Sealing frits

Details Sealing frits Sealing frits

1999-07-23

2001-09-18

Sample, David R (Department: 1755)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S006000, C501S015000, C501S017000, C501S026000, C501S069000, C501S072000

Reexamination Certificate

active

06291092

ABSTRACT:

TECHNICAL FIELD
This invention relates to sealing frits such as alkali-zinc silicate frits. More specifically, the frits are sealing frits for solid oxide fuel cells (SOFC).
BACKGROUND ART
Frist which seal in the temperature range of 600°-1000° C. represent an intermediate class of materials between the B
2
O
3
- or P
2
O
5
-based frits used for low temperature sealing of many commerical glass products and the diversifying frits used for high temperature joining of advanced ceramic, structural components. The low temperature frits are used at temperatures below 600° C. for sealing products such as cathode ray tubes (CRT), light bulbs and the like. The diversifying high temperature frits are used at temperatures above 1,000° C. to produce articles which may embody high temperature, fiber-reinforced, structural ceramics.
A very old product in the intermediate temperature range of sealing is a ZnO—B
2
O
3
—SiO
2
frit. Another is a Li
2
O-modified, ZnO—AI
2
O
3
—SiO
2
frit designed for use between 900°-1,000° C. Frits that seal in the intermediate range of 600°-800° C. are important in many industrial applications. The need for such frits became evident through requests for sealant frits for solid oxide fuel cells (SOFC).
DISCLOSURE OF INVENTION
In response to the demands of the market place, we have invented a class of alkali-zinc-silicate frits that produce seals in the intermediate temperature range of 600-1000. These frits are high strain point/high CTE frits that are B
2
O
3
free. They have properties that make them especially useful for planar SOFC applications. These properties are:
mechanical and chemical stability at 750°-800° during operation of the fuel cell;
sealing temperature up to 12000 ° C.;
effective barrier against the permeation of hydrogen gas; and
CTE in the range of 100-120×10
−7
/° C.
The combination of high viscosity and high coefficients of thermal expansion (CTE) is a somewhat contradictory requirement for a glass composition. Most high temperature sealing frits typically possess a combination of high viscosity and low CTE.


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