Compositions: ceramic – Ceramic compositions – Refractory
Reexamination Certificate
1998-06-09
2001-04-17
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Refractory
C501S095200, C501S097100, C501S097200, C501S097300
Reexamination Certificate
active
06218325
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fiber-reinforced ceramic green body and a sintered ceramic article each having a high mechanical strength and a high ability to be recycled.
A slip casting method is one of the well-known methods for manufacturing green bodies, in which a slip composition (aqueous dispersion or slurry including a ceramic powder) is poured into a cavity within a mold usually made of a water-absorbing material such as plaster (gypsum), etc., and then the water component of the slip composition is absorbed by the mold to form a green body. The green body thus obtained is sintered to provide a final sintered ceramic article for practical use. The slip casting method is suitable generally for producing a ceramic green body having a complicated shape. In slip casting a slip composition, an organic binder such as polyamide, carboxymethylcellulose, methylcellulose, polyvinyl alcohol, etc. is usually added to the slip composition as disclosed in Japanese Patent Laid-Open No. 61-6172 to improve the dry strength of the green bodies. However, since the use of the organic binder results in a large shrinkage of the green body, cracking is likely to occur in the green body during releasing it from the mold or during drying it.
Alternatively, it has been proposed to add an inorganic fiber to the slip composition. For example, Japanese Patent Laid-Open No. 5-505588 teaches to add glass whiskers, and Japanese Patent Laid-Open No. 7-267737 adds inorganic fibers of aluminum oxide, silicon nitride, etc. However, the inorganic fiber is left in the ceramic article even after the sintering process and affects the properties of the final sintered ceramic article. Therefore, the type of the inorganic fiber to be suitably usable and the addition amount thereof is limited.
Further, prior to adding the inorganic fiber, a pretreatment such as pulverization, classification, etc. for making the length and diameter of the inorganic fiber uniform is required. In addition, the use of the inorganic fiber involves a problem of generating noxious dusts of the inorganic fiber and a problem of decreasing the ability to recycle defective green bodies because the inorganic fiber is difficult to be removed from the defective green bodies.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a fiber-reinforced ceramic green body having a high green strength and a high ability of recycling defective green bodies, and a sintered ceramic article manufactured by sintering the fiber-reinforced ceramic green body.
As a result of the intense research in view of the above objects, the inventors have found that the addition of a specific organic fiber to a ceramic powder improves the green strength of a resultant ceramic green body and also increases the ability of recycling the defective green bodies. The present invention has been accomplished based on this finding.
Thus, in an aspect of the present invention, there is provided a fiber-reinforced ceramic green body containing an organic fiber which is uniformly dispersed throughout the green body. In another aspect of the present invention, there is provided a sintered ceramic article manufactured by sintering the above fiber-reinforced ceramic green body.
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patent: 0436220 (1991-07-01), None
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Chemical Abstracts; 105:28740 CA, “Manufacture of Porous Ceramic Article”, Takeuchi et al., Mar. 1986.
Itoh Naoki
Koizumi Atsushi
Miki Yuuji
Birch & Stewart Kolasch & Birch, LLP
Group Karl
Honda Giken Kogyo Kabushiki Kaisha
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