On the Reduction of Nickelferrite with Hydrogen

Abstract

In the current investigation, the reduction rate of a nickelferrite pellet with hydrogen gas has been measured by the thermobalance method at temperatures between 400° and 900°C. The reduction process of nickelferrite has also been examined by means of X-ray analysis, infrared absorption spectra and transmission electron microscopy. The exerimental results obtained are as follows:
(1) The beginning point of the reduction of nickelferrite with hydrogen gas is about 315°C and the reduction curves of nickelferrite pellets in the range 0 to 80% reduction agree with the experimental equation derived by Mckewan, which is commonly used for the reaction controlled by the interfacial area.
(2) Apparent activation energies on the hydrogen reduction of the nickelferrite pellet are 15.8 kcal/mol below 600°C and 9.1 kcal/mol above 600°C, respectively. The values show an approximate agreement with those obtained previously for iron oxide.
(3) The rate of reduction of the nickelferrite pellet is proportional to the hydrogen pressure at 500° and 700°C.
(4) According to the data obtained from X-ray analysis and infrared absorption spectra, it is found that nickelferrite is decomposed into magnetite, metallic nickel and iron at 500°C, and magnetite, wustite, metallic nickel and iron at 700°C. The reduction products, metallic nickel and iron, finally form iron-nickel alloy.