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 2 vol%) 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 456 kJ/mol. The addition of 2 vol% CNTs reduced the sintering activation energy to 172 kJ/mol. The significant reduction of the activation energy with the addition of only 2 vol% 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.