EFFECT OF TEMPERATURE AND TIME ON THE STRUCTURE OF MAGNETITE COMPACTS

Magnetite compacts prepared by hydrogen reduction of hematite were ind urated at 973-1273 K for 15-120 min in an inert nitrogen atmosphere to study the potential changes in the structure which are similar to tho se taking place during gaseous reduction of iron oxides. The structure of the indurated compacts was examined using a reflected light micros cope and a mercury pressure porosimeter. Total porosity, pore surface area, average pore size and shrinkage were measured and correlated to the induration conditions. The structure of magnetite showed lower por osity and surface area and larger pore size as compacts were sintered at high temperatures. Analysis of the sintering shrinkage data based o n the different sintering mechanisms models, indicated that grain boun dary diffusion, at an activation energy of 105-107 kJ/mole, was the pr edominant controlling mechanism. A comparative study of the structural changes of hematite and magnetite under the same reduction temperatur e was presented.