Compositions: ceramic – Ceramic compositions – Devitrified glass-ceramics
Patent
1984-02-10
1986-05-06
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Devitrified glass-ceramics
501 5, 501 10, C03C 1002, C03C 1004, C03C 1014
Patent
active
045872244
ABSTRACT:
A phase transformation-toughened glass ceramic and a process for making it are disclosed. A mixture of particulate network-forming oxide, network-modifying oxide, and zirconium oxide is heated to yield a homogeneous melt, and this melt is then heat-treated to precipitate an appreciable quantity of tetragonal zirconia, which is retained at ambient temperature to form a phase transformation-toughened glass ceramic. Nucleating agents and stabilizing agents may be added to the mixture to facilitate processing and improve the ceramic's properties. Preferably, the mixture is first melted at a temperature from 1200.degree. to 1700.degree. C. and is then heat-treated at a temperature within the range of 800.degree. to 1200.degree. C. in order to precipitate tetragonal ZrO.sub.2.
The composition, as well as the length and temperature of the heat-treatment, must be carefully controlled to prevent solution of the precipitated tetragonal zirconia and subsequent conversion to the monoclinic phase.
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Subbaro, E. C.; "Zirconia-an Overview" in Science and Technology of Zirconia, Heuer & Hobbs, eds., Am. Ceramic Soc., 1981.
Yokoishi, S. et al., "Effect of Heat Treatments for Precipitation of ZrO.sub.2 on Transparency of Glass Ceramics in the ZrO-Al.sub.2 O.sub.3 -SiO.sub.2 System", Yogyo-Kyokai-shi 88 [1] 13 (1980), pp. 13-21.
Claussen, N.; "Design of Transformation-Toughened Ceramics" in Science & Technology of Zirconia, A. H. Heuer & L. W. Hobbs, eds., Am. Ceramic Soc., 1981.
Fagherazzi, G. et al.; "A Structural Study of Metastable Tetragonal Zirconia in an Al.sub.2 O.sub.3 -ZrO.sub.2 -SiO.sub.2 -Na.sub.2 O Glass Ceramic System".
Sircar, A. et al., "Phase Equilibria in Ternary Systems Containing Zirconia Silica, IV, Na.sub.2 O-ZrO.sub.2 -SiO.sub.2 ", Trans. Brit. Ceramic Soc. V69, 131-135, 1970.
Das, C. R., "Chemical Durability of Sodium Silicate Glasses Containing Al.sub.2 O & ZrO.sub.2 ", Heuer & Hobbs, eds., Am. Ceramic Soc., 1981.
Keefer Keith D.
Michalske Terry A.
Bell Mark L.
Hightower Judson R.
McMillan Armand
Sopp Albert
The United States of America as represented by the United States
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