Abstract: A honeycomb structure having crystal phases of aluminum titanate and mullite, which is obtained by sintering a honeycomb molding made of a mixture comprising titania powder, alumina powder, silica powder and mullite powder, the mixture containing 1-10 parts by mass of silica powder and 5-30 parts by mass of mullite powder per the total amount (100 parts by mass) of the titania powder and the alumina powder, and the mullite powder containing 40-60% by mass of particles having particle sizes of 10-50 gm and 5-30% by mass of particles having particle sizes of 3 gm or less, and its production method.

Abstract: A method for producing a ceramic honeycomb filter having predetermined plugs comprising immersing the end portions of a ceramic honeycomb structure having large numbers of flow paths, with its end surface covered with a mask provided with holes only at positions corresponding to the predetermined flow paths, in a plugging material slurry, so that the plugging material slurry is introduced into the end portions of the predetermined flow paths, and removing plugging material protrusions formed in the flow paths that should not be plugged.

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: A ceramic honeycomb structure having a large number of flow paths partitioned by porous cell walls, the cell walls comprising at least main crystals of aluminum titanate, in which MgO and SiO2 are dissolved to form a solid solution, and glass phases, the glass phases containing 40-80% by mass of SiO2 and 1-20% by mass of MgO, the average size of the glass phases being 30 ?m or less in a cross section of the cell walls, and the area ratio of the glass phases to the total area of the main crystals of aluminum titanate and the glass phases being 2-12% in a cross section of the cell walls, and its production method.

Abstract: A method for producing an aluminum-titanate-based ceramic honeycomb structure comprising blending TiO2 source powder and Al2O3 source powder with a TiO2/Al2O3 molar ratio of 45/55 to 55/45, and a sintering aid and/or a molding aid to prepare a moldable material, extrusion-molding the moldable material, and drying and sintering the resultant extrudate, the TiO2 source powder having a particle size distribution (mass-based frequency distribution relative to [log(particle size)]), in which both the maximum frequency in a particle size range of 0.2-4 ?m and the maximum frequency in a particle size range of 10-100 ?m are larger than those in other ranges than the two particle size ranges.

Abstract: A ceramic honeycomb structure having a large number of flow paths partitioned by porous cell walls, the cell walls comprising at least main crystals of aluminum titanate, in which MgO and SiO2 are dissolved to form a solid solution, and glass phases, the glass phases containing 40-80% by mass of SiO2 and 1-20% by mass of MgO, the average size of the glass phases being 30 ?m or less in a cross section of the cell walls, and the area ratio of the glass phases to the total area of the main crystals of aluminum titanate and the glass phases being 2-12% in a cross section of the cell walls, and its production method.

Abstract: A ceramic honeycomb filter comprising a honeycomb structure having large numbers of flow paths partitioned by porous cell walls, and plugs alternately formed in the flow paths on the exhaust-gas-inlet and outlet sides, the outlet-side plugs having porosity of 65% or less, and the upstream-side end surfaces of the outlet-side plugs having surface roughness Ra of 13-50 ?m.

Abstract: A method for producing a honeycomb filter from a honeycomb structure having large numbers of flow paths partitioned by cell walls, comprising inserting a tubular member into each of the flow paths, and injecting a plugging material into each of the flow paths from the tubular member to form a plug in each of the flow paths at a position separate from the end surface of the honeycomb structure, the tubular member having an outer diameter that is 40-90% of the opening size of the flow path, the plugging material comprising at least a ceramic material having a maximum particle size that is 85% or less of the inner diameter of the tubular member, and an average particle size of 1 ?m or more.

Abstract: A ceramic honeycomb structure having a large number of flow paths partitioned by porous cell walls, the cell walls comprising at least main crystals of aluminum titanate, in which MgO and SiO2 are dissolved to form a solid solution, and glass phases, the glass phases containing 40-80% by mass of SiO2 and 1-20% by mass of MgO, the average size of the glass phases being 30 ?m or less in a cross section of the cell walls, and the area ratio of the glass phases to the total area of the main crystals of aluminum titanate and the glass phases being 2-12% in a cross section of the cell walls, and its production method.

Abstract: A ceramic honeycomb structure having porous cell walls defining large numbers of flow paths, the cell walls having porosity of 55-70%, an average pore diameter of 10-40 ?m, a concave area ratio CR (projected area ratio of portions lower than an average surface determined from cell wall surface roughness by a least square method) of 0.32-0.6, and an average concave depth Hconcave (average depth of portions lower than the average surface) of 0.02-0.1 mm.

Abstract: A method for producing a ceramic honeycomb filter having predetermined plugs comprising immersing the end portions of a ceramic honeycomb structure having large numbers of flow paths, with its end surface covered with a mask provided with holes only at positions corresponding to the predetermined flow paths, in a plugging material slurry, so that the plugging material slurry is introduced into the end portions of the predetermined flow paths, and removing plugging material protrusions formed in the flow paths that should not be plugged.

Abstract: A honeycomb structure having a crystal phase composed of aluminum titanate and mullite, which is obtained by sintering a honeycomb molding made of a mixture comprising titania powder, alumina powder, silica powder and mullite powder, the mixture containing 1-10 parts by mass of silica powder and 5-30 parts by mass of mullite powder per the total amount (100 parts by mass) of the titania powder and the alumina powder, and the mullite powder containing 40-60% by mass of particles having particle sizes of 10-50 ?m and 5-30% by mass of particles having particle sizes of 3 ?m or less, and its production method.

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: An apparatus for cleaning an exhaust gas containing nitrogen oxide and particulate matter and discharged from a diesel engine, wherein the apparatus comprises a porous ceramic honeycomb filter and an SCR catalytic converter in this order from upstream, wherein the honeycomb filter has pluralities of flow paths partitioned by porous cell walls and a catalyst supported by the porous cell walls, with desired flow paths sealed by plugs, and wherein at least one plug on the side of an exhaust gas inlet is separate inward from an exhaust gas inlet end. A ratio D/V of the diameter D (mm) of the honeycomb filter to the displacement V (liter) of the diesel engine is preferably 15 mm/liter or more. The honeycomb filter and an SCR catalytic converter are preferably contained in one case.

Abstract: A ceramic honeycomb structure comprising a ceramic honeycomb body comprising axial grooves on its periphery and cell walls constituting a larger number of flow paths inside the grooves, and a peripheral wall layer covering the grooves, wherein there are stress release portions at least partially in the peripheral wall layer and/or between the peripheral wall layer and the grooves. The thermal expansion coefficient of the peripheral wall layer is preferably smaller than those of the cell walls in a radial direction. The peripheral wall layer is preferably formed on the ceramic honeycomb body formed by removing a peripheral wall from a ceramic green body, before or after firing the ceramic honeycomb body.

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: A ceramic honeycomb filter comprising a honeycomb structure having large numbers of flow paths partitioned by porous cell walls, and plugs alternately formed in the flow paths on the exhaust-gas-inlet and outlet sides, the outlet-side plugs having porosity of 65% or less, and the upstream-side end surfaces of the outlet-side plugs having surface roughness Ra of 13-50 ?m.

Abstract: A method for producing an aluminum-titanate-based ceramic honeycomb structure comprising blending TiO2 source powder and Al2O3 source powder with a TiO2/Al2O3 molar ratio of 45/55 to 55/45, and a sintering aid and/or a molding aid to prepare a moldable material, extrusion-molding the moldable material, and drying and sintering the resultant extrudate, the TiO2 source powder having a particle size distribution (mass-based frequency distribution relative to [log(particle size)]), in which both the maximum frequency in a particle size range of 0.2-4 ?m and the maximum frequency in a particle size range of 10-100 ?m are larger than those in other ranges than the two particle size ranges.

Abstract: A ceramic honeycomb structure comprising a ceramic honeycomb body comprising axial grooves on its periphery and cell walls constituting a larger number of flow paths inside the grooves, and a peripheral wall layer covering the grooves, wherein there are stress release portions at least partially in the peripheral wall layer and/or between the peripheral wall layer and the grooves. The thermal expansion coefficient of the peripheral wall layer is preferably smaller than those of the cell walls in a radial direction. The peripheral wall layer is preferably formed on the ceramic honeycomb body formed by removing a peripheral wall from a ceramic green body, before or after firing the ceramic honeycomb body.

Abstract: A ceramic honeycomb filter comprising pluralities of ceramic honeycomb structures each having large numbers of flow paths partitioned by cell walls, which are bonded in the direction of the flow paths, predetermined flow paths being sealed by plugs, plugs formed at one end of at least one honeycomb structure being bonded to at least part of plugs formed at one end of a honeycomb structure adjacent to the end of this honeycomb structure.