title: Citrate milling of oxides: from poly-dispersed micron scale to nearly mono-dispersed nanoscale.
abstract: Complex (multivalent/mixed valent) oxides involving two or more cations (e.g. ABO3, AB2O4 and A2B2O7) exhibit the most fascinating range of physical and chemical properties amongst the family of materials systems. There is growing interest in nanoscale forms of such oxides which emanates from the novel changes in their properties with size. To obtain nanomaterials with a high degree of crystallinity it is desirable to first make crystalline oxide powders by high temperature processing and then mill them down to nanometer size. In this paper we show that simple citric acid treatment of BiFeO3 and Bi2O3 powders leads to the desired micron-scale to nanoscale transformation, yielding nearly monodispersed nanoparticles. Importantly, these are highly dispersible and stable in water. By performing similar experiments on Fe3O4 and Fe2O3 we have elucidated the possible mechanism, which hinges on valence-controlled dissolution and ripening phenomena.
authors: National Chemical Laboratory (CSIR-NCL), Council of Scientific and Industrial Research, Pashan, Pune 411008, India.
authors: Parvez A
authors: PA
authors: Shaikh
authors: Abhik
authors: A
authors: Banerjee
authors: Onkar
authors: O
authors: Game
authors: Yesappa
authors: Y
authors: Kolekar
authors: Sangeeta
authors: S
authors: Kale
authors: Satishchandra
authors: S
authors: Ogale
mesh_terms: D001729:Bismuth / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D014867:Water / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D014867:Water; C000499:ferric oxide; D019343:Citric Acid; C033301:bismuth oxide; D001729:Bismuth