On the reaction kinetics of Ni with amorphous carbon

The kinetics of the graphitisation of thin films of amorphous carbon (a-C) by supported Ni particles was investigated by in situ transmission electron microscopy. Ni particles were deposited on a-C films at temperatures from 350 to 500 °C, and reactions with the support were recorded at 600 up to 720 °C. The activity was found to strongly depend on temperature. Reactions generally started with encapsulation of Ni particles with a graphite shell, out of which the metal was eventually expelled and spread on the substrate, which was then graphitised. The propagation speed of the reaction front, and the increase with time of its length and of the graphitised area were measured as function of temperature. Through this, an activation energy of 1.8 ± 0.2 eV was determined; such result is significantly comparable to the theoretical estimate of 1.6 eV, reported by other authors.