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-Pottuz, et al.. Accurate characterization of pure silicon-substituted hydroxyapatite powders synthesized by a new precipitation route. Acta Materialia, Elsevier, 2013, 9 (6)

The structural changes generated in surface regions of single crystal Ni targets by femtosecond laser irradiation are investigated experimentally and computationally for laser fluences that, in the multipulse irradiation regime, produce sub-100 nm high spatial frequency surface structures. Detailed experimental characterization of the irradiated targets combining electron back scattered diffraction analysis with high-resolution transmission electron microscopy reveals the presence of multiple nanoscale twinned domains in the irradiated surface regions of single crystal targets with (111) surface orientation. Atomistic- and continuum-level simulations performed for experimental irradiation conditions reproduce the generation of twinned domains and establish the conditions leading to the formation of growth twin boundaries in the course of the fast transient melting and epitaxial regrowth of the surface regions of the irradiated targets. The observation of growth twins in the irradiated Ni(111) targets provides strong evidence of the role of surface melting and resolidification in the formation of high spatial frequency surface structures. This also suggests that the formation of twinned domains can be used as a sensitive measure of the levels of liquid undercooling achieved in short pulse laser processing of metals.

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The mechanical behavior of h1 0 0i-oriented MgO nanocubes is investigated using in situ transmission electron microscopy (TEM) compression tests at room temperature and molecular dynamics simulations. Experiments show high strength and ductility, in addition to specific deformation mechanisms interpreted by the simulation. The nucleation and the propagation of 1/2h1 1 0i{1 1 0} dislocations are at the onset of the plastic deformation. The different deformation processes as well as the possible formation of a dislocation network during compression are discussed.

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