Method for making cordierite honeycomb

Abstract

A sintered ceramic that exhibits an average linear coefficient of thermal expansion (25-800° C.) below about 5.0×10 ° C. , a total porosity between the range of 20% to about 30%. Furthermore, the sintered ceramic article exhibits a pore size distribution such that at least about 86% of pores are of a pore size of less than about 2 &mgr;m. Lastly, the ceramic article exhibits an interconnected pore structure with the pores exhibiting a generally elongated shape, i.e., the pores are predominately oriented with their long axis in the plane of the webs. This invention also relates to a method for producing a sintered cordierite ceramic article involving first compounding and plasticizing a cordierite-forming inorganic powder batch comprising a platy talc having median particle of size less than about 2 &mgr;m, and preferably a talc morphology index greater than about 0.75. The batch further comprises at least 4% by weight of the inorganic powder batch mixture of a dispersible Al O -forming source having a specific surface area in excess of 50 m /g and one or more of the components of kaolin, calcined kaolin, silica, and corundum, each having a median particle sizes less than 5 &mgr;m. The plasticized powder batch thus provided is next formed into a green honeycomb by extrusion through a honeycomb extrusion die and the green honeycomb is fired to a temperature and for a time sufficient to convert the green honeycomb into a crystallized cordierite ceramic article having the aforementioned properties.