High-density high-dispersity Al-metal oxide dispersion pellet as well as preparation method and application thereof
By grinding and vacuum sintering under an inert atmosphere, combined with ball milling or acoustic resonance mixing technology, the problem of poor mixing uniformity of Al-metal oxide core pellets is solved, and the preparation of core pellets with high density and high diffusion is achieved, which improves the reactor safety and productivity.
Patent Information
- Application Number
- CN202411249026.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2024-12-13
AI Technical Summary
The existing Al-metal oxide diffusion core pellet preparation process has problems such as poor mixing uniformity, low density and difficult to control the stability of the finished product, which affects the safety and production efficiency of the reactor.
Using the integrated mixing and press-firing method, Al powder and metal oxide powder are ground in an inert atmosphere, and then sintered in a vacuum environment, combined with ball milling or acoustic resonance mixing technology, Al powder and metal oxide are realized. uniform mixing and high density densification.
The preparation of Al-metal oxide core pellets with high density and diffusion is achieved, which improves the density and diffusion of the core pellets, reduces component deviations, simplifies the process flow and reduces costs.
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Figure CN119132684A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of nuclear material preparation, and in particular to a high-density and high-dispersion Al-metal oxide dispersion core block and a preparation method and application thereof. Background Art
[0002] Placing transuranic target materials in a high flux reactor for irradiation, where the target nucleus continuously captures neutrons, undergoes multiple (n, γ) reactions and β-decays, is currently the only way to mass produce superheavy elements such as Am and Cm. Therefore, the performance of the target cores used in high flux reactors is crucial to achieve the transformation of nuclides and the production of more strategically significant materials.
[0003] Although the metal state of transuranium element targets has good thermal conductivity, their chemical properties are too active and are not suitable for reactor irradiation; their oxides are extremely stable, but have poor thermal conductivity, and many target nuclei have very large neutron reaction cross sections. During the irradiation process, they not only have obvious self-shielding effects, but also release a lot of heat, which will inevitably lead to target temperature rise and sintering. The dissolution of MA oxide targets ceramicized by high-temperature sintering is very difficult, which in turn affects the subsequent extraction of key materials. Dispersed target core blocks are target forms in which microspheres containing minor actinide nuclides (MA) are evenly dispersed in an inert metal or ceramic matrix. Among them, Al powder is used more in the inert matrix. This is because metal Al is a light metal with a low atomic number. Its excellent thermal conductivity can improve the overall thermal conductivity of the target core block, reduce the target temperature of the irradiation, and prevent the sintering and ceramicization of transuranium element oxides. At the same time, Al powder can also be used as a diluent to reduce the concentration of target nuclei in the target block, reduce the self-shielding effect of the target nuclei during the irradiation process, and reduce the heat released by the unit volume of the target block. On the other hand, the thermal neutron reaction cross section of Al is very small, only 2.2×10 -25 cm 2 , which has little effect on the neutron flux density of the reactor.
[0004] Taking into account the mechanical load of stress and strain caused by long-term strong neutron irradiation, scouring and corrosion of high-temperature and high-flow coolant in high-flux reactors, and changes in temperature and pressure in the reactor, the prepared target core blocks must have good physical and chemical stability and good mechanical strength to meet the harsh operating conditions in the reactor.
[0005] At present, the preparation processes of Al-metal oxide dispersion core blocks mainly include co-hot extrusion and powder metallurgy sintering. Among them, the co-hot extrusion method is a commonly used method abroad. This method pre-presses the mixed powder in the mold, loads the pressed blank into the aluminum alloy cladding tube, and then uses a co-extruder to perform hot extrusion at 610°. This method can obtain nearly fully dense core blocks, and there is no gap at the interface between the core block and the cladding, achieving metallurgical bonding and facilitating heat conduction. However, when the content of hard and brittle metal oxides is high, co-hot extrusion is more difficult, and under 610° conditions, Al easily forms intermetallic compounds with metal oxides, affecting the quality of the core blocks. In addition, the process is difficult and the equipment is expensive, the scrap rate is high, and the production efficiency is low.
[0006] Another preparation process is to cold press at room temperature by traditional powder metallurgy method, and then sinter at a lower temperature to prepare Al-metal oxide dispersion core blocks. The process and equipment are relatively simple, with high yield and high production efficiency. However, this process also has some shortcomings, such as the large difference in relative molecular mass between Al powder and metal oxide, which makes it difficult to mix evenly, the high proportion of metal oxide has an adverse effect on the density of the dispersion core block, and the dimensional stability of the core block is difficult to control. Yin Bangyue and others from the China Institute of Atomic Energy compared the hot pressing and cold pressing processes of Al-20% UO2 dispersion core blocks. The study found that the density of the dispersion core blocks prepared by vacuum hot pressing and sintering is low and prone to cracking. High-density dispersion core blocks can not only improve the thermal conductivity of the core blocks, but also improve the irradiation safety of the target, thereby increasing the nuclide loading of the target material of the irradiated target and improving the economic efficiency of irradiation nuclide production. Therefore, the research on the preparation process of high-density Al-metal oxide dispersion core blocks is particularly important, and new preparation processes need to be developed to be suitable for practical applications.
[0007] Spark plasma sintering (SPS) is a process that pressurizes powder while applying a controllable DC pulse current to induce local Joule heating, plasma activation and other unique effects, thereby achieving rapid, low-temperature and efficient densification of materials. Compared with traditional methods, it has the advantages of fast heating rate, short sintering time and effective suppression of grain growth, and is expected to become a solution to the drawbacks of the existing pressing-sintering process.
[0008] Chinese patent CN201710472261.7 discloses a method for preparing an Al-NpO2 dispersion core block. The preparation method comprises the following steps: 1) powder mixing: mixing aluminum powder, NpO2 powder, polyethylene glycol powder, stearic acid powder, and paraffin powder uniformly in a mass ratio of 1: (0.25-0.27): (0.06-0.18): (0.06-0.18): (0.06-0.18); 2) compression molding: placing the mixed powder in a mold for compression molding, and forming an Al-NpO2 dispersion core block green body after demolding; 3) vacuum sintering: vacuum sintering the obtained Al-NpO2 dispersion core block green body to obtain an Al-NpO2 dispersion core block. The preparation method of the Al-NpO2 dispersion core block of the invention can reduce the oxidation of aluminum powder during the preparation process and further improve the density of the prepared Al-NpO2 dispersion core body. However, the powder mixing process using a mixer in this patent is prone to agglomeration of metal oxides, resulting in poor dispersion uniformity. Summary of the invention
[0009] The purpose of the present invention is to provide a high-density and high-dispersivity Al-metal oxide dispersion core block and its preparation method and application. Since there are great differences in melting point, density, etc. between the matrix material (Al powder) and the metal oxide, particles of different densities and particle sizes produce particle convection during the mixing process, resulting in poor material mixing uniformity, which in turn leads to random distribution of fission nuclides inside the core block, bringing many uncertainties to the reactor in terms of thermal and neutrons, affecting the safety of the reactor. Therefore, the core block is required to have the characteristics of high dispersivity (uniformity) and high density. The present invention can effectively mix Al powder and metal oxide powder uniformly by integrating mixing and pressing, and the prepared core block has the advantages of high density and good dispersivity.
[0010] The purpose of the present invention can be achieved by the following technical solutions:
[0011] A method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block, the specific steps are as follows:
[0012] S1, mixing Al powder and metal oxide, and grinding them under an inert atmosphere to obtain a mixed powder;
[0013] S2. Vacuum sintering the mixed powder obtained in step S1 to obtain a high-density and high-dispersion Al-metal oxide dispersed core block.
[0014] Furthermore, in step S1, the particle size of the Al powder is in the range of 10-100 microns.
[0015] Furthermore, in step S1, the metal oxide is selected from neodymium oxide, tantalum oxide, cerium oxide, uranium oxide, plutonium oxide or americium oxide.
[0016] Furthermore, in step S1, the mass fraction of the metal oxide in the mixed powder is 3%-25%.
[0017] Furthermore, in step S1, the mixing method is selected from ball milling mixing, acoustic resonance mixing or three-dimensional mixer mixing.
[0018] In the above further, the ball milling mixing method is as follows:
[0019] Al powder and metal oxide are placed in an agate mortar and premixed for a certain period of time, and then the premixed powder is placed in a ball mill, and then anhydrous ethanol is added and ball milled in an inert atmosphere to obtain a mixed powder.
[0020] In the above, the ball mill is provided with grinding balls, the ball-to-material ratio is (15-25):1, and the grinding balls are Carbide ball 100g and Made of carbide balls.
[0021] Furthermore, the ball mill jar and the grinding balls are both made of cemented carbide.
[0022] As a preferred technical solution, the ball mill uses a P5 planetary ball mill produced by Fritsch Company of Germany to homogenize the premixed powder.
[0023] Furthermore, in the above, the premixing time is 8 to 12 minutes, preferably 10 minutes.
[0024] In the above, further, the ball milling time is 2 to 4 hours and the rotation speed is 100-200 r / min.
[0025] Furthermore, the acoustic resonance mixing method is as follows:
[0026] Al powder and metal oxide are premixed to obtain premixed powder, and the premixed powder is homogenized by an acoustic resonance mixer to obtain a mixed powder.
[0027] In the above, the acoustic resonance mixer contains a mixing medium, and the mixing medium is Carbide balls.
[0028] Furthermore, in the acoustic resonance mixer, the gravitational acceleration of the mixing is 80-100 g, and the mixing time is 8-12 min.
[0029] Furthermore, in step S1, the inert atmosphere is an argon atmosphere.
[0030] Furthermore, in step S2, the sintering temperature is 500-600°C, the sintering pressure is 20-50MPa, and the sintering time is 5-10min.
[0031] As a preferred technical solution, the vacuum sintering is carried out on a SPS-3.20MK-Ⅳ spark plasma sintering system produced by Sinter Land Co., Ltd. of Japan.
[0032] The present invention also provides a high-density and high-dispersion Al-metal oxide dispersion core block, which is composed of Al particles and metal oxides. The metal oxides are distributed around the Al particles, the particles are tightly combined, and the composition deviation is small.
[0033] In addition, the present invention also provides an application of a high-density and high-dispersion Al-metal oxide dispersion pellet, which can be used for the preparation of irradiated target dispersed nuclear fuel, transmutation material, etc. in the production of special materials.
[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0035] 1. The process of the present invention is simple, the cost is low, the reaction process of each step is fast and easy to control, and the prepared core block has the advantages of high density and good dispersion.
[0036] 2. The present invention can achieve full mixing and homogenization of Al-metal oxide by mixing Al powder and metal oxide and can achieve rapid and high-quality molding of Al-metal oxide core blocks by pressure sintering, and can prepare core blocks with high density and high dispersion.
[0037] 3. Compared with the prior art, the present invention adopts the method of grinding, mixing, pressing and sintering to improve the mixing uniformity, reduce the component deviation, and thus improve the dispersion degree of the metal oxide powder in the core block. BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 Schematic diagram of the microstructure of Al-Nd2O3 dispersion core blocks sintered at different temperatures, where (a) is 560℃ and (b) is 580℃;
[0039] Figure 2 Schematic diagram of the TEM microstructure of Al-CeO2 dispersed core blocks after sintering at 580°C, where (a) and (b) are TEM microstructures, and (c) and (d) are HRTEM microstructures. DETAILED DESCRIPTION
[0040] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0041] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.
[0042] Example 1
[0043] This embodiment provides a method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block, and the specific steps are as follows:
[0044] (1) 17 g of Al powder and 3 g of Nd2O3 powder were premixed in an agate mortar for 10 minutes, and then the premixed powders were placed in a ball mill and ball milled under an argon atmosphere. Carbide ball 100g and The carbide ball is composed of 300g, the ball-to-material ratio is 20:1, and 2ml of anhydrous ethanol is added as a process control agent to prevent Al powder from sticking. The speed is 100r / min, and the ball milling time is 2h.
[0045] (2) The mixed powder obtained in step 1) was placed in a graphite mold in a glove box for vacuum sintering, and Al-Nd2O3 dispersed core blocks were prepared at a sintering temperature of 560°C.
[0046] like Figure 1 As shown in a, Nd2O3 in the Al-Nd2O3 dispersed core is distributed around the Al particles without obvious agglomeration. When the temperature is higher than 560°C, the dispersed core particles are tightly bound without obvious voids. EDS is used to analyze the uniformity of Nd2O3 distribution in the dispersed core. Figure 1 The deviation of Nd2O3 content in a from that in the powder before pressing is 5.4%.
[0047] Example 2
[0048] This embodiment provides a method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block, and the specific steps are as follows:
[0049] (1) 15 g of Al powder and 5 g of Nd2O3 powder were premixed in an agate mortar for 10 minutes, and then the premixed powders were placed in a ball mill and ball milled under an argon atmosphere. Carbide ball 100g and 300g carbide ball, ball-to-material ratio: 20:1, 2ml anhydrous ethanol is added as a process control agent to prevent Al powder from sticking. The speed is 200r / min, and the ball milling time is 4h.
[0050] (2) The mixed powder obtained in step 1) was placed in a graphite mold in a glove box for vacuum sintering, and Al-Nd2O3 dispersed core blocks were prepared at a sintering temperature of 580°C.
[0051] like Figure 1 As shown in b, the Al-Nd2O3 dispersed pellet sample exhibits a higher density. The composition deviation of Nd2O3 is 3.9%.
[0052] Example 3.
[0053] This embodiment provides a method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block, and the specific steps are as follows:
[0054] (1) 17 g of Al powder and 3 g of CeO2 powder were premixed to obtain Al-CeO2 composite powder, and the Al-CeO2 composite powder was homogenized using a MixBox-G1 acoustic resonance mixer produced by Zhengzhou Abrasives and Grinding Research Institute. The cemented carbide ball is used as the mixing medium, the mixing gravity acceleration is 90g, and the mixing time is 10min.
[0055] (2) The mixed powder obtained in step 1) was placed in a graphite mold in a glove box for vacuum sintering, and Al-CeO2 dispersed core blocks were prepared at a sintering temperature of 580°C.
[0056] like Figure 2 As shown in the figure, the density of the Al-CeO2 dispersed core block sample reaches 98.5% of the theoretical density, and the CeO2 particles are mainly distributed at the aluminum grain boundaries and are relatively evenly distributed. High-resolution images show that the interface between the oxide and the aluminum matrix is clear and tightly bonded within the nanoscale range, and no other new phases are generated ( Figure 2 ). Figure 2 The deviation of CeO2 content in the powder from that before pressing is 5wt%.
[0057] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.
Claims
1. A method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block, characterized in that: The specific steps are as follows: S1, mixing Al powder and metal oxide, and grinding them under an inert atmosphere to obtain a mixed powder; S2. Vacuum sintering the mixed powder obtained in step S1 to obtain a high-density and high-dispersion Al-metal oxide dispersed core block.
2. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 1, characterized in that: In step S1, the particle size of the Al powder is in the range of 10-100 microns.
3. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 1, characterized in that: In step S1, the metal oxide is selected from neodymium oxide, tantalum oxide, cerium oxide, uranium oxide, plutonium oxide or americium oxide; The mass fraction of the metal oxide in the mixed powder is 3%-25%.
4. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 1, characterized in that: In step S1, the mixing method is selected from ball milling mixing, acoustic resonance mixing or three-dimensional mixer mixing; The inert atmosphere is an argon atmosphere.
5. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 4, characterized in that: The method of ball milling mixing is as follows: Al powder and metal oxide are placed in an agate mortar and premixed for a certain period of time, and then the premixed powder is placed in a ball mill, and then anhydrous ethanol is added and ball milled in an inert atmosphere to obtain a mixed powder.
6. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 5, characterized in that: The ball mill is provided with grinding balls, and the ball-to-material ratio is (15-25):1; The premixing time is 8 to 12 minutes, the ball milling time is 2 to 4 hours, and the rotation speed is 100-200 r / min.
7. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 4, characterized in that: The method of acoustic resonance mixing is as follows: Al powder and metal oxide are premixed to obtain premixed powder, and the premixed powder is homogenized by an acoustic resonance mixer to obtain a mixed powder.
8. The method for preparing a high-density and high-dispersion Al-metal oxide dispersion core block according to claim 1, characterized in that: In step S2, the sintering temperature is 500-600°C, the sintering pressure is 20-50MPa, and the sintering time is 5-10min.
9. A high-density and high-dispersion Al-metal oxide dispersion core block, characterized in that: The Al-metal oxide dispersion core block obtained by the preparation method described in any one of claims 1 to 8 consists of Al particles and metal oxides, wherein the metal oxides are distributed around the Al particles, the particles are tightly bound, and the composition deviation is small.
10. An application of the high-density and high-dispersion Al-metal oxide dispersion pellets as claimed in claim 9, characterized in that: The Al-metal oxide dispersion core block can be used for the preparation of irradiation target dispersed nuclear fuel and transmutation material in the production of special materials.