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Issele H.,CEA Grenoble | Issele H.,CNRS Materials Science and Engineering | Mercier D.,CEA Grenoble | Mercier D.,CNRS Materials Science and Engineering | And 2 more authors.
e-Journal of Surface Science and Nanotechnology

The Young's modulus of a titanium nitride thin film has been investigated in this study by means of nanoindentation technique. Nanoindentation measurements have been coupled to analytical models and finite elements simulation to decorrelate the effect of substrate from the Young's modulus evaluation. Whereas analytical models did not lead to a converging solution towards experimental measurements, an identification based on finite elements calculations is shown necessary. Simulated contact stiffness versus contact areas have been fit with experiments and have led to a Young's modulus of 2007±20 GPa for a 180 nm thin film of TiN deposited on a 100 silicon substrate. This study confirms the property of the TiN deposited in thin films to have a different Young's modulus from a bulk TiN. © 2012 The Surface Science Society of Japan. Source

Van Landeghem H.P.,CNRS Jean Lamour Institute | Van Landeghem H.P.,University of Lorraine | Goune M.,University of Lorraine | Goune M.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | And 4 more authors.
Scripta Materialia

Annealing conditions leading to the crystallization of amorphous silicon nitride occurring upon nitriding of Fe-Si alloys have been found. A brief thermodynamic explanation for the occurrence of this unexpected amorphous-to-crystal transition is given. The crystalline precipitates were found to be α-Si3N4 and follow the orientation relationship given by (11̄0)α-Fe//(101̄0) α-Si3N4 with [111]α-Fe//[0001] α-Si3N4. This transition happens in precipitates with a constant Si3N4 composition. This structural change also leads to a morphological change from the initial cube-like shape to a hexagonal prism. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Messe O.M.D.M.,Rolls-Royce | Lachambre J.,MATEIS | King A.,Synchrotron Soleil | Buffiere J.Y.,MATEIS | Rae C.M.F.,Rolls-Royce
Advanced Materials Research

Evaluation of superalloy component life in turbine engines requires a detailed understanding of how fatigue crack initiation and short crack propagation contribute to fatigue life. However most investigations have been carried out post-mortem and in two dimensions. New techniques are able to fully resolve cracks propagating in four dimensions (space and time), enabling characterisation of their local environments and allowing a much deeper understanding of fatigue mechanics. Nickel-based superalloys experiencing high cycle fatigue have shown a high sensitivity to microstructure during initiation and short crack propagation. Using high energy X-rays and the combination of Diffraction Contrast Tomography (DCT) and Phase Contrast Tomography (PCT), we followed a fatigue crack initiated from a Focused Ion Beam (FIB) milled notch at room temperature. Analyses have been carried out to fully characterise the crack and its environment. We tracked the evolution of the crack and interactions with the microstructure. Subsequently, postmortem investigations have been carried out to corroborate results obtained from the tomographs and to provide more local information of fatigue crack propagation. © (2014) Trans Tech Publications, Switzerland. Source

Miguez-Pacheco V.,Friedrich - Alexander - University, Erlangen - Nuremberg | Buttner T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Macon A.L.B.,Imperial College London | Jones J.R.,Imperial College London | And 6 more authors.
Journal of Non-Crystalline Solids

Incorporation of therapeutic ions into the structure of bioactive glasses for direct stimulation of cells is a very attractive approach for tissue engineering strategies. Lithium has recently been identified as a biologically active ion which can stimulate osteoblast cell activity. In this study, lithium-containing bioactive glasses (Li-BGs) where Li2O substitutes Na2O in different amounts (2.5, 5 and 10 wt.% Li2O) in 45S5 bioactive glass (BG) were produced and made into 3D scaffolds by the foam replica method. The structural changes that occur after heat treatment, the effect of lithium-content on the bioactivity of the glasses and their lithium ion release profiles were investigated. The results show that the novel Li-BG formulations exhibit the formation of an apatite-like layer on their surface after immersion in SBF for 1 day thus confirming their high surface reactivity, similar to undoped 45S5 BG. XRD results showed that the Li-doped BGs crystallize mainly to combeite (Na2Ca2Si3O9) and silicorhenanite (SiO4(PO4)2Ca5) but also Li6P6O18 and Li3PO4 phases were detected. In terms of lithium ion release, the formulations at 2.5 wt.% and 5 wt.% Li2O content were the only ones to be within the therapeutic range (< 8.3 ppm). © 2015 Elsevier B.V. All rights reserved. Source

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