A method for producing beta"-alumina ceramics based on gel-casting

Abstract

The application provides a preparation method of beta" alumina ceramic based on gel injection molding, and belongs to the field of inorganic non-metallic materials. The method comprises the following steps: obtaining beta" alumina ceramic precursor powder with a set beta" phase content; adding monomers and a crosslinking agent into a solvent, and then performing first ball milling to obtain a premix liquid; adding the beta" alumina ceramic precursor powder and a dispersing agent into the premix liquid, and then performing second ball milling to obtain a first slurry; performing vacuum degassing on the first slurry to obtain a second slurry; adding an initiator into the second slurry, and then performing third ball milling to obtain a third slurry; placing the third slurry into a mold for solidification, and then performing demolding to obtain a green body; and performing glue removal and sintering on the green body to obtain the beta" alumina ceramic. The process parameters of the preparation method of the beta" alumina ceramic are reasonably designed, so that the comprehensive performance of the beta" alumina ceramic is improved.

Description

Technical Field

[0001] This application relates to the field of inorganic non-metallic materials technology, and in particular to a method for preparing β"-alumina ceramics based on gel casting. Background Technology

[0002] β-alumina ceramics are used as solid electrolyte materials in sodium-sulfur / nickel batteries due to their excellent sodium-ion conductivity, making them a crucial core component in solid-state battery systems. They possess a crystal structure composed of overlapping alumina-oxygen blocks and sodium-oxygen layers. Al³⁺ ions are densely packed within the tetrahedral voids formed by oxygen ions, with these densely packed layers separated by sparse [NaO] layers. - By linking the Al-O-Al chains, Na ions can shuttle between the densely packed layers at high temperatures. When the temperature reaches above 250°C, β-alumina ceramics exhibit ionic conductivity close to that of aqueous salts, making them the preferred solid-state electrolyte for many sodium-based batteries (such as sodium-sulfur batteries and Zebra batteries).

[0003] However, existing β"-alumina ceramics have certain drawbacks in terms of β" content, green body processing ability, sintered bulk density, and mechanical properties. Therefore, improving the overall performance of β"-alumina ceramics is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a method for preparing β"-alumina ceramics based on gel casting to solve the following technical problem: how to improve the comprehensive performance of β"-alumina ceramics.

[0005] This application provides a method for preparing β"-alumina ceramics based on gel casting, the method comprising:

[0006] β-alumina ceramic precursor powder with a set β" phase content was obtained;

[0007] The monomer and crosslinking agent are added to the solvent, and then the first ball milling is performed to obtain the premixed solution;

[0008] The β"-alumina ceramic precursor powder and dispersant were added to the premixed liquid, and then subjected to a second ball milling to obtain the first slurry.

[0009] The first slurry is degassed under vacuum to obtain the second slurry;

[0010] An initiator is added to the second slurry, followed by a third ball milling process to obtain a third slurry;

[0011] The third slurry is placed into a mold for curing, and then demolded to obtain a raw blank; and

[0012] The green body is debinded and sintered to obtain β"-alumina ceramic.

[0013] Optionally, the β" phase content is set to ≥95%.

[0014] Optionally, the mass concentration of the premixed liquid is 10% to 20%, wherein the mass ratio of the monomer to the crosslinking agent is (4 to 6):1, the monomer includes one or more of methacrylamide, acrylamide and hydroxymethylacrylamide, and the crosslinking agent includes N,N'-methylenebisacrylamide.

[0015] Optionally, the mass of the dispersant accounts for 0.1% to 0.3% of the mass of the β-alumina ceramic precursor powder, and the dispersant includes one or more of sodium polymethacrylate, sodium hexametaphosphate, and sodium polyacrylate.

[0016] Optionally, the mass ratio of the β-alumina ceramic precursor powder to the premixed liquid is (1-2.3):1, the solid content of the first slurry is 50%-70%, the ball-to-material ratio of the second ball mill is (3-5):1, and the second ball milling time is 10-15 hours.

[0017] Optionally, the initiator accounts for 10% to 12% of the mass of the monomer, and the initiator includes one or more of ammonium persulfate and sodium persulfate.

[0018] Optionally, the curing temperature is 80℃~100℃, and the curing holding time is 10h~15h.

[0019] Optionally, the temperature for discharging the adhesive is 500℃~600℃, and the heat preservation time for discharging the adhesive is 1.5h~2.5h.

[0020] Optionally, the sintering temperature is 1600℃~1650℃, and the sintering holding time is 20min~40min.

[0021] Optionally, the β"-alumina ceramic satisfies at least one of the following properties: β" content ≥95%, bulk density reaching more than 96% of the theoretical bulk density, and four-point bending strength ≥250 MPa.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a method for preparing β"-alumina ceramics based on gel casting, comprising: obtaining β"-alumina ceramic precursor powder with a set β" phase content; adding monomers and crosslinking agents to a solvent, followed by a first ball milling to obtain a premix; adding the β"-alumina ceramic precursor powder and a dispersant to the premix, followed by a second ball milling to obtain a first slurry; subjecting the first slurry to vacuum degassing to obtain a second slurry; adding an initiator to the second slurry, followed by a third ball milling to obtain a third slurry; placing the third slurry into a mold for curing, followed by demolding. A green body is obtained; and the green body is debinded and sintered to obtain β"-alumina ceramic. This application rationally designs the process parameters for the preparation method of β"-alumina ceramic. Through multi-stage ball milling combined with the addition of a dispersant, the dispersibility and uniformity of the ceramic powder in the solvent are effectively improved. Vacuum degassing effectively removes air bubbles from the slurry, further improving the slurry's fluidity. By adding an initiator to the slurry and controlling the curing temperature and holding time, the chemical reaction between the monomer and the crosslinking agent is fully carried out, forming a stable three-dimensional gel network structure, which helps ensure the uniformity of curing and the strength of the green body. During the debinding and sintering stages, reasonable process control can further reduce impurities and defects in the ceramic, improving the sintering quality. This improves the overall performance of β"-alumina ceramic. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart illustrating a method for preparing β"-alumina ceramics based on gel casting, as provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0031] The inventive concept of this application is as follows:

[0032] Gel casting is an advanced ceramic forming process that combines the principles of polymer chemical reactions. Ceramic powder, organic monomers, crosslinking agents, initiators, and catalysts are mixed into a slurry, which is then injected into a mold. Temperature-induced polymerization of the organic monomers forms a three-dimensional network structure called a gel, which then solidifies the ceramic powder in situ to form a ceramic green body. Gel casting offers advantages such as good green body uniformity, high strength, direct machining capability, no need for expensive equipment, and no special requirements for the molds.

[0033] Developing a low-cost, high-β-phase-content β-alumina ceramic preparation technique using gel casting is an effective means to improve the overall performance of β-alumina ceramics. However, applying gel casting to the preparation of β-alumina ceramics requires overcoming the following challenges:

[0034] I. Slurry preparation and solid content control

[0035] Balancing Solid Content and Performance: The solid content of the slurry is a key factor affecting the performance of the formed green body. Higher solid content helps increase the density and strength of the green body, but excessively high solid content will lead to increased slurry viscosity, making it difficult to flow and inject into the mold, and may also cause performance degradation after sintering, such as coarse grains and decreased strength. Therefore, it is necessary to precisely control the solid content of the slurry to find the optimal balance between performance and processability.

[0036] Selection and dosage of dispersants: To reduce the viscosity of the slurry and improve its fluidity, dispersants are usually added. However, the selection and dosage of dispersants need to be strictly controlled to avoid adverse effects on the surface properties of the ceramic powder and the performance of the formed green body.

[0037] II. Control of the gelation process

[0038] Polymerization rate: The gelation process involves the polymerization of monomers induced by temperature to form a three-dimensional network structure. Precise control of the reaction rate is necessary to ensure sufficient strength and stability of the gel, while avoiding problems caused by reactions that are too fast or too slow, such as excessive brittleness or insufficient strength in the gel.

[0039] Air bubble removal: During the gelation process, the presence of air bubbles can severely affect the quality and performance of the preform. Therefore, effective measures need to be taken to remove air bubbles from the slurry to ensure the density and uniformity of the molded preform.

[0040] III. Sintering Process Optimization

[0041] Sintering temperature and time: The sintering temperature and time of β-alumina ceramics have a significant impact on the properties of the finished product. Optimization of sintering process parameters is necessary to ensure that the ceramic material possesses excellent mechanical properties and thermal stability.

[0042] Figure 1 This is a schematic flowchart illustrating a method for preparing β"-alumina ceramics based on gel casting, as provided in an embodiment of this application.

[0043] Please see Figure 1 To address the aforementioned technical problems, this application provides a method for preparing β"-alumina ceramics based on gel casting, the method comprising:

[0044] S1. Obtain β-alumina ceramic precursor powder with a set β" phase content;

[0045] In some embodiments, the β" phase content is set to ≥95%.

[0046] A high β" phase content means that the ceramic material will have superior properties, such as higher strength, better thermal stability, and superior electrical properties. Limiting the β" phase content of β"-alumina ceramic precursor powder to ≥95% contributes to achieving a β" phase content ≥95% in β"-alumina ceramics. For example, the β" phase content of the β"-alumina ceramic precursor powder can be 95%, 96%, 97%, 98%, 99%, etc.

[0047] S2. Add the monomer and crosslinking agent to the solvent, and then perform the first ball milling to obtain the premixed solution;

[0048] Monomers and cross-linking agents are key components in the formation of the gel network; they are dissolved in a solvent to form a homogeneous premix. The first ball milling process helps promote the uniform mixing of these components, laying the foundation for subsequent steps.

[0049] In some embodiments, the mass concentration of the premixed liquid is 10% to 20%, wherein the mass ratio of the monomer to the crosslinking agent is (4 to 6):1, the monomer includes one or more of methacrylamide, acrylamide and hydroxymethylacrylamide, and the crosslinking agent includes N,N'-methylenebisacrylamide.

[0050] The mass concentration of the premix is ​​a crucial parameter, directly impacting the uniformity, flowability, and final product performance of the subsequent slurry. Limiting the premix concentration to within the range of 10% to 20% ensures that monomers and crosslinking agents can fully dissolve and mix uniformly in the solvent. Good solubility ensures their uniform distribution throughout the premix, providing a solid foundation for subsequent reactions with other components (such as ceramic precursor powders). Simultaneously, it contributes to the uniformity of polymerization and crosslinking, as well as the flowability and stability of the slurry, avoiding localized uneven reactions. For example, the mass concentration of the premix can be 10%, 12%, 14%, 16%, 18%, 20%, etc.

[0051] In gel casting, the mass ratio of monomer to crosslinking agent is a crucial parameter, directly affecting the rate of gelation and the formation of a three-dimensional gel network structure. Setting the mass ratio of monomer to crosslinking agent within the range of (4–6):1 allows for control of the curing rate, ensuring that the reaction is neither too rapid, leading to localized agglomeration and stress concentration, nor too slow, resulting in low production efficiency. This contributes to the formation of a uniform, dense, and stable three-dimensional gel network structure, guaranteeing the strength of the green body. For example, the mass ratio of monomer to crosslinking agent can be 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc.

[0052] S3. The β"-alumina ceramic precursor powder and dispersant are added to the premixed liquid, and then a second ball milling is performed to obtain the first slurry;

[0053] The ceramic precursor powder and dispersant are added to the premix, and then thoroughly mixed and uniformly dispersed in the solvent through a second ball milling process. The addition of the dispersant helps reduce the agglomeration of powder particles and improves the uniformity and flowability of the slurry.

[0054] In some embodiments, the mass of the dispersant accounts for 0.1% to 0.3% of the mass of the β-alumina ceramic precursor powder, and the dispersant includes one or more of sodium polymethacrylate, sodium hexametaphosphate, and sodium polyacrylate.

[0055] The main function of dispersants is to adsorb onto the surface of ceramic powder particles, preventing particle agglomeration through electrostatic repulsion or steric hindrance, thereby improving the dispersibility of the powder in the solvent. The amount of dispersant added is crucial for ensuring good dispersibility of β"-alumina ceramic precursor powder in the solvent, as well as the stability and flowability of the final slurry. Controlling the mass of the dispersant within the range of 0.1% to 0.3% of the β"-alumina ceramic precursor powder mass helps to form a stable slurry system and improves the slurry flowability. However, excessive dispersant can aggregate or form micelle structures, which increases the viscosity of the system. For example, the mass percentage of the dispersant in the β"-alumina ceramic precursor powder mass can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0056] In some embodiments, the mass ratio of the β-alumina ceramic precursor powder to the premixed liquid is (1-2.3):1, the solid content of the first slurry is 50%-70%, the ball-to-material ratio of the second ball mill is (3-5):1, and the ball milling time is 10-15 hours.

[0057] The mass ratio of β"-alumina ceramic precursor powder to premixed liquid is a key process parameter that directly affects the strength of the green body and the density and microstructure of the sintered product. Setting this ratio within the range of (1 to 2.3):1 helps to improve the strength of the green body, enhance the density and microstructure after sintering, avoid defect formation, and also improve the controllability and stability of the process. For example, the mass ratio of β"-alumina ceramic precursor powder to the premixed liquid can be 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.3:1, etc.

[0058] Limiting the solid content of the first slurry to 50% to 70% can reduce shrinkage and deformation after drying, help improve the strength of the green body, and improve the sintering density and microstructure after sintering. For example, the solid content of the first slurry can be 50%, 55%, 60%, 65%, 70%, etc.

[0059] Limiting the ball-to-material ratio of the second ball mill to (3-5):1 and the milling time to 10-15 hours can improve grinding efficiency and contribute to the uniformity of the slurry. For example, the ball-to-material ratio of the second ball mill can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc., and the milling time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, etc.

[0060] S4. The first slurry is degassed under vacuum to obtain the second slurry;

[0061] The slurry may contain air bubbles, which can cause defects inside the preform during the molding process. Therefore, a vacuum degassing process is needed to remove the air bubbles and obtain a second slurry free of air bubbles.

[0062] S5. Add an initiator to the second slurry, and then perform a third ball milling to obtain a third slurry;

[0063] The addition of the initiator is a key step in starting the gelation reaction. The third ball milling process ensures that the initiator is evenly dispersed in the slurry, preparing it for the subsequent curing process.

[0064] In some embodiments, the initiator accounts for 10% to 12% of the mass of the monomer, and the initiator includes one or more of ammonium persulfate and sodium persulfate.

[0065] Limiting the initiator's mass to 10% to 12% of the monomer's mass effectively initiates the polymerization reaction and controls the reaction rate, allowing sufficient time for subsequent molding. Examples include initiators comprising 10%, 10.5%, 11%, 11.5%, and 12% of the monomer's mass.

[0066] S6. The third slurry is placed into a mold for curing, and then demolded to obtain a raw blank; and

[0067] A slurry containing an initiator is injected into a mold. By controlling the temperature and time, the monomers undergo a polymerization reaction to form a three-dimensional network-like gel, thereby solidifying the ceramic powder in situ into a green body. After solidification, the mold is removed to obtain a complete green body.

[0068] In some embodiments, the curing temperature is 80℃ to 100℃, and the curing holding time is 10h to 15h.

[0069] The curing temperature and holding time are key factors in ensuring sufficient chemical reaction between monomers and crosslinking agents to form a stable three-dimensional gel network structure. The curing temperature is limited to 80℃–100℃, and the holding time is 10h–15h, resulting in a moderate chemical reaction rate between the monomers and crosslinking agents. Too low a temperature leads to a slow reaction rate, requiring a longer curing time; while too high a temperature may trigger unnecessary side reactions, affecting the structure and performance of the gel network. Simultaneously, this ensures that the monomers and crosslinking agents in the entire slurry system react fully to form a uniform gel network. Furthermore, by controlling the curing temperature and holding time, the gel network can gradually shrink and densify during formation, thereby reducing the risk of stress concentration. For example, the curing temperature can be 80℃, 85℃, 90℃, 95℃, 100℃, etc., and the holding time can be 10h, 11h, 12h, 13h, 14h, 15h, etc.

[0070] Ensure sufficient chemical reaction between monomers and crosslinking agents to guarantee uniform curing.

[0071] S7. The green blank is debinded and sintered to obtain β"-alumina ceramic.

[0072] The green body contains a certain amount of organic matter (such as monomers, crosslinking agents, dispersants, etc.), which needs to be removed through a debinding process before sintering. After debinding, sintering is performed to form a dense aggregate between ceramic particles, resulting in β"-alumina ceramics with excellent properties.

[0073] In some embodiments, the temperature of the adhesive discharge is 500℃~600℃, and the heat preservation time of the adhesive discharge is 1.5h~2.5h.

[0074] The temperature for debinding is limited to 500℃~600℃, and the holding time for debinding is 1.5h~2.5h. This effectively and completely removes organic matter and avoids the formation of pores on the ceramic surface due to high-temperature debinding, which would affect the ceramic's performance. For example, the debinding temperature can be 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, etc., and the holding time can be 1.5h, 1.7h, 1.9h, 2.0h, 2.2h, 2.4h, 2.5h, etc.

[0075] In some embodiments, the sintering temperature is 1600℃~1650℃, and the sintering holding time is 20min~40min.

[0076] The sintering temperature is limited to 1600℃~1650℃, and the holding time is 20min~40min, which helps to achieve optimal ceramic density and uniform microstructure. Too low a temperature results in low ceramic density, while too high a temperature leads to abnormal grain growth. For example, the sintering temperature can be 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, etc., and the holding time can be 20min, 22min, 25min, 30min, 35min, 40min, etc.

[0077] In some embodiments, the β"-alumina ceramic satisfies at least one of the following properties: β" content ≥95%, bulk density reaching more than 96% of the theoretical bulk density, and four-point bending strength ≥250 MPa.

[0078] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0079] Example 1

[0080] This embodiment provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0081] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0082] S21. Add 4 parts of methacrylamide (C4H7NO) and 1 part of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 28.5 parts of water, and then perform a first ball milling for 15 minutes to obtain a well-mixed premix.

[0083] S31. Add 30 parts of β"-alumina ceramic precursor powder and 0.003 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) to the premixed liquid, and then perform a second ball milling with a ball-to-material ratio of 3:1 and a grinding time of 12h to obtain the first slurry.

[0084] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0085] S51. Add 0.4 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0086] S61. The third slurry is placed into a mold and kept in a 90°C oven for 12 hours to cure. Then, it is demolded to obtain a green blank with a strength of 15 MPa.

[0087] S71. The green body is subjected to debinding at 500°C for 2 hours and sintered at 1600°C for 2 hours to obtain β"-alumina ceramic. The β"-alumina ceramic has a β" content ≥95% and a sintered bulk density of 3.216 g / cm³. 3 It reaches 98.95% of the theoretical bulk density and has a four-point bending strength of 286 MPa.

[0088] Example 2

[0089] This embodiment provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0090] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0091] S21. Add 10 parts of methacrylamide (C4H7NO) and 2 parts of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 108 parts of water, and then perform a first ball milling for 15 minutes to obtain a well-mixed premix.

[0092] S31. 160 parts of β"-alumina ceramic precursor powder and 0.32 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) were added to the premixed liquid, and then a second ball milling was carried out with a ball-to-material ratio of 3:1 and a grinding time of 12h to obtain the first slurry.

[0093] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0094] S51. Add 1.1 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0095] S61. The third slurry is placed into a mold and kept in a 90°C oven for 12 hours to cure. Then, it is demolded to obtain a green blank with a strength of 15 MPa.

[0096] S71. The green body is subjected to debinding at 500℃ for 2 hours and sintered at 1600℃ for 2 hours to obtain β"-alumina ceramic. The β"-alumina ceramic has a β" content ≥95% and a sintered bulk density of 3.184 g / cm³. 3 It reaches 97.97% of the theoretical bulk density and has a four-point bending strength of 268 MPa.

[0097] Example 3

[0098] This embodiment provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0099] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0100] S21. Add 12 parts of methacrylamide (C4H7NO) and 2 parts of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 80 parts of water, and then perform a first ball milling for 15 minutes to obtain a uniformly mixed premix; wherein,

[0101] S31. 135 parts of β"-alumina ceramic precursor powder and 0.4 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) were added to the premixed liquid, and then a second ball milling was carried out with a ball-to-material ratio of 5:1 and a grinding time of 12h to obtain the first slurry.

[0102] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0103] S51. Add 1.44 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0104] S61. The third slurry is placed into a mold and kept in an 80°C oven for 12 hours to cure. Afterward, it is demolded to obtain a green blank with a strength of 23 MPa.

[0105] S71. The green body is subjected to debinding at 500°C for 2 hours and sintered at 1620°C for 2 hours to obtain β"-alumina ceramic. The β"-alumina ceramic has a β" content ≥95% and a sintered bulk density of 3.208 g / cm³. 3 It reaches 98.71% of the theoretical bulk density and has a four-point bending strength of 274 MPa.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0108] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0109] S21. Add 12 parts of methacrylamide (C4H7NO) and 6 parts of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 60 parts of water, and then perform a first ball milling for 15 minutes to obtain a well-mixed premix.

[0110] S31. 135 parts of β"-alumina ceramic precursor powder and 0.3 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) were added to the premixed liquid, and then a second ball milling was carried out with a ball-to-material ratio of 5:1 and a grinding time of 12h to obtain the first slurry.

[0111] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0112] S51. Add 1.44 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0113] S61. The third slurry is placed into a mold and kept in an 80°C oven for 12 hours to cure. Then, it is demolded to obtain a green blank with a strength less than 5 MPa.

[0114] S71. The green body is subjected to debinding at 500°C for 2 hours and sintered at 1620°C for 2 hours to obtain β"-alumina ceramic. The β"-alumina ceramic has a β" content ≥95% and a sintered bulk density of 2.922 g / cm³. 3 It only reaches 89.9% of the theoretical bulk density, and the four-point bending strength is 64 MPa.

[0115] Comparative Example 2

[0116] This comparative example provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0117] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0118] S21. Add 10 parts of methacrylamide (C4H7NO) and 2 parts of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 108 parts of water, and then perform a first ball milling for 15 minutes to obtain a well-mixed premix.

[0119] S31. 160 parts of β"-alumina ceramic precursor powder and 0.48 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) were added to the premixed liquid, and then a second ball milling was carried out with a ball-to-material ratio of 3:1 and a grinding time of 12h to obtain the first slurry.

[0120] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0121] S51. Add 1.1 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0122] S61. The third slurry is placed into a mold and kept in a 90°C oven for 12 hours to cure. Afterward, it is demolded to obtain a green blank with a strength of 16 MPa.

[0123] S71. The green body is subjected to debinding at 500℃ for 2 hours and sintered at 1550℃ for 2 hours to obtain β"-alumina ceramic. The β" content of the β"-alumina ceramic is ≥95%, and the sintered bulk density of the ceramic is 3.014 g / cm³. 3 It only reaches 92.7% of the theoretical bulk density, and the four-point bending strength is 124 MPa.

[0124] Comparative Example 3

[0125] This comparative example provides a method for preparing β"-alumina ceramics based on gel casting, including the following steps:

[0126] S11. A β-alumina ceramic precursor powder with a β" phase content of 98% was prepared by solid-state synthesis.

[0127] S21. Add 10 parts of methacrylamide (C4H7NO) and 2 parts of N'-methylenebisacrylamide (linear molecular formula: CH2=CHCONH)2CH2) to 108 parts of water, and then perform a first ball milling for 15 minutes to obtain a well-mixed premix.

[0128] S31. Add 80 parts of β"-alumina ceramic precursor powder and 0.1 parts of sodium polyacrylate dispersant (CAS No.: 9003-04-7) to the premixed liquid, and then perform a second ball milling with a ball-to-material ratio of 3:1 and a grinding time of 12h to obtain the first slurry.

[0129] S41. The first slurry is degassed under vacuum to obtain the second slurry;

[0130] S51. Add 1.1 parts of initiator ammonium persulfate ((NH4)2S2O8) to the second slurry, and then perform a third ball milling for 15 minutes to obtain a third slurry;

[0131] S61. The third slurry is placed into a mold and kept in a 90°C oven for 12 hours to cure. Afterward, it is demolded to obtain a green blank with a strength of 10 MPa.

[0132] S71. The green body is subjected to debinding at 500℃ for 2 hours and sintered at 1550℃ for 2 hours to obtain β"-alumina ceramic. The β" content of the β"-alumina ceramic is ≥95%, and the sintered bulk density of the ceramic is 2.936 g / cm³. 3 It only reaches 90.3% of the theoretical bulk density, and the four-point bending strength is 92 MPa.

[0133] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0134] In this embodiment of the invention, the rational design of the process parameters for the preparation method of β"-alumina ceramics helps to improve dispersibility and uniformity, improve slurry flowability, optimize the curing process, and improve sintering quality, thereby improving the overall performance of β"-alumina ceramics.

[0135] In this embodiment of the invention, the prepared β"-alumina ceramic has a high β" content, strong green body processing ability, high bulk density after sintering, and excellent mechanical properties.

[0136] In this embodiment of the invention, the β" content of the β"-alumina ceramic is ≥95%, the bulk density reaches more than 96% of the theoretical bulk density, and the four-point bending strength is ≥250 MPa.

[0137] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing β"-alumina ceramics based on gel casting, characterized in that, The method includes: β"-alumina ceramic precursor powder with a set β" phase content ≥ 99% was obtained; The monomer and crosslinking agent are added to the solvent, and then ball milling is performed to obtain a premixed solution with a mass concentration of 10% to 20% and a mass ratio of monomer to crosslinking agent of (4 to 6):

1. The β"-alumina ceramic precursor powder and dispersant are added to the premixed liquid, and then subjected to a second ball milling to obtain a first slurry. The mass ratio of the dispersant to the mass of the β"-alumina ceramic precursor powder is 0.1% to 0.3%, and the solid content of the first slurry is 50% to 70%. The first slurry is degassed under vacuum to obtain the second slurry; An initiator is added to the second slurry, followed by a third ball milling process to obtain a third slurry. The initiator accounts for 10% to 12% of the mass of the monomer. The third slurry is placed into a mold for curing, and then demolded to obtain a raw blank; and The green body was debinded and sintered to obtain β"-alumina ceramic; The curing temperature is 80℃~100℃, and the curing holding time is 10h~15h; The temperature for discharging the adhesive is 500℃~600℃, and the heat preservation time for discharging the adhesive is 1.5h~2.5h; The sintering temperature is 1600℃~1620℃, and the sintering holding time is 2h; The β-alumina ceramic meets the following properties: bulk density reaches more than 96% of the theoretical bulk density, and four-point bending strength is ≥250MPa.

2. The method according to claim 1, characterized in that, The monomer includes one or more of methacrylamide, acrylamide, and hydroxymethylacrylamide, and the crosslinking agent includes N,N'-methylenebisacrylamide.

3. The method according to claim 1, characterized in that, The dispersant includes one or more of sodium polymethacrylate, sodium hexametaphosphate, and sodium polyacrylate.

4. The method according to claim 1, characterized in that, The mass ratio of the β-alumina ceramic precursor powder to the premixed liquid is (1~2.3):1, the ball-to-material ratio of the second ball mill is (3~5):1, and the time of the second ball mill is 10h~15h.

5. The method according to claim 1, characterized in that, The initiator includes one or more of ammonium persulfate and sodium persulfate.

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