Honeycomb structure
There is provided a honeycomb structure 10 comprising a honeycomb segment joined body 10 having a plurality of honeycomb segments 2 integrally joined with one another at a joint face of each of the honeycomb segments by means of a bonding material layer 9 and having a plurality of cells 5 functioning as fluid passages disposed in parallel with one another in a direction of central axis. Porosity in an outside portion of the bonding material layer 9 (portion from the interface of the joint face of honeycomb segments to the point corresponding to 20% thickness of the total bonding material layer) is smaller than that in the central portion located on the inner side of the outside portion.
1. A honeycomb structure comprising a honeycomb segment joined body having a plurality of honeycomb segments integrally joined with one another at a joint face of each of the honeycomb segments by means of a bonding material layer and having a plurality of cells functioning as fluid passages disposed in parallel with one another in a direction of central axis,
wherein porosity in an outside portion of the bonding material layer, defined as a portion from the interface of the joint face of honeycomb segments to the point corresponding to 20% thickness of the total bonding material layer, is smaller than that in a central portion located on an inner side of the outside portion, the bonding material layer contains an inorganic fiber having an average length in the direction of the longer axis of 125 μm or more having a shot content ratio of 10 to 50% by mass.
2. The honeycomb structure according to claim 1 , wherein the bonding material layer satisfies the relation of strength (MPa)/Young's modulus (GPa)>1.0×10 −3 .
3. The honeycomb structure according to claim 1 , wherein the bonding material layer satisfies the relation of strength (MPa)/Young's modulus (GPa)>2.5×10 −3 .
4. The honeycomb structure according to claim 1 , wherein the bonding material layer satisfies the relation of strength (MPa)/Young's modulus (GPa)>3.5×10 −3 .
5. The honeycomb structure according to claim 1 , wherein the outside portion of the bonding material layer has a porosity of 5 to 40%, and the central portion has a porosity of 25 to 90%.
6. The honeycomb structure according to claim 1 , wherein the outside portion of the bonding material layer has a porosity of 10 to 30%, and the central portion has a porosity of 30 to 70%.
7. The honeycomb structure according to claim 1 , wherein the inorganic fiber has an inorganic fiber content ratio of 20 to 45% by mass and has an average diameter of 1 to 20 μm in a cross-section perpendicular to the longer axial direction.
8. The honeycomb structure according to claim 1 , wherein the bonding material layer has a thickness of 0.5 to 3 mm.
9. The honeycomb structure according to claim 1 , wherein the honeycomb segment is constituted by silicon carbide (SiC) or by silicon-silicon carbide based composite material formed by the use of the silicon carbide (SiC) as a framework and silicon (Si) as a bonding material.