Compositions: ceramic – Ceramic compositions – Refractory
Patent
1990-10-11
1991-11-12
Dixon, Jr., William R.
Compositions: ceramic
Ceramic compositions
Refractory
501121, 501122, 501128, 428328, C04B 3518, C04B 3520, C04B 3522
Patent
active
050647903
ABSTRACT:
This invention relates to processes for preparing ceramic articles which are especially suited for electronic applications. The process involves taking a shaped article which has been formed from a magnesium exchanged zeolite powder, the zeolite selected from the group consisting of philipsite, harmotome, gismondine, zeolite B, zeolite ZK-19 and zeolite W, and sintering it at a temperature of about 1,000.degree. C. to 1,350.degree. C. for about 1 to about 6 hours. The magnesium exchanged zeolite has a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of about 2.3 to about 2.8 and a sodium content less than 0.5 weight percent. The ceramic article that is formed has a substantially crystalline cordierite phase and has a density of at least 90% of its theoretical density. A preferred process involves calcining the magnesium exchanged zeolite powder at a temperature of about 600.degree.-800.degree. C. to collapse the zeolite framework and give upon sintering a cordierite ceramic article which is substantially crack free. A preferred magnesium exchanged zeolite is magnesium exchanged zeolite B. This invention also relates to a substantially crack free and crystalline cordierite ceramic article, the cordierite represented by the empirical formula 2.0.+-.0.1 MgO:2 Al.sub. 2 O.sub.3 :5.0.+-.0.2 SiO.sub.2 and has an average grain size of about 10 to about 500 nanometers.
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J. R. Moyer et al., "Synthesis of Oxide Ceramic Powders by Aqueous Coprecipitation", Materials Research Soc. Symposium, 73, p. 117 (1986).
D. W. Breck, Zeolite Molecular Sieves, J. Wiley & Sons, N.Y. (1974), pp. 483-496.
Bedard Robert L.
Flanigen Edith M.
Dixon Jr. William R.
Green Anthony J.
McBride Thomas K.
Molinaro Frank S.
Snyder Eugene I.
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