Swift heavy ion irradiation of elemental metal nanoparticles embedded in a silica matrix yields a spherical to rod-like shape transformation, with the direction of elongation aligned to that of the incident ion beam.  Large and once spherical nanoparticles become progressively more rod-like while subject to dissolution and fragmentation.  Small nanoparticles below a critical diameter remain spherical and do not elongate but instead dissolve in the matrix.  For this report, we examine the shape transformation for a variety of metals with the aim of achieving mechanistic insight into the transformation process.  We identify subtle metal-specific differences.  For example, the width of elongated nanoparticles saturates at a value comparable to the critical diameter for transformation and is well correlated with the metal melting temperature and energy required for vaporisation.  Furthermore, we show the elongation process necessitates the formation of a molten ion track in the silica matrix.  This track confines the nanoparticle elongation and as a consequence the saturated nanoparticle width does not exceed the molten ion track diameter

M. Ridgway*, Australian National University, Australia
R. Giulian, Australian National University, Australia
D. Sprouster, Australian National University, Australia
P. Kluth, Australian National University, Australia
L. Araujo, Australian National University, Australia
D. Llewellyn, Australian National University, Australia
A. Byrne, Australian National University, Australia
F. Kremer, Universidade Federal do Rio Grande do Sul, Brazil
P. Fichtner, Universidade Federal do Rio Grande do Sul, Brazil
G. Rizza, Ecole Polytechnique, France
H. Amekura, National Institute for Materials Science, Japan
M. Toulemonde, Laboratoire CIRIL-GANIL, France

*presenting author