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Instruments / Technical Area	Publication Details	Published
	Anomalous behavior in the atomic structure of Nb3Sn under high pressure Irene Schiesaro , Simone Anzellini , Rita Loria , Raffaella Torchio , Tiziana Spina , René Flükiger , Tetsuo Irifune , Enrico Silva , Carlo Meneghini Crystals 11 DOI: 10.3390/cryst11040331 Open Access Show Abstract ▼ Abstract: In the present study, the local atomic structure of a Nb3Sn superconductor sample has been probed by X-ray absorption fine structure (XAFS) as a function of hydrostatic pressure (from ambient up to 26 GPa) using a diamond anvil cell set-up. The analysis of the Nb-K edge extended X-ray absorption fine structure (EXAFS) data was carried out combining standard multi shell structural refinement and reverse Monte Carlo method to provide detailed in situ characterization of the pressure-induced evolution of the Nb local structure in Nb3Sn. The results highlight a complex evolution of Nb chains at the local atomic scale, with a peculiar correlated displacement of Nb–Nb and Nb–Nb–Nb configurations. Such a local effect appears related to anomalies evidenced by X-ray diffraction in other superconductors belonging to the same A15 crystallographic structure.	Mar 2021
B16-Test Beamline B18-Core EXAFS I08-Scanning X-ray Microscopy beamline (SXM)	Studying the onset of galvanic steel corrosion in situ using thin films: film preparation, characterization and application to pitting Debi Garai , Vladyslav Solokha , Axel Wilson , Ilaria Carlomagno , Ajay Gupta , Mukul Gupta , V. R. Reddy , Carlo Meneghini , Francesco Carla , Christian Morawe , Jorg Zegenhagen Journal Of Physics: Condensed Matter DOI: 10.1088/1361-648X/abd523 Diamond Proposal Number(s): [17145] Open Access Show Abstract ▼ Abstract: This work reports about a novel approach for investigating surface processes during the early stages of galvanic corrosion of stainless steel in situ by employing ultra-thin films and synchrotron X-radiation. Characterized by X-ray techniques and voltammetry, such films, sputter deposited from austenitic steel, were found representing useful replicas of the target material. Typical for stainless steel, the surface consists of a passivation layer of Fe- and Cr-oxides, a couple of nm thick, that is depleted of Ni. Films of ≈ 4 nm thickness were studied in situ in an electrochemical cell under potential control (-0.6 to +0.8 V vs Ag/AgCl) during exposure to 0.1 M KCl. Material transport was recorded with better than 1/10 monolayer sensitivity by X-ray spectroscopy. Leaching of Fe was observed in the cathodic range and the therefor necessary reduction of Fe-oxide appears to be accelerated by atomic hydrogen. Except for minor leaching, reduction of Ni, while expected from Pourbaix diagram, was not observed until at ≈ +0.8 V Cr-oxide was removed from the film. After couple of minutes exposure at +0.8 V, the current in the electrochemical cell revealed a rapid pitting event that was simultaneously monitored by X-ray spectroscopy. Continuous loss of Cr and Ni was observed during the induction time leading to the pitting, suggesting a causal connection with the event. Finally, a spectroscopic image of a pit was recorded ex situ with 50 nm lateral and 1 nm depth resolution by soft X-ray scanning absorption microscopy at the Fe L2,3-edges by using a 80 nm film on a SiN membrane, which is further demonstrating the usefulness of thin films for corrosion studies.	Dec 2020
B16-Test Beamline B18-Core EXAFS Optics	Swelling of steel film by hydrogen absorption at cathodic potential in electrolyte Debi Garai , Ilaria Carlomagno , Vladyslav Solokha , Axel Wilson , Carlo Meneghini , Christian Morawe , Vadim Murzin , Ajay Gupta , Jorg Zegenhagen Physica Status Solidi (b) 3 DOI: 10.1002/pssb.202000055 Open Access Show Abstract ▼ Abstract: An ≈4 nm FeCrNi film, deposited on a Ru/B4C multilayer (ML), is used to study cathodic hydrogen charging in electrolyte. A thin film on a ML allows obtaining precise quantitative information on surface metal composition and oxidation state using the X‐ray standing wave technique combined with near‐edge X‐ray absorption spectroscopy. The metal composition is found being close to the composition of stainless steel (SS) 304, and, as for bulk steel, the outer 2 nm passive layer, consisting of oxidized iron and chromium, is depleted of nickel. Overall, it is found that the film represented a useful replica of the surface of bulk steel. Following exposure to 0.1 m KCl electrolyte at −0.6 V versus Ag/AgCl, 11.3 (±3)% swelling of the film by hydrogen absorption is observed. The estimated absorbed amount is exceeding reported bulk absorption under similar conditions by more than an order of magnitude. Strong hydrogen absorption appears to be enabled by the 2D character of the thin film, i.e., a significantly lower associated strain energy compared with bulk absorption. The strong surface swelling is suggested to be related to the lowering of the pitting corrosion resistance of SS surfaces reported following hydrogen exposure.	Apr 2020
I08-Scanning X-ray Microscopy beamline (SXM)	Zinc incorporation in marine bivalve shells grown in mine-polluted seabed sediments: a case study in the Malfidano mining area (SW Sardinia, Italy) Daniela Medas , Ilaria Carlomagno , Carlo Meneghini , Giuliana Aquilanti , Tohru Araki , Diana Bedolla , Carla Buosi , Maria Antonietta Casu , Alessandra Gianoncelli , Andrei C. Kuncser , V. Adrian Maraloiu , Giovanni De Giudici Environmental Science And Pollution Research 209 DOI: 10.1007/s11356-018-3504-y Diamond Proposal Number(s): [16496] Show Abstract ▼ Abstract: Zinc incorporation into marine bivalve shells belonging to different genera (Donax, Glycymeris, Lentidium, and Chamelea) grown in mine-polluted seabed sediments (Zn up to 1% w/w) was investigated using x-ray diffraction (XRD), chemical analysis, soft x-ray microscopy combined with low-energy x-ray fluorescence (XRF) mapping, x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). These bivalves grew their shells, producing aragonite as the main biomineral and they were able to incorporate up to 2.0–80 mg/kg of Zn, 5.4–60 mg/kg of Fe and 0.5–4.5 mg/kg of Mn. X-ray absorption near edge structure (XANES) analysis revealed that for all the investigated genera, Zn occurred as independent Zn mineral phases, i.e., it was not incorporated or adsorbed into the aragonitic lattice. Overall, our results indicated that Zn coordination environment depends on the amount of incorporated Zn. Zn phosphate was the most abundant species in Donax and Lentidium genera, whereas, Chamelea shells, characterized by the highest Zn concentrations, showed the prevalence of Zn-cysteine species (up to 56% of total speciation). Other Zn coordination species found in the investigated samples were Zn hydrate carbonate (hydrozincite) and Zn phosphate. On the basis of the coordination environments, it was deduced that bivalves have developed different biogeochemical mechanisms to regulate Zn content and its chemical speciation and that cysteine plays an important role as an active part of detoxification mechanism. This work represents a step forward for understanding bivalve biomineralization and its significance for environmental monitoring and paleoreconstruction.	Oct 2018
I15-Extreme Conditions	The Effect of Hydrostatic Pressure on the Superconducting and Structural Properties of Nb3Sn: Ab-initio Modelling and SR-XRD Investigation Rita Loria , Gianluca De Marzi , Simone Anzellini , Luigi Muzzi , Nicola Pompeo , Fabrizio Gala , Enrico Silva , Carlo Meneghini Ieee Transactions On Applied Superconductivity DOI: 10.1109/TASC.2016.2642398 Diamond Proposal Number(s): [14589] Show Abstract ▼ Abstract: We report on the investigations of the structural and superconducting properties of Nb3Sn in the GPa range by Angular Dispersive Synchrotron X-Ray Diffraction and abinitio calculations based on Density Functional Theory. X-Ray Diffraction experiments were carried out on Nb3Sn technological samples to explore the equation of state at room temperature and at pressures up to 43.5 GPa: we observe an anomaly in the PV curve in the region 5-10 GPa. The ab-initio calculated lattice parameter of Nb3Sn as a function of pressure has been used as an input for the calculation of the phonon dispersion curves and of the electronic band structures along different high symmetry directions in the Brillouin zone. The critical temperature has been calculated as a function of the hydrostatic pressure by means of the Allen-Dynes modification of the McMillan formula: we found that its behaviour is dictated mostly by the electronic contribution, but evident anomalies up to 6 GPa arise from phonons. These findings are a clue that Nb3Sn could have some structural instabilities with impact on its superconducting properties when subjected to a pressure of a few GPa and they represent an important step to understand and optimize the performances of Nb3Sn materials under the hard operational conditions of high field superconducting magnets.	Dec 2016
	Structure and magnetism of cobalt at high pressure and low temperature R. Torchio , C. Marini , Y. O. Kvashnin , I. Kantor , O. Mathon , G. Garbarino , C. Meneghini , S. Anzellini , F. Occelli , P. Bruno , A. Dewaele , S. Pascarelli Physical Review B 94 DOI: 10.1103/PhysRevB.94.024429 Show Abstract ▼ Abstract: The magnetic and structural properties of cobalt were investigated under high pressure (160 GPa) and low temperature (50 K), by synchrotron K-edge x-ray magnetic circular dichroism and x-ray diffraction. A quasihydrostatic equation of state was measured up to 160 GPa. We found that uniaxial stress plays a role in the hexagonal close packed-face centered cubic (hcp-fcc) structural transition pressure. Also, our data provide the first experimental evidence that changes of the c/a ratio pressure derivative are related to the magnetic behavior. The complete extinction of ferromagnetism is observed above 130 GPa in a mixed hcp-fcc phase with no recovery upon cooling to 50 K, indicating that cobalt at 150 GPa is very likely nonmagnetic, i.e., characterized by zero local spin polarization. Density functional theory calculations point out that the K-edge x-ray magnetic circular dichroism (XMCD) signal is related to the 4p orbital moment rather than to the total spin moment and allow us to get a deeper insight into the K-edge XMCD measurements interpretation. The combination of novel theoretical results and experimental outputs provides a detailed scenario of the structural and magnetic properties of cobalt at these extreme conditions answering some previously unsolved issues.	Jul 2016

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