Fiber aggregate and fabricating method of the same

摘要

A fiber aggregate contains fine carbon fibers and fine boron nitride fibers. Desirably the boron nitride fibers form an outer layer portion of the fiber aggregate and the fine carbon fibers form a core portion of the fiber aggregate. Desirably the fine carbon fibers and the fine boron nitride fibers are twisted with each other. Desirably the fine carbon fibers are carbon nanotubes and the fine boron nitride fibers are boron nitride nanotubes. Desirably the fiber aggregate further contains boron-containing fine carbon fibers. The fine boron nitride fibers are formed by substituting carbon atoms of fine carbon fibers by boron atoms and nitrogen atoms. The fiber aggregate is fabricated by mixing a fiber aggregate that contains fine carbon fibers with boron and heating the fiber aggregate mixed with the boron in a nitrogen atmosphere to transform some of the fine carbon fibers into fine boron nitride fibers.