JPH0816031B2 - Ceramic composite and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic composite excellent in high temperature strength and toughness and a method for producing the same.

[Prior Art] Conventionally, fine ceramics have been expected as a high-temperature structural material for ceramics engines, for example, because they have excellent toughness and their characteristic deterioration at high temperatures is small. However, such fine ceramics are still insufficient in reliability for practical use, and it is necessary to improve their high temperature characteristics and toughness.

Various methods have been studied for such purposes, and in particular, research has been conducted on fiber composites produced by mixing various fibers in ceramics with various compositions. (See Japanese Patent Publication No. 60-35316) Above all, the development of a method called whiskers for strengthening by mixing a fibrous single crystal has been rapidly advanced.

[Problems to be Solved by the Invention] When the fine ceramics and the fibers are compounded in the conventional method, it becomes difficult to sinter the ceramics, and the strength, high temperature characteristics and toughness expected of the original ceramics matrix can be obtained. It's difficult.

For this reason, in the prior art, the hot pressing method had to be used as the sintering method. However,
The hot press has a problem that the manufacturing process is complicated and the cost required therefor is very high.

[Means for Solving the Problems] As a result of various studies in view of the above problems, the present inventors have found that an intervening layer is present between the ceramic matrix and the ceramic fibers to form the matrix and the fibers. It has been found that the strength of the interface is controlled and the high temperature strength and toughness are significantly improved.

That is, the present invention is a ceramics composite in which ceramics fibers are dispersed in a ceramics matrix,
There is an intervening layer at the interface between the ceramic fiber and the ceramic matrix, and a strong bond is made.The ceramic matrix is Si ₃ N ₄ , SiC, ZrO ₂ , Al ₂ O ₃ , or AlN, and the ceramic fiber is Si. _{It is} a whisker of ₃ N ₄ , SiC, or AlN, and the intervening layer is an oxide of any of Al, Si, Mg, and Group IIIb elements.

The intervening layer serves to obtain the adhesive strength between the ceramic fiber and the ceramic matrix, which cannot be obtained only by the ordinary compounding.

To obtain the composite of the present invention, Si ₃ N ₄ , SiC,
After the ceramic fibers, which are either whiskers of AlN, are precipitated from the vapor phase, the intervening layer, which is an oxide of any of Al, Si, Mg, and IIIb elements, is precipitated from the vapor phase on the ceramic fibers. , And Si ₃ N ₄ , SiC, ZrO ₂ , Al
_A method for producing a ceramic composite characterized by precipitating a ceramic matrix component, which is either ₂ O ₃ or AlN, from a gas phase, repeating the steps to obtain a preform, and densifying the preform by heating. To use.

The formation of the intervening layer by vapor-phase deposition has a great effect on maintaining the interface structure between the fiber and the matrix, and thus brings about an effect of excellent high temperature strength and toughness. In particular, a method of vapor-depositing fibers, an intervening layer, and a matrix, repeating such steps to obtain a preform, and heating and densifying the preform is more effective.

Example Next, an example will be described.

Example 1 SiC whiskers (average diameter 0.2 μ, aspect ratio 50) were placed in a CVD apparatus, and Al ₂ O ₃ was added to 0.02 μ by the CVD method.
Coated. Then, Al ₂ O ₃ powder having an average particle size of 0.5 μ was mixed with this using ultrasonic waves.

The obtained mixed powder was sintered by hot pressing at 1700 ° C. for 2 hours under a pressure of 200 kg / cm ^{2 in} a vacuum.

The Charpy impact value of the obtained sintered body was 0.1 Kgm / cm ^2, which was 5 times the impact value of the sintered body in which the fibers were not coated with Al ₂ O ₃ .

Example 2 SiC whiskers were grown on a carbon substrate in a CVD apparatus by using the CVD method. The reaction used was an iron catalyst with silicon tetrachloride and methane. Grown SiC
The surface of the whiskers was coated with Al ₂ O ₃ as in Example 1, and subsequently, metal Si was vapor-phase deposited in the whiskers by the CVD method. Repeat the above steps in the same device
A preform of Si-SiC whiskers was synthesized. The obtained preform was reaction-sintered at around 1400 ° C in N ₂ gas flow,
An inventive composite of Si ₃ N ₄ —SiC whiskers was obtained.

Obtained Charpy impact value of the complex 0.07Kgm / cm ² at 0.02Kgm those which do not contain whiskers / cm ^2, compared to 0.04Kgm / cm ² but containing whiskers to be surface treated, is greatly improved There is.

In addition to the above examples, Si ₃ N ₄ , SiC, AlN whiskers and A
l ₂ O ₃ , SiO ₂ , MgO, Sc ₂ O ₃ , Y ₂ O ₃ , intervening layers of other group III oxides and Si ₃ N ₄ , SiC, ZrO ₂ , Al ₂ O ₃ and AlN matrix The effectiveness of the present invention was confirmed also in a combination complex other than the above-mentioned examples.

[Advantages of the Invention] The present invention significantly improves the strength of the interface between the fiber and the matrix in the fiber reinforced ceramics and is excellent in high temperature strength and toughness, and is suitable for high temperature structural materials such as ceramics engines. The material is obtained.

Claims (2)

[Claims] 1. A ceramic composite in which ceramic fibers are dispersed in a ceramic matrix, an intervening layer is present at the interface between the ceramic fibers and the ceramic matrix, and a strong bond is formed, and the ceramic matrix is Si ₃ N ₄ , SiC. , ZrO ₂ , Al ₂ O ₃ , or AlN,
A ceramic composite, wherein the ceramic fibers are whiskers of any one of Si ₃ N ₄ , SiC, and AlN, and the intervening layer is an oxide of any of Al, Si, Mg, and IIIb group elements. 2. A ceramic fiber, which is a whisker of Si ₃ N ₄ , SiC, or AlN, is deposited from a vapor phase on a substrate, and then an oxide of any of Al, Si, Mg, and Group IIIb elements. And depositing an intervening layer that is from the vapor phase on the ceramic fibers, and depositing a ceramic matrix component that is any one of Si ₃ N ₄ , SiC, ZrO ₂ , Al ₂ O ₃ , and AlN from the vapor phase. A method for producing a ceramic composite, comprising repeating a process to obtain a preform, and heating and densifying the preform.