Preparation method of high-density microcrystalline foamed ceramic

Abstract

A method for preparing high-density microcrystalline foamed ceramics relates to the field of building material preparation technology. The method includes raw material system configuration, raw material pretreatment, batching and mixing, molding, segmented temperature-controlled foaming and crystallization firing, and post-treatment steps. The raw material system, by mass percentage, includes 60%–95% industrial solid waste, 1%–4% foaming agent, 2%–16% foam stabilizer, and 2%–20% flux. Through dry ball milling, mold forming, and a gradient heating + multi-stage heat preservation firing process, precise matching of foaming and crystallization is achieved. The obtained product has a bulk density of 0.45–1.2 g / cm³. 3 It possesses a compressive strength ≥12MPa, a thermal conductivity of 0.15~0.30W / (m・K), a water absorption rate ≤0.5%, a porosity of 30%~50%, and a pore size of 50~300μm, combining high density, excellent mechanical properties, and thermal insulation performance. This invention significantly improves the resource utilization rate of industrial solid waste, reduces raw material costs and energy consumption, is environmentally friendly, and has wide applicability, suitable for use in various fields such as building load-bearing insulation and industrial equipment insulation.

Description

Technical Field

[0001] This invention belongs to the technical field of building material preparation, and specifically discloses a method for preparing high-density microcrystalline foamed ceramics, which is particularly suitable for application scenarios with high requirements for density and mechanical properties, such as building structural materials, industrial thermal insulation and load-bearing materials, and high-end decorative materials. Background Technology

[0002] Foamed ceramics, as a green and environmentally friendly porous material, possess core advantages such as thermal insulation and fire resistance, and have been widely used in building insulation, industrial kiln insulation, and other fields. In current technologies, the research and development of foamed ceramics primarily focuses on increasing porosity, with its bulk density typically maintained at 0.2~0.4 g / cm³. 3 This results in low compressive strength of the product (generally <10MPa), which severely limits its application in load-bearing structures and scenarios with high mechanical performance requirements.

[0003] To improve the density and mechanical strength of foamed ceramics, existing technologies often employ methods such as increasing aggregate content or raising firing temperature. However, these methods have significant drawbacks: Firstly, simply increasing aggregate content leads to a sharp decrease in porosity, negating the inherent lightweight and heat-insulating advantages of foamed ceramics. Secondly, excessively high firing temperatures not only increase energy consumption but also easily cause pore coalescence and coarsening, affecting the uniformity of product performance. Furthermore, the foaming and crystallization processes in existing technologies are difficult to precisely match, often resulting in pore collapse or incomplete crystallization, leading to significant fluctuations in product performance. Moreover, existing solid waste-based foamed ceramics often suffer from poor performance stability due to unreasonable raw material ratios. Additionally, the utilization rate of industrial solid waste resources needs improvement, and some processes also suffer from high raw material costs and insufficient environmental friendliness.

[0004] Therefore, developing a method for preparing high-density microcrystalline foamed ceramics that combines high density, excellent mechanical properties and thermal insulation properties, as well as low raw material costs and good environmental friendliness, has significant practical significance and application value. Summary of the Invention

[0005] This invention aims to overcome the technical defects of existing foamed ceramics, such as insufficient density and mechanical properties, poor matching between foaming and crystallization, and low solid waste utilization rate. It provides a method for preparing high-density microcrystalline foamed ceramics. By optimizing the raw material system formula and segmented temperature control process parameters, it achieves uniform pore distribution and full crystal development, and significantly improves the density and mechanical strength of the product while ensuring thermal insulation performance.

[0006] The technical solution adopted by this invention to achieve its purpose is as follows: A method for preparing high-density microcrystalline foamed ceramic includes the following steps: S1. Raw material system configuration: by mass percentage, including 60%~95% industrial solid waste, 1%~4% foaming agent, 2%~16% foam stabilizer, and 2%~20% flux; of which SiO2+Al2O3 ≥70% is contained in the industrial solid waste; S2. Raw material pretreatment: Dry grinding of raw materials; S3. Ingredient Mixing: The raw materials are dry-mixed without adding water; S4. Molding: The mixed powder is filled into a refractory mold and shaped, and then dried. S5. Segmented temperature-controlled foaming and crystallization firing: First, it undergoes low-temperature debinding treatment, then pre-melting foaming treatment, crystallization densification treatment, and finally slow cooling treatment; S6. Post-processing: demolding, cutting, surface treatment.

[0007] Preferably, in step S1, the industrial solid waste is at least one of the scraps and cutting mud generated during the production of microcrystalline foamed ceramics, which serves as the ceramic matrix skeleton to achieve efficient resource utilization of industrial solid waste; the total content of impurities Fe2O3 and Na2O in the raw material system is ≤5%.

[0008] Preferably, in step S1, the foam stabilizer is kaolin or bentonite or a mixture of both, with a mass ratio of 1:(0.5~2), achieving uniform foaming through synergistic effect; the flux is glass powder or calcined talc, which can lower the firing temperature and promote liquid phase formation; the foaming agent is one or both of silicon carbide and sodium bicarbonate.

[0009] Preferably, in step S2, the raw material pretreatment includes: drying each raw material to a moisture content of <1%, using a dry ball milling process, controlling the ball-to-material ratio to 3:1 to 5:1, the rotation speed to 300 to 500 r / min, and the milling time to 4 to 10 h, so that the final powder particle size D50 is 10 to 30 μm, thereby improving the reactivity and mixing uniformity of the raw materials.

[0010] Preferably, in the ingredient mixing step S3, each pretreated raw material is accurately weighed according to the formula ratio and added to a ball mill for dry mixing for 4-8 hours to ensure that there is no agglomeration or segregation of the components.

[0011] Preferably, in step S4, the mixed powder is loaded into the refractory mold, gently vibrated to compact it, the filling thickness is controlled to be 4~10cm, the surface is scraped flat, and the formed green body is placed in a drying oven and dried at 80~220℃ for 2~4h to remove free water and prevent the green body from cracking due to rapid evaporation of moisture during the firing process.

[0012] Preferably, in step S5, the specific parameters are as follows: Low-temperature debinding treatment: heating at a rate of 2~5℃ / min to 400~600℃ and holding for 10~90min to remove organic dispersants and residual moisture, preventing bubbling during foaming; Pre-melting foaming treatment: heating at a rate of 3~8℃ / min to 800~950℃ and holding for 10~90min to form an initial liquid phase, decomposing the composite foaming agent to generate gas and forming uniform small pores; Crystallization and densification treatment: heating at a rate of 5~8℃ / min to 1050~1200℃ and holding for 10~90min to promote microcrystal precipitation and pore wall densification, simultaneously improving product density and mechanical strength; Slow cooling treatment: cooling at a rate of 2~4℃ / min to 600℃ and then naturally cooling to reduce thermal stress and prevent product cracking.

[0013] Preferably, in step S6, the post-processing step includes demolding after the product has cooled to room temperature, cutting to the target size with a diamond saw blade, and then polishing with a surface planer to remove the outer skin, thereby improving the product's appearance quality and dimensional accuracy.

[0014] The beneficial effects of this invention are: 1. Excellent product performance: The resulting high-density microcrystalline foamed ceramic has a bulk density of 0.45~1.2 g / cm³. 3 It has a compressive strength ≥12 MPa, a thermal conductivity of 0.15~0.30W / (m・K), a water absorption rate ≤0.5%, a porosity of 30%~50% and a uniform pore size distribution (50~300μm), and combines high density, excellent mechanical properties and thermal insulation properties, breaking through the application limitations of traditional foamed ceramics. 2. Strong process innovation: Through the synergistic design of foaming agent and foam stabilizer, combined with segmented temperature-controlled firing process, the foaming and crystallization processes are precisely matched, effectively avoiding the problems of pore collapse or coarsening, and the product performance is highly stable. 3. Environmentally friendly and low-cost: Using industrial solid waste as the main raw material (accounting for 60%~95%), it significantly improves the utilization rate of solid waste resources and greatly reduces raw material costs; the process is mainly dry, with low energy consumption and low pollution, which meets the requirements of green production development. 4. Wide applicability: Various forms of products, such as boards and blocks, can be prepared by adjusting the molding method, and are suitable for multiple fields such as building load-bearing insulation, industrial equipment insulation, and high-end decorative materials. Detailed Implementation

[0015] 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Example 1

[0016] Raw material formula (by weight): 80% microcrystalline foamed ceramic scraps, 2% silicon carbide foaming agent, 15% foam stabilizer (kaolin: bentonite = 1:1), and 3% glass powder flux. Raw material pretreatment: The microcrystalline foamed ceramic scraps were crushed to 1cm, and all raw materials were dried to a moisture content of 1%. They were then dry-milled (ball-to-material ratio 4:1, speed 400r / min) for 6h to control the powder D50=20μm. Ingredient mixing: Dry mixing for 6 hours, without adding water (dry molding); Molding and drying: The filling is 4cm thick and dried at 200℃ for 4 hours using a mold. Firing process: Low-temperature debinding: Heat to 500℃ at a heating rate of 3℃ / min and hold for 45min; Pre-melting foaming: Heat to 900℃ at a heating rate of 5℃ / min and hold for 60min; Crystallization and densification: Heat to 1150℃ at a heating rate of 6℃ / min and hold for 90min; Slow cooling: Cool to 600℃ at a cooling rate of 3℃ / min and then allow to cool naturally. Post-processing: After the product cools to room temperature, it is demolded, cut to the target size using a diamond saw blade, and then polished with a surface planer to remove the outer skin, thereby improving the product's appearance quality and dimensional accuracy. Example 2

[0017] Raw material formula (by weight): 90% microcrystalline foam scraps, 1% silicon carbide foaming agent, 5% foam stabilizer (kaolin: bentonite = 1:1), and 4% calcined talc flux; Raw material pretreatment: The microcrystalline foamed ceramic scraps were crushed to 1cm, and all raw materials were dried to a moisture content of 1%. They were then dry-milled (ball-to-material ratio 4:1, speed 400r / min) for 6h to control the powder D50=20μm. Ingredient mixing: Dry mixing for 6 hours; Molding and drying: The filling is 4cm thick and dried at 200℃ for 4 hours using a mold. Firing process: Low-temperature debinding: Heat to 550℃ at a heating rate of 3℃ / min and hold for 40min; Pre-melting foaming: Heat to 920℃ at a heating rate of 5℃ / min and hold for 50min; Crystallization and densification: Heat to 1140℃ at a heating rate of 6℃ / min and hold for 40min; Slow cooling: Cool to 600℃ at a cooling rate of 3℃ / min and then allow to cool naturally. Post-processing: After the product cools to room temperature, it is demolded, cut to the target size using a diamond saw blade, and then polished with a surface planer to remove the outer skin, thereby improving the product's appearance quality and dimensional accuracy. Example 3

[0018] Raw material formula (mass percentage): 80% microcrystalline foam scrap, 15% cutting mud, 1% foaming agent silicon carbide, 2% foam stabilizer (kaolin: bentonite = 1:1), 2% flux (glass powder). Raw material pretreatment: The microcrystalline foamed ceramic scraps were crushed to 1cm, and all raw materials were dried to a moisture content of 1%. They were then dry-milled (ball-to-material ratio 4:1, speed 400r / min) for 6h to control the powder D50=20μm. Ingredient mixing: Dry mixing for 6 hours; Molding and drying: The filling is 4cm thick and dried at 200℃ for 4 hours using a mold. Firing process: Low-temperature debinding: Heat to 450℃ at a heating rate of 2℃ / min and hold for 50min; Pre-melting foaming: Heat to 880℃ at a heating rate of 4℃ / min and hold for 70min; Crystallization and densification: Heat to 1160℃ at a heating rate of 5℃ / min and hold for 80min; Slow cooling: Cool to 600℃ at a cooling rate of 2℃ / min and then allow to cool naturally. Post-processing: After the product cools to room temperature, it is demolded, cut to the target size using a diamond saw blade, and then polished with a surface planer to remove the outer skin, thereby improving the product's appearance quality and dimensional accuracy.

[0019] Example of effect - performance Test methods: The performance tests were conducted in accordance with JG / T506-2016 "Microcrystalline Foamed Boards and Blocks for Tailings". Specifically, the test methods for bulk density, compressive strength, flexural strength, water absorption, and porosity were carried out according to GB / T 5486 "Test Methods for Inorganic Rigid Thermal Insulation Products"; the test method for thermal conductivity was carried out according to GB / T 10295 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method"; pore size distribution was determined using the mercury porosimetry method (AutoPore IV 9500 mercury porosimeter), with a test range of 0.003~360μm.

[0020] Table 1 Performance Test Table for Foamed Ceramics Therefore, the high-density microcrystalline foam material prepared by this invention has excellent properties such as high specific gravity, high compressive strength and flexural strength, low thermal conductivity, low water absorption and uniform pore distribution.

[0021] This invention uses industrial solid waste microcrystalline foamed ceramic scraps as the main raw material to prepare foamed ceramics. It not only solves the problem of unmanageable waste generated during the production process, but also reduces the manufacturing cost of foamed ceramics. The foamed ceramics produced have excellent properties such as high density, high strength and low thermal conductivity, which greatly improves the quality of foamed ceramics.

[0022] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the scope of the technology disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-density microcrystalline foamed ceramic, characterized in that, Includes the following steps: S1. Raw material system configuration: by mass percentage, it includes 60%~95% industrial solid waste, 1%~4% foaming agent, 2%~16% foam stabilizer, and 2%~20% flux; of which SiO2+Al2O3 ≥ 70% is contained in the industrial solid waste; S2. Raw material pretreatment: Dry grinding of raw materials; S3. Ingredient Mixing: The raw materials are dry-mixed without adding water; S4. Molding: The mixed powder is filled into a refractory mold and shaped, and then dried. S5. Segmented temperature-controlled foaming and crystallization firing: First, it undergoes low-temperature debinding treatment, then pre-melting foaming treatment, crystallization densification treatment, and finally slow cooling treatment; S6. Post-processing: demolding, cutting, surface treatment.

2. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S1, the industrial solid waste is at least one of the scraps and cutting mud generated during the production of microcrystalline foamed ceramics; the total content of impurities Fe2O3 and Na2O in the raw material system is ≤5%.

3. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S1, the foam stabilizer is kaolin or bentonite or a mixture of both, with a mass ratio of 1:(0.5~2); the flux is glass powder or calcined talc; and the foaming agent is one or both of silicon carbide and sodium bicarbonate.

4. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S2, the raw material pretreatment includes: drying each raw material to a moisture content of ≤1%, using a dry ball milling process, controlling the ball-to-material ratio to be 3:1 to 5:1, the rotation speed to be 300 to 500 r / min, and the milling time to be 4 to 10 h, so that the final powder particle size D50 is 10 to 30 μm.

5. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S3, dry mixing is performed for 4-8 hours.

6. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S4, the filling thickness is 4~10cm, and the drying process parameters are: drying at 80~220℃ for 2~4h.

7. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S5, the specific parameters are as follows: Low-temperature debinding treatment: Heat to 400~600℃ at a heating rate of 2~5℃ / min and hold for 10~90min; Pre-melting foaming treatment: Heat to 800~950℃ at a heating rate of 3~8℃ / min and hold for 10~90min; Crystallization and densification treatment: Heat to 1050~1200℃ at a heating rate of 5~8℃ / min and hold for 10~90min; Slow cooling treatment: Cool to 600℃ at a cooling rate of 2~4℃ / min and then cool naturally.

8. The method for preparing high-density microcrystalline foamed ceramic according to claim 1, characterized in that, In step S6, the post-processing steps include demolding, diamond saw cutting, surface planing, and skin removal.

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