JP2987415B2 - Method for producing boron nitride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-pressure boron nitride from low-pressure boron nitride using dynamic high pressure.

[0002]

2. Description of the Related Art Boron nitride is one of ceramics having excellent characteristics, and has been widely used as a new functional material. Among them, cubic boron nitride, which is high-pressure phase boron nitride, has the same hardness as diamond and is expected to be used in a wide range of applications as cutting tools and abrasives. Is produced by applying a static high pressure or a dynamic high pressure to low-pressure boron nitride.

In the method using a static high pressure, cubic boron nitride is produced from hexagonal boron nitride by using a nitride of an alkali metal or an alkaline earth metal as a catalyst, and is also industrially produced.

Further, there are many methods for producing cubic boron nitride from various low-pressure phase boron nitrides by utilizing dynamic high pressure caused by shock waves generated by explosives of explosives or collision of a high-speed projectile. Although reported, there are many problems with conversion rates and industrial processes. In these manufacturing methods,
Generally, in order to increase the impact pressure, a low pressure phase boron nitride as a raw material and a matrix such as a metal powder are mixed and subjected to impact compression. Hexagonal boron nitride is the most common low-pressure phase boron nitride as a raw material, but in this case, cubic boron nitride is hardly produced by one impact compression, and cubic boron nitride and hexagonal boron nitride are hardly formed. The wurtz-type boron nitride, which is the intermediate phase of crystalline boron nitride, is generated, and the work of shock-compressing the wurtz-type boron nitride is repeated, whereby the cubic boron nitride increases little by little, and the impact compression is reduced. Only after a few repetitions are the X-ray diffraction peaks slightly noticeable. Therefore, impact compression must be repeated a considerable number of times in order to sufficiently increase the conversion rate of the raw material to cubic boron nitride, which is unsuitable as an industrial production method.

[0005] In addition, a method using amorphous boron nitride or rhombohedral boron nitride as a raw material is also known. In this case, cubic boron nitride can be obtained by a single impact compression. Since the amorphous boron nitride and the rhombohedral boron nitride require a special manufacturing process, there is also a problem in securing the raw materials.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional method for producing cubic boron nitride utilizing dynamic high pressure, and does not require a raw material requiring a special production method step. It is another object of the present invention to provide a production method capable of obtaining cubic boron nitride at a high conversion rate by only one impact compression.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on a method of producing cubic boron nitride from a low-pressure phase boron nitride by an impact compression method. The present inventors have found that the conversion rate from boron nitride to cubic boron nitride is greatly affected, and completed the present invention. That is, the present invention applies a dynamic high pressure to a mixture in which low-pressure phase boron nitride is uniformly dispersed in a matrix to transfer low-pressure phase boron nitride to high-pressure phase boron nitride. A method for producing high-pressure phase boron nitride, characterized by using the following particles.

In the present invention, hexagonal boron nitride having a particle diameter of 100 μm or less and a particle shape close to spherical is preferably used as the low-pressure phase boron nitride as a raw material. It is preferable that the hexagonal boron nitride has a small particle size and a shape close to a sphere because the conversion rate to cubic boron nitride tends to be improved. An intermediate phase, wurtz-type boron nitride, can also be used.

The matrix acts as a pressure medium,
It has the effect of amplifying the impact compression force, and its material is made of metals such as copper, tungsten, iron, nickel and cobalt or inorganic metals such as carbonates, sulfates and hydroxides of alkali metals and alkaline earth metals. Compounds can be used. In the method of the present invention, a matrix having a particle diameter of about 10 μm to 500 μm and a particle shape of a sphere, preferably a true sphere is used as the matrix. The reason that the conversion rate from hexagonal boron nitride to cubic boron nitride is greatly improved by using spherical particles as a matrix is that when spherical matrix particles are closely packed, they are surrounded by these particles. It is considered that the sample was pressed isotropically and brought into a good compression state.

In the method of the present invention, first, a powder of hexagonal boron nitride as a raw material and a powder of a matrix component are
Desirably, the matrix component is uniformly mixed at a ratio of 50 to 98% by weight with respect to 50 to 2% by weight of hexagonal boron nitride. Next, this raw material mixture is filled in a metal container. As the material of the metal container, brass, stainless steel, chromium steel, or the like can be used, and the shape can be any shape such as a tubular shape or a pox shape.
Next, the raw material mixture filled in the metal container is subjected to various impact compression treatment apparatuses, for example, JP-A-58-93598, JP-A-58-95546, and JP-A-58-95.
No. 547, Japanese Patent Application Laid-Open No. 58-104629 or Japanese Patent Application Laid-Open No. 2-222723, etc., using a cylindrical or flat type impact compression processing device, a high-speed driven by an explosion of an explosive. A shock compression process is performed by a shock wave with high temperature and high pressure generated by the collision of the flying object.

FIG. 1 shows a preferred example of an apparatus used in the method of the present invention, and is a longitudinal sectional view of a flat type impact compression processing apparatus. This processing device is a known device,
Plane detonation wave generator 2, explosive 3, flying member 4, flying member support cylinder 5, momentum supplement members 6, 7, 8, protective container 9,
It is composed of a sample container 10, a sample 11, and a void 12. In this device, when the primer is detonated, a plane detonation wave is formed by the plane detonation wave generator, and the explosive is detonated on a plane. Due to the planar explosion of the explosive, the flying member is driven while maintaining its planarity and collides with the protective container, generating a planar shock wave. The plane shock wave propagates from the protective container to the sample container and then to the sample. When the collision wave passes through the sample, the sample is shock-compressed and is in a state of high temperature and high pressure.

As the explosive 3, nitromethane, hexogen, pen slit or high melting point explosive (HMX) is used. As the plane detonation wave generator 2, a saturated hydrazine solution of hydrazine nitrate, nitromethane or the like is used. it can.

Further, the shock wave generated by the explosion of the explosive can be applied to the container containing the sample via a high-speed flying object, or directly to the container containing the raw material. That is, in FIG. 1, the flying member 4 and the flying member supporting cylinder 5 are removed, the explosive 3 is made to explode in a state of being in contact with the container containing the sample, and the shock wave due to the explosion of the explosive is directly added to the container containing the sample. Can also. The amount of explosive used varies greatly depending on the shape of the device used, the method of transmitting shock waves, and the like, but it is preferable that the shock pressure applied to the material be 300,000 to 1,000,000 atmospheres.

[0014]

Next, the present invention will be described more specifically with reference to examples. Example 1 As described below, a mixture of 8% by weight of hexagonal boron nitride and 92% by weight of spherical copper powder was subjected to impact compression treatment using the apparatus shown in FIG. 1 to produce cubic boron nitride. Hexagonal boron nitride having an average particle size of 3.2 μm was used as a raw material, and spherical copper powder having a particle size of 74 to 147 μm was used as a matrix. Both were uniformly mixed to obtain a sample. This sample was used for inner diameter 2
0mm, 30mm outside diameter steel (SS41) sample container 1
0 was filled so that the bulk density was 80% of the true density and the thickness was 4 mm. The sample container 10 is loaded into a brass protective container 9 having an inner diameter of 30 mm and an outer diameter of 50 mm, and a double momentum capturing member 6, 7 (inner diameter of 50 mm, outer diameter of 66 mm, and inner diameter of 66 m) is provided around the container.
m, a steel (SS41) cylinder having an outer diameter of 76 mm), and the periphery thereof was similarly surrounded by lead having a thickness of 45 mm as a momentum capturing member 8. The outer diameter of 76
A rigid vinyl chloride flying member support cylinder 5 having a diameter of 71 mm and a thickness of 3 mm is mounted thereon.
A mm flying steel member 4 was placed. As explosive 3, an aqueous solution of an inorganic salt as a binder was added to a high melting point explosive (HMX) 15
230 g of the substance added by weight% was used. The explosive 3 was inserted into the top of a plane detonation wave generator 2 composed of a saturated hydrazine solution of hydrazine nitrate and nitromethane.
It was detonated with a No. 1 electric detonator.

A sample was taken out of the collected sample container by machining, and the metal was dissolved with nitric acid and hydrochloric acid, separated, washed and dried to obtain a powdery substance. When boron nitride other than cubic boron nitride was removed from the powdered material by a hydrofluoric acid treatment method, 4% of the raw material hexagonal boron nitride was removed.
0% by weight of material remained. When this substance was recovered and analyzed by powder X-ray diffraction, the diffraction peak showed a single phase of cubic boron nitride alone. From this result, the conversion rate from the raw material hexagonal boron nitride to cubic boron nitride was 4%.
It was estimated to be 0% by weight.

Example 2 Impact compression treatment was carried out in the same manner as in Example 1 except that the matrix was spherical iron powder having a particle size of 74 to 147 μm, and the product was analyzed. The conversion from hexagonal boron nitride to cubic boron nitride was estimated to be 25% by weight.

Example 3 Impact compression treatment was carried out in the same manner as in Example 1 except that the matrix was a spherical calcium carbonate powder having a particle size of 74 to 147 μm, and the product was analyzed. The conversion from hexagonal boron nitride to cubic boron nitride was estimated to be 20% by weight.

Comparative Example 1 Example 1 except that the shape of the matrix particles was scaly.
The impact compression treatment was carried out in the same manner as in the above, and the product was analyzed. Cubic boron nitride is hardly produced,
The conversion was estimated to be less than 1% by weight.

Comparative Example 2 Example 2 except that the particle shape of the matrix was scaly.
The impact compression treatment was carried out in the same manner as in the above, and the product was analyzed. Cubic boron nitride is hardly produced,
The conversion was estimated to be less than 1% by weight.

Comparative Example 3 Impact compression treatment was carried out in the same manner as in Example 3 except that a large particle size calcium carbonate powder having a particle size of 74 to 147 μm was pulverized into a matrix to form a matrix.
The product was analyzed. Cubic boron nitride was hardly produced, and the conversion was estimated to be 1% by weight or less.

Example 4 A sample subjected to impact compression treatment in the same manner as in Comparative Example 1 was treated with a mixture of sulfuric acid and sodium fluoride to remove hexagonal boron nitride, leaving 30% by weight of a substance. When this substance was analyzed by a powder X-ray diffraction method, the diffraction peak showed wurtzoidal boron nitride, and cubic boron nitride was hardly detected. This wurtz-type boron nitride was used in place of hexagonal boron nitride, and shock compression was performed in the same manner as in Example 1. As a result, the conversion rate from wurtz-type boron nitride to cubic boron nitride was It was estimated to be 45% by weight. Comparative Example 4 As a result of subjecting a wurtzite boron nitride to compression impact treatment in the same manner as in Example 4 except that scale-like matrix particles were used, the conversion rate from the wurtzite boron nitride to cubic boron nitride was 2 % By weight.

[0022]

According to the method of shock compression by mixing hexagonal boron nitride and a matrix composed of spherical particles according to the present invention, the conversion rate from hexagonal boron nitride to cubic boron nitride is: 20% by weight or more. The obtained cubic boron nitride is a polycrystalline body composed of crystallites of several tens to several thousand degrees, and is dense particles of several μm to several hundred μm,
The polycrystalline cubic boron nitride sintered body having good performance as an abrasive, and further sintering the particles, has no cleavage property and reflects the characteristics of the polycrystalline body having high toughness,
It is also excellent as a material for cutting tools made of iron-based materials, which are difficult to cut with Dakimond. Further, the matrix composed of spherical particles has an effect of increasing the conversion rate even when other ceramics such as diamond, silicon nitride, silicon carbide, etc. are produced by the impact compression method.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a planar shock compression processing apparatus as an example of a shock compression processing apparatus for performing a method of the present invention.

[Description of Signs] 1 Detonator 2 Plane detonation wave generator 3 Explosive 4 Flying member 5 Flying member support cylinder 6, 7, 8 Momentum capturing member 9 Protective container 10 Sample container 11 Sample 12 Void

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yozo Kakudate 1-1-1 Higashi, Tsukuba City, Ibaraki Prefecture Inside the Chemical Technology Research Institute, Industrial Technology Institute (72) Inventor Thinba State 1-1-1 Higashi Tsukuba City, Ibaraki Prefecture Industrial Technology Institute Chemical Within the Technical Research Institute (72) Inventor Hiroshi Yamawaki 1-1-1 Higashi, Tsukuba, Ibaraki Pref.Industrial Technology Institute, Research Institute for Chemical Technology (72) Inventor Shigeru Fujiwara 1, Kokufucho, Tochigi City, Tochigi Pref. 72) Inventor Kyoichiro Narita 1 Kokufucho, Tochigi City, Tochigi Pref. Central Research Laboratory, Mitsui Mining Co., Ltd. (56) References JP-A-52-90500 (JP, A) (58) Fields investigated (Int. Cl. ⁶⁾ , DB name) B01J 3/08 C01B 21/064

Claims (1)

(57) [Claims] 1. A high dynamic pressure is applied to a mixture in which low-pressure phase boron nitride is uniformly dispersed in a matrix to convert the low-pressure phase boron nitride into high-pressure phase boron nitride. A method for producing high-pressure phase boron nitride, comprising using particles of