A method for preparing uranium oxide nanoparticles

Abstract

The application relates to a preparation method of uranium oxide nanoparticles, and belongs to the technical field of nanometer material preparation, which comprises the following steps: 1, preparation of a precursor solution; 2, template impregnation and drying to obtain a uranium oxide precursor blank; and 3, ceramic treatment, grinding and screening to obtain the uranium oxide nanoparticles. The preparation method of the uranium oxide nanoparticles is simple in experiment process, convenient in operation control and suitable for large-scale production of the nanoparticles. The prepared uranium oxide nanoparticles are good in dispersity, high in phase purity, adjustable in average particle size in the range of 30-500 nm, and can meet the application in the fields of catalysis and nuclear fuel preparation technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial preparation, and particularly relates to a preparation method of uranium oxide nanoparticles. BACKGROUND

[0002] Nanoparticles are zero-dimensional nanomaterials. Due to the super-high specific surface area, the proportion of surface atoms is significantly increased compared with macroscopic bulk materials, which leads to changes in material physical and chemical properties related to the surface, so that nanoparticles exhibit many special properties in terms of light, electricity, heat, magnetism, catalysis and the like. However, compared with conventional materials, the synthesis and performance of uranium oxide nanoparticles are still limited at home and abroad.

[0003] Uranium oxide includes UO2, U3O8, UO3, U2O5, U4O9 and the like. Among them, U3O8 is the most stable phase, and UO2 is of great concern as a nuclear fuel.

[0004] UO2 is an important nuclear fuel, but UO2 fuel pellets have problems such as low thermal conductivity, uneven burnup, and the ability to resist radiation damage needs to be further improved. Studies have shown that UO2 nanoparticles as raw materials to prepare UO2 fuel pellets with nanocrystalline structure can help improve the burnup of the fuel pellets; nanocrystallization of UO2 and compounding of UO2 nanoparticles with high thermal conductivity components are also important technical approaches to improve the thermal conductivity of the fuel pellets. In addition, as a catalyst, UO2 nanoparticles can be used to catalyze alcohol dehydrogenation reactions. U3O8 is also a high-efficiency and stable catalyst. Studies have shown that U3O8 nanoparticles can be used to catalyze the degradation of volatile organic compounds such as benzene and the oxidation of alcohols such as benzyl alcohol. In addition, U3O8 has excellent stability in high-temperature environments containing Cl2, which makes it have high-efficiency and stable catalytic performance in catalyzing the oxidation of HCl and the degradation of chlorine-containing organic pollutants. The composite material of U3O8 particles and graphene has excellent electrocatalytic performance, and its stability is also higher than that of traditional Pt / C catalysts.

[0005] But there are few studies on the preparation of uranium oxide nanoparticles. Rath et al. prepared rod-like UO2 nanoparticles with a diameter of 80 nm and a length of 500 nm by irradiation method, but the UO2 nanoparticles prepared by the method have poor stability and will be rapidly oxidized. Ma et al. prepared UO2 nanoparticles by solvothermal method, which will be oxidized and corroded into uraninite in water. Gao et al. prepared U3O8 cubic nanoparticles with a length of 100-200 nm and a width of 20-100 nm by hydrothermal method. The technology for synthesizing nanoparticles based on solvothermal method / hydrothermal method is relatively mature, but there are problems of low yield, complicated experimental process and difficulty in large-scale production in the preparation of uranium oxide nanoparticles by the method. Ishani Majumder et al. designed and synthesized four kinds of organic uranium complexes, and successfully prepared U3O8 nanoparticles with a particle size of 50-100 nm by pyrolysis of the complexes. The method for preparing U3O8 nanoparticles has a simple process, but the raw materials for synthesizing the organic uranium complexes are high in cost and difficult to be prepared in large quantities. SUMMARY

[0006] In view of the problems in the preparation of uranium oxide nanoparticles in the prior art, the purpose of the present application is to provide a preparation method of uranium oxide nanoparticles. The uranium oxide nanoparticles prepared by the method have the characteristics of good particle dispersion, high phase purity and adjustable particle size, and the method has a simple preparation process and is suitable for large-scale production of nanoparticles.

[0007] The preparation method of the uranium oxide nanoparticles is carried out according to the following steps:

[0008] I. Preparation of precursor solution: dissolve uranyl salt and organic additive in a mixed solvent of deionized water and ethanol, stir uniformly, and then stand and age to prepare a uranium oxide precursor solution;

[0009] II. Template impregnation and drying: place the foam template in the uranium oxide precursor solution prepared in step I, and stand and treat in a low vacuum environment, and then dry in an air environment to obtain a uranium oxide precursor blank;

[0010] III. Ceramization treatment and grinding and screening: carry out ceramization treatment on the uranium oxide precursor blank obtained in step II, and grind and screen the product to obtain uranium oxide nanoparticles.

[0011] Further, the uranyl salt in step I is uranyl nitrate, uranyl chloride or uranyl acetate.

[0012] Further, the organic additive in step I is F127 or P123.

[0013] Further, the mass ratio of the uranyl salt to the organic additive in step I is 1-30:0.1-10.

[0014] Further, the mass-volume ratio of the mixed solvent of the uranyl salt, the organic additive, the deionized water and the ethanol is 1-30 g:0.1-10 g:6-120 mL.

[0015] Further, the volume ratio of the deionized water to the ethanol in the mixed solvent of the deionized water and the ethanol is 1-20:5-100.

[0016] Further, the foam template in step two is a polyurethane foam template, a melamine foam template, a polystyrene foam template, a poly-4-methyl-1-pentene foam template or a carbon foam template.

[0017] Further, the vacuum degree in step two is 10-50 kPa, the vacuum treatment time is 1-5 min, and the drying time is 12-48 h.

[0018] Further, the uranium oxide nanoparticles in step three are U3O8 nanoparticles, and the ceramic treatment process of the U3O8 nanoparticles is as follows: the uranium oxide precursor blank is placed in a muffle furnace and calcined at a high temperature in air, the calcination temperature is 500-800 ℃, the temperature rising rate is 1-5 ℃ / min, the holding time is 1-24 h, and the calcined material is ground and sieved to obtain the U3O8 nanoparticles.

[0019] Further, the uranium oxide nanoparticles in step three are UO2 nanoparticles, and the ceramic treatment process of the UO2 nanoparticles is as follows: the uranium oxide precursor blank is placed in a muffle furnace and calcined at a high temperature in air, the calcination temperature is 500-800 ℃, the temperature rising rate is 1-5 ℃ / min, the holding time is 1-24 h, the calcined material is reduced by hydrogen, the hydrogen reduction temperature is 500-800 ℃, the temperature rising rate is 1-5 ℃ / min, the holding time is 1-4 h, and the final product is ground and sieved to obtain the UO2 nanoparticles.

[0020] The present application comprises the following beneficial effects:

[0021] I. The present application provides a preparation method of uranium oxide nanoparticles, and the prepared uranium oxide nanoparticles have good dispersibility, high phase purity, and an average particle size in the range of 30-500 nm which can be adjusted.

[0022] II. The present application first introduces a foam template into the preparation of nanoparticles, deposits the uranium oxide precursor on the surface of the foam template skeleton, and ingeniously utilizes the space confinement effect of the foam template to inhibit the growth of the nanoparticles in the later calcination process, thereby realizing effective control of the particle size.

[0023] Third, the organic additive used in the application is a block copolymer, which is used to adjust the rheological property of the uranium oxide precursor solution, so as to realize the regulation of the precursor deposition amount on the surface of the template skeleton; meanwhile, the block copolymer is also a soft template, and a large amount of mesopores introduced in the calcination process can avoid the agglomeration of the nanoparticles, and is beneficial to improve the dispersibility of the nanoparticles.

[0024] Fourth, the UO2 nanoparticles prepared by the application have high stability and good oxidation resistance.

[0025] Fifth, the preparation method of the uranium oxide nanoparticles provided by the application has simple experimental process, convenient operation control, does not need expensive experimental equipment, and is suitable for large-scale production of nanoparticles. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is an XRD pattern of U3O8 nanoparticles;

[0027] Figure 2 is an SEM photo of U3O8 nanoparticles;

[0028] Figure 3 is an XRD pattern of UO2 nanoparticles;

[0029] Figure 4 is a particle size distribution curve of UO2 nanoparticles. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear and explicit, the spirit of the disclosed content will be described in detail below, and any person skilled in the art can make changes and modifications to the technology taught by the content of the application without departing from the spirit and scope of the content of the application.

[0031] The illustrative embodiments of the application and the description thereof are used to explain the application, but are not as limitation of the application.

[0032] Embodiment 1:

[0033] A preparation method of uranium oxide nanoparticles, specifically realized by the following steps:

[0034] I. 5.0g of uranyl nitrate and 1.5g of F127 are dissolved in 2.0mL of deionized water and 20mL of ethanol mixed solvent, stirred uniformly, and then aged for 1 day to prepare a uranium oxide precursor solution;

[0035] II. The polyurethane foam template is placed in the uranium oxide precursor solution prepared in step I, and is treated by standing in a low vacuum environment, the vacuum treatment time is 1min, and the vacuum degree is 15kPa; then dried in air, the drying time is 24h, to obtain a uranium oxide precursor blank body;

[0036] III. Put the obtained uranium oxide precursor blank in a muffle furnace, and calcine in air at a high temperature, the calcination temperature is 800℃, the heating rate is 4℃ / min, and the holding time is 2h. The calcined material is ground and sieved to obtain U3O8 nanoparticles.

[0037] The XRD pattern of the U3O8 nanoparticles obtained in this example is shown in Figure 1 The results show that the nanoparticle phase purity is high, and no other phase exists except the U3O8 characteristic peak.

[0038] Example 2:

[0039] A method for preparing uranium oxide nanoparticles, specifically implemented by the following steps:

[0040] I. Dissolve 12.7g of uranyl acetate and 5.0g of P123 in a mixed solvent of 4.0mL of deionized water and 45mL of ethanol, stir uniformly, and then stand for aging for 5 days to prepare a uranium oxide precursor solution;

[0041] II. Put the carbon foam template into the uranium oxide precursor solution prepared in step I, and stand for treatment in a low vacuum environment, the vacuum treatment time is 4min, and the vacuum degree is 45kPa; then dry in air, the drying time is 36h, to obtain a uranium oxide precursor blank;

[0042] III. Put the obtained uranium oxide precursor blank in a muffle furnace, and calcine in air at a high temperature, the calcination temperature is 650℃, the heating rate is 2℃ / min, and the holding time is 8h. The calcined material is ground and sieved to obtain U3O8 nanoparticles.

[0043] The U3O8 nanoparticles obtained in this example are characterized by a scanning electron microscope, as shown in Figure 2 The U3O8 nanoparticles have uniform particle size and are fine.

[0044] Example 3:

[0045] A method for preparing uranium oxide nanoparticles, specifically implemented by the following steps:

[0046] I. Dissolve 8.5g of uranyl chloride and 2.5g of F127 in a mixed solvent of 1.5mL of deionized water and 40mL of ethanol, stir uniformly, and then stand for aging for 2 days to prepare a uranium oxide precursor solution;

[0047] II. Put the poly-4-methyl-1-pentene foam template into the uranium oxide precursor solution prepared in step I, and place it in a low vacuum environment for treatment, with a vacuum treatment time of 3 min and a vacuum degree of 20 kPa; then dry it in air for 12 h to obtain a uranium oxide precursor blank;

[0048] III. Put the uranium oxide precursor blank obtained in step II into a muffle furnace, and calcine it in air at a calcination temperature of 600 DEG C, a temperature rising rate of 1 DEG C / min, and a holding time of 15 h; then reduce the calcined material by hydrogen at a hydrogen reduction temperature of 800 DEG C, a temperature rising rate of 5 DEG C / min, and a holding time of 1 h; and finally grind and sieve the final product to obtain UO2 nanoparticles.

[0049] The XRD pattern of the UO2 nanoparticles obtained in this example is shown in Figure 3 The results show that the nanoparticle phase purity is high, and no other phase exists except the UO2 characteristic peak.

[0050] Example 4:

[0051] A method for preparing U3O8 nanoparticles, which is realized by the following steps:

[0052] I. Dissolve 15.0 g of uranyl nitrate and 3.0 g of F127 in a mixed solvent of 4.0 mL of deionized water and 55 mL of ethanol, stir uniformly, and then place it for aging for 4 days to prepare a uranium oxide precursor solution;

[0053] II. Put the carbon foam template into the uranium oxide precursor solution prepared in step I, and place it in a low vacuum environment for treatment, with a vacuum treatment time of 5 min and a vacuum degree of 30 kPa; then dry it in air for 20 h to obtain a uranium oxide precursor blank;

[0054] III. Put the uranium oxide precursor blank obtained in step II into a muffle furnace, and calcine it in air at a calcination temperature of 700 DEG C, a temperature rising rate of 2 DEG C / min, and a holding time of 4 h; then reduce the calcined material by hydrogen at a hydrogen reduction temperature of 700 DEG C, a temperature rising rate of 2 DEG C / min, and a holding time of 2 h; and finally grind and sieve the final product to obtain UO2 nanoparticles.

[0055] The UO2 nanoparticles obtained in this example are detected for particle distribution by a nano-laser particle size instrument Figure 4 ), and it can be found that the average particle size of the UO2 nanoparticles is about 165 nm, the particle size distribution is relatively narrow, and the particle dispersity is good. After the UO2 nanoparticles are stored in an aqueous solution for 180 days, the nanoparticle phase does not change, showing excellent stability.

Claims

1. A method for preparing uranium oxide nanoparticles, characterized in that... The preparation method is carried out according to the following steps: I. Preparation of precursor solution: Dissolve uranyl salt and organic additives in a mixed solvent of deionized water and ethanol, stir evenly, and allow to stand for aging to obtain uranium oxide precursor solution.

2. Template impregnation and drying: The foam template is placed in the uranium oxide precursor solution obtained in step 1 and left to stand under low vacuum. Then it is dried in air to obtain uranium oxide precursor blank. The foam template is a polyurethane foam template, a melamine foam template, a polystyrene foam template, a poly-4-methyl-1-pentene foam template, or a carbon foam template; III. Ceramicization treatment, grinding and sieving: The uranium oxide precursor green body obtained in step II is subjected to ceramicization treatment, and the product is ground and sieved to obtain uranium oxide nanoparticles. The uranyl salt mentioned in step one is uranyl nitrate, uranyl chloride, or uranyl acetate; The organic additive mentioned in step one is F127 or P123; The uranium oxide nanoparticles mentioned in step three are U3O8 nanoparticles. The ceramicization process of the U3O8 nanoparticles is as follows: the uranium oxide precursor blank is placed in a muffle furnace and calcined in air at a high temperature of 500~800 ℃, a heating rate of 1~5 ℃ / min, and a holding time of 1~24 h. The calcined material is then ground and sieved to obtain U3O8 nanoparticles. Alternatively, the uranium oxide nanoparticles mentioned in step three are UO2 nanoparticles, and the ceramicization process of the UO2 nanoparticles is as follows: the uranium oxide precursor blank is placed in a muffle furnace and calcined in air at a high temperature of 500~800 ℃, a heating rate of 1~5 ℃ / min, and a holding time of 1~24 h. The calcined material is then reduced with hydrogen at a temperature of 500~800 ℃, a heating rate of 1~5 ℃ / min, and a holding time of 1~4 h. The final product is then ground and sieved to obtain UO2 nanoparticles.

2. The method for preparing uranium oxide nanoparticles according to claim 1, characterized in that... The mass ratio of uranyl salt to organic additive mentioned in step one is 1~30 : 0.1~10.

3. The method for preparing uranium oxide nanoparticles according to claim 1, characterized in that... The mass-to-volume ratio of the uranyl salt, organic additive, and the mixed solvent of deionized water and ethanol is 1~30 g : 0.1~10 g : 6~120 mL.

4. The method for preparing uranium oxide nanoparticles according to claim 1, characterized in that... The volume ratio of deionized water to ethanol in the mixed solvent of deionized water and ethanol is 1~20 : 5~100.

5. The method for preparing uranium oxide nanoparticles according to claim 1, characterized in that... The vacuum level mentioned in step two is 10~50 kPa, the vacuum treatment time is 1~5 min, and the drying time is 12~48 h.

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