Positron annihilation in polyvinylalcohol doped with CuCl2 |
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Authors: | Hamdy F M Mohamed Y Ito A M A El-Sayed E E Abdel-Hady |
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Institution: | (1) Research Center for Nuclear Science and Technology, The University of Tokyo, Tokai, 319-11 Ibaraki, (Japan);(2) Department of Physics, Faculty of Science, El-Minia University, El-Minia, (Egypt);(3) Present address: Faculty of Science, El-Minia University, Egypt |
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Abstract: | Positron annihilation lifetime spectra were measured forpolyvinylalcohol (PVA) doped with CuCl2 (0.5 to 5.0 wt%) at temperature range from room temperature to 160°C. For a fresh pure PVA (without annealing) 3 belowT
g was larger in the heating runs than in the cooling runs, but aboveT
g, 3 was the same for both runs. The larger 3 values in the heating run were considered to be due to the existence of strain brought forth in the process of preparation. For annealed pure PVA 3 was the same for the heating and the cooling runs andT
g was shifted to lower temperature, 88 and 80°C for fresh and annealed samples, respectively. This shift was attributed to loss of H-bonded water in the annealed pure PVA by heating above 100°C. BothI
3
0
and 3 were decreased by the added CuCl2, being interpreted as the result of inhibition and quenching, respectively. The results show that both the inhibition coefficient and the quenching rate constantk were smaller than the corresponding values in liquids. The small diffusion constant ofo-Ps estimated fromk implies thato-Ps is not very mobile in the polymer. |
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