electrically conductive honeycomb body that includes a porous honeycomb structure including a plurality of intersecting porous walls arranged to provide a matrix of cells, the porous walls including wall surfaces that define a plurality of channels extending from an inlet end to an outlet end of the structure. The porous walls include ceramic composite material that includes at least one carbide phase and at least one silicide phase, each carbide and silicide phase including one or more metals selected from the group consisting of Si, Mo, Ti, Zr and W.

A pillar shaped honeycomb structure, including: an outer peripheral wall; and a porous partition wall disposed inside the outer peripheral wall, the a porous partition wall defining a plurality of cells, each of the cells extending from one end face to other end face to form a flow path, wherein a surface of the porous partition wall in the cells comprise a collecting layer having an average pore diameter lower than that of the porous partition wall; and wherein magnetic particles having a Curie point of 700° C. or higher are provided either or both between the surfaces of the porous partition wall and the collecting layer, and on the collecting layer.

A pillar shaped honeycomb structure, including: an outer peripheral wall; and a porous partition wall disposed inside the outer peripheral wall, the a porous partition wall defining a plurality of cells, each of the cells extending from one end face to other end face to form a flow path, wherein a surface of the porous partition wall in the cells comprise a collecting layer having an average pore diameter lower than that of the porous partition wall; and wherein magnetic particles having a Curie point of 700° C. or higher are provided either or both between the surfaces of the porous partition wall and the collecting layer, and on the collecting layer.

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 μm and less than or equal to 12 μm. 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 μm and less than or equal to 40 μm.

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 μm and less than or equal to 12 μm. 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 μm and less than or equal to 40 μm.

A ceramic honeycomb filter has (a) cross section areas of intake flow paths being larger than those of discharge flow paths; (b) the intake and discharge flow paths having octagonal cross section shapes with four-fold rotation symmetry each obtained by cutting off four corners from a square; (c) the intake and discharge flow paths being alternately arranged in a first direction and a second direction perpendicular to the first direction, such that their opposing sides are parallel; (d) the opening ratio of the intake flow paths being 45-60%; (e) the number of the flow paths per cm.sup.2 being 30-60; (f) the thickness t1 of a cell wall between an intake flow path and a discharge flow path adjacent to that intake flow path being 0.150-0.260 mm; and (g) the thickness t2 of a cell wall between adjacent intake flow paths meeting 1.175<t2/t1<1.6.

A ceramic honeycomb filter has (a) cross section areas of intake flow paths being larger than those of discharge flow paths; (b) the intake and discharge flow paths having octagonal cross section shapes with four-fold rotation symmetry each obtained by cutting off four corners from a square; (c) the intake and discharge flow paths being alternately arranged in a first direction and a second direction perpendicular to the first direction, such that their opposing sides are parallel; (d) the opening ratio of the intake flow paths being 45-60%; (e) the number of the flow paths per cm.sup.2 being 30-60; (f) the thickness t1 of a cell wall between an intake flow path and a discharge flow path adjacent to that intake flow path being 0.150-0.260 mm; and (g) the thickness t2 of a cell wall between adjacent intake flow paths meeting 1.175<t2/t1<1.6.

A honeycomb structure has a plurality of cells formed by a plurality of partition walls. The partition walls are formed of a porous material composed predominantly of cordierite. Each partition wall includes surface layer portions having a porosity of 50% or more and an inside portion having a porosity of 50% or more, the surface layer portions being portions ranging respectively from opposite surfaces to a depth corresponding to 25% of the thickness of the partition wall, and the inside portion being the other portion. The surface layer portions and the inside portion both include pores having axial pore widths of less than 30 μm and pores having axial pore widths of 30 μm or more. A mean axial pore width in the surface layer portions is smaller than a mean axial pore width in the inside portion.

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 each of the cells, wherein the partition wall is composed of a material containing cordierite as a main component thereof, a number per unit area of pores which exist at a surface of the partition wall and which have equivalent circle diameters exceeding 3.0 μm is 1400 per mm.sup.2 or more, and, in a pore diameter distribution which indicates a cumulative pore volume of the partition wall, with a log pore diameter on a horizontal axis and a log differential pore volume (cm.sup.3/g) on a vertical axis, a half-value width of a first peak that includes a maximum value of the log differential pore volume is 0.30 or less.

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 each of the cells, wherein the partition wall is composed of a material containing cordierite as a main component thereof, a number per unit area of pores which exist at a surface of the partition wall and which have equivalent circle diameters exceeding 3.0 μm is 1400 per mm.sup.2 or more, and, in a pore diameter distribution which indicates a cumulative pore volume of the partition wall, with a log pore diameter on a horizontal axis and a log differential pore volume (cm.sup.3/g) on a vertical axis, a half-value width of a first peak that includes a maximum value of the log differential pore volume is 0.30 or less.