Alumina-based foamed ceramic and preparation method thereof

Abstract

According to the preparation method, aluminum oxide powder and calcium aluminate cement are taken as matrix raw materials, lithium carbonate is taken as a coagulant, a direct foaming method is combined with a calcium aluminate cement rapid curing process, and the aluminum oxide-based foamed ceramic is obtained through high-humidity environment maintenance, drying and sintering treatment. The lithium carbonate can promote the generation of a nucleation source, accelerate the hydration reaction and realize rapid curing; a new flaky hydration product Ca4Al2CO9. 11H2O (C4AcH11) can be generated in a high-humidity curing environment, and the hydration product Ca4Al2CO9. 11H2O (C4AcH11) and Al (OH) 3 (AH3) gel generated by hydration are interwoven to form an internal interlocking structure, so that improvement of the strength of a porous ceramic green body is promoted, the curing time is shortened, and rapid demolding of a foamed ceramic material is realized. The material has the excellent properties of short preparation process period, uniform product pore diameter, high strength, low heat conductivity coefficient and the like, and is a preferred material for an industrial kiln thermal insulation layer.

Description

TECHNICAL FIELD

[0001] The present application relates to an alumina-based foam ceramic and a preparation method thereof, in particular to an alumina-based foam ceramic with rapid solidification, short curing and demolding time, good heat preservation and high strength, and a preparation method thereof, and belongs to the technical field of foam ceramics. BACKGROUND

[0002] Alumina-based foam ceramics are widely used in thermal insulation, sound absorption and catalyst carrier due to their stable chemical properties, high strength, high temperature resistance, good thermal shock resistance, large specific surface area and low cost. The common preparation methods of alumina-based foam ceramics include direct foaming method, sacrificial template method and pore-forming agent addition method. The direct foaming method can prepare foam ceramics with a porosity of more than 80%, which can significantly reduce the thermal conductivity of ceramics and improve the thermal insulation performance of foam ceramics. However, in the process of preparing ceramics by direct foaming method, the low viscosity and low solid content of the ceramic slurry are the key to introducing gas to obtain high-porosity ceramics. However, the removal of high solvent in the slurry requires a long curing time, which affects the pore size and strength of the ceramic green body after curing, and prolongs the production cycle, which is not conducive to the industrial production of porous ceramics.

[0003] At present, in order to shorten the production cycle of alumina foam ceramics, scholars have conducted a lot of research. For example, CN103787691A discloses a preparation method of alumina foam ceramic, which uses polyether and polyester polyol as solvent, toluene diisocyanate as curing agent, and triethylene diamine, N,N-dimethylcyclohexylamine and stannous octoate as curing catalyst. CN104311118B discloses a super-light alumina foam ceramic and a preparation method thereof, which uses sugar and ceramic fine powder to mix and heat, foams at high temperature, solidifies and sintering to prepare alumina foam ceramic. CN105753507B discloses a preparation method of silicon carbide-calcium hexaluminate composite porous ceramic, which uses foaming method and calcium aluminate cement solidification combined method to obtain porous silicon carbide-calcium hexaluminate ceramic through high temperature sintering.

[0004] The above-mentioned prior art has certain advantages, but still has the following problems: (1) a large amount of organic matter is used in the main preparation process, and a large amount of toxic gas and carbon dioxide will be discharged during sintering, polluting the environment; (2) the process is complex and energy is wasted because the preparation process needs to be heated to 200℃ for insulation; (3) the curing time is long, the production cycle is long, and the long curing time also leads to uneven pore distribution, affecting the thermal insulation effect and high temperature strength of the foam ceramic.

[0005] Therefore, it is a research focus to develop an alumina foam ceramic with simple process, environmental friendliness, short curing time, uniform pore distribution, good thermal insulation effect and high mechanical strength. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides an alumina-based foam ceramic, which has small and uniformly distributed pore sizes, and good heat preservation effect and mechanical strength.

[0007] The specific technical solutions of the present application are as follows: An alumina-based foam ceramic, the raw materials of the foam ceramic are: alumina powder, calcium aluminate cement powder, dispersant, foaming agent, foam stabilizer, coagulant and water.

[0008] Further, in the above foam ceramic, the alumina powder and the calcium aluminate cement powder are base raw materials, wherein the alumina powder is 80-95 parts by weight, for example 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts. The calcium aluminate cement powder is 5-20 parts by weight, for example 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts.

[0009] Further, the dispersant, foaming agent, foam stabilizer and coagulant are used as auxiliary agents, and water is used as a solvent. The amount of dispersant is 0.1-1wt% of the total mass of base raw materials (i.e. the sum of alumina powder and calcium aluminate cement powder, the same below), for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%.

[0010] Further, the foaming agent is 0.1-2wt% of the total mass of base raw materials, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%.

[0011] Further, the foam stabilizer is 0.1-1wt% of the total mass of base raw materials, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%.

[0012] Further, the coagulant is 0.1-0.5wt% of the mass of calcium aluminate cement powder, for example 0.10%, 0.20%, 0.30%, 0.40%, 0.50%.

[0013] Further, the water is 40-60wt% of the total mass of the base material, for example, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%.

[0014] Further, the alumina powder is one or both of alpha-alumina and tabular corundum, the Al2O3 content of the alumina powder is ≥99wt%, and the Na2O content is ≤0.1wt%. The average particle size of the alumina powder is 1-20μm.

[0015] Further, the calcium aluminate cement is a hydraulic cementitious material with calcium aluminate (CA) and calcium dialuminate (CA2) as the main mineral components, the Al2O3 content of the calcium aluminate cement powder is 60-75wt%, and the CaO content is 25-40wt%. The particle size of the calcium aluminate cement powder is 2-30μm.

[0016] Further, the setting accelerator is lithium carbonate, which can promote the formation of nucleation source Li2Al4O7(H2O) 11 and accelerate the progress of the hydration reaction to generate solid hydration products and achieve rapid solidification. The Li2CO3 content of the lithium carbonate is ≥99.9wt%, and the particle size of the lithium carbonate is ≤20μm.

[0017] Further, the dispersant is one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium lignosulfonate, and ammonium citrate.

[0018] Further, the foaming agent is one or more of sodium dodecyl sulfonate and sodium dodecyl sulfate.

[0019] Further, the foam stabilizer is one or both of sodium alginate and carboxymethyl cellulose. The molecular weight of the carboxymethyl cellulose is 180, and the molecular weight of the sodium alginate is 216.

[0020] The application also provides a preferred method for preparing an alumina-based foam ceramic, which uses alumina powder and calcium aluminate cement powder as base materials, adopts a direct foaming method combined with a lithium carbonate-promoted calcium aluminate cement hydration rapid solidification process, and obtains an alumina-based foam ceramic material after curing, demolding, drying, and sintering. This method has rapid solidification, short curing and demolding time, and greatly shortens the production cycle.

[0021] Further, the above method comprises the following steps: (1) mixing and ball-milling alumina powder, calcium aluminate cement powder, a dispersant, a foaming agent, a foam stabilizer, a setting accelerator, and water to obtain a suspension slurry; (2) mechanically stirring the suspension slurry to fully foam to obtain a foamed slurry; (3) injecting the foamed slurry into a mold for curing, and demolding after curing to obtain a porous body; (4) drying the porous body, and high-temperature sintering after drying to obtain an alumina-based foam ceramic.

[0022] Further, in step (1), the raw materials are fully mixed and uniformly mixed by ball milling, and the ball milling time is 3-5 hours, for example, 3h, 3.5h, 4h, 4.5h, 5h.

[0023] Further, in step (2), the suspension slurry is mechanically stirred in a stirring barrel, and the rotor speed is 800-1500 revolutions per minute, for example, 800 revolutions per minute, 900 revolutions per minute, 1000 revolutions per minute, 1100 revolutions per minute, 1200 revolutions per minute, 1300 revolutions per minute, 1400 revolutions per minute, 1500 revolutions per minute, and the mechanical stirring time is generally 5-15 minutes, for example, 5 minutes, 10 minutes, 15 minutes.

[0024] Further, in step (3), the curing temperature is 40-60℃, for example, 40℃, 45℃, 50℃, 55℃, 60℃, the curing humidity is 60%-80%, for example, 60%, 65%, 70%, 75%, 80%, and the curing time is 2-6 hours, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h and 6h. Lithium carbonate is combined with high humidity curing, and lithium carbonate can promote the formation of nucleation source Li2Al4O7(H2O) 11 , accelerate the progress of the hydration reaction, generate solid hydration products, and achieve rapid curing; the high-humidity curing environment can generate new sheet-shaped hydration products Ca4Al2CO9·11H2O (C4AcH 11 ), which interweave with the hydration-generated Al(OH)3(AH3) gel to form an internal interlocking structure, promote the improvement of the strength of the porous ceramic green body, reduce the curing time, achieve rapid demolding of the alumina-based foam ceramic material, and fix the pore size.

[0025] Further, in step (4), the drying is vacuum drying. The drying temperature is 100-120℃, for example, 100℃, 105℃, 110℃, 115℃, 120℃, and the drying time is 15-20 hours, for example, 15h, 15.5h, 16h, 16.5h, 17h, 17.5h, 18h, 18.5h, 19h, 19.5h, 20h.

[0026] Furthermore, in step (4), the high-temperature sintering temperature is 1400~1650℃, for example 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, 1650℃, and the holding time is 3~6 hours, for example 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h. This invention employs a special heating program, raising the temperature from room temperature to the sintering temperature at different rates. Specifically: from room temperature to 500℃, the heating rate is 10-20℃ / min, for example, 10℃ / min, 15℃ / min, or 20℃ / min; above 500℃ to 1200℃, the heating rate is 5-10℃ / min, for example, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min; above 1200℃, the heating rate is 3-4℃ / min, for example, 3℃ / min or 4℃ / min. The hydration products of calcium aluminate cement decompose at 500℃ to 1200℃ to generate 12CaO·7Al2O3 (C 12 (A7) Reducing the heating rate from 10-20℃ / min to 5-10℃ / min can alleviate the thermal stress caused by the rapid decomposition of hydration products and prevent crack formation; at 1200℃, the heating rate can be further reduced to C 12 The reaction of A7 with alumina to form CaO·6Al2O3 (CA6) and the sufficient time for the sintering reaction both contribute to improving the strength of foam ceramics.

[0027] This invention uses calcium aluminate cement as a curing agent. By controlling the curing humidity and adding the accelerator lithium carbonate, rapid solidification of the green body can be achieved, resulting in small and uniformly distributed pores. The alumina-based foam ceramic obtained by this invention has a bulk density of 0.48~0.57 g / cm³. 3 It has an apparent porosity of 80-90%, an average pore size of 65-115 μm, a room temperature compressive strength of 3.8-6.8 MPa, and a thermal conductivity of 0.08-0.15 W / (m·K) at 200℃.

[0028] The present invention has the following beneficial effects: 1. This invention uses calcium aluminate cement as a fixative and lithium carbonate as a setting accelerator. The introduction of lithium carbonate can react with the calcium dialuminate (CA2) phase and water in the calcium aluminate cement to generate Li2Al4O7(H2O). 11 It can act as a nucleation source, promoting the nucleation reaction during the hydration of calcium aluminate cement. The presence of a large number of nucleation sources will accelerate the hydration reaction. The continuous progress of this reaction can continuously consume the solvent water in the slurry, generate solid hydration products, accelerate solidification, and achieve rapid solidification.

[0029] 2. This invention employs a high-humidity curing environment, which can generate new hydration products Ca4Al2CO9·11H2O(C4AcH 11 The hydration product has a plate-like structure, which can interweave with the Al(OH)3(AH3) gel generated during hydration to form an internal interlocking structure. This is beneficial for improving the strength of porous ceramic green bodies, reducing curing time, and enabling rapid demolding of alumina-based foam ceramic materials.

[0030] 3. Rapid hydration reaction can accelerate the consumption of solvent water in the foam ceramic slurry, inhibit the austenitic ripening behavior in the foam ceramic slurry, and prevent bubbles from merging and growing under Laplace pressure, which is beneficial for obtaining ceramic green bodies with uniform pore size. As is well known, the pore size and uniformity of ceramics have an important influence on their strength and thermal conductivity. The porous ceramics prepared by this invention have small and uniformly distributed pore sizes, which is beneficial for improving the strength and thermal insulation performance of foam ceramics.

[0031] 4. The sintering process of this invention can guarantee the hydration product Li2Al4O7(H2O) 11 With Ca4Al2CO9·11H2O(C4AcH 11 During sintering, lithium carbonate undergoes complete decomposition and reacts fully with alumina. Trace amounts of lithium carbonate react with alumina to generate a small amount of transition liquid phase. This liquid phase accelerates the diffusion of aluminum and calcium ions, speeds up the formation of the sintering neck, and improves the strength of the foam ceramic. Furthermore, the aforementioned hydration product C4AcH... 11 It will decompose during sintering and react with alumina to form calcium hexaaluminate, which is in the form of flakes and can interlock with alumina particles to further improve the strength of foam ceramics.

[0032] 5. This invention improves the thermal insulation performance and strength of foam ceramics through a combination of raw material selection, curing, and sintering processes. The process is simple, low-cost, energy-efficient, has a short curing time, high production efficiency, and is environmentally friendly, making it suitable for industrial production. The resulting alumina-based foam ceramics exhibit well-developed sintered necks, small and uniformly distributed pores, high mechanical properties, low thermal conductivity, and excellent thermal insulation, making it a preferred material for insulation layers in industrial kilns. Attached Figure Description

[0033] Figure 1 This is a microstructure diagram of the alumina-based foam ceramic obtained in Example 1. Detailed Implementation

[0034] The following description illustrates exemplary embodiments of the present invention, including various details to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions, operations, and structures are omitted in the following description.

[0035] Unless otherwise defined, the technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, the present invention describes materials and methods hereinafter. In case of conflict, the definitions included herein shall prevail.

[0036] In the following examples and comparative examples, all raw materials used were commercially available products. Specifically: the alumina powder contained ≥99 wt% Al₂O₃, ≤0.1 wt% Na₂O, and had a particle size distribution ranging from 1 to 10 μm. The calcium aluminate cement powder contained 60-75 wt% Al₂O₃, 25-40 wt% CaO, and had a particle size distribution ranging from 2 to 30 μm. The lithium carbonate contained ≥99.9 wt% Li₂CO₃ and had a particle size ≤20 μm.

[0037] Example 1 A rapidly solidifying alumina-based foam ceramic material comprises the following raw materials by weight: 90 parts α-alumina powder, 10 parts calcium aluminate cement powder, 0.3 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.03 parts lithium carbonate, and 60 parts water. The dispersant is sodium tripolyphosphate, the foaming agent is sodium dodecyl sulfonate, and the foam stabilizer is sodium alginate.

[0038] The preparation method of alumina-based foam ceramic material is as follows: 1. According to the above raw material composition, place alumina powder and calcium aluminate cement powder in a ball mill jar, then add water, dispersant, foaming agent, foam stabilizer and lithium carbonate, and ball mill for 3 hours to obtain a suspension slurry; 2. Transfer the suspended slurry to a mixing tank for mechanical mixing. Adjust the rotor to a speed of 1200-1500 revolutions per minute and run it for 10 minutes to obtain a foamed slurry. 3. Inject the foam slurry into the mold and transfer it to the curing box. Cure it for 2 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold to obtain a porous green body. 4. Transfer the porous preform to a vacuum drying oven and dry it at 100~110℃ for 18 hours; 5. The dried porous preform is placed in a high-temperature sintering furnace and heated from room temperature to 1500℃ in an air atmosphere. It is then held at 1500℃ for 3 hours to obtain alumina-based foam ceramic material. The heating program is as follows: 10℃ / min from room temperature to 500℃, 5℃ / min from 500℃ to 1200℃, and 3℃ / min after 1200℃.

[0039] The microstructure of the obtained alumina-based foam ceramic material is as follows: Figure 1 As shown in the figure, the aperture is small and the distribution is uniform.

[0040] Example 2 A rapidly solidifying alumina-based foam ceramic material comprises the following raw materials by weight: 85 parts tabular corundum, 15 parts calcium aluminate cement powder, 0.5 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.03 parts lithium carbonate, and 60 parts water. The dispersant is sodium hexametaphosphate, the foaming agent is sodium dodecyl sulfate, and the foam stabilizer is sodium alginate.

[0041] The preparation method of alumina-based foam ceramic material is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing box. Cure it for 3 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold to obtain a porous green body. 4. Same as Example 1; 5. Same as Example 1.

[0042] Example 3 A rapidly solidifying alumina-based foam ceramic material comprises the following raw material components by weight: 95 parts α-alumina powder, 5 parts calcium aluminate cement powder, 0.3 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.01 parts lithium carbonate, and 60 parts water. The dispersant is sodium tripolyphosphate, the foaming agent is sodium dodecyl sulfonate, and the foam stabilizer is carboxymethyl cellulose.

[0043] The preparation method of alumina-based foam ceramic material is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing chamber. Cure it for 6 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold to obtain a porous green body. 4. Same as Example 1; 5. Same as Example 1.

[0044] Example 4 A rapidly solidifying alumina-based foam ceramic material, the raw material composition by weight is the same as in Example 1. The preparation method is as follows: 1. According to the above raw material composition, place alumina powder and calcium aluminate cement powder in a ball mill jar, then add water, dispersant, foaming agent, foam stabilizer and lithium carbonate, and ball mill for 3 hours to obtain a suspension slurry; 2. Transfer the suspended slurry to a mixing tank for mechanical mixing. Adjust the rotor to a speed of 1000-1150 revolutions per minute and run it for 15 minutes to obtain a foamed slurry. 3. Inject the foam slurry into the mold and transfer it to the curing chamber. Cure it for 3 hours at a curing temperature of 60℃ and a curing humidity of 60%. Demold to obtain a porous green body. 4. Transfer the porous preform to a vacuum drying oven and dry it at 100~110℃ for 18 hours; 5. The dried porous preform is placed in a high-temperature sintering furnace and heated from room temperature to 1450℃ in an air atmosphere. It is then held at 1450℃ for 3 hours to obtain alumina-based foam ceramic material. The heating program is as follows: 20℃ / min for room temperature to 500℃, 10℃ / min for 500℃ to 1200℃, and 4℃ / min after 1200℃.

[0045] Example 5 A rapidly solidifying alumina-based foam ceramic material, the raw material composition by weight is the same as in Example 1. The preparation method is as follows: 1. According to the above raw material composition, place alumina powder and calcium aluminate cement powder in a ball mill jar, then add water, dispersant, foaming agent, foam stabilizer and lithium carbonate, and ball mill for 3 hours to obtain a suspension slurry; 2. Transfer the suspended slurry to a mixing tank for mechanical mixing. Adjust the rotor speed to 1200-1500 revolutions per minute and run for 10 minutes to obtain foamed slurry. 3. Inject the foam slurry into the mold and transfer it to the curing box. Cure it for 3 hours at a curing temperature of 50℃ and a curing humidity of 70%. Demold to obtain a porous green body. 4. Transfer the porous preform to a vacuum drying oven and dry it at 100~110℃ for 20 hours; 5. The dried porous preform is placed in a high-temperature sintering furnace and heated from room temperature to 1650℃ in an air atmosphere. It is then held at 1650℃ for 3 hours to obtain alumina-based foam ceramic material. The heating program is as follows: 15℃ / min from room temperature to 500℃, 8℃ / min from 500℃ to 1200℃, and 4℃ / min after 1200℃.

[0046] Comparative Example 1 An alumina-based foam ceramic material has the following raw material composition by weight: 90 parts α-alumina powder, 10 parts calcium aluminate cement powder, 0.3 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.1 parts triethanolamine, and 60 parts water. The dispersant is sodium tripolyphosphate, the foaming agent is sodium dodecyl sulfonate, and the foam stabilizer is sodium alginate.

[0047] The preparation method of alumina-based foam ceramic material is as follows: 1. According to the above raw material composition, place alumina powder and calcium aluminate cement powder in a ball mill jar, then add water, dispersant, foaming agent, foam stabilizer and triethanolamine, and ball mill for 3 hours to obtain a suspension slurry; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing chamber. Cure it for 12 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold to obtain a porous green body. 4. Same as Example 1; 5. Same as Example 1.

[0048] Comparative Example 2 An alumina-based foam ceramic material has the following raw material composition by weight: 90 parts α-alumina powder, 10 parts calcium aluminate cement powder, 0.3 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.005 parts lithium carbonate, and 60 parts water. The dispersant is sodium tripolyphosphate, the foaming agent is sodium dodecyl sulfonate, and the foam stabilizer is sodium alginate.

[0049] The preparation method of alumina-based foam ceramic material is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing box. Cur the mold for 18 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold the mold to obtain a porous preform. 4. Same as Example 1; 5. Same as Example 1.

[0050] Comparative Example 3 An alumina-based foam ceramic material has the following raw material composition by weight: 90 parts α-alumina powder, 10 parts calcium aluminate cement powder, 0.3 parts dispersant, 1 part foaming agent, 0.5 parts foam stabilizer, 0.6 parts lithium carbonate, and 60 parts water. The dispersant is sodium tripolyphosphate, the foaming agent is sodium dodecyl sulfonate, and the foam stabilizer is sodium alginate.

[0051] The preparation method of alumina-based foam ceramic material is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing chamber. Cure it for 8 hours at a curing temperature of 45℃ and a curing humidity of 80%. Demold to obtain a porous green body. 4. Same as Example 1; 5. Same as Example 1.

[0052] Comparative Example 4 A rapidly solidifying alumina-based foam ceramic material, the raw material composition by weight is the same as in Example 1. The preparation method is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Inject the foam slurry into the mold and transfer it to the curing box. Cure it for 10 hours at a curing temperature of 45℃ and a curing humidity of 50%. Demold to obtain a porous green body. 4. Same as Example 1; 5. Same as Example 1.

[0053] Comparative Example 5 A rapidly solidifying alumina-based foam ceramic material, the raw material composition by weight is the same as in Example 1. The preparation method is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Same as Example 1; 4. Same as Example 1; 5. Place the dried porous blank in a high-temperature sintering furnace and heat it from room temperature to 1500℃ at a heating rate of 3℃ / min in an air atmosphere. Then, keep it at 1500℃ for 3 hours to obtain alumina-based foam ceramic material.

[0054] Comparative Example 6 A rapidly solidifying alumina-based foam ceramic material, the raw material composition by weight is the same as in Example 1. The preparation method is as follows: 1. Same as Example 1; 2. Same as Example 1; 3. Same as Example 1; 4. Same as Example 1; 5. The dried porous preform is placed in a high-temperature sintering furnace and heated from room temperature to 1500℃ in an air atmosphere. It is then held at 1500℃ for 3 hours to obtain alumina-based foam ceramic material. The heating program is as follows: the heating rate is 10℃ / min from room temperature to 1200℃, and the heating rate is 3℃ / min after 1200℃.

[0055] The properties of the above-mentioned alumina-based foam ceramics were tested. The bulk density and apparent porosity were tested using Archimedes' drainage method (GB / T 1966-2024), the average pore size was statistically analyzed using image software, the compressive strength at room temperature was tested using GB / T 1964-2023, and the thermal conductivity at 200℃ was tested using the water flow plate method (YB / T 4130-2005).

[0056] Table 1

Claims

1. An alumina-based foam ceramic, characterized in that, The raw materials are: alumina powder, calcium aluminate cement powder, dispersant, foaming agent, foam stabilizer, accelerator and water; wherein the alumina powder is 80-95 parts by weight, the calcium aluminate cement powder is 5-20 parts by weight, and the accelerator is lithium carbonate.

2. The alumina-based foam ceramic according to claim 1, characterized in that: The accelerator is 0.1~0.5wt% of the calcium aluminate cement powder; preferably, the particle size of the accelerator is ≤20μm.

3. The alumina-based foam ceramic according to claim 1 or 2, characterized in that: The alumina powder is one or both of α-alumina and tabular corundum; preferably, the average particle size of the alumina powder is 1~20μm.

4. The alumina-based foam ceramic according to claim 1 or 2, characterized in that: The calcium aluminate cement powder contains 60-75 wt% Al2O3 and 25-40 wt% CaO; preferably, the calcium aluminate cement powder has a particle size of 2-30 μm.

5. The alumina-based foam ceramic according to any one of claims 1-4, characterized in that: The dispersant is at least one of sodium tripolyphosphate, sodium hexametaphosphate, sodium lignosulfonate, and ammonium citrate; preferably, the foaming agent is at least one of sodium dodecyl sulfonate and sodium dodecyl sulfate; preferably, the foam stabilizer is at least one of sodium alginate and carboxymethyl cellulose.

6. The alumina-based foam ceramic according to any one of claims 1-5, characterized in that: The dispersant is 0.1-1 wt% of the total mass of alumina powder and calcium aluminate cement powder, the foaming agent is 0.1-2 wt% of the total mass of alumina powder and calcium aluminate cement powder, the foam stabilizer is 0.1-1 wt% of the total mass of alumina powder and calcium aluminate cement powder, and the water is 40-60 wt% of the total mass of alumina powder and calcium aluminate cement powder.

7. The alumina-based foam ceramic according to any one of claims 1-6, characterized in that: Its bulk density is 0.48~0.57 g / cm³. 3 It has an apparent porosity of 80-90%, an average pore size of 65-115 μm, a room temperature compressive strength of 3.8-6.8 MPa, and a thermal conductivity of 0.08-0.15 W / (m·K) at 200℃.

8. A method for preparing alumina-based foam ceramic according to any one of claims 1-7, characterized in that: Includes the following steps: (1) Alumina powder, calcium aluminate cement powder, dispersant, foaming agent, foam stabilizer, coagulant and water are mixed and ball-milled to obtain a suspension slurry; (2) Mechanically stir the suspension slurry until it is fully foamed to obtain a foam slurry; (3) Inject the foam slurry into the mold for curing, and demold after curing to obtain a porous blank; (4) The porous blank is dried and then sintered at high temperature to obtain alumina-based foam ceramic.

9. The preparation method according to claim 8, characterized in that: In step (1), the ball milling time is 3 to 5 hours; Preferably, in step (2), the mechanical stirring is performed at a speed of 800-1500 rpm for 5-15 minutes.

10. The preparation method according to claim 8, characterized in that: In step (3), the curing temperature is 40~60℃, the curing humidity is 60%~80%, and the curing time is 2~6 hours; Preferably, in step (4), the high-temperature sintering temperature is 1400~1650℃, the holding time is 3~6 hours, and the temperature is raised to the sintering temperature at room temperature according to different heating rates. The heating rate is 10-20℃ / min for room temperature to 500℃, 5-10℃ / min for temperatures above 500℃ to 1200℃, and 3-4℃ / min for temperatures above 1200℃.

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