Silicon carbide ceramic honeycomb structure and its production method
A silicon carbide ceramic honeycomb structure having large numbers of axially penetrating flow paths partitioned by porous silicon carbide cell walls, the cell walls comprising silicon carbide particles as aggregate and binder layers for binding the silicon carbide particles, the binder layers having at least a cordierite phase and a spinel phase, and the molar ratio M1 of the cordierite phase [=cordierite phase/(cordierite phase+spinel phase)] being 0.4-0.9.
1. A silicon carbide ceramic honeycomb structure having large numbers of axially penetrating flow paths partitioned by porous silicon carbide cell walls,
said cell walls comprising silicon carbide particles as aggregate and binder layers for binding said silicon carbide particles, and containing no metallic silicon,
said binder layer consisting of a cordierite phase and a spinel phase, or consisting of a cordierite phase, a spinel phase, and at least one optional component selected from the group consisting of cristobalite, mullite and forsterite,
the molar ratio M1 of said cordierite phase [=cordierite phase/(cordierite phase+spinel phase)] being 0.4-0.9,
the porosity of said cell walls being 38-50%, and
the median pore diameter of said cell walls being 5-20 μm.
2. A method for producing the silicon carbide ceramic honeycomb structure according to claim 1 , comprising the steps of formulating, mixing and blending silicon carbide particles, a binder consisting of alumina source particles and magnesia source particles, and an organic binder to form a moldable material, extrusion-molding said moldable material to a honeycomb shape, drying the resultant green body, and sintering the green body in a temperature range of 1200-1350° C. in an air atmosphere,
said organic binder being at least one selected from the group consisting of methylcellulose, ethylcellulose, ethyl methylcellulose, carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl ethylcellulose, and
said moldable material containing neither metallic silicon nor pore-forming material.
3. The method for producing a silicon carbide ceramic honeycomb structure according to claim 2 , wherein said alumina source particles and said magnesia source particles are formulated at a molar ratio M2 [=(Al 2 O 3 )/(Al 2 O 3 +MgO)] of 0.32-0.50.
4. The method for producing a silicon carbide ceramic honeycomb structure according to claim 2 , wherein said alumina source particles and said magnesia source particles are 6-15% by mass in total, per 100% by mass of said silicon carbide particles.
5. The method for producing a silicon carbide ceramic honeycomb structure according to claim 2 , wherein said alumina source particles are alumina or aluminum hydroxide particles, and said magnesia source particles are magnesium oxide or hydroxide particles, in said binder.
6. The method for producing a silicon carbide ceramic honeycomb structure according to claim 3 , wherein said alumina source particles and said magnesia source particles are 6-15% by mass in total, per 100% by mass of said silicon carbide particles.
7. The method for producing a silicon carbide ceramic honeycomb structure according to claim 3 , wherein said alumina source particles are alumina or aluminum hydroxide particles, and said magnesia source particles are magnesium oxide or hydroxide particles, in said binder.
8. The method for producing a silicon carbide ceramic honeycomb structure according to claim 4 , wherein said alumina source particles are alumina or aluminum hydroxide particles, and said magnesia source particles are magnesium oxide or hydroxide particles, in said binder.