A method for preparing a graphene double-layer heterostructure wave-absorbing structure based on fused deposition 3D printing

Abstract

The application discloses a method for preparing a graphene double-layer heterogeneous wave-absorbing structure based on fused deposition 3D printing, and relates to the technical field of wave-absorbing materials. The method comprises the following steps: original graphene is oxidized by adopting a Hummers method, and then macromolecular chains are grafted through derivative modification to obtain modified graphene; printing wire materials of a wave-transparent layer are prepared from the modified graphene; printing wire materials of a wave-absorbing layer are prepared from the original graphene and the modified graphene; the printing wire materials of the wave-transparent layer are used to print and prepare a wave-transparent layer cube with the modified graphene oriented along an X-0° direction, then the wave-transparent layer cube is cut perpendicularly to the X direction to obtain a flat plate with the modified graphene oriented along a Z-0° direction; and the flat plate is used as a substrate, and the printing wire materials of the wave-absorbing layer are used to print and prepare a wave-absorbing layer cube with the original graphene and the modified graphene both oriented along an X-Y direction on the substrate, so that the double-layer heterogeneous wave-absorbing structure is obtained. The structure of the application exhibits excellent wide-frequency wave-absorbing capacity under low graphene content, and has excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wave-absorbing materials, in particular to a method for preparing a graphene double-layer heterogeneous wave-absorbing structure based on fused deposition 3D printing. BACKGROUND

[0002] Graphene is considered as an efficient microwave absorber due to its high electrical conductivity, high specific surface area, high thermal conductivity and low density. However, the single component and structure of original graphene have poor impedance performance due to the electromagnetic incompatibility, and electromagnetic waves are almost reflected instead of being dissipated, resulting in extremely limited wave-absorbing performance. Common improvement methods are to modify the surface of graphene, such as loading magnetic particles and surface oxidation, or to construct special microstructures, such as porous structure and honeycomb structure, to improve the interface performance and introduce multiple reflections, so as to improve the wave-absorbing performance of the overall structure. However, the above improvement methods all rely on complex preparation processes and high graphene addition amount, resulting in poor mechanical performance of the prepared wave-absorbing component, and it is difficult to achieve wide-frequency and high-efficiency absorption of electromagnetic waves, which cannot meet the actual application requirements. Based on this, the present application proposes a method for preparing a graphene double-layer heterogeneous wave-absorbing structure based on fused deposition 3D printing to realize wide-frequency and high-efficiency absorption of electromagnetic waves at low graphene loading and maintain good mechanical performance. SUMMARY

[0003] The main purpose of the present application is to provide a method for preparing a graphene double-layer heterogeneous wave-absorbing structure based on fused deposition 3D printing, aiming to solve the technical problems that the existing wave-absorbing structure is difficult to achieve wide-frequency and high-efficiency absorption of electromagnetic waves and has poor mechanical performance.

[0004] To achieve the above-mentioned purpose, the present application proposes a method for preparing a graphene double-layer heterogeneous wave-absorbing structure based on fused deposition 3D printing, comprising the following steps:

[0005] The original graphene is subjected to oxidation treatment by Hummers method to obtain graphene oxide; and the graphene oxide is subjected to derivative modification by active oxygen-containing functional groups to graft macromolecular chains on the surface of the graphene oxide, thereby obtaining modified graphene;

[0006] The modified graphene, a thermoplastic matrix and a plasticizing agent are blended, and then dried and screw-extruded to obtain wave-transparent layer printing filaments; and wave-absorbing layer printing filaments are prepared from the original graphene and the modified graphene;

[0007] The wave-transparent layer printing filaments are used to prepare a wave-transparent layer cube by fused deposition 3D printing, the modified graphene in the wave-transparent layer cube is oriented along the X-0° direction, and the wave-transparent layer cube is cut vertically to the X direction to obtain a flat plate with the modified graphene oriented along the Z-0° direction, which is an upper wave-transparent structure;

[0008] Using the upper wave-transparent structure as a substrate, fused deposition modeling (FDM) is used to print a wave-absorbing layer cube on the substrate through the wave-absorbing layer printing filament. The original graphene and modified graphene in the wave-absorbing layer cube are oriented along the XY direction, thus obtaining a double-layer heterogeneous wave-absorbing structure.

[0009] Optionally, the step of oxidizing the raw graphene using the Hummers method to obtain graphene oxide includes:

[0010] After stirring and mixing the original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide, the mixture was heated in an oil bath to 75℃-85℃ and kept at that temperature for 4.5h-5.5h. After cooling naturally to room temperature, ice water was added for dilution, and the mixture was then filtered and washed until the pH reached 6.8-7.2. Finally, the mixture was dried at room temperature for 45h-50h to obtain pre-oxidized graphene.

[0011] The pre-oxidized graphene was added to concentrated sulfuric acid, followed by potassium permanganate. The mixture was stirred in an ice bath for 0.8-1.2 hours and reacted at 45-55°C for 8-72 hours. Then, it was placed in ice water and hydrogen peroxide was added for continuous stirring. When a bright yellow color appeared, the mixture was allowed to stand for 45-50 hours. The supernatant was discarded to obtain the lower precipitate. The lower precipitate was washed with deionized water and hydrochloric acid until the pH reached 6.8-7.2. The precipitate was then dried at room temperature for 45-50 hours to obtain graphene oxide.

[0012] Optionally, the step of derivatizing and modifying the graphene oxide by means of active oxygen-containing functional groups, thereby grafting macromolecular chains onto the surface of the graphene oxide to obtain modified graphene, includes:

[0013] The graphene oxide was added to anhydrous ethanol and ultrasonically dispersed for 25-35 minutes. Then, a silane coupling agent containing a large molecular chain was added and magnetically stirred. The mixture was heated in a water bath to 65-75°C and kept at that temperature for 8-12 hours. After cooling naturally to room temperature, the mixture was filtered and washed to remove ungrafted silane coupling agent. Finally, it was dried at room temperature for 45-50 hours to obtain modified graphene.

[0014] Optionally, the macromolecular chain includes one of an alkane chain, a siloxane chain, and a fluorine-containing chain.

[0015] Optionally, the step of blending the modified graphene, thermoplastic matrix, and plasticizer, followed by drying and screw extrusion to obtain the wave-transparent layer printing filament includes:

[0016] The modified graphene, thermoplastic matrix, and plasticizer were added to a mixer, along with grinding balls of different diameters, and the rotation speed was set to 45 r / min. -1 -55r·min -1 The mixing time is 6-10 hours to obtain the mixture;

[0017] After drying the mixture at 110℃-130℃ for 11h-13h, the mixture is added into a screw machine and extruded into a filament through different heating zones, and after cooling, the filament is wound around a reel by a traction wheel to obtain the wave-transparent layer printing filament;

[0018] wherein the temperatures of the different heating zones are set to 327℃, 339℃, 343℃, 346℃, 345℃, 343℃ and 341℃ respectively; the screw rotation speed in the screw machine is 30r·min -1 -40r·min -1 , and the winding speed is 9mm·s -1 -13mm·s -1 .

[0019] Optionally, in the step of drying and screw extruding the modified graphene, thermoplastic matrix and plasticizer to obtain the wave-transparent layer printing filament, the thermoplastic matrix comprises one of polylactic acid, ABS, nylon, polycarbonate, polyphenylene sulfide, polyetherimide, polyether ether ketone and polyether ketone ketone.

[0020] Optionally, in the step of drying and screw extruding the modified graphene, thermoplastic matrix and plasticizer to obtain the wave-transparent layer printing filament, the content of the modified graphene in the wave-transparent layer printing filament is 1wt%-20wt%.

[0021] Optionally, in the step of preparing the wave-absorbing layer printing filament from the original graphene and the modified graphene, the mass ratio of the original graphene to the modified graphene is (1-5):(6-9); and the total content of the original graphene and the modified graphene in the wave-absorbing layer printing filament is 1wt%-10wt%.

[0022] Optionally, in the step of preparing the wave-transparent layer cube from the wave-transparent layer printing filament by FDM 3D printing, and orienting the modified graphene in the wave-transparent layer cube along the X-0° direction, the step comprises:

[0023] drawing a model to be printed and slicing, determining a printing rate and a slice thickness, placing the wave-transparent layer printing filament in an FDM device, selecting a printing needle, starting printing according to a digital model along the X-0° direction to prepare a wave-transparent layer cube, and orienting the modified graphene in the wave-transparent layer cube along the X-0° direction;

[0024] wherein the diameter of the printing needle is set to 0.25mm-0.8mm.

[0025] Optionally, in the step of cutting the wave-transparent layer cube in the direction perpendicular to the X direction to obtain a flat plate with the modified graphene oriented in the Z-0° direction, the thickness of the flat plate is 0.5 mm-4 mm.

[0026] Optionally, in the step of taking the upper wave-transparent structure as a substrate, using fused deposition 3D printing, and preparing a wave-absorbing layer cube on the substrate by printing the wave-absorbing layer filament, so that the original graphene and the modified graphene in the wave-absorbing layer cube are both oriented in the X-Y direction, to obtain a double-layer heterogeneous wave-absorbing structure, the step includes:

[0027] placing the wave-absorbing layer filament in the FDM device, taking the upper wave-transparent structure as a substrate, selecting a printing needle, starting printing in the 0°+90° or 45° direction according to the digital model, preparing a wave-absorbing layer cube on the substrate, so that the original graphene and the modified graphene in the wave-absorbing layer cube are both oriented in the X-Y direction, and after printing is completed, placing the substrate upward, to obtain a double-layer heterogeneous wave-absorbing structure with the upper modified graphene oriented in the Z-0° direction and the lower original graphene and modified graphene both oriented in the X-Y direction;

[0028] wherein the diameter of the printing needle is set to 0.25 mm-0.8 mm, and the thickness of the wave-absorbing layer cube is 0.5 mm-4 mm.

[0029] The beneficial effects of the present application include:

[0030] By oxidizing and modifying the original graphene, the present application can not only break the large conjugated structure of the original graphene, regulate the conductivity of the original graphene, and introduce dipole polarization, but also introduce reaction sites to graft macromolecular chains, improve the problem of easy agglomeration between the original graphenes, further improve the orientation degree of the original graphenes in the printing direction, and improve the impedance matching of the original graphenes, thereby improving the wave-absorbing performance of the overall structure.

[0031] The present application constructs an upper wave-transparent structure with excellent impedance and conducive to the vertical orientation of graphene, which is a honeycomb-like structure, and a lower wave-absorbing structure with excellent wave-absorbing performance and in-plane longitudinal and lateral orientation of graphene, and the double-layer heterogeneous wave-absorbing structure composed of the two structures exhibits excellent wideband wave-absorbing ability at low graphene content and low thickness.

[0032] By vertically arranging the modified graphene as a wave-transparent channel, and benefiting from the excellent mechanical properties and dense composite structure of the modified graphene, the present application can make the overall structure have excellent mechanical properties compared with the traditional method of introducing voids or cavities, and can meet the use requirements of most scenes.

[0033] The application is prepared based on the principle of fused deposition 3D printing, and the structure design of the "wave-transparent" and "wave-absorbing" structure is flexible for optimization, which not only has high material utilization rate and less post-processing technology, but also can shorten the design and manufacturing cycle and reduce the production cost, and at the same time, various complex structures can be designed according to the service requirements, so as to realize flexible and efficient customization of the target component, and provide a fast way for the development and flexible batch production of the wave-absorbing component. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the drawings shown.

[0035] Figure 1 The modification process of the modified graphene described in the embodiments of the present application is shown in the schematic diagram.

[0036] Figure 2 The schematic diagram of the fused deposition 3D printing for preparing the double-layer heterogeneous wave-absorbing structure described in the embodiments of the present application is shown, wherein (a) is a schematic diagram of the lower layer original graphene and the modified graphene oriented along the X-Y direction; (b) is a schematic diagram of the upper layer modified graphene oriented along the Z-0° direction; (c) is a schematic diagram of the orientation of the original graphene and the modified graphene in the wave-absorbing layer printing wire material;

[0037] Figure 3 The schematic diagram of adding a roller device in the FDM device described in the embodiments of the present application is shown.

[0038] Figure 4 The schematic diagram of the effect of the double-layer heterogeneous wave-absorbing structure on electromagnetic waves is shown.

[0039] The implementation, functional characteristics and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] Currently, the common improvement method of graphene wave-absorbing structure is to modify the surface of graphene, such as loading magnetic particles, surface oxidation, or constructing special microstructure, such as porous structure, honeycomb structure, to improve the interface performance and introduce multiple reflections, so as to improve the overall structure of the wave-absorbing performance. However, the above improvement methods all depend on complex preparation process and high graphene addition amount, resulting in poor mechanical properties of the prepared wave-absorbing component, difficult to realize the wide frequency and efficient absorption of electromagnetic wave, and unable to meet the actual application requirements. The emerging additive manufacturing (3D printing) technology is based on the principle of discrete accumulation, which uses automatic control to accumulate materials layer by layer to realize the rapid manufacturing of complex parts, and has the advantages of flexible structure design, integrated processing and molding, high preparation precision and short preparation period, which provides a new way for the preparation of wave-absorbing parts with complex structure. Among them, the fused deposition 3D printing technology (FDM) is a method that melts various fusible filaments or granules through heating, and then solidifies them layer by layer on the machine printing platform to finally obtain a three-dimensional component. During the material melting and deposition process, the internal filler will be oriented along the path direction, forming an anisotropic special configuration, which provides a new way for the design and preparation of new wave-absorbing components.

[0042] In view of the technical problems existing in the prior art, the embodiment of the present application provides a method for preparing graphene double-layer heterostructure wave-absorbing structure based on fused deposition 3D printing, comprising the following steps:

[0043] S1, using Hummers method to oxidize the original graphene to obtain graphene oxide; then, the graphene oxide is derivatized and modified by active oxygen-containing functional groups to graft macromolecular chains on the surface of the graphene oxide, thereby obtaining modified graphene.

[0044] The present application uses Hummers method to oxidize the original graphene, thereby preparing graphene oxide with a large number of oxygen-containing functional groups on the surface of the conjugated structure which is partially destroyed. Then, the graphene oxide is derivatized and modified to introduce reaction sites on the surface of the graphene oxide to graft macromolecular chains, thereby regulating the conductivity of the original graphene, introducing dipole polarization, improving the problem of easy agglomeration of the original graphene, and further improving the orientation degree of the original graphene along the printing direction and the impedance matching of the original graphene, thereby improving the overall structure of the wave-absorbing performance.

[0045] Specifically, the Hummers method refers to a method of using inorganic strong protonic acid to treat the original graphene, so that the strong acid small molecules enter the interlayer of the graphene, and then a strong oxidizing agent is used for oxidation. The graphene oxide obtained by the Hummers method has a folded sheet structure and contains a large number of oxygen-containing functional groups, and has good dispersibility in aqueous solution. The original graphene is the first discovered two-dimensional material composed of one layer of carbon atom units without treatment.

[0046] The step of oxidizing the original graphene by the Hummers method to obtain the graphene oxide includes:

[0047] After the original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide are stirred and uniformly mixed, oil bath heating is performed to 75-85 DEG C and kept for 4.5-5.5 h, then natural cooling to room temperature, ice water is added for dilution, then suction filtration and washing to pH 6.8-7.2, drying at room temperature for 45-50 h to obtain the pre-oxidized graphene;

[0048] The pre-oxidized graphene is added into concentrated sulfuric acid, then potassium permanganate is added, ice bath stirring is performed for 0.8-1.2 h, and then reaction is performed at 45-55 DEG C for 8-72 h, then the mixture is placed in ice water, hydrogen peroxide is added for continuous stirring, when bright yellow color appears, standing for 45-50 h, then the supernatant is discarded, the lower precipitate is obtained, the lower precipitate is washed by deionized water and hydrochloric acid respectively to pH 6.8-7.2, drying at room temperature for 45-50 h to obtain the graphene oxide.

[0049] Further, the step of derivatizing the graphene oxide by active oxygen-containing functional groups to graft macromolecular chains on the surface of the graphene oxide to obtain the modified graphene includes:

[0050] The graphene oxide is added into anhydrous ethanol, ultrasonic dispersion is performed for 25-35 min, then the silane coupling agent containing macromolecular chains is added and magnetic stirring is performed, water bath heating is performed to 65-75 DEG C and kept for 8-12 h, then natural cooling to room temperature, then suction filtration and washing to remove the ungrafted silane coupling agent, drying at room temperature for 45-50 h to obtain the modified graphene.

[0051] The grafted macromolecular chains include one of alkane chain, siloxane molecular chain and fluorine-containing molecular chain, preferably the fluorine-containing molecular chain.

[0052] S2, after the modified graphene, the thermoplastic matrix and the plasticizing agent are blended, drying and screw extrusion are performed to obtain the wave-transparent layer printing filament; then the original graphene and the modified graphene are used to prepare the wave-absorbing layer printing filament.

[0053] In the specific implementation process, the step of blending the modified graphene, the thermoplastic matrix and the plasticizing agent, then drying and screw extruding to obtain the wave-transparent layer printing filament includes:

[0054] The modified graphene, the thermoplastic matrix and the plasticizing agent are added into a mixer, grinding balls with different diameters are added, the rotation speed is set to 45-55 r·min -1 -55r·min -1 , and the mixing time is 6-10 h to obtain the mixed material;

[0055] After drying the mixture at 110℃-130℃ for 11h-13h, the mixture is added into a screw machine and extruded into a filament through different heating zones, and after cooling, the filament is wound around a reel by a traction wheel to obtain the wave-transparent layer printing filament;

[0056] wherein the temperatures of the different heating zones are set as 327℃, 339℃, 343℃, 346℃, 345℃, 343℃ and 341℃ respectively; the rotation speed of the screw in the screw machine is 30r·min -1 -40r·min -1 , and the winding speed is 9mm·s -1 -13mm·s -1 .

[0057] Specifically, the thermoplastic matrix includes one of polylactic acid, ABS, nylon, polycarbonate, polyphenylene sulfide, polyetherimide, polyether ether ketone and polyether ketone ketone, which can be selected according to the temperature and environmental use requirements. The plasticizer can be selected from N-butylbenzenesulfonamide and phthalate.

[0058] wherein the content of the modified graphene in the wave-transparent layer printing filament is 1wt%-20wt%, preferably 2.4wt%.

[0059] In the specific implementation process, the step of preparing the wave-absorbing layer printing filament from the original graphene and the modified graphene includes:

[0060] After blending the original graphene, the modified graphene, the thermoplastic matrix and the plasticizer, drying and screw extrusion are performed, wherein the steps of blending, drying and screw extrusion are the same as those for preparing the wave-transparent layer printing filament.

[0061] wherein the mass ratio of the original graphene to the modified graphene is (1-5):(6-9), preferably 1:9; and the total content of the original graphene and the modified graphene in the wave-absorbing layer printing filament is 1wt%-10wt%, preferably 1.5wt%.

[0062] S3, a wave-transparent layer cube is prepared from the wave-transparent layer printing filament by fused deposition 3D printing, so that the modified graphene in the wave-transparent layer cube is oriented along the X-0° direction, and the wave-transparent layer cube is cut perpendicular to the X direction to obtain a flat plate with the modified graphene oriented along the Z-0° direction, which is the upper wave-transparent structure.

[0063] In the specific implementation process, the step of preparing the wave-transparent layer cube from the wave-transparent layer printing filament by fused deposition 3D printing, so that the modified graphene in the wave-transparent layer cube is oriented along the X-0° direction, includes:

[0064] The model to be printed is drawn by Materialise Magics software, then sliced by Cura software to determine the printing rate and slice thickness, the wave-transparent layer printing wire is placed in the FDM device, the printing needle is selected, and the wave-transparent layer cubic is prepared by starting printing along the X-0° direction according to the digital model, and the modified graphene in the wave-transparent layer cubic is oriented along the X-0° direction.

[0065] Preferably, the diameter of the printing needle is 0.25mm-0.8mm, preferably 0.6mm; and the thickness of the flat plate is 0.5mm-4mm, preferably 1.2mm.

[0066] The application arranges the modified graphene vertically to the plane as a "wave-transparent" channel, thereby obtaining a "honeycomb wave-transparent" structure with excellent upper layer impedance and facilitating electromagnetic wave incidence, and benefiting from the excellent mechanical properties and dense composite structure of the modified graphene, which can make the overall structure have excellent mechanical properties compared with the traditional method of introducing voids or cavities.

[0067] In the specific implementation process, a roller pressing device can be added to the FDM device, as shown in Figure 3 As shown, by pressing the wave-transparent layer printing wire, the orientation degree of the modified graphene in the wave-transparent layer printing wire along the plane can be improved, and the interlayer bonding force can be improved, thereby increasing the excellent mechanical properties and density of the upper layer wave-transparent structure.

[0068] S4, taking the upper layer wave-transparent structure as a substrate, using fused deposition 3D printing, preparing a wave-absorbing layer cubic on the substrate by the wave-absorbing layer printing wire, so that the original graphene and the modified graphene in the wave-absorbing layer cubic are oriented along the X-Y direction, that is, a double-layer heterogeneous wave-absorbing structure is obtained.

[0069] In the specific implementation process, the wave-absorbing layer printing wire is placed in the FDM device, the upper layer wave-transparent structure is taken as a substrate, the printing needle is selected, and the wave-absorbing layer cubic is prepared on the substrate by starting printing along the 0°+90° or 45° direction according to the digital model, so that the original graphene and the modified graphene in the wave-absorbing layer cubic are oriented along the X-Y direction, and after printing is completed, the substrate is placed upward, that is, a double-layer heterogeneous wave-absorbing structure with the upper layer modified graphene oriented along the Z-0° direction and the lower layer original graphene and modified graphene oriented along the X-Y direction is obtained.

[0070] Preferably, the diameter of the printing needle is 0.25mm-0.8mm, preferably 0.8mm, and the thickness of the wave-absorbing layer cubic is 0.5mm-4mm, preferably 1.6mm.

[0071] The application utilizes the characteristics of FDM to first prepare a certain thickness of a cube with modified graphene oriented in the X-0° direction, then cut perpendicular to the X direction to obtain a certain thickness of a flat plate with the modified graphene oriented in the Z-0° direction, forming a wave-transparent structure similar to a honeycomb, then continue to print a certain thickness of a wave-absorbing structure containing original graphene and modified graphene on the flat plate as a substrate, with a path of 0°+90° or 45°, after printing, the workpiece is taken out and the substrate is placed upwards, thereby obtaining a "wave-transparent-wave-absorbing" double-layer heterostructure with the upper layer of graphene oriented in the Z-0° direction and the lower layer of graphene oriented in the X-Y direction, the upper layer of graphene of the double-layer heterostructure is vertically oriented, which is conducive to electromagnetic wave incidence and has excellent impedance, and the lower layer of graphene is in-plane oriented longitudinally and transversely, which has excellent wave-absorbing performance, thereby realizing wide-frequency and high-efficiency absorption of electromagnetic waves under low graphene load and maintaining good mechanical properties of the structure. The double-layer heterostructure is prepared by using the principle of additive manufacturing, which not only has high material utilization and less post-processing process, can shorten the design and manufacturing cycle and reduce production costs, but also can design various complex structures according to service requirements, thereby realizing flexible and efficient customization of target components.

[0072] It should be noted that the method is not only suitable for a variety of low-dielectric thermoplastic substrates, but also suitable for low-dielectric ceramic matrix composites formed by precursor transformation, such as wave-absorbing silicon oxide, silicon nitride and aluminum oxide.

[0073] In addition, the application is not only suitable for fused deposition 3D printing, but also suitable for a variety of additive manufacturing processes, such as ink direct writing forming wave-absorbing polyvinyl alcohol. At the same time, in addition to using wire as the printing raw material, it can also be formed by granular material fused deposition.

[0074] The above technical solutions of the application will be described in detail below in combination with specific embodiments.

[0075] Embodiment 1

[0076] A method for preparing a graphene double-layer heterostructure wave-absorbing structure based on fused deposition 3D printing, comprising the following steps:

[0077] S1, modification of original graphene.

[0078] As shown in Figure 1 , the original graphene is oxidized according to the improved Hummers method. The oxidation process mainly has two stages:

[0079] Pre-oxidation stage: add original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide into a beaker and stir, heat to 80℃ in an oil bath and keep for 5h, naturally cool to room temperature, slowly add 500mL ice water for dilution, finally extract and wash to pH 7, and dry at room temperature for 48h to obtain pre-oxidized graphene.

[0080] Oxidation stage: the above pre-oxidized graphene is added into 120 mL of concentrated sulfuric acid, 9 g of potassium permanganate is slowly added, stirred in an ice bath for 1 h, the temperature is adjusted to 50 DEG C and reacted for 12 h. The product obtained is put into ice water, appropriate hydrogen peroxide is added and stirred constantly, when the solution color starts to show bright yellow, it can be left to stand for 48 h and the supernatant is poured off, the lower layer of precipitate is washed with deionized water and hydrochloric acid respectively to make the pH about 7, and dried at room temperature for 48 h to obtain the desired graphene oxide.

[0081] The graphene oxide is further modified by active oxygen-containing functional groups, 3 g of graphene oxide is added into 500 mL of anhydrous ethanol, dispersed by ultrasonic for 30 min, then 500 mg of fluorine-containing silane coupling agent is added and magnetically stirred, heated to 70 DEG C in a water bath for 10 h, naturally cooled to room temperature, finally filtered and washed to remove the ungrafted coupling agent, and dried at room temperature for 48 h to obtain the modified graphene.

[0082] S2, preparation of printing filaments.

[0083] Preparation of wave-transparent layer printing filaments:

[0084] The modified graphene, polyether ether ketone and plasticizer are added into the mixing cylinder of the V-type mixer, and grinding balls of different diameters are added, the driving motor is started, and the parameters are set as follows: rotation speed 50 r·min -1 , mixing time 8 h, and the mixed material is taken out from the discharge port after mixing is completed; since the powder mixing time is as long as 8 h, in order to ensure the quality of the extruded filaments, the mixed material needs to be dried, the drying temperature is set to 120 DEG C, and the drying time is set to 12 h; then the blended and dispersed and dried mixed material is added into the feeding port of the screw machine, the solid state is changed to glass state and then to viscous flow state through different heating zones, and finally the required composite material filaments are extruded from the die, cooled by the air cooling tank, wound by the traction wheel, and then the wave-transparent layer printing filaments are obtained.

[0085] The temperature of different heating zones is set to 327 DEG C, 339 DEG C, 343 DEG C, 346 DEG C, 345 DEG C, 343 DEG C and 341 DEG C respectively; the rotation speed of the screw is 35 r·min -1 , and the winding speed is 11 mm·s -1 ; the content of the modified graphene in the wave-transparent layer printing filaments is 2.4 wt%.

[0086] Preparation of wave-absorbing layer printing filaments:

[0087] The original graphene, modified graphene, polyether ether ketone and plasticizer are added into the mixing cylinder of the V-type mixer, and the remaining steps are the same as those for preparing the wave-transparent layer printing filaments.

[0088] The mass ratio of the original graphene and the modified graphene is 1:9; the total content of the original graphene and the modified graphene in the wave-absorbing layer printing filament is 1.5wt%.

[0089] S3, fused deposition 3D printing of the upper wave-transparent structure.

[0090] The model to be printed is drawn by Materialise Magics software, and then sliced by Cura software; before printing, the wave-transparent layer printing filament needs to be tested for printability to determine the appropriate printing rate and slice thickness; the wave-transparent layer printing filament is placed in the FDM device, the nozzle diameter is selected to be 0.6mm, and according to the digital model, printing is started along the X-0° direction to prepare a cube with a certain thickness of the modified graphene oriented along the X-0° direction, and then the printed cube is cut perpendicular to the X direction to obtain a flat plate with a thickness of 1.2mm, in which the modified graphene is oriented along the Z-0° direction.

[0091] S4, fused deposition 3D printing of the lower wave-absorbing structure.

[0092] As shown in Figure 2 , the wave-absorbing layer printing filament is placed in the FDM device, the upper wave-transparent structure is used as the substrate, the nozzle diameter is selected to be 0.8mm, and according to the digital model, printing is started along the 45° direction to prepare a cube with a thickness of 1.6mm in which the original graphene and the modified graphene are both oriented along the X-Y direction, i.e. the lower wave-absorbing structure; after printing, the workpiece is taken out and the substrate is placed upward to obtain a "wave-transparent-wave-absorbing" heterostructure in which the upper modified graphene is oriented along the Z-0° direction and the lower original graphene and modified graphene are both oriented along the X-Y direction, and the action process of the electromagnetic wave on the heterostructure is as shown in Figure 4 .

[0093] After testing, the tensile strength of the double-layer hetero wave-absorbing structure reaches 104MPa, and the bending strength reaches 134MPa, which has excellent mechanical properties, far superior to conventional porous structures.

[0094] Test Example

[0095] The wave-absorbing ability of the upper wave-transparent structure, the lower wave-absorbing structure and the double-layer hetero wave-absorbing structure prepared according to the method described in Example 1 and the graphene wave-absorbing structure prepared by the traditional method are tested respectively, and the test results are shown in Table 1.

[0096] Table 1

[0097]

[0098] Note: The smaller the reflection loss (RL), the stronger the ability of the wave-absorbing material to absorb electromagnetic waves, i.e. the higher the degree of reduction of electromagnetic wave interference.

[0099] As shown in Table 1, the double-layer heterogeneous wave-absorbing structure of the application exhibits excellent broadband wave-absorbing capacity at low graphene content (2.4wt% in the upper layer + 1.5wt% in the lower layer) and low thickness (1.2mm in the upper layer + 1.6mm in the lower layer), the reflection loss is less than -10dB in the 8GHz-18GHz band, achieving full absorption in the band, and the effective wave-absorbing (RL<-10dB) bandwidth can reach 8.2GHz, compared with the traditional wave-absorbing structure, the broadband wave-absorbing capacity of the double-layer heterogeneous wave-absorbing structure is significantly improved.

[0100] The above is only an optional embodiment of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made by using the content of the application specification and drawings, or directly / indirectly applied in other related technical fields within the inventive concept of the application are included in the patent protection scope of the application.

Claims

1. A method for preparing a graphene double-layer heterostructure wave-absorbing structure based on fused deposition 3D printing, characterized in that, The method comprises the following steps: The original graphene is oxidized by a Hummers method to obtain graphene oxide; the graphene oxide is modified by active oxygen-containing functional groups to graft macromolecular chains on the surface of the graphene oxide, thereby obtaining modified graphene; The modified graphene, a thermoplastic matrix and a plasticizer are blended, dried and screw-extruded to obtain a wave-transparent layer printing filament; a wave-absorbing layer printing filament is prepared from the original graphene and the modified graphene; A wave-transparent layer cube is prepared from the wave-transparent layer printing filament by a fused deposition 3D printing method, the modified graphene in the wave-transparent layer cube is oriented along an X-0° direction, and the wave-transparent layer cube is cut perpendicularly to the X direction to obtain a flat plate in which the modified graphene is oriented along a Z-0° direction, which is an upper wave-transparent structure; A wave-absorbing layer cube is prepared on the substrate by the wave-absorbing layer printing filament through a fused deposition 3D printing method, the original graphene and the modified graphene in the wave-absorbing layer cube are oriented along an X-Y direction, thereby obtaining a double-layer heterostructure wave-absorbing structure.

2. The method for fabricating graphene double-layer hetero-structure wave-absorbing structure based on fused deposition 3D printing according to claim 1, characterized in that, The step of oxidizing the original graphene by the Hummers method to obtain graphene oxide comprises: The original graphene, concentrated sulfuric acid, potassium persulfate and phosphorus pentoxide are stirred and uniformly mixed, heated to 75-85 DEG C in an oil bath and kept for 4.5-5.5 hours, naturally cooled to room temperature, diluted by adding ice water, filtered and washed until the pH is 6.8-7.2, and dried at room temperature for 45-50 hours to obtain pre-oxidized graphene; The pre-oxidized graphene is added to concentrated sulfuric acid, potassium permanganate is added, stirred in an ice bath for 0.8-1.2 hours, reacted at 45-55 DEG C for 8-72 hours, placed in ice water, continuously stirred by adding hydrogen peroxide, and when a bright yellow color appears, the mixture is left to stand for 45-50 hours, the supernatant is discarded, and the lower precipitate is washed with deionized water and hydrochloric acid until the pH is 6.8-7.2, and dried at room temperature for 45-50 hours to obtain graphene oxide.

3. The method for fabricating graphene double-layer hetero-structure wave-absorbing structure based on FDM 3D printing according to claim 1, characterized in that, The step of modifying the graphene oxide by active oxygen-containing functional groups to graft macromolecular chains on the surface of the graphene oxide to obtain modified graphene comprises: The graphene oxide is added to anhydrous ethanol, ultrasonically dispersed for 25-35 minutes, a silane coupling agent containing macromolecular chains is added and magnetically stirred, heated to 65-75 DEG C in a water bath and kept for 8-12 hours, naturally cooled to room temperature, filtered and washed to remove ungrafted silane coupling agent, and dried at room temperature for 45-50 hours to obtain modified graphene.

4. The method for fabricating graphene double-layer hetero-structured wave-absorbing structure based on FDM 3D printing according to claim 1 or 3, characterized in that, The macromolecular chains comprise one of an alkane chain, a siloxane molecular chain and a fluorine-containing molecular chain.

5. The method for fabricating graphene double-layer hetero-structure wave-absorbing structure based on FDM 3D printing according to claim 1, wherein, The step of blending the modified graphene, a thermoplastic matrix and a plasticizer, drying and screw-extruding to obtain a wave-transparent layer printing filament comprises: The modified graphene, thermoplastic matrix and plasticizer are added into a mixer, and grinding balls with different diameters are added, and the rotating speed is set to 45 r·min -1 - 55 r·min -1 , and the mixing time is 6 h-10 h to obtain a mixture; The mixture is dried at 110-130 DEG C for 11-13 hours, added to a screw machine and extruded through different heating zones to obtain a wave-transparent layer printing filament, which is wound around a traction wheel after cooling. Wherein, the temperature of different heating zones are set as: 327℃, 339℃, 343℃, 346℃, 345℃, 343℃ and 341℃ respectively; the screw rotation speed in the screw machine is 30r·min -1 -40r·min -1 , and the winding speed is 9mm·s -1 -13mm·s -1 .

6. The method for fabricating graphene double-layer hetero-structured wave-absorbing structure based on FDM 3D printing according to claim 1 or 5, characterized in that, In the step of blending the modified graphene, the thermoplastic matrix and the plasticizer, and then drying and screw extruding to obtain the printed filament of the wave-transparent layer, the thermoplastic matrix comprises one of polylactic acid, ABS, nylon, polycarbonate, polyphenylene sulfide, polyetherimide, polyether ether ketone and polyether ketone ketone.

7. The method for fabricating graphene double-layer hetero-structured wave-absorbing structure based on fused deposition 3D printing according to claim 1 or 5, characterized in that, In the step of blending the modified graphene, the thermoplastic matrix and the plasticizer, and then drying and screw extruding to obtain the printed filament of the wave-transparent layer, the content of the modified graphene in the printed filament of the wave-transparent layer is 1wt%-20wt%.

8. The method for fabricating graphene double-layer hetero-structure wave-absorbing structure based on FDM 3D printing according to claim 1, wherein, In the step of preparing the printed filament of the wave-absorbing layer from the original graphene and the modified graphene, the mass ratio of the original graphene to the modified graphene is (1-5):(6-9), and the total content of the original graphene and the modified graphene in the printed filament of the wave-absorbing layer is 1wt%-10wt%.

9. The method for fabricating graphene double-layer hetero-structured wave-absorbing structure based on FDM 3D printing according to claim 1, wherein, In the step of preparing the wave-transparent layer cube from the printed filament of the wave-transparent layer by the fused deposition 3D printing, and orienting the modified graphene in the wave-transparent layer cube along the X-0° direction, the step comprises: drawing a model to be printed and slicing, determining a printing rate and a slice thickness, placing the printed filament of the wave-transparent layer in an FDM device, selecting a printing needle, starting printing according to a digital model along the X-0° direction to prepare the wave-transparent layer cube, and orienting the modified graphene in the wave-transparent layer cube along the X-0° direction; wherein the diameter of the printing needle is set to 0.25mm-0.8mm.

10. The method for fabricating graphene double-layer hetero-structured wave-absorbing structure based on fused deposition 3D printing according to claim 1, wherein, In the step of cutting the wave-transparent layer cube perpendicularly to the X direction to obtain a flat plate with the modified graphene oriented along the Z-0° direction, the thickness of the flat plate is 0.5mm-4mm.

11. The method of claim 1, wherein the graphene double-layer heterostructure is prepared by fused deposition 3D printing. In the step of preparing the wave-absorbing layer cube on the substrate from the printed filament of the wave-absorbing layer by the fused deposition 3D printing, and orienting the original graphene and the modified graphene in the wave-absorbing layer cube along the X-Y direction, i.e. obtaining the double-layer heterogeneous wave-absorbing structure, the step comprises: placing the printed filament of the wave-absorbing layer in an FDM device, selecting a printing needle, starting printing according to a digital model along the 0°+90° or 45° direction to prepare the wave-absorbing layer cube on the substrate, orienting the original graphene and the modified graphene in the wave-absorbing layer cube along the X-Y direction, and placing the substrate upward after printing, i.e. obtaining the double-layer heterogeneous wave-absorbing structure with the upper modified graphene oriented along the Z-0° direction and the lower original graphene and modified graphene oriented along the X-Y direction; wherein the diameter of the printing needle is set to 0.25mm-0.8mm, and the thickness of the wave-absorbing layer cube is 0.5mm-4mm.

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