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 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 structure comprising a pillar-shaped honeycomb structure body having a porous partition wall disposed so as to surround a plurality of cells, wherein let that A denotes an absolute value of open frontal area (%) in a plane of the honeycomb structure body orthogonal to the extending direction of the cells and P denotes an absolute value of porosity (%) of the partition wall, the honeycomb structure has a value represented by the following expression (1) that is 0.05 to 0.12, let that D denotes an average pore diameter (m) of the partition wall and G denotes a geometric surface area (mm.sup.2/mm.sup.3) of the partition wall, the honeycomb structure has a value represented by the following expression (2) that is 8 to 50 (μm×mm.sup.2/mm.sup.3), and the honeycomb structure has a hydraulic diameter of the cells that is 1.1 mm or more,
(1−A/100)×(1−P/100),  Expression (1)
D×G.  Expression (2)

A honeycomb structure, including: a pillar-shaped honeycomb structure body having a first end face and a second end face and including a porous partition wall disposed so as to surround a plurality of cells, the plurality of cells extending from the first end face to the second end face and serving as a through channel of fluid, wherein the partition wall has a porosity of 45 to 65%, the partition wall has an average pore diameter of 15 to 25 μm, and the partition wall has a cumulative pore volume, which is measured by mercury intrusion porosimetry, such that a pore volume ratio of pores having pore diameters of 10 μm or less relative to the overall pore volume of the partition wall is 10% or less, and a pore volume ratio of pores having pore diameters of 40 μm or more is 10% or less.

A circumferential coating material to be applied to a circumferential surface of a honeycomb structure made of ceramics formed by extrusion, the circumferential coating material including a ceramic raw material that forms a circumferential coating layer, wherein the ceramic raw material contains: a ceramic mixture of first ceramic particles having particulate shapes, and second ceramic particles having particulate shapes and an average particle diameter different from an average particle diameter of the first ceramic particles; and a fiber material having an elongated strip-like shape, wherein the ceramic mixture has particle size distribution including at least two local maximum values, and the fiber material has an average fiber length ranging from 30 to 100 μm in a longitudinal direction.

A method to form a laminar integral skin of a honeycomb structure is provided. The method includes extruding a ceramic precursor batch through a die with feedholes in entry side and slots in exit face of the die to form the honeycomb structure. In a region on the periphery of the die configured to form the cell matrix, a series of concentric slots around the matrix in the exit face of the die are configured to feed skin onto the matrix. Ring sections between concentric slots are angled away from the center and a mask is disposed on top of the periphery producing a channel for extruded skin to meet and bond to extruded matrix. Optionally, slots in the skin-forming ring sections enhance knitting between laminar skin layers. The die and honeycomb body having uniform integral skin are also provided.

Provided is a honeycomb filter, including: a pillar-shaped honeycomb substrate having an inflow end face and an outflow end face and including a porous partition wall surrounding a plurality of cells; and a plugging portion disposed at any one of ends of the cells at the inflow end face and at the outflow end face. In a cross section orthogonal to an extending direction of the cells, inflow cells have a pentagonal or a hexagonal shape, and outflow cells have a square shape. The cells are configured that the inflow cells surround one outflow cell and one side of an inflow cell and one side of an adjacent outflow cell are parallel to each other. The partition wall is configured that thickness of a first partition wall disposed between the inflow cells and the outflow cells is larger than thickness of a second partition wall disposed between the inflow cells.

A pillar-shaped honeycomb structure body of a honeycomb structure includes a circumferential cell structure, a central cell structure and a boundary wall therebetween. On a surface orthogonal to the cells there are a circumferential reinforcing region having the partition wall thicker than a basic partition wall thickness in the circumferential cell structure and existing outside a range of a distance from a centroid of the surface; and at least one of a first boundary reinforcing region having the partition wall thicker than the basic partition wall thickness and existing in a range of a distance from the centroid within a range of the circumferential cell structure and a second boundary reinforcing region having the partition wall thicker than a basic partition wall thickness in the central cell structure and existing outside of a range of a distance from the centroid within a range of the central cell structure.

An electric heating support includes an electrically conductive honeycomb structure having an outer peripheral wall and porous partition walls disposed on an inner side of the outer peripheral wall, the porous partition walls defining a plurality of cells, each cell penetrating from one end face to other end face to form a flow path. A pair of metal terminals are disposed so as to face each other across a central axis of the honeycomb structure, each metal terminal being joined to a surface of the honeycomb structure via a welded portion. The honeycomb structure is composed of ceramics and a metal. The honeycomb structure contains 40% by volume or less of the metal. The welded portion of the honeycomb structure has a surface containing 40% by volume or more of the metal.

A pillar-shaped honeycomb structure including an outer peripheral side wall, a plurality of first cells provided on an inner peripheral side of the outer peripheral side wall, the first cells extending from a first end surface to a second end surface, each opening on the first end surface and having a sealing portion with an average void ratio of 4% or less on the second end surface, and a plurality of second cells provided on the inner peripheral side of the outer peripheral side wall, the second cells extending from the first end surface to the second end surface, each having a sealing portion with an average void ratio of 4% or less on the first end surface and opening on the second end surface, the first cells and the second cells being alternately arranged adjacent to each other with a partition wall interposed therebetween.