High-temperature-resistant light stealth coating material and preparation method thereof

Abstract

The invention relates to a high-temperature-resistant light stealth coating material and a preparation method thereof, and belongs to the technical field of functional materials, the high-temperature-resistant light stealth coating material comprises the following raw materials: boride, silicide, a titanate fluxing agent, metal coated carbide, a zinc oxide coated nano carbon material and a sintering aid; according to the prepared high-temperature-resistant light stealth coating material, the infrared emissivity at the wavelength of 3-5 [mu] m is 0.231-0.245, the infrared emissivity at the wavelength of 8-14 [mu] m is 0.424-0.441, the tensile bonding strength is 40.8-46.4 MPa, and the thermal shock resistance frequency is 153-167.

Description

Technical Field

[0001] The present invention relates to a high-temperature resistant lightweight stealth coating material and a preparation method thereof, belonging to the technical field of functional materials. Background Art

[0002] With the development of military technology, the role and status of aircraft in the battlefield have been continuously improved. Correspondingly, modern reconnaissance and aiming technologies have also been continuously improved, which has severely tested the survival ability of aircraft. In order to improve the survival ability of aircraft, stealth technology has emerged. Stealth technology refers to a comprehensive technology that reduces the risk of an object being detected, tracked, and attacked by changing the detectable characteristic information emitted by the object and suppressing the signals it emits, so as to improve the survival ability of military targets. Stealth technology mainly includes infrared stealth, radar stealth, visible light stealth, and magnetic stealth, etc. Among them, in the guided detection weaponry used by various military powers, infrared guidance occupies a dominant position, reaching more than 90%, and the proportion of infrared detection also reaches more than 30%. It has become an essential method for military reconnaissance and is related to national defense security.

[0003] Infrared stealth technology reduces the energy of the infrared radiation of an object by changing the structural design or using infrared physical principles, so as to achieve the purpose of reducing the detectability of the object. Its technical means mainly include changing the infrared radiation characteristics of the object, reducing the infrared radiation intensity of the object, and adjusting the propagation path of infrared radiation, etc. Usually, the infrared radiation sources of an aircraft mainly include the thermal radiation of the engine, the high-temperature airflow ejected from the tail nozzle, the infrared radiation of the aircraft skin, and the reflection of the environment, etc. For example, an aero-engine generally operates under high pressure, high speed, and high temperature during operation, so it becomes one of the main infrared radiation sources of an aircraft. The technical ways to achieve infrared stealth usually include cooling, shielding, or coating a coating material with a low infrared emissivity. Among them, coating a low infrared emissivity coating is a simple, convenient, and effective technical way to improve the infrared stealth performance of an aircraft.

[0004] Infrared rays are electromagnetic waves with frequencies between microwaves and visible light, and their wavelengths are between 760 nm and 1 mm. According to infrared physics, objects above absolute zero (-273.15 °C) inevitably radiate infrared energy to the outside world. The infrared radiation energy of an object conforms to the Stefan-Boltzmann law, that is, W = σET 4 , where W is the total radiation energy of the object, σ is the Boltzmann constant of 5.67032×10 -8 W·m -2 ·k -4 , E is the infrared emissivity of the object, T is the absolute temperature of the object, and the infrared emissivity of the object surface also conforms to the Hagen-Ruben law, that is, E≈2×(2ε 0 ωρ) ½, where ε 0 is the dielectric constant of the object, ω is the angular frequency of the electromagnetic wave, and ρ is the resistivity of the object. The radiation ability of an object is determined by the emissivity and temperature. Therefore, reducing the surface emissivity of the object and controlling the surface temperature of the object are the basic ways to achieve infrared stealth. However, in order to ensure that the aircraft has sufficient power and thrust-to-weight ratio, the method of reducing the surface temperature is not very feasible. Therefore, surface engineering technology is usually used to cover a layer of high-temperature resistant and low-infrared-emission coating on the target surface to reduce the surface emissivity of the target and achieve infrared stealth. The lower the resistivity of the material, the better its conductivity and the lower its infrared emissivity.

[0005] Currently, the infrared low-emissivity coating materials with application potential in medium- and high-temperature environments are roughly divided into two categories: metal coating materials and inorganic low-reflectivity coating materials. Although metal coating materials have significant advantages such as low price, good conductivity, and low infrared emissivity, the heat resistance of metal materials is generally poor, and the working temperature can generally only be in the range of 600-800°C, which is not suitable for serving in higher-temperature environments, or can only be used in high-temperature environments for a short time. This limits its use for infrared stealth in the engine parts of aircraft. Inorganic low-emissivity coatings generally use ceramic materials with high temperature resistance and low thermal conductivity as the surface layer, and are compounded on the surface of high-temperature components in the form of coatings or thin films to achieve the effect of reducing the infrared emissivity of the target surface. This type of material has extremely high heat resistance and can be used for a long time at high temperatures. Especially in the 3-5μm wavelength band, it has a low infrared emissivity, and the infrared emissivity changes little with temperature. It can also achieve the compatibility of multiple stealth functions. Therefore, inorganic low-emissivity coating materials are currently the type of materials reported more and with more significant effects, and they dominate the field of infrared stealth materials. However, compared with metal coating materials, inorganic low-emissivity coating materials also have very obvious deficiencies in infrared stealth. First, the conductivity of inorganic low-emissivity coating materials is difficult to match that of metal coating materials, especially high-temperature resistant ceramic coatings. Therefore, their infrared emissivity is generally higher than that of metal coatings, which will inevitably cause a decline in the infrared stealth effect. Second, inorganic low-emissivity coating materials generally have the disadvantages of being too brittle and insufficient bonding strength with the substrate, resulting in poor high-temperature thermal shock resistance, limited service life in high-temperature environments, and a risk of sudden failure. Finally, due to the above two defects, inorganic low-emissivity coating materials often need to maintain a certain thickness to make up for the above two deficiencies. Therefore, it is difficult for inorganic low-emissivity coating materials to achieve a relatively thin thickness to meet the lightweight requirements of aircraft. Therefore, developing inorganic low-emissivity coating materials with high temperature resistance, good high-temperature thermal shock resistance, light weight, high conductivity, and good infrared stealth effect is the key to solving the infrared stealth problem of the high-temperature power propulsion parts of aircraft.

[0006] Chinese Patent CN117230399A discloses a dispersion-strengthened composite powder for infrared stealth materials, its preparation method, and an infrared stealth coating. The preparation method includes: mixing metal powder, ceramic powder, polyvinyl alcohol, and water, and performing ball milling and granulation to obtain agglomerated powder; performing high-frequency plasma treatment on the agglomerated powder to obtain a dispersion-strengthened composite powder for infrared stealth materials; the metal powder includes one or more of Al, Cu, Au, Ag, Ni, and Pt; the ceramic powder is a nano negative temperature coefficient thermosensitive semiconductor ceramic, and the nano negative temperature coefficient thermosensitive semiconductor ceramic includes a high-temperature type ceramic powder and a medium-low temperature type ceramic powder. This dispersion-strengthened composite powder for infrared stealth materials has extremely high density, sphericity, and fluidity. The ceramic phase is uniformly dispersed in the metal, enhancing the hardness, wear resistance, temperature resistance, and other properties of the metal material. It can be used for 3D printing infrared stealth equipment or spraying infrared stealth coatings. The infrared stealth coating prepared by this patent adds a large amount of metal powder, and its high-temperature resistance performance is definitely not particularly good. Among the data disclosed in its examples, it only clearly states that the coating shows no abnormality after 50 high-temperature cyclic thermal shocks at 900°C. Whether it can be used at higher temperatures is not disclosed in this patent. However, judging from the powder composition and preparation method described in the patent, where the ceramic phase is uniformly dispersed in the metal, it can be generally determined that the metal is the main phase in this coating, so the metal content will not be too low, and thus the high-temperature resistance performance is definitely limited.

[0007] Chinese Patent CN110002900A discloses an environmental barrier-infrared stealth integrated coating, a coated composite material, and its preparation method. The coating is a multi-layer stacked structure, and the multi-layer stacked structure sequentially includes a silicon bonding layer, an antioxidant layer, and a low infrared emissivity / filling layer from the inside to the outside. The antioxidant layer is a mullite single coating or a mullite / BSAS composite coating, and the low infrared emissivity / filling layer is a Bi 2 O 3 -ZnO-based glass coating. The present invention also correspondingly provides a coated composite material and its preparation method. The environmental barrier-infrared stealth integrated coating of the present invention adopts a multi-layer stacked structure, and the thermal expansion coefficients of each functional layer gradually change slowly, weakening the thermal mismatch between layers and endowing the coating with excellent thermal shock resistance. The infrared stealth coating designed in this patent has a very complex structure, and it is conceivable that its preparation process is cumbersome and the difficulty of precise control of the preparation process is high. Moreover, in the low infrared emissivity / filling layer, there are also noble metal fillers such as Ag, Pd, Au, and Pt, and its manufacturing cost is relatively high.

[0008] As can be seen from the above, the infrared stealth coating materials currently used in the high-temperature parts of aircraft still have prominent problems such as poor high-temperature resistance, unsatisfactory high-temperature thermal shock resistance, high infrared emissivity caused by low conductivity, and difficulty in achieving light weight. Therefore, developing a high-temperature resistant and lightweight stealth coating material is crucial for enhancing the anti-strike ability of military aircraft. Summary of the Invention

[0009] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides a high-temperature resistant and lightweight stealth coating material and its preparation method, achieving the following invention purposes: preparing a high-temperature resistant and lightweight stealth coating material with good high-temperature resistance, excellent high-temperature thermal shock resistance, high conductivity, and low infrared emissivity.

[0010] To achieve the above invention purposes, the present invention adopts the following technical solutions: A high-temperature resistant and lightweight stealth coating material and its preparation method, the raw material composition of the high-temperature resistant and lightweight stealth coating material includes boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nano-carbon material, and sintering aid; The mass ratio of the boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nano-carbon material, and sintering aid is 20~100:30~150:1~5:1~10:1~8:1~4; The boride is one of titanium boride, zirconium boride, calcium boride, hafnium boride, vanadium boride, chromium boride, silicon boride, manganese boride, manganese diboride, manganese tetraboride, molybdenum boride, molybdenum diboride, molybdenum pentaboride, any two or any combination of two or more; The particle size of the boride is 0.5~3μm; The silicide is one of titanium silicide, zirconium silicide, tantalum silicide, tungsten silicide, molybdenum trisilicide, pentamolybdenum trisilicide, molybdenum disilicide, any two or any combination of two or more; The particle size of the silicide is 0.5~3μm; The titanate flux is one of potassium titanate, lithium titanate, magnesium titanate, barium titanate, lead titanate, zinc titanate, any two or any combination of two or more; The particle size of the titanate flux is 0.1~1μm; In the metal-coated carbide, the metal is one of nickel, cobalt or a combination of nickel and cobalt, and the carbide is one of zirconium carbide, titanium carbide, vanadium carbide, tungsten carbide, any two or any combination of two or more; The particle size of the carbide is 1~100nm; In the zinc oxide-coated nano-carbon material, the nano-carbon material is one of carbon nanotubes, carbon nanofibers, nano-carbon spheres, graphene, nano-scale conductive carbon black, nano-scale graphite powder, any two of them, or any combination of two or more of them; The particle size of the nano-carbon material is 1 to 100 nm; The sintering aid is one of silicon phosphate and boron phosphate or a combination of the two; The particle size of the sintering aid is 0.1 to 1 μm; The following is a further improvement of the above technical solution: Step 1: Preparation of metal-coated carbide For the preparation of the metal-coated carbide, one of electroless plating method, hydrothermal hydrogen reduction method, and precipitation reduction method is used; In the electroless plating method, the carbide powder is dispersed in the electroless plating solution at the nano-scale, and then by controlling the temperature, pH value, and stirring rate of the plating solution, nickel ions, cobalt ions, or a mixture of nickel and cobalt ions contained in the electroless plating solution are controllably reduced to elemental nickel, elemental cobalt, or a mixture of the two elemental substances under the action of a reducing agent and adhered and coated on the surface of the carbide powder to form a metal-coated carbide; The electroless plating solution is composed of one or a mixture of two of nickel salts and cobalt salts, a complexing agent, a stabilizer, a reducing agent, and a dispersant; The complexing agent is an aliphatic carboxylic acid; The stabilizer is one of thiocyanate and thiourea; The reducing agent is one of sodium hypophosphite, hydrazine, and sodium borohydride; The dispersant is a non-ionic surfactant that promotes the dispersion of the carbide powder, specifically one of alkyl glycoside surfactants, long-chain fatty alcohol polyoxyethylene ether surfactants, and alkylphenol polyoxyethylene ether surfactants, any two of them, or any combination of two or more of them; In the hydrothermal hydrogen reduction method, the carbide powder, catalyst, dispersant, nickel salt solution, cobalt salt solution, or a mixed solution of nickel salt and cobalt salt are added to an autoclave, and by controlling the appropriate reaction temperature and reaction pressure, hydrogen is used to reduce and deposit nickel ions, cobalt ions, or a mixture of nickel and cobalt ions on the surface of the carbide powder to form a metal-coated carbide; The catalyst is one of palladium chloride and anthraquinone; The dispersant is one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and polyoxyethylene monooctylphenyl ether, any two of them, or any combination of two or more of them; The reaction temperature is 110 to 160 °C; The reaction pressure is 1 to 5 MPa; In the precipitation reduction method, one or a mixture of nickel salts and cobalt salts is dissolved in deionized water to form an aqueous solution. The temperature of the aqueous solution is controlled, and then carbide powder is added. After being strongly stirred and dispersed evenly, ammonia water is added to form nickel hydroxide or cobalt hydroxide precipitate adsorbed on the surface of the carbide powder. After the reaction is completed, the carbide powder is dried, and the dried powder is reduced at high temperature with hydrogen to obtain metal-coated carbide; The nickel salt is one of nickel chloride, nickel nitrate, nickel sulfate, nickel phosphate, nickel acetate, any two of them, or any combination of two or more of them; The cobalt salt is one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt phosphate, cobalt acetate, any two of them, or any combination of two or more of them.

[0011] Step 2: Preparation of zinc oxide-coated nanocarbon material First, the nanocarbon material is oxidized, and then added to anhydrous monohydric alcohol. After the nanocarbon material is dispersed into the state of nano single particles, an alkaline aqueous solution is added to adjust the pH value, and then an alcohol solution of zinc salt is added. After stirring and reacting completely at room temperature, filtration is carried out. The filtered solid is washed with deionized water and anhydrous ethanol until neutral, and then dried to obtain zinc oxide-coated nanocarbon material; For the oxidation treatment, the method is as follows: The nanocarbon material is added to a mixed solution of concentrated nitric acid and hydrogen peroxide, and kept at a constant temperature of 70-90°C. After stirring and refluxing for 1-2 hours, filtration is carried out. The filtered solid is washed with deionized water until neutral, and then dried to obtain the oxidized nanocarbon material; The alkaline aqueous solution is one of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia water; For the adjustment of the pH value, the pH value is adjusted to 10-12; The alcohol solution of zinc salt is composed of zinc salt, alkanolamine, and anhydrous monohydric alcohol; The zinc salt is one of zinc stearate, zinc acetate, and zinc salicylate; The alkanolamine is one of isobutanolamine, monoethanolamine, diethanolamine, and triethanolamine; The anhydrous monohydric alcohol is one of methanol and ethanol, or a mixture of methanol and ethanol.

[0012] Step 3: Preparation of high-temperature lightweight stealth coating material The high-temperature lightweight stealth coating material is prepared by atmospheric plasma spraying technology, which has the advantages of high automation degree, layered coating structure, and simple operation; The surface of the substrate to be sprayed must be rust-removed, degreased, and sandblasted in advance. Then, according to the mass ratio of the raw material composition of the high-temperature resistant lightweight stealth coating material, the raw material powders are mixed evenly to obtain a mixed powder. After adding the mixed powder to the spraying equipment, control the arc voltage at 60 - 90V, the arc current at 500 - 700A, the main gas argon flow rate at 50 - 65L / min, the secondary gas hydrogen flow rate at 20 - 35L / min, the powder feeding speed at 10 - 20g / min, and the spraying distance at 90 - 120mm. Spray the mixed powder evenly onto the surface of the substrate to finally obtain a high-temperature resistant lightweight stealth coating material with a thickness of 120 - 260μm.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The high-temperature resistant lightweight stealth coating material prepared by the present invention uses micron-level borides and silicides as the main raw materials. All the micron-level borides and silicides defined in the specification have very high melting points (all above 1800°C) and very good electrical conductivity, which ensures that the prepared stealth coating has very good high-temperature resistance. At the same time, due to the good electrical conductivity, according to the Hagen-Ruben law, that is, E≈2×(2ε 0 ωρ) ½ , it can also be inferred that these micron-level borides and silicides with good electrical conductivity will reduce the infrared emissivity of the coating material by reducing the resistivity of the coating. 2. The present invention enhances the bonding strength between the molten thermal spraying powder and the substrate through the design of coating nano-level carbides with nickel and cobalt. The main principle is that the two metal elements of nickel and cobalt have relatively low melting points and relatively high reaction activities, and are particularly easy to form metal alloys or metal-ceramic phase alloys with the metal elements on the surface of the metal substrate or the non-metal elements on the surface of the ceramic substrate. Moreover, the present invention defines the carbide as nano-level, mainly using the huge specific surface area of the nano-level carbide to increase the contact area between the metal-coated nano-level carbide and the substrate, and enhance the reaction degree between the metal-coated nano-level carbide and the substrate surface by increasing the contact area. In addition, the carbides defined in the present invention, namely zirconium carbide, titanium carbide, vanadium carbide, and tungsten carbide, all have very good electrical conductivity. These strongly conductive nano-particles can not only enhance the bonding strength but also effectively fill the gaps between the micron-level borides and silicides, improve the overall electrical conductivity of the coating, and further reduce the overall infrared emissivity of the coating. 3. The zinc oxide-coated nano-carbon material prepared by the present invention mainly aims to utilize the strong electrical conductivity of the nano-carbon material and the size complementary effect between the nano-scale particles of the nano-carbon material and the micro-scale borides and silicides to further enhance the electrical conductivity and density of the overall coating. Since the coating preparation method selected in the present invention is thermal spraying, the powder transported by this process method can reach a high temperature of 1500 °C and above. During this high-temperature process, the nano-carbon material is extremely prone to oxidation and combustion. Therefore, the present invention uses zinc oxide to coat the surface of the nano-carbon material. Zinc oxide has a melting point as high as 1975 °C and also has the electrical conductivity of a semiconductor. Therefore, on the premise of effectively protecting the nano-carbon material from high-temperature oxidation, it has no substantial impact on the high-temperature electrical conductivity of the nano-carbon material in the coating. Therefore, the zinc oxide-coated nano-carbon material prepared in the present invention plays a very crucial role in reducing the infrared emissivity of the coating; 4. The titanate flux added in the present invention has a relatively low melting point. During the thermal spraying process, when the powder is close to the surface of the substrate, the titanate can wrap the high-melting-point powder in a molten liquid or semi-liquid form. Therefore, it can effectively transfer the heat generated by the thermal spraying equipment to the high-melting-point powder, promote the melting on the surface of the high-melting-point powder, and then promote the bonding strength between the high-melting-point powder and the surface of the substrate. In addition, the liquid or semi-liquid substance generated by the melting of the titanate itself also has very good bonding strength with the surface of the substrate. Therefore, the titanate flux can effectively improve the bonding strength between the coating material and the surface of the substrate; 5. The phosphosilicate and phosphoborate added in the present invention are both viscous glassy substances after high-temperature melting. Therefore, after melting, they can effectively adhere to the surface of the substrate, and the heat transfer of the liquid viscous melt formed by these two substances is relatively faster compared to the high-melting-point powder. Therefore, it can effectively enhance the transfer of the heat generated by the thermal spraying equipment to the surface of the substrate, and thus can play an auxiliary role in sintering the high-melting-point powder on the surface of the substrate, ultimately promoting the hot-melt bonding strength between the high-melting-point powder and the surface of the substrate; 6. The high-temperature lightweight stealth coating material prepared by the present invention has an infrared emissivity of 0.231 - 0.245 at a wavelength of 3 - 5 μm, an infrared emissivity of 0.424 - 0.441 at a wavelength of 8 - 14 μm, a tensile bonding strength of 40.8 - 46.4 MPa, and the number of thermal shock resistance is 153 - 167. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a scanning electron microscope photograph of the surface of the high-temperature lightweight stealth coating material obtained in Example 1 magnified 1000 times; Figure 2 It is a scanning electron microscope photograph of the surface of the high-temperature lightweight stealth coating material obtained in Example 1 magnified 10000 times. DETAILED DESCRIPTION OF THE INVENTION

[0015] The preferred embodiments of the present invention will be described below. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0016] Example 1: Preparation method of a high-temperature resistant lightweight stealth coating material Step 1: Preparation of metal-coated carbide The metal-coated carbide is prepared by electroless plating; The carbide powder is dispersed in the electroless plating solution at the nanoscale. Then, by controlling the temperature of the plating solution, the pH value of the plating solution, and the stirring rate, the nickel ions contained in the electroless plating solution are controllably reduced to elemental nickel under the action of a reducing agent and adhere to coat the surface of the carbide powder, forming a metal-coated carbide; The carbide powder is zirconium carbide; The particle size of the zirconium carbide is 30 nm; The electroless plating solution is composed of a nickel salt, a complexing agent, a stabilizer, a reducing agent, and a dispersant; The mass ratio of the carbide powder, nickel salt, complexing agent, stabilizer, reducing agent, dispersant, and deionized water is 15:20:0.5:0.06:3:0.3:160; The complexing agent is citric acid; The stabilizer is sodium thiocyanate; The reducing agent is sodium hypophosphite; The dispersant is alkyl polyglycoside APG0810; The nickel salt is nickel sulfate; The temperature of the plating solution is 65 °C, the pH value of the plating solution is 5.6, and the stirring rate is 200 revolutions per minute.

[0017] Step 2: Preparation of zinc oxide-coated nano-carbon material First, the nano-carbon material is subjected to oxidation treatment, and then added to anhydrous monohydric alcohol. After the nano-carbon material is dispersed to the nano-single particle state, an alkaline aqueous solution is added to adjust the pH value, and then an alcohol solution of a zinc salt is added. After stirring and reacting completely at room temperature, filtration is carried out. The filtered solid is washed with deionized water and anhydrous ethanol until neutral, and then dried to obtain a zinc oxide-coated nano-carbon material; The nano-carbon material is a carbon nanotube; The particle size of the carbon nanotube is 30 nm; The oxidation treatment method is as follows: The nano-carbon material is added to a mixed solution of concentrated nitric acid and hydrogen peroxide, heated to 80 °C, stirred and refluxed for 1.5 hours, then filtered. The filtered solid is washed with deionized water until neutral, and then dried to obtain the oxidized nano-carbon material; The mass ratio of the concentrated nitric acid to the hydrogen peroxide is 3:10; The mass concentration of hydrogen peroxide in the hydrogen peroxide solution is 10%; The alkaline aqueous solution is a sodium hydroxide aqueous solution; When adjusting the pH value, the pH value is adjusted to 11; The alcoholic solution of zinc salt is composed of zinc salt, alkanolamine and anhydrous monohydric alcohol; The mass ratio of the zinc salt, alkanolamine and anhydrous monohydric alcohol is 5:0.3:45; The zinc salt is zinc stearate; The alkanolamine is isobutanolamine; The anhydrous monohydric alcohol is ethanol.

[0018] Step 3, Preparation of high-temperature lightweight stealth coating material The raw material composition of the high-temperature lightweight stealth coating material includes boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nano-carbon material, and sintering aid; The mass ratio of the boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nano-carbon material, and sintering aid is 80:50:2:6:5:2; The boride is titanium boride; The particle size of the boride is 2 μm; The silicide is titanium silicide; The particle size of the silicide is 1 μm; The titanate flux is potassium titanate; The particle size of the titanate flux is 0.6 μm; In the metal-coated carbide, the metal is nickel and the carbide is zirconium carbide; The particle size of the carbide is 30 nm; In the zinc oxide-coated nano-carbon material, the nano-carbon material is a carbon nanotube; The particle size of the nano-carbon material is 30 nm; The sintering aid is silicon phosphate; The particle size of the sintering aid is 0.3 μm; The high-temperature lightweight stealth coating material is prepared by atmospheric plasma spraying technology, which has the advantages of high automation degree, layered structure of the coating, and simple operation; The surface of the substrate to be sprayed must be rust-removed, degreased, and sandblasted in advance. Then, according to the mass ratio of the raw material composition of the high-temperature resistant lightweight stealth coating material, the raw material powders are evenly mixed to obtain a mixed powder. After adding the mixed powder to the spraying equipment, control the arc voltage at 80V, the arc current at 650A, the main gas argon flow rate at 60L / min, the secondary gas hydrogen flow rate at 30L / min, the powder feeding speed at 16g / min, and the spraying distance at 110mm. Spray the mixed powder evenly onto the surface of the substrate to finally obtain a high-temperature resistant lightweight stealth coating material with a thickness of 200μm.

[0019] Example 2: A preparation method of a high-temperature resistant lightweight stealth coating material Step 1: Preparation of metal-coated carbide The metal-coated carbide is prepared by a hydrothermal hydrogen reduction method; In the hydrothermal hydrogen reduction method, the carbide powder, catalyst, dispersant, and nickel salt solution are added to an autoclave, and the appropriate reaction temperature and reaction pressure are controlled. Hydrogen is used to reduce and deposit nickel ions on the surface of the carbide powder to form a metal-coated carbide; The carbide powder is titanium carbide; The particle size of the titanium carbide is 1nm; The catalyst is palladium chloride; The dispersant is sodium dodecylbenzenesulfonate; The mass ratio of the carbide powder, catalyst, dispersant, and nickel salt solution is 10:0.3:1:90; In the nickel salt solution, the mass fraction of the nickel salt is 15%; The reaction temperature is 120°C; The reaction pressure is 2MPa; The nickel salt is nickel nitrate.

[0020] Step 2: Preparation of zinc oxide-coated nano-carbon material First, the nano-carbon material is oxidized, then added to anhydrous monohydric alcohol. After dispersing the nano-carbon material into a nano-single particle state, then add an alkaline aqueous solution to adjust the pH value, and then add an alcohol solution of zinc salt. After stirring and reacting completely at room temperature, filter. The filtered solid is washed with deionized water and anhydrous ethanol until neutral, and then dried to obtain a zinc oxide-coated nano-carbon material; The nano-carbon material is graphene; The particle size of the graphene is 1nm; For the oxidation treatment, the method is: add the nano-carbon material to a mixed solution of concentrated nitric acid and hydrogen peroxide, keep the temperature constant at 70°C, stir and reflux for 1 hour, then filter. The filtered solid is washed with deionized water until neutral, and then dried to obtain the oxidized nano-carbon material; The mass ratio of the concentrated nitric acid to the hydrogen peroxide is 3:10; The mass concentration of hydrogen peroxide in the hydrogen peroxide is 10%; The alkaline aqueous solution is a potassium hydroxide aqueous solution; When adjusting the pH value, the pH value is adjusted to 10; The alcoholic solution of the zinc salt is composed of a zinc salt, an alkanolamine substance, and an anhydrous monohydric alcohol; The zinc salt is zinc acetate; The alkanolamine substance is diethanolamine; The anhydrous monohydric alcohol is methanol.

[0021] Step 3. Preparation of the high-temperature resistant lightweight stealth coating material The raw material composition of the high-temperature resistant lightweight stealth coating material includes a boride, a silicide, a titanate flux, a metal-coated carbide, a zinc oxide-coated nano-carbon material, and a sintering aid; The mass ratio of the boride, the silicide, the titanate flux, the metal-coated carbide, the zinc oxide-coated nano-carbon material, and the sintering aid is 20:30:1:1:1:1; The boride is zirconium boride; The particle size of the boride is 0.5 μm; The silicide is zirconium silicide; The particle size of the silicide is 0.5 μm; The titanate flux is lithium titanate; The particle size of the titanate flux is 0.1 μm; In the metal-coated carbide, the metal is nickel and the carbide is titanium carbide; The particle size of the carbide is 1 nm; In the zinc oxide-coated nano-carbon material, the nano-carbon material is graphene; The particle size of the nano-carbon material is 1 nm; The sintering aid is boron phosphate; The particle size of the sintering aid is 0.1 μm; The high-temperature resistant lightweight stealth coating material is prepared by an atmospheric plasma spraying technique, and this technique has the advantages of high automation degree, a layered structure of the coating, and simple operation; The surface of the substrate to be sprayed must be rust-removed, degreased, and sandblasted in advance. Then, according to the mass ratio of the raw material composition of the high-temperature resistant lightweight stealth coating material, the raw material powders are mixed evenly to obtain a mixed powder. After adding the mixed powder to the spraying equipment, control the arc voltage at 60V, the arc current at 500A, the main gas argon flow rate at 50L / min, the secondary gas hydrogen flow rate at 20L / min, the powder feeding speed at 10g / min, and the spraying distance at 90mm. Spray the mixed powder evenly onto the surface of the substrate to finally obtain a high-temperature resistant lightweight stealth coating material with a thickness of 120μm.

[0022] Example 3: Preparation method of a high-temperature resistant lightweight stealth coating material Step 1: Preparation of metal-coated carbide The metal-coated carbide is prepared by the precipitation reduction method; In the precipitation reduction method, nickel salt is dissolved in deionized water to form an aqueous solution. Control the temperature of the aqueous solution, then add carbide powder. After strong stirring and uniform dispersion, add ammonia water to make nickel form nickel hydroxide precipitation adsorbed on the surface of the carbide powder. After the reaction is completed, dry the carbide powder. After high-temperature reduction of the dried powder by hydrogen, metal-coated carbide is obtained; The carbide powder is vanadium carbide; The particle size of the vanadium carbide is 100nm; The nickel salt is dissolved in deionized water to form an aqueous solution, and the mass concentration of the nickel salt is 13%; The nickel salt is nickel acetate; The mass ratio of the nickel salt dissolved in deionized water to form an aqueous solution, the carbide powder, and ammonia water is 20:2:11; The mass concentration of ammonia in the ammonia water is 4%; For the high-temperature reduction by hydrogen, the reduction temperature is 160°C.

[0023] Step 2: Preparation of zinc oxide-coated nano-carbon material First, oxidize the nano-carbon material, then add it to anhydrous monohydric alcohol. After dispersing the nano-carbon material into nano-single particle state, then add an alkaline aqueous solution to adjust the pH value, and then add an alcohol solution of zinc salt. After stirring at room temperature until the reaction is complete, filter. The filtered solid is washed with deionized water and anhydrous ethanol until neutral, and then dried to obtain zinc oxide-coated nano-carbon material; The nano-carbon material is nano-scale conductive carbon black; The particle size of the nano-scale conductive carbon black is 100nm; For the oxidation treatment, the method is as follows: Add the nanocarbon material into the mixed solution of concentrated nitric acid and hydrogen peroxide, keep the temperature constant at 90 °C, stir and reflux for 2 hours, then filter. Wash the filtered solid with deionized water until it is neutral, and then dry it to obtain the oxidized nanocarbon material. The alkaline aqueous solution is ammonia water. For the pH adjustment, the pH value is adjusted to 12. The alcoholic solution of zinc salt consists of zinc salt, alkanolamine and anhydrous monohydric alcohol. The mass ratio of the zinc salt, alkanolamine and anhydrous monohydric alcohol is 5:0.3:45. The zinc salt is zinc salicylate. The alkanolamine is triethanolamine. The anhydrous monohydric alcohol is ethanol.

[0024] Step 3: Preparation of the high-temperature resistant lightweight stealth coating material The raw material composition of the high-temperature resistant lightweight stealth coating material includes boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nanocarbon material, and sintering aid. The mass ratio of the boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nanocarbon material, and sintering aid is 100:150:5:10:8:4. The boride is calcium boride. The particle size of the boride is 3 μm. The silicide is tantalum silicide. The particle size of the silicide is 3 μm. The titanate flux is magnesium titanate. The particle size of the titanate flux is 1 μm. In the metal-coated carbide, the metal is nickel and the carbide is vanadium carbide. The particle size of the carbide is 100 nm. In the zinc oxide-coated nanocarbon material, the nanocarbon material is nanoscale conductive carbon black. The particle size of the nanocarbon material is 100 nm. The sintering aid is silicon phosphate. The particle size of the sintering aid is 1 μm. The high-temperature resistant lightweight stealth coating material is prepared by atmospheric plasma spraying technology, which has the advantages of high automation degree, layered coating structure, and simple operation. The surface of the substrate to be sprayed must be rust-removed, degreased, and sandblasted in advance. Then, according to the mass ratio of the raw material composition of the high-temperature resistant lightweight stealth coating material, the raw material powders are evenly mixed to obtain a mixed powder. After adding the mixed powder into the spraying equipment, control the arc voltage at 90V, the arc current at 700A, the main gas argon flow rate at 65L / min, the secondary gas hydrogen flow rate at 35L / min, the powder feeding speed at 20g / min, and the spraying distance at 120mm. Spray the mixed powder evenly onto the substrate surface to finally obtain a high-temperature resistant lightweight stealth coating material with a thickness of 260μm.

[0025] Example 4: A preparation method of a high-temperature resistant lightweight stealth coating material Step 1: Preparation of metal-coated carbide On the basis of Example 1, replace nickel salt, i.e., nickel sulfate, with cobalt sulfate, and other operations are the same as in Example 1; The operations of Steps 2 and 3 are the same as in Example 1.

[0026] Comparative Example 1: On the basis of Example 1, without performing Step 1, the preparation of metal-coated carbide, and in Step 3, the preparation of the high-temperature resistant lightweight stealth coating material, replace 6 parts of metal-coated carbide with 6 parts of carbide in equal amount. The specific operations are as follows: Do not perform Step 1, the preparation of metal-coated carbide The operation of Step 2 is the same as in Example 1; Step 3: Preparation of the high-temperature resistant lightweight stealth coating material Replace 6 parts of metal-coated carbide with 6 parts of carbide in equal amount, and other operations are the same as in Example 1; The carbide is zirconium carbide; The particle size of the carbide is 30nm.

[0027] Comparative Example 2: On the basis of Example 1, without performing Step 2, the preparation of zinc oxide-coated nano-carbon material, and in Step 3, the preparation of the high-temperature resistant lightweight stealth coating material, replace 5 parts of zinc oxide-coated nano-carbon material with 5 parts of nano-carbon material in equal amount. The specific operations are as follows: The operation of Step 1 is the same as in Example 1; Do not perform Step 2, the preparation of zinc oxide-coated nano-carbon material; Step 3: Preparation of the high-temperature resistant lightweight stealth coating material Replace 5 parts of zinc oxide-coated nano-carbon material with 5 parts of nano-carbon material in equal amount, and other operations are the same as in Example 1; The nano-carbon material is carbon nanotube; The particle size of the nano-carbon material is 30nm.

[0028] Comparative Example 3: Based on Example 1, in Step 3, the preparation of the high-temperature resistant lightweight stealth coating material, without adding titanate flux, replace 2 parts of titanate flux with 2 parts of boride in equal amount. The specific operation is as follows: The operations of Steps 1 and 2 are the same as those in Example 1; Step 3, the preparation of the high-temperature resistant lightweight stealth coating material Replace 2 parts of titanate flux with 2 parts of boride in equal amount, and other operations are the same as those in Example 1.

[0029] Comparative Example 4: Based on Example 1, in Step 3, the preparation of the high-temperature resistant lightweight stealth coating material, without adding sintering aid, replace 2 parts of sintering aid with 2 parts of boride in equal amount. The specific operation is as follows: The operations of Steps 1 and 2 are the same as those in Example 1; Step 3, the preparation of the high-temperature resistant lightweight stealth coating material Replace 2 parts of sintering aid with 2 parts of boride in equal amount, and other operations are the same as those in Example 1.

[0030] Performance test: For the high-temperature resistant lightweight stealth coating materials obtained in Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4, conduct tests on indicators such as infrared emissivity, tensile bond strength: 1. Infrared emissivity: Heat the sample of the high-temperature resistant lightweight stealth coating material to 1100 °C, and measure the hemispherical infrared radiation intensities of the sample and the standard blackbody in the ranges of 3 - 5 μm and 8 - 14 μm under the same conditions to obtain the infrared emissivity; 2. Tensile bond strength: Conduct the test according to "GB / T 8642-2002 Thermal spraying - Determination of tensile bond strength"; 3. Number of thermal shock resistance: Adopt the water quenching method. Heat the sample in a box-type resistance furnace at a set temperature of 1100 °C for 10 minutes, then quickly take it out and quench it into clean water at about 20 °C. When the sample cools to room temperature in the water, take it out and dry it with an electric hair dryer, which completes one thermal shock experiment. Repeat this cycle until visible cracks, peeling or spalling and other phenomena appear on the surface of the sample, and record the number of thermal shocks experienced at this time, which is the number of thermal shock resistance; The results are shown in Table 1: Table 1

[0031] As can be seen from the data in Table 1, the infrared emissivities of Examples 1-4 at a wavelength of 3-5 μm are all below 0.25, and the infrared emissivities at a wavelength of 8-14 μm do not exceed 0.5. Moreover, the tensile bonding strength of the coating is greater than 40 MPa, and the number of thermal shock resistance is more than 150 times. This shows that the high-temperature resistant lightweight stealth coating material obtained by the present invention has remarkable advantages such as good high-temperature resistance, excellent high-temperature thermal shock resistance, and low infrared emissivity; the carbide added in Comparative Example 1 was not metal-coated, and the infrared emissivity of Comparative Example 1 increased significantly, the tensile bonding strength decreased particularly sharply, and the number of thermal shock resistance also dropped to the lowest. This shows that after the carbide is metal-coated, it can mainly improve the bonding strength between the coating material and the substrate surface, and improve the thermal shock resistance by enhancing the bonding strength. Moreover, the metal-coated carbide may improve the overall conductivity of the coating by increasing the density of the coating during the coating formation process. Therefore, the metal-coated carbide can also reduce the infrared emissivity; the nano-carbon material added in Comparative Example 2 was not zinc oxide-coated, and the infrared emissivity of Comparative Example 2 increased to the maximum, and the tensile bonding strength and the number of thermal shock resistance also decreased significantly. This shows that zinc oxide coating of nano-carbon materials can prevent the nano-carbon materials from being oxidized and ablated during high-temperature spraying, and thus can ensure that the nano-carbon materials enter the coating material matrix in a relatively complete nano-structure, playing the role of enhancing the conductivity of the coating and reducing the infrared emissivity; in Comparative Example 3, no titanate flux was added, and the infrared emissivity of Comparative Example 3 increased significantly, and the tensile bonding strength and the number of thermal shock resistance decreased greatly. It can be seen that the titanate flux plays a very important role in improving the interfacial adhesion between the coating and the substrate, and also plays a role in reducing the infrared emissivity of the coating; in Comparative Example 4, no sintering aid was added, and the infrared emissivity of Comparative Example 4 increased significantly, and the tensile bonding strength and the number of thermal shock resistance decreased sharply. This shows that the sintering aid plays a very crucial role in the bonding strength between the coating and the substrate, and may affect the infrared emissivity of the coating by influencing the density of the coating.

[0032] In the attached drawings Figure 1 and Figure 2 are respectively the scanning electron microscope photos of the surface of the high-temperature resistant lightweight stealth coating material obtained in Example 1 magnified 1000 times and 10000 times. From the Figure 1 view of the 1000-fold magnification, the surface of the coating is very flat, relatively dense as a whole, without pore defects. From the Figure 2 view of the 10000-fold magnification, various raw material powders in the coating are fused together, and the pores formed after fusion are extremely tiny, almost all in the sub-micron to nano level. This shows that the high-temperature resistant lightweight stealth coating material prepared by the present invention has a very high density.

[0033] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent replacements or changes, shall be covered by the protection scope of the present invention.

Claims

1. A high temperature resistant lightweight stealth coating material, characterized by: The raw material composition of the high temperature resistant lightweight stealth coating material includes boride, silicide, titanate flux, metal coated carbide, zinc oxide coated nano carbon material, and sintering aid; The boride is one of titanium boride, zirconium boride, calcium boride, hafnium boride, vanadium boride, chromium boride, silicon boride, manganese monoboride, manganese diboride, manganese tetraboride, molybdenum monoboride, molybdenum diboride, and molybdenum pentaboride, any two of them, or a combination of any two or more thereof; The silicide is one, any two or a combination of any two or more of titanium silicide, zirconium silicide, tantalum silicide, tungsten silicide, molybdenum silicide, molybdenum silicide, or molybdenum disilicide; The titanate flux is one of potassium titanate, lithium titanate, magnesium titanate, barium titanate, lead titanate, and zinc titanate, or any two or a combination of any two or more thereof; In the metal-coated carbide, the metal is one of nickel and cobalt or a combination of nickel and cobalt, and the carbide is one of zirconium carbide, titanium carbide, vanadium carbide, and tungsten carbide, any two of them, or a combination of any two or more of them; In the zinc oxide coated nano-carbon material, the nano-carbon material is one, any two or a combination of any two or more of carbon nanotubes, carbon nanofibers, nano-carbon balls, graphene, nano-scale conductive carbon black, and nano-scale graphite powder; The sintering aid is one of silicon phosphate and boron phosphate or a combination of the two.

2. The high temperature resistant lightweight stealth coating material according to claim 1, characterized in that: The metal-coated carbide is prepared by a method selected from the group consisting of a chemical plating method, a hydrothermal hydrogen reduction method, and a precipitation reduction method; The zinc oxide coated nano-carbon material has a preparation method comprising: firstly subjecting the nano-carbon material to an oxidation treatment, then adding the nano-carbon material to an anhydrous monohydric alcohol, dispersing the nano-carbon material to a nano single particle state, then adding an alkaline aqueous solution to adjust the pH value, then adding an alcohol solution of a zinc salt, stirring at room temperature to complete the reaction, filtering, washing the filtered solid with deionized water and anhydrous ethanol to neutrality, and then drying to obtain the zinc oxide coated nano-carbon material.

3. The high temperature resistant lightweight stealth coating material according to claim 2, characterized in that: The chemical plating method disperses carbide powder in a chemical plating solution at a nanometer scale, and then controls the plating solution temperature, the plating solution pH value and the stirring rate, so that the nickel ions, cobalt ions or nickel-cobalt ions contained in the chemical plating solution are controllably reduced to single nickel, single cobalt or a mixture of two single elements of nickel and cobalt under the action of a reducing agent, and the nickel ions, cobalt ions or nickel-cobalt ions are attached and coated on the surface of the carbide powder to form a metal-coated carbide; The chemical plating solution is composed of a mixture of one or both of a nickel salt and a cobalt salt, a complexing agent, a stabilizer, a reducing agent, and a dispersant; The complexing agent is an aliphatic carboxylic acid; The stabilizer is one of thiocyanate and thiourea; The reducing agent is one of sodium hypophosphite, hydrazine and sodium borohydride; The dispersant is a nonionic surfactant that promotes the dispersion of carbide powder, specifically one of alkyl glycoside surfactants, long-chain fatty alcohol polyoxyethylene ether surfactants, and alkylphenol polyoxyethylene ether surfactants, or a combination of any two or more of them.

4. The high temperature resistant lightweight stealth coating material according to claim 2, characterized in that: The hydrothermal hydrogen reduction method comprises adding carbide powder, catalyst, dispersant, nickel salt solution or cobalt salt solution or a mixed solution of nickel salt and cobalt salt into an autoclave, controlling appropriate reaction temperature and reaction pressure, and using hydrogen to reduce and deposit nickel ions, cobalt ions or both nickel and cobalt ions on the surface of the carbide powder to form metal-coated carbide; The catalyst is one of palladium chloride and anthraquinone; The dispersant is one, any two or a combination of any two or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate and polyethylene glycol monooctylphenyl ether; The reaction temperature is 110-160°C; The reaction pressure is 1-5 MPa.

5. The high temperature resistant lightweight stealth coating material according to claim 2, characterized in that: The precipitation reduction method comprises dissolving one of nickel salt and cobalt salt or a mixture of the two in deionized water to prepare an aqueous solution, controlling the temperature of the aqueous solution, then adding carbide powder, vigorously stirring and dispersing the solution, and then adding ammonia water to make nickel or cobalt generate nickel hydroxide or cobalt hydroxide precipitate adsorbed on the surface of the carbide powder. After the reaction is completed, the carbide powder is dried, and the dried powder is reduced by hydrogen at high temperature to obtain a metal-coated carbide. The nickel salt is one, any two or a combination of any two or more of nickel chloride, nickel nitrate, nickel sulfate, nickel phosphate and nickel acetate; The cobalt salt is one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt phosphate and cobalt acetate, or any two or a combination of any two or more thereof.

6. The high temperature resistant lightweight stealth coating material according to claim 2, characterized in that: The oxidation treatment method comprises: adding the nano-carbon material to a mixture of concentrated nitric acid and hydrogen peroxide, maintaining the temperature at 70-90°C, stirring and refluxing for 1-2 hours, filtering, washing the filtered solid with deionized water until it is neutral, and then drying to obtain the nano-carbon material after oxidation treatment; The alkaline aqueous solution is one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and an ammonia solution; The pH value is adjusted to 10-12; The alcohol solution of zinc salt is composed of zinc salt, alcohol amine substance and anhydrous monohydric alcohol; The zinc salt is one of zinc stearate, zinc acetate and zinc salicylate; The alcoholamine substance is one of isobutanolamine, monoethanolamine, diethanolamine and triethanolamine; The anhydrous monohydric alcohol is one of methanol and ethanol or a mixture of methanol and ethanol.

7. The high temperature resistant lightweight stealth coating material according to claim 1, characterized in that: The mass ratio of the boride, silicide, titanate flux, metal-coated carbide, zinc oxide-coated nano-carbon material and sintering aid is 20-100:30-150:1-5:1-10:1-8:1-4.

8. The high temperature resistant lightweight stealth coating material according to claim 1, characterized in that: The particle size of the boride is 0.5-3 μm; The particle size of the silicide is 0.5-3 μm.

9. The high temperature resistant lightweight stealth coating material according to claim 1, characterized in that: The particle size of the titanate flux is 0.1-1 μm; The particle size of the carbide is 1 to 100 nm; The particle size of the nano carbon material is 1-100 nm; The particle size of the sintering aid is 0.1-1 μm.

10. The method for preparing the high temperature resistant lightweight stealth coating material according to claim 1, characterized in that: The surface of the substrate to be sprayed must be derusted, degreased, and sandblasted in advance, and then the raw material powders are evenly mixed according to the mass ratio of the raw material composition of the high-temperature resistant lightweight stealth coating material to obtain a mixed powder. After the mixed powder is added to the spraying equipment, the arc voltage is controlled to be 60~90V, the arc current is 500~700A, the main gas argon flow rate is 50~65L / min, the auxiliary gas hydrogen flow rate is 20~35 L / min, the powder feeding speed is 10~20g / min, the spraying distance is 90~120mm, and the mixed powder is evenly sprayed onto the surface of the substrate to finally obtain a high-temperature resistant lightweight stealth coating material with a thickness of 120~260μm.

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