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Journal of Nanomaterials
Volume 2013, Article ID 612894, 7 pages
Research Article

Synthesis and Magnetorheology Study of Iron Oxide and Iron Cobalt Oxide Suspensions

1Institute of Organic and Polymeric Materials, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao E. Road, Taipei 10648, Taiwan
2Center Condensed Matter Science, National Taiwan University, Taipei, Taiwan

Received 9 March 2013; Revised 25 May 2013; Accepted 27 May 2013

Academic Editor: Anjan Barman

Copyright © 2013 Syang-Peng Rwei et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This study investigates the magnetorheology (MR) of polydimethylsiloxane (PDMS) that contains magnetic powders of various compositions, shapes, and concentrations. Two magnetic powders, Fe3O4 and CoFe2O4, were synthesized. TEM images reveal that a powder of spherical particles was obtained at high temperature. A powder with nonspherical star shape was synthesized at low temperature. A rheological test confirmed a typical Bingham behavior for all the MR fluids prepared in this study. Experimental results demonstrated that the cobalt ferrite exhibited a more superior yield stress than the ferrite compound. A magnetic powder of larger particles was found to have higher yield stress. Moreover, the spherical particles yielded a higher yield stress than the star-shaped particles. The “saturated magnetic strength” increased with the loading of the magnetic powder. Finally, the results demonstrate that 12 wt% CoFe2O4 nanopowder (10 nm) dispersed in the PDMS liquid exhibited a large range of yield stresses (0 to 644 Pa).