Porous material and manufacturing method thereof

Abstract

To provide a manufacturing method of a porous material capable of avoiding a hardness from being lowered by a heat treatment, and the porous material obtained by the method.SOLUTION: A manufacturing method of a porous material includes: compacting a mixed powder of a base powder including a metallic material and a supporting powder at a temperature lower than a recrystallization temperature of the metallic material; and causing the compacted mixed powder to have contact with a solvent to melt and remove the supporting powder. According to the manufacturing method of a porous material, a metallic material is provided in which a hardness of a metal skeleton part of the porous material is equal to or higher than a hardness of a metallic material as a raw material included in the metal skeleton part, in the porous material including the metallic material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a porous material and a method for manufacturing the same.

Background Art

[0002] Porous materials have many pores and are used in various fields such as filters, catalysts, heat exchangers, medical artificial bones and implants, electrode materials, cushioning materials, and sound-absorbing materials due to their air permeability and large specific surface area.

[0003] Porous materials formed of generally used metal materials are produced by methods that involve a heat treatment process, such as electroplating, casting, foaming, combustion synthesis, and powder sintering. However, due to changes in the material properties of the metal materials, such as a decrease in hardness due to a heat load above the recrystallization temperature of the metal material constituting the porous material, and a phase transformation and the formation of an alloy layer due to a heat load above the melting point of the metal material, there is a risk of significantly reducing mechanical properties such as hardness, tensile strength, yield strength, and fatigue strength. Generally, when the hardness of a porous body is insufficient, there is a risk of causing a decrease in mechanical properties, and it is difficult to use in fields where high mechanical properties are required. In particular, in composite materials obtained by mixing alloys, mixtures of metals, and metals and inorganic compounds, the tendency for a decrease in mechanical properties due to heat treatment becomes prominent. Therefore, it is necessary to select metals, metal mixtures, and composite materials in consideration of the heat influence, and the materials that can be used are limited.

[0004] For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2015-74820) describes a method for producing a porous material by subjecting the surface of the skeleton of a foamed resin to a conductive treatment, performing nickel plating and tin plating, and then thermally decomposing and removing the resin part. However, in this method, high-temperature heating of 1000°C is required for the thermal decomposition and removal of the resin part, and since it exceeds the recrystallization temperature of nickel, there is a risk of a significant decrease in hardness. In addition, since it is a method limited to metal species that can be plated, the metal materials that can be used are limited. Further, since it is necessary to circulate the plating solution, only pore diameters of several hundred μm or more can be formed. Furthermore, the environmental load increases due to the thermal decomposition and removal of the resin part.

[0005] In Patent Document 2 (Japanese Patent Application Laid-Open No. 2016-83813) and Patent Document 3 (Japanese Patent Application Laid-Open No. 2011-42873), a method is described in which a mixed powder obtained by mixing titanium powder, silicon carbide powder, etc. with sodium chloride powder and aluminum powder is pressure-sintered, and then sodium chloride is removed by washing with water to produce a porous material. However, this method has a problem that the hardness decreases because the recrystallization temperature of the aluminum part is exceeded due to the heat load caused by sintering. Furthermore, since a metal material such as aluminum that can be sintered at a temperature lower than the melting point of sodium chloride (810 ° C) is used as an essential component, the metal materials that can be used are limited.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present disclosure is to provide a method for producing a porous material that can avoid a decrease in hardness due to heat treatment, and a porous material obtained thereby.

Means for Solving the Problems

[0008] The present inventors have found that the above problems can be solved by compressing and solidifying a mixed powder of a raw material powder and a support powder of a metal material, and then dissolving and removing the support powder. Examples of embodiments of the present disclosure are listed in the following items [1] to

[12] . [1] A method for producing a porous material, the method comprising: Compressing and solidifying a mixed powder of a raw material powder containing a metallic material and a support powder at a temperature below the recrystallization temperature of the metallic material; Bringing the compressed and solidified mixed powder into contact with a solvent to dissolve and remove the support powder, a method for producing a porous material. [2] The method according to item 1, wherein the compression and solidification is performed by an explosion compaction method. [3] The method according to item 1 or 2, wherein the metallic material includes at least one metallic material selected from the group consisting of pure metals, alloys, and combinations thereof. [4] The method according to any one of items 1 to 3, wherein the metallic material includes two or more metallic materials. [5] The method according to any one of items 1 to 4, wherein the raw material powder further includes an inorganic compound. [6] The method according to any one of items 1 to 5, wherein the support powder includes a water-soluble salt and the solvent includes water. [7] The method according to any one of items 1 to 6, wherein the compression and solidification is performed in a state where a layer formed from a first mixed powder and a layer formed from a second mixed powder having a composition different from that of the first mixed powder are laminated. [8] A porous material containing a metallic material, wherein the hardness of the metallic skeleton portion of the porous material is equal to or greater than the hardness of the metallic material as a raw material constituting the metallic skeleton portion. [9] The porous material according to item 8, wherein the metallic material includes at least one metallic material selected from the group consisting of pure metals, alloys, and combinations thereof.

[10] The porous material according to item 8 or 9, wherein the metallic material includes two or more metallic materials, and the hardness of the metallic skeleton portion of the porous material is equal to or greater than the hardness of the metallic material as a raw material constituting the metallic skeleton portion.

[11] The porous material according to any one of items 8 to 10, further contains an inorganic compound, and the hardness of the metal skeleton part of the porous material is equal to or higher than the hardness of the metal material as the raw material constituting the metal skeleton part.

[12] The porous material according to any one of items 8 to 11, has two or more types of porous layers with different structures and / or compositions of the metal skeleton part.

Advantages of the Invention

[0009] The present disclosure can provide a method for manufacturing a porous material capable of avoiding a decrease in hardness due to heat treatment, and a porous material obtained thereby.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments. The upper limit value and the lower limit value in each numerical range of the following embodiments can be arbitrarily combined to form an arbitrary numerical range.

[0012] 《Method for Manufacturing Porous Material》 The method for manufacturing a porous material of the present disclosure includes compressing and solidifying a mixed powder of a raw material powder containing a metal material and a support powder at a temperature below the recrystallization temperature of the metal material, and removing the support powder from the compressed and solidified mixed powder. The removal of the support powder can be performed by bringing the compressed and solidified mixed powder into contact with a solvent to dissolve and remove the support powder. In the present disclosure, the "porous material" refers to a material containing many voids. According to the method of the present disclosure, since compression and solidification are performed at a temperature below the recrystallization temperature of the metal material, it is possible to avoid a decrease in the hardness of the metal material due to heat treatment. In addition, there is no need to consider the influence of heat treatment, and there is a wider range of choices for the material of the porous material compared to conventional methods in which the available metals are limited, such as plating or pressure sintering. Therefore, according to the present disclosure, even with various combinations such as a single pure metal, an alloy, a mixture of two or more pure metals and / or alloys, and a composite material of a pure metal or alloy and an inorganic compound, using a wide variety of metals, a porous material is provided in which the hardness of the metal skeleton portion is equal to or higher than the hardness of the metal material as a raw material. Furthermore, it is possible to reduce the environmental load compared to conventional methods including thermal decomposition and removal of the resin portion.

[0013] 〈Raw material powder〉 The raw material powder contains a metallic material. The metallic material preferably contains at least one metallic material selected from the group consisting of pure metals, alloys, and combinations thereof. The pure metal is preferably a metal belonging to Groups 1 to 14, more preferably Groups 3 to 13 of the periodic table, although not limited thereto. Specifically, examples of the metal include iron, nickel, copper, aluminum, titanium, chromium, cobalt, zinc, gold, silver, and tungsten. For example, in addition to aluminum used as the metal of the porous body in Patent Documents 2 and 3, materials such as nickel and tungsten, which are high melting point metals and generally difficult to make porous, can also be used. The alloy is preferably a combination of two or more of the above metals, for example, an alloy mainly composed of iron, nickel, copper, aluminum, titanium, chromium, cobalt, zinc, gold, silver, or tungsten listed above. The "main component" refers to the metal with the largest weight ratio in the metal composition of the alloy. Specifically, examples of the alloy include stainless steel, brass, cupronickel, bronze, solder, duralumin, and nichrome. Stainless steel is preferred because it has high mechanical properties and corrosion resistance. The porous material of stainless steel may be used as the metal support material (metal support) of a metal-supported type SOFC (solid oxide fuel cell). The pure metal and the alloy are not limited to pure or high-purity pure metals and alloys, and pure metals and alloys containing a certain amount of impurities can also be used. The impurities may be other metal elements or non-metal elements such as carbon, phosphorus, and sulfur.

[0014] The metallic material may be used alone or may contain two or more metallic materials. For example, the metallic material may contain two or more pure metals, two or more alloys, or a combination of one or more pure metals and one or more alloys. Examples of the combination of a pure metal and an alloy include pure aluminum and stainless steel. Even when the metallic material contains aluminum with low hardness and stainless steel with high hardness, the hardness of both materials can be increased. When the metallic material contains two or more metallic materials, their mixing ratio is not particularly limited.

[0015] The metal material is in the form of powder, and its average particle size is, although not limited, preferably 0.1 μm to 1000 μm. The upper limit value of the average particle size of the metal material may be, for example, 800 μm or less, 500 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. The lower limit value that can be combined with these upper limit values is, for example, 0.5 μm or more, 1 μm or more, 5 μm or more, or 10 μm or more. The particle size distribution of the metal material preferably contains 30% or more of powder with a particle size of 500 μm or less, and more preferably contains 30% or more of powder with a particle size of 250 μm or less. If the proportion of powder with a particle size larger than 500 μm is 30% or less, it is easy to mix homogeneously with the support powder and the inorganic compound, and a more homogeneous porous material can be obtained.

[0016] In addition to the metal material, the raw material powder may further contain an inorganic compound. When the raw material powder further contains an inorganic compound in addition to the metal material, the porous material can be used for various applications. For example, it can be used as a catalyst or as a fuel electrode (such as a mixture of Ni + YSZ) of an SOFC. Also, for example, when it contains a glass component, there is an advantage that the inorganic compound can be expected to act as a solidification aid. The inorganic compound is not particularly limited as long as it is a solid inorganic compound at normal temperature, and preferably includes inorganic materials such as oxides, nitrides, carbides, and borides of metals or non-metals. Specifically, examples of the inorganic compound include SiO2, TiO2, Al2O3, ZrO2, yttria-stabilized zirconia (YSZ), TiN, SiC, and WC, etc. From the above-mentioned viewpoints, Al2O3 and YSZ are preferred. The inorganic compound may be used alone or in combination of two or more.

[0017] The inorganic compound is in the form of a powder, and its average particle size is preferably from 0.1 μm to 1000 μm, although it is not limited. The upper limit value of the average particle size of the inorganic compound may be, for example, 800 μm or less, 500 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. The lower limit values that can be combined with these upper limit values are, for example, 0.5 μm or more, 1 μm or more, 5 μm or more, or 10 μm or more. The particle size distribution of the inorganic compound preferably contains 30% or more of powder with a size of 500 μm or less, and more preferably contains 30% or more of powder with a size of 250 μm or less. If the proportion of powder with a particle size larger than 500 μm is 30% or less, it is easy to mix homogeneously with the support powder and the metal powder, and a more homogeneous porous material can be obtained.

[0018] When the raw material powder further contains an inorganic compound in addition to the metal material, the mixing ratio of the inorganic compound, with the total volume of the above raw material powder being 100% by volume, is preferably more than 0% by volume and 90% by volume or less, more preferably 80% by volume or less, still more preferably 70% by volume or less, even more preferably 60% by volume or less, particularly preferably 50% by volume or less, 40% by volume or less, 30% by volume or less, 20% by volume or less, or 10% by volume or less. The lower limit values that can be combined with these upper limit values are preferably 1% by volume or more, more preferably 5% by volume or more, and still more preferably 10% by volume or more.

[0019] 〈Support powder〉 The support powder is solid at room temperature and is not particularly limited as long as it is a material (hereinafter also referred to as "soluble material") that easily dissolves in a solvent (water or organic solvent). Examples of the soluble material preferably include water-soluble salts such as sodium chloride, potassium chloride, potassium aluminum sulfate (alum), and magnesium sulfate.

[0020] The support powder is in powder form, and its average particle size is, although not limited, preferably 0.1 μm to 1000 μm. The upper limit value of the average particle size of the support powder may be, for example, 800 μm or less, 500 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. The lower limit value that can be combined with these upper limit values is, for example, 0.5 μm or more, 1 μm or more, 5 μm or more, or 10 μm or more. By adjusting the average particle size of the support powder, the pore diameter of the porous material can be adjusted.

[0021] 〈Mixed powder〉 The mixed powder contains the raw material powder and the support powder described above. The mixing ratio of the raw material powder and the support powder is not limited. For example, taking the total volume of the mixed powder as 100% by volume, the raw material powder can be 10% to 90% by volume, and the support powder can be 10% to 90% by volume. The upper limit value of the mixing ratio of the raw material powder may be, for example, 80% by volume or less, 70% by volume or less, 60% by volume or less, 50% by volume or less, 40% by volume or less, 30% by volume or less, or 20% by volume or less, and the lower limit value that can be combined with these upper limit values is, for example, 20% by volume or more, 30% by volume or more, 40% by volume or more, 50% by volume or more, 60% by volume or more, 70% by volume or more, or 80% by volume or more. The upper limit value of the mixing ratio of the support powder may be, for example, 80% by volume or less, 70% by volume or less, 60% by volume or less, 50% by volume or less, 40% by volume or less, 30% by volume or less, or 20% by volume or less, and the lower limit value that can be combined with these upper limit values is, for example, 20% by volume or more, 30% by volume or more, 40% by volume or more, 50% by volume or more, 60% by volume or more, 70% by volume or more, or 80% by volume or more. By adjusting the mixing ratio of the raw material powder and the support powder, the porosity of the porous material can be adjusted.

[0022] The mixed powder may be used alone as one type of mixed powder, or two or more types of mixed powders having different compositions may be combined and used. For example, compression and solidification can be performed in a state where a layer formed from the first mixed powder and a layer formed from the second mixed powder having a composition different from that of the first mixed powder are laminated. That is, two or more types of mixed powders having different compositions are sequentially introduced into the same jig, formed into layers, and then squeezed together, so that a plurality of types of porous materials can be compression-solidified in an integrated state (hereinafter, also referred to as "one-shot molding"). By one-shot molding, a porous material having two or more types of porous layers with different structures and / or compositions can be easily obtained without separately molding and laminating different porous materials. The composition of the mixed powder includes parameters such as the material types of the raw material powder and the support powder, the mixing ratio of the materials, the average particle size, and the particle size distribution. The structure and / or composition of the porous layer includes the porosity and pore diameter of the porous layer, etc., as well as the material types, content ratios, and distributions of the metal material and any inorganic compound constituting the porous layer.

[0023] 〈Compression and Solidification〉 In compression solidification, the mixed powder described above is compression-solidified at a temperature below the recrystallization temperature of the metal material. By doing so, it is possible to avoid a decrease in the hardness of the metal material due to heat treatment, the range of material selection for the porous material is wide, and it is also possible to reduce the environmental load. The recrystallization temperature is the temperature at which a pure metal or alloy undergoes recrystallization as defined in JIS G 0201. This temperature is significantly affected by the purity, composition, degree of plastic strain within the crystal, and overheating time of the pure metal and alloy, and the physical properties of the metal material change. For example, the recrystallization temperature of A1100-H112 of JIS H 4000 is about 180°C, the recrystallization temperature of NW2200 of JIS H 4551 is about 600°C, and the recrystallization temperature of SUS304L of JIS G 4305 is about 530°C. The upper limit value of the temperature of compression solidification is not limited as long as it is below the recrystallization temperature, but preferably it can be 150°C or lower, or 100°C or lower. The lower limit value of the temperature of compression solidification that can be combined with these upper limit values is not limited as long as compression solidification can be performed, but preferably it can be 40°C or higher, 70°C or higher, or 90°C or higher.

[0024] The method of compression solidification is not particularly limited as long as the mixed powder can be compressed and formed into a predetermined shape at a temperature below the recrystallization temperature of the metal material. Preferably, the explosive compaction method can be mentioned as the method of compression solidification. The explosive compaction method is a method of instantaneously compression-solidifying using a shock wave generated by explosives, and generally used methods such as the cylindrical convergence method and the uniaxial compression method can be used. When it is desired to obtain a columnar or cylindrical compressed body, the cylindrical convergence method is selected, and when it is desired to obtain a plate-shaped compressed body, the uniaxial compression method is selected. In addition, when obtaining a cylindrical compressed body, a cylindrical convergence method with a core material in the center can be used. Note that the explosive compaction method utilizes the energy of explosives and although there is an assumed instantaneous heat effect, the effect is limited and does not lead to recrystallization throughout the compressed body.

[0025] An explosive is a type of gunpowder that generates a detonation wave. Specifically, examples of explosives include ammonium nitrate; nitrate esters such as PETN (pentaerythritol tetranitrate) and nitroglycerin; nitro compounds such as TNT (trinitrotoluene); and nitramines such as cyclotrimethylene trinitramine and cyclotetramethylene tetranitramine. An explosive may be used alone, or two or more types may be mixed and used, or a mixture of other explosive components or components other than explosives may be used.

[0026] In order to firmly solidify the metal powder, the detonation velocity is preferably 1,500 to 8,000 m / s, and more preferably 2,000 to 5,000 m / s. The detonation velocity is appropriately selected according to the characteristics of the metal powder and the compression method.

[0027] When compression solidification is performed using a shock wave, it can be compression solidified with a shock wave using a liquid as a medium. Preferably, water is used as the liquid. When a shock wave using water as a medium (hereinafter referred to as an underwater shock wave) is used, the duration for which the pressure of the shock wave itself persists is longer than when air is used as a medium. Also, when water is used as a medium, it is extremely easy to keep the temperature lower (below the recrystallization temperature of the metal material) than when air is used as a medium.

[0028] The following is an example of a method for compressing and solidifying powder using shock waves, which will be described with reference to the drawings. The present disclosure is not limited in any technical scope by these specific examples. FIG. 1 is a schematic diagram showing an example of an apparatus for applying a shock wave to powder by the cylindrical convergence method. In FIG. 1, a metal pipe 1 for powder filling is filled with a mixed powder 2 for pressing. Both ends of the metal pipe 1 for powder filling are sealed by metal plugs 3. The metal pipe 1 for powder filling is placed vertically on a resin bottom plate 8 and covered with a resin pipe 5 with a buffer 4 set on the upper part of the metal plug 3 at the upper end. The buffer 4 serves to prevent the pipe 1 from breaking when the detonation pressure first reaches the upper part of the metal pipe 1 for powder filling located directly below the initiation point, and to induce a uniform pressure in the radial direction of the pipe 1. An explosive 6 is loaded in the space between the metal pipe 1 for powder filling and the resin pipe 5. A detonator 7 is installed above the explosive 6. When the explosive 6 is detonated by the detonator 7, the mixed powder 2 is compressed in the radial direction by the shock wave generated by the explosive 6.

[0029] FIG. 2 is a schematic diagram showing an example of an apparatus for applying a shock wave to powder by the cylindrical convergence method. It is the same as the apparatus of FIG. 1 except that the metal pipe 1 for powder filling of the apparatus of FIG. 1 is covered with a metal flying pipe 9 to form a double-tube structure. Generally, since a substance (metal flying pipe 9) with a density higher than that of the explosive is made to fly and collide at high speed, it is possible to compress at a higher pressure than the apparatus of FIG. 1. Also, by filling water between the double tubes, it is possible to compress and solidify using water as a medium.

[0030] FIG. 3 is a schematic diagram showing an example of an apparatus for applying a shock wave to powder by the uniaxial compression method. In FIG. 3, the mixed powder 2 for pressing is laid on the bottom surface of a metal jig 11, and a metal jig 10 is placed on the mixed powder 2. The explosive 6 is directly placed on the metal jig 10 inside the metal jig 11. A container filled with the explosive 6 may be placed on the metal jig 10. A detonator 7 is installed above the explosive 6. When the explosive 6 is detonated by the initiation part 7, the mixed powder 2 is compressed in the downward direction by the shock wave generated by the explosive 6.

[0031] By increasing the shock wave, it is preferable that the relative density of the mixed powder after compression and solidification is 90 to 99%. Here, the relative density is based on the density (100%) assuming that the target mixed powder is compressed so as to completely fill the interstitial volume, and represents the actual density of the mixed powder after compression and solidification in %, and is expressed by the following formula. Relative density = (actual density) ÷ (reference density) × 100

[0032] 〈Removal of support powder〉 By bringing the compressed and solidified mixed powder (hereinafter also referred to as "compressed body") into contact with a solvent and dissolving and removing the support powder, pores are formed at the locations where the support powder was scattered, and a porous material is obtained. Since there is no heat load above the recrystallization temperature, the hardness of the metal skeleton part of the obtained porous material can be made equal to or higher than the hardness of the metal material as the raw material (raw material before compression and solidification) constituting the metal skeleton part.

[0033] The method for dissolving and removing the support powder is not limited, but examples include a method of immersing the compressed body in a solvent to elute the support powder. If necessary, physical stimuli such as heating the solvent, flowing the solvent, or rocking the compressed body may be applied. The temperature during the treatment does not exceed the recrystallization temperature of the metal material, and the upper limit value of the temperature when removing the support powder can preferably be 200°C or lower, 150°C or lower, or 100°C or lower. The lower limit value that can be combined with these upper limit values can preferably be 40°C or higher, 70°C or higher, or 90°C or higher.

[0034] 〈Examples of embodiments〉 An example of a preferred embodiment of the present disclosure will be described. Using the apparatus of FIG. 1 or FIG. 2, a mixed powder 2 for pressing, which is a mixture of a raw material powder made of a metal material (for example, nickel powder) and a support powder (for example, NaCl powder), is naturally filled into a metal pipe 1 for powder filling. The mixed powder 2 can also be pre-compressed if necessary. Next, the mixed powder 2 is instantaneously compressed by a high-pressure shock wave by the explosion compaction method. The temperature in the explosion compaction method is about 80° C., and the recrystallization temperature of the metal material (nickel) is not reached. The compressed compact is taken out from the metal pipe 1 for powder filling, and the compact is washed with water. At this time, since the support powder (NaCl powder) is dissolved in water and removed, pores are formed at the locations where the support powder was scattered, and a porous material can be obtained. Furthermore, due to the compression of the metal material and the absence of a heat load above the recrystallization temperature, the hardness of the metal skeleton portion of the obtained porous material can be made equal to or higher than the hardness of the metal material (nickel) as the raw material constituting the metal skeleton portion.

[0035] 《Porous Material》 The porous material of the present disclosure is a porous material containing a metal material, and the hardness of the metal skeleton portion of the porous material is equal to or higher than the hardness of the metal material as the raw material constituting the metal skeleton portion. The metal skeleton portion means the structural part of the porous material composed of the metal material. When the porous material contains an inorganic compound in addition to the metal material, the metal skeleton portion means the part composed of the metal material in its structure. The porous material of the present disclosure can be obtained by the method for producing the porous material of the present disclosure described above.

[0036] 〈Hardness〉 The hardness is a value determined in accordance with the Vickers hardness test - test method of JIS Z 2244 and the ultra-micro load hardness test method of JIS Z 2255. The hardness of the metal skeleton part of the porous material is preferably 1.05 times or more, more preferably 1.1 times or more, still more preferably 1.15 times or more, even more preferably 1.2 times or more, particularly preferably 1.3 times or more, 1.4 times or more, or 1.5 times or more, based on the hardness of the metal material as the raw material. The upper limit of the hardness of the metal skeleton part of the porous material combined with these lower limit values is not limited, but can be, for example, 3 times or less, 2.5 times or less, or 2 times or less, based on the hardness of the metal material as the raw material. For example, even if the selected metal material is a hard and high melting point metal such as tungsten or molybdenum, the hardness of the metal skeleton part can be 1.05 times or more the hardness of tungsten and molybdenum as the raw material.

[0037] 〈Material〉 The metal material contained in the porous material preferably contains at least one metal material selected from the group consisting of pure metals, alloys, and combinations thereof. The details regarding the type of the metal material are as described above. It is more preferable that the metal material contains two or more metal materials, and the hardness of the part corresponding to each metal material in the metal skeleton part of the porous material is not less than the hardness of each metal material as the raw material constituting the metal skeleton part. The porous material may further contain an inorganic compound in addition to the metal material. The details regarding the type of the inorganic compound are as described above. When the porous material further contains an inorganic compound in addition to the metal material, it is more preferable that the hardness of the part corresponding to each metal material in the metal skeleton part of the porous material is not less than the hardness of each metal material as the raw material constituting the metal skeleton part.

[0038] 〈Porosity〉 The porosity of the porous material is preferably 5% or more and 95% or less, more preferably 15% or more and 85% or less, and still more preferably 20% or more and 80% or less. When the porosity is 5% or more, it is easy to remove the support powder, and when the porosity is 95% or less, the porous material can obtain sufficient mechanical strength. The porosity can be adjusted by adjusting the mixing ratio of the raw material powder and the support powder.

[0039] 〈Pore diameter〉 The pore diameter of the porous material is preferably 0.1 μm or more and 3000 μm or less. The upper limit value of the pore diameter is, for example, 2000 μm or less, 1500 μm or less, 1000 μm or less, 800 μm or less, 500 μm or less, 250 μm or less, or 200 μm or less. The lower limit value of the pore diameter is, for example, 0.5 μm or more, or 1 μm or more. When the pore diameter is 0.1 μm or more, it is easy to remove the support powder, and when the pore diameter is 3000 μm or less, the porous material can obtain sufficient mechanical strength. The pore diameter can be adjusted by adjusting the average particle diameter and the particle size distribution of the support powder.

[0040] 〈Laminated structure〉 The porous material may have two or more types of porous layers having different structures and / or compositions. Such a laminated structure can be obtained by performing compression and solidification in a state where a layer formed from the first mixed powder and a layer formed from a second mixed powder having a composition different from that of the first mixed powder are laminated as described above.

Examples

[0041] Hereinafter, examples and comparative examples of the present disclosure will be shown, but the present disclosure is not limited to these examples and comparative examples.

[0042] 《Measurement and evaluation methods》 〈Average particle diameter, particle size distribution〉 The measurement of the average particle size and particle size distribution was carried out in accordance with the particle size analysis - laser diffraction / scattering method of JIS Z 8825 and the general rules for the sieving test method of JIS Z 8815. For the powder adjusted within a predetermined particle size range by sieving, the sieved range was taken as the particle size range of the powder.

[0043] 〈Porosity〉 The measurement of the porosity was carried out in accordance with the open porosity measurement method described in the method for measuring the sintered body density and open porosity of fine ceramics of JIS R 1634. When the porosity exceeded 80%, the porous material was processed into a 5 mm cube size, and the porosity was calculated from the weight in the dry state and the true density. The calculation method is as follows. Porosity (vol%) = (dry weight ÷ apparent volume) ÷ true density × 100

[0044] 〈Pore diameter〉 The pore diameter was measured with an electron microscope (SEM). Specifically, the obtained porous material was cut, and the cross-section was observed with an electron microscope. The length of the pore part was measured at 10 points or more, and that range was taken as the pore diameter.

[0045] 〈Hardness〉 The measurement of the hardness was carried out in accordance with the Vickers hardness test - test method of JIS Z 2244 and the method for ultra-micro load hardness test of JIS Z 2255. When the metal skeleton part was in an ultra-micro region where it could not be applied with a micro Vickers hardness tester, a nanoindentation tester was used. As a result of the hardness measurement, if the hardness of the metal skeleton part of the porous material was equal to or higher than the hardness of the metal material as the raw material, the evaluation was ○, and if it was less than the material strength, the evaluation was ×.

[0046] 《Examples and Comparative Examples》 〈Example 1〉 As the metal powder, pure aluminum (Al) powder (average particle size: about 3 μm) was used, and as the support powder, sodium chloride (NaCl) powder (sieve fraction particle size: 250 - 800 μm) was used. The Al powder and the NaCl powder were mixed at a volume ratio of Al powder: 50 vol%, NaCl powder: 50 vol%, and naturally filled into the metal pipe 2 for powder filling. Using an explosive with a detonation velocity of 2500 m / s, compression was performed by the method shown in Fig. 1 to produce a compressed body. The obtained compressed body was immersed in water, and NaCl was eluted to make it porous, thereby obtaining an Al porous material.

[0047] Next, as a result of measuring the porosity of the produced Al porous material according to JIS R 1634, the porosity was 52%. As a result of measuring the pore diameter of the cross section of the Al porous material using an electron microscope (SEM), it was 200 - 800 μm. As a result of measuring the hardness of the Al part of the Al porous material according to JIS Z 2244, it had a high hardness, which was 1.5 times the hardness of the Al material.

[0048] <Example 2> As the metal powder, pure nickel (Ni) powder (average particle size: about 3 μm) was used, and as the support powder, sodium chloride (NaCl) powder (average particle size: about 20 μm) was used. The Ni powder and the NaCl powder were mixed at a volume ratio of Ni powder: 30 vol%, NaCl powder: 70 vol%, and naturally filled into the metal jig 11. Using an explosive with a detonation velocity of 3500 m / s, compression was performed by the method shown in Fig. 3 to produce a compressed body. The obtained compressed body was immersed in water, and NaCl was eluted to make it porous, thereby obtaining a Ni porous material.

[0049] Next, as a result of measuring the porosity of the produced Ni porous material according to JIS R 1634, the porosity was 69%. As a result of measuring the pore diameter of the cross section of the Ni porous material using an electron microscope (SEM), it was 1 - 100 μm. As a result of measuring the hardness of the Ni part of the Ni porous material according to JIS Z 2244, it had a high hardness, which was 1.7 times the hardness of the Ni material.

[0050] <Example 3> As the metal powder, pure tungsten (W) powder (average particle size: about 5 μm) was used, and as the support powder, sodium chloride (NaCl) powder (screening particle size: <150 μm) was used. The W powder and the NaCl powder were mixed at a volume ratio of W powder: 60 vol%, NaCl powder: 40 vol%, and naturally filled into the metal pipe 2 for powder filling. Using an explosive with a detonation velocity of 2500 m / s, compression was carried out by the method shown in Fig. 2 to produce a compressed body. The obtained compressed body was immersed in water to elute NaCl and make it porous, thereby obtaining a W porous material.

[0051] Next, the porosity of the produced W porous material was measured according to JIS R 1634, and the result was that the porosity was 43%. The pore diameter of the cross-section of the W porous material was measured using an electron microscope (SEM), and the result was 10 to 150 μm. The hardness of the W part of the W porous material was measured according to JIS Z 2244, and the result was that it had a high hardness, which was 1.2 times the hardness of the W material.

[0052] <Example 4> As the metal powder, a mixture of pure aluminum (Al) powder (screening particle size: <150 μm) and SUS316L powder (screening particle size: <150 μm) was used, and as the support powder, sodium chloride (NaCl) powder (screening particle size: 250 - 800 μm) was used. The volume ratios of the Al powder, SUS316L powder, and NaCl powder were Al powder: 5 vol%, SUS316L: 20 vol%, and NaCl powder: 75 vol% respectively. They were mixed and naturally filled into the metal jig 11. Using an explosive with a detonation velocity of 2500 m / s, compression was carried out by the method shown in Fig. 3 to produce a compressed body. The obtained compressed body was immersed in water to elute NaCl and make it porous, thereby obtaining a (Al + SUS316L) mixed porous material.

[0053] Next, as a result of measuring the porosity of the fabricated (Al + SUS316L) mixed porous material according to JIS R 1634, the porosity was 72%. As a result of measuring the pore diameter using an electron microscope (SEM) for the cross-section of the (Al + SUS316L) mixed porous material, it was 200 - 800 μm. As a result of measuring the hardness of the Al part and the SUS316L part of the (Al + SUS316L) mixed porous material according to JIS Z 2244, the Al part had a hardness 1.5 times that of the Al material, and the SUS316L part had a hardness 1.2 times that of the SUS316L material, respectively, and both had high hardness.

[0054] 〈Example 5〉 As the metal powder, a mixture of pure nickel (Ni) powder (screened particle size: <50 μm) and Al2O3 powder (screened particle size: <10 μm) was used, and as the support powder, sodium chloride (NaCl) powder (screened particle size: 250 - 800 μm) was used. The volume ratios of the Ni powder, Al2O3 powder, and NaCl powder were mixed at Ni powder: 70 vol%, Al2O3: 15 vol%, and NaCl powder: 15 vol% and naturally filled into the metal jig 11. Using an explosive with a detonation velocity of 2500 m / s, it was compressed by the method shown in Figure 3 to produce a compressed body. Next, the obtained compressed body was immersed in water to elute NaCl and make it porous, thereby obtaining a (Ni + Al2O3) mixed porous material.

[0055] Next, as a result of measuring the porosity of the fabricated (Ni + Al2O3) mixed porous material according to JIS R 1634, the porosity was 13%. As a result of measuring the pore diameter using an electron microscope (SEM) for the cross-section of the (Ni + Al2O3) mixed porous material, it was 200 - 800 μm. As a result of measuring the hardness of the Ni part of the (Ni + Al2O3) mixed porous material according to JIS Z 2244, it had a hardness 1.5 times that of the Ni material and had high hardness.

[0056] 〈Example 6〉 As the metal powder, SUS316L powder (screening particle size: <150 μm) was used, and as the support powder, sodium chloride (NaCl) powder (screening particle size: 100 - 150 μm) was used. The volume ratio of each of the SUS316L powder and the NaCl powder was mixed at SUS316L powder: 60 vol%, NaCl powder: 40 vol%, and naturally filled into the metal jig 11 to form the first layer.

[0057] Next, a mixture of pure nickel (Ni) powder (screening particle size: about 50 μm) and yttria-stabilized zirconia (YSZ) powder (average particle size: about 3 μm) was used as the metal powder, and sodium chloride (NaCl) powder (screening particle size: 100 - 150 μm) was used as the support powder. They were mixed at volume ratios of Ni powder: 30 vol%, YSZ: 30 vol%, and NaCl powder: 40 vol%, and naturally filled on top of the first layer of the metal jig 11 to form the second layer.

[0058] Next, an explosive with a detonation velocity of 3500 m / s was used to compress it by the method shown in Figure 3 to produce a compressed body. The obtained compressed body was immersed in water, and NaCl was eluted to make it porous, thereby obtaining a (Ni + YSZ / SUS316L) mixed laminated porous material.

[0059] Next, as a result of measuring the porosity of the produced (Ni + YSZ / SUS316L) mixed laminated porous material according to JIS R 1634, the porosity was 42%. As a result of measuring the pore diameter using an electron microscope (SEM) for the cross-section of the (Ni + YSZ / SUS316L) mixed laminated porous material, it was 100 - 150 μm. As a result of measuring the hardness of the Ni part and the SUS316L part of the (Ni + YSZ / SUS316L) mixed laminated porous material according to JIS Z 2244, the Ni part had a hardness 1.7 times that of the Ni material, and the SUS316L part had a hardness 1.2 times that of the SUS316L material and had a high hardness.

[0060] 〈Comparative Example 1〉 As the metal powder, pure aluminum (Al) powder (average particle size: about 3 μm) was used, and as the support powder, sodium chloride (NaCl) powder (sieved particle size: 250 - 800 μm) was used. The Al powder and the NaCl powder were mixed at a volume ratio of Al powder: 50 vol%, NaCl powder: 50 vol%, and a pre-compressed body was produced using a hand press machine. The (Al + NaCl) pre-compressed body was heat-treated at 650 °C to produce an (Al + NaCl) sintered body. The (Al + NaCl) sintered body was immersed in water to elute NaCl and make it porous, thereby obtaining an Al sintered porous material.

[0061] Next, the porosity of the produced Al sintered porous material was measured according to JIS R 1634, and the result was that the porosity was 51%. As a result of measuring the pore diameter using an electron microscope (SEM) for the cross-section of the Al porous material, it was 200 - 800 μm. As a result of measuring the hardness of the Al part of the Al sintered porous material according to JIS Z 2244, the hardness was reduced to 0.8 times that of the Al material.

[0062] <Comparative Example 2> As the metal powder, pure nickel (Ni) powder (average particle size: about 3 μm) was used, and as the support powder, sodium chloride (NaCl) powder (average particle size: about 20 μm) was used. The Ni powder and the NaCl powder were mixed at a volume ratio of Ni powder: 30 vol%, NaCl powder: 70 vol%, and a pre-compressed body was produced using a hand press machine. Next, the (Ni + NaCl) pre-compressed body was heat-treated at 780 °C, but since it was lower than the sintering temperature of Ni, a good sintered body could not be obtained. Furthermore, the (Ni + NaCl) pre-compressed body was heat-treated at 900 °C, but melting of NaCl was observed and a good sintered body could not be obtained.

[0063] [Table 1]

[0064] Figure 4 is a photograph of the appearance of the porous material of Example 2. Figure 5 is a cross-section of the porous material composed of Ni of Example 2. Figure 6 is a cross-section of the porous material composed of W of Example 3. [Industrial Applicability]

[0065] According to the method for manufacturing a porous material of the present disclosure, since a decrease in hardness due to heat treatment can be avoided, a wide variety of metal species can be used to increase the hardness of the metal skeleton portion of the obtained porous material to be equal to or higher than that of the raw material in various combinations such as a single pure metal, an alloy, a mixture of two or more pure metals and / or alloys, and a composite material of a pure metal or an alloy and an inorganic compound. In addition, the method for manufacturing a porous material of the present disclosure has a low environmental impact and is therefore extremely useful industrially. The porous material of the present disclosure has applicability to weight reduction of structures, filters, catalysts, heat exchangers, medical artificial bones and implants, electrode materials, buffer materials, soundproof materials, etc. Note that the applicability of the present disclosure is not limited thereto.

Explanation of reference numerals

[0066] 1 Metal pipe for powder filling 2 Mixed powder 3 Metal plug 4 Buffer 5 Resin pipe for explosive loading 6 Explosive 7 Detonator 8 Resin bottom plate 9 Metal flying pipe 10 Metal jig 10 11 Metal concave jig 11

Claims

Claim 1 A method for manufacturing a porous material, the method comprising: compressing and solidifying a mixed powder of a raw material powder containing a metal material and a support powder at a temperature below the recrystallization temperature of the metal material; contacting the compressed and solidified mixed powder with a solvent to dissolve and remove the support powder. A method for manufacturing a porous material comprising these steps. Claim 2 The method according to claim 1, wherein the compression and solidification is performed by an explosive compaction method. Claim 3 The method according to claim 1 or 2, wherein the metal material includes at least one metal material selected from the group consisting of pure metals, alloys, and combinations thereof. Claim 4 The method according to claim 1 or 2, wherein the metal material includes two or more metal materials. Claim 5 The method according to claim 1 or 2, wherein the raw material powder further includes an inorganic compound. Claim 6 The method according to claim 1 or 2, wherein the support powder includes a water-soluble salt and the solvent includes water. Claim 7 The method according to claim 1 or 2, wherein the compression and solidification is performed in a state where a layer formed from a first mixed powder and a layer formed from a second mixed powder having a composition different from that of the first mixed powder are laminated. Claim 8 A porous material containing a metal material, wherein the hardness of the metal skeleton portion of the porous material is equal to or greater than the hardness of the metal material as the raw material constituting the metal skeleton portion. Claim 9 The porous material according to claim 8, wherein the metal material includes at least one metal material selected from the group consisting of pure metals, alloys, and combinations thereof. Claim 10 The porous material according to claim 8 or 9, wherein the metal material includes two or more metal materials, and the hardness of the metal skeleton portion of the porous material is equal to or greater than the hardness of the metal material as the raw material constituting the metal skeleton portion. Claim 11 The porous material according to claim 8 or 9, wherein the porous material further includes an inorganic compound, and the hardness of the metal skeleton portion of the porous material is equal to or greater than the hardness of the metal material as the raw material constituting the metal skeleton portion. Claim 12 The porous material according to claim 8 or 9, wherein the porous material has two or more porous layers having different structures and / or compositions of the metal skeleton portion.

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