Process for manufacturing boron nitride fibers and fibers obtained

This invention relates to high performance boron nitride fibers and to a manufacturing method of the present invention utilizes a fibres.La borylborazine precursor of formula (I): [(NHR) 2B (NR) 3B3N3H3dans wherein R represents a hydrogen atom or an alkyl, cycloalkyl or aryl, said group comprising from 1 to 30 carbon atoms.