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Biogenic iron compounds: XRD, Mossbauer and FTIR study

100%

Shopska M., Cherkezova-Zheleva Z., Paneva D., Iliev M., Kadinov G., Mitov I., Groudeva V.

Open Chemistry

2013

vol. 11

issue 2

215-227

Materials based on biogenic iron oxides, which are a product of the metabolic activities of the neutrophilic iron-oxidizing bacteria (NIOB) from Sphaerotilus-Leptothrix group, were investigated. Natural microbial probes were collected from freshwater flow from Vitosha Mountain (Bulgaria) and cultivated under laboratory conditions in respect to select suitable cultures and conditions (nutrition media) for biomaterial accumulation of biogenic oxides. Samples were studied by physicochemical methods: X-ray diffraction, Mossbauer spectroscopy and IR spectroscopy. Their phase composition and physicochemical properties were obtained. Presence of both amorphous and crystal phase (ultra- and highly dispersed particles) was proved. Iron-containing compound in the natural biomass consists of α-FeOOH. The cultivated materials have more complex composition with iron-containing ingredients as α-FeOOH, Γ-FeOOH, Γ-Fe2O3 and Fe3O4. The sample of natural biomass was tested in reaction of CO oxidation and it showed potential to be used as catalyst support. [...]

Characterization of superparamagnetic MgxZn1−x Fe2O4 powders

100%

Kassabova-Zhetcheva V., Pavlova L., Samuneva B., Cherkezova-Zheleva Z., Mitov I., Mikhov M.

Open Chemistry

2007

vol. 5

issue 1

107-117

Structural and magnetic properties of Mgx Zn1−x Fe2O4 powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mgx Zn1−x Fe2O4 (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones. [...]

Copper-cobalt ferrites as catalysts for methanol decomposition

84%

Velinov N., Koleva K., Tsoncheva T., Paneva D., Manova E., Tenchev K., Kunev B., Genova I., Mitov I.

Open Chemistry

2014

vol. 12

issue 2

250-259

Copper-cobalt ferrites with composition Cu1−xCoxFe2O4, where x= 0.2 and 0.8 were prepared by thermal treatment of co-precipitated precursor. The obtained materials were characterized by TG-DSC, XRD, Transmission and Conversion Electron Mössbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic properties of ferrites were tested in methanol decomposition to CO and hydrogen.

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3 Open Chemistry

1 2014

1 2013

1 2007

3 Mitov I.

2 Cherkezova-Zheleva Z.

2 Paneva D.

1 Genova I.

1 Groudeva V.

1 Iliev M.

1 Kadinov G.

1 Kassabova-Zhetcheva V.

1 Koleva K.

1 Kunev B.

1 Manova E.

1 Mikhov M.

1 Pavlova L.

1 Samuneva B.

1 Shopska M.

1 Tenchev K.

1 Tsoncheva T.

1 Velinov N.

Search results

Biogenic iron compounds: XRD, Mossbauer and FTIR study

Characterization of superparamagnetic MgxZn1−x Fe2O4 powders

Copper-cobalt ferrites as catalysts for methanol decomposition