Mg / MgO magnesium-based composite material with gradient impedance structure as well as preparation method and application of Mg / MgO magnesium-based composite material

Abstract

The invention discloses an Mg / MgO magnesium-based composite material with a gradient impedance structure as well as a preparation method and application of the Mg / MgO magnesium-based composite material, and relates to the technical field of electromagnetic shielding materials. The preparation method specifically comprises the following steps: taking magnesium powder in an inert atmosphere, and carrying out ball milling treatment for different times to respectively obtain magnesium powder with different oxygen contents; paving the magnesium powder with different oxygen contents in a reaction device according to the sequence of the ball milling treatment time from short to long in an inert atmosphere; and carrying out vacuum hot pressed sintering on the reaction device, and then cooling to obtain the Mg / MgO magnesium-based composite material with the gradient impedance structure. Through the synergistic effect of gradient impedance design and hot pressing sintering, electromagnetic wave reflection on the surface of the material is remarkably reduced, and the electromagnetic wave absorption efficiency is enhanced. The electromagnetic shielding effectiveness of the prepared composite material in the X wave band is remarkably improved, efficient electromagnetic shielding dominated by absorption is achieved, and secondary electromagnetic pollution is effectively reduced.

Description

Technical Field

[0001] This invention relates to a Mg / MgO magnesium-based composite material with a gradient impedance structure, its preparation method and application, belonging to the field of electromagnetic shielding material technology. Background Technology

[0002] With the rapid development of 5G communication technology, electromagnetic pollution and electromagnetic interference between devices are becoming increasingly serious problems. Magnesium and its alloys, due to their high specific strength and inherent electromagnetic shielding properties, are considered ideal structural-functional integrated materials and have broad application prospects in portable electronic devices and communication fields.

[0003] Traditional metallic electromagnetic shielding materials primarily rely on the strong skin effect induced by high electrical conductivity to reflect electromagnetic waves. However, this reflection-dominated shielding mechanism is prone to secondary electromagnetic pollution. Current research on improving the shielding performance of magnesium-based materials focuses on increasing their electrical conductivity through alloying, heat treatment, or texture control. However, this often contradicts strategies for improving the material's mechanical strength (such as introducing lattice defects), leading to a mismatch between strength and shielding performance.

[0004] In recent years, related technologies have introduced a second phase (such as metal particles, carbon materials, or ferrites) into a magnesium matrix to increase interfacial polarization and enhance electromagnetic wave absorption. However, due to the strong skin effect of metallic materials, reflection loss (SE) is high. R It is usually still higher than the absorption loss (SE). A Layered structures and gradient impedance design have been shown to effectively control the impedance matching between materials and free space, reduce surface reflection, and promote the entry and absorption of electromagnetic waves into the material's interior. However, how to achieve a controllable gradient impedance structure in magnesium-based composite materials and thereby obtain electromagnetic shielding materials with high absorption performance still requires further investigation. Summary of the Invention

[0005] To address the shortcomings of related technologies, this invention provides a Mg / MgO magnesium-based composite material with a gradient impedance structure, its preparation method, and its application. This method achieves a gradient change in the internal impedance of the material through a simple and controllable process, enabling the composite material to possess highly efficient electromagnetic shielding performance dominated by absorption. This solves the problem of constructing a controllable gradient impedance structure in magnesium-based composite materials and thereby obtaining electromagnetic shielding materials with high absorption performance.

[0006] One objective of this invention is to provide a method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure, specifically including the following steps: (1) Powder pretreatment: Magnesium powder was taken under an inert atmosphere (preferably argon atmosphere) and ball milled for different times to obtain magnesium powder with different oxygen contents.

[0007] (2) Gradient powder spreading: Under an inert atmosphere (preferably argon atmosphere), magnesium powder with different oxygen contents obtained in step (1) is spread in a reaction device (preferably a hot press mold as the reaction device) in order of ball milling time from short to long.

[0008] (3) Sintering: The reaction device of step (2) is subjected to vacuum hot pressing sintering and then cooled to obtain a Mg / MgO magnesium-based composite material with a gradient impedance structure along the thickness direction.

[0009] Preferably, the ball milling times of magnesium powder in step (1) are t, t+n, t+2n, t+3n..., where n is 4 and t is 2h.

[0010] Preferably, the ball milling conditions in step (1) are as follows: ball milling is carried out under the conditions of a ball-to-material ratio of 5:1, a ball milling speed of 150 rpm, and a vacuum degree of 5-10 Pa.

[0011] More preferably, the purity of the magnesium powder in step (1) is 99.9%.

[0012] Preferably, the thickness of each layer of magnesium powder in step (2) is 2 mm; the number of magnesium powder layers is 6.

[0013] Preferably, the conditions for vacuum hot pressing sintering in step (3) are: sintering for 3 hours under the conditions of vacuum degree of 5-10 Pa, sintering pressure of 30-70 MPa, and sintering temperature of 580-620℃.

[0014] The second objective of this invention is to provide a Mg / MgO magnesium-based composite material with a gradient impedance structure prepared by the method of this invention.

[0015] The third objective of this invention is to provide an application of Mg / MgO magnesium-based composite material with a gradient impedance structure prepared by the method of this invention in the field of electromagnetic interference shielding.

[0016] Mechanism of the invention: The Mg / MgO magnesium-based composite material with a gradient impedance structure prepared in this invention exhibits a significantly reduced electromagnetic wave reflection from the material surface due to the synergistic effect of gradient impedance design (ball milling time control and layered powder spreading) and hot pressing sintering. This is achieved by a gradual increase in MgO content along the thickness direction from the bottom (electromagnetic wave incident surface) to the top. The electromagnetic shielding mechanism is as follows: Figure 2 As shown, the numerous MgO-Mg heterojunctions within the Mg / MgO magnesium-based composite material with gradient impedance structure prepared in this invention provide conditions for interfacial polarization and multi-level reflection of electromagnetic waves, thereby synergistically enhancing absorption loss (SE). A ).

[0017] The beneficial effects of this invention are: (1) This invention achieves a transformation of the electromagnetic shielding mechanism of the composite material from "reflection-dominated" to "absorption-dominated" through the synergistic effect of gradient impedance design (ball milling time control and layered powder spreading) and hot pressing sintering. In the X-band (12.4GHz), the absorption shielding effectiveness (SE) A The reflective shielding effectiveness (SE) is significantly improved. R This reduces the amount of electromagnetic pollution, effectively minimizing secondary electromagnetic pollution.

[0018] (2) The gradient impedance structure of the present invention works synergistically with a large number of MgO-Mg heterostructures inside, and dissipates electromagnetic wave energy through multiple mechanisms such as weakening the skin effect, inducing interface polarization, and promoting multiple reflections, resulting in excellent shielding performance.

[0019] (3) The present invention achieves gradient regulation of powder oxidation degree through simple ball milling time control, and then forms impedance gradient structure in one step through layered powder spreading and hot pressing sintering. The process is simple and controllable.

[0020] (4) The Mg / MgO magnesium-based composite material with gradient impedance structure prepared by the present invention maintains the lightweight characteristics of magnesium alloys and provides a new design idea for the development of high-performance “absorption type” metal-based electromagnetic shielding materials. It has important application value in the fields of aerospace, defense and military industry and high-end electronic equipment. Attached Figure Description

[0021] Figure 1 Figure 1 shows the metallographic (OM) structure and electron probe microanalysis (EPMA) analysis of the Mg / MgO magnesium-based composite material with gradient impedance structure prepared in Example 1 of this invention. Figure 1(a) shows the overall morphology of the metallographic (OM) structure of the Mg / MgO magnesium-based composite material with gradient impedance structure prepared in Example 1; Figure 1(b) shows the upper region; Figure 1(c) shows the middle region; and Figure 1(d) shows the EPMA analysis of the lower region.

[0022] Figure 2 This is a schematic diagram of the electromagnetic shielding mechanism of the Mg / MgO magnesium-based composite material with a gradient impedance structure prepared in this invention.

[0023] Figure 3 Figure (a) shows a comparison of the electromagnetic shielding performance of the Mg / MgO magnesium-based composite material with a gradient impedance structure prepared in Comparative Example 1 and Example 1 of this invention; Figure (a) shows the total shielding effectiveness (SE). T Figure (b) shows the reflection shielding effectiveness (SE). R Figure (c) shows the absorption and shielding effectiveness (SE). A ). Detailed Implementation

[0024] To better illustrate the purpose, technical solution, and advantages of this invention, the following detailed description will be provided in conjunction with specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments and comparative examples of this invention are commercially available analytical grade reagents. The magnesium powder used in the embodiments and comparative examples of this invention has a purity of 99.9% by mass percentage. This invention utilizes a small amount of oxygen pre-adhered to the magnesium powder and the inner wall of the ball milling device to achieve the preparation of magnesium powders with different oxygen contents during vacuum ball milling, wherein the longer the ball milling time, the higher the oxygen content of the magnesium powder.

[0025] Example 1 A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 2, 6, 10, 14, 18 and 22 hours respectively under the conditions of ball-to-powder ratio of 5:1, rotation speed of 150 rpm and vacuum degree of 8 Pa. The oxygen content was controlled by different ball-milling times to obtain 6 kinds of magnesium powder with different oxygen contents.

[0026] (2) Gradient powder spreading: Under an argon atmosphere, the six magnesium powders with different oxygen contents obtained in step (1) are spread into a hot press mold (i.e., a graphite mold) in order of ball milling time from short to long. The thickness of each layer of magnesium powder is 2 mm, forming a 6-layer structure.

[0027] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum hot pressing sintering furnace and vacuum hot pressing is performed for 3 hours under the conditions of vacuum degree 8 Pa, temperature 600℃ and pressure 50 MPa. After that, it is cooled with the furnace to obtain a Mg / MgO magnesium-based composite material block with a gradient impedance structure.

[0028] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 1 of this invention were characterized. The metallographic structure of this example is shown in the figure below. Figure 1 As shown, Figure 1 As shown in (a), the metallographic structure reveals a gradual increase in the dark phase (MgO) from the bottom to the top of the sample, and electron probe microanalysis (EPMA) confirms a gradient increase in oxygen content (see [reference]). Figure 1 (bd)). The electromagnetic shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 1 was tested in the X-band (8.2-12.4 GHz). The test results are as follows: Figure 3As shown in (ac), tests revealed that this embodiment, due to the synergistic effect of gradient impedance design (ball milling time control and layered powder spreading) and hot pressing sintering, generates a large number of MgO-Mg heterostructures within the material. This provides conditions for interfacial polarization and multi-level reflection of electromagnetic waves, thereby synergistically enhancing absorption loss. At 12.4 GHz, SE A Up to 49dB, its absorption and shielding effectiveness (SE) A It is far superior to the reflective shielding effectiveness (SE). R This indicates that the shielding mechanism is primarily based on absorption.

[0029] Example 2 A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 2, 6, 10, 14, 18 and 22 hours respectively under the conditions of ball-to-powder ratio of 5:1, rotation speed of 150 rpm and vacuum degree of 5 Pa. The oxygen content was controlled by different ball milling times to obtain 6 kinds of magnesium powder with different oxygen contents.

[0030] (2) Gradient powder spreading: Under an argon atmosphere, the six magnesium powders with different oxygen contents obtained in step (1) are spread into a hot press mold (i.e., a graphite mold) in order of ball milling time from short to long. The thickness of each layer of magnesium powder is 2 mm, forming a 6-layer structure.

[0031] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum hot pressing sintering furnace and vacuum hot pressing is performed for 3 hours under the conditions of vacuum degree 10 Pa, temperature 620 °C and pressure 30 MPa. After that, it is cooled with the furnace to obtain a Mg / MgO magnesium-based composite material block with a gradient impedance structure.

[0032] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 2 of this invention were characterized. Metallographic analysis showed a gradual increase in the dark phase (MgO) from the bottom to the top of the sample. Electron probe microanalysis (EPMA) confirmed a gradient increase in oxygen content. Electron shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 2 was tested in the X-band (8.2-12.4 GHz). The tests showed that due to the synergistic effect of the gradient impedance design (ball milling time control and layered powder spreading) and hot pressing sintering, a large number of MgO-Mg heterojunctions were generated inside the material, providing conditions for interface polarization and multi-level reflection of electromagnetic waves, thereby synergistically enhancing absorption loss. At 12.4 GHz, the SE... A Up to 38dB, its absorption and shielding effectiveness (SE) A It is far superior to the reflective shielding effectiveness (SE).R This indicates that the shielding mechanism is primarily based on absorption.

[0033] Example 3 A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 2, 6, 10, 14, 18 and 22 hours respectively under the conditions of ball-to-powder ratio of 5:1, rotation speed of 150 rpm and vacuum degree of 10 Pa. The oxygen content was controlled by different ball milling times to obtain 6 kinds of magnesium powder with different oxygen contents.

[0034] (2) Gradient powder spreading: Under an argon atmosphere, the six magnesium powders with different oxygen contents obtained in step (1) are spread into a hot press mold (i.e., a graphite mold) in order of ball milling time from short to long. The thickness of each layer of magnesium powder is 2 mm, forming a 6-layer structure.

[0035] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum hot pressing sintering furnace and vacuum hot pressing is performed for 3 hours under the conditions of vacuum degree 5 Pa, temperature 580℃ and pressure 70 MPa. After that, it is cooled with the furnace to obtain a Mg / MgO magnesium-based composite material block with a gradient impedance structure.

[0036] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 3 of this invention were characterized. Metallographic analysis showed a gradual increase in the dark phase (MgO) from the bottom to the top of the sample. Electron probe microanalysis (EPMA) confirmed a gradient increase in oxygen content. Electron shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Example 3 was tested in the X-band (8.2-12.4 GHz). The tests showed that due to the synergistic effect of the gradient impedance design (ball milling time control and layered powder spreading) and hot pressing sintering, a large number of MgO-Mg heterojunctions were generated inside the material, providing conditions for interface polarization and multi-level reflection of electromagnetic waves, thereby synergistically enhancing absorption loss. At 12.4 GHz, the SE... A Up to 43dB, its absorption and shielding effectiveness (SE) A It is far superior to the reflective shielding effectiveness (SE). R This indicates that the shielding mechanism is primarily based on absorption.

[0037] Comparative Example 1 A method for preparing a pure magnesium material with impedance properties specifically includes the following steps: Magnesium powder was laid in a graphite mold under an argon atmosphere, with a thickness of 12 mm. The graphite mold was then placed in a vacuum hot-pressing sintering furnace and sintered for 3 hours under vacuum conditions of 8 Pa, 600 °C, and 50 MPa. After cooling in the furnace, a pure magnesium material block with impedance properties was obtained.

[0038] The microstructure and electromagnetic shielding performance of the pure magnesium material bulk with impedance properties prepared in Comparative Example 1 of this invention were characterized. The metallographic micrographs clearly show that the material has a uniform, non-layered structure. The dark phase content shows a gradual increase from the bottom layer to the surface. Electromagnetic shielding performance of the pure magnesium material bulk with impedance properties prepared in Comparative Example 1 was tested in the X-band (8.2-12.4 GHz). The tests showed that at 12.4 GHz, the SE... A Only 2dB, such as Figure 3 As shown in (ac), its shielding effectiveness decreases with increasing frequency, and it is mainly due to reflection mechanism (SE). R SE A Since no MgO was added in Comparative Example 1, the material could not further dissipate electromagnetic energy through interfacial polarization, dipole relaxation, or magnetic loss mechanisms. This resulted in it exhibiting electromagnetic shielding characteristics of high reflection and low absorption, which not only failed to achieve efficient attenuation but also easily caused secondary electromagnetic pollution due to strong reflection.

[0039] Comparative Example 2 A method for preparing a Mg / MgO magnesium-based material with impedance properties specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 10 hours at a ball-to-material ratio of 5:1, a rotation speed of 150 rpm, and a vacuum degree of 8 Pa to obtain magnesium oxide powder.

[0040] (2) Powder spreading: Under an argon atmosphere, the magnesium oxide powder obtained in step (1) is spread in a hot press mold (i.e., a graphite mold) with a thickness of 12 mm.

[0041] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum hot pressing sintering furnace and vacuum hot pressing is performed for 3 hours under the conditions of vacuum degree 8 Pa, temperature 600℃ and pressure 50 MPa. After that, it is cooled with the furnace to obtain a Mg / MgO magnesium-based material block with impedance properties.

[0042] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based material bulk with impedance properties prepared in Comparative Example 2 of this invention were characterized. The metallographic structure showed that the material was uniform overall with no obvious differences in layered structure. Electromagnetic shielding performance of the Mg / MgO magnesium-based material bulk with impedance properties prepared in Comparative Example 2 was tested in the X-band (8.2-12.4 GHz). The test results showed that at 12.4 GHz, the SE... A The energy loss was only 25 dB. This is because the comparative example did not construct a gradient impedance structure and only used magnesium powder with a fixed oxygen content as the impedance material. As a result, it was impossible to construct a multi-electromagnetic wave absorption mechanism and the multi-level reflection loss enhancement with absorption shielding effect was not formed. In addition, the comparative example did not construct a gradient impedance structure, and the MgO nanoparticles did not form a large number of MgO-Mg heterostructures in the magnesium matrix. As a result, the energy loss of electromagnetic waves in the propagation path inside the material was low, and the shielding mechanism dominated by absorption was not performing well.

[0043] Comparative Example 3 A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 2, 6, 10, 14, 18 and 22 hours respectively under the conditions of ball-to-powder ratio of 5:1, rotation speed of 150 rpm and vacuum degree of 8 Pa. The oxygen content was controlled by different ball-milling times to obtain 6 kinds of magnesium powder with different oxygen contents.

[0044] (2) Gradient powder spreading: Under an argon atmosphere, the six magnesium powders with different oxygen contents obtained in step (1) are spread into a hot press mold (i.e., a graphite mold) in the order of ball milling time from long to short. The thickness of each layer of magnesium powder is 2 mm, forming a 6-layer structure.

[0045] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum hot pressing sintering furnace and vacuum hot pressing is performed for 3 hours under the conditions of vacuum degree 8 Pa, temperature 600℃ and pressure 50 MPa. After that, it is cooled with the furnace to obtain a Mg / MgO magnesium-based composite material block with a gradient impedance structure.

[0046] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based composite material with a gradient impedance structure prepared in Comparative Example 3 of this invention were characterized. Metallographic images show the microstructure differences between the two layers of the composite material after sintering. The dark phase content decreases progressively from the bottom layer to the surface layer. Electromagnetic shielding performance of the Mg / MgO magnesium-based composite material with a gradient impedance structure prepared in Comparative Example 3 was tested in the X-band (8.2-12.4 GHz). The tests showed that at 12.4 GHz, the SE... AThe result is only 17dB. This is because the high magnesium oxide content in the composite material can significantly reduce the skin effect of the metal surface, thereby reducing the reflection of electromagnetic waves by the material. However, reversing the powder spreading order causes most of the electromagnetic waves to be reflected on the surface of the composite material, resulting in poor absorption and shielding performance of the material.

[0047] Comparative Example 4 A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure specifically includes the following steps: (1) Powder pretreatment: Magnesium powder (weighed under argon atmosphere) was ball-milled for 2, 6, 10, 14, 18 and 22 hours respectively under the conditions of ball-to-powder ratio of 5:1, rotation speed of 150 rpm and vacuum degree of 8 Pa. The oxygen content was controlled by different ball-milling times to obtain 6 kinds of magnesium powder with different oxygen contents.

[0048] (2) Gradient powder spreading: Under an argon atmosphere, the six magnesium powders with different oxygen contents obtained in step (1) are spread into a hot press mold (i.e. a graphite mold) in order of ball milling time from short to long to form a six-layer structure.

[0049] (3) Sintering and molding: The graphite mold from step (2) is placed in a vacuum sintering furnace and sintered for 3 hours under vacuum conditions of 8 Pa and 600 °C. After cooling with the furnace, a Mg / MgO magnesium-based composite material block with a gradient impedance structure is obtained.

[0050] The microstructure and electromagnetic shielding performance of the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Comparative Example 4 of this invention were characterized. The metallographic images showed the external phase microstructure of the composite material after sintering, but did not clearly show the microstructural differences between the upper and lower layers. From the bottom layer to the surface, the dark phase content did not show a layer-by-layer increasing trend. Electromagnetic shielding performance tests were conducted on the Mg / MgO magnesium-based composite material bulk with a gradient impedance structure prepared in Comparative Example 4 in the X-band (8.2-12.4 GHz). The tests showed that at 12.4 GHz, the SE... A The shielding efficiency is only 9 dB. This is because the comparative example did not perform pressure molding on the magnesium powder with different oxygen contents laid in the gradient, which directly led to a loose, porous, and layered microstructure in the material; the gradient impedance design failed, the electromagnetic wave absorption loss was greatly reduced, and the overall shielding effectiveness was close to that of pure Mg; the mechanical properties could not meet the application requirements. Ultimately, the material will lose its core advantage of "absorption-dominant electromagnetic shielding" and will not be able to achieve the required high performance.

[0051] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a Mg / MgO magnesium-based composite material with a gradient impedance structure, characterized in that, Specifically, the following steps are included: (1) Powder pretreatment: Magnesium powder was taken under an inert atmosphere and ball milled for different times to obtain magnesium powder with different oxygen contents. (2) Gradient powder spreading: Under an inert atmosphere, magnesium powder with different oxygen contents obtained in step (1) is spread in the reaction apparatus in order of ball milling time from short to long; (3) Sintering: The reaction device of step (2) is subjected to vacuum hot pressing sintering and then cooled to obtain a Mg / MgO magnesium-based composite material with a gradient impedance structure along the thickness direction.

2. The method for preparing the Mg / MgO magnesium-based composite material with a gradient impedance structure according to claim 1, characterized in that, The ball milling times for magnesium powder in step (1) are t, t+n, t+2n, t+3n..., where n is 4 and t is 2h.

3. The method for preparing the Mg / MgO magnesium-based composite material with a gradient impedance structure according to claim 1, characterized in that, The conditions for ball milling in step (1) are as follows: ball milling is carried out at a ball-to-material ratio of 5:1, a ball milling speed of 150 rpm, and a vacuum degree of 5-10 Pa.

4. The method for preparing the Mg / MgO magnesium-based composite material with a gradient impedance structure according to claim 1, characterized in that, In step (2), the thickness of each layer of magnesium powder is 2mm; the number of magnesium powder layers is 6.

5. The method for preparing the Mg / MgO magnesium-based composite material with a gradient impedance structure according to claim 1, characterized in that, The conditions for vacuum hot pressing sintering in step (3) are: sintering for 3 hours under the conditions of vacuum degree of 5-10 Pa, sintering pressure of 30-70 MPa, and sintering temperature of 580-620℃.

6. The Mg / MgO magnesium-based composite material with a gradient impedance structure is prepared by the method according to any one of claims 1 to 5.

7. The application of the Mg / MgO magnesium-based composite material with a gradient impedance structure as described in claim 6 in the field of electromagnetic interference shielding.

Images