MgO@CF reinforcers with FeNi3 / Co and CNTs encapsulated on the surface of graphite, their preparation methods and applications

Abstract

The application discloses a kind of surface deposition graphite package FeNi3 / Co and CNTs's MgO@CF reinforcement and its preparation method and application, including the following steps: the surface of unsized carbon fiber is roughened and activated, grafted oxygen-containing functional group, washes and dries, then it is immersed magnesium source solution, calcined in inert atmosphere after drying, and carbon fiber MgO@CF wrapped with MgO nanometer film is prepared;MgO@CF is immersed in the mixed solution of iron source, cobalt source and nickel source, dried, and heated in reducing atmosphere, which is reduced to metal nano catalyst particles;The product obtained is used for catalytic chemical vapor deposition, and the growth of carbon material on the surface is obtained.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a MgO@CF reinforcement with FeNi3 / Co and CNTs encapsulated on a surface-deposited graphite layer, its preparation method, and its application. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] The rapid development of modern advanced communication technologies has brought tremendous convenience to our society. However, electromagnetic radiation and pollution problems are also intensifying imperceptibly, posing a threat to precision electronic components and human health. To address this serious issue, designing highly efficient, thin, and lightweight electromagnetic wave absorbing materials is crucial. Electromagnetic wave absorbers must also possess other advantages to meet the requirements of emerging electronic products, such as mass production capability, high environmental adaptability, and excellent mechanical properties.

[0004] Carbon-based materials, such as graphene, fullerenes, and carbon nanotubes (CNTs), have long attracted researchers' attention due to their advantages such as low density, reliable physicochemical stability, large specific surface area, and high dielectric loss, making them suitable for various fields such as adsorption catalysis, energy storage, thermal insulation, and electromagnetic interference shielding. Among them, carbon fiber (CF), due to its excellent toughness, specific strength, and specific modulus, is often only used as a reinforcing material. With in-depth research, its applications in electromagnetic wave absorption, photocatalysis, and batteries have been gradually discovered. However, CNTs / CF have very high electrical conductivity, and very little magnetic metal catalyst can remain in ordinary CCVD processes because the amount of catalyst used is usually small, and the top growth mode of CNTs may cause some catalyst to collapse from the top of the CNTs after catalysis. These factors hinder further optimization of impedance matching and effective absorption bandwidth. It is speculated that increasing the concentration of metal catalyst is a good way to optimize impedance matching by increasing the content of residual magnetic material in the product. However, adding metal at high growth temperatures can easily cause more severe corrosion on the CF surface, which is detrimental to the development of its mechanical properties. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a MgO@CF reinforcer with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a MgO@CF reinforcer with FeNi3 / Co and CNTs encapsulated by surface deposition of graphite, comprising the following steps:

[0008] The surface of unsized carbon fibers was roughened and activated, oxygen-containing functional groups were grafted onto them, they were washed and dried, then impregnated with a magnesium source solution, dried and calcined in an inert atmosphere to prepare carbon fibers MgO@CF coated with MgO nanofilms.

[0009] A mixed solution of iron, cobalt and nickel sources was impregnated with MgO@CF, dried, and then heated in a reducing atmosphere to reduce it to metal nanocatalyst particles.

[0010] The obtained product was subjected to catalytic chemical vapor deposition to grow carbon materials on the surface, resulting in a MgO@CF reinforced material with graphite-encapsulated FeNi3 / Co and carbon nanotubes.

[0011] Under the influence of MgO nanofilms, the growth mechanism of CNTs is a bottom-end growth mode rather than a top-end growth mode, which is conducive to the retention of more magnetic metal catalysts.

[0012] The purpose of grafting oxygen-containing functional groups onto the surface of carbon fibers is to promote the absorption of Mg cations on the carbon fiber surface. 2+ It adsorbs and distributes it evenly.

[0013] In catalytic chemical vapor deposition, after reaching the designated temperature, acetylene is introduced into the furnace and decomposed into active carbon atoms and active hydrogen atoms by the catalyst FeNi3 / Co. Once the dissolved active carbon atoms in the catalyst reach saturation, they precipitate on the catalyst surface, forming a graphite layer. Large catalyst particles exhibit lower catalytic activity and are prone to deactivation, resulting in graphite-encapsulated FeNi3 / Co. Smaller catalyst particles, on the other hand, exhibit high activity and efficiency, catalyzing the formation of CNTs. The graphite-encapsulated FeNi3 / Co and CNTs are uniformly distributed on the MgO@CF surface.

[0014] Magnesium oxide nanofilms, denoted as MgO@CF, are uniformly distributed on the carbon fiber surface. Next, graphite-encapsulated FeNi3 / Co particles and carbon nanotubes are uniformly grown on the MgO@CF surface. This creates abundant heterogeneous interfaces between the materials, which contribute to the attenuation of electromagnetic waves.

[0015] In some embodiments, the oxygen-containing functional group is CO, C=O, or OC=O.

[0016] In some embodiments, the magnesium source is Mg(NO3)2 or Mg(CH3COO)2.

[0017] Preferably, the concentration of the magnesium source solution is 0.05-2M.

[0018] Preferably, the solvent for the magnesium source solution is ethanol or water. Ethanol or water is selected by comprehensively considering the volatility of the solvent, the solubility of the salt, and the purity of the subsequent furnace atmosphere.

[0019] In some embodiments, the calcination temperature is 400-800℃ and the calcination time is 5-20 min.

[0020] The preferred calcination temperature is 450℃.

[0021] In some embodiments, in the mixed solution of iron source, cobalt source and nickel source, the concentration of iron source is 0.01-0.03M; the concentration of cobalt source is 0.01-0.03M; the concentration of nickel source is 0.03-0.09M; and the molar ratio of iron source, cobalt source and nickel source is 1:1:3.

[0022] Preferably, the solvent for the mixed solution of iron, cobalt and nickel sources is ethanol or water.

[0023] In some embodiments, the heating temperature in the reducing atmosphere is 400-800°C, preferably 450°C, and the reduction time is 5-20 min.

[0024] Preferably, the reduction is carried out under an inert atmosphere.

[0025] In some embodiments, the temperature of catalytic chemical vapor deposition is 550-800°C, preferably 700°C, and the deposition time is 5-20 min.

[0026] Preferably, the atmosphere in the catalytic chemical vapor deposition process is a mixture of N2, C2H2, and H2. The flow rates of N2, C2H2, and H2 in the furnace atmosphere are 0.01-0.6 L / min, respectively.

[0027] Secondly, the present invention provides a MgO@CF reinforcer with FeNi3 / Co and CNTs encapsulated by surface-deposited graphite, which is prepared by the aforementioned preparation method.

[0028] Thirdly, the present invention provides the application of the MgO@CF reinforcement containing FeNi3 / Co and CNTs encapsulated on the surface of the aforementioned graphite in the fabrication of electromagnetic wave protection devices.

[0029] Synthesizing a thin film on the surface of carbon (CF) can protect the CF structure from etching by the catalyst and H2, while also serving as a support for uniform catalyst adhesion and efficient growth of carbon materials. Furthermore, it can introduce more heterogeneous interfaces to promote the dissipation of electromagnetic radiation.

[0030] The interaction between the catalyst and the support is one of the important factors in selecting a suitable support for catalytic chemical vapor deposition (CCVD), affecting the yield and quality of the resulting carbon material. Compared with other supports, MgO has significant advantages, such as simple preparation, low cost, tunable morphology, high surface activity, high temperature resistance, environmental friendliness, weak ferromagnetism, and stable growth, and is often used as a catalytic template for various gaseous carbon sources.

[0031] Furthermore, MgO is a solid base catalyst with graphitization capabilities. Particularly for nano-MgO support materials with large surface areas, they exhibit high metal salt loading efficiency, stabilizing metal catalyst particles and adjusting their size and morphology through strong metal / support interactions. This is beneficial for the bottom-end growth mode of carbon materials such as CNTs, thus retaining more magnetic metallic substances in the final product. Under the protection of MgO, higher concentrations of catalyst can be used to catalyze the growth of carbon materials without severely damaging the carbide structure.

[0032] Transition metals (such as Fe, Co, Ni, and Cu) are commonly used in CCVD because nano-transition metal particles can decompose hydrocarbons and possess high carbon diffusion capacity, low vapor pressure, and high melting point. The Fe-Co-Ni ternary catalytic system exhibits high catalytic activity. Meanwhile, the remaining ferromagnetic metal nanomaterials possess high saturation magnetization, quantum size effect, and high melting point, enabling strong electromagnetic wave absorption over a wide frequency range. These are ideal choices for preparing high-performance ultrathin microwave absorbers, such as Fe₂Co, Fe₂Ni, FeNi₃, and Co. Among them, FeNi₃ is a soft magnetic permalloy with high saturation magnetization, low coercivity, and a high Snoek limit.

[0033] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0034] This invention successfully prepared a novel CF-based multi-component heterostructure by first synthesizing a simple nano-coating on the surface of CF, followed by a batch-controlled, high-concentration catalyst system-catalyzed CCVD process. The introduction of MgO nanofilms not only expands the heterogeneous interface to attenuate more electromagnetic radiation, but also makes it possible to improve the mechanical properties of CF at high catalyst concentrations. Due to the improved impedance matching of ferromagnetic FeNi3 / Co, as well as the synergistic effect of enhanced conductivity loss, additional polarization loss, and appropriate magnetic loss, the sample with dual dielectric and magnetic properties exhibits "light, thin, wide, and strong" electromagnetic wave absorption capabilities, which also meets the multifunctional development requirements of modern electromagnetic wave absorbers.

[0035] By efficiently synthesizing MgO nanofilms and adjusting the concentration of CCVD catalyst, layered graphite-encapsulated FeNi3 / Co and CNTs were grown on MgO@CF. Thanks to ideal impedance matching and a sufficient dielectric-magnetic dual loss mechanism, more electromagnetic waves entered the absorber and were effectively converted into thermal or magnetic energy for dissipation, thus the sample achieved excellent electromagnetic wave attenuation capabilities.

[0036] The relative integrity of the CF structure and the growth of various carbon materials also result in outstanding monofilament tensile strength in the samples. Therefore, this invention provides an attractive strategy for the large-scale production of modified CF-based hybrid materials applicable to multiple fields. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0038] Figure 1 This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 1 of this invention;

[0039] Figure 2 This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 2 of the present invention.

[0040] Figure 3 This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 3 of the present invention. Detailed Implementation

[0041] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] The present invention will be further described below with reference to the embodiments.

[0043] Example 1

[0044] Step 1: Unsized carbon fiber (CF) is continuously passed through a 5 wt.% ammonium dihydrogen phosphate aqueous solution and electrochemically anolyzed for 5 min with a current of 0.2 A under the condition that the bottom graphite plate is used as the cathode, thereby obtaining a rougher surface with rich oxygen-containing functional groups. Then it is washed and dried.

[0045] Step 2: The CF obtained in Step 1 is continuously immersed in a 0.2M Mg(NO3)2 ethanol solution to uniformly adsorb the precursor Mg(NO3)2. After drying, it is placed in a horizontal tube furnace heated to 450℃ and decomposed in a N2 atmosphere into a MgO nanofilm uniformly coated on the surface of the CF to obtain MgO@CF.

[0046] Step 3: The MgO@CF obtained in Step 2 is passed through an ethanol solution containing 0.01M Fe(NO3)3, 0.01M Co(NO3)2 and 0.03M Ni(NO3)2 at a certain rate. After drying, it is placed in a tube furnace at 450℃ and reduced to metal nanocatalyst particles by H2 at 0.3L / min under N2 protection.

[0047] Step 4: The sample obtained in Step 3 was continuously fed into a tubular catalytic chemical vapor deposition (CCVD) furnace with the temperature raised to 700℃ for the growth of carbon materials. The atmosphere inside the furnace was a mixture of 0.3 L / min N2, 0.15 L / min C2H2 and 0.15 L / min H2. After the growth was completed, a MgO@CF reinforced body with graphite-encapsulated FeNi3 / Co and carbon nanotubes (CNTs) deposited on the surface was obtained and named GFNC / MF.

[0048] Step 5: The tensile strength of the GFNC / MF reinforcement is tested according to the standard GB / T 31290-2022. After being ground into powder, it is mixed with molten paraffin to prepare a composite material for use in the field of electromagnetic wave absorption.

[0049] The product powder (23 wt.%) was uniformly mixed with molten paraffin and pressed into a coaxial ring with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.00 mm. The electromagnetic parameters of GFNC / MF / paraffin in the range of 2-18 GHz were tested using an Agilent PNA-N5244A vector network analyzer to calculate its microwave absorption performance.

[0050] Calculations show that the minimum reflection loss of GFNC / MF / paraffin can reach -77.55dB (3.40mm), and the effective absorption bandwidth can reach 3.28GHz (1.28mm) (the minimum reflection loss of unsized CF / paraffin is -31.60dB (3.00mm), and the effective absorption bandwidth is 4.00GHz (1.22mm)). Furthermore, the monofilament tensile strength of GFNC / MF, tested according to national standards, is 4.94GPa, an increase of 17.9% compared to unsized CF (4.19GPa).

[0051] Figure 1This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 1 of the present invention.

[0052] Example 2

[0053] Step 1: Unsized carbon fiber (CF) is continuously passed through a 5 wt.% ammonium dihydrogen phosphate aqueous solution and electrochemically anolyzed for 5 min with a current of 0.2 A under the condition that the bottom graphite plate is used as the cathode, thereby obtaining a rougher surface with rich oxygen-containing functional groups. Then it is washed and dried.

[0054] Step 2: The CF obtained in Step 1 is continuously immersed in a 0.2M Mg(NO3)2 ethanol solution to uniformly adsorb the precursor Mg(NO3)2. After drying, it is placed in a horizontal tube furnace heated to 450℃ and decomposed in a N2 atmosphere into a MgO nanofilm uniformly coated on the surface of the CF to obtain MgO@CF.

[0055] Step 3: The MgO@CF obtained in Step 2 is passed through an ethanol solution containing 0.02M Fe(NO3)3, 0.02M Co(NO3)2 and 0.06M Ni(NO3)2 at a certain rate. After drying, it is placed in a tube furnace at 450℃ and reduced to metal nanocatalyst particles by H2 at 0.3L / min under N2 protection.

[0056] Step 4: The sample obtained in Step 3 was continuously fed into a tubular catalytic chemical vapor deposition (CCVD) furnace with the temperature raised to 700℃ for the growth of carbon materials. The atmosphere inside the furnace was a mixture of 0.3 L / min N2, 0.15 L / min C2H2 and 0.15 L / min H2. After the growth was completed, a MgO@CF reinforced body with graphite-encapsulated FeNi3 / Co and carbon nanotubes (CNTs) deposited on the surface was obtained and named GFNC / MF.

[0057] Step 5: The tensile strength of the GFNC / MF reinforcement is tested according to the standard GB / T 31290-2022. After being ground into powder, it is mixed with molten paraffin to prepare a composite material for use in the field of electromagnetic wave absorption.

[0058] The product powder (23 wt.%) was uniformly mixed with molten paraffin and pressed into a coaxial ring with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.00 mm. The electromagnetic parameters of GFNC / MF / paraffin in the 2-18 GHz range were tested using an Agilent PNA-N5244A vector network analyzer to calculate its absorption performance. Calculations showed that the minimum reflection loss of GFNC / MF / paraffin reached -72.08 dB (1.38 mm), and the effective absorption bandwidth reached 4.88 GHz (1.44 mm) (compared to -31.60 dB (3.00 mm) and 4.00 GHz (1.22 mm) for unsized CF / paraffin). Furthermore, the monofilament tensile strength of GFNC / MF, tested according to national standards, was 4.70 GPa, an increase of 12.2% compared to unsized CF (4.19 GPa).

[0059] Figure 2 This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 2 of the present invention.

[0060] Example 3

[0061] Step 1: Unsized carbon fiber (CF) is continuously passed through a 5 wt.% ammonium dihydrogen phosphate aqueous solution and electrochemically anolyzed for 5 min with a current of 0.2 A under the condition that the bottom graphite plate is used as the cathode, thereby obtaining a rougher surface with rich oxygen-containing functional groups. Then it is washed and dried.

[0062] Step 2: The CF obtained in Step 1 is continuously immersed in a 0.2M Mg(NO3)2 ethanol solution to uniformly adsorb the precursor Mg(NO3)2. After drying, it is placed in a horizontal tube furnace heated to 450℃ and decomposed in a N2 atmosphere into a MgO nanofilm uniformly coated on the surface of the CF to obtain MgO@CF.

[0063] Step 3: The MgO@CF obtained in Step 2 is passed through an ethanol solution containing 0.03M Fe(NO3)3, 0.03M Co(NO3)2 and 0.09M Ni(NO3)2 at a certain rate. After drying, it is placed in a tube furnace at 450℃ and reduced to metal nanocatalyst particles by H2 at 0.3L / min under N2 protection.

[0064] Step 4: The sample obtained in Step 3 was continuously fed into a tubular catalytic chemical vapor deposition (CCVD) furnace with the temperature raised to 700℃ for the growth of carbon materials. The atmosphere inside the furnace was a mixture of 0.3 L / min N2, 0.15 L / min C2H2 and 0.15 L / min H2. After the growth was completed, a MgO@CF reinforced body with graphite-encapsulated FeNi3 / Co and carbon nanotubes (CNTs) deposited on the surface was obtained and named GFNC / MF.

[0065] Step 5: The tensile strength of the GFNC / MF reinforcement is tested according to the standard GB / T 31290-2022. After being ground into powder, it is mixed with molten paraffin to prepare a composite material for use in the field of electromagnetic wave absorption.

[0066] The product powder (23 wt.%) was uniformly mixed with molten paraffin and pressed into a coaxial ring with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of 2.00 mm. The electromagnetic parameters of GFNC / MF / paraffin in the 2-18 GHz range were tested using an Agilent PNA-N5244A vector network analyzer to calculate its absorption performance. Calculations showed that the minimum reflection loss of GFNC / MF / paraffin reached -24.49 dB (1.22 mm), and the effective absorption bandwidth reached 4.24 GHz (1.39 mm) (compared to -31.60 dB (3.00 mm) and 4.00 GHz (1.22 mm) for unsized CF / paraffin). Furthermore, the monofilament tensile strength of GFNC / MF, tested according to national standards, was 4.26 GPa, an increase of 1.7% compared to unsized CF (4.19 GPa).

[0067] Figure 3 This is a scanning electron microscope image of the MgO@CF reinforcement with graphite-encapsulated FeNi3 / Co and CNTs deposited on its surface, obtained in Example 3 of the present invention.

[0068] Table 1

[0069]

[0070] Table 1 shows the scanning morphology and transmission structure information of MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on their surface obtained in Examples 1, 2, and 3 of this invention. Combined with... Figure 1 , 2In general, with sufficient carbon source, increasing catalyst concentration leads to an increase in the density and length of the deposited carbon material, resulting in graphite-encapsulated FeNi3 / Co and smaller diameter CNTs on the CF surface. Specifically, Example 2 exhibits a relatively uniform surface distribution, while Examples 1 and 3 both display a distinct bark-like surface, with the "bark" content increasing with increasing catalyst concentration.

[0071] Table 2

[0072]

[0073]

[0074] Table 2 shows the X-ray diffraction patterns of MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on their surfaces, obtained in Examples 1, 2, and 3 of this invention. All examples exhibit distinct diffraction peaks near 2θ = 26.0°, 42.9°, and 44.2°, corresponding to the (002) crystal plane of graphite C, the (200) crystal plane of MgO, and the (111) crystal plane of FeNi3 / Co, respectively. The X-ray diffraction results indirectly confirm the successful synthesis of MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on their surfaces, and the XRD peak intensities are closely related to the analysis in Table 4.

[0075] Table 3

[0076]

[0077] Table 3 shows the Raman spectra of untreated, unsized CF (marked as 0) and MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on their surfaces, obtained in Examples 1, 2, and 3 of this invention. The Raman curves for all examples are at 1350 cm⁻¹. -1 (D belt) and 1580cm -1 The area near the (G band) exhibits two typical peaks, describing lattice defects in carbon atoms and sp, respectively. 2 In-plane stretching vibrations of carbon atoms. The intensity ratio of the D and G bands (R = I) D / I G R values ​​are typically used to characterize the degree of graphitization (inversely proportional). Notably, compared to unsizing CF, the R values ​​for Examples 1, 2, and 3 are all lower, increasing with increasing catalyst concentration. This is partly because the growth of the graphitic carbon material increases the overall degree of graphitization. On the other hand, the deposition of carbon material is accompanied by the formation of amorphous carbon. Therefore, increasing the loading of the former also leads to an increase in amorphous carbon, reducing the orderliness of the CF surface.

[0078] Table 4

[0079]

[0080] Table 4 shows the magnetic property test curves of MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on the surface, obtained in Examples 1, 2, and 3 of this invention. Due to the formation of the magnetic metal alloy FeNi3 / Co, all curves exhibit an S-shaped curve with low coercivity, indicating that the samples are soft magnetic materials. When the external magnetic field reaches 10000 Oe, all samples reach the saturation magnetization (M). S This highlights their ferromagnetic behavior. Examples 1, 2, and 3 of M... S The values ​​were 1.07, 2.28, and 2.40 emu / g, respectively. Example 1 had the lowest M. S This is attributed to the lowest catalyst concentration, while Example 3 inevitably achieved the highest M. S The value (attributed to the highest catalyst concentration) favors increased magnetic loss. This indicates that M S This can be optimized by introducing a high-permeability component with ferromagnetic properties. The coercivity (H) of the three samples... C The values ​​were 34.98, 108.70, and 412.88 Oe, respectively. Example 3 had the highest H. C This value helps to enhance eddy current loss.

[0081] Table 5

[0082]

[0083] Table 5 shows the electromagnetic wave absorption performance of untreated, unsized CF (marked as 0) and MgO@CF reinforcements with graphite-encapsulated FeNi3 / Co and CNTs deposited on their surfaces, obtained in Examples 1, 2, and 3 of this invention, demonstrating their minimum reflection loss (RL). min The effective absorption bandwidth (EAB), and its corresponding frequency band (f) and thickness (t) were determined. Overall, within the test range of 2-18 GHz, Examples 1, 2, and 3 exhibited superior electromagnetic wave absorption capabilities compared to the un-sizing CF, with Example 2 showing the best absorption performance. Magnetic FeNi3 / Co, appropriately defective CNTs, and the MgO nanocoating together improved the impedance matching of the CF. The synergistic effect of optimized impedance matching and high attenuation loss enabled the examples to achieve highly efficient microwave attenuation performance.

[0084] Table 6

[0085]

[0086] Table 6 shows the monofilament tensile properties of untreated, unsized CF (marked as 0) and MgO@CF reinforcements with graphite-coated FeNi3 / Co and CNTs obtained in Examples 1, 2 and 3 of this invention, demonstrating their average monofilament tensile strength and the amount of increase relative to unsized CF.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing MgO@CF reinforcements with surface-deposited graphite encapsulating FeNi3 / Co and CNTs, characterized in that: Includes the following steps: The surface of unsized carbon fibers was roughened and activated, oxygen-containing functional groups were grafted onto them, they were washed and dried, then impregnated with a magnesium source solution, dried and calcined in an inert atmosphere to prepare carbon fibers MgO@CF coated with MgO nanofilms. A mixed solution of iron, cobalt and nickel sources was impregnated with MgO@CF, dried, and then heated in a reducing atmosphere to reduce it to metal nanocatalyst particles. The obtained product was subjected to catalytic chemical vapor deposition to grow carbon materials on the surface, resulting in a MgO@CF reinforced material with graphite-encapsulated FeNi3 / Co and carbon nanotubes. The magnesium source is Mg(NO3)2; the concentration of the magnesium source solution is 0.05-2M; the solvent of the magnesium source solution is ethanol or water; the calcination temperature is 400-800℃, and the calcination time is 5-20min. In the mixed solution of iron, cobalt, and nickel sources, the concentration of the iron source is 0.01-0.03 M; the concentration of the cobalt source is 0.01-0.03 M; and the concentration of the nickel source is 0.03-0.09 M. Under the influence of MgO nanofilms, the growth mechanism of CNTs is a bottom-end growth mode.

2. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 1, characterized in that: The oxygen-containing functional group is CO, C=O, or OC=O.

3. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 1, characterized in that: The method for roughening and activating the carbon fiber surface is electrochemical anodizing.

4. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 1, characterized in that: The solvent for the mixed solution of iron, cobalt and nickel sources is ethanol or water.

5. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 1, characterized in that: The heating temperature in the reducing atmosphere is 400-800℃, and the reduction time is 5-20 minutes.

6. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 5, characterized in that: The reduction was carried out under an inert atmosphere.

7. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 1, characterized in that: The temperature for catalytic chemical vapor deposition is 550-800℃, and the deposition time is 5-20 min.

8. The method for preparing MgO@CF reinforcement with surface-deposited graphite encapsulating FeNi3 / Co and CNTs according to claim 7, characterized in that: The atmosphere used in the catalytic chemical vapor deposition process is a mixture of N2, C2H2 and H2.

9. A MgO@CF reinforcer with surface-deposited graphite encapsulating FeNi3 / Co and CNTs, characterized in that: It is prepared by any one of the preparation methods described in claims 1-8.

10. The application of the MgO@CF reinforcement with FeNi3 / Co and CNTs encapsulated by surface-deposited graphite as described in claim 9 in the fabrication of electromagnetic wave protection devices.

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