation vacancies and heterostructure engineering in EAB modulation remain unclear. Both anion and cation vacancies exist in oxides. Compared to anion vacancies, cation vacancies have larger ionic radii, making them more advantageous for anchoring carriers. Several DFT calculations have also shown that the presence of cation vacancies reduces the energy barrier for ion diffusion and increases the electronic conductivity of the material. Therefore, utilizing cation vacancies and heterostructure engineering to broaden the EABs of oxides holds great potential and is a pressing research topic. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and provide a CoMn metal oxide electromagnetic wave absorption material and its preparation method and application. Through simple hydrothermal reaction, heat treatment process and grinding, an excellent and stable electromagnetic wave absorption material is prepared to solve the problem of narrow EAB and low electromagnetic wave absorption performance of metal oxides.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first object of the present invention is to provide a preparation method of a CoMn metal oxide electromagnetic wave absorption material, and the composition of the CoMn metal oxide is Co 3-x Mn x O4, where 0 < x < 3; the preparation method includes the following steps:

[0007] S1: Configure raw materials according to the molar ratio in Co 3-x Mn x O4; fully stir the metal salt raw materials magnetically in deionized water to obtain a metal salt solution;

[0008] S2: Perform a hydrothermal reaction on the obtained metal salt solution to obtain a precursor solution;

[0009] S3: Centrifuge and wash the obtained precursor solution, and dry it in a vacuum drying oven and then grind it to obtain precursor metal oxide powder;

[0010] S4: After calcining the obtained precursor metal oxide powder, obtain metal oxide powder, which is the CoMn metal oxide electromagnetic wave absorption material.

[0011] Preferably, in step S1, the manganese source is manganese sulfate monohydrate with a purity of not less than 99.9%, and the cobalt source is cobalt nitrate hexahydrate with a purity of not less than 99.9%.

[0012] Preferably, the metal ions include cobalt in the cobalt source and manganese in the manganese source; the molar ratio of the total amount of metal ions (the total amount of cobalt in the cobalt source and manganese in the manganese source): urea: ammonium persulfate is 5:3:1.

[0013] Preferably, in step S1, the metal salt solution is obtained by magnetic stirring, and the stirring time is 20 - 40 min.

[0014] As a further preferred scheme of the preparation method of the present invention, among them: in step S1, the metal salt solution is obtained by magnetic stirring, and the stirring time is 30 min.

[0015] Preferably, in step S2, the hydrothermal reaction temperature is 160 - 180 °C, and the reaction time is 180 - 240 min.

[0016] Preferably, in step S2, the hydrothermal reaction is carried out in a hydrothermal reaction kettle with a capacity of 100 ml.

[0017] Preferably, in step S3, the centrifugal washing is to alternately wash three times with deionized water and ethanol solution respectively.

[0018] Further preferably, in step S3, the centrifugal washing is performed by alternating washing with deionized water and ethanol solution three times respectively.

[0019] Preferably, in step S4, the calcination temperature is 350-450° C., and the calcination time is 2-4 hours.

[0020] The second object of the present invention is to provide a CoMn metal oxide electromagnetic wave absorbing material prepared by the above method, which has excellent electromagnetic wave absorbing performance.

[0021] The third object of the present invention is to provide an application of a CoMn metal oxide electromagnetic wave absorber, wherein the CoMn metal oxide electromagnetic wave absorbing material is used for electromagnetic wave absorption.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The metal oxide prepared by the present invention has excellent electromagnetic wave absorption performance, and can be prepared into an excellent and stable electromagnetic wave absorption material through a simple hydrothermal reaction, heat treatment process, and grinding. The preparation process is simple and easy. Through a simple hydrothermal reaction, heat treatment process, and grinding technology, a CoMn metal oxide electromagnetic wave absorption material with excellent and stable electromagnetic wave absorption performance can be prepared, which has great application prospects.

[0024] (2) The present invention dopes an appropriate amount of Mn element so that it occupies the Co atoms and vacancies in the Co3O4 crystal and induces the formation of heterogeneous phases and defects, thereby optimizing its dielectric properties and adjusting its electromagnetic wave absorption performance.

[0025] (3) The absorber comprising the CoMn metal oxide electromagnetic wave absorbing material of the present invention has a minimum reflection loss of -52.1 dB when the thickness is only 2.52 mm, and has a wide EAB of 7.75 GHz, showing an extraordinary electromagnetic wave absorption capability.

[0026] (4) The CoMn metal oxide electromagnetic wave absorbing material provided by the present invention is low-cost, eco-friendly, and can effectively reduce electromagnetic radiation interference / pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0028] Figure 1The XRD patterns of the CoMn metal oxide electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1 are shown;

[0029] Figure 2 The SEM images of the CoMn metal oxide electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1 are shown, wherein a is Comparative Example 1, b is Example 1, c is Example 2, and d is Example 3;

[0030] Figure 3 It is a graph of the electromagnetic wave absorption performance of the CoMn metal oxide electromagnetic wave absorption material prepared in Examples 1 to 3 and Comparative Example 1, wherein a is Comparative Example 1, b is Example 1, c is Example 2, and d is Example 3. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the embodiments of the specification. Any features such as preparation methods, materials, structures or composition ratios not explicitly described in this technical solution are deemed to be common technical features disclosed in the prior art.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0034] The present technical solution provides a method for preparing a CoMn metal oxide material, comprising the following steps:

[0035] According to the composition of Co 3-x Mn x O4 configuration raw materials, where 0≤x≤3;

[0036] The metal salt raw material is fully magnetically stirred in deionized water to obtain a metal salt solution;

[0037] subjecting the metal salt solution to a high-temperature and high-pressure hydrothermal reaction to prepare a precursor solution;

[0038] The precursor solution is centrifuged and washed multiple times, and then fully dried in a vacuum drying oven and ground to obtain a precursor metal oxide powder;

[0039] The prepared precursor metal oxide powder is calcined at high temperature to obtain the metal oxide powder.

[0040] The raw materials are manganese sulfate monohydrate with a purity of not less than 99.9%, cobalt nitrate hexahydrate, deionized water, urea and ammonium persulfate.

[0041] In the present invention, unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0042] Example 1

[0043] This embodiment provides a Co 3-x Mn x The preparation method of O4 metal oxide electromagnetic wave absorbing material comprises the following steps:

[0044] (1) Cobalt nitrate hexahydrate, manganese sulfate monohydrate, urea and ammonium persulfate with a purity of not less than 99.9% are mixed according to the nominal composition of Co 2.4 Mn 0.6 O4, fully magnetically stirred in deionized water for 30 minutes to prepare a metal salt solution, wherein the molar ratio of total metal ion: urea: ammonium persulfate is 5:3:1, the total amount of metal ions is fixed at 5 mmol, and the deionized water is 40 ml;

[0045] (2) placing the metal salt solution prepared in step (1) into the inner lining of a high-pressure reactor, and placing the high-pressure reactor in the center of a muffle furnace, heating the muffle furnace to 180° C. at a heating rate of 2.0° C. / min, keeping the temperature for 240 min, and then taking out the metal salt solution after sufficient cooling to obtain the precursor solution;

[0046] (3) washing the metal salt solution obtained in step (2) with deionized water and ethanol solution three times alternately to obtain a precipitate sample, which was placed in a vacuum drying oven at 60° C. and dried for 12 h to obtain a metal oxide precursor powder;

[0047] (4) After the metal oxide precursor powder sample obtained in step (3) is fully ground, it is placed in a muffle furnace for calcination, and the temperature is increased from room temperature to 350°C at a heating rate of 2.0°C / min, and the temperature is kept for 4 hours. After the temperature is kept, it is slowly cooled in the furnace to obtain a calcined metal oxide powder sample, i.e., a CoMn metal oxide electromagnetic wave absorbing material.

[0048] Example 2

[0049] This embodiment provides a Co 3-x Mn x Preparation method of O4 metal oxide electromagnetic wave absorbing material, the difference between Example 2 and Example 1 is the amount of raw materials added, the amount of raw materials added in this embodiment is the same as Co1.5 Mn 1.5 The ratio of O4 was matched, and the other steps were the same as in Example 1.

[0050] Example 3

[0051] This embodiment provides a Co 3-x Mn x Preparation method of O4 metal oxide electromagnetic wave absorbing material, the difference between Example 3 and Example 1 is the amount of raw materials added, the amount of raw materials added in this embodiment is the same as Co 0.6 Mn 2.4 The ratio of O4 was matched, and the other steps were the same as in Example 1.

[0052] Comparative Example 1

[0053] This comparative example is a Co 3-x Mn x Preparation method of O4 metal oxide electromagnetic wave absorbing material. The difference between this comparative example and Example 1 is the amount of raw materials added. The amount of raw materials added in this comparative example matches the ratio of Co3Mn0O4, and the other steps are the same as Example 1.

[0054] Phase analysis: In order to illustrate the effect of Mn doping on the CoMn phase content and observe the change of CoMn phase content, XRD tests were performed on the electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1. The results are as follows: Figure 1 As shown in the figure, it can be seen that the electromagnetic wave absorbing materials prepared in Comparative Example 1 and Example 1 are both [Fd-3m:2] type cubic structure Co3O4; the electromagnetic wave absorbing material prepared in Example 2 contains [Fd-3m:2] type cubic structure Co3O4 and [I 41 / amd:1] type intermetallic phase (Co,Mn)(Co,Mn)2O4; the electromagnetic wave absorbing material prepared in Example 3 contains [I 41 / amd:1] type intermetallic phase (Co,Mn)(Co,Mn)2O4 and [I 41 / amd:1] type intermetallic phase (Co,Mn)2O4.

[0055] Table 1 is based on Figure 1 The results show the phase content and lattice constant of the CoMn metal oxide electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1. 3-δ The contents of O4 are 100wt.%, 100wt.%, 90.97wt.% and 0% respectively. It can be seen that appropriate concentration of Mn element doping can reduce the cubic Co 3-δ The formation of O4, and if the doping concentration is high, it will destroy the Co 3-δThe [Fd-3m:2] type cubic structure of O4 forms a (Co,Mn)(Co,Mn)2O4 intermetallic phase.

[0056] Table 1 Phase contents and lattice constants of the CoMn metal oxide electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1.

[0057]

[0058] Morphology analysis: In addition, in order to illustrate the effect of Mn element doping on the surface morphology of CoMn oxide, the electromagnetic wave absorbing materials prepared in Examples 1 to 3 and Comparative Example 1 were observed under a scanning electron microscope. The results are as follows: Figure 2 As shown, significant morphological differences can be observed between Comparative Example 1 and Examples 1-3. The CoMn metal oxide prepared in Comparative Example 1 is nanospheres with a diameter of approximately 200 nm. However, in Examples 1-3, as the Mn doping concentration increases, the prepared CoMn metal oxide gradually evolves from nanospheres to nanowire structures. These findings further demonstrate the ability of ion doping to regulate the growth process of Co3O4 crystals, thereby effectively adjusting heterogeneous structures.

[0059] Wave absorbing performance analysis: The CoMn metal oxide electromagnetic wave absorbing materials prepared in Comparative Example 1 and Examples 1 to 3 were mixed with paraffin wax in a mass ratio of 50%:50% and pressed into ring-shaped absorber samples (D) of different thicknesses (2.0 to 2.5 mm). 外 =(7.00)mm,d 内 =(3.04)mm), and the electromagnetic wave absorption performance test was carried out. The results are as follows Figure 3 As shown in the figure, it can be seen that Example 2 shows extraordinary absorption capacity. In the case of a thickness of only 2.52mm, a wide EAB is observed at 7.75GHz and the minimum reflection loss value is -52.1dB. In contrast, a narrow EAB is observed in Comparative Example 1, Example 1 and Example 3, and the electromagnetic wave absorption performance is not high; all ion-doped Co 3-x Mn x O4 absorber samples were compared and EAB values ​​were observed. It was found that Co modified by ion doping 3-x Mn x O4 has a wider EAB than the undoped sample, highlighting the strong correlation between the heterostructure and the introduced cation defect configuration; compared with the single oxide (Example 1 and Comparative Example 1), Examples 2 and 3 with dual-phase structures exhibit stronger absorption performance at thinner thicknesses, indicating the advantage of heterostructure configuration for EMW absorption.

[0060] In summary, the present invention promotes the formation of heterostructure phases and cation vacancies by doping an appropriate amount of Mn element into Co metal oxide, thereby promoting dielectric polarization behavior and improving electromagnetic wave absorption performance. This is of great significance for the further development and wide application of CoMn metal oxide absorbing materials.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for preparing a CoMn metal oxide electromagnetic wave absorber, characterized in that: The composition of the CoMn metal oxide is Co 3-x Mn x O4, where x = 1.5; The preparation method comprises the following steps: Cobalt source, manganese source, urea and ammonium persulfate were mixed according to Co 3-x Mn x The metal salt raw material is configured in a molar ratio of O4; the metal salt raw material is stirred in deionized water to obtain a metal salt solution; subjecting the prepared metal salt solution to a hydrothermal reaction to prepare a precursor solution; The obtained precursor solution is centrifuged, washed, dried, and then ground to obtain precursor metal oxide powder; The obtained precursor metal oxide powder is subjected to high temperature calcination to obtain metal oxide powder, namely CoMn metal oxide electromagnetic wave absorbing material; The CoMn metal oxide electromagnetic wave absorbing material and paraffin are mixed in a mass ratio of 50%:50% and then pressed into an absorber; The hydrothermal reaction temperature is 160-180°C, and the reaction time is 180-240 minutes; The high temperature calcination temperature is 350-450° C., and the calcination time is 2-4 hours.

2. The method for preparing a CoMn metal oxide electromagnetic wave absorber according to claim 1, characterized in that: In step S1, the manganese source is manganese sulfate monohydrate with a purity of not less than 99.9%, and the cobalt source is cobalt nitrate hexahydrate with a purity of not less than 99.9%.

3. The method for preparing a CoMn metal oxide electromagnetic wave absorber according to claim 1, characterized in that: The metal ions include cobalt from the cobalt source and manganese from the manganese source; The molar ratio of total metal ions: urea: ammonium persulfate is 5:3:

1.

4. The method for preparing a CoMn metal oxide electromagnetic wave absorber according to claim 1, characterized in that: The metal salt solution is obtained by magnetic stirring, and the stirring time is 20 to 40 minutes.

5. The method for preparing a CoMn metal oxide electromagnetic wave absorber according to claim 1, characterized in that: The hydrothermal reaction was carried out in a hydrothermal reactor with a capacity of 100 ml.

6. The method for preparing a CoMn metal oxide electromagnetic wave absorber according to claim 1, characterized in that: The centrifugal washing is performed by washing the sample three times with deionized water and ethanol solution alternately.

7. A CoMn metal oxide electromagnetic wave absorber, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 6.

8. Use of the CoMn metal oxide electromagnetic wave absorber according to claim 7, characterized in that: The CoMn metal oxide electromagnetic wave absorber is used for electromagnetic wave absorption.

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