دانلود مقاله : An experimental investigation of aqueous-phase synthesis of magnetite nanoparticles

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.