纳米Cu固体材料微结构的正电子湮没研究

Microstructure of Nanocrystalline Cu Investigated by Positron Annihilation Spectroscopy

纳米材料的性能不仅与纳米晶粒本身的结构有关,而且与纳米晶体之间界面的微观结构有关.纳米粉在压实成纳米块过程中很难消除微孔洞,并且在压实过程中也会给晶粒引入结构缺陷.本文用正电子湮没谱学研究了纳米Cu固体材料微结构,发现在两种不同条件下压制成型的纳米Cu固体内部的晶粒界面均存在着单空位及空位团等缺陷.空位团的大小随着压制压力的增加而略有减小.通过退火实验发现纳米Cu固体的界面缺陷具有较好的热稳定性.即使在900℃高温下退火也只能使部分缺陷得到恢复,但是低压力下压制的样品中的缺陷恢复需要更高的温度.

The property of nano-material is closely related with the grain boundaries and crystallites.There are always large number of vacancy type defects in the grain boundary region.They can be studied by Positron annihilation spectroscopy.In this paper,microstructure of nanocrystalline Cu was studied by positron annihilation spectroscopy.Vacancy-type defects including monovacancies and vacancy clusters were observed in the grain boundary region of two nanocrystalline Cu samples prepared under different conditions.The size of vacancy-clusters increases with the decrease of compression pressure.Annealing of the nanocrystalline Cu samples indicates that the defects in the grain boundaries have high thermal stability.Only part of the defects can be recovered after annealing at temperatures as high as 900 ℃.Recovery of the defects requires higher temperature for samples prepared at lower pressure.