A direct writing preparation method for multi-layer gradient absorbing material ink

Abstract

This invention belongs to the field of radar wave absorbing material preparation, and particularly relates to a direct-write method for preparing multilayer gradient absorbing materials. This invention prepares environmentally friendly water-based GO highly conductive ink and GO magnetic ink. The direct-write method enables the preparation of lightweight multilayer absorbing materials. Surface treatment of the nano-magnetic and nano-conductive particles to coat their surfaces with -NH2 improves their dispersion uniformity in the GO slurry and allows them to form bonds with the -COOH and -OH functional groups on the GO surface, improving the printability of the slurry. The magnetic material undergoes a gradient structure design; the spacing between the upper layer filaments is 0.8–1.5 mm, improving the impedance matching of the air interface and facilitating the entry of electromagnetic waves into the material; the spacing between the lower layer filaments is 0.5–1.0 mm, which facilitates electromagnetic wave attenuation and improves the material's absorption performance. The apparent density of the multilayer absorbing material prepared by this method is 0.3–1 g / cm³. 3 It has a microwave absorption performance of -20dB at 2mm, making it a lightweight microwave absorbing material.

Description

Technical Field

[0001] This invention belongs to the field of radar wave absorbing material preparation, and particularly relates to a method for preparing multilayer gradient radar wave absorbing material ink by direct writing. Background Technology

[0002] With the increasing integration of electronic devices and the continuous improvement of power density, the electromagnetic compatibility issues of electronic devices are becoming increasingly serious. Therefore, radar wave absorbing materials are needed to attenuate and absorb excess incident electromagnetic waves. Through the material's own electrical and magnetic loss capabilities, electromagnetic energy can be converted into heat energy to ensure the normal operation of electronic devices.

[0003] While traditional microwave absorbing coatings offer excellent absorption performance, their high absorber content and density make them unsuitable for the miniaturization, integration, and lightweighting demands of electronic devices. Furthermore, increasing the absorption bandwidth often requires composites of two or even multiple layers, adding to the complexity of the fabrication process. Therefore, it is necessary to explore new methods for preparing microwave absorbing materials. Summary of the Invention

[0004] The main objective of this invention is to propose a method for preparing and applying multilayer gradient structure microwave absorbing materials, in order to solve some of the aforementioned problems.

[0005] The technical solution of this invention: a method for direct writing preparation of ink for multilayer gradient microwave absorbing materials, characterized by comprising the following steps:

[0006] S1: Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material and the Hummers method.

[0007] S2: Collect the graphene oxide dispersion from step S1, heat and stir at 58-62℃, and centrifuge to obtain graphene oxide slurry;

[0008] S3: Nano-conductive particles and nano-magnetic particles are added to an ethanol / water mixed solution and ultrasonically dispersed. Then, silane coupling agent KH-550 is added dropwise. Under argon protection, the temperature is raised to 75-80℃ and reacted for 2-4 hours. After overnight aging, the mixture is filtered, washed, and dried to obtain modified conductive particles and modified magnetic particles.

[0009] S4: Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar and ground until they are evenly mixed. The mixture is then heated at 60℃~65℃ for 30min~1h to obtain graphene oxide slurry. Graphene oxide slurry and modified conductive particles are added to a quartz mortar and ground until they are evenly mixed to obtain graphene oxide conductive ink. GO slurry and modified magnetic particles are added to a quartz mortar and ground until they are evenly mixed to obtain graphene oxide magnetic ink.

[0010] S5: Fill the graphene oxide conductive ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the A controller of the three-axis ink direct writing machine, set the spacing between 1-2 layers of filaments to 0.5mm and input it into the direct writing machine control software, adjust the needle inner diameter, ink extrusion pressure and printing speed, and print to obtain the required lower layer conductive material;

[0011] S6: Fill the printing syringe with graphene oxide magnetic ink, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the B controller of the three-axis ink direct writing machine, set the spacing between 3-4 layers of filaments to 0.5-1mm, and the spacing between 5-6 layers of filaments to 0.8-1.5mm, input the information into the direct writing machine control software, adjust the needle inner diameter, ink extrusion pressure, and printing speed, and print to obtain the required upper layer gradient structure material;

[0012] S7: The multilayer gradient material obtained by printing graphene oxide is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80℃~90℃ for 6-8 hours to obtain the multilayer gradient structure material.

[0013] In step S2, the centrifugation speed is 8000-10000 rpm, and the solid content of the graphene oxide slurry is 2-4 wt%.

[0014] In step S3, the volume ratio of ethanol to water is 1:1 to 1:2, and the molar ratio of nanoparticles to KH-550 is 1:3 to 1:5.

[0015] In step S4, the solid content of the GO conductive ink is 15-25 wt%, wherein the ratio of GO to nano-conductive particles is 7:3, and the nano-conductive particles are Ag nanoparticles, Cu nanoparticles, and Al nanoparticles; the solid content of the GO magnetic ink is 20-35 wt%, wherein the ratio of GO to nano-magnetic particles is 9:1-7:3, and the nano-magnetic particles are Ni nanoparticles, γ-Fe2O3 nanoparticles, and Fe3O4 nanoparticles.

[0016] Whether the printed structure is formed in step S5 is affected by the rheological properties of the ink, the inner diameter of the needle, the ink extrusion pressure, and the printing speed; the inner diameter of the printing needle is 200-500μm, the ink extrusion pressure is 15-25psi, and the printing speed is 10-30mm / s.

[0017] In step S6, the needle inner diameter is 300-500 μm, the ink extrusion pressure is 20-30 psi, and the printing speed is 10-30 mm / s.

[0018] The multilayer absorbing material is a lightweight absorbing material.

[0019] The apparent density of the multilayer absorbing material is 0.3 to 1 g / cm3, and its wave absorption performance can reach -20 dB at a thickness of 2 mm.

[0020] The conductive nanoparticles and magnetic nanoparticles have a particle size of 500 nm to 1 μm.

[0021] The technical advantages of this invention are as follows: This invention utilizes graphene oxide, a two-dimensional independent sheet material, and leverages the abundant -OH and -COOH functional groups on its sheet surface to hybridize it with conductive and magnetic nanoparticles to prepare microwave absorbing ink. Through multi-layer gradient structure design, the microwave absorption performance of the material is enhanced. Finally, using ink direct writing technology, the multi-layer gradient structure microwave absorbing material is printed, achieving the preparation of a lightweight and efficient multi-layer gradient structure microwave absorbing material.

[0022] Overall, the technical solution of the present invention has the following beneficial effects compared with the prior art:

[0023] (1) This invention prepares environmentally friendly water-based GO highly conductive ink and GO magnetic ink, and realizes the preparation of lightweight multilayer microwave absorbing materials by ink direct writing method;

[0024] (2) Surface treatment of nano-magnetic particles and nano-conductive particles to coat their surfaces with -NH2 improves their dispersion uniformity in GO paste and enables them to form bonds with -COOH and -OH functional groups on the GO surface, thereby improving the printability of the paste.

[0025] (3) Gradient structure design of magnetic materials (e.g.) Figure 1 , Figure 2 As shown, the spacing between the upper filaments is 0.8–1.5 mm, which improves the impedance matching of the air interface of the absorbing material and facilitates the entry of electromagnetic waves into the material; the spacing between the lower filaments is 0.5–1.0 mm, which is beneficial for the attenuation and loss of electromagnetic waves and improves the absorption performance of the material.

[0026] (4) The apparent density of the multilayer absorbing material prepared by this method is 0.3–1 g / cm³. 3 The absorption performance can reach -20dB at 2mm (e.g., Figure 3 As shown, it is a lightweight microwave absorbing material. Attached Figure Description

[0027] Figure 1 Schematic diagram of a multi-layer gradient structure;

[0028] Figure 2 Schematic diagram of a multi-layered gradient structure cross-section;

[0029] Figure 3 Reflectivity of multi-layer gradient structure absorbing materials. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings:

[0031] A method for preparing multilayer gradient microwave absorbing material ink by direct writing, characterized by comprising the following steps:

[0032] S1: Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material and the Hummers method.

[0033] S2: Collect the graphene oxide dispersion from step S1, heat and stir at 58-62°C, and centrifuge to obtain graphene oxide slurry; the centrifugation speed is 8000-10000 rpm, and the solid content of the graphene oxide slurry is 2-4 wt%.

[0034] S3: Conductive and magnetic nanoparticles were added to an ethanol / water mixture and ultrasonically dispersed. Then, silane coupling agent KH-550 was added dropwise. The mixture was reacted at 75–80°C for 2–4 hours under argon protection, aged overnight, filtered, washed, and dried to obtain modified conductive and magnetic particles. The ethanol / water volume ratio was 1:1–1:2, and the molar ratio of nanoparticles to KH-550 was 1:3–1:5. The particle size of the conductive and magnetic nanoparticles was 500 nm–1 μm.

[0035] S4: Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar and ground until homogeneous. The mixture is then heated at 60℃~65℃ for 30min~1h to obtain graphene oxide slurry. Graphene oxide slurry and modified conductive particles are added to a quartz mortar and ground until homogeneous to obtain graphene oxide conductive ink. GO slurry and modified magnetic particles are added to a quartz mortar and ground until homogeneous to obtain graphene oxide magnetic ink. The GO conductive ink has a solid content of 15~25wt%, where the GO:nanoconductive particle ratio is 7:3, and the nanoconductive particles are Ag nanoparticles, Cu nanoparticles, and Al nanoparticles. The GO magnetic ink has a solid content of 20~35wt%, where the GO:nanomagnetic particle ratio is 9:1~7:3, and the nanomagnetic particles are Ni nanoparticles, γ-Fe2O3 nanoparticles, and Fe3O4 nanoparticles.

[0036] S5: Graphene oxide conductive ink is filled into a printing syringe. Air bubbles are removed from the ink using a planetary vacuum degassing machine. The syringe is then installed into the A controller of a three-axis ink direct-write machine. The spacing between the 1-2 layers of filaments is set to 0.5mm and input into the direct-write machine control software. The needle inner diameter, ink extrusion pressure, and printing speed are adjusted to print the desired lower conductive material. The formation of the printed structure is affected by the ink rheological properties, needle inner diameter, ink extrusion pressure, and printing speed. The needle inner diameter for printing is 200-500μm, the ink extrusion pressure is 15-25psi, and the printing speed is 10-30mm / s.

[0037] S6: Graphene oxide magnetic ink is filled into a printing syringe. Air bubbles are removed from the ink using a planetary vacuum degassing machine. The syringe is then installed into the B controller of a three-axis ink direct-write machine. The spacing between the 3rd and 4th layer filaments is set to 0.5–1 mm, and the spacing between the 5th and 6th layer filaments is set to 0.8–1.5 mm. This information is input into the direct-write machine control software. The needle inner diameter, ink extrusion pressure, and printing speed are adjusted to obtain the desired upper-layer gradient structure material. The needle inner diameter is 300–500 μm, the ink extrusion pressure is 20–30 psi, and the printing speed is 10–30 mm / s.

[0038] S7: The multilayer gradient material obtained by printing graphene oxide is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80℃~90℃ for 6-8 hours to obtain the multilayer gradient structure material.

[0039] The multilayer gradient absorbing material is a lightweight absorbing material with an apparent density of 0.3 to 1 g / cm3 and a wave absorption performance of -20 dB at a thickness of 2 mm.

[0040] Example 1:

[0041] 1. Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material via the Hummers method;

[0042] 2. Collect the graphene oxide dispersion from step 1 and centrifuge at high speed to obtain a 3wt% graphene oxide slurry;

[0043] 3. Nano-silver conductive particles and nano-nickel magnetic particles were added to a 1:1 volume ratio ethanol / water mixed solution, ultrasonically dispersed, and then KH-550 was added dropwise. The mixture was heated to 80℃ under argon protection and reacted for 2 hours. After overnight aging, the mixture was filtered, washed and dried to obtain modified conductive particles and modified magnetic particles.

[0044] 4. Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar in a mass ratio of 100:10:5 and ground until homogeneous. The mixture is then magnetically stirred and heated at 60°C for 30 minutes to obtain graphene slurry. Graphene slurry and modified silver conductive particles are added to a quartz mortar in a mass ratio of 7:3 and ground until homogeneous to obtain GO conductive ink. GO slurry and modified nickel magnetic particles are added to a quartz mortar in a mass ratio of 7:3 and ground until homogeneous to obtain graphene magnetic ink.

[0045] 5. Fill the graphene silver conductive ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the A controller of the three-axis ink direct writing machine, set the spacing between the 1st and 2nd filament layers to 0.5mm and input it into the direct writing machine control software, adjust the needle inner diameter to 400μm, the ink extrusion pressure to 15psi, and the printing speed to 10mm / min, and print to obtain the required lower conductive material.

[0046] 6. Fill the graphene magnetic ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the B controller of the three-axis ink direct writing machine, set the spacing between the 3rd and 4th filament layers to 0.8mm and the spacing between the 5th and 6th filament layers to 1.2mm, input the settings into the direct writing machine control software, adjust the needle inner diameter to 500μm, the ink extrusion pressure to 20psi, and the printing speed to 10mm / min, and print to obtain the desired upper layer microwave absorbing gradient structure material.

[0047] 7. Finally, the multi-layer gradient material obtained by GO printing is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80°C for 12 hours to obtain the multi-layer gradient structure material.

[0048] Example 2:

[0049] 1. Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material via the Hummers method;

[0050] 2. Collect the graphene oxide dispersion from step 1 and centrifuge at high speed to obtain a 3wt% graphene oxide slurry;

[0051] 3. Nano-silver conductive particles and nano-γ-Fe2O3 magnetic particles were added to a 1:1 volume ratio ethanol / water mixed solution, ultrasonically dispersed, and then KH-550 was added dropwise. The mixture was heated to 80℃ under argon protection and reacted for 2 hours. After overnight aging, the mixture was filtered, washed and dried to obtain modified silver conductive particles and modified γ-Fe2O3 magnetic particles.

[0052] 4. Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar in a mass ratio of 100:10:5 and ground until homogeneous. The mixture is then magnetically stirred and heated at 60°C for 30 minutes to obtain graphene slurry. Graphene slurry and modified silver conductive particles are added to a quartz mortar in a mass ratio of 7:3 and ground until homogeneous to obtain GO conductive ink. GO slurry and modified γ-Fe2O3 magnetic particles are added to a quartz mortar in a mass ratio of 9:1 and ground until homogeneous to obtain graphene γ-Fe2O3 magnetic ink.

[0053] 5. Fill the graphene silver conductive ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the A controller of the three-axis ink direct writing machine, set the spacing between the 1st and 2nd filament layers to 0.5mm and input it into the direct writing machine control software, adjust the needle inner diameter to 400μm, the ink extrusion pressure to 15psi, and the printing speed to 10mm / min, and print to obtain the required lower conductive material.

[0054] 6. Fill the graphene magnetic ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the B controller of the three-axis ink direct writing machine, set the spacing between 3-4 layers of filaments to 1.0 mm and the spacing between 5-6 layers of filaments to 1.5 mm, input the settings into the direct writing machine control software, adjust the needle inner diameter to 600 μm, the ink extrusion pressure to 20 psi, and the printing speed to 10 mm / min, and print to obtain the desired upper layer microwave absorbing gradient structure material.

[0055] 7. Finally, the multi-layer gradient material obtained by GO printing is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80°C for 16 hours to obtain the multi-layer gradient structure material.

[0056] Example 3:

[0057] 1. Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material via the Hummers method;

[0058] 2. Collect the graphene oxide dispersion from step 1 and centrifuge at high speed to obtain a 3wt% graphene oxide slurry;

[0059] 3. Nano-silver conductive particles and nano-Fe3O4 magnetic particles were added to a 1:2 volume ratio ethanol / water mixed solution, ultrasonically dispersed, and then KH-550 was added dropwise. The mixture was heated to 80℃ under argon protection and reacted for 2 hours. After overnight aging, the mixture was filtered, washed and dried to obtain modified silver conductive particles and modified Fe3O4 magnetic particles.

[0060] 4. Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar in a mass ratio of 100:10:5 and ground until homogeneous. The mixture is then magnetically stirred and heated at 60°C for 30 minutes to obtain graphene slurry. Graphene slurry and modified silver conductive particles are added to a quartz mortar in a mass ratio of 7:3 and ground until homogeneous to obtain GO conductive ink. GO slurry and modified Fe3O4 magnetic particles are added to a quartz mortar in a mass ratio of 7:3 and ground until homogeneous to obtain graphene Fe3O4 magnetic ink.

[0061] 5. Fill the graphene silver conductive ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the A controller of the three-axis ink direct writing machine, set the spacing between the 1st and 2nd filament layers to 0.5mm and input it into the direct writing machine control software, adjust the needle inner diameter to 400μm, the ink extrusion pressure to 15psi, and the printing speed to 10mm / min, and print to obtain the required lower conductive material.

[0062] 6. Fill the graphene Fe3O4 magnetic ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the B controller of the three-axis ink direct writing machine, set the spacing between 3-4 layers of filaments to 1.0 mm and the spacing between 5-6 layers of filaments to 1.5 mm, input the settings into the direct writing machine control software, adjust the needle inner diameter to 500 μm, the ink extrusion pressure to 30 psi, and the printing speed to 10 mm / min, and print to obtain the desired upper layer microwave absorbing gradient structure material.

[0063] 7. Finally, the multi-layer gradient material obtained by GO printing is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80°C for 16 hours to obtain the multi-layer gradient structure material.

Claims

1. A method for preparing multilayer gradient microwave absorbing material ink by direct writing, characterized in that, Includes the following steps: S1: Aqueous dispersion of graphene oxide was prepared using 100-mesh flake graphite as raw material and the Hummers method. S2: Collect the graphene oxide dispersion from step S1, heat and stir at 58~62℃, and centrifuge to obtain graphene oxide slurry; S3: Nano-conductive particles and nano-magnetic particles are added to an ethanol / water mixed solution and ultrasonically dispersed. Then, silane coupling agent KH-550 is added dropwise. Under argon protection, the temperature is raised to 75~80℃ and reacted for 2h~4h. After overnight aging, the mixture is filtered, washed and dried to obtain modified conductive particles and modified magnetic particles. S4: Graphene oxide slurry, ascorbic acid, and deionized water are added to a quartz mortar and ground until homogeneous. The mixture is then heated at 60℃~65℃ for 30 minutes to 1 hour to obtain a graphene slurry. The graphene slurry and modified conductive particles are added to a quartz mortar and ground until homogeneous to obtain graphene conductive ink. The graphene slurry and modified magnetic particles are added to a quartz mortar and ground until homogeneous to obtain graphene magnetic ink. The graphene conductive ink has a solid content of 15~25wt%, with a graphene:nanoconductive particle ratio of 7:3, and the nanoconductive particles are Ag nanoparticles, Cu nanoparticles, and Al nanoparticles. The graphene magnetic ink has a solid content of 20~35wt%, with a graphene:nanomagnetic particle ratio of 9:1~7:3, and the nanomagnetic particles are Ni nanoparticles, γ-Fe2O3 nanoparticles, and Fe3O4 nanoparticles. S5: Fill the graphene conductive ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the A controller of the three-axis ink direct writing machine, set the spacing between 1-2 layers of filaments to 0.5mm and input it into the direct writing machine control software, adjust the needle inner diameter, ink extrusion pressure and printing speed, and print to obtain the required lower layer conductive material; S6: Fill the graphene magnetic ink into the printing syringe, remove air bubbles from the ink using a planetary vacuum degassing machine, install it into the B controller of the three-axis ink direct writing machine, set the spacing between 3-4 layers of filaments to 0.5-1mm, and the spacing between 5-6 layers of filaments to 0.8-1.5mm, input the information into the direct writing machine control software, adjust the needle inner diameter, ink extrusion pressure, and printing speed, and print to obtain the required upper layer gradient structure material; S7: The multilayer gradient material obtained by printing graphene oxide is immersed in liquid nitrogen to quickly fix the printed structure, then freeze-dried and heat-treated at 80℃~90℃ for 6-8 hours to obtain the multilayer gradient structure material.

2. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: In step S2, the centrifugation speed is 8000~10000 rpm, and the solid content of the graphene oxide slurry is 2~4 wt%.

3. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: In step S3, the volume ratio of ethanol to water is 1:1 to 1:2, and the molar ratio of nanoparticles to KH-550 is 1:3 to 1:

5.

4. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: Whether the printed structure is formed in step S5 is affected by the rheological properties of the ink, the inner diameter of the needle, the ink extrusion pressure, and the printing speed; the inner diameter of the printing needle is 200~500μm, the ink extrusion pressure is 15-25 psi, and the printing speed is 10~30 mm / s.

5. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: In step S6, the needle inner diameter is 300~500μm, the ink extrusion pressure is 20-30 psi, and the printing speed is 10~30 mm / s.

6. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: Multilayer absorbing material is a lightweight absorbing material.

7. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: The apparent density of the multilayer absorbing material is 0.3~1 g / cm³. 3 Its wave absorption performance can reach -20dB at 2mm.

8. The method for preparing multilayer gradient absorbing material ink by direct writing according to claim 1, characterized in that: The conductive nanoparticles and magnetic nanoparticles have a particle size of 500 nm to 1 μm.

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