JPH05254944A - Production of sialon-based composite ceramics - Google Patents

Abstract

PURPOSE:To produce sialon-based composite ceramics having a small grain size and excellent dynamic characteristics at a low cost while ensuring a high degree of freedom of selection of powdery starting materials. CONSTITUTION:A powdery mixture prepd. by mixing SiO2 powder with AlN powder in 0.5-1.5 molar ratio of SiO2 to AlN is sintered at 1,400-1,600 deg.C under reduced pressure or in an inert atmosphere or the powdery mixture is compacted and the resulting compact is sintered at 1,400-1,600 deg.C under reduced pressure or in an inert atmosphere. The objective sialon-based composite ceramics are obtd. by utilizing a substitution reaction and a solid-solution reaction at the time of sintering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing sialon-based composite ceramics. In particular, parts for internal combustion engines (diesel engines, etc.), parts for aerospace, extrusion dies, molding dies, metal cutting tools, casting nozzles, welding nozzles, location pins, heat resistant protection tubes, high temperature gas pipes , Melting crucibles, rolling rolls, parts for continuous casting equipment, etc. that require high mechanical strength in addition to heat resistance and corrosion resistance, IC substrates in the electronic industry, steppers in semiconductor manufacturing equipment (XY The present invention relates to a method for producing a sialon-based composite ceramic suitable for applications such as stages, reticles, wafer holders, etc., which require low thermal expansion characteristics.

[0002]

BACKGROUND OF THE INVENTION As is well known, sialon-based composite ceramics are oxynitride-based ceramics having an intermediate composition between oxide ceramics and nitride ceramics, and are excellent in heat resistance and corrosion resistance and low in resistance. Since it exhibits thermal expansion characteristics, it is expected to be applied to parts for internal combustion engines and the like.

Such sialon-based composite ceramics have hitherto been disclosed, for example, in "Jou", published by Chapmanand Hall in England.
rnal of Materials Science ", Volume 11, 1135
Pp. 1158 (1976) and Uchida Otsuru, "Silicon Nitride Ceramics 2", pp. 109-116 (May 15, 1990), Si ₃ N ₄ powder and A
It is manufactured by pulverizing and mixing with 1 ₂ O ₃ powder and sintering the resulting mixed powder. However, these methods have problems as described below.

That is, in all of these conventional methods, since the Si ₃ N ₄ powder and the Al ₂ O ₃ powder are crushed and mixed, the particle size is fine and the particle size between both powders is large. Uniform mixing is difficult unless powders that do not differ are used. When a mixed powder having poor uniformity is used, segregation occurs during sintering, internal defects are formed, and the resulting sialon-based composite ceramic has poor mechanical properties. That is, the conventional method has a small degree of freedom in selecting the raw material powder.

Further, the conventional methods, as Al ₂ O ₃ powder, usually using the α-Al ₂ O ₃ powder, the α-Al ₂ O ₃ is the X phase from the vicinity of 1600 ° C. during sintering ( 1700 to produce a mullite phase), which melts
Sudden contraction begins to occur from around ℃. for that reason,
As the sintering temperature, a high temperature of 1700 ° C. or higher is usually required, which increases the manufacturing cost. Further, when sintered at such a high temperature, crystal grains grow and the crystal grain size becomes coarse,
The resulting sialon-based composite ceramic becomes brittle. Further, abnormal grain growth is likely to occur and defects due to the abnormal grain growth are likely to occur, resulting in poor mechanical properties and reliability.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the conventional method and not only have a high degree of freedom in selecting the raw material powder, but also be able to sinter at a lower temperature, It is an object of the present invention to provide a method for producing a sialon-based composite ceramic having a fine crystal particle size and excellent mechanical properties at low cost.

[0007]

In order to achieve the above object, the present invention uses SiO ₂ powder and AlN powder as SiO 2.
_The powder obtained by mixing ₂ / AlN in a molar ratio of 0.5 to 1.5 was used under reduced pressure or in an inert atmosphere to produce 14
Provided is a method for producing a sialon-based composite ceramic, which comprises performing pressure sintering at 00 to 1600 ° C. The mixed powder may be molded and then sintered. According to this method, a sialon having a β-sialon represented by the general formula as Si _6-z Al _z O _z N _8-z (z ≦ 4) such as Si ₃ Al ₃ O ₃ N ₅ as a main component is used. A composite ceramic material can be obtained.

The present invention also relates to SiO ₂ powder and AlN.
A powder obtained by mixing the powder with SiO ₂ / AlN in a molar ratio of 1.5 to 3.0 is subjected to pressure sintering at 1450 to 1650 ° C. under reduced pressure or an inert atmosphere. Provided is a method for producing a sialon-based composite ceramic. The mixed powder may be molded and then sintered.
Also by this method, it is possible to obtain a sialon-based composite ceramics such as Si ₃ Al ₃ O ₃ N ₅ whose main component is the β-sialon represented by the above general formula.

Further, according to the present invention, SiO ₂ powder and Al
N ₂ powder and SiO ₂ / AlN in a molar ratio of 3.0 to 5.0
The present invention provides a method for producing a sialon-based composite ceramics, which comprises press-sintering powders obtained by mixing as described above under reduced pressure or in an inert atmosphere at 1400 to 1500 ° C. The mixed powder may be molded and then sintered. According to this method, a sialon-based composite ceramic containing sialon as a main component which does not comply with the above general formula is produced.

That is, according to the present invention, unlike the conventional method, the mixed powder of Si ₃ N ₄ powder and Al ₂ O ₃ powder is not used as the raw material powder, but SiO ₂ powder and A ₂
A mixed powder with 1N powder is used to obtain a sialon-based composite ceramic by utilizing a substitution reaction and a solid solution reaction during sintering. Hereinafter, the present invention will be described in more detail according to the manufacturing process.

In the present invention, first, a mixed powder containing SiO ₂ powder and AlN powder is prepared. The average particle size of the SiO ₂ powder or AlN powder is 3.0 μm so that the sintering described later can be performed more quickly and more uniformly.
It is preferably m or less. However, this 3.0 μm
The following range is much wider than the conventional method using a mixed powder of Si ₃ N ₄ powder and Al ₂ O ₃ powder. That is, in the present invention, even coarser powder can be used.

The mixing operation may be dry or wet. However, the wet mixing method is preferable because the dispersibility can be further improved. For example, isopropyl alcohol, ethyl alcohol,
An organic dispersion medium such as ethylene glycol or dimethyl sulfoxide is added, well mixed by an attrition mill, a ball mill or the like, and pulverized to obtain a mixed powder. After mixing and pulverizing, it is preferable to dry under reduced pressure using a rotary evaporator or the like in order to prevent segregation due to the difference in specific gravity. As a result, the secondary agglomeration is well deflocculated, and a mixed powder in which the primary particles are extremely uniformly dispersed can be obtained.

The mixed powder has a molar ratio of SiO ₂ / AlN of 0.5 to 5.0. Within this range, it is determined in consideration of the average particle diameter of the SiO ₂ powder or AlN powder, the presence or absence of the addition of the third component described below, the addition amount, the sintering conditions, and the like. If this ratio is less than 0.5, the reaction described below does not sufficiently occur, and a large amount of AlN remains. On the other hand, when it exceeds 5.0, on the contrary, a large amount of SiO ₂ remains. The mixed powder contains mechanical properties such as density, hardness, strength, toughness and Young's modulus of the obtained sialon composite ceramics, thermal properties such as thermal conductivity and thermal expansion coefficient, and electrical properties such as electrical conductivity. Third, for the purpose of changing
Ingredients can be added.

For example, in the case of accelerating the reaction to be described later at the time of sintering and densifying to increase the density, Li ₂ O, Y ₂ O ₃ , CaO, M having an average particle diameter of 2.0 μm or less is used.
Powders of gO and Ln ₂ O ₃ (Ln is a lanthanoid excluding La and Ce) are added in the range of 0.5 to 15% by weight.

If CeO ₂ or Al ₂ O ₃ powder is added in the range of 5 to 40% by weight, these will form a solid solution with sialon produced during sintering, and the density will be improved.

Further, when it is desired to improve the strength and toughness, ZrO ₂ or Al having an average particle size of 2.0 μm or less is used.
₂ O ₃ powder is added in the range of 5 to 40 wt.
Powder of ₃ N ₄ % is added in the range of 5-70 wt.

When it is desired to improve strength and toughness, it is 5 to 40.
Addition of whiskers in the range of volume% is also effective.

That is, when a whisker is added, when a crack progresses in the sialon-based composite ceramics, the whisker deflects the crack and further branches it to absorb the breaking energy, and also the breaking effect causes the breaking. Since the energy is attenuated, the fracture strength and toughness are dramatically improved. Ceramic whiskers such as SiC and Si ₃ N ₄ can be used as the whiskers. The addition of whiskers is preferably in the range of 5-40% by volume. Below 5% by volume,
Improvement of fracture strength and toughness cannot be expected, and 40% by volume
When it exceeds, since the whiskers have low sinterability, the density of the obtained sialon-based composite ceramics is lowered. The whiskers are preferably dispersed in advance in an organic solvent such as ethyl alcohol, isopropyl alcohol or toluene together with a dispersant such as polyethyleneimine or trichlorooctadecylsilane and using ultrasonic waves.

When it is desired to improve hardness or Young's modulus, SiC or B ₄ having an average particle diameter of 3.0 μm or less is used.
C, TiC, ZrC, WC powder, average particle size 2.0
Powders of Si ₃ N ₄ or c-BN, TiN, and ZrN having a size of μm or less are added in the range of 5 to 40% by weight.

Further, particularly when it is desired to reduce the coefficient of thermal expansion, TiO ₂ or c-B having an average particle size of 2.0 μm or less is used.
N powder is added in the range of 3 to 10% by weight.

Furthermore, particularly when it is desired to improve the thermal conductivity and the electrical conductivity, powders of SiC, B ₄ C, TiC, ZrC, and WC having an average particle diameter of 3.0 μm or less, and an average particle diameter of 2 Si ₃ N ₄ or c-BN or Ti with a thickness of 0.0 μm or less
Powders of N and ZrN are added in the range of 5 to 40% by weight.

Si having an average particle size of 7.0 μm or less
When powders of Al, Ti, and Fe are added in the range of 1 to 20% by weight, the toughness of the obtained sialon-based composite ceramics is improved, and variations in strength and hardness can be reduced.

In the present invention, next, the mixed powder prepared as described above is sintered. There are two ways to do this.

First, the mixed powder is processed by a dry hydrostatic molding method,
This is a method of molding into a desired shape using a die molding method, a wet slip casting molding method, an injection molding method, etc., and then sintering the molded body under pressure or without pressure. The other is a method of pressure sintering using a hot press molding method, a hot isostatic pressing method (HIP method) or the like without molding the mixed powder. In either case, sintering is 0.1 To
rr. Perform in the following reduced pressure atmosphere or in an inert atmosphere such as nitrogen gas or argon gas. The sintering temperature is in the range of 1400 to 1650 ° C., although it varies depending on the composition of the mixed powder, the presence / absence of addition of the third component, the addition amount thereof, and the like.

In the case of sintering accompanied by pressurization, the temperature is raised to the sintering temperature at a rate of 5 to 10 ° C./minute so as to prevent temperature distribution, and the temperature is maintained for a desired time for sintering. At this time, the pressurization may be performed before the temperature rise, or may be gradually performed according to the temperature rise rate. It is also possible not to pressurize at all during the temperature rise but pressurize when the desired sintering temperature is reached. Even in the case of sintering without pressure, 5 to 1
The temperature is raised to the sintering temperature at a rate of 0 ° C./minute.

The sialon-based composite ceramics can be obtained by the above-mentioned sintering. The composition of the sialon-based composite ceramics obtained varies depending on the composition of the mixed powder and the sintering conditions such as the sintering temperature.

That is, the composition of the mixed powder is 0.5 ≦ Si.
If O ₂ /AlN<1.5, sintering 1400
It is performed in the range of up to 1600 ° C. The obtained sialon-based composite ceramics mainly contains β-sialon represented by the general formula, Si _6-z Al _z O _z N _8-z (z ≦ 4), such as Si ₃ Al ₃ O ₃ N ₅ Becomes In addition, Si ₁₆ Al ₁₀ O ₂₁ N ₄ and Si ₃ Al ₃ O _{3 + 1.5x} N
_5-x (x ≦ 2), sialon such as Si ₁₂ Al ₁₈ O ₃₉ N ₈ and Si ₃ N ₄ are easily generated.

The production process of sialon is presumed to be as follows. That is, SiO ₂ and AlN first undergo a substitution reaction of 3SiO ₂ + 4AlN → Si ₃ N ₄ + 2Al ₂ O ₃ from around 1300 ° C. by atomic diffusion due to melting of SiO ₂ , and further with Si ₃ N ₄ . Al ₂ O ₃
It is presumed that and cause a solid solution reaction of Si ₃ N ₄ + Al ₂ O ₃ + AlN → Si ₃ Al ₃ O ₃ N ₅ to produce sialon.

Further, the composition of the mixed powder is 1.5 ≦ SiO ₂
/ AlN <3.0, sintering 1450 to 1650
Perform in the range of ℃. The obtained sialon-based composite ceramics are mainly composed of Si ₃ Al ₃ O ₃ N _5, etc.
In addition to the β-sialon represented by the above general formula, Si ₃ Al ₃ O _{3 + 1.5x} N _5-x (x ≦
2), Si ₃ Al _2.67 N ₄ O ₄ , Si ₂ Al ₃ O ₇ N,
SiAlON such as Si ₆ Al ₁₀ O ₂₁ N ₄ is easily generated.
In addition, Y ₂ O ₃ , Ln ₂ O ₃ powder, Mg
When O and CaO powders are added, M _x Si ₁₂ Al ₁₂ O ₁₆ N formed by solid solution of the element M contained therein
It is a sialon-based composite ceramic containing α-sialon represented by ₁₆ (x ≦ 0.4) as the main component. In particular, S
When the ratio of iO ₂ is high, α-sialon is often preferentially deposited.

Furthermore, the composition of the mixed powder is 3.0 ≦ SiO.
_{If 2 /} AlN <5.0, sintering is 1400-150
Perform in the range of 0 ° C. The sialon-based composite ceramics obtained are Si ₂ Al ₃ O ₇ N, Si ₆ Al ₁₀ O ₂₁ N ₄ ,
Si ₃ Al ₃ O _{3 + 1.5x} N _5-x (x ≦ 2), Si ₃ Al ₇
O ₃ N ₉ , Al ₆ Si ₆ N ₈ O ₉ , Si ₆ Al ₁₀ O ₂₁ N
_It includes sialon that does not comply with the above general formula, such as ₄ . In addition, Al ₃ O ₃ N, Al ₂ SiO ₅ , A
l ₆ Si ₂ O ₁₃ , Al ₂ O ₃ , Si ₂ ON ₂ , Si ₃ N
_In some cases, _{4 and the} like are generated at the same time, and SiO ₂ and AlN remain. In this case, if the glass component is crystallized by a cooling process after sintering or a heat treatment after sintering, a sialon-based composite ceramic having higher strength can be obtained. The heat treatment conditions differ depending on the glass component, but in the case of the SiO ₂ glass component, 700 to 12
It may be about 2 to 200 hours at 00 ° C.

[0031]

【Example】

Example 1 SiO ₂ powder having an average particle diameter of 0.02 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the SiO ₂ / AlN molar ratio was 1, and these powders had a diameter of 10 mm.
Using a ball mill having the SiC balls of No. 3 as a grinding medium, the mixture was mixed in ethanol for 12 hours, ground, and dried to obtain a mixed powder.

Next, the mixed powder was hot-pressed and sintered at 1400 ° C. for 30 minutes under a reduced pressure of 0.1 Torr.
The applied pressure was 20 MPa.

The obtained sintered body was identified by X-ray diffraction. As a result, Si ₃ Al ₃ O ₃ N ₅ and Si ₃ Al ₃ O ₆ N were obtained.
_The main component is ₃ sialon, and in addition to this, Si ₃ N ₄ etc. were recognized.

When observed by an electron microscope, the crystal grains were almost columnar with a width of 0.2 to 0.3 μm and a length of 1 to 2 μm. According to the conventional method described above, 3
Since the particles are about 5 μm in size, it can be seen that the particles are extremely fine. Further, the density was 3.04 g / m ³ Bending strength: 170 MPa Vickers hardness: 1280 Fracture toughness: 2.4 MPa · m ^1/2 Thermal expansion coefficient: 2.4 × 10 ⁻⁶ / K. The density was measured by the Archimedes method. The bending strength was measured according to JIS R1601.
Furthermore, the beakers hardness was according to JIS Z2244. Furthermore, the fracture toughness was determined by the microindentation method (load: 10 kgf) using a Vickers indenter according to JIS R1607. The coefficient of thermal expansion is
It was determined as an average coefficient of thermal expansion from room temperature to 200 ° C. using a DL-7000 type contact thermal expansion meter manufactured by Vacuum Riko Co., Ltd.

Example 2 SiO ₂ powder having an average particle size of 0.02 μm and AlN powder having an average particle size of 0.3 μm were prepared so that the molar ratio of SiO ₂ / AlN was 1, and the average particle size was further adjusted. The diameter is 0.
2 μm of Y ₂ O ₃ powder was added to 5% by weight,
This was mixed in ethanol for 12 hours using a ball mill using a 10 mm diameter SiC ball as a grinding medium.
It was crushed and dried to obtain a mixed powder.

Next, the above mixed powder was mixed with N at 3000 ml / min.
Sintering was performed by hot pressing at 1550 ° C. for 60 minutes in ₂ air streams. The applied pressure was 20 MPa.

The sintered body thus obtained was identified in the same manner as in Example 1. As a result, Si ₃ Al ₃ O ₃ N ₅ and Si ₃ Al _2.67 N ₄ were identified.
O ₄ was the main component. The crystal grains had substantially the same size and shape as those in Example 1. In addition, Example 1
When evaluated in the same manner as above, the density was 3.16 g / m ³ Bending strength: 390 MPa Vickers hardness: 1360 Fracture toughness: 2.6 MPa · m ^1/2 Thermal expansion coefficient: 1.9 × 10 ⁻⁶ / K.

Example 3 SiO ₂ powder having an average particle diameter of 1.2 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the molar ratio SiO ₂ / AlN was 1, and the moldability was further improved. 2% by weight of stearic acid was added to improve the
A ball mill using 0 mm SiC balls as a grinding medium was mixed in ethanol for 12 hours, ground, and dried to obtain a mixed powder.

Next, the above-mentioned mixed powder was preformed into a plate shape by using a mold, put in a plastic bag, and subjected to rubber press rubber press molding. The pressure applied during pre-molding was 30 MPa, and the pressure applied during rubber press molding was 1 MPa.
It was set to 00 MPa. The inside of the bag was depressurized to 0.1 Torr.

Next, the above-mentioned molded body was subjected to 3000 ml / min of N ₂
Sintering was performed at 1550 ° C. for 120 minutes in an air stream. The pressure was normal pressure.

When the obtained sintered body was identified in the same manner as in Example 1, Y ₃ Al ₅ O ₁₂ was found in addition to β-sialon of Si ₃ Al ₃ O ₃ N ₅ as a main component. .. The crystal grains had substantially the same size and shape as those in Example 1. Also, when evaluated in the same manner as in Example 1, density: 3.02 g / m ³ bending strength: 220 MPa Vickers hardness: 1180 fracture toughness: 1.4 MPa · m ^1/2 thermal expansion coefficient: 2.4 × 10 ⁻⁶ / It was K.

Example 4 SiO ₂ powder having an average particle diameter of 1.2 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the molar ratio of SiO ₂ / AlN was 2, and the average particle was further adjusted. Diameter is 0.2
μm Y ₂ O ₃ powder was added so as to be 5% by weight, and this was mixed in ethanol for 12 hours using a ball mill with a SiC ball having a diameter of 10 mm as a grinding medium, ground, dried, and mixed. A powder was obtained.

Next, the above-mentioned mixed powder is mixed with N of 3000 mm / min.
Sintering was performed by hot pressing at 1450 ° C. for 60 minutes in ₂ air streams. The applied pressure was 20 MPa.

The obtained sintered body was identified in the same manner as in Example 1. As a result, Y _0.2 (Si, Al) ₁₂ (O, N) ₁₆ α-sialon and Si ₃ Al ₃ O ₃ N ₅ β were obtained. The main component is type sialon, and in addition to this, SiO ₂ and AlN were recognized. The crystal grains had substantially the same size and shape as those in Example 1.

Next, the sintered body was heat-treated at 1100 ° C. for 48 hours. Crystals of SiO ₂ were observed in the sintered body after the heat treatment. Further, when evaluated in the same manner as in Example 1, density: 3.09 g / m ³ flexural strength: 450 MPa Vickers hardness: 1430 fracture toughness: 2.8 MPa · m ^1/2 thermal expansion coefficient: 0.9 × 10 ⁻⁶ / It was K.

Example 5 SiO ₂ powder having an average particle diameter of 1.8 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the molar ratio SiO ₂ / AlN was 2, and the average particle Diameter is 0.2
Using a ball mill in which 1 μ% of stearic acid was added to improve the moldability, and 1 μ% of Y ₂ O ₃ powder of μm was added, and using SiC balls of 10 mm in diameter as grinding media. Then in ethanol 1
The mixture was mixed for 2 hours, pulverized, and dried to obtain a mixed powder.

Next, the above-mentioned mixed powder was preformed into a plate shape by using a die, put in a plastic bag and subjected to rubber press rubber press molding. The pressure applied during pre-molding was 30 MPa, and the pressure applied during rubber press molding was 1 MPa.
It was set to 00 MPa. The inside of the bag was depressurized to 0.1 Torr.

Next, the above-mentioned molded body was subjected to 3000 ml / min of N ₂
Sintering was performed at 1550 ° C. for 120 minutes in an air stream. The pressure was normal pressure.

When the obtained sintered body was identified in the same manner as in Example 1, Si ₂ Al ₃ O ₇ N and Si ₆ Al ₁₀ O were identified.
The β-sialon of ₂₁ N ₄ and Si ₃ Al ₃ O ₃ N ₅ was observed. The crystal grains had substantially the same size and shape as those in Example 1. Further, when evaluated in the same manner as in Example 1, density: 2.86 g / m ³ bending strength: 260 MPa Vickers hardness: 1160 fracture toughness: 1.6 MPa · m ^1/2 thermal expansion coefficient: 1.4 × 10 ⁻⁶ / K Example 6 SiO ₂ powder having an average particle diameter of 0.02 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the molar ratio SiO ₂ / AlN was 4, and the average particle diameter was 0.
2 μm of Y ₂ O ₃ powder was added to 5% by weight,
This was mixed in ethanol for 12 hours using a ball mill using a 10 mm diameter SiC ball as a grinding medium.
It was crushed and dried to obtain a mixed powder.

Next, the above-mentioned mixed powder is mixed with N of 3000 mm / min.
Sintering was carried out by hot pressing at 1400 ° C. for 60 minutes in _two air streams. The applied pressure was 20 MPa.

The obtained sintered body was identified in the same manner as in Example 1. As a result, it was found that Si ₃ Al ₃ O ₃ N ₅ β-sialon and S were used.
i ₂ Al ₃ O ₇ N is the main component, and in addition to this, SiO ₂ and A
1N was observed. The crystal grains had substantially the same size and shape as those in Example 1. Also, when evaluated in the same manner as in Example 1, density: 2.74 g / m ³ bending strength: 110 MPa Vickers hardness: 1180 fracture toughness: 1.2 MPa · m ^1/2 thermal expansion coefficient: 0.8 × 10 ⁻⁶ / It was K.

Example 7 SiO ₂ powder having an average particle diameter of 1.8 μm and AlN powder having an average particle diameter of 0.3 μm were prepared so that the molar ratio of SiO ₂ / AlN was 4, and the average particle diameter was 4 μm. Diameter is 0.2
Using a ball mill in which Y ₂ O ₃ powder of μm was added to 2% by weight and 1% by weight of stearic acid was added to improve moldability, and SiC balls having a diameter of 10 mm were used as grinding media. Then in ethanol 1
The mixture was mixed for 2 hours, pulverized, and dried to obtain a mixed powder.

Next, the above-mentioned mixed powder was preformed into a plate shape by using a mold, and further put into a plastic bag and subjected to rubber press molding. The pressure applied during preforming is 30.
The pressure was 100 MPa at the time of rubber press molding. The inside of the bag was depressurized to 0.1 Torr.

Next, the above-mentioned molded body was subjected to 3000 ml / min of N ₂
Sintering was performed at 1450 ° C. for 90 minutes in an air stream. The pressure was normal pressure.

When the obtained sintered body was identified in the same manner as in Example 1, Si ₂ Al ₃ O ₇ N and Al ₂ SiO ₅ were the main components, and in addition, SiO ₂ and AlN were recognized. The crystal grains had substantially the same size and shape as those in Example 1. Further, when evaluated in the same manner as in Example 1, density: 2.69 g / m ³ flexural strength: 85 MPa Vickers hardness: 1060 fracture toughness: 1.8 MPa · m ^1/2 thermal expansion coefficient: 0.8 × 10 ⁻⁶ / It was K.

[0056]

According to the present invention, a powder obtained by mixing SiO ₂ powder and AlN powder so that the molar ratio of SiO ₂ / AlN becomes 0.5 to 5.0 is used under reduced pressure or in an inert atmosphere. Since it is pressure-sintered at 1400 to 1650 ° C. or the mixed powder is molded and the molded body is sintered at 1400 to 1650 ° C. under reduced pressure or in an inert atmosphere, as shown in the examples. It is possible to obtain a sialon-based composite ceramic having fine crystal particles and excellent mechanical properties. Also, as in the conventional method, Si ₃ N ₄ powder and Al ₂ O ₃
It does not mix with powder while crushing it, and because it uses the substitution reaction and solid solution reaction to produce sialon, it not only has a high degree of freedom in selecting the raw material powder, but also can be sintered at a lower temperature. The manufacturing cost can be kept low.

Claims (7)

[Claims] 1. A SiO ₂ powder and an AlN powder are mixed with SiO ₂ /
A powder obtained by mixing AlN in a molar ratio of 0.5 to 1.5 was subjected to 1400 under reduced pressure or an inert atmosphere.
A method for producing a sialon-based composite ceramic, which comprises press-sintering at 1600C. 2. A SiO ₂ powder and an AlN powder are mixed with SiO ₂ /
A powder obtained by mixing AlN in a molar ratio of 0.5 to 1.5 is molded, and the molded body is sintered at 1400 to 1600 ° C. under reduced pressure or in an inert atmosphere. , A method for producing a sialon-based composite ceramic. 3. SiO ₂ powder and AlN powder are mixed with SiO ₂ /
The powder obtained by mixing AlN in a molar ratio of 1.5 to 3.0 was subjected to 1450 under reduced pressure or an inert atmosphere.
A method for producing a sialon-based composite ceramic, which comprises press-sintering at ˜1650 ° C. 4. SiO ₂ powder and AlN powder are mixed with SiO ₂ /
A powder obtained by mixing AlN in a molar ratio of 1.5 to 3.0 is molded, and the molded body is sintered at 1450 to 1650 ° C. under reduced pressure or in an inert atmosphere. , A method for producing a sialon-based composite ceramic. 5. A SiO ₂ powder and an AlN powder are mixed with SiO ₂ /
A powder obtained by mixing AlN in a molar ratio of 3.0 to 5.0 is prepared under reduced pressure or in an inert atmosphere at 1400.
A method for producing a sialon-based composite ceramic, which comprises performing pressure sintering at ˜1500 ° C. 6. A SiO ₂ powder and an AlN powder are mixed with SiO ₂ /
A powder obtained by mixing AlN in a molar ratio of 3.0 to 5.0 is molded, and the molded body is sintered at 1400 to 1500 ° C. under reduced pressure or in an inert atmosphere. , A method for producing a sialon-based composite ceramic. 7. A mixed powder containing Li ₂ O, Y ₂ O ₃ and Ca.
0.5 of an oxide powder selected from O, MgO and Ln ₂ O ₃ (Ln is a lanthanoid excluding La and Ce) is used.
Added in the range of 15 to 15% by weight.
The method for producing a sialon-based composite ceramic according to 4, 5, or 6.