JPH11140579A - Silicon nitride composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicon nitride composite material having high magnetic permeability and excellent in wear resistance as well as in mechanical strength. SOLUTION: In this silicon nitride type composite material, a roundish Fe-Si or Fe-Al-Si alloy phase 13 of >=40 vol.% by volume ratio is dispersed in a base phase 12 of dense silicon nitride. Further, a grain boundary phase 14, containing aluminum(Al), silicon(Si), yttrium(Y), oxygen(O), and nitrogen(N), exists in the boundary part between the base phase 12 and the alloy phase 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride composite material having high magnetic permeability and abrasion resistance and a method for producing the same.

[0002]

2. Description of the Related Art As a material for a thermoelectric element utilizing the Seebeck effect, iron silicide (FeSi ₂ ) which is a soft magnetic material having a high initial magnetic permeability is widely used. However, iron silicide (FeSi ₂ ) is brittle and easily wears when used for sliding parts. Also, sendust (Fe-Al-Si), which is obtained by adding a small amount of aluminum (Al) to iron silicide (FeSi ₂ ) and reacting the same, has a high magnetic permeability but is very brittle, so that powder having a particle size of about 10 μm was used. In addition, it is used for dust cores and magnetic heads after being hardened with an insulating adhesive. However, for sliding parts such as magnetic heads, materials having better wear resistance are desired.

[0003]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a silicon nitride composite material having high magnetic permeability, excellent mechanical strength, and excellent wear resistance, and a method for producing the same. .

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, the structure of the present invention is that a dense silicon nitride (Si ₃ N ₄ ) mother phase is provided with a rounded Fe—Si alloy phase or Fe—Al— phase. Si alloy phase is dispersed, and aluminum (Al), silicon (Si), yttrium (Y),
It is characterized by the presence of a grain boundary phase containing oxygen (O 2) and nitrogen (N 2).

Further, the constitution of the present invention is that a dense Fe-Si alloy phase or Fe-Al-Si alloy phase having a roundness occupying 40 vol% or more by volume in a dense silicon nitride (Si ₃ N ₄ ) matrix. Are dispersed, and aluminum (Al), silicon (Si), yttrium (Y),
It is characterized by the presence of a grain boundary phase containing oxygen (O 2) and nitrogen (N 2).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A silicon nitride-based composite material according to the present invention comprises an atomized powder of iron or an iron-aluminum alloy, silicon nitride (Si ₃ N ₄ ) powder, and alumina (Al ₂ O).
_3), and a molded body from a powder mixture of sintering aid powder such as Itsutoria (Y ₂ O _3), the molded article is calcined in an inert atmosphere such as nitrogen atmosphere. During firing, iron and silicon nitride react to form Fe-Si. In the compact obtained by firing, a strongly bonded Fe-Si exists as a dispersed phase inside a matrix made of silicon nitride. The matrix phase composed of silicon nitride, which is a continuous phase, has extremely excellent wear resistance, and the silicide of iron, such as FeSi ₂ -Fe ₃ Si ₅ which is a dispersed phase, is formed from atomized powder of iron or an iron alloy. Rounded.

In the silicon nitride-based composite material according to the present invention, since iron alloy (iron silicide) particles dispersed in the silicon nitride matrix are rounded, an iron alloy squared in the silicon nitride matrix is used. When the silicon nitride-based composite material is subjected to an external force, the degree of stress concentration exerted by the dispersed phase of the iron alloy on the parent phase is smaller than that of the dispersed silicon nitride-based composite material, and the mechanical strength of the silicon nitride-based composite material is reduced. Enhance. By the way, in a silicon nitride-based composite material in which the squared iron alloy is dispersed in the matrix of silicon nitride, if the addition amount of the iron alloy exceeds about 3 vol%, the squared portion of the iron alloy when exposed to an external force becomes It exerts stress concentration on the phase and cracks occur.

[0008] Since iron silicide (Fe-Si) has excellent thermoelectric properties, when the silicon nitride-based composite material according to the present invention is arranged on a sliding surface to form a thermoelectric element, the thermoelectric element has a friction of the sliding surface. The heat generates an electromotive force based on the baking effect.

[0009]

FIG. 1 is a cross-sectional view schematically showing the structure of a silicon nitride-based composite material according to the present invention. The silicon nitride-based composite material according to the present invention comprises a dense silicon nitride (Si ₃ N ₄ ) matrix 12.
In addition, rounded Fe occupying more than 40vol% by volume
-Si or Fe-Al-Si alloy phase 13 is dispersed,
At the boundary between the alloy phase 2 and the alloy phase 13, aluminum (Al), silicon (Si), yttrium (Y
), Oxygen (O 2), and nitrogen (N 2). The composition of the alloy phase 13 is Fe ₃ Si ₅ , FeSi ₂ , FeSi ₂ -Fe ₃ S
i ₅ silicified iron, such as. The particle size of silicon nitride in the mother phase 12 is 5 to 50 μm, and the particles of iron silicide in the alloy phase 13 are round and have a particle size of 10 to 100 μm. The grain boundary phase 14 is glassy.

[0010] The silicon nitride composite material according to the present invention is obtained by atomizing a raw material containing iron to produce rounded atomized particles, and adding the atomized particles to a silicon nitride powder containing a sintering aid. When a compact is formed from the mixture and the compact is fired in an inert atmosphere at a temperature of 1400 ° C. or higher, the silicon nitride powder reacts with the atomized particles to cause Fe ₃ Si ₅ , FeSi ₂ , FeSi ₂ —Fe ₃ Si ₅ Produce iron silicide.

[Example 1] 92 wt% of silicon nitride (Si ₃ N ₄ ) powder having a particle size of 5 to 10 μm and alumina (Al
₂ O ₃₎ and 3 wt% of the powder, Itsutoria (Y ₂ O ₃₎ 5 wt powder
% Of the first mixed powder, and 60 parts (volume) of the first mixed powder and a particle diameter of 50 μm or less (preferably 4 μm).
(0 to 50 μm) and 40 parts (by volume) of atomized powder of iron (Fe) to obtain a second mixed powder. A molded body is formed from the second mixed powder, and the molded body is heated at a temperature of about 1800 ° C.
It was fired in a nitrogen atmosphere at 100 atm for about 6 hours.

When the obtained fired body, that is, the silicon nitride-based composite material of the present invention was observed by X-ray diffraction, the silicon nitride-based composite material of the present invention contained Si (Fe) as a raw material during firing. (Silicon) is diffused and FeSi ₂ -Fe ₃ Si ₅
Was generated. When the structure of the silicon nitride-based composite material according to the present invention was observed with a transmission electron microscope, it was found that aluminum (Al), silicon (Si), yttrium (Y), oxygen It was found that a grain boundary phase 14 containing (O 2) and nitrogen (N 2) was present, and the grain boundary phase 14 firmly bonds the mother phase 12 and the alloy phase 13.

The silicon nitride-based composite material according to the present invention has physical properties such as the amount of wear, strength, and thermoelectromotive force as shown in Table 1.

[Table 1] Product of the present invention Conventional product (center dust) Specific wear (mm3 / N · m) 1.0 4.5 Strength (MPa) 750 320 Vickers hardness Hv 1200 650 Thermal electromotive force at 800 ° C. ( mV) 15 24 Initial permeability 10500 16200 A sleeve-like molded body was formed from the raw materials having the compounding ratio of Example 1 and fired in the same manner, and as shown in FIG. 2, the silicon nitride-based composite material according to the present invention. A sleeve 2 having an outer diameter of 20 mm, an inner diameter of 15 mm, and a length of 20 mm was prepared.

Comparative Example 92 wt% of silicon nitride powder, 3 wt% of alumina powder and 5 wt% of yttria powder described in Example 1
% Of the first mixed powder and the second mixed powder in which the mixing ratio of the atomized powder of iron is variously changed, and the molded body is fired in the same manner as in the example. Thus, a large number of sleeve-like bodies 2 having an outer diameter of 20 mm, an inner diameter of 15 mm, and a length of 20 mm were prepared.

As shown in FIG. 2, after the outer peripheral surface of each sleeve 2 of the embodiment 1 and the comparative example is finished smoothly, the outer peripheral surface 3 of the sleeve 2 is provided with a P-type semiconductor and an N-type. The electrode layer 4 with the semiconductor interposed and the heat absorbing layer 5 were brazed. Rotary shaft 7 fitted and supported in a slide bearing 6 made of a sleeve-like body 2
When the number of rotations and the electromotive force generated in the electrode layer 4 were measured, as shown in FIG. 3, Fe—Si or Fe occupied in the matrix 12 composed of silicon nitride constituting the silicon nitride-based composite material.
It was found that when the proportion of the -Al-Si alloy phase 13 exceeds 40 vol%, the electromotive force is significantly increased as compared with the case where the proportion of the alloy phase in the silicon nitride mother phase is 40 vol% or less.

As shown in FIG. 4, when the rotational speed of the rotating shaft 7 is increased, the amount of frictional heat is increased, and the electromotive force is increased.

When the rotating shaft 7 is rotated for a long time, the sliding bearing 6 gradually wears, and accordingly, the frictional heat is reduced and the thermoelectromotive force is also reduced. Therefore, the wear amount can be known from the magnitude of the thermoelectromotive force, and the time for replacing the slide bearing can be known.

[Example 2] A silicon nitride-based composite material having silicon nitride as a mother phase was prepared under the same conditions as in Example 1 except that atomized powder of an iron-aluminum (Fe-Al) alloy was used instead of iron. Produced. That is, 92 wt% of silicon nitride (Si ₃ N ₄ ) powder, 3 wt% of alumina (Al ₂ O ₃ ) powder,
A first mixed powder containing 5 wt% of yttria (Y ₂ O ₃ ) powder was prepared, and 60 parts (volume) of the first mixed powder and iron
A second mixed powder was obtained by mixing 40 parts (volume) of atomized powder of an aluminum alloy. A compact was formed from the second mixed powder, and the compact was fired at a temperature of about 1800 ° C. in a nitrogen atmosphere at 100 atm for about 6 hours.

As shown in FIG. 5, a magnetic head was manufactured from the obtained silicon nitride composite material. The magnetic heads are provided on magnetic cores 21 and 22 made of ferrite, which are separated from each other by a shield plate 26.
4 are wound, and a thin plate 25 made of the silicon nitride composite material according to the present invention is disposed at the end of each of the magnetic cores 21 and 22, that is, at the portion that comes into sliding contact with the magnetic tape.

A sliding friction test was conducted in which a magnetic head using the silicon nitride-based composite material according to the present invention and a conventional magnetic head using Sendust (Fe-Al-Si) were brought into contact with a magnetic tape to slide. However, as shown in FIG. 6, it was confirmed that the magnetic head using the silicon nitride-based composite material according to the present invention had better wear resistance than the conventional one.

[0022]

According to the present invention, as described above, a dense silicon nitride matrix having a volume fraction of more than 40 vol%
e-Si or Fe-Al-Si alloy phase is dispersed, and aluminum (Al), silicon (Si), yttrium (Y), oxygen (O 2), nitrogen (N
), And particularly by using atomized iron or iron alloy powder, iron or iron alloy is converted into rounded silicide particles in a dense silicon nitride matrix. Since it is dispersed, a silicon nitride-based composite material having high mechanical strength, excellent magnetic permeability and wear resistance, and suitable for a magnetic head, a heat-resistant slide bearing, and the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of a silicon nitride-based composite material according to the present invention.

FIG. 2 is a perspective view showing a sliding bearing using the silicon nitride-based composite material according to the present invention.

FIG. 3 is a diagram showing a relationship between a dispersion amount of iron silicide contained in a silicon nitride-based composite material of the sliding bearing and a thermoelectromotive force.

FIG. 4 is a diagram showing a relationship between a rotational speed of a shaft supported by the sliding bearing and a thermoelectromotive force.

FIG. 5 is a plan sectional view of a magnetic head using a silicon nitride-based composite material according to the present invention.

FIG. 6 is a diagram showing a result of a sliding friction test of the magnetic head.

[Explanation of symbols]

2: sleeve-like body 3: outer peripheral surface 4: electrode layer 5: endothermic layer 6: bearing 7: rotating shaft 12: mother phase 13: alloy phase 14: grain boundary phase 21: magnetic core 22: magnetic core 23: erasing coil 24: Recording coil 25: Thin plate 26: Shield plate

Claims (6)

[Claims] A rounded Fe-Si alloy phase or Fe-Al-Si alloy phase is dispersed in a dense silicon nitride (Si ₃ N ₄ ) mother phase, and the mother phase and the alloy phase are separated from each other. A silicon nitride-based composite material, characterized in that a grain boundary phase containing aluminum (Al), silicon (Si), yttrium (Y), oxygen (O 2), and nitrogen (N 2) exists at a boundary portion of the silicon nitride composite material. 2. A dense Fe-Si alloy phase or Fe-Al-Si alloy phase having a volume fraction of 40 vol% or more is dispersed in a dense silicon nitride (Si ₃ N ₄ ) matrix. Aluminum (Al), silicon (Si), yttrium (Y), oxygen (O), nitrogen (N) at the boundary between the mother phase and the alloy phase.
A silicon nitride-based composite material, characterized by having a grain boundary phase containing: _{3. The} silicon nitride composite material according to claim 1, wherein the composition of the alloy phase is represented by Fe ₃ Si ₅ or FeSi ₂ . 4. The silicon nitride-based composite material according to claim 1, wherein said composite material is used for a magnetic head. 5. A plate-like body or a cylindrical body comprising said composite material, wherein one surface is a sliding surface and the other surface is connected to an electrode layer and a heat-absorbing layer. The silicon nitride-based composite material according to claim 1, wherein the temperature difference between the composite material and the electric power is converted into electric power. 6. A step of atomizing a raw material containing iron to produce rounded atomized particles, and forming a molded body from a mixture obtained by adding the atomized particles to silicon nitride powder containing a sintering aid. Forming, and firing the formed body in an inert atmosphere at a temperature of 1400 ° C. or more, and reacting the silicon nitride powder and the atomized particles to generate iron silicide. And a method for producing a silicon nitride-based composite material.