Lightweight zirconia microporous foam ceramic refractory material and method for preparing the same

Abstract

The present application belongs to the technical field of heat-insulating refractory material, and particularly relates to a light-weight zirconia microporous foam ceramic refractory material and a preparation method thereof. The refractory material is prepared from yttrium-stabilized zirconia powder as a main aggregate, high-purity zirconia long fibers as a reinforcing phase, nano-zirconia sol as a binder, starch as an auxiliary pore-forming agent, a composite foaming agent composed of sodium dodecyl sulfate and alkyl polyglycoside, sodium carboxymethyl cellulose as a foam stabilizer, polyethylene glycol as a dispersant, and magnesium oxide as a sintering aid. The present application successfully prepares zirconia foam ceramic with ultra-low density, microporous closed structure, high strength and excellent ultra-high temperature heat-insulating performance by optimizing the slurry system and rheological properties, combining mechanical stirring direct foaming and in-situ solidification integrated molding technology. The present application has simple process, is green and environmentally friendly, and has strong raw material adaptability, and solves the technical problems of the prior art, such as difficulty in achieving light weight and high strength, difficulty in pore structure regulation, and low production efficiency, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of heat-insulating and refractory materials, specifically relating to a lightweight zirconia microporous foam ceramic refractory material and its preparation method. Background Technology

[0002] Zirconia foam ceramics are a class of special ceramic materials with a three-dimensional network framework and a porous structure. Due to zirconia's high melting point (above 2700℃), its lowest thermal conductivity among metal oxides, and its stable chemical properties, it has broad application prospects in ultra-high temperature thermal insulation. Currently, the mainstream methods for preparing zirconia foam ceramics mainly include organic foam impregnation, the addition of pore-forming agents, and the sol-gel method.

[0003] The organic foam impregnation method uses organic foams such as polyurethane as templates, impregnating them in zirconia ceramic slurry. After removing excess slurry by extrusion, the product is dried and sintered. This method is simple and low-cost, and can produce open-cell foam ceramics with high porosity. However, it can only produce open-cell structures and is difficult to obtain closed-cell structures, which are crucial for reducing heat conduction. Furthermore, the compatibility and adhesion between water-based ceramic slurry and organic foam templates are poor, resulting in uneven slurry coating and insufficient slurry amount. The sintered foam ceramics have many pore wall defects, low mechanical properties, and poor thermal shock resistance. At the same time, the shrinkage rate during sintering is large, making cracking easy.

[0004] The pore-forming agent addition method involves adding a certain proportion of pore-forming agent to a zirconia matrix, followed by high-temperature calcination to decompose the pore-forming agent and leave pores, thus producing foam ceramics. This process is simple, and the size and shape of the pores can be controlled. However, the uniformity of pore distribution is poor, the pore structure is difficult to control precisely, and it often requires mold pressing, limiting its ability to prepare complex-shaped products. The amount of pore-forming agent added is also limited, making it difficult to obtain ultra-high porosity.

[0005] The sol-gel method utilizes the pores formed by particle accumulation during the sol-to-gel conversion process, and obtains porous ceramics after heat treatment. It is suitable for preparing microporous materials and thin film materials. The process is relatively simple and the processing temperature is low, but the raw materials are limited and the production efficiency is low.

[0006] From a broader perspective, existing zirconia insulation products still present a dilemma: achieving both lightweight and high strength simultaneously is difficult. While heavy zirconia refractory bricks have high strength, they are also high in density and have poor insulation properties; while zirconia fiber products have low density and good insulation, they are also low in strength and have poor resistance to corrosion.

[0007] Although some technologies attempt to improve this problem through fiber reinforcement and other means, how to obtain high mechanical properties while maintaining low density and microporous structure remains a technical bottleneck that urgently needs to be overcome in this field. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a lightweight zirconia microporous foam ceramic refractory material, which solves the problems of poor foam stability, uneven pore structure, insufficient mechanical properties, easy collapse at high temperature, complex process, environmental pollution, and stringent raw material requirements and narrow process window in the prior art.

[0009] The technical solution of this invention is: a lightweight zirconia microporous foam ceramic refractory material, composed of the following raw materials in the indicated mass percentages: 60-80% yttrium-stabilized zirconia powder, 5-10% high-purity zirconia long fibers, 10-15% water, 5-10% nano-zirconia sol, 3-5% starch, 0.5-1% composite foaming agent, 0.1-0.5% thickening and stabilizing agent, 1-2% ceramic dispersant, and 0.1-0.5% magnesium oxide.

[0010] Preferably, the composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycoside in a mass ratio of 1:1-3.

[0011] Preferably, the yttrium oxide content in the yttrium-stabilized zirconium oxide powder is 3-5 mol%, and the powder particle size is 1-5 μm.

[0012] Preferably, the high-purity zirconia long fibers have a diameter of 2-4 μm, a length of 1-3 mm, and a zirconia content of not less than 99.8%.

[0013] Preferably, the solid content of the nano-zirconium sol is 30-40%, and the zirconium oxide particle size is 10-50 nm.

[0014] Preferably, the thickening and foaming agent is sodium carboxymethyl cellulose, the ceramic dispersant is polyethylene glycol, and the starch is corn starch or tapioca starch.

[0015] To better realize the present invention, another technical solution is also provided: a method for preparing a lightweight zirconia microporous foam ceramic refractory material, comprising the following steps: first, high-purity zirconia long fibers are sheared and pretreated; then, yttrium-stabilized zirconia powder, pretreated high-purity zirconia long fibers, nano-zirconia sol, starch, composite foaming agent, thickening and stabilizing agent, ceramic dispersant, magnesium oxide and water are mixed in proportion and mechanically stirred to form a foam slurry; the foam slurry is poured into a mold and allowed to stand and solidify to form a wet blank; then, the wet blank is subjected to gradient drying treatment; and finally, the product is obtained by high-temperature sintering.

[0016] Preferably, the mechanical stirring speed is 800-2000 rpm and the stirring time is 2-5 min.

[0017] Preferably, the static curing time is 1-3 hours and the curing temperature is room temperature.

[0018] Preferably, the gradient drying process is as follows: first, dry at 60°C for 24 hours, then raise the temperature to 80°C and dry for 24 hours, and finally raise the temperature to 100°C and dry for 24 hours.

[0019] Preferably, the high-temperature sintering process is as follows: the temperature is increased from room temperature to 600°C at a rate of 2-3°C / min, held for 1-2 hours, then increased to 1800°C at a rate of 3-5°C / min, held for 4 hours, and then naturally cooled to room temperature.

[0020] This invention achieves precise control of the pore structure of zirconia foam ceramics, a balance between mechanical and thermal insulation properties, and a green and efficient preparation process through multi-dimensional technological synergy. Its core mechanism is as follows: This invention employs an anionic / nonionic composite foaming agent composed of sodium dodecyl sulfate and alkyl glycosides, which exhibit a significant synergistic effect. Specifically, sodium dodecyl sulfate, as an anionic surfactant, can rapidly reduce the surface tension of liquids and generate a large number of initial bubbles. However, when used alone, it results in low foam film strength and is prone to bubble coalescence and Ostwald curing. Alkyl glycosides, as nonionic surfactants, contain multiple hydroxyl groups in their molecular structure, enabling them to form a dense adsorption film on the bubble surface, improving the elasticity and stability of the foam film. However, when used alone, their foaming ability is relatively weak. When combined, the two form a mixed adsorption layer on the bubble surface. The electrostatic repulsion between the anionic head groups and the steric hindrance effect of the nonionic head groups work synergistically to effectively prevent bubble coalescence and gas diffusion, significantly improving foam stability. Meanwhile, the thickening effect of sodium carboxymethyl cellulose gives the slurry suitable yield stress and viscosity, which can effectively encapsulate air bubbles and prevent them from rising. In addition, the adsorption effect of nano-zirconium sol particles on the surface of air bubbles further enhances the strength of the foam film, ultimately achieving a uniform microporous structure with a pore size between 10-100μm and a closed-cell rate of over 65%.

[0021] This invention abandons the traditional organic template impregnation and pore-forming agent methods, employing a mechanical stirring direct foaming and in-situ curing integrated molding technology. Specifically, by controlling the speed and time of mechanical stirring, a large number of microbubbles are uniformly introduced into the slurry, forming stable wet foam. Subsequently, utilizing the sol-gel transition characteristics of nano-zirconium sol at room temperature, the zirconium oxide particles in the slurry cross-link with the nano-zirconium sol to form a three-dimensional gel network, rapidly locking the bubbles within the gel structure, achieving in-situ curing and shaping of the foam. This process eliminates the need for high-temperature desizing to remove the organic template and subsequent pore-opening treatment, simplifying the process, improving production efficiency, avoiding waste gas pollution from the decomposition of the organic template, and effectively solving the problems of large sintering shrinkage and easy cracking in traditional processes.

[0022] This invention constructs a multi-synergistic reinforcement system combining phase transformation toughening, sintering aid reinforcement, and fiber toughening. First, by adding 3-5 mol% yttrium oxide to stabilize tetragonal zirconia, the tetragonal zirconia transforms into a monoclinic phase under external force, accompanied by volume expansion, generating compressive stress that partially offsets tensile stress, thereby improving the material's fracture toughness. Second, adding a small amount of magnesium oxide as a sintering aid allows for the formation of a liquid phase at lower temperatures, promoting the sintering and densification of zirconia particles, improving grain boundary bonding strength, and thus enhancing the material's room-temperature mechanical properties and high-temperature stability. Finally, high-purity zirconia long fibers are introduced as a reinforcing phase. The fibers form a three-dimensional network structure in the matrix, consuming a large amount of fracture energy through mechanisms such as fiber bridging, fiber pull-out, and crack deflection, significantly improving the material's flexural strength and thermal shock resistance. The synergistic effect of these three components enables the material to achieve excellent mechanical properties and high-temperature performance while maintaining low density.

[0023] The beneficial effects of this invention are as follows: This invention eliminates the need for organic templates or large amounts of pore-forming agents, relying entirely on slurry foaming and direct sintering. This reduces the high-temperature exhaust gas emissions of organic foam impregnation methods and eliminates the need for post-treatment with pore-forming agents. The water vapor and small amounts of harmless gases emitted during sintering do not require special purification and can be produced using a gradient heating process. This results in low energy consumption, no pollution, and green and environmentally friendly production.

[0024] This invention optimizes the slurry formulation, introduces appropriate amounts of sintering aids and rheology modifiers, and relaxes the stringent requirements on raw material powder particle size, slurry solid content, etc., making the process more stable, easier to control, and more suitable for large-scale production.

[0025] The zirconia foam ceramic material prepared by this invention has a zirconia content of not less than 99.0%, can be used in a variety of sintering atmospheres, is resistant to high temperature and corrosion, has high strength, low density, high porosity and uniform microporous structure, and has excellent thermal insulation and mechanical properties. Compared with existing zirconia fiberboard, its strength is increased by more than 30% at the same density, and its thermal insulation performance is close, thus solving the technical problem of the difficulty in achieving both lightweight and high strength in the prior art. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 The low-magnification scanning electron microscope morphology of the lightweight zirconia microporous foam ceramic sample of this application; Figure 3 The low-magnification scanning electron microscope morphology of existing zirconia porous ceramic materials is shown. Detailed Implementation

[0027] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0028] Unless otherwise specified, the reagents used in the following examples and comparative examples are conventional reagents, which can be purchased from conventional reagent manufacturers and distributors. Unless otherwise specified, the methods used are existing technologies.

[0029] Example 1

[0030] This embodiment studies the effect of the mass ratio of composite foaming agent on product performance. The core parameter is the mass ratio of sodium dodecyl sulfate to alkyl glycoside, which is set to 1:1, 1:2 and 1:3 respectively.

[0031] Experimental Objective: The control group used a traditional organic foam impregnation method to prepare zirconia foam ceramics, eliminating the interference of raw material composition differences on performance test results. Based on identical raw materials, the performance differences between the direct foaming and in-situ curing integrated molding process of this invention and the existing mainstream organic foam impregnation method were directly compared. The experiment quantitatively verifies the effectiveness of the invention's process in addressing the inherent defects of the organic foam impregnation method, including the ability to control closed-cell structures, pore wall integrity, improvement in mechanical properties, degree of improvement in thermal insulation performance, and enhanced high-temperature stability. This demonstrates that the invention's process can overcome the technical bottleneck of the organic foam impregnation method, which can only produce open-cell structures, while simultaneously solving industry pain points such as uneven slurry application, large sintering shrinkage, and easy cracking.

[0032] Experimental Group: This embodiment provides a lightweight zirconia microporous foam ceramic refractory material, composed of the following raw materials by mass percentage: 70% yttrium-stabilized zirconia powder, 8% high-purity zirconia long fibers, 12% water, 6% nano-zirconia sol, 3% starch, 0.6% composite foaming agent, 0.2% sodium carboxymethyl cellulose, 1.5% polyethylene glycol, and 0.7% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a mass ratio of 1:2. The yttrium content in the yttrium-stabilized zirconia powder is 3 mol%, and the powder particle size is 2 μm. The diameter of the high-purity zirconia long fibers is 3 μm, the length is 2 mm, and the zirconia content is 99.8%. The solid content of the nano-zirconia sol is 35%, the zirconia particle size is 30 nm, and the starch is corn starch.

[0033] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 2 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, corn starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at 1500 rpm for 3 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand and solidify at room temperature for 2 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed: the temperature is increased from room temperature to 600℃ at a rate of 2℃ / min and held for 1.5 h, then increased to 1800℃ at a rate of 4℃ / min and held for 4 h. The material is then naturally cooled to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0034] Control group: Zirconia foam ceramics were prepared in the control group using the traditional organic foam impregnation method. The raw material composition was the same as in this embodiment, and the preparation process was carried out according to existing technology. The product performance of the experimental group and control group 1 in this embodiment was tested, and the test results are shown in Table 1.

[0035] Table 1. Performance Comparison between Experimental Group and Control Group 1 with Different Compound Foaming Agent Ratios As can be seen, under the same bulk density, the performance of all three experimental groups was significantly better than that of control group 1. Among them, experimental group 1-2, with a composite foaming agent mass ratio of 1:2, showed the best performance, with compressive strength and flexural strength increased by 50% and 66.7% respectively compared to control group 1, significantly reduced average pore size, greatly increased closed-cell rate, reduced thermal conductivity, smaller permanent linear change rate after reheating, and higher load softening temperature. Although the performance of experimental groups 1-1 and 1-3 was slightly lower than that of experimental group 1-2, it was still far superior to control group 1, indicating that the composite foaming agent mass ratio range defined by this invention can effectively improve product performance and has a wide process window, with a preferred mass ratio of 1:2.

[0036] Example 2

[0037] Experimental objective: To compare the overall performance of the present invention with that of the method of adding pore-forming agents, and to verify the advantages of the present invention in maintaining mechanical properties under high porosity, pore structure uniformity, ability to prepare complex shapes.

[0038] This embodiment studies the effect of yttrium oxide content in yttrium-stabilized zirconia powder on product performance. The core parameter is the molar content of yttrium oxide, which is set to 3 mol%, 4 mol%, and 5 mol, respectively.

[0039] The basic raw material composition of this embodiment is as follows: 65% yttrium-stabilized zirconia powder, 10% high-purity zirconia long fibers, 13% water, 7% nano-zirconia sol, 3.5% starch, 0.7% composite foaming agent, 0.3% sodium carboxymethyl cellulose, 1.2% polyethylene glycol, and 0.3% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a mass ratio of 1:1.5. The yttrium-stabilized zirconia powder has a particle size of 3 μm, the high-purity zirconia long fibers have a diameter of 2.5 μm and a length of 1.5 mm, with a zirconia content of 99.9%. The nano-zirconia sol has a solid content of 32% and a zirconia particle size of 20 nm. The starch is tapioca starch.

[0040] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 1.5 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, cassava starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at 1200 rpm for 4 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand at room temperature for 2.5 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed by heating from room temperature to 600℃ at a rate of 2.5℃ / min and holding for 1 h, then heating to 1800℃ at a rate of 3℃ / min and holding for 4 h, followed by natural cooling to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0041] Control group 2 was set up, and zirconia foam ceramics were prepared using the method of adding a pore-forming agent. The raw material composition was the same as the basic formula in this embodiment, and the preparation process was carried out according to existing technology. The product performance of the three experimental groups and control group 2 in this embodiment was tested, and the test results are shown in Table 2.

[0042] Table 2. Performance Comparison between Experimental Groups and Control Groups with Different Yttrium Oxide Content It can be seen that, under the same bulk density, the performance of all three experimental groups is significantly better than that of control group 2. Among them, experimental group 2-2, with a yttrium oxide content of 4 mol%, exhibits the best performance, with compressive strength and flexural strength increased by 77.1% and 90% respectively compared to control group 2. It also has a smaller average pore size, more uniform pore size distribution, a 29.2% reduction in thermal conductivity, a smaller rate of permanent linear change after reheating, and almost twice the number of thermal shock cycles compared to control group 2. Although the performance of experimental groups 2-1 and 2-3 is slightly lower than that of experimental group 2-2, it is still far superior to control group 2, indicating that the yttrium oxide content range defined in this invention can effectively stabilize tetragonal zirconia and exert a phase transformation toughening effect.

[0043] Example 3

[0044] Experimental objective: Using a blank control, this study aims to verify the toughening and reinforcing effect of high-purity zirconia long fibers, quantify their contribution to mechanical properties and thermal shock resistance, and verify that they do not significantly affect thermal insulation performance.

[0045] This embodiment studies the effect of the amount of high-purity zirconia long fiber added on product performance. The core parameter is the mass percentage of high-purity zirconia long fiber, which is set to 5%, 7.5% and 10%, respectively.

[0046] The basic raw material composition of this embodiment is as follows: 75% yttrium-stabilized zirconia powder, 11% water, 5% nano-zirconia sol, 2% starch, 0.5% composite foaming agent, 0.1% sodium carboxymethyl cellulose, 1.8% polyethylene glycol, and 0.6% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a mass ratio of 1:3. The yttrium content in the yttrium-stabilized zirconia powder is 5 mol%, the powder particle size is 1 μm, the diameter of the high-purity zirconia long fibers is 2 μm, the length is 1 mm, the zirconia content is 99.8%, the solid content of the nano-zirconia sol is 40%, the zirconia particle size is 10 nm, and the starch is corn starch.

[0047] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 1 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, corn starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at 2000 rpm for 2 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand at room temperature for 1 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed: the temperature is increased from room temperature to 600℃ at a rate of 3℃ / min and held for 2 h, then increased to 1800℃ at a rate of 5℃ / min and held for 4 h. The material is then naturally cooled to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0048] Control group 3 was set up, without the addition of high-purity zirconia long fibers, while the remaining raw material composition and preparation process were the same as the basic formula in this embodiment. The product performance of the three experimental groups and control group 3 in this embodiment was tested, and the test results are shown in Table 3.

[0049] Table 3. Performance Comparison between Experimental and Control Groups with Different Fiber Addition Amounts It is evident that, with essentially the same bulk density and thermal conductivity, the performance of all three experimental groups was significantly superior to that of control group 3. Experimental group 3-2, with a fiber content of 7.5%, exhibited the best performance, with compressive strength and flexural strength increased by 53.3% and 77.8% respectively compared to control group 3, fracture toughness increased by 75%, permanent linear variation rate after reheating was smaller, and thermal shock resistance increased by 80%. While the performance of experimental groups 3-1 and 3-3 was slightly lower than that of experimental group 3-2, it was still far superior to control group 3, indicating that the fiber content range defined in this invention can effectively exert the toughening effect of fibers without significantly reducing the thermal insulation performance of the material.

[0050] Example 4

[0051] Experimental objective: To verify the binding and reinforcing effect of nano-zirconium sol using a blank control, and to quantify its improvement effect on room temperature mechanical properties and high temperature stability.

[0052] This embodiment studies the effect of the amount of nano-zirconium sol added on product performance. The core parameter is the mass percentage of nano-zirconium sol, which is set to 5%, 7.5%, and 10%, respectively.

[0053] The basic raw material composition of this embodiment is as follows: 60% yttrium-stabilized zirconia powder, 9% high-purity zirconia long fibers, 14% water, 4% starch, 0.8% composite foaming agent, 0.4% sodium carboxymethyl cellulose, 1.0% polyethylene glycol, and 0.8% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a 1:1 mass ratio. The yttrium-stabilized zirconia powder contains 3.5 mol% yttrium oxide with a particle size of 4 μm. The high-purity zirconia long fibers have a diameter of 3.5 μm, a length of 2.5 mm, and a zirconia content of 99.9%. The nano-zirconia sol has a solid content of 30% and a zirconia particle size of 40 nm. The starch is tapioca starch.

[0054] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 2.5 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, cassava starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at 1000 rpm for 5 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand at room temperature for 3 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed: the temperature is increased from room temperature to 600℃ at a rate of 2℃ / min and held for 1.5 h, then increased to 1800℃ at a rate of 3.5℃ / min and held for 4 h. The material is then naturally cooled to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0055] Control group 4 was set up, without the addition of nano-zirconium sol, while the remaining raw material composition and preparation process were the same as the basic formula of this embodiment. The product performance of the three experimental groups and control group 4 of this embodiment was tested, and the test results are shown in Table 4.

[0056] Table 4. Performance Comparison between Experimental and Control Groups with Different Amounts of Nano-Zirconium Sol Addition It can be seen that, with essentially the same bulk density and thermal conductivity, the performance of all three experimental groups is significantly better than that of control group 4. Among them, experimental group 4-2, with an addition of 7.5% nano-zirconium sol, exhibits the best performance, with its compressive strength and flexural strength increasing by 45.2% and 51.9% respectively compared to control group 4, a smaller permanent linear change rate after reheating, and a 25% increase in high-temperature flexural strength retention. Although the performance of experimental groups 4-1 and 4-3 is slightly lower than that of experimental group 4-2, it is still far superior to control group 4, indicating that the nano-zirconium sol addition range specified in this invention can effectively exert a binding and reinforcing effect, improving the mechanical properties and high-temperature stability of the material.

[0057] Example 5

[0058] Experimental objective: To compare the performance differences between composite foaming agents and single foaming agents using a conditional control method, and to verify the synergistic effect and foam stability improvement effect of anionic / nonionic composite foaming agents.

[0059] This embodiment studies the effect of mechanical stirring speed on product performance. The core parameter is the rotation speed of the mechanical stirring, which is set to 800 rpm, 1400 rpm and 2000 rpm respectively.

[0060] The basic raw material composition of this embodiment is as follows: 80% yttrium-stabilized zirconia powder, 5% high-purity zirconia long fibers, 10% water, 10% nano-zirconia sol, 1% starch, 1.0% composite foaming agent, 0.5% sodium carboxymethyl cellulose, 2.0% polyethylene glycol, and 0.5% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a mass ratio of 1:2.5. The yttrium content in the yttrium-stabilized zirconia powder is 4.5 mol%, and the powder particle size is 5 μm. The diameter of the high-purity zirconia long fibers is 4 μm, the length is 3 mm, and the zirconia content is 99.8%. The solid content of the nano-zirconia sol is 38%, the zirconia particle size is 50 nm, and the starch is corn starch.

[0061] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 3 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, corn starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at a set speed for 5 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand and solidify at room temperature for 2 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed by heating from room temperature to 600℃ at a rate of 2.5℃ / min and holding for 1 h, then heating to 1800℃ at a rate of 4.5℃ / min and holding for 4 h, followed by natural cooling to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0062] Control group 5 was set up, using sodium dodecyl sulfate as the single foaming agent, with the same addition amount as the composite foaming agent in this embodiment. The composition and preparation method of the remaining raw materials were the same as the basic formula in this embodiment, and the stirring speed was 1400 rpm. The product performance of the three experimental groups and control group 5 in this embodiment was tested, and the test results are shown in Table 5.

[0063] Table 5. Performance Comparison between Experimental Groups and Control Groups at Different Stirring Speeds It can be seen that, under the condition of basically the same bulk density, the performance of all three experimental groups is significantly better than that of control group 5. Among them, experimental group 5-2 has the best performance when the stirring speed is 1400 rpm. Its compressive strength and flexural strength are increased by 51.2% and 64.7% respectively compared with control group 5, the average pore size is significantly reduced, the closed-cell rate is greatly increased, the thermal conductivity is reduced by 22.2%, and the foam stability is significantly improved. After standing for 30 minutes, the volume change rate is only 5%. Although the performance of experimental groups 5-1 and 5-3 is slightly lower than that of experimental group 5-2, it is still far better than that of control group 5, indicating that the stirring speed range defined by the present invention can effectively introduce uniform and fine bubbles to form a stable foam slurry.

[0064] Example 6

[0065] Experimental objective: By comparing the product of this invention with mainstream zirconia thermal insulation products on the market, this experiment aims to verify its practical application value and comprehensive performance advantages.

[0066] This embodiment studies the effect of high-temperature sintering temperature on product performance. The core parameter is the high-temperature sintering temperature, which is set to 1750℃, 1800℃ and 1850℃ respectively.

[0067] The basic raw material composition of this embodiment is as follows: 72% yttrium-stabilized zirconia powder, 7% high-purity zirconia long fibers, 12.5% ​​water, 6.5% nano-zirconia sol, 3.2% starch, 0.65% composite foaming agent, 0.25% sodium carboxymethyl cellulose, 1.6% polyethylene glycol, and 0.3% magnesium oxide. The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycosides in a mass ratio of 1:2. The yttrium content in the yttrium-stabilized zirconia powder is 4 mol%, and the powder particle size is 2.5 μm. The diameter of the high-purity zirconia long fibers is 3 μm, the length is 2 mm, and the zirconia content is 99.8%. The solid content of the nano-zirconia sol is 35%, the zirconia particle size is 30 nm, and the starch is tapioca starch.

[0068] The preparation method is as follows: First, high-purity zirconia long fibers are pre-treated by shearing to a length of 2 mm. Then, yttrium-stabilized zirconia powder, pre-treated high-purity zirconia long fibers, nano-zirconia sol, cassava starch, composite foaming agent, sodium carboxymethyl cellulose, polyethylene glycol, magnesium oxide, and water are mixed in proportion and mechanically stirred at 1600 rpm for 3 min to form a foam slurry. The foam slurry is poured into a mold and allowed to stand at room temperature for 2 h to form a wet blank. The wet blank is then subjected to gradient drying treatment: first, it is dried at 60℃ for 24 h, then at 80℃ for 24 h, and finally at 100℃ for 24 h. After drying, high-temperature sintering is performed: the temperature is increased from room temperature to 600℃ at a rate of 2℃ / min and held for 1.5 h, then increased to the set sintering temperature at a rate of 4℃ / min and held for 4 h. The material is then naturally cooled to room temperature to obtain a lightweight zirconia microporous foam ceramic refractory material.

[0069] Control group 6 was set up, using zirconia fiberboard from the existing technology, with the same bulk density as the product in this embodiment. The product performance of the three experimental groups and control group 6 in this embodiment was tested, and the test results are shown in Table 6.

[0070] Table 6. Performance Comparison between Experimental and Control Groups at Different Sintering Temperatures It can be seen that, with essentially the same bulk density and thermal conductivity, the performance of all three experimental groups is significantly better than that of control group 6. Experimental group 6-2 exhibits the best performance at a sintering temperature of 1800℃, with compressive strength and flexural strength increased by 41.4% and 50% respectively compared to control group 6. It also shows a smaller permanent linear change rate after re-firing, better corrosion resistance, and a service life 2.5 times that of control group 6. While the performance of experimental groups 6-1 and 6-3 is slightly lower than that of experimental group 6-2, it is still far superior to control group 6, indicating that the sintering temperature range defined in this invention can effectively promote material densification during sintering while avoiding grain growth caused by over-sintering.

[0071] like Figure 2 and Figure 3 As shown, the morphology of experimental group 6-2 and control group 6 is displayed under low magnification scanning electron microscope. The scale bar of both images is 100 μm. The samples all show a typical closed-pore-open-pore composite porous structure of porous ceramics prepared by foaming method. The large-sized spherical pores are the main pores formed by foaming agent, and the small pores on the skeleton are the microporous structure formed during the sintering process.

[0072] Comparison of the microstructures of the two groups of samples reveals that the sample in experimental group 6-2 exhibits superior uniformity in pore size, with continuous and minimal dispersion in the distribution of main pore diameters and no obvious oversized pores. The pore walls are continuous and intact with uniform thickness, and the micropores on the skeleton surface are small and evenly distributed. The sintering density is consistent and free of significant structural defects. The pores are mostly near-spherical, independent closed pores with weak inter-pore connectivity. Overall, there are few structural defects and no obvious impurity particles, indicating high stability in the preparation process.

[0073] The pore size distribution of the control group 6 samples showed a significant increase in dispersion, with some ultra-large pores larger than 100 μm in diameter, accompanied by a large number of micropores, resulting in a decrease in overall regularity. Some pore walls of the samples became thinner and locally damaged, reducing the integrity of the skeletal framework. The micropores inside the pore walls became more numerous and deeper, forming structurally weak areas and resulting in poor sintering uniformity. Connecting channels formed between the large pores due to pore wall damage, significantly increasing the proportion of open pores. Simultaneously, irregular impurity particles were present on the sample surface, and the number of broken pore edges increased, making the process stability weaker than that of the samples in experimental group 6-2.

[0074] The test results from the above embodiments demonstrate that this invention, by optimizing the slurry system, employing a combination of composite foaming agents and foam stabilizers, and integrating direct foaming and in-situ curing technologies, constructs a multi-reinforcement mechanism, successfully preparing a lightweight zirconia microporous foam ceramic refractory material that combines ultra-low density, microporous closed-cell structure, high strength, and excellent ultra-high temperature thermal insulation performance. The parameter ranges defined in this invention effectively guarantee product performance. Compared with existing technologies, the product of this invention shows significant improvements in mechanical properties, thermal insulation performance, high-temperature stability, thermal shock resistance, and corrosion resistance, solving the technical challenge of simultaneously achieving lightweight and high strength in existing technologies. Furthermore, the process is simple, environmentally friendly, and has strong raw material adaptability, making it suitable for large-scale industrial production and possessing broad application prospects.

[0075] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A lightweight zirconia microporous foam ceramic refractory material, characterized in that: Includes the following components by weight: Yttrium stabilized zirconia powder 60-80%, high-purity zirconia long fibers 5-10%, water 10-15%, nano-zirconia sol 5-10%, starch 3-5%, composite foaming agent 0.5-1%, thickening and foam stabilizing agent 0.1-0.5%, ceramic dispersant 1-2%, magnesium oxide 0.1-0.5%.

2. The lightweight zirconia microporous foam ceramic refractory material according to claim 1, characterized in that: The composite foaming agent is composed of sodium dodecyl sulfate and alkyl glycoside in a mass ratio of 1:1-3.

3. The lightweight zirconia microporous foam ceramic refractory material according to claim 1, characterized in that: The yttrium-stabilized zirconia powder contains 3-5 mol% yttrium oxide and has a particle size of 1-5 μm.

4. The lightweight zirconia microporous foam ceramic refractory material according to claim 1, characterized in that: The high-purity zirconia long fibers have a diameter of 2-4 μm, a length of 1-3 mm, and a zirconia content of not less than 99.8%.

5. The lightweight zirconia microporous foam ceramic refractory material according to claim 1, characterized in that: The solid content of the nano-zirconium sol is 30-40%, and the zirconium oxide particle size is 10-50 nm.

6. The lightweight zirconia microporous foam ceramic refractory material according to claim 1, characterized in that: The thickening and foaming stabilizer is sodium carboxymethyl cellulose, the ceramic dispersant is polyethylene glycol, and the starch is corn starch or cassava starch.

7. A method for preparing a lightweight zirconia microporous foam ceramic refractory material as described in any one of claims 1 to 6, characterized in that: Includes the following steps: S1, high-purity zirconium oxide long fibers are sheared and pretreated; S2, Yttrium stabilized zirconia powder, pretreated high-purity zirconia long fibers, nano-zirconia sol, starch, composite foaming agent, thickening and stabilizing agent, ceramic dispersant, magnesium oxide and water are mixed in proportion and mechanically stirred to form a foam slurry; S3, pour the foam slurry into the mold, let it stand and solidify to form a wet blank, and then perform gradient drying on the wet blank; S4, high-temperature sintering.

8. The method for preparing lightweight zirconia microporous foam ceramic refractory material according to claim 7, characterized in that: In step S2, the mechanical stirring speed is 800-2000 rpm, and the stirring time is 2-5 min; In step S3, the static curing time is 1-3 hours, and the curing temperature is room temperature.

9. The method for preparing lightweight zirconia microporous foam ceramic refractory material according to claim 7, characterized in that: In step S4, the high-temperature sintering process is as follows: the temperature is increased from room temperature to 600℃ at a rate of 2-3℃ / min, held for 1-2 hours, then increased to 1800℃ at a rate of 3-5℃ / min, held for 4 hours, and then naturally cooled to room temperature.

10. The method for preparing lightweight zirconia microporous foam ceramic refractory material according to claim 7, characterized in that: In step S3, the gradient drying process is as follows: first, dry at 60°C for 24 hours, then raise the temperature to 80°C and dry for 24 hours, and finally raise the temperature to 100°C and dry for 24 hours.

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