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-  

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2014
• Volume: 125
• Issue: 3
• Pages: 793-797

Dates

published

2014-03

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Identifiers

DOI

10.12693/APhysPolA.125.793