Ultralow thermal conductivity external wall external insulation foam ceramic and preparation method thereof

Abstract

The application relates to an ultra-low thermal conductivity external wall external insulation foam ceramic and a preparation method thereof, and belongs to the technical field of thermal insulation materials. The preparation method of the ultra-low thermal conductivity external wall external insulation foam ceramic comprises the following steps: (1) mixing boron carbide, iron oxide, fluorite, albite and potassium feldspar to obtain a mixture; (2) ball milling the mixture into mixed powder I; (3) uniformly stirring the mixed powder I and aluminum nitride powder to prepare a foaming agent; (4) ball milling solid waste raw materials into solid waste powder; (5) mixing the foaming agent, the solid waste powder and water, and uniformly stirring to prepare mixed powder II; (6) pressing the mixed powder II into a green body; and (7) sintering the green body to obtain the foam ceramic. The prepared foam ceramic has the structural feature that small pores surround large pores, and can simultaneously meet the indexes of density, strength and thermal conductivity, and meets the requirements of the national standard of "external wall external insulation foam ceramic", and can be used for external wall external insulation.

Description

Technical Field

[0001] This invention relates to an ultra-low thermal conductivity external wall insulation foam ceramic and its preparation method, belonging to the field of insulation material technology. Background Technology

[0002] The construction industry is a pillar industry in my country and also a major contributor to carbon emissions. With the comprehensive advancement of my country's "dual carbon" goals, green, energy-saving, environmentally friendly, and low-carbon development has become the keynote of the construction industry. Driven by both policy guidance and market demand, the building materials industry is experiencing a favorable situation of multi-faceted growth. Within the building materials industry, wall materials are an important basic building material, which can be further divided into two main categories: exterior wall materials and interior wall materials. Exterior wall materials primarily function as insulation, mainly consisting of polystyrene boards and polyurethane boards, but they suffer from problems such as lack of fire resistance, easy aging, and short lifespan.

[0003] Foam ceramics are porous ceramic materials containing numerous pores, possessing characteristics such as lightweight, thermal insulation, fire resistance, water resistance, and aging resistance. Used in the construction industry as exterior wall insulation boards and interior partition boards, they represent an important development direction in the current building materials industry, aligning with the high-quality development needs of the construction sector. Furthermore, the production of foam ceramics can utilize and dispose of large quantities of solid waste tailings, generating economic benefits while also producing significant environmental, ecological, and social benefits.

[0004] Currently, most foam ceramic products on the market use silicon carbide as a foaming agent, and their density is mostly between 400-600 kg / cm³. 3 Within the specified range, the compressive strength exceeds 6MPa, meeting the requirements for indoor partition walls. However, for exterior wall insulation, which prioritizes lightweight and thermal insulation, commercially available foam ceramic products generally suffer from high density and high thermal conductivity. Taking the S-type foam ceramic board in the national standard "Exterior Wall Insulation Foam Ceramics" (GB / T 33500-2017) as an example, it is difficult for commercially available foam ceramic products to simultaneously achieve a density ≤160kg / m³. 3 The performance indicators are: compressive strength ≥ 0.2 MPa, thermal conductivity ≤ 0.06 W / (m·K); taking the L-shaped foam ceramic board in the national standard "External Wall Insulation Foam Ceramics" (GB / T 33500-2017) as an example, although foam ceramic products on the market can achieve ≤ 280 kg / m³, 3 While meeting the density requirements and compressive strength requirements of ≥0.6MPa, it is difficult to satisfy the thermal conductivity index of ≤0.1W / (m·k), which makes it impossible for many foam ceramic companies to use their foam ceramic products for external wall insulation. Summary of the Invention

[0005] In view of the fact that current foam ceramic products on the market are unable to meet the national standard requirements for "external wall insulation foam ceramics", namely, the inability to simultaneously achieve the required density, strength and thermal conductivity, this invention provides an ultra-low thermal conductivity external wall insulation foam ceramic and its preparation method.

[0006] The technical solution provided by this invention is as follows:

[0007] The first objective of this invention is to provide a method for preparing ultra-low thermal conductivity external wall insulation foam ceramics, the steps of which are as follows:

[0008] (1) Boron carbide, iron oxide, fluorite, albite and potassium feldspar are mixed in a weight ratio of 1:(0.8~1.2):(1.4~1.9):(4~7):(5~8) to obtain a mixture;

[0009] (2) Grind the mixture into mixed powder I;

[0010] (3) Mix the mixed powder I with aluminum nitride powder at a weight ratio of (13~18):1 and stir evenly to make a foaming agent;

[0011] (4) Grind the solid waste raw materials into solid waste powder;

[0012] (5) Mix the foaming agent, solid waste powder and water in a weight ratio of 1:(93~102):(6.7~8.8) and stir evenly to prepare mixed powder II;

[0013] (6) Press the mixed powder II into a blank;

[0014] (7) Sinter the green body to obtain the foam ceramic.

[0015] The effects of adopting the above technical solution are that boron carbide and aluminum nitride generate gas through oxidation reaction at high temperature, thereby forming pores in the high-temperature molten ceramic matrix; iron oxide is an oxygenating agent that can accelerate the oxidation of boron carbide and aluminum nitride, which has the effect of shortening the firing time of foam ceramics and adjusting the pore size; fluorite is a viscosity modifier that can improve the high-temperature viscosity of the molten matrix, thereby adjusting the pore size of the foam ceramics; sodium feldspar and potassium feldspar are fluxes that can lower the melting point of the green body, which has the effect of improving the continuity of the molten matrix and adjusting the firing temperature of the foam ceramics.

[0016] Based on the above technical solution, the present invention can be further improved as follows:

[0017] Furthermore, the boron carbide has a particle size of 1~3μm, the mixed powder I has an average particle size of 1~3μm, the aluminum nitride powder has a particle size of 40~50μm, and the solid waste powder has an average particle size of 3~5μm.

[0018] The advantages of the above technical solutions are as follows: Boron carbide has a particle size of 1~3μm. During high-temperature sintering, the smaller boron carbide particles have a larger contact area with the molten matrix, resulting in a high oxidation gas generation rate. This allows the molten matrix to form pores quickly, and the earlier the pores are formed, the easier it is for them to aggregate into larger pores, resulting in large pores with a diameter of 4~6mm in the foam ceramic. In addition, the boron oxide generated by the oxidation of boron carbide has an excellent fluxing effect, which can significantly reduce the viscosity of the molten matrix. The lower the viscosity of the matrix, the easier it is for the pores to aggregate into larger pores. Aluminum nitride powder has a particle size of 40~50μm. The larger aluminum nitride particles have a smaller contact area with the matrix, resulting in a lower oxidation gas generation rate. This makes the molten matrix form pores more slowly, and the later-formed pores are less likely to aggregate, remaining as independent small pores. Furthermore, the alumina generated by the oxidation of aluminum nitride significantly increases the viscosity of the molten matrix, thereby preventing the small pores from aggregating into larger pores, and the diameter of the small pores remains at 1~2mm.

[0019] Furthermore, in step (4), the solid waste raw materials include one or more of the following: river silt, metallurgical solid waste, mining solid waste, fuel ash, ceramic tile waste, and stone sawdust.

[0020] The effect of adopting the above technical solution is that the solid waste raw materials are prepared from solid waste tailings, and the proportion is very high. It can dispose of a large amount of solid waste tailings, and has good environmental protection, ecological and social benefits.

[0021] Further, in step (4), the total weight percentage of the solid waste raw materials is ≥89% for silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for ≥66% by weight, aluminum oxide accounts for ≥17% by weight, sodium oxide accounts for ≥2% by weight and potassium oxide accounts for ≥4% by weight.

[0022] Further, in step (6), the mixed powder II is pressed into a blank under a pressure of 0.6~0.9MPa.

[0023] Furthermore, in step (7), the sintering temperature of the blank is 1160~1230℃ and the sintering time is 14~21min.

[0024] The second objective of this invention is to provide an ultra-low thermal conductivity external wall insulation foam ceramic, which is made by the above-mentioned preparation method of ultra-low thermal conductivity external wall insulation foam ceramic.

[0025] The technical solution provided by this invention has the following advantages compared with the prior art:

[0026] (1) The foaming agent of the present invention contains both small-diameter boron carbide and large-diameter aluminum nitride, which makes the foam ceramic prepared by the present invention have the structural feature of "small pores surrounding large pores". The porous structure of "small pores surrounding large pores" can reduce the density of the foam ceramic and reduce the heat transfer rate in the foam ceramic, thus reducing the thermal conductivity of the foam ceramic.

[0027] (2) At high temperature, the aluminum nitride in the foaming agent of the present invention generates nano-alumina which reacts with molten silicon oxide to form mullite phase. The high strength and low thermal conductivity of mullite help to improve the strength of the pore wall and reduce its thermal conductivity, thereby giving the foam ceramic of the present invention higher strength and lower thermal conductivity.

[0028] (3) The foaming agent described in this invention is formulated from inexpensive and readily available commercial raw materials, and the formulation process is simple, which has the significant advantage of low preparation cost.

[0029] (4) The density of the foam ceramic prepared by this invention is 153~248 kg / m³. 3 With a thermal conductivity of 0.056~0.092W / (m·k) and a compressive strength of 0.32~0.85MPa, it can balance density, strength and thermal conductivity, meet the requirements of the national standard for "external wall insulation foam ceramics" (GB / T 33500-2017), and can be used for external wall insulation. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the preparation method of the external wall insulation foam ceramic of the present invention.

[0031] Figure 2 An optical photograph of the foam ceramic prepared in Example 1 of this invention;

[0032] Figure 3 An optical photograph of the foam ceramic prepared in Example 2 of this invention;

[0033] Figure 4 An optical photograph of the foam ceramic prepared in Example 3 of this invention;

[0034] Figure 5 An optical photograph of the foam ceramic prepared in Example 4 of this invention. Detailed Implementation

[0035] 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.

[0036] The flowchart of the preparation method of the external wall insulation foam ceramic of the present invention is as follows: Figure 1 As shown.

[0037] Example 1

[0038] A method for preparing ultra-low thermal conductivity external wall insulation foam ceramic includes the following steps:

[0039] (1) Mix boron carbide, iron oxide, fluorite, albite, and potassium feldspar in a weight ratio of 1:1.2:1.9:7:8;

[0040] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 3 μm;

[0041] (3) Mix powder I with aluminum nitride powder with a particle size of 50 μm at a weight ratio of 13:1 and stir evenly to make a foaming agent;

[0042] (4) The solid waste raw material with a total weight ratio of 92.3% of silicon oxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 66.7% of silicon oxide, a weight ratio of 17.8% of aluminum oxide, a weight ratio of 3.5% of sodium oxide and a weight ratio of 4.3% of potassium oxide is ball-milled into solid waste powder with an average particle size of 5μm.

[0043] (5) Mix the foaming agent obtained in step (3) with the solid waste powder obtained in step (4) and water at a weight ratio of 1:102:8.8, and stir evenly to make mixed powder II;

[0044] (6) The mixed powder II is pressed into a green body under a pressure of 0.6 MPa;

[0045] (7) The green body obtained in step (6) is fired at 1160℃ for 21 min to obtain the foam ceramic. An optical photograph of the prepared external wall insulation foam ceramic is shown below. Figure 2 As shown.

[0046] Example 2

[0047] A method for preparing ultra-low thermal conductivity external wall insulation foam ceramic includes the following steps:

[0048] (1) Mix boron carbide, iron oxide, fluorite, albite and potassium feldspar in a weight ratio of 1:1:1.7:6:7;

[0049] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0050] (3) Mix the mixed powder I with aluminum nitride powder with a particle size of 45μm at a weight ratio of 15:1 and stir evenly to make a foaming agent;

[0051] (4) The solid waste raw material with a total weight ratio of 91.8% for silicon oxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 67.1% for silicon oxide, a weight ratio of 17.3% for aluminum oxide, a weight ratio of 3.3% for sodium oxide and a weight ratio of 4.1% for potassium oxide was ball-milled into solid waste powder with an average particle size of 4μm.

[0052] (5) Mix the foaming agent obtained in step (3) with the solid waste powder obtained in step (4) and water in a weight ratio of 1:99:8.2 and stir evenly to make mixed powder II;

[0053] (6) The mixed powder II is pressed into a green body under a pressure of 0.7 MPa;

[0054] (7) The green body obtained in step (6) is fired at 1180℃ for 18 minutes to obtain the foam ceramic. An optical photograph of the prepared external wall insulation foam ceramic is shown below. Figure 3 As shown.

[0055] Example 3

[0056] A method for preparing ultra-low thermal conductivity external wall insulation foam ceramic includes the following steps:

[0057] (1) Mix boron carbide, iron oxide, fluorite, albite and potassium feldspar in a weight ratio of 1:0.9:1.5:5:6;

[0058] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0059] (3) Mix the mixed powder I with aluminum nitride powder with a particle size of 45 μm at a weight ratio of 16:1 and stir evenly to make a foaming agent;

[0060] (4) The solid waste raw material with a total weight ratio of 93.4% for silicon oxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 67.6% for silicon oxide, a weight ratio of 17.5% for aluminum oxide, a weight ratio of 3.7% for sodium oxide and a weight ratio of 4.6% for potassium oxide is ball-milled into solid waste powder with an average particle size of 3μm.

[0061] (5) Mix the foaming agent obtained in step (3) with the solid waste powder obtained in step (4) and water in a weight ratio of 1:96:7.4, and stir evenly to make mixed powder II;

[0062] (6) The mixed powder II is pressed into a green body under a pressure of 0.8 MPa;

[0063] (7) The green body obtained in step (6) is fired at 1200℃ for 16 minutes to obtain the foam ceramic. An optical photograph of the prepared external wall insulation foam ceramic is shown below. Figure 4 As shown.

[0064] Example 4

[0065] A method for preparing ultra-low thermal conductivity external wall insulation foam ceramic includes the following steps:

[0066] (1) Mix boron carbide, iron oxide, fluorite, albite, and potassium feldspar in a weight ratio of 1:0.8:1.4:4:5;

[0067] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 1 μm;

[0068] (3) Mix the mixed powder I with aluminum nitride powder with a particle size of 40 μm at a weight ratio of 18:1 and stir evenly to make a foaming agent;

[0069] (4) The solid waste raw material with a total weight ratio of 90.9% for silicon oxide, aluminum oxide, sodium oxide and potassium oxide, a weight ratio of 66.4% for silicon oxide, a weight ratio of 17.3% for aluminum oxide, a weight ratio of 3.1% for sodium oxide and a weight ratio of 4.1% for potassium oxide is ball-milled into solid waste powder with an average particle size of 5μm.

[0070] (5) Mix the foaming agent obtained in step (3) with the solid waste powder obtained in step (4) and water in a weight ratio of 1:93:6.7 and stir evenly to make mixed powder II;

[0071] (6) The mixed powder II is pressed into a green body under a pressure of 0.9 MPa;

[0072] (7) The green body obtained from solid waste (6) is fired at 1230℃ for 14 minutes to obtain the foamed ceramic. An optical photograph of the prepared external wall insulation foamed ceramic is shown below. Figure 5 As shown.

[0073] The physical and mechanical properties of the foam ceramics obtained in Examples 1-4 were tested:

[0074] 1. Density, compressive strength and volumetric water absorption rate are tested in accordance with the national standard "Test Methods for Inorganic Rigid Thermal Insulation Products, GB / T5486-2008";

[0075] 2. The fire resistance rating is tested in accordance with the national standard "Classification of Combustion Performance of Building Materials and Products, GB8624-2012";

[0076] 3. The thermal conductivity was tested in accordance with the national standard "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method, GB / T10294-2008".

[0077] The test results are shown in Table 1.

[0078] Table 1. Test results of the physical and mechanical properties of foam ceramics in Examples 1-4

[0079]

[0080] As shown in Table 1, the density of the foam ceramics prepared by this invention is 153~248 kg / m³. 3 The thermal conductivity is 0.056~0.092 W / (m·K), the compressive strength is 0.32~0.85 MPa, and the volumetric water absorption rate is 1.5~1.8%. Referring to the index range of the national standard "External Wall Insulation Foamed Ceramics" (GB / T 33500-2017), the foamed ceramics prepared in Examples 1-4 of this invention belong to types L, M, and S, respectively. Among them, the performance of the foamed ceramic prepared in Example 1 is better than the minimum index requirement for type L; the performance of the foamed ceramics prepared in Examples 2 and 3 is better than the minimum index requirement for type M; and the performance of the foamed ceramic prepared in Example 4 is better than the minimum index requirement for type S.

[0081] Figure 2-5 These are optical photographs of the foam ceramics prepared in Examples 1-4 of this invention. Figure 2-5 It can be seen that the foam ceramic prepared by the present invention has a porous structure with small pores surrounding large pores. Specifically, the large pores are independent and not connected to each other, with a pore diameter of about 4 to 6 mm. The small pores are distributed in the pore walls of the large pores, and the small pores are also independent and not connected to each other, with a pore diameter of about 1 to 2 mm.

[0082] 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 preparing ultra-low thermal conductivity external wall insulation foam ceramic, characterized in that, Includes the following steps: (1) Boron carbide, iron oxide, fluorite, albite and potassium feldspar are mixed in a weight ratio of 1:(0.8~1.2):(1.4~1.9):(4~7):(5~8) to obtain a mixture; the particle size of the boron carbide is 1~3μm; (2) The mixture is ball-milled into mixed powder I; the average particle size of mixed powder I is 1~3μm; (3) Mix the mixed powder I with aluminum nitride powder at a weight ratio of (13~18):1 and stir evenly to make a foaming agent; the particle size of the aluminum nitride powder is 40~50μm; (4) Grind the solid waste raw materials into solid waste powder; (5) Mix the foaming agent, solid waste powder and water in a weight ratio of 1:(93~102):(6.7~8.8) and stir evenly to prepare mixed powder II; (6) Press the mixed powder II into a blank; (7) The green body is sintered at a temperature of 1160~1230℃ for 14~21 min to obtain the foamed ceramic; The density of the foamed ceramic is 153~248 kg / m³. 3 The thermal conductivity is 0.056~0.092W / (m·k), and the compressive strength is 0.32~0.85MPa.

2. The preparation method of ultra-low thermal conductivity external wall insulation foam ceramic according to claim 1, characterized in that, The average particle size of the solid waste powder is 3~5μm.

3. The method for preparing ultra-low thermal conductivity external wall insulation foam ceramic according to claim 1, characterized in that, In step (4), the solid waste raw materials include one or more of the following: river silt, metallurgical solid waste, mining solid waste, fuel ash, ceramic tile waste, and stone sawdust.

4. The preparation method of ultra-low thermal conductivity external wall insulation foam ceramic according to claim 1 or 3, characterized in that, In step (4), the total weight percentage of the solid waste raw materials is ≥89% for silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for ≥66% by weight, aluminum oxide accounts for ≥17% by weight, sodium oxide accounts for ≥2% by weight and potassium oxide accounts for ≥4% by weight.

5. The method for preparing ultra-low thermal conductivity external wall insulation foam ceramic according to claim 1, characterized in that, In step (6), the mixed powder II is pressed into a blank under a pressure of 0.6~0.9MPa.

6. A foam ceramic for external wall insulation with ultra-low thermal conductivity, characterized in that, It is made by the preparation method of ultra-low thermal conductivity external wall insulation foam ceramic as described in any one of claims 1-5.

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