Disclosed is a honeycomb ceramic article that exhibits a primary crystalline phase of cordierite having a coefficient of thermal expansion (CTE), wherein CTE<1.5×10−7/° C. over the temperature range of about 25° C. to about 800° C.; a total porosity, P, of at least 28%, a transverse I-ratio, IT, of less than 0.92; and a pore size distribution wherein at least 60% of the total pore volume is comprised of pores having diameters between 0.5 μm and 5.0 μm. Also provided is a ceramic honeycomb article comprising a phase of cordierite and exhibiting a mean CTE<1.0×10−7/° C. (from 25 to 800° C.) in at least one direction, and 28%≦P≦33%. Methods of manufacturing ceramic articles comprising the aforementioned cordierite compositions are also disclosed.
Description
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 illustrates a graphical plot of % Porosity versus CTE according to embodiments of the present invention and comparative embodiments.
Claims
1. A ceramic honeycomb article, comprising:
a ceramic with a phase of cordierite which exhibits
a coefficient of thermal expansion in at least one direction<1.5×10−7/° C. across the temperature range from 25° C. to 800° C.;a total porosity, P, of ≧28%;an transverse I ratio, IT, of <0.92; anda pore size distribution wherein ≧60% of a total pore volume of the ceramic has a pore diameter of between 0.5 μm to 5 μm.
2. The ceramic honeycomb article of claim 1 wherein the composition consists essentially of:
from about 49 to about 53 percent by weight SiO2,from about 33 to about 38 percent by weight Al2O3, andfrom about 12 to about 16 percent by weight MgO.
3. The ceramic honeycomb article of claim 1, further comprising a mean pore diameter, d50, in the range from 2.0 μm to 4.0 μm.
4. The ceramic honeycomb article of claim 1 wherein the transverse I ratio, IT, is ≦0.90.
5. The ceramic honeycomb article of claim 1 wherein the transverse I ratio, IT, is ≦0.87.
6. The ceramic honeycomb article of claim 1 wherein the coefficient of thermal expansion is ≦1.0×10−7/° C. across the temperature range from 25° C. to 800° C.
7. The ceramic honeycomb article of claim 6 wherein the coefficient of thermal expansion is ≦0.8×10−7/° C. across the temperature range from 25° C. to 800° C.
8. The ceramic honeycomb article of claim 7 wherein the coefficient of thermal expansion is ≦0.5×10−7/° C. across the temperature range from 25° C. to 800° C.
9. The ceramic honeycomb article of claim 1 wherein P≦40%.
10. The ceramic honeycomb article of claim 1 wherein P≧30%.
11. The ceramic honeycomb article of claim 10 wherein 30%≦P≦36%.
12. The ceramic honeycomb article of claim 1 wherein P≦33%.
13. The ceramic honeycomb article of claim 1, further comprising a modulus of rupture strength, MOR, wherein MOR>300 psi for a 600/4 cell geometry.
14. The ceramic article of claim 13, further comprising a modulus of rupture strength, MOR, wherein MOR>350 psi for a 600/4 cell geometry.
15. The ceramic article of claim 14, further comprising a modulus of rupture strength, MOR, wherein MOR>400 psi for a 600/4 cell geometry.
16. The ceramic article of claim 1, further comprising d90<15 μm.
17. The ceramic article of claim 1, further comprising:
CTE≦1.0×10−7/° C.; andP≧30%.
18. A ceramic honeycomb article, comprising:
a ceramic with a phase of cordierite which exhibits
a coefficient of thermal expansion in at least one direction<1.0×10−7/° C.across the temperature range from 25° C. to 800° C.; and
a total porosity, P, of 28%≦P≦33%.
19. The ceramic honeycomb article of claim 18, wherein the composition consists essentially of:
from about 49 to about 53 percent by weight SiO2,from about 33 to about 38 percent by weight Al2O3, andfrom about 12 to about 16 percent by weight MgO.
20. The ceramic honeycomb article of claim 18, further comprising a mean pore diameter, d50, in the range from 2.0 μm to 6.0 μm.
21. The ceramic honeycomb article of claim 18, further comprising a transverse I ratio, IT, of ≦0.90.
22. The ceramic honeycomb article of claim 18, wherein the coefficient of thermal expansion is ≦0.9×10−7/° C. across the temperature range from 25° C. to 800° C.
23. The ceramic honeycomb article of claim 18, wherein the coefficient of thermal expansion is ≦0.3×10−7/° C. across the temperature range from 25° C. to 800° C.
24. The ceramic honeycomb article of claim 18, wherein the coefficient of thermal expansion is ≦−0.4×10−7/° C. across the temperature range from 25° C. to 800° C.
25. The ceramic honeycomb article of claim 18, wherein P≧30%.
26. The ceramic honeycomb article of claim 18, exhibiting a modulus of rupture strength, MOR, wherein MOR>300 psi for a 600/4 cell geometry.
27. The ceramic article of claim 18, further comprising:
CTE≦0.5×10−7/° C.; andP≧30%.
28. A method of manufacturing a ceramic honeycomb article having a sintered phase cordierite composition, comprising the steps of:
providing a plasticized cordierite precursor batch composition having
an inorganic powder batch composition containing
at least one talc source having a mean particle size of at least 8 μm and a morphology index of at least 0.30 and not more than 0.85;one or more alumina-forming sources, wherein the alumina-forming sources have a weighted average median particle size that does not exceed 5 μm; andat least 20 weight percent of an alumino-silicate source comprising at least one raw kaolin and, optionally, at least one calcined kaolin, wherein the weighted average median particle size of the kaolin+calcined kaolin mixture does not exceed 6 μm; anda binder system;forming an extruded green body from the plasticized cordierite precursor batch composition; andfiring the green body under conditions effective to convert the green body into a ceramic article comprising a sintered phase cordierite composition, wherein the sintered phase cordierite composition exhibits
a coefficient of thermal expansion, CTE, in at least one direction<1.5×10−7/° C. across a temperature range from 25° C. to 800° C.; anda total porosity, P, of ≧28%.
29. The method of claim 28, wherein the conditions effective further comprise:
i) firing the green body at a temperature of at least 1390° C. when the weighted average median particle size of the alumina-forming sources is less than 1 μm;ii) firing the green body at a temperature of at least 1400° C.; when the weighted average median particle size of the alumina-forming source is in the range of from 1 μm to 3 μm; andiii) firing the green body at a temperature of at least 1405° C. when the weighted average median particle size of the alumina-forming source is greater than 3 μm.
30. The method of claim 28, further comprising at least one dispersible alumina-forming source having a dispersed median particle size of not more than 0.5 μm.
31. The method of claim 30, wherein the dispersible alumina-forming source is present in an amount of from 1 wt % to 5 wt % of the inorganic powder batch composition.
32. The method of claim 30, wherein the dispersible alumina-forming source has a specific surface area of at least 50 m2/g.
33. The method of claim 28, wherein the talc source has a morphology index of at least 0.40 and not more than 0.80.
34. The method of claim 28, wherein the talc source has a morphology index of at least 0.50 and not more than 0.70.
35. The method of claim 28, wherein the sintered phase cordierite composition has a mean pore diameter in the range of from 2.0 μm to 6.0 μm.
36. The method of claim 28, wherein the sintered phase cordierite composition comprises:
28%≦P≦40%, andCTE<1.5×10−7/° C.
37. The method of claim 28, wherein the sintered phase cordierite composition comprises:
28%≦P≦33%, andCTE<1.0×10−7/° C.
38. The method of claim 28, wherein the plasticized cordierite precursor batch composition does not comprise a non-crystalline silica.
Patent Application
20070141301
