Synthesis and Thermo-Mechanical Properties of Sol-Gel Derived Zirconia Toughened Alumina Nanocomposite

$Al_2O_3-ZrO_2$ composite precursor powder containing 5-15mol% $ZrO_2$ is prepared by wet chemical route. The washed gel containing pseudoboehmite and amorphous zirconia are characterized with respect to DTA/TG, XRD and IR spectroscopy. In the calcined powder phase evolution of $Al_2O_3$ follows the sequence: pseudoboehmite \rightarrow bayerite \rightarrow boehmite \rightarrow $\Upsilon - Al_2O_3$ \rightarrow $ \theta -Al_2O_3$ \rightarrow $\alpha -Al_2O_3$; while that of $ZrO_2$ follows amorphous $ZrO_2$ \rightarrow $t-ZrO_2$ \rightarrow $(t + m)-ZrO_2$. However, the crystallization behavior of aluminum-hydroxide is somewhat affected with addition of zirconia. FTIR study reveal the number of M-OH and M-O bond increases on increasing mol% of $ZrO_2$ due to a change in the cationic charge of the composite powder. The formation of amorphous material before crystallization can also be predicted from TEM study, where particle exhibits different morphology; and show smooth, distinct and faceted surfaces at different temperature. A bimodal particle size distribution is observed because of both unagglomerated and partial..