Positron Annihilation in MnFe_2O_4/MCM-41 Nanocomposite

• Authors: M. Wiertel , Z. Surowiec , W. Gac , M. Budzyński
• Languages of publication: EN

Abstracts

EN

In the paper results of studies of MnFe_2O_4/MCM-41 nanocomposites have been presented. The influence of manganese ferrite loading on changes of porous properties of mesoporous MCM-41 structure was studied by means of N_2 sorption/desorption method and positron annihilation lifetime spectroscopy. Disappearance of the longest-lived ortho-positronium component (τ_5) of pure MCM-41 mesoporous material in the positron annihilation lifetime spectra of MnFe_2O_4/MCM-41 measured in vacuum is a result of either o-Ps quenching or the Ps inhibition mechanism. Filling of pores in the studied nanocomposites by air at ambient pressure causes partial reappearance of the (τ_5) component except for the sample with maximum ferrite content. Both the (τ_5) component lifetime and intensity are suppressed together with increasing MnFe_2O_4 content by chemical quenching and inhibition of Ps formation occur. Observed anti-quenching effect of air is a result of two processes: neutralization of some surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O_2 molecules.

Keywords

EN

78.70.Bj; 34.80.Lx; 78.67.Bf; 62.23.Pq; 68.43.-h; 75.50.Gg; 78.47.D-

Discipline

• 68.43.-h: Chemisorption/physisorption: adsorbates on surfaces
• 78.70.Bj: Positron annihilation(for positron states, see 71.60.+z in electronic structure of bulk materials; for positronium chemistry, see 82.30.Gg in physical chemistry and chemical physics)
• 75.50.Gg: Ferrimagnetics
• 78.67.Bf: Nanocrystals, nanoparticles, and nanoclusters
• 62.23.Pq: Composites (nanosystems embedded in a larger structure)
• 78.47.D-: Time resolved spectroscopy (>1 psec)
• 34.80.Lx: Recombination, attachment, and positronium formation

• Journal: Acta Physica Polonica A
• Year: 2014
• Volume: 125
• Issue: 3
• Pages: 793-797

Dates

published

2014-03

Contributors

author

M. Wiertel

• Department of Nuclear Methods, Faculty of Mathematics, Physics and Computer Science Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

author

Z. Surowiec

• Department of Nuclear Methods, Faculty of Mathematics, Physics and Computer Science Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

author

W. Gac

• Department of Chemical Technology, Faculty of Chemistry, Maria Curie-Skłodowska University pl. M. Curie-Skłodowskiej 3, 20-031 Lublin, Poland

author

M. Budzyński

• Department of Nuclear Methods, Faculty of Mathematics, Physics and Computer Science Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland

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Identifiers

DOI

10.12693/APhysPolA.125.793