Composite having radiation-shielding function and method for manufacturing composite having radiation-shielding function

Abstract

The present invention developed a composite having a novel structure containing, in a high content, a powder having a radiation-shielding function.　Provided is a composite having a radiation-shielding function and a method for producing the same. The composite comprises a preform made from a mixture containing a liquid silica-based binder and one or more radiation-shielding powders selected from 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, the radiation-shielding powder(s) being contained in the range from 3% to 85% in total. All of the voids in the preform are impregnated and filled with molten aluminum and solidification is allowed to occur to form a composite, or 25% or more of the voids in the preform are impregnated with a liquid organic / inorganic sealing agent and solidification is allowed to occur to form a composite. The liquid silica-based binder has properties that allow the preform to be formed at a temperature at which the radiation-shielding powder(s) does not decompose.

Description

Composite with radiation shielding function and method for manufacturing the composite with radiation shielding function

[0001] The present invention relates to a composite having a radiation-shielding function and a method for producing the composite having a radiation-shielding function. More specifically, the present invention relates to a composite having a radiation-shielding function, which is a specific inorganic powder or metal powder having a radiation-shielding effect, and a method for producing the composite having a radiation-shielding function. ２ O ３ ) powder, boron carbide (B ４ C) Powder, boron oxide (B ２ O ３ ) powder, boron (B) powder, barium sulfate (BaSO ４ ) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W ２ O ３ ) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO ３ ) powder, iron (Fe) powder, iron oxide (Fe ２ O ３ The present invention relates to a composite obtained by firstly impregnating pores of a porous preform containing at least one selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, and a low-melting-point alloy of the low-melting-point metal and another metal, each having a melting point of 200° C. or higher and 900° C. or lower, and then solidifying the pores of the porous preform, which contains at least one selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, and a ferrite powder mainly composed of iron oxide (hereinafter, these powders are collectively referred to as radiation-shielding powders), or secondly, impregnating the pores of the porous preform with a liquid organic / inorganic sealing agent, and then heat-treating and solidifying the pores to form a composite (hereinafter, these may be collectively referred to as a composite), and a method for manufacturing the composite. In particular, the present invention relates to a technology that enables the realization of a composite obtained by combining the radiation-shielding powders listed above while suppressing decomposition of the radiation-shielding powder.

[0002] In medical settings, radiation-shielding shielding materials are used in consideration of X-rays and other radiation generated by medical devices and medical equipment. In the nuclear industry, materials that shield against radiation such as X-rays, gamma rays, and neutrons are used to form containers and devices for handling and storing unused nuclear fuel. Radiation-shielding materials are required to have good heat dissipation properties to block radiation and prevent nuclear chain reactions. Metals such as lead (Pb) and tungsten (W) are commonly used as radiation-shielding materials. However, in recent years, there has been an increasing demand for radiation-shielding materials that are lightweight, have high heat dissipation properties, and have a high radiation-shielding effect, particularly for structural members that require radiation-shielding effects.

[0003] Conventional radiation shielding materials generally use metallic lead or metallic tungsten. However, these materials have a high specific gravity, and structural materials made from materials with a high specific gravity are quite heavy, so the range of their use is limited. As listed below, in order to create a structure with a lightweight radiation shielding effect, B, which has a low specific gravity and a radiation shielding effect, is used. ４ C powder and BaSO ４ Materials have been proposed that combine powder with resin or metal, but the content of these radiation-shielding powders in the structure is low, limiting the range of their application.

[0004] In Patent Document 1, the following B ４ A method for producing an aluminum radiation shield containing C has been proposed. Specifically, boron carbide (B ４ C) A mixed powder compact consisting of powder and aluminum powder is prepared, and sintered at a low temperature of 10 to 50°C by vacuum sintering, HIP, or hot pressing. ４ A radiation shielding body has been proposed in which B and aluminum are mixed together, then heated and melted, and then cast. ４ The C content is limited to the range of 0.5 to 5 mass % or less, and if the C content exceeds this range, the viscosity of the molten metal increases, making casting difficult. ４ It has been difficult to manufacture a radiation shield having a C content of more than 5% by volume.

[0005] In addition, Patent Document 2 discloses a method for producing boron carbide (B ４ C) A method is disclosed in which an inorganic binder or the like is added to a mixture of particles and aluminum borate whiskers, the mixture is molded, the molded product is sintered in an argon atmosphere at a high temperature of 1250°C for 4 hours to produce a preform, and the preform is impregnated with molten aluminum alloy at high pressure to produce a radiation-shielding composite. In this method, boron carbide and ceramic whiskers are mixed and sintered at a high temperature of 1100 to 1400°C to produce a preform that can withstand high-pressure aluminum impregnation, and the preform is then impregnated with molten aluminum alloy to produce a composite. This method has the problems of being expensive because the preform must be produced at a high temperature, and further, the boron carbide content can only be 1 to 15 wt %, making it impossible to increase the boron carbide content in the radiation-shielding composite.

[0006] In addition, Patent Document 3 discloses a method for producing boron carbide (B ４ It is disclosed that a solid piece of aluminum alloy that melts at 580°C to 610°C is placed on top of a preform made from a mixture of a boron-containing ceramic powder, such as that represented by C), and a metal powder containing aluminum, and the solid piece is heated to an infiltration temperature at which the solid piece melts and infiltrated for 1 minute to 24 hours to obtain a composite. According to the investigations of the present inventors, this method requires a long reaction time because the aluminum alloy is spontaneously impregnated (infiltrated) into the preform, and furthermore, the aluminum alloy is unstable in air. ４ C ３ In addition, the preform may not be completely impregnated, and therefore a dense radiation-shielding composite cannot be stably obtained.

[0007] Furthermore, Patent Document 4 proposes a method for producing a composite by heating a mixed powder of boron carbide powder and aluminum alloy powder, or a mixed powder compact thereof, to a predetermined temperature and maintaining the temperature, and forging or rolling the mixture under conditions of a semi-molten state. According to the inventors' investigations, this method was unable to produce composites with a large area or thick walls because the forming was performed at a high temperature. Furthermore, this technique involves forced forging in a semi-molten state, which causes problems such as non-uniformity between the radiation-shielding powder and the aluminum alloy, and the inability to produce products with a wall thickness of 10 mm or more.

[0008] Furthermore, Patent Document 5 proposes a container material in which boron fiber is composited with a boron-containing aluminum alloy base material. However, the boron fiber content is still low and boron fiber is expensive, so the range of use is limited.

[0009] Japanese Patent Application Laid-Open No. 2002-20828 Japanese Patent Application Laid-Open No. 2003-121590 Japanese Patent No. 4426293 Japanese Patent Application Laid-Open No. 60-096746 Japanese Patent Application Laid-Open No. 10-319183

[0010] As mentioned above, the radiation shielding materials of the prior art are heavy when metallic lead or metallic tungsten is used in the radiation shielding powder, or when boron carbide (B ４ C) and barium sulfate (BaSO ４ In all of the composites using powders such as those represented by fluorine-containing silica (F-1), the content of the powder with radiation shielding effect was low, and a high content could not be achieved. Furthermore, materials in which radiation-shielding powder is mixed with gypsum, rubber, or resin have been proposed as prior art. However, materials using rubber as a matrix are organic, and therefore difficult to use for long periods at temperatures above 200°C. Furthermore, materials using gypsum as a matrix have the problem that a dehydration reaction of the gypsum occurs when used for long periods at temperatures above 100°C, making them unable to be used for long periods at high temperatures.

[0011] In response to the above-mentioned situation of the prior art, the present inventors have ４ C powder and BaSO ４We believe that if a technology could be developed that could control the content of materials (raw materials) with a high content of radiation-shielding powders such as gadolinium oxide, strontium oxide, and iron oxide from low to high, and that could prepare materials that could be used at high temperatures, the range of radiation-shielding applications for structural members (structures) and radiation-related machine parts would be greatly expanded. Furthermore, even if radiation-shielding powders such as tungsten powder and molybdenum powder, which have a high specific gravity of 10 or more, could be composited with other materials at a content that allows them to stably exert their radiation-shielding effect, and if a lightweight composite material could be made, it could be used in some applications, and the range of uses would be greatly expanded.

[0012] In light of the current state of the art, the present inventors have recognized that a highly practical composite material with radiation-shielding function having the following properties is desired: That is, a composite with high strength and a high content of radiation-shielding powder, particularly a content of 3 v % or more, preferably 60 v % or more, and more preferably up to 85 v %, a wall thickness of 5 mm or more, preferably 10 mm or more, a high radiation-shielding effect, lightweight, and usable for large structures, architectural wall materials, and machine protective structures, as well as a composite of a low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of such a low-melting-point metal with another metal (hereinafter, these may be referred to as "aluminum, etc."), all of which have high thermal conductivity. Note that low-melting-point metals other than zinc, tin, and lead can also be used as long as they do not impair the objectives of the present invention. In this specification, volume % will also be abbreviated as "v %," and mass % will also be abbreviated as "w %."

[0013] Therefore, an object of the present invention is to develop a composite having a novel configuration that contains a high content of a powder having radiation-shielding function (radiation-shielding powder) and has a high radiation-shielding effect. Another object of the present invention is to develop a variety of composites in which the radiation-shielding powder content is controlled depending on the application, from a low content of 3v% to a high content of 85v%, for example, and that have the strength required for structures such as parts and members that constitute buildings or machines. A further object of the present invention is to develop a new technology that can provide an excellent composite with radiation-shielding powder, which is a composite with aluminum metal powder, aluminum alloy powder, or ceramic powder that has heat resistance and high thermal conductivity and has a matrix of molten aluminum metal or aluminum alloy.

[0014] The above object is achieved by the present invention described below. That is, the present invention provides a first composite having a radiation-shielding function as follows: [1] A composite having a radiation-shielding function, which comprises a powder having a radiation-shielding effect, and the powder is composited together in a total amount of 3% by volume or more and 85% by volume or less, a porous molded body (preform) which is a molded and fired product of a mixture containing one or more of the radiation-shielding powders 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 mainly composed of iron oxide, and a non-powdered silica-based binder, and all of the voids of the porous molded body (preform) are impregnated and filled with at least one of a molten low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, which has a melting point of 200°C or more and 900°C or less, or a low-melting-point alloy of the low-melting-point metal with another metal, and the melting point is solidified to form a composite; A composite having a radiation-shielding function, wherein the non-powdered silica-based binder is at least one liquid silica-based binder selected from the group consisting of a liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and a silica alkoxide made of silica and an organic substance and cured by heating at a temperature of 900°C or less, and the non-powdered silica-based binder has a property that allows the molded and fired product to be formed into a porous molded body (preform) at a temperature at which the radiation-shielding powder is not decomposed. In addition to the above-listed silica-based binders, the non-powdered silica-based binder having the above configuration may be water glass (sodium silicate), colloidal silica, etc.

[0015] A preferred embodiment of the first composite having a radiation-shielding function is as follows: [2] The mixture is a mixture of 100 parts by mass of the radiation-shielding powder and the liquid silica-based binder in an amount of SiO ２The composite having a radiation-shielding function according to the above [1], wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

[0016] The present invention also provides a second composite having a radiation-shielding function as follows: [3] A composite having a radiation-shielding function, comprising a powder having a radiation-shielding effect, the powder being composited together, in a total amount of 3% by volume or more and 85% by volume or less, a composite having a radiation-shielding function, characterized in that the composite has a constitution in which at least 25% by volume of pores of a porous molded body (preform) is impregnated with a liquid organic / inorganic sealing agent, and solidified to form a composite, the porous molded body (preform) being a molded and fired product of a mixture containing one or more types of powder having a 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 mainly composed of iron oxide, and a non-powdered silica-based binder; and the porous molded body (preform) is formed by molding and firing the mixture at a temperature at which the radiation-shielding powder is not decomposed.

[0017] The preferred embodiment of the second composite having a radiation-shielding function is as follows: [4] The non-powdered silica-based binder is at least one liquid silica-based binder selected from the group consisting of water glass (sodium silicate), colloidal silica, liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and silica alkoxide made of silica and an organic substance and cured by heating at a temperature of 900°C or less, and the mixture is a mixture of the liquid silica-based binder and SiO2 with respect to 100 parts by mass of the radiation-shielding powder. ２[5] The composite having a radiation-shielding function according to the above [3] or [4], wherein the liquid organic / inorganic pore-blocking agent is present in the voids of the porous molded body (preform) as a solidified product of the organic / inorganic pore-blocking agent and / or a heat-treated product of the organic / inorganic pore-blocking agent, and the solidified product of the organic / inorganic pore-blocking agent and / or the heat-treated product of the organic / inorganic pore-blocking agent occupies 25% by volume or more of the voids (100% by volume) of the porous molded body (preform) before impregnation, and when the entire preform after impregnation is taken as 100% by volume, the solidified product of the organic / inorganic pore-blocking agent and / or the heat-treated product of the organic / inorganic pore-blocking agent occupies 5% by volume or more. [6] The liquid organic / inorganic sealing agent has a low viscosity of 50 mPa·s or less and contains 30 mass% or more of non-volatile components. ３ ) ４ Alternatively, the methyl silicate may be partially hydrolyzed to form a dimer or tetramer oligomer, and the non-volatile content of the liquid methyl silicate compound may be adjusted to 30% by mass or more. ２ H ５ ) ４ Alternatively, the composite having a radiation-shielding function according to any one of items [3] to [5] above is at least one selected from the group consisting of: a liquid ethylsilicate compound obtained by partially hydrolyzing the ethylsilicate to form a dimer or tetramer oligomer, and adjusted to have a non-volatile content of 30% by mass or more; a silicone resin or derivative thereof having a siloxane bond, and adjusted to have a non-volatile content of 30% by mass or more; and a liquid alkoxysilane compound that is an alkoxysilane derivative and reacts with moisture in the air to undergo a condensation reaction to produce a silicone-oxygen organic compound (Si—O—R).

[0018] As another embodiment, the present invention provides the following first method for producing a composite having a radiation-shielding function: [7] A method for producing a composite having a radiation-shielding function, which comprises a matrix of at least one of a molten low-melting-point metal selected from the group consisting of aluminum metal, an aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and another metal, and which contains a powder having a radiation-shielding effect in a total amount of 3% by volume or more and 85% by volume or less, the method comprising: a step of adding a non-powdered silica-based binder to one or more of the 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 mainly composed of iron oxide, and mixing the mixture to form a porous molded body (preform), and then firing the resulting molded body at a temperature of 300°C or higher and 900°C or lower, wherein the non-powdered silica-based binder used in the step is at least one liquid silica-based binder selected from the group consisting of a liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and a silica alkoxide made of silica and an organic substance and heat-cured at a temperature of 900°C or lower; and a step of casting a molten metal of at least one low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and another metal, which has been melted at a temperature of 300°C or more and 900°C or less, into the porous molded body (preform) obtained in the step (a), and holding the molten metal at a high pressure of 20 MPa or more and 200 MPa or less for 3 to 15 minutes to impregnate the porous molded body (preform) with the molten metal, and then removing the composite impregnated with the molten metal within 15 minutes and cooling it, thereby suppressing decomposition of the radiation-shielding powder in the composite. Preferred embodiments of the above-mentioned first method for producing a composite having a radiation-shielding function are as follows.[8] The mixture contains 100 parts by mass of the radiation-shielding powder and SiO. ２ The method for producing a composite having a radiation-shielding function according to the above [7], wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

[0019] As another embodiment, the present invention provides the following second method for producing a composite having radiation-shielding function: [9] A method for producing a composite having radiation-shielding function, which comprises preparing a composite containing a total of 3 volume % or more and 85 volume % or less of powders having radiation-shielding effect, the powders being composited together, the composite comprising: one or more powders having 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 containing iron oxide as the main component, and adding a non-powdered silica-based binder to the powder, molding the mixture, and then firing the obtained molded body at a temperature of 300° C. or more and 900° C. or less to produce a porous molded body (preform); and a compounding step of: vacuum-impregnating voids of the porous molded body (preform) obtained in the step of producing the porous molded body (preform) with a liquid organic / inorganic sealing agent containing 30% by mass or more of non-volatile components and having a viscosity of 50 mPa s or less, or impregnating the voids of the porous molded body (preform) under a pressure of 10 atmospheres or less by applying pressure after vacuum impregnation, and then heating the voids to a temperature of 200°C or more and 900°C or less, so that a solidified product of the liquid organic / inorganic sealing agent and / or a heat-treated product of the liquid organic / inorganic sealing agent remains in an amount of 25% by volume or more relative to 100% by volume of the voids of the porous molded body (preform), and compounding the radiation-shielding powder with a component derived from the liquid organic / inorganic sealing agent.

[0020] A preferred embodiment of the second method for producing a composite having a radiation-shielding function is as follows:

[10] The liquid organic / inorganic sealing agent has a low viscosity of 50 mPa·s or less and contains 30 mass % or more of non-volatile components, and is a methyl silicate Si(OCH３ ) ４ Alternatively, the methyl silicate may be partially hydrolyzed to form a dimer or tetramer oligomer, and the non-volatile content of the liquid methyl silicate compound may be adjusted to 30% by mass or more. ２ H ５ ) ４ Alternatively, the method for producing a composite having a radiation-shielding function according to the above item [9], wherein the compound is at least one selected from the group consisting of a liquid ethylsilicate compound obtained by partially hydrolyzing the ethylsilicate to form a dimer or tetramer oligomer and adjusted to have a non-volatile content of 30% by mass or more; a silicone resin or derivative thereof having a siloxane bond and adjusted to have a non-volatile content of 30% by mass or more; and a liquid alkoxysilane compound which is an alkoxysilane derivative and reacts with moisture in the air to undergo a condensation reaction to produce a silicone-oxygen organic compound (Si—O—R).

[0021]

[11] The non-powdered silica-based binder is at least one liquid silica-based binder selected from the group consisting of water glass (sodium silicate), colloidal silica, liquid silicone resin, silicone resin solution obtained by dissolving silicone resin in an organic solvent, and silica alkoxide made of silica and an organic substance and heat-cured at a temperature of 900°C or less, and the mixture is prepared by mixing the liquid silica-based binder with SiO2 in an amount of 100 parts by mass of the radiation-shielding powder. ２ The method for producing a composite having a radiation-shielding function according to the above [9] or

[10] , wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

[0022]

[12] Furthermore, in the step of producing the porous molded body (preform), when aluminum powder, aluminum alloy powder, or ceramic powder is added to the radiation-shielding powder, and the total amount of the aluminum metal powder, aluminum alloy powder, or ceramic powder and the radiation-shielding powder is 100 mass%, the non-powdered silica-based binder is SiO ２ The method for producing a composite having a radiation-shielding function according to the above [7] or [8], wherein the porous molded body (preform) is produced by adding 0.5 to 10 mass % of the compound in terms of the amount of the compound.

[0023] Conventionally, structures containing radiation-shielding powder have generally been produced by mixing the radiation-shielding powder with aluminum, rubber, or resin to form a composite. In contrast, the present invention stably provides a first composite having a radiation-shielding function, which has a similar configuration in that it uses a molded body (preform) containing a radiation-shielding powder whose filling rate is controlled from a low to a high level, and which is obtained by impregnating all of the voids of the molded body (preform) with a molten metal such as aluminum and solidifying the voids to form a composite. Alternatively, the present invention stably provides a second composite having a radiation-shielding function, which has a configuration in which at least 25% by volume of the voids of the molded body (preform) are impregnated with a liquid organic / inorganic sealing agent and solidifying the voids to form a composite. Furthermore, by applying each production method of the present invention according to the intended use of the composite and skillfully utilizing the two types of configurations described above, various composites having high practical value and suitable for desired properties can be stably produced, for example, in which the filling rate of the radiation-shielding powder is controlled from a low to a high level and which have excellent radiation-shielding function and exhibit strength suited to the intended purpose. The technical features of the present invention are as follows.

[0024] The first feature of the present invention is to provide a method for producing gadolinium oxide (Gd ２ O ３ ) powder, boron carbide (B ４ C) Powder, boron oxide (B ２ O ３ ) powder, boron (B) powder, barium sulfate (BaSO ４ ) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W ２ O ３ ) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO ３ ) powder, iron (Fe) powder, iron oxide (Fe ２ O ３One advantage of the present invention is that it is possible to use one or more types of radiation-shielding powders appropriately selected from a large group of radiation-shielding powders having different functions and properties, including ferrite powders containing iron oxide as a main component and ferrite powders containing iron oxide as a main component, depending on the intended use, etc. In other words, the present invention makes it possible to provide a variety of radiation-shielding composites that are composed of a single radiation-shielding powder or various combinations of radiation-shielding powders.

[0025] Among the radiation-shielding powders constituting the composite of the present invention, for example, boron carbide containing boron is said to have a radiation shielding effect against neutron rays, tungsten or tungsten carbide against gamma rays and X-rays, and barium sulfate containing barium against X-rays and gamma rays. In contrast, the present invention makes it possible to provide composites of various configurations with different radiation-shielding functions, as described below. That is, it is possible to provide not only composites obtained by impregnating a single powder of a specific radiation-shielding powder group specified in the present invention with a molten metal such as aluminum or a liquid organic / inorganic sealing agent and then solidifying the powder, but also composites obtained by impregnating two types of radiation-shielding powders, i.e., boron carbide and tungsten, or boron carbide and barium sulfate, or, as needed, three types of radiation-shielding powders, i.e., boron carbide, tungsten, or barium sulfate, with a molten metal such as aluminum or a liquid organic / inorganic sealing agent and then solidifying the powder. As described above, according to the present invention, by appropriately selecting the radiation-shielding powder specified in the present invention, it is possible to provide a composite that can simultaneously shield against X-rays, gamma rays, and neutron rays.

[0026] A second feature of the present invention is that it is possible to provide a composite having a radiation-shielding function in which the volume fraction of the radiation-shielding powder can be freely controlled from 3 v % to 85 v %, for example, by adjusting the particle size and blending ratio of the various radiation-shielding powders listed above, or, in the case of the first composite, by adding aluminum powder or aluminum alloy powder as needed. According to the present invention, it is possible to manufacture a structure made of a composite having a radiation-shielding function that achieves a filling fraction (volume fraction) of the radiation-shielding powder of 50 v % or more, which is required for a particularly high shielding effect.

[0027] A third feature of the present invention is that the radiation-shielding composite provided by the present invention can be made into the following two different types of configurations. First, in either configuration, a porous molded body (preform) is used, which is a molded and fired product of a mixture containing one or more types of radiation-shielding powder selected from the group of radiation-shielding powders specified in the present invention and a non-powdered silica-based binder. Then, all of the voids of the porous molded body (preform) are impregnated and filled with a molten metal of at least one low-melting-point metal, which has a melting point of 200° C. or more and is selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal with another metal, and the molten metal is solidified to form a composite, and a first composite having a high content of radiation-shielding powder with an aluminum matrix or the like can be provided. Furthermore, by impregnating at least 25% by volume of the pores of the porous molded body (preform) with a liquid organic / inorganic sealing agent, and then heating the preform at a temperature of 200°C or higher and 900°C or lower, the liquid organic / inorganic sealing agent is solidified and composited, thereby providing a second composite having a different configuration and a high content of radiation-shielding powder.

[0028] Furthermore, in the case of any of the composites having the above-described configurations, the non-powdered silica-based binder used in preparing the preform has the property of being able to form the preform at a temperature at which the radiation-shielding powder used for the composite is not decomposed, thereby achieving the following effects. That is, with such a configuration, the composite having a radiation-shielding function of the present invention has high strength because the radiation-shielding powder specified in the present invention is bound by aluminum or an organic / inorganic sealing agent. Furthermore, the radiation-shielding powder used is not decomposed, and the composite can be used at high temperatures of 300°C or higher. Hereinafter, the terms "molten aluminum" and "molten aluminum" used in the specification of the present invention refer to molten aluminum metal as a representative example. That is, in the specification of the present invention, the terms "molten aluminum" and "molten aluminum" are used to refer not only to molten aluminum metal but also to molten aluminum of a low-melting-point metal selected from the group consisting of aluminum alloys, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal with another metal (e.g., low-melting-point alloy solders mainly composed of tin or lead, and zinc alloys). In the specification of the present invention, the term "molten aluminum" refers to a low-melting-point metal or low-melting-point alloy having a melting point of 200°C or higher. In addition, in the present invention, it is preferable to use a low-melting-point metal or low-melting-point alloy having a melting point of 300°C or higher. That is, according to the studies of the present inventors, when a low-melting-point metal or low-melting-point alloy having a melting point of less than 300°C is used, the heat resistance of the resulting composite may not be sufficient depending on the application, and this is not preferable.

[0029] The fourth feature of the present invention is that, according to the study by the present inventors, when aluminum metal or aluminum alloy molten at a high temperature is used as the molten metal for compounding with the radiation-shielding powder, which is an example of the first composite, the following problem has been encountered, but this problem has been solved. Specifically, according to the present invention, it becomes possible to use as a raw material various radiation-shielding powders that have been difficult to use for the following reasons, and it becomes possible to produce a composite that can be stably used even at temperatures of 300°C or higher. For example, when aluminum metal or aluminum alloy is used, which shows a decomposition reaction with moisture in the air when reacting with aluminum, it is possible to use various radiation-shielding powders that have been difficult to use for the following reasons, and it becomes possible to produce a composite that can be stably used even at temperatures of 300°C or higher. ４C ３ and Al by reaction with molten aluminum at high temperatures. ２ O ３ , BaO and SO ２ It is also possible to use as a raw material even radiation-shielding powders such as barium sulfate, which undergoes a decomposition reaction to form barium sulfate, and strontium sulfate, tungsten, iron powder, and aluminum borate, which undergo oxidative degradation, thermal decomposition, and the generation of unstable substances at temperatures above 900° C. Therefore, since it becomes possible to use a wide variety of radiation-shielding powders as specified in the present invention, the range of applications of the composite can be significantly expanded according to the present invention.

[0030] 1 is a schematic diagram showing the casting of molten aluminum 1 into a preform 2, performed in a first manufacturing method. It is a schematic diagram showing the placement of a heated preform 2 in a mold of a press 10 and the pouring of molten aluminum 1. It is a schematic diagram showing the casting of molten aluminum 1 into a preform 2 using an upper punch 5 and a lower punch 4 of a high-pressure press, followed by impregnation. It is a schematic diagram showing the removal of a composite 3 in a state in which the impregnated molten aluminum has solidified by pushing up the lower punch 4 after cooling. It is a schematic diagram for explaining the outline of a reduced-pressure vessel 30 used when impregnating voids in a preform 2 with a liquid organic / inorganic sealing agent 31, performed in a second manufacturing method.

[0031] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0032] The composite having a radiation-shielding function of the present invention is a composite having a radiation-shielding function, which contains a powder having a radiation-shielding effect in a range of 3% by volume or more and 85% by volume or less in total, and the powder is obtained by compounding powders having a radiation-shielding effect, and ２ O ３ ) powder, boron carbide (B ４ C) Powder, boron oxide (B ２ O ３ ) powder, boron (B) powder, barium sulfate (BaSO ４ ) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W ２O ３ ) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO ３ ) powder, iron (Fe) powder, iron oxide (Fe ２ O ３ The present invention is characterized in that the first composite is formed using a porous molded body (preform) that is a molded and fired product made of a mixture containing one or more types of radiation-shielding powder selected from the group consisting of a ferrite powder containing iron oxide as a main component and a non-powdered silica-based binder. The first composite is configured such that molten aluminum is impregnated and filled into all voids of the porous molded body (preform) and the mixture is solidified to form a composite, and the second composite is configured such that at least 25% by volume of the voids of the porous molded body (preform) is impregnated with a liquid organic / inorganic sealing agent and the mixture is solidified to form a composite. Furthermore, both the first composite and the second composite are characterized in that the non-powdered silica-based binder constituting the composite has a property that allows the molded and fired product, that is, the porous molded body (preform) (hereinafter, also simply referred to as a preform), to be formed at a temperature at which the radiation-shielding powder is not decomposed. Examples of non-powder silica-based binders having the above-mentioned properties that can be suitably used in the present invention will be given below.

[0033] The first composite or the second composite having a radiation-shielding function of the present invention having the above-mentioned configuration can be produced by, for example, the production method of the present invention comprising the first means or the second means described below, which can provide a stable composite while suppressing decomposition of the radiation-shielding powder. Therefore, a composite of good quality that meets the intended use and provides the various effects of the present invention described above can be easily and stably prepared.

[0034] The first composite having a radiation-shielding function of the present invention, which is configured by impregnating and filling all of the voids in a preform having the specific configuration described above with "molten aluminum" and then solidifying to form a composite, can be easily and stably prepared by the first production method of the present invention described below. As mentioned above, "molten aluminum" and "molten aluminum" refer to a molten metal of at least one of aluminum metal, aluminum alloy, low-melting-point metal, and low-melting-point alloy, each having a melting point of 200°C or higher, preferably 300°C or higher and 900°C or lower.

[0035] The first manufacturing method of the present invention is a method for manufacturing a composite having a radiation-shielding function, which contains an aluminum matrix and a powder having a radiation-shielding effect in a total amount of 3 volume % or more and 85 volume % or less, and the powder contains one or more kinds of 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 containing iron oxide as a main component. a process of molding a mixture obtained by adding a non-powdered silica-based binder to a certain powder and mixing it, and then firing the resulting molded body at a temperature of 300°C or higher and 900°C or lower to produce a porous molded body (preform); and a process of casting molten aluminum into the preform obtained in the process at a temperature of 300°C or higher and 900°C or lower, and holding the preform at a high pressure of 20 MPa or higher and 200 MPa or lower for 3 to 15 minutes, for example, 3 to 5 minutes, in order to impregnate the preform with the molten aluminum. After that, the composite in a state in which the molten aluminum has been impregnated is immediately taken out and cooled, thereby decomposing the radiation-shielding powder in the composite, and ４ C ３ and a step of suppressing the generation of unstable substances such as:

[0036] In the first manufacturing method of the present invention, further, in the step of preparing the preform, aluminum powder, aluminum alloy powder, or ceramic powder is added to the radiation-shielding powder, and when the total amount of the aluminum powder, aluminum alloy powder, or ceramic powder and the radiation-shielding powder is 100 mass %, the non-powdered silica-based binder is SiO ２ A preform can also be produced by adding 0.5 to 10 mass % of the powder, calculated as a powder content. This configuration makes it easier to prepare a composite having a radiation-shielding function, which contains aluminum or an aluminum alloy as a matrix and a powder having a radiation-shielding effect, the powder content being appropriately controlled within a range of 3 to 85 volume % in total. This will be described later.

[0037] The second composite having a radiation-shielding function of the present invention, which is configured by impregnating at least 25% by volume or more of the voids of a preform having the specific configuration described above with a liquid organic / inorganic sealing agent and solidifying the agent to form a composite, can be easily and stably prepared by the second production method of the present invention described below.

[0038] The second manufacturing method of the present invention is a method for manufacturing a composite having a radiation-shielding function, which comprises preparing a composite containing a total of 3 to 85 volume % of powders having a radiation-shielding effect, the powders being composited together, the composite comprising one or more types of 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 containing iron oxide as a main component, and adding a non-powdered silica-based binder to the powder, and then molding the mixture obtained. and a compounding step of vacuum-impregnating, into voids of the preform obtained in the preform-producing step, a liquid organic / inorganic sealing agent containing 30% by mass or more of non-volatile components and having a viscosity of 50 mPa s or less, or a step of impregnating the preform at a pressure of 10 atmospheres or less by applying pressure after vacuum impregnation, and then heating the preform at a temperature of 300°C or more and 900°C or less, so that a solidified product of the liquid organic / inorganic sealing agent and / or a heat-treated product of the liquid organic / inorganic sealing agent remains in an amount of 25% by volume or more relative to 100% by volume of the voids of the preform, thereby compounding the radiation-shielding powder with a component derived from the liquid organic / inorganic sealing agent.

[0039] <Process for Producing Porous Molded Body (Preform)> The following describes in detail the first and second methods for producing the composite having a radiation-shielding function of the present invention. As described above, the process for producing the porous molded body (preform) constituting the first and second production methods is the same. Therefore, the process for producing the preform will be described first.

[0040] [Radiation-shielding powder as raw material, etc.] In the present invention, gadolinium oxide (Gd ２ O ３ ) powder, boron carbide (B ４ C) Powder, boron oxide (B ２ O ３) powder, boron powder, barium sulfate (BaSO ４ ) powder, strontium oxide (SrO) powder, tungsten (W) powder, tungsten oxide (W ２ O ３ ) powder, tungsten carbide (WC) powder, molybdenum (Mo) powder, molybdenum oxide (MoO ３ ) powder, iron (Fe) powder, iron oxide (Fe ２ O ３ In the present invention, one or more types selected from the group consisting of lead powder, lead oxide powder, and ferrite powder mainly composed of iron oxide are used. In conventional techniques, lead powder or lead oxide powder is generally used alone as the radiation-shielding powder. However, in the present invention, these radiation-shielding powders are not used because they increase the weight of the structure (composite) and are environmentally hazardous. In addition, these materials have low melting points and are therefore unsuitable for the manufacturing method of the present invention, which is useful for effectively obtaining the composite of the present invention.

[0041] In the present invention, in addition to the radiation-shielding powders listed above, for example, aluminum powder, aluminum alloy powder, or ceramic powder can be added to reduce the packing rate of the radiation-shielding powder in the first composite. In this way, it becomes possible to freely control the packing rate (volume rate) of the radiation-shielding powder constituting the composite of the present invention over a wide range. In this case, in the step of producing a porous molded body (preform) constituting the production method of the present invention, aluminum powder, aluminum alloy powder, or ceramic powder is further added as needed to the specific radiation-shielding powder specified in the present invention, and the non-powdered silica-based binder is added in an amount of SiO 2 to make up 100% by volume of the total volume of these powders. ２ A preform is produced by adding 0.5 to 10 mass % (w %) of the aluminum powder or aluminum alloy powder or ceramic powder as needed. The production method is the same as the production method of the composite of the present invention, except that aluminum powder, aluminum alloy powder, or ceramic powder is used as needed. Therefore, the following description will explain the method of producing a preform including any of the above-mentioned optional configurations.

[0042] The average particle size of the radiation-shielding powder used in the production 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 is preferably 0.3 μm or more and 500 μm or less. The reason for setting the average particle size to 0.3 μm or more is that materials with an average particle size smaller than 0.3 μm tend to have particles that easily aggregate and form clumps. Furthermore, when two or more types of powder are used, uniform mixing may be difficult, which is undesirable. In addition, there is a tendency for the silica-based binder added to the powder to be difficult to uniformly mix. Furthermore, when a powder with an average particle size less than 0.3 μm is used, the powder filling rate in a preform obtained by press molding, CIP molding, slip casting, or the like tends to be low, which may make it impossible to produce a preform with a high volume fraction (Vf) of the radiation-shielding powder, which is a characteristic of the present invention. On the other hand, when a large powder exceeding 500 μm is used, the powder packing property is also poor, and there is a risk that a preform with a high Vf cannot be produced, as in the case of using a powder with an average particle size that is too small. Furthermore, according to the studies of the present inventors, since the coarse particles described above have a small surface area, the binder effect of the silica-based binder added to the radiation-shielding powder and the aluminum powder or the like used as needed is low, and it becomes impossible to produce a strong preform, which is also undesirable in this respect.

[0043] The "average particle size" of the radiation-shielding powder and the aluminum powder or the like used as needed in the present invention is the particle size (median diameter) at an integrated value of 50% in the particle size distribution determined by a laser diffraction / scattering method.

[0044] Although it varies depending on the type and particle size of the radiation-shielding powder, according to the studies of the present inventors, the volume fraction (Vf) of the preform usually obtained in the preform production step constituting the production method of the present invention is generally around 50 v%. According to the studies of the present inventors, when increasing the volume fraction Vf of the radiation-shielding powder in the preform, it is preferable to blend particles having a large average particle size and particles having a small average particle size so that the small particles are interposed between the large particles. Furthermore, in the present invention, when two or more types of radiation-shielding powders are blended, the blend may be radiation-shielding powders of the same type but different average particle sizes, or radiation-shielding powders of different types. When it is desired to produce a preform with a required Vf in the present invention, the blend of particles to be used in producing the preform may be determined by previously conducting a test blend and calculating the bulk specific gravity of the preform. According to the investigations of the present inventors, by using the manufacturing method of the present invention, it is possible to produce a preform having a Vf of up to 85v% by appropriately blending particles, and as a result, it is possible to provide a composite having a high content of radiation-shielding powder, which could not be produced using conventional techniques.

[0045] Various situations can be considered when using a radiation-shielding composite. For example, the higher the volume fraction (Vf) of the radiation-shielding powder in a structure having a radiation-shielding function, the greater the radiation-shielding effect. However, depending on the application, a lower Vf may be acceptable, or the Vf of the radiation-shielding powder may be reduced in consideration of production costs. In contrast, according to an embodiment of the manufacturing method of the present invention, in which aluminum powder or the like is used as needed, the content of the radiation-shielding powder in the produced preform can be appropriately controlled within a wider range by a very simple means of adding a required amount of aluminum powder or the like to the specific radiation-shielding powder specified in the present invention. For example, a preform with a radiation-shielding powder Vf of 50 v % will be impregnated with 50 v % of molten aluminum in the next step. In contrast to this, 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, aluminum alloy, or specific low-melting point metal or specific low-melting point alloy impregnated in a later step (referred to in the specification of the present invention as "molten aluminum") will be the amount of aluminum in the composite, and the amount of aluminum in the structure having a radiation-shielding function made from the composite can be increased. In other words, by adding aluminum powder or the like to the preform, it becomes possible to freely control the volume fraction Vf in the structure having a radiation-shielding function.

[0046] As described above, the manufacturing method of the present invention can easily produce a composite comprising a radiation-shielding powder and molten aluminum, in which the blending amount of the radiation-shielding powder is controlled over a wide range, such as 3 v % to 85 v %, by appropriately using means such as a blending method that combines large particles and small particles of a specific radiation-shielding powder or the addition of aluminum powder or the like as needed. According to the studies of the present inventors, a composite containing less than 3 v % of the radiation-shielding powder has an excessively low radiation-shielding effect and is therefore not practical. Furthermore, according to the studies of the present inventors, it is difficult to achieve a Vf of 85 v % or more with conventional techniques, even when particle blending and various molding methods are utilized.

[0047] [Step of Preparing a Preform] In the step of preparing a preform, which constitutes the manufacturing method of the present invention, first, a material for forming the preform is prepared as follows. One or more types of powder are selected from the specific radiation-shielding powder group described above and specified in the present invention, and aluminum powder or the like, added as needed, are thoroughly stirred and mixed using a ball mill, a paddle stirrer, or the like. For example, when tungsten powder (specific gravity: 19.3) and boron carbide powder (specific gravity: 2.52), which have different specific gravities, are used as radiation-shielding powders and aluminum powder (specific gravity: 2.7) is added as needed, it is preferable to use a V-type mixer or a drum rotary mixer in which the entire mixing container rotates in order to prevent separation due to the difference in specific gravities.

[0048] Next, a mixture of the radiation-shielding powder specified in the present invention and an aluminum powder or the like, which is used as needed, is mixed with a non-powdered silica-based binder to form a molded mixture, and the molded body obtained is fired at a temperature of 300° C. or higher and 900° C. or lower to prepare a porous molded body (preform). These components will be described below.

[0049] (Non-powdered silica-based binder) In any of the composites of the present invention, the non-powdered silica-based binder is suitably at least one liquid silica-based binder (hereinafter also referred to as "liquid silica-based binder") selected from the group consisting of water glass (sodium silicate), colloidal silica, a liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and a silica alkoxide made of silica and an organic substance and heat-cured at a temperature of 900° C. or less. The liquid silica-based binder is added in a required amount depending on the amount of the radiation-shielding powder, etc., used.

[0050] The amount of the liquid silica binder used in the present invention is determined by the ratio of SiO ２In terms of the total weight of the radiation-shielding powder, it is appropriate to add, for example, about 0.5 to 10 parts by mass of the radiation-shielding powder mixture containing aluminum powder and the like as needed. According to the studies of the present inventors, an amount of less than 0.5 parts by mass is not preferable because it does not exert enough strength as a binder. On the other hand, even if the amount exceeds 10 parts by mass, the function as a binder is exerted, but the relative content of the radiation-shielding powder becomes low, so there is no need to add more than this amount.

[0051] The liquid silica-based binders such as the above-mentioned ethyl silicate are compounds of silica (Si) and organic substances, and are thermally decomposed to produce ultrafine SiO ２ Water glass is made by heating sodium silicate dissolved in water to produce ultrafine SiO ２ As the colloidal silica, it is preferable to use one in which extremely fine silica particles of several tens of mμ (nm) or less are dispersed as a colloid in water or an organic solvent. The reason for using these silica-based binders is to strengthen the preform to be used in the next step.

[0052] Pyrolyzed at low temperature to produce SiO ２ Ethyl silicate and silicone resins, which contain silica that changes to SiO at low temperatures, ２ Ultrafine SiO dispersed in water glass or solvent to produce ２ According to the investigations of the present inventors, these silica-based binders are ultrafine powders, and in the process of the manufacturing method of the present invention, they go from a state where they are uniformly mixed in the preform at the molecular level to an amorphous (non-crystalline) state, and then to an ultrafine powder SiO 2 while remaining uniform. ２ is generated, a strong preform can be produced.

[0053] In the next step, the prepared mixed powder, which is the raw material for the preform, is molded and fired to produce a preform. It is important in the present invention to prevent decomposition of the radiation-shielding powder during the process of producing the composite of the present invention, so as not to impair the intended function of the present invention. Therefore, in the production method of the present invention, the firing temperature when producing the preform by molding and firing must be a low temperature of 900°C or less. In contrast, all of the liquid silica-based binders used in the present invention exhibit sufficient binding effects even at temperatures below 900°C. Here, when using silica-based binders in ordinary ceramic production processes, silica powders with sizes ranging from submicrons to several μm are generally used. In conventional techniques, when silica powder is used as a binder, the preform must be produced by firing at a temperature of 1100°C or higher in order to ensure the strength of the resulting preform. However, the above-mentioned conventional techniques cannot be applied to the composite technology of the present invention. In the manufacturing method of the present invention, when a preform is manufactured by molding and firing, or when the manufactured preform is impregnated with molten aluminum, it is necessary to prevent decomposition of the radiation-shielding powder, so the temperature must be low, 900° C. or lower. This point will be described later.

[0054] In the production method of the present invention, the liquid silica-based binder as described above is added little by little to one or more types of uniformly mixed radiation-shielding powder that may contain the aluminum powder, etc. As a mixer to be used in this process, it is preferable to use a Henschel mixer that stirs at high speed with high shear force or a mixer equipped with a birdcage-shaped rotor made of thin wires. Furthermore, when adding the liquid silica-based binder, an appropriate amount of an organic binder such as PVA or PVB may be added as needed within a range that does not impair the object of the present invention.

[0055] Next, a mixture containing the radiation-resistant shielding powder obtained by adding the liquid silica-based binder and uniformly mixing it as described above is used to produce a molded body by a general method such as press molding, tapping molding, or CIP molding.

[0056] In the manufacturing method of the present invention, the molded body obtained as described above is heated and fired at a temperature of 300°C to 900°C to harden it and produce a preform. According to the investigations of the present inventors, at temperatures below 300°C, the effect of the silica-based binder cannot be exerted, and a strong preform cannot be produced. On the other hand, at temperatures of 300°C or higher, the effect of the added liquid silica-based binder is exerted, and a strong preform can be produced. Furthermore, for the following reasons, in the manufacturing method of the present invention, it is necessary to produce a preform by firing at a temperature of 900°C or lower.

[0057] For example, boron carbide (B ４ When C) is used, BO and CO are reacted at high temperatures in the air. ２ Since there is a risk of decomposition, it is necessary to sinter it at a temperature of 900°C or less. ４ When using C), if aluminum powder or the like is added as needed, Al generated from boron carbide and aluminum at high temperatures will ４ C ３ may undergo the following decomposition reaction: ４ C ３ is unstable and reacts with moisture in the air to form Al(OH) ３ and CH ３ However, there is no Al in the complex. ４ C ３ It is not desirable for this to remain. ４ C + Al → Al ４ C ３ +B

[0058] When barium sulfate is used as the radiation shielding powder, BaSO ４ At high temperatures, BaO and SO ２ In this case too, firing at a high temperature is not preferred because the decomposition reaction shown below may occur. Also, firing at a high temperature above 900°C is not preferred because the decomposition reaction shown below may occur: Al + BaSO ４ →BaO+Al ２ O ３ +SO (gas)

[0059] When tungsten (W) is used as the radiation shielding powder, tungsten turns into WO when heated in air. ３ This is undesirable because it reduces the effect of adding a silica-based binder. According to the study by the present inventors, in order to suppress the series of reactions described above, it is preferable to set the firing temperature of the molded body to a temperature of 900°C or less. By doing so, decomposition and oxidation are suppressed, and it becomes possible to manufacture a stable preform of radiation-shielding powder.

[0060] <Composite Production Step> Next, in the first production method of the present invention, molten aluminum is impregnated and filled at high pressure into all of the voids of the porous molded body (preform) produced as described above, and then solidified to produce a first composite having a radiation-shielding function. In the second production method of the present invention, a liquid organic / inorganic sealing agent is vacuum-impregnated into some or all of the voids of the preform, or the liquid is impregnated under pressure after vacuum impregnation, and then the sealing agent is heated to a temperature of 300°C or higher and 900°C or lower to solidify and form a composite, thereby producing a second composite having a radiation-shielding function. The steps for producing the first composite or the second composite in the first production method of the present invention or the second production method of the present invention will be described below.

[0061] [First Manufacturing Method] In the first manufacturing method of the present invention, a composite having radiation-shielding properties is prepared, comprising an aluminum matrix and a total of 3 to 85 volume % of a powder having radiation-shielding properties. Specifically, a preform prepared as described above is used, and a molten metal of a low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal with another metal (in this specification, these molten metals are also referred to as "molten aluminum" to represent aluminum metal and aluminum alloys) is cast into the preform at a temperature of 300 to 900°C. The preform is then held at a high pressure of 20 to 200 MPa for 3 to 15 minutes, e.g., 3 to 5 minutes, to impregnate the entire voids of the preform with the molten aluminum. The preform is then immediately removed and cooled within 15 minutes of the start of impregnation to obtain a first composite. More specifically, the composite is formed using the following procedure.

[0062] The temperature of the molten aluminum to be impregnated is set to a temperature equal to or higher than the melting point 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 metal or aluminum alloys, the temperature is set to about 700°C to 800°C. Furthermore, when using a low-melting-point alloy, a temperature of about 350°C to 500°C is appropriate for solder alloys, and a temperature of about 450°C to 550°C is appropriate for zinc alloys. Regardless of the type of molten metal used, in the present invention, it is necessary to impregnate the voids in the preform produced as described above with molten metal at 900°C or less.

[0063] First, the preform previously produced is preheated at a temperature of 300°C or higher and 900°C or lower in order to be impregnated with molten aluminum. If the preform is preheated to a low temperature below 300°C, the impregnated molten aluminum will cool and solidify quickly in the process of casting and impregnating the molten aluminum, which will be described below, making it difficult to impregnate the entire voids of the preform, which is not preferable. According to the studies of the present inventors, if the preform is preheated to a temperature of 300°C or higher, the molten aluminum will impregnate the entire voids of the preform. However, if the preheating temperature exceeds 900°C, for example, boron carbide, which is a radiation shielding powder, and the aluminum used for impregnation with the molten aluminum will react to form Al. ４ C ３ may be generated, or BaSO ４ However, this is not preferable because it may cause a decomposition reaction.

[0064] Next, the process of impregnating the preheated preform with molten aluminum to form a composite will be described with reference to Fig. 1. Specifically, the preform produced as described above is impregnated with molten aluminum in the following order to form a composite.

[0065] (1) As shown in FIG. 1A, a preform 2 preheated to 300°C to 900°C is placed on the lower punch 4 of a press 10 that has been preheated to approximately 200°C to 300°C using a burner or the like. Next, molten aluminum 1 melted to a temperature of 300°C to 900°C is cast into the press 10. When using aluminum metal or an aluminum alloy, the molten aluminum is preferably heated to a temperature of 700°C to 900°C. (2) Next, as shown in FIG. 1B, an upper punch 5 of the press 10 is placed on the press 10 and a load is applied. A load is applied to the upper punch 5 of the press 10 so that the pressure of the molten aluminum 1 becomes 20 MPa to 200 MPa, thereby impregnating the pores (voids) of the preform 2 with the molten aluminum 1. At this time, the load is maintained for 3 to 15 minutes in order to impregnate the voids of the preform 2 with the molten aluminum 1. (3) Next, as shown in Fig. 1C , immediately after the preform 2 has been impregnated (specifically, within about 15 minutes after the start of impregnation with the molten aluminum), the preform 2 is pushed up from the bottom of the lower punch 4, and the composite 3 impregnated with the molten aluminum 1 is immediately removed. The composite 3 is then cooled in as short a time as possible to solidify the impregnated molten aluminum 1.

[0066] Below, we will explain the points to be noted in the process of impregnating the molten aluminum 1 into the preform 2, which is a series of porous molded bodies described above. First, when using aluminum metal or an aluminum alloy, a casting temperature of less than 600°C is not preferable because the molten aluminum hardens in a short time and does not impregnate the entire voids of the preform. On the other hand, as explained above, when the casting temperature exceeds 900°C, for example, the molten aluminum hardens in a short time and does not impregnate the entire voids of the preform. ４ C) decomposes to Al ４ C ３ is generated, or barium sulfate (BaSO ) is added to the radiation shielding powder. ４ ) is used, BaSO ４ This is not preferable because it may cause thermal decomposition.

[0067] In the first manufacturing method of the present invention, the pressure for impregnation with the molten aluminum is 20 MPa or more and 200 MPa or less. A pressure of less than 20 MPa is not preferable because the pressure is too low and the molten aluminum may not impregnate the entire voids of the preform. Since sufficient impregnation is achieved at a pressure of 20 MPa or more and 200 MPa or less, there is no need to apply pressure exceeding 200 MPa. According to the studies of the present inventors, good impregnation can be achieved even at a pressure of, for example, about 100 MPa.

[0068] The composite obtained by high pressure infiltration is held for 3 minutes, preferably 5 minutes, and then removed from the mold within at least 15 minutes from the start of infiltration of the molten aluminum. If the composite obtained by high pressure infiltration of the molten aluminum into the voids of the preform is held in the mold for a long time exceeding 15 minutes, for example, boron carbide and aluminum may react to form Al ４ C ３ may be generated, or BaSO ４ This must be avoided because it may decompose and form a complex that is contrary to the provisions of the present invention.

[0069] In the above explanation, a method of high-pressure impregnation of a porous molded body (preform) with molten aluminum using a high-pressure press as shown in FIG. 1 has been exemplified. However, the present invention is not limited to this, and any machine may be used as long as it is configured to be able to cast and fill molten aluminum at 20 MPa or more into the preform. For example, a die-casting machine, a squeeze-casting machine, or the like may also be used. Note that the cooled composite is surrounded by aluminum, which is removed by machining to extract the composite. According to the first manufacturing method of the present invention described above, it is possible to produce a first composite having a stable and dense radiation-shielding function, in which the radiation-shielding powder contains 3% to 85% by volume of Vf.

[0070] [Second Manufacturing Method] In the second manufacturing method of the present invention, a second composite having a configuration with a radiation-shielding function can be prepared, which is formed by compounding a solidified material resulting from a liquid organic / inorganic sealing agent in a state where the solidified material is present in an amount of 25% by volume or more relative to 100% by volume of voids in the preform obtained as described above, and which contains a powder having a radiation-shielding effect in a total amount within the range of 3% by volume or more and 85% by volume or less.

[0071] (Liquid organic / inorganic sealing agent) In the second production method of the present invention, the liquid organic / inorganic sealing agent that characterizes the second production method is preferably a low-viscosity organic / inorganic sealing agent having a viscosity of 50 mPa·s or less and containing 30 mass % or more of non-volatile components, for example, the following three liquid compounds, used alone or in combination: (1) liquid ethyl silicate having a first alcohol Si bond [Si(OC ２ H ５ ) ４ ] or a liquid oligomer in which a part of the ethyl silicate is hydrolyzed to form a dimer or a tetramer, or similar methyl silicate [Si(OCH ３ ) ４ and liquid alkoxide compounds such as partially hydrolyzed liquid oligomers thereof, which are adjusted so that the content of non-volatile components is 30 mass % or more.

[0072] (2) Type 2: Liquid silicone or its derivatives having a siloxane bond as the main chain, as shown in the following general formula, or silicone or its derivatives adjusted so that the non-volatile components when diluted and dissolved in a solvent are 30% by mass or more. In the general formula, R is an organic group such as a methyl group, ethyl group, vinyl group, phenyl group, or acetyl group. Specifically, for example, liquid compounds such as silicone oil or silicone adhesive dissolved in an organic solvent can be used.

[0073] (3) A third type alkoxysilane derivative is a liquid alkoxysilane compound that reacts with moisture in the air to undergo a condensation reaction to generate a silicone-oxygen organic compound (Si—O—R) as shown in the following reaction formula. For example, a compound such as the one-component room temperature curing sealant described in Japanese Patent No. 3816354 can be used. Examples of such a compound include commercially available products such as Permeate (registered trademark, manufactured by D&D Co., Ltd.).

[0074]

[0075] (Method of Composite Formation) In the second production method of the present invention, a radiation-shielding powder is used as a raw material to obtain a second composite having a configuration with a radiation-shielding function, in which a solidified material resulting from a liquid organic / inorganic sealing agent is present in the voids of the preform produced as described above in an amount of 25% by volume or more relative to 100% by volume. Specifically, the voids of a porous molded body (preform) are vacuum-impregnated with a liquid organic / inorganic sealing agent containing 30% by mass or more of non-volatile components and having a viscosity of 50 mPa s or less, or after vacuum impregnation, the preform is pressurized to 10 atmospheres or less, and then heated to a temperature of 300°C or more and 900°C or less, so that a solidified product of the liquid organic / inorganic sealing agent and / or a heat-treated product of the liquid organic / inorganic sealing agent remains in 25% by volume (1 / 4) or more of the voids of the preform, assuming that the entire voids of the preform are 100% by volume, thereby compounding the radiation-shielding powder and the components derived from the liquid organic / inorganic sealing agent. That is, since the proportion of the entire voids in the preform is about 15% by volume to 40% by volume, the components derived from the organic / inorganic sealing agent remain in the voids in an amount of 1 / 4 or more of the total voids, i.e., 4% by volume to 10% by volume or more. In other words, the obtained composite has a configuration in which the fired product of the mixture containing the radiation-shielding powder constituting the preform accounts for a high proportion of 60 to 85 v %, the component derived from the organic / inorganic sealant accounts for 4 to 10 v %, and the remainder is voids. Note that, in the present invention, the amount of the liquid silica-based binder to be mixed with the radiation-shielding powder is set to 100 parts by mass of the radiation-shielding powder, and the liquid silica-based binder is mixed with SiO ２ Since it is preferable to add about 0.5 to 10 parts by mass of the radiation-shielding powder in terms of the total mass, a composite having a high ratio of the radiation-shielding powder can be obtained. These points also apply to the first composite obtained by the first production method.

[0076] The liquid organic / inorganic sealing agent used in the second manufacturing method of the present invention, as exemplified above, preferably has a low viscosity of 50 mPa·s or less so that it can be easily impregnated into the preform. If the viscosity exceeds 50 mPa·s, the organic / inorganic sealing agent will not easily penetrate into the fine parts of the preform, which may prevent a strong composite from being obtained. It is also important that the liquid organic / inorganic sealing agent contains 30 wt% or more of nonvolatile matter relative to 100 wt% of the sealing agent. In the second manufacturing method of the present invention, the organic / inorganic sealing agent is impregnated into the voids of the preform so that it accounts for at least 25 v% of the total voids (100 v%) of the preform, and then the preform is heated to 200°C to 900°C to composite the radiation-shielding powder and the organic / inorganic sealing agent. That is, by heating at the above-mentioned temperatures, the liquid organic / inorganic sealing agent impregnated in the voids of the preform becomes a solidified liquid organic / inorganic sealing agent or a heat-treated liquid organic / inorganic sealing agent, both of which are solid, and remains in the voids of the preform.

[0077] The preform used in the manufacturing method of the present invention, which is prepared as described above, is a porous body having voids of about 15 to 40 v % relative to 100 v % of the entire preform. Therefore, the second composite obtained by the second manufacturing method of the present invention, in which a liquid organic / inorganic sealing agent is impregnated into the preform and then heat-treated, is a composite in which the solidified liquid organic / inorganic sealing agent and / or the heat-treated liquid organic / inorganic sealing agent accounts for 25 v % or more of the voids in the preform, assuming the entire voids in the preform are 100 v %. This means that the second composite obtained by the second manufacturing method of the present invention is a composite in which the solidified liquid organic / inorganic sealing agent and / or the heat-treated liquid organic / inorganic sealing agent is fixed in some (25 v % or more) or all of the voids in the preform.

[0078] According to the inventors' investigations, if the amount of the solidified liquid organic / inorganic sealing agent and / or the heat-treated liquid organic / inorganic sealing agent in the composite obtained by the second production method of the present invention is less than 25 v % relative to the total voids (100 v %) of the preform, a composite having a strong and practical radiation-shielding function cannot be obtained. Furthermore, a preferred configuration of the second composite obtained by the second production method of the present invention is, in addition to the above, that the amount of the solidified liquid organic / inorganic sealing agent and / or the heat-treated liquid organic / inorganic sealing agent remaining in the voids is about 5 v % or more relative to the total voids (100 v %) of the preform. For example, if the voids in the preform account for 20 v %, then 25% (1 / 4) of that, i.e., 5 v % of the total voids (100 v %), will be the organic / inorganic sealing agent. In the above example, the fired product of the mixture containing the radiation-shielding powder that constitutes the preform accounts for 80 v %. As described above, the amount of the liquid silica-based binder to be mixed with the radiation-shielding powder when preparing the preform is 100 parts by mass of the liquid silica-based binder in an amount of SiO ２ It is preferable to add about 0.5 to 10 parts by mass in terms of the total amount of the radiation-shielding powder, silica-based binder, and organic / inorganic sealing agent constituting the composite of the above example, which therefore shows a high ratio of 70 to 79.5 v %, resulting in a strong composite.

[0079] In the second manufacturing method of the present invention, the silica-based binder required for producing the preform and the liquid organic / inorganic sealing agent impregnated into the resulting preform may be the same compound. However, the liquid organic / inorganic sealing agent used for impregnating the voids in the preform must be impregnated into the preform so that the organic / inorganic sealing agent impregnated into the voids in the preform ultimately remains in a solidified state. Therefore, it is necessary for the liquid organic / inorganic sealing agent to have a low viscosity of 50 mPa·s or less and a non-volatile content of 30 wt% or more. Therefore, any silica-based binder that meets these requirements can be used in combination.

[0080] As mentioned above, in the second manufacturing method of the present invention, the preform impregnated with the liquid organic / inorganic sealing agent is heat-treated at a temperature of 200°C or higher and 900°C or lower. The reason for setting the heating temperature at 200°C or higher is as follows: By setting the heating temperature at 200°C or higher, the liquid alkoxysilane compound that generates siloxane bonds, ethyl silicate oligomers, or silicone oxygen organic compounds (Si-O-R) in the compound used as the liquid organic / inorganic sealing agent is thermally decomposed, and the compound functions as a silica-based binder or a Si-OR-based organic / inorganic binder, thereby strengthening the preform. In addition, the reason for setting the heating temperature at 900°C or lower is that the B that constitutes the preform is heated to a temperature of 900°C or lower. ４ C and BaSO ４ This is to prevent the powder, which has a radiation shielding effect and contains the above, from being decomposed or oxidized.

[0081] The procedure of the second manufacturing method of the present invention will be outlined with reference to FIG. 2 . In FIG. 2 , 30 denotes a reduced pressure vessel used in the second manufacturing method of the present invention. A preform 32 is placed in an interior container 34 installed inside the reduced pressure vessel 30, before the voids thereof are impregnated with an organic / inorganic sealing agent 31. The opening and closing jig 33 of the reduced pressure vessel 30 is closed, and the interior of the reduced pressure vessel 30 is depressurized using a vacuum pump (not shown) through a pressure reduction port 36 provided on the reduced pressure vessel 30. Once the pressure inside the reduced pressure vessel 30 has reached approximately zero pressure, the organic / inorganic sealing agent 31 is gradually introduced into the interior container 34 from an organic / inorganic sealing agent introduction container 35. The amount of organic / inorganic sealing agent 31 introduced is determined in advance to be an amount sufficient to completely impregnate the preform 32 with the organic / inorganic sealing agent 31 and to completely immerse the preform 32.

[0082] After the organic / inorganic sealing agent 31 is introduced as described above, a vacuum is maintained for approximately 5 to 10 minutes, allowing the organic / inorganic sealing agent 31 to be vacuum-impregnated into the voids of the preform 32. After the impregnation is complete, the pressure vessel 30 is gradually opened to the atmosphere, and air is introduced into the reduced pressure vessel 30. After the pressure inside the reduced pressure vessel 30 has returned to atmospheric pressure, air that has been decompressed to approximately 10 atmospheres using compressed air from a compressor or the like (not shown) is gradually introduced through the pressure port 37, and after pressurizing to approximately 4 atmospheres, this is kept for approximately 5 to 10 minutes, allowing the organic / inorganic sealing agent 31 to be impregnated into the preform 32.

[0083] Thereafter, the compressed air in the reduced pressure vessel 30 is gradually released, and once atmospheric pressure is reached, the preform in which the solidified liquid organic / inorganic sealing agent and / or the heat-treated liquid organic / inorganic sealing agent is fixed in the voids is taken out, gradually dried, and heated to 300 to 400°C to obtain a second composite having a radiation-shielding function.

[0084] Next, the present invention will be described in more detail with reference to examples and comparative examples. The present invention will be specifically described using examples and comparative examples of two manufacturing methods: a method in which molten aluminum is impregnated into the voids of a porous molded body (preform), which is a molded and fired product made from a mixture of radiation-shielding powder and a non-powdered silica-based binder, to form a composite; and a method in which an organic / inorganic sealing agent is impregnated into the voids to form a composite. The present invention is not limited in any way by the following examples. In the text, % refers to volume % unless otherwise specified. Due to the special circumstances that require handling of radiation in measuring the shielding effect, the radiation shielding rates of the composites of Examples 1 to 3 were measured by an external measurement institution. The radiation shielding rates measured by the external institution were higher than those of conventional materials.

[0085] <Example of method for impregnating a preform with molten aluminum - Preparation of first composite> [Example 1] B having an average particle size of 16 μm ４450 g of C powder #800 (manufactured by Dojin Sangyo Co., Ltd.) was mixed for 30 minutes in a V-type mixer. 5 g of ethyl silicate was added to the mixed powder as a liquid binder, and the whole was placed in a Henschel mixer, which applies shear force to the powder, and stirred at high speed for 15 minutes to mix uniformly. The resulting mixed powder was placed in a 100 mm x 100 mm mold, a lid was placed on it, and the pressure was 160 kgf / cm. ２ The molded body was placed in a sintering furnace, heated to 400°C at a rate of 50°C / hour, and then sintered at 400°C for 3 hours, followed by natural cooling. The resulting sintered body (preform) had a size of 100mm x 100mm x 35mm and weighed 449g. ４ Calculated from the true specific gravity of 2.51 of the preform (C), this preform had a bulk specific gravity of 1.31, a boron carbide filling rate (Vf) of 52%, and voids of 48%. The preform was heated at a rate of 100°C / hour and held at 500°C, and left in a heated state to wait for the next aluminum impregnation step using a high-pressure press.

[0086] A mold with an inner diameter of 300 mm installed in a high-pressure press was heated to approximately 250°C using a burner. The preform, which had been left in a heated state, was then placed in the mold of the press, and molten aluminum melted at 800°C was poured into the mold, followed by high-pressure casting as described below. As shown in FIGS. 1A and 1B , molten aluminum 1 melted at 800°C was poured into the mold containing preform 2, and immediately thereafter, the upper punch 5 of the press 10 was lowered and a load was applied to the upper punch 5 so that the pressure of the molten aluminum 1 became 70 MPa. As mentioned above, since the inner diameter of the mold was 300 mm, the load of the press 10 was approximately 500 tons.

[0087] After the load was applied and maintained for 5 minutes, the upper punch 5 was removed, and the lower punch 4 was immediately pushed up to lift the impregnated body (composite) 3 to the upper side of the press (see FIG. 1C ), where it was allowed to cool naturally. After it had cooled to a level where it could be handled, the solidified aluminum surrounding the composite 3 was removed by machining, and the composite 3 was taken out.

[0088] The specific gravity of the composite material removed was measured and found to be 2.61. This value was almost the same as the calculated value when the voids in the preform were completely impregnated with aluminum. ４ It was concluded that the composite was a dense composite of C and aluminum. The content (volume filling rate) of light boron carbide, which has a specific gravity of 2.52, was high at 52v%, making it possible to produce a lightweight composite with a specific gravity of 2.61. In addition, a portion of the composite was cut out and subjected to X-ray diffraction measurement of the surface, revealing that B ４ Al produced by decomposition of C ４ C ３ The generation of could not be confirmed.

[0089] The B obtained above ４ An external measurement organization was commissioned to measure the radiation shielding effect of a material with a C volume filling rate (Vf) of 52v% and a thickness of 35 mm. As a result, the shielding effect against neutrons from the isotope of californium (Cf), Cf252, was 61%, a high value. Furthermore, a bending test was conducted on the composite of this example based on JIS-R1061, and the strength was 183 MPa. These facts indicate that the composite obtained in this example is a result of the lightweight and excellent radiation shielding effect of B used as the raw material. ４ C powder is compounded without decomposition, and B ４ This indicates that it is a useful material that effectively combines the properties of C powder.

[0090] [Example 2] B with an average particle size of 70 μm ４ 230 g of C powder #180 (manufactured by Dojin Sangyo Co., Ltd.) and B powder having an average particle size of 16 μm, the same as that used in Example 1, were mixed. ４ 260 g of C powder #800 was mixed for 30 minutes in a V-type mixer. 15 g of ethyl silicate was added as a liquid binder to the mixed powder, and the mixture was mixed for 15 minutes in a Henschel mixer in the same manner as in Example 1.

[0091] The obtained mixed raw material was press-molded and sintered in the same manner as in Example 1 to obtain a 100 mm x 100 mm x 26 mm molded product having a bulk density of 1.66 and a B ４A preform with a C filling rate Vf of 66% and a porosity of 34v% was produced. The obtained preform was placed in a mold of a high-pressure press in the same manner as in Example 1, and was impregnated under high pressure with molten aluminum melted at 800°C. Thereafter, it was naturally cooled in the same manner as in Example 1, and the solidified aluminum around the composite was removed.

[0092] The specific gravity of this composite was 2.57, which was almost the same as the calculated value when the voids in the preform were impregnated with aluminum. ４ It was a dense composite made of C and aluminum. In addition, X-ray diffraction was performed on the surface of the composite in the same manner as in Example 1. As a result, as in Example 1, Al ４ C ３ As mentioned above, the formation of B particles with different average particle diameters was not observed. ４ By combining C powder and using it as a raw material, B ４ A composite with a filling rate of 66v% of C powder, which is higher than that in Example 1, was produced. ４ Despite the high C loading, a lightweight composite with a specific gravity of 2.57 was produced.

[0093] The B obtained above ４ An external measurement organization was commissioned to measure the radiation shielding effect of a material with a C volume filling rate (Vf) of 66v% and a thickness of 26 mm. As a result, the shielding effect against neutrons from the isotope of californium (Cf), Cf252, was 31%, which was a high value. Furthermore, a bending test was conducted on the composite of this example based on JIS-R1061, and the strength was 193 MPa. These facts indicate that the composite obtained in this example is a result of the lightweight and excellent radiation shielding effect of B used as the raw material. ４ C powder is compounded without decomposition, and B ４ This indicates that it is a useful material that effectively combines the properties of C powder.

[0094] [Example 3] Barium sulfate (BaSO ) having an average particle size of 15 μm ４820 g of A-200 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.), a powder of silicone resin, was uniformly mixed in the same manner as in Example 1. As a liquid binder, a soluble silicone resin KR-200 (manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in ethanol to prepare a silicone resin solution with a concentration of 20 wt % by mass. 50 g of the prepared silicone resin solution was then added to the mixed BaSO4 solution. ４ The mixture was added to the powder and stirred at high speed in a Henschel mixer in the same manner as in Example 1.

[0095] The preform produced by the same method and procedure as in Example 1 had a size of 100 mm × 100 mm × 28 mm, a bulk density of 2.92, and was made of BaSO ４ The filling rate of BaSO was 65v%. Next, in the same manner as in Example 1, the preform was infiltrated under high pressure with molten aluminum at 800°C and processed, and a composite was taken out. The specific gravity of the composite was 3.86, which was almost the same as the calculated value (theoretical value). ４ It was confirmed that the material was a dense composite consisting of titanium and aluminum.

[0096] The BaSO obtained above ４ The radiation shielding effect of a material with a volume filling factor (Vf) of 65v% and a thickness of 28mm was measured by an external measurement organization. As a result, the projection efficiency of cesium (Cs) gamma rays Cs137 was 35%, and the shielding efficiency of X-rays 150Kv was 99.5%, which were high values. Furthermore, a bending test was carried out on the composite of this example based on JIS-R1061, and the strength was 193 MPa, which was high. These facts indicate that the composite obtained in this example is a high-strength material that can be used in combination with the BaSO4 raw material, which is lightweight and has excellent radiation shielding effect. ４ The powder is composited in its original state without decomposition, and BaSO ４ This shows that it is a useful material that effectively combines the properties of powder.

[0097] [Example 4] B with an average particle size of 16 μm ４250 g of C powder #800 (manufactured by Dojin Sangyo Co., Ltd.) and 270 g of WA-100 (manufactured by Yamaishi Metals Co., Ltd.), an aluminum powder with an average particle size of 18 μm, were used as raw material powders and uniformly mixed in the same manner as in Example 1. 10 g of liquid ethyl silicate (manufactured by Colcoat Co., Ltd.) was added as a binder to this mixture, and the mixture was stirred at high speed using a Henschel mixer in the same manner as in Example 1.

[0098] The preform produced by the same method and procedure as in Example 1 had a size of 100 mm x 100 mm x 33 mm, a bulk density of 1.30, and B ４ The total filling rate of the C powder and aluminum powder (Al powder) was 50v%. Next, in the same manner as in Example 1, the preform was high-pressure impregnated with molten aluminum melted at 800°C, processed, and a composite was extracted. The specific gravity of the composite in this example was 2.65, which was almost the same as the calculated value when all of the voids in the preform were impregnated with molten aluminum.

[0099] Two types of raw powder B ４ Since the volume ratio of C powder to Al powder is approximately 1:1, about 50v% of the preform is aluminum powder. Therefore, the amount of aluminum in the obtained composite is 75v% in total, including the aluminum impregnated in the preform. Therefore, the composite is composed of 75v% aluminum powder and the remaining 25v% B. ４ From the above, it was confirmed that it is possible to control the concentration of the radiation shielding powder by mixing an appropriate amount of aluminum powder into the raw material of the preform. ４ By using C powder, it was possible to manufacture a lightweight composite with a specific gravity of 2.65. Furthermore, when a bending test was carried out on the composite of this example in accordance with JIS-R1061, the strength was as high as 182 MPa.

[0100] [Example 5] BaSO with an average particle size of 15 μm ４A preform raw material was prepared by adding 280 g of powder A-200 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.) and 395 g of aluminum powder WA-100 (manufactured by Yamaishi Metals Co., Ltd.) having an average particle size of 18 μm to 50 g of a 20 wt % solution of silicone resin KR-200 dissolved in ethanol, the same as used in Example 3. The raw materials were stirred at high speed using a Henschel mixer in the same manner as in Example 1.

[0101] Thereafter, a preform was produced by the same method and procedure as in Example 1. The preform had a size of 100 mm x 100 mm x 38 mm, a bulk density of 1.77, and was made of BaSO. ４ The total filling rate (Vf) of the powder and Al powder was 55v%.

[0102] Next, the preform obtained above was high-pressure impregnated with molten aluminum at 800°C in the same manner as in Example 1, and processed to extract a composite. The specific gravity of the prepared composite was 2.99, which was almost identical to the calculated value for a dense body. In the composite of this example, 70v% of the preform was aluminum powder, so the total aluminum content in the composite, including the impregnated aluminum, was 84v%, and the remaining 16v% was BaSO ４ The composite of this example was a composite made of barium sulfate powder. As in the composite of Example 4, the composite of this example is an example in which it is possible to control the concentration of barium sulfate powder, which is a radiation-shielding powder, in the composite by mixing aluminum powder into the raw materials of the preform. Furthermore, a bending test was conducted on the composite of this example in accordance with JIS-R1061, and the result was a high strength of 212 MPa.

[0103] [Example 6] B with an average particle size of 16 μm ４ 270 g of C powder #800 (manufactured by Dojin Sangyo Co., Ltd.) and BaSO 4 with an average particle size of 15 μm ４ 495 g of powder A-200 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.) was used as raw material powder and uniformly mixed in the same manner as in Example 1. 15 g of liquid ethyl silicate (manufactured by Colcoat Co., Ltd.) was added as a binder to this, and the mixture was stirred at high speed using a Henschel mixer in the same manner as in Example 1.

[0104] Thereafter, a preform was produced by the same method and procedure as in Example 1. The preform had a size of 100 mm x 100 mm x 38 mm, a bulk density of 2.00, and B ４ C and BaSO ４ The total powder filling factor (Vf) was 57v%.

[0105] Next, in the same manner as in Example 1, the composite was impregnated with molten aluminum at 800°C, processed, and extracted. The specific gravity of the prepared composite was 3.16, which was almost the same as the calculated value when the preform was impregnated with molten aluminum. The obtained composite was B ４ C is 28.5v%, BaSO ４ The content of the powder was 28.5v%, and that of aluminum was 43v%. As shown in this example, it was confirmed that a composite containing two types of radiation-shielding powders can be produced by the manufacturing method of the present invention. Furthermore, a bending test was carried out on the composite of this example in accordance with JIS-R1061, and the result was a high strength of 199 MPa.

[0106] [Example 7] B with an average particle size of 16 μm ４ 380 g of C powder #800 (manufactured by Dojin Sangyo Co., Ltd.) and 1270 g of tungsten metal powder W-4 (manufactured by Nippon Shinkinzoku Co., Ltd.) having an average particle size of 3 μm were used and uniformly mixed in the same manner as in Example 1. In this case, water glass No. 4 (manufactured by Fuji Chemical Co., Ltd.) diluted with water was used as a binder, and SiO ２ The mixture was added in an amount equivalent to 16 g per minute and stirred at high speed with a Henschel mixer in the same manner as in Example 1. A preform was then produced in the same manner and procedure as in Example 1. The preform had a size of 100 mm x 100 mm x 32 mm, a bulk specific gravity of 5.18, and B ４ The total filling rate (Vf) of C and tungsten W was 68%.

[0107] Next, in the same manner as in Example 1, the composite was high-pressure impregnated with molten aluminum at 800°C, processed, and extracted. The specific gravity of the composite was 6.04, which was almost the same as the calculated value when the preform was impregnated with molten aluminum. The obtained composite was B ４The composite had 48.5v% C, 20.4v% tungsten, and 32v% aluminum. Furthermore, a bending test was carried out on the composite of this example in accordance with JIS-R1061, and the result was a high strength of 192 MPa.

[0108] As shown in this example, a composite containing two types of radiation-shielding powders could be produced by the method of the present invention, as in Example 6. Furthermore, the composite in this example contained 20.4 v% tungsten, and had a specific gravity of 6.04, which was significantly lighter than the specific gravity of 19.5 of pure tungsten.

[0109] [Example 8] B having the same average particle size as Example 1 and 16 μm ４ Using C powder #800 (manufactured by Dojin Sangyo Co., Ltd.), an ethyl silicate binder was added in the same manner, followed by mixing, molding, and firing to prepare a preform measuring 100 mm x 100 mm x 35 mm, also with a bulk density of 1.31, a boron carbide filling rate (Vf) of 52%, and a void content of 48 v%. The preform was heated and left to stand at a temperature of 400°C.

[0110] In the same manner as in Example 1, the preform was placed in a mold with an inner diameter of 300 mm heated to 250°C, and a low-melting-point alloy (zinc alloy: ZDC2, specific gravity 6.8) melted at 500°C was cast into it, which was then high-pressure impregnated at 70 MPa (500 t press load). After holding for 10 minutes, the mixture was immediately cooled, cooled to room temperature, and the composite was removed. The specific gravity of the composite was 4.18, and it was a composite material in which the low-melting-point zinc alloy was impregnated to almost 100%. ４ There was no decomposition reaction due to the generation of C. Furthermore, a bending test was carried out on the composite of this example in accordance with JIS-R1061, and the result was a high strength of 223 MPa.

[0111] [Comparative Examples 1 and 2] The same B as used in Example 1 ４To 450 g of this mixture (net volume 182 ml) were added 2 g of fine silica powder (manufactured by Yamamori Tsuchimoto Seisakusho Co., Ltd.) having an average particle size of 1.2 μm and 3 g of water, and the mixture was inserted into a mold and press-molded in the same manner as in Example 1. The molded bodies were fired at different temperatures of 400° C. and 800° C., respectively, and then cooled. In both cases, the obtained molded bodies lacked preform strength, could not be handled, and could not be subjected to high-pressure impregnation with molten aluminum, regardless of the firing temperature.

[0112] [Comparative Examples 3 and 4] The same B as used in Example 1 ４ C powder, and to 450 g of this (net volume 182 ml) was added 4 g of fine silica powder of LeoSeal QS-9 (manufactured by Tokuyama Corporation) having an average particle size of 22 nm (22 mμ) and 64 g of water. The mixed powder was prepared in the same manner as in Example 1 and inserted into a mold for press molding. The molded bodies obtained by press molding were fired at different temperatures of 400°C or 800°C, and then cooled. Regardless of the firing temperature, the molded bodies after firing lacked preform strength, could not be handled, and could not be subjected to high-pressure impregnation with molten aluminum.

[0113] Comparative Example 5: B was extracted in the same manner as in Example 1. ４ A preform of C was produced, and the resulting preform was placed in a mold and cast using molten aluminum in the same manner as in Example 1. However, in this comparative example, molten aluminum melted at a temperature above 900°C was used, and after holding the temperature at a temperature above 900°C for 20 minutes, a composite was produced in the same manner as in Example 1. When the surface of the composite was processed, it was found to be blackened, so a portion was scraped off and examined by X-ray diffraction. As a result, it was found that the main raw material B ４ In addition to C, Al was also found at 2θ = 31.8°, 35.8°, 40.1°, and 55°. ４ C ３ From this, it can be seen that in the case of the composite of this comparative example, if the composite is kept in a high temperature state in the press mold for a long time, the B of the raw material of the preform ４ It was confirmed that C was partially decomposed and did not form a good composite.

[0114] Comparative Example 6: BaSO having an average particle size of 15 μm, similar to that used in Example 5 ４ 890 g of powder A-200 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.) was mixed uniformly in the same manner as in Example 1. Then, 50 g of a 20 wt % solution of silicone resin KR-200 in ethanol, the same as used in Example 3, was added, and the mixture was stirred at high speed with a Henschel mixer in the same manner as in Example 1.

[0115] The preform produced by the same method and procedure as in Example 1 had a size of 100 mm x 100 mm x 33 mm and was made of BaSO ４ The filling rate of the composite was 60v%. Next, the composite was set in a mold in the same manner as in Example 1, impregnated with molten aluminum at 950°C, and processed, and then removed. The surface was processed and visually observed, revealing many pores. The reason for this was that BaSO ４ When heated at high temperatures, BaO and SO ２ This is thought to be because it decomposed into

[0116] Table 1 shows the preparation conditions of the preforms in Examples 1 to 8 and Comparative Examples 1 to 6, and the properties and evaluations of the obtained composites in Examples 1 to 8 and Comparative Examples 5 and 6. In Table 1, the "yes" and "no" of decomposition indicate whether decomposition was observed in the radiation-shielding powder constituting each composite.

[0117]

[0118] <Example of Method for Impregnating Preform with Organic / Inorganic Sealing Agent - Preparation of Second Composite> Next, the second production method of the present invention, in which a radiation-shielding composite is produced by impregnating the voids of a porous molded body (preform) with a special liquid organic / inorganic sealing agent, will be described with reference to Examples and Comparative Examples. The reason why bending tests were conducted on the composites in the following Examples is as follows. When the voids of a preform are impregnated with a liquid organic / inorganic sealing agent, components derived from the organic / inorganic sealing agent remain in the voids of the preform. Here, in the case of the second composite configured such that the voids of the preform are impregnated with a liquid organic / inorganic sealing agent, it is not necessary to impregnate all of the voids of the preform, as in the case of impregnation with molten aluminum described above, and some voids may remain. According to the inventors' investigations, even in such a configuration, as long as the liquid organic / inorganic sealing agent occupies 25% by volume or more of the 100% by volume of voids in the preform before impregnation with the liquid organic / inorganic sealing agent, the resulting composite has sufficient strength and can be used as a building material such as a wall material or ceiling material. In other words, by conducting a bending test on the resulting composite to confirm its strength, it can be confirmed that a sufficient amount of solidified organic / inorganic sealing agent and / or heat-treated organic / inorganic sealing agent remains in the voids of the preform. As shown below, the composites of the examples have sufficient strength and are of the configuration specified in the present invention.

[0119] [Example 9] A material composition similar to that used in the formulation of Example 1 described above was used, and B ４ Using 270 g of C powder #800 (manufactured by Dojin Sangyo Co., Ltd.), the mixture was mixed, molded, fired, and cooled in the same manner to prepare a preform having a size of 100 mm x 100 mm x 20 mm and a weight of 262 g. The obtained preform was made of boron carbide (B ４ The bulk density was calculated to be 1.31 from the true specific gravity of 2.51 of C), the filling rate (Vf) of boron carbide was 52v%, and the voids were 48v%.

[0120] As the organic / inorganic sealing agent, Permeate HS-200 (trade name, manufactured by D&D Corporation, hereinafter simply referred to as "Permeate") was used, which has a viscosity of 15.5 mPa·s, a specific gravity of 1.15, siloxane bonds, and a non-volatile content of 85 wt %. Using a reduced pressure vessel 30 as shown in the schematic diagram of FIG. 2, a preform 32 was impregnated with permeate, which is a liquid organic / inorganic sealing agent 31, as described below. The preform 32 obtained above was placed in an interior vessel 34 placed inside the reduced pressure vessel 30, and a weight (not shown) was placed on top to prevent it from floating. Permeate was then poured into the interior vessel 34 via an organic / inorganic sealing agent pouring vessel 35, so that the entire preform was immersed in the permeate.

[0121] A vacuum was drawn across the entire reduced pressure vessel 30 via the pressure reduction port 36 using a vacuum pump (not shown), and this was maintained for 10 minutes. Thereafter, the vacuum was released to return the pressure inside the reduced pressure vessel 30 to normal pressure, and then air from a compressor (not shown) was reduced in pressure to 4 atmospheres using a pressure reducing device (not shown) and slowly introduced into the reduced pressure vessel 30, pressurizing the entire reduced pressure vessel to 4 atmospheres. This was maintained for 5 minutes, and the permeate was pressure-impregnated into the preform 32.

[0122] After that, the pressure vessel 30 was returned to atmospheric pressure, and the preform 32 was taken out of the indoor vessel 34 and left to stand overnight. After that, the temperature was increased at a rate of 50°C / hour, and a heat treatment was carried out at 400°C for 3 hours to produce a composite having a radiation shielding function. The specific gravity of this material (composite) was measured, and the composite was found to have a specific gravity of B ４ The material had 52 v % C, 30 v % organic / inorganic sealing agent (62.5 v % of the voids in the preform), and 18 v % voids. The specific gravities of the obtained materials (composites) are summarized in Table 2.

[0123] B obtained above ４The radiation shielding effect of a material (composite) with a volume filling rate (Vf) of 52v% C powder and a thickness of 20 mm was measured by an external measurement organization. The shielding rate for neutrons from the isotope of californium (Cf), Cf252, was measured and found to be 30%, a high value. There is no other shielding material that has shown such a high neutron shielding rate at a thickness of 20 mm. This result indicates that the composite obtained in this example is made of lightweight B powder, which is used as a raw material and has excellent radiation shielding effect. ４ The C powder is not decomposed and is compounded in its original state, ４ This indicates that this composite is a useful material that effectively combines the properties of C powder. A 3mm x 4mm x 40mm test piece for measuring bending strength was prepared from the composite obtained above and subjected to a bending test in accordance with JIS-R1061. The result was a strength of 25MPa. This value is approximately 5 to 10 times that of gypsum board and concrete board, measured using the same method, confirming that this material is suitable for use as an exterior wall material and radiation storage container.

[0124] [Example 10] The same material as used in the formulation of Example 2 above, B having an average particle size of 70 μm, was used. ４ 230 g of C powder #180 (manufactured by Dojin Sangyo Co., Ltd.) and B powder with an average particle size of 16 μm ４ Using 100 g of C powder #800, a molded body of 100 mm x 100 mm x 20 mm was prepared in the same manner as in Example 2. This molded body was fired at 400°C in the same manner as in Example 1, resulting in a preform weighing 235 g and having a bulk density of 1.66. ４ The volume filling rate (Vf) of C was about 66v%, and the voids were 32v%. The obtained preform was vacuum impregnated with permeate in the same manner as in Example 8, and then heat-treated at 400°C to obtain B ４ A radiation shielding material was obtained having 66 v % C, 19 v % permeate (organic / inorganic sealing agent) (59.4 v % of the voids in the preform), and 15% voids.

[0125] B obtained above ４The radiation shielding effect of a composite material with a volume filling rate (Vf) of 66% and a thickness of 20 mm was measured by an external measurement organization. The shielding factor for neutron radiation from the isotope Cf252 of californium (Cf) was measured, and the result was a high value of 34%. Furthermore, a bending test piece was prepared in the same manner as in Example 8, and the bending strength was measured, showing a high value of 41 MPa.

[0126] [Example 11] The same material as used in the formulation of Example 3 was used, and barium sulfate (BaSO) with an average particle size of 15 μm was used. ４ 240 g of A-200 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.), a powder of silicone resin, was used and mixed uniformly in the same manner as in Example 1. As a binder, a silicone resin solution was used, prepared by dissolving a soluble silicone resin KR-200 (manufactured by Shin-Etsu Chemical Co., Ltd.) in ethanol to a concentration of 20 wt % by mass. 15 g of the prepared silicone resin solution was then added to the mixed BaSO4 solution. ４ The mixture was added to the powder and stirred at high speed in a Henschel mixer in the same manner as in Example 1 to obtain a mixed powder.

[0127] The mixed powder obtained above was placed in a 60 mm diameter mold and subjected to a pressure of 160 kg / cm ２ This was then heated at 400°C in the same manner as in Example 1 to prepare a preform in the shape of a disk with a diameter of 60 mm, a thickness of 27.8 mm, and a weight of 235 g. The bulk density of the obtained preform was 2.95, and the thickness of BaSO ４ The volume was 65v% and the void was 35v%.

[0128] Next, a liquid organic / inorganic sealing agent was used on the preform obtained above to obtain a composite body as follows. ２ The preform obtained above was immersed in a container containing ethyl silicate oligomer manufactured by Colcoat Co., Ltd., containing 40 wt % of ethyl silicate in terms of phosphate conversion, and the preform was impregnated with the ethyl silicate under vacuum and pressure of 4 atmospheres. The impregnated body impregnated with the liquid organic / inorganic sealing agent was then removed from the container, left in the air for 48 hours, and then heat-treated at 400°C for 3 hours to remove BaSO. ４ 65v%, SiO produced from ethyl silicate ２A composite having a radiation shielding function was obtained in which the nonvolatile content was 10v% (28.6v% of the voids in the preform) and the remainder was 23v%.

[0129] The BaSO obtained above ４ An external measurement organization was commissioned to measure the radiation shielding effect of a material (composite) with a powder volume filling rate (Vf) of 65v% and a thickness of 27.8mm. The results showed high values ​​of 36% projection efficiency for cesium (Cs) gamma rays Cs137 and 99.7% shielding efficiency for 150Kv X-rays. Furthermore, bending test specimens were prepared in the same manner as in Example 1, and the bending strength was measured. The result was a high value of 28MPa, confirming that the material is fully usable as a structural material.

[0130] [Example 12] The same material as used in the formulation of Example 6, B having an average particle size of 16 μm, was used. ４ 54 g of C powder and BaSO with an average particle size of 15 μm ４ 7 g of ethyl silicate was added as a liquid binder to 110 g of powder A-200 (trade name), and the raw materials were mixed and press-molded in the same manner as in Example 1, followed by firing at 400°C to obtain a preform weighing 165 g, measuring 60 mmφ x 30 mm, and having a bulk density of 1.93. The obtained preform was B ４ C 29v%, BaSO ４ The volume fraction was 29v% and the void volume was 42v%.

[0131] Using a reduced pressure vessel 30 as shown in FIG. 2 and liquid ethyl silicate as the organic / inorganic sealing agent 31, the preform 32 obtained above was immersed in the ethyl silicate liquid, vacuum impregnated, and then heat-treated at 400° C. to obtain a composite having a radiation shielding function. The obtained composite was B ４ C 29v%, BaSO ４ 29v%, SiO of ethyl silicate ２ The nonvolatile content was 17v% (40.4v% of the voids in the preform) and the voids were 25v%.

[0132] The B obtained above ４ C powder, BaSO ４The radiation shielding effect of a material (composite) containing the powder and a liquid organic / inorganic sealing agent was measured by an external measurement organization. The results showed high values ​​of 25% projection efficiency for cesium (Cs) gamma rays Cs137 and 98% shielding efficiency for 150 kV X-rays. In addition, bending test pieces were prepared in the same manner as in the other examples, and the bending strength was measured. The value was high at 32 MPa, confirming that the material is suitable for industrial use as a structural member.

[0133] Table 2 shows the specific powders constituting the preforms used to form the composites of Examples 9 to 12, the amounts of organic / inorganic sealing agents in the voids of the preforms and in the composites, and the radiation shielding effects.

[0134] [Comparative Examples 7 to 10] Test pieces were prepared using the preforms used in preparing the composites of Examples 9 to 12, which had the configurations shown in Table 2, but which had not been impregnated with a liquid organic / inorganic sealing agent and compounded, and the bending strength was measured in the same manner as in the examples. The measurement results obtained are summarized in Table 3. For comparison, the bending strength multiplier for each composite of Examples 9 to 12 is shown in parentheses. As shown in Table 3, it was confirmed that the bending strength of the composites of the examples, in which the organic / inorganic sealing agent was compounded with the preform, was significantly improved compared to the materials of the comparative examples.

[0135]

[0136] [Comparative Example 11] The same bulk density as that prepared in Example 9 was 1.31, and B ４ A preform having a filling rate (Vf) of C of 52v% and a void of 48v% was used, and composited with an organic / inorganic sealing agent as described below to obtain a composite of Comparative Example 11. As a liquid organic / inorganic sealing agent, Permeate HS-200 having a viscosity of 15.5 mPa·s, a specific gravity of 1.15, a siloxane bond, and a non-volatile content of 85w% was used, which was diluted with ethanol to adjust the non-volatile content to 20w%. Then, after impregnating with a liquid organic / inorganic sealing agent in the same manner as in Example 9, a composite material was obtained by heat treatment. From the results of weight measurement, the material was B ４The material had 52v% C, 8v% organic / inorganic sealing agent (16.0v% of the voids in the preform), and 36v% voids. When the bending strength of this material was measured in the same manner as in the examples, the bending strength was 11 MPa, which was not high. The reason for this is thought to be due to the low amount of organic / inorganic composite agent in the voids in the preform.

[0137] Comparative Example 12: A bulk specific gravity of 2.95 was obtained using the same BaSO4 powder as that prepared in Example 11. ４ A preform having a filling rate (Vf) of 65v% and voids of 35v% was used, and composited with an organic / inorganic sealing agent as described below to obtain a composite of Comparative Example 12. The liquid organic / inorganic sealing agent was obtained by diluting the liquid ethyl silicate oligomer solution used in Example 11 with water to obtain SiO ２ The nonvolatile content of the solution was adjusted to 10 wt %. The preform was impregnated with the liquid organic / inorganic sealing agent in the same manner as in Example 11, and then heat-treated to obtain a composite material. The weight measurement revealed that the material contained BaSO ４ 65v%, SiO produced from ethyl silicate ２ The nonvolatile content was 4v% (11v% of the voids in the preform), and the remainder of the voids was 31v%. The bending strength of this material was measured in the same manner as in the examples, and the bending strength was 9 MPa, which was low.

[0138] [Comparative Example 13] The same bulk density as that prepared in Example 9 was 1.31, and B ４ A preform having a filling rate (Vf) of 52v% and a void volume of 48v% was used, and composited with an organic / inorganic sealing agent as described below to obtain a composite of Comparative Example 13. A solution of silicone resin KR2201 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) with a viscosity of 150 mPa.m dissolved in ethanol with a non-volatile content of 40w% was used as the liquid organic / inorganic sealing agent. The silicone resin solution was impregnated into a preform using the same procedure as in Example 9, and then heat-treated to obtain a composite material. The obtained material was B. ４ The Vf of C is 52v%, and SiO produced from silicone resin ２The nonvolatile content was 3v% (6.2v% of the voids in the preform), and the voids were 45v%. When the bending strength of this material was measured using the same method as in the examples, the bending strength was 6 MPa, which was low. The reason for this is thought to be that the silicone resin solution, which has a high viscosity, did not sufficiently impregnate the preform, and the impregnation amount of the organic / inorganic sealing agent was low.

[0139]

[0140] 1: Molten aluminum 2: Preform 3: Composite impregnated with molten aluminum 4: Lower punch 5: Upper punch 10: Press 30: Vacuum pressure vessel 31: Organic / inorganic sealing agent 32: Preform 33: Opening and closing jig for vacuum pressure vessel 34: Indoor vessel 35: Organic / inorganic sealing agent charging vessel 36: Vacuum outlet 37: Pressurization outlet 38: Pressure gauge

Claims

1. A composite having a radiation-shielding function, which contains a powder having a radiation-shielding effect in a composite amount of 3% by volume or more and 85% by volume or less, a porous molded body (preform) which is a molded and fired product of a mixture containing one or more of the radiation-shielding powders 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 mainly composed of iron oxide, and a non-powdered silica-based binder, and all of the voids of the porous molded body (preform) are impregnated and filled with at least one of a molten low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, which has a melting point of 200°C or more and 900°C or less, or a low-melting-point alloy of the low-melting-point metal with another metal, and the melting point is solidified to form a composite; a liquid silica-based binder that is at least one selected from the group consisting of a liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and a silica alkoxide that is made of silica and an organic substance and that is heat-cured at a temperature of 900°C or less; and a composite having a radiation-shielding function, characterized in that the non-powdered silica-based binder has a property that allows the molding and firing product, that is, a porous molded body (preform), to be formed at a temperature at which the radiation-shielding powder is not decomposed.

2. The mixture is prepared by mixing the liquid silica-based binder with SiO2 for 100 parts by mass of the radiation-shielding powder. ２ 2. The radiation-shielding composite according to claim 1, wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

3. A composite having a radiation-shielding function, which contains a powder having a radiation-shielding effect in a composite amount of 3% by volume or more and 85% by volume or less, a composite having a radiation-shielding function, characterized in that the composite has a constitution in which at least 25% by volume of pores of a porous molded body (preform) is impregnated with a liquid organic / inorganic sealing agent, and solidified to form a composite, the porous molded body (preform) being a molded and fired product of a mixture containing one or more types of powder having a 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 mainly composed of iron oxide, and a non-powdered silica-based binder; and the porous molded body (preform) is formed by molding and firing the mixture at a temperature at which the radiation-shielding powder is not decomposed.

4. The non-powdered silica-based binder is at least one liquid silica-based binder selected from the group consisting of water glass (sodium silicate), colloidal silica, liquid silicone resin, silicone resin solution obtained by dissolving silicone resin in an organic solvent, and silica alkoxide made of silica and organic matter that is heat-cured at a temperature of 900°C or less, and the mixture is a mixture of the liquid silica-based binder and SiO2 with respect to 100 parts by mass of the radiation-shielding powder. ２ 4. The radiation-shielding composite according to claim 3, wherein the amount of the compound added is 0.5 to 10 parts by mass in terms of the total mass of the compound.

5. A composite having a radiation-shielding function according to claim 3 or 4, wherein the liquid organic / inorganic pore-blocking agent is present in the voids of the porous molded body (preform) as a solidified product of the organic / inorganic pore-blocking agent and / or a heat-treated product of the organic / inorganic pore-blocking agent, and the solidified product of the organic / inorganic pore-blocking agent and / or the heat-treated product of the organic / inorganic pore-blocking agent occupies 25% by volume or more of the 100% by volume of the voids in the porous molded body (preform) before impregnation, and when the entire preform after impregnation is taken as 100% by volume, the solidified product of the organic / inorganic pore-blocking agent and / or the heat-treated product of the organic / inorganic pore-blocking agent occupies 5% by volume or more.

6. The liquid organic / inorganic sealing agent has a low viscosity of 50 mPa·s or less and contains 30 mass% or more of non-volatile components, ３ ) ４ Alternatively, the methyl silicate may be partially hydrolyzed to form a dimer or tetramer oligomer, and the non-volatile content of the liquid methyl silicate compound may be adjusted to 30% by mass or more. ２ H ５ ) ４ or a liquid ethylsilicate compound obtained by partially hydrolyzing the ethylsilicate to form a dimer or tetramer oligomer, and adjusted to have a non-volatile content of 30% by mass or more; a silicone resin or derivative thereof having a siloxane bond and adjusted to have a non-volatile content of 30% by mass or more; or a liquid alkoxysilane compound that is an alkoxysilane derivative and reacts with moisture in the air to undergo a condensation reaction to produce a silicone-oxygen organic compound (Si—O—R).

7. A method for producing a composite having radiation-shielding function, comprising a matrix of at least one of a molten low-melting metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting alloy of said low-melting metal with another metal, and containing a powder having a radiation-shielding effect in a total amount of 3% by volume or more and 85% by volume or less, the method comprising: a step of adding a non-powdered silica-based binder to one or more of the 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 mainly composed of iron oxide, and mixing the mixture to form a porous molded body (preform), and then firing the resulting molded body at a temperature of 300°C or higher and 900°C or lower, wherein the non-powdered silica-based binder used in the step is at least one liquid silica-based binder selected from the group consisting of a liquid silicone resin, a silicone resin solution obtained by dissolving a silicone resin in an organic solvent, and a silica alkoxide made of silica and an organic substance and heat-cured at a temperature of 900°C or lower; and a step of casting a molten metal of at least one low-melting-point metal selected from the group consisting of aluminum metal, aluminum alloy, zinc, tin, and lead, or a low-melting-point alloy of the low-melting-point metal and another metal, which has been melted at a temperature of 300°C or more and 900°C or less, and which has a melting point of 200°C or more and 900°C or less, into the porous molded body (preform) obtained in the step of casting, and then holding the molten metal at a high pressure of 20 MPa or more and 200 MPa or less for 3 to 15 minutes in order to impregnate the porous molded body (preform) with the molten metal, and then removing the composite impregnated with the molten metal within 15 minutes and cooling it, thereby suppressing decomposition of the radiation-shielding powder in the composite.

8. The mixture is prepared by mixing the liquid silica-based binder with SiO2 for 100 parts by mass of the radiation-shielding powder. ２ The method for producing a composite having a radiation-shielding function according to claim 7, wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

9. A method for producing a composite having radiation shielding properties, which comprises preparing a composite containing a total of 3 to 85 volume % of powders having radiation shielding properties, the powders being composited together, the composite comprising: one or more types of powders having radiation shielding properties 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 mainly composed of iron oxide; a non-powdered silica-based binder is added to the powder, the mixture is mixed, and the resulting molded body is fired at a temperature of 300 to 900°C to produce a porous molded body (preform); and a compounding step of: vacuum-impregnating voids of the porous molded body (preform) obtained in the step of producing the porous molded body (preform) with a liquid organic / inorganic sealing agent containing 30% by mass or more of non-volatile components and having a viscosity of 50 mPa s or less, or impregnating the voids of the porous molded body (preform) under a pressure of 10 atmospheres or less by applying pressure after vacuum impregnation, and then heating the voids to a temperature of 200°C or more and 900°C or less, so that a solidified product of the liquid organic / inorganic sealing agent and / or a heat-treated product of the liquid organic / inorganic sealing agent remains in an amount of 25% by volume or more relative to 100% by volume of the voids of the porous molded body (preform), and compounding the radiation-shielding powder with a component derived from the liquid organic / inorganic sealing agent.

10. The liquid organic / inorganic sealing agent has a low viscosity of 50 mPa·s or less and contains 30 mass% or more of non-volatile components, ３ ) ４ Alternatively, the methyl silicate may be partially hydrolyzed to form a dimer or tetramer oligomer, and the non-volatile content of the liquid methyl silicate compound may be adjusted to 30% by mass or more. ２ H ５ ) ４ or a liquid ethylsilicate compound obtained by partially hydrolyzing the ethylsilicate to form a dimer or tetramer oligomer and adjusting the non-volatile content to 30% by mass or more; a silicone resin or derivative thereof having a siloxane bond and adjusting the non-volatile content to 30% by mass or more; or a liquid alkoxysilane compound which is an alkoxysilane derivative and reacts with moisture in the air to undergo a condensation reaction to produce a silicone-oxygen organic compound (Si—O—R).

11. The non-powdered silica-based binder is at least one liquid silica-based binder selected from the group consisting of water glass (sodium silicate), colloidal silica, liquid silicone resin, silicone resin solution obtained by dissolving silicone resin in an organic solvent, and silica alkoxide made of silica and organic matter that is heat-cured at a temperature of 900°C or less, and the mixture is prepared by mixing the liquid silica-based binder with SiO2 for 100 parts by mass of the radiation-shielding powder. ２ The method for producing a composite having a radiation-shielding function according to claim 9 or 10, wherein 0.5 to 10 parts by mass of the compound is added in terms of the amount of the compound.

12. Furthermore, in the step of producing the porous molded body (preform), when aluminum powder, aluminum alloy powder, or ceramic powder is added to the radiation-shielding powder and the total of the aluminum metal powder, aluminum alloy powder, or ceramic powder and the radiation-shielding powder is taken as 100 mass %, the non-powdered silica-based binder is SiO ２ 9. The method for producing a composite having a radiation-shielding function according to claim 7 or 8, wherein the porous molded body (preform) is produced by adding 0.5 to 10 mass % of the inorganic filler in terms of the amount of the inorganic filler.

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