Spherical cerium oxide and preparation method thereof

Abstract

The invention relates to the technical field of materials, in particular to spherical cerium oxide and a preparation method thereof. The preparation method comprises the following steps: mixing a cerium source solution and a precipitant solution with the concentration greater than that of the cerium source solution, and carrying out ultrasonic treatment and aging to obtain a mixed solution; carrying out a first hydrothermal reaction on the mixed solution, washing with deionized water and an organic solvent in sequence after the reaction is completed, carrying out a second hydrothermal reaction in an organic solvent system, washing, and drying to obtain a cerium oxide primary product; and roasting the cerium oxide primary product to obtain the spherical cerium oxide. A self-template method is adopted for bubbling; the cerium source solution and the precipitant solution are subjected to ultrasonic pretreatment, nano ions are dispersed, and the agglomeration risk is reduced; meanwhile, after the first hydrothermal reaction, the second hydrothermal reaction is continuously carried out in an organic solvent system, so that the connection among particles is favorably opened, the agglomeration is reduced, and the particle size is reduced. The cerium oxide prepared by the method is controllable in spherical morphology, good in dispersity and uniform in particle size distribution.

Description

Technical Field

[0001] The present invention relates to the field of material technology, in particular to spherical cerium oxide and a preparation method thereof. Background Art

[0002] Chemical Mechanical Polishing (CMP) is an ultra-precision machining technology that combines chemical etching and mechanical grinding. Its basic principle is that the workpiece surface material chemically reacts with the oxidant in the polishing liquid to form a soft layer. Under a certain pressure, rotating polishing liquid abrasive particles and polishing pads mechanically remove the soft layer, exposing the workpiece surface again. Chemical and mechanical actions alternate until the two reach equilibrium, completing the workpiece surface polishing.

[0003] Due to the multivalent state of cerium and its readily convertible nature, substances on the film surface that come into contact with the polishing slurry are easily oxidized or removed by complex formation. This makes cerium oxide (CeO2) an excellent material for chemical mechanical polishing of film materials. Compared to conventional polishing abrasives, cerium oxide (CeO2) abrasives offer advantages such as high polishing efficiency, excellent finish, and long life, making them essential for polishing films in advanced manufacturing processes. The morphology of cerium oxide (CeO2) abrasives is a key parameter influencing polishing results. Spherical cerium oxide offers the best polishing quality. Traditional cerium oxide nanoparticle preparation methods require high-temperature calcination, resulting in large grains and severe agglomeration, which can easily scratch silicon wafer surfaces. Even after ball milling and dispersion, it is difficult to completely avoid a certain amount of large grains in the finished product. Furthermore, conventional spherical cerium oxide preparation methods, such as the addition of surfactants or mechanical grinding, involve complex process steps and introduce impurities, impacting product quality. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a spherical cerium oxide and a preparation method thereof, which uses a self-template method, does not add surfactants or adopt mechanical grinding processes, and adds pre-treatment and post-treatment steps to improve agglomeration and simplify the preparation process.

[0005] The present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing spherical cerium oxide, comprising the following steps:

[0007] (1) mixing a cerium source solution and a precipitant solution, wherein the concentration of the precipitant solution is greater than the concentration of the cerium source solution, sonicating, and aging to obtain a mixed solution;

[0008] (2) subjecting the mixed solution to a first hydrothermal reaction, washing with deionized water and an organic solvent after the reaction is completed, and subjecting the mixed solution to a second hydrothermal reaction in an organic solvent system, washing, and drying to obtain a primary cerium oxide product;

[0009] (3) calcining the primary cerium oxide to obtain spherical cerium oxide.

[0010] Furthermore, the preparation method meets the following conditions:

[0011] (t·T·c) / f<15, and 4≤t≤12, 110≤T≤200, 0.1≤c≤2, 5≤f≤60;

[0012] Wherein: t is the first hydrothermal reaction time, in h; T is the first hydrothermal reaction temperature, in °C; c is the concentration of the precipitant solution, in mol / L; f is the ultrasonic frequency, in KHz.

[0013] Furthermore, in step (1), the concentration of the cerium source solution is 0.1 to 1 mol / L;

[0014] Preferably, the concentration of the cerium source solution is 0.1 to 0.5 mol / L, and the concentration of the precipitant solution is 0.2 to 1 mol / L;

[0015] Preferably, the cerium source is any one of cerium chloride, cerium sulfate, and cerium nitrate;

[0016] The precipitant is any one or more of ammonia water, hydrogen peroxide, urea, ammonium carbonate, and ammonium bicarbonate.

[0017] Furthermore, step (1) includes:

[0018] (101) The cerium source is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a cerium source solution;

[0019] (102) The precipitant is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a precipitant solution;

[0020] (103) Add the precipitant solution to the cerium source solution and control the addition rate to 5–10 mL / min;

[0021] (104) After mixing, ultrasonic dispersion was performed at a frequency of 5–60 kHz for more than 1 h and then aged for 4–8 h.

[0022] Furthermore, the ultrasonic frequency f is 40 to 60 KHz.

[0023] Furthermore, step (2) includes:

[0024] (201) The mixed solution was transferred to a hydrothermal reactor, preheated to 60–95 °C, and then subjected to the first hydrothermal reaction at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min;

[0025] (202) After the reaction is completed, the mixture is washed with deionized water and then with an organic solvent. After filtration, a second hydrothermal reaction is carried out at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min in the organic solvent system.

[0026] (203) After the reaction was completed, the product was washed with an organic solvent and dried at 80–120 °C for 4–6 h to obtain the initial cerium oxide.

[0027] Furthermore, the first hydrothermal reaction time t is 4 to 8 hours; the first hydrothermal reaction temperature T is 120 to 160°C.

[0028] Furthermore, the organic solvent is a substance that can form hydrogen bonds with water;

[0029] Preferably, the organic solvent is a substance containing -CHO, -COOH, -CO-, -OH, or -NH2 groups.

[0030] Furthermore, the calcination temperature in step (3) is 600-1000°C.

[0031] On the other hand, the present invention also provides spherical cerium oxide prepared according to the above preparation method.

[0032] The present invention's method for preparing spherical cerium oxide utilizes a self-templated bubbling process; ultrasonic pretreatment of the cerium source solution and precipitant solution disperses the nanoparticles and reduces the risk of agglomeration; and a second hydrothermal reaction in an organic solvent system, following the first hydrothermal reaction, helps to break up interparticle connections, reduce agglomeration, and reduce particle size. The present method is simple, does not require the addition of surfactants, and does not employ mechanical grinding. The resulting cerium oxide exhibits a controllable spherical morphology, good dispersibility, and uniform particle size distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 is a SEM image of cerium oxide prepared in Example 1 of the present invention;

[0035] Figure 2is a SEM image of cerium oxide prepared in Comparative Example 1 of the present invention;

[0036] Figure 3 This is a SEM image of cerium oxide prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0038] The present invention provides a method for preparing spherical cerium oxide, comprising the following steps:

[0039] (1) mixing a cerium source solution and a precipitant solution, wherein the concentration of the precipitant solution is greater than the concentration of the cerium source solution, sonicating, and aging to obtain a mixed solution;

[0040] (2) subjecting the mixed solution to a first hydrothermal reaction, washing with deionized water and an organic solvent after the reaction is completed, and subjecting the mixed solution to a second hydrothermal reaction in an organic solvent system, washing, and drying to obtain a primary cerium oxide product;

[0041] (3) calcining the primary cerium oxide to obtain spherical cerium oxide.

[0042] The preparation method of spherical cerium oxide of the present invention comprises the following steps: the concentration of the precipitant solution is greater than that of the cerium source solution; an excess of the precipitant is used as a template; no surfactant is added; and a self-template method is used for bubbling; the cerium source solution and the precipitant solution are subjected to ultrasonic pretreatment to disperse nano-ions and reduce the risk of agglomeration; and after the first hydrothermal reaction, a second hydrothermal reaction is continued in an organic solvent system, which helps to open the connection between particles, reduce agglomeration, and reduce the particle size.

[0043] During the preparation process of cerium oxide, hard agglomerates will form due to the presence of water. Continuing to carry out a second hydrothermal reaction in an organic solvent system can achieve sufficient dehydration and prevent agglomeration. After the first hydrothermal reaction, water washing is first performed to wash away most impurities, and then an organic solvent washing is performed to wash away most of the water. At the same time, compared with only conventional water washing and solvent washing processes, the second hydrothermal reaction in an organic solvent also helps to better dissolve and remove impurities, and the prepared cerium oxide has a higher purity.

[0044] The present invention utilizes a combined conventional hydrothermal reaction and an organic solvent hydrothermal reaction, rather than a direct organic solvent hydrothermal reaction. This prevents the organic solvent reaction from affecting the final morphology of the cerium oxide. The cerium oxide produced using the present method exhibits controllable morphology, uniform particle size distribution, good dispersibility, and high purity.

[0045] In some specific embodiments of the present invention, the preparation method meets the following conditions:

[0046] (t·T·c) / f<15, and 4≤t≤12, 110≤T≤200, 0.1≤c≤2, 5≤f≤60;

[0047] Wherein: t is the first hydrothermal reaction time, in h; T is the first hydrothermal reaction temperature, in °C; c is the concentration of the precipitant solution, in mol / L; f is the ultrasonic frequency, in KHz.

[0048] The present invention defines the parameters of the first hydrothermal reaction temperature, time, precipitant solution concentration, and ultrasonic frequency, as well as their mutual relationships. The longer the reaction time t, the more likely the nanoparticles are to form aggregates, resulting in an increase in particle size. The reaction temperature T affects the grain generation rate and the crystal growth rate. The temperature at which the grain generation rate is maximum is much lower than the temperature required for the fastest crystal growth rate. Therefore, low temperature is conducive to grain generation but not conducive to grain growth. Therefore, fine crystals can be obtained at low temperatures. Conversely, increasing the temperature can reduce the viscosity of the solution, increase the mass transfer coefficient Kd, and accelerate the growth rate of the crystals. According to crystal growth theory, the greater the supersaturation of the solution, the greater the crystal growth rate. As the ultrasonic frequency increases, the nanoparticles become more dispersed and the more difficult it is to form aggregates. Therefore, by regulating the size of each parameter, it is helpful to synthesize cerium oxide with different particle sizes. After a lot of research and creative experiments, the inventors found that when the first hydrothermal reaction time t, the hydrothermal reaction temperature T, the precipitant solution concentration c, and the ultrasonic frequency f satisfy (t·T·c) / f<15, and 4≤t≤12, 110≤T≤200, 0.1≤c≤2, and 5≤f≤60, spherical cerium oxide with appropriate particle size, uniform particle size distribution, and good dispersibility can be prepared.

[0049] In some specific embodiments of the present invention, the value of (t·T·c) / f can be 1.0, 1.5, 2, 2.3, 2.6, 2.8, 3, 3.2, 3.6, 4.0, 4.5, 4.8, 5.0, 5.2, 5.5, 5.8, 6.0, 6.4, 6.6, 6.8, 7.0, 7.2, 7.5, 7.9, 8.0, 8.6, 9.0, 9.2, 9.6, 10.0, 10.5, 11.0, 11.5, 12.0, 12.8, 13.0, 13.6, 14.0, 14.8; preferably, the value of (t·T·c) / f is 3 to 12.

[0050] In some specific embodiments of the present invention, in step (1), the concentration of the cerium source solution is 0.1 to 1 mol / L, and the concentration of the precipitant solution is greater than the concentration of the cerium source solution; the present invention adopts a self-templating method, and the excess precipitant solution provides the template. Specifically, the concentration of the cerium source solution is 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, or any range consisting of the above values; preferably, the concentration of the cerium source solution is 0.1 to 0.5 mol / L. Specifically, the concentration of the precipitant solution is 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L, 1.6mol / L, 1.7mol / L, 1.8mol / L, 1.9mol / L, 2mol / L or any range consisting of the above values; preferably, the concentration of the precipitant solution is 0.2-1mol / L.

[0051] In some specific embodiments of the present invention, the cerium source is any one of cerium chloride, cerium sulfate, and cerium nitrate; and the precipitant is any one or more of ammonia, hydrogen peroxide, urea, ammonium carbonate, and ammonium bicarbonate. The precipitant is a component that, upon heating, can generate a gas such as O2, CO2, or NH3. Any other precipitant that meets these requirements is within the scope of protection of the present invention.

[0052] In some specific embodiments of the present invention, step (1) includes:

[0053] (101) The cerium source is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a cerium source solution;

[0054] (102) The precipitant is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a precipitant solution;

[0055] (103) Add the precipitant solution to the cerium source solution and control the addition rate to 5–10 mL / min;

[0056] (104) After mixing, ultrasonic dispersion was performed at a frequency of 5–60 kHz for more than 1 h and then aged for 4–8 h.

[0057] Ultrasonic dispersion of the cerium source solution and the precipitant solution, and ultrasonic aging of the mixture prior to the hydrothermal reaction, can improve the agglomeration of the nanoparticles, enhance the dispersion, and help reduce the risk of agglomeration in the prepared cerium oxide. Specifically, the ultrasonic frequency f can be 5 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 60 kHz, or any range thereof; preferably, the ultrasonic frequency f is 40 to 60 kHz.

[0058] In some specific embodiments of the present invention, step (2) includes:

[0059] (201) The mixed solution was transferred to a hydrothermal reactor, preheated to 60–95 °C, and then subjected to the first hydrothermal reaction at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min;

[0060] (202) After the reaction is completed, the mixture is washed with deionized water and then with an organic solvent. After filtration, a second hydrothermal reaction is carried out at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min in the organic solvent system.

[0061] (203) Washing and drying at 80-120 °C for 4-6 h yields a preliminary product of cerium oxide.

[0062] The present invention, after a conventional hydrothermal reaction, is first washed with deionized water and then washed with an organic solvent to remove water, while continuing to heat and dissolve in an organic solvent system to perform a hydrothermal reaction, which helps to open the connection between particles, reduce agglomeration, and reduce particle size. Specifically, the first and second hydrothermal reaction times are 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, and 12h; preferably, the first and second hydrothermal reaction times are 4 to 8h. Specifically, the first and second hydrothermal reaction temperatures are 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C; preferably, the first and second hydrothermal reaction temperatures are 120 to 160°C.

[0063] In some embodiments of the present invention, the organic solvent is a substance capable of forming hydrogen bonds with water. Preferably, the organic solvent is a substance containing -CHO, -COOH, -CO-, -OH, or -NH2 groups. Other organic solvents capable of forming hydrogen bonds with water are also within the scope of the present invention and are not specifically listed. More specifically, the organic solvent is any one of ethanol, acetic acid, acetone, phenol, and ethanolamine.

[0064] In some embodiments of the present invention, the calcination temperature in step (3) is 600-1000°C.

[0065] The spherical cerium oxide and its preparation method of the present invention will be further described below with reference to specific examples.

[0066] Example 1

[0067] A method for preparing spherical cerium oxide comprises the following steps:

[0068] (1) Cerium chloride is used as the cerium source and dissolved in water. 3+ The cerium source solution was prepared by ultrasonically dispersing the precipitant at a concentration of 0.1 mol / L at a frequency of 40 kHz for 1 hour. A precipitant solution was prepared by dissolving ammonia water in water at a concentration of 0.2 mol / L and ultrasonically dispersing the precipitant at a frequency of 40 kHz for 1 hour. The precipitant solution was added to the cerium source solution at a dropwise addition rate of 5 mL / min. After the addition was completed, the solution was ultrasonically dispersed at a frequency of 40 kHz for 1 hour. The solution was then aged for 4 hours to obtain a mixed solution.

[0069] (2) The mixed solution was transferred to a hydrothermal kettle, preheated to 80°C, maintained at a heating rate of 5°C / min, and the first hydrothermal reaction was carried out at 160°C for 4 hours; after the reaction was completed, it was washed with deionized water 5 times, then washed with ethanol 5 times, filtered, and ethanol was used as the solvent, and the second hydrothermal reaction was carried out at 160°C in the hydrothermal kettle at a heating rate of 5°C / min for 12 hours; after washing with clean water and filtering, it was dried at 80°C for 4 hours to obtain a primary cerium oxide product;

[0070] (3) The primary cerium oxide is calcined at 600°C to obtain spherical cerium oxide.

[0071] Examples 2-32, Comparative Examples 1-7

[0072] The preparation methods of cerium oxide in Examples 2-32 and Comparative Examples 1-7 are similar to those in Example 1, with the only difference being some process parameters, as shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076]

[0077]

[0078] The morphology, particle size, and dispersibility of the cerium oxide prepared in Examples 1-32 and Comparative Examples 1-7 were tested. Specifically, to characterize the dispersibility of the synthesized cerium oxide, the zeta potential was measured using a nanoparticle size analyzer. The test method was as follows: 5 wt% cerium oxide was dissolved in deionized water, the pH was adjusted to 10, 3 wt% sodium hexametaphosphate was added, and ultrasonic dispersion was performed for 1 hour. After that, the zeta potential was measured using a nanoparticle size analyzer.

[0079] (1) The test results of Examples 1-23 and Comparative Examples 1-7 are shown in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] From the test results of Examples 1-23 in Table 2, it can be seen that the cerium oxide prepared by the preparation method of the present invention has a controllable spherical morphology, uniform particle size distribution, appropriate particle size, and little agglomeration. Figure 1 As shown, the cerium oxide prepared in Example 1 has a distinct spherical morphology, a particle size between 100-150 μm, a uniform particle size distribution, and good dispersibility. Furthermore, when the first hydrothermal reaction time t, the first hydrothermal reaction temperature T, the precipitant solution concentration C, and the ultrasonic frequency f satisfy (t·T·c) / f<15, and 4≤t≤12, 110≤T≤200, 0.1≤c≤2, and 5≤f≤60, it is more conducive to preparing spherical cerium oxide with appropriate particle size, uniform particle size distribution, and good dispersibility.

[0084] It can be seen from the test results of Example 1 and Example 15 that when the first hydrothermal reaction time t, the first hydrothermal reaction temperature T, the precipitant solution concentration C and the ultrasonic frequency f meet the above ranges, but the value of (t·T·c) / f is too large, the particle size distribution uniformity of cerium oxide is relatively poor; it can be seen from the test results of Example 1 and Examples 16-17 that when the ultrasonic frequency f satisfies 5≤f≤60, the particle size distribution of the obtained cerium oxide is better; it can be seen from the test results of Example 1 and Examples 18-20 that when the first hydrothermal reaction temperature T satisfies 110≤T≤200, the particle size and uniformity of cerium oxide are better; it can be seen from the test results of Example 1 and Examples 21-23 that when the first hydrothermal reaction time t satisfies 4≤t≤12, the particle size of cerium oxide can be guaranteed to be within a more optimal range to prevent the risk of agglomeration. It can be seen that there is a strong correlation between the first hydrothermal reaction time t, the first hydrothermal reaction temperature T, the precipitant solution concentration C and the ultrasonic frequency f. When all of the above-mentioned limiting conditions are met, the performance of the obtained cerium oxide is better.

[0085] According to the test results of Comparative Example 1 and Figure 2 It can be seen that when the concentration of the precipitant is reduced and there is no excess precipitant to provide a template, the morphology of the obtained cerium oxide changes and spherical cerium oxide is not formed; when no ultrasonic dispersion and aging pretreatment are performed in Comparative Example 2, and no preheating treatment is performed in Comparative Example 3, the particle size distribution of the obtained cerium oxide is uneven and the dispersibility is worse than that in Example 1, which further illustrates that the pretreatment processes such as ultrasonic dispersion, aging, and preheating in the present invention can effectively reduce the particle size of cerium oxide, promote uniform particle size distribution, and improve dispersibility; when no cleaning post-treatment is performed after conventional hydrothermal synthesis in Comparative Example 4, as shown in Table 2 and Figure 3 It can be seen that the particle size is significantly increased and the particle size distribution is uneven; in Comparative Examples 5 and 6, when only water washing or only ethanol washing is performed after conventional hydrothermal synthesis, the particle size distribution is uneven; this shows that adding a washing process and combining water washing and ethanol washing can significantly reduce the particle size and promote uniform particle size distribution; in Comparative Example 7, when hydrothermal synthesis is not performed under an organic solvent, the particle size increases and the particle size distribution is uneven, indicating that the post-hydrothermal synthesis treatment process under an organic solvent system helps to reduce agglomeration and reduce particle size.

[0086] (2) The test results of Example 1 and Examples 24-26 are shown in Table 3.

[0087] Table 3

[0088] Example Morphology Particle size / μm Zeta potential / V Particle size distribution Example 1 Spherical 100-150 -62 0.42 Example 24 Spherical 100-150 -58 0.63 Example 25 Spherical 100-150 -60 0.45 Example 26 Spherical 100-150 -62 0.53

[0089] It can be seen from the test results of Example 1 and Examples 24-26 that under the preparation method of cerium oxide of the present invention, when different substances that can form hydrogen bonds with water are used as organic solvents, cerium oxide with spherical morphology, uniform particle size distribution and appropriate particle size can be obtained.

[0090] (3) The test results of Example 1 and Examples 27-28 are shown in Table 4.

[0091] Table 4

[0092] Example Morphology Particle size / μm Zeta potential / V Particle size distribution Example 1 Spherical 100-150 -62 0.42 Example 27 Spherical 100-150 -59 0.50 Example 28 Spherical 100-150 -62 0.39

[0093] It can be seen from the test results of Example 1 and Examples 27-28 that, under the preparation method of cerium oxide of the present invention, cerium oxide with spherical morphology, uniform particle size distribution and appropriate particle size can be obtained by using different cerium sources.

[0094] (4) The test results of Example 1 and Examples 29-32 are shown in Table 5.

[0095] Table 5

[0096] Example Morphology Particle size / μm Zeta potential / V Particle size distribution Example 1 Spherical 100-150 -62 0.42 Example 29 Spherical 100-150 -59 0.48 Example 30 Spherical 100-150 -60 0.51 Example 31 Spherical 100-150 -59 0.43 Example 32 Spherical 100-150 -61 0.47

[0097] It can be seen from the test results of Example 1 and Examples 29-32 that, under the preparation method of cerium oxide of the present invention, cerium oxide with spherical morphology, uniform particle size distribution and appropriate particle size can be obtained by using different precipitants.

[0098] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in this field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing spherical cerium oxide, characterized in that: The following steps are involved: (1) mixing a cerium source solution and a precipitant solution, wherein the concentration of the precipitant solution is greater than the concentration of the cerium source solution, sonicating, and aging to obtain a mixed solution; (2) subjecting the mixed solution to a first hydrothermal reaction, washing with deionized water and an organic solvent after the reaction is completed, and subjecting the mixed solution to a second hydrothermal reaction in an organic solvent system, washing, and drying to obtain a primary cerium oxide product; (3) calcining the primary cerium oxide to obtain spherical cerium oxide.

2. The method for preparing spherical cerium oxide according to claim 1, wherein The preparation method of spherical cerium oxide meets the following conditions: (t·T·c) / f<15, and 4≤t≤12, 110≤T≤200, 0.1≤c≤2, 5≤f≤60; Where: t is the first hydrothermal reaction time, unit is h; T is the temperature of the first hydrothermal reaction, in °C; c is the concentration of the precipitant solution, in mol / L; f is the ultrasonic frequency, in KHz.

3. The method for preparing spherical cerium oxide according to claim 1 or 2, wherein: In step (1), the concentration of the cerium source solution is 0.1 to 1 mol / L; Preferably, the concentration of the cerium source solution is 0.1 to 0.5 mol / L, and the concentration of the precipitant solution is 0.2 to 1 mol / L; Preferably, the cerium source is any one of cerium chloride, cerium sulfate, and cerium nitrate; The precipitant is any one or more of ammonia water, hydrogen peroxide, urea, ammonium carbonate, and ammonium bicarbonate.

4. The method for preparing spherical cerium oxide according to claim 1, wherein Step (1) includes: (101) The cerium source is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a cerium source solution; (102) The precipitant is dissolved in water and ultrasonically dispersed at a frequency of 5 to 60 kHz for more than 1 h to obtain a precipitant solution; (103) Add the precipitant solution to the cerium source solution and control the addition rate to 5–10 mL / min; (104) After mixing, ultrasonic dispersion was performed at a frequency of 5–60 kHz for more than 1 h and then aged for 4–8 h.

5. The method for preparing spherical cerium oxide according to claim 2 or 4, characterized in that: The ultrasonic frequency f is 40~60KHz.

6. The method for preparing spherical cerium oxide according to claim 1, wherein Step (2) includes: (201) The mixed solution was transferred to a hydrothermal reactor, preheated to 60–95 °C, and then subjected to the first hydrothermal reaction at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min; (202) After the reaction is completed, the mixture is washed with deionized water and then with an organic solvent. After filtration, a second hydrothermal reaction is carried out at 110–200 °C for 4–12 h at a heating rate of 5–10 °C / min in the organic solvent system. (203) After the reaction was completed, the product was washed with an organic solvent and dried at 80–120 °C for 4–6 h to obtain the initial cerium oxide.

7. The method for preparing spherical cerium oxide according to claim 2 or 6, wherein: The first hydrothermal reaction time t is 4 to 8 hours; the first hydrothermal reaction temperature T is 120 to 160°C.

8. The method for preparing spherical cerium oxide according to claim 1, wherein The organic solvent is a substance that can form hydrogen bonds with water; Preferably, the organic solvent is a substance containing -CHO, -COOH, -CO-, -OH, or -NH2 groups.

9. The method for preparing spherical cerium oxide according to claim 1, wherein The calcination temperature in step (3) is 600-1000°C.

10. Spherical cerium oxide prepared by the preparation method according to any one of claims 1 to 9.

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