Influence of processing on the carbon fibre/SiAlON interface

Carbon fibre reinforced SiAlON composites were prepared by slurry infiltration of continuous carbon fibre tows, winding, filter pressing and uniaxial hot pressing. XRD, mechanical testing, and SEM were used to characterize the composites. Results showed that materials prepared by hot pressing were brittle. A phase analysis revealed traces of 2H and 3C silicon carbide, believed to have formed via a gas phase reaction at the fibre matrix interface. To minimize this reaction, a two-fold approach was adopted. First, a low temperature processing route using a low eutectic sintering aid was used to establish the lower bound for silicon carbide. Second, low porosity/high green density composite specimens were prepared by improving the slurry infiltration process and a two-step hot pressing cycle used to maximize densification at a lower temperature.