JPH0687651A - Production of aluminum titanate sintered compact - Google Patents

Abstract

(57) [Summary] [Object] The present invention is to provide a production method capable of obtaining an aluminum titanate sintered body having sufficient thermal decomposition stability in addition to sufficient low thermal expansion. To aim. [Structure] An Al ₂ TiO ₅ powder obtained by mixing Al ₂ O ₃ powder and TiO ₂ powder and calcining and synthesizing the mixed powder at a synthesis temperature of 1400 ° C. or higher is used.

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 an aluminum titanate sintered body.

[0002]

_2. Description of the Related Art Ceramics made of an Al ₂ TiO ₅ (aluminum titanate) sintered body has the characteristics of low thermal expansion coefficient, excellent heat resistance strength, and low thermal conductivity. It is used as a heat insulating material used under temperature conditions, for example, as a wall member provided on a wall surface of a passage through which combustion gas passes in an automobile engine.

Conventionally, as one of the methods for producing the material powder used in the method for producing an Al ₂ TiO ₅ sintered body, Al ₂ O ₃ powder and TiO ₂ powder are mixed, and this mixed powder is temporarily used. A method is adopted in which baking synthesis is performed to cause a solid phase reaction, and then the synthesized powder is crushed (blended).

[0004]

By the way, Al ₂ Ti
The O ₅ sintered body undergoes thermal decomposition under the influence of ambient temperature during use, and a part thereof is decomposed into TiO ₂ and Al ₂ O ₃ . Especially Al ₂
Thermal decomposition is likely to occur when the TiO ₅ sintered body is used under a temperature condition of around 1000 ° C. Al ₂ TiO ₅ is TiO
_When decomposed into ₂ and Al ₂ O ₃ , the original low thermal expansion property and heat resistance will be lost. As a result, Al ₂ TiO
₅ Members made of sintered body are not suitable for the application.

For example, when a heat insulating member made of an Al ₂ TiO ₅ sintered body is used, if Al ₂ TiO ₅ decomposes into TiO ₂ and Al ₂ O _{3 under} the influence of ambient temperature, it is necessary as a heat insulating member. The above properties are lost and it cannot be used as a heat insulating member.

Therefore, in the conventional production of Al ₂ TiO ₅ sintered bodies, various sintering aids added to the powder may be combined in order to improve low thermal expansion, heat resistance strength and thermal decomposition stability. Being tried.

However, when Al ₂ TiO ₅ is provided with a sufficiently low thermal expansion property and heat resistance strength by the method using this sintering aid, sufficient thermal decomposition stability may not be obtained. .

Therefore, in the method for producing the above Al ₂ TiO ₅ sintered body, it is necessary to control the characteristics of the synthetic raw material powder in order to achieve both low thermal expansion property, heat resistance strength and thermal decomposition stability. become.

The present invention has been made in view of the above circumstances, and provides a manufacturing method capable of obtaining an aluminum titanate sintered body having sufficient low thermal expansion and heat resistance and sufficient thermal decomposition stability. The purpose is to do.

[0010]

Means and Actions for Solving the Problems The inventors of the present invention have conducted various studies on a method for obtaining a required Al ₂ TiO ₅ sintered body, and as a result, the following has been found.

The inventor has calcined and mixed a mixed powder of Al ₂ O ₃ powder and TiO ₂ powder to cause a solid phase reaction, and then crushes (mixes) the synthesized powder to obtain Al ₂ Ti.
In the method of obtaining O ₅ powder, Al ₂ O ₃ powder and TiO ₂
Attention was paid to the synthesis temperature when calcination-synthesizing the mixed powder with the _two powders.

Then, several kinds of Al ₂ TiO ₅ powders were produced by calcination synthesis at different synthesis temperatures, and a sintered body was produced by using each of these several types of powders. Next, several kinds of Al ₂ TiO ₅ sintered bodies produced were tested for low thermal expansion, heat resistance and thermal decomposition stability.

As a result, it was found that the temperature at the time of calcination synthesis affects the thermal decomposition stability of the sintered body in the method for producing powder. It was also found that when the temperature during calcination synthesis is within a certain range, sufficient thermal decomposition stability can be obtained in addition to low thermal expansion and heat resistance, and the synthesis temperature is 1400 ° C or higher. .

The present invention has been made based on such knowledge. That is, the method for producing an Al ₂ TiO ₅ sintered body is an Al ₂ TiO ₅ powder obtained by mixing Al ₂ O ₃ powder and TiO ₂ powder and calcining and synthesizing the mixed powder at a temperature of 1400 ° C. or higher. Is used.

In the method for producing a sintered body of the present invention, first, TiO 2
₂ powder and Al ₂ O ₃ powder are mixed, this mixed powder is calcined and synthesized to cause a solid phase reaction, and then the synthesized powder is crushed (blended) to prepare a material powder. Ti
The mixing ratio of the O ₂ powder and the Al ₂ O ₃ powder is 1 mol: 1 mol. In this method, calcination synthesis is 1400
℃, preferably 1500 ℃, more preferably 1560
Perform at a temperature above ℃. A sintering aid is added to the powder that is calcined and synthesized. As the sintering aid to be added, MgO,
Examples thereof include SiO ₂ .

Next, a molded body is molded from the obtained material powder. Next, the obtained molded body is sintered to obtain Al ₂ TiO _2.
5 Manufacture a sintered body. This sintering is performed by atmospheric pressure sintering. The sintering temperature is 1450 ° C to 1600 ° C.

The obtained Al ₂ TiO ₅ sintered body has excellent low thermal expansion property and heat resistance strength, and further has sufficient thermal decomposition stability because thermal decomposition during use is suppressed to a low rate. is doing. Conventionally, Al ₂ TiO ₅ sintered body is about 1
When used under the temperature condition of passing through the temperature range of 000 ° C., the rate of thermal decomposition was high, but the Al ₂ TiO ₅ sintered body produced according to the present invention shows a higher rate of thermal decomposition in this area. It can be kept extremely low.

The Al ₂ TiO ₅ sintered body of the present invention is used as a heat insulating material used under severe temperature conditions, for example, as a wall member provided on the wall surface of a passage for passing combustion gas in an automobile engine.

[0019]

EXAMPLE 1 mol of Al ₂ O ₃ powder and TiO ₂ powder:
Wet mixing was performed at a ratio of 1 mol. The obtained mixed powder was calcined and synthesized in the atmosphere at a temperature of 1300 ° C. to 1600 ° C. for 2 hours to obtain an Al ₂ TiO ₅ powder. This Al
₂ TiO ₅ powder was adjusted to have an average particle size of 1,5 μm to 2,0 μm, and then the powder was mixed with MgO 2 wt% as a sintering aid,
4 wt% of SiO ₂ was added.

Next, Al ₂ TiO ₅ powder is pressed to form a compact having a size of 50 mm × 50 mm × 6 mm, and the compact is heated in the air at a temperature of 1450 to 1550 ° C. for 2 minutes.
It sintered by time and the sintered compact was obtained.

Tests were carried out on the obtained sintered body to examine the thermal expansion characteristics, strength, and thermal decomposition characteristics.
In the test for investigating the thermal expansion characteristics, the history of the thermal expansion curve at room temperature to 1000 ° C. heating and cooling was investigated. The strength was measured by the 3-point bending test method. The thermal decomposition characteristics were examined for the ratio of decomposition of Al ₂ TiO ₅ into TiO ₂ and Al ₂ O ₃ after heating the sintered body at a temperature of 1000 ° C. for 100 hours in the air. The results of these tests are shown in Table 1.

[0022]

[Table 1]

The relationship between the material powder synthesis temperature, the sintering temperature of the sintered body, and the thermal decomposition characteristics of the sintered body is shown in the diagram of FIG. The relationship between the strength of the bonded body is shown in the diagram of FIG. 2, and the relationship between the material powder synthesis temperature, the sintering temperature of the sintered body and the thermal expansion characteristics of the sintered body is shown in the diagram of FIG.

As a result of a test for examining each of these characteristics, Al ₂
When the calcination synthesis temperature in the step of producing Al ₂ TiO ₅ powder is 1400 ° C. or higher, the TiO ₅ sintered body is
It can be seen that, in addition to excellent thermal expansion characteristics and strength, thermal decomposition characteristics are also excellent. Further, it is found that the sintering temperature is preferably around 1500 ° C.

[0025]

As described above, according to the method for producing an aluminum titanate sintered body of the present invention, a mixed powder of Al ₂ O ₃ powder and TiO ₂ powder is calcined and synthesized at a temperature of 1400 ° C. or higher. By using the Al ₂ TiO ₅ powder obtained as described above, it is possible to obtain an aluminum titanate sintered body having sufficient low thermal expansion and heat resistance and sufficient thermal decomposition stability.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a material powder synthesis temperature, a sintering temperature of a sintered body, and a thermal decomposition characteristic of the sintered body.

FIG. 2 is a diagram showing the relationship between the material powder synthesis temperature, the sintering temperature of the sintered body, and the strength of the sintered body.

FIG. 3 is a diagram showing the relationship between the material powder synthesis temperature, the sintering temperature of the sintered body, and the thermal expansion characteristics of the sintered body.

Claims (1)

[Claims] 1. A titanic acid characterized by using Al ₂ TiO ₅ powder obtained by mixing Al ₂ O ₃ powder and TiO ₂ powder and calcining and synthesizing the mixed powder at a temperature of 1400 ° C. or higher. Manufacturing method of aluminum sintered body.