A reusable firewall and its preparation method

Abstract

This invention relates to the field of refractory materials, and more particularly to a reusable fire barrier and its preparation method, comprising the following components by weight: 30-50 parts high-alumina bauxite, 40-50 parts silicon carbide, 10-15 parts alumina micropowder, 5-15 parts multilayer composite refractory material, 5-10 parts aluminum dihydrogen phosphate, 3-8 parts silicon carbide fiber, 2-5 parts nano-alumina, and 1-3 parts boron carbide. The surface layer of the multilayer composite refractory material is a glass phase change material, the middle layer includes boron carbide microcapsules and a metal-based phase change material, and the inner layer is a ceramic-based phase change material. The phase change material and the boron carbide microcapsule system form a synergistic mechanism of temperature gradient response and multi-scale repair, significantly improving the fire barrier's self-healing ability and service life under extreme high temperatures, thus achieving reusability, high-temperature stability, and self-healing capability of the refractory material. In addition, the mass ratio of boron carbide microcapsules in the middle layer to metal-based phase change material is 7:3, in which the unencapsulated nickel-based alloy is used to deal with mild damage, while the nickel-based alloy inside the microcapsules is used to deal with severe damage, enabling the firewall to be reused multiple times.

Description

Technical Field

[0001] This invention relates to the field of fire resistance, and in particular to a reusable fire barrier and its preparation method. Background Technology

[0002] Refractory materials, with their ultra-high refractoriness of no less than 1580℃ and stable physicochemical properties under high-temperature environments, are widely used in the manufacture of structural materials for high-temperature kilns and thermal equipment, as well as industrial high-temperature containers and components, providing crucial support for national construction and industrial development. However, existing refractory materials generally suffer from the problem of not being reusable. After repeated use, refractory materials are prone to cracking, spalling, or deformation due to high-temperature thermal and mechanical stress, leading to a significant decrease in their thermal insulation and refractoriness, thereby shortening their service life and increasing maintenance costs.

[0003] Currently, some technologies have attempted to improve the performance of refractory materials by adding reinforcing fibers. For example, the patented technology "Fiber-reinforced Refractory Castable and its Preparation Method" (CN202211452504.8) proposes adding metallic aluminum fibers or magnesium-aluminum alloy fibers to refractory castables to improve the mechanical toughness of the material. However, this method has limited effect on improving mechanical toughness and is difficult to significantly reduce the damage rate of refractory products. Another patented technology, "Ceramic Fiber Refractory Castable and its Preparation Method" (CN201910073196.X), enhances the performance of refractory castables by introducing stainless steel fibers. However, stainless steel fibers are easily oxidized at high temperatures to form oxides such as FeO, Fe2O3, and Fe3O4, leading to a decrease in material strength and volume expansion, which in turn damages the structural stability of the material. At the same time, the presence of iron oxide also significantly reduces the refractoriness of the refractory material.

[0004] In summary, existing technologies cannot fundamentally solve the problem of reusable refractory materials. Therefore, developing a fire barrier with excellent mechanical toughness, high-temperature stability, and reusability has significant practical importance and application value. This invention aims to provide an innovative fire barrier design and its preparation method to overcome the shortcomings of existing technologies and meet the urgent industrial demand for high-performance refractory materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a reusable fire wall and its preparation method. By introducing a multi-layered composite refractory material, a fire wall with excellent mechanical toughness, high-temperature stability, and reusability is ultimately obtained.

[0006] The specific technical solution of the present invention is as follows:

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a reusable fire wall, comprising the following components by weight: 30-50 parts of high-alumina bauxite, 40-50 parts of silicon carbide, 10-15 parts of alumina micro powder, 5-15 parts of multi-layer composite refractory material, 5-10 parts of aluminum dihydrogen phosphate, 3-8 parts of silicon carbide fiber, 2-5 parts of nano-alumina, and 1-3 parts of boron carbide.

[0008] Furthermore, the high-alumina bauxite contains Al2O3 ≥ 85wt%, and the alumina micro powder with D50 ≤ 5μm contains Al2O3 ≥ 98wt%.

[0009] Furthermore, the silicon carbide contains 30% coarse particles with a diameter of 1–3 mm, 40% medium particles with a diameter of 0.1–1 mm, 25% fine particles with a diameter of 0.01–0.1 mm, and 5% micro powder with a diameter of less than 10 μm.

[0010] Furthermore, the silicon carbide fibers have a diameter of 0.02–0.1 mm and a length of 0.5–1 mm, while the nano-alumina has a diameter of 20–50 nm.

[0011] Furthermore, the multilayer composite refractory material includes microcapsules, metal-based phase change materials, ceramic-based phase change materials, and glass phase change materials. The outer layer is a high borosilicate glass phase change material, the middle layer includes boron carbide microcapsules and nickel-based alloy (Ni-Cr-Co) metal-based phase change materials, and the inner layer is a zirconium boride-silicon carbide (ZrB2-SiC) ceramic-based phase change material.

[0012] Furthermore, the shell material of the microcapsule is boron carbide, and the core repair agent is a nickel-based alloy.

[0013] Because fire walls develop cracks, peeling, and deformation after repeated use, leading to a decrease in heat insulation and fire resistance, this invention employs refractory materials with self-healing capabilities. When cracks appear in the material, a repair agent is released and fills the cracks, automatically repairing micro-cracks at high temperatures. Furthermore, the self-healing mechanism of carbide shell microcapsules is combined with various phase change materials to form a composite self-healing system, further improving the repair effect and reliability.

[0014] Each layer of the multi-layered composite structure has a different function. When the upper layer is damaged, the lower layer material repairs itself through thermal activation or chemical reaction. The first repair stage (800–1000℃): The glass phase change material melts, filling microcracks and sealing the surface to prevent oxygen penetration. The second repair stage (1200–1400℃): Microcapsules rupture, releasing a nickel-based alloy that flows into the cracks. Simultaneously, the metal-based phase change material melts and combines with the alloy to form a metal-ceramic composite repair layer. The third repair stage (>1600℃): The ceramic-based phase change material partially melts, repairing deep cracks and enhancing stability in high-temperature areas. The phase change material and the boron carbide microcapsule system form a synergistic mechanism of temperature gradient response and multi-scale repair, significantly improving the self-repair capability and service life of the firewall under extreme high temperatures.

[0015] The preparation method of multilayer composite refractory materials specifically includes the following steps:

[0016] (1) Preparation of microcapsules: 10-20 μm boron carbide is coated on the surface of nickel-based alloy particles by electrostatic spraying, and then high-temperature sintering is carried out to form a boron carbide shell layer to obtain microcapsules;

[0017] (2) Raw material pretreatment: High borosilicate, nickel-based alloy and zirconium carbide-silicon carbide ball milling were respectively wet ball milled, dried and sieved. The sieved nickel-based alloy and boron carbide microcapsules were mixed evenly at a mass ratio of 3:7 to obtain the powder required to form the surface, middle and inner layers of the multi-layer composite refractory material.

[0018] (3) Centrifugal rotation molding: First, inject the inner layer of zirconium boride-silicon carbide ceramic matrix material into the rotating mold, and centrifuge at 500-1000 rpm to make it evenly adhere to the inner wall of the mold, forming an inner layer of 0.5-1 mm. After the inner layer has been initially solidified for 5-10 min, inject the middle layer of boron carbide microcapsules and nickel-based alloy mixture, and keep the centrifugal speed constant to form a middle layer of 1-2 mm. Finally, inject the high borosilicate glass phase, and centrifuge at a low speed of 200-300 rpm to smooth the surface layer, forming a surface layer of 0.5-1 mm, and obtain a dense multi-layer composite refractory green body;

[0019] (4) Segmented sintering:

[0020] Low-temperature pre-sintering: The multi-layer composite refractory green obtained in step (3) is sintered in a nitrogen stream at 500-600℃ (heating rate 2℃ / min) for 1-2 hours; medium-temperature sintering: sintered in a mixed stream of argon and hydrogen with a volume ratio of 20:1 at 1000-1200℃ (heating rate 5℃ / min) for 0.5-1 hours; high-temperature densification: sintered in a vacuum at 1500-1600℃ (heating rate 10℃ / min) for 2-3 hours.

[0021] (5) Post-processing: The green body of the multi-layer composite refractory obtained in step (4) is coated with a silicon carbide coating with a thickness of 50-100 μm, and sintered at 1200-1400℃ for 1.5-2h in a mixed gas flow of methyltrichlorosilane and hydrogen with a volume ratio of 5:2. Then, after 3 thermal cycles, room temperature → 500℃ → water cooling, the multi-layer composite refractory can be obtained.

[0022] Furthermore, in step (2), the ball milling time for wet ball milling is 8 to 12 hours, and the rotation speed is 300 to 500 r / min.

[0023] Furthermore, the nickel-based alloy spherical particles in steps (1) and (2) all have a diameter of 50–100 μm.

[0024] The sintering process of this multi-layered composite refractory material achieves multi-scale structural synergistic optimization through gradient temperature control: First, in the low-temperature pre-sintering stage at 500–600℃, the surface softening of glass particles induces particle rearrangement to eliminate forming stress and penetrates into the pores of the intermediate layer to form a 5–10 μm mechanical anchoring structure, while simultaneously activating the active sites on the microcapsule surface; subsequently, during the medium-temperature sintering process at 1000–1200℃, the nickel-based alloy microcapsules partially melt and form a continuous repair network with the metal-based phase change material, significantly reducing porosity. The glass phase and the intermediate layer form an interdiffusion interface, significantly improving the strength of the multi-layered composite refractory material; after entering the high-temperature densification stage at 1500–1600℃, the zirconium boride-silicon carbide ceramic matrix material forms a three-dimensional network skeleton through a eutectic reaction, and the glass phase completely melts and penetrates into the intermediate layer, achieving deep chemical metallurgical bonding. Finally, through three cycles of 1200℃ water cooling, the difference in thermal expansion coefficients between the ceramic and glass phases induces residual compressive stress to inhibit crack propagation, while simultaneously activating the borate network structure of the glass phase and shortening the repair response time. This process significantly improves the high-temperature structural stability and self-healing efficiency of materials through temperature gradient control, interfacial metallurgical bonding, and stress field optimization, providing a reliable guarantee for long-life applications in extreme environments.

[0025] A method for preparing a reusable firewall specifically includes the following steps:

[0026] S1: Mix high-alumina bauxite, silicon carbide particles, alumina micro powder, silicon carbide fiber, nano alumina, and boron carbide evenly, and ball mill for 5-15 minutes to obtain aggregate;

[0027] S2: Add multi-layer composite refractory material and aluminum dihydrogen phosphate to the aggregate obtained in step S1, and ball mill for 5-15 minutes to obtain a mixture;

[0028] S3: Add water to the mixture obtained in step S2, stir evenly, pour into the mold, compact in layers, let stand, and demold to obtain the fire wall blank.

[0029] S4: Sinter the formed fire wall blank at 1200-1500℃ for 2-4 hours. After sintering, allow it to cool naturally to room temperature to obtain a reusable fire wall.

[0030] Furthermore, the ball milling speed in steps S1 and S2 is 200-300 rpm.

[0031] Furthermore, in step S3, the weight ratio of the mixture to water is 20:1 to 5.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention proposes a reusable firewall and its preparation method, comprising high-alumina bauxite, silicon carbide particles, alumina micropowder, multi-layer composite refractory material, aluminum dihydrogen phosphate, silicon carbide fiber, nano-alumina, and boron carbide. The multi-layer composite refractory material has a glass phase change material (GMT) as its outer layer, a middle layer comprising boron carbide microcapsules and a metal-based GMT, and an inner layer comprising a ceramic-based GMT. The GMT and the boron carbide microcapsule system form a synergistic mechanism of temperature gradient response and multi-scale repair, significantly improving the firewall's self-healing ability and service life under extreme high temperatures. This achieves reusability, high-temperature stability, and self-healing capability of the refractory material, making it suitable for extreme high-temperature scenarios such as steel metallurgy and aerospace. Furthermore, the mass ratio of the boron carbide microcapsules to the metal-based GMT in the middle layer is 7:3. The unencapsulated nickel-based alloy addresses minor damage, while the nickel-based alloy within the microcapsules addresses severe damage, enabling the firewall to be reused multiple times. Detailed Implementation

[0034] The technical solution of the present invention will be further described below through specific embodiments. Unless otherwise specified, the raw materials and equipment used in the present invention can be purchased from the market or are commonly used in the art. The methods in the embodiments are conventional methods in the art unless otherwise specified.

[0035] Example 1

[0036] A reusable fire barrier comprises the following components by weight: 30 parts high-alumina bauxite, 40 parts silicon carbide, 10 parts alumina micropowder, 5 parts multi-layer composite refractory material, 5 parts aluminum dihydrogen phosphate, 3 parts silicon carbide fiber, 2 parts nano-alumina, and 1 part boron carbide. The high-alumina bauxite contains ≥85% Al2O3, the alumina micropowder has a D50 ≤5μm and contains ≥98wt% Al2O3, the silicon carbide contains 30% coarse particles with a diameter of 1–3 mm, 40% medium particles with a diameter of 0.1–1 mm, 25% fine particles with a diameter of 0.01–0.1 mm, and 5% micropowder with a diameter less than 10 μm, the silicon carbide fiber has a diameter of 0.02 mm and a length of 0.5 mm, and the nano-alumina has a diameter of 20 nm.

[0037] The multi-layered composite refractory material comprises microcapsules, metal-based phase change materials, ceramic-based phase change materials, and glass phase change materials. The outer layer is a high-borosilicate glass phase change material with a thickness of 0.5 mm. The middle layer consists of boron carbide microcapsules and a nickel-based alloy (Ni-Cr-Co) metal-based phase change material. The inner layer is a zirconium boride-silicon carbide (ZrB2-SiC) ceramic-based phase change material. The shell material of the microcapsules is boron carbide with a thickness of 1 μm, and the core repair agent is a nickel-based alloy.

[0038] The preparation method of multi-layer composite refractory materials specifically includes the following steps:

[0039] (1) Preparation of microcapsules: 10μm boron carbide is coated on the surface of nickel-based alloy particles with a diameter of 50μm by electrostatic spraying, and then high-temperature sintering is carried out to form a boron carbide shell to obtain microcapsules.

[0040] (2) Raw material pretreatment: High borosilicate, nickel-based alloy and zirconium boride-silicon carbide ball mills were respectively wet ball milled at a speed of 300 r / min for 8 h, then dried and sieved. The nickel-based alloy with a diameter of 50 μm after sieving was mixed with boron carbide microcapsules at a mass ratio of 3:7 to obtain the powder required to form the surface, middle and inner layers of the multilayer composite refractory material.

[0041] (3) Centrifugal rotation molding: First, inject the inner layer of zirconium boride-silicon carbide ceramic matrix material into the rotating mold, and centrifuge at 500 rpm to make it evenly adhere to the inner wall of the mold, forming an inner layer of 0.5 mm. After the inner layer has been initially solidified for 5 min, inject the middle layer of boron carbide microcapsules and nickel-based alloy mixture, keep the centrifugal speed constant, and form a 1 mm middle layer. Finally, inject the high borosilicate glass phase, and centrifuge at 200 rpm to make the surface smooth, forming a 0.5 mm surface layer, and obtain a dense multi-layer composite refractory green body;

[0042] (4) Segmented sintering:

[0043] Low-temperature pre-sintering: The multi-layer composite refractory green obtained in step (3) is sintered at 500℃ (heating rate 2℃ / min) in a nitrogen flow for 1 h; medium-temperature sintering: sintered at 1000℃ (heating rate 5℃ / min) in a mixed flow of argon and hydrogen with a volume ratio of 20:1 for 0.5 h; high-temperature densification: sintered at 1500℃ (heating rate 10℃ / min) in a vacuum for 2 h.

[0044] (5) Post-processing: The green body of the multi-layer composite refractory obtained in step (4) is coated with a silicon carbide coating with a thickness of 50 μm, and sintered at 1200 °C for 1.5 h in a mixed gas flow of methyltrichlorosilane and hydrogen with a volume ratio of 5:2. Then, after 3 thermal cycles, room temperature → 500 °C → water cooling, the multi-layer composite refractory can be obtained.

[0045] A method for preparing a reusable firewall specifically includes the following steps:

[0046] S1: Mix high-alumina bauxite, silicon carbide particles, alumina micro powder, silicon carbide fiber, nano alumina, and boron carbide evenly, and ball mill at 200 rpm for 5 minutes to obtain aggregate;

[0047] S2: Add multi-layer composite refractory material and aluminum dihydrogen phosphate to the aggregate obtained in step S1, and ball mill for 5 minutes to obtain a mixture;

[0048] S3: Add water to the mixture obtained in step S2. The weight ratio of the mixture to water is 20:1. After stirring evenly, pour it into the mold, compact it in layers, let it stand, and demold to obtain the fire wall blank.

[0049] S4: The formed fire wall blank is sintered at 1200℃ for 2 hours. After sintering, it is naturally cooled to room temperature to obtain a reusable fire wall.

[0050] Example 2

[0051] A reusable fire barrier comprises the following components by weight: 50 parts high-alumina bauxite, 50 parts silicon carbide, 15 parts alumina micropowder, 15 parts multi-layer composite refractory material, 10 parts aluminum dihydrogen phosphate, 8 parts silicon carbide fiber, 5 parts nano-alumina, and 3 parts boron carbide. The high-alumina bauxite contains ≥85% Al2O3, the alumina micropowder has a D50 ≤5μm and contains ≥98wt% Al2O3, the silicon carbide contains 30% coarse particles with a diameter of 1–3 mm, 40% medium particles with a diameter of 0.1–1 mm, 25% fine particles with a diameter of 0.01–0.1 mm, and 5% micropowder with a diameter less than 10 μm, the silicon carbide fiber has a diameter of 0.1 mm and a length of 1 mm, and the nano-alumina has a diameter of 50 nm.

[0052] The multi-layered composite refractory material comprises microcapsules, metal-based phase change materials, ceramic-based phase change materials, and glass phase change materials. The outer layer is a high-borosilicate glass phase change material with a thickness of 1 mm. The middle layer consists of boron carbide microcapsules and a nickel-based alloy (Ni-Cr-Co) metal-based phase change material. The inner layer is a zirconium boride-silicon carbide (ZrB2-SiC) ceramic-based phase change material. The shell material of the microcapsules is boron carbide with a thickness of 5 μm, and the core repair agent is a nickel-based alloy.

[0053] The preparation method of multilayer composite refractory materials specifically includes the following steps:

[0054] (1) Preparation of microcapsules: 20μm boron carbide is coated on the surface of nickel-based alloy particles with a diameter of 100μm by electrostatic spraying, and then high-temperature sintering is carried out to form a boron carbide shell to obtain microcapsules;

[0055] (2) Raw material pretreatment: High borosilicate, nickel-based alloy and zirconium boride-silicon carbide ball mills were respectively subjected to wet ball milling at a speed of 500 r / min for 12 h, then dried and sieved. The nickel-based alloy with a diameter of 100 μm after sieving was mixed with boron carbide microcapsules at a mass ratio of 3:7 to obtain the powder required to form the surface, middle and inner layers of the multi-layer composite refractory material.

[0056] (3) Centrifugal rotation molding: First, inject the inner layer of zirconium boride-silicon carbide ceramic matrix material into the rotating mold, centrifuge at 1000 rpm to make it evenly adhere to the inner wall of the mold, forming a 1 mm inner layer. After the inner layer has been initially solidified for 10 min, inject the middle layer of boron carbide microcapsules and nickel-based alloy mixture, keep the centrifugal speed constant, and form a 2 mm middle layer. Finally, inject the high borosilicate glass phase, centrifuge at 300 rpm to make the surface smooth, forming a 1 mm surface layer, and obtain a dense refractory green body.

[0057] (4) Segmented sintering:

[0058] Low-temperature pre-sintering: The multi-layer composite refractory green obtained in step (3) is sintered at 600℃ (heating rate 2℃ / min) in a nitrogen flow for 2 hours. Medium-temperature sintering: Sintered at 1200℃ (heating rate 5℃ / min) in a mixed flow of argon and hydrogen with a volume ratio of 20:1 for 1 hour. High-temperature densification: Sintered at 1600℃ (heating rate 10℃ / min) in a vacuum for 3 hours.

[0059] (5) Post-processing: The green body of the multi-layer composite refractory obtained in step (4) is coated with a silicon carbide coating with a thickness of 100 μm, and sintered at 1400 °C for 2 h in a mixed gas flow of methyltrichlorosilane and hydrogen with a volume ratio of 5:2. Then, after 3 thermal cycles, room temperature → 500 °C → water cooling, the multi-layer composite refractory can be obtained.

[0060] A method for preparing a reusable firewall specifically includes the following steps:

[0061] S1: Mix high-alumina bauxite, silicon carbide particles, alumina micro powder, silicon carbide fiber, nano alumina, and boron carbide evenly, and ball mill at 300 rpm for 15 minutes to obtain aggregate;

[0062] S2: Add multi-layer composite refractory material and aluminum dihydrogen phosphate to the aggregate obtained in step S1, and ball mill for 15 minutes to obtain a mixture;

[0063] S3: Add water to the mixture obtained in step S2. The weight ratio of the mixture to water is 4:1. After stirring evenly, pour it into the mold, compact it in layers, let it stand, and demold to obtain the fire wall blank.

[0064] S4: The formed fire wall blank is sintered at 1500℃ for 4 hours. After sintering, it is naturally cooled to room temperature to obtain a reusable fire wall.

[0065] Example 3

[0066] A reusable fire barrier comprises the following components by weight: 40 parts high-alumina bauxite, 45 parts silicon carbide, 12 parts alumina micropowder, 10 parts multi-layer composite refractory material, 8 parts aluminum dihydrogen phosphate, 5 parts silicon carbide fiber, 3 parts nano-alumina, and 2 parts boron carbide. The high-alumina bauxite contains ≥85% Al2O3, the alumina micropowder has a D50 ≤5μm and contains ≥98wt% Al2O3, the silicon carbide contains 30% coarse particles with a diameter of 1–3 mm, 40% medium particles with a diameter of 0.1–1 mm, 25% fine particles with a diameter of 0.01–0.1 mm, and 5% micropowder with a diameter less than 10 μm, the silicon carbide fiber has a diameter of 0.06 mm and a length of 0.8 mm, and the nano-alumina has a diameter of 35 nm.

[0067] The multi-layered composite refractory material comprises microcapsules, metal-based phase change materials, ceramic-based phase change materials, and glass phase change materials. The outer layer is a high-borosilicate glass phase change material with a thickness of 0.75 mm. The middle layer consists of boron carbide microcapsules and a nickel-based alloy (Ni-Cr-Co) metal-based phase change material. The inner layer is a zirconium boride-silicon carbide (ZrB2-SiC) ceramic-based phase change material. The shell material of the microcapsules is boron carbide with a thickness of 3 μm, and the core repair agent is a nickel-based alloy.

[0068] The preparation method of multilayer composite refractory materials specifically includes the following steps:

[0069] (1) Preparation of microcapsules: 15μm boron carbide is coated on the surface of nickel-based alloy particles with a diameter of 75μm by electrostatic spraying, and then high-temperature sintering is carried out to form a boron carbide shell layer to obtain microcapsules.

[0070] (2) Raw material pretreatment: High borosilicate, nickel-based alloy and zirconium carbide-silicon carbide ball mills were respectively wet ball milled at a speed of 400 r / min for 10 h, then dried and sieved. The nickel-based alloy with a diameter of 75 μm after sieving was mixed with boron carbide microcapsules at a mass ratio of 3:7 to obtain the powder required to form the surface, middle and inner layers of the multi-layer composite refractory material.

[0071] (3) Centrifugal rotation molding: First, inject the inner layer of zirconium boride-silicon carbide ceramic matrix material into the rotating mold, and centrifuge at 750 rpm to make it evenly adhere to the inner wall of the mold, forming an inner layer of 0.75 mm. After the inner layer has been initially solidified for 7.5 min, inject the middle layer of boron carbide microcapsules and nickel-based alloy mixture, and keep the centrifugal speed constant to form a middle layer of 1.5 mm. Finally, inject the high borosilicate glass phase, and centrifuge at a low speed of 250 rpm to make the surface smooth, forming a surface layer of 0.75 mm, and obtain a dense multi-layer composite refractory green body;

[0072] (4) Segmented sintering:

[0073] Low-temperature pre-sintering: The multi-layer composite refractory green obtained in step (3) is sintered at 550℃ (heating rate 2℃ / min) in a nitrogen flow for 1.5h; medium-temperature sintering: sintered at 1100℃ (heating rate 5℃ / min) in a mixed flow of argon and hydrogen with a volume ratio of 20:1 for 0.75h; high-temperature densification: sintered at 1550℃ (heating rate 10℃ / min) under vacuum for 2.5h.

[0074] (5) Post-processing: The green body of the multi-layer composite refractory obtained in step (4) is coated with a silicon carbide coating with a thickness of 75 μm, and sintered at 1300°C for 1.75 h in a mixed gas flow of methyltrichlorosilane and hydrogen with a volume ratio of 5:2. Then, after 3 thermal cycles, room temperature → 500°C → water cooling, the multi-layer composite refractory can be obtained.

[0075] A method for preparing a reusable firewall specifically includes the following steps:

[0076] S1: Mix high-alumina bauxite, silicon carbide particles, alumina micro powder, silicon carbide fiber, nano alumina, and boron carbide evenly, and ball mill at 250 rpm for 10 min to obtain aggregate;

[0077] S2: Add multi-layer composite refractory material and aluminum dihydrogen phosphate to the aggregate obtained in step S1, and ball mill for 10 minutes to obtain a mixture;

[0078] S3: Add water to the mixture obtained in step S2. The weight ratio of the mixture to water is 20:3. After stirring evenly, pour it into the mold, compact it in layers, let it stand, and demold to obtain the fire wall blank.

[0079] S4: The formed fire wall blank is sintered at 1350℃ for 3 hours. After sintering, it is naturally cooled to room temperature to obtain a reusable fire wall.

[0080] Comparative Example 1

[0081] The difference between Comparative Example 1 and Example 3 is that the multilayer composite refractory material lacks an intermediate layer.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 3 is that the multilayer composite refractory material lacks an inner layer.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 3 is that the microcapsules in the middle layer of the multilayer composite refractory material are directly replaced with nickel-based alloys with the shell removed.

[0086] Test results:

[0087] 1. The six samples obtained from the examples and comparative examples were subjected to fire resistance tests, compressive strength tests and thermal shock resistance tests according to ISO1893, GB / T3002-2017 and ISO10545-11, respectively. The results are shown in Table 1 below.

[0088] 2. The crack repair efficiency of the six samples obtained from the examples and comparative examples was tested.

[0089] Detection method: In-situ observation with high temperature microscope: A 1mm crack was pre-fabricated at 1200℃, and the repair time and filling effect were recorded. The results are shown in Table 1 below.

[0090] 3. Reusability testing

[0091] Testing method: Simulate actual working conditions (1200℃→room temperature cycle), record the number of times the material was used before failure, and test indicators such as compressive strength and repair efficiency after every 5 cycles.

[0092] Table 1 shows the performance test results of the firewalls obtained in the embodiments and comparative examples.

[0093] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Refractoriness (°C) ≥1750 ≥1750 ≥1750 ≥1700 ≤1600 ≥1700 Compressive strength (1600℃) ≥60MPa ≥60MPa ≥60MPa ≤40MPa ≤50MPa ≤30MPa Thermal shock resistance (strength retention rate) ≥90％ ≥90％ ≥90％ ≤60％ ≤70％ ≤50％ Self-healing efficiency (1mm crack) ≥95％ ≥95％ ≥95％ ≤30％ ≤50％ ≤60％ Antioxidant properties (mass loss) ≤1％ ≤1％ ≤1％ ≤3％ ≤5％ ≥5％ Number of times to reuse ≥10 times ≥10 times ≥10 times ≤5 times ≤6 times ≤3 times

[0094] As shown in Table 1, the synergistic effect of the surface, middle, and inner layers of the multi-layer composite refractory material significantly improves high-temperature stability and repair efficiency through the above-mentioned test items. Furthermore, the microcapsules, through their boron carbide shell, protect the repair agent from oxidation and enable on-demand release, showing a significantly better effect compared to Comparative Example 3. In contrast, due to the necessity of the process, the absence of any layer in Comparative Examples 1 and 2 resulted in a substantial performance decline, demonstrating the irreplaceable nature of the multi-layer design.

[0095] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A reusable firewall, characterized in that, It includes the following components by weight: 30-50 parts of high-alumina bauxite, 40-50 parts of silicon carbide, 10-15 parts of alumina micro powder, 5-15 parts of multi-layer composite refractory material, 5-10 parts of aluminum dihydrogen phosphate, 3-8 parts of silicon carbide fiber, 2-5 parts of nano alumina, and 1-3 parts of boron carbide. The multi-layered composite refractory material includes microcapsules, metal-based phase change materials, ceramic-based phase change materials, and glass phase change materials. The outer layer is a high borosilicate glass phase change material, the middle layer includes boron carbide microcapsules and nickel-based alloy metal-based phase change materials, and the inner layer is a zirconium boride-silicon carbide ceramic-based phase change material.

2. The reusable fire barrier according to claim 1, characterized in that, The high-alumina bauxite contains Al2O3 ≥ 85wt%, alumina micro powder D50 ≤ 5μm containing Al2O3 ≥ 98wt%, silicon carbide contains 30% coarse particles with a diameter of 1-3mm, 40% medium particles with a diameter of 0.1-1mm, 25% fine particles with a diameter of 0.01-0.1mm, and 5% micro powder with a diameter of less than 10μm, silicon carbide fibers with a diameter of 0.02-0.1mm and a length of 0.5-1mm, and nano-alumina with a diameter of 20-50nm.

3. A reusable fire barrier according to claim 1, characterized in that, The shell material of the microcapsule is boron carbide, and the core repair agent is a nickel-based alloy.

4. A reusable fire barrier according to claim 1, characterized in that, The preparation method of the multi-layer composite refractory material specifically includes the following steps: (1) Preparation of microcapsules: 10-20 μm boron carbide is coated on the surface of nickel-based alloy particles by electrostatic spraying, and then high-temperature sintering is carried out to form a boron carbide shell layer to obtain microcapsules; (2) Raw material pretreatment: High borosilicate, nickel-based alloy and zirconium boride-silicon carbide ball mill were wet ball milled, dried and sieved. The sieved nickel-based alloy and boron carbide microcapsules were mixed evenly at a mass ratio of 3:7 to obtain the powder required to form the surface, middle and inner layers of the multi-layer composite refractory material. (3) Centrifugal rotation molding: First, inject the inner layer of zirconium boride-silicon carbide ceramic matrix material into the rotating mold, and centrifuge at 500-1000 rpm to make it evenly adhere to the inner wall of the mold, forming an inner layer of 0.5-1 mm. After the inner layer has been initially solidified for 5-10 min, inject the mixture of microcapsules and nickel-based alloy, keep the centrifugal speed constant, and form an intermediate layer of 1-2 mm. Finally, inject the high borosilicate glass phase, and centrifuge at a low speed of 200-300 rpm to make the surface smooth, forming a surface layer of 0.5-1 mm, and obtain a dense multi-layer composite refractory green body; (4) Segmented sintering: Low-temperature pre-firing: The multi-layer composite refractory green obtained in step (3) is sintered in a nitrogen stream at 500-600℃ with a heating rate of 2℃ / min for 1-2 hours. Medium-temperature sintering: In a mixed stream of argon and hydrogen with a volume ratio of 20:1, the green is sintered at 1000-1200℃ with a heating rate of 5℃ / min for 0.5-1 hours. High-temperature densification: Under vacuum, the green is sintered at 1500-1600℃ with a heating rate of 10℃ / min for 2-3 hours. (5) Post-processing: The green body of the multi-layer composite refractory obtained in step (4) is coated with a silicon carbide coating with a thickness of 50-100 μm, and sintered at 1200-1400℃ for 1.5-2h in a mixed gas flow of methyltrichlorosilane and hydrogen with a volume ratio of 5:

2. Then, after 3 thermal cycles, room temperature → 500℃ → water cooling, the multi-layer composite refractory can be obtained.

5. A reusable fire barrier according to claim 4, characterized in that, In step (2), the wet ball milling time is 8 to 12 hours and the rotation speed is 300 to 500 r / min.

6. A reusable firewall according to claim 4, characterized in that, The nickel-based alloy spherical particles in steps (1) and (2) have a diameter of 50–100 μm.

7. A method for preparing a reusable firewall according to any one of claims 1 to 6, characterized in that, The method includes the following steps: S1: Mix high-alumina bauxite, silicon carbide particles, alumina micro powder, silicon carbide fiber, nano alumina, and boron carbide evenly, and ball mill for 5-15 minutes to obtain aggregate; S2: Add multi-layer composite refractory material and aluminum dihydrogen phosphate to the aggregate obtained in step S1, and ball mill for 5-15 minutes to obtain a mixture; S3: Add water to the mixture obtained in step S2, stir evenly, pour into the mold, compact in layers, let stand, and demold to obtain the fire wall blank. S4: Sinter the formed fire wall blank at 1200-1500℃ for 2-4 hours. After sintering, allow it to cool naturally to room temperature to obtain a reusable fire wall.

8. The method for preparing a reusable firewall according to claim 7, characterized in that, In steps S1 and S2, the ball milling speed is 200-300 rpm.

9. The method for preparing a reusable firewall according to claim 7, characterized in that, In step S3, the weight ratio of the mixture to water is 20:1 to 5.