7.
The mechanistic pathway of MgO-Al
2O
3 reaction in solid state to form MgAl
2O
4 spinel was investigated to correlate the kinetic parameters with ratio of reactants (MgO:Al
2O
3) and with the presence of a doping agent, TiO
2. The time-temperature-expansion data of oxide compacts was analyzed using several model free analyses and model based (linear and non-linear) kinetic algorithms. These indicated that spinel formation process can be best described by single step with n-dimensional Avrami equation for every MgO:Al
2O
3 ratio, irrespective of titania dopant. The activation energy (E
a) of the process was proportional to % spinel formed in each system and validated with quantitative XRD analysis. The higher value of Avrami coefficient (n) in 90 wt% Al
2O
3 compositions has been explained with geometric considerations of powder packing. Incorporations of 1% TiO
2 in the MgO: Al
2O
3 oxide compact did not markedly affect the reaction model, frequency factor and Activation energy.
相似文献