The positron lifetime spectra and ionic conductivity have been measured for polymeric electrolyte PEU LiClO_(4)as a function of temperature in the range of 120￣360 K and as a function of Li salt concentration at room...The positron lifetime spectra and ionic conductivity have been measured for polymeric electrolyte PEU LiClO_(4)as a function of temperature in the range of 120￣360 K and as a function of Li salt concentration at room temperature.From the temperature dependence of positron annihilation parameters,the glass transition and subtransition are observed,and the glass transition temperature T_(g)of pure PEU is determined to be 240 K.Above T_(g),the free volume hole size dramatically increases with temperature.The variations of positron annihilation parameters and ionic conductivities with respect to Li salt concentration at room temperature indicate that the Li salt mainly diffuses into the amorphous region in PEU LiClO_(4).The increase of Li salt concentration brings about an increase in the number of carried ions,and a reduction of the fractional free volume.展开更多
Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium （o-Ps） lifetime is significantly shortened whe...Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium （o-Ps） lifetime is significantly shortened when some oxygen is introduced into ni- trogen gas and that the o-Ps collisional quenching rate for an oxy- gen molecule is （28.0±0.4） ±ts%amagat（1 amagat 2.69± 1025 m-3）. It is found that the o-Ps annihilation rate in oxygen of latin at room temperature is （25.5±0.5） us-1 and that the effective num- ber of electrons per oxygen molecule available for 27 annihilation of positron in the o-Ps is （34.6±0.4）.展开更多
文摘The positron lifetime spectra and ionic conductivity have been measured for polymeric electrolyte PEU LiClO_(4)as a function of temperature in the range of 120￣360 K and as a function of Li salt concentration at room temperature.From the temperature dependence of positron annihilation parameters,the glass transition and subtransition are observed,and the glass transition temperature T_(g)of pure PEU is determined to be 240 K.Above T_(g),the free volume hole size dramatically increases with temperature.The variations of positron annihilation parameters and ionic conductivities with respect to Li salt concentration at room temperature indicate that the Li salt mainly diffuses into the amorphous region in PEU LiClO_(4).The increase of Li salt concentration brings about an increase in the number of carried ions,and a reduction of the fractional free volume.
基金Supported by the National Natural Science Foundation of China(10975108and10974149)the Research Fund for the Doctoral Program of Higher Education of China(20090141120069)
文摘Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium （o-Ps） lifetime is significantly shortened when some oxygen is introduced into ni- trogen gas and that the o-Ps collisional quenching rate for an oxy- gen molecule is （28.0±0.4） ±ts%amagat（1 amagat 2.69± 1025 m-3）. It is found that the o-Ps annihilation rate in oxygen of latin at room temperature is （25.5±0.5） us-1 and that the effective num- ber of electrons per oxygen molecule available for 27 annihilation of positron in the o-Ps is （34.6±0.4）.
