DEVELOPMENT OF NANO ZIRCONIA TOUGHENED ALUMINA FOR CERAMIC ARMOR APPLICATIONS

The brittle nature of ceramics can limit their ability to resist multiple ballistic impacts. The present work focuses on investigating the possibility of using a toughened nanostructured ceramic, viz. nano zirconia toughened alumina (ZTA), as a potential ceramic armour. The material comprises of 10 - 20 wt% nano yttria stabilised zirconia (nanoYSZ) in a submicron alumina matrix. Using varied sintering conditions, ZTA samples with a range of alumina and zirconia grain sizes were produced. The effects of the yttria content, amount of zirconia and grain sizes of both YSZ and alumina on the mechanical properties of the ZTA were studied. It was found that 15% 1.5Y-ZTA provided both high hardness and toughness. In addition, the coarsening of zirconia grains benefited toughness enhancement due to the increased transformability of the zirconia grains. Using a modified split Hopkinson pressure bar, the samples were subjected to high strain rate (2x10(-3) - 4x10(4) s(-1)) tests; the ZTA samples with zirconia contents >= 15 wt% showed the best performance. A micro-Raman study on the post-tested samples suggested that the transformation toughening absorbed the energy from the impact and protected the samples from breaking.