Non-conductive ferromagnets based on core double-shell nanoparticles for radio-electric applications.

Hélène Takacs,Hanako Okuno,Pierre-Henri Jouneau,Florence Duclairoir,Vanessa Hermán,Gwenolé Tallec,Jean-Hervé Tortai,Bernard Viala,Juvenal Alarcon Ramos

doi:10.1186/s40064-016-2099-3

Abstract

Two fabrication schemes of magnetic metal-polymer nanocomposites films are described. The nanocomposites are made of graphene-coated cobalt nanoparticles embedded in a polystyrene matrix. Scheme 1 uses non-covalent chemistry while scheme 2 involves covalent bonding with radicals. Preservation of the net-moment of cobalt and electrical insulation are achieved by means of a core double-shell structure of cobalt–graphene–polystyrene. The graphene shell has two functions: it is a protective layer against metal core oxidation and it serves as the functionalization surface for polymer grafting as well. The polystyrene shell is used as an insulating layer between nanoparticles and improves nanoparticles dispersion inside the polystyrene matrix. The theoretical maximum volume filling ratio estimated at ~30 % is almost reached. The nanocomposites are shown to undergo percolation behavior but retain low conductivity (<1 S/m) at the highest filling ratio reached ~25 % leading to extremely low losses (10−3) at high frequency. Such low conductivity values are combined with large magnetization, as high as 0.9 T. Ability for radiofrequency applications is discussed in regards to the obtained magnetization.

Highlights

Polymer nanocomposites are attractive materials due to the ability to tailor final properties
Recent works on nanocomposites of cobalt were reported but magnetization degradation was observed indicating that stable nanoparticles are needed (Nelo et al 2010; Raj et al 2014)
Nanocomposites formulations The overall preparation was based on sonochemistry

Summary

Background

Polymer nanocomposites are attractive materials due to the ability to tailor final properties They consist in nanometer fillers embedded in a matrix. Recent works on nanocomposites of cobalt were reported but magnetization degradation was observed indicating that stable nanoparticles are needed (Nelo et al 2010; Raj et al 2014). They can be protected with a shell that must be a protection against surface oxidation and spin-quenching especially with cobalt (van Leeuwen et al 1994). Particles need to be strongly bound to the polymer to get a cohesive structure It was reported with Co/C grafted elastomers in (Fuhrer et al 2009).

Methods

Results and discussion

10-2 Series-B

Conclusion