A honeycomb structure includes honeycomb segments each having a porous partition wall defining a plurality of cells, and includes a porous bonding layer containing a crystalline anisotropic ceramic and disposed so as to bond side surfaces of the honeycomb segments to each other. A ratio of a pore volume (cc/g) of a fine pore defined as a pore in the bonding layer having a pore diameter of 10 μm or more and less than 50 μm with respect to a pore volume (cc/g) of a coarse pore defined as a pore in the bonding layer having a pore diameter of 50 μm or more and 300 μm or less is from 2.0 to 3.5, the pore volume of the fine pore is from 0.15 to 0.4 cc/g, and the pore volume of the coarse pore is from 0.05 to 0.25 cc/g.

A plugged honeycomb structure in which in a cross section of a honeycomb structure body which is perpendicular to an extending direction of cells, inflow cells are disposed to surround an outflow cell, and the number of the inflow cells is larger than the number of the outflow cells, and the cross section has a plurality of intersecting portions of partition walls each defining the inflow cells which are adjacent to each other, and in 60% or more of a total number of the intersecting portions, a relation between a diameter (D.sub.1) of a circle inscribed in the intersecting portion and a diameter (D.sub.0) of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies D.sub.1/(√2×D.sub.0)=1.20 to 1.80

Nano-porous corundum ceramics and methods of manufacture are disclosed. The method of forming nano-porous corundum ceramics includes milling corundum powder in aqueous slurry with beads. The method further includes processing the slurry by a liquid shaping process to form a gelled body. The method further includes sintering the gelled body between 600° C. to 1000° C.

A microwave drying method includes: an introduction step of disposing a honeycomb formed body while keeping an axis direction X of cells of the honeycomb formed body vertically and introducing the honeycomb formed body into a drying furnace capable of irradiating with microwaves; a reflector placing step of placing a microwave reflector having a function to reflect the microwaves above and/or below around the honeycomb formed body; and a microwave drying step of irradiating with the microwaves while controlling temperature of an inside of the honeycomb formed body by the microwave reflector so that any one of the end faces (e.g., end face) of the honeycomb formed body reaches 100° C. to dry the honeycomb formed body after the other part of the honeycomb formed body reaches 100° C.

A manufacturing method includes a mixing step, a kneading step of kneading a wet mixture, a liquid adding step of further adding a liquid to a kneaded material, a forming step of extruding a forming material of which viscosity is adjusted into a honeycomb formed body, a drying step of drying the honeycomb formed body, and a dimension measuring step of measuring a dry dimension of a honeycomb dried body that has been dried, where in the liquid adding step, the amount of the liquid to be added is adjusted based on the result of measuring the dry dimension of the honeycomb dried body.

A honeycomb structure has partition walls defining a plurality of polygonal cells which become through channels for a fluid, a structure end face vertical to an axial direction has at least two cell regions possessing mutually different cell structures and surrounded by circumferential portions, and in the cell regions adjacent to each other, to first partition walls of a first cell structure of one first cell region, second partition walls of a second cell structure of the other or second cell region are tilted.

A honeycomb structure has a pillar-shaped honeycomb structure body having porous partition walls which defines cells which forms a passage of liquid extended from an inflow end face toward an outflow end face, a circumferential wall arranged to surround a circumference of the partition walls. The honeycomb structure body has an outermost circumference cell structure including a complete cell arranged at the outermost circumference of the honeycomb structure body, a center cell structure formed by the cells arranged at a center part at an inner side to the outermost circumference cell structure, and a boundary wall arranged at a boundary part between the outermost circumference cell structure and the center cell structure. The outermost circumference cell structure and the center cell structure are formed as different structures to each other, and a thickness of the boundary wall is set to be thicker than a thickness of the circumferential wall.

A honeycomb structure includes a honeycomb structure body including porous partition walls defining a plurality of cells serving as fluid passages extending from an inflow end face to an outflow end face. The partition walls have a porosity of 45 to 65%; the open frontal area of the pores having an equivalent circle diameter of 10 μm or more, of the pores open on the surface of each partition wall, is 20 to 50%; the pore density of the pores having an equivalent circle diameter of 10 μm or more is 200 to 1,000 pores/mm.sup.2; the median opening diameter of the pores having an equivalent circle diameter of 10 μm or more is 40 to 60 μm; the circularity of the pores having an equivalent circle diameter of 10 μm or more is 1.8 to 4.0; and the partition walls have a wet area of 16,500 μm.sup.2 or more.

The manufacturing method of the honeycomb structure includes a mounting step of mounting an extruded honeycomb formed body on a firing setter disposed on a shelf plate, and a firing step of firing the honeycomb formed body mounted on the firing setter to form the honeycomb structure, and in the mounting step, the firing setter is used in which a value obtained by dividing an area of a formed body end face of the honeycomb formed body by an area of a honeycomb mounting surface of the firing setter which faces the formed body end face and at least a part of which comes in contact with the formed body end face is in a range of 2.5 to 20.0.

The manufacturing method of the honeycomb structure includes a raw material preparing step of adding the powder of porous silica as the inorganic pore former to a forming raw material and kneading the forming raw material to prepare the kneaded forming raw material, an extruding step of extruding the obtained forming raw material to form a honeycomb formed body, and a firing step of firing the extruded honeycomb formed body to form a honeycomb structure containing a cordierite component, and an amount of oil to be absorbed by the porous silica to be added to the forming raw material is in a range of 50 to 190 ml/100 g, and a BET specific surface area of the porous silica is in a range of 340 to 690 m.sup.2/g.