Room-temperature-curing high-temperature high-emission coating and preparation method thereof

Abstract

The invention discloses a room-temperature-curing high-temperature high-emission coating and a preparation method thereof. The preparation method comprises the following steps: compounding an aluminum chromium phosphate base solution, Mg-MOF-74 (curing agent) and a characteristic filler to prepare a coating; the composite coating is coated on a matrix and then cured at room temperature to prepare the high-temperature and high-emission coating. The prepared Mg-MOF-74 is synthesized under the conditions of normal temperature and normal pressure, and compared with a traditional hydrothermal method, the operation is simple, and the yield is improved; according to the invention, a metal-organic framework (Mg-MOF-74) is ingeniously introduced into a coating system, and room temperature curing of the coating can be realized and the curing speed of the coating can be regulated and controlled by regulating and controlling the magnesium ion release speed of the Mg-MOF-74; the emissivity of the characteristic filler used in the experiment is increased in a high-temperature environment, and meanwhile, the coating prepared by the method can form a porous structure in the high-temperature environment, so that the emissivity of the coating is increased, and the thermal conductivity of the coating is reduced. According to the room-temperature-curing high-temperature high-emission coating, a porous system with multiple different pore size distributions is obtained by adjusting the proportion of all the components, the high-temperature emissivity is improved, the preparation method is simple, continuous large-scale preparation can be achieved, the coating is suitable for industrial amplification application, and meanwhile different materials can be designed according to actual needs.

Description

Technical Field

[0001] The present invention belongs to the field of materials, and particularly relates to a room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof. Background Technique

[0002] In deep space exploration missions, when a spacecraft re-enters the Earth's atmosphere, due to air friction, the surface temperature of the spacecraft will rapidly increase and can reach several thousand degrees Celsius; in the space environment, due to the lack of atmospheric protection, the spacecraft will be directly exposed to extreme temperature difference environments. In order to effectively control the surface temperature of the spacecraft and reduce heat accumulation, high-emissivity coatings are usually used on the surface of heat-insulating materials to achieve rapid heat dissipation. High-emissivity coatings have high heat radiation capabilities. They can effectively dissipate heat and improve the heat radiation efficiency, thereby helping the spacecraft maintain an appropriate temperature.

[0003] During long-term use, high-temperature and high-emissivity coatings may encounter problems such as degradation, attenuation, and even cracking of the coating structure, resulting in a decrease in the radiation effect. Especially in harsh environmental conditions such as high temperature, high humidity, and strong radiation, the stability of the coating is more easily affected; currently, the emissivity of most coatings decreases to varying degrees as the temperature increases; room-temperature curing enables the application of coatings on spacecraft to provide designers with more flexible, efficient, and environmentally friendly options, making the construction more convenient and the application more extensive. Therefore, developing coatings with low thermal conductivity, strong durability, and an increasing emissivity with increasing temperature is of great significance for achieving long-term stable high heat radiation, extending the service life of materials, and coping with harsh environmental conditions. Summary of the Invention

[0004] Object of the Invention: Aiming at the defects in the existing application technologies, the present invention aims to provide a room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof, and explore a coating prepared at low temperature and with optimized structure in a high-temperature environment and having a high emissivity. The prepared room-temperature curing high-temperature and high-emissivity coating has excellent high-temperature stability and high emissivity, and can resist high-temperature harsh environments.

[0005] The object of the present invention is to provide a room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof. To achieve the above object, the present invention is mainly realized through the following technical solutions: 1. A room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof, characterized in that the room-temperature curing high-temperature and high-emissivity coating dissipates heat to the environment in an infrared radiation manner. The room-temperature curing high-temperature and high-emissivity coating includes a chromium aluminum phosphate-based liquid, characteristic fillers, and a curing agent. The preparation raw materials of the room-temperature curing high-temperature and high-emissivity coating, calculated by weight percentage, include the following components: 40-60 parts by weight of chromium aluminum phosphate-based liquid, 1-5 parts by weight of Mg-MOF-74 (curing agent), and 20-30 parts by weight of characteristic fillers.

[0006] The coating preparation method includes the following steps: Step 1: Weigh phosphoric acid and deionized water, add them into a three-necked flask, keep stirring magnetically at 80 °C for 20 min for full dilution. Add Al(OH)3 and keep stirring magnetically until it is completely dissolved. Then add CrO3 and react for 1 h. Use a dropping funnel to drip methanol into the mixed solution. Stop dripping when the solution shows a transparent dark green color, and continue heating for 60 min to end the reaction; Step 2: Dissolve 2,5-dihydroxyterephthalic acid and magnesium nitrate hexahydrate in ethanol respectively for standby. Take the ethanol solution of 2,5-dihydroxyterephthalic acid into a flask, add 2-methylimidazole to the above flask and dissolve it. Finally, add the ethanol solution of magnesium nitrate hexahydrate while stirring. After stirring at room temperature for 6 h, centrifuge and filter. The solid part obtained is the curing agent Mg-MOF-74; Step 3: Use a high-speed disperser to disperse and uniformly mix the special fillers, dry them for standby. Remove the oil stain on the surface of the substrate, then polish the substrate surface with sandpaper, clean and dry it for standby; Step 4: Mix the aluminum chromophosphate-based liquid obtained in Step 1, the Mg-MOF-74 obtained in Step 2, and the special fillers obtained in Step 3, and stir evenly to obtain a composite coating; Step 5: Coat the composite coating obtained in Step 4 on the substrate processed in Step 2, carry out room temperature curing, and repeat the above operations until the required coating thickness is reached, then the high-temperature and high-emissivity coating is obtained.

[0007] 2. Further: In the above Step 1, in the aluminum chromophosphate-based liquid, Cr:Al:P = 1:1~3:3~9, and the solid content of the aluminum chromophosphate-based liquid is 40%~60%.

[0008] 3. Further, in the above Step 2, the molar ratio of 2,5-dihydroxyterephthalic acid to magnesium nitrate hexahydrate is 1:0.1 - 10, and the particle size of the Mg-MOF-74 is 0.1~10 μm.

[0009] 4. Further, in the above Step 3, the special fillers are one or more of aluminum powder, zirconia, alumina, hollow microspheres, silicon carbide, zirconium boride, TaSi2, MoSi2, with a particle size of 1~50 μm and excellent dispersibility.

[0010] 5. Further, in the above Step 3, first remove the oil stain on the surface of the substrate, then polish the substrate surface with 100-mesh and 400-mesh sandpapers in sequence, and finally clean it with clear water and ethanol respectively, and take it out to dry.

[0011] 6. Further, in Step 4, the characteristic filler and Mg-MOF-74 are ground and mixed evenly first, and then added to the resin matrix in small amounts multiple times. After mixing evenly, it is reserved for use. The ratio of the characteristic filler to the resin is 1:1 to 2.

[0012] 7. Further, in Step 5, the thickness of the composite protective coating by high-energy laser ablation is about 1 to 2 mm, and the thickness of each coating does not exceed 0.5 mm.

[0013] The beneficial effects of the present invention are as follows: I. The curing agent used in this experiment can not only achieve room-temperature curing of chromium aluminum phosphate, but also regulate its curing rate. At present, the medium and low-temperature curing of chromium aluminum phosphate resin has been mature, and there are also many choices of curing agents. However, there are few reports on the curing agents used for room-temperature curing. The present invention ingeniously introduces metal-organic frameworks into the coating system to achieve room-temperature curing of the coating.

[0014] II. The room-temperature curing high-temperature high-emissivity coating of the present invention has excellent high-temperature resistance and long-term stability. After the chromium aluminum phosphate base liquid used in this experiment is heat-treated at high temperature, the formed P2O5-Cr2O3-Al2O3 ternary system does not decompose until it melts at 1800 °C; the characteristic filler used in this experiment undergoes a ceramization transformation at high temperature, and can form a porous ceramic phase with high strength, high hardness, high-temperature tolerance and chemical stability; in a high-temperature environment, a large number of holes will gradually form inside the coating. While the pore structure increases the emissivity, it can greatly reduce the thermal conductivity of the film, weaken the heat transfer between the material and the outside world, and increase the heat dissipation of the system to the environment, thereby realizing the protection of the substrate in a high-temperature environment.

[0015] III. The room-temperature curing high-temperature high-emissivity coating of the present invention is applicable to many fields in addition to deep space exploration, such as buildings, the energy industry, industrial heating equipment, protection and military applications, etc. In all these fields, the key advantage of the room-temperature curing high-temperature high-emissivity coating is that it can effectively reduce the absorption of heat and the influence of thermal radiation, thereby improving the durability, efficiency and safety of the equipment. At the same time, it is convenient for construction and has a wide range of applications.

[0016] It should be noted that the above description does not disclose all the embodiments of the present invention and all the advantages of the present invention. Description of the Drawings

[0017] Figure 1 SEM image of Mg-MOF-74 obtained in Example 1 Figure 2 TG diagram of the coating obtained in Example 1 Figure 3 Room-temperature infrared emission spectrum of the coating obtained in Example 1 Figure 4 SEM images of the coating obtained in Example 1 at different temperatures Figure 4 SEM images of the coating obtained in Example 1 at different temperatures: a) room temperature; b) 400 °C; c) 500 °C; d) 600 °C; e) 700 °C; f) 800 °C Figure 5 High-temperature infrared emission spectrum of the coating obtained in Example 1 Detailed implementation manners

[0018] Example 1 Step 1: Weigh 20 g of phosphoric acid and 10 g of deionized water, add them to a 100-ml three-necked flask, stir magnetically and mix evenly, and dilute sufficiently. After the diluted phosphoric acid is heated to 80 °C, add 4.51 g of Al(OH)3, stir at a constant temperature until the liquid in the flask becomes transparent, then add 1.933 g of CrO3 and continue to react for 1 h. Finally, use a dropping funnel to slowly add a slight excess of methanol to the mixed solution, continue to heat for 60 min, and after the reaction ends, a transparent dark green solution is obtained, which is the aluminum chromophosphate base solution; Step 2: Dissolve 0.495 g of 2,5-dihydroxyterephthalic acid and 1.825 g of magnesium nitrate hexahydrate in ethanol respectively for standby. Place the ethanol solution of 2,5-dihydroxyterephthalic acid in a flask, add 0.82 g of 2-methylimidazole to the above flask and dissolve it. Finally, while stirring, add the ethanol solution of magnesium nitrate hexahydrate. After stirring at room temperature for 6 h, centrifuge and filter. The solid part obtained is the curing agent Mg-MOF-74; Step 3: Use a high-speed disperser to uniformly mix 10 g of silicon carbide whiskers, 5 g of alumina, and 15 g of zirconium diboride, dry them and use them as special fillers for standby. Remove the oil stain on the surface of the substrate, polish the substrate with sandpaper, and keep it clean and dry for standby; Step 4: Mix 3 g of the aluminum chromophosphate base solution, 2 g of the special filler, and 0.06 g of Mg-MOF-74, and stir evenly to obtain a composite coating; Step 5: Coat the composite coating on the treated substrate, cure for 24 h, and repeat the above operations until the required coating thickness is reached, and then a high-temperature and high-emissivity coating is obtained.

[0019] Example 2 Step 1: Weigh 60 g of phosphoric acid and 30 g of deionized water, add them to a 100 ml three-necked flask (equipped with a condenser reflux device), stir magnetically and mix evenly to fully dilute. Wait until the diluted phosphoric acid heats up to 80 °C, add 9.02 g of Al(OH)3, stir at a constant temperature until the liquid in the flask becomes transparent, then add 1.933 g of CrO3 and continue to react for 1 h. Finally, use a dropping funnel to slowly add a slightly excessive amount of methanol to the mixed solution, continue to heat for 60 min, and after the reaction ends, a transparent dark green solution is obtained, which is the aluminum chromophosphate-based solution. Step 2: Dissolve 0.495 g of 2,5-dihydroxyterephthalic acid and 1.825 g of magnesium nitrate hexahydrate in ethanol respectively for standby. Put the ethanol solution of 2,5-dihydroxyterephthalic acid into a flask, add 0.82 g of 2-methylimidazole to the above flask and dissolve it. Finally, add the ethanol solution of magnesium nitrate hexahydrate while stirring. After stirring at room temperature for 6 h, centrifuge and filter, and the solid part obtained is the curing agent Mg-MOF-74. Step 3: Use a high-speed disperser to evenly mix 5 g of silicon carbide whiskers, 15 g of zirconia, and 10 g of zirconium diboride, dry them and reserve them as special fillers. Remove the oil stain on the surface of the substrate and polish the substrate with sandpaper, and reserve it after cleaning and drying. Step 4: Mix 4 g of the aluminum chromophosphate-based solution, 2 g of the special filler, and 0.08 g of Mg-MOF-74, and stir evenly to obtain a composite coating. Step 5: Coat the composite coating on the treated substrate, cure for 24 h, and repeat the above operations until the required coating thickness is reached, then a high-temperature and high-emissivity coating is obtained.

[0020] As described above, these are only the implementation schemes of the present invention. The present invention is not limited to the above specific implementation manners. Those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Any technical solutions based on the idea of the present invention fall within the protection scope of the present invention. Any changes and related substitutions that those skilled in the art can think of within the technical scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A room-temperature curing high-temperature and high-emissivity coating and its preparation method, characterized in that, The room temperature curing high temperature high emission coating is prepared at low temperature and has an optimized structure under high temperature environment. The room temperature curing high temperature high emission coating includes a chromium aluminum phosphate base liquid, a characteristic filler and a curing agent. The raw materials for preparing the room temperature curing high temperature high emission coating include the following components in weight percentage: 40 to 60 parts by weight of the chromium aluminum phosphate base liquid, 1 to 5 parts by weight of Mg-MOF-74 (curing agent), and 20 to 30 parts by weight of the characteristic filler.

2. The coating preparation method comprises the following steps: Step 1, weigh phosphoric acid and deionized water and add them into a three-necked flask, stir magnetically at 80°C for 20 min, dilute thoroughly, add Al(OH)3 and stir magnetically at 80°C until it is completely dissolved, add CrO3 and react for 1 h, use a dropping funnel to drop methanol into the mixed solution, stop dropping when the solution turns transparent dark green, continue heating for 60 min, and the reaction is finished; Step 2: Dissolve 2,5-dihydroxyterephthalic acid and magnesium nitrate hexahydrate in ethanol respectively for later use. Take the ethanol solution of 2,5-dihydroxyterephthalic acid in a flask, add 2-methylimidazole to the flask and fully dissolve it. Finally, add the ethanol solution of magnesium nitrate hexahydrate while stirring. After stirring at room temperature for 6 hours, centrifuge and filter. The solid part is the curing agent Mg-MOF-74. Step 3: Use a high-speed disperser to disperse and evenly mix the characteristic filler, dry it and set it aside; remove the oil stain on the surface of the substrate and polish the substrate with sandpaper, clean and dry it and set it aside; Step 4: Mix the aluminum chromium phosphate base liquid obtained in step 1, the Mg-MOF-74 obtained in step 2, and the characteristic filler obtained in step 3, and stir evenly to obtain a composite coating; Step 5: Apply the composite coating obtained in step 4 on the substrate treated in step 3, cure it at room temperature and repeat the above operation until the desired coating thickness is reached, thus obtaining a high-temperature and high-emission coating.

3. A room temperature curing high temperature and high emissivity coating and its preparation method according to claim 1, characterized in that: In the step 1, the Cr:Al:P ratio in the chromium aluminum phosphate based liquid is 1:1-3:3-9, and the solid content of the chromium aluminum phosphate based liquid is 40%-60%.

4. A room-temperature curable high-temperature and high-emissivity coating and a preparation method thereof according to claim 1, characterized in that: In the step 2, the molar ratio of the 2,5-dihydroxyterephthalic acid to magnesium nitrate hexahydrate is 1:0.1-10, and the particle size of the Mg-MOF-74 is 0.1-10 μm.

5. A room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof according to claim 1, characterized in that: In the step three, the characteristic filler is one or more of aluminum powder, zirconium oxide, alumina, hollow microspheres, silicon carbide, zirconium boride, TaSi2, and MoSi2, with a particle size of 1 to 50 μm and excellent dispersibility.

6. A room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof according to claim 1, characterized in that: In the step three, the oil stains on the surface of the substrate are first removed, and then the surface of the substrate is polished with 100-mesh and 400-mesh sandpapers in turn, and finally washed with clean water and ethanol respectively, and taken out and dried.

7. A room temperature curable high temperature and high emissivity coating and a preparation method thereof according to claim 1, characterized in that: In the step 4, the characteristic filler and Mg-MOF-74 are first ground and mixed evenly, and then added into the resin matrix in small amounts and multiple times, and then mixed evenly for use. The ratio of the characteristic filler to the resin is 1:1-2.

8. A room-temperature curing high-temperature and high-emissivity coating and a preparation method thereof according to claim 1, characterized in that: In the step 4, the thickness of the high temperature and high emission coating is about 0.5 to 2 mm, and the thickness of each coating does not exceed 0.5 mm.

9. A room-temperature-curing high-temperature and high-emissivity coating with high-temperature stability, characterized in that, Obtained according to any one of claims 1 to 7.

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