Alumina ceramic slurry, preparation method thereof and alumina ceramic

Abstract

The invention discloses aluminum oxide ceramic slurry, a preparation method thereof and aluminum oxide ceramic. The alumina ceramic slurry comprises 70-80 parts of alumina raw powder, 20-30 parts of deionized water, 0.5-1% of a dispersant, 3-6% of a composite binder, 1-10% of a plasticizer, 1-5% of a lubricant and a proper amount of an antifoaming agent, wherein the mass of the dispersant, the mass of the composite binder, the mass of the plasticizer and the mass of the lubricant are taken as the reference. Wherein the composite binder is prepared from polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate according to the mass ratio of (2 to 4.5) to (0.2 to 1.2) to (0.1 to 0.6) to (0.1 to 0.6). The viscosity of the slurry is stabilized at 200-300 mPa.s, after the slurry is subjected to spray granulation, cold isostatic pressing molding and high-temperature sintering, the density of the obtained aluminum oxide ceramic is larger than or equal to 3.94 g / cm < 3 >, the bending strength is larger than or equal to 400 MPa, and the strict requirement of semiconductor equipment for the high-performance aluminum oxide ceramic is met. The preparation method is stable in process and good in repeatability, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of alumina ceramic preparation, in particular to an alumina ceramic slurry, a preparation method thereof and alumina ceramic. BACKGROUND

[0002] In the preparation of high-purity alumina ceramic (such as used for semiconductor equipment cavities, insulating parts and the like), spray granulation is a key process. The sphericity, strength and particle size distribution of the granulated powder directly affect the green body packing density and sintering uniformity, and then determine the density and mechanical properties of the final ceramic body.

[0003] Traditional processes mostly use a single binder (such as polyvinyl alcohol PVA or polyacrylic acid PAA). However, although PVA has strong adhesion, the molecular chain is rigid and easy to cause high brittleness and easy breakage of the granulated powder; PAA has good flexibility but insufficient adhesion strength, and the green body has low strength. Both of them alone are difficult to effectively wrap high-hardness alumina particles, resulting in poor sphericity, rough surface and high porosity of the granulated powder, and finally the sintered ceramic body has a density lower than 3.90 g / cm3 and a bending strength less than 350 MPa, which cannot meet the requirements of semiconductor-grade applications.

[0004] In addition, the viscosity of the slurry is a core parameter affecting the quality of spray granulation. Too low viscosity (<200 mPa·s) leads to droplet splashing and fine particles; too high viscosity (>300 mPa·s) causes difficulty in atomization and irregular particles. The prior art lacks precise control means for the viscosity of the slurry.

[0005] Therefore, it is urgent to develop an alumina ceramic slurry system with good wrapping property, controllable rheology and high formability. SUMMARY

[0006] The purpose of the application is to provide an alumina ceramic slurry and a preparation method thereof, by designing a specific composition of a four-component composite binder system (PVA / GA / PAA / DOM), the viscosity of the slurry is synergistically controlled in the range of 200-300 mPa·s, the sphericity and strength of the granulated powder are significantly improved, and finally high-density (≥3.94 g / cm3) and high-bending-strength (≥400 MPa) alumina ceramic is obtained.

[0007] The application provides an alumina ceramic slurry, which is obtained by mixing and ball-milling raw materials including the following mass fractions:

[0008] 70-80 parts of alumina raw powder,

[0009] 20-30 parts of deionized water,

[0010] 0.5%-1% of the mass of the alumina raw powder of a dispersant,

[0011] a composite binder accounting for 3-6% of the mass of the alumina raw powder,

[0012] a plasticizer accounting for 1-10% of the mass of the alumina raw powder,

[0013] a lubricant accounting for 1-5% of the mass of the alumina raw powder,

[0014] a defoaming agent in an appropriate amount,

[0015] wherein,

[0016] the composite binder comprises polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate in a mass ratio of (2-4.5):(0.2-1.2):(0.1-0.6):(0.1-0.6).

[0017] Preferably, in the composite binder, the mass ratio of polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate is 3.5:0.6:0.4:0.4.

[0018] Preferably, the addition amount of the composite binder is 4% of the mass of the alumina raw powder.

[0019] Preferably, the addition amount of the dispersant is 0.7% of the mass of the alumina raw powder.

[0020] Preferably, the plasticizer is selected from one or more of polyethylene glycol, glycerol and polyvinyl chloride.

[0021] Preferably, the plasticizer is composed of polyethylene glycol and glycerol, wherein the addition amount of polyethylene glycol is 3% of the mass of the alumina raw powder and the addition amount of glycerol is 1% of the mass of the alumina raw powder.

[0022] Preferably, the lubricant is selected from one of water-based paraffin and stearic acid emulsion.

[0023] Preferably, the lubricant is stearic acid emulsion, and the addition amount of the lubricant is 1.6% of the mass of the alumina raw powder.

[0024] The application also provides a preparation method of the alumina ceramic slurry as described in any one of the above, comprising the following steps:

[0025] S1, preparing a composite binder:

[0026] S11, weighing polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate according to the proportion;

[0027] S12, adding the weighed polyvinyl alcohol into deionized water, heating to 80-90℃ and stirring until completely dissolved to form a uniform solution to obtain a first solution, wherein the mass ratio of polyvinyl alcohol to water in the first solution is 1:4;

[0028] S13, cool the first solution to 50~65℃, adjust the pH value to 3~5, add the weighed glutaraldehyde and stir for 30~60min to achieve cross-linking modification of polyvinyl alcohol, and obtain the second solution;

[0029] S14, after cooling the second solution to room temperature, add the weighed polyacrylic acid and dioctyl maleate in sequence, continue stirring for 30-60 minutes, then seal and let stand for 3-5 hours to mature, defoam and stabilize the system to obtain the composite adhesive.

[0030] S2, ball mill:

[0031] S21, Weigh out alumina powder, deionized water and dispersant in proportion;

[0032] S22, add the weighed deionized water to the ball mill jar, and add the weighed dispersant to the deionized water, and stir in the ball mill jar for 5~15 minutes;

[0033] S23, add the weighed alumina raw powder into the ball mill jar and ball mill for 3-4 hours to obtain alumina slurry;

[0034] S3, Pulping:

[0035] S31, weigh out the composite adhesive, plasticizer and lubricant according to the proportion;

[0036] S32, Transfer the alumina slurry to the mixing tank;

[0037] S33, the weighed composite binder, plasticizer and lubricant are added to the mixing tank in sequence, and the mixture is stirred for 20 to 40 minutes after the first additive is added before the next additive is added.

[0038] S34. Based on the foaming situation on the slurry surface, add an appropriate amount of defoamer and continue stirring for 20-40 minutes until there are no bubbles on the slurry surface, thus obtaining the alumina ceramic slurry.

[0039] This application also provides an alumina ceramic, which is prepared from the alumina ceramic slurry described in any of the above claims.

[0040] The above-mentioned technical solution of this application has the following advantages over the prior art:

[0041] 1. Through the synergistic effect of the components of the composite binder, the viscosity of the slurry can be precisely controlled, and the viscosity of the slurry can be stably controlled at 200~300 mPa·s, which meets the optimal atomization window for spray granulation.

[0042] 2. The sphericity of the granulated powder was significantly improved. SEM observation showed that the particles were round and smooth, with a sphericity >0.92.

[0043] 3. The ceramic body has excellent properties, with a density ≥3.94 g / cm³ after sintering and a flexural strength ≥400 MPa;

[0044] 4. It has good process stability and high batch repeatability, making it suitable for mass production of semiconductor-grade alumina ceramics. Attached Figure Description

[0045] 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, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a SEM image of the granulated powder obtained in Example 1 of this application;

[0047] Figure 2 This is a SEM image of the granulated powder obtained in Comparative Example 1 of this application. Detailed Implementation

[0048] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] In the embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. The system embodiments described below are merely illustrative. For example, the division of units and modules is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or modules can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, and can be electrical, mechanical, or other forms.

[0050] In addition, each functional unit in the various embodiments of this application can be integrated into a single processor, or each unit can be a separate device, or two or more units can be integrated into a single device; each functional unit in the various embodiments of this application can be implemented in hardware or in the form of hardware plus software functional units.

[0051] Those skilled in the art will understand that all or part of the steps of the following method embodiments can be implemented by program instructions and related hardware. The aforementioned program instructions can be stored in a computer-readable storage medium. When the program instructions are executed, they perform the steps of the following method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" or "several" means two or more, unless otherwise explicitly specified.

[0053] This application provides an alumina ceramic slurry, which is obtained by ball milling a specific mass fraction of raw materials. In this embodiment, the raw material composition of the alumina ceramic slurry includes 70-80 parts of alumina powder, 20-30 parts of deionized water, 0.5%-1% of a dispersant by mass of alumina powder, 3%-6% of a composite binder by mass of alumina powder, 1%-10% of a plasticizer by mass of alumina powder, 1%-5% of a lubricant by mass of alumina powder, and an appropriate amount of defoamer. The composite binder includes polyvinyl alcohol, glutaraldehyde, polyacrylic acid, and dioctyl maleate in a mass ratio of (2-4.5):(0.2-1.2):(0.1-0.6):(0.1-0.6).

[0054] In this embodiment, alumina powder, as the main raw material, is a key factor determining the final ceramic properties. Its crystal structure endows the ceramic with excellent thermal, electrical, and mechanical properties.

[0055] The content of alumina powder is controlled at 70-80 parts. This range ensures that the ceramic has sufficient strength and stability during subsequent molding and sintering processes, and also provides a basis for the role of other additives.

[0056] Deionized water plays an important role in dissolving and dispersing other components in slurry, enabling various raw materials to be mixed evenly and form a stable slurry system.

[0057] Dispersants adsorb onto the surface of alumina particles through electrostatic repulsion and / or steric hindrance, increasing the absolute value of the particle zeta potential and weakening van der Waals attraction, thereby effectively de-agglomerating and stabilizing the suspension system. Adding 0.5% to 1% dispersant by weight of the alumina powder can reduce slurry viscosity, increase the upper limit of solids content, prevent particle re-agglomeration after ball milling, and ensure uniform coating by subsequent binders, providing a foundation for obtaining high-sphericity granulated powder.

[0058] A composite binder comprising 3% to 6% of the alumina powder mass is used to construct a quaternary synergistic composite binder system by using polyvinyl alcohol (PVA), glutaraldehyde (GA), polyacrylic acid (PAA), and dioctyl maleate (DOM) in a mass ratio of (2 to 4.5): (0.2 to 1.2): (0.1 to 0.6): (0.1 to 0.6). This system enables precise control of the rheological properties and particle interfacial behavior of high-solids-content alumina slurry. Among them, PVA, as the main adhesive backbone, forms a continuous network in water, providing basic adhesion; GA undergoes acetalization with the hydroxyl groups on the PVA molecular chain under acidic conditions (pH 3~5) to form a cross-linked structure, which significantly improves the water resistance and thermal stability of the adhesive and inhibits the "shell-core" defects caused by migration to the particle surface during the drying process; PAA is rich in carboxyl groups and has strong electronegativity, which can be firmly adsorbed on the surface of positively charged alumina particles and interpenetrate with the PVA-GA network through hydrogen bonds to form a three-dimensional encapsulation structure, effectively improving particle dispersibility and sphericity of granulated powder; DOM, as a flexible plasticizer, is inserted between polymer chains, lowers the glass transition temperature of the system, improves the toughness of the adhesive film, and reduces the generation of microcracks during granulation, compaction, and debinding processes.

[0059] The synergistic effect of the above components ensures that the viscosity of the slurry is stably controlled within the ideal spray granulation window of 200~300 mPa·s. This ensures that the droplets fully shrink into spheres during atomization, while avoiding splashing due to excessively low viscosity or uneven atomization due to excessively high viscosity. This reduces defects in the green body before sintering and improves the density and mechanical properties of the final ceramic body.

[0060] Plasticizers, comprising 1% to 10% of the alumina powder mass, penetrate between the binder molecular chains, weakening interchain hydrogen bonds or van der Waals forces, increasing free volume, thereby lowering the glass transition temperature and improving film flexibility. The plasticizers effectively improve the ductility of the binder film, alleviate internal stress concentration during drying and debinding, inhibit cracking and pulverization of the granulated powder, enhance green body integrity, and, in synergy with lubricants, optimize powder flowability, facilitating uniform filling during cold isostatic pressing.

[0061] Lubricant, accounting for 1% to 5% of the mass of alumina powder, forms a thin lubricating film on the particle surface, reducing the coefficient of friction between particles and between particles and the mold, significantly improving the flowability of the granulated powder; improving the uniformity of green compact filling density, reducing molding stratification or density gradient; facilitating demolding, avoiding edge damage of the pressed compact, and improving the yield.

[0062] Defoamers reduce the surface tension of the bubble liquid film, causing bubbles to burst or inhibiting their formation. They eliminate air introduced during stirring and transfer, preventing residual bubbles in the slurry from causing internal voids or surface depressions in the granulated powder. This ensures a dense particle structure and regular morphology, and prevents bubbles from expanding during sintering to form large pore defects that affect the strength and airtightness of the ceramic body.

[0063] In summary, the alumina ceramic slurry of this embodiment exhibits excellent rheological properties, with a stable viscosity of 200-300 mPa·s and a solid content of 70-80%. It shows no sedimentation or flocculation, making it suitable for industrial spray granulation. The granulated powder exhibits high sphericity; scanning electron microscopy (SEM) reveals round, smooth particles with a sphericity ≥0.92, demonstrating good flowability. The green body exhibits high strength and few defects, with tight interparticle bonding, resulting in a more than 20% increase in compressive strength, and the absence of hollow, broken, or agglomerated particles. The sintered ceramic body demonstrates superior performance, with a final alumina ceramic density ≥3.94 g / cm³ and a flexural strength ≥400 MPa, meeting the stringent requirements of semiconductor equipment for high-purity, high-strength, and highly dense ceramic components. The process exhibits good repeatability, with clearly defined component ratios and addition sequences, resulting in minimal batch-to-batch performance fluctuations and promising prospects for industrial application.

[0064] Specifically, in this embodiment, the dispersant can be anionic or polymeric dispersants such as ammonium polyacrylate or ammonium citrate.

[0065] In one embodiment, the mass ratio of polyvinyl alcohol, glutaraldehyde, polyacrylic acid, and dioctyl maleate in the composite binder is 3.5:0.6:0.4:0.4. At this ratio, the PVA crosslinking density is moderate, the PAA provides sufficient electronegativity for adsorption on the alumina surface, and the DOM effectively buffers internal stress, balancing rigidity and flexibility. This results in a slurry viscosity of approximately 158 mPa·s, the most regular granulated powder morphology, a ceramic density of 3.942 g / cm³, a flexural strength of 426 MPa, and optimal overall performance.

[0066] In one embodiment, the amount of composite binder added is 4% of the mass of the alumina powder. At 4%, the amount of composite binder is just right to ensure complete particle coating without affecting sintering densification. This ensures sphericity while avoiding sintering defects caused by excessive organic matter, achieving a synergistic improvement in both density and strength. Too little composite binder can lead to insufficient coating, while too much can result in excessively high slurry viscosity or excessive residual carbon.

[0067] In one embodiment, the amount of dispersant added is 0.7% of the mass of the alumina powder. This amount of dispersant is sufficient to maximize the zeta potential of the alumina particles, achieve electrostatic stability, prevent agglomeration after ball milling, and make the slurry solid content reach more than 75% and have good fluidity. This lays the foundation for the uniform distribution of the subsequent binder and indirectly ensures the consistency of sphericity.

[0068] In one embodiment, the plasticizer is selected from one or more of polyethylene glycol, glycerol, and polyvinyl chloride. These substances contain multiple hydroxyl groups, which can insert into the polymer chains, weaken intermolecular forces, improve flexibility, reduce particle breakage during granulation and compaction, enhance the integrity of the green body, and reduce the risk of sintering cracking.

[0069] In one embodiment, the plasticizer is composed of polyethylene glycol and glycerol, wherein the amount of polyethylene glycol added is 3% of the mass of the alumina powder, and the amount of glycerol added is 1% of the mass of the alumina powder. The long chain of polyethylene glycol enhances film-forming properties, while the small molecule of glycerol has strong permeability. Together, they synergistically improve the interparticle interface bonding, effectively increasing the compressive strength of the granulated powder and improving the uniformity of the green body density, ultimately resulting in a ceramic body without localized porosity.

[0070] In one embodiment, the lubricant is selected from water-based paraffin wax and stearic acid emulsion. Both water-based paraffin wax and stearic acid emulsion are anionic emulsions, which can reduce the coefficient of friction between particles, improve powder flowability, facilitate droplet shrinkage into spheres during spray granulation, and improve sphericity.

[0071] In one embodiment, the lubricant is a stearic acid emulsion, and the amount of lubricant added is 1.6% of the mass of the alumina powder. Stearate can be partially adsorbed on the surface of alumina to form a lubricating layer, and it has good compatibility with PVA / PAA. The 1.6% lubricant addition effectively ensures that the angle of repose of the granulated powder is below 30°, resulting in excellent flowability, high sieve yield, and improved batch stability.

[0072] This application also provides a method for preparing the alumina ceramic slurry according to any of the above embodiments, comprising the following steps:

[0073] S1, Preparation of composite adhesive:

[0074] S11, weigh out polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate in proportion;

[0075] S12, add the weighed polyvinyl alcohol to deionized water, heat to 80~90℃ and stir until completely dissolved to form a homogeneous solution to obtain the first solution, wherein the mass ratio of polyvinyl alcohol to water in the first solution is 1:4;

[0076] S13, cool the first solution to 50~65℃, adjust the pH value to 3~5, add the weighed glutaraldehyde and stir for 30~60min to achieve cross-linking modification of polyvinyl alcohol, and obtain the second solution;

[0077] S14. After cooling the second solution to room temperature, add the weighed polyacrylic acid and dioctyl maleate in sequence, continue stirring for 30-60 minutes, seal and let stand for 3-5 hours to mature, defoam and stabilize the system to obtain the composite adhesive.

[0078] S2, ball mill:

[0079] S21, Weigh out alumina powder, deionized water and dispersant in proportion;

[0080] S22, add the weighed deionized water to the ball mill jar, and add the weighed dispersant to the deionized water, and stir in the ball mill jar for 5~15 minutes;

[0081] S23, add the weighed alumina raw powder into a ball mill jar and ball mill for 3-4 hours to obtain alumina slurry;

[0082] S3, Pulping:

[0083] S31, weigh out the composite adhesive, plasticizer and lubricant according to the proportion;

[0084] S32, Transfer the alumina slurry to the mixing tank;

[0085] S33, the weighed composite binder, plasticizer and lubricant are added to the mixing tank in sequence, and the previous additive is stirred for 20 to 40 minutes before the next additive is added.

[0086] S34. Depending on the foaming situation on the slurry surface, add an appropriate amount of defoamer and continue stirring for 20-40 minutes until there are no bubbles on the slurry surface to obtain alumina ceramic slurry.

[0087] A step-by-step process for preparing composite binders and slurry formulation is defined. Principle: PVA is first cross-linked and modified before PAA / DOM is introduced to avoid competitive reactions between components; additives are added step-by-step with stirring for 30 minutes to ensure molecular-level dispersion. Results: The binder has a uniform structure, the slurry is free of flocculation and bubbles, and the viscosity reproducibility error is <5%, ensuring feasibility for industrial scale-up.

[0088] This application also provides an alumina ceramic, which is prepared from the alumina ceramic slurry described in any of the above embodiments.

[0089] In this embodiment, the alumina ceramic prepared from the above slurry achieves close packing of high sphericity granulated powder, and the low-defect green body is sintered to obtain a high-density structure, ultimately resulting in a ceramic body with a density ≥3.94 g / cm³ and a flexural strength ≥400 MPa, meeting the dual requirements of semiconductor devices for mechanical properties and purity.

[0090] To more comprehensively and thoroughly verify the effectiveness and superiority of the alumina ceramic slurry, its preparation method, and the alumina ceramics proposed in this application, a series of experimental studies in the following examples and comparative proportions were designed and conducted. By strictly controlling variables, meticulously recording all experimental data, and conducting in-depth analysis of the results, the aim is to provide solid data support and practical basis for the practical application of this application.

[0091] In the following examples and comparative examples, all process conditions remain consistent except for the specified variables:

[0092] Alumina raw powder: purity ≥ 99.99%, D50 = 0.5μm

[0093] Dispersant: Ammonium polyacrylate, added at 0.7% of the mass of alumina powder.

[0094] Plasticizer: Polyethylene glycol (3% of the mass of alumina powder) + Glycerol (1% of the mass of alumina powder)

[0095] Lubricant: Stearic acid emulsion, added at 1.6% of the mass of the alumina powder.

[0096] Slurry viscosity test: 25°C, rotational viscometer (Brookfield)

[0097] Example 1:

[0098] (1) Preparation of composite adhesive: Weigh polyvinyl alcohol (PVA), glutaraldehyde (GA), polyacrylic acid (PAA), and dioctyl maleate (DOM) in the ratio of PVA:GA:PAA:DOM=3.5:0.6:0.4:0.4; add the weighed polyvinyl alcohol to deionized water, heat to 80~90℃ and stir until completely dissolved to form a homogeneous solution to obtain the first solution, wherein the mass ratio of polyvinyl alcohol to water in the first solution is 1:4; cool the first solution to 50~65℃, adjust the pH value to 3~5, add the weighed glutaraldehyde and stir for 30min to achieve crosslinking modification of polyvinyl alcohol to obtain the second solution; after cooling the second solution to room temperature, add the weighed polyacrylic acid and dioctyl maleate in sequence, stir for 30min after each additive is added, then seal and let stand for 4h to mature, defoam and stabilize the system to obtain the composite adhesive;

[0099] (2) Ball milling: Weigh alumina powder, deionized water and dispersant according to the proportion, wherein alumina powder is 75 parts and deionized water is 25 parts; add the weighed deionized water to the ball milling jar and add the weighed dispersant to the deionized water, and stir in the ball milling jar for 10 min; add the weighed alumina powder to the ball milling jar and ball mill for 4 h to obtain alumina slurry;

[0100] (3) Slurry preparation: Weigh the composite binder, plasticizer and lubricant according to the proportion. The amount of composite binder added is 4% of the mass of alumina powder. Transfer the alumina slurry to the mixing tank. Add the weighed composite binder, plasticizer and lubricant to the mixing tank in sequence. After adding the first additive, stir for 30 minutes before adding the next additive. According to the foaming of the slurry surface, add an appropriate amount of defoamer and continue stirring for 30 minutes until there are no bubbles on the slurry surface to obtain alumina ceramic slurry.

[0101] (4) Spray granulation: Set the granulation parameters as follows: inlet temperature is 200℃, outlet temperature is 100℃, atomizer speed is 9000rpm. Use a high-speed centrifugal spray dryer to spray granulate the alumina ceramic slurry to obtain granulated powder. Pass the granulated powder through 60-mesh and 300-mesh sieves, and select the granulated powder with a moderate size and normal distribution for molding.

[0102] (5) Molding: Fill the granulated powder into the mold and place it on the vibration platform to compact it. Set the vibration time to 250s, set the molding equipment parameters to a maximum pressure of 130Mpa and a maximum pressure holding time of 300s, and place the powder after vibration into a cold isostatic press for molding.

[0103] (6) Sintering: Set the sintering equipment parameters as follows: heating rate 4℃ / min, glue discharge temperature 600℃, glue discharge time 4h, maximum sintering temperature 1600℃, maximum sintering temperature holding time 6h. After sintering, alumina ceramic products are obtained.

[0104] SEM image of the granulated powder obtained in Example 1 is shown below. Figure 1 As shown.

[0105] Example 2 (Variable: Reduced PVA content in composite adhesive):

[0106] In step (1), PVA:GA:PAA:DOM = 2.5:0.6:0.4:0.4, and the remaining parameters and procedures are the same as in Example 1.

[0107] Example 3 (Variable: Increased PVA content in composite adhesive):

[0108] In step (1), PVA:GA:PAA:DOM = 4:0.6:0.4:0.4, and the remaining parameters and process are the same as in Example 1.

[0109] Example 4 (Variable: The amount of composite binder added is 1% of the mass of alumina powder):

[0110] In step (3), the amount of composite binder added is 3% of the mass of alumina powder, and the remaining parameters and process are the same as in Example 1.

[0111] Example 5 (Variable: The amount of composite binder added is 6% of the mass of alumina powder):

[0112] In step (3), the amount of composite binder added is 6% of the mass of alumina powder, and the remaining parameters and process are the same as in Example 1.

[0113] Comparative Example 1 (using only PVA, added at 4% of the mass of alumina powder):

[0114] In step (1), only PVA is used, and the amount added is 4% of the mass of the alumina powder. GA, PAA and DOM are not added. The other parameters and processes are the same as in Example 1.

[0115] The SEM image of the granulated powder obtained in Comparative Example 1 is shown below. Figure 2 As shown.

[0116] Comparative Example 2 (Variable: No DOM added to the composite adhesive):

[0117] In step (1), PVA:GA:PAA:DOM = 3.5:0.6:0.4:0, and the remaining parameters and procedures are the same as in Example 1.

[0118] Comparative Example 3 (Variable: The amount of composite binder added is 1% of the mass of alumina powder):

[0119] In step (3), the amount of composite binder added is 1% of the mass of alumina powder, and the remaining parameters and procedures are the same as in Example 1.

[0120] Comparative Example 4 (Variable: The amount of composite binder added is 8% of the mass of alumina powder):

[0121] In step (3), the amount of composite binder added is 8% of the mass of alumina powder, and the remaining parameters and process are the same as in Example 1.

[0122] Comparative Example 5 (Variable: PAA content in the composite adhesive is higher than 0.6%):

[0123] In step (1), PVA:GA:PAA:DOM = 3.5:0.6:1.2:0.4, and the remaining parameters and procedures are the same as in Example 1.

[0124] Comparative Example 6 (Variable: PAA content in the composite adhesive is less than 0.1):

[0125] In step (1), PVA:GA:PAA:DOM = 3.5:0.6:0.05:0.4, and the remaining parameters and procedures are the same as in Example 1.

[0126] Table 1. Comparison of performance data between each embodiment and the comparative example.

[0127] Binder type Mass ratio Addition amount (%) Slurry viscosity (mPa-s) Sphericity (%) Body density (g / cm3) Bending strength (MPa) Example 1 PVA:GA:PAA:DOM 3.5:0.6:0.4:0.4 4 225 0.93 3.945 426 Example 2 PVA:GA:PAA:DOM 2.5:0.6:0.4:0.4 4 214 0.91 3.942 412 Example 3 PVA:GA:PAA:DOM 4:0.6:0.4:0.4 4 238 0.90 3.941 405 Example 4 PVA:GA:PAA:DOM 3.5:0.6:0.4:0.4 3 209 0.90 3.940 402 Example 5 PVA:GA:PAA:DOM 3.5:0.6:0.4:0.4 6 249 0.91 3.943 418 Comparative Example 1 PVA / 4 426 0.78 3.880 342 Comparative Example 2 PVA:GA:PAA:DOM 3.5:0.6:0.4:0 4 412 0.84 3.905 375 Comparative Example 3 PVA:GA:PAA:DOM 3.5:0.6:0.4:0.4 1 124 0.80 3.860 330 Comparative Example 4 PVA:GA:PAA:DOM 3.5:0.6:0.4:0.4 8 442 0.87 3.895 358 Comparative Example 5 PVA:GA:PAA:DOM 3.5:0.6:1.2:0.4 4 408 0.83 3.910 382 Comparative Example 6 PVA:GA:PAA:DOM Comparative Example 7 PVA:GA:PAA:DOM Comparative Example 8 PVA:GA:PAA:DOM Comparative Example 9 PVA:GA:PAA:DOM Comparative Example 10 PVA:GA:PAA:DOM Comparative Example 11 PVA:GA:PAA:DOM Comparative Example 12 PVA:GA:PAA:DOM Comparative Example 13 PVA:GA:PAA:DOM Comparative Example 14 PVA:GA:PAA:DOM Comparative Example 15 PVA:GA:PAA:DOM Comparative Example 16 PVA:GA:PAA:DOM Comparative Example 17 PVA:GA:PAA:DOM Comparative Example 18 PVA:GA:PAA:DOM Comparative Example 19 PVA:GA:PAA:DOM Comparative Example 3.5:0.6:0.05:0.4 4 431 0.82 3.898 368

[0128] In the table above, mass ratio refers to the mass ratio of each component of the binder, addition amount refers to the amount of composite binder added (as a percentage of the mass of alumina raw powder), slurry viscosity refers to the viscosity of alumina ceramic slurry, sphericity refers to the sphericity of granulated powder, ceramic body density refers to the ceramic body density of alumina ceramic products, and flexural strength refers to the flexural strength of alumina ceramic products.

[0129] Analysis and explanation of experimental results:

[0130] By comparing and analyzing the slurry viscosity, granulation powder sphericity, ceramic density, and flexural strength data of each embodiment and comparative example in Table 1, the influence of three core variables—component integrity, mass ratio of each component, and addition amount—on the rheological properties of alumina ceramic slurry and the performance of the final product is revealed. The specific analysis is as follows:

[0131] I. Core Conclusion: Under appropriate formulation and dosage, the quaternary composite binder (PVA-GA-PAA-DOM) can significantly improve slurry stability, sphericity of granulated powder, and mechanical properties of ceramics.

[0132] Experimental data show that Examples 1-5 (all using PVA-GA-PAA-DOM quaternary binder) exhibit excellent performance in slurry viscosity control, granulation powder sphericity, and ceramic properties. Among them:

[0133] The slurry viscosity remained stable within the range of 200~300 mPa·s;

[0134] The sphericity of the granulated powder is ≥ 0.90;

[0135] The density of the porcelain body is ≥ 3.940 g / cm³;

[0136] Bending strength ≥ 400MPa.

[0137] Among all the comparative examples, at least one key indicator was significantly worse than that of the example, especially the performance of Comparative Example 1 (using PVA only) and Comparative Example 2 (without DOM), which was severely degraded. This further verifies that the quaternary synergistic system is the key to achieving high-performance alumina ceramics.

[0138] II. Comparative Analysis of Differential Variables

[0139] 1. The influence of the composition of composite adhesive components: It must contain PVA, GA, PAA and DOM, none of which can be omitted.

[0140] This variable was verified by comparing Example 1 with Comparative Examples 1 and 2:

[0141] Comparative Example 1 (PVA only): The slurry viscosity was as high as 426 mPa·s (>300), far exceeding the ideal range of 200~300 mPa·s, which led to difficulties in atomization, uneven droplets, rough surface of granulated powder, many edges and corners, and a sphericity of only 0.78; the density of the ceramic body after sintering was as low as 3.880 g / cm³, and the flexural strength was only 342 MPa.

[0142] Comparative Example 2 (PVA:GA:PAA:DOM=3.5:0.6:0.4:0): Although it is a ternary system, it lacks the plasticizing effect of DOM, the adhesive film is brittle, the granulated powder is easily broken, the sphericity is 0.84, the density is 3.905 g / cm³, and the strength is 375 MPa, which still do not meet the standards.

[0143] Cause analysis:

[0144] PVA provides main chain adhesion, GA crosslinking enhances heat resistance, PAA anchors the particle surface, and DOM, as a flexible plasticizer, effectively reduces intermolecular forces and improves film toughness. The absence of DOM will disrupt the rigid-flexible balance, increasing the risk of green body cracking and ultimately affecting the density and strength of the ceramic body.

[0145] Conclusion: PVA, GA, PAA and DOM are all indispensable components in the quaternary system. Among them, DOM is an indispensable plasticizing component in the quaternary system. Its presence can significantly improve the mechanical properties of granulated powder and the comprehensive mechanical properties of sintered ceramics.

[0146] 2. The effect of the mass ratio of each component in the composite adhesive: Both excessively high and low PVA proportions will reduce performance.

[0147] This variable was verified through comparison in Examples 1, 2, and 3 (all with an addition amount of 4%, only the PVA ratio changed):

[0148] Example 1 (PVA=3.5): Viscosity 225 mPa·s, sphericity 0.93, density 3.945 g / cm³, strength 426 MPa, this is the optimal combination;

[0149] Example 2 (PVA=2.5): Viscosity 214 mPa·s (low), although it can still form spheres, the PVA content is insufficient, the encapsulation ability is weak, the sphericity is slightly reduced to 0.91, and the strength is 412 MPa;

[0150] Example 3 (PVA=4.0): Viscosity 238 mPa·s. Excessive PVA content leads to excessive chain segment entanglement, decreased fluidity, sphericity reduced to 0.90, and strength 405 MPa.

[0151] Cause analysis:

[0152] PVA is the main viscosity control factor. 3.5 parts PVA ensures sufficient adhesion while leaving room for PAA / DOM to play an interfacial regulation role; when PVA < 3.0, the coating is incomplete, and when PVA > 4.0, it hinders atomization uniformity.

[0153] Conclusion: In composite adhesives, the PVA mass ratio should ideally be controlled between 3.0 and 4.0 to achieve controllable viscosity and balanced particle coating.

[0154] 3. Effect of composite adhesive addition amount: 4% is the optimal value; too low or too high is unfavorable.

[0155] This variable was verified by comparing "Examples 1, 4, 5" with "Comparative Examples 3, 4" (the ratio was fixed at 3.5:0.6:0.4:0.4):

[0156] Example 1 (4%): Viscosity 225 mPa·s, sphericity 0.93, density 3.945 g / cm³, strength 426 MPa, best performance;

[0157] Example 4 (3%): viscosity 209 mPa·s, but the amount of binder was insufficient, the particles were not completely coated, sphericity 0.90, strength 402 MPa;

[0158] Example 5 (6%): viscosity 249 mPa·s, increased organic residue, slightly increased carbon defects during sintering, strength 418 MPa, slightly lower than Example 1;

[0159] Comparative Example 3 (1%): Viscosity 124 mPa·s (too low), due to the extremely low addition amount, the particles were not fully coated, sphericity 0.80, density 3.860 g / cm³, strength 330 MPa;

[0160] Comparative Example 4 (8%): ​​Viscosity 442 mPa·s > 300, difficult to atomize, and excessive organic matter leads to incomplete glue removal, density 3.895 g / cm³, strength 358 MPa.

[0161] Cause analysis:

[0162] Too little addition will result in incomplete coating; too much addition will lead to excessive viscosity, increased carbon residue, and hinder densification. 4% is the balance point for achieving complete coating and clean sintering.

[0163] Conclusion: The optimal amount of composite adhesive should be controlled between 3% and 6%, with 4% being the optimal value.

[0164] 4. The effect of PAA content: It needs to be maintained at around 0.4; too high or too low a level is unfavorable.

[0165] This variable was verified using examples 5 and 6:

[0166] Comparative Example 5 (PAA=1.2): Excessive carboxyl concentration caused local charge shielding, resulting in slight flocculation, with viscosity rising to 408 mPa·s, sphericity 0.83, and strength 382 MPa;

[0167] Comparative Example 6 (PAA=0.05): Insufficient adsorption sites, PVA-GA network cannot firmly anchor particles, granulated powder structure is loose, sphericity is 0.82, strength is 368MPa.

[0168] Cause analysis:

[0169] PAA (carboxyl groups) forms a strong chemical adsorption on the alumina surface, which is key to achieving a tight bond between alumina powder particles and the binder. However, excessive PAA will compromise electrostatic stability, while insufficient PAA will prevent effective anchoring.

[0170] Conclusion: The PAA mass ratio should be controlled at around 0.4 to achieve optimal interfacial bonding.

[0171] III. Summary: Optimal Process Parameters and Core Functional Principles

[0172] Optimal process parameters:

[0173] Adhesive type: PVA-GA-PAA-DOM quaternary composite system

[0174] Quality ratio: PVA:GA:PAA:DOM = 3.5:0.6:0.4:0.4

[0175] Amount added: 4% of the mass of alumina powder.

[0176] Slurry viscosity: 225 mPa·s (within the ideal range of 200~300 mPa·s)

[0177] Core operating principle:

[0178] Quaternary composite binders have a synergistic effect: PVA provides the skeleton, GA crosslinking enhances thermal stability, PAA achieves particle anchoring, and DOM imparts flexibility; none of the four can be omitted.

[0179] Slurry viscosity is a key indicator connecting the formulation and molding quality. Only by controlling it at 200~300 mPa·s can high sphericity granulated powder be obtained.

[0180] The sphericity of granulated powder is highly positively correlated with the final ceramic properties; a sphericity ≥ 0.90 is the basis for achieving high-density, high-strength ceramics.

[0181] This application successfully solves the problems of high brittleness, poor sphericity, and low strength of traditional single binders by precisely controlling the binder system, and realizes the preparation of high-performance ceramics with high solid content slurry (75%), which has good prospects for industrial application.

[0182] In summary, this application, through the design and optimization of the PVA-GA-PAA-DOM quaternary composite binder system, significantly improves the sphericity of granulated powder and the overall performance of ceramics while ensuring the slurry viscosity remains stable at 200~300 mPa·s. It breaks through the bottleneck of alumina ceramic forming and sintering quality in the prior art and has good practical value and industrial application prospects.

[0183] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0184] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0185] The steps of the methods or algorithms described in conjunction with the embodiments disclosed in this embodiment can be implemented directly using hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0186] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in these embodiments 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 disclosed herein.

Claims

1. An alumina ceramic slurry, characterized in that, The alumina ceramic slurry is obtained by ball milling a mixture of raw materials comprising the following parts by weight: 70-80 parts of alumina raw powder 20-30 parts deionized water A dispersant comprising 0.5% to 1% of the mass of the alumina powder. A composite binder comprising 3% to 6% of the alumina powder by weight. Plasticizer comprising 1% to 10% of the mass of alumina raw powder. A lubricant comprising 1% to 5% of the mass of the alumina powder. Defoamer in appropriate amount, in, The composite adhesive comprises polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate in a mass ratio of (2~4.5):(0.2~1.2):(0.1~0.6):(0.1~0.6).

2. The alumina ceramic slurry according to claim 1, characterized in that, In the composite adhesive, the mass ratio of polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate is 3.5:0.6:0.4:0.

4.

3. The alumina ceramic slurry according to claim 2, characterized in that, The amount of the composite binder added is 4% of the mass of the alumina powder.

4. The alumina ceramic slurry according to claim 1, characterized in that, The amount of dispersant added is 0.7% of the mass of the alumina powder.

5. The alumina ceramic slurry according to claim 1, characterized in that, The plasticizer is selected from one or more of polyethylene glycol, glycerol, and polyvinyl chloride.

6. The alumina ceramic slurry according to claim 5, characterized in that, The plasticizer is composed of polyethylene glycol and glycerol, wherein the amount of polyethylene glycol added is 3% of the mass of the alumina powder and the amount of glycerol added is 1% of the mass of the alumina powder.

7. The alumina ceramic slurry according to claim 1, characterized in that, The lubricant is selected from water-based paraffin wax and stearic acid emulsion.

8. The alumina ceramic slurry according to claim 7, characterized in that, The lubricant is a stearic acid emulsion, and the amount of lubricant added is 1.6% of the mass of the alumina powder.

9. A method for preparing the alumina ceramic slurry according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1, Preparation of composite adhesive: S11, weigh out polyvinyl alcohol, glutaraldehyde, polyacrylic acid and dioctyl maleate in proportion; S12, add the weighed polyvinyl alcohol to deionized water, heat to 80~90℃ and stir until completely dissolved to form a homogeneous solution to obtain the first solution, wherein the mass ratio of polyvinyl alcohol to water in the first solution is 1:4; S13, cool the first solution to 50~65℃, adjust the pH value to 3~5, add the weighed glutaraldehyde and stir for 30~60min to achieve cross-linking modification of polyvinyl alcohol, and obtain the second solution; S14, after cooling the second solution to room temperature, add the weighed polyacrylic acid and dioctyl maleate in sequence, continue stirring for 30-60 minutes, then seal and let stand for 3-5 hours to mature, defoam and stabilize the system to obtain the composite adhesive. S2, ball mill: S21, Weigh out alumina powder, deionized water and dispersant in proportion; S22, add the weighed deionized water to the ball mill jar, and add the weighed dispersant to the deionized water, and stir in the ball mill jar for 5~15 minutes; S23, add the weighed alumina raw powder into the ball mill jar and ball mill for 3-4 hours to obtain alumina slurry; S3, Pulping: S31, weigh out the composite adhesive, plasticizer and lubricant according to the proportion; S32, transfer the alumina slurry to the mixing tank; S33, the weighed composite binder, plasticizer and lubricant are added to the mixing tank in sequence, and the mixture is stirred for 20 to 40 minutes after the first additive is added before the next additive is added. S34. Based on the foaming situation on the slurry surface, add an appropriate amount of defoamer and continue stirring for 20-40 minutes until there are no bubbles on the slurry surface, thus obtaining the alumina ceramic slurry.

10. An alumina ceramic, characterized in that, It is prepared from the alumina ceramic slurry according to any one of claims 1-8.

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