A high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating and its preparation method

Abstract

This invention provides a high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coating and its preparation method, comprising the following components in parts by weight: rare earth compound hollow spheres: 40-50 parts; nano-rod-shaped rare earth phosphate: 15-20 parts; inorganic binder: 30-40 parts; dispersant: 0.1-1 parts; water: 15-20 parts. The rare earth compound hollow spheres used in this invention achieve a synergistic effect of high reflectivity and low thermal conductivity. Combined with the network reinforcement structure of nano-rod-shaped rare earth phosphate and the ceramicized composite binder system, the coating obtained by applying the coating exhibits an infrared reflectivity ≥0.85 in the 1-5μm band, an adhesion strength ≥8.0MPa, a thermal conductivity ≤0.15W / (m·K) (800℃), thermal shock resistance ≥50 cycles, and high-temperature durability (1600℃) ≥100h. When applied to refractory bricks, it can reduce the cold surface temperature by at least 150℃.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature functional coatings technology, and in particular relates to a high-temperature resistant, low thermal conductivity, and high reflectivity heat-insulating coating and its preparation method. Background Technology

[0002] Industrial kilns are high-energy-consuming equipment in industries such as metallurgy, building materials, and chemicals. Their furnace walls are usually constructed with refractory bricks to withstand high-temperature environments. However, during long-term service at temperatures above 1000℃, a large amount of heat energy is lost through the refractory materials of the furnace walls in the form of heat conduction and heat radiation.

[0003] Traditionally, a composite structure of working layer-insulation layer-protective layer is formed by increasing the thickness of the furnace wall and setting a heat insulation layer on the outside of the working layer. The working layer uses fiber furnace lining and is coated with heat insulation paint to reduce heat loss and energy consumption. However, increasing the thickness of the furnace wall leads to a significant increase in the cost of materials, construction, and space occupied. The composite structure is the current mainstream solution, but because the insulation material cannot withstand excessively high temperatures, its application is limited by the temperature on the back of the working layer. If the working layer is too thin or damaged, the insulation layer will fail quickly. The fiber furnace lining in the working layer has a significant energy-saving effect, but its mechanical strength and erosion resistance are poor, and it is prone to crystallization and powdering due to chemical corrosion. Existing insulation coatings generally use materials with low thermal conductivity such as hollow glass microspheres, hollow ceramic microspheres, aerogel, and aluminum silicate fiber, which are difficult to guarantee the coating's resistance to thermal shock, corrosion, and high-temperature aging. Summary of the Invention

[0004] In view of this, the present invention aims to overcome the defects in the prior art and proposes a high-temperature resistant, low thermal conductivity, and high reflectivity heat-insulating coating and its preparation method.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows: In a first aspect, the present invention provides a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating, comprising the following components in parts by weight: Hollow spheres of rare earth compounds: 40-50 parts; Nanorod-shaped rare earth phosphate: 15-20 parts; Inorganic binder: 30-40 parts; Dispersant: 0.1-1 part; Water: 15-20 parts.

[0006] Preferably, the rare earth compound hollow spheres possess low thermal conductivity and high reflectivity, specifically being CeO2 hollow spheres, La2Ce2O7 hollow spheres, La2Zr2O7 hollow spheres, Y2Zr2O7 hollow spheres, Gd2Zr2O7 hollow spheres, LaAlO3 hollow spheres, and LaAl... 11 O 18One or more of hollow spheres, or a mixture thereof.

[0007] Preferably, the hollow spheres of the rare earth compound have a particle size of 10-50 μm and a wall thickness of 1-3 μm.

[0008] Preferably, the method for preparing the hollow spheres of the rare earth compound includes the following steps: a. After mixing deionized water and dispersant evenly, add rare earth compound powder while stirring, continue stirring for 0.5-1 hour, and then grind to the particle size D of the slurry. 90 Reaching 80-120nm; In some embodiments of the present invention, the sand milling is carried out in a sand mill, using zirconia beads as the grinding media, and the sand milling is performed for 20-24 hours.

[0009] b. Add a polymer to the slurry after sand milling, and continue sand milling for 10-15 minutes to obtain a nano slurry; c. Spray-dry the nano-slurry to obtain precursor microspheres with a hollow structure; d. Heat the precursor microspheres to 400-600℃ and hold for 1-2 hours to slowly remove organic matter such as binders and dispersants, avoiding sphere breakage or excessive cracks caused by rapid gas escape; then heat to 1000-1200℃ and hold for 2-4 hours to finally obtain rare earth compound hollow spheres.

[0010] Preferably, the rare earth compound powder is CeO2, La2Ce2O7, La2Zr2O7, Y2Zr2O7, Gd2Zr2O7, LaAlO3, or LaAl. 11 O 18 One or more of the powders.

[0011] Preferably, the polymer is polyvinyl alcohol (PVA) and / or polyethylene glycol (PEG).

[0012] Preferably, the mass ratio of the deionized water, dispersant, rare earth compound powder, and polymer is 1000:(15-20):(300-400):(10-15).

[0013] Preferably, the stirring rate in step a is 400-600 r / min.

[0014] Preferably, in step c, the spray drying is carried out in a spray dryer with an inlet temperature of 220-250°C, an outlet temperature of 100-120°C, and a feed rate of 10-20 mL / min.

[0015] Preferably, the heating rate for heating to 400 - 600 °C in step d is 0.5 - 1 °C / min, and the heating rate for heating to 1000 - 1200 °C is 3 - 5 °C / min.

[0016] Preferably, the material of the nanorod-shaped rare earth phosphate is lanthanum phosphate (LaPO4), yttrium phosphate (YPO4), cerium phosphate (CePO4), or lanthanum cerium phosphate (La 1-x Ce x PO4 (0 < x < 1)). The nanorod-shaped rare earth phosphate is a one-dimensional nanorod-shaped crystal.

[0017] Preferably, the diameter of the nanorod-shaped rare earth phosphate is 2 - 10 nm, and the length is 100 - 400 nm.

[0018] Preferably, the preparation method of the nanorod-shaped rare earth phosphate is as follows: S1. Dissolve rare earth carbonate in deionized water to obtain a rare earth carbonate solution; S2. Under the conditions of a temperature of 50 - 80 °C and stirring, dropwise add phosphoric acid solution to the rare earth carbonate solution. After the dropping is completed, react for 1 - 2 h; S3. Filter and wash the reaction product of step S2, and dry it at a temperature of 50 - 80 °C for 4.5 - 5.5 h to obtain the nanorod-shaped rare earth phosphate.

[0019] Preferably, the rare earth carbonate is one or a mixture of lanthanum carbonate, cerium carbonate, and yttrium carbonate.

[0020] Preferably, the concentration of the rare earth carbonate solution in step S1 is 60 - 90 g / L.

[0021] Preferably, the mass fraction of the phosphoric acid solution in step S2 is 35% - 45%.

[0022] Preferably, the mass ratio of the rare earth carbonate solution in step S1 to the phosphoric acid solution in step S2 is (1500 - 2000) : (50 - 80).

[0023] Preferably, the stirring rate in step S2 is 1300 - 1500 r / min.

[0024] Preferably, the inorganic binder is a mixed binder of aluminum dihydrogen phosphate solution and zirconium sol with a mass ratio of (4 - 7) : (6 - 3), wherein the solid content of the aluminum dihydrogen phosphate solution is 25 - 40%, and the solid content of the zirconium sol is 25 - 35%.

[0025] ]>Preferably, the dispersant is one or a mixture of polyacrylate, polycarboxylate, sodium hexametaphosphate, and sodium tripolyphosphate.

[0026] Secondly, the present invention provides a method for preparing the above-mentioned high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating, the method comprising the following steps: Step 1: Mix water and dispersant thoroughly to obtain a dispersant solution; Step 2: Add nanorod-shaped rare earth phosphate powder to the dispersant solution while stirring and continue stirring until a suspension is formed; Step 3: Add rare earth compound hollow spheres to the suspension and continue stirring to disperse all powder particles to obtain a slurry; Step 4: Add the inorganic binder to the slurry obtained in step 3 while stirring, and continue stirring. Step 5: Transfer the slurry obtained in Step 4 to a sealed container and let it stand for 8-12 hours to obtain a high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coating.

[0027] Preferably, the stirring speed in step 1 is 300-500 r / min, and the stirring time is 10-15 min.

[0028] Preferably, the stirring speed in step 2 is 800-1200 r / min, and the stirring time is 40-60 min.

[0029] Preferably, the stirring speed in step 3 is 400-600 r / min, and the stirring time is 30-45 min.

[0030] Preferably, the stirring speed in step 4 is 400-600 r / min, and the stirring time is 30-45 min.

[0031] The hollow rare-earth compound spheres (rare-earth oxides or composite oxides) selected in this invention exhibit low thermal conductivity and high reflectivity. They show weak absorption and strong scattering of photons in the 1-5 μm infrared band, resulting in high intrinsic infrared reflectivity. Furthermore, these materials possess fluorite or pyrochlore-type structures, with significant differences in atomic weights and complex electronic configurations within their crystal lattices. This reduces the mean free path of phonons, thereby lowering lattice thermal conductivity. Additionally, the hollow rare-earth compound spheres have a wall thickness of only 1-3 μm and an internal closed air cavity, blocking continuous heat conduction paths and significantly reducing the proportion of solid-phase thermal conductivity in the coating. The closed structure also reduces convective heat transfer at high temperatures, minimizing convective heat loss. During preparation, the hollow spheres are sintered at 1000-1200℃ to form a dense shell, possessing excellent mechanical strength and high-temperature stability. They do not soften or collapse at high temperatures, maintaining the integrity of the hollow structure and ensuring the coating's thermal insulation and reflective performance during long-term high-temperature service.

[0032] In this invention, nanorod-shaped rare earth phosphates interweave and overlap within the coating, forming a continuous three-dimensional network structure inside the macroscopic framework composed of micron-sized hollow spheres. When the coating is subjected to thermal or mechanical stress, the nanorods prevent microcracks from propagating into macroscopic cracks by bridging cracks and deflecting them, thereby improving the coating's toughness, adhesion strength, and thermal shock resistance. Furthermore, while the nanorods fill some of the voids between the micron-sized hollow spheres, this filling is not dense; the network they form itself introduces a large number of nanoscale pores, further reducing the coating's thermal conductivity by refining the pores within the coating.

[0033] Compared with the prior art, the present invention has the following advantages: (1) The rare earth compound hollow spheres used in this invention are composed of cerium oxide, lanthanum cerate, rare earth aluminate, or rare earth zirconate. They have intrinsically low emissivity (≤0.15) and high reflectivity (≥0.85) in the 1~5μm band, thereby reducing the absorption of thermal radiation inside the kiln. At the same time, these rare earth compounds have fluorite, pyrochlore, or perovskite structures. Due to strong phonon scattering caused by oxygen vacancies or lattice distortion, they have a low thermal conductivity of 0.8~3.0W / (m·K). After being granulated into hollow spheres, a closed pore cavity is formed inside, further reducing the thermal conductivity to 0.05~0.15W / (m·K), blocking heat conduction through the coating. The synergistic mechanism of high reflectivity and low thermal conductivity can reduce the heat absorption and heat conduction loss of the kiln wall, reduce the energy consumption of kiln operation, and at the same time reduce high-temperature thermal stress damage to the furnace body, extending the service life of the furnace body. (2) The coating system of the present invention adopts an all-inorganic component design. The one-dimensional crystal structure of nanorod-shaped rare earth phosphates cross-over in the coating to form a network structure. On the one hand, it increases the phonon scattering interface and further reduces the thermal conductivity of the coating; on the other hand, the inorganic binder fills the gaps in the network, enhancing the mechanical strength and erosion resistance of the coating. (3) The mixed binder system of aluminum dihydrogen phosphate and zirconium sol in this invention forms initial bonding through polycondensation reaction at medium and low temperatures, and further ceramicizes at high temperatures (>1000℃) to generate a high-temperature resistant phosphate and alumina zirconate network, which forms a strong chemical bond and mechanical interlock with the surface of the refractory brick matrix, giving the coating excellent thermal shock resistance and high-temperature durability. (4) The coating of the present invention is applied to the surface of refractory bricks, so that the coating has an infrared reflectivity ≥0.85 in the 1-5μm band, an adhesion strength ≥8.0MPa, a thermal conductivity ≤0.15W / (m·K) (800℃), a thermal shock resistance ≥50 times, and a high temperature durability (1600℃) ≥100h. When applied to refractory bricks, it can reduce the cold surface temperature by at least 150℃. Attached Figure Description

[0034] Figure 1This is a SEM image of the hollow cerium oxide spheres in Example 1 of the present invention; Figure 2 This is a TEM image of the nanorod-shaped LaPO4 in Example 1 of the present invention; Figure 3 Photograph of a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating applied to the surface of refractory bricks. Detailed Implementation

[0035] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] In this document, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​falling within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0038] In this article, the terms "multiple" or "more than" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0039] In this document, the terms "preferred" and "more preferred" are used only to describe implementation methods or embodiments with better effects, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0040] In this document, terms such as "further" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0041] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0042] In this document, the term "about" means a specified value of + / - 10%, preferably + / - 5%, and more preferably + / - 1%.

[0043] In this article, the terms “include,” “including,” “have,” “contain,” etc., are all open-ended terms, meaning that they include but are not limited to.

[0044] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0045] The present invention will be described in detail below with reference to the embodiments.

[0046] Example 1: (1) Preparation of cerium oxide hollow spheres: 1000g of deionized water and 15g of BYK-154 dispersant were mixed and stirred evenly at a rate of 500r / min. 350g of cerium oxide (CeO2) powder was added, and stirring was continued for 0.5h to obtain cerium oxide slurry. Zirconia beads were used as grinding media and the slurry was sand-milled in a sand mill for 22h until the particle size D of the slurry was achieved. 90 Upon reaching a particle size of 100 nm, 10 g of polyvinyl alcohol (PVA) was added, and milling continued for 10 min to obtain cerium oxide nanoparticle slurry. The cerium oxide nanoparticle slurry was then spray-dried to obtain cerium oxide precursor microspheres with a hollow structure. The spray dryer had an inlet temperature of 230℃, an outlet temperature of 110℃, and a feed rate of 15 mL / min. The cerium oxide precursor microspheres were heated to 500℃ at a rate of 1℃ / min and held for 1.5 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1000℃ at a rate of 3℃ / min and held for 2 h to allow the hollow spheres to fully crystallize and densify, forming a robust shell, resulting in hollow cerium oxide spheres (particle size 10 μm, wall thickness 1 μm). Their SEM images are shown below. Figure 1 As shown.

[0047] (2) Preparation of nanorod-shaped LaPO4: Lanthanum carbonate was dissolved in deionized water to obtain 1600g of a 65g / L lanthanum carbonate solution. The solution was heated to 50℃ while stirring at a stirring rate of 1300r / min. Stirring was continued, and 55g of a 35% phosphoric acid solution was added dropwise. After the addition was complete, the reaction was continued for 1h. The reaction product was filtered and washed, and dried at 80℃ for 4.5h to obtain nanorod-shaped LaPO4 (diameter 2nm, length 150nm). Its TEM image is shown below. Figure 2 As shown.

[0048] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials by weight as follows: 40g of cerium oxide (CeO2) hollow spheres (particle size 10μm, wall thickness 1μm), 15g of nanorod-shaped LaPO4 (diameter 2nm, length 150nm), 30g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 25%, zirconium sol solid content 25%, weight ratio 4:6), 0.1g of BYK-154 dispersant, and 15g of water.

[0049] Preparation steps: 1) Place water and dispersant in a high-speed mixer and stir at 300 rpm for 10 minutes until homogeneous; 2) Add nanorod-shaped LaPO4 under stirring, increase the rotation speed to 800 r / min, and disperse at high speed for 40 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 400 r / min, add cerium oxide hollow spheres, and stir for 30 min until the particles are fully wetted and dispersed; 4) While stirring at 400 r / min, add the aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 25%, zirconium sol solid content 25%, weight ratio 4:6), and continue stirring for 30 min; 5) Transfer to a sealed container and let stand for 8 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0050] Example 2: (1) Preparation of hollow lanthanum cerate spheres: 1000g of deionized water and 18g of BYK-154 dispersant were mixed and stirred at 400r / min until homogeneous. 300g of lanthanum cerate (La₂Ce₂O₇) powder was added, and stirring was continued for 0.5h to obtain a lanthanum cerate slurry. Zirconia beads were used as the grinding media, and the slurry was milled in a sand mill for 20h until the particle size D of the slurry was achieved. 90 Upon reaching a particle size of 90 nm, 15 g of polyvinyl alcohol (PVA) was added, and milling continued for 12 min to obtain lanthanum cerate nanoparticle slurry. The lanthanum cerate nanoparticle slurry was then spray-dried to obtain lanthanum cerate precursor microspheres with a hollow structure. The spray dryer had an inlet temperature of 220℃, an outlet temperature of 100℃, and a feed rate of 10 mL / min. The lanthanum cerate precursor microspheres were heated to 500℃ at a rate of 1℃ / min and held for 1.5 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1000℃ at a rate of 3℃ / min and held for 3 h to obtain hollow lanthanum cerate spheres (particle size 20 μm, wall thickness 2 μm).

[0051] (2) Preparation of nanorod-shaped CePO4: Cerium carbonate was dissolved in deionized water to obtain 1500g of a 60g / L cerium carbonate solution. The solution was heated to 65℃ while stirring at a stirring rate of 1400r / min. Stirring was continued, and 50g of a 35% phosphoric acid solution was added dropwise. After the addition was complete, the reaction was continued for 2h. The reaction product was filtered, washed, and dried at 50℃ for 5.5h to obtain nanorod-shaped CePO4 (4nm in diameter and 200nm in length).

[0052] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials by weight as follows: 42 g of hollow lanthanum cerate (La2Ce2O7) spheres (particle size 20μm, wall thickness 2μm), 16 g of nanorod-shaped CePO4 (diameter 4nm, length 200nm), 32 g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 30%, zirconium sol solid content 28%, weight ratio 5:5), 0.3 g of SN-DISPERSANT 5029 dispersant, and 16 g of water.

[0053] Preparation method: 1) Place water and dispersant in a high-speed mixer and stir at 350 rpm for 12 minutes until homogeneous; 2) Add nanorod-shaped CePO4 under stirring, increase the rotation speed to 900 r / min, and disperse at high speed for 45 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 450 r / min, add lanthanum cerate hollow spheres, and stir for 35 min until the particles are fully wetted and dispersed; 4) While stirring at 450 r / min, add the aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 30%, zirconium sol solid content 28%, weight ratio 5:5), and continue stirring for 35 min; 5) Transfer to a sealed container and let stand for 9 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0054] Example 3: (1) Preparation of hollow lanthanum aluminate spheres: 1000g of deionized water and 20g of BYK-154 dispersant were mixed and stirred at 600r / min until homogeneous. 400 parts of lanthanum aluminate (LaAlO3) powder were added, and stirring was continued for 1 hour to obtain a lanthanum aluminate slurry. Zirconia beads were used as the grinding media, and the slurry was milled in a sand mill for 20 hours until the particle size D of the slurry was achieved. 90 Upon reaching a particle size of 120 nm, 10 parts of polyvinyl alcohol (PVA) were added, and milling continued for 15 min to obtain lanthanum aluminate nano-slurry. The lanthanum aluminate nano-slurry was then spray-dried to obtain lanthanum aluminate precursor microspheres with a hollow structure. The spray dryer had an inlet temperature of 250℃, an outlet temperature of 120℃, and a feed rate of 20 mL / min. The lanthanum aluminate precursor microspheres were heated to 400℃ at a rate of 0.5℃ / min and held for 2 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1100℃ at a rate of 4℃ / min and held for 2.5 h to obtain hollow lanthanum aluminate spheres (particle size 30 μm, wall thickness 3 μm).

[0055] (2) Preparation of nanorod-shaped La 0.5 Ce 0.5 PO4: Lanthanum carbonate and cerium carbonate in the same molar ratio were dissolved in deionized water to obtain 2000g of a 60g / L lanthanum carbonate and cerium carbonate solution. The solution was heated to 70℃ with stirring at a stirring rate of 1500r / min. While stirring continued, 70g of a 40% phosphoric acid solution was added dropwise. After the addition was complete, the reaction was continued for 1.5h. The reaction product was filtered, washed, and dried at 80℃ for 4.5h to obtain nanorod-shaped La. 0.5 Ce 0.5 PO4 (diameter 2nm, length 100nm).

[0056] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials according to the following proportions by weight: 45g of hollow lanthanum aluminate (LaAlO3) spheres (30μm in diameter, 3μm in wall thickness), and nanorod-shaped La... 0.5 Ce 0.5 18g of PO4 (diameter 2nm, length 100nm), 35g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 35%, zirconium sol solid content 30%, weight ratio 6:4), 0.5g of sodium hexametaphosphate dispersant, and 18g of water.

[0057] Preparation steps: 1) Place water and dispersant in a high-speed mixer and stir at 400 rpm for 13 minutes until homogeneous; 2) Add nanorod-shaped La while stirring. 0.5 Ce 0.5 PO4, increase the rotation speed to 1000 r / min, and disperse at high speed for 50 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 500 r / min, add lanthanum aluminate hollow spheres, and stir for 40 min until the particles are fully wetted and dispersed; 4) Stir at 500 r / min, add aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 35%, zirconium sol solid content 30%, weight ratio 6:4), and stir for 40 min. 5) Transfer to a sealed container and let stand for 10 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0058] Example 4: (1) Preparation of lanthanum zirconate hollow spheres: 1000g of deionized water and 16g of BYK-154 dispersant were mixed and stirred evenly at a rate of 450r / min. 360g of lanthanum zirconate (La2Zr2O7) powder was added, and stirring was continued for 0.5h to obtain lanthanum zirconate slurry. Zirconia beads were used as the grinding medium and the slurry was milled in a sand mill for 24h until the particle size D of the slurry was achieved. 90Upon reaching a particle size of 80 nm, 10 g of polyethylene glycol (PEG) was added, and milling continued for 15 min to obtain lanthanum zirconate nano-slurry. The lanthanum zirconate nano-slurry was then spray-dried to obtain lanthanum zirconate precursor microspheres with a hollow structure. The spray dryer had an inlet temperature of 240 °C, an outlet temperature of 110 °C, and a feed rate of 18 mL / min. The lanthanum zirconate precursor microspheres were heated to 550 °C at a rate of 0.5 °C / min and held for 4 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1200 °C at a rate of 5 °C / min and held for 2 h to obtain hollow lanthanum zirconate spheres (particle size 45 μm, wall thickness 4.5 μm).

[0059] (2) Preparation of nanorod-shaped La 0.5 Ce 0.5 PO4: Lanthanum carbonate and cerium carbonate in equal molar ratios were dissolved in deionized water to obtain 2000g of a 90g / L lanthanum carbonate and cerium carbonate solution. The solution was heated to 80℃ with stirring at a stirring rate of 1300r / min. While stirring continued, 80g of a 45% phosphoric acid solution was added dropwise. After the addition was complete, the reaction was continued for 2 hours. The reaction product was filtered, washed, and dried at 80℃ for 4.5 hours to obtain nanorod-shaped La. 0.5 Ce 0.5 PO4 (diameter 2.5nm, length 350nm).

[0060] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials according to the following proportions by weight: 48g of hollow lanthanum zirconate (La₂Zr₂O₇) spheres (particle size 45μm, wall thickness 2.5μm), and nanorod-shaped La₂Zr₂O₇. 0.5 Ce 0.5 19g of PO4 (diameter 2.5nm, length 350nm), 38g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 40%, zirconium sol solid content 32%, weight ratio 7:3), 0.8g of sodium tripolyphosphate dispersant, and 19g of water.

[0061] Preparation steps: 1) Place water and dispersant in a high-speed mixer and stir at 450 rpm for 14 minutes until homogeneous; 2) Add nanorod-shaped La while stirring. 0.5 Ce 0.5 PO4, increase the rotation speed to 1100 r / min, and disperse at high speed for 55 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 550 r / min, add lanthanum zirconate hollow spheres, and stir for 42 min until the particles are fully wetted and dispersed; 4) While stirring at 550 r / min, add the aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 40%, zirconium sol solid content 32%, weight ratio 7:3), and continue stirring for 42 min; 5) Transfer to a sealed container and let stand for 11 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0062] Example 5: (1) Preparation of hollow spheres containing cerium oxide and lanthanum cerate: 1000g of deionized water and 18g of BYK-154 dispersant were mixed and stirred evenly at a rate of 600r / min. 200g of cerium oxide (CeO2) powder and 200g of lanthanum cerate (La2Ce2O7) powder were added, and stirring was continued for 0.5h to obtain a slurry containing cerium oxide and lanthanum cerate. Zirconia beads were used as the grinding medium and the slurry was milled in a sand mill for 23h until the particle size D of the slurry was achieved. 90 Upon reaching a particle size of 90 nm, 13 g of polyethylene glycol (PEG) was added, and milling continued for 10 min to obtain a mixed nano-slurry of cerium oxide and lanthanum cerate. The mixed nano-slurry of cerium oxide and lanthanum cerate was then spray-dried to obtain hollow cerium oxide and lanthanum cerate mixed precursor microspheres. The spray dryer had an inlet temperature of 235 °C, an outlet temperature of 115 °C, and a feed rate of 12 mL / min. The cerium oxide and lanthanum cerate mixed precursor microspheres were heated to 500 °C at a rate of 1 °C / min and held for 1.5 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1050 °C at a rate of 3 °C / min and held for 3.5 h to obtain a mixture of hollow cerium oxide and hollow lanthanum cerate spheres (particle size 30 μm, wall thickness 3.5 μm).

[0063] (2) Preparation of nanorod-shaped YPO4: Yttrium carbonate was dissolved in deionized water to obtain 1800g of 75g / L yttrium carbonate solution. The solution was heated to 75℃ while stirring at a stirring rate of 1350r / min. Stirring was continued, and 80g of 38% phosphoric acid solution was added dropwise. After the addition was completed, the reaction was continued for 2h. The reaction product was filtered and washed, and dried at 70℃ for 5.5h to obtain nanorod-shaped YPO4 (diameter 8nm, length 400nm).

[0064] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials by weight as follows: 50g of a mixture of cerium oxide (CeO2) hollow spheres and lanthanum cerate (La2Ce2O7) hollow spheres (weight ratio 1:1, particle size 30μm, wall thickness 3.5μm), 20g of nanorod-shaped YPO4 (diameter 8nm, length 400nm), 40g of a binder mixture of aluminum dihydrogen phosphate solution and zirconium sol (aluminum dihydrogen phosphate solution solid content 35%, zirconium sol solid content 35%, weight ratio 5:5), 1g of polyacrylate dispersant, and 20g of water.

[0065] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Preparation method: 1) Place water and dispersant in a high-speed mixer and stir at 500 rpm for 15 minutes until homogeneous; 2) Add nanorod-shaped YPO4 under stirring, increase the rotation speed to 1200 r / min, and disperse at high speed for 60 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 600 r / min, add the hollow spheres of cerium oxide and lanthanum cerate, and stir for 45 min until the particles are fully wetted and dispersed; 4) While stirring at 600 r / min, add the aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 35%, zirconium sol solid content 35%, weight ratio 5:5), and continue stirring for 45 min; 5) Transfer to a sealed container and let stand for 12 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0066] Example 6: (1) Preparation of hollow spheres containing gadolinium zirconate and lanthanum hexaaluminate: 1000g of deionized water and 18g of BYK-154 dispersant were mixed and stirred evenly at a rate of 550r / min. 200g of gadolinium zirconate (Gd2Zr2O7) powder and 100g of lanthanum hexaaluminate (LaAl) were then added. 11 O 18 The powder was stirred for another 0.5 hours to obtain a mixed slurry of gadolinium zirconate and lanthanum hexaaluminate. Zirconia beads were used as the grinding media, and the slurry was milled in a sand mill for 21 hours until the particle size D of the slurry was achieved. 90 Upon reaching a particle size of 110 nm, 12 g of polyethylene glycol (PEG) was added, and milling continued for 12 min to obtain a mixed nano-slurry of gadolinium zirconate and lanthanum hexaaluminate. The mixed nano-slurry of gadolinium zirconate and lanthanum hexaaluminate was spray-dried to obtain hollow-structured mixed precursor microspheres of gadolinium zirconate and lanthanum hexaaluminate. The inlet temperature of the spray dryer was 225 °C, the outlet temperature was 108 °C, and the feed rate was 13 mL / min. The mixed precursor microspheres of gadolinium zirconate and lanthanum hexaaluminate were heated to 450 °C at a rate of 1 °C / min and held for 1.5 h to remove binders, dispersants, and other organic matter. The temperature was then increased to 1150 °C at a rate of 3.5 °C / min and held for 2.5 h to obtain a mixture of hollow gadolinium zirconate and hollow lanthanum hexaaluminate spheres (particle size 18 μm, wall thickness 1.5 μm).

[0067] (2) Preparation of nanorod-shaped LaPO4: Lanthanum carbonate was dissolved in deionized water to obtain 2000g of 80g / L lanthanum carbonate solution. The solution was heated to 70℃ while stirring at a stirring rate of 1300r / min. Stirring was continued, and 80g of 40% phosphoric acid solution was added dropwise. After the addition was completed, the reaction was continued for 2h. The reaction product was filtered and washed, and dried at 80℃ for 5h to obtain nanorod-shaped LaPO4 (diameter 6nm, length 250nm).

[0068] (3) Preparation of high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coatings: Weigh the raw materials by weight: gadolinium zirconate (Gd₂Zr₂O₇) hollow spheres and lanthanum hexaaluminate (LaAl₂O₇). 11 O 18 The mixture consisted of 43g of hollow spheres (weight ratio 2:1, particle size 18μm, wall thickness 1.5μm), 17g of nanorod-shaped LaPO4 (diameter 6nm, length 250nm), 33g of a binder mixture of aluminum dihydrogen phosphate solution and zirconium sol (aluminum dihydrogen phosphate solution solid content 32%, zirconium sol solid content 26%, weight ratio 4:6), 0.4g of OROTAN 1124 dispersant, and 17g of water.

[0069] Preparation method: 1) Place water and dispersant in a high-speed mixer and stir at 380 rpm for 11 minutes until homogeneous; 2) Add nanorod-shaped LaPO4 under stirring, increase the rotation speed to 950 r / min, and disperse at high speed for 48 min to form a stable suspension; 3) Reduce the rotation speed of the suspension to 480 r / min, add the hollow spheres of gadolinium zirconate and lanthanum hexaaluminate, and stir for 38 min until the particles are fully wetted and dispersed; 4) While stirring at 480 r / min, add the aluminum dihydrogen phosphate solution and zirconium sol mixed binder (aluminum dihydrogen phosphate solution solid content 32%, zirconium sol solid content 26%, weight ratio 4:6), and continue stirring for 38 min; 5) Transfer to a sealed container and let it stand for 8.5 hours to obtain a high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating.

[0070] Comparative Example 1: The preparation steps for cerium oxide (CeO2) hollow spheres are the same as in Example 1.

[0071] Weigh the raw materials by weight as follows: 55g of cerium oxide (CeO2) hollow spheres (particle size 10μm, wall thickness 1μm), 30g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 25%, zirconium sol solid content 25%, weight ratio 4:6), 0.1g of BYK-154 dispersant, and 15g of water.

[0072] Other preparation methods are the same as in Example 1.

[0073] Comparative Example 2: Cerium oxide (CeO2) solid spheres: 100g of commercially available cerium oxide (particle size 40μm, purity 99.999%) was placed in a ball mill jar, using zirconia beads as the grinding medium at a ball-to-material ratio of 3:1. 200g of anhydrous ethanol was added, and the mixture was ball-milled for 6 hours using a planetary ball mill, followed by vacuum drying at 55℃ for 8 hours. After drying, the powder was ground and sieved to obtain powder with a particle size between 1250 mesh and 1600 mesh standard sieves, thus obtaining D. 50 Solid cerium oxide (CeO2) spheres (10 μm in diameter) with a diameter of 10 μm.

[0074] The preparation steps for nanorod-shaped LaPO4 are the same as in Example 1.

[0075] Weigh the raw materials by weight as follows: 40g of solid cerium oxide (CeO2) spheres (10μm in diameter), 15g of nanorod-shaped LaPO4 (2nm in diameter and 150nm in length), 30g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (25% solid content of aluminum dihydrogen phosphate solution and 25% solid content of zirconium sol, weight ratio 4:6), 0.1g of BYK-154 dispersant, and 15g of water.

[0076] The preparation method is the same as in Example 1.

[0077] Comparative Example 3: The preparation steps for cerium oxide (CeO2) hollow spheres are the same as in Example 1.

[0078] Weigh the raw materials by weight as follows: 40g of cerium oxide (CeO2) hollow spheres (particle size 10μm, wall thickness 1μm), 15g of aluminum silicate fiber (diameter 5μm, length 200μm), 30g of a mixture of aluminum dihydrogen phosphate solution and zirconium sol binder (aluminum dihydrogen phosphate solution solid content 25%, zirconium sol solid content 25%, weight ratio 4:6), 0.1g of BYK-154 dispersant, and 15g of water.

[0079] The preparation method is the same as in Example 1.

[0080] Comparative Example 4: The preparation steps for cerium oxide (CeO2) hollow spheres are the same as in Example 1.

[0081] The preparation steps for nanorod-shaped LaPO4 are the same as in Example 1.

[0082] Weigh the following raw materials by weight (g): 40g of cerium oxide (CeO2) hollow spheres (particle size 10μm, wall thickness 1μm), 15g of nanorod-shaped LaPO4 (diameter 2nm, length 150nm), 30g of aluminum dihydrogen phosphate solution (solid content 25%), 0.1g of BYK-154 dispersant, and 15g of water.

[0083] The preparation method is the same as in Example 1.

[0084] The coatings from Examples 1-6 and Comparative Examples 1-4 were applied to high-alumina refractory bricks and cured at room temperature for 12 hours, held at 500°C for 2 hours, and held at 1200°C for 3 hours to obtain coating samples with a coating thickness of 400 μm. Figure 3 As shown, performance tests were conducted: infrared emissivity in the 1-5μm band at room temperature was measured using an infrared spectrometer; the coating adhesion strength was tested using the pull-out method; the thermal conductivity of the coating was tested using the laser scintillation method; thermal shock resistance was assessed by thermal shock cycling at 1000℃, and the number of coating peelings or cracks was recorded; the coating condition was evaluated and its high-temperature durability was tested by maintaining a constant temperature of 1600℃ for 100 hours; the coated surface of the refractory brick was heated at 1200℃ for 20 minutes, and the temperature of the cold surface on the other side of the refractory brick was measured. The results are shown in Table 1.

[0085] Table 1 Test results of sample performance

[0086] By comparing the examples and comparative examples, it can be seen that the present invention achieves a coating with high reflectivity, low thermal conductivity, and high adhesion to the refractory brick substrate through the synergistic effect of high reflectivity, low thermal conductivity, nanorod-shaped rare earth phosphate, and composite binder, thereby reducing the cold surface temperature of the refractory brick and reducing heat loss.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating, characterized in that: The components include the following parts by weight: Hollow spheres of rare earth compounds: 40-50 parts; Nanorod-shaped rare earth phosphate: 15-20 parts; Inorganic binder: 30-40 parts; Dispersant: 0.1-1 part; Water: 15-20 parts.

2. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 1, characterized in that: The rare earth compound hollow spheres are CeO2 hollow spheres, La2Ce2O7 hollow spheres, La2Zr2O7 hollow spheres, Y2Zr2O7 hollow spheres, Gd2Zr2O7 hollow spheres, LaAlO3 hollow spheres, and LaAl 11 O 18 One or more of the following hollow spheres; the particle size of the rare earth compound hollow spheres is 10-50 μm and the wall thickness is 1-3 μm.

3. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 1, characterized in that: The nanorod-shaped rare earth phosphate is made of lanthanum phosphate, yttrium phosphate, cerium phosphate, or lanthanum phosphate and cerium phosphate; the diameter of the nanorod-shaped rare earth phosphate is 2-10 nm and the length is 100-400 nm.

4. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 1, characterized in that: The method for preparing the hollow spheres of the rare earth compound includes the following steps: a. After mixing deionized water and dispersant evenly, add rare earth compound powder while stirring, continue stirring for 0.5-1 hour, and then grind to the particle size D of the slurry. 90 Reaching 80-120nm; b. Add a polymer to the slurry after sand milling, and continue sand milling for 10-15 minutes to obtain a nano slurry; c. Spray-dry the nano-slurry to obtain precursor microspheres with a hollow structure; d. Heat the precursor microspheres to 400-600℃ and hold for 1-2 hours; The temperature is then raised to 1000-1200℃ and held for 2-4 hours to finally obtain hollow spheres of rare earth compounds.

5. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 4, characterized in that: The rare earth compound powder is CeO2, La2Ce2O7, La2Zr2O7, Y2Zr2O7, Gd2Zr2O7, LaAlO3, LaAl 11 O 18 One or more of the powders.

6. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 4, characterized in that: The mass ratio of the deionized water, dispersant, rare earth compound powder, and polymer is 1000:(15-20):(300-400):(10-15).

7. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 1, characterized in that: The preparation method of the nanorod-shaped rare earth phosphate is as follows: S1. Dissolve rare earth carbonates in deionized water to obtain a rare earth carbonate solution. S2. Under the conditions of 50-80℃ and stirring, add phosphoric acid solution dropwise to the rare earth carbonate solution. After the addition is complete, let the reaction proceed for 1-2 hours. S3. Filter and wash the reaction product from step S1, and dry it at 50-80℃ for 4.5-5.5h to obtain nanorod-shaped rare earth phosphate.

8. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 7, characterized in that: The rare earth carbonate is one or more of lanthanum carbonate, cerium carbonate, and yttrium carbonate, or a mixture thereof.

9. The high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to claim 7, characterized in that: The concentration of the rare earth carbonate solution in step S1 is 60-90 g / L; The mass fraction of the phosphoric acid solution in step S2 is 35%-45%; The mass ratio of the rare earth carbonate solution in step S1 to the phosphoric acid solution in step S2 is (1500-2000):(50-80).

10. The method for preparing the high-temperature resistant, low-thermal-conductivity, high-reflectivity heat-insulating coating according to any one of claims 1-9, characterized in that: The preparation method includes the following steps: Step 1: Mix water and dispersant thoroughly to obtain a dispersant solution; Step 2: Add nanorod-shaped rare earth phosphate powder to the dispersant solution while stirring and continue stirring until a suspension is formed; Step 3: Add rare earth compound hollow spheres to the suspension and continue stirring to disperse all powder particles to obtain a slurry; Step 4: Add the inorganic binder to the slurry obtained in step 3 while stirring, and continue stirring. Step 5: Transfer the slurry obtained in step 4 to a sealed container and let it stand for 8-12 hours to obtain a high-temperature resistant, low-thermal-conductivity, and high-reflectivity heat-insulating coating.

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