JP7035549B2 - Complex molding method - Google Patents

Description

The present invention relates to a method for forming a complex.

A composite in which a carbon material or the like is dispersed in a metal material is known.
As a method for producing the composite, Patent Document 1 describes a step of forming a medium body containing a granulated body of carbon nanomaterial and a ceramic fiber material into a required shape and firing to obtain a preform, and the preform. Specific manufacturing methods are disclosed that include the step of impregnating and solidifying the molten metal. However, as shown in the examples of Patent Document 1, the method did not improve the thermal conductivity of the complex.

Further, as another production method, Patent Document 2 discloses a method of adding a composite powder in which a metal powder surrounds a ceramic-coated nanocarbon to an aluminum bath water and casting it. In the embodiment of Patent Document 1, the nanocarbon is ceramic-coated by the sol-gel method, and the nanocarbon and the metal powder are mixed by a ball mill.
According to Patent Document 2, the reaction between nanocarbon and liquid aluminum can be suppressed by the above-mentioned production method. However, the above-mentioned manufacturing method has many manufacturing processes, and has problems in terms of productivity and manufacturing cost.

Japanese Unexamined Patent Publication No. 2013-181232 JP-A-2015-203155

For example, in the field of vehicles, electrification of vehicles is being considered, and mounting of various electronic components in vehicles is being considered. Since electronic components generate heat, there is an increasing demand for heat dissipation technology in vehicles.
The present inventors have studied to improve heat dissipation by arranging a member having high thermal conductivity around an electronic component. As one means, for example, copper having high thermal conductivity, diamond, or the like has been considered, but there are problems of weight increase and cost.
On the other hand, as the metal member in the vehicle, a cast product is partially used from the viewpoint of productivity and the like. The present inventors focused on such a metal member and studied to improve the thermal conductivity.

The present invention has been made from such a viewpoint, and an object of the present invention is to provide a method for forming a complex capable of obtaining a complex having excellent thermal conductivity.

The method for forming a complex according to the present invention is as follows.
A method for forming a complex in which a heat conductive material is dispersed.
A mixture containing a fiber material made of a simple substance of metal and the heat conductive material, and
The process of preparing a molten metal made of an alloy containing the metal and
The step of arranging the mixture in the mold or in the injection path of the molten metal, and
It has a step of injecting the molten metal into the mold and casting.

According to the present invention, it is possible to provide a method for forming a complex capable of obtaining a complex having excellent thermal conductivity.

FIG. 1 is a flowchart showing an example of a method for forming a complex according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing an example of a casting apparatus used for molding a complex. FIG. 3 is a graph showing the results of thermal conductivity evaluation of Examples and Comparative Examples.

First, with reference to FIG. 1, a method for forming a complex according to this embodiment will be described. FIG. 1 is a flowchart showing an example of a method for forming a complex according to the present embodiment. The method for forming the composite shown in the example of FIG. 1 includes a step (S1) of preparing a mixture containing a fiber material made of a single metal and a heat conductive material, and separately, the same metal as the metal of the fiber material. A step of preparing a molten metal made of an alloy containing the above (S2), a step of arranging the mixture in a mold or in an injection path of the molten metal (S3), and injecting the molten metal into the mold. It has a step of casting (S4). The method for forming the complex of the present embodiment is not limited to the order shown in FIG. 1, and for example, the step of preparing the molten metal (S2) may be before the step of preparing the mixture (S1). It may be after the step of arranging the mixture (S3), or it may be simultaneous with the above S1 or S3. The details will be described below.

In this embodiment, the mixture contains a fiber material made of a simple substance of a metal and a heat conductive material, and may further contain other components as long as the effects of the present invention are not impaired.

In this practice, it is presumed as follows, although it is still unclear that a complex having excellent thermal conductivity can be formed by using the above-mentioned mixture.
In Patent Document 1, a ceramic fiber material such as alumina having a high melting point is used as the fiber material. It is presumed that such a ceramic fiber material does not melt even during casting and forms an interface with aluminum or the like as a base material after molding. In addition, it is presumed that the formation of aluminum carbide (Al ₄ C ₃ ) and the like is promoted because the carbon nanomaterial is also heated. As a result of these, it is presumed that the thermal conductivity decreases.
On the other hand, in this implementation, a fiber material made of a single metal having a melting point slightly higher than the melting point of the alloy for molten metal described later (for example, the melting point of the alloy + 500 ° C. or less) is used. Therefore, it is presumed that it is difficult for the fiber material to melt with the alloy to form an interface during casting. Further, it is presumed that the heat of fusion is required and absorbed when the fiber material is melted, so that the surface temperature of the heat conductive material is suppressed from becoming high and the decrease in thermal conductivity is suppressed.
Therefore, according to the method for forming a complex according to the present embodiment, a complex having high thermal conductivity can be obtained.

The metal in the fiber material made of a simple substance of metal is a metal contained in an alloy for molten metal described later, and may be appropriately selected. The metal preferably has a melting point higher than the melting point of the alloy described later and is 1800 ° C. or lower, and is preferably a metal having a melting point of the alloy + 500 ° C. or lower.
In this implementation, the metal of the fiber material is aluminum (melting point: 660 ° C.), zinc (melting point: 420 ° C.), magnesium (melting point: 650 ° C.), among others, from the viewpoints of melting point, thermal conductivity, light weight, mechanical strength, etc. ) Is preferable, and aluminum is more preferable.
In this embodiment, the fiber material made of a single metal is a fiber material made of substantially a single metal, but may contain other metals inevitably mixed. Examples of other metals that are inevitably mixed include, but are not limited to, iron, silicon, and the like. In this embodiment, the fiber material composed of a single metal may be 98% by mass or more as a single metal, and 99% by mass or more is preferably a single metal.

As a modification, if the melting point of the fiber material is higher than the melting point of the alloy described later and the metal is 1800 ° C. or lower, or if the melting point of the fiber material is the melting point of the alloy + 500 ° C. or less, a single unit is used. Even if it is a fiber material other than the fiber material made of metal, it is difficult to form an interface with the alloy, and a composite having high thermal conductivity can be obtained.

The shape of the fiber material is not particularly limited, but can be appropriately selected from, for example, those having a diameter of 0.5 μm or more and 1000 μm or less, preferably 1 μm or more and 500 μm or less in diameter.

In this embodiment, the heat conductive material is appropriately selected from at least a material having a higher thermal conductivity than the alloy described later. In this implementation, a carbon-based material is preferable because it has excellent thermal conductivity and is lightweight.
Examples of the carbon-based material include carbon nanomaterials such as carbon nanotubes, carbon nanocoils, and carbon nanofilaments, diamond particles, and the like, and among them, carbon nanomaterials are preferable.
The shape of the carbon nanomaterial is not particularly limited, but can be appropriately selected from those having a diameter of 0.4 nm or more and 200 nm or less, for example.

In this embodiment, the ratio of the fibrous material to the heat conductive material in the mixture is not particularly limited, but the mass ratio of the fiber material to the heat conductive material is preferably 1:99 to 99: 1, preferably 10:90 to. It is more preferably 90:10.

Other components that may be included in the mixture include, for example, dispersants used in the preparation of the mixture.
The dispersant can be appropriately selected from known ones. Above all, when the metal is aluminum, it is preferable to use ammonium nitrate as a dispersant. When ammonium nitrate is used, aluminum nitride is produced during casting, and high thermal conductivity can be obtained.

The method for preparing the mixture is not particularly limited as long as it is a method in which the fiber material and the heat conductive material are dispersed. For example, a fiber material, a heat conductive material, a dispersant, and other components are mixed with a solvent such as alcohol, dispersed by a known method, and then the solvent is removed and dried. A granular mixture in which the fiber material and the heat conductive material are dispersed can be obtained.

The alloy to be the molten metal in this embodiment is an alloy containing the metal of the fiber material. The alloy is preferably an alloy containing the metal as a main component. In this embodiment, the main component of the alloy means an alloy having a metal ratio of 50% by mass or more, and an alloy having a metal ratio of 80% by mass or more is preferable. In general, the melting point of an alloy tends to be lower than the melting point of a single metal. Therefore, by selecting such an alloy, it is possible to select an alloy having a melting point lower than that of the fiber material. As such an alloy, an alloy known as an alloy for casting can be appropriately selected and used.

As the alloy containing aluminum as a main component, an alloy containing at least one selected from silicon, magnesium, and copper is preferable. Specific examples thereof include an aluminum alloy bullion for casting specified in JIS H 2211 (2010) and an aluminum alloy bullion for die casting specified in JIS H 2118 (2006).
As the alloy containing zinc as a main component, an alloy containing at least one selected from aluminum, magnesium, and copper is preferable, and an alloy containing aluminum is more preferable. Specific examples thereof include zinc alloy bullions for die casting specified in JIS H 2201 (2015).
Further, as the alloy containing magnesium as a main component, an alloy containing at least one selected from aluminum and zinc is preferable. Specific examples thereof include magnesium alloy metal for casting specified in JIS H 2221 (2006) and magnesium alloy metal for die casting specified in JIS H 2222 (2006).

The method for preparing the molten metal made of the above alloy is not particularly limited. Usually, it can be prepared by preparing an alloy having a desired composition and heating the alloy to a temperature higher than the melting point. For example, after preparing each metal simple substance so as to have a desired composition and melting each of them. It may be prepared by mixing.

Next, the step (S3) of arranging the mixture will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing an example of a casting apparatus used for molding a complex. In the example of FIG. 2, a mold 1 for forming the cavity 2, a sleeve 3 connected to the mold 1, and a plunger 4 for injecting the molten metal 6 in the sleeve 3 into the cavity 2 are provided. The plunger 4 may be provided with an opening 5 for injecting the molten metal 6. The casting apparatus shown in the example of FIG. 2 has a minimum configuration for die casting, and other parts may have any conventionally known configuration. Further, the casting method is not particularly limited in the method for forming the composite of the present embodiment, and casting may be performed by any known casting method such as a low pressure casting method or a gravity casting method, and known suitable for these casting methods. Equipment can be used.

In this embodiment, the mixture is placed in the mold 1 or in the injection path of the molten metal. The injection path of the molten metal may be a connection portion between the sleeve 3 and the mold 1, or may be inside the sleeve 3. When arranged in the sleeve 3, the mixture may be put into the molten metal 6.
The mixture may be used in the form of the above-mentioned granules, or the granular mixture may be wrapped in aluminum foil or the like that melts by heating during casting, or may be evaporated or decomposed by heating during casting. It may be used by being attached to an adhesive or the like.

Next, the molten metal is poured into the mold and cast. In the example of FIG. 2, the plunger 4 is operated by hydraulic pressure or the like, and the molten metal 6 in the sleeve 3 is injected into the cavity 2 and cast to obtain a molded complex.
The composite obtained by the above-mentioned molding method of the composite has excellent thermal conductivity even when the heat conductive material is dispersed in the alloy and the content ratio of the heat conductive material is, for example, 1% by volume or less. It becomes a complex.
The composite obtained by this practice preferably has a heat conductive material content of 1% by volume or more and 50% by volume or less, and more preferably 20% by volume or more and 30% by volume or less.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. It should be noted that these descriptions do not limit the present invention.

<Production Example 1: Preparation of mixture>
A carbon nanotube having a diameter of 150 nm, a pure aluminum fiber having a diameter of 150 μm, and a dispersant were put into ethanol so as to have a mass ratio of 1: 3: 1 and dispersed to prepare a slurry-like dispersion liquid. .. Then, the dispersion was molded and dried to obtain a granular mixture.

<Example 1>
After 13 g of the mixture obtained in Production Example 1 is placed in the mold 1 of the production apparatus of FIG. 2, a molten metal of an aluminum alloy (ADC12) is poured into the mold 1 and cast to form a composite of Example 1. I got a body.

<Example 2>
After 13 g of the mixture obtained in Production Example 1 is placed in the sleeve 3 (inside the molten metal 6) of the manufacturing apparatus of FIG. 2, the mixture is poured into the mold 1 together with the molten metal 6 of the aluminum alloy (ADC12) and cast. Then, the complex of Example 2 was obtained.

<Example 3>
In Example 2, a complex of Example 3 was obtained in the same manner as in Example 2 except that the amount of the mixture was changed to 26 g.

<Comparative Example 1>
In Example 1, a cast product of Comparative Example 1 was obtained in the same manner as in Example 1 except that the mixture was not used.

[Evaluation of thermal conductivity]
The complexes or castings obtained in Examples and Comparative Examples were attached to heaters, respectively, the heater was heated for 720 seconds, the temperature of the heater during that period was monitored, and relative evaluation was performed. It can be evaluated that the lower the measured temperature of the heater, the better the heat dissipation, that is, the thermal conductivity. The results are shown in FIG.
As shown in the results of FIG. 3, in Comparative Example 1, the heater rose up to 80 ° C., whereas in Example 2, for example, the temperature rose only up to 44 ° C., indicating excellent heat dissipation. Was done. As described above, the complex produced by this practice has excellent thermal conductivity.

1 Mold 2 Cavity 3 Sleeve 4 Plunger 5 Opening 6 Molten

Claims (1)

A method for forming a complex in which a heat conductive material including a carbon-based material is dispersed.
A mixture containing a fiber material made of a simple substance of metal and the heat conductive material, and
The process of preparing a molten metal made of an alloy containing the metal and
The step of arranging the mixture in the mold or in the injection path of the molten metal, and
It has a step of injecting the molten metal into the mold and casting.
The melting point of the metal in the fiber material is higher than the melting point of the alloy and is not less than the melting point of the alloy + 500 ° C.
How to form a complex.

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