High-temperature-resistant low-shrinkage nano-composite refractory for holding furnace and preparation method thereof

Abstract

The application belongs to the technical field of refractory insulation materials, and discloses a kind of nano composite refractory material for high-temperature low-shrinkage insulation furnace and a preparation method thereof.The material uses surface layer transition type modified lightweight refractory aggregate, low-shrinkage alumina-silica matrix, inorganic binder, water reducing agent and exhaust fiber as main raw materials.During preparation, first, the lightweight refractory aggregate is modified by using zirconium phytic acid-silicon aluminum double complex nano ceramic precursor and aluminum-silica locking powder, and then is compounded with low-shrinkage alumina-silica matrix slurry in batches, to obtain the refractory material through forming, curing and drying.The material obtained by the application has the characteristics of low bulk density, small drying shrinkage, good high-temperature dimensional stability and excellent anti-cracking performance, and is suitable for insulation furnace lining material.

Description

Technical Field

[0001] This invention belongs to the field of refractory and heat-insulating materials technology, specifically relating to a nanocomposite refractory material for high-temperature resistant and low-shrinkage heat-insulating furnaces and its preparation method. Background Technology

[0002] During long-term service, the lining materials of industrial furnaces and kilns such as holding furnaces, heating furnaces, heat treatment furnaces, and smelting auxiliary furnaces not only need to withstand high temperatures but also need to ensure thermal insulation, volume stability, crack resistance, and workability. Existing refractory materials for holding furnaces are mostly composed of lightweight aggregates, aluminosilicate fine powders, inorganic binders, and additives. Lightweight mullite aggregates, alumina hollow spheres, and lightweight corundum aggregates are introduced to reduce the material's bulk density and thermal conductivity. However, lightweight refractory aggregates typically have many open pores and high water absorption rates, easily absorbing moisture and binder from the slurry during mixing. This leads to uneven slurry distribution, localized water loss in the matrix, reduced workability, and significant shrinkage stress during drying and heating.

[0003] To improve the high-temperature performance of lightweight refractory materials, existing technologies include adding silica powder, activated alumina powder, zircon powder, cordierite powder, or nano-oxides to enhance matrix density and thermal shock resistance. However, directly adding nano- or ultrafine powders to the matrix can easily lead to agglomeration, making it difficult to distribute them uniformly at the aggregate-matrix interface. The interface transition zone remains a weak point prone to high-temperature shrinkage and thermal cycling cracking. Some technologies use silica sol, alumina sol, or phosphate binders to impregnate and modify lightweight aggregates. However, conventional impregnation methods can easily allow the binder to penetrate the internal pores of the aggregate, filling the insulating pore structure and increasing bulk density and thermal conductivity, thus affecting insulation performance. Furthermore, existing lightweight refractory materials often experience poor drainage of internal moisture and volatiles during furnace drying and initial heating, leading to bulging, cracking, and even bursting. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a high-temperature resistant, low-shrinkage, heat-insulating nanocomposite refractory material for furnaces and its preparation method. This material uses surface-modified lightweight refractory aggregate, low-shrinkage aluminosilicate matrix, inorganic binder, water-reducing agent, and exhaust fiber as raw materials. The lightweight aggregate is surface-modified using a zirconium phytate-alumina silica double-complex nano-ceramic precursor and aluminosilicate locking powder, and then composited with the low-shrinkage matrix in stages to obtain a refractory material possessing heat insulation, low shrinkage, and high-temperature stability.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces, excluding water for slurry preparation, comprises, by weight, 55-80 parts of surface transitional modified lightweight refractory aggregate, 18-40 parts of low-shrinkage aluminosilicate matrix, 4-12 parts of inorganic binder, 0.1-0.5 parts of water-reducing agent, and 0.03-0.20 parts of exhaust fiber; The surface transitional modified lightweight refractory aggregate is a lightweight refractory aggregate treated with phytate zirconium-silica alumina double complex nano-ceramic precursor and aluminosilicate locked powder; the phytate zirconium-silica alumina double complex nano-ceramic precursor is made from raw materials including phytic acid, zirconium source, silicon source and aluminum source; the low shrinkage aluminosilicate matrix includes mullite fine powder, active α-Al2O3 micro powder, silica micro powder, cordierite fine powder and zircon powder.

[0006] More preferably, based on the raw materials for preparing the surface transition type modified lightweight refractory aggregate, the surface transition type modified lightweight refractory aggregate is prepared from 65-85 parts of lightweight refractory aggregate, 4-12 parts of phytate zirconium-silica alumina double complex nano-ceramic precursor, and 5-15 parts of aluminosilicate locked powder; the lightweight refractory aggregate is one or more of lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate; the particle size of the lightweight refractory aggregate is 0.5-5 mm, and the bulk density is 0.60-1.60 g / cm3.

[0007] More preferably, the phytate-zirconium-silica-alumina dual-complex nanoceramic precursor is prepared by weight of 5-15 parts of phytate aqueous solution, 5-20 parts of zirconium source, 15-35 parts of silica sol, 10-30 parts of aluminum source, 2-8 parts of active α-Al₂O₃ micro powder, 1-6 parts of silica micro powder, 0.05-0.5 parts of dispersant, and 10-40 parts of deionized water; the phytate aqueous solution has a mass concentration of 40-60%; the zirconium source is one or more of zirconium acetate solution, zirconium ammonium carbonate solution, and zirconium oxynitrate; the aluminum source is aluminum sol or boehmite aqueous dispersion; and the dispersant is one or more of polycarboxylate dispersant, ammonium polyacrylate, and ammonium polymethacrylate.

[0008] More preferably, the phytate zirconium-silicon aluminum dual-complex nanoceramic precursor is prepared by the following method: phytate aqueous solution, a portion of deionized water and zirconium source are mixed and complexed to obtain phytate zirconium complex solution; silica sol, aluminum source, active α-Al2O3 micro powder, silica micro powder, dispersant and remaining deionized water are mixed and dispersed, and then combined and dispersed with the phytate zirconium complex solution to obtain the phytate zirconium-silicon aluminum dual-complex nanoceramic precursor.

[0009] More preferably, the aluminosilicate locking powder is obtained by mixing mullite fine powder, active α-Al2O3 micro powder, silica micro powder and cordierite fine powder in a mass ratio of (3-8):(1-5):(0.5-3):(0.5-3); the particle size of the mullite fine powder and cordierite fine powder is 200-325 mesh, the D50 of the active α-Al2O3 micro powder is 0.3-3 μm, and the D50 of the silica micro powder is 0.1-1 μm.

[0010] More preferably, the low-shrinkage aluminosilicate matrix is ​​obtained by mixing mullite fine powder, active α-Al2O3 micro powder, silica micro powder, cordierite fine powder and zircon powder in a mass ratio of (8-18):(4-10):(2-6):(3-8):(1-4); the inorganic binder is one or more of silica sol, alumina sol and aluminum dihydrogen phosphate; the water-reducing agent is a polycarboxylate water-reducing agent; and the exhaust fiber is polypropylene fiber.

[0011] A method for preparing a high-temperature resistant, low-shrinkage nanocomposite refractory material for a heat-insulating furnace includes the following steps: S1. Mix the lightweight refractory aggregate with water to remove surface free water and obtain pre-wetted lightweight refractory aggregate; S2. The pre-wetted lightweight refractory aggregate is rolled and mixed with phytic acid zirconium-silica aluminum double complex nano-ceramic precursor, and intermittent negative pressure treatment is performed to remove free slurry between particles to obtain surface wetted modified aggregate. S3. The surface wet modified aggregate is mixed with aluminosilicate locking powder by rolling, and then dried and pre-ceramicized to obtain surface transition type modified lightweight refractory aggregate. S4. The surface transition type modified lightweight refractory aggregate is premixed according to particle size to obtain a modified lightweight refractory aggregate mixture. S5. Mix the low-shrinkage aluminosilicate matrix, inorganic binder, water-reducing agent, steam-venting fiber and water to obtain a low-shrinkage aluminosilicate matrix slurry containing steam-venting fiber; S6. The low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added to the modified lightweight refractory aggregate mixture in several batches for mixing to obtain a composite material. The composite material is then allowed to stand and molded, cured, and dried in stages to obtain a high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces.

[0012] More preferably, in step S1, the amount of water adsorbed by the pre-wetted lightweight refractory aggregate is 20-60% of the water adsorption of the lightweight refractory aggregate in 24 hours; in step S2, the negative pressure of the intermittent negative pressure treatment is -0.08 to -0.03 MPa, and the number of negative pressure treatments is 1 to 5.

[0013] More preferably, in step S3, the temperature of the pre-ceramic stabilization treatment is 300–550°C, and the treatment time is 1–4 hours.

[0014] More preferably, in step S4, the surface transition modified lightweight refractory aggregate includes 3-5mm coarse-grained modified aggregate, 1-3mm medium-grained modified aggregate, and 0.5-1mm fine-grained modified aggregate, with a mass ratio of 1:(0.5-1.2):(0.2-0.8); in step S6, the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added in two batches. The first batch is 40-70% of the total mass of the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers, and the second batch is the remaining low-shrinkage aluminosilicate matrix slurry containing exhaust fibers.

[0015] The beneficial effects of this invention are: This invention constructs a system of "lightweight aggregate surface nano-modification—alumina-silica powder locking—low-shrinkage matrix staged composite," resulting in refractory materials that possess high-temperature resistance, low shrinkage, thermal insulation, and crack resistance. In the phytate-zirconium-silica-alumina dual-complex nano-ceramic precursor, phytate can complex with the zirconium source and form a composite precursor system with the silicon and aluminum sources. This precursor is preferentially distributed on the surface layer and surface openings of the lightweight refractory aggregate through a rolling process, avoiding the large amount of binder entering the internal thermal insulation pores of the aggregate due to conventional impregnation methods. This improves the surface activity and interfacial bonding ability of the aggregate while maintaining its low bulk density and thermal insulation performance. The alumina-silica locking powder further adheres to the surface of the surface-wetted modified aggregate, forming a transition layer on the outer layer of the aggregate with a composition similar to the low-shrinkage alumina-silica matrix. The process reduces interfacial stress concentration between lightweight aggregates and the matrix due to differences in thermal expansion and sintering shrinkage. The synergistic effect of mullite fine powder, active α-Al2O3 micro powder, silica micro powder, cordierite fine powder, and zircon powder in the low-shrinkage aluminosilicate matrix can improve high-temperature structural stability and reduce volume changes during drying and high-temperature use. The process of adding the matrix slurry in stages helps to reduce the breakage of lightweight aggregates and local slurry enrichment, and improves the uniformity of the internal component distribution of the material. A small amount of venting fibers forms venting channels during the heating process, which can reduce the risk of bulging, cracking, and bursting during oven drying and initial heating. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Unless otherwise stated, all raw materials used in the following examples and comparative examples are commercially available products. The zirconium acetate solution has a ZrO2 mass fraction of 20%; the silica sol has a SiO2 mass fraction of 30% and a particle size of 10–30 nm; the alumina sol has an Al2O3 mass fraction of 20% and a dispersed particle size of 20–80 nm; the active α-Al2O3 micropowder is a commercially available reactive alumina micropowder for refractory materials, with α-Al2O3 as its main crystalline phase, an Al2O3 mass content of not less than 99%, a D50 of 0.8 μm, and a specific surface area of ​​8 m² / g; the silica micropowder has a D50 of 0.5 μm; the zircon powder has a particle size of 325 mesh and a ZrSiO4 mass content of not less than 95%; the polycarboxylate superplasticizer is a powdered polycarboxylate superplasticizer; and the polypropylene fiber has a length of 6 mm and a diameter of 20 μm. The 24-hour water absorption of lightweight refractory aggregate is determined as follows: The dried lightweight refractory aggregate is immersed in water for 24 hours, then removed, the surface water is drained, and the aggregate is weighed. The 24-hour water absorption is calculated based on the mass difference before and after immersion.

[0018] Example 1: This example provides a nanocomposite refractory material for high-temperature resistant and low-shrinkage heat-insulating furnaces. Excluding water for slurry preparation, the raw materials used in the preparation, by weight, include: 75 parts of surface transitional modified lightweight refractory aggregate, 20 parts of low-shrinkage aluminosilicate matrix, 6 parts of inorganic binder, 0.20 parts of water-reducing agent, and 0.08 parts of exhaust fiber; the inorganic binder is silica sol, the water-reducing agent is polycarboxylate water-reducing agent, and the exhaust fiber is polypropylene fiber.

[0019] I. Preparation of Zirconium Phytate-Silica Alumina Dual Complex Nanoceramic Precursors By weight, take 8 parts of a 50% phytic acid aqueous solution, 8 parts of a zirconium acetate solution, 20 parts of silica sol, 15 parts of alumina sol, 3 parts of active α-Al₂O₃ micropowder, 2 parts of silica micropowder, 0.10 parts of ammonium polyacrylate, and 20 parts of deionized water. Add 8 parts of the 50% phytic acid aqueous solution, 10 parts of deionized water, and 8 parts of zirconium acetate solution to a reaction vessel and stir at 40°C for 60 min to obtain a phytic acid-zirconium complex solution. Add 20 parts of silica sol, 15 parts of alumina sol, 3 parts of active α-Al₂O₃ micropowder, 2 parts of silica micropowder, 0.10 parts of ammonium polyacrylate, and the remaining 10 parts of deionized water to a dispersion vessel and disperse for 30 min to obtain a silica-alumina composite dispersion. Add the phytic acid-zirconium complex solution to the silica-alumina composite dispersion and continue stirring for 60 min to obtain a phytic acid-zirconium-silica-alumina dual-complex nanoceramic precursor.

[0020] II. Preparation of Nanocomposite Refractory Materials for High-Temperature Resistant and Low-Shrinkage Insulating Furnaces S1. Take 82 parts by weight of lightweight refractory aggregate, which is composed of lightweight mullite aggregate, alumina hollow spheres, and porous cordierite aggregate in a mass ratio of 50:30:20. All three aggregates are sieved to control the particle size to 0.5–5 mm. The bulk density of the lightweight refractory aggregate obtained after mixing in the 50:30:20 mass ratio is 0.80 g / cm³. Mix the 82 parts of lightweight refractory aggregate with water for 5 minutes, then drain off the surface free water to obtain pre-wetted lightweight refractory aggregate. The moisture content of the pre-wetted lightweight refractory aggregate is 30% of the water absorbed by the lightweight refractory aggregate in 24 hours.

[0021] S2. Place the pre-wetted lightweight refractory aggregate in a rolling mixer, add 5 parts of phytate zirconium-silica aluminum double complex nano-ceramic precursor, roll mix for 10 min, and perform intermittent negative pressure treatment during the rolling mixing process. The negative pressure is -0.04 MPa, and the negative pressure treatment is performed twice, with each negative pressure treatment lasting 1 min. After the negative pressure treatment is completed, the free slurry between particles is removed by sieving through a sieve to obtain the surface wet modified aggregate.

[0022] S3. The aluminosilicate locking powder is obtained by mixing mullite fine powder, active α-Al2O3 micro powder, silica micro powder and cordierite fine powder in a mass ratio of 4:2:1:1, wherein the particle size of both mullite fine powder and cordierite fine powder is 325 mesh. Five parts of the aluminosilicate locking powder are added to the surface wetted modified aggregate, and the mixture is continued to be rolled and mixed for 8 minutes. Then, it is dried at 100℃ for 4 hours, followed by pre-ceramic stabilization treatment at 350℃ for 2 hours. After cooling, a surface transition type modified lightweight refractory aggregate is obtained.

[0023] S4. Take 75 parts of surface transition type modified lightweight refractory aggregate and premix it at a mass ratio of 3-5mm coarse-grained modified aggregate, 1-3mm medium-grained modified aggregate and 0.5-1mm fine-grained modified aggregate of 1:0.6:0.3 to obtain modified lightweight refractory aggregate mixture.

[0024] S5. By weight, 8.37 parts of mullite fine powder, 4.19 parts of activated α-Al₂O₃ micro powder, 2.33 parts of silica micro powder, 3.72 parts of cordierite fine powder, and 1.39 parts of zircon powder are mixed to obtain 20 parts of low-shrinkage aluminosilicate matrix. The 20 parts of low-shrinkage aluminosilicate matrix, 6 parts of silica sol, 0.20 parts of polycarboxylate superplasticizer, 0.08 parts of polypropylene fiber, and 4 parts of slurry water are mixed to obtain a low-shrinkage aluminosilicate matrix slurry containing exhaust fibers.

[0025] S6. The low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added to the modified lightweight refractory aggregate mixture in two batches. The first addition is 50% of the total mass of the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers. After mixing evenly, the remaining low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added, and mixing continues to obtain a composite material. The composite material is allowed to stand for 30 minutes and then placed into a 40mm×40mm×160mm mold for vibration molding. The vibration time is 60s. It is cured for 24 hours at 20-25℃ and relative humidity not less than 70%, and then dried at 110℃ for 12 hours and 160℃ for 8 hours in sequence to obtain a high-temperature resistant, low-shrinkage, heat-insulating nanocomposite refractory material for furnaces.

[0026] Example 2: This example provides a high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces. Excluding water for slurry preparation, the raw materials used in its preparation, by weight, include: 60 parts of surface transitional modified lightweight refractory aggregate, 35 parts of low-shrinkage aluminosilicate matrix, 10 parts of inorganic binder, 0.40 parts of water-reducing agent, and 0.15 parts of exhaust fiber. The inorganic binder is composed of silica sol and aluminosilicate in a 1:1 mass ratio; the water-reducing agent is a polycarboxylate water-reducing agent; and the exhaust fiber is polypropylene fiber.

[0027] I. Preparation of Zirconium Phytate-Silica Alumina Dual Complex Nanoceramic Precursors By weight, 12 parts of a 50% phytic acid aqueous solution, 16 parts of a zirconium acetate solution, 30 parts of silica sol, 25 parts of alumina sol, 7 parts of active α-Al₂O₃ micropowder, 5 parts of silica micropowder, 0.40 parts of polymethyl methacrylate, and 35 parts of deionized water were taken. The 12 parts of the 50% phytic acid aqueous solution, 18 parts of deionized water, and 16 parts of zirconium acetate solution were added to a reaction vessel and stirred at 45°C for 70 min to obtain a phytic acid-zirconium complex solution. The 30 parts of silica sol, 25 parts of alumina sol, 7 parts of active α-Al₂O₃ micropowder, 5 parts of silica micropowder, 0.40 parts of polymethyl methacrylate, and the remaining 17 parts of deionized water were added to a dispersion vessel and dispersed for 35 min to obtain a silica-alumina composite dispersion. The phytic acid-zirconium complex solution was added to the silica-alumina composite dispersion, and stirring was continued for 70 min to obtain a phytic acid-zirconium-silica-alumina dual-complex nanoceramic precursor.

[0028] II. Preparation of Nanocomposite Refractory Materials for High-Temperature Resistant and Low-Shrinkage Insulating Furnaces S1. Take 70 parts by weight of lightweight refractory aggregate, which is composed of lightweight mullite aggregate, porous cordierite aggregate, and lightweight corundum aggregate in a mass ratio of 40:30:30. All three aggregates (lightweight mullite, porous cordierite, and lightweight corundum) are sieved to control the particle size to 0.5–5 mm. The bulk density of the lightweight refractory aggregate obtained after mixing in the 40:30:30 mass ratio is 1.30 g / cm³. Mix the 70 parts of lightweight refractory aggregate with water for 6 minutes, then drain off the surface free water to obtain pre-wetted lightweight refractory aggregate. The moisture content of the pre-wetted lightweight refractory aggregate is 50% of the water absorbed by the lightweight refractory aggregate in 24 hours.

[0029] S2. Add the pre-wetted lightweight refractory aggregate obtained in step S1 to a rolling mixer, then add 10 parts of phytate zirconium-silica alumina double-complexed nano-ceramic precursor, and roll mix for 12 min. During the rolling process, intermittent negative pressure treatment is performed simultaneously at a negative pressure of -0.07 MPa, 4 times, with each negative pressure treatment lasting 1 min. After the negative pressure treatment is completed, the free slurry between particles is drained to obtain the surface wetted modified aggregate.

[0030] S3. Mullite fine powder, active α-Al2O3 micro powder, silica micro powder, and cordierite fine powder are mixed in a mass ratio of 7:4:2.5:2.5 to obtain aluminosilicate locking powder, wherein the particle size of both mullite fine powder and cordierite fine powder is 325 mesh. 12 parts of aluminosilicate locking powder are added to the surface-wet modified aggregate obtained in step S2, and the mixture is continued to be rolled and mixed for 10 minutes to allow the aluminosilicate locking powder to adhere to the aggregate surface. The resulting material is then dried at 110℃ for 5 hours, followed by pre-ceramic stabilization treatment at 500℃ for 3 hours. After cooling, a surface transition type modified lightweight refractory aggregate is obtained.

[0031] S4. Take 60 parts of surface transition type modified lightweight refractory aggregate and premix it at a mass ratio of 3-5mm coarse-grained modified aggregate, 1-3mm medium-grained modified aggregate and 0.5-1mm fine-grained modified aggregate of 1:1.0:0.6 to obtain modified lightweight refractory aggregate mixture.

[0032] S5. By weight, 13.66 parts of mullite fine powder, 7.68 parts of activated α-Al₂O₃ micro powder, 4.70 parts of silica micro powder, 5.97 parts of cordierite fine powder, and 2.99 parts of zircon powder are mixed to obtain 35 parts of low-shrinkage aluminosilicate matrix. The 35 parts of low-shrinkage aluminosilicate matrix, 5 parts of silica sol, 5 parts of alumina sol, 0.40 parts of polycarboxylate superplasticizer, 0.15 parts of polypropylene fiber, and 6 parts of slurry water are mixed to obtain a low-shrinkage aluminosilicate matrix slurry containing exhaust fibers.

[0033] S6. The low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added to the modified lightweight refractory aggregate mixture in two batches. The first addition is 65% of the total mass of the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers. After mixing evenly, the remaining low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added, and mixing continues to obtain a composite material. The composite material is allowed to stand for 30 minutes and then placed into a 40mm×40mm×160mm mold for vibration molding. The vibration time is 60s. It is cured for 24 hours at 20-25℃ and relative humidity not less than 70%, and then dried at 110℃ for 12 hours and 160℃ for 8 hours in sequence to obtain a high-temperature resistant, low-shrinkage, heat-insulating nanocomposite refractory material for furnaces.

[0034] Example 3: This example provides a nanocomposite refractory material for a high-temperature resistant, low-shrinkage insulating furnace. Excluding water for slurry preparation, the raw materials for preparing the refractory material, by weight, include: 68 parts of surface transitional modified lightweight refractory aggregate, 28 parts of low-shrinkage aluminosilicate matrix, 8 parts of inorganic binder, 0.30 parts of water-reducing agent, and 0.10 parts of exhaust fiber. The inorganic binder is composed of silica sol and aluminosilicate in a mass ratio of 5:3, the water-reducing agent is a polycarboxylate water-reducing agent, and the exhaust fiber is polypropylene fiber.

[0035] I. Preparation of Zirconium Phytate-Silica Alumina Dual Complex Nanoceramic Precursors By weight, take 10 parts of a 50% phytic acid aqueous solution, 12 parts of a zirconium acetate solution, 25 parts of silica sol, 20 parts of alumina sol, 5 parts of active α-Al₂O₃ micropowder, 3 parts of silica micropowder, 0.20 parts of ammonium polyacrylate, and 25 parts of deionized water. Add 10 parts of the 50% phytic acid aqueous solution, 12 parts of deionized water, and 12 parts of zirconium acetate solution to a reaction vessel and stir at 40°C for 60 min to obtain a phytic acid-zirconium complex solution. Add 25 parts of silica sol, 20 parts of alumina sol, 5 parts of active α-Al₂O₃ micropowder, 3 parts of silica micropowder, 0.20 parts of ammonium polyacrylate, and the remaining 13 parts of deionized water to a dispersion vessel and disperse for 30 min to obtain a silica-alumina composite dispersion. Add the obtained phytic acid-zirconium complex solution to the silica-alumina composite dispersion within 8 min and continue stirring for 60 min to obtain a phytic acid-zirconium-silica-alumina dual-complex nanoceramic precursor.

[0036] II. Preparation of Nanocomposite Refractory Materials for High-Temperature Resistant and Low-Shrinkage Insulating Furnaces S1. Take 75 parts of lightweight refractory aggregate, which is composed of lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate in a mass ratio of 50:20:20:10. All lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate are sieved to control the particle size to 0.5–5 mm. The bulk density of the lightweight refractory aggregate obtained after mixing according to the above mass ratio is 1.05 g / cm³. Mix 75 parts of lightweight refractory aggregate with water for 5 minutes. After mixing, drain the surface free water to obtain pre-wetted lightweight refractory aggregate. The moisture content of the pre-wetted lightweight refractory aggregate is 40% of the water absorbed by the lightweight refractory aggregate in 24 hours.

[0037] S2. Place the pre-wetted lightweight refractory aggregate obtained in step S1 into a rolling mixer, add 8 parts of phytate-zirconium-silica-alumina double-complexed nano-ceramic precursor, and roll mix for 11 min. During the rolling mixing process, intermittent negative pressure treatment is performed at a negative pressure of -0.05 MPa, 3 times, with each negative pressure treatment lasting 1 min. After the negative pressure treatment is completed, the free slurry between particles is removed by sieving through a sieve to obtain the surface wetted modified aggregate.

[0038] S3. Mullite fine powder, active α-Al2O3 micro powder, silica micro powder, and cordierite fine powder are pre-mixed at a mass ratio of 5:3:1.5:1.5 to obtain aluminosilicate locking powder, wherein the particle size of both mullite fine powder and cordierite fine powder is 325 mesh. Take 9 parts of aluminosilicate locking powder and add it to the surface moist modified aggregate obtained in step S2, and continue to roll and mix for 9 minutes to make the aluminosilicate locking powder adhere to the surface of the surface moist modified aggregate; then dry the obtained material at 100℃ for 4 hours, and then pre-ceramicize and stabilize it at 450℃ for 2 hours. After cooling to room temperature, a surface transition type modified lightweight refractory aggregate is obtained.

[0039] S4. Take 68 portions of the surface transition type modified lightweight refractory aggregate obtained in step S3, and premix them according to the mass ratio of 3-5mm coarse-grained modified aggregate, 1-3mm medium-grained modified aggregate and 0.5-1mm fine-grained modified aggregate of 1:0.8:0.4 to obtain the modified lightweight refractory aggregate mixture.

[0040] S5. By weight, 11.20 parts of mullite fine powder, 6.53 parts of activated α-Al2O3 micro powder, 3.73 parts of silica micro powder, 4.67 parts of cordierite fine powder, and 1.87 parts of zircon powder are mixed to obtain 28 parts of low-shrinkage aluminosilicate matrix. The 28 parts of low-shrinkage aluminosilicate matrix, 5 parts of silica sol, 3 parts of alumina sol, 0.30 parts of polycarboxylate superplasticizer, 0.10 parts of polypropylene fiber, and 5 parts of slurry water are mixed to prepare a low-shrinkage aluminosilicate matrix slurry containing exhaust fibers.

[0041] S6. The low-shrinkage aluminosilicate matrix slurry containing exhaust fibers obtained in step S5 is added to the modified lightweight refractory aggregate mixture obtained in step S4 in two batches. The first addition is 60% of the total mass of the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers. After mixing evenly, the remaining low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added, and mixing continues to obtain a composite material. The composite material is allowed to stand for 30 minutes and then placed into a 40mm×40mm×160mm mold for vibration molding for 60 seconds. After molding, it is cured for 24 hours at 20-25℃ and relative humidity not less than 70%, and then dried sequentially at 110℃ for 12 hours and 160℃ for 8 hours to obtain a high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces.

[0042] Comparative Example 1: In this comparative example, the surface transition modified lightweight refractory aggregate was replaced with the same type and particle size distribution of unmodified lightweight refractory aggregate. The remaining low-shrinkage aluminosilicate matrix, inorganic binder, water-reducing agent, steam-venting fiber, slurry water, molding, curing and drying conditions were the same as in Example 3.

[0043] The unmodified lightweight refractory aggregate is obtained by mixing lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate in a mass ratio of 50:20:20:10. The lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate are all screened to control the particle size to 0.5-5 mm. The bulk density of the unmodified lightweight refractory aggregate obtained after mixing in the above mass ratio is 1.05 g / cm3.

[0044] During preparation, 68 parts of unmodified lightweight refractory aggregate were taken and premixed according to the mass ratio of 3-5 mm coarse aggregate, 1-3 mm medium aggregate and 0.5-1 mm fine aggregate in Example 3 of 1:0.8:0.4 to obtain unmodified lightweight refractory aggregate mixture; then, following the method of steps S5-S6 in Example 3, the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers was added to the unmodified lightweight refractory aggregate mixture in two batches. After mixing, standing, vibration molding, curing and segmented drying, the refractory material of Comparative Example 1 was obtained.

[0045] Comparative Example 2: In this comparative example, no aluminosilicate locking powder was added or the aluminosilicate locking powder was rolled over during the preparation of the modified lightweight refractory aggregate. 68 parts of surface transition type modified lightweight refractory aggregate were replaced with 68 parts of modified lightweight refractory aggregate that had only been treated with phytate zirconium-silica aluminum double complex nano-ceramic precursor.

[0046] In specific preparation, the preparation method of the phytate zirconium-silica alumina dual-complex nano-ceramic precursor is the same as in Example 3; 75 parts of the same lightweight refractory aggregate as in Example 3 are taken and pre-wetted, rolled and mixed, and subjected to intermittent negative pressure treatment according to the methods of steps S1 and S2 in Example 3 to obtain surface wet modified aggregate; then, without adding aluminosilicate locking powder, the surface wet modified aggregate is directly dried at 100°C for 4 hours, and then pre-ceramicized and stabilized at 450°C for 2 hours. After cooling to room temperature, the modified lightweight refractory aggregate treated only with the phytate zirconium-silica alumina dual-complex nano-ceramic precursor is obtained.

[0047] Take 68 portions of the modified lightweight refractory aggregate treated only with phytate zirconium-silica alumina double complex nano-ceramic precursor, and perform particle premixing, low-shrinkage aluminosilicate matrix slurry compounding, static setting, vibration molding, curing and segmented drying according to the methods of steps S4 to S6 in Example 3 to obtain the refractory material of Comparative Example 2.

[0048] Comparative Example 3: In preparing the modified lightweight refractory aggregate, this comparative example did not use the phytate zirconium-silica alumina double complex nano-ceramic precursor. In order to maintain the consistency of liquid addition, the 8 parts of phytate zirconium-silica alumina double complex nano-ceramic precursor in Example 3 were replaced with 8 parts of deionized water to obtain the modified lightweight refractory aggregate treated only with aluminosilicate locked powder.

[0049] In the specific preparation, 75 parts of the same lightweight refractory aggregate as in Example 3 were taken and pre-wetted according to the method of step S1 in Example 3 to obtain pre-wetted lightweight refractory aggregate; the pre-wetted lightweight refractory aggregate was placed in a rolling mixing device, 8 parts of deionized water were added, and the rolling mixing and intermittent negative pressure treatment conditions in step S2 in Example 3 were followed. After the negative pressure treatment was completed, the free liquid between the particles was drained through a screen to obtain surface wet aggregate.

[0050] Mullite fine powder, activated α-Al₂O₃ micro powder, silica micro powder, and cordierite fine powder were pre-mixed at a mass ratio of 5:3:1.5:1.5 to obtain aluminosilicate locking powder, wherein the particle size of both mullite fine powder and cordierite fine powder was 325 mesh. Nine parts of aluminosilicate locking powder were added to the surface wet aggregate and mixed by rolling for 9 minutes to allow the aluminosilicate locking powder to adhere to the surface of the surface wet aggregate. The resulting material was then dried at 100℃ for 4 hours, and then pre-ceramicized and stabilized at 450℃ for 2 hours. After cooling to room temperature, modified lightweight refractory aggregate treated only with aluminosilicate locking powder was obtained.

[0051] Take 68 portions of the modified lightweight refractory aggregate that has only been treated with aluminosilicate locked powder, and carry out particle premixing, low-shrinkage aluminosilicate matrix slurry compounding, static setting, vibration molding, curing and segmented drying according to the methods of steps S4 to S6 in Example 3 to obtain the refractory material of Comparative Example 3.

[0052] Comparative Example 4: In preparing modified lightweight refractory aggregate, the pre-wetting treatment in step S1 and the intermittent negative pressure rolling treatment of the precursor in step S2 of Example 3 were replaced with atmospheric pressure impregnation treatment. Except for the above differences, the types of raw materials, the amount of raw materials, the treatment of aluminosilicate locked powder, the pre-ceramic stabilization treatment, the low-shrinkage aluminosilicate matrix slurry composite, the molding, curing and drying conditions were the same as those in Example 3.

[0053] In specific preparation, the preparation method of the phytate zirconium-silica alumina double-complexed nano-ceramic precursor is the same as in Example 3. Take 75 parts of the same lightweight refractory aggregate as in Example 3, add 8 parts of the phytate zirconium-silica alumina double-complexed nano-ceramic precursor, stir until the surface of the lightweight refractory aggregate is wetted by the precursor, and let it stand for 30 minutes under normal pressure. Then, filter out the free slurry between particles through a sieve to obtain the normal pressure wetted modified aggregate. Premix mullite fine powder, active α-Al2O3 micro powder, silica micro powder and cordierite fine powder in a mass ratio of 5:3:1.5:1.5 to obtain aluminosilicate locked powder, wherein the particle size of mullite fine powder and cordierite fine powder is 325 mesh. Nine parts of aluminosilicate locking powder were added to the atmospheric pressure impregnated modified aggregate and rolled and mixed for 9 minutes to allow the aluminosilicate locking powder to adhere to the surface of the atmospheric pressure impregnated modified aggregate. The resulting material was then dried at 100°C for 4 hours, followed by pre-ceramic stabilization treatment at 450°C for 2 hours. After cooling to room temperature, atmospheric pressure impregnated modified lightweight refractory aggregate was obtained. Sixty-eight parts of the atmospheric pressure impregnated modified lightweight refractory aggregate were then subjected to particle size premixing, low-shrinkage aluminosilicate matrix slurry compounding, static setting, vibration molding, curing, and segmented drying according to steps S4-S6 in Example 3 to obtain the refractory material of Comparative Example 4.

[0054] Performance testing To verify the technical effects of the present invention, performance tests were conducted on the refractory materials obtained in Examples 1-3 and Comparative Examples 1-4.

[0055] (1) Bulk density test: The test was conducted in accordance with GB / T 2998-2015 "Test method for bulk density and true porosity of shaped heat-insulating refractory products". After drying each group of samples to constant weight at 110℃, the sample size and drying mass were measured and the bulk density was calculated. Three parallel samples were tested for each group and the average value of the results was taken.

[0056] (2) Thermal conductivity test: The test was conducted in accordance with GB / T 5990-2021 "Test methods for thermal conductivity, specific heat capacity and thermal diffusivity of refractory materials (hot wire method)". After drying, each group of samples was placed in a thermal conductivity test device and the thermal conductivity was measured at 800℃. Three parallel samples were tested for each group, and the average value of the results was taken.

[0057] (3) Test of permanent linear change rate under heating: The test was conducted in accordance with GB / T 5988-2022 "Test Method for Permanent Linear Change of Refractory Materials under Heating". After drying each group of samples, the initial length L0 was measured. Then, the samples were placed in an electric furnace and heated to 1200℃ and held for 3 hours. After cooling to room temperature, the length L1 after treatment was measured. The permanent linear change rate under heating was calculated as (L1-L0) / L0×100%. Three parallel samples were tested for each group, and the average value of the results was taken.

[0058] (4) Room temperature compressive strength test: The test shall be conducted in accordance with GB / T 5072-2023 "Test Method for Room Temperature Compressive Strength of Refractory Materials". After heat treatment at 1200℃ for 3 hours and cooling to room temperature, each group of specimens shall be cut into test specimens that meet the standard requirements for compressive strength. The specimens shall be placed in a compression testing machine for compression test, the maximum failure load shall be recorded, and the room temperature compressive strength shall be calculated according to the ratio of the maximum failure load to the pressure area. Three parallel specimens shall be tested in each group, and the average value of the results shall be taken.

[0059] The test results are shown in the table below.

[0060] Table 1. Overall performance test results of different embodiments and comparative examples

[0061] As shown in Table 1, the bulk density of the refractory materials obtained in Examples 1-3 is 0.93-1.17 g·cm⁻³, and the thermal conductivity at 800℃ is 0.36-0.42 W·m⁻¹·K⁻¹, exhibiting good thermal insulation performance while maintaining a lightweight structure. The absolute value of the permanent linear change rate after heating at 1200℃ for 3 hours is only 0.11%-0.19%, significantly lower than that of Comparative Examples 1-4, indicating a significant improvement in the material's high-temperature dimensional stability. The zirconium phytate-alumina silica double-complex nanoceramic precursor forms a zirconium-, silicon-, and aluminum-containing nano-transitional structure on the surface of the lightweight aggregate. The aluminosilicate locking powder further fills and stabilizes the aggregate surface interface, transforming the simple physical contact between the lightweight aggregate and the low-shrinkage aluminosilicate matrix into a continuous transitional bond, reducing interfacial debonding, shrinkage cracks, and localized thermal bridges at high temperatures. Comparative Example 1, without surface modification, showed the most significant shrinkage and strength degradation; Comparative Examples 2 and 3 lacked locking powder or precursors, resulting in insufficient interfacial stability; Comparative Example 4, using atmospheric pressure impregnation, exhibited inferior modification uniformity compared to intermittent negative pressure rolling treatment. In summary, this invention achieves a comprehensive improvement in low thermal conductivity, low shrinkage, and high post-heat treatment strength through the synergistic effect of surface transition modification and a low-shrinkage matrix.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A nanocomposite refractory material for high-temperature resistant, low-shrinkage heat-insulating furnaces, characterized in that, Apart from the water used for slurry preparation, the raw materials used in the preparation, by weight, include: 55-80 parts of surface transition type modified lightweight refractory aggregate, 18-40 parts of low shrinkage aluminosilicate matrix, 4-12 parts of inorganic binder, 0.1-0.5 parts of water-reducing agent, and 0.03-0.20 parts of steam-venting fiber; The surface transitional modified lightweight refractory aggregate is a lightweight refractory aggregate treated with phytate zirconium-silica alumina double complex nano-ceramic precursor and aluminosilicate locked powder; the phytate zirconium-silica alumina double complex nano-ceramic precursor is made from raw materials including phytic acid, zirconium source, silicon source and aluminum source; the low shrinkage aluminosilicate matrix includes mullite fine powder, active α-Al2O3 micro powder, silica micro powder, cordierite fine powder and zircon powder.

2. The high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces according to claim 1, characterized in that, The surface transition type modified lightweight refractory aggregate is prepared by weight parts of the following: 65-85 parts of lightweight refractory aggregate, 4-12 parts of phytate zirconium-silica alumina double-complexed nano-ceramic precursor, and 5-15 parts of aluminosilicate locked powder; the lightweight refractory aggregate is one or more of lightweight mullite aggregate, alumina hollow spheres, porous cordierite aggregate, and lightweight corundum aggregate; the particle size of the lightweight refractory aggregate is 0.5-5 mm, and the bulk density is 0.60-1.60 g / cm³.

3. The high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces according to claim 1, characterized in that, The phytate-zirconium-silica-alumina dual-complex nanoceramic precursor is prepared by weight of 5-15 parts of phytate aqueous solution, 5-20 parts of zirconium source, 15-35 parts of silica sol, 10-30 parts of aluminum source, 2-8 parts of active α-Al₂O₃ micro powder, 1-6 parts of silica micro powder, 0.05-0.5 parts of dispersant, and 10-40 parts of deionized water; the phytate aqueous solution has a mass concentration of 40-60%; the zirconium source is one or more of zirconium acetate solution, zirconium ammonium carbonate solution, and zirconium oxynitrate; the aluminum source is aluminum sol or boehmite aqueous dispersion; and the dispersant is one or more of polycarboxylate dispersant, ammonium polyacrylate, and ammonium polymethacrylate.

4. The high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces according to claim 3, characterized in that, The phytate zirconium-silicon aluminum dual-complex nanoceramic precursor is prepared by the following method: phytic acid aqueous solution, a portion of deionized water and zirconium source are mixed and complexed to obtain phytate zirconium complex solution; silica sol, aluminum source, active α-Al2O3 micro powder, silica micro powder, dispersant and remaining deionized water are mixed and dispersed, and then combined and dispersed with the phytate zirconium complex solution to obtain the phytate zirconium-silicon aluminum dual-complex nanoceramic precursor.

5. The high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces according to claim 2, characterized in that, The aluminosilicate locking powder is obtained by mixing mullite fine powder, active α-Al2O3 micro powder, silica micro powder and cordierite fine powder in a mass ratio of (3-8):(1-5):(0.5-3):(0.5-3); the particle size of the mullite fine powder and cordierite fine powder is 200-325 mesh, the D50 of the active α-Al2O3 micro powder is 0.3-3 μm, and the D50 of the silica micro powder is 0.1-1 μm.

6. The high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces according to claim 1, characterized in that, The low-shrinkage aluminosilicate matrix is ​​obtained by mixing mullite fine powder, active α-Al2O3 micro powder, silica micro powder, cordierite fine powder and zircon powder in a mass ratio of (8-18):(4-10):(2-6):(3-8):(1-4); the inorganic binder is one or more of silica sol, alumina sol and aluminum dihydrogen phosphate; the water-reducing agent is a polycarboxylate water-reducing agent; and the exhaust fiber is polypropylene fiber.

7. A method for preparing a high-temperature resistant, low-shrinkage nanocomposite refractory material for a heat-insulating furnace as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Mix the lightweight refractory aggregate with water to remove surface free water and obtain pre-wetted lightweight refractory aggregate; S2. The pre-wetted lightweight refractory aggregate is rolled and mixed with phytic acid zirconium-silica aluminum double complex nano-ceramic precursor, and intermittent negative pressure treatment is performed to remove free slurry between particles to obtain surface wetted modified aggregate. S3. The surface wet modified aggregate is mixed with aluminosilicate locking powder by rolling, and then dried and pre-ceramicized to obtain surface transition type modified lightweight refractory aggregate. S4. The surface transition type modified lightweight refractory aggregate is premixed according to particle size to obtain a modified lightweight refractory aggregate mixture. S5. Mix the low-shrinkage aluminosilicate matrix, inorganic binder, water-reducing agent, steam-venting fiber and water to obtain a low-shrinkage aluminosilicate matrix slurry containing steam-venting fiber; S6. The low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added to the modified lightweight refractory aggregate mixture in several batches for mixing to obtain a composite material. The composite material is then allowed to stand and molded, cured, and dried in stages to obtain a high-temperature resistant, low-shrinkage nanocomposite refractory material for heat-insulating furnaces.

8. The preparation method according to claim 7, characterized in that, In step S1, the amount of water adsorbed by the pre-wetted lightweight refractory aggregate is 20-60% of the water adsorption of the lightweight refractory aggregate in 24 hours; in step S2, the negative pressure of the intermittent negative pressure treatment is -0.08 to -0.03 MPa, and the number of negative pressure treatments is 1 to 5.

9. The preparation method according to claim 7, characterized in that, In step S3, the temperature of the pre-ceramic stabilization treatment is 300–550°C, and the treatment time is 1–4 hours.

10. The preparation method according to claim 7, characterized in that, In step S4, the surface transition type modified lightweight refractory aggregate includes 3-5mm coarse-grained modified aggregate, 1-3mm medium-grained modified aggregate, and 0.5-1mm fine-grained modified aggregate. The mass ratio of the coarse-grained modified aggregate, the medium-grained modified aggregate, and the fine-grained modified aggregate is 1:(0.5-1.2):(0.2-0.8). In step S6, the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers is added in two parts. The first addition is 40-70% of the total mass of the low-shrinkage aluminosilicate matrix slurry containing exhaust fibers, and the second addition is the remaining low-shrinkage aluminosilicate matrix slurry containing exhaust fibers.

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