JP4299295B2 - Method for producing carbon nanocomposite metal molded product - Google Patents

Description

  The present invention relates to a method for producing a composite metal molded article obtained by combining a carbon nanomaterial with a matrix metal material.

  In recent years, special carbon fibers called carbon nanofibers have attracted attention as reinforcing materials, and their utilization methods have been proposed. The carbon nanofiber is formed by winding a sheet of carbon atoms arranged in a hexagonal network in a cylindrical shape, and has a diameter of 1.0 nm (nanometer) to 150 nm and is at a nano level. Called carbon nanotubes (hereinafter referred to as carbon nanomaterials). The length is several μm to 100 μm.

  Since the carbon nanomaterial is fine, it is easy to aggregate and is difficult to uniformly mix with the matrix metal as the base material.

Therefore, a technique has been proposed in which a carbon nanomaterial is mixed with a low melting point metal material in a semi-molten state to form a composite (see, for example, Patent Document 1).
JP 2004-136363 A (FIG. 1)

Patent document 1 is demonstrated based on the following figure.
FIG. 8 is a diagram for explaining the basic structure of the prior art. 101 is a melting furnace, 102 is an inclined cooling plate, 103 is a stirring means, 104 is a mixing device, 105 is a pump, 106 is an injection device, and 107 is a mold. It is.

  First, the metal material 111 is melted in the melting furnace 101. The molten metal 112 flows to the inclined cooling plate 102 and cools to the semisolid temperature. The semi-solidified metal material 113 is put into the mixing device 104 and the carbon nanomaterial 114 is added and mixed by the stirring means 103.

The obtained composite material remains in a semi-solid state and is supplied to the injection device 106 using the pump 105 and injected into the mold 107 to obtain carbon nanocomposite molded products 115 and 115.
Alternatively, the composite material obtained by the mixing device 104 is once made into a granular material 116. The granular material 116 is supplied to the injection device 106, returned to a semi-solid state in the injection device 106, and injected into the mold 107, thereby obtaining carbon nanocomposite molded products 115 and 115.

  If the carbon nanomaterial 114 is added to the completely melted metal material with the mixing device 104 and stirred, the carbon nanomaterial 114 actively flows. However, the carbon nanomaterial has poor wettability and the carbon nanomaterial and the metal material. The carbon nanomaterial floats on the surface of the molten metal or settles on the bottom of the molten metal due to a difference in specific gravity with respect to the density of the molten metal.

  In this regard, in the technique of Patent Document 1, since the metal material is in a semi-solid state, even if the carbon nano material 114 is added to the semi-solid state metal material 113 and stirred, the carbon nano material 114 is floated or precipitated. There is an advantage that a uniform dispersion can be expected as a result.

As a result of verification by the present inventors, it has been found that the strength of the carbon nanocomposite molded article 115 manufactured by the technique of Patent Document 1 does not increase as expected.
That is, the technique of Patent Document 1 has room for improvement in terms of strength.

  The present invention provides an improved technology capable of obtaining a carbon nanocomposite metal molded product with higher strength in a method for producing a carbon nanocomposite metal molded product based on the premise that a carbon nanomaterial is added to a semi-solidified metal material. The issue is to provide.

  The present inventors observed the cross section of the carbon nanocomposite molded article manufactured by the technique of Patent Document 1 with a microscope. It was confirmed that the dispersion of the carbon nanomaterial was good. However, when the carbon nanomaterial was further enlarged and observed, it was found that a large number (multiple) of carbon nanomaterials were aggregated in an intertwined state.

  That is, in FIG. 8, when the carbon nanomaterial 114 is already agglomerated at the time of introduction into the mixing apparatus 104, the mixing apparatus 104 is mixed with the metal material 113 in a semi-molten state without being loosened. Can be considered.

  Therefore, a treatment for loosening the carbon nanomaterial was added before being put into the mixing apparatus. As a result, a carbon nanocomposite molded article with high strength could be obtained. From this finding, the present invention described below has been completed.

  The invention according to claim 1 includes a step of mixing a carbon nanomaterial and a metal powder to obtain a carbon nanocomposite metal powder, a step of pressing the carbon nanocomposite metal powder to obtain a preformed product, A step of obtaining a compression-molded article by allowing the molded article to be heated in a state of being heated to a half-melting temperature and then allowing to cool; and a step of preparing a semi-molten metal obtained by heating the same kind of metal as the metal powder to a half-melting temperature; A step of obtaining the semi-molten kneaded product by charging the semi-molten metal with the compression molded product and kneading the compression molded product while warming to the semi-molten temperature; And a step of supplying a carbon nanocomposite metal molded article to the cavity.

  The invention according to claim 2 includes a step of mixing a carbon nanomaterial and a metal powder to obtain a carbon nanocomposite metal powder, a step of pressing the carbon nanocomposite metal powder to obtain a preformed product, A step of obtaining a compression-molded article by allowing the molded article to be heated in a state of being heated to a half-melting temperature and then allowing to cool; and a step of preparing a semi-molten metal obtained by heating the same kind of metal as the metal powder to a half-melting temperature; A step of obtaining the semi-molten kneaded product by charging the semi-molten metal with the compression molded product and kneading the compressed molded product while warming to the semi-molten temperature; and cooling the semi-molten kneaded product. A solid kneaded product, and the solid kneaded product is supplied to a metal injection machine, heated to a semi-solidification temperature by the metal injection machine, and then supplied to a mold cavity to obtain a carbon nanocomposite metal molded product. Process and consist of The features.

  According to a third aspect of the present invention, in the step of obtaining a kneaded material in a semi-molten state, the amount of the semi-molten metal and / or the amount of the compression molded product to be introduced into the semi-molten metal is controlled, whereby the carbon nanocomposite metal molding It is characterized by controlling the addition rate of the carbon nanomaterial in the carbon nanocomposite metal molded product obtained in the step of obtaining the product.

  The invention according to claim 4 is characterized in that, in the step of obtaining a compression molded product, a shearing force is simultaneously applied when pressurizing the preform.

In the invention according to claim 5, the carbon nanomaterial used in the step of obtaining the carbon nanocomposite metal powder is a metal-attached carbon nanoparticle formed by attaching a carbide-forming metal containing an element that reacts with carbon to form a compound on the surface. It is characterized by using a material.

  In the invention according to claim 6, the metal-attached carbon nanomaterial is obtained by mixing the carbon nanomaterial and the carbide-forming metal, placing the obtained mixture in a vacuum furnace, evaporating the carbide-forming metal under a high temperature vacuum, It is obtained by adhering to the surface of a nanomaterial.

  The invention according to claim 7 is characterized in that the carbide-forming metal is Ti or Si.

  The invention according to claim 8 is characterized in that the material of the metal powder is any one of Mg, Mg alloy, Al, and Al alloy.

  In the invention according to claim 1, when the step of obtaining the carbon nanocomposite metal powder by mixing the carbon nanomaterial and the metal powder is performed, the aggregation of the carbon nanomaterial is released and the carbon nanomaterial is coated on the metal powder. Therefore, reaggregation of the carbon nanomaterial can be suppressed.

  Next, a process for obtaining a compression-molded product is carried out by pressurizing a preformed product obtained by pressing and solidifying the carbon nanocomposite metal powder while being heated to a semi-melting temperature, and then agglomerating in the mixing step. Since the carbon nanomaterial thus unwound and compressed is deformed in a solid-liquid coexisting temperature state, a compression molded product in which the carbon nanomaterial is sufficiently dispersed can be obtained.

  When a compression molded product in which carbon nanomaterials are sufficiently dispersed is kneaded with a separately prepared semi-molten metal, the heat of the semi-molten metal is absorbed and the compression molded product returns to a semi-molten state. Since carbon nanomaterials are prevented from fluidizing by the surrounding semi-molten metal, there is no fear of aggregation. If the kneaded material is supplied to the mold cavity in this state, a high-strength carbon nanocomposite metal molded product in which the carbon nanomaterial is uniformly dispersed can be obtained.

  That is, claim 1 includes a step of obtaining a carbon nanocomposite metal powder, a step of pressing the carbon nanocomposite metal powder to obtain a preformed product, and pressurizing the preformed product while being heated to a semi-melting temperature. The carbon nanomaterial is dispersed before mixing (kneading) by carrying out a step of obtaining a compression molded product by allowing to cool after being carried out. By these steps, it can be said that it has succeeded in eliminating the aggregation of carbon nanomaterials before mixing, which has been conventionally generated.

  In addition, since the semi-molten kneaded material obtained in the step of obtaining the semi-molten kneaded material is supplied to the mold cavity, the manufacturing time is shortened, and mass production is possible. Can be easily lowered.

  The invention according to claim 2 is similar to claim 1 in that a step of obtaining a carbon nanocomposite metal powder, a step of pressing the carbon nanocomposite metal powder to obtain a preform, and a semi-melting of the preform It is characterized in that the carbon nanomaterial is dispersed before mixing (kneading) by carrying out a step of obtaining a compression-molded product by allowing to cool after being pressurized in a heated state. By these steps, it can be said that it has succeeded in eliminating the aggregation of carbon nanomaterials before mixing, which has been conventionally generated.

  The second aspect of the present invention provides a step of obtaining a semi-molten kneaded material, a step of cooling the semi-molten kneaded material to obtain a solid kneaded material, and supplying the solid kneaded material to a metal injector. The method differs from claim 1 in that it includes a step of heating to a semi-solidification temperature with this metal injector and then supplying it to the mold cavity. Since the semi-molten kneaded material can be replaced with a solid kneaded material and stored, Claim 2 is suitable for small rod production.

The invention according to claim 3 controls the addition rate of the carbon nanomaterial in the carbon nanocomposite metal molded product by controlling the amount of the semi-molten metal and / or the amount of the compression molded product put into the semi-molten metal. It is characterized by that. In the compression molded product obtained in the process of obtaining the compression molded product, the carbon nanomaterial addition rate is set high, and the amount of the semi-molten metal and / or the amount of the compression molded product charged into the semi-molten metal is controlled in the subsequent step. Thus, a desired carbon nanomaterial addition rate can be achieved.
Therefore, it is possible to use one type or a few types of compression molded products prepared in advance.

  The invention according to claim 4 can effectively destroy the oxide film surrounding the powder surface by simultaneously applying a shearing force when pressurizing the preform. If the oxide film can be broken, the powders can be brought into close contact with each other, and the mechanical strength of the compression molded product can be increased.

The invention according to claim 5 is characterized in that a metal-attached carbon nanomaterial is used in the step of obtaining the carbon nanocomposite metal powder. Carbon nanomaterials have low wettability, but carbide-forming metals have high wettability. By using the metal-attached carbon nanomaterial having such a carbide-forming metal attached to the surface, the wettability of the carbon nanomaterial can be improved.

In the invention according to claim 6, the metal-attached carbon nanomaterial is obtained by mixing the carbon nanomaterial and the carbide-forming metal, placing the obtained mixture in a vacuum furnace, evaporating the carbide-forming metal under a high temperature vacuum, It is obtained by adhering to the surface of a material.
Since the carbide-forming metal produces a compound with carbon, and this compound exhibits a bonding action, the carbide-forming metal can be firmly bonded to the carbon nanomaterial.

The invention according to claim 7 is characterized in that the carbide-forming metal is Ti or Si.
Both Si and Ti are metals having a melting point that can be deposited under vacuum, and also have good wettability with molten matrix metal. Since both Si and Ti are easily available, and especially Si is inexpensive, it is suitable for widely spreading the method of the present invention.

The invention according to claim 8 is characterized in that the material of the metal powder is any one of Mg, Mg alloy, Al, and Al alloy.
Mg, Mg alloy, Al, and Al alloy are lightweight metals, and carbon nanomaterials are included in these metals to increase the mechanical strength, thereby reducing the structural material that is lightweight and has excellent strength, thermal conductivity, and wear resistance. Can be provided.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is an explanatory view of a step of obtaining a carbon nanocomposite metal powder and a step of obtaining a preformed product according to the present invention.

(A): A carbon nanomaterial 11 having a fiber diameter (average value) of 10 nm to 200 nm is prepared, and a metal powder 12 having a particle diameter (average value) of 4 mm or less is prepared. The metal powder 12 is preferably Mg, Mg alloy, Al, or Al alloy.
Mg has a strong oxidation reaction. Below 2 mm, the oxidation reaction reaches a dangerous area. Therefore, normally, when using Mg or Mg alloy, the particle size (average value) is preferably 2 to 4 mm. However, when a small amount of powder is used in an inert atmosphere with sufficiently high inertness, the danger can be avoided, so that even if it is less than 2 mm, it can be used.

  (B): Premixing is performed. The premixing may be performed by putting appropriate amounts of the carbon nanomaterial 11 and the metal powder 12 in a container and shaking the container.

  (C): The carbon nanomaterial 11 and the metal powder 12 are kneaded in earnest by a mechanical alloy method. The mechanical alloy method is based on the “method of alloying in the solid phase using a high energy attritor or ball mill” defined in JIS Z2500, or the mechanical alloying method defined in JIS H7004 “several types of raw material powders in a high energy mill. It is a mechanical mixing method in a broad sense that refers to a method of mechanically stirring, mixing, grinding, and realizing an alloy state by solid-phase reaction. Since it is a well-known method, description of an apparatus and a principle is abbreviate | omitted.

  (D): As described above, the carbon nanomaterial 11 is agglomerated and the carbon nanocomposite metal powder 13 having a form in which the metal powder 12 is coated with an infinite number of carbon nanomaterials 11 is obtained. That is, (a) to (c) described above correspond to the step of obtaining the carbon nanocomposite metal powder.

(E): A die 15 is set on the lower punch 14, and the carbon nanocomposite metal powder 13 is filled in the die 15.
(F): Insert the upper punch 16 into the die 15 and press and harden the carbon nanocomposite metal powder 13 while maintaining the temperature at about 150 ° C. Thus, the preform 17 (see also FIG. 2A) can be obtained.
(E) and (f) described above correspond to the process of obtaining the preform 17.

  Some powders are difficult to compact due to the nature of the powder. In this case, it is put into a metal can and pressurized.

FIG. 2 is an explanatory view of a process for obtaining a compression molded product according to the present invention.
(A): The preform 17 manufactured in the previous step is shown.
(B): A preform 17 is placed on a lower punch 19 that can freely manage atmosphere, temperature, and press pressure, surrounded by a heater 21, and kept in a non-oxidizing atmosphere such as vacuum or argon gas. The metal powder 12 shown in a) is kept at the half-melting temperature, and is pressed down by the upper punch 22.

  For example, if the metal powder is ASTM AZ91D (magnesium alloy die cast JIS H 5303 MDC1D equivalent), the semi-melting temperature is set to 585 ° C., and the pressure of the punch 22 is set to 100 to 200 MPa.

Instead of the above (b), the following (c) may be carried out.
(C): Preliminary product 17 is placed on lower punch 19 of an apparatus capable of freely performing atmospheric management, temperature management, press pressure management and rotation, surrounded by heater 21, and kept in a non-oxidizing atmosphere such as vacuum or argon gas. The metal powder 12 shown in 1 (a) is kept at the half-melting temperature and is reduced by the upper punch 22.

  During this reduction, the lower punch 19 and the upper punch 22 are rotated in reverse directions at a low speed of about 5 revolutions per minute. By simultaneously applying a shearing force when pressurizing the preform, the oxide film surrounding the powder surface can be effectively destroyed. If the oxide film can be broken, the powders can be brought into close contact with each other, and the mechanical strength of the compression molded product can be increased.

  In the above (b) or (c), a step of obtaining a compression-molded product by pressurizing the preformed product 17 obtained by pressing and solidifying the carbon nanocomposite metal powder while being heated to a half-melting temperature, and then allowing to cool. However, the aggregation is released in the mixing step, and the dusted carbon nanomaterial is compressed and deformed in the solid-liquid coexistence temperature state, so that the carbon nanomaterial is further dispersed.

The above (a) to (c) correspond to the step of obtaining a compression molded product.
(D): A compression molded product 23 in which carbon nanomaterials are sufficiently dispersed is shown.

FIG. 3 is an explanatory diagram from the step of preparing a semi-molten metal according to the present invention to the step of obtaining a carbon nanocomposite metal molded product.
In (a), the same kind of metal as the metal powder (see reference numeral 12 in FIG. 1 (a)) is put into a high-temperature tank 26 provided with stirring means 25, and heated to a half-melting temperature to prepare a half-molten metal 27. .

  Next, the compression molded product 23 obtained in the previous step is put into the semi-molten metal 27 and sufficiently stirred by the stirring means 25. Then, the compression molded product 23 is kneaded in a state where the half-melting temperature is reached. As a result, a kneaded product 28 of the semi-molten metal 27 and the compression molded product 23 is completed.

  That is, in (a), a step of preparing a semi-molten metal 27 obtained by heating the same kind of metal as the metal powder to a semi-molten temperature, and a compression-molded product 23 is introduced into the semi-molten metal 27. And a step of obtaining a kneaded product 28 in a semi-molten state by kneading while warming to a semi-melting temperature.

In this step, the content of the carbon nanomaterial can be controlled in the following manner.
For example, the amount of the semi-molten metal 27 prepared in the high-temperature tank 26 is 1200 g, the amount of the compression-molded product 23 charged in the high-temperature tank 26 is 300 g, and the carbon nanomaterial previously included in the compression-molded product 23 is 10% by mass (30 g ).

  The content of the carbon nanomaterial can be controlled by changing the amount of the compression molded product 23 while keeping the amount of the semi-molten metal 27 constant. It can also be controlled by changing the amount of the metal 27, or by changing both the amount of the semi-molten metal 27 and the amount of the compression molded product 23.

The ratio of the carbon nanomaterial contained in the kneaded material 28 to be obtained is 2% by mass according to the calculation formula of (30 / (1200 + 300)) × 100 = 2.
That is, by adjusting the amount of the semi-molten metal 27 and the amount of the compression molded product 23, the ratio of the carbon nanomaterial contained in the kneaded material 28 can be arbitrarily set.

  This setting can also be implemented by adjusting the carbon nanomaterial content of the compression molded product 23 itself. However, in this case, it is necessary to prepare many types of compression molded products 23 having different contents. In this regard, according to the present invention, the compression-molded product 23 prepared in advance can be completed with one kind or few kinds.

In (b), the kneaded material 28 is supplied from the high-temperature tank 26 to the metal injector 31 using the pump means 29, and the kneaded material 28 in a semi-molten state is converted into a mold 32 by the injection action of the metal injector 31. To the cavity 33.
(C) shows the carbon nanocomposite metal molded products 34 and 34 taken out from the mold 32.
That is, in (b), the step of supplying the kneaded material 28 in a semi-molten state to the cavity 33 of the mold 32 to obtain the carbon nanocomposite metal molded product 34 is performed.

  In the above steps, when the compression molded product 23 in which the carbon nanomaterial is sufficiently dispersed is kneaded with the separately prepared semi-molten metal 27, the heat of the semi-molten metal 27 is absorbed and the compression molded product 27 is in a semi-molten state. Return to. Since carbon nanomaterials are prevented from fluidizing by the surrounding semi-molten metal, there is no fear of aggregation. If the kneaded material 28 is supplied to the cavity 33 of the mold 32 in this state, a high-strength carbon nanocomposite metal molded product 34 in which the carbon nanomaterial is uniformly dispersed can be obtained.

  Furthermore, by subjecting the carbon nanocomposite metal molded product 34 to hot rolling or hot extrusion, the metal structure can be refined and properties such as mechanical strength can be improved.

FIG. 4 is a diagram for explaining another embodiment of FIG.
In (a), the same kind of metal as the metal powder (see reference numeral 12 in FIG. 1 (a)) is put into a high-temperature tank 26 provided with stirring means 25, and heated to a half-melting temperature to prepare a half-molten metal 27. .

  Next, the compression molded product 23 obtained in the previous step is put into the semi-molten metal 27 and sufficiently stirred by the stirring means 25. Then, the compression molded product 23 is kneaded in a state where the half-melting temperature is reached. As a result, a kneaded product 28 of the semi-molten metal 27 and the compression molded product 23 is completed.

  That is, in (a), a step of preparing a semi-molten metal 27 obtained by heating the same kind of metal as the metal powder to a semi-molten temperature, and a compression-molded product 23 is introduced into the semi-molten metal 27. And a step of obtaining a kneaded product 28 in a semi-molten state by kneading while warming to a semi-melting temperature.

In (b), the semi-molten kneaded material 28 taken out from the high-temperature tank 26 is once cooled to form a solid kneaded material 35. The solid kneaded material 35 can be arbitrarily stored and stored.
That is, in (b), a step of cooling the semi-molten kneaded material 28 to obtain a solid kneaded material 35 is performed.

In (c), the solid kneaded material 35 is supplied to the metal injection machine 31. In the metal injection machine 31, the solid kneaded material 35 is heated to a semi-melting temperature. Then, the kneaded material in a semi-molten state is supplied to the cavity 33 of the mold 32 by an injection action.
(D) shows the carbon nanocomposite metal molded products 34 and 34 taken out from the mold 32.
That is, in (c), the solid kneaded material is supplied to a metal injection machine, heated to the semi-solidification temperature with this metal injection machine, and then supplied to the mold cavity to obtain a carbon nanocomposite metal molded product. .

  Furthermore, by subjecting the carbon nanocomposite metal molded products 34, 34 to hot rolling or hot extrusion, the metal structure can be refined and properties such as mechanical strength can be improved.

  The method of FIG. 3 described above can be called a “direct method”, and the method of FIG. 4 can be called an “indirect method”. The advantages and disadvantages of these methods are described in the following table.

The metal injection machine can inject 50 g of a semi-molten kneaded product at one time.
In the direct method, since the kneaded material in a semi-molten state is supplied to the metal injection machine, injection was possible in a cycle time of 1 minute. As a result, processing of 3 kg per hour can be performed.

  In the indirect method, it is necessary to dissolve the solid kneaded material to a semi-molten state with a metal injector, and one cycle time is 15 minutes. As a result, the throughput per hour remains at 0.2 kg.

The direct method has a high production capacity and can produce a carbon nanocomposite metal molded product at a low cost. However, since the material change is difficult, it is suitable for mass production of a small variety.
Although the indirect method is low in terms of production capacity, the degree of freedom in production is high and it is suitable for high-mix low-volume production.

Next, the improvement technique of the carbon nanomaterial 11 shown to Fig.1 (a) is demonstrated.
FIG. 5 is an explanatory view when the carbon nanomaterial is surface-treated for preparation according to the present invention.
(A): A carbon nanomaterial 41 is prepared. For example 10g. The carbon nanomaterial 41 may be the same as the carbon nanomaterial 11 shown in FIG. 1A, but the sign is changed for convenience.
(B): Si powder 42 as a carbide forming metal is prepared. For example 1g.

(C): Carbon nanomaterial 41 and Si powder 42 are put in mortar 43 and mixed with pestle 44 for 15 to 30 minutes.
(D): The obtained mixture 45 is put in an alumina container 46 and covered with an alumina lid 47. The lid 47 employs a non-sealing lid to allow ventilation between the inside and the outside of the container 46.

  (E): A vacuum furnace 50 including a sealed furnace body 51, heating means 52 for heating the inside of the furnace body 51, pedestals 53 and 53 on which the container 46 is placed, and a vacuum pump 54 for evacuating the inside of the furnace body 51. Prepare the container 46 in the vacuum furnace 50.

  Although the heating conditions and pressure conditions in the vacuum furnace 50 will be described with reference to the following diagram, the Si powder in the mixture 45 evaporates when heated under vacuum. This steam stirs the space formed by the container 46 and the lid 47 so as to foam. Such an action is called bubbling stirring. The carbon nanomaterial is loosened by this bubbling agitation, and Si vapor comes into contact with the surface of the loosened carbon nanomaterial to form a compound and adhere as Si fine particles.

  To summarize FIG. 5, a step of mixing the carbon nanomaterial 51 with a metal powder 42 containing an element that reacts with carbon to form a compound, and the resulting mixture 45 is placed in a vacuum furnace 50, and the metal is obtained under high temperature vacuum. A vapor deposition treatment step of evaporating the powder 42 and attaching the vapor to the surface of the carbon nanomaterial 41.

FIG. 6 is a graph of the furnace temperature and the pressure in the furnace corresponding to Si. The horizontal axis represents time, and the vertical axis represents the furnace temperature and the furnace pressure.
Start to 5:00: The furnace temperature is raised from room temperature to 300 ° C. over 5 hours at a vacuum degree of 6 × 10 ⁻³ Pa.

5:00 to 9:00: The furnace temperature is raised from 300 ° C. to 1400 ° C. over 4 hours at a vacuum degree of 5.3 × 10 ^{−3 to} 2.1 × 10 ⁻² Pa.
9 o'clock to 19 o'clock: Hold for 10 hours under conditions of a vacuum degree of 2.1 × 10 ⁻² Pa and 1400 ° C.

Since the melting point of Si is 1427 ° C., the temperature is maintained at a temperature just below the melting point (1350 to 1400 ° C.), and Si is maintained in a saturated vapor pressure state at this temperature. At 1350 ° C., the saturated vapor pressure is about 1.3 × 10 ⁻³ Pa, and at 1400 ° C., the saturated vapor pressure is about 2.1 × 10 ⁻² Pa. Since this degree of vacuum can be easily achieved in a vacuum furnace, the treatment temperature is suitably 1350 to 1400 ° C. However, 1350 ° C. has a low evaporation rate, and 1400 ° C. has a high evaporation rate.

  Next, SiC (silicon carbide) which is a compound of Si and carbon will be described. The standard free energy of formation of SiC is −39.6 kJ / mol at 1400 ° C., and this condition can be satisfied. Therefore, it is considered that Si vapor reacts with carbon of the carbon nanomaterial to become SiC.

Therefore, if the mixture is placed in a semi-sealed container and the Si powder is evaporated, bubbling agitation occurs, and Si fine particles can adhere to the carbon nanomaterial.
The long holding time of 10 hours was aimed at sufficient agitation and reaction. Of course, the holding time may be increased or decreased depending on conditions such as the mixing ratio and the processing amount.

After 19:00: Although the heating means is stopped, furnace cooling is performed while maintaining a vacuum degree of 1.1 × 10 ⁻³ Pa. Furnace cooling is a technique for cooling a product very gradually.

  FIG. 7 is an enlarged view of the metal-attached carbon nanomaterial manufactured by the method of the present invention. The metal-attached carbon nanomaterial 55 is uniformly attached to the carbon nanomaterial 41 that is not aggregated and the surface of the carbon nanomaterial 41. It consists of a large number of Si fine particles 56. As described above, these Si fine particles 56 are obtained by crystallizing Si, which is an element that reacts with carbon to form a compound.

  Further, it is important that the Si fine particles 56 are attached to the carbon nanomaterial 41 through SiC which is a carbide. The carbon nanomaterial 41 itself has poor wettability. Therefore, there is a possibility that the bonding strength is insufficient if it is simple Si particles. In this regard, by attaching Si fine particles to the surface of the carbon nanomaterial 41, a SiC reaction layer is formed at the interface, and the Si fine particles 56 can be firmly attached to the carbon nanomaterial 41.

  The metal-attached carbon nanomaterial 55 described above may be replaced with the carbon nanomaterial 11 shown in FIG. 1A, and an appropriate amount of the metal-attached carbon nanomaterial 55 and the metal powder 12 may be mixed.

Incidentally, although a detailed description is omitted, can be replaced with Si as a carbide-forming metal (metal containing an element forming a compound by reacting with carbon-containing) the Ti obtain the same mechanical strength improving effect It was. Furthermore, Zr (zirconium) and V (vanadium) can be adopted as the carbide forming metal in addition to Si and Ti.
However, both Si and Ti are easily available, and especially Si is inexpensive, and therefore, it is suitable for widely spreading the method of the present invention.

  In addition to Mg and Mg alloy having a melting point of about 650 ° C., the metal powder (matrix metal material) includes Al and Al alloy having a melting point of about 660 ° C., Sn and Sn alloy having a melting point of about 232 ° C., melting point Pb and Pb alloys having a melting point of about 327 ° C. can be adopted, and the type is arbitrary as long as the melting point is a low melting point metal or low melting point alloy that does not exceed 700 ° C.

  In particular, Mg, Mg alloy, Al, and Al alloy are lightweight metals, and carbon nanomaterials are included in these metals to increase mechanical strength, making them lightweight and having excellent strength, thermal conductivity, and wear resistance. Material can be provided.

  The present invention is suitable for a method for producing a composite metal molded article obtained by combining a carbon nanomaterial with a matrix metal material.

It is explanatory drawing of the process of obtaining the carbon nanocomposite metal powder which concerns on this invention, and the process of obtaining a preform. It is explanatory drawing of the process of obtaining the compression molded product which concerns on this invention. It is explanatory drawing from the process of preparing the semi-molten metal which concerns on this invention to the process of obtaining a carbon nanocomposite metal molded product. It is a figure explaining another Example of FIG. It is explanatory drawing when surface-treating a carbon nanomaterial for the preparation which concerns on this invention. It is a graph of the furnace temperature and the furnace pressure corresponding to Si. It is an enlarged view of the metal adhesion carbon nanomaterial manufactured with the method of this invention. It is a figure explaining the basic composition of the conventional technology.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11, 41 ... Carbon nanomaterial, 12 ... Metal powder, 13 ... Carbon nano composite metal powder, 17 ... Preliminary molded product, 23 ... Compression molded product, 27 ... Semi-molten metal, 28 ... Semi-molten kneaded material, 32 ... Die 33 to cavity 34 34 carbon nanocomposite metal molded product 35 solid kneaded material 42 carbide forming metal (Si powder) 50 vacuum furnace 55 metal adhering carbon nanomaterial

Claims (8)

  Mixing carbon nanomaterial and metal powder to obtain carbon nanocomposite metal powder, pressing and solidifying the carbon nanocomposite metal powder to obtain a preformed product, and heating the preformed product to a semi-melting temperature A step of obtaining a compression-molded product by allowing it to cool after being pressurized in a pressed state, a step of preparing a semi-molten metal obtained by heating the same kind of metal as the metal powder to a semi-molten temperature, and the compression to the semi-molten metal A step of obtaining a semi-molten kneaded product by charging the molded product and kneading the compression-molded product while warming it to the semi-melting temperature, and supplying the semi-molten kneaded product to the cavity of the mold A method for producing a carbon nanocomposite metal molded product, comprising: obtaining a composite metal molded product.   Mixing carbon nanomaterial and metal powder to obtain carbon nanocomposite metal powder, pressing and solidifying the carbon nanocomposite metal powder to obtain a preformed product, and heating the preformed product to a semi-melting temperature A step of obtaining a compression-molded product by allowing it to cool after being pressurized in a pressed state, a step of preparing a semi-molten metal obtained by heating the same kind of metal as the metal powder to a semi-molten temperature, and the compression to the semi-molten metal A step of obtaining a semi-molten kneaded product by charging the molded product and kneading the compression-molded product while warming to a semi-melting temperature, and a step of cooling the semi-molten kneaded product to obtain a solid kneaded product And supplying the solid kneaded material to a metal injection machine, heating it to a semi-solidification temperature with the metal injection machine, and then supplying it to a mold cavity to obtain a carbon nanocomposite metal molded product. Carbon Roh method for manufacturing a composite metal molded products.   Carbon obtained in the step of obtaining the carbon nanocomposite metal molded product by controlling the amount of the semi-molten metal and / or the compression molded product to be charged into the semi-molten metal in the step of obtaining the semi-molten kneaded product The method for producing a carbon nanocomposite metal molded article according to claim 1 or 2, wherein the addition rate of the carbon nanomaterial in the nanocomposite metal molded article is controlled.   4. The method for producing a carbon nanocomposite metal molded article according to claim 1, wherein in the step of obtaining the compression molded article, a shearing force is simultaneously applied when the preform is pressurized. The carbon nanomaterial used in the step of obtaining the carbon nanocomposite metal powder uses a metal-attached carbon nanomaterial obtained by attaching a carbide-forming metal containing an element that generates a compound by reacting with carbon to the surface. The method for producing a carbon nanocomposite metal molded article according to any one of claims 1 to 4.   The metal-attached carbon nanomaterial is a mixture of a carbon nanomaterial and a carbide-forming metal, and the resulting mixture is placed in a vacuum furnace to evaporate the carbide-forming metal under a high temperature vacuum and adhere to the surface of the carbon nanomaterial. The method for producing a carbon nanocomposite metal shaped article according to claim 5, wherein the method is obtained.   The method for producing a carbon nanocomposite metal molded article according to claim 5 or 6, wherein the carbide-forming metal is Ti or Si.   The method for producing a carbon nanocomposite metal molded article according to any one of claims 1 to 7, wherein the material of the metal powder is any one of Mg, Mg alloy, Al, and Al alloy.

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