A method for preparing a multilayer structure heat protection coating material of heat-conducting, radiation composite shielding

Abstract

The application relates to a preparation method of a heat-conducting, radiation-composite-shielded multilayer structure heat protection coating material, and belongs to the technical field of high-temperature heat protection and radiation heat control. The application aims to solve the problem that the existing heat protection coating technology cannot meet the heat-conducting, radiation-penetrating composite shielding. The method comprises the following steps: one, surface pretreatment of a base; two, preparation of a low-heat-conducting layer; three, preparation of a high-absorption layer; and four, preparation of a high-reflecting layer. The effective thermal conductivity of the heat-conducting, radiation-composite-shielded multilayer structure heat protection coating material prepared by the application is less than 1 W / (m*K), the infrared transmittance in the 0.5-10 mu m wave band is less than 0.12, and the infrared reflectivity is greater than 0.4. Compared with the existing multilayer composite structure heat protection coating, the multilayer structure coating reduces the heat radiation penetration and reduces the direct impact of the heat radiation on the base, and simultaneously has low thermal conductivity and high-temperature heat stability; and the application is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature thermal protection and radiation heat control, and particularly relates to a preparation method of a multilayer structure thermal protection coating material with heat conduction and radiation composite shielding. BACKGROUND

[0002] With the development of high-temperature combustion technology, the high-temperature demand of hot end components is continuously increasing, and the research on thermal protection coatings with low thermal conductivity has been the focus of scholars at home and abroad. So far, for the research and development of thermal protection coatings, scholars pay more attention to the low thermal conductivity of coating materials, without focusing on the influence of high-temperature radiation penetration on the substrate. At present, the extreme temperature of the hot end component can reach above 1500℃, according to the Planck blackbody radiation law, the thermal radiation energy is mainly distributed in the wavelength range of 0.5-10μm, and as the temperature rises, the thermal radiation energy will be concentrated in a shorter wavelength range. Short-wavelength electromagnetic waves are usually less scattered and absorbed, and have strong penetration ability. At extreme temperatures, the thermal shock caused by high-temperature thermal radiation penetration is one of the main reasons for the thermal damage of hot end components. Therefore, thermal protection coatings with only low thermal conductivity cannot meet the thermal protection needs of hot end components at the present stage and in the future, and it is extremely important to study a thermal protection coating with heat conduction and radiation composite shielding in multiple high-temperature environments.

[0003] On March 28, 2023, a Chinese patent (CN115849958A) disclosed a thermal protection coating of ceramic matrix composite material and its preparation method and application. The coating takes ceramic matrix material as the substrate, Yb2O3 and CaO co-doped HfO2 as the heat insulation layer material, and adopts atmospheric plasma spraying to prepare a multilayer composite thermal protection coating with the structure of sealing layer, oxidation-resistant adhesive layer and heat-insulating burn-resistant layer. The coating features improved temperature resistance, but does not consider the influence of high-temperature (above 1000℃) thermal radiation penetration. On December 30, 2022, a Chinese patent (CN115537812A) disclosed a high-temperature oxidation-resistant coating for composite thermal protection. The coating takes SiC / C as the substrate, silicon carbide, iridium boride, metallic iridium and hafnium boride as the material, and constitutes a multilayer alternating thermal protection coating for high-temperature oxidation resistance. The coating does not consider the influence of high-temperature (above 1000℃) thermal radiation penetration. On February 15, 2022, a Chinese patent (CN114045456A) disclosed a high-temperature-resistant composite coating containing rare earth aluminates and a preparation method. An oxidation film layer, a metal adhesive layer and a rare earth aluminates ceramic layer structure composite coating are prepared by atmospheric plasma spraying. The coating can withstand high temperatures of 1800℃, but does not consider the influence of thermal radiation penetration. In summary, the multilayer thermal protection coatings proposed by scholars ignore the combined influence of thermal radiation penetration and heat conduction, and therefore the research and development of heat conduction and radiation composite shielding coatings are extremely important. SUMMARY

[0004] The purpose of this invention is to solve the problem that existing thermal protective coating technologies cannot meet the requirements of composite shielding that allows for thermal conductivity and radiation penetration, and to provide a method for preparing a multilayer thermal protective coating material that provides composite shielding that allows for thermal conductivity and radiation penetration.

[0005] This invention addresses the shortcomings in current research on thermal protective coatings and the urgent needs in the field of thermal protection. It proposes a method for preparing a thermally conductive and radiative composite shielding thermal protective coating (i.e., a multi-layered thermal protective coating material with thermal conductivity and radiative composite shielding) with a reflective layer / absorption layer / low thermal conductivity layer structure.

[0006] A method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding is specifically carried out according to the following steps:

[0007] I. Substrate Surface Pretreatment:

[0008] Remove dust, grease and impurities from the substrate surface, and then activate the substrate surface to obtain the pretreated substrate;

[0009] II. Preparation of a low thermal conductivity layer:

[0010] A heat insulation layer with low thermal conductivity is prepared on the surface of a substrate by spraying.

[0011] The thermal conductivity of the insulation layer with low thermal conductivity described in step two is less than 2 W / (m·K);

[0012] The functional components of the heat insulation layer mentioned in step two are one or a combination of ZrO2, Si3N4 and rare earth acid ceramics;

[0013] III. Preparation of the high-absorption layer:

[0014] An intermediate layer with high infrared absorption is prepared on the heat insulation layer by spraying.

[0015] The functional components of the intermediate layer with high infrared absorption described in step three have high infrared absorption in the 0.5μm to 10μm band, and are one or a combination of transition metal oxides, carbon-based materials and narrow bandgap semiconductor materials.

[0016] IV. Preparation of a high-reflectivity layer:

[0017] A high-reflectivity layer was prepared on a high-infrared-absorbing intermediate layer by spraying, and after polishing, a multi-layer thermal protection coating material with thermal conductivity and radiation shielding was finally obtained.

[0018] The functional components of the high-reflectivity layer mentioned in step four have high infrared reflectivity in the 0.5μm to 10μm band and can be any one of metal oxides, two-dimensional materials and noble metals;

[0019] The multi-layer thermal protection coating material with thermal conductivity and radiation composite shielding described in step four has an effective thermal conductivity of less than 1 W / (m·K), an infrared transmittance of less than 0.12 in the 0.5μm to 10μm band, and an infrared reflectance of greater than 0.4.

[0020] The principle of this invention:

[0021] This invention prepares a multilayer thermally conductive and radiative composite shielding coating (i.e., a multilayer thermally conductive and radiative composite shielding material) with high reflectivity, high absorption, and low thermal conductivity using a spraying method. This multilayer structure exhibits low thermal conductivity and resists radiation penetration, achieving composite shielding of both thermal conductivity and radiation. The first high-reflectivity layer (outermost layer) uses a material with a large complex refractive index modulus to achieve full-band reflection of high-temperature thermal radiation. The second layer (middle layer) is a high-absorption layer, requiring a material with a high absorption coefficient. Simultaneously, the wavelengths of the high absorption coefficient and the high refractive index wavelengths of the reflective layer should be staggered to ensure good complementarity between the reflection and absorption bands, further contributing to thermal radiation shielding. The third layer is a low-thermal-conductivity layer (innermost layer), using a material with low thermal conductivity, high thermal stability, and a low coefficient of thermal expansion. Based on the first and second layers, photon heat transfer is hindered; based on the third layer, phonon heat transfer is hindered. According to the blackbody radiation law, at high temperatures (above 1000℃), the radiation energy is mainly distributed in the 0.5-10μm band. This thermal protective coating reduces the transmittance in this band, thereby reducing the thermal shock of radiation to the substrate. At the same time, through the low thermal conductivity layer, the overall thermal conductivity of the coating is reduced. This composite structure makes the overall thermal conductivity of the coating less than 1W / (m·K).

[0022] Advantages of this invention:

[0023] I. This invention proposes a method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding. Compared with existing multilayer composite thermal protection coatings, this multilayer coating reduces thermal radiation penetration and reduces the direct impact of thermal radiation on the substrate, while also possessing low thermal conductivity and high-temperature thermal stability.

[0024] Second, the materials used in the thermal protective coating proposed in this invention are moderately priced, the preparation process is simple, it can be prepared by spraying, and the process parameters are adjustable, making it suitable for large-scale production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a multi-layer thermal protection coating material with thermal conductivity and radiation composite shielding as described in this invention. In the figure, 1 is the substrate, 2 is the low thermal conductivity layer, 3 is the high absorption layer, and 4 is the high reflectivity layer.

[0026] Figure 2The cross-sectional morphology image obtained by SEM scanning of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protection coating material prepared in Example 1;

[0027] Figure 3 The figures show the infrared reflectance and infrared transmittance spectra. In the figure, (a) is the infrared reflectance spectrum of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1; and (b) is the infrared transmittance spectrum of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1.

[0028] Figure 4 The infrared transmittance spectrum of the TiO2 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 1;

[0029] Figure 5 The infrared transmittance spectrum of the Fe2O3 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 2 was obtained.

[0030] Figure 6 The infrared transmittance spectrum of the ZrO2 monolayer thermal protective coating prepared in Comparative Example 3 is shown. Detailed Implementation

[0031] Specific Implementation Method 1: This implementation method describes a method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding, which is specifically completed according to the following steps:

[0032] I. Substrate Surface Pretreatment:

[0033] Remove dust, grease and impurities from the substrate surface, and then activate the substrate surface to obtain the pretreated substrate;

[0034] II. Preparation of a low thermal conductivity layer:

[0035] A heat insulation layer with low thermal conductivity is prepared on the surface of a substrate by spraying.

[0036] The thermal conductivity of the insulation layer with low thermal conductivity described in step two is less than 2 W / (m·K);

[0037] The functional components of the heat insulation layer mentioned in step two are one or a combination of ZrO2, Si3N4 and rare earth acid ceramics;

[0038] III. Preparation of the high-absorption layer:

[0039] An intermediate layer with high infrared absorption is prepared on the heat insulation layer by spraying.

[0040] The functional components of the intermediate layer with high infrared absorption described in step three have high infrared absorption in the 0.5μm to 10μm band, and are one or a combination of transition metal oxides, carbon-based materials and narrow bandgap semiconductor materials.

[0041] IV. Preparation of a high-reflectivity layer:

[0042] A high-reflectivity layer was prepared on a high-infrared-absorbing intermediate layer by spraying, and after polishing, a multi-layer thermal protection coating material with thermal conductivity and radiation shielding was finally obtained.

[0043] The functional components of the high-reflectivity layer mentioned in step four have high infrared reflectivity in the 0.5μm to 10μm band and can be any one of metal oxides, two-dimensional materials and noble metals;

[0044] The multi-layer thermal protection coating material with thermal conductivity and radiation composite shielding described in step four has an effective thermal conductivity of less than 1 W / (m·K), an infrared transmittance of less than 0.12 in the 0.5μm to 10μm band, and an infrared reflectance of greater than 0.4.

[0045] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the substrate in step one can be any one of a metal-based material or a ceramic-based composite material; the metal-based material can be carbon steel, aluminum alloy, titanium alloy, or nickel-based alloy; the ceramic-based composite material can be C / C, C / SiC, or SiC / SiC; in step one, water, methanol, ethanol, ammonia, potassium hydroxide solution, nitric acid, or hydrochloric acid are used to clean the substrate to remove dust, grease, and impurities from the substrate surface. Other steps are the same as in Specific Implementation Method One.

[0046] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the mass fraction of ammonia water is 1% to 5%, the mass fraction of potassium hydroxide solution is 5% to 10%, the mass fraction of nitric acid is 10% to 30%, and the mass fraction of hydrochloric acid is 10% to 20%. Other steps are the same as in Specific Implementation Method One or Two.

[0047] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: in step one, a mechanical sandblasting process is used to activate the surface of the substrate; the sandblasting material used in the mechanical sandblasting process is silica sand, quartz sand, or ceramic beads, the sandblasting pressure is 0.2MPa to 0.6MPa, the sandblasting distance is 100mm to 300mm, and the sandblasting angle is 45° to 90°. The other steps are the same as in Specific Implementation Methods One to Three.

[0048] Specific Implementation Method Five: The difference between this implementation method and Specific Implementation Methods One to Four is that the rare earth acid ceramic mentioned in step two is... type, type, The type is defined as follows: A is one or a combination of several of Sc, Yb, Lu, Er, Tm, Dy, Ho, La, Y, Gd, Ti, Sm, Nd, and Eu; B is Zr, Ce, or Hf; and C is Ta or Nb. Other steps are the same as in specific embodiments one through four.

[0049] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the particle size of the functional components of the insulation layer described in step two is 1μm to 10μm; the thickness of the insulation layer with low thermal conductivity on the substrate in step two is 0.01mm to 1mm, the density is greater than 70%, and the thermal conductivity is less than 2W / mK. Other steps are the same as in Specific Implementation Methods One to Five.

[0050] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the transition metal oxide mentioned in step three is Fe3O4, Fe2O3, CuO, MnO2, Co2O3, or ZnO; the carbon-based material is nano-carbon black or graphene; and the narrow bandgap semiconductor material is cadmium selenide or bismuth selenide. The other steps are the same as in Specific Implementation Methods One through Six.

[0051] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that: the thickness of the intermediate layer with high infrared absorption in step three is 0.01mm to 2mm, the density is greater than 60%, and the absorption coefficient is greater than 10000cm². -1 The other steps are the same as those in Specific Implementation Methods One through Seven.

[0052] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the metal oxide mentioned in step four is TiO2 or Al2O3; the two-dimensional material is BN, indium selenide, or a transition metal dichalcogenide; the noble metal is Pt or a Pt alloy; the thickness of the high-reflectivity layer mentioned in step four is 0.01 mm to 1 mm, the density is greater than 60%, and the complex refractive index modulus is greater than 2. Other steps are the same as in Specific Implementation Methods One to Eight.

[0053] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that: the specific polishing method described in step four is as follows: remove debris and dirt from the surface of the metallographic polishing machine's worktable, install a 300-mesh grinding disc on the turntable for coarse grinding, adjust the metallographic polishing machine parameters, set the rotation speed to 300 r / min, and the grinding time to 3 min; replace with an 800-mesh grinding disc for fine grinding, adjust the metallographic polishing machine parameters, set the rotation speed to 600 r / min, and the grinding time to 2 min, resulting in an average surface roughness Ra of the coating less than 2 μm; the spraying method described in steps two, three, and four is: thermal spraying or slurry spraying; the binder in the slurry spraying is one or a combination of potassium silicate, aluminum silicate, silica sol, and aluminum phosphate. Other steps are the same as in Specific Implementation Methods One through Nine.

[0054] The beneficial effects of the present invention are verified using the following embodiments:

[0055] Example 1: The preparation method of a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding of TiO2 / Fe2O3 / ZrO2 is carried out according to the following steps:

[0056] I. Substrate Surface Pretreatment:

[0057] Anhydrous ethanol was used as a solvent to remove dust, grease and impurities from the surface of the substrate, and then the surface of the substrate was activated to obtain a pretreated substrate.

[0058] The substrate mentioned in step one is an aluminum alloy with a thickness of 3mm and a grade of 6061;

[0059] In step one, a mechanical sandblasting process is used to activate the surface of the substrate. The sandblasting material used in the mechanical sandblasting process is quartz sand, the sandblasting pressure is 0.2MPa, the sandblasting distance is 100mm, and the sandblasting angle is 45°.

[0060] II. Preparation of a low thermal conductivity layer:

[0061] A ceramic powder with low thermal conductivity is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto the pretreated substrate surface using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours and then cured at 240℃ for 1 hour to obtain a substrate covered with a ceramic underlayer with low thermal conductivity.

[0062] The ceramic powder with low thermal conductivity mentioned in step two is ZrO2 with a particle size of 2μm;

[0063] The adhesive mentioned in step two is sodium silicate;

[0064] The mass ratio of the ceramic powder with low thermal conductivity to the binder mentioned in step two is 3:2;

[0065] The process parameters for the slurry spraying method described in step two are: air pressure 2MPa, spraying distance 300mm, and spraying time 15s.

[0066] In step two, the thickness of the ceramic substrate with low thermal conductivity is 0.25 mm and the density is 77%.

[0067] III. Preparation of the high-absorption layer:

[0068] The powder with high infrared absorption is thoroughly mixed with a binder to obtain the mixed powder. The mixed powder is then sprayed onto the surface of a substrate covered by a ceramic underlayer with low thermal conductivity using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours and then cured at 240℃ for 1 hour to obtain a substrate covered by an intermediate layer with high infrared absorption.

[0069] The powder with high infrared absorption mentioned in step three is Fe2O3;

[0070] The adhesive mentioned in step three is sodium silicate;

[0071] The mass ratio of the powder with high infrared absorption to the binder in step three is 3:2;

[0072] The process parameters for the slurry spraying method described in step three are: air pressure 2MPa, spraying distance 300mm, and spraying time 50s.

[0073] In step three, the thickness of the intermediate layer with high infrared absorption is 0.95 mm, the density is 71%, and the absorption coefficient is 46895 cm⁻¹. -1 ;

[0074] IV. Preparation of a high-reflectivity layer:

[0075] Highly reflective powder is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto the substrate surface covered by a high infrared absorption intermediate layer using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours, then cured at 240℃ for 1 hour, and then polished to obtain a substrate covered by a high reflective layer. This is a multi-layer thermal protection coating material with thermal conductivity and radiation shielding of TiO2 / Fe2O3 / ZrO2.

[0076] The highly reflective powder mentioned in step four is TiO2;

[0077] The adhesive mentioned in step four is sodium silicate;

[0078] The mass ratio of the highly reflective powder to the binder mentioned in step four is 3:2;

[0079] The process parameters for the slurry spraying method described in step four are: air pressure 2MPa, spraying distance 300mm, and spraying time 25s.

[0080] The specific method for polishing in step four is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the speed to 600 r / min, and the grinding time to 2 min;

[0081] In step four, the high-reflectivity layer of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-conducting composite shielding multilayer thermal protection coating has a thickness of 0.3 mm and a density of 73%; the average surface roughness of the coating is 0.8 μm, and the complex refractive index modulus is 2.31.

[0082] The optical properties of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1 were tested using a Fourier transform spectrometer. The transmittance of the coating in the 0.5-10 μm band was measured to be 0.044 and the reflectance to be 0.48.

[0083] The thermal conductivity of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1 was measured using a laser thermal conductivity meter. The thermal conductivity of the coating at high temperature (1000℃) was found to be 0.95 W / (m·K).

[0084] Example 2: The preparation method of a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding of Al2O3 / ZnO / Y3NbO7 is carried out according to the following steps:

[0085] I. Substrate Surface Pretreatment:

[0086] Anhydrous ethanol was used as a solvent to remove dust, grease and impurities from the surface of the substrate, and then the surface of the substrate was activated to obtain a pretreated substrate.

[0087] The substrate mentioned in step one is a nickel-based alloy with a thickness of 3mm, and the nickel-based alloy type is GH4169;

[0088] In step one, a mechanical sandblasting process is used to activate the surface of the substrate; the sandblasting material used in the mechanical sandblasting process is silica sand, the sandblasting pressure is 0.3MPa, the sandblasting distance is 120mm, and the sandblasting angle is 45°.

[0089] II. Preparation of a low thermal conductivity layer:

[0090] Powder is sprayed onto the pretreated substrate surface using a thermal spraying method to obtain a substrate covered with a ceramic underlayer with low thermal conductivity.

[0091] The ceramic powder with low thermal conductivity mentioned in step two is Y3NbO7 with a particle size of 1.5μm. The preparation method is as follows: A certain amount of Y2O3 and Nb2O5 are weighed and placed in a ball mill jar, zirconia grinding balls are added (ball-to-material ratio 3:1), and an appropriate amount of anhydrous ethanol is added. The mixture is ball-milled for 24 hours at a speed of 200 r / min. The milled powder is then placed in a drying oven at 90℃ and kept at that temperature for 6 hours. After passing through a 200-mesh sieve, the powder is placed in a box furnace and calcined at 1600℃ for 8 hours to obtain Y3NbO7. The mass ratio of Y2O3 to Nb2O5 is 2.55:1.

[0092] The thermal spraying method described in step two is atmospheric plasma spraying. The process parameters are as follows: argon is used as the main gas and hydrogen is used as the auxiliary gas. The main gas flow rate is 40 NLPM, the auxiliary gas flow rate is 10 NLPM, the carrier gas flow rate is 3 NLPM, the plasma spray gun power is 42.5 kW, the powder feeder speed is 25 rpm, and the nozzle distance is 100 mm.

[0093] In step two, the thickness of the ceramic substrate with low thermal conductivity is 0.25 mm and the density is 85%.

[0094] III. Preparation of the high-absorption layer:

[0095] A powder with high infrared absorption is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto the surface of a substrate covered by a ceramic underlayer with low thermal conductivity using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours and then cured at 240℃ for 1 hour to obtain a substrate covered by an intermediate layer with high infrared absorption.

[0096] The powder with high infrared absorption mentioned in step three is ZnO;

[0097] The adhesive mentioned in step three is sodium silicate;

[0098] The mass ratio of the powder with high infrared absorption to the binder in step three is 3:2;

[0099] The process parameters for the slurry spraying method described in step three are: air pressure 2MPa, spraying distance 300mm, and spraying time 65s.

[0100] In step three, the intermediate layer with high infrared absorption has a thickness of 0.95 mm, a density of 78%, and an absorption coefficient of 9896.5 cm⁻¹.-1 ;

[0101] IV. Preparation of a high-reflectivity layer:

[0102] Highly reflective powder is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto a substrate surface covered by a high infrared absorption intermediate layer using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours, then cured at 240℃ for 1 hour, and finally polished to obtain a substrate covered by a high reflective layer. This is a multi-layer thermal protection coating material with Al2O3 / ZnO / Y3NbO7 thermal conductivity and radiation shielding composite structure.

[0103] The highly reflective powder mentioned in step four is Al2O3;

[0104] The adhesive mentioned in step four is sodium silicate;

[0105] The mass ratio of the highly reflective powder to the binder mentioned in step four is 3:2;

[0106] The process parameters for the slurry spraying method described in step four are: air pressure 2MPa, spraying distance 300mm, and spraying time 20s.

[0107] The specific method for polishing in step four is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the speed to 600 r / min, and the grinding time to 2 min;

[0108] In step four, the high-reflectivity layer of the Al2O3 / ZnO / Y3NbO7 thermally conductive and radiation-conducting composite shielding multilayer thermal protection coating has a thickness of 0.3 mm and a density of 74%; the average surface roughness of the coating is 0.5 μm, and the complex refractive index modulus is 2.07.

[0109] The optical properties of the Al2O3 / ZnO / Y3NbO7 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 2 were tested using a Fourier transform spectrometer. The transmittance of the coating in the 0.5-10 μm band was measured to be 0.089 and the reflectance to be 0.45.

[0110] The thermal conductivity of the Al2O3 / ZnO / Y3NbO7 multilayer thermal protective coating material with thermal conductivity and radiation shielding prepared in Example 2 was measured using a laser thermal conductivity meter. The thermal conductivity of the coating at high temperature (1000℃) was found to be 0.89 W / (m·K).

[0111] Comparative Example 1: TiO2 / ZrO2 dual-layer thermal protection coating, specifically completed according to the following steps:

[0112] I. Substrate Surface Pretreatment:

[0113] Anhydrous ethanol was used as a solvent to remove dust, grease and impurities from the surface of the substrate, and then the surface of the substrate was activated to obtain a pretreated substrate.

[0114] The substrate mentioned in step one is an aluminum alloy with a thickness of 3mm, and the aluminum alloy type is 6061;

[0115] In step one, a mechanical sandblasting process is used to activate the surface of the substrate. The sandblasting material used in the mechanical sandblasting process is quartz sand, the sandblasting pressure is 0.2MPa, the sandblasting distance is 100mm, and the sandblasting angle is 45°.

[0116] II. Preparation of a low thermal conductivity layer:

[0117] Powder is sprayed onto the pretreated substrate surface using a thermal spraying method to obtain a substrate covered with a ceramic underlayer with low thermal conductivity.

[0118] The ceramic powder with low thermal conductivity mentioned in step two is ZrO2 with a particle size of 2μm;

[0119] The thermal spraying method described in step two is atmospheric plasma spraying. The process parameters are as follows: argon is used as the main gas and hydrogen as the auxiliary gas; the main gas flow rate is 40 NLPM; the auxiliary gas flow rate is 10 NLPM; the carrier gas flow rate is 3 NLPM; the plasma spray gun power is 42.5 kW; the powder feeder speed is 25 rpm; and the nozzle distance is 100 mm. The ceramic underlayer with low thermal conductivity on the substrate in step two has a thickness of 0.8 mm and a density of 87%.

[0120] III. Preparation of a high-reflectivity layer:

[0121] Highly reflective powder is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto the surface of a substrate covered with a ceramic underlayer having low thermal conductivity using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours, then cured at 240℃ for 1 hour, and then polished to obtain a substrate covered with a highly reflective layer, which is the TiO2 / ZrO2 double-layer thermal protection coating.

[0122] The highly reflective powder mentioned in step three is TiO2;

[0123] The adhesive mentioned in step three is sodium silicate;

[0124] The mass ratio of the highly reflective powder to the binder mentioned in step three is 3:2;

[0125] The process parameters for the slurry spraying method described in step three are: air pressure 2MPa, spraying distance 300mm, and spraying time 40s.

[0126] The specific method for polishing in step three is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the speed to 600 r / min, and the grinding time to 2 min;

[0127] In step three, the thickness of the high-reflectivity layer in the TiO2 / ZrO2 double-layer thermal protection coating is 0.7 mm, the density is 79%, the average surface roughness of the coating is 0.5 μm, and the complex refractive index modulus is 2.31.

[0128] The optical properties of the TiO2 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 1 were tested using a Fourier transform spectrometer. The transmittance of the coating in the 0.5-10 μm band was measured to be 0.27 and the reflectance to be 0.45.

[0129] The thermal conductivity of the TiO2 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 1 was measured using a laser thermal conductivity meter. The thermal conductivity of the coating at high temperature (1000℃) was found to be 1.98 W / (m·K).

[0130] Comparative Example 2: Fe2O3 / ZrO2 dual-layer thermal protective coating, specifically completed according to the following steps:

[0131] I. Substrate Surface Pretreatment:

[0132] Anhydrous ethanol was used as a solvent to remove dust, grease and impurities from the surface of the substrate, and then the surface of the substrate was activated to obtain a pretreated substrate.

[0133] The substrate mentioned in step one is an aluminum alloy with a thickness of 3mm, and the aluminum alloy type is 6061;

[0134] In step one, a mechanical sandblasting process is used to activate the surface of the substrate. The sandblasting material used in the mechanical sandblasting process is quartz sand, the sandblasting pressure is 0.2MPa, the sandblasting distance is 100mm, and the sandblasting angle is 45°.

[0135] II. Preparation of a low thermal conductivity layer:

[0136] Powder is sprayed onto the pretreated substrate surface using a thermal spraying method to obtain a substrate covered with a ceramic underlayer with low thermal conductivity.

[0137] The ceramic powder with low thermal conductivity mentioned in step two is ZrO2 with a particle size of 2μm;

[0138] The thermal spraying method described in step two is atmospheric plasma spraying. The process parameters are as follows: argon is used as the main gas and hydrogen is used as the auxiliary gas. The main gas flow rate is 40 NLPM, the auxiliary gas flow rate is 10 NLPM, the carrier gas flow rate is 3 NLPM, the plasma spray gun power is 42.5 kW, the powder feeder speed is 25 rpm, and the nozzle distance is 100 mm.

[0139] In step two, the thickness of the ceramic substrate with low thermal conductivity is 0.55 mm and the density is 85.4%.

[0140] III. Preparation of the high-absorption layer:

[0141] High-absorption powder is thoroughly mixed with a binder to obtain a mixed powder. The mixed powder is then sprayed onto the surface of a substrate covered with a ceramic underlayer with low thermal conductivity using a slurry spraying method. The coating thickness can be controlled by the spraying time. The prepared coating is dried at room temperature (25℃) for 5 hours, then cured at 240℃ for 1 hour, and then polished to obtain a substrate covered with a high-absorption layer, which is the Fe2O3 / ZrO2 double-layer thermal protection coating.

[0142] The highly absorbent powder mentioned in step three is Fe2O3;

[0143] The adhesive mentioned in step three is sodium silicate;

[0144] The mass ratio of the highly absorbent powder to the binder mentioned in step three is 3:2;

[0145] The process parameters for the slurry spraying method described in step three are: air pressure 2MPa, spraying distance 300mm, and spraying time 55s.

[0146] The specific method for polishing in step three is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the speed to 600 r / min, and the grinding time to 2 min;

[0147] In step three, the high-absorption layer of the Fe2O3 / ZrO2 bilayer thermal protective coating has a thickness of 0.95 mm, a density of 71%, and an absorption coefficient of 46895 cm⁻¹. -1The average surface roughness of the coating is 0.65 μm.

[0148] The optical properties of the Fe2O3 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 2 were tested using a Fourier transform spectrometer. The transmittance of the coating in the 0.5-10 μm band was measured to be 0.22 and the reflectance to be 0.21.

[0149] The thermal conductivity of the Fe2O3 / ZrO2 double-layer thermal protective coating prepared in Comparative Example 2 was measured using a laser thermal conductivity meter. The thermal conductivity of the coating at high temperature (1000℃) was found to be 1.9 W / (m·K).

[0150] Comparative Example 3: ZrO2 single-layer thermal protective coating, specifically completed according to the following steps:

[0151] I. Substrate Surface Pretreatment:

[0152] Anhydrous ethanol was used as a solvent to remove dust, grease and impurities from the surface of the substrate, and then the surface of the substrate was activated to obtain a pretreated substrate.

[0153] The substrate mentioned in step one is an aluminum alloy with a thickness of 3mm, and the aluminum alloy type is 6061;

[0154] In step one, a mechanical sandblasting process is used to activate the surface of the substrate. The sandblasting material used in the mechanical sandblasting process is quartz sand, the sandblasting pressure is 0.2MPa, the sandblasting distance is 100mm, and the sandblasting angle is 45°.

[0155] II. Preparation of a low thermal conductivity layer:

[0156] A ceramic powder with low thermal conductivity is sprayed onto the pretreated substrate surface using a thermal spraying method to obtain a substrate covered with a ceramic underlayer with low thermal conductivity, which is a ZrO2 single-layer thermal protective coating.

[0157] The ceramic powder with low thermal conductivity mentioned in step two is ZrO2 with a particle size of 2μm;

[0158] The thermal spraying method described in step two is atmospheric plasma spraying. The process parameters are as follows: argon is used as the main gas and hydrogen is used as the auxiliary gas. The main gas flow rate is 40 NLPM, the auxiliary gas flow rate is 10 NLPM, the carrier gas flow rate is 3 NLPM, the plasma spray gun power is 42.5 kW, the powder feeder speed is 25 rpm, and the nozzle distance is 100 mm.

[0159] In step two, the ceramic substrate with low thermal conductivity has a thickness of 1.2 mm and a density of 82%.

[0160] The specific method for polishing in step two is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the speed to 600 r / min, and the grinding time to 2 min;

[0161] The average surface roughness of the ZrO2 single-layer thermal protective coating described in step two is 0.75 μm;

[0162] The optical properties of the ZrO2 monolayer thermal protective coating prepared in Comparative Example 3 were tested using a Fourier transform spectrometer. The results showed that the coating had a transmittance of 0.75 and a reflectance of 0.17 in the 0.5-10 μm band.

[0163] The thermal conductivity of the ZrO2 single-layer thermal protective coating prepared in Comparative Example 3 was measured using a laser thermal conductivity meter. The thermal conductivity of the coating at high temperature (1000℃) was found to be 2.3 W / (m·K).

[0164] Figure 2 The cross-sectional morphology image obtained by SEM scanning of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protection coating material prepared in Example 1;

[0165] from Figure 2 It can be seen that the coating of this structure is uniformly distributed inside, has a small number of pores, and the coating thicknesses are as follows: low thermal conductivity layer thickness 0.25mm, high absorption layer thickness 0.95mm, and high reflectivity layer thickness 0.3mm.

[0166] Figure 3 The figures show the infrared reflectance and infrared transmittance spectra. In the figure, (a) is the infrared reflectance spectrum of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1; and (b) is the infrared transmittance spectrum of the TiO2 / Fe2O3 / ZrO2 thermally conductive and radiation-shielding multilayer thermal protective coating material prepared in Example 1.

[0167] from Figure 3 It can be seen that the multi-layer thermal protective coating material has high reflectivity and absorptivity in the 0.5-10μm band, and the coating transmittance is less than 0.1 in the entire band.

[0168] Figure 4 The infrared transmittance spectrum of the TiO2 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 1;

[0169] from Figure 4It can be seen that the transmittance of this double-layer structure reaches more than 0.2 in the 1-5μm band. Compared with the three-layer structure, the lack of a high absorption layer greatly increases its transmittance.

[0170] Figure 5 The infrared transmittance spectrum of the Fe2O3 / ZrO2 bilayer thermal protective coating prepared in Comparative Example 2 was obtained.

[0171] from Figure 5 It can be seen that the transmittance of this double-layer structure reaches more than 0.2 in the 2-5μm band, indicating that the lack of a high-reflectivity layer increases its transmittance.

[0172] Figure 6 The infrared transmittance spectrum of the ZrO2 monolayer thermal protective coating prepared in Comparative Example 3 is shown.

[0173] from Figure 6 It can be seen that the transmittance of a single-layer ZrO2 structure coating reaches over 0.75. Compared with the above structure, the lack of a high absorption layer and a high reflection layer significantly increases the transmittance.

Claims

1. A method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding, characterized in that... The preparation method is specifically carried out according to the following steps: I. Substrate Surface Pretreatment: Remove dust, grease and impurities from the substrate surface, and then activate the substrate surface to obtain the pretreated substrate; II. Preparation of a low thermal conductivity layer: A heat insulation layer with low thermal conductivity is prepared on the surface of a substrate by spraying. The functional components of the heat insulation layer mentioned in step two are one or a combination of ZrO2, Si3N4 and rare earth acid ceramics; The rare earth salt ceramics mentioned in step two are type, type, Type, wherein A is one or a combination of several of Sc, Yb, Lu, Er, Tm, Dy, Ho, La, Y, Gd, Sm, Nd and Eu; B is Zr, Ce or Hf; C is Ta or Nb; the thickness of the insulating layer with low thermal conductivity on the substrate in step two is 0.01mm~1mm, the density is greater than 70%, and the thermal conductivity is less than 2W / mK; III. Preparation of the high-absorption layer: An intermediate layer with high infrared absorption is prepared on the heat insulation layer by spraying. The functional components of the intermediate layer with high infrared absorption described in step three have high infrared absorption in the 0.5μm~10μm band and are one or a combination of transition metal oxides, carbon-based materials and narrow bandgap semiconductor materials. The transition metal oxide mentioned in step three is Fe3O4, Fe2O3, CuO, MnO2, Co2O3, or ZnO; the carbon-based material is nano-carbon black or graphene; and the narrow bandgap semiconductor material is cadmium selenide or bismuth selenide. In step three, the thickness of the intermediate layer with high infrared absorption is 0.01 mm to 2 mm, the density is greater than 60%, and the absorption coefficient is greater than 10000 cm⁻¹. -1 ; IV. Preparation of a high-reflectivity layer: A high-reflectivity layer was prepared on a high-infrared-absorbing intermediate layer by spraying, and after polishing, a multi-layer thermal protection coating material with thermal conductivity and radiation shielding was finally obtained. The functional components of the high-reflectivity layer mentioned in step four have high infrared reflectivity in the 0.5μm~10μm band and can be any one of metal oxides, two-dimensional materials and noble metals; The metal oxide mentioned in step four is TiO2 or Al2O3; the two-dimensional material is BN, indium selenide or a transition metal dichalcogenide; the noble metal is Pt or a Pt alloy. The high-reflectivity layer mentioned in step four has a thickness of 0.01mm to 1mm, a density greater than 60%, and a complex refractive index modulus greater than 2. The multi-layer thermal protection coating material with thermal conductivity and radiation composite shielding described in step four has an effective thermal conductivity of less than 1 W / (m·K), an infrared transmittance of less than 0.12 in the 0.5μm~10μm band, and an infrared reflectance of greater than 0.

4.

2. The method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding according to claim 1, characterized in that... The substrate mentioned in step one is any one of metal matrix material and ceramic matrix composite material; the metal matrix material is carbon steel, aluminum alloy, titanium alloy or nickel-based alloy; the ceramic matrix composite material is C / SiC; in step one, water, methanol, ethanol, ammonia, potassium hydroxide solution, nitric acid or hydrochloric acid are used to clean the substrate to remove dust, grease and impurities from the substrate surface.

3. The method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding according to claim 2, characterized in that... The ammonia solution has a mass fraction of 1% to 5%, the potassium hydroxide solution has a mass fraction of 5% to 10%, the nitric acid has a mass fraction of 10% to 30%, and the hydrochloric acid has a mass fraction of 10% to 20%.

4. The method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding according to claim 1, characterized in that... In step one, a mechanical sandblasting process is used to activate the surface of the substrate. The sandblasting material used in the mechanical sandblasting process is silica sand, quartz sand or ceramic beads, the sandblasting pressure is 0.2MPa~0.6MPa, the sandblasting distance is 100mm~300mm, and the sandblasting angle is 45~90°.

5. The method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding according to claim 1, characterized in that... The powder particle size of the functional components of the heat insulation layer mentioned in step two is 1μm~10μm.

6. The method for preparing a multilayer thermal protection coating material with thermal conductivity and radiation composite shielding according to claim 1, characterized in that... The specific polishing method described in step four is as follows: remove debris and dirt from the surface of the metallographic grinding and polishing machine's worktable, install a 300-grit grinding disc on the turntable for coarse grinding, adjust the metallographic grinding machine parameters, set the rotation speed to 300 r / min, and the grinding time to 3 min; replace with an 800-grit grinding disc for fine grinding, adjust the metallographic grinding machine parameters, set the rotation speed to 600 r / min, and the grinding time to 2 min, with the average surface roughness Ra of the coating being less than 2 μm; the spraying method described in steps two, three, and four is: thermal spraying or slurry spraying; the binder in the slurry spraying is one or a combination of potassium silicate, aluminum silicate, silica sol, and aluminum phosphate.

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