Abstract: A method for producing a ceramic honeycomb structure comprising aluminum titanate as a main crystal, comprising the steps of mixing titania powder, alumina powder and amorphous silica powder, the molar ratio of the titania powder to the alumina powder being 45:55 to 55:45, the amount of the amorphous silica powder being 1-10 parts by mass per 100 parts by mass of the total of the titania powder and the alumina powder, to produce a moldable material; extruding said moldable material in a honeycomb shape; drying it; and then sintering it at 1300-1700° C.

Abstract: In a ceramic honeycomb structure having large numbers of flow paths partitioned by porous cell walls, the cell walls have a porosity of 55-75%, with an average pore diameter Da of 10-30 ?m and a pore area ratio Sa of 10-30% on their surfaces, and the average length La of the pores at their openings and the average width Lb of the pores at depth La from the surfaces of the cell walls meet the condition of 1.1<Lb/La<5 in an arbitrary vertical cut surface of the cell walls. In the cordierite-based ceramic honeycomb structure, the ceramic contains Fe and a spinel, the amount of the spinel being 4% or less by an X-ray diffraction intensity ratio, and most of the spinel having particle sizes in a range of 0.01-5 ?m.

Abstract: A process for producing a ceramic honeycomb structure containing aluminum titanate as main crystals, characterized by extruding a plastic green earth consisting of 45:55 to 55:45, in molar ratio, titania powder and alumina powder, or of 100 parts by mass of the sum of such titania powder and alumina powder mixed with 1 to 10 parts by mass of amorphous silica powder so as to form a honeycomb configuration, drying the same and firing the dried extrudate at 1300° to 1700° C.

Abstract: In a ceramic honeycomb structure having large numbers of flow paths partitioned by porous cell walls, the cell walls have a porosity of 55-75%, with an average pore diameter Da of 10-30 ?m and a pore area ratio Sa of 10-30% on their surfaces, and the average length La of the pores at their openings and the average width Lb of the pores at depth La from the surfaces of the cell walls meet the condition of 1.1<Lb/La<5 in an arbitrary vertical cut surface of the cell walls. In the cordierite-based ceramic honeycomb structure, the ceramic contains Fe and a spinel, the amount of the spinel being 4% or less by an X-ray diffraction intensity ratio, and most of the spinel having particle sizes in a range of 0.01-5 ?m.

Abstract: A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through the porous partition walls to remove particulates from the exhaust gas, wherein one end of each flow path is provided with a sealer, such that sealers of the flow paths in an inlet and an outlet of the ceramic honeycomb structure in a desired pattern; wherein the partition walls have thickness of 0.1-0.5 mm and a porosity of 50-80%; wherein the porosity of the sealers is larger than that of partition walls; and wherein the depth of the sealers is 3-15 mm.

Abstract: A ceramic honeycomb filter comprising a ceramic honeycomb structure having porous partition walls defining a plurality of flow paths for flowing an exhaust gas through the porous partition walls to remove particulates from the exhaust gas, wherein one end of each flow path is provided with a sealer, such that sealers of the flow paths in an inlet and an outlet of the ceramic honeycomb structure in a desired pattern; wherein the partition walls have thickness of 0.1-0.5 mm and a porosity of 50-80%; wherein the porosity of the sealers is larger than that of partition walls; and wherein the depth of the sealers is 3-15 mm.