Alexey Romanov

Abstract:

The paper discusses experimentally detected phenomenon of internal cavity formation in icosahedral small copper particles as a result of their annealing. Icosahedral small particle has six five-fold symmetry axes and disclination-type defects inside. Particle consists of 20 tetrahedral region with local fcc atomic arrangement joined via twin boundaries.<br />Our experiments showed that the annealed icosahedral particles have large internal cavities (up to 80 volume %) surrounded by a shell made of metal oxide. The found cavities were examined in scanning electron microscope equipped with focused-ion beam gun. To investigate the structural and phase transformations occurring in the process of icosahedral particle annealing, differential scanning calorimetry (DSC) was applied.<br />It has been shown that the formation of cavities in microparticles was promoted by (i) the presence of oxygen in the surrounding atmosphere and (ii) high internal stresses in the particle interior. The role of disclination-type defects as the sources of internal stresses in the mechanism of internal cavity formation is elucidated.<br />This work has been supported by the grant No 14.B25.31.0011 of the Ministry of Education and Science of Russian Federation (resolution # 220) at Togliatti State University.