Zirconium oxide slurry with high solid content as well as preparation process and application of zirconium oxide slurry

Abstract

The invention provides high-solid-content zirconium oxide slurry which comprises the following raw materials in percentage by mass: 90% of yttrium-stabilized zirconium oxide powder, 4.1-5.1% of a dispersing agent, 0.9-1.2% of a nucleating agent and 4.0-5% of an environmental solvent, and the particle size of the zirconium oxide powder is 200-500 nm. The preparation process comprises the following steps: adding the dispersing agent, the nucleating agent and the environmental solvent into a ball mill for ball milling and mixing; zirconium oxide powder is added into the ball mill for continuous ball milling; adding the obtained slurry into an ultrasonic disperser for retreatment; and then filtering and degassing to obtain the high-solid-content zirconium oxide slurry. The zirconium oxide slurry prepared by the preparation method disclosed by the invention can maintain relatively low viscosity, good dispersity, fluidity and stability while having high solid content, shows huge potential in application of high-precision coating, spraying, 3D printing, high-performance ceramic forming and the like, and particularly has a good application prospect in a process requiring high solid content and not sacrificing fluidity. The method is an ideal choice.

Description

Technical Field

[0001] The present invention relates to the technical field of zirconium oxide slurry preparation, and in particular to a high-solid content zirconium oxide slurry and a preparation process and application thereof. Background Art

[0002] Zirconia, chemically inactive, possesses a high melting point, high resistivity, high refractive index, and low thermal expansion coefficient, making it an important high-temperature resistant material, ceramic insulation, and ceramic opacifier. It is also the primary raw material for artificial diamonds. Zirconia (ZrO2) slurry is primarily composed of zirconium oxide powder, combined with appropriate amounts of dispersants, liquid media, and other additives.

[0003] Zirconia slurry is widely used in spray granulation process, coating preparation, ceramic forming, spraying and additive manufacturing.

[0004] In the manufacturing process of electronic components, zirconia refractory substrates are commonly used as carriers in electronic components. The uneven size of zirconia particles and low particle density on the carriers are one of the important reasons for the decline in the quality of component products. Zirconia coatings are widely used in mechanical equipment, chemical equipment, automotive industry, aerospace and other fields, but the zirconia coatings in the prior art have problems with insufficient adhesion and durability. In the ceramic forming and sintering process, the properties of zirconia slurry play a key role in obtaining high-quality finished products. However, the zirconia slurry in the prior art cannot be well balanced due to its high solid content and low viscosity, and it is easy for particles to settle or be unevenly distributed, resulting in insufficient density of the finished ceramic products. Zirconia ceramics have excellent mechanical properties, such as high fracture toughness and flexural strength. Therefore, they are also widely used in the field of ceramic additive manufacturing. However, there are still many defects, mainly insufficient fluidity that affects the uniformity of spraying and coating, especially in applications that require higher precision (such as 3D printing, spraying, etc.). Viscosity and fluidity problems may lead to molding errors, low density of products, cracks, and mechanical properties that do not meet requirements.

[0005] The common cause of these problems is a low solids content in zirconia slurries. However, higher solids content often leads to poorer slurry viscosity and fluidity, which can cause problems during the molding process, particularly in spraying and coating applications, where the desired properties cannot be achieved. Maintaining a low viscosity requires a lower solids content in zirconia ceramic slurries. Therefore, maintaining good dispersibility and fluidity in high-solids slurries, and balancing viscosity with solids content, remains a major research challenge. Furthermore, conventional slurries use organic solvents as the liquid medium, which can cause environmental pollution. Sintering aids are often added to conventional zirconia slurries to lower the sintering temperature and improve sintering efficiency. However, sintering aids can affect the final purity and properties of the zirconia and, in certain applications (such as biomedical materials), can adversely affect the product, compromising sintering quality and performance. Slurries prepared using conventional processes also exhibit poor stability, exhibiting delamination, uneven dispersion, sedimentation, or agglomeration after a period of time. This leads to unstable slurry properties, impacting the quality and consistency of the final product. These are key issues that urgently need to be addressed in technological research and development. Summary of the Invention

[0006] In view of the defects in the prior art, the purpose of the present invention is to provide a high solid content zirconium oxide slurry and its preparation process and application.

[0007] The object of the present invention is achieved through the following solutions:

[0008] A first aspect of the present invention provides a high-solids zirconia slurry comprising the following raw materials in percentage by weight: 90% yttrium-stabilized zirconia powder, 4.1-5.1% dispersant, 0.9-1.2% tuberculin, and 4.0-5% environmental solvent. The zirconia powder has a particle size of 200 nm to 500 nm. Preferably, the zirconia powder, dispersant, tuberculin, and environmental solvent are 90%, 4.5%, 1%, and 4.5%.

[0009] By adopting the above technical solution, we select yttrium-stabilized zirconia powder with a small particle size and surface treatment (to remove surface impurities), and control the powder particle size within the range of 200nm-500nm. This not only improves the mechanical properties and surface smoothness of the material, but also reduces particle agglomeration and improves the dispersibility of the slurry.

[0010] Preferably, the dispersant is at least one of polyvinyl pyrrolidone and polyacrylamide, preferably polyacrylamide.

[0011] PVP molecules can be adsorbed on the surface of zirconium oxide particles to form a protective film, which prevents the particles from approaching and agglomerating with each other through electrostatic repulsion and steric hindrance effects. At the same time, the solubility and film-forming properties of PVP also help to form a stable dispersion system. Polyacrylamide molecules form an adsorption layer on the surface of zirconium oxide particles. This adsorption layer is like a "barrier". When other particles approach, it will produce steric hindrance, preventing the particles from getting closer and agglomerating. The polar groups on the polyacrylamide molecular chain (such as carboxyl, amide, etc.) can form chemical bonds with the polar sites on the particle surface through chemical reactions, or be adsorbed through physical effects such as electrostatic effects and hydrogen bonds. This strong binding force allows polyacrylamide to firmly adhere to the particle surface, enhance the binding force between the particles and the dispersant, and facilitate dispersion. The hydrophilic groups of polyacrylamide form hydrogen bonds with water molecules, so that the particle surface is surrounded by a hydration layer, which increases the repulsion between particles and promotes dispersion.

[0012] Preferably, the anti-tuberculosis agent is at least one of sodium alginate, polyvinyl alcohol, and hydroxypropyl methylcellulose, preferably sodium alginate.

[0013] Through the above technical solution, surfactants such as sodium alginate are used to prevent the zirconium oxide powder from settling or agglomerating during storage, thereby enhancing the long-term stability of the slurry. Hydroxypropyl methylcellulose has good film-forming properties, which can effectively protect the internal particles from being destroyed and prevent particle aggregation. It can also serve as an effective suspending agent to improve the stability of solid particles, prevent them from settling or agglomerating, and improve the storage and use of the slurry. The solution of polyvinyl alcohol in water has a certain surface activity, which can reduce the surface tension between liquids, which is conducive to the stabilization of polyvinyl alcohol in the dispersed system. In addition, polyvinyl alcohol can be adsorbed on the surface of the colloidal particles to form a protective film, which helps to prevent aggregation between particles, thereby maintaining the stability of the dispersed system.

[0014] Preferably, the environmental solvent is weak alkaline water, and the pH of the weak alkaline water is 7.5-8. Water-based solvents have low toxicity and volatility, can reduce environmental pollution, improve operational safety, and meet the requirements of modern green manufacturing.

[0015] A second aspect of the present invention provides a process for preparing a high solid content zirconium oxide slurry, comprising the following steps:

[0016] (1) adding part of the dispersant, tuberculin, and environmental solvent into a ball mill and mixing;

[0017] (2) adding a portion of yttrium-stabilized zirconia powder to the ball mill and continuing ball milling;

[0018] (3) Repeat steps (1) and (2) until all components are added and the pH value of the slurry in the ball mill is maintained at 7.0-7.5;

[0019] (4) adding the slurry obtained in step (3) into an ultrasonic disperser for further processing to further disperse the zirconium oxide particles;

[0020] (5) The slurry obtained by ultrasonic dispersion in step (4) is filtered to remove undispersed zirconium oxide particles and impurities, and then degassed to finally obtain a high-solid content zirconium oxide slurry.

[0021] A vacuum degasser can be used to degas the slurry to remove any bubbles that may be present in the solution, preventing them from interfering with subsequent molding and coating processes.

[0022] Preferably, during the treatment process after the yttrium-stabilized zirconia powder is added, the temperature change of the slurry is monitored in real time to ensure that the temperature of the slurry is between 20°C and 40°C.

[0023] A third aspect of the present invention provides applications of the high solid content zirconia slurry, including spray granulation, coating preparation, additive manufacturing, and ceramic product production.

[0024] The 90% solids zirconia slurry in this invention exhibits excellent fluidity and viscosity through rational formulation optimization. Despite its high solids content, this slurry exhibits improved processability and handling compared to 60% solids slurries, thanks to meticulous control of dispersion technology, rheological adjustments, and solvent selection. This characteristic makes 90% solids zirconia slurry a promising choice for applications such as high-precision coatings, spraying, and 3D printing, making it an ideal choice for processes requiring a high solids content without sacrificing fluidity.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The zirconia slurry prepared by this invention maintains a low viscosity, excellent dispersibility, fluidity, and stability while having a solids content of up to 90%. It exhibits better processability and operability than a slurry with a solids content of 60%. It demonstrates great potential in applications such as high-precision coating, spraying, and 3D printing, and is an ideal choice for processes requiring a high solids content without sacrificing fluidity.

[0027] 2. The zirconia slurry and preparation process thereof of the present invention not only effectively solve the problems of poor dispersibility and poor stability in the preparation of zirconia slurry in traditional processes, but also improve the quality and stability of the slurry through optimized ultrasonic dispersion, temperature control and stabilization treatment, thereby ensuring the quality and consistency of the final product, reducing dependence on sintering aids, and improving product performance and production efficiency. Its environmental protection, no need for sintering aids, and precise control make it a preparation method that better meets the needs of modern manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0029] Figure 1 This is an electron microscope photo of zirconium oxide slurry in the prior art;

[0030] Figure 2 This is an electron microscope photograph of the zirconium oxide slurry particles obtained in Example 1-1 of the present invention after coarse screening and before polishing;

[0031] Figure 3 This is an electron microscope photograph of the zirconium oxide slurry particles obtained in Example 1-1 of the present invention after fine screening and polishing. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0033] Based on the existing technology, zirconia slurry still has a series of problems such as poor dispersibility, high viscosity, dependence on sintering aids, and environmental pollution. These problems limit the application range and performance stability of the slurry. In particular, in scenarios requiring high-precision and high-performance materials, traditional processes face great challenges. The present invention solves this problem by rationally selecting dispersants, adding tuberculators, controlling particle size, and using environmentally friendly solvents. Specifically, the analysis and solution are carried out from the following aspects:

[0034] 1. Yttrium-stabilized zirconia powder: Selecting yttrium-stabilized zirconia powder with appropriate particle size is very important for the dispersibility of high-solid content slurries. Too large a particle size will increase the viscosity of the slurry and affect its processing performance. Therefore, yttrium-stabilized zirconia powder with a smaller particle size and surface treatment is selected, and the powder particle size is controlled within the range of 200nm-500nm. This not only improves the mechanical properties and surface smoothness of the material, but also reduces the agglomeration phenomenon between particles and improves the dispersibility of the slurry. Ensure the dispersion effect and fluidity. The surface treatment of yttrium-stabilized zirconia powder is to activate the surface of zirconia and ensure that there are no other impurities on the surface. For example, long-term exposure of zirconia to water molecules and carbon dioxide in humid ambient air will cause the surface of zirconia to undergo hydroxylation reaction to produce zirconium hydroxide or zirconium carbonate, resulting in agglomeration. Activation calcination helps to eliminate surface hydroxylation.

[0035] 2. Dispersant: The selection of dispersant is key to ensuring slurry stability. The function of the dispersant is to reduce the time and energy required to complete the dispersion process by using a wetting dispersant, stabilize the dispersed body, modify the surface properties of the particles, and adjust the mobility of the particles. The dispersant in high-solids slurries needs to have strong dispersing ability. The use of high-efficiency inorganic or organic dispersants can effectively reduce the surface energy of zirconia powder and reduce powder agglomeration. According to the particle size, surface characteristics and viscosity of the zirconia powder, combined with the characteristics of different dispersants and reasonable ratios, the dispersion effect can be significantly improved and the slurry can be stabilized.

[0036] 3. Tuberculation agent: In order to enhance the long-term stability of the slurry, surfactants are used (to prevent the zirconia powder from settling or agglomerating during storage). These tuberculation agents not only enhance the dispersibility of the slurry, but also act as tubers after reaching the atomization temperature.

[0037] 4. Environmentally friendly solvent: Use water-based solvents. Water-based solvents have low toxicity and volatility, can reduce environmental pollution, improve operational safety, and meet the requirements of modern green manufacturing. The viscosity of the slurry can be adjusted by adjusting the proportion of environmental solvent to ensure good slurry fluidity.

[0038] 5. pH Adjustment: Maintaining an appropriate pH is crucial for the dispersibility and stability of high-solids slurries. Excessively low or high pH values can affect the effectiveness of the dispersant. Typically, the pH of a 90% solids zirconia solution should be maintained between 7.0 and 7.5. This can be adjusted by adding an alkaline solution or hydrochloric acid. When adjusting the pH, caution should be exercised to avoid excessive pH, which can reduce dispersibility.

[0039] 6. Viscosity adjustment and solid content optimization: To address the issue of excessive slurry viscosity when the solid content is too high, use an appropriate amount of dispersant to ensure the fluidity of the slurry while maintaining a high solid content. While adjusting the viscosity, maintain the effects of the dispersant and tuberculator to avoid sedimentation or uneven distribution of the slurry at high solids content.

[0040] Based on the above analysis, the high solid content zirconium oxide slurry of the present invention includes the following raw materials in percentage by mass:

[0041] The invention comprises 90% zirconium oxide powder, 4.1-5.1% dispersant, 0.9-1.2% tuberculin and 4.0-5% environmental solvent. The particle size of the zirconium oxide powder is 200nm-500nm.

[0042] The equipment, materials and preparation process required for the slurry of the present invention are as follows:

[0043] 1. Equipment:

[0044] 1. High-energy ball mill: Used to disperse zirconium oxide powder into the solution, ensuring uniform distribution of zirconium oxide particles and preventing agglomeration. High-speed ball mills replace traditional high-speed agitators and become key equipment for initial mixing and powder dispersion. High-speed ball mills offer enhanced crushing and dispersion capabilities. Through high-frequency impact and grinding, they initially mix and crush zirconium oxide powder and liquid medium, reducing particle size. This effectively reduces agglomeration of zirconium oxide particles and improves dispersion in a short period of time.

[0045] (1) Structural composition: High-speed ball mill includes ball mill barrel, grinding balls, transmission system, control system and temperature control system.

[0046] Ball mill barrel: A container for holding zirconium oxide powder and solvent, filled with grinding balls.

[0047] Grinding balls: When rotating at high speed, the grinding balls will hit the zirconium oxide powder, grinding it into smaller particles, helping the powder to mix better with the solvent.

[0048] Transmission system: provides power to the ball mill to make the grinding balls rotate at high speed.

[0049] Control system: It can adjust the speed, time and other parameters of the ball mill to ensure the dispersion and running-in effects.

[0050] Temperature control system: used to adjust and monitor the temperature during the ball milling process to avoid excessive heat generated by friction that affects the slurry quality.

[0051] (2) Working Principle: The high-speed ball mill physically crushes the zirconium oxide powder through the rotation and impact of the grinding balls, promoting the mixing and dispersion of the powder and the solvent. The high-speed rotating grinding balls can accelerate the collision between the powder particles, improve the dispersion effect, thereby reducing the agglomeration of the zirconium oxide particles and obtaining a more uniform slurry.

[0052] 2. Ultrasonic disperser: The high-frequency vibration of ultrasound generates a cavitation effect, which further disperses the powder and destroys the agglomerate structure of the zirconium oxide powder to achieve a uniform dispersion effect, especially at a high solid content, ensuring a good dispersion effect;

[0053] (1) Structural composition: The ultrasonic disperser includes an ultrasonic generator, a transducer, an ultrasonic probe and a temperature control system.

[0054] Ultrasonic generator: provides ultrasonic electrical signals and converts electrical energy into ultrasonic vibrations.

[0055] Transducer: Converts electrical signals into mechanical vibrations and transmits them to the probe.

[0056] Ultrasonic probe: transmits vibrations into the liquid mixture, breaking up the agglomerates of the zirconium oxide powder through vibration.

[0057] Temperature control system: Real-time monitoring of temperature changes during ultrasonic dispersion, precise adjustment of the slurry temperature during processing, maintaining a stable slurry temperature, and avoiding thermal degradation or thermal cracking of zirconia powder due to excessively high temperatures, thereby ensuring the effectiveness of the dispersant.

[0058] (2) Working principle: The ultrasonic probe generates periodic pressure changes through mechanical vibration, which produces the expansion and bursting effect of tiny bubbles, forming a local high temperature and high pressure environment, breaking up powder agglomerations and improving the dispersion effect.

[0059] 3. Agitator: used to evenly mix the ingredients in the slurry;

[0060] 4. Graduated cylinder and electronic balance: used to accurately measure the mass of each component;

[0061] 5. pH meter: used to adjust the pH of the solution;

[0062] 6. The temperature control system includes a temperature sensor, a heating device, and a cooling device. The temperature sensor is used to monitor the temperature of the local working environment in real time; the heating device provides heat as needed to keep the working environment temperature from being too low and maintain the slurry temperature within the ideal range; the cooling device is used to automatically start the cooling system when the ambient temperature is too high to reduce the ambient temperature and prevent the slurry from overheating due to the high ambient temperature.

[0063] 7. Vacuum degasser: used to remove bubbles in the solution to ensure the uniformity and stability of the slurry.

[0064] 8. Slurry stabilizer: The stabilizer is used to further improve the long-term stability of the slurry and prevent stratification or sedimentation during storage.

[0065] (1) Structural composition: The stabilizer includes a stirring device, a dispersant addition port and a flow control valve.

[0066] Stirring device: Maintain the uniformity of the slurry through low-speed stirring.

[0067] Dispersant addition port: Add appropriate amount of dispersant to prevent powder agglomeration.

[0068] Flow regulating valve: adjust the amount of tuberculin added as needed.

[0069] (2) Working principle: The stabilizer keeps the slurry uniform during long-term storage by continuously stirring it lightly and adding a tuberculin, thus preventing powder from settling.

[0070] 2. Materials:

[0071] 1. Yttrium-stabilized zirconia powder (ZrO2): Select zirconia powder with appropriate particle size (200-500 nanometers);

[0072] 2. Dispersant: used to prevent zirconium oxide powder from agglomerating; polyacrylamide (model: AD8085, CAS 9003-05-8, sourced from Dongguan Aoda Environmental Protection New Materials Co., Ltd.);

[0073] 3. Tuberculosis: used to improve the tuberculosis and fluidity of the slurry; sodium alginate (product number: 937673, CAS9005-38-3, from J&K Technology Co., Ltd.);

[0074] 4. Environmental solvent: weak alkaline water, pH 7.5-8.

[0075] 3. The preparation process of high solid content zirconium oxide slurry includes the following steps:

[0076] The required amounts of the raw material components are weighed in advance according to the mass percentage: zirconium oxide powder, dispersant, tuberculin, and environmental solvent.

[0077] (1) Add part of the dispersant, tuberculin and environmental solvent to a ball mill and mix; generally, add a small amount of each raw material first, for example, about 10% of the required amount of each raw material, and ball mill until the surface and bottom of the ball mill have a certain degree of wetness;

[0078] (2) Add some zirconium oxide powder to the ball mill and continue ball milling; observe the dispersibility, fluidity, viscosity, etc. of the slurry. If the dispersibility is not high, add a small amount of dispersant. If the fluidity is too low, add an appropriate amount of environmental solvent and dispersant. If the slurry is too diluted, add zirconium oxide. If the viscosity is too low, add a tuberculin. If the viscosity is too high, add water and dispersant.

[0079] High-energy ball milling effectively pulverizes and disperses zirconium oxide powder in a short period of time through the high-speed motion of the balls, reducing particle agglomeration and achieving a uniformly distributed mixing effect. The ball milling process is controlled to last 20-40 minutes per mill, at a speed of 800-1000 rpm and a temperature of 20-40°C to ensure uniform particle size distribution. The particle size and dispersion are controlled by adjusting the milling time, typically 30 minutes, to achieve a uniform zirconium oxide powder particle size and avoid excessive slurry viscosity caused by overdispersion. During the milling process, the slurry temperature must be adjusted to maintain a constant temperature of 20-40°C using the mill's built-in temperature control system.

[0080] (3) Repeat steps (1) and (2) until all components are added and the pH value of the slurry in the ball mill is maintained at 6.5-7.5 to achieve optimal dispersibility and stability.

[0081] (4) The slurry obtained in step (3) is added to an ultrasonic disperser for further processing to further disperse the zirconium oxide particles. The high-frequency vibration of the ultrasonic disperser (ultrasonic vibration frequency 20-40kHz, ultrasonic dispersion time is generally 30-60 minutes) can cause the bubbles in the liquid to collapse violently, resulting in a tiny bubble explosion effect, breaking the agglomeration of the zirconium oxide powder itself caused by the production, storage, transportation process, etc., to form a more uniform slurry. The degree of dispersion of the slurry is controlled by adjusting the ultrasonic power and processing time to ensure that the zirconium oxide particles can be evenly dispersed in the liquid medium. During the ultrasonic dispersion process, the slurry is appropriately heated or cooled using a built-in temperature control system (when the ambient temperature is too low, it can be appropriately heated during ultrasound, and when the ambient temperature is too high, it can be appropriately cooled during ultrasound, that is, a lower temperature is selected for ultrasound) to ensure complete dissolution of the dispersant and further enhance the dispersion effect.

[0082] An external temperature control system is used to control the working environment temperature to prevent the slurry from being overheated or underheated during the dispersion process, which could affect its performance. An automatic temperature control system is used to increase and maintain the temperature according to a set temperature control curve, gradually increasing the temperature and maintaining it within a specific time period to ensure that the organic components and solvents in the slurry are completely volatilized and prevent uneven dispersion.

[0083] (5) The ultrasonically dispersed slurry from step (4) is filtered to remove undispersed zirconium oxide particles and impurities to ensure the uniformity and purity of the final slurry. Filtering can be performed using a mesh filter cloth or an activated carbon filter; then, a vacuum degasser is used to degas the slurry to obtain a high-solids zirconium oxide slurry. The degassing process removes any bubbles that may be present in the solution to prevent them from interfering with subsequent molding and coating processes.

[0084] Testing and Adjustment: After preparation, the slurry is tested for dispersibility, rheology, viscosity, and stability. A particle size analyzer is used to check the uniformity of the zirconium oxide particles. If necessary, the slurry's properties can be further adjusted by adding more dispersant or adjusting the solvent ratio.

[0085] Storage: Prepared 90% solids zirconia slurry should be stored in a sealed container to prevent water and solvent evaporation to ensure long-term stability. During storage, the slurry should be checked regularly. If any precipitation or agglomeration occurs, redisperse it. A slurry stabilizer can also be used to continuously stir the slurry to prevent sedimentation or agglomeration of the zirconia particles during storage.

[0086] In the preparation process of the present invention, a high-speed ball mill first mixes zirconia powder with a solvent and preliminarily disperses the powder; then, an ultrasonic disperser further breaks up agglomerates of the zirconia powder to improve the dispersion effect; during the dispersion process, a temperature control system continuously monitors and adjusts the slurry temperature to ensure that the temperature is within the ideal range to avoid thermal cracking and powder degradation; finally, a slurry stabilizer ensures the long-term stability of the slurry by continuously stirring lightly and adding a tuberculin.

[0087] Specifically,

[0088] (1) The combination of high-speed ball milling and ultrasonic dispersion significantly improves the dispersibility of zirconia powder in liquid. High-speed ball milling can effectively reduce the size of zirconia powder particles, while ultrasonic dispersion further breaks up agglomerates through the cavitation effect, making the powder more evenly dispersed. This ensures the consistency and uniformity of the slurry, avoids the particle agglomeration phenomenon that occurs in traditional processes, and thus improves product quality.

[0089] (2) The long-term stability of the slurry has been significantly improved by adding a stabilizer and using ultrasonic dispersion technology. The continuous mild stirring of the stabilizer and the use of a dispersant can prevent the zirconia powder from settling or stratifying during storage, ensuring the uniformity of the slurry and avoiding the risk of stratification or precipitation in the finished slurry.

[0090] (3) The use of an advanced temperature control system can accurately monitor and adjust the temperature of the slurry and the temperature of the slurry during storage, which can also help maintain the uniformity of the slurry. This allows the slurry to avoid thermal degradation, thermal cracking or uneven dispersion of the zirconia powder caused by excessive temperatures throughout the preparation process. At the same time, the temperature control system ensures that the heat generated during the ultrasonic dispersion process is dissipated in a timely manner, thereby preventing the impact of excessive temperatures on the slurry quality.

[0091] (4) Because the dispersibility and stability of the zirconium oxide slurry of the present invention are optimized, no additional sintering aids are required during the preparation process. This reduces the negative impact that the additives may have on the product (such as additive toxicity and environmental pollution), reduces production costs, and improves the purity of the final product.

[0092] (5) This process effectively improves the rheological properties, particle uniformity, and dispersibility of the zirconia slurry by combining ultrasonic dispersion and high-speed ball milling. The improved slurry has higher fluidity and better viscosity control, making it suitable for more sophisticated molding processes such as ceramic molding and spraying. In addition, the uniformity and stability of the slurry enhance the strength, density, toughness, and other properties of the finished product, improving the overall performance, reliability, and uniformity of the final product.

[0093] (6) By combining high-speed ball milling and ultrasonic dispersion, the slurry preparation time is significantly shortened. Compared with the traditional stirring dispersion method, ultrasonic dispersion can obtain higher quality slurry in a shorter time, thus improving production efficiency.

[0094] (7) The use of environmentally friendly solvents and a preparation method that does not require sintering aids avoids the use of toxic solvents and sintering aids, reducing pollution to the environment. In addition, the precise temperature control system and stable preparation process also reduce energy waste, meeting the requirements of green manufacturing and sustainable development. Because the tuberculin sodium alginate can act as a sintering aid, there is no need to add other sintering aids, which also helps to improve the fluidity of the slurry and reduce the viscosity of the slurry.

[0095] (8) The formulation and preparation process of the present invention are highly scalable and suitable for production at different scales. They can also be adjusted to meet varying requirements, such as zirconia particle size and slurry concentration. Therefore, this process can be used not only for the preparation of zirconia microspheres but also for the production of other ceramic slurries.

[0096] The zirconia slurry and preparation process of the present invention not only effectively address the poor dispersibility and stability issues encountered in traditional zirconia slurry preparation processes, but also improve the slurry's quality and stability through optimized ultrasonic dispersion, temperature control, and stabilization. This ensures the quality and consistency of the final product, reduces reliance on sintering aids, and enhances product performance and production efficiency. Its environmentally friendly, sintering aid-free, and precise control characteristics make it a preparation method that better meets the needs of modern manufacturing.

[0097] The viscosity of the slurry prepared in the present invention was measured by a rotational rheometer (AR 1500ex, TA Instruments, US) at 25°C for 30 seconds. -1 The test was carried out at a shear rate of .

[0098] Example 1

[0099] Table 1. Screening of dispersants and their contents

[0100]

[0101]

[0102] From the data analysis in Table 1, it can be seen that in the high solid content zirconia formula of the present invention, as the dispersant content increases, the slurry viscosity decreases. When the dispersant content is in the range of 4.1-5.1%, the viscosity of the obtained slurry is less than 340 mPa·s, and the fluidity also meets the requirements. Among them, the dispersant is polyacrylamide with a content of 4.5% and 5.1% (Examples 1-1, 1-3), and the slurry viscosity is relatively low. Considering the cost, the formula of Example 1-1 is selected as the preferred example for optimization screening of other components.

[0103] Example 2

[0104] Table 2. Screening of tuberculin agents and their contents

[0105]

[0106] From the data analysis in Table 2, it can be seen that in the high solid content zirconium oxide formula of the present invention, as the content of the tuberculin increases, the viscosity of the slurry increases accordingly. When the content of the tuberculin is in the range of 0.9-1.2%, the viscosity of the obtained slurry is less than 270 mPa·s, and the fluidity also meets the requirements. Among them, the tuberculin is hydroxypropyl methylcellulose with a content of 0.9% and 1% (Examples 2-1, 1-1), and the slurry viscosity is relatively low. Combined with the data in Table 1, sodium alginate with a content of 1% is selected as the tuberculin for optimization screening of other components.

[0107] Example 3

[0108] Table 3. Screening ball milling time and ultrasonic time

[0109]

[0110] As can be seen from the data analysis in Table 3, in the high-solids zirconia formulation of the present invention, the milling time of the high-energy ball mill and the dispersion time of the ultrasonic disperser also affect the viscosity of the slurry. Experiments have found that the ball milling time is more suitable when maintained at 20-40 minutes. Within this time range, the slurry viscosity decreases first and then increases with the increase in ball milling time (Examples 3-1, 1-1, and 3-2), with 30 minutes being the optimal time. In addition, the time required for conventional zirconia slurry grinding is 4-6 hours. Our formulation can greatly shorten the grinding time, achieving the effect of grinding for 4-6 hours half an hour after adding the formulation to the ball mill.

[0111] The viscosity, stability and fluidity of the high-solid-content zirconium oxide slurry prepared by the present invention can be adjusted according to needs through the various components. In addition, no sedimentation occurs within 20-30 hours of placement. After sedimentation occurs after 2-3 months of placement, the settled part can still be evenly mixed by shaking again. There is no slurry that cannot be dispersed, such as bottom lumps, so the service life is longer and the scope and field of application are wider.

[0112] Comparative Example 1

[0113] Table 4. Comparative experimental data of dispersant dosage

[0114]

[0115]

[0116] From the data analysis in Table 4, it can be seen that when the zirconium oxide content is high, the dispersant content is too high or too low, and is not within the scope of the present invention, the viscosity of the resulting slurry will increase. This is because the role of the dispersant in the slurry is to affect the rheological properties of the slurry by changing the interaction force between particles and the interaction force between molecules. When the dispersant is too low, the interaction force between particles increases, resulting in an increase in the viscosity of the slurry and a deterioration in fluidity; when the dispersant is too high, due to excessive addition, it will hinder the normal dispersion of the particles, resulting in an increase in the viscosity of the slurry and a deterioration in the rheological properties. In addition, if no dispersant is added, the solid particles in the slurry are prone to agglomeration, resulting in an uneven slurry and easy sedimentation.

[0117] Comparative Example 2

[0118] Table 5. Comparative experimental data of tuberculin dosage

[0119]

[0120] From the data analysis in Table 5, it can be seen that when the zirconium oxide content is high, the tuberculin content is too high or too low, and is not within the scope of the present invention, the viscosity of the resulting slurry will increase. This is because the tuberculin mainly plays the role of bonding and stabilizing the particles in the slurry. When the tuberculin is too low, the interaction force between the particles is weakened, the cohesive force of the slurry is reduced, and the viscosity decreases. Slurries with low viscosity are prone to sedimentation and stratification, affecting the uniformity and stability of the slurry; when the tuberculin is too high, the viscosity of the slurry increases and the rheological properties deteriorate due to excessive addition. In addition, if the tuberculin is not added, the solid particles in the slurry are prone to agglomeration, resulting in uneven slurry, which also affects the viscosity and is easy to settle.

[0121] Comparative Example 3

[0122] Table 6. Comparative test data of ball milling time and ultrasonic time

[0123]

[0124] From the data analysis in Table 6, it can be seen that if the ball milling time is less than 20 minutes, the particles are not fully ground and the particle size is too large, resulting in the raw material zirconium oxide particle size being too large and poor slurry dispersion, and the slurry stirring will also be uneven; if the ball milling time is more than 40 minutes, the particle size after grinding is too small and difficult to disperse. At the same time, too long a grinding time will also make the temperature in the ball mill too high, resulting in the volatilization of the environmental solvent and the increase of the solid content, resulting in the slurry viscosity itself being too high. If the ultrasonic time is too short, the slurry will be unevenly dispersed and easy to agglomerate. If the ultrasonic time is too long, the slurry temperature will rise, and the zirconium oxide powder will be thermally degraded or unevenly dispersed.

[0125] The zirconium oxide slurry prepared in Example 1-1 of the present invention was photographed using a cryo-double-beam electron microscope. Figure 2 As shown in the figure, it can be found that the surface of the zirconium oxide particles is smooth, with good integrity and few defects. Figure 3 As shown in the figure, after screening and surface polishing, it can be seen that the surface of the zirconium oxide particles is smooth and defect-free, the particle size is uniform, and the consistency is very high. Figure 1 As shown in the figure, due to the low solid content, the surface of the spheres with the same particle size produced has huge defects, and the slurry particle size is uneven and varies greatly, so it can only be used in products with low spraying requirements.

[0126] The present invention uses low-molecular sodium alginate as a tuberculin (weakly alkaline) when the zirconium oxide content is as high as 90%, because the slurry made from low-molecular sodium alginate has low viscosity; selects polyacrylamide as a dispersant (the aqueous solution of non-ionic polyacrylamide is weakly acidic), and uses weakly alkaline water as a solvent to keep the slurry pH at 7.0-7.5; because the properties of the zirconium oxide solution are affected by the pH, when the pH is generally alkaline, two problems can be solved: one is meteorite craters (that is, defects with obvious concave surfaces); the other is the slurry viscosity problem, because the existing spray technology slurry viscosity is too high, which can lead to clogging of the nozzle and is not suitable for large-scale, long-term, stable production. Therefore, the present invention selects low-molecular sodium alginate with a weak alkaline property as the tuberculin, and weakly acidic non-ionic polyacrylamide as the dispersant, and then adds weakly alkaline water to ensure that the pH of the slurry is neutral or weakly alkaline, so that the slurry can maintain low viscosity and good fluidity under high content conditions.

[0127] Although the 90% solid content zirconia slurry of the present invention contains more solid particles, its viscosity and fluidity are better than those of the conventional 60% solid content slurry. The reasons are:

[0128] Higher particle density and lower solvent requirements: 90% solids slurries have a higher proportion of solid particles and a relatively lower proportion of liquid, meaning more solid particles are physically interacting within the slurry. Therefore, despite the high solids content, the smaller particle size and the optimal ratio of the nucleating agent, dispersant, and environmental solvent ensure moderate interaction, making adhesion less likely and thus preventing excessive slurry viscosity.

[0129] Optimized interparticle forces: At high solids contents, the fluidity of a slurry is primarily influenced by the interparticle forces. Proper surface treatment of the particles can reduce surface energy and interparticle adsorption, allowing the slurry to maintain good fluidity even at high solids contents. This allows slurries with a 90% solids content to maintain a high solids ratio without sacrificing fluidity.

[0130] Due to the advantages of high solid content, slurry viscosity and fluidity, the zirconia slurry prepared by the present invention shows great potential in applications such as high-precision coating, spraying, 3D printing and high-performance ceramic molding. It is an ideal choice in processes that require high solid content without sacrificing fluidity:

[0131] 1. In the spray granulation process, the 90% solid content zirconium oxide slurry exhibits excellent fluidity and viscosity, which is crucial for the preparation of high-quality particles. Spray granulation is a process that forms uniform particles by spraying liquid slurry into small droplets and quickly evaporating the solvent with hot air. Because the 90% solid content slurry can maintain good fluidity and moderate viscosity after formula optimization, it has the following advantages in the spray process:

[0132] (1) Good particle morphology and consistency: Due to the high solid content of the slurry, particles with uniform particle size can be effectively generated. By adjusting the viscosity of the slurry, it is possible to ensure that the particles maintain a good shape during the spraying process, avoiding irregular particles caused by too thin slurry or excessively large particles caused by too high viscosity.

[0133] (2) Improved particle density: A higher solid content allows the particles formed after spray granulation to better maintain structural density during the sintering process, enhancing the mechanical strength and thermal stability of the particles. At the same time, the fluidity of these particles is more suitable for subsequent coating or sintering processes, avoiding the problems of loose particles and unstable morphology that occur during the granulation process of traditional low-solid content slurries.

[0134] (3) Improved production efficiency: In the spray granulation process of 90% solid content slurry, less solvent content means shorter drying time and higher production efficiency. This not only helps to reduce energy consumption, but also improves the utilization rate of slurry in the production process and reduces material waste.

[0135] (4) Particle control and operability: By precisely controlling the viscosity and fluidity of the slurry, the particle size during the spray granulation process can be precisely controlled to meet the needs of different applications. In particular, in applications requiring high-precision and high-density particles, a 90% solids content slurry can provide better particle properties and meet the requirements of high-performance materials.

[0136] 2. Spraying and coating: 90% solid content zirconium oxide slurry solves the defects of zirconium oxide microspheres themselves (such as Figure 1 Defects such as craters in the middle of the zirconia spheres can lead to poor sphericity, which can clog the nozzle, and craters can reduce the durability and other performance benefits of the spheres. This allows for uniform coating during the coating and spraying process, avoiding the sagging and dripping problems that can occur with low-solids slurries during film formation. Its high viscosity also helps improve coating adhesion and durability, making it suitable for demanding applications such as high-performance ceramic coatings and thermal barrier coatings.

[0137] 3. Additive Manufacturing (3D Printing): In additive manufacturing applications, the fluidity and viscosity of the slurry directly impact the accuracy and surface quality of the printing process. Zirconia slurry with a 90% solids content exhibits low viscosity and excellent fluidity, enabling it to be deposited more precisely on the printing platform, thereby improving printing accuracy, especially in detail processing and high-resolution printing.

[0138] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A high solid content zirconium oxide slurry, characterized in that: The invention comprises the following raw materials in percentage by mass: 90% yttrium-stabilized zirconia powder, 4.1-5.1% dispersant, 0.9-1.2% tuberculin, and 4.0-5% environmental solvent. The particle size of the yttrium-stabilized zirconia powder is 200nm-500nm.

2. The high solid content zirconium oxide slurry according to claim 1, characterized in that: The dispersant is at least one of polyvinyl pyrrolidone and polyacrylamide.

3. The high solid content zirconium oxide slurry according to claim 2, characterized in that: The dispersant is polyacrylamide.

4. The high solid content zirconium oxide slurry according to claim 1, characterized in that: The tuberculin agent is at least one of sodium alginate, polyvinyl alcohol, and hydroxypropyl methylcellulose.

5. The high solid content zirconium oxide slurry according to claim 4, characterized in that: The tuberculin agent is sodium alginate.

6. The high solid content zirconium oxide slurry according to claim 1, characterized in that: The environmental solvent is weak alkaline water.

7. The high solid content zirconium oxide slurry according to claim 6, characterized in that: The pH of the weak alkaline water is 7.5-8.

8. A process for preparing the high solid content zirconium oxide slurry according to any one of claims 1 to 7, characterized in that: The steps include: (1) adding part of the dispersant, tuberculin and environmental solvent into a ball mill and mixing; (2) adding a portion of yttrium-stabilized zirconia powder to the ball mill and continuing ball milling; (3) Repeat steps (1) and (2) to maintain the pH value of the slurry in the ball mill at 7.0-7.5; (4) adding the slurry obtained in step (3) into an ultrasonic disperser for further processing to further disperse the zirconium oxide particles; (5) The slurry obtained by ultrasonic dispersion in step (4) is filtered to remove undispersed zirconium oxide particles and impurities, and then degassed to finally obtain a high-solid content zirconium oxide slurry.

9. The process for preparing high solid content zirconium oxide slurry according to claim 8, characterized in that: During the treatment process after adding the yttrium-stabilized zirconia powder, the temperature change of the slurry is monitored in real time to ensure that the temperature of the slurry is between 20°C and 40°C.

10. Use of the high solid content zirconium oxide slurry according to any one of claims 1 to 7, characterized in that: The applications mentioned include spray granulation, coating preparation and additive manufacturing.

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