Formation, Structure and Properties of Boron Nitride Fibers from PolymerPrecursors

摘要

This report describes a study of possible polymer precursor-based routes tooriented boron nitride fibers, with emphasis on the formation of continuous polyborate gel fibers and subsequent nitridation. Results from preliminary investigations of polyborazylene, polyborazine and decaborane-diamine as precursors for boron nitride fibers are also included. Formation, via a sol-gel route, of a polyborate gel fiber containing no metal counter ion is a major accomplishment of this research. Incorporation in the precursor of rheological aids that are fugitive during subsequent pyrolysis/nitridation is seen to be advantageous in the formation of processable polyborate fibers. Whether suitable schemes exist for generating high orientation in the trial boron nitride fiber remains an unanswered question with all the precursors. Nonoxide precursors suffer, in addition, due to their high cost and chemical instabilities prior to their conversion to BN fibers.