Abstract
In this paper, the relaxation kinetics of the oxidation process of the YBaCo(4)O(7+δ) , Y(0.95)Ti(0.05)BaCo(4)O(7+δ) and Y(0.5)Dy(0.5)BaCo(4)O(7+δ) oxygen carriers is studied with isothermal reaction data. XRD analysis for fresh samples shows that all the samples have YBaCo(4)O(7+δ) structure. Scanning electron microscopy images of samples show that the samples consist of porous agglomerates of primary particles. Isothermal TG experiments are conducted with temperatures of 290°C, 310°C, 330°C and 350°C, respectively. It is found that the Avrami-Eroféev model describes solid-phase changes in the oxygen absorption process adequately. The results show that the distributed activation energies of the oxidation process obtained by the Avrami-Eroféev model are 42.079 kJ mol(-1), 42.944 kJ mol(-1) and 41.711 kJ mol(-1) for the YBaCo(4)O(7+δ) , Y(0.95)Ti(0.05)BaCo(4)O(7+δ) and Y(0.5)Dy(0.5)BaCo(4)O(7+δ) oxygen carriers, respectively. The kinetic model was obtained to predict the oxygen carrier conversion of oxygen absorption for different time durations. The kinetic parameters obtained here are quite vital when this material is used in reactors.