Cerium dioxide particle and preparation method thereof

Abstract

The invention discloses cerium dioxide particles and a preparation method thereof, the preparation method comprises the following steps: 1) cerium salt and fluxing salt are mixed and ground to obtain initial mixed salt; (2) mixing and grinding the initial mixed salt and a surface additive to obtain mixed salt containing the surface additive; 3) roasting the mixed salt containing the surface additive to obtain a roasted product; 4) cleaning the roasted product, and drying the solid obtained after cleaning to obtain cerium dioxide particles; wherein the molar ratio of the cerium salt to the fluxing salt is less than or equal to 1: 3; no additional solvent is added in the step 1), the step 2) and the step 3). According to the preparation method disclosed by the invention, the fluxing salt is adopted as an auxiliary agent for reaction, no extra solvent is added, alkali is not needed to be added for preparing a precursor, and the generation amount of waste liquid can be reduced while the cerium dioxide with good dispersity, narrow particle size distribution and average particle size less than or equal to 130nm can be obtained.

Description

Technical Field

[0001] The invention relates to cerium dioxide particles and a preparation method thereof. Background Art

[0002] Cerium dioxide can be used for polishing materials, glass additives, automobile exhaust purification, cable fillers, etc. When used in polishing fields such as precision optics, cover glass, and semiconductors, in order to improve the polishing rate and surface quality, the cerium dioxide abrasive needs to have uniform particle size distribution, controllable morphology, and good dispersibility.

[0003] At present, there are many methods for preparing cerium dioxide, such as precipitation method, hydrothermal method, microwave reaction method, etc. Among them, precipitation method is the most widely used method in industry. This method has a simple process, but the prepared cerium dioxide is easy to agglomerate. The powder prepared by hydrothermal method has small particle size, uniform distribution, and light particle agglomeration, but it needs to be carried out in a high-pressure reactor, and the safety performance is low. The microwave reaction method has a short reaction time, high equipment cost, and high operation requirements.

[0004] A document reports a method for preparing spherical nano-cerium oxide, which includes the following steps: adding a certain amount of flux salt to water and stirring to dissolve, then adding insoluble cerium salt to the solution of flux salt and water, stirring evenly to obtain a uniformly dispersed slurry; stirring and drying the obtained slurry to obtain a dry, uniform, and fine powder; and calcining the obtained powder to obtain nano-cerium oxide.

[0005] There are also documents reporting a method for preparing nano-scale cerium oxide for rough polishing of silicon substrates, including: preparing a soluble cerium salt aqueous solution; preparing an alkali solution; adding a fluxing salt to the soluble cerium salt solution to obtain a mixed solution of the soluble cerium salt and the fluxing salt; slowly adding an alkali solution to the mixed solution of the soluble cerium salt and the fluxing salt to obtain a colloid, heating for reaction, filtering after the reaction is completed, and drying to obtain a precursor; calcining the precursor in a muffle furnace to obtain a calcined precursor; repeatedly centrifuging and washing the calcined precursor with water in a centrifuge to obtain nano-cerium oxide.

[0006] Both of the above documents use the flux salt method, but both require the addition of water as a solvent to prepare a solution containing cerium salt and / or flux salt, which produces a large amount of waste liquid. One of the documents also requires the addition of alkali solution to form a colloid, which is more complicated. In addition, the particle size distribution of the nano cerium oxide obtained in one of the documents is relatively wide. Summary of the invention

[0007] One object of the present invention is to provide a method for preparing cerium dioxide particles, which also uses flux salt as an auxiliary agent, but does not add any additional solvent (for example, no additional water, alcohol, etc. are added as solvents). In the prior art, water or alcohol is generally added as a solvent to prepare a solution to prepare nano-cerium oxide. Therefore, it is not easy to think of omitting the solvent to prepare cerium dioxide with good dispersibility in the present invention. Furthermore, the preparation method of the present invention can reduce the amount of waste liquid generated. In addition, the preparation method can obtain cerium dioxide particles with a narrow distribution, good dispersibility, and spherical shape with an average particle size of 80 to 130 nm. Another object of the present invention is to provide cerium dioxide particles prepared according to the preparation method as described above.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] In one aspect, the present invention provides a method for preparing cerium dioxide particles, comprising the following steps:

[0010] 1) mixing and grinding the cerium salt and flux salt to obtain an initial mixed salt;

[0011] 2) mixing and grinding the initial mixed salt and the surface additive to obtain a mixed salt containing the surface additive;

[0012] 3) roasting the mixed salt containing the surface additive to obtain a roasted product;

[0013] 4) washing the calcined product, and drying the solid obtained after washing to obtain cerium dioxide particles;

[0014] in,

[0015] In step 1), the molar ratio of the cerium salt to the flux salt is less than or equal to 1:3;

[0016] No additional solvent is added in step 1), step 2) and step 3). The present invention unexpectedly found that cerium dioxide particles with good dispersibility and narrow particle size distribution can be obtained by omitting solvents such as water or alcohol for reaction.

[0017] In the present invention, the molar ratio of the cerium salt to the flux salt may be less than or equal to 1:3, preferably less than or equal to 1:5, more preferably 1:5 to 15, such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15. This is conducive to obtaining cerium dioxide with good dispersibility and narrow particle size distribution.

[0018] In step 1) and step 2), the purpose of grinding is to make the mixture more uniform. The equipment used for grinding is not particularly limited. In the laboratory, a mortar can be used for grinding.

[0019] According to the method for preparing cerium dioxide particles of the present invention, preferably, in step 1), the fluxing salt is selected from at least one of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate and lithium chloride. This is conducive to obtaining cerium dioxide with good dispersibility and narrow particle size distribution.

[0020] In the present invention, the flux salt may be selected from at least one of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate and lithium chloride. Preferably, the flux salt is selected from at least two of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate and lithium chloride. More preferably, the flux salt is selected from two of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate and lithium chloride.

[0021] According to a specific embodiment of the present invention, the flux salt is sodium chloride and potassium chloride, and the molar ratio of sodium chloride to potassium chloride can be 0.5 to 1:1, preferably 0.8 to 1:1.

[0022] According to the method for preparing cerium dioxide particles of the present invention, preferably, the cerium salt is selected from at least one of cerium nitrate, cerium chloride, cerium sulfate, cerium acetate and cerium carbonate. The cerium salt may contain crystal water or may not contain crystal water.

[0023] According to one embodiment of the present invention, the cerium salt is selected from one of cerium nitrate hexahydrate, cerium chloride heptahydrate, cerium sulfate tetrahydrate, cerium acetate dihydrate, and cerium carbonate.

[0024] According to a preferred embodiment of the present invention, the cerium salt is selected from cerium nitrate hexahydrate and cerium chloride heptahydrate.

[0025] According to the method for preparing cerium dioxide particles of the present invention, preferably, the molar ratio of the cerium salt to the flux salt is 1:5 to 15. This is conducive to forming cerium dioxide with good dispersibility and narrow particle size distribution.

[0026] According to the method for preparing cerium dioxide particles of the present invention, preferably, step 1) comprises the following specific steps: grinding the cerium salt and the flux salt separately, mixing the ground cerium salt and the ground flux salt, and grinding again to obtain an initial mixed salt. The purpose of grinding separately is to obtain powder. The purpose of mixing the ground cerium salt and the ground flux salt and then grinding again is to make the mixing more uniform. The equipment used for grinding is not particularly limited. In the laboratory, a mortar can be used for grinding.

[0027] According to the method for preparing cerium dioxide particles of the present invention, preferably, in step 2), the mass ratio of the surface additive to the initial mixed salt is 0.1 to 1: 1. This is conducive to forming cerium dioxide particles with an average particle size of less than or equal to 130 nm and a narrow particle size distribution.

[0028] In the present invention, the surface additive can be an ionic surfactant, a nonionic surfactant, an organic acid, a high molecular polymer, etc. The mass ratio of the surface additive to the initial mixed salt can be 0.1 to 1:1, preferably 0.2 to 0.8:1, more preferably 0.2 to 0.5:1, such as 0.2:1, 0.25:1, 0.4:1, 0.5:1 (i.e. 1:2).

[0029] According to the method for preparing cerium dioxide particles of the present invention, preferably, in step 2), the surface additive is selected from at least one of polyethylene glycol, polyvinyl pyrrolidone, citric acid, hexadecyltrimethylammonium chloride, sodium hexametaphosphate, sorbitol, glycine and glutamic acid.

[0030] According to one embodiment of the present invention, the surface additive is selected from polyvinyl pyrrolidone (PVP) or citric acid.

[0031] According to the method for preparing cerium dioxide particles of the present invention, preferably, in step 3), the calcination temperature is 700-1000° C., and the calcination time is 2-6 hours.

[0032] In the present invention, the calcination temperature may be 700 to 1000° C., preferably 750 to 950° C., and more preferably 800 to 900° C. The heating rate during calcination may be 1 to 10° C. / min, preferably 3 to 7° C. / min, such as 5 to 6° C. / min. The calcination time may be 2 to 6 hours, preferably 2 to 4 hours.

[0033] According to the method for preparing cerium dioxide particles of the present invention, preferably:

[0034] In step 4), the roasted product is centrifuged and washed with water and alcohol in sequence, wherein the alcohol is selected from at least one of methanol, ethanol and isopropanol;

[0035] In step 4), the drying temperature is 70-100° C. and the drying time is 3-10 hours.

[0036] During centrifugal washing, the alcohol used is preferably ethanol. The centrifugal washing can be performed using a commercially available centrifuge without particular limitation. Water can be used for centrifugal washing two to three times, and then alcohol can be used for centrifugal washing one to two times. The centrifugal speed during centrifugal washing is 4000 to 9000 r / min, preferably 5000 to 8000 r / min, and more preferably 6000 to 7000 r / min. The time for each centrifugal washing can be 1 to 8 minutes, preferably 3 to 5 minutes.

[0037] In the present invention, the drying temperature may be 70 to 100° C., preferably 80 to 90° C. The drying time may be 3 to 10 hours, preferably 5 to 9 hours.

[0038] On the other hand, the present invention also provides a cerium dioxide particle, which is prepared according to the preparation method as described above, and has an average particle size of 80 to 130 nm, which can be greater than 80 nm and less than 130 nm, and preferably greater than 90 nm and less than 130 nm. The quasi-spherical dioxide particles referred to in the present invention refer to particles whose morphology of the obtained cerium dioxide particles is basically spherical, or close to spherical.

[0039] In some embodiments, the average particle size of the obtained cerium dioxide particles is 90 to 130 nm. In other embodiments, the average particle size of the obtained cerium dioxide particles is 90 to 100 nm. In still other embodiments, the average particle size of the obtained cerium dioxide particles is 120 to 130 nm. In still other embodiments, the average particle size of the obtained cerium dioxide particles is 110 to 120 nm. The obtained cerium dioxide particles have good dispersibility.

[0040] The preparation method of the cerium dioxide particles of the present invention uses a flux salt as an auxiliary agent, and does not need to add any additional solvent as a reaction solvent, for example, no additional water or alcohol is added as a reaction solvent, and no alkali is added to prepare a precursor. The preparation method can reduce the amount of waste liquid generated, reduce costs, and is more environmentally friendly. The preparation method of the present invention is completed under normal pressure conditions, without pressurization, and the conditions are mild. In addition, the preparation method of the present invention can obtain cerium dioxide particles with an average particle size of 80 to 130 nm, a narrow distribution, good dispersibility, and a spherical structure with controllable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the XRD pattern of the cerium dioxide particles obtained in Example 1.

[0042] Figure 2 This is the SEM image of the cerium dioxide particles obtained in Example 1.

[0043] Figure 3 This is the SEM image of the cerium dioxide particles obtained in Example 2.

[0044] Figure 4 This is the SEM image of the cerium dioxide particles obtained in Example 3.

[0045] Figure 5 This is the SEM image of the cerium dioxide particles obtained in Comparative Example 1. DETAILED DESCRIPTION

[0046] Here is the test method:

[0047] XRD: X'Pert PRO X-ray diffractometer was used for testing.

[0048] SEM: The images were tested using a ZEISS Sigma 500 field emission scanning electron microscope.

[0049] Example 1

[0050] 5 mmol of cerium nitrate hexahydrate, 25 mmol of sodium chloride and 25 mmol of potassium chloride were ground into powders respectively, then mixed and ground again to obtain an initial mixed salt.

[0051] The initial mixed salt and the surface additive PVP are mixed and ground to obtain a mixed salt containing the surface additive, wherein the mass ratio of PVP to the initial mixed salt is 1:2.

[0052] The mixed salt containing the surface additive is placed in a box furnace, heated to 800°C at a heating rate of 5°C / min, and calcined at 800°C for 4 hours, and naturally cooled to room temperature in the furnace to obtain a calcined product.

[0053] The calcined product was centrifugally washed twice with deionized water and once with ethanol, the centrifugal speed was 6000 r / min, and the time of each centrifugal washing was 5 minutes. The solid obtained after washing was dried to obtain cerium dioxide particles.

[0054] The XRD results of the obtained cerium dioxide particles are shown in Figure 1 , SEM results are shown in Figure 2 .Depend on Figure 1 It can be seen that cerium dioxide was obtained in this embodiment. Figure 2 It can be seen that the cerium dioxide particles are basically spherical. 50 particles are selected to calculate the average particle size of the cerium dioxide particles, which is about 126.9 nm.

[0055] Example 2

[0056] 5 mmol of cerium nitrate hexahydrate, 25 mmol of sodium chloride and 25 mmol of potassium chloride were ground into powders respectively, then mixed and ground again to obtain an initial mixed salt.

[0057] The initial mixed salt and the surface additive PVP are mixed and ground to obtain a mixed salt containing the surface additive, wherein the mass ratio of PVP to the initial mixed salt is 1:4.

[0058] The mixed salt containing the surface additive is placed in a box furnace, heated to 800°C at a heating rate of 5°C / min, and calcined at 800°C for 2h, and naturally cooled to room temperature in the furnace to obtain a calcined product.

[0059] The calcined product was centrifugally washed twice with deionized water and once with ethanol, the centrifugal speed was 6000 r / min, and the time of each centrifugal washing was 5 minutes. The solid obtained by washing was dried to obtain cerium dioxide particles.

[0060] The SEM results of the obtained cerium dioxide particles are shown in Figure 3 .Depend on Figure 3 It can be seen that the cerium dioxide particles are basically spherical. 50 particles are selected to calculate the average particle size of the cerium dioxide particles, which is about 114.6 nm.

[0061] Example 3

[0062] 5 mmol of cerium nitrate hexahydrate, 25 mmol of sodium chloride and 25 mmol of potassium chloride were ground into powders respectively, then mixed and ground again to obtain an initial mixed salt.

[0063] The initial mixed salt and the surface additive citric acid are mixed and ground to obtain a mixed salt containing the surface additive, wherein the mass ratio of citric acid to the initial mixed salt is 1:4.

[0064] The mixed salt containing the surface additive is placed in a box furnace, heated to 800°C at a heating rate of 5°C / min, and calcined at 800°C for 4 hours, and naturally cooled to room temperature in the furnace to obtain a calcined product.

[0065] The calcined product was centrifugally washed twice with deionized water and once with ethanol, the centrifugal speed was 6000 r / min, and the time of each centrifugal washing was 5 minutes. The solid obtained by washing was dried to obtain cerium dioxide particles.

[0066] The SEM results of the obtained cerium dioxide particles are shown in Figure 4 .Depend on Figure 4 It can be seen that the cerium dioxide particles are basically spherical. 50 particles are selected to calculate the average particle size of the cerium dioxide particles, which is about 98.6 nm.

[0067] Comparative Example 1

[0068] 5 mmol of cerium nitrate hexahydrate, 25 mmol of sodium chloride and 25 mmol of potassium chloride were ground into powders respectively, then mixed and ground again to obtain an initial mixed salt.

[0069] The initial mixed salt was placed in a box furnace, heated to 800°C at a heating rate of 5°C / min, calcined at 800°C for 4 hours, and naturally cooled to room temperature in the furnace to obtain a calcined product.

[0070] The calcined product was centrifugally washed twice with deionized water and once with ethanol, the centrifugal speed was 6000 r / min, and the time of each centrifugal washing was 5 minutes. The solid obtained by washing was dried to obtain cerium dioxide particles.

[0071] The SEM results of the obtained cerium dioxide particles are shown in Figure 5 .Depend on Figure 5It can be seen that the cerium dioxide particles are basically spherical. 50 particles are selected to calculate the average particle size of the cerium dioxide particles, which is about 181.5 nm.

[0072] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing cerium dioxide particles, characterized in that: The following steps are involved: 1) mixing and grinding the cerium salt and flux salt to obtain an initial mixed salt; 2) mixing and grinding the initial mixed salt and the surface additive to obtain a mixed salt containing the surface additive; 3) roasting the mixed salt containing the surface additive to obtain a roasted product; 4) washing the calcined product, and drying the solid obtained after washing to obtain cerium dioxide particles; in, In step 1), the molar ratio of the cerium salt to the flux salt is less than or equal to 1:3; No additional solvent is added in step 1), step 2) and step 3).

2. The preparation method according to claim 1, characterized in that: In step 1), the flux salt is selected from at least one of sodium chloride, potassium chloride, potassium nitrate, sodium nitrate and lithium chloride.

3. The preparation method according to claim 1, characterized in that: The cerium salt is selected from at least one of cerium nitrate, cerium chloride, cerium sulfate, cerium acetate and cerium carbonate.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the cerium salt to the flux salt is 1:5-15.

5. The preparation method according to claim 1, characterized in that: Step 1) comprises the following specific steps: grinding the cerium salt and the flux salt respectively, mixing the ground cerium salt and the ground flux salt, and grinding again to obtain an initial mixed salt.

6. The preparation method according to claim 1, characterized in that: In step 2), the mass ratio of the surface additive to the initial mixed salt is 0.1 to 1:

1.

7. The preparation method according to claim 1, characterized in that: In step 2), the surface additive is selected from at least one of polyethylene glycol, polyvinyl pyrrolidone, citric acid, hexadecyltrimethylammonium chloride, sodium hexametaphosphate, sorbitol, glycine, and glutamic acid.

8. The preparation method according to claim 1, characterized in that: In step 3), the calcination temperature is 700-1000° C. and the calcination time is 2-6 hours.

9. The preparation method according to claim 1, characterized in that: In step 4), the roasted product is centrifuged and washed with water and alcohol in sequence, wherein the alcohol is selected from at least one of methanol, ethanol and isopropanol; In step 4), the drying temperature is 70-100° C. and the drying time is 3-10 hours.

10. A cerium dioxide particle, characterized in that: The invention is prepared according to the preparation method according to any one of claims 1 to 9, and has an average particle size of 80 to 130 nm.

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