Preparation of Ultrafine Magnetic Particles Using Microemul-sions and Vesicles

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In recent years, there has been an increasing demand for the preparation of ultrafine magnetic oxides of uniforms size which are mainly used in computer data storage, audio and video recording, magnetic fluids and fabrication of certain microwave devices. The difficulty of obtaining uniform-sized nanoparticles of magnetic oxides stems from the fact that their preparations are mostly done in bulk aqueous media in which uncontrolled nucleation and grain growth cannot be prevented. Synthesis of these compounds (gamma-Fe2O3, Fe3O4, CrO2, Cobalt doped Fe2O3 and barium ferrite) in constrained microreactors such as the aqueous cores of water-in-oil microemulsions or the inner part of single-compartment vesicles seems to be a promising alternative although these techniques are still under development. In this project, methods are used to optimize and control the ultralow size and the narrow particle size distribution by proper modulation of certain physico-chemical conditions of the microemulsion and vesicular systems. Further, the project examines how to make quantitative correlations between the morphology (size, shape, and size-distribution) and structure of the product microparticles and the physico-chemical properties of the surfactant system. The results of the study delineate the similarities as well as the differences between the two types of microreactors (microemulsions and vesicles) in relation to chemical reactions in them. The solid precipitate obtained from such microreactors may be different from that precipitated in a large aqueous medium. Not only might these experiments lead to the production of monodispersed ultrafine magnetic particles, but they might also provide a greater fundamental understanding of interfacial chemistry in relation to nucleation and crystal growth in microreactors. This project exploits the expertise of two research groups (Rhode Island and University of Florida).