JP4190407B2 - Composite metal body - Google Patents

Description

  The present invention relates to a composite metal body obtained by sintering metal particles mixed with conductive fibers.

The inventors have developed an electric contact material in which a contact layer through which a current flows is formed using metal particles (composite metal powder) whose outer surface is modified with carbon nanofibers (including carbon nanotubes) (patent application). 2002-344916). In the case of this composite metal powder, the end of the carbon nanofiber protrudes in a sea urchin shape from the outer surface of the metal particle.
Japanese Patent Application No. 2002-344916

  In order to form the contact layer of the electrical contact material using the composite metal powder, the composite metal powder is bound with a binder such as a resin, compressed and formed into a required shape, and the molded product is fired. It is necessary to sinter the metal particles.

As described above, the composite metal powder bound with the binder is compression-molded to crush the gaps between the composite metal powders by compressing them to obtain a high-density sintered body.
However, the strength of carbon nanofibers is high, and when compression molding is performed, the gap between the composite metal powders collapses when the carbon nanofibers are bent by the applied pressure, but when the applied pressure is removed, the carbon nanofibers gradually recover. As a result, the gaps were revived, and as a result, only a sintered body having a low density, and therefore inferior in strength and conductivity was obtained.

The present invention has been made to solve the above problems, and its object is to
It is in providing the composite metal body which is excellent in characteristics, such as electroconductivity and heat conductivity.

  The composite metal body according to the present invention has a composite metal powder in which at least the outer surface of the metal particles is modified with a plurality of conductive fibers, and an average particle diameter of 1/10 or less of the average particle diameter of the composite metal powder. Conductive particles or conductive fibrous bodies having an average diameter of 1/10 or less of the average particle diameter of the composite metal powder and a binder are mixed, the mixture is molded, the molded product is fired, and metal particles are obtained. It is characterized by binding.

  In addition, the composite metal body according to the present invention has a conductive powder and at least the outer surface of a metal particle having an average particle size of 1/10 or less of the average particle size of the conductive powder is modified with a plurality of conductive fibers. The composite metal powder thus prepared and a binder are mixed, the mixture is molded, and the molded product is baked to bind the conductive powder.

Further, the composite metal body according to the present invention is a composite metal powder in which at least the outer surface of metal particles having an average particle diameter of 1/10 or less of the average diameter of the conductive fiber body is modified with a plurality of conductive fibers. And a binder, the mixture is molded, the molded product is baked to bind the conductive fibrous body.
Metal fibers or carbon nanofibers can be used for the conductive fibers.

  ADVANTAGE OF THE INVENTION According to this invention, the composite metal body excellent in characteristics, such as electroconductivity and heat conductivity, can be provided. This composite metal body can be suitably used for electric contact members such as brushes and commutators, relays, switches and connectors in motors and generators, radiators for heating elements, bearing materials, and the like.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
In the present invention, a composite metal powder in which at least the outer surface of the metal particles is modified with a plurality of conductive fibers is used.
Specifically, the metal particle (composite metal powder 12) modified with the conductive fiber is, as shown in FIG. 1, the base side of the conductive fiber 14 is buried in the metal particle 10 and the tip side protrudes. State where both ends are buried and the middle part is exposed.
Some of the conductive fibers 14 are entirely embedded in the metal particles 10.
Thus, the composite metal powder 12 in which the outer peripheral surface of the metal particle 10 is modified with the conductive fiber 14 is mixed with another material, molded, and fired to form a composite metal body.
Note that metal fibers and carbon nanofibers (CNF) can be used as the conductive fibers.

As described above, in order to modify the metal particles 10 with the conductive fibers 14, the conductive fibers are scattered in a non-oxidizing atmosphere, and the molten metal is converted into particles by a pump such as a piezoelectric pump in the non-oxidizing atmosphere. By injecting into fiber, it can be formed by attaching and fixing conductive fibers to the particles or the surface of the fibers, or by crushing, granulating or forming a metal in which conductive fibers are dispersed by kneading.
Alternatively, after conducting plating by dispersing conductive fibers in the plating solution on the metal particles attached to the cathode surface, the metal particles are separated from the cathode surface, thereby modifying the metal particles with the conductive fibers. Can be obtained.

When CNF is used as the conductive fiber, the CNF may be either a single-walled carbon nanotube or a multi-walled carbon nanotube, and may be CNF having one end or both ends closed with a fullerene cup.
In addition, the thing of the form whose length is 100 times or more of a diameter is suitable for CNF.
CNF having a diameter of several nm to several hundred nm (for example, 300 nm) or less is preferably used.

In the case of CNF having a diameter of less than 15 nm, the conductivity is lowered. In the CNF having a diameter of less than 15 nm, conductivity occurs when the two integers n and m (chiral index) that determine the chiral vector specifying the spiral direction of the crystal structure are as follows.
That is, when n−m = a multiple of 3 or n = m.
Conductive fibers having a diameter of 15 nm or more have conductivity even when the chiral index is other than the above conditions.

The metal to be modified is a conductive metal such as copper, aluminum or silver.
The metal particles referred to here are spherical, non-spherical, and flaky particles, and are not limited to the shape.

In the present invention, as described above, the composite metal powder 12 obtained by various methods is used.
In the first embodiment of the present invention, as described above, the composite metal powder 12 in which at least the outer surface of the metal particle 10 is modified with a plurality of conductive fibers 14, and the average particle diameter of the composite metal powder 12 Conductive particles 16 having an average particle diameter of 1/10 or less of the above, or conductive fiber bodies 16 having an average diameter of 1/10 or less of the average particle diameter of the composite metal powder 12, and a binder, The mixture is formed, and the formed product is fired to bind the metal particles 10.

  The average particle diameter of the conductive particles 16 mixed in the composite metal powder 12 or the average diameter of the conductive fiber body 16 (which is a conductive fiber body to be distinguished from the conductive fibers of the composite metal powder) 16 is defined as the composite metal powder. By setting the average particle size to 12 or less of the average particle size of 12, the conductive metal particles 16 or the conductive fiber body 16 can sufficiently fill the gaps between the composite metal powders 12. If the composite metal powder 12 is a sphere, if the gap between the spheres is filled with one other sphere (closest packed), the diameter of the other sphere is about 9 times the diameter of the sphere. / 100.

  As the binder, an appropriate resin or metal binder can be used. When the composite metal powder 12 and the conductive particles 16 or the conductive fiber bodies 16 are mixed together with a binder and formed into a required shape, the gaps between the composite metal powders 12 are formed by the conductive particles 16 and the conductive fiber bodies 16. Therefore, it is not necessary to perform compression molding that crushes the gap as in the prior art, and molding with a slight compression force that only binds the materials through a binder is possible. Therefore, the conductive fiber (especially CNF) 14 is not bent more than necessary at the time of molding, and even when the compressive force is removed, a gap is not generated by the spring back as in the prior art.

The molded body formed as described above is fired in a reducing or inert atmosphere, and the composite metal body 20 can be produced by sintering the metal particles 10 (the metal particles 10 of the composite metal powder 12). In addition, when resin is used for the binder, the binder is scattered and disappears. A schematic cross-sectional view of the composite metal body 20 thus obtained is shown in FIG. In FIG. 2, 10 is a metal particle, 14 is a conductive fiber, 16 is a conductive particle or a conductive fiber body.
The composite metal body 20 has a high density and is excellent in properties such as conductivity, thermal conductivity, and strength. Therefore, it can be suitably used for electric contact members such as brushes, commutators, relays, switches, connectors, etc. in motors and generators, radiators for heating elements, bearing materials, and the like.

In the second embodiment of the present invention, the conductive powder 18 and at least the outer surface of the metal particle 10 having an average particle size of 1/10 or less of the average particle size of the conductive powder 18 are a plurality of conductive materials. The composite metal powder 12 modified with the fibers 14 is mixed with a binder, the mixture is molded, and the molded product is baked to bind the conductive powder 18 (FIG. 3).
Alternatively, the composite in which at least the outer surface of the conductive fiber body 18 and the metal particle 10 having an average particle diameter of 1/10 or less of the average diameter of the conductive fiber body 18 is modified with a plurality of conductive fibers 14. The metal powder 12 and a binder are mixed, the mixture is molded, and the molded product is fired to bind the conductive fiber body 18 (FIG. 3).

  In the second embodiment, the average particle diameter of the conductive powder 18 and the average diameter of the conductive fiber body 18 are larger than the average particle diameter of the composite metal powder 12, and the gap between the conductive powders 18 and the conductive fibers It is a case where the gap between the bodies 18 is filled with the composite metal powder 12, and the gap is obtained by using the conductive powder 18, the conductive fiber body 18, and the composite metal powder 12 having the relationship between the average particle diameter and the average diameter. Can be filled with the composite metal powder 12, and a sintered body having a high density can be obtained. FIG. 3 shows a cross-sectional explanatory view of the composite metal body 20 in the second embodiment. In FIG. 3, 18 is a conductive powder or conductive fiber body, and 12 is a composite metal powder.

It is explanatory drawing of composite metal powder. It is a section explanatory view of the composite metal object in a 1st embodiment. It is sectional explanatory drawing of the composite metal body in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal particle 12 Composite metal powder 14 Conductive fiber 16 Conductive particle or conductive fiber body (FIG. 2)
18 Conductive powder or conductive fiber (Figure 3)
20 Composite metal

Claims (5)

  Composite metal powder in which at least the outer surface of the metal particles is modified with a plurality of conductive fibers, and conductive particles having an average particle diameter of 1/10 or less of the average particle diameter of the composite metal powder, or the composite metal powder Conductive fiber bodies having an average diameter of 1/10 or less of the average particle diameter of the above and a binder are mixed, the mixture is molded, and the molded product is fired to bind metal particles. Composite metal body.   Mixing a conductive powder, a composite metal powder in which at least the outer surface of metal particles having an average particle size of 1/10 or less of the average particle size of the conductive powder is modified with a plurality of conductive fibers, and a binder And forming the mixture, firing the molded product, and binding a conductive powder.   A conductive fiber body, a composite metal powder in which at least an outer surface of metal particles having an average particle diameter of 1/10 or less of an average diameter of the conductive fiber body is modified with a plurality of conductive fibers, and a binder A composite metal body comprising: mixing, molding the mixture, firing the molding, and binding a conductive fibrous body.   The composite metal body according to claim 1, wherein the conductive fiber is a metal fiber.   The composite metal body according to claim 1, wherein the conductive fiber is a carbon nanofiber.

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