Tailoring of keV-ion beams by image charge when transmitting through rhombic and rectangular shaped nanocapillaries.

We report on an unexpected effect of tailoring transmission profiles of Ne(7+) ions through nanocapillaries of rhombic and rectangular cross sections in mica. We find that capillaries of rhombic cross sections produce rectangular shaped ion transmission profiles and, vice versa, that capillaries of rectangular geometry give a rhombic beam shape. This shaping effect only occurs for transmitted ions and is absent for the small fraction of neutralized particles. The experimental findings and simulations of the projectile trajectories give clear evidence that the observed effect is due to the image forces experienced by the transmitting ions. This novel beam shaping mechanism suggests applications for the guiding, focusing, and shaping of ion beams.

Gamma-radiation induced synthesis of freestanding nickel nanoparticles.

A versatile method to produce metallic nickel nanoparticles is demonstrated. Metallic Ni nanoparticles have been synthesized from aqueous solution of NiCl2 using γ-radiation induced reduction. To prevent Ni re-oxidation, post-irradiation treatment was elaborated. Structural and compositional analyses were executed using X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. These studies reveal that the synthesized material consists of fcc Ni particles having size of 3.47 ± 0.71 nm. The nanoparticles have a tendency to agglomerate to the larger clusters. The latter are partially oxidized to form thin amorphous/poor-crystalline Ni(OH)2/NiO layers at the surface. Magnetization measurements demonstrate that the nanomaterial exhibit ferromagnetic-like behaviour with magnetization 30% lower than that in bulk Ni. The large active surface area (ECSA, 39.2 m2 g-1) and good electrochemical reversibility, confirmed by the electrochemical studies, make the synthesized material a potential candidate as an active component for energy storage devices.

Atomic and electronic structure of amorphous Al-Zr alloy films.

Amorphous Al(73)Zr(27) alloy film, grown and then subjected to heat treatments at 400 and 700 °C, was studied using a combination of x-ray diffraction and soft x-ray spectroscopic techniques. The Al L(2,3) and Al K x-ray absorption spectroscopy (XAS) and Al L(2,3) x-ray emission spectroscopy (XES) used allowed probing the unoccupied and occupied Al 3s, d states and unoccupied Al 3p states in the sample studied. An irreversible transition from amorphous alloy to a mixture of polycrystalline alloy and amorphous alloy, and then to an amorphous oxide phase was observed. After the annealing at 400 °C the Al L(2,3) spectra obtained by XAS could be explained as sums of spectra from amorphous Al(73)Zr(27) alloy and (poly)crystalline Al. This indicates that the sample consists of a mixture of Al-rich crystalline and Zr-enhanced amorphous alloys, as compared to the stoichiometry of the as-deposited Al(73)Zr(27) sample, and that the electronic wavefunctions in the crystalline and amorphous regions can be considered to be confined within the respective regions. The relative amounts of Al atoms were found to be around 1:3 in the crystalline and amorphous phases, respectively, as deduced from the analysis of changes in the electronic structure using Al L(2,3) XAS data. The interpretation was confirmed by the Al K XAS and Al L(2,3) XES. Upon further annealing at 700 °C the polycrystalline phase transformed into amorphous oxide, while the amorphous alloy phase underwent gradual oxidation. The important finding was that the greater part of the sample remained in the amorphous state throughout the temperature regimes described.