A kind of corrosion-resistant ceramic sagger and preparation method thereof

Abstract

The present application provides a corrosion-resistant ceramic sagger and a preparation method thereof, wherein the corrosion-resistant ceramic sagger includes an aggregate layer and a matrix layer, wherein the aggregate layer includes the following raw materials in parts by mass: 30-50 parts of yttrium-stabilized zirconia, 20-30 parts of silicon carbide, and 15-25 parts of magnesium-aluminum spinel; the matrix layer includes the following raw materials in parts by mass: 40-50 parts of mullite micropowder, 30-40 parts of cordierite micropowder, and 10-20 parts of a binder. The corrosion-resistant ceramic sagger of the present invention and its preparation method optimize the raw material ratio and preparation process, so that after the sagger is immersed in a 900°C molten salt environment for 72 hours, the corrosion depth is ≤0.19mm, which is 6-8 times longer than the life of the traditional corundum sagger, and has broad application prospects.

Description

Technical Field

[0001] The present application relates to the technical field of saggers, and in particular to a corrosion-resistant ceramic sagger and a preparation method thereof. Background Art

[0002] At present, the actual production of synthetic lithium-ion battery positive electrode materials generally adopts high-temperature solid-phase synthesis method, and the high-temperature resistant saggers used in the synthesis process are generally cordierite, mullite, quartz and corundum. Among them, cordierite and corundum are the most commonly used. However, since the raw materials used for synthetic lithium-ion positive electrode materials will decompose during the synthesis process to produce lithium oxide (Li2O) with strong permeability and reactivity, the alkaline substance Li2O reacts chemically with the acidic substances and amphoteric oxides in the sagger at high temperatures, thereby corroding the high-temperature resistant sagger, which greatly reduces the service life of the high-temperature resistant sagger.

[0003] Existing saggers are composite materials obtained by mixing multiple raw materials evenly, pressing them into shape, and then sintering them. After being eroded, this type of sagger has a small amount of difficult-to-peel-off positive electrode material on its surface. After being scrapped, it becomes industrial waste and can easily cause heavy metal pollution.

[0004] At present, in the saggers used for the synthesis of lithium-ion battery positive electrode materials, for high alkaline raw materials, the saggers are corroded during repeated use. Therefore, how to improve the corrosion resistance of the saggers, reduce heavy metal pollution, and improve the production efficiency of enterprises is a problem that needs to be solved urgently. Summary of the Invention

[0005] The present application is made in view of the above problems, and its purpose is to provide a corrosion-resistant ceramic sagger and a preparation method thereof.

[0006] Specifically, the first aspect of the present application provides a corrosion-resistant ceramic sagger, comprising an aggregate layer and a matrix layer, wherein the aggregate layer comprises the following raw materials in parts by mass: 30-50 parts of yttrium-stabilized zirconia, 20-30 parts of silicon carbide, and 15-25 parts of magnesia-aluminum spinel;

[0007] The matrix layer comprises the following raw materials in parts by mass: 40-50 parts of mullite micropowder, 30-40 parts of cordierite micropowder and 10-20 parts of CeO2 modified silica sol.

[0008] Furthermore, the particle size of the yttrium-stabilized zirconia is 60-80 nm.

[0009] A second aspect of the present application provides a method for preparing the corrosion-resistant ceramic sagger, comprising the following steps:

[0010] S1: ball-milling the aggregates yttrium-stabilized zirconia, silicon carbide, and magnesia-aluminum spinel respectively, and then mixing them evenly to obtain a mixed aggregate;

[0011] The matrix mullite micropowder, cordierite micropowder, binder and deionized water are mixed, ball-milled, and then spray-granulated to obtain spherical matrix particles;

[0012] S2: Customize a graphite mold, fill the mixed aggregate and spherical matrix particles into the graphite mold cavity, and use isostatic pressing to prepare the sagger body;

[0013] S3: drying, sintering, heat-insulating, and cooling the sagger body to obtain a sagger sintered body;

[0014] S4: Spraying silicon nitride on the surface of the sagger sintered body, and then performing secondary sintering to obtain the sagger.

[0015] Furthermore, in step S1, the yttrium-stabilized zirconia, silicon carbide, and magnesium-aluminum spinel are ball-milled for 2-3 hours at a rotation speed of 200-260 rpm.

[0016] Furthermore, in step S1, the mixing ratio of the matrix mullite powder, cordierite powder, binder and deionized water is 1.2-1.5:1.

[0017] Furthermore, in step S1, the matrix mullite powder, cordierite powder, binder and water are mixed and ball-milled for 4-5 hours to make the slurry viscosity ≤200 mPa·s.

[0018] Furthermore, the inlet temperature of the spray granulation in step S1 is 280-320° C., and the outlet temperature is 110-130° C.; and / or the particle size of the spherical matrix particles is 80-120 μm.

[0019] Furthermore, the mixed aggregate and the spherical matrix particles in step S2 are mixed in a ratio of 1.2-1.8:1, a polyvinyl alcohol solution is added to the mixed aggregate, and stirred until the moisture content of the mixed aggregate reaches 8-10%; and / or

[0020] The pressure during the isostatic pressing process is 80-100 MPa, and the pressure is maintained for 5-10 minutes.

[0021] Furthermore, the method for sintering the sagger body in step S3 is:

[0022] Raise the temperature to 1000-1100°C at 2-5°C / min and keep warm for 30-60 minutes;

[0023] Under protective atmosphere, continue to raise the temperature at 2-5℃ / min to 1400-1500℃ and keep it at this temperature for 2-3h.

[0024] Furthermore, in step S4, the secondary sintering temperature is 800-850° C. and the time is 1-1.5 h.

[0025] The present invention has the following beneficial effects:

[0026] 1. The saggar aggregate layer of the present invention includes yttrium-stabilized zirconia, which reacts with molten salt at high temperature to form a dense ZrO2-Y2O3 layer, blocking Li + / Na + Infiltration, thus playing a role in corrosion resistance, silicon carbide has high thermal conductivity, can buffer thermal stress, at the same time silicon carbide preferentially oxidizes in an oxidizing atmosphere to form SiO2 glass phase, and the Y in yttrium stabilized zirconia 3+ A Y-Si-O composite phase is formed, and a corrosion-resistant gradient layer is formed through gradient sintering. The added magnesium aluminum spinel (MgAl2O4) has amphoteric characteristics, and its spinel structure can react with Li2O to generate LiAlO2 and MgO stable phases, forming a chemical buffer layer.

[0027] The matrix layer adopts a composite system of mullite and cordierite powders, which have similar thermal expansion coefficients and are densely packed through particle size distribution, with a porosity of ≤15%. 4+ Can capture free Li + Generate CeLiO2 passivation film, and the Ce-O-Si bond formed by rare earth elements at high temperature can effectively block Li + diffusion.

[0028] 2. The preparation method of the present invention uses an isostatic pressing process (80-100MPa) to form a mechanically interlocking structure between the aggregate layer and the matrix layer. Densification and the formation of a corrosion-resistant layer are achieved through precise temperature control during sintering. Testing has shown that after immersion in a 900°C molten salt environment for 72 hours, the corrosion depth of the sagger is ≤0.22mm, which is several times longer than the lifespan of traditional corundum saggers. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0030] Figure 1 This is an appearance diagram of the sagger prepared in Example 1.

[0031] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative work are within the scope of protection of this application.

[0033] Obviously, the following descriptions are merely some examples or embodiments of the present application. Those skilled in the art can apply the present application to other similar scenarios without inventive effort. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, changes in design, manufacturing, or production based on the technical content disclosed in the present application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in the present application.

[0034] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0035] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0036] A first aspect of the present invention provides a corrosion-resistant ceramic sagger, comprising an aggregate layer and a matrix layer, wherein the aggregate layer comprises the following raw materials in parts by mass: 30-50 parts of yttria-stabilized zirconia, 20-30 parts of silicon carbide, and 15-25 parts of magnesia-aluminum spinel;

[0037] The matrix layer comprises the following raw materials in parts by mass: 40-50 parts of mullite micropowder, 30-40 parts of cordierite micropowder and 10-20 parts of CeO2 modified silica sol.

[0038] The particle size of the yttrium-stabilized zirconia is 60-80 nm and is purchased from Jiaozuo Zhongcheng New Materials Co., Ltd. The mass fraction thereof is any value or any range of values ​​selected from 30 parts, 35 parts, 40 parts, 45 parts, and 50 parts. If the mass fraction is lower than 30 parts, the corrosion resistance of the sagger will be insufficient, and if the mass fraction is higher than 50 parts, the cost of the sagger will be too high and the overall performance of the sagger may be affected.

[0039] The particle size of the silicon carbide is preferably 1-5 μm, and is purchased from Shanghai Chaowei Nano Technology Co., Ltd., and its mass fraction is any value or any range of values ​​among 20 parts, 22 parts, 25 parts, 27 parts, and 30 parts. A mass fraction lower than 20 parts will result in insufficient thermal conductivity of the sagger, and a mass fraction higher than 30 parts may result in increased brittleness of the sagger.

[0040] The particle size of the magnesia-alumina spinel is preferably 5-10 μm, and it is purchased from Gongyi Jufeng Refractory Material Co., Ltd., and its mass fraction is any value or any range of values ​​among 15 parts, 18 parts, 20 parts, 22 parts, and 25 parts. A mass fraction lower than 15 parts will lead to a decrease in the corrosion resistance of the sagger, and a mass fraction higher than 25 parts may affect the sintering performance of the sagger.

[0041] The particle size of the mullite micropowder is 200 mesh, and its mass fraction is any value or range of 40 parts, 42 parts, 45 parts, 48 ​​parts, and 50 parts. If it is less than 40 parts, the matrix layer of the sagger may be insufficiently strong, and if it is greater than 50 parts, the density of the sagger may decrease, affecting its corrosion resistance. The particle size of the cordierite micropowder is 200 mesh, and its mass fraction is any value or range of 30 parts, 32 parts, 35 parts, 38 parts, and 40 parts. Its thermal expansion coefficient is similar to that of the mullite micropowder, which helps to achieve close packing and reduce porosity. The binder is a CeO2-modified silica sol, and its mass fraction is selected within the range of 10-20 parts, which can both ensure the molding performance of the sagger and improve its corrosion resistance.

[0042] The preparation method of the CeO2 modified silica sol is as follows: placing silica sol in a reaction vessel, adjusting the pH to 9-11, adding Ce(NO3)3·6H2O solution, stirring and reacting at 60-80°C for 2-4 hours to obtain CeO2 modified silica sol. The amount of Ce(NO3)3·6H2O added is 2-5% of the mass of the silica sol. Through this modification method, Ce 4+ Can be evenly dispersed in silica sol.

[0043] A second aspect of the present application provides a method for preparing the corrosion-resistant ceramic sagger, comprising the following steps:

[0044] S1: ball-milling the aggregates yttrium-stabilized zirconia, silicon carbide, and magnesia-aluminum spinel respectively, and then mixing them evenly to obtain a mixed aggregate;

[0045] The matrix mullite micropowder, cordierite micropowder, binder and deionized water are mixed, ball-milled, and then spray-granulated to obtain spherical matrix particles;

[0046] S2: Customize a graphite mold, fill the mixed aggregate and spherical matrix particles into the graphite mold cavity, and use isostatic pressing to prepare the sagger body;

[0047] S3: drying, sintering, heat-insulating, and cooling the sagger body to obtain a sagger sintered body;

[0048] S4: Spraying silicon nitride on the surface of the sagger sintered body, and then performing secondary sintering to obtain the sagger.

[0049] In this embodiment, the yttrium-stabilized zirconia, silicon carbide, and magnesium-aluminum spinel are ball-milled for 2-3 hours at a rotation speed of 200-260 rpm to a size of 200 mesh.

[0050] In this embodiment, the mixing ratio of the matrix mullite powder, cordierite powder, binder and deionized water in step S1 is 1.2-1.5:1.

[0051] In this embodiment, in step S1, the matrix mullite powder, cordierite powder, binder, and water are mixed and ball-milled for 4-5 hours to a slurry viscosity of ≤200 mPa·s. This ensures uniform mixing of the slurry, uniform distribution of the matrix particles, and absence of agglomeration, which facilitates the subsequent spray granulation process.

[0052] In this embodiment, the inlet temperature of the spray granulation in step S1 is 280-320°C, and the outlet temperature is 110-130°C; and / or the particle size of the spherical matrix particles is 80-120 μm. By controlling the inlet and outlet temperatures, the spherical matrix particles can be ensured to have a regular morphology, uniform particle size distribution, and a certain strength, which is beneficial for the subsequent forming and sintering processes. The particle size of the spherical matrix particles is 80-120 μm. Spherical matrix particles within this particle size range have good filling properties and fluidity, which is beneficial for the densification of the sagger body and the improvement of its corrosion resistance.

[0053] In the present embodiment, the mixed aggregate and spherical matrix particles described in step S2 are mixed in a ratio of 1.2-1.8: 1, 3-5 parts of polyvinyl alcohol solution are added to the mixed aggregate, and the mixed aggregate is stirred until the moisture content of the mixed aggregate is 8-10%; the pressure during the isostatic pressing process is 80-100 MPa, and the pressure is maintained for 5-10 min. The present invention is divided into an inner and outer two-layer cavity by customizing a graphite mold, the inner wall is sprayed with a BN coating for anti-sticking, and the mixed aggregate and spherical matrix particles are respectively filled into the graphite mold, the thickness of the mixed aggregate is 5-8 mm, and the thickness of the spherical matrix particles is 8-12 mm. Polyvinyl alcohol solution is added as a binder in an amount of 3-5 parts, which can effectively improve the forming performance of the mixture and make the sagger body more dense. The pressure during the isostatic pressing process is 80-100 MPa, and the pressure is maintained for 5-10 min, so that the mixed aggregate and spherical matrix particles can form a mechanical interlocking structure, further improving the strength and corrosion resistance of the sagger.

[0054] In this embodiment, the sagger body is dried at room temperature in step S3 and then sintered as follows: the temperature is raised to 1000-1100°C at a rate of 2-5°C / min and held for 30-60 minutes. During this process, the silica sol is dehydrated, forming a Ce-Si-O gel network that initially bonds and inhibits interlayer delamination. Under a protective atmosphere, the temperature is further raised to 1400-1500°C at a rate of 2-5°C / min. During this process, yttrium-stabilized zirconia reacts with silicon carbide to form a ZrC-ZrSiO4 gradient layer (1-2 μm), forming an outer anti-corrosion barrier. Under a protective atmosphere, the temperature is held at 1400-1500°C for 2-3 hours. MgAl2O4 pre-reacts with the molten salt to form a LiAlO2-MgO composite phase, sealing the pores and reducing porosity. Finally, the furnace is cooled, with the cooling rate controlled at ≤5°C / min (accelerated below 800°C) to prevent mullite phase transformation cracking.

[0055] In this embodiment, in step S4, a silicon nitride coating is sprayed on the surface of the sagger sintered body; the secondary sintering temperature is 800-850°C and the time is 1-1.5 hours, forming a surface silicon nitride sealing layer with a thickness of 0.5-1μm. The silicon nitride coating is a slurry composed of silicon nitride powder, high-purity water, and silica sol in a ratio of 1.2-1.3:1:2.8-3.3. The silicon nitride powder has a particle size of 10-30μm, and the colloidal particles of the silica sol are 10-20nm. This sealing layer not only enhances the surface hardness and wear resistance of the sagger, but also further blocks the penetration of molten salt, improving the overall corrosion resistance.

[0056] Example 1

[0057] A corrosion-resistant ceramic sagger comprising an aggregate layer and a matrix layer, wherein the aggregate layer comprises the following raw materials in parts by mass: 38 parts of yttrium-stabilized zirconia, 23 parts of silicon carbide, and 20 parts of magnesium-aluminum spinel;

[0058] The matrix layer comprises the following raw materials in parts by mass: 44 parts of mullite micropowder, 36 parts of cordierite micropowder and 13 parts of CeO2 modified silica sol;

[0059] The preparation method of the corrosion-resistant ceramic sagger comprises the following steps:

[0060] S1: ball milling the aggregates yttrium-stabilized zirconia, silicon carbide, and magnesium-aluminum spinel separately for 3 h at a speed of 200 rpm, and then mixing them evenly to obtain a mixed aggregate;

[0061] Mullite micropowder, cordierite micropowder, binder and deionized water were mixed in a ratio of 1.5:1, ball-milled for 5 h to make the slurry viscosity ≤ 200 mPa·s, and then spray-granulated to obtain spherical matrix particles; the inlet temperature of the spray granulation was 300°C and the outlet temperature was 120°C; the particle size of the spherical matrix particles was 100 μm;

[0062] S2: Customize a graphite mold, add 3 parts of polyvinyl alcohol solution to the mixed aggregate, mix well and fill the graphite mold, then fill the spherical matrix particles into the graphite mold, and use isostatic pressing technology at 80 MPa for 8 minutes to prepare the sagger body;

[0063] S3: Dry the sagger body at room temperature, then heat it to 1050°C at a rate of 3°C / min and keep it at that temperature for 60 minutes. Then, continue heating it to 1450°C at a rate of 3°C / min under a nitrogen atmosphere and keep it at that temperature for 3 hours. Finally, cool it in the furnace to obtain a sagger body.

[0064] S4: Spray silicon nitride on the surface of the sagger sintered body, and then perform secondary sintering at a temperature of 800℃ for 1 hour to obtain the sagger. Figure 1 .

[0065] Example 2

[0066] This embodiment is basically the same as embodiment 1, except that 45 parts of yttrium-stabilized zirconia are used.

[0067] Example 3

[0068] This embodiment is basically the same as embodiment 1, except that 28 parts of silicon carbide are used.

[0069] Example 4

[0070] This embodiment is substantially the same as embodiment 1, except that the amount of mullite micropowder is 48 parts and the amount of cordierite micropowder is 32 parts.

[0071] Example 5

[0072] This embodiment is basically the same as embodiment 1, except that 17 parts of CeO2 modified silica sol are used.

[0073] Example 6

[0074] This embodiment is substantially the same as embodiment 1, except that in step S2, the matrix mullite powder, cordierite powder, binder, and deionized water are mixed in a ratio of 1.2:1 and ball-milled for 4 h.

[0075] Example 7

[0076] This embodiment is basically the same as embodiment 1, except that in step S4, after drying, the temperature is raised to 1050° C. at 5° C. / min and kept at this temperature for 40 minutes. In a nitrogen atmosphere, the temperature is further raised to 1500° C. at 5° C. / min and kept at this temperature for 2 hours.

[0077] Example 8

[0078] This embodiment is basically the same as embodiment 1, except that the secondary sintering temperature is 850° C. and the time is 1.5 h.

[0079] Comparative Example 1

[0080] This comparative example is substantially the same as Example 1, except that the aggregate layer does not contain yttrium-stabilized zirconia.

[0081] Comparative Example 2

[0082] This comparative example is substantially the same as Example 1, except that yttrium-stabilized zirconia is replaced by zirconium oxide.

[0083] Comparative Example 3

[0084] This comparative example is basically the same as Example 1, except that silica sol replaces CeO2-modified silica sol.

[0085] Comparative Example 4

[0086] This comparative example is substantially the same as Example 1, except that spray granulation is not performed in step S2.

[0087] Comparative Example 5

[0088] This comparative example is basically the same as Example 1, except that, in step S3, the isostatic pressing process is used instead of the conventional pressing method.

[0089] Comparative Example 6

[0090] This comparative example is basically the same as Example 1, except that, in step S4, the temperature is not increased in steps, but directly increased to 1450° C. at a rate of 5° C. / min and kept at that temperature for 3 h.

[0091] Comparative Example 7

[0092] This comparative example is basically the same as Example 1, except that in step S5, the sagger sintered body is not sprayed with a silicon nitride coating.

[0093] Experimental Case

[0094] Li2CO3-Na2CO3-K2CO3 was used as a mixed molten salt, and the molar ratio of Li2CO3, Na2CO3, and K2CO3 was 4:3:3. The saggers prepared in Examples 1-8 and Comparative Examples 1-7 were statically immersed in the mixed molten salt at 900°C. The test cycles were 24h, 48h, and 72h. The corrosion depth of each sagger was detected. The results are shown in Table 1.

[0095]

[0096] As can be seen from the above table, the saggers prepared in Examples 1-8 of the present invention showed excellent performance in the corrosion resistance test, especially in a mixed molten salt environment. After 48 hours and 72 hours of static immersion tests, the corrosion depth of the saggers of Examples 1-8 was significantly lower than that of the saggers of Comparative Examples 1-6. The reason may be that the present invention uses yttrium-stabilized zirconia, silicon carbide and magnesium-aluminum spinel as the main components of the aggregate layer. These materials not only have high corrosion resistance, but also can form stable compounds during the sintering process, further enhancing the corrosion resistance barrier of the sagger. At the same time, by optimizing the particle size and ratio of these raw materials, the balance between the thermal conductivity, strength and sintering performance of the sagger is ensured. The selection of mullite micropowder and cordierite micropowder in the matrix layer, and the application of CeO2 modified silica sol as a binder, further enhance the overall performance of the sagger. The particle size and ratio optimization of mullite micropowder and cordierite micropowder help to achieve close stacking, reduce porosity, and thus improve the density and corrosion resistance of the sagger. The preparation and application of CeO2 modified silica sol not only enhances the forming performance of the sagger, but also improves the corrosion resistance of the sagger through modification.

[0097] During the manufacturing process, meticulous control of key steps, including custom graphite molds, isostatic pressing, step-by-step sintering, and spray-coating with silicon nitride, ensures the optimization of the sagger's microstructure and properties. In particular, the isostatic pressing process creates a mechanical interlocking structure between the mixed aggregate and the spherical matrix particles, further enhancing the sagger's strength and corrosion resistance. Furthermore, the implementation of steps such as step-by-step sintering and spray-coating with silicon nitride helps form a dense corrosion barrier and surface sealing layer, further enhancing the sagger's corrosion resistance.

[0098] From Comparative Examples 1-7, it can be seen that in Comparative Example 1, when the aggregate layer does not contain yttrium-stabilized zirconia, the corrosion resistance of the sagger is significantly reduced. The reason may be that the high corrosion resistance of yttrium-stabilized zirconia is lacking. Yttrium-stabilized zirconia reacts with molten salt at high temperature to form a dense ZrO2-Y2O3 layer, which blocks the Li + / Na +Penetration, when there is a lack of yttrium-stabilized zirconia, the corrosion barrier of the sagger cannot be effectively formed, resulting in a significant increase in the corrosion depth. In Comparative Example 2, ordinary zirconia is used instead of yttrium-stabilized zirconia. Although zirconia also has certain corrosion resistance, its stability is not as good as yttrium-stabilized zirconia, so the corrosion resistance of the sagger is also reduced. In Comparative Example 3, unmodified silica sol is used as a binder, lacking the modification effect of CeO2, resulting in a decrease in the forming performance and corrosion resistance of the sagger. In Comparative Example 4, spray granulation is not performed, so that the morphology and particle size distribution of the matrix particles are uneven, affecting the density and corrosion resistance of the sagger. In Comparative Example 5, conventional press molding is used instead of isostatic pressing, and a mechanical interlocking structure cannot be formed, resulting in a decrease in the strength and corrosion resistance of the sagger. In Comparative Example 6, step-by-step heating is not used, and direct high-temperature sintering may cause uneven stress inside the sagger, resulting in cracks, affecting the corrosion resistance. In Comparative Example 7, the sintered body of the sagger was not sprayed with a silicon nitride coating, lacking a surface sealing layer, which reduced the corrosion resistance of the sagger. In summary, the corrosion-resistant ceramic sagger and its preparation method of the present invention achieve excellent corrosion resistance by optimizing the raw material ratio, preparation process and microstructure, and have broad application prospects.

[0099] The reasons why Examples 1-8 have higher compressive strength than Comparative Examples 1-7 are: first, the saggers in the examples use a specific raw material ratio, such as yttria-stabilized zirconia, silicon carbide, and magnesia-alumina spinel as the main components of the aggregate layer. These materials not only have high corrosion resistance but also form stable compounds during the sintering process, enhancing the structural strength of the sagger. At the same time, the optimized ratio of mullite and cordierite powders in the matrix layer, as well as the use of CeO2-modified silica sol, further enhance the overall strength and density of the sagger.

[0100] Secondly, key steps in the manufacturing process, such as isostatic pressing, step-by-step sintering, and spray-coating with silicon nitride, all have a positive impact on the compressive strength of the sagger. The isostatic pressing process creates a mechanical interlocking structure between the mixed aggregate and the spherical matrix particles, improving the internal bonding strength of the sagger. Step-by-step sintering helps reduce thermal stress during sintering, preventing cracks and thus maintaining the integrity of the sagger. Spray-coating with silicon nitride forms a dense surface seal, further enhancing the sagger's compressive properties.

[0101] In contrast, the saggers in the comparative examples had deficiencies in raw material ratio, preparation process, or microstructure, resulting in low compressive strength. For example, the lack of yttrium-stabilized zirconia in Comparative Example 1 prevented the sagger from effectively forming an anti-corrosion barrier, while also affecting its structural strength. Conventional press molding, instead of isostatic pressing, was used in Comparative Example 5, preventing the formation of a mechanical interlocking structure, resulting in a weakened internal bond of the sagger. These deficiencies directly impacted the compressive strength of the sagger.

[0102] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A corrosion-resistant ceramic sagger, characterized in that: The corrosion-resistant ceramic sagger comprises an aggregate layer and a matrix layer, wherein the aggregate layer comprises the following raw materials in parts by mass: 30-50 parts of yttrium-stabilized zirconia, 20-30 parts of silicon carbide, and 15-25 parts of magnesium-aluminum spinel; The matrix layer comprises the following raw materials in parts by mass: 40-50 parts of mullite micropowder, 30-40 parts of cordierite micropowder and 10-20 parts of CeO2 modified silica sol.

2. A method for preparing the corrosion-resistant ceramic sagger according to claim 1, characterized in that: The following steps are involved: S1: ball-milling yttrium-stabilized zirconia, silicon carbide, and magnesia-aluminum spinel separately, and then mixing them evenly to obtain a mixed aggregate; The matrix mullite micropowder, cordierite micropowder, binder CeO2 modified silica sol and water are mixed, ball milled, and then spray granulated to obtain spherical matrix particles; S2: Customize a graphite mold, fill the mixed aggregate and spherical matrix particles into the graphite mold cavity, and use isostatic pressing to prepare the sagger body; S3: drying, sintering, heat-insulating, and cooling the sagger body to obtain a sagger sintered body; S4: Spraying silicon nitride on the surface of the sagger sintered body, and then performing secondary sintering to obtain the sagger.

3. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: In step S1, the yttrium-stabilized zirconia, silicon carbide, and magnesium-aluminum spinel are ball-milled for 2-3 hours at a rotation speed of 200-260 rpm.

4. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: In step S1, the mixing ratio of the matrix mullite micropowder, cordierite micropowder, binder CeO2 modified silica sol and water is 1.2-1.5:

1.

5. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: In step S1, the matrix mullite powder, cordierite powder, binder CeO2 modified silica sol and water are mixed and ball milled for 4-5 hours to make the slurry viscosity ≤200 mPa·s.

6. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: The inlet temperature of the spray granulation in step S1 is 280-320° C., and the outlet temperature is 110-130° C.; and / or the particle size of the spherical matrix particles is 80-120 μm.

7. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: The mixed aggregate and spherical matrix particles in step S2 are mixed in a ratio of 1.2-1.8:1, polyvinyl alcohol solution is added to the mixed aggregate, and stirred until the moisture content of the mixed aggregate is 8-10%; and / or The pressure during the isostatic pressing process is 80-100 MPa, and the pressure is maintained for 5-10 minutes.

8. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: The method for sintering the sagger body in step S3 is: Raise the temperature to 1000-1100°C at 2-5°C / min and keep warm for 30-60 minutes; Under protective atmosphere, continue to raise the temperature at 2-5℃ / min to 1400-1500℃ and keep it at this temperature for 2-3h.

9. The method for preparing the corrosion-resistant ceramic sagger according to claim 2, characterized in that: The secondary sintering temperature in step S4 is 800-850° C. and the time is 1-1.5 hours.

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