Disclosed is a method of manufacturing a porous ceramic body, which includes: (S1) mixing silica powders having a particle size of 0.045˜0.5 mm, zircon flour and wax, thus preparing a ceramic mixture; (S2) placing the ceramic mixture into a mold, thus producing a green body; and (S3) sintering the green body at high temperature, thus obtaining a porous ceramic body, wherein the silica having a particle size of 0.1˜0.5 mm is contained in an amount of 50˜80 wt % based on the total weight of the porous ceramic body; and also which produces a bulk porous ceramic body having good strength and leaching properties with excellent dimensional stability and shape stability.

One aspect of the heat insulator of the present invention includes a porous sintered body having a porosity of 70 vol % or more and less than 91 vol %, and pores having a pore size of 0.8 μm or more and less than 10 μm occupy 10 vol % or more and 70 vol % or less of the total pore volume, while pores having a pore size of 0.01 μm or more and less than 0.8 μm occupy 5 vol % or more and 30 vol % or less of the total pore volume. The porous sintered body is formed from an MgAl.sub.2O.sub.4 (spinel) raw material and fibers formed of an inorganic material, the heat conductivity of the heat insulator at 1000° C. or more and 1500° C. or less is 0.40 W/(m.Math.K) or less, and the weight ratio of Si relative to Mg in the porous sintered body is 0.15 or less.

One aspect of the heat insulator of the present invention includes a porous sintered body having a porosity of 70 vol % or more and less than 91 vol %, and pores having a pore size of 0.8 μm or more and less than 10 μm occupy 10 vol % or more and 70 vol % or less of the total pore volume, while pores having a pore size of 0.01 μm or more and less than 0.8 μm occupy 5 vol % or more and 30 vol % or less of the total pore volume. The porous sintered body is formed from an MgAl.sub.2O.sub.4 (spinel) raw material and fibers formed of an inorganic material, the heat conductivity of the heat insulator at 1000° C. or more and 1500° C. or less is 0.40 W/(m.Math.K) or less, and the weight ratio of Si relative to Mg in the porous sintered body is 0.15 or less.

In a porous body, a surface layer thickness Ts takes a relatively small value satisfying P≧0.54 Ts (formula (1)), the surface layer thickness Ts being derived by a microstructure analysis using the porous-body data that is prepared through three-dimensional scanning of a region including a surface (inflow plane 61) of the porous body. Here, P denotes a porosity [%] of the porous body, and 0%<P<100% and 0 μm<Ts are assumed. The surface layer thickness Ts is derived as a distance in a thickness direction (X direction) between a surface-layer region start plane 92 in which a straight-pore opening ratio becomes 98% or less for the first time and a surface-layer region end plane 93 in which the straight-pore opening ratio becomes 1% or less for the first time.

In a porous body, a surface layer thickness Ts takes a relatively small value satisfying P≧0.54 Ts (formula (1)), the surface layer thickness Ts being derived by a microstructure analysis using the porous-body data that is prepared through three-dimensional scanning of a region including a surface (inflow plane 61) of the porous body. Here, P denotes a porosity [%] of the porous body, and 0%<P<100% and 0 μm<Ts are assumed. The surface layer thickness Ts is derived as a distance in a thickness direction (X direction) between a surface-layer region start plane 92 in which a straight-pore opening ratio becomes 98% or less for the first time and a surface-layer region end plane 93 in which the straight-pore opening ratio becomes 1% or less for the first time.

The method of predicting a formed body density includes: a correlation calculating step of obtaining the correlation between the formed body density of the formed body and the porosity of the fired body; and a formed body density predicting step including: in a case of preparing a kneaded material A from a ceramic raw material having substantially the same composition as a ceramic raw material used for preparing a kneaded material, preparing a formed body B by forming the kneaded material A, preparing a dried body C by drying the formed body B, and preparing a fired body D having a desired porosity by firing the dried body C, calculating a predicted value of the formed body density of the formed body B corresponding to the desired porosity of the fired body D using the correlation.

The method of predicting a formed body density includes: a correlation calculating step of obtaining the correlation between the formed body density of the formed body and the porosity of the fired body; and a formed body density predicting step including: in a case of preparing a kneaded material A from a ceramic raw material having substantially the same composition as a ceramic raw material used for preparing a kneaded material, preparing a formed body B by forming the kneaded material A, preparing a dried body C by drying the formed body B, and preparing a fired body D having a desired porosity by firing the dried body C, calculating a predicted value of the formed body density of the formed body B corresponding to the desired porosity of the fired body D using the correlation.

A porous ceramic honeycomb body (10) including intersecting walls that form channels (22) extending axially from a first end face to a second end face and layered plugs (62) comprised of a first layer (64) disposed on channel walls and a second layer (66) disposed inward toward an axial center of each respective channel on the first layer. The plugs seal at least one of a first portion of the channels at the first end face and a second portion of channels at the second end face of the porous ceramic honeycomb body.

A porous ceramic honeycomb body (10) including intersecting walls that form channels (22) extending axially from a first end face to a second end face and layered plugs (62) comprised of a first layer (64) disposed on channel walls and a second layer (66) disposed inward toward an axial center of each respective channel on the first layer. The plugs seal at least one of a first portion of the channels at the first end face and a second portion of channels at the second end face of the porous ceramic honeycomb body.

A porous material includes an aggregate in which oxide films are formed on surfaces of particle bodies, and a binding material that contains cordierite and binds the aggregate together in a state where pores are formed. The binding material or the oxide films contain a rare-earth component that excludes Ce.