Method for producing aluminum substrate

Abstract

Provided is a method for producing Al-based particles with which it is possible to efficiently or easily obtain Al-based particles. According to the present invention, an Al-based foil is brought into contact with a molten salt, thereby obtaining a particle-dispersed molten salt (one example of an Al-based material) in which Al-based particles (liquid phase) are dispersed in the molten salt. If a molten salt is dispersed by particles, an Al-based powder (one example of an Al base material) including Al-based particles (solid phase) can be efficiently or simply obtained, for example. As a result, it is possible to obtain an Al-based powder having a desired particle size distribution even when the Al-based particle group is classified. For example, the Al base foil has a thickness of 0.5 mm or less and further 0.1 mm. The Al-based foil can be supplied to the molten salt as a chopped foil sheet. As a result, an Al-based powder having a particle size distribution containing fine particles can be easily obtained. For example, a mixed salt containing NaCl and KCl can be used as the molten salt.

Description

Technical Field

[0001] The present invention relates to a method for producing an aluminum substrate, etc. Background Art

[0002] Pure aluminum (Al) and Al alloys are used in various products and fields. For example, Al-based particles (powders) including pure Al and Al alloys are used as composite material raw materials (fillers or base materials such as thermal conductive fillers and conductive fillers), sintering raw materials, chemical reaction raw materials (aluminothermic reaction agents, etc.), pigments, etc.

[0003] Al-based powders are generally produced by spraying (atomization method) of Al-based melt, dispersing (melt-spin method) of Al-based melt, scattering (melt-extraction method) of Al-based melt, crushing (ball mill method, grinding method) of Al-based flakes, etc., as described in the following non-patent document 1. In addition, in recent years, a method for producing Al-based particles using a molten salt has also been proposed, and there are records related to the following patent document.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-191148

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-215569

[0008] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-20062

[0009] Patent Document 4: Japanese Patent Application No. 2018-511776

[0010] Patent Document 5: Japanese Patent Application No. 2019-502890

[0011] Non-patent literature

[0012] Non-patent document 1: Iwao Osamu, Method for producing aluminum powder, Light Metals (1987) 646-655 Summary of the invention

[0013] Problems to be solved by the invention

[0014] In Patent Document 1, a molten salt of aluminum chloride is injected into molten sodium to obtain aluminum particles coated with sodium chloride. Metallic sodium is difficult to use as a reducing agent from the viewpoints of safety and cost.

[0015] In Patent Document 2, metal A particles are subjected to substitution reaction with ions of metal B which is more noble than metal A in a molten salt serving as a reaction medium, thereby obtaining alloy particles in which metal B is precipitated and diffused in the metal A particles. However, Patent Document 2 does not specifically describe Al-based particles.

[0016] Patent Documents 3 to 5 describe a melting method using a molten salt, etc. However, none of the Patent Documents describe specifically Al-based particles.

[0017] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for obtaining aluminum-based particles by a novel method different from the conventional ones.

[0018] Means for solving problems

[0019] The present inventors have conducted intensive research to solve this problem and have newly discovered that when Al-based foil is added to a molten salt (pool), it does not become a coagulated melt (lump) but becomes dispersed particles (liquid phase). Based on this discovery, the present invention described below has been completed.

[0020] 《Manufacturing method of aluminum substrate》

[0021] (1) The present invention is a method for producing an aluminum substrate, wherein an aluminum-based foil is brought into contact with a molten salt to obtain aluminum-based particles.

[0022] The present invention may be, for example, a method for producing an aluminum substrate comprising a melting step of placing an aluminum-based foil in a molten salt layer to melt the aluminum-based foil, and a collecting step of collecting aluminum-based particles obtained after the melting step.

[0023] (2) According to the production method of the present invention, aluminum-based particles (Al-based particles) or an aluminum substrate (Al substrate) based on the Al-based particles can be obtained simply, efficiently, or with high yield.

[0024] Incidentally, the standard free energy of formation of representative metal elements (such as Na, K, Mg, Ca, etc. / specific metal elements) constituting molten salts when they become halides (such as chlorides, bromides, etc.) is much smaller than the standard free energy of formation of Al when it becomes an oxide. Therefore, according to the manufacturing method of the present invention, Al-based particles in which at least a portion of the oxides (such as oxide films on the surface) located on the aluminum-based foil (Al-based foil) are removed (reduced) can be obtained. In addition, as long as the Al-based particles are surrounded by molten salts or their solidified salts (including film-like), oxidation is suppressed. Therefore, according to the manufacturing method of the present invention, refined Al-based particles that do not contain oxides, etc. can also be obtained.

[0025] Furthermore, the Al-based particles (liquid phase) obtained from the Al-based foil are easily spheroidized in the molten salt. Therefore, according to the production method of the present invention, an Al substrate including (spheroidized) Al-based particles having a uniform particle shape can also be obtained.

[0026] 《Al-based particles / Al substrate》

[0027] (1) The Al-based particles may be in a liquid phase state, a solid phase state, or a solid-liquid coexistence state (semi-molten state).

[0028] A particle group formed by a collection of liquid Al-based particles or an Al-based melt obtained by combining (linking) the particles can be a form of an Al substrate. Specifically, the Al-based particles are liquid-phase particles, and the Al-based melt obtained from the liquid-phase particles can be understood as the Al substrate of the present invention.

[0029] The Al-based powder obtained by the particle group formed by the solid phase Al-based particles gathering (collecting) can also be a form of the Al substrate. Specifically, the Al-based particles are solid phase particles formed by the solidification of liquid phase particles, and the Al-based powder obtained from the solid phase particles can be understood as the Al substrate of the present invention.

[0030] (2) The Al-based particles may not be separated (separated, extracted, captured, recovered, etc.) from the molten salt or the solidified salt thereof. In other words, the Al-based particles and the molten salt and / or the solidified salt may coexist as one form of the Al substrate.

[0031] For example, the Al-based particles may be liquid-phase particles, and the particle-dispersed molten salt formed by dispersing the liquid-phase particles in a molten salt may be understood as the Al substrate. Alternatively, the Al-based particles may be solid-phase particles formed by solidifying liquid-phase particles, and the particle-dispersed solidified salt formed by dispersing the solid-phase particles in a solidified salt formed by solidifying a molten salt may be understood as the Al substrate. Furthermore, the type (temperature) of the molten salt may be adjusted, for example, the particle-dispersed molten salt obtained by dispersing solid-phase particles of the Al-based particles in a molten salt may be understood as the Al substrate.

[0032] It should be noted that the particle-dispersed molten salt or the particle-dispersed solidified salt can be understood as an independent trading object, or can be understood as a temporary (interim) intermediate (intermediate raw material, etc.) for obtaining an Al-based melt, Al-based powder, etc.

[0033] (3) Al-based ingots, Al-based castings (final products, intermediate products, etc.), Al-based sintered bodies (raw materials, products), Al-based composite bodies (raw materials, products), powders, etc. formed from Al-based particles obtained from Al-based foils can also be understood as specific examples of Al substrates. It should be noted that the powder as an example of the Al substrate can be used as a filler material for maintaining the particle shape, as well as a molten material to be melted, a sintering material to be formed or fired, etc.

[0034] "other"

[0035] (1) The term “collected” as used herein refers to a state in which a plurality of particles (liquid phase particles or solid phase particles) exist. In addition, “dispersed” refers to a state in which the plurality of particles exist in another medium (molten salt or solidified salt). In either case, the degree, form, etc. thereof are not limited.

[0036] (2) Concentration, composition and particle size distribution in this specification are expressed as mass ratio (mass %) relative to the entire object (melt, pellets, etc.) unless otherwise specified. Mass % is expressed simply as "%" where appropriate.

[0037] (3) Unless otherwise specified, "x to y" in this specification includes a lower limit x and an upper limit y. Any numerical value included in the various numerical values ​​or numerical ranges described in this specification can be used as a new lower limit or upper limit to set a new range such as "a to b". BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1A This is a photograph of an Al-based foil (0.018 mm thick × 25 mm square).

[0039] Figure 1B It is a photograph of an Al-based foil (0.3 mm thick × 1 mm wide).

[0040] Figure 1C This is a photograph of an Al-based foil (0.3 mm thick × 3 mm square).

[0041] Figure 2 Schematic diagram illustrating the production process of Al-based particles (powder).

[0042] Figure 3 This is a table showing the correspondence between the morphology (thickness, size) of the Al-based foil as a raw material and the morphology (photograph) of the obtained Al-based particles.

[0043] Figure 4 It is a SEM image of Al-based particles obtained from Al-based foil (0.011 mm thick × 25 mm square).

[0044] Figure 5This is a bar graph showing the relationship between the thickness of the Al-based foil (25 mm square) as a raw material and the particle size distribution of the obtained Al-based particles.

[0045] Fig. 6A It is a bar graph showing the relationship between the size of the Al-based foil (0.3 mm thickness) as a raw material and the particle size distribution of the obtained Al-based particles.

[0046] Figure 6B This is a bar graph showing the relationship between the size of the Al-based foil (0.1 mm thickness) as a raw material and the particle size distribution of the obtained Al-based particles.

[0047] Figure 6C This is a bar graph showing the relationship between the size of the Al-based foil (0.018 mm thickness) as a raw material and the particle size distribution of the obtained Al-based particles. DETAILED DESCRIPTION

[0048] One or more components arbitrarily selected from the present specification may be added to the components of the present invention described above. The contents described in the present specification may be components related to the method or components related to an object (eg, Al-based particles, Al substrate).

[0049] 《Al-based foil》

[0050] (1) For the Al-based foil used as the raw material, a foil obtained by processing (rolling, etc.) an Al substrate (plate material, ingot, etc.) to a desired thickness can be used, or an Al substrate that has been formed into a foil can be used directly. The Al substrate can be waste materials recovered from the market, factories, etc., or its recycled materials (blocks, plates, foils, etc.). The recovered or regenerated Al-based foil can be used directly, or it can be pre-treated by ink removal, cleaning, etc., thickness adjustment, etc. Al-based foil laminated with resins, etc. can be added directly to the molten salt, or it can be added to the molten salt after removing the laminated layer. The Al-based foil may have wrinkles, bends, bends, etc., or it may not have wrinkles, bends, bends, etc.

[0051] (2) The Al-based foil may be pure aluminum (pure Al) or an aluminum alloy (Al alloy). Al-based foils having different compositional components may be used in a mixed state. The compositional components of the Al-based foil used as the raw material are reflected in the compositional components of the obtained Al-based particles. Therefore, the composition and ratio of the Al-based foil used as the raw material may be adjusted to obtain Al-based particles having the desired composition.

[0052] (3) The thickness and size of the Al-based foil can be appropriately selected. The thickness and size (dimensions other than thickness) of the Al-based foil (foil) added to the molten salt can also be adjusted according to the desired particle size distribution of the Al-based particle group (powder). In this case, Al-based foils (foils) of different thicknesses and / or sizes can also be mixed. Generally, the thinner and / or smaller the Al-based foil (foil), the greater the proportion of fine (small-diameter) Al-based particles. Conversely, the thicker and / or larger the Al-based foil (foil), the greater the proportion of coarse (large-diameter) Al-based particles.

[0053] The thickness of the Al-based foil has an upper limit (below 0.5 mm, 0.3 mm, 0.2 mm, 0.1 mm, 0.07 mm, 0.03 mm, and 0.02 mm, for example. Its lower limit (above 0.5 mm, and above 0.001 mm, 0.005 mm, and further 0.008 mm) for example. The thickness of the Al-based foil is measured by a micrometer or the like. The thickness of the Al-based foil may have a deviation of about ±10%. The arithmetic mean of the thickness measured at any number of locations (for example, 10 locations) may also be appropriately used as the thickness of the Al-based foil. Unless otherwise specified, the "foil" referred to in this specification refers to a thickness of less than 0.5 mm (less than 0.2 mm or even less than 0.1 mm).

[0054] The size of the foil is, for example, 200 mm, 150 mm, 100 mm, 50 mm, 30 mm, 20 mm, 10 mm, 5 mm, 1 mm in maximum length. Its minimum length is, for example, 10 mm, 5 mm, 1 mm, or even 0.5 mm. The size of the foil can also be adjusted according to the thickness of the foil. For example, a larger foil can be used when it is thinner, and a smaller foil can be used when it is thicker. It should be noted that the foil is obtained by, for example, shredding Al-based foil (raw material) using a pulverizer or the like.

[0055] Molten Salt

[0056] Molten salts may be made of, for example, stable metal halides (particularly chlorides and / or bromides). Metal elements constituting halides may be, for example, one or more of Ca, Na, Li, Sr, K, Mg, Cs, Ba, etc. In particular, halides of Na and / or K are inexpensive and stable, and are therefore suitable for molten salts.

[0057] The temperature of the molten salt can also be adjusted by the raw material ratio (composition adjustment) of the molten salt. The temperature of the molten salt is preferably set to at least the melting temperature of the Al-based foil (exceeding the melting temperature of the Al-based foil). The molten salt is not limited to a single layer, but can also be a multilayer. The molten salt can be a molten salt pool (tank) having at least a depth or amount sufficient to immerse the Al-based foil. It should be noted that, usually, the Al-based particles (liquid phase) are retained or settled below the molten salt due to the density difference.

[0058] 《Al-based particles》

[0059] (1) The particle size of the Al-based particles (regardless of the particle shape, referred to as "particle diameter") may be constant or distributed. The thinner and smaller the Al-based foil is melted, the more likely it is that a particle size distribution with more fine Al-based particles will be produced.

[0060] The Al-based particles may be liquid-phase particles or solid-phase particles obtained from Al-based foil (sheet) as they are, or liquid-phase particles or solid-phase particles in which particles are connected (combined) to each other and integrated (larged in diameter) or alloyed. The Al particles may be used directly or may be used after adjusting the particle size (classification). According to the manufacturing method of the present invention, an Al powder composed of Al-based particles having a particle size exceeding 1.7 mm can be obtained, and an Al powder composed of Al-based particles having a particle size less than 0.1 mm can also be obtained.

[0061] It should be noted that the particle size (or particle diameter) of the powder referred to in this specification is determined by sieving unless otherwise specified, and is expressed by the nominal mesh hole (mesh hole size) of the sieve (according to JIS Z 8801). The particle size α~β (α<β) refers to the particles (groups) that do not pass through the sieve with a nominal mesh hole αμm but pass through the sieve with a nominal mesh hole βμm. The particle size α~ refers to the particles (groups) that do not pass through the sieve with a nominal mesh hole αμm. The particle size ~β refers to the particles (groups) that pass through the sieve with a nominal mesh hole βμm. It is believed that the particle size of the liquid phase particles is roughly equal to the particle size of the solid phase particles, except for the heat shrinkage part.

[0062] (2) Al-based particles and Al-based materials have various uses. For example, Al-based powder (solid-phase particles) as one form thereof can be used as a filler (thermal conductive filler, conductive filler, etc.) for composite materials dispersed in a base material (resin, dissimilar metal, ceramic, etc.), a raw material powder for sintered materials (main element powder or alloy element powder, etc.), a raw material (reducing agent, etc.) for chemical reactions (aluminothermic reaction, etc.), a pigment added to paint, etc.

[0063] Example

[0064] The Al-based foil is added to a molten salt to produce Al-based particles (liquid phase particles), which are then solidified. The present invention will be described in more detail based on such specific examples.

[0065] 《Sample Preparation》

[0066] (1) Raw materials

[0067] As raw materials, various foils of different sizes (size (plane size) and thickness) were prepared. All foils were made of pure Al (JIS1000 series / purity 99% or more) and had a size of 100 mm×100 mm or more (Al-based foil). The thickness of the foil was any one of 0.011 mm, 0.018 mm, 0.025 mm, 0.05 mm, 0.1 mm, 0.3 mm, or 0.8 mm.

[0068] The sizes of the foil pieces are 25 mm square (roughly square), 3 mm square, 5 mm wide (25 mm long), and 1 mm wide (25 mm long). The 5 mm wide and 1 mm wide pieces are both sized by cutting the 25 mm square foil pieces into pieces of a specified width.

[0069] The foil or foil sheet is cut (shredded) in the air using metal scissors. In this way, various foil sheets are obtained. The appearance of a part of it is shown in Figure 1A to Figure 1C .

[0070] (2) Molten salt

[0071] 100 g of a mixed salt of potassium chloride and sodium chloride (KCl-44 mass % NaCl) was placed in an alumina crucible (B3 manufactured by Nikkato Corporation) and heated in a furnace to 700° C. Thus, a molten salt (layer, pool) composed of the mixed salt was obtained.

[0072] (3) Melting process

[0073] like Figure 2 As shown, for each foil piece, a step of putting the foil piece (2.5 g) into a molten salt (100 g) to melt the foil piece was performed. In this step, stirring was not performed, and the foil piece was left to stand until each foil piece was dispersed and melted in the molten salt (about 10 minutes).

[0074] (4) Collection process

[0075] The crucible after the melting process is placed outside the furnace to cool (cooling process) to solidify the molten salt (particle-dispersed molten salt) (solidification process). The solidified product (particle-dispersed solidified salt) taken out of the crucible is washed with water (water washing process / salting-off process). The particles remaining after the salt is removed are filtered and dried (filtration process, drying process). The particle groups corresponding to each foil obtained in this way are shown in Figure 3 .

[0076] (5) Grading process

[0077] Each particle group was classified by sieving. The sieves used had opening sizes (mesh sizes) of 1.7 mm, 0.85 mm, 0.425 mm, 0.212 mm, and 0.106 mm. The particle size distribution (mass ratio) of each particle group is shown in Figure 5and Figure 6A to Figure 6C (They are collectively referred to as "Figure 6"). Figure 5 The relationship between the thickness of the foil (25 mm square) used as the raw material and the particle size distribution of the obtained pellets is shown in FIG6 . The relationship between the size of the foil and its particle size distribution is shown in FIG6 .

[0078] (6) Comparison samples

[0079] An Al block (50 g) was added to a crucible containing the molten salt (100 g) to melt the Al block. The Al melt (block) formed in the molten salt was stirred with an alumina rod to disperse the Al melt in the molten salt in a granular form. The solidified product obtained by cooling the crucible was washed with water in the same manner as the above method, and the obtained particles were filtered, dried and classified.

[0080] "observe"

[0081] The SEM image and its magnified image of the particles (particle size: ~0.212 mm) obtained by using a 0.011 mm thick × 25 mm square foil observed with a scanning electron microscope (SEM) are shown in Figure 4 .

[0082] "evaluate"

[0083] (1) Particle shape

[0084] Depend on Figure 4 It is known that the Al-based particles obtained by contacting the Al-based foil with the molten salt are substantially spherical even without stirring in the melting step. The shape of the Al-based particles of the comparative sample is a slightly flat spherical shape.

[0085] (2) Particle size distribution

[0086] Depend on Figure 5 It is known that the thinner the Al-based foil is, the more fine particles are included in the particle size distribution, while the thicker the Al-based foil is, the more large particles are included in the particle size distribution.

[0087] Depend on Fig. 6A It can be seen that when using Al-based foil with a thickness of 0.3 mm or more (exceeding), particles with large particle sizes are stably obtained regardless of their size. This is believed to be because the thick Al-based foil (sheet) gradually melts from each end surface, and there are more opportunities for it to combine with other Al-based particles (liquid phase) before spheroidization. It should be noted that the Al-based particles of the comparative sample are almost all larger than 1.7 mm in size.

[0088] Depend on Figure 6B and Figure 6CIt can be seen that the particle size distribution can be adjusted by the thickness of the Al-based foil and the size of the foil. For example, if a thin and small foil is used, a powder with a particle size distribution containing more fine particles is obtained. It is believed that this is because the thin and small foil melts in a short time and spheroidizes, making it easy to disperse. This tendency is significant when the thickness of the Al-based foil is less than 0.1 mm (or less) or the width of the Al-based foil is less than 1 mm (or less).

[0089] In addition, Al-based particles (liquid phase) having a particle size (diameter) of about 2 mm or less are difficult to be integrated and are likely to maintain a dispersed state in the molten salt.

[0090] Thus, according to the present invention, by using Al-based foil, a particle-dispersed molten salt in which Al-based particles are dispersed in a molten salt can be obtained. Furthermore, a desired Al base material (powder, etc.) can be obtained efficiently or simply from the particle-dispersed molten salt.

Claims

1. A method for manufacturing an aluminum substrate, Aluminum-based particles are obtained by contacting an aluminum-based foil with a molten salt.

2. A method for manufacturing an aluminum substrate, comprising: A melting step, in which the aluminum-based foil is placed in a molten salt layer to melt the aluminum-based foil; and A collecting step is to collect the aluminum-based particles obtained after the melting step.

3. The method for producing an aluminum substrate according to claim 1 or 2, The aluminum-based foil includes shredded foil pieces.

4. The method for producing an aluminum substrate according to claim 1 or 2, The thickness of the aluminum-based foil is less than 0.1 mm.

5. The method for producing an aluminum substrate according to claim 1 or 2, The molten salt includes a mixed salt.

6. The method for producing an aluminum substrate according to claim 5, The mixed salt comprises NaCl and KCl.

7. The method for producing an aluminum substrate according to claim 1 or 2, The aluminum-based particles are liquid phase particles, The aluminum substrate is a particle-dispersed molten salt in which the liquid phase particles are dispersed in the molten salt.

8. The method for producing an aluminum substrate according to claim 1 or 2, The aluminum-based particles are liquid phase particles, The aluminum substrate is an aluminum-based melt obtained from the liquid phase particles.

9. The method for producing an aluminum substrate according to claim 1 or 2, The aluminum-based particles are solid phase particles formed by solidification of liquid phase particles. The aluminum substrate is a particle-dispersed solidified salt in which solid phase particles are dispersed in a solidified salt formed by solidifying the molten salt.

10. The method for producing an aluminum substrate according to claim 1 or 2, The aluminum-based particles are solid phase particles formed by solidification of liquid phase particles. The aluminum substrate is an aluminum-based powder including the solid phase particles.

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