JP2003020281A - Reaction synthesis of non-oxidize system boron nitride composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a non-oxide system boron nitride composite material having high strength, such as aluminum nitride, aluminum oxynitride and sialon, which consists of porous materials having the structure finer than the composite material obtained by mechanical mixing of the conventional raw material powder by the reaction on a site, and having high density or a multiplicity of closed cells. SOLUTION: This method for manufacturing the non-oxide system boron nitride composite material comprises adding the aluminum nitride or the aluminum nitride and aluminum oxide or silicon nitride and aluminum oxide in accordance with the nitration reaction of aluminum boride and adding a sintering assistant at need thereto and subjecting the mixture to ordinary pressure sintering. Accordingly, the composite material which consists of the porous material having the high density or a multiplicity of the closed cells and has the homogenous and fine structure and excellent mechanical properties can be manufactured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a non-oxide type silicon nitride composite, and more specifically to a novel non-oxide having high strength and high corrosion resistance by in-situ reaction. The present invention relates to a method for producing a boron nitride composite material. The present invention provides a non-oxide type boron nitride composite material that can be used in many applications such as heat resistant materials, heat shock resistant materials, and corrosion resistant materials.

[0002]

2. Description of the Related Art Non-oxide ceramics silicon nitride,
Aluminum nitride, silicon carbide, aluminum oxynitride, sialon, etc. are excellent in heat resistance and corrosion resistance, and are therefore applied to many industrial fields. Further, since a composite material in which boron nitride is dispersed in these ceramics has further improved corrosion resistance, heat resistance and thermal shock resistance, the composite material is strongly expected to be applied to the steel industry and the like. Conventionally, for example,
As a method for producing a composite of silicon nitride and boron nitride, for example, an oxide of a rare earth element or an oxide sintering aid such as Al ₂ O ₃ is added to a mixture of silicon nitride powder and boron nitride powder. A method of mixing, molding the mixture, and then sintering is known.

However, in the above-mentioned composite of silicon nitride and boron nitride, the oxide sintering aid added and mixed to supplement the difficulty of sintering the raw material silicon nitride is There is a problem that it remains as a glassy or crystalline oxide in the grain boundary phase of the sintered body that is the base material and reduces the thermal shock resistance of the obtained composite. Further, conventionally, with respect to a method for producing a composite of silicon nitride and boron nitride, in particular, in order to improve the thermal shock resistance of the resulting composite, in a mixture of silicon nitride powder and boron nitride powder, β-sialon powder, A method for producing a composite of silicon nitride and boron nitride is characterized in that aluminum nitride powder and oxide powder of rare earth element are added and mixed as sintering aids, and the mixture is molded and then sintered. (JP-A-6-
100369).

Further, in order to produce an aluminum nitride-boron nitride composite ceramic which has both excellent thermal conductivity and electrical characteristics and is also excellent in workability, the oxygen content is 1% by weight or less and the specific surface area is Of 3 m ³ / g or less, a nitrogen nitride powder having an oxygen content of 1 wt% or less and a specific surface area of 3 m ³ / g or less, and a sintering aid are mixed, and then a nitrogen atmosphere is formed. There has been proposed a method for producing an aluminum nitride-boron nitride composite ceramic, which is characterized by firing under constant pressure or pressure (Japanese Patent Laid-Open No. 11-157936). The composite material is basically manufactured by mechanically mixing and sintering boron nitride particles. However, with this method, the particles of boron nitride are usually coarse, and it is difficult to obtain a high-strength material. If these properties can be improved, it is expected that the use of the composite will be further expanded.

As described above, the composite material of non-oxide ceramics and boron nitride is manufactured by mechanically mixing boron nitride particles as a raw material and sintering the mixed powder. However, with this method, the boron nitride particles of the obtained composite material are likely to become coarse. Boron nitride has a large thermal expansion anisotropy and cracks easily occur at the interface. Therefore, if the particles become coarse, there is a problem in that the strength of the obtained composite material decreases. Therefore, in this method, the boron nitride powder is preferably fine particles having a particle size of 2 μm or less, but such powder is expensive and it is difficult to completely remove the coarse powder. is there. Furthermore, even if the particles are fine, it is difficult to avoid agglomeration of the particles in the case of mechanical mixing.

[0006]

Under these circumstances, the inventors of the present invention, in view of the above-mentioned prior art, can certainly solve the problems of the above-mentioned prior art by a new non-oxide type boron nitride composite. As a result of intensive research aimed at developing a method for producing a body, it is possible to produce a dense non-oxide boron nitride composite composed of a porous body with many closed pores by utilizing an in-situ reaction. The present invention has been completed and the present invention has been completed. The present invention, by utilizing in-situ reaction, very fine boron nitride flakes are dispersed in a matrix of non-oxide ceramics, and strength, corrosion resistance,
An object of the present invention is to provide a method for producing a porous non-oxide type boron nitride composite material having excellent thermal shock resistance and the like, which is dense or has closed pores.

[0007]

The present invention for solving the above-mentioned problems comprises the following technical means. (1) The raw material powder of aluminum boride (AlB ₂ ) is
Sintering in a nitrogen atmosphere with or without molding,
A method for producing an aluminum nitride-boron nitride composite material, which comprises synthesizing an AlN-BN composite material by utilizing the nitriding reaction. (2) The raw material powder of aluminum boride (AlB ₂ ) is
Sintering in a nitrogen atmosphere with or without molding,
When utilizing the nitriding reaction, the amount of boron nitride is adjusted from 1 vol% to 64 by adding aluminum nitride.
The method for producing an aluminum nitride-boron nitride composite material according to the above (1), which is adjusted to vol%. (3) The production method according to (1) or (2) above, wherein the material is produced by pressureless sintering from 1600 ° C to 2200 ° C. (4) The raw material powder of aluminum boride (AlB ₂ )
Sintering in a nitrogen atmosphere with or without molding,
When utilizing the nitriding reaction, aluminum oxide (Al
₂ O ₃ ) and aluminum nitride are simultaneously added to synthesize an AlON-BN composite, which is a method for producing an aluminum oxynitride-boron nitride composite. (5) The raw material powder of aluminum boride (AlB ₂ )
Sintering in a nitrogen atmosphere with or without molding,
When utilizing the nitriding reaction, by adding aluminum oxide and silicon nitride (Si ₃ N ₄ ) simultaneously, S
A method for producing a sialon-boron nitride composite material, which comprises synthesizing an iAlO-BN composite material.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail. In the present invention, aluminum boride is placed in a nitrogen atmosphere and the following reaction is utilized to synthesize an aluminum nitride-boron nitride composite material. AlB ₂ + 1.5N ₂ = AlN + 2BN The obtained phase composition is aluminum nitride 36.51% by volume and boron nitride 63.49% by volume. The aluminum boride powder preferably has an average particle size of 5 μm or less and is uniform.

Further, in the present invention, an aluminum nitride-boron nitride composite material having an arbitrary composition is manufactured by adding aluminum nitride powder to the above raw material powder. The aluminum nitride powder preferably has an average particle size of 1 μm or less.

In the present invention, aluminum oxynitride-boron nitride composite material is synthesized by placing aluminum oxide and aluminum boride in a nitrogen atmosphere and utilizing the following reaction. 9Al ₂ O ₃ + 5AlB ₂ + 7.5N ₂ = AlON + 1
0BN where AlON = 9Al ₂ O ₃ .5AlN. Further, in the present invention, a sialon-boron nitride composite material is synthesized by placing silicon nitride, aluminum oxide and aluminum boride in a nitrogen atmosphere and utilizing the following reaction. Si ₃ N ₄ + Al ₂ O ₃ + AlB ₂ + N ₂ = SiA
lON + BN In this case, the composition of sialon, Si _6-Z Al _Z O _Z N
The z value in _8-Z changes depending on the mixing ratio of the raw material powder.

The aluminum oxide powder has an average particle size of 1 μm or less and is uniform, the aluminum boride powder has an average particle size of 5 μm or less, and the silicon nitride powder has an average particle size of 1 μm or less. Particle size is 2μ
It is preferable that it is uniform at m or less. Yttrium oxide or the like can be used as the sintering aid, and the mixing ratio thereof is preferably 10% by weight or less. Each of the steps of mixing, molding, and sintering the raw material powders described above can be carried out by a conventional means. Press molding, injection molding,
A suitable method is, for example, forming by an appropriate forming means such as slip casting, placing in a nitrogen atmosphere, and sintering at 1600 ° C to 2200 ° C.

[0012]

EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples. Example (1) Production of composite material To aluminum boride powder having a grain size of 10 μm or less, aluminum nitride powder, aluminum oxide and aluminum nitride, or aluminum oxide and silicon nitride were added, and boron nitride was added at 15% by volume to 30% by volume. The contained aluminum nitride-boron nitride composite material, aluminum oxynitride-boron nitride composite material, and sialon-boron nitride composite material were manufactured. Table 1 shows the sample names and raw material compositions. The average particle size is about 2 μm for aluminum boride powder, about 0.9 μm for aluminum nitride powder, about 0.2 μm for aluminum oxide powder, and about 0.5 μm for silicon nitride powder. 5% by weight of yttrium oxide (Y ₂ O ₃ ) was added to these raw material powders as a sintering aid, and sintering was performed at 1800 ° C. or 1900 ° C. for 2 hours in a nitrogen atmosphere having a purity of 99.9%. In order to sufficiently nitrid the aluminum boride, the raw material was held at a temperature of 1600 ° C. for 8 hours while the temperature was rising. The nitrogen pressure was 8 atm.

(2) Details of the properties of the resulting composite material are shown in Table 1. When the amount of boron nitride is 15% by volume, the total porosity is 7.2% and there are many closed pores, whereas when the amount of boron nitride is 30% by volume, the total porosity is 23.7%. There are many open pores. It is speculated that this is because the amount of boron nitride exceeds the critical value of percolation in the latter case.

When aluminum oxynitride-boron nitride composite material is synthesized by adding aluminum oxide, the closed porosity is 14.4 out of the total porosity of 17.6% of the obtained material.
%, Indicating high strength. Simultaneous addition of silicon nitride and aluminum oxide resulted in a sialon-boron nitride composite. In this case, 1% by weight as a sintering aid
Of yttrium oxide was added.

Comparative Example As a comparative example, T1, T2 and T3 are shown in Table 1. For example, a sample for a comparative example was manufactured by sintering a mixed powder of boron nitride (average particle size 4 μm) and aluminum boride under normal pressure. The three-point bending strength of the obtained sintered body is 65
MPa (T1), 53 MPa (T2), and 92 MPa
(T3), which is remarkably low as compared with the examples.

[0016]

[Table 1]

As is clear from Table 1, the sintered bodies of the examples of the present invention have higher density and higher strength than the sintered bodies of the comparative examples. Further, according to the present invention, it is possible to produce a porous body having many closed pores even if it is porous. Needless to say, the present invention is not limited to the formulation of the above-mentioned examples.

[0018]

As described in detail above, the present invention is based on the nitriding reaction of aluminum boride and is carried out under normal pressure sintering such as aluminum nitride-boron nitride, aluminum oxynitride-boron nitride and sialon-boron nitride. The present invention relates to a non-oxide type boron nitride composite material and a method for producing the same, and according to the present invention, 1) non-oxide type nitriding in which very fine boron nitride flakes are uniformly dispersed in a non-oxide matrix. Able to manufacture and provide boron composite materials, 2) Utilizing a simple nitriding reaction of aluminum boride, a high-strength non-oxide nitriding consisting of a dense, closed-pore porous structure A boron composite material can be obtained, 3) the material produced by the present invention has a homogeneous structure, is excellent in strength characteristics, and is useful as a steel industrial member, a high temperature structural member, 4), Machinable property is good, it is capable of easily processed into complex shaped parts, special effect can be attained.

Claims (5)

[Claims] 1. A raw material powder of aluminum boride (AlB ₂ ) is molded or sintered without being molded in a nitrogen atmosphere, and the nitriding reaction is utilized to synthesize an AlN-BN composite. A method for producing an aluminum nitride-boron nitride composite material, comprising: _2. A raw material powder of aluminum boride (AlB ₂ ) is molded or sintered without being molded in a nitrogen atmosphere, and aluminum nitride is added when utilizing the nitriding reaction. , The amount of boron nitride is 1 vol%
To 64 vol% of the aluminum nitride-boron nitride composite material according to claim 1. 3. The manufacturing method according to claim 1, wherein the material is manufactured by pressureless sintering from 1600 ° C. to 2200 ° C. 4. A raw material powder of aluminum boride (AlB ₂ ) is molded or not molded and sintered in a nitrogen atmosphere, and when the nitriding reaction is utilized, aluminum oxide (Al ₂ O _{3) is used.} ) And aluminum nitride are added at the same time to synthesize an AlON-BN composite, a method for producing an aluminum oxynitride-boron nitride composite material. 5. A raw material powder of aluminum boride (AlB ₂ ) is molded or not molded and sintered in a nitrogen atmosphere, and when utilizing the nitriding reaction, aluminum oxide and silicon nitride (Si) are used. by adding ₃ N ₄₎ at the same time, sialon and wherein the synthesis of SiAlO-BN composites - method for producing boron nitride composites.