A method for preparing a high porosity uranium carbide-based porous ceramic material

Abstract

The application relates to a preparation method of high-porosity uranium carbide-based porous ceramic material and relates to the technical field of foam ceramic material preparation.The application aims to solve the problems of low porosity, difficult microstructure regulation and possible radioactive powder pollution in the operation process of the existing uranium carbide porous ceramic material.The method comprises the following steps: 1) preparation of a precursor solution;2) impregnation of a porous template in the precursor solution, followed by drying in air, wherein the above steps are repeated 1-6 times to obtain a porous material blank; and 3) high-temperature ceramic treatment of the porous material blank to obtain the uranium carbide-based porous ceramic material.The preparation method of the uranium carbide-based porous ceramic material can avoid radioactive dust pollution, and the experimental process is simple and convenient to control.The prepared uranium carbide-based porous ceramic material has high porosity and adjustable microstructure, and can meet the application in the field of online isotope separation technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of foam ceramic material preparation, and particularly relates to a preparation method of high-porosity uranium carbide-based porous ceramic material. BACKGROUND

[0002] The online isotope separation beam device (ISOL) can generate radioactive nuclear beams with good quality, wide energy range and adjustable beam energy, and is an important platform for nuclear physics frontier basic research, and also has wide application in the fields of material science, biological medicine and the like. The target-source system in the ISOL device is a key link for generating radioactive nuclear beams, and specifically relates to the interaction of a high-energy proton beam and a target, the generation, diffusion and extraction of a radioactive nuclide, and determines the generation efficiency of the radioactive nuclide and the quality of the nuclear beam. Therefore, the device has high requirements for the material selection and development of the target, the ISOL target should have a high melting point and thermal conductivity, a large reaction cross section and a high generation efficiency, and the microstructure of the target material also directly affects the release efficiency of the radioactive nuclide in the target material, and the powder, flake or fiber microstructure has a shorter diffusion distance, which is beneficial to the rapid diffusion of the radioactive nuclide.

[0003] Uranium carbide is an important nuclear material, and has a high melting point, thermal conductivity and uranium atom percentage content. In addition, the uranium element in the uranium carbide can have a fission reaction with a high-energy proton to generate a plurality of different radioactive nuclides, which reduces the design requirements for the ISOL target. Therefore, in recent years, the porous uranium carbide material has been widely concerned as a primary target of the ISOL device. The uranium carbide target is usually prepared by a powder sintering method, that is, uranium oxide powder or uranium oxalate powder is used as a uranium source, graphite, carbon nanotubes, graphene and the like are used as a carbon source, the mixture is ball milled, and then the uranium carbide, uranium carbide-graphite porous ceramic material is prepared by a carbothermal reduction reaction under high-temperature conditions. However, the uranium carbide material prepared by the method has a low porosity, and the microstructure is difficult to control, and radioactive powder pollution may exist in the operation process. SUMMARY

[0004] The application aims to solve the problems of the low porosity of the existing porous uranium carbide ceramic material, the difficulty in microstructure control and the possible radioactive powder pollution in the operation process, and provides a preparation method of high-porosity uranium carbide-based porous ceramic material.

[0005] The preparation method of the high-porosity uranium carbide-based porous ceramic material is prepared according to the following steps: one, dissolving a uranyl salt and an organic additive in a mixed solution of deionized water, N,N-dimethylformamide and ethanol, stirring and aging for 1-5 days to prepare a precursor solution;

[0006] II. Put the porous template into the precursor solution prepared in step I, and remove the residual gas in the porous template under low vacuum environment, then dry in air, the above steps are repeated 1-6 times to obtain the porous material blank;

[0007] III. Put the porous material blank obtained in step II into a high temperature furnace for ceramic treatment, the treatment temperature is 1450-1850℃, the vacuum degree is 10 -3 -1000Pa, the holding time is 1-24h, and the obtained uranium carbide-based porous ceramic material is cooled to room temperature after the ceramic treatment.

[0008] Further, the mass / volume ratio of the uranyl salt, the organic additive, deionized water, N,N-dimethylformamide and ethanol in step I is 3.0-35.0g: 1.0-10.0g: 1.0-10.0mL: 1.0-10.0mL: 10-100mL.

[0009] Further, the mass / volume ratio of the uranyl salt, the organic additive, deionized water, N,N-dimethylformamide and ethanol in step I is 5.0-30.0g: 2.0-8.0g: 2.0-8.0mL: 2.0-8.0mL: 20-80mL.

[0010] Further, the mass / volume ratio of the uranyl salt, the organic additive, deionized water, N,N-dimethylformamide and ethanol in step I is 10.0-20.0g: 4.0-6.0g: 4.0-6.0mL: 4.0-6.0mL: 30-60mL.

[0011] Further, the uranyl salt is uranyl nitrate, uranyl chloride or uranyl acetate, with a purity of >99.0%.

[0012] Further, the organic additive is F127 or P123, with a purity of ≥99.9%.

[0013] Further, the porous template in step II is a polyurethane porous template, a melamine porous template, a polystyrene porous template, a poly-4-methyl-1-pentene porous template or a porous carbon template.

[0014] Further, the vacuum degree of the low vacuum environment in step II is 10-50kPa, the standing treatment time under the low vacuum environment is 1-3min, and the drying time in air is 12-48h.

[0015] Further, the temperature rising conditions for the ceramic treatment in step III are as follows: the temperature rising rate is 0.3-1℃ / min in the temperature range of room temperature-800℃, and the temperature rising rate is 1-3℃ / min above 800℃.

[0016] Further, the porous material blank obtained in step two is placed in a high-temperature furnace for ceramic treatment in step three, the treatment temperature is 1500-1700℃, the vacuum degree is 10 -3 ~1000Pa, and the holding time is 1-20h.

[0017] The present application comprises the following beneficial effects:

[0018] First, the porosity of the prepared uranium carbide-based porous ceramic material can be regulated in a large range according to design requirements, and the maximum porosity of the material is up to about 95%, realizing the preparation of high-porosity uranium carbide-based porous ceramic material.

[0019] Second, the template method is used to prepare the uranium carbide-based porous ceramic material, the microstructure of the material can be regulated by selecting porous templates with different microstructure characteristics, and the porous ceramic material well replicates the shape of the template, realizing the near-net forming of the uranium carbide-based porous ceramic material.

[0020] Third, the wet method is used to prepare the uranium carbide-based porous ceramic material, avoiding the problem of radioactive dust pollution, and the experimental process is simple and easy to control. The high-porosity uranium carbide-based porous ceramic material prepared by the method has great application value in the field of online isotope separation technology. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a photo of a uranium carbide-based porous ceramic sample;

[0022] Figure 2 is an XRD spectrum of a uranium carbide-based porous ceramic sample. DETAILED DESCRIPTION

[0023] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer and more apparent, the spirit of the present application will be described in detail below, and any person skilled in the art can make changes and modifications to the technology taught by the present application content without departing from the spirit and scope of the present application content.

[0024] The illustrative embodiments of the present application and their descriptions are used to explain the present application, but not as a limitation of the present application.

[0025] Embodiment 1:

[0026] A preparation method of a high-porosity uranium carbide-based porous ceramic material, which is realized according to the following steps:

[0027] 1. Dissolve 6.0 g of uranyl chloride and 2.0 g of F127 in a mixed solvent of 3.0 mL of deionized water, 3.0 mL of N,N-dimethylformamide and 30 mL of ethanol, stir for 24 h and then age for 4 days to obtain the precursor solution.

[0028] 2. Place the poly-4-methyl-1-pentene porous template in the precursor solution prepared in step 1, and let it stand under low vacuum to remove residual gas inside the porous template. The vacuum treatment time is 2 min and the vacuum degree is 20 kPa. Then dry it in air for 24 h. Repeat the above steps 3 times to obtain a porous material preform.

[0029] 3. Place the porous material blank obtained in step 2 into a high-temperature furnace for high-temperature ceramicization treatment. The treatment temperature is 1600℃, the heating rate is 0.3℃ / min in the temperature range of room temperature to 800℃, the heating rate is 2℃ / min in the temperature range of 800℃ to 1600℃, the vacuum degree is 100Pa, the holding time is 8h, and the uranium carbide-based porous ceramic material is cooled to room temperature. The sample is taken out and transferred to a glove box.

[0030] Macroscopic photographs of the uranium carbide-based porous ceramic samples prepared in this embodiment are shown below. Figure 1 As shown, the uranium carbide-based porous ceramic material has a complete and defect-free structure with a porosity of ~84%. X-ray diffraction analysis indicates that the porous ceramic material is of the UC phase. The mechanical properties of the uranium carbide-based porous ceramic sample were tested, and its compressive strength was 0.8 MPa.

[0031] In this embodiment, the ceramicization treatment of the porous material under a low vacuum environment is beneficial to the structural stability of the porous material and reduces the carbothermic reduction reaction temperature. After being subjected to a low vacuum environment, carbothermic reduction occurs at a higher temperature to obtain uranium carbide-based porous materials.

[0032] Example 2:

[0033] A method for preparing a high-porosity uranium carbide-based porous ceramic material is specifically implemented according to the following steps:

[0034] 1. Dissolve 17.6g of uranyl nitrate and 4.5g of F127 in a mixed solvent of 6.0mL of deionized water, 2.5mL of N,N-dimethylformamide and 50mL of ethanol. Stir for 24h and then age for 2 days to obtain the precursor solution.

[0035] 2. Place the melamine porous template in the precursor solution prepared in step 1, and let it stand under low vacuum to remove residual gas inside the porous template. The vacuum treatment time is 1 min and the vacuum degree is 30 kPa. Then dry it in air for 36 h. Repeat the above steps twice to obtain a porous material blank.

[0036] III. The porous material blank obtained in step II is placed in a high-temperature furnace for high-temperature ceramic treatment, the treatment temperature is 1550℃, the temperature rising rate is 1℃ / min in the temperature range of room temperature to 800℃, the temperature rising rate is 3℃ / min in the temperature range of 800 to 1550℃, the vacuum degree is 1Pa, the holding time is 10h, and the obtained uranium carbide-based porous ceramic material is cooled to room temperature, the sample is taken out and transferred to a glove box.

[0037] The porosity of the uranium carbide-based porous ceramic sample prepared in this example is about 95%, and the X-ray diffractometer analysis shows that the main phase of the porous ceramic material is UC2. Figure 2

[0038] Example 3:

[0039] A preparation method of a high-porosity uranium carbide-based porous ceramic material, specifically implemented by the following steps:

[0040] I. 15.3g of uranyl chloride, 8.0g of P123 are dissolved in 5.0mL of deionized water, 7.5mL of N,N-dimethylformamide and 75mL of ethanol mixed solvent, stirred for 24h and aged for 5 days to prepare a precursor solution;

[0041] II. The polystyrene porous template is placed in the precursor solution prepared in step I, and the residual gas inside the porous template is removed under low vacuum environment, the vacuum treatment time is 3min, and the vacuum degree is 15kPa; then dried in air, the drying time is 12h, the above steps are cycled 5 times to obtain a porous material blank;

[0042] III. The porous material blank obtained in step II is placed in a high-temperature furnace for high-temperature ceramic treatment, the treatment temperature is 1550℃, the temperature rising rate is 1℃ / min in the temperature range of room temperature to 800℃, the temperature rising rate is 3℃ / min in the temperature range of 800 to 1550℃, the vacuum degree is 1Pa, the holding time is 10h, and the obtained uranium carbide-based porous ceramic material is cooled to room temperature, the sample is taken out and transferred to a glove box. -2

[0043] The compressive strength of the uranium carbide-based porous ceramic sample prepared in this example is 1.7MPa, and the X-ray diffractometer analysis shows that the phase of the porous ceramic material is UC2 and graphite.

[0044] Example 4:

[0045] A preparation method of a high-porosity uranium carbide-based porous ceramic material, specifically implemented by the following steps:

[0046] ​​I. A precursor solution was prepared by dissolving 14.8 g of uranyl acetate and 1.2 g of F127 in a mixed solvent of 2.5 mL of deionized water, 5.0 mL of N,N-dimethylformamide and 45 mL of ethanol, stirring for 24 h and aging for 3 days;

[0047] II. The poly-4-methyl-1-pentene porous template was placed in the precursor solution prepared in step I, and the residual gas inside the porous template was removed by static treatment under low vacuum for 1 min at a vacuum degree of 25 kPa, followed by drying in air for 48 h. The above steps were repeated 4 times to obtain a porous material blank;

[0048] III. The porous material blank obtained in step II was subjected to high-temperature ceramic treatment in a high-temperature furnace at a treatment temperature of 1500 °C, a temperature rising rate of 0.5 °C / min in the temperature range of room temperature to 800 °C, a temperature rising rate of 1 °C / min in the temperature range of 800 to 1500 °C, a vacuum degree of 1000 Pa, and a holding time of 6 h, and was cooled to room temperature to obtain a uranium carbide-based porous ceramic material. The sample was taken out and transferred to a glove box. The uranium carbide-based porous ceramic sample prepared in this example was analyzed by an X-ray diffractometer, and the results showed that the material phase was UC and UO2.

Claims

1. A method for preparing a high-porosity uranium carbide-based porous ceramic material, characterized in that... This method is prepared according to the following steps:

1. Dissolve uranyl salt and organic additives in a mixed solution of deionized water, N,N-dimethylformamide and ethanol, stir and age for 1-5 days to obtain a precursor solution; 2. Place the porous template in the precursor solution prepared in step 1, and let it stand in a low vacuum environment to remove residual gas inside the porous template. Then dry it in air. Repeat the above steps 1 to 6 times to obtain a porous material blank. Third, the porous material preform obtained in step two is placed in a high-temperature furnace for ceramic treatment at a temperature of 1450~1850℃ and a vacuum degree of 10. -3 Uranium carbide-based porous ceramic material obtained by holding at ~1000Pa for 1~24h and then cooling to room temperature after ceramicization treatment; The mass-to-volume ratio of uranyl salt, organic additives, deionized water, N,N-dimethylformamide, and ethanol mentioned in step one is 3.0~35.0g: 1.0~10.0g: 1.0~10.0mL: 1.0~10.0mL: 10~100mL; The porous template mentioned in step two is a melamine porous template, a polystyrene porous template, or a poly-4-methyl-1-pentene porous template; The vacuum degree of the low vacuum environment mentioned in step two is 10~50kPa, the standing treatment time in the low vacuum environment is 1~3min, and the drying time in air is 12~48h; the organic additive is F127 or P123 with a purity ≥99.9%.

2. The method for preparing a high-porosity uranium carbide-based porous ceramic material according to claim 1, characterized in that... The mass-to-volume ratio of uranyl salt, organic additives, deionized water, N,N-dimethylformamide, and ethanol mentioned in step one is 5.0~30.0g: 2.0~8.0g: 2.0~8.0mL: 2.0~8.0mL: 20~80mL.

3. The method for preparing a high-porosity uranium carbide-based porous ceramic material according to claim 2, characterized in that... The mass-to-volume ratio of uranyl salt, organic additives, deionized water, N,N-dimethylformamide, and ethanol mentioned in step one is 10.0~20.0g: 4.0~6.0g: 4.0~6.0mL: 4.0~6.0mL: 30~60mL.

4. The method for preparing a high-porosity uranium carbide-based porous ceramic material according to claim 1, characterized in that... The uranyl salt is uranyl nitrate, uranyl chloride, or uranyl acetate, with a purity > 99.0%.

5. The method for preparing a high-porosity uranium carbide-based porous ceramic material according to claim 1, characterized in that... The heating conditions for the ceramization treatment in step three are as follows: heating rate of 0.3~1℃ / min in the temperature range of room temperature to 800℃, and heating rate of 1~3℃ / min above 800℃.

6. The method for preparing a high-porosity uranium carbide-based porous ceramic material according to claim 1, characterized in that... In step three, the porous material preform obtained in step two is placed in a high-temperature furnace for ceramic treatment at a temperature of 1500~1700℃ and a vacuum degree of 10. -3 ~1000Pa, heat preservation time is 1~20h.

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