Method for manufacturing an aluminum substrate

Abstract

To provide a production method enabling base particles to be obtained efficiently or in a simplified manner.SOLUTION: Particle dispersion molten salt (an example of an Al base material) in which Al base particles (liquid phase) are dispersed in the molten salt, can be obtained by bringing an Al base foil into contact with molten salt. By passing through the particle dispersion molten salt, Al base powder (an example of the Al material) consisting of Al base particles (solid phase), for example, can be obtained efficiently or in a simplified manner. By classifying an Al base particle group, the Al base powder with a desired particle size distribution can be obtained. The Al base foil, for example, has a thickness of 0.5 mm or less, or further 0.1 mm. The Al base foil as shredded foil pieces may be supplied to the molten salt. This allows the Al base powder with a particle size distribution including fine particles to be easily obtained. As the molten salt, mixed salt containing NaCl and KCl for example is preferably used.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an aluminum base material and the like.

Background Art

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

[0003] Al-based powders are generally manufactured by spraying of Al-based molten metal (atomization method), dispersion of Al-based molten metal (melt spinning method), scattering of Al-based molten metal (melt extraction method), pulverization of Al-based pieces (ball mill method, attritor method), etc., as also described in Non-Patent Document 1 below. Furthermore, in recent years, a method for manufacturing Al-based particles using molten salt has also been proposed, and there are descriptions related to the following patent documents.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] 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 as a reducing agent is difficult to use from the viewpoints of safety, cost, etc.

[0007] In Patent Document 2, in a molten salt serving as a reaction medium, metal A particles and ions of a metal B nobler than metal A are subjected to a substitution reaction to obtain alloy particles in which metal B is deposited and diffused on the metal A particles. However, there is no specific description regarding Al-based particles in Patent Document 2.

[0008] Patent Documents 3 to 5 describe a melting method using a molten salt and the like. None of the patent documents have a specific description regarding Al-based particles.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for obtaining aluminum-based particles by a new method different from the conventional ones.

Means for Solving the Problems

[0010] As a result of intensive studies to solve this problem, the present inventor newly found that when an Al-based foil is put into a molten salt (pool), it does not become an aggregated molten metal (mass) but becomes dispersed particles (liquid phase). By developing this discovery, the present invention described below has been completed.

[0011] 《Method for Manufacturing Aluminum Base Material》 (1) The present invention is a method for manufacturing an aluminum base material that obtains aluminum-based particles by bringing an aluminum-based foil into contact with a molten salt.

[0012] The present invention may also be a method for manufacturing an aluminum base material including, for example, a melting step of putting an aluminum-based foil into a molten salt layer and dissolving it, and a collecting step of collecting the aluminum-based particles obtained after the melting step.

[0013] (2) According to the manufacturing method of the present invention, aluminum-based particles (Al-based particles) or an aluminum-based substrate (Al-based substrate) based on the Al-based particles can be obtained simply, efficiently, or with a high yield.

[0014] Incidentally, the standard free energy of formation when typical metal elements (e.g., Na, K, Mg, Ca, etc. / specific metal elements) constituting the molten salt become halides (e.g., chlorides, bromides, etc.) is much smaller than the standard free energy of formation when Al becomes an oxide. Therefore, according to the manufacturing method of the present invention, Al-based particles in which at least a part of the oxide (such as the oxide film on the surface) existing in the aluminum-based foil (Al-based foil) is removed (reduced) can be obtained. Further, as long as the Al-based particles are surrounded by the molten salt or its solidified salt (including the film-like form), the state of oxidation is suppressed. Therefore, according to the manufacturing method of the present invention, purified Al-based particles containing no oxides or the like can also be obtained.

[0015] Furthermore, the Al-based particles (liquid phase) obtained from the Al-based foil are likely to be spheroidized in the molten salt. Therefore, according to the manufacturing method of the present invention, an Al-based substrate composed of Al-based particles with uniform particle shapes (spheroidized) can also be obtained.

[0016] 《Al-based particles / Al-based substrate》 (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).

[0017] A particle group in which the liquid-phase Al-based particles are aggregated (collected) or an Al-based molten metal obtained from the bonding (connection) thereof can be a form of the Al-based substrate. Specifically speaking, if the Al-based particles are liquid-phase particles, the Al-based molten metal obtained from these liquid-phase particles may be regarded as the Al-based substrate according to the present invention.

[0018] Al-based powder obtained from a particle group in which the solid-phase Al-based particles are aggregated (collected) can also be a form of the Al-based substrate. Specifically speaking, if the Al-based particles are solid-phase particles formed by solidification of liquid-phase particles, the Al-based powder obtained from these solid-phase particles may be regarded as the Al-based substrate according to the present invention.

[0019] (2) The Al-based particles do not necessarily have to be in a separated (separated, extracted, collected, recovered, etc.) state from the molten salt and its solidified salt. That is, a substance in which the Al-based particles coexist with the molten salt and / or the solidified salt can also be a form of the Al-based material.

[0020] For example, the Al-based particles are liquid-phase particles, and a particle-dispersed molten salt in which the liquid-phase particles are dispersed in the molten salt may be regarded as an Al-based material. Further, the Al-based particles are solid-phase particles obtained by solidifying the liquid-phase particles, and a particle-dispersed solidified salt in which the solid-phase particles are dispersed in the solidified salt obtained by solidifying the molten salt may be regarded as an Al-based material. Furthermore, by adjusting the type (temperature) of the molten salt, for example, a particle-dispersed molten salt in which the solid-phase particles of the Al-based particles are dispersed in the molten salt can also be regarded as an Al-based material.

[0021] Note that the particle-dispersed molten salt or the particle-dispersed solidified salt may be regarded as an independent transaction object, or may be regarded as a temporary (provisional) intermediate (intermediate raw material, etc.) for obtaining an Al-based molten metal, Al-based powder, etc.

[0022] (3) An Al-based ingot, Al-based casting (final product, intermediate product, etc.), Al-based sintered body (material, product), Al-based composite (material, product), powder, etc. formed via the Al-based particles obtained from the Al-based foil may also be regarded as specific examples of the Al-based material. Note that the powder, which is an example of the Al-based material, may be used not only as a filler in which the particle form is maintained, but also as a molten metal raw material to be melted, a sintering raw material to be formed and sintered, etc.

[0023] 《Others》 (1) "Collection" as used in this specification refers to a state in which a plurality of particles (liquid-phase particles or solid-phase particles) are present. "Dispersion" refers to a state in which the plurality of particles are present in another medium (molten salt or solidified salt). In either case, the degree, form, etc. are not limited.

[0024] (2) Unless otherwise specified, the concentration, composition, and particle size distribution referred to in this specification are indicated as mass ratios (mass %) with respect to the whole of the object (molten metal, particles, etc.). Appropriately, mass % is simply indicated as "%".

[0025] (3) Unless otherwise specified, "x to y" as used in this specification includes the lower limit value x and the upper limit value y. For any numerical value included in various numerical values or numerical ranges described in this specification, a range such as "a to b" can be newly established with the new numerical value as the new lower limit value or upper limit value.

Brief Description of the Drawings

[0026]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Embodiments for Carrying Out the Invention

[0027] One or more components arbitrarily selected from this specification can be added to the components of the present invention described above. The content described in this specification can be either a methodological component or a component related to an object (for example, Al-based particles, Al-based material).

[0028] 《Al-based Foil》 (1) As the Al-based foil used as a raw material, an Al-based material (plate material, ingot, etc.) processed (rolled, etc.) to a desired thickness may be used, or an Al-based material already in the form of a foil may be used as it is. The Al-based material may be waste materials recovered from the market, factories, etc. or recycled materials thereof (block-shaped, plate-shaped, foil-shaped, etc.). The recovered or recycled Al-based foil may be used as it is, or may be subjected to pretreatment such as ink removal and cleaning, or thickness adjustment. The Al-based foil laminated with a resin or the like may be added to the molten salt as it is, or the laminated layer may be removed and then added to the molten salt. The Al-based foil may or may not have wrinkles, folds, bends, etc.

[0029] (2) The Al-based foil may be pure aluminum (pure Al) or an aluminum alloy (Al alloy). Al-based foils with different component compositions may be used in a mixed state. The component composition of the raw material Al-based foil is reflected in the component composition of the obtained Al-based particles. Therefore, the components and formulation of the raw material Al-based foil may be adjusted to obtain Al-based particles with a desired composition.

[0030] (3) The thickness and size of the Al-based foil are appropriately selected. According to the particle size distribution of the desired Al-based particle group (powder), the thickness and size (size other than thickness) of the Al-based foil (foil piece) added to the molten salt may be adjusted. At this time, Al-based foils (foil pieces) with different thicknesses and / or sizes may be mixed. Usually, the thinner and / or smaller the Al-based foil (foil piece), the higher the proportion of fine (small-diameter) Al-based particles. Conversely, the thicker and / or larger the Al-based foil (foil piece), the higher the proportion of coarse (large-diameter) Al-based particles.

[0031] The thickness of the Al-based foil, for example, has upper limit values (threshold values that are ~ or less, and further ~ or less) of 0.5 mm, 0.3 mm, 0.2 mm, 0.1 mm, 0.07 mm, 0.03 mm, 0.02 mm. Specifically speaking, the lower limit values (threshold values that are ~ or more, and further ~ or more) are, for example, 0.001 mm, 0.005 mm, and further 0.008 mm. The thickness of the Al-based foil is measured by a micrometer or the like. There may be a variation of about ±10% in the thickness of the Al-based foil. The arithmetic mean value of the thickness measured at arbitrary locations (for example, 10 locations) may be appropriately used as the thickness of the Al-based foil. Unless otherwise specified, the "foil" referred to in this specification means the case where the thickness is 0.5 mm or less (0.2 mm or less, and further less than 0.1 mm).

[0032] The size of the foil piece, for example, has maximum lengths of 200 mm, 150 mm, 100 mm, 50 mm, 30 mm, 20 mm, 10 mm, 5 mm, 1 mm. Its minimum length is, for example, 10 mm, 5 mm, 1 mm, and further 0.5 mm. The size of the foil piece may be adjusted according to the thickness of the foil piece. For example, when it is thin, a large foil piece may be used, and when it is thick, a small foil piece may be used. The foil piece is obtained, for example, by shredding an Al-based foil (raw material) with a shredder or the like.

[0033] 《Molten Salt》 For the molten salt, for example, stable metal halides (especially chlorides and / or bromides) may be used as raw materials. The metal elements constituting the halide are, 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 suitable for the molten salt.

[0034] The temperature of the molten salt may be adjusted by adjusting the raw material composition (component adjustment) of the molten salt. The temperature of the molten salt should be at least equal to or higher than (exceed) the melting temperature of the Al-based foil. The molten salt is not limited to a single layer and may be a multi-layer. The molten salt should be a molten salt reservoir (tank) with a depth or amount sufficient for at least immersing the Al-based foil. Usually, Al-based particles (liquid phase) stay or settle below the molten salt due to the density difference.

[0035] 《Al-based Particles》 (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 pieces are melted, the more likely a particle size distribution with fine Al-based particles will occur.

[0036] The Al-based particles may be liquid-phase particles or solid-phase particles as obtained from Al-based foil (pieces), or liquid-phase particles or solid-phase particles in which the particles are connected (bonded) and integrated (increased in diameter) or alloyed. The Al particles may be used as they are, or may be used after particle size adjustment (classification). According to the manufacturing method of the present invention, it is possible to obtain Al powder composed of Al-based particles with a particle size exceeding 1.7 mm, and it is also possible to obtain Al powder composed of Al-based particles with a particle size less than 0.1 mm.

[0037] Note that the particle size (or particle diameter) of the powder referred to in this specification is specified by sieving and expressed by the nominal mesh size of the sieve (in accordance with JIS Z 8801), unless otherwise specified. The particle size α~β (α < β) means that it consists of particles (group) that do not pass through a sieve with a nominal mesh size of α μm and pass through a sieve with a nominal mesh size of β μm. The particle size α~ means that it consists of particles (group) that did not pass through a sieve with a nominal mesh size of α μm. The particle size ~β means that it consists of particles (group) that passed through a sieve with a nominal mesh size of β μm. The particle diameter of the liquid-phase particles is considered to be approximately equal to the particle diameter of the solid-phase particles, excluding the thermal shrinkage.

[0038] (2) The Al-based particles and Al-based materials have various applications. For example, in one form, the Al-based powder (solid-phase particles) can be used as a filler (such as a thermal conductivity filler or a conductive filler) that is dispersed in a base material (resin, dissimilar metal, ceramics, etc.) to form a composite material, a raw material powder for a sintering material (such as a main element powder or an alloy element powder), a raw material (such as a reducing agent) that causes a chemical reaction (such as a thermite reaction), a pigment added to a paint, etc.

Examples

[0039] An Al-based foil was added to a molten salt to produce Al-based particles (liquid-phase particles), which were then solidified. The present invention will be described in more detail based on such specific examples.

[0040] 《Sample Preparation》 (1) Raw Materials As raw materials, various foil pieces with different dimensions (size (planar size) and thickness) were prepared. All the foil pieces used were foils (Al-based foils) made of pure Al (JIS 1000 series / purity 99% or more) with a size of 100 mm × 100 mm or more. The thickness of the foil was either 0.011 mm, 0.018 mm, 0.025 mm, 0.05 mm, 0.1 mm, 0.3 mm, or 0.8 mm.

[0041] The size of the foil pieces was 25 mm square (roughly square), 3 mm square, 5 mm wide (length 25 mm), and 1 mm wide (length 25 mm). Both the 5 mm width and 1 mm width were sized by further cutting the 25 mm square foil pieces into a predetermined width.

[0042] Cutting (fragmenting) of the foil or foil pieces was performed using metal scissors in an air atmosphere. Thus, various foil pieces were obtained. The appearance of some of them is shown in FIGS. 1A to 1C.

[0043] (2) Molten Salt 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.

[0044] (3) Melting Process As shown in FIG. 2, the process of charging and melting the foil pieces (2.5 g) into the molten salt (100 g) was performed for each foil piece. During this process, stirring was not performed, and the mixture was allowed to stand (for about 10 minutes) until each foil piece was dispersed and melted in the molten salt.

[0045] (4) Collection Process The crucible after the melting process was cooled outside the furnace (cooling process), and the molten salt (particle-dispersed molten salt) was solidified (solidification process). The solidified product (particle-dispersed solidified salt) taken out from the crucible was washed with water (water washing process / salt removal process). The particles remaining after the removal of salts were filtered and dried (filtration process, drying process). The particle groups corresponding to each foil piece thus obtained are collectively shown in Fig. 3.

[0046] (5) Classification process Each particle group was classified by a sieve. Five types of sieves with opening dimensions (mesh sizes) of 1.7 mm, 0.85 mm, 0.425 mm, 0.212 mm, and 0.106 mm were used. The particle size distribution (mass ratio) of each particle group is shown in Fig. 5 and Figs. 6A to 6C (collectively simply referred to as "Fig. 6"). Fig. 5 shows the relationship between the thickness of the foil piece (25 mm square) used as the raw material and the particle size distribution of the obtained particle group. Fig. 6 shows the relationship between the size of the foil piece and its particle size distribution.

[0047] (6) Comparative sample An Al block (50 g) was put into a crucible containing the above-mentioned molten salt (100 g), and the Al block was melted. The Al melt (block) formed in the molten salt was stirred with an alumina rod, and the Al melt was dispersed in the molten salt in a granular form. In the same manner as the above-mentioned method, the solidified product obtained by cooling the crucible was washed with water, and then the obtained particles were filtered, dried, and classified.

[0048] 《Observation》 The SEM image and its enlarged image of the particles (particle size: < 0.212 mm) obtained using a foil piece with a thickness of 0.011 mm × 25 mm square were observed with a scanning electron microscope (SEM) and are shown in Fig. 4.

[0049] 《Evaluation》 (1) Particle shape As is clear from Fig. 4, it was found that the Al-based particles obtained by bringing the Al-based foil piece into contact with the molten salt became almost spherical even without stirring during the melting process. The shape of the Al-based particles of the comparative sample was a slightly flattened sphere.

[0050] (2) Particle size distribution As is clear from Fig. 5, the thinner the Al-based foil used, the more fine particles were contained in the particle size distribution obtained. Conversely, the thicker the Al-based foil used, the more particles with a larger particle size were contained in the particle size distribution obtained.

[0051] As is clear from Fig. 6A, when an Al-based foil with a thickness of 0.3 mm or more (exceeding) was used, particles with a large particle size were stably obtained regardless of their size. It is considered that the thick Al-based foil (piece) gradually melted from each end face and had more opportunities to combine with other Al-based particles (liquid phase) before spheroidization. Incidentally, most of the Al-based particles in the comparative sample had a particle size exceeding 1.7 mm.

[0052] As is clear from Fig. 6B and Fig. 6C, it was found that the particle size distribution could be adjusted by the thickness of the Al-based foil and the size of the foil piece. For example, when a thin and small foil piece was used, a powder with a particle size distribution containing relatively fine particles was obtained. It is considered that the thin and small foil piece melted and spheroidized in a short time and became easy to disperse. Such a tendency was remarkable when the thickness of the Al-based foil was 0.1 mm or less (even less) or the width of the Al-based foil piece was 1 mm or less (even less).

[0053] Incidentally, Al-based particles (liquid phase) with a particle size (diameter) of approximately 2 mm or less were difficult to integrate and tended to maintain a dispersed state in the molten salt.

[0054] Thus, according to the present invention, by using an 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-based material (powder, etc.) can be efficiently or simply obtained from the particle-dispersed molten salt.

Claims

1. A manufacturing method for obtaining an aluminum base material composed of a molten salt in which aluminum base particles in a molten state or a semi-molten state are dispersed by putting an aluminum base foil into the molten salt.

2. A manufacturing method for obtaining an aluminum base material composed of a molten salt or a solidified salt in which aluminum base particles in a solid state are dispersed by putting an aluminum base foil into a molten salt and adjusting the temperature of the molten salt in which the obtained aluminum base particles in a molten state or a semi-molten state are dispersed.

3. The manufacturing method of the aluminum base material according to Claim 1 or 2, wherein the aluminum base foil is composed of shredded foil pieces.

4. The manufacturing method of the aluminum base material according to Claim 1 or 2, wherein the aluminum base foil has a thickness of less than 0.1 mm.

5. The manufacturing method of the aluminum base material according to Claim 1 or 2, wherein the molten salt is composed of a mixed salt.

6. The manufacturing method of the aluminum base material according to Claim 5, wherein the mixed salt contains NaCl and KCl.

7. The manufacturing method of the aluminum base material according to Claim 1 or 2, wherein the aluminum base material is used to obtain an aluminum base molten metal.

8. The manufacturing method of the aluminum base material according to Claim 1 or 2, wherein the aluminum base material is used to obtain aluminum base powder.

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