The kinetics of reduction at relatively low temperatures with hydrogen of pure and doped metastable non-stoichiometric magnetite
with 1 at% Mn, Co, Ni and Cu and also with 5 at % Ni and Cu have been investigated by using isothermal thermogravimetry in
the temperature range 300–400°C. With increase in the concentration of the dopant (5 at% Ni and Cu), the reactivity increases.
The activation energies for pure magnetite varies from 7 to 9 kcal/mole with the preparation temperature of precursorf Fe2O3 (250–400°C), being the lowest for those prepared at the lowest temperatures. The corresponding activation energies for the
reduction of doped samples (Fe, M)3−zO4, it depends, apart from their porosity and surface areas, on the nature of the solute atom, amount of disorder, whether it
occupies the tetrahedral (A) or octahedral (B) sites in the non-stoichiometric spinel and possibly on hydrogen ‘Spill over’
Authors:D. Seetharamacharyulu, R. M. Mallya, and V. R. Pai Verneker
A study has been made of the differential thermal analysis of (i) potassium perchlorate in powdered form, (ii) potassium perchlorate in pelletized form, (iii) potassium perchlorate recrystallized from liquid NH3, and (iv) potassium perchlorate preheated for 24 hours at 375°. Pretreatment of potassium perchlorate leads to a desensitization of both endothermic and exothermic processes. Additionally, the pretreatment tends to convert the symmetric exotherm into an asymmetric exotherm due to merging of the two exotherms. An analysis of the factors causing asymmetry in the exotherm has thrown fresh light on the mechanism of thermal decomposition of potassium perchlorate.