A foamed ceramic with high refractory limit and its preparation method

Abstract

This invention belongs to the field of foamed ceramics technology and relates to a foamed ceramic with a high fire resistance limit and its preparation method, including the following steps: (1) mixing aluminum trifluoride and barium titanate to obtain mixed pellets; (2) ball milling the mixed pellets into mixed powder I; (3) mixing aluminum nitride powder with mixed powder I to prepare a composite foaming agent; (4) preparing solid waste raw materials; (5) adding ceramic desiccant to the solid waste raw materials and ball milling the solid waste raw materials into solid waste powder; (6) mixing the composite foaming agent, solid waste powder and water evenly to prepare mixed powder II; (7) pressing mixed powder II into a green body; (8) sintering the green body to obtain the foamed ceramic. The fire resistance limit of the foamed ceramic prepared by this invention is much higher than the first-class fire resistance rating requirement of non-load-bearing exterior walls, and also meets the first-class fire resistance rating requirement of firewalls. In addition, under the condition of comparable density, the foamed ceramic of this invention has higher compressive strength.

Description

Technical Field

[0001] This invention relates to a foamed ceramic with a high refractory limit and its preparation method, belonging to the field of foamed ceramic technology. Background Technology

[0002] Foamed ceramics are a new type of building material that combines lightweight, heat insulation, fire resistance, and waterproofing, representing a significant development direction for the current building materials industry. Classified by density, foamed ceramics can be used in the construction field as exterior wall insulation boards and interior partition boards. When used as exterior wall insulation boards, foamed ceramics eliminate the problems associated with polystyrene and polyurethane boards, such as lack of fire resistance, easy aging, and short lifespan. When used as interior partition boards, foamed ceramics avoid the problems of heavy weight, poor heat insulation performance, large drying shrinkage, and easy moisture absorption and cracking found in aerated concrete blocks and sintered porous bricks. Furthermore, the production of foamed ceramics can utilize and dispose of large amounts of solid waste tailings, bringing economic benefits while also generating significant environmental, ecological, and social benefits, aligning with the high-quality development needs of the green, energy-saving, environmentally friendly, and low-carbon construction industry.

[0003] Currently, foamed ceramic products on the market share similar overall performance and manufacturing processes, thus exhibiting common problems. In terms of performance, their density is generally around 450 kg / m³. 3 The compressive strength is generally around 6.0 MPa, and the thermal conductivity is generally around 0.25 W / (m·K). In terms of manufacturing process, almost all foamed ceramic products use silicon carbide as the foaming agent. Due to the limitations of the foaming agent, they generally suffer from low fire resistance ratings. According to the national standard "Code for Fire Protection Design of Buildings, GB50016-2014", foamed ceramic products, when used in civil building components, can only be used as non-load-bearing exterior walls because their fire resistance rating is far lower than the fire resistance rating of firewalls (i.e., fire resistance rating ≥ 3h). Even so, only a few products reach the Class II fire resistance rating (i.e., fire resistance rating ≥ 1h) for non-load-bearing exterior walls, while most products only reach the Class III fire resistance rating (i.e., fire resistance rating ≥ 0.5h), severely limiting the application of foamed ceramic products. Summary of the Invention

[0004] The purpose of this invention is to provide a foamed ceramic with a high refractory limit and a method for preparing the same, so as to solve the technical problems existing in the prior art as described above.

[0005] One objective of this invention is to provide a method for preparing foamed ceramics with a high refractoriness limit, comprising the following steps:

[0006] (1) Mix aluminum trifluoride and barium titanate to obtain mixed pellets;

[0007] (2) The mixture obtained in step (1) is ball-milled into mixed powder I;

[0008] (3) Aluminum nitride powder is mixed with mixed powder I to prepare a composite foaming agent;

[0009] (4) Prepare solid waste raw materials;

[0010] (5) After adding ceramic desiccant to the solid waste raw material obtained in step (4), the solid waste raw material is ball-milled into solid waste powder;

[0011] (6) Mix the composite foaming agent obtained in step (3), the solid waste powder obtained in step (5), and water evenly to make mixed powder II;

[0012] (7) Press the mixed powder II into a blank;

[0013] (8) The green body obtained in step (7) is sintered to obtain a foamed ceramic with a high refractory limit.

[0014] The effect of adopting the above technical solution is that a composite foaming agent is prepared by a mixture of aluminum nitride, aluminum trifluoride, and barium titanate. Aluminum nitride generates gas through an oxidation reaction at high temperatures, thereby forming pores in the high-temperature molten ceramic matrix. Barium titanate is used to increase the oxidation rate of aluminum nitride, thereby shortening the firing time of the foamed ceramic and improving the uniformity of the pore structure. Aluminum trifluoride promotes the formation of a mullite phase in the high-temperature molten ceramic matrix, thereby increasing the compressive strength and refractoriness of the foamed ceramic and reducing its thermal conductivity. The ceramic descaling agent is used to improve the fluidity and uniformity of the solid waste raw materials, thereby improving the stability and uniformity of the foamed ceramic.

[0015] Based on the above technical solution, the present invention can be further improved as follows:

[0016] Furthermore, the average particle size of the mixed powder I is 1-3 μm, the particle size of the aluminum nitride powder is 40-60 μm, and the average particle size of the solid waste powder is 3-5 μm.

[0017] Further, in step (1), the weight ratio of aluminum trifluoride to barium titanate is 1:(0.6-0.8).

[0018] Further, in step (3), the weight ratio of the aluminum nitride powder to the mixed powder I is 1:(6.2~8.7).

[0019] Further, in step (4), the total weight percentage of silicon oxide, aluminum oxide, sodium oxide, and potassium oxide in the solid waste raw material is ≥89.5%, the weight percentage of silicon oxide is ≥66%, the weight percentage of aluminum oxide is ≥17%, the weight percentage of sodium oxide is ≥2.8%, and the weight percentage of potassium oxide is ≥3.7%. The solid waste raw material is prepared from inorganic solid wastes such as river silt, metallurgical solid waste, mining solid waste, fuel ash, tile waste, and stone sawdust.

[0020] Furthermore, in step (5), the weight of the ceramic desiccant added is 0.5 to 0.7% of the weight of the solid waste raw material.

[0021] Further, in step (5), the ceramic decolloiding agent has a modulus of 2.8 to 3.1 and a density of 1.41 to 1.44 g / cm³. 3 Water glass.

[0022] Further, in step (6), the weight ratio of the composite foaming agent, solid waste powder and water is (3.6-7.5):100:(6.6-8.7).

[0023] Furthermore, in step (7), a blank is formed using a pressure of 0.2 to 0.4 MPa.

[0024] Furthermore, in step (8), the sintering temperature is 1213-1225℃ and the sintering time is 21-24min.

[0025] The second objective of this invention is to provide a foamed ceramic with a high refractory limit, which is prepared by the above-mentioned method for preparing a foamed ceramic with a high refractory limit.

[0026] The technical solution provided by this invention has the following advantages compared with the prior art:

[0027] 1. In the present invention, during high-temperature sintering, the nano-alumina formed by the oxidation of aluminum nitride has high activity and readily reacts with the silica in the molten matrix to form a mullite phase; and the aluminum trifluoride in the composite foaming agent will undergo the following reactions in sequence to promote the formation of a mullite phase in the ceramic matrix.

[0028] AlF3 + H2O → AlOF + 2HF↑

[0029] SiO2 + 4HF↑ → SiF4↑ + 2H2O

[0030] 2AlOF↑ + SiF4↑ + 2H2O → Al2SiO4F2 + 4HF↑

[0031] 4Al2SiO4F2→Al6Si2O 13 +Al₂O₃ + 2SiF₄↑

[0032] Under high temperature conditions, mullite has excellent mechanical properties and creep resistance. This invention benefits from the high mullite content, which enables the prepared foamed ceramic to have a high refractory limit of ≥3h.

[0033] 2. The composite foaming agent of the present invention is formulated from inexpensive and readily available commercial raw materials, and the formulation process is simple, thus having the advantage of low preparation cost.

[0034] 3. When the foamed ceramic prepared by this invention is used in civil building components, its fire resistance rating is far higher than the Class I fire resistance rating (fire resistance rating ≥ 1h) requirement for non-load-bearing exterior walls, and also meets the Class I fire resistance rating (fire resistance rating ≥ 3h) requirement for firewalls. Furthermore, under similar density conditions, the foamed ceramic of this invention has a higher compressive strength than other foamed ceramic products on the market. Attached Figure Description

[0035] Figure 1 This is a flowchart of the preparation method of the foamed ceramic with high refractory limit of the present invention. Detailed Implementation

[0036] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0037] The flowchart of the preparation method of the foamed ceramic with high refractoriness of the present invention is as follows: Figure 1 As shown.

[0038] Example 1

[0039] A method for preparing foamed ceramics with high refractoriness, comprising the following steps:

[0040] (1) Aluminum trifluoride and barium titanate were mixed at a weight ratio of 1:0.6 to obtain mixed pellets;

[0041] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 1 μm;

[0042] (3) Aluminum nitride powder with a particle size of 40 μm is mixed with mixed powder I at a weight ratio of 1:8.7 to prepare a composite foaming agent;

[0043] (4) River silt, metallurgical solid waste, mining solid waste, fuel ash, tile waste and stone sawdust are mixed to form a solid waste raw material with a total weight ratio of 91.4% for silicon dioxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 67.2% for silicon dioxide, a weight ratio of 17.3% for aluminum oxide, a weight ratio of 3.1% for sodium oxide and a weight ratio of 3.8% for potassium oxide.

[0044] (5) Add 0.5% by weight of water glass (modulus 2.8, density 1.44 g / cm³) to the solid waste material obtained in step (4). 3 After that, the solid waste raw material is ball-milled into solid waste powder with an average particle size of 3μm;

[0045] (6) The composite foaming agent obtained in step (3), the solid waste powder obtained in step (5) and water are mixed in a weight ratio of 3.6:100:6.6 and stirred evenly to make mixed powder II;

[0046] (7) The mixed powder II is formed into a green body under a pressure of 0.2 MPa;

[0047] (8) The green body obtained in step (7) is fired at 1213°C for 24 minutes to obtain the foamed ceramic of the present invention.

[0048] Example 2

[0049] A method for preparing foamed ceramics with high refractoriness, comprising the following steps:

[0050] (1) Aluminum trifluoride and barium titanate were mixed at a weight ratio of 1:0.7 to obtain mixed pellets;

[0051] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0052] (3) Aluminum nitride powder with a particle size of 45 μm is mixed with mixed powder I at a weight ratio of 1:7.8 to prepare a composite foaming agent;

[0053] (4) River silt, metallurgical solid waste, mining solid waste, fuel ash, tile waste and stone sawdust are mixed to form a solid waste raw material with a total weight ratio of 92.7% for silicon dioxide, 67.5% for silicon dioxide, 17.6% for aluminum oxide, 3.5% for sodium oxide and 4.1% for potassium oxide.

[0054] (5) Add 0.5% by weight of water glass (modulus 2.9, density 1.43 g / cm³) to the solid waste material obtained in step (4). 3 After that, the solid waste raw material is ball-milled into solid waste powder with an average particle size of 4μm;

[0055] (6) The composite foaming agent obtained in step (3), the solid waste powder obtained in step (5) and water are mixed in a weight ratio of 4.8:100:7.1 and stirred evenly to make mixed powder II;

[0056] (7) The mixed powder II is formed into a green body under a pressure of 0.3 MPa;

[0057] (8) The green body obtained in step (7) is fired at 1217°C for 23 minutes to obtain the foamed ceramic of the present invention.

[0058] Example 3

[0059] (1) Aluminum trifluoride and barium titanate were mixed at a weight ratio of 1:0.7 to obtain mixed pellets;

[0060] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0061] (3) Aluminum nitride powder with a particle size of 50 μm is mixed with mixed powder I at a weight ratio of 1:6.9 to prepare a composite foaming agent;

[0062] (4) River silt, metallurgical solid waste, mining solid waste, fuel ash, tile waste and stone sawdust are mixed to form a solid waste raw material with a total weight ratio of 92.5% for silicon dioxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 67.4% for silicon dioxide, a weight ratio of 17.5% for aluminum oxide, a weight ratio of 3.4% for sodium oxide and a weight ratio of 4.2% for potassium oxide.

[0063] (5) Add 0.6% by weight of water glass (modulus 3.0, density 1.42 g / cm³) to the solid waste material obtained in step (4). 3 After that, the solid waste raw material is ball-milled into solid waste powder with an average particle size of 4μm;

[0064] (6) The composite foaming agent obtained in step (3), the solid waste powder obtained in step (5) and water are mixed in a weight ratio of 6.1:100:7.7 and stirred evenly to make mixed powder II;

[0065] (7) The mixed powder II is formed into a green body under a pressure of 0.3 MPa;

[0066] (8) The green body obtained in step (7) is fired at 1221°C for 22 minutes to obtain the foamed ceramic of the present invention.

[0067] Example 4

[0068] A method for preparing foamed ceramics with high refractoriness, comprising the following steps:

[0069] (1) Aluminum trifluoride and barium titanate were mixed at a weight ratio of 1:0.8 to obtain mixed pellets;

[0070] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 3 μm;

[0071] (3) Aluminum nitride powder with a particle size of 60 μm is mixed with mixed powder I at a weight ratio of 1:6.2 to prepare a composite foaming agent;

[0072] (4) River silt, metallurgical solid waste, mining solid waste, fuel ash, tile waste and stone sawdust are mixed to form a solid waste raw material with a total weight ratio of 91.9% for silicon dioxide, 66.7% for silicon dioxide, 17.6% for aluminum oxide, 3.3% for sodium oxide and 4.3% for potassium oxide.

[0073] (5) Add 0.7% by weight of water glass (modulus 3.1, density 1.41 g / cm³) to the solid waste material obtained in step (4). 3 After that, the solid waste raw material is ball-milled into solid waste powder with an average particle size of 5μm;

[0074] (6) The composite foaming agent obtained in step (3), the solid waste powder obtained in step (5) and water are mixed in a weight ratio of 7.5:100:8.7 and stirred evenly to make mixed powder II;

[0075] (7) The mixed powder II is formed into a green body under a pressure of 0.4 MPa;

[0076] (8) The green body obtained in step (7) is fired at 1225°C for 21 min to obtain the foamed ceramic of the present invention.

[0077] The foamed ceramics obtained in Examples 1-4 were subjected to physical and mechanical property tests. Density, compressive strength, and volumetric water absorption were tested according to the national standard "Test Methods for Inorganic Rigid Thermal Insulation Products, GB / T5486-2008"; fire resistance limit was tested according to the national standard "Fire Resistance Test Methods for Building Components Part 1: General Requirements, GB / T9978.1-2008"; and fire resistance rating was tested according to the national standard "Classification of Combustion Performance of Building Materials and Products, GB8624-2012".

[0078] The test results are shown in Table 1.

[0079] Table 1. Test results of the physical and mechanical properties of foamed ceramics in Examples 1-4

[0080]

[0081] As can be seen from Table 1, the densities of the foamed ceramics prepared in Examples 1-4 range from 426 to 597 kg / m³. 3It has a compressive strength of 6.8–11.2 MPa, a volume water absorption rate of 1.1–1.7%, a thermal conductivity of 0.21–0.29 W / (m·k), a fire resistance limit of 3.1–3.6 h, and a fire rating of A1, which meets the requirements of Class I fire resistance for firewalls.

[0082] Currently, the density of commercially available foamed ceramic products is generally around 450 kg / m³. 3 The compressive strength is generally around 6.0 MPa, and the thermal conductivity is generally around 0.25 W / (m·K). Compared to commercially available foamed ceramic products, the foamed ceramic prepared in Example 3 has a slightly higher density of 485 kg / m³. 3 However, the thermal conductivity is still as low as 0.24 W / (m·K); the foamed ceramic prepared in Example 4 has a slightly lower density of 426 kg / m³. 3 However, it still has a higher compressive strength of 6.8 MPa, and a lower thermal conductivity of only 0.21 W / (m·K). The above comparison shows that, compared with commercially available foamed ceramics, the foamed ceramics prepared in Examples 3-4 of this invention have higher compressive strength and lower thermal conductivity at the same density.

[0083] Furthermore, in Examples 1-4, as the amount of composite foaming agent and the proportion of aluminum nitride in the composite foaming agent increased, the density, compressive strength, and fire resistance of the foamed ceramics gradually decreased, while the volumetric water absorption rate gradually increased. This demonstrates that the overall performance of foamed ceramics can be effectively adjusted by regulating the amount of composite foaming agent and the proportion of aluminum nitride in the composite foaming agent.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a foamed ceramic having a high fire resistance limit, characterized by, Includes the following steps: (1) Aluminum trifluoride and barium titanate are mixed to obtain mixed pellets; the weight ratio of aluminum trifluoride and barium titanate is 1:(0.6~0.8). (2) The mixture obtained in step (1) is ball-milled into mixed powder I; (3) Aluminum nitride powder is mixed with mixed powder I to form a composite foaming agent; the weight ratio of aluminum nitride powder to mixed powder I is 1: (6.2~8.7). (4) Prepare solid waste raw materials; (5) After adding ceramic desiccant to the solid waste raw material obtained in step (4), the solid waste raw material is ball-milled into solid waste powder; (6) Mix the composite foaming agent obtained in step (3), the solid waste powder obtained in step (5), and water evenly to make mixed powder II; the weight ratio of the composite foaming agent, solid waste powder, and water is (3.6~7.5):100:(6.6~8.7). (7) Press the mixed powder II into a blank; (8) The green body obtained in step (7) is sintered to obtain foamed ceramic with high refractory limit.

2. The method for preparing foamed ceramics with high refractoriness according to claim 1, characterized in that, The average particle size of the mixed powder I is 1~3μm, the particle size of the aluminum nitride powder is 40~60μm, and the average particle size of the solid waste powder is 3~5μm.

3. The method for preparing foamed ceramics with high refractoriness according to claim 1, characterized in that, In step (4), the total weight percentage of silicon oxide, aluminum oxide, sodium oxide and potassium oxide in the solid waste raw material is ≥89.5%, the weight percentage of silicon oxide is ≥66%, the weight percentage of aluminum oxide is ≥17%, the weight percentage of sodium oxide is ≥2.8%, and the weight percentage of potassium oxide is ≥3.7%.

4. The method for preparing foamed ceramics with high refractoriness according to claim 1, characterized in that, In step (5), the weight of the ceramic desiccant added is 0.5 to 0.7% of the weight of the solid waste raw material.

5. The method for preparing foamed ceramics with high refractoriness according to claim 1, characterized in that, In step (7), a blank is made using a pressure of 0.2~0.4MPa.

6. The method for preparing foamed ceramics with high refractoriness according to claim 1, characterized in that, In step (8), the sintering temperature is 1213~1225℃ and the sintering time is 21~24min.

7. A foamed ceramic with a high refractoriness limit, characterized in that, It is prepared by the method for preparing foamed ceramics with high refractory limit as described in any one of claims 1-6.

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