Kinetics of high temperature reaction in Ni-Al system: influence of mechanical activation.

High temperature (>1000 K) reaction kinetics in the stoichiometric (1:1 by molar ratio) Al-Ni system was investigated by using the, so-called, electrothermal analysis (ETA) method. ETA is the only technique that allows studying kinetics of a heterogeneous gasless reaction at temperatures above the melting points of the precursors. Special attention was focused on methodological aspects of the ETA method. Two different reaction systems were studied: (i) initial Al/Ni clad particles; (ii) the same powders but after 15 min of high energy ball milling. Analysis of the obtained results leads to the conclusion that such mechanical treatment decreases the apparent activation energies of the reaction in the Ni-Al system, from 47 +/- 7 kcal/mol for the initial powder to 25 +/- 3 kcal/mol after ball milling. Comparison of these data with those reported previously was also made.