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Open Access Nano Express

Nearly Monodispersion CoSm Alloy Nanoparticles Formed by an In-situ Rapid Cooling and Passivating Microfluidic Process

Yujun Song1* and Laurence L Henry2

Author Affiliations

1 Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, 100191, Beijing, China

2 Department of Physics, Southern University A & M College, Baton Rouge, LA, 70813, USA

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Nanoscale Research Letters 2009, 4:1130-1134  doi:10.1007/s11671-009-9369-8

Published: 14 June 2009

Abstract

An in siturapid cooling and passivating microfluidic processhas been developed for the synthesis of nearly monodispersed cobalt samarium nanoparticles (NPs) with tunable crystal structures and surface properties. This process involves promoting the nucleation and growth of NPs at an elevated temperature and rapidly quenching the NP colloids in a solution containing a passivating reagent at a reduced temperature. We have shown that Cobalt samarium NPs having amorphous crystal structures and a thin passivating layer can be synthesized with uniform nonspherical shapes and size of about 4.8 nm. The amorphous CoSm NPs in our study have blocking temperature near 40 K and average coercivity of 225 Oe at 10 K. The NPs also exhibit high anisotropic magnetic properties with a wasp-waist hysteresis loop and a bias shift of coercivity due to the shape anisotropy and the exchange coupling between the core and the thin oxidized surface layer.

Keywords:
Nanoparticles; Microfluidic reactor; Synthesis; Monodispersion; Alloy; Cobalt; Samarium