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High toughness ceramic composites consisting of ceramic body reinforced with metal fiber
| Details |
Inventors: Saito, Makoto; Mizoguchi, Takao;
Assignee: Kabushiki Kaisha Kobe Seiko Sho (Kobe, JP)
Primary Examiner: Dixon, Jr.; William R.
Assistant Examiner: Hunter, Jr.; James M.
Attorney, Agent or Firm: Oblon, Fisher, Spivak, McClelland & Maier
Described herein is a high toughness ceramic composite of the fiber reinforced type, comprising: metal fiber integrally anchored in a ceramic matrix and having a shape of triangular waves forming bent portions alternately on the opposite sides thereof with an angle .theta. of the bent portions in a range between 60.degree. and 165.degree., a ratio of d/H (a ratio of the amplitude H of the waves to the diameter d of the fiber) in a range between 0.025 and 0.6, and a ratio of .rho./d (a ratio of the radius of curvature .rho. at the apex of the bent portion to the fiber diameter d) greater than 1, inclusive. |
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DETAILED DESCRIPTION The brittleness which is the greatest drawback of the ceramic material means that the material is fractured by application of small energy.
It implies that a fracture is caused by a small stress and that, once a crack occurs, it will propagate easily and quickly to destruct the whole body of the material.
Since ceramics are extremely low in plastic deformability, a crack can be initiated even from a very fine defect or impurity.
In order to enhance the strength, it is necessary to prevent the occurrence of crack, that is to say, to minimize the size of defects and impurities.
The fine ceramics, which constitutes a main stream in the development of ceramics for structural materials, has been developed on the basis of this concept.
It aims at the suppression of crack initiation by enhancing the fineness and purity of ceramic raw material powders, and by the use of an HIP or hot pressing processes.
However, with the methods of this sort, the strength is still affected by impurities or defects, and the level of strength varies depending upon the effective volume of the material (because the probability of existence of crack initiation defects or the like is proportional to the effective volume).
Furthermore, no improvement has been made to eliminate the problem that when a crack, once occurs, it will immediately propagate to cause destruction of the material as a whole.
This causes the ceramic to lack reliability as a structural material.
The present invention contemplates to solve the above-mentioned problems by the provision of a high toughness ceramic composite which has a large number of metal fiber filaments intergrally anchored in a ceramic matrix.
The metal fiber filaments (FIG.
2) have a shape of alternate triangular waves consisting of alternating bent portions with an angle .
theta.
between 60.
degree.
and 165.
degree.
(Preferably in a range between 75.
degree.
and 150.
degree.
, more preferably between 90.
degree.
and 135.
degree.
), a ratio of d/H (a ratio of the height or amplitude H of the waves to the diameter d of the fiber filaments) in a range between 0
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Fuel Cells 
