Method for preparing beta ''-aluminum oxide ceramic membrane through tape casting

Abstract

The invention provides a method for preparing a beta ''-aluminum oxide ceramic membrane through tape casting, and belongs to the field of conductive ceramic materials. The method comprises the following steps: carrying out first ball milling on a high-purity aluminum-containing compound, a sodium-containing compound, a stabilizer, a dispersant and a solvent to obtain first slurry; adding a binder, a plasticizer and a foam inhibitor into the first slurry to obtain second slurry; performing second ball milling on the second slurry to obtain third slurry; defoaming the third slurry to obtain fourth slurry with set viscosity; carrying out tape casting on the fourth slurry to obtain an aluminum oxide green body; and degumming, pre-sintering and sintering the aluminum oxide green body to obtain the beta ''-aluminum oxide ceramic membrane. Therefore, the beta ''-aluminum oxide ceramic membrane with controllable thickness, stable quality and low resistivity is obtained, and the application performance of the beta''-aluminum oxide ceramic membrane is improved.

Description

Technical Field

[0001] The present application relates to the technical field of conductive ceramic materials, and in particular to a method for preparing a β"-alumina ceramic film by tape casting. Background Art

[0002] As a new type of high-performance and high-efficiency energy storage battery, sodium-ion solid-state batteries are widely used in the future energy field. As the demand for energy continues to increase in the future, the importance of energy storage sodium batteries will become increasingly prominent. For example, renewable energy power generation companies such as wind power and solar power in extreme environments (such as high heat, high cold, high salt corrosion, etc.) are equipped with large-capacity, safe and reliable energy storage systems; provide power for manned submarines, army combat vehicles, underwater platforms, etc.; provide backup power for large indoor electricity users such as fifth-generation mobile communication technology (5G) communication base stations and data centers, etc. Energy storage sodium batteries have broad application prospects. β"-alumina ceramics have high sodium ion conductivity and are the core material of sodium-ion solid-state batteries. Their quality and stability and consistency have a profound impact on the electrochemical properties and safety characteristics of sodium-ion solid-state batteries.

[0003] The existing β"-alumina ceramic preparation process generally uses γ or α ultrafine alumina and auxiliary materials to dry mix for a long time, press and form ceramics, and then sinter to obtain ceramics containing β" phase electrolyte. This process is prone to increase of impurities in sintered alumina ceramics due to uneven mixing of powders, and the conductivity is reduced. In addition, the product is affected by the forming equipment and does not meet the requirements of large-size ceramic production. At the same time, in order to improve the conductivity of electrolyte ceramics, China has gradually developed a β"-alumina ceramic membrane preparation process, which increases the ionic conductivity of β"-alumina ceramic membranes by reducing the thickness of electrolyte ceramics. The tape casting method is used to prepare membranes to produce β"-alumina ceramic membranes, which has high production efficiency and can be operated continuously. However, due to the fact that the raw materials come from the early synthetic β"-alumina, the further forming and sintering of β"-alumina into porcelain is affected by many factors, and the application performance of the produced β"-alumina ceramic membranes is poor. Therefore, how to improve the application performance of β"-alumina ceramic membranes is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for preparing a β"-alumina ceramic membrane by tape casting to solve the following technical problem: how to improve the application performance of the β"-alumina ceramic membrane.

[0005] The present application provides a method for preparing a β"-alumina ceramic membrane by tape casting, the method comprising:

[0006] The high-purity aluminum-containing compound, the sodium-containing compound, the stabilizer, the dispersant and the solvent are subjected to a first ball milling to obtain a first slurry;

[0007] Adding a binder, a plasticizer and an antifoaming agent to the first slurry to obtain a second slurry;

[0008] subjecting the second slurry to a second ball milling to obtain a third slurry;

[0009] Degassing the third slurry to obtain a fourth slurry with a set viscosity;

[0010] Performing tape casting on the fourth slurry to obtain an alumina green body; and

[0011] The alumina green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0012] Optionally, the mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, and the mass m4 of the dispersant satisfy the following relationship:

[0013] m1:m2:m3=100:(12-18):(1-2.5); and / or,

[0014] m4:(m1+m2+m3)=(0.005~0.01):1.

[0015] Optionally, the high-purity aluminum-containing compound includes: at least one of alumina trihydrate, alumina monohydrate and alumina; and / or,

[0016] The sodium-containing compound comprises: at least one of sodium oxide, sodium carbonate and aluminum hydroxide; and / or,

[0017] The stabilizer comprises: at least one of lithium-containing oxides, magnesium-containing oxides, aluminates, carbonates and oxalates; and / or,

[0018] The dispersant comprises: at least one of oleic acid, triolein and fish oil; and / or,

[0019] The solvent includes at least one of ethanol, ethyl acetate, butanone and xylene.

[0020] Optionally, the mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, the mass m4 of the dispersant, the mass m5 of the binder, the mass m6 of the plasticizer and the mass m7 of the defoamer satisfy the following relationship:

[0021] m5: (m1+m2+m3)=(0.06-0.1): 1; and / or,

[0022] m6:m5=(0.8-1.2):1; and / or,

[0023] m7: (m1+m2+m3)=(0.0005~0.005):1.

[0024] Optionally, the binder includes: polyvinyl butyral; and / or,

[0025] The plasticizer comprises: at least one of polyethylene glycol and dibutyl phthalate; and / or,

[0026] The foam suppressor includes: a fatty acid lipid mixture.

[0027] Optionally, the solid content of the third slurry is 50% to 65%; and / or,

[0028] The set viscosity is 10000mPa·s to 20000mPa·s.

[0029] Optionally, the debinding temperature is 450° C. to 550° C., and the debinding time is 8 h to 12 h.

[0030] Optionally, the pre-burning temperature is 900° C. to 1100° C., and the pre-burning time is 1 h to 2 h.

[0031] Optionally, the sintering temperature is 1600° C. to 1650° C., and the sintering time is 1 h to 2 h.

[0032] Optionally, the first ball milling time is 12h to 18h; and / or,

[0033] The second ball milling time is 8 h to 12 h.

[0034] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0035] The present application provides a method for preparing β"-alumina ceramic membrane by tape casting, comprising: subjecting a high-purity aluminum-containing compound, a sodium-containing compound, a stabilizer, a dispersant and a solvent to a first ball milling to obtain a first slurry; adding a binder, a plasticizer and a defoaming agent to the first slurry to obtain a second slurry; subjecting the second slurry to a second ball milling to obtain a third slurry; degassing the third slurry to obtain a fourth slurry with a set viscosity; tape casting the fourth slurry to obtain an alumina green body; and debinding, pre-sintering and sintering the alumina green body to obtain a β"-alumina ceramic membrane. First, a sodium-containing compound is added to assist the transformation of the alumina grain structure from the α phase to the β" phase, and a stabilizer is added to inhibit the transformation of the β" phase to the β' phase caused by the volatilization of high-temperature sodium. Secondly, the aluminum-containing compound, sodium-containing compound and stabilizer are further crushed, depolymerized and uniformly mixed through the first ball milling. Thirdly, the particles in the slurry are further refined through the second ball milling to improve its uniformity and stability during the tape casting process. At the same time, through two ball millings, the powder is prevented from being wrapped by organic substances such as binders and plasticizers, thereby avoiding the agglomeration of the powder. Finally, the alumina green body is subjected to debinding and sintering treatment with a pre-sintering agent to obtain a β"-alumina ceramic film with controllable thickness, stable quality and low resistivity. This improves the application performance of the β"-alumina ceramic film. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0037] In order to more clearly illustrate the embodiments of the present application 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 A schematic flow chart of a method for preparing a β"-alumina ceramic membrane by tape casting provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0040] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0041] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used 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 article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0042] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0043] Figure 1 A schematic flow chart of a method for preparing a β"-alumina ceramic membrane by tape casting provided in an embodiment of the present application.

[0044] See also Figure 1 The present application provides a method for preparing a β"-alumina ceramic membrane by tape casting, the method comprising:

[0045] S1, performing a first ball milling on a high-purity aluminum-containing compound, a sodium-containing compound, a stabilizer, a dispersant and a solvent to obtain a first slurry;

[0046] After wet grinding, the first slurry is obtained. At this time, the raw material particles in the slurry have been refined and evenly dispersed in the solvent.

[0047] In some embodiments, the mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, and the mass m4 of the dispersant satisfy the following relationship:

[0048] m1:m2:m3=100:(12-18):(1-2.5); and / or,

[0049] m4:(m1+m2+m3)=(0.005~0.01):1.

[0050] During the sintering process of alumina green body, the main role of sodium-containing compounds is to assist the transformation of alumina grain structure from α phase to β" phase. This transformation is crucial for the preparation of β"-alumina ceramic membranes with high sodium ion conductivity. By adding an appropriate amount of sodium-containing compounds, a chemical environment conducive to the formation of β" phase can be formed during the sintering process, thereby promoting the directional growth and phase transformation of alumina grains. The mass ratio of sodium-containing compounds to aluminum-containing compounds is limited to the range of (12-18):100, and the theoretical molar ratio of sodium-containing compounds to aluminum-containing compounds to form β"-alumina is optimal. This means that during the sintering process, the sodium-containing compounds can completely react and embed into the alumina lattice to form a stable β" phase structure. At the same time, the prepared β"-alumina ceramic membrane has high purity and excellent performance, and the content of β" phase can reach more than 95%. If the mass ratio of sodium-containing compounds to aluminum-containing compounds is greater than 18:100, the excess sodium-containing compounds will react with the aluminum-containing compounds during the sintering process to form sodium metaaluminate (NaAlO 2) and other impurities. These impurities will reduce the quality of the β"-alumina ceramic membrane and may cause its ionic conductivity to decrease. And too many sodium ions may destroy the stability of the alumina lattice, causing the structure of the ceramic membrane to become unstable, thus affecting its performance and service life. If the mass ratio of the sodium-containing compound to the aluminum-containing compound is less than 12:100, the sodium-containing compound and the aluminum-containing compound cannot reach the optimal molar ratio for forming the β" phase. This will cause a part of the alumina grain structure to transform into the β' phase or other unfavorable phases, thereby reducing the β" phase content and ionic conductivity of the β"-alumina ceramic membrane. At the same time, due to the reduction in the β" phase content, the overall performance of the ceramic membrane may be affected, including mechanical strength, thermal stability and ionic conductivity. During the sintering process, the main function of the stabilizer is to inhibit the transformation of the β" phase to the β' phase due to the volatilization of high-temperature sodium. At high temperatures, sodium elements are easily volatilized, which may cause the β" phase structure in the alumina ceramic membrane to be unstable and then transformed into β' phase or other unfavorable phase structures. The addition of stabilizers can react with sodium-containing compounds and aluminum-containing compounds to form a stable chemical structure, thereby effectively inhibiting this phase change. The mass ratio of stabilizer to aluminum-containing compound is limited to (1-2.5):100, and the stabilizer can completely react with sodium-containing compounds and aluminum-containing compounds to form a stable chemical structure. This structure helps to inhibit the transformation of β" phase to β' phase and maintain a high content of β" phase in the alumina ceramic membrane. By precisely controlling the ratio of stabilizer, the performance of alumina ceramic membrane can be optimized, including improving its ionic conductivity, mechanical strength and thermal stability. If the mass ratio of stabilizer to aluminum-containing compound is greater than 2.5:100, The stabilizer that does not participate in the phase change reaction of the sodium-containing compound and the aluminum-containing compound will become an impurity component in the alumina ceramic membrane. These impurities may affect the electrical conductivity of the ceramic membrane and reduce its ion conduction efficiency. And too much stabilizer may cause the structure of the ceramic membrane to become uneven, thereby affecting its overall performance. In addition, the stabilizer itself may have some characteristics that are not conducive to the performance of the ceramic membrane, such as reducing mechanical strength or increasing thermal expansion coefficient; if the mass ratio of the stabilizer to the aluminum-containing compound is less than 1:100, the stabilizer fails to complete the phase change reaction with all the sodium-containing compounds and aluminum-containing compounds. This may cause the remaining sodium-containing compounds and aluminum-containing compounds to undergo adverse phase changes during high-temperature sintering, such as the transformation of the alumina grain structure from the α phase to the β' phase. And due to the incomplete phase change, the content of the β" phase in the alumina ceramic membrane will decrease. This will lead to a decrease in the performance of the ceramic membrane, especially the ionic conductivity performance. Dispersants can be used to improve the dispersibility of raw material powders (such as alumina powder, sodium-containing compounds, etc.) in solvents. When preparing alumina ceramic membrane slurry, the raw powders tend to agglomerate to form larger particle clusters due to high surface energy and mutual attraction. These clusters not only affect the uniformity of the slurry, but also cause the structure of the ceramic membrane to be uneven during the subsequent tape casting and sintering process, thus affecting its performance.When the dispersant effectively improves the dispersibility of the raw materials in the solvent, the slurry will become more uniform. The uniformity of the slurry has an important influence on the performance of the final prepared alumina ceramic membrane. Uniform slurry can ensure the formation of green bodies with uniform thickness and dense structure during the tape casting process. During the sintering process, these green bodies will more easily form ceramic membranes with excellent properties, such as high ionic conductivity, good mechanical strength and thermal stability. Exemplarily, m2 can be 12, 13, 14, 15, 16, 17, 18, etc., and m3 can be 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, etc.

[0051] In some embodiments, the high-purity aluminum-containing compound includes: at least one of alumina trihydrate, alumina monohydrate and alumina; and / or,

[0052] The sodium-containing compound comprises: at least one of sodium oxide, sodium carbonate and aluminum hydroxide; and / or,

[0053] The stabilizer comprises: at least one of lithium-containing oxides, magnesium-containing oxides, aluminates, carbonates and oxalates; and / or,

[0054] The dispersant comprises: at least one of oleic acid, triolein and fish oil; and / or,

[0055] The solvent includes at least one of ethanol, ethyl acetate, butanone and xylene.

[0056] S2, adding a binder, a plasticizer and an antifoaming agent to the first slurry to obtain a second slurry;

[0057] Add a binder, a plasticizer and a foam suppressant to the first slurry. The binder is used to improve the strength and flexibility of the green body; the plasticizer improves the rheological properties of the slurry, making it easier to cast; and the foam suppressant prevents bubbles from being generated during the preparation and molding of the slurry.

[0058] In some embodiments, the mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, the mass m4 of the dispersant, the mass m5 of the binder, the mass m6 of the plasticizer, and the mass m7 of the defoamer satisfy the following relationship:

[0059] m5: (m1+m2+m3)=(0.06-0.1): 1; and / or,

[0060] m6:m5=(0.8-1.2):1; and / or,

[0061] m7:(m1+m2+m3)=(0.0005~0.005):1.

[0062] The addition of binders, plasticizers and defoamers is intended to improve the rheological properties of the slurry, increase the strength and flexibility of the green body, and prevent the formation of bubbles during the preparation and molding process. Binders are important components in the slurry, which can provide the necessary structural strength during the formation of the green body. Before sintering, the binder can maintain close contact between the alumina particles and prevent the particles from separating during drying or handling. At the same time, the binder can also promote the bonding between the alumina particles during the sintering process, thereby improving the density and mechanical strength of the final ceramic membrane. The addition of plasticizers is mainly to improve the rheological properties of the slurry and make it easier to tape-cast. Plasticizers can reduce the viscosity of the slurry and increase its fluidity, so that the slurry can be evenly spread on the conveyor belt of the tape-casting machine. In addition, plasticizers can also improve the flexibility of the green body, making it less likely to crack or deform during subsequent processing. The formation of bubbles is a common problem during the preparation and molding of the slurry. The presence of bubbles can cause defects inside the green body, which in turn affects the performance of the final ceramic membrane. The addition of defoamers is to prevent this from happening. The foam suppressant can destroy the surface tension of bubbles, causing them to dissipate or burst quickly, thereby ensuring the uniformity and stability of the slurry. For example, m5 can be 0.06, 0.07, 0.08, 0.09, 0.10; m6 can be 0.8, 0.9, 1, 1.1, 1.2, etc.; m7 can be 0.0005, 0.001, 0.0015, 0.0025, 0.0035, 0.0045, 0.005, etc.

[0063] In some embodiments, the binder includes: polyvinyl butyral; and / or,

[0064] The plasticizer comprises: at least one of polyethylene glycol and dibutyl phthalate; and / or,

[0065] The foam suppressor includes: a fatty acid lipid mixture.

[0066] In some embodiments, the fatty acid lipid mixture includes: a high-carbon alcohol fatty acid ester complex, fatty acid glyceride and fatty acid amide.

[0067] S3, subjecting the second slurry to a second ball milling to obtain a third slurry;

[0068] The second slurry is further ball-milled to obtain a third slurry. The purpose of this step is to further refine the particles in the slurry and improve its uniformity and stability during the tape casting process.

[0069] In some embodiments, the solid content of the third slurry is 50% to 65%; and / or,

[0070] The set viscosity of the fourth slurry is 10000 mPa·s to 20000 mPa·s.

[0071] Solid content refers to the proportion of solid components in the slurry. Limiting the solid content of the third slurry to 50% to 65% can ensure that the slurry has good fluidity and plasticity during the tape casting process, and also help to improve the density and mechanical strength of the final ceramic film. Viscosity is an indicator of the flow resistance of the slurry, which determines the spreading ability and uniformity of the slurry during the tape casting process. Limiting the viscosity of the third slurry to 10000mPa·s to 20000mPa·s can ensure that the slurry can be evenly spread on the conveyor belt of the tape casting machine to form a green body with uniform thickness and dense structure. Illustratively, the solid content of the third slurry may be 50%, 52%, 55%, 57%, 60%, 62%, 65%, etc.; the viscosity of the third slurry may be 10000 mPa·s, 11000 mPa·s, 12000 mPa·s, 13000 mPa·s, 14000 mPa·s, 15000 mPa·s, 17000 mPa·s, 19000 mPa·s, 20000 mPa·s, etc.

[0072] S4, degassing the third slurry to obtain a fourth slurry with a set viscosity;

[0073] S5, performing tape casting molding on the fourth slurry to obtain an alumina green body;

[0074] The third slurry is degassed to remove bubbles. At the same time, the viscosity of the slurry is adjusted to make it more suitable for tape casting. The treated slurry is formed by a tape casting machine. The tape casting machine spreads the slurry evenly on the conveyor belt through a scraper to form an alumina green body of a certain thickness and width.

[0075] S6, debinding, pre-sintering and sintering the alumina green body to obtain a β"-alumina ceramic film.

[0076] In some embodiments, the thickness of the β"-alumina ceramic film is 0.05 mm to 0.3 mm.

[0077] In some embodiments, the relative theoretical sintered density is ≥98%, the β" phase content is ≥95%, and the ionic conductivity at 100°C is ≥0.010S·cm -1 .

[0078] The organic additives (such as binders, plasticizers, etc.) in the green body are discharged at high temperature. This step is to prevent them from having an adverse effect on the performance of the ceramic membrane during the subsequent sintering process. The green body is preheated at a lower temperature. The purpose of pre-sintering is to further remove impurities and moisture in the green body and make its structure more stable. The green body is sintered at high temperature. During the sintering process, a solid phase reaction occurs between the alumina particles to form a dense ceramic membrane.

[0079] In some embodiments, the debinding temperature is 450° C. to 550° C., and the debinding time is 8 h to 12 h.

[0080] The main purpose of debinding is to remove organic matter (such as binders, plasticizers, etc.) in the green body to avoid the generation of gas or volatiles during the subsequent sintering process, which may cause defects in the ceramic membrane. The debinding temperature is limited to 450℃~550℃, and the debinding time is 8h~12h. The organic matter can fully volatilize, and the alumina green body will not be deformed or defective due to excessive volatilization. If the debinding temperature is greater than 550℃, the debinding volatilization speed is too fast, which makes the alumina green body prone to deformation and defects. If the debinding temperature is lower than 450℃, the organic matter will not be completely volatilized during the debinding stage, and the subsequent rapid volatilization at high temperature will cause deformation of the sintered ceramic and defects such as pores. The debinding temperature may be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 520°C, 540°C, 550°C, etc., and the debinding time may be 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 12h, etc.

[0081] In some embodiments, the pre-firing temperature is 900° C. to 1100° C., and the pre-firing time is 1 h to 2 h.

[0082] The purpose of pre-sintering is to further remove residual organic matter in the green body and promote the initial bonding between alumina particles to prepare for the subsequent sintering process. The pre-sintering temperature is limited to 900℃~1100℃, and the pre-sintering time is 1h~2h. The green body can be fully pre-sintered without causing abnormal grain growth due to excessive temperature. The pre-sintering temperature can be 900℃, 920℃, 950℃, 980℃, 1000℃, 1050℃, 1080℃, 1100℃, etc., and the pre-sintering time can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, etc.

[0083] In some embodiments, the sintering temperature is 1600° C. to 1650° C., and the sintering time is 1 h to 2 h.

[0084] Sintering is the last and most critical step in the preparation process of alumina ceramic membrane. It determines the final structure and performance of the ceramic membrane. The sintering temperature is limited to 1600℃~1650℃, and the sintering time is 1h~2h. The alumina particles can be fully combined to form a dense ceramic membrane. At the same time, the content of β" phase can reach more than 95%, and the sintering density reaches more than 98.5% of the theoretical density. Exemplarily, the sintering temperature can be 1600℃, 1605℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, etc., and the sintering time can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, etc.

[0085] In some embodiments, the first ball milling time is 12 hours to 18 hours; and / or,

[0086] The second ball milling time is 8 h to 12 h.

[0087] The time of the first ball milling is limited to 12h~18h, and the time of the second ball milling is limited to 8h~12h. The aluminum compound, the sodium compound and the stabilizer are fully ground, dispersed and depolymerized to ensure that the raw materials are mixed evenly, and the particle size meets the requirements of tape casting; if the time of the first ball milling is greater than 18h or the time of the second ball milling is greater than 12h, the powder particle size is too fine, the particle size distribution is uneven, the green body is easy to crack during molding, and the thickness is thin; if the time of the first ball milling is less than 12h or the time of the second ball milling is less than 8h, the powder raw materials are not fully mixed evenly, the β"-alumina ceramic film β" phase is low, and the impurity content is high. At the same time, the particle size is coarse and the distribution is wide, which does not meet the requirements of tape casting. The reason for the two ball millings is that during the mixing of the three powders with binders, plasticizers and other additives, the powders are easy to agglomerate and be wrapped by organic matter, resulting in uneven mixing of the powders and poor slurry uniformity, resulting in the presence of large particles that are not dispersed and agglomerated, and the formed β"-alumina ceramic film β" phase is low and the quality is poor. For example, the first ball milling time can be 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, etc., and the second ball milling time can be 8 h, 9 h, 10 h, 11 h, 12 h, etc.

[0088] In summary, the method for preparing β"-alumina ceramic membrane by tape casting provided in the present application has many advantages, which are mainly reflected in the following aspects: 1. Advantages of material selection and crystal phase control. Addition of sodium-containing compounds: This method effectively assists the transformation of the alumina grain structure from the α phase to the β" phase by adding sodium-containing compounds. This crystal phase transformation is crucial to improving the conductivity and other properties of the alumina ceramic membrane. Addition of stabilizer: Adding stabilizer can inhibit the transformation of β" phase to β' phase caused by high temperature sodium volatilization, thereby maintaining the stability and performance of ceramic membrane. 2. Optimization of process. Two-time ball milling process: First ball milling: further crush, depolymerize and evenly mix aluminum-containing compounds, sodium-containing compounds and stabilizers, laying the foundation for subsequent chemical reactions and crystal phase transformations. Second ball milling: further refine the particles in the slurry to improve its uniformity and stability during the tape casting process. At the same time, through two ball millings, organic substances such as binders and plasticizers are prevented from wrapping the powder, thereby preventing the agglomeration of the powder and ensuring the uniformity and density of the ceramic membrane. Tape casting technology: Tape casting is a typical tape casting process. A method for forming a green body, a two-dimensional structured sheet or plate. This method has the advantages of simple equipment, stable process, continuous operation, high production efficiency, and high degree of automation. Through tape casting, an alumina green body with uniform thickness and dense structure can be obtained. Debinding, pre-sintering and sintering treatment: The debinding process can remove organic matter in the green body to avoid the generation of gas or volatiles during the sintering process, which may cause defects in the ceramic membrane. The pre-sintering process further removes residual organic matter and promotes the initial bonding between alumina particles. The sintering process is the key step for the alumina particles to fully combine to form a dense ceramic membrane. By precisely controlling the sintering temperature and time, a β"-alumina ceramic membrane with excellent performance can be obtained. 3. Improvement of product performance. Controllable thickness: Through tape casting technology, the thickness of the ceramic membrane can be precisely controlled to meet the needs of different application scenarios. Stable quality: This method has a stable process, can be operated continuously, has high production efficiency, and can ensure the stable and reliable quality of the produced ceramic membrane. Low resistivity: β"-alumina ceramic membrane has a low resistivity, which is crucial for its application in electrochemical devices. The ceramic membrane prepared by this method has excellent electrical conductivity. Superior application performance: The β"-alumina ceramic membrane prepared by this method has the characteristics of high electrical conductivity, high density, high strength and uniform microstructure, and can be widely used in sodium-sulfur batteries and various electrochemical devices. The method of preparing β"-alumina ceramic membrane by tape casting shows significant advantages in material selection and crystal phase control, process optimization and product performance improvement. These advantages make this method have broad application prospects and market demand in the field of preparation of alumina ceramic membranes.

[0089] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0090] Example 1

[0091] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0092] (1) 100 g of high-purity α-alumina, 12 g of sodium oxide, 1.5 g of lithium carbonate and oleic acid were mixed in an azeotropic solvent of ethanol and ethyl acetate and ball-milled for 16 h.

[0093] The amount of oleic acid added is 0.5wt% of the powder.

[0094] (2) PVB, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 8 hours to obtain a uniform slurry.

[0095] The amount of PVB added is 8wt% of the powder, the amount of dibutyl phthalate added is 8wt% of the powder, the amount of antifoaming agent added is 0.05wt% of the powder, and the solid content of the slurry is controlled at 55%;

[0096] (3) degassing the slurry, controlling the slurry viscosity at 10000 mPa·s, and tape casting to obtain an alumina green body;

[0097] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0098] The debinding temperature is 450°C, the debinding time is 12h; the pre-burning temperature is 900°C, the pre-burning time is 2h; the sintering temperature is 1600°C, and the sintering time is 2h.

[0099] Example 2

[0100] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0101] (1) 100 g of high-purity α-alumina, 16 g of sodium carbonate, 2.0 g of lithium oxalate and oleic acid were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 14 h.

[0102] The amount of oleic acid added is 0.5wt% of the powder.

[0103] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 8 hours to obtain a uniform slurry.

[0104] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 8wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.05wt% of the powder, and the solid content of the slurry is controlled at 55%

[0105] (3) degassing the slurry, controlling the slurry viscosity at 12000 mPa·s, and tape casting to obtain an alumina green body;

[0106] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0107] The debinding temperature is 500°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 2h; the sintering temperature is 1650°C, and the sintering time is 2h.

[0108] Example 3

[0109] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0110] (1) 100 g of high-purity α-alumina, 14 g of sodium oxide, 1.5 g of lithium oxide and triolein were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 16 h.

[0111] The amount of triolein added is 0.5wt% of the powder.

[0112] (2) PVB, polyethylene glycol and antifoaming agent were added in sequence and mixed by ball milling for 10 hours to obtain a uniform slurry.

[0113] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol added is 8wt% of the powder, the amount of antifoaming agent added is 0.05wt% of the powder, and the solid content of the slurry is controlled at 60%.

[0114] (3) degassing the slurry, controlling the slurry viscosity at 16000 mPa·s, and tape casting to obtain an alumina green body;

[0115] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0116] The debinding temperature is 550°C, the debinding time is 8h; the pre-burning temperature is 1000°C, the pre-burning time is 2h; the sintering temperature is 1600°C, and the sintering time is 2h.

[0117] Example 4

[0118] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0119] (1) 100 g of high-purity alumina monohydrate, 16 g of sodium oxide, 2.0 g of lithium oxide and oleic acid were mixed in an azeotropic solvent of ethanol and ethyl acetate and ball-milled for 16 h.

[0120] The amount of oleic acid added is 1.0wt% of the powder.

[0121] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 10 hours to obtain a uniform slurry.

[0122] The amount of PVB added is 8wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 6.4wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.2wt% of the powder, and the solid content of the slurry is controlled at 60%.

[0123] (3) degassing the slurry, controlling the slurry viscosity at 14000 mPa·s, and tape casting to obtain an alumina green body;

[0124] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0125] The debinding temperature is 550°C, the debinding time is 8h; the pre-burning temperature is 1100°C, the pre-burning time is 1h; the sintering temperature is 1620°C, and the sintering time is 2h.

[0126] Example 5

[0127] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0128] (1) 100 g of high-purity alumina monohydrate, 18 g of sodium oxide, 2.0 g of magnesium hydroxide and oleic acid were mixed in an azeotropic solvent of ethanol and ethyl acetate and ball-milled for 18 h.

[0129] The amount of oleic acid added is 0.5wt% of the powder.

[0130] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 12 hours to obtain a uniform slurry.

[0131] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 12wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.4wt% of the powder, and the solid content of the slurry is controlled at 65%

[0132] (3) degassing the slurry, controlling the slurry viscosity at 20000 mPa·s, and tape casting to obtain an alumina green body;

[0133] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0134] The debinding temperature is 500°C, the debinding time is 8h; the pre-burning temperature is 1100°C, the pre-burning time is 1h; the sintering temperature is 1600°C, and the sintering time is 2h.

[0135] Example 6

[0136] This embodiment provides a method for preparing a β"-alumina ceramic film by tape casting, the steps are as follows:

[0137] (1) 100 g of high-purity alumina monohydrate, 16 g of sodium carbonate, 2.5 g of lithium carbonate and oleic acid were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 12 h.

[0138] The amount of oleic acid added is 0.8wt% of the powder.

[0139] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 12 hours to obtain a uniform slurry.

[0140] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 10wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.3wt% of the powder, and the solid content of the slurry is controlled at 60%.

[0141] (3) degassing the slurry, controlling the slurry viscosity at 18000 mPa·s, and tape casting to obtain an alumina green body;

[0142] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0143] The debinding temperature is 450°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 1h; the sintering temperature is 1650°C, and the sintering time is 1h.

[0144] Comparative Example 1

[0145] (1) 100 g of high-purity alumina monohydrate, 10 g of sodium carbonate, 1.5 g of lithium carbonate and oleic acid were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 14 h.

[0146] The amount of oleic acid added is 0.8wt% of the powder.

[0147] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 12 hours to obtain a uniform slurry.

[0148] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 10wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.3wt% of the powder, and the solid content of the slurry is controlled at 60%.

[0149] (3) degassing the slurry, controlling the slurry viscosity at 18000 mPa·s, and tape casting to obtain an alumina green body;

[0150] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0151] The debinding temperature is 450°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 1h; the sintering temperature is 1550°C, and the sintering time is 2h.

[0152] Comparative Example 2

[0153] (1) 100 g of high-purity alumina monohydrate, 12 g of sodium carbonate, 1.5 g of lithium oxide and oleic acid were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 8 h.

[0154] The amount of oleic acid added is 0.8wt% of the powder.

[0155] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 6 hours to obtain a uniform slurry.

[0156] The amount of PVB added is 10wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 10wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.3wt% of the powder, and the solid content of the slurry is controlled at 60%.

[0157] (3) degassing the slurry, controlling the slurry viscosity at 12000 mPa·s, and tape casting to obtain an alumina green body;

[0158] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0159] The debinding temperature is 450°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 1h; the sintering temperature is 1600°C, and the sintering time is 2h.

[0160] Comparative Example 3

[0161] (1) 100 g of high-purity α-alumina, 12 g of sodium carbonate, 1.5 g of lithium oxide and oleic acid were mixed in an azeotropic solvent of ethanol and butanone and ball-milled for 14 h.

[0162] The amount of oleic acid added is 0.8wt% of the powder.

[0163] (2) PVB, polyethylene glycol, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 8 hours to obtain a uniform slurry.

[0164] The amount of PVB added is 8wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 9.6wt% of the powder, the ratio of polyethylene glycol to dibutyl phthalate is 2:1, the amount of antifoaming agent added is 0.1wt% of the powder, and the solid content of the slurry is controlled at 55%

[0165] (3) degassing the slurry, controlling the slurry viscosity at 14000 mPa·s, and tape casting to obtain an alumina green body;

[0166] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0167] The debinding temperature is 600°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 1h; the sintering temperature is 1700°C, and the sintering time is 2h.

[0168] Comparative Example 4

[0169] (1) 100 g of high-purity α-alumina, 10 g of sodium oxide, 1.5 g of magnesium oxalate and oleic acid were mixed in an azeotropic solvent of ethanol and ethyl acetate and ball-milled for 14 h.

[0170] The amount of oleic acid added is 0.85wt% of the powder.

[0171] (2) PVB, dibutyl phthalate and antifoaming agent were added in sequence and mixed by ball milling for 10 hours to obtain a uniform slurry.

[0172] The amount of PVB added is 6wt% of the powder, the amount of polyethylene glycol and dibutyl phthalate added is 7.2wt% of the powder, the amount of antifoaming agent added is 0.1wt% of the powder, and the solid content of the slurry is controlled at 55%.

[0173] (3) degassing the slurry, controlling the slurry viscosity at 12000 mPa·s, and tape casting to obtain an alumina green body;

[0174] (4) The green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

[0175] The debinding temperature is 500°C, the debinding time is 10h; the pre-burning temperature is 1000°C, the pre-burning time is 1h; the sintering temperature is 1580°C, and the sintering time is 2h.

[0176] The thickness, sintered density, β" phase content and ionic conductivity at 100°C of the β"-alumina ceramic films of Examples 1 to 6 and Comparative Examples 1 to 4 were tested, and the test results are shown in Table 1.

[0177] Table 1 Performance of β"-alumina ceramic membranes of Examples 1 to 6 and Comparative Examples 1 to 4

[0178]

[0179]

[0180] It can be seen from Table 1 that, according to the comparison between Examples 1 to 6 and Comparative Examples 1 to 4, the β"-alumina ceramic membrane prepared by tape casting provided in the embodiments of the present invention has obvious advantages in sintering density, β" phase content and ionic conductivity at 100°C, and the thickness of the β"-alumina ceramic membrane is controllable from 0.05mm to 0.3mm, the production batch stability is high, the operation is simple, the cost is low, and the technical requirements of high-performance β"-alumina solid electrolyte ceramics are met.

[0181] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0182] In an embodiment of the present application, a method for preparing a β"-alumina ceramic membrane by tape casting is provided to solve the problems of poor production quality and stability of existing β"-alumina ceramic membranes and complex large-scale production operations. The β"-alumina ceramic membrane produced by the present invention has a high sintering density, high ionic conductivity, and a uniform microstructure.

[0183] In the embodiment of the present application, the aluminum-containing compound, the sodium-containing compound and the stabilizer are further crushed, depolymerized and uniformly mixed by wet grinding, and a uniform slurry is obtained by adding a binder, a plasticizer and other casting aids, and the slurry viscosity is controlled to cast alumina green bodies of different thicknesses, and a β"-alumina ceramic film with a controllable thickness of 0.05mm to 0.3mm, stable quality and low resistivity is obtained after debinding and sintering treatment with a pre-sintering agent. The relative theoretical sintering density is ≥98%, the β" phase content is ≥95%, and the ionic conductivity at 100°C is ≥0.010S·cm -1 The ceramic grain structure is uniform, meeting the technical requirements of high-performance β"-alumina solid electrolyte ceramics.

[0184] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing a β"-alumina ceramic film by tape casting, characterized in that: The method comprises: The high-purity aluminum-containing compound, the sodium-containing compound, the stabilizer, the dispersant and the solvent are subjected to a first ball milling to obtain a first slurry; Adding a binder, a plasticizer and an antifoaming agent to the first slurry to obtain a second slurry; subjecting the second slurry to a second ball milling to obtain a third slurry; Degassing the third slurry to obtain a fourth slurry with a set viscosity; Performing tape casting on the fourth slurry to obtain an alumina green body; and The alumina green body is subjected to debinding, pre-sintering and sintering to obtain a β"-alumina ceramic film.

2. The method according to claim 1, characterized in that The mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, and the mass m4 of the dispersant satisfy the following relationship: m1:m2:m3=100:(12-18):(1-2.5); and / or, m4: (m1+m2+m3)=(0.005~0.01):

1.

3. The method according to claim 2, characterized in that The high-purity aluminum-containing compound includes at least one of alumina trihydrate, alumina monohydrate and alumina; and / or, The sodium-containing compound comprises: at least one of sodium oxide, sodium carbonate and aluminum hydroxide; and / or, The stabilizer comprises: at least one of lithium-containing oxides, magnesium-containing oxides, aluminates, carbonates and oxalates; and / or, The dispersant comprises: at least one of oleic acid, triolein and fish oil; and / or, The solvent includes at least one of ethanol, ethyl acetate, butanone and xylene.

4. The method according to claim 1, characterized in that: The mass m1 of the high-purity aluminum-containing compound, the mass m2 of the sodium-containing compound, the mass m3 of the stabilizer, the mass m4 of the dispersant, the mass m5 of the binder, the mass m6 of the plasticizer and the mass m7 of the defoamer satisfy the following relationship: m5: (m1+m2+m3)=(0.06-0.1): 1; and / or, m6:m5=(0.8-1.2):1; and / or, m7: (m1+m2+m3)=(0.0005~0.005):

1.

5. The method according to claim 4, characterized in that The binder comprises: polyvinyl butyral; and / or, The plasticizer comprises: at least one of polyethylene glycol and dibutyl phthalate; and / or, The foam suppressor includes: a fatty acid lipid mixture.

6. The method according to claim 1, characterized in that The solid content of the third slurry is 50% to 65%; and / or, The set viscosity is 10000mPa·s to 20000mPa·s.

7. The method according to claim 1, characterized in that The debinding temperature is 450° C. to 550° C., and the debinding time is 8 h to 12 h.

8. The method according to claim 1, characterized in that The pre-firing temperature is 900° C. to 1100° C., and the pre-firing time is 1 hour to 2 hours.

9. The method according to claim 1, characterized in that: The sintering temperature is 1600° C. to 1650° C., and the sintering time is 1 h to 2 h.

10. The method according to claim 1, characterized in that The first ball milling time is 12h to 18h; and / or, The second ball milling time is 8 h to 12 h.

Images