Preparation method and application of core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material

Abstract

The present invention discloses a core-shell structure metal-organic nanosheet loaded silicon carbide nanowire material, its preparation method and application. It relates to the field of core-shell structure material preparation, and the method includes uniformly adsorbing bimetallic ions (Ni 2+ / Co 2+ or Ni 2+ / Zn 2+ ) precursor, using 2-methylimidazole as an organic induction molecule, in a mixed solvent system of methanol and water at room temperature to form a bimetallic-organic nanosheet-loaded silicon carbide nanowire core-shell structure. This composite material is then calcined in air to produce a derivative bimetallic oxide / carbon / SiC nanowire composite material with a core-shell structure and excellent electromagnetic wave absorption properties. This method is economical, environmentally friendly, lightweight, safe, efficient, and can be prepared in large quantities.

Description

Technical Field

[0001] The invention relates to a core-shell structured metal-organic nanosheet loaded silicon carbide nanowire material and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorption materials. Background Art

[0002] It is well known that structural design is of great significance for the development of electromagnetic wave absorption (EMA) performance of materials. In particular, the construction of core-shell structures has many advantages in improving the EMA performance of materials. For example, it can effectively reduce the electrical conductivity of the material, improve impedance matching, and increase interfacial polarization. In addition, the formation of core-shell composite structures can also improve the friction resistance and corrosion resistance of the material, which has a good guiding role in the design of excellent absorbing materials.

[0003] Metal-organic frameworks (MOFs) have been extensively studied in the field of electromagnetic wave absorption due to their unique composition, structure, and properties. Two-dimensional metal-organic nanosheets (2D-MOS) possess large lateral dimensions and surface area, which facilitates the material's ability to receive electromagnetic wave signals. Silicon carbide nanowires (SiC NWs) possess a one-dimensional structure, a large aspect ratio, and excellent dielectric properties. The design of composite core-shell structures by combining two-dimensional MOFs with silicon carbide nanowires (2D-MOS@SiC) can enhance the material's unit receiving area for electromagnetic signals, impedance matching, interfacial polarization, and multi-component synergistic attenuation, thereby yielding materials with excellent electromagnetic wave absorption properties. However, current methods for preparing these core-shell materials are complex and energy-intensive. Designing simple, environmentally friendly, and economical methods for preparing these materials, as well as multi-metal 2D-MOS@SiC and its derivatives with diverse components, easily tunable electromagnetic parameters, and excellent absorption properties, remains a research hotspot and a challenge, and remains a significant challenge. Summary of the Invention

[0004] The present invention aims to provide an economical, environmentally friendly, efficient, simple, and rapid method for preparing bimetallic-organic nanosheet-supported silicon carbide nanowires with a core-shell structure, making them commercially viable. Furthermore, derivatives of these materials exhibit excellent electromagnetic wave absorption properties. In this paper, silicon carbide nanowires are replaced by SiC NWs.

[0005] The technical solution of the present invention:

[0006] The present invention provides a method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material, comprising the following steps:

[0007] S1: Methanol, water, and SiC NWs are mixed in a preset ratio and subjected to ultrasonic treatment to form SiC NWs dispersion A;

[0008] S2 adding nickel chloride hexahydrate and cobalt chloride hexahydrate to dispersion A according to a preset ratio and ultrasonically mixing them to obtain a mixed dispersion B;

[0009] The concentration of S3 SiC NWs in the methanol and water mixed solution A is 0.75-3 mg / ml, and the ultrasonic treatment time of SiC NWs in the solution is 30-90 min;

[0010] S4: adding a preset amount of 2-methylimidazole methanol solution dropwise to the mixed dispersion B while continuously stirring the mixed dispersion B to obtain a mixed dispersion C;

[0011] In the mixed dispersion C, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1-3:15, the total concentration of cobalt and nickel is 0.05-0.16 mmol / ml, and the volume ratio of methanol to water is 2-4:1;

[0012] The metal salt is composed of cobalt chloride and nickel chloride in the mixed dispersion B;

[0013] S5: centrifuging the mixed dispersion C, washing and drying the centrifuged product to obtain a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material.

[0014] Preferably, in S1:

[0015] The amount of the methanol used is 10 ml, the amount of the water used is 10 ml, and the amount of the SiC NWs used is 30 mg.

[0016] Preferably, in said S2,

[0017] The amount of nickel chloride hexahydrate used is 0.715 g, and the amount of cobalt chloride hexahydrate used is 0.429 g;

[0018] In step S4, a preset amount of 2-methylimidazole methanol solution is added dropwise to the mixed dispersion B while the mixed dispersion B is continuously stirred, specifically:

[0019] At room temperature, the mixed dispersion B was stirred at a rate of 400 rpm using a magnetic stirrer for 2 hours, and the 2-methylimidazole methanol solution was added dropwise within the 2 hours. After the addition was completed, the mixture was stirred at a rate of 400 rpm for 3 hours.

[0020] In step S4, the preset amount of 2-methylimidazole methanol solution is prepared by weighing 1.97 g of 2-methylimidazole into a beaker and adding 10 ml of methanol, and dissolving the mixture with ultrasound to obtain the preset amount of 2-methylimidazole methanol solution.

[0021] The present invention also provides a method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material, comprising the following steps:

[0022] S1: Methanol, water, and SiC NWs are mixed in a preset ratio and ultrasonically treated for a certain period of time to form SiC NWs dispersion A;

[0023] S2 adding nickel chloride hexahydrate and zinc nitrate hexahydrate to dispersion A according to a preset ratio and ultrasonically mixing them to obtain a mixed dispersion B;

[0024] The concentration of S3 SiC NWs in dispersion A was 0.75–3 mg / ml, and the ultrasonic treatment time of SiC NWs in the solution was 30–90 min;

[0025] S4: adding a preset amount of 2-methylimidazole methanol solution dropwise to the mixed dispersion B while continuously stirring the mixed dispersion B to obtain a mixed dispersion C;

[0026] In the mixed dispersion C, the molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1-3:15, the total concentration of zinc and nickel is 0.05-0.16 mmol / ml, and the volume ratio of methanol to water is 2-4:1;

[0027] The metal salt is composed of zinc nitrate and nickel chloride in the mixed dispersion B;

[0028] S5: centrifuging the mixed solution C, washing and drying the centrifugal product to obtain a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material.

[0029] Preferably, in S1:

[0030] The amount of the methanol used is 10 ml, the amount of the water used is 10 ml, and the amount of the SiC NWs used is 30 mg.

[0031] In S2, the amount of nickel chloride hexahydrate is 0.715 g, and the amount of zinc nitrate hexahydrate is 0.535 g;

[0032] In step S4, a preset amount of 2-methylimidazole methanol solution is added dropwise to the mixed dispersion B while the mixed dispersion B is continuously stirred, specifically:

[0033] At room temperature, the mixed dispersion B was stirred at a rate of 400 rpm using a magnetic stirrer for 2 hours, and the 2-methylimidazole methanol solution was added dropwise within the 2 hours. After the addition was completed, the mixture was stirred at a rate of 400 rpm for 3 hours.

[0034] In step S4, the preset amount of 2-methylimidazole methanol solution is prepared by weighing 1.97 g of 2-methylimidazole into a beaker and adding 10 ml of methanol, and dissolving the solution with ultrasound assistance to obtain the preset amount of 2-methylimidazole methanol solution.

[0035] Preferably, in step S5, the cleaning is performed by using methanol, and the drying is performed by vacuum drying.

[0036] The present invention also provides an application of a core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire material in electromagnetic wave absorption, comprising the following steps:

[0037] The core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material prepared by the preparation method according to any one of claims 1 or 4 is heated in an open tubular furnace to 400 degrees Celsius and kept at 400 degrees Celsius for 1 hour to obtain a calcined product; the calcined product is mixed with paraffin and then subjected to electromagnetic wave absorption.

[0038] Preferably, the core-shell structured metal-organic nanosheets loaded with silicon carbide nanowire material are heated in an open tube furnace;

[0039] The calcined product was mixed with paraffin wax at a mass ratio of 4:1 to prepare annular sheets with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.2 mm;

[0040] Electromagnetic parameter testing was performed using a network analyzer in the 2-18 GHz frequency range. Agilent PNA software was used to output electromagnetic parameters according to the Nicolson, Ross, and Weir algorithm.

[0041] When the thickness is 2 mm, the maximum absorption intensity is -21.05 dB and the maximum absorption width is 5.44 GHz.

[0042] Preferably, the core-shell structured metal-organic nanosheets loaded with silicon carbide nanowire material are heated in an open tube furnace;

[0043] The calcined product was mixed with paraffin wax in a mass ratio of 4:1 to prepare annular sheets with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm and a thickness of 2.2 mm;

[0044] Electromagnetic parameter testing was performed using a network analyzer in the 2-18 GHz frequency band for electromagnetic wave absorption testing;

[0045] Use Agilent PNA software to output electromagnetic parameters according to the Nicolson and Ross and Weir algorithm:

[0046] When the thickness is 3 mm, it shows the maximum absorption intensity, corresponding to a peak of -47.80 dB. When the thickness is 2.5 mm, it has the maximum absorption width, reaching 6.04 GHz.

[0047] Compared with the existing related technologies, the present invention has the following significant advantages:

[0048] 1. For the core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire structure 2D-MOS@SiC, (1) the present invention is simple, efficient, economical and environmentally friendly. Under room temperature, the core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire is obtained by stirring in a methanol and water mixed solution system; (2) the optimal molar ratio of the bimetallic ions in the preparation of Co, Ni-2D-MOS@SiC is selected to be n Co 2+ :n Ni 2+ =0.6:1, (3) the optimal volume ratio of the mixed reaction solvent is selected as Vmethanol:Vwater=2-4:1; (4) the preparation method of Co,Ni-2D-MOS@SiC core-shell structure bimetallic-organic nanosheets loaded silicon carbide nanowires is expanded to the preparation application of Zn,Ni-2D-MOS@SiC core-shell structure bimetallic-organic nanosheets loaded silicon carbide nanowires.

[0049] 2. For the core-shell structure 2D-MOS@SiC derived electromagnetic absorption materials, (1) the multi-component synergistic effect of two-dimensional metal-organic nanosheet derivatives and SiC nanowire functional materials with good dielectric properties, as well as the construction of the core-shell structure, further promotes the responsiveness of the composite material to electromagnetic signals, thereby improving the material's absorption of electromagnetic waves; (2) the calcination atmosphere is air, avoiding the use of relatively expensive inert gases (argon or nitrogen, etc.), which has the characteristics of safety, economy, and energy saving.

[0050] 3. The reaction process of the present invention is simple, low in temperature, easy to control, and does not require large-scale equipment and harsh reaction conditions, and can achieve large-scale mass production.

[0051] 4. The material prepared by the present invention has a good electromagnetic response absorption effect, and the density of the sample is relatively low. When the addition ratio in a matrix such as paraffin is small, a good electromagnetic wave absorption effect can be obtained. The sample is in powder form and can be mixed with a polymer resin and a binder to make a composite material. It can be processed into any shape as needed and can also be used as a coating additive. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(30)-1 sample prepared in Example 1 of the present invention.

[0053] Figure 2 This is a transmission electron microscope image of the Co,Ni-2D-MOS@SiC(30)-1 sample prepared in Example 1 of the present invention.

[0054] Figure 3 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(30)-1 / 3 sample prepared in Example 2 of the present invention.

[0055] Figure 4 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(30)-2 / 5 sample prepared in Example 3 of the present invention.

[0056] Figure 5 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(30)-3 / 5 sample prepared in Example 4 of the present invention.

[0057] Figure 6 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-1 sample prepared in Example 5 of the present invention.

[0058] Figure 7 This is a transmission electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-1 sample prepared in Example 5 of the present invention.

[0059] Figure 8 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-1 / 3 sample prepared in Example 6 of the present invention.

[0060] Figure 9 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-2 / 5 sample prepared in Example 7 of the present invention.

[0061] Figure 10 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-3 / 5 sample prepared in Example 8 of the present invention.

[0062] Figure 11 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(15)-1 sample prepared in Example 9 of the present invention.

[0063] Figure 12 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(60)-1 sample prepared in Example 10 of the present invention.

[0064] Figure 13 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(15)-1 sample prepared in Example 11 of the present invention.

[0065] Figure 14 This is a scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(60)-1 sample prepared in Example 12 of the present invention.

[0066] Figure 15 These are electronic photographs of the Co, Ni-2D-MOS@SiC(30)-1 and Zn, Ni-2D-MOS@SiC(30)-1 samples in the present invention and the Co, Ni-2D-MOS@SiC(30)-1-D and Zn, Ni-2D-MOS@SiC(30)-1-D samples after calcination.

[0067] Figure 16 This is a scanning electron microscope image of the Co,Ni-2D-MOS@SiC(30)-1-D sample in the present invention.

[0068] Figure 17 The scanning electron microscope image of the Zn,Ni-2D-MOS@SiC(30)-1-D sample in the present invention is shown in FIG.

[0069] Figure 18 This is a diagram of the wave absorption performance of the Co,Ni-2D-MOS@SiC(30)-1-D sample in the present invention.

[0070] Figure 19 This is a diagram of the wave absorption performance of the Zn,Ni-2D-MOS@SiC(30)-1-D sample in the present invention. DETAILED DESCRIPTION

[0071] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0072] The present invention provides a simple, economical, environmentally friendly and rapid preparation method for a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material, which has a commercial application prospect, and the derivatives of this type of material have good electromagnetic wave absorption performance. The core-shell structured bimetallic nanosheet material loaded with SiC nanowire material is prepared by ultrasonic dispersion of SiC nanowires, nickel ions (Ni 2+ ) and cobalt ions (Co 2+), a bimetallic ion solution system of SiC nanowires is prepared in a certain proportion, and then reacted with an imidazole compound in a methanol and water mixed solution at room temperature for 3 hours to obtain a core-shell structure 2D-MOS@SiC. In this method, the preferred bimetallic ion molar ratio is n M 2+ (Co 2+ , Zn 2+ ):nNi 2+ =0.6:1, and the preferred volume ratio of methanol to water in the mixed reaction solution is Vmethanol:Vwater=2-4:1. 2. The core-shell structure metal-organic nanosheet-loaded silicon carbide nanowire materials Co, Ni-2D-MOS@SiC(30)-1 and Zn, Ni-2D-MOS@SiC(30)-1 prepared above are treated in the same manner to obtain an electromagnetically responsive absorbing material. The preferred process is as follows: a certain mass of Co, Ni-2D-MOS@SiC(30)-1 and Zn, Ni-2D-MOS@SiC(30)-1 materials are weighed respectively in a tube furnace, which is not sealed. In an air environment, the heating rate is 2°C / min, the furnace temperature is adjusted to 400°C, and after keeping warm for 1 hour, the temperature is naturally lowered to obtain Co, Ni-2D-MOS@SiC(30)-1-D and Zn, Ni-2D-MOS@SiC(30)-1-D materials with electromagnetic response characteristics. The present invention is further described below by way of examples:

[0073] Example 1

[0074] The preparation method of the thin-layer two-dimensional nanosheet-modified silicon carbide nanowire structure material sample Co,Ni-2D-MOS@SiC(30)-1 of the present invention is as follows:

[0075] First, 10 ml of methanol and 10 ml of water were measured and placed in a 50 ml beaker, and 30 mg (1.5 mg / ml) of silicon carbide nanowires were added to the mixed solution, and ultrasonic-assisted dispersion was performed for 45 minutes. Subsequently, 0.715 g (3 mmol) of nickel chloride hexahydrate and 0.429 g (1.8 mmol) of cobalt chloride hexahydrate were added to the silicon carbide nanowire dispersion, ultrasonic-assisted dissolution was performed, and then uniform mixing and stirring (about 300 rpm) were performed at room temperature for 2 hours. During this process, a methanol solution of 2-methylimidazole was prepared, 1.97 g (24 mmol) of 2-methylimidazole was weighed and placed in a beaker, and 10 ml of methanol was added for ultrasonic-assisted dissolution. Next, the uniform stirring process was continued, and the prepared 2-methylimidazole methanol solution was slowly added dropwise to the above-mentioned mixed metal ion solution, and the stirring reaction was continued for 3 hours. Co,Ni-2D-MOS@SiC(30)-1 was obtained through centrifugation, methanol washing, vacuum drying and other processes.

[0076] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 3:15, the total concentration of cobalt and nickel is 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 1 and Figure 2 The scanning and transmission electron micrographs of the sample Co,Ni-2D-MOS@SiC(30)-1 show that the cobalt and nickel bimetallic-organic nanosheets form multi-folded sheets wrapped around the surface of the silicon carbide nanowires, where the cobalt and nickel bimetallic-organic nanosheets serve as the shell layer and the silicon carbide nanowires serve as the core, forming a core-shell structure material.

[0077] Example 2

[0078] The nickel chloride hexahydrate in Example 1 was changed to 0.238 g (1 mmol), and the cobalt chloride hexahydrate was changed to 0.143 g (0.6 mmol). The molar amount of each metal salt ion was equivalent to 1 / 3 of the amount of each metal salt in Example 1. The other implementation conditions and steps were exactly the same as those in Example 1 to obtain Co,Ni-2D-MOS@SiC(30)-1 / 3.

[0079] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1:15, the total concentration of cobalt and nickel is 0.05 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 3 This is a scanning electron microscope image of the sample Co,Ni-2D-MOS@SiC(30)-1 / 3. It can be seen from the figure that the Co,Ni-2D-MOS@SiC(30)-1 / 3 obtained in this case presents the same core-shell structural characteristics as Co,Ni-2D-MOS@SiC(30)-1. The difference is that the sample in this case has relatively fewer shell nanosheets.

[0080] Example 3

[0081] The nickel chloride hexahydrate in Example 1 was changed to 0.285 g (1.2 mmol), and the cobalt chloride hexahydrate was changed to 0.171 g (0.72 mmol). The molar amount of each metal salt ion was equivalent to 2 / 5 of the amount of the metal salt in Example 1. The other implementation conditions and steps were exactly the same as those in Example 1 to obtain Co,Ni-2D-MOS@SiC(30)-2 / 5.

[0082] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1.2:15, the total concentration of cobalt and nickel is 0.064 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 4This is a scanning electron microscope image of the sample Co,Ni-2D-MOS@SiC(30)-2 / 5. It can be seen from the figure that the Co,Ni-2D-MOS@SiC(30)-2 / 5 obtained in this case presents the same core-shell structural characteristics as Co,Ni-2D-MOS@SiC(30)-1. The difference is that the shell nanosheets of the sample in this case are relatively few.

[0083] Example 4

[0084] The nickel chloride hexahydrate in Example 1 was changed to 0.429 g (1.8 mmol), and the cobalt chloride hexahydrate was changed to 0.257 g (1.08 mmol). The molar amount of each metal salt ion was equivalent to 3 / 5 of the amount of the metal salt in Example 1. The other implementation conditions and steps were exactly the same as those in Example 1 to obtain Co,Ni-2D-MOS@SiC(30)-3 / 5.

[0085] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1.8:15, the total concentration of cobalt and nickel is 0.096 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 5 This is a scanning electron microscope image of the sample Co,Ni-2D-MOS@SiC(30)-3 / 5. It can be seen from the figure that the Co,Ni-2D-MOS@SiC(30)-3 / 5 obtained in this case presents the same core-shell structural characteristics as Co,Ni-2D-MOS@SiC(30)-1. The difference is that the shell nanosheets of the sample in this case are relatively few.

[0086] Example 5

[0087] The cobalt chloride hexahydrate in Example 1 was replaced with zinc nitrate hexahydrate, and the added amount was 0.535 g (1.8 mmol). The mass of nickel chloride hexahydrate remained unchanged. The other implementation conditions and steps were exactly the same as those in Example 1 to obtain Zn,Ni-2D-MOS@SiC(30)-1.

[0088] In this example, the molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 0.2:1, the total concentration of zinc and nickel is 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 6 and Figure 7The scanning and transmission electron micrographs of the sample Zn, Ni-2D-MOS@SiC(30)-1 in Example 5 are shown respectively. As can be seen from the figure, the prepared Zn, Ni-2D-MOS@SiC(30)-1 presents a wrinkled stacked layered nanosheet-coated silicon carbide nanowire structure, in which zinc and nickel bimetallic-organic nanosheets serve as the shell layer and silicon carbide nanowires serve as the core, forming a core-shell structure material. The Zn, Ni-2D-MOS@SiC(30)-1 obtained in this example and the sample Co, Ni-2D-MOS@SiC(30)-1 in Example 1 both present a two-dimensional thin sheet-loaded silicon carbide nanowire structure, but due to the different radii of the cobalt and zinc elements in the constituent elements, there are certain differences in the morphology and structure. Taking advantage of this feature, the preparation of Zn, Ni-2D-MOS@SiC(30)-1 further expands the development of core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire materials.

[0089] Example 6

[0090] The nickel chloride hexahydrate in Example 5 was changed to 0.238 g (1 mmol), and the zinc nitrate hexahydrate was changed to 0.1785 g (0.6 mmol). The molar amount of each metal salt ion was equivalent to 1 / 3 of the amount of each metal salt in Example 5. The other implementation conditions and steps were exactly the same as those in Example 1 to obtain Zn,Ni-2D-MOS@SiC(30)-1 / 3.

[0091] In this embodiment, the molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1:15, the total concentration of zinc and nickel is 0.05 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 8 This is a scanning electron microscope image of the sample Zn,Ni-2D-MOS@SiC(30)-1 / 3. It can be seen from the figure that the Zn,Ni-2D-MOS@SiC(30)-1 / 3 obtained in this case presents similar morphological and structural characteristics to Zn,Ni-2D-MOS@SiC(30)-1.

[0092] Example 7

[0093] The nickel chloride hexahydrate in Example 5 was changed to 0.285 g (1.2 mmol), and the zinc nitrate hexahydrate was changed to 0.2142 g (0.72 mmol). The molar amount of each metal salt ion was equivalent to 2 / 5 of the amount of the metal salt in Example 5. The other implementation conditions and steps were exactly the same as those in Example 5 to obtain Zn,Ni-2D-MOS@SiC(30)-2 / 5.

[0094] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1.2:15, the total concentration of cobalt and nickel is 0.064 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 9 This is a scanning electron microscope image of the sample Zn,Ni-2D-MOS@SiC(30)-2 / 5. It can be seen from the figure that the Zn,Ni-2D-MOS@SiC(30)-2 / 5 obtained in this case presents similar morphological and structural characteristics to Zn,Ni-2D-MOS@SiC(30)-1.

[0095] Example 8

[0096] The nickel chloride hexahydrate in Example 5 was changed to 0.429 g (1.80 mmol), and the zinc nitrate hexahydrate was changed to 0.323 g (1.08 mmol). The molar amount of each metal salt ion was equivalent to 3 / 5 of the amount of the metal salt in Example 5. The other implementation conditions and steps were exactly the same as those in Example 5 to obtain Zn,Ni-2D-MOS@SiC(30)-3 / 5.

[0097] In this embodiment, the molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate is 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole is 1.8:15, the total concentration of cobalt and nickel is 0.096 mmol / ml, and the volume ratio of methanol to water in the reaction solution is 2:1. Figure 10 This is a scanning electron microscope image of the sample Zn,Ni-2D-MOS@SiC(30)-3 / 5. It can be seen from the figure that the Zn,Ni-2D-MOS@SiC(30)-3 / 5 obtained in this case presents similar morphological and structural characteristics to Zn,Ni-2D-MOS@SiC(30)-1.

[0098] Comparative Example 1

[0099] The mass of the silicon carbide nanowires in Example 1 was changed to 15 mg (0.75 mg / ml), and the other operating conditions and steps were exactly the same as in Example 1 to obtain Co,Ni-2D-MOS@SiC(15)-1. The molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate was 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole was 0.2:1, the total concentration of cobalt and nickel was 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution was 2:1. Figure 11 This is a scanning electron microscope image of the sample Co,Ni-2D-MOS@SiC(15)-1. It can be seen from the figure that the Co,Ni-2D-MOS@SiC(15)-1 obtained in this case presents similar morphological and structural characteristics to Co,Ni-2D-MOS@SiC(30)-1. The difference is that the shell nanosheets of the sample in this case are thicker.

[0100] Comparative Example 2

[0101] The silicon carbide nanowires in Example 1 were replaced with 60 mg (3 mg / ml) and the other operating conditions and steps were identical to those in Example 1 to obtain Co,Ni-2D-MOS@SiC(60)-1. The molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate was 0.6:1, the molar ratio of the total amount of metal salt to 2-methylimidazole was 0.2:1, the total concentration of cobalt and nickel was 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution was 2:1. Figure 12 This is a scanning electron microscope image of the sample Co,Ni-2D-MOS@SiC(60)-1. It can be seen from the figure that the Co,Ni-2D-MOS@SiC(60)-1 obtained in this case presents similar morphological and structural characteristics to Co,Ni-2D-MOS@SiC(30)-1.

[0102] Comparative Example 3

[0103] The amount of silicon carbide nanowires in Example 5 was changed to 15 mg (0.75 mg / ml), and the other operating conditions and steps were exactly the same as in Example 1 to obtain Zn,Ni-2D-MOS@SiC(15)-1. The molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate was 0.6:1, the molar ratio of the total amount of metal salts to 2-methylimidazole was 0.2:1, the total concentration of cobalt and nickel was 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution was 2:1. Figure 13 This is a scanning electron microscope image of the sample Zn,Ni-2D-MOS@SiC(15)-1. It can be seen from the figure that the Zn,Ni-2D-MOS@SiC(15)-1 obtained in this case presents similar morphological and structural characteristics to Zn,Ni-2D-MOS@SiC(30)-1.

[0104] Comparative Example 4

[0105] The amount of silicon carbide nanowires in Example 5 was changed to 60 mg, and the other operating conditions and steps were identical to those in Example 1 to obtain Zn,Ni-2D-MOS@SiC(60)-1. The molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate was 0.6:1, the molar ratio of the total amount of metal salts to 2-methylimidazole was 0.2:1, the total concentration of cobalt and nickel was 0.16 mmol / ml, and the volume ratio of methanol to water in the reaction solution was 2:1. Figure 13 This is a scanning electron microscope image of the sample Zn,Ni-2D-MOS@SiC(60)-1. It can be seen from the figure that the Zn,Ni-2D-MOS@SiC(60)-1 obtained in this case presents similar morphological and structural characteristics to Zn,Ni-2D-MOS@SiC(30)-1.

[0106] Comparison of Examples 1-8 and Comparative Examples 1-4 shows that the present invention can prepare core-shell structured metal-organic nanosheets loaded with silicon carbide nanowire materials by adjusting the total molar amount of mixed bimetallic ions and the amount of silicon carbide nanowires used. In this process, the molar ratio of the mixed metal ions is controlled to be nM 2+ (Co 2+ ,Zn 2+ ):nNi 2+ =0.6:1. The preparation of two-dimensional structured metal-organic nanosheet materials has been explored and discussed in detail in our previous work.

[0107] Preparation and performance test analysis of absorbing samples:

[0108] The present invention only further processes the samples prepared in Example 1 and Example 5 to demonstrate their application potential in the field of electromagnetic wave absorption. The steps for preparing the absorbing samples are as follows:

[0109] The sample Co, Ni-2D-MOS@SiC(30)-1 in the core-shell structure embodiment 1 and the sample Zn, Ni-2D-MOS@SiC(30)-1 in the embodiment 5 were placed in an open tube furnace, and then heated to 400 degrees Celsius and kept warm for 1 hour to obtain the calcined samples Co, Ni-2D-MOS@SiC(30)-1-D and Zn, Ni-2D-MOS@SiC(30)-1-D, respectively. The heating rate was 3 degrees Celsius per minute. Subsequently, Co, Ni-2D-MOS@SiC(30)-1-D and Zn, Ni-2D-MOS@SiC(30)-1-D were mixed with paraffin wax to prepare electromagnetic parameter test samples.

[0110] Figure 15 The electron micrographs of Co,Ni-2D-MOS@SiC(30)-1 and Zn,Ni-2D-MOS@SiC(30)-1 samples before and after calcination in a tube furnace are shown. The samples are in powder form before and after calcination. Due to their different elemental compositions, Co,Ni-2D-MOS@SiC(30)-1 and Zn,Ni-2D-MOS@SiC(30)-1 exhibit different colors. It is clear that Co,Ni-2D-MOS@SiC(30)-1 is light yellow, while Zn,Ni-2D-MOS@SiC(30)-1 is light green. Their respective calcined products also exhibit color differences. Figure 16 and Figure 17The following are scanning electron microscope images of Co,Ni-2D-MOS@SiC(30)-1-D and Zn,Ni-2D-MOS@SiC(30)-1-D, respectively. It can be seen from the figure that after calcination, Co,Ni-2D-MOS@SiC(30)-1-D and Co,Ni-2D-MOS@SiC(30)-1-D still retain the original nanosheet-wrapped silicon carbide nanowire structure, and many nanoparticles are formed on the surface two-dimensional nanosheets, with gaps distributed between the particles. The electromagnetic parameters of the sample Co,Ni-2D-MOS@SiC(30)-1-D were calculated and analyzed to draw the reflection loss curve under different absorber thicknesses, as shown in the figure. Figure 18 As shown in the figure, it can be seen that Co,Ni-2D-MOS@SiC(30)-1-D exhibits good electromagnetic wave absorption performance at different calculated thicknesses. When the thickness is 2 mm, the maximum absorption intensity is -21.05 dB and the maximum absorption width is 5.44 GHz. Figure 19 The reflection loss curve of the sample Zn,Ni-2D-MOS@SiC(30)-1-D at different thicknesses is shown. It can be seen from the figure that when the thickness is 3 mm, the maximum reflection loss value is -47.80 dB, and when the thickness is 2.5 mm, it has the maximum absorption width, reaching 6.04 GHz, indicating that Zn,Ni-ZIF@(30 mg)SiC-1-D also has excellent electromagnetic wave absorption performance.

[0111] The electromagnetic reflection loss values ​​used in this case study are derived from the calculation of electromagnetic parameters, which were measured using a network analyzer (VNA, N5245A, Agilent, USA) in the 2-18 GHz frequency range. The mass ratio of the Co, Ni-ZIF@(30 mg)SiC-D and Zn, Ni-ZIF@(30 mg)SiC-1 samples to paraffin wax was 4:1. All samples were pressed into a standard annular ring (inner diameter: 3.04 mm, outer diameter: 7.00 mm) using the same mold to maintain geometric shape certainty. The thickness of all rings was maintained at 2.2 mm. Agilent PNA software automatically outputs the relevant electromagnetic parameters based on the Nicolson, Ross, and Weir algorithm.

[0112] The present invention is based on the ZIF-67 and ZIF-8 metal-organic framework materials. By introducing nickel ions as a second metal source, two-dimensional lamellar nanosheets are constructed, which are then coated with silicon carbide nanowires to obtain a two-dimensional structured metal-organic nanosheet-modified silicon carbide nanowire material. In this process, the optimal ratio of SiC content to mixed metal ions is selected, and a mixed solution of water and methanol is used as the reaction solvent, ultimately making the prepared material exhibit a two-dimensional nanosheet-modified one-dimensional nanowire structure. By high-temperature carbonization in an air atmosphere, the porous, lightweight metal / carbon composite material obtained demonstrates its excellent potential as an electromagnetic wave absorption material. The invention's preparation process is simple, low-temperature, easy to control, and does not require large-scale equipment or harsh reaction conditions, making it possible to achieve large-scale mass production.

[0113] The above examples are merely illustrative examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications based on the descriptions may be made. It is not necessary and impossible to provide an exhaustive list of all embodiments. However, obvious variations or modifications arising from the spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material, characterized in that: The following steps are involved: S1: Methanol, water, and SiC NWs are mixed in a preset ratio and subjected to ultrasonic treatment to form SiC NWs dispersion A; S2 adding nickel chloride hexahydrate and cobalt chloride hexahydrate to dispersion A according to a preset ratio and ultrasonically mixing them to obtain a mixed dispersion B; The concentration of S3 SiC NWs in dispersion A was 0.75–3 mg / ml, and the ultrasonic treatment time of SiC NWs in the solution was 30–90 min; S4, at room temperature, while continuously stirring the mixed dispersion B, dropwise adding a predetermined amount of 2-methylimidazole methanol solution to the mixed dispersion B to obtain a mixed dispersion C; wherein the mixed dispersion C comprises a molar ratio of cobalt chloride hexahydrate to nickel chloride hexahydrate of 0.6:1, a molar ratio of the total amount of metal salt to 2-methylimidazole of 1 to 3:15, a total concentration of cobalt and nickel of 0.05 to 0.16 mmol / ml, and a volume ratio of methanol to water of 2 to 4:1; The metal salt is composed of cobalt chloride and nickel chloride in the mixed dispersion B; S5: centrifuging the mixed dispersion C, washing and drying the centrifuged product to obtain a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material.

2. The method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material according to claim 1, wherein: In S1: The amount of the methanol used was 10 ml, the amount of the water used was 10 ml, and the amount of the SiC NWs used was 30 mg.

3. The method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material according to claim 2, wherein: In the S2, The amount of nickel chloride hexahydrate used is 0.715 g, and the amount of cobalt chloride hexahydrate used is 0.429 g; In step S4, a preset amount of 2-methylimidazole methanol solution is added dropwise to the mixed dispersion B while the mixed dispersion B is continuously stirred, specifically: The mixed dispersion B was stirred at a constant speed of 400 rpm for 2 hours using a magnetic stirrer, and the 2-methylimidazole methanol solution was added dropwise within the 2 hours. After the addition was completed, the mixture was stirred at a constant speed of 400 rpm for 3 hours. In step S4, the preset amount of 2-methylimidazole methanol solution is prepared by weighing 1.97 g of 2-methylimidazole into a beaker and adding 10 ml of methanol, and dissolving the mixture with ultrasound to obtain the preset amount of 2-methylimidazole methanol solution.

4. A method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material, characterized in that: The following steps are involved: S1: Methanol, water, and SiC NWs are mixed in a preset ratio and ultrasonically treated for a certain period of time to form SiC NWs dispersion A; S2 adding nickel chloride hexahydrate and zinc nitrate hexahydrate to dispersion A according to a preset ratio and ultrasonically mixing them to obtain a mixed dispersion B; The concentration of S3 SiC NWs in dispersion A was 0.75–3 mg / ml, and the ultrasonic treatment time of SiC NWs in the solution was 30–90 min; S4, at room temperature, while continuously stirring the mixed dispersion B, dropwise adding a predetermined amount of 2-methylimidazole methanol solution to the mixed dispersion B to obtain a mixed dispersion C; wherein the mixed dispersion C comprises a molar ratio of zinc nitrate hexahydrate to nickel chloride hexahydrate of 0.6:1, a molar ratio of the total amount of metal salt to 2-methylimidazole of 1 to 3:15, a total concentration of zinc and nickel of 0.05 to 0.16 mmol / ml, and a volume ratio of methanol to water of 2 to 4:1; The metal salt is composed of zinc nitrate and nickel chloride in the mixed dispersion B; S5: centrifuging the mixed solution C, washing and drying the centrifugal product to obtain a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material.

5. The method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material according to claim 4, characterized in that: In S1: The amount of the methanol used was 10 ml, the amount of the water used was 10 ml, and the amount of the SiC NWs used was 30 mg.

6. The method for preparing a core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material according to claim 5, characterized in that: In the S2, The amount of nickel chloride hexahydrate used is 0.715 g, and the amount of zinc nitrate hexahydrate used is 0.535 g; In step S4, a preset amount of 2-methylimidazole methanol solution is added dropwise to the mixed dispersion B while the mixed dispersion B is continuously stirred, specifically: The mixed dispersion B was stirred at a constant speed of 400 rpm for 2 hours using a magnetic stirrer, and the 2-methylimidazole methanol solution was added dropwise within the 2 hours. After the addition was completed, the mixture was stirred at a constant speed of 400 rpm for 3 hours. In step S4, the preset amount of 2-methylimidazole methanol solution is prepared by weighing 1.97 g of 2-methylimidazole into a beaker and adding 10 ml of methanol, and dissolving the solution with ultrasound assistance to obtain the preset amount of 2-methylimidazole methanol solution.

7. The method for preparing a core-shell structured metal-organic nanosheet-supported silicon carbide nanowire material according to any one of claims 1 or 4, characterized in that: In the step S5, the cleaning is performed by using methanol, and the drying is performed by vacuum drying.

8. Application of a core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire material in electromagnetic wave absorption, characterized in that: The following steps are involved: The core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material prepared by the preparation method according to any one of claims 1 or 4 is heated in an open tubular furnace to 400 degrees Celsius and kept at 400 degrees Celsius for 1 hour to obtain a calcined product; the calcined product is mixed with paraffin and then subjected to electromagnetic wave absorption.

9. The application of a core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire material in electromagnetic wave absorption according to claim 8, characterized in that: The core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material prepared by the preparation method according to claim 1 is heated in an open tube furnace; The calcined product was mixed with paraffin wax in a mass ratio of 4:1 to prepare annular sheets with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm and a thickness of 2.2 mm; Electromagnetic parameter testing was performed using a network analyzer in the 2-18 GHz frequency range. Agilent PNA software was used to output electromagnetic parameters according to the Nicolson, Ross, and Weir algorithm. When the thickness is 2 mm, the maximum absorption intensity is -21.05 dB and the maximum absorption width is 5.44 GHz.

10. The application of a core-shell structured bimetallic-organic nanosheet-loaded silicon carbide nanowire material in electromagnetic wave absorption according to claim 8, characterized in that: The core-shell structured metal-organic nanosheet-loaded silicon carbide nanowire material prepared by the preparation method according to claim 4 is heated in an open tube furnace; The calcined product was mixed with paraffin wax in a mass ratio of 4:1 to prepare annular sheets with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm and a thickness of 2.2 mm; Electromagnetic parameter testing was performed using a network analyzer in the 2-18 GHz frequency band for electromagnetic wave absorption testing; Use Agilent PNA software to output electromagnetic parameters according to the Nicolson and Ross and Weir algorithm: When the thickness is 3 mm, it shows the maximum absorption intensity, corresponding to a peak of -47.80 dB. When the thickness is 2.5 mm, it has the maximum absorption width, reaching 6.04 GHz.

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