In an exhaust gas purification filter, a partition wall has communicating pores. Each communicating pore has a surface opening on the gas-inflow-side surface and a plurality of portions, each portion having a diameter being reduced and then increased from the surface opening, one of the portions, whose diameter is the smallest, being defined as an inlet neck portion. As viewed in cross section in a thickness direction of the partition wall, the surface opening of each communication pore has a diameter defined as a surface opening diameter, the inlet neck portion of each communication pore has a diameter defined as an inlet neck diameter. The inlet neck diameter is smaller than the surface opening diameter, and an average value of the inlet neck diameters is 15 μm or less. A surface opening ratio of the communicating pores in plan view of the gas-inflow-side partition wall surface is 40% or more.

An exhaust gas purification filter is used so as to support a NO.sub.X purification catalyst. The exhaust gas purification filter includes a honeycomb structure portion and a plug portion. The honeycomb structure portion includes a partition wall and cells. Numerous pores are formed in the partition wall. The cells are partitioned by the partition walls and form a flow path for an exhaust gas. The plug portion alternately seals an inflow end surface or an outflow end surface for the exhaust gas in the cells. The partition wall has a gas permeability coefficient that is equal to or greater than 0.35×10.sup.−12 m.sup.2, a pore volume ratio of pore diameters of 9 μm or less that is equal to or less than 25%, and an average pore diameter that is equal to or greater than 12 μm.

An exhaust gas purification filter includes a plurality of cells each extending from an inflow end face to an outflow end face, a porous partition wall forming the cells in a partitioned manner, inflow-side sealing parts sealing openings on an inflow end face side of outflow cells where the exhaust gas flows out, and outflow-side sealing parts sealing openings on an outflow end face side of inflow cells where the exhaust gas flows in. Each of the inflow-side sealing parts has a porosity of less than 60%. The partition wall has a porosity of 60% or more and 70% or less. Assuming a pore size, at which cumulative pore volume is 50% in pore size distribution of the inflow-side sealing parts, is d50.sub.Pin, and a pore size, at which cumulative pore volume is 50% in pore size distribution of the partition wall, is d50.sub.B, the pore size d50.sub.Pin is less than 18 μm, and the pore size d50.sub.B is 18 μm or more and 25 μm or less.

Provided is an exhaust gas purifying filter used with a HC purifying catalyst supported thereon. Numerous pores are formed in partitions of the exhaust gas purifying filter. In a cross-section of the partition, pores are open at a passage surface, having an open end of which the opening diameter is 50 μm or larger. In the cross-section of the partitions, the partitions include a narrow part where a pore diameter is 5 μm or more and the pore diameter becomes a minimum in a region. In the cross-section of the partitions, the region is positioned between a pair of virtual lines L.sub.1 and L.sub.2 extending from opposing sides of the opening end to a passage surface positioned opposite to the opening end along the wall thickness direction X, Z. The pore diameter at the narrow part is 6% or more and less than or equal to 20% of the opening diameter.

A pillar shaped honeycomb structure, including: an outer peripheral wall; and porous partition walls disposed inside the outer peripheral wall, the partition walls defining a plurality of cells, each of the cells penetrating from one end face to other end face to form a flow path, wherein one or both of the one end face and the other end face includes a groove portion; and wherein at least one annular conductive loop containing a conductive material is embedded in the groove portion.

An exhaust gas purification catalyst device includes a honeycomb base material and an inlet-side coat layer, wherein: the honeycomb base material includes a plurality of cells partitioned by porous partition walls, the plurality of cells including inlet-side cells and outlet-side cells and being configured such that exhaust gas that has flowed into the inlet-side cells passes through the partition walls and is exhausted from the outlet-side cells; and the inlet-side coat layer is present on the surface sides of the partition walls of the inlet-side cells, with the proportion of 4-9 μm through-pores in the through-pore diameter distribution of the partition walls being at least 80 vol %, and the peak pore diameter measured using a mercury porosimeter being at least 3.0 μm greater than the peak through-pore diameter measured using a perm porometer.

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 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 are multi-zone catalyst articles, methods of manufacturing multi-zone catalyst articles, and methods for controlling emissions in diesel engine exhaust streams with multi-zone catalyst articles, where the emission treatment system of various embodiments effectively treats diesel engine exhaust with a single multi-zone catalyst article.

A honeycomb body having a porous ceramic honeycomb structure with a first end, a second end, and a plurality of walls having wall surfaces defining a plurality of inner channels. A highly porous layer is disposed on one or more of the wall surfaces of the honeycomb body. The highly porous layer has a porosity greater than 90%, and has an average thickness of greater than or equal to 0.5 μm and less than or equal to 10 μm. A method of making a honeycomb body includes depositing a layer precursor on a ceramic honeycomb body and binding the layer precursor to the ceramic honeycomb body to form the highly porous layer.