摘要
CuO/Al2O3 catalysts were prepared by mixing CuO and environment of the catalysts are characterized by positron v-AI203 nanopowders. Microstrueture and chemical annihilation spectroscopy. The positron annihilation lifetime measurements reveal two long lifetime components 73 and τ4, which correspond to ortho-positronium （o- Ps） annihilating in mierovoids and large pores, respectively. With increasing CuO content from 0 to 40 wt%, both 3-4 and its intensity I4 show significant decrease, which indicates quenching effect of o-Ps. The para-positronium （p-Ps） intensities derived from multi-Gaussian fitting of the coincidence Doppler broadening spectra also decreases gradually with increasing CuO content. This excludes the possibility of spin-conversion of positronium. Therefore, the chemicM quenching by CuO is probably responsible for the decrease of o-Ps lifetime. Variation in the o-Ps annihilation rate A4 （1/T4） as a function of CuO content can be well fitted by a straight line, and the slope of the fitting line is （1.83 ± 0.05） × 10^7 s-1.
CuO/Al2O3 catalysts were prepared by mixing CuO and environment of the catalysts are characterized by positron v-AI203 nanopowders. Microstrueture and chemical annihilation spectroscopy. The positron annihilation lifetime measurements reveal two long lifetime components 73 and τ4, which correspond to ortho-positronium （o- Ps） annihilating in mierovoids and large pores, respectively. With increasing CuO content from 0 to 40 wt%, both 3-4 and its intensity I4 show significant decrease, which indicates quenching effect of o-Ps. The para-positronium （p-Ps） intensities derived from multi-Gaussian fitting of the coincidence Doppler broadening spectra also decreases gradually with increasing CuO content. This excludes the possibility of spin-conversion of positronium. Therefore, the chemicM quenching by CuO is probably responsible for the decrease of o-Ps lifetime. Variation in the o-Ps annihilation rate A4 （1/T4） as a function of CuO content can be well fitted by a straight line, and the slope of the fitting line is （1.83 ± 0.05） × 10^7 s-1.
基金
Supported by the Program for New Century Excellent Talents in University, the National Natural Science Foundation of China under Grant Nos 10875088 and 10974149, and the National Science Fund for Talent Training in Basic Science under Grant No J0830310.
