The effect of carbon nanotubes on the sintering behaviour of zirconia

The sintering behaviour and activation energy of Y2O3 partially stabilised ZrO2 and ZrO2–CNT (0.5 and 2vol%) composites was determined using spark plasma sintering (SPS) under isothermal conditions. The sintering activation energy for the Y2O3 partially stabilised ZrO2 was found to be 456kJ/mol. The addition of 2vol% CNTs reduced the sintering activation energy to 172kJ/mol. The significant reduction of the activation energy with the addition of only 2vol% CNTs is attributed to the formation of a percolating network of CNTs providing a lower energy diffusion pathway. The sintering mechanism was found to be grain boundary diffusion for all samples suggesting that the presence of CNTs does not change the sintering mechanism but does lower the activation energy for the rate limiting step in the sintering process.