JPS6369757A - Composite ceramics and manufacture - Google Patents

Abstract

(57) [Abstract] 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 composite ceramics and a method for producing the same, and in particular, 51gN4-Si which has excellent oxidation resistance, airtightness, and toughness.
This invention relates to a C-based composite material and its manufacturing method.

[Conventional technology]

Generally used as engineering ceramics suitable for structural materials such as engines and turbines.

S 1sNi and S i C are considered. A composite ceramic of 5iaN4 and SiC, in particular, a sintered body in which either one or both of 51gN4 and SiC is produced by a reaction sintering method is 5i8Nt.

A sintered body made of SiC alone has better thermal shock resistance, and is attracting attention as a structural or functional material.

The conventional manufacturing method of 5isN+-SiC composite material is a method using an organic Si polymer compound (Japanese Patent Application Laid-Open No. 56-20574).
(Japanese Patent Laid-Open No. 58-8816) and a method of reaction sintering in a nitrogen atmosphere using Si powder and SiC powder as starting materials (Japanese Patent Laid-Open No. 58-8816).
These sintered bodies are porous and have a high gas permeability, have an apparent porosity of 10 to 30%, and have poor oxidation resistance, which may be inconvenient depending on the application.

A method for improving this oxidation resistance and airtightness is 2) sputtering. A method of coating the surface using a CVD method or the like is considered, but such a method requires complicated and expensive equipment, lacks mass production, and is not possible for products with complex shapes, so it is not suitable for industrial use. There wasn't.

The present inventors have conducted various studies on methods for improving oxidation resistance and airtightness that do not have the above drawbacks.

It has been found that it is sufficient to form a glass layer of 5iC)z on the surface of the SigN-SiC sintered body, and that this also improves toughness.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration oxidation resistance and airtightness, and has problems when used in the atmosphere, at high temperatures, or in areas that require airtightness.

The purpose of this research is to provide 51
An object of the present invention is to provide a gN4-SiC composite material.

[Means for Solving the Problems] The present invention provides a composite ceramic in which the Si and particles on the surface of an S1sN4-SiC composite material and the voids between the 5isN4 particles are filled with a glass phase containing SiOz as a main component; The present invention provides a method for producing composite ceramics, characterized in that the obtained Si 11N4-S i C composite material is treated at 1000 to 1300° C. in an oxygen-containing gas atmosphere.

In the sintered body of the present invention, as shown in FIG. It is 30 μm. The main component of the glass layer is 5ift and S
i, S 1aN4*5izN20, etc. are slightly mixed. This glass layer allows oxygen and 5iaN+-S
Reaction with iC-based composite material is suppressed. Therefore, the oxidation rate decreases rapidly.

In the present invention, it is important that the heat treatment temperature is 1000 to 1300°C, preferably 1100 to 1250°C. If it is lower than 1000°C, oxidation will occur on the surface and the weight will increase, but no vitreous film will be formed. Low antioxidant effect. In addition, when the temperature exceeds 1300℃, the antioxidant effect decreases to 130℃.
Although it is almost equivalent to 0°C, the thickness of the glass film becomes large and the dimensional accuracy deteriorates, which is not preferable.

In the present invention, since the 51gNa-SiC composite material has open pores (continuous pores), when subjected to heat treatment, a glassy thin film forms inside the sintered body. Si
Formed on the surface of the C particles, the bonding strength between the 51 g N4 particles and the SiC particles increases, making it possible to improve toughness. However, if the heating temperature is higher than 1000℃, 5ia
The oxidation of N+ particles becomes intense, weakening the original strength of the ceramic. Therefore, it is necessary that the temperature is 1000 to 1300°C, and within this range, strength and toughness can be improved.

In the present invention, the molding binder contains 1 to 20 parts by weight of an organic polymer compound such as polyvinyl butyral or polyethylene, an organic silicon polymer compound such as a silicon imide compound or a polysilane compound, a thermoplastic resin, a plasticizer, a lubricant, etc. However, it is preferable that the relative density of the sintered body is 80% or more.

In the present invention, 5iaN4 powder may be added to the starting material consisting of metal Si powder and SiC powder.

Appropriate amount of 5iaNi powder converts metal Si into 5i by nitriding reaction.
This is because it becomes a nucleus when changing to the sN4 phase and promotes the nitriding reaction. Also, metal Si powder.

Commercially available SiC powder and 51 g Na powder can be used as they are, or rounded particles pulverized by a mill or the like may be used.

In the present invention, the reason why the thickness of the glass phase is set to 0.5 to 50 μm is that if it is thinner than 0.5 μm, it has no effect on toughness, if it is thicker than 0.5 μm, the toughness increases, and if it is thicker than 50 μm, it is difficult to improve the toughness. Strength weakens and toughness decreases. Therefore, if the thickness is 0.5 to 50 μm, oxidation resistance and airtightness are good, and bending strength and toughness can be increased.

[Effect]

In the present invention, 5iO
By filling it with a glass phase containing z as a main component, a composite material with excellent oxidation resistance, airtightness, and high toughness can be obtained.

〔Example〕

<Example 1> 60 parts by weight of SiC powder with an average particle size of 1 μm and an average particle size of 0.
A raw material was prepared by adding 9 parts by weight of polyethylene resin as a molding aid to a mixed powder of 40 parts by weight of 9 μm metal Si powder. This raw material was molded using a mechanical press under a pressure of 10
0100O/co? , diameter 50nm at molding temperature 160℃
, and a thickness of 10 mm was molded. After decomposing and volatilizing the molding aid from this molded body,
The mixture was heated stepwise to 350° C. to obtain 51 g of Nt-SiC composite material.

This was placed in an electric furnace and treated in the atmosphere under the heat treatment conditions shown in Table 1 to obtain a sintered body. The characteristic values of the sintered body are
Shown in the table.

Next, S i l IN! after heat treatment! -S i C-based composite materials were oxidized at a temperature of 1000'C for 300 hours and 1000 hours, and the physical properties after oxidation were measured. Table 2 shows the results.

Table 1 Figure 1 shows the surface and cross-section of a sintered body after heat treatment of Nα5 of a product of the present invention. This shows that the surface is completely covered with an oxide film. Also, it can be seen from the cross-sectional view that the oxide film fills the pores on the surface.

From Table 2, it can be seen that the products of the present invention have excellent oxidation resistance, high bending strength, and excellent airtightness.

<Example 2> Fracture toughness value Kyc was determined for the sample obtained in Example 1 after oxidation at 1000° C. (in the atmosphere), and Krc was measured by the notched beam method. The results are shown in Table 3.

Table 3 This shows that the products of the present invention have excellent toughness.

<Example 3> Si sNa -S obtained in Example 1 before heat treatment
The iC-based composite was oxidized at 1200°C for varying oxidation times from several minutes to several hours, and the thickness of the glass phase formed on the surface was reduced to 0.
Various composite materials having a thickness of 3 μm to 100 μm were prepared, and the fracture toughness value 2 and bending strength were measured.

The results are shown in Table 4. This shows that the product of the present invention has excellent bending strength and toughness.

Table 4 〔Effect of the invention〕 According to the present invention, oxidation resistance, airtightness, and toughness are improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the surface (a) and cross section (b) of a 51gN4-SiC composite material produced by the method of the present invention. 1... SiC particles, 2... 5iaN4 particles, 3 mountain voids, 4... oxide film (glass layer).

Claims (1)

[Claims] 1. In the Si_8N_4-SiC composite material, the voids between the SiC particles on the surface and the Si_3N_4 particles are
Composite ceramics characterized by being filled with a glass phase whose main component is O_2. 2. The composite ceramic according to claim 1, wherein the thickness of the glass phase on the surface is 0.5 to 50 μm. 3. A method for producing composite ceramics, which comprises heat-treating a Si_3N_4-SiC-based composite material at a temperature of 1000 to 1300°C in an oxygen-containing gas atmosphere.