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Wyszukujesz frazę "MCM-41 porous silica" wg kryterium: Temat


Wyświetlanie 1-4 z 4
Tytuł:
Synthesis and characterization of iron - cobalt nanoparticles embedded in mesoporous silica MCM - 41
Autorzy:
Surowiec, Z.
Wiertel, M.
Budzyński, M.
Gac, W.
Powiązania:
https://bibliotekanauki.pl/articles/147878.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
cobalt
iron
MCM-41 porous silica
Mössbauer effect
superparamagnetic nanoparticles
Opis:
Fe1.xCox/MCM-41 nanocomposite materials were prepared by wet impregnation of the silica mesoporous support with aqueous solution of iron and cobalt salt mixtures. Samples, after calcination, were reduced at 573 K in order to obtain homogeneous distribution of (Fe-Co)3O4 oxide species over the MCM-41 support. Bimetallic systems were achieved through high temperature reduction, carried out at 1073 K. The temperature-programmed reduction studies indicated complex nature of the oxide species. The phase analysis of the obtained samples after low temperature reduction process carried out by means of X-ray diffraction method and using 57Fe Mossbauer spectroscopy revealed the presence of nanostructured magnetite- and maghemite-like phases. The samples with higher cobalt contents (x . 0.2) contained additionally bimetallic phases. The complete transformation of oxide phases to bimetallic Fe-Co systems occurred during reduction process in hydrogen at 1073 K. It was observed that high temperature processing caused partial transformation of highly dispersed iron oxide nanocrystallites into fayalite species embedded in the silica walls.
Źródło:
Nukleonika; 2013, 58, 1; 87-92
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of annealing temperature on structural and magnetic properties of MnFe2O4 nanoparticles
Autorzy:
Surowiec, Z.
Wiertel, M.
Gac, W.
Budzyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/146127.pdf
Data publikacji:
2015
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
manganese ferrite
MCM-41 porous silica
Mössbauer effect
superparamagnetic nanoparticles
Opis:
Nanoparticles of manganese ferrite were obtained by the impregnation of highly ordered mesoporous MCM-41 silica support. The investigated sample contained 20% wt. Fe. The obtained nanocrystallites were strongly dispersed in silica matrix and their size was about 2 nm. The sample annealing at 500°C led to increase of particle size to about 5 nm. The Mössbauer spectroscopy investigations performed at room temperature show on occurrence of MnFe2O4 nanoparticle in superparamagnetic state for the sample annealed in all temperatures. The coexistence of superparamagnetic and ferromagnetic phase was observed at liquid nitrogen temperature. The sample annealed at 400°C and 500 °C has bigger manganese ferrite particle and better crystallized structure. One can assign them the discrete hyperfi ne magnetic field components.
Źródło:
Nukleonika; 2015, 60, 1; 137-141
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An application of Mössbauer spectroscopy in the studies of iron - molybdenum silica mesoporous materials
Autorzy:
Surowiec, Z.
Wiertel, M.
Marynowska, A.
Gac, W.
Zawadzki, W.
Powiązania:
https://bibliotekanauki.pl/articles/147814.pdf
Data publikacji:
2013
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
iron
MCM-41 porous silica
molybdenum
Mössbauer effect
superparamagnetic nanoparticles
Opis:
Iron-molybdenum silica mesoporous materials were obtained by the application of direct hydrothermal method. Four samples with different metal contents relative to silica were investigated. Incorporation of iron and molybdenum ions in the synthesis stage led to structural changes of the MCM-41 support. With an increasing metals content, cylindrical pores of silica initially transformed into bottle-ink type pores, and then into the slit-like ones. Mössbauer spectroscopy investigations indicated that Fe ions were embedded in the silica walls and then formed nanosized crystallites in the pores. Superparamagnetic phase was observed at liquid nitrogen temperature.
Źródło:
Nukleonika; 2013, 58, 1; 137-141
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron annihilation study of iron oxide nanoparticles in mesoporous silica MCM-41 template
Autorzy:
Surowiec, Z.
Wiertel, M.
Zaleski, R.
Budzyński, M.
Goworek, J.
Powiązania:
https://bibliotekanauki.pl/articles/148449.pdf
Data publikacji:
2010
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
positron annihilation
Mössbauer effect
MCM-41 porous silica
superparamagnetic nanoparticles
Opis:
The subject of investigation were the samples obtained by impregnation of MCM-41 template with an aqueous solution prepared from Fe(NO3)3ź9H2O. As a result of such a procedure, iron oxides deposits on MCM-41 were formed. The Mössbauer studies revealed an occurrence of Fe3O4 nanocrystallites in the both ferri- and superparamagnetic states. Almost 80% small particles exist in a paramagnetic state. The positron annihilation lifetime spectroscopy (PALS) spectra were measured in air or in vacuum. The long-lived ortho-positronium (o-Ps) components and their intensities are time dependent due to air molecules interaction with iron oxide nanocrystallites and silica walls surfaces. The adsorption of air on the nanocrystallites surface causes a total screening of their surface and a raise of the o-Ps lifetime values. Observed anti-quenching effect is a result of competition of two phenomena: practically switching off a pick-off mechanism related to interaction of o-Ps with magnetite nanoparticles and considerably weaker usual quenching by paramagnetic oxygen molecules.
Źródło:
Nukleonika; 2010, 55, 1; 91-96
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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