Preparation method of calcium defect type pyrochlore ceramic solidified body
By employing a method for preparing calcium-deficient pyrochlore ceramic solidified bodies, and through multiple high-temperature sintering and grinding processes, the problem of numerous impurity phases in the ceramic solidified bodies was solved, achieving a crystal structure dominated by the pyrochlore phase, thereby improving the containment and stability of highly radioactive waste.
Patent Information
- Application Number
- CN202511791432.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-01-20
AI Technical Summary
Existing technologies make it difficult to prepare ceramic solidified bodies that are mainly composed of pyrochlore phase, as there are many impurity phases, which affects the containment and chemical stability of highly radioactive waste.
The preparation method of calcium-deficient pyrochlore ceramic solidified body involves wet grinding the raw materials CaCO3, CeO2, and TiO2 in anhydrous ethanol until uniform, pressing them into tablets, and sintering them at high temperatures multiple times. The grinding and pressing process is repeated, and finally, the solidified body is cooled in air to maintain the high-temperature phase structure.
It effectively reduces the generation of impurity phases, ensures that the crystal phase is mainly pyrochlore, and improves the containment and chemical stability of highly radioactive waste.
Smart Images
Figure CN121362039A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of high-level nuclear waste treatment, and particularly relates to a preparation method of a calcium-deficient pyrochlore ceramic solidified body. BACKGROUND
[0002] With the increasing exhaustion of traditional energy, people pay more and more attention to non-fossil energy utilization. Nuclear energy is green, clean, economical and efficient, and therefore attracts much attention. In recent years, China is in the peak period of nuclear power development. According to statistics, the nuclear power under construction in China is the largest in the world. However, a new problem will inevitably arise with nuclear power generation, that is, the radioactivity waste derived from nuclear fuel in the cycle is an important problem restricting the safety and sustainable development of the nuclear energy industry. Among them, high-level radioactive waste usually has high radiation level, high biological toxicity and long half-life. How to safely and effectively treat high-level waste is the key and difficulty in nuclear waste treatment.
[0003] In order to prevent high-level waste from affecting the safety of human beings and the entire biosphere, scientists propose to first solidify the high-level waste and then perform deep geological disposal. Currently, three solidification technologies for treating high-level waste have been developed: glass solidification, ceramic solidification and glass-ceramic solidification. Glass solidification has realized engineering and is the international mainstream way of high-level waste disposal, but its inclusion rate is low, and the long-term radiation stability needs to be improved. Some minerals containing radioactivity (such as Th, U, Pu, etc.) in nature can exist stably for a long time and will not cause safety problems such as nuclide leakage to the ecological environment. Inspired by this, people found that ceramic solidification is a more stable solidification method, which has good inclusion and chemical stability for radioactive nuclides, which meets the basic requirements of solidification disposal.
[0004] The chemical formula of pyrochlore mineral phase is A2B2O7. A site can contain large cations (such as Ca, U, Th, lanthanide series elements). It has excellent application prospects in solidifying actinide and rare earth nuclides of high-level waste. In the past research, it is hoped that all Ce exists in the form of Ce 4+ , so as to obtain single-phase pyrochlore, but the prepared samples often contain perovskite and fluorite impurities. Therefore, how to prepare ceramic solidification with less impurities has become an urgent problem to be solved. SUMMARY
[0005] The technical problem solved by the present application is to provide a preparation method of a calcium-deficient pyrochlore ceramic solidified body. The pyrochlore obtained by the method has less impurities, and the crystal phase is mainly pyrochlore phase.
[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows:
[0007] A method for preparing a calcium-deficient pyrochlore ceramic solidification body, raw materials CaCO3, CeO2 and TiO2 are added to ethanol and wet-mixed, then pressed into a sheet, sintered at high temperature, crushed and ground, re-pressed into a sheet and sintered at high temperature again; the grinding, pressing and sintering are repeated several times, and after the last sintering, the sample is taken out and cooled in air; the pressing is performed at a pressure of 5-50 MPa, and the sintering temperature is 1000-1800℃.
[0008] The mass percentages of the raw materials CaCO3, CeO2 and TiO2 in the ceramic solidification body are 15-25wt%, 20-30wt% and 45-60wt% respectively.
[0009] The above method is performed according to the following steps:
[0010] Step one, the raw materials CaCO3, TiO2 and CeO2 are weighed and mixed in a marver, then ethanol is added for wet-mixing to make the mixture more uniform;
[0011] Step two, the particles are further ground after wet-mixing, the powder is put into a mold, and the sample is pressed into a sheet at a pressure of 5-50 MPa;
[0012] Step three, the formed sample is put into a high-temperature furnace and sintered at 1000-1800℃ for 12-36 hours;
[0013] Step four, after cooling in the furnace, the sample is taken out, crushed and ground, re-pressed into a sheet and sintered again at 1000-1800℃ in a high-temperature furnace for 1-9 days; the grinding, pressing and sintering are repeated 2-9 times;
[0014] Step five, after the last sintering, the sample is taken out and cooled in air at high temperature to maintain its phase structure at high temperature.
[0015] In step two, the pressure is 47 MPa (polyvinyl butyral adhesive can be added as needed to ensure molding).
[0016] In steps three and four, the heating rate is 10℃ / min.
[0017] In step four, after re-pressing, the sample is sintered again at 1200℃ in a high-temperature furnace for 24 hours; the grinding, pressing and sintering are repeated 4 times, and the sintering temperatures are 1200℃, 1300℃, 1400℃ and 1500℃, and the holding times are 2 days, 1 day, 2 days and 5 days respectively.
[0018] The calcium-deficient pyrochlore ceramic solidification body obtained by the above method.
[0019] The application of the above preparation method in the field of high-level radioactive waste treatment.
[0020] In view of the problems existing in the current high-level radioactive nuclear waste solidification, the inventors establish a preparation method of calcium-deficient pyrochlore ceramic solidification body. The raw materials CaCO3, CeO2 and TiO2 are uniformly wet-milled in anhydrous ethanol, then are pressed into a sheet, sintered at high temperature, crushed and ground, re-pressed into a sheet and continuously sintered at high temperature; the grinding, pressing and sintering are repeated for multiple times, and after the last sintering, the sample is taken out and cooled in air, and the calcium-deficient pyrochlore ceramic solidification body is obtained. The pressing is performed at a pressure of 5-50 MPa, and the sintering temperature is 1000-1800 ℃. The preparation method of the application reduces the generation of impurities by designing Ca-deficient composition, and the crystal phase is mainly pyrochlore phase. In summary, the application can be used for treating actinide and rare earth elements in high-level radioactive waste, and is a new solidification method. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 XRD pattern of the ceramic solidification body prepared for Example 1.
[0022] Figure 2 XRD pattern of the ceramic solidification body prepared for Example 2.
[0023] Figure 3 XRD pattern of the ceramic solidification body prepared for Example 3.
[0024] Figure 4 XRD pattern of the ceramic solidification body prepared for Example 4.
[0025] Figure 5 XRD pattern of the ceramic solidification body prepared for Example 5.
[0026] Figure 6 XRD pattern of the ceramic solidification body prepared for Example 6. DETAILED DESCRIPTION
[0027] Example 1
[0028] Step one, the raw materials CaCO3, TiO2 and CeO2 are weighed and mixed in a marquis mortar, and after a period of time, anhydrous ethanol is added for wet milling, so that the components are more uniformly mixed, and a mixture is obtained. The amount of each raw material is shown in Table 1.
[0029] Step two, after wet milling, the particles are further ground, and the powder is placed in a mold and pressed into a sheet under a pressure of 47 MPa.
[0030] Step three, the shaped sample is placed in a high-temperature furnace and sintered at 1200 ℃ for 24 hours.
[0031] Step four, after furnace cooling, take out, broken grinding, re-pressing tablet after continue in high temperature furnace 1200 ℃ again sintering, heat preservation time is 24 h. Again repeat grinding pressing tablet, repeat sintering at 1200 ℃ 4 times can, heat preservation time is 2 days, 1 day, 2 days, 5 days. Heating rate is 10 ℃ / min
[0032] Step five, after the last sintering, directly in high temperature, the sample is taken out and placed in air cooling, to keep its phase structure at high temperature.
[0033] Results: as shown in Figure 1 X-ray powder diffraction data show that the sample is pyrochlore structure.
[0034] Example 2
[0035] Step one, take the raw material CaCO3, TiO2, CeO2 weighing after grinding in agate mortar mixed, a period of time after adding anhydrous ethanol wet grinding, so that the composition is more uniform, get the mixture. The amount of each raw material is shown in Table 1;
[0036] Step two, continue to grind the particles after wet grinding, put the powder into the mold, under the pressure of 47 MPa, the sample is pressed into a tablet.
[0037] Step three, the sample after molding is put into a high temperature furnace at 1400 ℃ sintering, heat preservation 24 hours.
[0038] Step four, after furnace cooling, take out, broken grinding, re-pressing tablet after continue in high temperature furnace 1400 ℃ again sintering, heat preservation time is 24 h. Again repeat grinding pressing tablet, repeat sintering at 1400 ℃, heat preservation time is 5 days. Heating rate is 10 ℃ / min.
[0039] Step five, after the last sintering, directly in high temperature, the sample is taken out and placed in air cooling, to keep its phase structure at high temperature.
[0040] Results: as shown in Figure 2 X-ray powder diffraction data show that the sample is pyrochlore structure.
[0041] Example 3
[0042] Step one, take the raw material CaCO3, TiO2, CeO2 weighing after grinding in agate mortar mixed, a period of time after adding anhydrous ethanol wet grinding, so that the composition is more uniform, get the mixture. The amount of each raw material is shown in Table 1;
[0043] Step two, continue to grind the particles after wet grinding, put the powder into the mold, under the pressure of 47 MPa, the sample is pressed into a tablet.
[0044] Step three, the shaped sample is put into a high temperature furnace to sinter at 1500°C, and the holding time is 24 hours.
[0045] Step four, after cooling in the furnace, the sample is taken out, crushed and ground, re-pressed into tablets, and then sintered again at 1500°C in a high temperature furnace, with a holding time of 24 hours. The grinding and pressing are repeated again, and the sintering is repeated at 1500°C, with a holding time of 5 days. The heating rate is 10°C / min.
[0046] Step five, after the last sintering, the sample is directly taken out and placed in air to cool at high temperature, so as to maintain the phase structure at high temperature.
[0047] Results: As shown in Table 1, the X-ray powder diffraction data show that the sample is of pyrochlore structure. Figure 3
[0048] Example 4
[0049] Step one, the raw materials CaCO3, TiO2, and CeO2 are weighed and mixed in a marver mortar, and after a period of time, anhydrous ethanol is added for wet grinding, so that the components are mixed more uniformly, to obtain a mixture. The amount of each raw material is shown in Table 1.
[0050] Step two, after wet grinding, the particles are further ground, and the powder is put into a mold to press the sample into tablets under a pressure of 47 MPa.
[0051] Step three, the shaped sample is put into a high temperature furnace to sinter at 1400°C, and the holding time is 24 hours.
[0052] Step four, after cooling in the furnace, the sample is taken out, crushed and ground, re-pressed into tablets, and then sintered again at 1400°C in a high temperature furnace, with a holding time of 24 hours. The grinding and pressing are repeated again, and the sintering is repeated at 1400°C, with a holding time of 5 days. The heating rate is 10°C / min.
[0053] Step five, after the last sintering, the sample is directly taken out and placed in air to cool at high temperature, so as to maintain the phase structure at high temperature.
[0054] Results: As shown in Table 1, the X-ray powder diffraction data show that the sample is of pyrochlore structure. Figure 4
[0055] Example 5
[0056] Step one, the raw materials CaCO3, TiO2, and CeO2 are weighed and mixed in a marver mortar, and after a period of time, anhydrous ethanol is added for wet grinding, so that the components are mixed more uniformly, to obtain a mixture. The amount of each raw material is shown in Table 1.
[0057] Step two, after wet grinding, continue to grind the particles, put the powder into the mold, and press the sample into a sheet under a pressure of 47 MPa.
[0058] Step three, put the shaped sample into a high-temperature furnace to sinter at 1200°C for 24 hours.
[0059] Step four, after cooling in the furnace, take out, crush and grind, re-press into a sheet, and continue to sinter at 1200°C in a high-temperature furnace for 24 hours. Repeat grinding and pressing, and repeat sintering at 1200°C for 4 times, with holding times of 2 days, 1 day, 2 days, and 5 days, respectively. The heating rate is 10°C / min.
[0060] Step five, after the last sintering, directly take out the sample and place it in air to cool under high temperature, so as to maintain its phase structure at high temperature.
[0061] Results: As shown in Table 2, the X-ray powder diffraction data show that the sample is of pyrochlore structure. Figure 5
[0062] Example 6
[0063] Step one, weigh the raw materials CaCO3, TiO2, and CeO2, grind and mix them in an agate mortar, add anhydrous ethanol to wet grind after a period of time, so that the ingredients are mixed more uniformly, and obtain a mixture. The amount ratio of each raw material is shown in Table 1.
[0064] Step two, after wet grinding, continue to grind the particles, put the powder into the mold, and press the sample into a sheet under a pressure of 47 MPa.
[0065] Step three, put the shaped sample into a high-temperature furnace to sinter at 1300°C for 24 hours.
[0066] Step four, after cooling in the furnace, take out, crush and grind, re-press into a sheet, and continue to sinter at 1300°C in a high-temperature furnace for 24 hours. Repeat grinding and pressing, and repeat sintering at 1300°C for 5 days. The heating rate is 10°C / min.
[0067] Step five, after the last sintering, directly take out the sample and place it in air to cool under high temperature, so as to maintain its phase structure at high temperature.
[0068] Results: As shown in Table 2, the X-ray powder diffraction data show that the sample is of pyrochlore structure. Figure 6
[0069]
Claims
1. A method for producing a calcium-deficient pyrochlore ceramic solidified body, characterized by: The raw materials CaCO3, CeO2 and TiO2 are wet ground in anhydrous ethanol, uniformly mixed, and then pressed into a tablet, sintered at high temperature, crushed and ground, re-pressed into a tablet, and then sintered at high temperature again; the grinding, pressing and sintering are repeated for several times, and after the last sintering, the sample is taken out and cooled in air, thus obtaining the product; the pressing is performed at a pressure of 5-50 MPa, and the sintering temperature is 1000-1800°C.
2. The method of claim 1, wherein: The mass percentage of the raw materials CaCO3, CeO2 and TiO2 in the ceramic solidified body is 15-25wt%, 20-30wt% and 45-60wt%, respectively.
3. The method of claim 1, wherein The operation is performed according to the following steps: Step one, the raw materials CaCO3, TiO2 and CeO2 are weighed and then ground and mixed in an agate mortar, and then anhydrous ethanol is added for wet grinding, so that the components are mixed more uniformly, thus obtaining a mixture; Step two, after wet grinding, the particles are further ground, and the powder is put into a mold, and the sample is pressed into a tablet at a pressure of 5-50 MPa; Step three, the shaped sample is put into a high-temperature furnace and sintered at 1000-1800°C for 12-36 hours; Step four, after cooling in the furnace, the sample is taken out, crushed and ground, re-pressed into a tablet, and then sintered again at 1000-1800°C in a high-temperature furnace for 1-9 days; the grinding, pressing and sintering are repeated for 2-9 times; Step five, after the last sintering, the sample is directly taken out and cooled in air at high temperature, so as to maintain its phase structure at high temperature.
4. The method of claim 3, wherein In step two, the pressure is 47 MPa.
5. The method of claim 3, wherein In steps three and four, the heating rate is 10°C / min.
6. The method of claim 3, wherein In step four, after re-pressing, the sample is sintered again at 1200°C in a high-temperature furnace for 24 hours; the grinding, pressing and sintering are repeated for 4 times, and the sintering temperature is 1200°C, 1300°C, 1400°C and 1500°C, respectively, and the holding time is 2 days, 1 day, 2 days and 5 days, respectively.
7. The calcium-deficient pyrochlore ceramic solidified body obtained by the preparation method of any one of claims 1-6.
8. The use of the preparation method of any one of claims 1-6 in the field of treating high-level radioactive waste.