MOFs (Metal-Organic Frameworks) enhanced nano ceramic coating material, preparation method and application of MOFs enhanced nano ceramic coating material to heat-insulating film

Abstract

The invention relates to the technical field of coatings, in particular to an MOFs enhanced nano ceramic coating material, a preparation method and application of the MOFs enhanced nano ceramic coating material to a heat insulation film. The preparation method comprises the following steps: firstly, coating the surface of Al2O3 / ZrO2 nano composite ceramic with ZIF-8 through an in-situ growth method to form MOFs enhanced nano ceramic composite powder with a core-shell structure; performing amino modification by using an amino silane coupling agent, and grafting polyacrylic acid by using an amidation reaction catalyzed by DCC / DMAP (dicyclohexylcarbodiimide / dimethylaminopyridine), so as to obtain surface carboxylated modified nano ceramic composite powder; and finally, mixing and dispersing the modified powder with organic silicon resin containing hydroxyl functional groups, a polyvinylpyrrolidone dispersing agent, a polyether modified polydimethylsiloxane flatting agent, a polyoxyethylene polyoxypropylene glycerol ether defoaming agent and ethanol to obtain the MOFs enhanced nano ceramic coating material. The coating has low thermal conductivity and high mechanical strength, and the powder has good dispersion stability in the coating, so that the coating can be widely applied to the field of heat-insulating films.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a MOFs-reinforced nano-ceramic coating material, its preparation method, and its application in heat insulation films. Background Technology

[0002] In recent years, with the rapid development of aerospace, new energy, and electronic devices, the demand for high-performance thermal insulation materials has become increasingly urgent. Among various thermal insulation materials, nano-ceramic coatings have been widely studied and applied in the field of thermal protection under high-temperature environments due to their excellent thermal stability, chemical inertness, and mechanical properties. In particular, combining nano-ceramic coatings with polymer-based thermal insulation films can impart excellent thermal insulation functions while maintaining the flexibility of the substrate, making it one of the research hotspots in this field. However, how to further improve the thermal insulation efficiency, structural density, and long-term service stability of the coating remains a key issue in current materials design and engineering applications.

[0003] Currently, research on nano-ceramic coatings for thermal insulation films mainly focuses on oxide systems, such as zirconium oxide, alumina, and titanium oxide. These methods construct ceramic insulation layers on polymer substrates through sol-gel methods, physical vapor deposition, or nanoparticle composites. While these methods can reduce thermal conductivity to some extent, they generally suffer from the following problems: First, nano-ceramic coatings are prone to microcracks and pores during film formation, leading to unstable thermal insulation performance and easy peeling under thermal cycling conditions. Second, the interfacial bonding between traditional nano-ceramic coatings and polymer substrates is weak, making it difficult to achieve good thermal matching and limiting their long-term reliability in flexible thermal insulation films. Third, the thermal conductivity control range of existing coating materials is limited, making it difficult to achieve efficient thermal insulation while maintaining thin layer thickness, thus restricting their application expansion in space-constrained scenarios.

[0004] Therefore, there is an urgent need to develop a novel nano-ceramic coating material that combines excellent thermal insulation performance, good interfacial bonding strength, and process adaptability through interfacial chemical bonding and surface functionalization modification, so as to overcome the shortcomings of existing technologies and meet the urgent demand for high-performance thermal insulation films in high-end application fields. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to propose a MOF-enhanced nano-ceramic coating material to solve the problems in the prior art, such as weak bonding between MOFs and ceramic interfaces, poor dispersibility of fillers in coatings, and difficulty in achieving both thermal insulation and mechanical properties.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing MOF-reinforced nano-ceramic coating materials includes the following steps: Step 1: Add Al2O3 / ZrO2 nanocomposite ceramics to the first solvent and disperse by ultrasonication to obtain a composite ceramic material dispersion. Add 2-methylimidazole to the composite ceramic material dispersion. After complete dissolution, add zinc salt solution under stirring conditions and react. After the reaction is completed, centrifuge, wash, and dry to obtain MOFs-reinforced nanoceramic composite powder. Step 2: Disperse the MOFs-reinforced nano-ceramic composite powder in a second solvent, add a silane coupling agent containing amino functional groups, react, centrifuge, wash, and dry to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Disperse the amino-modified MOFs-enhanced nano-ceramic composite powder in a third solvent, add a polymer containing carboxyl functional groups, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react, centrifuge, wash and dry to obtain the modified nano-ceramic composite powder. Step 4: Mix the modified nano-ceramic composite powder, binder containing reactive functional groups, dispersant, leveling agent, defoamer, and solvent, and stir to disperse to obtain the MOFs-enhanced nano-ceramic coating material.

[0007] Preferably, in step one, the mass concentration of the composite ceramic material dispersion is 5%-10%, the mass of zinc salt in the zinc salt solution is 10%-30% of the mass of Al2O3 / ZrO2 nanocomposite ceramics in the composite ceramic material dispersion, the molar ratio of zinc salt to 2-methylimidazole in the zinc salt solution is 1:8, and the reaction conditions are stirring at 20-40℃ for 2-12 hours.

[0008] Preferably, the first solvent comprises methanol, and the zinc salt comprises zinc nitrate.

[0009] The first solvent may also include any one of ethanol, isopropanol, and N,N-dimethylformamide (DMF), and the zinc salt may also include any one of zinc acetate and zinc chloride.

[0010] Preferably, the Al2O3 / ZrO2 nanocomposite ceramic is prepared by the following steps: The nano-Al2O3 / nano-ZrO2 mixed powder was mixed with ethanol, ball-milled, dried, ground, pressed into tablets, annealed, and then ground and sieved to obtain Al2O3 / ZrO2 nanocomposite ceramics. In the nano-Al2O3 / nano-ZrO2 mixed powder, the mass ratio of nano-Al2O3 to nano-ZrO2 is 1:(0.5-2), the ball milling time is 8-12 h, the annealing temperature range is room temperature to 1000℃, and the heating rate is 5℃·min. -1The annealing temperature intervals are 100℃, and the holding time at each annealing temperature is 1.5-2.5h.

[0011] Preferably, in step one, ZIF-8 is used as a metal-organic framework material, utilizing the Al-OH groups, Zr-OH groups, and oxygen vacancies on the surface of the composite ceramic material particles as nucleation sites, through Zn... 2+ The coordination bonding between the nucleation sites anchors the composite ceramic material particles to the surface of the particles and grows outward along the surface of the composite ceramic material particles to form a core-shell composite structure in which ZIF-8 uniformly coats the composite ceramic material particles.

[0012] Preferably, in step two, the mass of the silane coupling agent containing amino functional groups is 5%-20% of the mass of the MOFs-reinforced nano-ceramic composite powder; the amount of the second solvent is 10-30 times the mass of the MOFs-reinforced nano-ceramic composite powder; and the reaction conditions are a stirring speed of 400-800 r / min and a reaction temperature of 60-80℃ for 3-6 h.

[0013] The second solvent includes ethanol, and the silane coupling agent containing an amino functional group includes γ-aminopropyltriethoxysilane (silane coupling agent KH550).

[0014] Preferably, the second solvent may further include any one of isopropanol, n-butanol, and ethylene glycol methyl ether, and the silane coupling agent containing an amino functional group may further include any one of γ-aminopropyltrimethoxysilane (silane coupling agent KH-540) and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (silane coupling agent KH-791).

[0015] Preferably, in step two, the silanoxy group in the silane coupling agent containing the amino functional group is hydrolyzed to form a silanol group. The silanol group can react with the hydroxyl group on the surface of the composite ceramic material particles to form a silicon-oxygen bond, and may also interact with the hydroxyl group or metal site on the ZIF-8 surface. At the same time, the amino functional group at its end provides an active site for the subsequent grafting reaction.

[0016] Preferably, in step three, the mass ratio of amino-modified MOFs-reinforced nano-ceramic composite powder, the third solvent, the polymer containing carboxyl functional groups, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 10:(150-300):(1-4):(0.5-2):(0.05-0.2), and the reaction is carried out under the condition of stirring at 20-40℃ for 6-12 hours.

[0017] Preferably, the third solvent comprises N,N-dimethylformamide, and the polymer containing carboxyl functional groups comprises polyacrylic acid; The number average molecular weight of the polymer containing carboxyl functional groups is 1000-20000 Da.

[0018] Preferably, the third solvent may further include dimethyl sulfoxide, and the polymer containing carboxyl functional groups may further include at least one of polymethacrylic acid and acrylic acid-maleic anhydride copolymer.

[0019] Preferably, in step three, the carboxyl functional groups in the polymer containing carboxyl functional groups are activated by N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine to form an activated carboxyl ester intermediate. The activated carboxyl ester intermediate undergoes a nucleophilic substitution reaction with the amino functional groups on the surface of the amino-modified MOFs-reinforced nano-ceramic composite powder to form amide bonds.

[0020] Preferably, in step four, the mass ratio of the modified nano-ceramic composite powder, the binder containing reactive functional groups, the dispersant, the leveling agent, the defoamer, and the solvent is (10-40):(20-60):(0.5-5):(0.1-2):(0.1-2):(20-60). The conditions for stirring and dispersing are as follows: dispersion is carried out using a high-speed disperser with a dispersion linear velocity of 5-20 m / s and a dispersion time of 60-120 min. During the dispersion process, the temperature of the mixing system is controlled to not exceed 50°C. After dispersion, the viscosity of the mixing system at 25°C is 50-500 mPa·s.

[0021] Preferably, the binder containing reactive functional groups includes an organosilicon resin containing hydroxyl functional groups, the dispersant includes polyvinylpyrrolidone, the leveling agent includes polyether-modified polydimethylsiloxane, the defoamer includes polyoxyethylene polyoxypropylene glycerol ether, and the solvent includes ethanol.

[0022] The present invention also discloses a MOFs-enhanced nano-ceramic coating material, which is prepared by the preparation method of MOFs-enhanced nano-ceramic coating material as described above.

[0023] Application of a MOF-reinforced nano-ceramic coating material as described above in heat insulation films.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, ZIF-8 is grown in situ on the surface of Al2O3 / ZrO2 nanocomposite ceramic particles, forming a core-shell composite structure with ceramic particles as the core and ZIF-8 as the shell. In this structure, ZIF-8 utilizes Al-OH, Zr-OH, and oxygen vacancies on the surface of the ceramic particles as nucleation sites, and Zn... 2+ The coordination bonding between the ZIF-8 shell and the nucleation site achieves chemical anchoring, forming Zn-O-Al and Zn-O-Zr type coordination bonds between the ZIF-8 shell and the ceramic core. Compared with the physical mixing method where MOFs and ceramics rely solely on van der Waals forces for bonding, the ZIF-8 shell in this invention is less prone to detachment during subsequent processing and use. The coating showed no cracking or peeling after 100 thermal cycling tests (-40~80℃), significantly improving long-term service stability. This invention employs an aminosilane coupling agent to aminate MOF-reinforced nano-ceramic composite powder, followed by grafting of carboxyl-containing polymers via an amidation reaction, constructing a bilayer chemically modified structure on the powder surface. The silanol groups in the aminosilane condense with the hydroxyl groups on the ceramic surface to form siloxane bonds, while the amino group interacts with uncoordinated Zn on the ZIF-8 surface. 2+ Coordination bonds are formed, achieving complete coating of the core-shell composite powder; subsequently, the carboxyl-containing polymer undergoes an amidation reaction with the surface amino groups under DCC / DMAP catalysis, introducing high-density carboxyl groups. The carboxylated surface layer forms strong hydrogen bond interactions with the binder containing hydroxyl, amino, or ether oxygen functional groups, solving the technical problem of easy agglomeration and difficult dispersion of inorganic nanofillers in organic binders. This invention achieves a simultaneous improvement in thermal insulation and mechanical properties by synergistically matching the porous structure of the ZIF-8 shell with the high hardness of the Al2O3 / ZrO2 nanocomposite ceramic core, and by designing the interfacial compatibility between the surface carboxylated modified powder and the functional group-containing binder. This breakthrough overcomes the technical bottleneck of traditional nano-ceramic coatings where thermal insulation and mechanical properties are difficult to balance. Attached Figure Description

[0025] Figure 1 These are SEM and TEM images of the MOFs-enhanced nano-ceramic composite powder prepared in Example 4 of this invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1 This embodiment provides a method for preparing Al2O3 / ZrO2 nanocomposite ceramics, including the following steps: Nano-Al₂O₃ powder (20 nm particle size, 99.9% purity) and nano-ZrO₂ powder (20 nm particle size, 99.9% purity, tetragonal phase) were mixed at a mass ratio of 1:0.5 to obtain a nano-Al₂O₃ / nano-ZrO₂ mixed powder. This mixed powder was then mixed with ethanol at a mass ratio of 5:1 and added to a ball mill along with zirconia grinding balls (3 mm diameter, ball-to-powder mass ratio of 8:1). The mixture was ball-milled at 300 r / min for 10 h. After ball milling, the slurry was removed and vacuum-dried at 50 °C. After drying to constant weight in a drying oven, the powder is ground to obtain a uniformly dispersed powder. The powder is pressed into a round sheet and placed in a muffle furnace. The temperature is increased from room temperature to 1000℃ at a heating rate of 5℃ / min. An annealing temperature point is set every 100℃ (i.e., 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃). Each annealing temperature point is held for 2 hours. After annealing, the powder is naturally cooled to room temperature in the furnace to obtain an annealed block. The annealed block is ground and sieved, and the powder passing through the sieve is collected to obtain Al2O3 / ZrO2 nanocomposite ceramic. The average particle size of the Al2O3 / ZrO2 nanocomposite ceramic was determined to be 50 nm by a laser particle size analyzer.

[0028] Example 2 This embodiment provides a method for preparing Al2O3 / ZrO2 nanocomposite ceramics. The only difference from Example 1 is that the mass ratio of nano-Al2O3 powder to nano-ZrO2 powder is 1:2, and the average particle size of the resulting Al2O3 / ZrO2 nanocomposite ceramics is 50 nm.

[0029] Example 3 This embodiment provides a method for preparing Al2O3 / ZrO2 nanocomposite ceramics. Compared with Example 1, the only difference is that the mass ratio of nano-Al2O3 powder to nano-ZrO2 powder is 1:1, and the average particle size of the resulting Al2O3 / ZrO2 nanocomposite ceramics is 50 nm.

[0030] Example 4 This embodiment provides a method for preparing MOF-enhanced nano-ceramic coating materials, including the following steps: Step 1: Add 10g of the Al2O3 / ZrO2 nanocomposite ceramic prepared in Example 1 to 190g of methanol, and ultrasonically disperse at 50kHz for 30min to obtain a composite ceramic material dispersion with a mass concentration of 5%. Add 2-methylimidazole to the composite ceramic material dispersion and stir until completely dissolved. Then, slowly add zinc nitrate solution (prepared by mixing zinc nitrate and ethanol at a mass-volume ratio of 0.15g / 5mL) under stirring. The mass of zinc nitrate in the zinc nitrate solution is 1g, which means that the mass of zinc nitrate is 10% of the mass of Al2O3 / ZrO2 nanocomposite ceramic in the composite ceramic material dispersion. The molar ratio of zinc nitrate to 2-methylimidazole is 1:8. Stir and react at 20℃ for 12h. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain MOFs-reinforced nano-ceramic composite powder. Step 2: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 100g of ethanol (i.e., the amount of ethanol is 10 times the mass of MOFs-reinforced nano-ceramic composite powder), add 0.5g of γ-aminopropyltriethoxysilane (i.e., the mass of γ-aminopropyltriethoxysilane is 5% of the mass of MOFs-reinforced nano-ceramic composite powder), and react at 60℃ for 6 hours with stirring at 400r / min. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Disperse 10g of amino-modified MOFs-reinforced nano-ceramic composite powder in 150g of N,N-dimethylformamide, add 1g of polyacrylic acid (number average molecular weight of 1000 Da), 0.5g of N,N'-dicyclohexylcarbodiimide and 0.05g of 4-dimethylaminopyridine, stir and react at 20℃ for 12h. After the reaction is completed, centrifuge and wash three times with N,N-dimethylformamide, then wash three times with ethanol, and dry in a vacuum drying oven at 50℃ to constant weight to obtain modified nano-ceramic composite powder; Step 4: Take 10g of modified nano-ceramic composite powder, 20 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20mg KOH / g, average molecular weight 5600), 0.5 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 0.1 parts of polyether-modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 0.1 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 20 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 5m / s for 120min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, MOFs-reinforced nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 50 mPa·s using a rotational viscometer (25℃, rotor #2).

[0031] Example 5 This embodiment provides a method for preparing MOF-enhanced nano-ceramic coating materials, including the following steps: Step 1: Add 10g of the Al2O3 / ZrO2 nanocomposite ceramic prepared in Example 2 to 90g of methanol, and ultrasonically disperse at 50kHz for 30min to obtain a composite ceramic material dispersion with a mass concentration of 10%. Add 2-methylimidazole to the composite ceramic material dispersion and stir until completely dissolved. Then, slowly add zinc nitrate solution (prepared by mixing zinc nitrate and ethanol at a mass-volume ratio of 0.15g / 5mL) under stirring. The mass of zinc nitrate in the zinc nitrate solution is 3g, which means that the mass of zinc nitrate is 30% of the mass of Al2O3 / ZrO2 nanocomposite ceramic in the composite ceramic material dispersion. The molar ratio of zinc nitrate to 2-methylimidazole is 1:8. Stir and react at 40℃ for 2h. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain MOFs-reinforced nanoceramic composite powder. Step 2: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 300g of ethanol (the amount of ethanol is 30 times the mass of MOFs-reinforced nano-ceramic composite powder), add 2g of N-β-aminoethyl-γ-aminopropyltrimethoxysilane (the mass of N-β-aminoethyl-γ-aminopropyltrimethoxysilane is 20% of the mass of MOFs-reinforced nano-ceramic composite powder), and react at 80℃ for 3h with stirring at 800r / min. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Disperse 10g of amino-modified MOFs-reinforced nano-ceramic composite powder in 300g of N,N-dimethylformamide, add 4g of polyacrylic acid (number average molecular weight of 20000 Da), 2g of N,N'-dicyclohexylcarbodiimide and 0.2g of 4-dimethylaminopyridine, stir and react at 40℃ for 6h. After the reaction is completed, centrifuge and wash three times with N,N-dimethylformamide, then wash three times with ethanol, and dry in a vacuum drying oven at 50℃ to constant weight to obtain modified nano-ceramic composite powder; Step 4: Take 40 parts of modified nano-ceramic composite powder, 60 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20 mg KOH / g, average molecular weight 5600), 5 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 2 parts of polyether modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 2 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 60 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 20 m / s for a dispersion time of 60 min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, MOFs-reinforced nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 500 mPa·s using a rotational viscometer (25℃, rotor #2).

[0032] Example 6 This embodiment provides a method for preparing MOF-enhanced nano-ceramic coating materials, including the following steps: Step 1: Add 10g of the Al2O3 / ZrO2 nanocomposite ceramic prepared in Example 3 to 115g of methanol, and ultrasonically disperse at 50kHz for 30min to obtain a composite ceramic material dispersion with a mass concentration of 8%. Add 2-methylimidazole to the composite ceramic material dispersion and stir until completely dissolved. Then, slowly add zinc nitrate solution (prepared by mixing zinc nitrate and ethanol at a mass-volume ratio of 0.15g / 5mL) under stirring. The mass of zinc nitrate in the zinc nitrate solution is 2g, which means that the mass of zinc nitrate is 20% of the mass of Al2O3 / ZrO2 nanocomposite ceramic in the composite ceramic material dispersion. The molar ratio of zinc nitrate to 2-methylimidazole is 1:8. Stir and react at 30℃ for 8h. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain MOFs-reinforced nanoceramic composite powder. Step 2: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 200g of ethanol (the amount of ethanol is 20 times the mass of MOFs-reinforced nano-ceramic composite powder), add 1.25g of γ-aminopropyltrimethoxysilane (the mass of γ-aminopropyltrimethoxysilane is 12.5% ​​of the mass of MOFs-reinforced nano-ceramic composite powder), and react at 70℃ for 4.5h with stirring at 600r / min. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 225g of N,N-dimethylformamide, add 2.5g of polyacrylic acid (number average molecular weight of 10000 Da), 1.25g of N,N'-dicyclohexylcarbodiimide and 0.125g of 4-dimethylaminopyridine, stir and react at 30℃ for 9h. After the reaction is completed, centrifuge, wash three times with N,N-dimethylformamide, then wash three times with ethanol, and dry in a vacuum drying oven at 50℃ to constant weight to obtain modified nano-ceramic composite powder; Step 4: Take 25 parts of modified nano-ceramic composite powder, 40 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20 mg KOH / g, average molecular weight 5600), 2.75 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 1.05 parts of polyether-modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 1.05 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 40 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 12.5 m / s for 75 min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, MOFs-reinforced nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 275 mPa·s using a rotational viscometer (25℃, rotor #2).

[0033] Comparative Example 1 This comparative example provides a method for preparing a nano-ceramic coating material, including the following steps: Step 1: Disperse 10g of the Al2O3 / ZrO2 nanocomposite ceramics prepared in Example 1 in 100g of ethanol, i.e., the amount of ethanol is 10 times the mass of the Al2O3 / ZrO2 nanocomposite ceramics. Add 0.5g of γ-aminopropyltriethoxysilane, i.e., the mass of γ-aminopropyltriethoxysilane is 5% of the mass of the Al2O3 / ZrO2 nanocomposite ceramics. React at 60℃ for 6h with stirring speed of 400r / min. After the reaction is completed, centrifuge, wash with ethanol 3 times, and dry to constant weight in a vacuum drying oven at 50℃ to obtain amino-modified Al2O3 / ZrO2 nanocomposite ceramics. Step 2: Disperse 10g of Al2O3 / ZrO2 nanocomposite ceramics in 150g of N,N-dimethylformamide, add 1g of polyacrylic acid (number average molecular weight of 1000 Da), 0.5g of N,N'-dicyclohexylcarbodiimide and 0.05g of 4-dimethylaminopyridine, stir and react at 20℃ for 12h. After the reaction is completed, centrifuge and wash three times with N,N-dimethylformamide, then wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain modified nano-ceramic composite powder; Step 3: Take 10g of modified nano-ceramic composite powder, 20 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20mg KOH / g, average molecular weight 5600), 0.5 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 0.1 parts of polyether-modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 0.1 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 20 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 5m / s for 120min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, the nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 48 mPa·s using a rotational viscometer (25℃, rotor #2).

[0034] Comparative Example 2 This comparative example provides a method for preparing MOF-enhanced nano-ceramic coating materials, including the following steps: Step 1: Add 10g of the Al2O3 / ZrO2 nanocomposite ceramic prepared in Example 1 to 190g of methanol, and ultrasonically disperse at 50kHz for 30min to obtain a composite ceramic material dispersion with a mass concentration of 5%. Add 2-methylimidazole to the composite ceramic material dispersion and stir until completely dissolved. Then, slowly add zinc nitrate solution (prepared by mixing zinc nitrate and ethanol at a mass-volume ratio of 0.15g / 5mL) under stirring. The mass of zinc nitrate in the zinc nitrate solution is 1g, which means that the mass of zinc nitrate is 10% of the mass of Al2O3 / ZrO2 nanocomposite ceramic in the composite ceramic material dispersion. The molar ratio of zinc nitrate to 2-methylimidazole is 1:8. Stir and react at 20℃ for 12h. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain MOFs-reinforced nano-ceramic composite powder. Step 2: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 150g of N,N-dimethylformamide, add 1g of polyacrylic acid (number average molecular weight of 1000 Da), 0.5g of N,N'-dicyclohexylcarbodiimide and 0.05g of 4-dimethylaminopyridine, stir and react at 20℃ for 12h. After the reaction is completed, centrifuge and wash three times with N,N-dimethylformamide, then wash three times with ethanol, and dry in a vacuum drying oven at 50℃ to constant weight to obtain modified nano-ceramic composite powder; Step 3: Take 10g of modified nano-ceramic composite powder, 20 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20mg KOH / g, average molecular weight 5600), 0.5 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 0.1 parts of polyether-modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 0.1 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 20 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 5m / s for 120min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, MOFs-reinforced nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 52 mPa·s using a rotational viscometer (25℃, rotor #2).

[0035] Comparative Example 3 This comparative example provides a method for preparing a MOF-reinforced nano-ceramic coating material, including the following steps: Step 1: Add 10g of the Al2O3 / ZrO2 nanocomposite ceramic prepared in Example 1 to 190g of methanol, and ultrasonically disperse at 50kHz for 30min to obtain a composite ceramic material dispersion with a mass concentration of 5%. Add 2-methylimidazole to the composite ceramic material dispersion and stir until completely dissolved. Then, slowly add zinc nitrate solution (prepared by mixing zinc nitrate and ethanol at a mass-volume ratio of 0.15g / 5mL) under stirring. The mass of zinc nitrate in the zinc nitrate solution is 1g, which means that the mass of zinc nitrate is 10% of the mass of Al2O3 / ZrO2 nanocomposite ceramic in the composite ceramic material dispersion. The molar ratio of zinc nitrate to 2-methylimidazole is 1:8. Stir and react at 20℃ for 12h. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain MOFs-reinforced nano-ceramic composite powder. Step 2: Disperse 10g of MOFs-reinforced nano-ceramic composite powder in 100g of ethanol (i.e., the amount of ethanol is 10 times the mass of MOFs-reinforced nano-ceramic composite powder), add 0.5g of γ-aminopropyltriethoxysilane (i.e., the mass of γ-aminopropyltriethoxysilane is 5% of the mass of MOFs-reinforced nano-ceramic composite powder), and react at 60℃ for 6 hours with stirring at 400r / min. After the reaction is completed, centrifuge, wash three times with ethanol, and dry to constant weight in a vacuum drying oven at 50℃ to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Take 10g of amino-modified MOFs-reinforced nano-ceramic composite powder, 20 parts of organosilicon resin containing hydroxyl functional groups (double-terminated hydroxypropyl polydimethylsiloxane, hydroxyl value 20mg KOH / g, average molecular weight 5600), 0.5 parts of polyvinylpyrrolidone dispersant (PVP K15, number average molecular weight 10,000), 0.1 parts of polyether-modified polydimethylsiloxane leveling agent (leveling agent BYK-307), 0.1 parts of polyoxyethylene polyoxypropylene glycerol ether defoamer (defoamer GPE), and 20 parts of ethanol, mix them, and disperse them using a high-speed disperser at a dispersion linear velocity of 5m / s for 120min. During the dispersion process, control the temperature of the mixed system to not exceed 50℃. After dispersion, MOFs-reinforced nano-ceramic coating material is obtained. The viscosity of the MOFs-reinforced nano-ceramic coating material was measured to be 55 mPa·s using a rotational viscometer (25℃, rotor #2).

[0036] Structural characterization and performance testing: (1) The microstructure of the MOFs-reinforced nano-ceramic composite powder prepared in Example 4 was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that the MOF-reinforced nano-ceramic composite powder exhibits a clear core-shell structure, with the ZIF-8 shell layer uniformly coating the surface of the Al2O3 / ZrO2 nano-composite ceramic particles, and the average particle size of the MOF-reinforced nano-ceramic composite powder is 95 nm.

[0037] (2) The coating materials obtained in Examples 4-6 and Comparative Examples 1-3 were applied to steel plate substrates of the same specifications (150mm×75mm×2mm, Q235 cold-rolled steel plate) using the same spraying process. The spraying pressure was 0.4MPa, the spraying distance was 20cm, and the wet film thickness was controlled at 150±20μm. After spraying, the coating was cured at room temperature for 24h, and then placed in a box furnace. The temperature was increased to 200℃ at 5℃ / min and kept at that temperature for 2h. The coating was then cooled to room temperature with the furnace to obtain a dry film coating sample. The adhesion of coated samples is determined using the pull-off method (GB / T5210-2006), the pencil hardness of coated samples is determined using the pencil scratch method (GB / T6739-2022), the flexibility of coated samples is determined using the shaft bending method (GB / T1731-2020), the impact resistance of coated samples is determined using the falling weight impact method (GB / T1732-2020), and the impact resistance of coated samples is determined using the steady-state heat flow method (GB / T10297-2015). The thermal conductivity of the coating samples was measured. The thermal stability of the coating samples was determined using thermogravimetric analysis (TGA / DSC) with a Mettler Toledo simultaneous thermal analyzer. The thermal cycling stability of the coating samples was determined using a high and low temperature test chamber, cycling 100 times (-40℃ for 30 min → 80℃ for 30 min). The salt spray resistance of the coating samples was determined using a neutral salt spray test (5% NaCl, 35℃, 72 h) according to standard GB / T1771-2007. The results are shown in Table 1. Table 1 As shown in Table 1, the coating material prepared by this invention has excellent mechanical properties, thermal insulation properties, and weather resistance. The adhesion of Examples 4-6 all reached above 8.5 MPa, which is much higher than that of Comparative Examples 1-3; the pencil hardness reached 3H-6H, which is significantly better than that of Comparative Examples 1-3; in the flexibility and impact resistance tests, Examples 4-6 showed no cracks or peeling, while Comparative Examples 1-3 showed varying degrees of cracks and peeling; in terms of thermal conductivity, Examples 4-6 were as low as 0.28-0.35 W / (m·K), while Comparative Examples 1-3 were as high as 0.55-0.72 W / (m·K); In terms of thermal stability, the thermal decomposition temperatures of Examples 4-6 were all above 385℃, and the mass retention rate at 600℃ was greater than 82%, while the thermal decomposition temperatures of Comparative Examples 1-3 were only 355-370℃. After 100 thermal cycle tests, the coatings of Examples 4-6 showed no cracking or peeling, while Comparative Examples 1-3 showed obvious cracking or even peeling. After 72 hours of salt spray testing, the coatings of Examples 4-6 showed no blistering or rust, while Comparative Examples 1-3 showed blistering, rust spots, or even severe rust. Compared to Example 4, in Comparative Example 1, no ZIF-8 shell was formed on the surface of the Al2O3 / ZrO2 nanocomposite ceramic. The coating adhesion decreased from 8.5 MPa to 3.2 MPa, a decrease of 62.4%, while the thermal conductivity increased from 0.35 W / (m·K) to 0.68 W / (m·K), an increase of 94.3%. After 100 thermal cycles, the coating showed obvious cracking, and blistering and rust spots appeared after salt spray testing. This indicates that the ZIF-8 shell is anchored to the ceramic core surface through the formation of Zn-O-Al and Zn-O-Zr type coordination bonds, significantly enhancing the interfacial bonding strength of the coating. At the same time, the porous structure of ZIF-8 plays a key role in reducing the thermal conductivity of the coating. In Comparative Example 2, the MOFs-reinforced nano-ceramic composite powder was not modified with amino groups, and the coating adhesion decreased to 4.5 MPa. The thermal conductivity increased to 0.55 W / (m·K), microcracks appeared after thermal cycling, and local blistering occurred after salt spray testing. This indicates that amino modification provides necessary reaction sites for the subsequent DCC / DMAP-catalyzed amidation reaction. The absence of amino modification will lead to the inability of polyacrylic acid to be effectively grafted, insufficient carboxyl group density on the powder surface, and weakened interfacial bonding with the binder. In Comparative Example 3, without carboxyl modification, the coating adhesion decreased to 2.8 MPa, the thermal conductivity increased to 0.72 W / (m·K), severe cracking and peeling occurred after thermal cycling, and severe corrosion occurred after salt spray testing. This indicates that after carboxyl modification, strong hydrogen bond interactions are formed between the high-density carboxyl groups on the powder surface and the hydroxyl-containing organosilicon resin. If carboxyl modification is missing, the powder and binder rely only on physical mixing and cannot form an effective interfacial bond, resulting in a comprehensive deterioration of coating performance.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing MOFs-reinforced nano-ceramic coating materials, characterized in that, Includes the following steps: Step 1: Add Al2O3 / ZrO2 nanocomposite ceramics to the first solvent and disperse by ultrasonication to obtain a composite ceramic material dispersion. Add 2-methylimidazole to the composite ceramic material dispersion. After complete dissolution, add zinc salt solution under stirring conditions and react. After the reaction is completed, centrifuge, wash, and dry to obtain MOFs-reinforced nanoceramic composite powder. Step 2: Disperse the MOFs-reinforced nano-ceramic composite powder in a second solvent, add a silane coupling agent containing amino functional groups, react, centrifuge, wash, and dry to obtain amino-modified MOFs-reinforced nano-ceramic composite powder. Step 3: Disperse the amino-modified MOFs-enhanced nano-ceramic composite powder in a third solvent, add a polymer containing carboxyl functional groups, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, react, centrifuge, wash and dry to obtain the modified nano-ceramic composite powder. Step 4: Mix the modified nano-ceramic composite powder, binder containing reactive functional groups, dispersant, leveling agent, defoamer, and solvent, and stir to disperse to obtain the MOFs-enhanced nano-ceramic coating material.

2. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 1, characterized in that, In step one, the mass concentration of the composite ceramic material dispersion is 5%-10%, the mass of zinc salt in the zinc salt solution is 10%-30% of the mass of Al2O3 / ZrO2 nanocomposite ceramics in the composite ceramic material dispersion, the molar ratio of zinc salt to 2-methylimidazole in the zinc salt solution is 1:8, and the reaction conditions are stirring at 20-40℃ for 2-12 hours. The first solvent includes methanol, and the zinc salt includes zinc nitrate.

3. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 1, characterized in that, The Al2O3 / ZrO2 nanocomposite ceramic in step one is prepared by the following steps: The nano-Al2O3 / nano-ZrO2 mixed powder was mixed with ethanol, ball-milled, dried, ground, pressed into tablets, annealed, and then ground and sieved to obtain Al2O3 / ZrO2 nanocomposite ceramics. In the nano-Al2O3 / nano-ZrO2 mixed powder, the mass ratio of nano-Al2O3 to nano-ZrO2 is 1:(0.5-2), the ball milling time is 8-12 h, the annealing temperature range is room temperature to 1000℃, and the heating rate is 5℃·min. -1 The annealing temperature intervals are 100℃, and the holding time at each annealing temperature is 1.5-2.5h.

4. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 1, characterized in that, In step two, the mass of the silane coupling agent containing amino functional groups is 5%-20% of the mass of the MOFs-reinforced nano-ceramic composite powder; the amount of the second solvent is 10-30 times the mass of the MOFs-reinforced nano-ceramic composite powder; and the reaction conditions are a stirring speed of 400-800 r / min and a reaction temperature of 60-80℃ for 3-6 h. The second solvent includes ethanol, and the silane coupling agent containing an amino functional group includes γ-aminopropyltriethoxysilane.

5. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 1, characterized in that, In step three, the mass ratio of amino-modified MOFs-reinforced nano-ceramic composite powder, the third solvent, the polymer containing carboxyl functional groups, N,N'-dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 10:(150-300):(1-4):(0.5-2):(0.05-0.2), and the reaction is carried out under the condition of stirring at 20-40℃ for 6-12 hours.

6. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 5, characterized in that, The third solvent includes N,N-dimethylformamide, and the polymer containing carboxyl functional groups includes polyacrylic acid; The number average molecular weight of the polymer containing carboxyl functional groups is 1000-20000 Da.

7. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 1, characterized in that, In step four, the mass ratio of modified nano-ceramic composite powder, binder containing reactive functional groups, dispersant, leveling agent, defoamer, and solvent is (10-40):(20-60):(0.5-5):(0.1-2):(0.1-2):(20-60). The conditions for stirring and dispersing are: dispersion is carried out using a high-speed disperser, the dispersion linear velocity is 5-20 m / s, the dispersion time is 60-120 min, and the temperature of the mixing system is controlled not to exceed 50℃ during the dispersion process.

8. The method for preparing a MOFs-reinforced nano-ceramic coating material according to claim 7, characterized in that, The binder containing reactive functional groups includes an organosilicon resin containing hydroxyl functional groups, the dispersant includes polyvinylpyrrolidone, the leveling agent includes polyether-modified polydimethylsiloxane, the defoamer includes polyoxyethylene polyoxypropylene glycerol ether, and the solvent includes ethanol.

9. A MOF-reinforced nano-ceramic coating material, characterized in that, The MOFs-enhanced nano-ceramic coating material was prepared using the preparation method described in any one of claims 1-8.

10. The application of the MOFs-enhanced nano-ceramic coating material as described in claim 9 on a heat insulation film.

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