Microstructure and Mechanical Properties of Al10SiMg Fabricated by Pulsed Laser Powder Bed Fusion

A series of high-density Al10SiMg specimens were fabricated using a custom built pulsed laser powder bed fusion unit operating with a pulsed-laser source. The fabricated components were analyzed using optical microscopy, computerized tomography (CT), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) mapping, and X-ray diffraction (XRD). A significantly refined cellular microstructure was observed, where Al cell diameter refinement upto ~210 nm was obtained throughout the component. Age hardening T6 treatment was also performed to investigate the heat treatment response of this fine microstructure. The mechanical properties in the as-built condition were assessed by microhardness testing (136 HV) and compressive tests (true compressive yield strength of 380 MPa and true ultimate compressive strength of 485 MPa). On the other hand, the mechanical responses of T6 specimens displayed strength reduction while demonstrating enhanced ductility.by R. Choua, A. Ghosha, S. C. Choua, Manas Paliwal and M. Brochu

Reactivity of a dearomatised pincer CoIIBr complex with PNCNHC donors: Alkylation and Si-H bond activation: Via metal-ligand cooperation

The double aminolysis reaction of [Co{N(SiMe3)2}2] by the salt 1-(6-((dicyclohexylphosphaneyl)methyl)pyridin-2-yl)-3-(2,6-diisopropylphenyl)-1H-imidazol-3-ium bromide, which contains one phosphane, one pyridine and one imidazolium groups, of formula [o-Cy2PCH2(C5H3N)(o-C3H3N2DiPP)]Br and abbreviated as (CyPNpyrCim)Br, was previously shown to afford the Co(ii) complex [Co(CyP∗NaCNHC)Br] (1) containing a dearomatised picolyl moiety in the tridentate, anionic donor ligand CyP∗NaCNHC (Na = anionic amido, P∗ = vinylic P donor). We now report that formation of 1 is preceded by an intermediate tentatively assignable to the 5-coordinate Co(ii) complex [Co(CyPNpyrCNHC){N(SiMe3)2}Br] (2). The reaction of 1 with LiCH2SiMe3 afforded the dark purple, paramagnetic [Co(CyP∗NaCNHC)CH2SiMe3] (3) with a low spin d7 CoII; the electronic configurations of 1 and 3 were corroborated by EPR spectroscopy. Addition of excess (≥4 equiv.) H2SiPh2 to a solution of 1 gave the diamagnetic [Co(CyP(SiHPh2)NCNHC)Br] (4) following Si-H activation and silylation of the ligand backbone at the α-CHP. Reduction of CoII to CoI by silanes is uncommon. © The Royal Society of Chemistry 2018

Electronic communication in "chain-like" trimetallic ruthenium complexes with two C7 carbon-rich conjugated bridges

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Modelling of flawed riveted structures for EC inspection in aeronautics

International audienceWithin the framework of a collaborative project between CEA and EADS, a semi-analytical model based on a Volume Integral Method (VIM) has been developed so as to simulate the Eddy Current (EC) inspection of riveted structures in aeronautics. The modeling is the one of a layered planar structure with a flaw located nearby a fastener. The VIM involving dyadic Green's functions is considered, a fastener and a flaw being introduced as a variation of conductivity in a stack of slabs. This semi-analytical approach is compared to a Finite-Element one (FE) developed by LGEP and is validated with experimental data acquired on an aeronautical configuration

Interdigitated conducting tetrathiafulvalene-based coordination networks

Assembly of a novel ethylenedithio-tetrathiafulvalene (EDT-TTF) derivative bearing two adjacent 4-thiopyridyl groups with M(NCS)2 nodes (M = Fe, Co) leads to two isostructural 1D coordination polymers showing an enhancement of their electronic conductivity by six orders of magnitude (10[superscript -6] vs. 10[superscript -12] S cm[superscript -1), upon surface oxidation by iodine and subsequent generation of EDT-TTF-based radicals.National Science Foundation (Award 1122374

High-temperature ferromagnetism in Co-doped CeO2 synthesized by the coprecipitation technique

The aim of the present study is to check the influence of annealing under vacuum and a mixture of N-2-H-2 atmosphere on the magnetic properties of polycrystalline Co-doped CeO2 diluted magnetic oxides (DMOs) with Co concentrations of 5 at% synthesized using the coprecipitation technique. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) showed for all samples the expected CeO2 cubic fluorite-type structure and that Co ions are uniformly distributed inside the samples. Room-temperature Raman and photoluminescence (PL) spectroscopies indicate an increase in the concentration of oxygen vacancies upon Co doping and further annealing. Field dependent magnetization measurements revealed a paramagnetic behavior for as-prepared Co-doped CeO2, while a ferromagnetic behavior appears when the same samples are annealed under vacuum or N-2-H-2 atmosphere. Temperature dependent magnetization measurements suggest that the observed ferromagnetism is due to the presence of metallic Co clusters with nanometric size and broad size distribution. These results are supported by electron paramagnetic resonance studies

Modulation of self-assembly and magnetism of Cu(II) grids in solution

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