A honeycomb structure body has an outer skin, cells arranged in an inside of the outer skin, and partition walls having pores. The partition walls are arranged in the inside of the outer skin. Each of the cells is surrounded by the partition walls. The pores have communicating pores which communicate with each other adjacent cells. Exhaust gas emitted from an engine passes adjacent cells through the communicating pores. The number of the communicating pores is at a density of not less than 18000 [pores/0.25 mm.sup.2] before a catalyst is supported in the pores. An exhaust gas purification filter having the honeycomb structure body with the catalyst is arranged in an exhaust gas pipe to purify exhaust gas containing PM emitted from an engine.

A compound honeycomb body comprising a first honeycomb section having a volume V1 and a second honeycomb section fluidly connected to the first honeycomb having a volume V2 is provided. The first honeycomb section comprises a low mass high porosity porous ceramic substrate. The second honeycomb section comprises a standard porous ceramic substrate. Wherein V1/V2 comprises a ratio in a range from about 50/50 to about 10/90.

A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall. The honeycomb structure body includes a plurality of cells defined by the partition wall so as to extend from a first end face to a second end face of the honeycomb structure body, the partition wall is formed by a porous body including a silicon phase as a main phase and an oxide, and the oxide includes a first oxide made of an alkali earth metal oxide, Al.sub.2O.sub.3, and SiO.sub.2.

The honeycomb structure body has a dense part at a part in axial direction including a center region of the inflow end face, the dense part having a change ratio of porosity calculated by the following Expression (1) that is 2 to 8%, and has an outside-diameter increasing part, and the honeycomb structure body has a change ratio of average diameter calculated by the following Expression (2) that is 0.2 to 3%,
(1Px/Py)100, Expression (1): in Expression (1), Px denotes the porosity (%) at the center region of the inflow end face, and Py denotes the porosity (%) of a circumferential region of the inflow end face.
(1Dx/Dy)100, Expression (2): in Expression (2), Dx denotes the average diameter (mm) of the inflow end face, and Dy denotes the average diameter (mm) of the outflow end face.

The honeycomb structure body has a dense part having a change ratio of porosity calculated by the following Expression (1) that is 1 to 5%. The honeycomb structure body also has an outside-diameter decreasing part in which the outside diameter decreases from the inflow end face to the outflow end face. The honeycomb structure body has a change ratio of average diameter calculated by the following Expression (2) that is 0.2 to 3%.
(1P.sub.x/P.sub.y)100,Expression (1): in Expression (1), P.sub.x denotes the porosity (%) at the center region of the outflow end face, and Py denotes the porosity (%) of a circumferential region of the outflow end face other than the center region.
(1D.sub.x/D.sub.y)100,Expression (2): in Expression (2), D.sub.x denotes the average diameter (mm) of the outflow end face, and D.sub.y denotes the average diameter (mm) of the inflow end face.

An exhaust gas purification filter is provided which has a high capture ratio of particulate matter even when having a high porosity. The exhaust gas purification filter has a case, partition walls and cells. The partition walls are porous, and the interior of the case is partitioned into a plurality of the cells by the partition walls. The partition walls have a plurality of communicating pores which communicate between cells adjacent to respective partition walls. The degree of tortuosity L/T of the communicating pores satisfies L/T1.1, where T m is the thickness of the partition walls and L m is the average flow path length of the communicating pores. Furthermore the exhaust gas purification filter is manufactured using porous silica having a tapped bulk density that is no greater than a predetermined value.

A honeycomb filter includes a pillar-shaped honeycomb substrate and a plugging portion provided at an end portion on either an inflow or outflow end face side of cells, wherein, in a section orthogonal to the cell extending direction, the shapes of an inflow cell having the plugging portion and an outflow cell having the plugging portion are hexagonal. In the plurality of cells, a plurality of inflow cells surround one outflow cell such that one side of the inflow cell and one side of the outflow cell adjacent to the inflow cell are parallel. The partition wall includes a first partition wall and a second partition wall, at least one of the first partition walls is configured such that a ratio of a thickness of the second partition wall to the first partition wall is 1.0 to 2.5, and a total open frontal area is 35% to 95%.

The present invention provides a honeycomb structured body capable of achieving more effective use of a catalyst in partition walls and having excellent exhaust gas conversion performance. The present invention relates to a honeycomb structured body including: a honeycomb fired body in which multiple through-holes are arranged longitudinally in parallel with one another with a partition wall therebetween, wherein the honeycomb fired body contains ceria-zirconia composite oxide particles and alumina particles, the partition wall of the honeycomb fired body contains macropores having a pore size of 2 to 50 m, and in an electron microscope image of a cross section of the partition wall, the percentage of the area occupied by pores having a pore size of 5 to 15 m is at least 85% of the total area of the macropores.

An outer periphery coating material being coated onto an outer peripheral surface of a ceramic honeycomb structure to form an outer periphery coated layer. The outer periphery coating material comprises: a particle mixture containing cordierite particles and amorphous silica particles in a mass ratio of from 40:60 to 80:20; and from 10 to 30% by mass of crystalline inorganic fibers in an outer percentage relative to the particle mixture. An average particle diameter of the cordierite particles is different from an average particle diameter of the amorphous silica particles.

In one aspect, a material structure is disclosed, which includes a macroscopic porous substrate configured to receive a flow of a medium for passage of at least a portion thereof through the porous substrate. At least one porous coating is disposed on at least a portion of an inner surface of the porous substrate, wherein the porous coating comprises a matrix having a plurality of interconnected passages. The porous substrate and the coating are configured to treat at least one contaminant, if any, present in the flowing medium.