Preparation method of novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material and product of novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material

Abstract

The invention discloses a preparation method of a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material and a product prepared by the preparation method, ultrathin 2D CoFe2O4 nanosheets and 1D CNTs are grown in situ between layers and on the surface of 2D layered Mo-MXene through a double molten salt etching process and a hydrothermal synthesis method, and the 2D layered Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material is prepared by the preparation method of the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material. The 2D / 2D / 1D multi-dimensional heterostructure electromagnetic wave absorbing material which is tight in heterogeneous interface combination, appropriate in impedance matching and stable in structure is formed, so that the multi-frequency band requirement of a novel electromagnetic wave absorbing material is well met, the variety of the multi-frequency electromagnetic wave absorbing material is expanded, and the application prospect is wide. The problems that in the prior art, an electromagnetic wave absorbing material is single in absorbing frequency band and unbalanced in impedance matching are effectively solved, and a brand new method is provided for construction of Mo-MXene-based multi-frequency electromagnetic wave absorbing materials.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic wave absorption technology, and in particular to a preparation method of a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material and a product thereof. Background Art

[0002] With the continuous advancement of electronic devices and wireless communication technologies, electromagnetic waves have become ubiquitous in our daily lives. While the development of electromagnetic waves has brought great convenience to human life, the radiation and pollution problems they cause are also becoming increasingly serious, affecting human health and the proper functioning of precision electronic equipment. Furthermore, with the escalating military confrontations between countries, military radar detection technology is also rapidly developing. Therefore, the development of electromagnetic wave absorbing materials is particularly important. The rapid development of electromagnetic wave absorbing materials in recent years and the increasingly complex operating environments have placed higher demands on high-efficiency electromagnetic wave absorbing materials that can absorb waves across multiple frequency bands.

[0003] Two-dimensional (2D) Mo₂TiC₂ MXene (Mo-MXene) shows great potential in electromagnetic wave absorption due to its excellent mechanical properties, multilayer structure, hydrophilicity, tunable conductivity, and abundant surface functional groups. However, the high conductivity of single 2D Mo-MXene makes electromagnetic waves easily reflected from its surface, leading to impedance mismatch. Furthermore, the 2D layered structure is susceptible to stacking due to van der Waals forces, which severely reduces electromagnetic wave absorption. Therefore, the development of efficient Mo-MXene-based electromagnetic wave absorption materials, especially those with multiband absorption properties, is of great significance but remains a significant challenge. Studies have shown that the construction of multiphase composites or heterogeneous structures can simultaneously inherit multiple loss mechanisms, thereby improving electromagnetic wave absorption efficiency. For example, the introduction of one-dimensional (1D) materials into layered materials such as Mo-MXene can construct three-dimensional (3D) conductive networks and charge transfer channels, enhancing conductivity losses and promoting high-frequency electromagnetic wave absorption. In contrast, the introduction of magnetic components into Mo-MXene can introduce magnetic loss mechanisms, optimize impedance matching, and improve low-frequency electromagnetic wave absorption. However, existing electromagnetic wave absorption materials still suffer from a single absorption band and unbalanced impedance matching. The urgent need to address the technical challenges of Mo-MXene lies in constructing a multi-component and multi-level heterogeneous structure to enrich the electromagnetic loss mechanism, extend the electromagnetic wave attenuation path, improve electromagnetic loss capability, and achieve multi-band electromagnetic wave absorption. Furthermore, developing a low-cost, high-yield method for preparing Mo-MXene materials and finding a simple and effective process for synthesizing multi-band Mo-MXene-based electromagnetic wave absorption materials remain key technical challenges in the field of electromagnetic wave absorption materials. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art and provide a method for preparing a novel multi-band Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorber. Using a dual molten salt etching process and a hydrothermal synthesis method, ultrathin 2D CoFe2O4 nanosheets and 1D CNTs are in situ grown between and on the surface of 2D layered Mo-MXene. This results in a 2D / 2D / 1D multidimensional heterostructured electromagnetic wave absorber with tight heterointerface bonding, optimal impedance matching, and structural stability, effectively meeting the multi-band requirements of novel electromagnetic wave absorbers. Another object of the present invention is to provide products produced using this method for preparing the novel multi-band Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorber.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material, comprising the following steps:

[0007] (1) Preparation of 2D layered Mo2TiC2 MXene

[0008] Mo2TiAlC2 MAX ceramics are used as raw materials and concentrated hydrofluoric acid is used as an etchant. After mixing and stirring according to the mass volume ratio of Mo2TiAlC2 MAX: concentrated hydrofluoric acid = 0.5-1g: 10-30mL, 2D layered Mo2TiC2 MXene powder is obtained by centrifugation, washing and drying.

[0009] (2) Preparation of sandwich-like 2D / 2D Mo-MXene / CoFe2O4

[0010] The 2D layered Mo2TiC2 MXene powder is used as a raw material, and a transition metal source and a metal salt are combined and ground at a mass ratio of 2D layered Mo2TiC2 MXene: transition metal source: metal salt = 0.8-1.2: 2.5-5: 1-3 to obtain a mixed powder, wherein the transition metal source is CoCl2·6H2O and FeCl2·4H2O, and the molar ratio of CoCl2·6H2O: FeCl2·4H2O = 2-4:1; the mixed powder is heat-treated at 700-900°C in a nitrogen atmosphere for 6-10 hours to obtain a sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4 powder;

[0011] (3) Preparation of 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructures

[0012] (3-1) Using ethanol and deionized water as solvents, a carbon source and the sandwich-shaped 2D / 2DMo-MXene / CoFe2O4 powder as raw materials, mixing them in a mass ratio of ethanol: deionized water: carbon source: sandwich-shaped 2D / 2DMo-MXene / CoFe2O4 = 0.5-1.5: 0.5-1.5: 0.3-2: 8-12, stirring, and ultrasonicating to obtain a precursor reaction solution;

[0013] (3-2) The precursor reaction liquid is subjected to a hydrothermal reaction at a temperature of 60 to 120° C. for 2 to 8 hours. The obtained suspension is collected by centrifugation, washed, and dried to obtain an electromagnetic wave absorption material having a 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructure with a multi-level heterostructure and a three-dimensional conductive network.

[0014] Furthermore, in step (1) of the present invention, the mixing and stirring are carried out at a temperature of 50-70° C. for 48-96 hours; the rotation speed of the centrifugal collection is 3000-8000 r / min, and the centrifugal collection time is 5-20 minutes; the washing solution is deionized water, and the washing is carried out to a pH value ≥6; the drying temperature is 60-100° C., and the drying time is 12-48 hours.

[0015] Furthermore, in step (2) of the present invention, a transition metal source is first added and ground for 30 to 90 minutes, and then a metal salt is added and ground for 30 to 90 minutes; during the heat treatment, nitrogen is introduced at a flow rate of 200 to 400 mL / min, and the temperature is raised to 700 to 900°C at a rate of 5°C / min.

[0016] Furthermore, in step (3-1) of the present invention, the stirring time is 30 to 60 minutes, and the ultrasonic time is 10 to 30 minutes. In step (3-2), the centrifugal collection speed is 3000 to 5000 r / min, and the centrifugal collection time is 5 to 15 minutes. The washing solution is deionized water, the drying temperature is 50 to 90° C., and the drying time is 12 to 48 hours.

[0017] In the above scheme, the metal salts of the present invention are NaCl and KCl, and the carbon source is carbon nanotubes.

[0018] The present invention utilizes the method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material to prepare a product. The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material has a minimum reflection loss value of -19.9 to 0 dB in the C band of 4 to 8 GHz and a minimum reflection loss value of -46.62 to 0 dB in the Ku band of 12 to 18 GHz within a thickness of 1 to 5 mm.

[0019] The present invention has the following beneficial effects:

[0020] (1) The present invention uses Mo2TiAlC2 MAX, transition metal source and metal salt as raw materials, adopts double molten salt process, and in situ grows ultrathin 2D CoFe2O4 nanosheets between and on the surface of 2D layered Mo-MXene layers. Then, using carbon nanotubes as carbon source, a hydrothermal synthesis method is used to construct a 1D CNTs conductive network between the Mo-MXene / CoFe2O4 heterostructure layers, forming a 2D / 2D / 1D multidimensional heterostructure with tight heterogeneous interface bonding, suitable impedance matching and stable structure. The present invention not only expands the types of multi-frequency electromagnetic wave absorption materials, but also develops a new type of electromagnetic wave absorption material with excellent absorption performance, covering the C and Ku bands (within a thickness of 1 to 5 mm, the minimum reflection loss value in the C band (4 to 8 GHz) can reach -19.9 dB, and the minimum reflection loss value in the Ku band (12 to 18 GHz) can reach -46.62 dB). It can also achieve adjustable Mo-MXene multilayer structure, controllable CoFe2O4 nanosheet thickness, and tight heterogeneous interface bonding, effectively overcoming the problems of single absorption band and unbalanced impedance matching of electromagnetic wave absorption materials in the prior art.

[0021] (2) The present invention uses concentrated hydrofluoric acid as an etchant to effectively etch away the Al layer in Mo2TiAlC2 MAX, forming a 2D layered structure of Mo2TiC2 MXene, which has a relatively large specific surface area and rich surface functional groups (hydroxyl groups, terminal oxygen, etc.), which makes it possible to grow 2D CoFe2O4 nanosheets in situ.

[0022] (3) The present invention uses NaCl and KCl as metal salts to form a molten salt at high temperature, which can further exfoliate the multilayer Mo2TiC2 MXene and effectively form a few-layer Mo2TiC2 MXene structure. The few-layer Mo2TiC2 MXene obtained by the molten salt method is very thin and has a large specific surface area. Importantly, the addition of CoCl2 and FeCl2 during the molten salt process enables the in situ growth of CoFe2O4 nanosheets, thereby improving the stability of the multi-level heterostructure and providing rich interfacial polarization properties.

[0023] (4) The addition of carbon nanotubes (CNTs) to the reaction system of the present invention as a conductive network aims to bridge the layers of 2D Mo-MXene, thereby constructing a three-dimensional conductive network and charge transfer channel, enhancing electrical conduction loss, and promoting high-frequency absorption of electromagnetic waves. Furthermore, 1D CNTs can inhibit the stacking of MXene sheets, increase the interfacial polarization effect, and extend the electromagnetic wave attenuation path, thereby improving electrical loss capacity.

[0024] (5) The present invention provides a new method for the construction of Mo-MXene-based multi-frequency absorbing materials, and the process method is highly repeatable, easy to control, low-cost, and easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be described in further detail below with reference to the embodiments and accompanying drawings:

[0026] Figure 1 This is a scanning electron microscope image of the Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material prepared in an embodiment of the present invention;

[0027] Figure 2 3 is a graph showing the relationship between the optimal reflection loss and frequency of the electromagnetic wave absorbing materials prepared in the embodiments and comparative examples of the present invention. DETAILED DESCRIPTION

[0028] Example 1:

[0029] This embodiment provides a method for preparing a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material, and the steps are as follows:

[0030] (1) Preparation of 2D layered Mo2TiC2 MXene

[0031] Using Mo2TiAlC2MAX ceramic as raw material and 40% concentrated hydrofluoric acid as etchant, 20mL of concentrated hydrofluoric acid was measured and transferred to a Teflon liner with a volume of 100mL. 2g of Mo2TiAlC2MAX was slowly added and magnetically stirred at 55°C for 72h. The resulting suspension was centrifuged at 6000r / min for 8min and washed with deionized water to a pH value ≥6. It was then dried at 70°C for 24h to obtain 2D layered Mo2TiC2MXene powder.

[0032] (2) Preparation of sandwich-like 2D / 2D Mo-MXene / CoFe2O4

[0033] 0.2 g of the above-mentioned 2D layered Mo2TiC2 MXene powder was weighed and transferred to an agate mortar. 0.535 g of CoCl2·6H2O and 0.1491 g of FeCl2·4H2O were added in sequence and ground at room temperature for 30 min. Then, 0.140 g of NaCl and 0.152 g of KCl were added in sequence and ground at room temperature for 30 min to obtain a mixed powder. The mixed powder was placed in a porcelain boat and placed in the middle of a quartz tube furnace. Nitrogen was introduced at a flow rate of 300 mL / min and the temperature was increased to 750°C at 5°C / min for heat treatment for 8 h to obtain a sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4 powder.

[0034] (3) Preparation of 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructures

[0035] (3-1) Using ethanol and deionized water as solvents, carbon nanotubes and the above-mentioned sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4 powder as raw materials, 5 mL of deionized water and 5 mL of ethanol were measured and transferred to a 25 mL beaker. 50 mg of the above-mentioned Mo-MXene / CoFe2O4 and 5 mg of carbon nanotubes were added in sequence. The mixture was magnetically stirred for 45 min and ultrasonicated for 20 min at room temperature to obtain a precursor reaction solution.

[0036] (3-2) The precursor reaction solution was transferred to a Teflon-lined container with a volume of 50 mL and placed in a high-pressure reactor. A hydrothermal reaction was carried out at 80°C for 4 h. The obtained suspension was collected by centrifugation at 4000 r / min for 10 min, washed three times with deionized water, and dried at 80°C for 24 h to obtain an electromagnetic wave absorption material with a 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructure having a multi-level heterostructure and a three-dimensional conductive network.

[0037] Example 2:

[0038] This embodiment provides a method for preparing a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material, which differs from the first embodiment in that 2.5 mg of carbon nanotubes are added in step (3-1).

[0039] Example 3:

[0040] This embodiment provides a method for preparing a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material, which differs from the first embodiment in that 10 mg of carbon nanotubes are added in step (3-1).

[0041] Comparative Example:

[0042] The sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4 powder prepared in step (2) of Example 1 is used as the final electromagnetic wave absorbing material.

[0043] The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material prepared in the embodiment of the present invention is as follows Figure 1 As shown in the figure, ultrathin 2D CoFe2O4 nanosheets are in situ grown between and on the surface of 2D layered Mo-MXene by a double molten salt process, forming a sandwich-like 2D / 2D heterostructure with tight interface bonding and stable structure; then a 1D CNTs conductive network is constructed between the Mo-MXene / CoFe2O4 heterostructure layers by a hydrothermal synthesis method, forming a 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs multidimensional heterostructure with tight heterogeneous interface bonding, suitable impedance matching and stable structure.

[0044] The optimal reflection loss and frequency relationship curves of the electromagnetic wave absorbing materials prepared in the embodiments of the present invention and the comparative examples are as follows: Figure 2 As shown:

[0045] The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material prepared in Example 1 has a minimum reflection loss value of -19.9 dB in the C band of 4 to 8 GHz and a minimum reflection loss value of -46.62 dB in the Ku band of 12 to 18 GHz within a thickness of 1 to 5 mm.

[0046] The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material prepared in Example 2 has a minimum reflection loss value of -8.2 dB in the C band of 4 to 8 GHz and a minimum reflection loss value of -9.78 dB in the Ku band of 12 to 18 GHz within a thickness of 1 to 5 mm.

[0047] The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material prepared in Example 3 has a minimum reflection loss value of -9.33 dB in the C band of 4 to 8 GHz and a minimum reflection loss value of -5.32 dB in the Ku band of 12 to 18 GHz within a thickness of 1 to 5 mm.

[0048] The electromagnetic wave absorbing material prepared in the comparative example is a sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4. Within a thickness of 1 to 5 mm, the minimum reflection loss value in the X-band of 8 to 12 GHz is -3.76 dB.

Claims

1. A method for preparing a novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material, characterized in that The following steps are involved: (1) Preparation of 2D layered Mo2TiC2 MXene Mo2TiAlC2MAX ceramics are used as raw materials and concentrated hydrofluoric acid is used as an etchant. After mixing and stirring according to the mass volume ratio of Mo2TiAlC2MAX:concentrated hydrofluoric acid = 0.5-1g:10-30mL, 2D layered Mo2TiC2MXene powder is obtained by centrifugation, washing and drying. (2) Preparation of sandwich-like 2D / 2D Mo-MXene / CoFe2O4 The 2D layered Mo2TiC2 MXene powder is used as a raw material, and a transition metal source and a metal salt are combined and ground at a mass ratio of 2D layered Mo2TiC2 MXene: transition metal source: metal salt = 0.8-1.2: 2.5-5: 1-3 to obtain a mixed powder, wherein the transition metal source is CoCl2·6H2O and FeCl2·4H2O, and the molar ratio of CoCl2·6H2O: FeCl2·4H2O = 2-4:1; the mixed powder is heat-treated at 700-900°C in a nitrogen atmosphere for 6-10 hours to obtain a sandwich-shaped 2D / 2D Mo-MXene / CoFe2O4 powder; (3) Preparation of 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructures (3-1) Using ethanol and deionized water as solvents, a carbon source and the sandwich-shaped 2D / 2DMo-MXene / CoFe2O4 powder as raw materials, mixing them in a mass ratio of ethanol: deionized water: carbon source: sandwich-shaped 2D / 2DMo-MXene / CoFe2O4 = 0.5-1.5: 0.5-1.5: 0.3-2: 8-12, stirring, and ultrasonicating to obtain a precursor reaction solution; (3-2) The precursor reaction liquid is subjected to a hydrothermal reaction at a temperature of 60 to 120° C. for 2 to 8 hours. The obtained suspension is collected by centrifugation, washed, and dried to obtain an electromagnetic wave absorption material having a 2D / 2D / 1D Mo-MXene / CoFe2O4 / CNTs heterostructure with a multi-level heterostructure and a three-dimensional conductive network.

2. The method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to claim 1, characterized in that: In the step (1), the mixture is mixed and stirred at a temperature of 50 to 70° C. for 48 to 96 hours; the rotation speed of the centrifugal collection is 3000 to 8000 r / min, and the centrifugal collection time is 5 to 20 minutes; the washing solution is deionized water, and the washing is performed to a pH value ≥ 6; the drying temperature is 60 to 100° C., and the drying time is 12 to 48 hours.

3. The method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to claim 1, characterized in that: In the step (2), a transition metal source is first added and ground for 30 to 90 minutes, and then a metal salt is added and ground for 30 to 90 minutes; during the heat treatment, nitrogen is introduced at a flow rate of 200 to 400 mL / min, and the temperature is raised to 700 to 900° C. at a rate of 5° C. / min.

4. The method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to claim 1, characterized in that: In the step (3-1), the stirring time is 30 to 60 minutes, and the ultrasonic time is 10 to 30 minutes.

5. The method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to claim 1, characterized in that: In the step (3-2), the rotation speed of the centrifugal collection is 3000-5000 r / min, and the centrifugal collection time is 5-15 min; the washing solution is deionized water, the drying temperature is 50-90° C., and the drying time is 12-48 h.

6. The method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to claim 1, characterized in that: The metal salts are NaCl and KCl, and the carbon source is carbon nanotubes.

7. A product obtained by the method for preparing the novel multi-frequency Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorbing material according to any one of claims 1 to 6.

8. The product according to claim 7, characterized in that: The Mo-MXene / CoFe2O4 / CNTs electromagnetic wave absorption material has a minimum reflection loss value of -19.9 to 0 dB in the C band of 4 to 8 GHz and a minimum reflection loss value of -46.62 to 0 dB in the Ku band of 12 to 18 GHz within a thickness of 1 to 5 mm.

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