title: Size dependent allotropic transition of Co fine particles.
abstract: In order to investigate the size dependent allotropic transition of Co in wide size range, nanometer scaled (9 nm-350 nm) and micrometer sized (1 microm-18 microm) Co particles were prepared by laser induced pyrolysis, reduction as well as high temperature annealing treatment. In wide size range, from 9 nm to 10 microm for example, the crystal structure of the Co particles is dependent on their thermal history in which the particle involved in preparation or in annealing treatment. Only when the particle size is very large, much greater than 10 microm for example, the fcc-hcp transformation could occur during the cooling from high temperautre. According to the effect of surface energy on the martensitic transformation, the size dependent allotropic transformation of Co was discussed.
authors.affiliation: Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China.
authors.forename: Guojun
authors.initials: G
authors.lastname: Ma
authors.forename: Xinqing
authors.initials: X
authors.lastname: Zhao
authors.forename: S
authors.initials: S
authors.lastname: Veintemillas-Verdaguer