TWI804800B - Neutron moderator material and method for producing the same - Google Patents

Abstract

The present invention relates to a neutron moderator material and a method for producing the same. Metal fluoride powders, lithium fluoride powders and aluminum metal powders are utilized to fabricate the neutron moderator material, and a composite powder is formed by multiple stages of dry mixing processes. Next, the composite powder is subjected to a hot pressing process to form the neutron moderator material. The neutron moderator material has fine and uniform structures and high relative density, therefore being applied in a boron neutron capture therapy device.

Description

Neutron moderating material and manufacturing method thereof

The invention relates to a composite material, in particular to a neutron moderator material and a manufacturing method thereof.

Targeted radiation therapy is a commonly used method for cancer treatment, and targeted radiation therapy is mainly carried out by using the mechanism of Boron Neutron Capture Therapy (BNCT). The principle of BNCT is to first inject boron-containing drugs that are pro-cancer cells into the body of cancer patients, so as to combine with cancer cells through blood circulation. When the concentration of boron-containing drugs is high enough to gather at the cancer cell site, a thermal neutron beam with appropriate energy is emitted from the atomic furnace or accelerator-type neutron beam source generator and irradiated on the tumor site. Since thermal neutrons will react with boron-containing drugs, they will be split into radioactive particles with high biological destructive ability, thus destroying the DNA structure of cancer cells. Since the range of these radiation particles does not exceed the diameter range of a single cancer cell, the damage of radiation particles to normal cells can be minimized when destroying the DNA structure of cancer cells. According to this, normal cell tissues near the cancer cells can be protected.

The neutron energy suitable for BNCT is 1eV to 10keV, so the high-energy neutron rays generated by the neutron beam source generator can pass through moderator materials to decelerate and reduce its energy. Generally, metal fluoride-aluminum-lithium fluoride composite materials are used as thermal neutron moderator materials, in which the content of metal aluminum is 20 volume percent to 50 volume percent, the content of lithium fluoride is less than 2 volume percent, and the others are metal fluorides . A prior art proposes a BNCT thermal neutron moderator material, the composition of which is aluminum fluoride-aluminum-lithium fluoride, and the content of lithium fluoride is 1 volume percent. The prior art uses a hot isostatic pressing process (Hot Isostatic Pressing; HIP) to make the composite material. However, this prior art does not clearly disclose how to uniformly disperse the lithium fluoride ceramic powder with a very small content in the composite material, and it does not clearly disclose how to use a heat isostatic pressing process to manufacture neutron moderator materials. In addition, the hot equalization process generally needs to fill the powder into a metal container first, and then perform vacuum canning. Then, the sealed metal container is put into the heat equalization equipment, and the gas is used as the pressure medium to pressurize the metal container isotropically, thereby completing the molding and densification of the composite material. Since the heat isostatic pressing process is affected by the binding force of the metal container, its material yield is generally only 65% to 80%, so it has a relatively high manufacturing cost.

In view of this, there is an urgent need to provide a neutron moderating material and a manufacturing method thereof, so as to improve the defect of low yield of the conventional neutron moderating material manufacturing method.

Therefore, one aspect of the present invention is to provide a kind of neutron moderation material The production method of the present invention uses a multi-stage dry powder mixing process to mix powder materials, and densifies the composite powder with a hot pressing process, so that a uniform and dense neutron moderator material can be obtained.

Another aspect of the present invention is to provide a neutron moderator material, which is produced by the aforementioned production method.

According to an aspect of the present invention, a method for manufacturing a neutron moderator material is proposed. In this manufacturing method, metal fluoride powder, lithium fluoride powder and metal aluminum powder are firstly provided. However, the metal fluoride powder does not contain lithium fluoride. Based on 100 volume percent of the neutron moderator material, the amount of metal aluminum powder used is 20 volume percent to 50 volume percent, the amount of lithium fluoride powder used is 0.5 volume percent to 2 volume percent, and the balance is metal fluoride powder . Then, a first dry powder mixing process is performed on the lithium fluoride powder and a part of the metal aluminum powder to form the metal aluminum-lithium fluoride composite powder. Next, the metal fluoride powder, the remaining metal aluminum powder and the aforementioned metal aluminum-lithium fluoride composite powder are subjected to a second dry powder mixing process to form a metal fluoride-metal aluminum-lithium fluoride composite powder . After that, the metal fluoride-metal aluminum-lithium fluoride composite powder is subjected to a hot pressing process to form a neutron moderator material.

According to some embodiments of the present invention, the aforementioned metal fluoride powder includes magnesium fluoride, aluminum fluoride and/or calcium fluoride.

According to some embodiments of the present invention, the average particle diameter of the aforementioned lithium fluoride powder is 1 μm to 3 μm.

According to some embodiments of the present invention, the average particle diameter of the aforementioned aluminum metal powder is 5 μm to 15 μm.

According to some embodiments of the present invention, the aforementioned metal fluoride powder, The purity of lithium fluoride powder and metal aluminum powder is greater than 99%.

According to some embodiments of the present invention, when performing the aforementioned first dry powder mixing process, the volume ratio of the lithium fluoride powder to a part of the metal aluminum powder is 0.05 to 0.1.

According to some embodiments of the present invention, the mixing time of the first dry powder mixing process is 0.5 hour to 1 hour, and the mixing time of the second dry powder mixing process is 0.5 hour to 1 hour.

According to some embodiments of the present invention, the temperature of the aforementioned hot pressing process is 550° C. to 620° C., and the pressure of the hot pressing process is 5 MPa to 55 MPa.

According to some embodiments of the present invention, the aforementioned hot pressing process lasts from 1 hour to 6 hours.

According to another aspect of the present invention, a neutron moderating material is proposed, which is manufactured by the aforementioned manufacturing method. Among them, the relative density of the neutron moderating material is not less than 99.5%, and the particle size of the largest particle in the neutron moderating material is not greater than 500 μm.

The application of the neutron moderator material and its production method of the present invention is to mix metal fluoride powder, lithium fluoride powder and metal aluminum powder in multiple stages, so that the lithium fluoride powder is evenly embedded in the metal aluminum powder The surface of the body can be made into a composite powder with a uniform structure. Secondly, through the densification of the hot pressing process, the formed neutron moderator material can have a dense structure, which can meet the application requirements of neutron capture equipment. In addition, the present invention mixes powder materials through a dry powder mixing process, so there is no need to use mixing carriers such as organic solvents, so it can reduce the production cost of materials and meet the requirements of environmental protection and waste reduction.

100: method

110, 120, 130, 140, 150: operation

In order to have a more complete understanding of the embodiments of the present invention and their advantages, please refer to the following descriptions together with the corresponding drawings. It must be emphasized that the various features are not drawn to scale and are for illustration purposes only. The contents of the related drawings are explained as follows.

FIG. 1 is a schematic flow chart illustrating a method for manufacturing a neutron moderating material according to some embodiments of the present invention.

FIG. 2A and FIG. 2B respectively show the electron micrographs of the neutron moderating material of Example 1 and Example 2 of the present invention.

The making and using of embodiments of the invention are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are illustrative only and do not limit the scope of the invention.

Please refer to FIG. 1 , which is a schematic flowchart illustrating a method for manufacturing neutron moderating materials according to some embodiments of the present invention. In the method 100, metal fluoride powder, lithium fluoride powder and metal aluminum powder are provided first, and a first dry powder mixing process is performed on the lithium fluoride powder and part of the metal aluminum powder to obtain metal Aluminum-lithium fluoride composite powder, as shown in operation 110 and operation 120 . The metal fluoride powder does not contain lithium fluoride. In some embodiments, the metal fluoride powder may include magnesium fluoride, aluminum fluoride, calcium fluoride, other suitable metal fluorides, or any mixture of the foregoing materials. in other implementations In the example, in order to improve the properties of the prepared neutron moderator material, the purity of the metal fluoride powder, lithium fluoride powder and metal aluminum powder are all greater than 99%.

Based on 100 volume percent of the neutron moderator material obtained later, the amount of metal aluminum powder can be 20 volume percent to 50 volume percent, the amount of lithium fluoride powder can be 0.5 volume percent to 2 volume percent, and the remaining amount It is metal fluoride powder. When the amount of the metal aluminum powder, lithium fluoride powder and metal fluoride powder is not within the aforementioned range, the subsequent composite material cannot meet the application requirements of neutron moderator materials.

When performing the first dry powder mixing process, the lithium fluoride powder and part of the metal aluminum powder can be mixed using technical means or equipment commonly used in the technical field of the present invention, so no further details are given here. Among them, since the hardness of lithium fluoride powder is higher than that of metal aluminum powder, the ceramic powder of lithium fluoride is embedded in the metal aluminum-lithium fluoride composite powder formed in the first dry powder mixing process. Buried on the surface of metal aluminum powder. In some embodiments, in order to improve the mixing and embedding effect of the first dry powder mixing process, the average particle size of the metal aluminum powder is preferably larger than the average particle size of the lithium fluoride powder. In some specific examples, the average particle size of the lithium fluoride powder may be 1 μm to 3 μm, and the average particle size of the aluminum metal powder may be 5 μm to 15 μm. When the average particle size of lithium fluoride and/or metal aluminum powder is within the aforementioned range, lithium fluoride powder can be more evenly embedded on the surface of metal aluminum powder, which helps to increase the neutrons produced. The nature of the moderating material.

When performing the first dry powder mixing process, the volume ratio of the lithium fluoride powder to a part of the metal aluminum powder can be 0.05 to 0.1. When the volume ratio of lithium fluoride powder to metal aluminum powder is within the aforementioned range, the lithium fluoride powder can be more Evenly embedded on the surface of the metal aluminum powder, it helps to improve the properties of the obtained neutron moderator material. Secondly, in order to improve the mixing uniformity of the lithium fluoride powder and the metal aluminum powder, the mixing time of the first dry powder mixing process can be 0.5 hour to 1 hour.

After operation 120, the formed metal aluminum-lithium fluoride composite powder, the metal fluoride powder and the remaining metal aluminum powder are added to the powder mixing equipment to perform the second dry powder mixing process, and A metal fluoride-metal aluminum-lithium fluoride composite powder may be formed, as shown in operation 130 . In some embodiments, operation 120 and operation 130 can be performed in the same powder mixing equipment, so after performing operation 120, the metal fluoride powder and the remaining metal aluminum powder can be directly added to the powder mixing equipment. However, the present invention is not limited thereto. In other embodiments, operation 120 and operation 130 can also be performed in different powder mixing equipment. Similarly, the second dry powder mixing process can be mixed using technical means or equipment commonly used in the technical field of the present invention, so details will not be described here. In some embodiments, the mixing time of the second dry powder mixing process may range from 0.5 hour to 1 hour.

The aforementioned first dry powder mixing process and the second dry powder mixing process do not add additional organic solvents or other carriers with similar effects, so the first dry powder mixing process and the second dry powder mixing process of the present invention can reduce The use of solvents meets the requirements of environmental protection and waste reduction.

After performing operation 130 , the formed metal fluoride-metal aluminum-lithium fluoride composite powder is subjected to a hot pressing process to obtain the neutron moderator material of the present invention, as shown in operation 140 and operation 150 . During the hot pressing process, metal fluoride-metal aluminum-lithium fluoride composite powder can be formed under high temperature and high pressure Type and densification, so that the neutron moderating material has a relative density of not less than 99.5%, and in the neutron moderating material, the particle size of the largest particle is not greater than 500 μm. Therefore, the neutron moderating material prepared in this case has a fine and uniform structure, which can meet the needs of the application.

In some embodiments, the temperature of the hot pressing process may be 550° C. to 620° C., and the pressure may be 5 MPa to 55 MPa. When the temperature and pressure of the hot pressing process are within the aforementioned range, the metal fluoride-metal aluminum-lithium fluoride composite powder can be more effectively densified to form a neutron moderator material that can meet the application requirements. In these embodiments, the time of the hot pressing process may be 1 hour to 6 hours. When the time of the hot pressing process is within this range, the hot pressing process can have a better densification effect on the metal fluoride-metal aluminum-lithium fluoride composite powder, which helps to improve the properties of the neutron moderator material .

Secondly, after the hot pressing process, the yield of the neutron moderating material produced by the present invention is not less than 95%, so the production method of the present invention can effectively produce the neutron moderating material and reduce its production cost.

In some application examples, the neutron moderating material produced by the hot pressing process of the present invention has a specific composition and has a dense and uniform structure, so it can be used as a neutron moderating material for boron neutron capture therapy equipment.

The following examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention. Anyone skilled in this art can make various changes and modifications without departing from the spirit and scope of the present invention.

Example 1

First, provide 58.5% by volume of magnesium fluoride, 40% by volume percentage of metallic aluminum and 1.5% by volume of lithium fluoride, and the purity of magnesium fluoride, metallic aluminum and lithium fluoride is greater than 99.5%, wherein the average particle size of metallic aluminum is 5 μm, and the average particle size of lithium fluoride is 1 μm. Then, put 1.5 volume percent of lithium fluoride and 15 volume percent of metal aluminum into a high-efficiency mixing device to perform the first dry powder mixing process to form metal aluminum-lithium fluoride composite powder. Wherein, the time of the first dry powder mixing process is 30 minutes.

After the first dry powder mixing process, 25 volume percent aluminum and 58.5 volume percent magnesium fluoride are added to the high-efficiency mixing equipment for the second dry powder mixing process with metal aluminum-lithium fluoride composite powder , and form magnesium fluoride-metal aluminum-lithium fluoride composite powder. Wherein, the time of the first dry powder mixing process is 60 minutes.

Next, pour the formed magnesium fluoride-metal aluminum-lithium fluoride composite powder into a graphite hot-pressing mold, and perform a hot-pressing process at 550° C. and a pressure of 50 MPa. After hot pressing and densification for 6 hours, the magnesium fluoride-metal aluminum-lithium fluoride composite material (i.e. neutron moderator material) of Example 1 can be obtained, and its composition is 58.5% magnesium fluoride-40% Metal aluminum-1.5% lithium fluoride, and the microstructure of the neutron moderator material in Example 1 was observed with an electron microscope (as shown in FIG. 2A ). The yield of neutron moderating material in Example 1 was 96%.

Example 2

First, provide 69% by volume of aluminum fluoride, 30% by volume of metallic aluminum, and 1% by volume of lithium fluoride, and the purity of aluminum fluoride, metallic aluminum, and lithium fluoride are all greater than 99.5%, and the average particle size of metallic aluminum path is 10 μm, and the average particle size of lithium fluoride is 2 μm. Then, put 1 volume percent of lithium fluoride and 20 volume percent of metal aluminum into a high-efficiency mixing device to perform the first dry powder mixing process to form metal aluminum-lithium fluoride composite powder. Wherein, the time of the first dry powder mixing process is 45 minutes.

After the first dry powder mixing process, 10 volume percent aluminum and 69 volume percent aluminum fluoride are added to the high-efficiency mixing equipment for the second dry powder mixing process with metal aluminum-lithium fluoride composite powder , to form aluminum fluoride-metal aluminum-lithium fluoride composite powder. Wherein, the time of the first dry powder mixing process is 45 minutes.

Next, the formed aluminum fluoride-metal aluminum-lithium fluoride composite powder was poured into a graphite hot-pressing mold, and a hot-pressing process was carried out at 620° C. under a pressure of 5 MPa. After hot pressing and densification for 3 hours, the aluminum fluoride-metal aluminum-lithium fluoride composite material (i.e. neutron moderator material) of Example 2 can be obtained, and its composition is 69% aluminum fluoride-30% Metal aluminum-1% lithium fluoride, and the microstructure of the neutron moderator material in Example 2 was observed with an electron microscope (as shown in Figure 2B). The yield of neutron moderating material in Example 2 was 99.9%.

Please refer to FIG. 2A and FIG. 2B . Both the neutron moderating materials prepared in Example 1 and Example 2 have dense and uniform structures, so they can be applied to neutron capture devices. Among them, the relative density of the neutron moderating material in Example 1 is 99.6%, and the particle size of the largest particle structure is less than 250 μm, while the relative density of the neutron moderating material in Example 2 is 99.9%, and the largest particle structure is The particle size is less than 150μm.

Accordingly, with the neutron moderator material and the manufacturing method thereof of the present invention, the metal fluoride powder, the lithium fluoride powder and the metal aluminum powder are mixed in stages to effectively embed the lithium fluoride powder On the surface of the metal aluminum powder, it can help to improve the properties of the neutron moderator material. Among them, through the staged dry powder mixing process, metal fluoride powder, lithium fluoride powder and metal aluminum powder can be uniformly mixed, which helps to improve the quality of neutron moderator materials, and can improve their Yield. In addition, since the powder mixing process of the present invention does not need to add additional organic solvents or other liquid carriers, it can meet the requirements of environmental protection and waste reduction, and can reduce production costs.

Although the present invention has been disclosed above in terms of implementation, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field of the present invention can make various modifications and changes without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

100: method

110, 120, 130, 140, 150: operation

Claims (6)

A method for manufacturing a neutron moderating material, comprising: providing a metal fluoride powder, a lithium fluoride powder and a metal aluminum powder, wherein the metal fluoride powder includes magnesium fluoride, aluminum fluoride and/or fluorine Calcium chloride, the metal fluoride powder does not contain lithium fluoride, based on 100 volume percent of the neutron moderator material, the amount of one of the metal aluminum powders is 20 volume percent to 50 volume percent, and the amount of the lithium fluoride powder One dosage is 0.5 volume percent to 2 volume percent, and the balance is the metal fluoride powder, wherein an average particle diameter of the lithium fluoride powder is 1 μm to 3 μm, and an average particle diameter of the metal aluminum powder is 5 μm to 15 μm; performing a first dry powder mixing process on the lithium fluoride powder and a part of the metal aluminum powder to form a metal aluminum-lithium fluoride composite powder, wherein the lithium fluoride powder and the Part of the metal aluminum powder has a volume ratio of 0.05 to 0.1, and the lithium fluoride powder system is embedded on a surface of the part of the metal aluminum powder; the metal fluoride powder, the remaining metal aluminum The powder and the metal aluminum-lithium fluoride composite powder are subjected to a second dry powder mixing process to form a metal fluoride-metal aluminum-lithium fluoride composite powder; and the metal fluoride-metal aluminum-fluorine The lithium compound powder is subjected to a hot pressing process to form the neutron moderator material. The manufacturing method of the neutron moderating material according to claim 1, wherein the purity of the metal fluoride powder, the lithium fluoride powder and the metal aluminum powder is all greater than 99%. The manufacturing method of the neutron moderating material as described in claim 1, wherein the mixing time of the first dry powder mixing process is 0.5 hours to 1 hour, and the mixing time of the second dry powder mixing process is 0.5 hours to 1 hour. 1 hour. The manufacturing method of neutron moderating material as described in Claim 1, wherein the temperature of one of the hot pressing processes is 550°C to 620°C, and the pressure of one of the hot pressing processes is 5MPa to 55MPa. The manufacturing method of the neutron moderating material according to claim 4, wherein one of the hot pressing processes takes 1 hour to 6 hours. A neutron moderating material produced by the manufacturing method as described in any one of claims 1 to 5, wherein a relative density of the neutron moderating material is not less than 99.5%, and the neutron moderating material contains The diameter of the largest particle is not greater than 500 μm.

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