Synthesis and characterization of nano-structured molybdenum-iron intermetallics by gas-solid reaction technique

International Conference on Materials, Processing and Product Engineering 2015

El-Geassy, A.A.^1 ; Seetheraman, S.^2

Central Metallurgical Research and Development Institute, P.O. Box 87-Helwan, Cairo, Egypt^1

Royal Institute of Technology, KTH, Stockholm

SE-100 44, Sweden^2

关键词: Ammonium molybdate;    Decomposition reaction;    Iron intermetallics;    Isothermal reduction;    Macro- and microstructure;    Reduction conditions;    Synthesis and characterizations;    Visual observations;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/119/1/012012/pdf
DOI  :  10.1088/1757-899X/119/1/012012

来源: IOP

【 摘 要 】

Ammonium molybdate and ferrous oxalate were used for the synthesis of nano-structured Mo-Fe intermetallics. Co-precipitation technique was applied to produce Mo/Fe precursors containing 58/42, 72/28 and 30/70 mass% respectively. The different phases formed were identified by XRD. The macro- and microstructures were microscopically examined by Reflected Light Microscope (RLM) and Scanning Electron Microscope (SEM) coupled with Electron Dispersion Spectroscopy (EDS). TG-DTA-DSC technique was applied to follow up the behavior of precursors up to 900oC (10K/min.). Endothermic peaks were detected at 97.8, 196.9 and 392.7oC due to the decomposition reactions to produce MoO3and Fe2O3. The exothermic peak resulted at 427.8oC is due to the solid state reaction between these oxides to form Fe2(MoO4)3. Precursors were isothermally reduced at 600-850oC in a flow of purified H2and the O2-weight loss from the reduction reactions was continuously recorded as a function of time. The isothermal reduction behavior of precursors was investigated. The structures of reduced products and the different phases formed were investigated and correlated with the reduction conditions. At >60% reduction extents, Fe2(MoO4)3] phase was first reduced to Fe2MoO3O8before the formation of FeMo, while FeMoO4and MoO2were reduced to FeMo and Mo. In precursors containing higher content of Fe2O3, FeMo, Fe3Mo and Fe phases were produced. The visual observation of reduced samples showed that the volume was gradually shrinking with rise in temperature up to 800oC and beyond which a measurable swelling was observed reaching about 170% at 900oC.