Corrosion-resistant crucible and method of making the same

Abstract

This invention relates to the field of refractory materials technology, and more particularly to a corrosion-resistant sagger and its preparation method. By introducing recycled cordierite waste and corundum ceramic roller waste, the raw material cost is reduced by approximately 30-40%. By controlling the coarse-to-fine ratio of the cordierite and the gradation of the corundum ceramic roller waste, an ideal "cordierite-mullite-cristobalite" composite phase structure is formed, which also helps to reduce the apparent porosity of the sagger and improve the firing strength. The rational closed-pore structure blocks the penetration of corrosive media, thus improving corrosion resistance. Results show that the corrosion-resistant sagger product prepared by this invention has a density of 2.05-2.20 g / cm³. 3 It exhibits a porosity of 19-26%, a strength of 12-23 MPa, resistance to salt corrosion >50 cycles, and a salt spray sintering life >100 cycles. This invention significantly reduces raw material and energy costs and utilizes industrial waste to improve the corrosion resistance and service life of the sagger.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, and in particular to a corrosion-resistant crucible and its preparation method. Background Technology

[0002] Saggers are indispensable firing vessels in the sintering process of powder metallurgy, electronic ceramics, and new energy materials (such as positive and negative electrode materials for lithium batteries). During the sintering process of lithium battery materials, acidic or alkaline volatiles containing lithium and fluorine are usually generated, so the inner wall of the sagger is required to have good corrosion resistance.

[0003] The existing sagger manufacturing process suffers from the following pain points: High cost: It mainly relies on expensive primary cordierite and alumina raw materials.

[0004] High energy consumption: Wet ball milling and spray granulation processes are commonly used, and drying and firing processes consume extremely high amounts of energy.

[0005] Low utilization of solid waste: Cordierite waste and waste rollers generated during the production process are usually regarded as landfill, which not only wastes resources but also occupies land.

[0006] Insufficient corrosion resistance: In the high-temperature water vapor and corrosive atmosphere of lithium battery cathode materials (such as ternary materials and lithium cobalt oxide), the service life of ordinary crucibles is usually only 30 to 50 times.

[0007] Therefore, there is an urgent need to develop a crucible formula and process that can make large-scale use of industrial waste, significantly reduce energy consumption, and greatly improve corrosion resistance life. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a corrosion-resistant sagger and its preparation method. This invention uses a large amount of industrial waste as raw material, resulting in low production costs, significantly reduced energy consumption, and the prepared sagger exhibits excellent corrosion resistance and a long service life.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a corrosion-resistant sagger, prepared from raw materials comprising the following weight percentages: Cordierite: 30-45%; Corundum ceramic roller waste: 15~30%; 1# soil: 10~18%; 2# soil: 5~10%; Fused silica: 3~8%; Alumina: 7~15%; The cordierite material is composed of recycled cordierite waste and new cordierite material, and the mass ratio of recycled cordierite waste to new cordierite material is 1:(1~3). In terms of particle size, the cordierite material is composed of coarse cordierite and fine cordierite. The particle size of the coarse cordierite is 1~2.5mm, and the particle size of the fine cordierite is <0.5mm. The mass ratio of the coarse cordierite to the fine cordierite is (1~2):1. The corundum ceramic roller waste is composed of medium-sized particles and fine particles. The particle size of the medium-sized particles is 0.5~1.5mm, and the particle size of the fine particles is 60~100 mesh. The mass ratio of the medium-sized particles to the fine particles is 1:(1~2). The No. 1 soil is high-alumina kaolin; The soil in question #2 is black mud.

[0010] Preferably, the mass content of alumina in the No. 1 soil is >38%; and the particle size of the No. 1 soil is <250 mesh.

[0011] Preferably, the mass content of alumina in the No. 2 soil is 32-35%, and the particle size of the No. 2 soil is <300 mesh.

[0012] Preferably, the alumina content in the corundum ceramic roller waste is 85-95% by mass and the zirconium content is 1-5% by mass.

[0013] Preferably, the particle size of the fused silica and alumina is <120 mesh.

[0014] Preferably, the bulk density of the corrosion-resistant crucible is 2.05~2.20 g / cm³. 3 It has an apparent porosity of 19-26%, a room temperature flexural strength of 12-23 MPa, and a salt spray sintering life of more than 100 cycles.

[0015] This invention provides a method for preparing the corrosion-resistant sagger described above, comprising the following steps: pre-wetting and mixing cordierite rough with water to obtain a first mixture; wherein the weight of the water is 2-5% of the total weight of all solid raw materials; The first mixture is sequentially mixed with particles from corundum ceramic roller waste and fine particles from corundum ceramic roller waste to obtain the second mixture. The second mixture is mixed with soil #1 and soil #2 to obtain the third mixture; The third mixture is mixed with cordierite fines, fused silica and alumina to obtain a fourth mixture; The fourth mixture is dry-granulated and then pressed into shape to obtain a sagger green body. The raw sagger blanks are dried and fired sequentially to obtain the corrosion-resistant sagger.

[0016] Preferably, the firing temperature is 1300~1360℃ and the holding time is 4~8 hours.

[0017] Preferably, the pressing pressure is 50~120 MPa.

[0018] Preferably, the drying temperature is 100~120℃ and the time is 24~36 hours.

[0019] This invention provides a corrosion-resistant sagger. By introducing recycled cordierite waste and corundum ceramic roller waste, the raw material cost is reduced by approximately 30% to 40%. By controlling the coarse-to-fine ratio of the cordierite and the gradation of the corundum ceramic roller waste, an ideal "cordierite-mullite-cristobalite" composite phase structure is formed, which also helps to reduce the apparent porosity of the sagger and improve the firing strength. The reasonable closed-pore structure blocks the penetration of corrosive media, thereby improving corrosion resistance. In addition, the introduction of fused silica effectively reduces the coefficient of thermal expansion, while the appropriate addition of alumina increases the density and hardness of the matrix.

[0020] This invention provides a method for preparing the corrosion-resistant crucible described in the above-mentioned scheme. This invention uses dry granulation instead of wet ball milling, reducing energy consumption by approximately 25%.

[0021] The results of the examples show that the bulk density of the sagger prepared by the present invention is 2.05~2.20 g / cm³. 3 The apparent porosity is 19-26%; the room temperature flexural strength can reach 12-23 MPa; the salt spray sintering life is >100 cycles; in the sintering environment of lithium battery cathode materials, the service life is greater than 100 cycles (estimated based on the salt spray sintering life), far exceeding the industry average (30-50 cycles). Attached Figure Description

[0022] Figure 1 These are photographs of the salt spray test in Example 1; Figure 2 A photograph of the actual sagger prepared in Example 2. Detailed Implementation

[0023] This invention provides a corrosion-resistant sagger, prepared from raw materials comprising the following weight percentages: Cordierite: 30-45%; Corundum ceramic roller waste: 15~30%; 1# soil: 10~18%; 2# soil: 5~10%; Fused silica: 3~8%; Alumina: 7~15%.

[0024] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0025] The raw materials for preparing the corrosion-resistant sagger provided by this invention, by weight percentage, include 30-45% cordierite, which in specific embodiments can be 30%, 35%, 38%, 40%, 42%, or 45%. In this invention, the cordierite is composed of recycled cordierite waste and virgin cordierite, with a mass ratio of recycled cordierite waste to virgin cordierite of 1:(1-3), which in specific embodiments can be 1:1, 1:1.5, 1:2, 1:2.5, or 1:3. This invention uses a portion of recycled cordierite waste to replace virgin cordierite, reducing the production cost of the sagger. By controlling the ratio of recycled waste to virgin material within the above range, the strength of the sagger can be prevented from decreasing.

[0026] In this invention, the cordierite material, in terms of particle size, is composed of coarse cordierite and fine cordierite. The coarse cordierite has a particle size of 1-2.5 mm, and the fine cordierite has a particle size of <0.5 mm. The mass ratio of coarse cordierite to fine cordierite is (1-2):1, which can be 1:1, 1.5:1, or 2:1 in specific embodiments. By controlling the coarse-to-fine ratio of the cordierite material, this invention helps to improve the density during pressing and molding, and also forms an ideal "cordierite-mullite-cristobalite" composite phase structure. Crizobalite provides a more suitable coefficient of thermal expansion, is more resistant to thermal shock, and increases the number of uses. Moreover, the fine crizobalite particles help to seal pores on the surface of the product, improving corrosion resistance. Existing technologies commonly use fine cordierite, which, while exhibiting low porosity and high strength, suffers from poor corrosion resistance due to the lack of coarse grains. Conversely, using entirely coarse cordierite, although it generates a cordierite-mullite-cristobalite composite phase, results in insufficient strength of the resulting sagger due to the lack of interstitial filling and reinforcement from finer materials. This invention employs a rationally proportioned coarse-fine gradation to generate a cordierite-mullite-cristobalite composite phase, while simultaneously using finer materials for interstitial filling and reinforcement. This approach ensures both the strength and corrosion resistance of the sagger.

[0027] The raw materials for preparing the corrosion-resistant sagger provided by this invention, by weight percentage, include 15-30% corundum ceramic roller waste, which in specific embodiments can be 15%, 20%, 22%, 25%, 28%, or 30%. In this invention, the alumina content in the corundum ceramic roller waste is preferably 85-95% by mass, and the zirconium oxide content is preferably 1-5% by mass. In this invention, the corundum ceramic roller waste is composed of medium and fine particles, the medium particles having a particle size of 0.5-1.5 mm and the fine particles having a particle size of 60-100 mesh, with a mass ratio of medium to fine particles of 1:(1-2). This invention uses corundum ceramic roller waste to replace part of the alumina, which is beneficial for waste utilization and reducing production costs. This invention controls the particle size distribution of the corundum ceramic roller waste, which is beneficial for improving the density of the green body during molding, thereby reducing apparent porosity.

[0028] The raw materials for preparing the corrosion-resistant crucible provided by this invention, by weight percentage, include 10-18% #1 clay, which can be 10%, 12%, 14%, 16%, or 18% in specific embodiments. In this invention, the #1 clay is high-alumina kaolin; the mass content of alumina in the #1 clay is preferably >38%; and the particle size of the #1 clay is preferably <250 mesh. In this invention, the functions of the #1 clay include: enhancing the strength of the corrosion-resistant crucible; filling fine pores to increase density; and adjusting the alumina content.

[0029] The raw materials for preparing the corrosion-resistant crucible provided by this invention, by weight percentage, include 5-10% of No. 2 soil, which can be 5%, 6%, 7%, 8%, 9%, or 10% in specific embodiments. In this invention, the No. 2 soil is black mud; the mass content of alumina in the No. 2 soil is preferably 32-35%, and the particle size of the No. 2 soil is preferably <300 mesh. The use of black mud as the No. 2 soil in this invention has the advantage of good binding properties.

[0030] The raw materials for preparing the corrosion-resistant sagger provided by this invention, by weight percentage, include 3-8% fused silica, which in specific embodiments can be 3%, 4%, 5%, 6%, 7%, or 8%. In this invention, the particle size of the fused silica is preferably 120 mesh. Since the fused silica has undergone a phase transformation, the fused silica used in this invention is more favorable for the sintering process than conventional quartz, and also more conducive to enhancing the strength of the green body.

[0031] The raw materials for preparing the corrosion-resistant crucible provided by the present invention, by weight percentage, include 7-15% alumina, which in specific embodiments can be 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. In the present invention, the particle size of the alumina is preferably <120 mesh.

[0032] In this invention, the bulk density of the corrosion-resistant crucible is 2.05~2.20 g / cm³. 3 It has an apparent porosity of 19-26% and a room temperature flexural strength of 12-23 MPa.

[0033] In this invention, the corrosion-resistant crucible has a salt spray sintering life of >100 cycles, and it is further inferred that its service life in the sintering environment of lithium battery cathode material is greater than 100 cycles; and its tolerance in the salt corrosion environment is greater than 50 cycles.

[0034] This invention provides a method for preparing the corrosion-resistant sagger described above, comprising the following steps: pre-wetting and mixing cordierite rough with water to obtain a first mixture; wherein the weight of the water is 2-5% of the total weight of all raw materials; Particles from corundum ceramic roller waste and fine particles from corundum ceramic roller waste are added sequentially to the first mixture to obtain the second mixture; The second mixture is mixed with soil #1 and soil #2 to obtain the third mixture; The third mixture is mixed with cordierite fines, fused silica and alumina to obtain a fourth mixture; The fourth mixture is dry-granulated and then pressed into shape to obtain a sagger green body. The raw sagger blanks are dried and fired sequentially to obtain the corrosion-resistant sagger.

[0035] The present invention involves initially wetting and mixing cordierite coarse material with water to obtain a first mixture.

[0036] In this invention, the weight of the water is preferably 2-5% of the total weight of all solid raw materials, and in specific embodiments it can be 2%, 3%, 4% or 5%. This invention induces a slightly viscous consistency in the first mixture through initial wetting.

[0037] After obtaining the first mixture, the present invention sequentially mixes the first mixture with particles from the waste corundum ceramic roller and fine particles from the waste corundum ceramic roller to obtain the second mixture.

[0038] The present invention preferably adds particles of corundum ceramic roller waste and fine particles of corundum ceramic roller waste to the first mixture in sequence.

[0039] In this invention, the mixing time after adding the particles from the corundum ceramic roller waste is preferably 3 to 5 minutes; the mixing time after adding the fine particles from the corundum ceramic roller waste is preferably 5 to 10 minutes.

[0040] After obtaining the second mixture, the present invention mixes the second mixture with soil #1 and soil #2 to obtain the third mixture.

[0041] In this invention, it is preferable to add No. 1 soil and No. 2 soil to the second mixture for mixing. This invention does not impose a specific time limit on the mixing process; as long as the mixture is homogeneous, it is acceptable. In an embodiment of this invention, the mixing time is 5 minutes.

[0042] After obtaining the third mixture, the present invention mixes the third mixture with cordierite fines, fused quartz and alumina to obtain the fourth mixture.

[0043] In this invention, cordierite fines, fused silica, and alumina are preferably added to the third mixture for mixing. In this invention, the mixing is preferably carried out under stirring conditions, with a stirring speed preferably of 60-120 rpm and a mixing time preferably of 3-8 minutes. In this invention, clay is added first, which forms a coating film on the water-wetted aggregate. Then, fused silica and alumina are added, which helps to form independent particles and increases the flowability of the powder. Furthermore, the cordierite coarse and fines are added separately in this invention, ensuring uniform mixing; and the fines are lighter, and their later addition coats the coarses, facilitating better green body strength and density during molding. In this invention, the third mixture is a powder, unlike conventional wet ball milling slurry.

[0044] After obtaining the fourth mixture, the present invention performs dry granulation on the fourth mixture and then presses it into shape to obtain a sagger green body.

[0045] This invention does not impose special requirements on the dry granulation process; a well-known dry granulation process in the art can be used. Wet ball milling is commonly used in related technologies, as it helps maintain raw material uniformity and powder flowability, but subsequent spray drying granulation is necessary, resulting in higher efficiency. This application, however, avoids spray drying granulation while ensuring raw material uniformity by controlling the feeding sequence, thus reducing energy consumption.

[0046] In this invention, the pressing pressure is preferably 50~120 MPa, and in specific embodiments it can be 50, 70, 80, 100, 110 or 120 MPa.

[0047] After obtaining the sagger blank, the present invention will dry and fire the sagger blank in sequence to obtain the corrosion-resistant sagger.

[0048] In this invention, the drying temperature is preferably 100~120℃, and in specific embodiments it can be 100, 110 or 120℃; the drying time is preferably 24~36 hours, and in specific embodiments it can be 24, 28, 30, 32 or 36 hours. In this invention, the residual moisture content of the dried green body is less than 0.5%.

[0049] In this invention, the firing temperature is preferably 1300~1360℃, and in specific embodiments it can be 1300, 1310, 1320, 1330, 1340, 1350 or 1360℃; the firing holding time is preferably 4~8 hours, and in specific embodiments it can be 4, 5, 6, 7 or 8 hours. In this invention, the firing is preferably carried out in a tunnel kiln or a shuttle kiln.

[0050] The corrosion-resistant sagger and its preparation method provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0051] In the following embodiments, the particle size of the coarse cordierite is 1~2.5mm, and the particle size of the fine cordierite is <0.5mm; the particle size of No. 1 soil is <250 mesh; the particle size of No. 2 soil is <300 mesh; the particle size of fused silica and alumina is <120 mesh; the particle size of the corundum ceramic roller waste is 0.5~1.5mm, and the particle size of the fine corundum ceramic roller waste is 60~100 mesh.

[0052] Example 1 By weight percentage, the sagger formula is as follows: 42% cordierite (waste:new material = 1:2, coarse:fine = 1.5:1), 22% corundum ceramic roller waste (medium particles:fine particles = 1:1.5), 14% No. 1 soil, 8% No. 2 soil, 5% fused silica, and 9% alumina.

[0053] The preparation method is as follows: Add the aggregate (cordierite coarse material) into the mixer and premix with 3% water; Add the granules from the corundum ceramic roller waste and mix for 4 minutes, then add the fine granules from the corundum ceramic roller waste and mix for 6 minutes. Then add #1 soil and #2 soil and mix for 5 minutes; Add cordierite fines, fused silica, and alumina, and mix at 100 rpm for 4 minutes; Dry pressing, pressure 100 MPa; Dry at 110℃ for 30 hours; The sagger is fired at 1340℃ and held for 6 hours. After naturally cooling to room temperature, a corrosion-resistant sagger is obtained.

[0054] Density: 2.18 g / cm³ 3 Apparent porosity: 21%; Strength: 22.5 MPa; Salt spray sintering life: 115 cycles.

[0055] The apparent porosity, strength, and density were tested according to conventional ceramic / refractory material performance testing methods; the sintering life was tested using a simulated salt spray test: a mixture of soda and salt totaling 200g (mass ratio of soda to salt of 3:1) was placed in an alumina crucible inverted inside a sagger, the crucible was sealed with refractory clay, and the mixture was kept at 1050℃ for 2 hours and then cooled. This cycle was repeated until the erosion depth was >1.0mm (static crucible method). Figure 1 These are photos from a salt spray test. Note: Due to space limitations in the testing equipment, a sample block was used for the test.

[0056] Example 2 By weight percentage, the sagger formula is as follows: 38% cordierite (waste:new material = 1:1, coarse:fine = 2:1), 28% corundum ceramic roller waste (medium particles:fine particles = 1:1), 12% No. 1 soil, 6% No. 2 soil, 3% fused silica, and 13% alumina.

[0057] The preparation method is as follows: Add the aggregate (cordierite coarse material) into the mixer and premix with 4% water; Add the granules from the corundum ceramic roller waste and mix for 3 minutes, then add the fine granules from the corundum ceramic roller waste and mix for 5 minutes; add No. 1 soil and No. 2 soil and mix for 5 minutes. Add cordierite fines, fused silica, and alumina, and mix at 120 rpm for 3 minutes; Dry pressing (pressure 120MPa); Dry at 105℃ for 36 hours; Firing at 1320℃ and holding for 8 hours, followed by natural cooling to room temperature, yields a corrosion-resistant sagger (as shown in the actual photo). Figure 2 (As shown).

[0058] Performance testing: Density: 2.20 g / cm³ 3 Apparent porosity: 19%; Strength: 23.0 MPa; Resistance to boiling in 10% NaCl solution (simulated corrosion, 4 hours of heat treatment each time): >55 times without peeling.

[0059] Example 3 By weight percentage, the sagger formula is as follows: 45% cordierite (waste:new material = 1:3, coarse:fine = 1:1), 15% corundum ceramic roller waste (medium particles:fine particles = 1:2), 10% No. 1 soil, 10% No. 2 soil, 8% fused silica, and 12% alumina.

[0060] The preparation method is as follows: Add the aggregate (cordierite coarse material) to the mixer and premix with 2% water; Add the granules of the corundum ceramic roller waste and mix for 5 minutes, then add the fine granules of the corundum ceramic roller waste and mix for 8 minutes. Add soil #1 and soil #2 and mix for 5 minutes; Add cordierite fines, fused silica, and alumina, and mix at 60 rpm for 8 minutes; Dry pressing (pressure 50MPa); Dry at 120℃ for 24 hours; Firing at 1360℃ and holding for 4 hours.

[0061] Performance testing: Density: 2.05 g / cm³ 3 Apparent porosity: 26%; Strength: 12.0 MPa; Salt spray sintering life: 105 cycles.

[0062] Comparative Example 1 The only difference from Example 1 is that all cordierite used is conventional fine cordierite (particle size < 0.5 mm). Performance testing: Density: 1.95 g / cm³ 3 Apparent porosity: 18.3%; Strength: 9.6 MPa; Salt spray sintering life: 41 cycles.

[0063] The results of Example 1 and Comparative Example 1 show that if the gradation optimization is not carried out after replacing part of the cordierite material with cordierite recycled waste (all cordierite fine material is used), the resulting sagger has a low porosity but poor corrosion resistance.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A corrosion-resistant sagger, characterized in that, It is prepared from raw materials comprising the following weight percentages: Cordierite: 30-45%; Corundum ceramic roller waste: 15~30%; 1# soil: 10~18%; 2# soil: 5~10%; Fused silica: 3~8%; Alumina: 7~15%; The cordierite material is composed of recycled cordierite waste and new cordierite material, and the mass ratio of recycled cordierite waste to new cordierite material is 1:(1~3). In terms of particle size, the cordierite material is composed of coarse cordierite and fine cordierite. The particle size of the coarse cordierite is 1~2.5mm, and the particle size of the fine cordierite is <0.5mm. The mass ratio of the coarse cordierite to the fine cordierite is (1~2):

1. The corundum ceramic roller waste is composed of medium-sized particles and fine particles. The particle size of the medium-sized particles is 0.5~1.5mm, and the particle size of the fine particles is 60~100 mesh. The mass ratio of the medium-sized particles to the fine particles is 1:(1~2). The No. 1 soil is high-alumina kaolin; The soil in question #2 is black mud.

2. The corrosion-resistant sagger according to claim 1, characterized in that, The mass content of alumina in the No. 1 soil is >38%; the particle size of the No. 1 soil is <250 mesh.

3. The corrosion-resistant sagger according to claim 1, characterized in that, The mass content of alumina in the No. 2 soil is 32-35%, and the particle size of the No. 2 soil is <300 mesh.

4. The corrosion-resistant sagger according to claim 1, characterized in that, The alumina content in the corundum ceramic roller waste is 85-95% by mass, and the zirconium content is 1-5% by mass.

5. The corrosion-resistant sagger according to claim 1, characterized in that, The particle size of the fused silica and alumina is <120 mesh.

6. The corrosion-resistant sagger according to claim 1, characterized in that, The bulk density of the corrosion-resistant crucible is 2.05~2.20 g / cm³. 3 It has an apparent porosity of 19-26%, a room temperature flexural strength of 12-23 MPa, and a salt spray sintering life of more than 100 cycles.

7. The method for preparing the corrosion-resistant sagger according to any one of claims 1 to 6, characterized in that, Includes the following steps: Cordierite rough material is initially moistened and mixed with water to obtain a first mixture; the weight of the water is 2-5% of the total weight of all solid raw materials. The first mixture is sequentially mixed with particles from corundum ceramic roller waste and fine particles from corundum ceramic roller waste to obtain the second mixture. The second mixture is mixed with soil #1 and soil #2 to obtain the third mixture; The third mixture is mixed with cordierite fines, fused silica and alumina to obtain a fourth mixture; The fourth mixture is dry-granulated and then pressed into shape to obtain a sagger green body. The raw sagger blanks are dried and fired sequentially to obtain the corrosion-resistant sagger.

8. The preparation method according to claim 7, characterized in that, The firing temperature is 1300~1360℃, and the holding time is 4~8 hours.

9. The preparation method according to claim 7, characterized in that, The pressure for compression molding is 50~120 MPa.

10. The preparation method according to claim 7, characterized in that, The drying temperature is 100~120℃, and the time is 24~36 hours.

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