COATING OF FINE-GRAINED SILICON-NITRIDE WHISKERS ON FIBER-LIKE SILICON-NITRIDE

Fine-grained silicon nitride (Si3N4) whiskers were coated on Si3N4 fib ers through a vapor-liquid-solid mechanism under the following process . After the oxide glass of a Si-Al-Y-O system was coated on seed Si3N4 fibers, the coated fibers were heated at 1490 degrees C and 700 torr in the vapor of the Si-N system which was generated by decomposition o f amorphous Si3N4. The resulting specimens looked just like rose twigs . The Si3N4 whiskers were precipitated by nucleation in a liquid phase generated by melting of the oxide glass layers on the Si3N4 fibers.