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Nomura K.,University of Tokyo | Rykov A.I.,University of Tokyo | Rykov A.I.,Mossbauer Effect Data Center | Navarro A.M.M.,National University of La Plata | And 4 more authors.
Hyperfine Interactions | Year: 2014

The magnetic properties and Mössbauer results for SnO2 doped with 57Fe are reviewed, and the values of isomer shift and quadrupole splitting are compared with the results obtained by ab initio calculations. It is concluded that the exchange interactions between oxygen defects and magnetic atoms are responsible for long range magnetic interactions of dilute Fe ions dispersed in SnO2. Fe atom precipitated clusters may be formed in highly Fe doped SnO2 samples by annealing at relatively high temperatures for several hours. The reduction of the particle size to nano-scale dimensions induces magnetization, which can be associated with oxygen defects. We have measured the nuclear inelastic scattering (NIS) spectra of Fe oxides, and 57Fe and (Co or Mn) doped SnO2 synthesized mainly by sol-gel methods and we have derived the vibration density of states (VDOS). The local phonons are sensitive to the presence of precipitated clusters. © 2013 Springer Science+Business Media Dordrecht. Source

Guan J.,Laboratory of Advanced Materials and Catalytic Engineering | Chen X.,Laboratory of Advanced Materials and Catalytic Engineering | Zhang L.,Laboratory of Advanced Materials and Catalytic Engineering | Wang J.,Mossbauer Effect Data Center | Liang C.,Laboratory of Advanced Materials and Catalytic Engineering
Physica Status Solidi (A) Applications and Materials Science | Year: 2016

Fe3Si-Al2O3 nanocomposite has been prepared by mechanical alloying of Fe3O4, Al and Si powder mixture and heat treatment. Powder XRD patterns, TEM and HRTEM images and XPS spectra revealed the crystalline transformations from raw materials to Fe3Si-Al2O3 nanocomposite during mechanical alloying and annealing and from Fe to Fe3Si to a mixture of Fe3Si, Fe5Si3 and FeSi with the proportion of Si in raw materials increasing. The average particle size of smaller Fe3Si nanoparticles was about 20nm and the aggregation under high temperature leaded to larger Fe3Si nanoparticles with average particle size of about 60nm. 57Fe Mössbauer spectra illustrated the existence of amorphous phases and effectively supplemented other characterisation results. The samples exhibited ferromagnetic behaviour with hysteresis loops and their saturation magnetisations decreased with the proportion of Si in samples increasing. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Jin C.,CAS Dalian Institute of Chemical Physics | Jin C.,Mossbauer Effect Data Center | Wang Y.,CAS Dalian Institute of Chemical Physics | Tang H.,CAS Dalian Institute of Chemical Physics | And 5 more authors.
Journal of Sol-Gel Science and Technology | Year: 2015

Abstract: The well-defined rattle-type magnetic silica nanocomposite had been synthesized through a facile sol–gel process accompanied by a hard-template method. Structural characterizations indicated that the fabricated nanocomposite, denoted as γ-Fe2O3@SiO2–@mSiO2, was composed of nonporous silica-coating magnetic iron oxide encapsulated in mesoporous silica hollow sphere. The textural parameters of the nanocomposite are adjustable by controlling the preparation conditions. The unique structure of the prepared nanocomposite showed relatively high methylene blue adsorption capability and can be used for removal of dye from aqueous solution. In addition, some active metallic nanoparticles (such as Pt, Pd) can be introduced into the cavity of γ-Fe2O3@SiO2–@mSiO2 to construct confined integrated catalytic system. The designed Pt-based integrated nanocatalyst exhibited not only high activity and selectivity, but also an excellent reusability for the selective hydrogenation of nitrobenzol to aniline. The existence of magnetic core in the nanocomposite provides a facile separation from liquid solution. Graphical Abstract: Rattle-type nanocomposite with nonporous silica-coating magnetic iron oxide nanoparticles encapsulated in mesoporous silica hollow sphere had been prepared. This unique nanocomposite exhibits excellent adsorption capability for methylene blue dye. After loaded with Pt nanoparticles, the formed functional nanoreactor is very active for selective hydrogenation of nitrobenzol to aniline and shows outstanding reusability. [Figure not available: see fulltext.] © 2015 Springer Science+Business Media New York Source

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