High-temperature-resistant graphene-based wave-absorbing coating powder capable of being used for plasma spraying as well as preparation method and application of high-temperature-resistant graphene-based wave-absorbing coating powder

Abstract

The invention provides high-temperature-resistant graphene-based wave-absorbing coating powder capable of being used for plasma spraying, a preparation method and application, and relates to the field of electromagnetic wave absorbing materials. The preparation method of the high-temperature-resistant graphene-based wave-absorbing coating powder capable of being used for plasma spraying comprises the following steps: preparing hydrotalcite powder, preparing hydrotalcite / graphene oxide composite particles, shearing and coating, and carrying out heat treatment. According to the high-temperature-resistant graphene-based wave-absorbing coating powder capable of being used for plasma spraying, the preparation method and the application, the electromagnetic wave absorption performance of the coating powder can be improved, meanwhile, the high temperature resistance, the wear resistance, the oxidation resistance and the heat insulation performance of the coating powder are effectively improved, and the high-temperature wave-absorbing performance and the long-term high-temperature stability of the coating powder are further improved.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic wave absorbing materials, and in particular to a high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying, a preparation method and an application thereof. Background Art

[0002] With the continuous development of technology, higher requirements are also put forward for the stealth performance, electromagnetic compatibility, etc. of aircraft. Plasma spraying technology can be used to prepare coatings with special functions, such as stealth coatings, electromagnetic shielding coatings, etc. During the execution of existing flight missions, aircraft often face extremely harsh working environments. For example, when the engine of an aircraft is flying at high speed, its components have to withstand high temperature, high pressure and the erosion of high-speed airflows. Under the above-mentioned harsh conditions, the performance of traditional wave-absorbing materials will rapidly decline, thereby affecting the reliability and service life of the engine. In the prior art, plasma spraying technology can prepare coatings with high temperature resistance, wear resistance and oxidation resistance on the surface of engine components, thereby improving the performance and durability of engine components, enhancing the stable operation performance of the engine under complex working conditions, and improving the efficiency of the aircraft.

[0003] At the same time, in the industrial field, on some electronic devices that work in high-temperature environments for a long time (such as industrial furnaces, kilns, high-temperature laboratory equipment, etc.), the coatings formed by plasma spraying can protect the electronic components of high-temperature equipment from high temperature and electromagnetic interference; specifically in high-temperature equipment such as industrial furnaces and kilns, the high-temperature resistant wave-absorbing coatings formed by plasma spraying can be used as heat insulation and wave-absorbing materials, reduce heat loss, avoid the adverse effects of high temperature and electromagnetic interference on the equipment, and at the same time reduce the electromagnetic radiation of the equipment to the surrounding environment.

[0004] However, the existing wave-absorbing coatings formed by plasma spraying are prone to oxidation failure in a long-term high-temperature environment, resulting in a decline in their wave-absorbing and heat-insulating performance, and they cannot maintain good wave-absorbing performance in a high-temperature environment for a long time. Their high-temperature wave-absorbing performance and long-term high-temperature stability need to be further improved.

[0005] Therefore, providing a high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying, a preparation method and an application thereof, while improving its electromagnetic wave absorption performance, effectively improving its high-temperature resistance, wear resistance, oxidation resistance and heat-insulating performance, and further improving its high-temperature wave-absorbing performance and long-term high-temperature stability, has important technical significance and research value for the field of wave-absorbing materials. Summary of the Invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying, a preparation method and an application thereof, which can improve its electromagnetic wave absorption performance while effectively improving its high-temperature resistance, wear resistance, oxidation resistance and heat-insulating performance, and further improving its high-temperature wave-absorbing performance and long-term high-temperature stability.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A preparation method of a high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying, comprising the following steps: preparing hydrotalcite powder, preparing hydrotalcite / graphene oxide composite particles, shear coating, and heat treatment; The method for preparing the hydrotalcite / graphene oxide composite particles is to place an aqueous dispersion of hydrotalcite powder and graphene oxide in a closed environment, perform hydrothermal treatment, and then obtain hydrotalcite / graphene oxide composite particles after centrifugal washing and drying; The method of shear coating is to mix the hydrotalcite / graphene oxide composite particles with an aqueous aluminum phosphate dispersion, perform shear granulation to form particles with a particle size of 10 - 20 μm, and dry to obtain a first solid powder; mix the first solid powder with an aqueous aluminum phosphate dispersion, perform shear granulation to form particles with a particle size of 15 - 30 μm, and dry to obtain a second solid powder; The second solid powder is subjected to heat treatment to obtain a high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying.

[0008] Preferably, the hydrotalcite powder is at least one of the following: magnesium-aluminum hydrotalcite powder, zinc-aluminum hydrotalcite powder, calcium-aluminum hydrotalcite powder, sulfate-type hydrotalcite powder, nitrate-type hydrotalcite powder.

[0009] Preferably, in the preparation of the hydrotalcite / graphene oxide composite particles, the mass-volume ratio of the hydrotalcite powder, graphene oxide, and water is (1 - 2 g):(3 - 6 g):(50 - 80 mL); The hydrothermal treatment temperature is 170 - 180 °C, and the hydrothermal treatment time is 36 - 48 h.

[0010] Preferably, in the shear coating, the concentration of the aqueous aluminum phosphate dispersion is 5 - 10 g / L; The rotation speed of the shear granulation is 10000 - 12000 rpm, and the shear granulation time is 5 - 10 min.

[0011] Preferably, in the heat treatment, the heat treatment temperature is 1000 - 1050 °C, and the heat treatment time is 10 - 12 h.

[0012] Furthermore, the method for preparing the hydrotalcite powder is to use a mixed aqueous solution containing a magnesium salt, an aluminum salt, and Na2CO3, and perform electrolysis treatment under a constant current condition; after the electrolysis treatment is completed, obtain the hydrotalcite powder through filtration, washing, and drying; The molar ratio of the magnesium salt, aluminum salt, and Na2CO3 in the mixed aqueous solution is (2 - 3):1:(1.5 - 2.5).

[0013] Preferably, the electrolysis current density is controlled to be 25 - 28 mA / cm 2 , the electrolysis voltage is 5 - 10 V, the electrolysis temperature is 40 - 60 °C, and the electrolysis time is 1.5 - 2 h.

[0014] A high-temperature resistant graphene-based radar-absorbing coating powder for plasma spraying, prepared by the foregoing preparation method, with a particle size of 15 - 30 μm, a porosity of 6 - 10%, and a dielectric constant of 12.3 - 17.6.

[0015] An application of the foregoing high-temperature resistant graphene-based radar-absorbing coating powder for plasma spraying, using the high-temperature resistant graphene-based radar-absorbing coating powder for plasma spraying to form a radar-absorbing coating by plasma spraying.

[0016] Preferably, the main gas flow rate of plasma spraying is controlled to be 30 - 100 SLPM, the carrier gas flow rate is 8 - 10 SLPM, the arc voltage is 30 - 60 V, the arc current is 500 - 600 A, the spraying speed is 10 - 20 cm / s, the spraying angle is 85 - 90°, the powder melting temperature is 1100 - 1300 °C, the substrate preheating temperature is 200 - 400 °C, and the spraying thickness is 2 - 3 mm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The high-temperature resistant graphene-based radar-absorbing coating powder for plasma spraying of the present invention uses magnesium aluminum carbonate hydrotalcite (Mg6Al2(CO3)(OH) 16 ·4H2O) and graphene oxide materials as core components, and forms a composite structure by surface coating with aluminum phosphate (AlPO4). Among them, after the hydrotalcite / graphene oxide radar-absorbing powder is coated with AlPO4, the complete coating of single or multiple hydrotalcite / graphene oxide composite particles can be realized, and the oxidation path can be effectively blocked through densification treatment, significantly improving the antioxidant performance of the radar-absorbing coating. At the same time, through the synergistic effect of the layered structures of hydrotalcite and graphene, using the unique lamellar charge effect and ion exchange characteristics of hydrotalcite, a multi-level interface structure is formed with graphene sheets, significantly enhancing the interfacial polarization loss; the charge transfer and dipole interaction between the hydrotalcite lamella and the graphene sheet effectively regulate the dielectric constant of the radar-absorbing coating, improve the impedance matching performance, and significantly enhance its radar-absorbing performance. Further, the present invention uses a shear granulation technology to coat a dense aluminum phosphate shell on the outer layer of the hydrotalcite / graphene oxide composite particles, further improving the high-temperature resistance, wear resistance, antioxidant and heat insulation performance of the radar-absorbing coating. And through the synergistic effect of the foregoing technical means, the high-temperature radar-absorbing performance and long-term high-temperature stability of the radar-absorbing coating are further improved, effectively broadening the application range of the radar-absorbing coating.

[0018] (2) The preparation method of the high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying of the present invention. The structure and morphology of the prepared graphene / hydrotalcite wave-absorbing material are beneficial to electromagnetic wave absorption, and can be targeted regulated according to the characteristics of plasma spraying during the preparation process. By cooperating with the plasma spraying technology to apply this graphene-based wave-absorbing coating powder, a composite electromagnetic wave-absorbing coating with excellent wave-absorbing performance, high temperature resistance, wear resistance, oxidation resistance, and heat insulation performance can be prepared, which has broad application prospects in the fields of aerospace, electronic communication, etc.

[0019] (3) The preparation method of the high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying of the present invention has a simple preparation process, is easy to operate, has good repeatability, low production cost, and has the advantages of environmental friendliness, cleanliness, and non-toxicity, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 It is the scanning electron microscope (SEM) picture of the hydrotalcite / graphene oxide composite particles prepared in Example 3.

[0021] Figure 2 It is the scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) diagrams of the high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying prepared in Example 3.

[0022] Figure 3 It is the target effect picture after plasma spraying using the high-temperature resistant graphene-based wave-absorbing coating powder for plasma spraying in Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention are now described. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0024] It should be noted that the terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used here, "first", "second", etc. are used to distinguish similar objects and are not used to describe a specific order or sequence. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0025] An embodiment of the present invention provides a high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying, which is a hydrotalcite / graphene oxide composite microwave absorbing powder prepared by shear granulation coating; specifically, AlPO4 is used to coat single or several hydrotalcite / graphene oxide composite particles, and the graphene oxidation path is blocked through densification treatment; the particle size of the high-temperature resistant graphene-based microwave absorbing coating powder is 15-30 μm, the porosity is 6-10% (preferably 8-9%), the dielectric constant is 12.3-17.6 (preferably 14-15.5), and the distribution of graphene and hydrotalcite lamellae in the particles has a certain order.

[0026] Among them, the hydrotalcite is at least one of the following: magnesium-aluminum hydrotalcite, zinc-aluminum hydrotalcite, calcium-aluminum hydrotalcite, sulfate-type hydrotalcite, nitrate-type hydrotalcite.

[0027] An embodiment of the present invention also provides a preparation method of a high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying: 1. Raw material process characteristics: The multilayer graphene oxide sheets are 2-4 μm, the particle size of the hydrotalcite powder is 0.5-1 μm, the mass ratio of the multilayer graphene oxide sheets to the hydrotalcite is 2-3:1, and the concentration of the aluminum phosphate aqueous solution is 6-8 wt%.

[0028] 2. Process process characteristics, including the following steps: (1) Prepare a mixed aqueous solution containing a magnesium salt, an aluminum salt and Na2CO3, and perform electrolysis treatment under a constant current condition; control the electrolysis current density to be 25 mA / cm 2 , the electrolysis voltage is 5-10 V, the electrolysis temperature is 40-60 °C, and the electrolysis time is 1.5-2 h; after the electrolysis treatment is completed, filter to obtain the electrolysis reaction product, wash the electrolysis reaction product with deionized water until neutral, and dry to obtain magnesium aluminum carbonate hydrotalcite powder.

[0029] Among them, the molar ratio of the magnesium salt, the aluminum salt and Na2CO3 in the mixed aqueous solution is (2-3):1:(1.5-2.5).

[0030] The magnesium salt is preferably Mg(NO3)2, and the aluminum salt is preferably Al(NO3)3.

[0031] The anode material used in the electrolysis treatment is magnesium; the cathode material is graphite.

[0032] (2) Place the aqueous dispersion of magnesium aluminum carbonate hydrotalcite powder and graphene oxide in a hydrothermal autoclave, provide a high-temperature and high-pressure reaction environment, perform hydrothermal treatment, and then centrifuge, wash and dry to obtain a hydrotalcite / graphene oxide composite powder A (i.e., hydrotalcite / graphene oxide composite particles).

[0033] Among them, the mass-volume ratio of magnesium aluminum carbonate hydrotalcite powder, graphene oxide, and water is (1-2 g):(3-6 g):(50-80 mL).

[0034] The hydrothermal treatment temperature is 170-180 °C, and the hydrothermal treatment time is 36-48 h.

[0035] (3) Mix the hydrotalcite / graphene oxide composite powder A with an AlPO4 aqueous dispersion with a concentration of 5-10 g / L, and perform shear granulation to form particulate matter with a particle size of 10-20 μm, and dry it to obtain solid powder B (i.e., the first solid powder); mix the solid powder B (i.e., the first solid powder) again with an AlPO4 aqueous dispersion with a concentration of 5-10 g / L, and perform shear granulation to form particulate matter with a particle size of 15-30 μm, and dry it to obtain solid powder C (i.e., the second solid powder).

[0036] Among them, the mass-volume ratio of the hydrotalcite / graphene composite powder A to the AlPO4 aqueous dispersion is (5-10 g):1000 mL.

[0037] The mass-volume ratio of the solid powder B to the AlPO4 aqueous dispersion is (5-10 g):1000 mL.

[0038] The rotational speed of the shear rotor for shear granulation is 10000 rpm, and the shear granulation time is 5-10 min.

[0039] The drying temperature is 400-500 °C.

[0040] (4) The solid powder C (i.e., the second solid powder) is heat-treated to obtain a high-temperature-resistant graphene-based wave-absorbing coating powder for plasma spraying.

[0041] Among them, the heat treatment temperature is 1000 °C, and the heat treatment time is 10-12 h.

[0042] The embodiments of the present invention also provide an application of a high-temperature-resistant graphene-based wave-absorbing coating powder for plasma spraying. Plasma spraying is carried out using the high-temperature-resistant graphene-based wave-absorbing coating powder, and the main gas flow rate of the plasma spraying is controlled to be 30-100 SLPM, the carrier gas flow rate is 8-10 SLPM, the arc voltage is 30-60 V, the arc current is 500-600 A, the spraying speed is 10-20 cm / s, the spraying angle is 85-90°, the powder melting temperature is 1100-1300 °C, the substrate preheating temperature is 200-400 °C, and the spraying thickness is 2-3 mm.

[0043] The main gas is preferably nitrogen, and the carrier gas is preferably argon.

[0044] The following further illustrates the present invention in conjunction with some specific embodiments.

[0045] In the following examples and comparative examples of the present invention, the graphene oxide used was the AP-3 type graphene oxide purchased from Luobei Yunshan Carbon Industry, and the remaining raw materials were all conventional commercially available products.

[0046] Example 1 This example provides a method for preparing a high-temperature-resistant graphene-based microwave absorption coating powder for plasma spraying, specifically as follows: Step 1, prepare hydrotalcite powder: Weigh 3 mol of Mg(NO3)2 and 1 mol of Al(NO3)3, dissolve them in 1 L of deionized water, stir evenly to prepare a mixed solution of Mg(NO3)2 and Al(NO3)3; weigh 1.5 mol of Na2CO3, dissolve it in 1 L of deionized water to prepare a Na2CO3 solution; mix the mixed solution of Mg(NO3)2 and Al(NO3)3 with the Na2CO3 solution, and perform electrolysis treatment under a constant current condition, controlling the electrolysis current density to be 25 mA / cm 2 , the electrolysis voltage is 8 V, the electrolysis temperature is 50 °C, and the electrolysis time is 1.7 h; after the electrolysis treatment is completed, filter to obtain the electrolysis reaction product, and repeatedly wash the electrolysis reaction product with deionized water until the filtrate is neutral; dry the washed electrolysis reaction product in an oven to obtain magnesium aluminum carbonate hydrotalcite powder.

[0047] Among them, the anode material used in the electrolysis treatment is magnesium; the cathode material is graphite.

[0048] Step 2, prepare hydrotalcite / graphene oxide composite particles: Weigh 2 g of magnesium aluminum carbonate hydrotalcite powder and 6 g of graphene oxide, add them to 80 mL of deionized water, stir evenly, then transfer the mixture to a hydrothermal reactor, seal it, and perform hydrothermal treatment at 180 °C for 42 h; after the hydrothermal treatment is completed, take out the hydrothermal reactor and cool it to room temperature; centrifuge the reaction product to obtain a solid, wash the solid several times with deionized water to remove unreacted impurities; dry the washed solid in an oven to obtain hydrotalcite / graphene composite powder A (i.e., hydrotalcite / graphene oxide composite particles).

[0049] Step 3, shear coating: Mix the hydrotalcite / graphene composite powder A with 1 L of an aluminum phosphate aqueous dispersion (aluminum phosphate concentration: 5 g / L), place it in a high-speed shear mixer, and shear and stir at a speed of 10,000 revolutions per minute for 10 min to form particulate matter with a particle size of 10 - 20 μm. The particulate matter is dried at 400 °C to obtain a solid powder B (i.e., the first solid powder); mix the solid powder B (i.e., the first solid powder) again with 1 L of an aluminum phosphate aqueous dispersion (aluminum phosphate concentration: 5 g / L), shear and stir at a speed of 10,000 revolutions per minute for 10 min to form particulate matter with a particle size of 15 - 30 μm. The particulate matter is dried at 400 °C to obtain a solid powder C (i.e., the second solid powder).

[0050] Step 4, heat treatment: Put the solid powder C (i.e., the second solid powder) into a high-temperature furnace and perform heat treatment at 1000 °C for 12 h; after the heat treatment is completed, cool it to room temperature to obtain a high-temperature resistant graphene-based microwave absorbing coating powder that can be used for plasma spraying.

[0051] This embodiment also provides a high-temperature resistant graphene-based microwave absorbing coating powder that can be used for plasma spraying and is prepared by the aforementioned method. Its particle size is 15 - 30 μm, the porosity is 8.3%, and the dielectric constant is 14.2.

[0052] This embodiment also provides the application of the aforementioned high-temperature resistant graphene-based microwave absorbing coating powder that can be used for plasma spraying. Specifically, plasma spraying is carried out using the high-temperature resistant graphene-based microwave absorbing coating powder, controlling the main gas (nitrogen) flow rate of plasma spraying to be 50 SLPM, the carrier gas (argon) flow rate to be 8 SLPM, the arc voltage to be 40 V, the arc current to be 550 A, the spraying speed to be 15 cm / s, the spraying angle to be 85°, the powder melting temperature to be 1250 °C, the substrate preheating temperature to be 300 °C, and the spraying thickness to be 2 mm.

[0053] After testing, the microwave absorbing coating formed by plasma spraying using the high-temperature resistant graphene-based microwave absorbing coating powder has a flat tensile strength of 12.33 MPa at room temperature and 12.96 MPa at 200 °C, and the microwave absorbing coating has good anti-deformation ability.

[0054] Example 2 This embodiment provides a preparation method for a high-temperature resistant graphene-based microwave absorbing coating powder that can be used for plasma spraying, specifically as follows: Step 1, prepare hydrotalcite powder: Weigh 3 mol of Mg(NO3)2 and 1 mol of Al(NO3)3, dissolve them in 1 L of deionized water, stir evenly to prepare a mixed solution of Mg(NO3)2 and Al(NO3)3; weigh 1.5 mol of Na2CO3, dissolve it in 1 L of deionized water to prepare a Na2CO3 solution; mix the mixed solution of Mg(NO3)2 and Al(NO3)3 with the Na2CO3 solution, and carry out electrolysis treatment under a constant current condition, controlling the electrolysis current density to be 25 mA / cm 2 , the electrolysis voltage is 9 V, the electrolysis temperature is 45 °C, and the electrolysis time is 1.5 h; after the electrolysis treatment is completed, filter to obtain the electrolysis reaction product, and repeatedly wash the electrolysis reaction product with deionized water until the filtrate is neutral; dry the washed electrolysis reaction product in an oven to obtain magnesium aluminum carbonate hydrotalcite powder.

[0055] Among them, the anode material used in the electrolysis treatment is magnesium; the cathode material is graphite.

[0056] Step 2, prepare hydrotalcite / graphene oxide composite particles: Weigh 2 g of magnesium aluminum carbonate hydrotalcite powder and 5 g of graphene oxide, add them to 80 mL of deionized water, stir evenly, then transfer the mixed solution to a hydrothermal reactor, seal it, and carry out hydrothermal treatment at 180 °C for 42 h; after the hydrothermal treatment is completed, take out the hydrothermal reactor and cool it to room temperature; centrifuge the reaction product to obtain a solid, wash the solid several times with deionized water to remove unreacted impurities; dry the washed solid in an oven to obtain hydrotalcite / graphene composite powder A (i.e., hydrotalcite / graphene oxide composite particles).

[0057] Step 3, shear coating: Mix the hydrotalcite / graphene composite powder A with 1 L of aluminum phosphate aqueous dispersion (aluminum phosphate concentration 5 g / L), place it in a high-speed shear mixer, shear and stir at a speed of 10,000 revolutions per minute for 10 min to form particles with a particle size of 10 - 20 μm, and dry the particles at 400 °C to obtain solid powder B (i.e., the first solid powder); mix the solid powder B (i.e., the first solid powder) again with 1 L of aluminum phosphate aqueous dispersion (aluminum phosphate concentration 5 g / L), shear and stir at a speed of 10,000 revolutions per minute for 10 min to form particles with a particle size of 15 - 30 μm, and dry the particles at 400 °C to obtain solid powder C (i.e., the second solid powder).

[0058] Step 4, heat treatment: Put the solid powder C (i.e., the second solid powder) into a high-temperature furnace and carry out heat treatment at 1000 °C for 12 h; after the heat treatment is completed, cool it to room temperature to obtain a high-temperature-resistant graphene-based microwave absorption coating powder that can be used for plasma spraying.

[0059] This embodiment also provides a high-temperature resistant graphene-based microwave absorption coating powder for plasma spraying prepared by the aforementioned method, with a particle size of 15 - 30 μm, a porosity of 8.1%, and a dielectric constant of 15.2.

[0060] This embodiment also provides an application of the aforementioned high-temperature resistant graphene-based microwave absorption coating powder for plasma spraying. Specifically, plasma spraying is carried out using the high-temperature resistant graphene-based microwave absorption coating powder, controlling the main gas (nitrogen) flow rate of plasma spraying to be 60 SLPM, the carrier gas (argon) flow rate to be 9 SLPM, the arc voltage to be 42 V, the arc current to be 560 A, the spraying speed to be 15 cm / s, the spraying angle to be 85°, the powder melting temperature to be 1200 °C, the substrate preheating temperature to be 300 °C, and the spraying thickness to be 2 mm.

[0061] After testing, the microwave absorption coating formed by plasma spraying using the high-temperature resistant graphene-based microwave absorption coating powder has a flat tensile strength of 12.42 MPa at room temperature and a flat tensile strength of 13.02 MPa at 200 °C, and the microwave absorption coating has good anti-deformation ability.

[0062] Example 3 This embodiment provides a preparation method of a high-temperature resistant graphene-based microwave absorption coating powder for plasma spraying, specifically as follows: Step 1, prepare hydrotalcite powder: Weigh 3 mol of Mg(NO3)2 and 1 mol of Al(NO3)3, dissolve them in 1 L of deionized water, stir evenly to prepare a mixed solution of Mg(NO3)2 and Al(NO3)3; weigh 1.5 mol of Na2CO3, dissolve it in 1 L of deionized water to prepare a Na2CO3 solution; mix the mixed solution of Mg(NO3)2 and Al(NO3)3 with the Na2CO3 solution, and carry out electrolysis treatment under a constant current condition, controlling the electrolysis current density to be 25 mA / cm 2 , the electrolysis voltage to be 10 V, the electrolysis temperature to be 40 °C, and the electrolysis time to be 1.8 h; after the electrolysis treatment is completed, filter to obtain the electrolysis reaction product, and repeatedly wash the electrolysis reaction product with deionized water until the filtrate is neutral; dry the washed electrolysis reaction product in an oven to obtain magnesium aluminum carbonate hydrotalcite powder.

[0063] Among them, the anode material used in the electrolysis treatment is magnesium; the cathode material is graphite.

[0064] Step 2, prepare hydrotalcite / graphene oxide composite particles: Weigh 2 g of magnesium aluminum carbonate hydrotalcite powder and 4 g of graphene oxide, add them to 80 mL of deionized water, stir evenly, transfer the mixture to a hydrothermal autoclave, seal it, and perform hydrothermal treatment at 180 °C for 42 h. After the hydrothermal treatment, take out the hydrothermal autoclave and cool it to room temperature. Centrifuge the reaction product to obtain a solid, wash the solid with deionized water several times to remove unreacted impurities. Dry the washed solid in an oven to obtain hydrotalcite / graphene composite powder A (i.e., hydrotalcite / graphene oxide composite particles), and its scanning electron microscope (SEM) image is as shown in Figure 1 shown.

[0065] Step 3, shear coating: Mix hydrotalcite / graphene composite powder A with 1 L of aluminum phosphate aqueous dispersion (aluminum phosphate concentration 5 g / L), place it in a high-speed shear mixer, shear and stir at a speed of 11,000 revolutions per minute for 8 min to form particles with a particle size of 10 - 20 μm. Dry the particles at 400 °C to obtain solid powder B (i.e., the first solid powder). Mix solid powder B (i.e., the first solid powder) again with 1 L of aluminum phosphate aqueous dispersion (aluminum phosphate concentration 5 g / L), shear and stir at a speed of 11,000 revolutions per minute for 8 min to form particles with a particle size of 15 - 30 μm. Dry the particles at 400 °C to obtain solid powder C (i.e., the second solid powder).

[0066] Step 4, heat treatment: Put solid powder C (i.e., the second solid powder) into a high-temperature furnace and perform heat treatment at 1000 °C for 12 h. After the heat treatment, cool it to room temperature to obtain a high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying, and its scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) images are as shown in Figure 2 shown.

[0067] This example also provides a high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying prepared by the aforementioned method, with a particle size of 15 - 30 μm, a porosity of 8.4%, and a dielectric constant of 15.1 This example also provides the application of the aforementioned high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying. Specifically, use the high-temperature resistant graphene-based microwave absorbing coating powder for plasma spraying, control the main gas (nitrogen) flow rate of plasma spraying at 60 SLPM, the carrier gas (argon) flow rate at 10 SLPM, the arc voltage at 45 V, the arc current at 570 A, the spraying speed at 17 cm / s, the spraying angle at 85°, the powder melting temperature at 1300 °C, the substrate preheating temperature at 300 °C, and the spraying thickness at 2 mm. The effect diagram of the target after plasma spraying is as shown in Figure 3 shown.

[0068] After testing, the flat tensile strength of the wave-absorbing coating formed by plasma spraying with the heat-resistant graphene-based wave-absorbing coating powder is 12.49 MPa at room temperature and 13.11 MPa at 200 °C, and the wave-absorbing coating has good anti-deformation ability.

[0069] Comparative Example 1 Comparative Example 1 uses the preparation method of the heat-resistant graphene-based wave-absorbing coating powder of Example 1. The difference is that in the shear coating of step 3, the solid powder B (i.e., the first solid powder) obtained by shear granulation and drying of the hydrotalcite / graphene composite powder A and the aluminum phosphate aqueous dispersion is directly used in the heat treatment of step 4; the re-mixing and shear granulation of the solid powder B (i.e., the first solid powder) and the aluminum phosphate aqueous dispersion are omitted.

[0070] Comparative Example 2 Comparative Example 2 uses the preparation method of the heat-resistant graphene-based wave-absorbing coating powder of Example 2. The difference is that in the shear coating of step 3, the solid powder B (i.e., the first solid powder) obtained by shear granulation and drying of the hydrotalcite / graphene composite powder A and the aluminum phosphate aqueous dispersion is directly used in the heat treatment of step 4; the re-mixing and shear granulation of the solid powder B (i.e., the first solid powder) and the aluminum phosphate aqueous dispersion are omitted.

[0071] Comparative Example 3 Comparative Example 3 uses the preparation method of the heat-resistant graphene-based wave-absorbing coating powder of Example 3. The difference is that in the shear coating of step 3, the solid powder B (i.e., the first solid powder) obtained by shear granulation and drying of the hydrotalcite / graphene composite powder A and the aluminum phosphate aqueous dispersion is directly used in the heat treatment of step 4; the re-mixing and shear granulation of the solid powder B (i.e., the first solid powder) and the aluminum phosphate aqueous dispersion are omitted.

[0072] Effect Verification In order to verify the high-temperature wave-absorbing performance of the coating powders of each example and comparative example, the coating powders in Examples 1-3 and Comparative Examples 1-3 were respectively subjected to microwave absorption tests at 200 °C. The test method is as follows: The electromagnetic wave absorption performance test is mainly to measure the complex permittivity and complex permeability of the material and through the following formula: (1) (2) The quality of the wave-absorbing performance can be intuitively reflected by the reflection loss (RL) value. Its calculation can be based on the transmission line theory, and the formula is as follows: (3) (4) Among them, f, d, and c are the frequency, absorber thickness, and the speed of light in free space, respectively; Z0 is the space impedance; Zin is the input impedance. When the reflection loss RL value < -10 dB, it means that 90.00% of the electromagnetic waves are effectively absorbed. When the reflection loss RL value < -20 dB, it means that 99.00% of the electromagnetic waves are effectively absorbed. When the reflection loss RL value < -30 dB, it means that 99.90% of the electromagnetic waves are effectively absorbed. The attenuation of electromagnetic waves in the material can be expressed by the following formula: (5) The reflection loss value of the material is calculated. The electromagnetic wave absorption performance of the sample is studied using an Agilent VNA N5245A network vector analyzer. The powder sample is mixed with paraffin at a mass ratio of 40 wt%, stirred evenly in the molten state of paraffin, and pressed into a mold with an inner diameter of 3.04 mm and an outer diameter of 7 mm to prepare a hollow coaxial cylinder. The test frequency range is 2 - 18 GHz, the number of sampling points is 201, the real and imaginary parts of the complex permittivity and complex permeability of the sample are recorded, and the dielectric loss tangent and magnetic loss tangent are calculated through the ratio of the real and imaginary parts. The test results are shown in the following table: As can be seen from the above table, the coated powder materials in Examples 1 - 3 and Comparative Examples 1 - 3 show the best microwave absorption performance in the X and Ku bands in a high-temperature environment of 200 °C, with good high-temperature resistance, oxidation resistance, high-temperature wave absorption performance, and high-temperature stability. And when the mass ratio of magnesium aluminum carbonate hydrotalcite to graphene oxide is 1:2, the hydrotalcite acts as a spacer layer between the graphene sheets, and the two form a multi-level interface structure. At this time, the reflection loss value of the composite material is the smallest and the absorption bandwidth is the largest. Therefore, Example 3 has more excellent electromagnetic wave absorption performance than other examples.

[0074] The high-temperature resistant graphene-based wave-absorbing coating powder material of the present invention can be used for plasma spraying, using magnesium aluminum carbonate hydrotalcite (Mg6Al2(CO3)(OH) 16·4H2O) and graphene oxide materials as the core components, and form a composite structure by surface coating with aluminum phosphate (AlPO4). Among them, after the hydrotalcite / graphene oxide microwave absorbing powder is coated with AlPO4, the complete coating of single or multiple hydrotalcite / graphene oxide composite particles can be realized, and the oxidation path can be effectively blocked through densification treatment, significantly improving the antioxidant performance of the microwave absorbing coating. At the same time, through the synergistic effect of the layered structures of hydrotalcite and graphene, using the unique lamellar charge effect and ion exchange characteristics of hydrotalcite, a multi-level interface structure is formed with graphene sheets, significantly enhancing the interfacial polarization loss; the charge transfer and dipole interaction between the hydrotalcite lamellae and graphene sheets effectively regulate the dielectric constant of the microwave absorbing coating, improve the impedance matching performance, and significantly enhance its microwave absorbing performance. Further, in the present invention, through the shear granulation technology, a dense aluminum phosphate shell is coated on the outer layer of the hydrotalcite / graphene oxide composite particles, further improving the high temperature resistance, wear resistance, antioxidant and heat insulation performance of the microwave absorbing coating. And through the synergistic effect of the foregoing technical means, the high temperature microwave absorbing performance and long-term high temperature stability of the microwave absorbing coating are further improved.

[0075] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0076] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant graphene-based radar absorbing coating powder that can be used for plasma spraying, characterized in that: The method comprises the following steps: preparing hydrotalcite powder, preparing hydrotalcite / graphene oxide composite particles, shear coating, and heat treatment; The method for preparing the hydrotalcite / graphene oxide composite particles is to place hydrotalcite powder and an aqueous dispersion of graphene oxide in a closed environment, perform hydrothermal treatment, and then perform centrifugal washing and drying to obtain the hydrotalcite / graphene oxide composite particles; The shear coating method comprises mixing the hydrotalcite / graphene oxide composite particles with the aluminum phosphate aqueous dispersion, performing shear granulation to form particles with a particle size of 10-20 μm, and drying to obtain a first solid powder; mixing the first solid powder with the aluminum phosphate aqueous dispersion, performing shear granulation to form particles with a particle size of 15-30 μm, and drying to obtain a second solid powder; The second solid powder is heat-treated to obtain a high-temperature resistant graphene-based radar absorbing coating powder that can be used for plasma spraying.

2. The method for preparing high temperature resistant graphene-based radar absorbing coating powder that can be used for plasma spraying according to claim 1, characterized in that: The hydrotalcite powder is at least one of the following: magnesium-aluminum hydrotalcite powder, zinc-aluminum hydrotalcite powder, calcium-aluminum hydrotalcite powder, sulfate-type hydrotalcite powder, and nitrate-type hydrotalcite powder.

3. The method for preparing high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying according to claim 1, characterized in that: In the preparation of the hydrotalcite / graphene oxide composite particles, the mass volume ratio of hydrotalcite powder, graphene oxide, and water is (1-2 g): (3-6 g): (50-80 mL); The hydrothermal treatment temperature is 170-180°C, and the hydrothermal treatment time is 36-48h.

4. The method for preparing high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying according to claim 1, characterized in that: In the shear coating, the concentration of the aluminum phosphate aqueous dispersion is 5-10 g / L; The rotation speed of shear granulation is 10000-12000rpm, and the shear granulation time is 5-10min.

5. The method for preparing high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying according to claim 1, characterized in that: In the heat treatment, the heat treatment temperature is 1000-1050° C. and the heat treatment time is 10-12 hours.

6. The method for preparing high temperature resistant graphene-based radar absorbing coating powder for plasma spraying according to claim 1, characterized in that: The method for preparing hydrotalcite powder comprises: using a mixed aqueous solution containing magnesium salt, aluminum salt and Na2CO3, and performing electrolysis treatment under constant current conditions; after the electrolysis treatment is completed, filtering, washing and drying to obtain hydrotalcite powder; The molar ratio of magnesium salt, aluminum salt and Na2CO3 in the mixed aqueous solution is (2-3):1:(1.5-2.5).

7. The method for preparing high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying according to claim 6, characterized in that: Control the electrolysis current density to 25-28 mA / cm 2 , the electrolysis voltage is 5-10V, the electrolysis temperature is 40-60℃, and the electrolysis time is 1.5-2h.

8. A high temperature resistant graphene-based microwave absorbing coating powder that can be used for plasma spraying, characterized in that: The nanostructured carbon nanotubes are prepared by the preparation method according to any one of claims 1 to 7, with a particle size of 15 to 30 μm, a porosity of 6 to 10%, and a dielectric constant of 12.3 to 17.

6.

9. An application of the high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying as claimed in claim 8, characterized in that: The high temperature resistant graphene-based microwave absorbing coating powder is used for plasma spraying to form a microwave absorbing coating.

10. The use of the high temperature resistant graphene-based microwave absorbing coating powder for plasma spraying according to claim 9, characterized in that: The main gas flow rate of plasma spraying is controlled to be 30-100SLPM, the carrier gas flow rate is 8-10SLPM, the arc voltage is 30-60V, the arc current is 500-600A, the spraying speed is 10-20cm / s, the spraying angle is 85-90°, the powder melting temperature is 1100-1300℃, the substrate preheating temperature is 200-400℃, and the spraying thickness is 2-3mm.

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