A kind of infrared low emissivity coating and preparation method thereof

Abstract

The present invention provides an infrared low-emissivity coating, the raw materials for preparing the coating include an inorganic phosphate adhesive, an infrared low-emissivity filler and a surfactant; wherein the infrared low-emissivity filler is prepared by sintering and ball-milling barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide in sequence. In this solution, the infrared low-emissivity filler is first prepared using barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide as raw materials, and ball-milling is performed on the filler, which is conducive to the synergistic effect of conductivity and crystal vibration, thereby significantly reducing the infrared emissivity of the filler in a high-temperature environment. The infrared low-emissivity filler prepared above is mixed with an inorganic phosphate adhesive and a surfactant, and an infrared low-emissivity coating is prepared by a blade coating method, so that the coating has good temperature resistance and low infrared emissivity at high temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared stealth materials, and in particular to a low infrared emissivity coating and a preparation method thereof. Background Art

[0002] High-temperature-resistant, low-emissivity infrared materials play a crucial role in the survivability of targets. Low-emissivity infrared coatings are a key focus of infrared technology research due to their simple preparation process, unrestricted workpiece shape, and unchanged target appearance and the original metal substrate. Like other coatings, high-temperature-resistant, low-emissivity coatings are prepared by mixing fillers, adhesives, and additives in a specific proportion, dispersing them, applying them, and curing them.

[0003] However, in the related art, the organic adhesive used in the infrared low-emissivity coating has poor temperature resistance and is easily oxidized and decomposed at high temperatures. In addition, the low-emissivity filler has a low melting point and cannot work normally at high temperatures, resulting in the prepared coating being unable to work normally at high temperatures.

[0004] Therefore, based on the above problems, there is an urgent need to provide an infrared low-emissivity coating and a preparation method thereof. Summary of the Invention

[0005] The embodiments of the present invention provide a low-emissivity infrared coating and a preparation method thereof, which can solve the problem of high infrared emissivity in high-temperature environments in related technologies.

[0006] In a first aspect, the present invention provides an infrared low-emissivity coating, the raw materials for preparing the coating include an inorganic phosphate adhesive, an infrared low-emissivity filler and a surfactant; wherein the infrared low-emissivity filler is obtained by sintering and ball-milling barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide in sequence.

[0007] Preferably, the preparation method of the inorganic phosphate adhesive is as follows:

[0008] Phosphoric acid and aluminum hydroxide are mixed for reaction to obtain a first reactant; zinc oxide and magnesium oxide are added to the first reactant and mixed to obtain the inorganic phosphate adhesive.

[0009] More preferably, the molar ratio of phosphoric acid, aluminum hydroxide, zinc oxide and magnesium oxide is (2.5-3.5):1:0.2:0.05.

[0010] More preferably, the reaction temperature is 75-85° C. and the reaction time is 1-2 h.

[0011] Preferably, the preparation method of the infrared low emissivity filler is as follows:

[0012] S1 mixes barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide and sinter them to obtain Ba x Sr 1-x Al2Si2O8 ceramic powder;

[0013] S2 will Ba x Sr 1-x The Al2Si2O8 ceramic powder is ball-milled to obtain the infrared low-emissivity material.

[0014] Preferably, in step S1, the amount ratio of barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide is (0.2-0.3): (0.7-0.8): 1:2.

[0015] Preferably, the sintering temperature is 1400-1600° C., and the sintering time is 2-4 hours.

[0016] Preferably, in step S1, the temperature is increased in stages during the sintering process; wherein the heating rate in the first stage is 10-15°C / min, and the heating rate in the second stage is 4-8°C / min.

[0017] Preferably, in step S2, the rotation speed of the ball mill is 350-450 r / min, the time is 5-7 h, and the ball-to-material ratio is (4-5):1.

[0018] Preferably, the surfactant is a silane coupling agent or sodium dodecylbenzenesulfonate.

[0019] Preferably, the mass ratio of the inorganic phosphate binder, the infrared low emissivity filler and the surfactant is (45-55):(90-110):(0.045-0.05).

[0020] In a second aspect, the present invention further provides a method for preparing the infrared low emissivity coating according to any one of the first aspects above, characterized in that the preparation method comprises the following steps:

[0021] (1) preparing an inorganic phosphate binder and an infrared low emissivity filler respectively;

[0022] (2) stirring and mixing the inorganic phosphate binder, the infrared low emissivity filler and the surfactant in a certain proportion to obtain an infrared low emissivity coating;

[0023] (3) Scraping the infrared low emissivity coating onto the pre-treated target substrate and curing the coating to obtain the infrared low emissivity coating.

[0024] Preferably, in step (3), the curing is carried out in stages; wherein the temperature of the first stage curing is 20-30°C and the time is 20-24 hours; the temperature of the second stage curing is 450-550°C and the time is 2-3 hours.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) In the present invention, first, barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide are used as raw materials to prepare infrared low emissivity filler. During the preparation of the filler, barium carbonate and strontium carbonate are doped to prepare Ba x Sr 1-x Al2Si2O8 ceramic powder can increase the mobility of carriers in the ceramic powder, thereby increasing the conductivity of the filler; in addition, the x Sr 1- x The ball milling of Al2Si2O8 ceramic powder can, on the one hand, control the morphology and size of the powder. On the other hand, the ball milling process causes the molecules and atoms in the ceramic powder to vibrate and rotate, thereby enhancing the powder's absorption in the infrared band. In this way, under the synergistic effect of conductivity and crystal vibration, the infrared emissivity of the filler in a high-temperature environment can be significantly reduced. Finally, the infrared low-emissivity filler prepared above is mixed with an inorganic phosphate binder and a surfactant, and a low-emissivity infrared coating is prepared by a doctor blade coating method, which makes the coating have good heat resistance and low infrared emissivity at high temperatures.

[0027] (2) The preparation method of the infrared low-emissivity coating in the present invention has the advantages of simple process operation and low cost, and the prepared coating has both good high-temperature resistance and low infrared emissivity, and the infrared emissivity at a high temperature of 800°C is less than 0.35. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a curve diagram of infrared emissivity variation with temperature in the 3-5 μm band of an infrared low-emissivity powder filler and a coating prepared therefrom provided in Example 1 of the present invention; the powder in the figure is the infrared low-emissivity filler. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In order to solve one or more of the above problems, an embodiment of the present invention provides an infrared low-emissivity coating, the raw materials for preparing the coating include an inorganic phosphate adhesive, an infrared low-emissivity filler and a surfactant; wherein the infrared low-emissivity filler is prepared by sintering and ball-milling barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide in sequence.

[0032] In the embodiment of the present invention, firstly, a low-emissivity infrared filler is prepared using barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide as raw materials. During the preparation of the filler, barium carbonate and strontium carbonate are doped to prepare Ba x Sr 1-x Al2Si2O8 ceramic powder can increase the mobility of carriers in the ceramic powder, thereby increasing the conductivity of the filler; in addition, the x Sr 1- x Ball-milling Al2Si2O8 ceramic powders not only controls the powder's morphology and size, but also causes the molecules and atoms within the powder to vibrate and rotate, enhancing the powder's infrared absorption. This, through the synergistic effects of conductivity and crystal vibration, significantly reduces the filler's infrared emissivity at high temperatures. Finally, the resulting low-emissivity infrared filler is mixed with an inorganic phosphate binder and a surfactant, and a low-emissivity infrared coating is prepared by doctor blade coating. This coating exhibits excellent heat resistance and low infrared emissivity at high temperatures.

[0033] According to some preferred embodiments, the preparation method of the inorganic phosphate binder is as follows:

[0034] mixing phosphoric acid and aluminum hydroxide to obtain a first reactant; adding zinc oxide and magnesium oxide to the first reactant and mixing to obtain the inorganic phosphate adhesive;

[0035] Preferably, the molar ratio of phosphoric acid, aluminum hydroxide, zinc oxide and magnesium oxide is (2.5-3.5):1:0.2:0.05 (for example, it can be 2.5:1:0.2:0.05, 2.8:1:0.2:0.05, 3.1:1:0.2:0.05 or 3.5:1:0.2:0.05);

[0036] More preferably, the reaction temperature is 75-85°C (for example, 75°C, 78°C, 80°C, 82°C or 85°C), and the reaction time is 1-2h (for example, 1h, 1.5h or 2h).

[0037] In this embodiment, phosphoric acid, aluminum hydroxide, zinc oxide and magnesium oxide are used as raw materials, and the reaction conditions are controlled to prepare an inorganic phosphate adhesive, which is conducive to ensuring good adhesion and good high temperature resistance of the coating.

[0038] It should also be noted that in the process of preparing inorganic phosphate in this embodiment, when zinc oxide and magnesium oxide are added to the first reactant, 200 to 300 mL of water is first added to the first reactant for dilution, and after adding zinc oxide and magnesium oxide, water is added to the reaction system again to adjust the pH value of the mixed solution to between 2.0 and 4.0.

[0039] According to some preferred embodiments, the preparation method of the infrared low emissivity filler is as follows:

[0040] S1 mixes barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide and sinter them to obtain Ba x Sr 1-x Al2Si2O8 ceramic powder;

[0041] S2 will Ba x Sr 1-x The Al2Si2O8 ceramic powder is ball-milled to obtain the infrared low-emissivity material.

[0042] In this embodiment, in order to obtain a filler with low infrared emissivity at high temperature, a high temperature resistant Ba x Sr 1-x Al2Si2O8 ceramic powder, and prepare Ba by doping barium carbonate and strontium carbonate x Sr 1-x Al2Si2O8 ceramic powder, the doping of strontium elements can make the crystal structure of the ceramic powder undergo phase change, reduce the lattice constant, make the migration of carriers in the powder easier, and then increase the mobility of carriers in the ceramic powder, so that the conductivity of the filler is increased; in addition, the doping of Ba x Sr 1-xBall milling of Al2Si2O8 ceramic powder not only controls the powder's morphology and size, increasing the filler's infrared emissivity, but also causes the molecules and atoms within the ceramic powder to vibrate and rotate. This vibrational process resonates with infrared light, enhancing the powder's absorption in the infrared band. Therefore, the synergistic effects of conductivity and crystal vibration in the powder of this embodiment significantly reduce the filler's infrared emissivity in high-temperature environments.

[0043] According to some preferred embodiments, in step S1, the amount ratio of barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide is (0.2-0.3): (0.7-0.8): 1:2 (for example, it can be 0.2:0.8:1:2, 0.25:0.75:1:2 or 0.3:0.7:1:2).

[0044] Through experimental research of the present invention, it is found that if the strontium carbonate doped in barium carbonate, aluminum oxide and silicon dioxide is too low, the lattice in the powder will be distorted, thereby increasing the dipole moment and reducing the conductivity of the ceramic powder, thereby increasing the infrared emissivity of the ceramic powder material. When the doping amount of strontium carbonate is within the above range, the crystal structure in the ceramic powder will undergo a phase change, the lattice constant will decrease, and the crystal structure will be denser. In this way, when the carriers in the ceramic powder migrate, only less energy is required to cross the energy barrier of the grain boundary, thereby increasing the mobility of the carriers in the ceramic powder, thereby effectively reducing the infrared emissivity of the ceramic powder. Therefore, in this embodiment, the doping ratio of barium carbonate and strontium carbonate during the sintering process is controlled, which is beneficial to ensure that Ba x Sr 1-x On the basis of the good temperature resistance of Al2Si2O8 ceramic powder, it is further ensured that the ceramic powder has a higher electrical conductivity, which is conducive to reducing its infrared emissivity, so that the infrared low-emissivity filler has both good high-temperature resistance and low infrared emissivity, so that the coating obtained by using it as a filler and the inorganic phosphate prepared by the above method as a binder has a low infrared emissivity at high temperature.

[0045] It should be noted that, in this embodiment, before sintering, barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide are added to a nylon tank with polyacrylate ammonium dispersant and polyacrylamide for more uniform mixing of the powders, and the ball milling is performed at a rotation speed of 350 to 450 r / min, a time of 5 to 7 h, and a ball-to-material ratio of (4 to 5):1.

[0046] According to some preferred embodiments, the sintering temperature is 1400-1600°C (for example, 1400°C, 1450°C, 1500°C, 1550°C or 1600°C), and the sintering time is 2-4h (for example, 2h, 3h or 4h).

[0047] In this embodiment, the sintering temperature and time of the powder are controlled within the above-mentioned range, which is conducive to the formation of better crystallinity of the ceramic powder, and further conducive to ensuring better high-temperature resistance and lower infrared emissivity of the ceramic powder; if the sintering temperature is too low, it is not conducive to ensuring better crystallinity of the ceramic powder, and thus is not conducive to ensuring better comprehensive performance of the ceramic powder. Generally speaking, increasing the temperature is conducive to further increasing the crystallinity of the material in the ceramic powder, but the increase in temperature has little effect on the crystallinity of the material, which will cause a large waste of energy.

[0048] According to some preferred embodiments, in step S1, the temperature is increased in stages during the sintering process; wherein the heating rate of the first stage is 10 to 15°C / min (for example, it can be 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min or 15°C / min), and the heating rate of the second stage is 4 to 8°C / min (for example, it can be 4°C / min, 5°C / min, 6°C / min, 7°C / min or 84°C / min).

[0049] In this embodiment, the temperature is increased in stages during the sintering process, and the heating rate of each stage is controlled. This facilitates sufficient reaction between the powders during the sintering process, thereby ensuring good high-temperature resistance and low infrared emissivity of the ceramic powder. Specifically, during the sintering process in this embodiment, the temperature is first increased from room temperature to 200°C at a rate of 10-15°C / min. After reaching 200°C, the temperature is then increased to the sintering temperature at a rate of 4-8°C / min.

[0050] According to some preferred embodiments, in step S2, the ball milling speed is 350-450 r / min (for example, it can be 350 r / min, 380 r / min, 400 r / min, 420 r / min or 450 r / min), the time is 5-7 h (for example, it can be 5 h, 6 h or 7 h), and the ball-to-material ratio is (4-5):1 (for example, it can be 4:1, 4.5:1 or 5:1).

[0051] In this embodiment, the inventors, after extensive research, discovered that ball milling the sintered ceramic powder can improve the morphology and size of the ceramic powder while ensuring the high-temperature resistance of the ceramic powder and further reduce the infrared emissivity of the low-emissivity filler. By controlling the milling parameters during the ball milling process, the revolution of the milling jar can generate centripetal acceleration several times, or even dozens of times, the same as the acceleration of gravity. Under the strong centrifugal force, the grinding balls and powder tumble at high speed in the milling jar, and the mutual friction between them generates a strong shear force on the powder. The mechanical ball milling method changes the microscopic morphology of the powder from spherical to flaky, thereby reducing the specific surface area of ​​the powder particles and, in turn, the infrared emissivity of the filler. On the other hand, during the ball milling process of powder, the molecules and atoms in the crystal will produce lattice vibrations. The effect of lattice vibrations on the infrared emissivity of the powder can be regarded as the interaction or even strong coupling between photons and phonons. When photons and phonons have the same frequency and wave vector, they can resonate, interact and exchange energy, and their resonant frequency just includes the infrared window band of 3 to 5 μm. Therefore, the lattice vibration will produce resonant absorption of infrared light, thereby further reducing the infrared emissivity of the filler.

[0052] In this embodiment, the ceramic powder is ground from a spherical shape to a flake shape by controlling the ball milling parameters during the ball milling process, and the particle size of the flake powder is preferably 4 to 6 μm, which is conducive to ensuring the good high temperature resistance and low infrared emissivity of the infrared low emissivity filler.

[0053] According to some preferred embodiments, the surfactant is a silane coupling agent or sodium dodecylbenzenesulfonate.

[0054] In this embodiment, by mixing an inorganic phosphate binder and an infrared low-emissivity agent and adding a small amount of a surfactant, the prepared coating can be ensured to have good fluidity and solubility, which is conducive to ensuring that the final coating has a good surface morphology.

[0055] It should be noted that the surfactants in the embodiments of the present invention include but are not limited to the types mentioned above.

[0056] According to some preferred embodiments, the mass ratio of the inorganic phosphate binder, the infrared low emissivity filler and the surfactant is (45-55):(90-110):(0.045-0.05) (for example, it can be 45:90:0.045, 50:100:0.05 or 55:110:0.046).

[0057] In this embodiment, when preparing an infrared low-emissivity coating, the inorganic phosphate binder, infrared low-emissivity filler, and surfactant are preferably adjusted to the above-mentioned ranges, which helps ensure that the final coating has excellent adhesion, high-temperature resistance, and low infrared emissivity. For example, if the amount of inorganic phosphate binder added is too low, it is not conducive to ensuring good mechanical properties and temperature resistance of the final coating, making the coating prone to cracking during use. If the amount of inorganic phosphate binder added is too high, it is not conducive to ensuring low infrared emissivity of the coating. If the amount of infrared low-emissivity filler added is too low, it is not conducive to ensuring good temperature resistance and low infrared emissivity of the coating. If the amount of infrared emissivity filler added is too high, it is not conducive to ensuring good film-forming properties of the coating.

[0058] An embodiment of the present invention further provides a method for preparing any of the above-mentioned low-emissivity infrared coatings, the method comprising the following steps:

[0059] (1) preparing an inorganic phosphate binder and an infrared low emissivity filler respectively;

[0060] (2) stirring and mixing the inorganic phosphate binder, the infrared low emissivity filler and the surfactant in a certain proportion to obtain an infrared low emissivity coating;

[0061] (3) Scraping the infrared low emissivity coating onto the pre-treated target substrate and curing the coating to obtain the infrared low emissivity coating.

[0062] In this embodiment, by first preparing an inorganic phosphate adhesive and an infrared low-emissivity filler, the prepared inorganic phosphate adhesive has the advantages of strong adhesion, good high-temperature resistance, low price, low toxicity and pollution, and weak infrared absorption ability. The prepared infrared low-emissivity filler has both good high-temperature resistance and low infrared emissivity. By combining the inorganic phosphate adhesive and the infrared low-emissivity filler with each other and adding a large amount of surfactant, it is beneficial to prepare an infrared low-emissivity coating with good adhesion and fluidity, which is beneficial to scrape the coating onto the target substrate surface by scraping, and then obtain an infrared low-emissivity coating with good stability at high temperature, which can meet the requirements of the hot end components for infrared stealth performance under high temperature conditions.

[0063] It should be noted that when applying the infrared low-emissivity coating to the surface of the target substrate, the substrate is first pretreated. The pretreatment method is as follows: for example, the target substrate is a GH3030 high-temperature alloy plate (diameter 4.5 cm, thickness 1.2 mm). First, the substrate is polished with 400-mesh sandpaper. Then, the substrate is subjected to the following surface treatments in sequence: degreasing (immersion in a saturated ethanol solution of potassium hydroxide for 120 hours), water washing, natural air drying, sandpaper polishing, ultrasonic water washing, and oven drying. The above pretreatment operation is conducive to further ensuring good adhesion between the coating and the substrate. At the same time, it should be noted that the thickness of the coating after scraping is preferably 240 to 250 μm.

[0064] According to some preferred embodiments, in step (3), the curing is staged curing; wherein the temperature of the first stage curing is 20-30°C (for example, 20°C, 22°C, 25°C, 28°C or 30°C), and the time is 20-24h (for example, 20h, 21h, 22h, 23h or 24h); the temperature of the second stage curing is 450-550°C (for example, 450°C, 480°C, 500°C, 520°C or 550°C), and the time is 2-3h (for example, 2h, 2.5h or 3h).

[0065] After the paint is scraped on the surface of the substrate, the infrared low-emissivity filler is dispersed in the paint on the surface of the substrate. There are a large number of interfaces between the particles in the coating, which causes the infrared radiation to be repeatedly reflected on the interface, increasing the path of the infrared radiation to pass through the medium, and the infrared radiation is absorbed while passing through the medium. In this embodiment, in order to make the filler particles in the paint tightly connected together on the surface of the substrate, and at the same time make the particles in the paint tightly connected to form a dense coating, after the paint is scraped on the surface of the substrate, the coating is first placed at room temperature for 20 to 24 hours to dry naturally. After drying, the humidity of the coating is 55 to 57%, and then it is cured at a temperature of 450 to 500°C. During the high-temperature curing process, the powder particles in the coating are connected to each other to form a more uniform structure, reducing the area of ​​the grain boundary, and the structure is more complete. The smooth surface makes it easier to reduce the infrared emissivity of the coating surface.

[0066] In order to more clearly illustrate the technical solutions and advantages of the present invention, an infrared low-emissivity coating and a preparation method thereof are described in detail below through several embodiments.

[0067] Example 1:

[0068] (1) preparing an inorganic phosphate binder and an infrared low emissivity filler respectively;

[0069] Inorganic phosphate binder: 3.1 mol of phosphoric acid and 1 mol of aluminum hydroxide were mixed and reacted at 80°C for 1 hour to obtain a first reactant; 200 mL of deionized water was added to the first reactant, followed by 0.2 mol of zinc oxide and 0.05 mol of magnesium oxide, and stirred until fully dissolved; finally, deionized water was added to 1 L, such that the pH value of the mixture was between 2.0 and 4.0, to obtain an inorganic phosphate binder;

[0070] Infrared low emissivity filler:

[0071] S1: Barium carbonate, strontium carbonate, aluminum oxide, silicon dioxide, polyacrylate dispersant, and polyacrylamide were added to a nylon jar in a molar ratio of 0.25:0.75:1:2 and mixed and ball-milled at a speed of 450 r / min and a ball-to-material ratio of 5:1. After ball milling for 3 hours, the mixture was placed in a high-temperature sintering furnace at 1600°C for 3 hours and naturally cooled to room temperature of 25°C to obtain Ba 0.25 Sr 0.75 Al2Si2O8 ceramic powder; wherein, during the sintering process, the heating rate from room temperature (25°C) to 200°C is 15°C / min, and the heating rate from 200°C to 1600°C is 6°C / min;

[0072] S2: Will Ba 0.25 Sr 0.75 Al2Si2O8 ceramic powder was placed in a nylon jar and ball-milled at a speed of 400 r / min for 6 hours to obtain infrared low-emissivity filler; wherein, corundum balls were used as grinding balls, and the ball-to-material ratio was 5:1.

[0073] (2) mixing 50 g of the above-mentioned inorganic phosphate binder, 100 g of infrared low-emissivity filler, and 0.05 g of a surfactant (silane coupling agent), and stirring to obtain an infrared low-emissivity coating;

[0074] (3) The above-mentioned infrared low-emissivity coating was applied to the pretreated target substrate surface (GH3030 high-temperature alloy plate) by a scraping method. The coating thickness was 250 μm. It was first placed at room temperature (25°C) for curing for 24 hours, and then cured at 500°C for 2 hours to obtain an infrared low-emissivity coating.

[0075] Example 2:

[0076] (1) preparing an inorganic phosphate binder and an infrared low emissivity filler respectively;

[0077] Inorganic phosphate binder: 3.1 mol of phosphoric acid and 1 mol of aluminum hydroxide were mixed and reacted at 80°C for 1 hour to obtain a first reactant; 200 mL of deionized water was added to the first reactant, followed by 0.2 mol of zinc oxide and 0.05 mol of magnesium oxide, and stirred until fully dissolved; finally, deionized water was added to 1 L, such that the pH value of the mixture was between 2.0 and 4.0, to obtain an inorganic phosphate binder;

[0078] Infrared low emissivity filler:

[0079] S1: Barium carbonate, strontium carbonate, aluminum oxide, silicon dioxide, polyacrylate dispersant, and polyacrylamide were added to a nylon jar in a molar ratio of 0.2:0.8:1:2 and mixed and ball-milled at a speed of 450 r / min and a ball-to-material ratio of 5:1. After ball milling for 3 hours, the mixture was placed in a high-temperature sintering furnace at 1500°C for 3 hours and naturally cooled to room temperature of 25°C to obtain Ba 0.2 Sr 0.8 Al2Si2O8 ceramic powder; wherein, during the sintering process, the heating rate from room temperature (25°C) to 200°C is 13°C / min, and the heating rate from 200°C to 1500°C is 5°C / min;

[0080] S2: Will Ba 0.2 Sr 0.8 Al2Si2O8 ceramic powder was placed in a nylon jar and ball-milled at a speed of 450 r / min for 5 hours to obtain infrared low-emissivity material; wherein, corundum balls were used as grinding balls, and the ball-to-material ratio was 5:1.

[0081] (2) 55 g of the above-mentioned inorganic phosphate binder, 110 g of infrared low-emissivity filler and 0.45 g of surfactant (sodium dodecylbenzenesulfonate) were mixed and stirred to obtain an infrared low-emissivity coating;

[0082] (3) The above-mentioned infrared low-emissivity coating was applied to the pretreated target substrate surface (GH3030 high-temperature alloy plate) by a scraping method. The coating thickness was 250 μm. It was first placed at room temperature (25°C) for curing for 24 hours, and then cured at 500°C for 2 hours to obtain an infrared low-emissivity coating.

[0083] Example 3:

[0084] Example 3 is basically the same as Example 1, except that: in step (1), when preparing the infrared low-emissivity filler, in step S1, the molar ratio of barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide is 0.1:0.9:1:2.

[0085] Example 4:

[0086] Example 4 is basically the same as Example 1, except that: in step (1), when preparing the infrared low-emissivity filler, in step S1, the molar ratio of barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide is 0.5:0.5:1:2.

[0087] Example 5:

[0088] Example 5 is substantially the same as Example 1, except that in step (2), the contents of the inorganic phosphate binder and the infrared low-emissivity filler are 60 g and 100 g, respectively.

[0089] Example 6:

[0090] Example 6 is substantially the same as Example 1, except that in step (2), the contents of the inorganic phosphate binder and the infrared low-emissivity filler are 50 g and 120 g, respectively.

[0091] Comparative Example 1:

[0092] Comparative Example 1 is basically the same as Example 1, except that, in step (1), when preparing the infrared low-emissivity filler, barium carbonate, aluminum oxide and silicon dioxide, polyacrylate ammonium dispersant and polyacrylamide in a molar ratio of 1:1:2 are added to a nylon jar and mixed and ball-milled at a speed of 400 r / min, and the ball-to-material ratio is set to 5:1. After ball milling for 3 hours, it is placed in a high-temperature sintering furnace and sintered at 1600°C for 3 hours. After naturally cooling to room temperature of 25°C, BaAl2Si2O8 ceramic powder is obtained; wherein, during the sintering process, the heating rate from room temperature (25°C) to 200°C is 13°C / min, and the heating rate from 200°C to 1600°C is 5°C / min.

[0093] Comparative Example 2:

[0094] Comparative Example 2 is substantially the same as Example 1, except that, in step (1), when preparing the infrared low emissivity filler, step S2 is not included, i.e., Ba 0.25 Sr 0.75 The Al2Si2O8 ceramic powder is not subjected to ball milling treatment.

[0095] Comparative Example 3:

[0096] Comparative Example 3 is substantially the same as Example 1, except that in step (1), the inorganic phosphate adhesive is replaced with an organosilicon adhesive of the same mass.

[0097] Comparative Example 4:

[0098] Comparative Example 4 is basically the same as Example 1, except that, in step (3), the above-mentioned infrared low-emissivity coating is applied to the pretreated target substrate surface (GH3030 high-temperature alloy plate) by a scraping method, and then directly placed at room temperature (25°C) for curing for 24 hours without high-temperature curing to obtain an infrared low-emissivity coating.

[0099] The coatings prepared in the examples and comparative examples were subjected to emissivity tests, and the test results are shown in Table 1. The testing method is as follows: the infrared emissivity of the coatings in the above examples and comparative examples is measured using an IR-2 dual-band infrared emissivity meter and a BC-1 precision temperature controller. First, the IR-2 dual-band infrared emissivity meter is turned on, and the temperature of the black body is set to 430°C. After the black body is heated to 430°C and stabilized for half an hour, 3-5 μm and 8-14 μm band filters are installed on the lens, respectively. After calibrating the instrument, the average emissivity at room temperature (25°C) is first measured. Then, the BC-1 precision temperature controller is turned on, and the target temperatures of the temperature controller are set to room temperature, 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C and 800°C, respectively. After the temperature of the temperature controller and the sample are stable, the corresponding infrared emissivities are recorded.

[0100] Table 1

[0101]

[0102] As can be seen from Table 1, the coating prepared in Example 1 of the present invention has both good high temperature resistance and low infrared emissivity. Specifically, the infrared emissivity in the 3-5 μm and 8-14 μm bands meets the low infrared emissivity (<0.35) in an environment of 25-800 ° C.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An infrared low emissivity coating, characterized in that: The coating is prepared by using raw materials including an inorganic phosphate binder, an infrared low-emissivity filler, and a surfactant. The infrared low-emissivity filler is prepared by sequentially sintering and ball-milling barium carbonate, strontium carbonate, aluminum oxide, and silicon dioxide. The molar ratio of barium carbonate, strontium carbonate, aluminum oxide, and silicon dioxide is (0.2-0.3):(0.7-0.8):1:

2. The preparation method of the inorganic phosphate adhesive is as follows: phosphoric acid and aluminum hydroxide are mixed for reaction to obtain a first reactant; zinc oxide and magnesium oxide are added to the first reactant, and the mixture is mixed to obtain the inorganic phosphate adhesive.

2. The coating according to claim 1, characterized in that The molar ratio of phosphoric acid, aluminum hydroxide, zinc oxide and magnesium oxide is (2.5~3.5):1:0.2:0.

05.

3. The coating according to claim 1, characterized in that The reaction temperature is 75-85° C. and the reaction time is 1-2 hours.

4. The coating according to claim 1, characterized in that The preparation method of the infrared low emissivity filler is as follows: S1 mixes barium carbonate, strontium carbonate, aluminum oxide and silicon dioxide and sinter them to obtain Ba x Sr 1-x Al2Si2O8 ceramic powder; S2 will Ba x Sr 1-x The Al2Si2O8 ceramic powder is ball-milled to obtain the infrared low-emissivity material.

5. The coating according to claim 4, characterized in that In step S1, the sintering temperature is 1400-1600° C. and the sintering time is 2-4 hours.

6. The coating according to claim 4, characterized in that In step S1, the temperature is increased in stages during the sintering process; wherein the heating rate of the first stage is 10-15°C / min, and the heating rate of the second stage is 4-8°C / min.

7. The coating according to claim 4, characterized in that In step S2, the ball milling speed is 350-450 r / min, the time is 5-7 h, and the ball-to-material ratio is (4-5):

1.

8. The coating according to claim 1, characterized in that The surfactant is sodium dodecylbenzenesulfonate.

9. The coating according to claim 1, characterized in that The mass ratio of the inorganic phosphate binder, the infrared low emissivity filler and the surfactant is (45~55):(90~110):(0.045~0.05).

10. A method for preparing an infrared low emissivity coating according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) Preparing inorganic phosphate binder and infrared low emissivity filler respectively; (2) stirring and mixing the inorganic phosphate binder, the infrared low emissivity filler and the surfactant in a certain proportion to obtain an infrared low emissivity coating; (3) Scraping the infrared low emissivity coating onto the pre-treated target substrate, and curing to obtain the infrared low emissivity coating.

11. The preparation method according to claim 10, characterized in that: In step (3), the curing is carried out in stages; wherein the temperature of the first stage curing is 20-30°C and the time is 20-24 hours; the temperature of the second stage curing is 450-550°C and the time is 2-3 hours.

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