THE SYNTHESIS OF NICKEL ALUMINIDES BY MULTILAYER SELF-PROPAGATING COMBUSTION

The synthesis of Ni-Al intermetallic thin films by self-propagating combustion reactions was investigated for the 1:1 and 3:1 Ni/Al stoichiometries. The dependence of the combustion wave velocity on the individual layer thickness was determined. The marked decrease in velocity with layer thickness was consistent with results of modeling studies on multilayer systems. Activation energies for the synthesis of NiAl were determined to be in the range 127.9 to 149.8 kJ . mol(-1), and those for the synthesis of Ni3Al were found to be in the range 133.8 to 146.3 kJ . mol(-1). In the case of NiAl, the experimental value is attributed to a diffusion process of Al in NiAl. Differential thermal analysis (DTA) showed the sequence of steps in the formation of NiAl and Ni3Al. The dependence of the thermal peaks on the heating rate for both cases was found to be consistent with theory. The activation energies obtained from the DTA analysis were compared to previous results obtained with relatively thin layers.