Micro-porous silicon carbide-based electromagnetic shielding material and preparation method thereof

Abstract

The present application relates to a kind of micro-porous silicon carbide-based electromagnetic shielding material and its preparation method.The preparation method of the micro-porous silicon carbide-based electromagnetic shielding material includes: (1) graphene, carbon nanotube and polyvinylpyrrolidone PVP are ultrasonically dispersed into solvent, after obtaining suspension, printing slurry is obtained by evaporating solvent;(2) using 3D printing technology, according to 3D printing model, printing slurry is built into micro-network interconnection, macroscopic structure dense three-dimensional graphene / carbon nanotube structure;(3) after three-dimensional graphene / carbon nanotube structure is removed polymer PVP by heat treatment, three-dimensional graphene / carbon nanotube skeleton is obtained;(4) using chemical vapor deposition, in situ SiC matrix is wrapped graphene and carbon nanotube surface in graphene / carbon nanotube skeleton, finally, micro-porous silicon carbide-based electromagnetic shielding material is obtained.

Description

Technical Field

[0001] This invention relates to a microporous silicon carbide-based electromagnetic shielding material and its preparation method, belonging to the field of functional composite materials. Background Technology

[0002] Silicon carbide (SiC) possesses unique properties such as a low coefficient of thermal expansion, high thermal conductivity, and high strength, making it a promising candidate for applications in semiconductor materials and high-performance structural materials. In complex integrated electronic systems, electromagnetic interference phenomena such as electromagnetic information leakage and electromagnetic crosstalk are unavoidable among highly integrated electronic circuits, posing numerous application challenges to key materials based on silicon carbide. Therefore, optimizing the electromagnetic shielding performance of silicon carbide-based materials has attracted widespread attention.

[0003] Carbon-based nanomaterials possess excellent electrical properties and high specific surface area, enabling them to significantly reflect electromagnetic waves and reduce electrical conductivity losses. They can be used as nanofillers to optimize the electromagnetic shielding performance of silicon carbide materials. Currently, macroscopically assembling carbon-based nanomaterials into specific three-dimensional network structures is considered an effective way to optimize their electromagnetic shielding performance. The resulting three-dimensional structure allows for multiple scattering of incident electromagnetic waves, increasing the probability of reflection and reducing losses in the transmission path. Simultaneously, the excellent electrical properties can convert the electromagnetic energy of electromagnetic waves into heat energy for dissipation. However, constructing a continuous and stable three-dimensional network structure is crucial, and the interfacial bonding between carbon-based nanomaterials and silicon carbide is a key factor limiting its performance. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a microporous silicon carbide-based electromagnetic shielding material and its preparation method, thereby improving the electromagnetic shielding performance of silicon carbide-based materials used in integrated circuit systems.

[0005] On the one hand, this invention provides a microporous silicon carbide-based electromagnetic shielding material with micropore sizes of 100–300 nm and porosity of 50%–80%, enabling multiple scattering of electromagnetic waves. The interface structure formed by SiC on the surfaces of graphene and carbon nanotubes can achieve interface polarization, effectively increasing the loss of electromagnetic waves by the composite material, and ultimately achieving a shielding effect for electromagnetic waves based on reflection and absorption.

[0006] On the other hand, the present invention provides a method for preparing a microporous silicon carbide-based electromagnetic shielding material, the specific steps of which include the following: (1) Graphene, carbon nanotubes and polyvinylpyrrolidone (PVP) are ultrasonically dispersed in a solvent to obtain a suspension, and then the solvent is evaporated to obtain a printing paste. (2) Using 3D printing technology, the printing paste is constructed into a three-dimensional graphene / carbon nanotube structure with interconnected micro-networks and dense macro-structure according to the 3D printing model; (3) After heat treatment to remove the polymer PVP from the three-dimensional graphene / carbon nanotube structure, a three-dimensional graphene / carbon nanotube framework is obtained. (4) By using chemical vapor deposition to in situ encapsulate the SiC matrix on the surface of graphene and carbon nanotubes in the graphene / carbon nanotube framework, a micro-porous silicon carbide-based electromagnetic shielding material is finally obtained.

[0007] In this invention, graphene and carbon nanotubes are used as carbon-based nano-reinforcing materials, and polyvinylpyrrolidone (PVP) is used as a dispersant and thickener. A solvent is added, and dispersion is achieved in an ultrasonic cell disruptor. The solvent is evaporated to obtain a printing slurry. A densely packed three-dimensional graphene / carbon nanotube structure is constructed using 3D printing technology. The three-dimensional structure is heat-treated to remove the polymer PVP, resulting in a three-dimensional graphene / carbon nanotube framework. A high-purity SiC matrix is ​​grown in situ on the surface of graphene and carbon nanotubes using chemical vapor deposition, resulting in a three-dimensional graphene / carbon nanotube-reinforced SiC-based composite material.

[0008] Preferably, the graphene has a two-dimensional size of 20–80 μm and has 3–10 layers; the carbon nanotubes have a diameter of 5–20 nm and a length of 30–80 μm.

[0009] Preferably, the solvent is at least one selected from ethyl acetate, isopropanol, and dimethylformamide. Preferably, the ultrasonic dispersion process is performed using an ultrasonic cell disruptor with an ultrasonic power of 100–500 W for 1–5 hours.

[0010] Preferably, the printing paste has high viscosity and high modulus; the high viscosity is as high as 10 when the shear rate is 50 / s. 2 Pa; the high modulus is up to 10 Pa; 4 Storage modulus in Pa. Specifically, the viscosity reaches as high as 10 when the shear rate is 50 / s (similar to the shear rate during 3D printing). 2 Pa; with up to 10 Pa; 4 The storage modulus of Pa enables self-supporting properties, ensuring stable molding of the printed three-dimensional structure.

[0011] Preferably, the 3D printing operating parameters include: air pressure on the printing nozzle of 0.6–2 MPa, nozzle movement speed of 5–15 mm / s, nozzle diameter of 0.3–0.6 mm, interlayer spacing of 0.3–0.6 mm, and intralayer filament spacing of 0.3–0.6 mm. Ensuring consistency in nozzle diameter, interlayer spacing, and intralayer filament spacing is crucial for obtaining macroscopically dense three-dimensional graphene / carbon nanotubes.

[0012] Preferably, the operating parameters of the heat treatment include: a temperature of 600–1000°C and a time of 0.5–2 hours; more preferably, the heating rate of the heat treatment is 2°C / minute. A lower heating rate ensures that the three-dimensional structure will not deform due to the internal stress generated by the pyrolysis of PVP.

[0013] Preferably, the operating parameters of the chemical vapor deposition include: a reaction temperature of 950–1150 °C, a reaction time of 1–25 hours, and a flow rate of methyltrichlorosilane reaction gas of 100–400 mL / min.

[0014] Specifically, the porous silicon carbide-based electromagnetic shielding material prepared according to the above-described preparation method provided by the present invention has an interconnected network structure of graphene, carbon nanotubes, and SiC, with a micropore size of 100-300 nm and a porosity of 50%-80%, achieving multiple scattering of electromagnetic waves.

[0015] The porous silicon carbide-based electromagnetic shielding material, with a thickness of 2 mm, has a minimum shielding efficiency of -45.3 dB and an average shielding efficiency of -37.2 dB in the X-band (8–12 GHz).

[0016] Beneficial effects:

[0017] 1) This invention utilizes a three-dimensional graphene / carbon nanotube structure as a support and a SiC matrix as an encapsulation to construct a microporous composite network structure, exhibiting excellent electrical properties and enabling direct reflection of electromagnetic waves on the material surface. The micropore size of the silicon carbide-based electromagnetic shielding material is 100–300 nm, with a porosity of 50%–80%, enabling multiple scattering of electromagnetic waves. When electromagnetic waves are incident inside the material, they can be multiple-scattered by this microstructure, extending the transmission path and increasing losses during transmission. Furthermore, the conductive network also achieves conductivity loss for electromagnetic waves.

[0018] 2) The introduction of high-purity SiC matrix by chemical vapor deposition enables the in-situ grown SiC matrix to bond well with graphene and carbon nanotubes, effectively solving the problem of difficult interface control of carbon-based nano-reinforcement.

[0019] 3) The preparation method provided by the present invention is simple and easy to operate, and can be mass-produced at a low cost under existing technical conditions. Attached Figure Description

[0020] Figure 1 The viscosity and modulus of the 3D printing slurry prepared in Example 1 are shown.

[0021] Figure 2 Optical photographs of the three-dimensional graphene / carbon nanotube structure and the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2 are shown.

[0022] Figure 3 The surface SEM image of the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2 is shown.

[0023] Figure 4 The cross-sectional SEM image of the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2 is shown.

[0024] Figure 5 The trends of average shielding efficiency values ​​in the X-band (8-12 GHz) are shown for the composite materials prepared in Examples 1-4 (deposition times 1h, 5h, 10h, 25h) and Comparative Example 1. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and the following embodiments. It should be understood that the accompanying drawings and the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0026] The following exemplifies a method for preparing a microporous silicon carbide-based electromagnetic shielding material provided by the present invention. The preparation method mainly includes the preparation of slurry, 3D printing of dense three-dimensional structure, and preparation of three-dimensional graphene / carbon nanotube / SiC composite material.

[0027] Preparation of the slurry. Graphene, carbon nanotubes, and polyvinylpyrrolidone (PVP) were added to a solvent (e.g., ethyl acetate, isopropanol, dimethylformamide, etc.), with a graphene:carbon nanotube:PVP ratio of 5:1:15 and a graphene:solvent ratio of 1:50. PVP can improve the steric hindrance of the dispersion, achieving uniform dispersion of graphene and carbon nanotubes, while effectively increasing the viscosity and modulus of the slurry. Therefore, PVP can act as both a dispersant and a thickener. Uniform dispersion was achieved using ultrasound, with the power of each process ranging from 100 to 500 W and the duration from 1 to 5 hours. Excess solvent was evaporated, and a high-viscosity and high-modulus 3D printing slurry was obtained under continuous stirring.

[0028] 3D printing of dense three-dimensional structures. Three-dimensional graphene / carbon nanotube structures are prepared by 3D printing the slurry prepared in (1) according to the required model size. The 3D printing parameters include: air pressure on the printing nozzle of 0.6–2 MPa, nozzle movement speed of 5–15 mm / s, nozzle diameter of 0.3–0.6 mm, interlayer spacing of 0.3–0.6 mm, and intralayer filament spacing of 0.3–0.6 mm. Maintaining consistency in nozzle diameter, interlayer spacing, and intralayer filament spacing is crucial for obtaining macroscopically dense three-dimensional graphene / carbon nanotube structures.

[0029] Three-dimensional graphene / carbon nanotube / SiC composite materials were prepared. The three-dimensional graphene / carbon nanotube structure obtained in step (2) was heat-treated to remove the polymer PVP, resulting in a three-dimensional graphene / carbon nanotube framework. This process required a low heating rate to prevent structural deformation caused by microstructural internal stress resulting from PVP thermal decomposition. High-purity SiC matrix was introduced in situ into the three-dimensional graphene / carbon nanotube framework using chemical vapor deposition (CVD) technology to prepare a SiC-based electromagnetic shielding material with optimized three-dimensional graphene / carbon nanotube network. The specific operation of CVD was as follows: the temperature was increased to the reaction temperature at a heating rate of 5°C / min under an argon atmosphere; hydrogen was used as the carrier gas, and the reaction gas methyltrichlorosilane was introduced for a reaction time of 1–25 hours.

[0030] Methyltrichlorosilane is a precursor material for SiC matrix. During chemical vapor deposition, it undergoes high-temperature pyrolysis to obtain a high-purity SiC matrix. The flow rate of methyltrichlorosilane ranges from 100 to 400 mL / min. Too low a flow rate makes it difficult to improve the density of the three-dimensional structure, while too high a flow rate causes excess methyltrichlorosilane to block the exhaust passage upon cooling. The pyrolysis temperature range for methyltrichlorosilane is 950–1150 °C. Too low a temperature leads to incomplete pyrolysis, producing a large amount of free carbon, while too high a temperature causes a transformation in the crystal form of the resulting SiC matrix.

[0031] The SiC-based electromagnetic shielding material prepared in this invention possesses a through-and-interconnected conductive network structure composed of graphene and carbon nanotubes. Its excellent conductivity enables surface reflection of electromagnetic waves by the composite material. The high specific surface area of ​​the composite material allows for multiple scattering of electromagnetic waves, increasing the loss during transmission. The microscopic conductive network also contributes to reducing electromagnetic wave conductivity loss. This composite material constructs a continuous and stable three-dimensional network structure. Furthermore, the in-situ growth method optimizes the interfacial bonding between SiC, graphene, and carbon nanotubes, significantly improving the electromagnetic shielding performance of the SiC material.

[0032] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0033] Example 1

[0034] The specific steps are as follows: (1) Add 0.5g graphene, 0.1g carbon nanotubes and 1.5g PVP to 25ml ethyl acetate and ultrasonically disperse at 400W for 1 hour to obtain a uniformly dispersed graphene / carbon nanotube / PVP suspension; evaporate the solvent ethyl acetate and continue stirring to obtain a 3D printing slurry with high viscosity and high modulus. (2) The model size of the three-dimensional graphene / carbon nanotube structure was set to 30mm × 18mm × 2mm. During the 3D printing process, the nozzle pressure was 0.8MPa, the moving speed was 12mm / s, the nozzle diameter was 0.5mm, the interlayer spacing was 0.5mm, and the spacing between intralayer filaments was 0.5mm. Specifically, adjacent layers of the three-dimensional graphene / carbon nanotube structure were in close contact with adjacent intralayer filaments, maintaining a dense overall macroscopic structure. (3) The polymer PVP in the three-dimensional graphene / carbon nanotube structure was removed by heat treatment to obtain the three-dimensional graphene / carbon nanotube framework. The heating rate of this process was 2℃ / min, the temperature was 800℃, and the time was 1 hour. (4) A SiC matrix was in situ introduced into a three-dimensional graphene / carbon nanotube structure by chemical vapor deposition, wherein the flow rate of the precursor methyltrichlorosilane was set to 260 mL / min. The reaction temperature of the process was 1050 °C and the reaction time was 1 hour, thus preparing a SiC-based electromagnetic shielding material with optimized three-dimensional graphene / carbon nanotube network.

[0035] like Figure 5 The average electromagnetic shielding efficiency of the composite material in the X-band was measured to be -18.7 dB using a vector analyzer.

[0036] Example 2

[0037] The operation steps (1) to (3) are the same as in Example 1. The only difference between step (4) and Example 1 is that the reaction time for chemical vapor deposition is 5 hours.

[0038] like Figure 5The average electromagnetic shielding efficiency of the composite material in the X-band was measured to be -25.3 dB using a vector analyzer.

[0039] Example 3

[0040] The operation steps (1) to (3) are the same as in Example 1. The only difference between step (4) and Example 1 is that the reaction time for chemical vapor deposition is 10 hours.

[0041] like Figure 5 The average electromagnetic shielding efficiency of the composite material in the X-band was measured to be -29.5 dB using a vector analyzer.

[0042] Example 4

[0043] The operation steps (1) to (3) are the same as in Example 1. The only difference between step (3) and Example 1 is that the reaction time for chemical vapor deposition is 25 hours.

[0044] like Figure 5 The average electromagnetic shielding efficiency of the composite material in the X-band was measured to be -37.2 dB using a vector analyzer.

[0045] Comparative Example 1

[0046] The operation steps (1) to (2) are the same as in Example 1, except that the heat treatment in step (3) and the chemical vapor deposition process in step (4) are not performed.

[0047] like Figure 5 The average electromagnetic shielding efficiency of the composite material in the X-band was measured to be -7.9 dB using a vector analyzer.

[0048] Figure 1 The viscosity and modulus of the 3D printing slurry prepared in Example 1 are shown. This slurry exhibits significant shear-thinning properties, ensuring smooth extrusion during the printing process. At a shear rate of 50 / s (similar to the shear rate in 3D printing), the slurry viscosity reaches as high as 10. 2 Pa; the slurry has a high strength of up to 10 Pa; 4 Pa's storage modulus has obvious self-supporting characteristics, which ensures the stable forming of the printed three-dimensional structure.

[0049] Figure 2 These are physical optical photographs of the three-dimensional graphene / carbon nanotube structure and the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2. The three-dimensional graphene / carbon nanotube structure maintains macroscopic compactness, with no gaps between adjacent layers and adjacent filaments within the layers; the SiC introduced by chemical vapor deposition is wrapped around the surface of graphene and carbon nanotubes, and the reduction in its macroscopic size can be attributed to the pyrolysis of the polymer PVP.

[0050] Figure 3This is a surface SEM image of the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2. It can be observed that granular SiC matrix is ​​grown on the surface of the three-dimensional graphene / carbon nanotube structure. This sparsely grown surface structure enables surface reflection of electromagnetic waves, which is beneficial for electromagnetic waves to penetrate into the material.

[0051] Figure 4 This is a cross-sectional SEM image of the three-dimensional graphene / carbon nanotube / SiC composite material prepared in Example 2. The carbon nanotubes form a porous network-like framework structure, while the SiC matrix grows in situ on the surface of the carbon nanotubes, effectively protecting the structural stability. The pore size of this porous structure ranges from 100 to 300 nm, enabling multiple scattering of electromagnetic waves.

[0052] Figure 5 The average shielding efficiency of the composite materials prepared in Examples 1-4 (deposition times of 1h, 5h, 10h, and 25h) and Comparative Example 1 is shown as a trend in the X-band. With the increase in the amount of SiC matrix introduced, a through-type conductive network structure is formed inside the composite material, which can cause multiple scattering of electromagnetic waves. Simultaneously, the interface structure formed by SiC on the surfaces of graphene and carbon nanotubes can achieve interface polarization, effectively increasing the loss of electromagnetic waves by the composite material. Ultimately, based on reflection and absorption, a shielding effect against electromagnetic waves is achieved.

[0053] Table 1 shows the electromagnetic shielding performance information of the composite materials prepared in Examples 1-4 and Comparative Example 1.

[0054] Table 1:

Claims

1. A method for preparing a microporous silicon carbide-based electromagnetic shielding material, characterized in that, include: (1) Graphene, carbon nanotubes, and polyvinylpyrrolidone (PVP) are ultrasonically dispersed in a solvent to obtain a suspension, and then the solvent is evaporated to obtain a high-viscosity printing paste; the graphene has a two-dimensional size of 20–80 μm and has 3–10 layers; the carbon nanotubes have a diameter of 5–20 nm and a length of 30–80 μm; the high viscosity is as high as 10 when the shear rate is 50 / s. 2 Pa; (2) Using 3D printing technology, the printing paste is constructed into a three-dimensional graphene / carbon nanotube structure with interconnected micro-networks and dense macro-structure according to the 3D printing model; the printing nozzle diameter, interlayer spacing and intralayer filament spacing are kept consistent; (3) After removing the polymer PVP by heat treatment, a microporous three-dimensional graphene / carbon nanotube framework is obtained; the working parameters of the heat treatment include: temperature of 600 to 1000℃ and time of 0.5 to 2 hours. (4) By using chemical vapor deposition to in situ encapsulate the SiC matrix on the surface of graphene and carbon nanotubes in the graphene / carbon nanotube framework, a micro-porous silicon carbide-based electromagnetic shielding material is finally obtained. The microporous silicon carbide-based electromagnetic shielding material has a micropore size of 100–300 nm and a porosity of 50%–80%.

2. The preparation method according to claim 1, characterized in that, The solvent is at least one of ethyl acetate, isopropanol, and dimethylformamide.

3. The preparation method according to claim 1, characterized in that, The printing paste has a high modulus; the high modulus is up to 10. 4 Pa's storage modulus.

4. The preparation method according to claim 1, characterized in that, The parameters of the 3D printing process include: air pressure on the printing nozzle is 0.6-2 MPa, printing nozzle moving speed is 5-15 mm / s, printing nozzle diameter is 0.3-0.6 mm, interlayer spacing is 0.3-0.6 mm, and intralayer monofilament spacing is 0.3-0.6 mm.

5. The preparation method according to claim 1, characterized in that, The heating rate of the heat treatment is 2°C / minute.

6. The preparation method according to claim 1, characterized in that, The operating parameters for the chemical vapor deposition include: a reaction temperature of 950–1150 °C, a reaction time of 1–25 hours, and a flow rate of methyltrichlorosilane as the reaction gas of 100–400 mL / min.

7. A microporous silicon carbide-based electromagnetic shielding material prepared by the preparation method according to any one of claims 1-6, characterized in that, Graphene, carbon nanotubes, and SiC grown on their surfaces form an interconnected network structure. The microporous silicon carbide-based electromagnetic shielding material, with a thickness of 2 mm, has a minimum shielding efficiency of -45.3 dB and an average shielding efficiency of -37.2 dB in the X-band.

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