Ceramic slurry, ceramic casting slurry, their preparation methods and applications

Abstract

This application provides a ceramic slurry, a ceramic casting slurry, a preparation method thereof, and its application. The ceramic slurry comprises aluminum nitride-coated particles and an organic solvent. The aluminum nitride-coated particles are uniformly dispersed in the organic solvent. The solid content of the ceramic slurry is 60-79 wt%, the D50 of the aluminum nitride-coated particles is 0.8-1.8 μm, and the viscosity of the ceramic slurry is 0-1000 cP. The aluminum nitride-coated particles include aluminum nitride particles and a dispersant adsorbed on the surface of the aluminum nitride particles. The mass ratio of the dispersant to the aluminum nitride particles is (0.1-0.6):100. The dispersant adsorbs on the surface of the aluminum nitride particles to form a stable adsorption layer, reducing the surface free energy of the aluminum nitride particles, weakening the van der Waals forces between the aluminum nitride particles, and effectively inhibiting secondary agglomeration between the aluminum nitride particles. This allows the ceramic slurry to maintain low viscosity even at high solid content, thereby giving the ceramic slurry good fluidity and meeting the requirements for casting to prepare ceramic green bodies.

Description

Technical Field

[0001] This application relates to the field of electronic ceramic materials, and more specifically, to a ceramic slurry, a ceramic casting slurry, a method for preparing the same, and its application. Background Technology

[0002] With the rapid development of electronic information technology, power electronics technology, and next-generation communication technologies, electronic devices are constantly evolving towards higher power density, higher integration, and higher reliability. The heat generated by electronic devices during operation is continuously increasing, placing higher demands on the thermal conductivity, dimensional stability, and reliability of packaging materials and heat dissipation substrates. Against this backdrop, ceramic materials with high thermal conductivity, excellent electrical insulation properties, and good thermal matching characteristics are gradually becoming an important development direction in the field of high-end electronic packaging.

[0003] Aluminum nitride (AlN) ceramics, due to their high thermal conductivity, good insulation, and thermal expansion coefficient matching that of silicon, have been widely used in power electronic packaging, LED substrates, and 5G communication devices. A high solid content is a crucial prerequisite for obtaining ceramic substrates with high thermal conductivity; however, increasing the solid content significantly reduces the fluidity and dispersion stability of the slurry. Therefore, obtaining AlN slurry with moderate viscosity and good fluidity under high solid content conditions is a key step in the tape casting process. Existing technologies, such as Chaozhou Sanhuan Company's "A Method for Preparing Aluminum Nitride Green Blanks by Tape Casting" (CN103121238A), improve the compactness of the green body through a conventional formulation of organic solvent-dispersant-plasticizer-binder. However, the dispersant system is mainly composed of a single resin / small molecule, with a solid content range of (35~52.5wt%), which is insufficient to meet the tape casting requirements of slurries with higher solid content. Furthermore, the method and application of "a preparation method and application of an insulating and highly thermally conductive aluminum nitride dispersion" (CN108084742A) achieves stable dispersion of nano-AlN in organic or resin systems through coupling agents and dispersing aids such as PVP. However, its working conditions are low solid content (1~50wt%) and low shear coating environment, focusing on organic modification of the powder surface, and it does not provide a solution / optimization for the poor rheological properties of high solid content slurries. Overall, although the above technologies have achieved certain results in solvent system selection, coupling agent modification, and application of conventional polymeric dispersants, they generally suffer from relatively simple dispersant system composition, insufficient optimization of dispersant types and ratios, and a lack of optimization for the rheological properties and dispersibility of high solid content AlN slurries. This results in slurry viscosity remaining high and insufficient fluidity when pursuing higher solid content, limiting the subsequent addition of binders and plasticizers and stable casting molding.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The main objective of this application is to provide a ceramic slurry, a ceramic casting slurry, a preparation method thereof, and an application thereof, in order to solve the problems of high viscosity, insufficient fluidity, and poor molding stability of high solids content AlN slurries in the prior art.

[0006] To achieve the above objectives, according to the first aspect of this application, a ceramic slurry is provided, comprising aluminum nitride coated particles and an organic solvent, wherein the aluminum nitride coated particles are uniformly dispersed in the organic solvent, the solid content of the ceramic slurry is 60wt%~79wt%, the D50 of the aluminum nitride coated particles is 0.8~1.8μm, and the viscosity of the ceramic slurry is 0~1000cP; wherein the aluminum nitride coated particles comprise aluminum nitride particles and a dispersant adsorbed on the surface of the aluminum nitride particles, and the mass ratio of the dispersant to the aluminum nitride particles is (0.1~0.6):100.

[0007] Furthermore, the dispersant is selected from at least one of polyvinylpyrrolidone, trioleic acid glyceride, and castor oil.

[0008] Furthermore, the dispersant is polyvinylpyrrolidone.

[0009] Furthermore, the organic solvent is selected from at least one of ethanol, isopropanol, n-butanol, and ethylene glycol monoethyl ether.

[0010] Furthermore, the organic solvent is a mixture of ethanol and isopropanol, with a mass ratio of (1~3):1.

[0011] To achieve the above objectives, according to a second aspect of this application, a method for preparing a ceramic slurry is provided, the method comprising: step S1, providing a dispersant and an organic solvent, and mixing the dispersant and the organic solvent to form a premix;

[0012] Step S2: Provide aluminum nitride powder, disperse the aluminum nitride powder in the premixed liquid to obtain ceramic slurry;

[0013] The definitions of dispersant and organic solvent are the same as those in the first aspect of this application.

[0014] Furthermore, the mass ratio of aluminum nitride powder to organic solvent is 3:(0.8~2).

[0015] Furthermore, the mass ratio of aluminum nitride powder to organic solvent is 3:(0.8~1.5).

[0016] Furthermore, the mass ratio of aluminum nitride powder to organic solvent is 3:(0.8~1).

[0017] Further, in step S1, the dispersant and organic solvent are mixed to form a premixed liquid by a first ball milling process, wherein the ball-to-material ratio of the first ball milling is (1~3):1, the first ball milling speed is 300~500 rpm, and the first ball milling time is 12~24 h.

[0018] Furthermore, in step S2, aluminum nitride powder is added to the premixed liquid in n portions for dispersion, where 1 ≤ n ≤ 4. When n ≥ 2, the time interval between two adjacent additions is 6 to 12 hours.

[0019] Furthermore, the time interval between two consecutive additions is 6 to 8 hours.

[0020] Further, in step S2, the aluminum nitride powder is dispersed into the premixed liquid by a second ball milling process, wherein the ball-to-material ratio of the second ball milling is (1~3):1, the rotation speed of the second ball milling is 300~500 rpm, and the second ball milling time is 6~24h.

[0021] To achieve the above objectives, according to a third aspect of this application, a ceramic casting slurry is provided, comprising a ceramic slurry and a binder and a plasticizer dispersed in the ceramic slurry, wherein the ceramic slurry is the ceramic slurry provided in the first aspect of this application or the ceramic slurry obtained by the preparation method provided in the second aspect of this application.

[0022] Furthermore, based on the mass of aluminum nitride powder, the amount of binder added is 3wt%~7wt%; the amount of plasticizer added is 3wt%~6wt%.

[0023] Furthermore, the adhesive is selected from at least one of polyvinyl butyral, polyvinyl alcohol (PVA), and polymethyl methacrylate (PMMA).

[0024] Furthermore, the plasticizer is selected from at least one of PEG2000, PEG400, PEG200, and dibutyl phthalate (DBP).

[0025] To achieve the above objectives, according to a fourth aspect of this application, a method for preparing a ceramic casting slurry is provided, the method comprising: dispersing a binder and a plasticizer in a ceramic slurry by a third ball mill to obtain a ceramic casting slurry.

[0026] Furthermore, the ball-to-material ratio of the third ball mill is (1~3):1, the rotation speed of the third ball mill is 300~500 rpm, and the milling time is 12~24h.

[0027] To achieve the above objectives, according to the fifth aspect of this application, the application of the ceramic slurry provided in the first aspect, the ceramic slurry obtained by the preparation method provided in the second aspect, the ceramic casting slurry provided in the third aspect, or the ceramic casting slurry obtained by the preparation method provided in the fourth aspect in the preparation of ceramic green bodies is provided.

[0028] By applying the technical solution of this application, in the ceramic slurry provided by this application, the dispersant is adsorbed on the surface of aluminum nitride particles to form a stable adsorption layer. This adsorption layer reduces the surface free energy of aluminum nitride particles and weakens the van der Waals attraction between aluminum nitride particles. On the other hand, it effectively inhibits the secondary agglomeration between aluminum nitride particles through steric hindrance and solvation effect, so that the ceramic slurry maintains a low viscosity of 0~1000cP under the high solid content of 60wt%~79wt%, thereby giving it good fluidity and meeting the requirements of ceramic slurry for the preparation of ceramic green bodies by tape casting. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 Photographs of ceramic slurries prepared according to Examples 1-3 and Comparative Example 3 of this application at different standing times are shown;

[0031] Figure 2 The particle size distribution diagrams of the ceramic slurries prepared according to Examples 1-3 and Comparative Example 3 of this application are shown.

[0032] Figure 3 A photograph of a ceramic green body prepared from a ceramic casting slurry according to Example 22 of this application is shown. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0034] As described in the background section of this application, existing high-solids-content AlN slurries suffer from problems such as high viscosity, insufficient fluidity, and poor molding stability. To address these issues, this application provides a ceramic slurry, a ceramic casting slurry, its preparation method, and its application.

[0035] In a first typical embodiment of this application, a ceramic slurry is provided, comprising aluminum nitride coated particles and an organic solvent. The aluminum nitride coated particles are uniformly dispersed in the organic solvent. The solid content of the ceramic slurry is 60wt%~79wt%, the D50 of the aluminum nitride coated particles is 0.8~1.8μm, and the viscosity of the ceramic slurry is 0~1000cP. The aluminum nitride coated particles comprise aluminum nitride particles and a dispersant adsorbed on the surface of the aluminum nitride particles, and the mass ratio of the dispersant to the aluminum nitride particles is (0.1~0.6):100.

[0036] In this application, the solid content of the ceramic slurry refers to (mass of aluminum nitride particles / total mass of ceramic slurry) × 100%.

[0037] In the ceramic slurry provided in this application, the dispersant is adsorbed on the surface of aluminum nitride particles to form a stable adsorption layer. This adsorption layer reduces the surface free energy of the aluminum nitride particles and weakens the van der Waals attraction between the aluminum nitride particles. On the other hand, it effectively inhibits the secondary agglomeration between aluminum nitride particles through steric hindrance and solvation effects, so that the ceramic slurry maintains a low viscosity of 0~1000 cP under high solid content conditions of 60wt%~79wt%, thereby giving it good fluidity and meeting the requirements of ceramic slurry for ceramic green body preparation by tape casting.

[0038] In this application, the amount of dispersant added has a significant impact on the dispersion effect and rheological properties. When the amount of dispersant added is too low, the dispersant molecules are insufficient to completely cover the surface of aluminum nitride particles, and there is still a strong van der Waals attraction between the particles, which easily forms an agglomeration structure, resulting in increased slurry viscosity and poor rheological properties, especially when the solid content is high. When the amount of dispersant added is too high, the excess dispersant molecules will exist in the slurry in a free state. On the one hand, this will increase the volume fraction of organic components in the system, leading to an increase in the overall viscosity of the slurry. On the other hand, the excess dispersant may cause intermolecular entanglement or form a "soft bridging" structure between particles, which will weaken the dispersion effect and reduce the rheological stability of the slurry.

[0039] Specifically, the solid content of the ceramic slurry is any value or a range between any two of the following: 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%; the D50 of the aluminum nitride coated particles is 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1... The viscosity of the ceramic slurry is any value or a range between any two of the following: 0.4μm, 1.5μm, 1.6μm, 1.7μm, and 1.8μm; the viscosity of the ceramic slurry is any value or a range between any two of the following: 0cP, 10cP, 20cP, 50cP, 100cP, 200cP, 500cP, 800cP, and 1000cP; the mass ratio of the dispersant to the aluminum nitride particles is any value or a range between any two of the following: 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, and 0.6:100.

[0040] In some specific embodiments, the dispersant is selected from any one or a mixture of polyvinylpyrrolidone (PVP), trioleic acid glyceride and castor oil. Since polyvinylpyrrolidone has a lower viscosity and better flowability, polyvinylpyrrolidone (PVP) is preferred as the dispersant.

[0041] In some embodiments, the organic solvent is selected from any one or more of ethanol, isopropanol, n-butanol, and ethylene glycol monoethyl ether, preferably a mixture of ethanol and isopropanol, with a mass ratio of (1~3):1, to further improve the dispersion stability of aluminum nitride-coated particles in the slurry. Specifically, the mass ratio of ethanol to isopropanol is any value from 1:1, 2:1, 3:1, or any range between the two.

[0042] In a second typical embodiment of this application, a method for preparing a ceramic slurry is provided, the method comprising: step S1, providing a dispersant and an organic solvent, and mixing the dispersant and the organic solvent to form a premixed liquid; step S2, providing aluminum nitride powder, and dispersing the aluminum nitride powder into the premixed liquid to obtain a ceramic slurry; wherein the dispersant and the organic solvent are the same as those in the first typical embodiment.

[0043] In this application, a dispersant and an organic solvent are first premixed to form a uniform premix, and then aluminum nitride powder is added to the premix for dispersion. This allows the dispersant to adsorb onto the surface of the aluminum nitride particles, forming aluminum nitride-coated particles. The aluminum nitride-coated particles are uniformly and stably dispersed in the organic solvent, thereby effectively improving the dispersion state of the aluminum nitride particles under conditions of high solid content, reducing slurry viscosity, and improving rheological properties. Furthermore, the full adsorption and stable coverage of the dispersant on the surface of the aluminum nitride particles prevents agglomeration between the aluminum nitride particles, laying the foundation for the subsequent preparation of aluminum nitride ceramic green bodies with uniform surface and complete structure.

[0044] It should be noted that after aluminum nitride powder is added to the premixed liquid, the aluminum nitride powder is dispersed in the premixed liquid in the form of aluminum nitride particles.

[0045] To further ensure a more uniform dispersion of the dispersant and aluminum nitride powder, in some embodiments, the mass ratio of aluminum nitride powder to organic solvent is 3:(0.8~2). Specifically, the mass ratio of aluminum nitride powder to organic solvent is any value from 3:0.8, 3:1, 3:1.5, 3:2, or any value in between.

[0046] In some embodiments, in step S1, the dispersant and organic solvent are mixed by a first ball mill to form a premixed liquid, wherein the ball-to-material ratio of the first ball mill is (1~3):1, the first ball milling speed is 300~500 rpm, and the first ball milling time is 12~24 h. In this application, the dispersant and organic solvent are mixed by a first ball milling under the conditions of a ball-to-material ratio of (1~3):1, a speed of 300~500 rpm, and a time of 12~24 h, which further improves the dissolution rate and molecular-level dispersion uniformity of the dispersant in the organic solvent, thereby avoiding the phenomenon of local aggregation or incomplete activation of the dispersant due to insufficient mixing; the premixed liquid serves as the basic environment for the subsequent dispersion of aluminum nitride powder, and its highly uniform stability ensures that the aluminum nitride powder can be efficiently adsorbed and uniformly coated during the step-by-step addition process, effectively inhibiting the formation of agglomerates, thereby laying a key foundation for the rheological properties and long-term stability of the entire slurry system, which is conducive to achieving the consistency and forming quality of the ceramic slurry in the subsequent casting molding process. Specifically, the ball-to-material ratio of the first ball mill is any value of 1:1, 2:1, 3:1, or any range between two of them; the rotational speed of the first ball mill is any value of 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, or any range between two of them; and the milling time is any value of 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any range between two of them.

[0047] In some embodiments, in step S2, aluminum nitride powder is added to the premixed liquid in n portions for dispersion, where 1 ≤ n ≤ 4. When n ≥ 2, the time interval between two adjacent additions is 6 to 12 hours, preferably 6 to 8 hours. By gradually adding aluminum nitride powder to the premixed liquid in 1 to 4 portions, with a time interval of 6 to 12 hours between each addition, preferably 6 to 8 hours, the local concentration of aluminum nitride powder that would result from a single addition and instantaneous agglomeration can be effectively avoided. Furthermore, the phased and delayed addition method ensures that each newly added aluminum nitride powder can fully contact the dispersant in the premixed liquid, allowing sufficient time for the dispersant molecules to complete directional adsorption and stable encapsulation on the powder surface, further improving the uniformity and stability of aluminum nitride powder dispersion, thereby effectively suppressing viscosity fluctuations and sedimentation tendencies in the ceramic slurry. Compared to adding all at once, phased addition can further reduce the local instantaneous solid content. To avoid large-scale direct contact and rapid agglomeration of aluminum nitride powder upon addition, the dispersant has sufficient time and space to participate in the powder surface adsorption process. With the successive addition of aluminum nitride powder, the system forms a dispersion structure dominated by single particles or soft agglomerates, rather than hard agglomerates that are difficult to disperse. This dispersion structure still has a certain degree of rearrangement under high solid content conditions. Under external shearing, it can undergo interparticle slippage and rearrangement, thereby significantly reducing the yield stress and apparent viscosity of the ceramic slurry, changing the overall fluidity, and making the prepared ceramic slurry have excellent rheological properties and long-term stability, laying a good foundation for the repeatability and consistency of subsequent molding processes.

[0048] Specifically, n is any value among 1, 2, 3, and 4; the time interval between two consecutive additions is any value among 6h, 7h, 8h, 9h, 10h, 11h, and 12h, or any range between two of them.

[0049] In some embodiments, in step S2, aluminum nitride powder is dispersed into the premixed liquid by a second ball milling process. The ball-to-powder ratio of the second ball milling is (1~3):1, the milling speed is 300~500 rpm, and the milling time is 6~24 h. In this application, dispersing aluminum nitride into the premixed liquid by a second ball milling process allows the aluminum nitride powder to be subjected to appropriate mechanical shearing and impact energy interactions in the premixed liquid. This further breaks down the strong van der Waals forces and surface adsorption agglomeration between powder particles, achieving uniform dispersion at high solid content. This further improves the uniformity and stability of the slurry, thereby improving rheological properties and providing a ceramic slurry with lower viscosity and higher stability for subsequent casting processes. Specifically, the ball-to-material ratio of the second ball mill is any value of 1:1, 2:1, 3:1, or any range between two; the rotational speed of the second ball mill is any value of 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, 500 rpm, or any range between two; and the milling time is any value of 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any range between two.

[0050] In some embodiments, the particle size D50 of the aluminum nitride powder is 3.2~3.5μm. The second ball milling process further refines and disperses the aluminum nitride powder in the premixed liquid, ensuring that the refined aluminum nitride particles are uniformly dispersed in the ceramic slurry. Specifically, the particle size D50 of the aluminum nitride powder is any value from 3.2μm, 3.3μm, 3.4μm, and 3.5μm, or a range between any two.

[0051] In a third typical embodiment of this application, a ceramic casting slurry is provided, which includes a ceramic slurry and a binder and a plasticizer dispersed in the ceramic slurry, wherein the ceramic slurry is the ceramic slurry provided in the first typical embodiment or the ceramic slurry prepared in the second typical embodiment.

[0052] In this application, the solid content of ceramic casting slurry refers to (mass of aluminum nitride particles / total mass of ceramic casting slurry) × 100%.

[0053] The ceramic casting slurry provided in this application uses the ceramic slurry obtained by the aforementioned preparation method as the base system, ensuring that the aluminum nitride particles have achieved sufficient and stable surface coating in the organic solvent. The uniform adsorption of the dispersant on the surface of the aluminum nitride particles effectively inhibits the agglomeration between particles under high solid content conditions, allowing the binder and plasticizer to be uniformly dispersed in the ceramic slurry during subsequent introduction without causing a sudden increase in viscosity or phase separation, thereby significantly improving the rheological stability and forming uniformity of the ceramic casting slurry. This ceramic casting slurry does not require additional adjustment of the dispersion state before casting, and exhibits excellent fluidity and coating consistency during casting. The resulting green body has uniform thickness, a smooth surface, and is free of cracks or orange peel defects, providing a good structural foundation for subsequent high-temperature sintering. It is suitable for the large-scale preparation of high thermal conductivity aluminum nitride ceramic substrates.

[0054] In some embodiments, based on the mass of aluminum nitride powder, the amount of binder added is 3wt% to 7wt%; the amount of plasticizer added is 3wt% to 6wt%. Appropriate amounts of binder and plasticizer can ensure the mechanical strength and flexibility required for green body forming, while avoiding problems such as casting difficulties and forming defects caused by excessive viscosity. Specifically, the amount of binder added is any value from 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, or any range between two; the amount of plasticizer added is any value from 3wt%, 4wt%, 5wt%, 6wt%, or any range between two.

[0055] In some preferred embodiments, the adhesive is selected from one or more of polyvinyl butyral, polyvinyl alcohol (PVA), and polymethyl methacrylate (PMMA).

[0056] In some preferred embodiments, the plasticizer is selected from any one or more of PEG2000 (polyethylene glycol, molecular weight 2000), PEG400 (polyethylene glycol, molecular weight 400), PEG200 (polyethylene glycol, molecular weight 200), and dibutyl phthalate (DBP).

[0057] In some embodiments of this application, the method for preparing ceramic casting slurry includes: first adding a binder and a plasticizer to a casting solvent, stirring and mixing to obtain a slurry, and then adding the slurry to a ceramic slurry and passing it through a third ball mill to obtain a ceramic casting slurry.

[0058] The specific type of casting solvent is not limited, and any organic solvent capable of effectively dispersing the binder and plasticizer is acceptable. To further improve the dispersion efficiency of the binder and plasticizer and facilitate mixing with the ceramic slurry, a mixed solvent of ethanol and isopropanol in a mass ratio of 2:1 is preferred as the casting solvent.

[0059] The ceramic casting slurry preparation method provided in this application allows for the introduction of binders and plasticizers into high-solids ceramic slurries, and the preparation of ceramic casting slurries with excellent flowability can be achieved without adjusting the dispersion state through other steps. This provides a good structural basis for the subsequent preparation of ceramic green bodies and is suitable for the large-scale preparation of ceramic green bodies.

[0060] In some embodiments, the ball-to-material ratio of the third ball mill is (1~3):1, the rotation speed of the third ball mill is 300~500 rpm, and the milling time is 12~24 h. Dispersing the binder and plasticizer into the ceramic slurry via third ball milling allows them to be subjected to appropriate mechanical shear and impact energy interactions, further promoting uniform dispersion of the binder and plasticizer in the ceramic slurry. This further improves the uniformity and stability of the ceramic casting slurry, thereby improving its rheological properties and providing a high-quality ceramic slurry with low viscosity, high stability, and no sedimentation for subsequent casting processes. Specifically, the ball-to-material ratio of the third ball mill is any value of 1:1, 2:1, or 3:1, or a range between any two; the rotational speed of the third ball mill is any value of 300 rpm, 320 rpm, 340 rpm, 360 rpm, 380 rpm, 400 rpm, 420 rpm, 440 rpm, 460 rpm, 480 rpm, or 500 rpm, or a range between any two; and the milling time is any value of 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, or 24 h, or a range between any two.

[0061] In the fifth typical embodiment of this application, the ceramic slurry provided in the first typical embodiment, the ceramic slurry prepared by the method of preparing the ceramic slurry provided in the second typical embodiment, the ceramic casting slurry provided in the third typical embodiment, or the ceramic casting slurry prepared by the method of preparing the ceramic casting slurry provided in the fourth typical embodiment are used in the preparation of ceramic green bodies.

[0062] In some embodiments, ceramic green bodies are prepared by vacuum degassing, sieving, and casting. The vacuum degassing time is 30-90 min, the sieving process involves filtering through a 150-250 mesh sieve, the casting rate is 0.05 m / s-0.1 m / s, and the scraper height is 300-500 μm. Appropriate vacuum degassing time, sieving, casting rate, and scraper height can further improve the density uniformity and surface quality of the ceramic green body. Vacuum degassing further removes air bubbles introduced into the ceramic slurry or casting slurry due to agitation, improving surface smoothness, optimizing rheological properties, and reducing defects such as cracking and deformation during subsequent drying. Sieving removes agglomerates and coarse particles, ensuring a more uniform particle distribution in the ceramic slurry or casting slurry and preventing stress concentration or density differences during subsequent forming. Controlling the casting rate allows for the preparation of the required ceramic substrate thickness, facilitating continuous and large-scale production, ensuring product consistency and production efficiency.

[0063] Specifically, the vacuum degassing time is any value or a range between 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, and 90 min; the sieve mesh for sieving is any value or a range between 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh, 200 mesh, 210 mesh, 220 mesh, 230 mesh, 240 mesh, and 250 mesh; the casting speed... The rate is any value among 0.05 m / s, 0.06 m / s, 0.07 m / s, 0.08 m / s, 0.09 m / s, and 0.1 m / s, or any value between any two; the scraper height is any value among 300 μm, 320 μm, 340 μm, 360 μm, 380 μm, 400 μm, 420 μm, 440 μm, 460 μm, 480 μm, and 500 μm, or any value between any two.

[0064] To further improve the rate of preparing ceramic green bodies after the above-mentioned vacuum degassing, sieving, and casting processes, in some embodiments, the casting process further includes a drying process. The lower heating temperature of the drying process is 40~80°C, and the upper heating temperature of the drying process is 40~80°C. Specifically, the lower heating temperature of the drying process is any value or a range between any two of 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and 80°C; the upper heating temperature of the drying process is any value or a range between any two of 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, and 80°C.

[0065] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0066] Example 1

[0067] This embodiment provides a ceramic slurry, the preparation method of which includes the following steps:

[0068] (1) Based on the mass of aluminum nitride powder, weigh 0.6 wt% of polyvinylpyrrolidone (PVP) dispersant, and weigh the organic solvent according to the mass ratio of aluminum nitride powder to organic solvent of 3:2. Mix the dispersant and organic solvent and then perform a first ball milling to obtain a premixed liquid. The organic solvent is a mixture of ethanol and isopropanol, with a mass ratio of ethanol to isopropanol of 2:1. The ball-to-material ratio of the first ball mill is 3:1, the first ball milling speed is 300 rpm, and the first ball milling time is 24 h.

[0069] (2) Aluminum nitride powder is added to the premixed liquid in one go for a second ball milling process to obtain ceramic slurry. The ball-to-powder ratio of the second ball mill is 3:1, the ball milling speed is 300 rpm, and the ball milling time is 24 h.

[0070] Example 2

[0071] The difference between this embodiment and Example 1 is that the dispersant in step (1) is trioleic acid glyceride.

[0072] Example 3

[0073] The difference between this embodiment and embodiment 1 is that the dispersant in step (1) is castor oil.

[0074] Example 4

[0075] Compared with Example 1, the difference in this embodiment is that in the adjustment step (1), the organic solvent is weighed according to the mass ratio of aluminum nitride powder to organic solvent of 2:1, the ball-to-material ratio of the first ball mill is 1:1, the rotation speed of the first ball mill is 500 rpm, and the time of the first ball mill is 12h.

[0076] Example 5

[0077] The difference between this embodiment and embodiment 1 is that, in step (1), the organic solvent is weighed according to the mass ratio of aluminum nitride powder to organic solvent of 3:0.8.

[0078] Example 6

[0079] The difference between this embodiment and embodiment 1 is that in step (1), the organic solvent is weighed according to the mass ratio of aluminum nitride powder to organic solvent of 3:1, and the amount of polyvinylpyrrolidone (PVP) dispersant added is 0.1wt.

[0080] Example 7

[0081] The difference between this embodiment and embodiment 6 is that the amount of polyvinylpyrrolidone (PVP) dispersant added in step (1) is adjusted to 0.3 wt%.

[0082] Example 8

[0083] The difference between this embodiment and embodiment 7 is that step (2) is adjusted, and aluminum nitride powder is added to the premixed liquid in two separate additions, with a time interval of 12 hours between the two additions, and the total time for the second ball milling is 24 hours.

[0084] Example 9

[0085] The difference between this embodiment and embodiment 7 is that step (2) is adjusted, and aluminum nitride powder is added to the premixed liquid in three parts, with an 8-hour interval between the three additions, and the total time for the second ball milling is 24 hours.

[0086] Example 10

[0087] The difference between this embodiment and embodiment 7 is that in step (2), aluminum nitride powder is added to the premixed liquid in four batches, and the time interval between the four additions is 6 hours, and the total time of the second ball milling is 24 hours.

[0088] Example 11

[0089] The difference between this embodiment and embodiment 8 is that in step (1), the mass ratio of ethanol to isopropanol is 1:1.

[0090] Example 12

[0091] The difference between this embodiment and embodiment 8 is that in step (1), the mass ratio of ethanol to isopropanol is 3:1.

[0092] Example 13

[0093] The difference between this embodiment and embodiment 8 is that in step (1), the mass ratio of ethanol to isopropanol is 5:1.

[0094] Example 14

[0095] The difference between this embodiment and embodiment 8 is that in step (1), the mass ratio of ethanol to isopropanol is 1:2.

[0096] Example 15

[0097] The difference between this embodiment and embodiment 8 is that in step (1), only ethanol is used as the organic solvent.

[0098] Example 16

[0099] The difference between this embodiment and embodiment 8 is that the organic solvent in step (1) is adjusted to be a mixture of ethanol and diethyl ether.

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 1 is that, in step (1), the amount of polyvinylpyrrolidone (PVP) dispersant added is 0.05 wt% based on the mass of aluminum nitride powder.

[0102] Comparative Example 2

[0103] The difference between this comparative example and Example 1 is that, in step (1), the amount of polyvinylpyrrolidone (PVP) dispersant added is 2wt% based on the mass of aluminum nitride powder.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 1 is that the dispersant in step (1) is adjusted to be oleic acid.

[0106] Comparative Example 4

[0107] The difference between this comparative example and Example 8 is that the amount of organic solvent in step (1) is adjusted, and the organic solvent is weighed according to the mass ratio of aluminum nitride powder to organic solvent of 1:1.

[0108] Comparative Example 5

[0109] The difference between this comparative example and Example 8 is that the amount of organic solvent in step (1) is adjusted, and the organic solvent is weighed according to the mass ratio of aluminum nitride powder to organic solvent of 6:1.

[0110] Comparative Example 6

[0111] The difference between this comparative example and Example 8 is that the premixed liquid in step (1) was not prepared. Instead, the polyvinylpyrrolidone (PVP) dispersant, aluminum nitride powder and organic solvent were directly mixed and subjected to a first ball milling process to obtain a ceramic slurry.

[0112] Comparative Example 7

[0113] Compared with Example 8, this comparative example adjusts the step (2) by adding aluminum nitride powder into the premixed liquid in five batches, with a time interval of 6 hours between the five additions, and the total time of the second ball milling is 30 hours.

[0114] Experimental Example 1

[0115] The particle size of aluminum nitride coated particles and the viscosity of ceramic slurries prepared in Examples 1-16 and Comparative Examples 1-7 were tested.

[0116] The specific testing method is as follows:

[0117] (1) The test conditions for aluminum nitride coated particle size testing are as follows: the aluminum nitride coated particle size test is carried out by laser particle size analysis at room temperature. Before the test, the sample is appropriately ultrasonically stirred and dispersed in an ethanol solvent system to avoid particle agglomeration. During the test, the wet test mode is used and carried out at room temperature. The results are characterized by the average particle size in the form of volume distribution.

[0118] (2) The viscosity test conditions are as follows: The viscosity test of the slurry is carried out at room temperature. A rotational viscometer is used to measure the viscosity of the slurry at a rotation speed of 100 rpm.

[0119] The test results are shown in Table 1.

[0120] Table 1

[0121]

[0122] Note: (1) The solid content of ceramic slurry refers to (mass of aluminum nitride particles / total mass of ceramic slurry) × 100%;

[0123] (2) In Comparative Examples 3 and 5-6, “-” indicates that the slurry is too viscous to be tested.

[0124] Figure 1 These are photographs of ceramic slurries prepared in Examples 1-3 and Comparative Example 3 of this application at different standing times. Figure 1 In the figure, (a) is the initial photo of the above four ceramic slurries, (b) is the photo of the above four ceramic slurries after standing for 24 hours, and (c) is the photo of the above four ceramic slurries after standing for 48 hours. Figure 1 In the diagram, tube A contains the ceramic slurry prepared in Example 1, tube B contains the ceramic slurry prepared in Example 2, tube C contains the ceramic slurry prepared in Comparative Example 3, and tube D contains the ceramic slurry prepared in Example 3. Figure 1 It can be seen that the ceramic slurry with polyvinylpyrrolidone (PVP) dispersant in Example 1 (tube A) showed no significant sedimentation after standing for 24 and 48 hours; while the ceramic slurry with trioleic acid glyceride dispersant in Example 2 (tube B) showed relatively significant sedimentation after standing for 24 hours, and even more significant sedimentation after standing for 48 hours; the ceramic slurry with oleic acid dispersant in Comparative Example 3 (tube C) showed no significant sedimentation after standing for 24 hours due to the slurry being too viscous, and only showed partial sedimentation after standing for 48 hours; the ceramic slurry with castor oil dispersant in Example 3 (tube D) showed no significant sedimentation after standing for 24 hours, and only showed partial sedimentation after standing for 48 hours. Therefore, the ceramic slurry provided by Example 1, which uses polyvinylpyrrolidone (PVP) as a dispersant, has the best dispersion effect.

[0125] Figure 2 The images show the particle size distribution of aluminum nitride-coated particles in the ceramic slurries prepared in Examples 1-3 and Comparative Example 3 of this application. Figure 2 In the figure, (a), (b), (c), and (d) are particle size distribution diagrams of aluminum nitride coated particles in the ceramic slurries prepared in Example 1, Comparative Example 3, Example 2, and Example 3, respectively. Figure 2 It can be seen that the D50 of the aluminum nitride coated particles in Examples 1-3 is all in the range of 0.8~1.8 μm. The D50 of the aluminum nitride coated particles in the ceramic slurry prepared in Comparative Example 3 is 2.74 μm. It can be seen that the D50 of the aluminum nitride coated particles in the ceramic slurry prepared by adding oleic acid as a dispersant is larger than that when polyvinylpyrrolidone, trioleic acid glyceride, and castor oil are used as dispersants. The larger particle size of the aluminum nitride coated particles will lead to a decrease in the packing density of the green body. During the debinding process, after the organic matter is removed, the particles are difficult to rearrange effectively, and the pores cannot be further contracted by the filling of fine particles. This results in residual pores inside the green body after debinding, making densification difficult and affecting the structural integrity in the subsequent sintering process.

[0126] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0127] As can be seen from Examples 1-16 and Comparative Examples 1-7, the ceramic slurry prepared in Examples 1-16 has better dispersibility under high solid content conditions and has suitable viscosity and flowability compared to the ceramic slurry prepared in Comparative Examples 1-7. In contrast, the ceramic slurry prepared in Comparative Examples 1-7 has poor dispersibility and viscosity that is too high or too low, which is not conducive to its subsequent application in ceramic green bodies.

[0128] Comparing Examples 1-3 with Comparative Example 3, it can be seen that when polyvinylpyrrolidone is used as the dispersant, the aluminum nitride coated particles in the prepared ceramic slurry have a smaller particle size, better dispersibility, and lower viscosity. This is because polyvinylpyrrolidone, as a polymeric dispersant, can preferentially adsorb onto the surface of aluminum nitride powder. Through physical adsorption or weak chemical interaction between the polar groups and the nitrides on the powder surface, a stable adsorption layer is formed on the particle surface. In Comparative Example 3, the ceramic slurry prepared using oleic acid as the dispersant has a high viscosity after the addition of oleic acid, and its fluidity is almost unmeasurable. The ceramic slurries prepared in Examples 2-3 with glyceryl triglyceride and castor oil as dispersants have poorer fluidity than those in Example 1.

[0129] Comparing Examples 1, 6-7, and Comparative Examples 1-2, it is evident that ceramic slurries prepared with a dispersant addition amount ranging from 0.1% to 0.6 wt% exhibit excellent dispersibility and flowability under high solids content conditions. This is because when the dispersant addition amount is too low, the dispersant molecules are insufficient to completely cover the surface of the aluminum nitride powder, and strong van der Waals forces and surface attraction still exist between particles, forming an agglomerate structure, resulting in high slurry viscosity and poor flowability. Conversely, when the dispersant addition amount is too high, the viscosity increases. This is because excessive dispersant exists in a free state in the system, easily causing entanglement between dispersants or forming "soft bridging" structures between particles. Therefore, within a suitable range, the dispersant addition amount can achieve good dispersibility and flowability under high solids content conditions.

[0130] Comparing Examples 1, 8-10, and Comparative Example 7, it is evident that the ceramic slurry prepared by adding aluminum nitride powder multiple times exhibits better dispersibility, maintaining low viscosity and good flowability. Within a reasonable range of multiple additions, the powder is fully dissolved under the action of the dispersant, maintaining a relatively uniform particle size distribution. Multiple additions are beneficial for achieving a stable dispersion. However, excessive additions, while further reducing particle size, result in a significantly increased specific surface area. The insufficient surface area covered by a unit of dispersant can lead to secondary contact between particles, causing a decrease in system stability. Therefore, the multiple additions of aluminum nitride powder should be within a reasonable range to better promote the dispersibility and stability of the ceramic slurry.

[0131] As can be seen from Examples 1-16 and Comparative Example 6, mixing the dispersant in an organic solvent to obtain a premix before adding aluminum nitride powder results in a ceramic slurry with superior dispersibility and flowability. In Comparative Example 6, the dispersant, organic solvent, and aluminum nitride powder were mixed in one step. The aluminum nitride powder was prone to severe agglomeration in the initial stage of mixing, and even under the same ball milling conditions, it was difficult to disperse it sufficiently, leading to increased viscosity and poor flowability of the ceramic slurry. Therefore, mixing the dispersant in an organic solvent to obtain a premix before adding aluminum nitride powder is beneficial for obtaining a ceramic slurry with more stable flowability under high solid content conditions.

[0132] Comparing Examples 1, 4-6, 11-16, and Comparative Examples 4-5, it can be seen that the amount of organic solvent added directly affects the solid content. Adjusting the amount of organic solvent added within a suitable range is necessary to prepare ceramic slurries with a high solid content. Furthermore, the organic solvent is a mixture of ethanol and isopropanol, and a suitable mass ratio between the two is beneficial for further dispersion of the ceramic slurry. Ceramic slurries prepared using mixed solvents other than ethanol and isopropanol or using a single solvent have poor dispersibility and flowability.

[0133] Example 17

[0134] This embodiment provides a ceramic casting slurry, which is prepared according to the following steps:

[0135] (1) Preparation of adhesive solution: Based on the mass of aluminum nitride powder, weigh 16wt% of casting solvent, 6wt% of polyvinyl butyral (PVB) binder and 4wt% of PEG2000 plasticizer, add the binder and plasticizer to the casting solvent, stir and mix for 30min to obtain adhesive solution; wherein, the casting solvent is a mixture of ethanol and isopropanol in a mass ratio of 2:1;

[0136] (2) Preparation of ceramic casting slurry: The above-mentioned adhesive liquid was added to the ceramic slurry prepared in Example 1 and ball milled for the third time to obtain ceramic casting slurry. The ball-to-material ratio of the third ball mill was 3:1, the rotation speed of the third ball mill was 300 rpm, and the ball milling time was 24 h.

[0137] Examples 18-32

[0138] Examples 18-32 each provide a ceramic casting slurry, which differs from Example 17 in that the ceramic slurry provided in Examples 2-16 is used to replace the ceramic slurry provided in Example 1.

[0139] Example 33

[0140] The difference between this embodiment and Example 24 is that the amount of polyvinyl butyral (PVB) added is adjusted to 7wt%, and the amount of PEG2000 added is adjusted to 3wt%.

[0141] Example 34

[0142] The difference between this embodiment and Example 24 is that the amount of polyvinyl butyral (PVB) added is adjusted to 3 wt%, and the amount of PEG2000 added is adjusted to 6 wt%.

[0143] Example 35

[0144] The difference between this embodiment and Example 24 is that the amount of polyvinyl butyral (PVB) added is adjusted to 12wt%, and the amount of PEG2000 added is adjusted to 10wt%.

[0145] Experimental Example 2

[0146] The particle size and viscosity of the ceramic casting slurries prepared in Examples 17-35 were tested. The particle size and viscosity were tested using the same methods as in Example 1, and the results are shown in Table 2.

[0147] Table 2

[0148]

[0149] Note: (1) The solid content of ceramic casting slurry refers to (mass of aluminum nitride particles / total mass of ceramic casting slurry) × 100%; (2) In Example 35, "-" indicates that the casting slurry is too viscous to be tested.

[0150] As shown in Table 2, comparing Examples 17-34 with Example 35, the ceramic casting slurries prepared in Examples 17-34 have moderate viscosity, meeting the requirements for slurry in the casting process for preparing ceramic green bodies. When the amount of binder or plasticizer added is too high or too low, the slurry viscosity deviates from the reasonable process range, resulting in excessively high or low viscosity. This increases the difficulty of subsequent degassing, filtration, and casting operations, hindering stable slurry processing and process control, and consequently, making the casting process for ceramic green bodies unsuitable.

[0151] Experimental Example 3

[0152] The ceramic casting slurry provided in Example 24 was sequentially subjected to vacuum degassing, sieving, casting, and drying to obtain a ceramic green body (e.g., ...). Figure 3 As shown in the figure, the vacuum degassing time is 30 minutes. After degassing, the material is filtered through a 200-mesh sieve, followed by casting. The casting rate is controlled at 0.05 m / s, the scraper height is 300 μm, and during the drying process, the heating temperature of both the upper and lower surfaces is controlled at 60℃. Figure 3 It can be seen that the prepared ceramic green body has a smooth surface and a complete structure.

[0153] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A ceramic slurry, characterized in that, The ceramic slurry comprises aluminum nitride coated particles and an organic solvent. The aluminum nitride coated particles are uniformly dispersed in the organic solvent. The solid content of the ceramic slurry is 60wt%~79wt%, the D50 of the aluminum nitride coated particles is 0.8~1.8μm, and the viscosity of the ceramic slurry is 0~1000cP. The aluminum nitride coated particles comprise aluminum nitride particles and a dispersant adsorbed on the surface of the aluminum nitride particles, and the mass ratio of the dispersant to the aluminum nitride particles is (0.1~0.6):

100.

2. The ceramic slurry according to claim 1, characterized in that, The dispersant is selected from at least one of polyvinylpyrrolidone, trioleic acid glyceride and castor oil; And / or, the dispersant is polyvinylpyrrolidone; And / or, the organic solvent is selected from at least one of ethanol, isopropanol, n-butanol, and ethylene glycol monoethyl ether; And / or, the organic solvent is a mixture of ethanol and isopropanol, and the mass ratio of the two is (1~3):

1.

3. A method for preparing a ceramic slurry, characterized in that, The preparation method includes: Step S1: Provide a dispersant and an organic solvent, and mix the dispersant and the organic solvent to form a premix; Step S2: Provide aluminum nitride powder, disperse the aluminum nitride powder in the premixed liquid, and obtain the ceramic slurry; The dispersant and the organic solvent are defined as in claim 1 or 2.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the aluminum nitride powder to the organic solvent is 3:(0.8~2), preferably 3:(0.8~1.5).

5. The preparation method according to claim 3, characterized in that, In step S1, the dispersant and the organic solvent are mixed by a first ball mill to form the premixed liquid, wherein the ball-to-material ratio of the first ball mill is (1~3):1, the first ball mill speed is 300~500 rpm, and the first ball milling time is 12~24 h.

6. The preparation method according to any one of claims 3 to 5, characterized in that, In step S2, the aluminum nitride powder is added to the premixed liquid in n portions for dispersion, where 1 ≤ n ≤ 4. When n ≥ 2, the time interval between two adjacent additions is 6 to 12 hours, preferably 6 to 8 hours. And / or, in step S2, the aluminum nitride powder is dispersed into the premixed liquid by a second ball milling process, wherein the ball-to-material ratio of the second ball milling process is (1~3):1, the rotation speed of the second ball milling process is 300~500 rpm, and the ball milling time is 6~24 h.

7. A ceramic casting slurry, characterized in that, The ceramic casting slurry includes a ceramic slurry and a binder and a plasticizer dispersed in the ceramic slurry, wherein the ceramic slurry is the ceramic slurry according to claim 1 or 2 or the ceramic slurry obtained by the preparation method according to any one of claims 3 to 6.

8. The ceramic casting slurry according to claim 7, characterized in that, Based on the mass of the aluminum nitride powder, the amount of binder added is 3wt%~7wt%; the amount of plasticizer added is 3wt%~6wt%; And / or, the adhesive is selected from at least one of polyvinyl butyral, polyvinyl alcohol, and polymethyl methacrylate; And / or, the plasticizer is selected from at least one of PEG2000, PEG400, PEG200, and dibutyl phthalate.

9. A method for preparing the ceramic casting slurry according to claim 7 or 8, characterized in that, The preparation method includes: dispersing the binder and the plasticizer in the ceramic slurry through a third ball mill to obtain the ceramic casting slurry.

10. The application of the ceramic slurry according to claim 1 or 2, the ceramic slurry obtained by the preparation method according to any one of claims 3 to 6, the ceramic casting slurry according to claim 7 or 8, or the ceramic casting slurry obtained by the preparation method according to claim 9 in the preparation of ceramic green bodies.

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