ACTA

Positron Annihilation in MnFe₂O₄/MCM-41 Nanocomposite

M. Wiertel^a, Z. Surowiec^a, W. Gac^b and M. Budzyński^a
^aDepartment of Nuclear Methods, Faculty of Mathematics, Physics and Computer Science, Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin, Poland
^bDepartment of Chemical Technology, Faculty of Chemistry, Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 3, 20-031 Lublin, Poland

Full Text PDF

In the paper results of studies of MnFe₂O₄/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 N₂ sorption/desorption method and positron annihilation lifetime spectroscopy. Disappearance of the longest-lived ortho-positronium component (τ₅) of pure MCM-41 mesoporous material in the positron annihilation lifetime spectra of MnFe₂O₄/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 (τ₅) component except for the sample with maximum ferrite content. Both the (τ₅) component lifetime and intensity are suppressed together with increasing MnFe₂O₄ 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 O₂ molecules.

DOI: 10.12693/APhysPolA.125.793
PACS numbers: 78.70.Bj, 34.80.Lx, 78.67.Bf, 62.23.Pq, 68.43.-h, 75.50.Gg, 78.47.D-