Fine porosity low-microcracked ceramic honeycombs and methods thereof
Disclosed are high-porosity cordierite honeycomb substrates having fine pore size, narrow pore size distribution, little or no microcracking, and a high thermal shock resistance. The porous ceramic honeycomb substrates generally include a primary cordierite ceramic phase as defined herein. Also disclosed are methods for making and using the cordierite substrates.
1. A method for making a porous ceramic honeycomb body, the method comprising:
providing a plasticized ceramic forming precursor batch composition, comprising:
an inorganic powder batch composition comprising:
an inorganic powder batch mixture comprising a magnesium source having a median particle size diameter D 50 less than or equal to 15 microns, an alumina forming source having a median particle size diameter D 50 less than or equal to 8 microns, and a silica forming source having a median particle size diameter D 50 less than or equal to 15 microns
at least 0.5 wt % of at least one glass forming metal oxide source comprising an yttrium source, a lanthanum source, or a combination thereof;
an organic binder;
a pore-forming agent present in a sufficient amount to achieve a porosity of at least 50% in the resulting fired honeycomb body; and
a liquid vehicle present as a super addition in an amount of from 15 to 60 wt % of the inorganic powder batch composition;
forming a honeycomb green body from the precursor batch composition; and
firing the honeycomb green body to form the porous ceramic honeycomb body comprising a primary cordierite ceramic phase having a median pore size diameter d 50 less than 7.9 microns; an elastic modulus ratio E 900° C. /E 25° C . of not greater than 1.01; and a thermal shock parameter (TSP) of at least 450° C.; where TSP is (MOR 25° C. /E 25° C. )(CTE 500-900° C. ) −1 , MOR 25° C. /E 25° C . is at least 0.14×10 −2 (0.14%), MOR 25° C . is the modulus of rupture strength at 25° C., E 25° C . is the Young's elastic modulus at 25° C., E 900° C . is the elastic modulus at 900° C. measured during heating, and CTE 500-900° C . is the high temperature thermal expansion coefficient at from about 500° C. to 900° C. during heating.
2. The method of claim 1 , wherein the pore-forming agent is a particulate material having a median particle size diameter D 50 less than or equal to 20 microns.
3. The method of claim 1 , wherein the plasticized ceramic forming precursor batch composition, comprises:
an inorganic powder batch mixture comprising talc having a median particle size diameter D 50 less than or equal to 10 microns, an alumina forming source having a median particle size diameter D 50 less than or equal to 8 microns, and a silica forming source having a median particle size diameter D 50 less than or equal to 10 microns;
at least 0.5 wt. % of a glass forming yttrium oxide source; and
the pore forming agent having a median particle size diameter D 50 less than or equal to 15 microns.