Characterization of Dip‐Coated Boron Nitride on Silicon Carbide Fibers

Abstract

Amorphous boron nitride thin coatings (∼0.2 μm) have been formed on Nicalon and C‐Nicaion (pre‐carbon‐coated Nicalon) yarns via dip coating in boric acid solution followed by heating and nitriding in NH 3 gas at 1000°C. X‐ray photoelectron spectroscopy (XPS) and Auger electron spec‐troscopy (AES) studies have shown the formation of boron nitride. The coating was boron rich and contains oxygen. The N/B and O/B ratios range from 0.6 to 0.8 and from 0.1 to 0.25, respectively. Tensile strength measurements revealed that the BN‐coated C‐Nicalon yarn maintained ∼85% of its original strength while BN‐coated Nicalon lost ∼85% of its original strength. Auger depth profiles showed that there was a consumption of carbon during the heating and nitridation process for both BN‐coated Nicalon and C‐Nicalon fibers. However, the depletion of carbon in BN‐coated Nicalon fibers was much more severe than that in BN‐coated C‐Nicalon fibers.