High-purity aluminum oxide brick prepared from corundum-aluminum hydroxide-aluminum nitride ingredients and process of high-purity aluminum oxide brick

Abstract

The invention relates to a high-purity aluminum oxide brick prepared from corundum-aluminum hydroxide-aluminum nitride ingredients and a production process thereof, the high-purity aluminum oxide brick adopts an overall gradient design, the gradient distribution is as follows: a 1 / 4L working layer A, a 1 / 4L gradient transition layer I B1, a 1 / 4L gradient transition layer II B2 and a 1 / 4L heat insulation layer C, the gradient transition layer I B1 is a mixed ratio of 2 / 3 of the working layer A and 1 / 3 of the heat insulation layer C by weight, and the gradient transition layer II B2 is a mixed ratio of 2 / 3 of the working layer A and 1 / 3 of the heat insulation layer C by weight; and the gradient transition layer II B2 is formed by mixing 1 / 3 of the working layer A and 2 / 3 of the heat insulation layer C according to the weight ratio. The preparation method comprises the steps of raw material weighing, wet grinding, forming, drying and high-temperature sintering, formed green bricks are dried for 48-72 h at the temperature of 120 DEG C, heat preservation is conducted for 7 days for 168 h at the temperature of 650 DEG C, heat preservation is conducted for 6-8 h at the temperature of 1750-1800 DEG C, and sintering is conducted. The obtained high-purity aluminum oxide brick is excellent in performance, high in bonding strength on the working layer A, the gradient transition layer I B1, the gradient transition layer II B2 and the heat insulation layer C, good in overall performance, low in heat conductivity coefficient and good in heat preservation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-purity alumina brick prepared from corundum-aluminum hydroxide-aluminum nitride batch and a process thereof, and belongs to the field of refractory materials in inorganic non-metallic material science. BACKGROUND

[0002] High-purity reaction furnaces have high temperature, temperature fluctuation, pressure, corrosion, explosion and other dangerous factors in use, and the working conditions are relatively harsh, and the flue gas composition is complex, so the refractory lining of the reaction furnace has high requirements, and high-strength, good corrosion resistance and good thermal shock resistance refractory materials need to be selected. At present, the commonly used configuration of the lining refractory material in the reaction furnace is three layers: the first layer is heavy brick, the second layer is light brick, and the third layer is heat-insulating castable. The advantages of the three-layer refractory material design are: the first layer of heavy refractory brick has high strength, good wear resistance and good corrosion resistance, and can withstand harsh working environments, the second layer of light heat-insulating brick has low thermal conductivity, small heat capacity and good heat preservation effect, and the third layer of light castable has low thermal conductivity, good heat preservation effect and strong adaptability to shape. However, this three-layer design still has obvious defects: due to the low strength of the second layer and the third layer of light refractory material, the second layer and the third layer at the bottom of the reaction furnace are often compacted and collapsed in long-term thermal load operation, causing deformation of the lining structure.

[0003] In order to eliminate the hidden danger of brick collapse caused by deformation, the refractory brick adopts large-volume arc-shaped bricks, and the extrusion stress and friction force of the large-angle slope surface of the large-volume arc-shaped bricks can resist the gravity and load of the heavy brick to eliminate the hidden danger of brick falling and collapse. However, the large-volume arc-shaped bricks must be customized according to the diameter of each reaction furnace, and the slope surface of the arc-shaped bricks of different diameters is different, so different diameters must use molds suitable for the diameters, causing great waste of molds and high cost. When there is an order, the mold must be opened first and then produced, causing a very tight delivery period, and when there is no order, the tunnel kiln used for sintering products is idling, causing great waste of fuel.

[0004] Through reasonable block number matching of two or three small-volume trapezoidal bricks, different diameters can be adapted without opening molds according to the diameter of each reaction furnace, which can reduce mold cost and save delivery period. In addition, small-volume trapezoidal bricks can adapt to different diameters of kilns and solve the problem of variable diameter, and can be produced as standard bricks even when there is no order, so as to avoid waste of fuel due to idling of the tunnel kiln. However, since the reaction furnace currently adopts a three-layer design, the second layer and the third layer of the lining of the reaction furnace are light refractory materials, deformation is inevitable, and the extrusion stress and friction force of the small-angle slope surface of the small-volume trapezoidal bricks are insufficient to resist the gravity and load of the heavy brick, so the hidden danger of brick falling and kiln collapse is inevitable.

[0005] The precondition for eliminating the falling of small volume trapezoidal bricks is only one, that is, the second layer and the third layer must not be deformed, and the base of the load must have sufficient strength, and the light weight refractory material cannot reach the requirement of sufficient high strength after long-term thermal operation. Therefore, the solution is to abandon the current three-layer design idea, that is, not to use the design of the first layer of heavy bricks, the second layer of light bricks and the third layer of light castable, but to use the overall design method. To achieve the design of the whole brick, it is necessary to meet the harsh process conditions of service and the effect of energy saving and heat preservation, and the gradient material design idea can solve this problem. According to the gradient design idea, the high-purity alumina brick prepared by using corundum-aluminum hydroxide-aluminum nitride gradient design and preparation of the formula has the working layer performance meeting the harsh working condition environment of the reaction furnace, and the heat preservation effect of the heat insulation layer is good, and the working layer to the heat insulation layer of the whole brick is gradually transitioned by gradient. SUMMARY

[0006] The present application discards the three-layer design of the reaction furnace currently used, and adopts the overall gradient design, and the formula of the high-purity alumina brick prepared by using corundum-aluminum hydroxide-aluminum nitride gradient change has four parts, the formula of the working layer is A, the formula of the heat preservation and heat insulation layer is C, and A to C is transition layer one B1 (2 / 3A+1 / 3C) and transition layer two B2 (1 / 3A+2 / 3C) respectively. The formula of the transition layer one B1 is a mixture of 2 / 3A and 1 / 3C by weight, and the formula of the transition layer two B2 is a mixture of 1 / 3A and 2 / 3C by weight. The total length L of the gradient brick is 300-400mm, and the thicknesses of A layer, transition layer one B1 (2 / 3A+1 / 3C), and transition layer two B2 (1 / 3A+2 / 3C), and C layer are 1 / 4L, 1 / 4L, 1 / 4L, and 1 / 4L respectively.

[0007] The working layer A layer of the high-purity alumina brick prepared by using corundum-aluminum hydroxide-aluminum nitride according to the present application, the raw material ratio is as follows by weight:

[0008] (1) plate-shaped corundum with a particle size of 5-3mm, 10-20 parts;

[0009] (2) plate-shaped corundum with a particle size of 3-1mm, 10-15 parts;

[0010] (3) plate-shaped corundum with a particle size of ≤0.045mm, 30-50 parts;

[0011] (4) aluminum carbide with a particle size of ≤0.010mm, 10-20 parts;

[0012] (5) additional aluminum sol + 2.5-3 parts.

[0013] The heat preservation and insulation layer C layer of the high-purity alumina brick prepared from the corundum-aluminum hydroxide-aluminum nitride batch according to the present application has the following raw material ratio by weight:

[0014] (1) 20-38 parts of alumina hollow spheres with a particle size of 2-1 mm;

[0015] (2) 25-30 parts of mesoporous alumina with a particle size of 0.5-0.088 mm;

[0016] (3) 5-10 parts of aluminum nitride with a particle size of 0.5-0.088 mm;

[0017] (4) 8-10 parts of metallic aluminum powder with a particle size of ≤0.045 mm;

[0018] (5) 10-25 parts of aluminum hydroxide with a particle size of ≤0.045 mm;

[0019] (6) 10-15 parts of aluminum nitride powder with a particle size of ≤0.020 mm;

[0020] (7) 15-30 parts of carbon black powder with a particle size of ≤0.010 mm;

[0021] (8) 3-6 parts of aluminum carbonate with a particle size of ≤0.010 mm,

[0022] (9) 2.5-3 parts of additional aluminum sol.

[0023] The transition layer one B1 of the high-purity alumina brick prepared from the corundum-aluminum hydroxide-aluminum nitride batch according to the present application has the formula (2 / 3A+1 / 3C), and the transition layer two B2 has the formula (1 / 3A+2 / 3C) by analogy.

[0024] The high-purity alumina brick prepared from the corundum-aluminum hydroxide-aluminum nitride batch according to the present application has a gradient transition formula, and the working layer A layer, the gradient transition layer one B1, the gradient transition layer two B2 and the heat preservation and insulation layer C layer have high bonding strength and no interface peeling problem between layers, and the overall performance of the brick is good.

[0025] The production process of the high-purity alumina brick according to the present application includes four main process steps of (1) batching and mixing, (2) forming, (3) drying and (4) sintering.

[0026] (1) Batching and mixing:

[0027] The required raw materials are weighed according to the proportion, and the A material of the working layer, the C material of the heat preservation and insulation layer, the B1 material (2 / 3A+1 / 3C) of the gradient transition layer one and the B2 material (1 / 3A+2 / 3C) of the gradient transition layer two are respectively batched and separately mixed.

[0028] The configuration of the working layer A material: the raw materials are tabular corundum with a particle size of 5-3 mm, 10-20 parts, tabular corundum with a particle size of 3-1 mm, 10-15 parts, tabular corundum with a particle size of ≤0.045 mm, 30-50 parts, aluminum carbide with a particle size of ≤0.010 mm, 10-20 parts, and additional aluminum sol + 2.5-3 parts, in terms of weight parts.

[0029] The configuration of the thermal insulation layer C material: the raw materials are alumina hollow spheres with a particle size of 2-1 mm, 20-38 parts, mesoporous alumina with a particle size of 0.5-0.088 mm, 25-30 parts, aluminum nitride with a particle size of 0.5-0.088 mm, 5-10 parts, aluminum metal powder with a particle size of ≤0.045 mm, 8-10 parts, aluminum hydroxide with a particle size of ≤0.045 mm, 10-25 parts, aluminum nitride powder with a particle size of ≤0.020 mm, 10-15 parts, carbon black powder with a particle size of ≤0.010 mm, 15-30 parts, aluminum carbonate with a particle size of ≤0.010 mm, 3-6 parts, and additional aluminum sol + 2.5-3 parts, in terms of weight percentage.

[0030] The configuration of the gradient transition layer one B1 material: the B1 material is a mixture of 2 / 3 A and 1 / 3 C, in terms of weight parts.

[0031] The configuration of the gradient transition layer two B2 material: the B2 material is a mixture of 1 / 3 A and 2 / 3 C, in terms of weight parts.

[0032] The configuration steps of the working layer A material:

[0033] Fine powder premixing. The tabular corundum with a particle size of ≤0.045 mm, the aluminum carbide with a particle size of ≤0.010 mm, and the A powder are strongly mixed for 20 minutes, and are ready for use. Denoted as A powder.

[0034] Mixing and grinding. The tabular corundum with a particle size of 5-3 mm, the tabular corundum with a particle size of 3-1 mm, the aluminum sol as a binder, and the premixed A powder are mixed and strongly ground together for 30 minutes. Denoted as A material.

[0035] The configuration steps of the thermal insulation layer C material:

[0036] Fine powder premixing. The mesoporous alumina with a particle size of 0.5-0.088 mm, the aluminum nitride with a particle size of 0.5-0.088 mm, the aluminum metal with a particle size of ≤0.045 mm, the aluminum hydroxide with a particle size of ≤0.045 mm, the aluminum nitride with a particle size of ≤0.020 mm, the carbon black powder with a particle size of ≤0.010 mm, and the aluminum carbonate with a particle size of ≤0.010 mm are strongly mixed for 20 minutes, and are ready for use. Denoted as C powder.

[0037] Mixing and grinding. The alumina hollow spheres with a particle size of 2-1 mm, the aluminum sol as a binder, and the premixed C powder are mixed and strongly ground together for 30 minutes. Denoted as C material.

[0038] Gradient transition layer B configuration method:

[0039] Gradient transition layer one, material B1 (2 / 3A + 1 / 3C), is made by mixing 2 / 3 of the weight of material A and 1 / 3 of the weight of material C. The premixing and grinding of the fine powder are the same as those for materials A and B. Similarly, gradient transition layer two, material B2 (1 / 3A + 2 / 3C), is made by mixing 1 / 3 of the weight of material A and 2 / 3 of the weight of material C. The premixing and wet grinding of the fine powder are the same as those for materials A and C.

[0040] (2) Molding:

[0041] Fabric. Divide the mold into four sections using cardboard. In each section, pour in material A, transition layer 1 B1 (2 / 3A + 1 / 3C), transition layer 2 B2 (1 / 3A + 2 / 3C), and material C in sequence. After spreading and smoothing slightly, remove the cardboard.

[0042] Pressing. After the material is laid out, it is machine-pressed or hydraulically formed.

[0043] (3) Drying:

[0044] Dry the brick blanks at 120℃ for 48~72 hours.

[0045] (4) Sintering:

[0046] Sintering is carried out at 650℃ for 7 days (168 hours) and at 1750~1800℃ for 6~8 hours.

[0047] A high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride feedstock utilizes plate-shaped corundum with large, high-strength, and high-temperature resistant crystals. It features small pores with numerous closed pores, exhibiting excellent resistance to erosion and thermal shock, and minimal re-firing shrinkage. Mesoporous alumina offers good erosion resistance, high operating temperature, and low thermal conductivity, providing a thermal barrier to prevent heat conduction. Hollow alumina spheres possess high strength, while their bulk density is only half that of corundum products, which helps reduce kiln weight and enhance insulation.

[0048] During long-term sintering at a low temperature of 650℃, metallic aluminum powder and carbon black powder slowly react to form aluminum carbide, which enhances the sintering of the brick blank and stabilizes the working layer A, transition layers B1 and B2, and thermal insulation layer C. The bonding strength between the working layer A, transition layers B1 and B2, and thermal insulation layer C is high, preventing interlayer delamination and resulting in good overall brick performance. The added aluminum carbide, aluminum nitride, aluminum carbonate, and aluminum hydroxide all contribute to a stable brick blank structure. As the temperature continues to rise to ultra-high temperature sintering of 1750~1800℃, the added aluminum carbide, aluminum nitride, aluminum carbonate, and aluminum hydroxide decompose into alumina, carbon dioxide gas, and water gas. The alumina retains the volume of the blank composed of aluminum carbide, aluminum nitride, aluminum carbonate, and aluminum hydroxide, while the evaporated gases leave pores, resulting in an excellent thermal insulation brick body.

[0049] The working layer A of the alumina brick of the present invention has the following properties: bulk density 2.7~2.9 g·cm³. -1 Withstand pressure strength ≥ 80 MPa; thermal conductivity ≤ 1.5 W·m when operating at 1800℃. -1 ·K -1 The thermal insulation layer C has the following properties: bulk density 1.15~1.25 g·cm³. -1 Compressive strength ≥ 20 MPa, thermal conductivity ≤ 0.5 W·m at 1000℃ -1 ·K -1 .

[0050] The advantages of the high-purity alumina brick prepared by the corundum-alumina hydroxide-alumina nitride formulation of the present invention are: (1) The working layer has high mechanical strength, good wear resistance, high load softening temperature, good erosion resistance, and good thermal shock resistance. It can resist the harsh working environment such as high temperature, temperature fluctuation, pressure, and corrosion in the reactor. Its insulation layer has a high load softening temperature and low thermal conductivity, achieving both heat preservation function and sufficient support strength without deformation; (2) The working layer and the insulation layer gradually transition from gradient, with good interface bonding strength and good overall brick integrity; (3) The alumina brick of the present invention has a high alumina content and does not pollute the electronic products prepared in the reactor; (4) The insulation layer has a low thermal conductivity and good heat preservation effect. Detailed Implementation

[0051] Example 1

[0052] The high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride of the present invention adopts a gradient transition formula. The required raw materials are weighed according to the proportion, and the A material of the working layer, the C material of the heat insulation layer, the B1 material of the first gradient transition layer (2 / 3A+1 / 3C), and the B2 material of the second gradient transition layer (1 / 3A+2 / 3C) are each separately prepared and mixed separately.

[0053] The production process of Example 1 includes four main process steps: (i) ingredient preparation and mixing, (ii) molding, (iii) drying, and (iv) sintering.

[0054] (a) Ingredient preparation and mixing:

[0055] The working layer A of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0056] (1) 20 parts of tabular corundum with a particle size of 5-3 mm;

[0057] (2) 10 parts of tabular corundum with a grain size of 3~1 mm;

[0058] (3) 50 parts of tabular corundum with a particle size ≤ 0.045 mm;

[0059] (4) 10 parts of aluminum carbide with a particle size ≤ 0.010 mm;

[0060] (5) Add aluminum sol + 3 parts.

[0061] The thermal insulation layer C of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0062] (1) Hollow alumina spheres with a particle size of 2~1 mm, 38 parts;

[0063] (2) 25 parts of mesoporous alumina with a particle size of 0.5~0.088 mm;

[0064] (3) 10 parts of aluminum nitride with a particle size of 0.5~0.088mm;

[0065] (4) 8 parts of metallic aluminum powder with a particle size ≤ 0.045 mm;

[0066] (5) 25 parts of aluminum hydroxide with a particle size ≤ 0.045 mm;

[0067] (6) 10 parts of aluminum nitride powder with a particle size ≤ 0.020 mm;

[0068] (7) 30 parts of carbon black powder with a particle size ≤ 0.010 mm;

[0069] (8) 3 parts of aluminum carbonate with a particle size ≤ 0.010 mm.

[0070] (9) Add aluminum sol + 3 parts.

[0071] The configuration of the high-purity alumina brick gradient transition layer B1 material of the present invention: expressed in parts by weight, B1 material is a mixture of 2 / 3 A and 1 / 3 C.

[0072] The configuration of the high-purity alumina brick gradient transition layer B2 material of the present invention: expressed in parts by weight, the B2 material is a mixture of 1 / 3 A and 2 / 3 C.

[0073] Preparation steps for working layer A material:

[0074] Fine powder premixing. Premix ≤0.045mm tabular corundum and ≤0.010mm aluminum carbide particles vigorously for 20 minutes, then set aside. Labelled as Powder A.

[0075] Mixing and milling. Add aluminum sol as a binder to tabular corundum with a particle size of 5-3 mm and 3-1 mm, then add premixed A powder and mix vigorously for 30 minutes. This mixture is designated as material A.

[0076] Preparation steps for insulation layer C material:

[0077] Fine powder premixing. Mesoporous alumina (0.5~0.088 mm), aluminum nitride (0.5~0.088 mm), metallic aluminum (≤0.045 mm), aluminum hydroxide (≤0.045 mm), aluminum nitride (≤0.020 mm), carbon black powder (≤0.010 mm), and aluminum carbonate powder (≤0.010 mm) are vigorously mixed for 20 minutes and set aside. This mixture is designated as powder C.

[0078] Mixing and milling. Add aluminum sol as a binder to hollow alumina spheres with a particle size of 2-1 mm, then add the premixed C powder, and mix and mill vigorously for 30 minutes. This mixture is designated as C material.

[0079] Gradient transition layer B configuration method:

[0080] Gradient transition layer one, material B1 (2 / 3A + 1 / 3C), is made by mixing 2 / 3 of the weight of material A and 1 / 3 of the weight of material C. The premixing and grinding of the fine powder are the same as those for materials A and B. Similarly, gradient transition layer two, material B2 (1 / 3A + 2 / 3C), is made by mixing 1 / 3 of the weight of material A and 2 / 3 of the weight of material C. The premixing and wet grinding of the fine powder are the same as those for materials A and C.

[0081] (II) Molding:

[0082] Fabric. Divide the mold into four sections using cardboard. In each section, pour in material A, transition layer 1 B1 (2 / 3A + 1 / 3C), transition layer 2 B2 (1 / 3A + 2 / 3C), and material C in sequence. After spreading and smoothing slightly, remove the cardboard.

[0083] Pressing. After the material is laid out, it is machine-pressed or hydraulically formed.

[0084] (iii) Drying:

[0085] The brick blanks were dried at 120℃ for 72 hours.

[0086] (iv) Sintering:

[0087] Sintering was carried out at 650℃ for 7 days (168 hours) and at 1750℃ for 8 hours.

[0088] After preparation, the properties were checked. The properties of the working layer A of the alumina brick in Example 1 were: bulk density 2.89 g·cm³. -1 Withstands pressure of 90 MPa and has a thermal conductivity of 1.48 W·m when operating at 1800℃. -1 ·K -1 The thermal insulation layer C has the following properties: bulk density 1.16 g·cm³. -1 It has a compressive strength of 21 MPa and a thermal conductivity of 0.48 W·m at 1000℃. -1 ·K -1 .

[0089] Example 2

[0090] The high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride of the present invention adopts a gradient transition formula. The required raw materials are weighed according to the proportion, and the A material of the working layer, the C material of the heat insulation layer, the B1 material of the first gradient transition layer (2 / 3A+1 / 3C), and the B2 material of the second gradient transition layer (1 / 3A+2 / 3C) are each separately prepared and mixed separately.

[0091] The production process of Example 2 includes four main process steps: (i) ingredient preparation and mixing, (ii) molding, (iii) drying, and (iv) sintering.

[0092] (a) Ingredient preparation and mixing:

[0093] The working layer A of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0094] (1) 10 parts of tabular corundum with a particle size of 5-3 mm;

[0095] (2) 15 parts of tabular corundum with a grain size of 3~1 mm;

[0096] (3) 30 parts of tabular corundum with a particle size ≤ 0.045 mm;

[0097] (4) 20 parts of aluminum carbide with a particle size ≤ 0.010 mm;

[0098] (5) Add 2.5 parts of aluminum sol.

[0099] The thermal insulation layer C of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0100] (1) Hollow alumina spheres with a particle size of 2~1 mm, 20 parts;

[0101] (2) 30 parts of mesoporous alumina with a particle size of 0.5~0.088 mm;

[0102] (3) 5 parts of aluminum nitride with a particle size of 0.5~0.088mm;

[0103] (4) 10 parts of metallic aluminum powder with a particle size ≤ 0.045 mm;

[0104] (5) 10 parts of aluminum hydroxide with a particle size ≤ 0.045 mm;

[0105] (6) 15 parts of aluminum nitride powder with a particle size ≤ 0.020 mm;

[0106] (7) 15 parts of carbon black powder with a particle size ≤ 0.010 mm;

[0107] (8) 6 parts of aluminum carbonate with a particle size ≤ 0.010 mm.

[0108] (9) Add 2.5 parts of aluminum sol.

[0109] The configuration of the high-purity alumina brick gradient transition layer B1 material of the present invention: expressed in parts by weight, B1 material is a mixture of 2 / 3 A and 1 / 3 C.

[0110] The configuration of the high-purity alumina brick gradient transition layer B2 material of the present invention: expressed in parts by weight, the B2 material is a mixture of 1 / 3 A and 2 / 3 C.

[0111] Preparation steps for working layer A material:

[0112] Fine powder premixing. Premix ≤0.045mm tabular corundum and ≤0.010mm aluminum carbide particles vigorously for 20 minutes, then set aside. Labelled as Powder A.

[0113] Mixing and milling. Add aluminum sol as a binder to tabular corundum with a particle size of 5-3 mm and 3-1 mm, then add premixed A powder and mix vigorously for 30 minutes. This mixture is designated as material A.

[0114] Preparation steps for insulation layer C material:

[0115] Fine powder premixing. Mesoporous alumina (0.5~0.088 mm), aluminum nitride (0.5~0.088 mm), metallic aluminum (≤0.045 mm), aluminum hydroxide (≤0.045 mm), aluminum nitride (≤0.020 mm), carbon black powder (≤0.010 mm), and aluminum carbonate powder (≤0.010 mm) are vigorously mixed for 20 minutes and set aside. This mixture is designated as powder C.

[0116] Mixing and milling. Add aluminum sol as a binder to hollow alumina spheres with a particle size of 2-1 mm, then add the premixed C powder, and mix and mill vigorously for 30 minutes. This mixture is designated as C material.

[0117] Gradient transition layer B configuration method:

[0118] Gradient transition layer one, material B1 (2 / 3A + 1 / 3C), is made by mixing 2 / 3 of the weight of material A and 1 / 3 of the weight of material C. The premixing and grinding of the fine powder are the same as those for materials A and B. Similarly, gradient transition layer two, material B2 (1 / 3A + 2 / 3C), is made by mixing 1 / 3 of the weight of material A and 2 / 3 of the weight of material C. The premixing and wet grinding of the fine powder are the same as those for materials A and C.

[0119] (II) Molding:

[0120] Fabric. Divide the mold into four sections using cardboard. In each section, pour in material A, transition layer 1 B1 (2 / 3A + 1 / 3C), transition layer 2 B2 (1 / 3A + 2 / 3C), and material C in sequence. After spreading and smoothing slightly, remove the cardboard.

[0121] Pressing. After the material is laid out, it is machine-pressed or hydraulically formed.

[0122] (iii) Drying:

[0123] The brick blanks were dried at 120℃ for 48 hours.

[0124] (iv) Sintering:

[0125] Sintering was carried out at 650℃ for 7 days (168 hours) and at 1800℃ for 6 hours.

[0126] After preparation, the performance was checked. The performance of the working layer A of the gradient alumina brick in Example 2 was as follows: bulk density 2.72 g·cm³. -1 Withstands pressure of 82 MPa and has a thermal conductivity of 1.45 W·m when operating at 1800℃. -1 ·K -1 The thermal insulation layer C has the following properties: bulk density 1.24 g·cm³. -1 Withstanding pressure of 22 MPa, thermal conductivity of 0.43 W·m at 1000℃ -1 ·K -1 .

[0127] Example 3

[0128] The high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride of the present invention adopts a gradient transition formula. The required raw materials are weighed according to the proportion, and the A material of the working layer, the C material of the heat insulation layer, the B1 material of the first gradient transition layer (2 / 3A+1 / 3C), and the B2 material of the second gradient transition layer (1 / 3A+2 / 3C) are each separately prepared and mixed separately.

[0129] The production process of Example 3 includes four main process steps: (i) ingredient preparation and mixing, (ii) molding, (iii) drying, and (iv) sintering.

[0130] (a) Ingredient preparation and mixing:

[0131] The working layer A of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0132] (1) 15 parts of tabular corundum with a particle size of 5-3 mm;

[0133] (2) 13 parts of tabular corundum with a grain size of 3-1 mm;

[0134] (3) 40 parts of tabular corundum with a particle size ≤ 0.045 mm;

[0135] (4) 15 parts of aluminum carbide with a particle size ≤ 0.010 mm;

[0136] (5) Add aluminum sol + 3 parts.

[0137] The thermal insulation layer C of the high-purity alumina brick of the present invention has the following raw material composition by weight:

[0138] (1) Hollow alumina spheres with a particle size of 2~1 mm, 29 parts;

[0139] (2) 28 parts of mesoporous alumina with a particle size of 0.5~0.088 mm;

[0140] (3) 7 parts of aluminum nitride with a particle size of 0.5~0.088mm;

[0141] (4) 9 parts of metallic aluminum powder with a particle size ≤ 0.045 mm;

[0142] (5) 17 parts of aluminum hydroxide with a particle size ≤ 0.045 mm;

[0143] (6) 13 parts of aluminum nitride powder with a particle size ≤ 0.020 mm;

[0144] (7) 22 parts of carbon black powder with a particle size ≤ 0.010 mm;

[0145] (8) 5 parts of aluminum carbonate with a particle size ≤ 0.010 mm.

[0146] (9) Add aluminum sol + 3 parts.

[0147] The configuration of the high-purity alumina brick gradient transition layer B1 material of the present invention: expressed in parts by weight, B1 material is a mixture of 2 / 3 A and 1 / 3 C.

[0148] The configuration of the high-purity alumina brick gradient transition layer B2 material of the present invention: expressed in parts by weight, the B2 material is a mixture of 1 / 3 A and 2 / 3 C.

[0149] Preparation steps for working layer A material:

[0150] Fine powder premixing. Premix ≤0.045mm tabular corundum and ≤0.010mm aluminum carbide particles vigorously for 20 minutes, then set aside. Labelled as Powder A.

[0151] Mixing and milling. Add aluminum sol as a binder to tabular corundum with a particle size of 5-3 mm and 3-1 mm, then add premixed A powder and mix vigorously for 30 minutes. This mixture is designated as material A.

[0152] Preparation steps for insulation layer C material:

[0153] Fine powder premixing. Mesoporous alumina (0.5~0.088 mm), aluminum nitride (0.5~0.088 mm), metallic aluminum (≤0.045 mm), aluminum hydroxide (≤0.045 mm), aluminum nitride (≤0.020 mm), carbon black powder (≤0.010 mm), and aluminum carbonate powder (≤0.010 mm) are vigorously mixed for 20 minutes and set aside. This mixture is designated as powder C.

[0154] Mixing and milling. Add aluminum sol as a binder to hollow alumina spheres with a particle size of 2-1 mm, then add the premixed C powder, and mix and mill vigorously for 30 minutes. This mixture is designated as C material.

[0155] Gradient transition layer B configuration method:

[0156] Gradient transition layer one, material B1 (2 / 3A + 1 / 3C), is made by mixing 2 / 3 of the weight of material A and 1 / 3 of the weight of material C. The premixing and grinding of the fine powder are the same as those for materials A and B. Similarly, gradient transition layer two, material B2 (1 / 3A + 2 / 3C), is made by mixing 1 / 3 of the weight of material A and 2 / 3 of the weight of material C. The premixing and wet grinding of the fine powder are the same as those for materials A and C.

[0157] (II) Molding:

[0158] Fabric. Divide the mold into four sections using cardboard. In each section, pour in material A, transition layer 1 B1 (2 / 3A + 1 / 3C), transition layer 2 B2 (1 / 3A + 2 / 3C), and material C in sequence. After spreading and smoothing slightly, remove the cardboard.

[0159] Pressing. After the material is laid out, it is machine-pressed or hydraulically formed.

[0160] (iii) Drying:

[0161] The brick blanks were dried at 120℃ for 48 hours.

[0162] (iv) Sintering:

[0163] Sintering was carried out at 650℃ for 7 days (168 hours) and at 1800℃ for 6 hours.

[0164] After preparation, the performance was checked. The performance of the working layer A of the gradient alumina brick in Example 3 was as follows: bulk density 2.80 g·cm³. -1 Withstands pressure of 86 MPa and has a thermal conductivity of 1.47 W·m when operating at 1800℃. -1 ·K -1 The thermal insulation layer C has the following properties: bulk density 1.21 g·cm³. -1 Withstanding pressure of 22MPa, thermal conductivity at 1000℃ ≤0.45W·m -1 ·K -1 .

Claims

1. A high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride feedstock and the process thereof, characterized in that: The design employs an overall gradient pattern, with the gradient distribution as follows: a 1 / 4L working layer A, a 1 / 4L gradient transition layer B1, a 1 / 4L gradient transition layer B2, and a 1 / 4L insulation layer C. Working layer A, transition layer B1, transition layer B2, and insulation layer C are poured into the mold sequentially. The production process is as follows: A, B1, B2, and C are added to a press for machine pressing or hydraulic forming; the formed brick blanks are dried at 120℃ for 48-72 hours; after holding at 650℃ for seven days (168 hours), they are sintered at 1750-1800℃ for 6-8 hours.

2. The high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride as described in claim 1, characterized in that its raw material formulation is as follows: The working layer A material: expressed in parts by weight, the raw materials are 10-20 parts of tabular corundum with a particle size of 5-3 mm, 10-15 parts of tabular corundum with a particle size of 3-1 mm, 30-50 parts of tabular corundum with a particle size ≤0.045 mm, 10-20 parts of aluminum carbide with a particle size ≤0.010 mm, plus 2.5-3 parts of aluminum sol; The insulation layer C material is characterized by the following by weight percentage: 20-38 parts of hollow alumina spheres with a particle size of 2-1 mm, 25-30 parts of mesoporous alumina with a particle size of 0.5-0.088 mm, 5-10 parts of aluminum nitride with a particle size of 0.5-0.088 mm, 8-10 parts of metallic aluminum powder with a particle size ≤0.045 mm, 10-25 parts of aluminum hydroxide with a particle size ≤0.045 mm, 10-15 parts of aluminum nitride powder with a particle size ≤0.020 mm, 15-30 parts of carbon black powder with a particle size ≤0.010 mm, 3-6 parts of aluminum carbonate with a particle size ≤0.010 mm, and 2.5-3 parts of added aluminum sol. The gradient transition layer B1 material is characterized in that, expressed in parts by weight, B1 material is a mixture of 2 / 3 A and 1 / 3 C. The gradient transition layer B2 material is characterized in that, expressed in parts by weight, B2 material is a mixture of 1 / 3 A and 2 / 3 C.

3. A high-purity alumina brick prepared from corundum-alumina hydroxide-alumina nitride feedstock and its process, comprising weighing raw materials, wet grinding, molding, drying and high-temperature firing, characterized in that: Weigh the required raw materials according to the proportions, and separately prepare and mix the A material of the working layer, the C material of the heat insulation layer, the B1 material of the gradient transition layer (2 / 3A+1 / 3C), and the B2 material of the gradient transition layer (1 / 3A+2 / 3C).

4. As described in claim 3, characterized in that: Working layer A material: Fine powder premixing. Premix ≤0.045mm tabular corundum and ≤0.010mm aluminum carbide particles vigorously for 20 minutes, then set aside. Labelled as Powder A. Mixing and milling. Add aluminum sol as a binder to tabular corundum with a particle size of 5-3 mm and 3-1 mm, then add pre-mixed A powder and mix vigorously for 30 minutes. This mixture is designated as material A. Insulation layer C material: Fine powder premixing. Mesoporous alumina (0.5~0.088 mm), aluminum nitride (0.5~0.088 mm), metallic aluminum (≤0.045 mm), aluminum hydroxide (≤0.045 mm), aluminum nitride (≤0.020 mm), carbon black powder (≤0.010 mm), and aluminum carbonate powder (≤0.010 mm) are vigorously mixed for 20 minutes and set aside. This mixture is designated as powder C. Mixing and milling. Add aluminum sol as a binder to hollow alumina spheres with a particle size of 2-1 mm, then add the premixed C powder, and mix vigorously for 30 minutes. This mixture is designated as C material. Gradient transition layer B: Gradient transition layer one, material B1 (2 / 3A + 1 / 3C), is made by mixing 2 / 3 of the weight of material A and 1 / 3 of the weight of material C. The premixing and grinding of the fine powder are the same as those for materials A and B. Similarly, gradient transition layer two, material B2 (1 / 3A + 2 / 3C), is made by mixing 1 / 3 of the weight of material A and 2 / 3 of the weight of material C. The premixing and wet grinding of the fine powder are the same as those for materials A and C.