Arrhenius parameters determination in non-isothermal conditions for mechanically activated Ag2O-graphite mixture
(1. Department of Mineral Processing Engineering, Shahid Bahonar University of Kerman, Kerman, Iran;
2. Department of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran)
2. Department of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran)
Abstract: The non-isothermal kinetics of mechanochemical reduction of Ag2O with graphite was studied by DSC and TGA with a model of fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin. To evaluate the kinetics parameters, Ag2O–graphite mixture of as-received and milled for 2 and 4 h samples were selected. Based on the results obtained by Vyazovkin method calculation, however, the difference between the maximum and minimum values of activation energy is less than 20%-30% of the average activation energy ((99.38±2.36) kJ/mol) and thermal decomposition of mechanically activated Ag2O for 2 h is a multi-step process. Moreover, the thermal decomposition of mechanically activated Ag2O–graphite powder activated for 4 h is a single-step process (the average activation energy=(93.68±2.26) kJ/mol). The kinetics modeling shows that the complexity of thermal decomposition of as-received Ag2O–graphite mixture is higher than that of the others. While, the autocatalytic tendency of as-received Ag2O–graphite mixture is lower than that of the others.
Key words: mechanical activation; Vyazovkin method; kinetic modeling; Sestak–Berggren model; integral master plot method; silver oxide