Journal of Nanomedicine & Nanotechnology

Dielectric properties of the composites containing superparamagnetism particles

2^nd World Congress on Nanoscience and Nanotechnology

August 10-11, 2018 Osaka, Japan

Masaru Matsuo

Dalian University of Technology, China

Keynote: J Nanomed Nanotechnol

Abstract:

Superparamagnetism particles have been applied to magnetic fluids, microwave absorption materials, drug delivery systems and pigments. The high magnetization under external applied magnetic field could be obtained by using Zn-doped Fe3O4 nanoparticles. By the replacement of Fe3+ ions by Zn2+ ions in A-site of Fe3O4 crystal unit with inverse-spinel ferrite, the super-exchange interaction between spins of Fe3+ existing in A-site and B-site becomes weakened, while the double-exchange interaction between Fe3+ and Fe2+ in B-site remains. This indicates that the magnetization increases with Zn doping. Different from the general concept, however, the highest magnitude was x=0.2 when Zn-doped Fe3O4 is represented as ZnxFe3-xO4 (0???x???1). To investigate such contradiction, the crystallinity and crystal size of Fe3O4 by the doping were evaluated using X-ray and dielectric measurements. The crystallinity and crystal size decreased with increasing x up to 0.4 but they increased beyond 0.5 inversely. This indicated that Fe3O4 crystal cannot accept further doping by Zn2+ to maintain ZnxFe3-xO4 crystal. This is since Zn doping resulted in the damage of the Fe3O4 crystal, since the atomic size (74 pm) of Zn2+ is bigger than that of Fe3+ (64 pm). As for Mg doping represented as MgxFe3-xO4, Fe3O4 crystal accepted Mg2+ up to x=1 because of similar size of Mg2+ (65 pm). In this case, Fe3+ ion in A-site becomes zero and crystal structure of Fe3O4 crystal was collapsed. The crystallinity and crystal size were sensitive to their dielectric properties. The complex impedance for Mg0.6Fe2.4O4 and MgFe2O4 with no crystal domain can be represented by Kramers-Kronig relation which has been utilized for amorphous materials, while that for Fe3O4 and Zn0.2Fe2.8O4 can be represented by the equivalent circuit model with three units relating to suppressed circle by Cole-Cole plots. The three units correspond to particle (grain) resistance, grain boundary resistance and interface resistance between electrode and grains indicating the existence of crystal particles. The dielectric behaviors of superparamagnetism particles were in good agreement with X-ray diffraction profiles. The DC component of conductivity (frequency???0) was highest for Zn0.2Fe2.8O4 with the highest magnetization.

Biography :

Masaru Matsuo has completed his PhD at Kyoto University in Japan and he was a Professor of Nara Women’s University. After his retirement, he became a full time Professor of Dalian University of Technology in China. Since 2014, he is a Visiting Professor of Dalian University of Technology. He has published more than 200 papers in refereed journal articles. He is IUPAC Fellow and Certificate of Membership Award of ACS (2015-2018). He has received Award of Society of Fiber Science and Technology of Japan and Certificate of Friendship Award of Liaoning Province in China on September 2011.

E-mail: mm-matsuo@live.jp