The influence of oxygen content on the structure and properties of silicon oxynitride (Si-O-N) fibers

In this work, PCS fibers, cured with different oxygen contents, were conducted by pyrolysis nitridation for carbon removal and amination in the ammonia atmosphere, and then through condensation/nitridation reaction at high temperature in the nitrogen atmosphere to produce silicon oxynitride fibers. Results of XRD, EPMA and TEM showed that, all of the elements in the ceramic fibers dispersed uniformly, and as the oxygen content in the cured fibers increased, it also increased in the ceramic fibers but with a drop in mechanical properties. However, the ceramic yield rose first and then fell because of the phase decomposition at high temperature. Indicated by the results of XRD and TEM, even after heat treatment at 1500°C, ceramic fibers were still amorphous regardless of how much the oxygen content was. The oxygen maybe play a role like impurity in the fibers, which inhibites the crystallization of silicon nitride.