Porous material, honeycomb structure, and method of producing porous material
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.
1. A porous material comprising:
an aggregate in which oxide films are formed on surfaces of particle bodies, said particle bodies including SiC particles; and
a binding material that contains cordierite and binds said aggregate together in a state where pores are formed,
wherein said porous material contains Ce,
said binding material contains a rare-earth component other than Ce, said rare-earth component including Y,
at least part of said rare-earth component exists as , Y 2 Si 2 O 7 ,
a ratio of a mass of said rare-earth component other than Ce in terms of an oxide is in a range of 0.44 to 1.85 mass % of said porous material as a whole,
a percentage of amorphous component in said binding material is less than 50 mass %,
a percentage of said binding material in said porous material is greater than 15.0 mass % and less than or equal to 50 mass %, and
an alkali metal component is contained in said porous material, and a ratio of a mass of said alkali metal component in terms of an oxide is less than 0.1 mass % of said porous material as a whole.
2. The porous material according to claim 1 , wherein said oxide films contain cristobalite.
3. The porous material according to claim 2 , wherein a ratio of a mass of said cristobalite is in a range of 3.0 to 25.0 mass % of said porous material as a whole.
4. The porous material according to claim 1 , wherein said porous material contains Na or K as said alkali metal component.
5. The porous material according to claim 1 , wherein a thermal expansion coefficient in a temperature range of 40° C. to 200° C is less than or equal to 5.5 ppm/K.
6. A honeycomb structure that is a tubular member made of the porous material according to claim 1 and having an interior partitioned into a plurality of cells by partition walls.
7. A method of producing a porous material, comprising:
a) obtaining a compact by molding a mixture of an aggregate raw material, a raw material of binding material, and a pore forming material;
b) obtaining a fired compact by firing said compact at a temperature of 1300 to 1600° C. in an inert atmosphere; and
c) obtaining a porous material by subjecting said fired compact to oxidation treatment at a temperature of 1150 to 1350 ° C. in an oxidizing atmosphere.
wherein said aggregate raw material is a non-oxide material,
said aggregate comprising oxide films formed on surfaces of the particle bodies, said particle bodies including SiC particles,
said raw material of binding material contains a rare-earth component other than Ce, said rare-earth component including Y,
said porous material comprises a binding material that contains cordierite and binds said aggregate together in a state where pores are formed,
said porous material contains Ce,
at least part of said rare-earth component exists in said binding material as Y 2 Si 2 O 7 ,
a ratio of a mass of said rare-earth component other than Ce in terms of an oxide is in a range of 0.44 to 1.85 mass % of said porous material as a whole,
a percentage of amorphous component in said binding material is less than 50 mass %,
a percentage of said binding material in said porous material is greater than 15.0 mass % and less than or equal to 50 mass %, and
an alkali metal component is contained in said porous material, and a ratio of a mass of said alkali metal component in terms of an oxide is less than 0.1 mass % of said porous material as a whole.