Effect of AlN as sintering aid on hot-pressed ZrB₂-SiC ceramic composite

ZrB₂-SiC ceramic composites were prepared from commercially available powders by hot-pressing, and aluminum nitride (AlN) was added as a sintering aid. Sinterability, microstructure and mechanical properties were investigated and compared to the composite without AlN. It was shown that the addition of AlN greatly improved the powder sinterability and enabled the production of nearly full dense composite. The flexure strength, hardness and fracture toughness were improved with a small amount (5 vol.%) of AlN due to the improvement in densification and inhibition of grain growth. Meanwhile the sinterability and mechanical properties were greatly enhanced with the introduction of finer starting powders. However, the flexural strength and fracture toughness were not improved much when more AlN was added.