Composite having radiation shielding function and method for producing composite having radiation shielding function

Abstract

The purpose of the present invention is to develop a composite having a novel configuration and containing a powder having a radiation-shielding function at a high content rate. A composite having a radiation shielding function, which contains a radiation shielding powder in an amount of 3-85% in total, and which is obtained by impregnating / filling molten aluminum into all the voids of a preform and solidifying and compositing the same, and a method for producing the composite, or a complex obtained by impregnating 25% or more of the voids of the preform with a liquid organic / inorganic sealant, curing, and compounding, the preform being formed from a mixture, the radiation shielding powder is selected from the group consisting of gadolinium oxide, boron carbide, boron oxide, boron, barium sulfate, strontium oxide, tungsten, tungsten oxide, tungsten carbide, molybdenum, molybdenum oxide, iron powder, iron oxide powder and ferrite powder, and the silica-based binder is in a liquid state. The liquid silica-based binder has the characteristic of being capable of forming a preform at a temperature at which the radiation shielding powder does not decompose.

Description

Technical Field

[0001] This invention relates to a composite having radiation shielding function and a method for manufacturing a composite having radiation shielding function. Specifically, it relates to: a composite comprising gadolinium oxide (Gd₂O₃) powder, boron carbide (B₄C) powder, boron oxide (B₂O₃) powder, boron (B) powder, barium sulfate (BaSO₄) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W₂O₃) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO₃) powder, iron (Fe) powder, iron oxide (Fe₂O₃) powder, and a ferrite powder with iron oxide as the main component (hereinafter referred to as...). The invention relates to a composite material having radiation shielding function, formed by first impregnating and solidifying a molten metal selected from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of such low-melting-point metal and other metals with a melting point of 200°C or higher and 900°C or lower, within the pores of a porous preform of at least one of these (also collectively referred to as radiation shielding powder groups). Alternatively, it relates to a method for manufacturing a composite material having radiation shielding function formed by impregnating and solidifying a liquid organic-inorganic sealing agent with heat treatment. Specifically, the invention relates to a technique capable of forming a composite material from radiation shielding powders while suppressing the decomposition of the aforementioned radiation shielding powders. Background Technology

[0002] In medical settings, shielding materials are used to protect against X-rays and radiation generated by medical instruments and equipment. Additionally, in the nuclear energy industry, materials that shield against X-rays, gamma rays, and neutron rays are used in the fabrication of containers and devices for handling and storing unused nuclear fuel. For radiation shielding materials, good heat dissipation is required to shield against radiation and prevent nuclear chain reactions. Metals such as lead (Pb) and tungsten (W) are commonly used as radiation shielding materials, but in recent years, especially for structural components requiring effective radiation shielding, lightweight materials with high heat dissipation and strong radiation shielding capabilities have become increasingly desirable.

[0003] Traditional radiation shielding materials typically use metallic lead and tungsten. However, these materials have a high specific gravity, making structures made from them quite heavy and limiting their applications. As listed below, to create lightweight structures with radiation shielding properties, materials combining low-density B4C or BaSO4 powders with resins or metals have been proposed. However, the low content of these radiation-shielding powders in the structures limits their application.

[0004] Patent Document 1 discloses a method for manufacturing an aluminum radiation shield containing boron carbide (B4C) as described below. Specifically, the proposed method involves preparing a pressed powder body containing a mixture of boron carbide (B4C) powder and aluminum powder, then sintering it at a low temperature of 10-50°C using vacuum sintering, high-intensity injection (HIP), and hot pressing to fuse the B4C with the aluminum. This is followed by heating and melting to cast the radiation shield. In this method, the B4C content in the radiation shield is limited to a range of 0.5-5% by mass or less. Above this content, the viscosity of the casting melt increases, making casting difficult. Therefore, it is difficult to manufacture radiation shields with a higher radiation shielding effect and a B4C content exceeding 5% by mass.

[0005] Furthermore, Patent Document 2 discloses the following method: An inorganic binder is added to a mixture of boron carbide (B4C) particles and aluminum borate whiskers, and the mixture is shaped. The shaped material is then sintered in an argon atmosphere at 1250°C for 4 hours to produce a preform. Molten aluminum alloy is then impregnated into the preform under high pressure to create a radiation shielding composite. In this method, boron carbide is mixed with ceramic whiskers and sintered at 1100~1400°C to create a preform resistant to high-pressure aluminum impregnation. Molten aluminum alloy is then impregnated to create the composite. This method has the following problems: because the preform must be produced at high temperatures, the cost is high, and the boron carbide content can only be 1~15 wt%, making it impossible to increase the boron carbide content in the radiation shielding composite.

[0006] Furthermore, Patent Document 3 discloses the following method: a solid sheet of aluminum alloy molten at 580°C to 610°C is placed on top of a preform made of a mixture of boron-containing ceramic powder (represented by boron carbide (B4C)) and metal powder containing aluminum. The mixture is heated to the melting point of the solid sheet and infiltrated for 1 minute to 24 hours to obtain a composite. According to the researchers of the present invention, in this method, since the aluminum alloy is allowed to naturally infiltrate (melt-infiltrate) into the preform, a long reaction time is required. In addition, if unstable Al4C3 is formed in the air, the infiltration of the preform may not reach 100%, and a dense radiation shielding composite cannot be stably obtained.

[0007] Furthermore, Patent Document 4 proposes a method for manufacturing a composite by heating a mixture of boron carbide powder and aluminum alloy powder, or a mixture of these powders, to a predetermined temperature and holding it therewhile forging or rolling it in a semi-molten state. According to the inventors' research, this method, due to the high temperature at which forming is performed, cannot manufacture composites with large areas or thick walls. Additionally, because forging is forced in a semi-molten state, there is a problem that the radiation shielding powder and aluminum alloy become uneven, or that products with wall thicknesses of 10 mm or more cannot be manufactured.

[0008] Furthermore, Patent Document 5 proposes a container material made by combining boron fibers with a boron-containing aluminum alloy matrix. However, the boron fiber content remains low, and boron fibers are expensive, thus limiting their application.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2002-20828

[0012] Patent Document 2: Japanese Patent Application Publication No. 2003-121590

[0013] Patent Document 3: Japanese Patent No. 4426293

[0014] Patent Document 4: Japanese Patent Application Publication No. 60-096746

[0015] Patent Document 5: Japanese Patent Application Publication No. 10-319183 Summary of the Invention

[0016] The problem the invention aims to solve

[0017] As listed above, existing radiation shielding materials suffer from increased weight when using lead or tungsten in the radiation shielding powder, or low content of radiation-shielding powder in any composite material using powders such as boron carbide (B4C) or barium sulfate (BaSO4), making it impossible to achieve high content. Furthermore, existing technologies have proposed preforms made by mixing radiation shielding powder into gypsum, rubber, or resin. However, when using rubber as a matrix, the organic material makes it difficult to use for extended periods above 200°C. Additionally, when using gypsum as a matrix, prolonged use at temperatures above 100°C causes dehydration and decomposition of the gypsum, hindering its long-term use at high temperatures.

[0018] In view of the actual situation of the prior art, the inventors believe that if a technology is developed that can control the content of materials (bulks) with high contents of radiation shielding powders such as B4C powder, BaSO4 powder, or others such as gadolinium oxide, strontium oxide, and iron oxide to a low to high content, and that can be used at high temperatures, the application range of radiation shielding as structural components (structures) and parts of radiation-related machinery will be significantly increased. Furthermore, it is believed that even radiation shielding powders such as tungsten powder and molybdenum powder with a specific gravity of 10 or higher can be compounded with other materials at a content that can stably exert a radiation shielding effect, and thus produced as lightweight composite materials, which can be used according to their applications, thereby significantly increasing their range of applications.

[0019] The inventors have recognized that, in light of the actual conditions of the prior art, a composite material with radiation shielding function that is highly practical is desired, possessing the following characteristics. Specifically, a composite material is desired that is: high in strength and with a high content of radiation shielding powder, particularly 3% or more, preferably 60% or more, more preferably 85%; with a wall thickness of 5 mm or more, preferably 10 mm or more; exhibiting a large radiation shielding effect; lightweight; and suitable for use in large structures; and a composite material with high thermal conductivity, selected from a low-melting-point metal chosen from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of such low-melting-point metal with other metals (hereinafter sometimes referred to as "aluminum, etc."). It should be noted that the low-melting-point metal may be any metal other than zinc, tin, and lead, as long as it does not impair the purpose of this invention. In this specification, volume percentage is also referred to as "v%", and mass percentage is also referred to as "w%".

[0020] Therefore, the object of the present invention is to develop a novel composite with a high content of radiation-shielding powder (radiation-shielding powder) that provides a high radiation-shielding effect. Furthermore, the object of the present invention is to develop composites in which the content of radiation-shielding powder is controlled, for example, from low to high levels (3% to 85% depending on the application), and which possess the strength required for structural components such as building parts or mechanical parts. Moreover, the object of the present invention is to develop a new technology that provides composites that are excellent composites of aluminum metal powder, aluminum alloy powder, or ceramic powder with high heat resistance and thermal conductivity, and which are based on molten aluminum metal or aluminum alloy powder.

[0021] Solution for solving the problem

[0022] The above objective is achieved by the present invention described below. That is, the present invention provides a first composite having radiation shielding function.

[0023] [1] A composite material with radiation shielding function, characterized in that it is made by compositing powder with radiation shielding effect, and the powder is contained in a total volume of more than 3% and less than 85% of the powder.

[0024] The composite is composed of the following: it is formed by impregnating / filling all the voids of a porous molded body (preform) with at least one of a low-melting-point metal selected from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and other metals, with a melting point of 200°C or higher and 900°C, and then curing and composite it. The porous molded body (preform) is a molded / fired product formed by a mixture containing one or more of the aforementioned powders with radiation shielding effects selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron powder, boron oxide powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and a non-powdered silica-based binder.

[0025] The aforementioned non-powdered silica-based adhesive is a liquid silica-based adhesive, etc. The liquid silica-based adhesive is selected from at least one of the following groups: liquid silicone resin or a silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed from silica and organic matter that undergoes heat curing at a temperature below 900°C.

[0026] The aforementioned non-powdered silica-based binder has the characteristic of being able to form a porous molded body (preform) as the aforementioned molded / sintered product at a temperature at which the aforementioned radiation shielding powder is not decomposed.

[0027] In addition to the substances listed above, the non-powdered silica-based binders described above can also be water glass (sodium silicate), colloidal silica, etc.

[0028] The following are examples of preferred embodiments of the first composite having radiation shielding function.

[0029] [2] According to the above [1], the composite having radiation shielding function, wherein the aforementioned mixture is formed by adding 0.5 to 10 parts by mass of the aforementioned liquid silica-based binder (calculated as SiO2) to 100 parts by mass of the aforementioned radiation shielding powder.

[0030] In addition, the present invention provides a second composite having radiation shielding function.

[0031] [3] A composite material with radiation shielding function, characterized in that it is made by compositing powder with radiation shielding effect, and the powder is contained in a total volume of more than 3% and less than 85% of the powder.

[0032] The composite is composed of a liquid organic-inorganic sealing agent impregnated into at least 25% by volume of the voids of a porous molded body (preform) and then cured and composited. The porous molded body (preform) is a molded / fired product formed by a mixture containing one or more of the aforementioned powders with radiation shielding effect selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron powder, boron oxide powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and a non-powdered silica-based binder. The non-powdered silica-based binder has the characteristic of being able to form a porous molded body (preform) as the aforementioned molded / fired product at a temperature at which the aforementioned radiation shielding powder is not decomposed.

[0033] The following are examples of preferred embodiments of the second composite having radiation shielding function.

[0034] [4] According to the composite with radiation shielding function described in [3] above, wherein the aforementioned non-powdered silica-based binder is a liquid silica-based binder, and the liquid silica-based binder is selected from at least one of the following groups: water glass (sodium silicate), colloidal silica, liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heating and curing at a temperature below 900°C. The aforementioned mixture is formed by adding 0.5 to 10 parts by weight of the aforementioned liquid silica-based binder, calculated as SiO2, to 100 parts by weight of the aforementioned radiation shielding powder.

[0035] [5] According to the above [3] or [4], the composite with radiation shielding function, wherein the aforementioned liquid organic-inorganic sealing agent exists in the voids of the aforementioned porous molded body (preform) in the form of a cured organic-inorganic sealing agent and / or a heat-treated organic-inorganic sealing agent, the cured organic-inorganic sealing agent and / or the heat-treated organic-inorganic sealing agent occupying more than 25% of 100% of the voids of the porous molded body (preform) before impregnation, and when the preform after impregnation is set to 100% of the total volume, the cured organic-inorganic sealing agent and / or the heat-treated organic-inorganic sealing agent occupying more than 5% of the total volume.

[0036] [6] The composite material with radiation shielding function according to any one of [3] to [5] above, wherein,

[0037] The aforementioned liquid organic-inorganic sealing agent is a low-viscosity substance with a viscosity of less than 50 mPa·s and containing more than 30% by mass of non-volatile components, selected from at least one of the following substances:

[0038] The oligomers of methyl silicate Si(OCH3)4 or the dimers or tetramers formed by the partial hydrolysis of methyl silicate are adjusted to form a liquid methyl silicate compound with a non-volatile component of more than 30% by mass.

[0039] The dimer or tetramer oligomer of ethyl silicate Si(OC2H5)4 or the partially hydrolyzed ethyl silicate is adjusted to form a liquid ethyl silicate compound with a non-volatile component of more than 30% by mass.

[0040] Organosilicon resins or their derivatives having siloxane bonds and having a non-volatile content of 30% or more by mass;

[0041] Liquid alkoxysilane compounds, as alkoxysilane derivatives, undergo condensation reactions with moisture in the air to generate organosilicon-oxygen compounds (Si-OR).

[0042] The present invention provides a method for manufacturing a first composite with radiation shielding function as another embodiment.

[0043] [7] A method for manufacturing a composite with radiation shielding function, characterized in that it is a method for manufacturing a composite for preparing a composite with radiation shielding function, wherein the composite uses at least one of a low-melting-point metal selected from the group consisting of aluminum, aluminum alloy, zinc, tin and lead, or a low-melting-point alloy of the low-melting-point metal and other metals as a matrix, and contains powder with radiation shielding effect in a total volume percentage of 3% or more and 85% or less, and the manufacturing method includes the following steps:

[0044] A process for producing a porous preform is described, comprising adding a non-powdered silica-based binder to one or more of the aforementioned radiation-shielding powders selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and mixing the resulting mixture, shaping the mixture, and firing the resulting preform at a temperature of 300°C or higher and 900°C or lower to produce a preform. The non-powdered silica-based binder used in this process is a liquid silica-based binder, wherein the liquid silica-based binder is selected from at least one of the group consisting of liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heat curing at a temperature of 900°C or lower.

[0045] In this process, a porous molded body (preform) is formed by casting a molten liquid of at least one of the following: aluminum, aluminum alloy, zinc, tin, and lead, with a melting point of 200°C to 900°C or a low-melting-point alloy of the same metal and other metals. The molten liquid is then held under a high pressure of 20 MPa to 200 MPa for 3 to 15 minutes to allow it to permeate the porous molded body (preform). The composite body in which the molten liquid has been permeated is then removed and cooled within 15 minutes to suppress the decomposition of the radiation shielding powder in the composite body.

[0046] The following are preferred embodiments of the manufacturing method of the first composite having radiation shielding function described above.

[0047] [8] According to the manufacturing method of the composite with radiation shielding function described in [7] above, the aforementioned mixture is formed by adding 0.5 to 10 parts by mass of the aforementioned liquid silica-based binder (calculated as SiO2) to 100 parts by mass of the aforementioned radiation shielding powder.

[0048] The present invention provides a method for manufacturing a second composite with radiation shielding function as another embodiment.

[0049] [9] A method for manufacturing a composite with radiation shielding function, characterized in that the preparation involves a composite of powders with radiation shielding effect, containing the powders in a total volume percentage of 3% or more and 85% or less, wherein the manufacturing method comprises the following steps:

[0050] A process of producing a porous preform by adding a non-powdered silica-based binder to one or more of the aforementioned radiation-shielding powders selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and mixing the mixture thereon, shaping the resulting mixture, and firing the resulting preform at a temperature of 300°C or higher and 900°C or lower.

[0051] A composite process is described in which a liquid organic-inorganic sealing agent containing 30% or more of non-volatile components and with a viscosity of 50 mPa·s or less is vacuum impregnated into the voids of a porous molded body (preform) obtained in the process of making a porous molded body (preform). Alternatively, after vacuum impregnation, the mixture is pressurized and impregnated at a pressure of 10 atmospheres or less, and then heated to a temperature of 200°C or higher and 900°C or lower, so that the solidified product of the aforementioned liquid organic-inorganic sealing agent and / or the heat-treated product of the aforementioned liquid organic-inorganic sealing agent remain at 25% or more of 100% by volume relative to the voids of the aforementioned porous molded body (preform). This process is used to composite the aforementioned radiation shielding powder with the components derived from the aforementioned liquid organic-inorganic sealing agent.

[0052] The following are preferred embodiments of the manufacturing method of the aforementioned second radiation shielding composite.

[0053]

[10] According to the manufacturing method of the composite with radiation shielding function described in [9] above, wherein,

[0054] The aforementioned liquid organic-inorganic sealing agent is a low-viscosity substance with a viscosity of less than 50 mPa·s and containing more than 30% by mass of non-volatile components, selected from at least one of the following substances:

[0055] The oligomers of methyl silicate Si(OCH3)4 or the dimers or tetramers formed by the partial hydrolysis of methyl silicate are adjusted to form a liquid methyl silicate compound with a non-volatile component of more than 30% by mass.

[0056] The dimer or tetramer oligomer of ethyl silicate Si(OC2H5)4 or the partially hydrolyzed ethyl silicate is adjusted to form a liquid ethyl silicate compound with a non-volatile component of more than 30% by mass.

[0057] Organosilicon resins or their derivatives having siloxane bonds and having a non-volatile content of 30% or more by mass;

[0058] Liquid alkoxysilane compounds, as alkoxysilane derivatives, undergo condensation reactions with moisture in the air to generate organosilicon-oxygen compounds (Si-OR).

[0059]

[11] In the method for manufacturing a composite with radiation shielding function as described in [9] or

[10] above, the aforementioned non-powdered silica-based binder is a liquid silica-based binder, wherein the liquid silica-based binder is selected from at least one of the following groups: water glass (sodium silicate), colloidal silica, liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heating and curing at a temperature below 900°C. The aforementioned mixture is formed by adding 0.5 to 10 parts by weight of the aforementioned liquid silica-based binder, calculated as SiO2, to 100 parts by weight of the aforementioned radiation shielding powder.

[0060]

[12] According to the manufacturing method of the composite with radiation shielding function described in [7] or [8] above, in the aforementioned process of making a porous molded body (preform), aluminum powder or aluminum alloy powder or ceramic powder is further added to the aforementioned radiation shielding powder. When the total amount of the aluminum metal powder or aluminum alloy powder or ceramic powder and the aforementioned radiation shielding powder is set to 100% by mass, the aforementioned non-powdered silica-based binder, which is converted to SiO2, is added to make a porous molded body (preform).

[0061] The effects of the invention

[0062] Conventionally, structures containing radiation-shielding powder are typically manufactured by mixing radiation-shielding powder with aluminum, rubber, or resin to form a composite. In contrast, according to the present invention, a first composite having radiation-shielding function is formed by using a molded body (preform) containing radiation-shielding powder at a controlled low to high filling rate, with the same configuration, and by stably providing molten aluminum or the like into all the voids of the molded body (preform) and then composited in a solidified state; or a second composite having radiation-shielding function is formed by impregnating at least 25% by volume of a liquid organic-inorganic sealing agent into the voids of the aforementioned molded body (preform) and then solidifying and composited. Furthermore, by applying the various manufacturing methods of the present invention according to the intended use of the composite, and by cleverly utilizing the two configurations described above, it is possible to stably obtain various composites with high practical value, such as those where the radiation-shielding powder is controlled at a low to high filling rate and exhibits excellent radiation-shielding function with strength suitable for the intended purpose, and which are suitable for desired characteristics. The technical features of the present invention are described below.

[0063] A first feature of the present invention can be exemplified by the following aspect: it enables the use of one or more radiation shielding powders appropriately selected from various groups of radiation shielding powders with different functionalities and properties, as specified in the present invention, including gadolinium oxide (Gd₂O₃) powder, boron carbide (B₄C) powder, boron oxide (B₂O₃) powder, boron (B) powder, barium sulfate (BaSO₄) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W₂O₃) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO₃) powder, iron (Fe) powder, iron oxide (Fe₂O₃) powder, and ferrite powder with iron oxide as the main component. That is, according to the present invention, it is possible to provide various radiation shielding composites composed of individual or various combinations of radiation shielding powders.

[0064] In the radiation shielding powder group constituting the composite of the present invention, it is said that, for example, boron carbide containing boron has a radiation shielding effect against neutron rays; tungsten or tungsten carbide has a radiation shielding effect against gamma rays and X-rays; and barium sulfate containing barium has a radiation shielding effect against X-rays and gamma rays. In contrast, according to the present invention, as listed below, it is possible to provide composites with various compositions having different radiation shielding functions. That is, not only can composites formed by impregnating and curing each powder of the specific radiation shielding powder group specified in the present invention with a molten aluminum or liquid organic-inorganic sealing agent, but also composites formed by impregnating and curing, for example, two types of radiation shielding powders—boron carbide and tungsten, or boron carbide and barium sulfate, or, as needed, three types—boron carbide and tungsten, and barium sulfate—with a molten aluminum or liquid organic-inorganic sealing agent, are provided. Thus, according to the present invention, by appropriately selecting the radiation shielding powder specified in the present invention, it is also possible to provide composites capable of simultaneously shielding X-rays, gamma rays, and neutron rays.

[0065] As a second feature of the present invention, for example, by adjusting the particle size and formulation of the various radiation shielding powders listed above, and furthermore, by adding aluminum powder or aluminum alloy powder as needed in the case of a first composite, it is possible to provide a composite with radiation shielding function in which the volume fraction of the radiation shielding powder can be freely controlled from 3v% to 85v%. According to the present invention, it is particularly possible to manufacture a structure composed of a composite with radiation shielding function that achieves a filling rate (volume fraction) of radiation shielding powder of 50v% or more, which requires a high shielding effect.

[0066] As a third feature of the present invention, the following aspects can be cited: the composite with radiation shielding function provided by the present invention can be made into two different configurations. First, in any configuration, a porous molded body (preform) is used, which is a molded / fired product formed by a mixture containing one or more radiation shielding powders selected from the radiation shielding powder group specified in the present invention and a non-powdered silica-based binder. Moreover, a first composite with a high content of radiation shielding powder based on aluminum, etc., can be provided. The first composite is configured by impregnating / filling all the voids of the porous molded body (preform) with a molten low-melting-point metal selected from the group consisting of aluminum, aluminum alloy, zinc, tin and lead, or a low-melting-point alloy of the low-melting-point metal and other metals with a melting point of 200°C or higher and 900°C or lower, and then solidifying and composite it. In addition, a second composite with a high content of radiation shielding powder can be provided. The second composite is formed by impregnating at least 25% by volume of the voids in the above-mentioned porous molded body (preform) with a liquid organic-inorganic sealing agent, and then heating it to a temperature of 200°C or higher and 900°C or lower to solidify and composite the liquid organic-inorganic sealing agent.

[0067] Furthermore, in the case of any of the above-described composite compositions, the non-powdered silica-based binders used in the production of the preform all possess the characteristic of forming the preform at a temperature at which the radiation shielding powder used in the composite process does not decompose, thereby achieving the following effect. That is, through this configuration, the radiation shielding composite of the present invention becomes a high-strength composite formed by bonding the radiation shielding powder specified in the present invention using aluminum or other organic-inorganic sealing agents, and the radiation shielding powder used does not decompose, allowing it to be used even at high temperatures above 300°C. Hereinafter, the term "molten aluminum" or "molten aluminum" in the specification of the present invention will be used to describe molten aluminum metal as an example. That is, in the specification of this invention, the term "molten aluminum" or "molten aluminum" is used to refer not only to molten aluminum metal, but also to molten low-melting-point metals selected from the group consisting of aluminum alloys, zinc, tin, and lead, or low-melting-point alloys of such low-melting-point metals with other metals (e.g., solders made of low-melting-point alloys with tin and / or lead as the main components, and / or zinc alloys, etc.). The low-melting-point metal or low-melting-point alloy referred to as "molten aluminum" in the specification of this invention refers to those with a melting point of 200°C or higher. Furthermore, in this invention, it is preferable to use low-melting-point metals or low-melting-point alloys with a melting point of 300°C or higher. That is, according to the research of the present inventors, when low-melting-point metals or low-melting-point alloys with melting points below 300°C are used, the heat resistance of the resulting composite is sometimes insufficient, depending on its intended use, and therefore is not preferred.

[0068] The fourth feature of the present invention can be exemplified by the following aspects: According to the research of the present inventors, in the case where, as an example of the first composite, molten aluminum metal or aluminum alloy at high temperature is used as the melt when composited with radiation shielding powder, the following problems exist, but these problems can be solved. Specifically, according to the present invention, various radiation shielding powders that are difficult to use for the following reasons can be used as raw materials; for example, composites that can be used stably even at temperatures above 300°C can be manufactured. For example, even radiation shielding powders such as boron carbide (which reacts with aluminum to form Al4C3 and exhibits decomposition reaction with moisture in the air), barium sulfate (which reacts with molten aluminum at high temperatures to form decomposition reactions into Al2O3, BaO, and SO2), and strontium sulfate, tungsten, iron powder, and aluminum borate powder, which undergo oxidation, thermal decomposition, and the formation of unstable substances at temperatures above 900°C, can be used as raw materials. Therefore, a wide variety of radiation shielding powders as specified in the present invention can be utilized, and thus, according to the present invention, the application range of the composite can be significantly expanded. Attached Figure Description

[0069] Figure 1 is a schematic diagram showing the casting of a preform 2 using molten aluminum 1 in the first manufacturing method.

[0070] Figure 1A This is a schematic diagram showing a heated preform 2 placed inside the mold of the press 10 and molten aluminum 1 injected.

[0071] Figure 1B This is a schematic diagram showing the process of casting molten aluminum 1 into the preform 2 using the upper punch 5 and lower punch 4 of a high-pressure press, and then allowing it to permeate.

[0072] Figure 1C This is a schematic diagram showing the situation where the composite 3, after cooling, is removed by pushing the upper and lower punch 4 and the solidified aluminum molten material is taken out.

[0073] Figure 2 This is a schematic diagram illustrating the general outline of a pressure-reducing vessel 30 used in the second manufacturing method to impregnate the preform 2 with a liquid organic-inorganic sealing agent 31. Detailed Implementation

[0074] The preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0075] The composite with radiation shielding function of the present invention is characterized in that it is formed by combining powders with radiation shielding effect, and the powders are contained in a total volume range of 3% to 85% or more. The composite uses a porous molded body (preform), which is a molded / fired product formed by a mixture. The mixture contains one or more radiation shielding powders selected from the group consisting of gadolinium oxide (Gd2O3) powder, boron carbide (B4C) powder, boron oxide (B2O3) powder, boron (B) powder, barium sulfate (BaSO4) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W2O3) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO3) powder, iron (Fe) powder, iron oxide (Fe2O3) powder, and ferrite powder with iron oxide as the main component, as well as a non-powdered silica-based binder. Furthermore, the first composite is formed by impregnating / filling molten aluminum into all the voids of the aforementioned porous molded body (preform) and then curing and composite it. The second composite is formed by impregnating liquid organic-inorganic sealing agent into at least 25% by volume of the voids of the aforementioned porous molded body (preform) and then curing and composite it. Moreover, both the first and second composites are characterized in that the aforementioned non-powdered silica-based binder constituting the composite has the characteristic of being able to form a porous molded body (preform) (hereinafter also simply referred to as preform) as the aforementioned molded / sintered product at a temperature at which the aforementioned radiation shielding powder is not decomposed. Examples of non-powdered silica-based binders with the above-mentioned characteristics suitable for use in the present invention will be described later.

[0076] The first or second composite of the present invention with radiation shielding function as described above, for example, by the manufacturing method of the present invention including the first or second scheme listed below, can suppress the decomposition of radiation shielding powder and obtain a stable composite. Therefore, it is possible to easily and stably prepare a high-quality composite that meets the intended use and has the various effects of the present invention listed above.

[0077] The first composite with radiation shielding function of the present invention can be easily and stably prepared by the first manufacturing method of the present invention described below. The first composite is formed by impregnating / filling "molten aluminum" into all the voids of a preform containing the specific structure described above, and then solidifying and composite it. It should be noted that, as described above, "molten aluminum" and "molten aluminum" refer to the molten metal of aluminum, aluminum alloy, low-melting-point metal and low-melting-point alloy with a melting point of 200°C or higher, preferably 300°C or higher and 900°C or lower.

[0078] The first manufacturing method of the present invention is characterized in that it is a method for manufacturing a composite having a radiation shielding function, wherein the composite uses aluminum as a matrix and contains powder having a radiation shielding effect in a total volume range of 3% to 85% or more, and the manufacturing method includes the following steps: adding a non-powdered powder to one or more of the aforementioned powders having a radiation shielding effect selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component. A process involves mixing a silica-based binder, molding the resulting mixture, and firing the resulting molded body at a temperature of 300°C to 900°C to produce a porous molded body (preform); and a process involves casting molten aluminum into the preformed body obtained in this process at a temperature of 300°C to 900°C, maintaining the molten aluminum in the preformed body under a high pressure of 20 MPa to 200 MPa for 3 to 15 minutes, for example, about 3 to 5 minutes, and then immediately removing the composite body in the state of being infiltrated with the molten aluminum and cooling it to suppress the decomposition of radiation shielding powder and the formation of unstable substances such as Al4C3 in the composite body.

[0079] In the first manufacturing method of the present invention, in the aforementioned step of producing the preform, aluminum powder, aluminum alloy powder, or ceramic powder may be added to the aforementioned radiation shielding powder. With the total amount of the aluminum powder, aluminum alloy powder, or ceramic powder and the aforementioned radiation shielding powder set to 100% by mass, 0.5 to 10% by mass of the aforementioned non-powdered silica-based binder (converted to SiO2) may be added to produce the preform. With this configuration, it is easier to prepare a composite material with radiation shielding function, which is based on aluminum or aluminum alloy and contains powder with radiation shielding effect, appropriately controlled within a total volume range of 3% to 85% by volume. This will be described later.

[0080] The second composite with radiation shielding function of the present invention can be easily and stably prepared by the second manufacturing method of the present invention described below. The second composite is formed by impregnating at least 25% by volume of a liquid organic-inorganic sealing agent into the voids of a preform containing the above-described specific structure, and then curing and compounding it.

[0081] The second manufacturing method of the present invention is characterized in that it prepares a composite containing a powder having a radiation shielding effect, which is formed by combining powders having a radiation shielding effect, and the total volume percentage is between 3% and 85% or less. The manufacturing method comprises the following steps: adding a non-powdered silica-based binder to one or more of the aforementioned powders having a radiation shielding effect selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and mixing them; molding the resulting mixture; and then heating the resulting molded body at 300°C or higher. A process for producing a porous molded body (preform) by firing at a temperature below 900°C; a composite process for combining the radiation shielding powder with the components derived from the liquid organic-inorganic sealant. The preform obtained in the process of producing the preform is then vacuum impregnated with a liquid organic-inorganic sealant containing 30% or more of non-volatile components and having a viscosity of 50 mPa·s or less. Alternatively, after vacuum impregnation, the preform is impregnated under pressure at a pressure of 10 atmospheres or less, and then heated to a temperature of 300°C or higher and 900°C or lower. This process ensures that the solidified product of the aforementioned liquid organic-inorganic sealant and / or the heat-treated product of the liquid organic-inorganic sealant retain 25% or more of the solidified product relative to 100% of the voids of the aforementioned preform.

[0082] <Fabrication process of porous preforms>

[0083] Hereinafter, detailed descriptions will be provided of the manufacturing methods for the first and second radiation-shielding composites of the present invention, respectively. As described above, the steps for producing the porous molded body (preform) constituting the first and second manufacturing methods are the same. Therefore, the steps for producing the preform will be described first.

[0084] [Radiation shielding powders, etc., of raw materials]

[0085] In this invention, the radiation shielding powder used as a raw material for manufacturing the preform is selected from one or more of the following groups: gadolinium oxide (Gd₂O₃) powder, boron carbide (B₄C) powder, boron oxide (B₂O₃) powder, boron powder, barium sulfate (BaSO₄) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W₂O₃) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO₃) powder, iron (Fe) powder, iron oxide (Fe₂O₃) powder, and ferrite powder with iron oxide as the main component. In the prior art, lead powder and lead oxide powder are typically used alone as radiation shielding powders. However, in this invention, these radiation shielding powders are not used because, in addition to considering the environmental impact of increased weight as a structure (composite), their low melting points make them unsuitable for the manufacturing method of this invention, which is useful for effectively obtaining the composite of this invention.

[0086] In this invention, in addition to the radiation shielding powders listed above, aluminum powder, aluminum alloy powder, or ceramic powder may be added, for example, to reduce the filling rate of the radiation shielding powder in the first composite. This allows for free control of the filling rate (volume fraction) of the radiation shielding powder constituting the composite of this invention within a wide range. In this case, during the manufacturing process of the porous molded body (preform) constituting the manufacturing method of this invention, aluminum powder, aluminum alloy powder, or ceramic powder is further added to the specific radiation shielding powder specified in this invention as needed, and 0.5 to 10% (w%) of the aforementioned non-powdered silica-based binder (converted to SiO2) is added to 100% of the total volume of these powders to produce the preform. This method is the same as the manufacturing method of the composite of this invention, except that aluminum powder, aluminum alloy powder, or ceramic powder is used as needed. Therefore, in the following description, the method for producing the preform includes any of the above-described configurations.

[0087] The radiation shielding powder used in the manufacturing method of the present invention, and the aluminum powder, aluminum alloy powder, or ceramic powder (hereinafter also referred to as "aluminum powder, etc.") used as needed, preferably have an average particle size of 0.3 μm or more and 500 μm or less. The reason for having an average particle size of 0.3 μm or more is that in materials with an average particle size smaller than this, particles tend to aggregate, easily forming what is called clumps. Furthermore, when using two or more powders, there is concern that uniform mixing may be difficult, which is not preferred. Additionally, there is a tendency to make it difficult to uniformly mix the silica-based binder added to the aforementioned powder. Furthermore, when using powders with an average particle size less than 0.3 μm, there is a tendency for the powder filling rate in the preform obtained by molding such as pressure molding, CIP molding, or casting to decrease, thus raising concerns that it may be impossible to produce a preform with a high volume fraction (Vf) of the radiation shielding powder that imparts the characteristics of the present invention. On the other hand, when using large powders exceeding 500 μm, the powder filling properties are also poor, and similarly, there is concern that it may be impossible to produce a preform with a high Vf, as with the case of using powders with an excessively small average particle size. Furthermore, according to the research of the inventors, the coarse particles described above have a small surface area, resulting in a low bonding effect when silica-based binders are added to radiation shielding powder and aluminum powder or the like as needed, making it impossible to produce a strong preform, and therefore this is not preferred.

[0088] The "average particle size" of the radiation shielding powder and the aluminum powder used as needed in this invention is the particle size (median particle size) when the cumulative value of the particle size distribution obtained by laser diffraction / scattering method is 50%.

[0089] Although the volume fraction (Vf) varies depending on the type and particle size of the radiation shielding powder, according to the research of the present invention, the volume fraction (Vf) of the preform typically obtained in the preform manufacturing process constituting the manufacturing method of the present invention is usually around 50% v%. According to the research of the present invention, when increasing the volume fraction (Vf) of the radiation shielding powder in the preform, it is preferable to mix particles with large average particle size and particles with small average particle size, mixing in a manner where small particles are incorporated between large particles. Furthermore, in the present invention, when mixing two or more types of radiation shielding powder, it can be a mixture of radiation shielding powders of the same type with different average particle sizes, or a mixture of radiation shielding powders of different types. When it is desired to produce a preform with the Vf required in the present invention, a trial mixing is performed beforehand, and the particle composition for producing the preform is determined by calculating the loose specific gravity of the preform. According to the research of the inventors, by using the manufacturing method of the present invention, a preform with a Vf of 85% can be produced by appropriate blending of particles. As a result, a composite with a high content of radiation shielding powder that cannot be manufactured by conventional techniques can be achieved.

[0090] In the use of composites with radiation shielding functions, various situations are considered. For example, a higher volume fraction (Vf) of the radiation shielding powder in a structure with radiation shielding function results in a greater radiation shielding effect. However, it is also conceivable that the Vf may be lower depending on the application, or that the Vf of the radiation shielding powder may be reduced to reduce production costs. In this regard, according to the embodiment of the manufacturing method of the present invention, which forms a structure using aluminum powder, etc. as needed, the content of radiation shielding powder in the produced preform can be appropriately controlled within a wider range by means of an extremely simple method of adding the required amount of aluminum powder, etc., to the specific radiation shielding powder specified in the present invention. For example, in a preform with a Vf of 50v% for the radiation shielding powder, 50v% of molten aluminum is impregnated in a subsequent process. In contrast, for example, if a preform formed by adding aluminum powder is used, the total amount of aluminum in the preform and the molten aluminum metal or aluminum alloy or a specific low-melting-point metal or alloy (referred to as "molten aluminum" in this specification) impregnated in subsequent processes constitutes the amount of aluminum in the composite. Therefore, it is possible to increase the amount of aluminum in the structure with radiation shielding function made from this composite. That is, by adding aluminum powder or the like to the preform, the volume fraction Vf in the structure with radiation shielding function can be freely controlled.

[0091] As described above, for example, by appropriately using and employing formulations of large and small particles of specific radiation shielding powder, and by adding aluminum powder as needed, the manufacturing method according to the present invention simplifies the production of composites composed of radiation shielding powder and molten aluminum, where the mixing amount can be controlled within a wide range of 3v% to 85v% of the Vf (filling rate) of the radiation shielding powder. According to the researchers of the present invention, in composites with a radiation shielding powder content of less than 3v%, the radiation shielding effect becomes excessively low, and therefore impractical. Furthermore, according to the researchers of the present invention, in the prior art, even using particle mixing and various forming methods, it is difficult to achieve a Vf of 85v% or higher.

[0092] [Process for manufacturing preforms]

[0093] In the process of producing a preform in the manufacturing method of the present invention, the forming material of the preform is first prepared as described below. One or more powders are selected from the specific radiation shielding powder group previously described in the present invention, and aluminum powder or the like, which is added as needed, is thoroughly mixed using a ball mill, a paddle mixer, or the like. For example, when using tungsten powder (specific gravity: 19.3) and boron carbide powder (specific gravity: 2.52) with different specific gravities as radiation shielding powders, and aluminum powder (specific gravity: 2.7) is mixed as needed, a V-type mixer or a drum rotary mixer with a rotating mixing container is preferably used to prevent separation caused by the difference in specific gravity.

[0094] Next, a non-powdered silica-based binder is added to a mixture of the radiation shielding powder specified in the present invention and aluminum powder or the like, which is used as needed, and the mixture is then shaped. The resulting shaped body is then fired at a temperature of 300°C or higher and 900°C or lower to produce a porous shaped body (preform). These structures will be described below.

[0095] (Non-powder silica-based adhesive)

[0096] As a non-powdered silica-based binder constituting the present invention, in the case of any composite, a liquid silica-based binder (hereinafter also referred to as "liquid silica-based binder") is suitable, for example. The liquid silica-based binder is at least one selected from the group consisting of water glass (sodium silicate), colloidal silica, liquid silicone resin or a silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed from silica and organic matter that undergoes heat curing at a temperature below 900°C. The amount of these liquid silica-based binders added is determined according to the amount of radiation shielding powder, etc., used.

[0097] The appropriate amount of the liquid silica-based binder used in this invention, as described above, is approximately 0.5 to 10 parts by weight (converted to SiO2) relative to 100 parts by weight of the mixture powder containing radiation shielding powder such as aluminum powder as needed. According to the researchers of this invention, amounts less than 0.5 parts by weight result in low strength as a binder, which is therefore undesirable. On the other hand, even amounts exceeding 10 parts by weight function as a binder, but since the relative content of radiation shielding powder becomes low, it is unnecessary to add more than that.

[0098] The aforementioned liquid silica-based binders, such as tetraethyl or ...

[0099] By using tetraethyl orthosilicate containing silica, which transforms into SiO2 through thermal decomposition at low temperatures, silicone resin, water glass that also generates SiO2 at low temperatures, or colloidal silica containing ultrafine SiO2 dispersed in a solvent, it is possible to uniformly mix the binder and the radiation shielding powder. According to the researchers of the present invention, these silica-based binders are ultrafine powders. Furthermore, in the manufacturing method of the present invention, ultrafine SiO2 powder is uniformly generated from a state of uniform mixing at the molecular level within the preform, through an amorphous (non-crystalline) state, thus enabling the fabrication of a robust preform.

[0100] In the next step, the mixed powder of raw materials prepared above as the preform is formed / fired to produce a preform. Importantly, during the manufacture of the composite of the present invention, the radiation shielding powder must not decompose in order to avoid compromising the target function of the invention. Therefore, in the manufacturing method of the present invention, the firing temperature for forming / firing the preform must be low, below 900°C. For this purpose, the liquid silica-based binder used in the present invention fully exerts its effect as a binder even at temperatures below 900°C. Here, in the case of using silica-based binders in conventional ceramic manufacturing processes, submicron to several μm silica powder is typically used. Furthermore, in the prior art, when silica powder is used as a binder, firing at temperatures above 1100°C is necessary to achieve the strength of the resulting preform. However, the above-described prior art cannot be applied to the composite of the present invention. In the manufacturing method of this invention, when forming / firing to produce a preform, or when molten aluminum is impregnated into the produced preform, it is necessary to prevent the decomposition of the radiation shielding powder; therefore, a low temperature of 900°C or below is required. This will be described later.

[0101] In the manufacturing method of the present invention, a small amount of the liquid silica-based binder described above is added each time to a radiation shielding powder that may contain one or more of the aforementioned aluminum powders, which are uniformly mixed. Preferably, a Henschel mixer with high-speed shearing and stirring, or a mixer with a birdcage-shaped rotating body made of fine iron wire, is used. Furthermore, when adding the liquid silica-based binder, an appropriate amount of organic binder such as PVA or PVB may be added as needed without compromising the purpose of the present invention.

[0102] Next, using the mixture of radiation-shielding powder obtained by adding liquid silica-based binder as described above and mixing it uniformly, a molded body is produced by conventional pressing, hammering, CIP molding, or other methods.

[0103] In the manufacturing method of the present invention, the molded body obtained as described above is heated and sintered at a temperature of 300°C to 900°C and then cured to produce a preform. According to the research of the present inventors, the effect of the silica-based binder cannot be achieved at temperatures below 300°C, and a strong preform cannot be produced. On the other hand, at temperatures above 300°C, the effect of the added liquid silica-based binder can be achieved, and a strong preform can be produced. Furthermore, for the following reasons, in the manufacturing method of the present invention, the preform must be produced by sintering at a temperature below 900°C.

[0104] For example, when using boron carbide (B4C) as a radiation shielding powder, there is a concern that it may decompose into BO and CO2 at high temperatures in air; therefore, sintering must be carried out at a temperature below 900°C. Furthermore, when using boron carbide (B4C) as the forming material of a preform, and adding aluminum powder or the like as needed, Al4C3, sometimes formed from a portion of the boron carbide and aluminum, undergoes the following decomposition reaction at high temperatures. The Al4C3 produced in this reaction is unstable and reacts with moisture in the air, decomposing into Al(OH)3 and CH3. However, it is undesirable for Al4C3 to remain in the composite.

[0105] B4C + Al → Al4C3 + B

[0106] Furthermore, when barium sulfate is used as a radiation shielding powder, BaSO4 decomposes into BaO and SO2 at high temperatures, so high-temperature firing is not preferable. Additionally, the decomposition reaction described below may sometimes occur, therefore firing at temperatures exceeding 900°C is not preferred.

[0107] Al + BaSO4 → BaO + Al2O3 + SO (gas)

[0108] When using tungsten (W) as the radiation shielding powder, tungsten turns into WO3 at high temperatures in air, which impairs the effectiveness of adding silica-based binders, making it undesirable. According to the researchers of the present invention, in order to suppress the aforementioned series of reactions, the firing temperature of the molded article is preferably set to a temperature below 900°C. This suppresses decomposition and oxidation, enabling the manufacture of a stable preform of the radiation shielding powder.

[0109] <Composite Manufacturing Process>

[0110] Next, in the first manufacturing method of the present invention, a first composite having radiation shielding function is manufactured. The first composite is formed by impregnating / filling molten aluminum into all the voids of a porous molded body (preform) as described above under high pressure and then solidifying it. Furthermore, in the second manufacturing method of the present invention, a second composite having radiation shielding function is manufactured. The second composite is formed by vacuum impregnating a liquid organic-inorganic sealing agent into part or all of the voids of the preform, or by impregnating under pressure after vacuum impregnation, and then solidifying it at a temperature of 300°C or higher and 900°C or lower. Hereinafter, the manufacturing processes of the first composite or the second composite in the first manufacturing method or the second manufacturing method of the present invention will be described respectively.

[0111] [First Manufacturing Method]

[0112] In the first manufacturing method of the present invention, a composite material with radiation shielding function is prepared. This composite material uses aluminum as a matrix and contains powder with radiation shielding effect in a total volume range of 3% to 85% or less. Specifically, using a preform prepared as previously described, a molten metal selected from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and other metals (in this specification, substances containing such molten metals are also referred to as "molten aluminum," represented by aluminum and aluminum alloys) is cast into the preform at a temperature of 300°C to 900°C. The molten aluminum is then held at a high pressure of 20 MPa to 200 MPa for 3 to 15 minutes, for example, about 3 to 5 minutes, to allow the molten aluminum to permeate the entire void space of the preform. Afterward, the molten aluminum is immediately removed and cooled within 15 minutes of the start of permeation, resulting in the first composite material. More specifically, the composite is performed according to the steps described below.

[0113] The temperature of the molten aluminum used for impregnation is set above the melting temperature of each metal, typically about 50°C to 150°C higher than the melting point of each metal. For example, in the case of aluminum or aluminum alloys, the temperature is set to around 700°C to 800°C. Furthermore, when using low-melting-point alloys, it is appropriate to set the temperature to around 350°C to 500°C for solder alloys and around 450°C to 550°C for zinc alloys. Regardless of the type of molten metal used, in this invention, it is necessary to impregnate the voids of the preform prepared as described above with a molten metal at a temperature below 900°C.

[0114] First, in order to allow for the impregnation of molten aluminum, the previously prepared preform is preheated at a temperature of 300°C or higher but below 900°C. When the preheating temperature of the preform is below 300°C, the molten aluminum to be impregnated will rapidly cool and solidify during the casting / impregnation process described below, making it difficult to impregnate the entire void space of the preform, which is therefore undesirable. According to the researchers of the present invention, if the preheating temperature of the preform is 300°C or higher, the molten aluminum will impregnate the entire void space of the preform. However, at preheating temperatures exceeding 900°C, for example, boron carbide, sometimes used as a radiation shielding powder, reacts with the aluminum supplied for impregnation to form Al4C3, or BaSO4 undergoes a decomposition reaction, which is also undesirable.

[0115] Next, the process of impregnating a preformed body preheated as described above with molten aluminum and then laminating it will be explained with reference to FIG1. ​​Specifically, the preformed body prepared as described above is impregnated with molten aluminum and then laminated in the following order.

[0116] (1) such as Figure 1A As shown, a preform 2, preheated at 300°C to 900°C, is placed on the lower punch 4 of a press 10, which has been preheated at approximately 200°C to 300°C using a burner or similar device. Next, molten aluminum 1, melted at 300°C to 900°C, is cast in the press 10. If aluminum metal or an aluminum alloy is used, a molten aluminum melt at 700°C to 900°C is preferred.

[0117] (2) Next, as Figure 1B As shown, the upper punch 5 of the press 10 is placed and a load is applied. The upper punch 5 of the press 10 is loaded to make the pressure of the molten aluminum 1 reach 20 MPa to 200 MPa, causing the molten aluminum 1 to permeate the pores (voids) of the preform 2. At this time, the loaded state is maintained for 3 to 15 minutes with the aim of permeating the voids of the preform 2 with the molten aluminum 1.

[0118] (3) Next, as Figure 1C As shown, immediately after impregnation of the preform 2 (specifically, within approximately 15 minutes from the start of molten aluminum impregnation), the composite 3, impregnated with molten aluminum 1, is lifted from the bottom of the lower punch 4 and immediately removed. Then, the composite 3 is cooled for as short a time as possible to solidify the impregnated molten aluminum 1.

[0119] The following explains aspects to be noted in the impregnation process of the aforementioned series of molten aluminum 1 into the preform 2, which is a porous molded body. First, when using aluminum metal or aluminum alloy, if the casting temperature is below 600°C, the molten aluminum may solidify within a short time without penetrating the entire porous structure of the preform, which is undesirable. On the other hand, at casting temperatures exceeding 900°C, as mentioned above, for example, boron carbide (B4C) in radiation shielding powder decomposes to form Al4C3, or if barium sulfate (BaSO4) is used in the radiation shielding powder, BaSO4 may thermally decompose, which is also undesirable.

[0120] In the first manufacturing method of the present invention, the impregnation pressure of the molten aluminum is set to 20 MPa or more and 200 MPa or less. Below 20 MPa, the pressure is too low, and sometimes the molten aluminum does not impregnate the entire void space of the preform, which is therefore undesirable. Sufficient impregnation is achieved at 20 MPa or more and 200 MPa or less, so it is not necessary to apply pressure exceeding 200 MPa. According to the research of the present inventors, good impregnation can be achieved, for example, even at a pressure of around 100 MPa.

[0121] After holding the composite obtained by high-pressure impregnation for 3 minutes, preferably about 5 minutes, it should be removed from the mold within at least 15 minutes from the start of the impregnation with molten aluminum. If the composite obtained by high-pressure impregnation of molten aluminum into the voids of the preform is held in the mold for a longer period than 15 minutes, boron carbide may sometimes react with aluminum to form Al4C3, or BaSO4 may decompose, resulting in a composite that violates the provisions of this invention, and therefore must be avoided.

[0122] The above description illustrates a method for high-pressure impregnation of molten aluminum into a porous preform using a high-pressure press, as shown in Figure 1. However, the present invention is not limited to this; any structure capable of casting molten aluminum into the preform at a pressure of 20 MPa or higher is acceptable. For example, a die-casting machine or a squeeze casting machine can also be used. It should be noted that the cooled composite is surrounded by aluminum, and therefore is removed by machining. According to the first manufacturing method of the present invention described above, a first composite with a stable and dense structure possessing radiation shielding function, containing 3% to 85% vf of radiation shielding powder, can be produced.

[0123] [Second Manufacturing Method]

[0124] In the second manufacturing method of the present invention, a second composite having a radiation shielding function can be prepared. The second composite is configured as follows: it is composited in a state in which a cured product derived from a liquid organic-inorganic sealing agent has a void volume of 100% or more relative to the preform obtained as described above, and contains powder having a radiation shielding effect in a total volume range of 3% or more and 85% or less.

[0125] (Liquid organic-inorganic sealing agent)

[0126] In the second manufacturing method of the present invention, as a liquid organic-inorganic sealing agent that imparts the characteristics of the second manufacturing method, it is preferable to use, alone or in combination, three liquid compounds listed below that have a low viscosity of less than 50 mPa·s and contain more than 30% by mass of non-volatile components.

[0127] (1) The first type

[0128] Liquid tetraethyl or methyl silicate [Si(OC2H5)4] containing alcohol Si bonds, or liquid oligomers formed by partial hydrolysis of tetraethyl or methyl silicate to form dimers or tetramers, as well as liquid alkoxides such as methyl silicate [Si(OCH3)4] and their liquid oligomers formed by partial hydrolysis, are adjusted to form alkoxide compounds with a non-volatile content of 30% by mass or more.

[0129] (2) The second type

[0130] The following general formula refers to a liquid organosilicon or its derivative thereof with a siloxane bond as the main chain, wherein the non-volatile component dissolved in a solvent is adjusted to be more than 30% by mass. In the general formula, R represents an organic group such as methyl, ethyl, vinyl, phenyl, or acetyl. Specifically, for example, liquid compounds such as silicone oil and / or organosilicon adhesives dissolved in organic solvents can be used.

[0131]

[0132] (3) The third type

[0133] As alkoxysilane derivatives, liquid alkoxysilane compounds undergo a condensation reaction with moisture in the air as shown in the following reaction formula to generate organosilicon-oxygen compounds (Si-OR). For example, compounds such as the single-component room-temperature curing sealing agent described in Japanese Patent No. 3816354 can be used. As such products, commercially available products such as Permeate (registered trademark, manufactured by D&D CORPORATION) can be used.

[0134]

[0135] (Combined approach)

[0136] In the second manufacturing method of the present invention, a second composite having a radiation shielding function is obtained. The second composite is configured such that a solidified product of an organic-inorganic sealing agent derived from a liquid is present in 25% or more of 100% of the voids of a preform made by using radiation shielding powder as a raw material. As a specific step, a liquid organic-inorganic sealing agent containing at least 30% by mass of non-volatile components and with a viscosity of less than 50 mPa·s is vacuum impregnated into the voids of a porous preform (preform). Alternatively, after vacuum impregnation, the preform is pressurized and impregnated at a pressure of less than 10 atmospheres, then heated to a temperature of 300°C to 900°C. This process ensures that the solidified product of the aforementioned liquid organic-inorganic sealing agent and / or the heat-treated product of the liquid organic-inorganic sealing agent remain at least 25% by volume (1 / 4) of the total voids, assuming the total voids of the preform are 100% by volume. This results in the composite of the radiation shielding powder with the components derived from the liquid organic-inorganic sealing agent. That is, the total voids account for approximately 15% to 40% by volume in the preform, thus the components derived from the organic-inorganic sealing agent remain at least 1 / 4, or 4% to 10% by volume, within the voids. In other words, the resulting composite has the following composition: the sintered product comprising the radiation shielding powder mixture constituting the preform accounts for as high as 60% to 85% of the composition, the component derived from the organic-inorganic sealing agent accounts for 4% to 10% or more of the composition, and the remainder is voids. It should be noted that, in this invention, for the amount of liquid silica-based binder mixed in the radiation shielding powder, it is preferable to add approximately 0.5 to 10 parts by mass of liquid silica-based binder (calculated as SiO2) relative to 100 parts by mass of the radiation shielding powder, thus obtaining a composite with a high proportion of radiation shielding powder. These aspects also apply to the first composite obtained by the first manufacturing method.

[0137] In the liquid organic-inorganic sealing agent of the previous example used in the second manufacturing method of the present invention, a low-viscosity organic-inorganic sealing agent with a viscosity of 50 mPa·s or less is preferably used, so as to facilitate impregnation into the preform. When the viscosity exceeds 50 mPa·s, the organic-inorganic sealing agent is difficult to impregnate into the details of the preform, so there is a concern that a strong composite may not be obtained. In addition, it is important that the liquid organic-inorganic sealing agent contains more than 30 wt% of non-volatile components relative to 100 wt% of the sealing agent. In the second manufacturing method of the present invention, after the organic-inorganic sealing agent is impregnated into the voids in such a way that it is present in at least 25 wt% of the voids relative to 100 wt% of the preform, the mixture is heated to 200°C to 900°C to composite the radiation shielding powder with the organic-inorganic sealing agent. That is, by heating at the above temperature, the liquid organic-inorganic sealing agent that has penetrated into the pores of the preform becomes a solid, a solidified product of the liquid organic-inorganic sealing agent or a heat-treated product of the liquid organic-inorganic sealing agent, and remains in the pores of the preform.

[0138] As previously explained, the preform used in the manufacturing method of the present invention for producing the composite is a porous body with approximately 15 to 40 vol% of voids relative to 100 vol% of the preform as a whole. Therefore, the second composite obtained by the second manufacturing method of the present invention, which involves impregnating the preform with a liquid organic-inorganic sealing agent and then performing heat treatment, is a composite in which, when the overall voids of the preform are set to 100 vol%, the cured product of the liquid organic-inorganic sealing agent and / or the heat-treated product of the liquid organic-inorganic sealing agent constitutes at least 25 vol% of the preform. This means that the second composite obtained by the second manufacturing method of the present invention is a composite in which the cured product of the liquid organic-inorganic sealing agent and / or the heat-treated product of the liquid organic-inorganic sealing agent are fixed in a portion (25 vol% or more) or all of the voids of the preform.

[0139] According to the research of the inventors, when the amount of the cured liquid organic-inorganic sealing agent and / or the heat-treated liquid organic-inorganic sealing agent in the composite obtained by the second manufacturing method of the present invention is less than 25% of the total 100% of the voids in the preform, it is impossible to produce a robust and practically effective composite with radiation shielding function. Furthermore, as a preferred configuration of the second composite obtained by the second manufacturing method of the present invention, in addition to the above, examples can be made where the amount of the cured liquid organic-inorganic sealing agent and / or the heat-treated liquid organic-inorganic sealing agent remaining in the voids is about 5% or more of the total 100% of the preform. For example, when the voids account for 20% of the preform, 25% (1 / 4), that is, 5% of the total 100% of the preform, becomes the organic-inorganic sealing agent. In the above example, the calcined mixture comprising the radiation shielding powder constituting the preform accounts for 80% of the total. As described above, the amount of liquid silica-based binder mixed in the radiation shielding powder during preform fabrication is preferably about 0.5 to 10 parts by mass (converted to SiO2) of liquid silica-based binder per 100 parts by mass of radiation shielding powder. Therefore, the total amount of radiation shielding powder, silica-based binder, and organic-inorganic sealing agent constituting the composite described above exhibits a ratio as high as 70 to 79.5 vol%, resulting in a robust composite.

[0140] In the second manufacturing method of the present invention, the silica-based binder required for producing the preform and the liquid organic-inorganic sealant impregnated in the obtained preform can also be the same compound. However, the liquid organic-inorganic sealant used when impregnating the voids of the preform needs to penetrate the preform, ultimately leaving the impregnated organic-inorganic sealant in a solidified state. Therefore, it needs to be low-viscosity with a viscosity of 50 mPa·s or less and contain more than 30 wt% of non-volatile components. Therefore, any silica-based binder that meets these conditions can be used.

[0141] As described above, in the second manufacturing method of the present invention, the preform impregnated with a liquid organic-inorganic sealing agent is heat-treated at a temperature of 200°C or higher and 900°C or lower. The heating temperature is set to 200°C or higher for the following reasons: This is because by setting the heating temperature to 200°C or higher, the siloxane bonds, oligomers of ethyl silicate, or liquid alkoxysilane compounds that form organosilicon-or-organic compounds (Si-OR) in the compound used as the liquid organic-inorganic sealing agent are decomposed by heating, allowing them to function as silica-based binders or Si-OR-based organic-inorganic binders, thereby strengthening the preform. Furthermore, setting the heating temperature to 900°C or lower is to prevent the decomposition or oxidation of radiation-shielding powders containing B4C, BaSO4, etc., constituting the preform.

[0142] Reference Figure 2 A summary of the steps of the second manufacturing method of the present invention will be described. Figure 2 The 30 in the figure refers to the pressure vessel used in the second manufacturing method of the present invention. A preform 32, in a state prior to the impregnation of the organic-inorganic sealing agent 31 into the voids, is placed in an inner container 34 located within the pressure vessel 30. The opening and closing fixture 33 of the pressure vessel 30 is closed, and a vacuum pump (not shown) is used to depressurize the pressure vessel 30 through a depressurization port 36 located within it. When the pressure vessel 30 reaches approximately zero pressure after depressurization, the organic-inorganic sealing agent 31 is gradually added from the organic-inorganic sealing agent injection container 35 into the inner container 34. At this time, the amount of organic-inorganic sealing agent 31 added is predicted in advance, indicating the amount by which the organic-inorganic sealing agent 31 will impregnate the entire preform 32, and thus the entire preform 32 will be impregnated.

[0143] As described above, after adding the organic-inorganic sealing agent 31, a vacuum is maintained for approximately 5-10 minutes to allow the organic-inorganic sealing agent 31 to permeate the voids in the preform 32. After permeation, atmospheric pressure is gradually introduced into the pressure-reducing vessel 30. Once the pressure-reducing vessel 30 reaches atmospheric pressure, compressed air from a compressor (not shown) is gradually introduced through the pressurization port 37 to a pressure reduced to approximately 10 atmospheres. After pressurization to approximately 4 atmospheres, the pressure is maintained for approximately 5-10 minutes to allow the organic-inorganic sealing agent 31 to permeate the preform 32.

[0144] Afterwards, the compressed air in the pressure vessel 30 is gradually released to atmospheric pressure. Then, the preform containing the solidified material of liquid organic-inorganic sealing agent fixed in the gap and / or the heat-treated material of the liquid organic-inorganic sealing agent is taken out, slowly dried, and heated to 300~400℃ to obtain a second composite material with radiation shielding function.

[0145] [Example]

[0146] Next, examples and comparative examples will be provided to further illustrate the invention in detail. The invention will be specifically described using examples and comparative examples of two manufacturing methods: one involving impregnating molten aluminum into the voids of a porous molded body (preform) and compounding it, and the other involving impregnating an organic-inorganic sealing agent into the voids of a porous molded body (preform) and compounding it. The porous molded body (preform) is a molded / fired product formed from a mixture containing a non-powdered silica-based binder in radiation shielding powder. The invention is not limited to any of the following examples. Unless otherwise specified, % refers to volume %. Due to the specific circumstances requiring radiation treatment in the measurement of shielding effectiveness, the radiation shielding efficiency of the composites of Examples 1 to 3 was measured by an external testing institution. The radiation shielding efficiency values ​​measured by the external institution showed higher values ​​than those of conventional blanks.

[0147] <An example of a method for impregnating a preform with molten aluminum - Preparation of the first composite>

[0148] [Example 1]

[0149] 450g of B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16μm was mixed in a V-type mixer for 30 minutes. 5g of ethyl silicate as a liquid binder was added to the mixed powder, and the mixture was then placed into a Henschel mixer that applies shear force to the powder and stirred at high speed for 15 minutes until uniformly mixed. The resulting mixture was then placed into a 100mm × 100mm mold, covered, and stirred at 160kgf / cm². 2 The preform was pressed and shaped under pressure. It was then placed in a firing furnace and heated to 400°C at a rate of 50°C / hour, and held at 400°C for 3 hours, followed by natural cooling. The resulting sintered body (preform) had a shape of 100mm × 100mm × 35mm and a weight of 449g. Based on the true specific gravity of boron carbide (B4C) of 2.51, the preform had a loose specific gravity of 1.31, a boron carbide filling rate (Vf) of 52%, and a porosity of 48%. The preform was heated at a rate of 100°C / hour and held at 500°C, remaining in this heated state in preparation for subsequent aluminum infiltration using a high-pressure press.

[0150] A 300φ inner diameter mold fitted to a high-pressure press is heated to approximately 250°C using a burner. Then, the preform, waiting in the heated state, is placed into the mold of the press, and molten aluminum at 800°C is poured into the mold for high-pressure casting. Figure 1A and Figure 1B As shown, molten aluminum 1, melted at 800°C, is injected into the aforementioned mold containing the preform 2. Immediately afterward, the upper punch 5 of the press 10 is lowered, and a load is applied to the upper punch 5 to make the pressure of the molten aluminum 1 reach 70 MPa. As mentioned above, the inner diameter of the mold is 300 φ, therefore the load on the press 10 is equivalent to approximately 500 t.

[0151] After maintaining the above-mentioned load for 5 minutes, remove the upper punch 5 and immediately lift the lower punch 4 to raise the impregnated body (composite) 3 to the upper side of the press (refer to...). Figure 1C The composite 3 is then allowed to cool naturally. After cooling in a manageable manner, the solidified aluminum surrounding the composite 3 is removed by machining, and the composite 3 is then removed.

[0152] The specific gravity of the extracted composite was measured to be 2.61. This value is approximately consistent with the calculated value where aluminum is completely impregnated into the voids of the molded body, thus concluding that the extracted composite is a dense composite of B4C and aluminum. A lightweight composite with a specific gravity of 2.61 can be produced by achieving a high content (volume filling rate) of up to 52 vol% of lightweight boron carbide (specific gravity 2.52). Furthermore, X-ray diffraction analysis of a portion of the obtained composite did not confirm the formation of Al4C3 due to B4C decomposition.

[0153] For the B4C blank with a volume filler ratio (Vf) of 52% and a thickness of 35 mm obtained above, an external testing agency was commissioned to measure its radiation shielding effect. The results showed a high shielding effect of 61% against the neutron radiation Cf252 of the californium (Cf) isotope. Furthermore, a bending test was conducted on the composite of this embodiment based on JIS-R1061, resulting in a high strength of up to 183 MPa. These findings indicate that the composite obtained in this embodiment is a useful blank that effectively combines the lightweight B4C powder used in the raw material in its original state without decomposition, thus retaining all the properties of B4C powder.

[0154] [Example 2]

[0155] 230 g of B4C powder #180 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 70 μm and 260 g of B4C powder #800 with an average particle size of 16 μm, the same as used in Example 1, were mixed in a V-mixer for 30 minutes. 15 g of ethyl silicate as a liquid binder was then added to the mixed powder, and the mixture was mixed in the same manner as in Example 1 using a Henschel mixer for 15 minutes.

[0156] The obtained mixed raw materials were pressed and fired using the same method as in Example 1 to produce a preform with a shape of 100mm × 100mm × 26mm, a bulk density of 1.66, a B4C filling rate (Vf) of 66%, and a porosity of 34v%. The obtained preform was placed into a mold of a high-pressure press using the same method as in Example 1, allowing molten aluminum at 800°C to impregnate it under high pressure. Afterward, it was allowed to cool naturally using the same method as in Example 1, removing the solidified aluminum around the composite.

[0157] The composite has a specific gravity of 2.57, which is approximately consistent with the calculated value when aluminum is impregnated into the voids of the preform. It is a dense composite composed of B4C and aluminum. Furthermore, X-ray diffraction of the composite surface was performed using the same method as in Example 1. As a result, similar to the case in Example 1, no formation of Al4C3 or the like was observed. As described above, by combining B4C powders with different average particle sizes as raw materials, it is possible to produce a composite with a B4C powder filling rate higher than the 66v% in Example 1. Furthermore, it is possible to produce a lightweight composite with a specific gravity of 2.57 despite a high B4C filling rate.

[0158] For the B4C blank with a volume filler ratio (Vf) of 66v% and a thickness of 26mm obtained above, an external testing agency was commissioned to measure its radiation shielding effect. The results showed a high shielding effect of 31% against the neutron radiation Cf252 of the californium (Cf) isotope. Furthermore, a bending test was conducted on the composite of this embodiment based on JIS-R1061, resulting in a high strength of up to 193 MPa. These findings indicate that the composite obtained in this embodiment is a useful blank that effectively combines the lightweight B4C powder used in the raw material in its original state without decomposition, thus retaining all the properties of B4C powder.

[0159] [Example 3]

[0160] 820 g of barium sulfate (BaSO4) powder, namely A-200 (trade name, manufactured by Takehara Chemical Industrial Co., Ltd.), with an average particle size of 15 μm, was uniformly mixed using the same method as in Example 1. As a liquid binder, a silicone-based resin solution with a mass concentration of 20 wt% was prepared by dissolving soluble silicone resin KR-200 (manufactured by Shin-Etsu Chemical Co., Ltd.) in ethanol. Then, 50 g of the prepared silicone-based resin solution was added to the mixed BaSO4 powder, and the mixture was stirred at high speed using a Henschel mixer, as in Example 1.

[0161] The preform, prepared using the same methods and steps as in Example 1, has a shape of 100mm × 100mm × 28mm, a bulk density of 2.92, and a BaSO4 filling rate of 65 v%. Next, using the same method as in Example 1, molten aluminum at 800°C was high-pressure impregnated into the preform and processed to obtain the composite. The composite has a specific gravity of 3.86, which is approximately consistent with the calculated (theoretical) value, confirming that it is a dense composite composed of BaSO4 and aluminum.

[0162] For the BaSO4 blank with a volume filler ratio (Vf) of 65v% and a thickness of 28mm obtained above, an external testing institution was commissioned to measure its radiation shielding effect. The results showed a 35% shielding effect against cesium (Cs) gamma rays (Cs137) and a shielding effect of up to 99.5% against X-rays at 150kV. Furthermore, a bending test was conducted on the composite of this embodiment based on JIS-R1061, resulting in a high strength of up to 193MPa. These results demonstrate that the composite obtained in this embodiment is a useful blank that effectively combines the lightweight and radiation-shielding BaSO4 powder used in the raw material in its original state without decomposition, and effectively retains the properties of BaSO4 powder.

[0163] [Example 4]

[0164] 250g of B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16μm and 270g of aluminum powder WA-100 (manufactured by Yamaishi Metal Co., Ltd.) with an average particle size of 18μm were used as raw material powders and were uniformly mixed using the same method as in Example 1. 10g of liquid ethyl silicate (manufactured by Colcoat Co., Ltd.) was added as a binder, and the mixture was stirred at high speed using a Henschel mixer as in Example 1.

[0165] The preform, prepared using the same method and steps as in Example 1, has a shape of 100mm × 100mm × 33mm, a loose specific gravity of 1.30, and a total filling rate of 50v% for B4C powder and aluminum powder (Al powder). Next, using the same method as in Example 1, molten aluminum melted at 800°C was high-pressure impregnated into the preform, and the composite was processed to remove it. The specific gravity of the composite in this example is 2.65, which is approximately consistent with the calculated value of molten aluminum impregnating all the voids in the preform.

[0166] The volume ratio of B4C powder to Al powder in the two raw material powders is approximately 1:1, therefore, about 50 v% of the preform is aluminum powder. Thus, the amount of aluminum in the resulting composite, including the aluminum infiltrated into the preform, is 75 v%, meaning that the composite composition consists of 75 v% aluminum powder and the remaining 25 v% B4C powder. From the above, it can be confirmed that by mixing aluminum powder in an appropriate amount into the raw materials of the preform, the concentration of the radiation shielding powder can be controlled. Furthermore, under the above conditions, by using B4C powder in the raw materials of the preform, a lightweight composite with a specific gravity of 2.65 can be produced. Additionally, a bending test was conducted on the composite of this embodiment based on JIS-R1061, resulting in a high strength of up to 182 MPa.

[0167] [Example 5]

[0168] To prepare the raw material for the preform, 280g of BaSO4 powder A-200 (trade name, manufactured by Takehara Chemical Industrial Co., Ltd.) with an average particle size of 15μm and 395g of aluminum powder WA-100 (manufactured by Yamaishi Metal Co., Ltd.) with an average particle size of 18μm were added to a 20w% solution of silicone resin KR-200 dissolved in ethanol, the same solution used in Example 3. This raw material was stirred at high speed using a Henschel mixer, as in Example 1.

[0169] Subsequently, a preform with a shape of 100mm × 100mm × 38mm was produced by the same method and steps as in Example 1, with a bulk density of 1.77 and a total filling ratio (Vf) of 55v for BaSO4 powder and Al powder.

[0170] Next, using the same method as in Example 1, molten aluminum at 800°C was high-pressure impregnated into the preform obtained above and processed to remove the composite. The specific gravity of the prepared composite was 2.99, which is approximately consistent with the calculated value of the dense body. The composite of this example is as follows: 70 v% of the preform is aluminum powder, therefore, according to the total amount of aluminum impregnated, the composite contains 84 v% aluminum, and the remaining 16 v% is BaSO4 powder. Thus, the composite of this example, like the composite of Example 4, is an example where the concentration of the radiation shielding powder, i.e., barium sulfate powder, in the composite can be controlled by mixing aluminum powder into the raw materials of the preform. In addition, a bending test was conducted on the composite of this example based on JIS-R1061, and the result was a high strength of up to 212 MPa.

[0171] [Example 6]

[0172] 270 g of B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16 μm and 495 g of BaSO4 powder A-200 (trade name, manufactured by Takehara Chemical Industrial Co., Ltd.) with an average particle size of 15 μm were used as raw material powders and were uniformly mixed in the same manner as in Example 1. 15 g of liquid ethyl silicate (manufactured by Colcoat Co., Ltd.) as a binder was added, and the mixture was stirred at high speed using a Henschel mixer in the same manner as in Example 1.

[0173] Subsequently, a preform was prepared using the same method and steps as in Example 1, having a shape of 100mm × 100mm × 38mm, a bulk density of 2.00, and a total filling ratio (Vf) of 57v for B4C and BaSO4 powders.

[0174] Next, using the same method as in Example 1, molten aluminum at 800°C was impregnated and processed to obtain the composite. The specific gravity of the prepared composite was 3.16, which is approximately consistent with the calculated value of molten aluminum impregnation in the preform. The obtained composite had a B4C content of 28.5 v%, a BaSO4 content of 28.5 v%, and an aluminum content of 43 v%. As shown in this example, it was confirmed that a composite containing two radiation shielding powders can be manufactured using the manufacturing method of the present invention. Furthermore, a bending test was conducted on the composite of this example based on JIS-R1061, and the result showed a high strength of up to 199 MPa.

[0175] [Example 7]

[0176] 380g of B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16μm and 1270g of tungsten metal powder W-4 (manufactured by JAPAN NEW METALS CO., LTD.) with an average particle size of 3μm were uniformly mixed using the same method as in Example 1. At this time, water glass No. 4 (manufactured by Fuji Chemical Co., Ltd.) was diluted with water and added to a volume equivalent to 16g of SiO2. The mixture was then stirred at high speed using a Henschel mixer, as in Example 1. A preform was then prepared using the same method and steps as in Example 1. The preform had a shape of 100mm × 100mm × 32mm, a bulk density of 5.18, and a total filling ratio (Vf) of 68% for B4C and tungsten W.

[0177] Next, using the same method as in Example 1, molten aluminum at 800°C was high-pressure impregnated and processed to remove the composite. The specific gravity of the composite was 6.04, which is approximately consistent with the calculated value of molten aluminum impregnation in the preform. The resulting composite had a B4C content of 48.5 v%, a tungsten content of 20.4 v%, and an aluminum content of 32 v. Furthermore, a bending test was conducted on the composite of this example based on JIS-R1061, and the result showed a high strength of up to 192 MPa.

[0178] As shown in this embodiment, a composite containing two types of radiation shielding powders can be manufactured using the method of the present invention, similar to that in Embodiment 6. Furthermore, the composite in this embodiment contains 20.4 vol% tungsten, but has a specific gravity of 6.04, making it a much lighter composite than the 19.5 specific gravity of tungsten alone.

[0179] [Example 8]

[0180] Using the same B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16 μm as in Example 1, ethyl silicate binder was added in the same manner, followed by mixing, shaping, and firing to produce a preform measuring 100 mm × 100 mm × 35 mm with the same loose specific gravity of 1.31, a boron carbide filling rate (Vf) of 52%, and a porosity of 48 V%. The preform was then heated and left to stand at 400 °C.

[0181] Using the same method as in Example 1, the preform was placed in a mold with an inner diameter of 300 mm φ heated to 250°C, and a low-melting-point alloy (zinc alloy: ZDC2, specific gravity 6.8) molten at 500°C was cast. High-pressure impregnation was performed at 70 MPa (with a press load of 500 t), held for 10 minutes, and then immediately cooled to room temperature. The composite was then removed. The specific gravity of this composite was 4.18, indicating that it was a composite material with almost 100% impregnation of the low-melting-point zinc alloy. No decomposition reaction due to the presence of B4C was observed. Furthermore, a bending test was conducted on the composite of this example based on JIS-R1061, resulting in a high strength of up to 223 MPa.

[0182] [Compare Examples 1 and 2]

[0183] The same B4C powder used in Example 1 was mixed, and 2g of silica powder (manufactured by Yamamori Tsuchimoto INC.) with an average particle size of 1.2μm and 3g of water were added to 450g (net volume 182ml). The mixture was then inserted into a mold and pressed into shape, as in Example 1. The molded body was fired at different temperatures of 400°C or 800°C and then cooled. The resulting molded body lacked the strength of the preform at any firing temperature, making it unsuitable for handling and high-pressure impregnation with molten aluminum.

[0184] [Compare Examples 3 and 4]

[0185] The same B4C powder used in Example 1 was mixed, and 4g of Reolosil QS-9 (manufactured by Tokuyama Corporation) micronized silica powder with an average particle size of 22nm (22μm) and 64g of water were added to 450g (net volume 182ml). The prepared powder mixture was inserted into a mold and pressed into shape, similar to the procedure in Example 1. The resulting molded body was fired and cooled at different temperatures of 400°C and 800°C. The fired molded body lacked the strength of the preform at any firing temperature, making it unsuitable for handling and high-pressure impregnation with molten aluminum.

[0186] [Comparative Example 5]

[0187] A B4C preform was prepared using the same method as in Example 1. The preform was placed in a mold and cast using molten aluminum, similar to Example 1. However, in this comparative example, molten aluminum melted at over 900°C was used. After holding at over 900°C for 20 minutes, a composite was prepared using the same method as in Example 1. The surface of the composite was processed, resulting in a blackened surface. Therefore, a portion was removed and investigated by X-ray diffraction. The results showed that, in addition to the main raw material B4C, small peaks of Al4C3 were identified at 2θ = 31.8°, 35.8°, 40.1°, and 55°. This confirms that in the case of the composite in this comparative example, if the composite is held at a high temperature for a long time in the mold, the B4C of the preform becomes partially decomposed, and the composite cannot be in a good state.

[0188] [Comparative Example 6]

[0189] 890 g of BaSO4 powder A-200 (trade name, manufactured by Takehara Chemical Industrial Co., Ltd.), with an average particle size of 15 μm, used in Example 5, was uniformly mixed using the same method as in Example 1. Then, 50 g of a 20 w% solution of silicone resin KR-200 dissolved in ethanol, used in Example 3, was added and stirred at high speed using a Henschel mixer, just as in Example 1.

[0190] The preform, prepared using the same method and steps as in Example 1, has a shape of 100mm × 100mm × 33mm and a BaSO4 filling rate of 60% v%. Next, it is placed in a mold using the same method as in Example 1, impregnated with molten aluminum at 950°C, and processed. The composite is then removed. The surface is processed and visually observed, revealing numerous pores. This is believed to be due to the decomposition of BaSO4 into BaO and SO2 upon heating at high temperatures.

[0191] Table 1 summarizes the preparation conditions of the preforms in Examples 1-8 and Comparative Examples 1-6, as well as the characteristics and evaluation of each composite obtained in Examples 1-8 and Comparative Examples 5 and 6. In Table 1, "present" or "absent" indicates whether decomposition was confirmed in the radiation shielding powder constituting each composite.

[0192]

[0193] <An example of a method for impregnating an organic-inorganic sealing agent into a preform - Preparation of a second composite>

[0194] Next, examples and comparative examples will be described for the second manufacturing method of the present invention, which involves impregnating a special liquid organic-inorganic sealant into the voids of a porous molded body (preform). Bending tests were conducted on the composites of the following examples for the following reasons: When the liquid organic-inorganic sealant is impregnated into the voids of the preform, components originating from the organic-inorganic sealant remain within the voids of the preform. Here, in the case of the second composite with the liquid organic-inorganic sealant impregnated into the voids of the preform, it is not necessary to impregnate all the voids of the preform as in the case of impregnation with molten aluminum, as previously described; a portion of the voids may remain. According to the research of the present inventors, in such a configuration, as long as the liquid organic-inorganic sealant accounts for more than 25% by volume of 100% of the voids of the preform before impregnation, the resulting composite also has sufficient strength and can be used as a building material such as a wall material or roofing material. In other words, if the resulting composite is subjected to a bending test to confirm its strength, it can be confirmed that a sufficient amount of cured organic-inorganic sealing agent and / or heat-treated organic-inorganic sealing agent remains in the voids of the preform. As described below, the composite of the embodiment has sufficient strength and is the configuration specified in this invention.

[0195] [Example 9]

[0196] Using the same type of materials as those used in the formulation of Example 1 described above, 270g of B4C powder #800 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 16μm was mixed, shaped, fired, and cooled using the same method to produce a preform weighing 262g with a shape of 100mm × 100mm × 20mm. The resulting preform has the following characteristics: a true specific gravity of 2.51 for boron carbide (B4C), a loose specific gravity of 1.31, a boron carbide filling rate (Vf) of 52v%, and a porosity of 48v%.

[0197] As an organic-inorganic sealing agent, Permeate HS-200 (trade name, manufactured by D&D Corporation, hereinafter referred to as Permeate), with a viscosity of 15.5 mPa·s, a specific gravity of 1.15, siloxane bonds, and a non-volatile content of 85 wt%, was used. It was used in… Figure 2The pressure vessel 30 shown in the schematic diagram is used to impregnate a preform 32 with Permeate, which is a liquid organic-inorganic sealing agent 31, as described below. The preform 32 obtained above is placed in an inner container 34 disposed within the pressure vessel 30, forming a state in which a weight (not shown) is placed so that it does not float. Permeate is then added to the inner container 34 via an organic-inorganic sealing agent injection container 35, so that the entire preform is impregnated with Permeate.

[0198] The entire pressure-reducing vessel 30 is evacuated to a vacuum level using a vacuum pump (not shown) via pressure-reducing port 36 and maintained for 10 minutes. Afterwards, the vacuum is released, allowing the pressure-reducing vessel 30 to return to atmospheric pressure. Then, air from a compressor (not shown) at 7 atmospheres is slowly introduced into the pressure-reducing vessel 30 to 4 atmospheres using a pressure-reducing device (not shown), pressurizing the entire pressure-reducing vessel to 4 atmospheres and maintaining this pressure for 5 minutes, allowing the permeate to impregnate the preform 32 under pressure.

[0199] Afterwards, the pressure vessel 30 was restored to atmospheric pressure, and the preform 32 was removed from the indoor container 34 and left to stand naturally for 24 hours. Then, it was heated at 400°C for 3 hours at a rate of 50°C / hour to produce a composite with radiation shielding function. Based on the measured specific gravity of the blank (composite), the composite is a blank with 52v% B4C, 30v% organic-inorganic sealing agent (62.5v% within the voids of the preform), and 18v% void space. The specific gravity of the obtained blank (composite) is summarized in Table 2.

[0200] For the blank (composite) with a volume filler ratio (Vf) of 52% and a thickness of 20 mm obtained above for B4C powder, an external testing institution was commissioned to measure its radiation shielding effect. The shielding effect of the neutron radiation Cf252 of the californium (Cf) isotope was measured, and the result showed a shielding effect of 30%, which is a high value. There are no examples of shielding materials that show such a high neutron radiation shielding effect with a thickness of 20 mm. This result indicates that the composite obtained in this embodiment is a useful blank that effectively combines the lightweight B4C powder used in the raw material in its original state without decomposition, and effectively retains the properties of B4C powder. On the other hand, a 3 mm × 4 mm × 40 mm test piece for measuring bending strength was made from the composite obtained above, and a bending test was conducted based on JIS-R1061. The result was a strength of 25 MPa. This value is about 5 to 10 times that of gypsum board and concrete board measured using the same method, thus confirming that it is a blank material that can be fully used for exterior wall materials and radiation storage containers.

[0201] [Example 10]

[0202] Using the same materials as in the formulation of Example 2, namely 230g of B4C powder #180 (manufactured by DOUJINSANGYO Co., Ltd.) with an average particle size of 70μm and 100g of B4C powder #800 with an average particle size of 16μm, a 100mm × 100mm × 20mm molded body was prepared using the same method as in Example 2. This molded body was fired at 400°C in the same manner as in Example 1, resulting in a preform with a weight of 235g and a bulk density of 1.66. The volume filler (Vf) of the B4C in the obtained preform was approximately 66v%, and the porosity was 32v%. Using the obtained preform, Permeate was vacuum impregnated in the same manner as in Example 8, and then heat-treated at 400°C to obtain a radiation shielding material with 66 v% B4C, 19 v% Permeate (organic-inorganic sealing agent) (59.4 v% in the voids of the preform), and 15% voids.

[0203] For the blank (composite) with a volume filler ratio (Vf) of 66v% and a thickness of 20mm obtained above-mentioned B4C powder, an external testing agency was commissioned to measure the radiation shielding effect. The shielding efficiency of the neutron radiation Cf252 of the californium (Cf) isotope was measured, and the result showed a shielding efficiency of 34%, which is a high value. In addition, a bending test piece was prepared in the same manner as in Example 8, and the bending strength was measured, showing a value as high as 41MPa.

[0204] [Example 11]

[0205] Using 240g of barium sulfate (BaSO4) powder A-200 (trade name, manufactured by Takehara Chemical Industrial Co., Ltd.), which is the same material used in the formulation of Example 3 with an average particle size of 15μm, it was uniformly mixed using the same method as in Example 1. As a binder, a silicone-based resin solution with a mass concentration of 20 wt% was prepared by dissolving a soluble silicone resin KR-200 (manufactured by Shin-Etsu Chemical Co., Ltd.) in ethanol. Then, 15g of the prepared silicone-based resin solution was added to the mixed BaSO4 powder, and the mixture was stirred at high speed using a Henschel mixer in the same manner as in Example 1 to obtain a mixed powder.

[0206] The mixed powder obtained above is placed into a 60mm φ mold, and then subjected to a pressure of 160kg / cm³. 2The material was pressed and shaped under pressure, and then heated at 400°C in the same manner as in Example 1 to form a preform with a diameter of 60 mm φ × 27.8 mm and a thickness of 235 g. The preform had a bulk density of 2.95, a BaSO4 content of 65 v%, and a porosity of 35 v%.

[0207] Next, a liquid organic-inorganic sealing agent was used in the preform obtained above to obtain a composite as described below. A tetraethyl orthosilicate oligomer manufactured by Colcoat Co, Ltd., containing 40 wt% SiO2 (converted from SiO2), was placed in a container to impregnate the preform obtained above. The tetraethyl orthosilicate was then impregnated into the preform under vacuum and pressure of 4 atmospheres. The impregnated body with the liquid organic-inorganic sealing agent was then removed from the container, placed in air for 48 hours, and then heat-treated at 400°C for 3 hours to obtain a composite with radiation shielding function, containing 65 wt% BaSO4, 10 wt% non-volatile SiO2 generated from tetraethyl orthosilicate (28.6 wt% in the voids of the preform), and the balance 23 wt%.

[0208] For the blank (composite) with a volume filler ratio (Vf) of 65v% and a thickness of 27.8mm obtained above from BaSO4 powder, an external testing institution was commissioned to measure its radiation shielding effect. The results showed a 36% shielding rate against γ-rays (Cs137) and a high shielding rate of 99.7% against X-rays at 150kV. Furthermore, bending test pieces were prepared using the same procedure as in Example 1, and the bending strength was measured, showing a high value of 28MPa, confirming that it is a material suitable for use as a structural component.

[0209] [Example 12]

[0210] In a mixture of 54g of B4C powder with an average particle size of 16μm and 110g of BaSO4 powder (A-200, trade name) with an average particle size of 15μm, which were used in the formulation of Example 6, 7g of ethyl silicate as a liquid binder was added. The mixture was then pressed and shaped as in Example 1, and fired at 400°C to obtain a preform weighing 165g with a shape of 60mm φ × 30mm and a bulk density of 1.93. The obtained preform had a B4C content of 29v%, a BaSO4 content of 29v%, and a porosity of 42v%.

[0211] use Figure 2The pressure vessel 30 shown and the liquid ethyl silicate as the organic-inorganic sealing agent 31 were operated in the same manner as in Example 8, immersing the preform 32 obtained above in the liquid ethyl silicate. After vacuum impregnation, it was heat-treated at 400°C to obtain a composite with radiation shielding function. The obtained composite had a B4C content of 29 v%, a BaSO4 content of 29 v%, a non-volatile SiO2 content of ethyl silicate of 17 v% (40.4 v% in the voids of the preform), and a void size of 25 v.

[0212] The blank (composite) obtained above, comprising B4C powder, BaSO4 powder, and a liquid organic-inorganic sealing agent, was commissioned to an external testing agency to determine its radiation shielding effectiveness. The results showed a 25% shielding rate against cesium (Cs) gamma rays (Cs137) and a high shielding rate of 98% against X-rays at 150 kV. Furthermore, bending test pieces were prepared using the same methods as in other embodiments, and the bending strength was measured, yielding a value as high as 32 MPa, confirming that the blank is suitable for industrial application as a structural component.

[0213] Table 2 summarizes the implementation methods of the specific powders used in the formation of the composites constituting Examples 9-12, the amounts of organic and inorganic sealing agents in the voids of the preforms and in the composites, and the radiation shielding effect.

[0214]

[0215] [Comparative Examples 7-10]

[0216] Test pieces were made from the preforms of Examples 9-12, which were prepared using the composites with the configurations shown in Table 2, without impregnation with the liquid organic-inorganic sealing agent and in a composite state. The flexural strength was measured in the same manner as in the Examples. The results are then summarized in Table 3. For comparison, the ratio of the flexural strength of each composite of Examples 9-12 is shown in parentheses. As shown in Table 3, it was confirmed that the composites of the Examples, which were formed by combining the organic-inorganic sealing agent with the preforms, significantly improved the flexural strength compared to the blanks of the Comparative Examples.

[0217]

[0218] [Comparative Example 11]

[0219] Using the same preform prepared in Example 9 with a specific gravity of 1.31, a B4C filling rate (Vf) of 52 v%, and a void fraction of 48 v%, a composite with an organic-inorganic sealing agent was prepared as described below to obtain the composite of Comparative Example 11. As the liquid organic-inorganic sealing agent, Permeate HS-200, with a viscosity of 15.5 mPa·s, a specific gravity of 1.15, and having siloxane bonds and a non-volatile content of 85 w%, was used. This was diluted with ethanol to adjust the non-volatile content to 20 w%. Then, after impregnating the liquid organic-inorganic sealing agent using the same steps as in Example 9, a heat treatment was performed to obtain the composite blank. According to the gravimetric analysis, this blank had a B4C content of 52 v%, an organic-inorganic sealing agent content of 8 v% (16.0 v% in the voids of the preform), and a void fraction of 36 v%. The flexural strength of this preform was also measured using the same method as in the example, and the result was a flexural strength of 11 MPa, which is not considered high. This is believed to be due to the low amount of organic-inorganic sealing agent present in the voids of the preform.

[0220] [Comparative Example 12]

[0221] Using the same preform prepared in Example 11 with a specific gravity of 2.95, a BaSO4 filling rate (Vf) of 65 v%, and a void content of 35 v%, a composite with an organic-inorganic sealing agent was prepared as described below to obtain the composite of Comparative Example 12. As the liquid organic-inorganic sealing agent, the liquid ethyl silicate oligomer solution used in Example 11 was diluted with water to form a solution with a non-volatile SiO2 content of 10 v%. Then, after impregnating the preform with the liquid organic-inorganic sealing agent using the same procedure as in Example 11, a heat treatment was performed to obtain the composite blank. According to the gravimetric analysis, this blank had a BaSO4 content of 65 v%, a non-volatile SiO2 content of 4 v% (11 v% in the voids of the preform) of ethyl silicate, and a void balance of 31 v%. The flexural strength of this blank was also measured using the same method as in the Example, and the result was a flexural strength of 9 MPa, which is low.

[0222] [Comparative Example 13]

[0223] Using the same preform prepared in Example 9 with a specific gravity of 1.31, a B4C filling rate (Vf) of 52 v%, and a void fraction of 48 v%, a composite with an organic-inorganic sealing agent was performed as described below to obtain the composite of Comparative Example 13. As the liquid organic-inorganic sealing agent, a silicone resin solution of KR220L (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) with a non-volatile content of 40 w% and a viscosity of 150 mPa·s dissolved in ethanol was used. The silicone resin solution was impregnated into the preform using the same procedure as in Example 9, and then heat-treated to obtain the composite blank. The obtained blank had a B4C Vf of 52 v%, a non-volatile SiO2 content of 3 v% generated from the silicone resin (6.2 v% in the voids of the preform), and a void fraction of 45 v%. The flexural strength of this blank was also measured using the same method as in the Example, and the result was a flexural strength of 6 MPa, which is low. The reason is believed to be that the high viscosity of the silicone resin solution did not fully penetrate into the preform, and the penetration amount of the organic-inorganic sealing agent was low.

[0224]

[0225] Explanation of reference numerals in the attached figures

[0226] 1: Molten aluminum

[0227] 2: Preform

[0228] 3: Composites impregnated with molten aluminum

[0229] 4: Lower punch

[0230] 5: Upper punch

[0231] 10: Press machine

[0232] 30: Pressure reducing vessel

[0233] 31: Organic-inorganic sealing agents

[0234] 32: Preform

[0235] 33: Opening and closing fixtures for pressure-reducing vessels

[0236] 34: Indoor containers

[0237] 35: Organic and inorganic sealing agents are added to the container.

[0238] 36: Pressure relief port

[0239] 37: Pressurization port

[0240] 38: Pressure gauge

Claims

1. A composite material with radiation shielding function, characterized in that, It is made by compounding powders with radiation shielding effect, and contains the powder in a total range of more than 3% by volume and less than 85% by volume. The composite is composed of the following: it is formed by impregnating / filling all the voids of a porous molded body (preform) with molten low-melting-point metal selected from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and other metals, with a melting point of 200°C or higher and 900°C, and then curing and composite it. The porous molded body (preform) is a molded / fired product formed by a mixture containing one or more of the following powders with radiation shielding effect selected from the group consisting of gadolinium oxide powder, boron carbide powder, boron powder, boron oxide powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and a non-powdered silica-based binder. The non-powdered silica-based binder is a liquid silica-based binder, which is selected from at least one of the following groups: liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heating and curing at a temperature below 900°C. The non-powdered silica-based binder has the characteristic of being able to form a porous molded body (preform) as the molded / fired product at a temperature at which the radiation shielding powder is not decomposed.

2. The composite material with radiation shielding function according to claim 1, wherein, The mixture is formed by adding 0.5 to 10 parts by weight of the liquid silica-based binder (equivalent to SiO2) to 100 parts by weight of the radiation shielding powder.

3. A composite material with radiation shielding function, characterized in that, It is made by compounding powders with radiation shielding effect, and contains the powder in a total range of more than 3% by volume and less than 85% by volume. The composite is composed of a liquid organic-inorganic sealing agent impregnated into at least 25% by volume of the pores of a porous molded body (preform) and then cured and composited. The porous molded body (preform) is a molded / fired product formed by a mixture containing one or more of the following powders with radiation shielding effect selected from gadolinium oxide powder, boron carbide powder, boron powder, boron oxide powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component, and a non-powdered silica-based binder. The non-powdered silica-based binder has the characteristic of being able to form a porous molded body (preform) as the molded / fired product at a temperature at which the radiation shielding powder is not decomposed.

4. The composite material with radiation shielding function according to claim 3, wherein, The non-powdered silica-based binder is a liquid silica-based binder, which is selected from at least one of the following groups: water glass (sodium silicate), colloidal silica, liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heating and curing at a temperature below 900°C. The mixture is formed by adding 0.5 to 10 parts by weight of the liquid silica-based binder (converted to SiO2) to 100 parts by weight of the radiation shielding powder.

5. The composite material with radiation shielding function according to claim 3 or 4, wherein, The liquid organic-inorganic sealing agent exists in the pores of the porous molded body (preform) in the form of a cured organic-inorganic sealing agent and / or a heat-treated organic-inorganic sealing agent. The cured organic-inorganic sealing agent and / or the heat-treated organic-inorganic sealing agent occupy more than 25% by volume of 100% of the pores of the porous molded body (preform) before impregnation, and when the entire preform after impregnation is set as 100% by volume, the cured organic-inorganic sealing agent and / or the heat-treated organic-inorganic sealing agent occupy more than 5% by volume.

6. The composite material with radiation shielding function according to any one of claims 3 to 5, wherein, The liquid organic-inorganic sealing agent is a low-viscosity substance with a viscosity of less than 50 mPa·s and containing more than 30% by mass of non-volatile components, selected from at least one of the following substances: The oligomers of methyl silicate Si(OCH3)4 or the dimers or tetramers formed by the partial hydrolysis of methyl silicate are adjusted to form a liquid methyl silicate compound with a non-volatile component of more than 30% by mass. The dimer or tetramer oligomer of ethyl silicate Si(OC2H5)4 or the partially hydrolyzed ethyl silicate is adjusted to form a liquid ethyl silicate compound with a non-volatile component of more than 30% by mass. Organosilicon resins or their derivatives having siloxane bonds and having a non-volatile content of 30% or more by mass; Liquid alkoxysilane compounds, as alkoxysilane derivatives, undergo condensation reactions with moisture in the air to generate organosilicon-oxygen compounds (Si-OR).

7. A method for manufacturing a composite with radiation shielding function, characterized in that, It is a method for manufacturing a composite with radiation shielding function, wherein the composite uses at least one of a low-melting-point metal selected from the group consisting of aluminum, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and other metals as a matrix, and contains powder with radiation shielding effect in a total volume range of 3% to 85% or more. The manufacturing method includes the following steps: A process for producing a porous preform (preform) involves adding a non-powdered silica-based binder to one or more of the following powders having radiation shielding effects: gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component. The resulting mixture is then shaped, and the resulting preform is fired at a temperature between 300°C and 900°C. The non-powdered silica-based binder used in this process is a liquid silica-based binder, which is selected from at least one of the following groups: liquid silicone resin or a silicone resin solution obtained by dissolving silicone resin in an organic solvent, and alcohol-based silica formed from silica and organic matter that undergoes heat curing at a temperature below 900°C. In this process, a porous molded body (preform) is formed by casting a molten metal selected from the group consisting of aluminum, aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of the same metal and other metals, which has a melting point of 200°C to 900°C. The molten metal is then held under a high pressure of 20 MPa to 200 MPa for 3 to 15 minutes to allow it to permeate the porous molded body (preform). The composite body in the state of being permeated with the molten metal is then removed and cooled within 15 minutes to suppress the decomposition of the radiation shielding powder in the composite body.

8. The method for manufacturing a composite with radiation shielding function according to claim 7, wherein, The mixture is formed by adding 0.5 to 10 parts by weight of the liquid silica-based binder (equivalent to SiO2) to 100 parts by weight of the radiation shielding powder.

9. A method for manufacturing a composite with radiation shielding function, characterized in that, The preparation method involves combining powders with radiation shielding effect to form a composite containing the powders in a total volume range of 3% to 85% or more. The manufacturing method includes the following steps: A process of producing a porous preform by adding a non-powdered silica-based binder to one or more of the following powders having radiation shielding effect: gadolinium oxide powder, boron carbide powder, boron oxide powder, boron powder, barium sulfate powder, strontium oxide powder, tungsten powder, tungsten oxide powder, tungsten carbide powder, molybdenum powder, molybdenum oxide powder, iron powder, iron oxide powder, and ferrite powder with iron oxide as the main component; shaping the resulting mixture; and firing the resulting preform at a temperature of 300°C or higher and 900°C. A composite process is described in which a liquid organic-inorganic sealing agent containing 30% or more of non-volatile components and with a viscosity of 50 mPa·s or less is vacuum impregnated into the voids of a porous preform (preform) obtained in the process of making a porous preform (preform). Alternatively, after vacuum impregnation, the preform is impregnated under pressure at 10 atmospheres or less, and then heated to a temperature of 200°C or higher and 900°C or lower. This process is described in which the solidified product of the liquid organic-inorganic sealing agent and / or the heat-treated product of the liquid organic-inorganic sealing agent remain at 25% or more of 100% of the voids of the porous preform (preform). This process is used to composite the radiation shielding powder with the components derived from the liquid organic-inorganic sealing agent.

10. The method for manufacturing a composite with radiation shielding function according to claim 9, wherein, The liquid organic-inorganic sealing agent is a low-viscosity substance with a viscosity of less than 50 mPa·s and containing more than 30% by mass of non-volatile components, selected from at least one of the following substances: The oligomers of methyl silicate Si(OCH3)4 or the dimers or tetramers formed by the partial hydrolysis of methyl silicate are adjusted to form a liquid methyl silicate compound with a non-volatile component of more than 30% by mass. The dimer or tetramer oligomer of ethyl silicate Si(OC2H5)4 or the partially hydrolyzed ethyl silicate is adjusted to form a liquid ethyl silicate compound with a non-volatile component of more than 30% by mass. Organosilicon resins or their derivatives having siloxane bonds and having a non-volatile content of 30% or more by mass; Liquid alkoxysilane compounds, as alkoxysilane derivatives, undergo condensation reactions with moisture in the air to generate organosilicon-oxygen compounds (Si-OR).

11. The method for manufacturing a composite with radiation shielding function according to claim 9 or 10, wherein, The non-powdered silica-based binder is a liquid silica-based binder, which is selected from at least one of the following groups: water glass (sodium silicate), colloidal silica, liquid silicone resin or silicone resin solution formed by dissolving silicone resin in an organic solvent, and alcohol-based silica formed by heating and curing at a temperature below 900°C. The mixture is formed by adding 0.5 to 10 parts by weight of the liquid silica-based binder (converted to SiO2) to 100 parts by weight of the radiation shielding powder.

12. The method for manufacturing a composite with radiation shielding function according to claim 7 or 8, wherein, In the process of making the porous molded body (preform), aluminum powder, aluminum alloy powder, or ceramic powder is further added to the radiation shielding powder. When the total amount of the aluminum metal powder, aluminum alloy powder, or ceramic powder and the radiation shielding powder is set to 100% by mass, a non-powdered silica-based binder of 0.5 to 10% by mass (equivalent to SiO2) is added to make the porous molded body (preform).

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