Iron oxide nanoparticles fabricated by electric explosion of wire: Focus on magnetic nanofluids

Nanoparticles of iron oxides (MNPs) were prepared using the electric explosion of wire technique (EEW). The main focus was on the fabrication of de-aggregated spherical nanoparticles with a narrow size distribution. According to XRD the major crystalline phase was magnetite with an average diameter of MNPs, depending on the fraction. Further separation of air-dry EEW nanoparticles was performed in aqueous suspensions. In order to provide the stability of magnetite suspension in water, we found the optimum concentration of the electrostatic stabilizer (sodium citrate and optimum pH level) based on zeta-potential measurements. The stable suspensions still contained a substantial fraction of aggregates which were disintegrated by the excessive ultrasound treatment. The separation of the large particles out of the suspension was performed by centrifuging. The structural features, magnetic properties and microwave absorption of MNPs and their aqueous solutions confirm that we were able to obtain an ensemble in which the magnetic contributions come from the spherical MNPs. The particle size distribution in fractionated samples was narrow and they showed a similar behaviour to that expected of the superparamagnetic ensemble. Maximum obtained concentration was as high as 5 % of magnetic material (by weight). Designed assembly of de-aggregated nanoparticles is an example of on-purpose developed magnetic nanofluid. Copyright © 2012 Author(s)

Carbon coated Nickel Nanoparticles in Polyacrylamide Ferrogels: Interaction with Polymeric Network and Impact on Swelling

Polyacrylamide ferrogels with embedded magnetic nanoparticles of metallic nickel (Ni) and nanoparticles of nickel coated with a carbon shell (Ni@C) were synthesized by radical polymerization in water. The effect of the carbon shell on the interaction of Ni and Ni@C nanoparticles with polyacrylamide matrix and on swelling ratio of the ferrogels has been studied. The deposition of carbon on the surface of Ni nanoparticles worsens their interaction with polyacrylamide but at the same time elevates the water uptake by ferrogels

Magnetic properties and giant magnetoimpedance effect for CoFeMoSiB surface modified amorphous ribbons covered by water based ferrofluid

Giant magnetoimpedance (GMI) effect is a powerful technique for magnetic label detection. Co-based amorphous ribbons are cheap materials showing high GMI effect at low operation frequencies for close to zero magnitostriction compositions. In this work magnetic properties and GMI were studied for CoFeMoSiB amorphous ribbons in as-quenched and surface modified states without and in the presence of water-based ferrofluid with electrostatic stabilization of γ-Fe2O3 nanoparticles. Surface modification by ultrasound treatment resulted in appearance of round defects with average diameter of about 150 micrometers. The GMI difference for as-quenched ribbons in absence and in the presence of ferrofluid was measured for the frequency range of 0.5 to 10 MHz. Although proposed surface modification by the ultrasound treatment did not improve the sensitivity limit for ferrofluid detection, it did not decrease it either. Observed changes of GMI are useful for understanding of functionality of GMI biosensors. © 2018 The Authors, published by EDP Sciences.The work was supported in part by the Government of the B is acknowledged for financial support under th e Elkartek Program, the Project Micro4Fab (KK -206/01 30)00 and the Ministry of dE ucation and Science of the RF Project N 055 , within the state job 3.21.61 20/17.9 . We thank I.V. Beketov , A.I . Medvedev and A. Larr anga for special support. Selected measurements were made at SGIKER services of .UPV/EH

Magnetostriction in ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles

Magnetostriction of ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles was studied in 420 mT uniform magnetic field. Ferrogel with physical networking was based on natural polysaccharide - guar gum, which gelates due to formation of H-bonds. Ferrogel with chemical networking was synthesized by radical polymerization of acrylamide. Magnetostriction of the physical ferrogel resulted in the increase of length of the gel specimen along the field lines and in the proportional decrease of its width in the direction across the field lines. In case of chemical ferrogel, both the length and the width increased in the uniform magnetic field leading to the increase of the ferrogel volume. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-19-00090The work was performed under financial support from Russian Science Foundation grant 18-19-00090

HYGIENIC ASSESSMENT OF QUALITY OF ENVIRONMENT IN SHELEKHOV (IRKUTSK REGION)

The aim of the research was to give an assessment of quality of environment and ensuring sanitary and epidemiologic wellbeing of the population of Shelekhov region. The research was conducted with use of data of municipal information fund of social-hygienic monitoring of Territorial Department of Administration of Rospotrebnadzor of Shelekhov, Shelekhov and Slyudanka regions during 2007-2011. Complex assessment of pollution of atmospheric air in ground layer was conducted by Ktotal index and Hazard index (HI). Upon the results of laboratory researches the assessment of pollution of soils in residential area of the city. Data of control of contents of fluorine, zinc, cadmium, lead and copper is used, total hazard is estimated with use of Ksoil index. The analysis of morbidity was conducted on the data of report form N 12. As the result of insufficient measures on the sanitary protection of water-supply sources low effectiveness of water-treatment the large part of drinking water samples that didn't meet the hygienic requirements was found: 2,5-3,7 % - based on the sanitary-chemical indices and about 3 % - based on the indices of microbiological safety. It was found that 100 % of soil samples didn't correspond to the claims of hygienic normative in fluorine contents. The territory of the city is characterized by the high level of air pollution with harmful admixtures of anthropogenic nature. The dust with silicon oxides and gaseous compounds of fluoride, benz(a)pyrene, sulfur dioxide, manganese, nitrogen oxides, carbonic oxide, formaldehyde were found to be priority chemical substances which may pollute atmospheric air. Respiratory organs, blood, eyes, immune and nervous systems were found to be the most loaded with the non-cancerogenic risk that may conform with actual data on the children's morbidity rate. During the period of 2003-2011 the morbidity rate of respiratory organs, blood, eyes as well as nervous systems was found to be higher in the children in Shelekhov than the average one in Irkutsk region. Thus the main role of formation of unfavorable environmental situation in Shelekhov was found to be associated with the pollution by hydrogen fluoride as well as by benz(a)pyrene. The environmental pollution and other unfavorable factors may significantly deteriorate the state of population health of the city

Planetary migration in evolving planetesimals discs

In the current paper, we further improved the model for the migration of planets introduced in Del Popolo et al. (2001) and extended to time-dependent planetesimal accretion disks in Del Popolo and Eksi (2002). In the current study, the assumption of Del Popolo and Eksi (2002), that the surface density in planetesimals is proportional to that of gas, is released. In order to obtain the evolution of planetesimal density, we use a method developed in Stepinski and Valageas (1997) which is able to simultaneously follow the evolution of gas and solid particles for up to 10^7 yrs. Then, the disk model is coupled to migration model introduced in Del Popolo et al. (2001) in order to obtain the migration rate of the planet in the planetesimal. We find that the properties of solids known to exist in protoplanetary systems, together with reasonable density profiles for the disk, lead to a characteristic radius in the range 0.03-0.2 AU for the final semi-major axis of the giant planet.Comment: IJMP A in prin

Electomagnetic absorption of composites based on epoxy resin and metallic iron nanoparticles

The heat losses originated from the electro-magnetic absorption in magnetic epoxy-based composites with embedded metallic iron nanoparicles were studied by Calvet microcalorimetry. Iron magnetic nanoparticles (MNPs) were synthesized by electrical explosion of wire (EEW) method; they were non-agglomerated, spherical in shape and had a weight average diameter 85 nm. Composites based on the cured epoxy-dian resin contained MNPs in weight content varying from 10% up to 70%. To study the heat loss in alterating magnetic field commercial Calvet microcalorimeter was equiped by two coils in the serial connection placed in the calorimeter cells; one of the coils contained a sample of composite the other was a reference. The electromagnetic adsorption was studied in the alternating magnetic field up to 1700 A/m in 67-214 kHz frequency range. The measured values of the specific power losses revealed linear dependence on iron MNPs content in composite and non-linear increasing function of the field frequency. © 2018 The Authors, published by EDP Sciences.This work is supported in part by the project for basic research of UD RAS. The assistance of Shchipanova T. A. in the measurements of hysteresis loops for composites is appreciated

Preparation of alumina nanoparticle suspensions with narrow particle size distribution

Dynamic light scattering (DLS) was applied to the study of the process of the preparing deaggregated water suspensions of alumina nanopowders with specific surface areas of 20-140 m2/g. Nanopowders were prepared by the electric explosion of wire and laser evaporation and, according to electron microscopy (TEM), consisted of nonagglomerated spherical nanoparticles with lognormal size distribution. According to DLS, nonsedimenting water suspensions of alumina nanoparticles, stabilized by sodium citrate at a 5 mM concentration, contain substantial fraction of aggregates. The dynamics of the change in the mean average size of aggregates under exhaustive ultrasound treatment of suspensions with 10 g/l concentration for 1.5-4 h by two types of ultrasonic processors was studied. It was shown that the mean average size of aggregates exponentially diminishes by 1.5-2 times and the fraction of individual particles in suspension enlarges from 45 to 85%. Sequentially centrifuging the suspension at 18000 g separates the remaining aggregates and results in suspensions of individual alumina nanoparticles. Particle size distributions in these suspensions obtained by TEM and DLS are the same within experimental error. © 2013 Pleiades Publishing, Ltd