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Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy

100%
Ferreira Marques M., Gordo P., de Lima A., Queiroz D., Norberta de Pinho M., Major P., Kajcsos Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1359-1364
EN
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the CO_2 gas permeability through the membranes.
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Positron and Positronium Trapping in Heat Treated Zeolites (Ceramics), the Effect of Swift Heavy Ion Irradiation

68%
Major P., Kajcsos Z., Liszkay L., Zalán P., Kosanović C., Bosnar S., Subotić B., Lázár K., Skuratov V., Havancsák K., Gordo P., Ferreira Marques M.
Acta Physica Polonica A
|
2008
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vol. 113
|
issue 5
1441-1446
EN
A systematic study of zeolite precursor gels, zeolites, and products of their recrystallization to ceramics was carried out in presence of various alkali ions. The investigation of radiation damage induced by high-energy ion beam irradiation with swift heavy ions (Bi ions at 670 MeV energy with 4×10^{12} ion/cm^2 fluence) was also included. The shortening of lifetimes found after irradiation in ceramics might probably be ascribed to interactions of o-Ps with free radicals and other quenching agents created through the ion irradiation. These lifetime-shortening interactions probably partly hide the o-Ps trapping in free volume sites.
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