The first crystal structures of a dinuclear iron(II) complex with three N1,N2-1,2,4-triazole bridges in the high-spin and low-spin states are reported. Its sharp spin transition, which was probed using X-ray, calorimetric, magnetic, and (57)Fe Mossbauer analyses, is also delineated in the crystalline state by variable-temperature fluorimetry for the first time.

Electron Beam Melting (EBM), a powder bed additive layer manufacturing process, was used to produce Ti-6Al-4V specimens, whose microstructure, texture, and tensile properties were fully characterized. The microstructure, analyzed by optical microscopy, SEM/EBSD and X-ray diffraction, consists in fine α lamellae. Numerical reconstruction of the parent β phase highlighted the columnar morphology of the prior β grains, growing along the build direction upon solidification of the melt pool. The presence of grain boundary α GB along the boundaries of these prior β grains is indicative of the diffusive nature of the β-α phase transformation. Texture analysis of the reconstructed high temperature β phase revealed a strong o0014 pole in the build direction. For mechanical characterization, tensile specimens were produced using two different build themes and along several build orientations, revealing that vertically built specimens exhibit a lower yield strength than those built horizontally. The effect of post processing, either mechanical or thermal, was extensively investigated. The influence of surface finish on tensile properties was clearly highlighted. Indeed, mechanical polishing induced an increase in ductilitydue to the removal of critical surface defectsas well as a significant increase of the apparent yield strengthcaused by the removal of a $ 150 mm rough surface layer that can be considered as mechanically inefficient and not supporting any tensile load. Thermal post-treatments were performed on electron beam melted specimens, revealing that subtransus treatments induce very moderate microstructural changes, whereas supertransus treatments generate a considerably different type of microstructure, due to the fast β grain growth occurring above the transus. The heat treatments investigated in this work had a relatively moderate impact on the mechanical properties of the parts.

Applying a constant voltage to superconducting nanowires we find that its IV-characteristic exhibits an unusual S-behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: jc2 at which the pure superconducting state becomes unstable and jc1 < jc2 at which the phase slip state is realized in the system. PACS numbers: 74.25. Op, 74.20.De, The majority of the experiments on the resistive state in quasi-one dimensional systems were performed in the constant current regime and at temperatures close to T c . It is extremely difficult to apply voltage to a superconductor because the current density induced by the applied electric field inevitably reaches the critical value and destroys superconductivity in the sample. The decrease of the superconducting current by the appearance of phase slip centers [1,2,3,4,5] is not effective in this case because of the large heating of the sample at low temperatures. At temperatures close to T c the heating can be suppressed due to the low value of the critical currents but in this case the applied electric field does not penetrate deep into the sample because of the existence of regions near the N-S boundary where the drop of the applied voltage occurs [6,7].This situation drastically changes with the appearance of nano-technology and the ability to create long (to allow the appearance of phase slip centers) superconducting wires with a small cross section (to decrease the effect of heating). In this Letter we present results on the behavior of such nanowires in the constant voltage regime. We found that the I-V characterestic in this case has a remarkable S-shape. Our theoretical analysis based on the time-dependent Ginzburg-Landau equations (TDGL) shows that such a behavior is a direct consequence of the dynamics of the superconducting condensate and we predict new unusual features which still need additional experimental study.The superconducting nanowires were prepared by electrodeposition into nanopores of homemade track-etched polycarbonate membranes [8]. For the lead nanowires, a 22 µm thick membrane (with pore diameter ∼ 40 nm and pore density ∼ 4·10 9 cm −2 ) and an aqueous solution of 40.4 g/l Pb(BF 4 ) 2 , 33.6 g/l HBF 4 and 15 g/l H 3 BO 3 were used [9], while in the case of the tin nanowires, a 50 µm thick membrane (with pore diameter ∼ 55 nm and pore density ∼ 2·10 9 cm −2 ) and an electrolyte of 41.8 g/l Sn(BF 4 ) 2 in water solution were applied. Constant potential of -0.5 V versus an Ag/AgCl reference electrode was used in a three-electrode configuration in order to reduce the Pb 2+ or Sn 2+ ions into the nanopores. As shown in Fig. 1, the nanowires are cylindrical and the diameter is uniform along their length. In order to perform elec-

Experimental results on the phase slip process in superconducting lead nanowires are presented under two different experimental conditions: constant applied current or constant voltage. Based on these experiments we established a simple model which gives us the condition of the appearance of phase slip centers in a quasione-dimensional wire. The competition between two relaxations times ͑relaxation time of the absolute value of the order parameter ͉͉ and relaxation time of the phase of the order parameter in the phase slip center ) governs the phase slip process. Phase slips, as periodic oscillations in time of the order parameter, are only possible if the gradient of the phase grows faster than the value of the order parameter in the phase slip center, or equivalently if Ͻ ͉͉ .

Arrays of granular superconducting Pb and Sn nanowires (40–55 nm in diameter and 22 or 50 μm long) have been prepared by electrodeposition in nanoporous membranes. A simple technique has been developed to perform electrical transport measurement on a single nanowire. By sweeping the dc current inside the nanowire, we observed the formation of phase-slip-centers far below the critical temperature. In contrast, in voltage-driven experiments, an interesting S-shaped behavior has been observed in the nucleation region of these phase-slip-centers.