A high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating and its preparation method

Abstract

This invention relates to a high-absorption, high-temperature-resistant high-entropy niobate ceramic photothermal coating. The coating is composed of the following raw materials in parts by weight: 8-16 parts light-absorbing pigment, 2-4 parts filler, 20-40 parts binder, 22-65 parts ultrapure water, and 10-15 parts additives. The light-absorbing pigment is a high-entropy niobate ceramic A3NbO7, where A is any five elements selected from Pr, Mn, Co, La, Fe, Sm, Gd, and Yb, in equimolar ratios. The invention also discloses a method for preparing this high-entropy niobate ceramic photothermal coating. This invention exhibits excellent solar energy absorption performance, and the resulting coating possesses excellent adhesion, thermal shock resistance, and corrosion resistance, making it applicable to high-temperature concentrated solar power generation systems, photothermal de-icing, and seawater desalination.

Description

Technical Field

[0001] This invention relates to the field of high-temperature solar energy absorption, and in particular to a high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating and its preparation method. Background Technology

[0002] Solar thermal power generation (CSP) is one of the most promising power generation technologies in future renewable energy systems. It can efficiently utilize abundant but intermittent solar energy resources to provide stable, dispatchable, and low-cost electricity. To further reduce the levelized cost of power (LCOE) of existing commercial CSP plants, researchers are actively researching next-generation CSP technologies with higher operating temperatures and power generation efficiencies. Solar thermal absorption coatings are the core component of CSP technology, absorbing the full spectrum of solar energy and converting it into heat energy stored in molten salt for power generation. Therefore, solar thermal absorption coatings should possess high solar absorptivity, excellent oxidation resistance, and high-temperature thermal stability across the solar spectrum. Currently, the most widely used high-temperature solar absorption coating is Pyromark 2500, based on spinel, which is considered the gold standard in the CST industry. However, after operating at 850°C for 2350 hours, the emissivity of this coating decreases to approximately 0.94. Therefore, developing absorption coatings with excellent high-temperature thermal stability and full-spectrum absorption characteristics is crucial for next-generation CSP technologies.

[0003] Rare earth niobate (RE3NbO7) ceramics (RE = Dy, Y, Er, Yb) possess excellent chemical and high-temperature thermal stability and good mechanical properties, and are often used as high-temperature thermal barrier coatings. However, a single element of this type of material has a wide band gap, which is detrimental to solar energy absorption. Although elemental doping can reduce the band gap of the material, it is an effective way to improve its solar energy absorption capacity. However, single-element or dual-element doping can easily introduce unstable intermediate phases, reducing the high-temperature thermal stability of the material.

[0004] High-entropy ceramics are a novel type of compound obtained by randomly doping five or more metallic elements at cation sites. These materials possess a rich compositional space, providing an effective platform for optimizing material functional properties. Furthermore, they exhibit high configurational entropy, leading to entropy-assisted thermal stability effects, typically manifesting as a single-phase solid solution structure with excellent high-temperature thermal stability. Therefore, simultaneously doping RE sites with multiple transition metals and rare earth metals to reduce the band gap is a very promising strategy for improving solar energy absorption capacity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-performance, high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating.

[0006] Another technical problem to be solved by the present invention is to provide a method for preparing the high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating.

[0007] To solve the above problems, the present invention provides a high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating, characterized in that: the photothermal coating is composed of the following raw materials in parts by mass: 8-16 parts of light-absorbing pigment, 2-4 parts of filler, 20-40 parts of binder, 22-65 parts of ultrapure water, and 10-15 parts of additives; the light-absorbing pigment is high-entropy niobate ceramic A3NbO7, wherein A is any five elements selected from Pr, Mn, Co, La, Fe, Sm, Gd, and Yb, and the metal elements are in equimolar ratio.

[0008] The light-absorbing pigment is prepared by the following method: using AO in a molar ratio of 3:5 x Using Nb₂O₅ as raw material, the mixture is ball-milled, dried, and ground to obtain a powder mixture. This powder mixture is then calcined at high temperature in air and cooled to room temperature to obtain a powder material with a defective fluorite crystal structure and a particle size of 50-600 nm; the AO x Pr6O 11 The powder contains any five of the following: Mn2O3, CoO, La2O3, Fe2O3, Sm2O3, Gd2O3, and Yb2O3, with each metal atom in an equal molar ratio.

[0009] The conditions for ball milling and mixing refer to using a planetary ball mill for ball milling, with a ball milling speed of 300~500 r / min, a ball milling time of 5~12 hours, and a ball-to-material-to-water mass ratio of 2~5:1:3; the ball milling process is as follows: first ball mill for 1 hour, then pause for 10 minutes, then ball mill for 1 hour, pause for 10 minutes, and so on, in a cycle.

[0010] The conditions for high-temperature calcination are: calcination temperature of 900~1500℃, heating rate of 3~10℃ / min, and calcination time of 2~6 hours; the cooling method is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

[0011] The filler is one or more of calcium carbonate, porous quartz powder, white carbon black, mica powder and bentonite, with a particle size of 50~200nm.

[0012] The binder is at least one of polysilazane, polyimide, and rare earth phosphate.

[0013] The additives refer to a mixture obtained by uniformly mixing leveling agent, dispersant and defoamer in a mass ratio of 1:1:1 to 1:2:3.

[0014] The leveling agent is one or two of the following: Deqian 810 silicone leveling agent - polyether modified polysiloxane, AFCONA-3587 - polyether modified organosilicon, and AFCONA-3085 - polyether modified organosilicon; the dispersant is sodium oleate C. 17 H 33 The defoamer is one or more of COONa, carboxylates, sulfate esters, and sulfonates; the defoamer is one or two of TEGO Antifoam 3062 polyether defoamer, AFCONA-2035-fluorocarbon modified silicone, and AFCONA-2040-fluorocarbon modified silicone.

[0015] The coating formed by this photothermal coating has a thickness of 50~100μm; and the coating operates at a temperature range of 700~1000℃; and its absorptivity in the solar wavelength range of 0.3~2.5μm is not less than 0.95.

[0016] The preparation method of the high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating as described above is characterized by: firstly, weighing according to the formula, then mixing and dispersing ultrapure water, binder, and additives evenly, adding light-absorbing pigments and fillers, stirring at a speed of 600~1200 r / min for 60~100 min using a high-speed disperser, then dispersing and grinding to a fineness of 15~30 μm using a sand mill or ball mill, and finally filtering through a 100~200 mesh wire mesh to obtain the high-entropy niobate ceramic photothermal coating.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. In this invention, the high-entropy coating prepared by multi-element doping of A3NbO7 reduces the band gap to 1.98 eV. This is because the complementary electron distribution of multiple transition elements or rare earth elements near the Fermi level increases the impure energy level, and the abundant elemental selectivity at the A site also increases the optimization space for the material's band gap. Furthermore, due to the lattice distortion effect, the material easily generates oxygen vacancies, which also introduce intermediate energy levels, improving the coating's solar energy absorption rate to above 0.95.

[0019] 2. The coating prepared using the coating of this invention has a smooth, dense surface, is free of bubbles and cracks, which is beneficial to improving the thermal stability and high-temperature corrosion resistance of the absorption coating under high-temperature conditions. At the same time, the high-entropy pigment has a high configurational entropy, which reduces the Gibbs free energy and exhibits a single-phase solid solution structure, which is also beneficial to improving high-temperature thermal stability and molten salt corrosion resistance.

[0020] 3. The coating prepared by the present invention was subjected to molten salt corrosion at 700°C (molten salt is Na2SO4+K2SO4 with a mass ratio of 1:1) for 240 hours. After high-temperature molten salt corrosion, the coating was smooth, dense, free of blistering and cracking, indicating that the coating prepared by the present invention has excellent resistance to high-temperature molten salt corrosion.

[0021] 4. The coating prepared on ceramic fiber board using the coating of the present invention underwent a 72-hour thermal stability test in an air environment at 1300℃. The structure and solar energy absorption rate of the coating showed only slight changes, indicating that the coating has excellent high-temperature resistance.

[0022] 5. This invention is simple to operate, has high production efficiency, and requires no complex heat treatment process, making it applicable to high-temperature concentrated solar power generation systems, solar thermal de-icing, seawater desalination, and other fields. Furthermore, the excellent high-temperature thermal stability and molten salt corrosion resistance of the coating prepared using this invention also make it suitable for thermal protection of power plant boilers. Attached Figure Description

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1 This is Embodiment 1 of the present invention (Pr 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 XRD pattern of NbO7.

[0025] Figure 2 This is Embodiment 2 of the present invention (Pr 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 XRD pattern of NbO7.

[0026] Figure 3 This is Embodiment 2 of the present invention (Pr 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 Solar absorption spectrum of NbO7 powder material in the 0.3 ~ 2.5 μm wavelength range.

[0027] Figure 4 Example 3 of the present invention (Fe) 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 XRD pattern of NbO7.

[0028] Figure 5 This is Example 4 (Sm) of the present invention 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 XRD pattern of NbO7. Detailed Implementation

[0029] A high-absorption, high-temperature-resistant high-entropy niobate ceramic photothermal coating is disclosed, comprising the following raw materials in parts by weight (g): 8-16 parts light-absorbing pigment, 2-4 parts filler, 20-40 parts binder, 22-65 parts ultrapure water, and 10-15 parts additives. The light-absorbing pigment is a high-entropy niobate ceramic A3NbO7, wherein A is any five elements selected from Pr, Mn, Co, La, Fe, Sm, Gd, and Yb, and the metal elements are in equimolar ratios.

[0030] The light-absorbing pigment was prepared by the following method: AO in a molar ratio of 3:5 x Using Nb2O5 as raw material, AO x Pr6O 11 The powder is composed of any five of the following: Mn₂O₃, CoO, La₂O₃, Fe₂O₃, Sm₂O₃, Gd₂O₃, and Yb₂O₃, with each metal having an equimolar ratio of atoms. It is ball-milled using a planetary ball mill at a speed of 300–500 r / min for 5–12 hours, with a ball-to-material-to-water mass ratio (g / g) of 2–5:1:3. The milling process involves milling for 1 hour, followed by a 10-minute pause, then milling for another hour, followed by a 10-minute pause, and this cycle is repeated. The mixture is then dried and ground to obtain a powdered mixture. This powder is then calcined in air at a temperature of 900–1500℃, a heating rate of 3–10℃ / min, and a calcination time of 2–6 hours. The mixture is then cooled to room temperature using one of the following methods: furnace cooling, air quenching, or liquid nitrogen quenching, resulting in a powder material with a defective fluorite crystal structure and a particle size of 50–600 nm.

[0031] The filler is one or more of calcium carbonate, porous quartz powder, white carbon black, mica powder, and bentonite, with a particle size of 50-200 nm. These fillers can reduce coating costs, increase coating thickness, and enhance coating hardness and wear resistance.

[0032] The binder is at least one of polysilazane, polyimide, and rare earth phosphate.

[0033] Additives refer to a mixture obtained by uniformly mixing leveling agents, dispersants, and defoamers in a mass ratio (g / g) of 1:1:1 to 1:2:3. The leveling agent is one or two of the following: Deqian 810 silicone leveling agent - polyether modified polysiloxane, AFCONA-3587 - polyether modified organosilicon, and AFCONA-3085 - polyether modified organosilicon. The dispersant is sodium oleate C. 17 H 33One or more of COONa, carboxylates, sulfate esters (RO-SO3Na, where R represents an organic group), and sulfonates (R-SO3Na, where R represents an organic group). The defoamer is one or two of TEGO Antifoam 3062 polyether defoamer, AFCONA-2035-fluorocarbon modified silicone, and AFCONA-2040-fluorocarbon modified silicone.

[0034] A method for preparing a high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating:

[0035] First, weigh the ingredients according to the formula. Then, mix and disperse the ultrapure water, binder, and additives evenly. Add the light-absorbing pigment and filler. Use a high-speed disperser to stir at a speed of 600~1200r / min for 60~100min. Then, use a sand mill or ball mill to disperse and grind to a fineness of 15~30μm. Finally, filter through a 100~200 mesh screen to obtain the high-entropy niobate ceramic photothermal coating.

[0036] The resulting photothermal coating has a thickness of 50~100μm; and the coating operates at a temperature range of 700~1000℃; with an absorptivity of not less than 0.95 in the solar wavelength range of 0.3~2.5μm.

[0037] Example 1

[0038] (1) Light-absorbing pigments (Pr) 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 Preparation of NbO7

[0039] Weigh out Pr6O 11 Zirconia balls (3 mol), Sm2O3 (3 mol), Co2O3 (3 mol), La2O3 (3 mol), Fe2O3 (3 mol), and Nb2O5 (5 mol) powders were prepared. Zirconia balls, raw materials, and ultrapure water were added to a ball mill jar at a ball mill ratio of 2:1:3 (g / g). The jar was placed on the ball mill and milled for 1 hour at 300 r / min, followed by a 10-minute pause. This constituted one milling cycle. Milling was repeated for another 1 hour at 300 r / min, for a total of 12 hours to obtain a mixed powder. The resulting mixed powder was then dried, ground, and placed in a muffle furnace. The furnace was heated to 900℃ in air (heating rate 3℃ / min) and calcined for 6 hours. Afterward, it was air-quenched and cooled to room temperature to obtain a single-phase (Pr) oxide. 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6)NbO7.

[0040] The result (Pr) 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 The particle size of NbO7 is 20 nm, and the specific surface area is 50 m². 2 / g. Its XRD characterization shows that (Pr 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 NbO7 has a defective fluorite-type crystal structure (such as...) Figure 1 (As shown).

[0041] (2) Preparation of high-entropy niobate ceramic photothermal coating

[0042] Paint formulation: 8g (Pr 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 NbO7, 2g calcium carbonate, 20g polysilazane, 22g ultrapure water, 10g additives (2g Deqian 810 silicone leveling agent - polyether modified polysiloxane + 2g sodium oleate C) 17 H 33 COONa+6gTEGOAntifoam 3062 (polyether defoamer).

[0043] Preparation process: After ultrapure water, polysilazane, and additives are mixed and dispersed evenly, (Pr) is added. 0.6 Sm 0.6 Co 0.6 La 0.6 Fe 0.6 NbO7 and calcium carbonate were first stirred at 600-1200 rpm for 60-100 min using a high-speed disperser, then dispersed and ground to a fineness of 15-30 μm using a sand mill or ball mill. Finally, the mixture was filtered through a 100-200 mesh screen to obtain a high-entropy niobate ceramic photothermal coating, which was then sealed and stored. The solar energy absorption coating prepared using this coating showed an absorptivity of 0.965 in the solar energy band of 0.3-2.5 μm.

[0044] Example 2

[0045] (1) Light-absorbing pigments (Pr) 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 Preparation of NbO7

[0046] Weigh out Pr6O11 Zirconia balls (3 mol), Mn2O3 (3 mol), Gd2O3 (3 mol), La2O3 (3 mol), Sm2O3 (3 mol), and Nb2O5 (5 mol) powders were prepared. Zirconia balls, raw materials, and ultrapure water were added to a ball mill jar at a ball mill ratio of 4:1:3 (g / g). The jar was placed on the ball mill and milled for 1 hour at 400 r / min, followed by a 10-minute pause. This constituted one milling cycle. Milling was repeated for another 1 hour at 400 r / min, for a total of 8 hours to obtain a mixed powder. The resulting mixed powder was then dried, ground, and placed in a muffle furnace. The furnace was heated to 1000℃ in air (heating rate 3℃ / min) and calcined for 6 hours. Afterward, it was air-quenched and cooled to room temperature to obtain a single-phase (Pr) oxide. 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 )NbO7.

[0047] The result (Pr) 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 The particle size of NbO7 is 20 nm, and the specific surface area is 50 m². 2 / g. Its XRD characterization shows that (Pr 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 NbO7 has a defective fluorite-type crystal structure (such as...) Figure 2 (As shown). Its absorptivity in the solar energy band of 0.3~2.5μm is 0.87, as... Figure 3 As shown.

[0048] (2) Preparation of high-entropy niobate ceramic photothermal coating

[0049] Paint formulation: 16g (Pr 0.6 Mn 0.6 Gd 0.6 La 0.6 Sm 0.6 NbO7, 4g porous quartz powder, 40g polyimide, 65g ultrapure water, 15g additives (5g AFCONA-3587-polyether modified organosilicon + 5g carboxylate + 5g AFCONA-2035-fluorocarbon modified organosilicon).

[0050] Preparation process: After ultrapure water, polyimide, and additives are mixed and dispersed evenly, (Pr) is added. 0.6 Mn0.6 Gd 0.6 La 0.6 Sm 0.6 NbO7 and porous quartz powder were first stirred at 600-1200 r / min for 60-100 min using a high-speed disperser, then dispersed and ground to a fineness of 15-30 μm using a sand mill or ball mill. Finally, the mixture was filtered through a 100-200 mesh screen to obtain a high-entropy niobate ceramic photothermal coating, which was then sealed and stored. The solar energy absorption coating prepared using this coating has an absorptivity of 0.96 in the solar energy band of 0.3-2.5 μm.

[0051] Example 3

[0052] (1) Light-absorbing pigments (Fe) 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 Preparation of NbO7

[0053] Weigh out Fe2O3 (3 mol), Mn2O3 (3 mol), Co2O3 (3 mol), La2O3 (3 mol), Gd2O3 (3 mol), and Nb2O5 (5 mol) powders respectively. Add zirconia balls, raw materials, and ultrapure water to a ball mill jar at a ball mill ratio of 4:1:3 (ball:material:water mass ratio). Place the jar on a ball mill and mill for 1 hour at 400 r / min, then pause for 10 minutes, repeating this as one milling cycle. Mill for another hour at 400 r / min, for a total of 8 hours to obtain a mixed powder. Dry and grind the milled powder, then place it in a muffle furnace and heat it to 1300℃ in air (heating rate 8℃ / min) for 4 hours. Then air quench and cool to room temperature to obtain a single-phase (Fe2O3) powder. 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 )NbO7.

[0054] The obtained (Fe) 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 The particle size of NbO7 is 20 nm, and the specific surface area is 50 m². 2 / g. Its XRD characterization showed that (Fe 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 NbO7 has a defective fluorite-type crystal structure (such as...) Figure 4 (As shown).

[0055] (2) Preparation of high-entropy niobate ceramic photothermal coating

[0056] Paint formulation: 10g (Fe 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 NbO7, 3g white carbon black, 30g rare earth phosphate, 40g ultrapure water, 12g additives (2g AFCONA-3085-polyether modified organosilicon + 4g sulfate ester salt + 6g AFCONA-2040-fluorocarbon modified organosilicon).

[0057] Preparation process: After uniformly dispersing ultrapure water, rare earth phosphate, and additives, add (Fe) 0.6 Mn 0.6 Co 0.6 La 0.6 Gd 0.6 NbO7 and silica were first stirred at 600-1200 rpm for 60-100 min using a high-speed disperser, then dispersed and ground to a fineness of 15-30 μm using a sand mill or ball mill. Finally, the mixture was filtered through a 100-200 mesh screen to obtain a high-entropy niobate ceramic photothermal coating, which was then sealed and stored. The solar energy absorption coating prepared using this coating exhibited an absorptivity of 0.968 in the solar energy band of 0.3-2.5 μm.

[0058] Example 4

[0059] (1) Light-absorbing pigments (Sm) 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 Preparation of NbO7

[0060] Weigh out 3 mol of Sm₂O₃, 3 mol of Fe₂O₃, 3 mol of Gd₂O₃, 3 mol of La₂O₃, 3 mol of Yb₂O₃, and 5 mol of Nb₂O₅ powder respectively. Add zirconia balls, raw materials, and ultrapure water to a ball mill jar at a ball mill ratio of 2:1:3 (g / g). Place the jar on the ball mill and mill for 1 hour at 500 r / min, then pause for 10 minutes, repeating this as one milling cycle. Mill for another 1 hour at 500 r / min, for a total of 5 hours to obtain a mixed powder. Dry and grind the milled powder, then place it in a muffle furnace and heat it to 1500℃ in air (heating rate 10℃ / min) for 2 hours. Then air quench and cool to room temperature to obtain single-phase (Sm₂O₃)₂O₅ powder.0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 )NbO7.

[0061] The result (Sm) 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 The particle size of NbO7 is 20 nm, and the specific surface area is 50 m². 2 / g. Its XRD characterization shows that (Sm 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 NbO7 has a defective fluorite-type crystal structure (such as...) Figure 5 (As shown).

[0062] (2) Preparation of high-entropy niobate ceramic photothermal coating

[0063] Paint formulation: 14g (Sm 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 NbO7, 4g bentonite, 35g rare earth phosphate, 55g ultrapure water, 14g additives (2g Deqian 810 silicone leveling agent - polyether modified polysiloxane + 2g AFCONA-3587 - polyether modified organosilicon + 4g sulfonate + 3g TEGO Antifoam 3062 polyether defoamer + 3g AFCONA-2035 - fluorocarbon modified organosilicon).

[0064] Preparation process: After uniformly dispersing ultrapure water, rare earth phosphate, and additives, add (Sm) 0.6 Fe 0.6 Gd 0.6 La 0.6 Yb 0.6 NbO7 and bentonite were first stirred at 600-1200 r / min for 60-100 min using a high-speed disperser, then dispersed and ground to a fineness of 15-30 μm using a sand mill or ball mill. Finally, the mixture was filtered through a 100-200 mesh screen to obtain a high-entropy niobate ceramic photothermal coating, which was then sealed and stored. The solar energy absorption coating prepared using this coating has an absorptivity of 0.955 in the solar energy band of 0.3-2.5 μm.

[0065] [Performance Testing]

[0066] The coatings prepared in Examples 1-4 were applied to substrates (nickel-based alloy 625) using a spraying method, and then placed in a muffle furnace at 300°C for 1 hour, followed by furnace cooling. The dry film thickness was 20-60 μm. The coating performance was tested. The results are shown in Table 1.

[0067] 1. Solar energy absorption rate

[0068] The method was performed using a Lambda 950 UV-Vis-NIR spectrophotometer (including a 150mm integrating sphere) from the United States, in accordance with the national standard GB / T26974-2011.

[0069] Test results: The coating exhibits a solar energy absorption rate of no less than 0.95 in the 0.3~2.5μm wavelength range, demonstrating excellent solar energy absorption characteristics.

[0070] 2. Adhesion

[0071] The adhesion of the coating was tested using the pull-out method, with reference to ASTM D 4541, "Determination of the pull-out strength of coatings using a portable adhesion tester".

[0072] Test results: The coating pull-out strength is greater than 5 MPa.

[0073] 3. Thermal shock resistance

[0074] The coating was placed in an air atmosphere in a box furnace and heated to 700°C at a heating rate of 5°C / min. After holding at that temperature for 30 minutes, it was removed and cooled by water quenching. This process was repeated 10 times, and the coating surface was observed.

[0075] Test results: The coating surface is intact, with no peeling or cracks.

[0076] 4. Coating salt spray corrosion resistance test

[0077] Artificial Atmosphere Corrosion Test - Salt Spray Test (NSS), Test Standard: GB / T 10125-2012.

[0078] Test results: After 1000 hours of salt spray testing, the coating remained intact and no corrosion occurred.

[0079] Table 1. Coating performance of coatings produced using the coatings prepared in Examples 1-4

[0080]

[0081] As shown in Table 1, the high-entropy niobate ceramic photothermal coating prepared by the present invention has good solar energy absorption performance, and the resulting coating has excellent adhesion, thermal shock resistance and corrosion resistance.

[0082] The above description only illustrates the preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

Claims

1. A high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating, characterized in that: The photothermal coating is composed of the following raw materials in parts by weight: 8-16 parts of light-absorbing pigment, 2-4 parts of filler, 20-40 parts of binder, 22-65 parts of ultrapure water, and 10-15 parts of additives; the light-absorbing pigment is a high-entropy niobate ceramic A3NbO7, wherein A is any five elements selected from Pr, Mn, Co, La, Fe, Sm, Gd, and Yb, and transition metal elements and rare earth metal elements are present in the same molar ratio among the five elements.

2. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 1, characterized in that: The light-absorbing pigment is prepared by the following method: using AO in a molar ratio of 3:5 x Using Nb₂O₅ as raw material, the mixture is ball-milled, dried, and ground to obtain a powder mixture. This powder mixture is then calcined at high temperature in air and cooled to room temperature to obtain a powder material with a defective fluorite crystal structure and a particle size of 50-600 nm; the AO x Pr6O 11 The five oxides are any five of the following: Mn2O3, CoO, La2O3, Fe2O3, Sm2O3, Gd2O3, and Yb2O3 powders, and all five oxides contain both transition metal oxides and rare earth metal oxides, with each metal atom in an equal molar ratio.

3. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 2, characterized in that: The conditions for ball milling and mixing refer to using a planetary ball mill for ball milling, with a ball milling speed of 300~500 r / min, a ball milling time of 5~12 hours, and a ball-to-material-to-water mass ratio of 2~5:1:3; the ball milling process is as follows: first ball mill for 1 hour, then pause for 10 minutes, then ball mill for 1 hour, pause for 10 minutes, and so on, in a cycle.

4. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 2, characterized in that: The conditions for high-temperature calcination are: calcination temperature of 900~1500℃, heating rate of 3~10℃ / min, and calcination time of 2~6 hours; the cooling method is one of furnace cooling, air quenching cooling, and liquid nitrogen quenching cooling.

5. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 1, characterized in that: The filler is one or more of calcium carbonate, porous quartz powder, white carbon black, mica powder and bentonite, with a particle size of 50~200nm.

6. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 1, characterized in that: The binder is at least one of polysilazane, polyimide, and rare earth phosphate.

7. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 1, characterized in that: The additives refer to a mixture obtained by uniformly mixing leveling agent, dispersant and defoamer in a mass ratio of 1:1:1 to 1:2:

3.

8. The high-absorption, high-temperature-resistant, high-entropy niobate ceramic photothermal coating as described in claim 7, characterized in that: The leveling agent is one or two of the following: Deqian 810 silicone leveling agent - polyether modified polysiloxane, AFCONA-3587 - polyether modified organosilicon, and AFCONA-3085 - polyether modified organosilicon; the dispersant is sodium oleate C. 17 H 33 The defoamer is one or more of COONa, carboxylates, sulfate esters, and sulfonates; the defoamer is one or two of TEGO Antifoam 3062 polyether defoamer, AFCONA-2035-fluorocarbon modified silicone, and AFCONA-2040-fluorocarbon modified silicone.

9. A high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating as described in any one of claims 1 to 8, characterized in that: The coating formed by this photothermal coating has a thickness of 50~100μm; and the coating operates at a temperature range of 700~1000℃; and its absorptivity in the solar wavelength range of 0.3~2.5μm is not less than 0.

95.

10. The preparation method of a high-absorption, high-temperature resistant, high-entropy niobate ceramic photothermal coating as described in claim 9, characterized in that: First, weigh the ingredients according to the formula. Then, mix and disperse the ultrapure water, binder, and additives evenly. Add the light-absorbing pigment and filler. Use a high-speed disperser to stir at a speed of 600~1200r / min for 60~100min. Then, use a sand mill or ball mill to disperse and grind to a fineness of 15~30μm. Finally, filter through a 100~200 mesh screen to obtain the high-entropy niobate ceramic photothermal coating.

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