A method for preparing spherical ceria particles
High-sphericity cerium dioxide spherical particles were prepared by hydrothermal synthesis and segmented calcination, which solved the problems of uneven morphology and poor dispersibility of cerium dioxide particles in the prior art, and achieved efficient polishing effect and low-cost production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN RARE METAL MATERIALS RES INST CO LTD
- Filing Date
- 2023-09-11
- Publication Date
- 2026-05-19
AI Technical Summary
Existing technologies make it difficult to prepare cerium dioxide particles with uniform size, consistent morphology, and good dispersibility, resulting in poor polishing performance in chemical mechanical polishing.
A hydrothermal synthesis method was adopted, using sodium hypochlorite as an oxidant and combined with a surfactant and an ethylene glycol-water solvent system. By controlling the hydrothermal reaction conditions, a Ce(OH)4 precursor with high sphericity was generated. Cerium dioxide particles with high sphericity were obtained by staged calcination.
Cerium dioxide spherical particles with uniform size, consistent morphology, and strong monodispersity were obtained, which met the abrasive requirements of chemical mechanical polishing, reduced the preparation cost, and improved the polishing effect.
Smart Images
Figure CN117142511B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of micro-nano powder synthesis technology, specifically relating to a method for preparing cerium dioxide spherical particles. Background Technology
[0002] In recent years, with the widespread application of rare earth polishing powders in chemical mechanical polishing (CMP), cerium-based polishing powders have been widely used as abrasives in CMP due to their advantages such as strong cutting ability, short polishing time, high polishing precision, and clean operating environment. To improve the polishing rate of CMP and reduce surface scratches caused by the planarization process, the cerium dioxide particles (CeO2) used as abrasives need to have uniform size, consistent morphology, and good dispersibility. However, current mainstream commercially produced cerium dioxide mainly obtains the final product through the thermal decomposition of cerium salts (such as cerium carbonate, cerium hydroxide, or cerium nitrate), followed by mechanical grinding and classification. Although this method can yield highly chemically active cerium dioxide, the size and morphology of the resulting particles are difficult to control, resulting in poor polishing performance. Therefore, optimizing the preparation process of cerium dioxide and achieving controllable synthesis of cerium dioxide particles is the fundamental solution to this problem.
[0003] Currently, various methods for preparing cerium dioxide have been developed, such as the sol-gel method, precipitation method, hydrothermal (solvothermal) method, and solid grinding and calcination method. The morphology of the cerium dioxide obtained varies greatly depending on the method. Among these, the hydrothermal (solvothermal) method can obtain crystalline cerium dioxide nanoparticles at relatively low temperatures, but it requires a high-pressure reactor and has many limitations regarding precursor concentration and solvent type. The precipitation method is the most widely used method for liquid-phase chemical synthesis of high-purity nanoparticles. It is simple and produces powders with good properties, but this method still cannot solve the problem of nanoparticle agglomeration and cannot obtain monodisperse nanoparticles. Summary of the Invention
[0004] The technical problem to be solved by this invention is to provide a method for preparing spherical cerium dioxide particles, addressing the shortcomings of the prior art. This method employs a hydrothermal synthesis method, using NaClO as the oxidant, combined with the addition of a surfactant as a dispersant and an ethylene glycol-water solvent system, so that Ce... 4+ A high-sphericity Ce(OH)4 precursor is generated through hydrothermal reaction, and the agglomeration phenomenon during the hydrothermal crystallization process is reduced, thereby controlling the morphology of cerium dioxide spherical particles and obtaining cerium dioxide spherical particle nanoparticles with uniform size, consistent morphology, and strong monodispersity. This solves the agglomeration problem and the limitations of equipment and solvents in the preparation of cerium dioxide particles by existing methods.
[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing cerium dioxide spherical particles, characterized in that: firstly, cerium nitrate hexahydrate is dissolved in ethylene glycol as a raw material, then the surfactant polyvinylpyrrolidone is added, followed by the addition of an oxidant sodium hypochlorite aqueous solution and high-speed shearing and stirring. The pH value of the resulting solution is adjusted to 7-8.5 with ammonia water. Then, the resulting clear mixture is loaded into a hydrothermal reactor for hydrothermal reaction. After centrifugation, the resulting precipitate is washed and dried to obtain an orange-red precursor powder. The precursor powder is then placed in a muffle furnace for calcination to obtain light yellow cerium dioxide spherical particles.
[0006] The method for preparing spherical cerium dioxide particles described above is characterized in that the surfactant polyvinylpyrrolidone can be replaced with polyethylene glycol, hydroxypropyl cellulose, or hydroxypropyl methylcellulose, and the amount of surfactant added is 2% to 5% of the total mass of the hydrothermal reaction system; the effective chlorine content of the sodium hypochlorite aqueous solution is 10%; and the volume ratio of ethylene glycol to sodium hypochlorite aqueous solution is 15:1 to 6:1. Typically, the amount of sodium hypochlorite aqueous solution added should meet the requirement of using at least 2.5 mL of NaClO aqueous solution for every 1 g of cerium nitrate hexahydrate treated. This invention ensures that cerium dioxide is in the form of dispersed particles by controlling the type of surfactant.
[0007] The above-mentioned method for preparing spherical cerium dioxide particles is characterized in that the high-speed shear stirring speed is 10000 rpm to 12000 rpm, and the time is 30 min; the mass concentration of the ammonia water used to adjust the pH value is 20% to 30%; and the hydrothermal reaction temperature is 150℃ to 180℃, and the time is 4 h to 6 h. This invention, by controlling the speed and time of high-speed shear stirring, ensures uniform mixing of the components in the solution; by controlling the temperature of the hydrothermal reaction, it avoids excessively low temperatures that would prevent cerium dioxide from maintaining high sphericity and dispersibility, and excessively high temperatures that would cause significant agglomeration and overgrowth of the cerium dioxide product, resulting in blocky, needle-like, or flaky particles. Combined with controlling the hydrothermal reaction time, it ensures the highest yield of cerium dioxide without significant agglomeration.
[0008] The method for preparing cerium dioxide spherical particles described above is characterized in that the centrifugation speed is 8000 rpm to 10000 rpm and the time is 3 min to 5 min; the washing is performed 2 to 4 times, and deionized water is used as the solvent; and the drying time is 6 h to 8 h.
[0009] The method for preparing cerium dioxide spherical particles described above is characterized in that the calcination temperature is 300℃~600℃, and a segmented heating method is adopted: first, the temperature is raised to 200℃ and held for 1 hour, and then the temperature is rapidly raised to the target calcination temperature and held for 2 hours. This invention employs segmented calcination, first decomposing Ce(OH)4 generated by the hydrothermal reaction into CeO2 at 200℃, and then rapidly raising the temperature to promote the increase of CeO2 crystallinity and improve the mechanical strength of the resulting cerium dioxide spherical particles.
[0010] Compared with the prior art, the present invention has the following advantages:
[0011] 1. This invention employs a hydrothermal synthesis method, utilizing an oxidant to react with cerium nitrate hexahydrate, thereby converting Ce... 3+ Oxidized to Ce 4+ Simultaneously, by adding a surfactant as a dispersant and using an ethylene glycol-water solvent system, Ce 4+ Under the temperature and pressure conditions inside the hydrothermal reactor, Ce(OH)4 undergoes a hydrolysis reaction with water to generate Ce(OH)4. The surfactant and ethylene glycol-water solvent system help disperse Ce(OH)4 and maintain its high sphericity, thus allowing Ce to... 4+ Under hydrothermal conditions, it reacts with water to generate a Ce(OH)4 precursor with high sphericity and reduces the agglomeration phenomenon during the hydrothermal crystallization process, thereby controlling the morphology of cerium dioxide spherical particles and obtaining cerium dioxide spherical particle nanoparticles with uniform size, consistent morphology and strong monodispersity, which meets the abrasive requirements of CMP.
[0012] 2. This invention utilizes the moderate oxidizing power of NaClO to first make Ce... 3+ Oxidized to Ce under normal pressure 4+ Meanwhile, NaCl obtained from the decomposition of NaClO after the reaction is used as a stabilizer, which greatly reduces the agglomeration of precursor particles and further improves the monodispersity of cerium dioxide spherical particles. In addition, NaClO aqueous solution is an inexpensive and readily available industrial product, which helps to reduce the preparation cost.
[0013] 3. The cerium dioxide spherical particles prepared by this invention have high purity and uniform particle size. By adjusting process parameters such as hydrothermal temperature, hydrothermal time, cerium ion concentration, surfactant addition amount, ethylene glycol to water ratio, calcination temperature and calcination time, the size and crystallinity of the nano-cerium dioxide particles can be controlled. In addition, the cerium dioxide spherical particles have good dispersibility. At the same time, the preparation conditions are mild, the process is simple and easy to operate, and it has the potential to be applied to large-scale industrial production.
[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0015] Figure 1 The image shows the XRD pattern of the cerium dioxide spherical particles prepared in Example 1 of this invention.
[0016] Figure 2a This is a high-magnification SEM image of the cerium dioxide spherical particles prepared in Example 1 of the present invention.
[0017] Figure 2b This is a low-magnification SEM image of the cerium dioxide spherical particles prepared in Example 1 of the present invention.
[0018] Figure 3a This is a high-magnification SEM image of the cerium dioxide spherical particles prepared in Example 2 of the present invention.
[0019] Figure 3b This is a high-magnification SEM image of the cerium dioxide spherical particles prepared in Example 2 of the present invention. Detailed Implementation
[0020] Example 1
[0021] The specific process of this embodiment is as follows: First, 0.5g of cerium nitrate hexahydrate is dissolved in 15mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 0.35g of the surfactant polyvinylpyrrolidone is added, followed by 1.5mL of sodium hypochlorite aqueous solution with an available chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 10,000 rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 8.5 by adding ammonia solution with a mass concentration of 25%~30%. The clarified mixture was then placed in a 20 mL hydrothermal reactor and kept at 160 °C for 6 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 8000 rpm for 3 min, washed 4 times with deionized water, and then dried in a forced-air drying oven at 60 °C for 8 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 300 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0022] Figure 1 The image shows the XRD pattern of the cerium dioxide spherical particles prepared in this embodiment. Figure 1 It can be seen that the XRD diffraction data peaks of the cerium dioxide spherical particles are consistent with the CeO2PDF card data, and the crystallinity is high.
[0023] Figures 2a-2b These are high-magnification and low-magnification SEM images of the cerium dioxide spherical particles prepared in this embodiment. Figures 2a-2b It can be seen that the cerium dioxide spherical particles are spherical in shape, relatively uniformly dispersed, and have no obvious agglomeration. The particle size is about 300 nm.
[0024] Example 2
[0025] The specific process of this embodiment is as follows: First, 2.5g of cerium nitrate hexahydrate is dissolved in 75mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 4.25g of the surfactant polyvinylpyrrolidone is added, followed by 7.5mL of an aqueous solution of sodium hypochlorite with an available chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 10,000 rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 7 by adding ammonia solution with a mass concentration of 25%~30%. The obtained clarified mixture was placed in a 100 mL hydrothermal reactor and kept at 180 °C for 6 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 10,000 rpm for 5 min, washed 4 times with deionized water, and then placed in a forced-air drying oven and dried at 60 °C for 8 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 400 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0026] Figures 3a-3b These are high-magnification and low-magnification SEM images of the cerium dioxide spherical particles prepared in this embodiment. Figures 3a-3b It can be seen that the cerium dioxide spherical particles are spherical in shape, relatively uniformly dispersed, and have no obvious agglomeration. The particle size is about 250 nm.
[0027] Example 3
[0028] The specific process of this embodiment is as follows: First, 4g of cerium nitrate hexahydrate is dissolved in 60mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 2.25g of surfactant polyethylene glycol is added, followed by 10mL of sodium hypochlorite aqueous solution with an effective chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 10,000 rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 8.5 by adding ammonia solution with a mass concentration of 25%~30%. The obtained clarified mixture was placed in a 100 mL hydrothermal reactor and kept at 150 °C for 6 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 8000 rpm for 3 min, washed 4 times with deionized water, and then placed in a forced-air drying oven and dried at 60 °C for 8 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 500 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0029] Example 4
[0030] The specific process of this embodiment is as follows: First, 1g of cerium nitrate hexahydrate is dissolved in 75mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 1.6g of surfactant hydroxypropyl methylcellulose is added, followed by 2.5mL of sodium hypochlorite aqueous solution with an available chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 12000rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 8 by adding ammonia solution with a mass concentration of 25%~30%. The obtained clarified mixture was placed in a 20 mL hydrothermal reactor and kept at 160 °C for 4 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 10,000 rpm for 3 min, washed twice with deionized water, and then placed in a forced-air drying oven and dried at 60 °C for 8 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 600 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0031] Example 5
[0032] The specific process of this embodiment is as follows: First, 0.5g of cerium nitrate hexahydrate is dissolved in 15mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 0.9g of surfactant hydroxypropyl methylcellulose is added, followed by 1.5mL of sodium hypochlorite aqueous solution with an available chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 12000rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 7 by adding ammonia solution with a mass concentration of 25%~30%. The obtained clarified mixture was placed in a 100 mL hydrothermal reactor and kept at 160 °C for 6 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 10,000 rpm for 3 min, washed twice with deionized water, and then placed in a forced-air drying oven and dried at 60 °C for 6 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 600 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0033] Example 6
[0034] The specific process of this embodiment is as follows: First, 0.5g of cerium nitrate hexahydrate is dissolved in 30mL of ethylene glycol and stirred at room temperature for 1 hour. Then, 0.3g of the surfactant polyvinylpyrrolidone is added, followed by 2mL of an aqueous solution of sodium hypochlorite with an available chlorine content of 10%. At this point, the solution changes from colorless to orange. The solution is then stirred at 10,000 rpm for 30 minutes using a high-speed shear mixer, at which point the solution turns yellow. The resulting solution is then adjusted to pH 8.5 by adding ammonia solution with a mass concentration of 25%~30%. The obtained clarified mixture was placed in a 50 mL hydrothermal reactor and kept at 160 °C for 6 h for hydrothermal reaction. The resulting orange solid precipitate was centrifuged at 12000 rpm for 3 min, washed 4 times with deionized water, and then placed in a forced-air drying oven and dried at 60 °C for 8 h to obtain an orange-red precursor powder. The precursor powder was then ground and placed in a muffle furnace for calcination. The temperature was first raised to 200 °C and held for 1 h, and then raised to 600 °C at a heating rate of 10 °C / min and held for 2 h to obtain pale yellow cerium dioxide spherical particles.
[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.
Claims
1. A method for preparing cerium dioxide spherical particles, characterized in that, First, cerium nitrate hexahydrate was dissolved in ethylene glycol as a raw material. Then, the surfactant polyvinylpyrrolidone was added, followed by the addition of sodium hypochlorite aqueous solution as an oxidant and high-speed shearing and stirring. The pH of the resulting solution was adjusted to 7-8.5 with ammonia. The resulting clear mixture was then placed in a hydrothermal reactor for hydrothermal reaction. After centrifugation, the resulting precipitate was washed and dried to obtain an orange-red precursor powder. The precursor powder was then calcined in a muffle furnace to obtain pale yellow cerium dioxide spherical particles. The hydrothermal reaction was carried out at a temperature of 150℃-180℃ for 4-6 hours.
2. The method for preparing cerium dioxide spherical particles according to claim 1, characterized in that, The surfactant polyvinylpyrrolidone can also be replaced with polyethylene glycol, hydroxypropyl cellulose or hydroxypropyl methylcellulose, and the amount of surfactant added is 2% to 5% of the total mass of the hydrothermal reaction system; the effective chlorine content of the sodium hypochlorite aqueous solution is 10%; the volume ratio of ethylene glycol to sodium hypochlorite aqueous solution is 15:1 to 6:
1.
3. The method for preparing cerium dioxide spherical particles according to claim 1, characterized in that, The high-speed shear stirring is performed at a speed of 10,000 rpm to 12,000 rpm for 30 minutes; the ammonia concentration used to adjust the pH is 20% to 30%.
4. The method for preparing cerium dioxide spherical particles according to claim 1, characterized in that, The centrifugation speed is 8000rpm~10000rpm, and the time is 3min~5min; the washing number is 2~4 times, and the solvent used is deionized water; the drying time is 6h~8h.
5. The method for preparing cerium dioxide spherical particles according to claim 1, characterized in that, The roasting temperature is 300℃~600℃, and the heating is carried out in stages: first, the temperature is raised to 200℃ and held for 1 hour, and then the temperature is rapidly raised to the target roasting temperature and held for 2 hours.