15 research outputs found
Large enhanced dielectric permittivity in polyaniline passivated core-shell nano magnetic iron oxide by plasma polymerization
Commercial samples of Magnetite with size ranging from 25â30nm were coated with polyaniline by
using radio frequency plasma polymerization to achieve a core shell structure of magnetic nanoparticle
(core)âPolyaniline (shell). High resolution transmission electron microscopy images confirm the core
shell architecture of polyaniline coated iron oxide. The dielectric properties of the material were
studied before and after plasma treatment. The polymer coated magnetite particles exhibited a large
dielectric permittivity with respect to uncoated samples. The dielectric behavior was modeled using a
MaxwellâWagner capacitor model. A plausible mechanism for the enhancement of dielectric
permittivity is propose
Evidence for intergranular tunnelling in polyaniline passivated α-Fe nanoparticles
Nanoparticles are of immense importance both from the fundamental and
application points of view. They exhibit quantum size effects which are
manifested in their improved magnetic and electric properties. Mechanical
attrition by high energy ball milling (HEBM) is a top down process for
producing fine particles. However, fineness is associated with high surface
area and hence is prone to oxidation which has a detrimental effect on the
useful properties of these materials. Passivation of nanoparticles is known to
inhibit surface oxidation. At the same time, coating polymer film on
inorganic materials modifies the surface properties drastically. In this work a
modified set-up consisting of an RF plasma polymerization technique is
employed to coat a thin layer of a polymer film on Fe nanoparticles produced
by HEBM. Ball-milled particles having different particle size ranges are
coated with polyaniline. Their electrical properties are investigated by
measuring the dc conductivity in the temperature range 10â300 K. The low
temperature dc conductivity (IâV ) exhibited nonlinearity. This nonlinearity
observed is explained on the basis of the critical path model. There is
clear-cut evidence for the occurrence of intergranular tunnelling. The results
are presented here in this paperCochin University of Science and TechnologyNanotechnology 17 (2006) 4765â477
Contact potential induced enhancement of magnetization in polyaniline coated nanomagnetic iron oxides by plasma polymerization
The present work derives motivation from the so called surface/interfacial magnetism in core shell
structures and commercial samples of Fe3O4 and c Fe2O3 with sizes ranging from 20 to 30 nm were
coated with polyaniline using plasma polymerization and studied. The High Resolution
Transmission Electron Microscopy images indicate a core shell structure after polyaniline coating
and exhibited an increase in saturation magnetization by 2 emu/g. For confirmation, plasma
polymerization was performed on maghemite nanoparticles which also exhibited an increase in
saturation magnetization. This enhanced magnetization is rather surprising and the reason is found
to be an interfacial phenomenon resulting from a contact potential.Cochin University of Science and TechnologyAppl. Phys. Lett. 103, 162414 (2013