A honeycomb structure includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells, which serving as fluid through channels extending from a first end face to a second end face, wherein the plurality of cells includes: large opening cells having a large opening area on the first end face and the second end face; and small opening cells having an opening area smaller than that of the large opening cells on the first end face and the second end face, a ratio of an opening diameter of the large opening cells to an opening diameter of the small opening cells is larger than 1.11 and smaller than 1.28, and the opening diameter of the small opening cells is larger than 0.78 mm, and a cell density of the honeycomb structure body is larger than 93 pcs/cm.sup.2 and smaller than 104 pcs/cm.sup.2.

A method for producing a porous body, comprising a raw-material mixing step of mixing talc having an average particle size of 1 μm or more and 18 μm or less, alumina, an auxiliary raw material containing a material that undergoes a eutectic reaction with talc and being prepared in an amount so as to satisfy a weight ratio of 0.5% or more and 1.5% or less by weight relative to the talc, and a pore-forming agent, to provide green body, and a molding and firing step of molding the green body to provide a compact and firing this compact at a firing temperature of 1350° C. to 1440° C.

Methods of firing ceramic-forming honeycomb bodies are disclosed that include heating the honeycomb bodies and blocking furnace gases from flowing through the honeycomb body by placing a layer selected from the group consisting of a graphite layer, a graphite-containing layer, an activated carbon layer, or an amorphous carbon layer adjacent an endface of the honeycomb body. Heating removes organic pore-forming material and graphite pore-forming material in the honeycomb body. The layer oxidizes to form a porous layer after firing to a first temperature, and furnace gases flow through the honeycomb body.

A honeycomb body with a honeycomb structure having an inner zone of a first plurality of walls and an outer zone of a second plurality of walls at least partially surrounding the inner zone. The honeycomb structure has Pi that is greater than Po and MPSi that is greater than MPSo, wherein Pi is an average bulk porosity of the first plurality of walls, Po is an average bulk porosity of the second plurality of walls, MPSi is a median pore size of pores in the first plurality of walls, and MPSo is a median pore size of pores in the second plurality of walls. Various honeycomb structures, honeycomb extrusion apparatus, and co-extrusion methods are disclosed.

Methods of firing ceramic honeycomb bodies are disclosed that include heating the ceramic honeycomb bodies and blocking furnace gases from flowing through the ceramic honeycomb body by placing an aluminum metal layer adjacent an endface of the honeycomb body. Heating removes organic pore-forming material and graphite pore-forming material in the ceramic honeycomb body. The aluminum metal layer oxidizes to form a porous Al2O3 layer after firing to a first temperature, and furnace gases flow through the ceramic honeycomb body.

Methods for applying a surface treatment to a plugged honeycomb body comprising porous wall includes: atomizing particles of an inorganic material into liquid-particulate-binder droplets comprised of an aqueous vehicle, a binder material, and the particles, evaporating substantially all of the aqueous vehicle from the droplets to form agglomerates comprised of the particles and the binder material, and depositing the agglomerates onto the porous walls of the plugged honeycomb body, wherein the agglomerates are disposed on, or in, or both on and in, the porous walls. Plugged honeycomb bodies comprising porous walls and inorganic material deposited thereon are also disclosed.

A method for applying a surface treatment to a plugged honeycomb body comprising porous wall includes: mixing particles of an inorganic material with a liquid vehicle and a binder material to form a liquid-particulate-binder stream; mixing the liquid-particulate-binder stream with an atomizing gas, directing the liquid-particulate-binder stream into an atomizing nozzle thereby atomizing the particles into liquid-particulate-binder droplets comprised of the liquid vehicle, he binder material, and the particles; conveying the droplets toward the plugged honeycomb body by a gaseous carrier stream, wherein the gaseous carrier stream comprises a carrier gas and the atomizing gas; evaporating substantially all of the liquid vehicle from the droplets to form agglomerates comprised of the particles and the binder material; depositing the agglomerates onto the porous walls of the plugged honeycomb body; wherein the deposited agglomerates are disposed on, or in, or both on and in, the porous walls.

Methods and compositions for reducing gas seepage into a cement slurry. One method includes adding a formulation to the cement slurry, the formulation comprising at least one component responsive to a predetermined concentration of hydrocarbon gas in the cement slurry, where upon the cement slurry reaching the predetermined concentration of hydrocarbon gas, the hydrocarbon gas undergoes at least a partial oxidation caused by the formulation to quicken the setting time of the cement slurry via release of heat by an exothermic reaction.

The honeycomb structure is equipped with a pillar-shaped honeycomb structure body having a porous partition wall that defines a plurality of cells extending from an inflow end face to an outflow end face and serving as a through channel of a fluid and a circumferential wall placed to surround the circumference of the partition wall. The honeycomb structure body has, in a face orthogonal to an extending direction of the cells of the honeycomb structure body, a circumferential cell structure, a center cell structure, and a boundary wall placed at a boundary between the circumferential cell structure and the center cell structure and incomplete cells of 5% or more to 50% or less of the total number of the incomplete cells of the center cell structure is communicated with incomplete cells of the circumferential cell structure with each other.

A tray including a plate-shaped portion for arranging a plurality of prismatic honeycomb structures having an outer peripheral side surface and partition walls provided on an inner peripheral side of the outer peripheral side surface, the partition walls partitioning a plurality of cells forming flow paths from a first end surface to a second end surface, the plate-shaped portion including: a plurality of corrugated plate-shaped placing portions for placing the prismatic honeycomb structures with the outer peripheral side surface in contact with the placing portions; flat plate-shaped non-placing portions adjacent to each of the corrugated plate-shaped placing portions; and partition walls erected between adjacent corrugated plate-shaped placing portions to prevent the outer peripheral side surfaces of adjacent prismatic honeycomb structures from contacting each other.