In-situ generation method of carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C and application thereof

Abstract

The application discloses an in-situ generation method of a carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C and application thereof, and belongs to the technical field of electromagnetic shielding functional composite materials. The method uses iron nitrate nonahydrate as an iron source, ammonium molybdate tetrahydrate as a molybdenum source, ammonium metatungstate hydrate as a tungsten source, and multi-walled carbon nanotubes as a carbon source. A precursor is prepared through mixing and dispersing in a whole aqueous phase system, drying and grinding, and a ternary composite carbide (without separate Fe3C generation) is generated in-situ through one-step carbon thermal reduction. The results show that the conductivity of the optimal sample (C: total metal = 15:1, Fe: Mo: W = 2:1:1, 1000 DEG C carbon thermal reduction) reaches 2.00 S / cm, and the average electromagnetic shielding efficiency in the X wave band is up to 31.1 dB. The method does not need organic solvents, is simple in process, controllable in phase, and friendly to the environment, and the prepared composite material has wide application prospects in the fields of electromagnetic protection and electromagnetic interference suppression.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding functional composite material preparation technology, specifically involving an in-situ generation method of carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C and its application. Background Technology

[0002] With the rapid development of 5G communication, intelligent electronic devices, and industrial electrical systems, electromagnetic radiation and electromagnetic interference problems are becoming increasingly prominent, and there is an urgent need to develop new electromagnetic shielding materials that are lightweight, high-performance, broadband-compatible, and environmentally friendly.

[0003] Traditional metallic shielding materials suffer from drawbacks such as high density, susceptibility to corrosion, and poor impedance matching; single carbon-based materials primarily exhibit reflection loss and insufficient absorption shielding capabilities. Single-metal carbides (such as Mo2C and WC) have excellent conductivity but weak magnetic loss; while bimetallic carbides can enhance synergistic effects, their loss mechanisms remain relatively simple.

[0004] Fe3W3C, as an intermetallic carbide, possesses both excellent ferromagnetism and high conductivity. When combined with Mo2C and WC, it can form a "conductivity-magnetism-polarization" multi-loss system. However, existing preparation processes generally suffer from problems such as complex steps, the need for large amounts of organic solvents, poor phase controllability, and the easy formation of impurity phase Fe3C, making it difficult to balance green environmental protection with high performance.

[0005] Therefore, there is an urgent need in the field for a method for the in-situ controllable synthesis of pure-phase Mo2C-WC-Fe3W3C ternary composite carbides in an all-aqueous phase without organic solvents. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide an in-situ generation method for carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an in-situ generation method for a carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C, comprising, Ferric nitrate nonahydrate, ammonium molybdate tetrahydrate, and ammonium metatungstate hydrate were dissolved in deionized water and stirred at room temperature until completely dissolved to obtain a homogeneous and transparent solution. Multi-walled carbon nanotubes were added to the solution and ultrasonically treated until the multi-walled carbon nanotubes were uniformly dispersed to obtain a precursor solution. The precursor solution was dried, and the solid product was ground to obtain precursor powder. The precursor powder was heated to 500℃ under a high-purity argon atmosphere and held for 1 h, then heated to 800~1000℃ and held for 3 h, and then cooled to room temperature in the furnace to obtain a carbon-based electromagnetic shielding material of Mo2C-WC-Fe3W3C ternary composite carbide generated in situ.

[0010] In a preferred embodiment of the method described in this invention, the precursor solution contains a total molar ratio of C to metal (Fe+Mo+W) of 10:1 to 20:1.

[0011] In a preferred embodiment of the method described in this invention, the precursor solution contains a molar ratio of Fe, Mo, and W of 1:1:1 to 4:1:1.

[0012] In a preferred embodiment of the method described in this invention, the molar ratio of C to the total metal is 15:1.

[0013] In a preferred embodiment of the method described in this invention, the molar ratio of Fe, Mo, and W is 2:1:1.

[0014] In a preferred embodiment of the method described in this invention, the precursor solution is dried at a temperature of 100°C.

[0015] In a preferred embodiment of the method described in this invention, the heating rate is 5°C / min.

[0016] Another objective of this invention is to overcome the shortcomings of the prior art and provide a carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C.

[0017] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of the carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C in the field of electromagnetic protection and electromagnetic interference suppression.

[0018] Beneficial effects of this invention: This invention provides a simple, environmentally friendly, phase-controllable, and shielding-performance method for preparing Mo2C-WC-Fe3W3C ternary composite carbide carbon-based electromagnetic shielding material. The invention uses multi-walled carbon nanotubes as the carbon source to participate in the carbothermic reaction, simultaneously achieving the pyrolysis, reduction, and carbonization of three metal salts. Fe preferentially reacts with W to generate Fe3W3C intermetallic carbides, with no separate Fe3C formation. Ultimately, a composite system of Mo2C-WC-Fe3W3C ternary composite carbide and graphitized carbon framework is formed, constructing a three-dimensional continuous conductive network and multiple loss mechanisms to achieve highly efficient broadband electromagnetic shielding.

[0019] The entire preparation process of this invention involves no organic solvents, the reaction conditions are controllable, and it is suitable for large-scale production. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 The image shows the XRD pattern of the carbon-based electromagnetic shielding material, which is a ternary composite carbide Mo2C-WC-Fe3W3C, in an embodiment of the present invention.

[0021] Figure 2 This is a diagram showing the electromagnetic shielding effectiveness of the sample treated at 800℃ in an embodiment of the present invention.

[0022] Figure 3 This is a diagram showing the electromagnetic shielding effectiveness of the sample treated at 900℃ in an embodiment of the present invention.

[0023] Figure 4 This is a diagram showing the electromagnetic shielding effectiveness of a sample treated at 1000℃ in an embodiment of the present invention.

[0024] Figure 5 This is a diagram showing the shielding effectiveness of pure multi-walled carbon nanotubes under the same compression conditions of this invention. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. All raw materials used in the present invention are commercially available products.

[0026] Example 1 This embodiment provides an in-situ generation method for carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C. The main method is as follows: (1) According to the total molar ratio of C to metal (Fe+Mo+W) of 20:1 and the molar ratio of Fe:Mo:W of 1:1:1, weigh out ferric nitrate nonahydrate, ammonium molybdate tetrahydrate and ammonium metatungstate hydrate respectively, dissolve them in 50 mL of deionized water, stir at room temperature until completely dissolved, and obtain a homogeneous transparent solution. Among them, the total number of the three metals corresponding to the Fe:Mo:W molar ratio of 1:1:1 is 3 mmol; the number of Fe, Mo and W metal atoms is 1 mmol each; the amount of ferric nitrate nonahydrate (Fe(NO3)3·9H2O) is 1 mmol; and the amount of ammonium molybdate tetrahydrate ((NH4)6Mo7O) is 1 mmol. 24The dosage of ·4H2O was 0.143 mmol, and the dosage of ammonium metatungstate hydrate ((NH4)6H2W) was 0.143 mmol. 12 O 40 The dosage of nH2O was 0.083 mmol; Add 0.06 mol of multi-walled carbon nanotubes to the solution and sonicate for 30 min until the multi-walled carbon nanotubes are uniformly dispersed to obtain the precursor solution.

[0027] (2) The precursor solution was placed in a forced-air drying oven and dried at a constant temperature of 100°C. The solid product was thoroughly ground to obtain precursor powder.

[0028] (3) The precursor powder was placed in a tube furnace and heated to 500 ℃ at a rate of 5 ℃ / min under the protection of high-purity argon atmosphere. The temperature was held for 1 h, then heated to 800 ℃ and held for 3 h. The furnace was then cooled to room temperature to obtain the carbon-based electromagnetic shielding material of the in-situ generated Mo2C-WC-Fe3W3C ternary composite carbide.

[0029] (4) The carbon-based electromagnetic shielding material of Mo2C-WC-Fe3W3C ternary composite carbide is mixed with paraffin at a mass ratio of 1:2. The mixture is stirred thoroughly in the molten state and hot-pressed into a standard sheet of 22.86 mm × 10.16 mm and 2 mm thickness for shielding performance testing.

[0030] Example 2 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 2:1:1 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 1.

[0031] Example 3 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 4:1:1 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 1.

[0032] Example 4 The difference between this embodiment and embodiment 1 is that the calcination temperature in step (3) is 900℃, while the other processes are the same as in embodiment 1.

[0033] Example 5 The difference between this embodiment and embodiment 2 is that the calcination temperature in step (3) is 900℃, while the other processes are the same as in embodiment 2.

[0034] Example 6 The difference between this embodiment and embodiment 3 is that the calcination temperature in step (3) is 900℃, while the other processes are the same as in embodiment 3.

[0035] Example 7 The difference between this embodiment and embodiment 1 is that the calcination temperature in step (3) is 1000℃, while the other processes are the same as in embodiment 1.

[0036] Example 8 The difference between this embodiment and embodiment 2 is that the calcination temperature in step (3) is 1000℃, while the other processes are the same as in embodiment 2.

[0037] Example 9 The difference between this embodiment and embodiment 3 is that the calcination temperature in step (3) is 1000℃, while the other processes are the same as in embodiment 3.

[0038] The XRD pattern of the Mo2C-WC-Fe3W3C ternary composite carbide carbon-based electromagnetic shielding material is shown in [reference]. Figure 1 It can be seen that all samples show obvious broadened diffraction peaks near 2θ=26.54°, which correspond to the (002) crystal plane of graphitic carbon in multi-walled carbon nanotubes, indicating that the carbon matrix in the system is mainly composed of low-crystallinity graphitized carbon.

[0039] Meanwhile, the diffraction characteristic peaks of all samples were completely matched with the W3Fe3C standard PDF card (#04-007-2726), Mo2C standard PDF card (#04-003-0962), and W2C standard PDF card (#04-003-6143), confirming the successful in-situ formation of W3Fe3C-Mo2C-W2C ternary composite carbides. No obvious impurity phases were formed, and all Fe participated in the formation of W3Fe3C intermetallic carbides, with no individual Fe3C formed.

[0040] As the molar ratio of Fe to Mo and W increases, the intensity of the characteristic peak of W3Fe3C gradually increases, while the intensity of the characteristic peaks of Mo2C and W2C shows a regular change, indicating that the phase composition of ternary composite carbides can be flexibly controlled by adjusting the Fe:Mo:W molar ratio. As the carbothermic temperature increases from 800℃ to 1000℃, the characteristic peaks of the ternary carbides gradually become sharper and their intensity increases significantly. The crystallinity of each phase in the sample prepared at 1000℃ is good, indicating that the process conditions can achieve the controllable synthesis of ternary composite carbides.

[0041] The effect of process parameters on the phase composition: As the carbothermic temperature increases from 800℃ to 1000℃, the characteristic peaks of the three carbides gradually become sharper and their intensity increases significantly, indicating that increasing the temperature can effectively promote the crystal growth of each phase; adjusting the Fe:Mo:W molar ratio can flexibly adjust the relative content of the three carbides and achieve precise control of the phase composition.

[0042] Example 10 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 1:2:1 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 1.

[0043] Example 11 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 1:4:1 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 1.

[0044] Example 12 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 1:1:2 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 1.

[0045] Example 13 The difference between this embodiment and embodiment 1 is that the Fe:Mo:W molar ratio in step (1) is 1:1:4 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 1.

[0046] Example 14 The difference between this embodiment and embodiment 4 is that the Fe:Mo:W molar ratio in step (1) is 1:2:1 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 4.

[0047] Example 15 The difference between this embodiment and embodiment 4 is that the Fe:Mo:W molar ratio in step (1) is 1:4:1 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 4.

[0048] Example 16 The difference between this embodiment and embodiment 4 is that the Fe:Mo:W molar ratio in step (1) is 1:1:2 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 4.

[0049] Example 17 The difference between this embodiment and embodiment 4 is that the Fe:Mo:W molar ratio in step (1) is 1:1:4 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 4.

[0050] Example 18 The difference between this embodiment and embodiment 7 is that the Fe:Mo:W molar ratio in step (1) is 1:2:1 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 7.

[0051] Example 19 The difference between this embodiment and embodiment 7 is that the Fe:Mo:W molar ratio in step (1) is 1:4:1 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 7.

[0052] Example 20 The difference between this embodiment and embodiment 7 is that the Fe:Mo:W molar ratio in step (1) is 1:1:2 (the total number of moles of the three metals is 4 mmol), and the other processes are the same as in embodiment 7.

[0053] Example 21 The difference between this embodiment and embodiment 7 is that the Fe:Mo:W molar ratio in step (1) is 1:1:4 (the total number of moles of the three metals is 6 mmol), and the other processes are the same as in embodiment 7.

[0054] Electrical conductivity and electromagnetic shielding performance: Conductivity was tested using a four-probe tester, in accordance with GB / T 30142-2013; electromagnetic shielding effectiveness in the X-band (8.2~12.4GHz) was tested using the waveguide method, with a sample thickness of 2 mm.

[0055] Table 1. Conductivity and average electromagnetic shielding effectiveness

[0056] The electromagnetic shielding effectiveness diagram of the sample treated at 800°C in the examples is shown below. Figure 2 For the electromagnetic shielding effectiveness diagram of the sample treated at 900℃, please refer to [reference needed]. Figure 3 For the electromagnetic shielding effectiveness diagram of the sample treated at 1000℃, please refer to [reference needed]. Figure 4 .

[0057] The results show that the Mo2C-WC-Fe3W3C ternary composite carbide carbon-based electromagnetic shielding material prepared in this invention exhibits excellent conductivity and electromagnetic shielding performance under optimized process conditions. The carbothermic temperature significantly affects performance: as the temperature increases from 800℃ to 1000℃, the overall conductivity and shielding effectiveness of the sample improve. At 1000℃, the crystallinity of each phase is highest, the conductive network is most complete, and the performance is optimal. The trimetallic ratio is key to performance control: when Fe:Mo:W=2:1:1, the three carbides form the best synergistic effect, achieving a conductivity of 2.00 S / cm and an average electromagnetic shielding effectiveness of 31.1 dB in the X-band, far exceeding the standard requirement of 20 dB for civilian electromagnetic protection.

[0058] Figure 5The image shows the shielding effectiveness of pure multi-walled carbon nanotubes under the same compression conditions of this invention. The measured conductivity of the pure multi-walled carbon nanotubes is 0.05 S / cm, and the average shielding effectiveness is only about 15.1 dB. The optimal sample of this invention reaches 31.1 dB, which is far higher than the civilian electromagnetic protection standard.

[0059] The material utilizes in-situ generated Mo2C, WC, and Fe3W3C to interconnect with a graphitized carbon framework, constructing a three-dimensional continuous conductive network that permeates the entire material and provides core conductive losses. Fe3W3C, as a ferromagnetic component, provides strong magnetic losses, and numerous heterogeneous interfaces are formed between the three carbides and between the carbides and the carbon matrix, resulting in abundant interfacial polarization and dipole polarization losses. The porous structure of the carbon nanotubes further induces multiple scattering of electromagnetic waves, ultimately achieving X-band broadband and efficient electromagnetic shielding through a multi-synergistic mechanism of conductive loss, magnetic loss, polarization loss, and multiple scattering.

[0060] This invention utilizes deionized water as the sole dispersion medium throughout the entire preparation process, without the participation of any organic solvents or the generation of toxic or harmful byproducts. This aligns with the requirements of green chemistry and dual-carbon development, addressing the industry pain point of organic solvent pollution in traditional bimetallic carbide preparation processes. This invention prepares the target product through a single step of aqueous dispersion, drying and grinding, and carbothermic reduction. The process is short, simple to operate, and the reaction conditions are controllable, requiring no complex equipment or harsh reaction environments, making it suitable for large-scale industrial production. By controlling the molar ratio of total metal to C, the trimetallic ratio, and the carbothermic temperature, the pure-phase controllable synthesis of Mo2C-WC-Fe3W3C ternary composite carbides can be achieved without the formation of impurity Fe3C, a core advantage distinguishing this system from traditional multimetallic carbides. Fe3W3C possesses both ferromagnetism and high conductivity, forming multiple synergistic loss mechanisms with Mo2C and WC. The optimal sample achieves an average electromagnetic shielding effectiveness of 31.1 dB in the X-band, further improving the shielding performance compared to mono / bimetallic carbide systems.

[0061] The nonahydrate of ferric nitrate, the tetrahydrate of ammonium molybdate, and the ammonium metatungstate hydrate multi-walled carbon nanotubes used in this invention are all commercially available bulk raw materials, widely available and inexpensive. The prepared composite material can be combined with various matrices such as resin, paraffin, and textile substrates, and is suitable for applications in multiple fields such as flexible electronics, building protection, industrial electromagnetic protection, and textile functional finishing, and has broad market application prospects.

[0062] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for in-situ generation of a carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C, characterized in that: include, Ferric nitrate nonahydrate, ammonium molybdate tetrahydrate, and ammonium metatungstate hydrate were dissolved in deionized water and stirred at room temperature until completely dissolved to obtain a homogeneous and transparent solution. Multi-walled carbon nanotubes were added to the solution and ultrasonically treated until the multi-walled carbon nanotubes were uniformly dispersed to obtain a precursor solution. The precursor solution was dried, and the solid product was ground to obtain precursor powder. The precursor powder was heated to 500℃ under a high-purity argon atmosphere and held for 1 h, then heated to 800~1000℃ and held for 3 h, and then cooled to room temperature in the furnace to obtain a carbon-based electromagnetic shielding material of Mo2C-WC-Fe3W3C ternary composite carbide generated in situ.

2. The method as described in claim 1, characterized in that: The precursor solution contains a total molar ratio of C to metal (Fe+Mo+W) of 10:1 to 20:

1.

3. The method as described in claim 1 or 2, characterized in that: The precursor solution contains Fe, Mo, and W in a molar ratio of 1:1:1 to 4:1:

1.

4. The method as described in claim 2, characterized in that: The molar ratio of C to total metals is 15:

1.

5. The method as described in claim 3, characterized in that: The molar ratio of Fe, Mo, and W is 2:1:

1.

6. The method as described in claim 1, characterized in that: The precursor solution is dried at a temperature of 100°C.

7. The method as described in claim 1 or 6, characterized in that: The heating rate is 5°C / min.

8. The carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C prepared by the method of any one of claims 1 to 7.

9. The application of the carbon-based electromagnetic shielding material Mo2C-WC-Fe3W3C as described in claim 8 in the field of electromagnetic protection and electromagnetic interference suppression.

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