THE SYNTHESIS OF NICKEL ALUMINIDES BY MULTILAYER SELF-PROPAGATING COMBUSTION

The synthesis of Ni-Al intermetallic thin films by self-propagating co mbustion reactions was investigated for the 1:1 and 3:1 Ni/Al stoichio metries. The dependence of the combustion wave velocity on the individ ual layer thickness was determined. The marked decrease in velocity wi th 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 attribu ted to a diffusion process of Al in NiAl. Differential thermal analysi s (DTA) showed the sequence of steps in the formation of NiAl and Ni3A l. The dependence of the thermal peaks on the heating rate for both ca ses was found to be consistent with theory. The activation energies ob tained from the DTA analysis were compared to previous results obtaine d with relatively thin layers.