화학공학소재연구정보센터
Materials Science Forum, Vol.363-3, 266-268, 2001
Temperature-dependent electron acceptor properties of zeolite Y: a combined Mossbauer and positron lifetime spectroscopy study
An unusual temperature dependence of the concentration of nucleogenic Fe(2+), ions, formed after the (57)Co(EC)(57) Fe nuclear transition, has been observed by Mossbauer spectroscopy in zeolite Y. The observed temperature dependence could be explained by the assumption of an electron acceptor process that changes with the temperature. To prove this assumption we have applied positron lifetime spectroscopy, as in zeolites the formation of positronium atoms takes place similarly to the formation of Fe(2+) after the decay of (57)Co nuclids. In both processes the surrounding zeolite matrix plays the role of a competing electron acceptor. The results proved that both multicharged iron ions and positrons do compete for electrons with the zeolite matrix. The zeolite matrix behaves as it has two states having different electron acceptor properties. The density of these states varies with the temperature and the activation energy for the transformation is about 2.4 kJ/mol, as proved by the two methods independently.