High-purity corundum brick resistant to high temperature thermal shock and preparation method thereof

Abstract

The application relates to the technical field of corundum refractory materials, and discloses a high-purity corundum brick with high-temperature thermal shock resistance and a preparation method thereof; the high-purity corundum brick is a single alpha-Al2O3 phase, and raw material components of the high-purity corundum brick include, in parts by weight, corundum particles 55-65, corundum fine powder 25-36, alpha-Al2O3 micro powder 4-12, alpha-Al2O3 nano powder 0.5-3, soluble inorganic magnesium salt sintering aid, binder and dispersant. The application reduces the sintering temperature through gradation design of the alumina powder and selection of the sintering aid, and the obtained product is a single alpha-Al2O3 phase, has excellent high-temperature thermal shock resistance, and can be used in a working environment above 1800 DEG C.

Description

Technical Field

[0001] This invention relates to the field of corundum refractory materials technology, and more specifically, to a high-purity corundum brick resistant to high-temperature thermal shock and its preparation method. Background Technology

[0002] High-purity corundum bricks are a high-quality refractory product, mainly used in important high-temperature sections of chemical and metallurgical kilns. Domestic research on high-purity alumina furnace bricks for sintering furnaces in high-purity applications is limited. Domestically, alumina raw materials are mainly electrofused and then cast to form alumina fused cast bricks. To reduce melting temperature and post-casting shrinkage, alumina nanoparticles, sodium oxide, or silicon dioxide are often introduced into the raw materials as sintering aids. However, this results in alumina fused cast materials failing to meet the high-temperature resistance requirements above 1700℃.

[0003] Chinese patent CN105237003A reduces the amount of α-Al2O3 nanopowder by adding titanium dioxide micro powder and ruthenium micro powder to the raw materials, but the high-purity corundum bricks prepared have poor mechanical properties in high-temperature environments above 1700℃.

[0004] Therefore, it is necessary to develop a high-purity corundum brick that can be used in high-temperature environments above 1800℃. Summary of the Invention

[0005] To address the aforementioned technical problems in existing technologies, this invention provides a high-purity corundum brick resistant to high-temperature thermal shock and its preparation method. By optimizing the particle size distribution of alumina raw materials and the preparation method, alumina furnace bricks with low density and thermal conductivity, a microporous structure, and simultaneously high strength, high thermal shock resistance, and heat insulation properties are prepared.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A high-purity corundum brick resistant to high-temperature thermal shock, wherein the high-purity corundum brick is a single α-Al2O3 phase, and its raw material components, by weight, include: 55-65 parts of corundum particles, 25-36 parts of fine corundum powder, 4-12 parts of α-Al2O3 micro powder, 0.5-3 parts of α-Al2O3 nano powder, soluble inorganic magnesium salt sintering aid, binder, and dispersant;

[0008] The amount of the soluble inorganic magnesium salt sintering aid (based on MgO content) is 0.15-0.25% of the total amount of corundum particles, corundum fine powder, α-Al2O3 micro powder and α-Al2O3 nano powder.

[0009] The amount of the adhesive used is 5-10% of the total amount of α-Al2O3 micro powder and α-Al2O3 nano powder;

[0010] The amount of the dispersant is 0.25-2.5% of the total amount of α-Al2O3 micro powder and α-Al2O3 nano powder.

[0011] Preferably, the corundum particles are fused alumina particles with a particle size of 1-3 mm and an Al2O3 content of ≥99.5%; the corundum fine powder is fused alumina fine powder with a particle size of 0.01-0.05 mm and an Al2O3 content of ≥99.5%; the α-Al2O3 micro powder is α-Al2O3 micro powder with a particle size d50 of 1-4 μm and an Al2O3 content of ≥99.6%; and the α-Al2O3 nano powder is α-Al2O3 nano powder with an average particle size of 30-50 nm and an Al2O3 content of ≥99.9%.

[0012] Preferably, the specific surface area of ​​the α-Al₂O₃ nanoparticles is (80±5) m². 2 / g.

[0013] Preferably, the adhesive is any one or a mixture of PVA, starch, or boehmite sol adhesive.

[0014] Preferably, the soluble inorganic magnesium salt sintering aid is any one or a mixture of two of magnesium nitrate and magnesium sulfate.

[0015] It should be noted that the soluble inorganic magnesium salt additive in this application is added in the form of an aqueous solution. Adding it in liquid phase facilitates the dispersion of the additive and promotes sintering. The magnesium salt additive actually decomposes into MgO during the sintering process. Therefore, this application selects magnesium nitrate or magnesium sulfate, which can decompose into MgO during sintering, as the additive, and its dosage is calculated based on the MgO content.

[0016] Preferably, the dispersant includes any one of ammonium citrate and hydrochloric acid.

[0017] The present invention also provides a method for preparing the above-mentioned high-purity corundum brick, which includes the following steps:

[0018] S1. Mix α-Al2O3 micro powder, α-Al2O3 nano powder suspension, dispersant, aqueous solution of soluble inorganic magnesium salt sintering aid, binder and water, and ball mill to obtain matrix green slurry;

[0019] S2. The matrix green slurry obtained in step S1 is spray-dried to obtain spherical α-Al2O3 particles with a particle size of 50μm-100μm.

[0020] S3. Mix the spherical α-Al2O3 particles, corundum particles, and corundum fine powder obtained in step S2 evenly, press them into shape, dry them, and sinter them at 1300℃-1700℃ to obtain high-purity corundum bricks.

[0021] Preferably, in step S1, the solid content of alumina in the slurry is 35-45%. More preferably, the solid content of alumina in the slurry is 40%.

[0022] Preferably, in step S1, the α-Al2O3 nanopowder suspension is a suspension formed by dissolving α-Al2O3 nanopowder in water. The amount of water used is not limited, as long as it forms a suspension and is thoroughly mixed with the α-Al2O3 nanopowder.

[0023] Preferably, in step S2, the spray drying temperature is 160-200°C. More preferably, the spray drying temperature is 180°C.

[0024] Preferably, in step S3, the sintering time is 4-6 hours; preferably, the sintering temperature is 1400-1500℃.

[0025] Preferably, in step S3, the pressing method is any one of compression molding, extrusion molding, or isostatic pressing.

[0026] In this invention, corundum particles and fine corundum powder are used as aggregates for furnace bricks. Combined with α-Al2O3 micro powder and α-Al2O3 nano powder as a matrix, a uniform furnace brick structure can be obtained, ensuring high strength of the furnace bricks. At the same time, the introduction of α-Al2O3 micro powder and α-Al2O3 nano powder can increase sintering performance and reduce sintering temperature. The hollow spherical α-Al2O3 particles obtained by spray granulation have a microporous structure that increases the thermal shock resistance and heat insulation of corundum bricks, while reducing weight.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The high-purity corundum brick of the present invention is a single α-Al2O3 phase, which has good high temperature resistance, thermal shock resistance and high temperature strength, high manufacturing precision, safe and reliable use and long service life.

[0029] The method of this invention significantly reduces the sintering temperature of high-purity corundum by combining particle size distribution with sintering aids. Simultaneously, it improves the porosity of the material by producing spherical particles through spray granulation. Furthermore, the molding process is simple and convenient, resulting in products with high strength. It also allows for better mixing of ceramic powder and pore-forming agents, leading to a more uniform pore size distribution. Attached Figure Description

[0030] Figure 1 The image shows the XRD pattern of the high-purity corundum brick prepared in Example 1.

[0031] Figure 2 The image shows a SEM image of the high-purity corundum brick prepared in Example 2.

[0032] Figure 3The image shows a SEM image of the high-purity corundum brick prepared in Comparative Example 6.

[0033] Figure 4 SEM images of the products after calcination at different spray-drying inlet temperatures.

[0034] Among them, (a) 120℃, (b) 140℃, (c) 160℃, (d) 180℃, and (e) 200℃. Detailed Implementation

[0035] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0037] In this invention, the corundum particles are fused alumina particles with a particle size of 1-3 mm and an Al2O3 content of ≥99.5%; the corundum fine powder is fused alumina fine powder with a particle size of 0.01-0.05 mm and an Al2O3 content of ≥99.5%; the α-Al2O3 micro powder is α-Al2O3 micro powder with a particle size d50 of 1-4 μm and an Al2O3 content of ≥99.6%; and the α-Al2O3 nano powder is α-Al2O3 nano powder with an average particle size of 30-50 nm and an Al2O3 content of ≥99.9%. All other raw materials, unless otherwise specified, are commercially available products.

[0038] The raw material amounts used in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0039] Table 1. Raw material consumption amounts for Examples 1-3 and Comparative Examples 1-3

[0040]

[0041]

[0042] Example 1

[0043] A method for preparing high-temperature thermal shock resistant high-purity corundum bricks, comprising the following steps:

[0044] S1. According to the dosage of Example 1 in Table 1, α-Al2O3 micro powder, α-Al2O3 nano powder suspension (α-Al2O3 nano powder mixed with an appropriate amount of water), dispersant (ammonium citrate), aqueous solution of soluble inorganic magnesium salt sintering aid (magnesium sulfate solution), binder (mixture of PVA and pseudoboehmite) and an appropriate amount of water are mixed, heated to 90°C until a paste is formed, and after cooling, it is poured into a ball mill jar. Two drops of oleyl alcohol are added to it and ball milled for 12 hours to obtain a matrix green slurry with a solid content of 40%.

[0045] S2. The matrix green slurry obtained in step S1 is spray-dried at 180°C to obtain spherical α-Al2O3 particles with a particle size of 50μm-100μm.

[0046] S3. Mix the spherical α-Al2O3 particles, corundum particles, and corundum fine powder obtained in step S2 evenly, press them into shape by isostatic pressing, dry them, and sinter them at 1400℃ for 5 hours to obtain high-purity corundum bricks.

[0047] Example 2

[0048] A method for preparing high-temperature thermal shock resistant high-purity corundum bricks, comprising the following steps:

[0049] S1. According to the dosage of Example 2 in Table 1, α-Al2O3 micro powder, α-Al2O3 nano powder suspension (α-Al2O2 nano powder mixed with an appropriate amount of water), dispersant (ammonium citrate), aqueous solution of soluble inorganic magnesium salt sintering aid (magnesium nitrate solution), binder (mixture of starch and PVA) and an appropriate amount of water are mixed and heated to 90°C until a paste is formed. After cooling, the mixture is poured into a ball mill jar, 2 drops of oleyl alcohol are added, and the mixture is ball milled for 12 hours to obtain a matrix green slurry with a solid content of 40%.

[0050] S2. The matrix green slurry obtained in step S1 is spray-dried at 200℃ to obtain spherical α-Al2O3 particles with a particle size of 50μm-100μm.

[0051] S3. Mix the spherical α-Al2O3 particles, corundum particles, and corundum fine powder obtained in step S2 evenly, mold them into shape, dry them, and sinter them at 1500℃ for 6 hours to obtain high-purity corundum bricks.

[0052] Example 3

[0053] A method for preparing high-temperature thermal shock resistant high-purity corundum bricks, comprising the following steps:

[0054] S1. According to the dosage of Example 3 in Table 1, α-Al2O3 micro powder, α-Al2O3 nano powder suspension (α-Al2O3 nano powder mixed with an appropriate amount of water), dispersant (hydrochloric acid), aqueous solution of soluble inorganic magnesium salt sintering aid (magnesium sulfate solution), binder (mixture of starch and PVA) and an appropriate amount of water are mixed, heated to 90°C until a paste is formed, and after cooling, it is poured into a ball mill jar. Two drops of oleyl alcohol are added to it and ball milled for 12 hours to obtain a matrix green slurry with a solid content of 35%.

[0055] S2. The matrix green slurry obtained in step S1 is spray-dried at 160℃ to obtain spherical α-Al2O3 particles with a particle size of 50μm-100μm.

[0056] S3. Mix the spherical α-Al2O3 particles, corundum particles, and corundum fine powder obtained in step S2 evenly, extrude them into shape, dry them, and sinter them at 1700℃ for 4 hours to obtain high-purity corundum bricks.

[0057] Comparative Example 1

[0058] High-purity corundum bricks were prepared according to the component dosages of Comparative Example 1 in Table 1, following the preparation method of Example 2.

[0059] Comparative Example 2

[0060] High-purity corundum bricks were prepared according to the component dosages in Comparative Example 2 in Table 1, following the preparation method of Example 2.

[0061] Comparative Example 3

[0062] High-purity corundum bricks were prepared according to the component dosages of Comparative Example 3 in Table 1, following the preparation method of Example 2.

[0063] Comparative Example 4

[0064] High-purity corundum bricks were prepared according to the component dosages in Example 2 of Table 1 and the preparation method of Example 2.

[0065] Among them, the soluble magnesium salt sintering aid magnesium nitrate is added in solid form.

[0066] Comparative Example 5

[0067] High-purity corundum bricks were prepared according to the component dosages in Example 2 of Table 1, following the preparation method described in Example 2.

[0068] The amount of soluble inorganic magnesium salt sintering aid (calculated as MgO) is 0.3g.

[0069] Comparative Example 6

[0070] According to the component dosage in Example 2 in Table 1, the preparation method is as follows: dry mix corundum particles, corundum fine powder and α-Al2O3 micro powder, add an appropriate amount of α-Al2O3 nanopowder suspension in deionized water, magnesium nitrate aqueous solution and dispersant, and then press the resulting powder; heat treat and sinter at 1400℃ for 5 hours.

[0071] Performance testing

[0072] 1. XRD analysis was performed on the high-purity corundum brick obtained in Example 1, such as... Figure 1 As shown, it is a single α-Al2O3 phase.

[0073] 2. SEM tests were performed on the high-purity corundum bricks obtained in Example 2 and Comparative Example 6, such as... Figure 2-3 As shown, the high-purity corundum bricks obtained in Comparative Example 6, which were not spray-dried and granulated, were denser, had smaller pores, and had an uneven surface with more defects.

[0074] The matrix green slurry prepared in Example 2 was spray-dried and granulated at inlet temperatures of 120°C, 140°C, 160°C, 180°C, and 200°C, respectively. The results are as follows: Figure 4 As shown, when the inlet temperature is between 160-200℃, especially 180℃, the hollow α-Al2O3 spherical particles obtained are more regular and have uniform pores.

[0075] 3. Mechanical performance testing

[0076] The high-purity corundum bricks prepared in Examples 1-3 and Comparative Examples 1-6 were tested for compressive strength, compressive strength after 10 thermal shocks, density, and flexural strength at room temperature. The test methods are as follows:

[0077] Density testing standard: GB / T4472-2011 Determination of density and relative density of chemical products.

[0078] The standard for porosity testing is GB / T 2997-2015, which specifies the test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products.

[0079] Flexural strength at room temperature: GB / T 3001-2017 Test method for flexural strength of refractory materials at room temperature.

[0080] Compressive strength at room temperature: GB / T 5072-2008 Test method for compressive strength of refractory materials at room temperature.

[0081] Thermal shock resistance test method: Place the sample in a resistance furnace and hold it at 1800℃ for 20 minutes. Remove it and quench it in cold water, then place it in air for 20 minutes. Repeat this process ten times. Test the compressive strength.

[0082] The test results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] Analysis of Tables 1 and 2 reveals that the difference between Example 2 and Comparative Examples 1-3 lies in the change in the corundum powder gradation. The high-purity corundum bricks obtained in Example 2 exhibit significantly better compressive strength and high-temperature thermal shock resistance than those in Comparative Examples 1-3, demonstrating that the gradation design in this application has achieved unexpected technical effects. Comparison of Examples 2 and Comparative Examples 4-5 shows that when the sintering aid is added in solid form, the compressive strength decreases and the high-temperature thermal shock resistance drops sharply. When the sintering aid is excessive, both compressive strength and high-temperature thermal shock resistance decrease further. Comparison of Examples 2 and Comparative Example 6 clearly shows that the preparation method of spray-drying and granulating α-Al2O3 micro powder and nano powder, followed by mixing and pressing with corundum particles and fine corundum powder, is superior to the method without spray drying. The resulting high-purity corundum bricks have higher porosity, lower density, and better high-temperature thermal shock resistance.

[0087] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-purity corundum brick resistant to high-temperature thermal shock, characterized by, The high-purity corundum brick is single-phase α-Al2O3, and raw material components thereof include, in parts by weight, corundum particles 55-65, corundum fine powder 25-36, α-Al2O3 micro powder 4-12, α-Al2O3 nano powder 0.5-3, soluble inorganic magnesium salt sintering aid, binder, dispersant; The amount of the soluble inorganic magnesium salt sintering aid is 0.15-0.25% of the total amount of the corundum particles, the corundum fine powder, the α-Al2O3 micro powder and the α-Al2O3 nano powder in terms of MgO content; The amount of the binder is 5-10% of the total amount of the α-Al2O3 micro powder and the α-Al2O3 nano powder; The amount of the dispersant is 0.25-2.5% of the total amount of the α-Al2O3 micro powder and the α-Al2O3 nano powder; the corundum particles are fused corundum particles with a particle size of 1-3 mm and an Al2O3 content of ≥99.5%; the corundum fine powder is fused corundum fine powder with a particle size of 0.01-0.05 mm and an Al2O3 content of ≥99.5%; the α-Al2O3 micro powder is α-Al2O3 micro powder with a particle size d50 of 1-4 μm and an Al2O3 content of ≥99.6%; and the α-Al2O3 nano powder is α-Al2O3 nano powder with an average particle size of 30-50 nm and an Al2O3 content of ≥99.9%; The preparation method of the high-purity corundum brick includes the following steps: S1, mixing α-Al2O3 micro powder, α-Al2O3 nano powder suspension, dispersant, soluble inorganic magnesium salt sintering aid aqueous solution, binder and water to obtain a matrix green body slurry by ball milling; S2, spray drying the matrix green body slurry obtained in step S1 to obtain spherical α-Al2O3 particles with a particle size of 50 μm-100 μm; S3, uniformly mixing the spherical α-Al2O3 particles obtained in step S2 with corundum particles and corundum fine powder, pressing and forming, drying, and then sintering at 1300 ℃-1700 ℃ to obtain a high-purity corundum brick.

2. The high purity corundum brick according to claim 1, characterized in that The binder is any one or mixture of multiple of PVA, starch or pseudoboehmite sol binder.

3. The high purity corundum brick according to claim 1, characterized in that, The soluble inorganic magnesium salt sintering aid is any one or mixture of multiple of magnesium nitrate and magnesium sulfate.

4. The high purity corundum brick according to claim 1, characterized in that, The dispersant includes any one of ammonium citrate and hydrochloric acid.

5. The method of producing high-purity corundum bricks according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: S1, mixing α-Al2O3 micro powder, α-Al2O3 nano powder suspension, dispersant, soluble inorganic magnesium salt sintering aid aqueous solution, binder and water to obtain a matrix green body slurry by ball milling; S2, spray drying the matrix green body slurry obtained in step S1 to obtain spherical α-Al2O3 particles with a particle size of 50 μm-100 μm; S3, uniformly mixing the spherical α-Al2O3 particles obtained in step S2 with corundum particles and corundum fine powder, pressing and forming, drying, and then sintering at 1300 ℃-1700 ℃ to obtain a high-purity corundum brick.

6. The production method according to claim 5, wherein In step S1, the solid content of alumina in the slurry is 35-45%.

7. The preparation method according to claim 5, characterized in that, In step S2, the temperature of the spray drying is 160-200 ℃.

8. The preparation method according to claim 5, characterized in that, The sintering time in step S3 is 4-6 hours.

9. The preparation method according to claim 5, characterized in that, The sintering temperature is 1400-1500°C.

10. The method of claim 6, wherein, In step S3, the press forming method is any one of die press forming, extrusion forming or isostatic press forming.

Images