JPH07108816B2 - High-pressure phase boron nitride composite material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high pressure phase boron nitride based composite material suitable for machine tool materials, heat sink materials, dielectric materials, engineering materials and the like.

[Prior Art] Cubic boron nitride (hereinafter abbreviated as c-BN) has hardness and thermal conductivity second only to diamond, and is superior to diamond in terms of stability against heat-resistant iron-based materials. In order to make use of this excellent characteristic, a c-BN-based composite material has been mainly proposed as a material for tools.

For example, JP-A-56-26771 discloses that c-BN powder and Si ₃ N ₄
Mix the powders, powder this, or after embossing,
Disclosed is a method for producing a sintered body for a cast iron cutting tool, which comprises sintering at ultra-high temperature, containing 20 to 50 vol% of c-BN, and the balance mainly consisting of Si ₃ N ₄ . Also, for example, Japanese Patent Laid-Open No.
No. 130167 also discloses that c-BN 40 to 80 vol% and Si ₃ N ₄ and ZrN
There is disclosed a method for producing a c-BN sintered body by mixing a powder of nitride such as 60% to 20% by volume with other impure impurities and treating the mixture at a pressure of 30 kb or more and a temperature of 1000 ° C. or more. There is.

[Problems to be Solved by the Invention] As described above, in a method of obtaining a sintered body by mixing c-BN powder and powders of other compounds such as Si ₃ N ₄ and subjecting them to ultrahigh pressure and high temperature treatment, inclusion of impurities In particular, since the impurity element is present at the interface of the powder particles, there is a problem in joining at the interface portion, and the compound effect is not always sufficiently exhibited. And, there is a problem that minute cracks are often generated in these particle-bonded portions and the material properties are deteriorated.

[Means for Solving Problems] The present invention provides a composite material of a high-pressure phase BN system which is completely different from the conventional one, and a composite material containing an atmospheric pressure phase boron nitride prepared by a chemical vapor deposition method. A high-pressure phase boron nitride-based composite material which is a high-pressure treated composite material containing 5-52 wt% high-pressure phase boron nitride.

It is well known that the properties of ceramics, especially fine ceramics, are extremely sensitive to the manufacturing method. This is true not only in the property as an electromagnetically functional material, but also in the property as a so-called structural material. A large difference occurs in characteristics and performance depending on the method of synthesizing and processing. This is because the structure and properties of fine ceramics are extremely sensitively affected by impurities (including trace amounts), particle size, surface state, and the like.

Ceramics synthesized by the chemical vapor deposition (CVD) method have extremely high purity. Therefore, the composite material containing the atmospheric phase BN synthesized by the CVD method used in the present invention is, of course, extremely excellent in terms of purity. Further, the BN composite ceramics synthesized by the CVD method is extremely characteristic in its structure. For example, in the VD method, nanometer-order TiN particles are dispersed in normal pressure BN / BN /
TiN composite materials can be synthesized. Also, dozens of nanometers
BN / Si ₃ N ₄ composite materials in which order-made Si ₃ N ₄ particles are dispersed can be produced separately.

Atmospheric pressure phase BN in the present invention, amorphous BN, turbostratic structure BN
(T-BN), hexagonal BN (h-BN) and rhombohedral BN (γ-
BN) is meant.

The material of the present invention is realized by subjecting the composite material composed of the normal pressure phase BN obtained by the CVD method having such excellent characteristics to ultrahigh pressure treatment and phase conversion into an ultrahigh hardness material containing the high pressure phase BN. It was done.

This is completely different from the one obtained by high-pressure sintering of a conventional mixture of C-BN powder and powder such as Si ₃ N ₄ . For example, in the case of a composite material composed of high-pressure phase BN and crystalline Si ₃ N ₄ , in addition to having extremely excellent adhesion at the interface between the two, it has a characteristic microstructure.

The composite material containing the high-pressure phase BN in the present invention, for example,
It is as follows. That is, (1) high pressure phase BN and Si
₃ N ₄ , composite material composed of TiN, AlN, ZrN and other nitride ceramics; (2) Composite material composed of high pressure phase BN and carbide ceramics such as SiC, TiC, B ₄ C; (3) High pressure phase BN and TiB ₂ , a composite material consisting of boride ceramics such as ZrB.

The high pressure phase BN means c-BN and w-BN (wurtzite boron nitride), with c-BN being preferred.

The content ratio of the high-pressure phase BN in the material of the present invention is 5 to 52 wt.
The range of% is appropriate for exerting the synergistic effect of the properties of the high-pressure phase boron nitride and the properties of other nitride ceramics and the like.

In the material of the present invention, high-pressure phase BN and crystalline Si ₃ N
_{The four} phases are those that can take an extremely wide variety of coexistence states.

For example, it is as shown in the figure. This figure shows the high-pressure phase obtained by observing the polished surface of the cut surface of the material of the present invention with an electron micrograph.
It is a schematic diagram which shows the form of BN. Columnar or fibrous morphology (Fig. 1), hook-shaped or U-shaped morphology (Fig. 2), dendritic columnar morphology (Fig. 3), donut-shaped or hollow sphere morphology ( (Fig. 4), the BN phase itself is more mesh-like (Fig. 5), the form in which foreign substances are included in the columnar BN (Fig. 6), uniform in the order of nanometers or tens of nanometers There are forms such as the dispersed form (FIG. 7).

As described above, the material of the present invention is a c-BN composite material having an extremely characteristic microstructure. The columnar, dendritic, and mesh-like c-BN effectively enhances the hardness and toughness of the material. Further, due to such a structure, an excellent composite effect is exhibited in thermal, electrical, mechanical and chemical properties.

Such a c-BN-based composite material having an extremely characteristic fine structure has never been realized by the conventional method using powder as a starting material.

In the present invention, the composite material containing the normal pressure phase BN is synthesized by the CVD method. BN / Si ₃ N ₄ composite material is, for example, BCl ₃ --SiCl ₄ --NH ₃
According to CVD of -H ₂ gas system. BN / TiN and BN / AlN are, for example, BCl
₃ -TiCl-NH ₃ -H _2, by _{BCl 3 -AlCl 3 -NH 3 -H 2} . The use of hydride or fluoride instead of chloride, the use of nitrogen-containing compounds such as N ₂ instead of NH ₃ , and the use of Ar etc. instead of H ₂ should be selected as necessary. In the case of carbide, hydrocarbon such as methane, CCl ₄ , CO ₂ etc. are used as the carbon source gas.

In this way, the material of the present invention is realized by subjecting the composite material containing the atmospheric pressure phase BN produced by the CVD method to high pressure treatment and phase conversion into the high pressure phase BN.

The high-pressure treatment means includes static high-pressure treatment and dynamic high-pressure treatment. The former is, for example, 800
An example of a preferable specific condition under the condition of ℃ or more and 6 GPa or more is a method of treating at a temperature of 1800 ° C. to 2200 ° C. for 5 to 30 minutes under a pressure of 7 GPa. The latter is a method of applying an impact to a material using an explosion.

In static high-pressure treatment, it becomes a c-BN type material. In the case of impact pressure treatment, when the normal pressure phase BN is h-BN, it becomes w-BN, and γ-
In the case of BN, it becomes c-BN.

The static high pressure treatment is preferable from the viewpoint of easily controlling the fine structure of the obtained c-BN composite material. In this case, when a composite material consisting of amorphous or turbostratic BN and amorphous nitride (amorphous Si ₃ N ₄ etc.) is used as a starting material, c-BN obtained is obtained.
It is more preferable because it is easy to control the precipitation morphology of c-BN in the composite material.

EXAMPLES Next, the present invention will be described with reference to examples.

To prepare a BN / Si ₃ N ₄ composite ceramic by Examples _{1,2 BCl 3 -SiCl 4 -NH 3 -H} 2 gas system CVD method. From infrared absorption spectrum and chemical analysis, it was confirmed that it consisted of BN and Si ₃ N ₄ . The Si ₃ N ₄ content was 54.1 wt%. From the result of X-ray diffraction, the substance was amorphous. No crystals of Si ₃ N ₄ were observed. In addition, it is a colorless transparent plate-like body with a density of 2.08 g /
It was cm ³ . This amorphous sample was subjected to a high pressure treatment at a pressure of 7 GPa and a temperature of 1800 ° C. for 10 minutes using an octahedral high pressure apparatus (Example 1). Further, high pressure treatment was carried out for 10 minutes even at a pressure of 7 GPa and a temperature of 2200 ° C. (Example 2).

The sample thus obtained was a sintered body. When this was subjected to X-ray diffraction measurement, only the diffraction lines of c-BN and β-Si ₃ N ₄ were observed in both Example 1 and Example 2. The fractured surface was polished and observed under a high-power electron microscope.
It was possible to determine the distribution structure of. The fifth in the first embodiment
The structure of the figure was recognized. The size of coarse particles is about 1 μm
And the inside was more finely reticulated.

On the other hand, in Example 2, the structures shown in FIGS. 1 to 4 and FIGS. 6 and 7 were recognized. Thickness of columnar part of c-BN phase is about 0.1 μm
Met. The micro Vickers hardness of Example 1 is 4000 kg
/ mm ² , that of Example 2 was 4700 kg / mm ² . Load 500g
The presence of cracks was not observed when the area around the indentation was observed. Also, no crack was observed at the interface between the c-BN phase and Si ₃ N ₄ .

[Effects of the Invention] The high-pressure phase BN, especially c-BN, is a superhard material second only to diamond, and has excellent thermal conductivity and chemical stability. The high-pressure BN-based composite material of the present invention is a new material in which various characteristics of the ceramics are synergistically added by combining them with nitride ceramics and carbide ceramics while making the most of these characteristics.

The new material has extremely high industrial applicability as a mechanical tool material having high hardness and high toughness, a heat sink material, a dielectric material, and an engineering material having excellent wear resistance.

[Brief description of drawings]

 1 to 7 are schematic views of the microstructure of the material of the present invention. 1 ... High-pressure phase BN 2 ... Phase of nitride, carbide, boride, etc.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 999999999 Toshio Hirai 3-4-91 Takamori, Izumi City, Miyagi Prefecture (71) Applicant 999999999 Ken Ken Masumoto 3-8-22, Uesugi, Sendai City, Miyagi Prefecture Inventor Hiroyuki Nakae 1-14-7 Kamioo, Aso-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Yukio Matsunami 4-67, 1-67, Futamatagawa, Asahi-ku, Yokohama-shi, Kanagawa Nihon Kagaku Kogyo Co., Ltd. 202 (72) Inventor, Akifumi Onodera Kyoto 17-12 Hinooka-Isutani-cho, Yamashina-ku, Kyoto (72) Inventor Toshio Hirai 3-4-91 Takamori, Izumi-shi, Miyagi Prefecture (72) Ken Ken Masumoto 3-8-22, Uesugi, Sendai-shi, Miyagi (56) References Special Kai 62-108718 (JP, A) JP 62-108712 (JP, A) JP 59-207811 (JP, A) JP 60-204674 (JP, A)

Claims (1)

[Claims] 1. A high-pressure phase boron nitride-based composite material produced by a chemical vapor deposition method and containing a normal-pressure phase boron nitride, which is subjected to high-pressure treatment to obtain a composite material containing 5 to 52 wt% of high-pressure phase boron nitride. Composite material.