1,472 research outputs found

    Synthesis of the Single Phase i-AlCuFe Bulk Quasicrystal by Spray Forming

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    In the present study, an icosahedral single phase bulk quasicrystalline material based on Al62Cu25.5Fe12.5 has been synthesised by a spray forming route. Microstructural characterization showed an average grain size of 10 m. The oversprayed fine powder showed the presence of - and -phases, whereas, the deposit consited of the fully single phase bulk quasicrystalline material with compositional homogeneity. The hardness and fracture toughness measurements were carried out at different indentation loads of 50-500 g. The hardness values varied in the range 10.4-8.1 GPa and fracture toughness was seen to decrease with increasing load. The varionan of hardness with load, which is known as indentation size effect (ISE) has been established clearly. Fracture toughness value was constant in the load range from 200 to 500 g at 1.2 MPa.m1/2. The cracking pattern after indentation at higher has been observed to be intergranular as well as transgranular. The evolution of the single phase bulk quasicrystalline material has been discussed in light of the unique combination of atomization and deposition process elements in spray forming technique

    Novel microstructural characteristics and properties of spray formed Al-RE-TM based alloys

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    Recent studies on the synthesis of bulk Al-RE (Rare Earth)-TM (Transition Metal) based alloys, from melt spun ribbons and gas atomized powders, have shown that a partially amorphous or nano-crystalline structures lead to a high specific strength. In the present study, therefore, spray atomization and deposition process has been used to produce plates of Al85Y8Ni5Co2 (deposit D1) and Al83Y5La5Ni5Co2 (deposit D2) based alloys so as to synthesize bulk deposit of nano-crystalline and/or partial amorphous matrix composite in a single step. The rapid solidification and high undercooling of droplets during atomization and a chilling effect on undercooled liquid upon deposition are expected to give rise to the above microstructural features. The microstructural features of deposits as well as overspray powders were studied using optical, scanning and transmission electron microscope. The alloys invariably showed a large fraction of nano-crystalline and amorphous structures, characterized by featureless regions at optical resolution, along with distribution of primary equilibrium phases. The differential scanning calorimetric (DSC) analysis of the deposits showed all the crystallization peaks as is observed during crystallization of fully amorphous melt spun ribbons of respective compositions. A glass transition phenomenon is observed in Al-Y-Ni-Co based deposit. The transmission electron microscopy of deposit D1 showed the presence of 50-100 nm size fcc-Al precipitates in an amorphous matrix decorated with 5-20 nm fcc-Al crystallites. The annealing treatment of deposits at different temperatures, determined from the crystallization peaks of the deposit, showed precipitation of nanoscale fcc-Al and intermetallic phases giving rise to a remarkable increase in hardness. The bulk hardness of the deposits D1 and D2 was 391 and 427 HV, respectively. Whereas, the heat treated deposits showed a bulk hardness value of 476 HV for deposit D1 at 298 oC and 582 HV for deposit D2 at 380 oC. An attempt has been made to bring out the possible mechanism of microstructural evolution during spray deposition of these alloys, and the effect of microstructural features on the mechanical properties has been discussed

    From spin liquid to magnetic ordering in the anisotropic kagome Y-Kapellasite Y3Cu9(OH)19Cl8: a single crystal study

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    Y3Cu9(OH)19Cl8 realizes an original anisotropic kagome model hosting a rich magnetic phase diagram [M. Hering et al, npj Computational Materials 8, 1 (2022)]. We present an improved synthesis of large phase-pure single crystals via an external gradient method. These crystals were investigated in details by susceptibility, specific heat, thermal expansion, neutron scattering and local muSR and NMR techniques. At variance with polycristalline samples, the study of single crystals gives evidence for subtle structural instabilities at 33K and 13K which preserve the global symmetry of the system and thus the magnetic model. At 2.1K the compound shows a magnetic transition to a coplanar (1/3,1/3) long range order as predicted theoretically. However our analysis of the spin wave excitations yields magnetic interactions which locate the compound closer to the phase boundary to a classical jammed spin liquid phase. Enhanced quantum fluctuations at this boundary may be responsible for the strongly reduced ordered moment of the Cu2+, estimated to be 0.075muB from muSR

    Effect of cyclosporin A on proteinuria in the course of glomerulopathy associated with WT1 mutations

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    Denys–Drash syndrome (DDS) is characterized by progressive glomerulopathy caused by diffuse mesangial sclerosis (DMS), genitourinary defects, and a higher risk of developing Wilms’ tumor. It is commonly assumed that the DMS is unresponsive to any medications. In this report, we present a patient with Denys–Drash syndrome, in whom the cyclosporine A (CsA) was found to induce total remission. This observation and observations of other authors confirm that in genetic forms of nephrotic syndrome, the proteinuric effect of CsA may be due to a non-immunologic mechanism. We confirm the beneficial effect of CsA treatment in DDS; however, the potential nephrotoxicity of this drug will probably not allow long-term use

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+→Ό+ÎœW^+ \rightarrow \mu^+\nu and W−→Ό−ΜW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector