Cerium dioxide as well as preparation method and application thereof

Abstract

The invention relates to cerium dioxide and a preparation method and application thereof, and the preparation method of the hexagonal cerium dioxide comprises the following steps: (1) carrying out first mixing on cerium salt, doped metal salt, a solvent, inorganic acid and organic acid to obtain a first mixture; the doped metal salt comprises praseodymium salt and / or neodymium salt; (2) under a hydrothermal condition, carrying out second mixing on the first mixture, ammonia water and ammonium salt to obtain a second mixture with the pH value of 3.5-6, and carrying out sol-gel reaction to obtain hexagonal cerium dioxide sol; and (3) carrying out post-treatment on the hexagonal cerium dioxide sol to obtain the hexagonal cerium dioxide. According to the preparation method of the hexagonal cerium dioxide, provided by the invention, a mixing process and a reaction process of cerium salt and specific raw materials are designed, so that the hexagonal cerium dioxide with regular particle shape, good size uniformity and high purity and crystallinity is obtained.

Description

[0001] This application is a divisional application of patent application number 202510099709.X (the original application was filed on January 22, 2025, and the invention was entitled: A cerium dioxide and its preparation method and application). Technical Field

[0002] This invention relates to the field of oxide preparation technology, and in particular to a cerium dioxide, its preparation method, and its application. Background Technology

[0003] Polishing technology holds significant research importance in modern manufacturing, with a wide range of applications covering multiple fields such as aerospace, automotive, semiconductors, and optics. Polishing technology not only significantly improves the surface quality of products but also enhances material properties and extends service life, thus playing an irreplaceable role in improving product competitiveness and meeting the demands of high-end manufacturing.

[0004] Cerium dioxide, due to its moderate hardness and strong chemical reactivity, can achieve high-precision and high-gloss surface treatment, and is known as the best polishing material. It has high polishing quality, high efficiency, and long service life, and is widely used in the polishing of TV picture tubes, eyeglass lenses, optical glass, aviation glass, integrated circuit substrates, liquid crystal displays, photomask substrates, and gemstone products. Its excellent polishing performance makes it play an important role in many high-precision processing fields. For example, prior art CN116285699A discloses a high-performance rare earth polishing powder for high-generation glass, comprising the following raw materials in parts by weight: 50-80 parts of doped cerium dioxide and 10-16 parts of embedded friction-reducing particles. This high-performance rare earth polishing powder is prepared by the following steps: adding doped cerium dioxide and embedded friction-reducing particles into a mixing tank and mixing evenly, then crushing and classifying, controlling the particle size D50: 0.5-5μm, D100: 2-20μm. The resulting polishing powder is composed of doped cerium dioxide and embedded friction-reducing particles, which reduces scratches on high-generation glass during polishing and reduces the generation of polishing debris, thereby improving the utilization rate of polishing powder and making high-generation glass less prone to surface defects, thus achieving high polishing efficiency and high polishing quality.

[0005] Despite the numerous advantages of cerium dioxide in the field of polishing technology, some shortcomings have also emerged with the development of technology and processes. For example, cerium dioxide polishing powder is usually prepared using a pulverization process, resulting in uneven particle size, which affects polishing quality and easily causes scratches and defects on the surface of the polished workpiece. Secondly, the purity of commercially available cerium dioxide polishing powder is usually between 70% and 80%, which limits its application in high-precision polishing. In addition, ultrafine and nano-sized cerium dioxide polishing powders, due to their large surface area and high surface energy, are prone to agglomeration in liquid media, affecting product stability and polishing effect.

[0006] Currently, cerium dioxide is commonly prepared using methods such as hydrothermal methods, chemical precipitation methods, and spray pyrolysis methods. However, the cerium dioxide prepared by these commonly used methods has low purity and poor product uniformity, thus affecting the quality and polishing effect of the cerium dioxide.

[0007] Therefore, how to prepare cerium dioxide particles with good product uniformity, high purity and excellent polishing effect has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, one objective of this invention is to provide a spherical cerium dioxide, its preparation method, and its applications. The preparation method employed in this invention involves introducing a doped metal salt into a cerium salt, then mixing it with an inorganic acid and an organic acid. The resulting product is then mixed with ammonia and an ammonium salt under hydrothermal conditions, and the resulting mixture undergoes a sol-gel reaction under alkaline conditions within a specific pH range to obtain a spherical cerium dioxide sol. This sol is then combined with post-processing to obtain spherical cerium dioxide particles, which exhibit regular shape, good size uniformity, and high purity and crystallinity.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing spherical cerium dioxide, the method comprising the following steps:

[0011] (1) A first mixture is obtained by mixing cerium salt, doped metal salt, solvent, inorganic acid and organic acid;

[0012] The doped metal salts include praseodymium salts and / or neodymium salts;

[0013] (2) Under hydrothermal conditions, the first mixture is mixed with ammonia and ammonium salt to obtain a second mixture with a pH of 8-10. After sol-gel reaction, a spherical cerium dioxide sol is obtained.

[0014] (3) The spherical cerium dioxide sol is post-treated to obtain the spherical cerium dioxide.

[0015] In this invention, the pH can be selected in the range of "8-10", such as 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8 or 10, etc.

[0016] The preparation method provided by this invention involves mixing cerium salt and doped metal salt with inorganic and organic acids in a solvent to obtain a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid radicals. Then, under hydrothermal conditions, the composite cerium salt and composite doped metal salt react with ammonia and ammonium salt to obtain a highly active intermediate. By precisely controlling the pH of the reaction solution within the range of 8-10, a sol-gel reaction is carried out under alkaline conditions at a specific pH. The highly active intermediate can stably crystallize to form cerium dioxide seed crystals of a specific shape. The seed crystals maintain their specific shape and continue to grow uniformly, forming spherical nuclei of uniform size and regular morphology. The nuclei gel, resulting in a spherical cerium dioxide sol. The obtained sol undergoes a post-processing process to finally obtain spherical cerium dioxide particles with high purity and crystallinity. This invention also introduces specific praseodymium salts and / or neodymium salts into the cerium salt as doped metal salts to promote morphological control and improve crystallinity, thereby enhancing the polishing effect of the obtained material. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The cerium dioxide prepared has a near-spherical morphology, and is regular in shape, uniform in particle size, has good crystallinity, and high purity. It can be widely used in semiconductor chemical mechanical polishing (CMP), high-end optical polishing, or cosmetics and other fields.

[0017] Preferably, the ratio of the molar amount of cerium ions in the cerium salt to the total molar amount of doped metal ions in the doped metal salt in step (1) is (100-5000):1, for example, 100:1, 500:1, 1000:1, 1500:1, 2000:1, 2500:1, 3000:1, 3500:1, 4000:1, 4500:1 or 5000:1, etc.

[0018] If the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low, and the cerium ion content is too low, the particles will not be able to form, and the high-performance spherical cerium dioxide will not be obtained. If the molar ratio is too high, and the doped metal ion content is too low, the morphology of cerium dioxide will be affected, and the crystallinity of the obtained product will be worse.

[0019] Preferably, the doped metal salt in step (1) includes praseodymium salt and neodymium salt.

[0020] Preferably, when the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium ions in the praseodymium salt to neodymium ions in the neodymium salt is (1-10):1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0021] Preferably, the cerium salt in step (1) includes any one or a combination of at least two of Ce2(CO3)3, Ce(NO3)3, CeCl3 or Ce2(SO4)3.

[0022] Preferably, the praseodymium salt in step (1) includes any one or a combination of at least two of Pr2(CO3)3, Pr(NO3)3, PrCl3 or Pr2(SO4)3.

[0023] Preferably, the neodymium salt in step (1) includes any one or a combination of at least two of Nd2(CO3)3, Nd(NO3)3, NdCl3 or Nd2(SO4)3.

[0024] Preferably, the mass ratio of the cerium salt to the solvent in step (1) is 1:(100-200), for example, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0025] In this invention, if the mass ratio of cerium salt to solvent is too low and the amount of solvent added is too high, the reaction rate will be low and the reaction yield will be low. In fact, when the amount of cerium salt added is extremely low, it will be impossible to obtain spherical cerium dioxide particles. If the mass ratio of the two is too high and the amount of solvent added is too low, the reaction rate will be too fast, but the uniformity of the product particles will be poor.

[0026] Preferably, the specific process of the first mixing in step (1) includes: mixing the cerium salt, the doped metal salt, the solvent and the inorganic acid, and then adding an organic acid to continue mixing to obtain the first mixture.

[0027] In the preparation of near-spherical cerium dioxide, the present invention employs a mixed process of adding inorganic acid first and then organic acid, which is beneficial for obtaining near-spherical cerium dioxide with good particle morphology and improves the particle uniformity of near-spherical cerium dioxide.

[0028] Preferably, the cerium salt, doped metal salt, solvent and inorganic acid are mixed for 1-6 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0029] Preferably, the time for adding the organic acid and continuing to mix is ​​6-18 hours, such as 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours.

[0030] Preferably, the volume ratio of the inorganic acid to the organic acid is (1.5-2.5):1, for example, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1, etc.

[0031] In the preparation of spherical cerium dioxide, if the volume ratio of inorganic acid to organic acid is too low and the amount of inorganic acid added is too small, the reaction rate will slow down, resulting in incomplete preparation of spherical cerium dioxide and affecting the preparation of spherical cerium dioxide. If the volume ratio of inorganic acid to organic acid is too high and the amount of organic acid added is too small, the content of spherical cerium dioxide in the final product will decrease, the product purity will be low, and the particle uniformity of spherical cerium dioxide will also deteriorate.

[0032] Preferably, the inorganic acid includes nitric acid.

[0033] Preferably, the concentration of the inorganic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0034] Preferably, the organic acid includes any one of formic acid, acetic acid, butyric acid, hexanoic acid, or oxalic acid.

[0035] Preferably, the concentration of the organic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0036] Preferably, the ratio of the total volume of the inorganic acid and organic acid to the volume of the solvent in step (1) is 3:(220-280), for example, 3:220, 3:225, 3:230, 3:235, 3:240, 3:245, 3:250, 3:255, 3:260, 3:265, 3:270, 3:275 or 3:280, etc.

[0037] In this invention, if the ratio of the total volume of inorganic acid and organic acid to the volume of solvent is too low, the amount of acid added will be relatively too high, which will affect the preparation of spherical cerium dioxide and lead to the generation of impurities and low product purity during the reaction process. If the volume ratio of the two is too high, the amount of acid added will be relatively too low, which will lead to a decrease in the reaction rate and incomplete reaction during the preparation of spherical cerium dioxide, which will also affect the purity of the obtained product.

[0038] Preferably, the rotation speed of the first mixing in step (1) is 200-600 rpm, such as 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm.

[0039] If the rotation speed of the first mixing step (1) is too low, the uniformity of the raw material mixing will be poor, resulting in poor morphological uniformity of the obtained spherical cerium dioxide and poor particle size consistency. If the rotation speed of the first mixing step (1) is too high, foam and microbubbles are likely to occur during the mixing process, affecting the reaction of spherical cerium dioxide and thus affecting the morphology and performance of the obtained particles.

[0040] Preferably, the specific process of the second mixing in step (2) includes: under the hydrothermal conditions, the ammonia water and the ammonium salt are simultaneously mixed with the first mixture to obtain the second mixture.

[0041] In the preparation method of quasi-spherical cerium dioxide of the present invention, if either ammonia or ammonium salt is missing, the reaction rate will decrease, the reaction will be incomplete, the particle morphology will change, and high-purity quasi-spherical cerium dioxide cannot be obtained.

[0042] Preferably, the mass ratio of ammonia water to ammonium salt in step (2) is (3.5-4.5):2, for example, 3.5:2, 3.6:2, 3.7:2, 3.8:2, 3.9:2, 4.0:2, 4.1:2, 4.2:2, 4.3:2, 4.4:2 or 4.5:2, etc.

[0043] In this invention, if the mass ratio of ammonia to ammonium salt is too low and the amount of ammonia added is relatively small, the reaction to prepare spherical cerium dioxide will be incomplete, and spherical cerium dioxide with high purity and good crystallinity cannot be obtained. If the mass ratio of ammonia to ammonium salt is too high and the amount of ammonium salt added is relatively small, the reaction rate to prepare spherical cerium dioxide will be reduced, affecting production efficiency and the morphology of the cerium dioxide obtained subsequently.

[0044] Preferably, the concentration of the ammonia water is 1-35 wt%, such as 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0045] Preferably, the temperature of the hydrothermal conditions in step (2) is 30-100℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃.

[0046] In this invention, if the hydrothermal temperature is too low, the reaction will not be able to occur, and a highly active intermediate cannot be obtained, thus affecting the preparation of spherical cerium dioxide; if the temperature is too high, energy consumption will increase and the uniformity of product morphology will deteriorate.

[0047] Preferably, the pressure of the hydrothermal conditions in step (2) is 0.1-20 MPa, such as 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa or 20 MPa.

[0048] Preferably, the mixing time in step (2) is 0.1-5h, for example 0.1h, 0.5h, 1h, 1.5h, 2h, 3h, 3.5h, 4h, 4.5h or 5h.

[0049] This invention regulates the pH of the resulting second mixture to a specific range by adjusting the relative amounts of the first mixture, ammonia, and ammonium salt added.

[0050] Preferably, the temperature of the sol-gel reaction in step (2) is 50-160℃, such as 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃.

[0051] Preferably, the pH during the sol-gel reaction in step (2) is maintained at 8-10, such as 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8 or 10.

[0052] In this invention, the pH of the reactants during the sol-gel reaction can be controlled within a specific range by adding ammonia and nitric acid to the raw materials.

[0053] Preferably, the sol-gel reaction in step (2) is also accompanied by stirring.

[0054] Preferably, the stirring speed is 10-500 rpm, such as 10 rpm, 20 rpm, 50 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.

[0055] In the preparation of spherical cerium dioxide, if the stirring speed during the sol-gel reaction is too low, the reaction will be incomplete, which will affect the morphology of cerium dioxide and reduce the uniformity of the obtained spherical cerium dioxide particles. If the stirring speed during the sol-gel reaction is too high, bubbles will be generated, affecting the reaction between substances and thus affecting the morphology and properties of the obtained cerium dioxide.

[0056] In this invention, the sol-gel reaction in step (2) is still carried out in a hydrothermal reactor, only the reaction temperature is adjusted and the stirring process is added.

[0057] Preferably, the solid content of the sol-gel reaction in step (2) until the spherical cerium dioxide sol is obtained is 0.1-40 wt%, for example, 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0058] Preferably, the post-processing in step (3) includes: concentrating the spherical cerium dioxide sol obtained in step (2), and then centrifuging, drying and deagglomerating to obtain the spherical cerium dioxide.

[0059] Preferably, the concentration temperature is 120-180℃, such as 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃.

[0060] Preferably, the concentration pressure is 0.1-100 MPa, for example 0.1 MPa, 0.5 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa or 100 MPa.

[0061] Preferably, the product is concentrated to a solid content ≥60wt%, such as 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%.

[0062] In the preparation of spherical cerium dioxide, this invention controls the solid content of the concentrated product to facilitate the separation of nanoparticles after centrifugation. If the solid content of the concentrated product is too low, the yield of spherical cerium dioxide will decrease.

[0063] Preferably, the centrifugation speed is 500-5000 rpm, such as 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, or 5000 rpm.

[0064] Preferably, the drying temperature is 300-1100℃, such as 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃ or 1100℃.

[0065] Preferably, the drying time is 2-12 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0066] Preferably, the deagglomeration method includes any one of gas phase jetting, convection jetting, or air milling.

[0067] In a second aspect, the present invention provides a quasi-spherical cerium dioxide, which is prepared by the preparation method described in the first aspect, wherein the quasi-spherical cerium dioxide includes a doping element, and the doping element includes praseodymium and / or neodymium.

[0068] The spherical cerium dioxide particles provided by this invention have regular morphology, good particle uniformity, high crystallinity, and high purity. Specifically, praseodymium and / or neodymium elements, as dopants of cerium dioxide, can promote the regulation of cerium dioxide morphology and improve the crystallinity of the obtained spherical cerium dioxide particles.

[0069] Preferably, the particle size D50 of the spherical cerium dioxide is 5-500nm, such as 5nm, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm.

[0070] Preferably, the specific surface area of ​​the spherical cerium dioxide is 20-250 m². 2 / g, for example 20m 2 / g、40m 2 / g、60m 2 / g、80m 2 / g, 100m 2 / g、120m 2 / g, 140m 2 / g, 160m 2 / g、180m 2 / g、200m 2 / g、220m 2 / g、240m 2 / g or 250m 2 / g etc.

[0071] Thirdly, the present invention provides an application of the quasi-spherical cerium dioxide according to the second aspect, wherein the quasi-spherical cerium dioxide is applied in semiconductor chemical mechanical polishing (CMP), optical polishing, or cosmetics.

[0072] The spherical cerium dioxide provided by this invention is applicable to any field of study that can be conceived by those skilled in the art.

[0073] The second objective of this invention is to provide a hexagonal cerium dioxide, its preparation method, and its application. The preparation method employed in this invention involves introducing a doped metal salt into a cerium salt, then mixing it with an inorganic acid and an organic acid. The resulting product is then mixed with ammonia and an ammonium salt under hydrothermal conditions, and the resulting mixture undergoes a sol-gel reaction under weakly acidic conditions within a specific pH range to obtain a hexagonal cerium dioxide sol. This sol is then combined with post-processing to obtain hexagonal cerium dioxide particles, which exhibit regular shape, good size uniformity, and high purity and crystallinity.

[0074] To achieve this objective, the present invention adopts the following technical solution:

[0075] Fourthly, the present invention provides a method for preparing hexagonal cerium dioxide, the method comprising the following steps:

[0076] (1) A first mixture is obtained by mixing cerium salt, doped metal salt, solvent, inorganic acid and organic acid;

[0077] The doped metal salts include praseodymium salts and / or neodymium salts;

[0078] (2) Under hydrothermal conditions, the first mixture is mixed with ammonia and ammonium salt to obtain a second mixture with a pH of 3.5-6. After sol-gel reaction, hexagonal cerium dioxide sol is obtained.

[0079] (3) The hexagonal cerium dioxide sol is post-treated to obtain the hexagonal cerium dioxide.

[0080] In this invention, the pH can be selected in the range of "3.5-6", such as 3.5, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 or 6, etc.

[0081] The preparation method provided by this invention introduces specific praseodymium salts and / or neodymium salts as doped metal salts into cerium salts, which promotes the control of product morphology and improves the crystallinity of the obtained product during subsequent reactions. Then, by mixing cerium salts and doped metal salts with inorganic and organic acids in a solvent, a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid anions are obtained. Then, under hydrothermal conditions, the composite cerium salt and the composite doped metal salt can react with ammonia and ammonium salts to obtain a highly active intermediate. The pH value of the reaction solution is precisely controlled to be within the range of 3.5-6. Under the weakly acidic conditions of a specific pH value, the sol-gel reaction is carried out. The highly active intermediate can stably crystallize to form cerium dioxide seed crystals of a specific shape. The seed crystals maintain a specific shape and continue to grow uniformly to form hexagonal crystal nuclei of uniform size and regular morphology. The crystal nuclei gelle, thereby obtaining a hexagonal cerium dioxide sol. The obtained sol is then subjected to a post-processing process to finally obtain hexagonal cerium dioxide particles with high purity and crystallinity. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The prepared cerium dioxide has a hexagonal morphology with regular shape, good particle uniformity, and high crystallinity and purity. It can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0082] Preferably, the ratio of the molar amount of cerium ions in the cerium salt to the total molar amount of doped metal ions in the doped metal salt in step (1) is (500-50000):1, for example, 500:1, 1000:1, 5000:1, 10000:1, 15000:1, 20000:1, 25000:1, 30000:1, 35000:1, 40000:1, 45000:1 or 500000:1, etc.

[0083] If the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low, the particles will not be able to form, affecting the growth morphology of hexagonal cerium dioxide and making it impossible to obtain high-performance hexagonal cerium dioxide. If the molar ratio is too high, the crystallinity of the obtained hexagonal cerium dioxide will be poor, and the morphology of cerium dioxide will also be affected.

[0084] Preferably, the doped metal salt in step (1) includes praseodymium salt and neodymium salt.

[0085] Preferably, when the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium ions in the praseodymium salt to neodymium ions in the neodymium salt is (1-10):1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0086] Preferably, the cerium salt in step (1) includes any one or a combination of at least two of Ce2(CO3)3, Ce(NO3)3, CeCl3 or Ce2(SO4)3.

[0087] Preferably, the praseodymium salt in step (1) includes any one or a combination of at least two of Pr2(CO3)3, Pr(NO3)3, PrCl3 or Pr2(SO4)3.

[0088] Preferably, the neodymium salt in step (1) includes any one or a combination of at least two of Nd2(CO3)3, Nd(NO3)3, NdCl3 or Nd2(SO4)3.

[0089] Preferably, the mass ratio of the cerium salt to the solvent in step (1) is 1:(100-200), for example, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0090] Preferably, the specific process of the first mixing in step (1) includes: mixing the cerium salt, the doped metal salt, the solvent and the organic acid, and then adding an inorganic acid to continue mixing to obtain the first mixture.

[0091] In the preparation of hexagonal cerium dioxide, the present invention adopts a mixed process of adding organic acid first and then inorganic acid, which is beneficial to forming hexagonal cerium dioxide with good morphological uniformity and high particle uniformity in subsequent processes.

[0092] Preferably, the cerium salt, doped metal salt, solvent and organic acid are mixed for 1-6 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0093] Preferably, the time for adding the inorganic acid and continuing to mix is ​​12-24 hours, such as 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, or 24 hours.

[0094] Preferably, the volume ratio of the inorganic acid to the organic acid is (2.8-4):1, for example, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1 or 4:1, etc.

[0095] In the preparation of hexagonal cerium dioxide, if the volume ratio of inorganic acid to organic acid is too low and the amount of inorganic acid added is relatively small, the reaction for preparing hexagonal cerium dioxide will be incomplete, affecting the preparation of hexagonal cerium dioxide. If the volume ratio of inorganic acid to organic acid is too high and the amount of organic acid added is relatively small, the content of hexagonal cerium dioxide in the final product will be reduced, the product purity will be low, and the particle size uniformity of hexagonal cerium dioxide will be affected.

[0096] Preferably, the inorganic acid includes nitric acid.

[0097] Preferably, the concentration of the inorganic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0098] Preferably, the organic acid includes any one of formic acid, acetic acid, butyric acid, hexanoic acid, or oxalic acid.

[0099] Preferably, the concentration of the organic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0100] Preferably, the ratio of the total volume of the inorganic acid and organic acid to the volume of the solvent in step (1) is 3:(150-210), for example, 3:150, 3:155, 3:160, 3:165, 3:170, 3:175, 3:180, 3:185, 3:190, 3:195, 3:200, 3:205 or 3:210, etc.

[0101] In this invention, if the ratio of the total volume of inorganic acid and organic acid to the volume of solvent is too low, the amount of acid added will be relatively too high, which will affect the preparation of hexagonal cerium dioxide, leading to an increase in impurity content during the reaction process of preparing hexagonal cerium dioxide and a decrease in the purity of the obtained hexagonal cerium dioxide particles; if the volume ratio of the two is too high, the amount of acid added will be relatively too low, which will lead to a decrease in the reaction rate, incomplete reaction during the preparation of hexagonal cerium dioxide, and affect the purity of the obtained hexagonal cerium dioxide.

[0102] Preferably, the rotation speed of the first mixing in step (1) is 1000-15000 rpm, such as 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 11000 rpm, 12000 rpm, 13000 rpm, 14000 rpm, or 15000 rpm.

[0103] In the preparation of hexagonal cerium dioxide, if the rotation speed of the first mixing step (1) is too low, it will affect the morphological uniformity and size uniformity of the hexagonal cerium dioxide; if the rotation speed of the first mixing step (1) is too high, a large number of microbubbles will be generated, affecting the reaction process of preparing hexagonal cerium dioxide.

[0104] Preferably, the specific process of the second mixing in step (2) includes: under the hydrothermal conditions, the first mixture is first mixed with the ammonium salt, and then the ammonia water is added to the resulting mixture to obtain the second mixture.

[0105] In the preparation method of hexagonal cerium dioxide of the present invention, in the hydrothermal reaction, a process is adopted in which a first mixture is first mixed with an ammonium salt, and then ammonia water is added for mixing. This process aims to control the reaction rate and reaction process, thereby facilitating the preparation of hexagonal cerium dioxide with good particle uniformity.

[0106] Preferably, the mixing time of the first mixture and the ammonium salt is 0.5-3h, for example 0.5h, 1h, 1.5h, 2h, 2.5h or 3h.

[0107] Preferably, the product obtained by mixing the first mixture and the ammonium salt is mixed with ammonia water for 0.1-3 hours, such as 0.1 hours, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0108] Preferably, the mass ratio of ammonia to ammonium salt is (4.8-6):2, such as 4.8:2, 5:2, 5.2:2, 5.4:2, 5.6:2, 5.8:2 or 6:2.

[0109] In the preparation method of hexagonal cerium dioxide of this invention, if the mass ratio of ammonia to ammonium salt is too low or too high, it will affect the reaction process of preparing hexagonal cerium dioxide, resulting in incomplete reaction and thus affecting the morphology and purity of cerium dioxide.

[0110] Preferably, the concentration of the ammonia water is 1-35 wt%, such as 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0111] Preferably, the temperature of the hydrothermal conditions in step (2) is 30-100℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃.

[0112] In this invention, if the hydrothermal temperature is too low, the reaction will not occur, and a highly active intermediate cannot be obtained, thus affecting the preparation of hexagonal cerium dioxide; if the temperature is too high, it will lead to increased energy consumption and poor product morphology uniformity.

[0113] Preferably, the pressure of the hydrothermal conditions in step (2) is 0.1-20 MPa, such as 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa or 20 MPa.

[0114] This invention regulates the pH of the resulting second mixture to a specific range by adjusting the relative amounts of the first mixture, ammonia, and ammonium salt added.

[0115] Preferably, the temperature of the sol-gel reaction in step (2) is 50-160℃, such as 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃.

[0116] Preferably, the pH during the sol-gel reaction in step (2) is maintained at 3.5-6, such as 3.5, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 or 6.

[0117] In this invention, the pH of the reactants during the sol-gel reaction can be controlled within a specific range by adding ammonia and nitric acid to the raw materials.

[0118] Preferably, the sol-gel reaction in step (2) is also accompanied by stirring.

[0119] Preferably, the stirring speed is 200-2000 rpm, such as 200 rpm, 400 rpm, 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm, or 2000 rpm.

[0120] In the preparation of hexagonal cerium dioxide, if the stirring speed during the sol-gel reaction is relatively low, the uniformity of the morphology and particle size of the obtained hexagonal cerium dioxide particles will decrease; if the stirring speed during the sol-gel reaction is too high, the uniformity of the particle size will decrease.

[0121] In this invention, the sol-gel reaction in step (2) is still carried out in a hydrothermal reactor, only the reaction temperature is adjusted and the stirring process is added.

[0122] Preferably, the solid content of the hexagonal cerium dioxide sol obtained by the sol-gel reaction in step (2) is 0.1-40 wt%, for example, 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0123] Preferably, the specific process of the post-processing in step (3) includes: concentrating the hexagonal cerium dioxide sol obtained in step (2), and then centrifuging, drying and deagglomerating to obtain the hexagonal cerium dioxide.

[0124] Preferably, the concentration temperature is 120-180℃, such as 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃.

[0125] Preferably, the concentration pressure is 0.1-100 MPa, for example 0.1 MPa, 1 MPa, 5 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa or 100 MPa.

[0126] Preferably, the product is concentrated to a solid content ≥60wt%, such as 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%.

[0127] In the preparation of hexagonal cerium dioxide, this invention controls the solid content of the concentrated product to facilitate the separation of nanoparticles after centrifugation. If the solid content of the concentrated product is too low, the yield of the final hexagonal cerium dioxide will decrease.

[0128] Preferably, the centrifugation speed is above 2000 rpm, such as 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm or 5000 rpm.

[0129] Preferably, the drying temperature is 300-1100℃, such as 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃ or 1100℃.

[0130] Preferably, the drying time is 2-12 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0131] Preferably, the specific process for deagglomeration includes any one of gas phase jetting, convection jetting, or air milling.

[0132] Fifthly, the present invention provides a hexagonal cerium dioxide, which is prepared by the preparation method described in the fourth aspect, wherein the hexagonal cerium dioxide includes a doping element, and the doping element includes praseodymium and / or neodymium.

[0133] The hexagonal cerium dioxide provided by this invention has a regular morphology, good particle uniformity, high crystallinity and high purity. Specifically, praseodymium and / or neodymium elements, as dopants of cerium dioxide, can promote the regulation of cerium dioxide morphology and improve the crystallinity of the obtained hexagonal cerium dioxide particles.

[0134] Preferably, the particle size D50 of the hexagonal cerium dioxide is 5-500nm, such as 5nm, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm.

[0135] Preferably, the side length of the hexagonal cerium dioxide is 60-160nm, such as 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm or 160nm.

[0136] Preferably, the thickness of the hexagonal cerium dioxide is 2-20 nm, such as 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm.

[0137] Preferably, the specific surface area of ​​the hexagonal cerium dioxide is 100-250 m². 2 / g, for example, 100m 2 / g、110m 2 / g、120m 2 / g、130m 2 / g, 140m 2 / g, 150m 2 / g, 160m 2 / g、170m 2 / g、180m 2 / g、190m 2 / g、200m 2 / g、210m 2 / g、220m 2 / g、230m 2 / g、240m 2 / g or 250m 2 / g etc.

[0138] In a sixth aspect, the present invention provides an application of hexagonal cerium dioxide according to the fifth aspect, wherein the hexagonal cerium dioxide is used in semiconductor chemical mechanical polishing (CMP), optical polishing, or cosmetics.

[0139] The hexagonal cerium dioxide provided by this invention is applicable to any field of study that can be conceived by those skilled in the art.

[0140] The third objective of this invention is to provide a triangular cerium dioxide, its preparation method, and its application. The preparation method employed in this invention involves introducing a doped metal salt into a cerium salt, then mixing it with an inorganic acid and an organic acid. The resulting product is then mixed with ammonia and an ammonium salt under hydrothermal conditions, and the resulting mixture undergoes a sol-gel reaction under strong acid conditions within a specific pH range to obtain a triangular cerium dioxide sol. This sol is then combined with post-processing to produce triangular cerium dioxide particles, which exhibit regular shape, good size uniformity, and high purity and crystallinity.

[0141] To achieve this objective, the present invention adopts the following technical solution:

[0142] In a seventh aspect, the present invention provides a method for preparing triangular cerium dioxide, the method comprising the following steps:

[0143] (1) A first mixture is obtained by mixing cerium salt, doped metal salt, solvent, inorganic acid and organic acid;

[0144] The doped metal salts include praseodymium salts and / or neodymium salts;

[0145] (2) Under hydrothermal conditions, the first mixture is mixed with ammonia and ammonium salt to obtain a second mixture. The pH of the second mixture is 1-3. After sol-gel reaction, triangular cerium dioxide sol is obtained.

[0146] (3) The triangular cerium dioxide sol is post-treated to obtain the triangular cerium dioxide.

[0147] In this invention, the pH can be selected in the range of "1-3", such as 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3, etc.

[0148] The preparation method provided by this invention involves mixing cerium salt and doped metal salt with inorganic and organic acids in a solvent to obtain a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid radicals. Then, under hydrothermal conditions, the composite cerium salt and composite doped metal salt react with ammonia and ammonium salt to obtain a highly active intermediate. By precisely controlling the pH of the reaction solution within the range of 1-3, a sol-gel reaction is carried out under strongly acidic conditions at a specific pH. The highly active intermediate can stably crystallize to form cerium dioxide seed crystals of a specific shape. The seed crystals maintain their specific shape and continue to grow uniformly, forming triangular crystal nuclei of uniform size and regular morphology. The nuclei gel, resulting in a triangular cerium dioxide sol. The obtained sol undergoes a post-processing process to finally obtain a large quantity of high-purity and highly crystalline triangular cerium dioxide particles. This invention also introduces specific praseodymium salts and / or neodymium salts into the cerium salt as doped metal salts, promoting the control of product morphology and improving the crystallinity of the product, thereby improving the polishing effect of the obtained material. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The prepared cerium dioxide has a triangular and regular shape, uniform particles, good crystallinity, and high purity, and can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0149] Preferably, the ratio of the molar amount of cerium ions in the cerium salt in step (1) to the total molar amount of doped metal ions in the doped metal salt is (1000-500000):1, for example, 1000:1, 5000:1, 10000:1, 50000:1, 100000:1, 200000:1, 300000:1, 400000:1 or 500000:1, etc.

[0150] If the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low, the particles will not be able to form, affecting the growth morphology of cerium dioxide, and even making it impossible to obtain triangular cerium dioxide; if the molar ratio is too high, the resulting product will have poor crystallinity, and may not be applicable to the polishing field, and will also affect the morphology of cerium dioxide.

[0151] Preferably, the doped metal salt in step (1) includes praseodymium salt and neodymium salt.

[0152] Preferably, when the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium ions in the praseodymium salt to neodymium ions in the neodymium salt is (1-10):1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0153] Preferably, the cerium salt in step (1) includes any one or a combination of at least two of Ce2(CO3)3, Ce(NO3)3, CeCl3 or Ce2(SO4)3.

[0154] Preferably, the praseodymium salt in step (1) includes any one or a combination of at least two of Pr2(CO3)3, Pr(NO3)3, PrCl3 or Pr2(SO4)3.

[0155] Preferably, the neodymium salt in step (1) includes any one or a combination of at least two of Nd2(CO3)3, Nd(NO3)3, NdCl3 or Nd2(SO4)3.

[0156] Preferably, the mass ratio of the cerium salt to the solvent in step (1) is 1:(100-200), for example, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0157] Preferably, the specific process of the first mixing in step (1) includes: mixing the cerium salt, the doped metal salt, the solvent and the organic acid, and then adding an inorganic acid to continue mixing to obtain the first mixture.

[0158] Preferably, the cerium salt, doped metal salt, solvent and organic acid are mixed for 1-6 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0159] Preferably, the time for adding the inorganic acid and continuing to mix is ​​12-24 hours, such as 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, or 24 hours.

[0160] In the preparation of triangular cerium dioxide, this invention employs a mixed process of adding organic acid first and then inorganic acid, aiming to control the reaction rate and improve the uniformity of the prepared triangular cerium dioxide particles.

[0161] Preferably, the volume ratio of the inorganic acid to the organic acid is (6-10):3, such as 6:3, 6.5:3, 7:3, 7.5:3, 8:3, 8.5:3, 9:3, 9.5:3 or 10:3, etc.

[0162] In the preparation of triangular cerium dioxide, the present invention aims to control the reaction by adjusting the volume ratio of inorganic acid and organic acid, so as to avoid the relative volume of inorganic acid and organic acid being too low or too high, which would affect the morphology and particle uniformity of the prepared triangular cerium dioxide.

[0163] Preferably, the inorganic acid includes nitric acid.

[0164] Preferably, the concentration of the inorganic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0165] Preferably, the organic acid includes any one of formic acid, acetic acid, butyric acid, hexanoic acid, or oxalic acid.

[0166] Preferably, the concentration of the organic acid is 0.1-20 wt%, for example, 0.1 wt%, 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, or 20 wt%.

[0167] Preferably, the ratio of the total volume of the inorganic acid and organic acid to the volume of the solvent in step (1) is 3:(80-140), for example, 3:80, 3:85, 3:90, 3:95, 3:100, 3:105, 3:110, 3:115, 3:120, 3:125, 3:130, 3:135 or 3:140, etc.

[0168] In this invention, if the ratio of the total volume of inorganic acid and organic acid to the volume of solvent is too low, and the amount of acid added is too large, it will affect the preparation of triangular cerium dioxide, resulting in the generation of impurities and low product purity during the reaction process of preparing triangular cerium dioxide. If the volume ratio of the two is too high, and the amount of acid added is too low, it will lead to a decrease in the reaction rate and incomplete reaction during the preparation of triangular cerium dioxide, which will also affect the purity of the obtained product.

[0169] Preferably, in step (1), the rotation speed of the first mixing is 1000-2000 rpm, such as 1000 rpm, 1200 rpm, 1400 rpm, 1600 rpm, 1800 rpm or 2000 rpm.

[0170] In this invention, if the rotation speed of the first mixing in step (1) is too low, it will affect the reaction process in the preparation of triangular cerium dioxide, thereby affecting the morphology and particle size uniformity of triangular cerium dioxide; if the rotation speed of the first mixing in step (1) is too high, a large number of microbubbles will be generated, which will reduce the particle size uniformity of the prepared triangular cerium dioxide particles.

[0171] Preferably, the specific process of the second mixing in step (2) includes: under the hydrothermal conditions, mixing the first mixture with the ammonia water first, and then adding the ammonium salt to the resulting mixture to obtain the second mixture.

[0172] In the preparation method of triangular cerium dioxide of the present invention, under hydrothermal conditions, a first mixture is first mixed with ammonia water, and then ammonium salt is added and mixed. This is intended to control the reaction process, thereby facilitating the preparation of triangular cerium dioxide with excellent morphology and properties.

[0173] Preferably, the mixing time between the first mixture and the ammonia water is 0.5-3 hours, such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0174] Preferably, the mixing time for adding ammonium salt to the product obtained after mixing the first mixture and the ammonia water is 0.1-3h, for example, 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h or 3h.

[0175] Preferably, the mass ratio of ammonia to ammonium salt is (8-12):2, such as 8:2, 8.5:2, 9:2, 9.5:2, 10:2, 10.5:2, 11:2, 11.5:2 or 12:2, etc.

[0176] In the preparation method of triangular cerium dioxide of this invention, if the mass ratio of ammonia water to ammonium salt is too low or too high, it will affect the reaction process of the preparation of triangular cerium dioxide, thereby affecting the morphology and purity of triangular cerium dioxide.

[0177] Preferably, the concentration of the ammonia water is 1-35 wt%, such as 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0178] Preferably, the temperature of the hydrothermal conditions in step (2) is 30-100℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃.

[0179] Preferably, the pressure of the hydrothermal conditions in step (2) is 0.1-20 MPa, such as 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa or 20 MPa.

[0180] This invention regulates the pH of the resulting second mixture to a specific range by adjusting the relative amounts of the first mixture, ammonia, and ammonium salt added.

[0181] Preferably, the temperature of the sol-gel reaction in step (2) is 50-160℃, such as 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃.

[0182] Preferably, the pH during the sol-gel reaction in step (2) is maintained at 1-3, such as 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.

[0183] In this invention, the pH of the reactants during the sol-gel reaction can be controlled within a specific range by adding ammonia and nitric acid to the raw materials.

[0184] Preferably, the sol-gel reaction in step (2) is also accompanied by stirring.

[0185] Preferably, the stirring speed is 300-3000 rpm, such as 300 rpm, 600 rpm, 900 rpm, 1200 rpm, 1500 rpm, 1800 rpm, 2100 rpm, 2400 rpm, 2700 rpm or 3000 rpm.

[0186] In the preparation of triangular cerium dioxide, if the stirring speed during the sol-gel reaction is relatively low, the uniformity of the morphology and particle size of the obtained triangular cerium dioxide particles will decrease; if the stirring speed during the sol-gel reaction is too high, the uniformity of the particle size will decrease.

[0187] In this invention, the sol-gel reaction in step (2) is still carried out in a hydrothermal reactor, only the reaction temperature is adjusted and the stirring process is added.

[0188] Preferably, the solid content of the triangular cerium dioxide sol obtained by the sol-gel reaction in step (2) is 0.1-40 wt%, for example, 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%.

[0189] Preferably, the post-processing process includes: concentrating the triangular cerium dioxide sol obtained in step (2), and then centrifuging, drying and deagglomerating to obtain the triangular cerium dioxide.

[0190] Preferably, the concentration temperature is 120-180℃, such as 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃.

[0191] Preferably, the concentration pressure is 0.1-100 MPa, for example 0.1 MPa, 1 MPa, 5 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa or 100 MPa.

[0192] Preferably, the product is concentrated to a solid content ≥60wt%, such as 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%.

[0193] In the preparation of triangular cerium dioxide, this invention controls the solid content of the concentrated product to facilitate the separation of nanoparticles after centrifugation. If the solid content of the concentrated product is too low, the yield of the final triangular cerium dioxide will decrease.

[0194] Preferably, the centrifugation speed is 2000-6000 rpm, such as 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm, or 6000 rpm.

[0195] Preferably, the drying temperature is 300-1100℃, such as 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃ or 1100℃.

[0196] Preferably, the drying time is 2-12 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or 12 hours.

[0197] Eighthly, the present invention provides a triangular cerium dioxide, which is prepared by the preparation method described in the seventh aspect, wherein the triangular cerium dioxide includes a doping element, the doping element including praseodymium and / or neodymium.

[0198] The triangular cerium dioxide provided by this invention has a regular morphology, good particle uniformity, high crystallinity and high purity. Specific praseodymium and / or neodymium elements are used as dopant elements to promote the regulation of cerium dioxide morphology and improve the crystallinity of the obtained triangular cerium dioxide particles.

[0199] Preferably, the particle size D50 of the triangular cerium dioxide is 5-500nm, such as 5nm, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm or 500nm.

[0200] Preferably, the triangular cerium dioxide comprises triangular nanosheet cerium dioxide and / or triangular pyramidal cerium dioxide.

[0201] Preferably, the triangular cerium dioxide includes triangular nanosheet cerium dioxide and triangular pyramidal cerium dioxide.

[0202] Preferably, the mass ratio of the triangular nanosheet cerium dioxide to the triangular pyramidal cerium dioxide is 2:(0.1-1), for example, 2:0.1, 2:0.2, 2:0.3, 2:0.4, 2:0.5, 2:0.6, 2:0.7, 2:0.8, 2:0.9 or 2:1, etc.

[0203] Preferably, the triangular nanosheet cerium dioxide has a side length of 80-300nm, such as 80nm, 120nm, 160nm, 200nm, 240nm, 280nm or 300nm, and a thickness of 2-20nm, such as 2nm, 4nm, 6nm, 8nm, 10nm, 12nm, 14nm, 16nm, 18nm or 20nm.

[0204] Preferably, the side length of the triangular pyramidal cerium dioxide is 50-180nm, such as 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm or 180nm.

[0205] Preferably, the specific surface area of ​​the triangular cerium dioxide is 10-200 m². 2 / g, for example, 10m 2 / g、20m 2 / g、40m 2 / g、60m 2 / g、80m 2 / g, 100m 2 / g、120m 2 / g, 140m 2 / g, 160m 2 / g、180m 2 / g or 200m 2 / g etc.

[0206] In a ninth aspect, the present invention provides an application of triangular cerium dioxide according to the eighth aspect, wherein the triangular cerium dioxide is applied in semiconductor chemical mechanical polishing (CMP), optical polishing, or cosmetics.

[0207] The triangular cerium dioxide provided by this invention is applicable to any field of study that can be conceived by those skilled in the art.

[0208] Compared with the prior art, the present invention has at least the following beneficial effects:

[0209] (1) The preparation method adopted in this invention introduces a doped metal salt into cerium salt, and then mixes it with inorganic acid and organic acid. The product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the mixture is subjected to sol-gel reaction under alkaline conditions within a specific range to obtain spherical cerium dioxide sol. Then, combined with post-processing, spherical cerium dioxide particles are obtained. The particles have regular shape, good size uniformity, and high purity and crystallinity.

[0210] (2) The preparation method adopted in this invention introduces a doped metal salt into cerium salt, and then mixes it with inorganic acid and organic acid. The product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the mixture is subjected to sol-gel reaction under weak acid conditions within a specific range to obtain hexagonal cerium dioxide sol. Hexagonal cerium dioxide particles are then obtained by combining post-processing. The particles have regular shape, good size uniformity, and high purity and crystallinity.

[0211] (3) The preparation method adopted in this invention introduces a doped metal salt into cerium salt, and then mixes it with inorganic acid and organic acid. The product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the mixture is subjected to sol-gel reaction under strong acid conditions within a specific range to obtain triangular cerium dioxide sol. Then, triangular cerium dioxide particles are obtained by combining post-processing. The particles have regular shape, good size uniformity, and high purity and crystallinity. Attached Figure Description

[0212] Figure 1 This is a scanning electron microscope image of the spherical cerium dioxide from Example 1.

[0213] Figure 2 This is a scanning electron microscope image of the hexagonal cerium dioxide from Example 21.

[0214] Figure 3 This is a scanning electron microscope image of the triangular cerium dioxide from Example 31.

[0215] Figure 4 This is a magnified scanning electron microscope image of the triangular cerium dioxide from Example 31. Detailed Implementation

[0216] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0217] Example 1

[0218] This embodiment provides a method for preparing spherical cerium dioxide, which specifically includes the following steps:

[0219] (A) Ce(NO3)3, Pr(NO3)3, Nd(NO3)3, 3wt% nitric acid and water were mixed at 400 rpm for 4 h, and then 5wt% acetic acid was added and the mixture was continued at 400 rpm for 8 h. The molar ratio of Ce(NO3)3, Pr(NO3)3 and Nd(NO3)3 was 1000:1:1, the mass ratio of Ce(NO3)3 to water was 1:150, and the volume ratio of nitric acid, acetic acid and water was 2:1:240, to obtain the first mixture.

[0220] (B) Under hydrothermal conditions of 95°C and 5 MPa, the first mixture obtained in step (A) was mixed with ammonia and ammonium nitrate in a mass ratio of 4:2 in a hydrothermal reactor for 0.5 h. The concentration of ammonia was 1.5 wt%, and a second mixture with a pH of 8.9 was obtained. Then, the pH of the mixture was maintained at 8.9, and the temperature in the hydrothermal reactor was maintained at 150°C for sol-gel reaction. The sol-gel reaction was also accompanied by stirring at 300 rpm until a spherical cerium dioxide sol with a solid content of 30 wt% was obtained in the reactor.

[0221] (C) The spherical cerium dioxide sol obtained in step (B) is concentrated at 120°C under a pressure of 5 MPa until a sol with a solid content of 95 wt% is obtained. The obtained sol is centrifuged at 3000 rpm to obtain a solid product. Then, the obtained solid product is dried at 300°C for 8 hours. After deagglomeration by air milling, spherical cerium dioxide is obtained. The specific surface area of ​​the obtained spherical cerium dioxide is 214 m². 2 / g.

[0222] Example 2

[0223] This embodiment provides a method for preparing spherical cerium dioxide, which specifically includes the following steps:

[0224] (A) CeCl3, PrCl3, NdCl3, 3wt% nitric acid and water were mixed at 200 rpm for 5 h, and then 1wt% n-butyric acid was added and the mixture was continued at 200 rpm for 15 h. The molar ratio of CeCl3, PrCl3 and NdCl3 was 5000:5:1, the mass ratio of CeCl3 to water was 1:100, and the volume ratio of nitric acid, n-butyric acid and water was 1.5:1:220, to obtain the first mixture.

[0225] (B) Under hydrothermal conditions of 100°C and 10 MPa, the first mixture obtained in step (A) is mixed with ammonia and ammonium chloride in a mass ratio of 3.5:2 in a hydrothermal reactor for 2 hours. The concentration of ammonia is 2 wt%, and a second mixture with a pH of 8 is obtained. Then, the pH of the mixture is maintained at 8, and the temperature in the hydrothermal reactor is maintained at 160°C for sol-gel reaction. The sol-gel reaction is also accompanied by stirring at a speed of 50 rpm until a spherical cerium dioxide sol with a solid content of 20 wt% is obtained in the reactor.

[0226] (C) The spherical cerium dioxide sol obtained in step (B) is concentrated at 180°C under a pressure of 10 MPa until a sol with a solid content of 85 wt% is obtained. The obtained sol is centrifuged at 4500 rpm to obtain a solid product. Then, the obtained solid product is dried at 500°C for 6 h. After deagglomeration by gas phase spraying, spherical cerium dioxide is obtained.

[0227] Example 3

[0228] This embodiment provides a method for preparing spherical cerium dioxide, which specifically includes the following steps:

[0229] (A) Ce(SO4)3, Pr(SO4)3, Nd(SO4)3, 3wt% nitric acid and water were mixed at 600 rpm for 4 h, and then 3wt% acetic acid was added and the mixture was continued at 600 rpm for 16 h. The molar ratio of Ce(SO4)3, Pr(SO4)3 and Nd(SO4)3 was 3000:2:1, the mass ratio of Ce(SO4)3 to water was 1:200, and the volume ratio of nitric acid, acetic acid and water was 2.5:1:280, to obtain the first mixture.

[0230] (B) Under hydrothermal conditions of 30°C and 0.5 MPa, the first mixture obtained in step (A) was mixed with ammonia and ammonium sulfate in a mass ratio of 4.5:2 in a hydrothermal reactor for 5 hours. The concentration of ammonia was 5 wt%, and a second mixture with a pH of 10 was obtained. Then, the pH of the mixture was maintained at 10, and the temperature in the hydrothermal reactor was maintained at 160°C for sol-gel reaction. The sol-gel reaction was accompanied by stirring at 100 rpm until a spherical cerium dioxide sol with a solid content of 40 wt% was obtained in the reactor.

[0231] (C) The spherical cerium dioxide sol obtained in step (B) is concentrated at 150°C under a pressure of 8 MPa until a sol with a solid content of 70 wt% is obtained. The obtained sol is centrifuged at 5000 rpm to obtain a solid product. Then, the obtained solid product is dried at 1000°C for 12 h. After deagglomeration by convection jet, spherical cerium dioxide is obtained.

[0232] Example 4

[0233] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step (A) is 50:1:1. All other aspects are the same as in Example 1.

[0234] Example 5

[0235] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step (A) is 12000:1:1. All other aspects are the same as in Example 1.

[0236] Example 6

[0237] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, step (A) involves mixing nitric acid and organic acid with Ce(NO3)3, Pr(NO3)3, Nd(NO3)3 and water at a speed of 400 rpm for 12 hours. All other aspects are the same as in Example 1.

[0238] Example 7

[0239] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step (A) is 0.5:1:120. All other contents are the same as in Example 1.

[0240] Example 8

[0241] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step (A) is 4:1:400. All other aspects are the same as in Example 1.

[0242] Example 9

[0243] The only difference between this embodiment and Embodiment 1 is that in the preparation method provided in this embodiment, the mixing speed in step (A) is 100 rpm. All other contents are the same as in Embodiment 1.

[0244] Example 10

[0245] The only difference between this embodiment and Embodiment 1 is that in the preparation method provided in this embodiment, the mixing speed in step (A) is 700 rpm. All other contents are the same as in Embodiment 1.

[0246] Example 11

[0247] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step (B) is 2:2. All other aspects are the same as in Example 1.

[0248] Example 12

[0249] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step (B) is 6:2. All other aspects are the same as in Example 1.

[0250] Example 13

[0251] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the sol-gel reaction in step (B) is not stirred. All other contents are the same as in Example 1.

[0252] Example 14

[0253] The only difference between this embodiment and Example 1 is that in the preparation method provided in this embodiment, the stirring speed for the sol-gel reaction in step (B) is 600 rpm. All other aspects are the same as in Example 1.

[0254] Example 15

[0255] The only difference between this embodiment and Example 1 is that the solid content of the concentrated product in step (C) of the preparation method provided in this embodiment is 50 wt%. All other contents are the same as in Example 1.

[0256] Comparative Example 1

[0257] The only difference between this comparative example and Example 1 is that the addition of the organic acid acetic acid in step (A) is omitted in the preparation method provided in this comparative example. All other aspects are the same as in Example 1.

[0258] Comparative Example 2

[0259] The only difference between this comparative example and Example 1 is that the addition of ammonium nitrate in step (B) is omitted in the preparation method provided in this comparative example. All other aspects are the same as in Example 1.

[0260] Comparative Example 3

[0261] The only difference between this comparative example and Example 1 is that, in the preparation method provided in this comparative example, the pH of the second mixture in step (B) is maintained at 7. All other aspects are the same as in Example 1.

[0262] Comparative Example 4

[0263] The only difference between this comparative example and Example 1 is that, in the preparation method provided in this comparative example, the pH of the second mixture in step (B) is maintained at 11. All other aspects are the same as in Example 1.

[0264] The final products obtained from the above embodiments and comparative examples were tested to detect the particle size, crystallinity, and impurity content of the products. The particle size distribution was calculated based on the particle size using the formula: Dispersion = (D90 - D10) / D50. The impurity content in the products was tested using inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the content of elements other than cerium dioxide nanoparticles. The results are shown in Table 1.

[0265] Table 1

[0266] Particle size D50 (nm) Particle size distribution Impurity content (ppm) Crystallinity (%) Example 1 120 1.53 <1 99 Example 2 100 2.31 <1 98 Example 3 140 2.05 <1 99 Example 4 300 5.67 <100 72 Example 5 150 4.67 <100 89 Example 6 350 6.67 <100 85 Example 7 280 9.78 <1000 69 Example 8 200 10.91 <1000 66 Example 9 450 11.21 <100 71 Example 10 220 6.72 <1000 83 Example 11 780 11.87 <10000 42 Example 12 250 6.97 <10 73 Example 13 - - <100 0 Example 14 200 20.87 <100 91 Example 15 130 1.67 <10 96 Comparative Example 1 - - - - Comparative Example 2 330 10.47 <10 54 Comparative Example 3 280 6.67 <10 67 Comparative Example 4 330 11.94 <10 84

[0267] As can be seen from Table 1:

[0268] (1) As can be seen from Examples 1 to 3, the preparation method of the present invention introduces doped metal salt into cerium salt, then mixes it with inorganic acid and organic acid, and the resulting product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the resulting mixture is subjected to sol-gel reaction under alkaline conditions within a specific range to obtain spherical cerium dioxide sol, and then combined with post-processing process to obtain spherical cerium dioxide particles, which have regular particle shape, good size uniformity and high purity and crystallinity.

[0269] Figure 1 Scanning electron microscope (SEM) images of the spherical cerium dioxide prepared in Example 1 are provided. As can be seen from the figures, the cerium dioxide prepared by the present invention using specific processes and parameters is spherical, and the morphology of the obtained spherical cerium dioxide is regular and the particle size is uniform.

[0270] (2) By comparing Examples 1 and Examples 4-5, it can be seen that if the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low and the cerium ion content is too low, the particles will not be able to be formed and the spherical cerium dioxide with excellent morphology and performance will not be obtained; if the molar ratio of the two is too high and the content of the doped metal ions is too low, the morphology of cerium dioxide will be affected and the crystallinity of the obtained product will be poor.

[0271] (3) By comparing Example 1 and Example 6, it can be seen that if the preparation process of adding inorganic acid first and then organic acid is changed, and inorganic acid and organic acid are mixed at the same time, the resulting cerium dioxide will have high particle size dispersion, poor particle size uniformity, and affect the purity and crystallinity of the product.

[0272] (4) By comparing Examples 1 and 7-8, it can be seen that in the preparation of spherical cerium dioxide, if the volume ratio of inorganic acid to organic acid is too low and the amount of inorganic acid added is relatively small, the reaction rate will slow down, which will lead to incomplete reaction in the preparation of spherical cerium dioxide, thereby affecting the preparation of spherical cerium dioxide and causing the performance of the obtained product to deteriorate; if the volume ratio of inorganic acid to organic acid is too high and the amount of organic acid added is relatively small, the content of spherical cerium dioxide in the final product will decrease, the product purity will be low, and the particle uniformity of spherical cerium dioxide will also deteriorate.

[0273] (5) By comparing Example 1 and Examples 9-10, it can be seen that if the mixing speed in step (A) of the present invention is too low, the uniformity of the raw material mixing is poor, which ultimately results in poor uniformity of the morphology of the obtained spherical cerium dioxide and poor consistency of particle size, thereby affecting the purity and crystallinity of the product; if the mixing speed in step (A) is too high, foam and microbubbles are easily generated during the mixing process, which affects the reaction of spherical cerium dioxide, thereby affecting the morphology and performance of the obtained particles.

[0274] (6) By comparing Examples 1 and 11-12, it can be seen that if the mass ratio of ammonia to ammonium salt is too low and the amount of ammonia added is relatively small, the reaction to prepare spherical cerium dioxide will be incomplete, and the purity and crystallinity of the obtained spherical cerium dioxide will be poor. If the mass ratio of ammonia to ammonium salt is too high and the amount of ammonium salt added is relatively small, the reaction rate to prepare spherical cerium dioxide will be reduced, affecting the production efficiency and the morphology of the subsequently obtained cerium dioxide.

[0275] (7) By comparing Example 1 and Example 13-14, it can be seen that if the stirring process of the sol-gel reaction is omitted, the particles will not be able to form; if the stirring speed in the sol-gel reaction process is too high, the uniformity of the spherical cerium dioxide particles will decrease.

[0276] (8) By comparing Example 1 and Example 15, it can be seen that if the solid content of the concentrated product of the present invention is too low, although it has little effect on the particle size, particle size dispersion, purity and crystallinity of the product, it will lead to a decrease in the content of the obtained spherical cerium dioxide.

[0277] (9) By comparing Example 1 and Comparative Example 1, it can be seen that if the addition of organic acid is omitted in this invention, the internal reaction will not be able to proceed smoothly, and a highly active intermediate will not be obtained, which will affect the preparation of spherical cerium dioxide and thus make it impossible to prepare cerium dioxide.

[0278] (10) By comparing Example 1 and Comparative Example 2, it can be seen that if the addition of ammonium salt is omitted in the present invention, the reaction efficiency will be reduced, the reaction will be incomplete, and the shape of the particles will be affected.

[0279] (11) By comparing Example 1 and Comparative Examples 3-4, it can be seen that if the pH is controlled outside the range of 8-10, the pH will affect the morphology of cerium dioxide if it is too low or too high, resulting in irregular morphology of the generated cerium dioxide particles, which cannot be formed into a regular morphology of spherical shape, thus leading to a decrease in the crystallinity of the particles.

[0280] In summary, the preparation method provided by this invention involves mixing cerium salt and doped metal salt with inorganic and organic acids in a solvent to obtain a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid radicals. Then, under hydrothermal conditions, the composite cerium salt and composite doped metal salt react with ammonia and ammonium salt to obtain a highly active intermediate. By precisely controlling the pH of the reaction solution within the range of 8-10, a sol-gel reaction is carried out under alkaline conditions at a specific pH. The highly active intermediate can stably crystallize to form cerium dioxide seed crystals of a specific shape. The seed crystals maintain their specific shape and continue to grow uniformly, forming spherical nuclei of uniform size and regular morphology. The nuclei gel, resulting in a spherical cerium dioxide sol. The obtained sol undergoes a post-processing process to finally obtain spherical cerium dioxide particles with high purity and crystallinity. This invention also introduces specific praseodymium salts and / or neodymium salts into the cerium salt as doped metal salts, promoting the control of the product's morphology and improving its crystallinity, thereby enhancing the polishing effect of the obtained material. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The cerium dioxide prepared has a near-spherical morphology, and is regular in shape, uniform in particle size, has good crystallinity, and high purity. It can be widely used in semiconductor chemical mechanical polishing (CMP), high-end optical polishing, or cosmetics and other fields.

[0281] Example 16

[0282] This embodiment provides a method for preparing hexagonal cerium dioxide, which specifically includes the following steps:

[0283] (I) Ce(NO3)3, Pr(NO3)3, Nd(NO3)3, acetic acid with a concentration of 3wt% and water are mixed at a speed of 2000 rpm for 4 h. Then, nitric acid with a concentration of 7wt% is added and the mixture is mixed at a speed of 2000 rpm for 20 h. The molar ratio of Ce(NO3)3, Pr(NO3)3 and Nd(NO3)3 is 10000:1:1, the mass ratio of Ce(NO3)3 to water is 1:150, and the volume ratio of nitric acid, acetic acid and water is 3:1:280 to obtain the first mixture.

[0284] (II) Under hydrothermal conditions of 95℃ and 5MPa, the first mixture obtained in step (I) and ammonium nitrate were mixed in a hydrothermal reactor for 2 hours, and then ammonia was added for 0.5 hours of mixing. The mass ratio of ammonia to ammonium nitrate was 5:2 and the concentration of ammonia was 20wt%. A second mixture with a pH of 5 was obtained. Then, the pH of the mixture was maintained at 5 and the temperature in the hydrothermal reactor was maintained at 150℃ for sol-gel reaction. The sol-gel reaction was accompanied by stirring at 300rpm until a hexagonal cerium dioxide sol with a solid content of 30wt% was obtained in the reactor.

[0285] (III) The hexagonal cerium dioxide sol obtained in step (II) is concentrated at 120°C under a pressure of 5 MPa until a sol with a solid content of 95 wt% is obtained. The obtained sol is centrifuged at 3400 rpm to obtain a solid product. Then, the obtained solid product is dried at 300°C for 8 hours. After deagglomeration by air milling, hexagonal cerium dioxide is obtained with a specific surface area of ​​198 m². 2 / g.

[0286] Example 17

[0287] This embodiment provides a method for preparing hexagonal cerium dioxide, which specifically includes the following steps:

[0288] (I) CeCl3, PrCl3, NdCl3, 6wt% n-butyric acid and water were mixed at 1000 rpm for 4.5 h, and then 8wt% nitric acid was added and the mixture was continued at 1000 rpm for 20.5 h. The molar ratio of CeCl3, PrCl3 and NdCl3 was 50000:5:1, the mass ratio of CeCl3 to water was 1:100, and the volume ratio of nitric acid, n-butyric acid and water was 4:1:300 to obtain the first mixture.

[0289] (II) Under hydrothermal conditions of 40℃ and 1MPa, the first mixture obtained in step (I) and ammonium chloride were mixed in a hydrothermal reactor for 3 hours, and then ammonia was added and mixed for another 3 hours. The mass ratio of ammonia to ammonium chloride was 6:2 and the concentration of ammonia was 5wt%. A second mixture with a pH of 3.5 was obtained. Then, the pH of the mixture was maintained at 3.5 and the temperature in the hydrothermal reactor was maintained at 50℃ for sol-gel reaction. The sol-gel reaction was accompanied by stirring at 200rpm until a hexagonal cerium dioxide sol with a solid content of 40wt% was obtained in the reactor.

[0290] (III) The hexagonal cerium dioxide sol obtained in step (II) is concentrated at 180°C under a pressure of 10 MPa until a sol with a solid content of 85 wt% is obtained. The obtained sol is centrifuged at 2000 rpm to obtain a solid product. Then, the obtained solid product is dried at 500°C for 6 h and deagglomerated by gas phase spraying to obtain hexagonal cerium dioxide.

[0291] Example 18

[0292] This embodiment provides a method for preparing hexagonal cerium dioxide, which specifically includes the following steps:

[0293] (I) Ce(SO4)3, Pr(SO4)3, Nd(SO4)3, acetic acid with a concentration of 3wt% and water are mixed at a speed of 15000 rpm for 4 h. Then, nitric acid with a concentration of 2wt% is added and the mixture is mixed at a speed of 15000 rpm for 16 h. The molar ratio of Ce(SO4)3, Pr(SO4)3 and Nd(SO4)3 is 1500:2:1, the mass ratio of Ce(SO4)3 to water is 1:200, and the volume ratio of nitric acid, acetic acid and water is 2.8:1:240 to obtain the first mixture.

[0294] (II) Under hydrothermal conditions of 100℃ and 10MPa, the first mixture obtained in step (I) and ammonium sulfate were mixed in a hydrothermal reactor for 0.5h, and then ammonia was added and mixed for another 0.5h. The mass ratio of ammonia to ammonium sulfate was 4.8:2 and the concentration of ammonia was 35wt%, resulting in a second mixture with a pH of 6. Then, the pH of the mixture was maintained at 6, and the temperature in the hydrothermal reactor was maintained at 160℃ for sol-gel reaction. The sol-gel reaction was accompanied by stirring at 1000rpm until a hexagonal cerium dioxide sol with a solid content of 20wt% was obtained in the reactor.

[0295] (III) The hexagonal cerium dioxide sol obtained in step (II) is concentrated at 150°C under a pressure of 8 MPa until a sol with a solid content of 70 wt% is obtained. The obtained sol is centrifuged at 4000 rpm to obtain a solid product. Then, the solid product is dried at 1000°C for 12 h. After deagglomeration by convection jet, hexagonal cerium dioxide is obtained.

[0296] Example 19

[0297] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step (Ⅰ) is 400:1:1. All other aspects are the same as in Example 16.

[0298] Example 20

[0299] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step (Ⅰ) is 110000:1:1. All other aspects are the same as in Example 16.

[0300] Example 21

[0301] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, step (I) involves mixing nitric acid and organic acid with Ce(NO3)3, Pr(NO3)3, Nd(NO3)3 and water at a speed of 2000 rpm for 24 hours. All other aspects are the same as in Example 16.

[0302] Example 22

[0303] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step (I) is 2:1:210. All other aspects are the same as in Example 16.

[0304] Example 23

[0305] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step (I) is 5:1:420. All other aspects are the same as in Example 16.

[0306] Example 24

[0307] The only difference between this embodiment and Embodiment 16 is that in the preparation method provided in this embodiment, the mixing speed in step (I) is 900 rpm. All other contents are the same as in Embodiment 16.

[0308] Example 25

[0309] The only difference between this embodiment and Embodiment 16 is that in the preparation method provided in this embodiment, the mixing speed in step (I) is 16000 rpm. All other contents are the same as in Embodiment 16.

[0310] Example 26

[0311] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step (II) is 4:2. All other contents are the same as in Example 16.

[0312] Example 27

[0313] The only difference between this embodiment and Example 16 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step (II) is 7:2. All other contents are the same as in Example 16.

[0314] Example 28

[0315] The only difference between this embodiment and Example 1 is that the stirring process is omitted in step (II) of the sol-gel reaction in the preparation method provided in this embodiment. All other contents are the same as in Example 1.

[0316] Example 29

[0317] The only difference between this embodiment and Example 16 is that, in the preparation method provided in this embodiment, the stirring speed for the sol-gel reaction in step (II) is 2200 rpm. All other aspects are the same as in Example 16.

[0318] Example 30

[0319] The only difference between this embodiment and Example 16 is that the solid content of the concentrated product in step (III) of the preparation method provided in this embodiment is 50 wt%. All other contents are the same as in Example 16.

[0320] Comparative Example 5

[0321] The only difference between this comparative example and Example 16 is that the addition of organic acid in step (I) is omitted in the preparation method provided in this comparative example. All other aspects are the same as in Example 16.

[0322] Comparative Example 6

[0323] The only difference between this comparative example and Example 16 is that the preparation method provided in this comparative example omits the addition of ammonium nitrate in step (II). All other aspects are the same as in Example 16.

[0324] Comparative Example 7

[0325] The only difference between this comparative example and Example 16 is that in the preparation method provided in this comparative example, step (Ⅲ) adjusts the pH to 2. All other aspects are the same as in Example 1.

[0326] Comparative Example 8

[0327] The only difference between this comparative example and Example 16 is that in the preparation method provided in this example, step (III) adjusts the pH to 7. All other aspects are the same as in Example 16.

[0328] The final products obtained from the above embodiments and comparative examples were tested to detect the particle size, crystallinity, and impurity content of the products. The particle size distribution was calculated based on the particle size using the formula: Dispersion = (D90 - D10) / D50. The impurity content of the products was tested using inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the content of elements other than cerium dioxide nanoparticles. The results are shown in Table 2.

[0329] Table 2

[0330] Particle size D50 (nm) Particle size distribution Impurity content (ppm) Crystallinity (%) Example 16 180 1.33 <1 100 Example 17 120 2.07 <1 99 Example 18 200 1.67 <1 99 Example 19 380 4.29 <1000 77 Example 20 260 7.28 <100 93 Example 21 430 5.37 <100 67 Example 22 360 7.67 <100 39 Example 23 560 6.67 <100 53 Example 24 780 5.73 <100 72 Example 25 230 13.74 <100 64 Example 26 370 11.54 <10000 68 Example 27 200 5.69 <10000 76 Example 28 1000 10.67 <100 29 Example 29 220 15.77 <100 76 Example 30 180 2.17 <100 88 Comparative Example 5 - - - - Comparative Example 6 230 7.67 <10 68 Comparative Example 7 235 5.13 <10 44 Comparative Example 8 195 6.87 <10 75

[0331] As can be seen from Table 2:

[0332] (1) As can be seen from Examples 16 to 18, the preparation method of the present invention introduces doped metal salt into cerium salt, then mixes it with inorganic acid and organic acid, and the resulting product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the resulting mixture is subjected to sol-gel reaction under weak acid conditions within a specific range to obtain hexagonal cerium dioxide sol, and then combined with post-processing process to obtain hexagonal cerium dioxide particles, which have regular particle shape, good size uniformity and high purity and crystallinity.

[0333] Figure 2 Scanning electron microscope (SEM) images of the hexagonal cerium dioxide particles obtained in Example 16 are provided. As shown in the images, the particles exhibit a plate-like hexagonal structure, and their morphology is regular and their size is uniform. Furthermore, the average side length of the hexagons obtained in Example 16 is 120 nm, and the average thickness is 5 nm.

[0334] (2) By comparing Examples 16 and 19-20, it can be seen that if the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low, it will affect the uniformity and morphological consistency of the hexagonal cerium dioxide particles, as well as the purity and crystallinity of the obtained particles; if the molar ratio is too high, it will affect the morphology and polishing performance of the hexagonal cerium dioxide particles.

[0335] (3) By comparing Example 16 and Example 21, it can be seen that if the preparation process of adding inorganic acid first and then organic acid is changed, and inorganic acid and organic acid are mixed at the same time, the uniformity of the particle size of the hexagonal cerium dioxide particles obtained in the end will be poor and the crystallinity will decrease.

[0336] (4) By comparing Examples 16 and 22-23, it can be seen that in the preparation of hexagonal cerium dioxide, if the volume ratio of inorganic acid to organic acid is too low and the amount of inorganic acid added is relatively too small, the reaction for preparing hexagonal cerium dioxide will be incomplete, affecting the preparation of hexagonal cerium dioxide and thus affecting the performance of the hexagonal cerium dioxide product; if the volume ratio of inorganic acid to organic acid is too high and the amount of organic acid added is relatively too small, the content of hexagonal cerium dioxide in the final product will be reduced, the purity and crystallinity of the product will be low, and the uniformity of the particle size of hexagonal cerium dioxide will be affected.

[0337] (5) By comparing Examples 16 and 24-25, it can be seen that if the mixing speed in step (I) is too low, it will affect the morphological uniformity and size uniformity of hexagonal cerium dioxide, and lead to a decrease in particle performance; if the mixing speed in step (I) is too high, a large number of microbubbles will be generated, affecting the reaction process of preparing hexagonal cerium dioxide, resulting in poor particle size uniformity and low crystallinity of hexagonal cerium dioxide.

[0338] (6) By comparing Examples 16 and 26-27, it can be seen that if the mass ratio of ammonia to ammonium salt in the preparation of hexagonal cerium dioxide is too low or too high, it will lead to incomplete reaction in the preparation of hexagonal cerium dioxide, thereby affecting the morphology, purity and crystallinity of cerium dioxide.

[0339] (7) By comparing Examples 16 and 28-29, it can be seen that if the stirring process of the sol-gel reaction is omitted, the reaction will be incomplete, resulting in the formation of large particles and thus the crystallinity of the final particles will be extremely low. If the stirring speed during the sol-gel reaction is too high, microbubbles will be generated, affecting the reaction and thus affecting the morphology and properties of hexagonal cerium dioxide.

[0340] (8) By comparing Examples 16 and 30, it can be seen that if the solid content of the concentrated product of the present invention is too low, although it has little effect on particle size, particle size dispersion, purity and crystallinity of cerium dioxide, it will lead to a decrease in the content of the obtained hexagonal cerium dioxide.

[0341] (9) By comparing Example 16 and Comparative Example 5, it can be seen that if the addition of organic acid is omitted in this invention, the internal reaction will not be able to proceed smoothly, and the composite metal salt and highly active intermediate will not be obtained, thus affecting the preparation of hexagonal cerium dioxide, so that cerium dioxide cannot be prepared.

[0342] (10) By comparing Example 16 and Comparative Example 6, it can be seen that if the addition of ammonium salt is omitted in the present invention, the reaction efficiency will be reduced, the reaction will be incomplete, and the shape of the particles will be affected.

[0343] (11) By comparing Example 16 and Comparative Examples 7-8, it can be seen that if the pH is controlled outside the range of 3.5-6, the pH will be too low or too high, which will affect the morphology of cerium dioxide, resulting in irregular morphology of the generated cerium dioxide particles, which cannot be formed into a regular hexagonal morphology, thereby affecting the preparation content of hexagonal cerium dioxide, and thus leading to a decrease in the crystallinity of the particles.

[0344] In summary, the preparation method provided by this invention introduces specific praseodymium and / or neodymium salts as doped metal salts into cerium salts, promoting the control of product morphology and improving the crystallinity of the obtained product during subsequent reactions. Then, by mixing the cerium salt and the doped metal salt with inorganic and organic acids in a solvent, a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid radicals are obtained. Subsequently, under hydrothermal conditions, the composite cerium salt and the composite doped metal salt react with ammonia and ammonium salts to obtain a highly active intermediate. Precise control ensures the pH value of the reaction solution is within the range of 3.5-6. Under weakly acidic conditions at a specific pH value, a sol-gel reaction is carried out, allowing the highly active intermediate to stably crystallize into cerium dioxide seed crystals of a specific shape. These seed crystals maintain their specific shape and continue to grow uniformly, forming hexagonal nuclei of uniform size and regular morphology. The nuclei gel, resulting in a hexagonal cerium dioxide sol. The obtained sol undergoes a post-processing process to finally obtain hexagonal cerium dioxide particles with high purity and crystallinity. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The prepared cerium dioxide has a hexagonal morphology with regular shape, good particle uniformity, and high crystallinity and purity. It can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0345] Example 31

[0346] This embodiment provides a method for preparing triangular cerium dioxide, which specifically includes the following steps:

[0347] S1. Ce(NO3)3, Pr(NO3)3, Nd(NO3)3, acetic acid with a concentration of 10 wt% and water are mixed at 1500 rpm for 5 h. Then, nitric acid with a concentration of 8 wt% is added and the mixture is mixed at 1500 rpm for 19 h. The molar ratio of Ce(NO3)3, Pr(NO3)3 and Nd(NO3)3 is 80000:1:1, the mass ratio of Ce(NO3)3 to water is 1:150, and the volume ratio of nitric acid, acetic acid and water is 8:3:400 to obtain the first mixture.

[0348] S2. Under hydrothermal conditions of 95℃ and 5MPa, the first mixture obtained in step S1 and ammonia water are mixed in a hydrothermal reactor for 2 hours, and then ammonium nitrate is added and mixed for 1 hour. The mass ratio of ammonia water to ammonium nitrate is 10:2 and the concentration of ammonia water is 5wt%, resulting in a second mixture with a pH of 2. Then, the pH of the mixture is maintained at 2, and the temperature in the hydrothermal reactor is maintained at 150℃ for sol-gel reaction. During the sol-gel reaction, stirring is also carried out at a speed of 2000rpm until a triangular cerium dioxide sol with a solid content of 30wt% is obtained in the reactor.

[0349] S3. The triangular cerium dioxide sol obtained in step S2 is concentrated at 120°C under a pressure of 5 MPa until a sol with a solid content of 95 wt% is obtained. The obtained sol is centrifuged at 3500 rpm to obtain a solid product. Then, the obtained solid product is dried at 300°C for 8 hours. After deagglomeration by air milling, triangular cerium dioxide is obtained. The specific surface area of ​​the obtained triangular cerium dioxide is 151 m². 2 / g.

[0350] Example 32

[0351] This embodiment provides a method for preparing triangular cerium dioxide, which specifically includes the following steps:

[0352] S1. CeCl3, PrCl3, NdCl3, 12wt% n-butyric acid and water are mixed at 1000 rpm for 3 h, then 12wt% nitric acid is added and the mixture is mixed at 1000 rpm for 20 h. The molar ratio of CeCl3, PrCl3 and NdCl3 is 500000:5:1, the mass ratio of CeCl3 to water is 1:100, and the volume ratio of nitric acid, n-butyric acid and water is 6:3:420, to obtain the first mixture.

[0353] S2. Under hydrothermal conditions of 50℃ and 1MPa, the first mixture obtained in step S1 and ammonia water are mixed in a hydrothermal reactor for 3 hours, and then ammonium chloride is added and mixed for another 3 hours. The mass ratio of ammonia water to ammonium chloride is 8:2 and the concentration of ammonia water is 20wt%, resulting in a second mixture with a pH of 3. Then, the pH of the mixture is maintained at 3, and the temperature in the hydrothermal reactor is maintained at 50℃ for sol-gel reaction. During the sol-gel reaction, stirring is also carried out at a speed of 300rpm until a triangular cerium dioxide sol with a solid content of 20wt% is obtained in the reactor.

[0354] S3. The triangular cerium dioxide sol obtained in step S2 is concentrated at 180°C under a pressure of 10 MPa until a sol with a solid content of 85 wt% is obtained. The obtained sol is centrifuged at 2300 rpm to obtain a solid product. Then, the obtained solid product is dried at 500°C for 6 h. After deagglomeration by gas phase spraying, triangular cerium dioxide is obtained.

[0355] Example 33

[0356] This embodiment provides a method for preparing triangular cerium dioxide, which specifically includes the following steps:

[0357] S1. Ce(SO4)3, Pr(SO4)3, Nd(SO4)3, acetic acid with a concentration of 8wt% and water are mixed at 2000 rpm for 5 h. Then, nitric acid with a concentration of 13wt% is added and the mixture is mixed at 2000 rpm for 20 h. The molar ratio of Ce(SO4)3, Pr(SO4)3 and Nd(SO4)3 is 3000:2:1, the mass ratio of Ce(SO4)3 to water is 1:200, and the volume ratio of nitric acid, acetic acid and water is 10:3:350 to obtain the first mixture.

[0358] S2. Under hydrothermal conditions of 100℃ and 10MPa, the first mixture obtained in step S1 is mixed with ammonia in a hydrothermal reactor for 0.5h, and then ammonium sulfate is added and mixed for another 0.5h. The mass ratio of ammonia to ammonium sulfate is 12:2, and the concentration of ammonia is 20wt%, resulting in a second mixture with a pH of 1. Then, the pH of the mixture is maintained at 1, and the temperature in the hydrothermal reactor is maintained at 160℃ for sol-gel reaction. The sol-gel reaction is accompanied by stirring at 3000rpm until a triangular cerium dioxide sol with a solid content of 40wt% is obtained in the reactor.

[0359] S3. The triangular cerium dioxide sol obtained in step S2 is concentrated at 150°C under a pressure of 8 MPa until a sol with a solid content of 70 wt% is obtained. The obtained sol is centrifuged at 3000 rpm to obtain a solid product. Then, the obtained solid product is dried at 1000°C for 12 h. After deagglomeration by convection jet, triangular cerium dioxide is obtained.

[0360] Example 34

[0361] The only difference between this embodiment and Embodiment 31 is that in the preparation method of triangular cerium dioxide provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step S1 is 800:1:1. All other aspects are the same as in Embodiment 31.

[0362] Example 35

[0363] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the molar ratio of Ce(NO3)3, Pr(NO3)3, and Nd(NO3)3 in step S1 is 1100000:1:1. All other contents are the same as in Example 31.

[0364] Example 36

[0365] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, step S1 involves mixing nitric acid and organic acid with Ce(NO3)3, Pr(NO3)3, Nd(NO3)3 and water at a speed of 1500 rpm for 24 hours. All other contents are the same as in Example 31.

[0366] Example 37

[0367] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step S1 is 5:3:290. All other aspects are the same as in Example 31.

[0368] Example 38

[0369] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the volume ratio of nitric acid, acetic acid, and water in step S1 is 12:3:550. All other aspects are the same as in Example 31.

[0370] Example 39

[0371] The only difference between this embodiment and Embodiment 31 is that in the preparation method provided in this embodiment, the mixing speed in step S1 is 900 rpm. All other aspects are the same as in Embodiment 31.

[0372] Example 40

[0373] The only difference between this embodiment and Embodiment 31 is that in the preparation method provided in this embodiment, the mixing speed in step S1 is 2200 rpm. All other aspects are the same as in Embodiment 31.

[0374] Example 41

[0375] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step S2 is 6:2. All other aspects are the same as in Example 31.

[0376] Example 42

[0377] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the mass ratio of ammonia to ammonium nitrate in step S2 is 14:2. All other aspects are the same as in Example 31.

[0378] Example 43

[0379] The only difference between this embodiment and Example 31 is that in the preparation method provided in this embodiment, the sol-gel reaction in step S2 is not stirred. All other aspects are the same as in Example 31.

[0380] Example 44

[0381] The only difference between this embodiment and Example 31 is that, in the preparation method provided in this embodiment, the stirring speed for the sol-gel reaction in step S2 is 3100 rpm. All other aspects are the same as in Example 31.

[0382] Example 45

[0383] The only difference between this embodiment and Example 31 is that the solid content of the concentrated product in step S3 of the preparation method provided in this embodiment is 50 wt%. All other contents are the same as in Example 31.

[0384] Comparative Example 9

[0385] The only difference between this comparative example and Example 31 is that the addition of organic acid in step S1 is omitted in the preparation method provided in this comparative example. All other aspects are the same as in Example 31.

[0386] Comparative Example 10

[0387] The only difference between this comparative example and Example 31 is that the addition of ammonium nitrate in step S2 is omitted in the preparation method provided in this comparative example. All other aspects are the same as in Example 31.

[0388] Comparative Example 11

[0389] The only difference between this comparative example and Example 31 is that in the preparation method provided in this comparative example, step S2 adjusts the pH of the second mixture to 4. All other aspects are the same as in Example 31.

[0390] Comparative Example 12

[0391] The only difference between this comparative example and Example 31 is that Pr(NO3)3 and Nd(NO3)3 are omitted in the preparation method provided in this comparative example. All other contents are the same as in Example 31.

[0392] The final products obtained from the above embodiments and comparative examples were tested to detect the particle size, crystallinity, and impurity content of the products. The particle size distribution was calculated based on the particle size using the formula: Dispersion = (D90 - D10) / D50. The impurity content of the products was tested using inductively coupled plasma optical emission spectrometry (ICP-OES) to determine the content of other elements in the products besides cerium dioxide nanoparticles. The results are shown in Table 3.

[0393] Table 3

[0394] Particle size D50 (nm) Particle size distribution Impurity content (ppm) Crystallinity (%) Example 31 190 2.15 <1 99 Example 32 220 2.37 <1 99 Example 33 280 1.67 <1 99 Example 34 430 5.29 <10000 74 Example 35 360 7.37 <1000 88 Example 36 490 7.37 <1000 79 Example 37 630 7.67 <1000 52 Example 38 760 6.67 <1000 49 Example 39 780 5.73 <1000 82 Example 40 930 11.97 <1000 72 Example 41 1070 10.33 <10000 84 Example 42 300 4.97 <10000 76 Example 43 1400 10.67 <100 54 Example 44 220 5.77 <100 83 Example 45 180 2.17 <100 92 Comparative Example 9 - - - - Comparative Example 10 230 7.67 <10 87 Comparative Example 11 235 5.13 <100 52 Comparative Example 12 195 6.87 <100 58

[0395] As can be seen from Table 3:

[0396] (1) As can be seen from Examples 31 to 33, the preparation method of the present invention introduces doped metal salt into cerium salt, then mixes it with inorganic acid and organic acid, and the resulting product is mixed with ammonia and ammonium salt under hydrothermal conditions, and the pH of the resulting mixture is subjected to sol-gel reaction under strong acid conditions within a specific range to obtain triangular cerium dioxide sol, and then triangular cerium dioxide particles are obtained by combining post-processing. The particles have regular shape, good size uniformity, and high purity and crystallinity.

[0397] Figure 3 and Figure 4 Scanning electron microscope (SEM) images of the triangular cerium dioxide prepared by the process in Example 31 are provided. As shown in the images, the nanoparticles exhibit both sheet-like triangular and triangular pyramidal shapes. The mass ratio of the triangular nanosheet cerium dioxide and the triangular pyramidal tetrahedral cerium dioxide obtained in Example 31 is approximately 4:1. The triangular nanosheet cerium dioxide has an average side length of 200 nm and an average thickness of 8 nm, while the triangular pyramidal cerium dioxide has an average side length of 160 nm.

[0398] (2) By comparing Examples 31 and 34-35, it can be seen that if the molar ratio of cerium ions in the cerium salt to the doped metal ions in the doped metal salt is too low, it will affect the formation of the final triangular cerium dioxide particles, resulting in uneven morphology and size of the triangular cerium dioxide and a decrease in polishing performance; if the molar ratio of the two is too high, it will affect the formation of the final triangular cerium dioxide particles, resulting in uneven morphology and size.

[0399] (3) By comparing Examples 31 and 36, it can be seen that if the preparation process of adding organic acid first and then inorganic acid is changed, and inorganic acid and organic acid are mixed at the same time, the morphology of triangular cerium dioxide will be affected, resulting in poor particle size uniformity.

[0400] (4) By comparing Examples 31 and 37-38, it can be seen that in the preparation process of triangular cerium dioxide, the present invention can control the reaction by adjusting the volume ratio of inorganic acid and organic acid, avoid the relative volume of inorganic acid and organic acid being too low or too high, which would affect the morphology and particle uniformity of the prepared triangular cerium dioxide, reduce the impurity content in cerium dioxide, and improve the crystallinity of the product.

[0401] (5) By comparing Examples 31 and 39-40, it can be seen that if the mixing speed in step S1 is too low, the reaction process in the preparation of triangular cerium dioxide will be affected, thereby affecting the morphology and particle size uniformity of triangular cerium dioxide; if the mixing speed in step S1 is too high, a large number of microbubbles will be generated, which will reduce the particle size uniformity of the prepared triangular cerium dioxide particles.

[0402] (6) By comparing Examples 31 and 41-42, it can be seen that if the mass ratio of ammonia to ammonium salt is too low and the amount of ammonia added is too small, the reaction will be incomplete, the particles will agglomerate, the resulting triangular particles will have a larger particle size and a deviation in uniformity; if the mass ratio of ammonia to ammonium salt is too high and the amount of ammonium salt added is too small, the reaction that affects the preparation process of triangular cerium dioxide will occur, the uniformity of the particles will decrease, and the crystallinity of the product will be affected.

[0403] (7) By comparing Examples 31 and 43-44, it can be seen that if the stirring process of the sol-gel reaction is omitted, the reaction will be uneven, the particles will agglomerate, the morphology and size will be out of control, and the crystallinity will be reduced. If the stirring speed is too high during the sol-gel reaction, a large number of microbubbles will be generated, which will affect the performance of the final product.

[0404] (8) By comparing Examples 31 and 45, it can be seen that if the solid content of the concentrated product of the present invention is too low, although it has little effect on the particle size, particle size dispersion, purity and crystallinity of the product, it will lead to a decrease in the content of triangular cerium dioxide and a decrease in the crystallinity of the final product.

[0405] (9) By comparing Example 31 and Comparative Example 9, it can be seen that if the addition of organic acid is omitted in the present invention, the internal reaction will not be able to proceed smoothly, and a highly active intermediate will not be obtained, which will affect the preparation of triangular cerium dioxide, or even prevent the preparation of cerium dioxide particles.

[0406] (10) By comparing Example 31 and Comparative Example 10, it can be seen that if the addition of ammonium salt is omitted in the present invention, the reaction in the preparation process of triangular cerium dioxide will be affected, so that cerium dioxide products cannot be prepared.

[0407] (11) By comparing Example 31 and Comparative Example 11, it can be seen that if the pH is adjusted too high, it will affect the morphology of cerium dioxide, resulting in irregular morphology of the generated cerium dioxide particles, which cannot be formed into a regular triangular shape, thereby affecting the preparation content of triangular cerium dioxide, and thus causing the crystallinity of the particles to decrease.

[0408] (12) By comparing Example 31 and Comparative Example 12, it can be seen that if the doping metal element is omitted in the present invention, the morphology of cerium dioxide particles will be affected, the hardness and crystallinity of the particles will be worse, and the polishing effect of cerium dioxide particles will be affected.

[0409] In summary, the preparation method provided by this invention involves mixing cerium salt and doped metal salt with inorganic and organic acids in a solvent to obtain a composite cerium salt and a composite doped metal salt containing both inorganic and organic acid radicals. Then, under hydrothermal conditions, the composite cerium salt and composite doped metal salt react with ammonia and ammonium salt to obtain a highly active intermediate. By precisely controlling the pH of the reaction solution within the range of 1-3, a sol-gel reaction is carried out under strongly acidic conditions at a specific pH. The highly active intermediate can stably crystallize to form cerium dioxide seed crystals of a specific shape. The seed crystals maintain their specific shape and continue to grow uniformly, forming triangular crystal nuclei of uniform size and regular morphology. The nuclei gel, resulting in a triangular cerium dioxide sol. The obtained sol undergoes a post-processing process to finally obtain a large quantity of high-purity and highly crystalline triangular cerium dioxide particles. This invention also introduces specific praseodymium salts and / or neodymium salts into the cerium salt as doped metal salts, promoting the control of product morphology and improving the crystallinity of the product, thereby improving the polishing effect of the obtained material. The preparation method adopted in this invention has a short reaction time, is simple to operate, and is easy to mass-produce. The prepared cerium dioxide has a triangular and regular shape, uniform particles, good crystallinity, and high purity, and can be widely used in semiconductor CMP polishing, high-end optical polishing, or cosmetics and other fields.

[0410] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing hexagonal cerium dioxide, characterized in that, The preparation method includes the following steps: (1) A first mixture is obtained by mixing cerium salt, doped metal salt, solvent, inorganic acid and organic acid; The doped metal salts include praseodymium salts and / or neodymium salts; (2) Under hydrothermal conditions, the first mixture is mixed with ammonia and ammonium salt to obtain a second mixture with a pH of 3.5-6. After sol-gel reaction, hexagonal cerium dioxide sol is obtained. (3) The hexagonal cerium dioxide sol is post-treated to obtain the hexagonal cerium dioxide.

2. The preparation method according to claim 1, characterized in that, The ratio of the molar amount of cerium ions in the cerium salt to the total molar amount of doped metal ions in the doped metal salt in step (1) is (500-50000):1; Preferably, the doped metal salt in step (1) includes praseodymium salt and neodymium salt; Preferably, when the doped metal salt includes praseodymium salt and neodymium salt, the molar ratio of praseodymium ions in the praseodymium salt to neodymium ions in the neodymium salt is (1-10):

1.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of the cerium salt to the solvent in step (1) is 1:(100-200).

4. The preparation method according to any one of claims 1-3, characterized in that, The specific process of the first mixing in step (1) includes: mixing the cerium salt, the doped metal salt, the solvent and the organic acid, and then adding the inorganic acid to continue mixing to obtain the first mixture; Preferably, the volume ratio of the inorganic acid to the organic acid is (2.8-4):1; Preferably, the inorganic acid includes nitric acid; Preferably, the organic acid includes any one of formic acid, acetic acid, butyric acid, hexanoic acid, or oxalic acid; Preferably, the ratio of the total volume of the inorganic acid and organic acid in step (1) to the volume of the solvent is 3:(150-210); Preferably, in step (1), the rotation speed of the first mixing is 1000-15000 rpm.

5. The preparation method according to any one of claims 1-4, characterized in that, The specific process of the second mixing in step (2) includes: under the hydrothermal conditions, the first mixture is first mixed with the ammonium salt, and then the ammonia water is added to the resulting mixture to obtain the second mixture; Preferably, the mass ratio of ammonia water to ammonium salt is (4.8-6):2; Preferably, the concentration of the ammonia solution is 1-35 wt%. Preferably, the temperature of the hydrothermal conditions in step (2) is 30-100℃; Preferably, the pressure of the hydrothermal conditions in step (2) is 0.1-20 MPa.

6. The preparation method according to any one of claims 1-5, characterized in that, The temperature for the sol-gel reaction in step (2) is 50-160℃; Preferably, the sol-gel reaction in step (2) is also accompanied by stirring; Preferably, the stirring speed is 200-2000 rpm; Preferably, the solid content of the hexagonal cerium dioxide sol obtained by the sol-gel reaction in step (2) is 0.1-40 wt%.

7. The preparation method according to any one of claims 1-6, characterized in that, The specific process of post-processing in step (3) includes: concentrating the hexagonal cerium dioxide sol obtained in step (2), and then centrifuging, drying and deagglomerating to obtain the hexagonal cerium dioxide; Preferably, the concentration temperature is 120-180℃; Preferably, the concentration pressure is 0.1-100 MPa; Preferably, the product is concentrated to a solid content ≥ 60 wt%. Preferably, the centrifugation speed is 2000 rpm or higher; Preferably, the drying temperature is 300-1100℃; Preferably, the drying time is 2-12 hours.

8. A hexagonal cerium dioxide, characterized in that, The hexagonal cerium dioxide is prepared by the preparation method according to any one of claims 1-7, and the hexagonal cerium dioxide includes doping elements, including praseodymium and / or neodymium.

9. The hexagonal cerium dioxide according to claim 8, characterized in that, The particle size D50 of the hexagonal cerium dioxide is 5-500 nm; Preferably, the side length of the hexagonal cerium dioxide is 60-160 nm; Preferably, the thickness of the hexagonal cerium dioxide is 2-20 nm; Preferably, the specific surface area of ​​the hexagonal cerium dioxide is 100-250 m². 2 / g.

10. An application of the hexagonal cerium dioxide according to claim 8 or 9, characterized in that, The hexagonal cerium dioxide is used in semiconductor chemical mechanical polishing, optical polishing, or cosmetics.

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