Mechanosynthesis and process characterization of nanostructured manganese ferrite

• Published in: Materials chemistry and physics Vol. 90; no. 1; pp. 172 - 177
• Main Authors: Padella, F., Alvani, C., Barbera, A. La, Ennas, G., Liberatore, R., Varsano, F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2005
• Subjects: Hydrogen production; Manganese ferrite; Mechanosynthesis; Nanostructured ferrite; Rietveld method; Manganese ferrite; Rietveld method; Nanostructured ferrite; Mechanosynthesis; Hydrogen production
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2004.10.033

Nanocrystalline MnFe 2O 4 particles were synthesized by a high-energy ball milling technique, starting from a manganosite (MnO) and hematite (α-Fe 2O 3) stoichiometric powder mixture. The mechanosynthesis process was performed at room temperature both in hardened steel and in tungsten carbide vials. X-ray powder diffraction quantitative phase analysis by the Rietveld method was used to study the chemical transformations promoted by the milling action. The nanocrystalline MnFe 2O 4 spinel phase begins to appear after 10 h of milling and reaches its maximum content (≈0.8 molar fraction) after 35 h of milling. A prolonged milling time induces a dramatic contamination of the powder mixture, when hardened stainless steel was adopted, due to metallic iron originating from vial and balls debris. Ball milling is able to induce a redox reaction between Fe III and metallic iron, transforming the MnFe 2O 4 spinel phase into a wüstite type (Fe, Mn)O phase. The yield of the hydrogen production reaction on synthetised materials is reported.