Influence of High-Energy Ball Milling on Reaction Kinetics in the Ni-Al System: An Electrothermorgaphic Study

摘要

A new electrothermographic method, viz. high-speed temperature scanning, was applied to kinetic studies of reactions taking place in the Ni-Al system, including those after mechanical activation in a planetary ball mill. Treatment of the temperature profiles taken at different heating rates in terms of the Kissinger-Akahira-Sunose (KAS) approximation gave activation energy E for non-activated mixtures: E = 155 kJ/mol (for temperature range 650-850°C). But for mechanically activated mixtures, the characteristic points (reaction onset temperature, temperature of maximum reaction rate) were found to decrease with increasing heating rate, which makes the KAS method inapplicable to these compositions. It has been concluded that mechanical treatment leads to significant changes in the reaction kinetics, possibly due to splitting the reaction route into two stages the first of which has very low activation energy.