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2014 | 125 | 3 | 793-797
Article title

Positron Annihilation in MnFe_2O_4/MCM-41 Nanocomposite

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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
Year
Volume
125
Issue
3
Pages
793-797
Physical description
Dates
published
2014-03
References
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Document Type
Publication order reference
YADDA identifier
bwmeta1.element.bwnjournal-article-appv125n330kz
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