正电子技术在材料科学中.pdfVIP

正电子概况XII 正电子技术在材料科学中 的应用 nanoparticles 叶邦角 核固体物理研究室 Laboratory of Nuclear Solid State Physics, USTC PDF 文件使用 pdfFactory 试用版本创建 耀 Positron for Nano-particles 一. 纳米粒子 . 纳米粒子嵌入 三. 纳米粒子在表面 PDF 文件使用 pdfFactory 试用版本创建 ÿ 一. 纳米粒子 PDF 文件使用 pdfFactory 试用版本创建 ÿ 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 ÌÿÌ lComparison with the experimental results of the calculated mean positron lifetime in Ag nanocrystallites as a function of grain size. PDF 文件使用 pdfFactory 试用版本创建 ÌÿÌ PDF 文件使用 pdfFactory 试用版本创建 ÌÌ PDF 文件使用 pdfFactory 试用版本创建 ÌÌ S-参数 PDF 文件使用 pdfFactory 试用版本创建 ÿ Conclusions (1)The mean positron lifetime has been found to decrease with an increase in the size of the grains. At large grain size, comparable to the diffusion length, annihilation occurs in the bulk state. (2) The diffusion c