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Microstructure of Bentonite in Iron Ore Green Pellets

Published online by Cambridge University Press:  07 January 2014

Iftekhar U. Bhuiyan ,
Johanne Mouzon ,
Birgit Schröppel ,
Andres Kaech ,
Illia Dobryden ,
Seija P.E. Forsmo  and
Jonas Hedlund
Iftekhar U. Bhuiyan
Affiliation:
Chemical Technology, Luleå University of Technology, SE-971 87 Luleå, Sweden
Johanne Mouzon*
Affiliation:
Chemical Technology, Luleå University of Technology, SE-971 87 Luleå, Sweden
Birgit Schröppel
Affiliation:
Natural and Medical Sciences Institute (NMI), University of Tübingen, 72 770 Reutlingen, Germany
Andres Kaech
Affiliation:
Center for Microscopy and Image Analysis, University of Zurich, CH-8006 Zurich, Switzerland
Illia Dobryden
Affiliation:
Division of Physics, Luleå University of Technology, SE-971 87 Luleå, Sweden
Seija P.E. Forsmo
Affiliation:
LKAB, R&D, SE-983 81 Malmberget, Sweden
Jonas Hedlund
Affiliation:
Chemical Technology, Luleå University of Technology, SE-971 87 Luleå, Sweden
*
*Corresponding author. E-mail: johanne.mouzon@ltu.se
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Abstract

Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

Keywords

microstructurehigh pressure freezingplunge freezingfreeze fracturecryo-SEMbentonitemagnetiteiron oregreen pellets
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 20 , Issue 1 , February 2014 , pp. 33 - 41
Copyright
Copyright © Microscopy Society of America 2014 

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