Lightweight alumina foam ceramic refractory material and method of making

Abstract

The application discloses a light-weight alumina foam ceramic refractory material and a preparation method thereof, and relates to the technical field of ceramic materials. In the preparation of the light-weight alumina foam ceramic refractory material, acetylacetone zirconium, yttrium nitrate hexahydrate and aluminum nitrate nonahydrate are mixed to prepare a spinning solution for electrostatic spinning; the spinning is simultaneously performed by using a nano-spray technology to load nano-aluminum titanate; and after high-temperature heat treatment, the doped modified zirconia fiber is prepared by defibrating and dispersing; the alumina micropowder, hollow alumina, high-temperature foaming agent, doped modified zirconia fiber and sintering aid are mixed, ball milled, sieved to prepare alumina-based mixed powder; the alumina-based mixed powder is molded to prepare a green body, and after sintering and cooling, the light-weight alumina foam ceramic refractory material is prepared. The light-weight alumina foam ceramic refractory material prepared by the application has the advantages of light weight, low thermal conductivity, high compressive strength, high bending strength and good thermal shock resistance.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a lightweight alumina foam ceramic refractory material and its preparation method. Background Technology

[0002] With the rapid development of aviation, aerospace, national defense, transportation, and other fields, many requirements have been placed on related structural and functional materials that are difficult for traditional materials to meet, leading to the continuous development of various new materials. Porous ceramics are a new type of ceramic material, initially used only as bacterial filtration materials. With continuous improvements in manufacturing processes and the emergence of various high-performance porous ceramic products, the application fields and scope of porous ceramic materials are constantly expanding. Because porous ceramics possess excellent properties such as good permeability, low density, high strength, large specific surface area, low thermal conductivity, and high temperature and corrosion resistance, they are widely used in metallurgy, chemical industry, environmental protection, energy, biology, food, and pharmaceutical fields as components for filtration, separation, diffusion, gas distribution, heat insulation, sound absorption, chemical packing, bioceramics, chemical sensors, and catalyst supports. Porous ceramics with a porosity higher than 80% are called foam ceramics.

[0003] However, porosity and strength are inherently contradictory in porous materials; increasing porosity inevitably leads to a decrease in strength. Various methods for preparing porous ceramics, such as gas foaming, pore-forming agent addition, organic foam impregnation, sol-gel methods, and self-propagating high-temperature synthesis, have been continuously developed, with the fundamental goal of obtaining porous ceramic materials with high porosity and high strength. However, these processes primarily use water as a medium to achieve the forming process of porous ceramics. Water often causes significant shrinkage of the green body during the subsequent drying process, resulting in material deformation and posing challenges to the manufacture of ceramics with high porosity. Therefore, traditional raw material systems and preparation processes have become bottlenecks in simultaneously obtaining porous ceramics with high porosity and high strength. Summary of the Invention

[0004] The purpose of this invention is to provide a lightweight alumina foam ceramic refractory material and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A lightweight alumina foam ceramic refractory material is obtained by molding alumina-based mixed powder into a green body, sintering it, and then cooling it.

[0007] The alumina-based mixed powder is prepared by ball milling and sieving alumina micro powder, hollow alumina, high-temperature foaming agent, doped modified zirconium oxide fiber, and sintering aid.

[0008] The doped and modified zirconia fiber is prepared by electrospinning a spinning solution made of zirconium acetylacetonate, yttrium nitrate hexahydrate and aluminum nitrate nonahydrate, while simultaneously loading nano-aluminum titanate using nano-spraying technology, followed by heat treatment and dispersion.

[0009] As an optimization, the hollow alumina has an average particle size of 500 nm and was purchased from Hangzhou Jiuli Biomaterials Co., Ltd.

[0010] As an optimization, the high-temperature foaming agent includes calcium carbonate and silicon carbide.

[0011] As an optimization, the sintering aids include borax, titanium dioxide, manganese dioxide, magnesium oxide, and lanthanum oxide.

[0012] A method for preparing a lightweight alumina foam ceramic refractory material includes the following preparation steps:

[0013] (1) Azirconium acetylacetonate, anhydrous methanol, yttrium nitrate hexahydrate, polyethylene oxide and aluminum nitrate nonahydrate were mixed and stirred to prepare a spinning solution, which was loaded into a spinning needle tube. A nano-atomizer containing a nano-aluminum titanate ethanol dispersion was placed at the collecting drum, with the spray direction orthogonal to the collecting drum. Electrospinning was performed. The solution was collected from the collecting drum and dried. It was then placed in a muffle furnace for heat treatment, naturally cooled to room temperature, and dispersed in a high-speed stirrer to obtain doped modified zirconium oxide fiber.

[0014] (2) Alumina micro powder, hollow alumina, calcium carbonate, silicon carbide, doped modified zirconium oxide fiber, borax, titanium dioxide, manganese dioxide, magnesium oxide and lanthanum oxide are mixed evenly, added to a planetary ball mill for grinding, and sieved to obtain alumina-based mixed powder.

[0015] (3) The alumina-based mixed powder is molded into a blank in a mold, added to a sintering furnace for sintering, and cooled to obtain a lightweight alumina foam ceramic refractory material.

[0016] As an optimization, the doped and modified zirconia fiber in step (1) is prepared by mixing 10-12 parts of zirconium acetylacetonate, 10-12 parts of anhydrous methanol, 0.8-0.9 parts of yttrium nitrate hexahydrate, 0.1-0.15 parts of polyethylene oxide, and 1-1.2 parts of aluminum nitrate nonahydrate by mass fraction. The mixture is stirred at 300-400 r / min for 30-40 min at room temperature to prepare a spinning solution. The solution is loaded into a spinning needle tube, with the needle tip 18 cm away from the collecting roller. A nano-atomizer containing 40-50 parts of nano-aluminum titanate ethanol dispersion is placed in the collecting roller. At a location where the spray direction is orthogonal to the collecting drum, and the distance between the nano-atomizer and the collecting drum is 18cm, electrospinning is performed at a voltage of 18~20KV, a spinning feed speed of 1ml / h, room temperature, and 40%~50%RH. After being collected from the collecting drum, the nano-atomizer is placed in a vacuum oven and vacuum dried at 70~80℃ for 10~12h. Then, it is transferred to a muffle furnace and heated to 1400~1500℃ at a heating rate of 1℃ / min and held for 20~30min. After naturally cooling to room temperature, it is dispersed in a high-speed stirrer and cut to a length of 3~5mm to obtain the final product.

[0017] As an optimization, the weight-average molecular weight of the polyethylene oxide in step (1) is 1 million, and it was purchased from Shanghai Aladdin Chemical Reagent Co., Ltd.

[0018] As an optimization, the nano-aluminum titanate ethanol dispersion in step (1) contains 3wt% nano-aluminum titanate.

[0019] As an optimization, the nano aluminum titanate is AM-Al2TiO5-001-3 with an average particle size of 500nm, and was purchased from Zhejiang Yamei Nanotechnology Co., Ltd.

[0020] As an optimization, the alumina-based mixed powder in step (2) is prepared by mixing 5-6 parts of alumina micro powder, 2.5-3.5 parts of hollow alumina, 0.8-0.9 parts of calcium carbonate, 0.4-0.5 parts of silicon carbide, 1.2-1.5 parts of doped modified zirconium oxide fiber, 0.2-0.24 parts of borax, 0.3-0.32 parts of titanium dioxide, 0.12-0.15 parts of manganese dioxide, 0.04-0.05 parts of magnesium oxide, and 0.005-0.007 parts of lanthanum oxide by mass, adding the mixture to a planetary ball mill, and grinding it at a rotation speed of 320-360 r / min, a running speed of 350-400 r / min, with zirconium oxide balls as the grinding medium and a ball-to-material ratio of 2:1 for 100-120 min, and then passing it through an 800-mesh sieve.

[0021] As an optimization, the lightweight alumina foam ceramic refractory material in step (3) is prepared by molding alumina-based mixed powder into a blank in a mold under a pressure of 2-3 MPa, adding it to a sintering furnace preheated to 850-900℃ under an argon atmosphere, heating it to 1200℃ at a heating rate of 4-6℃ / min, switching to an air atmosphere, heating it to 1450-1550℃ at a heating rate of 2-3℃ / min for 2-3 hours, cooling it to 800℃ at a rate of 20℃ / min, and then naturally cooling it to room temperature.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0023] In preparing lightweight alumina foam ceramic refractory material, this invention first mixes zirconium acetylacetonate, yttrium nitrate hexahydrate, and aluminum nitrate nonahydrate to form a spinning solution for electrospinning. Simultaneously, nano-aluminum titanate is loaded using nano-spraying technology. After high-temperature heat treatment, the mixture is dispersed to obtain doped modified zirconium oxide fibers. Alumina micropowder, hollow alumina, a high-temperature foaming agent, doped modified zirconium oxide fibers, and a sintering aid are mixed, ball-milled, and sieved to obtain an alumina-based mixed powder. The alumina-based mixed powder is then molded into a green body, sintered, and cooled to obtain the lightweight alumina foam ceramic refractory material.

[0024] First, a spinning solution composed of zirconium acetylacetonate, yttrium nitrate hexahydrate, and aluminum nitrate nonahydrate was used to produce precursor fibers via electrospinning. Zirconia fibers are high-strength and high-performance fibers, but they are prone to monoclinic and tetragonal phase transformations at high temperatures, leading to changes in density and properties. The introduction of yttrium doping can effectively improve the high-temperature stability of zirconium oxide. Aluminum doping, embedded between zirconium oxide grains, can effectively hinder the growth of zirconium oxide grains, resulting in a denser grain arrangement and reducing defects and voids on the surface of the zirconium oxide fibers. Aluminum doping also refines the zirconium oxide grains. The effect is to improve its strength; while zirconia fiber has excellent performance, it also has a high coefficient of thermal expansion, which leads to its unsatisfactory thermal shock resistance. Nano aluminum titanate, on the other hand, has a low coefficient of thermal expansion and good high temperature resistance. When preparing precursor fibers by electrospinning, nano aluminum titanate is simultaneously loaded onto the fibers using nano-spraying technology. This ensures that the nano aluminum titanate is uniformly loaded onto the fibers, unlike impregnation which can cause uneven loading. The effectively dispersed nano aluminum titanate can effectively improve the thermal shock resistance of zirconia fiber and improve its compatibility in the alumina matrix.

[0025] Secondly, ball milling is used to mix alumina micro powder, hollow alumina, high-temperature foaming agent, doped modified zirconia fiber, and sintering aids. This effectively reduces the particle size of each raw material, ensuring uniform mixing and improving sintering performance. The introduction of hollow alumina, through its hollow structure, increases porosity. The high-temperature foaming agent is a mixture of calcium carbonate and silicon carbide. Calcium carbonate decomposes at approximately 700°C, generating carbon dioxide gas and calcium oxide, which acts as a lower-temperature foaming agent and preferentially decomposes to release gas for foaming. Silicon carbide, in an air atmosphere, reacts with oxygen in the air at temperatures above 1000°C to generate gas, which can act as a higher-temperature foaming agent, continuing the gas release from calcium carbonate for foaming. Furthermore, the calcium oxide and silicon oxide generated after the decomposition of calcium carbonate and silicon carbide can both be incorporated into the alumina grains as reinforcing phases, helping to improve mechanical strength. Calcium carbonate and silicon carbide also act synergistically as foaming agents, decomposing and releasing gas at different temperatures to ensure sufficient internal gas throughout the sintering process. To prevent the formation of pores due to late foaming and the loss of gas due to premature foaming, the introduction of modified zirconia fibers effectively improves the toughness and mechanical strength of the matrix through pull-out, bridging, and crack deflection. The addition of borax as a sintering aid allows for the formation of a molten matrix at 900-1100℃ during high-temperature sintering. This molten matrix with a certain viscosity effectively seals the pores formed by internal gas release, thus preserving the pore structure, preventing pore structure collapse due to gas escape, and improving... Sintering efficiency; the addition of manganese dioxide, titanium dioxide, and magnesium oxide also improves the sintering performance of alumina. Magnesium oxide reduces the interfacial energy between alumina crystals and the solid solution by forming a thin magnesium aluminum spinel solid solution, thereby reducing the diffusion rate of particles and inhibiting the abnormal growth of alumina crystals, thus refining the crystal microstructure. Manganese dioxide and titanium dioxide promote the sintering of alumina by forming a limited substitution solid solution with alumina and lowering the sintering temperature. The addition of lanthanum oxide refines the grains and improves mechanical strength.

[0026] Finally, the alumina-based mixed powder is molded to form a green body. During sintering, since the decomposition temperature of calcium carbonate is around 700℃, while the melting of borax to form a molten matrix requires 900~1100℃, most of the gas produced by the decomposition of calcium carbonate escapes and is lost, reducing foaming efficiency. Therefore, the green body is not subjected to a heating process; the sintering furnace is preheated to 850~900℃ before the green body is placed in. Because heat needs time to be conducted from the outside to the inside, the outer layer of borax has already melted at the high temperature, thus possessing a certain ability to trap gas. Calcium carbonate enters the decomposition stage simultaneously with borax. Since the outer layer of borax has already melted, the decomposition of calcium carbonate inside is trapped by the molten matrix, thus reducing gas escape. At this point, sintering is carried out in an inert atmosphere. Silicon carbide does not decompose and release gas. Instead, the sintering atmosphere is changed to air only after the molten matrix is ​​fully formed, i.e., at 1200℃. This controls the timing of gas release during silicon carbide oxidation, preventing premature oxidation of silicon carbide before the molten matrix is ​​fully formed and avoiding gas loss. Oxygen in the air diffuses into the molten matrix and reacts with silicon carbide to undergo oxidation. The carbon dioxide generated by silicon carbide oxidation cannot escape from the matrix and can only accumulate inside the molten matrix, eventually completing foaming and leaving closed-cell pores inside the matrix. The lightweight alumina foam ceramic refractory material prepared using this method has a high porosity, and most of it consists of closed-cell pores. Closed-cell pores have better performance in terms of refractory and heat insulation than open-cell pores, effectively improving heat insulation performance and reducing thermal conductivity. Detailed Implementation

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

[0028] The material information used in all the following embodiments and comparative examples is as follows:

[0029] Nano aluminum titanate ethanol dispersion: contains 3wt% nano aluminum titanate;

[0030] Nano aluminum titanate: Model number AM-Al2TiO5-001-3, average particle size 500nm, purchased from Zhejiang Yamei Nanotechnology Co., Ltd.

[0031] Polyethylene oxide: weight average molecular weight is 1 million, purchased from Shanghai Aladdin Chemical Reagent Co., Ltd.

[0032] Alumina micro powder: average particle size 100μm, purchased from Zibo Qimingxing New Materials Co., Ltd.;

[0033] Hollow alumina: average particle size 500 nm, purchased from Hangzhou Jiuli Biomaterials Co., Ltd.

[0034] Silicon carbide: Model XH-SiC-010, average particle size 10μm, purchased from Shanghai Xiaohuang Nanotechnology Co., Ltd.

[0035] Example 1:

[0036] A method for preparing a lightweight alumina foam ceramic refractory material, comprising the following preparation steps:

[0037] (1) By mass fraction, 10 parts zirconium acetylacetonate, 10 parts anhydrous methanol, 0.8 parts yttrium nitrate hexahydrate, 0.1 parts polyethylene oxide, and 1 part aluminum nitrate nonahydrate are mixed evenly and stirred at 300 r / min for 40 min at room temperature to prepare a spinning solution. The solution is loaded into a spinning needle tube, with the needle tip 18 cm away from the collecting roller. A nano-atomizer containing 40 parts of nano-aluminum titanate ethanol dispersion is placed at the collecting roller, with the spray direction orthogonal to the collecting roller. The distance between the initiator and the collecting roller is 18cm. Electrospinning is carried out at a voltage of 18KV, a spinning feed speed of 1ml / h, room temperature, and 40%RH. After being collected from the collecting roller, the fibers are placed in a vacuum oven and vacuum dried at 70℃ for 12h. Then, they are transferred to a muffle furnace and heated to 1400℃ at a heating rate of 1℃ / min and held for 30min. After being naturally cooled to room temperature, the fibers are dispersed in a high-speed stirrer and cut to a length of 3mm to obtain doped modified zirconia fibers.

[0038] (2) By mass, 5 parts of alumina micro powder, 2.5 parts of hollow alumina, 0.8 parts of calcium carbonate, 0.4 parts of silicon carbide, 1.2 parts of doped modified zirconium oxide fiber, 0.2 parts of borax, 0.3 parts of titanium dioxide, 0.12 parts of manganese dioxide, 0.04 parts of magnesium oxide and 0.005 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is ground at a rotation speed of 320 r / min, a running speed of 350 r / min, zirconium oxide balls as the grinding medium, and a ball-to-material ratio of 2:1 for 120 min. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder.

[0039] (3) The alumina-based mixed powder is molded into a blank in a mold with a pressure of 2MPa. It is then added to a sintering furnace preheated to 850°C under an argon atmosphere. The temperature is increased to 1200°C at a heating rate of 6°C / min. The temperature is then changed to an air atmosphere and increased to 1550°C at a heating rate of 2°C / min for 2 hours. The temperature is then cooled to 800°C at a rate of 20°C / min and then naturally cooled to room temperature to obtain a lightweight alumina foam ceramic refractory material.

[0040] Example 2:

[0041] A method for preparing a lightweight alumina foam ceramic refractory material, comprising the following preparation steps:

[0042] (1) By mass fraction, 11 parts zirconium acetylacetonate, 11 parts anhydrous methanol, 0.85 parts yttrium nitrate hexahydrate, 0.12 parts polyethylene oxide, and 1.1 parts aluminum nitrate nonahydrate were mixed evenly and stirred at 350 r / min for 35 min at room temperature to prepare a spinning solution. The solution was loaded into a spinning needle tube, with the needle tip 18 cm away from the collecting roller. A nano-atomizer containing 45 parts of nano-aluminum titanate ethanol dispersion was placed at the collecting roller, with the spray direction perpendicular to the collecting roller. The distance between the atomizer and the collecting roller was 18cm. Electrospinning was carried out at a voltage of 19KV, a spinning feed speed of 1ml / h, room temperature, and 45%RH. After being collected from the collecting roller, the fibers were placed in a vacuum oven and vacuum dried at 75℃ for 11h. They were then transferred to a muffle furnace and heated to 1450℃ at a heating rate of 1℃ / min and held for 25min. After being naturally cooled to room temperature, the fibers were dispersed in a high-speed stirrer and cut to a length of 4mm to obtain doped modified zirconia fibers.

[0043] (2) By mass, 5.5 parts of alumina micro powder, 3 parts of hollow alumina, 0.85 parts of calcium carbonate, 0.45 parts of silicon carbide, 1.35 parts of doped modified zirconium oxide fiber, 0.22 parts of borax, 0.31 parts of titanium dioxide, 0.135 parts of manganese dioxide, 0.045 parts of magnesium oxide and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is ground at a rotation speed of 340 r / min, a running speed of 375 r / min, zirconium oxide balls as the grinding medium, and a ball-to-material ratio of 2:1 for 110 min. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder.

[0044] (3) The alumina-based mixed powder is molded into a blank in a mold with a pressure of 2.5 MPa. It is then added to a sintering furnace preheated to 875°C under an argon atmosphere and heated to 1200°C at a heating rate of 5°C / min. The temperature is then changed to an air atmosphere and heated to 1500°C at a heating rate of 2.5°C / min for 2.5 hours. The temperature is then cooled to 800°C at a rate of 20°C / min and then naturally cooled to room temperature to obtain a lightweight alumina foam ceramic refractory material.

[0045] Example 3:

[0046] A method for preparing a lightweight alumina foam ceramic refractory material, comprising the following preparation steps:

[0047] (1) By mass fraction, 12 parts zirconium acetylacetonate, 12 parts anhydrous methanol, 0.9 parts yttrium nitrate hexahydrate, 0.15 parts polyethylene oxide, and 1.2 parts aluminum nitrate nonahydrate were mixed evenly and stirred at 400 r / min for 30 min at room temperature to prepare a spinning solution. The solution was loaded into a spinning needle tube, with the needle tip 18 cm away from the collecting roller. A nano-atomizer containing 50 parts of nano-aluminum titanate ethanol dispersion was placed at the collecting roller, with the spray direction perpendicular to the collecting roller. The distance between the atomizer and the collecting roller is 18cm. Electrospinning is carried out at a voltage of 20KV, a spinning feed speed of 1ml / h, room temperature, and 50%RH. After being collected from the collecting roller, the fibers are placed in a vacuum oven and vacuum dried at 80℃ for 10h. Then, they are transferred to a muffle furnace and heated to 1500℃ at a heating rate of 1℃ / min and held for 20min. After being naturally cooled to room temperature, the fibers are dispersed in a high-speed stirrer and cut to a length of 5mm to obtain doped modified zirconia fibers.

[0048] (2) By mass, 6 parts of alumina micro powder, 3.5 parts of hollow alumina, 0.9 parts of calcium carbonate, 0.5 parts of silicon carbide, 1.5 parts of doped modified zirconium oxide fiber, 0.24 parts of borax, 0.32 parts of titanium dioxide, 0.15 parts of manganese dioxide, 0.05 parts of magnesium oxide and 0.007 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is ground at a rotation speed of 360 r / min, a running speed of 400 r / min, zirconium oxide balls as the grinding medium, and a ball-to-material ratio of 2:1 for 100 min. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder.

[0049] (3) The alumina-based mixed powder is molded into a blank in a mold with a pressure of 3MPa. It is then added to a sintering furnace preheated to 900℃ under an argon atmosphere, heated to 1200℃ at a heating rate of 4℃ / min, switched to an air atmosphere, heated to 1450℃ at a heating rate of 3℃ / min and sintered for 3h. It is then cooled to 800℃ at a rate of 20℃ / min and then naturally cooled to room temperature to obtain a lightweight alumina foam ceramic refractory material.

[0050] Comparative Example 1:

[0051] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 1 and Example 2 lies in the different step (1). Step (1) is modified as follows: 11 parts by mass of zirconium acetylacetonate, 11 parts of anhydrous methanol, 0.85 parts of yttrium nitrate hexahydrate, and 0.12 parts of polyethylene oxide are mixed evenly and stirred at 350 r / min for 35 min at room temperature to prepare a spinning solution. The solution is loaded into a spinning needle tube, with the distance between the needle tip and the collecting roller being 18 cm. A nano-atomizer containing 45 parts of nano-aluminum titanate ethanol dispersion is placed in... At the collecting drum, the spray direction was orthogonal to the collecting drum, and the distance between the nano-atomizer and the collecting drum was 18 cm. Electrospinning was performed at a voltage of 19 KV, a spinning feed speed of 1 ml / h, room temperature, and 45% RH. After being collected from the collecting drum, the fibers were placed in a vacuum oven and vacuum dried at 75°C for 11 h. Then, they were transferred to a muffle furnace and heated to 1450°C at a heating rate of 1°C / min, held at that temperature for 25 min, and allowed to cool naturally to room temperature. The fibers were then dispersed in a high-speed stirrer and cut to a length of 4 mm to obtain doped modified zirconia fibers. The remaining steps were the same as in Example 2.

[0052] Comparative Example 2:

[0053] The difference between the preparation method of the lightweight alumina foam ceramic refractory material of Comparative Example 2 and Example 2 lies in the different steps (1). Step (1) is modified as follows: 11 parts zirconium acetylacetonate, 11 parts anhydrous methanol, 0.85 parts yttrium nitrate hexahydrate, 0.12 parts polyethylene oxide, and 1.1 parts aluminum nitrate nonahydrate are mixed evenly by mass and stirred at 350 r / min for 35 min at room temperature to prepare a spinning solution. The solution is loaded into a spinning needle tube with a needle tip and a collection roller distance of 18 cm. Electrospinning is performed at a voltage of 19 KV, a spinning feed speed of 1 ml / h, room temperature, and 45% RH. The solution is collected from the collection roller and placed in a vacuum oven to be vacuum dried at 75 °C for 11 h. It is then transferred to a muffle furnace and heated to 1450 °C at a heating rate of 1 °C / min and held for 25 min. The solution is then naturally cooled to room temperature and dispersed in a high-speed stirrer. The length is cut to 4 mm to obtain doped modified zirconium oxide fibers. The remaining steps are the same as in Example 2.

[0054] Comparative Example 3:

[0055] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 3 and Example 2 lies in step (1). Step (1) is modified as follows: 11 parts by mass of zirconium acetylacetonate, 11 parts of anhydrous methanol, 0.85 parts of yttrium nitrate hexahydrate, and 0.12 parts of polyethylene oxide are mixed evenly and stirred at 350 r / min for 35 min at room temperature to prepare a spinning solution. The solution is loaded into a spinning needle tube with a needle tip 18 cm away from the collecting roller. Electrospinning is performed at a voltage of 19 KV, a spinning feed speed of 1 ml / h, room temperature, and 45% RH. After collection from the collecting roller, the solution is placed in a vacuum oven and vacuum dried at 75 °C for 11 h. The solution is then transferred to a muffle furnace and heated to 1450 °C at a heating rate of 1 °C / min, held for 25 min, and naturally cooled to room temperature. The solution is then dispersed in a high-speed stirrer and cut to a length of 4 mm to obtain doped modified zirconium oxide fibers. The remaining steps are the same as in Example 2.

[0056] Comparative Example 4:

[0057] The preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 4 differs from that in Example 2 in that step (1) is omitted, and step (2) is modified as follows: 5.5 parts by mass of alumina micro powder, 3 parts of hollow alumina, 0.85 parts of calcium carbonate, 0.45 parts of silicon carbide, 0.22 parts of borax, 0.31 parts of titanium dioxide, 0.135 parts of manganese dioxide, 0.045 parts of magnesium oxide, and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is then ground for 110 minutes at a rotation speed of 340 r / min, a running speed of 375 r / min, and zirconium oxide balls as the grinding media, with a ball-to-material ratio of 2:1. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder. The remaining steps are the same as in Example 2.

[0058] Comparative Example 5:

[0059] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 5 and Example 2 lies in step (2). Step (2) is modified as follows: 8.5 parts by mass of alumina micro powder, 0.85 parts of calcium carbonate, 0.45 parts of silicon carbide, 1.35 parts of doped modified zirconium oxide fiber, 0.22 parts of borax, 0.31 parts of titanium dioxide, 0.135 parts of manganese dioxide, 0.045 parts of magnesium oxide, and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is then ground for 110 minutes at a rotation speed of 340 r / min, a running speed of 375 r / min, and zirconium oxide balls as the grinding medium, with a ball-to-material ratio of 2:1. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder. The remaining steps are the same as in Example 2.

[0060] Comparative Example 6:

[0061] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 6 and Example 2 lies in step (2). Step (2) is modified as follows: 5.5 parts by mass of alumina micro powder, 3 parts of hollow alumina, 1.3 parts of silicon carbide, 1.35 parts of doped modified zirconia fiber, 0.22 parts of borax, 0.31 parts of titanium dioxide, 0.135 parts of manganese dioxide, 0.045 parts of magnesium oxide, and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is then ground for 110 minutes at a rotation speed of 340 r / min, a running speed of 375 r / min, and zirconia balls as the grinding medium with a ball-to-material ratio of 2:1. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder. The remaining steps are the same as in Example 2.

[0062] Comparative Example 7:

[0063] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 7 and Example 2 lies in step (2). Step (2) is modified as follows: 5.5 parts by mass of alumina micro powder, 3 parts of hollow alumina, 1.3 parts of calcium carbonate, 1.35 parts of doped modified zirconia fiber, 0.22 parts of borax, 0.31 parts of titanium dioxide, 0.135 parts of manganese dioxide, 0.045 parts of magnesium oxide, and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is then ground for 110 minutes at a rotation speed of 340 r / min, a running speed of 375 r / min, and zirconia balls as the grinding media with a ball-to-material ratio of 2:1. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder. The remaining steps are the same as in Example 2.

[0064] Comparative Example 8:

[0065] The difference between the preparation method of the lightweight alumina foam ceramic refractory material in Comparative Example 8 and Example 2 lies in step (2). Step (2) is modified as follows: 5.5 parts by mass of alumina micro powder, 3 parts of hollow alumina, 0.85 parts of calcium carbonate, 0.45 parts of silicon carbide, 1.35 parts of doped modified zirconia fiber, 0.22 parts of borax, and 0.006 parts of lanthanum oxide are mixed evenly and added to a planetary ball mill. The mill is then ground for 110 minutes at a rotation speed of 340 r / min, a running speed of 375 r / min, and zirconia balls as the grinding media with a ball-to-material ratio of 2:1. The mixture is then passed through an 800-mesh sieve to obtain alumina-based mixed powder. The remaining steps are the same as in Example 2.

[0066] Comparative Example 9:

[0067] The difference between the preparation method of the lightweight alumina foam ceramic refractory material of Comparative Example 9 and Example 2 lies in step (3). Step (3) is modified as follows: the alumina-based mixed powder is molded into a blank in a mold under a pressure of 2.5 MPa, added to a sintering furnace under an argon atmosphere, heated from room temperature to 1200°C at a heating rate of 5°C / min, then switched to an air atmosphere, heated to 1500°C at a heating rate of 2.5°C / min, sintered for 2.5 h, cooled to 800°C at a rate of 20°C / min, and then naturally cooled to room temperature to obtain the lightweight alumina foam ceramic refractory material. The remaining steps are the same as in Example 2.

[0068] Comparative Example 10:

[0069] The preparation method of the lightweight alumina foam ceramic refractory material of Comparative Example 10 differs from that of Example 2 in step (3). Step (3) is modified as follows: the alumina-based mixed powder is molded into a blank in a mold under a pressure of 2.5 MPa, and then placed in a sintering furnace preheated to 875°C in an air atmosphere. The temperature is increased to 1200°C at a heating rate of 5°C / min, then increased to 1500°C at a heating rate of 2.5°C / min, and sintered for 2.5 h. The temperature is then cooled to 800°C at a rate of 20°C / min, and then naturally cooled to room temperature to obtain the lightweight alumina foam ceramic refractory material. The remaining steps are the same as in Example 2.

[0070] Test Example 1:

[0071] Compressive strength test: The compressive strength of the prepared lightweight alumina foam ceramic refractory material was tested in accordance with GB / T 5486-2008. The test was carried out at a pressurization rate of 10 mm / min until the sample was broken. The compressive strength was calculated and recorded. Each group of samples was tested in parallel 10 times and the average value was recorded.

[0072] Bending strength test: The bending strength of the prepared lightweight alumina foam ceramic refractory material was tested according to GB / T 1965-2023. The test was carried out at a speed of 0.5 mm / min. The compressive strength was calculated and recorded. Each group of samples was tested in parallel 10 times, and the average value was recorded.

[0073] Thermal shock resistance test: The thermal shock resistance of the prepared lightweight alumina foam ceramic refractory material was tested in accordance with GB / T 30873-2014. The air quenching method was used. Ten samples were tested in parallel in each group, and the lowest number of thermal shocks was recorded.

[0074] The results are shown in Table 1.

[0075] Table 1

[0076] Compressive strength / MPa Bending strength / MPa thermal shock count Example 1 6.53 4.57 49 Example 2 6.61 4.62 51 Example 3 6.55 4.58 48 Comparative Example 1 5.89 3.83 46 Comparative Example 2 6.32 4.22 34 Comparative Example 3 5.34 2.94 31 Comparative Example 4 9.68 6.48 11 Comparative Example 5 6.89 4.71 49 Comparative Example 6 14.37 9.39 43 Comparative Example 7 20.45 15.44 39 Comparative Example 8 6.74 4.72 47 Comparative Example 9 7.03 5.12 46 Comparative Example 10 6.65 4.67 47

[0077] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-10 in Table 1 reveals that the lightweight alumina foam ceramic refractory material prepared by the present invention has good compressive strength, flexural strength and thermal shock resistance.

[0078] By comparing the data in the table, the data in Comparative Example 1 shows that aluminum doping modification of zirconia fibers effectively improves the strength of zirconia fibers, thereby increasing compressive strength and flexural strength.

[0079] By comparing the data in the table, the data in Comparative Example 2 shows that the loading of nano-aluminum titanate effectively improves the thermal shock resistance of zirconia fibers, and thus improves the thermal shock resistance of foam ceramics. The loading of aluminum titanate also improves the compatibility of zirconia fibers in the matrix, thereby improving compressive strength and flexural strength.

[0080] By comparing the data in the table, the data in Comparative Example 3 shows that the simultaneous aluminum doping and aluminum titanate loading modification of zirconia fibers achieved a synergistic effect, resulting in improvements in both compressive strength and flexural strength.

[0081] By comparing the data in the table, the data in Comparative Example 4 shows that the addition of doped modified zirconia fiber effectively improves thermal shock resistance. As for the inverse increase in compressive strength and flexural strength, it is due to the significant decrease in porosity.

[0082] By comparing the data in the table, the increase in strength and the decrease in thermal shock resistance in Comparative Example 6 are caused by the decrease in porosity. This shows that the increase in porosity also improves the thermal shock resistance of the matrix from another perspective. At the same time, due to the decrease in porosity, the density of the foam ceramic increases, and thus the strength increases.

[0083] By comparing the data in the table, the increase in strength and the decrease in thermal shock resistance in Comparative Example 7 are caused by the decrease in porosity. This shows that the increase in porosity also improves the thermal shock resistance of the matrix from another perspective. At the same time, due to the decrease in porosity, the density of the foam ceramic increases, and thus the strength increases.

[0084] Test Example 2:

[0085] Fire resistance and heat insulation performance test: The thermal conductivity of the prepared lightweight alumina foam ceramic refractory material is tested to evaluate its fire resistance and heat insulation performance. The test is carried out in accordance with GB / T 32064-2015. Each group of samples is tested 5 times and the average value is recorded.

[0086] Density test: The bulk density of the prepared lightweight alumina foam ceramic refractory material was tested according to GB / T 2997-2015. Each group of samples was tested 5 times, and the average value was recorded.

[0087] True porosity test: The total porosity of the prepared lightweight alumina foam ceramic refractory material was tested in accordance with GB / T 2997-2015. Each group of samples was tested 5 times, and the average value was recorded.

[0088] Closed porosity test: The closed porosity of the prepared lightweight alumina foam ceramic refractory material was tested according to GB / T 2997-2015. Each group of samples was tested 5 times, and the average value was recorded.

[0089] The results are shown in Table 2.

[0090] Table 2

[0091] Thermal conductivity / W·m⁻¹·K⁻¹ Bulk density / g·cm-3 Total porosity Closed porosity Example 1 0.134 0.38 91.4% 89.6% Example 2 0.128 0.37 91.8% 89.8% Example 3 0.135 0.39 91.2% 89.6% Comparative Example 1 0.141 0.44 90.1% 88.4% Comparative Example 2 0.148 0.47 89.6% 86.9% Comparative Example 3 0.189 0.57 87.4% 84.3% Comparative Example 4 0.304 0.84 78.9% 73.4% Comparative Example 5 0.215 0.51 84.6% 86.9% Comparative Example 6 0.324 1.09 75.9% 74.3% Comparative Example 7 0.396 1.47 67.3% 66.2% Comparative Example 8 0.383 0.62 86.2% 84.3% Comparative Example 9 0.287 0.81 82.1% 79.8% Comparative Example 10 0.192 0.59 86.9% 83.6%

[0092] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-10 in Table 2 reveals that the lightweight alumina foam ceramic refractory material prepared by this invention has good fire resistance and heat insulation properties, low density, and high porosity and closed porosity.

[0093] By comparing the data in the table, the data in Comparative Examples 1, 2, and 3 show that the modification of zirconia fibers improves the strength of zirconia fibers, thereby improving the strength of the pore walls, allowing them to withstand pores with thinner pore walls, thus increasing the porosity, and thereby improving the thermal insulation performance and reducing the thermal conductivity.

[0094] By comparing the data in the table, the data in Comparative Example 4 shows that the addition of doped modified zirconia fibers effectively improves the strength of the matrix, thereby improving the strength of the pore walls, allowing thinner pore walls to withstand pores, thus increasing the porosity, and thereby improving the thermal insulation performance and reducing the thermal conductivity.

[0095] By comparing the data in the table, the data in Comparative Example 5 shows that the introduction of hollow alumina increases the total porosity and reduces the thermal conductivity through its own pores.

[0096] The data comparison in the table shows that the addition of both calcium carbonate and silicon carbide as foaming agents effectively foamed the material, increased porosity, reduced bulk density and thermal conductivity, and improved thermal insulation performance.

[0097] By comparing the data in the table, the data in Comparative Example 8 shows that the addition of the sintering aid system of manganese dioxide, titanium dioxide and magnesium oxide effectively promoted the sintering of alumina and increased the porosity. At the same time, the thermal conductivity of magnesium oxide is lower than that of alumina, and the introduction of magnesium oxide significantly reduced the thermal conductivity.

[0098] By comparing the data in the table, the data in Comparative Example 9 shows that preheating the sintering furnace effectively improves the utilization rate of calcium carbonate foaming agent, improves porosity, thereby reducing thermal conductivity and improving insulation performance.

[0099] By comparing the data in the table, the data in Comparative Example 10 shows that changing the control atmosphere during the sintering process effectively improved the utilization rate of the foaming agent silicon carbide, improved the porosity, thereby reducing the thermal conductivity and improving the heat insulation performance.

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lightweight alumina foam ceramic refractory material, characterized in that, The lightweight alumina foam ceramic refractory material is obtained by molding alumina-based mixed powder into a green body, sintering it, and then cooling it. The alumina-based mixed powder is prepared by ball milling and sieving alumina micro powder, hollow alumina, high-temperature foaming agent, doped modified zirconium oxide fiber, and sintering aid. The doped and modified zirconium oxide fiber is prepared by electrospinning a spinning solution made of zirconium acetylacetonate, yttrium nitrate hexahydrate and aluminum nitrate nonahydrate, and simultaneously loading nano-aluminum titanate using nano-spraying technology, followed by heat treatment and decomposition dispersion. The high-temperature foaming agent includes calcium carbonate and silicon carbide; The sintering aids include borax, titanium dioxide, manganese dioxide, magnesium oxide, and lanthanum oxide; The alumina-based mixed powder, by mass parts, consists of 5-6 parts alumina micro powder, 2.5-3.5 parts hollow alumina, 0.8-0.9 parts calcium carbonate, 0.4-0.5 parts silicon carbide, 1.2-1.5 parts doped modified zirconium oxide fiber, 0.2-0.24 parts borax, 0.3-0.32 parts titanium dioxide, 0.12-0.15 parts manganese dioxide, 0.04-0.05 parts magnesium oxide, and 0.005-0.007 parts lanthanum oxide. The sintering process involves adding the green body into a sintering furnace preheated to 850-900°C under an argon atmosphere, heating it to 1200°C at a heating rate of 4-6°C / min, switching to an air atmosphere, and sintering at 1450-1550°C at a heating rate of 2-3°C / min for 2-3 hours.

2. The lightweight alumina foam ceramic refractory material according to claim 1, characterized in that, The hollow alumina has an average particle size of 500 nm.

3. A method for preparing a lightweight alumina foam ceramic refractory material according to any one of claims 1 to 2, characterized in that, The preparation steps include the following: (1) Azirconium acetylacetonate, anhydrous methanol, yttrium nitrate hexahydrate, polyethylene oxide and aluminum nitrate nonahydrate were mixed and stirred to prepare a spinning solution, which was loaded into a spinning needle tube. A nano-atomizer containing a nano-aluminum titanate ethanol dispersion was placed at the collecting drum, with the spray direction orthogonal to the collecting drum. Electrospinning was performed. The solution was collected from the collecting drum and dried. It was then placed in a muffle furnace for heat treatment, naturally cooled to room temperature, and dispersed in a high-speed stirrer to obtain doped modified zirconium oxide fiber. (2) Alumina micro powder, hollow alumina, calcium carbonate, silicon carbide, doped modified zirconium oxide fiber, borax, titanium dioxide, manganese dioxide, magnesium oxide and lanthanum oxide are mixed evenly, added to a planetary ball mill for grinding, and sieved to obtain alumina-based mixed powder. (3) The alumina-based mixed powder is molded into a blank in a mold, added to a sintering furnace for sintering, and cooled to obtain a lightweight alumina foam ceramic refractory material.

4. The method for preparing a lightweight alumina foam ceramic refractory material according to claim 3, characterized in that, In step (1), the doped and modified zirconium oxide fiber is prepared by mixing 10-12 parts of zirconium acetylacetonate, 10-12 parts of anhydrous methanol, 0.8-0.9 parts of yttrium nitrate hexahydrate, 0.1-0.15 parts of polyethylene oxide, and 1-1.2 parts of aluminum nitrate nonahydrate by mass. The mixture is stirred at 300-400 r / min for 30-40 min at room temperature to prepare a spinning solution. The solution is then loaded into a spinning needle tube, with the needle tip 18 cm away from the collecting roller. A nano-atomizer containing 40-50 parts of nano-aluminum titanate ethanol dispersion is placed at the collecting roller. The spray direction is orthogonal to the collecting drum, and the distance between the nano-atomizer and the collecting drum is 18cm. Electrospinning is carried out at a voltage of 18~20KV, a spinning feed speed of 1ml / h, room temperature, and 40%~50%RH. After being collected from the collecting drum, the nano-atomizer is placed in a vacuum oven and vacuum dried at 70~80℃ for 10~12h. Then, it is transferred to a muffle furnace and heated to 1400~1500℃ at a heating rate of 1℃ / min and held for 20~30min. After naturally cooling to room temperature, it is dispersed in a high-speed stirrer and cut to a length of 3~5mm to obtain the final product.

5. The method for preparing a lightweight alumina foam ceramic refractory material according to claim 3, characterized in that, The weight-average molecular weight of the polyethylene oxide mentioned in step (1) is 1 million.

6. The method for preparing a lightweight alumina foam ceramic refractory material according to claim 3, characterized in that, The nano aluminum titanate ethanol dispersion in step (1) contains 3 wt% nano aluminum titanate.

7. The method for preparing a lightweight alumina foam ceramic refractory material according to claim 3, characterized in that, The planetary ball mill described in step (2) has a rotation speed of 320~360 r / min, a running speed of 350~400 r / min, a grinding medium of zirconia balls, a ball-to-material ratio of 2:1, a grinding time of 100~120 min, and a sieve mesh size of 800 mesh.

8. The method for preparing a lightweight alumina foam ceramic refractory material according to claim 3, characterized in that, The molding pressure in step (3) is 2~3MPa; the cooling is carried out at a rate of 20℃ / min to 800℃, and then naturally cooled to room temperature.