Compositions: ceramic – Ceramic compositions – Refractory
Patent
1986-07-11
1989-12-19
Lander, Ferris H.
Compositions: ceramic
Ceramic compositions
Refractory
501 9, 501 12, C04B 3502
Patent
active
048883140
ABSTRACT:
The present invention relates to a cordierite (2MgO.2Al.sub.2 O.sub.3.5SiO.sub.2) type ceramic powder sintering at low-temperature defined in that its composition is: 60 to 50% SiO.sub.2, 5 to 20% MgO and 20 to 40% Al.sub.2 O.sub.3, and in that its specific surface area is not less than 50 m.sup.2 /g, this powder having a fritting temperature of less than 1,100.degree. C.
The invention also relates to a process for the preparation of this powder, which consists in preparing a mixed alcoholic solution of an aluminum and silicon salt, in preparing a solution of an alcohol-soluble magnesium salt, in mixing the two solutions, in padding a hydrolyzing agent in the form of a totally volatile weak base to the solution, which leads to the formation of a gel, in subjecting the said gel to a first thermal treatment at a temperature not exceeding 450.degree. C., and in subjecting the said powder to a second thermal treatment at a temperature of between 450.degree. C. and 900.degree. C.
By a sintering which may be carried out at a temperature lower than 950.degree. C., the powder obtained leads to dielectric ceramics which have a coefficient of expansion less than 1.10.sup.-6 C.sup.-1, and a dielectric constant less than 5.
REFERENCES:
patent: 4367292 (1983-01-01), Sano et al.
patent: 4608215 (1986-08-01), Goaczy et al.
Chem Abst., vol. 102, #14, Abst. 118404N, p. 311, 4/85, Cordierite Sinter Having Low Thermol Expansion Coefficient.
Journal of Non Crystalline Solids, vol. 63, No. 112, 2/1984, Pancrazietol Preparation of Gels in the CaO--Al.sub.2 O.sub.3 --SiO.sub.2 System from Metal Alkoxides.
Bernier Jean-Claude
Poix Paul J. L.
Rehspringer Jean-Luc
Vilmin Gabriel G. J.
Vilminot Serge
Center National De La Recherche Scientifique (C.N.R.S.)
Lander Ferris H.
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