Ablation laser femtoseconde de verres métalliques de Cu_x Zr_(1−x) : une étude par dynamique moléculaire

L’ablation laser de verres métalliques de CuxZr1−x (x = 0.33, 0.50 et 0.67) et d’un alliage métallique cristallin de CuZr2 dans la structure C11b a été étudiée par dynamique moléculaire (DM) combinée à un modèle à deux températures (TTM). Le seuil d’ablation (Fth) a été déterminé pour chacun des 4 échantillons et s'est avéré plus bas pour les échantillons plus riches en Cu étant donné que la cohésion du Cu est plus faible que celle du Zr dans tous les échantillons. Pour x=0.33, Fth est plus bas pour le cristal que pour l’amorphe car le couplage électron-phonon est plus faible dans ce dernier, ce qui implique que l’énergie est transférée plus lentement du système électronique vers le système ionique pour le a-CuZr2 que le c-CuZr2. La vitesse de l’onde de pression créée par l’impact du laser croît avec la fluence dans l’échantillon cristallin, contrairement aux échantillons amorphes dans lesquels sa vitesse moyenne est relativement constante avec la fluence. Ceci est expliqué par le fait que le module de cisaillement croît avec la pression pour le cristal, ce qui n’est pas le cas pour les verres métalliques étudiés. Finalement, la zone affectée par la chaleur (HAZ) a été étudiée via la profondeur de fusion et les déformations plastiques. La plus faible température de fusion des échantillons amorphes implique que la profondeur de fusion est plus importante dans ceux-ci que dans l’échantillon cristallin. Dans les verres métalliques, les déformations plastiques ont été identifiées sous forme de zones de transformation par cisaillement (STZ) qui diffusent et fusionnent à plus haute fluence. Aucune déformation plastique importante n’a été identifiée dans le c-CuZr2 mis à part de légères déformations près du front de fusion causées par les contraintes résiduelles. Ce travail a ainsi permis d’améliorer notre compréhension de l’ablation laser sur les verres métalliques et de l’étendue des dommages qu’elle peut entraîner.

Adsorption of Cr(VI) from aqueous solution by hydrous zirconium oxide

A type of ZrO(2)center dot nH(2)O Was synthesized and its Cr(VI) removal potential was investigated in this study. The kinetic study, adsorption isotherm, pH effect, thermodynamic study and desorption were examined in batch experiments. The kinetic process was described by a pseudo-second-order rate model very well. The Cr(VI) adsorption tended to increase with a decrease of pH. The adsorption data fitted well to the Langmuir model. The adsorption capacity increased from 61 to 66 mg g(-1) when the temperature was increased from 298 to 338 K. The positive values of both Delta H degrees and Delta S degrees suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption. Delta G degrees values obtained were negative indicating a spontaneous adsorption process. The effective desorption of Cr(VI) on ZrO(2)center dot nH(2)O could be achieved using distilled water at pH 12. (C) 2009 Elsevier B.V. All rights reserved.

Artificial Pinning Center Studies in BI2212 Tapes and Bulks With Zirconium Oxide Inclusion

Zirconium oxide inclusion in Bi2212 superconducting tapes and bulks was studied as possible artificial pinning centers (APC). In order to analyze the zirconium oxide APC addition in Bi2212 samples, magnetization measurements were performed in bulks and transport properties measurements were performed on tapes. In magnetization measurements, the critical current densities are proportional to the width of the magnetization loop at each applied magnetic field. Addition of ZrO(2) in Bi2212 superconductors broadened the magnetization loop and enhanced the critical current densities at 4.2 K in bulks, as a clear indication that ZrO(2) addition improved the pinning and acted as APCs. In contrast, the transport critical current densities decreased in tapes.

Characteristic zirconium-rich coring structures in Mg-Zr alloys

The most characteristic feature of the microstructure of a magnesium alloy that contains more than a few tenths per cent soluble zirconium is the zirconium-rich cores that exist in most grains. The morphology, distribution and composition of cores observed in a Mg-0.56%Zr alloy and the small particles present in them were investigated. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Optical properties of zirconium oxynitride films: the effect of composition, electronic and crystalline structures

tThis work is devoted to the investigation of zirconium oxynitride (ZrOxNy) films with varied opticalresponses prompted by the variations in their compositional and structural properties. The films wereprepared by dc reactive magnetron sputtering of Zr, using Ar and a reactive gas mixture of N2+ O2(17:3).The colour of the films changed from metallic-like, very bright yellow-pale and golden yellow, for low gasflows to red-brownish for intermediate gas flows. Associated to this colour change there was a significantdecrease of brightness. With further increase of the reactive gas flow, the colour of the samples changedfrom red-brownish to dark blue or even to interference colourations. The variations in composition dis-closed the existence of four different zones, which were found to be closely related with the variationsin the crystalline structure. XRD analysis revealed the change from a B1 NaCl face-centred cubic zirco-nium nitride-type phase for films prepared with low reactive gas flows, towards a poorly crystallizedover-stoichiometric nitride phase, which may be similar to that of Zr3N4with some probable oxygeninclusions within nitrogen positions, for films prepared with intermediate reactive gas flows. For highreactive gas flows, the films developed an oxynitride-type phase, similar to that of -Zr2ON2with someoxygen atoms occupying some of the nitrogen positions, evolving to a ZrO2monoclinic type structurewithin the zone where films were prepared with relatively high reactive gas flows. The analysis carriedout by reflected electron energy loss spectroscopy (REELS) revealed a continuous depopulation of thed-band and an opening of an energy gap between the valence band (2p) and the Fermi level close to 5 eV.The ZrN-based coatings (zone I and II) presented intrinsic colourations, with a decrease in brightness anda colour change from bright yellow to golden yellow, red brownish and dark blue. Associated to thesechanges, there was also a shift of the reflectivity minimum to lower energies, with the increase of thenon-metallic content. The samples lying in the two last zones (zone III, oxynitride and zone IV, oxide films)revealed a typical semi-transparent-optical behaviour showing interference-like colourations only dueto the complete depopulation of the d band at the Fermi level. The samples lying in these zones presentedalso an increase of the optical bandgap from 2 to 3.6 eV.

First examples of aliphatic zirconium MOFs and their influence of inorganic anions on their crystal structures

Aus: CrystEngComm, Vol. 17.2015, H. 2, S. 331-337

Podoconiosis in the Ethiopian Rift Valley - Role of beryllium and zirconium

A geogenic origin has been proposed in the aetiology of non-filarial elephantiasis of the feet and legs, recently renamed podoconiosis. Soil collected in an area of the Ethiopian Rift Valley, the borough of Ocholo, known for its high prevalence of podoconiosis (5.06%), has been submitted to mineral analysis. High values of sulphur (S), cerium (Ce), lanthanum (La) and neodymium (Nd), typical for basaltic bedrocks, were found. Of special interest were the values for zirconium (Zr) and beryllium (Be), 618 +/- 87 ppm and 4.6 +/- 0.5 ppm respectively, twice as high as those recorded for soils sampled in neighbouring areas where the prevalence of podoconiosis is low. To be noted also, a high content in vanadium, above 250 ppm, in half of the soil samples collected in this region. Year-long exposure of unprotected feet to Zr and Be, known for their ability to induce granuloma formation in the lymphoid tissue of man, and present in a clay rich in colloidal silica particle, highly abrasive to skin, is doubtlessly a factor involved in the development of lymph node sclerosis leading to elephantiasis.

Biocompatibility of an x-shaped zirconium implant in deep sclerectomy in rabbits.

BACKGROUND: The aim of this study was to evaluate the mid-term biocompatibility of a new x-shaped implant made of zirconium in an animal model of glaucoma surgery. METHODS: Preoperatively, ultrasound biomicroscopy (UBM), intraocular pressure (IOP) and outflow facility (OF) data were acquired. Upon surgery, one eye was chosen randomly to receive an implant, while the other received none. Ten rabbits went through a 1-, 2-, 3-, 4- and 6-month follow-up. IOP was measured regularly, UBM performed at 1, 3 and 6 months after surgery. At the end of the follow-up, OF was again measured. Histology sections were analyzed. RESULTS: For both groups IOP control was satisfactory, while OF initially increased at month 1 to resume preoperative values thereafter. Eyes with implants had larger filtration blebs which decreased faster than in eyes without the implant. Drainage vessel density, inflammatory cell number and fibrosis were higher in tissues near the implant. CONCLUSIONS: The zirconium implant initially promoted the positive effects of the surgery (IOP control, OF increase). Nevertheless, after several months, foreign body reactions and fibrosis had occurred on some implants that restrained the early benefit of such a procedure. Modifications of the zirconium implant geometry could enhance the overall success rate.

Pi*-pi* bonding interactions generated by halogen oxidation of zirconium(IV) redox-active ligand complexes.

The new complex, [Zr(pda)2]n (1, pda2- = N,N'-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi2 with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ZrX2(disq)2 (3, X = Cl, Br, I; disq- = N,N'-bis(neo-pentyl)-ortho-diiminosemiquinonate) in which each redox-active ligand has been oxidized by one electron. The oxidation products 3a-c have been structurally characterized and display an unusual parallel stacked arrangement of the disq- ligands in the solid state, with a separation of approximately 3 A. Density functional calculations show a bonding-type interaction between the SOMOs of the disq- ligands to form a unique HOMO while the antibonding linear combination forms a unique LUMO. This orbital configuration leads to a closed-shell-singlet ground-state electron configuration (S = 0). Temperature-dependent magnetism measurements indicate a low-lying triplet excited state at approximately 750 cm-1. In solution, 3a-c show strong disq--based absorption bands that are invariant across the halide series. Taken together these spectroscopic measurements provide experimental values for the one- and two-electron energies that characterize the pi-stacked bonding interaction between the two disq- ligands.

Influence du cuivre sur la santé des ouvriers en bronze, communication à la Société du bon-accord...

Comprend : Rapport relatif à une proposition du bureau de la Société du bon-accord ayant pour but de changer l'article 6 du règlement... lu à l'Assemblée générale de juillet 1869

Biocompatibility of an x-shaped zirconium implant in deep sclerectomy in rabbits

ABSTRACT : Background : The aim of this study was to evaluate the midterm biocompatibility of a new x-shaped implant made of zirconium in an animal model of glaucoma surgery. Methods : Preoperatively, ultrasound biomicroscopy (UBM), intraocular pressure (IOP) and outflow facility (OF) data were acquired. Upon surgery, one eye was chosen randomly to receive an implant, while the other received none. Ten rabbits went through a 1-, 2-, 3-, 4- and 6-month follow-up. [OP was measured regularly, UBM performed at 1, 3 and 6 months after surgery. At the end of the follow-up, OF was again measured. Histology sections were analyzed. Results : For both groups IOP control was satisfactory, while OF initially increased at month 1 to resume preoperative values thereafter. Eyes with implants had larger filtration blebs which decreased faster than in eyes without the implant. Drainage vessel density, inflammatory cell number and fibrosis were higher in tissues near the implant. Conclusions : The zirconium implant initially promoted the positive effects of the surgery (IOP control, OF increase). Nevertheless, after several months, foreign body reactions and fibrosis had occurred on some implants that restrained the early benefit of such a procedure. Modifications of the zirconium implant geometry could enhance the overall success rate.