JP3214729B2 - Method for producing silicon nitride reaction sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a silicon nitride (hereinafter referred to as Si)
₍ Referred to as 3N ₄ ).

[0002]

2. Description of the Related Art Conventionally, in producing a Si ₃ N ₄ reactive sintered body, a molded body made of metallic Si powder is reacted with nitrogen gas to synthesize Si ₃ N ₄ and at the same time, the Si ₃ N _{4 is produced.}
Is generally adopted.

[0003]

However, according to the conventional method, the dimensional change in the sintering process is extremely small, so that an Si ₃ N ₄ reaction sintered body having a final shape or a shape close to the final shape can be obtained. there other hand, since the Si ₃ N ₄ on the surface of the molded product at an early stage fast reaction rate of the nitride is generated in the coating form, penetration of the nitrogen gas into the internal compact is hindered by the Si ₃ N _4, Si ₃ The nitridation inside the N ₄ reaction sintered body is insufficient, and the nitridation rate is about 80% even at the maximum value, so that high density and high strength Si ₃ N ₄
There was a problem that a reaction sintered body could not be obtained.

[0004] In view of the above, the present invention uses a raw material powder in which a specific metal powder is dispersed, thereby forming a compact and a metal Si powder (strictly speaking, metal Si particles) as a component thereof into the inside thereof. It is an object of the present invention to provide the above-mentioned production method capable of obtaining a Si ₃ N ₄ reaction sintered body having a high density and a high strength.

[0005]

According to the present invention, Si ₃ N _{4 is provided.}
The production method of the reaction sintered body is as follows:
The particle size distribution is modified Andreasen's (Andreasen) filling formula Dm = 1− (R / Rmax) ^q (where Rmax is the maximum particle radius and R is an arbitrary particle half)
Diameter, q is a coefficient, Dm is an arbitrary value from the maximum particle radius Rmax
In the molded body obtained using particles up to the particle radius R
(Dm ≦ 0.75).
When the large particle radius Rmax is constant, the coefficient q is 0.2
Prepare one set so that 5 ≦ q ≦ 0.5,
Ni powder is added to the metal Si powder as a metal powder for accelerating nitriding.
Disperse 0.0085% by weight ≦ Ni powder ≦ 5% by weight
Molding a molded body using the raw material powder,
Primary sintering process to react the body with nitrogen gas
Obtaining an intermediate containing synthetic Si ₃ N ₄ by
The intermediate is subjected to a pickling treatment to remove the Ni component from the intermediate.
Eluting, and reacting the intermediate with nitrogen gas
Performing a secondary reaction sintering process of synthesizing Si ₃ N ₄ by
Are sequentially performed.

[0006] In the production method of this, instead of the Ni powder, Co powder or Fe powder is used. in this case,
The amount of Co powder added is 0.0085% by weight ≦ Co powder ≦
It is set to 4.5% by weight, and the amount of Fe powder added is set to 0.01% by weight ≦ Fe powder ≦ 4% by weight.

[0007]

The pickling treatment is performed on the intermediate,
The sintering process to obtain the intermediate is called primary reaction sintering process.
U. By this pickling treatment, Ni components and the like are eluted and formed.
Pores in the secondary reaction sintering process
Because it becomes an entry path for nitrogen, the nitrogen in the Si ₃ N ₄
Conversion ratio A> 80%, especially using Ni powder or Co powder
Can be increased to A = 100%
You. In addition, Ni components and the like are contained in the Si ₃ N ₄ reaction sintered body.
Is regarded as an impurity, but Ni is formed by the pickling process.
When elution is performed, the effect of Ni component on strength
Relaxing and increasing the strength of the Si ₃ N ₄ reaction sintered body
it can.

[0008] The Contact, but rarely is that all of the Ni component or the like is eluted by acid pickling, Ni components, etc. The remaining, by pickling treatment, when present is independently miniaturization In addition, when they are agglomerated, they are redispersed and miniaturized, so that they do not cause a reduction in the strength of the Si ₃ N ₄ reaction sintered body.

However, if the amount of Ni powder or the like deviates from the above range, the nitriding rate of the Si ₃ N ₄ reaction sintered body is greatly reduced, and the strength of the reaction sintered body is extremely reduced.

The radius of the particles constituting the powder changes continuously
In a continuous particle system that
Andreazen (Andreasen) filling method
The formula is known.

This filling equation is given by Dm = (R / Rmax) ^q
In expressed, Rmax maximum particle half diameter, R is any particle
Radius, q is a coefficient, Dm is arbitrary from the maximum particle radius Rmax
Of a molded article obtained using particles up to a particle radius R of
Filling rate.

However, the particle size distribution of the metal Si powder is
When set according to Andreazen's filling formula, the formula is
Since it is a filling type when the continuous particle system takes close packing,
The filling factor in the form becomes too high, and metal Si
The nitridation reaction of the components is an exothermic reaction as described above.
As a result , cracks, collapses, etc. occur in the Si ₃ N ₄ reaction sintered body.
You.

Therefore, the rate of volume increase due to the nitriding reaction is 25%.
%, The relative density of the molded body is 75%,
Therefore, the filling rate was set to 0.75 and the nitriding was set to 10
If it is advanced by 0%, there are no defects such as cracks and no pores.
Thus, a Si ₃ N ₄ reaction sintered body can be obtained.

From these facts, the inventors of the present invention have reported that metal Si
Maximum and minimum particle radii Rmax and Rmi of the powder
n is set to a predetermined value, and the filling rate Dm in the molded body is
As a result of conducting a number of experiments at 0.75,
The filling formula of azene is given by Dm = 1− (R / Rmax) ^q (
However, Dm ≦ 0.75), and the maximum particle radius Rma
When x is constant, the coefficient q is set to 0.25 ≦ q ≦ 0.5.
When set, the particle size distribution of metallic Si powder is optimized to achieve high density
To obtain high-strength and high-strength Si ₃ N ₄ reaction sintered body
I determined what I could do.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a manufacturing process of a Si ₃ N ₄ reaction sintered body using Ni powder as a metal powder for accelerating nitriding will be described with reference to FIGS. For convenience, description of a direct reaction between the metal Si component and the nitrogen gas in the molded body (or the intermediate) is omitted.

In FIG. 1A, Ni powder is added to the metal Si powder.
The powder is added in the range of 0.009% by weight ≦ Ni powder ≦ 2.2% by weight, and the both powders are sufficiently wet-mixed to prepare a raw material powder in which the Ni powder is dispersed in the metal Si powder. The compact 1 is formed by performing compression molding using the powder, and then the compact 1 is dried.

In FIG. 1B, the temperature of the molded body 1 is increased in a nitrogen gas atmosphere. In this heating process, the Ni component Ni diffuses into the metal Si powder.
The i-component Ni reacts to produce silicide NiSi ₃ .

[0018] In FIG. 1 (c), the phase Tonariru nitrogen gas N ₂ from the gap between the metal Si component Si diffuses into silicide NiSi ₃ enters inside the molded body 1, silicide NiSi ₃
Is the nitrogen diffusion layer NiSi ₃ —N.

In FIG. 1D, the surface of the compact 1 is formed of Si ₃ by the reaction between the metal Si component Si and the nitrogen gas N _2.
N ₄ is formed in the form of a film. In this case, the film Si ₃
The entry of nitrogen gas N ₂ into the inside of the molded body 1 is not completely prevented by N ₄ .

In FIG. 2E, a nitrogen diffusion layer NiSi
_{In 3-} N, first, the Ni component reacts with the N component, that is, the N component is taken in by the Ni component, so that nitride NiN is generated. Since this nitride NiN is in a non-equilibrium state, the N component is dissociated, and the dissociated N component is added to the metal Si component, so that the inside of the molded body 1 is nitrided to synthesize Si ₃ N _4. You.

As described above, the nitridation reaction occurring on the surface side and inside of the molded body 1 is an exothermic reaction, so that the metal Si component Si expands thermally, whereby the Ni component Ni is compressed and deformed by the surrounding metal Si component Si. At the same time, a part of the Si ₃ N ₄ is leached out between the adjacent two Si metal components Si, and the leached portion a breaks the film-like Si ₃ N ₄ . Although only one extruded portion a is shown in the drawing, a large number of extruded portions a actually occur and the film-like Si ₃ N ₄ is broken at many locations.

Such a phenomenon occurs around 1250 ° C., and at this stage, S
i ₃ N ₄ has been produced, and thus the compact 1 has been transformed into an intermediate 2 containing synthetic Si ₃ N ₄ .

In FIG. 2 (f), the nitrogen gas
The i ₃ N ₄ breaks into the intermediate body 2 through the gap between the Ni component Ni and the Si ₃ N ₄ around the Si component Si from the broken portion, and diffuses into the silicide NiSi ₃ around the Ni component Ni to diffuse nitrogen. layer NiSi ₃ -N is generated.

In FIG. 2G, a nitrogen diffusion layer NiSi
_{In the case of 3-} N, the N component is taken in by the Ni component and then the dissociated N component is added to the metal Si component in the same manner as described above, so that Si ₃ N ₄ is synthesized.

[0025] In parallel with the synthesis the Si ₃ N ₄ as described above, is also performed Si ₃ N ₄ synthesis reaction as shown in FIG. In order to simplify the description, a reaction performed between one metal Si powder and one Ni powder will be described.

In FIG. 3 (a), when the temperature of the molded body is increased in a nitrogen gas atmosphere, the Ni component Ni diffuses into the metal Si powder so as to penetrate the metal Si powder in the course of the temperature increase. Since Ni and the Si component Si react, the metal S
Silicide NiSi ₃ is generated to divide the i-powder.

[0027] In FIG. 3 (b), the nitrogen gas N ₂ is diffused into the silicide NiSi _3, mainly the outer side of the silicide NiSi ₃ is nitrogen diffusion layer NiSi ₃ -N. In nitrogen diffusion layer NiSi ₃ -N, first, and the Ni component and N component reacts, i.e. so Tokagomi of N component by Ni component is performed nitride NiN is generated. This nitride Ni
Since N is in a non-equilibrium state, the N component is dissociated, and the dissociated N component is added to the metal Si component. Therefore, nitriding is performed to synthesize Si ₃ N ₄ around the silicide NiSi _3. . On the surface side of the metal Si powder, the metal Si component Si
Reacts with the nitrogen gas N ₂ to form Si ₃ N ₄ in a film form.

By such a nitriding reaction, the metal Si powder is divided into a plurality of small pieces having Si ₃ N ₄ on the entire outer peripheral portion.

The Si ₃ N ₄ reaction sintered body 3 is manufactured through the above steps. The nitriding rate A of the reaction sintered body 3 varies depending on the amount of Ni powder added.
<A ≦ 98%.

In the manufacturing process of the Si ₃ N ₄ reaction sintered body,
The elution of the Ni component by the pickling treatment is performed on the intermediate 2 after the completion of the step of FIG. When the intermediate 2 is subjected to the pickling treatment, the elution of the Ni component can be performed relatively efficiently and sufficiently.
The pores generated by the elution of the Ni component contribute to nitriding as a gas entrance path into the intermediate body 2 in the secondary reaction sintering process, and are finally filled with Si ₃ N ₄ .

FIG . 4 shows a filling rate Dm = 0.
75 shows the particle size distribution when the maximum particle radius Rmax of the metal Si powder is set to 10 μm and the coefficient q is changed in the range of 0.25 to 0.6. From FIG. 4, the curve tends to rise as the coefficient q increases, and therefore the minimum particle radius R for obtaining the filling factor Dm = 0.75 is obtained.
min tends to be large.

When the coefficient q is set to 0.25 ≦ q ≦ 0.5, the particles on the minimum particle radius side have an appropriate size.
The pores in the compact are adjusted to a size suitable for nitriding and dispersed, and efficient nitriding is performed, so that the density and strength of the Si ₃ N ₄ reaction sintered body are increased. Is achieved.

If the coefficient q is q> 0.5, the pores become large and the dispersion becomes insufficient because the particles on the minimum particle radius side are too large, whereby the nitriding efficiency is reduced and the Si ₃ N ₄ reaction firing is reduced. The density and strength of the compact are reduced. On the other hand, when the coefficient q is q <0.25, the particles on the minimum particle radius side are too small, so that the pores become small and the entry of nitrogen gas into the molded body is hindered, whereby the Si ₃ N ₄ reaction sintering is performed. The body becomes low density and low strength.

Example 1 Nitriding was promoted to a 99.5% pure metal Si powder having a maximum particle radius of 10 μm, a minimum particle radius of 0.15 μm, and a particle size distribution of a coefficient q = 0.33 (shown in FIG. 4). Ni powder having an average particle radius of 0.1 μm was added as a metal powder for use in a range of 0.005% by weight ≦ Ni powder ≦ 8% by weight, and both powders were sufficiently wet-mixed to prepare various raw material powders.

Each of the raw material powders is subjected to compression molding under the conditions of a pressing force of 120 MPa to obtain a 6 mm long, 22 mm wide,
A 74 mm long plate-like compact was formed, and each compact was 110
A drying treatment was performed at 4 ° C. for 4 hours. Filling rate Dm of each compact
Was 0.68 to 0.72 (relative density 68 to 72%).

Each compact was placed in a sintering furnace, heated in a nitrogen gas atmosphere, and subjected to a reaction sintering process for reacting each compact with nitrogen gas to synthesize Si ₃ N ₄ . Subsequently, various types of Si ₃ N ₄ reaction sintered bodies were obtained by furnace cooling.

As shown in FIG. 5, the temperature was raised to 650 ° C. at a rate of 10 ° C./min.
Hold at time → Heat up to 1000 ° C at the same heating rate and hold at that temperature for 0.5 hour → Heat up to 1200 ° C at the same heating rate and hold at that temperature for 0.5 hour → At the same heating rate 1
The temperature is raised to 250 ° C. and held at that temperature for 0.5 hour → The temperature is raised to 1350 ° C. at a rate of 5 ° C./min and the temperature is raised to 1350 ° C.
Hold time → Heat up to 1400 ° C at a rate of 2 ° C / min and hold at that temperature for 0.5 hour → 1450 at the same rate
The temperature was raised to ° C. and maintained at that temperature for 1 hour.

As the various raw material powders, the above-described metal Si powder, a Co powder having the same average particle radius as described above, dispersed in the same addition range as described above, and the above-mentioned metal Si powder, Prepare a dispersion of Fe powder having an average particle radius in the same addition range as above,
Using these raw material powders, various Si ₃
An N ₄ reaction sintered body was obtained.

With respect to various Si ₃ N ₄ reaction sintered bodies, Ni
When the relationship between the amounts of the powder, the Co powder and the Fe powder and the nitriding ratio A was determined, the results shown in FIG. 6 were obtained. In the drawing, line Ni corresponds to the case where Ni powder is used, line Co corresponds to the case where Co powder is used, and line Fe corresponds to the case where Fe powder is used. Since the rate of weight increase by the nitridation reaction of the metallic Si component is 66.4%, the nitriding rate A of the Si ₃ N ₄ reaction sintered body showing this weight increasing rate is A = 100.
%.

As is clear from FIG. 6, the amount of Ni powder added was 0.009% by weight ≦ Ni powder ≦ 2.2.
% By weight, and for Co powder and Fe powder, the added amount thereof is 0.01% by weight ≦ Co powder or F powder.
e powder ≦ 2 wt%, each Si ₃ N
₍₄ ) The nitriding ratio A of the reaction sintered body can be set to A> 80%. The nitriding promotion effect of these powders is Fe powder, Co powder,
It increases in the order of Ni powder, and when Ni powder is used, the nitriding ratio A can be increased to about 98%. In addition, Si ₃ N ₄ in which the amount of Ni powder or the like is set within the above range is set.
No defects such as cracks and collapse occurred in the reaction sintered body.

If the amount of Ni powder or the like is less than the lower limit or exceeds the upper limit, not only the nitriding ratio A of the Si ₃ N ₄ reaction sintered body becomes A <80%, but also The reaction sintered body collapsed. This is because the nitridation reaction inside the molded body proceeds rapidly below the lower limit, and the intermetallic compound, that is, the production amount of NiSi ₃ or the like increases above the upper limit. It is.

Si ₃ N using Ni powder or Co powder
The physical properties of the _four reaction sintered bodies whose nitriding rate A was A ≧ 95% were examined, and the results shown in Table 1 were obtained. The bending strength was measured by a three-point bending test at room temperature.

[0043]

[Table 1]

From Table 1, it can be seen that each Si ₃ N ₄ reaction sintered body has a small amount of pores and high strength. If the amount of the Ni powder or the like exceeds the upper limit, the strength of the Si ₃ N ₄ reaction sintered body is extremely reduced, and a thermal expansion coefficient of 1% or more is generated.

Example 2 Various raw material powders obtained by dispersing the Ni powder in Example 1 and C
A molded product similar to that of Example 1 was obtained using various raw material powders in which o powder was dispersed and various raw material powders in which Fe powder was dispersed.

Each compact was placed in a sintering furnace, heated in a nitrogen gas atmosphere, subjected to a primary reaction sintering process for reacting each compact with nitrogen gas, and then cooled in a furnace. Various intermediates containing synthetic Si ₃ N ₄ were produced.

Each intermediate was subjected to a pickling treatment to elute Ni components and the like from the intermediate, and then each intermediate was sufficiently dried. In this pickling treatment, hydrochloric acid and nitric acid are mixed at a volume ratio of 7%.
A 5% aqueous mixed acid solution mixed in pairs 3 was used.

Each intermediate is placed again in a sintering furnace, heated in a nitrogen gas atmosphere, and reacted with the nitrogen gas to synthesize Si ₃ N ₄ for secondary reaction sintering. And then cooled in a furnace to obtain various Si ₃ N ₄ reaction sintered bodies.

The temperature raising conditions in the primary reaction sintering are the same as those in the first half of FIG. That is, the temperature is raised to 650 ° C. at a rate of 10 ° C./min and maintained at that temperature for 0.5 hour → The temperature is raised to 1000 ° C. at the same temperature rising rate and maintained at that temperature for 0.5 hour → the same temperature increase The temperature was raised to 1200 ° C. at a rate and held at that temperature for 0.5 hour → the temperature was raised to 1250 ° C. at the same rate and held at that temperature for 0.5 hour.

FIG. 5 shows the temperature rising condition in the secondary reaction sintering process.
Is almost the same as the latter half of That is, at a heating rate of 5 ° C./min,
The temperature is raised to 350 ° C. and maintained at that temperature for 1 hour → The temperature is raised to 1400 ° C. at a rate of 2 ° C./min and the temperature is raised to 0.5 ° C.
Time keeping → The temperature was raised to 1450 ° C. at the same heating rate and kept at that temperature for 1 hour.

For various Si ₃ N ₄ reaction sintered bodies, Ni 3
When the relationship between the amounts of powder, Co powder and Fe powder added and the nitriding ratio A was determined, the results shown in FIG. 7 were obtained. In the drawing, line Ni corresponds to the case where Ni powder is used, line Co corresponds to the case where Co powder is used, and line Fe corresponds to the case where Fe powder is used. The nitriding ratio A was determined in the same manner as in Example-1 .

As is clear from FIG. 7, the addition amount of Ni powder is set to 0.0085% by weight ≦ Ni powder ≦ 5% by weight, and the addition amount of Co powder is set to 0.0085% by weight ≦ 85%. By setting the Co powder to 4.5% by weight and the addition amount of Fe powder to 0.01% by weight ≦ Fe powder ≦ 4% by weight, the nitriding of each Si ₃ N ₄ reaction sintered body can be performed. The ratio A can be A> 80%. The nitriding promoting effects of these powders are Fe powder, C
o powder and Ni powder in this order. When Ni powder is used, the addition amount is 0.03% by weight ≦ Ni powder ≦ 4% by weight, and when Co powder is used, the addition amount is By setting 0.05% by weight ≦ Co powder ≦ 0.4% by weight, the nitriding ratio A of the Si ₃ N ₄ reaction sintered body
Can be set to A = 100%. Further, when Fe powder is used, the nitriding rate A of the Si ₃ N ₄ reaction sintered body is set to 97% ≦ A ≦ by setting the addition amount to 0.07% by weight ≦ Fe powder ≦ 0.3% by weight. It is possible to increase to 98%. In addition, no defects such as cracks and collapse occurred in the Si ₃ N ₄ reaction sintered body in which the addition amount of Ni powder and the like was set in the above range.

When the physical properties of the Si ₃ N ₄ reaction sintered body in which the amount of Ni powder or the like was set within the above range were examined, the pore volume, the crystal form of Si ₃ N ₄ , the shrinkage and the thermal expansion were found to be acid. Although substantially the same as when the washing treatment was not performed (Table 1), the Ni component and the like were fined. For example, when the added amount was 0.1% by weight or less, the size of the Ni component and the like was reduced. 4
0 to 50 mμ, and the strength was higher than when no pickling treatment was performed, and furthermore, there was little variation. For example, when 0.2% by weight of Ni powder is used, Si ₃ N ₄
The bending strength of the reaction sintered body at room temperature under a three-point bending test was 460 MPa.

[ Example-3 ] The filling formula of the modified andreazen, Dm = 1- (R / R
max) Purity 99.5 adjusted for particle size distribution according to ^q
% Metal Si powder, 0.2% by weight of Ni powder having an average particle radius of 0.1 μm dispersed therein to obtain various raw material powders (1) to (1).
7) was prepared. The particle size distribution of the metal Si powder in each of the raw material powders (1) to (17) is as shown in Table 2 and FIG.

[0055]

[Table 2]

[0056] Using each raw material powder (1) to (17), Example -
In the same manner as in step 2 , that is, by pickling, various Si
₃ N ₄ reaction sintered body (1) to (17) [the Si ₃ N ₄ reaction sintered body (1) to (17) each raw material powder (1) - (17)
Corresponding to). The nitriding ratio A in these Si ₃ N ₄ reaction sintered bodies (1) to (17) is 97% ≦ A ≦ 10
It was 0%.

For comparison, three kinds of raw material powders (18) to (20) were prepared by dispersing the same amount of the same Ni powder as above in three kinds of commercially available metal Si powder having the same purity as above. Among the commercially available metal Si powders, those used for the raw material powder (18) had a maximum particle radius of 5 μm, and those used for the raw material powders (19) and (20) had a maximum particle radius of 2.5 μm each. there were.

FIG. 9 shows the particle size distribution of each commercially available metal Si powder. In this drawing, the reference numerals of the respective lines are made coincident with the reference numerals (18) to (19) of the respective raw material powders for convenience. Comparing FIG. 8 with FIG. 9, in FIG. 8, since the particle size is adjusted, the change from the maximum particle radius to the minimum particle radius draws a smooth curve, but in FIG. 9, since the particle size adjustment is not performed. The change from the maximum particle radius to the minimum particle radius draws a jerky line.

[0059] Using each raw material powder (18) to (20), Example
Various Si ₃ N ₄ reaction sintered bodies in the same manner as in -2 (18)
To (20) [Each Si ₃ N ₄ reaction sintered body (18) to (2)
0) corresponds to each of the raw material powders (18) to (20)].

Further, each commercially available metal Si powder was used as a raw material powder (2
1) as to (23), the same method as Example 1, i.e. three kinds of Si in a manner that does not perform the pickling ₃ N ₄ reaction sintered body (21) to (23) [the Si ₃ N ₄ reaction Sintered body (2
1) to (23) correspond to the respective raw material powders (21) to (23)]. In this case, the raw material powders (21) to (2)
3) corresponds to the metal Si powder of each of the raw material powders (18) to (20).

Each of the Si ₃ N ₄ reaction sintered bodies (1) to (1)
7), (18) to (20), and (21) to (23) were subjected to a three-point bending test at room temperature, and their bending strengths were measured. The results shown in FIG. 10 were obtained.

As is clear from FIG. 10, each Si ₃ N ₄
In the reaction sintered bodies (1) to (17), the strength tends to decrease as the maximum particle radius of the metal Si powder increases, and the coefficient q is increased when metal Si powders having the same maximum particle radius are used. The strength tends to decrease as becomes larger.

Although depending on the strength required for the Si ₃ N ₄ reaction sintered body, the metal Si powder has a maximum particle radius Rm.
When ax is constant and a coefficient q having a particle size distribution of 0.25 ≦ q ≦ 0.5 is used, high-strength Si ₃
An N ₄ reaction sintered body can be obtained.

The maximum particle radius and the minimum particle radius of the metal Si powder are not particularly limited. However, if the maximum particle radius is increased, the pores in the compact become larger and the diffusion distance of nitrogen is increased. The amount of coarse pores and the amount of unreacted Si increase. On the other hand, when the minimum particle radius is reduced, the handleability of the metal Si powder deteriorates accordingly, and the metal Si powder reacts with oxygen in the air to form an oxide film, which prevents nitriding by the oxide film. Considering these points, the upper limit of the maximum particle radius of the metal Si powder is 22 μm, and the lower limit of the minimum particle radius is 0.025 μm.
m is desirable.

Each of the Si ₃ N ₄ reaction sintered bodies (1
Regarding 8) to (20) and (21) to (23), the filling factor in the compact was 0.48 to 0.52 (relative density of 48) because the metal Si powder had the above particle size distribution.
% To 52%), and the filling rate Dm =
0.68 to 0.72, which is extremely low.
Also, those using Ni powder (18) to (20): 58% ≦
A ≦ 65%, while no Ni powder was used (2
In 1) to (23), it was found that 50% ≦ A ≦ 60%, which was bad.

Due to these, the strength of each of the Si ₃ N ₄ reaction sintered bodies (18) to (20) and (21) to (23) is
The particle size distribution is lower than that of each of the Si ₃ N ₄ reaction sintered bodies (1) to (17) using the metal Si powder adjusted as described above.

[0067]

According to the present invention, a raw material powder obtained by dispersing a specific amount of Ni powder, Co powder or Fe powder as a metal powder for accelerating nitriding in a metal Si powder is used. The pickling process is incorporated in the manufacturing process to use the pores formed as a gas entrance path into the intermediate during the secondary reaction sintering process, and the pore size and pore distribution in the compact are optimized for nitriding. By specifying the particle size distribution of the metal Si powder in such a state, it is possible to obtain a Si ₃ N ₄ reaction sintered body that has achieved high density and high strength.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first half of a manufacturing process of a Si ₃ N ₄ reaction sintered body.

FIG. 2 is an explanatory diagram showing a latter half of a manufacturing process of a Si ₃ N ₄ reaction sintered body.

FIG. 3 is an explanatory view showing a main part of a manufacturing process of a Si ₃ N ₄ reaction sintered body.

FIG. 4 is a graph showing an example of a particle size distribution of a metal Si powder.

FIG. 5 is a graph showing conditions for raising the temperature of a Si ₃ N ₄ reaction sintered body.

FIG. 6 is a graph showing an example of the relationship between the addition amount of Ni powder, Co powder, or Fe powder and the nitriding ratio.

FIG. 7 is a graph showing another example of the relationship between the addition amount of Ni powder, Co powder or Fe powder and the nitriding ratio.

FIG. 8 is a graph showing another example of the particle size distribution of the metal Si powder.

FIG. 9 is a graph showing a particle size distribution of a commercially available metal Si powder.

FIG. 10 is a graph showing the relationship between the maximum particle radius of metal Si powder and bending strength.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naoki Ota 1-10-1 Shinsayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (56) References JP-A-59-207874 (JP, A) 59-501823 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/584-35/596 C04B 35/65

Claims (3)

(57) [Claims] 1. Particle size distribution of metallic Si powder
However, the modified Andreasen (Andreasen) filling formula Dm = 1− (R / Rmax) ^q (where Rmax is the maximum particle radius and R is an arbitrary particle half)
Diameter, q is a coefficient, Dm is an arbitrary value from the maximum particle radius Rmax
In the molded body obtained using particles up to the particle radius R
(Dm ≦ 0.75).
When the large particle radius Rmax is constant, the coefficient q is 0.2
Prepare one set so that 5 ≦ q ≦ 0.5,
Ni powder is added to the metal Si powder as a metal powder for accelerating nitriding.
Disperse 0.0085% by weight ≦ Ni powder ≦ 5% by weight
Molding a molded body using the raw material powder,
Primary sintering process to react the body with nitrogen gas
Obtaining an intermediate containing synthetic silicon nitride by:
The intermediate is subjected to a pickling treatment to remove the Ni component from the intermediate.
Eluting, and reacting the intermediate with nitrogen gas
Performing a secondary reaction sintering process to synthesize silicon nitride by
Are sequentially performed . 2. Particle size distribution of metallic Si powder
However, the modified Andreasen (Andreasen) filling formula Dm = 1− (R / Rmax) ^q (where Rmax is the maximum particle radius and R is an arbitrary particle half)
Diameter, q is a coefficient, Dm is an arbitrary value from the maximum particle radius Rmax
In the molded body obtained using particles up to the particle radius R
(Dm ≦ 0.75).
When the large particle radius Rmax is constant, the coefficient q is 0.2
Prepare one set so that 5 ≦ q ≦ 0.5,
Co powder as the metal powder for promoting nitriding is added to the metal Si powder.
Powder is dispersed at 0.0085% by weight ≦ Co powder ≦ 4.5% by weight
Molding a molded body using the raw material powder,
A primary reaction sintering process is performed to react the compact with nitrogen gas.
Obtaining an intermediate containing synthetic silicon nitride by
And subjecting the intermediate to an acid washing treatment to remove Co from the intermediate.
Eluting the components and reacting the intermediate with nitrogen gas.
Performs secondary reaction sintering to synthesize silicon nitride
And a step of sequentially performing the steps . 3. Particle size distribution of metal Si powder
However, the modified Andreasen (Andreasen) filling formula Dm = 1− (R / Rmax) ^q (where Rmax is the maximum particle radius and R is an arbitrary particle half)
Diameter, q is a coefficient, Dm is an arbitrary value from the maximum particle radius Rmax
In the molded body obtained using particles up to the particle radius R
(Dm ≦ 0.75).
When the large particle radius Rmax is constant, the coefficient q is 0.25
Prepare one set so that ≦ q ≦ 0.5, and
Fe powder as metal powder for promoting nitriding
In which 0.01% by weight ≦ Fe powder ≦ 4% by weight is dispersed
Forming a molded body using the powder;
By performing a primary reaction sintering process to react
Obtaining an intermediate comprising synthetic silicon nitride,
The body is pickled and the Fe component is eluted from the intermediate.
And nitriding by reacting the intermediate with nitrogen gas.
And a step of performing a secondary reaction sintering process for synthesizing silicon.
A method for producing a silicon nitride reaction sintered body.