Cement to make thermal shock resistant ceramic honeycomb structures and method to make them
View Patent ↗A ceramic honeycomb structure comprised of at least two separate smaller ceramic honeycombs that have been adhered together by a cement comprised of inorganic fibers and a binding phase wherein the smaller honeycombs and fibers are bonded together by the binding phase which is comprised of an amorphous silicate, aluminate or alumino-silicate glass and the cement has at most about 5% by volume of other inorganic particles. The cement may be made in the absence of other inorganic and organic additives while achieving a shear thinning cement, for example, by mixing oppositely charged inorganic binders in water together so as to make a useful cement for applying to the smaller honeycombs to be cemented.
1. A ceramic honeycomb structure comprised of at least two separate smaller ceramic honeycombs that have been adhered together by a cement comprised of inorganic fibers and a binding phase wherein the smaller honeycombs and fibers are bonded together by the binding phase which is comprised of an amorphous silicate, aluminate or alumino-silicate glass and the cement has at most about 5% by volume of other inorganic particles and the inorganic fibers have an average length by number from 100 micrometers to 1000 micrometers, wherein the binding phase has therein a crystalline phase that has a discontinuous thermal expansion coefficient from 0° C. to 1400° C.
2. The ceramic honeycomb structure of claim 1 , wherein the inorganic fibers have a length distribution such that at least 90% of the fibers have a length between 100 to 1000 micrometers.
3. The ceramic honeycomb structure of claim 1 , wherein the cement is in the absence of any other inorganic particles.
4. The ceramic honeycomb structure of claim 3 , wherein at least 90% by number of the fibers have a length between 100 micrometers and 1000 micrometers.
5. The ceramic honeycomb structure of claim 4 , wherein at least 95% by number of the fibers have a length between 100 micrometers and 1000 micrometers.
6. The ceramic honeycomb structure of claim 1 , wherein the average length of the fibers is from 100 to 500 micrometers.
7. The ceramic honeycomb structure of claim 6 , wherein the average length is at least 150 micrometers.
8. The ceramic honeycomb structure of claim 7 , wherein the average length is at most 400 micrometers.
9. The ceramic honeycomb structure of claim 1 , wherein the crystalline phase is quartz, tridymite, christobalite or combination thereof.
10. The ceramic honeycomb structure of claim 1 , wherein the fibers are alkaline earth alumino-silicate fibers, alkaline earth silicate or combination thereof.
11. The ceramic honeycomb structure of claim 10 , wherein the fibers are alkaline earth alumino-silicate fiber.
12. The ceramic honeycomb structure of claim 11 , wherein the alkaline earth of the alkaline earth alumino-silicate fiber is Mg.
13. The ceramic honeycomb structure of claim 12 , wherein the smaller honeycombs are comprised of mullite.
14. The ceramic honeycomb structure of claim 13 , wherein the smaller honeycombs are acicular mullite.
15. The ceramic honeycomb structure of claim 1 , wherein the coefficient of thermal expansion of the cement is within about ten percent (10%) of 5.5 ppm/° C.
16. The ceramic honeycomb structure of claim 1 , wherein the fiber contains zirconium.