Mechanics-shielding integrated magnesium-based composite material and preparation method thereof

Abstract

The application discloses a kind of mechanical-shielding integrated magnesium-based composite material and preparation method thereof, it is related to metal-based composite material preparation technical field.The preparation method of mechanical-shielding integrated magnesium-based composite material of the present application is as follows: porous graphene is prepared by etching graphene with acid solution;Mix the porous graphene with magnesium powder, ball mill to obtain the powder after ball milling;The powder after ball milling is subjected to spark plasma sintering to obtain sintered block;The sintered block is subjected to hot extrusion, and the mechanical-shielding integrated magnesium-based composite material is obtained after cooling;The present application utilizes the synergistic effect of porous graphene and magnesium matrix to induce the generation of high-density nano-MgO at the interface, enhance the interfacial bonding strength and improve the mechanical properties of the composite material.The porous structure and spark plasma sintering synergistically reduce electromagnetic wave reflection, and the electromagnetic wave absorption is enhanced through multiple interface loss and polarization loss.The obtained composite material realizes efficient electromagnetic shielding dominated by absorption in the X-band, effectively inhibits secondary pollution.

Description

Technical Field

[0001] This invention relates to a mechanical-shielding integrated magnesium-based composite material and its preparation method, belonging to the field of metal matrix composite material preparation technology. Background Technology

[0002] The rapid development of wireless communication, commercial portable devices, and military electronic products has led to serious problems of electromagnetic radiation and pollution. Electromagnetic interference not only disrupts digital signal transmission but also harms human health; therefore, it is crucial to develop broadband materials with high electromagnetic interference shielding (SE) effectiveness.

[0003] Improving electromagnetic interference (EMI) shielding performance primarily relies on enhancing absorption and reflection effects. Traditional metal shielding materials (such as steel and copper) mainly rely on reflection, which can easily cause secondary pollution and have high density; while stealth technology prefers materials with high absorption efficiency. Recent research has focused on preparing metal-based composite shielding materials by adding graphite, carbon fiber, graphene, and carbon nanotube fillers. These materials require both excellent mechanical load-bearing capacity and high-efficiency EMI shielding performance. Traditional metal materials (such as pure magnesium and magnesium alloys) have the advantage of low density, but they suffer from inherent defects such as low mechanical strength and poor plasticity; traditional electromagnetic shielding materials (such as copper and aluminum foil) face problems such as high density, susceptibility to corrosion, and a single shielding mechanism (mainly reflection, which easily causes secondary electromagnetic pollution).

[0004] Magnesium alloys, as the lightest metallic structural materials, possess certain electromagnetic shielding properties. However, their alloying processes only improve shielding effectiveness in the low-frequency band, and the mechanism remains primarily reflection. Research has confirmed that composite structures can enable metallic materials to surpass their electromagnetic wave absorption advantages in terms of reflection. For example, the layered structure of FeSiB metallic glass coated with Ni-Cu-P and the porous, multi-level structure assembled from copper nanosheets both exhibit excellent electromagnetic wave absorption performance. Based on this, it is speculated that the absorption performance of magnesium alloys may be related to their porous structure. Electronic equipment and weapon casing components need to possess both electromagnetic interference resistance and mechanical properties. Graphene nanosheets (GNSs), due to their excellent mechanical properties, have become an ideal reinforcing phase for metal matrix composites (MMCs). Summary of the Invention

[0005] To address the shortcomings of related technologies, this invention provides a mechanical-shielding integrated magnesium-based composite material and its preparation method. The magnesium-based composite material prepared by this invention can effectively bear loads and hinder dislocation movement, optimize interfacial bonding, and the porous structure of graphene can absorb and disperse external stress, which helps to improve the toughness of the composite material, reduce crack propagation, and enhance the fatigue resistance of the material, thereby improving the comprehensive mechanical properties of the composite material. At the same time, it can improve the electromagnetic shielding effectiveness of the magnesium-based composite material and achieve lightweighting. The porous structure constructed by porous graphene can form nano-defects inside the material and increase the number of nano-MgO at the interface, thereby improving the dipole polarization and interfacial polarization of the composite material under the action of electromagnetic waves and enhancing the electromagnetic shielding effectiveness of the composite material.

[0006] One objective of this invention is to provide a method for preparing a mechanically-shielded integrated magnesium-based composite material, specifically comprising the following steps: (1) Preparation of porous graphene: Graphene is prepared by etching it with an acid solution and then annealing it under an inert atmosphere.

[0007] (2) Ball milling treatment: The porous graphene obtained in step (1) is mixed with magnesium powder to obtain a mixed powder. The mixed powder is ball milled to obtain a ball-milled powder.

[0008] (3) Sintering: The ball-milled powder obtained in step (2) is subjected to discharge plasma sintering to obtain a sintered block.

[0009] (4) Hot extrusion: The sintered block obtained in step (3) is hot extruded and cooled to obtain a mechanical-shielding integrated magnesium-based composite material.

[0010] Preferably, the acid solution in step (1) is an aqueous HCl solution with a mass percentage concentration of 10%; the conditions for the acid solution to corrode the graphene are: immersing the graphene in the acid solution and corroding it at 20~28℃ for 0.5~1.2h; the conditions for the annealing treatment are: annealing at 900℃ for 20~40min.

[0011] More preferably, the mixed atmosphere in step (1) consists of hydrogen and argon; the hydrogen content in the mixed atmosphere is 5% by volume percentage, and the remainder is argon; the flow rate of the mixed atmosphere is 100 mL / min.

[0012] More preferably, step (1) involves selectively etching graphene defect sites or specific regions with an acid solution to form pores and prepare porous graphene. The pore distribution obtained by etching graphene with an acid solution is relatively random, and the etching preferentially occurs at the defect sites of graphene, making it easy to achieve high porosity. Extending the etching time or increasing the concentration of the acid solution can improve the porosity.

[0013] More preferably, the preparation method of graphene in step (1) is as follows: prepare an anhydrous ethanol dispersion of graphene oxide with an addition amount of 1 mg / mL, then add ferrocene to the anhydrous ethanol dispersion of graphene oxide at a mass ratio of 1:7 of graphene oxide to ferrocene, and ultrasonically disperse to obtain a mixed system; keep the mixed system at 180°C for 4 hours and then cool it, then filter to separate the solid material, wash and dry the solid material, and then anneal at 900°C for 4 hours at a flow rate of 100 mL / min in a mixed atmosphere (the hydrogen content in the mixed atmosphere is 5% by volume percentage, and the remainder is argon) to obtain graphene.

[0014] More preferably, the inert atmosphere in step (1) is an argon atmosphere.

[0015] Preferably, the content of porous graphene in the mixed powder in step (2) is 0.2-1% by mass, and the remainder is magnesium powder.

[0016] Preferably, the conditions for ball milling in step (2) are: ball milling for 13 to 17 hours at a ball-to-material ratio of 20:1 and a ball milling speed of 120 to 180 rpm.

[0017] Preferably, the conditions for the discharge plasma sintering in step (3) are: sintering at a vacuum of 6~10Pa, a sintering temperature of 550~600℃, and a sintering pressure of 25~35MPa for 15min.

[0018] Preferably, the conditions for hot extrusion in step (4) are: hot extrusion temperature of 300℃ and extrusion ratio of (12~26):1.

[0019] Another object of the present invention is to provide a mechanical-shielding integrated magnesium-based composite material prepared by the method of the present invention.

[0020] Mechanism of the invention: This invention obtains porous graphene by etching graphene with an acid solution to form a rich porous structure, which significantly increases the contact area with the magnesium matrix and induces the formation of high-density nano-MgO at the interface. This transition phase effectively eliminates the interface compatibility difference between graphene and the magnesium matrix, thereby enhancing the interface bonding force, enabling the load to be effectively transferred and avoiding performance degradation caused by interface peeling under stress. Figure 1The porous graphene nanoparticles prepared by this invention possess the characteristics of a porous graphene nanopore structure, retaining the continuous two-dimensional network of graphene while providing high specific surface area and tunable transport channels through abundant nanopores. Simultaneously, the porous structure of the porous graphene acts as a stress buffer region, absorbing and dispersing external stress, reducing local stress concentration. Its sheet structure, by hindering dislocation movement and extending the dislocation slip path through its porous features, delays crack initiation and propagation, thereby improving the material's toughness and fatigue resistance. Regarding electromagnetic properties, the defect sites and nano-MgO at the interfaces of the porous graphene significantly enhance dipole polarization and interfacial polarization capabilities. Under the action of an alternating electromagnetic field, charge undergoes directional migration and accumulation, forming a polarization relaxation process that converts electromagnetic wave energy into heat energy. The numerous heterogeneous interfaces constructed by the porous structure (such as graphene-magnesium matrix, graphene-nano-MgO, and pore-matrix) promote multiple reflections and scatterings of electromagnetic waves, extending their propagation path and enhancing energy attenuation. The porous structure constructed by acid solution corrosion in this invention exhibits... The electroplasma sintering, ball milling, and hot extrusion processes form a synergistic mechanism, constructing abundant heterogeneous interfaces and providing rich interfacial polarization sites for the composite material prepared in this invention. This also reduces the overall equivalent dielectric constant of the composite material. Through rapid heating and pulsed electric field application, this invention eliminates microscopic defects and interfacial voids caused by the porous structure, achieving homogenization of the material's surface structure and electrical properties. Optimizing the crystallographic texture of the matrix and the orientation distribution of graphene results in a continuous impedance gradient layer on the material surface. The smoother impedance gradient layer on the material surface significantly reduces direct reflection of incident electromagnetic waves at the interface, effectively guiding electromagnetic waves into the material for multiple dissipations. This replaces traditional reflective shielding with a highly efficient absorption-type shielding mechanism, fundamentally preventing the formation of secondary electromagnetic radiation.

[0021] The beneficial effects of this invention are: (1) The present invention uses porous graphene as a reinforcing phase to increase the number density of nano-MgO at the interface between graphene and Mg matrix during the preparation of composite materials, thereby improving the mechanical properties of composite materials by improving the interfacial bonding ability between the two.

[0022] (2) In this invention, porous graphene is added to magnesium-based metal materials as a functional enhancement phase. By increasing the number of nano-defects and interface nano-MgO, the dipole polarization and interface polarization of the composite material under the action of electromagnetic waves can be improved, thereby improving the absorption and loss capacity of the composite material for electromagnetic waves.

[0023] (3) The present invention uses spark plasma sintering process to prepare composite materials. This process can be sintered and formed at a temperature lower than the melting point of the composite material, which consumes less energy than the traditional casting process.

[0024] (4) The present invention uses hot extrusion processing technology to prepare composite materials. A higher extrusion ratio can further improve the density of composite materials and refine the grains, so that the prepared composite materials have better comprehensive performance.

[0025] (5) The porous graphene-reinforced magnesium-based composite material prepared by the present invention has excellent room temperature tensile strength and elongation through the synergistic effect of porous graphene construction, plasma discharge sintering, ball milling and hot extrusion processes; the porous graphene-reinforced magnesium-based composite material prepared by the present invention has excellent total shielding effectiveness. Attached Figure Description

[0026] Figure 1 This is a scanning image of the porous graphene microstructure of the present invention.

[0027] Figure 2 This is a comparison chart of the total shielding effectiveness of the porous graphene magnesium-based composite materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0028] Figure 3 The graphs show the room temperature tensile mechanical properties of the porous graphene-magnesium composite materials prepared in Examples 1, 1, and 2 of this invention. Detailed Implementation

[0029] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used were commercially available analytical grade reagents.

[0030] Example 1 A method for preparing a mechanically-shielded integrated magnesium-based composite material, specifically including the following steps: (1) Preparation of porous graphene: Prepare an anhydrous ethanol dispersion of graphene oxide and sonicate for 30 min to ensure uniform dispersion of graphene oxide. The amount of graphene oxide added to the dispersion is 1 mg / mL. Add ferrocene to the anhydrous ethanol dispersion of graphene oxide at a mass ratio of 1:7. Continue sonication for 30 min to obtain a uniformly dispersed mixture. Place the mixture in a Teflon-lined autoclave, heat it to 180°C in a muffle furnace, keep it at that temperature for 4 h, and then cool it to room temperature. Filter to separate the solid material and use anhydrous ethanol. The ferrocene was cleaned with alcohol and dried in air. Then, it was placed in a quartz tube and annealed at 900°C for 4 hours at a flow rate of 100 mL / min in a mixed atmosphere (the hydrogen content in the mixed atmosphere was 5% by volume, and the balance was argon) to decompose the ferrocene into iron / austenitic nanolayers, thus obtaining graphene. The graphene was then immersed in a 10% HCl aqueous solution at 25°C for 1 hour to remove the nanolayers. The crude porous graphene product after acid etching was separated by filtration. Subsequently, the graphene oxide was reduced by annealing at 900°C for 30 minutes in an argon atmosphere, thus obtaining porous graphene.

[0031] (2) Ball milling treatment: 29.94g of pure magnesium powder and 0.06g of porous graphene were mixed to obtain a mixed powder (the content of porous graphene in the mixed powder was 0.2% by mass percentage, and the remainder was magnesium powder). The mixed powder was placed in a stainless steel ball mill jar and ball milled for 15 hours at 150rpm using a planetary ball mill under an argon atmosphere with a ball-to-material ratio of 20:1 to obtain a uniform ball-milled powder.

[0032] (3) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 8 Pa. The sintering temperature was 580℃, the sintering pressure was 30MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0033] (4) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 26:1 to obtain a rectangular mechanical-shielding integrated magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm, namely a porous graphene-reinforced magnesium-based composite material.

[0034] The mechanical and electromagnetic shielding integrated magnesium-based composite material block prepared in Example 1 of this invention was subjected to mechanical and electromagnetic shielding performance tests. The composite material prepared in this example was processed into tensile specimens by wire cutting, and its room temperature tensile properties were tested. The mechanical strength was 233 MPa. See [link to relevant documentation]. Figure 3Electromagnetic shielding performance of the composite material bulk material prepared in Example 1 was tested in the X-band (8.2-12.4 GHz). The tests showed that due to the porous graphene design, the porous graphene channel structure introduces a large number of heterogeneous interfaces, causing multiple reflections and scattering of electromagnetic waves, extending their propagation path within the material, and enhancing energy attenuation. This synergistically enhances absorption loss, resulting in a total shielding effectiveness of up to 93 dB. (See [link to relevant documentation]). Figure 2 .

[0035] Example 2 (1) Preparation of porous graphene: Prepare an anhydrous ethanol dispersion of graphene oxide and sonicate for 30 min to ensure uniform dispersion of graphene oxide. The amount of graphene oxide added to the dispersion is 1 mg / mL. Add ferrocene to the anhydrous ethanol dispersion of graphene oxide at a mass ratio of 1:7. Continue sonication for 30 min to obtain a uniformly dispersed mixture. Place the mixture in a Teflon-lined autoclave, heat it to 180°C in a muffle furnace, keep it at that temperature for 4 h, and then cool it to room temperature. Filter to separate the solid material and use anhydrous ethanol. The ferrocene was cleaned with alcohol and dried in air. Then, it was placed in a quartz tube and annealed at 900°C for 4 hours at a flow rate of 100 mL / min in a mixed atmosphere (the hydrogen content in the mixed atmosphere was 5% by volume, and the balance was argon) to decompose the ferrocene into iron / austenitic nanolayers, thus obtaining graphene. The graphene was then immersed in a 10% HCl aqueous solution at 25°C for 1 hour to remove the nanolayers. The crude porous graphene product after acid etching was separated by filtration. Subsequently, the graphene oxide was reduced by annealing at 900°C for 30 minutes in an argon atmosphere, thus obtaining porous graphene.

[0036] (2) Ball milling treatment: 29.88g of pure magnesium powder and 0.12g of porous graphene were mixed to obtain a mixed powder (the content of porous graphene in the mixed powder was 0.4% by mass percentage, and the remainder was magnesium powder). The mixed powder was placed in a stainless steel ball mill jar and ball milled for 15 hours at 150 rpm under an argon atmosphere with a ball-to-material ratio of 20:1 to obtain a uniform ball-milled powder.

[0037] (3) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 8 Pa. The sintering temperature was 580℃, the sintering pressure was 30MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0038] (4) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 26:1 to obtain a rectangular mechanical-shielding integrated magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm, namely a porous graphene-reinforced magnesium-based composite material.

[0039] Mechanical and electromagnetic shielding performance tests were conducted on the integrated mechanical-shielding magnesium-based composite material block prepared in Example 2 of this invention. The composite material prepared in this example was processed into tensile specimens by wire cutting, and its room temperature tensile properties were tested, with a mechanical strength of 206 MPa. Electromagnetic shielding performance tests were performed on the composite material block prepared in Example 2 in the X-band (8.2-12.4 GHz). The tests showed that due to the porous graphene design, the porous graphene channel structure introduces a large number of heterogeneous interfaces, causing multiple reflections and scattering of electromagnetic waves, extending their propagation path within the material, and enhancing energy attenuation, thereby synergistically enhancing absorption loss, resulting in a total shielding effectiveness of up to 79 dB.

[0040] Example 3 A method for preparing a mechanically-shielded integrated magnesium-based composite material, specifically including the following steps: (1) Preparation of porous graphene: Prepare an anhydrous ethanol dispersion of graphene oxide and sonicate for 30 min to ensure uniform dispersion of graphene oxide. The amount of graphene oxide added to the dispersion is 1 mg / mL. Add ferrocene to the anhydrous ethanol dispersion of graphene oxide at a mass ratio of 1:7. Continue sonication for 30 min to obtain a uniformly dispersed mixture. Place the mixture in a Teflon-lined autoclave, heat it to 180°C in a muffle furnace, keep it at that temperature for 4 h, and then cool it to room temperature. Filter to separate the solid material and use anhydrous ethanol. The ferrocene was cleaned and air-dried. It was then placed in a quartz tube and annealed at 900°C for 4 hours at a flow rate of 100 mL / min under a mixed atmosphere (5% hydrogen by volume, with the remainder being argon) to decompose the ferrocene into an iron / austenitic nanolayer, yielding graphene. The graphene was then immersed in a 10% HCl aqueous solution at 28°C for 0.5 hours to remove the nanolayer. The acid-etched porous graphene crude product was filtered and separated. Subsequently, it was annealed at 900°C for 20 minutes under an argon atmosphere to reduce graphene oxide, thus obtaining porous graphene.

[0041] (2) Ball milling treatment: 29.7g of pure magnesium powder and 0.3g of porous graphene were mixed to obtain a mixed powder (the content of porous graphene in the mixed powder was 1% by mass percentage, and the remainder was magnesium powder). The mixed powder was placed in a stainless steel ball mill jar and ball milled at 120rpm for 17h under an argon atmosphere with a ball-to-material ratio of 20:1 to obtain a uniform ball-milled powder.

[0042] (3) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 6 Pa. The sintering temperature was 550℃, the sintering pressure was 25MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0043] (4) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 12:1 to obtain a rectangular mechanical-shielding integrated magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm, namely a porous graphene-reinforced magnesium-based composite material.

[0044] Mechanical and electromagnetic shielding performance tests were conducted on the integrated mechanical-shielding magnesium-based composite material block prepared in Example 3 of this invention. The composite material prepared in this example was processed into tensile specimens by wire cutting, and its room temperature tensile properties were tested, with a mechanical strength of 193 MPa. Electromagnetic shielding performance tests were performed on the composite material block prepared in Example 3 in the X-band (8.2-12.4 GHz). The tests showed that due to the porous graphene design, the porous graphene channel structure introduces a large number of heterogeneous interfaces, causing multiple reflections and scattering of electromagnetic waves, extending their propagation path within the material, and enhancing energy attenuation, thereby synergistically enhancing absorption loss, resulting in a total shielding effectiveness of up to 73 dB.

[0045] Example 4 A method for preparing a mechanically-shielded integrated magnesium-based composite material, specifically including the following steps: (1) Preparation of porous graphene: Prepare an anhydrous ethanol dispersion of graphene oxide and sonicate for 30 min to ensure uniform dispersion of graphene oxide. The amount of graphene oxide added to the dispersion is 1 mg / mL. Add ferrocene to the anhydrous ethanol dispersion of graphene oxide at a mass ratio of 1:7. Continue sonication for 30 min to obtain a uniformly dispersed mixture. Place the mixture in a Teflon-lined autoclave, heat it to 180°C in a muffle furnace, keep it at that temperature for 4 h, and then cool it to room temperature. Filter to separate the solid material and use anhydrous ethanol. The ferrocene was cleaned and air-dried. It was then placed in a quartz tube and annealed at 900°C for 4 hours at a flow rate of 100 mL / min under a mixed atmosphere (5% hydrogen by volume, with the remainder being argon) to decompose the ferrocene into an iron / austenitic nanolayer, yielding graphene. The graphene was then immersed in a 10% HCl aqueous solution at 20°C for 1.2 hours to remove the nanolayer. The acid-etched porous graphene crude product was filtered and separated. Subsequently, it was annealed at 900°C for 40 minutes under an argon atmosphere to reduce graphene oxide, thus obtaining porous graphene.

[0046] (2) Ball milling treatment: 29.94g of pure magnesium powder and 0.06g of porous graphene were mixed to obtain a mixed powder (the content of porous graphene in the mixed powder was 0.2% by mass percentage, and the remainder was magnesium powder). The mixed powder was placed in a stainless steel ball mill jar and ball milled at 180rpm for 13h under an argon atmosphere with a ball-to-material ratio of 20:1 to obtain a uniform ball-milled powder.

[0047] (3) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 10 Pa. The sintering temperature was 600℃, the sintering pressure was 35MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0048] (4) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 20:1 to obtain a rectangular mechanical-shielding integrated magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm, namely a porous graphene-reinforced magnesium-based composite material.

[0049] The mechanical and electromagnetic shielding performance of the integrated mechanical-shielding magnesium-based composite material block prepared in Example 4 of this invention was tested. The composite material prepared in this example was processed into tensile specimens by wire cutting, and its room temperature tensile properties were tested, with a mechanical strength of 184 MPa. Electromagnetic shielding performance of the composite material block prepared in Example 4 was tested in the X-band (8.2-12.4 GHz). The test results showed that due to the porous graphene design, the porous graphene channel structure introduces a large number of heterogeneous interfaces, causing multiple reflections and scattering of electromagnetic waves, extending their propagation path within the material, and enhancing energy attenuation, thereby synergistically enhancing absorption loss, with a total shielding effectiveness of up to 68 dB.

[0050] Comparative Example 1 This comparative example uses the same method as Example 1 to prepare magnesium-based materials, the difference being that no porous graphene reinforcement is added in this comparative example.

[0051] (1) Ball milling treatment: Weigh 30g of pure magnesium powder and place it in a stainless steel ball mill jar. Under the conditions of ball-to-material ratio of 20:1 and argon atmosphere, use a planetary ball mill at 150rpm for 15h to obtain uniform ball-milled powder.

[0052] (2) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 8 Pa. The sintering temperature was 580℃, the sintering pressure was 30MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0053] (3) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 26:1 to obtain a rectangular magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm.

[0054] The composite material prepared in this comparative example was processed into a tensile specimen by wire cutting, and its room temperature tensile properties were tested. The mechanical property results are as follows: Figure 3 As shown, the mechanical strength is 165 MPa; and the shielding effectiveness of the composite material in the X-band (8.2-12.4 GHz) was measured using the waveguide method, with the shielding effectiveness results as follows. Figure 2 As shown, the electromagnetic shielding effectiveness is 37dB.

[0055] Comparative Example 1 did not add graphene reinforcement, thus lacking the dislocation hindrance mechanism brought by porous graphene. It could not induce the generation of nano-MgO at the interface to enhance the interfacial bonding, nor did it have the stress buffer and heterogeneous interface provided by the porous structure. As a result, its mechanical strength and electromagnetic shielding effectiveness were low, exhibiting the inherent low strength, poor plasticity and single shielding mechanism of pure magnesium matrix, which is mainly based on reflection.

[0056] Comparative Example 2 This comparative example uses the same method as Example 1 to prepare magnesium-based materials, the difference being that this comparative example adds a common graphene reinforcement.

[0057] (1) Ball milling treatment: 29.94g of pure magnesium powder and 0.06g of graphene powder were mixed to obtain a mixed powder (the content of graphene powder in the mixed powder was 0.2% by mass percentage, and the remainder was magnesium powder). The mixed powder was placed in a stainless steel ball mill jar and ball milled for 15 hours at 150rpm under an argon atmosphere with a ball-to-material ratio of 20:1 to obtain a uniform ball-milled powder.

[0058] (2) Sintering: The ball-milled powder was taken out in a vacuum glove box, and then a graphite mold was used to perform discharge plasma sintering under a vacuum of 8 Pa. The sintering temperature was 580℃, the sintering pressure was 30MPa, and the holding time was 15min, resulting in a sintered block with a diameter of 30mm and a thickness of about 25mm.

[0059] (3) Hot extrusion: After the surface of the sintered block is smoothed by sandpaper, it is hot extruded at 300℃ with an extrusion ratio of 26:1 to obtain a rectangular magnesium-based composite material with a width of about 11mm and a thickness of about 2.7mm, namely ordinary graphene-reinforced magnesium-based composite material.

[0060] The ordinary graphene-reinforced magnesium-based composite material prepared in this comparative example was processed into tensile specimens by wire cutting. Tensile tests were then conducted to determine its room temperature tensile properties. The mechanical property results are as follows: Figure 3 As shown, the mechanical strength is 192 MPa; and the shielding effectiveness of the porous graphene-reinforced magnesium composite material in the X-band (8.2-12.4 GHz) was measured using the waveguide method. The shielding effectiveness results are as follows. Figure 2 As shown, the electromagnetic shielding effectiveness is 66dB.

[0061] Although Comparative Example 2 added ordinary graphene reinforcement, it was not treated with acid solution corrosion and failed to form a porous structure. Therefore, the contact area between graphene and magnesium matrix was small, the number of nano-MgO induced at the interface was limited, the interfacial bonding strength was insufficient, and it lacked a large number of heterogeneous interfaces and polarization sites introduced by the porous structure. It could not effectively achieve multiple reflections, scattering and polarization loss of electromagnetic waves, resulting in poor mechanical strength and electromagnetic shielding effectiveness.

[0062] 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 mechanically-shielded integrated magnesium-based composite material, characterized in that, Specifically, the following steps are included: (1) Preparation of porous graphene: Graphene is prepared by etching it with an acid solution and then annealing it under an inert atmosphere. (2) Ball milling treatment: The porous graphene obtained in step (1) is mixed with magnesium powder to obtain a mixed powder. The mixed powder is ball milled to obtain a ball-milled powder. (3) Sintering and shaping: The ball-milled powder obtained in step (2) is subjected to discharge plasma sintering to obtain a sintered block; (4) Hot extrusion: The sintered block obtained in step (3) is hot extruded and cooled to obtain a mechanical-shielding integrated magnesium-based composite material.

2. The preparation method of the mechanical-shielding integrated magnesium-based composite material according to claim 1, characterized in that, The acid solution in step (1) is an aqueous HCl solution with a mass percentage concentration of 10%; the conditions for the acid solution to corrode the graphene are: immersing the graphene in the acid solution and corroding it at 20~28℃ for 0.5~1.2h; the conditions for the annealing treatment are: annealing at 900℃ for 20~40min.

3. The method for preparing the mechanical-shielding integrated magnesium-based composite material according to claim 1, characterized in that, The content of porous graphene in the mixed powder in step (2) is 0.2-1% by mass, and the remainder is magnesium powder.

4. The method for preparing the mechanical-shielding integrated magnesium-based composite material according to claim 1, characterized in that, The conditions for ball milling in step (2) are: ball ratio of 20:1, ball milling speed of 120~180 rpm, and ball milling for 13~17 hours.

5. The method for preparing the mechanical-shielding integrated magnesium-based composite material according to claim 1, characterized in that, The conditions for the discharge plasma sintering in step (3) are: sintering at a vacuum of 6~10Pa, a sintering temperature of 550~600℃, and a sintering pressure of 25~35MPa for 15min.

6. The method for preparing the mechanical-shielding integrated magnesium-based composite material according to claim 1, characterized in that, The conditions for hot extrusion in step (4) are: hot extrusion temperature of 300℃ and extrusion ratio of (12~26):

1.

7. The mechanical-shielding integrated magnesium-based composite material prepared by the method according to any one of claims 1 to 6.

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