JPS63139057A - Manufacture of silicon nitride base ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing silicon nitride ceramics having mechanical strength that can withstand temperatures from room temperature to high temperatures.

[Conventional technology]

The mechanical strength of silicon nitride ceramics has deteriorated,
Because it has excellent oxidation resistance and wear resistance, it is expected to be used as a new structural member.

However, silicon nitride ceramics have the disadvantage that their mechanical strength significantly decreases at high temperatures, so they cannot be applied to high-temperature components.

Therefore, various attempts have been made to improve the high temperature strength of silicon nitride ceramics. For example, a method has been proposed in which At203 is used as a sintering aid and dissolved in 5i5N4 in the final sintered body so that no grain boundary glass phase remains, or a method in which the grain boundary glass layer is crystallized by heat treatment. has been done.

However, such conventional high-temperature strength improvement methods have the disadvantage that the room-temperature strength decreases as the grain boundary glass phase decreases. It has been difficult to provide high-quality ceramics.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION In view of the conventional circumstances, an object of the present invention is to provide a method for producing silicon nitride ceramics that can stably maintain excellent strength from room temperature to high temperature.

[Means for solving problems]

The method for producing silicon nitride ceramics of the present invention comprises
At least 0.1% by weight of silicon nitride powder, 0.1 to 10% by weight of group IIIa element oxide powder, and a total strength of 0.1 to 10% by weight
Alumina powder and aluminum nitride powder having a molar ratio of 0.5 to 2.0 by weight are mixed, and this mixed powder is heated to 1600 to 1850 molar ratio in a non-oxidizing atmosphere.
The sintered body was sintered at 160 °C in a non-oxidizing atmosphere.
It is characterized in that it is densified by hot isostatic pressing at 0 to 2000°C, and then heat treated at 1200 to 1600°C in a non-oxidizing atmosphere.

[For production]

In the method for producing silicon nitride ceramics of the present invention, the reason why the silicon nitride powder is 80% by weight or more is that 80% by weight or more is used.
This is because if it is less than % by weight, the properties of silicon nitride ceramics cannot be maintained due to a decrease in oxidation resistance and heat resistance.

As oxides of group IIIa elements, Y2O5, CeO2
However, if the amount added is less than 0.1% by weight, it will not be effective as a sintering aid, and if it exceeds 10% by weight, the oxidation resistance and high temperature strength will be significantly reduced.

The total amount of alumina powder and aluminum nitride powder is 0.
．． If it is less than 1% by weight, there is no effect of improving high-temperature strength, and if it exceeds 10% by weight, high-temperature strength is significantly reduced. Further, it is desirable to use the alumina powder and the aluminum nitride powder in equal molar numbers, but if the molar ratio is within the range of 0.5 to 2.0, silicon nitride ceramics with good characteristics can be obtained. Furthermore, using a polytype containing silicon oxide as aluminum nitride also stabilizes the composition and yields favorable results.

In the method of the present invention, a mixed powder obtained by mixing each of the above-mentioned powders is heated in a non-oxidizing atmosphere such as vacuum, nitrogen gas or argon gas for 30 minutes or more at <1600 to 1850°C as usual to prevent oxidation of silicon nitride. , preferably 1
Sinter for 20 minutes or more. The obtained sintered body is densified by hot isostatic pressing at 1600 to 2000°C in a non-oxidizing atmosphere. The hot isostatic pressing is preferably carried out using a nitrogen-containing gas at 100 atmospheres or more for 30 minutes or more. Finally, the dense sintered body is heated to 1200 to 1600°C in a non-oxidizing atmosphere.
By performing heat treatment preferably for 60 minutes or more, grain boundary phases whose crystallization has been delayed are crystallized.

The silicon nitride ceramic thus produced has a porosity of 2% or less and a bending strength of 80 kg/cm at room temperature.
+m2 or more and bending strength at high temperature (1200℃) is 70
kg/m2 or more, showing excellent properties.

〔Example〕

Example 1 Ila was added to α-type Si3N4 powder (average particle size 0°5 μm).
Group oxides include Y2O3, CeO2 or Gd2O3 powder (purity 99.9%, average particle size 0.5 μm), α-type At2
05 powder (average particle size: 0.5 μm) and AtN powder (purity: 99%, average particle size: 1.0 μm) were added in the proportions shown in Table 1, and mixed in a ball mill for 3 days.

The mixed powder was sintered at 1800° C. for 2 hours in nitrogen gas at 4 atmospheres. The obtained sintered body was further subjected to hot isostatic pressing at 1800°C for 1 hour in nitrogen gas at 1000 atmospheres,
Next, heat treatment was performed at 1400° C. for 10 hours in nitrogen gas.

Density (%) and bending strength at room temperature and high temperature (1200°C) (klil/++) of the obtained Si3N4 ceramics
m2) was measured and the results are shown in Table 1.

Table 1 (Note) *marks are comparative examples.

Example 2 The samples in Table 1, Table 1 of Example 1 were sintered, hot isostatically pressed (HIP) and heat treated under the conditions shown in Table 2.

The properties of each sintered body after heat treatment were measured in the same manner as in Example 1 and are shown in Table 2.

Table 2 [Effects of the Invention] According to the present invention, it is possible to provide a silicon nitride ceramic that can stably maintain excellent strength from room temperature to high temperature.

Procedural amendment dated August 24, 1988 1, Indication of the case 1985 Patent Application No. 285689λ Title of the invention Method for manufacturing silicon nitride ceramics 3, Relationship to the case by the person making the amendment Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (213) Sumitomo Electric Industries, Ltd. 4, Agent 5, Date of amendment order 6, Number of inventions increased by amendment Page 5, line 4 of the specification Add the following sentence next to "Do this for 30 minutes or more."

"It is difficult to densify this composition without hot isostatic pressing, and hot isostatic pressing is an essential requirement of the present invention."

Claims (1)

[Claims] (1) 80% by weight or more of silicon nitride powder and 0.1 to 1
0% by weight of group IIIa element oxide powder and a total amount of 0
．． Alumina powder and aluminum nitride powder having a mutual molar ratio of 1 to 10% by weight are mixed in the range of 0.5 to 2.0, and this mixed powder is heated to 1600% by weight in a non-oxidizing atmosphere.
sintered at ~1850°C, the sintered body was densified by hot isostatic pressing at 1600-2000°C in a non-oxidizing atmosphere, and then densified at 1200-16°C in a non-oxidizing atmosphere.
1. A method for producing silicon nitride ceramics, characterized by heat treatment at 00°C.