Preparation method of Yb2O3 ceramic core
By adding sintering aids such as calcium oxide or silicon dioxide to Yb2O3 powder, high-density Yb2O3 ceramic core blocks were prepared, solving the problems of melting risk and insufficient density of metal ytterbium core blocks, and realizing efficient preparation of lutetium-177.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA INSTITUTE OF ATOMIC ENERGY
- Filing Date
- 2024-02-28
- Publication Date
- 2026-06-05
AI Technical Summary
Ytterbium metal pellets are prone to melting during reactor irradiation, and existing technologies make it difficult to prepare high-density Yb2O3 ceramic pellets to meet the preparation requirements of lutetium-177.
Yb2O3 powder is mixed with sintering aids such as calcium oxide or silicon dioxide, pressed into shape, and sintered at a preset sintering temperature to form a dense Yb2O3 ceramic core, thereby reducing the sintering temperature and increasing the density.
Yb2O3 ceramic cores with a density of 90%–96% were prepared to meet the reactor irradiation requirements, avoid the risk of melting, and increase the yield of lutetium-177.
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Figure CN118084490B_ABST
Abstract
Description
Technical Field
[0001] The embodiments of this application relate to ceramic molded articles based on rare earth compounds, specifically to a method for preparing Yb2O3 ceramic core blocks. Background Technology
[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.
[0003] Lutetium-177 can be used in medical imaging and targeted therapy for small tumors, and has high research value in the field of nuclear medicine internal radiation therapy. Lutetium-177 can be prepared by irradiating ytterbium-containing pellets in a reactor. However, due to the low melting point of metallic ytterbium, there is a risk of melting during reactor irradiation; therefore, other ytterbium-containing materials are needed as raw materials to manufacture irradiation pellets. Summary of the Invention
[0004] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.
[0005] The embodiments of this application provide a method for preparing Yb2O3 ceramic core blocks. The preparation method includes the following steps: mixing a sintering aid or sintering aid raw material with Yb2O3 powder to form a mixture; pressing the mixture into shape, and then sintering it at a preset sintering temperature to form a ceramic core block; wherein the sintering aid includes at least one of calcium oxide or silicon dioxide, and the sintering aid raw material can generate the sintering aid at the preset sintering temperature.
[0006] Tests show that the preparation method provided in the embodiments of this application can produce Yb2O3 ceramic core blocks with high density. Attached Figure Description
[0007] Other objects and advantages of this application will become apparent from the following description of embodiments of this application with reference to the accompanying drawings, and will help to provide a comprehensive understanding of this application.
[0008] Figure 1 This is a schematic flowchart of the preparation method provided in the embodiments of this application.
[0009] Figure 2 This is a photograph of a Yb2O3 ceramic core block prepared according to the preparation method provided in the embodiments of this application.
[0010] Explanation of reference numerals in the attached figures:
[0011] 10. Yb2O3 ceramic core block.
[0012] It should be noted that the accompanying drawings are not necessarily drawn to scale, but are shown only in a schematic manner without affecting the reader's understanding. Detailed Implementation
[0013] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.
[0014] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.
[0015] As mentioned earlier, due to the low melting point of ytterbium, ytterbium pellets pose a risk of melting during reactor irradiation. This invention reveals that Yb₂O₃ has a melting point of 2372°C, eliminating the risk of melting during reactor irradiation, and can be used to manufacture irradiation pellets.
[0016] In the process of preparing lutetium-177 by reactor irradiation, in order to effectively utilize the reactor's neutron flux and increase the yield of lutetium-177, it is necessary to sinter Yb₂O₃ into a dense ceramic core. The inventors of this application have discovered that, due to the high melting point of Yb₂O₃, the sintering temperature for preparing dense Yb₂O₃ ceramic cores typically needs to be above 1800℃ to achieve a density greater than 90% of the theoretical density. If the sintering temperature is too low, the resulting Yb₂O₃ ceramic core will have a lower density, which is insufficient for the preparation of lutetium-177.
[0017] To address the aforementioned technical problems, embodiments of this application provide a method for preparing Yb₂O₃ ceramic core blocks, such as... Figure 1The diagram illustrates a flow chart of a preparation method provided in an embodiment of this application. This preparation method may include the following steps: S1: mixing a sintering aid or sintering aid raw material with Yb₂O₃ powder to form a mixture; S2: pressing the mixture into shape, and then sintering it at a preset sintering temperature to form a ceramic core. The sintering aid includes at least one of calcium oxide or silicon dioxide, and the sintering aid raw material is capable of generating the sintering aid at the preset sintering temperature.
[0018] Tests show that sintering Yb₂O₃ powder alone at temperatures above 1700℃ yields Yb₂O₃ ceramic cores with a density of 6.2 g / cm³. 3 The density is approximately 67% TD of the theoretical density; the density of the Yb2O3 ceramic core obtained according to the preparation method provided in the embodiments of this application is 8.3–8.8 g / cm³. 3 The relative density can reach 90% to 96% TD. Compared with ceramic cores obtained by sintering Yb2O3 powder alone, the Yb2O3 ceramic cores obtained by the preparation method provided in the embodiments of this application have a higher density.
[0019] like Figure 2 As shown, it illustrates a schematic diagram of a Yb2O3 ceramic core block prepared according to the preparation method provided in the embodiments of this application. Figure 2 As can be seen, the Yb2O3 ceramic core 10 prepared according to the preparation method provided in the embodiments of this application is white and ceramic in shape with good density.
[0020] In some embodiments, the preset sintering temperature in step S2 can be 1500-1600℃. As mentioned above, when sintering Yb2O3 powder alone, the sintering temperature needs to reach above 1700℃, and the resulting Yb2O3 ceramic core has a relatively low density. However, in the embodiments of this application, by adding a sintering aid including at least one of calcium oxide or silicon dioxide, not only can the density of the sintered Yb2O3 ceramic core be significantly increased, but the sintering temperature of the Yb2O3 ceramic can also be reduced.
[0021] It is easy to understand that there are many types of sintering aids, and selecting a suitable substance from these is very important for this application. First, some substances need to be pre-selected based on theory. Specifically, based on melting point and phase diagram, substances that can form a low-temperature (relative) eutectic with ytterbium oxide, or substances with low melting points that can play a role in liquid-phase sintering during ytterbium oxide sintering, are selected. Then, these substances are tested to further screen suitable sintering aids.
[0022] The inventors of this application discovered that when sintering Yb₂O₃ ceramic cores using other types of sintering aids, the density of the sintered Yb₂O₃ ceramic cores did not change significantly compared to those without sintering aids when the sintering temperature was below 1700°C. However, when the sintering temperature was above 1700°C, the excessively high sintering temperature caused the sintered Yb₂O₃ ceramic cores to exhibit a translucent glassy state rather than ceramic. Furthermore, since the Yb₂O₃ ceramic cores are used for irradiation within a reactor, the sintering aid must not adversely affect the reactor or the irradiated products. For example, some substances have a large neutron absorption cross-section, which would reduce the reactor's reactivity; others, after reactor irradiation, would generate long-lived or highly radioactive isotopes, which are unsuitable as sintering aids. Therefore, the sintering aids selected in the embodiments of this application, including at least one of calcium oxide or silicon dioxide, are not easily conceived or obtainable through a limited number of experiments.
[0023] In some embodiments, when the sintering aid includes calcium oxide, the raw material for the sintering aid may include substances that can generate calcium oxide during the sintering process. Examples of raw materials for the sintering aid include calcium oxalate, calcium carbonate, calcium nitrate, and calcium hydroxide.
[0024] In some embodiments, the sintering aid may be a mixture of magnesium oxide and silicon dioxide. A mixture of magnesium oxide and silicon dioxide is advantageous for achieving a lower sintering temperature.
[0025] In embodiments where the combustion aid includes magnesium oxide, the combustion aid raw material may include substances that can generate magnesium oxide during sintering, such as magnesium oxalate, magnesium carbonate, magnesium nitrate, magnesium hydroxide, etc.
[0026] In some embodiments, when the sintering aid is a mixture of magnesium oxide and silicon dioxide, the mass percentage of magnesium oxide in the sintering aid can be less than the mass percentage of silicon dioxide to facilitate increasing the density of the Yb₂O₃ ceramic core. Preferably, the mass percentage of silicon dioxide can be twice the mass percentage of magnesium oxide.
[0027] In some embodiments, the sintering aid may also be a mixture of calcium oxide and aluminum oxide. Calcium oxide and aluminum oxide have a low eutectic point, which is beneficial for reducing the sintering temperature of the Yb2O3 ceramic core.
[0028] In some embodiments, when the sintering aid includes aluminum oxide, the raw material for the sintering aid may include substances that can generate aluminum oxide during the sintering process. For example, the raw material for the sintering aid may be aluminum hydroxide.
[0029] In some embodiments, when the sintering aid is a mixture of calcium oxide and aluminum oxide, the mass percentage of calcium oxide in the sintering aid can be substantially equal to the mass percentage of aluminum oxide, in order to improve the density of the Yb2O3 ceramic core.
[0030] In some embodiments, calcium oxide alone, silicon dioxide alone, or a mixture of calcium oxide and silicon dioxide can be selected as the sintering aid. When the sintering aid is a mixture of calcium oxide and silicon dioxide, the mass percentage of calcium oxide in the sintering aid can be less than the mass percentage of silicon dioxide to facilitate increasing the density of the Yb₂O₃ ceramic core. Preferably, the mass percentage of silicon dioxide can be twice the mass percentage of calcium oxide.
[0031] In some embodiments, in step S1, the mass percentage of the sintering aid in the mixture can be 0.1%-1%. It is easy to understand that when the type of added sintering aid is a sintering aid raw material, the amount of the added sintering aid raw material is converted into the amount of the corresponding sintering aid generated.
[0032] In some embodiments, the step of mixing the sintering aid or sintering aid raw material with Yb2O3 powder to form a mixture in step S1 may include the following: mixing the sintering aid or sintering aid raw material with Yb2O3 powder, followed by ball milling to form a mixture.
[0033] Ball milling allows for a more uniform mixing of the sintering aid or sintering aid raw material with the Yb2O3 powder.
[0034] In some embodiments, the sintering aid or sintering aid raw material and Yb2O3 powder can be placed in a ball mill and ball-milled for 4 to 12 hours.
[0035] In some embodiments, step S2, prior to pressing the mixture, may further include: adding a binder to the mixture and pressing the mixture with the binder added. The binder can bond the powder particles in the mixture together, which facilitates better pressing.
[0036] In some embodiments, in step S2, the binder added to the mixture can be an aqueous PVA solution or stearic acid. The aqueous PVA solution can be a 2%-5% aqueous PVA solution, preferably a 2.5% aqueous PVA solution.
[0037] In some embodiments, when the binder is a PVA aqueous solution, after adding the binder, the binder can be stirred with a mixture formed by mixing the sintering aid or sintering aid raw material with Yb2O3 powder to ensure uniform mixing of the sintering aid or sintering aid raw material, Yb2O3 powder, and binder. The uniformly mixed material is then placed in a dryer for drying at a preset drying temperature for a preset time. Afterward, the dried material can be removed, crushed, and sieved to obtain material for pressing and molding. The preset drying temperature can be 30-70℃, preferably 50℃. The drying time can be 2-8 hours, preferably 4 hours. The sieve mesh size can be 60-120 mesh, preferably 100 mesh. This treatment is beneficial for increasing the density of the Yb2O3 ceramic core.
[0038] In some embodiments, when the adhesive is stearic acid, the mass percentage of stearic acid added can be 0.1%-1%, preferably 0.5% by mass.
[0039] In some embodiments, when the binder is stearic acid, after adding stearic acid to the mixture, the mixture can be placed in a ball mill for ball milling. Then, the uniformly mixed powder after ball milling can be pressed into a cake shape under a certain pressure. The pressed cake is then crushed and sieved to obtain the material for pressing and molding. The ball milling time can be 2-10 hours, for example, 6 hours. The pressing pressure can be 30-100 MPa, for example, 50 MPa. The sieve mesh size can be 60-120 mesh, preferably 100 mesh. This treatment is more conducive to improving the density of the Yb₂O₃ ceramic core.
[0040] In some embodiments, in step S2, the material obtained after crushing and sieving can be loaded into a mold and pressed into a blank under a pressure of 100-400 MPa for a period of time. The pressing time can be 5-20 seconds, preferably 10 seconds.
[0041] In the pressing and molding process of ceramic materials before sintering, the holding time is typically several minutes. The inventors of this application have discovered that, due to the small size of the Yb₂O₃ ceramic core used for irradiation, [see...]. Figure 2The core block is cylindrical, with a diameter of less than 1.5 cm and a thickness of less than 1 cm. When pressing such small blanks, holding the pressure for several minutes can easily lead to uneven volume expansion after sintering. Since multiple Yb₂O₃ ceramic core blocks need to be stacked axially within the target during the fabrication of the irradiation target, the dimensional uniformity of the Yb₂O₃ ceramic core blocks is crucial. The inventors of this application have discovered that shortening the holding time to 5-20 seconds results in better dimensional uniformity of the Yb₂O₃ ceramic core blocks formed after sintering from the demolded blank. Figure 2 As shown.
[0042] In some embodiments, after pressing, the blank can be sintered at a preset sintering temperature for a predetermined time, and then naturally cooled in the furnace to obtain Yb2O3 ceramic core blocks. The sintering process can be carried out in an air atmosphere muffle furnace. The sintering time can be 2-8 hours, for example, 4 hours.
[0043] The preparation method of Yb2O3 ceramic core provided in this application is described in detail below with reference to specific embodiments.
[0044] Example 1
[0045] The sintering aid is calcium oxide, accounting for 0.5% of the mass percentage of the mixture of sintering aid and Yb2O3 powder. The sintering aid is added to the Yb2O3 powder and ball-milled for 4 hours. The binder is a 2.5% PVA aqueous solution, and the binder is added to the mixture at a ratio of 17 ml of binder per 100 g of mixture. The mixture is then dried at 50°C for 4 hours. The dried material is crushed and sieved through a 100-mesh sieve. The sieved material is then placed into a mold for pressing at a pressure of 200 MPa for 10 seconds. The pressed blank is then sintered at 1500°C for 4 hours and allowed to cool naturally in the furnace to obtain Yb2O3 ceramic core blocks.
[0046] The average density of the Yb₂O₃ ceramic core measured at room temperature was 8.54 g / cm³. 3 Its relative density is approximately 92.6%.
[0047] Example 2
[0048] The sintering aids were magnesium oxide and silicon dioxide, accounting for 0.25% and 0.5% of the mass percentage of the sintering aid and Yb2O3 powder mixture, respectively. The sintering aid was added to the Yb2O3 powder and ball-milled for 4 hours. The binder was stearic acid, which was added to the mixture at a mass percentage of 0.5% and ball-milled for 6 hours. The ball-milled powder was then pressed into cakes at a pressure of 50 MPa. The pressed material was crushed and sieved through a 100-mesh sieve. The sieved material was then placed into a mold and pressed at a pressure of 250 MPa for 10 seconds. The pressed blanks were then sintered at 1600℃ for 6 hours and allowed to cool naturally in the furnace to obtain Yb2O3 ceramic core blocks.
[0049] The average density of the Yb₂O₃ ceramic core measured at room temperature was 8.69 g / cm³. 3 Its relative density is approximately 94.2%.
[0050] Example 3
[0051] The sintering aids were calcium oxide and silicon dioxide, accounting for 0.25% and 0.5% of the mass percentage of the sintering aid and Yb2O3 powder mixture, respectively. The sintering aids were added to the Yb2O3 powder and ball-milled for 6 hours. The binder was a 2.5% PVA aqueous solution, and the binder and mixture were mixed evenly at a ratio of 17 ml binder per 100 g of mixture. The mixture was then dried at 50°C for 4 hours. After drying, the material was crushed and passed through a 100-mesh sieve. The sieved material was then placed into a mold and pressed under a pressure of 300 MPa for 10 seconds. The pressed blank was then sintered at 1600°C for 4 hours and allowed to cool naturally in the furnace to obtain Yb2O3 ceramic core blocks.
[0052] The average density of the Yb₂O₃ ceramic core measured at room temperature was 8.72 g / cm³. 3 Its relative density is approximately 94.6%.
[0053] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.
[0054] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.
Claims
1. A method for preparing a Yb₂O₃ ceramic core, comprising: A mixture is formed by mixing sintering aid or sintering aid raw material with Yb2O3 powder; The mixture is pressed into shape and then sintered at a preset sintering temperature to form the ceramic core block; The sintering aid raw material can generate the sintering aid at the preset sintering temperature; The sintering aid is a mixture of magnesium oxide and silicon dioxide, wherein the mass percentage of magnesium oxide in the sintering aid is less than the mass percentage of silicon dioxide; or, the sintering aid is a mixture of calcium oxide and aluminum oxide, wherein the mass percentage of calcium oxide in the sintering aid is equal to the mass percentage of aluminum oxide; or the sintering aid is a mixture of calcium oxide and silicon dioxide, wherein the mass percentage of calcium oxide in the sintering aid is less than the mass percentage of silicon dioxide. The combustion aid accounts for 0.1%-1% of the mass percentage of the mixture; The preset sintering temperature is 1500-1600℃, and the sintering time is 2-8 hours.
2. The preparation method according to claim 1, wherein, The steps of mixing a sintering aid or sintering aid raw material with Yb2O3 powder to form a mixture include: The sintering aid or sintering aid raw material is mixed with Yb2O3 powder, and then ball-milled to form the mixture.
3. The preparation method according to claim 1, wherein, Before pressing the mixture into shape, the process also includes: A binder is added to the mixture, and the mixture with the binder is pressed into shape.
4. The preparation method according to claim 3, wherein, The adhesive is an aqueous solution of PVA or stearic acid.