After-treatment of boron nitride-coated substrate, especially fiber used in fiber-reinforced composite, comprises tempering in ammonia at high temperature

摘要

After-treatment of substrates coated with boron nitride (BN) comprises tempering in ammonia at 1000-1600 deg C. An Independent claim is also included for BN-coated substrates in which the BN layer has a hydrolysis resistance <= 40 mg m<-2>, determined by boiling under reflux in distilled water for 60 minutes and determining the amount of hydrolysable BN from the ammonium and borate ion concentrations, measured photometrically using Nesslers reagent and Azomethin H respectively.