Tatiana S. Gendler

Iron-Based Amorphous Magnetic Phase Formation in the Course of Fe and Fe2O3 Mechanical Activation

Solid phase high energy mechanochemical interaction of α-Fe2O3(hematite) and Fe in powder mixture have been studied. The formation of amorphous iron-based magnetic phase in this process was detected by means of Mossbauer spectroscopy and magnetic measurements. The amount of this phase increases with Fe addition in reduced mixture. Its thermal stability have been studied by magnetic and DCS measurements at constant α-Fe2O3 and gradually increased Fe concentrations.

The Influence of Surface Active Substances Various Concentrations on Goethite Nanoparticles Magnetic Properties

Goethite nanopowder was prepared in the process of chemical precipitation of iron salt (FCl3) and alkali (NaOH) with addition of various surface active substances (SAS): cation-active cetylpyridinium chloride (CPC), anion-active sodium dodecyl sulphate (SDS) and complexon EDTA. The concentrations of SAS were 0.3% and 1%. It could be deduced from TEM data that these SASes unambiguously influence sizes of prepared goethite particles, compared with samples, obtained without SAS: in case of adding 1% SDS and EDTA significant crystal growth takes place. To explain this situation the study of magnetic characteristics and phase composition of obtained nanoparticles was carried out using Mossbauer spectroscopy and thermomagnetic analysis (TMA). It was suggested, that different organic Fe3+- complexes formed on goethite surface under SAS influence take part in the goethite crystallization process.

Comparative Analysis of γ-Fe2O3 Nanoparticles Magnetic Interactions in Different Polymeric Nanocomposites

The comparative study of Fe2O3 4-10nm nanoparticles incorporated in arabinogalactan and polyvinyl alcohol matrixes was performed by means of magnetic measurements in wide 5-900K temperature range, Mossbauer spectroscopy and transmission electron microscopy. The processes of nanoparticles different self-organization inside various polymer matrixes were revealed. These processes lead to unusual magnetic behavior of initially superparamagnetic nanoparticles owing to interparticle interactions.

Influence of Surface Active Substances on Magnetic Properties of Goethite Nanoparticles

To receive monosized goethite (α-FeOOH) nanoparticles powders in the process of chemical precipitation of iron salt and alkali various surface active substances (SAS) with concentration of 0.3% were added to water: C12H25NaO4S (anion active), C12H38ClN (cation active) and EDTA – C10H14O8N2Na2 (complexon). It has been determined that the magnetic properties of the nanoparticles under investigation change in comparison with the nanoparticles obtained without SAS addition. In all the samples under study very interesting saturation magnetization temperature dependences have been obtained. They indicate the difference in goethite temperature phase transformations connected with various surface layers formed on the nanoparticles under SAS influence.

Amorphous Shell Formation on the Iron Particles during Mechanosynthesis in Fe2O3/Fe/(Ga,Al) Mixtures

Amorphous shell formation on the Fe-particles surface in course of mechanochemical nanocomposite synthesis in Fe2O3+Fe, Fe2O3+Al+Fe, and Fe2O3+Ga+Fe powders mixtures have been observed by Mössbauer spectroscopy and magnetic measurements.

Magnetic Properties Dependence of Polymer Nanocomposite on Iron Oxide nanoparticles Concentration

To study the nature of anisotropy effects in samples of polymer (PVA) films containing nanoparticles of magnetite, depth selective conversion Mossbauer spectroscopy (for layer‐by‐layer phase and magnetic analysis), natural remanent magnetization Jn measurements in three mutual — orthogonal directions and atomic force microscopy were used. These investigations revealed formation of the “in plane” direction of linear Fe3O4 nanoparticles chains and their number increases with nanoparticles concentration growth in the samples.

Magnetodeformational Anisotropy of FeGa/PU Hybrid Nanocomposite via Particle Concentration and Spatial Orientation

The present work has been undertaken to research effects of structure, morphology, volume fraction, spatial arrangement of magnetostrictive intermetallic FeGa alloy particles dispersed in modified polyurethane matrix. Correlation of composite magnetic behavior with structure and mechanical properties has been obtained by measurements of magnetostriction, remanent magnetization anisotropy, SEM, and dynamical mechanical analysis. Anisotropic chain structures of magnetic particles within the polymer with different interparticle interactions were observed. The increase of the magnetostrictive response with tailor-made magnetic anisotropy induced by magnetic particles volume fraction has been demonstrated

Investigation of Hydrothermally Synthesized Greigite Magnetic Properties

Greigite (Fe3S4) is an iron sulfide with inverse spinel structure, same as the structure of magnetite. Half-metallic properties in combination with ferrimagnetic nature of greigite puts this mineral in a fairly narrow group of materials that are potentially suitable for spintronics [1]. In this paper, we have conducted a comparative study of magnetic properties of two crystalline greigite samples obtained by hydrothermal synthesis with different parameters.Conducted Mossbauer spectroscopy study has shown that there are two magnetically non-equivalent B-site iron positions. The interpretation of this result was given using a model for magnetite from [2]. Unusual temperature dependencies of effective magnetic fields for A-and B-site iron atoms were obtained. It was found that coercive magnetic parameters as well as greigite stability depend on the synthesis procedure. Stepwise thermomagnetic analysis in saturating field allowed us to obtain the synthesized greigite critical temperatures of structural stability (T ~ 240oC), after which the sequential process of greigite transformation to pyrite, metastable maghemite (or magnetite) and finally to hematite begins. All of the found greigite peculiarities not only expand the knowledge about this complicated ferrimagnetic phase but can be used as guidance for optimal synthesis conditions.

Magnetic Properties and Thermal Stability of xFe (100-x)SiO2 (x=5-95) Powder Nanocomposites

The study of Fe/SiO2 nanocomposites magnetic properties and structure relationships was performed in dependence on Fe to SiO2 relative concentration and type of precursors preparation (mechanical mixing or ultrasonic homogenization). Thermal metallization method in hot hydrogen of initial reagents [хFeOOH and (100-x)SiO2] was applied for nanocermets production. It was determined that formation of air-tight shell on the particles surface affects the nanocomposites magnetization values and their air temperature stability.

The influence of surface-active substances on the crystallization process and magnetic properties of goethite nanoparticles

To prevent the process of aggregation and growth of α-FeOOH nanoparticles, during chemical syntheses various surface-active substances (SASs) with a concentration of 3 g/dm3 were added into the solution. The applied SASs were: cetylpyridinium chloride (CPC), sodium dodecyl sulphate (SDS), and complexone EDTA. Using various methods it was found that SAS molecules have a dual effect on the obtained nanoparticles: on one hand SAS application increases the number of small α-FeOOH nanoparticles with sizes of 2–5nm. On the other hand, SAS molecules react with surface atoms of the nanoparticles and form additional compounds.