Description
The present work investigates the effect of carbon nanotube (CNT) content on nickel-aluminides produced by combustion synthesis. CNTs were milled with Ni powder at 0, 1, 2, and 3 volume percent, then combined with Al powder, compacted, and processed by combustion synthesis. A novel set up during combustion synthesis allowed for the two modes of ignition, thermal explosion and self-propagating high temperature synthesis (SHS), to be studied simultaneously. This highlighted both the electrically resistive and heat-sink properties of the CNTs, showcased individually in both ignition modes and leading to an interplay between their effects. The resulting phases, microstructure, porosity, and hardness values were investigated and discussed. Overall, higher CNT content led to higher porosity levels and more intermediate phases. This was seen most dramatically in the SHS region compared to the region where direct electric current was applied during combustion. Because of this, hardness values decreased in regions where SHS occurred. However, in regions that experienced thermal explosion, increased CNT content led to an increase in microhardness, despite the CNT content being directly related with higher porosity and lower conversation rates of Ni3Al.
