JPH05246765A - Compact for producing cubic boron nitride sintered compact - Google Patents

Abstract

(57) [Summary] [Structure] A cubic boron nitride characterized by being formed by impregnating a hexagonal boron nitride molded body having an air permeability of 0.01 to 0.3 cm ² / sec with a cubic boron nitriding catalyst. Provided is a molded body for producing a sintered body. [Effects] According to the present invention, c-B to h-BN compacts is obtained.
Impregnation of the N-ized catalyst becomes easy and uniform, and even when the h-BN compact is thick, the catalyst is stably and uniformly impregnated to the center portion. Therefore, a thick c-BN sintered body can be manufactured with high quality and high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cubic boron nitride sintered compact for producing a cubic boron nitride sintered compact with high purity, high density, high hardness and high yield.

[0002]

BACKGROUND OF THE INVENTION Cubic boron nitride (hereinafter abbreviated as c-BN) has a high hardness and chemical stability comparable to diamond, and therefore has a high speed. In addition to being used as an industrial material for high-precision processing, it is also used as a heat sink material due to its extremely good thermal conductivity, and is also being applied to electronic materials because of its semiconductor properties. ..

In order to fully exhibit such characteristics, c-BN is required to be a high-purity, high-density sintered body. Such a c-BN sintered body is generally produced by using hexagonal boron nitride (hereinafter abbreviated as h-BN) powder as a starting material and converting it into c-BN under high temperature and high pressure conditions. However, in the conversion of c-BN under such high temperature and high pressure conditions, a manufacturing apparatus becomes large and it is difficult to control the manufacturing conditions.

Therefore, as a manufacturing method for solving such a problem, in Japanese Patent Publication No. 59-5547, a catalyst material such as M ₃ B ₂ N ₄ (M represents an alkaline earth metal) in boron nitride is used. There is proposed a method for producing c-BN under a condition of low temperature and low pressure as compared with the above-mentioned production method, using a starting material mixed with.

Further, in Japanese Patent Publication No. 60-28782, a h-BN molded body produced by a hot pressing method, which is obtained by diffusing and impregnating the above catalyst with a catalyst, is used as a precursor.
A method of manufacturing a BN sintered body has also been proposed.

However, the present inventor has
In the manufactured h-BN compact, h-BN particles are
They are intimately joined at the contact part, and B ₂O₃Etc.
The more oxides are present on the surface of the raw material powder, the stronger the bond strength.
Therefore, the density is 1.8 and the porosity is high.
g / cm³When using the following low density compacts
Also, the h-BN compact was impregnated with a c-BN-forming catalyst.
In this case, there are some parts that cannot be impregnated locally,
In the case of using the h-BN molded body of No. 2, c-
We found that there are problems such as impregnation with BN catalyst.
It was Further, it is described in the above Japanese Patent Publication No. 60-28782.
As described above, the h-BN compact was preliminarily subjected to 2 in nitrogen gas.
It is calcined at a temperature of 100 ° C. for 2 hours or more to reduce the oxygen content to 0.
When it is less than 3% by weight, h-BN crystal grains grow.
However, there is also a problem that impregnation is further reduced due to this.
I found out.

Therefore, thick-walled hexagonal boron nitride (hB
N) A cubic boron nitride catalyst (c-BN catalyst) is evenly distributed up to the center even when a molded body is used.
Therefore, there has been a demand for a compact capable of producing a cubic boron nitride (c-BN) sintered body with high purity and high hardness at a high yield even under low temperature and low pressure conditions.

[0008]

Means and Actions for Solving the Problems As a result of intensive investigations by the present inventors in order to meet the above-mentioned demands, as a result, the impregnating property of the c-BN-forming catalyst to the h-BN molded body is determined by the ventilation of the h-BN molded body. The air permeability is 0.01 cm ² /
The h-BN compact having a size smaller than sec has a low catalyst impregnation property even if its porosity is high, and impregnation of the catalyst reaches a depth of about 0.5 mm from the surface at most (hence, the h by the hot pressing method described above). -BN compacts have poor catalyst impregnation due to low air permeability even when they have low density and high porosity), and when the air permeability is such low, the surface layer part of h-BN compacts It was also found that the dispersion of the impregnated amount was locally observed in the case of.

On the other hand, the air permeability of the h-BN molded body is 0.
When the range is 01 to 0.3 cm ² / sec, c−B
When the N-catalyst impregnability is remarkably increased and the c-BN catalyst is diffused and impregnated, even if the h-BN compact has a thick wall (1 mm or more), the impregnation of the catalyst uniformly proceeds up to its central portion. According to the present invention, it has been found that it is possible to prevent or reduce a decrease in yield due to poor catalyst impregnation and a variation in the amount of catalyst impregnated between the surface and the inside, whereby a c-BN sintered body can also be manufactured with high quality and high yield. Came to make.

Therefore, according to the present invention, the air permeability is 0.01 to.
Provided is a molded product for producing a cubic boron nitride sintered body, which is obtained by impregnating a hexagonal boron nitride molded product of 0.3 cm ² / sec with a cubic boron nitride conversion catalyst.

The present invention will be described in more detail below. The molded body for producing a c-BN sintered body of the present invention is h-B.
It is obtained by uniformly impregnating an N molded body with a c-BN catalyst.

Here, in the present invention, the h-BN molded product has an air permeability of 0.01 to 0.3 cm ² / se.
c, preferably 0.05 to 0.2 cm ² / sec, and by using an h-BN molded product having an air permeability in this range, the h-BN molded product has a thickness of 1 mm or more, Even if it is 1 to 5 mm, it is c
-BN catalyst is uniformly diffused and impregnated. In this case, if the air permeability is less than 0.01 cm ² / sec,
The c-BN catalyst is 0.5 mm from the surface of the h-BN compact
It reaches only a certain depth, and the impregnated amount locally varies in the surface layer portion of the h-BN compact, so that the object of the present invention cannot be achieved. Also, the air permeability is 0.3 cm ^2.
If it exceeds / sec, the mechanical strength of the h-BN compact will be weakened, making handling difficult, which is not preferable.

In the present invention, the value of the air permeability is obtained by substituting the value measured by the apparatus of FIG. 1 into the following formula (1) using a h-BN compact having a diameter of 20 mm and a thickness of 5 mm as a test piece. It is the value obtained by

Here, in FIG. 1, 1 is a test gas (nitrogen gas) cylinder, 2 is a test gas feeder, 3 is a pressure gauge, 4
Is a test piece, 5 is a packing, 6 is a test piece holder, and 7 is a flow meter, so that the thickness direction in the test piece holder 6 faces the test gas flowing into the holder 6 through the packing 5. A test gas is passed through the attached test piece 4, and the air permeability is obtained from the following formula (1).

[0015]

[Equation 1]

Such an air permeability is 0.01 to 0.3 cm
^{As a} method of obtaining an h-BN molded body having ² / sec,
High-purity h-BN powder 200-10,000 kg / c
m ² and more preferably after applying hydrostatic pressure under a pressure of 1000 to 5000 kg / cm ² , an inert gas (for example, nitrogen,
1500 to 2100 ° C. in an atmosphere such as argon,
More preferably, a method of firing at atmospheric pressure at a temperature of 1700 to 2000 ° C. is recommended.

In this case, it is necessary to use the h-BN powder whose water content is adjusted to 1% by weight or less by drying or the like, and the water content of the h-BN powder exceeds 1% by weight. When the hydrostatic pressure is applied, the adhesive force between the particles becomes stronger, which causes cracks in the molded body during depressurization, or the number of ventilation holes in the molded body decreases, resulting in low air permeability in the molded body after firing. Such problems easily occur.

The pressing degree, firing temperature and time of the h-BN powder are as described above.
The molded body has the above-mentioned air permeability and its density is 1.5.
˜2 g / cm ³ , particularly 1.6 to 1.9 g / cm ³ is preferable from the viewpoint of obtaining a good c-BN sintered body.

The h-BN compact is impregnated with a c-BN catalyst. C impregnated in this h-BN compact
As the BN-forming catalyst, M ₃ B ₂ N ₄ and M ₃ N ₂ (however, M
Is an alkaline earth metal such as Mg or Ca).

As a method of impregnating the h-BN compact with the c-BN catalyst, the h-BN compact is embedded in the above-mentioned c-BN catalyst and the temperature is set to 1000 at a temperature of an inert gas such as nitrogen gas. ~ 1500 ° C, preferably 1200 ~ 1300
A method of heat treatment at 1 ° C. for 1 to 10 hours, preferably 2 to 7 hours is suitably adopted.

The c-BN of the present invention thus obtained
The hydrogenated catalyst-impregnated molded body is converted into a c-BN sintered body by a known method. In this case, in order to obtain a good c-BN sintered body, a temperature of 1200 to 1500 ° C. and a pressure of 3 to 7 GPa are used. It is preferable to adopt.

[0022]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 5 and Comparative Examples 1 to 3 h-BN powder having a water content of 1.5% by weight was dried at a temperature of 180 ° C. for various drying times to obtain the water content shown in Table 1. Different powders were prepared, filled in a rubber mold, and subjected to isostatic pressing under the conditions shown in Table 1 to obtain a molded product, which was then fired in a nitrogen gas atmosphere to manufacture an h-BN molded product. .. A sample having a diameter of 20 mm and a thickness of 5 mm was taken from this molded body, and the air permeability was measured according to the method described above. The results are also shown in Table 1. The water content is measured by heating the sample using an infrared moisture meter.
It was calculated from the weight change before and after heating.

Next, these samples were embedded in Mg ₃ N ₂ and heat-treated at 1200 ° C. for 2 hours in a nitrogen atmosphere to impregnate the catalyst. The cross section of the sample after the catalyst impregnation was examined visually and by EPMA to evaluate the impregnation property. In this case, the case where the inside was uniformly impregnated was good, and the case where the impregnation was not locally performed or the difference in Mg concentration between the surface and the central portion was twice or more was determined to be poor impregnability.
The results are also shown in Table 1.

[0025]

[Table 1]

As is clear from the results shown in Table 1, the h-BN compact according to the present invention had a good catalyst impregnation property. On the other hand, in the case of Comparative Example 1, the air permeability was very good, but the strength was weak, and there was a problem in handling. In Comparative Examples 2 and 3, since the raw material powder had a high water content, the air permeability was low, only the surface layer of the h-BN compact was impregnated, and the catalyst impregnation property was poor.

[0027]

According to the present invention, c to h-BN compacts is obtained.
-The BN-ized catalyst is easily and uniformly impregnated, and even when the h-BN compact is thick, the catalyst is stably and uniformly impregnated to the center. Therefore, a thick c-BN sintered body can be manufactured with high quality and high yield.

[Brief description of drawings]

FIG. 1 is a schematic view showing an apparatus for measuring air permeability in the present invention.

[Explanation of symbols]

 1 Test gas (nitrogen gas) 2 Test gas supply device 3 Pressure gauge 4 Test piece 5 Packing 6 Test piece holder 7 Flow meter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B28B 3/00 102 9261-4G C01B 21/064 M (72) Inventor Shu Kashida Gunma Prefecture Annaka 2-13-1, Isobe, Ichi Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (1)

[Claims] 1. An air permeability of 0.01 to 0.3 cm ² / se.
A molded body for producing a cubic boron nitride sintered body, which is obtained by impregnating a hexagonal boron nitride molded body of c with a cubic boron nitride forming catalyst.