부산대학교 도서관

This work reports on the formation kinetics of magnesium aluminate spinel (MAS), from [alpha]-Al.sub.2O.sub.3 and MgO nanopowders. A non-isothermal kinetic analysis was performed by the thermodilatometric analysis (TDA) for the first time. The measurements were carried out using a dilatometer on compact samples with heating rates from 3 to 11 °C min.sup.-1. Phases formed during the spinelisation process, in specimens heat-treated in both the dilatometer and furnace, were characterized by X-ray diffraction (XRD). The use of pure nano-oxide powders to produce spinel reduced the formation temperature and activation energy. MAS started to form, in the furnace heat-treated specimens, at 1000 °C and its formation was complete at 1400 °C. For specimens heated in the dilatometer, MAS formation temperature increased from 1002 to 1061 °C with the increase in heating rate from 3 to 11 °C min.sup.-1. The activation energy for spinelisation, under non-isothermal conditions, was calculated by linear reaction models (Integral isoconversional methods) using Flynn-Wall-Ozawa (FWO) method. Boswell, and Kissinger equations. The average activation energy (E.sub.a), correlation coefficient (R.sup.2), Avrami parameter (n), and dimensionality of crystal growth (m) were equal to 293.31 kJ mol.sup.-1, 0.99, 1.22, and 0.98, respectively. The Johnson-Mehl-Avrami (JMA) reaction model, following Ligero method (Differential isoconversional methods), was used to analyze spinelisation kinetics under non-isothermal conditions. The average activation energy (E.sub.a), correlation coefficient (R.sup.2), Avrami parameter (n), and the frequency factor (k.sub.0) were found to be 283.90 kJ mol.sup.-1, 0.99, 1.2, and 4.17 x 10.sup.8 s.sup.-1, respectively.
Author(s): N. Saheb [sup.1] [sup.2], S. Lamara [sup.3], F. Sahnoune [sup.3], S. F. Hassan [sup.1] [sup.2] Author Affiliations: (1) grid.412135.0, 0000 0001 1091 0356, Department of Mechanical Engineering, King Fahd [...]