INSTITUTE OF PHYSICS PUBLISHING NANOTECHNOLOGY Nanotechnology 15(2004)467-472 PIL:S0957-448404)62779-6 Trapping of positrons at grain boundaries in nanoparticle systems V Thakur,S B Shrivastava and M K Rathore School of Studies in Physics,Vikram University.Ujjain(MP)-456010.India E-mail:vandanathakurl @rediffmail.com Abstract The positron annihilation in nanoparticle materials has been discussed in terms of the thermal diffusion of positrons at grain surfaces and trapping at the grain interfaces and interfacial defects.The diffusion trapping model has been applied to obtain the mean lifetime of positrons as a function of grain size and temperature and the S-parameter of the annihilation radiation as a function of grain size in Ag,Nb,Zn-Al and Zn-Al-Mg nanocrystallites.The calculated mean positron lifetimes have beencompared with the available experimental results. PDF文件使用"pdfFactory" 试用版本创建l.fineprint..cnAbstract The positron annihilation in nanoparticle materials has been discussed in terms of the thermal diffusion of positrons at grain surfaces and trapping at the grain interfaces and interfacial defects. The diffusion trapping model has been applied to obtain the mean lifetime of positrons as a function of grain size and temperature and the S-parameter of the annihilation radiation as a function of grain size in Ag, Nb, Zn–Al and Zn–Al–Mg nanocrystallites. The calculated mean positron lifetimes have beencompared with the available experimental results. PDF 文件使用 "pdfFactory" 试用版本创建 Ìwww.fineprint.cn ÿÌ