A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls provided, surrounding a plurality of cells which serve as fluid through channels extending from an inflow end face to an outflow end face, and porous plugging portions provided either at the ends on the inflow end face or the outflow end face of the cells, wherein the plugging portions are composed of a porous material, the honeycomb structure has a central region and a circumferential region, and a ratio of an area of the circumferential region with respect to that of the central region ranges from 0.1 to 0.5, a plugging length L1 in the cell extending direction of a central plugging portion in the central region is larger than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 7 to 9 mm, and L2 from 3 to 6 mm.

A honeycomb filter includes a pillar-shaped honeycomb structure having porous partition walls provided, surrounding a plurality of cells which serve as fluid through channels extending from an inflow end face to an outflow end face, and porous plugging portions provided either at the ends on the inflow end face or the outflow end face of the cells, wherein the plugging portions are composed of a porous material, the honeycomb structure has a central region and a circumferential region, and a ratio of an area of the circumferential region with respect to that of the central region ranges from 0.1 to 0.5, a plugging length L1 in the cell extending direction of a central plugging portion in the central region is larger than a plugging length L2 of a circumferential plugging portion in the circumferential region, L1 ranges from 7 to 9 mm, and L2 from 3 to 6 mm.

In a process for manufacturing a component for an emissions treatment unit, green ceramic product is extruded through a die to form an extrusion having a honeycomb substrate structure with an array of parallel, linear tubular cells extending along its length, the cells bounded by walls dividing adjacent cells from one another. A ceramic unit is obtained by cutting off, curing and firing a length of the extrusion a length of the extrusion. Following the firing, a mixture of a flowable, uncured curable material and a particulate metal component is injected from an end of the ceramic unit into selected ones of the cells so as to block the selected cells over at least a part of their lengths while maintaining all of the walls of the ceramic unit. The injected mixture is then cured to render it solid.

In a process for manufacturing a component for an emissions treatment unit, green ceramic product is extruded through a die to form an extrusion having a honeycomb substrate structure with an array of parallel, linear tubular cells extending along its length, the cells bounded by walls dividing adjacent cells from one another. A ceramic unit is obtained by cutting off, curing and firing a length of the extrusion a length of the extrusion. Following the firing, a mixture of a flowable, uncured curable material and a particulate metal component is injected from an end of the ceramic unit into selected ones of the cells so as to block the selected cells over at least a part of their lengths while maintaining all of the walls of the ceramic unit. The injected mixture is then cured to render it solid.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion provided at an open end on a first end face side or a second end face side of the cells, wherein the partition wall is composed of a material containing cordierite as a main component, a porosity of the partition wall is 60 to 70%, an average pore diameter of the partition wall is 20 to 30 μm, an open porosity of pores existing at the partition wall surface and having equivalent circle diameters exceeding 1.5 μm is 31% or more, and, in a pore diameter distribution which indicates a cumulative pore volume of the partition wall, a half-value width of a first peak including a maximum value of a log differential pore volume is 0.20 or less.

A ceramic body exhibiting % P≥50%, df≤0.36, and a combined weight percentage of crystalline phases containing cordierite and indialite of at least 85 wt %, and up to 10 wt % of a crystalline pseudobrookite structured phase, such as armalcolite. The ceramic body contains, as expressed on an oxide basis, either: 1% wt % to 11% wt % titania and 89% wt % to 99% wt % MgO, Al.sub.2O.sub.3, and SiO.sub.2 that have relative weight ratios of MgO:Al.sub.2O.sub.3:SiO.sub.2 within the field defined by 15.6:34.0:50.4, 12.6:34.0:53.4, 13.9:30.7:55.4, and 16.9:30.7:52.4, or 2.5% to 11% titania and 89% wt % to 97.5% wt % MgO, Al.sub.2O.sub.3, and SiO.sub.2 that have relative weight ratios of MgO:Al.sub.2O.sub.3:SiO.sub.2 within the field defined by 15.6:34.0:50.4, 12.6:34.0:53.4, 12.0:35.7:52.3, and 15.0:35.7:49.3. Batch composition mixtures and methods of manufacturing ceramic bodies using the batch compositions are provided, as are other aspects.

A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall so as to surround a plurality of cells extending from a first end face to a second end face, and a circumferential coating layer composed of a circumferential coating material coated on at least a part of circumference of the honeycomb structure body, wherein the circumferential coating layer has a printing area for printing on the surface thereof, the printing area has a lightness (L*) in L*a*b* color space (CIE1976) defined by International Commission on Illumination (CIE) of 35 or more, and the printing area has a surface roughness Ra of 30 μm or less.

A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall so as to surround a plurality of cells extending from a first end face to a second end face, and a circumferential coating layer composed of a circumferential coating material coated on at least a part of circumference of the honeycomb structure body, wherein the circumferential coating layer has a printing area for printing on the surface thereof, the printing area has a lightness (L*) in L*a*b* color space (CIE1976) defined by International Commission on Illumination (CIE) of 35 or more, and the printing area has a surface roughness Ra of 30 μm or less.

Defect detection systems include at least one nozzle for delivering a CO.sub.2 particulate fluid to an inlet end of a plugged honeycomb body. Defects in the honeycomb, if any, are determined by monitoring CO.sub.2 particulate flow at the outlet end of the honeycomb body. Methods for detecting defects in plugged honeycomb bodies are also disclosed.

A water-treating ceramic filter unit comprising a filter having pluralities of flow paths partitioned by porous ceramic cell walls and plugs alternately sealing the one-side or other-side ends of the flow paths; a housing containing the filter such that water to be treated is supplied from one end of the filter, and that the treated water is discharged from the other end of the filter; and seal members disposed on the outer edge portions of both end surfaces of the filter for longitudinally sandwiching and fixing the filter to the housing; the maximum of a gap between a side surface of the filter and the housing being equal to or less than the equivalent diameter of the flow paths.