JPH10273359A - Highly strong aluminous sintered product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminous sintered product having high strengths from room temperature to high temperatures, and to provide a method for producing the same. SOLUTION: Alumina powder having an average particle diameter of <=2 μm is mixed with 0.001-0.5 vol.% of silicon nitride and/or sialon having an average particle diameter of <=1 μm or an organic silicon compound, and subsequently sintered at a temperature of >=1200 deg.C to obtain the highly strong aluminous sintered product which has a relative density of >=96% and in which 0.001-0.5 vol.% of inorganic crystal particles 2 comprising the silicon nitride and/or the sialon and having an average particle diameter of <=1 μm are dispersed and contained in an alumina matrix comprising crystal particles 1 having an average particle diameter of 10 μm through a layer 2 reacting with the matrix.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to corrosion-resistant, abrasion-resistant and heat-resistant parts such as precision processed products such as wafer polishing plates and jigs for semiconductor manufacturing equipment, pumps, valves, parts for crushers, and parts for wire drawing machines. Parts, cutting tools, IC package substrates,
The present invention relates to a high-strength alumina sintered body used for a heat-resistant member used at a high temperature and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, alumina-based sintered bodies have been widely used for industrial machine parts because of their excellent abrasion resistance, corrosion resistance, moderate strength, and low cost, and also have high insulation properties. With the establishment of metallized wiring technology, it is widely used as an insulating substrate such as a wiring substrate.

This alumina-based sintered body is generally prepared by adding SiO ₂ , CaO, MgO as a sintering aid to alumina powder.
It is produced by adding an oxide such as, for example, and then firing at a temperature of 1500 to 1700 ° C.

However, since the strength of such an alumina-based sintered body is at most about 300 to 400 MPa,
Since it cannot be used as a part or a cutting tool that requires further strength as an industrial machine part, high strength has been promoted.

Therefore, conventionally, it has been proposed to increase the strength by dispersing silicon carbide or zirconia in alumina, as disclosed in JP-A-61-122164 and JP-A-6-122164.
It has been proposed in, for example, JP-A-3-139044.

[0006]

However, in a sintered body in which a carbide such as silicon carbide is dispersed in alumina, the carbide is easily oxidized to an oxide in a high-temperature oxidizing atmosphere, and the sintered body lacks oxidation resistance. Problem, and 100
The strength at a temperature exceeding 0 ° C. was low.

Further, a system in which zirconia is dispersed has a high strength at room temperature, but has a problem that the strength is extremely reduced from around 900 ° C., so that it cannot be used in a temperature range exceeding that.

Accordingly, an object of the present invention is to provide an alumina-based sintered body having high strength from room temperature to a high temperature and a method for producing the same.

[0009]

Means for Solving the Problems The high-strength alumina-based sintered body of the present invention comprises an alumina matrix composed of crystal grains having an average particle diameter of 10 μm or less, and a reaction layer with the matrix having an average particle diameter of 1 μm or less. 0.001 to 0.5 of inorganic crystal particles made of silicon nitride and / or sialon
% By volume, and the relative density is 96%.
% Or more.

In addition, as a method for producing such a sintered body, a matrix forming component comprising an alumina powder having an average particle size of 2 μm or less is added to a silicon nitride and / or sialon powder having an average particle size of 1 μm or less, An organosilicon compound which can be changed into them by an inorganic crystal particle forming component is defined as silicon nitride or sialon in an amount of 0.1%.
001 to 0.5% by volume, and the mixture was formed into a predetermined shape, and then fired at a temperature of 1200 ° C. or higher.
The method is characterized in that while forming a reaction layer between the matrix and the inorganic crystal particles, the relative density is increased to 96% or more.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The alumina ceramics of the present invention is a dense body having a relative density of 96% or more, particularly 98% or more, composed of a matrix composed of alumina and dispersed particles composed of inorganic crystals dispersed in the matrix. Consists of The alumina matrix has an average particle size of 10
It is necessary to be constituted by fine crystal grains of μm or less, particularly 5 μm or less, and further 2 μm or less. If the average grain size of the alumina crystals is larger than 10 μm, the strength of the sintered body will be extremely reduced.

On the other hand, the inorganic crystal particles dispersed in the alumina matrix are made of silicon nitride (Si ₃ N ₄ ) and / or sialon. These dispersed particles are contained in an alumina matrix in an amount of 0.001 to 0.5% by volume, particularly 0.005 to 0.1% by volume, and more preferably 0.005 to 0.1% by volume.
It is necessary to disperse at a rate of 0.08% by volume,
If the amount of the dispersed particles is less than 0.001% by volume, the effect of improving the strength cannot be obtained, and if the amount exceeds 0.5% by volume, it is difficult to densify and the relative density of 96% or more cannot be achieved. Sialon is Si _6-Z Al _Z O _Z N
The crystal lattice of β-sialon or sialon represented by _8-Z (where 0 <z ≦ 4), in which Y or a rare earth element penetrates, may be used. It is important that the dispersed particles are dispersed as particles having an average particle diameter of 1 μm or less, particularly 0.5 μm or less. If the particle diameter is larger than 1 μm, the strength of the sintered body does not improve. The dispersed particles are dispersed and contained in the alumina crystal particles and at the grain boundaries.

Alumina constituting the matrix itself is excellent in oxidation resistance at high temperatures but low in high-temperature strength, whereas silicon nitride or sialon is excellent in strength at high temperatures, but oxidized in an oxidizing atmosphere. It has the property to be.

According to the present invention, as shown in FIG. 1 showing the state of dispersed particles in the alumina crystal grains, or FIG. 2 showing the state of dispersed particles in the alumina crystal grain boundaries,
As described above, a very small amount of silicon nitride or sialon crystal particles 2 are dispersed through the reaction layer 3 within the alumina crystal particles 1 of the alumina matrix or at the grain boundaries of the alumina crystal particles 1, thereby improving the alumina properties. The strength at high temperatures can be significantly improved without impairing the oxidation resistance.

This is because the alumina crystal particles 1 shown in FIG.
Inorganic dispersed particles 2 existing in the grains through the reaction layer 3
However, while the residual stress field due to the difference in thermal expansion between the two expands, the dispersed particles 2 present at the grain boundaries in FIG. It is presumed that they did. The reaction layer 3 is formed of an amorphous layer containing alumina, trace amounts of nitrogen and silicon.

As a method for producing such a high-strength alumina sintered body, an alumina powder having an average particle diameter of 2 μm or less, preferably 1 μm or less is used as a component forming a matrix. If the average particle size of the alumina powder exceeds 2 μm, insufficient densification is caused, and the strength is reduced.

Further, as the dispersed particle forming component, silicon nitride powder and / or sialon powder having an average particle diameter of 1 μm or less, especially 0.5 μm or less, or organosilicon which can be changed to silicon nitride and / or sialon by thermal decomposition. Add compound. Examples of such organosilicon compounds include polysilazane and polycarbosilazane. When silicon nitride powder and / or sialon powder is used, if the average particle size exceeds 1 μm, the strength characteristics cannot be improved, and the silicon oxynitride powder has substantially the same properties as the powder particles in the sintered body. Since it exists in a particle size, if it exceeds 1 μm, the particle size in the sintered body increases, and the characteristic effect cannot be achieved.

These dispersed particle sources are converted to silicon nitride or sialon in an amount of 0.001 to 0.5% by volume, particularly 0.005 to 0.1% by volume, and more preferably 0.005 to 0.1% by volume.
Mix so that the ratio is 0.08% by volume. If the amount is less than 0.001% by volume, the effect of improving the strength cannot be expected, and if it exceeds 0.5% by volume, it becomes difficult to achieve a high density. When an inorganic compound that can be converted into silicon nitride and / or sialon by thermal decomposition is used, the amount is expressed in terms of the form after thermal decomposition.

Next, when a silicon nitride powder or a sialon powder is added, the mixed powder is added to a desired molding means,
For example, it is formed into an arbitrary shape by a die press, a cold isostatic press, injection molding, extrusion molding, or the like. When the organic silicon compound is added, after the mixed powder is once thermally decomposed to generate silicon nitride or sialon,
Formed by the above method, or after forming a mixture containing an organosilicon compound into a predetermined shape, nitrogen gas or a mixed gas of nitrogen gas and hydrogen gas is thermally decomposed to produce silicon nitride or sialon. .

The temperature at which the organosilicon compound is thermally decomposed is preferably equal to or lower than the temperature at which densification of alumina starts, and is preferably equal to or lower than 1000 ° C. If the temperature exceeds 1000 ° C., the densification of alumina starts, and the pyrolysis gas is trapped inside the sintered body, ignoring the densification, which may cause a decrease in density and a decrease in strength.

The molded body obtained in this manner is heated to 1200 ° C. or more, preferably 1300 ° C. to 155 in a nitrogen atmosphere.
Bake at a temperature of 0 ° C. The sintering is performed by hot pressing, normal pressure sintering, or hot isostatic sintering. If the firing temperature at this time does not reach 1200 ° C., the densification is insufficient and the density is reduced, or the formation of the reaction layer is insufficient and the strength is reduced. When hot pressing is performed, molding and firing can be performed simultaneously.

[0022]

【Example】

Example 1 (Samples Nos. 1 to 23, 26 and 27) Alumina powder having a purity of 99.99% and a crystal grain size of 0.
2μm Taimicron TM- manufactured by Daimei Chemical Co., Ltd.
DAR (A-1) was used. As a silicon nitride powder, a silicon nitride powder (B-
1) As a sialon powder, a powder of Z = 1 (C-1) manufactured by Ube Industries, which was manufactured by pulverizing the zirconium powder having a z value of 1 to 3 so that the average particle size is about 0.5 μm, Powder (C-
2) A powder (C-3) with Z = 3 was prepared. For comparison, Al ₂ O ₃ powder having a crystal grain size of 1.2 μm (A-2)
And a silicon nitride powder having an average particle size of 1.8 μm (B-2)
Was prepared.

The above-mentioned alumina powder and silicon nitride powder or sialon powder are weighed in combinations and amounts shown in Tables 1 and 2, mixed in an organic solvent using alumina balls, and dried using an evaporator. I got

For firing, hot press firing (HP) and atmosphere firing (PLS) were used. In the case of hot press firing, put this powder in a carbon mold and
It baked at the calcination temperature shown in a table under Pa pressure. In the case of firing in an atmosphere, the powder was subjected to hydrostatic pressure treatment at a pressure of 3 t / cm ² to produce a molded body, and fired in a nitrogen gas at normal pressure at firing temperatures shown in Tables 1 and 2.

A test piece was cut out from the obtained sintered body and polished. Then, the specific gravity was determined based on JISR2205, and the relative density was determined. As the strength value, a strength at room temperature and 1400 ° C. was obtained from a four-point bending test based on JISR1601. The surface of the test piece was mirror-finished and thermally etched in a nitrogen atmosphere, and the surface in the sintered body was observed. Further, the particle size of the matrix and the dispersed particles was observed, measured and measured by an electron microscope photograph. The results are shown in Tables 1 and 2.

Example 2 (Sample Nos. 24 and 25) Alumina powder was crushed and dispersed in an organic solvent using alumina media, and then polysilazane N-N510 manufactured by Tonen Co., Ltd. was placed in a glow box purged with nitrogen. (D-1)
Was added in the amount shown in Table 2 in terms of silicon nitride, and the mixture was sealed and mixed again. Then, the mixed powder to which the organosilicon compound was added was dried, thermally decomposed in a mixed gas of nitrogen and 4% hydrogen at 800 ° C. to produce silicon nitride, lightly crushed again, and sized. For sintering, the sized powder prepared as described above was placed in a carbon mold and subjected to hot press sintering at a temperature shown in Table 2 by applying a pressure of 30 MPa in nitrogen gas.

From the obtained sintered body, the relative density, the room temperature based on JISR1601 and
It was determined from a four-point bending test at 400 ° C. Also, the surface of the test piece is mirror-finished and thermally etched in a nitrogen atmosphere.
The average particle size of the alumina matrix and the average particle size of the dispersed particles in the sintered body were measured. Table 2 shows the obtained results.

[0028]

[Table 1]

[0029]

[Table 2]

As a result of the measurement, when the dispersion particles forming components B-1 and C-1 to C-3 having an average particle diameter of 1 μm or less were used, and when the organosilicon compound was used, the dispersion particles were all Fine particles having an average particle size of 0.5 μm or less were dispersed in the alumina crystal grains and at the grain boundaries.

However, in sample No. 27 using powder (B-2) having an average particle size exceeding 1 μm, the dispersed particles had a size of 1.8 μm, and as a result, even if a reaction layer was formed. No improvement in strength was seen.

In addition, sample No. 1 containing no dispersed particles
Is 170 MPa at room temperature strength of 450 MPa and 1400 ° C. strength.
Very low with MPa. Samples Nos. 8, 9, and 21 in which the content of the inorganic crystal particles exceeded 0.5% by volume, Sample No. 13 in which the average particle size of the alumina matrix of the sintered body exceeded 10 μm, and the average particle size of the inorganic crystal particles In Sample No. 27 having a diameter exceeding 1 μm, no effect of improving mechanical strength was obtained. Sample No. 26, in which the average particle size of alumina powder as a raw material exceeds 2 μm, and a sintering temperature of 1200,
In sample No. 10 lower than 100 ° C., the relative density was 96%.
% Could not be achieved.

On the other hand, the sintered body of the present invention containing silicon nitride or sialon having an average particle diameter of 1 μm or less at a ratio of 0.001 to 0.5% by volume has a room temperature strength of 6%.
It exhibited excellent mechanical strength of not less than 00 MPa and strength of 1400 ° C. not less than 300 MPa. In addition, it exhibited excellent properties equivalent to alumina in high-temperature oxidation resistance.

[0034]

As described above, since the alumina-based sintered body of the present invention has excellent bending strength from room temperature to high temperature, it can be used for precision processed products such as wafer polishing plates and jigs for semiconductor manufacturing equipment. Corrosion-, wear- and heat-resistant parts such as pumps, valves, parts for crushers, parts for wire drawing machines, cutting tools,
It can be used for IC package substrates, heat-resistant members used at high temperatures, and the like.

[Brief description of the drawings]

FIG. 1 is a view for explaining a state of dispersed particles in alumina crystal grains of an alumina sintered body of the present invention.

FIG. 2 is a view for explaining a state of dispersed particles at an alumina crystal grain boundary of the alumina-based sintered body of the present invention.

[Explanation of symbols]

 1 alumina crystal particles 2 dispersed particles 3 reaction layer

Claims (3)

[Claims] 1. An alumina matrix composed of crystal grains having an average particle diameter of 10 μm or less, and inorganic crystal grains composed of silicon nitride and / or sialon having an average particle diameter of 1 μm or less interposed between 0.001 and 0.001 through a reaction layer with the matrix. 0.5
% By volume, and the relative density is 96%.
% High-strength alumina-based sintered body, wherein 2. The high-strength alumina sintered body according to claim 1, wherein said inorganic crystal particles are dispersed in said alumina crystal particles and at grain boundaries thereof. 3. A matrix-forming component comprising an alumina powder having an average particle diameter of 2 μm or less, and a silicon nitride and / or sialon powder having an average particle diameter of 1 μm or less, or an organosilicon compound which can be changed to them by thermal decomposition. As a crystal particle-forming component, silicon nitride or sialon is mixed at a ratio of 0.001 to 0.5% by volume, the mixture is formed into a predetermined shape, and then fired at a temperature of 1200 ° C. or more, and the matrix and the A method for producing a high-strength alumina-based sintered body, comprising densifying a relative density of 96% or more while forming a reaction layer with inorganic crystal particles.