A.P. Safronov

Fe 45 Ni 55 Magnetic Nanoparticles Obtained by Electric Explosion of Wire for the Development of Functional Composites

Fe45Ni55 magnetic nanoparticles (MNPs) were obtained by the electric explosion of wire technique. FeNi MNPs/copolymer of 95 wt% butylacrylate and 5 wt% methacrylic acid composites in the range of 5-90 wt% of MNPs were prepared with focus on their microwave applications. Interaction between the MNPs and polymeric matrix, structure, their magnetic properties, and the composites were studied.

Tailoring functional properties of Ni nanoparticles-acrylic copolymer composites with different concentrations of magnetic filler

Magnetic composites with nickel nanoparticles synthesized by the method of the electrical explosion of wire were prepared with acrylic copolymer containing 95u2009wt.u2009% of butylacrylate and 5u2009wt.u2009% of methacrylic acid. Two series of composites were made with Ni content covering the range from 5 to 90u2009wt.u2009% and differing in the degree of aggregation. In one series of composites, the aggregates were irregularly shaped globules with dimensions varying in 1–40u2009μm range. In the other, chain-like fragments were observed. As expected, the saturation magnetization value of the composites showed a linear dependence on concentration but the coercive field was slightly higher for the aggregated case for a given concentration. Microwave absorption studies of the composites showed both strong zero field absorption and ferromagnetic resonance (FMR). The FMR results were different for the two types of samples; however, each set can be explained by taking into account the distribution of local magnetic fields due to random p...

Core-Shell Fine Structure of FeNi Magnetic Nanoparticles Produced by Electrical Explosion of Wire

Fe45Ni55 magnetic nanoparticles (MNPs) were fabricated by electric explosion of wire. In order to reduce the pyrophoricity of the MNPs, oxygen passivation was performed leading to the creation of the surface barrier layer. The surface features of MNPs are important for the development of MNPs containing composites (polymer/MNPs microwave absorbers or composites for power electronic devices). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy and X-ray photoelectronic spectroscopy (XPS) were used for structural characterization. XPS analysis of the samples was conducted varying the electron exit angle with respect to the surface. The main phase is the FeNi fcc metallic core and the barrier layer is an iron-nickel NiFe2O4 oxide with a thickness of 2-6 nm. Small toroidal cores of 1.5 cm in diameter were prepared by hot pulse pressing. Their structure was studied by XRD, SEM-EDX techniques. The magnetic properties of the cores were measured using double coil winding. Obtained materials are interesting for power and electronic applications.

Surface Modification of Thin Iron Films in Aromatic Solvents at Ambient Conditions

Recently we reported interesting phenomenon resulting in formation of irregular polycyclic structures on the surface of Fe or Ni nanoparticles immersed in toluene at ambient conditions. The objectives of the present work were to test the possibility of ambient deposition of carbon on the surface of Fe film, to study the kinetics of the deposition and to characterize the structure of the deposits. Periodic structural and magnetic measurements were performed on the dry samples just taken out of toluene. We observed that carboneous layers on the Fe surface are formed rather fast – they can be initially detected after about one week treatment.

Magnetoimpedance Effect in CoFeMoSiB As-Quenched and Surface Modified Amorphous Ribbons in the Presence of Igon Oxide Nanoparticles of Water-Based Ferrofluid

Giant magnetoimpedance (GMI) has been proposed as a powerful technique for biosensing. In GMI biosensors based on the magnetic label detection the change of the impedance of sensitive element under the application of an external magnetic field was analyzed in the presence of magnetic nanoparticles in a test solution. Amorphous ribbon-based GMI biodetectors have an advantage of low operation frequency and low cost. In this work, magnetic and GMI properties of amorphous Co68.6Fe3.9Mo3.0Si12.0B12.5 ribbons were studied in as-quenched and surface modified states both without and in the presence of maghemite ferrofluid. After the surface modification the coercivity was slightly increased and saturation magnetization decreased in good agreement with increase of the surface roughness, a decrease of magnetic elements concentrations in the surface layer, and formation of a surface protective oxide layer. The GMI difference for as-quenched ribbons in absence and in the presence of ferrofluid was measurable for the frequency range of 2 to 10u2009MHz and the current intensities of 1 to 20u2009mA. Although the proposed surface modification by the ultrasound treatment did not improve the sensitivity limit for ferrofluid detection, it did not decrease it either.

Development of Polymer-Permalloy Film Composites with or without Nanoparticles for Sensor and Microwave Applications

We have prepared spherical nanoparticles (MNPs) of FeNi and Ni by the method of the electric explosion of wire and fabricated series of polymer/MNPs and polymer/MNPs/FeNi film composites aiming to develop a technology of fabrication of magnetic composites.