A porous ceramic structure intended to form the reinforcement of a ceramic matrix composite component, the structure having a connected porosity delimited by an internal surface which includes a plurality of first points, each first point being associated with a second point aligned with this first point along a normal to the internal surface taken at the first point, the structure being divisible into a plurality of unit volumes of a size less than or equal to 5 mm3 in each of which: a characteristic pore length, corresponding to the maximum of the distance separating each first point from its associated second point, is less than or equal to 0.5 mm; and a porosity ratio is greater than or equal to 50%.

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 porous honeycomb structure including cell channels passing through an interior of the porous honeycomb structure and partitioned by porous partition walls, wherein the porous partition walls include skeleton portions containing an aggregate and a bonding material, and pore portions formed among the skeleton portions and through which a fluid can flow; and the porous partition walls have a porosity of 40 to 48% as measured by a mercury intrusion method, and a cumulative 50% pore diameter (D50) from a large pore side of 6 to 10 μm in a volume-based cumulative distribution of pore diameters measured by the mercury intrusion method, and a maximum pore diameter observed with a scanning electron microscope of 40 μm or less, and a ratio of a contact area between the aggregate and the bonding material to a surface area of the bonding material observed with the scanning electron microscope of 61 to 80%.

A plugged honeycomb structure includes a honeycomb structure body having a porous partition wall disposed to surround a plurality of cells; and a plugging portion disposed at one end of the cells, wherein, in a section orthogonal to the extending direction of the cell, the cells each have a shape that is polygon, and one of the inflow cells and another are adjacent to each other with the partition wall therebetween, and in the section orthogonal to the extending direction of the cell, a total area of the inflow cell is larger than a total area of the outflow cell, a porosity of the partition wall is 38% or more, a thickness of the partition wall is 125 μm or more and 280 μm or less, a cell density of the honeycomb structure body is 31.0 cells/cm.sup.2 or more, and an air-permeability resistance of the partition wall is 4.5×10.sup.7Pa.Math.s/m.sup.2 or less.

A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall defining a plurality of cells serving as fluid through channels extending from a first end face to a second end face, and having a circumferential wall disposed so as to encompass the circumference of the partition wall, wherein a thickness of the partition wall is 50 to 132 μm, a porosity of the partition wall is 40 to 55%, an open frontal area of pores on the surface of the partition wall per unit surface area of the partition wall is 10 to 15%, and a percentage (S.sub.0˜10/S.sub.all×100%) of the ratio of an opening area S.sub.0˜10 of the pores having an opening diameter of 10 μm or less to a total opening area S.sub.all of the pores opened to the surface of the partition wall is 90% or more.

A method for producing a conductive honeycomb structure includes: a forming step of extruding a forming raw material to obtain a honeycomb formed body; a drying step of drying the honeycomb formed body to obtain a honeycomb dried body; and a firing step of firing the honeycomb dried body to obtain a honeycomb fired body. The forming step includes controlling a volume fraction of a portion that can form pores of the honeycomb formed body so that an absolute value of a difference in the volume fraction of the portion that can form the pores in predetermined regions of the honeycomb formed body relative to a previously set, predetermined porosity of the honeycomb fired body is within 0.5%. The predetermined porosity is a porosity preset for each of the predetermined regions of the honeycomb fired body.

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.

Provided is an exhaust purification filter that is able to reduce pressure loss and that has high exhaust purification performance and particulate matter trapping performance. This exhaust purification filter comprises a filter substrate having a wall flow structure, and an exhaust purification catalyst supported on a partition wall of the filter substrate. The volume-based median pore diameter (D50) of the filter substrate is 18 μm or greater, the full width at half maximum of the pore distribution of the filter substrate is 7 μm to 15 μm, and the exhaust purification catalyst is supported in an unevenly distributed manner in a high-density layer in which the density of the exhaust purification catalyst is relatively high and a low-density layer in which the density of the exhaust purification catalyst is relatively low.

An exhaust gas purification filter includes a plurality of cells extending in a filter axial direction, a porous partition separating and defining the plurality of cells, and a sealing section sealing the plurality of cells alternately at both filter ends. In the exhaust gas purification filter, the partition has a void volume of a reduced dale, Vvv, and a material volume of a reduced peak, Vmp, as volume parameters determined in noncontact surface roughness measurement on a surface of the partition, with their total value being 1.8 μm.sup.3/μm.sup.2 or less.

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)