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Ordered Nanoporous Silica Modified with Nanoparticles of Lanthanide Oxides

100%
Zeleňáková A., Kapusta O., Zeleňák V.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
218-219
EN
Lanthanide oxide nanoparticles were encapsulated inside of pores of highly ordered periodic silica of SBA15 type with hexagonal symmetry. The magnetic properties of such nanoperticles were investigated. The structural characterization using the SAXS, XANES, XRD, and N_{2} adsorption measurements showed the presence of lanthanide oxides of Ln_{2}O_{3} type (Ln=La, Pr, Nd, Gd, Eu), with the size of about 5 nm, incorporated in nanoporous channel system. Their magnetic properties, studied by SQUID apparatus, showed the weak antiferromagnetic ordering at 2 K in the nanocomposites Gd_{2}O_{3}@SBA15, Pr_{2}O_{3}@SBA15 and Nd_{2}O_{3}@SBA15. This behaviour of the nanoparticles is caused by blocking process of magnetic moments, which at 300 K exhibit the superparamagnetism, evidenced from ZFC/FC magnetization.
2
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Magnetocaloric Effect in Gd₂O₃@SiO₂ Nanocomposite

88%
Zeleňáková A., Hrubovčák P., Berkutova A., Kapusta O., Zeleňák V.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
810-812
EN
Nanocomposite consisting of Gd₂O₃ nanoparticles embedded in periodical porous silica matrix was investigated with respect to its magnetocaloric properties. Series of field (up to 5 T) dependence of magnetization data were recorded in temperature range 2-52 K. The data were subsequently processed employing Maxwell relation in order to calculate magnetic entropy change (Δ S_M) of the system. Examined nanocomposite exhibited reasonably high value of Δ S_M ≈ 29 J/(kg K) at maximal field change 5 T at the temperature of 2 K which suggests that this material could be feasible for cryomagnetic refrigeration applications.
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Fe₂O₃ and Gd₂O₃ Nanoparticles Embedded in Mesoporous Silica: Magnetic Properties Comparison

88%
Kapusta O., Zeleňáková A., Hrubovčák P., Girman V., Zeleňák V.
Acta Physica Polonica A
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2017
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vol. 131
|
issue 4
860-862
EN
Nanocomposite materials containing Fe₂O₃ and Gd₂O₃ nanoparticles with the same concentration were prepared by nanocasting method. At this procedure silica matrix serves as nanoreactor for growth of nanoparticles. Temperature and external dc field dependences of the magnetization both samples were compared. Composite containing Fe₂O₃ nanoparticles shows superparamagnetic behaviour with blocking temperature around 45 K. Otherwise, paramagnetic properties were observed for the sample with Gd₂O₃ (above 10 K). Additionally, due to free pores the silica matrix could serve as medium to increase the number of bonded water molecules. These properties together with appropriate magnetic characteristics make studied materials suitable for magnetic resonance imaging applications.
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