Premium
Influence of Manganese Oxide and Silica on the Morphological Structure of Hematite Compacts
Author(s) -
ElGeassy A.A.,
Nasr M.I.,
Mousa E.A.
Publication year - 2010
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.1002/srin.200900121
Subject(s) - materials science , swelling , hematite , manganese , whiskers , volume (thermodynamics) , isothermal process , wüstite , metal , sintering , ferrite (magnet) , metallurgy , chemical engineering , composite material , thermodynamics , physics , engineering
Abstract Dry compacts of pure Fe 2 O 3 and Fe 2 O 3 doped with either (2–6 mass%) MnO 2 , (2.5–7.5 mass%) SiO 2 or with both (2–6% MnO 2 + 7.5% SiO 2 ) were indurated at 1373 K for 6 hours and physically and chemically characterized. The fired compacts were isothermally reduced with pure CO gas at 1073–1373 K. The O 2 ‐weight loss was continuously recorded as a function of time using TGA technique. The external volume of pure and doped compacts was measured at different reduction conditions and the volume change was calculated. The structural changes accompanying the reduction process were visually and microscopically examined and the different phases were identified by X‐ray diffraction analysis. After firing, manganese ferrite (MnFe 2 O 4 ) phase was identified in MnO 2 ‐doped compacts. In pure Fe 2 O 3 compacts, the external volume of compacts was increased with reduction temperature, showing a maximum swelling value at 1198 K. Catastrophic swelling was observed in MnO 2 ‐doped Fe 2 O 3 compacts, the volume change increased with MnO 2 content showing catastrophic swelling in compacts containing 6%MnO 2 at 1248 K. The catastrophic swelling was attributed to the formation of dense metallic iron whiskers and plates in a highly porous structure. Unlike in MnO 2 ‐doped samples, no considerable volume changes were detected in SiO 2 ‐doped Fe 2 O 3 and (MnO 2 + SiO 2 )‐doped Fe 2 O 3 compacts where the presence of silica greatly hindered the swelling phenomenon at all reduction temperatures.