Alumina fiber and alumina fiber aggregate

Abstract

There is provided an alumina fiber capable of fixing a honeycomb carrier while maintaining elasticity for a long period of time even in a severe usage environment, and an alumina fiber aggregate formed of the fiber. Problems in a gripping material of an automotive honeycomb carrier are solved by applying an alumina fiber containing from 70 to 98% by mass of alumina and from 2 to 30% by mass of silica, having an average fiber diameter of from 3.0 to 8.0 μm, a ratio of fibers having a fiber diameter exceeding 10 μm being 5% or less in terms of the number of fibers and a size of a mullite crystallite contained in each fiber of from 10 to 1500 Å, and by forming an alumina fiber aggregate by using the fibers.

1 . An alumina fiber having:
 a chemical composition comprising an alumina of from 70% by mass to 98% by mass and a silica of from 2% by mass to 30% by mass,   an average fiber diameter of from 3.0 μm to 8.0 μm,   a ratio of fibers having a fiber diameter exceeding 10 μm being 5% or less based on the number of fibers, and   a size of a mullite crystallite contained in each fiber of from 10 Å to 1500 Å.   
     
     
         2 . The alumina fiber according to  claim 1 , having a specific surface area of the alumina fiber being from 0.1 m 2 /g to 70 m 2 /g. 
     
     
         3 . An alumina fiber aggregate containing the alumina fiber according to  claim 1 . 
     
     
         4 . An alumina fiber aggregate containing the alumina fiber according to  claim 2 .