| NUKLEONIKA 2013, 58(1):229-233
GAS FILLING OF SBA-15 SILICA MICROPORES PROBED BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY (PALS)Marek Gorgol1, Radosław Zaleski1, Agnieszka Kierys2 1 Maria Curie-Skłodowska University, Institute of Physics, Department of Nuclear Methods, 1 M. Curie-Skłodowskiej Sq., 20-031 Lublin, Poland 2 Maria Curie-Skłodowska University, Faculty of Chemistry, Department of Adsorption, 3 M. Curie-Skłodowskiej Sq., 20-031 Lublin, Poland Positron annihilation lifetime measurements were conducted in situ while two gasses (nitrogen and oxygen, respectively) were introduced into the SBA-15 porous silica sample. Slow changes in lifetime spectra were observed during a long lasting gas interaction with the sample. Introduced gases slowly filled the free volumes, starting from the smallest ones, especially small micropores. In the presence of a gas, the rate of change of ortho-positronium (o-Ps) and unbound positron intensity was larger than the rate of change of lifetime. This suggests the existence of an additional process, which reduces the number of ortho-positronium atoms due to the interaction with the gas. Moreover, the process of filling pores with gas was slower than the process of emptying them while the gas was pumped out. Close X |