CN112831678B - Aluminum/aluminum fluoride composite ceramic neutron moderator and preparation method thereof - Google Patents
Aluminum/aluminum fluoride composite ceramic neutron moderator and preparation method thereof Download PDFInfo
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- CN112831678B CN112831678B CN202011601529.0A CN202011601529A CN112831678B CN 112831678 B CN112831678 B CN 112831678B CN 202011601529 A CN202011601529 A CN 202011601529A CN 112831678 B CN112831678 B CN 112831678B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
- C22C29/005—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides comprising a particular metallic binder
Abstract
The invention discloses an aluminum/aluminum fluoride composite ceramic neutron moderator and a preparation method thereof, wherein the preparation method comprises the following steps: mixing Al powder and AlF3Mixing the powder and the LiF powder according to a proportion, and filling inert gas for protection to obtain mixed powder; the mixed powder is filled into a rubber mold, and is pressed by isostatic pressing to obtain a green body, and the green body is processed to obtain a pressing block suitable for hot-pressing sintering, or the mixed powder is pressed into the pressing block on a press; hot pressing and sintering the pressed block to obtain Al/AlF3A sintered body; mixing Al/AlF3The sintered body is ground and cut, and then combined to form a neutron moderator.
Description
Technical Field
The invention belongs to the field of material preparation and processing, and particularly relates to an aluminum/aluminum fluoride composite ceramic neutron moderator and a preparation method thereof.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The Boron Neutron Capture Therapy (BNCT) technology is to selectively contain10Injecting the medicine B into human blood, enriching the medicine in tumor cells, irradiating the focus part with hyperthermia neutron beam,10b absorbs neutrons and emits high-energy, short-range alpha particles and7li ions, these particles can kill tumor cells while avoiding damage to normal tissue cells. In BNCT technology application, the required epithermal neutron energy is between 1eV and 10keV, and the neutron energy spectrum of a reactor is generally a mixed spectrum with various energies between 0MeV and 20MeV, so that a specially designed neutron moderating material is required to be adopted for filtering.
At present, aluminum/aluminum fluoride (Al/AlF)3) The composite material is the most common neutron moderating material in BNCT technology, and is compact and pore-free Al/AlF3Neutron slowThe sintering of the chemical material mainly adopts a hot-pressing sintering or hot isostatic pressing sintering process.
Existing neutron moderating materials are used to moderate high-speed neutrons, particularly fission neutrons, into epithermal neutrons. The material is an air-hole-free compact composite material containing 20-50 vol% of aluminum and 80-50 vol% of aluminum fluoride, and is prepared by a hot isostatic pressing process, and the prepared neutron moderating piece has the following typical dimensions: 700X 1000 mm. Hot isostatic pressing sintering is costly and, with current technology, hot isostatic pressing cannot produce large size ceramic materials. The neutron moderating body is assembled by small blocks.
Further, Al/AlF for neutron moderation3The composite material is prepared by mixing AlF3Weighing and mixing Al according to the mass ratio of 1: 1-9: 1, adding a sintering aid, performing ball milling, and screening; the powder is filled into a hot-pressing die for hot-pressing sintering to obtain Al/AlF3A composite material. The internal space of the hot-pressing die is 100mm multiplied by 100mm, and the height is 150 mm. Prepared Al/AlF3The density of the composite material is 2.6g/cm3The above.
According to the current plant technology, the dense aluminum fluoride-based neutron moderators with overall dimensions greater than 700 × 700 × 1000mm required for the production of BNCT technology are difficult to achieve, and the assembly of the moderators can only be achieved by splicing. However, the fewer the seams, the more beneficial the moderation and effect of neutrons.
Al/AlF hot-pressed sintering by taking Al powder and aluminum fluoride powder as raw materials3In the preparation process of the composite ceramic moderator, the following problems often exist: 1) the dry-method mixed Al powder has explosion risk; 2) when the hot-pressing sintering is carried out under vacuum or under the protection of inert gas, part of powder is easily pumped into a vacuum system in the vacuumizing process; 3) for a large block body with a larger sintering size, the phenomenon of uneven density of the sintered body is easy to occur; 4) the neutron moderation effect is affected by the presence of many seams due to the splicing of small blocks.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention aims to provide an aluminum/aluminum fluoride composite ceramic neutron moderator and a preparation method thereof.
In order to solve the technical problems, the technical scheme of the invention is as follows:
in a first aspect, the invention provides a method for preparing an aluminum/aluminum fluoride composite ceramic neutron moderator, which comprises the following steps:
mixing Al powder and AlF3Mixing the powder and the LiF powder according to a proportion, and filling inert gas for protection to obtain mixed powder;
the mixed powder is filled into a rubber mold, and is pressed by isostatic pressing to obtain a green body, and the green body is processed to obtain a pressing block suitable for hot-pressing sintering;
hot pressing and sintering the pressed block to obtain Al/AlF3A sintered body;
mixing Al/AlF3The sintered body is ground and cut, and then combined to form a neutron moderator.
In a second aspect, the invention provides an aluminum/aluminum fluoride composite ceramic neutron moderator prepared by the preparation method.
Compared with the prior art, the invention has the beneficial technical effects that:
the invention overcomes the defects of the prior art, and powder is mixed under the protection of inert gas, especially argon, so that the explosion risk is avoided; the problems that powder enters a vacuum system of a hot pressing furnace and the density of a sintered body is not uniform are solved by adopting an isostatic pressing green body; the Al/AlF with the diameter not less than 400mm, the height adjustable within 40-600mm, the relative density more than 96 percent and uniform density is prepared by a hot-pressing sintering process3And assembling the sintered body by mechanical processing means such as a sawing machine, a grinding machine, a processing center and the like to obtain the neutron moderating body which has a seamless central part and meets the technical requirement of BNCT.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a schematic structural view of a neutron moderator produced in example 1 of the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In a first aspect, the invention provides a method for preparing an aluminum/aluminum fluoride composite ceramic neutron moderator, which comprises the following steps:
mixing Al powder and AlF3Mixing the powder and the LiF powder according to a proportion, and filling inert gas for protection to obtain mixed powder;
the mixed powder is filled into a rubber mold, and is pressed by isostatic pressing to obtain a green body, and the green body is processed to obtain a pressing block suitable for hot-pressing sintering, or the mixed powder is pressed into the pressing block on a press;
hot pressing and sintering the pressed block to obtain Al/AlF3A sintered body;
mixing Al/AlF3The sintered body is ground and cut, and then combined to form a neutron moderator.
In some embodiments, the pressure of isostatic pressing is 80-160 MPa.
In some embodiments, Al powder, AlF3The mass ratio of the powder to the LiF powder is 30-35:64-69: 1.
Further, Al powder and AlF3Median particle diameter (d) of powders and LiF powders50) Are all less than 10 μm.
In some embodiments, during the hot-pressing sintering process, firstly, vacuum is pumped, protective gas is filled, and then, temperature rise and hot-pressing sintering are carried out.
Further, the protective gas is argon, nitrogen or hydrogen.
Furthermore, the temperature rise speed is 2-10 ℃/min.
Further, the temperature of the hot-pressing sintering after temperature rise is 600-670 ℃.
Furthermore, the hot-pressing pressure of the hot-pressing sintering is 25-35 MPa.
In a second aspect, the invention provides an aluminum/aluminum fluoride composite ceramic neutron moderator prepared by the preparation method.
Example 1
Al/AlF of the invention3The neutron moderating body has the characteristics of high density, few seams and high neutron moderating efficiency. The preparation method comprises the following steps:
the method comprises the following steps of: 28 parts of Al powder with the purity of more than 99.9 percent and 70 parts of AlF with the purity of more than 99.99 percent3Putting the powder and 2 parts of LiF powder with the purity of more than 99.99 percent into a mixer, filling argon for protection, and mixing for 20-60min to obtain a mixture, wherein the medium particle diameters (d) of the three kinds of powder50) Are all less than 10 μm.
The green compact is prepared: and (3) putting the mixture into a rubber mold, performing isostatic pressing under the isostatic pressure of 120MPa, and processing the blank to obtain a block suitable for hot-pressing sintering.
Performing hot-pressing sintering: and (3) putting the pressed block into a C/C mould of the graphite lining, and carrying out hot-pressing sintering in a hot-pressing furnace. And in the hot-pressing sintering process, vacuumizing, heating to 630 ℃ at the heating rate of 5 ℃/min, preserving heat for 1h, and keeping the hot-pressing pressure at 30 MPa. Then naturally cooling to obtain Al/AlF3And (3) sintering the body.
Step four, processing: the Al/AlF is processed by adopting the existing general processing equipment and means3The sintered body is subjected to processing such as grinding and cutting to obtain a composite member, and the composite member is combined to form a neutron moderator.
Al/AlF from this example3The sintered body had a diameter of 400mm, a height of 500mm, a relative density of 97%, a compressive strength of 200MPa and a Hardness (HRB) of 62.
Example 2
Al/AlF of the invention3The neutron moderating body has the characteristics of high density, few seams and high neutron moderating efficiency. The preparation method comprises the following steps:
the method comprises the following steps of: 25 parts of Al powder with the purity of more than 99.9 percent and 74 parts of AlF with the purity of more than 99.99 percent3Putting the powder and 1 part of LiF powder with the purity of more than 99.99 percent into a mixer, filling argon for protection, and mixing for 30min to obtain a mixture, wherein the medium particle diameters (d) of the three kinds of powder are50) Are all less than 10 μm.
The green compact is prepared: and (3) putting the mixture into a rubber mold, performing isostatic pressing with the isostatic pressure of 100MPa, and processing the blank to obtain a block suitable for hot-pressing sintering.
Performing hot-pressing sintering: and (3) loading the blank into a C/C mold of the graphite bushing, and carrying out hot-pressing sintering in a hot-pressing furnace. In the hot-pressing sintering process, firstly, vacuum pumping is carried out, then argon is filled, the temperature is heated to 650 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 1h, and the hot-pressing pressure is 30 MPa. Subsequently, it is naturally cooled.
Step four, processing: the Al/AlF is processed by adopting the existing general processing equipment and means3The sintered body is subjected to processing such as grinding and cutting to obtain a composite member, and the composite member is combined to form a neutron moderator.
Al/AlF from this example3The sintered body had a size of 300X 100mm, a relative density of 98%, a compressive strength of 240MPa and a Hardness (HRB) of 65.
Example 3
Al/AlF of the invention3The neutron moderating body has the characteristics of high density, few seams and high neutron moderating efficiency. The preparation method comprises the following steps:
the method comprises the following steps of: 35 parts of Al powder with the purity of more than 99.9 percent and 64 parts of AlF with the purity of more than 99.99 percent3Putting the powder and 1 part of LiF powder with the purity of more than 99.99 percent into a mixer, filling argon for protection, and mixing for 30min to obtain a mixture, wherein the medium particle diameters (d) of the three kinds of powder are50) Are all less than 10 μm.
The green compact is prepared: and (3) putting the mixture into a rubber mold, performing isostatic pressing under the isostatic pressure of 120MPa, and processing the blank to obtain a block suitable for hot-pressing sintering.
Performing hot-pressing sintering: and (3) putting the pressed block into a C/C mould of the graphite lining, and carrying out hot-pressing sintering in a hot-pressing furnace. In the hot-pressing sintering process, firstly, vacuumizing is carried out, argon, nitrogen or hydrogen is filled, the temperature is heated to 630 ℃ at the heating rate of 8 ℃/min, the temperature is kept for 1h, and the hot-pressing pressure is 30 MPa. Subsequently, it is naturally cooled.
Step four, processing: the Al/AlF is processed by adopting the existing general processing equipment and means3The sintered body is subjected to processing such as grinding and cutting to obtain a composite member, and the composite member is combined to form a neutron moderator.
Al/AlF from this example3The sintered body had a diameter of 420mm, a height of 100mm, a relative density of 99%, a compressive strength of 260MPa and a Hardness (HRB) of 66.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (5)
1. A preparation method of an aluminum/aluminum fluoride composite ceramic neutron moderator is characterized by comprising the following steps: the method comprises the following steps:
(1) mixing Al powder and AlF3Mixing the powder and the LiF powder according to a proportion, and filling inert gas for protection to obtain mixed powder; the Al powder and AlF3The mass ratio of the powder to the LiF powder is 25-35:65-75: 1;
(2) the mixed powder is filled into a rubber mold, and is pressed by isostatic pressing to obtain a green body, and the green body is processed to obtain a pressing block suitable for hot-pressing sintering;
(3) hot pressing and sintering the pressed block to obtain Al/AlF3A sintered body; the hot-pressing sintering is vacuum hot-pressing sintering or protective gas hot-pressing sintering, and the method comprises the following specific steps of: firstly, vacuumizing, or filling protective gas after vacuumizing, then heating, and carrying out hot-pressing sintering; the temperature rising speed is 2-10 ℃/min, the temperature of hot-pressing sintering after temperature rising is 630-670 ℃, and the hot-pressing pressure is 25-35 MPa;
(4) mixing Al/AlF3Grinding and cutting the sintered body, and combining the sintered body into a neutron moderator;
the Al/AlF3The diameter of the sintered body is not less than 400mm, and the height is in the range of 40-600 mm.
2. The method of preparing an aluminum/aluminum fluoride composite ceramic neutron moderator of claim 1, wherein: al powder and AlF3The medium particle size of the powder and the LiF powder is less than 10 mu m.
3. The method of preparing an aluminum/aluminum fluoride composite ceramic neutron moderator of claim 1, wherein: the protective gas is argon, nitrogen or hydrogen.
4. The method of preparing an aluminum/aluminum fluoride composite ceramic neutron moderator of claim 1, wherein: the temperature rising speed is 5-8 ℃/min.
5. The aluminum/aluminum fluoride composite ceramic neutron moderator prepared by the preparation method of any one of claims 1 to 4.
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| CN115872746A (en) * | 2023-01-03 | 2023-03-31 | 中国原子能科学研究院 | Magnesium fluoride composite ceramic and preparation method thereof |
| CN116375473A (en) * | 2023-03-30 | 2023-07-04 | 山东亚赛陶瓷科技有限公司 | Magnesium fluoride-based composite neutron moderating material and preparation method thereof |
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| FI92890C (en) * | 1993-06-14 | 1995-01-10 | Otatech Oy | Moderator material for neutrons and their use |
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| CN105957576B (en) * | 2016-04-27 | 2017-10-20 | 华南协同创新研究院 | A kind of moderation of neutrons Al/AlF3Composite and preparation method thereof |
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