Rare earth coated refractory fiber and method of making same

Abstract

This invention provides a rare earth-coated refractory fiber and its preparation method. The refractory fiber is prepared from raw materials comprising the following parts by weight: 3-10 parts of nano-rare earth phosphate, 3-10 parts of modified refractory fiber bundles, 0.5-1.5 parts of dispersant, and 85-95 parts of water. The nano-rare earth phosphate is prepared using a sol-gel method and coated onto the surface of activated and modified refractory fibers. After drying and calcination, a coating layer with a thickness of 10-50 nm is formed. This rare earth-coated refractory fiber exhibits excellent high-temperature resistance, corrosion resistance, and resistance to crystallization and powdering, solving the problems of poor structural stability and short service life of traditional refractory fibers at high temperatures.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials, and in particular relates to a rare earth-coated refractory fiber and its preparation method. Background Technology

[0002] Refractory fibers, as lightweight heat-insulating refractory materials, have advantages such as low thermal conductivity, light weight, and convenient construction, and are widely used in high-temperature heat insulation and corrosion-resistant applications in industrial kilns, metallurgical smelting, aerospace, and other environments. Currently, mainstream refractory fibers on the market, such as aluminosilicate fibers, alumina fibers, and zirconium oxide fibers, while meeting the requirements of conventional high-temperature conditions, have significant technical shortcomings in ultra-high temperature and complex corrosive environments. On the one hand, they have poor high-temperature stability; long-term use above 1200℃ easily leads to crystal phase transformation, loose structure, and rapid strength decay. After 3 hours of insulation at 1400℃, the flexural strength retention rate is only 55-60%, the pulverization rate is ≥5%, and the service life is short. On the other hand, their corrosion resistance is insufficient; they are easily corroded in acidic or alkaline media or sulfur- or chlorine-containing corrosive atmospheres. Immersion in 5% hydrochloric acid for 24 hours results in a mass loss rate ≥1.5%, limiting their application in complex conditions. Summary of the Invention

[0003] In view of this, the present invention aims to propose a rare earth-coated refractory fiber and its preparation method. The rare earth-coated refractory fiber solves the problems of easy pulverization at high temperature and poor corrosion resistance of existing refractory fibers, and achieves a synergistic improvement in high temperature resistance and corrosion resistance, thereby extending the service life of refractory fibers in high temperature environments.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: 3-10 parts of nano-rare earth phosphate, 3-10 parts of modified refractory fiber bundle, 0.5-1.5 parts of dispersant, and 85-95 parts of water; wherein the nano-rare earth phosphate is a phosphate containing lanthanum and / or cerium, the modified refractory fiber bundle is obtained by modification with silane coupling agent KH550, and the dispersant is PEG.

[0005] The silane coupling agent is KH550 (3-aminopropyltriethoxysilane). After KH550 is hydrolyzed in ethanol, the triethoxysilyl group at one end is converted into silanol. The silanol undergoes a dehydration condensation reaction with the silanol and aluminol on the surface of the refractory fiber to form covalent bonds Si-O-Si and Si-O-Al. The amino group at the other end can coordinate with rare earth metal ions in rare earth phosphates and can also form strong hydrogen bonds with the hydroxyl groups of phosphate groups, so that rare earth phosphates are firmly adsorbed on the surface of refractory fibers.

[0006] The dispersant is PEG (polyethylene glycol). The ether bonds and terminal hydroxyl groups of PEG can form multiple hydrogen bonds with the hydroxyl groups of the phosphate groups on the surface of rare earth phosphates, forming a hydrophilic polyether hydration film on the surface, which effectively prevents the agglomeration of rare earth phosphate particles and ensures that the slurry system is a uniform suspension. On the other hand, it can also form weak hydrogen bonds with the amino groups of KH550 on the fiber bundle surface, which is conducive to the uniform distribution of dispersed rare earth phosphates on the active layer of the modified refractory fiber bundle surface. In addition, the hydrophilic polyether chains of PEG can reduce the interfacial tension between rare earth phosphates and the surface of modified refractory fiber bundles, promote the spreading and wetting of the slurry on the fiber surface, and facilitate the uniform coating of rare earth phosphates on the surface of modified refractory fiber bundles.

[0007] Lanthanum and cerium possess excellent high-temperature and structural stability, meeting the material performance requirements of this invention. Using lanthanum and cerium as raw materials can not only effectively alleviate the current stockpiling of lanthanum and cerium in the rare earth industry and improve the utilization rate of light rare earth resources, but also significantly reduce raw material costs, combining economic benefits with resource utilization value.

[0008] Nano-rare earth phosphates possess a monazite-type crystal structure. This type of crystal has high bond energy and low lattice distortion energy. Under high-temperature environments, its crystal phase will not undergo phase transformation or lattice collapse, and it can maintain a complete crystal structure for a long time, exhibiting excellent high-temperature stability. In addition, nano-rare earth phosphates have a small size effect and high specific surface area, which can form a non-porous, dense coating film on the surface of refractory fibers. This effectively isolates corrosive media from contact with the fiber matrix, improving corrosion resistance.

[0009] Furthermore, the nano-rare earth phosphates are LaPO4, CePO4, and La. x Ce 1-x One or more of PO4, 0 < x < 1, nano-rare earth phosphates are prepared by sol-gel method, with a particle size of 20-100 nm.

[0010] Furthermore, the sol-gel method includes the following steps: a. Dissolve the rare earth salt in a solvent to obtain solution A, and dissolve the phosphorus source and complexing agent in a solvent to obtain solution B; b. At 40-60℃, while stirring, add solution B dropwise to solution A at a rate of 1-5 drops / second; after the addition is complete, adjust the pH of the system to 3.0-4.5; then continue stirring at 40-60℃ to form a uniform and transparent composite sol; c. After vacuum drying and grinding, the composite sol is placed in a muffle furnace and sintered in stages to obtain nano-rare earth phosphate powder.

[0011] Further, in step a, 0.08-0.12 mol of rare earth salt is dissolved in 1 L of solvent, and 0.08-0.12 mol of phosphorus source and 0.16-0.24 mol of complexing agent are dissolved in 1 L of solvent. The solvent is a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1. Rare earth salts are one or more of the following: lanthanum nitrate hexahydrate (La(NO3)3·6H2O), cerium nitrate hexahydrate (Ce(NO3)3·6H2O), lanthanum chloride hexahydrate (LaCl3·6H2O), and cerium chloride hexahydrate (CeCl3·6H2O); The phosphorus source is one or more of the following: ammonium dihydrogen phosphate (NH4H2PO4), diammonium hydrogen phosphate ((NH4)2HPO4), and phosphoric acid (H3PO4); The complexing agent is one or more of citric acid, ethylene glycol, and ethylenediaminetetraacetic acid.

[0012] Further, in step b, solution A is placed in a constant temperature water bath and preheated to 40-60℃, maintaining temperature fluctuation ≤±1℃, and the stirring speed is 400-800rpm; the dropping speed error of solution B is ≤±0.2 drops / second; the stirring speed during pH adjustment is 200-400rpm, and the pH adjustment rate is ≤0.1pH / minute; after pH adjustment, the stirring speed is 200-400rpm, and stirring is carried out for 2-4 hours.

[0013] Furthermore, in step c, the vacuum drying conditions are: 60-80℃, vacuum degree of -0.08~-0.1MPa, and vacuum drying for 16-24h; The segmented heating sintering method is as follows: First, heat the furnace to 350-500℃ at a rate of 1-3℃ / min and hold for 1-3 hours; then heat the furnace to 800-1000℃ at a rate of 3-5℃ / min and hold for 2-4 hours; after sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature with the furnace, with a cooling rate ≤5℃ / min.

[0014] Furthermore, the preparation method of the modified refractory fiber bundle is as follows: Ⅰ. Cut the refractory fiber matrix into fiber bundles of 10-15cm, and clean them in sequence with deionized water using ultrasonic cleaning and immersion in anhydrous ethanol to remove surface oil and dust. Then, dry them in a vacuum drying oven. II. The treated fiber bundles were soaked in an ethanol solution of silane coupling agent KH550 and then dried in a vacuum drying oven to obtain surface-activated modified refractory fiber bundles.

[0015] Furthermore, in step I, ultrasonic cleaning is performed for 15-20 minutes, followed by immersion in anhydrous ethanol for 8-15 minutes, and vacuum drying at 80-100℃ for 1-2 hours; the refractory fiber matrix is ​​one of aluminosilicate fiber, mullite fiber, or alumina fiber. In step II, the concentration of silane coupling agent KH550 is 0.5-0.9wt%, soaking for 1-2 hours, and then vacuum drying at 100-120℃ for 2-4 hours.

[0016] Furthermore, the molecular weight of PEG is 2000-6000.

[0017] The present invention also provides a method for preparing rare earth-coated refractory fibers as described above, the method comprising the following steps: S1. Weigh out the water and dispersant according to the ratio and place them in a mixer to mix evenly; S2. While stirring, add nano-rare earth phosphate powder at a rate of 1-5 g / min until a uniform, stable rare earth phosphate slurry without visible agglomerates is formed. S3. The modified refractory fiber bundles are immersed in the above rare earth phosphate slurry, first ultrasonically assisted impregnation, and then allowed to stand at room temperature for impregnation. S4. The fiber bundle is pulled out of the slurry at a uniform speed of 5-15 mm / min, suspended in a ventilated place, and allowed to drip naturally to remove excess slurry from the surface. Then it is placed in a forced-air drying oven to dry, and then transferred to a muffle furnace for segmented heating and sintering. After natural cooling to room temperature, rare earth coated refractory fiber is obtained, with a coating thickness of 10-50 nm.

[0018] The thickness of the coating layer is affected by a variety of factors, including the characteristics of the slurry system, the dip-coating process, and the post-treatment process.

[0019] Furthermore, in step S1, the mixture is stirred at a speed of 300-500 rpm for 10-15 minutes; In step S2, the stirring rate when adding nano-rare earth phosphate powder is 300-800 rpm, and after it is completely added, the stirring rate is increased to 800-1200 rpm, and the stirring is carried out for 40-60 minutes. In step S3, ultrasonic-assisted immersion for 25-45 minutes, followed by room temperature immersion for 30-45 minutes; In step S4, allow it to drip naturally for 5-15 minutes; The drying conditions are as follows: first dry at 40-80℃ for 2-3 hours, then raise the temperature to 80-120℃ and dry for 4-6 hours; The segmented heating sintering method is as follows: heat the temperature to 180-220℃ at a heating rate of 1-2℃ / min and hold for 2-3 hours; then heat the temperature to 700-750℃ at a heating rate of 3-5℃ / min and hold for 2-3 hours.

[0020] Compared with existing technologies, the rare earth-coated refractory fiber, its preparation method, and its application described in this invention have the following advantages: (1) The nano-rare earth phosphate used in this invention has a monazite-type crystal phase structure. This type of crystal has high bond energy and low lattice distortion energy. Under high temperature environment, its crystal phase will not undergo phase transformation or lattice collapse, and it can maintain a complete crystal structure for a long time, exhibiting excellent high temperature stability. In addition, the nano-rare earth phosphate has a small size effect and high specific surface area, which can form a non-porous dense coating film on the surface of refractory fiber, effectively isolating the contact between corrosive media and the fiber matrix, and improving corrosion resistance.

[0021] (2) In the preparation process of the nano-rare earth phosphate used in this invention, a stable complexation reaction system is constructed by precisely controlling the solution drop acceleration rate and pH adjustment rate, which effectively inhibits the aggregation of nanoparticles in the sol stage and improves the product dispersibility. At the same time, the segmented heating sintering process takes into account both the thoroughness of organic matter removal and the orderliness of crystal growth, which is beneficial to the preparation of nano-rare earth phosphate powder.

[0022] (3) The KH550 and dispersant PEG used in this invention work together without interfering with each other, ensuring a firm and uniform coating. This dense coating layer can reduce the high-temperature heat conduction channels of the refractory fiber. The thermal conductivity at 800℃ is ≤0.040W / (m•K), and the heat preservation and energy saving effect is outstanding.

[0023] (4) The present invention uses a nano-rare earth phosphate coating layer to suppress the high-temperature crystal phase transformation of refractory fibers. The flexural strength retention rate of rare earth coated refractory fibers after 3 hours of heat preservation at 1400℃ is ≥92% and the pulverization rate is ≤1.2%, which improves the high-temperature resistance, anti-crystallization and pulverization ability and mechanical strength of refractory fibers, and solves the problems of poor structural stability and short service life of traditional refractory fibers at high temperatures.

[0024] (5) The nano-rare earth phosphate coating used in this invention has strong chemical inertness and can prevent acid and alkali corrosive media from penetrating into the substrate. The mass loss rate after soaking in 5% hydrochloric acid or 5% sodium hydroxide for 24 hours is ≤0.5%, which is suitable for complex corrosive environments. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a SEM image of the rare earth-coated refractory fiber obtained in Example 1 of the present invention. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO4 5 parts, modified aluminum silicate fiber bundle 5 parts, polyethylene glycol (PEG4000) dispersant 1 part, water 89 parts.

[0029] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.5 Ce 0.5 PO4 (1) Weigh 0.05 mol of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) powder and 0.05 mol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely clear and transparent, and prepare solution A; (2) Weigh 0.1 mol of ammonium dihydrogen phosphate (NH4H2PO4) and 0.2 mol of citric acid, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 50°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 600 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 3 drops / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 4. During the adjustment process, keep the stirring speed at 300 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 50°C water bath at 300 rpm for 3 hours to form a uniform and transparent composite sol. (4) Transfer the above sol to an open container and place it in a vacuum drying oven at 70℃ with a vacuum degree of -0.1MPa for 20 hours to obtain a composite dry gel. Grind the dry gel and place it in a muffle furnace. Use a segmented heating and sintering process: first, heat to 400℃ at a rate of 2℃ / min and hold for 2 hours; then heat to 900℃ at a rate of 4℃ / min and hold for 3 hours. After sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature at a cooling rate of ≤5℃ / min to obtain nano-La. 0.5 Ce 0.5 PO4 powder with a particle size of 50 nm.

[0030] II. Preparation of modified aluminosilicate fiber bundles (1) Cut the aluminum silicate fiber matrix into 10cm fiber bundles, ultrasonically clean them with deionized water for 15min, soak them in anhydrous ethanol for 15min to remove surface oil and dust, and dry them in a vacuum drying oven at 90℃ for 2h. (2) Soak the fiber bundles in an ethanol solution of 0.7wt% 3-aminopropyltriethoxysilane (KH550) for 1.5h, and dry them in a vacuum drying oven at 110℃ for 3h to obtain surface-activated modified aluminum silicate fiber bundles.

[0031] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 400 rpm for 13 min until well mixed; (2) Add nano-rare earth phosphate La at a stirring speed of 3 g / min under a stirring speed of 500 rpm. 0.5 Ce 0.5 After PO4 is completely added, increase the stirring speed to 1000 rpm and continue high-speed dispersion for 50 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified aluminum silicate fiber bundles in the above rare earth phosphate slurry, and ultrasonically assisted impregnate for 35 min, and then let them stand at room temperature for 40 min. (4) The fiber bundle is pulled out of the slurry at a uniform speed of 10 mm / min, suspended in a ventilated place, and allowed to drip naturally for 10 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven and dried at 60℃ for 2.5 h. The temperature is then raised to 100℃ and dried for another 5 h. The bundle is then transferred to a muffle furnace and heated to 200℃ at a rate of 1.5℃ / min, held for 2.5 h, and then heated to 700℃ at a rate of 4℃ / min, held for 2.5 h. The bundle is then allowed to cool naturally to room temperature to obtain the rare earth-coated refractory fiber product. Figure 1 As shown, the thickness of the coating layer is 30 nm.

[0032] Example 2 A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: 6 parts of nano-rare earth phosphate LaPO4, 6 parts of modified mullite fiber bundles, 1 part of polyethylene glycol (PEG2000) dispersant, and 92 parts of water.

[0033] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of LaPO4 (1) Weigh 0.1 mol of lanthanum chloride hexahydrate (LaCl3·6H2O) powder, dissolve it in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, and stir until completely clear and transparent to prepare solution A; (2) Weigh 0.1 mol of diammonium hydrogen phosphate ((NH4)2HPO4) and 0.2 mol of citric acid, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 50°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 700 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 1 drop / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 4.5. During the adjustment process, keep the stirring speed at 300 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 50°C water bath at 300 rpm for 4 hours to form a uniform and transparent composite sol. (4) Transfer the above sol to an open container and place it in a vacuum drying oven at 75°C with a vacuum degree of -0.1MPa for 19 hours to obtain a composite dry gel. After grinding the dry gel, place it in a muffle furnace and use a segmented heating sintering process: first, heat the temperature to 450°C at a rate of 2°C / min and hold for 2 hours; then heat the temperature to 1000°C at a rate of 4°C / min and hold for 2.5 hours. After sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature with the furnace at a cooling rate of ≤5°C / min to obtain nano LaPO4 powder with a particle size of 40nm.

[0034] II. Preparation of modified mullite fiber bundles (1) Cut the mullite fiber matrix into 15cm fiber bundles, ultrasonically clean them with deionized water for 20min, soak them in anhydrous ethanol for 10min to remove surface oil and dust, and dry them in a vacuum drying oven at 100℃ for 1.5h. (2) The surface-activated modified mullite fiber bundles were obtained by soaking in an ethanol solution of 0.6wt% 3-aminopropyltriethoxysilane (KH550) for 1h and then drying in a vacuum drying oven at 100℃ for 4h.

[0035] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 450 rpm for 15 min until well mixed; (2) Add LaPO4 at a stirring speed of 500 rpm at a rate of 3 g / min. After it is completely added, increase the stirring speed to 1100 rpm and continue high-speed dispersion for 50 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified mullite fiber bundles in the above rare earth phosphate slurry, and impregnate with ultrasonic assistance for 35 minutes, and then let them stand at room temperature for 40 minutes. (4) The fiber bundle is pulled out from the slurry at a uniform speed of 11 mm / min, suspended in a ventilated place, and allowed to drip naturally for 12 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven at 65℃ for 3 h, heated to 110℃, and dried for another 5.5 h. It is then transferred to a muffle furnace and heated to 210℃ at a rate of 2℃ / min, held for 3 h, heated to 750℃ at a rate of 4.5℃ / min, held for 3 h, and allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product with a coating thickness of 40 nm.

[0036] Example 3 A rare earth-coated refractory fiber is prepared from the following raw materials in parts by weight: 4 parts of nano-rare earth phosphate CePO4, 4 parts of modified alumina fiber bundle, 0.5 parts of polyethylene glycol (PEG6000) dispersant, and 85 parts of water.

[0037] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of CePO4 (1) Weigh 0.1 mol of cerium chloride hexahydrate (CeCl3·6H2O) powder, dissolve it in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely clear and transparent, and prepare solution A; (2) Weigh 0.1 mol of ammonium dihydrogen phosphate (NH4H2PO4) and 0.2 mol of ethylene glycol, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 50°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 600 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 1 drop / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 3.5. During the adjustment process, keep the stirring speed at 400 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 50°C water bath at 400 rpm for 2.5 hours to form a uniform and transparent composite sol. (4) Transfer the above sol to an open container and place it in a vacuum drying oven at 65°C with a vacuum degree of -0.1MPa for 21 hours to obtain a composite dry gel. After grinding the dry gel, place it in a muffle furnace and use a segmented heating sintering process: first, heat the temperature to 400°C at a rate of 1.5°C / min and hold for 3 hours; then heat the temperature to 1000°C at a rate of 4°C / min and hold for 3 hours; after sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature with the furnace at a cooling rate of ≤5°C / min to obtain nano CePO4 powder with a particle size of 60nm.

[0038] II. Preparation of modified alumina fiber bundles (1) Cut the alumina fiber matrix into 13cm fiber bundles, ultrasonically clean them with deionized water for 17min, soak them in anhydrous ethanol for 12min to remove surface oil and dust, and dry them in a vacuum drying oven at 100℃ for 1h. (2) Soak the fiber bundles in an ethanol solution of 0.8wt% 3-aminopropyltriethoxysilane (KH550) for 1h, and dry them in a vacuum drying oven at 110℃ for 3h to obtain surface-activated modified alumina fiber bundles.

[0039] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 350 rpm for 11 min until well mixed; (2) At a stirring speed of 500 rpm, CePO4 was added at a rate of 3 g / min. After it was completely added, the stirring speed was increased to 900 rpm and the mixture was continuously dispersed at high speed for 45 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified alumina fiber bundle in the above rare earth phosphate slurry, ultrasonically assisted impregnation for 30 min, and then let it stand at room temperature for 35 min. (4) The fiber bundle is pulled out from the slurry at a uniform speed of 8 mm / min, suspended in a ventilated place, and allowed to drip naturally for 8 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven at 50℃ for 2 h, heated to 90℃, and dried for another 6 h. It is then transferred to a muffle furnace and heated to 190℃ at a rate of 1℃ / min, held for 2 h, heated to 700℃ at a rate of 3.5℃ / min, held for 3 h, and allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product with a coating thickness of 20 nm.

[0040] Example 4 A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.3 Ce 0.7 PO4 5 parts, modified aluminum silicate fiber bundle 5 parts, polyethylene glycol (PEG4000) dispersant 0.5 parts, water 86 parts.

[0041] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.3 Ce 0.7 PO4 (1) Weigh 0.03 mol of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) powder and 0.07 mol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, and stir until completely clear and transparent to prepare solution A; (2) Weigh 0.1 mol of phosphoric acid (H3PO4) and 0.2 mol of citric acid, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 60°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 500 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 1 drop / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 4.5. During the adjustment process, keep the stirring speed at 300 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 60°C water bath at 300 rpm for 2.5 hours to form a uniform and transparent composite sol. (4) The above sol was transferred to an open container and placed in a vacuum drying oven at 65°C with a vacuum degree of -0.08MPa for 22 hours to obtain a composite dry gel. The dry gel was ground and placed in a muffle furnace for a segmented heating and sintering process: first, the temperature was increased to 400°C at a rate of 2°C / min and held for 2 hours; then, the temperature was increased to 1000°C at a rate of 4°C / min and held for 2 hours. After sintering, the power supply to the muffle furnace was turned off, and the product was allowed to cool naturally to room temperature at a cooling rate of ≤5°C / min to obtain nano-La. 0.3 Ce 0.7 PO4 powder with a particle size of 60 nm.

[0042] II. Preparation of modified aluminosilicate fiber bundles (1) Cut the aluminum silicate fiber matrix into 15cm fiber bundles, ultrasonically clean them with deionized water for 15min, soak them in anhydrous ethanol for 15min to remove surface oil and dust, and dry them in a vacuum drying oven at 100℃ for 1.5h. (2) Soak the fiber bundles in an ethanol solution of 0.6wt% 3-aminopropyltriethoxysilane (KH550) for 2h, and dry them in a vacuum drying oven at 100℃ for 4h to obtain surface-activated modified aluminum silicate fiber bundles.

[0043] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 450 rpm for 11 min until well mixed; (2) Add La at a stirring speed of 600 rpm at a rate of 2 g / min. 0.3 Ce 0.7 After PO4 is completely added, increase the stirring speed to 1100 rpm and continue high-speed dispersion for 45 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified aluminum silicate fiber bundles in the above rare earth phosphate slurry, ultrasonically assisted impregnation for 30 min, and then let them stand at room temperature for 45 min. (4) The fiber bundle is pulled out from the slurry at a uniform speed of 11 mm / min, suspended in a ventilated place, and allowed to drip naturally for 11 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven at 65℃ for 2 h, heated to 90℃, and dried for another 5.5 h. It is then transferred to a muffle furnace and heated to 210℃ at a rate of 2℃ / min, held for 3 h, heated to 750℃ at a rate of 4.5℃ / min, held for 2 h, and allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product with a coating thickness of 35 nm.

[0044] Example 5 A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.4 Ce0.6 PO4 5 parts, modified alumina fiber bundle 5 parts, polyethylene glycol (PEG2000) dispersant 0.5 parts, water 88 parts.

[0045] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.4 Ce 0.6 PO4 (1) Weigh 0.04 mol of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) powder and 0.06 mol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely clear and transparent, and prepare solution A; (2) Weigh 0.1 mol of ammonium dihydrogen phosphate (NH4H2PO4) and 0.2 mol of ethylenediaminetetraacetic acid, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 45°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 700 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 2 drops / second, with a dropping speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the dropping process. After the dropping is completed, slowly adjust the pH value of the system to 4. During the adjustment process, keep the stirring speed at 400 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 45°C water bath at 400 rpm for 3.5 hours to form a uniform and transparent composite sol. (4) The above sol was transferred to an open container and placed in a vacuum drying oven at 70°C with a vacuum degree of -0.08 MPa for 19 hours to obtain a composite dry gel. The dry gel was ground and placed in a muffle furnace for a segmented heating and sintering process: first, the temperature was increased to 400°C at a rate of 1.5°C / min and held for 3 hours; then, the temperature was increased to 1000°C at a rate of 4°C / min and held for 2 hours. After sintering, the power supply to the muffle furnace was turned off, and the product was allowed to cool naturally to room temperature at a cooling rate of ≤5°C / min to obtain nano-La. 0.4 Ce 0.6 PO4 powder with a particle size of 70 nm.

[0046] II. Preparation of modified alumina fiber bundles (1) Cut the alumina fiber matrix into 12cm fiber bundles, ultrasonically clean them with deionized water for 18min, soak them in anhydrous ethanol for 10min to remove surface oil and dust, and dry them in a vacuum drying oven at 95℃ for 1.5h. (2) The modified alumina fiber bundles were soaked in an ethanol solution of 0.6wt% 3-aminopropyltriethoxysilane (KH550) for 2h and then dried in a vacuum drying oven at 110℃ for 3h to obtain surface-activated modified alumina fiber bundles.

[0047] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 380 rpm for 12 min until well mixed; (2) Add La at a stirring speed of 400 rpm at a rate of 2 g / min. 0.4 Ce 0.6 After PO4 is completely added, increase the stirring speed to 1100 rpm and continue high-speed dispersion for 50 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified alumina fiber bundles in the above rare earth phosphate slurry, and ultrasonically assisted impregnate for 40 min, and then let them stand at room temperature for 35 min. (4) The fiber bundle is pulled out from the slurry at a uniform speed of 9 mm / min, suspended in a ventilated place, and allowed to drip naturally for 10 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven at 55℃ for 3 h, heated to 105℃, and dried for another 4.5 h. It is then transferred to a muffle furnace and heated to 205℃ at a rate of 2℃ / min, held for 3 h, heated to 700℃ at a rate of 4.5℃ / min, held for 3 h, and allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product with a coating thickness of 25 nm.

[0048] Example 6 A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.9 Ce 0.1 PO4 5 parts, modified mullite fiber bundles 5 parts, polyethylene glycol (PEG6000) dispersant 1 part, water 90 parts.

[0049] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.9 Ce 0.1 PO4 (1) Weigh 0.09 mol of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) powder and 0.01 mol of cerium nitrate hexahydrate (Ce(NO3)3·6H2O), dissolve them in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely clear and transparent, and prepare solution A; (2) Weigh 0.1 mol of ammonium dihydrogen phosphate (NH4H2PO4) and 0.2 mol of citric acid, dissolve them together in 1 L of a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:1, stir until completely dissolved, and prepare solution B; (3) Preheat solution A to 50°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 500 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 1 drop / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 3.5. During the adjustment process, keep the stirring speed at 400 rpm and the pH adjustment rate ≤ 0.1 pH / minute. After the adjustment is completed, stir the mixed solution in a 50°C water bath at 400 rpm for 2.5 hours to form a uniform and transparent composite sol. (4) The above sol was transferred to an open container and placed in a vacuum drying oven at 75°C with a vacuum degree of -0.08 MPa for 22 hours to obtain a composite dry gel. The dry gel was ground and placed in a muffle furnace for a segmented heating and sintering process: first, the temperature was increased to 450°C at a rate of 2.5°C / min and held for 1.5 hours; then, the temperature was increased to 950°C at a rate of 3.5°C / min and held for 3.5 hours. After sintering, the power supply to the muffle furnace was turned off, and the product was allowed to cool naturally to room temperature at a cooling rate of ≤5°C / min to obtain nano-La. 0.9 Ce 0.1 PO4 powder with a particle size of 50 nm.

[0050] II. Preparation of modified mullite fiber bundles (1) Cut the mullite fiber matrix into 14cm fiber bundles, ultrasonically clean them with deionized water for 15min, soak them in anhydrous ethanol for 10min to remove surface oil and dust, and dry them in a vacuum drying oven at 90℃ for 1.5h. (2) The surface-activated modified mullite fiber bundles were obtained by soaking in an ethanol solution of 0.7wt% 3-aminopropyltriethoxysilane (KH550) for 1h and then drying in a vacuum drying oven at 110℃ for 3.5h.

[0051] III. Preparation of Rare Earth-Coated Refractory Fibers (1) Place water and dispersant in a high-speed mixer and stir at 450 rpm for 13 min until well mixed; (2) Add La at a stirring rate of 4 g / min under a stirring rate of 600 r / min. 0.9 Ce 0.1 After PO4 is completely added, increase the stirring speed to 1100 rpm and continue high-speed dispersion for 55 minutes to form a stable rare earth phosphate slurry. (3) Immerse the modified mullite fiber bundles in the above rare earth phosphate slurry, and ultrasonically assisted impregnate for 40 min, and then let them stand at room temperature for 45 min. (4) The fiber bundle is pulled out from the slurry at a uniform speed of 11 mm / min, suspended in a ventilated place, and allowed to drip naturally for 9 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven at 65℃ for 2 h, heated to 90℃, and dried for another 5.5 h. It is then transferred to a muffle furnace and heated to 205℃ at a rate of 1℃ / min, held for 2 h, heated to 750℃ at a rate of 3.5℃ / min, held for 2 h, and allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product with a coating thickness of 40 nm.

[0052] Comparative Example 1: Nano-rare earth phosphate A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: 5 parts modified aluminosilicate fiber bundle, 1 part polyethylene glycol (PEG4000) dispersant, and 89 parts water.

[0053] The preparation method of rare earth coated refractory fiber is as follows: I. The preparation steps of the modified aluminum silicate fiber bundle are the same as in Example 1.

[0054] II. Preparation of rare earth-coated refractory fibers (1) Place water and dispersant in a high-speed mixer and stir at 400 rpm for 13 min until well mixed; (2) Immerse the modified aluminum silicate fiber bundle in the above solution, and ultrasonically assisted impregnate for 35 min, and then let it stand at room temperature for 40 min. (3) The fiber bundle is lifted out of the solution at a uniform speed of 10 mm / min, suspended in a ventilated place, and allowed to drip naturally for 10 min to remove excess slurry from the surface. It is then placed in a forced-air drying oven and dried at 60℃ for 2.5 h. The temperature is then raised to 100℃ and dried for another 5 h. The bundle is then transferred to a muffle furnace and heated to 200℃ at a rate of 1.5℃ / min. The temperature is held for 2.5 h, and then heated to 700℃ at a rate of 4℃ / min. The temperature is held for 2.5 h and then allowed to cool naturally to room temperature to obtain the rare earth coated refractory fiber product.

[0055] Comparative Example 2: Unmodified Fibers A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO4 5 parts, unmodified aluminum silicate fiber bundles 5 parts, polyethylene glycol (PEG4000) dispersant 1 part, water 89 parts.

[0056] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.5 Ce 0.5 PO4 is the same as in Example 1.

[0057] II. Preparation of Unmodified Aluminosilicate Fiber Bundles (1) Cut the aluminum silicate fiber matrix into 10cm fiber bundles, ultrasonically clean them with deionized water for 15min, soak them in anhydrous ethanol for 15min to remove surface oil and dust, and dry them in a vacuum drying oven at 90℃ for 2h. (2) Soak in ethanol again for 1.5h, and dry in a vacuum drying oven at 110℃ for 3h to obtain unmodified aluminum silicate fiber bundles.

[0058] III. Preparation of rare earth-coated refractory fibers is the same as in Example 1.

[0059] Comparative Example 3: Replacement of Dispersant The difference from Example 1 is that the dispersant is CMC (sodium carboxymethyl cellulose).

[0060] A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO45 parts, modified aluminum silicate fiber bundles 5 parts, CMC (carboxymethyl cellulose sodium) dispersant 1 part, water 89 parts.

[0061] The preparation method of rare earth coated refractory fiber is the same as in Example 1, except that the dispersant is CMC, and the final product of rare earth coated refractory fiber is obtained.

[0062] Comparative Example 4: Replacement of silane coupling agent The difference from Example 1 is that the silane coupling agent is KH560 (γ-(2,3-epoxypropoxy)propyltrimethoxysilane).

[0063] A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO4 5 parts, modified aluminum silicate fiber bundle 5 parts, polyethylene glycol (PEG4000) dispersant 1 part, water 89 parts.

[0064] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.5 Ce 0.5 PO4 is the same as in Example 1.

[0065] II. Preparation of modified aluminosilicate fiber bundles (1) Cut the aluminum silicate fiber matrix into 10cm fiber bundles, ultrasonically clean them with deionized water for 15min, soak them in anhydrous ethanol for 15min to remove surface oil and dust, and dry them in a vacuum drying oven at 90℃ for 2h. (2) The surface-activated modified aluminum silicate fiber bundles were obtained by soaking in 0.7wt% KH560 (γ-(2,3-epoxypropoxy)propyltrimethoxysilane) ethanol solution for 1.5h and drying in a vacuum drying oven at 110℃ for 3h.

[0066] III. Preparation of rare earth-coated refractory fibers is the same as in Example 1.

[0067] Comparative Example 5: Different preparation processes for nano-rare earth phosphates The difference from Example 1 is that the solution drop acceleration rate and pH adjustment rate were not controlled as required.

[0068] A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO4 5 parts, modified aluminum silicate fiber bundle 5 parts, polyethylene glycol (PEG4000) dispersant 1 part, water 89 parts.

[0069] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.5 Ce 0.5 PO4 Steps (1)-(2) are the same as in Example 1.

[0070] (3) Preheat solution A to 50°C in a constant temperature water bath, keeping the temperature fluctuation ≤ ±1°C. At the same time, turn on the magnetic stirrer and keep the stirring speed stable at 600 rpm. Use a precision peristaltic pump to slowly add solution B to solution A at a rate of 9 drops / second, with an addition speed error ≤ ±0.2 drops / second. Continuously monitor the pH value of the system during the addition process. After the addition is completed, slowly adjust the pH value of the system to 4. During the adjustment process, keep the stirring speed at 300 rpm and the pH adjustment rate at 0.4-0.5 pH / minute. After the adjustment is completed, stir the mixed solution in a 50°C water bath at 300 rpm for 3 hours to obtain a turbid suspension.

[0071] Step (4) is the same as in Example 1.

[0072] II. Preparation of modified aluminum silicate fiber bundles is the same as in Example 1.

[0073] III. Preparation of rare earth-coated refractory fibers: Same as in Example 1, finally obtaining the finished rare earth-coated refractory fiber product.

[0074] Comparative Example 6: Different sintering processes for nano-rare earth phosphates The difference from Example 1 is that the nano-rare earth phosphate sintering adopts a direct isothermal sintering process.

[0075] A rare earth-coated refractory fiber is prepared from raw materials comprising the following parts by weight: nano-rare earth phosphate La 0.5 Ce 0.5 PO4 5 parts, modified aluminum silicate fiber bundle 5 parts, polyethylene glycol (PEG4000) dispersant 1 part, water 89 parts.

[0076] The preparation method of rare earth coated refractory fiber is as follows: I. Preparation of La 0.5 Ce 0.5 PO4 Steps (1)-(3) are the same as in Example 1.

[0077] (4) Transfer the above sol to an open container and place it in a vacuum drying oven at 70℃ with a vacuum degree of -0.1MPa for 20 hours to obtain a composite dry gel. Grind the dry gel and place it in a muffle furnace for direct isothermal sintering: heat to 900℃ at a rate of 4℃ / min and hold for 5 hours. After sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature at a cooling rate of ≤5℃ / min to obtain La. 0.5 Ce 0.5 PO4 powder with a particle size of 1500-2000 nm.

[0078] II. Preparation of modified aluminum silicate fiber bundles is the same as in Example 1.

[0079] III. Preparation of rare earth-coated refractory fibers: Same as in Example 1, finally obtaining the finished rare earth-coated refractory fiber product.

[0080] Performance tests were conducted on the finished products of Examples 1-6 and Comparative Examples 1-6: the flexural strength retention rate after being kept at 1400℃ for 3 hours was tested using the three-point bending method; the pulverization rate after being kept at 1400℃ for 3 hours was tested using the vibrating sieving method; the thermal conductivity at 800℃ was tested using the laser flash method; and the mass loss rate after being immersed in 5% hydrochloric acid or 5% sodium hydroxide solution for 24 hours was tested using the weight loss method. The results are shown in Table 1.

[0081] Table 1 Test results of sample performance

[0082] As shown in the table above, the refractory fiber prepared according to the method of the present invention has a flexural strength retention rate of ≥92% after being kept at 1400℃ for 3 hours, a pulverization rate of ≤1.2%, a thermal conductivity of ≤0.040W / (m·K) at 800℃, and a mass loss rate of ≤0.5% after soaking in 5% hydrochloric acid or 5% sodium hydroxide for 24 hours. It has excellent high temperature resistance, corrosion resistance, and anti-crystallization and pulverization properties, solving the problems of poor structural stability and short service life of traditional refractory fibers at high temperatures.

[0083] Comparative Example 1: No nano-rare earth phosphate. It is only a modified fiber. After high-temperature calcination, the fiber is prone to crystal phase transformation, loose structure, and rapid strength decay. Its flexural strength, acid and alkali corrosion resistance, and anti-powdering ability are all significantly reduced.

[0084] In Comparative Example 2, the fibers were not modified, and the coating layer was only physically adhered to the fibers without chemical bonding. After sintering, the coating was prone to peeling off and powdering.

[0085] In Comparative Example 3, changing the dispersant failed to suppress the agglomeration of nano-rare earth phosphates, resulting in flocculent precipitation in the slurry, severe material accumulation during lifting, a coating thickness exceeding 50 nm, and easy sagging, with extremely poor coating uniformity.

[0086] Comparative Example 4, when the silane coupling agent was replaced, showed weak coordination ability with nano-rare earth phosphate, resulting in poor bonding between the coating layer and the fiber, and easy cracking and detachment after high-temperature sintering.

[0087] The preparation and sintering processes of the nano-rare earth phosphates in Comparative Examples 5 and 6 are different, and neither can obtain stable nano-rare earth phosphates. When this powder is used to prepare rare earth phosphate slurry, it is easy to encounter problems such as agglomerates that cannot be dispersed and poor slurry dispersion stability. When the refractory fiber is subsequently stretched and coated, it will lead to defects such as severely uneven coating thickness and poor density, and the effect of uniform nano-scale coating cannot be achieved.

[0088] 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 rare earth-coated refractory fiber, characterized in that, It is prepared from the following raw materials in parts by weight: 3-10 parts of nano-rare earth phosphate, 3-10 parts of modified refractory fiber bundles, 0.5-1.5 parts of dispersant, and 85-95 parts of water; wherein, the nano-rare earth phosphate is a phosphate containing lanthanum and / or cerium, the modified refractory fiber bundles are obtained by modification with silane coupling agent KH550, and the dispersant is PEG.

2. The rare earth-coated refractory fiber according to claim 1, characterized in that, Nano-rare earth phosphates are LaPO4, CePO4, and La x Ce 1-x One or more of PO4, 0 < x < 1, nano-rare earth phosphates are prepared by sol-gel method, with a particle size of 20-100 nm.

3. The rare earth-coated refractory fiber according to claim 2, characterized in that, The sol-gel method includes the following steps: a. Dissolve the rare earth salt in a solvent to obtain solution A, and dissolve the phosphorus source and complexing agent in a solvent to obtain solution B; b. At 40-60℃, while stirring, add solution B dropwise to solution A at a rate of 1-5 drops / second; after the addition is complete, adjust the pH of the system to 3.0-4.5; then continue stirring at 40-60℃ to form a uniform and transparent composite sol; c. After vacuum drying and grinding, the composite sol is placed in a muffle furnace and sintered in stages to obtain nano-rare earth phosphate powder.

4. The rare earth-coated refractory fiber according to claim 3, characterized in that, In step a, 0.08-0.12 mol of rare earth salt is dissolved in 1 L of solvent, and 0.08-0.12 mol of phosphorus source and 0.16-0.24 mol of complexing agent are dissolved in 1 L of solvent. The solvent is a mixed solution of deionized water and anhydrous ethanol with a volume ratio of 1:

1. Rare earth salts are one or more of lanthanum nitrate hexahydrate, cerium nitrate hexahydrate, lanthanum chloride hexahydrate, and cerium chloride hexahydrate; The phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid; The complexing agent is one or more of citric acid, ethylene glycol, and ethylenediaminetetraacetic acid.

5. The rare earth-coated refractory fiber according to claim 3, characterized in that, In step b, solution A is placed in a constant temperature water bath and preheated to 40-60℃, with temperature fluctuations maintained at ≤±1℃, and the stirring speed is 400-800rpm; the dropping speed error of solution B is ≤±0.2 drops / second; the stirring speed during pH adjustment is 200-400rpm, and the pH adjustment rate is ≤0.1pH / minute; after pH adjustment, the stirring speed is 200-400rpm, and stirring is carried out for 2-4 hours.

6. The rare earth-coated refractory fiber according to claim 3, characterized in that, In step c, the vacuum drying conditions are: 60-80℃, vacuum degree of -0.08~-0.1MPa, and vacuum drying for 16-24h; The segmented heating sintering method is as follows: First, heat the temperature to 350-500℃ at a rate of 1-3℃ / min and hold for 1-3 hours; then heat the temperature to 800-1000℃ at a rate of 3-5℃ / min and hold for 2-4 hours. After sintering, turn off the power to the muffle furnace and allow the product to cool naturally to room temperature with the furnace at a rate of ≤5℃ / min.

7. The rare earth-coated refractory fiber according to claim 1, characterized in that, The preparation method of modified refractory fiber bundles is as follows: Ⅰ. Cut the refractory fiber matrix into fiber bundles of 10-15cm, clean them with deionized water by ultrasonic cleaning and soak them in anhydrous ethanol in sequence to remove surface oil and dust, and then dry them in a vacuum drying oven. II. The treated fiber bundles were soaked in an ethanol solution of silane coupling agent KH550 and then dried in a vacuum drying oven to obtain surface-activated modified refractory fiber bundles.

8. The rare earth-coated refractory fiber according to claim 7, characterized in that, In step I, ultrasonic cleaning is performed for 15-20 minutes, followed by immersion in anhydrous ethanol for 8-15 minutes, and vacuum drying at 80-100℃ for 1-2 hours. The refractory fiber matrix is ​​one of aluminosilicate fiber, mullite fiber, or alumina fiber. In step II, the concentration of silane coupling agent KH550 is 0.5-0.9wt%, soaking for 1-2 hours, and then vacuum drying at 100-120℃ for 2-4 hours.

9. A method for preparing rare earth-coated refractory fibers as described in any one of claims 1-8, characterized in that, The method includes the following steps: S1. Weigh out the water and dispersant according to the ratio and place them in a mixer to mix evenly; S2. While stirring, add nano-rare earth phosphate powder at a rate of 1-5 g / min until a uniform, stable rare earth phosphate slurry without visible agglomerates is formed. S3. The modified refractory fiber bundles are immersed in the above rare earth phosphate slurry, first ultrasonically assisted impregnation, and then allowed to stand at room temperature for impregnation. S4. The fiber bundle is pulled out of the slurry at a uniform speed of 5-15 mm / min, suspended in a ventilated place, and allowed to drip naturally to remove excess slurry from the surface. Then it is placed in a forced-air drying oven to dry, and then transferred to a muffle furnace for segmented heating and sintering. After natural cooling to room temperature, rare earth coated refractory fiber is obtained, with a coating thickness of 10-50 nm.

10. The method for preparing rare earth-coated refractory fibers according to claim 9, characterized in that, In step S1, stir at a speed of 300-500 rpm for 10-15 minutes; In step S2, the stirring rate when adding nano-rare earth phosphate powder is 300-800 rpm, and after it is completely added, the stirring rate is increased to 800-1200 rpm, and the stirring is carried out for 40-60 minutes. In step S3, ultrasonic-assisted impregnation is performed for 25-45 minutes, followed by static impregnation at room temperature for 30-45 minutes. In step S4, allow it to drip naturally for 5-15 minutes; The drying conditions are as follows: first dry at 40-80℃ for 2-3 hours, then raise the temperature to 80-120℃ and dry for 4-6 hours; The segmented heating sintering method is as follows: heat the temperature to 180-220℃ at a heating rate of 1-2℃ / min and hold for 2-3 hours; then heat the temperature to 700-750℃ at a heating rate of 3-5℃ / min and hold for 2-3 hours.

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