چکیده :
A newly developed mechanochemical process for the simple aqueous phase synthesis of crystalline magnetite
nanoparticles has been experimentally investigated. In this process, a suspension of ferric hydroxide
precursor is milled at room temperature using a horizontal tumbling ball mill consisting of a stainless
steel pot and balls. Ferric hydroxide is transformed to magnetite without the use of a reducing agent. As a
model starting material for the investigation, a pH-adjusted suspension of crystalline goethite was used.
As the milling time increased, goethite disappeared along with the simultaneous formation of magnetite.
A single phase of magnetite was obtained after 16 h of milling. A reaction mechanism for the formation of
magnetite has been proposed based on oxidation–reduction reactions, in which the corrosion of iron in
the pot and balls plays an important role. Free electrons are generated by the release of ferrous ions from
the stainless steel in an anodic reaction, which then reduce goethite to ferrous hydroxide in a cathodic
reaction. The solid phase reaction between ferrous hydroxide and goethite produces magnetite. Not only
could the mechanochemical effect induced by the collision of balls accelerate the corrosion even under
alkaline conditions, it can also promote the formation and crystallization of magnetite.
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