A filter including a plurality of pillar-shaped honeycomb structure segments made of porous ceramics, side faces of the segments being bonded together via a bonding material, wherein each of the pillar-shaped honeycomb structure segments includes an outer peripheral side wall, and partition walls partitioning a plurality of cells extending from a first end face to a second end face, and in each of the pillar-shaped honeycomb structure segments, an average porosity of the outer peripheral side wall is lower than that of the partition walls.

A honeycomb structure includes a central area and a reinforced outer peripheral area. For a reference boundary cell having cell walls with different wall thicknesses on two sides parallel with an imaginary parallel line, a thin wall thickness t1<a thick wall thickness t3, an inner wall thickness t2<an outer wall thickness t4, t1=t2, and t3=t4. The honeycomb structure includes a reference cross-shaped unit having a thin wall, an inner wall, a cell wall, and a cell wall and a reference cross-shaped unit having a thick wall, an outer wall, a cell wall, and a cell wall. The honeycomb structure also includes a plurality of cross-shaped units extending vertically and horizontally from alternate cell vertexes arranged from a reference cell vertex as a starting point. In both the central area and the reinforced outer peripheral area, the cell walls of each cross-shaped unit have a substantially equal wall thickness.

A particulate filter, including: a pillar-shaped honeycomb structure portion having a plurality of first cells extending from a first end face to a second end face, the first end face being open and the second end face being plugged, and a plurality of second cells extending from the first end face to the second end face, the first end face being plugged and the second end face being open, in which the first cells and the second cells are alternately arranged adjacent to each other with porous partition walls interposed therebetween; and a low thermal conductive layer covering a part or the whole of an outer peripheral side surface of the pillar-shaped honeycomb structure portion, the thermal conductivity in a thickness direction of the low thermal conductive layer being 0.6 W/(m.Math.K) or less.

A coating material for a honeycomb structure, the coating material containing: from 1% by mass to 10% by mass of first ceramic fibers having an average axial length of from 80 m to 200 m in an inorganic raw material; and from 0.1% by mass to 15% by mass of second ceramic fibers having an average axial length of from 50 m to 70 m in the inorganic raw material.

A first circumferential wall disposed in a circumference of partition walls has no interface with the outermost circumference partition wall in a circumferential portion constituted by the partition walls whose wall thickness is larger than that of a central portion constituted by the partition walls in a central region. A maximum thickness of a total of the first circumferential wall and a second circumferential wall disposed to surround an outer side of the first circumferential wall is 1.2-3.0 mm, a difference between the maximum thickness and a minimum thickness of the total is 0.2-1.5 mm, and there is satisfied a relation, 0.5(TBTA)SB/SA100(%)9.0 in which TB and TA indicate average thicknesses (m) of the partition walls in the circumferential and central portion respectively, and SB and SA indicate areas (cm.sup.2) of the circumferential portion and the honeycomb structure in the cross section respectively.

The honeycomb structure includes a pillar-shaped honeycomb structure body, and a circumferential coating layer disposed to surround a circumference of the honeycomb structure body, and cells which are formed at an outermost circumference of the honeycomb structure body and in which peripheries of the cells are defined by the partition walls without any lacks are defined as outermost circumference complete cells, and in a cross section of the honeycomb structure body which is perpendicular to an extending direction of the cells a minimum distance T (mm) among distances from the outermost circumference complete cells to the surface of the circumferential coating layer and a porosity P (%) of the circumferential coating layer satisfy relations of Equation (1) and Equation (2) as follows:
1.5T16(100P).sup.1.4; andEquation (1):
20P75Equation (2).

In a porous composite, a base material has a honeycomb structure whose inside is partitioned into a plurality of cells. In the plurality of cells, a plurality of first cells whose one ends in the longitudinal direction are sealed, and a plurality of second cells whose other ends in the longitudinal direction are sealed are arranged alternately. A collection layer covers inner surfaces of the plurality of first cells. An overall Sa that is an arithmetical mean height Sa indicating a surface roughness of a surface of the collection layer in the plurality of first cells is greater than or equal to 0.1 m and less than or equal to 12 m. An overall mean thickness that is a mean thickness of the collection layer in the plurality of first cells is greater than or equal to 10 m and less than or equal to 40 m.

A ceramic honeycomb body comprising a peripheral skin layer and a fiber extending around the outer periphery of a honeycomb core, the fiber embedded in the peripheral skin layer is described. A method of making a honeycomb body having a fiber extending around the outer periphery of a honeycomb core and embedded in the peripheral skin layer is also described.

A honeycomb structure includes a honeycomb substrate including latticed partition walls which define a plurality of cells extending from one end face to the other end face and forming through channels for fluid and a honeycomb outer wall, and a flange portion attached to a part of the honeycomb outer wall of the honeycomb substrate, and including latticed flange partition walls which define a plurality of flange cells extending from one flange end face to the other flange end face and a flange outer wall, and in the honeycomb substrate, a ratio of a non-outer wall region in which the honeycomb outer wall is not disposed is in a range of 10 to 90% to a total area of a substrate circumferential surface.

A honeycomb formed body containing a ceramics raw material, he honeycomb formed body including: a pillar shaped honeycomb structure portion having a plurality of rectangular cells, the cells being defined by partition walls and extending from a first end face to a second end face to form flow paths; an outer peripheral portion having outer peripheral portions X where the partition walls are covered with an outer peripheral wall; and outer peripheral portions Y where the partition walls are exposed. Each of the outer peripheral portions X includes a tapered portion having a gradually deceasing thickness of the outer peripheral wall toward a boundary portion with an adjacent outer peripheral portion Y. The tapered portion requires a length equal to or more than one time of an average cell pitch in the outer peripheral direction until thickness of the outer peripheral wall is halved.