Study of Various Properties of Silica Gel by Positron Annihilation

Abstract

Free volume dependent fluorescence property of PMMA composite: Positron annihilation studies AIP Conf. Proc. 1512, 126 (2013); 10.1063/1.4790943 Interlaboratory comparison of positron annihilation lifetime measurements for synthetic fused silica and polycarbonate J. Appl. Phys.The lifetimes of o-positronium in .silica gel adsorbed with various amounts of water, n-hexane, or nitro-ethan~ were measured. The fractIOn of o-positronium escaping the condensed phase can be related to t e specific area. ~nd the pore volume of the silica gel. The mean life of o-positronium in the pores is found t~ b~rvery sensItive to t~e surface properties of silica gel. The formation of free radicals on the surface o ISllca. and the reactIOns between these free radicals and o-positronium are suggested as the exp anatlOns.

Positronium formation in sol–gel-prepared silica-based glasses: temperature and positron-irradiation effect

“…They assumed that Ps interacts with the pore surface. The fact that Ps interacts on the internal surface in silica gel has been known since ago (Chuang and Tao, 1973 (Saito et al, 1995). Such centers could be created by ultravioletirradiation (Saito and Hyodo, 1997) or electron-irradiation (Hasegawa et al, 1996).…”

Study on the effect of atmospheric gases adsorbed in MnFe2O4/MCM-41 nanocomposite on ortho-positronium annihilation

“…However, it seems that the differences in chemical interaction and screening effect because of the blocking of active sites on the pore surface for the both used atmospheric gases may play a certain role [21]. Moreover, it is possible to observe long-lived components in positron lifetime spectra even by using strongly quenching o-Ps gas, which is oxygen.…”

Positron Annihilation in MnFe_2O_4/MCM-41 Nanocomposite

“…It is known that the adsorption of small amounts of the molecules on the pore surface increases the o-Ps lifetime, due to the blocking of active sites on the pore surface causing partial quenching of o-Ps [17]. In the case of the investigated samples probably a coating of MnFe 2 O 4 deposits by monolayer of predominantly N 2 molecules from air takes place.…”