JP2006216884A - Whisker-formed magnetic material and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a whisker-formed magnetic material having a high strength and a large surface area which can be manufactured by a simple process, and a method for manufacturing the same. <P>SOLUTION: The whisker-formed magnetic material is provided with whiskers on a surface of a sintered body of linked magnetic particles. The magnetic particle includes a magnetic element and an element composing a whisker. The average diameter of the magnetic particles is ten or more times of the average thickness of the whiskers. The magnetic particles are linked in a line shape or in a porous body shape. The whisker-formed magnetic material is formed by linking the magnetic particles mutually by a heat treatment under an atmosphere of inert gas containing a minute amount of oxygen, while magnetizing the magnetic particles. Sintering process is performed at a temperature under a Curie point of the magnetic particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a whisker-forming magnetic body and a manufacturing method thereof, and more particularly, a whisker-forming magnetic body having a remarkably large surface area, in which fine whiskers are densely grown on a magnetic body connected in an arbitrary shape, and a manufacturing method thereof. About.

Conventionally, as a method for producing oxide whiskers, a titanium-vanadium (Ti-V) alloy layer or a titanium-molybdenum (Ti-Mo) alloy layer is formed on the surface of a porous substrate by sputtering, and the surface is obtained by oxidation treatment. It has been proposed to form titanium oxide whiskers (see, for example, Patent Document 1).
JP 2003-335520 A

  However, in this method, it is necessary to prepare a porous substrate in advance. Further, sputtering film formation and oxidation treatment steps are required.

A method for forming magnesia whiskers in which an alloy-forming substrate containing magnesium (Mg) is heated in a mixed gas of CO gas and CO ₂ gas has also been proposed (see, for example, Patent Document 2).
Japanese Patent No. 3121888

  However, in this case, the raw material powder is press-molded to obtain a whisker-forming base material, but the whisker is only obtained in the molded body on the premise of collecting the whisker. In addition, a binder or the like is used during pressing.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to provide a whisker-forming magnetic body having a high strength and a large surface area that can be manufactured by a simple process and a method for manufacturing the same. It is to provide.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by using a magnetic material that can be sintered in a continuous shape as a raw material powder, and the present invention has been completed. It came to do.

  That is, the whisker-forming magnetic body of the present invention is formed by connecting sintered bodies of magnetic particles, and has a whisker on the surface thereof.

  In addition, a preferred form of the whisker-forming magnetic material of the present invention is characterized by containing an element having magnetism and an element constituting the whisker.

  Furthermore, another preferred embodiment of the whisker-forming magnetic body of the present invention is characterized in that the magnetic particles are linearly connected.

  Yet another preferred embodiment of the whisker-forming magnetic material of the present invention is characterized in that the magnetic particles are connected in a porous form.

  The method for producing a whisker-forming magnetic body according to the present invention includes the step of heat-treating the magnetic particles in an inert gas atmosphere and in the presence of a trace amount of oxygen while exciting the magnetic particles. Are connected to each other.

  Furthermore, a preferred embodiment of the method for producing a whisker-forming magnetic material of the present invention is characterized in that, in the heat treatment, the magnetic particles are fired at a temperature lower than the Curie point of the magnetic particles.

  According to the present invention, a whisker-forming magnetic body having high strength and a large surface area can be obtained by a simple process.

  Hereinafter, the whisker-forming magnetic body of the present invention will be described in detail. In the claims and the specification, “%” represents a mass percentage unless otherwise specified.

As described above, the whisker-forming magnetic body of the present invention is formed by connecting sintered bodies of magnetic particles. In other words, the magnetic particles are in a sintered state (chemically bonded to each other).
Moreover, the magnetic particle which comprises the said whisker formation magnetic body equips the surface with a whisker.
Here, “magnetism” refers to ferromagnetism.

Thus, by using magnetic particles, since raw material particles can be held in contact with each other in a magnetic field as shown in FIG. 1, whisker-forming magnetism in which magnetic particles are firmly connected is used. The body is obtained.
In addition, in combination with the fine structure due to the presence of whiskers, it can be used not only as a carrier for supporting filters, various chemicals and catalysts, but also as a fine conductive material, cushion material, and vibration isolator. For example, it can be used as a current collector in a fuel cell (FC) or a capacitor. When used as a current collector for FC, it is extremely useful for protecting the electrode from breakage due to its anti-vibration effect and cushioning properties.

Here, it is preferable that the magnetic particles include an element having magnetism and an element constituting a whisker.
At this time, since both the magnetic element and the whisker constituent element are contained in the raw material powder, it is not necessary to supply the raw material from the outside, and the productivity is improved.

  Examples of magnetic elements include iron, cobalt, nickel, and the like. For example, oxide permanent magnets containing these (iron oxide, chromium oxide, spinel ferrite, magnet brambitite type ferrite, etc.), rare earth magnets (rare earth, Nickel alloy, misch metal, etc.) can be used.

As the whisker constituent element, an element having a high vapor pressure is desirable. Examples include manganese (Mn), chromium (Cr), aluminum (Al), indium (In), gallium (Ga), scandium (Sc), germanium (Ge), tin (Sn), and zinc (Zn). . These whisker constituent elements include, for example, nickel (Ni), cobalt (Co), iron (Fe), titanium (Ti), copper (Cu), silver (Ag), molybdenum (Mo), tungsten (W) and the like. Alloys can also be used. Also, ceramics containing these whisker constituent elements can be used.
Assuming that whisker formation is caused by VLS growth, these raw materials may contain a low melting point component such as phosphorus (P). This is because the low melting point component is easily melted locally on the surface of the raw material, which triggers the formation of the trunk. However, it is not always necessary to add the low melting point component to the raw material, and it is considered that the content as an inevitable impurity is sufficient. In addition, whiskers can be formed even when these components are not included.

  The content ratio of the magnetic element and the whisker constituent element must be such that the magnetic particles are not lost. Typically, the ratio can be 50 to 99: 1 to 50 in terms of mass.

The whisker is preferably fine to some extent with respect to the magnetic particles. Therefore, the average diameter of the magnetic particles is preferably 10 times or more the average thickness of the whiskers.
In this case, a magnetic material having strength and a large surface area can be obtained. In addition, when a whisker is large with respect to a magnetic particle, the intensity | strength of a magnetic body will fall.
Specifically, a whisker-forming magnetic material having an average diameter of magnetic particles of 0.1 to 100 μm and an average thickness of whiskers of 0.01 to 10 μm is obtained.

Furthermore, the connection state of the magnetic particles can be made linear or porous by changing the magnitude of the magnetic field at the time of production, heat treatment conditions, and the like.
In this case, the whisker-forming magnetic body is effective because it can be easily designed into a shape such as a thin wire that is difficult to process or a porous body having a small diameter.
In addition, the above “linear” means that the magnetic particles are linearly connected and not agglomerated (not a shape obtained by ordinary firing), as shown in FIG. In extreme cases, there may be a state in which the particles are connected one by one.
Further, the “porous state” means that the magnetic particles are connected to other magnetic particles adjacent in all directions as shown in FIG. 3 to form a porous body as a whole.

Next, the manufacturing method of the whisker forming magnetic body of this invention is demonstrated in detail.
In the method for producing a whisker-forming magnetic body according to the present invention, when the above-described whisker-forming magnetic body is produced, heat treatment is performed in an inert gas atmosphere and in the presence of a trace amount of oxygen while exciting magnetic particles.
By heating in the magnetic field in this way, the magnetic particles are connected to each other without using a binder or a pore former. In addition, magnetic particles can be connected and whiskers can be formed in one firing step.

In the heat treatment, the magnetic particles are preferably sintered and connected at a temperature lower than the Curie point of the magnetic particles. That is, it is preferable to fire the magnetic particles at a temperature lower than the Curie point of the magnetic particles.
In this case, it is effective because the connection shape of the magnetic particles can be controlled by applying a magnetic field.
It should be noted that the ferromagnetic material loses its ferromagnetism at a high temperature, and changes to a paramagnetic material when the Curie point is exceeded. When a paramagnetic material is formed, the connected particles cannot maintain a connected state.

  Further, as the inert gas, argon, nitrogen, helium, neon, krypton, xenon and radon, or any combination of these can be used.

  Furthermore, in the heat treatment, it is necessary that a small amount of oxygen be present together with these inert gases. This is because the whisker grows as an oxide. However, the concentration of the oxygen is sufficient to remain when the inert gas is fed into the heating furnace (about 1 to 1000 ppm).

  In the heat treatment, the firing temperature depends on the furnace to be used and the size and shape of the sample. For example, when the volume of the heating furnace is 3 L, the inert gas is 0.1 to 5 L / min. And can be baked at 900 to 1100 ° C. for 30 to 1000 minutes.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

Example 1
An iron piece magnetized with a permanent magnet was prepared as a material containing a magnetic element. This was covered with Ni alloy powder containing 10% Mn having an average particle diameter of 10 μm as a whisker forming material, and excess powder was dropped to obtain magnetic particles.
Next, the magnetic particles were put into a heating furnace, argon was introduced as an inert gas at 1 l / min, and baked at 1050 ° C. for 1 hour.
After cooling, a porous sintered metal was formed, and the presence of whiskers was observed on this surface.

  The photograph of the obtained whisker formation magnetic body is shown in FIG. Moreover, when the composition analysis of the whisker was performed by EDX, only Mn and O were detected.

(Comparative Example 1)
A Ti-20 wt% V alloy target was used to form a sputter film on an alumina substrate. The obtained Ti-V alloy film had a thickness of 2 to 3 μm and a columnar crystal structure similar to that of a normal sputtered metal film.
Next, the Ti—V alloy coating was oxidized. At this time, the temperature was gradually raised to 700 ° C. over about 3 hours in air diluted to about 1% with argon gas, and then maintained at 700 ° C. for 22 hours.

  When the surface of the Ti-V alloy film after the oxidation treatment was observed with a scanning electron microscope, several tens of titanium oxide whiskers were densely grown on the entire surface of the base material in the order of several tens per square um. When the X-ray diffraction measurement of the titanium oxide whisker was performed, only the diffraction line of the rutile type titanium oxide was obtained.

  From Example 1 and Comparative Example 1, it can be seen that in the present invention, a whisker-forming magnetic body having a large surface area can be obtained by a simple process. Moreover, in this invention, it can manufacture easily also in the shape which is not proposed conventionally that the whisker is formed in the magnetic particle connected linearly.

It is an enlarged photograph which shows an example of the magnetic particle connected linearly in the magnetic field. It is an enlarged photograph which shows an example in which the whisker was formed in the magnetic particle connected linearly. It is an enlarged photograph which shows an example in which the whisker was formed in the magnetic particle connected by the porous form.

Claims (7)

  A whisker-forming magnetic body comprising a sintered body of magnetic particles connected to each other and having whiskers on a surface thereof.   The whisker-forming magnetic body according to claim 1, wherein the magnetic particles include an element having magnetism and an element constituting a whisker.   The whisker-forming magnetic body according to claim 1 or 2, wherein an average diameter of the magnetic particles is 10 times or more an average thickness of the whisker.   The whisker-forming magnetic body according to any one of claims 1 to 3, wherein the magnetic particles are linearly connected.   The whisker-forming magnetic body according to any one of claims 1 to 3, wherein the magnetic particles are connected in a porous shape. In producing the whisker-forming magnetic body according to any one of claims 1 to 5,
A method for producing a whisker-forming magnetic material, wherein the magnetic particles are heat-treated in an inert gas atmosphere and in the presence of a trace amount of oxygen while exciting the magnetic particles, and the magnetic particles are connected to each other.   A method for producing a whisker-forming magnetic body, characterized in that, in the heat treatment, the magnetic particles are fired at a temperature lower than the Curie point of the magnetic particles.

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