Natalia E. Kazantseva

The formation mechanism of iron oxide nanoparticles within the microwave-assisted solvothermal synthesis and its correlation with the structural and magnetic properties

Magnetic nanoparticles based on Fe3O4 were prepared by a facile and rapid one-pot solvothermal synthesis using FeCl3·6H2O as a source of iron ions, ethylene glycol as a solvent and NH4Ac, (NH4)2CO3, NH4HCO3 or aqueous NH3 as precipitating and nucleating agents. In contrast to previous reports we reduce the synthesis time to 30 minutes using a pressurized microwave reactor without the requirement of further post-treatments such as calcination. Dramatically reduced synthesis time prevents particle growth via Ostwald ripening thus the obtained particles have dimensions in the range of 20 to 130 nm, they are uniform in shape and exhibit magnetic properties with saturation magnetization ranging from 8 to 76 emu g(-1). The suggested method allows simple particle size and crystallinity tuning resulting in improved magnetic properties by changing the synthesis parameters, i.e. temperature and nucleating agents. Moreover, efficiency of conversion of raw material into the product is almost 100%.

The influence of interfaces on the dielectric properties of MnZn-based hybrid polymer composites

In the present paper we report on the specific features of the dielectric properties of a MnZn ferrite/Al based composite. Previously, it has been shown that high-frequency magnetic losses in such hybrid composites (HCs) can be enhanced due to the formation of a core-shell-like structure of a composite, in which ferrite particles are immersed into a conducting medium formed by a continuous network of conducting particles that spans throughout the polymer matrix. Simultaneously, one can vary the dielectric properties of HCs by changing the type and the concentration of conducting particles. Dielectric constant and ac conductivity measurements of MnZn-based composites have been made over the frequency range of 10 Hz–100 kHz in temperature interval from −30 to 100 °C and at ambient temperature up to 3 GHz. The results obtained show that addition of aluminum into the MnZn ferrite/polyurethane composite leads to a decrease in the dc conductivity due to the insulating barrier of Al–Al2O3. On the other hand, ac ...

Maghemite based silicone composite for arterial embolization hyperthermia

Maghemite nanoparticle based silicone composite for application in arterial embolization hyperthermia is developed. It possesses embolization ability, high heating efficiency in alternating magnetic fields and radiopaque property. The initial components of the composite are selected so that the material stays liquid for 20min, providing the opportunity for transcatheter transportation and filling of the tumour vascular system. After this induction period the viscosity increases rapidly and soft embolus is formed which is able to occlude the tumour blood vessels. The composite is thermally stable up to 225°C, displays rubber-elastic properties and has a thermal expansion coefficient higher than that of blood. Maghemite nanoparticles uniformly distributed in the composite provide its rapid heating (tens of °Cmin(-1)) due to Neel magnetization relaxation. Required X-ray contrast of composite is achieved by addition of potassium iodide.

Magnetic Iron Oxide Nanoparticles for High Frequency Applications

Magnetic properties of iron oxide nanoparticles synthesized by microwave solvothermal method are reported. The effect of the nucleating agent on the composition, size, morphology and microstructure of nanoparticles was studied with a view to their correlation with magnetic properties. It is shown that a soft magnetic material with high value of magnetization saturation and high-frequency dispersion of complex permeability can be obtained by an appropriate choice of the nucleating agent.

Multicomponent Magnetic Particles With Controllable Electromagnetic Properties

In this paper, we focus on preparation and investigation of magnetic and dielectric properties of multicomponent particles with core-shell structure comprising of low-anisotropy MnZn ferrite (core) and polyaniline containing nanoparticles of noble metals (shell). The main advantage of such hybrid magnetic materials is that their electromagnetic properties can be effectively controlled by synthesis conditions. Developed materials can find their potential application as magnetic fillers in the preparation of electromagnetic wave absorbers, where high permeability, high magnetic loss, and optimum ratio between the permeability and permittivity are of high importance.

Heating Efficiency of Iron Oxide Nanoparticles in Hyperthermia: Effect of Preparation Conditions

The correlation between magneto-structural properties of iron oxide nanoparticles and their heating efficiency in ac magnetic fields is investigated. Nanoparticles with an average size of 13 nm and narrow size distribution are synthesized by coprecipitation of ferrous and ferric salts in an alkaline medium in which the salts ratio is systematically varied. To obtain nanoparticles with single-phase composition, the prepared samples are annealed at 200 °C. The lattice parameters of all nanoparticles deduced from X-ray diffraction analysis correspond to multiphase composition, i.e., to a mixture of magnetite and maghemite phases. However, low-temperature Mossbauer spectroscopy revealed complete transformation of magnetite to maghemite in annealed samples. The annealed samples show slightly higher value of specific loss power at a certain frequency and amplitude of ac magnetic field compared with other samples.